Pulverized toner and its manufacturing method

Abstract

To provide a pulverized toner capable of reducing concentration difference between a printing part and a non-printing part in a halftone image after continuous printing, and improving handling property with an electric field and reducing damage on the printing part due to transfer residual even in high-humidity environment, to suppress deterioration in concentration difference, and a method for manufacturing the pulverized toner.SOLUTION: In a pulverized toner 10 composed of base particles 11 and an external additive, the base particles 11 contain at least a mold release agent, a grinding aid 15, and a binder resin. The pulverized toner 10 contains metal oxide fine particles containing at least strontium titanate 13 as the external additive, where a ratio of the grinding aid 15 and the mold release agent is 0.5:1 to 4:1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pulverized toner used in an image forming apparatus that utilizes an electrophotographic system, and a method for producing the same. [Background technology]

[0002] Toners (toners for developing electrostatic images) used in electrophotographic image forming devices such as copiers, multifunction machines, and printers can be broadly classified into pulverized toners produced by pulverization and polymerized toners produced by polymerization, based on the manufacturing method. The toner base particles contain binder resins, colorants, release agents, charge control agents, and other components, all of which are collectively referred to as internal additives. Meanwhile, the fine particles that adhere to the toner surface and play an important role in controlling the toner's chargeability, fluidity, antiblocking properties, and other properties are referred to as external additives.

[0003] Generally, printed materials include not only photographs, which are printed evenly across the entire surface, but also text, where only specific lines are printed repeatedly. This results in different amounts of development between the printed area and the area where no text is printed, leading to issues such as drum film wear and development damage accumulating in only one area, resulting in density changes in only the previous printed line of the halftone image immediately after text printing. In addition, regular ultra-fine powder has a large amount of wax exposed and is highly adhesive.

[0004] Patent Document 1 discloses a toner for electrostatic development, which comprises a kneaded toner consisting of at least a resin, a pigment, and a charge control agent, wherein at least one of the resins is a crystalline polyester, and is kneaded so that the absorbance value when irradiated with light having a wavelength of 2003 nm is 0.001 to 0.3, and the toner comprises at least the resin, the pigment, and the charge control agent, and further comprises a grinding aid (see claims 1 and 8).It also discloses that strontium titanate may be used as an external toner additive (see paragraph

[0057] of the specification). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-47688 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of these problems with the prior art, the object of the present invention is to provide a pulverized toner and a method for manufacturing the same that can reduce the density difference between printed and non-printed areas in halftone images after continuous printing, improve handling properties under an electric field even in high humidity environments, reduce damage to printed areas due to transfer residue, and suppress deterioration of density differences. [Means for solving the problem]

[0007] In order to achieve the above object, one embodiment of the pulverized toner of the present invention is a pulverized toner composed of base particles and external additives, characterized in that the base particles contain at least a release agent, a grinding aid, and a binder resin, the external additives contain metal oxide microparticles containing at least strontium titanate, and the ratio of the grinding aid to the release agent is 0.5:1 to 4:1.

[0008] Here, the grinding aid may be a styrene copolymer and the binder resin may be a polyester resin, but the combination is not limited to this.The amount of the grinding aid added is preferably 1 to 10%.

[0009] The grinding aid may be an α-methylstyrene copolymer, and the dispersion diameter of the α-methylstyrene copolymer in the flakes is preferably 50 to 700 nm. The softening point of the α-methylstyrene copolymer is preferably 114 to 126°C.

[0010] The strontium titanate may be silica-modified. In this case, the particle size of the silica-doped strontium titanate is preferably 30 to 50 nm. The molar ratio Si / Ti of the silicon (Si) of the silica to the titanium (Ti) of the strontium titanate in the external additive is preferably 0.03 or more and less than 1. The ratio of the silica-doped strontium titanate is preferably 0.1 to 1.0 parts.

[0011] The percentage of particles having a particle size of 2 μm or less is preferably 3 to 15%.

[0012] The number of parts of small silica is preferably 0.3 to 2.0 parts.

[0013] In addition, a method for producing pulverized toner according to another embodiment of the present invention is characterized by comprising: a mixing step of mixing raw materials including the binder resin; a melting and kneading step of melting and kneading the mixture obtained in the mixing step; a pulverizing step of cooling and pulverizing the molten and kneaded product obtained in the melting and kneading step; a classification step of classifying the pulverized product obtained in the pulverizing step; and a stirring step of adding the external additive to the toner base particles obtained in the classification step and stirring the mixture. [Effects of the Invention]

[0014] According to one embodiment of the pulverized toner of the present invention, the density difference between printed and non-printed areas in halftone images after continuous printing is reduced, and handling properties due to an electric field are improved even in high humidity environments, reducing damage to printed areas due to transfer residue and preventing the density difference from worsening.

[0015] According to another embodiment of the method for producing pulverized toner of the present invention, such pulverized toner can be produced. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an explanatory diagram illustrating a schematic configuration of pulverized toner according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing an outline of a method for producing pulverized toner according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the negatively charged pulverized toner according to the embodiment of the present invention will be specifically described with reference to examples and comparative examples, and measurement methods will also be described.

[0018] (Schematic configuration of toner 10) FIG. 1 is an explanatory diagram showing a schematic configuration of pulverized toner according to one embodiment of the present invention.

[0019] As shown in FIG. 1, the toner 10 is composed of base particles 11 containing at least a binder resin (not shown), wax 14 (an example of a release agent), and FTR 15 (an example of a grinding aid), and an external additive containing at least small silica 12 and strontium titanate (SrTiO3) 13.

[0020] Here, FTR is the trade name of an α-methylstyrene copolymer manufactured by Mitsui Chemicals, Inc., but it goes without saying that products from other companies may be used instead.

[0021] In this way, by adding FTR as a grinding aid, the polarity of the FTR results in the presence of the FTR around the wax after kneading. Furthermore, the FTR acts as the starting point for grinding, improving grindability but generating ultrafine powder. By using FTR in combination with strontium titanate, the adverse effects of ultrafine powder can be reduced, and a development system with improved image quality can be provided, thanks to the drum refreshing effect of the ultrafine powder and strontium titanate in non-image areas.

[0022] The grinding aid FTR increases grindability, producing ultrafine powder of 2 μm or less. Furthermore, FTR surrounds the wax, preventing its exposure and reducing adhesion. Adding strontium titanate to a toner containing ultrafine powder produces a moderate amount of fogging in non-image areas, providing a polishing effect on areas where no characters were printed during continuous printing. This reduces the density difference (△) between printed and non-printed areas in halftone images after continuous printing. Furthermore, silica modification of strontium titanate improves handling in electric fields, even in high-humidity environments, reducing damage to printed areas due to transfer residue and preventing the density difference (△) from worsening.

[0023] The raw materials of the toner may contain additives such as a binder resin and a grinding aid, a release agent, a colorant, a charge control agent, and a magnetic material.

[0024] Examples of binder resin materials include polyester resins, polystyrene resins such as styrene-acrylic resins, (meth)acrylic acid ester resins, polyolefin resins, polyurethane resins, and epoxy resins, and one of these may be used alone or two or more may be used in combination.

[0025] The polyester resin used as the binder resin is usually obtained by a known method of condensation polymerization reaction, esterification, or transesterification of one or more selected from dihydric alcohol components and trihydric or higher polyhydric alcohol components and one or more selected from dicarboxylic acids and trihydric or higher polycarboxylic acids.

[0026] The conditions for the polycondensation reaction may be appropriately set depending on the reactivity of the monomer components, and the reaction may be terminated when the polymer has reached suitable physical properties. For example, the reaction temperature is about 170 to 250°C, and the reaction pressure is about 5 mmHg to atmospheric pressure.

[0027] Examples of the dihydric alcohol component include alkylene oxide adducts of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol; Examples of suitable olefin copolymers include diols such as ethanol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenol A; propylene adducts of bisphenol A; ethylene adducts of bisphenol A; and hydrogenated bisphenol A.

[0028] Examples of trihydric or higher polyhydric alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose (cane sugar), 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0029] In the present invention, the above dihydric alcohol components and trihydric or higher polyhydric alcohol components can be used alone or in combination of two or more.

[0030] Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, n-dodecylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, and acid anhydrides or lower alkyl esters thereof.

[0031] Examples of trivalent or higher polyvalent carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and acid anhydrides or lower alkyl esters thereof.

[0032] In the present invention, the above dicarboxylic acids and tricarboxylic or higher polycarboxylic acids can be used alone or in combination of two or more.

[0033] The polyester resin preferably has a weight-average molecular weight of 3,000 to 50,000. If the weight-average molecular weight of the polyester resin is less than 3,000, the peelability at high fixing temperatures may be poor. On the other hand, if the weight-average molecular weight exceeds 50,000, the low-temperature fixability may be poor.

[0034] The polyester resin preferably has an acid value of 5 to 30 mgKOH / g. If the acid value of the polyester resin is less than 5 mgKOH / g, the charging characteristics of the resin will be reduced and the charge control agent will be difficult to disperse in the polyester resin, which may adversely affect the charge buildup and charging stability during continuous use. On the other hand, if the acid value of the polyester resin exceeds 30 mgKOH / g, the hygroscopicity will be high and the charging properties may become unstable.

[0035] The grinding aid may be a material known as a grinding aid. For example, wax may also be used. However, it is preferable to use a material that does not change the toner's properties other than grindability, such as color gamut, transparency, charging performance, and fixing properties. Examples of such grinding aids include aromatic petroleum resins described in JP-A-4-257868, aliphatic petroleum resins described in JP-A-7-199534, hydrogenated petroleum resins described in JP-A-8-278658, and copolymer resins described in JP-A-6-184249 or JP-A-8-333425.

[0036] More specifically, the aromatic petroleum resin is preferably a C7 to C10 resin, and examples thereof include "Petcol 130," "Petcol 140," and "Petcol 150" manufactured by Tosoh Corporation, "Neopolymer 130," "Neopolymer 140," "Neopolymer 150," "Neopolymer 160," and "Neopolymer 170" manufactured by Japan Synthetic Resin Co., Ltd., and "FTR-2120," "Petrogin 30," and "Petrogin 50" manufactured by Mitsui Chemicals, Inc.

[0037] Aliphatic petroleum resins are preferably those made primarily from the C4-C5 fraction of cracked oil fractions produced during the thermal cracking of naphtha, etc., and include materials polymerized, if necessary, with diene olefins, etc., and hydrogenated aliphatic petroleum resins in which some or all of the carbon-carbon double bonds have been hydrogenated. The term "aliphatic" as used herein includes alicyclic petroleum resins. The number-average molecular weight of the aliphatic petroleum resin is typically 200-5000, preferably 300-3000, and more preferably 400-2500. The softening point is typically 60-170°C, preferably 65-160°C, and more preferably 70-150°C.

[0038] As the hydrogenated petroleum resin, hydrogenated petroleum resins whose main raw material is dicyclopentadiene and hydrogenated petroleum resins whose main raw material is C6 to C8 aromatic hydrocarbons are preferred, and the hydrogenation rate is preferably 50% or more, more preferably 75% or more.

[0039] The copolymer resin is preferably a copolymer resin containing a styrene-based monomer and an indene-based monomer, and more preferably a copolymer of a styrene-based monomer represented by the following general formula (I) and an indene-based monomer represented by the following general formula (II). In the following general formula (I), R1, R2, R3, and R4 may be the same or different and represent a hydrogen atom or an alkyl group having 4 or less carbon atoms. In the following general formula (II), R5, R6, and R7 may be the same or different and represent a hydrogen atom or an alkyl group having 6 or less carbon atoms. The molar ratio of (I) / (II) is preferably 40 / 60 to 80 / 20, and the softening point Tm is preferably 100 to 170°C.

[0040] [ka]

[0041] Another preferred copolymer resin is a hydrocarbon resin obtained by copolymerizing a vinyl aromatic hydrocarbon with a fraction containing unsaturated hydrocarbons having 4 to 5 carbon atoms, such as a by-product of petroleum refining or petroleum cracking, in the presence of a Friedel-Crafts catalyst. The hydrocarbon resin preferably contains 2 to 100 parts by weight of structural units derived from unsaturated hydrocarbons having 4 to 5 carbon atoms per 100 parts by weight of structural units derived from vinyl aromatic hydrocarbons. Furthermore, copolymers obtained by graft copolymerization of the hydrocarbon resin with an unsaturated carboxylic acid alkyl ester are also suitable. In this case, the content of structural units derived from the unsaturated carboxylic acid alkyl ester is preferably 0.1 to 10% by weight. The weight-average molecular weight of the hydrocarbon resin is preferably 300 to 3,000.

[0042] The charge control agent may be a positively or negatively charged charge control agent, such as nigrosine dyes and their derivatives, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, triphenylmethane derivatives, guanidine salts, and amidine salts.

[0043] On the other hand, examples of charge control agents for negative charging include oil-soluble dyes such as oil black and Spiron black, metal-containing azo compounds, azo complex dyes, metal naphthenate salts, metal complexes and metal salts of salicylic acid and its derivatives (metals include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylate salts, and resin acid soaps.

[0044] Examples of release agents include petroleum waxes such as paraffin wax and its derivatives, microcrystalline wax and its derivatives, Fischer-Tropsch wax and its derivatives, polyolefin wax and its derivatives, polypropylene wax and its derivatives, hydrocarbon synthetic waxes such as polyolefin polymer wax (e.g., low-molecular-weight polyethylene wax) and its derivatives, carnauba wax and its derivatives, rice wax and its derivatives, candelilla wax and its derivatives, plant-based waxes such as Japan wax, animal-based waxes such as beeswax and spermaceti, fatty acid amides, phenolic fatty acid esters and their derivatives, silicone polymers, and higher fatty acids. These may be used alone or in combination. Derivatives include oxides, block copolymers of vinyl monomers and wax, and graft-modified products of vinyl monomers and wax. The wax content is not particularly limited, but is preferably 0.5 to 10 parts by weight per 100 parts by weight of the binder resin.

[0045] Examples of colorants include pigments and dyes of black, yellow, magenta, and cyan. Note that the color of the toner is not limited to these, and the toner may be colored in other colors, and a colorant corresponding to the color may be used.

[0046] Examples of black colorants include inorganic pigments such as carbon black and complex oxide black; and organic pigments such as aniline black.

[0047] Carbon black is classified into channel black, roller black, disc black, gas furnace black, oil furnace black, thermal black, acetylene black, etc. depending on the production method, etc., and an appropriate carbon black can be selected from these according to the design properties of the toner to be obtained.

[0048] Examples of yellow colorants include organic pigments such as CI Pigment Yellow 1, CI Pigment Yellow 5, CI Pigment Yellow 12, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 180, and CI Pigment Yellow 185, which are classified by the Color Index; nitro dyes such as CI Acid Yellow 1; and oil-soluble dyes such as CI Solvent Yellow 2, CI Solvent Yellow 6, CI Solvent Yellow 14, CI Solvent Yellow 15, CI Solvent Yellow 19, and CI Solvent Yellow 21.

[0049] Examples of magenta colorants include organic pigments such as CI Pigment Red 49, CI Pigment Red 57, CI Pigment Red 81, CI Pigment Red 122, CI Solvent Red 19, CI Solvent Red 49, CI Solvent Red 52, CI Basic Red 10, and CI Disperse Red 15, which are classified by the Color Index.

[0050] Examples of cyan colorants include organic pigments such as CI Pigment Blue 15, CI Pigment Blue 16, CI Solvent Blue 55, CI Solvent Blue 70, CI Direct Blue 25, CI Direct Blue 86, and KET.BLUE 111, which are classified by the Color Index.

[0051] Examples of magnetic materials include magnetite powder, γ-hematite powder, and various ferrite powders, and one of these may be used alone or two or more of them may be used in combination.

[0052] (Toner manufacturing method) FIG. 2 is a flowchart showing an outline of a method for producing pulverized toner according to another embodiment of the present invention.

[0053] In the mixing step (step S1), a binder resin, a grinding aid, a charge control agent, a release agent, a colorant, and a magnetic material are dry-mixed in a mixer to prepare a mixture. At this time, all of the raw materials may be mixed at once, or mixing may be performed multiple times and some materials may be added later.

[0054] Examples of mixers include Henschel-type mixers such as Henschel Mixer (trade name, manufactured by Mitsui Mining Co., Ltd. (now Nippon Coke and Engineering Co., Ltd.)), Super Mixer (trade name, manufactured by Kawata Corporation), and Mechaminor (trade name, manufactured by Okada Seiko Co., Ltd.), as well as mixers such as Angmill (trade name, manufactured by Hosokawa Micron Corporation), Hybridization System (trade name, manufactured by Nara Machinery Works, Ltd.), and Cosmo System (trade name, manufactured by Kawasaki Heavy Industries, Ltd.).

[0055] In the melt-kneading step (step S2), the mixture that has been through the mixing step is melt-kneaded in a kneader to produce a kneaded product in which various materials are dispersed in the binder resin.

[0056] Examples of the kneading machine include a kneader, a twin-screw extruder, a two-roll mill, a three-roll mill, a lab blast mill, etc. Specific examples of the kneading machine include a single-screw or twin-screw extruder such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, or PCM-30 (all trade names, manufactured by Ikegai Corporation), and an open-roll type kneading machine such as Kneadex (trade name, manufactured by Mitsui Mining Co., Ltd.). The above-mentioned mixing step and melt-kneading step may both be performed multiple times, and the mixing step may be performed multiple times in succession. Furthermore, the mixing step may be performed again after the melt-kneading step, and finally, the melt-kneading step may be performed before the pulverization and classification step. Furthermore, the pulverized material that has been subjected to the pulverization and classification step may be used as the material for the mixing step.

[0057] Specifically, in this embodiment, a masterbatch containing a part of the binder resin (L-form) and a colorant is first prepared by dry-mixing the part of the binder resin and the colorant, followed by melt-kneading.

[0058] In the cooling and pulverizing step (step S3) and the classification step (step S4), the kneaded material that has been through the melt-kneading step is pulverized by a pulverizer, and the pulverized material is classified by a classifier. That is, after the kneaded material is pulverized to reduce the particle size, the fine powder that has become too small is classified and removed from the product.

[0059] Examples of the pulverizer include a hammer mill, a cutting mill, a speed mill, etc. Examples of the classifier include a classifier that utilizes centrifugal force or wind power, such as a rotary wind classifier (rotary wind classifier).

[0060] In the external addition step (step S5), the toner particles that have been subjected to the classification step are mixed with an external additive to obtain a toner.

[0061] External additives generally have the function of improving the transportability and chargeability of the toner, as well as the agitation property with the carrier when the toner is used in a two-component developer.

[0062] The external additive for the toner of the present invention is an externally added fine powder of silica and strontium titanate to which silica has been added, the surface of which has been hydrophobized with a silane compound.

[0063] (external silica) The externally added silica preferably has an average primary particle size of 40 nm or less.

[0064] If the average primary particle diameter of the externally added silica exceeds 40 nm, the effect of imparting fluidity to the toner decreases, and toner scattering may occur due to poor toner mixing, etc. On the other hand, if the average primary particle diameter of the externally added silica is too small, it becomes significantly embedded in the toner particles, and it may not be possible to sufficiently adjust the chargeability and fluidity throughout long-term use, and the lower limit is about 6 nm.

[0065] The average primary particle size of the externally added silica is preferably 6 to 17 nm, and more preferably 7 to 12 nm.

[0066] Examples of externally added silica include silica particles commonly used in the technical field, such as dry-process silica particles such as fumed silica obtained by burning silicon tetrachloride and arc-process silica in which silica is atomized in the gas phase using high energy such as plasma; wet-process silica particles such as precipitation-process silica synthesized under alkaline conditions using an aqueous sodium silicate solution as a raw material and gel-process silica synthesized under acidic conditions; colloidal silica particles obtained by polymerizing acidic silicic acid in an alkaline state; and sol-gel-process silica particles obtained by hydrolysis of an organic silane compound, which may be surface-treated with a surface treatment agent to improve the electrical properties of the photoreceptor.

[0067] Surface treatment agents include those commonly used in the art, such as hexamethyldisilazane (HMDS), dimethyl-dichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS).

[0068] Commercially available hydrophobized silica particles may be used, or silica particles that have not been hydrophobized may be subjected to a treatment before use.

[0069] (externally added fine powder) The externally added fine powder is made of strontium titanate with added silica, and the surface of the core is hydrophobized with a silane compound.

[0070] The externally added fine powder is not particularly limited, but can be produced, for example, by the following method.

[0071] Solution 1, prepared by adjusting the pH to 1.0 with hydrochloric acid and peptizing metatitanic acid, is mixed with solution 2, an aqueous strontium chloride solution, and solution 3, an aqueous sodium silicate solution, in a ratio such that the (Sr+Si) / Ti molar ratio is 1.2. The resulting mixed solution is heated to 80°C under a nitrogen gas atmosphere, and an aqueous sodium hydroxide solution is added at a rate of 1 equivalent / hour. The resulting fine powder is then surface-coated with a silane coupling agent using a surface treatment method commonly used in the art, thereby producing the product.

[0072] Silane coupling agents include hexamethyldisilazane (HMDS), dimethyl-dichlorosilane (DDS), octylsilane (OTAS), and polydimethylsiloxane (PDMS).

[0073] The molar ratio Si / Ti of silicon Si of silica to titanium Ti of strontium titanate in the externally added fine powder is not particularly limited, but is preferably 0.03 or more and less than 1.

[0074] If the molar ratio Si / Ti is less than 0.03, the conductivity of the externally added fine powder becomes high, and when a toner containing the externally added fine powder is left in a high-humidity environment, the rate of charge loss increases, and the fog value may increase. On the other hand, if the molar ratio Si / Ti is 1 or more, the negative charge property of silica is strongly expressed, so when a toner containing the externally added fine powder is continuously printed in a low-humidity environment, the toner becomes excessively charged, which deteriorates its mixing with the toner supplied from the cartridge, and the fog value may increase due to toner scattering.

[0075] The average primary particle size of the externally added fine powder is about 30 to 50 nm.

[0076] The average primary particle size of the externally added fine powder is preferably larger than that of the externally added silica. If the average primary particle size of the externally added fine powder is smaller than that of the externally added silica, polishing properties may not be exhibited.

[0077] The average primary particle size of the externally added fine powder is preferably 35 to 45 nm.

[0078] (Amount of external additives added) The amount of externally added silica is not particularly limited, but is preferably an amount corresponding to a coverage rate of 50 to 150% of the toner base particles.

[0079] If the amount of externally added silica is an amount corresponding to a coverage rate of less than 50% on the toner base particles, the charge amount of the toner will decrease, but the fluidity may decrease. On the other hand, if the amount of externally added silica is an amount corresponding to a coverage rate of more than 150% on the toner base particles, the externally added silica may come off the toner base particles and contaminate the developer.

[0080] The coverage is more preferably 80 to 100%.

[0081] The amount of the externally added fine powder is preferably an amount corresponding to a coverage rate of 2 to 15% of the toner base particles.

[0082] When the amount of externally added fine powder is an amount corresponding to a coverage of less than 2% of the toner base particles, the effects of the present invention may not be achieved.On the other hand, when the amount of externally added fine powder is an amount corresponding to a coverage of more than 10% of the toner base particles, the effect of the fine powder in suppressing the charge amount of the toner becomes so great that the charge amount may be reduced too much.

[0083] A more preferable amount of externally added fine particles is an amount corresponding to a coverage rate of 5 to 10% with respect to the toner base particles.

[0084] Here, the "coverage" is a value calculated from the average primary particle diameter of the external additive and the surface area of ​​the toner base particle, assuming that the entire surface of the toner base particle is covered with the external additive in a most dense state as 100%, and that each particle of the external additive has the same average primary particle diameter.

[0085] (Manufacturing method) In this embodiment, 100 parts by weight of L-form resin (glass transition temperature approximately 60°C, softening temperature approximately 70°C) and 10 parts by weight of carbon black (MA-77, manufactured by Mitsubishi Chemical Corporation) were mixed and dispersed in a Henschel mixer, and then melt-kneaded using an open-roll kneader such as a Kneadex. The mixing conditions in the Henschel mixer were a rotation speed of 550 rpm and a time of 2 minutes.

[0086] To the masterbatch, 0.5 parts by weight of charge control agent, 2.7 parts by weight of wax, 6.2 parts by weight of grinding aid (Mitsui Chemicals, Inc., FTR-2120), and 51.0 parts by weight of resin were added, mixed and dispersed in a Henschel mixer, and then melt-kneaded using a twin-screw extruder. The mixing conditions in the Henschel mixer were a rotation speed of 1200 rpm and a rotation time of 5 minutes. The operating conditions of the twin-screw extruder were a cylinder set temperature of 110°C, a barrel rotation speed of 250 rpm, and a raw material feed rate of 10 kg / hour. The resulting kneaded product was cooled on a cooling belt and then coarsely crushed in a speed mill equipped with a φ1 mm screen to obtain a coarsely crushed product with a particle size of 1 mm.

[0087] The coarsely crushed material obtained above was finely crushed using a counter jet mill (product name: AFG, manufactured by Hosokawa Micron Corporation) to obtain finely crushed particles having a volume average particle size of 5.5 μm.

[0088] The finely pulverized particles were classified using a rotary classifier (trade name: TSP Separator, manufactured by Hosokawa Micron Corporation) to obtain particles with a volume average particle diameter of 6.0 μm containing no external additives.

[0089] 100 parts by weight of unadded fine particles and 1 part by weight of a small-particle external additive (product name: R976S, manufactured by AEROSIL) which is an organic-inorganic composite fine particle having an average primary particle diameter of 7 nm were added to a Henschel mixer, and the mixture was stirred and mixed for 30 seconds at a peripheral speed of 40 m / sec. 0.65 parts by weight of strontium titanate (product name: SWS-450CF, manufactured by Titan Kogyo Co., Ltd.) having an average primary particle diameter of 30 to 50 nm was then added to the Henschel mixer, and the mixture was stirred and mixed for 90 seconds at a peripheral speed of 40 m / sec. The resulting mixture was sieved through a 200-mesh sieve to obtain the toner of Example 1-3.

[0090] (Details of Examples and Comparative Examples) Tables 1 and 2 show various conditions and evaluation results of image quality for each example and comparative example.

[0091] [Table 1]

[0092] [Table 2]

[0093] Among these, Examples 1-3 are the basic ones, and the conditions are as follows.

[0094] Specifically, a styrene copolymer was used as the grinding aid, with a quantity of 5% by weight of the toner and a softening point of 117.5°C. The FTR dispersion diameter in the flakes was 200nm, the quantity of release agent was 2.5% by weight of the toner, and the toner resin type was polyester. Silica-modified SrTiO3 was used as the external additive, with a particle diameter of 40nm and a part number of 0.3.

[0095] In Comparative Example 1-1, the amount of grinding aid was set to 1.0%, and the other conditions were the same.

[0096] In Comparative Example 1-2, the amount of grinding aid was set to 12%, but the other conditions were the same.

[0097] Comparative Example 2-1 does not use SrTiO3 and uses only silica as an external additive, but other conditions are the same.

[0098] In Examples 1-1 to 1-6, the amount of grinding aid was 1.5, 3, 5, 8, 10, and 0.8%, respectively, and in Example 1-6, the amount of release agent was 1.6% by weight of the toner; other conditions were the same.

[0099] The ratio of grinding aid to release agent can be 0.5:1 to 4:1, preferably 1.2:1 to 3.2:1, and more preferably 0.8:1 to 3.5:1. If the ratio of grinding aid to release agent is outside the range of 1.2:1 to 3.2, or even outside the range of 0.5:1 to 4:1, image quality tends to deteriorate. In contrast, a ratio of grinding aid to release agent of 0.5:1 to 4:1, preferably 1.2:1 to 3.2:1, can improve image quality. Furthermore, a ratio of 0.8:1 to 3.5:1 can further improve image quality.

[0100] The amount of grinding aid added can be 0.8 to 10%, preferably 1 to 10%, and more preferably 3 to 8%. If the amount of grinding aid added is less than 1%, or even less than 0.8%, or more than 10%, image quality tends to deteriorate. In contrast, if the amount of grinding aid added is 0.8 to 10%, preferably 1 to 10%, image quality can be improved. Furthermore, if it is 3 to 8%, image quality can be further improved.

[0101] In Example 2-1, the resin type of the toner was changed to a styrene-acrylic type, but the other conditions were the same.

[0102] In Example 2-2, the type of grinding aid was changed to a styrene-acrylic resin, but the other conditions were the same.

[0103] In Example 2-3, the type of grinding aid was changed to a styrene-acrylic resin, and the resin type of the toner was changed to a styrene-acrylic resin, but the other conditions were the same.

[0104] In Examples 2-4, the type of grinding aid was changed to styrene-acrylic copolymer, but the other conditions were the same.

[0105] In Example 2-5, the type of grinding aid was changed to a styrene-acrylic copolymer, and the type of resin in the toner was changed to a styrene-acrylic type, but the other conditions were the same.

[0106] In Examples 4-1 to 4-5, the FTR dispersion diameters in the flakes were set to 50, 100, 250, 400, and 700 nm, respectively, and the other conditions were the same.

[0107] In Examples 5-1 to 5-4, the softening points of the styrene copolymers were set to 113, 114, 126, and 127° C., respectively, and the other conditions were the same.

[0108] In Examples 7-1 to 7-6, the particle sizes of the silica-modified SrTiO3 were set to 30, 35, 45, 50, 25, and 55, respectively, and the other conditions were the same.

[0109] In Example 6-1, SrTiO3 not modified with silica was used as the external additive, and other conditions were the same.

[0110] In Examples 9-1 to 9-4, the number of parts of SrTiO3 was set to 0.09, 0.1, 1.0, and 1.1 parts, respectively, and the other conditions were the same.

[0111] The grinding aid (alpha-methylstyrene) tends to exist around the wax due to its polarity. Its presence around the wax makes it easier for it to become the starting point for grinding, improving grindability. When grindability improves, the amount of ultra-fine powder increases, which generally makes filming more likely to occur, but the inclusion of strontium titanate in the ultra-fine powder has a drum refreshing effect, improving halftone (HT) reproducibility.

[0112] If the ratio of grinding aid to release agent is less than 0.5, the effect of the aid is not exerted (Comparative Example 1-1), grindability deteriorates, and image quality deteriorates. On the other hand, if the ratio exceeds 4 (Comparative Example 1-2), the amount of ultrafine powder increases more than necessary, causing filming and packing, and image quality deteriorates.

[0113] As grinding aids, styrene copolymers, styrene-acrylic resins, and styrene-acrylic copolymers were used, and as binder resins, polyester and styrene-acrylic resins were used (Examples 2-1 to 2-5). Because good results were obtained in terms of image quality, styrene copolymers were used as grinding aids and polyester binder resins.

[0114] The dispersion diameter of FTR in the flakes is preferably 50 nm to 700 nm, and more preferably 100 nm to 400 nm. If the dispersion diameter of FTR is too small, it cannot exist around the wax, resulting in poor grindability and poor image quality. Conversely, if the dispersion diameter is too large, the FTR does not become the starting point for grinding, resulting in poor grindability and poor image quality. In contrast, if the dispersion diameter of FTR in the flakes is 50 nm to 700 nm, grindability can be improved, and image quality can be improved. Furthermore, if it is 100 nm to 400 nm, grindability can be further improved, and image quality can be further improved.

[0115] The softening point of the styrene copolymer can be 113 to 127°C, preferably 114 to 126°C, and more preferably 116 to 123°C. If the softening point of the styrene copolymer is less than 113°C or more than 127°C, the image quality deteriorates. In contrast, if the softening point of the styrene copolymer is 113 to 127°C, the image quality can be improved. If the softening point is 114 to 126°C, the image quality can be further improved (Examples 5-1 to 5-4). Furthermore, if the softening point is 116 to 123°C, the image quality can be further improved (Examples 4-1 to 4-5).

[0116] The particle diameter of the silica-doped strontium titanate can be 25 nm to 55 nm, preferably 30 nm to 50 nm, and more preferably 35 nm to 45 nm. If the particle diameter of the silica-doped strontium titanate is less than 25 nm, or even less than 30 nm, high charging occurs in low-humidity environments, which can lead to poor developability. If the particle diameter exceeds 55 nm, or even more so, 50 nm, charging properties decrease, resulting in toner being printed even in non-image areas (fog). High fog can easily lead to poor image quality. In contrast, if the particle diameter of the silica-doped strontium titanate is 25 nm to 55 nm, or preferably 30 nm to 50 nm, it is possible to improve developability and suppress fogging, thereby improving image quality. Furthermore, if the particle diameter is 35 nm to 45 nm, it is possible to further improve developability and further suppress fogging, thereby further improving image quality (Examples 7-1 to 7-6).

[0117] In Comparative Example 2-1, which does not contain strontium titanate in the external additive, high charging occurs in a low humidity environment, causing deterioration in developability.

[0118] Strontium titanate that is not modified with silica exhibits a decrease in charging ability in a high humidity environment, leading to a deterioration in transferability (Example 6-1).

[0119] Silica-modified strontium titanate is less likely to experience a decrease in chargeability in a high humidity environment, and good transferability can be obtained (Example 1-3, etc.).

[0120] The FTR used as a grinding aid has a softening point of 114 to 126°C and a Gardner color of 2 or less.

[0121] The molar ratio Si / Ti of silicon (Si) of silica to titanium (Ti) of strontium titanate in the externally added fine powder is not particularly limited, but is preferably 0.03 or more but less than 1, and more preferably 0.05 to 0.8. If the molar ratio Si / Ti is less than 0.03, the conductivity of the externally added fine powder increases. When a toner containing the externally added fine powder is left in a high-humidity environment, the charge loss rate increases, which can lead to an increase in fog value. On the other hand, if the molar ratio Si / Ti is 1 or more, the negative charging characteristics of silica are strongly expressed. Therefore, when a toner containing the externally added fine powder is continuously printed in a low-humidity environment, the toner becomes overcharged, which can lead to poor mixing with the toner supplied from the cartridge, resulting in an increase in fog value due to toner scattering. In contrast, when the molar ratio Si / Ti of silicon (Si) of silica to titanium (Ti) of strontium titanate in the externally added fine powder is 0.03 or more but less than 1, the increase in fog value can be suppressed. Furthermore, when the molar ratio Si / Ti is 0.05 to 0.8, the increase in fog value can be further suppressed.

[0122] The ratio of silica-doped strontium titanate to the toner can be 0.09 to 1.1 parts, preferably 0.1 to 1.0 parts, and more preferably 0.2 to 0.8 parts. If the amount of titanate is less than 0.09 parts, or even less than 0.1 parts, the drum refreshing effect is not achieved, and filming occurs, which tends to deteriorate image quality. If the amount of titanate is more than 1.1 parts, or even more than 1.0 parts, charging properties deteriorate (decreases), and fogging due to toner scattering tends to increase. In contrast, when the ratio of silica-doped strontium titanate to the toner is 0.09 to 1.1 parts, preferably 0.1 to 1.0 parts, filming can be suppressed and fogging can be reduced. Furthermore, when the amount is 0.2 to 0.8 parts, filming can be further suppressed and fogging can be further reduced (Examples 9-1 to 9-4).

[0123] The proportion of externally added toner particles of 2 μm or less is preferably 3% to 15% by number, and more preferably 3% to 10%. If the proportion of particles of 2 μm or less is less than 3%, unevenness in density occurs when HT printing is performed after continuous printing, resulting in poor image quality. If it exceeds 15%, filming and packing on the drum occur, resulting in poor image quality. In contrast, if the proportion of externally added toner particles of 2 μm or less is 3% to 15% by number, image quality can be improved. Furthermore, if the proportion is 3% to 10%, image quality can be further improved.

[0124] The amount of small silica is preferably 0.3 to 2 parts, more preferably 0.5 to 1.5 parts, based on the toner. If it is less than 0.3 parts, the charging ability decreases and the fogging value due to toner scattering increases. If it exceeds 2 parts, filming and packing on the drum occur, deteriorating image quality. In contrast, if the amount of small silica is 0.3 to 2 parts based on the toner, the fogging value can be reduced and image quality can be improved. Furthermore, if it is 0.5 to 1.5 parts, the charging ability can be further improved, the fogging value can be further reduced, and image quality can be further improved.

[0125] The FTR dispersion diameter in the flakes, image quality (shade), ID, and image quality (fog) were measured as follows.

[0126] FTR dispersion diameter in flakes: Measured by observing the cross section of the toner using a scanning transmission electron microscope (STEM) Image quality (shade): After continuous printing (especially text), a halftone (HT) image is output, and the difference between the ID (image density) of the part where text was not printed during the continuous printing and the ID of the part where text was printed during the continuous printing. Measure the image density at the measurement location using an ID:X-Rite (X-Rite) or similar.

[0127] Image quality (fog): Using a whiteness meter (product name: manufactured by Nippon Denshoku Industries Co., Ltd.), the difference in whiteness of the paper before and after printing (image formation) is measured.

[0128] The present invention is not limited to the above-described embodiments, but can be embodied in various other forms. Therefore, the above-described embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not limited in any way by the text of the specification. Furthermore, all modifications and variations within the equivalent range of the claims are within the scope of the present invention. [Explanation of symbols]

[0129] 10 Toner 11 Base particle 12 Small Silica 13 Strontium titanate 14 Wax 15 FTR (an example of a grinding aid)

Claims

1. In a pulverized toner composed of base particles and external additives, the base particles contain at least a release agent, a grinding aid, and a binder resin; The external additives include fine powder of strontium titanate to which silica has been added and the core surface of which has been hydrophobized with a silane compound, and silica particles having an average primary particle diameter of 6 to 17 nm, The pulverized toner is characterized in that the ratio of the pulverizing aid and the releasing agent is 0.5:1 to 4:

1.

2. The pulverized toner according to claim 1 , The pulverized toner, wherein the pulverization aid is a styrene copolymer, and the binder resin is a polyester resin.

3. The pulverized toner according to claim 2, The pulverized toner is characterized in that the pulverization aid is an α-methylstyrene copolymer, and the dispersion diameter of the pulverization aid in the base particles is 50 to 700 nm.

4. The pulverized toner according to claim 3, The pulverized toner is characterized in that the softening point of the α-methylstyrene copolymer is 114 to 126°C.

5. The pulverized toner according to any one of claims 1 to 4, The pulverized toner is characterized in that the particle diameter of the fine powder is 30 to 50 nm.

6. The pulverized toner according to any one of claims 1 to 5, The pulverized toner is characterized in that the molar ratio Si / Ti of silicon Si of said silica to titanium Ti of said strontium titanate in said fine powder is 0.03 or more and less than 1.

7. The pulverized toner according to any one of claims 1 to 6, The pulverized toner is characterized in that the amount of the fine powder added is 0.1 to 1.0 parts by weight per 100 parts by weight of the base particles.

8. The pulverized toner according to any one of claims 1 to 7, The pulverized toner is characterized in that the ratio of the number of base particles having a particle diameter of 2 μm or less is 3 to 15%.

9. The pulverized toner according to any one of claims 1 to 8, The pulverized toner is characterized in that the amount of the silica particles added is 0.3 to 2.0 parts by weight per 100 parts by weight of the base particles.

10. The method for producing the pulverized toner according to any one of claims 1 to 9, a mixing step of mixing raw materials containing the binder resin; a melt-kneading step of melt-kneading the mixture obtained in the mixing step; a crushing step of crushing the melt-kneaded product obtained in the melt-kneading step after cooling; a classification step of classifying the pulverized material obtained in the pulverization step; a stirring step of adding the external additive to the toner base particles obtained in the classification step and stirring the mixture; A method for producing pulverized toner, comprising:

Images