JP2015175880A - Production method of capsule toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a capsule toner for electrostatic charge image development excellent in heat-resistant storage property, by which a fine shell layer (capsule film) can be formed.SOLUTION: The production method of a capsule toner for electrostatic charge image development comprises: finely pulverizing an anionic coarse pulverized material comprising at least a binder resin, a colorant, and a release agent in an aqueous medium in which at least either of a cationic monomer and a cationic prepolymer is dispersed, so as to obtain a core; and then polymerizing a shell layer on the surface of the core to form a shell layer on the surface of the core.

Description

  The present invention relates to a method for producing a capsule toner for developing an electrostatic image used for developing an electrostatic latent image formed in electrophotography.

  The capsule toner includes a core and a shell layer (capsule film) formed on the surface of the core. Patent Document 1 includes a step of dispersing a powder toner in a solid state in an aqueous medium in which a dispersant is dissolved, a step of mixing a raw material containing a thermosetting resin monomer or prepolymer with the dispersion, A step of converting the raw material into a resin without melting the powder toner and coating the surface of the toner with a thin film containing the thermosetting resin, wherein the powder toner is a pulverized toner. A manufacturing method is disclosed.

  However, the method for producing a toner described in Patent Document 1 has a problem that a dense shell layer (capsule film) cannot be formed and heat resistance storage stability is poor.

JP 2004-138985 A

  An object of the present invention is to provide a method for producing a capsule toner for developing an electrostatic charge image, which can form a dense shell layer (capsule film) and has excellent heat-resistant storage stability.

  In the present invention, an anionic coarsely pulverized product containing at least a binder resin, a colorant and a release agent is finely pulverized in an aqueous medium in which at least one of a cationic monomer and a cationic prepolymer is dispersed. The gist of the present invention is a method for producing a capsule toner for developing an electrostatic charge image, in which after the core is obtained, the shell layer is polymerized on the surface of the core to form the shell layer on the surface of the core.

  According to the present invention, in the process of finely pulverizing a coarsely pulverized product in an aqueous medium, a cationic monomer or a cationic prepolymer (for example, an initial condensate) adheres to the surface of the coarsely pulverized product. Since a strong and uniform shell layer can be formed, a toner having excellent heat resistant storage stability can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

  In the method for producing an electrostatic image developing capsule toner according to the present embodiment, an aqueous medium in which at least one of a cationic monomer and a cationic prepolymer is dispersed contains at least a binder resin, a colorant, and a release agent. The anionic coarsely pulverized product is finely pulverized and then the shell layer is polymerized.

  The electrostatic charge image developing capsule toner manufactured by the manufacturing method according to the present embodiment includes a large number of toner particles (hereinafter also simply referred to as “toner particles”). Each toner particle has a structure in which a cationic shell layer (capsule film) is formed on the surface of an anionic core. In this embodiment, the shell layer is not limited to a single layer, and may be a multilayer. In the case of a multilayer, at least the outermost layer preferably has a cationic property.

  When the core has an anionic property, the material of the cationic shell layer can be attracted to the core surface when the shell layer is formed. Specifically, for example, a negatively charged core in an aqueous medium and a shell layer material positively charged in the aqueous medium are electrically attracted to each other, and a shell layer is formed on the surface of the core. This makes it easy to form a uniform shell layer on the surface of the core without highly dispersing the core in the aqueous medium using a dispersant.

  The core is composed of a binder resin and an internal additive (colorant, release agent, charge control agent, magnetic powder, etc.).

  In the core, since the binder resin occupies most of the core component (for example, 85% or more), the polarity of the binder resin greatly affects the polarity of the entire core. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, a methyl group, etc., the core has a strong tendency to become anionic, and the binder resin has an amino group, an amine, an amide group, etc. The core has a greater tendency to become cationic.

  An indicator that the core is anionic is that the zeta potential of the core measured in an aqueous medium adjusted to pH 4 exhibits a negative polarity. The zeta potential of the core preferably shows a value of -5 mV or less, and more preferably shows a value of -10 mV or less.

  In this embodiment, another indicator that the core is anionic is that the triboelectric charge with the standard carrier shows a value of -1 μC / g or less, preferably -10 μC / g or less. The triboelectric charge amount is an indicator of whether the core is charged in positive or negative polarity and the ease with which the core is charged. The triboelectric charge amount of the core when rubbed with a standard carrier can be measured by, for example, a QM meter (for example, MODEL 210HS-2A manufactured by TREK).

  Hereinafter, the overall configuration of the core constituting the toner particles, the binder resin, the internal additive (colorant, release agent, charge control agent, magnetic powder), the overall configuration of the shell layer, and the components of the shell layer (charge control agent) The external additives will be described in order.

〔core〕
The core constituting the toner particles of the present embodiment includes a binder resin and an internal additive (colorant, release agent, charge control agent, and magnetic powder). However, it is not essential that the core has all of the above components, and unnecessary components (charge control agent, magnetic powder, etc.) may be omitted depending on the intended use of the toner.

[Binder resin (core)]
The binder resin is preferably composed of a resin having, for example, an ester group, a hydroxyl group, an ether group, an acid group, a methyl group, or a carboxyl group as a functional group. As the resin constituting the binder resin, a resin having a functional group such as a hydroxyl group or a carboxyl group in the molecule is preferable. The core (binder resin) having such a functional group easily reacts with the shell layer material (for example, methylol melamine) to be chemically bonded. When such a chemical bond occurs, the bond between the core and the shell layer becomes strong.

  As the resin constituting the binder resin, a thermoplastic resin is preferable. Preferred examples of the thermoplastic resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. Examples thereof include resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. 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 to the recording medium, respectively.

(Binder resin composed of styrene acrylic resin)
The styrene acrylic resin constituting the binder resin is a copolymer of a styrene monomer and an acrylic monomer.

  Preferable examples of the styrenic monomer include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chloro. Examples include styrene and p-ethylstyrene.

  Preferable examples of the acrylic monomer include (meth) acrylic acid, particularly (meth) acrylic acid alkyl ester or (meth) acrylic acid hydroxyalkyl ester.

  Examples of the (meth) acrylic acid alkyl ester 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, and 2-ethylhexyl (meth) acrylate are preferred.

  Examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxy (meth) acrylate. Propyl is preferred.

  When preparing a styrene acrylic resin, a hydroxyl group can be introduced into the styrene acrylic resin by using a monomer having a hydroxyl group (p-hydroxystyrene, m-hydroxystyrene, hydroxyalkyl (meth) acrylate, etc.). . For example, the hydroxyl value of the resulting styrene acrylic resin can be adjusted by appropriately adjusting the amount of the monomer having a hydroxyl group.

  When preparing the styrene acrylic resin, a carboxyl group can be introduced into the styrene acrylic resin by using (meth) acrylic acid as a monomer. For example, the acid value of the resulting styrene acrylic resin can be adjusted by appropriately adjusting the amount of (meth) acrylic acid used.

  In order to improve the strength and fixability of the core, the number average molecular weight (Mn) of the styrene acrylic resin constituting the binder resin is preferably 2000 or more and 3000 or less. The molecular weight distribution (ratio Mw / Mn of number average molecular weight (Mn) and mass average molecular weight (Mw)) 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.

(Binder resin composed of polyester resin)
The polyester resin constituting the binder resin is obtained, for example, by condensation polymerization or cocondensation polymerization of a divalent or trivalent or higher alcohol component and a divalent or trivalent or higher carboxylic acid component.

  Preferable examples of the divalent or trivalent or higher alcohol component include diols, bisphenols, and trivalent or higher alcohols.

  Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5 -Pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol are preferred.

  As bisphenols, for example, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylenated bisphenol A are preferable.

  Examples of the trivalent 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, 1,3,5-trihydroxymethyl Benzene is preferred.

  Preferable examples of the divalent or trivalent or higher carboxylic acid component include divalent carboxylic acid or trivalent or higher carboxylic acid. Further, these carboxylic acid components may be used as ester-forming derivatives (acid halides, acid anhydrides, lower alkyl esters, etc.). Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  Examples of the divalent carboxylic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid. Alkyl or alkenyl succinic acids are preferred. Furthermore, examples of the alkenyl succinic acid include 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, and n-dodecenyl succinic acid. , Isododecyl succinic acid, and isododecenyl succinic acid are preferable.

  Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4. -Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid are preferred.

  When the polyester resin is produced, the acid value of the polyester resin and the amount of the divalent or trivalent or higher alcohol component and the amount of the divalent or trivalent or higher carboxylic acid component are appropriately adjusted. The hydroxyl value can be adjusted. Moreover, when the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  In order to improve the strength and fixability of the core, the polyester resin constituting the binder resin preferably has a number average molecular weight (Mn) of 1200 or more and 2000 or less. The molecular weight distribution of the polyester resin (ratio Mw / Mn between the number average molecular weight (Mn) and the mass average molecular weight (Mw)) is preferably 9 or more and 20 or less. Gel permeation chromatography can be used for the measurement of Mn and Mw of the polyester resin.

  In order to obtain a strong anionic property of the binder resin, the hydroxyl value (OHV value) and the acid value (AV value) of the binder resin are each preferably 10 mgKOH / g or more.

  The solubility index (SP value) of the binder resin is preferably 10 or more, and more preferably 15 or more. When the SP value is 10 or more, it approaches the SP value of water (23), so that the affinity with water can be improved, and the wettability of the binder resin to the aqueous medium is improved. Therefore, the dispersibility of the core containing the binder resin in the aqueous medium is improved without using a dispersant, and the core is easily dispersed uniformly in the aqueous medium.

  The glass transition point (Tg) of the binder resin is preferably equal to or lower than the curing start temperature of the shell material (for example, thermosetting resin) included in the shell layer. If such a binder resin is used, sufficient fixability can be obtained even in a high-speed fixing system. The curing start temperature of thermosetting resins such as melamine resins is generally about 55 ° C to 100 ° C. Therefore, Tg of the binder resin is preferably 20 ° C. or higher and 55 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower. When the Tg of the binder resin is 20 ° C. or higher, the core is less likely to aggregate when the shell layer is formed.

  The Tg of the binder resin can be obtained from the change point of the specific heat in the endothermic curve by measuring the endothermic curve of the binder resin using a differential scanning calorimeter (for example, DSC-6200, manufactured by Seiko Instruments Inc.). . Specifically, 10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, and an endothermic curve of the binder resin is obtained under the conditions of a measurement temperature range of 25 to 200 ° C. and a heating rate of 10 ° C./min. And a method of obtaining Tg of the binder resin based on the obtained endothermic curve.

  The softening point (Tm) of the binder resin is preferably 100 ° C. or less, and more preferably 95 ° C. or less. When the Tm of the binder resin is 100 ° C. or lower, it becomes possible for the toner to obtain sufficient fixability even during high-speed fixing. Moreover, Tm of binder resin can be adjusted by combining the several binder resin material which has different Tm.

  For the Tm of the binder resin, for example, a measurement sample is set in a Koka-type flow tester (for example, CFT-500D, manufactured by Shimadzu Corporation), and the sample is melted and flowed out under a predetermined condition. ) / S-curve with respect to stroke (mm)), and Tm of the binder resin can be read from the obtained S-curve.

[Colorant (core)]
As the colorant, for example, a known pigment or dye can be used according to the color of the toner particles. 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.

(Black colorant)
The core of the toner particles according to the present embodiment may contain a black colorant. The black colorant is composed of, for example, carbon black. In addition, a colorant that has been adjusted to black using a colorant such as a yellow colorant, a magenta colorant, or a cyan colorant can also be used as the black colorant.

(Coloring agent)
The core of the toner particles according to the exemplary embodiment may contain a color colorant such as a yellow colorant, a magenta colorant, and a cyan colorant.

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

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

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

[Release agent (core)]
The release agent is used for the purpose of improving the fixing property and offset resistance of the toner. In order to improve the fixing property and the offset resistance, 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. It is more preferable that the amount is not more than parts.

  In one example, the release agent is preferably composed of an aliphatic hydrocarbon wax such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax. In another example, the release agent is preferably composed of an oxide of an aliphatic hydrocarbon wax such as an oxidized polyethylene wax or a block copolymer of oxidized polyethylene wax. In another example, it is preferable that the release agent is composed of a plant-based wax such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax. In another example, it is preferable that the release agent is composed of animal wax such as beeswax, lanolin, spermaceti. In another example, it is preferable that the release agent is composed of a mineral wax such as ozokerite, ceresin, and vetrolactam. In another example, it is preferable that the mold release agent is composed of waxes mainly composed of fatty acid esters such as montanic acid ester wax and caster wax. In another example, it is preferable that the release agent is composed of a wax obtained by deoxidizing a part or all of a fatty acid ester such as deoxidized carnauba wax.

[Charge control agent (core)]
The core may contain a charge control agent. In this embodiment, since the core has an anionic property (negative chargeability), a negatively chargeable charge control agent may be used in the core. The charge control agent is used for the purpose of improving the charge stability and charge rise characteristics and obtaining a toner having excellent durability and stability. The charge rising characteristic is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

[Magnetic powder (core)]
The core may contain magnetic powder. When toner is used as a one-component developer, the amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, and 40 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the total amount of toner. It is more preferable.

  Magnetic powder is, for example, iron (ferrite, magnetite, etc.), ferromagnetic metal (cobalt, nickel, etc.), an alloy containing iron and / or ferromagnetic metal, a compound containing iron and / or ferromagnetic metal, and ferromagnetic such as heat treatment. It is preferably made of a ferromagnetic alloy and chromium dioxide that have been subjected to a heat treatment.

  The particle size of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When the particle size of the magnetic powder is in such a range, the magnetic powder is easily dispersed uniformly in the binder resin.

[Shell layer]
As the shelling material for forming the shell layer, so-called in-situ polymerization can be performed in which a cationic capsule material is ionically attracted to an anionic core (core material) and attached to the surface of the core for surface polymerization. If it is material, there will be no limitation in particular, A thermosetting material is preferable. The thermosetting material, those which are generically referred to as an amino resin having an amino group (-NH ₂₎ is preferred. Examples of amino resins include melamine resins or derivatives thereof (such as methylol melamine), guanamine resins or derivatives thereof (such as benzoguanamine), acetoguanamines, spiroguanamines, sulfoamide resins, urea (urea) resins or derivatives thereof, glyoxal resins, and anilines. Resin. These can be used alone or in combination of two or more.

  Examples of the amino resin include materials having a nitrogen element in the molecular skeleton, and examples thereof include thermosetting resins such as polyimide resin, maleide polymer, bismuth imide, amino bismuth imide, and bismuth imide triazine.

  Furthermore, amino aldehyde resin is mentioned as an amino resin. An amino aldehyde resin is obtained by condensation polymerization of an amino compound (triazine compound, etc.) such as melamine, guanamine, etc., by addition polymerization by reaction with an aldehyde such as formaldehyde, and methylolation (generally alkylolation). The resin is a generic name for the resin, and specific examples include melamine formaldehyde resin, urea formaldehyde resin, and melamine urea aldehyde resin.

  As the shelling material, a cationic monomer such as an aminoaldehyde resin containing a nitrogen element such as melamine resin, guanamine resin, urea resin, or a cationic prepolymer is used, but on the surface of anionic solid particles in an aqueous system. A melamine formaldehyde initial condensate (prepolymer) capable of adsorbing moderately and encapsulating and maintaining dispersion stability so that the toner particles do not aggregate until the capsule curing reaction is completed is more preferable. This is particularly important for the balance between the affinity of water and the toner particle surface in order to adsorb moderately on the surface of the anionic solid particle in water and to perform in-situ polymerization on the surface of the toner particle. The shelling material is adsorbed on the toner particle surface to form an interaction with the functional group (—OH group, —COOH group) on the toner particle surface, and the cores do not aggregate until the curing reaction of the shelling material is completed. This is because it is necessary to maintain the dispersion stability of the core in water. That is, there is a proper region where the affinity for water is high or low.

  The thickness of the shell layer is 20 nm or less, and preferably 1 nm or more and 10 nm or less. If the shell layer is too thick, sufficient fixability cannot be obtained. The thickness of the shell layer means the thickness converted into the case of the resin constituting the shell layer (for example, a thermosetting resin such as a melamine resin) alone, and a modifier or the like is added to the thermosetting resin. When flexibility is given, it is not limited to the above range. In the case of a thermoplastic capsule, if the film is thin, a sufficient blocking effect cannot be obtained, so that it tends to be a thick film of 50 nm or more.

  The thickness of the shell layer can be measured, for example, as follows. That is, the toner particles are sufficiently dispersed in a room temperature curable epoxy resin and cured in an atmosphere of 40 ° C. for 2 days to obtain a cured product. This cured product is dyed with osmium tetroxide, and then cut out with a microtome (for example, EM UC6, manufactured by Leica Co., Ltd.) with a diamond knife to obtain a thin sample having a thickness of about 200 nm. And the cross section of this sample is image | photographed with a transmission electron microscope (TEM) (for example, JEOL Co., Ltd. make, JSM-6700F).

  The thickness of the shell layer is measured by analyzing the TEM image with image analysis software (for example, WinROOF, manufactured by Mitani Corporation). Specifically, two straight lines that are orthogonal to each other at the approximate center of the cross section of the toner particle 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 measured lengths is taken as the thickness of the shell layer of one toner particle that is the measurement target. The thickness of the shell layer is measured for 10 or more toner particles contained in the toner, and the average value of the 10 or more obtained measurement values is used as the evaluation value.

  In addition, when the thickness of the shell layer is small, the interface between the core and the shell layer on the TEM image becomes unclear, which may make it difficult to measure the thickness of the shell layer. In such a case, the thickness of the shell layer is measured by combining TEM imaging and electron energy loss spectroscopy (EELS) to clarify the interface between the core and the shell layer. Specifically, the thickness of the shell layer is specified by mapping an element (nitrogen element) characteristic of the material of the shell layer using EELS in the TEM image.

[Charge control agent (shell layer)]
In this embodiment, since the shell layer has a cationic property (positive chargeability), a positively chargeable charge control agent may be used in the shell layer.

(External additive)
In this embodiment, an external additive may be attached to the surface of the shell layer in order to improve the fluidity and handleability of the toner particles. Hereinafter, the particles before being treated with the external additive are referred to as “toner mother particles”. From the viewpoint of improving fluidity and handling properties, the amount of the external additive used is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. It is more preferable that the amount is not more than parts.

  The external additive is preferably composed of, for example, silica or a metal oxide such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1 μm or less from the viewpoint of improving fluidity and handling properties.

  Next, a case where the toner according to the exemplary embodiment is mixed with a carrier and used as a two-component developer will be described. In order to obtain a desired image density and suppress toner scattering, 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 more preferable that the amount is not more than mass%.

[Carrier]
For example, it is preferable to use a magnetic carrier. A magnetic carrier is comprised from the carrier core material and the resin layer which coat | covers a carrier core material, for example. Alternatively, a carrier core material in which magnetic particles are dispersed in a resin may be coated with a resin layer.

  In one example, the carrier core material is composed of particles such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, or cobalt, or these materials and metals such as manganese, zinc, and aluminum. It is preferably composed of alloy particles. In another example, the carrier core material is preferably composed of particles of iron-nickel alloy, iron-cobalt alloy, or the like. In another example, the carrier core material is titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, lead zirconate It is preferably composed of ceramic particles such as lithium niobate. In another example, the carrier core material is preferably composed of particles of a high dielectric constant material such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt.

  The resin layer covering the carrier core material is, for example, a (meth) acrylic polymer, a styrene polymer, a styrene- (meth) acrylic copolymer, an olefin polymer (polyethylene, chlorinated polyethylene, polypropylene, etc.), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride Etc.), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, and amino resin.

  In order to improve magnetism and fluidity, 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 can be measured by observing with an electron microscope or the like.

  Next, a capsule toner manufacturing method according to the present embodiment will be described.

  In the method for producing a capsule toner according to the present embodiment, a coarsely pulverized product finely pulverized in advance is dispersed in an aqueous medium in which at least one of a cationic monomer and a cationic prepolymer is dispersed, and polymerization of the shell layer is performed. Rather than being performed, the coarsely pulverized product is characterized by being finely pulverized in the aqueous medium. According to this production method, a cationic monomer or a cationic prepolymer (for example, an initial polymer) adheres to the surface of the coarsely pulverized product in the course of pulverizing the coarsely pulverized product in an aqueous medium. Therefore, a strong and uniform shell layer can be formed, and heat resistant storage stability is improved.

  The volume average particle diameter of the coarsely pulverized product before being finely pulverized in the aqueous medium is preferably 6 μm or more and 500 nm or less. When the volume average particle diameter of the coarsely pulverized product is less than 6 μm, the coarsely pulverized product is finely pulverized in advance, so there is no need to finely pulverize it. The coarsely pulverized product is dispersed in the aqueous medium to form a shell layer. Even if this polymerization is carried out, there is a possibility that a shell layer cannot be sufficiently formed, and there is a tendency to obtain a toner having poor heat-resistant storage stability.

[Formation of coarsely pulverized core]
The core is formed, for example, by a pulverization classification method (melt kneading method). According to this method, the internal additive can be favorably dispersed in the binder resin.

(Core formation by pulverization classification)
The binder resin material and the internal additive material are mixed, and the mixture is melt-kneaded. Next, the melt kneaded product is pulverized to obtain a coarsely pulverized product.

  In this way, a coarsely pulverized product before fine pulverization is produced. In this case, the volume average particle diameter of the coarsely pulverized product is preferably 6 μm or more as described above.

[Formation of shell layer]
In forming the shell layer, first, the pH of the solvent is adjusted. The pH of the solvent is preferably adjusted to about 4 with an acidic substance, for example. By adjusting the pH of the dispersion to the acidic side of about 4, the polycondensation reaction of the material used for forming the shell layer is promoted. Subsequently, the material of the cationic shell layer is dissolved in a solvent (aqueous medium) whose pH is adjusted.

(Fine pulverization of coarsely pulverized product)
Subsequently, the coarsely pulverized product prepared by the above-described method is added to the aqueous medium in which the shell layer material is dissolved, and the coarsely pulverized product is finely pulverized and dispersed. When the core is uniformly dispersed in the solvent, a uniform shell layer is easily obtained. Specifically, a predetermined amount (for example, 1500 g) of a pulverized member (for example, glass beads having a diameter of 1 mm) is added to an aqueous medium in which the material of the shell layer to which the coarsely pulverized material is added is dissolved, and a tabletop sand mill or the like is used. For a predetermined time (for example, 3 hours).

  The pulverized member is not limited to glass beads, and can be appropriately selected from members having high hardness, acid resistance, and the like that do not chemically change the toner material, such as zirconia beads and alumina beads. Further, the method of fine pulverization is not limited to the method using the pulverization member, and the coarsely pulverized product can be finely pulverized without using the pulverization member.

  As a method for satisfactorily dispersing the core, for example, a method in which the dispersion is mechanically dispersed using an apparatus capable of powerfully stirring the dispersion is preferable. Examples of the apparatus that can be vigorously stirred include Hibismix manufactured by Primix. However, the method is not limited to this, and the method of dispersing the core is arbitrary.

  Subsequently, after the pulverized member such as the glass beads is removed by filtration or the like, the temperature of the solvent to which the core is added is set to a desired temperature, and the temperature is maintained (insulated) for a predetermined time. And formation of a shell layer (for example, hardening reaction) advances at this temperature. At this time, the softened core may become spherical due to shrinkage of the core due to surface tension.

  In order to promote the formation of the shell layer, the temperature (reaction temperature) of the solution at the time of forming the shell layer is preferably 40 ° C. or more and 95 ° C. or less, and preferably 50 ° C. or more and 80 ° C. or less. More preferred. Further, when the binder resin constituting the core is composed of a resin having a hydroxyl group or a carboxyl group (for example, a polyester resin), and the shell layer is composed of a cationic monomer or prepolymer, If the temperature is 40 ° C. or higher and 95 ° C. or lower, the hydroxyl group or carboxyl group exposed on the core surface reacts with the methylol group of the resin constituting the shell layer to form the binder resin and shell layer constituting the core. A covalent bond is easily formed between the resin and the resin. This makes it possible to form a shell layer on the core surface that is firmly bonded to the core surface.

  Subsequently, the pH of the solvent is adjusted to 7, for example, and the contents of the flask are cooled to room temperature. This solvent includes toner base particles composed of an anionic core and a cationic shell layer covering the surface of the core.

〔Washing〕
After the toner base particles are formed, the toner base particles are washed. For example, a wet cake of toner base particles is filtered from the dispersion using a Buchner funnel, and the wet cake of toner base particles is dispersed again in ion-exchanged water to wash the toner base particles. And the same washing | cleaning by ion-exchange water is repeated several times, and a filtrate and washing water are collect | recovered as waste water. However, the method is not limited to this, and the toner mother particle cleaning method is arbitrary.

  The electrical conductivity of the filtrate is preferably 10 μS / cm or less in order to suppress the environmental fluctuation of the toner charge amount from increasing. The electrical conductivity of the filtrate can be measured using, for example, Horiba COND METER ES-51 manufactured by Horiba, Ltd.

[Dry]
For example, the toner base particles after washing are dried by a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, or a vacuum dryer. At this time, if a spray dryer is used, aggregation of toner mother particles during drying can be suppressed. However, the method is not limited to this, and the method for drying the toner base particles is arbitrary.

(External)
An external additive is adhered to the surface of the toner base particles. As a method for attaching the external additive, for example, the conditions are adjusted so that the external additive is not buried in the surface of the toner base particles, and the toner base particles and the external additive are mixed with a mixer such as a Henschel mixer or a Nauta mixer. A method of mixing is preferred. However, the method is not limited to this, and an external addition method for the toner base particles is arbitrary. For example, when a spray dryer is used in the drying process, a dispersion of external additives such as silica can be sprayed together with a dispersion of toner base particles. As a result, the drying process and the external addition process can be performed simultaneously.

  According to the capsule toner manufacturing method according to the present embodiment described above, a capsule toner excellent in heat-resistant storage stability can be obtained. This capsule toner can be suitably used in an image forming apparatus to which an electrophotographic method or the like is applied.

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

  Prior to Examples and Comparative Examples, coarsely pulverized products were produced as follows.

[Production Example 1]
(Preparation of coarsely pulverized product 1)
A polyester resin having the following characteristics was used as a binder resin. The polyester resin had an OHV value of 2 mgKOH / g, AV of 3 mgKOH / g, Tm of 100 ° C., and Tg of 48 ° C. For 100 parts by mass of this polyester resin, C.I. I. 5 parts by weight of pigment blue 15: 3 (phthalocyanine pigment) and 5 parts by weight of ester wax (manufactured by NOF Corporation, WEP-3) as a release agent were mixed and mixed using a mixer (Henschel mixer). Chips kneaded with a twin-screw extruder (Ikegai, PCM-30) were pulverized to a volume average particle size of 80 μm with a mechanical pulverizer (Turbo Kogyo, turbo mill) to obtain a coarsely pulverized product 1.

(Measurement of charge amount of core equivalent 1)
The charge amount of the coarsely pulverized product 1 produced as described above was measured as follows. That is, first, the chips kneaded based on the preparation of the coarsely pulverized product were pulverized to a volume average particle size of 6 μm by a mechanical pulverizer (Turbo Kogyo Co., Ltd., turbo mill). Then, it classify | categorized with the classifier (The Nippon Steel Mining Co., Ltd. make, Elbow Jet), and obtained the core equivalent 1 with a volume average particle diameter of 6 micrometers. Next, using a Turbula mixer (manufactured by Shinmaru Enterprises Co., Ltd., model number T2F, setting condition 96 rpm), 10 g of standard carrier N-01 (standard carrier for negatively charged polarity toner provided by the Imaging Society of Japan) 7% by mass of the core equivalent 1 was mixed with the standard carrier for 30 minutes. The charge amount of the coarsely pulverized product when the obtained mixture was rubbed with a standard carrier as a measurement sample was measured with a QM meter (manufactured by TREK, MODEL 210HS-2A). As a result, the charge amount of the core equivalent 1 was −1 μC / g, which showed anionic property.

[Production Example 2]
(Preparation of coarsely pulverized product 2)
A polyester resin having the following characteristics was used as a binder resin. This polyester resin had an OHV value of 4 mgKOH / g, AV of 8 mgKOH / g, Tm of 100 ° C., and Tg of 48 ° C. Using this polyester resin, a coarsely pulverized product 2 having a volume average particle diameter of 80 μm was obtained in the same manner as the coarsely pulverized product 1.

(Measurement of charge amount of core equivalent 2)
As a result of measuring the charge amount of the core equivalent product 2 in the same manner as described above, it was -7 μC / g, which showed anionic property.

[Production Example 3]
(Preparation of coarsely pulverized product 3)
A polyester resin having the following characteristics was used as a binder resin. The polyester resin had an OHV value of 10 mgKOH / g, AV of 22 mgKOH / g, Tm of 100 ° C., and Tg of 48 ° C. Using this polyester resin, a coarsely pulverized product 3 having a volume average particle diameter of 80 μm was obtained through the same steps as those of the coarsely pulverized product 1.

(Measurement of charge amount of core equivalent 3)
As a result of measuring the charge amount of the core equivalent product 3 in the same manner as described above, it was −10 μC / g, which showed anionic property.

[Production Example 4]
(Preparation of coarsely pulverized product 4)
A polyester resin having the following characteristics was used as a binder resin. The polyester resin had an OHV value of 20 mg KOH / g, AV of 40 mg KOH / g, Tm of 100 ° C., and Tg of 48 ° C. Using this polyester resin, a coarsely pulverized product 4 having a volume average particle diameter of 80 μm was obtained through the same steps as the coarsely pulverized product 1.

(Measurement of charge amount of core equivalent 4)
As a result of measuring the charge amount of the core equivalent product 4 in the same manner as described above, it was −20 μC / g and anionic.

[Comparative Production Example 5]
(Preparation of coarsely pulverized product 5)
A styrene acrylic resin having the following characteristics was used as a binder resin. The styrene acrylic copolymer had an AV of 2 mgKOH / g, a Tm of 100 ° C., and a Tg of 48 ° C. Using this styrene acrylic resin, a coarsely pulverized product 5 having a volume average particle diameter of 80 μm was obtained through the same steps as the coarsely pulverized product 1.

(Measurement of charge amount of core equivalent 5)
As a result of measuring the charge amount of the core equivalent product 5 in the same manner as described above, it was +10 μC / g, indicating a cationic property.

[Comparative Production Example 6]
(Preparation of core 6)
The kneaded chips were pulverized to a volume average particle size of 80 μm in the same manner as in the preparation of the coarsely pulverized product 3 described above. Then, after finely pulverizing to a volume average particle diameter of 6 μm with a mechanical pulverizer (turbo industry, turbo mill), classification with a classifier (manufactured by Nippon Steel Mining Co., Ltd., Elbow Jet), the volume average particle diameter is 6 μm. A core 6 was obtained.

(Measurement of charge amount of core 6)
As a result of measuring the charge amount of the core 6 in the same manner as described above, it was −10 μC / g, which showed anionic property.

[Example 1]
(Preparation of capsule toner)
To a vessel of a tabletop sand mill (manufactured by Hayashi Shoten Co., Ltd.), 300 ml of ion exchange water was added, and 1N hydrochloric acid was added to adjust the pH of the aqueous medium in the vessel to 4. To this was added 6.6 g of a cationic hexamethylolated material (Milben 607, Showa Denko KK), which is a shelling material, and dissolved. To this aqueous solution, 300 g of the coarsely pulverized product 1 was added, and 300 g of ion-exchanged water was further added. 1500 g of glass beads having a diameter of 1 mm were added thereto, and the mixture was treated for 3 hours in a high mode using a desktop sand mill. The solution obtained by filtering and removing the glass beads is put into a 1-liter three-necked flask, set in a 30 ° C. water bath, and stirred using a stirrer (IKA, product number: RW20 Digital) at a stirring speed of 100 rpm. The temperature was raised at a rate of 1 ° C./min while maintaining at 70 ° C. for 2 hours. Thereafter, 1N-sodium hydroxide solution (neutralizing agent) was added to neutralize to pH 7, and the capsule toner was recovered from the dispersion by filtration.

(Washing and drying)
After the toner base particles (core and shell layers) were formed, the dispersion was subjected to suction filtration (solid-liquid separation) using a Buchner funnel (Nutche). As a result, wet cake-like toner base particles were obtained. Thereafter, toner mother particles were dispersed in ion exchange water. Further, filtration and dispersion were repeated to wash the toner base particles. Filtration and dispersion were repeated until the conductivity of a dispersion obtained by dispersing 10 g of toner base particles in 100 g of ion-exchanged water was 4 μS / cm or less. If this electrical conductivity is 10 μS / cm or less, it is considered that the chargeability of the toner is hardly affected. An electrical conductivity meter “HORIBA ES-51” manufactured by HORIBA, Ltd. was used for the measurement of conductivity. The added shell layer material (monomer or resin) was hardly contained in the filtrate. The TOC (total organic carbon) concentration of the filtrate after washing and the washing solution was 8 mg / L or less, respectively. An online TOC meter (“TOC-4200” manufactured by Shimadzu Corporation) was used to measure the TOC concentration.

  Subsequently, the washed wet cake-like toner base particles were crushed, and the toner base particles were dried using a vacuum oven.

(External)
100 parts by mass of the toner base particles after drying and 1 part by mass of dry silica fine particles (“REA90” manufactured by Nippon Aerosil Co., Ltd.) are mixed using a 5 L mixer (“Henschel mixer” manufactured by Nippon Coke Industries, Ltd.). Mixed. As a result, a capsule toner having an external additive attached to the surface of the toner base particles was produced.

[Example 2]
A capsule toner was prepared in the same manner as in Example 1 except that instead of the coarsely pulverized product 1, the coarsely pulverized product 2 prepared above was used.

Example 3
A capsule toner was prepared in the same manner as in Example 1 except that the coarsely pulverized product 3 prepared above was used instead of the coarsely pulverized product 1.

Example 4
A capsule toner was prepared in the same manner as in Example 1 except that instead of the coarsely pulverized product 1, the coarsely pulverized product 4 prepared above was used.

[Comparative Example 1]
A capsule toner was prepared in the same manner as in Example 1 except that the coarsely pulverized product 5 prepared above was used instead of the coarsely pulverized product 1.

[Comparative Example 2]
Example except that 5.3 g of an anionic resol resin (manufactured by DIC, TD4304) was used instead of 6.6 g of cationic hexamethylolated product (Milben 607, manufactured by Showa Denko KK) as the shelling material In the same manner as in Example 3, a capsule toner was prepared.

[Comparative Example 3]
A three-necked flask with a capacity of 1 liter equipped with a thermometer and a stirring blade was prepared, and the temperature in the flask was maintained at 30 ° C. using a water bath. And 300 ml of ion-exchange water was put in the flask, and 1N hydrochloric acid was further added to adjust the pH of the aqueous medium in the flask to 4. Into the flask, 6.6 g of hexamethylolated material (Milben 607, Showa Denko KK) as a shelling material was added, and the contents of the flask were stirred to dissolve the hexamethylolated product in an aqueous medium. Next, 300 g of the coarsely pulverized product 6 prepared above was added to the flask (an acidic aqueous solution in which the shell material was dissolved), and the mixture was sufficiently stirred. Further, 300 ml of ion-exchanged water was added, the temperature was increased at a rate of 1 ° C./min while stirring, and the temperature was maintained at 70 ° C. for 2 hours, and then the dispersion was cooled to room temperature at a rate of 1 ° C./min. Next, 1N-aqueous sodium hydroxide solution (neutralizing agent) was added to neutralize the dispersion until pH 7 was reached, and the capsule toner was recovered from the dispersion by filtration. Thereafter, in the same manner as in Example 1, after washing and drying, dry silica fine particles were externally added to prepare a capsule toner.

≪Evaluation≫
Using the capsule toners of Examples and Comparative Examples, each characteristic was evaluated according to the following criteria. These results are also shown in Table 1 below.

[Polymerizability of shell layer]
The evaluation of the polymerization of the shell layer was evaluated as x when the toner aggregated and solidified during the reaction, and ○ when the toner did not aggregate.

[Fixability]
(Creation of carrier)
After diluting 30 g of polyamideimide resin with 2 L of water, 120 g of tetrafluoroethylene-6 fluoropropylene copolymer (FEP) was dispersed, and further a coating layer forming liquid in which 3 g of silicon oxide was dispersed was obtained. The coating layer forming solution and 10 kg of non-coated ferrite EF-35B (manufactured by Powdertech Co., Ltd., 35 μm) were charged into a fluidized bed coating apparatus (Freund Sangyo Co., Ltd., flow coater FM-MINI) for coating. Then, it baked at 250 degreeC for 1 hour, and produced the carrier.

(Development of developer)
300 g of the carrier and 30 g of the capsule toner of the example or comparative example are weighed into a 500 ml plastic bottle and mixed with a tumbler mixer (T2F type, manufactured by Shinmaru Enterprises) for 30 minutes to produce a developer. did.

The color fixing machine (Kyocera Document Solutions, TASKalfa 5550ci) modified so that the fixing temperature can be varied as an evaluation machine was used to identify the minimum fixing temperature. The prepared two-component developer was put into a cyan developing device of an evaluation machine, and a sample (toner) was put into a cyan toner container of the evaluation machine. The evaluation conditions were that a nip of 8 mm was formed at a linear speed of 200 mm / sec, the fixing temperature was increased from 100 ° C. to 200 ° C. in increments of 5 ° C., and the minimum fixing temperature was measured. The nip passing time was 40 msec. A solid image was formed on a paper by developing 1.0 mg / cm ² of toner on a 90 g / cm ² paper, and the fixability was evaluated by passing it through a fixing device adjusted in temperature. The fixability was confirmed by a rub test (measurement of fixing peeling width of folds). Specifically, the minimum fixing temperature was determined by the following method.

The paper with the solid image fixed thereon was subjected to a rubbing test. 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 folded portion of the paper (the portion where the solid image was fixed) 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 1 mm or less was defined as the lowest fixing temperature.
(Evaluation)
○: Minimum fixing temperature is 160 ° C. or lower ×: Minimum fixing temperature is 165 ° C. or higher

[Heat resistant storage stability]
3 g of capsule toner was weighed in a 20 g plastic container, and was taken out after heating at 60 ° C. for 3 hours in an oven. The mixture was allowed to stand for 30 minutes in an environment of 25 ° C. × 65%, and then the stored capsule toner was placed on a sieve having an aperture of 105 μm whose mass was known, and its weight was measured. A sieve having a mesh size of 105 μm, a known mass of 63 μm, and a known mass of 45 μm was set on a powder tester (PT-E, manufactured by Hosokawa Micron Corporation), and the stacked sieve was vibrated using a powder tester for 5 memories for 30 seconds. Thereafter, the weight of each sieve was measured to determine the mass of the capsule toner remaining on each sieve. Using the obtained mass of the capsule toner remaining on each sieve, the degree of aggregation of the capsule toner after heat-resistant storage was calculated from the following formula, and the heat-resistant storage stability was evaluated according to the following evaluation criteria.
(Weight on 105 μm sieve) / 3 × 100 (a)
(Weight on 63 μm sieve) / 3 × 100 × 3/5 (b)
(Weight on 45 μm sieve) / 3 × 100 × 1/5 (c)
Aggregation degree (%) = (a) + (b) + (c)
◎: Less than 2% aggregation degree ○: More than 2% aggregation degree and less than 15% ×: More than 15% aggregation degree

  From the results of Table 1 above, Examples 1 to 4 were excellent in fixability and heat-resistant storage stability because the shell layer had good polymerizability and a thin and tough shell layer could be formed. In Examples 1 to 4, since the toner kneaded material is pulverized using glass beads in an aqueous medium, the wettability is improved by instantaneous contact with the aqueous medium while a new interface is generated, and the polymerization reaction It is thought that later heat resistant storage stability is improved.

On the other hand, Comparative Example 1 uses the cationic coarsely pulverized product 5 and toner aggregation occurs and solidifies, so that the fixability and heat resistant storage stability cannot be evaluated.
In Comparative Example 2, an anionic shell monomer was used, and toner aggregation occurred and solidified, so that the fixability and heat resistant storage stability could not be evaluated.
In Comparative Example 3, the core 6 pulverized in advance was used, and the shell layer could not be sufficiently formed.

  INDUSTRIAL APPLICABILITY The present invention can be used as a method for producing a capsule toner for developing an electrostatic image used for developing an electrostatic latent image formed in electrophotography.

Claims (3)

  A core was obtained by finely pulverizing an anionic coarsely pulverized material containing at least a binder resin, a colorant and a release agent in an aqueous medium in which at least one of a cationic monomer and a cationic prepolymer was dispersed. Thereafter, a shell layer is polymerized on the surface of the core, and the shell layer is formed on the surface of the core.   The capsule toner for developing an electrostatic charge image according to claim 1, wherein the coarsely pulverized material is finely pulverized using a pulverizing member in an aqueous medium, the pulverized member is removed from the aqueous medium, and then the shell layer is polymerized. Manufacturing method.   The method for producing a capsule toner for electrostatic image development according to claim 2, wherein the pulverizing member is a bead.