Electrostatic charge image developing toner

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 a toner for developing electrostatic images used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing and the like, and a method for producing the same. [Background technology]

[0002] In recent years, the demand for toner performance has been increasing along with the increase in printer speed. In order to stabilize the charge of the toner and improve its flowability, the formulation of external additives added to the toner particles has also been improved, and toners using large and small external additives have been studied from the viewpoints of the toner's start-up property, durability, etc.

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

[0004] Patent Document 2 discloses a magnetic toner having magnetic toner particles containing a binder resin and a magnetic material, and a first external additive, the first external additive being: 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 100 or more and 250 or less, 4) The shape factor SF-2 is 105 or more and 250 or less, The magnetic toner has a silica coverage of the surface of the magnetic toner particles measured by ESCA of 40.0% or more and 70.0% or less, and the magnetic toner is placed in a measurement container, a load of 5.8 kPa is applied to the placed magnetic toner to form a toner layer in the measurement container, and then a propeller blade whose outermost edge rotates at a peripheral speed of 100 mm / sec is inserted vertically into the toner layer in the measurement container, and the propeller blade is moved at a constant speed through the toner layer while rotating, and the total energy calculated from the rotational torque and vertical load is 80.0 mJ or more and 140.0 mJ or less. Furthermore, the magnetic toner contains silica having a number average particle size of 5 nm or more and 30 nm or less as a second external additive, and the content of the second external additive is i) 0.1 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the magnetic toner particles, ii) 10% by mass or more and 50% by mass or less based on the content of the first external additive; It is stated that:

[0005] Patent Document 3 discloses an invention relating to a positively charged toner for developing electrostatic images, which contains colored resin particles including a binder resin, a colorant, and a charge control agent, and an external additive, and which is characterized in that the external additives include external additive A and external additive B, the external additive A being 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, the content of the fatty acid alkali metal salt particles or fatty acid alkaline earth metal salt particles being 0.01 to 0.5 parts by weight relative to 100 parts by weight of the colored resin particles, and the external additive B being spherical silica fine particles having a number-average primary particle size of 40 to 200 nm and a sphericity of 1 to 1.3, the content of the spherical silica fine particles being 0.2 to 2 parts by weight relative to 100 parts by weight of the colored resin particles. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-71614 [Patent Document 2] JP 2015-45860 A [Patent Document 3] JP 2010-128312 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, toner particles with a high circularity have a low adhesion to printer components, and therefore have high transferability and excellent print density and image quality, but the collision energy between toner particles during frictional charging is large. Therefore, even if large and small external additives are used, the large external additives on the toner surface are detached and the spacer effect is lost, causing the small external additives to be buried, and the charging property is significantly reduced. In addition, under high temperature and high humidity, the surface of the toner particles is plasticized, making the burial of the small external additives even more pronounced, resulting in blurred images.

[0008] The present invention relates to a toner for developing electrostatic images, which has a high initial image density and is capable of suppressing image blurring under high temperature and high humidity conditions, and a method for producing the same. [Means for solving the problem]

[0009] The present invention relates to [1] A toner for developing electrostatic images, comprising toner base particles containing a binder resin and a colorant and having a circularity of 0.950 to 0.995, and 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, and the BET specific surface area of ​​the silica particles A is 70 m 2 / g or more 150m 2 / g or less, and a shape index represented by the ratio of the number average particle diameter to the BET converted particle diameter is 2.0 or more, and the shape index of the silica particles B is less than 2.0; and [2] A method for producing a toner for developing an electrostatic image, comprising a step of mixing toner base particles containing a binder resin and a colorant and having a circularity of 0.950 to 0.995, 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, and the BET specific surface area of ​​the silica particles A is 70 m 2 / g or more 150m 2 / g or less, a shape index represented by the ratio of a number average particle diameter to a BET converted particle diameter is 2.0 or more, and the shape index of the silica particles B is less than 2.0, and the toner base particles are produced by a method including a step of melting and kneading a mixture containing the binder resin and the colorant. Regarding. Effect of the Invention

[0010] The toner for developing electrostatic images of the present invention exerts the excellent effects of having a high initial image density and suppressing image blurring under high temperature and high humidity conditions. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a conventional silica. [Diagram 2] FIG. 2 is an example of a schematic cross-sectional view of cemented silica. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The toner for developing electrostatic images of the present invention contains toner base particles and an external additive including silica particles (silica particles A and B) having different number average particle diameters, and is characterized by the shape of the silica particles (silica particles A) having a larger number average particle diameter. Usually, particle size and BET specific surface area are negatively correlated. That is, the larger the number average particle size, the smaller the BET specific surface area. In contrast, the silica particles A in the present invention have a large number average particle size compared to silica particles of the same number average particle size, but have a large BET specific surface area and a small BET converted particle size (particle size) converted from the BET specific surface area, so that the ratio of the number average particle size to the BET converted particle size (shape index) is also large. Such characteristics are due to the shape of the silica particles A, and usually, silica particles exist in a partially aggregated state. Generally, silica particle aggregates are densely aggregated as shown in FIG. 1, whereas the aggregates contained in the silica particles A have gaps between the silica particles as shown in FIG. 2, and have multiple clear convexities on the surface like tetrapods. Silica particles with such a shape (hereinafter also referred to as "bonded silica particles") have a large contact area with the toner base particle surface, so they are difficult to detach from the toner base particle surface even with large collision energy, and the spacer effect is maintained, so that the burial of the small silica particles B is greatly suppressed. It is therefore believed that this can suppress the occurrence of printing defects that cause blurred images.

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

[0014] The shape index of the silica particles 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, 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 particles is a value calculated from the ratio of the number average particle size to the BET converted particle size (number average particle size / BET converted particle size).

[0015] The shape index of the silica particles 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, is 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 shape characteristics is usually less than 2.0.

[0016] The number average particle size of the silica particles A is larger than that of the silica particles B, and is preferably 80 nm or more, more preferably 90 nm or more, and even more preferably 100 nm or more, and from the viewpoint of suppressing detachment from the surface of the toner base particles, 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 the 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 charge rise property of the toner, 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 the silica particles is measured by counting not only primary particles but also aggregates of silica particles as one particle.

[0019] The difference in number average particle size between silica particles A and silica particles 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, even more preferably 90 nm or less.

[0020] The silica particles A can be produced by reacting water glass with sulfuric acid in warm water, filtering the resulting silica precipitate, washing with water, and drying, preferably by a precipitation method. The number-average particle size and BET specific surface area of ​​the resulting silica particles can be adjusted by adjusting the reaction conditions (temperature, drop speed of water glass and sulfuric acid into water, precipitation time of silica, etc.).

[0021] The silica particles A and / or silica particles B are preferably subjected to a hydrophobic treatment on the 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, cyclic silazane, etc. Commercially available products may be used, but for example, in the case of silica particles A, the bonded silica particles obtained by the above method may be surface-treated with one of these hydrophobic treatment agents alone, or in the case of two or more types, may be mixed, or may be surface-treated stepwise to impart surface treatment properties required according to the application.

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

[0023] The total content of the silica particles A and the 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 still 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, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the toner base particles, and is 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.

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

[0026] Examples of the binder resin include polyester resin, vinyl resin such as styrene-acrylic resin, epoxy resin, polycarbonate, polyurethane, and composite resin containing two or more of these resins. In the present invention, it is preferable that the binder resin contains a polyester resin from the viewpoint of low-temperature fixing property and production stability.

[0027] The polyester resin is preferably a polycondensation product of an alcohol component, including an alkylene oxide adduct of bisphenol A, and a carboxylic acid component.

[0028] Examples of the alkylene oxide adduct of bisphenol A include those represented by the 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 are the average number of moles of alkylene oxide added, each of which is a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) Preferred is a compound represented by the following formula:

[0031] From the viewpoint of low-temperature fixing ability, the content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, even more preferably 95 mol % or more, and even more preferably 100 mol %.

[0032] Examples of other alcohol components include aliphatic diols, bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trimethylolpropane and other trihydric or higher alcohols.

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

[0034] Examples of the aromatic dicarboxylic acid compound include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 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 in the carboxylic acid component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 100 mol%.

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

[0037] Examples of the trivalent or higher carboxylic acid compound include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0038] The alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monovalent carboxylic acid compound.

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

[0040] The polyester resin can be produced, for example, by polycondensing the raw material monomers, that is, an alcohol component and a carboxylic acid component, in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and further, if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc., at a temperature of 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 the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine, and tin compounds are preferred. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, relative to 100 parts by mass of the raw material monomer. Examples of the esterification promoter include gallic acid, etc. The amount of the esterification promoter used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, relative to 100 parts by mass of the raw material monomer. Examples of the polymerization inhibitor include tert-butylcatechol, etc. The amount of the 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, more preferably 0.1 parts by mass or less, relative to 100 parts by mass of the raw material monomer.

[0042] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc., and among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended 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 hot offset resistance, and is 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 fixability.

[0044] From the viewpoint of heat-resistant storage stability, 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, and from the viewpoint of low-temperature fixability, it is preferably 75° C. or lower, more preferably 70° C. or lower, and even more preferably 65° C. or lower.

[0045] The content of the polyester resin in the binder resin is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 100% by mass.

[0046] The content of the binder resin in the toner base particles 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 is preferably less than 100% by mass, more preferably 98% by mass or less, even more preferably 95% by mass or less.

[0047] As the colorant, dyes, pigments, magnetic materials, etc. used as colorants for toners can be used. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. can be mentioned. In the present invention, the toner may be either a black toner or a color toner.

[0048] From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the 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, relative to 100 parts by mass of the binder resin.

[0049] The toner base particles may contain additives such as a release agent, a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver, in addition to the binder resin and the colorant. It is preferable that the toner base particles contain a release agent and a charge control agent.

[0050] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts. These may be used alone 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 is preferably 160° C. or lower, more preferably 140° C. or lower, even more preferably 120° C. or lower, and even more preferably 110° C. or lower, from the viewpoint of low-temperature fixability.

[0052] The content of the release agent is, from the viewpoint of the low-temperature fixing property and offset resistance of the toner and the viewpoint of dispersibility in the binder resin, 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 is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 7 parts by mass or less, relative to 100 parts by mass of the binder resin.

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

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

[0055] Examples of the negatively chargeable charge control agent include metal-containing azo dyes such as "Varifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Industry Co., Ltd.), "Aizenspiron Black TRH", and "T-77" (manufactured by Hodogaya Chemical Industry Co., Ltd.); metal compounds of benzilic acid compounds such as "LR-147" and "LR-297" (all 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 Industry Co., Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Industry Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts such as "COPY CHARGE NX VP434 (Clariant), nitroimidazole derivatives, and organometallic compounds.

[0056] From the viewpoint of the charging stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0057] The method for producing the toner base particles may be any of the conventionally known methods such as a melt-kneading method, an emulsion phase inversion method, a polymerization method, etc. From the viewpoints of productivity and dispersibility of additives, the melt-kneading method, specifically, a method including a step of melt-kneading a mixture of raw materials containing a binder resin and a colorant, is preferred.

[0058] The raw materials to be subjected to melt kneading, including the binder resin and the colorant, may be kneaded all at once or in portions, but it is preferable to mix them in advance in a mixer such as a Henschel mixer or a ball mill and then supply them to the kneader.

[0059] The melt kneading can be carried out using a known kneading machine such as an internal kneader, a single-screw or twin-screw extruder, or an open roll type kneader. From the viewpoint of bringing the kneaded material to a high temperature state where it is sufficiently melted and improving wettability with additives, it is preferable to use a twin-screw extruder.

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

[0061] The pulverization step is a step of pulverizing the obtained kneaded product to obtain toner base particles. The kneaded product may be pulverized to a desired particle size all at once or in stages, but from the viewpoint of efficient and more uniform pulverization, it is preferable to perform the pulverization in two stages, that is, coarse pulverization and fine pulverization.

[0062] Examples of the crushing machine used for the coarse crushing include a hammer mill, an atomizer, and a rotoplex.

[0063] In the coarse pulverization, it is preferable to pulverize until the maximum diameter is 3 mm or less. The pulverized material having a maximum diameter of 3 mm or less can be obtained by coarsely pulverizing the kneaded material until the particle size is about 0.05 mm or more and 3 mm or less, and then passing the kneaded material through a sieve with 3 mm openings.

[0064] Examples of the pulverizer used for fine pulverization include jet mills such as a fluidized bed jet mill and an impact plate jet mill, and rotary mechanical mills. Among these, from the viewpoint of pulverization efficiency, the fluidized bed jet mill and the impact plate jet mill are preferred, and the impact plate jet mill is more preferred.

[0065] The degree of pulverization is preferably adjusted appropriately depending on the desired particle size of the toner.

[0066] Examples of classifiers used in the classification step include air flow classifiers, inertial classifiers, and sieve classifiers.

[0067] Examples of the phase inversion emulsification method include a method (A) in which a resin component, etc. is dissolved in an organic solvent to obtain an organic solvent solution of the resin component, etc., and an aqueous medium is added to the obtained solution to perform phase inversion emulsification, and a method (B) in which an aqueous medium is added to a resin mixture obtained by melting and mixing the resin component, etc., to perform phase inversion emulsification, etc. From the viewpoint of obtaining a homogeneous aqueous dispersion of core resin particles, the method (A) is preferred.

[0068] The organic solvent used for phase inversion emulsification is not particularly limited as long as it dissolves the resin, and examples thereof include methyl ethyl ketone.

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

[0070] The amount of the aqueous medium used is preferably 100 parts by mass or more and 3000 parts by mass or less relative to 100 parts by mass of the organic solvent. The aqueous medium used in step (I) may contain an alcohol solvent having a carbon number of 1 to 3, such as ethanol, but preferably contains water at 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.

[0071] When stirring the mixture, a commonly used mixing and stirring device such as an anchor blade can be used.

[0072] In the phase inversion emulsification method, it is preferable to treat the resin with a neutralizing agent. Examples of the neutralizing agent 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 the neutralizing agent added is preferably an amount that results in a degree of neutralization of about 50 to 100% based on the acid value of the polyester after the reaction to be subjected to neutralization.

[0073] A surfactant or the like may be used as a dispersant for the purpose of lowering the melt viscosity and melting point of the binder resin and improving the dispersibility of the resulting resin particles.

[0074] The solid content of the dispersion of resin particles containing a 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 viewpoints of the stability of the dispersion and the handleability of the dispersion in the aggregation step. The solid content includes non-volatile components such as resins and surfactants.

[0075] From the viewpoint of uniform aggregation in the subsequent step, the average particle size of the resin particles is preferably 0.05 μm or more, more preferably 0.10 μm or more, and even more preferably 0.15 μm or more, and is preferably 0.80 μm or less, more preferably 0.40 μm or less, and even more preferably 0.30 μm or less. In the present invention, the average particle size of the resin particles refers to the volume median particle size (D 50 ) and can be measured using a laser diffraction particle size measuring device, etc.

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

[0077] In step (II), the aggregation is performed, for example, by adding an aggregating agent to a mixed dispersion containing resin particles at 0° C. or more and 40° C. or less, and aggregating the resin particles in an aqueous medium to obtain aggregated particles. Furthermore, from the viewpoint of promoting aggregation, it is preferable to increase the temperature of the dispersion after adding the aggregating agent.

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

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

[0080] As the flocculant, in the organic system, cationic surfactants of quaternary salts, polyethyleneimine, etc. are used, and in the inorganic system, inorganic metal salts, inorganic ammonium salts, divalent or higher metal complexes, etc. are used. 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, and 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 to obtain a desired particle size, the amount of the aggregating agent used is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the binder resin, and is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less.

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

[0083] When the fused particles have grown to a suitable particle size for the toner, the aggregation may be stopped by adding an aggregation stopper or the like.

[0084] From the viewpoints of the particle size, particle size distribution, and shape control of the target toner, and the fusion property of the particles, the temperature in the system in the fusion step is preferably at least 2°C higher than the maximum glass transition temperature of the binder resin, more preferably at least 4°C higher, and even more preferably at least 6°C higher, and is preferably not higher than 30°C higher, more preferably not higher than 20°C higher than the maximum glass transition temperature of the binder resin. The stirring speed is preferably a speed at which aggregated particles do not settle. In the present invention, when 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] The fused particles obtained in the step (II) can be appropriately subjected to a solid-liquid separation step such as filtration, a washing step, and a drying step to obtain toner particles.

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

[0087] The toner base particles produced by the emulsion phase inversion method, polymerization method, etc. have a high circularity and are likely to be within the above range, but the toner base particles produced by the melt kneading method have a low circularity. If the circularity is low and outside the above range, it is preferable to further carry out a spheronization process.

[0088] Examples of spheronization include mechanical spheronization using a turbo mill, a kryptron, a faculty, etc., and hot air spheronization using a meteo rainbow, etc., but 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 preferably a batch-type surface modification device. As the batch-type surface modification device, a device having a classification means for continuously discharging and removing fine powder outside the device, a surface treatment means equipped with a hammer and a liner, and a guide means for dividing the inside of the device into a first space for introducing the treated object into the classification means and a second space for introducing the treated object into the surface treatment means, as described in JP 2018-194705 A, is preferred.

[0089] From the viewpoint of preventing surface deterioration of the toner due to heat generated during the surface modification and fusion inside the machine, it is preferable to control the temperature inside the apparatus by blowing cool air or passing a refrigerant through the jacket.

[0090] The volume median particle size of the toner base particles (D 50 ) is preferably 3 μm or more, more preferably 4 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less. 50) means the particle size at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle size.

[0091] The external addition treatment by mixing the toner base particles with the external additives can be carried out according to a conventional method, and a mixer such as a Henschel mixer can be used.

[0092] The toner of the present invention can be used as a toner for one-component development or as a two-component developer mixed with a carrier in an image forming apparatus of a one-component development system or a two-component development system, respectively. EXAMPLES

[0093] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties of resins and the like can be measured by the following methods.

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

[0095] [Glass transition temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled from that temperature at a rate of 10°C / min to 0°C. Next, measure while heating to 150°C at a rate of 10°C / min. The glass transition temperature is 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 rising part of the peak to the top of the peak.

[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 and heated to 200°C, then cooled from 200°C to 0°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, the amount of heat is measured, and the maximum endothermic peak temperature is taken as the melting point.

[0097] [Volume Median Particle Size and CV Value of Resin Particles, Colorant Particles, and Release Agent Particles] (1) Measuring device: Laser diffraction type particle size measuring device "LA-920" (manufactured by Horiba, Ltd.) (2) Measurement conditions: Put the sample dispersion in a measurement cell, add distilled water, and measure the volume median particle size (D 50 ) and volume average particle size (Dv). The CV value is calculated according to the following formula. CV value (%) = (Standard deviation of particle size distribution / Volume average particle size Dv) x 100

[0098] [Solid Content Concentration of Resin Particle Dispersion, Colorant Particle Dispersion, and Release Agent Particle Dispersion] Using an infrared moisture meter "FD-230" (Kett Electric Laboratory Co., Ltd.), measure the moisture (mass%) of 5 g of the measurement sample at a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 minutes, moisture content fluctuation range 0.05%). Calculate the solid content concentration according to the following formula. Solid concentration (mass%) = 100-moisture (mass%)

[0099] [Volume median particle diameter of agglomerated particles (D 50 )〕 Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50μm Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) 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, 30,000 particles are measured again, and the volume median particle size D is calculated from the particle size distribution. 50 Request.

[0100] [Volume median particle size of toner base particles (D 50 )〕 Measuring instrument: Coulter Multisizer III (manufactured by Beckman Coulter, Inc.) Aperture diameter: 100μm Analysis software: Multisizer III version 3.51 (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion liquid: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) was dissolved in the electrolyte to adjust the concentration to 5% by mass. Dispersion conditions: 10 mg of the measurement sample is added to 5 mL of the dispersion liquid, and dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Co., Ltd., output: 80 W). Then, 25 mL of electrolyte is added, and the mixture is further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion liquid. Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds. Then, 30,000 particles were measured, and the volume median particle size (D 50 ) is required.

[0101] [Circularity of toner base particles] Measurement equipment: Flow-type particle image analyzer "FPIA-3000" (Sysmex Corporation) Preparation of dispersion: Prepare a dispersion of fused particles by diluting with deionized water to a solids concentration of 0.001 to 0.05% by mass. Measurement mode: HPF measurement mode

[0102] [Number average particle size of external additives] The particle size (average of the long and short diameters) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the number average value of these is taken as the number average particle size. Here, among the particles observed in the SEM photograph, aggregates are also counted as one particle.

[0103] [BET specific surface area of ​​external additives] Measured by nitrogen adsorption method under the following conditions. Measurement device: Specific surface area measurement device "Micromeritics FlowSorbIII" (manufactured by Shimadzu Corporation) Sample size: 0.04~0.08g Degassing conditions: 40℃, 10 minutes Adsorption gas: Nitrogen gas

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

[0105] [Shape index of external additives] Calculate 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 promoter shown in Table 1 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 235°C under a nitrogen atmosphere, and then polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 210°C, and the reaction was carried out under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, thereby obtaining 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 2 L of xylene was placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a flow-down condenser, a dropping funnel, and a nitrogen inlet tube, and 880 g of styrene, 220 g of n-butyl acrylate, and 100 g of dibutyl peroxide as a radical polymerization initiator were placed in the dropping funnel. Under a nitrogen atmosphere, the xylene was heated to 135°C while stirring, and the mixture in the dropping funnel was dropped over 1 hour. After that, the temperature was raised to 200°C and held at 200°C for 2 hours, and then the pressure in the flask was further reduced and held at 8 kPa for 1 hour, and xylene was removed to obtain a styrene-acrylic resin (resin B). The softening point of the obtained resin was 115°C, and the glass transition temperature was 54°C.

[0109] Example 1 of the production of bonded silica particles Grafted silica particles were prepared by precipitation according to the following method. A 3-liter glass flask equipped with a metal stirring rod, a dropping nozzle, a heating device, and a thermometer was charged with 1000 mL of water and heated to 80°C. Next, while maintaining the pH value at 9 under stirring, 184 mL of water glass and 818 mL of sulfuric acid were dropped over 1 hour to allow silica to settle for 20 minutes. After that, sulfuric acid was continuously dropped to adjust the pH value to 3.5. The precipitated silica was separated from the suspension, washed with water, and then dried to obtain silica fine 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 and dried under a nitrogen stream at 220°C for 2 hours. The mixture was cooled to obtain hydrophobic silica particles A1.

[0110] Example 2 of the production of bonded silica particles Hydrophobic silica particles A2 having a number average particle size and a BET specific surface area different from those of silica particles A1 were obtained in the same manner as in Production Example 1, except that the drop time of the water glass and sulfuric acid was adjusted to 50 minutes and the settling time of silica was adjusted to 30 minutes.

[0111] Manufacturing Example 3 of Bonded Silica Particles Hydrophobic silica particles A3 having a number average particle size and a BET specific surface area different from those of silica particles A1 were obtained in the same manner as in Production Example 1, except that the drop time of the water glass and sulfuric acid was adjusted to 70 minutes and the settling time of the silica was adjusted to 10 minutes.

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

[0113] [Table 2]

[0114] Examples 1, 2, 4 to 7 and Comparative Examples 2 to 4 100 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 colorant "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 cm 2 The operating conditions were: barrel temperature 100°C, shaft rotation speed 200 r / min (shaft rotation peripheral speed 0.30 m / sec), mixture supply speed 10 kg / h (mixture supply amount per unit cross-sectional area of ​​the shaft 1.42 kg / h cm 2 ) was.

[0116] The kneaded product obtained was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Co., Ltd.), and a coarsely pulverized product having a volume median particle size of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. The coarsely pulverized product obtained was finely pulverized using a DS2 type air classifier (impingement plate type, manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the pulverization pressure so that the volume median particle size became 8.0 μm. The finely pulverized product obtained was classified using a DSX2 type air classifier (manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the static pressure (internal pressure) so that the volume median particle size became 8.5 μm, and a classified toner product was obtained.

[0117] The resulting classified toner product was spheronized using a surface modification device equipped with a hammer and a liner. The hammer was 12 pieces, and the dispersion rotation speed, classification rotation speed, air volume, input amount, and processing time were changed to perform spheronization processing to obtain a predetermined circularity, and toner base particles were obtained.

[0118] 100 parts by mass of the obtained toner base particles and the silica particles shown in Table 3 were mixed for 3 minutes at 2100 r / min (circumferential speed 29 m / sec) using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) to obtain a toner.

[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 vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the resin was dissolved over 2 hours at 73° C. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization with respect 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 (circumferential speed 88 m / min) to cause phase inversion emulsification. While continuing to maintain the temperature at 73°C, methyl ethyl ketone was distilled off under reduced pressure to obtain an aqueous dispersion. Thereafter, while continuing to stir at 280 r / min (circumferential speed 63 m / min), the aqueous dispersion was cooled to 30°C, and deionized water was added so that the solid concentration became 20 mass%, thereby obtaining a resin particle dispersion. The volume median particle diameter (D50 ) 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 "Neopelex 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 to 95°C to obtain a molten mixture. While maintaining the temperature at 90 to 95°C, a dispersion treatment was performed for 20 minutes using an ultrasonic homogenizer "US-600T" (manufactured by Nippon Seiki Seisakusho Co., Ltd.), and the mixture was cooled to room temperature. Deionized water was added to the obtained dispersion to adjust the solid content concentration to 20% by mass, and a release agent particle dispersion was obtained. The volume median particle diameter (D 50 ) was 0.22 μm and the CV value was 27%.

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

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

[0123] [Toner Production] In a 3-liter four-neck flask equipped with a dehydration tube, a stirrer, and a thermocouple, 500 g of resin particle dispersion, 14 g of release agent particle dispersion, 3 g of charge control agent particle dispersion, 26 g of colorant particle dispersion, and 10 g of a 10% by mass aqueous solution of polyoxyethylene (50) lauryl ether "EMULGEN 150" (Kao Corporation, nonionic surfactant) were mixed at a temperature of 25° C. Next, while stirring the mixture, a solution obtained 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 then raised to 65° C. over 2 hours to measure the volume median particle diameter (D 50 The temperature was maintained at 65° C. until the particle diameter reached 8.8 μm, to obtain a dispersion of aggregated particles.

[0124] To the obtained dispersion of aggregated particles, an aqueous solution prepared by mixing 18 g of sodium polyoxyethylene lauryl ether 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 was added. After that, the temperature was raised to 90°C over one hour, and the temperature was maintained at 90°C until the circularity reached 0.99, thereby obtaining a dispersion of fused particles in which the aggregated particles were fused together.

[0125] The obtained fused particle dispersion liquid was cooled to 30°C, and the dispersion liquid was subjected to suction filtration to separate the solid content, which was then washed with deionized water at 25°C and suction filtrated at 25°C for 2 hours. Thereafter, the solid content was vacuum dried at 33°C for 24 hours using a vacuum constant temperature dryer "DRV622DA" (manufactured by ADVANTEC Corporation) to obtain toner base particles. The volume median particle diameter (D 50 ) was 8.5 μm.

[0126] 100 parts by mass of the obtained toner base particles and the silica particles shown in Table 3 were mixed for 3 minutes at 2100 r / min (circumferential speed 29 m / sec) using a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) to obtain a toner.

[0127] Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that the classified toner product was not subjected to the spheronization treatment.

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

[0129] Test Example 2 [Image blurring under high temperature and humidity conditions] The toner was installed in a non-magnetic single-component developing device "OKI MICROLINE 5400" (manufactured by Oki Data Corporation), and an A4-sized solid black image was printed in a high-temperature, high-humidity environment (30°C, 90%). Next, 500 sheets were printed at a print rate of 1%, and then another A4-sized solid black image was printed. J paper (manufactured by Fuji Xerox) was used as the printing medium. The image density (ID1) of the initial solid black image at a center portion 5 cm from the bottom and the image density (ID2) of the center portion 5 cm from the bottom after 500 sheets were printed were measured using a reflection densitometer "RD-915" (manufactured by Gretag Macbeth Co., Ltd.) to confirm the difference in image density between the two. If the difference in image density did not exceed 0.4, another 500 sheets were printed, and printing was continued until the difference in image density exceeded 0.4. The results are shown in Table 3. The greater the number of printed sheets, the greater the effect of suppressing image blurring.

[0130] [Table 3]

[0131] From the above results, it is understood 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, in which the circularity of the toner base particles is low, the transferability is low, so that the image density is low and image blurring occurs. In Comparative Example 2, in which the shape index of the large particle size silica is small, the large particle size silica is easily detached, so that image blurring occurs. In Comparative Example 3, in which small particle size silica is not used, the charging property is low, so that the image density is low from the beginning and image blurring occurs. In Comparative Example 4, in which large particle size silica is not used, the durability is low and image blurring occurs. [Industrial Applicability]

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

Claims

1. An electrostatic charge image developing toner containing toner mother particles having a circularity of 0.950 or more and 0.995 or less and containing a binding resin and a colorant, and 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 conversion particle diameter to the number average particle diameter is 2.0 or more, and the shape index of the silica particles B is less than 2.

0.

2. The toner for electrostatic charge image development according to claim 1, wherein the mass ratio of silica particles A to silica particles B is 1 / 1 or more and 3 / 1 or less.

3. The toner for electrostatic charge image development according to claim 1, wherein the number average particle diameter of silica particles A is 80 nm or more and 130 nm or less.

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

5. A method for manufacturing an electrostatic charge image developing toner, comprising a step of mixing toner mother particles containing a binder resin and a colorant and having a circularity of 0.950 or more and 0.995 or less, and 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 to the BET conversion particle diameter of 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. A method for manufacturing an electrostatic charge image developing toner.

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