JP2012203180A - Toner for developing electrostatic latent image - Google Patents

Abstract

The present invention provides an electrostatic latent image developing toner capable of suppressing the occurrence of fogging and suppressing the occurrence of image defects due to a decrease in image density when printing for a long period of time or contamination of a developing device.
An inorganic fine powder and a resin fine powder made of styrene acrylic resin are adhered to the surface of toner base particles containing at least a binder resin and a colorant, and the desorption index of the resin fine powder from the toner is determined. 30 or less. The content of the resin fine powder is preferably 0.3 to 5 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner.
[Selection figure] None

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 (photoconductor) is charged by corona discharge or the like, and then exposed by a laser or the like to form an electrostatic latent image. The 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, etc., kneaded, pulverized, and classified to have an average particle size of 5 to 15 μm. The toner particles are 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 and inorganic metal fine powder are 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 printing rate for a long time, and the resin fine powder may be peeled off from the surface of the toner when the toner is stirred for a long time in the developing device. 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 resin fine powder.

  The present invention has been made in view of such circumstances, and an electrostatic latent image that can suppress the occurrence of fogging and can 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. An object is to provide a developing toner.

  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, and the resin fine powder is a styrene acrylic resin. The present inventors have found that the above problems can be solved by using a toner for developing an electrostatic latent image having a desorption index of 30 or less from the toner of the present invention, and have completed the present invention. 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 resin fine powder is a styrene acrylic resin,
A toner for developing an electrostatic latent image, wherein the resin fine powder has a desorption index of 30 or less measured by the following steps 1) to 8).
1) A surfactant solution containing toner is prepared by adding 1 g of toner to 100 ml of a surfactant solution prepared by mixing an anionic surfactant aqueous solution having a concentration of 7% by mass with distilled water at a volume ratio of 1: 1. Process,
2) A step of irradiating the surfactant solution containing the toner with ultrasonic waves at a frequency of 35 kHz and an output of 100 W for 30 minutes to obtain a toner dispersion (1 liquid);
3) A step of allowing the one liquid to stand for 3 hours to precipitate the toner;
4) A step of removing the supernatant liquid from the one liquid so as not to float the precipitated toner.
5) adding 100 ml of the surfactant solution to the precipitate in the one liquid from which the supernatant liquid has been removed,
6) A step of preparing a toner dispersion liquid (two liquids) by irradiating a surfactant solution containing precipitated toner with ultrasonic waves for 5 minutes under the same conditions as the preparation of the first liquid to disperse the toner;
7) The transmittance of the first and second liquids is measured with an ultraviolet-visible spectrophotometer, and the average value of the transmittance at a wavelength of 400 to 650 nm is obtained from the integral value of the transmittance in the wavelength range of 400 to 650 nm. Step and 8) From the average value of the transmittance of the obtained 1 and 2 liquids at a wavelength of 400 to 650 nm, the following formula:
Desorption index = (average transmittance of two liquids / average transmittance of one liquid−1) × 100
Calculating the desorption index of the resin fine powder from the toner.

  (2) The electrostatic latent image developing toner according to (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.

  (3) The electrostatic latent image developing toner according to (2), wherein the content of the resin fine powder is 0.5 to 2 parts by mass with respect to 100 parts by mass of the electrostatic latent image developing toner.

  (4) The electrostatic latent image developing toner according to any one of (1) to (3), wherein an average primary particle diameter of the resin fine powder is 30 to 300 nm.

  (5) The electrostatic latent image developing toner according to any one of (1) to (4), wherein the inorganic fine powder is selected from the group consisting of silica, titanium oxide, and a mixture thereof.

  According to the present invention, it is possible to provide an electrostatic latent image developing toner that can suppress the occurrence of fogging and 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. .

FIG. 1 is a diagram showing a transmission spectrum of a styrene acrylic resin fine powder at a wavelength of 400 to 650 nm.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

  The electrostatic latent image developing toner of the present invention (hereinafter also simply referred to as toner) is a resin fine powder comprising inorganic fine powder and styrene acrylic resin on the surface of toner base particles containing at least a binder resin and a colorant. And the desorption index of the resin fine powder from the toner is 30 or less. The toner base particles include at least a binder resin and a colorant, and may optionally include a release agent, a charge control agent, a magnetic powder, 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 magnetic powder, 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, A method for producing a toner for developing an electrostatic latent image 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 toner for developing an electrostatic latent image of the present invention is a surface of toner base particles in which a binder and, if necessary, a charge control agent, a release agent, and a magnetic powder component are blended in a binder resin. Further, an inorganic fine powder 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. On the other hand, 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 (photoconductor). 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]
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 to improve the charge rise 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 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 the fog and the latent image carrier are likely to be contaminated. When the amount of the charge control agent used is excessive, charging failure under high temperature and high humidity due to deterioration of environmental resistance, image failure, and contamination of the latent image carrier are likely to occur.

〔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.

[Magnetic powder]
In the electrostatic latent image developing toner, magnetic powder can be blended in the binder resin as desired. The type of magnetic powder to be blended with the toner is not particularly limited as long as the object of the present invention is not impaired. Examples of suitable magnetic powders include: irons such as ferrite and magnetite; ferromagnetic metals such as cobalt and nickel; alloys containing iron and / or ferromagnetic metals; compounds containing iron and / or ferromagnetic metals; A ferromagnetic alloy subjected to a ferromagnetization treatment such as chromium dioxide.

  The particle size of the magnetic powder is not limited as long as the object of the present invention is not impaired. The particle diameter of the specific magnetic powder is preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0.5 μm. When magnetic powder having a particle diameter in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

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

  The usage-amount of magnetic powder is not specifically limited in the range which does not inhibit the objective of this invention. When the toner is used as a one-component developer, the specific amount of the magnetic powder is preferably 35 to 60 parts by mass, more preferably 40 to 60 parts by mass when the total amount of toner is 100 parts by mass. If the amount of magnetic powder used is excessive, the image density may be easily lowered or the fixability may be extremely lowered when printing over a long period of time. If the amount of magnetic powder used is too small, fogging is likely to occur, and the image density may be likely to decrease when printing over a long period of time. When the toner is used as a two-component developer, the amount of magnetic powder used is preferably 20% by mass or less and more preferably 15% by mass or less when the total amount of toner is 100 parts by mass.

[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 a resin fine powder made of a styrene acrylic resin as an external additive, even when printing at a low density is performed for a long period of time, the image density is hardly lowered and the developing device is hardly contaminated, and the fog is easily suppressed.

  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 can be measured by a laser diffraction / scattering particle diameter measuring apparatus. As a laser diffraction scattering type particle diameter measuring device, for example, it can be measured by LA-950 (manufactured by Horiba, Ltd.).

  The amount of resin fine powder used is not particularly limited as long as the desorption index measured by the method described below is 30 or less. 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. When the amount of resin fine powder used is excessive, the desorption index of the resin fine powder tends to be high, and image defects due to contamination of the developing device (developing sleeve) are likely to occur.

[Inorganic fine powder]
In the present invention, an inorganic fine powder is used in addition to the resin fine powder as an external additive. The type of the inorganic fine powder 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 the inorganic fine powder since it has been conventionally used as an external additive for toner. Specific examples of suitable inorganic fine powders include metal oxides such as silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These inorganic fine powders can be used in combination of two or more.

  Among these inorganic fine powders, silica is preferable from the viewpoint of toner fluidity and storage stability, and titanium oxide is preferable from the viewpoint of cleanability of the surface of the latent image carrier. For this reason, it is preferable to use what is selected from the group which consists of a silica, titanium oxide, and these mixtures as an inorganic fine powder.

  The particle diameter of the inorganic fine powder 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.

  The volume specific resistance value of the inorganic fine powder can be adjusted by forming a coating layer made of tin oxide and antimony oxide on the surface of the inorganic fine powder and changing the thickness of the coating layer and the ratio of tin oxide and antimony oxide. .

  The usage-amount of inorganic fine powder is not specifically limited in the range which does not inhibit the objective of this invention. Typically, the amount of the inorganic fine powder used is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the toner particles before the external addition treatment. If the amount of inorganic fine powder used is too small, the hydrophobicity of the toner tends to decrease. As a result, it is easily affected by water molecules in the air in a high temperature and high humidity environment, and problems such as an extreme decrease in toner charge amount, a decrease in image density, and a decrease in toner fluidity are likely to occur. Further, if the amount of the inorganic fine powder used is excessive, there is a possibility that the image density is lowered due to excessive charge-up of the toner.

  As the inorganic fine powder, one whose surface is treated with a hydrophobizing agent can be used. 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 inorganic fine powders. 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 inorganic fine powder, a method of dropping or spraying hydrophobizing agent aminosilane, silicone oil, etc., while stirring inorganic fine powder at high speed, organic solvent of hydrophobizing agent being stirred A method of adding an inorganic fine powder to the solvent solution can be mentioned. The inorganic fine powder hydrophobized is obtained by heating after hydrophobizing. 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.

[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 electrostatic latent image developing toner are blended with a binder resin and, if necessary, an optional component such as a release agent, a charge control agent, and magnetic powder. It is obtained by adjusting to a desired particle size by classification.

  The method for producing toner mother particles by blending a binder resin with components such as a colorant, a release agent, a charge control agent, and magnetic powder is particularly limited as long as these components can be well dispersed in the binder resin. Not. 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, a charge control agent, and magnetic powder are mixed with a mixer or the like, and then uniaxial or biaxial extrusion is performed. Examples thereof include a method in which a binder resin and components blended in the binder resin are melt-kneaded by a kneader such as a machine, and the cooled kneaded material 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 desorption index of the resin fine powder of the electrostatic latent image developing toner is 30 or less, but the desorption index of the resin fine powder can be adjusted by adjusting the conditions of the external addition treatment. For example, the desorption index can be lowered 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 processing time.

The desorption index of the resin fine powder can be measured according to the following method.
<Desorption index measurement method>
1 g of toner is added to 100 ml of a surfactant solution in which a commercially available detergent having a concentration of an anionic surfactant of 7% by mass (manufactured by Kao Corporation) and distilled water are mixed at a volume ratio of 1: 1, and the toner is removed. A surfactant solution containing is prepared. The surfactant solution containing toner is irradiated with ultrasonic waves for 30 minutes at a frequency of 35 kHz and an output of 100 W by an ultrasonic cleaning device (UT-105S (manufactured by Sharp Manufacturing System Co., Ltd.)). ) One liquid is allowed to stand for 3 hours to precipitate the toner. After removing the supernatant so that the precipitated toner does not float, 100 ml of the above-mentioned surfactant solution is added to the one liquid from which the supernatant containing the precipitated toner has been removed. The surfactant solution containing the precipitated toner is irradiated with ultrasonic waves for 5 minutes under the same conditions as the preparation of one liquid to disperse the toner to prepare a toner dispersion liquid (two liquids). About 1 liquid and 2 liquids, the transmittance | permeability was measured with the ultraviolet visible spectrophotometer (UV-3100 (made by Shimadzu Corporation)), and the wavelength of 400-650 nm was determined from the integrated value of the transmittance in the wavelength range of 400-650 nm. The average value of the transmittance is obtained. The desorption index of the resin fine powder from the toner is calculated from the average value of the transmittances of the obtained 1 liquid and 2 liquid at a wavelength of 400 to 650 nm by the following formula.

<Desorption index formula>
Desorption index = (average transmittance of two liquids / average transmittance of one liquid−1) × 100

  According to such a measuring method, not only the resin fine powder originally released from the toner particles but also the resin fine powder that is easily detached from the toner particles by the ultrasonic irradiation for preparing one liquid is used. Disperse in one liquid in a state free from particles. Then, by allowing one liquid to stand for 3 hours, toner particles having a larger particle diameter than that of the external additive and inorganic fine powders such as silica and titanium oxide having a large specific gravity released from the toner particles are precipitated. To do. On the other hand, the resin fine powder detached from the toner continues to float in the supernatant of one liquid because the particle diameter and specific gravity are small. Therefore, by removing the supernatant of one liquid, the resin fine powder that is easily detached from the toner is removed.

  In addition, almost all of the inorganic fine powder that is easily detached from the toner particles by ultrasonic irradiation when preparing one liquid is detached. For this reason, the amount of the free inorganic fine powder is hardly changed by the ultrasonic treatment during the preparation of the two liquids. That is, the amount of toner particles and the amount of free inorganic fine powder contained in the first and second liquids hardly change.

  FIG. 1 shows transmittance at a wavelength of 400 to 650 nm when 0.01 part by mass of styrene acrylic resin fine powder is dispersed in 100 parts by mass of a surfactant used for measurement of the desorption index. 1 indicates that the styrene acrylic resin has absorption at a wavelength of 400 to 650 nm. For this reason, the one liquid containing the resin fine powder made of the styrene acrylic resin that is detached from the toner particles is lower in transmittance than the two liquids that do not contain the resin fine powder. Further, the larger the amount of resin fine powder in one liquid, the lower the transmittance of one liquid. Accordingly, as the amount of the resin fine powder in one liquid increases, the average value of the transmittance of the two liquids / the average value of the transmittance of the one liquid increases, and the value of the desorption index also increases. Therefore, the desorption index determined by the above equation is an index of the content per 1 g of the resin fine powder that is originally free or easily desorbed from the toner particles.

[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 toner for developing an electrostatic latent image of the present invention described above, the occurrence of fog can be suppressed, and 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 can be suppressed. 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 polyester resin, 5 parts by mass of release agent (Ester wax WEP-3: manufactured by NOF Corporation), positive charge control agent (Bontron P-51 (quaternary ammonium salt): manufactured by Orient Chemical Industry 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 (REA200 (manufactured by Nippon Aerosil Co., Ltd.)) and 0.5% by mass of titanium oxide (ST-100 (Titanium Industry Co., Ltd.) with respect to the mass of the toner base particles. Manufactured)) and 1.0% by mass of resin fine powder (FS-102, styrene acrylic resin (manufactured by Nippon Paint Co., Ltd.), average primary particle size 100 nm), blade peripheral speed 40 m / sec, mixing time 15 The mixture was mixed with a Henschel mixer at a jacket cooling water temperature of 20 ° C., and silica, titanium oxide, and resin fine powder were adhered to the surface of the toner base particles to obtain a toner. The desorption index of the resin fine powder of the obtained toner was measured according to the following method. The desorption index of the resin fine powder of the toner of Example 1 is shown in Table 1.

<Desorption index measurement method>
1 g of toner is added to a surfactant solution in which a commercially available detergent having a surfactant concentration of 7% by mass (manufactured by Kao Corporation) and distilled water are mixed at a volume ratio of 1: 1, and the surfactant containing the toner is added. An agent solution was obtained. The surfactant container containing the toner was irradiated with ultrasonic waves at a frequency of 35 kHz and an output of 100 W for 30 minutes using an ultrasonic cleaning device (UT-105S) to obtain a toner dispersion liquid (one liquid). One liquid was allowed to stand for 3 hours to cause toner precipitation. After removing the supernatant so as not to float the precipitated toner, 100 ml of the above surfactant solution was added to the precipitated toner. The surfactant solution containing the precipitated toner was irradiated with ultrasonic waves for 5 minutes under the same conditions as the preparation of one liquid to disperse the toner to prepare a toner dispersion liquid (two liquids). About 1 liquid and 2 liquids, the transmittance | permeability was measured with the ultraviolet visible spectrophotometer (UV-3100 (made by Shimadzu Corporation)), and the wavelength of 400-650 nm was determined from the integrated value of the transmittance in the wavelength range of 400-650 nm. The average value of transmittance was determined. The desorption index of the resin fine powder from the toner was calculated from the average value of the transmittances of the obtained 1 liquid and 2 liquid at a wavelength of 400 to 650 nm by the following formula.

<Desorption index formula>
Desorption index = (average transmittance of two liquids / average transmittance of one liquid−1) × 100

(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 image density of the toner of Example 1, fogging, and contamination of the developing device were evaluated according to the following methods. Table 1 shows the evaluation results of image density, occurrence of fogging, and contamination of the developing device of Example 1.

<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 in the non-image area of the paper on which the image evaluation pattern after printing of 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.

<Contamination of developer>
After continuous printing of 100,000 sheets in the image density evaluation, the amount of deposits on the sleeve roller in the developing unit was visually observed. The evaluation criteria are as follows.
○: No deposits are observed.
Δ: Slightly adhered matter is observed.
X: A lot of deposits are observed.

[Example 2, Example 3, and Comparative Examples 1-3]
Toner mother particles, a toner, and a two-component developer were prepared in the same manner as in Example 1 except that the external additive conditions for the toner were changed to the conditions shown in Table 1. For the toners of Example 2, Example 3, and Comparative Examples 1 to 3, the desorption index of the resin fine powder was measured in the same manner as in Example 1. Further, using the two-component developer containing the toners of Example 2, Example 3, and Comparative Examples 1 to 3, the image density and fogging of the toners of Example 2, Example 3, and Comparative Examples 1 to 3 were determined. Occurrence and contamination of the developer were evaluated. The evaluation results of the toners of Example 2 and Example 3 are shown in Table 1, and the evaluation results of the toners of Comparative Examples 1 to 3 are shown in Table 2.

[Example 4 and Comparative Example 4]
In addition to changing the resin fine powder to (styrene acrylic resin (Nippon Paint Co., Ltd. sample product), average primary particle size 70 nm) and changing external addition conditions to the conditions shown 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 4 and Comparative Example 4, the desorption index of the resin fine powder was measured in the same manner as in Example 1. Further, using the two-component developer containing the toner of Example 4 and Comparative Example 4, the image density of the toner of Example 4 and Comparative Example 4, occurrence of fogging, and contamination of the developing device were evaluated. 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]
In addition to changing the resin fine powder to (styrene acrylic resin (Nippon Paint Co., Ltd. sample product), average primary particle diameter 150 nm) and changing external addition conditions to the conditions shown 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 desorption index of the resin fine powder was measured in the same manner as in Example 1. Further, using the two-component developer containing the toner of Example 5 and Comparative Example 5, the toner density of Example 5 and Comparative Example 5, the occurrence of fogging, and the contamination of the developing device were evaluated. 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]
Except for changing the resin fine powder to a fine powder of polyester resin (sample product manufactured by Nippon Paint Co., Ltd., average primary particle size 250 nm) and changing external addition conditions to the conditions shown in Table 2, Examples In the same manner as in Example 1, toner mother particles, toner, and a two-component developer were prepared. For the toner of Comparative Example 6, the desorption index could not be measured because the material of the resin fine powder was not a styrene acrylic resin. Further, using the two-component developer containing the toner of Comparative Example 6, the image density of the toner of Comparative Example 6, the occurrence of fogging, and the contamination of the developing device were evaluated. The evaluation results of the toner of Comparative Example 6 are shown in Table 2.

  For example, from the comparison between Example 1 and Example 2, when resin fine powder having the same particle size is used, the resin fine powder in the toner increases as the peripheral speed of the blades during external addition processing increases and the strength of stirring increases. It can be seen that the desorption index of s. Further, it can be seen from comparison between Example 2 and Example 3 that when the peripheral speed of the blade is the same, the longer the mixing time, the lower the desorption index of the resin fine powder in the toner.

  According to Table 1, the toners of Examples 1 to 5, in which inorganic fine powder and resin fine powder are externally added and the resin fine powder has a desorption index of 30 or less, the occurrence of fog is suppressed, and the low concentration It can be seen that even after printing for a long period of time, a decrease in image density and contamination of the developing device hardly occur.

  According to Table 2, from Comparative Examples 1 to 5, when the desorption index of the resin fine powder exceeds 30, the image density is lowered after low-density printing for a long period of time, and the developer is easily contaminated. I understand that. Further, according to Comparative Examples 2 to 5, it can be seen that, particularly when the desorption index of the resin fine powder exceeds 50, fogging easily occurs in addition to a decrease in image density and contamination of the developing device. .

  Further, according to Comparative Example 6, when using a polyester resin fine powder instead of a styrene acrylic resin fine powder as a resin fine powder, after performing low density printing for a long period of time, a decrease in image density or development device It can be seen that contamination is likely to occur.

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 resin fine powder is a styrene acrylic resin,
A toner for developing an electrostatic latent image, wherein the resin fine powder has a desorption index of 30 or less measured by the following steps 1) to 8).
1) A surfactant solution containing toner is prepared by adding 1 g of toner to 100 ml of a surfactant solution prepared by mixing an anionic surfactant aqueous solution having a concentration of 7% by mass with distilled water at a volume ratio of 1: 1. Process,
2) A step of irradiating the surfactant solution containing the toner with ultrasonic waves at a frequency of 35 kHz and an output of 100 W for 30 minutes to obtain a toner dispersion (1 liquid);
3) A step of allowing the one liquid to stand for 3 hours to precipitate the toner;
4) A step of removing the supernatant liquid from the one liquid so as not to float the precipitated toner.
5) adding 100 ml of the surfactant solution to the precipitate in the one liquid from which the supernatant liquid has been removed,
6) A step of preparing a toner dispersion liquid (two liquids) by irradiating a surfactant solution containing precipitated toner with ultrasonic waves for 5 minutes under the same conditions as the preparation of the first liquid to disperse the toner;
7) The transmittance of the first and second liquids is measured with an ultraviolet-visible spectrophotometer, and the average value of the transmittance at a wavelength of 400 to 650 nm is obtained from the integral value of the transmittance in the wavelength range of 400 to 650 nm. Step and 8) From the average value of the transmittance of the obtained 1 and 2 liquids at a wavelength of 400 to 650 nm, the following formula:
Desorption index = (average transmittance of two liquids / average transmittance of one liquid−1) × 100
Calculating the desorption index of the resin fine powder from the 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 2, wherein the content of the resin fine powder is 0.5 to 2 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 resin fine powder has an average primary particle size of 30 to 300 nm.   The electrostatic latent image developing toner according to claim 1, wherein the inorganic fine powder is selected from the group consisting of silica, titanium oxide, and a mixture thereof.

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