Toner for developing electrostatic images

Abstract

To provide an electrostatic charge image developing toner which offers high initial image density and suppresses image blur in a high-temperature, high-humidity environment, and to provide a method of manufacturing the same.SOLUTION: An electrostatic charge image developing toner and a method of manufacturing the same are provided, the electrostatic charge image developing toner comprising toner base particles containing a binder resin and colorant and having a circularity in a range of 0.950 to 0.995, inclusive, and an external additive containing silica particles A and silica particles B having different number average particle diameters, where the silica particles A have a greater number average particle diameter than the silica particles B, a BET specific surface area in a range of 70 m2 / g to 150 m2 / g, inclusive, and a shape index of 2.0 or greater as expressed as a ratio of the number average particle diameter to a BET equivalent particle diameter, and the silica particles B have a shape index of less than 2.0.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, the demands on toner performance have increased with the rise in printer speeds. Efforts have been made to improve the formulation of external additives added to toner particles to stabilize the toner's charge and improve its fluidity, and toners using both large and small external additives are being considered from the perspective of toner startup speed and durability.

[0003] Patent Document 1 discloses an invention relating to a toner for developing electrostatic images, which contains at least toner matrix particles and an external additive, wherein the external additive is a particle containing at least inorganic particles A and silica particles B, wherein the inorganic particles A contain calcium titanate or barium titanate, and the number average particle size of the primary particles of the inorganic particles A is in the range of 40 to 80 nm, and the number average particle size of the primary particles of the silica particles B is in the range of 60 to 120 nm, and the circularity of the silica particles B is in the range of 0.95 to 1.00.

[0004] Patent Document 2 describes a magnetic toner comprising magnetic toner particles containing a binder resin and a magnetic material, and a first external additive, wherein the first external additive is 1) Silica fine particles, or resin composition-silica composite particles, 2) The number-average particle size is 70 nm or more and 200 nm or less. 3) The shape factor SF-1 is between 100 and 250, 4) The shape factor SF-2 is between 105 and 250, The invention discloses a magnetic toner characterized in that the silica coating rate on the surface of the magnetic toner particles, as measured by ESCA, is 40.0% or more and 70.0% or less, the magnetic toner is contained in a measuring container, a load of 5.8 kPa is applied to the contained magnetic toner to form a toner layer in the measuring container, a propeller-type blade with its outermost edge rotating at a peripheral speed of 100 mm / sec is vertically inserted into the toner layer in the measuring container, and the total energy calculated from the rotational torque and vertical load when the propeller-type blade is moved at a constant speed through the toner layer while rotating is 80.0 mJ or more and 140.0 mJ or less, and further, as a second external additive, the invention discloses silica having a primary particle number average particle size of 5 nm or more and 30 nm or less, and the content of the second external additive is i) With respect to 100 parts by mass of the magnetic toner particles, the amount is 0.1 parts by mass or more and 1.0 parts by mass or less. ii) Based on the content of the first external additive, the amount is 10% by mass or more and 50% by mass or less. It is stated that...

[0005] Patent Document 3 discloses an invention relating to a positively charged toner for electrostatic image development, which comprises colored resin particles comprising a binder resin, a colorant, and a charge control agent, and an external additive, wherein the external additive comprises external additive A and external additive B, and external additive A is fatty acid alkali metal salt particles or fatty acid alkaline earth metal salt particles having a number average primary particle size of 0.1 to 1 μm, and the content of the fatty acid alkali metal salt particles or fatty acid alkaline earth metal salt particles is 0.01 to 0.5 parts by weight per 100 parts by weight of colored resin particles, and external additive B is spherical silica fine particles having a number average primary particle size of 40 to 200 nm and a sphericity of 1 to 1.3, and the content of the spherical silica fine particles is 0.2 to 2 parts by weight per 100 parts by weight of colored resin particles. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-71614 [Patent Document 2] Japanese Patent Publication No. 2015-45860 [Patent Document 3] Japanese Patent Publication No. 2010-128312 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, toner particles with high circularity have low adhesion to printer components, resulting in high transferability and superior print density and image quality. On the other hand, the collision energy between toner particles during triboelectric charging is high. Therefore, even when using external additives of varying sizes, the larger particles of external additives detach from the toner surface, eliminating the spacer effect, causing the smaller particles to become embedded and significantly reducing the electrostatic charge. Furthermore, under high temperature and high humidity conditions, the surface of toner particles becomes plasticized, making the embedding of small-particle external additives even more pronounced and resulting in image streaking.

[0008] The present invention relates to a toner for electrostatic image development and a method for manufacturing the same, which has a high initial image density and suppresses image streaking under high temperature and high humidity conditions. [Means for solving the problem]

[0009] The present invention [1] A toner for developing electrostatic images, comprising toner matrix particles having a circularity of 0.950 or more and 0.995 or less, which contain a binder resin and a colorant, and an external additive containing silica particles A and silica particles B having different number-average particle sizes, wherein silica particles A have a larger number-average particle size than silica particles B, and the BET specific surface area of ​​silica particles A is 70 m². 2 / g or more 150m 2 A toner for developing electrostatic images, wherein the shape index expressed as the ratio of the number-average particle size to the BET-converted particle size is 2.0 or more, and the shape index of the silica particles B is less than 2.0, and 〔2〕 A method for manufacturing an electrostatic charge image developing toner, comprising a step of mixing toner mother particles having a circularity of 0.950 or more and 0.995 or less, containing a binder resin and a colorant, with an external additive containing silica particles A and silica particles B having different number average particle diameters, wherein the silica particles A have a larger number average particle diameter than the silica particles B, the BET specific surface area of the silica particles A is 70 m 2 / g or more and 150 m 2 / g or less, the shape index represented by the ratio of the BET converted particle diameter to the number average particle diameter is 2.0 or more, the shape index of the silica particles B is less than 2.0, and the toner mother particles are produced by a method including a step of melt-kneading a mixture containing the binder resin and the colorant. The method for manufacturing an electrostatic charge image developing toner relates to.

Effect of the Invention

[0010] The electrostatic charge image developing toner of the present invention has excellent effects such as a high initial image density and suppression of image fogging under high temperature and high humidity conditions.

Brief Description of the Drawings

[0011] [Figure 1] It is an example of a schematic cross-sectional view of conventional silica. [Figure 2] It is an example of a schematic cross-sectional view of bonded silica.

Embodiments for Carrying Out the Invention

[0012] The electrostatic charge image developing toner of the present invention contains toner mother particles and an external additive containing silica particles (silica particles A and B) having different number average particle diameters, and has a large feature in the shape of the silica particles (silica particles A) having a larger number average particle diameter. Generally, there is a negative correlation between the particle size of particles and the BET specific surface area. That is, as the number average particle size increases, the BET specific surface area decreases. In contrast, the silica particle A in the present invention has a large BET specific surface area and a small BET equivalent particle size (particle size) converted from the BET specific surface area, even though the number average particle size is large compared to silica particles with the same degree of number average particle size. Therefore, it has the characteristic that the value of the ratio (shape index) of the number average particle size to the BET equivalent particle size is also large. Such a characteristic is due to the shape of the silica particle A. Usually, silica particles exist in a partially aggregated state. Generally, the aggregates of silica particles are densely aggregated as shown in FIG. 1, while the aggregates contained in the silica particle A have gaps between the silica particles and have a plurality of distinct convex portions on the surface like a tetrapod as shown in FIG. 2. Such silica particles (hereinafter also referred to as "bonded silica particles") have a large contact area with the surface of the toner mother particles, so they are difficult to detach from the surface of the toner mother particles even for a large collision energy, and the spacer effect is maintained, so the burial of the small particle size silica particle B is significantly suppressed. Therefore, it is presumed that the occurrence of printing defects such as streaks in the image can be suppressed.

[0013] The BET specific surface area of the silica particle A is 70 m 2 / g or more, preferably 80 m 2 / g or more, more preferably 85 m 2 / g or more, and from the viewpoint of suppressing detachment from the surface of the toner mother particles, it is 150 m 2 / g or less, preferably 130 m 2 / g or less, more preferably 100 m 2 / g or less.

[0014] The shape index of the silica particle A is 2.0 or more, preferably 2.5 or more, more preferably 2.8 or more, and even more preferably 3.0 or more. And from the viewpoint of the durability of the toner, it is preferably 8.0 or less, more preferably 6.0 or less, and even more preferably 4.0 or less. In the present invention, the shape index of the silica particle is a value calculated from the ratio of the number average particle size to the BET equivalent particle size (number average particle size / BET equivalent particle size).

[0015] The shape index of silica particle B is less than 2.0, preferably 1.7 or less, more preferably 1.4 or less, and even more preferably 1.1 or less, and from the viewpoint of toner fluidity, preferably 0.8 or more, more preferably 0.9 or more, and even more preferably 1.0 or more. The shape index of commercially available silica particles that do not have any particular features in shape is usually less than 2.0.

[0016] The number-average particle size of silica particles A is larger than that of silica particles B, preferably 80 nm or more, more preferably 90 nm or more, and even more preferably 100 nm or more. Furthermore, from the viewpoint of suppressing detachment from the toner matrix particle surface, it is preferably 130 nm or less, more preferably 120 nm or less, and even more preferably 110 nm or less.

[0017] The number-average particle size of silica particles B is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more, and from the viewpoint of the toner's charge rise time, it is preferably 35 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less.

[0018] In this specification, the number-average particle size of silica particles is measured by treating not only primary particles but also aggregates of silica particles as a single particle.

[0019] The difference in the number-average particle size between silica particle A and silica particle B is preferably 60 nm or more, more preferably 70 nm or more, even more preferably 80 nm or more, and preferably 110 nm or less, more preferably 100 nm or less, and even more preferably 90 nm or less.

[0020] Silica particles A can preferably be produced by a sedimentation method, in which water glass and sulfuric acid are reacted in hot water, and the resulting silica precipitate is filtered, washed with water, and dried. By adjusting the reaction conditions (temperature, dropping rate of water glass and sulfuric acid into the water, silica sedimentation time, etc.), the number-average particle size and BET specific surface area of ​​the resulting silica particles can be adjusted.

[0021] It is preferable that silica particles A and / or silica particles B have been subjected to a hydrophobic treatment on their surface. Examples of hydrophobic treatment agents include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), polydimethylsiloxane, coupling agents having amino groups or quaternary ammonium bases, silicone oil, modified silicone oil, and cyclic silazane. Commercial products may be used, but for example, in the case of silica particles A, the bonded silica particles obtained by the above method can be surface-treated with one of these hydrophobic treatment agents alone, or with a mixture of two or more agents, or in a stepwise manner to impart the surface treatment characteristics required depending on the application.

[0022] The mass ratio of silica particle A to silica particle B is preferably 1 / 5 or more, more preferably 1 / 2 or more, and even more preferably 1 / 1 or more, from the viewpoint of suppressing the embedding of silica particle B, and from the viewpoint of toner fluidity, it is preferably 5 / 1 or less, more preferably 4 / 1 or less, and even more preferably 3 / 1 or less.

[0023] The total content of silica particles A and silica particles B in the external additive 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.

[0024] The content of the external additive is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and preferably 6 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of toner mother particles.

[0025] The toner matrix particles contain a binder resin and a colorant.

[0026] 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. However, in the present invention, it is preferable to include polyester resin from the viewpoint of low-temperature fixation and manufacturing stability.

[0027] The polyester resin is preferably a polycondensate of an alcohol component containing a bisphenol A alkylene oxide adduct and a carboxylic acid component.

[0028] The alkylene oxide adduct of bisphenol A is given by formula (I):

[0029] [ka]

[0030] (In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y represent the average number of moles of alkylene oxide added, each being a positive number, and the sum of x and y is 1 or greater, preferably 1.5 or greater, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) Compounds represented by are preferred.

[0031] From the viewpoint of low-temperature fixability, the content of the bisphenol A alkylene oxide adduct 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% in the alcohol component.

[0032] Other alcohol components include aliphatic diols, bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trivalent or higher alcohols such as trimethylolpropane, etc.

[0033] Examples of carboxylic acid components include aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, and trivalent or higher carboxylic acid compounds.

[0034] Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0035] From the viewpoint of image density, the carboxylic acid component preferably contains an aromatic dicarboxylic acid compound. The content of the aromatic dicarboxylic acid compound 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% of the carboxylic acid component.

[0036] Examples of aliphatic dicarboxylic acid compounds include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with hydrocarbon groups, glutaric acid, adipic acid, sebacic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0037] Examples of carboxylic acid compounds with a valency of 3 or higher include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0038] Furthermore, the alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monohydric carboxylic acid compound, as appropriate.

[0039] The equivalent ratio (COOH group / OH group) of the carboxyl group of the carboxylic acid component to the hydroxyl group of the alcohol component is preferably 0.6 or higher, more preferably 0.7 or higher, even more preferably 0.75 or higher, and preferably 1.2 or lower, more preferably 1.15 or lower, from the viewpoint of adjusting the softening point of the polyester resin.

[0040] Polyester resins can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component, which are raw material monomers, in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and optionally in the presence of an esterification co-catalyst, polymerization inhibitor, etc., at a temperature preferably 130°C or higher, more preferably 170°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

[0041] Examples of esterification catalysts include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine, with tin compounds being preferred. The amount of 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, and more preferably 1 part by mass or less, per 100 parts by mass of raw material monomer. Examples of esterification co-catalysts include gallic acid. The amount of esterification co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less, per 100 parts by mass of raw material monomer. Examples of polymerization inhibitors include tert-butylcatechol. The amount of polymerization inhibitor 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, and more preferably 0.1 parts by mass or less, per 100 parts by mass of raw material monomer.

[0042] In this invention, the polyester resin may be a polyester resin that has been modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins that have been grafted or blocked with phenol, urethane, epoxy, etc., by methods described in Japanese Patent Publication No. 11-133668, Japanese Patent Publication No. 10-239903, Japanese Patent Publication No. 8-20636, etc. Among modified polyester resins, urethane-modified polyester resins obtained by urethane elongation of polyester resin with a polyisocyanate compound are preferred.

[0043] The softening point of the polyester resin is preferably 90°C or higher, more preferably 100°C or higher, from the viewpoint of resistance to hot offset, and preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower, from the viewpoint of low-temperature fixing properties.

[0044] The glass transition temperature of the polyester resin is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher, from the viewpoint of heat-resistant storage, and preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower, from the viewpoint of low-temperature fixing properties.

[0045] The polyester resin content 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, in the binder resin.

[0046] The binder resin content is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, and preferably less than 100% by mass, more preferably 98% by mass or less, and even more preferably 95% by mass or less, in the toner mother particles.

[0047] As colorants, dyes, pigments, magnetic materials, etc., used as colorants for toners can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazoel, etc. In this invention, the toner may be either black toner or color toner.

[0048] From the viewpoint of improving the image density of the toner and its low-temperature fixability, the amount of colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the binder resin.

[0049] In addition to the binder resin and colorant, the toner matrix particles may contain additives such as release agents, charge control agents, magnetic powders, flowability improvers, conductivity modifiers, reinforcing fillers such as fibrous materials, antioxidants, and cleaning properties improvers, and it is preferable that they contain release agents and charge control agents.

[0050] Examples of mold release agents include hydrocarbon waxes and their oxides, such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; ester waxes such as carnauba wax, montane wax and their deoxidizing waxes, and fatty acid ester waxes; and fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts, etc., which can be used individually or in combination of two or more.

[0051] 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 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 fixation.

[0052] The release agent content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and 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, per 100 parts by mass of binder resin, from the viewpoint of low-temperature fixation and offset resistance of the toner and dispersibility in the binder resin.

[0053] The charge control agent is not particularly limited and may contain either a positively charged charge control agent or a negatively charged charge control agent.

[0054] Positively charged charge control agents include nigrosine dyes, such as "Nigrosine Base EX," "Oil Black BS," "Oil Black SO," "Bontron N-01," "Bontron N-04," "Bontron N-07," "Bontron N-09," and "Bontron N-11" (all manufactured by Orient Chemical Industries, Ltd.); triphenylmethane-based dyes containing tertiary amines as side chains; quaternary ammonium salt compounds, such as "Bontron P-51" (manufactured by Orient Chemical Industries, Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX." Examples include VP435 (manufactured by Clariant), polyamine resins such as AFP-B (manufactured by Orient Chemical Industries, Ltd.), imidazole derivatives such as PLZ-2001 and PLZ-8001 (both manufactured by Shikoku Chemicals, Ltd.), and styrene-acrylic resins such as FCA-701PT and FCA-201-PS (manufactured by Fujikura Chemicals, Ltd.).

[0055] Furthermore, as negative charge control agents, metal-containing azo dyes, such as "Barifast 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 benzyl acid compounds, such as "LR-147" and "LR-297" (both 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" Examples include VP434 (manufactured by Clariant), nitroimidazole derivatives, organometallic compounds, etc.

[0056] From the viewpoint of the charge 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, per 100 parts by mass of the binder resin.

[0057] The method for producing toner matrix particles may be any conventionally known method, such as melt-kneading, emulsification phase inversion, or polymerization. However, from the viewpoint of productivity and the dispersibility of additives, the melt-kneading method, specifically a method that includes a step of melt-kneading a mixture of raw materials containing a binder resin and a colorant, is preferred.

[0058] The raw materials for melt kneading, including the binder resin and colorant, may be kneaded all at once or in portions. However, it is preferable to mix them beforehand in a mixer such as a Henschel mixer or ball mill before supplying them to the kneader.

[0059] Melt mixing can be carried out using known kneaders such as closed-type kneaders, single-screw or twin-screw extruders, or open-roll type kneaders. However, from the viewpoint of bringing the mixture to a high temperature that sufficiently melts it and improving the wettability with the additives, it is preferable to use a twin-screw extruder.

[0060] After melt-kneading, it is preferable to cool the mixture appropriately until it reaches a hardness that allows for pulverization, and then perform a pulverization step and, if necessary, a classification step to obtain toner base particles. Here, cooling refers to cooling the mixture to a temperature between 0°C and 50°C, or to a temperature below the glass transition temperature of the binder resin in the mixture.

[0061] The grinding step involves grinding the resulting mixture to obtain toner base particles. The mixture may be ground all at once to the desired particle size, or it may be ground in stages. However, from the viewpoint of efficient and more uniform grinding, it is preferable to perform the grinding in two stages: coarse grinding and fine grinding.

[0062] Examples of grinders used for coarse grinding include hammer mills, atomizers, and Rotoplexes.

[0063] For coarse grinding, it is preferable to grind until the maximum diameter is 3 mm or less. A pulverized material with a maximum diameter of 3 mm or less can be obtained by coarsely grinding the kneaded material to a particle size of approximately 0.05 mm to 3 mm, and then passing it through a sieve with a mesh size of 3 mm.

[0064] Examples of grinders used for fine grinding include fluidized bed jet mills, impact plate jet mills, and rotary mechanical mills. Among these, fluidized bed jet mills and impact plate jet mills are preferred from the viewpoint of grinding efficiency, with impact plate jet mills being more preferred.

[0065] The degree of fine grinding is preferably adjusted as appropriate according to the desired toner particle size.

[0066] Classifiers used in the classification process include air-flow classifiers, inertial classifiers, and sieve classifiers.

[0067] Examples of phase inversion emulsification methods include (A) a method in which resin components are dissolved in an organic solvent to obtain an organic solvent solution of the resin components, and then an aqueous medium is added to the obtained solution to perform phase inversion emulsification; and (B) a method in which resin components are melted and mixed to obtain a resin mixture, and then an aqueous medium is added to the mixture to perform phase inversion emulsification. From the viewpoint of obtaining a homogeneous aqueous dispersion of resin particles for cores, method (A) is preferred.

[0068] The organic solvent used for phase inversion emulsification is not particularly limited as long as it can dissolve the resin, but an example is methyl ethyl ketone.

[0069] The amount of organic solvent used is preferably 30 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the binder resin.

[0070] The amount of aqueous medium used is preferably 100 parts by mass or more and 3000 parts by mass or less per 100 parts by mass of the organic solvent. The aqueous medium used in step (I) may contain an alcohol-based solvent with 1 to 3 carbon atoms, such as ethanol, but preferably contains 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 99% by mass or more of water.

[0071] When stirring the mixture, commonly used mixing and stirring devices such as anchor blades can be used.

[0072] In the phase inversion emulsification method, it is preferable to treat the resin with a neutralizing agent. Examples of neutralizing agents include alkali metals such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and organic bases such as ammonia, trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine. The amount of neutralizing agent added is preferably such that the degree of neutralization is about 50-100% of the acid value of the polyester after the reaction.

[0073] A surfactant or the like may be used as a dispersant to reduce the melt viscosity and melting point of the binder resin, and to improve the dispersibility of the resulting resin particles.

[0074] The solid content concentration of the dispersion of resin particles containing the binder resin obtained in step (I) is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of the stability of the dispersion and the ease of handling the dispersion in the flocculation step. The solid content includes non-volatile components such as resin and surfactant.

[0075] The average particle size of the resin particles is preferably 0.05 μm or more, more preferably 0.10 μm or more, even more preferably 0.15 μm or more, and preferably 0.80 μm or less, more preferably 0.40 μm or less, and even more preferably 0.30 μm or less, from the viewpoint of uniform aggregation in subsequent steps. In the present invention, the average particle size of the resin particles is the median particle size (D 50 This refers to the particle size that can be measured using a laser diffraction particle size analyzer or similar device.

[0076] Next, the resin particles obtained in step (I) are aggregated and fused together (step (II)).

[0077] In step (II), flocculation is performed, for example, by adding a flocculant to a mixed dispersion containing resin particles at a temperature of 0°C to 40°C, causing the resin particles to flocce in an aqueous medium to obtain flocculated particles. Furthermore, from the viewpoint of promoting flocculation, it is preferable to raise the temperature of the dispersion after adding the flocculant.

[0078] The temperature maintained during aggregation is preferably 45°C or higher, more preferably 50°C or higher, and preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower.

[0079] Furthermore, additives such as colorants, release agents, and charge control agents may be mixed with the binder resin beforehand when preparing the resin particles, or a dispersion solution may be prepared by dispersing each additive separately in a dispersion medium such as water, mixed with the resin particles, and subjected to the aggregation process.

[0080] As flocculants, organic flocculants include quaternary ammonium salt cationic surfactants and polyethyleneimines, while inorganic flocculants include inorganic metal salts, inorganic ammonium salts, and metal complexes with two or more valent progenitors. Examples of inorganic metal salts include metal salts such as sodium sulfate, sodium chloride, calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples of inorganic ammonium salts include ammonium sulfate, ammonium chloride, and ammonium nitrate.

[0081] From the viewpoint of controlling aggregation and obtaining the desired particle size, the amount of flocculant used is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, preferably 60 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of the binder resin.

[0082] Next, the aggregated particles containing at least a binder resin obtained in the aggregation step are heated and fused together to obtain toner particles (fusion step).

[0083] The aggregation of fused particles may be stopped by adding an anti-aggregation agent once the particles have grown to a suitable particle size for use as toner.

[0084] The temperature within the system during the fusion process is preferably 2°C higher, more preferably 4°C higher, and even more preferably 6°C higher than the maximum glass transition temperature of the binder resin, and preferably 30°C higher or lower, and more preferably 20°C higher or lower, from the viewpoint of the desired toner particle size, particle size distribution, shape control, and particle fusion properties. Furthermore, the stirring speed is preferably such that aggregated particles do not settle. In this invention, if two or more types of resins are used as the binder resin, the glass transition temperature of the resin with the highest glass transition temperature is used as the reference.

[0085] Toner particles can be obtained by subjecting the fused particles obtained in step (II) to a solid-liquid separation step such as filtration, a washing step, and a drying step as appropriate.

[0086] The circularity of the toner matrix particles is 0.950 or higher, preferably 0.955 or higher, more preferably 0.960 or higher, and 0.995 or lower, preferably 0.980 or lower, more preferably 0.970 or lower.

[0087] Toner matrix particles produced by emulsification phase inversion, polymerization, etc., have high circularity and are likely to fall within the above range, but toner matrix particles produced by melt kneading have low circularity. If the circularity is low and outside the above range, it is preferable to further perform a spheroidizing treatment.

[0088] Examples of spheroidization treatments include mechanical spheroidization using turbomills, cryptrons, faculty, etc., and hot air spheroidization using meteor rainbows, etc. However, in the present invention, a method using a mechanical surface modification device equipped with a hammer and a liner is preferred. The mechanical surface modification device preferably used in the present invention is a batch-type surface modification device. As the batch-type surface modification device, a device described in Japanese Patent Application Publication No. 2018-194705 is preferred, which has a classification means for continuously discharging and removing fine powder to the outside of the device, a surface treatment means equipped with a hammer and a liner, and a guide means that partitions the inside of the device into a first space for introducing the material to be treated into the classification means and a second space for introducing the material to be treated into the surface treatment means.

[0089] From the viewpoint of preventing toner surface deterioration due to heat generated during surface modification and internal fusion, it is preferable to control the temperature inside the device by blowing in cold air or passing a coolant through the jacket.

[0090] Volume median particle size of toner matrix particles (D 50 The volume median particle size (D) is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. 50) refers to the particle size at which the cumulative volume frequency, calculated using volume fractions, accounts for 50% of the total volume frequency, starting from the smallest particle size.

[0091] External additive treatment, which involves mixing toner base particles with external additives, can be carried out according to conventional methods, and a mixer such as a Henschel mixer can be used.

[0092] The toner of the present invention can be used as a one-component developing toner, or mixed with a carrier to form a two-component developing agent, in image forming apparatuses using either a one-component developing method or a two-component developing method. [Examples]

[0093] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples. The physical properties of resins, etc., can be measured by the following methods.

[0094] [Softening point of resin] Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of sample is heated at a heating rate of 6°C / min while a load of 1.96 MPa is applied by a plunger, and the sample is extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The amount of plunger descent of the flow tester is plotted against temperature, and the temperature at which half of the sample has flowed out is defined as the softening point.

[0095] [Glass transition temperature of resins] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample is weighed into an aluminum pan, heated to 200°C, and then cooled to 0°C at a rate of 10°C / min. Next, measurements are taken while heating to 150°C at a rate of 10°C / min. The temperature at the intersection of the extension of the baseline below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rise of the peak to the peak apex is defined as the glass transition temperature.

[0096] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of the sample is weighed into an aluminum pan, heated to 200°C, and then cooled from 200°C to 0°C at a rate of 10°C / min. Next, the sample is heated again at a rate of 10°C / min, the heat quantity is measured, and the maximum endothermic peak temperature is defined as the melting point.

[0097] [Volume median particle size and CV value of resin particles, colorant particles, and mold release agent particles] (1) Measuring device: Laser diffraction particle size analyzer "LA-920" (manufactured by Horiba, Ltd.) (2) Measurement conditions: Take the sample dispersion into a measuring cell, add distilled water, and adjust the concentration to the appropriate range for absorbance, using the medium particle size (D 50 The volume-average particle size (Dv) is measured. The CV value is calculated according to the following formula. CV value (%) = (Standard deviation of particle size distribution / Volume-average particle size Dv) × 100

[0098] [Solid content concentration of resin particle dispersion, colorant particle dispersion, and mold release agent particle dispersion] Using the infrared moisture meter "FD-230" (manufactured by Kett Scientific Research Institute Co., Ltd.), the moisture content (mass%) of a 5g sample is measured at a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 minutes, moisture content fluctuation range 0.05%). The solid content concentration is calculated according to the following formula. Solid content concentration (mass%) = 100-moisture (mass%)

[0099] [Volume median particle size of aggregated particles (D 50 )〕 • Measuring instrument: "Coulter Multisizer (Registered Trademark) III" (manufactured by Beckman Coulter, Inc.) • Aperture diameter: 50 μm • Analysis software: "Multisizer (registered trademark) III version 3.51" (manufactured by Beckman Coulter, Inc.) • Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) • Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte solution to adjust the concentration to a level that would allow for the measurement of 30,000 particle sizes in 20 seconds. Then, 30,000 particles were measured again, and the volume median particle size D was determined from the particle size distribution. 50 We seek.

[0100] [Medium volume particle size of toner matrix particles (D 50 )〕 • Measuring instrument: Coulter Multisizer III (manufactured by Beckman Coulter, Inc.) • Aperture diameter: 100 μm • Analysis software: Multisizer III version 3.51 (manufactured by Beckman Coulter, Inc.) • Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) • Dispersion: Prepared by dissolving polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" [manufactured by Kao Corporation, HLB (Griffin) = 13.6] in the electrolyte to adjust the concentration to 5% by mass. • Dispersion conditions: Add 10 mg of the sample to 5 mL of the dispersion and disperse for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80W). Then, add 25 mL of electrolyte and disperse for another minute using the ultrasonic disperser to prepare the sample dispersion. • Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles can be measured in 20 seconds. Then, the 30,000 particles are measured, and the volume median particle size (D) is determined from the particle size distribution. 50 )

[0101] [Circularity of toner matrix particles] • Measurement device: Flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) • Preparation of dispersion: Prepare the dispersion of fused particles by diluting it with deionized water to a solid content concentration of 0.001 to 0.05% by mass. • Measurement mode: HPF measurement mode

[0102] [Average particle size of external additives] The particle size (average of major and minor axes) of 500 particles is measured from scanning electron microscope (SEM) images, and the number-average value of these measurements is defined as the number-average particle size. Here, aggregates observed in the SEM images are also counted as one particle.

[0103] [BET specific surface area of ​​external additives] The measurement will be performed by nitrogen adsorption under the following conditions. • Measuring device: Specific surface area measuring device "Micromeritics FlowSorbIII" (manufactured by Shimadzu Corporation) Sample size: 0.04-0.08g Degassing conditions: 40°C, 10 minutes • Adsorbent gas: Nitrogen gas

[0104] [BET equivalent particle size of external additives] The calculation is performed based on the following formula. BET equivalent particle size=6000 / ([BET specific surface area]×ρ(density))

[0105] [Shape index of external additives] The calculation is performed based on the following formula. Shape index = [Number-average particle size] / [BET-equivalent particle size]

[0106] Resin manufacturing example 1 The alcohol component, carboxylic acid component, esterification catalyst, and esterification co-catalyst shown in Table 1 were placed in a 5-liter four-necked flask equipped with a nitrogen inlet tube, stirrer, and thermocouple. The mixture was heated to 235°C under a nitrogen atmosphere, and then polycondensed at 235°C for 6 hours. After that, the temperature was lowered to 210°C and the reaction was carried out under reduced pressure of 10 kPa until the softening point shown in Table 1 was reached to obtain a polyester resin (resin A). The physical properties of the obtained resin are shown in Table 1.

[0107] [Table 1]

[0108] Resin manufacturing example 2 In a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, drop-through condenser, dropping funnel, and nitrogen inlet tube, 2 L of xylene was added. In the dropping funnel, 880 g of styrene, 220 g of n-butyl acrylate, and 100 g of dibutyl peroxide as a radical polymerization initiator were added. Under a nitrogen atmosphere, the xylene was heated to 135°C while 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. After that, the pressure in the flask was further reduced and held at 8 kPa for 1 hour to remove the xylene and obtain styrene-acrylic resin (resin B). The softening point of the obtained resin was 115°C, and the glass transition temperature was 54°C.

[0109] Manufacturing Example 1 of Bonded Silica Particles Bonded silica particles were manufactured by sedimentation using the method described below. A 3-liter glass flask equipped with a metal stirring rod, a dropping nozzle, a heating device, and a thermometer was filled with 1000 mL of water and heated to 80°C. Next, while stirring and maintaining a pH of 9, 184 mL of water glass and 818 mL of sulfuric acid were added dropwise over 1 hour, allowing the silica to settle for 20 minutes. Subsequently, sulfuric acid was added dropwise to lower the pH to 3.5. The settled silica was then separated from the suspension, washed with water, and dried to obtain fine silica powder. 100 parts by mass of the obtained silica fine powder was placed in a reaction vessel, and 5 parts by mass of water and 10 parts by mass of hexamethyldisilazane were added under a nitrogen atmosphere. The reaction mixture was stirred at 150°C for 2 hours, and then stirred at 220°C for 2 hours under a nitrogen atmosphere and dried. By cooling this mixture, hydrophobic silica particles A1 were obtained.

[0110] Manufacturing Example 2 of Bonded Silica Particles Except for adjusting the dropping time of the water glass and sulfuric acid to 50 minutes and the sedimentation time of the silica to 30 minutes, hydrophobic silica particles A2, which differ from silica particles A1 in number-average particle size and BET specific surface area, were obtained in the same manner as in Production Example 1.

[0111] Manufacturing Example 3 of Bonded Silica Particles Except for adjusting the dropping time of the water glass and sulfuric acid to 70 minutes and the sedimentation time of the silica to 10 minutes, hydrophobic silica particles A3, which differ from silica particles A1 in number-average particle size and BET specific surface area, were obtained in the same manner as in Production Example 1.

[0112] Table 2 shows the physical properties of silica particles A1 to A3 and silica particles A4 and B1 used in the examples and comparative examples.

[0113] [Table 2]

[0114] Examples 1, 2, 4-7 and Comparative Examples 2-4 (Example 5 is for reference only.) 100 parts by mass of the binder resin shown in Table 3, 2.0 parts by mass of paraffin wax "HNP-9" (manufactured by Nippon Seiro Co., Ltd., melting point 75°C), 1.0 part by mass of charge control agent "Bontron E-304" (manufactured by Orient Chemical Industry Co., Ltd.), and 5.0 parts by mass of coloring agent "REGAL 330" (manufactured by Cabot Specialty Chemicals Inc.) were mixed for 1 minute using a Henschel mixer, and then melt-kneaded under the conditions shown below.

[0115] Co-rotating twin-screw extruder "PCM-30" (manufactured by Ikegai Co., Ltd., shaft diameter 2.9 cm, shaft cross-sectional area 7.06 cm²) 2 The following was used: barrel setting temperature 100°C, shaft rotation speed 200 r / min (shaft rotation peripheral speed 0.30 m / sec), mixture supply rate 10 kg / h (mixture supply amount per unit cross-sectional area of ​​the shaft 1.42 kg / h·cm). 2 ) was.

[0116] The resulting mixture was cooled and coarsely ground using a Rotoplex pulverizer (manufactured by Hosokawa Micron Corporation), and a coarse pulverized material with a median volume particle size of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. The obtained coarse pulverized material was finely ground using a DS2 type airflow classifier (impingement plate type, manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the grinding pressure so that the median volume particle size was 8.0 μm. The obtained fine pulverized material was classified using a DSX2 type airflow classifier (manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the static pressure (internal pressure) so that the median volume particle size was 8.5 μm, and toner-classified products were obtained.

[0117] The resulting toner classified material was spheroidized using a surface modification apparatus equipped with hammers and liners. Twelve hammers were used, and the dispersion rotation speed, classification rotation speed, airflow, input amount, and processing time were varied to perform the spheroidization process to obtain toner matrix particles with a predetermined degree of circularity.

[0118] Toner was obtained by mixing 100 parts by mass of the obtained toner matrix particles with the silica particles shown in Table 3 using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.) at 2100 r / min (peripheral speed 29 m / sec) for 3 minutes.

[0119] Example 3 [Preparation of resin particle dispersion] 300 g of resin A and 300 g of methyl ethyl ketone were placed in a 3-liter container equipped with a stirrer, reflux condenser, dropping funnel, thermometer, and nitrogen inlet tube, and the resin was dissolved at 73°C for 2 hours. To the resulting solution, a 5% by mass aqueous sodium hydroxide solution was added so that the degree of neutralization relative to the acid value of the resin was 60 mol%, and the mixture was stirred for 30 minutes. Next, while maintaining the temperature at 73°C, 600 g of deionized water was added over 60 minutes while stirring at 280 r / min (peripheral speed 88 m / min) to induce phase inversion emulsification. While continuing to maintain the temperature at 73°C, methyl ethyl ketone was removed under reduced pressure to obtain an aqueous dispersion. Then, while stirring at 280 r / min (peripheral speed 63 m / min), the aqueous dispersion was cooled to 30°C, and deionized water was added to obtain a resin particle dispersion by reducing the solid content concentration to 20% by mass. The median particle size (D) of the resin particles was then measured.50 The thickness was 0.1 μm, and the CV value was 24%.

[0120] [Preparation of release agent dispersion] In a 1-liter beaker, 120 g of deionized water was added, and 167 g of 15% by mass sodium dodecylbenzenesulfonate aqueous solution "Neoperex G-15" (anionic surfactant, manufactured by Kao Corporation) was dissolved. Then, 100 g of paraffin wax "HNP-9" (manufactured by Nippon Seiro Co., Ltd., melting point 75°C) was added, and the mixture was melted and stirred while maintaining the temperature at 90-95°C to obtain a molten mixture. While maintaining the temperature at 90-95°C, the mixture was dispersed for 20 minutes using an ultrasonic homogenizer "US-600T" (manufactured by Nippon Seiki Seisakusho Co., Ltd.), and then cooled to room temperature. Deionized water was added to the obtained dispersion to adjust the solid content concentration to 20% by mass to obtain a release agent particle dispersion. The median particle size (D) of the release agent particles was determined. 50 The saturation was 0.22 μm, and the CV value was 27%.

[0121] [Preparation of charge control agent dispersion] In a 1-liter beaker, 100g of the charge control agent "Bontron E-304" (manufactured by Orient Chemical Industry Co., Ltd.), 35g of polyoxyethylene (13) distyrenate phenyl ether "Emulgen A-60" (manufactured by Kao Corporation, a nonionic surfactant), and 300g of deionized water were mixed. The mixture was then dispersed for 1 hour at room temperature using a homomixer "TKAGI HOMOMIXER 2M-03" (manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotation speed of 8000 r / min. After that, it was subjected to 15-pass processing at a pressure of 150 MPa using a "Microfluidizer M-110EH" (manufactured by Microfluidics Inc.), and then passed through a 200-mesh filter. Deionized water was added to obtain a dispersion of charge control agent particles to a solid content concentration of 20% by mass. The volume-median particle size (D) of the charge control agent particles was determined. 50 The density was 0.15 μm, and the CV value was 25%.

[0122] [Preparation of colorant dispersion] In a 1-liter beaker, 100g of the coloring agent "REGAL 330" (manufactured by Cabot Specialty Chemicals Inc.), 35g of polyoxyethylene (13) distyrenate phenyl ether "Emulgen A-60" (manufactured by Kao Corporation, a nonionic surfactant), and 300g of deionized water were mixed. The mixture was then dispersed for 1 hour at room temperature using a homomixer "TKAGI HOMOMIXER 2M-03" (manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotation speed of 8000 r / min. After that, it was subjected to 15-pass processing at a pressure of 150 MPa using a "Microfluidizer M-110EH" (manufactured by Microfluidics Inc.), and then passed through a 200-mesh filter. Deionized water was added to obtain a dispersion of coloring agent particles to a solid content concentration of 24% by mass. The volume of the median particle size (D) of the coloring agent particles was measured. 50 The density was 0.15 μm, and the CV value was 25%.

[0123] [Toner manufacturing] In a 3-liter four-necked flask equipped with a dewatering tube, a stirrer, and a thermocouple, 500 g of resin particle dispersion, 14 g of mold release agent particle dispersion, 3 g of charge control agent particle dispersion, 26 g of coloring agent particle dispersion, and 10 g of a 10% by mass aqueous solution of polyoxyethylene (50) lauryl ether "Emulgen 150" (manufactured by Kao Corporation, a nonionic surfactant) were mixed at a temperature of 25°C. Next, while stirring the mixture, a solution prepared by dissolving 40 g of ammonium sulfate in 596 g of deionized water and adding a 4.8% by mass aqueous solution of potassium hydroxide to adjust the pH to 8.0 was added dropwise over 5 minutes at 25°C, and the temperature was raised to 65°C over 2 hours to determine the volume-median particle size (D) of the aggregated particles. 50 The mixture was maintained at 65°C until the particle size reached 8.8 μm, and a dispersion of aggregated particles was obtained.

[0124] To the resulting dispersion of aggregated particles, an aqueous solution was added, which consisted of 18 g of polyoxyethylene lauryl ether sodium sulfate "Emal E-27C" (manufactured by Kao Corporation, anionic surfactant, effective concentration 27% by mass), 429 g of deionized water, and 40 g of 0.1 mol / L aqueous sulfuric acid solution. Subsequently, the temperature was raised to 90°C over 1 hour, and then maintained at 90°C until the circularity reached 0.99, thereby obtaining a dispersion of fused particles in which the aggregated particles had fused together.

[0125] The obtained fused particle dispersion was cooled to 30°C, and the dispersion was filtered by suction to separate the solid components. The dispersion was then washed with deionized water at 25°C and filtered by suction at 25°C for 2 hours. Subsequently, vacuum drying was performed at 33°C for 24 hours using a vacuum constant-temperature dryer "DRV622DA" (manufactured by ADVANTEC) to obtain toner matrix particles. The median particle size (D) of the obtained toner matrix particles was measured. 50 The diameter was 8.5 μm.

[0126] Toner was obtained by mixing 100 parts by mass of the obtained toner matrix particles with the silica particles shown in Table 3 using a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.) at 2100 r / min (peripheral speed 29 m / sec) for 3 minutes.

[0127] Comparative Example 1 Toner was obtained in the same manner as in Example 1, except that the toner classification product was not subjected to spheroidization treatment.

[0128] Test Example 1 [Image Density] Toner was loaded into the non-magnetic single-component developer "OKI MICROLINE 5400" (manufactured by OKI Data Corporation), and 20 solid images were printed. The optical reflectance of these images was measured at 5 points using a reflectance densitometer "RD-915" (manufactured by Macbeth Corporation), and the average value of these measurements was evaluated as the image density (OD). The results are shown in Table 3.

[0129] Test Example 2 [Image blurring under high temperature and high humidity] Toner was installed in the non-magnetic single-component developer "OKI MICROLINE 5400" (manufactured by OKI Data Corporation), and a solid black A4 image was printed in a high-temperature, high-humidity environment (30°C, 90%). Next, 500 copies were printed at a print density of 1%, and then another solid black A4 image was printed. J-paper (manufactured by Fuji Xerox) was used as the printing medium. The image density of the central part 5 cm from the bottom of the initial solid black image (ID1) and the image density of the central part 5 cm from the bottom of the image after 500 copies were printed (ID2) were measured using a reflectivity densitometer "RD-915" (manufactured by Gretag Macbeth Corporation), and the difference in image density between the two was checked. If the difference in image density did not exceed 0.4, another 500 copies were printed, and printing continued until the difference in image density exceeded 0.4. The results are shown in Table 3. This indicates that the effect of suppressing image streaking is higher with a larger number of printed copies.

[0130] [Table 3]

[0131] From the results above, it can be seen that in Examples 1 to 7, the image density is high and the occurrence of image blurring is suppressed. In contrast, in Comparative Example 1, where the circularity of the toner matrix particles is low, the transferability is poor, resulting in low image density and image streaking. In Comparative Example 2, where the shape index of large-particle silica is small, the large-particle silica is easily detached, resulting in image streaking. In Comparative Example 3, which does not use small-particle silica, the electrostatic charge is low, resulting in low image density from the beginning and image streaking. In Comparative Example 4, which does not use large-particle silica, the durability is low, and image streaking occurs. [Industrial applicability]

[0132] The electrostatic image developing toner of the present invention is suitably used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like.

Claims

1. A toner for developing electrostatic images, comprising toner matrix particles with a circularity of 0.950 to 0.995 containing a binder resin and a colorant, and an external additive containing silica particles A and silica particles B with different number-average particle sizes, wherein silica particles A have a larger number-average particle size than silica particles B, and the BET specific surface area of ​​silica particles A is 85 m². 2 / g or more 150m 2 A toner for developing electrostatic images, wherein the shape index, expressed as the ratio of the number-average particle size to the BET-converted particle size, is 2.0 or greater, the shape index of the silica particle B is less than 2.0, and the mass ratio of the silica particle A to the silica particle B is 1 / 1 or greater and 3 / 1 or less.

2. The electrostatic image developing toner according to Claim 1, wherein the BET specific surface area of ​​silica particles A is 90 m² / g or more and 150 m² / g or less.

3. The toner for developing electrostatic images according to claim 1, wherein the number-average particle size of silica particles A is 80 nm or more and 130 nm or less.

4. The electrostatic image developing toner according to claim 1, wherein the number-average particle size of silica particles B is 20 nm or more and 35 nm or less.

5. A method for manufacturing electrostatic image developing toner, comprising the step of mixing toner matrix particles having a circularity of 0.950 to 0.995, which contain a binder resin and a colorant, with an external additive containing silica particles A and silica particles B having different number-average particle sizes, wherein silica particles A have a larger number-average particle size than silica particles B, and the BET specific surface area of ​​silica particles A is 85 m². 2 / g or more 150m 2 A method for producing toner for electrostatic image developing, wherein the shape index expressed as the ratio of the number-average particle size to the BET-converted particle size is 2.0 or more, the shape index of the silica particle B is less than 2.0, the mass ratio of the silica particle A to the silica particle B is 1 / 1 or more and 3 / 1 or less, and the toner matrix particles are produced by a method including the step of melting and kneading a mixture containing the binder resin and the colorant.

6. The manufacturing method according to claim 5, wherein melt kneading is performed by a twin-screw extruder.

Images