JP2012163634A - Toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner for electrostatic charge image development that suppresses the occurrence of image failure such as fogging so as to form images with excellent density, and prevents resin fine particles from adhering to a photoreceptor drum or a developing roller.SOLUTION: Toner for electrostatic charge image development includes a toner base particle containing at least a binder resin and colorant, and a resin fine particle and silica adhered on the surface of the toner base particle. The resin fine particles covers 10% or more and less than 20% of the surface of the toner base particle, and the silica covers 20% or more and less than 40% of the surface of the toner base particle. The average primary particle diameter of the resin fine particle is preferably 30 nm or more and less than 150 nm.

Description

  The present invention relates to a toner for developing an electrostatic image.

  In general, in an image forming method such as electrophotography or electrostatic recording, the surface of a photosensitive drum is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The image is developed with toner to form a toner image, and the toner image is transferred to a recording medium to obtain a high-quality image. Usually, toners applied to these development methods are 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 μm. The toner particles having a particle size of 15 μm or less are used. In addition, inorganic fine powders such as silica and titanium oxide, and inorganic metal fine powders are externally added to the toner for the purpose of imparting fluidity to the toner, controlling charging of the toner, and improving cleaning properties. .

  In recent years, in a toner used in such an image forming method, resin fine particles made of a polymer having a crosslinked structure are adhered to the toner surface, and the adhesion of the resin fine particles to the photosensitive drum or the developing roller is suppressed. Stabilization of quality over a long period of time is achieved. Further, since the resin fine particles are close to the binder resin of the toner and have an effect of suppressing charging failure, the use of such toner suppresses the generation of fog and the scattering of toner in the image forming apparatus. It is possible.

  As such a toner, for example, a toner in which a fluorinated acrylate homopolymer or copolymer having a crosslinked structure is attached to the surface of toner base particles (colored particles) has been proposed (Patent Document). 1).

Japanese Unexamined Patent Publication No. 07-005725

  However, the toner described in Patent Document 1 cannot form an image having a good density, cannot cause image defects such as fogging, and cannot suppress adhesion of resin fine particles to the photosensitive drum or the developing roller. There is a case where further improvement is required.

  The present invention has been made in view of such circumstances, can form an image with a good density, and can suppress the adhesion of resin fine particles to the photosensitive drum and the developing roller while suppressing the occurrence of image defects such as fogging. An object is to provide a toner for developing an electrostatic image.

  The present inventors attach resin fine particles having an average primary particle diameter of 30 nm or more and less than 150 nm and silica to the surface of toner mother particles containing at least a binder resin and a colorant, and thereby the surface of the toner mother particles by the resin fine particles. It was found that the above problems can be solved by an electrostatic charge image developing toner in which the coverage of the toner is 10% or more and less than 20%, and the surface coverage of the toner base particles with silica is 20% or more and less than 40%. It came to be completed. Specifically, the present invention provides the following.

(1) The resin fine particles and silica are attached to the surface of the toner base particles.
The toner base particles contain at least a binder resin and a colorant,
The surface coverage of the toner base particles with the resin fine particles is 10% or more and less than 20%, and the surface coverage of the toner base particles with the silica is 20% or more and less than 40%. toner.

  (2) The electrostatic image developing toner according to (1), wherein the resin fine particles have an average primary particle size of 30 nm or more and less than 150 nm.

  (3) The electrostatic image developing toner according to (1) or (2), which is a positively chargeable toner.

  (4) The resin fine particle according to any one of (1) to (3), wherein the resin fine particles are produced by emulsion polymerization of a plurality of addition polymerizable monomers including a polyfunctional monomer having a plurality of unsaturated bonds. Toner for developing electrostatic images.

  According to the present invention, it is possible to provide an electrostatic charge image developing toner capable of suppressing adhesion of resin fine particles to a photosensitive drum and a developing roller while suppressing occurrence of image defects such as fogging.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus.

  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 for developing an electrostatic charge image (hereinafter also simply referred to as toner) of the present invention is obtained by adhering resin fine particles and silica to the surface of toner base particles containing at least a binder resin and a colorant. The coverage of the surface of the mother particles is 10% or more and less than 20%, and the coverage of the surface of the toner mother particles with silica is 20% or more and less than 40%. The toner base particles include at least a binder resin and a colorant, and may optionally include a release agent, a charge control agent, and the like. In the toner of the present invention, other fine particles of silica may be adhered to the surface of the toner base particles together with the fine resin particles and silica. Furthermore, the toner of the present invention can be mixed with a carrier and used as a two-component developer. Hereinafter, a binder resin, a colorant, a release agent, a charge control agent, resin fine particles, silica, and other inorganic fine particles of silica, which are essential or optional components of the electrostatic image developing toner of the present invention, A method for producing an electrostatic charge image developing toner, a carrier used when the toner of the present invention is used as a two-component developer, and an image forming method will be described in order.

[Binder resin]
The toner for developing an electrostatic charge image of the present invention is obtained by adhering resin fine particles and silica described later to the surface of toner base particles containing at least a colorant and a binder resin. 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. Specific examples of the binder resin include styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, and polyvinyl alcohol. Examples thereof include thermoplastic resins such as resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, polystyrene resins and polyester resins are preferable from the viewpoints of dispersibility of the colorant in the toner, toner chargeability, and fixing properties to paper. Hereinafter, polystyrene resins and polyester resins will be described.

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

  As the polyester-based 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.

  As the alcohol component, a divalent or trivalent or higher alcohol can be used. 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.

  As the carboxylic acid component, a divalent or trivalent or higher carboxylic acid component 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, 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 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower.

  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 ° C. or higher and 65 ° C. or lower, and more preferably 50 ° C. or higher and 60 ° C. or lower. 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. On the other hand, when the glass transition point is too low, the strength of the binder resin is lowered, and the toner tends to adhere to the photosensitive drum or the like. When the glass transition point is too high, the low-temperature fixability of the toner tends to decrease.

  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]
The toner for developing an electrostatic charge image of the present invention contains a colorant in the binder resin. As the colorant that can be blended in the binder resin, known pigments and dyes can be used according to the color of the toner. Specific examples of suitable colorants to be added to the binder resin 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 Yellow pigments such as titanium yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow rake, permanent yellow NCG, tartrazine rake; Orange pigments such as Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange GK; Bengala, Cadmium Red, Lead Red, Mercury Cadmium, Permanent Red 4R, Li Red pigments such as all red, 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, etc. 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. Extender pigments, and the like. These colorants may be used in combination of two or more for the purpose of adjusting the toner to a desired hue.

〔Release agent〕
The toner for developing an electrostatic charge image of the present invention may contain a release agent in the binder resin for the purpose of improving the fixing property and offset resistance of the toner. The type of release agent that can be blended into the binder resin 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 waxes can be used in combination of two or more. By adding such a release agent to the toner, the occurrence of offset and image smearing (stain around the image when the image is rubbed) can be more efficiently suppressed.

  The amount of the release agent used is not particularly limited as long as the object of the present invention is not impaired. The specific amount of the release agent used is preferably 1 part by mass or more and 5 parts by mass or less when the total amount of toner is 100 parts by mass. If the amount of release agent used is too small, the desired effect may not be obtained with respect to the suppression of the occurrence of offset and image smearing. If the amount of release agent used is excessive, fusion between toners may occur. Depending on the case, the storage stability may decrease.

(Charge control agent)
The toner for developing an electrostatic charge image of the present invention may contain a positively or negatively chargeable charge control agent in the binder resin as long as the object of the present invention is not impaired. In the case of a positively chargeable toner, problems such as defective charging and contamination of the photosensitive member, the developing roller, etc. are likely to occur due to cracking of the silica and peeling of the resin fine particles. For this reason, the toner of the present invention is more preferably a positively chargeable toner containing a positively chargeable charge control material.

  The type of the 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 with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with 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.

  Specific examples of the negatively chargeable charge control agent include organometallic complexes and chelate compounds. Examples of organometallic complexes and chelate compounds include acetylacetone metal complexes such as aluminum acetylacetonate and iron (II) acetylacetonate, and salicylic acid metal complexes or salicylic acid systems such as chromium 3,5-di-tert-butylsalicylate. Metal salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are more preferable. 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 not particularly limited as long as the object of the present invention is not impaired. The use amount of the positively or negatively chargeable charge control agent is typically 1.5 parts by mass or more and 15 parts by mass or less, preferably 2.0 parts by mass when the total amount of the toner is 100 parts by mass. The amount is more preferably 8.0 parts by mass or less, and particularly preferably 3.0 parts by mass or more and 7.0 parts by mass or less. When the amount of the charge control agent used is too small, it is difficult to stably charge the toner to a predetermined polarity, so that the image density is lowered and the maintainability of the image density is liable to be lowered (maintaining the image density over a long period of time). It becomes difficult). In such a case, the charge control agent is difficult to uniformly disperse, and fogging and contamination of the photoreceptor are likely to occur. When the amount of the charge control agent used is excessive, poor charging at high temperature and high humidity due to deterioration of environmental resistance, image failure, and contamination of the photosensitive member are likely to occur.

[Resin fine particles]
The toner for developing an electrostatic charge image of the present invention is prepared after toner base particles having a desired particle diameter are prepared by blending components such as a colorant, a release agent, and a charge control agent in a binder resin. Further, resin fine particles made of various polymers and silica are adhered to the surface of the toner base particles.

  The polymer constituting the resin fine particles is not particularly limited as long as the object of the present invention is not hindered, and a polymer obtained by polycondensation such as polyester, polyamide, polyesteramide, polyimide, polycarbonate, etc., and one kind having an unsaturated bond Any of the polymers obtained by addition polymerization of the above monomers can be used. As the polymer constituting the resin fine particles, it is more preferable to use a polymer obtained by addition polymerization of one or more monomers having an unsaturated bond, since it is easy to prepare resin fine particles having a uniform particle diameter.

  Hereinafter, a polymer obtained by addition polymerization of one or more monomers having an unsaturated bond will be described. A polymer obtained by addition polymerization of one or more monomers having an unsaturated bond is added by combining a monofunctional monomer having one unsaturated bond with a polyfunctional monomer having a plurality of unsaturated bonds as necessary. Manufactured by polymerization.

  Specific examples of the monofunctional monomer include vinyl aromatic compounds such as styrene, p-chlorostyrene, vinyl naphthalene; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-acrylate (Meth) acrylates such as octyl, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide, etc. Other acrylic acid derivatives; ethylene unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide and vinyl fluoride; vinyl acetate, vinyl propionate, vinyl benzoate, butyric acid Bini Vinyl esters 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-vinyl carbazole, N-vinyl indole, N-vinyl compounds such as N-vinylpyrrolidene. These monofunctional monomers can be used in combination of two or more.

  Specific examples of the polyfunctional monomer include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate; divinylaniline, divinyl ether, And divinyl compounds such as divinyl sulfide and divinyl sulfone. These polyfunctional monomers can be used in combination of two or more. When a monofunctional monomer and a polyfunctional monomer are copolymerized, it is easy to increase the outflow start temperature of the polymer.

  The method for addition polymerization of a monomer having an unsaturated bond is not limited as long as the object of the present invention is not impaired, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like can be selected. Among these production methods, the emulsion polymerization method is preferred because it is easy to prepare resin fine particles having a uniform particle diameter.

  Polymerization initiators that can be used for addition polymerization of monomers having an unsaturated bond include potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, and 2,2′-azobis. Known polymerization initiators such as -2,4-dimethylvaleronitrile and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile can be used. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less based on the total amount of monomers.

  When the resin fine particles are produced by emulsion polymerization, the reaction solution is emulsified using a surfactant. In emulsion polymerization, at least one selected from the group consisting of a cationic surfactant, an anionic surfactant, and a nonionic surfactant can be used.

  Specific examples of the cationic surfactant include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl ammonium bromide and the like. Specific examples of the anionic surfactant include fatty acid soaps such as sodium stearate and sodium dodecanoate, and sulfonates such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate. Specific examples of the nonionic surfactant include polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene sorbitan monooleate ether, monodecanoyl sucrose, and the like.

  Among the polymers produced by combining these monomers, it is easy to produce resin fine particles with a uniform particle size, and since it has sufficient hardness, it is difficult to deform or drop off from the surface of the toner base particles, A polymer produced by emulsion polymerization of a plurality of addition-polymerizable monomers including a polyfunctional monomer having a plurality of unsaturated bonds is preferred because it hardly adheres to the surface of the photoreceptor or the developing roller. Specifically, a copolymer obtained by emulsion polymerization of styrene, methyl methacrylate, and divinylbenzene is particularly preferable. The ratio of styrene / methyl methacrylate in such a polymer is preferably 50/50 or more and 90/10 or less, and more preferably 50/50 or more and 80/20 or less as the mass ratio of the monomers. The amount of divinylbenzene used is preferably 5% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, based on the total mass of styrene, methyl methacrylate, and divinylbenzene.

  The average primary particle diameter of the resin fine particles used in the production of the toner of the present invention is not particularly limited as long as the object of the present invention is not impaired. The average primary particle diameter of the resin fine particles is typically preferably 30 nm or more and less than 150 nm. The average primary particle diameter of the resin fine particles can be adjusted by adjusting polymerization conditions, known pulverization methods, classification methods, and the like. When the average primary particle diameter of the resin fine particles is too small, a large amount of an emulsifier is used for the preparation of the resin fine particles, so that the resin fine particles are easily deformed and fog is likely to occur. When it is difficult to obtain a toner with excellent developability and the average primary particle size is excessive, the surface area of the resin fine particles adhering to the toner particles becomes small. It is easy to cause fogging. The average primary particle diameter of the 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.)).

〔silica〕
The toner for developing an electrostatic charge image of the present invention is prepared after toner base particles having a desired particle diameter are prepared by blending components such as a colorant, a release agent, and a charge control agent in a binder resin. The above-mentioned resin fine particles and silica are adhered. The type of silica used in the present invention is not particularly limited, and can be appropriately selected from various silicas conventionally used as external additives for toner.

  Specific examples of suitable silica include, for example, a dry high temperature hydrolysis method, which is a method of vaporizing silicon chloride such as silicon tetrachloride and synthesizing silica fine particles by gas phase reaction in a high temperature hydrogen flame. Fumed silica, silica produced by deflagration method that synthesizes silica fine particles by oxidizing the silica in an oxygen stream and cooling the silica vapor generated by the reaction heat, silica fine particles by hydrolysis of alkoxysilane And silica produced by a sol-gel method for synthesizing by a wet process and silica produced by a colloidal process for synthesizing silica fine particles by a wet process by hydrolysis of water glass.

  Silica having a surface treated with a hydrophobizing agent can be used. When silica hydrophobized is used, it is easy to suppress a decrease in charge amount under high temperature and high humidity, and it is easy to obtain a toner having excellent fluidity. As the hydrophobizing agent, for example, an aminosilane coupling agent can be used. Specific examples of the aminosilane coupling agent include γ-aminopropyltriethoxysilane, γ-aminopropylmethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ- (2-aminoethyl). -Γ-aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane and the like. In order to supplement the hydrophobizing effect, an aminosilane coupling agent and a hydrophobizing agent other than the aminosilane coupling agent can be used in combination. As the hydrophobizing agent other than the aminosilane coupling agent, hexamethyldisilazane is preferably used because of its excellent hydrophobizing effect and toner fluidity improving effect.

  Silicone oil can also be used as a hydrophobizing agent for silica. The type of silicone oil is not particularly limited as long as a desired hydrophobizing effect is obtained, and various silicone oils conventionally used as a hydrophobizing agent can be used. As the silicone oil, those having a linear siloxane structure are preferable, and any of non-reactive silicone oil and reactive silicone oil can be used. Specific examples of silicone oils include dimethyl silicone oil, phenylmethyl silicone oil, chlorophenyl silicone oil, alkyl silicone oil, chlorosilicone oil, polyoxyalkylene modified silicone oil, fatty acid ester modified silicone oil, methyl hydrogen silicone oil, silanol group-containing Examples include silicone oil, alkoxy group-containing silicone oil, acetoxy group-containing silicone oil, amino-modified silicone oil, carboxylic acid-modified silicone oil, alcohol-modified silicone oil, and the like.

  As a method of hydrophobizing silica, a method of dropping or spraying a hydrophobizing agent such as aminosilane or silicone oil while stirring silica at a high speed, or in a stirring hydrophobizing agent in an organic solvent solution. The method of adding an external additive is mentioned. By heating after the hydrophobization treatment, hydrophobized silica particles are obtained. When the hydrophobizing agent is dropped or sprayed, the hydrophobizing agent can be used as it is or diluted with an organic solvent or the like.

  The average primary particle diameter of silica used in the present invention is not particularly limited as long as the object of the present invention is not impaired. Typically, 7 nm to 500 nm is preferable, and 12 nm to 120 nm is more preferable. When the average primary particle diameter is too small, silica is buried in the toner base particles, which may cause a decrease in toner fluidity and a decrease in image density. When the average primary particle diameter is excessive, silica is easily detached from the toner base particles, and an image defect may occur in the formed image due to contamination of the photoreceptor and the developing roller.

[Other inorganic fine particles of silica]
The toner for developing an electrostatic charge image of the present invention is not limited to the purpose of the present invention, and other than silica, together with organic fine particles and silica, for the purpose of improving the fluidity, storage stability, cleaning properties, etc. of the toner. 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 other inorganic fine particles of silica 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 of silica 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. . Further, as the other inorganic fine particles of silica, those which have been subjected to a hydrophobic treatment in the same manner as silica can be used.

[Method for producing toner for developing electrostatic image]
The method for producing toner base particles used for the preparation of the toner of the present invention is not particularly limited as long as the components contained in the toner base particles are uniformly mixed. As a specific example of the method for producing toner base particles, the binder resin and the above-described components such as the colorant, charge control agent, and release agent are mixed by a mixer or the like, and then kneaded by an extruder or the like. Examples thereof include a method of melt-kneading with a machine, then cooling the kneaded product, and pulverizing and classifying it. 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 it is preferably 5 μm or more and 10 μm or less.

  The toner for developing an electrostatic charge image of the present invention is produced by adhering resin fine particles and silica to the toner base particles obtained as described above. The method for adhering the resin fine particles and silica to the toner base particles is not particularly limited. For example, the processing conditions are adjusted so that the resin fine particles and silica are not embedded in the toner base particles, and a Henschel mixer or Nauta A method of mixing toner base particles, resin fine particles, and silica by a mixer such as a mixer can be mentioned.

  In the toner for developing an electrostatic charge image of the present invention, the surface coverage of the toner base particles by the resin fine particles is 10% or more and less than 20%, and the coverage of the surface of the toner base particles by silica is 20% or more and less than 40%. is there. The coverage of the surface of the toner base particles with resin fine particles and the coverage of the surface of the toner base particles with silica can be measured according to the following methods. The surface coverage of the toner base particles with the resin fine particles and the surface coverage of the toner base particles with the silica are the amount of the resin fine particles and silica used when the resin fine particles and silica are attached to the toner base particles. It can be adjusted by adjusting. The coverage of the surface of the toner base particles with resin fine particles and the coverage of the surface of the toner base particles with silica can be measured according to the following methods.

<Measurement method of coverage with resin fine particles>
Using a field emission scanning electron microscope (JSM-7401F, manufactured by JEOL Ltd.), a photograph of toner particles at a magnification of 100,000 was taken at a pressurizing voltage of 0.5 Kv. The photographed electron micrograph was analyzed with image analysis software (WinROOF (manufactured by Mitani Corporation)), and for 30 toner particles, the surface area of the toner particles and the total area of the portions covered with the resin fine particles Was measured. Next, the coverage of each toner particle with resin fine particles was calculated based on the following equation. The average value of the coverage of the 30 toner particles with the resin fine particles was defined as the coverage of the toner with the resin fine particles. The surface area of the toner particles is the area inside the outline of the toner particles in the electron micrograph, and the area where the toner is coated with the resin fine particles is the area inside the outline of the resin particles in the electron micrograph. is there. Further, the resin fine particles and the silica attached to the surface of the toner can be distinguished by the hue in the electron micrograph. In the electron micrograph, resin fine particles are photographed with a darker hue than silica.
(Calculation formula of coverage with resin fine particles)
Covering rate by resin fine particles (%) = (total area where toner is covered by resin fine particles) ÷ (surface area of toner particles) × 100

<Measurement method of silica coverage>
In the same manner as the method for measuring the coverage with resin fine particles, an electron micrograph of toner particles with a magnification of 100,000 times is analyzed with image analysis software. About 30 toner particles, the surface area of the toner particles and the silica toner And the total area of the portions covered with. Next, the coverage of each toner particle with silica was calculated based on the following equation. The average value of the coverage of the 30 toner particles with silica was defined as the coverage of the toner with silica. The area of the portion where the toner is coated with silica is the area inside the outline of the silica particles in the electron micrograph.
(Calculation formula of coverage with silica)
Silica coverage (%) = (total area where the toner is coated with silica) / (surface area of toner particles) × 100

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

  Suitable carriers when the toner for developing an electrostatic charge image of the present invention is a two-component developer include those in which a carrier core material is coated with a resin. Specific examples of carrier core materials include particles 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 (tetrafluoroethylene / hexafluoropropylene copolymer) Resin, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, etc.), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, amino resin (Polyamide resin, polyimide resin, polyamide-imide resins, etc.) 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 the particle diameter measured by an electron microscope is preferably 20 μm or more and 200 μm or less, and more preferably 25 μm or more and 100 μm or less.

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 composition of the carrier and the surface structure, but is typically preferably 2.4 × 10 ³ kg / m ³ or more and 3.0 × 10 ³ kg / m ³ or less.

  When the electrostatic image developing toner of the present invention is used as a two-component developer, the toner content is preferably 1% by mass or more and 20% by mass or less, and preferably 3% by mass or more and 15% by mass with respect to the mass of the two-component developer. The mass% or less is preferable. 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.

(Image forming method)
The toner for developing an electrostatic charge image of the present invention can be used in various image forming apparatuses that form an image by a one-component development method or a two-component development method. Here, among the two-component development methods, a touch-down development method which is a development method suitable in terms of image quality and life will be described with reference to FIG. In the touch-down development method, fogging and toner scattering are likely to occur due to poor charging of the two-component developer, so that the effect of using the two-component developer containing the toner of the present invention is remarkable.

  In the touch-down development method, a magnetic brush is formed on the surface of the magnetic roller with a two-component developer, and only the toner is transferred from the magnetic brush to the surface of the developing roller that is disposed facing the photoconductor to form a toner layer. In this method, toner is ejected from the toner layer, and the electrostatic latent image on the surface of the photoreceptor is developed as a toner image.

  An image forming apparatus 10 of a touch-down development method illustrated in FIG. 1 includes a drum-shaped photoconductor 11, a charging unit 12 for charging the surface of the photoconductor 11, and an electrostatic latent image by exposing the surface of the photoconductor 11. The toner image is transferred from the photosensitive member 11 to the transfer member that moves on the endless belt 15. The exposure unit 13 forms a toner image by developing the electrostatic latent image with toner. A transfer unit 16 and a cleaning unit 17 for cleaning the surface of the photoreceptor are provided.

  As the photoreceptor 11, an inorganic photoreceptor such as selenium or amorphous silicon; an organic photoreceptor in which a single layer or a laminated photoreceptor layer containing a charge generating agent, a charge transport agent, a binder resin, etc. is formed on a conductive substrate. Etc. Examples of the charging unit 12 include a scorotron system, a charging roller, and a charging brush. As the exposure hand portion 13, the transfer portion 16, and the cleaning portion 17, known ones may be used.

  The developing unit 14 includes a magnetic roller 18 (developer carrying member) on which a magnetic brush is formed by a two-component developer, and toner transferred from a magnetic brush (not shown) formed on the magnetic roller 18. A developing roller 19 (toner carrier) on which a toner layer (not shown) is formed, a power source 20 for applying a direct current (DC) bias to the magnetic roller 18, and a direct current (DC) bias to the developing roller 19. , A power supply 24 for applying an alternating current (AC) bias to the developing roller 19, a regulation blade 26 for keeping the height of the magnetic brush formed on the magnetic roller 18 constant, and a toner container. Stirring the container 28, the stirring mixer 30 for charging the toner of the two-component developer, and the two-component developer supplied from the stirring mixer 30. A paddle mixer 34 to be supplied to the magnetic roller 18 and a partition plate 32 for partitioning between the stirring mixer 30 and the paddle mixer 34 (the developer is mixed through a flow path (not shown) between the partition plate 32 and a frame 36 described later). 30 to the paddle mixer 34), and a magnetic roller 18, a developing roller 19, a stirring mixer 30, and a frame 36 that houses the paddle mixer 34. The magnetic roller 18 has a plurality of fixed magnets disposed therein, and the sleeve-like magnetic roller 18 can rotate around the fixed magnet. Further, the developing roller 19 is disposed on the opposite side of the photoconductor 11.

  In the touch-down development type image forming apparatus shown in FIG. 1, for example, a charging process for charging the surface of the photoconductor 11 by the charging unit 12, and the surface of the photoconductor 11 is exposed by the exposure unit 13. A magnetic brush is formed by a two-component developer composed of a toner and a carrier, and a toner layer is formed by separating only the toner from the magnetic brush. An image is formed by a method including a developing step of attaching the exposed portion of the electrostatic latent image to a toner image.

  A specific image forming method is as follows. First, the charging unit 12 charges the surface of the photoconductor 11, and then the exposure unit 13 exposes the surface of the photoconductor 11 to form an electrostatic latent image. On the other hand, in the developing unit 14, the toner of the two-component developer is charged by the stirring mixer 30, the two-component developer is supplied to the magnetic roller 18 by the paddle mixer 34, and is carried on the surface of the magnetic brush. Then, only the toner is transferred from the magnetic brush to the surface of the developing roller 19 to form a toner layer on the surface of the developing roller 19.

  Then, the toner is ejected from the toner layer of the developing roller 19, and the toner is attached to the exposed portion of the electrostatic latent image of the photoreceptor 11 to develop the electrostatic latent image as a toner image. Next, the toner image is transferred from the photosensitive member 11 to the transfer target moving on the endless belt 15 by the transfer unit 16 to form an image. Separately, the surface of the photoconductor 11 after the transfer process is cleaned using the cleaning unit 17. The above steps are repeated.

  The toner supplied from the container 28 is mixed with a carrier by a stirring mixer 30 to be a two-component developer.

  According to the electrostatic image developing toner of the present invention described above, it is possible to suppress the occurrence of image defects such as fogging while forming an image with a good density, such as resin fine particles on the photosensitive drum and the developing roller. Adhesion can be suppressed. In the touch-down development method, the problem of adhesion of resin fine particles or the like to the photosensitive drum or the development roller is likely to occur. However, according to the electrostatic image developing toner of the present invention, image formation using the touch-down development method is possible. Such a problem can also be reduced or eliminated in the apparatus. Therefore, the electrostatic image developing toner of the present invention is suitably used in various image forming apparatuses regardless of the developing method.

  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 of silica)
100 g of dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) and 100 g of 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 200 g of toluene, and then diluted 10 times. Next, while stirring 200 g of fumed silica Aerosil # 90 (manufactured by Nippon Aerosil Co., Ltd.), a diluted solution of dimethylpolysiloxane and 3-aminopropyltrimethoxylane was gradually added dropwise, followed by ultrasonic irradiation and stirring for 30 minutes. And mixed. The obtained mixture was heated in a thermostat at 150 ° C., and then toluene was distilled off using a rotary evaporator to obtain a solid. The obtained solid was dried with a vacuum dryer at a set temperature of 50 ° C. until it was not reduced. Further, a silica A coarse powder was obtained by performing a treatment at 200 ° C. for 3 hours in a nitrogen stream in an electric furnace. The coarse powder of silica A was crushed by a jet mill and collected by a bag filter to obtain silica having an average primary particle diameter of 20 nm.

(Preparation of resin fine particles A)
A glass reactor equipped with a thermometer, reflux condenser, nitrogen gas inlet tube, and stirrer was charged with 200 parts by weight of deionized water and 2 parts by weight of sodium lauryl sulfate, and the temperature was raised to 80 ° C. in a nitrogen gas atmosphere. . Next, after adding 1 part by mass of ammonium persulfate with stirring, a mixture of monomers consisting of 30 parts by mass of methyl methacrylate, 60 parts by mass of styrene, and 10 parts by mass of divinylbenzene was added dropwise over 1 hour and stirred for 1 hour. The emulsion thus obtained was dried to obtain resin fine particles A having an average primary particle diameter of 75 nm. The average primary particle diameter of the resin fine particles A was measured according to the following method.

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

(Preparation of resin fine particle B)
Resin fine particles B were obtained in the same manner as the resin fine particles A except that the amount of sodium lauryl sulfate used was changed to 4 parts by mass. The average primary particle diameter of the resin fine particles B was 34 nm.

(Preparation of resin fine particles C)
Resin fine particles C were obtained in the same manner as the resin fine particles A except that the amount of sodium lauryl sulfate used was changed to 0.5 parts by mass. The average primary particle diameter of the resin fine particles C was 148 nm.

(Making toner mother particles)
Binder resin (styrene-acrylic resin) 100 parts by mass, release agent (carnauba wax, manufactured by Nippon Seiwa Co., Ltd.), colorant (carbon black, NIPex 60 (produced by Evonik Degussa)) ) 12 parts by mass and 1 part by mass of a positively chargeable charge control agent (BONTRON N-21 (manufactured by Orient Chemical Co., Ltd.)) were charged into a Henschel mixer and mixed, and then melted and kneaded by a twin screw extruder. The melt-kneaded product was cooled, coarsely pulverized with a hammer mill, and then finely pulverized with a turbo mill. The finely pulverized powder was classified by an air classifier to obtain toner base particles having a volume average particle diameter of 6.81 μm.

(Creation of carrier)
30 g of polyamideimide resin was diluted with 2 L of water to obtain a diluted solution. After 120 g of tetrafluoroethylene / hexafluoropropylene copolymer (FEP) was dispersed in the obtained diluted liquid, 3 g of silicon oxide was further dispersed to obtain a coating layer forming liquid. This coating layer forming liquid and 10 kg of non-coated ferrite carrier EF-35B (manufactured by Powdertech Co., Ltd., average particle diameter: 35 μm) were charged into a fluidized bed coating apparatus for coating. Then, baking was performed at 250 degreeC for 1 hour, and the carrier was obtained.

[Example 1]
To 2 kg of toner base particles, 28 g of silica and 20 g of resin fine particles A were added and mixed with a Henschel mixer at a speed of 40 m / s for 5 minutes to obtain a toner.

[Example 2]
A toner was obtained in the same manner as in Example 1 except that the amount of the resin fine particles A used was changed to 28 g.

Example 3
A toner was obtained in the same manner as in Example 1 except that the amount of silica used was changed to 36 g.

Example 4
A toner was obtained in the same manner as in Example 1 except that the amount of silica used was changed to 18 g.

Example 5
A toner was obtained in the same manner as in Example 1 except that the resin fine particles A were changed to resin fine particles B and the amount of resin fine particles used was changed to 12 g.

Example 6
A toner was obtained in the same manner as in Example 1 except that the resin fine particles A were changed to resin fine particles C and the amount of resin fine particles used was changed to 44 g.

[Comparative Example 1]
A toner was obtained in the same manner as in Example 1 except that the amount of silica used was changed to 40 g.

[Comparative Example 2]
A toner was obtained in the same manner as in Example 1 except that the amount of silica used was changed to 16 g.

[Comparative Example 3]
A toner was obtained in the same manner as in Example 1 except that the amount of resin fine particles A used was changed to 12 g.

[Comparative Example 4]
A toner was obtained in the same manner as in Example 1 except that the amount of resin fine particles A used was changed to 32 g.

[Comparative Example 5]
A toner was obtained in the same manner as in Example 1 except that the resin fine particles A were changed to resin fine particles B and the amount of resin fine particles used was changed to 16 g.

[Comparative Example 6]
A toner was obtained in the same manner as in Example 1 except that the resin fine particles A were changed to resin fine particles C and the amount of resin fine particles used was changed to 26 g.

  With respect to the toners obtained in Examples and Comparative Examples, the coverage of the toner base particle surface with resin fine particles and the coverage of the toner base particle surface with silica were measured according to the following methods. The obtained measurement results are shown in Table 1.

<Measurement method of coverage with resin fine particles>
Using a field emission scanning electron microscope (JSM-7401F, manufactured by JEOL Ltd.), a photograph of toner particles at a magnification of 100,000 was taken at a pressurizing voltage of 0.5 Kv. The photographed electron micrograph was analyzed with image analysis software (WinROOF (manufactured by Mitani Corporation)), and for 30 toner particles, the surface area of the toner particles and the total area of the portions covered with the resin fine particles Was measured. Next, the coverage of each toner particle with resin fine particles was calculated based on the following equation. The average value of the coverage of the 30 toner particles with the resin fine particles was defined as the coverage of the toner with the resin fine particles. The surface area of the toner particles is the area inside the outline of the toner particles in the electron micrograph, and the area where the toner is coated with the resin fine particles is the area inside the outline of the resin particles in the electron micrograph. is there. Further, the resin fine particles and the silica attached to the surface of the toner can be distinguished by the hue in the electron micrograph. In the electron micrograph, resin fine particles are photographed with a darker hue than silica.
(Calculation formula of coverage with resin fine particles)
Covering rate by resin fine particles (%) = (total area where toner is covered by resin fine particles) ÷ (surface area of toner particles) × 100

<Measurement method of silica coverage>
In the same manner as the method for measuring the coverage with resin fine particles, an electron micrograph of toner particles with a magnification of 100,000 times is analyzed with image analysis software. About 30 toner particles, the surface area of the toner particles and the silica toner And the total area of the portions covered with. Next, the coverage of each toner particle with silica was calculated based on the following equation. The average value of the coverage of the 30 toner particles with silica was defined as the coverage of the toner with silica. The area of the portion where the toner is coated with silica is the area inside the outline of the silica particles in the electron micrograph.
(Calculation formula of coverage with silica)
Silica coverage (%) = (total area where the toner is coated with silica) / (sum of toner particle surface areas) × 100

  Regarding the toners of the examples and comparative examples, a digital color multi-function machine (TASKalfa 500ci, Kyocera Mita) that employs a developing device that develops by a touch-down method, loaded with the developer containing the toner obtained in the examples and comparative examples. The measured values of image density, fogging and developing sleeve resistance were evaluated according to the following method. The developer used for the evaluation was prepared by mixing 30 g of the toner obtained in Examples and Comparative Examples and 300 g of a carrier for 30 minutes using a ball mill. Table 1 shows the evaluation results of the image density, fogging, and developing sleeve resistance of the toners of Examples and Comparative Examples.

<Image density evaluation method>
The reflection density of the solid image was measured using a spectrophotometer (Spectroeye (manufactured by X-Rite)). An image density of 1.20 or more was judged as good, and a density less than 1.20 was judged as bad.

<Cover evaluation method>
After 3,000 sheets were continuously printed at a printing rate of 0.2%, an original with a printing rate of 20% was printed and the maximum fog value was measured. The fog value was measured by (Spectroeye (manufactured by X-Rite)). A fog value of 0.008 or less was determined to be good, and a value exceeding 0.008 was determined to be poor.

<Development sleeve resistance evaluation>
The surface resistance at the center of the developing roller after continuous printing of 300,000 sheets at a printing rate of 5% was applied with 1,000 V with a high resistivity meter (Hiresta MCP-HT450, manufactured by Mitsubishi Chemical Corporation). And measured. A resistance value of less than 1.0 × 10 ⁸ is considered good, and 1.0 × 10 ⁸ or more is considered bad.

  The resin fine particles and silica adhere to the surface of the toner base particles, the coverage of the toner base particles by the resin fine particles is 10% or more and less than 20%, and the coverage of the toner base particles by silica is 20% or more and 40%. In each of the toners of Examples 1 to 6 that are less than 1%, the image density is good, the fog value is small, and the surface resistance of the developing roller due to adhesion of resin fine particles or silica to the developing roller is significantly increased. I couldn't.

  According to Comparative Example 1, it can be seen that when the silica coverage is 40% or more, the fogging value is high and it is difficult to obtain a good image. Further, according to Comparative Example 2, it can be seen that when the silica coverage is less than 20%, a good image cannot be obtained due to a decrease in image density.

  According to Comparative Examples 3 and 6, it can be seen that when the coverage of the resin fine particles is less than 10%, the fogging value becomes high and it is difficult to obtain a good image. Further, according to Comparative Examples 4 and 5, when the coverage of the resin fine particles is 20% or more, the surface resistance of the developing roller is remarkably increased due to adhesion of the resin fine particles detached from the toner surface. Recognize.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Photoconductor 12 Charging part 13 Exposure part 14 Developing part 15 Endless belt 16 Transfer part 17 Cleaning part 18 Magnetic roller 19 Developing roller 20 Power supply 22 Power supply 24 Power supply 26 Regulation blade 28 Container 30 Stirring mixer 32 Partition plate 36 Frame body

Claims (4)

Resin fine particles and silica are attached to the surface of the toner base particles,
The toner base particles contain at least a binder resin and a colorant,
The surface coverage of the toner base particles with the resin fine particles is 10% or more and less than 20%, and the surface coverage of the toner base particles with the silica is 20% or more and less than 40%. toner.   The electrostatic image developing toner according to claim 1, wherein an average primary particle diameter of the resin fine particles is 30 nm or more and less than 150 nm.   The electrostatic image developing toner according to claim 1, which is a positively charged toner.   4. The electrostatic image development according to claim 1, wherein the resin fine particles are produced by emulsion polymerization of a plurality of addition-polymerizable monomers including a polyfunctional monomer having a plurality of unsaturated bonds. 5. toner.

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