JP6059084B2 - Method for producing toner for developing electrostatic latent image - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner.

  In general, in electrophotography, the surface of an electrostatic latent image carrier is charged using corona discharge, and then exposed using a laser to form an electrostatic latent image. The formed electrostatic latent image is developed with toner to form a toner image. Further, the formed toner image is transferred to a recording medium to obtain a high quality image. Usually, toners applied to such electrophotography are mixed with a binder resin such as a thermoplastic resin, components such as a colorant, a charge control agent, a release agent, and a magnetic material, and then kneaded, pulverized, A toner particle (toner mother particle) having an average particle size of 5 μm or more and 10 μm or less is used after classification. For the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, and improving the cleaning property of the toner from the photosensitive drum, an inorganic fine powder such as silica or titanium oxide is used. Externally added to the base particles.

  For such toner, a low-melting-point binder resin was used for the purpose of obtaining good fixability in a lower temperature range, the purpose of improving storage stability at high temperatures, and the purpose of improving blocking resistance. A toner having a core-shell structure in which toner core particles are coated with a shell material made of a resin having a Tg higher than the glass transition point (Tg) of the binder resin of the toner core particles is used.

  As such a toner, a toner core particle containing a polyester resin or a resin in which a polyester resin and a vinyl resin are combined, styrene, and a co-polymerization of a (meth) acrylate monomer containing a polyalkylene oxide unit. A toner having a core-shell structure made of a shell layer made of a shell material containing coalescence has been proposed (Patent Document 1). In Patent Document 1, a toner having a core-shell structure is formed by covering the surface of toner core particles with resin particles dispersed in an aqueous medium in the presence of an organic solvent such as ethyl acetate.

JP 2011-70179 A

  However, since the toner shell layer described in Patent Document 1 is formed while the contact portion between the resin fine particles is dissolved in the organic solvent, there is almost no void between the resin particles, and the shape of the resin particles is It is a homogeneous film that remains. For this reason, when the toner described in Patent Document 1 is used to fix the toner on the recording medium, the shell layer may not be easily broken by the pressure applied to the toner. When the shell layer is not easily broken, it is difficult to satisfactorily fix the toner on the recording medium.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a toner for developing an electrostatic latent image, which is excellent in fixability and heat-resistant storage stability.

The present invention provides toner core particles containing at least a binder resin;
A toner for developing an electrostatic latent image comprising a shell layer covering the toner core particles,
The initial shell layer is formed using spherical resin fine particles,
When the surface of the toner for developing an electrostatic latent image is observed using a scanning electron microscope, a structure derived from the spherical resin fine particles in the shell layer is observed for toner particles having a particle diameter of 6 μm or more and 8 μm or less. not,
When observing a cross section of the electrostatic latent image developing toner using a transmission electron microscope, the inside of the shell layer is an interface between the resin fine particles in a direction substantially perpendicular to the surface of the toner core particles. The present invention relates to a toner for developing an electrostatic latent image in which cracks originating from the above are observed.

  According to the present invention, it is possible to provide a toner for developing an electrostatic latent image that is excellent in fixability and heat-resistant storage stability.

FIG. 3 is a schematic diagram illustrating a part of a cross section of the toner of the present invention. It is a figure explaining the measuring method of melting | fusing point using an elevated flow tester. 4 is a transmission electron micrograph of a cross section of the toner of Example 1. FIG. 6 is a transmission electron micrograph of a cross section of the toner of Comparative Example 1. FIG. 6 is a transmission electron micrograph of a cross section of the toner of Comparative Example 3. FIG.

  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 addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

The electrostatic latent image developing toner of the present invention (hereinafter also simply referred to as toner) comprises toner core particles containing at least a binder resin, and a shell layer covering the toner core particles. The shell layer covering the toner core particles is formed using spherical resin fine particles.
Further, when the surface of the toner of the present invention is observed with a scanning electron microscope, toner particles having a particle diameter of 6 μm or more and 8 μm or less have a structure derived from spherical resin fine particles on the surface of the shell layer. Not observed. The toner of the present invention is derived from the interface between the resin fine particles in a direction substantially perpendicular to the surface of the toner core particles inside the shell layer when the cross section of the toner is observed using a transmission electron microscope. Cracks are observed. Hereinafter, the toner structure and the toner material will be described.

[Toner structure]
In the toner of the present invention, the toner core particles are entirely covered with a shell layer. The covering state of the shell layer on the surface of the electrostatic latent image developing toner can be confirmed using a scanning electron microscope (SEM. Also, the degree of smoothing of the shell layer and the shell layer of the electrostatic latent image developing toner. The inside of the toner can be confirmed by observing the cross section of the toner using a transmission electron microscope (TEM), and a preferred embodiment of the toner of the present invention is a schematic diagram of the cross section of the toner observed using the TEM. The figure is shown in FIG.

  As shown in FIG. 1, in the electrostatic latent image developing toner 101, the shell layer 103 covers the entire surface of the toner core particles 102. The shell layer is formed by smoothing the outer surface of the resin fine particle layer formed by attaching the resin fine particle layer to the toner core particles with an external force.

  The thickness of the shell layer 103 is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.045 μm to 0.5 μm, and 0.045 μm to 0.3 μm. Most preferred. As will be described later, when the shell layer has a convex portion, the thickness of the shell layer may be uneven. In such a case where the thickness of the shell layer is not uniform, in the claims and the specification of the present application, the thickness of the thickest portion of the shell layer is defined as “the thickness of the shell layer”. .

  When the thickness of the shell layer is too thick, the shell layer is not easily broken by the pressure applied to the toner when the toner is fixed to the recording medium. In this case, the softening or melting of the binder resin or the release agent contained in the toner core particles does not proceed quickly, and the toner may not be fixed on the recording medium at a lower temperature than before. On the other hand, when the thickness of the shell layer is too thin, the strength of the shell layer is lowered. If the strength of the shell layer is low, the shell layer may be destroyed by an impact applied during transportation. When storing the toner at a high temperature, the release agent is applied to the toner surface from the location where the shell layer was destroyed. By oozing out, the toner may be aggregated.

  The thickness of the shell layer 103 can be measured by analyzing a TEM image of a cross section of the toner 101 using commercially available image analysis software. As commercially available image analysis software, software such as WinROOF (manufactured by Mitani Corporation) can be used.

  In the toner of the present invention, as shown in FIG. 1, the shell layer 103 preferably has a convex portion 105 on the interface between the toner core particle 102 and the shell layer 103 and between the two cracks 104. When the shell layer 103 has such a convex portion 105, the contact area between the toner core particle 102 and the shell layer 103 can be increased as compared with the case where the shell layer does not have the convex portion 105. By providing the convex portion 105 on the shell layer, the adhesion between the toner core particle 102 and the shell layer 103 is improved, and the shell layer 103 is difficult to peel from the toner core particle 102. For this reason, when the shell layer includes the convex portion 105, a toner having good heat-resistant storage stability can be obtained.

More specifically, the shell layer formed using resin fine particles of the toner for developing an electrostatic latent image of the present invention,
I) A step of attaching spherical resin fine particles to the surface of the toner core particles so as not to overlap the surface of the toner core particles in the vertical direction to form a resin fine particle layer covering the entire surface of the toner core particles; and II ) Forming a shell layer by smoothing the outer surface of the resin fine particle layer by deforming the resin fine particles in the resin fine particle layer by applying an external force to the outer surface of the resin fine particle layer;
Formed using a method including:

  When the surface of the toner of the present invention is observed using a scanning electron microscope, the shell layer is formed on the outer surface of the shell layer of toner particles having a particle diameter of 6 μm to 8 μm. As long as the structure derived from the spherical resin fine particles used in the above is not observed. If the state of the shell layer of the toner having a particle diameter of 6 μm or more and 8 μm or less is such a state, the shell layer is formed so that the surface of the core particle is not exposed in most of the toner particles contained in the toner. When the state of the outer surface of the shell layer is confirmed using observation with a scanning electron microscope, the particle diameter of the toner particles is an equivalent circle diameter calculated from the projected area of the toner on the electron microscope image.

  In the preferred embodiment of the shell layer shown in FIG. 1, the toner 101 has the entire surface of the toner core particles 102 covered with the shell layer 103. Further, since the shell layer 103 covers the entire surface of the toner core particles 102 so that the outer surface thereof is smooth, when the toner 101 is stored at a high temperature, the surface of the toner 101 having a component such as a release agent. It is difficult for ooze to occur.

  Further, since the toner 101 has voids (cracks) 105 inside the shell layer 103, when the toner is fixed on the recording medium, the shell layer based on the cracks is destroyed by the pressure applied to the toner. It is easy to happen. As a result, the toner 101 quickly fixes or melts components such as the binder resin and the release agent contained in the toner core particles 102, so that the toner is fixed on the recording medium at a lower temperature than before. can do.

[Toner material]
The toner of the present invention comprises toner core particles containing at least a binder resin and a shell layer covering the entire surface of the toner core particles. The toner core particles may contain components such as a release agent, a charge control agent, a colorant, and magnetic powder in the binder resin as necessary. The toner of the present invention may have a surface treated with an external additive as desired. Furthermore, the toner of the present invention can be mixed with a desired carrier and used as a two-component developer.

  Hereinafter, essential or optional components constituting the electrostatic latent image developing toner of the present invention, binder resin, release agent, charge control agent, colorant, magnetic powder, resin fine particles forming a shell layer, The external additive, the carrier used when the toner of the present invention is used as a two-component developer, and the method for producing the electrostatic latent image developing toner of the present invention will be described in order.

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

  The polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. Specific examples of other copolymerizable monomers copolymerizable with styrene include p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl chloride, vinyl bromide, And vinyl halides such as vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, (Meth) acrylic acid such as dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate Esters; acrylonitrile, metha Other acrylic acid derivatives such as rilonitrile and acrylamide; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrole , N-vinylcarbazole, N-vinylindole, and N-vinyl compounds such as N-vinylpyrrolidene. These copolymerizable monomers can be copolymerized with a styrene monomer in combination of two or more.

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

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

  Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid Divalent carboxylic acids such as acids, isododecyl succinic acid, and alkyl or alkenyl succinic acids such as isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5 -Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2, -Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Examples thereof include trivalent or higher carboxylic acids such as acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  When the binder resin is a polyester resin, the softening point of the polyester resin is preferably 70 ° C. or higher and 130 ° C. or lower, and more preferably 80 ° C. or higher and 120 ° C. or lower.

  When the toner of the present invention is used as a magnetic one-component toner, the binder resin has one or more functional groups selected from the group consisting of hydroxy groups, carboxyl groups, amino groups, and epoxy groups (glycidyl groups) as molecules. It is preferable to use the resin contained therein. By using a binder resin having these functional groups in the molecule, the dispersibility of components such as magnetic powder and charge control agent in the binder resin can be improved. The presence or absence of these functional groups can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR). The amount of these functional groups in the resin can be measured using a known method such as titration.

  As the binder resin, it is preferable to use a thermoplastic resin because it has good fixability to paper. However, not only the thermoplastic resin alone but also a crosslinking agent or a thermosetting resin is added to the thermoplastic resin. can do. By adding a cross-linking agent or thermosetting resin and introducing a partially cross-linked structure into the binder resin, the heat-resistant storage stability and durability of the toner can be improved without deteriorating the toner fixability. Can do. In addition, when using a thermosetting resin, 10 mass% or less is preferable with respect to the mass of binder resin, and the bridge | crosslinking part amount (gel amount) of binder resin extracted using a Soxhlet extractor is 0. It is more preferably 1% by mass or more and 10% by mass or less.

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

  The glass transition point (Tg) of the binder resin is preferably 40 ° C. or higher and 70 ° C. or lower. When the glass transition point is too high, the low-temperature fixability of the toner tends to decrease. When the glass transition point is too low, the heat resistant storage stability of the toner tends to be lowered.

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

  The weight average molecular weight (Mw) of the binder resin is preferably 20,000 or more and 300,000 or less, and more preferably 30,000 or more and 2,000,000 or less. The mass average molecular weight of the binder resin can be determined using a calibration curve prepared in advance using standard polystyrene resin using gel permeation chromatography (GPC).

  Further, when the binder resin is a polystyrene resin, the binder resin has peaks in the low molecular weight region and the high molecular weight region on the molecular weight distribution measured by means such as gel permeation chromatography. Is preferred. Specifically, it is preferable to have a low molecular weight region peak in the molecular weight range of 3,000 to 20,000, and a high molecular weight region peak in the molecular weight range of 300,000 to 1,500,000. Is preferred. Moreover, about polystyrene resin of such molecular weight distribution, the ratio (Mw / Mn) of the number average molecular weight (Mn) and the mass average molecular weight (Mw) is preferably 10 or more. When the binder resin has a low molecular weight region peak and a high molecular weight region peak in such a range in the molecular weight distribution, a toner that has excellent low-temperature fixability and can suppress high-temperature offset can be obtained.

〔Release agent〕
The toner core particles preferably contain a release agent for the purpose of improving fixability and offset resistance. As the release agent that can be contained in the toner core particles, a wax is preferable. Examples of the wax include carnauba wax, synthetic ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, montan wax, and rice wax. These release agents can be used in combination of two or more. By adding such a release agent to the toner, it is possible to more efficiently suppress the occurrence of offset and image smearing (dirt around the image when the image is rubbed).

  When a polyester resin is used as the binder resin, it is preferable to use one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax as a release agent from the viewpoint of compatibility. preferable. When a polystyrene resin is used as the binder resin, it is preferable to use Fischer-Tropsch wax and / or paraffin wax as the mold release agent from the viewpoint of compatibility.

  Fischer-Tropsch wax is a straight-chain hydrocarbon compound that is produced using the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide, and has few iso (iso) structure molecules and side chains.

  Among Fischer-Tropsch waxes, those having a mass average molecular weight of 1,000 or more and an endothermic peak bottom temperature observed using DSC measurement in the range of 100 ° C. or more and 120 ° C. or less are more preferable. Such Fischer-Tropsch waxes include Sazol wax C1 (endothermic peak bottom temperature: 106.5 ° C.), Sazol wax C105 (endothermic peak bottom temperature: 102.1 ° C.), available from Sazol, Zole wax SPRAY (endothermic peak bottom temperature: 102.1 ° C.).

  The amount of the release agent used is preferably 1% by mass or more and 10% by mass or less with respect to the total mass of the toner core particles. If the amount of the release agent used is too small, the desired effect may not be obtained for suppressing the occurrence of offset and image smearing in the formed image. If the amount of release agent used is excessive, the toner particles They are likely to be fused together, and the heat-resistant storage stability of the toner may be impaired.

(Charge control agent)
The toner core particles are used for the purpose of obtaining a toner having excellent durability and stability by improving the charge level of the toner and the charge rising property that is an indicator of whether or not the toner can be charged to a predetermined charge level in a short time. A control agent is preferably included. When developing with positively charged toner, a positively chargeable charge control agent is used. When developing with negatively charged toner, a negatively chargeable charge control agent is used.

  The charge control agent that can be contained in the toner core particles can be appropriately selected from charge control agents conventionally used in toners. Specific examples of the positively chargeable charge control agent include pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1, 2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, Azine compounds such as phthalazine, quinazoline, and quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azine Violet BO Direct dyes consisting of azine compounds such as azine brown 3G, azine light brown GR, azine dark green BH / C, azine deep black EW, and azine deep black 3RL; such as nigrosine, nigrosine salts, and nigrosine derivatives Nigrosine compounds; acid dyes composed of nigrosine compounds such as nigrosine BK, nigrosine NB, and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; benzylmethylhexyldecylammonium, decyltrimethylammonium chloride Quaternary ammonium salts. Among these positively chargeable charge control agents, a nigrosine compound is particularly preferable in that a more rapid charge rising property can be obtained. These positively chargeable charge control agents can be used in combination of two or more.

  A resin having a quaternary ammonium salt, carboxylate, or carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, and a carboxylate A styrene resin having a carboxylate, an acrylic resin having a carboxylate, a styrene-acrylic resin having a carboxylate, a polyester resin having a carboxylate, a styrene resin having a carboxyl group, an acrylic resin having a carboxyl group, Examples thereof include styrene-acrylic resins having a carboxyl group and polyester resins having a carboxyl group. The molecular weight of these resins may be an oligomer or a polymer.

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

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

  Specific examples of negatively chargeable charge control agents include organometallic complexes, chelate compounds, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid metal complexes, aromatic monocarboxylic acids, and Aromatic polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenols. Of these, organometallic complexes and chelate compounds are preferred. Examples of organometallic complexes and chelate compounds include acetylacetone metal complexes such as aluminum acetylacetonate and iron (II) acetylacetonate, and salicylic acid metal complexes such as chromium 3,5-di-tert-butylsalicylate. Salicylic acid metal salts are more preferred, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferred. These negatively chargeable charge control agents can be used in combination of two or more.

  The amount of the positively or negatively chargeable charge control agent used is preferably 0.1% by mass or more and 10% by mass or less based on the total mass of the toner core particles. If the amount of charge control agent used is too small, it will be difficult to stably charge the toner to a predetermined polarity, making it difficult to maintain the image density over a long period of time because the image density of the formed image will fall below the desired value. Sometimes it becomes. Further, since it is difficult to uniformly disperse the charge control agent in the toner core, the formed image is likely to be fogged or the latent image carrier is easily contaminated by the toner component. If the amount of charge control agent used is excessive, image defects in the formed image due to poor charging at high temperature and high humidity due to deterioration in environmental resistance, and contamination of the latent image carrier due to toner components may occur. It becomes easy.

[Colorant]
The toner core particles may contain a colorant as necessary. As the colorant that can be contained in the toner core particles, a known pigment or dye can be used in accordance with the color of the toner. Specific examples of suitable colorants that can be added to the toner include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, Yellows like Nickel Titanium Yellow, Naples Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, Monoazo Yellow, and Diazo Yellow Pigments; orange pigments such as red mouth yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, and indanthrene brilliant orange GK; Bengala, cadmium red , Red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B, and monoazo red Red pigments such as manganese purple, fast violet B, and purple pigments such as methyl violet lake; bitumen, cobalt blue, alkali blue lake, Victoria blue partially chlorinated, fast sky blue, indanthrene blue BC, and phthalocyanine blue Blue pigments such as: chrome green, chromium oxide, pigment green B, malachite green lake and final yellow green G; Emissions, antimony white, and white pigments such as zinc sulfide; barytes, barium carbonate, clay, silica, white carbon, talc, and include extender pigments such as alumina white. These colorants can be used in combination of two or more for the purpose of adjusting the toner to a desired hue.

  The amount of the colorant used is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less with respect to the total mass of the toner core particles.

  In addition, a colorant can also be used as a master batch in which a colorant is previously dispersed in a resin material such as a thermoplastic resin. When using a colorant as a masterbatch, the resin contained in the masterbatch is preferably the same type of resin as the binder resin.

[Magnetic powder]
The toner for developing an electrostatic latent image of the present invention can be made into a magnetic one-component developer by blending magnetic powder in a binder resin in toner core particles, if desired. Magnetic powders used when the toner is a magnetic one-component developer include irons such as ferrite and magnetite; ferromagnetic metals such as cobalt and nickel; iron and / or alloys containing ferromagnetic metals; iron, and And / or a compound containing a ferromagnetic metal; a ferromagnetic alloy subjected to a ferromagnetization treatment such as heat treatment; and chromium dioxide.

  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 magnetic powder having a particle diameter in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

  As the magnetic powder, for the purpose of improving the dispersibility in the binder resin, a powder that has been surface-treated using a surface treatment agent such as a titanium coupling agent or a silane coupling agent can be used.

  The amount of the magnetic powder used is preferably 35% by mass or more and 65% by mass or less, and more preferably 35% by mass or more and 55% by mass or less with respect to the total mass of the toner core particles. When the amount of magnetic powder used is excessive, it may be difficult to form an image having a desired image density or the fixability may be extremely lowered when an image is formed continuously for a long period of time. Further, when the amount of magnetic powder used is too small, the formed image is likely to be fogged or the image density may be lowered when printing is performed over a long period of time.

[Resin fine particles]
The resin fine particles forming the shell layer in the toner for developing an electrostatic latent image of the present invention are not particularly limited as long as the toner core particles can be coated. Since the shell layer having a predetermined structure can be easily formed, the resin fine particles forming the shell layer are preferably a polymer of a monomer having an unsaturated bond. The resin fine particles preferably contain a resin that can be synthesized by soap-free emulsion polymerization. This is because if resin fine particles are produced by soap-free emulsion polymerization, the particle diameters are uniform, and resin fine particles that contain little or no surfactant can be prepared.

  The monomer having an unsaturated bond is not particularly limited as long as it is a monomer capable of synthesizing a resin having sufficient physical properties as a shell layer. As the monomer having an unsaturated bond, a vinyl monomer is preferable. The vinyl group contained in the vinyl monomer may be substituted at the α-position with an alkyl group. Moreover, the vinyl group contained in the vinyl monomer may be substituted with a halogen atom. The alkyl group that the vinyl group may have is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. Moreover, the halogen atom that the vinyl group may have is preferably a chlorine atom or a bromine atom, and more preferably a chlorine atom.

  The vinyl monomer may have a nitrogen-containing polar functional group, or may have a fluorine-substituted hydrocarbon group. When a vinyl monomer having a nitrogen-containing polar functional group is used in producing the resin, positive chargeability can be imparted to the resulting resin. Further, when a vinyl monomer having a fluorine-substituted hydrocarbon group is used in producing a resin, negative chargeability can be imparted to the resulting resin. When the positively chargeable resin or the negatively chargeable resin is used as the material of the shell layer, the charge control agent is not added to the toner core particles or the amount of the charge control agent is reduced in the toner core particles. In addition, a toner that can be charged to a desired charge amount can be obtained.

  Specific examples of monomers having no nitrogen-containing polar functional group and fluorine-substituted hydrocarbon group among vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, and p-methylstyrene. , P-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, p- Styrenes such as n-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-ethoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene; ethylene, propylene, butylene And ethylenically unsaturated monoolefins such as isobutylene; vinyl chloride, vinylidene chloride, vinyl bromide, and Vinyl halides such as vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid n -Butyl, isobutyl (meth) acrylate, propyl (meth) acrylate, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, ( (Meth) acrylic acid esters such as 2-chloroethyl (meth) acrylate, phenyl (meth) acrylate, and methyl α-chloroacrylate; (meth) acrylic acid derivatives such as acrylonitrile; vinyl methyl ether, vinyl ethyl Ethers and vinyl ethers such as vinyl isobutyl ether Ethers; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; and vinyl naphthalenes. Among these, styrenes are preferable, and styrene is more preferable. These monomers can be used in combination of two or more.

Examples of vinyl monomers having a nitrogen-containing polar functional group include N-vinyl compounds, amino (meth) acrylic monomers, and methacrylonitrile (meth) acrylamide. Specific examples of N-vinyl compounds include N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone. Moreover, as a suitable example of an amino (meth) acrylic-type monomer, the compound represented by the following Formula is mentioned.
^{_{CH 2 = C (R 1)}} - (CO) -X-N (R 2) (R 3)
(In the formula, R ¹ represents hydrogen or a methyl group. R ² and R ³ each represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X represents —O—, —OQ— or —NH. Q represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a combination of these groups.)

In the above formula, specific examples of R ² and R ³ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, and tert-butyl group. N-pentyl group, iso-pentyl group, tert-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, n-undecyl group N-dodecyl group (lauryl group), n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group (stearyl group), n-nonadecyl group, and An n-icosyl group is mentioned.

  In the above formula, as specific examples of Q, methylene group, 1,2-ethane-diyl group, 1,1-ethylene group, propane-1,3-diyl group, propane-2,2-diyl group, propane- 1,1-diyl, propane-1,2-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group , Phenyl contained in octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, p-phenylene group, m-phenylene group, o-phenylene group, and benzyl group Examples thereof include a divalent group in which hydrogen is removed from the 4-position of the group.

  Specific examples of the amino (meth) acrylic monomer represented by the above formula include N, N-dimethylamino (meth) acrylate, N, N-dimethylaminomethyl (meth) acrylate, and N, N-diethylaminomethyl. (Meth) acrylate, 2- (N, N-methylamino) ethyl (meth) acrylate, 2- (N, N-diethylamino) ethyl (meth) acrylate, 3- (N, N-dimethylamino) propyl (meth) Acrylate, 4- (N, N-dimethylamino) butyl (meth) acrylate, pN, N-dimethylaminophenyl (meth) acrylate, pN, N-diethylaminophenyl (meth) acrylate, pN, N -Dipropylaminophenyl (meth) acrylate, p-N, N-di-n-butylaminophenyl (meth) acrylate P-N-laurylaminophenyl (meth) acrylate, pN-stearylaminophenyl (meth) acrylate, (pN, N-dimethylaminophenyl) methyl (meth) acrylate, (pN, N- Diethylaminophenyl) methyl (meth) acrylate, (pN, N-di-n-propylaminophenyl) methyl (meth) acrylate, (pN, N-di-n-butylaminophenyl) methylbenzyl (meth) Acrylate, (pN-laurylaminophenyl) methyl (meth) acrylate, (pN-stearylaminophenyl) methyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (Meth) acrylamide, 3- (N, N-dimethylamino) propyl (Meth) acrylamide, 3- (N, N-diethylamino) propyl (meth) acrylamide, pN, N-dimethylaminophenyl (meth) acrylamide, pN, N-diethylaminophenyl (meth) acrylamide, pN, N-di-n-propylaminophenyl (meth) acrylamide, pN, N-di-n-butylaminophenyl (meth) acrylamide, pN-laurylaminophenyl (meth) acrylamide, pN-stearylamino Phenyl (meth) acrylamide, (pN, N-dimethylaminophenyl) methyl (meth) acrylamide, (pN, N-diethylaminophenyl) methyl (meth) acrylamide, (pN, N-di-n- Propylaminophenyl) methyl (meth) acrylamide, (p-N, N- Monomers such as di-n-butylaminophenyl) methyl (meth) acrylamide, (pN-laurylaminophenyl) methyl (meth) acrylamide, and (pN-stearylaminophenyl) methyl (meth) acrylamide Is mentioned.

  The vinyl monomer having a fluorine-substituted hydrocarbon group is not particularly limited as long as it is used for the production of a fluorine-containing resin. Specific examples of the vinyl monomer having a fluorine-substituted hydrocarbon group include 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3, 3,4,4,5,5-octafluoroamyl acrylate, fluoroalkyl (meth) acrylates such as 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate, trifluorochloroethylene, vinylidene fluoride, trifluoride And ethylene tetrafluoride, trifluoropropylene, hexafluoropropene, and hexafluoropropylene. Among these, fluoroalkyl (meth) acrylates are preferable.

  As a method for addition polymerization of a monomer having an unsaturated bond, any method such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization can be selected. Among these production methods, the emulsion polymerization method is preferable because resin fine particles having a uniform particle diameter can be easily obtained.

  As the polymerization initiator that can be used for the polymerization of the vinyl monomer described above, potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′- Known polymerization initiators such as azobis-2,4-dimethylvaleronitrile and 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile can be used. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less based on the total mass of the monomers.

  As a polymerization method of the above-mentioned vinyl monomer, any method such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization can be selected. Among these production methods, the emulsion polymerization method is preferable because resin fine particles having a uniform particle diameter can be easily obtained.

  As a method for producing resin fine particles by the emulsion polymerization method, a soap-free emulsion polymerization method without using an emulsifier (surfactant) is preferable. In the soap-free emulsion polymerization method, a radical of an initiator generated in an aqueous phase binds a monomer slightly dissolved in the aqueous phase, and as the polymerization proceeds, particle nuclei of insoluble resin fine particles are formed. If the soap-free emulsion polymerization method is used, resin fine particles having a narrow particle size distribution can be obtained, and the average particle size of the resin fine particles can be easily controlled in the range of 0.03 μm to 1 μm. For this reason, if the soap-free emulsion polymerization method is used, resin fine particles having a uniform particle diameter can be obtained.

  By using resin fine particles having a uniform particle diameter obtained by the soap-free emulsion polymerization method, it is possible to reduce variations in the adhesion force of the resin fine particles to the toner core particles, thereby forming a uniform shell layer with a uniform thickness. . In addition, since the resin fine particles produced by the soap-free emulsion polymerization method are formed without using an emulsifier (surfactant), the resin fine particles obtained by the soap-free emulsion polymerization method are affected by moisture. A difficult shell layer can be formed.

  The resin fine particles may contain components such as the above-described colorant and charge control resin, if necessary. When the resin fine particles contain a sufficient amount of the charge control agent, the toner core particles may not contain the charge control agent.

  The glass transition point of the resin constituting the resin fine particles is preferably 45 ° C. or higher and 90 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower.

  When the glass transition point of the resin constituting the resin fine particles is too low, the resin fine particles are deformed too much, and cracks in a direction substantially perpendicular to the toner core particles are hardly formed inside the shell layer. In this case, even if pressure is applied to the toner at the time of fixing, the shell layer is unlikely to break down, so the toner may not be fixed on the recording medium at a lower temperature than before. Further, when the glass transition point of the resin constituting the resin fine particles is too low, the toner may aggregate when the toner is stored at a high temperature.

  On the other hand, when the glass transition point of the resin constituting the resin fine particles is too high, the resin fine particles are not deformed to a desired degree, and a shell layer having a predetermined shape may not be formed. In this case, since a gap remains between the resin fine particles, when the toner is stored at a high temperature, a component such as a release agent contained in the toner core particles may ooze out to the toner surface.

  The glass transition point of the resin constituting the resin fine particles can be determined from the change point of the specific heat of the resin constituting the resin fine particles using a differential scanning calorimeter (DSC). Hereinafter, the measuring method of the glass transition point using a differential scanning calorimeter (DSC) is demonstrated.

<Glass transition point measurement method>
Using a differential scanning calorimeter DSC-200 manufactured by Seiko Instruments Inc. as a measuring device, the endothermic curve of the resin constituting the resin fine particles is measured by a method based on JIS K 7121-1987. The glass transition point can be determined. 10 mg of resin constituting the resin fine particles is put in an aluminum pan, and an empty aluminum pan is used as a reference. Resin glass constituting resin fine particles from an endothermic curve of resin constituting resin fine particles obtained by measurement at room temperature and humidity under conditions of a measurement temperature range of 25 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min. A transition point can be obtained.

  The softening point of the resin constituting the resin fine particles is preferably from 100 ° C. to 250 ° C., more preferably from 110 ° C. to 240 ° C. The softening point of the resin constituting the resin fine particles is preferably higher than the softening point of the binder resin contained in the toner core particles, and more preferably 10 to 140 ° C. By setting the softening point of the resin constituting the resin fine particle in such a range, when the resin fine particle is embedded in the toner core particle, the portion of the resin fine particle that contacts the toner core particle is not easily deformed. Protrusions derived from the shape of the resin fine particles before forming the shell layer are easily formed on the surface.

  The softening point of the resin constituting the resin fine particles can be measured using a flow tester. Hereinafter, a method for measuring the softening point of the resin constituting the resin fine particles using a flow tester will be described.

<Softening point measurement method>
Using an elevated flow tester (CFT-500D (manufactured by Shimadzu Corporation)), the softening point (F _1/2 ) of the resin constituting the resin fine particles is measured. A molding die for preparing a measurement sample is filled with about 1.8 g of resin constituting resin fine particles, and a pressure of 4 MPa is applied to produce cylindrical resin fine particle pellets having a diameter of 1 cm and a length of 2 cm. The obtained pellets were set in a flow tester, and the plunger load was 30 kg, the die hole diameter was 1 mm, the die length was 1 mm, the heating rate was 4 ° C./min, and the measurement temperature range was 70 ° C. to 160 ° C. The softening point (Tm) of the resin constituting the resin fine particles is measured. The softening point (F _1/2 ) of the resin constituting the resin fine particles is read from the S-shaped curve relating to the temperature (° C.) and the stroke (mm) obtained by the flow tester.

A method for reading the softening point (F _1/2 ) of the resin constituting the resin fine particles will be described with reference to FIG. The maximum value of the stroke and S _1, the stroke value of the low-temperature side of the base line and S _2. The temperature at which the stroke value is (S ₁ + S ₂ ) / 2 on the S-curve is defined as the softening point (F _1/2 ) of the resin constituting the resin fine particles.

  The average particle diameter of the resin fine particles is preferably 30 nm to 1000 nm, more preferably 40 nm to 700 nm, particularly preferably 45 nm to 500 nm, and most preferably 45 nm to 300 nm. When resin fine particles having such a particle size are used, the surface of the toner core particles can be easily uniformly coated with a single layer made of resin fine particles, and a shell layer having a desired structure can be easily formed.

  When resin fine particles having an average particle size that is too small are used, a shell layer having a preferable thickness cannot be formed on the surface of the toner core particles, and a toner excellent in heat-resistant storage stability may not be obtained. On the other hand, when resin fine particles having an excessive average particle size are used, a toner having excellent heat-resistant storage stability cannot be obtained because the resin fine particles cannot be uniformly adhered to the surface of the toner core particles and a shell layer having a predetermined structure cannot be formed. There is a case.

  The average particle diameter of the resin fine particles can be adjusted by adjusting the polymerization conditions or using a method such as a known pulverization method or classification method. About the average particle diameter of resin fine particles, the particle diameter of 50 or more resin fine particles was measured from an electron micrograph taken using a field emission scanning electron microscope (JSM-6700F (manufactured by JEOL Ltd.)), The number average particle size can be calculated.

The mass average molecular weight (Mw) of the resin constituting the resin fine particles is preferably 5,000 or more and 100,000 or less. The mass average molecular weight (Mw) of the resin constituting the resin fine particles can be determined from a mass-based molecular weight distribution that can be measured using gel permeation chromatography (GPC). The molecular weight (M _p ) at the maximum peak in the mass-based molecular weight distribution measured using gel permeation chromatography of the resin constituting the resin fine particles is preferably 5,000 or more and 100,000 or less.

  In the case of using a resin constituting resin fine particles with Mw and Mp being too small, the resin fine particles may be deformed excessively, so that cracks in a direction substantially perpendicular to the toner core particles may not be formed inside the shell layer. is there. In this case, even if pressure is applied to the toner at the time of fixing, the shell layer is not easily broken, so that the toner may not be fixed on the recording medium. In addition, in the case of using a toner manufactured using a resin constituting a resin fine particle having Mw and Mp of resin constituting the resin fine particle, the toner may aggregate when the toner is stored at a high temperature. The

  On the other hand, when a resin constituting resin fine particles having excessive Mw and Mp is used, a desired degree of deformation of the resin fine particles does not occur, and a shell layer having a desired shape may not be formed. In this case, since a gap remains between the resin fine particles, a component such as a release agent contained in the toner core particles may ooze out to the toner surface when the toner is stored at a high temperature. Further, when a toner manufactured using a resin constituting resin fine particles having excessive Mw and Mp is used, the shell layer formed from the resin fine particles may not be easily broken when the toner is fixed. For this reason, the shell layer may impede toner fixing, and the toner may not be satisfactorily fixed on the recording medium.

  Hereinafter, a method for measuring a mass-based molecular weight distribution using gel permeation chromatography (GPC) will be described.

<Measurement method of molecular weight distribution>
At room temperature, 10 mg of resin fine particles are dissolved in 5 mL of tetrahydrofuran (THF). The obtained solution is filtered using a non-aqueous chromatographic disk having an aperture of 0.45 μm to obtain a sample solution. Measurement is performed under the following conditions using the obtained sample solution.
<Measurement conditions>
Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSK-GEL Super HZM-H (manufactured by Tosoh Corp.) 2 columns TSK goldcolumn Super HZ-H (manufactured by Tosoh Corp.) 1 eluent: Tetrahydrofuran (THF)
Flow rate: 0.200 mL / min Sample injection volume: 10 μL
Measurement temperature: 40 ° C
Detector: IR detector Calibration curve: From standard sample (TSK standard POLYSTYREN (manufactured by Tosoh Corporation)), F-380, F-128, F-40, F-10, F-4, F-1, and A -2500 is selected and created.

Regarding the resin constituting the resin fine particles, the temperature (T ₁ ) when the melt viscosity is 1.0 × 10 ⁵ Pa · s is 110 ° C. or more and 160 ° C. or less, and the melt viscosity is 1.0 × 10 ^4. The temperature (T ₂ ) at Pa · s is preferably 130 ° C. or higher and 170 ° C. or lower.

When a resin constituting resin fine particles having T ₁ and T _{2 that} are too low is used, the resin fine particles are excessively deformed, so that cracks in a direction substantially perpendicular to the toner core particles may not be formed inside the shell layer. In this case, even if pressure is applied to the toner at the time of fixing, the shell layer is unlikely to break down, so that the toner may not be fixed satisfactorily on the recording medium. In addition, when a toner manufactured using a resin constituting resin fine particles in which T ₁ and T ₂ are too low is used, the toner may aggregate when the toner is stored at a high temperature.

On the other hand, when a resin constituting resin fine particles having too high T ₁ and T ₂ is used, a desired degree of deformation of the resin fine particles does not occur, and a shell layer having a predetermined shape may not be formed. In this case, since a gap remains between the resin fine particles, a component such as a release agent contained in the toner core particles may ooze out to the toner surface when the toner is stored at a high temperature. In addition, when a toner manufactured using a resin constituting resin fine particles having too high T ₁ and T ₂ is used, the shell layer formed from the resin fine particles may not be easily broken when the toner is fixed. For this reason, the shell layer may hinder the fixing of the toner, and the toner may not be fixed satisfactorily on the recording medium.

T ₁ and T ₂ can be measured using a flow tester. Hereinafter, the measurement method of T ₁ and T ₂ using a flow tester is to use the same method as the measurement method of the softening point of the resin constituting the resin fine particles using the flow tester described above by appropriately changing the measurement conditions. it can.

  The amount of the resin fine particles 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 15 parts by mass or less with respect to 100 parts by mass of the toner core particles. If the amount of resin fine particles used is too small, the entire surface of the toner core particles may not be covered with the resin fine particles. When the entire surface of the toner core particles cannot be covered with the resin fine particles, the toner may aggregate during storage at high temperature, and the heat resistant storage stability may be lowered. If the amount of resin fine particles used is excessive, the shell layer may become thick. In this case, a toner having excellent fixability may not be obtained.

(External additive)
The toner of the present invention can be treated with an external additive as desired after forming a shell layer on the surface of the toner core particles. Hereinafter, the particles processed using the external additive are also referred to as “toner base particles”.

  Examples of the external additive include silica, metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These external additives can be used in combination of two or more.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

  The amount of the external additive used is preferably 0.1% by mass or more and 10% by mass or less, and preferably 0.2% by mass or more and 5% by mass or less with respect to the mass of toner base particles produced by forming a shell layer on the surface of the toner core particles. The mass% or less is more preferable. If the amount of the external additive used is too small, the hydrophobicity of the toner tends to decrease. As a result, it becomes susceptible to water molecules in the air in a high-temperature and high-humidity environment, such as a decrease in image density of a formed image due to an extreme decrease in toner charge amount, and a decrease in toner fluidity. Problems are likely to occur. Further, when the amount of the external additive used is excessive, there is a possibility that the image density is lowered due to excessive charge-up of the toner.

[Carrier]
The toner for developing an electrostatic latent image of the present invention can be mixed with a desired carrier and used as a two-component developer. When preparing a two-component developer, it is preferable to use a magnetic carrier as a carrier.

  Suitable carriers in the case where the electrostatic latent image developing toner of the present invention is used as a two-component developer include those in which a carrier core material is coated with a resin. Specific examples of carrier core materials include particles such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, and cobalt, and these materials and metals such as manganese, zinc, and aluminum. Particles of alloys with, particles such as iron-nickel alloys, and iron-cobalt alloys, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, Ceramic particles such as lithium titanate, lead titanate, lead zirconate, and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt, in resin And a resin carrier in which the magnetic particles are dispersed.

  Specific examples of the resin covering the carrier include (meth) acrylic polymer, styrene polymer, styrene- (meth) acrylic copolymer, olefin polymer (polyethylene, chlorinated polyethylene, polypropylene), poly Vinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride) Phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, and amino resin. These resins can be used in combination of two or more.

  The particle diameter of the carrier is a particle diameter measured using an electron microscope, and is preferably 20 μm or more and 200 μm or less, and more preferably 30 μm or more and 150 μm or less.

The apparent density of the carrier varies depending on the composition and surface structure of the carrier, but is typically preferably 2400 kg / m ³ or more and 3000 kg / m ³ or less.

  When the electrostatic latent image developing toner of the present invention is used as a two-component developer, the toner content is preferably 1% by mass or more and 20% by mass or less, and preferably 3% by mass or more with respect to the mass of the two-component developer. 15 mass% or less is preferable. By setting the toner content in the two-component developer within such a range, the image density of the formed image can be maintained at a desired density, or toner scattering inside the image forming apparatus can be suppressed to prevent contamination and transfer. Toner adhesion to paper can be suppressed.

[Method for producing toner for developing electrostatic latent image]
The method for producing the electrostatic latent image developing toner described above is not particularly limited as long as the toner core particles and the shell layer are formed to have a predetermined structure. Further, if necessary, the toner core particles coated with the shell layer may be used as toner base particles, and an external addition treatment may be performed to attach an external additive to the surface of the toner base particles. As a preferred method for producing the toner for developing an electrostatic latent image described above, a method for producing toner core particles, a method for forming a shell layer, and an external treatment method will be described in this order.

[Method for producing toner core particles]
The method for producing the toner core particles is not particularly limited as long as the method can satisfactorily disperse arbitrary components such as a colorant, a release agent, a charge control agent, and magnetic powder in the binder resin. As a specific example of a suitable method for producing toner core particles, a binder resin and components such as a colorant, a release agent, a charge control agent, and magnetic powder are mixed using a mixer, and then uniaxial or biaxial. Examples thereof include a method in which a binder resin and components blended in the binder resin are melt-kneaded using a kneader such as a screw extruder, and the cooled kneaded product is pulverized and classified. The average particle diameter of the toner core particles is generally preferably 5 μm or more and 10 μm or less.

[Method of forming shell layer]
The shell layer is formed using spherical resin fine particles. And more specifically,
I) A step of attaching spherical resin fine particles to the surface of the toner core particles so as not to overlap the surface of the toner core particles in the vertical direction to form a resin fine particle layer covering the entire surface of the toner core particles; and II ) Forming a shell layer by smoothing the outer surface of the resin fine particle layer by applying an external force to the outer surface of the resin fine particle layer to deform the resin fine particles in the resin fine particle layer;
Formed using a method including:

  As described above, as a method of forming the shell layer using the resin fine particles, a method using a mixing apparatus capable of mixing the toner core particles and the resin fine particles under dry conditions is preferable. Specifically, a shell layer is formed on the surface of the toner core particle by using a mixing device capable of applying a mechanical external force to the toner core particle having the resin fine particle attached to the surface while the resin fine particle is attached to the surface of the toner core particle. The method of forming is mentioned. As the mechanical external force, when the toner core particles move at a high speed in a narrow space in the mixing device, the toner core particles are displaced between each other, or the toner core particles are sheared between the toner core particles and the inner wall of the device, the rotor, or the stator. Examples include shearing force applied to the toner core particles, and impact force applied to the toner core particles by collision between the toner core particles or collision of the toner core particles with the inner wall of the apparatus.

  A more specific method will be described. First, by mixing the toner core particles and the resin fine particles in the mixing device, the resin fine particles are uniformly attached to the surface of the toner core particles so that the resin fine particles do not overlap in the direction perpendicular to the surface of the toner core particles. Let When a toner core particle having a large particle size and a resin fine particle having a small particle size are in contact with each other, there is a contact between the surface of the toner core particle that can be regarded as a flat surface and the surface of the resin fine particle. As a result, the resin fine particles are likely to adhere to the toner core particles. On the other hand, when the resin fine particles are in contact with each other, the curved surfaces of the two resin fine particles are in contact with each other, so that contact between the points occurs. Therefore, in the process of attaching the resin fine particles to the toner core particles, even if the resin fine particles are further attached to the resin fine particles attached to the surface of the toner core particles, the mechanical external force applied to the toner core particles to which the resin fine particles are attached using a mixing device. Thus, the resin fine particles adhering to the resin fine particles are easily separated from the resin fine particles. For these reasons, in the method described below, the toner core particles are coated with the resin fine particles so that the resin fine particles do not overlap in the direction perpendicular to the surface of the toner core particles.

  When the resin fine particles are adhered to the toner core particles, the mechanical external force is applied to the resin fine particle layer on the surface of the toner core particles. By applying a mechanical external force to the resin fine particle layer on the surface of the toner core particle, the resin fine particle is deformed while being embedded in the toner core particle, and the outer surface of the resin fine particle layer covering the entire surface of the toner core particle is smoothed. The layer changes to a shell layer. As described above, the smoothing proceeds on the outer surface of the shell layer, while the boundary surface between the resin fine particles remains inside the shell layer. For this reason, cracks in a direction substantially perpendicular to the surface of the toner core particles are formed inside the shell layer formed using the resin fine particles.

  At this time, if the material of the toner core particles is as hard as or slightly harder than the resin fine particles forming the shell layer, the inner surface of the shell layer (the surface on the toner core particle side) may be smooth. On the other hand, when the material of the toner core particles is softer than the resin fine particles forming the shell layer, when the resin fine particles are embedded in the toner core particles, the portions of the resin fine particles that come into contact with the toner core particles are not easily deformed. Convex portions derived from the shape of the fine particles before being changed into the shell layer are easily formed on the inner surface. In this case, the convex portion is formed between two cracks provided in the shell layer.

  In the above method, if the mechanical external force is weak, a desired degree of deformation of the resin fine particles does not occur, and a shell layer having a desired shape may not be formed. The conditions for forming the desired shape of the shell layer vary depending on the apparatus used to form the shell layer, but the operating conditions are stepwise so that the mechanical external force applied to the toner core particles coated with the resin fine particles becomes stronger. By changing the above and confirming the structure of the shell layer of the toner obtained under each condition, suitable conditions for forming a shell layer having a desired shape for various apparatuses can be determined. However, when the mechanical external force is too strong, the resin fine particles are deformed excessively, and cracks in a direction substantially perpendicular to the toner core particles are not formed inside the shell layer, or the mechanical external force is converted into heat. In some cases, the toner core particles or resin fine particles may be melted.

  As an apparatus capable of applying a mechanical external force to the toner core particles coated with the resin fine particles while coating the toner core particles with the resin fine particles, a hybridizer NHS-1 (manufactured by Nara Machinery Co., Ltd.), Cosmos System ( Kawasaki Heavy Industries, Ltd.), Henschel Mixer (Nihon Coke Industries, Ltd.), Multipurpose Mixer (Nihon Coke Industries, Ltd.), Composite (Nihon Coke Industries, Ltd.), Mechano-Fusion Device (Hosokawa Micron Corporation), Examples include Mechanomyl (Okada Seiko Co., Ltd.) and Nobilta (Hosokawa Micron Co., Ltd.).

[External treatment method]
The processing method of the toner base particles using the external additive is not particularly limited, and the toner base particles can be processed according to a conventionally known method. Specifically, the processing conditions are adjusted so that the particles of the external additive are not buried in the toner base particles, and the toner base particles using the external additive are mixed using a mixer such as a Henschel mixer or a Nauter mixer. Processing is performed.

  Since the electrostatic latent image developing toner of the present invention described above is excellent in fixing property and heat-resistant storage property, it can be suitably used in various image forming apparatuses.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the scope of the examples.

[Production Example 1]
(Manufacture of polyester resin)
1960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide were charged into a reaction vessel. Next, the inside of the reaction vessel was placed in a nitrogen atmosphere, and the temperature inside the reaction vessel was raised to 235 ° C. while stirring. Subsequently, after reacting at the same temperature for 8 hours, the inside of reaction container was pressure-reduced to 8.3 kPa and reacted for 1 hour. Thereafter, the reaction mixture was cooled to 180 ° C., and trimellitic anhydride was added to the reaction vessel so as to obtain a desired acid value. Subsequently, the temperature of the reaction mixture was raised to 210 ° C. at a rate of 10 ° C./hour, and the reaction was performed at the same temperature. After completion of the reaction, the contents in the reaction vessel were taken out and cooled to obtain a polyester resin.

[Production Example 2]
(Manufacture of toner core particles)
89 parts by mass of binder resin (polyester resin obtained in Production Example 1), 5 parts by mass of release agent (polypropylene wax 660P (manufactured by Sanyo Chemical Co., Ltd.)), charge control agent (P-51 (manufactured by Orient Chemical Industries, Ltd.) )) 1 part by mass and 5 parts by mass of a colorant (carbon black MA100 (manufactured by Mitsubishi Chemical Corporation)) were mixed using a mixer to obtain a mixture. Next, the mixture was melt-kneaded using a twin-screw extruder to obtain a kneaded product. The kneaded product is coarsely pulverized using a pulverizer (Rotoplex (manufactured by Toa Machinery Co., Ltd.)), and then the coarsely pulverized product is finely pulverized using a mechanical pulverizer (turbo mill (manufactured by Turbo Industry Co., Ltd.)). Thus, a finely pulverized product was obtained. Using a classifier (Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.)), the finely pulverized product was classified to obtain toner core particles having a volume average particle diameter (D ₅₀ ) of 7.0 μm. The volume average particle diameter of the toner core particles was measured using a Coulter Counter Multisizer 3 (manufactured by Beckman Coulter).

[Production Example 3]
(Production of resin fine particles A)
In a 1000 mL reaction vessel equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen introducing device, 450 mL of distilled water and 0.52 g of dodecyl ammonium chloride were charged. While stirring the contents of the reactor under a nitrogen atmosphere, the temperature inside the reaction vessel was raised to 80 ° C. After the temperature increase, 120 g of a potassium persulfate (polymerization initiator) aqueous solution having a concentration of 1% by mass and 200 g of ion-exchanged water were added to the reaction vessel. Next, a mixture consisting of 15 g of butyl acrylate, 165 g of methyl methacrylate, and 3.6 g of n-octyl mercaptan (chain transfer agent) was dropped into the reaction vessel over 1.5 hours, and then polymerization was performed for another 2 hours. An aqueous dispersion of resin fine particles was obtained. The obtained aqueous dispersion of resin fine particles was dried using freeze drying to obtain resin fine particles. The number average particle diameter of the resin fine particles was 102 nm. Further, the resin fine particles A had a glass transition point (Tg) of 49.6 ° C. and a softening point of 188 ° C.
The number average particle diameter of the resin fine particles was measured by first taking a picture of the resin fine particles at a magnification of 100,000 using a field emission scanning electron microscope (JSM-6700F (manufactured by JEOL Ltd.)). . The photographed electron micrograph was further enlarged as necessary, and the particle diameters of 50 or more resin fine particles were measured using a ruler and a caliper, and the number average particle diameter of the resin fine particles was calculated from the measured values.

(Production of resin fine particles B to E)
Resin particles B to E were obtained in the same manner as the resin particles A except that butyl acrylate and methyl methacrylate in the amounts shown in Table 1 were used. Table 1 shows the number average particle diameter, glass transition point, and softening point of the obtained resin fine particles B to E.

(Production of resin fine particles F to I)
Resin fine particles F to I were obtained in the same manner as the resin fine particles A except that the use amounts of dodecyl ammonium chloride shown in Table 2 were used. Table 2 shows the number average particle diameter of the obtained resin fine particles F to I.

(Production of resin fine particles J to M)
Changing the amount of butyl acrylate to 140 g, changing the amount of 165 g of methyl methacrylate to 30 g, and changing the amount of n-octyl mercaptan to the amount shown in Table 3 Otherwise, resin fine particles J to M were obtained in the same manner as resin fine particles A.

In accordance with the following molecular weight distribution measuring method using gel permeation chromatography (GPC), the resin-based fine particles A and the mass-based molecular weight distribution of the resins constituting J to M were measured. From the measured molecular weight distribution, the mass average molecular weight (Mw) of the resin fine particles A and J to M and the maximum peak molecular weight (M _p ) in the molecular weight distribution were determined. Resin fine particles A, and the Mw of the resin constituting the J to M, and _{M p} are shown in Table 3. In addition, Table 3 shows the number average particle diameter of the obtained resin fine particles J to M.

<Measurement method of molecular weight distribution>
At room temperature, 10 mg of resin fine particles were dissolved in 5 mL of tetrahydrofuran (THF). The obtained solution was filtered using a non-aqueous chromatographic disk having an aperture of 0.45 μm to obtain a sample solution. Using the obtained sample solution, measurement was performed under the following conditions.
(Measurement condition)
Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSK-GEL Super HZM-H (manufactured by Tosoh Corp.) 2 columns TSK goldcolumn Super HZ-H (manufactured by Tosoh Corp.) 1 eluent: Tetrahydrofuran (THF)
Flow rate: 0.200 mL / min Sample injection volume: 10 μL
Measurement temperature: 40 ° C
Detector: IR detector Calibration curve: From standard sample (TSK standard POLYSTYREN (manufactured by Tosoh Corporation)), F-380, F-128, F-40, F-10, F-4, F-1, and A -2500 was selected and created.

(Production of resin fine particles N and O)
Resin fine particles N and O were obtained in the same manner as the resin fine particles K except that the amount of n-octyl mercaptan used was changed to the amount shown in Table 4.

According to the following method, for the resin constituting the resin fine particles N and O, the temperature (T ₁ ) when the melt viscosity is 1.0 × 10 ⁵ Pa · s and the melt viscosity is 1.0 × 10 ⁴ Pa · s. The temperature (T ₂ ) when Further, T ₁ and T ₂ were also measured for the resins constituting the resin fine particles K and M. Table ₁ shows T ₁ and T ₂ of the resin constituting the resin fine particles K and M to O. In addition, Table 4 shows the number average particle diameters of the obtained resin fine particles N and O.

<Measurement of _{T 1} and _{T 2>}
T ₁ and T ₂ of the resin constituting the resin fine particles were measured using an elevated flow tester (CFT-500D (manufactured by Shimadzu Corporation)). A molding die for preparing a measurement sample was filled with about 1.2 g of resin constituting resin fine particles, and a pressure of 4 MPa was applied to produce cylindrical resin fine particle pellets having a diameter of 1 cm and a length of 2 cm. The obtained pellets were set in a flow tester, plunger load: 30 kg, die hole diameter: 1 mm, die length: 1 mm, preheating temperature: 70 ° C., preheating time: 300 seconds, heating rate: 4 ° C./min, Measurement temperature range: Measurement was performed under measurement conditions of 70 ° C. or higher and 160 ° C. or lower.

[Example 1, Comparative Example 1, and Comparative Example 2]
(Preparation of toner base particles)
Using 100 g of the toner core particles obtained in Production Example 2, 10 g of the resin fine particles A obtained in Production Example 3 were used to coat the toner core particles with the resin fine particles A to form a shell layer on the surface of the toner core particles. A powder processing apparatus (multipurpose mixer MP type (manufactured by Nippon Coke Kogyo Co., Ltd.)) was used for the shelling treatment, and the toner core particles and the resin fine particles A were introduced into the processing tank of the powder processing apparatus. Toner mother particles were obtained by processing at the indicated rotational speed and processing time. In Example 1, the temperature in the tank of the powder processing apparatus was controlled to be in the range of 50 ° C. or more and 60 ° C. or less.

(External processing)
To the obtained toner base particles, 2.0% by weight of titanium oxide (EC-100 (manufactured by Titanium Industry Co., Ltd.)) and 1.0% by weight of hydrophobic silica (RA) are added to the weight of the toner base particles. -200H (manufactured by Nippon Aerosil Co., Ltd.) was added and stirred and mixed at a rotational peripheral speed of 30 m / sec for 5 minutes using a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to obtain a toner.

[Comparative Example 3]
Using 100 g of the toner core particles obtained in Production Example 2, 10 g of the resin fine particles A obtained in Production Example 3 were used to coat the toner core particles with the resin fine particles A to form a shell layer on the surface of the toner core particles.

  For the formation of the shell layer, a surface modifying apparatus (fine particle coating apparatus SFP-01 type (manufactured by POWREC Co., Ltd.)) was used. The toner core particles were circulated in the fluidized bed of the surface reformer at an air supply temperature of 80 ° C. 300 g of the aqueous dispersion containing 10 g of resin fine particles A obtained in Production Example 3 was sprayed into the fluidized bed of the surface reforming device at a spray rate of 5 g / min for 60 minutes to obtain toner base particles. The obtained toner base particles were externally treated in the same manner as in Example 1 to obtain a toner of Comparative Example 3.

≪Confirmation of shell layer structure≫
According to the following method, the surfaces of the toners of Example 1 and Comparative Examples 1 to 3 were observed using a scanning electron microscope (SEM), and the state of the surface of the shell layer covering the toner core particles was confirmed. Further, according to the following method, photographs of cross sections of the toners of Example 1 and Comparative Examples 1 to 3 were taken using a transmission electron microscope (TEM). Using the obtained TEM photograph, the surface state of the shell layer, the internal state of the shell layer, and the shape of the internal surface of the shell layer were confirmed. A TEM photograph of the cross section of the toner of Example 1 is shown in FIG. 3, a TEM photograph of the cross section of the toner of Comparative Example 1 is shown in FIG. 4, and a TEM photograph of the cross section of the toner of Comparative Example 3 is shown in FIG.

<Method for observing toner surface>
The surface of the toner particles was observed at a magnification of 10,000 times using a scanning electron microscope (JSM-6700F (manufactured by JEOL Ltd.)).

<Method for photographing the cross section of the toner>
A sample in which the toner was embedded in a resin was prepared. Using a microtome (EM UC6 (manufactured by Leica Co., Ltd.)), a thin piece sample for cross-sectional observation of 200 nm thick toner was prepared from the obtained sample. The obtained flake sample was observed with a transmission electron microscope (TEM, JSM-6700F (manufactured by JEOL Ltd.)) at a magnification of 50,000 times, and an image of a cross section of an arbitrary toner was taken.

  The toner of Example 1 has a structure derived from spherical resin fine particles on the surface of the shell layer of toner particles having a particle diameter of 6 μm or more and 8 μm or less when the surface is observed with a scanning electron microscope (SEM). Not observed. Also, from the TEM photograph of the cross section of the toner of Example 1 shown in FIG. 3, it was confirmed that the outer surface of the shell layer of the toner of Example 1 was smooth. Furthermore, from the TEM photograph of the cross section of the toner of Example 1, it was confirmed that cracks in a direction substantially perpendicular to the surface of the toner core particles were present inside the shell layer of the toner of Example 1. Further, from the TEM photograph of the cross section of the toner of Example 1, it was confirmed that the shell layer of the toner of Example 1 had a convex portion between two cracks on the inner surface side.

  When the surfaces of the toners of Comparative Examples 1 and 2 were observed using an SEM, it was confirmed that the surfaces of the toner core particles were coated with resin fine particles in a spherical particle state. Also, from the TEM photograph of the cross section of the toner of Comparative Example 1 in FIG. 4, it was confirmed that the surface of the toner core particles of the toner of Comparative Example 1 was covered with resin fine particles in the particle state. When the cross section of the toner of Comparative Example 2 was observed using a TEM, the structure of the shell layer of the toner of Comparative Example 2 was the same as the structure of the shell layer of the toner of Comparative Example 1. A TEM photograph of the cross section of toner 2 was not taken.

  When the surface of the toner of Comparative Example 3 was observed with an SEM, a structure derived from spherical resin fine particles was not observed on the surface of the shell layer of toner particles having a particle diameter of 6 μm to 8 μm. Further, from the TEM photograph of the cross section of the toner of Comparative Example 3 shown in FIG. 5, it was confirmed that the outer surface of the shell layer of the toner of Comparative Example 3 was smooth. However, from the TEM photograph of the cross section of the toner of Comparative Example 3, it was not confirmed that cracks in a direction substantially perpendicular to the surface of the toner core particles were present inside the shell layer of the toner of Comparative Example 3.

≪Evaluation≫
According to the following method, the fixability and heat resistant storage stability of the toners of Example 1 and Comparative Examples 1 to 3 were evaluated. The evaluation results for each toner are shown in Table 5. For the fixability evaluation, the two-component developer obtained in Production Example 4 below was used.

[Production Example 4]
(Preparation of two-component developer)
A carrier (ferrite carrier (manufactured by Powdertech Co., Ltd.)) and 10% by mass of toner with respect to the mass of the ferrite carrier were mixed for 30 minutes using a ball mill to prepare a two-component developer.

<Fixability>
A page printer (FS-C5016N (manufactured by Kyocera Document Solutions)) modified for evaluation was used as an evaluation machine, and the evaluation machine was allowed to stand for 10 minutes with the power off, and then turned on and used. Then, using a fixing roller having a diameter of 30 mm and a linear speed of 100 mm / sec, the fixing temperature was set to 180 ° C., and an evaluation image was obtained in a normal temperature and normal humidity (20 ° C., 65% RH) environment. The image density before friction of the obtained evaluation image was measured using Gretag Macbeth Spectroeye (manufactured by Gretag Macbeth).
Next, the evaluation image was rubbed with a 1 kg weight covered with a fabric. Specifically, the evaluation image was rubbed by reciprocating the weight 10 times on the evaluation image so that only the weight of the weight was applied to the image. The image density of the image for evaluation after friction was measured using Gretag Macbeth Spectroeye (manufactured by Gretag Macbeth). According to the following formula, the fixing rate was calculated from the image density before and after friction. From the calculated fixing rate, fixing property was evaluated according to the following criteria.
○ Evaluation was accepted.
Fixing rate (%) = (image density after friction / image density before friction) × 100
○: Fixing rate is 95% or more Δ: Fixing rate is 90% or more and less than 95% ×: Fixing rate is less than 90%

<Heat resistant storage stability>
The toner was stored at 50 ° C. for 100 hours. Next, according to the manual of the powder tester (manufactured by Hosokawa Micron Co., Ltd.), the toner is sieved using a 140 mesh (opening 105 μm) sieve under the conditions of a rheostat scale of 5 and a time of 30 seconds. (%) Was calculated. The heat resistant storage stability was evaluated according to the following criteria. ○ Evaluation was accepted.
(Cohesion calculation formula)
Aggregation degree (%) = toner mass remaining on sieve / toner mass before sieving × 100
○: Aggregation degree is 20% or less Δ: Aggregation degree is more than 20%, 50% or less ×: Aggregation degree is more than 50%

  From Example 1, the toner comprises toner core particles containing at least a binder resin and a shell layer having a predetermined structure covering the entire surface of the toner core particles, and the shell layer has a predetermined surface on the outer surface of the resin fine particle layer. When a crack is observed in a direction substantially perpendicular to the surface of the toner core particles inside the shell layer when the cross section is observed using a transmission electron microscope. It can be seen that a toner having excellent fixability and heat-resistant storage stability can be obtained.

  From Comparative Examples 1 and 2, it can be seen that when the structure derived from spherical resin fine particles is observed on the surface of the shell layer of the toner core particles, the heat-resistant storage stability of the obtained toner is not good. When a structure derived from spherical resin fine particles is observed on the surface of the shell layer, gaps remain between the resin fine particles deformed to some extent that cover the shell layer. Therefore, components such as a release agent contained in the toner core particles It can be inferred that the toner surface oozes easily.

  Further, by observing the toners of Example 1, Comparative Example 1, and Comparative Example 2 with SEM, the smoothness of the surface of the formed shell layer increases as the rotational speed of the apparatus used for forming the shell layer is increased. It was confirmed.

  From Comparative Example 3, it can be seen that the fixability of the obtained toner is inferior when cracks in the direction substantially perpendicular to the surface of the toner core particles are not observed inside the shell layer. This is presumably because the shell layer does not easily break due to the pressure applied from the fixing nip of the fixing roller due to the absence of a crack serving as a starting point for the shell layer breaking within the shell layer.

[Example 2, Example 3, Comparative Example 4, and Comparative Example 5]
The toners of Example 2, Example 3, Comparative Example 4, and Comparative Example 5 were obtained in the same manner as Example 1 except that the resin fine particles described in Table 6 were used.

≪Confirmation of shell layer structure≫
According to the above method, the surfaces of the toners of Example 2, Example 3, Comparative Example 4 and Comparative Example 5 were observed using a scanning electron microscope (SEM), and the state of the surface of the shell layer covering the toner core particles It was confirmed. Moreover, according to the above method, photographs of the cross sections of the toners of Examples 2, 3, 4, and 5 were taken using a transmission electron microscope (TEM). Using the obtained TEM photograph, the surface state of the shell layer, the internal state of the shell layer, and the shape of the internal surface of the shell layer were confirmed.

  When the surface of the toner of Examples 2 and 3 was observed with a scanning electron microscope (SEM), a structure derived from spherical resin fine particles was observed on the surface of the shell layer of toner particles having a particle diameter of 6 μm to 8 μm. There wasn't. The cross sections of the toners of Examples 2 and 3 were observed using a TEM. The structure of the toner shell layer of Examples 2 and 3 is the structure of the toner shell layer of Example 1 shown in FIG. It was the same.

  When SEM observation of the surface of the toner of Comparative Example 4 was performed, for toner particles having a particle size of 6 μm or more and 8 μm or less, a structure derived from spherical resin fine particles was not observed on the surface of the shell layer. The cross section of the toner of Comparative Example 4 was observed using a TEM. The structure of the shell layer of the toner of Comparative Example 4 was the same as that of the toner shell layer of Comparative Example 3 shown in FIG. It was.

  When SEM observation of the surface of the toner of Comparative Example 5 was performed, it was confirmed that the surface of the toner core particles was coated with resin fine particles in a spherical particle state. The cross section of the toner of Comparative Example 5 was observed using a TEM. The structure of the toner shell layer of Comparative Example 5 was the same as that of the toner shell layer of Comparative Example 1 shown in FIG. It was.

≪Evaluation≫
In the same manner as the toner of Example 1, the fixability and heat resistant storage stability of the toners of Example 2, Example 3, Comparative Example 4, and Comparative Example 5 were evaluated. The evaluation results for each toner are shown in Table 6.

  From Examples 1 to 3, Comparative Example 4, and Comparative Example 5, the toner comprises toner core particles containing at least a binder resin, and a shell layer having a predetermined structure that covers the entire surface of the toner core particles. However, the outer surface of the resin fine particle layer is formed to be smoothed to a predetermined degree, and when the cross section is observed using a transmission electron microscope, the inner surface of the shell layer is substantially the same as the surface of the toner core particles. When a crack in the vertical direction is observed and the glass transition point of the resin fine particles is 50 ° C. or higher and 80 ° C. or lower, it can be seen that a toner excellent in fixability and heat resistant storage stability can be obtained.

[Examples 4 to 6, Comparative Example 6, and Comparative Example 7]
Toners of Examples 4 to 6, Comparative Example 6, and Comparative Example 7 were obtained in the same manner as in Example 1 except that the types and amounts of resin fine particles described in Table 7 were used.

≪Confirmation of shell layer structure≫
According to the above method, the surfaces of the toners of Examples 4 to 6, Comparative Example 6 and Comparative Example 7 were observed using a scanning electron microscope (SEM), and the state of the surface of the shell layer covering the toner core particles was confirmed. did. Further, according to the above method, photographs of the cross sections of the toners of Examples 4 to 6, Comparative Example 6 and Comparative Example 7 were taken using a transmission electron microscope (TEM). Using the obtained TEM photograph, the surface state of the shell layer, the internal state of the shell layer, and the shape of the internal surface of the shell layer were confirmed.

  When the surface of the toner of Examples 4 to 6 is observed with a scanning electron microscope (SEM), toner particles having a particle diameter of 6 μm or more and 8 μm or less have a structure derived from spherical resin fine particles on the surface of the shell layer. Not observed. Further, the cross sections of the toners of Examples 4 to 6 were observed using a TEM. The structure of the toner shell layer of Examples 4 to 6 is the structure of the toner shell layer of Example 1 shown in FIG. It was the same.

  When the surface of the toner of Comparative Example 6 was observed with an SEM, no structure derived from spherical resin fine particles was observed on the surface of the shell layer of toner particles having a particle diameter of 6 μm to 8 μm. The cross section of the toner of Comparative Example 6 was observed using TEM. The structure of the shell layer of the toner of Comparative Example 6 was the same as the structure of the shell layer of the toner of Comparative Example 3 shown in FIG.

  When the surface of the toner of Comparative Example 7 was observed with an SEM, it was confirmed that the surface of the toner core particles was covered with resin fine particles in a spherical particle state. The cross section of the toner of Comparative Example 7 was observed using a TEM, and the structure of the shell layer of the toner of Comparative Example 7 was the same as the structure of the shell layer of the toner of Comparative Example 1 shown in FIG.

≪Evaluation≫
In the same manner as the toner of Example 1, the fixability and heat resistant storage stability of the toners of Examples 4 to 6, Comparative Example 6 and Comparative Example 7 were evaluated. The evaluation results for each toner are shown in Table 7.

  From Examples 4 to 6, Comparative Example 6, and Comparative Example 7, the toner comprises toner core particles containing at least a binder resin, and a shell layer having a predetermined structure that covers the entire surface of the toner core particles. Is formed by smoothing the outer surface of the resin fine particle layer to a predetermined degree, and when the cross section is observed using a transmission electron microscope, the inside of the shell layer is formed with respect to the surface of the toner core particles. When cracks in the substantially vertical direction are observed, and the average particle diameter of the resin fine particles is 45 nm or more and 300 nm or less, it can be seen that a toner excellent in fixability and heat resistant storage stability can be obtained.

[Example 7, Example 8, Comparative Example 8, and Comparative Example 9]
Example 7 and Example 8 were performed in the same manner as in Example 1 except that resin fine particles of the type shown in Table 8 were used, and the conditions of the powder processing apparatus were the rotation speed and processing time described in Table 8. The toners of Comparative Example 8 and Comparative Example 9 were obtained.

≪Confirmation of shell layer structure≫
According to the above method, the surfaces of the toners of Example 7, Example 8, Comparative Example 8 and Comparative Example 9 were observed using a scanning electron microscope (SEM), and the state of the surface of the shell layer covering the toner core particles It was confirmed. In addition, according to the above method, photographs of cross sections of the toners of Example 7, Example 8, Comparative Example 8, and Comparative Example 9 were taken using a transmission electron microscope (TEM). Using the obtained TEM photograph, the surface state of the shell layer, the internal state of the shell layer, and the shape of the internal surface of the shell layer were confirmed.

  When the surface of the toner of Example 7 and Example 8 is observed with a scanning electron microscope (SEM), toner particles having a particle diameter of 6 μm to 8 μm have a structure derived from spherical resin fine particles on the surface of the shell layer. Not observed. The cross sections of the toners of Examples 7 and 8 were observed using a TEM. The structure of the toner shell layers of Examples 7 and 8 is the same as that of the toner shell layers of Example 1 shown in FIG. The structure was similar.

  When SEM observation of the surface of the toner of Comparative Example 8 was performed, for toner particles having a particle size of 6 μm or more and 8 μm or less, a structure derived from spherical resin fine particles was not observed on the surface of the shell layer. Further, the cross section of the toner of Comparative Example 8 was observed using a TEM. The structure of the shell layer of the toner of Comparative Example 8 is the same as the structure of the shell layer of the toner of Comparative Example 3 shown in FIG. there were.

  When SEM observation was performed on the surface of the toner of Comparative Example 9, it was confirmed that the surface of the toner core particles was covered with resin fine particles in a spherical particle state. The cross section of the toner of Comparative Example 9 was observed using a TEM. The structure of the shell layer of the toner of Comparative Example 9 is the same as the structure of the shell layer of the toner of Comparative Example 1 shown in FIG. there were.

≪Evaluation≫
In the same manner as the toner of Example 1, the fixability of the toners of Example 7, Example 8, Comparative Example 8, and Comparative Example 9 was evaluated. Further, the heat resistant storage stability of the toners of Example 7, Example 8, Comparative Example 8, and Comparative Example 9 was evaluated in the same manner as the toner of Example 1 except that the storage temperature of the toner was changed to 50 ° C. The evaluation results for each toner are shown in Table 8.

From comparison between Example 7 and Example 8 and Comparative Example 8 and Comparative Example 9, the molecular weight (M _p ) at the maximum peak in the mass-based molecular weight distribution measured using gel permeation chromatography is When the toner core particles are coated with resin fine particles made of a resin having a weight average molecular weight (Mw) of 5,000 to 100,000 and having a weight average molecular weight (Mw) of the resin constituting the resin fine particles of 5,000 to 100,000 When the cross section of the toner is observed using a transmission electron microscope, it can be seen that it is easy to obtain a toner in which cracks in the direction substantially perpendicular to the surface of the toner core particles are observed inside the shell layer. A toner having a shell layer having such a structure is excellent in fixability and heat-resistant storage stability.

[Example 9 and Comparative Example 10]
Implemented in the same manner as in Example 1 except that the type of resin fine particles was changed to the type shown in Table 9 and that the conditions of the powder processing apparatus were changed to the rotation speed and processing time shown in Table 9. The toners of Example 9 and Comparative Example 10 were obtained.

≪Confirmation of shell layer structure≫
According to the above method, the surfaces of the toners of Example 9 and Comparative Example 10 were observed using a scanning electron microscope (SEM), and the state of the surface of the shell layer covering the toner core particles was confirmed. Further, according to the above method, photographs of cross sections of the toners of Example 9 and Comparative Example 10 were taken using a transmission electron microscope (TEM). Using the obtained TEM photograph, the surface state of the shell layer, the internal state of the shell layer, and the shape of the internal surface of the shell layer were confirmed.

  When the surface of the toner of Example 9 was observed with a scanning electron microscope (SEM), a structure derived from spherical resin fine particles was not observed on the surface of the shell layer of toner particles having a particle diameter of 6 μm or more and 8 μm or less. . The cross section of the toner of Example 9 was observed using a TEM. The structure of the toner shell layer of Example 9 is the same as that of the toner shell layer of Example 1 shown in FIG. there were.

  When SEM observation of the surface of the toner of Comparative Example 10 was performed, for toner particles having a particle size of 6 μm or more and 8 μm or less, a structure derived from spherical resin fine particles was not observed on the surface of the shell layer. The cross section of the toner of Comparative Example 10 was observed using a TEM. The structure of the shell layer of the toner of Comparative Example 10 is the same as the structure of the shell layer of the toner of Comparative Example 3 shown in FIG. there were.

≪Evaluation≫
In the same manner as the toner of Example 1, the fixability of the toners of Example 9 and Comparative Example 10 was evaluated. In addition, the heat resistant storage stability of the toners of Example 9 and Comparative Example 10 was evaluated in the same manner as the toner of Example 1 except that the storage temperature of the toner was changed to 45 ° C. The evaluation results for each toner are shown in Table 9.

From a comparison between Example 8 and Example 9 and Comparative Example 9 and Comparative Example 10, the temperature (T ₁ ) when the melt viscosity is 1.0 × 10 ⁵ Pa · s is 110 ° C. or higher and 160 ° C. or lower. When the toner core particles are coated with resin fine particles made of a resin having a temperature (T ₂ ) of 130 ° C. or more and 170 ° C. or less when the melt viscosity is 1.0 × 10 ⁴ Pa · s. When the cross section is observed using a scanning electron microscope, it can be seen that it is easy to obtain a toner in which cracks in a direction substantially perpendicular to the surface of the toner core particles are observed inside the shell layer. A toner having a shell layer having such a structure is excellent in fixability and heat-resistant storage stability.

101 Toner for electrostatic latent image development 102 Toner core particle 103 Shell layer 104 Crack 105 Projection

Claims (4)

A production process of toner core particles containing at least a binder resin;
A method for producing a toner for developing an electrostatic latent image, comprising the step of producing a shell layer covering the toner core particles,
The manufacturing process of the shell layer includes the following processes I) and II):
I) A step of forming a resin fine particle layer that covers the entire surface of the toner core particle by adhering spherical resin fine particles to the surface of the toner core particle so as not to overlap the surface of the toner core particle in the vertical direction. When,
II) applying an external force to the outer surface of the resin fine particle layer and deforming the resin fine particles in the resin fine particle layer to smooth the outer surface of the resin fine particle layer to form a shell layer; Including
When the surface of the toner for developing an electrostatic latent image is observed using a scanning electron microscope, a structure derived from the spherical resin fine particles in the shell layer is observed for toner particles having a particle diameter of 6 μm or more and 8 μm or less. not,
When observing a cross section of the electrostatic latent image developing toner using a transmission electron microscope, the inside of the shell layer is an interface between the resin fine particles in a direction substantially perpendicular to the surface of the toner core particles. In addition, cracks derived from the average particle diameter of the resin fine particles are observed, and convex portions of the shell layer are observed on the interface between the toner core particles and the shell layer and between the two cracks. ,
The resin constituting the resin fine particles has a molecular weight (M _p ) at a maximum peak in a mass-based molecular weight distribution measured using gel permeation chromatography of 5,000 or more and 100,000 or less,
A method for producing a toner for developing an electrostatic latent image, wherein a resin constituting the resin fine particles has a mass average molecular weight (Mw) of 5,000 or more and 100,000 or less . Wherein the resin constituting the resin fine particles, the melt viscosity is at 1.0 × ¹⁰ 5 temperature at a Pa · s _{(T 1)} below 160 ° C. 110 ° C. or more and a melt viscosity of 1 · 0 × 10 ^The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein the temperature (T ₂ ) at ⁴ Pa · s is 130 ° C. or higher and 170 ° C. or lower. A production process of toner core particles containing at least a binder resin;
A method for producing a toner for developing an electrostatic latent image, comprising the step of producing a shell layer covering the toner core particles,
The manufacturing process of the shell layer includes the following processes I) and II):
I) A step of forming a resin fine particle layer that covers the entire surface of the toner core particle by adhering spherical resin fine particles to the surface of the toner core particle so as not to overlap the surface of the toner core particle in the vertical direction. When,
II) applying an external force to the outer surface of the resin fine particle layer and deforming the resin fine particles in the resin fine particle layer to smooth the outer surface of the resin fine particle layer to form a shell layer; Including
When the surface of the toner for developing an electrostatic latent image is observed using a scanning electron microscope, a structure derived from the spherical resin fine particles in the shell layer is observed for toner particles having a particle diameter of 6 μm or more and 8 μm or less. not,
When observing a cross section of the electrostatic latent image developing toner using a transmission electron microscope, the inside of the shell layer is an interface between the resin fine particles in a direction substantially perpendicular to the surface of the toner core particles. In addition, cracks derived from the average particle diameter of the resin fine particles are observed, and convex portions of the shell layer are observed on the interface between the toner core particles and the shell layer and between the two cracks. ,
The resin constituting the resin fine particles has a melt viscosity of 1.0 × 10 ⁵ Temperature at Pa · s (T ₁ ) Is 110 ° C. or higher and 160 ° C. or lower, and the melt viscosity is 1.0 × 10 ⁴ Temperature at Pa · s (T ₂ ) Is a method for producing a toner for developing an electrostatic latent image having a temperature of 130 ° C. or higher and 170 ° C. or lower. The method for producing a toner for developing an electrostatic latent image according to any one of claims 1 to 3, wherein a thickness of the shell layer formed by the production process of the shell layer is 0.045 µm or more and 0.3 µm or less. .