JP7757136B2 - Toner manufacturing method - Google Patents

Description

The present invention relates to a toner used in an electrophotographic image forming method.

In recent years, electrophotographic full-color copiers have become widely used and are beginning to be applied to the printing market. The printing market is now demanding high speed, high image quality, and high productivity while supporting a wide range of media (paper types). For example, even when the paper type is changed from thick paper to thin paper, there is a demand for media-constant speed capability, meaning that printing can continue without changing the process speed or fuser heating temperature setting to match the paper type.

From the perspective of media uniformity, toner is required to complete fixing properly over a wide range of fixing temperatures, from low to high. For example, toners that combine low-temperature fixing properties with hot offset resistance have been proposed, in which calcium carbonate is added to toner particles and utilizes the internal cohesion of calcium carbonate (Patent Documents 1 to 4).

Patent No. 06535988 Patent No. 06089726 JP 2016-114828 A Japanese Patent Application Publication No. 08-339095

Even if low-temperature fixability is improved and the image density is fixed at 100%, toner transfer due to rubbing may occur in areas with low image density (hereinafter referred to as "abrasion resistance"). In some cases, a simple improvement in low-temperature fixability alone is not enough to improve abrasion resistance. Furthermore, there is room for further consideration of abrasion resistance from the perspective of achieving higher image quality.

The object of the present invention is to provide a toner that solves the above problems and improves abrasion resistance.

The present invention relates to a toner having toner particles containing a binder resin and calcium carbonate particles, characterized in that, in X-ray diffraction measurement of the toner particles using CuKα radiation where θ is the Bragg angle, the calcium carbonate particles (i) have peaks at 2θ = 26.5° ± 0.5° and 29.5° ± 0.5°, (ii) the crystallite diameter of the crystals at 2θ = 29.5° ± 0.5° is 10 nm or more and 45 nm or less, and (iii) the ratio (a/b) of the peak intensity "a" at 2θ = 26.5° ± 0.5° to the peak intensity "b" at 2θ = 29.5° ± 0.5° is 0.15 or more and 0.24 or less.

The present invention makes it possible to provide a toner that has improved low-temperature fixability and excellent abrasion resistance for images.

The following describes in detail the preferred toner configurations for the present invention. Numerical ranges such as "XX or more and YY or less" and "XX to YY" refer to a range of values including the lower and upper limits, unless otherwise specified.

The toner of the present invention comprises toner particles containing a binder resin and calcium carbonate particles, and is characterized in that, in X-ray diffraction measurement of the toner particles using CuKα radiation where θ is the Bragg angle, the calcium carbonate particles (i) have peaks at 2θ = 26.5° ± 0.5° and 29.5° ± 0.5°, (ii) the crystallite diameter of the crystals at 2θ = 29.5° ± 0.5° is 10 nm or more and 45 nm or less, and (iii) the ratio (a/b) of the peak intensity "a" at 2θ = 26.5° ± 0.5° to the peak intensity "b" at 2θ = 29.5° ± 0.5° is 0.15 or more and 0.24 or less.

By adopting this configuration, we were able to provide a toner that has improved low-temperature fixing properties while also providing excellent abrasion resistance to images.

The present inventors believe that the mechanism by which the toner having the characteristic structure of the present invention improves the abrasion resistance is as follows.
To improve abrasion resistance, it is important to create a state in which the toner is fixed without being destroyed when rubbed. Adding calcium carbonate increased the interaction with the binder resin, improving abrasion resistance, but this was still insufficient in some cases. Therefore, the inventors conducted further studies and succeeded in achieving both low-temperature fixability and abrasion resistance by further strengthening the interaction with the binder resin per calcium carbonate particle. Although the specific mechanism has not been established, it is presumed as follows.

Calcium carbonate contains two crystallite faces: the (104) and (112) faces. X-ray diffraction (XRD) shows a crystalline phase peak for the (112) face at 2θ = 26.5° ± 0.5°. X-ray diffraction (XRD) shows a crystalline phase peak for the (104) face at 2θ = 29.5° ± 0.5°.

When the flat (104) plane is crushed, the surface roughness becomes pronounced, and highly active structures called steps appear. Because steps have a strong interaction with organic molecules, it is thought that increasing the number of steps can strengthen the interaction with the binder resin per calcium carbonate particle. In other words, if the peak intensity at 2θ = 29.5° ± 0.5°, which indicates the amount of (104) planes, decreases compared to the peak intensity at 2θ = 26.5° ± 0.5°, which indicates the amount of (112) planes, this means that the (104) planes have been lost and the number of steps has increased. It is estimated that in this state, the interaction with the binder resin per calcium carbonate particle becomes stronger.

While any method can be used to increase the number of steps on the (104) plane of calcium carbonate, it is preferable to apply mechanical stress to the calcium carbonate to break it and expose the steps. Examples of such methods include ball milling and solvent milling. Of these, a more preferable method is to increase the number of steps on the (104) plane by melt-kneading calcium carbonate with a binder resin. In this case, it is important to add more calcium carbonate than is conventionally added to toner. This allows the steps on the (104) plane to interact with the binder resin. The manufacturing method will be described later.

Calcium carbonate particles must have a crystallite diameter of 10 nm or more and 45 nm or less for crystals attributable to 2θ = 29.5° ± 0.5°, as determined by X-ray diffraction measurement of toner particles using CuKα radiation. When the crystallite diameter is within this range, the number of steps on the (104) plane of calcium carbonate increases, resulting in stronger interactions between the steps on the (104) plane and the binder resin, leading to improved abrasion resistance. If the crystallite diameter of the crystals attributable to 2θ = 29.5° ± 0.5° is less than 10 nm, the crystallite diameter is too small and this value cannot be achieved with calcium carbonate. If the crystallite diameter of the crystals attributable to 2θ = 29.5° ± 0.5° is greater than 45 nm, the number of steps on the (104) plane decreases, preventing the effects of the present invention from being achieved. To further enhance the effects of the present invention, it is more preferable that the crystallite diameter be 20 nm or more and 40 nm or less.

In X-ray diffraction measurement of the toner particles using CuKα radiation, the calcium carbonate particles must have a ratio of the peak intensity of the crystals at 2θ = 26.5 ± 0.5 to the peak intensity of the crystals at 2θ = 29.5 ± 0.5 of 0.15 or more and 0.24 or less. This ratio refers to the ratio a/b, where "a" is the peak intensity of the crystals at 2θ = 26.5 ± 0.5 and "b" is the peak intensity of the crystals at 2θ = 29.5 ± 0.5. When the intensity ratio is within this range, the steps on the (104) plane of the calcium carbonate interact with the binder resin, leading to improved abrasion resistance.
The ratio of the peak intensities is more preferably 0.15 or more and 0.20 or less.

Preferred material configurations are described below.
<Calcium carbonate particles>
It is important that the toner particles of the present invention contain calcium carbonate particles. The interaction between the (104) plane steps of calcium carbonate and the binder resin increases the toner cohesion force, allowing the toner to maintain a fixed state even when a small amount of calcium carbonate is used. This makes it possible to achieve both low-temperature fixability and abrasion resistance. Calcium carbonate is necessary because the (104) plane steps are necessary.

As for calcium carbonate, various conventionally known calcium carbonates can be used. Examples include light calcium carbonate, colloidal calcium carbonate, and heavy calcium carbonate.

In a cross section of the toner observed with a transmission electron microscope, the number-average particle size of the calcium carbonate particles is preferably 0.1 μm or more and 5.0 μm or less. When the particle size of the calcium carbonate particles is within this range, the interaction between the steps of the (104) plane and the binder resin increases the cohesive force, improving abrasion resistance. It is even more preferable that the particle size of the calcium carbonate particles is 0.2 μm or more and 0.7 μm or less.

In the cross section of the toner observed with a transmission electron microscope, the average aspect ratio (major axis/minor axis) of the calcium carbonate particles is preferably 1.5 or more and 6.0 or less. When the average aspect ratio (major axis/minor axis) of the calcium carbonate particles is within this range, the interaction between the steps of the (104) plane of the calcium carbonate and the binder resin increases the cohesive force, improving abrasion resistance. It is more preferable that the average aspect ratio (major axis/minor axis) of the calcium carbonate particles is 2.0 or more and 2.5 or less.

The content of calcium carbonate particles in the toner particles is preferably 3.0% by mass or more and 40% by mass or less. When the content of calcium carbonate particles in the toner particles is within this range, the interaction between the steps of the (104) plane of the calcium carbonate and the binder resin can be effectively expressed, improving abrasion resistance. It is more preferable that the content of calcium carbonate particles in the toner particles be 10 to 33% by mass.

<Binder resin>
The toner particles of the present invention contain a binder resin. As the binder resin, known polymers can be used, and specifically, for example, the following polymers can be used.

Homopolymers of styrene and its substituted derivatives, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, and styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenolic resin, natural resin-modified phenolic resin, natural resin-modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane resin, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone-indene resin, and petroleum-based resin. These resins may be used alone or in combination of two or more. Among these, amorphous polyester resins are preferred from the standpoint of abrasion resistance, as they readily interact with the steps on the (104) plane of calcium carbonate.

The binder resin may contain a crystalline polyester resin. Crystalline polyester resins readily interact with the (104) plane steps of calcium carbonate and are therefore preferred from the standpoint of abrasion resistance. The crystalline polyester resin is preferably a condensation polymer of an alcohol containing an aliphatic diol having 2 to 23 carbon atoms and a carboxylic acid containing an aliphatic dicarboxylic acid having 3 to 24 carbon atoms.

The crystalline polyester resin is more preferably a condensation polymer of an alcohol containing 80 mol% to 100 mol% (more preferably 85 mol% to 100 mol%) of an aliphatic diol having 4 to 12 carbon atoms, based on the total alcohol content of the crystalline polyester resin, and 80 mol% to 100 mol% (more preferably 85 mol% to 100 mol%) of an aliphatic dicarboxylic acid having 4 to 20 carbon atoms, based on the total carboxylic acid content of the crystalline polyester resin.

The aliphatic diol is preferably a straight-chain aliphatic diol, such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, or a derivative thereof. The derivative is not particularly limited as long as it can be obtained with a similar resin structure by condensation polymerization. For example, a derivative obtained by esterifying the diol can be used.

The aliphatic dicarboxylic acid is preferably a straight-chain aliphatic dicarboxylic acid, such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, hexadecanedioic acid, eicosanedioic acid, or derivatives thereof. The derivative is not particularly limited as long as it can be obtained with a similar resin structure by condensation polymerization. Examples include acid anhydrides of the dicarboxylic acids, and derivatives in which the dicarboxylic acid component is alkyl esterified or acid chlorideized.

On the other hand, the carboxylic acid may also be used in combination with a carboxylic acid other than the aliphatic dicarboxylic acid.

The content of the crystalline polyester resin is preferably 0.1 to 5.0% by mass, and more preferably 1.0 to 4.0% by mass, relative to the toner particles. When the content of the crystalline polyester resin is within this range, interaction with the (104) plane steps of calcium carbonate can be effectively expressed, contributing to improved abrasion resistance.

<Coloring Agent>
The toner particles may contain a colorant, such as a known organic pigment or oil-based dye, carbon black, or a magnetic material.

Cyan colorants include copper phthalocyanine compounds and their derivatives, anthraquinone compounds, and basic dye lake compounds. Specific examples include C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.

Magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specific examples include C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254, and C.I. Pigment Violet 19.

Yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specific examples include C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 191, and 194.

Black colorants include carbon black, magnetic materials, or those toned to black using the above-mentioned yellow colorants, magenta colorants, and cyan colorants. These colorants can be used alone or in combination. They can also be used in the form of a solid solution.

The colorant may be selected from the viewpoints of hue angle, saturation, brightness, light resistance, transparency on an OHP sheet, and dispersibility in toner particles.
The content of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

<Release Agent>
The toner particles may contain a release agent. Examples of the release agent include low-molecular-weight polyolefins such as polyethylene; silicones having a melting point; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, and stearic acid amide; ester waxes such as stearyl stearate; vegetable waxes such as carnauba wax, rice wax, candelilla wax, Japan wax, and jojoba oil; animal waxes such as beeswax; mineral and petroleum waxes such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, and ester wax; and modified products thereof.
The release agents may be used alone or in combination of two or more.

The melting point of the release agent is preferably 150°C or lower, more preferably 40°C or higher and 130°C or lower, and even more preferably 40°C or higher and 110°C or lower.
The content of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

<Manufacturing method>
The procedure for producing the toner of the present invention will be described.
The method for producing the toner is not particularly limited, and known methods such as emulsion aggregation, pulverization, and suspension polymerization can be used.
The method for producing a toner of the present invention is characterized by comprising: Step 1: melt-kneading a first mixture containing a part of a binder resin and calcium carbonate particles in a twin-screw extruder to obtain a molten mixture; and Step 2: melt-kneading a second mixture containing the molten mixture and the remaining binder resin.
Specifically, the toner production method of the present invention is preferably a toner production method including the following steps 1 and 2.

<Step 1>
Step 1 is a step of increasing the number of steps on the (104) plane of calcium carbonate.
In the raw material mixing step, predetermined amounts of binder resin, calcium carbonate, colorant particles, etc. are weighed, blended, and mixed. The mixing device is not particularly limited, but examples include a Henschel mixer (manufactured by Nippon Coke Company), a Supermixer (manufactured by Kawata Corporation), a Ribocone (manufactured by Okawara Manufacturing Co., Ltd.), a Nauta mixer, a Turbulizer, and a Cyclomix (manufactured by Hosokawa Micron Corporation), a Spiral Pin Mixer (manufactured by Pacific Machinery Works, Ltd.), and a Loedige mixer (manufactured by Matsubo Corporation). The mixture mixed using this mixing device is referred to as the first mixture.

Next, the first mixture is melt-kneaded in a twin-screw extruder. During this process, the calcium carbonate particles are rubbed against each other or against other materials, such as colorant particles, to reduce the (104) faces of the calcium carbonate particles and increase the number of steps (active surfaces). In addition, high shear force is required to further increase the number of steps. For this reason, high viscosity is required in step 1. This creates an interaction between the steps and the binder resin. Here, the melt-kneaded product produced in step 1 is defined as a "calcium carbonate particle dispersion."

When the content of the binder resin is Mr (mass%) and the content of the calcium carbonate particles is Mi (mass%) based on the mass of the first mixture in step 1, the Mr and Mi satisfy the following conditions:
15≦Mr≦75
0.17≦Mi/Mr≦1.3
This is because, when the ratio is in the above range, the number of (104) faces of the calcium carbonate particles can be reduced and the number of steps (active faces) can be increased by rubbing calcium carbonate particles against each other or rubbing calcium carbonate particles against pigment particles.

The melt-kneading device is not particularly limited, but examples include batch kneaders such as pressure kneaders and Banbury mixers, TEM extruders (manufactured by Toshiba Machine Co., Ltd.), TEX twin-screw kneaders (manufactured by The Japan Steel Works, Ltd.), PCM kneaders (manufactured by Ikegai Iron Works Co., Ltd.), and Kneedex (manufactured by Mitsui Mining Co., Ltd.). Continuous kneaders such as single-screw or twin-screw extruders are preferred over batch kneaders due to their advantages, such as continuous production. Additionally, the peripheral speed of the outer end of the kneading shaft is preferably 78 mm/s or higher. The peripheral speed is defined as the distance traveled per second by a point on the outer end of the kneading shaft of the extruder. The peripheral speed is calculated by multiplying the shaft diameter (mm) by the circumference of the shaft by the number of revolutions (rpm)/60. A peripheral speed within the above range reduces the number of (104) faces of the calcium carbonate particles and increases the number of steps (active surfaces).

The calcium carbonate particle dispersion obtained by melt-kneading is then rolled using a two-roll mill or the like, and cooled through a cooling process using water or the like.

The cooled calcium carbonate particle dispersion obtained above is then pulverized to the desired particle size in a pulverization process. In the pulverization process, the calcium carbonate particle dispersion is first coarsely pulverized using a crusher, hammer mill, feather mill, etc., and then finely pulverized using a Kryptron System (manufactured by Kawasaki Heavy Industries, Ltd.) or a Super Rotor (manufactured by Nisshin Engineering, Inc.), etc., to obtain calcium carbonate particle dispersion microparticles. These calcium carbonate particle dispersion microparticles are used as the second mixture.

<Step 2>
Step 2 is a step of obtaining a toner using the second mixture obtained in step 1.
In the raw material mixing step, predetermined amounts of the second mixture, binder resin, hydrocarbon wax, and the like are weighed and blended as toner raw materials. The mixing device is not particularly limited, but examples thereof include a Henschel mixer (manufactured by Nippon Coke Company), a Supermixer (manufactured by Kawata Corporation), a Ribocone (manufactured by Okawara Manufacturing Co., Ltd.), a Nauta mixer, a Turbulizer, and a Cyclomix (manufactured by Hosokawa Micron Corporation), a Spiral Pin Mixer (manufactured by Pacific Machinery Works, Inc.), and a Lödige mixer (manufactured by Matsubo Corporation). In step 2, the content of the remaining binder resin added additionally is preferably 30% by mass or more and 75% by mass or less, based on the mass of the second mixture. When the content is within this range, the calcium carbonate, which has many steps and is contained in the second mixture, interacts appropriately with the binder resin, improving abrasion resistance.

Next, the toner raw materials including the second mixture are melt-kneaded in a twin-screw extruder. In the melt-kneading process, a batch-type kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used, but a single-screw or twin-screw extruder is preferred due to its advantage of allowing for continuous production. The melt-kneading temperature is preferably around 100 to 200°C.

<Crushing process>
The pulverization step is a step in which the kneaded product obtained after steps 1 and 2 is cooled to a pulverizable hardness, and then mechanically pulverized to a toner particle size using a known pulverizer such as an impact plate jet mill, a fluidized bed jet mill, or a rotary mechanical mill. From the viewpoint of pulverization efficiency, it is desirable to use a fluidized bed jet mill as the pulverizer.
Examples of pulverizers include counter jet mills, micron jet mills, and inomizers (manufactured by Hosokawa Micron Corporation); IDS type mills and PJM jet pulverizers (manufactured by Nippon Pneumatic Mfg. Co., Ltd.); cross jet mills (manufactured by Kurimoto Iron Works); Urmax (manufactured by Nisso Engineering Co., Ltd.); SK Jet O Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.); and Super Rotor (manufactured by Nisshin Engineering Co., Ltd.).

<Classification process>
The classification step is a step in which the finely pulverized product obtained in the pulverization step is classified to obtain toner particles having a desired particle size distribution.
As a classifier used for classification, known devices such as an air classifier, an inertial classifier, a sieve classifier, etc. Specific examples include Cruseal, Micron Classifier, and Spedic Classifier (manufactured by Seishin Enterprise Co., Ltd.), Turbo Classifier (manufactured by Nisshin Engineering Inc.), Micron Separator, Turboflex (ATP), and TSP Separator (manufactured by Hosokawa Micron Corporation), Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and YM Microcut (manufactured by Yaskawa Corporation).

If necessary, inorganic fine particles such as silica, alumina, titania, etc., or resin fine particles such as vinyl resin, polyester resin, or silicone resin may be added to the toner particles produced through the above process by applying shear force in a dry state. These inorganic fine particles and resin fine particles function as external additives such as flow aids and cleaning aids.

The weight average particle size of the toner of the present invention is preferably 3.0 μm or more and 20.0 μm or less, and more preferably 4.0 μm or more and 10.0 μm or less.

The present invention will be described in more detail below using examples and comparative examples, but these do not limit the present invention in any way. Note that when simply referring to "parts", it means "parts by mass".
Various physical properties related to the present invention were measured by the following methods.

<Method for separating toner particles from toner>
A sucrose concentrate solution was prepared by adding 160 g of sucrose (Kishida Chemical) to 100 mL of ion-exchanged water and dissolving it in a hot water bath. A centrifuge tube was charged with 31 g of the sucrose concentrate and 6 mL of Contaminon N (a 10% by weight aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a dispersion. 1.0 g of toner was added to the dispersion, and toner clumps were broken up using a spatula or similar. The centrifuge tube was then shaken in a shaker. After shaking, the solution was transferred to a 50 mL glass tube for a swing-out rotor and centrifuged at 3,500 rpm for 30 minutes.
This operation separates the toner particles from the removed external additives. After visually confirming that the toner particles and the aqueous solution have been sufficiently separated, the toner particles are collected and filtered using a vacuum filter, and then dried in a dryer for at least one hour to obtain toner particles from which the external additives have been separated (filtrate 1).

<Method for measuring calcium carbonate content>
Filtrate 1 is immersed in 0.1 mol/L hydrochloric acid, treated with ultrasound for 10 minutes, and then left to stand for 3 hours. The resulting solution is filtered to obtain Filtrate 2. Since calcium carbonate reacts with and dissolves in hydrochloric acid, the calcium carbonate content Mc is determined by measuring the mass difference between Filtrate 2 and Filtrate 1.

<Method for measuring the aspect ratio of calcium carbonate particles>
Cross-sectional observation of the toner with a scanning electron microscope and evaluation of the aspect ratio of calcium carbonate particles can be carried out by cross-sectional observation as follows.
By observing the cross section of the toner, calcium carbonate particles are observed as a clear contrast.
The cross section of a toner particle can be prepared by placing the toner particles on carbon tape, sputtering PtPd for 60 seconds, and scraping it off with argon ion beam irradiation. The cross section image of the toner particle is obtained by backscattered electron imaging using a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation). The calcium carbonate particles in the cross section image of the toner particle are identified using an energy dispersive X-ray spectrometer (EDAX) or the like.
The aspect ratio of calcium carbonate particles is defined as the ratio of the major axis to the minor axis of the calcium carbonate particles. The major axis of calcium carbonate particles can be measured as the length in the longitudinal direction (the length of the long side) when the calcium carbonate particles are regarded as cubes. The minor axis of calcium carbonate particles can be measured as the length in the lateral direction (the length of the short side) when the calcium carbonate particles are regarded as rectangles. The aspect ratio is measured for 100 calcium carbonate particles, and the average value is taken as the aspect ratio.

<Method for measuring weight average particle size (D4) of toner particles>
The weight average particle size (D4) of the toner particles is measured using a precision particle size distribution measuring device equipped with a 50 μm aperture tube and using an electrical resistivity method, such as a Coulter Counter Multisizer 3 (registered trademark, manufactured by Beckman Coulter, Inc.), and the accompanying dedicated software for setting measurement conditions and analyzing measurement data, such as a Beckman Coulter Multisizer 3 Version 3.51 (manufactured by Beckman Coulter, Inc.), with an effective number of measurement channels of 25,000, and the measurement data is analyzed and calculated.
The aqueous electrolyte solution used for the measurement is prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of about 1 mass %, for example, "ISOTON II" (manufactured by Beckman Coulter).

Before carrying out the measurements and analysis, the dedicated software is set up as follows.
On the "Change Standard Measurement Method (SOM) screen" of the dedicated software, the total count number in control mode is set to 50,000 particles, the number of measurements is set to 1, and the Kd value is set to the value obtained using "Standard Particles 10.0 μm" (manufactured by Beckman Coulter). The threshold and noise level are automatically set by pressing the threshold/noise level measurement button. Also, the current is set to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and the aperture tube flush after measurement is checked.
In the dedicated software's "Pulse to particle size conversion setting screen," set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range to 1 μm or more and 30 μm or less.

The specific measurement method is as follows.
(1) Approximately 200 ml of the electrolyte solution is placed in a 250 ml round-bottom glass beaker designed specifically for the Multisizer 3, and the beaker is set on the sample stand. The stirrer rod is stirred counterclockwise at 24 revolutions per second. Then, the "aperture flush" function of the analysis software is used to remove any dirt or air bubbles from inside the aperture tube.

(2) Approximately 30 ml of the aqueous electrolyte solution is placed in a 100 ml flat-bottom glass beaker, and approximately 0.3 ml of a dilution of "Contaminon N" (a 10% aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted three times by mass with ion-exchanged water is added as a dispersant.

(3) A predetermined amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser, "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.), which has two built-in oscillators with an oscillation frequency of 50 kHz and an electrical output of 120 W, with a phase difference of 180 degrees, and approximately 2 ml of the Contaminon N is added to this water tank.

(4) Place the beaker from (2) into the beaker fixing hole of the ultrasonic disperser and operate the ultrasonic disperser. Then, adjust the height of the beaker so that the resonance state of the electrolyte solution surface in the beaker is maximized.

(5) While ultrasonic waves are being applied to the aqueous electrolyte solution in the beaker from step (4), approximately 10 mg of toner is added in small amounts to the aqueous electrolyte solution and dispersed. The ultrasonic dispersion process is then continued for an additional 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to be between 10°C and 40°C.

(6) Using a pipette, add the aqueous electrolyte solution (5) containing dispersed toner to the round-bottom beaker (1) placed in the sample stand, and adjust the measurement concentration to approximately 5%. Then, continue measuring until the number of particles measured reaches 50,000.

(7) The measurement data is analyzed using the dedicated software provided with the device to calculate the weight average particle size (D4). Note that when the dedicated software is set to Graph/Weight %, the "Average Diameter" on the Analysis/Weight Statistics (Arithmetic Mean) screen is the weight average particle size (D4).

<X-ray diffraction measurement method>
The X-ray diffraction measurement is carried out using a measurement device "RINT-TTRII" (manufactured by Rigaku Corporation) and control software and analysis software that come with the device.
The measurement conditions are as follows.
X-ray: Cu/50kV/300mA
Goniometer: Rotor horizontal goniometer (TTR-2)
Attachment: Standard sample holder Divergence slit: Open Divergence vertical limit slit: 10.00 mm
Scattering slit: open Receiving slit: open Counter: scintillation counter Scanning mode: continuous Scanning speed: 4.0000°/min.
Sampling width: 0.0200°
Scanning axis: 2θ/θ
Scanning range: 10.0000° to 40.0000°
Next, the toner particles are placed on the sample plate and the measurement is started.
For CuKα characteristic X-rays, an X-ray diffraction spectrum is obtained with the Bragg angle θ and the diffraction angle 2θ in the range of 3° to 35°, with the diffraction angle 2θ on the horizontal axis and the X-ray intensity on the vertical axis.

<Preparation of calcium carbonate particles>
Details of the calcium carbonate used in the examples and comparative examples are shown in Table 1. The aspect ratios and major diameters shown in Table 1 were determined from images of calcium carbonate particles alone as raw materials observed with a transmission electron microscope.

<Production Example of Crushed Calcium Carbonate Particles 7>
Diethylene glycol (DEG) and sodium chloride were kneaded at 40°C in a planetary kneader (TX-15, manufactured by Inoue Seisakusho Co., Ltd.). The kneaded mixture was charged into a mixing vessel with a stirrer containing calcium carbonate particles 7 shown in Table 1 above, and ion-exchanged water was added and stirred to dissolve the diethylene glycol and sodium chloride in the water. The solid content was filtered out, thoroughly washed with ion-exchanged water, and then vacuum-dried at 40°C for 24 hours to obtain crushed calcium carbonate particles 7. Details of the obtained crushed calcium carbonate particles are shown in Table 2. The aspect ratios and major axes shown in Table 2 were determined from images of calcium carbonate particles alone observed with a transmission electron microscope.
In the production of toner 20, the crushed calcium carbonate particles 7 were used.

<Production Example of Calcium Carbonate Particle Dispersion 1>
Pigment 30.4 parts by mass (cyan pigment: Pigment Blue 15:3, weight average particle size 102 nm)
Calcium carbonate particles 1 (C1) 21.6 parts by mass (light calcium carbonate Socal P3, number average particle size 0.4 μm)
Binder resin: 48.0 parts by mass (amorphous polyester A1: composition (molar basis) [polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane:isophthalic acid:terephthalic acid=100:50:50], softening temperature (Tm)=122°C, glass transition temperature (Tg)=70°C, SP value=22.6 (J/cm ³ ) ^0.5 )
The above materials were mixed using a Henschel mixer (FM-75, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of ²⁰ s for a rotation time of 5 min, and then kneaded at 120°C in a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation) (Step 1). The resulting kneaded mixture was cooled and coarsely pulverized in a pin mill to a weight average particle size of 100 μm or less, yielding a coarsely pulverized product of Pigment Dispersion 1. The melt viscosity of Amorphous Polyester A1 at 120°C was 2080 Pa sec. The number average particle size of the pigment in the resulting pigment dispersion was 55 nm.

<Production Examples of Calcium Carbonate Particle Dispersions 2 to 13 and 15 to 29>
Coarsely crushed calcium carbonate particle dispersions 2 to 13 and 15 to 29 were obtained in the same manner as in Production Example 1 of Calcium Carbonate Particle Dispersion 1, except that the blending ratios of the binder resin, calcium carbonate particles, and pigment were adjusted as shown in Table 3. In Table 3, Mr is the blending ratio of the binder resin, Mi is the blending ratio of the calcium carbonate particles, and Mp is the blending ratio of the pigment particles.

<Production Example of Calcium Carbonate Particle Dispersion 14>
The blending ratio of the binder resin, calcium carbonate particles, and pigment was the same as that of Calcium Carbonate Particle Dispersion 1. These materials were kneaded at 150°C using a planetary kneader (TX-15, manufactured by Inoue Seisakusho Co., Ltd.). The resulting kneaded product was cooled and coarsely pulverized using a pin mill to have a weight average particle size of 100 μm or less, thereby obtaining a coarsely pulverized product of Calcium Carbonate Particle Dispersion 14.

<Production Example of Toner 1>
Amorphous polyester A1: 80.0 parts by mass (composition (molar basis) [polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane:isophthalic acid:terephthalic acid=100:50:50], softening temperature (Tm)=122°C, glass transition temperature (Tg)=70°C, SP value=22.6 (J/cm ³ ) ^0.5 )
Calcium carbonate particle dispersion 1: 11.5 parts by mass Synthetic wax: 8.0 parts by mass (hydrocarbon wax, maximum endothermic peak temperature: 90°C)
The above materials were mixed using a Henschel mixer (FM-75, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 ^s for a rotation time of 5 min, and then kneaded using a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation) (Step 2). The resulting kneaded mixture was cooled and coarsely pulverized using a pin mill to obtain a coarsely pulverized product having a weight average particle size of 100 μm or less. The resulting coarsely pulverized product was then finely pulverized using a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.) by adjusting the rotation speed and number of passes to obtain the target particle size. Further, classification was performed using a rotary classifier (200TSP, manufactured by Hosokawa Micron Corporation) to obtain toner particles. The rotation speed of the rotary classifier (200TSP, manufactured by Hosokawa Micron Corporation) was adjusted to obtain the target particle size and particle size distribution, and classification was performed. To 100 parts by mass of the obtained toner particles, 1.8 parts by mass of silica fine particles having a specific surface area of 200 m ² /g measured by the BET method and hydrophobized with silicone oil were added, and mixed in a Henschel mixer (FM-75 model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 30 s ⁻¹ for a rotation time of 10 minutes to obtain Toner 1. The weight average particle diameter (D4) of the toner was 6.5 μm.

<Production Examples of Toners 2 to 19, 21 to 24, Comparative Toner 2, and Comparative Toners 4 and 5>
Toners 2 to 19, toners 21 to 24, comparative toner 2, and comparative toners 4 and 5 were obtained in the same manner as in the production example of toner 1, except that the conditions for the binder resin, crystalline polyester, and calcium carbonate particles were changed as shown in Table 4.

<Production Example of Toner 20>
Amorphous polyester A1 82.8 parts by mass (composition (molar basis) [polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane:isophthalic acid:terephthalic acid=100:50:50], softening temperature (Tm)=122°C, glass transition temperature (Tg)=70°C, SP value=22.6 (J/cm ³ ) ^0.5 )
Crushed calcium carbonate particles C7 4.31 parts by mass Crystalline polyester 0.50 parts by mass Synthetic wax i 8.0 parts by mass (hydrocarbon wax, maximum endothermic peak temperature 90°C)
The above materials were mixed using a Henschel mixer (FM-75, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 ^s for a rotation time of 5 min, and then kneaded using a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation). The resulting kneaded mixture was cooled and coarsely pulverized using a pin mill to obtain a coarsely pulverized product having a weight average particle size of 100 μm or less. The resulting coarsely pulverized product was then finely pulverized using a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.) by adjusting the rotation speed and number of passes to obtain the target particle size. Further, classification was performed using a rotary classifier (200TSP, manufactured by Hosokawa Micron Corporation) to obtain toner particles. The operating conditions of the rotary classifier (200TSP, manufactured by Hosokawa Micron Corporation) were such that the rotation speed was adjusted to obtain the target particle size and particle size distribution, and classification was performed. To 100 parts by mass of the obtained toner particles, 1.8 parts by mass of silica fine particles having a specific surface area of 200 m ² /g measured by the BET method and hydrophobized with silicone oil were added, and mixed in a Henschel mixer (FM-75 model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 30 s ⁻¹ for a rotation time of 10 minutes to obtain toner 20.

<Production Examples of Comparative Toner 1 and Comparative Toner 3>
Comparative toners 1 and 3 were obtained in the same manner as in the production example of toner 20, except that the conditions for the binder resin, crystalline polyester, and calcium carbonate particles added in the production example of toner 20 were changed as shown in Table 4.
The crystallinity of calcium carbonate particles was evaluated in Toners 1 to 24 and Comparative Toners 1 to 5. The results of the toner analysis are shown in Table 5.

<Production Example of Magnetic Core Particle 1>
Step 1 (weighing and mixing step):
The ferrite raw materials were weighed so as to have the above composition ratio: _{Fe2O3 62.7} parts, MnCO3 _29.5 parts, Mg(OH) ₂ 6.8 parts, _SrCO3 1.0 part. Then, the materials were pulverized and mixed for 5 hours in a dry vibration mill using stainless steel beads with a diameter of 1/8 inch.

Step 2 (pre-firing step):
The resulting pulverized material was made into pellets of approximately 1 mm square using a roller compactor. The pellets were passed through a vibrating sieve with 3 mm openings to remove coarse particles, and then through a vibrating sieve with 0.5 mm openings to remove fine particles. The pellets were then fired in a burner-type firing furnace at 1000°C for 4 hours in a nitrogen atmosphere (oxygen concentration 0.01% by volume) to produce calcined ferrite. The composition of the resulting calcined ferrite was as follows:
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.257, b = 0.117, c = 0.007, d = 0.393

Step 3 (pulverization step):
The obtained calcined ferrite was crushed to about 0.3 mm using a crusher, and then 30 parts of water was added to 100 parts of the calcined ferrite and crushed in a wet ball mill using zirconia beads with a diameter of 1/8 inch for 1 hour. The obtained slurry was crushed in a wet ball mill using alumina beads with a diameter of 1/16 inch for 4 hours to obtain a ferrite slurry (finely crushed calcined ferrite).

・Process 4 (granulation process):
To the ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 2.0 parts of polyvinyl alcohol as a binder were added per 100 parts of the calcined ferrite, and the mixture was granulated into spherical particles using a spray dryer (manufactured by Okawahara Kakoki Co., Ltd.). After adjusting the particle size of the resulting particles, the mixture was heated in a rotary kiln at 650°C for 2 hours to remove the organic components of the dispersant and binder.

Step 5 (firing step):
In order to control the firing atmosphere, the sample was heated from room temperature to 1300°C in a nitrogen atmosphere (oxygen concentration 1.00% by volume) in an electric furnace over a period of 2 hours, and then fired at 1150°C for 4 hours. The temperature was then lowered to 60°C over a period of 4 hours, the nitrogen atmosphere was returned to the air, and the sample was removed at a temperature of 40°C or below.

Step 6 (sorting step):
After crushing the agglomerated particles, low magnetic particles were removed by magnetic separation, and coarse particles were removed by sieving through a sieve with a mesh size of 250 μm to obtain magnetic core particles 1 having a volume distribution-based 50% particle size (D50) of 37.0 μm.

<Preparation of Coating Resin 1>
Cyclohexyl methacrylate monomer 26.8% by mass
Methyl methacrylate monomer 0.2% by mass
Methyl methacrylate macromonomer 8.4% by mass
(a macromonomer having a methacryloyl group at one end and a weight average molecular weight of 5,000)
Toluene 31.3% by mass
Methyl ethyl ketone 31.3% by mass
Azobisisobutyronitrile 2.0% by mass
Of the above materials, cyclohexyl methacrylate monomer, methyl methacrylate monomer, methyl methacrylate macromonomer, toluene, and methyl ethyl ketone were placed in a four-neck separable flask equipped with a reflux condenser, thermometer, nitrogen inlet tube, and stirrer, and nitrogen gas was introduced to create a sufficient nitrogen atmosphere. The mixture was then heated to 80°C, azobisisobutyronitrile was added, and the mixture was refluxed for 5 hours to polymerize. Hexane was poured into the resulting reaction mixture to precipitate the copolymer. The precipitate was then filtered and vacuum dried to obtain Coating Resin 1.

<Preparation of Coating Resin Solution 1>
33.3 mass% of polymer solution 1 (resin solids concentration 30%) prepared by dissolving 30 parts of coating resin 1 in 40 parts of toluene and 30 parts of methyl ethyl ketone,
Toluene 66.4% by mass, and Carbon black Regal 330 (manufactured by Cabot) 0.3% by mass
(Primary particle size 25 nm, nitrogen adsorption specific surface area 94 ^{m 2} /g, DBP oil absorption 75 mL/100 g)
The resulting dispersion was dispersed for 1 hour using zirconia beads having a diameter of 0.5 mm in a paint shaker. The resulting dispersion was filtered through a 5.0 μm membrane filter to obtain a coating resin solution 1.

<Production Example of Magnetic Carrier 1>
(Resin coating process):
Magnetic core particles 1 and coating resin solution 1 were added to a vacuum degassing kneader maintained at room temperature (the amount of coating resin solution 1 added was 2.5 parts as a resin component per 100 parts of magnetic core particles 1). After addition, the mixture was stirred at a rotation speed of 30 rpm for 15 minutes, and after a certain amount of the solvent (80 mass%) had volatilized, the mixture was heated to 80°C while mixing under reduced pressure, and the toluene was distilled off over 2 hours, after which the mixture was cooled. The obtained magnetic carrier was separated into low magnetic particles by magnetic separation, passed through a sieve with 70 μm openings, and then classified with an air classifier to obtain magnetic carrier 1 having a 50% particle size (D50) based on volume distribution of 38.2 μm.

<Production of Two-Component Developer 1>
To 92.0 parts of magnetic carrier 1, 8.0 parts of toner 1 were added and mixed in a V-type mixer (V-20, manufactured by Seishin Enterprises) to obtain two-component developer 1.

<Production of Two-Component Developers 2 to 24 and Comparative Two-Component Developers 1 to 5>
In the production example of two-component developer 1, the same operation was carried out except that the combinations were changed to toners 2 to 24 and comparative toners 1 to 5, to obtain two-component developers 2 to 24 and comparative two-component developers 1 to 5.
A modified Canon imageRUNNER ADVANCE C9075 PRO digital commercial printing printer was used as the image forming apparatus, and a two-component developer was placed in the developing unit for cyan. The DC voltage V _DC of the developer carrier, the charging voltage V _D of the electrostatic latent image carrier, and the laser power were adjusted so that the desired amount of toner was applied to the electrostatic latent image carrier or paper, and the evaluation described below was performed. The modifications included changing the fixing temperature and process speed so that they could be freely set.

Example 1
Using two-component developer 1, the abrasion resistance and low-temperature fixability were evaluated by the following methods.
<Test Example 1: Evaluation of Scratch Resistance>
Paper: OK Topcoat+, Oji Paper, 127 g/ ^m²
Evaluation image: Halftone image (image density: 0.20 or more and 0.25 or less)
The image density was measured using a Macbeth Reflection Densitometer RD918 (manufactured by Macbeth) in accordance with the attached instruction manual by measuring the relative density of the image in a white background area where the image density was 0.00, and the obtained relative density was taken as the image density value.
Paper (OK Top Coat+, manufactured by Oji Paper Co., Ltd., 127 g/ ^m² ) was placed on top of the image sample, and a 500 g weight was placed on top of it with a contact area of 12.6 ^cm² , and an abrasion resistance test was performed in which the paper was rubbed 10 times. After that, the toner adhering within the 12.6 ^cm² area of the paper (the area where the weight was placed) was measured with a fog meter, and the obtained fog value was evaluated according to the following criteria. The evaluation results are shown in Table 6.
[Evaluation criteria]
Rank A: Fog is 2% or less Rank B: Fog is 2% or more but less than 5% Rank C: Fog is 5% or more but less than 10% Rank D: Fog is 10% or more

<Test Example 2: Evaluation of low-temperature fixability>
Paper: CF-C104 (104.0g/m ² )
(Sold by Canon Marketing Japan Inc.)
Toner amount on paper: 0.90 mg/cm ²
Evaluation image: A 25 ^cm2 image was placed in the center of the A4 paper. Fixing test environment: Low temperature and low humidity environment: temperature 15°C/humidity 10% RH (hereinafter referred to as "L/L").
The DC voltage VDC of the developer carrier, the charging voltage VD of the electrostatic latent image carrier, and the laser power were adjusted so that the toner loading on the paper was as described above. The process speed was set to 300 mm/sec, the fixing temperature to 130°C, and the low-temperature fixability was evaluated. The image density reduction rate was used as an evaluation index for low-temperature fixability. The image density reduction rate was measured by first measuring the image density at the center using an X-Rite color reflection densitometer (500 series: manufactured by X-Rite). Next, the fixed image was rubbed (five times back and forth) with Silbon paper on the area where the image density was measured, with a load of 4.9 kPa (50 g/cm ² ), and the image density was measured again. The image density reduction rate (%) before and after rubbing was then measured. The evaluation results are shown in Table 6.
The evaluation criteria were as follows:
[Evaluation criteria]
Rank A: Density reduction rate less than 1.0% Rank B: Density reduction rate 1.0% or more and less than 5.0% Rank C: Density reduction rate 5.0% or more and less than 10.0% Rank D: Density reduction rate 10.0% or more

<Examples 2 to 24 and Comparative Examples 1 to 5>
The evaluation of abrasion resistance and low-temperature fixability was carried out in the same manner as in Example 1, except that the two-component developer 1 used was changed to two-component developers 2 to 24 and comparative two-component developers 1 to 5. The evaluation results are shown in Table 6.

In Comparative Example 1, calcium carbonate was added from step 2 onward to produce the toner. As a result, the number of steps on the (104) plane was small, and the peak intensity ratio was 0.14, which is outside the range for obtaining the effects of the present invention. It is presumed that this resulted in an unacceptable level of abrasion resistance.
In Comparative Example 2, the amount of calcium carbonate added in step 1 was small. As a result, it is presumed that the opportunity for calcium carbonate particles to rub against each other in step 1 was extremely reduced, resulting in a toner with a large crystallite size. It is presumed that the area for interaction with the resin was reduced, resulting in an unacceptable level of abrasion resistance.
In Comparative Example 3, calcium carbonate C5 was added from step 2. The resulting toner had a small number of steps on the (104) plane and a large crystallite size. As a result, it is presumed that the effects of the present invention were not fully achieved, and the abrasion resistance was at an unacceptable level.
In Comparative Example 4, calcium carbonate particles are not present in the toner. The interaction between calcium carbonate and resin is not obtained, and the toner cohesion force is reduced. As a result, it is presumed that the effect of the present invention is not fully obtained, and the abrasion resistance is at an unacceptable level.
In Comparative Example 5, the peripheral speed during production of the calcium carbonate particle dispersion was as low as 47.1 mm/s. As a result, steps on the (104) plane of the calcium carbonate particles were not easily formed, and the peak intensity ratio between the (104) plane and the (112) plane obtained from the XRD measurement was as low as 0.13. Therefore, it is presumed that the interaction with the binder resin was weak, resulting in an unacceptable level of abrasion resistance.
Among the examples, some toners were ranked B or C in low temperature fixability. This is thought to be due to the fact that the number of steps on the (104) plane of the calcium carbonate used was too large, resulting in poor low temperature fixability.
According to the present invention, it is possible to provide a toner that has improved low-temperature fixability and excellent abrasion resistance of images.

Claims (4)

A method for producing a toner , comprising:
The method for producing the toner includes:
Step 1: melt-kneading a first mixture containing a portion of the binder resin and calcium carbonate particles in a twin-screw extruder to obtain a molten mixture; and Step 2 : melt-kneading a second mixture containing the molten mixture and the remaining binder resin.
Including ,
When the content of the binder resin in the first mixture is defined as Mr (mass%) and the content of the calcium carbonate particles in the first mixture is defined as Mi (mass%), based on the mass of the first mixture, the Mr and the Mi satisfy the following conditions:
15≦Mr≦75
0.17≦Mi/Mr≦1.3
Fulfilling
The toner produced through the steps 1 and 2 has toner particles containing a binder resin and calcium carbonate particles,
In X-ray diffraction measurement of the toner particles using CuKα rays when the Bragg angle is θ, the calcium carbonate particles contained in the toner particles
(i) having peaks at 26.5°±0.5° and 29.5°±0.5° in 2θ;
(ii) the crystallite diameter of the crystals at 2θ = 29.5 ° ± 0.5 ° is 10 nm or more and 45 nm or less;
(iii) the ratio (a/b) of the peak intensity “a” at 2θ=26.5°±0.5° to the peak intensity “b” at 2θ=29.5°±0.5° is 0.15 or more and 0.24 or less;
A method for producing a toner comprising the steps of : The method for producing a toner according to claim 1 , wherein the content of the remaining binder resin added in step 2 is 30% by mass or more and 75% by mass or less, based on the mass of the second mixture. 3. The method for producing a toner according to claim 1 , wherein the peripheral speed of the outer end of the kneading shaft of the twin-screw extruder in the step 1 is 78 mm/s or more. In X-ray diffraction measurement of the toner particles using CuKα rays when the Bragg angle is θ, the calcium carbonate particles contained in the toner particles
4. The method for producing a toner according to claim 1, wherein a ratio (a/b) of a peak intensity "a" at 2θ=26.5°±0.5° to a peak intensity "b" at 2θ=29.5°±0.5° is 0.17 or more and 0.20 or less.