Method for producing yellow toner for developing electrostatic images

Abstract

To provide a method for manufacturing a yellow toner for electrostatic charge image development which is excellent in durability under low temperature and low humidity.SOLUTION: A method for manufacturing a yellow toner for electrostatic charge image development includes a step 1 of melting and kneading at least a binder resin and a coloring agent using an open roll type kneader, a step 2 of pulverizing the kneaded material obtained in the step 1, and then mixing the obtained pulverized material with inorganic fine particles, and a step 3 of pulverizing the mixed material obtained in the step 2, and classifying the pulverized material, wherein when a value obtained by dividing the total number of -NH-groups and -NH2 groups in one molecule by the molecular amount is an NH group amount, the coloring agent contains an organic yellow pigment having an NH group amount of 2.7 mmol / g or more, and the content of the organic yellow pigment is 6 pts.mass or more and 20 pts.mass or less with respect to 100 pts.mass of the binder resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a yellow 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] When producing toner by a melt-kneading method, a method has been investigated in which the kneaded product is pulverized in the presence of inorganic fine particles (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-328043 Summary of the Invention [Problem to be solved by the invention]

[0004] Full-color printing demands higher color development. Among the cyan, magenta, and yellow pigments commonly used in full-color toners, yellow, in particular, has a weaker coloring strength than the other colors. Therefore, to achieve the same coloring strength as the other colors, a larger amount of yellow pigment must be added. However, while adding a large amount of yellow pigment increases coloring strength, the pigment in the toner tends to aggregate, resulting in uneven distribution and uneven distribution on the toner surface. As a result, yellow toner is less stable in charge than other color toners, and its fluidity is more likely to deteriorate due to electrostatic aggregation. If the fluidity further decreases due to the detachment of silica from the toner surface during continuous printing, the toner layer formed by the developing roller and regulating blade will have an uneven thickness, making it more prone to smearing than other colors. As disclosed in Patent Document 1, by carrying out the grinding process of the kneaded material in the presence of inorganic fine particles in the toner manufacturing process, it is possible to make the inorganic fine particles adhere more firmly to the toner particles than when the inorganic fine particles are added as external additives. However, during continuous printing under low temperature and low humidity conditions, even the inorganic fine particles that have adhered to the toner in the grinding process tend to detach, resulting in a problem of reduced durability.

[0005] The present invention relates to a method for producing a yellow toner for developing electrostatic images, which has excellent durability under low temperature and low humidity conditions. [Means for solving the problem]

[0006] The present invention relates to a method for producing a yellow toner for developing electrostatic images, the method comprising: Step 1 of melt-kneading at least a binder resin and a colorant using an open-roll kneader; Step 2 of pulverizing the kneaded product obtained in Step 1 and then mixing the pulverized product with inorganic fine particles; and Step 3 of pulverizing and classifying the mixture obtained in Step 2, wherein the colorant contains an organic yellow pigment having an NH group amount of 2.7 mmol / g or more, where the NH group amount is defined as the total number of -NH- groups and -NH2 groups in one molecule divided by the molecular weight, and the content of the organic yellow pigment is 6 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the binder resin. [Effects of the Invention]

[0007] According to the method of the present invention, a yellow toner for developing electrostatic images having excellent durability under low temperature and low humidity conditions can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention provides a method for producing a yellow toner for developing electrostatic images (hereinafter simply referred to as toner or yellow toner) by using a specific organic yellow pigment as the yellow pigment when producing a yellow toner containing a binder resin and a yellow pigment by a melt-kneading method, and further performing a pulverization process in multiple stages, mixing the coarsely pulverized product of the kneaded mixture with inorganic fine particles, and then finely pulverizing the mixture. The reason why the method of the present invention provides a yellow toner with excellent durability under low temperature and low humidity conditions, even when the yellow pigment content is high, is not clear, but is presumed to be as follows. The following mechanism is presumed and is not intended to be limiting.

[0009] Under low temperature and low humidity conditions, the toner surface cools and hardens or shrinks, reducing the contact area between the toner and inorganic fine particles. As a result, during continuous printing under low temperature and low humidity conditions, inorganic fine particles that adhere more firmly than inorganic fine particles added as external additives due to mixing with the pulverized material in the pulverization process tend to detach, deteriorating the fluidity and durability of the toner and making it more likely to produce smudges. However, in the method of the present invention, a large amount of an organic yellow pigment with a large amount of NH groups is used, and the pigment is finely and highly dispersed in the toner, resulting in a large and uniform distribution of NH groups on the toner surface. This allows the inorganic fine particles to adhere to the toner surface not only by mechanical force but also more firmly and with a high coverage rate due to the interaction between the functional groups of the inorganic fine particles adhered to the toner surface, such as OH groups on the silica surface, and the NH groups of the pigment, and is therefore thought to make it possible to suppress detachment of the inorganic fine particles even under low temperature and low humidity conditions.

[0010] The method for producing a yellow toner of the present invention includes the following steps 1, 2, and 3.

[0011] Step 1 is a step of melt-kneading at least a binder resin and a colorant using an open-roll kneader.

[0012] Examples of binder resins include polyester resins, vinyl resins such as styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, and composite resins containing two or more of these resins. Among these, polyester resins are preferred from the viewpoint of low-temperature fixability.

[0013] The polyester resin is a polycondensation product of an alcohol component and a carboxylic acid component, and the alcohol component preferably contains an alkylene oxide adduct of bisphenol A from the viewpoint of charging properties.

[0014] Examples of alkylene oxide adducts of bisphenol A include polyoxypropylene adducts of 2,2-bis(4-hydroxyphenyl)propane and polyoxyethylene adducts of 2,2-bis(4-hydroxyphenyl)propane, and are represented by the formula (I):

[0015] [ka]

[0016] (wherein OR and RO are oxyalkylene groups, R is an ethylene group and / or propylene group, x and y are the average number of moles of alkylene oxide added and are each a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and even more preferably 2.5 or less.) A compound represented by the following formula is preferred.

[0017] The content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 100 mol%.

[0018] Examples of other alcohol components include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol; and trihydric or higher alcohols such as bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

[0019] From the viewpoint of durability, the carboxylic acid component preferably contains an aromatic dicarboxylic acid compound.

[0020] 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.

[0021] The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 100 mol%.

[0022] 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.

[0023] The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monocarboxylic acid compound, as appropriate.

[0024] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and carboxylic acid component.

[0025] 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, and is preferably 1.3 or less, more preferably 1.2 or less.

[0026] The polyester resin 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.

[0027] Examples of esterification catalysts 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 alcohol component and the carboxylic acid component combined. Examples of promoters for the esterification catalyst include gallic acid. The amount of the promoter 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 alcohol component and the carboxylic acid component combined. Examples of polymerization inhibitors 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, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0028] 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. Among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

[0029] The softening point of the polyester resin is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°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.

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

[0031] The polyester resin is preferably an amorphous resin. The crystallinity of a resin is expressed by the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the crystallinity index defined as 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 resin has a crystallinity index of more than 1.4, preferably more than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less. On the other hand, the crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 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.

[0032] The content of the polyester resin 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, even more preferably 95% by mass or more, and even more preferably 100% by mass.

[0033] The content of the polyester resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more, and is preferably 94% by mass or less, and more preferably 92% by mass or less.

[0034] 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 94% by mass or less, more preferably 92% by mass or less.

[0035] The colorant includes an organic yellow pigment having a specific amount of NH groups from the viewpoint of interaction with the inorganic fine particles.

[0036] The organic yellow pigment has an NH group content of 2.7 mmol / g or more, preferably 4.0 mmol / g or more, more preferably 7.0 mmol / g or more, and preferably 15.0 mmol / g or less, more preferably 13.0 mmol / g or less, and even more preferably 12.5 mmol / g or less, where the NH group content is the total number of -NH- groups and -NH2 groups in one molecule divided by the molecular weight.

[0037] As the organic yellow pigment, from the viewpoint of achieving a desired NH group amount, at least one selected from the group consisting of benzimidazolone pigments, isoindoline pigments, and condensed disazo pigments is more preferred.

[0038] Examples of benzimidazolone pigments include CI Pigment Yellow 180 (total number of -NH- groups and -NH2 groups in one molecule = 6, molecular weight = 733, amount of NH groups = 8.2 mmol / g).

[0039] Examples of isoindoline pigments include CI Pigment Yellow 185 (total number of -NH- groups and -NH2 groups in one molecule = 4, molecular weight = 337, amount of NH groups = 11.9 mmol / g).

[0040] Examples of condensed disazo pigments include CI Pigment Yellow 93 (total number of -NH- groups and -NH2 groups in one molecule = 4, molecular weight = 937, NH group amount = 4.3 mmol / g), CI Pigment Yellow 95 (total number of -NH- groups and -NH2 groups in one molecule = 4, molecular weight = 917, NH group amount = 4.4 mmol / g), and CI Pigment Yellow 155 (total number of -NH- groups and -NH2 groups in one molecule = 2, molecular weight = 717, NH group amount = 2.8 mmol / g).

[0041] From the viewpoint of heat-resistant storage stability of the yellow toner, the organic yellow pigment used in the present invention is preferably at least one selected from benzimidazolone pigments and isoindoline pigments, more preferably at least one selected from CI Pigment Yellow (PY) 180 and PY185, and even more preferably PY185.

[0042] The content of the organic yellow pigment is 6 parts by mass or more, preferably 7 parts by mass or more, more preferably 7.5 parts by mass or more, relative to 100 parts by mass of the binder resin, and from the viewpoint of low-temperature fixability, is preferably 20 parts by mass or less, preferably 17 parts by mass or less, more preferably 15 parts by mass or less.

[0043] The colorant may contain other colorants as long as the effects of the present invention are not impaired, but the content of the organic yellow pigment in the colorant is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Examples of other colorants include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, and disazo yellow.

[0044] The content of the colorant is preferably 6 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 7.5 parts by mass or more, relative to 100 parts by mass of the binder resin, and from the viewpoint of low-temperature fixability, is preferably 20 parts by mass or less, more preferably 17 parts by mass or less, and even more preferably 15 parts by mass or less.

[0045] In step 1, examples of raw materials that can be subjected to melt-kneading together with the binder resin and the colorant include additives such as a release agent, a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver.

[0046] 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.

[0047] 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.

[0048] The content of the release agent 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.

[0049] 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.

[0050] Examples of 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," "Bontron N-11," and "Bontron N-79" (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.).

[0051] 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.

[0052] From the viewpoint of the charging stability of the toner, the content of the charge control agent 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.

[0053] In step 1, the raw materials to be melt-kneaded are preferably premixed using a Henschel mixer or the like, and then fed to an open-roll kneader.

[0054] 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 open-roll kneader used in the present invention is provided with a raw material supply port and a kneaded material discharge port provided along the axial direction of the rolls, and from the viewpoint of production efficiency, it is preferably a continuous open-roll kneader.

[0055] The 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.

[0056] 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.

[0057] The temperature of the raw material inlet side of the high rotation roll is preferably 100° C. or higher, more preferably 120° C. or higher, and preferably 160° C. or lower, more preferably 150° C. or lower, from the viewpoint of reducing the mechanical force during melt-kneading and suppressing heat generation. From the same viewpoint, the temperature of the raw material inlet side of the low 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Step 2 is a step of pulverizing the kneaded product obtained in Step 1 and then mixing the pulverized product with inorganic fine particles. In this specification, the pulverization in Step 2 is also referred to as "coarse pulverization," and the pulverized product obtained is also referred to as "coarsely pulverized product."

[0064] Examples of the crusher used for coarse crushing include a hammer mill, an atomizer, and a rotoplex.

[0065] In the coarse pulverization, it is preferable to coarsely pulverize the kneaded material obtained in step 1 until the particle size is approximately 0.1 to 3 mm, and then pass it through a sieve with a mesh size of approximately 2 to 3 mm, and mix the pulverized material that has passed through the sieve with inorganic fine particles as a pulverized material (coarsely pulverized material) with a maximum diameter of 2 to 3 mm or less.

[0066] Examples of inorganic fine particles used in step 2 include silicon dioxide (silica), titanium dioxide, aluminum oxide, zinc oxide, magnesium oxide, cerium oxide, iron oxide, copper oxide, and tin oxide. Among these, from the viewpoint of durability, silica or titanium dioxide is preferred, silica is more preferred, and hydrophobic silica that has been subjected to a hydrophobic treatment is even more preferred. These can be used alone or in combination of two or more.

[0067] 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.

[0068] From the viewpoint of the chargeability, fluidity and durability of the toner, the average particle size of the inorganic fine particles is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more, and is preferably 40 nm or less, more preferably 20 nm or less.

[0069] The amount of inorganic fine particles used in step 2 is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.7 parts by mass or more, per 100 parts by mass of the coarsely pulverized material, from the viewpoint of the chargeability, fluidity, and durability of the toner, and is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and more preferably 5 parts by mass or less.

[0070] The coarsely pulverized material and the inorganic fine particles can be mixed using a mixer such as a Henschel mixer. It is preferable to mix them to such an extent that the inorganic fine particles adhere to the surface of the coarsely pulverized material.

[0071] Step 3 is a step of pulverizing and classifying the mixture obtained in step 2. In this specification, the pulverization in step 3 is also referred to as "fine pulverization."

[0072] Examples of mills used for fine pulverization include a fluidized bed counter jet mill, an impact plate jet mill, and a rotary mechanical mill.

[0073] The degree of pulverization is preferably adjusted appropriately depending on the desired toner particle size.

[0074] Examples of classifiers used for classification include air classifiers, inertial classifiers, and sieve classifiers.

[0075] The pulverization and classification may be carried out simultaneously or repeatedly depending on the specifications of the apparatus used and the production efficiency.

[0076] In the present invention, it is preferable to further carry out step 4 in which the classified product obtained in step 3 is mixed with an external additive, from the viewpoint of improving transferability.

[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 average particle size 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 external addition treatment by mixing the toner particles with the external additives can be carried out in accordance with a conventional method, and a mixer such as a Henschel mixer can be used.

[0081] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the amount of 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 toner particles (classified product) before treatment with the external additive, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

[0082] The volume median particle size (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% starting from the smallest particle size. In addition, when the toner is treated with an external additive, the volume median particle size of the toner particles before treatment with the external additive is taken as the volume median particle size of the toner.

[0083] The yellow toner obtained by the method of the present invention can be used as a toner for one-component development, or mixed with a carrier to form a two-component developer. [Example]

[0084] 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.

[0085] [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.

[0086] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan), weigh 0.01-0.02 g of sample into an aluminum pan, cool from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintain at 0°C for 1 minute. Then, measure at a rate of 10°C / min. The temperature of the peak with the largest area among the observed endothermic peaks is taken as the maximum endothermic peak temperature.

[0087] [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.

[0088] [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 measured, with the maximum endothermic peak temperature being the melting point.

[0089] [Average particle size of inorganic fine particles and external additives used in fine pulverization] The average particle size refers to the number-average particle size, and is calculated by measuring the particle sizes (average values ​​of major and minor axes) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these values ​​by number.

[0090] [Volume median particle size of toner (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, and a stainless steel stirring rod, and the mixture was heated to 235°C under a nitrogen atmosphere and reacted for 6 hours. The temperature was then lowered to 210°C and the reaction continued at 40 kPa until the softening point shown in Table 1 was reached, yielding an amorphous polyester resin (Resin A1). The physical properties of the resulting resin are shown in Table 1.

[0092] [Table 1]

[0093] Resin manufacturing example 2 A 10 L four-neck flask equipped with a thermometer, stainless steel stirrer, flow condenser, dropping funnel, and nitrogen inlet tube was charged with 2 L of xylene. The dropping funnel contained 880 g of styrene, 220 g of n-butyl acrylate, and 100 g of dibutyl peroxide as a radical polymerization initiator. Under a nitrogen atmosphere, the xylene was heated to 135°C with stirring, and the mixture in the dropping funnel was added dropwise over 1 hour. The temperature was then raised to 200°C and held at 200°C for 2 hours. The pressure in the flask was then reduced to 8 kPa and held for 1 hour. The xylene was then removed to obtain a styrene-acrylic resin (Resin A2). The resulting resin had a glass transition temperature of 54°C and a softening point of 115°C.

[0094] Examples 1 to 11 and Comparative Examples 1 and 2 The binder resin and yellow pigment shown in Table 2, 4 parts by mass of a release agent "HNP-9" (paraffin wax, melting point: 75°C, manufactured by Nippon Seiro Co., Ltd.), and 0.5 parts by mass of a charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.) were mixed for 1 minute using a Henschel mixer, and then melt-kneaded under the conditions shown below.

[0095] The resulting raw material mixture was fed to a continuous twin-open-roll kneader "Kneedex" (manufactured by Mitsui Mining Co., Ltd.) using a table feeder and kneaded to obtain a kneaded product. The continuous twin-open-roll kneader used here had a roll outer diameter of 0.14 m and an effective roll length of 0.8 m. The operating conditions were a rotation speed of the high-speed roll (front roll) of 75 r / min (33 m / min), a rotation speed of the low-speed roll (rear roll) of 50 r / min (22 m / min), and a roll gap of 0.1 mm. The heating and cooling medium temperatures within the rolls were set as follows: the temperature on the raw material inlet side of the high-speed roll was 150°C, the temperature on the kneaded material outlet side was 100°C, the temperature on the raw material inlet side of the low-speed roll was 75°C, and the temperature on the kneaded material outlet side was 30°C. The raw material mixture was fed at a rate of 10 kg / h, and the average residence time was approximately 5 minutes.

[0096] The resulting kneaded product was cooled to about 25°C, then coarsely pulverized in a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Corporation) and passed through a sieve with 2 mm openings to obtain a coarsely pulverized product with a maximum diameter of 2 mm or less. 100 parts by mass of the obtained coarsely pulverized product and the inorganic fine particles shown in Table 2 were mixed in a Henschel mixer for 2 minutes to obtain a coarsely pulverized product with the inorganic fine particles attached.

[0097] The coarsely ground material with the inorganic fine particles attached was finely ground and classified by upper limit (removal of coarse particles) using a counter jet mill "400AFG" (manufactured by Hosokawa Alpine Co., Ltd.). Furthermore, it was classified by lower limit (removal of fine particles) using a classifier "TTSP" (manufactured by Hosokawa Alpine Co., Ltd.) to obtain the volume median particle diameter (D 50 ) yielded toner particles of 6.5 μm.

[0098] 100 parts by mass of the obtained toner particles and 1 part by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1 part by mass of hydrophobic silica "RX-50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, average particle size: 40 nm) as external additives were mixed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) at 3000 r / min (circumferential speed: 32 m / sec) for 3 minutes to obtain a yellow toner.

[0099] Comparative Example 3 In the melt-kneading process, instead of a continuous two-open roll kneader, a co-rotating twin-screw extruder "PCM-30" (manufactured by Ikegai Co., Ltd., shaft diameter 2.9 cm, shaft cross-sectional area 7.06 cm) was used. 2 A yellow toner was obtained in the same manner as in Example 1, except that a twin-screw extruder was used. The operating conditions of the twin-screw extruder were a barrel setting temperature of 100°C, a shaft rotation speed of 200 r / min (a peripheral speed of the shaft rotation of 0.30 m / sec), a mixture supply rate of 10 kg / h (amount of mixture supplied per unit cross-sectional area of ​​the shaft of 1.42 kg / h cm). 2 ) was.

[0100] Comparative Example 4 A yellow toner was obtained in the same manner as in Example 1, except that the coarsely pulverized material was not mixed with inorganic fine particles, but was directly subjected to fine pulverization, upper limit classification (removal of coarse particles), and lower limit classification (removal of fine particles).

[0101] Test example [Image blurring under low temperature and low humidity conditions] Yellow toner was loaded onto an OKI MICROLINE 5400 non-magnetic single-component developer (Oki Electric Industry Co., Ltd.) and a black solid image (A4 size) was printed under a low-temperature, low-humidity environment (10°C, 20% relative humidity). 500 sheets were printed at a coverage rate of 1%, followed by another black solid image (A4 size). J paper (Fujifilm Business Innovation) was used as the printing medium. The image density (ID1) of the initial black solid image, measured at a center point 5 cm from the bottom, and the image density (ID2) of the initial black solid image, measured at a center point 5 cm from the bottom, after 500 sheets were printed, were measured using an RD-915 reflection densitometer (Gretag Macbeth) to confirm the difference in image density between the two. If the difference in image density did not exceed 0.4, another 500 sheets were printed. Printing was continued until the difference in image density exceeded 0.4. Durability under low-temperature, low-humidity conditions was evaluated based on the number of prints. The results are shown in Table 2. A higher number of prints indicates a greater suppression of image blurring.

[0102] [Table 2]

[0103] The above results show that durability under low temperature and low humidity conditions is good in Examples 1 to 11. On the other hand, it is clear that image blurring occurs early and durability is insufficient compared to the Examples in Comparative Example 1, which contains a small amount of organic yellow pigment, Comparative Example 2, which contains a small amount of NH groups in the organic yellow pigment, Comparative Example 3, which uses a twin-screw extruder instead of an open-roll kneader, and Comparative Example 4, which does not use inorganic fine particles in the pulverization process. [Industrial Applicability]

[0104] The electrostatic image developing yellow toner 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. A method for producing a yellow toner for developing electrostatic images, comprising: step 1 of melt-kneading at least a binder resin and a colorant using an open-roll kneader; step 2 of pulverizing the kneaded product obtained in step 1, and then mixing the pulverized product with inorganic fine particles; and step 3 of pulverizing and classifying the mixture obtained in step 2, wherein the colorant has an -NH- group and an -NH- group in one molecule. ２ a method for producing a yellow toner for developing electrostatic images, the toner comprising: an organic yellow pigment having an NH group amount of 2.7 mmol / g or more, where the NH group amount is the total number of groups divided by the molecular weight; a content of the organic yellow pigment being 6 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the binder resin; inorganic fine particles being hydrophobic silica; and a number average particle diameter of the inorganic fine particles being 5 nm or more and 40 nm or less.

2. 2. The method for producing a yellow toner for developing electrostatic images according to claim 1, wherein the amount of the inorganic fine particles used in step 2 is 0.3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the pulverized product.

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