JP6047483B2 - Toner for electrophotography - Google Patents

Description

  The present invention relates to an electrophotographic toner, and more particularly to a capsule toner (core-shell type toner).

  In recent years, image output devices are required to be smaller, more energy efficient, and faster than ever. For the toners used there, various required performances such as charging and fixing characteristics are becoming stricter, and in particular, low temperature fixability tends to be strongly demanded. If the surface temperature of the heating roll is too low, the entire toner particle layer is not sufficiently heated, and only the surface in contact with the heating roll softens and adheres to the heating roll. Since the toner on the transfer paper side is not softened, no adhesive force is generated. Eventually, the toner layer on the transfer paper is not fixed to the transfer paper, and almost transfers to the heating roll side. This phenomenon is called cold offset. On the contrary, when the temperature of the surface of the heating roll is too high, the viscosity of the melted toner is lowered. Along with this, the internal cohesive force of the melted toner layer is also drastically reduced and the adhesion force to the heating roll is lowered. As a result, the melted toner layer breaks and moves to both the transfer paper and the heating roll, which is called hot offset, and causes the contamination of the heating roll. The toner adhering to the heating roll is re-transferred to the transfer paper and stains the non-image area, resulting in a decrease in image quality. As described above, it is necessary to widen the temperature range of the non-offset temperature region where no cold offset or hot offset occurs with respect to the toner and to shift the non-offset temperature region to a lower temperature side.

  For this reason, techniques for improving offset resistance have been proposed, such as adding an anti-offset agent and designing a binder resin with a low molecular weight polymer component and a high molecular weight polymer component. However, the problem remains in achieving both offset resistance and low-temperature fixability, such as an increase in the softening point of the toner.

  Recently, due to the higher degree of freedom in designing the toner, a toner manufacturing method using a chemical method represented by a so-called aggregation association method in which fine particles are aggregated and associated from an aqueous dispersion of the toner composition to form toner particles has been actively used. It has been. Regardless of the pulverization method or chemical method, in order to expand the fixing temperature range and improve the offset resistance, methods for introducing a crosslinking component or a polymer component into the binder resin have been studied (for example, patents). References 1, 2). However, it is difficult to control the crosslink density with the technique of introducing a crosslinking component, and in particular, an emulsification group that produces toner particles by agglomeration and heat fusion by mixing a submicron resin particle dispersion and a colorant dispersion. It was difficult to control the particle shape with the legal method. On the other hand, the method of introducing a high molecular weight component is also inferior in low-temperature fixability because excessive heat energy is required in controlling the particle shape due to an increase in the viscosity of the binder resin, and the melt viscosity during fixing also increases. It was.

  Against this background, in order to achieve both the storage stability and the fixing property of the toner, a technique for improving the toner performance by coating the toner surface with a resin has been proposed (for example, Patent Document 3). However, even if the molecular weight of the film is set to be high, the low temperature component is included due to the molecular weight distribution, so that the heat storage stability during storage and transportation is not sufficient.

  In addition, a toner having a core-shell structure in which a shell is formed by dissolving or dispersing a thermosetting resin monomer or prepolymer in water and reacting on the surface of the core has been proposed (Patent Document 4). However, when shelling in water, it is difficult to selectively perform a thermosetting reaction on the surface of the hydrophobic core, and shelling cannot be performed efficiently, so a large amount of unreacted monomer remains and the toner is stored for a long time. It causes deterioration of stability.

Japanese Patent Laid-Open No. 61-110156 JP-A-9-204071 JP 2006-235027 A JP 2004-294467 A

  The present invention has been made in view of the above-mentioned problems, and can achieve both offset resistance and low-temperature fixability. The toner being stored or the image after fixing is thermally sufficiently stable. An object of the present invention is to provide an electrophotographic toner that has a sufficiently low melt viscosity and can exhibit high fluidity.

That is, the present invention provides an electrophotographic toner containing a capsule toner in which resin particles for a shell layer are attached to the surface of toner core particles containing at least a binder resin, the binder resin having a hydroxyl value and A polyester resin having an acid value of 10 mgKOH / g or more, and the resin fine particles are composed of a finely divided product of a crosslinked product of the following monomer (A1) and monomer (A2), The gist of the monomer (A1) is 30 to 60 parts by mass with respect to 100 parts by mass of the total amount of the monomer (A1) and the monomer (A2).
(A1) A vinyl monomer having an N-methylol group or an N-alkoxymethylol group.
(A2) Alkyl (meth) acrylate monomer.

  As described above, according to the present invention, both offset resistance and low-temperature fixability can be achieved, the toner being stored or the image after fixing is thermally sufficiently stable, and the melt viscosity during heating during fixing is high. Therefore, it is possible to provide an electrophotographic capsule toner that is sufficiently low and can exhibit high fluidity.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The electrophotographic toner according to this embodiment is a capsule toner for developing an electrostatic latent image. The toner of this embodiment is composed of a large number of toner particles.

  The toner particles are composed of a toner core (sometimes simply referred to as “core”), a shell layer formed on the surface of the core, and an external additive.

  The core is composed of a binder resin (binder) and an internal additive (colorant, release agent, magnetic powder, etc.). The core is covered with a shell layer. An external additive is attached to the surface of the shell layer. However, the configuration of the toner particles is not limited to the above. For example, if not necessary, the internal additive or the external additive may be omitted. The toner particles may have a plurality of shell layers on the surface of the core. In the case of having a plurality of shell layers on which toner particles are laminated, the outermost shell layer of the plurality of shell layers is preferably cationic.

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

[Binder resin (core)]
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.

(Binder resin composed of styrene acrylic resin)
The styrene acrylic resin constituting the binder resin is, for example, 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.

  In the present invention, (meth) acrylic acid means acrylic acid or methacrylic acid.

  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 for the measurement of Mn and Mw of the binder 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 changed. 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 binder 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 binder resin in the aqueous medium is improved without using a dispersant, and the binder resin fine particle dispersion is easily and uniformly dispersed in the aqueous medium.

  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 less, it is possible to obtain sufficient fixability even during high-speed fixing. Moreover, Tm of binder resin can be adjusted by combining several binder resin 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 is toned in black using a colorant such as a yellow colorant, a magenta colorant, or a cyan colorant can also be used.

(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.

[Magnetic powder (core)]
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 with respect to 100 parts by weight of the total toner in order to improve magnetism and fixability. 40 parts by mass or more and 60 parts by mass or less 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 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]
The shell layer according to the present embodiment uses a shell agent (resin fine particle dispersion) containing resin fine particles obtained by pulverizing a copolymer of the following monomer (A1) and monomer (A2). It is formed.
(A1) A vinyl monomer having an N-methylol group or an N-alkoxymethylol group.
(A2) Alkyl (meth) acrylate monomer.

<Monomer (A1)>
As the monomer (A1), a vinyl monomer having an N-methylol group or an N-alkoxymethylol group is used, and a vinyl monomer having an N-methylol group is preferred.

  As the vinyl monomer having an N-methylol group, N-methylol (meth) acrylamide and the like are preferable. The vinyl monomer having an N-alkoxymethylol group is preferably N-methoxymethylol (meth) acrylamide, N-butoxymethylol (meth) acrylamide or the like. One or more of these monomers (A1) are selected and used. Among these monomers (A1), N-methylol (meth) acrylamide is particularly preferable from the viewpoint of excellent heat curability at low temperatures.

  In the present invention, (meth) acryl means acryl or methacryl.

  The compounding quantity of the monomer (A1) in this embodiment is 5-60 mass parts with respect to 100 mass parts of total amounts of a monomer (A1) and a monomer (A2), and 15-60 mass parts. It is more preferable that it is, and it is most preferable that it is 30-50 mass parts. If the amount of monomer (A1) is too small, the crosslinking reaction will not proceed sufficiently, the heat-resistant storage stability and stress resistance of the toner particles will be reduced, and if the amount of monomer (A1) is too large. , The crosslink density is increased, and the low-temperature fixability is inhibited.

<Monomer (A2)>
As the monomer (A2), an alkyl (meth) acrylate monomer is used. Examples of the alkyl (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, Examples thereof include iso-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. One or more of these monomers (A2) are selected and used. Among these monomers (A2), methyl (meth) acrylate is particularly preferable from the viewpoint of excellent low-temperature fixability.

  In the present invention, (meth) acrylate means acrylate or methacrylate.

  As the monomer (A2) in the present embodiment, it is preferable to use a styrene monomer together with the alkyl (meth) acrylate monomer from the viewpoint of excellent stress resistance.

  Examples of the styrene monomer include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-ethylstyrene is mentioned. One or more of these are selected and used.

  Here, when using a styrene-type monomer together, the compounding quantity of a styrene-type monomer is 15 mass parts or less with respect to 100 mass parts of total amounts of a monomer (A1) and a monomer (A2). Preferably there is.

  Since the N-methylol group and the N-alkoxymethylol group in the monomer (A1) are crosslinkable functional groups, they are crosslinked by intermolecular cross-linking by dehydration condensation reaction and dealcoholization condensation reaction, and heated to a single amount. A crosslinked structure can be formed in the copolymer formed by the body (A1) and the monomer (A2). The condensation reaction is promoted by an acid catalyst. In the present embodiment, hydrophobic core particles are obtained by using resin fine particles (hydrophobic fine particles) obtained by pulverizing a copolymer of the monomer (A1) and the monomer (A2) as the shell agent. The resin fine particles can be efficiently attached to the surface of the resin. Furthermore, since the monomer (A1) has a crosslinkable functional group such as an N-methylol group, the crosslinkable functional group self-crosslinks on the surface of the core particle, thereby efficiently forming a shell layer that exhibits a sufficient function. Can be produced.

  The thickness (film thickness) of the shell layer is preferably 0.25 μm or less, and more preferably 0.17 μm or less. If the shell layer is too thick, sufficient fixability cannot be obtained.

  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. After dyeing this cured product with osmium tetroxide, it is cut out with a microtome (for example, EM UC6, manufactured by Leica Co., Ltd.) with a diamond knife set to obtain a thin piece sample having a thickness of 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 elements characteristic to the material (nitrogen element) of the shell layer using EELS in the TEM image.

(External additive)
The external additive is used to improve the fluidity and handleability of the toner particles and adheres to the surface of the shell layer. Hereinafter, the particles before being treated with the external additive are referred to as “toner mother particles”. In order to improve fluidity and handleability, 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 part by mass.

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

  In order to improve fluidity and handleability, the particle diameter of the external additive is preferably 0.01 μm or more and 1 μm or less.

  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 in the two-component developer is preferably 3% by mass or more and 20% by mass or less based on the mass of the two-component developer. More preferably, it is 5 mass% or more and 15 mass% or less.

[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. Magnetic particles may be dispersed in a resin layer covering the carrier core material.

  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 toner manufacturing method according to this embodiment will be described.

[Formation of core]
The core is formed by, for example, a pulverization classification method (melt kneading method) or an aggregation method. According to these methods, 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 and classified to obtain a core having a desired particle size. According to the pulverization classification method, the core can be formed more easily than the aggregation method.

(Core formation by agglomeration method)
Fine particles containing the core component are aggregated in an aqueous medium. Specifically, the aqueous dispersion (binder resin fine particle dispersion) containing the binder resin fine particles is obtained by making the binder resin material into a desired size in an aqueous medium. Subsequently, the binder resin fine particles are aggregated in the binder resin fine particle dispersion. Thereby, aggregated particles are formed (aggregation step).

[Formation of shell layer]
(Preparation of resin fine particle dispersion for shell agent)
For example, in a reaction vessel equipped with a stirrer, a nitrogen introducing tube and a cooling tube, as a polymerization solvent (n-propanol and the like), N-methylolacrylamide as the monomer (A1), and the monomer (A2) Of methyl methacrylate and the like, and heated to a predetermined temperature (preferably 65 ° C.) while blowing nitrogen gas. A solution obtained by dissolving a radical polymerization initiator (diluted hydrocarbon of t-hexyl peroxypivalate, etc.) in an organic solvent such as normal propyl alcohol (NPA) is dropped over a predetermined time (preferably 3 hours). . Further, after performing polymerization for a predetermined time (preferably 5 hours), the temperature is raised to a predetermined temperature (preferably 80 ° C.), and polymerization is performed at that temperature for a predetermined time (preferably 1 hour). This is dried under heating under a predetermined condition (preferably 140 ° C., 10 kPa) to remove the solvent, and crushed to obtain a coarsely pulverized product.

  Next, a pulverized product obtained by pulverizing the coarsely pulverized product to a predetermined size (preferably 10 μm or less), a cationic surfactant and an aqueous sodium hydroxide solution are mixed, and ion-exchanged water is further added to prepare a slurry. . Subsequently, the slurry is put into a pressure-resistant round bottom stainless steel container or the like, and the slurry in the container is heated and pressurized to a predetermined condition (preferably 140 ° C., 0.5 MPa) using a high-speed shearing emulsifying device CLEARMIX etc. The rotor is subjected to shear dispersion at a rotor rotational speed (preferably 20000 rpm) for a predetermined time (preferably 30 minutes). Thereafter, while stirring at a rotational speed (preferably 1500 rpm) until a predetermined temperature (preferably 50 ° C.) is reached, cooling is performed at a predetermined cooling rate (preferably 5 ° C./min) to prepare a resin fine particle dispersion.

  The volume average particle diameter (D50) of the resin fine particles is preferably 0.3 μm or less and more preferably 0.2 μm or less in order to form a thin shell layer (shell film). The volume average particle diameter (D50) of the resin fine particles can be measured using, for example, a laser diffraction particle size distribution measuring apparatus (for example, SALD-2200 manufactured by Shimadzu Corporation).

(Encapsulation: Shell layer formation process)
For example, a 1 L three-necked flask equipped with a thermometer and a stirring blade is prepared, and after the toner core particles, the anionic surfactant and ion-exchanged water prepared above are added, The temperature is maintained at a predetermined temperature (preferably 30 ° C.). A hydrochloric acid aqueous solution or the like is added thereto to adjust the pH to 4. Next, the resin fine particle dispersion prepared above is added, stirred for a predetermined time (preferably 15 minutes), and then heated to a predetermined temperature (preferably 55 ° C.) at a predetermined temperature increase rate (preferably 1 ° C./5 minutes). Raise the temperature. The mixture is stirred under predetermined conditions (preferably at 60 ° C. for 120 minutes) to advance the adhesion and film formation of resin fine particles. Next, the heating is stopped, and it is preferably rapidly cooled at 10 ° C./min and cooled to a predetermined temperature (preferably 25 ° C.). Thereafter, a neutralizing agent such as an aqueous sodium hydroxide solution is added to neutralize the solution to pH 7, filtered, washed and dried. An external additive (silica or the like) is added to the toner to produce a capsule toner in which the resin fine particles for the shell layer adhere to the surface of the toner core particles.

  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.

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

[Example 1]
(Production of low melting toner core)
A polyester resin was prepared by reacting paraphthalic acid with an alcohol (bisphenol A ethylene oxide adduct) obtained by adding ethylene oxide with bisphenol A as a skeleton. 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. 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 6 microns with a mechanical pulverizer (Turbo Kogyo, turbo mill). Thereafter, the toner was classified with a classifier (manufactured by Nippon Steel Mining Co., Ltd., Elbow Jet) to obtain a 6 micron toner core. The toner core had a shape index of 0.93, Tg of 49 ° C., and Tm of 90 ° C. When the triboelectric charge amount (anionic property) of this toner core was measured using a standard carrier N-01, it was −20 μC / g. Furthermore, the measured value of the zeta potential at pH 4 was −15 mV, which showed a clear anionic property. Each measurement of the toner core was performed as follows.

〔Particle size〕
The volume average particle size (D50) was measured using a Coulter Counter Multisizer 3 manufactured by Beckman Coulter.

[Tg of toner core]
By measuring the endothermic curve using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., DSC-6200), it was determined from the change point of the specific heat in the endothermic curve.

[Tm of toner core]
A sample is set in a Koka type flow tester (CFT-500D, manufactured by Shimadzu Corporation), and a 1 cm ³ sample is melted at a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² , and a heating rate of 6 ° C./min. The S-curve was obtained by allowing it to flow out, and the Tm of the toner core was read from the obtained S-curve.

[Triboelectric charge (anionic)]
Using a turbula mixer, standard carrier N-01 (standard carrier for negatively charged polarity toner provided by the Imaging Society of Japan) and a toner core of 7% by mass with respect to this standard carrier were mixed for 30 minutes. Then, the triboelectric charge amount of the toner core 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).

[Zeta potential of toner core]
0.2 g of toner core, 80 g of ion exchange water, and 20 g of 1% nonionic surfactant (polyvinylpyrrolidone, “K-85” manufactured by Nippon Shokubai Co., Ltd.) are mixed with a magnetic stirrer, and the toner core is uniformly dispersed. A liquid was obtained. Dilute hydrochloric acid was added to this dispersion to adjust the pH of the dispersion to 4. Then, using this dispersion as a measurement sample, the zeta potential of the toner core in the dispersion adjusted to pH 4 was measured with a zeta potential / particle size distribution measuring apparatus (Delsa Nano HC, manufactured by Beckman Coulter, Inc.).

(Preparation of resin fine particle dispersion for shell layer)
In a reaction vessel equipped with a stirrer, a nitrogen introducing tube and a cooling tube, 240 g of n-propanol (hereinafter abbreviated as NPA) as a polymerization solvent and N-methylolacrylamide (hereinafter referred to as N) as a monomer (A1). -4.5 g (5% by mass) abbreviated as MAA, and 85.5 g (95% by mass) methyl methacrylate (hereinafter abbreviated as MMA) as the monomer (A2), while blowing nitrogen gas Heated to 65 ° C. Thereto, 3 g of a hydrocarbon diluted product of t-hexyl peroxypivalate (manufactured by NOF Corporation, perhexyl PV) dissolved in 40 g of NPA as a radical polymerization initiator was dropped over 3 hours. After further polymerization for 5 hours, the temperature was raised to 80 ° C., and polymerization was performed at that temperature for 1 hour. This was heated and dried under reduced pressure at 140 ° C. and 10 kPa to remove the solvent, and crushed to obtain a coarsely pulverized product. 100 g of the coarsely pulverized product was pulverized to 10 μm or less, 1 g of a cationic surfactant (manufactured by Kao Corporation, Coatamine 24P) and 25 g of a 0.1N sodium hydroxide aqueous solution were mixed, and ion-exchanged water was further added. A total amount of 400 g of slurry was prepared. Subsequently, the slurry was put into a pressure-resistant round bottom stainless steel container, and the slurry in the container was heated to 140 ° C. and 0.5 MPa using a high-speed shearing emulsifying device CLEARMIX (M Technique Co., Ltd., CLM-2.2S). While being pressed, the mixture was sheared and dispersed for 30 minutes at a Claremix rotor speed of 20000 rpm. Thereafter, the mixture was cooled at a cooling rate of 5 ° C./min while stirring at 15000 rpm until reaching 50 ° C. to prepare a resin fine particle dispersion (particle size: 0.13 μm). The particle size (D50) of the resin fine particles was measured using a laser diffraction particle size distribution measuring apparatus (SALD-2200, manufactured by Shimadzu Corporation).

(Encapsulation: Shell layer formation process)
First, a 1 L three-necked flask equipped with a thermometer and a stirring blade was prepared, 300 g of the toner core particles prepared above, 1.5 g of an anionic surfactant (Eomar 0, manufactured by Kao Corporation), and 300 mL of ion-exchanged water. Then, the temperature in the flask was kept at 30 ° C. using a water bath. 2g hydrochloric acid aqueous solution 2g was added here and pH was adjusted to 4. Next, 160 g of the resin fine particle dispersion was added and stirred for 15 minutes (stirring speed: 150 rpm), and then heated to 55 ° C. at a heating rate of 1 ° C./5 minutes (stirring speed: 150 rpm). Stirring was performed at 60 ° C. for 120 minutes (stirring speed: 150 rpm), and adhesion of resin fine particles and film formation were advanced. Next, the heating was stopped, the solution was rapidly cooled at 10 ° C./min, and cooled to 25 ° C. Thereafter, an aqueous sodium hydroxide solution (neutralizing agent) was added to neutralize to pH 7, filtered, washed and dried to obtain toner mother particles. As a result of measuring the electrical conductivity of the filtrate using Horiba COND METER ES-51 manufactured by HORIBA, Ltd., it was 4 μS / cm. To this toner, 0.5 parts by mass of silica (REA90, manufactured by Nippon Aerosil Co., Ltd.) is added with respect to the mass of the toner base particles, and a capsule toner in which the resin particles for the shell layer are adhered to the surface of the toner core particles. Produced.

[Example 2]
Except for changing the blending amount of N-MAA, which is a raw material of the resin fine particle dispersion, to 13.5 g (15% by mass) and the blending amount of MMA to 76.5 g (85% by mass), the same as in Example 1. A resin fine particle dispersion (particle size: 0.13 μm) was prepared. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 3
Resin fine particle dispersion was carried out in the same manner as in Example 1 except that the amount of N-MAA as the raw material for the resin fine particle dispersion was changed to 27 g (30% by mass) and the amount of MMA was changed to 63 g (70% by mass). A liquid (particle size 0.17 μm) was prepared. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 4
Resin fine particle dispersion was carried out in the same manner as in Example 1, except that the amount of N-MAA as the raw material for the resin fine particle dispersion was changed to 54 g (60% by mass) and the amount of MMA was changed to 36 g (40% by mass). A liquid (particle size 0.14 μm) was prepared. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 5
The blending amount of N-MAA, which is a raw material of the resin fine particle dispersion, is changed to 13.5 g (15% by mass), the blending amount of MMA is changed to 63 g (70% by mass), and further styrene as the monomer (A2). A resin fine particle dispersion (particle size: 0.17 μm) was prepared in the same manner as in Example 1 except that 13.5 g (15% by mass) of (St) was blended. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 6
The blending amount of N-MAA, which is a raw material of the resin fine particle dispersion, is changed to 13.5 g (15% by mass), and 76.5 g of n-butyl methacrylate (hereinafter abbreviated as “BMA”) is used instead of MMA. A resin fine particle dispersion (particle size: 0.14 μm) was prepared in the same manner as in Example 1 except that 85% by mass) was added. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 7
In the production process of the resin fine particle dispersion, except for changing the rotor speed of the CLEARMIX, that is, after changing the rotor speed of the CLEARMIX to 10,000 rpm and shearing and dispersing for 30 minutes, stirring at 5000 rpm until 50 ° C., A resin fine particle dispersion (particle size: 0.22 μm) was prepared in the same manner as in Example 2 except that cooling was performed at a cooling rate of 5 ° C./min. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

Example 8
Except for using 13.5 g (15% by mass) of N-methoxymethylol methacrylamide (hereinafter abbreviated as “MMA”) instead of 13.5 g (15% by mass) of N-MAA which is a raw material for the resin fine particle dispersion. In the same manner as in Example 2, a resin fine particle dispersion (particle size: 0.13 μm) was prepared. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

[Comparative Example 1]
N-MAA, which is a raw material for the resin fine particle dispersion, is not blended, except that the amount of MMA is changed to 76.5 g (75% by mass) and the amount of styrene (St) is changed to 76.5 g (25% by mass). Produced a resin fine particle dispersion (particle size: 0.15 μm) in the same manner as in Example 1. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

[Comparative Example 2]
The same procedure as in Example 1 was conducted except that the amount of N-MAA as the raw material for the resin fine particle dispersion was changed to 58.5 g (65% by mass) and the amount of MMA was changed to 31.5 g (35% by mass). A resin fine particle dispersion (particle size: 0.13 μm) was prepared. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

[Comparative Example 3]
The amount of N-MAA, which is a raw material of the resin fine particle dispersion, is changed to 2.7 g (3 mass%), the amount of MMA is changed to 73.8 g (82 mass%), and further, 13.5 g of styrene (St) ( A resin fine particle dispersion (particle size: 0.14 μm) was prepared in the same manner as in Example 1 except that 15% by mass) was added. Then, using this resin fine particle dispersion, a capsule toner was produced in the same manner as in Example 1.

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

[Thickness of shell layer]
The thickness of the shell layer was measured according to the method described above. That is, the toner particles were 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. The cured product was dyed with osmium tetroxide, and then cut out with a microtome (EM UC6, manufactured by Leica Co., Ltd.) on which a diamond knife was set to obtain a thin piece sample having a thickness of 200 nm. And the cross section of this sample was image | photographed with the transmission electron microscope (TEM) (The JEOL Co., Ltd. make, JSM-6700F). Furthermore, the thickness of the shell layer was measured by analyzing the TEM image with image analysis software (Mitani Corporation, WinROOF). Specifically, two straight lines perpendicular to each other at the approximate center of the cross section of the toner particles were drawn, and the lengths of four locations on the two straight lines intersecting the shell layer were measured. Then, the average value of the four measured lengths was taken as the thickness of the shell layer of one toner particle to be measured. The thickness of the shell layer was measured for 10 or more toner particles contained in the toner, and the average value of the 10 or more obtained measurements was used as the evaluation value.

(Low temperature fixability)
(Development of developer)
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 109 kg of non-coated ferrite EF-35B (35 μm, manufactured by Powdertech Co., Ltd.) were charged into a fluidized bed coating apparatus for coating. Then, it baked at 250 degreeC for 1 hour, and obtained the carrier.

  300 g of the carrier and 30 g of the capsule toner of Examples and Comparative Examples are weighed into a 500 ml plastic bottle and mixed with a tumbler shaker mixer (T2F type, manufactured by Shinmaru Enterprises) for 30 minutes to obtain a developer. Produced.

Fixability evaluation was performed using the developer prepared as described above and a color printer FS-C5400DN (manufactured by Kyocera Document Solutions) as an evaluation machine. The fixing temperature was changed in the range of 80 to 180 ° C., and a 0.4 mg / cm ² toner unfixed image (patch) 2 cm × 2 cm was passed at a linear speed of 200 mm / s to confirm the presence or absence of offset. In the evaluation, the lowest fixing temperature (minimum fixing temperature) at which no offset occurred in any toner image was obtained, and evaluated according to the following criteria.
○: Minimum fixing temperature is less than 160 ° C ×: Minimum fixing temperature is 160 ° C or more

[Stress resistance]
Developers having a toner concentration of 10% by weight were prepared using the capsule toners of Examples and Comparative Examples, and stress resistance was evaluated using a color printer FS-C5400DN (manufactured by Kyocera Document Solutions) as an evaluation machine. The evaluation is performed by using the above-mentioned evaluation machine under an arbitrary environmental condition (HH (temperature 32.5 ° C., humidity 80%) / NN (temperature 23 ° C., humidity 50%) / LL (temperature 10 ° C., humidity 20%)). After the endurance test of 2000 sheets, the evaluation toner was taken out and observed five times with a magnification of 1000 times using an optical microscope, and the average number (3 counts) of crushed toner in 500 toners. went. The evaluation criteria are shown below.
A: There is no crushing toner and there is no practical problem. ○: There are 1 to 2 crushing toners, but there are no practical problems. Δ: 3 to 9 crushing toners exist, but there are no practical problems. : There are 10 or more crushed toners, and there are practical problems

[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. After standing for 30 minutes in an environment at 25 ° C. and 65%, the capsule toner after storage was placed by overlapping sieves with openings of 105 μm, 63 μm, and 45 μm, and placed on a powder tester (manufactured by Hosokawa Micron Corporation, PT-E). The agglomeration degree after heat-resistant storage was calculated from the following formula by oscillating 5 memories for 30 seconds, and the heat-resistant storage stability was evaluated. The evaluation criteria are shown below.
(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)
○: Aggregation degree of less than 15% ×: Aggregation degree of 15% or more

  From the result of the said Table 1, Examples 1-8 were all good in low temperature fixability, stress resistance, and heat-resistant storage stability.

On the other hand, since N-MAA which is a crosslinking component is not contained in the shell layer in Comparative Example 1, a low molecular weight component remains in the shell layer, and the stress resistance and heat resistant storage stability were inferior.
In Comparative Example 2, since the N-MAA content was high, the crosslinking density was high and the low-temperature fixability was inferior.
In Comparative Example 3, since the N-MAA content was low, the crosslinking reaction did not proceed sufficiently, and the stress resistance and heat resistant storage stability were inferior.

  The capsule toner according to the present invention is useful in an image forming apparatus to which electrophotography is applied.

Claims (3)

An electrophotographic toner containing a capsule toner in which resin particles for a shell layer are attached to the surface of toner core particles containing at least a binder resin, wherein the binder resin has a hydroxyl value and an acid value of 10 mgKOH, respectively. The resin fine particle is a finely divided product of a crosslinked product of the following monomer (A1) and monomer (A2): The blended amount of is 30 to 60 parts by mass with respect to 100 parts by mass of the total amount of the monomer (A1) and the monomer (A2).
(A1) A vinyl monomer having an N-methylol group or an N-alkoxymethylol group.
(A2) Alkyl (meth) acrylate monomer. The electrophotographic toner according to claim 1, wherein the polyester resin is synthesized from a bisphenol A ethylene oxide adduct and paraphthalic acid . The electrophotographic toner according to claim 1 , wherein the polyester resin has a hydroxyl value of 20 mg KOH / g and an acid value of 40 mg KOH / g .