JP6137978B2 - 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 a method such as 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. A high-quality image can be obtained by transferring the formed toner image to a recording medium. Usually, in the toner applied to such an electrophotographic method, a toner resin such as a colorant, a charge control agent, a release agent, and a magnetic material is mixed with a binder resin such as a thermoplastic resin. Thereafter, toner particles (toner mother particles) having an average particle diameter of 5 μm or more and 10 μm or less obtained through kneading, pulverization, and classification steps are used. For the purpose of imparting fluidity and suitable charging performance to the toner particles and facilitating cleaning of the toner particles from the surface of the photosensitive drum, an inorganic fine powder such as silica or titanium oxide is added to the toner base particles. Externally attached.

  As such a toner, toner core particles using a binder resin having a low melting point are included in the toner core particles for the purpose of improving low-temperature fixability, improving storage stability at high temperatures, and improving blocking resistance. Conventionally, a toner including toner particles having a core-shell structure, which is coated with a shell material made of a resin having a Tg higher than the glass transition point (Tg) of the binder resin is used.

  As the toner including toner particles having such a core-shell structure, toner core particles including a polyester resin or a resin in which a polyester resin and a vinyl resin are combined, styrene, and a (meth) acrylate including a polyalkylene oxide unit are used. There has been proposed a toner including toner particles having a core-shell structure including a shell layer made of a shell material containing a copolymer with a monomer of a system (Patent Document 1). The toner particles of the core-shell structure contained in the toner of Patent Document 1 are formed by coating the surface of the toner core particles with resin fine particles dispersed in an aqueous medium in the presence of an organic solvent such as ethyl acetate. Yes.

JP 2011-70179 A

  However, in the shell layer provided in the toner core particles contained in the toner described in Patent Document 1, since the contact portions between the resin fine particles are dissolved in the organic solvent, there are almost no gaps between the resin particles, and the resin particles This is a homogeneous film with the shape remaining. For this reason, when an image is formed using the toner described in Patent Document 1, the shell layer may not be easily destroyed even when pressure is applied to the toner particles when the toner particles are fixed on the recording medium. When the shell layer is not easily broken, it is difficult to satisfactorily fix the toner particles on the recording medium.

  Further, since the toner described in Patent Document 1 is manufactured using an organic solvent, the toner described in Patent Document 1 requires a great deal of labor and energy for the treatment and purification of the waste solvent after the toner is manufactured. Therefore, there is a problem that the toner cannot always be efficiently produced by a simple process.

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

The electrostatic latent image developing toner of the present invention includes toner core particles containing at least a binder resin,
An electrostatic latent image developing toner comprising toner particles comprising a shell layer covering the toner core particles,
The shell layer comprises an inner layer covering the toner core particles and an outer layer covering the inner layer;
The inner layer is formed using spherical first fine particles,
The outer layer is formed using spherical second fine particles,
The material of the first fine particles and the second fine particles is a resin,
The average particle size of the first fine particles is 100 nm or more and 300 nm or less,
The average particle size of the second fine particles is 50 nm or less,
When the surface of the toner particles is observed using a scanning electron microscope, a structure derived from the spherical second fine particles is not observed on the surface of the shell layer of the toner particles having a particle diameter of 6 μm or more and 8 μm or less. ,
When the cross section of the toner particle is observed using a transmission electron microscope, a crack derived from the interface between the first fine particles is observed inside the inner layer.

  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 and can be easily and efficiently produced.

FIG. 4 is a schematic view showing a part of a cross section of toner particles contained in the toner of the present invention. It is a schematic diagram showing a process of forming toner particles contained in the toner of the present invention. It is a figure explaining the measuring method of the softening point using an elevated flow tester. 3 is a transmission electron micrograph of a cross section of toner particles contained in the toner of Example 1. FIG. 10 is a transmission electron micrograph of a cross section of toner particles contained in a toner of Comparative Example 7. 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 toner particles contained in the electrostatic latent image developing toner (hereinafter also simply referred to as toner) of the present invention comprise toner core particles containing at least a binder resin and a shell layer covering the toner core particles. The shell layer includes an inner layer that covers the toner core particles and an outer layer that covers the inner layer. The inner layer is made of resin, and is formed using spherical first fine particles having an average particle diameter of 100 nm to 300 nm. The outer layer is made of resin and is formed using spherical second fine particles having an average particle diameter of 50 nm or less. When the surface of the toner particles contained in the toner of the present invention is observed using a scanning electron microscope, toner particles having a particle diameter of 6 μm or more and 8 μm or less are derived from spherical second fine particles on the surface of the shell layer. Is not observed. When observing the cross section of the toner particles contained in the toner using a transmission electron microscope, the inside of the inner layer contained in the shell layer is located at the interface between the first fine particles in a direction substantially perpendicular to the surface of the toner core particles. Derived cracks are observed. Hereinafter, the toner structure and the toner material will be described.

[Toner structure]
In the toner particles contained in the toner of the present invention, the entire surface of the toner core particles is coated with a shell layer. The state of the shell layer, which is the surface of the toner particles, can be confirmed using a scanning electron microscope (SEM). The degree of smoothing of the shell layer and the internal structure of the shell layer provided in the toner particles contained in the toner can be confirmed by observing the cross section of the toner particles using a transmission electron microscope (TEM). FIG. 1 shows a schematic diagram of a cross section of a toner observed using a TEM for a preferred embodiment of the toner particles contained in the toner of the present invention.

  As shown in FIG. 1, in the toner particle 101, the shell layer 103 covers the entire surface of the toner core particle 102. The shell layer 103 includes an inner layer 104 and an outer layer 105. As shown in FIG. 2, after the first fine particles 201 are attached to the toner core particles 102, the shell layer 103 further covers the surface of the first fine particles 201 with the second fine particles 202, and then the second resin fine particles 202. At the same time, the first fine particles 201 are deformed by an external force to smooth the outer surface of the layer composed of the second fine particles 202.

  Thus, the toner according to the present invention can be manufactured by a simple process that does not use an organic solvent.

  As shown in FIG. 2C, the shell layer 103 generally includes a first fine particle layer in which the first fine particles 201 are arranged in a direction perpendicular to the surface of the toner core particles 102, and a second fine particle 202. The second fine particle layer arranged without overlapping in the vertical direction with respect to the surface of the first fine particle layer is formed by being deformed by an external force. For this reason, the thickness of the shell layer 103 is usually determined by the particle diameter of the first fine particles 201 and the particle diameter of the second fine particles 202. The thickness of the shell layer is preferably from 100 nm to 350 nm, more preferably from 100 nm to 250 nm, and particularly preferably from 120 nm to 200 nm. As will be described later, when the shell layer 103 has the convex portion 106, the thickness of the shell layer 103 may not be uniform. As described above, in the case where the thickness of the shell layer 103 is not uniform, in the claims and the specification of the present application, the thickness of the thickest portion of the shell layer 103 is referred to as “the thickness of the shell layer”. To do.

  When an image is formed using toner containing toner particles having a shell layer that is too thick, the shell layer is not easily destroyed even when pressure is applied to the toner particles when fixing the toner particles 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 it is difficult to fix the toner particles on the recording medium in a low temperature range. On the other hand, a shell layer that is too thin has low strength. When the strength of the shell layer is low, the shell layer may be broken by an impact applied in a situation such as transportation. When the toner is stored at a high temperature, toner particles in which at least a part of the shell layer in the toner is broken may be aggregated together with other toner particles. This is because a component such as a release agent may ooze out on the surface of the toner particles through the portion where the shell layer is broken under high temperature conditions.

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

  As shown in FIG. 1, the shell layer 103 preferably has a convex portion 106 on the interface between the toner core particle 102 and the shell layer 103 and between two cracks 107 existing in the inner layer 104. When the shell layer 103 has such convex portions 106, the contact area between the toner core particles 102 and the shell layer 103 is larger than when the shell layer 103 does not have the convex portions 107. For this reason, when the shell layer 103 has the convex portion 106, the toner core particle 102 and the shell layer 103 are in good contact with each other, and the shell layer 103 is difficult to peel from the toner core particle 102. For this reason, the toner including the toner particles 101 including the shell layer 103 having the convex portions 106 is excellent in heat resistant storage stability.

The shell layer composed of an inner layer formed using spherical first fine particles and an outer layer formed using spherical second fine particles is preferably
I) A step of forming the first fine particle layer covering the entire surface of the toner core particle by adhering the spherical first fine particle to the surface of the toner core particle so as not to overlap the surface of the toner core particle in the vertical direction.
II) A second fine particle that covers the entire surface of the first fine particle layer by adhering the spherical second fine particle to the surface of the first fine particle layer so as not to overlap the surface of the first fine particle layer. And III) applying external force from the outer surface of the second fine particle layer to the first fine particle layer and the second fine particle layer, and from the resin contained in the first fine particle layer and the second fine particle layer. Deforming the spherical fine particles to form a shell layer composed of an inner layer of a predetermined shape and an outer layer made uniform and smooth,
Formed using a method including:

The following steps 1) and 2):
1) A step of attaching spherical first fine particles to the surface of the toner core particles so as not to overlap in a direction perpendicular to the surface of the toner core particles to form a first fine particle layer covering the entire surface of the toner core particles; And 2) applying an external force to the outer surface of the first fine particle layer to deform spherical fine particles made of a resin contained in the first fine particles,
According to the method including the toner, a toner including toner core particles having a smooth outer surface and a shell layer in which a crack derived from the interface of the first fine particles is observed can be prepared.

  The toner particles prepared by such a method include a shell layer having a structure similar to that of the shell layer included in the toner particles contained in the toner according to the present invention. For this reason, the toner manufactured by the method including the above steps 1) and 2) is excellent in low-temperature fixability and heat-resistant storage stability like the toner according to the present invention.

  However, when a shell layer having a structure similar to the shell layer provided in the toner particles included in the toner according to the present invention is formed using only the first fine particles, the first fine particle layer on the surface of the toner core particles is formed into a desired shape. There is a problem that it takes a very long time to deform.

  The degree of smoothing of the shell layer is used to form a shell layer on the outer 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 of the toner particles is observed using a scanning electron microscope. It is sufficient that the structure derived from the spherical second fine particles 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, a shell layer that covers the toner core particles in a desired state is formed in most of the toner particles contained in the toner. When the state of the outer surface of the shell layer is confirmed using 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 103 shown in FIG. 1, the entire surface of the toner core particle 102 is covered with the shell layer 103. Since the shell layer 103 includes an inner layer 104 that covers the surface of the toner core particle 102 and an outer layer 105 that covers the surface of the inner layer 104 and has a smooth outer surface, the toner particle 101 is stored at a high temperature. At this time, it is difficult for the component such as the release agent to ooze out to the surface of the toner particle 101.

  A void (crack) 107 exists inside the inner layer 104 in the shell layer 103. For this reason, when a pressure is applied to the toner particles when fixing the toner particles on the recording medium, the shell layer 103 is likely to be broken starting from the crack 107 in the inner layer 104. When the shell layer 103 is quickly broken, the softening or melting of components such as the binder resin and the release agent contained in the toner core particles 102 proceeds quickly, so that the toner particles 101 are recorded on the recording medium in a low temperature range. Easy to fix on top.

[Toner material]
The toner is composed of toner core particles containing at least a binder resin, and an inner layer and an outer layer, and a shell layer that covers 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. If desired, the toner particles contained in the toner may have a surface treated with an external additive. The toner can be mixed with a desired carrier and used as a two-component developer.

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

[Binder resin]
The toner core particles include 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. Of these resins, polystyrene resins and polyester resins are preferable from the viewpoints of dispersibility of the colorant in the binder resin, chargeability of the toner, and fixing properties to the paper. Hereinafter, the polystyrene resin and the polyester resin will be described.

  The polystyrene resin may be a styrene homopolymer or a copolymer of styrene and 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 condensation polymerization or co-condensation polymerization 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, 1,2,4 Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid , Trivalent or higher carboxylic acids such as 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 is used as a magnetic one-component toner, the binder resin has one or more functional groups selected from the group consisting of a hydroxy group, a carboxyl group, an amino group, and an epoxy group (glycidyl group) in the molecule. It is preferable to use a resin. 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, a thermoplastic resin is preferable because it is easy to obtain a toner having good fixability to paper, but the thermoplastic resin may be used together with a crosslinking agent or a thermosetting resin. By adding a cross-linking agent or a thermosetting resin and introducing a partially cross-linked structure into the binder resin, the heat-resistant storage stability and durability of the toner are improved without deteriorating the toner fixability. be able to. When the thermosetting resin is used together with the thermoplastic resin, the amount of the crosslinked part (gel amount) of the binder resin extracted using a Soxhlet extractor is preferably 10% by mass or less based on the mass of the binder resin. 0.1 mass% or more and 10 mass% or less are more preferable.

  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. It is done. 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. Toner produced using toner core particles containing a binder resin having a glass transition point that is too high tends to have low-temperature fixability. A toner produced using toner core particles containing a binder resin having a glass transition point that is too low tends to have low heat-resistant storage stability.

  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 a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be determined from the endothermic curve of the binder resin obtained by measurement under normal temperature and humidity under the measurement conditions of a temperature range of 25 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min. it can.

  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 a standard polystyrene resin using gel permeation chromatography (GPC).

  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. preferable. 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. Regarding the polystyrene-based resin having such a molecular weight distribution, the ratio (Mw / Mn) of the number average molecular weight (Mn) to the mass average molecular weight (Mw) is preferably 10 or more. By using a binder resin having a peak in each of a low molecular weight region and a high molecular weight region 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, 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 preparing the toner using toner core particles containing such a release agent, 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, one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax are used from the viewpoint of compatibility between the binder resin and the release agent. Preferably used. When a polystyrene resin is used as the binder resin, Fischer-Tropsch wax and / or paraffin wax is preferably used from the viewpoint of compatibility between the binder resin and the release agent.

  Fischer-Tropsch wax is a straight-chain hydrocarbon compound having a low content of iso (iso) structure molecules and side chains, which is produced by using a Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

  Among Fischer-Tropsch waxes, those having a mass average molecular weight of 1,000 or more and an endothermic peak bottom temperature observed by DSC measurement in the range of 100 ° C. or more and 120 ° C. or less are more preferable. As such Fischer-Tropsch wax, Sazol wax C1 (bottom temperature of endothermic peak: 106.5 ° C.), Sazol wax C105 (bottom temperature of endothermic peak: 102.1 ° C.), available from Sazol, And wax such as wax SPRAY (bottom temperature of endothermic peak: 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. When an image is formed using toner containing toner particles produced using toner core particles containing an excessive amount of a release agent, a desired effect can be obtained with respect to suppression of occurrence of offset and image smearing in the formed image. It may not be possible. A toner containing toner particles produced using toner core particles containing an excessive amount of a release agent may be easily fused with each other and may have low heat-resistant storage stability.

(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 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 and decyltrimethylammonium chloride Such quaternary ammonium salts are mentioned. 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. These resins may be oligomers or polymers.

  Among the resins that can be used as the positively chargeable charge control agent, a styrene-acrylic resin having a quaternary ammonium salt as a functional group is more preferable because the charge amount can be easily adjusted to a value within a desired range. In the styrene-acrylic resin having a quaternary ammonium salt as a functional group, specific examples of a preferable acrylic comonomer copolymerized with a styrene unit 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. When using a toner having a low charge control agent content, it is difficult to stably charge the toner to a predetermined polarity, so that the image density of the formed image falls below a desired value or the image density of the formed image is maintained for a long time. It may be difficult to maintain. Further, when the content of the charge control agent in the toner core particles is too small, the charge control agent is difficult to be uniformly dispersed in the binder resin. For this reason, when an image is formed using a toner containing toner particles produced using toner core particles containing an excessive amount of a charge control agent, the formed image is likely to be fogged or a latent component caused by the toner component is formed. Contamination of the image carrier is likely to occur. When forming an image using toner containing toner particles produced using toner core particles containing an excessive amount of charge control agent, contamination of the latent image carrier caused by the toner component and deterioration of the environmental resistance of the toner As a result, image defects are likely to occur in the formed image due to charging failure under high temperature and high humidity.

[Colorant]
The toner core particles may contain a colorant as necessary. A known pigment or dye can be used as a colorant in accordance with the color of the toner. Specific examples of colorants 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, nickel titanium yellow, and Naples yellow. , Yellow pigments such as 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; Orange pigments such as Orange, Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, and Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Red, Mercury Sulfide Cad Red pigments such as Um, Permanent Red 4R, Rizor 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; Purple pigments such as purple, fast violet B and methyl violet lake; blue pigments such as bitumen, cobalt blue, alkali blue lake, Victoria blue partial chlorinated, fast sky blue, indanthrene blue BC and phthalocyanine blue; chromium Green pigments such as green, chromium oxide, pigment green B, malachite green lake, and final yellow green G; zinc white, titanium oxide, antimony white, and White pigments such as zinc; 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.

  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 core particles may contain magnetic powder as necessary. A toner containing magnetic powder in a binder resin can be used as a magnetic one-component developer. As magnetic powder, iron such as ferrite and magnetite; ferromagnetic metal such as cobalt and nickel; alloy containing iron and / or ferromagnetic metal; compound containing iron and / or ferromagnetic metal; heat treatment Ferromagnetic alloys that have been subjected to ferromagnetization treatment such as: 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 a toner is prepared using magnetic powder having a particle diameter in such a range, 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 using toner containing toner particles produced using toner core particles containing an excessive amount of magnetic powder, it is difficult to form an image with a desired image density or to fix the toner when forming an image continuously for a long period of time. May be extremely reduced. When an image is formed using toner containing toner particles produced using toner core particles containing an excessive amount of magnetic powder, the formed image is likely to be fogged or formed when printing over a long period of time. In some cases, the image density is likely to decrease.

[First fine particles and second fine particles]
The shell layer is composed of an inner layer and an outer layer. The inner layer is formed using first fine particles that are resin fine particles having an average particle diameter of 100 nm to 300 nm. The outer layer is formed using second fine particles having an average particle diameter of 50 nm or less. The resin fine particles used as the first fine particles and the second fine particles are preferably fine particles made of a polymer of a monomer having an unsaturated bond because a shell layer having a predetermined structure can be formed. Monomers having an unsaturated bond are polymerized in the presence of a surfactant at a critical micelle concentration (CMC) or higher, or in the presence of a surfactant at a concentration below CMC or in the absence of a surfactant. Also good. As a method for polymerizing a monomer having an unsaturated bond, a soap-free emulsion polymerization method in which polymerization is performed in the presence of a surfactant having a concentration lower than CMC or in the absence of a surfactant is preferable. This is because if resin fine particles are produced by a soap-free emulsion polymerization method, the particle diameters are uniform, and resin fine particles that contain little or no surfactant can be prepared.

  The kind of monomer having an unsaturated bond is not particularly limited as long as a resin having sufficient physical properties as a shell layer can be synthesized. 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. 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 when producing a resin, positive chargeability can be imparted to the resulting resin. When a vinyl monomer having a fluorine-substituted hydrocarbon group is used in producing the 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 N-butyl acid, isobutyl (meth) acrylate, propyl (meth) acrylate, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylates such as 2-chloroethyl (meth) acrylate, phenyl (meth) acrylate, and methyl α-chloroacrylate; (meth) acrylic acid derivatives such as acrylonitrile; vinyl methyl ether, Vinyl ethers such as vinyl ethyl ether and 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, methacrylonitrile, and (meth) acrylamide. Specific examples of the N-vinyl compound include N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone. Preferable examples of the amino (meth) acrylic monomer include compounds represented by the following formula.
^{_{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 represents Q. C 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 group, 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, 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 phenyl 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- Examples include di-n-butylaminophenyl) methyl (meth) acrylamide, (pN-laurylaminophenyl) methyl (meth) acrylamide, and (pN-stearylaminophenyl) methyl (meth) acrylamide.

  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, Fluoroalkyl (meth) acrylates such as 3,4,4,5,5-octafluoroamyl acrylate, and 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate; trifluorochloroethylene, vinylidene fluoride, three Examples include fluoroolefins such as ethylene fluoride, tetrafluoroethylene, trifluoropropylene, hexafluoropropene, and hexafluoropropylene. Among these, fluoroalkyl (meth) acrylates are preferable.

  As an addition polymerization method of the 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.

  For the polymerization of the vinyl monomers described above, potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4 Known polymerization initiators such as -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 method for producing resin fine particles by an emulsion polymerization method, a soap-free emulsion polymerization method in which polymerization is performed in the presence of a surfactant having a concentration lower than CMC or in the absence of a surfactant is preferable. In the soap-free emulsion polymerization method, an initiator radical generated in an aqueous phase polymerizes a monomer slightly dissolved in the aqueous phase. As the polymerization proceeds, particle nuclei of insolubilized resin fine particles are formed. When the soap-free emulsion polymerization method is used, resin fine particles having a narrow particle size distribution are obtained, and the average particle size of the resin fine particles can be controlled in the range of 0.03 μm to 1 μm. When soap-free emulsion polymerization is performed, the average particle size of the resin fine particles produced by adding a small amount of a surfactant such as a cationic surfactant (for example, dodecyl ammonium chloride) to the reaction system and increasing or decreasing the amount added. The diameter can be controlled. Specifically, the average particle diameter of the resin fine particles obtained is reduced by increasing the amount of the surfactant used. As described above, when the soap-free emulsion polymerization method is used, it is easy to control the average particle diameter of the resin fine particles to be produced, and resin fine particles having a uniform particle diameter can be obtained.

  By using resin fine particles having a uniform particle size obtained by the soap-free emulsion polymerization method as the first fine particles or the second fine particles, the adhesion of the first fine particles to the toner core particles and the first fine particle layer formed on the surface of the toner core particles The variation in the adhesion force of the second fine particles to the surface can be reduced, so that a uniform inner layer and an outer layer can be formed. As a result, a uniform shell layer having a uniform thickness is formed. In the soap-free emulsion polymerization method, resin fine particles are produced by polymerization in the presence of a surfactant having a concentration lower than CMC or in the absence of a surfactant. That is, in the soap-free emulsion polymerization method, a surfactant is not used or only a small amount is used. For this reason, by forming the shell layer using resin fine particles obtained by the soap-free emulsion polymerization method, it is possible to form a shell layer that is not easily affected by moisture.

  The resin fine particles used as the first fine particles or the second fine particles may contain components such as the above-described colorant and charge control resin, if necessary. When either or both of the first fine particles and the second 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 used as the first fine particles or the second 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.

  By using the first fine particles or the second fine particles made of a resin having a glass transition point within such a range, it is easy to form cracks in the direction perpendicular to the toner core particles inside the inner layer, and the thickness is uniform. An inner layer and an outer layer can be formed.

  The glass transition point of the resin constituting the resin fine particles used as the first fine particles or the second fine particles can be obtained 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, a method based on JIS K 7121-1987 is used to measure the endothermic curve of the resin that constitutes the resin fine particle. The glass transition point can be determined. 10 mg of a measurement sample 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 under normal 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. higher than the softening point of the binder resin. When the shell layer is formed using resin fine particles made of a resin having a softening point in such a range, 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. If it does so, the convex part derived from the shape of the resin fine particle before changing into a shell layer will be easy to be formed in the inner surface of a shell layer.

  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 height of 2 cm. The obtained pellet is set in a flow tester, and resin fine particles are loaded under the conditions of a plunger load: 30 kg, a die hole diameter: 1 mm, a die length: 1 mm, a heating rate of 4 ° C./min, and a measurement temperature range of 70 to 160 ° C. The softening point (Tm) of the constituent resin 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 measurement.

How to read 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 first fine particles is 100 nm to 300 nm, preferably 100 nm to 250 nm, and more preferably 100 nm to 200 nm. When the surface of the toner core particles is coated with the inner layer using the first fine particles having such a particle size, the first fine particles can be transformed into a desired state in a short time. That is, by forming the inner layer using the first fine particles having such a particle size, a toner having excellent low-temperature fixability and heat-resistant storage stability can be produced in a short time.

  The average particle size of the second fine particles is 50 nm or less, preferably 20 nm or more and 50 nm or less, and more preferably 30 nm or more and 50 nm or less. By forming an outer layer that covers the surface of the inner layer using the second fine particles having such a particle size, the second fine particles are deformed in a short time, and the surface of the toner particles having a particle size of 6 μm or more and 8 μm or less is formed. When observing with an electron microscope, an outer layer can be formed in a short time on the surface so that a granular structure derived from the second fine particles is not observed. Further, the thin outer layer formed using the second fine particles having such a particle diameter is easily broken when fixing the toner particles. Accordingly, a toner having excellent low-temperature fixability and heat-resistant storage stability can be produced in a short time by forming the outer layer using the second fine particles having such a particle size.

  The average particle diameter of the resin fine particles used as the first fine particles or the second fine particles can be adjusted using a method such as a known pulverization method and a classification method in addition to the method of adjusting the polymerization conditions as described above. 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 (for example, 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 20,000 or more and 1,500,000 or less. The mass average molecular weight (Mw) of the resin constituting the resin fine particles can be measured using gel permeation chromatography according to a conventionally known method.

  The use amount of the first fine particles and the second fine particles is such that the surface of the toner core particles can be covered with the first fine particle layer arranged in a single layer without overlapping the first fine particles in the vertical direction, and the surface of the first fine particle layer is covered. In consideration of the particle diameter of the toner core particles and the particle diameters of the first fine particles and the second fine particles so that the second fine particles can be coated with the second fine particle layer arranged in a single layer without overlapping in the vertical direction, Determined. Typically, the amount of the first fine particles used is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the toner core particles. The amount of the second fine particles used is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner core particles.

(External additive)
The toner particles composed of the toner core particles and the shell layer covering the surface of the toner core particles may be treated with an external additive on the surface, if desired. 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 more preferably 0.2% by mass or more and 5% by mass or less with respect to the total mass of the toner base particles. Toner particles treated with an excessive amount of external additive have low hydrophobicity. A toner containing toner particles having low hydrophobicity is easily affected by water molecules in the air under a high temperature and high humidity environment. When using toner containing toner particles treated with an excessive amount of external additives, such as a decrease in image density of the formed image due to an extreme decrease in the charge amount of the toner particles, and a decrease in fluidity of the toner particles Problems are likely to occur. When the toner processed with an excessive amount of the external additive is used, there is a possibility that the density of the formed image is lowered due to excessive charge-up of the toner.

[Carrier]
The toner 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.

  A suitable carrier when the toner is a two-component developer includes a carrier core material coated with a resin. Specific examples of the carrier core material include particles of metal such as iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, and cobalt, and these materials and manganese, zinc, and aluminum. Particles of alloys with such metals, particles of alloys 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 Ceramics particles such as barium titanate, lithium titanate, lead titanate, lead zirconate, and lithium niobate, high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt And a resin carrier in which the magnetic particles are dispersed in a resin.

  Specific examples of the resin for coating the carrier core material include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorinated polyethylene, and polypropylene). ), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, and 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 measured using an electron microscope 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 carrier composition and surface structure, but typically it is preferably 2400 kg / m ³ or more and 3000 kg / m ³ or less.

  When the toner is used as a two-component developer, the toner content is preferably 1% by mass or more and 20% by mass or less, and more preferably 3% by mass or more and 15% by mass or less with respect to the mass of the two-component developer. By setting the toner content in the two-component developer in such a range, an image having an appropriate image density can be continuously formed, and toner scattering from the developing device is suppressed. Contamination and toner adhesion to transfer paper can be suppressed.

[Method for producing toner for developing electrostatic latent image]
The method for producing the toner of the present invention is not particularly limited as long as it can produce toner containing toner particles composed of toner core particles and a shell layer having a predetermined structure. If necessary, the toner core particles coated with the shell layer may be used as toner base particles, and an external addition process may be performed to attach an external additive to the surface of the toner base particles. As a preferred method for producing the toner of the present invention, a method for producing toner core particles, a method for forming a shell layer, and a method for external addition will be described below in order.

[Method for producing toner core particles]
The method for producing the toner core particles is not particularly limited as long as an arbitrary component such as a colorant, a release agent, a charge control agent, and magnetic powder can be well dispersed in the binder resin. As a specific example of a suitable method for producing toner core particles, a binder resin and a toner component such as a colorant, a release agent, a charge control agent, and magnetic powder are mixed using a mixer, 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 single screw or twin screw extruder, and the cooled kneaded material 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 forming the first fine particle layer covering the entire surface of the toner core particle by adhering the spherical first fine particle to the surface of the toner core particle so as not to overlap the surface of the toner core particle in the vertical direction.
II) A second fine particle that covers the entire surface of the first fine particle layer by adhering the spherical second fine particle to the surface of the first fine particle layer so as not to overlap the surface of the first fine particle layer. And III) applying external force from the outer surface of the second fine particle layer to the first fine particle layer and the second fine particle layer, and from the resin contained in the first fine particle layer and the second fine particle layer. Deforming the spherical fine particles to form a shell layer composed of an inner layer of a predetermined shape and an outer layer made uniform and smooth,
A shell layer is formed using a method including:

  As a method for forming the shell layer using the resin fine particles, a method using a mixing apparatus capable of mixing the toner core particles, the first fine particles, and the second fine particles under dry conditions is preferable. As a specific method, the first fine particle layer or the second fine particle layer on the surface of the toner core particle is obtained while attaching the first fine particle or the second fine particle to the surface of the toner core particle or the first fine particle layer covering the toner core particle. And a method of forming a shell layer on the surface of the toner core particles using a mixing device capable of applying a mechanical external force to the toner. The mechanical external force is caused by the shear between the toner core particles or between the toner core particles and the inner wall of the device, the rotor, or the stator when the toner core particles move at high speed in a narrow space in the mixing device. In addition, the impact force applied to the toner core particles due to the shearing force applied to the toner core particles and the collision between the toner core particles or the collision between the toner core particles and the inner wall of the apparatus can be mentioned.

  A more specific method will be described with reference to FIG. First, by mixing the toner core particles 102 and the first fine particles 201 in the mixing device, the first fine particles 201 overlap in a direction perpendicular to the surface of the toner core particles 102 as shown in FIG. The first fine particles 201 are uniformly attached to the surface of the toner core particles so as not to become misaligned. When the toner core particle 102 having a large particle diameter and the first fine particle 201 having a small particle diameter are in contact with each other, a surface is formed between the surface of the toner core particle 102 that can be regarded as a flat surface and the surface of the first fine particle 201. And contact with the surface occurs. Therefore, the first fine particles 201 can adhere to the toner core particles 102. On the other hand, when the first microparticles 201 come into contact with each other, the surfaces that are the curved surfaces of the two first microparticles 201 come into contact with each other. Therefore, in the process of attaching the first fine particles 201 to the toner core particles 102, even if the first fine particles 201 further adhere to the first fine particles 201 attached to the surface of the toner core particles 102, the mixing device The first fine particles 201 adhering to the first fine particles 201 are easily separated from the first fine particles 201 adhering to the toner core particles 102 by a mechanical external force applied to the adhering toner core particles 102. For this reason, in the method described below, the toner core particles 102 are coated with the first fine particles 201 so that the first fine particles 201 do not overlap in the direction perpendicular to the surface of the toner core particles 102.

  When the first fine particles 201 are attached to the toner core particles 201, the mechanical external force described above is applied to the first fine particle layer on the surface of the toner core particles 102. 2B, the first fine particles 201 are deformed while being embedded in the toner core particles 102 by the action of the mechanical external force, and the gaps between the first fine particles 201 are closed. The time required for the step of mixing the toner core particle 102 and the first fine particle 201 to form the first fine particle layer on the surface of the toner core particle 102 is not particularly limited as long as the first fine particle layer in a desired state can be formed. It is preferably from 20 minutes to 20 minutes, more preferably from 2 minutes to 15 minutes, and particularly preferably from 3 minutes to 10 minutes.

  Next, the second fine particles 202 are added to the toner core particles 102 covered with the first fine particle layer in the state shown in FIG. The toner core particles 102 coated with the first fine particle layer and the second fine particles 202 are mixed in a mixing device, and as shown in FIG. A second fine particle layer that covers the first fine particle layer is formed so that the second fine particles 202 do not overlap in the direction perpendicular to the surface of the fine particle layer.

  After the first fine particle layer and the second fine particle layer are formed on the surface of the toner core particle 102, the interface between the second fine particles 202 becomes unclear for the second fine particles 202 in the second fine particle layer by the external force applied by the mixing device. The surface of the second fine particle layer is smoothed by being deformed to the extent. At this time, while the smoothing proceeds in the second fine particle layer, the gap between the first fine particles 201 is eliminated inside the first fine particle layer while the boundary surface between the first fine particles 201 remains. The first fine particles 201 are deformed. By doing so, as shown in FIG. 2D, the surface of the toner core particle 102 is substantially perpendicular to the surface of the toner core particle 102, which is derived from the interface between the first microparticles 201. A shell layer 103 composed of an inner layer 104 having cracks 107 and a thin and uniform outer layer 105 covering the surface of the inner layer 104 is formed.

  The required time for the process of mixing the toner core particle 102 having the first fine particle layer and the second fine particle 202 and coating the toner core particle 102 with the shell layer 103 composed of the inner layer 104 and the outer layer 105 is a shell in a desired state. Although it will not specifically limit if the layer 103 can be formed, 5 to 30 minutes are preferable, 8 to 25 minutes are more preferable, 10 to 20 minutes are especially preferable.

  When the shell layer 103 is formed, if the material of the toner core particles 102 is the same as or slightly harder than the first fine particles 201, the inner surface of the inner layer 104 (the surface on the toner core particle 102 side) may be smooth. is there. On the other hand, when the material of the toner core particle 102 is softer than the first fine particle 201, the portion of the first fine particle 201 that contacts the toner core particle 102 is not easily deformed when the first fine particle 201 is embedded in the toner core particle 102. Therefore, the convex portion 106 derived from the shape of the first fine particles 201 before changing to the inner layer 104 is easily formed on the inner surface of the inner layer 104. In this case, the convex portion 106 is formed between the two cracks 107 provided in the inner layer 104.

  In the above method, when the mechanical external force is weak, the first fine particles 201 and the second fine particles 202 are not deformed to a desired degree, and the shell layer 103 having a predetermined shape may not be formed. Depending on the type of apparatus used to form the shell layer 103, conditions for forming the shell layer 103 having a predetermined shape are different, but are given to the toner core particles 102 covered with the first fine particle layer and the second fine particle layer. By changing the operating conditions step by step so that the mechanical external force becomes stronger, and confirming the structure of the shell layer 103 provided in the toner particles 101 obtained under each condition, a predetermined shell layer for various devices is obtained. Suitable conditions for forming 103 can be defined. However, when the mechanical external force is too strong, the first fine particles 201 and the second fine particles 202 are excessively deformed, and cracks 107 in a direction substantially perpendicular to the toner core particles 102 are not formed inside the inner layer 104, or mechanical When the external force is converted into heat, there may be a problem that the toner core particles 102, the first fine particles 201, and the second fine particles 202 are melted.

  As an apparatus capable of applying a mechanical external force to the toner core particle 102 coated with the first fine particle layer and the second fine particle layer while coating the toner core particle 102 using the first fine particle 201 and the second fine particle 202. Hybridizer NHS-1 (manufactured by Nara Machinery Co., Ltd.), Cosmos system (manufactured by Kawasaki Heavy Industries, Ltd.), Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.), multi-purpose mixer (manufactured by Nippon Coke Industries Co., Ltd.), composite (Nippon Coke Kogyo Co., Ltd.), Mechano-Fusion Device (Hosokawa Micron Co., Ltd.), Mechano Mill (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.

  The electrostatic latent image developing toner of the present invention described above is excellent in fixability and heat-resistant storage stability, and thus 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 that the acid value of the reaction mixture became a desired value. Next, the temperature of the reaction mixture was increased 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 was coarsely pulverized using a pulverizer (Rotoplex (manufactured by Toa Machinery Co., Ltd.)) to obtain a coarsely pulverized product. The coarsely pulverized product was finely pulverized using a mechanical pulverizer (Turbo Mill (manufactured by Turbo Industry Co., Ltd.)) to obtain a finely pulverized product. The finely pulverized product was classified using a classifier (Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.)) 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 to H)
To a 1000 mL reaction vessel equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen introduction device, 450 mL of distilled water and dodecyl ammonium chloride in the amount shown in Table 1 were charged. While stirring the contents of the reaction vessel 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 by freeze drying to obtain resin fine particles A to H having the number average particle diameters shown in Table 1. The number average particle diameter of the resin fine particles was measured according to the following procedure. The resin fine particles had a glass transition point (Tg) of 49.6 ° C. and a softening point of 188 ° C.

(Measurement method of number average particle diameter)
In order to measure the number average particle diameter of the resin fine particles, first, a photograph of the resin fine particles at a magnification of 100,000 times was taken using a field emission scanning electron microscope (JSM-7700F (manufactured by JEOL Ltd.)). The taken 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 measuring instrument such as a caliper. The number average particle diameter of the resin fine particles was calculated from the obtained measured values.

[Examples 1-6 and Comparative Examples 1-6]
[Preparation of toner base particles]
-Formation process of the 1st fine particle layer As the 1st step of shell layer formation, the 1st fine particle layer which coat | covers the surface of a toner core particle was formed in accordance with the following procedures.
First, with respect to 100 g of the toner core particles obtained in Production Example 2, resin fine particles (first fine particles) having the types, number average particle diameters, and masses shown in Tables 2 and 3 are adhered to the surface of the toner core particles. A first fine particle layer was formed. For the formation of the first fine particle layer, a powder processing apparatus (multipurpose mixer MP type (manufactured by Nippon Coke Industries Co., Ltd.)) was used. Specifically, after the toner core particles and the resin fine particles are put into the processing tank of the powder processing apparatus, the powder processing apparatus is operated at the rotation speed and processing time shown in Table 1 and Toner core particles having one fine particle layer were obtained. During the surface treatment, the internal temperature of the powder processing apparatus was controlled to 50 ° C. or higher and 60 ° C. or lower.

-Formation process of shell layer consisting of inner layer and outer layer As a second step of shell layer formation, after the surface of the first fine particle layer is coated with the second fine particle layer according to the following procedure, the first fine particle layer and the second fine particle layer Were changed to an inner layer and an outer layer, respectively, to form a shell layer composed of an inner layer and an outer layer on the surface of the toner core particles.
The types, number average particle diameters, and masses shown in Tables 2 and 3 with respect to the toner core particles having the first fine particle layer on the surface and 100 g of toner core particles in a state where the first fine particle layer is not formed. The second fine particles were adhered to the surface of the first fine particle layer to form a second fine particle layer. After the second fine particle layer is formed, the operation of the powder processing apparatus is continued, and the first fine particle layer and the second fine particle layer are changed to the inner layer and the outer layer, respectively, to form a shell layer on the surface of the toner core particles. did. For forming the shell layer, the same powder processing apparatus as used for forming the first fine particle layer was used. Specifically, after the second fine particles are added to the powder processing apparatus, the powder processing apparatus is operated at the rotation speed and processing time described in Tables 2 and 3, and the toner core particles are coated with the shell layer. Mother particles were obtained. During processing, the temperature in the tank of the powder processing apparatus was controlled to 50 ° C. or more and 60 ° C. or less.

(External processing)
The obtained toner base particles are composed of 2.0% by mass of titanium oxide (EC-100 (manufactured by Titanium Industry Co., Ltd.)) and 1.0% by mass of hydrophobic silica (RA) with respect to the mass of the toner base particles. -200H (Nippon Aerosil Co., Ltd.)). The toner base particles, titanium oxide, and hydrophobic silica were 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 7]
Using the same apparatus as the powder processing apparatus used in Example 1, 100 g of the toner core particles and the first fine particles having the types, number average particle diameters, and masses described in Table 2 were used. The toner of Comparative Example 7 was obtained in the same manner as in Example 1 except that toner base particles were obtained by processing for the treatment time.

[Comparative Example 8]
The shell layer is formed in a single step on the toner core particles by using the following surface modifying apparatus for forming the shell layer and using resin fine particles of the type, number average particle diameter, and mass shown in Table 2. A toner of Comparative Example 8 was obtained in the same manner as in Example 1 except that A specific method for forming the shell layer is as follows.

  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. First, the toner core particles were circulated at a supply air temperature of 80 ° C. in the fluidized bed of the surface reformer. Surface modification device for 60 minutes at a spray rate of 5 g / min with 300 g of an aqueous dispersion containing 10 g of resin fine particles obtained by adjusting the concentration of resin fine particles in the aqueous dispersion of resin fine particles obtained in Production Example 3. The fluidized bed was sprayed to form a shell layer on the surface of the toner core particles.

≪Confirmation of shell layer structure≫
According to the following method, the surfaces of the toner particles contained in the toners of Examples 1 to 6 and Comparative Examples 1 to 8 were observed using a scanning electron microscope (SEM), and the surface of the shell layer covering the toner core particles was observed. Checked the condition. According to the following method, photographs of cross sections of the toner particles contained in the toners of Examples 1 to 6 and Comparative Examples 1 to 8 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. FIG. 4 shows a cross-sectional TEM photograph of toner particles contained in the toner of Example 1, and FIG. 5 shows a cross-sectional TEM photograph of toner particles contained in the toner of Comparative Example 8.

<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 toner particles having a thickness of 200 nm was prepared from the obtained sample. The obtained flake sample was observed at a magnification of 50,000 times using a transmission electron microscope (TEM, JSM-6700F (manufactured by JEOL Ltd.)), and an image of a cross section of an arbitrary toner particle was taken.

  The toner particles contained in the toners of Examples 1 to 6, Comparative Example 1, Comparative Example 2, and Comparative Example 7 have a particle diameter of 6 μm to 8 μm when the surface thereof is observed using a scanning electron microscope (SEM). For the following toner particles, a structure derived from spherical second fine particles was not observed on the surface of the shell layer. From the TEM photograph of the cross section of the toner particles contained in the toner of Example 1 shown in FIG. 3, the outer surface of the shell layer of the toner particles is smooth, the inside of the shell layer of the toner particles, and the surface of the toner core particles. On the other hand, it was confirmed that cracks in the substantially vertical direction existed, and that the shell layer of the toner particles had a convex portion between the inner surface side and the two cracks. When the cross sections of the toners of Examples 2 to 6, Comparative Example 1, Comparative Example 2, and Comparative Example 7 were observed using TEM, Examples 2 to 6, Comparative Example 1, Comparative Example 2, and Comparative Example were used. Since the structure of the shell layer of the toner particles contained in the toner of Example 7 was the same as the structure of the shell layer of the toner particles contained in the toner of Example 1, Examples 2-6, Comparative Example 1, Comparative Example 2, And the TEM photograph of the cross section of the toner particles contained in the toner of Comparative Example 7 was not taken.

  The toner particles contained in the toner of Comparative Example 3 have a structure derived from spherical second 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 using an SEM. Was not observed. However, when the cross section of the toner particles contained in the toner of Comparative Example 3 was observed using a TEM, it was confirmed that the first fine particles were buried in the toner core particles and the inner layer having a desired structure was not formed. .

  When the surface of the toner particles contained in the toners of Comparative Examples 4 and 6 is observed using an SEM, the toner core particle surface remains in a spherical particle state with respect to toner particles having a particle diameter of 6 μm to 8 μm. It was confirmed that it was coated with two fine particles. From the TEM photographs of the cross-sections of the toner particles contained in the toners of Comparative Examples 4 and 6, the toner particles contained in the toners of Comparative Examples 4 and 6 have the same inner layer as the inner layer provided in the toner particles contained in the toner of Example 1. Was confirmed to be coated with the second fine particles in the particle state.

  The toner particles contained in the toner of Comparative Example 5 are substantially spherical particles derived from spherical resin fine particles in 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 using SEM. It was not observed, and it was confirmed that the outer surface of the shell layer was smooth. When the cross section of the toner particles contained in the toner of Comparative Example 5 was observed using a TEM, it was confirmed that the outer surface of the shell layer of the toner particles contained in the toner of Comparative Example 5 was smooth. It was confirmed that there were no cracks in a direction substantially perpendicular to the surface of the toner core particles.

  The toner particles contained in the toner of Comparative Example 8 are substantially spherical particles derived from spherical resin fine particles in 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 using SEM. It was not observed, and it was confirmed that the outer surface of the shell layer was smooth. From the TEM photograph of the cross section of the toner particles contained in the toner of Comparative Example 8 shown in FIG. 5, it was confirmed that the outer surface of the shell layer of the toner particles contained in the toner of Comparative Example 8 was smooth. However, from the TEM photograph of the cross section of the toner particles contained in the toner of Comparative Example 7, there is a crack in the direction substantially perpendicular to the surface of the toner core particles inside the shell layer of the toner particles contained in the toner of Comparative Example 8. It was confirmed not to.

≪Evaluation≫
According to the following method, the fixability and heat resistant storage stability of the toners of Examples 1 to 6 and Comparative Examples 1 to 8 were evaluated. The evaluation results for each toner are shown in Tables 2 and 3. A page printer (FS-C5016N (manufactured by Kyocera Document Solutions)) modified so that the fixing temperature can be adjusted was used as an evaluation machine. The evaluator was allowed to stand for 10 minutes with the power off, and then turned on and used. A two-component developer obtained according to the method described in Production Example 4 below was used for evaluation of fixing property, image density under a predetermined environment, and toner charge amount.

[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>
The fixing temperature was set to 180 ° C., and fixing was performed using a heat roller for fixing having a diameter of 30 mm and a linear speed of 100 mm / second. An image for evaluation was obtained using an evaluator in a room 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, the 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: The fixing rate is 90% or more and less than 95%.
X: 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 a powder tester (manufactured by Hosokawa Micron Corporation), the toner was sieved using a 140 mesh (mesh opening 105 μm) sieve under the conditions of rheostat scale 5 and time 30 seconds. After sieving, the mass of toner remaining on the sieve was measured. From the mass of the toner before sieving and the mass of the toner remaining on the sieving after sieving, the degree of aggregation (%) was determined according to the following formula. From the calculated degree of aggregation, 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
A: The degree of aggregation is 20% or less.
(Triangle | delta): Aggregation degree exceeds 20% and 50% or less.
X: Aggregation degree exceeds 50%.

From Examples 1-6,
A toner comprising toner particles composed of 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,
The shell layer is composed of an inner layer that covers the toner core particles and an outer layer that covers the inner layer.The inner layer is formed using spherical first fine particles.
The outer layer is formed using spherical second particulates,
The material of the first fine particles and the second fine particles is a resin,
The average particle diameter of the first fine particles is 100 nm or more and 300 nm or less,
The average particle size of the second fine particles is 50 nm or less,
-When observed using a scanning electron microscope, the toner particles having a specific range of particle diameters are not seen from the spherical second fine particles on the surface of the shell layer,
When observing the cross section using a transmission electron microscope, many cracks in a direction substantially perpendicular to the surface of the toner core particles are observed inside the shell layer.
It can be seen that the toner containing toner particles is excellent in fixability and heat-resistant storage stability.

  From the comparison between Examples 1 to 6 and Comparative Example 7, the shell layer having cracks in the direction substantially perpendicular to the surface of the toner core particles is used in two stages using two kinds of fine particles having different average particle diameters. It can be seen that the toner can be produced more efficiently in a shorter time than the production of toner containing toner particles having a shell layer having a similar structure using only one kind of fine particles.

  From Comparative Examples 1 and 2, it can be seen that toner including toner particles in which an inner layer is formed using resin fine particles having an average particle diameter of more than 300 nm as the first fine particles is inferior in fixability. This is because if the inner layer is formed using the first fine particles having a particle size that is too large, the shell layer becomes too thick, and even if heat and pressure are applied to the toner particles during fixing, the shell layer is not easily destroyed. It is done. When the shell layer is not destroyed, components contained in the toner core particles such as a release agent do not elute on the surface of the toner particles, and the toner particles are not easily fixed on the recording medium.

  From Comparative Example 3, it can be seen that a toner including toner particles in which an inner layer is formed using resin fine particles having an average particle diameter of less than 100 nm as the first fine particles is inferior in heat resistant storage stability. This is presumably because if the inner layer is formed using the first fine particles whose particle diameter is too small, the first fine particles are embedded in the toner core particles, and an extremely thin shell layer is formed.

  The toner particles contained in the toners of Comparative Examples 4 and 6 are manufactured by a method in which the outer layer is formed using the second fine particles having a particle size that is too large, or the processing time for forming the outer layer is extremely short. Therefore, when toner particles having a particle diameter within a predetermined range are observed using an SEM, second fine particles that remain in the form of particles are observed on the surface of the toner particles. In such toner particles contained in the toner, components contained in the toner core particles such as a release agent are passed through the cracks in the inner layer and the gaps between the particulate second fine particles contained in the outer layer. May ooze out. For these reasons, it is considered that the toners of Comparative Examples 4 and 6 are inferior in heat resistant storage stability.

  From the comparison of SEM observation of the toner particles contained in the toner of Example 1 and the toner particles contained in the toner of Comparative Example 6, the rotational speed of the powder processing apparatus when forming the outer layer using the second fine particles is increased. It was found that by extending the treatment time, substantially spherical particles derived from the second fine particles were not observed on the surface of the toner particles. That is, it can be seen that when the outer layer is formed, by increasing the rotational speed of the powder processing apparatus and extending the processing time, the deformation of the second fine particles proceeds and the smoothness of the outer surface of the shell layer increases.

  The toner particles contained in the toners of Comparative Examples 5 and 8 are processed at a high rotational speed and for a long time using a powder processing apparatus when forming the inner layer. Since the shell layer is formed, there are no cracks in the shell layer in a direction substantially perpendicular to the surface of the toner core particles. When toner particles having a shell layer that does not contain such cracks are fixed on a recording medium, the shell layer is not easily broken even if the toner particles are heated and pressurized during fixing. When the shell layer is not destroyed, components contained in the toner core particles such as a release agent do not elute on the surface of the toner co-toner particles, and the toner particles are not easily fixed on the recording medium.

DESCRIPTION OF SYMBOLS 101 Toner particle 102 Toner core particle 103 Shell layer 104 Inner layer 105 Outer layer 106 Convex part 107 Crack 201 First microparticle 202 Second microparticle

Claims (3)

Toner core particles containing at least a binder resin;
A method for producing a toner for developing an electrostatic latent image, comprising toner particles comprising a shell layer covering the toner core particles,
Steps I), II), and III) below:
I) A first fine particle layer that applies an external force and adheres the first fine particles to the toner core particles so as not to overlap in a direction perpendicular to the surface of the toner core particles, thereby covering the entire surface of the toner core particles. Forming process,
II) The second fine particles are adhered to the outer surface of the first fine particle layer so as not to overlap in the direction perpendicular to the surface of the first fine particle layer, thereby covering the entire outer surface of the first fine particle layer. A step of forming a second fine particle layer, and III) applying an external force to the outer surface of the second fine particle layer to deform the second fine particle in the second fine particle layer, whereby the outer surface of the second fine particle layer the by smoothing, to form the shell layer made of an inner layer and an outer layer, a shell layer forming step, the material of the first particle and the second particle comprises is a resin,
The average particle size of the first fine particles is 100 nm or more and 300 nm or less,
The average particle size of the second fine particles is 50 nm or less,
When the surface of the toner particles is observed using a scanning electron microscope, a structure derived from the spherical second fine particles is not observed on the surface of the shell layer of the toner particles having a particle diameter of 6 μm or more and 8 μm or less. ,
Manufacture of a toner for developing an electrostatic latent image, wherein a crack derived from an interface between the first fine particles is observed inside the inner layer when a cross section of the toner particles is observed using a transmission electron microscope. Method. The method for producing a toner for developing an electrostatic latent image according to claim 1 , wherein the thickness of the shell layer is 120 nm or more and 350 nm or less. When observing a cross section of the toner for developing an electrostatic latent image using a transmission electron microscope, when observing using a transmission electron microscope, on the interface between the toner core particles and the shell layer, and between two of said cracks, wherein the shell layer is convex portion having is observed, according to claim 1 or 2 electrostatic latent image producing method of the developing toner according to.