JP5629668B2 - Positively chargeable toner - Google Patents

Description

  The present invention relates to a positively chargeable toner.

  In general, in electrophotography, the surface of an electrostatic latent image carrier (photoconductor) is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The toner image is developed to form a toner image, and the toner image is transferred to a recording medium to obtain a high quality image. In general, the toner used for forming the toner image is mixed with a binder resin such as a thermoplastic resin, a colorant, a charge control agent, a release agent, a magnetic material and the like, kneaded, pulverized, and classified to have an average particle size of 5 A toner particle having a size of 10 μm to 10 μm is used. And for the purpose of imparting fluidity to the toner, controlling the charge amount of the toner, and improving the cleaning property of the toner remaining on the photoreceptor without being transferred, inorganic fine particles such as silica and titanium oxide. Is externally added to the toner.

  In recent years, toners used in such an image forming method in which resin fine particles are attached to the toner surface in addition to inorganic fine particles have been used. Since the resin fine particles are close to the binder resin of the toner and have an effect of suppressing charging failure of the toner, the use of such toner causes fogging in the formed image and scattering of the toner in the image forming apparatus. Can be suppressed.

  As a toner in which inorganic fine particles and resin fine particles are externally added, for example, a toner in which inorganic particles and crystalline resin particles are externally added and the melting temperature of the crystalline resin is 55 ° C. or higher and 100 ° C. or lower has been proposed. (Patent Document 1).

JP 2011-17913 A

  However, in the toner described in Patent Document 1, when printing with a low printing rate is performed for a long time, the resin fine particles may be detached from the surface of the toner by stirring the toner for a long time in the developing device. In this case, the resin fine particles adhering to the toner surface are reduced, and the spacer effect on the toner that the resin fine particles play is impaired, so that the toner particles adhere to each other, the toner and the carrier, or the toner and various members of the image forming apparatus. As a result, the image density of the formed image is less than a desired value, and the transferability of the toner is deteriorated.

  The present invention has been made in view of such circumstances, and provides a positively chargeable toner capable of suppressing the image density of a formed image from falling below a desired value even when printing over a long period of time. With the goal.

  The inventors of the present invention have disclosed an electrostatic latent image in which positively charged inorganic fine particles are attached to the surface of toner base particles containing at least a binder resin, a colorant, and a charge control agent. With respect to the toner for image development, the above problem is solved by satisfying a predetermined relationship among the mass (X) of the inorganic fine particles, the mass (Y) of the crystalline resin fine particles, and the mass (Z) of the toner base particles. As a result, the present invention has been completed. Specifically, the present invention provides the following.

(1) At least a binder resin, a colorant, and a charge control agent are provided on the surface of the toner-containing mother particles, and the crystalline resin fine particles to which the positively charged inorganic fine particles are attached are attached.
The mass ratio ((X) / (Y)) of the mass (X) of the inorganic fine particles and the mass (Y) of the crystalline resin fine particles is 5 to 100%,
A mass ratio (((X) + (Y)) / () of the total mass ((X) + (Y)) of the mass of the inorganic fine particles and the mass of the crystalline resin fine particles to the mass (Z) of the toner base particles. A positively chargeable toner in which Z)) is from 0.1 to 2.0%.

  (2) The positively chargeable toner according to (1), wherein the positively chargeable inorganic fine particles are positively chargeable silica.

  (3) The positively chargeable toner according to (1) or (2), wherein the mass ratio ((X) / (Y)) is 10 to 80%.

  (4) The positive chargeability according to any one of (1) to (3), wherein the mass ratio (((X) + (Y)) / (Z)) is 0.5 to 1.5%. toner.

  An object of the present invention is to provide a positively chargeable toner that can suppress the image density of a formed image from falling below a desired value even when printing over a long period of time.

It is a figure explaining the measuring method of the softening point by an elevating type flow tester.

  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 positively chargeable toner of the present invention (hereinafter also simply referred to as toner)
At least a binder resin, a colorant, and a charge control agent are provided on the surface of toner-containing mother particles, and crystalline resin fine particles having positively charged inorganic fine particles attached to the surface are attached.
The mass ratio ((X) / (Y)) of the mass (X) of the inorganic fine particles and the mass (Y) of the crystalline resin fine particles is 5 to 100%,
A mass ratio (((X) + (Y)) / () of the total mass ((X) + (Y)) of the mass of the inorganic fine particles and the mass of the crystalline resin fine particles to the mass (Z) of the toner base particles. Z)) relates to a positively chargeable toner having a content of 0.1 to 2.0%.

  In addition, the toner of the present invention may be obtained by adding, as desired, external inorganic fine particles other than the crystalline fine particles to the surface of the toner together with the crystalline resin fine particles. Furthermore, the toner of the present invention can be mixed with a desired carrier and used as a two-component developer.

  Hereinafter, for the positively chargeable toner of the present invention, essential or optional components, binder resin, colorant, charge control agent, release agent, crystalline resin fine particles treated with positively chargeable inorganic fine particles, and An external additive other than the crystalline resin fine particles, a method for producing a positively chargeable toner, and a carrier used when the toner of the present invention is used as a two-component developer will be described in order.

[Binder resin]
The positively chargeable toner of the present invention contains a binder resin, a colorant, and a charge control agent. If necessary, positively chargeable inorganic fine particles are formed on the surface of toner base particles containing a component such as a release agent. The adhered crystalline resin fine particles are adhered. The binder resin contained in the toner base particles is not particularly limited as long as it is a resin conventionally used as a binder resin for toner particles. Specific examples of the binder resin include styrene resin, acrylic resin, styrene acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether. And thermoplastic resins such as styrene resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, styrene acrylic resins and polyester resins are preferable from the viewpoints of dispersibility with respect to the colorant in the toner, chargeability of the toner, and fixing properties with respect to the paper. Hereinafter, the styrene acrylic resin and the polyester resin will be described.

  The styrene acrylic resin is a copolymer of a styrene monomer and an acrylic monomer. Specific examples of the styrene monomer include styrene, α-methylstyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-ethylstyrene, and the like. Specific examples of the acrylic monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, meta Examples include (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

  As the polyester resin, those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a 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, polytetramethylene glycol; bisphenol A, Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, Entaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4- Examples include trivalent or higher alcohols such as butanetriol, trimethylolethane, trimethylolpropane, and 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, isododecenyl succinic acid and the like or alkyl or alkenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphtha Tricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid , Tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, emporic trimer acid, and other trivalent or higher carboxylic acids. 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 80 to 150 ° C, and more preferably 90 to 140 ° C.

  As the binder resin, it is preferable to use a thermoplastic resin because it has good fixability. However, not only the thermoplastic resin alone but also a crosslinking agent or a thermosetting resin should be added to the thermoplastic resin. Can do. By introducing a partially crosslinked structure into the binder resin, it is possible to improve the storage stability, form retention, durability and the like of the toner without deteriorating the fixability.

  As the thermosetting resin that can be used together with the thermoplastic resin, for example, 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, cyanate resins and the like. 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 50 to 65 ° C, and more preferably 50 to 60 ° C. If the glass transition point of the binder resin is too low, the toners may be fused inside the developing unit of the image forming apparatus, or the storage stability may be reduced. May be partly fused. Further, when the glass transition point is too high, the strength of the binder resin is lowered, and the toner is likely to adhere to the latent image carrier (image carrier: photoconductor). If the glass transition point is too high, the toner tends to be difficult to fix well at low temperatures.

  In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC). More specifically, it can be determined by measuring an endothermic curve using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. An endothermic curve obtained by placing 10 mg of a measurement sample in an aluminum pan, using an empty aluminum pan as a reference, and measuring at a measurement temperature range of 25 to 200 ° C. and a temperature increase rate of 10 ° C./min. The glass transition point can be obtained more.

[Colorant]
As the colorant contained in the positively chargeable toner, a known pigment or dye can be used in accordance with the color of the toner particles. Specific examples of suitable colorants to be added to the toner include black pigments such as carbon black, acetylene black, lamp black, and aniline black; yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow , Yellow pigments such as Navels Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; Red Yellow Yellow Lead, Molybdenum Orange, Permanent Orange Orange pigments such as GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Tan, Mercury Cadmium, Permanent Red 4R, Lithium Red pigments such as Lured, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B; Purple such as Manganese Purple, Fast Violet B, Methyl Violet Lake Pigment: Blue pigment such as bitumen, cobalt blue, alkali blue lake, Victoria blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Final Yellow Green G Green pigments; white pigments such as zinc white, titanium oxide, antimony white, zinc sulfide; barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white, etc. It includes the quality pigments. These colorants may 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 not particularly limited as long as the object of the present invention is not impaired. Specifically, 1-10 mass parts is preferable with respect to 100 mass parts of binder resin, and 3-7 mass parts is more preferable.

[Charge control agent]
The purpose of the charge control agent is to improve the charge level of the toner and the charge start-up characteristic that is an indicator of whether or not the toner can be charged to a predetermined charge level in a short time, and to obtain a toner having excellent durability and stability. used. Since the toner of the present invention is a positively chargeable toner, a positively chargeable charge control agent is used.

  The type of the positively chargeable charge control agent is not particularly limited as long as the object of the present invention is not impaired, and 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, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine Direct dyes composed of azine compounds such as Laun 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Dep Black EW, and Azin Dee Black 3RL; Nigrosine Compounds such as Nigrosine, Nigrosine Salts, Nigrosine Derivatives; Nigrosine Acid dyes comprising nigrosine compounds such as BK, nigrosine NB, and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride It is done. Among these positively chargeable charge control agents, a nigrosine compound is particularly preferable in that a more rapid start-up property can be obtained. These positively chargeable charge control agents can be used in combination of two or more.

  Quaternary ammonium salts, carboxylates, or resins having a 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, a carboxylic acid Styrene resin having salt, acrylic resin having carboxylate, styrene-acrylic resin having carboxylate, polyester resin having carboxylate, styrene resin having carboxyl group, acrylic having carboxyl group 1 type, or 2 or more types, such as resin, the styrene-acrylic resin which has a carboxyl group, and the polyester-type resin which has a carboxyl group, are mentioned. The molecular weight of these resins is not particularly limited as long as the object of the present invention is not impaired, and may be an oligomer or a polymer.

  Among resins that can be used as a positively chargeable charge control agent, a styrene-acrylic copolymer having a quaternary ammonium salt as a functional group from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. A resin is more preferable. Specific examples of preferable acrylic comonomers to be copolymerized with styrene units in a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group include methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic acid. (Meth) such as iso-propyl, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 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 the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like. Specific examples of dialkyl (meth) acrylamide include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl (meth) acrylamide include dimethylaminopropylmethacrylamide. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  The amount of the positively chargeable charge control agent is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the positively chargeable charge control agent used is preferably 1.5 to 15 parts by mass, more preferably 2.0 to 8.0 parts by mass when the total amount of toner is 100 parts by mass. 3.0 to 7.0 parts by mass are particularly preferable. If the amount of charge control agent used is too small, it will be difficult to stably charge the toner to a predetermined polarity, so the image density of the formed image will fall below the desired value, or the image density of the formed image cannot be maintained over a long period of time. Sometimes. Further, in such a case, the charge control agent is difficult to disperse uniformly, and fogging in the formed image and contamination of the latent image carrier are likely to occur. If the amount of the charge control agent used is excessive, toner charging failure under high temperature and high humidity is likely to occur due to deterioration of environmental resistance. As a result, image formation in the formed image or toner on the latent image carrier Contamination is likely to occur.

[Release agent]
The positively chargeable toner may contain a release agent for the purpose of improving fixability and offset resistance. The type of release agent added to the toner is not particularly limited as long as the object of the present invention is not impaired. The mold release agent is preferably a wax, and examples of the wax include polyethylene wax, polypropylene wax, fluororesin-based wax, Fischer-Tropsch wax, paraffin wax, ester wax, montan wax, rice wax and the like. These release agents can be used in combination of two or more. By adding such a release agent to the toner, it is possible to more efficiently suppress the occurrence of offset and image smearing (dirt around the image when the image is rubbed).

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. The amount of the specific release agent used is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. If the amount of the release agent used is too small, the desired effect may not be obtained in terms of suppressing the occurrence of offset and image smearing in the formed image. If the amount of release agent used is excessive, In some cases, the storage stability of the toner may be reduced due to the fusing.

[Crystalline resin fine particles treated with positively chargeable inorganic fine particles]
In the toner of the present invention, crystalline resin fine particles treated with positively chargeable inorganic fine particles having positively charged inorganic fine particles attached to the surface thereof are used as external additives. Hereinafter, treatment with crystalline resin fine particles, positively chargeable inorganic fine particles, and positively chargeable inorganic fine particles will be described.

  The crystalline resin as the material of the crystalline resin fine particles is not particularly limited as long as the object of the present invention is not impaired, but a crystalline polyester resin is preferable. Crystalline polyester resin fine particles are preferable because of their high particle strength, excellent heat-resistant storage stability, good toner fluidity, and excellent compatibility with the binder resin when melted. Other crystalline resins include paraffin resins and side chain crystalline acrylic resins.

  When a crystalline polyester resin is used as the material for the crystalline resin fine particles, the crystallinity index is 0.90 or more and less than 1.10, preferably 0.98 to 1.05. The crystallinity index of the polyester resin can be adjusted by appropriately adjusting the type and amount of the alcohol component and carboxylic acid component that are monomers. The crystalline polyester resin fine particles may be used alone or in combination of two or more.

  The crystallinity index of the crystalline polyester resin can be determined by the ratio between the softening point of the polyester resin and the maximum peak temperature of the heat of fusion (softening point / maximum peak temperature of the heat of fusion). The softening point of the polyester resin is measured by a flow tester described later, and the maximum peak temperature of heat of fusion is measured by the above-described differential scanning calorimeter (DSC).

<Softening point measurement method>
The softening point is measured with a Koka flow tester (CFT-500D (manufactured by Shimadzu Corporation)). A mold for preparing a measurement sample is filled with about 1.8 g of toner, and a pressure of 4 MPa is applied to form a cylindrical toner pellet having a diameter of 1 cm and a length of 2 cm. The obtained pellets are set in a flow tester, and the softening point is measured at 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 is read from an S-shaped curve relating to temperature (° C.) and stroke (mm) obtained by the flow tester measurement.

A method of reading the softening point 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 in the S-curve is defined as the softening point of the measurement sample.

  As the crystalline polyester resin fine particles, those obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The components used when synthesizing the polyester resin include the following alcohol components and carboxylic acid components.

  A divalent or trivalent or higher alcohol can be used as the alcohol component. 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, polytetramethylene glycol; bisphenol A, Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, Entaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4- Examples include trivalent or higher alcohols such as butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  Among these alcohol components, an aliphatic diol having 2 to 8 carbon atoms is preferable because it facilitates crystallization of the polyester resin. Among the aliphatic diols, α, ω-alkanediols having 2 to 8 carbon atoms are more preferable because they facilitate the crystallization of polyester.

  In order to obtain a crystalline polyester resin, the aliphatic diol having 2 to 10 carbon atoms in the alcohol component is preferably 80 mol% or more, and more preferably 90 mol% or more. In order to obtain a crystalline polyester, the content of the component (single compound) contained in the alcohol component in the largest amount is preferably 70 mol% or more, more preferably 90 mol% or more. 100 mol% is most preferable.

  As the carboxylic acid component, a divalent or trivalent or higher carboxylic acid can be used. 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, 1,10-decanedicarboxylic 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 A divalent carboxylic acid such as alkyl or alkenyl succinic acid such as dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid and isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetri Rubonic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, Examples include trivalent or higher carboxylic acids such as 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empole trimer acid. It is done. 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.

  Among these carboxylic acid components, an aliphatic dicarboxylic acid having 2 to 16 carbon atoms is preferable, and α, ω-alkanedicarboxylic acid having 2 to 16 carbon atoms is preferable because crystallization of the polyester resin is easily promoted. More preferred.

  In order to obtain a crystalline polyester resin, the aliphatic dicarboxylic acid having 2 to 16 carbon atoms in the carboxylic acid component is preferably 70 mol% or more, and more preferably 90 mol% or more. In order to obtain a crystalline polyester, the content of the component (single compound) contained in the largest amount in the carboxylic component is preferably 70 mol% or more, more preferably 90 mol% or more. 100 mol% is most preferable.

  The melting point of the crystalline resin fine particles is preferably 110 to 130 ° C, and the softening point is preferably 120 to 140 ° C. As described above, the melting point of the crystalline resin fine particles can be measured using a differential scanning calorimeter (DSC), and the softening point can be measured using a flow tester.

  The weight average molecular weight (Mw) of the crystalline resin is preferably 500 to 10,000.

  The average primary particle diameter of the crystalline resin fine particles is preferably 50 to 1000 nm. The average primary particle diameter of the crystalline resin fine particles can be adjusted by adjusting the polymerization conditions when the crystalline resin fine particles are prepared by a polymerization method. Further, when the crystalline resin fine particles are adjusted by a pulverization method, the average primary particle diameter of the crystalline resin fine particles can be adjusted by appropriately adjusting the pulverization conditions and the classification conditions. The average primary particle diameter of the crystalline resin fine particles can be measured as the volume average particle diameter (D50) of the resin fine particles with an electrophoretic light scattering photometer (ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)).

  Moreover, the crystalline resin fine particles having a particle diameter adjusted to 50 to 1000 nm can be prepared using commercially available crystalline resin fine particles having an average primary particle exceeding 1000 nm. Specifically, crystalline resin fine particles having an average primary particle diameter of more than 1000 nm are dispersed in water containing a surfactant, and the dispersion is stirred while adjusting the heating temperature, heating time, pH, and the like. Crystalline resin fine particles having a particle size of 5 are obtained.

(Positively charged inorganic fine particles)
The positively chargeable inorganic fine particles are not particularly limited as long as the object of the present invention is not impaired. Specific examples of the inorganic fine particles having positive charge include inorganic oxides such as silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. Among these, positively charged silica fine particles are preferably used. By using the positively chargeable silica fine particles, the positive chargeability can be favorably imparted to the crystalline resin fine particles.

  Inorganic fine particles generally have a tendency to be negatively charged, and particularly silica has a strong negative chargeability. Therefore, when these inorganic fine powders are attached to the crystalline resin fine particles, inorganic fine particles having positively charged polar groups introduced on the surface thereof are used.

  The positively-charged silica fine particles are surfaced by a silane coupling agent having a functional group containing a nitrogen atom, such as an aminosilane coupling agent having a positively-charged polar group, or a silicone oil having a side chain containing a nitrogen atom. Examples thereof include treated silica fine particles. Since these silica fine particles have positively chargeable polar groups such as amino groups on the surface of the silica fine powder, they show positive chargeability.

  The average primary particle diameter of the positively chargeable inorganic fine particles is not particularly limited as long as the object of the present invention is not impaired. Typically, 20 nm or less is preferable, and 10 to 20 nm is more preferable. When the particle diameter of the positively chargeable inorganic fine particles exceeds 20 nm, the adhesion with the crystalline resin fine particles is reduced, and the positively chargeable inorganic fine particles move away from the crystalline resin fine particles and migrate to the toner base particles, so that developability is improved. descend.

(Treatment with positively chargeable inorganic fine particles)
The method for attaching the positively chargeable inorganic fine particles to the surface of the crystalline resin fine particles is not particularly limited, and can be appropriately selected from conventionally known methods. Specific examples of the method for treating crystalline resin fine particles with positively chargeable inorganic fine particles include a method of mixing positively chargeable inorganic fine particles and crystalline fine particles with a mixer such as a Henschel mixer or a Nauter mixer. .

  The mass ratio ((X) / (Y)) of the mass (X) of the positively charged inorganic fine particles attached to the crystalline resin fine particles and the mass (Y) of the crystalline resin fine particles is 5 to 100%, 10 to 80% is preferable. When the mass ratio ((X) / (Y)) is too small, the crystalline resin fine particles are likely to be negatively charged. The charged crystalline resin fine particles are developed on the non-image portion of the positively charged latent image carrier (image carrier: photoconductor). Then, the amount of the crystalline resin fine particles in the developing device is reduced, so that the spacer effect by the crystalline resin fine particles in the toner is impaired, and the transferability of the toner tends to be lowered.

  On the other hand, when the mass ratio ((X) / (Y)) exceeds 100%, excessively positively charged inorganic fine particles with respect to the crystalline resin fine particles are likely to be liberated in the developing device. When printing is performed for a long time at a high printing rate in this state, the positively charged inorganic fine particles charged in the positive polarity in the developing device tend to migrate to the surface of the weakly negatively charged toner base particles. In this case, the toner tends to be excessively positively charged, and the image density of the formed image tends to be lower than a desired value.

  On the other hand, the total mass ((X) + (Y)) of the mass (X) of the positively chargeable inorganic fine particles and the content (Y) of the crystalline resin fine particles with respect to the mass (Z) of the toner base particles. The ratio (((X) + (Y)) / (Z)) is 0.1 to 2.0%, more preferably 0.3 to 1.8%, and 0.5 to 1.5%. More preferred. When the mass ratio (((X) + (Y)) / (Z)) is too small, the toner base particles have a spacer effect due to the crystalline resin particles because the absolute amount of the crystalline resin particles is insufficient. Cannot be obtained, and the transferability of the toner tends to be lowered. Further, if the mass ratio (((X) + (Y)) / (Z)) is excessive, the positively chargeable inorganic fine particles released in the developing device are likely to increase, and the toner is likely to be excessively positively charged. Thus, the image density of the formed image is likely to fall below a desired value.

  Further, the ratio of the BET specific surface area (X) of the crystalline resin fine particles before adhesion of the positively chargeable inorganic fine particles to the BET specific surface area (Y) of the crystalline resin fine particles after the adhesion of the positively chargeable inorganic fine particles. The BET specific surface area ratio ((Y) / (X)) is preferably 1.05 to 1.5, and more preferably 1.1 to 1.4. The BET specific surface area of the crystalline resin fine particles can be measured using, for example, a specific surface area measuring device (HM MODEL-1208 (manufactured by Mountec Co., Ltd.)). By setting the BET specific surface area ratio ((Y) / (X)) in such a range, it is easy to obtain a toner in which the image density of the formed image is less than a desired value even when printing is performed for a long period of time.

[Other external additives other than crystalline resin fine particles]
The positively chargeable toner of the present invention is a crystalline resin fine particle to which positively chargeable inorganic fine particles are adhered for the purpose of improving the fluidity, storage stability, cleaning property, etc. of the toner within a range not impairing the object of the present invention. In addition, other inorganic fine particles may be attached to the surface of the toner base particles as an external additive.

  The type of inorganic fine particles used as the external additive is not particularly limited as long as the object of the present invention is not impaired, and can be appropriately selected from inorganic fine particles conventionally used for toners. Specific examples of suitable external additives include 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 average primary particle diameter of the other inorganic fine particles is not particularly limited as long as the object of the present invention is not impaired, and typically 0.01 μm or more and 1.0 μm or less is preferable.

  The volume-specific resistance value of other inorganic fine particles can be adjusted by forming a coating layer made of tin oxide and antimony oxide on the surface and changing the thickness of the coating layer and the ratio of tin oxide to antimony oxide. In addition, other inorganic fine particles that have been subjected to a hydrophobic treatment can be used.

[Method for producing positively chargeable toner]
The positively chargeable toner is manufactured by adhering the crystalline resin fine particles to which the positively chargeable inorganic fine particles are attached as external additives to the surface of the toner base particles.

  The toner base particles of the positively chargeable toner are obtained by blending a binder resin with a colorant, a charge control agent, and, if necessary, optional components such as a release agent, and then pulverizing and classifying the desired particles. Obtained by adjusting the diameter. In addition, magnetic powder can also be mix | blended when mix | blending a coloring agent, a mold release agent, a charge control agent, etc. with binder resin. In such a case, the amount of magnetic powder used is preferably 5% by mass or less with respect to 100 parts by mass of the binder resin.

  A method for producing toner base particles by blending a binder resin with components such as a colorant, a charge control agent, and a release agent is not particularly limited as long as these components can be well dispersed in the binder resin. As a specific example of a preferable method for producing toner mother particles, a binder resin and components such as a colorant, a charge control agent, and a release agent are mixed with a mixer or the like, and then a single screw or twin screw extruder or the like. Examples thereof include a method in which a binder resin and components blended in the binder resin are melt-kneaded by a kneader, and the cooled kneaded product is pulverized and classified. The average particle diameter of the toner base particles is not particularly limited as long as the object of the present invention is not impaired, but generally 5 to 10 μm is preferable.

  The method for attaching the external additive to the surface of the toner base particles is not particularly limited, and can be appropriately selected from conventionally known methods. Specifically, the processing conditions are adjusted so that the particles of the external additive are not embedded in the toner base particles, and the processing with the external additive is performed by a mixer such as a Henschel mixer or a Nauter mixer.

[Career]
The positively chargeable 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 suitable carrier when a positively chargeable toner is used as a two-component developer, a carrier core material coated with a resin can be used. Specific examples of carrier core materials include particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, etc., and particles of alloys of these materials with manganese, zinc, aluminum, etc. , Particles such as iron-nickel alloy, iron-cobalt alloy, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate , Ceramic particles such as lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt, resin carriers in which the above magnetic particles are dispersed in a resin, etc. Is mentioned.

  Specific examples of the resin covering the carrier core material include (meth) acrylic polymers, styrene polymers, styrene- (meth) acrylic copolymers, olefin polymers (polyethylene, chlorinated polyethylene, polypropylene, etc. ), Polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyfluoride) Vinylidene chloride, etc.), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, amino resin and the like. These resins can be used in combination of two or more.

  The particle diameter of the carrier is not particularly limited as long as the object of the present invention is not impaired, but is preferably 20 to 120 μm, more preferably 25 to 80 μm, as measured by an electron microscope.

The apparent density of the carrier is not particularly limited as long as the object of the present invention is not impaired. The apparent density varies depending on the carrier composition and surface structure, but typically 2000 to 2500 kg / m ³ is preferable.

  When the positively chargeable toner of the present invention is used as a two-component developer, the toner content is preferably 3 to 20% by mass and more preferably 5 to 15% by mass with respect to the mass of the two-component developer. By setting the toner content in the two-component developer within such a range, it is possible to maintain an appropriate image density and to suppress contamination of the image forming apparatus and adhesion of toner to transfer paper by suppressing toner scattering.

  According to the positively chargeable toner of the present invention described above, even when printing for a long period of time, the image density of the formed image is suppressed from falling below a desired value, and printing with a low printing rate for a long period is possible. However, it is possible to maintain a spacer effect on the toner by the crystalline resin fine particles and to suppress a decrease in toner transferability.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Production Example 1]
(Production example of crystalline resin fine particles a)
100 parts by mass of crystalline resin (High Wax 100P (Mitsui Chemicals, Inc., molecular weight 900, melting point 116 ° C., softening point 121 ° C.)), 900 parts by mass of distilled water, 2 parts by mass of surfactant (ethylene glycol monostearate) Was added to Claremix (manufactured by M Technique Co., Ltd.) and dispersed at 90 ° C. and a rotation speed of 10,000 rotations / minute for 10 minutes to obtain a dispersion of crystalline resin fine particles. Next, after the dispersion was cooled to 40 ° C., the dispersion was vacuum-dried at 25 ° C. with a vacuum dryer to obtain crystalline resin fine particles a having a particle diameter of 200 nm and a BET specific surface area of 50 m ² / g. The average primary particle diameter and the BET specific surface area of the crystalline resin fine particles a were measured according to the following methods.

<Average primary particle size measurement method>
The volume average particle diameter (D50) of the crystalline resin fine particles was measured with an electrophoretic light scattering photometer (ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)).

<Method for measuring BET specific surface area>
Using a BET specific surface area measuring device (HM MODEL-1208 (manufactured by Mountec Co., Ltd.)), 1 g of the sample was put in a dedicated cell, and the BET specific surface area was measured.

[Production Example 2]
[Production example of crystalline resin fine particles b and c]
Crystalline resin fine particles b having a particle diameter of 1000 nm and a BET specific surface area of 5 m ² / g were obtained in the same manner as in Production Example 1, except that the rotation speed of the Claire mix was changed to 3000 rotations / minute.

[Production Example 3]
Crystalline resin fine particles c having a particle diameter of 50 nm and a BET specific surface area of 80 m ² / g were obtained in the same manner as in Production Example 1 except that the rotation speed of the Claire mix was changed to 20000 rotations / minute.

[Example 1]
(Preparation of crystalline resin fine particles A treated with positively chargeable inorganic fine particles)
100 parts by mass of crystalline resin fine particles a and 20 parts by mass of positively charged inorganic fine particles (positively charged silica, REA200 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 12 nm)) are mixed with a multipurpose mixer (MP5 (Nippon Coke Industries, Ltd.). And the positively chargeable inorganic fine particles were adhered to the surface of the crystalline resin fine particles a to obtain crystalline resin fine particles A. The ratio ((Y) / (X)) of the BET specific surface area (X) of the crystalline resin fine particles a and the BET specific surface area (Y) of the crystalline resin fine particles A was 1.40.

(Toner base particle preparation)
As a binder resin, 100 parts by mass of a styrene-acrylic copolymer (SE-0040 (manufactured by Sekisui Chemical Co., Ltd.)), and as a colorant, 6 parts by mass of carbon black (MA-100 (manufactured by Mitsubishi Chemical Corporation)). , 4 parts by weight of nigrosine compound (N-07 (manufactured by Orient Chemical Co., Ltd.)) as the charge control agent, And mixed. The resulting mixture was melt kneaded with a twin screw extruder, cooled, and coarsely pulverized with a hammer mill. The coarsely pulverized powder was further finely pulverized with a mechanical pulverizer and then classified with an airflow classifier to obtain toner base particles having a volume average particle diameter of 6.8 μm.

(Toner preparation)
The obtained toner base particles, 1% by weight of crystalline resin fine particles A with respect to 100 parts by weight of the toner base particles, and 1.5% by weight of titanium oxide (JR-405 (manufactured by Teika Co., Ltd.)) And mixing with a Henschel mixer (FM-20B (manufactured by Nippon Coke Co., Ltd.)) under conditions of a blade peripheral speed of 3000 revolutions / minute, a mixing time of 10 minutes, and a jacket cooling water temperature of 5 ° C. Titanium was adhered to the surface of the toner base particles to obtain a toner.

(2-component developer preparation)
The carrier used in the developer for TASKalfa 5500i (composite machine (manufactured by Kyocera Mita Co., Ltd.)) and the externally-treated toner have a toner ratio of 12% by mass with respect to the total mass of the developer. The two-component developer was prepared by mixing for 30 minutes in a ball mill. Using the obtained two-component developer, a low density printing test and a standard density printing test were performed on the toner of Example 1 according to the following method. Table 2 shows the test results of the low density printing test and the standard density printing test of the toner of Example 1.

<Low density printing test>
A solid image was printed by a multifunction machine (TASKalfa 5500i (manufactured by Kyocera Mita Corporation)) in a normal temperature and humidity environment (20 ° C., 65% RH) to obtain an initial image. Thereafter, after continuous printing of 10,000 sheets at a document density of 0.2% in a normal temperature and humidity environment (20 ° C., 65% RH), a solid image was printed. The image density of the initial image and the solid image printed after printing 10,000 sheets was measured with a reflection densitometer (RD914, manufactured by Gretag Macbeth). From the evaluation results, an image density difference (ID1-ID2) between the image density (ID1) of the initial image and the image density (ID2) after continuous printing of 10,000 sheets was calculated. An image density difference of 0.2 or more is determined as “x”, an image density difference of 0.1 or more and less than 0.2 is determined as “Δ”, and an image density difference of 0.03 or more and less than 0.1 is determined as “◯”. Determination was made, and an image density difference of less than 0.03 was determined as ◎. About determination, it was set as the pass except x.

<Standard density printing test>
A solid image was printed by a multifunction machine (TASKalfa 5500i (manufactured by Kyocera Mita Corporation)) in a normal temperature and humidity environment (20 ° C., 65% RH) to obtain an initial image. Thereafter, after continuous printing of 10,000 sheets at a document density of 5% in a normal temperature and humidity environment (20 ° C., 65% RH), a solid image was printed. The image density of the initial image and the solid image printed after printing 10,000 sheets was measured with a reflection densitometer (RD914, manufactured by Gretag Macbeth). From the evaluation results, an image density difference (ID1-ID2) between the image density (ID1) of the initial image and the image density (ID2) after continuous printing of 10,000 sheets was calculated. An image density difference of 0.2 or more is determined as “x”, an image density difference of 0.1 or more and less than 0.2 is determined as “Δ”, and an image density difference of 0.03 or more and less than 0.1 is determined as “◯”. The image density difference of less than 0.03 was determined as “◎”. About determination, it was set as the pass except x.

[Example 2]
In the same manner as in Example 1, except that the crystalline resin fine particles b are used instead of the crystalline resin fine particles a and the amount of the positively chargeable inorganic fine particles is changed to 10 parts by mass. B was obtained. Toner mother particles, toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particles A were changed to the crystalline resin fine particles B. The toner of Example 2 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Example 2 are shown in Tables 1 and 2.

Example 3
In the same manner as in Example 1, except that the crystalline resin fine particles b are used instead of the crystalline resin fine particles a and the amount of the positively chargeable inorganic fine particles is changed to 5 parts by mass. C was obtained. Toner mother particles, toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particles A were changed to the crystalline resin fine particles C. The toner of Example 3 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Example 3 are shown in Tables 1 and 2.

Example 4
The crystalline resin fine particles c are used instead of the crystalline resin fine particles a, and 80 parts by mass of positively charged inorganic fine particles (positively charged silica, REA90 (manufactured by Nippon Aerosil Co., Ltd., 20 nm)) shown in Table 1 are used. A crystalline resin fine particle D was obtained in the same manner as in Example 1 except that it was used. Toner mother particles, toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particles A were changed to the crystalline resin fine particles D. The toner of Example 4 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Example 3 are shown in Tables 1 and 2.

Example 5
Using crystalline resin fine particles c instead of crystalline resin fine particles a, and 100 parts by mass of positively charged inorganic fine particles (positively charged silica, REA90 (produced by Nippon Aerosil Co., Ltd., 20 nm)) shown in Table 1 Crystalline resin fine particles E were obtained in the same manner as in Example 1 except that it was used. A toner base particle, a toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particle A was changed to the crystalline resin fine particle E. The toner of Example 5 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Example 3 are shown in Tables 1 and 2.

[Comparative Example 1]
Crystalline resin fine particles a were used as crystalline dendritic fine particles F as they were. Toner mother particles, toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particles A were changed to the crystalline resin fine particles F. The toner of Comparative Example 1 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Comparative Example 1 are shown in Tables 1 and 2.

[Comparative Example 2]
The crystallinity is the same as in Example 1 except that the amount of positively chargeable inorganic fine particles (positively chargeable silica, REA200 (Nippon Aerosil Co., Ltd., average primary particle size 12 nm)) used is changed to 4 parts by mass. Resin fine particles G were obtained. A toner base particle, a toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particle A was changed to the crystalline resin fine particle G. The toner of Comparative Example 2 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Example 3 are shown in Tables 1 and 2.

[Comparative Example 3]
The crystallinity is the same as in Example 1, except that the amount of positively chargeable inorganic fine particles (positively chargeable silica, REA200 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 12 nm)) is changed to 110 parts by mass. Resin fine particles H were obtained. A toner base particle, a toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particle A was changed to the crystalline resin fine particle H. The toner of Comparative Example 2 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Comparative Example 3 are shown in Tables 1 and 2.

[Comparative Example 4]
The toner base particles, toner, and two-component developer are the same as in Example 1 except that the amount of the crystalline resin fine particles A used is changed to 0.05 parts by weight with respect to 100 parts by weight of the toner base particles. Was prepared. The toner of Comparative Example 2 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Comparative Example 4 are shown in Tables 1 and 2. In Comparative Example 4, in both the low density printing test and the standard density printing test, a sufficient image density was not obtained with the initial image, and therefore the subsequent continuous printing test was not performed.

[Comparative Example 5]
Crystalline resin fine particles J were obtained in the same manner as in Example 1 except that 20 parts by mass of positively chargeable inorganic fine particles (silica (no positive charge), RY200 (Nippon Aerosil Co., Ltd., 12 nm)) was used. . Toner mother particles, toner, and a two-component developer were prepared in the same manner as in Example 1 except that the crystalline resin fine particles A were changed to the crystalline resin fine particles J. The toner of Comparative Example 5 was evaluated in the same manner as in Example 1. The evaluation results of the toner of Comparative Example 5 are shown in Tables 1 and 2.

  The crystalline resin fine particles used in the toners of Examples 1 to 5 were prepared by adhering 5 to 100 parts by mass of positively charged silica on the surface with respect to 100 parts by mass of untreated crystalline resin fine particles. is there. For this reason, in the toners of Examples 1 to 5, the negative charging property of the crystalline resin fine particles is suppressed, and the spacer effect due to the crystalline resin fine particles in the toner even for long-term printing at a low printing density. The image density was not impaired and the desired image density could be maintained.

  In the toners of Comparative Examples 1 and 2, the amount of positively-charged silica used is too small, and it is difficult to suppress the reduction of the crystalline resin fine particles in the developing device when printing is performed for a long time at a low printing density. For this reason, in the toners of Comparative Examples 1 and 2, the spacer effect due to the crystalline resin fine particles in the toner was gradually lost, and the desired image density could not be maintained.

  In the toner of Comparative Example 3, the amount of positively charged silica used is excessive. For this reason, the content of free positively chargeable silica contained in the toner is large, and the positively chargeable silica tends to adhere to the toner base particles. In this case, the toner is easily excessively positively charged, the printing period is extended, and the image density of the formed image is likely to be lowered.

  In the toner of Comparative Example 4, since the amount of the crystalline resin fine particles to which the positively charged silica is applied on the surface of the toner base particles is small, a sufficient spacer effect due to the crystalline resin fine particles cannot be obtained, and the low concentration In both the printing test and the standard density printing test, a sufficient image density was not obtained with the initial image. Further, the toner of Comparative Example 5 uses crystalline resin fine particles on the surface of which inorganic fine particles having no positive chargeability are applied. For this reason, when printing is performed for a long time at a low printing density, it is difficult to suppress the reduction of the crystalline resin fine particles in the developing device. For this reason, in the toner of Comparative Example 5, the spacer effect due to the crystalline resin fine particles in the toner was gradually lost, and the desired image density could not be maintained.

Claims (3)

At least a binder resin, a colorant, and a charge control agent to the surface of including toner mother particles, and the crystalline resin particles positively chargeable inorganic fine particles attached on the surface is assigned,
The positively chargeable inorganic fine particles are positively chargeable silica,
The mass ratio ((X) / (Y)) of the mass (X) of the inorganic fine particles and the mass (Y) of the crystalline resin fine particles is 5 to 100%,
A mass ratio (((X) + (Y)) / () of the total mass ((X) + (Y)) of the mass of the inorganic fine particles and the mass of the crystalline resin fine particles to the mass (Z) of the toner base particles. A positively chargeable toner in which Z)) is from 0.1 to 2.0%. The mass ratio ((X) / (Y) ) is 10 to 80% positively chargeable toner of the mounting serial to claim 1. The positively chargeable toner according to claim 1, wherein the mass ratio (((X) + (Y)) / (Z)) is 0.5 to 1.5%.

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