toner

Abstract

This toner provides the ability to form images with good color reproduction even with a small amount of toner, and offers excellent low-temperature fixing properties, resistance to hot offsetting, and heat resistance for storage. [Solution] The toner contains toner particles. The toner particles have a toner core and a shell layer that covers the surface of the toner core. The toner core contains a binder resin and a colorant. The binder resin contains amorphous polyester resin and crystalline polyester resin. The colorant content is 11.5 parts by mass or more and 17.1 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. The area ratio of the area covered by the shell layer on the surface of the toner core is 30% or more and 60% or less.

Description

Technical Field

[0001] The present invention relates to toner.

Background Art

[0002] In image formation using an image forming apparatus, a toner that can be fixed at a low temperature is required. For example, in the toner described in Patent Document 1, the toner particles have core particles containing a binder resin and a shell layer on the surface of the core particles. The shell layer contains a compound containing a nitrogen atom. The external additive includes organosilicon polymer particles. The difference between the work function Wa of the organosilicon polymer particles and the work function Wb of the toner particles satisfies the formula "0.00 eV < Wa - Wb ≤ 0.75 eV".

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the toner described in Patent Document 1 has room for improvement in terms of low-temperature fixing property. Also, although it is required to reduce the toner consumption from an environmental aspect, the toner described in Patent Document 1 is insufficient in forming an image with good color development with a small amount of toner. Further, the toner described in Patent Document 1 is also insufficient in terms of hot offset resistance and heat storage resistance.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a toner that can form an image with good color development even with a small amount of toner and is excellent in low-temperature fixing property, hot offset resistance, and heat storage resistance.

Means for Solving the Problems

[0006] The toner according to the present invention comprises toner particles. The toner particles have a toner core and a shell layer that covers the surface of the toner core. The toner core contains a binder resin and a colorant. The binder resin includes an amorphous polyester resin and a crystalline polyester resin. The content of the colorant is 11.5 parts by mass or more and 17.1 parts by mass or less per 100.0 parts by mass of the amorphous polyester resin. The area ratio of the area covered by the shell layer on the surface area of ​​the toner core is 30% or more and 60% or less. [Effects of the Invention]

[0007] The toner of the present invention can form images with good color development even with a small amount of toner, and has excellent low-temperature fixing properties, hot offset resistance, and heat storage resistance. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below. First, the terms used herein will be explained. Toner is an aggregate of toner particles (e.g., powder). External additives are an aggregate of external additive particles (e.g., powder). Evaluation results (values ​​indicating shape, physical properties, etc.) for powders (more specifically, toner particle powders, external additive particle powders, etc.) are, unless otherwise specified, the number average of values ​​measured for each of a considerable number of particles selected from the powder. The number average primary particle diameter is, unless otherwise specified, the number average of the equivalent circle diameter (Haywood diameter: the diameter of a circle having the same area as the projected area of ​​the primary particle) of primary particles measured using a scanning electron microscope. The number average primary particle diameter of powder is, for example, the number average of the equivalent circle diameters of 100 primary particles. Note that, unless otherwise specified, the number average primary particle diameter of powder refers to the number average primary particle diameter of particles in the powder. Volume median diameter (the cumulative 50% value in the volume-based particle size distribution D) 50Unless otherwise specified, ) is the median diameter measured using a laser diffraction / scattering particle size distribution analyzer ("LA-950" manufactured by Horiba, Ltd.). DBP absorption is the amount of dibutyl phthalate (DBP) absorbed by 100g of the sample, and is a value measured in accordance with JIS (Japanese Industrial Standards) K6221. Hereinafter, the compound name may be followed by "system" to comprehensively refer to the compound and its derivatives. When the polymer name is represented by "system" after the compound name, it means that the repeating unit of the polymer originates from the compound or its derivative. Acrylic and methacrylic may be comprehensively referred to as "(meth)acrylic". Acrylonitrile and methacrylonitrile may be comprehensively referred to as "(meth)acrylonitrile". Unless otherwise specified, the "main component" of a material means the component that is most abundant in the material by mass. Each component described in this specification may be used individually or in combination of two or more. The terms used in this specification have been explained above.

[0009] [toner] The toner according to an embodiment of the present invention will be described below. The toner of this embodiment contains toner particles. The toner particles have a toner core and a shell layer that covers the surface of the toner core. The toner core contains a binder resin and a colorant. The binder resin includes an amorphous polyester resin and a crystalline polyester resin. The colorant content is 11.5 parts by mass or more and 17.1 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. The area ratio of the area covered by the shell layer on the surface area of ​​the toner core is 30% or more and 60% or less.

[0010] Hereinafter, "the area ratio of the toner core surface area covered by the shell layer" may be referred to as "shell layer coverage rate."

[0011] The toner of this embodiment, having the above configuration, can form images with good color reproduction even with a small amount of toner, and has excellent low-temperature fixing properties, hot offset resistance, and heat storage resistance. The reason for this is presumed to be as follows.

[0012] From an environmental perspective, there is a demand to reduce toner consumption. To form images with good color reproduction using a small amount of toner, it is desirable to increase the colorant content per toner particle to improve the color reproduction per particle. However, since colorants are difficult to melt with heat, increasing the colorant content per toner particle tends to decrease the low-temperature fixability of the toner. Therefore, the inventors diligently studied and found that the colorant content per 100.0 parts by mass of amorphous polyester resin affects the elasticity of the toner core and, consequently, the elasticity of the toner particles. If the colorant content per 100.0 parts by mass of amorphous polyester resin is 17.1 parts by mass or less, toner particles with elasticity suitable for fixing can be obtained, and an excessive decrease in the low-temperature fixability of the toner can be suppressed. On the other hand, if the colorant content per 100.0 parts by mass of amorphous polyester resin is 11.5 parts by mass or more, the color reproduction per toner particle is improved, and images with good color reproduction can be formed. Therefore, by setting the colorant content per 100.0 parts by mass of amorphous polyester resin to 11.5 parts by mass or more and 17.1 parts by mass or less, it is possible to achieve both the formation of images with good color development using a small amount of toner and the suppression of an excessive decrease in the low-temperature fixability of the toner.

[0013] The toner core containing the amorphous polyester resin and colorant described above has moderate elasticity and melts easily at low temperatures. On the other hand, the shell layer covering the toner core has high heat resistance and does not melt easily at low temperatures. If the shell layer coverage rate is 60% or less, the toner core is not over-covered by the highly heat-resistant shell layer, improving the low-temperature fixation of the toner. On the other hand, if the shell layer coverage rate is 30% or more, the toner core is moderately covered by the highly heat-resistant shell layer, improving the toner's resistance to hot offset and heat storage.

[0014] The above explains why the toner of this embodiment can form images with good color reproduction even with a small amount of toner, and why it has excellent low-temperature fixing properties, hot offset resistance, and heat storage resistance.

[0015] <Toner particles> The toner particles contained in toner have a toner core and a shell layer. The shell layer covers the surface of the toner core. The surface area of ​​the toner core includes a covered area and an exposed area. The covered area is the part of the toner core's surface area that is covered by the shell layer. The exposed area is the part of the toner core's surface area where the surface of the toner core is exposed and not covered by the shell layer. The exposed area exists on the surface area of ​​the toner core, for example, scattered or in an island-like pattern.

[0016] As already mentioned, the shell layer coverage is 30% to 60%. To improve the toner's resistance to hot offset and heat storage, the shell layer coverage is preferably 40% or more. To improve the toner's low-temperature fixing performance, the shell layer coverage is preferably 50% or less. The shell layer coverage can be measured, for example, by observing toner matrix particles stained with ruthenium using a scanning electron microscope and binarizing the resulting backscattered electron image. The shell layer coverage can be adjusted, for example, in the shell layer formation process described later, by changing at least one of the following: the type of shell material, the amount of shell material added relative to the mass of the toner core, and the shelling pH.

[0017] <Toner Core> The toner core of the toner particles contains a binder resin and a colorant. The toner core may further contain internal additives (e.g., a mold release agent and at least one of the other components mentioned above) as needed.

[0018] As already mentioned, the content of the colorant is 11.5 parts by mass or more and 17.1 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. In order to balance the formation of images with good color development with a small amount of toner and the improvement of the toner's low-temperature fixing properties, when the colorant is a black colorant, the content of the black colorant is preferably 14.5 parts by mass or more and 15.5 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. For the same reason, when the colorant is a yellow colorant, the content of the yellow colorant is preferably 14.5 parts by mass or more and 15.5 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. For the same reason, when the colorant is a magenta colorant, the content of the magenta colorant is preferably 16.0 parts by mass or more and 17.0 parts by mass or less per 100.0 parts by mass of amorphous polyester resin. For the same reason, when the coloring agent is a cyanide coloring agent, the cyanide coloring agent content is preferably 11.5 parts by mass or more and 12.5 parts by mass or less per 100.0 parts by mass of amorphous polyester resin.

[0019] The colorant content per 100.0 parts by mass of amorphous polyester resin is measured, for example, by the following method: Specifically, the colorant concentration of the THF (tetrahydrofuran) solution in the toner core with a concentration of 0.25 mg / mL is measured using a turbidimeter. Using a calibration curve, the measured colorant concentration is converted to the mass WC of colorant contained in 10 mg of toner core. The THF-soluble component (corresponding to amorphous polyester resin) is separated from the toner core by filtration, and its mass is measured. From the measured mass, the mass WRA of amorphous polyester resin contained in 10 mg of toner core is determined. Then, the colorant content per 100.0 parts by mass of amorphous polyester resin is calculated using the formula "Colorant content = 100.0 × WC / WRA". Details of the measurement method for the colorant content per 100.0 parts by mass of amorphous polyester resin will be described later in the examples.

[0020] In order to adjust the content of the colorant with respect to 100.0 parts by mass of the amorphous polyester resin to be in the range of 11.5 parts by mass or more and 17.1 parts by mass or less, the colorant concentration measured using a turbidimeter is preferably in the following range. When the colorant is a black colorant, the colorant concentration measured using a turbidimeter is preferably 5000 or more and 6000 or less. When the colorant is a yellow colorant, the colorant concentration measured using a turbidimeter is preferably 850 or more and 950 or less. When the colorant is a cyan colorant, the colorant concentration measured using a turbidimeter is preferably 1500 or more and 1700 or less. When the colorant is a magenta colorant, the colorant concentration measured using a turbidimeter is preferably 1250 or more and 1450 or less.

[0021] (Binder resin) The content rate of the binder resin is preferably 60% by mass or more and 95% by mass or less, more preferably 75% by mass or more and 90% by mass or less, based on the mass of the toner core.

[0022] As already described, the binder resin includes an amorphous polyester resin and a crystalline polyester resin. When the toner core contains a crystalline polyester resin and an amorphous polyester resin as the binder resin, it is possible to obtain a toner with excellent low-temperature fixing properties while enhancing the dispersibility of the colorant and internal additives. The binder resin may further contain a resin other than the amorphous polyester resin and the crystalline polyester resin (hereinafter sometimes referred to as other binder resins) as necessary.

[0023] (Polyester resin) Polyester resins are classified into crystalline polyester resins and amorphous polyester resins. Crystalline polyester resins have a melting point. The melting point is the temperature of the maximum endothermic peak in the endothermic curve measured using a differential scanning calorimeter. This endothermic peak appears due to the melting of the crystalline parts of the crystalline polyester resin. On the other hand, it is often difficult to measure a clear melting point for amorphous polyester resins. Therefore, resins in which a clear endothermic peak cannot be determined in the endothermic curve measured using a differential scanning calorimeter can be judged to be amorphous polyester resins.

[0024] Polyester resins are obtained by condensation polymerization of one or more polyhydric alcohols and one or more polycarboxylic acids. Examples of polyhydric alcohols for synthesizing polyester resins include dihydric alcohols (more specifically, aliphatic diols, bisphenols, etc.) and trihydric or higher alcohols, as shown below. Examples of polycarboxylic acids for synthesizing polyester resins include dihydric carboxylic acids and trihydric or higher carboxylic acids, as shown below. Alternatively, polycarboxylic acid derivatives that can form ester bonds by condensation polymerization (e.g., anhydrides of polyhydric carboxylic acids or polycarboxylic acid halides) may be used instead of polyhydric carboxylic acids.

[0025] Examples of aliphatic diols, which are dihydric alcohols, include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α,ω-alkanediols (more specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, etc.), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0026] Examples of dihydric alcohols, such as bisphenols, include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

[0027] Examples of trivalent or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0028] Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkyl succinic acid, and alkenyl succinic acid. Examples of alkyl succinic acids include butyl succinic acid, octyl succinic acid, and isododecyl succinic acid. Examples of alkenyl succinic acids include butenyl succinic acid, octenyl succinic acid, dodecenyl succinic acid, and dodecenyl succinic acid.

[0029] Examples of carboxylic acids with a valency of 3 or higher include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalentricarboxylic acid, 1,2,4-naphthalentricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acids.

[0030] The following describes amorphous polyester resins among polyester resins. In one embodiment of amorphous polyester resins, the amorphous polyester resin is preferably a polymer of at least one bisphenol and at least one divalent carboxylic acid and a trivalent carboxylic acid, more preferably a polymer of at least one bisphenol A alkylene oxide adduct and alkenyl succinic acid, terephthalic acid and trimellitic acid, and even more preferably a polymer of bisphenol A propylene oxide adduct and bisphenol A ethylene oxide adduct and dodecenyl succinic anhydride, terephthalic acid and trimellitic anhydride.

[0031] In another embodiment of the amorphous polyester resin, the amorphous polyester resin is preferably a polymer of an aliphatic diol and a divalent carboxylic acid, and more preferably a polymer of 1,2-propanediol and adipic acid.

[0032] The softening point of the amorphous polyester resin is preferably 100°C to 150°C, and more preferably 120°C to 130°C. The glass transition temperature of the amorphous polyester resin is preferably 50°C to 130°C. The acid value of the amorphous polyester resin is preferably 5 mg KOH / g to 20 mg KOH / g. The hydroxyl value of the amorphous polyester resin is preferably 30 mg KOH / g to 45 mg KOH / g. The mass-average molecular weight of the amorphous polyester resin is preferably 70,000 to 110,000. The number-average molecular weight of the amorphous polyester resin is preferably 2,000 to 5,000.

[0033] The content of amorphous polyester resin in the binder resin is preferably 80.0% by mass or more and 95.0% by mass or less, more preferably 85.0% by mass or more and 90.0% by mass or less, and even more preferably 87.8% by mass or more and 88.4% by mass or less.

[0034] The content of amorphous polyester resin in the toner core is preferably 65.0% by mass or more and 90.0% by mass or less, more preferably 70.0% by mass or more and 80.0% by mass or less, and even more preferably 72.3% by mass or more and 76.3% by mass or less.

[0035] Next, we will describe crystalline polyester resins among polyester resins. Crystalline polyester resins are preferably polymers of at least one aliphatic diol and a divalent carboxylic acid, more preferably polymers of at least one α,ω-alkanediol and a divalent carboxylic acid, and even more preferably polymers of 1,4-butanediol, 1,6-hexanediol and fumaric acid, or polymers of ethylene glycol and sebacic acid.

[0036] The content of crystalline polyester resin is preferably 1.0 part by mass or more and 30.0 parts by mass or less, more preferably 10.0 parts by mass or more and 15.0 parts by mass or less, and even more preferably 12.5 parts by mass or more and 13.5 parts by mass or less, per 100.0 parts by mass of amorphous polyester resin.

[0037] The content of crystalline polyester resin in the binder resin is preferably 10.0% by mass or more and 15.0% by mass or less, more preferably 11.0% by mass or more and 12.0% by mass or less, and even more preferably 11.1% by mass or more and 11.6% by mass or less.

[0038] The content of crystalline polyester resin in the toner core is preferably 5.0% by mass or more and 15.0% by mass or less, more preferably 9.0% by mass or more and 10.0% by mass or less, and even more preferably 9.5% by mass or more and 9.6% by mass or less.

[0039] The crystalline polyester resin may be contained in the toner core, for example, in the form of a composite resin with other binder resins. If the polyhydric alcohol or polycarboxylic acid used to synthesize the crystalline polyester resin has a group (e.g., a vinyl group) that can react with the monomer used to synthesize the other binder resin, the crystalline polyester resin and the other binder resin are chemically bonded to form a composite resin. On the other hand, if the polyhydric alcohol or polycarboxylic acid used to synthesize the crystalline polyester resin does not have a group that can react with the monomer used to synthesize the other binder resin, the crystalline polyester resin and the other binder resin are mixed to form a composite resin.

[0040] When a crystalline polyester resin is contained in the toner core in the form of a composite resin with other binder resins, the softening point of the composite resin is preferably 70°C to 100°C, and more preferably 75°C to 90°C. The melting point of the composite resin is preferably 70°C to 100°C, and more preferably 75°C to 85°C. In order for the toner to have appropriate sharp melt properties, the crystallinity index of the composite resin is preferably 0.90 to 1.20. The crystallinity index of the resin corresponds to the ratio (Tm / Mp) of the softening point (Tm: unit °C) of the resin to the melting point (Mp: unit °C) of the resin.

[0041] When a crystalline polyester resin is contained in the toner core in the form of a composite resin with other binder resins, the acid value of the composite resin is preferably 1 mg KOH / g or more and 20 mg KOH / g or less. The hydroxyl value of the composite resin is preferably 10 mg KOH / g or more and 20 mg KOH / g or less. The mass-average molecular weight of the composite resin is preferably 20,000 or more and 30,000 or less. The number-average molecular weight of the composite resin is preferably 2,000 or more and 5,000 or less.

[0042] (Other binding resins) The binder resin may contain other binder resins as needed. To improve the low-temperature fixability of the toner, thermoplastic resins are preferred as the other binder resins. Examples of thermoplastic resins include styrene resin, acrylic resin, polyolefin resin (more specifically, polyethylene resin, polypropylene resin, etc.), vinyl resin (more specifically, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, etc.), polyamide resin, and urethane resin. Copolymers of these resins, i.e., copolymers in which any repeating units are introduced into the above resins (more specifically, styrene-acrylic resin, styrene-butadiene resin, etc.), can also be used as other binder resins.

[0043] To obtain a toner with excellent electrostatic stability while improving low-temperature fixation, styrene-acrylic resin is preferred as the other binder resin. Styrene-acrylic resin is a polymer of at least one styrene-based monomer and at least one acrylic acid-based monomer.

[0044] Examples of styrene monomers that can be used in the polymerization of styrene-acrylic resins used as other binders include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-hydroxystyrene, and 2-(ethoxymethyl)styrene. Styrene is preferred as the styrene monomer that can be used in the polymerization of styrene-acrylic resins used as other binders.

[0045] Examples of acrylic acid monomers that can be used in the polymerization of styrene-acrylic resins used as other binder resins include (meth)acrylic acid, alkyl (meth)acrylate esters, and hydroxyalkyl (meth)acrylate esters.

[0046] Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, and lauryl (meth)acrylate.

[0047] Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0048] As acrylic acid monomers that can be used for polymerization of styrene-acrylic resins used as other binder resins, alkyl (meth)acrylates are preferred, alkyl (meth)acrylates having 1 to 6 carbon atoms in the alkyl group are more preferred, and butyl (meth)acrylate is even more preferred.

[0049] As the styrene-acrylic resin, a polymer of styrene and an alkyl (meth)acrylate is preferred, a polymer of styrene and an alkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group is more preferred, a polymer of styrene and butyl (meth)acrylate is even more preferred, and a polymer of styrene and butyl methacrylate is particularly preferred.

[0050] If the binder resin contains other binder resins, the content of the other binder resins is preferably 0.1 parts by mass or more and 1.0 part by mass or less, and more preferably 0.5 parts by mass or more and 0.6 parts by mass or less, per 100.0 parts by mass of amorphous polyester resin.

[0051] If the binder resin contains other binder resins, the content of the other binder resins is preferably 1.0 part by mass or more and 10.0 parts by mass or less, more preferably 4.0 parts by mass or more and 5.5 parts by mass or less, and even more preferably 4.4 parts by mass or more and 5.1 parts by mass or less, per 100.0 parts by mass of crystalline polyester resin.

[0052] If the binder resin contains other binder resins, the content of the other binder resins in the binder resin is preferably 0.1% by mass or more and 3.0% by mass or less, more preferably 0.3% by mass or more and 1.0% by mass or less, and even more preferably 0.4% by mass or more and 0.6% by mass or less.

[0053] When the binder resin contains other binder resins, the content of the other binder resins in the toner core is preferably 0.1% by mass or more and 3.0% by mass or less, more preferably 0.2% by mass or more and 1.0% by mass or less, and even more preferably 0.3% by mass or more and 0.6% by mass or less.

[0054] (Coloring agent) From the viewpoint of forming high-quality images using toner, the colorant content is preferably 1 to 20 parts by mass, and more preferably 10 to 15 parts by mass, per 100 parts by mass of binder resin. For the same reason, the colorant content in the toner core is preferably 5% to 15% by mass, and more preferably 9% to 12% by mass.

[0055] As a colorant, known pigments or dyes can be used in accordance with the toner color. Examples of colorants include black colorants and colored colorants. Examples of colored colorants include yellow colorants, magenta colorants, and cyan colorants.

[0056] Examples of black colorants include carbon black. Alternatively, the black colorant may be a colorant that has been colored black using yellow, magenta, and cyan colorants.

[0057] As a yellow coloring agent, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of yellow coloring agents include CI Pigment Yellow (3, 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), Naphthol Yellow S, Hansa Yellow, and CI Bat Yellow.

[0058] As magenta colorants, one or more compounds selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolon compounds, thioindigo compounds, and perylene compounds can be used. Examples of magenta colorants include CI pigment reds (2, 3, 5, 6, 7, 19, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254).

[0059] As a cyanide colorant, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds can be used. Examples of cyanide colorants include CI pigment blue (1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66), phthalocyanine blue, CI bat blue, and CI acid blue.

[0060] (Release agent) Release agents are used, for example, to impart offset resistance to toner. From the viewpoint of providing sufficient offset resistance to toner, the release agent content is preferably 1 to 20 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of binder resin. For the same reason, the release agent content in the toner core is preferably 1% to 10% by mass, and more preferably 3% to 7% by mass.

[0061] Examples of mold release agents include aliphatic hydrocarbon waxes, oxides of aliphatic hydrocarbon waxes, plant waxes, animal waxes, mineral waxes, ester waxes mainly composed of fatty acid esters, and waxes in which some or all of the fatty acid esters have been deoxidized. Examples of aliphatic hydrocarbon waxes include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and Fischer-Tropsch waxes. Examples of oxides of aliphatic hydrocarbon waxes include oxidized polyethylene wax and block copolymers of oxidized polyethylene waxes. Examples of plant waxes include candelilla wax, carnauba wax, wood wax, jojoba wax, and rice wax. Examples of animal waxes include beeswax, lanolin, and whale wax. Examples of mineral waxes include ozokerite, ceresin, and petrolatum. Examples of ester waxes mainly composed of fatty acid esters include montanic acid ester wax and castor wax. Examples of waxes in which some or all of the fatty acid esters have been deoxidized include deoxidized carnauba wax. Ester waxes are preferred as release agents.

[0062] (Other ingredients) Other components that the toner core may contain include, for example, charge control agents, magnetic powders, compatibilizers, and other known additives.

[0063] <Shell layer> The shell layer of the toner particles contains, for example, a resin. Hereinafter, the "resin contained in the shell layer" may be referred to as "shell resin." The shell layer may further contain other components besides the shell resin as needed. To obtain a toner suitable for image formation, the thickness of the shell layer is preferably 1 nm to 400 nm, and more preferably 5 nm to 50 nm.

[0064] (Shell resin) The content ratio of the shell resin in the shell layer is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, and particularly preferably 100% by mass.

[0065] Examples of shell resins include thermosetting resins, thermoplastic resins, and mixtures of thermosetting resins and thermoplastic resins. To improve the low-temperature fixation of the toner, thermoplastic resins are preferred as the shell resin. Examples of thermoplastic resins include polyester resins, styrene resins, and styrene-acrylic resins. Among these, styrene-acrylic resins are preferred as the shell resin.

[0066] Styrene-acrylic resin is a polymer of at least one styrene-based monomer and at least one acrylic acid-based monomer. In the synthesis of styrene-acrylic resin, in addition to the styrene-based monomer and acrylic acid-based monomer, other monomers (hereinafter sometimes referred to as "other monomers") may be used as needed.

[0067] Examples of styrene monomers and acrylic acid monomers that can be used in the polymerization of styrene-acrylic resin used as a shell resin include those similar to those used in the polymerization of styrene-acrylic resin used as other binder resins.

[0068] When the shell resin contains styrene-acrylic resin, the content of styrene-acrylic resin in the shell resin is preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, and particularly preferably 100% by mass.

[0069] Suitable examples of styrene-acrylic resins used as shell resins include non-crosslinked styrene-acrylic resins, crosslinked styrene-acrylic resins, styrene-acrylic resins having cyano groups (CN groups), and styrene-acrylic resins having a quaternary ammonium base.

[0070] The shell layer preferably contains two or more types of resins, and more preferably contains two types of resins. That is, the shell resin preferably consists of two or more types of resins, and more preferably consists of two types of resins. Two or more types of resins are, for example, resins with different monomer compositions.

[0071] To balance the improvement of toner's low-temperature fixing properties with the improvement of toner's resistance to hot offset and heat storage, the shell layer preferably contains a cross-linked styrene-acrylic resin and a non-cross-linked styrene-acrylic resin. The content of the cross-linked styrene-acrylic resin is preferably 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of non-cross-linked styrene-acrylic resin.

[0072] To ensure sufficient positive charge in the toner, the shell layer preferably contains a styrene-acrylic resin having cyano groups and a styrene-acrylic resin having a quaternary ammonium base. The content of the styrene-acrylic resin having a quaternary ammonium base is preferably 5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the styrene-acrylic resin having cyano groups.

[0073] The following provides further explanations regarding non-crosslinked styrene-acrylic resins, crosslinked styrene-acrylic resins, styrene-acrylic resins having cyano groups, and styrene-acrylic resins having quaternary ammonium bases.

[0074] Non-crosslinked styrene-acrylic resin is a polymer of at least one styrene-based monomer and at least one acrylic acid-based monomer. Non-crosslinked styrene-acrylic resin does not have a crosslinked structure. That is, non-crosslinked styrene-acrylic resin does not have repeating units derived from the crosslinking agent.

[0075] The non-crosslinked styrene-acrylic resin is preferably a polymer of styrene, an alkyl (meth)acrylate, and a hydroxyalkyl (meth)acrylate. More preferably, the non-crosslinked styrene-acrylic resin is a polymer of styrene, an alkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group, and a hydroxyalkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group. The non-crosslinked styrene-acrylic resin is particularly preferably a polymer of styrene, butyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

[0076] Crosslinked styrene-acrylic resin has a crosslinked structure. A crosslinked styrene-acrylic resin is a polymer of at least one styrene monomer, at least one acrylic acid monomer, and a crosslinking agent. The crosslinking agent can introduce a crosslinked structure into the styrene-acrylic resin. The crosslinking agent is, for example, a crosslinkable monomer. Examples of crosslinkable monomers include compounds having two or more unsaturated bonds (e.g., carbon-carbon double bonds), more specifically divinylbenzene and diallyl phthalate. Examples of divinylbenzene include o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene. Examples of diallyl phthalate include diallyl isophthalate and diallyl orthophthalate. Divinylbenzene is preferred as the crosslinking agent.

[0077] The cross-linked styrene-acrylic resin is preferably a polymer of an alkyl (meth)acrylate ester and a compound having two or more unsaturated bonds with styrene. More preferably, the cross-linked styrene-acrylic resin is a polymer of an alkyl (meth)acrylate ester having 1 to 6 carbon atoms in the alkyl group, styrene, and divinylbenzene. The cross-linked styrene-acrylic resin is particularly preferably a polymer of methyl (meth)acrylate, styrene, and divinylbenzene.

[0078] A cyano group-containing styrene-acrylic resin is a polymer of at least one styrene-based monomer, at least one acrylic acid-based monomer, and a monomer containing a cyano group. Examples of monomers containing a cyano group include (meth)acrylonitrile.

[0079] The styrene-acrylic resin having a cyano group is preferably a polymer of 2-(ethoxymethyl)styrene, an alkyl (meth)acrylate, and (meth)acrylonitrile. More preferably, the styrene-acrylic resin having a cyano group is a polymer of 2-(ethoxymethyl)styrene, an alkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group, and (meth)acrylonitrile. The styrene-acrylic resin having a cyano group is particularly preferably a polymer of 2-(ethoxymethyl)styrene, butyl acrylate, and (meth)acrylonitrile.

[0080] Styrene acrylic resins having a quaternary ammonium base are polymers of at least one styrene monomer, at least one acrylic acid monomer, and a monomer having a quaternary ammonium base. Examples of monomers having a quaternary ammonium base include vinylbenzyltrialkylammonium salt, 2-(acryloyloxy)ethyltrialkylammonium salt, and 2-(methacryloyloxy)ethyltrialkylammonium salt. 2-(methacryloyloxy)ethyltrialkylammonium salt is preferred as the monomer having a quaternary ammonium base.

[0081] Examples of 2-(methacryloyloxy)ethyltrialkylammonium salts include 2-(methacryloyloxy)ethyltrimethylammonium salt (more specifically, 2-(methacryloyloxy)ethyltrimethylammonium chloride, etc.), 2-(methacryloyloxy)ethyldimethylethylammonium salt (more specifically, 2-(methacryloyloxy)ethyldimethylethylammonium chloride, etc.), and 2-(methacryloyloxy)ethyldimethyln-pentylammonium salt (more specifically, 2-(methacryloyloxy)ethyldimethyln-pentylammonium chloride, etc.).

[0082] The styrene-acrylic resin having a quaternary ammonium base is preferably a polymer of an alkyl (meth)acrylate, 2-(ethoxymethyl)styrene, a hydroxyalkyl (meth)acrylate, and a 2-(methacryloyloxy)ethyltrialkylammonium salt. More preferably, the styrene-acrylic resin having a quaternary ammonium base is a polymer of an alkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group, 2-(ethoxymethyl)styrene, a hydroxyalkyl (meth)acrylate having 1 to 6 carbon atoms in the alkyl group, and a 2-(methacryloyloxy)ethyltrimethylammonium salt. The styrene-acrylic resin having a quaternary ammonium base is particularly preferably a polymer of methyl methacrylate, 2-(ethoxymethyl)styrene, 2-hydroxyethyl methacrylate, and 2-(methacryloyloxy)ethyltrimethylammonium chloride.

[0083] (Other ingredients) Other components that the shell layer may contain include, for example, pH adjusters, emulsifiers, charge control agents, and other known additives.

[0084] <External additives> When toner particles contain an external additive, examples of the external additive include inorganic particles, more specifically silica particles and metal oxide particles (specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate). The surface of the external additive may be subjected to either or both positive charging treatment and hydrophobic treatment. The content of the external additive is preferably 0.5 parts by mass or more and 10.0 parts by mass or less per 100.0 parts by mass of toner matrix particles. The number-average primary particle diameter of the external additive is preferably 5 nm or more and 80 nm or less.

[0085] <Toner manufacturing method> The method for manufacturing the toner of this embodiment will now be described. The toner of this embodiment can be manufactured, for example, by performing a toner core formation step and a shell layer formation step. In addition, if necessary, an external additive step may be further performed after the shell layer formation step.

[0086] (Toner core formation process) In the toner core formation process, the toner core is formed by, for example, an agglomeration method or a grinding method.

[0087] The agglutination method includes, for example, an agglutination step and a unification step. In the agglutination step, fine particles containing components that make up the toner core are agglutinated in an aqueous medium to form agglutinated particles. In the unification step, the components contained in the agglutinated particles are unified in an aqueous medium to form the toner core.

[0088] Next, the grinding method will be described. The grinding method allows for the relatively easy formation of toner cores and reduces manufacturing costs. When forming toner cores by the grinding method, the toner core formation process includes, for example, a mixing step, a kneading step, and a grinding step. Furthermore, the toner core formation process may further include at least one of a fine grinding step and a classification step after the grinding step.

[0089] In the mixing step, the binder resin, colorant, and internal additives added as needed are mixed to obtain a mixture. In the kneading step, the obtained mixture is kneaded while melting to obtain a kneaded product. In the grinding step, the obtained kneaded product is cooled to, for example, room temperature (25°C), and then ground to obtain a pulverized product. If it is necessary to reduce the diameter of the pulverized product obtained in the grinding step, a fine grinding step may be performed to further grind the pulverized product. In addition, if it is necessary to standardize the particle size of the pulverized product, a classification step may be performed to classify the obtained pulverized product. Through the above steps, a toner core, which is a pulverized product, is obtained.

[0090] (Shell layer formation process) In the shell layer formation process, a shell layer is formed on the surface of the toner core. Examples of methods for forming the shell layer include in-situ polymerization, liquid curing, and coacervation. The following are examples of preferred methods.

[0091] First, a material for forming the shell layer (hereinafter sometimes referred to as the shell material) and the toner core obtained in the toner core formation process are placed in an aqueous medium. Examples of the shell material include shell resin, and more specifically, resin particles composed of shell resin. When the shell material is resin particles, the aqueous medium containing the resin particles and the toner core is heated to cause the resin particles to adhere to the surface of the toner core while the resin particles form a film, thereby forming a shell layer on the surface of the toner core. In this way, a toner matrix particle having a toner core and a shell layer covering the toner core is obtained.

[0092] The heating temperature of the aqueous medium containing the shell material and toner core (shelling temperature) is preferably higher than the glass transition temperature of the shell material. The shelling temperature is preferably 50°C to 90°C, and more preferably 60°C to 80°C. The heating time of the aqueous medium containing the shell material and toner core (shelling time) is preferably 0.1 hours to 5.0 hours, and more preferably 1.0 hour to 3.0 hours. The pH of the aqueous medium containing the shell material and toner core (shelling pH) is preferably 3 to 5. The higher the shelling pH, the less likely the shell material is to adhere to the toner core, and the lower the shell layer coverage tends to be. Conversely, the lower the shelling pH, the easier it is for the shell material to adhere to the toner core, and the higher the shell layer coverage tends to be.

[0093] (External addition process) In the external additive process, toner particles are obtained by attaching an external additive to the surface of toner matrix particles. One method for attaching the external additive to the surface of the toner matrix particles is to agitate the toner matrix particles and the external additive using a mixer or the like. [Examples]

[0094] The following describes examples of the present invention, but the present invention is not limited in any way to the scope of these examples. First, the method for measuring each physical property will be explained.

[0095] [Softening point] The softening point of the resin was measured using a high-temperature flow tester (Shimadzu Corporation "CFT-500D"). The softening point was defined as the temperature at which the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured by the high-temperature flow tester was equal to "(baseline stroke value + maximum stroke value) / 2".

[0096] [Glass transition temperature] The glass transition temperature of the resin was measured using a differential scanning calorimeter (DSC-6220, manufactured by Seiko Instruments Inc.) in accordance with JIS (Japanese Industrial Standards) K7121-2012.

[0097] [Melting point] The melting point of the resin was measured using a differential scanning calorimeter (DSC-6220, manufactured by Seiko Instruments Inc.). The temperature of the maximum endothermic peak in the endothermic curve obtained from the measurement (vertical axis: heat flow (DSC signal), horizontal axis: temperature) was defined as the melting point.

[0098] [Acid value and hydroxyl value] The acid value and hydroxyl value of the resin were measured in accordance with JIS (Japanese Industrial Standards) K0070-1992.

[0099] [Mass-average molecular weight and number-average molecular weight] The mass-average molecular weight and number-average molecular weight of the resin were measured by gel permeation chromatography (GPC). First, 10 mg of the resin was dissolved in 5 mL of tetrahydrofuran (THF) at room temperature over 2 hours to obtain a resin solution. The resin solution was filtered using a membrane filter (Tosoh Corporation's "Myshori Disc," pore size 0.45 μm, solvent-resistant) to obtain a sample solution. The sample solution was measured using a GPC measuring device (Tosoh Corporation's "HLC8120 GPC") under the following GPC measurement conditions. Next, the mass-average molecular weight and number-average molecular weight of the resin contained in the sample solution were calculated using molecular weight calibration curves prepared with standard polystyrene resin samples (TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, and A-500 from Tosoh Corporation).

[0100] (GPC measurement conditions) Detector: RI Columns: Shodex® KF-801, 802, 803, 804, 805, 806, and 807 7-section columns (manufactured by Showa Denko Corporation) Eluent:THF Flow rate: 1.0mL / min Oven temperature: 40.0℃ Sample solution injection volume: 0.10 mL

[0101] [Amorphous polyester resin] Amorphous polyester resin used for toner core formation was prepared using the following method. Details of the amorphous polyester resin are shown in Table 1 below.

[0102] [Table 1]

[0103] The terms used in Table 1 are as follows: Tm: Softening point Tg: Glass transition point Mw: mass average molecular weight Mn: Number average molecular weight BPA-PO: Bisphenol A propylene oxide adduct BPA-EO: Bisphenol A ethylene oxide adduct 1,2-PD:1,2-propanediol DSA: Dodecenyl Succinate Anhydride TPA: Terephthalic acid AA: Adipic acid TMA: Trimellitus anhydride -: Does not use the relevant monomer.

[0104] <Preparation of amorphous polyester resin (RA-A)> A four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was used as the reaction vessel. The monomers shown in the "RA-A" column of Table 1 were placed in the reaction vessel in the amounts indicated in that column. 4 g of dibutyltin oxide was added to the reaction vessel. The contents of the reaction vessel were reacted at 220°C for 9 hours under a nitrogen atmosphere with stirring. Subsequently, the contents of the reaction vessel were reacted at 220°C under a reduced pressure atmosphere (pressure 8 kPa) with stirring until the softening point of the reaction product resin reached the value shown in Table 1. As a result, amorphous polyester resin (RA-A) was obtained. The amorphous polyester resin (RA-A) was determined to be amorphous because no clear endothermic peak was observed in the endothermic curve measured using a differential scanning calorimeter. The softening point, glass transition temperature, acid value, hydroxyl value, mass-average molecular weight, and number-average molecular weight of the amorphous polyester resin (RA-A) are as shown in the "RA-A" column of Table 1.

[0105] <Preparation of amorphous polyester resin (RA-D)> Amorphous polyester resin (RA-D) was prepared in the same manner as the amorphous polyester resin (RA-A), except that the type and amount of monomers placed in the reaction vessel were as shown in the "RA-D" column of Table 1. The amorphous polyester resin (RA-D) was determined to be amorphous because no clear endothermic peak was observed in the endothermic curve measured using a differential scanning calorimeter. The softening point, glass transition temperature, acid value, hydroxyl value, mass-average molecular weight, and number-average molecular weight of the amorphous polyester resin (RA-D) are as shown in the "RA-D" column of Table 1.

[0106] [Composite resin] The composite resins used for forming the toner core were prepared using the following method. All of the composite resins were a combination of crystalline polyester resin and styrene-acrylic resin. Details of the composite resins are shown in Table 2 below.

[0107] [Table 2]

[0108] The terms used in Table 2 are as follows: Tm: Softening point Mp: Melting point Mw: mass average molecular weight Mn: Number average molecular weight 1,4-BD:1,4-butanediol 1,6-HD:1,6-Hexanediol EG: Ethylene glycol FA: Fumaric acid SA: Sebaciate ST: Styrene BM: Butyl methacrylate -: Does not use the relevant monomer.

[0109] <Preparation of composite resin (RC-a)> A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was used as the reaction vessel. The polyhydric alcohol monomer and polyhydric carboxylic acid monomer shown in the "RC-a" column of Table 2 were added to the reaction vessel in the amounts indicated in that column. 2.5 g of hydroquinone was added to the reaction vessel. The contents of the reaction vessel were reacted at 170°C for 5 hours under a nitrogen atmosphere with stirring. Subsequently, the contents of the reaction vessel were reacted at 210°C for 1.5 hours under a nitrogen atmosphere with stirring. Subsequently, the contents of the reaction vessel were reacted at 210°C for 1 hour under a reduced pressure atmosphere (pressure 8 kPa) with stirring. Subsequently, the pressure inside the reaction vessel was returned to atmospheric pressure, and the styrene monomer and acrylic acid monomer shown in the "RC-a" column of Table 2 were added to the reaction vessel in the amounts indicated in that column. The contents of the reaction vessel were reacted at 210°C for 1.5 hours with stirring. Next, the contents of the reaction vessel were reacted at 210°C for 1 hour under reduced pressure (8 kPa) with stirring. As a result, a composite resin (RC-a) of crystalline polyester resin and styrene-acrylic resin was obtained. The softening point, melting point, acid value, hydroxyl value, mass-average molecular weight, and number-average molecular weight of the composite resin (RC-a) are shown in the "RC-a" column of Table 2. The crystallinity index (i.e., Tm / Mp) of the composite resin (RC-a) was 1.08.

[0110] <Preparation of composite resin (RC-d)> The composite resin (RC-d) was prepared in the same manner as the composite resin (RC-a), except that the types and amounts of polyhydric alcohol monomers, polyhydric carboxylic acid monomers, styrene monomers, and acrylic acid monomers added to the reaction vessel were as shown in the "RC-d" column of Table 2. The composite resin (RC-d) was a composite resin of crystalline polyester resin and styrene-acrylic resin. The softening point, melting point, acid value, hydroxyl value, mass-average molecular weight, and number-average molecular weight of the composite resin (RC-d) were as shown in the "RC-d" column of Table 2. The crystallinity index (i.e., Tm / Mp) of the composite resin (RC-d) was 1.01.

[0111] [Release agent] The following commercially available release agents were used as release agents for forming the toner core. Release agent (W-1): Ester wax (Nissan Electrol® WEP-3, manufactured by NOF Corporation)

[0112] [Coloring agent] The following commercially available colorants were used as colorants for forming the toner core. Coloring agent (C-1): Black coloring agent (Mitsubishi Chemical Corporation "MA-100", carbon black, average primary particle size: 24 nm, DBP absorption: 100 cm²) 3 (100g) Coloring agent (C-2): Cyan coloring agent (DIC Corporation's "KET BLUE 111") Coloring agent (C-3): Magenta coloring agent (PERMANENT CARMINE 6902, manufactured by Sanyo Pigment Co., Ltd.) Coloring agent (C-4): Yellow coloring agent (Clariant "Hansa Brilliant Yellow 5GX-01") Coloring agent (C-5): Black coloring agent (Cabot Corporation's "REGAL® 330", carbon black) Coloring agent (C-6): Cyan coloring agent (DIC Corporation's "FASTOGEN® BLUE PA5380", CI Pigment Blue 15:3) Coloring agent (C-7): Magenta coloring agent ("CHROMOFINE MAGENTA 6870" manufactured by Dainichi Seika Kogyo Co., Ltd.) Coloring agent (C-8): Yellow coloring agent (SEIKAFAST YELLOW 2054K, manufactured by Dainichi Seika Kogyo Co., Ltd.) Coloring agent (C-9): Black coloring agent (Mitsubishi Chemical Corporation "#44", carbon black, average primary particle size: 24 nm, DBP absorption: 78 cm²) 3 (100g) Coloring agent (C-10): Cyan coloring agent (DIC Corporation's "KET BLUE 105")

[0113] [Shell particle suspension] The first shell particle suspension (SB) and (SE), and the second shell particle suspension (SC) and (SF), used for forming the shell layer, were prepared using the following method.

[0114] <Preparation of the first shell particle suspension (SB)> A four-necked flask equipped with a thermometer, stirring blades, reflux condenser, and monomer dropper port was used as the first reaction vessel. The first reaction vessel was placed in a water bath. 360 parts by mass of deionized water for emulsification and 2.0 parts by mass of reaction emulsifier (ADEKA Corporation's "Adekaria Soap® SR-1025") were added to the first reaction vessel. Subsequently, the temperature inside the first reaction vessel was raised to 80°C using the water bath. Subsequently, 30 parts by mass of styrene, 50 parts by mass of n-butyl acrylate, 20 parts by mass of 2-hydroxyethyl methacrylate, 3.2 parts by mass of reaction emulsifier (ADEKA Corporation's "Adekaria Soap® SR-1025"), and 40 parts by mass of deionized water for emulsification were added to the first reaction vessel. Using a high-speed shear emulsifier (M-Technique Co., Ltd.'s "Cleamix® CLM-2.2S"), the contents of the first reaction vessel were stirred at a stirring speed of 10,000 rpm for 5 minutes to emulsify the contents of the first reaction vessel. As a result, a monomer suspension MB was obtained.

[0115] Another four-necked flask equipped with a thermometer, stirring blades, reflux condenser, and monomer dropper port was used as the second reaction vessel. 0.2 parts by mass of ammonium persulfate were added to the second reaction vessel. Subsequently, 28.6 parts by mass of monomer suspension MB were added to the second reaction vessel, and emulsion polymerization was carried out for 30 minutes. Then, 114.5 parts by mass of monomer suspension MB were added dropwise to the second reaction vessel over 3 hours. After the dropwise addition was complete, the contents of the second reaction vessel were emulsion polymerized for a further 1 hour. Subsequently, 5.9 parts by mass of deionized water for dilution were added to the second reaction vessel. The temperature inside the second reaction vessel was cooled to 40°C. As a result, a first shell particle suspension (SB) was obtained. The first shell particles contained in the first shell particle suspension (SB) were composed of polymers of styrene, n-butyl acrylate, and 2-hydroxyethyl methacrylate.

[0116] <Preparation of the first shell particle suspension (SE)> A first shell particle suspension (SE) was prepared in the same manner as the first shell particle suspension (SB), except that 20 parts by mass of 2-(ethoxymethyl)styrene, 50 parts by mass of n-butyl acrylate, and 30 parts by mass of acrylonitrile were used instead of 30 parts by mass of styrene, 50 parts by mass of n-butyl acrylate, and 20 parts by mass of 2-hydroxyethyl methacrylate. The first shell particles contained in the first shell particle suspension (SE) were composed of a polymer of 2-(ethoxymethyl)styrene, n-butyl acrylate, and acrylonitrile.

[0117] <Preparation of the second shell particle suspension (SC)> A four-necked flask equipped with a thermometer, stirring blades, reflux condenser, and monomer dropper port was used as the first reaction vessel. The first reaction vessel was placed in a water bath. 200 parts by mass of deionized water for emulsification and 1.5 parts by mass of anionic surfactant (Kao Corporation's "Emal® 0") were added to the first reaction vessel. Subsequently, the temperature inside the first reaction vessel was raised to 80°C using the water bath. Subsequently, 45 parts by mass of methyl methacrylate, 50 parts by mass of styrene, 5 parts by mass of divinylbenzene as a crosslinking agent, 3 parts by mass of anionic surfactant (Kao Corporation's "Emal® 0"), and 40 parts by mass of deionized water for emulsification were added to the first reaction vessel. Using a high-speed shear emulsifier ("Cleamix® CLM-2.2S" manufactured by M-Technique Co., Ltd.), the contents of the first reaction vessel were stirred at a stirring speed of 10,000 rpm for 5 minutes to emulsify the contents of the first reaction vessel. As a result, a monomer suspension MC was obtained.

[0118] Another four-necked flask equipped with a thermometer, stirring blade, reflux condenser, and monomer dropper port was used as the second reaction vessel. 1.0 part by mass of ammonium persulfate was placed in the second reaction vessel. Subsequently, 100 parts by mass of the monomer suspension MC was added dropwise to the second reaction vessel over 3 hours to carry out emulsion polymerization. After the addition was complete, the contents of the second reaction vessel were allowed to undergo emulsion polymerization for a further 1 hour. As a result, a second shell particle suspension (SC) was obtained. The second shell particles contained in the second shell particle suspension (SC) were composed of a polymer of methyl methacrylate, styrene, and divinylbenzene.

[0119] <Preparation of the second shell particle suspension (SF)> A second shell particle suspension (SF) was prepared in the same manner as the second shell particle suspension (SC), except that 45 parts by mass of methyl methacrylate, 20 parts by mass of 2-(ethoxymethyl)styrene, 2 parts by mass of 2-hydroxyethyl methacrylate, and 2 parts by mass of 2-(methacryloyloxy)ethyltrimethylammonium chloride were used instead of 45 parts by mass of methyl methacrylate, 50 parts by mass of styrene, 5 parts by mass of divinylbenzene, and 3 parts by mass of anionic surfactant. The second shell particles contained in the second shell particle suspension (SF) were composed of polymers of methyl methacrylate, 2-(ethoxymethyl)styrene, 2-hydroxyethyl methacrylate, and 2-(methacryloyloxy)ethyltrimethylammonium chloride.

[0120] [toner] The toners used in the examples and comparative examples were prepared using the following method. Details of the toner core of each toner are shown in Tables 3 and 4 below. Details of the shell layer of each toner are shown in Tables 5 and 6 below.

[0121] [Table 3]

[0122] [Table 4]

[0123] The terms used in Tables 3 and 4 are as follows: Amorphous resin: Amorphous polyester resin %:mass% Part: Part by mass Percentage [%]: The percentage of the relevant component contained in the toner core (unit: mass%) Quantity [parts / 100 parts amorphous]: Colorant content in 100.0 parts by mass of amorphous polyester resin (unit: parts by mass)

[0124] [Table 5]

[0125] [Table 6]

[0126] <Making Toner (T-A1)> (Formation of toner core) Amorphous polyester resin (RA-A), a composite resin of crystalline polyester resin and styrene-acrylic resin (RC-a), a release agent (W-1), and a coloring agent (C-1) were placed in an FM mixer (FM-20B, manufactured by Nippon Coke Co., Ltd.) in amounts that matched the content ratios shown in Table 3. The content ratio of the coloring agent (C-1) was calculated using the formula "100.0 - (content ratio of amorphous polyester resin + content ratio of composite resin + content ratio of release agent)," and the amount of coloring agent (C-1) was added to achieve the calculated content ratio. The contents of the FM mixer were mixed using the FM mixer to obtain a mixture. The mixture was kneaded while melting using a twin-screw extruder (PCM-30, manufactured by Ikegai Co., Ltd.) under the conditions of a material supply speed of 6 kg / hour, a shaft rotation speed of 160 rpm, and a cylinder temperature of 120°C to obtain a kneaded product. The kneaded product was cooled. The cooled kneaded material was coarsely ground using a pulverizer (Rotoplex® 16 / 8 model, manufactured by Toa Machinery Works Co., Ltd.) to obtain coarse pulverized material. The coarse pulverized material was finely ground using a pulverizer (Turbomill RS, manufactured by Freund Turbo Co., Ltd.) to obtain fine pulverized material. The fine pulverized material was classified using an elbow jet (EJ-LABO, model EJ-L-3, manufactured by Nippon Steel Mining Co., Ltd.) to obtain toner cores with a median volume diameter of 7 μm.

[0127] (Formation of the shell layer) 100 mL of deionized water was placed in a three-necked flask equipped with a thermometer and stirring blades. The temperature of the flask contents was maintained at 30°C using a water bath. Dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents (corresponding to the shell formation pH) to 4. 150 mL of the first shell particle suspension (SB) and 10 mL of the second shell particle suspension (SC) were added to the flask as shell material. 300 g of toner mother particles were further added to the flask, and the contents of the flask were stirred at a speed of 200 rpm for 1 hour. Next, 300 mL of deionized water was added to the flask. While stirring the contents of the flask at a speed of 100 rpm, the temperature of the flask contents was raised to 70°C at a heating rate of 1°C / min. After heating, the temperature of the flask contents was maintained at 70°C for 2 hours while stirring at a speed of 100 rpm. By maintaining the temperature of the flask contents at 70°C, a shell layer was formed on the surface of the toner core. As a result, a dispersion of toner mother particles was obtained.

[0128] Next, the pH of the toner mother particle dispersion was adjusted to 7 using sodium hydroxide. Then, the toner mother particle dispersion was cooled to 25°C. Next, the toner mother particle dispersion was filtered using a Buchner funnel (filtration treatment) to obtain wet cake-like toner mother particles. The wet cake-like toner mother particles were redispersed in deionized water (dispersion treatment). This filtration and dispersion treatment was repeated five times to wash the toner mother particles. The washed toner mother particles were dispersed in a 50% by mass ethanol aqueous solution. In this way, a toner mother particle slurry was obtained. Next, using a continuous surface modification device (Freund Industrial Co., Ltd. "Coatmizer®"), the mixture was processed with a hot air temperature of 45°C and a blower airflow of 2 m³. 3 The toner matrix particle slurry was dried under the condition of [number] minutes. In this way, dried toner matrix particles were obtained.

[0129] (external attachment) 100.0 parts by mass of toner matrix particles, 1.2 parts by mass of hydrophobic silica particles (RA-200H, manufactured by Nippon Aerosil Co., Ltd.), and 0.8 parts by mass of titanium oxide particles (EC-100, manufactured by Titanium Industry Co., Ltd.) were mixed for 2 minutes using an FM mixer (FM-10B, manufactured by Nippon Coke Co., Ltd.) at a rotation speed of 3000 rpm and a jacket control temperature of 20°C. Through mixing, the external additives (hydrophobic silica particles and titanium oxide particles) adhered to the surface of the toner matrix particles, thereby obtaining toner particles. In this way, toner (T-A1) containing toner particles was obtained.

[0130] <Production of toner cartridges (T-A2) to (T-A22) and (T-B1) to (T-B16)> Toners (T-A2) to (T-A22) and (T-B1) to (T-B16) were prepared in the same manner as toner (T-A1), except that in the formation of the toner core, the type and content ratio of amorphous polyester resin, the type and content ratio of composite resin, the type and content ratio of release agent, and the type of colorant were as shown in Tables 3 and 4; in the formation of the toner core, the content ratio of the colorant was calculated from the formula "100.0 - (content ratio of amorphous polyester resin + content ratio of composite resin + content ratio of release agent)"; and in the formation of the shell layer, the type and amount of the first shell particle suspension and the type and amount of the second shell particle suspension were as shown in Tables 5 and 6.

[0131] In the preparation of each toner, the goal was to adjust the shelling pH to 4, but slight variations (approximately pH 4 ± 0.5) occurred in the shelling pH of each toner. The higher the shelling pH was above 4, the less the shell material adhered to the toner core, resulting in a tendency for the shell layer coverage to decrease. Conversely, the lower the shelling pH was below 4, the easier it was for the shell material to adhere to the toner core, resulting in a tendency for the shell layer coverage to increase. Therefore, even when the type and amount of the first shell particle suspension and the second shell particle suspension were the same, slight variations in shelling pH resulted in toners with different shell layer coverage.

[0132] [measurement] The colorant content and shell layer coverage rate for each toner were measured per 100.0 parts by mass of amorphous polyester resin using the following method. The measured colorant content is shown in Tables 3 and 4. The measured shell layer coverage rates are shown in Tables 5 and 6.

[0133] <Content of coloring agents> The mass WC of the colorant contained in 10 mg of toner core and the mass WRA of the amorphous polyester resin contained in 10 mg of toner core were measured using the following method. Then, the content of the colorant relative to 100.0 parts by mass of amorphous polyester resin was calculated using the formula "Colorant content = 100.0 × WC / WRA".

[0134] (Measurement of the mass WC of the coloring agent) 10 mg of toner core (i.e., toner core before shell layer formation) was placed in 40 mL of THF and sonicated for 2 minutes using an ultrasonic vibrator to obtain the first sample. In the first sample, the amorphous polyester resin dissolved in the THF, while the crystalline polyester resin, release agent, and colorant were dispersed in the THF without dissolving. The colorant concentration (i.e., turbidity) of the first sample was measured using a turbidimeter (NDR2000 wastewater colorant meter / color contamination meter manufactured by Nippon Denshoku Industries Co., Ltd.). The measured colorant concentration was converted to the mass of the colorant using a calibration curve. The converted value was defined as the mass WC of the colorant contained in 10 mg of toner core. The calibration curve was prepared in advance using toner cores with a known mass of colorant.

[0135] (Measurement of mass WRA of amorphous polyester resin) 10 mg of toner core (i.e., toner core before shell layer formation) was placed in 40 mL of THF and sonicated for 2 minutes at room temperature (25°C) using an ultrasonic vibrator to obtain a second sample. In the second sample, the amorphous polyester resin dissolved in the THF, while the crystalline polyester resin, release agent, and colorant were dispersed in the THF without dissolving. The second sample was filtered to obtain a filtrate from which the THF-insoluble components (specifically, the crystalline polyester resin, release agent, and colorant) had been removed. Since amorphous polyester resin was dissolved in the filtrate, the filtrate was dried and the mass of amorphous polyester resin was measured. The measured mass of amorphous polyester resin was defined as the WRA (Whole Gram Resistance) of amorphous polyester resin contained in 10 mg of toner core.

[0136] <Shell layer coverage> Toner matrix particles were placed on a ruthenium tetroxide solution and exposed to a ruthenium vapor atmosphere. Exposure resulted in staining of the toner matrix particles with ruthenium. The ruthenium-stained toner matrix particles were observed at a magnification of 50,000x using a scanning electron microscope (SEM, JEOL Ltd. "JSM-7600F") to obtain backscattered electron images of the toner matrix particles. Each pixel constituting the backscattered electron image showed a brightness value between 0 and 255. Using image analysis software (Mitani Corporation's "WinROOF"), the backscattered electron images were binarized based on a brightness value of 144. Note that the areas of the toner core surface covered by the shell layer tend to be easily stained with ruthenium and exhibit brightness values ​​of 144 or higher. Binarization was performed to calculate the total area of ​​the backscattered electron image of the toner matrix particles (A) and the area of ​​the region in the backscattered electron image with a brightness value of 144 or higher (A144). Then, the shell layer coverage rate (in %) was calculated using the formula "Shell layer coverage rate = 100 × (A144) / (A)". Whether the shell coverage rate was between 30% and 60% was determined by rounding the measured shell layer coverage rate to the nearest tenth.

[0137] [evaluation] The minimum fixing temperature, maximum fixing temperature, color development, and heat resistance of each toner were evaluated using the following method. The evaluation values ​​and judgments for each evaluation are shown in Tables 7 and 8 below.

[0138] <Two-component developer for evaluation> Two-component developers used to evaluate the minimum fixing temperature, maximum fixing temperature, and color development were prepared by the following method: 100 parts by mass of carrier (standard carrier "P-01" provided by the Image Science Society of Japan) and 7 parts by mass of toner (any of toners (T-A1) to (T-A22) and (T-B1) to (T-B16)) were mixed using a ball mill to prepare a two-component developer for evaluation.

[0139] <Evaluation unit> A modified multifunction printer (Kyocera Document Solutions Inc.'s "TASKalfa 7054ci") with adjustable fixing temperature was used as an evaluation machine for assessing the minimum fixing temperature, maximum fixing temperature, and color development. The line speed of the evaluation machine was set to 322 mm / second. A two-component developer for evaluation was put into the developing section of the evaluation machine, and toner was put into the toner container of the evaluation machine.

[0140] <Minimum fixing temperature> The toner load of the evaluation machine was 0.37 mg / cm². 2 The settings were adjusted as follows. Using the evaluation machine, an unfixed solid image was formed on a recording medium (monochrome / color copy paper, Fujifilm Business Innovation Co., Ltd. "C2"). The fixing temperature of the evaluation machine was increased by 5°C increments from 120°C within the range of 120°C to 220°C, and the unfixed solid image was fixed at each fixing temperature. The recording medium with the fixed solid image was folded in half so that the side with the formed image was facing inward. A 1kg weight covered with cloth was rubbed back and forth five times along the fold of the recording medium. Next, the folded recording medium was unfolded, and the presence or absence of toner peeling exceeding 1mm along the fold was checked. If there was no toner peeling exceeding 1mm, it was judged as a pass, and if there was toner peeling exceeding 1mm, it was judged as a fail. Among the fixing temperatures at which toner peeling was judged as passable, the lowest temperature was set as the minimum fixing temperature (evaluation value). The minimum fixing temperature was judged according to the following criteria. Note that the lower the minimum fixing temperature, the better the low-temperature fixing performance is judged to be.

[0141] (Criteria for minimum fixing temperature) A (Good): The minimum fixing temperature is 150°C or lower. B (Defective): The minimum fixing temperature is between 155°C and 160°C. C (particularly poor): Minimum fixing temperature is 165°C or higher.

[0142] <Maximum fixing temperature> The toner load of the evaluation machine was 0.25 mg / cm². 2 The settings were adjusted as follows. Using the evaluation machine, an unfixed solid image was formed on a recording medium (monochrome / color copy paper, Fujifilm Business Innovation Co., Ltd. "C2"). The fixing temperature of the evaluation machine was increased by 5°C from 120°C in the range of 120°C to 220°C, and the unfixed solid image was fixed at each fixing temperature. It was checked whether there was any contamination due to hot offset on the recording medium on which the solid image was fixed. Contamination due to hot offset is contamination caused by toner adhering to the fixing roller (for example, contamination that appears with each rotation cycle of the fixing roller). If contamination due to hot offset was present, the image density A of the contaminating area due to hot offset on the recording medium was measured using a fluorescence spectrophotometer (Konica Minolta, Inc. "FD-5"). In addition, the image density B of the unprinted recording medium was measured using a fluorescence spectrophotometer (Konica Minolta, Inc. "FD-5"). The contamination density was calculated using the formula "Contamination density = Image density A - Image density B". A contamination concentration of less than 0.005 was judged as passing, and a contamination concentration of 0.005 or higher was judged as failing. Among the fixing temperatures at which there was no contamination due to hot offset, or where there was contamination due to hot offset but the contamination concentration was judged as passing, the highest temperature was defined as the maximum fixing temperature (evaluation value). The maximum fixing temperature was determined according to the following criteria. Note that the higher the maximum fixing temperature, the better the resistance to hot offset is judged to be.

[0143] (Criteria for maximum fixing temperature) A (Good): The maximum fixing temperature is 205°C or higher. B (Defective): The maximum fixing temperature is between 190°C and 200°C. C (particularly poor): The maximum fixing temperature is 185°C or lower.

[0144] <Color development> The toner load of the evaluation machine was 0.37 mg / cm². 2 The settings were adjusted as follows. Using an evaluation machine, an unfixed solid image was formed on a recording medium (monochrome / color copy paper, Fujifilm Business Innovation Co., Ltd. "C2"). The unfixed solid image was fixed at a fixing temperature of 170°C. The image density (evaluation value) of the fixed solid image was measured using a fluorescence spectrophotometer (Konica Minolta, Inc. "FD-5"). Color development was judged according to the following criteria.

[0145] (Standards for the color development of black colorants) A1 (Good): Image density is 1.60 or higher. B1 (Poor): Image density is less than 1.60.

[0146] (Standards for color development of colorants other than black colorants) A2 (Good): Image density is 1.45 or higher. B2 (Poor): Image density is less than 1.45.

[0147] <Heat-resistant storage stability> 3g of toner was placed in a 20mL plastic container and left to stand in a constant temperature incubator set to 55°C for 3 hours. The toner after standing was used as the toner for heat-resistant storage evaluation. The toner for heat-resistant storage evaluation was sieved using a 200-mesh (75μm opening) sieve under the conditions of rheostat scale 5 and time 30 seconds, according to the manual for the Powder Tester (registered trademark) (manufactured by Hosokawa Micron Corporation). After sieving, the mass TA of the toner remaining on the sieve was measured. The degree of coagulation (evaluation value, unit: %) was calculated from the mass TB of the toner before sieving and the mass TA of the toner remaining on the sieve after sieving, according to the formula "Degree of coagulation = 100 × TA / TB". Heat-resistant storage was judged according to the following criteria.

[0148] (Standards for heat-resistant storage) A (Good): The degree of cohesion is 10% or less. B (Poor): The degree of cohesion is greater than 10% but less than or equal to 20%. C (particularly poor): The degree of cohesion is greater than 20%.

[0149] [Table 7]

[0150] [Table 8]

[0151] In Tables 7 and 8, "Value" refers to the evaluation value.

[0152] As shown in Table 4, the colorant content of toners (T-B1), (T-B3), (T-B5), and (T-B7) was more than 17.1 parts by mass per 100.0 parts by mass of amorphous polyester resin. As shown in Table 8, the evaluation of the minimum fixing temperature of toners (T-B1), (T-B3), (T-B5), and (T-B7) was poor.

[0153] As shown in Table 4, the colorant content of toners (T-B2), (T-B4), (T-B6), and (T-B8) was less than 11.5 parts by mass per 100.0 parts by mass of amorphous polyester resin. As shown in Table 8, the color development performance of toners (T-B2), (T-B4), (T-B6), and (T-B8) was poor.

[0154] As shown in Table 6, the shell layer coverage of toners (T-B9), (T-B11), (T-B13), and (T-B15) was over 60%. As shown in Table 8, the minimum fixing temperature evaluation of toners (T-B9), (T-B11), (T-B13), and (T-B15) was poor or particularly poor.

[0155] As shown in Table 6, the shell layer coverage of toners (T-B10), (T-B12), (T-B14), and (T-B16) was less than 30%. As shown in Table 8, the evaluation of the maximum fixing temperature and heat resistance storage performance of toners (T-B10), (T-B12), (T-B14), and (T-B16) were all poor.

[0156] On the other hand, as shown in Table 3, the colorant content of toners (T-A1) to (T-A22) was between 11.5 parts by mass and 17.1 parts by mass per 100.0 parts by mass of amorphous polyester resin. As shown in Table 5, the shell layer coverage of toners (T-A1) to (T-A22) was between 30% and 60%. As shown in Table 7, the evaluation of the minimum fixing temperature, maximum fixing temperature, color development performance, and heat resistance storage performance of toners (T-A1) to (T-A22) were all good.

[0157] Based on the above, the toners of the present invention, including toners (T-A1) to (T-A22), are judged to be able to form images with good color development even with a small amount of toner, and to have excellent low-temperature fixing properties, hot offset resistance, and heat storage resistance. [Industrial applicability]

[0158] The toner of the present invention can be used, for example, to form images in a copier, printer, or multifunction device.

Claims

1. Toner containing toner particles, The toner particle comprises a toner core and a shell layer that covers the surface of the toner core. The toner core contains a binder resin and a coloring agent. The aforementioned binder resin comprises an amorphous polyester resin and a crystalline polyester resin. The content of the coloring agent is 11.5 parts by mass or more and 17.1 parts by mass or less per 100.0 parts by mass of the amorphous polyester resin. A toner in which the area ratio of the surface area of ​​the toner core covered by the shell layer is 30% or more and 60% or less.

2. The toner according to claim 1, wherein the shell layer contains two types of resin.

3. The toner according to claim 1 or 2, wherein the shell layer contains a crosslinked styrene-acrylic resin and a non-crosslinked styrene-acrylic resin.

4. The toner according to claim 1 or 2, wherein the shell layer contains a styrene-acrylic resin having a cyano group and a styrene-acrylic resin having a quaternary ammonium base.

Images