Toner composition for electrostatic image development

Abstract

To provide a toner composition for electrostatic image development that does not contain titanium dioxide, exhibits excellent image density, charge amount, and charge stability, and is less prone to blotting during printing. [Solution] A toner composition for developing electrostatic images, comprising toner particles and an external additive, wherein the external additive comprises first silica particles, second silica particles, and third silica particles, the first silica particles being surface-treated with aluminum hydroxide and fatty acids, the content of the first silica particles being 1.0 to 1.5% by mass relative to the toner particles, the second silica particles being formed by a sol-gel method with an average particle diameter of 70 to 90 nm, the content of the second silica particles being 0.8 to 2.5% by mass relative to the toner particles, and the third silica particles having an average particle diameter of less than 10 nm.

Description

[Technical Field]

[0001] The present invention relates to a toner composition for electrostatic image development. More specifically, the present invention relates to a toner composition for electrostatic image development that does not contain titanium dioxide, exhibits excellent image density, charge amount, and charge stability, and is less prone to ink blotting during printing. [Background technology]

[0002] Conventionally, electrostatic image developers containing toner compositions have incorporated external additives such as titanium dioxide to produce stable images over long periods (see, for example, Patent Document 1). On the other hand, due to concerns about the health side effects of titanium dioxide, toner external additives that do not use titanium dioxide have also been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2003-122046 [Patent Document 2] Patent No. 6849581 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in recent years, high-speed machines have been used to increase manufacturing efficiency. When printing with such high-speed machines, image density, charge amount, and charge stability are inferior. In addition, the toner composition tends to accumulate on the developer carrier and drip down (drip). The toner additive described in Patent Document 2 does not use titanium dioxide, so the charge amount of the toner composition in the developer increases excessively, which tends to reduce developability and transferability. Furthermore, the toner additive described in Patent Document 2 does not have sufficient image density, charge amount, and charge stability, and there is room for improvement regarding drip.

[0005] This invention has been made in view of the above-mentioned conventional problems, and aims to provide a toner composition for electrostatic image development that does not contain titanium dioxide, exhibits excellent image density, charge amount, and charge stability, and is less prone to blotting during printing. [Means for solving the problem]

[0006] The inventors of the present invention conducted diligent studies to solve the above problems and found that the above problems can be solved by using, in addition to toner particles, a first silica particle surface-treated with aluminum hydroxide and fatty acid as an external additive, a second silica particle of a specific particle size formed by a sol-gel method, and a third silica particle of a specific particle size in combination, and thus completed the present invention. The present invention, which solves the above problems, mainly comprises the following configuration.

[0007] (1) A toner composition for developing electrostatic images, comprising toner particles and an external additive, wherein the external additive comprises first silica particles, second silica particles, and third silica particles, the first silica particles are surface-treated with aluminum hydroxide and fatty acids, the content of the first silica particles is 1.0 to 1.5% by mass relative to the toner particles, the second silica particles are formed by a sol-gel method and have an average particle diameter of 70 to 90 nm, the content of the second silica particles is 0.8 to 2.5% by mass relative to the toner particles, and the third silica particles have an average particle diameter of less than 10 nm.

[0008] With this configuration, the electrostatic image developing toner composition does not contain titanium dioxide and exhibits excellent image density, charge amount, and charge stability. Furthermore, the electrostatic image developing toner composition is less prone to ink blotting during printing.

[0009] (2) The electrostatic image developing toner composition according to (1), wherein the second silica particles are surface-treated with hexamethyldisilazane.

[0010] With this configuration, the toner composition for electrostatic image development has more appropriate image density and charge amount. In addition, the toner composition for electrostatic image development is less prone to ink blotting during printing.

[0011] (3) The first silica particles have an average particle diameter of 10 to 30 nm, and the electrostatic image developing toner composition is as described in (1) or (2).

[0012] With this configuration, the toner composition for electrostatic image development exhibits excellent charge stability and is less prone to charge degradation. Furthermore, the toner composition for electrostatic image development is less likely to cause contamination of materials due to the detachment of silica particles. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a toner composition for electrostatic image development that does not contain titanium dioxide, exhibits excellent image density, charge amount, and charge stability, and is less prone to ink blotting during printing. [Modes for carrying out the invention]

[0014] <Toner composition for developing electrostatic images> An electrostatic image developing toner composition (hereinafter also referred to as the toner composition) according to one embodiment of the present invention comprises toner particles and an external additive. The external additive comprises first silica particles, second silica particles, and third silica particles. The first silica particles are surface-treated with aluminum hydroxide and fatty acids. The content of the first silica particles is 1.0 to 1.5% by mass relative to the toner particles. The second silica particles are formed by the sol-gel method and have an average particle diameter of 70 to 90 nm. The content of the second silica particles is 0.8 to 2.5% by mass relative to the toner particles. The third silica particles have an average particle diameter of less than 10 nm. Each of these will be described below.

[0015] (Toner particles) The toner particles are not particularly limited. For example, the toner particles may include a binder resin, a colorant, and a release agent.

[0016] ·Binder resin The binder resin disperses the colorant contained in the toner composition, melts on the surface of the recording medium by the heat of the fixing roller during printing, and then solidifies to fix the colorant on the surface of the recording medium. It is formulated for this purpose.

[0017] The binder resin is not particularly limited. For example, the binder resin is a resin material such as styrene-based copolymers like polystyrene, styrene-methyl acrylate copolymer, styrene-acrylonitrile copolymer, polyester, epoxy resin, etc. The binder resins may be used in combination. Among these, the binder resin is preferably polyester in terms of being easily colored and obtaining a toner with vivid colors.

[0018] Note that the polyester is obtained by polymerizing a monomer composition composed of a dihydric or higher polyhydric alcohol and a polybasic acid. The dihydric alcohol used for the polymerization of the polyester is not particularly limited. For example, the dihydric alcohol is diols such as ethylene glycol, 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, etc., bisphenol A alkylene oxide adducts such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, etc.

[0019] The polyhydric alcohol with three or more hydroxyl groups is not particularly limited. For example, the polyhydric alcohol with three or more hydroxyl groups can include sorbitol, 1,2,3,6 - hexanetetrol, 1,4 - sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4 - butanetriol, 1,2,5 - pentanetriol, glycerin, 2 - methylpropanetriol, 2 - methyl - 1,2,4 - butanetriol, trimethylolethane, trimethylolpropane, 1,3,5 - trihydroxymethylbenzene, etc.

[0020] The dibasic polycarboxylic acid is not particularly limited. For example, the dibasic polycarboxylic acid can include maleic acid, fumaric acid, citraconic acid, itaconic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, anhydrides of these acids, etc.

[0021] The polybasic polycarboxylic acid with three or more carboxyl groups is not particularly limited. For example, the polybasic polycarboxylic acid with three or more carboxyl groups can include 1,2,4 - benzenetricarboxylic acid, 1,2,5 - benzenetricarboxylic acid, 1,2,4 - cyclohexanetricarboxylic acid, 2,5,7 - naphthalenetricarboxylic acid, 1,2,4 - naphthalenetricarboxylic acid, 1,2,5 - hexanetricarboxylic acid, 1,3 - dicarboxyl - 2 - methyl - 2 - methylenecarboxypropane, tetra(methylenecarboxyl)methane, 1,2,7,8 - octanetetracarboxylic acid, anhydrides of these acids, etc.

[0022] The content of the binder resin is not particularly limited. The content of the binder resin can be appropriately adjusted in consideration of the performance required for the toner, etc. For example, the content of the binder resin is preferably 50 - 95 parts by mass per 100 parts by mass of the toner particles.

[0023] · Colorant The colorant is blended to impart coloring power to the toner composition. [[ID= nineteen]]

[0024] The colorants are not particularly limited. For example, colorants include magnetic powders that exhibit black color, such as carbon black; cyan colorants such as copper phthalocyanine, methylene blue, and Victoria blue; magenta colorants such as rhodamine dye, dimethylquinacridone, dichloroquinacridone, and carmine red; and yellow colorants such as benzidine yellow, chromium yellow, naphthol yellow, and disazo yellow. Colorants may be used in combination.

[0025] The amount of colorant is not particularly limited. For example, it is preferable that the amount of colorant used in the toner composition is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of binder resin. Various masterbatches in which high-concentration pigments are pre-dispersed in resin are commercially available, and these may be purchased and used as colorants. In this case, the amount used can be determined by considering the concentration of pigment contained in the masterbatch so that the concentration of pigment contained in the toner composition falls within the above range.

[0026] • Release agent The release agent is not particularly limited, and various known waxes can be used. For example, waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long-chain hydrocarbon waxes such as paraffin wax and sazole wax, dialkylketone waxes such as distearyl ketone, carnauba wax, montane wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, distearyl maleate, and amide waxes such as ethylenediamine behenylamide and tristearyl trimellitate. Release agents may be used in combination. Among these, ester waxes and hydrocarbon waxes are preferred as release agents.

[0027] The content of the release agent is not particularly limited. For example, the content of the release agent can usually be in the range of 1 to 30 parts by mass, preferably 5 to 20 parts by mass, per 100 parts by mass of binder resin. The content of the release agent in the toner particles is preferably in the range of 3 to 15% by mass. By having the release agent content within the above range, the resulting toner composition provides good release properties between the fixing roller and the printed surface during the fixing process in printing. In addition, the toner composition is less prone to release agent seepage, and is less likely to cause static charge defects or filming.

[0028] Other ingredients In addition to the above, toner particles may also contain other components, such as charge regulators. Charge regulators are suitably blended to adjust the charge level of the toner composition.

[0029] The charge regulator is not particularly limited. For example, charge regulators include metal complexes such as nigrosine, basic dyes, and monoazo dyes, salts or complexes of carboxylic acids such as salicylic acid and dicarboxylic acids with metals such as chromium, zirconium, and aluminum, organic dyes, metal salts of naphthenic acid and higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, and resin-type charge regulators such as aromatic polycondensates. Charge regulators may be used in combination. Among these, it is preferable that the toner composition contains a resin-type charge regulator from the viewpoint of charge stability.

[0030] When a charge regulator is included, the amount of the charge regulator is not particularly limited. For example, the amount of charge regulator in the toner particles does not have to be included, but it is preferable to have 0.5% by mass or more. Alternatively, the amount of charge regulator in the toner particles is preferably 8% by mass or less. By having the charge regulator content within the above range, the resulting toner composition will have superior electrostatic properties.

[0031] (External additive) External additives are added to improve the electrostatic properties of toner particles by adhering to their surface, or to improve the fluidity of the toner composition by existing separately from the toner particles, or to improve printability.

[0032] The external additive of this embodiment includes first silica particles, second silica particles, and third silica particles.

[0033] The raw materials for each silica particle are not particularly limited. For example, the raw materials for silica particles may be naturally derived raw materials such as quartz sand, diatomaceous earth, volcanic ash, natural opal, flint, zeolite ore, sandstone, and shale, or synthetically derived raw materials such as sodium silicate (used in the water jacket method and sol-gel method), silane compounds (such as silicon alkoxides), silicon tetrachloride, silicate esters, by-products of silicon single crystal processing, silicone derivatives, and fused silica.

[0034] Furthermore, for environmental reasons, the silica particles may be made from recycled resources or by-products. For example, the silica particles may be obtained from rice straw ash, bagasse ash, waste glass, coal ash, etc.

[0035] The structure of each silica particle is not particularly limited. For example, the structure of the silica particle may be amorphous silica such as colloidal silica or precipitated silica, or it may be crystalline silica.

[0036] The morphology of each silica particle is not particularly limited. For example, the silica particles may be spherical silica, porous silica, flake-shaped silica, etc.

[0037] • First silica particle The first silica particles are silica particles surface-treated with aluminum hydroxide and fatty acids.

[0038] The fatty acid is not particularly limited. For example, it is preferable that the fatty acid contains at least one of either an alkylsilane with 8 to 12 carbon atoms or a saturated fatty acid with 16 to 20 carbon atoms. This results in a toner composition with good fluidity, chargeability, cleaning properties, etc. Among these, the fatty acid is preferably stearic acid. This results in a toner composition with better charge stability and environmental stability.

[0039] The method for surface-treating silica particles with aluminum hydroxide and fatty acids is not particularly limited. For example, the first silica is subjected to inorganic treatment with aluminum hydroxide and organic treatment with the above-mentioned fatty acids. An example of the inorganic treatment method is to add a salt such as aluminum chloride and hydrolyze it to precipitate aluminum hydroxide on the surface of the silica particles. An example of the organic treatment method is to add an alkali metal fatty acid salt and then add a strong acid such as sulfuric acid to precipitate the liberated fatty acids on the surface of the silica particles.

[0040] In this embodiment, the first silica particles have their resistance adjusted by inorganic treatment with aluminum hydroxide. Furthermore, the first silica particles are imparted hydrophobicity by organic treatment with fatty acids. As a result, the resulting toner composition exhibits excellent electrostatic properties and environmental stability.

[0041] The average particle diameter of the first silica particles is preferably 10 nm or more, and more preferably 13 nm or more. Furthermore, the average particle diameter of the first silica particles is preferably 30 nm or less, and more preferably 20 nm or less. By having the average particle diameter of the first silica particles within the above range, the toner composition has excellent charge stability and is less prone to charge degradation. In addition, the toner composition is less prone to contamination of materials due to the detachment of silica particles. In this embodiment, the average particle diameter of the first silica particles can be calculated by taking a transmission electron microscope image and processing the particles to determine the length of the major axis (nm) and the minor axis (nm) of each particle. The same applies to the second and third silica particles.

[0042] The BET specific surface area of ​​the first silica particle is not particularly limited. For example, the BET specific surface area of ​​the first silica particle is 70 m². 2 It is preferable that it be 80m or more / g 2 It is more preferable that the amount is greater than or equal to / g. Also, the BET specific surface area of ​​the first silica particle is 130m². 2 It is preferable that it be less than or equal to / g, and 120m 2 It is more preferable that the BET specific surface area of ​​the first silica particles is within the above range, thereby improving the toner charge amount, charge stability, and environmental stability of the toner composition.

[0043] The content of the first silica particles may be 1.0% by mass or more, and preferably 1.1% by mass or more, relative to the toner particles. Furthermore, the content of the first silica particles may be 1.5% by mass or less, and preferably 1.3% by mass or less, relative to the toner particles. If the content of the first silica particles is less than 1.0% by mass, the toner composition exhibits poor electrostatic stability. On the other hand, if the content of the first silica particles exceeds 1.5% by mass, the toner composition has a problem of being prone to ink blotting during printing.

[0044] The method for producing the first silica particles is not particularly limited. For example, the first silica particles can be produced by precipitation, sol-gel, fumed processes, and the like.

[0045] • Second silica particle The second type of silica particle is formed by the sol-gel method.

[0046] The sol-gel method is a method for obtaining silica by converting a liquid solution (sol) into a solid gel, and then firing or drying it. Specifically, the second silica particles are obtained by converting a liquid solution (a mixture of metal alkoxide, water, alcohol, catalyst, etc.) into a solid gel through hydrolysis and dehydration condensation, and then drying it.

[0047] Because the second silica particles are formed by the sol-gel method, the resulting toner composition tends to have an appropriate toner charge and superior charge stability compared to when they are formed by other methods (e.g., the fumed method).

[0048] The second silica particles may be surface-treated particles. The surface treatment is not particularly limited. For example, surface treatments include hydrophobic treatment, hydrophilic treatment, organic treatment, inorganic treatment, etc. Among these, hydrophobic treatment is preferred.

[0049] The method of hydrophobic treatment is not particularly limited. For example, one method of hydrophobic treatment involves contacting the surface of the second silica particles before hydrophobic treatment with a conventionally known hydrophobic treatment agent to chemically bond or attach hydrophobic functional groups or components to the surface of the inorganic oxide particles. The hydrophobic treatment agent for hydrophobicating the second silica particles is not particularly limited. For example, hydrophobic treatment agents include octyltriethoxysilane, polydimethylsiloxane, dimethyldichlorosilane, and hexamethyldisilazane. Hydrophobic treatment agents may be used in combination. Among these, it is preferable that the second silica particles are surface-treated with hexamethyldisilazane (HMDS). This results in good electrostatic stability of the toner composition.

[0050] The average particle diameter of the second silica particles should be 70 nm or larger, and preferably 75 nm or larger. Furthermore, the average particle diameter of the second silica particles should be 90 nm or smaller, and preferably 85 nm or smaller. If the average particle diameter of the second silica particles is less than 70 nm, the toner composition will experience reduced toner charge and charge stability, leading to a decrease in image density. On the other hand, if the average particle diameter of the second silica particles exceeds 90 nm, the toner composition will experience reduced toner charge and a decrease in image density.

[0051] The BET specific surface area of ​​the second silica particle is not particularly limited. For example, the BET specific surface area of ​​the second silica particle is 35 m². 2 It is preferable that it be 37m or more / g 2 It is more preferable that the amount is greater than or equal to / g. Furthermore, the BET specific surface area of ​​the second silica particle is 48m². 2 It is preferable that the amount be less than or equal to 45m 2 It is more preferable that the BET specific surface area of ​​the second silica particles is within the above range, thereby improving the toner charge amount, charge stability, and environmental stability of the toner composition.

[0052] The content of the second silica particles may be 0.8% by mass or more, and preferably 0.9% by mass or more, relative to the toner particles. Furthermore, the content of the second silica particles may be 2.5% by mass or less, and preferably 2.2% by mass or less, relative to the toner particles. If the content of the second silica particles is less than 0.8 parts by mass, the toner composition will have insufficient charge. On the other hand, if the content of the second silica particles exceeds 2.5% by mass, blotting is likely to occur during printing.

[0053] • Third silica particle The third type of silica particle has an average particle diameter of less than 10 nm.

[0054] The average particle size of the third silica particles should be less than 10 nm, and preferably 9 nm or less. Furthermore, the average particle size of the third silica particles is preferably 3 nm or more, and more preferably 6 nm or more. If the average particle size of the third silica particles exceeds 10 nm, the toner composition tends to have reduced image density.

[0055] The third silica particle may be a surface-treated particle. The surface treatment is not particularly limited. For example, surface treatments include hydrophobic treatment, hydrophilic treatment, organic treatment, inorganic treatment, etc. Among these, hydrophobic treatment is preferred.

[0056] The method of hydrophobic treatment is not particularly limited. For example, one method of hydrophobic treatment involves contacting a conventionally known hydrophobic agent with the surface of the third silica particles before hydrophobic treatment, thereby chemically bonding or attaching hydrophobic functional groups or components to the surface of the inorganic oxide particles. The hydrophobic agent for hydrophobicating the third silica particles is not particularly limited. For example, hydrophobic agents include octyltriethoxysilane, polydimethylsiloxane, dimethyldichlorosilane, and hexamethyldisilazane. Hydrophobic agents may be used in combination. Among these, it is preferable that the third silica particles are surface-treated with dimethyldicyclosilane (DDS). This results in a toner composition with good charge distribution.

[0057] The BET specific surface area of the third silica particles is not particularly limited. For example, the BET specific surface area of the third silica particles is preferably 180 m 2 / g or more, more preferably 210 m 2 / g or more. Also, the BET specific surface area of the third silica particles is preferably 300 m 2 / g or less, more preferably 270 m 2 / g or less. When the BET specific surface area of the third silica particles is within the above range, the toner composition has more excellent toner charge amount, charge stability, and environmental stability.

[0058] The content of the third silica particles is not particularly limited. For example, the content of the third silica particles is preferably 0.1% by mass or more, more preferably 0.5% by mass or more with respect to the toner particles. Also, the content of the third silica particles is preferably 2.0% by mass or less, more preferably 1.5% by mass or less with respect to the toner particles. When the content of the third silica particles is within the above range, the toner composition has good charge amount and charge stability.

[0059] The production method of the third silica particles is not particularly limited. For example, the third silica particles can be produced by a precipitation method, a sol-gel method, a fumed method, or the like.

[0060] Returning to the description of the external additives as a whole, in addition to the components described above, other external additives may be appropriately included. The other external additives are not particularly limited. For example, the other external additives are negatively charged lubricant particles, positively charged lubricant particles, inorganic oxide particles (excluding the above silica particles), and the like.

[0061] Positively charged lubricant particles are lubricant particles that become positively charged through frictional charging with carriers or charged blades. Such lubricant particles are well known, and metal salt particles of fatty acids are preferably exemplified. Metal salts of fatty acids include zinc stearate, aluminum stearate, calcium stearate, magnesium stearate, zinc laurate, zinc myristate, zinc palmitate, and zinc oleate. Among these, zinc stearate and magnesium stearate are preferred as metal salts of fatty acids.

[0062] Negatively charged lubricant particles are lubricant particles that become negatively charged due to frictional charging between them and carriers or charged blades. Such lubricant particles are well known, and polytetrafluoroethylene (PTFE), silicone, boron nitride, polymethyl methacrylate (PMMA), and polyvinylidene fluoride are preferred. Among these, boron nitride and polytetrafluoroethylene (PTFE) are preferred lubricant particles.

[0063] The inorganic oxide particles are not particularly limited. For example, inorganic oxide particles include zirconia, zinc oxide, chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, tellurium oxide, manganese oxide, and boron oxide.

[0064] It is preferable that the surface of the inorganic oxide particles is hydrophobized. The method of hydrophobization is not particularly limited. For example, one method of hydrophobization is to bring a conventionally known hydrophobic agent into contact with the surface of the inorganic oxide particles before hydrophobization, thereby chemically bonding or attaching hydrophobic functional groups or components to the surface of the inorganic oxide particles. The hydrophobic agent for hydrophobizing inorganic oxide particles is not particularly limited. For example, hydrophobic agents include octyltriethoxysilane, polydimethylsiloxane, dimethyldichlorosilane, and hexamethyldisilazane.

[0065] As described above, the toner composition of this embodiment does not contain titanium dioxide and exhibits excellent image density, charge amount, and charge stability. Furthermore, the toner composition is less prone to ink blotting during printing.

[0066] <Method for manufacturing a toner composition for developing electrostatic images> A method for manufacturing a toner composition for electrostatic image development according to one embodiment of the present invention (hereinafter also referred to as the toner composition manufacturing method) is a manufacturing method for manufacturing the above-described electrostatic image development toner composition. The method for manufacturing the toner composition is not particularly limited. For example, the method for manufacturing the toner composition includes steps of kneading, cooling and solidifying, then grinding, classifying, and adding external additives. Each of these steps is a step that is used in conventionally known methods for manufacturing toner compositions. That is, the method for manufacturing the toner composition of this embodiment can be used to produce a toner composition by conventionally known methods and using conventionally known manufacturing equipment.

[0067] More specifically, in the mixing process, each component of the toner particles described above is melted and mixed to produce a mixed product. Various conventionally known mixing devices (for example, double-con mixers, V-type mixers, drum-type mixers, super mixers, Henschel mixers, Nauta mixers, Mechanohybrid (manufactured by Nippon Coke Industries Co., Ltd.), etc.) can be used to mix each component. For melt mixing, batch-type kneaders such as pressurized kneaders and Banbury mixers, or continuous kneaders can be used, and single-screw or twin-screw extruders are the mainstream due to their advantage of being able to produce continuously. Examples include the KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), the TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the PCM kneader (manufactured by Ikegai Co., Ltd.), the twin-screw extruder (manufactured by KCK Co., Ltd.), the Co-kneader (manufactured by Buss Co., Ltd.), and the Nidex (manufactured by Nippon Coke Industries Co., Ltd.). Furthermore, a masterbatch containing the above-mentioned binder resin and colorant may be used as the toner material.

[0068] Subsequently, the kneaded material is cooled, and then the cooled kneaded material is pulverized (for example, coarsely pulverized using a pulverizer such as a crusher, hammer mill, or feather mill, and then further finely pulverized using a fine pulverizer such as a Cryptron system (manufactured by Kawasaki Heavy Industries, Ltd.), Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), Turbo Mill (manufactured by Freund Turbo Co., Ltd.), or air jet type pulverizer). The powder (pulverized material) obtained in the pulverization process is classified (for example, classified using a classifier or sieving machine such as an inertial classifier Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.), a centrifugal classifier Turboplex (manufactured by Hosokawa Micron Corporation), a TSP separator (manufactured by Hosokawa Micron Corporation), or Faculty (manufactured by Hosokawa Micron Corporation)). The median volume particle size (D50) of the toner particles after pulverization and classification is preferably 4 to 10 μm. In this embodiment, the median volume particle size (D50) is also called the volume-based median diameter, and represents the value at which the sum of the volumes of particles with a diameter smaller than this value and the sum of the volumes of particles with a diameter larger than this value each account for 50% of the total volume. The median volume particle size (D50) can be calculated by performing particle size distribution measurement. An example of a particle size distribution measuring device is the "Multisizer 3" manufactured by Beckman Coulter. Next, an external additive is added to the toner particles and stirred and mixed using various conventionally known mixing devices (for example, a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, a Mechanohybrid (manufactured by Nippon Coke Industries Co., Ltd.), etc.) to obtain a toner composition.

[0069] As described above, the method for manufacturing the toner composition of this embodiment does not require special equipment and can be used with existing equipment. Therefore, this manufacturing method prevents high costs for the toner composition. Furthermore, as described above, the resulting toner composition exhibits excellent image density, charge amount, and charge stability even without containing titanium dioxide. In addition, the toner composition is less prone to ink blotting during printing. [Examples]

[0070] The present invention will be described more specifically below with reference to examples. The present invention is not limited in any way to these examples. Unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass".

[0071] The raw materials used and the preparation method are shown below. <Method for manufacturing toner matrix particles> 62 parts of commercially available polyester resin (FC1588, manufactured by Mitsubishi Chemical Corporation) and 27 parts of commercially available polyester resin (FC2232, also manufactured by Mitsubishi Chemical Corporation) as binder resins, 3 parts of red coloring agent (carmine 6B pigment) and 3 parts of red coloring agent (dimethylquinacridone pigment) as colorants, and 5 parts of fatty acid ester wax (WE-10, manufactured by NOF Corporation) as a mold release agent were mixed in a Henschel mixer and then melt-kneaded using a twin-screw extruder. The resulting mixture was melted and solidified, coarsely ground in a Rotoplex, finely ground in a jet mill, and classified using an air classifier to obtain negatively charged toner matrix particles magenta with a median volume particle size of 6.5 μm.

[0072] 63 parts of commercially available polyester resin (FC1588, manufactured by Mitsubishi Chemical Corporation) as a binder resin, 27 parts of commercially available polyester resin (FC2232, also manufactured by Mitsubishi Chemical Corporation) as a binder resin, 5 parts of a blue coloring agent (copper phthalocyanine pigment), and 5 parts of fatty acid ester wax (WE-10, manufactured by NOF Corporation) as a release agent were mixed in a Henschel mixer and then melt-kneaded using a twin-screw extruder. The resulting mixture was melted and solidified, coarsely ground in a Rotoplex, finely ground in a jet mill, and classified using an air classifier to obtain negatively charged toner matrix particles of cyan with a median volume particle size of 6.5 μm.

[0073] 61 parts of commercially available polyester resin (FC1588, manufactured by Mitsubishi Chemical Corporation) as a binder resin, 26 parts of commercially available polyester resin (FC2232, also manufactured by Mitsubishi Chemical Corporation) as a binder resin, 8 parts of black coloring agent (carbon black) as a coloring agent, and 5 parts of fatty acid ester wax (WE-10, manufactured by NOF Corporation) as a mold release agent were mixed in a Henschel mixer and then melt-kneaded using a twin-screw extruder. The resulting mixture was melted and solidified, coarsely ground in a Rotoplex, finely ground in a jet mill, and classified using an air classifier to obtain negatively charged toner matrix particles black with a median volume particle size of 6.5 μm.

[0074] <Silica particles> Silica 1: MSW-03, manufactured by Teika Co., Ltd., surface-treated with inorganic treatment: aluminum hydroxide, organic treatment: stearic acid, particle size 15 nm, first silica particle Silica 2: QSG-80, manufactured by Shin-Etsu Chemical Co., Ltd., manufacturing method: sol-gel method, surface treatment: HMDS treatment, particle size 80 nm, BET specific surface area 40 m² 2 / g, second silica particle Silica 3:H05TD, manufactured by Wacker, manufacturing method: fumed process, surface treatment: HMDS treatment, particle size 50nm, BET specific surface area 50m² 2 / g Silica 4: MSN-005L, manufactured by Teika Co., Ltd., manufacturing method: fumed process, surface treatment: HMDS treatment, particle size 80 nm, BET specific surface area 33 m² 2 / g Silica 5:R976S, manufactured by Aerosil, manufacturing method: fumed process, surface treatment: DDS treatment, particle size 8nm, third type of silica particle

[0075] <Examples 1-7, Comparative Examples 1-7> (Preparation of toner composition) According to the mixing ratios (parts by mass) shown in Table 1 below, each component was added to 100.00 parts by mass of toner matrix particles, and the mixture was stirred in a Henschel mixer for 8 minutes to obtain the toner compositions of the examples and comparative examples.

[0076] [Table 1]

[0077] Printed materials were prepared using the toner compositions of the examples and comparative examples obtained above under the following conditions, and the image density, toner charge amount, charge stability, and ink blotting were evaluated. The results are shown in Table 1.

[0078] <Image density> Using a non-magnetic two-component negative-charged copier with a printing speed of 60 pages / minute (A4 size paper), 10,000 copies of the ISO chart ISO-IEC24712 were printed under conditions of 25°C and 50% humidity (NN environment). After printing a solid image, the image density was evaluated using a reflectance densitometer RD-914 (Macbeth Corporation). Magenta was considered acceptable if it was between 1.00 and 1.25, cyan if it was between 0.80 and 1.05, and black if it was between 1.30 and 1.50.

[0079] <Toner charge amount> Using a non-magnetic two-component negative-charge type copier with a printing speed of 60 pages / minute (A4 size paper), the toner charge amount was evaluated using a Q / M meter MODEL210HS-2A (manufactured by TREK) when printing 10,000 sheets of ISO chart ISO-IEC24712 in an environment of 25°C and 50% humidity (NN environment). A value of -15 μC / g or more and less than -35 μC / g was considered acceptable.

[0080] <Static Stability> Using a non-magnetic two-component negative-charge type copier with a printing speed of 60 pages / minute (A4 size paper), the initial and final toner charge levels after printing 10,000 sheets of the ISO chart ISO-IEC24712 were measured with a Q / M meter under conditions of 25°C and 50% humidity (NN environment). The difference was evaluated according to the following evaluation criteria. (Evaluation Criteria) ○: The difference was less than -5 μC / g. △: The difference was between -5 μC / g and -10 μC / g. ×: The difference was -10 μC / g or greater.

[0081] <Bottle falling> Using a non-magnetic two-component negative-charged copier with a printing speed of 60 pages / minute (A4 size paper), 10,000 sheets of the ISO chart ISO-IEC24712 were printed under conditions of 25°C and 50% humidity (NN environment). The presence or absence of toner aggregate contamination on the paper was evaluated according to the following evaluation criteria. (Evaluation Criteria) ○: There were no instances of the button dropping throughout the 10,000 prints. ×: Among 10,000 sheets, some instances of button drop were observed.

[0082] As shown in Table 1, the toner compositions of Examples 1 to 7 exhibited excellent image density, charge amount, and charge stability. Furthermore, the toner compositions of Examples 1 to 7 did not produce ink blotting during printing.

Claims

1. It contains toner particles and external additives. The aforementioned external additive comprises first silica particles, second silica particles, and third silica particles. The first silica particles are surface-treated with aluminum hydroxide and fatty acids. The content of the first silica particles is 1.0 to 1.5% by mass relative to the toner particles. The second silica particles are formed by the sol-gel method and have an average particle diameter of 70 to 90 nm. The content of the second silica particles is 0.8 to 2.5% by mass relative to the toner particles. The third silica particle is a toner composition for developing electrostatic images, wherein the average particle diameter is less than 10 nm.

2. The electrostatic image developing toner composition according to claim 1, wherein the second silica particles are surface-treated with hexamethyldisilazane.

3. The toner composition for developing electrostatic images according to claim 1 or 2, wherein the first silica particles have an average particle diameter of 10 to 30 nm.

Images