JP2012203045A - Toner for developing electrostatic latent image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner for developing an electrostatic latent image capable of suppressing occurrence of fogging, suppressing occurrence of image failure due to reduction in image density or contamination of a development counter when printing is performed over a long period of time and suppressing of occurrence of carrier spent in the case of using toner as a two-component developer.SOLUTION: By adhering resin fine powder composed of inorganic fine powder containing silica and a styrene acrylic resin to the surface of toner base particles containing at least a binder resin and a coloring agent, the isolation rate of silica is adjusted to 5 to 15% by mass and the BET specific surface area of the toner is adjusted to 2 to 3.5 m/g.

Description

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

  In general, in an image forming method such as electrophotography or electrostatic recording, the surface of an electrostatic latent image carrier (photosensitive member) is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The electrostatic latent 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. 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 particle size of ˜15 μm is used. 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 are used. Powder is externally added to the toner.

  In recent years, toners used in such an image forming method have been used in which resin fine powder is adhered to the toner surface in addition to inorganic fine powder. Resin fine powder is close to the binder resin of the toner and has a similar charge series and has the effect of suppressing poor charging of the toner. When such toner is used, the generation of fog and the scattering of the toner in the image forming apparatus are suppressed. Is possible.

As a toner using inorganic fine powder and resin fine powder as external additives, for example, a toner composition containing at least a binder resin and a colorant is present in the presence of an inorganic fine powder having an average primary particle size of 6 to 20 nm. A BET specific surface area of 1 is obtained by externally adding silica particles having an average primary particle diameter of 25 to 60 nm and resin fine powder to toner base particles having a volume median particle diameter of 3 to 8 μm obtained by pulverization in step 1. A color toner of .5 to 3.5 m ² / g has been proposed (Patent Document 1).

JP 2007-328324 A

  However, when the toner of Patent Document 1 is used, the occurrence of fog is not necessarily suppressed. In addition, the toner of Patent Document 1 may be printed with a low coverage for a long time, and silica or resin fine powder may be detached from the surface of the toner when the toner is stirred in the developing device for a long time. . In this case, an image defect is likely to occur due to a decrease in image density or contamination of the developing device (developing sleeve) with an external additive. In addition, when toner is mixed with a carrier and used as a two-component developer, the spent on which silica or resin fine powder adheres to the carrier is easily generated, and the toner is charged to a desired charge amount when printing is performed for a long period of time. May not be possible.

  The present invention has been made in view of such circumstances, can suppress the occurrence of fogging, can suppress the occurrence of image defects due to a decrease in image density and contamination of the developing device when printing over a long period of time. An object of the present invention is to provide an electrostatic latent image developing toner capable of suppressing the occurrence of carrier spent when used as a component developer.

The inventors of the present invention have inorganic fine powder and resin fine powder adhered to the surface of toner base particles containing at least a binder resin and a colorant, the inorganic fine powder contains silica, and the resin fine powder is styrene acrylic. It is found that the above problems can be solved by a toner for developing an electrostatic latent image, which is a resin based on silica, has a liberation rate of silica of 5 to 15% by mass, and a BET specific surface area of ² to 3.5 m ² / g. It came to complete. Specifically, the present invention provides the following.

(1) An inorganic fine powder and a resin fine powder are attached to the surface of toner base particles containing at least a binder resin and a colorant,
The inorganic fine powder contains silica,
The resin fine powder is a styrene acrylic resin,
The liberation rate of the silica is 5 to 15% by mass,
An electrostatic latent image developing toner having a BET specific surface area of ² to 3.5 m ² / g.

  (2) The electrostatic latent image developing toner according to (1), wherein the silica content is 0.1 to 10 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner.

  (3) For electrostatic latent image development according to (1) or (2), the content of the resin fine powder is 0.3 to 5 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner. toner.

  (4) The electrostatic latent image developing toner according to any one of (1) to (3), wherein the silica has an average primary particle diameter of 10 to 150 nm.

  (5) The electrostatic latent image developing toner according to any one of (1) to (4), wherein an average primary particle diameter of the resin fine powder is 30 to 300 nm.

  According to the present invention, the occurrence of fog can be suppressed, the occurrence of image defects due to image density reduction and contamination of the developing device when printing over a long period of time can be suppressed, and carrier spent when using toner as a two-component developer. It is possible to provide a toner for developing an electrostatic latent image that can suppress the occurrence of the above.

  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 latent image (hereinafter also simply referred to as toner) of the present invention comprises an inorganic fine powder containing silica and a styrene acrylic resin on the surface of toner base particles containing at least a binder resin and a colorant. A fine resin powder is adhered, the liberation rate of silica is 5 to 15% by mass, and the BET specific surface area of the toner is ² to 3.5 m ² / g. 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. 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 charge control agent, a release agent, a resin fine powder, and an inorganic fine powder, which are essential or optional components of the toner for developing an electrostatic latent image of the present invention, An image developing toner manufacturing method 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 electrostatic latent image developing toner of the present invention includes a binder resin and a colorant, and if necessary, the surface of toner base particles containing a charge control agent, a release agent and the like are mixed with silica. An inorganic fine powder containing styrene and a resin fine powder made of styrene acrylic resin are attached. 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 electrostatic latent image developing 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, 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. 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. When developing with positively charged toner, a positively chargeable charge control agent is used. When developing with negatively charged toner, a negatively chargeable charge control agent is used.

  The 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 amount of the positively or negatively chargeable charge control agent used is typically preferably 1.5 to 15 parts by mass, and 2.0 to 8.0 parts by mass when the total amount of toner is 100 parts by mass. Part is more preferable, and 3.0 to 7.0 parts by weight is particularly preferable. 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 may be lowered or the image density may not be maintained for a long time. In such a case, the charge control agent is difficult to uniformly disperse, and the fog and the latent image carrier are likely to be contaminated. If the amount of charge control agent used is excessive, toner charge failure under high temperature and high humidity is likely to occur due to deterioration of environmental resistance, and as a result, image defects and contamination of the latent image carrier are likely to occur. Become.

〔Release agent〕
The toner for developing an electrostatic latent image 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 waxes 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 release agent used is too small, the desired effect may not be obtained with respect to suppression of 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.

[Resin fine powder]
In the present invention, resin fine powder made of styrene acrylic resin is used as an external additive. The styrene acrylic resin can be prepared by addition polymerization of a monomer containing a styrene monomer and an acrylic monomer. By using resin fine powder made of styrene acrylic resin as an external additive, it is easy to suppress fusion between toners, adhesion of toner or resin fine powder to a developing sleeve, and fogging in a formed image.

  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.

  When producing a styrene acrylic resin, a monomer having one or more unsaturated bonds other than the styrene monomer and the acrylic monomer can be used as long as the object of the present invention is not impaired. . Specific examples of monomers other than styrene monomers and acrylic monomers include ethylene unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene; vinyl chloride, vinyl bromide, vinyl fluoride, etc. Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone Vinyl ketones; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidene. If desired, polyfunctional monomers 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; divinyl Divinyl compounds such as aniline, divinyl ether, divinyl sulfide and divinyl sulfone can also be copolymerized.

  The method for producing the styrene acrylic resin 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 preferable because it is easy to prepare resin fine powder having a uniform particle size.

  Polymerization initiators that can be used when producing styrene acrylic resins include potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 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 to 15% by mass relative to the total amount of monomers.

  When the resin fine powder is produced by emulsion polymerization, it may be polymerized using an emulsifier (surfactant) or may be polymerized in a non-emulsifier (soap-free) system. As the surfactant that can be used for the 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.

  30-300 nm is preferable and, as for the average primary particle diameter of resin fine powder, 50-150 nm is more preferable. The average primary particle diameter of the resin fine powder can be adjusted by adjusting polymerization conditions, a known pulverization method, classification method, or the like. The average primary particle diameter of the resin fine powder is obtained by obtaining an image obtained by observing the resin fine powder at a magnification of, for example, 10,000 times with a scanning electron microscope (SEM), and processing the obtained image with image analysis software. It can be measured by measuring the particle diameter of a sufficient number of resin fine powders to calculate the value.

  The usage-amount of resin fine powder is not specifically limited in the range which does not inhibit the objective of this invention. Typically, when the mass of the toner is 100 parts by mass, 0.3 to 5 parts by mass is preferable, and 0.5 to 2 parts by mass is more preferable. If the amount of resin fine powder used is too small, fogging tends to occur. If the amount of resin fine powder used is excessive, image defects are likely to occur due to contamination of the developing device (developing sleeve).

[Inorganic fine powder]
In the present invention, an inorganic fine powder is used together with a resin fine powder as an external additive, and the inorganic fine powder contains silica. By using silica as an external additive, the fluidity and storage stability of the toner can be improved.

  The addition amount of silica is not particularly limited as long as the silica liberation rate measured by the method described later is 5 to 15%, so long as the object of the present invention is not impaired. Typically, the addition amount of silica is preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass when the mass of the toner is 100 parts by mass. When silica is used in such an amount, it is easy to obtain a toner excellent in fluidity, storage stability, and cleaning properties.

  The average primary particle diameter of silica is not particularly limited as long as the object of the present invention is not impaired. Typically, 10 to 150 nm is preferable, and 12 to 80 nm is more preferable. When the silica particle diameter is in such a range, it is easy to obtain a toner having excellent fluidity, and the specific surface area of the toner is easily adjusted to a predetermined range.

  Silica can be used as hydrophobized silica surface-treated with a hydrophobizing agent. When silica hydrophobized is used, a decrease in charge amount under high temperature and high humidity conditions is suppressed, and a toner excellent in fluidity can be easily obtained. 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 silica is mentioned. The silica subjected to the hydrophobization treatment is obtained by heating after the hydrophobization treatment. 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.

  From the viewpoint of satisfactorily cleaning the latent image carrier, the inorganic fine powder may contain inorganic metal oxides such as alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate in addition to silica. preferable. When the inorganic fine powder contains an inorganic metal oxide, the amount of the inorganic metal oxide used is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass with respect to the mass of the electrostatic latent image developing toner. . When the amount of titanium oxide used is too small, cleaning of the latent image carrier tends to be insufficient. When the amount of titanium oxide used is excessive, the fluidity of the toner tends to deteriorate.

  The average primary particle diameter of the inorganic metal oxide is not particularly limited as long as the object of the present invention is not impaired, and typically 0.01 to 1.0 μm is preferable.

[Method for producing toner for developing electrostatic latent image]
The electrostatic latent image developing toner is produced by adhering the above-described resin fine powder and inorganic fine powder as external additives to the surface of toner base particles.

  The toner base particles in the toner for developing an electrostatic latent image are desired by pulverization / classification after blending a binder with a colorant and, if necessary, optional components such as a release agent and a charge control agent. It is obtained by adjusting the particle size of 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 release agent, and a charge control 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 base particles, a binder resin and components such as a colorant, a release agent, and a charge control 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.

The toner for developing an electrostatic latent image has a liberation rate of silica of 5 to 15% by mass and a BET specific surface area of ² to 3.5 m ² / g. Can be adjusted by adjusting the conditions of the external addition process. For example, the liberation rate and the BET specific surface area can be reduced by increasing the number of revolutions of a stirrer of a mixer such as a Henschel mixer or a Nauter mixer, or by increasing the treatment time. Further, the BET specific surface area of the toner can be adjusted by adjusting the temperature condition during the external addition process. By increasing the temperature during the external addition treatment, the BET specific surface area of the toner can be reduced. Further, the BET specific surface area of the toner can be adjusted by adjusting the particle diameter of the external additive. By increasing the particle diameter of the external additive, the BET specific surface area of the toner can be reduced.

  The liberation rate of silica can be measured according to the following method, and the BET specific surface area of the toner can be measured using, for example, a specific surface area measuring device (HM MODEL-1208 (manufactured by Mountec Co., Ltd.)).

<Method for measuring silica release rate>
The liberation rate of silica in the claims of the present application and in the specification is determined using the airflow classifier (DSX-2 (manufactured by Nippon Pneumatic Industrial Co., Ltd.)) and free silica from the toner under the following conditions. Classify and measure.
(Free silica separation conditions)
Sample supply rate: 100 g / min Supply section injection pressure: 0.2 MPa
Adjustable string: 80mm
Louver height: 10mm
Louver clearance: 5mm
Distance ring: 0mm
Center navel: 60mm
U damper: 45 °
Cyclone damper: 30 °
Blower total static pressure: -1400 mmAq (-13.73 kPa)

The mass of the silica in the toner 100g and _{A 1} g, the mass of the other external additives _A 2 _{g, A} 3 _g, and ··· _{A n} g. Further, after 100 g of the toner has been classified, the mass of silica contained in the toner is B ₁ g, and the mass of the other inorganic fine powders is B ₂ g, B ₃ g,... B _n g. Further, the silica content of the toner after the classification treatment is C ₁ mass%, and the contents of the other inorganic fine powders are C ₂ mass%, C ₃ mass%,. In this case, assuming that n (positive integer) types of components are used as the inorganic fine powder, an n-element primary simultaneous equation holds as follows.
_{B 1 / (100- (A 1} -B 1) - (A 2 -B 2) - ··· (A n -B n)) × 100 = C 1
_{B 2 / (100- (A 1} -B 1) - (A 2 -B 2) - ··· (A n -B n)) × 100 = C 2
...
_{B n / (100- (A 1} -B 1) - (A 2 -B 2) - ··· (A n -B n)) × 100 = C n
Here, the values of A _{1 to An} are determined from the amount of each component used when the toner is manufactured, or are contained in the toner before classification, for example, Si for silica, Ti for titanium oxide, and magnesium oxide. Can be obtained by measuring the content of elements characteristic of external additive components such as Mg with a fluorescent X-ray analyzer. Further, the values of C _{1 to} C _n can be obtained by measuring the content of elements characteristic of each external additive component in the classified toner by using a fluorescent X-ray analyzer. For example, ZSX100e (manufactured by Rigaku Corporation) can be used as the fluorescent X-ray analyzer.

Therefore, the values of B _{1 to} B _n can be obtained by substituting the values of A _{1 to An and} the values of C _{1 to} C _{n into} the above n-ary linear simultaneous equations. Since the amount of free silica removed by the classification operation contained in the toner before classification is A ₁ -B _1, it is calculated by calculating (A ₁ -B ₁ ) / A ₁ × 100. The liberation rate is required.

[Carrier]
The toner for developing an electrostatic latent image 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 electrostatic latent image developing toner 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 (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 is typically 2.0 to 2.5 g / cm ³ .

  When the electrostatic latent image developing toner of the present invention is used as a two-component developer, the toner content is preferably 1 to 20% by mass, and preferably 3 to 15% by mass, based on 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 electrostatic latent image developing toner of the present invention described above, it is possible to suppress the occurrence of fogging, to suppress the occurrence of image defects due to a decrease in image density or contamination of the developing device when printing over a long period of time, Generation of carrier spent can be suppressed when toner is used as a two-component developer. For this reason, the electrostatic latent image developing toner of the present invention is suitably used in various image forming apparatuses.

  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.

  A polyester resin used as a binder resin in Examples and Comparative Examples was produced according to the following formulation.

[Production example of polyester resin]
1960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 terephthalic acid, and 4 g of dibutyltin oxide were charged into a reaction vessel. The temperature was raised to 235 ° C. in a nitrogen atmosphere, and the reaction was performed at the same temperature for 8 hours, and then the pressure was reduced to 8.3 kPa and the reaction was performed at the same temperature for 1 hour. Next, after the reaction product was cooled to 180 ° C., trimellitic anhydride was added to adjust the acid value of the polyester resin to a desired value. Thereafter, the temperature was raised to 210 ° C. at a rate of 10 ° C./hour, and the reaction was carried out at the same temperature to obtain a polyester resin.

[Example 1]
(Toner base particle preparation)
87 parts by mass of a polyester resin, 5 parts by mass of a release agent (Ester wax WEP-3 (manufactured by NOF Corporation)), a positively chargeable charge control agent (Bontron P-51 (quaternary ammonium salt) (Orient Chemical Co., Ltd.) 3 parts by mass) and 5 parts by mass of carbon black (MA-100 (manufactured by Mitsubishi Chemical Corporation)) were mixed with a Henschel mixer. 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 7.0 μm.

(Toner preparation)
Toner base particles and 1.5% by mass of silica (RA200 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 15 nm)) and 0.5% by mass of titanium oxide (ST-) with respect to the mass of the toner base particles 100 (made by Titanium Industry Co., Ltd.) and 1.0% by mass of resin fine powder (FS-102, styrene acrylic resin (made by Nippon Paint Co., Ltd., average primary particle size 80 nm)), blade speed of 40 m / Second, mixing time 15 minutes, jacket cooling water temperature 20 ° C., mixed with a Henschel mixer (FM-20B (manufactured by Nippon Coke Co., Ltd.)), silica, titanium oxide, and resin fine powder are mixed into the toner base. The toner was obtained by adhering to the surface of the particles. The liberation rate of silica and the BET specific surface area of the obtained toner were measured according to the following methods. Table 1 shows the liberation rate of silica and the BET specific surface area of the toner of Example 1.

<Method for measuring the liberation rate of silica>
Using an airflow classifier (DSX-2 (manufactured by Nippon Pneumatic Industry Co., Ltd.)), free silica was classified from the toner under the following conditions.
(Free silica separation conditions)
Sample supply rate: 100 g / min Supply section injection pressure: 0.2 MPa
Adjustable string: 80mm
Louver height: 10mm
Louver clearance: 5mm
Distance ring: 0mm
Center navel: 60mm
U damper: 45 °
Cyclone damper: 30 °
Blower total static pressure: -1400 mmAq (-13.73 kPa)

The mass of silica in 100 g of toner is A ₁ g, and the mass of titanium oxide is A ₂ g. Further, the mass of silica contained in the toner after 100 g of toner is classified is B ₁ g, and the mass of titanium oxide is B ₂ g. Further, the silica content of the toner after the classification treatment is C ₁ mass%, and the titanium oxide content is C ₂ mass%. In this case, the following simultaneous equations hold.
_{B 1 / (100- (A 1} -B 1) - (A 2 -B 2)) × 100 = C 1
B ₂ / (100− (A ₁ −B ₁ ) − (A ₂ −B ₂ )) × 100 = C ₂
Here, the values of A ₁ and A ₂ were determined from the amount of the external additive used when the toner was produced. Further, the values of C ₁ and C ₂ were obtained by measuring the content of Si in silica and Ti in titanium oxide in the toner after the classification treatment with a fluorescent X-ray analyzer. In addition, ZSX100e (made by Rigaku Corporation) was used as a fluorescent X-ray analyzer.

The values of B ₁ and B ₂ were determined by substituting the values of A ₁ and A _{2 and} the values of C ₁ and C _{2 into} the above simultaneous equations. Next, (A ₁ -B ₁ ) / A ₁ × 100 was calculated to determine the liberation rate of silica.

<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.

(2-component developer preparation)
A carrier (average particle diameter of 45 μm) used for a developer used in a page printer (FS-C5400DN (manufactured by Kyocera Mita Corporation)) and a toner of 8% by mass with respect to the mass of a ferrite carrier are mixed with a ball mill. Was mixed for 30 minutes to prepare a two-component developer. Using the obtained two-component developer, the toner charge amount, image density, fog generation, carrier spent, and contamination of the developing device of Example 1 were evaluated according to the following methods. Table 1 shows the evaluation results of the toner charge amount, image density, fogging, carrier spent, and developer contamination of Example 1.

<Charge amount>
The charge amount was evaluated using a page printer (FS-C5400DN (manufactured by Kyocera Mita Corporation)). The developer is filled with the two-component developer obtained in Example 1, the toner container is filled with the toner obtained in Example 1, and the initial toner is charged in a normal temperature and humidity environment (20 ° C., 65% RH). The amount of charge was measured. Subsequently, 100,000 sheets were continuously printed at a printing rate of 0.1% in a normal temperature and humidity environment (20 ° C., 65% RH), and the charge amount of the toner after continuous printing was measured. The charge amount was measured with a charge amount measuring device (Q / M Meter 210HS (manufactured by TRek)).

<Image density>
An image evaluation pattern was printed by a page printer (FS-C5400DN (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 100,000 sheets at a printing rate of 0.1% in a normal temperature and humidity environment (20 ° C., 65% RH), an image evaluation pattern was printed. The image density of the solid image in the initial image and the image evaluation pattern printed after printing 100,000 sheets was measured with a reflection densitometer (RD914, manufactured by Gretag Macbeth). An image density of 1.30 or more was judged as ◯, and an image density of less than 1.30 was judged as x.

<Occurrence of fogging>
The image density of the non-image portion of the paper on which the image evaluation pattern after printing 100,000 sheets after printing was obtained in the image density evaluation was measured with a reflection densitometer (RD914, manufactured by Gretag Macbeth). A density of 0.010 or less was judged as ◯, and a density exceeding 0.010 was judged as x.

<Career spent>
A part of the two-component developer was collected after printing 100,000 sheets in the image density evaluation. The separated two-component developer was sieved into toner and carrier. A two-component developer was prepared using the obtained carrier and the toner of Example 1. Using the two-component developer containing the carrier after use, the charge amount of the toner was measured according to the method described above. Calculate the decrease rate of the initial charge amount of the toner measured using the two-component developer containing the carrier after use with respect to the initial charge amount of the toner measured using the two-component development containing an unused carrier, and the carrier spent. Evaluated. The worse the career spent, the greater the rate of decline. A rate of decrease in charge amount of less than 20% was judged as ◯, and 20% or more was judged as ×.

<Contamination of developer>
In the image density evaluation, after 100,000 sheets were continuously printed, the amount of deposits on the developing sleeve in the developing unit was visually observed. The evaluation criteria are as follows.
○: Almost no deposits are observed.
Δ: Slightly large amount of deposits is observed.
X: A lot of deposits are observed.

[Example 2, Example 3, and Comparative Examples 1-3]
Toner base particles, a toner, and a two-component developer were prepared in the same manner as in Example 1 except that the external addition conditions were changed to the conditions shown in Table 1 or Table 2. For the toners of Example 2, Example 3, and Comparative Examples 1 to 3, the liberation rate of silica and the specific surface area of the toner were measured in the same manner as in Example 1. In addition, using the two-component developer containing the toners of Example 2, Example 3, and Comparative Examples 1 to 3, the charge amount and image density of the toners of Example 2, Example 3, and Comparative Examples 1 to 3 were used. The occurrence of fog, the carrier spent, and the contamination of the developing device were evaluated. Table 1 shows the evaluation results of the toners of Example 2 and Example 3. Table 2 shows the evaluation results of the toners of Comparative Examples 1 to 3.

[Example 4 and Comparative Example 4]
Except for changing the silica to NA-50 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 30 nm) and changing the external addition conditions to the conditions shown in Table 1 or Table 2, the same manner as in Example 1 was performed. A toner base particle, a toner, and a two-component developer were prepared. For the toners of Example 4 and Comparative Example 4, the liberation rate of silica and the specific surface area of the toner were measured in the same manner as in Example 1. In addition, using the two-component developer containing the toner of Example 4 and Comparative Example 4, the toner charge amount, image density, fogging, carrier spent, and developer of Example 4 and Comparative Example 4 Contamination was assessed. The evaluation results of the toner of Example 4 are shown in Table 1, and the evaluation results of the toner of Comparative Example 4 are shown in Table 2.

[Example 5 and Comparative Example 5]
Other than changing the resin fine powder to FS-201 (styrene acrylic resin (manufactured by Nippon Paint Co., Ltd.), average primary particle size 60 nm) and changing external addition conditions to the conditions described in Table 1 or Table 2. In the same manner as in Example 1, toner base particles, toner, and a two-component developer were prepared. For the toners of Example 5 and Comparative Example 5, the liberation rate of silica and the specific surface area of the toner were measured in the same manner as in Example 1. In addition, using the two-component developer containing the toner of Example 5 and Comparative Example 5, the charge amount, image density, fogging, carrier spent, and developing of the toner of Example 5 and Comparative Example 5 Contamination was assessed. The evaluation results of the toner of Example 5 are shown in Table 1, and the evaluation results of the toner of Comparative Example 5 are shown in Table 2.

[Comparative Example 6]
Example 1 except that the resin fine powder was changed to FS-493 (acrylic resin (manufactured by Nippon Paint Co., Ltd.), average primary particle size: 70 nm) and the external addition conditions were changed to the conditions shown in Table 2. In the same manner, toner base particles, a toner, and a two-component developer were prepared. For the toner of Comparative Example 6, the silica liberation rate and the specific surface area of the toner were measured in the same manner as in Example 1. Further, using the two-component developer containing the toner of Comparative Example 6, the charge amount, image density, fogging, carrier spent, and contamination of the developing device of the toner of Comparative Example 6 were evaluated. The evaluation results of the toner of Comparative Example 6 are shown in Table 2.

  For example, according to a comparison between Example 1 and Example 2, it can be seen that the specific surface area of the toner can be reduced by increasing the temperature during external addition. This is probably because the external additive is easily embedded in the toner base particles. The toner of Example 2 has a higher silica liberation rate than the toner of Example 1 when the external additive treatment is performed at a high temperature, and it is easy to deform when the resin fine powder adheres to the toner base particles. This is probably because silica has become difficult to adhere.

  Further, according to Comparative Examples 3 and 4, when the external addition treatment is performed for a long time, the amount of the external additive embedded in the toner base particles increases, so that the silica liberation rate and the BET specific surface area of the toner are increased. It turns out that becomes small.

According to Table 1, silica and styrene acrylic resin are externally added, the liberation rate of silica is 5 to 15% by mass, and the BET specific surface area is ² to 3.5 m ² / g. It can be seen that the toners 1 to 5 can suppress the generation of fog, the decrease in image density when printing over a long period of time, the contamination of the developing device, and the generation of carrier spent.

According to Comparative Example 1, it can be seen that, when the BET specific surface area of the toner exceeds 3.5 m ² / g, there is no problem in image density and fog, but the carrier and the developing device are severely contaminated. This is considered to be because a large amount of the external additive was peeled off from the toner surface when the toner was kept stirred when the external additive was buried in the toner base particles at a low density and printed for a long time at a low concentration.

  According to Comparative Example 2, it can be seen that when the silica liberation rate exceeds 15% by mass, the image density tends to decrease when printing over a long period of time, and the developer is severely contaminated.

According to Comparative Example 3, when the liberation rate of silica is less than 5% by mass and the BET specific surface area of the toner is less than 2 m ² / g, the image density is lowered by charge-up, and the developing device is severely contaminated. I understand that.

According to Comparative Example 4, even when the BET specific surface area of the toner is less than 2 m ² / g, when the liberation rate of silica is 5 to 15% by mass, the image density decreases due to charge-up, carrier spent, and development It can be seen that the vessel is not easily contaminated. In this case, however, fogging occurred.

According to Comparative Example 5, even if the liberation rate of silica is less than 5% by mass, when the BET specific surface area of the toner is ² to 3.5 m ² / g, the carrier spent and the developing device are hardly contaminated. I understand. However, in this case, a decrease in image density due to charge-up could not be suppressed.

According to Comparative Example 6, when the resin fine powder of styrene acrylic resin is changed to another resin, for example, acrylic resin, the liberation rate of silica is 5 to 15% by mass, and the BET specific surface area of the toner is It can be seen that even at ^{2 to} 3.5 m ² / g, the developer is easily contaminated with toner or fine resin powder.

Claims (5)

Inorganic fine powder and resin fine powder are attached to the surface of the toner base particles containing at least a binder resin and a colorant,
The inorganic fine powder contains silica,
The resin fine powder is a styrene acrylic resin,
The liberation rate of the silica is 5 to 15% by mass,
An electrostatic latent image developing toner having a BET specific surface area of ² to 3.5 m ² / g.   The electrostatic latent image developing toner according to claim 1, wherein a content of the silica is 0.1 to 10 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner.   The electrostatic latent image developing toner according to claim 1, wherein the content of the resin fine powder is 0.3 to 5 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner.   The electrostatic latent image developing toner according to claim 1, wherein the silica has an average primary particle diameter of 10 to 150 nm.   The toner for electrostatic latent image development according to any one of claims 1 to 4, wherein an average primary particle diameter of the resin fine powder is 30 to 300 nm.