Method of manufacturing toner for electrostatic charge image development

Abstract

To provide a method of manufacturing toner for electrostatic charge image development superior in fog suppression and folding resistance of a print image in a high-temperature, high-humidity environment.SOLUTION: The present invention relates to a method of manufacturing toner for electrostatic charge image development that includes a process 1 of melting and kneading a mixture including at least binder resin, powder for toner and silica, and a process 2 of pulverizing and classifying the kneaded body obtained in the process 1 in the presence of the silica to obtain toner base particles, wherein the binder resin contains amorphous polyester resin A as a condensation polymer of an alcohol component and a carboxylic acid component including 60 mol% or more of aliphatic diol having 2 to 5 carbon atoms, and the toner base particles contain 0.8 to 15 mass% of silica.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a toner for developing electrostatic images, which is used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like. [Background technology]

[0002] From the viewpoint of improving the dispersibility of internal additives, there is a method of utilizing fine powder removed in a classification step in the manufacturing process of electrostatic image developing toner (hereinafter also simply referred to as "toner") (see Patent Document 1).

[0003] Furthermore, from the viewpoint of achieving both storage stability and flowability, the addition of hydrophobic silica to toner particles has been investigated (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-99351 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-242302 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been an increasing demand for electrophotographic printing in the field of flexible packaging printing, such as food packaging. From the perspective of stricter safety, there is a demand for toner containing polyester resin with a reduced content of structural units derived from bisphenol A monomers. However, increasing the content of structural units derived from aliphatic diol monomers in the polyester resin poses problems such as increased susceptibility to fogging, particularly in high-temperature and high-humidity environments, and increased susceptibility of images to cracking when printed matter is folded.

[0006] The present invention relates to a method for producing a toner for developing electrostatic images, which is excellent in preventing fogging under high temperature and high humidity conditions and in resistance to folding of printed images. [Means for solving the problem]

[0007] The present invention relates to a method for producing a toner for developing electrostatic images, the method comprising: Step 1 of melting and kneading a mixture containing at least a binder resin, a toner powder, and silica; and Step 2 of pulverizing and classifying the kneaded mixture obtained in Step 1 in the presence of silica to obtain toner base particles, wherein the binder resin contains an amorphous polyester resin A that is a polycondensate of an alcohol component and a carboxylic acid component, the alcohol component containing 60 mol % or more of an aliphatic diol having from 2 to 5 carbon atoms, and the toner base particles have a silica content of from 0.8 to 15 mass %. [Effects of the Invention]

[0008] The method of the present invention provides a toner for developing electrostatic images which is excellent in preventing fogging under high temperature and high humidity conditions and in bending resistance of printed images. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention is a method for producing a toner by a melt-kneading method using an amorphous polyester resin obtained from a short-chain aliphatic diol as a binder resin, by melt-kneading the amorphous polyester resin with a mixture containing a toner powder and silica, and then pulverizing the mixture in the presence of silica, thereby obtaining a toner with a predetermined amount of silica internally added. The reason why the toner obtained by the method of the present invention has excellent fog suppression and folding resistance of printed images under high temperature and high humidity conditions is not clear, but is presumed as follows. Note that the following mechanism is presumed and is not limited to this.

[0010] When the amount of aliphatic diol used as the alcohol component of a polyester resin is increased, the resin tends to contain a large amount of low-molecular-weight components, possibly due to the low reactivity of the aliphatic diol. When the amount of low-molecular-weight components increases, the mechanical strength of the printed image decreases, making the image more likely to crack when the printed material is folded. Furthermore, particularly in high-temperature, high-humidity environments, fogging is more likely to occur, possibly due to the effect of the low-molecular-weight components on the surface of the toner particles, which increases the adhesion between the toner and the photoreceptor. Therefore, in the present invention, we have found that the fold resistance of the resulting image is improved when producing a toner containing an amorphous polyester resin A, a polycondensate of an alcohol component and a carboxylic acid component, primarily composed of a short-chain aliphatic diol, as the binder resin by melt-kneading a mixture of toner powder and silica with a binder resin in advance and then pulverizing the resulting mixture in the presence of silica during melt-kneading. By pre-mixing silica, which tends to aggregate and has low dispersibility in the kneaded mixture, with the toner powder and then adding it internally to the toner particles, aggregation in the kneaded mixture is suppressed, allowing the silica to be melt-kneaded in a state where its dispersibility in the amorphous polyester resin A is improved. As a result, we believe that the interaction between the silica and the resin molecular chains is effectively expressed, improving the mechanical strength of the printed image. Furthermore, we believe that the silica added during pulverization of the kneaded mixture further covers the outside of the low-molecular-weight components exposed on the toner particle surface, firmly adhering to the toner particle surface and reducing the adhesion of the low-molecular-weight resin components, thereby suppressing fogging.

[0011] The method for producing the toner of the present invention includes the following steps 1 and 2.

[0012] Step 1 is a step of melting and kneading a mixture containing at least a binder resin, a toner powder, and silica.

[0013] The binder resin contains an amorphous polyester resin A which is a polycondensation product of an alcohol component containing 60 mol % or more of a short-chain aliphatic diol and a carboxylic acid component.

[0014] The short-chain aliphatic diol has 2 or more and 5 or less carbon atoms, and preferably 2 or more and 4 or less carbon atoms.

[0015] Examples of short-chain aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, and neopentyl glycol.

[0016] The content of the short-chain aliphatic diol in the alcohol component is 60 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, and 100 mol% or less.

[0017] Examples of alcohol components other than aliphatic diols include alkylene oxide adducts of bisphenol A, aromatic diols such as bisphenol A, hydrogenated bisphenol A, trihydric or higher alcohols such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

[0018] From the viewpoint of charging stability, the carboxylic acid component preferably contains an aromatic dicarboxylic acid compound.

[0019] Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0020] The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 60 mol% or more, more preferably 75 mol% or more, and even more preferably 85 mol% or more, and is 100 mol% or less, preferably 95 mol% or less, and more preferably 92 mol% or less.

[0021] Examples of other carboxylic acid components include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, aliphatic dicarboxylic acids such as glutaric acid, adipic acid, and sebacic acid, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0022] The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monocarboxylic acid compound, as appropriate.

[0023] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and carboxylic acid component.

[0024] The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups / OH groups) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, from the viewpoint of adjusting the softening point of the polyester resin, and is preferably 1.3 or less, more preferably 1.2 or less.

[0025] The amorphous polyester resin A can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and optionally in the presence of a co-catalyst, a polymerization inhibitor, etc., at a temperature of preferably 160°C or higher, more preferably 200°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

[0026] Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolaminate). The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the co-catalyst for the esterification catalyst include gallic acid. The amount of the co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0027] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like, by the methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636.

[0028] The softening point of the amorphous polyester resin A is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher, from the viewpoint of charging stability, and is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower, from the viewpoint of low-temperature fixability.

[0029] The crystallinity of a resin is expressed by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the value of [softening point / maximum endothermic peak temperature]. An amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the crystallinity index is greater than 1.4 or less than 0.6. On the other hand, a crystalline resin is a resin with a crystallinity index of 0.6 or more and 1.4 or less. The crystallinity of a resin can be adjusted by the types and ratios of raw material monomers, and production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. For crystalline resins, the maximum endothermic peak temperature is the melting point.

[0030] The glass transition temperature of the amorphous polyester resin A is preferably 40°C or higher, more preferably 50°C or higher, from the viewpoint of storage stability, and is preferably 80°C or lower, more preferably 70°C or lower, from the viewpoint of low-temperature fixability.

[0031] The content of the amorphous polyester resin A in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, and is 100% by mass or less.

[0032] The binder resin may contain a resin other than the amorphous polyester resin A to the extent that the effects of the present invention are not impaired. Examples of other resins include crystalline polyester resins, vinyl resins such as styrene-acrylic resins, polyamide resins, epoxy resins, polycarbonate resins, polyurethane resins, and composite resins containing two or more of these resins.

[0033] The content of the binder resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, even more preferably 95% by mass or less.

[0034] In the present invention, the toner powder is a composition containing a binder resin as the main component (60% by mass or more, preferably 80% by mass or more), and preferably contains, in addition to the binder resin, internal additives such as a colorant, a release agent, and a charge control agent. The binder resin preferably contains amorphous polyester resin A, and the toner powder more preferably contains the same binder resin, colorant, release agent, charge control agent, and other internal additives as the toner produced by the method of the present invention. Furthermore, the toner powder is preferably a powder obtained by a method including a step of melt-kneading a mixture containing a binder resin and, if necessary, internal additives.

[0035] From the viewpoint of dispersibility in the toner base particles, the silica is more preferably hydrophobic silica that has been subjected to a hydrophobic treatment.

[0036] Examples of hydrophobic treatment agents for hydrophobizing the surfaces of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazanes, silicone oils, aminosilanes, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0037] From the viewpoint of durability, the BET specific surface area of ​​silica is preferably 10 m 2 / g or more, more preferably 30m 2 / g or more, more preferably 80m 2 / g or more, and from the viewpoint of dispersibility in the toner base particles, it is preferably 350 m 2 / g or less, more preferably 320m 2 / g or less, more preferably 250m 2 / g or less.

[0038] From the viewpoint of dispersibility in the toner base particles, the number average particle diameter of the silica is preferably 5 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less.

[0039] The silica content in the mixture is preferably 0.8% by mass or more, more preferably 1.5% by mass or more, even more preferably 2% by mass or more, and preferably 25% by mass or less, more preferably 15% by mass or less, even more preferably 8% by mass or less.

[0040] The mixture containing a toner powder and silica may be a mixture in which silica is externally added to toner base particles after classification, or may be a product in which silica is mixed with the toner powder before classification by pulverizing the kneaded product in the presence of silica during the process of producing a toner powder by a melt-kneading method, and then further pulverizing the mixture; however, the latter is preferred from the viewpoint of the dispersibility of silica in the toner base particles. Therefore, the mixture containing a toner powder and silica is preferably a mixture obtained by a method including a step of melt-kneading a mixture containing an amorphous polyester resin A using an open-roll kneader, and a step of pulverizing the obtained kneaded product in the presence of silica, and the particle size may be adjusted by classification during or after pulverization.

[0041] Furthermore, in the present invention, the mixture containing a toner powder and silica may be the powder removed during classification in step 2 described below. That is, the powder removed during classification may be reused as a mixture containing a toner powder and silica for the melt-kneading in step 1. The powder removed during classification includes powder removed by upper limit classification (coarse powder) and powder removed by lower limit classification (fine powder), but from the viewpoint of production efficiency, in the present invention, it is preferable to use fine powder as the mixture containing a toner powder and silica.

[0042] The volume median particle size (D 50 From the viewpoint of productivity, the thickness is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 3.5 μm or more, and is preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 5 μm or less.

[0043] It is desirable to use the mixture containing the toner powder and silica in an amount such that the content of the mixture in the toner base particles is preferably 5% by mass or more, more preferably 8% by mass or more, even more preferably 10% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[0044] In step 1, examples of raw materials that can be subjected to melt-kneading together with the mixture containing the binder resin, toner powder, and silica include colorants, release agents, charge control agents, magnetic powders, flowability improvers, conductivity adjusters, reinforcing fillers such as fibrous substances, antioxidants, and additives such as cleaning property improvers.

[0045] As the colorant, dyes, pigments, magnetic materials, etc. used as toner colorants can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In the present invention, the toner may be either a black toner or a color toner.

[0046] From the viewpoint of improving the image density and low-temperature fixability of the toner, the amount of colorant used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0047] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, ethylene-propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts, and these may be used alone or in combination of two or more.

[0048] The melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of toner transferability, and is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower, from the viewpoint of low-temperature fixability.

[0049] The amount of the release agent used is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the binder resin, from the viewpoints of the low-temperature fixability and offset resistance of the toner and the dispersibility in the binder resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

[0050] The charge control agent is not particularly limited, and may contain either a positively chargeable charge control agent or a negatively chargeable charge control agent.

[0051] Positively chargeable charge control agents include nigrosine dyes such as "Nigrosine Base EX," "Oil Black BS," "Oil Black SO," "Bontron N-01," "Bontron N-04," "Bontron N-07," "Bontron N-09," and "Bontron N-11" (all manufactured by Orient Chemical Industries Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX Examples of suitable resins include polyamine resins such as "AFP-B" (manufactured by Orient Chemical Industries Co., Ltd.); imidazole derivatives such as "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Chemical Industry Co., Ltd.); and styrene-acrylic resins such as "FCA-701PT" and "FCA-201-PS" (manufactured by Fujikura Chemical Industries Co., Ltd.).

[0052] Examples of negatively chargeable charge control agents include metal-containing azo dyes such as "Balifast Black 3804," "Bontron S-31," "Bontron S-32," "Bontron S-34," and "Bontron S-36" (all manufactured by Orient Chemical Industries, Ltd.), "Eisenspiron Black TRH," and "T-77" (manufactured by Hodogaya Chemical Co., Ltd.); metal compounds of benzilic acid compounds such as "LR-147" and "LR-297" (manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds such as "Bontron E-81," "Bontron E-84," "Bontron E-88," and "Bontron E-304" (all manufactured by Orient Chemical Industries, Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts such as "COPY CHARGE NX VP434 (manufactured by Clariant), nitroimidazole derivatives, etc.; organometallic compounds, etc.

[0053] From the viewpoint of the charge stability of the toner, the amount of the charge control agent used is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0054] The mixture containing the binder resin, the toner powder, and silica, and further, if necessary, an internal additive such as a colorant, may be subjected to kneading all at once or in portions, but it is preferable to mix them in advance in a mixer such as a Henschel mixer or a ball mill, and then supply them to the melt kneading.

[0055] For melt kneading, known kneaders such as an internal kneader, a single-screw or twin-screw extruder, or an open-roll kneader can be used. In the present invention, however, it is preferable to use an open-roll kneader which can provide a physically high kneading shear.

[0056] An open-roll kneader refers to a kneading machine in which the kneading section is open and not sealed, and the heat of kneading generated during melt kneading can be easily dissipated. The two-open-roll kneader used in the present invention is equipped with two rolls, and is provided with a raw material supply port and a kneaded material discharge port provided along the axial direction of the rolls, and is preferably a continuous two-open-roll kneader from the viewpoint of production efficiency.

[0057] The two-open-roll kneader used in the present invention is preferably a kneader equipped with two rolls with different peripheral speeds, i.e., a roll with a high peripheral speed (high rotation roll) and a roll with a low peripheral speed (low rotation roll). In the present invention, from the viewpoint of dispersibility of the kneaded material, it is preferable that the high rotation roll functions as a heating roll and the low rotation roll functions as a cooling roll, that is, it is preferable that the set temperature of the high rotation roll is higher than that of the low rotation roll. When the set temperatures of the rolls on the raw material input side and the kneaded material discharge side are different, it is preferable that the set temperature of the high rotation roll is higher than that of the low rotation roll at least on the raw material input side, and it is more preferable that the set temperature of the high rotation roll is higher than that of the low rotation roll on both the raw material input side and the kneaded material discharge side.

[0058] The temperature of the rolls can be adjusted, for example, by the temperature of a heat medium passed through the inside of the rolls. The inside of each roll may be divided into two or more sections through which heat mediums of different temperatures are passed.

[0059] From the viewpoint of reducing the mechanical force during melt-kneading and suppressing heat generation, the temperature of the raw material inlet side of the high-speed rotation roll is preferably 80° C. or higher, more preferably 100° C. or higher, even more preferably 120° C. or higher, and preferably 160° C. or lower, more preferably 150° C. or lower. From the same viewpoint, the temperature of the raw material inlet side of the low-speed rotation roll is preferably 25° C. or higher, more preferably 40° C. or higher, and preferably 90° C. or lower, more preferably 80° C. or lower.

[0060] For both the high-speed rotation roll and the low-speed rotation roll, it is preferable that the temperature on the raw material input side is higher than that on the kneaded material discharge side, and the temperature difference between the raw material input side and the kneaded material discharge side is preferably 20°C or more, more preferably 30°C or more, from the viewpoint of preventing the kneaded material from detaching from the roll, reducing the mechanical force during melt kneading, and suppressing heat generation, and is preferably 60°C or less, more preferably 50°C or less.

[0061] The temperature of the raw material input side of the high rotation roll and the low rotation roll refers to the set temperature at the raw material input end, and the temperature of the kneaded material discharge side refers to the set temperature at the kneaded material discharge end.

[0062] From the viewpoint of reducing mechanical power during kneading and suppressing heat generation, the peripheral speed of the high-speed roll is preferably 2 m / min or more, more preferably 10 m / min or more, even more preferably 25 m / min or more, and preferably 100 m / min or less, more preferably 75 m / min or less, and even more preferably 50 m / min or less. From the same viewpoint, the peripheral speed of the low-speed roll is preferably 1 m / min or more, more preferably 5 m / min or more, even more preferably 15 m / min or more, and preferably 90 m / min or less, more preferably 60 m / min or less, and even more preferably 30 m / min or less. Furthermore, the ratio of the peripheral speeds of the two rolls (low-speed roll / high-speed roll) is preferably 1 / 10 or more, more preferably 3 / 10 or more, and preferably 9.9 / 10 or less, more preferably 8 / 10 or less.

[0063] There are no particular limitations on the structure, size, material, etc. of each roll. The roll surface has grooves used for kneading, and the shape of these grooves may be linear, spiral, wavy, or uneven.

[0064] After step 1, the obtained kneaded product is appropriately cooled until it reaches a pulverizable hardness, and then subjected to the subsequent step 2. Here, cooling means cooling the kneaded product to 0°C to 50°C, or cooling to a temperature equal to or lower than the glass transition temperature of the binder resin in the kneaded product.

[0065] In step 2, the kneaded product obtained in step 1 is pulverized and classified in the presence of silica to obtain toner base particles.

[0066] In pulverizing the kneaded material, the kneaded material may be pulverized to the desired particle size all at once or in stages. However, from the viewpoint of efficient and more uniform pulverization, it is preferable to perform the pulverization in two stages: coarse pulverization and fine pulverization.

[0067] Examples of the crusher used for coarse crushing include a hammer mill, a cutter mill, an atomizer, and a rotoplex.

[0068] In the coarse pulverization, the kneaded material is suitably coarsely pulverized until the particle size is about 0.1 to 3 mm, and then passed through a sieve with openings of about 2 to 3 mm, and the pulverized material that has passed through the sieve is preferably subjected to fine pulverization as pulverized material with a maximum diameter of 2 to 3 mm or less.

[0069] Examples of mills used for fine pulverization include jet mills such as fluidized bed jet mills and collision plate jet mills, and mechanical mills.

[0070] The degree of pulverization is preferably adjusted appropriately depending on the target particle size of the toner base particles.

[0071] Classifiers used for classification include air classifiers, inertial classifiers, sieve classifiers, etc. During the classification step, pulverized material removed due to insufficient pulverization may be subjected to the pulverization step again, and the pulverization step and classification step may be repeated as necessary.

[0072] In step 2, the pulverization and classification in the presence of silica is preferably carried out in the presence of silica, i.e., step 2 is preferably a step in which the kneaded product obtained in step 1 is pulverized (coarsely pulverized), mixed with silica, and then pulverized (finely pulverized) and classified. Therefore, the silica used in step 2 may be mixed with the kneaded product, but is preferably mixed with the pulverized product, and more preferably mixed with the coarsely pulverized product.

[0073] The silica used in step 2 is the same as that described as the silica contained in the mixture used in step 1, and the type and particle size of the silica may be the same as or different from the silica contained in the mixture used in step 1, but are preferably the same.

[0074] The silica content in the toner base particles obtained in step 2 is 0.8% by mass or more, preferably 2% by mass or more, more preferably 4% by mass or more, from the viewpoint of durability under high temperature and high humidity conditions, and is 15% by mass or less, preferably 12% by mass or less, more preferably 8% by mass or less, from the viewpoint of dispersibility in the toner base particles.

[0075] The volume median particle size of the toner base particles (D 50 ) is preferably 3 μm or more, more preferably 4 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less. 50 ) means the particle size at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle size.

[0076] The toner base particles obtained in step 2 can be used as a toner as is. However, in the present invention, from the viewpoint of improving transferability, it is preferable to further carry out step 3 in which the toner base particles obtained in step 2 are mixed with an external additive.

[0077] Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more of these may be used in combination. Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.

[0078] Examples of hydrophobic treatment agents for hydrophobizing the surfaces of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazanes, silicone oils, aminosilanes, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0079] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the number average particle diameter of the external additive is preferably 10 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 90 nm or less.

[0080] The toner base particles and the external additives can be mixed in a conventional manner using a mixer such as a Henschel mixer.

[0081] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the amount of the external additive used is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the toner base particles, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

[0082] The toner obtained by the method of the present invention can be used as a toner for one-component development as it is, or as a toner for two-component development mixed with a carrier, in an image forming apparatus of a one-component development system or a two-component development system, respectively. [Example]

[0083] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties of resins and the like were measured by the following methods.

[0084] [Softening point of resin] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of sample is heated at a temperature increase rate of 6°C / min while applying a load of 1.96 MPa with the plunger, and extruding it from a nozzle 1 mm in diameter and 1 mm in length. The plunger depression distance of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[0085] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample is weighed into an aluminum pan, cooled from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintained at 0°C for 1 minute. Then, measurements are performed at a rate of 10°C / min. The temperature of the peak with the largest peak area among the observed endothermic peaks is taken as the maximum endothermic peak temperature.

[0086] [Glass transition temperature of resin] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.01-0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled to 0°C at a rate of 10°C / min. The sample is then heated to 150°C at a rate of 10°C / min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the peak apex.

[0087] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C at a rate of 10°C / min, and cooled to -10°C at a rate of 5°C / min. The sample is then heated to 180°C at a rate of 10°C / min, and the calorific value is measured. The maximum endothermic peak temperature is taken as the melting point.

[0088] [BET specific surface area of ​​silica] Measured by nitrogen adsorption method under the following conditions. Measurement equipment: Specific surface area measurement equipment "Micromeritics FlowSorb III" (Shimadzu Corporation) Sample size: 0.04-0.08g Degassing conditions: 40°C, 10 minutes Adsorption gas: Nitrogen gas

[0089] [Number average particle size of silica and external additives] The particle sizes (average values ​​of major and minor diameters) of 500 particles are measured from a scanning electron microscope (SEM) photograph, and the number average value is calculated.

[0090] [Volume median particle size (D 50 ) Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 100 μm Analysis software: "Multisizer (registered trademark) III Version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) dissolved in the electrolyte to adjust the concentration to 5% by mass Dispersion conditions: 10 mg of the measurement sample was added to 5 mL of the dispersion, and the mixture was dispersed for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80 W). 25 mL of electrolyte was then added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion. Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds. Then, 30,000 particles were measured, and the volume median particle size (D 50 ) is found.

[0091] Resin manufacturing example 1 The alcohol component, carboxylic acid component, esterification catalyst, and cocatalyst shown in Table 1 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube fitted with a fractionating column through which hot water at 98°C was passed, a stirrer, and a thermocouple. The mixture was maintained at 180°C for 1 hour under a nitrogen atmosphere, then heated from 180°C to 235°C at a rate of 10°C / h. Polycondensation was then carried out at 235°C for 5 hours. The reaction was then continued at 235°C under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, yielding amorphous polyester resins (Resins A1 and A2). Their physical properties are shown in Table 1.

[0092] Resin manufacturing example 2 The alcohol component, carboxylic acid component other than trimellitic anhydride, esterification catalyst, and cocatalyst shown in Table 1 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube equipped with a fractionating column through which hot water at 98°C was passed, a stirrer, and a thermocouple. The mixture was maintained at 180°C for 1 hour under a nitrogen atmosphere, then heated from 180°C to 235°C at a rate of 10°C / h. Polycondensation was then carried out at 235°C for 5 hours. The temperature was then lowered to 210°C, and trimellitic anhydride shown in Table 1 was added. The mixture was reacted at 210°C for 1 hour, and then reacted at 210°C under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, yielding an amorphous polyester resin (Resin A3). The physical properties are shown in Table 1.

[0093] Resin manufacturing example 3 The alcohol component, carboxylic acid components other than trimellitic anhydride, esterification catalyst, and polymerization inhibitor shown in Table 1 were placed in a 5-liter four-neck flask equipped with a dehydration tube fitted with a nitrogen inlet tube, a stirrer, and a thermocouple. The temperature was raised to 235°C at a rate of 10°C / h under a nitrogen atmosphere and polycondensation was carried out for 7 hours. The temperature was then lowered to 200°C, and trimellitic anhydride shown in Table 1 was added. The temperature was raised to 210°C and polycondensation reaction was carried out up to the softening point shown in Table 1 to obtain an amorphous polyester resin (Resin A4). The physical properties of the resulting resin are shown in Table 1.

[0094] [Table 1]

[0095] Preparation Example 1 of a Mixture of Toner Powder and Silica 100 parts by mass of Resin A1, 5 parts by mass of colorant "ECB-301" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., phthalocyanine blue (pigment blue 15:3)), 4 parts by mass of release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C), and 0.5 parts by mass of charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.) were thoroughly mixed in a Henschel mixer, and then melt-kneaded using a continuous two-open roll kneader "Kneedex" (manufactured by Nippon Coke and Engineering Co., Ltd., roll outer diameter: 14 cm, effective roll length: 80 cm) under the conditions shown below.

[0096] The operating conditions of the continuous two-open roll kneader were a peripheral speed of 32.4 m / min for the high-speed roll (front roll), a peripheral speed of 21.7 m / min for the low-speed roll (back roll), and a roll gap of 0.1 mm. The temperatures of the heating medium and cooling medium in the rolls were 145°C on the raw material inlet side of the high-speed roll and 100°C on the kneaded material outlet side, and 75°C on the raw material inlet side of the low-speed roll and 35°C on the kneaded material outlet side. The feed rate of the raw material mixture was 10 kg / h, and the average residence time was approximately 3 minutes.

[0097] The resulting kneaded product was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Corporation), and a coarsely pulverized product with a volume median particle size of 2 mm or less was obtained using a sieve with 2 mm openings. The coarsely pulverized product was mixed with silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica, hydrophobic treatment agent: DMDS, number average particle size: 16 nm, BET specific surface area: 130 m). 2 The mixture was mixed with 5.8 parts by mass of silica (an amount that would result in a silica content of 5% by mass in the mixture) and the volume median particle size (D 50 The resulting mixture was finely pulverized and classified to a particle size of 4.2 μm, to obtain a mixture of toner powder and silica (Mixture 1).

[0098] Preparation Example 2 of a Mixture Containing Toner Powder and Silica Mixtures of powder for toner and silica (mixtures 2 to 6, 13, and 14) were obtained in the same manner as in Production Example 1, except that the type of amorphous polyester resin and the amount of silica mixed with the coarsely pulverized material were changed as shown in Table 2.

[0099] Preparation Example 3 of a Mixture Containing Toner Powder and Silica Instead of "R972," we used "RX300" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., number average particle size: 8 nm, hydrophobic treatment agent: HMDS, BET specific surface area: 300 m 2 A mixture of powder for toner and silica (Mixture 7) was obtained in the same manner as in Mixture 1, except that 100g of PEG-144 was used instead of PEG-144.

[0100] Preparation Example 4 of a Mixture Containing Toner Powder and Silica Instead of "R972," we used "RX50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, number average particle size: 40 nm, BET specific surface area: 50 m 2 A mixture of powder for toner and silica (Mixture 8) was obtained in the same manner as in Mixture 1, except that 100g of silica powder (100g / g) was used.

[0101] Preparation Example 5 of a Mixture Containing Toner Powder and Silica A mixture of toner powder and silica (Mixture 9) was obtained in the same manner as Mixture 1, except that "Fastgen Super Magenta R" (Pigment Red 122, manufactured by DIC Corporation) was used instead of "ECB-301" as the colorant.

[0102] Preparation Example 6 of a Mixture Containing Toner Powder and Silica A mixture of toner powder and silica (Mixture 10) was obtained in the same manner as Mixture 1, except that "Paliotol Yellow D1155" (DIC Corporation, Pigment Yellow 185) was used instead of "ECB-301" as the colorant.

[0103] Preparation Example 7 of a Mixture Containing Toner Powder and Silica A mixture of toner powder and silica (Mixture 11) was obtained in the same manner as Mixture 1, except that "Mogul L" (carbon black manufactured by Cabot Corporation) was used instead of "ECB-301" as the colorant.

[0104] Preparation Example 8 of a Mixture Containing Toner Powder and Silica A mixture of toner powder and silica (Mixture 12) was obtained in the same manner as in Mixture 1, except that a twin-screw extruder was used instead of the continuous two-open-roll kneader in the melt-kneading step. The operating conditions for the twin-screw extruder were a barrel temperature setting of 100°C, a shaft rotation speed of 200 r / min (circumferential speed of shaft rotation of 0.30 m / sec), and a mixture supply rate of 10 kg / h.

[0105] Preparation Example 9 of a Mixture of Toner Powder and Silica 100 parts by mass of Resin A1, 5 parts by mass of colorant "ECB-301" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., phthalocyanine blue (pigment blue 15:3)), 4 parts by mass of release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C), and 0.5 parts by mass of charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.) were thoroughly mixed in a Henschel mixer, and then melt-kneaded using a continuous two-open roll kneader "Kneedex" (manufactured by Nippon Coke and Engineering Co., Ltd., roll outer diameter: 14 cm, effective roll length: 80 cm) under the conditions shown below.

[0106] The operating conditions of the continuous two-open roll kneader were a peripheral speed of 32.4 m / min for the high-speed roll (front roll), a peripheral speed of 21.7 m / min for the low-speed roll (back roll), and a roll gap of 0.1 mm. The temperatures of the heating medium and cooling medium in the rolls were 145°C on the raw material inlet side of the high-speed roll and 100°C on the kneaded material outlet side, and 75°C on the raw material inlet side of the low-speed roll and 35°C on the kneaded material outlet side. The feed rate of the raw material mixture was 10 kg / h, and the average residence time was approximately 3 minutes.

[0107] The resulting kneaded product was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Corporation), and a coarsely pulverized product with a volume median particle size of 2 mm or less was obtained using a sieve with 2 mm openings. The coarsely pulverized product was mixed with silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica, hydrophobic treatment agent: DMDS, number average particle size: 16 nm, BET specific surface area: 130 m). 2 The mixture was mixed with 5.8 parts by mass of silica (an amount that would result in a silica content of 5% by mass in the mixture) and the volume median particle size (D 50 The fine powder obtained by classification was collected and used as a mixture of toner powder and silica (Mixture 15). The volume median particle diameter (D 50 ) was 4.1 μm.

[0108] [Table 2]

[0109] Example 1 100 parts by mass of Resin A1, 5 parts by mass of colorant "ECB-301" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., phthalocyanine blue (pigment blue 15:3)), 4 parts by mass of release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C), 0.5 parts by mass of charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.), and 15 parts by mass of a mixture of toner powder and silica shown in Table 3 were thoroughly mixed in a Henschel mixer, and then melt-kneaded using a continuous two-open roll kneader "Kneedex" (manufactured by Nippon Coke and Engineering Co., Ltd., roll outer diameter: 14 cm, effective roll length: 80 cm) under the conditions shown below.

[0110] The operating conditions of the continuous two-open roll kneader were a peripheral speed of 32.4 m / min for the high-speed roll (front roll), a peripheral speed of 21.7 m / min for the low-speed roll (back roll), and a roll gap of 0.1 mm. The temperatures of the heating medium and cooling medium in the rolls were 145°C on the raw material inlet side of the high-speed roll and 100°C on the kneaded material outlet side, and 75°C on the raw material inlet side of the low-speed roll and 35°C on the kneaded material outlet side. The feed rate of the raw material mixture was 10 kg / h, and the average residence time was approximately 3 minutes.

[0111] The resulting kneaded product was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Corporation) and sieved using a sieve with 2 mm openings to obtain a coarsely pulverized product with a volume median particle size of 2 mm or less. The obtained coarsely pulverized product was mixed with silica "R972" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, number average particle size: 16 nm, BET specific surface area: 130 m). 2 / g) (an amount that makes the silica content 5% by mass in the toner base particles) was mixed, and the volume median particle diameter (D 50 The resulting mixture was finely pulverized and classified so that the particle size became 6.0 μm, thereby obtaining toner base particles.

[0112] To 100 parts by mass of the obtained toner base particles, hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, number average particle diameter: 16 nm, BET specific surface area: 130 m) was added as an external additive. 2 1.0 part by mass of "RX50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, number average particle diameter: 40 nm) was added, and the mixture was mixed for 3 minutes at 3700 r / min using a Henschel mixer to perform external additive treatment, thereby obtaining a toner.

[0113] Examples 2 to 6, 13 and Comparative Examples 1 and 4 A toner was obtained in the same manner as in Example 1, except that the type of amorphous polyester resin, the type of mixture of toner powder and silica, and the amount of silica used to mix with the coarsely pulverized material were changed as shown in Table 3.

[0114] Example 7 Mixture 7 was used instead of Mixture 1, and "RX300" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, number average particle size: 8 nm, BET specific surface area: 300 m) was used instead of "R972" as silica to be mixed with the coarsely ground material. 2 A toner was obtained in the same manner as in Example 1, except that each of the above-mentioned toners (100g / g) was used.

[0115] Example 8 Mixture 8 was used instead of Mixture 1, and "RX50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, number average particle diameter: 40 nm, BET specific surface area: 50 m) was used instead of "R972" as silica to be mixed with the coarsely ground material. 2 A toner was obtained in the same manner as in Example 1, except that each of the above-mentioned toners (100g / g) was used.

[0116] Example 9 A toner was obtained in the same manner as in Example 1, except that Mixture 9 was used instead of Mixture 1, and Fastgen Super Magenta R (DIC Corporation, Pigment Red 122) was used as the colorant instead of ECB-301.

[0117] Example 10 A toner was obtained in the same manner as in Example 1, except that Mixture 10 was used instead of Mixture 1, and Paliotol Yellow D1155 (DIC Corporation, Pigment Yellow 185) was used instead of ECB-301 as the colorant.

[0118] Example 11 A toner was obtained in the same manner as in Example 1, except that Mixture 11 was used instead of Mixture 1, and "Mogul L" (carbon black, manufactured by Cabot Corporation) was used as the colorant instead of "ECB-301."

[0119] Example 12 A toner was obtained in the same manner as in Example 1, except that a twin-screw extruder was used instead of the continuous two-open-roll kneader in the melt-kneading step. The operating conditions of the twin-screw extruder were a barrel temperature setting of 100°C, a shaft rotation speed of 200 r / min (circumferential speed of shaft rotation of 0.30 m / sec), and a mixture supply rate of 10 kg / h.

[0120] Comparative Example 2 A toner was obtained in the same manner as in Example 1, except that Mixture 1 was not used.

[0121] Comparative Example 3 A toner was obtained in the same manner as in Example 1, except that 0.66 parts by mass of hydrophobic silica "R972" was used instead of mixture 1, and the amount of silica mixed with the coarsely ground material was changed to 5.1 parts by mass (an amount such that the silica content in the toner base particles was 5% by mass).

[0122] Test Example 1 [Fogging under high temperature and humidity (HH)] A non-magnetic single-component developer, "OKI MICROLINE 5400" (Oki Electric Industry Co., Ltd.), was filled with 50 g of toner and printed 5,000 images with a 1% coverage rate at 80°C and 30% relative humidity, with a 20-second break per page. J paper (Fujifilm Business Innovation Co., Ltd.) was used as the printing medium. After printing 5,000 images, one solid white image was printed and the power was turned off midway through the printing process. Scotch Mending Tape 810 (3M Japan, Ltd., 18 mm wide) was then cut to a length sufficient to fit the length of the photoreceptor. The toner on the photoreceptor surface was attached to the J paper, and the color density of the tape was measured at three locations on the photoreceptor, corresponding to both ends and the center, using a reflection densitometer, "RD-915" (Gretag Macbeth). The difference in color density between the tape itself before and after toner attachment was calculated, and the average of the three measurements was calculated. The results are shown in Table 3. A smaller value indicates better fogging suppression.

[0123] Test Example 2 [Bending Resistance] The toner was loaded into a copy machine "AR-505" (manufactured by Sharp Corporation) whose fixing unit was modified to enable fixing outside the machine, and a printout was obtained in an unfixed state (print area: 20 cm × 20 cm, toner adhesion amount: 0.5 mg / cm 2 Then, the image was fixed by adjusting the temperature of the fixing roll to 160°C using a fixing machine (fixing speed 300mm / sec) adjusted to a total fixing pressure of 40kgf. 2 The print was folded inward for 30 seconds, opened again, and the damaged image was wiped off with a soft cloth. The maximum width of the image defect after this was used as an index of the folding resistance of the print. The results are shown in Table 3. The smaller the maximum width of the image defect, the better the folding resistance of the print. The fixing paper used was "CopyBond SF-70NA" (manufactured by Sharp Corporation, 75 g / m 2 ) was used.

[0124] [Table 3]

[0125] From the above results, it is clear that in Examples 1 to 13, fogging under high temperature and high humidity conditions is suppressed, and toners that provide printed images with good bending resistance are obtained. In contrast, Comparative Example 1, which uses an amorphous polyester resin that does not contain a short-chain aliphatic diol, and Comparative Example 4, which has a low silica content in the toner base particles, exhibit fog and insufficient bending resistance. Furthermore, Comparative Example 2, in which silica is not added to the toner particles, and Comparative Example 3, in which silica is added directly to the toner particles rather than mixed with the toner powder, also exhibit insufficient bending resistance. [Industrial Applicability]

[0126] The toner for developing electrostatic images obtained by the method of the present invention is suitably used for developing latent images formed in electrostatic image developing methods, electrostatic recording methods, electrostatic printing methods and the like.

Claims

1. 1. A method for producing a toner for developing electrostatic images, comprising: Step 1: melt-kneading a mixture containing at least a binder resin, a toner powder, and silica; and Step 2: pulverizing and classifying the kneaded mixture obtained in Step 1 in the presence of silica to obtain toner base particles, wherein the binder resin contains an amorphous polyester resin A that is a polycondensate of an alcohol component and a carboxylic acid component, the alcohol component containing 60 mol % or more of an aliphatic diol having from 2 to 5 carbon atoms, and the toner base particles have a silica content of from 0.8% by mass to 15% by mass.

2. 2. The method for producing a toner for developing electrostatic images according to claim 1, wherein the mixture containing a powder for a toner and silica is a mixture obtained by a method comprising the steps of melt-kneading a mixture containing an amorphous polyester resin A using an open-roll kneader, and pulverizing the obtained kneaded mixture in the presence of silica.

3. 2. The method for producing a toner for developing electrostatic images according to claim 1, wherein the mixture containing the toner powder and silica is a powder removed by lower limit classification during classification in step 2.

4. 4. The method for producing a toner for developing electrostatic images according to claim 1, wherein the amount of the mixture containing the toner powder and silica is such that the content of the mixture in the toner base particles is 5% by mass or more and 25% by mass or less.

5. The BET specific surface area of ​​silica is 10 m ２ / g or more 350m ２ 4. The method for producing a toner for developing electrostatic images according to claim 1, wherein the toner has a molecular weight of 1 / g or less.

6. 4. The method for producing a toner for developing electrostatic images according to claim 1, further comprising a step 3 of mixing the toner base particles obtained in the step 2 with an external additive.

Images