JP4119424B2 - Method for producing toner for electrophotographic development - Google Patents

Description

The present invention relates to a process for producing an electrophotographic toner for developing an improved cleaning property.

  The so-called spherical toner, which has a high degree of spheroidization, has characteristics such as good fluidity, uniform charge, and high transfer efficiency, so attention is paid to spherical toner manufactured by suspension polymerization, emulsion polymerization aggregation method, etc. Has been. However, in practical use, the adherence to the photosensitive drum is high and the cleaning property is poor. Therefore, as a countermeasure against this, a large amount of an external additive having a large particle diameter is added to clean the spherical toner. Many attempts have been made to improve it.

However, when the atypification process is performed, the fluidity and transfer efficiency of the toner deteriorate, and the original performance of the spherical toner cannot be exhibited. Further, when a large amount of an external additive having a large particle diameter is added, the external additive is detached by long-time stirring in the developing machine, and the cleaning property is deteriorated.
In order to prevent the detachment of the toner external additive, Patent Document 1 proposes a method of adding inorganic fine particles while heating the toner particles dry.

JP2003-316071

  In Patent Document 1, inorganic fine particles are heated while being heated by a dry mixer such as a Henschel mixer or a supermixer in order to prevent the external additive from being detached from a toner having high sphericity or high surface smoothness by a polymerization method. There has been proposed a method in which inorganic fine particles are fused to the toner surface. However, in the case of dry mixing, the heat source is only the wall surface (jacket) of the container, and heat is transferred from the heat source to each toner particle via the toner particles and air. It is difficult to heat all the toner particles at the same temperature. For this reason, toner that has received strong heat and toner that has not received heat are mixed inside the container, and the fixed state of the inorganic fine particles becomes non-uniform, causing toner charge variations and poor cleaning. Further, when dry processing is performed at a high temperature, there is a high possibility that the toner particles are fused and aggregated.

Therefore, the present invention provides a toner for electrophotographic development that has improved charging variation and cleaning properties without impairing the high fluidity and uniform transfer efficiency of the toner prepared by suspension polymerization or emulsion polymerization aggregation . It is an object to provide a manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have confirmed that the fixed state of the inorganic fine particles to the toner particles satisfies the range of the following formula (1), and the inorganic fine particles are represented by the following formulas (2), ( In the case of satisfying the range of 3), the above-described charging variation and cleaning properties can be improved, and further, the fixed state of the inorganic fine particles becomes uniform by fusing the inorganic fine particles in the aqueous medium. As a result, the present invention has been completed. Here, the following formula (1) indicates a preferable range of the amount of inorganic fine particles embedded in the toner particles.

That is, the toner for electrophotographic development of the present invention is a toner base having a sphericity of 0.97 or more containing a colorant, wax, and charge control agent prepared in an aqueous medium by suspension polymerization or emulsion polymerization aggregation. Inorganic fine particles are fused to the surface of the particles, and the BET specific surface areas of the toner and the inorganic fine particles satisfy the following relational expressions (1), (2), and (3). .

In addition, the method for producing the toner for electrophotographic development of the present invention satisfying the relational expressions (1), (2) and (3) was produced in an aqueous medium by a suspension polymerization method or an emulsion polymerization aggregation method. To toner base particles having a sphericity of 0.97 or more containing a colorant, wax, and charge control agent, inorganic fine particles having a specific surface area of 60 m ² or less are heated in an aqueous medium to a temperature of Tg or more of the toner base particles. Then, the toner is produced by fusing the inorganic fine particles.

The hydrophobicity of the inorganic fine particles is preferably 30% or less. Furthermore, in the production method of the present invention, after the inorganic fine particles are fused, the surface of the toner particles is hydrophobized with a silane-based or titanium-based coupling agent .

  Since the toner of the present invention is produced by suspension polymerization or emulsion polymerization aggregation, the toner has a high degree of spheroidization, and thus has high fluidity and uniform transfer efficiency, and the relational expression (1), By satisfying the conditions (2) and (3), an appropriate amount of inorganic fine particles having an optimal BET specific surface area is fused to the surface of the toner base particles in an optimal fixing state, so that the inorganic fine particles are detached. This has the effect of preventing charging variation and improving cleaning properties.

  In addition, the toner manufacturing method according to the present invention employs a so-called wet processing method in which the inorganic fine particles are heated to a temperature equal to or higher than the Tg of the toner base particles in an aqueous system to fix the inorganic fine particles. Since the temperature in the system is uniform, and inorganic fine particles can be uniformly fused to all toner base particles, a toner satisfying the relational expressions (1), (2) and (3) can be easily obtained. Is obtained.

The toner of the present invention is obtained by fusing inorganic fine particles having a specific surface area of 60 m ² or less to the surface of toner base particles having a sphericity of 0.97 or more. The toner base particles contain a colorant, a wax, and a charge control agent in a binder resin that is a polymer prepared in an aqueous medium by a suspension polymerization method or an emulsion polymerization aggregation method.

(Binder resin)
The binder resin may be any resin that is usually used in the production of toner. For example, a styrene resin, an acrylic resin, a polyethylene resin, a polypropylene resin, a vinyl chloride resin, a polyester resin, Examples include polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, styrene-butadiene resins, etc., preferably styrene resins, especially styrene copolymer resins. It is good to do.

  The polystyrene copolymer resin is a copolymer having a styrene monomer as a main component. Examples of the styrene monomer include styrene, o-methyl styrene, p-methyl styrene and the like, and styrene is particularly preferable.

  Examples of other copolymerizable monomers that can be copolymerized with styrene include p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl chloride, vinyl bromide, and vinyl fluoride. Vinyl esters of vinyl acetate, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-acrylate (Meth) acrylic acid such as octyl, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate Esters; acrylonites Other acrylic acid derivatives such as ril, methacrylonitrile, acrylamide; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrole, N -N-vinyl compounds such as vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidene. These may be used alone or in combination of two or more with a styrene monomer. Preferably, the aliphatic alcohol (meth) acrylic acid ester having 1 to 12 carbon atoms, more preferably 3 to 8 carbon atoms is used alone or in combination of two or more.

(Coloring agent)
Examples of the colorant include inorganic pigments, organic pigments, synthetic dyes, and the like, and one or more kinds of pigments and / or one or more kinds of dyes may be used in combination. Examples of the inorganic pigment include metal powder pigments, metal oxide pigments, and carbon pigments. The colorant is usually blended at a ratio of 1 to 10 parts by mass with respect to 100 parts by mass of the binder resin.

  Examples of metal powder pigments include iron powder and copper powder. Examples of the metal oxide pigment include magnetite, ferrite, and bengara. Examples of the carbon pigments include carbon black and furnace black. Examples of the organic pigment include azo pigments, acidic dye pigments and basic dye pigments, mordant dye pigments, phthalocyanine pigments, quinacdrine pigments, and dioxane pigments.

  Examples of the azo pigments include benzidine yellow and benzidine orange. Examples of the acidic dye-based pigment and basic dye-based pigment include those obtained by precipitating a dye such as quinoline yellow, acid green, and alkali blue with a precipitating agent, or rhodamine, magenta, macalite green. And those obtained by precipitation with tannic acid or phosphomolybdic acid. Examples of the mordant dye-based pigments include metal salts of hydroxyanthraquinones. Examples of the phthalocyanine pigment include phthalocyanine blue and sulfonated copper phthalocyanine. Examples of the quinacridone pigment and dioxane pigment include quinacridone red and quinacridone violet.

  Examples of the synthetic dye include aniline black, azo dye, naphthoquinone dye, indigo dye, nigrosine dye, phthalocyanine dye, polymethine dye, tri- and diallylmethane dye, and the like.

(Charge control agent)
The charge control agent is added to improve the charge level and charge rising characteristics (indicator of whether to charge to a constant charge level in a short time), and to obtain characteristics such as excellent durability and stability. is there. That is, when the toner is positively charged for development, a positively chargeable charge control agent is added. When the toner is negatively charged for development, a negatively chargeable charge control agent can be added. .

  Such a charge control agent is not particularly limited. For example, specific examples of the positively chargeable charge control agent include quaternary ammonium compounds, pyridazines, pyrimidines, pyrazines, orthooxazines, metaoxazines. , 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, Azine compounds such as 5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, Azine brown 3G, azine light Direct dyes composed of azine compounds such as brown GR, azine dark green BH / C, azine deep black EW and azine black 3RL; nigrosine compounds such as nigrosine, nigrosine salt, nigrosine derivatives; nigrosine BK, nigrosine NB, nigrosine Z, etc. Examples include acid dyes composed of nigrosine compounds; metal salts of naphthenic naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride. One kind may be used alone, or two or more kinds may be used in combination. In particular, the nigrosine compound is optimal for use as a positively chargeable toner from the viewpoint of obtaining a quicker start-up property.

  In addition, a quaternary ammonium salt, a carboxylate, or a resin or oligomer having a carboxyl group as a functional group can also be used as the 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 Examples thereof include one or more of a resin, a styrene-acrylic resin having a carboxyl group, and a polyester resin having a carboxyl group. In particular, a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group is optimal from the viewpoint that the charge amount can be easily adjusted to a value within a desired range.

  In this case, preferred acrylic comonomers to be copolymerized with the styrene unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate. As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like ( Lower alkyl) aminoethyl (meth) acrylate; dimethylmethacrylamide, dimethylaminopropylmethacrylamide are preferred. 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.

  For example, organometallic complexes and chelate compounds are effective as the charge control agent exhibiting negative chargeability. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3,5-di-tert-butylsalicylate. In particular, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The above-described positively or negatively chargeable charge control agent is generally contained in the toner in a proportion of 1.5 to 15 parts by mass, preferably 2.0 to 8.0 parts by mass, more preferably 3.0 to 7.0 parts by mass. (The total amount of toner is 100 parts by mass). If the addition amount of the charge control agent is smaller than the above range, it tends to be difficult to stably charge the toner to a predetermined polarity, and the electrostatic latent image is developed using this toner to develop an image. When forming, the image density tends to decrease or the durability of the image density tends to decrease. In addition, the charge control agent tends to be poorly dispersed, causing so-called fogging, and the contamination of the photoconductor tends to be severe. On the other hand, when the charge control agent is used in a larger amount than the above range, it tends to cause defects such as environmental resistance, particularly poor charging under high temperature and high humidity and defective images, and contamination of the photoreceptor.

(wax)
The waxes used for improving the fixing property and the offset property are not particularly limited. For example, polyethylene wax, polypropylene wax, Teflon (registered trademark) wax, Fischer-Tropsch wax, paraffin wax, It is preferable to use carnauba wax, ester wax, montan wax, rice wax or the like. Two or more of these waxes may be used in combination. By adding such wax, offset property and image smearing can be more efficiently prevented.

  The waxes described above are not particularly limited, but generally, the wax is preferably blended in an amount of 1 to 10 parts by weight in the toner (the total amount of the toner is 100 parts by mass). If the addition amount of the wax is less than 1 part by mass, there is a tendency that the offset property, image smearing, etc. cannot be effectively prevented, while if it exceeds 10 parts by weight, the toners are fused together, Storage stability tends to decrease.

(Suspension polymerization method)
In the suspension polymerization method, a colorant, a wax, a charge control agent, a crosslinking agent, etc. are dispersed in a polymerizable monomer, and the monomer composition after the dispersion treatment is dispersed in an aqueous medium (for example, water or water miscible with water). The mixture is stirred in a solvent mixture with a solvent to obtain an appropriate particle size, and then a polymerization initiator is added and heated to polymerize the polymerizable monomer.

  Examples of the crosslinking agent that can be used in the present invention 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, and divinyl. And divinyl compounds such as aniline, divinyl ether, divinyl sulfide, and divinyl sulfone. These can be used alone or in combination of two or more. The addition amount of the crosslinking agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the monomer.

  Examples of the polymerization initiator used in the suspension polymerization method include 2,2-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis- (2,4-dimethylvaleronitrile), and 2,2 ′. -Azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. Azo-based / diazo-based polymerization initiators, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, peroxide-based polymerization initiators such as lauroyl peroxide, etc. Two or more types can be used in combination. The addition amount of the polymerization initiator is preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the monomer.

  When a suspension stabilizer is used, it is preferable to select a suspension stabilizer that is neutral or alkaline in water and can be easily removed by acid washing. Such suspension stabilizers include inorganic compounds such as tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, An organic compound such as ethyl cellulose, or a sodium salt thereof. The addition amount of the suspension stabilizer is preferably 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the monomer. Moreover, in order to refine | miniaturize these suspension stabilizers, you may add 0.001-0.5 weight part of surfactant with respect to 100 weight part of monomers. Examples of the surfactant herein include sodium dodecylbenzenesulfonate, sodium oleate, sodium laurate, potassium stearate, calcium oleate and the like.

  The suspension polymerization is carried out with stirring in an aqueous medium in which a polymerizable monomer, a colorant, a wax, a charge control agent, a crosslinking agent, a polymerization initiator, and the like are dispersed and a suspension stabilizer is contained. The amount of the aqueous medium is preferably 300 to 1000 parts by weight with respect to 100 parts by weight of the monomer. Further, in this stirring, the stirring speed and the stirring time may be adjusted so that the toner particles have a desired size, for example, 2000 to 10,000 rpm and 5 minutes to 1 hour. Thereafter, polymerization may be carried out at 50 to 90 ° C. for 2 to 20 hours while maintaining the particle state and stirring to such an extent that the particles can be prevented from settling. A dispersion is obtained.

  The obtained toner base particles have a sphericity of 0.97 or more and a Tg of 50 to 75 ° C., preferably 60 to 70 ° C. In order to achieve a sphericity of 0.97 or more, the stirring speed may be adjusted within the above range.

(Emulsion polymerization aggregation method)
In the emulsion polymerization aggregation method, a resin dispersion is generally prepared by emulsion polymerization, while an additive dispersion in which a colorant, wax, charge control agent and the like are dispersed in a solvent is prepared and mixed to form toner particles. In this method, aggregated particles corresponding to the diameter are formed and then fused to form toner particles. According to this method, toner particles having a high degree of spheroidization can be produced.

  In the emulsion polymerization for preparing the resin dispersion, for example, the same monomer, cross-linking agent, ion-exchanged water, and water-soluble polymerization initiator as exemplified in the suspension polymerization are mixed in a predetermined amount, and 10 to 90 What is necessary is just to carry out for about 1 to 24 hours at 10 degreeC and stirring speed 10-1000 rpm. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, water-soluble azo polymerization initiators such as 2,2′-azobis (2-amidinopropane) dihydrochloride, hydrogen peroxide And water-soluble radical polymerization initiators such as redox polymerization initiators in which the persulfate is combined with a reducing agent such as sodium bisulfite or sodium thiosulfate. In addition, it is preferable to perform superposition | polymerization in inert gas (for example, nitrogen gas etc.) atmosphere. The average particle diameter of the resin particles in the resin dispersion is preferably 0.01 to 1 μm.

  On the other hand, the additive dispersion is prepared by, for example, adding a predetermined amount of the above-described colorant, wax, charge control agent, etc. into an aqueous medium, and further adding a dispersant as necessary, using a dispersing means such as a ball mill. Obtained by dispersive mixing. Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the dispersant include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol And nonionic surfactants such as polyphenols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are preferable. The nonionic surfactant is preferably used in combination with the anionic surfactant or the cationic surfactant. The said surfactant can use 1 type (s) or 2 or more types.

  Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate and the like. Specific examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like.

  In order to form aggregated particles, for example, a salt such as sodium chloride is added as an aggregating agent. As a method for adding the flocculant, an aqueous solution of the dispersant may be added dropwise to the mixed dispersion obtained by mixing the resin dispersion and the additive dispersion with stirring for about 10 minutes to 24 hours. At this time, the temperature of the mixed dispersion is preferably less than the Tg of the resin in the resin dispersion.

  After the aggregated particles are grown, the temperature is raised to Tg of the resin in the resin dispersion to fuse the aggregated particles. The aggregation of the agglomerated particles is carried out with stirring for about 10 minutes to 24 hours to obtain a dispersion of toner base particles. The obtained toner base particles have a sphericity of 0.97 or more and a Tg of 50 to 75 ° C., preferably 60 to 70 ° C. In order to make the degree of spheroidization 0.97 or more, the stirring speed in each step of growth of aggregated particles and fusion of aggregated particles may be adjusted within the above range.

(Fusion of inorganic fine particles to toner base particles)
In order to fuse the inorganic fine particles to the surface of the toner base particles, the inorganic fine particles are fixed by heating to a temperature equal to or higher than the Tg of the toner base particles in an aqueous medium. Specifically, for example, a predetermined amount of inorganic fine particles are added to a dispersion of toner base particles obtained by the above-described suspension polymerization method or emulsion polymerization aggregation method, and the temperature is increased to Tg or more of the toner base particles while stirring. Heat.

  Examples of the inorganic fine particles include fine powders such as silica, titanium oxide, and aluminum oxide, which are generally used as external additives for toner particles. In addition, the inorganic fine particles used in the present invention should have a degree of hydrophobicity of 30% or less, preferably 10 to 20%. If the degree of hydrophobicity exceeds 30%, it is difficult to disperse in an aqueous medium. Absent. The degree of hydrophobicity can be determined by a methanol immersion method.

  The amount of inorganic fine particles added is 3 to 30 parts by weight with respect to 100 parts by weight of toner (that is, the ratio of M to 0.003 to 0.03 g with respect to 1 g of toner base particles), preferably 0.5 to 2. 0.0 part by weight should be added. When the added amount of the inorganic fine particles is less than 0.3 parts by weight, the cleaning property is deteriorated. On the contrary, when the added amount is more than 3 parts by weight, the fluidity is deteriorated and there is a possibility that the in-machine scattering occurs.

The inorganic fine particles are required to have a BET specific surface area Sa of 6 to 60 m ² / g, preferably 10 to 50 m ² / g. When the BET specific surface area Sa exceeds 60 m ² / g, the cleaning property is deteriorated. On the other hand, when the BET specific surface area Sa is less than 6 m ² / g, the fluidity is deteriorated, and there is a possibility that in-machine scattering occurs. The inorganic fine particles have an average particle size of 30 to 300 nm, preferably 40 to 200 nm.

  After adding a predetermined amount of inorganic fine particles to the dispersion of toner base particles, the mixture is heated to a temperature equal to or higher than Tg of the toner base particles, and the dispersion is stirred at 50 to 200 rpm for 5 to 120 minutes to fuse the inorganic fine particles.

  In particular, in the present invention, the BET specific surface area Sa of the inorganic fine particles, the BET specific surface area Stc of the toner particles before the fusing treatment of the inorganic fine particles, and the BET specific surface area St of the toner particles after the fusing treatment are expressed by the above formula (1). ) To satisfy the relationship. For that purpose, the BET specific surface areas Sa, Stc, and St may be adjusted so as to satisfy the relationship of the formula (1) by adjusting the stirring conditions and temperature conditions.

  In formula (1), (M × Sa + Stc−St) is the BET specific surface area of inorganic fine particles embedded in toner per gram, and (M × Sa) is the total BET of inorganic fine particles attached to the amount of toner per gram. Each specific surface area is shown. Therefore, the formula (1) shows that the optimum fixing state is that the BET specific surface area of the inorganic fine particles embedded in the toner is 20 to 60% of the total BET specific surface area (M × Sa) of the inorganic fine particles. Yes. This will be described with reference to FIGS. 1 (a) to 1 (b). FIG. 1 (a) shows a case where the lower limit of the formula (1) is exceeded, and the amount of embedded inorganic fine particles 2 in the toner particles 1 is insufficient. This indicates that the inorganic fine particles are easily detached. On the other hand, FIG. 1C shows a case where the upper limit value of the formula (1) is exceeded, indicating that the amount of the inorganic fine particles 2 embedded in the toner particles 1 is excessive. For this reason, in any case, the cleaning property is inferior. On the other hand, FIG. 1B shows a case where the formula (1) is satisfied, and shows that the amount of the embedded inorganic fine particles 2 is appropriate.

(Hydrophobic treatment)
A silane-based or titanium-based coupling agent is added to the dispersion of the toner base particles that have been subjected to the fusion treatment of the inorganic fine particles, and then the hydrophobic treatment is performed. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ- (methacryloyloxypropyl) trimethoxysilane, and β- (3,4- Epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (amino Ethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, etc. I can get lost.
Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tri-n-dodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis ( Ditridecyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, And titanate coupling agents such as isopropyltri (N-aminoethyl-aminoethyl) titanate.

In order to perform the hydrophobization treatment in an aqueous medium, for example, a solution obtained by dissolving the above coupling agent in a solvent is added to the dispersion and heated to a temperature equal to or higher than Tg of the toner base particles while stirring. As a solvent for dissolving the coupling agent, for example, a polar solvent such as acetone or a lower alcohol is preferably used.
The addition amount of the coupling agent is 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight, based on the toner weight.

(Toner preparation)
After the hydrophobization treatment, the dispersion is filtered, washed and dried. In order to impart fluidity to the obtained toner particles, an external additive (fluidizing agent) having a specific surface area of about 100 to 200 m ² / g may be added. Examples of such external additives include colloidal silica, hydrophobic silica, aluminum oxide, and titanium oxide. The external additive may be about 0.1 to 10 parts by weight with respect to 100 parts by weight of the toner particles. For the external addition, for example, a Henschel mixer or a Nauter mixer is preferably used.

  The obtained toner may be used as a one-component developer, or may be mixed with a carrier and used as a two-component developer. The carrier used for the two-component developer is not particularly limited, and examples thereof include magnetic metals such as iron, nickel, cobalt, and alloys thereof, alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, By sintering and atomizing magnetic materials such as nickel-zinc ferrite, manganese-magnesium ferrite, soft ferrite such as lithium ferrite, iron-based oxides such as copper-zinc ferrite, and mixtures thereof The produced magnetic particles and those obtained by coating the surfaces of the magnetic particles with a resin can be used.

  In addition, a magnetic material dispersed resin can be used as the carrier. In this case, the above magnetic material can be used as the magnetic material, and examples of the binder resin include vinyl resins, polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, and polyethers. Resins or mixtures thereof can be mentioned.

The particle diameter of the carrier is not particularly limited, but is generally 20 to 150 μm, particularly preferably 30 to 100 μm, expressed in terms of particle diameter by electron microscopy. Further, the apparent density of the carrier is preferably in the range of 2.2 to 3.0 g / cm ³ , although it varies depending on the composition of the magnetic material, the surface structure and the like when the magnetic material is mainly used.

Hereinafter, the toner for electrophotographic development of the present invention will be described in detail with reference to examples, but the present invention is not limited to only the following examples.
In the following examples, the degree of spheroidization was measured by FPIA manufactured by Sysmex Corporation. The BET specific surface area was measured with a specific surface area meter manufactured by Mountec.

[Example]
(A) Production of toner mother particles by suspension polymerization method 80 parts by weight of styrene, 20 parts by weight of 2-ethylhexyl methacrylate, 5 parts by weight of carbon black, 3 parts of low molecular weight polypropylene, 2 parts of charge control agent (P-51), divinyl After a mixed solution of 1 part of benzene (crosslinking agent) was sufficiently dispersed by a ball mill, 2 parts by weight of a polymerization initiator 2,2-azobis (2,4-dimethylvaleronitrile) was added, and these were added to ion-exchanged water 400. Added to parts by weight. Further, 5 parts by weight of tribasic calcium phosphate and 0.1 part by weight of sodium dodecylbenzenesulfonate were added as a suspension stabilizer, and the mixture was stirred at 7000 rpm for 20 minutes using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). Under an atmosphere, a polymerization reaction was performed at 70 ° C. and 100 rpm for 10 hours. After the polymerization reaction, acid washing was performed to remove tricalcium phosphate to obtain toner mother particle dispersion 1 having a volume average particle diameter of 8 μm.
The obtained toner base particles had a sphericity of 0.987, a Tg of 62 ° C., and a BET specific surface area of 1.23 m ² / g.

(B) Production of toner mother particles by emulsion polymerization aggregation method (b-1) Emulsion polymerization Styrene 20 parts by weight, butyl acrylate 3.5 parts by weight, divinylbenzene 0.2 parts by weight, persulfuric acid as water-soluble polymerization initiator 0.7 parts by weight of potassium and 200 parts by weight of ion-exchanged water are put into a round bottom flask and subjected to emulsion polymerization at 70 ° C. for 8 hours while stirring at 100 rpm with an anchor type stirring blade, and styrene having an average particle size of 0.3 μm. An acrylic resin dispersion was obtained.
(B-2) Preparation of additive dispersion 5 parts by weight of Carnauba Wax No. 1 (manufactured by Kato Hiroyuki), 2 parts by weight of Bontron P-51 (manufactured by Orient Chemical Co., Ltd.), CIPigment Red 122 (manufactured by Dainippon Ink and Company) Part by weight and 0.1 part by weight of sodium dodecylbenzenesulfonate were put into 200 parts by weight of ion-exchanged water, and dispersed and mixed for 3 hours in a ball mill to obtain an additive dispersion having an average particle size of 0.3 μm.
(b-3) Formation of Core Particles The above resin dispersion and additive dispersion were mixed, and agglomerates were grown for 1 hour at 40 ° C. while stirring at 100 rpm with an anchor type stirring blade in a round bottom flask. . During this 1 hour, 50 parts by weight of ion-exchanged water in which 0.5 part by weight of Nacl was dissolved as a flocculant was continuously added at a rate of 1 part by weight per minute for 50 minutes. After the coagulation growth, the temperature was raised to 70 ° C., and fusion was performed at 100 rpm for 30 minutes to obtain a toner base particle dispersion 2 having a volume average particle diameter of 8 μm.
The obtained toner base particles had a sphericity of 0.972, a Tg of 63 ° C., and a BET specific surface area of 1.39 m ² / g.

(c) External addition treatment of inorganic fine powder To the above dispersion 1 and dispersion 2, various inorganic fine particles shown in Tables 1 to 3 were added in predetermined addition amounts, and anchor type stirring was performed in a round bottom flask. The inorganic fine particles were fixed using a blade at 100 rpm and 70 ° C. for 2 minutes to 120 minutes. The degree of hydrophobicity of each inorganic fine particle is as follows.
(Inorganic fine particles) (Hydrophobicity)
Aerosil 50 (titanium oxide fine particles) 10%
Aerosil 130 (〃) 10%
Aerosil 90 (〃) 10%
MPT240 (〃) 70%
MPT804 (〃) 70%
CREL (〃) 5%
Subsequently, a silane coupling agent was added to the dispersion 1 and the dispersion 2. That is, a silane coupling agent (γ-aminopropyltriethoxysilane: TSL8331 (manufactured by GE Toshiba Silicone)) is dissolved in acetone and added so that the coupling agent component is 0.1% with respect to the toner weight. The mixture was stirred at 70 ° C. for 30 minutes. For samples C4, C5, and C6 in Table 3 (using titanium oxide as the inorganic fine particles), a titanate coupling agent (KR-TTS: manufactured by Ajinomoto Fine Techno Co., Ltd.) was used as a hydrophobizing agent.

(d) Preparation of Toner After the coupling agent treatment in (c) above, Dispersion 1 and Dispersion 2 are filtered, washed and dried, and then 100 parts by weight of toner particles and silica RA200HS (Nippon Aerosil) 0.8 The toner was obtained by mixing 2 parts by weight with a Henschel mixer for 2 minutes.

(e) Preparation of developer for evaluation 35 g of toner and 700 g of carrier (material: silicon resin coated ferrite carrier) for printer FS-8008C manufactured by Kyocera Mita Co., Ltd. are placed in a 500 ml plastic container and mixed at 100 rpm for 30 minutes. An evaluation developer was prepared.
1000 sheets of the developer were printed at a printing rate of 5% with the printer FS-8008C, and the cleaning property and the state of toner scattering were examined. The cleaning property was judged visually by peeling off the residual toner on the drum surface after passing through the cleaning blade.
◯: No cleaning residual toner after 1000 sheets printing Δ: Slight residual toner after 1000 sheets printing
X: Residual toner from the initial printing.
The toner scattering state was judged by visually observing the dirt in the printer. The test results are shown in Tables 1-3.

As is clear from Table 1, when the range of the above formula (1) is not satisfied (samples A1, A2, A6, and A7), all of them have poor cleaning properties. Had occurred.
As is clear from Table 2, when the BET specific surface area of the inorganic fine particles is below the range of the formula (2) (samples B1 and B2), the cleaning property is poor, and conversely, the range exceeds the range of the formula (2) (sample). In B5 and B6), the fluidity of the toner deteriorated and scattering in the machine occurred.
As is apparent from Table 3, when the BET specific surface area of the inorganic fine particles relative to the toner base particles is less than the range of the above formula (3) (samples C1 and C2), the cleaning property is poor, and conversely the range of the formula (3) is When exceeding (sample C6), the fluidity of the toner was deteriorated and scattering in the machine occurred.

[Comparative example]
As a comparative example of the dry treatment, dry external addition treatment was performed with a Henschel mixer while heating the core particles of the dispersion 1 by filtration, washing and drying under the conditions shown in Table 4.
When adjusting the buried state of the external additive while heating by dry treatment from Table 4, depending on the conditions, even if fusion aggregation due to heat occurs, or even when the above formulas (1) to (3) are satisfied The cleaning effect may be slightly insufficient. In the case of the dry type, it is presumed that there is a difference in the temperature of each toner particle due to poor thermal conductivity, and there is a variation in the embedded state for each particle. That is, by performing the heating treatment in an aqueous medium as in the method of the present invention, a uniform embedded state is obtained for each toner particle, and a sufficient cleaning effect is improved.

(A)-(c) is explanatory drawing which shows typically the fixed state of the inorganic fine particle to the toner particle after a melt | fusion process.

Explanation of symbols

1 Toner Particle 2 Inorganic Fine Particle

Claims (1)

  Toner base particles having a sphericity of 0.97 or more containing a colorant, wax, and charge control agent prepared in an aqueous medium by suspension polymerization or emulsion polymerization aggregation method, inorganic toner particles are added to the toner base in the aqueous medium. By heating to a temperature equal to or higher than the glass transition point (Tg) of the particles to fuse the inorganic fine particles, and then subjecting the toner particle surface to a hydrophobic treatment with a silane-based or titanium-based coupling agent, A method for producing a toner for electrophotographic development, characterized in that a toner satisfying the conditions (1), (2) and (3) is obtained.