Resin particles and method for producing same, aqueous dispersion, powder particles, resin composition, and electrostatic charge image developing toner

Abstract

To provide resin particles capable of achieving both suppression of aggregate generation over time and fold resistance.SOLUTION: Resin particles of a styrene-(meth)acrylate-based copolymer, in which, when a glass transition temperature obtained by a Fox equation from a ratio of constituent monomers of the entire resin particles is denoted by Tg1 and a glass transition temperature obtained by a Fox equation from a ratio of the constituent monomers calculated from surface analysis of the resin particles is denoted by Tg2, all of expression A, expression B, and expression C are satisfied, and a tetrahydrofuran-insoluble fraction is 80 mass% or more. Expression A: Tg1<10°C, Expression B: Tg2>10°C, and Expression C: 0°C<Tg2-Tg1<40°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to resin particles, a method for producing the same, an aqueous dispersion, powder particles, a resin composition, and a toner for developing electrostatic images. [Background technology]

[0002] Patent Document 1 discloses a toner for developing electrostatic images, which comprises toner base particles containing at least a binder resin, the toner base particles being formed by aggregation and fusion of binder resin fine particles and seed polymerized fine particles, the seed polymerized fine particles having an outer shell and a seed portion, the difference (Tg2-Tg1) between the glass transition temperature Tg1 of the seed portion and the glass transition temperature Tg2 of the outer shell being 50°C or more, the binder resin containing an amorphous resin having a glass transition temperature Tgm as a main component, and the Tgm being higher than the Tg1.

[0003] Patent Document 2 discloses a pressure-sensitive toner having toner particles containing a composite resin made of a styrene-based resin and a (meth)acrylic acid ester-based resin, in which the difference between the lowest and highest glass transition temperatures of the composite resin is 30°C or more, and the gel fraction of the toner particles is 1.0% by mass or more and 8.0% by mass or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-189408 [Patent Document 2] Japanese Patent Application Publication No. 2023-047238 Summary of the Invention [Problem to be solved by the invention]

[0005] When the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers of the whole resin particles is Tg1, and the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers calculated from the surface analysis of the resin particles is Tg2, the present disclosure aims to provide resin particles capable of achieving both suppression of aggregate generation over time and flexural fatigue resistance, compared to the case where any of the following formulas A, B or C is not satisfied, or the insoluble content in tetrahydrofuran is less than 80% by mass.

Means for Solving the Problems

[0006] Specific means for solving the above problems include the following aspects. <1> Resin particles of a styrene-(meth)acrylate copolymer, when the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers of the whole resin particles is Tg1, and the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers calculated from the surface analysis of the resin particles is Tg2, satisfying all of the following formulas A, B and C, and having an insoluble content in tetrahydrofuran of 80% by mass or more. Tg1 < 10°C Formula A Tg2 > 10°C Formula B 0°C < Tg2 - Tg1 < 40°C Formula C <2> The resin particles according to <1>, having a volume average particle diameter of 80 nm or more and less than 300 nm. <3> The storage elastic modulus G' at 40°C is 1×10 , , , , 5 , , 7 , , , ,

[0006] , , Pa or more and 1×10 7 Pa or less, the resin particles according to <1> or <2>. <4> A method for producing resin particles of a styrene-(meth)acrylate copolymer, wherein s A process for producing resin particles, which includes adding a plurality of emulsions containing styrene monomers and (meth)acrylate monomers at multiple stages in different ratios and polymerizing them, where the glass transition temperature determined by the Fox equation from the monomer ratio at the time when an emulsion with a monomer amount of 70% by mass relative to the total monomer amount of the resulting resin particles is added is designated as Tg3, and the glass transition temperature determined by the Fox equation from the monomer ratio of the emulsion added after that time is designated as Tg4, and which satisfies all of the following formulas D, E, and F. -45°C < Tg3 < 10°C Formula D Tg4 > 10°C Formula E 5°C < Tg < Tg4 - Tg3 < 60°C Formula F <5> In the step of polymerization, a surfactant is added, The method for producing resin particles according to <4>, wherein the addition amount of the surfactant is 0.5% by mass or more and less than 3.0% by mass based on the total mass of the resulting resin particles. <6> An aqueous dispersion containing the resin particles according to any one of <1> to <3>. <7> Powder particles containing the resin particles according to any one of <1> to <3>. <8> A resin composition containing the resin particles according to any one of <!> to <3>. <9> An electrostatic charge image developing toner containing the resin particles according to any one of <1> to <3>.

Advantages of the Invention

[0007] According to the invention according to <1>, when the glass transition temperature determined by the Fox equation from the ratio of the constituent monomers of the entire resin particles is designated as Tg1, and the glass transition temperature determined by the Fox equation from the ratio of the constituent monomers calculated from the surface analysis of the resin particles is designated as Tg2, resin particles are provided that can achieve both suppression of aggregate generation over time and flexural resistance, compared to cases where at least one of the above formulas A, B, or C is not satisfied, or where the insoluble content in tetrahydrofuran is less than 80% by mass. <!> According to the invention according to <2>, resin particles are provided that are more excellent in suppressing aggregate generation over time compared to cases where the volume average particle diameter is less than <80> nm or 300 nm or more. <3> According to the invention, the storage modulus G' at 40°C is 1 × 10 5 Less than Pa or 1×10 7 Compared with a case where the viscosity exceeds Pa, resin particles are provided which are more capable of suppressing the generation of aggregates over time and also having good bending resistance. <4> According to the invention related to (1), when the glass transition temperature calculated using the Fox equation from the constituent monomer ratio at the time when an emulsion is added, which contains 70 mass% of the constituent monomer amount of the entire resin particles to be obtained, is Tg3, and the glass transition temperature calculated using the Fox equation from the constituent monomer ratio of an emulsion added after that time is Tg4, a method for producing resin particles is provided that is more capable of suppressing the formation of aggregates over time and improving bending resistance than when at least one of formulas D, E, and F is not satisfied. <5> According to the present invention, a method for producing resin particles is provided in which a surfactant is added in the polymerization step, and the method has better suppression of aggregate formation over time than when the amount of surfactant added is less than 0.5 mass% or 3.0 mass% or more relative to the total mass of the resulting resin particles. <6> , <7> , <8> or <9> According to the invention, when Tg1 is the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers of the entire resin particle and Tg2 is the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers calculated from the surface analysis of the resin particle, there is provided an aqueous dispersion, powder particles, resin composition, or toner for developing electrostatic images, which uses resin particles that can suppress the generation of aggregates over time and achieve good bending resistance, compared to resin particles that do not satisfy at least one of formula A, formula B, or formula C, or that have a tetrahydrofuran-insoluble content of less than 80 mass %. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present disclosure. These descriptions and examples are illustrative of the embodiments. They are illustrative and do not limit the scope of the embodiments.

[0009] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0010] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0011] In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the composition may contain multiple types of particles corresponding to each component. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0012] In the present disclosure, "(meth)acrylic" is an expression that includes both acrylic and methacrylic, and "(meth)acrylate" is an expression that includes both acrylate and methacrylate. In the present disclosure, "toner for developing electrostatic images" is also referred to as "toner."

[0013] <Resin particles> The resin particles according to this embodiment are resin particles of a styrene-(meth)acrylate copolymer. When the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers of the entire resin particles is Tg1, and the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers calculated from the surface analysis of the resin particles is Tg2, all of the following formulas A, B, and C are satisfied, and the insoluble content in tetrahydrofuran is 80% by mass or more. Tg1 < 10°C Formula A Tg2 > 10°C Formula B 0°C < Tg2 - Tg1 < 40°C Formula C

[0014] Styrene-(meth)acrylate copolymer resin particles are generally produced in a dispersed liquid state such as emulsion polymerization. However, in the case of a copolymer with a low glass transition temperature, there is a problem that the particles tend to aggregate with each other, and it is difficult to achieve both good flexural fatigue resistance. In the resin particles according to this embodiment, when the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers is Tg1, and the glass transition temperature obtained by the Fox equation from the ratio of the constituent monomers calculated from the surface analysis of the copolymer is Tg, by satisfying all of the above formulas A, B, and C, the inside of the resin particles is a copolymer with a low glass transition temperature, and the surface layer of the resin particles is a copolymer with a high glass transition temperature, so that the surface of the resin particles becomes moderately hard, and aggregation of the particles is suppressed. In addition, since the insoluble content of the resin particles in tetrahydrofuran is 80% by mass or more, the resin particles become elastic, not only suppressing aggregation, but also making it easy to polymerize a copolymer with a high glass transition temperature on the particle surface layer, and making it easy to control the structure of the resin particles.

[0015] Hereinafter, the structure of the resin particles according to this embodiment will be described in detail.

[0016] (Glass transition temperatures Tg1 and Tg2) In the resin particles according to this embodiment, the glass transition temperature Tg1, which is obtained from the ratio of the constituent monomers of the entire resin particles by the Fox equation, is less than 10°C. From the viewpoint of achieving both suppression of aggregate generation over time and flexural resistance, for example, it is preferably -30°C or higher and less than 10°C, more preferably -20°C or higher and less than 5°C, and particularly preferably -10°C or higher and less than 0°C. In other words, the Tg1 satisfies Equation A, and from the viewpoint of suppressing aggregate generation over time, for example, it preferably satisfies Equation A-1, more preferably satisfies Equation A-2, and particularly preferably satisfies Equation A-3. Tg1 < 10°C Equation A -30°C ≤ Tg1 < 10°C Equation A-1 -20°C ≤ Tg1 < 5°C Equation A-2 -10°C ≤ Tg1 < 0°C Equation A-3

[0017] In the resin particles according to this embodiment, the glass transition temperature Tg2, which is obtained from the ratio of the constituent monomers calculated from the surface analysis of the resin particles by the Fox equation, is a temperature exceeding 10°C. From the viewpoint of achieving both suppression of aggregate generation over time and flexural resistance, for example, it is preferably exceeding 12°C and 45°C or lower, more preferably 14°C or higher and 35°C or lower, and particularly preferably 16°C or higher and 25°C or lower. In other words, the Tg2 satisfies Equation B, and from the viewpoint of suppressing aggregate generation over time, for example, it preferably satisfies Equation B-1, more preferably satisfies Equation B-2, and particularly preferably satisfies Equation B-3. Tg2 > 10°C Equation B 12°C < Tg2 ≤ 45°C Equation B-1 14°C ≤ Tg2 ≤ 35°C Equation B-2 16°C ≤ Tg2 ≤ 25°C Equation B-3

[0018] In the resin particles according to this embodiment, the value of Tg2 - Tg1 exceeds 0°C and is less than 40°C. From the perspective of suppressing the generation of aggregates over time, for example, it is preferably more than 10°C and 38°C or less, more preferably 15°C or more and 34°C or less, and particularly preferably 20°C or more and 30°C or less. In other words, the value of Tg2 - Tg1 satisfies Formula C. From the perspective of suppressing the generation of aggregates over time, for example, it preferably satisfies Formula C-1, more preferably satisfies Formula C-2, and particularly preferably satisfies Formula C-3. 0°C < Tg2 - Tg1 < 40°C Formula C 10°C < Tg2 - Tg1 ≤ 38°C Formula C-1 15°C ≤ Tg2 - Tg1 ≤ 34°C Formula C-2 20°C ≤ Tg2 - Tg1 ≤ 30°C Formula C-3

[0019] Here, the difference between the glass transition temperatures Tg1 and Tg2 according to the Fox equation is considered to mean that the styrene-based monomer and the (meth)acrylate-based monomer are not randomly bonded, and there are many components derived from styrene and they are localized on the particle surface, and there are many components derived from the (meth)acrylate-based monomer and they are localized inside the particles and are mixed. That is, the glass transition temperature of the polystyrene resin is about 100°C, and the glass transition temperature of the (meth)acrylic resin is usually lower than that. For example, since polyethyl acrylate is about -20°C, it is considered that the region with many styrene units is unevenly distributed on the surface of the resin particles.

[0020] The ratio of the constituent monomers of the styrene-(meth)acrylate copolymer in the entire resin particles is quantified by NMR analysis. The ratio of the constituent monomers of the styrene-(meth)acrylate copolymer on the surface of the resin particles is quantified from the following measurement. The resin particles are dried and the surface composition is analyzed using an X-ray photoelectron spectrometer (XPS). The XPS measurement device used is a JPS-9000MX manufactured by JEOL Ltd. The measurement uses MgKα rays as the X-ray source, an acceleration voltage of 10 kV, and an emission current of 30 mA. The ratio O(p) of oxygen elements to the total of carbon and oxygen elements in the resin particles is calculated using the following formula. O(p) = number of oxygen atoms / (number of carbon atoms + number of oxygen atoms) In addition, a resin consisting of only (meth)acrylate is prepared, and the ratio O(a) of oxygen elements in the (meth)acrylate is determined in the same manner. From these measurement results, when the sum of styrene and (meth)acrylate is set to 1, the surface (meth)acrylate ratio Wa(S) and the surface styrene ratio Ws(S) can be calculated using the following formulas. Wa(S)=O(p) / O(a) Ws(S)=1-(O(p) / O(a))

[0021] Then, the glass transition temperatures Tg1 and Tg2 are calculated from the ratio of each constituent monomer determined above using the Fox equation. Specifically, this is as follows. When the glass transition temperature of a homopolymer of a (meth)acrylate monomer is TgA (K), the (meth)acrylate monomer ratio (mass ratio: mass%) is WA, the glass transition temperature of a homopolymer of a styrene monomer is TgS (K), and the styrene monomer ratio (mass ratio: mass%) is WS, the target glass transition temperature Tg0 (K) can be calculated by the following Fox equation. Fox formula: 1 / Tg0=(WA / TgA)+(WS / TgS) Using the Fox formula, the glass transition temperature and ratio of each (meth)acrylate monomer and the glass transition temperature and ratio of the styrene monomer in the entire resin particle or on the surface of the resin particle are substituted, and Tg0 = "target glass transition temperature Tg1 or Tg2" is calculated using the Fox formula. The glass transition temperature of the homopolymer of the (meth)acrylate monomer and the glass transition temperature of the homopolymer of the styrene monomer may be an actually measured value or a catalog value.

[0022] In resin particles made of a styrene-(meth)acrylate copolymer, adjustment of Tg1, Tg2, etc. can be achieved by adjusting the polymerization conditions of the copolymer. In particular, to obtain resin particles in which a composition gradient occurs within the resin particles and regions rich in styrene units are unevenly distributed on the surface, when producing the resin particles by polymerization of a monomer-containing liquid containing a styrene-based monomer and a (meth)acrylate-based monomer, it is preferable to increase the content ratio of the styrene-based monomer to the (meth)acrylate-based monomer in the monomer-containing liquid as the polymerization progresses. "Increasing as the polymerization progresses" typically refers to gradually increasing the content ratio of the styrene-based monomer in the monomer-containing liquid, but also includes operations such as gradually increasing the content of the styrene-based monomer in the additional monomer when adding additional monomer to the monomer-containing liquid in multiple batches, or gradually increasing the amount of added styrene-based monomer to gradually increase the concentration of the styrene-based monomer in the monomer-containing liquid. For example, when preparing a styrene-(meth)acrylate-based copolymer by emulsion polymerization, the content of the styrene-based monomer in the emulsion can be gradually increased by adding the emulsion dropwise multiple times. Furthermore, it is also possible to control the progress of the reaction by adjusting the polymerization temperature, polymerization time, the method of adding the polymerization initiator, and the like.

[0023] (Tetrahydrofuran insolubles) The resin particles according to this embodiment have a tetrahydrofuran insoluble content (THF insoluble content) of 80% by mass or more, and from the viewpoint of both suppressing the formation of aggregates over time and achieving bending resistance, the content is preferably, for example, 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0024] A method for measuring the THF-insoluble content in this embodiment will be described. (1) 0.25 g of resin particles are weighed, 40 mL of tetrahydrofuran is added to the resin particles, and the mixture is mixed and stirred for 3 hours. (2) Then, the mixture obtained in (1) is centrifuged at 2,000 rpm (revolutions per minute) for 30 minutes. (3) Weigh 5 mL of the supernatant obtained after centrifugation in (2), transfer it to an aluminum dish, and evaporate and dry the tetrahydrofuran in a vacuum dryer adjusted to 50°C. (4) Calculate the THF insoluble content using the following formula from the difference in mass of the aluminum dish before and after drying. THF insoluble matter [%] = {0.25 - [(mass of supernatant and aluminum dish) - (mass of aluminum dish after drying)] × 8} / 0.25 × 100

[0025] (styrene-(meth)acrylate copolymer) The resin particles according to this embodiment are resin particles of a styrene-(meth)acrylate copolymer. The styrene-(meth)acrylate copolymer in the resin particles may be, for example, a resin obtained by radically polymerizing the following styrene monomer and (meth)acrylate monomer.

[0026] Examples of styrene-based monomers include styrene, α-methylstyrene, vinylnaphthalene, alkyl-substituted styrenes having alkyl chains such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene, halogen-substituted styrenes such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene, and fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene, etc. Among these, for example, styrene or α-methylstyrene is preferred.

[0027] Examples of (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, and (meth)acrylic acid. amyl, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, t-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-carboxyethyl (meth)acrylate, and the like.

[0028] As the (meth)acrylate monomer, from the viewpoint of inhibiting the generation of aggregates over time and facilitating adjustment of Tg1 and Tg2 of the styrene-(meth)acrylate copolymer, for example, a (meth)acrylate compound having an alkyl group with 2 to 12 carbon atoms (also referred to as "number of carbon atoms") is preferred, a (meth)acrylate compound having an alkyl group with 2 to 10 carbon atoms is more preferred, and a (meth)acrylate compound having an alkyl group with 4 to 7 carbon atoms is particularly preferred. Among these, as the (meth)acrylate monomer, for example, n-butyl (meth)acrylate is particularly preferred from the viewpoint of inhibiting the generation of aggregates over time and facilitating adjustment of Tg1 and Tg2 of the styrene-(meth)acrylate copolymer.

[0029] The styrene-(meth)acrylate copolymer in the resin particles according to this embodiment preferably has, for example, a crosslinked structure. Examples of crosslinking agents that form a crosslinked structure include aromatic polyfunctional vinyl compounds such as divinylbenzene and divinylnaphthalene; polyvinyl esters of aromatic polycarboxylic acids such as divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl homophthalate, divinyl trimesate, trivinyl trimesate, divinyl naphthalenedicarboxylate, and divinyl biphenylcarboxylate; divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridinedicarboxylate; vinyl esters of unsaturated heterocyclic carboxylic acids such as vinyl pyromucate, vinyl furancarboxylate, vinyl pyrrole-2-carboxylate, and vinyl thiophenecarboxylate; butanediol diacrylate, butanediol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, octanediol diacrylate, octanediol dimethacrylate, nonanediol diacrylate, nonanediol dimethacrylate, decanediol diacrylate, decanediol dimethacrylate, (meth)acrylic acid esters of linear polyhydric alcohols such as dodecanediol diacrylate, dodecanediol dimethacrylate, etc.; (meth)acrylic acid esters of branched or substituted polyhydric alcohols such as neopentyl glycol dimethacrylate, 2-hydroxy, 1,3-diacryloxypropane, etc.; polyfunctional vinyl esters of polycarboxylic acids such as polyethylene glycol di(meth)acrylate, polypropylene polyethylene glycol di(meth)acrylates, divinyl succinate, divinyl fumarate, vinyl maleate, divinyl maleate, divinyl diglycolate, vinyl itaconate, divinyl itaconate, divinyl acetonedicarboxylate, divinyl glutarate, divinyl 3,3'-thiodipropionate, divinyl trans-aconitate, trans-trivinyl aconitate, divinyl adipate, divinyl pimelate, divinyl suberate, divinyl azelaate, divinyl sebacate, divinyl dodecanedioate, and divinyl brassylate. The crosslinking agent may be used alone or in combination of two or more kinds.

[0030] Among these, it is preferable to use, as the crosslinking agent, for example, an alkylene glycol diacrylate having an alkylene chain with 6 or more carbon atoms. That is, it is preferable that the resin particles have, for example, a structural unit derived from an alkylene glycol diacrylate, and the alkylene chain in the alkylene glycol diacrylate has 6 or more carbon atoms. By using resin particles having structural units derived from alkylene glycol diacrylate and having an alkylene chain with 6 or more carbon atoms, the crosslinking density is reduced (i.e., the distance between crosslinking points is increased), and the elasticity of the resin particles can be prevented from becoming too high.

[0031] From the viewpoint of adjusting the crosslink density within an appropriate range, the number of carbon atoms in the alkylene chain in the alkylene glycol diacrylate is, for example, preferably 6 or more, more preferably 6 to 12, and even more preferably 8 to 12. More specific examples of the alkylene glycol diacrylate include 1,6-hexanediol acrylate, 1,6-hexanediol methacrylate, 1,8-octanediol diacrylate, 1,8-octanediol dimethacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol diacrylate, 1,10-decanediol dimethacrylate, 1,12-dodecanediol diacrylate, and 1,12-dodecanediol dimethacrylate, and among these, 1,10-decanediol diacrylate and 1,10-decanediol dimethacrylate are preferred. Other crosslinking agents include, for example, 2-carboxyethyl acrylate, and it is preferable to use at least one of them together with the above-mentioned alkylene glycol diacrylate.

[0032] In addition, when the resin particles are polymer particles of a resin particle forming composition containing a styrene-based monomer, a (meth)acrylate-based monomer, and a crosslinking agent, the Tg of the resin particles may be controlled by adjusting the amount of crosslinking agent contained in the composition. The content of the crosslinking agent in the resin particle forming composition is, for example, preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.2 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.3 parts by mass or more and 2.5 parts by mass or less, per 100 parts by mass of the total of the styrene-based monomer and the (meth)acrylate-based monomer.

[0033] (Volume average particle size) From the viewpoint of suppressing the generation of aggregates over time, the volume average particle size of the resin particles is, for example, preferably 50 nm or more and less than 350 nm, more preferably 80 nm or more and less than 300 nm, and even more preferably 100 nm or more and less than 250 nm.

[0034] The volume average particle size of the resin particles is measured using a particle size distribution obtained by measurement with a laser diffraction particle size distribution analyzer (e.g., LA-700 manufactured by Horiba, Ltd.), and the cumulative distribution for the volume of the divided particle size range (channel) is calculated from the small particle size side, and the particle size that accounts for 50% of the cumulative total of all particles is measured as the volume average particle size D50v.

[0035] (storage modulus) The storage modulus G' of the resin particles at 40°C is, for example, 1 × 10 5 Pa or more 1×10 7 Pa or less, and 5 Pa or more 1×10 7 Pa or less is more preferable, and 9×10 5 Pa or more 1×10 7 It is particularly preferable that the viscosity is 0.05 Pa or less.

[0036] The storage modulus G' of resin particles at 40°C is measured using a rheometer. Specifically, the resin particles to be measured are molded into a tablet shape at room temperature (e.g., 25°C) using a press molding machine to prepare a measurement sample. Then, using this measurement sample, dynamic viscoelasticity measurement is performed using a rheometer under the following conditions to obtain the storage modulus G'. -Measurement conditions- Measuring device: Rheometer ARES (manufactured by TA Instruments) Measuring jig: 8 mm parallel plate Gap: Adjusted to 4 mm Frequency: 1 Hz Measurement temperature: Measured under the condition of heating from 25°C to the maximum reachable temperature of 150°C Strain: 0.03 - 20% (automatic control) Heating rate: 1°C / min

[0037] (Method for producing resin particles) The method for producing resin particles according to this embodiment is not particularly limited, but it is a method for producing resin particles of a styrene-(meth)acrylate copolymer, which includes a step of adding and polymerizing a plurality of emulsions with different ratios of styrene monomer and (meth)acrylate monomer in multiple stages. When the glass transition temperature obtained by the Fox equation from the constitutional monomer ratio at the time of adding an emulsion having a monomer amount of 70% by mass based on the total constitutional monomer amount of the obtained resin particles is Tg3, and the glass transition temperature obtained by the Fox equation from the constitutional monomer ratio of the emulsion added after that time is Tg4, it is preferable to satisfy all of the following formulas D, E, and F. -45°C < Tg3 < 10°C Formula D Tg4 > 10°C Formula E 5°C < Tg4 - Tg3 < 60°C Formula F

[0038] The resin particles according to this embodiment are preferably, for example, resin particles produced by the method for producing resin particles according to this embodiment. Also, in the step of polymerization, a surfactant is added, and the addition amount of the surfactant is preferably, for example, 0.5% by mass or more and less than 3.0% by mass based on the total mass of the obtained resin particles.

[0039] - Glass transition temperatures Tg3 and Tg4 - In the method for producing resin particles according to the present embodiment, Tg3, which is the glass transition temperature determined by the Fox equation from the monomer ratio at the time when an emulsion having a monomer amount of 70% by mass with respect to the total monomer amount of the obtained resin particles is added, exceeds -45°C and is less than 10°C. From the viewpoint of achieving both suppression of aggregate generation over time and flex resistance, for example, it is preferably -40°C or higher and less than 5°C, more preferably -35°C or higher and less than 0°C, and particularly preferably -25°C or higher and -5°C or lower. In other words, the Tg3 satisfies Equation D, and from the viewpoint of suppressing aggregate generation over time, for example, it preferably satisfies Equation D-1, more preferably satisfies Equation D-2, and particularly preferably satisfies Equation D-3. -45°C < Tg3 < 10°C Equation D -40°C ≤ Tg3 < 5°C Equation D-1 -35°C ≤ Tg3 < 0°C Equation D-2 -25°C ≤ Tg3 ≤ -5°C Equation D-3

[0040] In the method for producing resin particles according to the present embodiment, Tg4, which is the glass transition temperature determined by the Fox equation from the monomer ratio of the emulsion added after adding the emulsion having a monomer amount of 70% by mass with respect to the total monomer amount of the obtained resin particles, is a temperature exceeding 10°C. From the viewpoint of achieving both suppression of aggregate generation over time and flex resistance, for example, it is preferably exceeding 12°C and 45°C or lower, more preferably 14°C or higher and 35°C or lower, and particularly preferably 16°C or higher and 25°C or lower. In other words, the Tg4 satisfies Equation E, and from the viewpoint of suppressing aggregate generation over time, for example, it preferably satisfies Equation E-1, more preferably satisfies Equation E-2, and particularly preferably satisfies Equation E-3. Tg4 > 10°C Equation E 12°C < Tg4 ≤ 45°C Equation E-1 14°C ≤ Tg4 ≤ 35°C Equation E-2 16°C ≤ Tg4 ≤ 25°C Equation E-3

[0041] In the resin particles according to this embodiment, the value of Tg4 - Tg3 exceeds 5°C and is less than 60°C, and from the viewpoint of achieving both suppression of aggregate generation over time and flexural fatigue resistance, for example, it is preferably more than 20°C and 48°C or less, more preferably 25°C or more and 44°C or less, and particularly preferably 30°C or more and 40°C or less. In other words, the value of Tg4 - Tg3 satisfies formula F and, from the viewpoint of suppressing aggregate generation over time, for example, preferably satisfies formula F-1, more preferably satisfies formula F-2, and particularly preferably satisfies formula F-3. 5°C < Tg4 - Tg3 < 60°C Formula F 20°C < Tg4 - Tg3 ≤ 48°C Formula F-1 25°C ≤ Tg4 - Tg3 ≤ 44°C Formula F-2 30°C ≤ Tg4 - Tg3 ≤ 40°C Formula F-3

[0042] - Polymerization step - The method for producing the resin particles according to this embodiment is not particularly limited, but it is a method for producing resin particles of a styrene-(meth)acrylate copolymer, and includes a step of adding an emulsion containing a styrene monomer and a (meth)acrylate monomer in multiple stages and polymerizing them. The emulsion preferably contains, for example, a styrene-based monomer and a (meth)acrylate-based monomer as monomers, and further contains a crosslinking agent.

[0043] Hereinafter, an example of the polymerization step will be described more specifically. The polymerization step includes, for example, a step of obtaining an emulsion containing a monomer, a crosslinking agent, a surfactant, and water (emulsion preparation step), a step of adding a polymerization initiator to the emulsion and heating to polymerize the monomer (first emulsion polymerization step), a step of adding an emulsion containing a monomer and a crosslinking agent to the reaction solution after the first emulsion polymerization step and heating to polymerize the monomer (second emulsion polymerization step). It is preferably included. Furthermore, in the second emulsion polymerization step, in order to adjust the composition of the particle surface, the emulsion may be adjusted by changing the ratio of the styrene-based monomer and the (meth)acrylate-based monomer, and the emulsion may be added multiple times.

[0044] --Emulsion preparation process-- This is a step of obtaining an emulsion containing a monomer, a crosslinking agent, a surfactant, and water. For example, it is preferable to obtain an emulsion by emulsifying a monomer, a crosslinking agent, a surfactant, and water using an emulsifier. Examples of emulsifiers include rotary agitators equipped with propeller-type, anchor-type, paddle-type, or turbine-type agitating blades; static mixers such as static mixers; rotor-stator emulsifiers such as homogenizers and Clearmix; mill-type emulsifiers equipped with a grinding function; high-pressure emulsifiers such as Manton-Gaulin pressure emulsifiers; high-pressure nozzle-type emulsifiers that generate cavitation under high pressure; high-pressure collision-type emulsifiers such as microfluidizers that apply shear force by causing liquids to collide with each other under high pressure; ultrasonic emulsifiers that generate cavitation using ultrasound; and membrane emulsifiers that emulsify through fine pores. The stirring speed and time during emulsification are not particularly limited except that emulsification is achieved, and it is preferable to select them appropriately depending on the desired particle size, etc. The heating temperature may be appropriately selected depending on the desired particle size, etc., but is preferably, for example, 35°C or higher and 85°C or lower.

[0045] As the monomer, it is preferable to use a styrene-based monomer and a (meth)acrylate-based monomer. As the crosslinking agent, those already mentioned above are applicable.

[0046] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. Among these, anionic surfactants are preferred. The surfactants may be used alone or in combination of two or more.

[0047] The emulsion may also contain a chain transfer agent. The chain transfer agent is not particularly limited, but a compound having a thiol component can be used. Specifically, alkyl mercaptans such as hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan are preferred. The mass ratio of the styrene-based monomer to the (meth)acrylate-based monomer in the emulsion (styrene-based monomer / (meth)acrylate-based monomer) is preferably, for example, from 0.2 to 1.1. The content of the crosslinking agent in the entire emulsion is preferably, for example, 0.5% by mass or more and 3% by mass or less.

[0048] --First emulsion polymerization step-- This is a process in which a polymerization initiator is added to the emulsion and heated to polymerize the monomers. Here, when carrying out the polymerization, it is preferable to stir the emulsion (reaction solution) containing the polymerization initiator with a stirrer, for example. Examples of the agitator include rotary agitators equipped with propeller-type, anchor-type, paddle-type, or turbine-type agitator blades. The stirring speed and time are not particularly limited as long as the thermoplastic resin is dissolved or dispersed in the solvent, and are preferably selected appropriately. As the polymerization initiator, for example, ammonium persulfate is preferably used. The monomer concentration in the emulsion is preferably, for example, 40% by mass or more and 70% by mass or less. The heating temperature during polymerization may be appropriately selected depending on the polymerization initiator, etc., but is preferably, for example, 60°C or higher and 85°C or lower.

[0049] --Second emulsion polymerization step-- This is a step in which an emulsion containing a monomer is added to the reaction solution after the first emulsion polymerization step, and the mixture is heated to polymerize the monomer. During polymerization, it is preferable to stir the reaction solution in the same manner as in the first emulsion polymerization step. In this step, the emulsion may be added in multiple portions by changing the ratio of the styrene-based monomer to the (meth)acrylate-based monomer in the emulsion containing the monomers. The emulsion containing the monomer is preferably obtained by emulsifying the monomer, surfactant, and water using an emulsifier, for example. The emulsion used in the second emulsion polymerization step preferably has a higher ratio of styrene-based monomers to all monomers in the emulsion than the emulsion used in the first emulsion polymerization step, and the ratio of styrene-based monomers to all monomers in the emulsion added in the second emulsion polymerization step is preferably 55% by mass or more and 70% by mass or less. The time point at which the emulsion is added, with a monomer amount of 70 mass% of the total constituent monomer amount of the resulting resin particles, may be either during the first emulsion polymerization step or the second emulsion polymerization step. For example, the monomer added in the first emulsion polymerization step is preferably 55 mass% or more and 85 mass% or less, more preferably 65 mass% or more and 75 mass% or less, and particularly preferably 70 mass% of the total constituent monomer amount of the resin particles.

[0050] The method for producing resin particles according to this embodiment may include known steps such as a step of isolating resin particles, a step of washing resin particles, and a step of drying resin particles. Known methods are used for isolation, washing, drying, etc. The washing method is not particularly limited, but from the viewpoint of electrostatic chargeability, it is preferable to carry out sufficient replacement washing with ion-exchanged water. The isolation method, for example, the solid-liquid separation method, is not particularly limited, but from the viewpoint of productivity, it is preferable to carry out suction filtration, pressure filtration, etc. The drying method is also not particularly limited, but from the viewpoint of productivity, it is preferable to carry out freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc.

[0051] As a method for producing the resin particles according to this embodiment, reference may be made to the polymerization granulation methods described in JP-A Nos. 5-43608, 5-222267, and 7-18003. Furthermore, the method for producing resin particles according to this embodiment may refer to the methods described in detail in "Ultrafine particles and materials" edited by the Materials Science Society of Japan, published by Shokabo in 1993, and "Production and applications of fine particles and powders" edited by Haruma Kawaguchi, published by CMC Publishing in 2005.

[0052] (Applications of resin particles) The resin particles according to the present embodiment may be used for any purpose, but are preferably used as image-forming resin particles, and more preferably as a toner for developing electrostatic images. In particular, the resin particles are particularly preferably used as an internal additive for a toner for developing electrostatic images. The resin particles according to this embodiment are also suitable for use as resin particles for powder coatings and toner displays, for example. Other applications include cosmetic base materials, rolling agents, abrasives, scrubbing agents, display spacers, materials for forming beads, light diffusing particles, resin reinforcing agents, refractive index control agents, toner particles, and anti-blocking particles. Furthermore, the resin particles according to this embodiment are preferably used in the form of, for example, an aqueous dispersion, powder particles, a resin composition, or the like, because they are excellent in inhibiting the generation of aggregates over time.

[0053] -Aqueous dispersion- The aqueous dispersion according to this embodiment is an aqueous dispersion containing the resin particles according to this embodiment. The aqueous dispersion may contain, in addition to the resin particles according to this embodiment and water, known components such as a surfactant, a water-soluble solvent, etc. From the viewpoints of suppressing the formation of aggregates and emulsion polymerization properties, the solids concentration of the aqueous dispersion is preferably, for example, 20% by mass or more and 45% by mass or less.

[0054] -Powder particles- The powder particles according to this embodiment are powder particles containing the resin particles according to this embodiment. The powder particles may contain known components such as colorants, magnetic materials, charge control agents, fillers, and external additives.

[0055] -Resin composition- The resin composition according to this embodiment is a resin composition containing the resin particles according to this embodiment. The resin composition preferably contains, for example, a binder, and more preferably contains a binder polymer. As the binder, a known binder can be used. Furthermore, the resin composition may contain known components such as colorants and fillers depending on the intended use of the resin composition.

[0056] -Toner for developing electrostatic images- The electrostatic image developing toner according to this embodiment is a toner for developing electrostatic images that contains the resin particles according to this embodiment. The toner for developing electrostatic images according to this embodiment preferably contains the resin particles according to this embodiment as an internal additive for toner particles (also referred to as "toner base particles"). The toner for developing electrostatic images according to this exemplary embodiment preferably contains, for example, toner particles and an external additive. The electrostatic image developing toner according to the present embodiment is used in a one-component or two-component electrostatic image developer, and the electrostatic image developer is used in an image forming apparatus or an image forming method.

[0057] The content of the resin particles is, for example, preferably 2% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles. By setting the content of the resin particles within the above range, it becomes easy to control the loss tangent tanδ of the toner particles at each temperature within the above range, which makes it easy to suppress the gloss difference and improves the low-temperature fixability.

[0058] ~Binder resin~ Examples of binder resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), and vinyl resins made of copolymers of two or more of these monomers. Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0059] As the binder resin, for example, a polyester resin is suitable. Examples of polyester resins include known polyester resins.

[0060] The polyester resin may be, for example, a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. As the polyester resin, a commercially available product or a synthesized product may be used.

[0061] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. As the polycarboxylic acid, a trivalent or higher carboxylic acid having a crosslinked or branched structure may be used in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0062] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, preferred polyhydric alcohols are aromatic diols and alicyclic diols, and more preferred are aromatic diols. As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0063] The glass transition temperature (Tg) of the polyester resin is, for example, preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K7121-1987 "Method for measuring transition temperature of plastics."

[0064] The weight average molecular weight (Mw) of the polyester resin is, for example, preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably, for example, 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the polyester resin is, for example, preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a Tosoh GPC HLC-8120GPC measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0065] The polyester resin can be obtained by a known production method, for example, by carrying out the reaction at a polymerization temperature of 180°C or higher and 230°C or lower, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation. If the raw material monomer is not soluble or compatible at the reaction temperature, a high-boiling solvent may be added as a solubilizer to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the solubilizer. If a monomer with poor compatibility is present, for example, the monomer with poor compatibility may be condensed in advance with the acid or alcohol to be polycondensed, and then polycondensed with the main component.

[0066] The content of the binder resin is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0067] ~Coloring agent~ Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, and the like. Examples of the dyes include various pigments such as phosphorus blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The colorant may be used alone or in combination of two or more kinds.

[0068] The colorant may be surface-treated as needed, or may be used in combination with a dispersant. Furthermore, a plurality of colorants may be used in combination.

[0069] The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0070] ~Mold release agent~ Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0071] The melting temperature of the release agent is, for example, preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0072] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0073] Other Additives Examples of other additives include known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0074] -Characteristics of toner particles, etc.- The toner particles may be toner particles of a single layer structure, or may be toner particles of a so-called core-shell structure composed of a core part (core particle) and a coating layer (shell layer) that coats the core part. The toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

[0075] The volume average particle size (D50v) of the toner particles is, for example, preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0076] The various average particle sizes and particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter). For the measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5 mass % aqueous solution of a surfactant (preferably, for example, sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of the electrolyte. The electrolyte solution containing the suspended sample is dispersed in an ultrasonic disperser for 1 minute, and the particle size distribution of particles in the range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. Based on the particle size distribution measured, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the smallest diameter side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v, the number particle size D16p, the particle size at 50% of the cumulative total as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at 84% of the cumulative total as the volume particle size D84v and the number particle size D84p. Using these, the volumetric particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 , the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 It is calculated as:

[0077] The average circularity of the toner particles is, for example, preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

[0078] The average circularity of toner particles is calculated by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the particle projected image)]. Specifically, this value is measured by the following method. First, the toner particles to be measured are sucked and collected, forming a flat flow, and a still image of the particles is captured by instantaneously activating a strobe light, and the particle image is analyzed using a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation).The number of samples to be sampled when calculating the average circularity is 3,500. When the toner contains external additives, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additives have been removed.

[0079] ~External additives~ Examples of external additives include inorganic particles, such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc.

[0080] The surfaces of inorganic particles as external additives may be subjected to, for example, a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0081] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate, and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0082] The amount of the external additive added is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less, based on the toner particles.

[0083] The toner for developing electrostatic images according to this embodiment preferably has a reflectance of 70% or more at the reflection peak in the spectral reflection spectrum for a solid image formed on coated paper.

[0084] ~Method for manufacturing electrostatic image developing toner~ The toner for developing electrostatic images according to this exemplary embodiment can be obtained by producing toner particles and then externally adding an external additive to the toner particles.

[0085] The toner particles may be produced by either a dry production method (for example, a kneading and pulverization method) or a wet production method (for example, an aggregation and coalescence method, a suspension polymerization method, a dissolution and suspension method). There are no particular limitations on these production methods, and any known production method may be used. Among these, it is preferable to obtain the toner particles by, for example, the aggregation and coalescence method. [Example]

[0086] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. All syntheses, processing, preparations, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise noted.

[0087] Example 1 (Preparation of emulsion (1-1)) Styrene: 28 parts n-Butyl acrylate: 42 parts 1,10-decanediol diacrylate: 0.7 parts Anionic surfactant (Eleminol MON-2, manufactured by Sanyo Chemical Industries, Ltd.): 0.8 parts Ion-exchanged water: 60 parts The above materials were placed in a mixing vessel equipped with a stirrer and stirred to prepare an emulsion (1-1).

[0088] (Preparation of emulsion (1-2)) Styrene: 18.6 parts n-Butyl acrylate: 11.4 parts 1,10-decanediol diacrylate: 0.3 parts Anionic surfactant (Eleminol MON-2, manufactured by Sanyo Chemical Industries, Ltd.): 0.4 parts Ion-exchanged water: 26 parts The above materials were placed in a mixing vessel equipped with a stirrer and stirred to prepare an emulsion (1-2).

[0089] (Preparation of styrene-(meth)acrylate copolymer particle dispersion (1)) A reaction vessel equipped with a stirrer and a nitrogen inlet tube was purged with nitrogen, and then 0.3 parts of an anionic surfactant (Eleminol MON-2, manufactured by Sanyo Chemical Industries, Ltd.) and 100 parts of ion-exchanged water were added. The reaction solution was heated in an oil bath with stirring until the temperature of the reaction solution reached 75°C. After adding 3 parts of the emulsion (1-1), 20 parts of an aqueous solution of ammonium persulfate whose concentration had been adjusted to 10% by mass was further added, and the mixture was maintained for 30 minutes. Then, while maintaining the temperature of the reaction solution at 75°C, emulsion (1-1) was gradually added dropwise to the reaction vessel over 150 minutes using a pump. At this point, an emulsion was added in an amount of monomers equivalent to 70% by mass of the total amount of monomers constituting the resulting resin particles. After maintaining the mixture for 30 minutes, emulsion (1-2) was further added dropwise over 90 minutes. After the dropwise addition was completed, the mixture was held for 60 minutes, after which 2 parts of 10% by weight ammonium persulfate was added, and the mixture was held for another 3 hours before being cooled to room temperature. The resulting resin particle dispersion was sieved through a 70 μm mesh sieve to remove any aggregates formed during the polymerization process, and ion-exchanged water was added to a solids concentration of 30% to give styrene-(meth)acrylate copolymer particle dispersion (1). The volume average particle size of the resin particles was 165 nm.

[0090] <Example 2> The amount of styrene used in preparing emulsion (1-1) was changed to 37.5 parts and the amount of n-butyl acrylate was changed to 32.6 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amounts of styrene and n-butyl acrylate used in preparing emulsion (1-2) were changed to 17.6 parts and 12.5 parts, respectively.

[0091] Example 3 The amount of styrene used in preparing emulsion (1-1) was changed to 9.1 parts and the amount of n-butyl acrylate to 60.9 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amounts of styrene and n-butyl acrylate used in preparing emulsion (1-2) were changed to 16.7 parts and 13.4 parts, respectively.

[0092] Example 4 The amount of styrene used in preparing emulsion (1-1) was changed to 32.2 parts and the amount of n-butyl acrylate was changed to 37.8 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amounts of styrene and n-butyl acrylate used in preparing emulsion (1-2) were changed to 22.5 parts and 7.5 parts, respectively.

[0093] <Example 5> The amount of 1,10-decanediol diacrylate used in preparing emulsion (1-1) was changed to 0.35 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amount of 1,10-decanediol diacrylate used in preparing emulsion (1-2) was changed to 0.15 parts.

[0094] Example 6 A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that 1,10-decanediol diacrylate was changed to 1,6-hexanediol methacrylate when preparing emulsion (1-1) and emulsion (1-2).

[0095] Example 7 The amount of anionic surfactant used in preparing emulsion (1-1) was changed to 0.07 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amount of anionic surfactant used in preparing emulsion (1-2) was changed to 0.03 parts.

[0096] Example 8 Styrene-(meth)acrylate copolymer particle dispersions were prepared in the same manner as in Example 1, except that when preparing emulsions (1-1) and (1-2), the anionic surfactant used in preparing styrene-(meth)acrylate copolymer particle dispersion (1) was changed to a nonionic surfactant (Emulgen 430, manufactured by Kao Corporation).

[0097] Example 9 The amount of anionic surfactant used in preparing emulsion (1-1) was changed to 0.07 parts. The amount of anionic surfactant used in preparing emulsion (1-2) was changed to 0.03 parts. A styrene-(meth)acrylate copolymer particle dispersion liquid was prepared in the same manner as in Example 1, except that the amount of anionic surfactant used in preparing the styrene-(meth)acrylate copolymer particle dispersion liquid (1) was changed to 1.3 parts.

[0098] Example 10 The amount of anionic surfactant used in preparing emulsion (1-1) was changed to 1.0 part. The amount of anionic surfactant used in preparing emulsion (1-2) was changed to 0.45 parts. A styrene-(meth)acrylate copolymer particle dispersion liquid was prepared in the same manner as in Example 1, except that the amount of anionic surfactant used in preparing the styrene-(meth)acrylate copolymer particle dispersion liquid (1) was changed to 0.05 parts.

[0099] Example 11 When preparing emulsion (1-1), the amount of styrene was changed to 7.0 parts, and n-butyl acrylate was changed to 63.0 parts of ethyl acrylate. A styrene-(meth)acrylate emulsion was prepared in the same manner as in Example 1, except that the amount of styrene used in the preparation of emulsion (1-2) was changed to 12.9 parts and n-butyl acrylate was changed to 17.1 parts of ethyl acrylate. A dispersion of acrylate copolymer particles was prepared.

[0100] Example 12 When preparing emulsion (1-1), the amount of styrene was changed to 34.3 parts, and n-butyl acrylate was changed to 35.7 parts of 2-ethylhexyl acrylate. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amount of styrene used in preparing emulsion (1-2) was changed to 20.4 parts and n-butyl acrylate was changed to 9.6 parts of 2-ethylhexyl acrylate.

[0101] <Comparative Example 1> (Preparation of emulsion (C1)) Styrene: 46.6 parts n-Butyl acrylate: 53.4 parts 1,10-decanediol diacrylate: 1.0 part Anionic surfactant (Eleminol MON-2, manufactured by Sanyo Chemical Industries, Ltd.): 1.2 parts Ion-exchanged water: 86 parts The above materials were placed in a mixing vessel equipped with a stirrer and stirred to prepare an emulsion (C1).

[0102] (Preparation of styrene-(meth)acrylate copolymer particle dispersion (C1)) A reaction vessel equipped with a stirrer and a nitrogen inlet tube was purged with nitrogen, and then 0.3 parts of an anionic surfactant (Eleminol MON-2, manufactured by Sanyo Chemical Industries, Ltd.) and 100 parts of ion-exchanged water were added. The reaction solution was heated in an oil bath with stirring until the temperature of the reaction solution reached 75°C. After adding 3 parts of the emulsion (C1), 20 parts of an aqueous solution of ammonium persulfate whose concentration had been adjusted to 10% by mass was further added, and the mixture was maintained for 30 minutes. Thereafter, while the temperature of the reaction solution was maintained at 75°C, the remaining emulsion (C1) was gradually added dropwise to the reaction vessel using a pump over 240 minutes. After the dropwise addition was completed, the mixture was held for 60 minutes, and then 2 parts of 10% by mass ammonium persulfate was added. The mixture was then held for another 3 hours, and then cooled to room temperature. The resulting resin particle dispersion was sieved through a 70 μm mesh sieve to remove any aggregates formed during the polymerization process, resulting in styrene-(meth)acrylate copolymer particle dispersion (C1). The volume average particle size of the resin particles was 170 nm.

[0103] <Comparative Example 2> The amount of styrene used in preparing emulsion (1-1) was changed to 7.0 parts and the amount of n-butyl acrylate to 63.0 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amounts of styrene and n-butyl acrylate used in preparing emulsion (1-2) were changed to 16.8 parts and 13.2 parts, respectively.

[0104] <Comparative Example 3> The amount of styrene used in preparing emulsion (1-1) was changed to 38.5 parts and the amount of n-butyl acrylate was changed to 31.5 parts. A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amounts of styrene and n-butyl acrylate used in preparing emulsion (1-2) were changed to 18.6 parts and 11.4 parts, respectively.

[0105] <Comparative Example 4> When preparing emulsion (1-1), 0.21 parts of 1,10-decanediol diacrylate was used. Change A styrene-(meth)acrylate copolymer particle dispersion was prepared in the same manner as in Example 1, except that the amount of 1,10-decanediol diacrylate used in preparing emulsion (1-2) was changed to 0.09 parts.

[0106] <Evaluation of aggregate formation suppression over time> The obtained styrene-(meth)acrylate copolymer particle dispersion was placed in a chamber at 40°C. The dispersion was then poured into a 70 μm mesh sieve, and 500 g of resin content was sieved. The aggregates remaining on the sieve were then collected. The collected aggregates were dried in a chamber at 40°C for one day and then weighed. A: The weight of the aggregate after drying is less than 0.5 g B: The weight of the aggregate after drying is 0.5 g or more and less than 2.5 g C: The weight of the aggregate after drying is 2.5 g or more and less than 6.0 g D: The weight of the aggregate after drying is 6.0 g or more.

[0107] <Bending resistance evaluation> The bending resistance was evaluated by preparing a toner using the obtained styrene-(meth)acrylate copolymer particle dispersion liquid. The toner was prepared according to the following procedure.

[0108] [Preparation of amorphous polyester resin dispersion (1)] Terephthalic acid: 28 parts by mole Isophthalic acid: 15 mole parts Suberic acid: 5 mol parts Trimellitic anhydride: 2 mole parts Bisphenol A propylene oxide 2 mole adduct: 6 mole parts Bisphenol A propylene oxide 3 mole adduct: 44 mole parts The above materials were charged into a reaction vessel equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a distillation column, and the temperature was raised to 190°C over 1 hour, followed by adding 1.2 parts of dibutyltin oxide per 100 parts of the above materials. The temperature was raised to 240°C over 6 hours while distilling off the generated water, and then the temperature was maintained at 240°C for 3 hours to continue the dehydration condensation reaction, followed by cooling to obtain amorphous polyester resin (1). The acid value of the amorphous polyester resin (1) was 11, and the glass transition temperature was 58°C.

[0109] Amorphous polyester resin (1): 100 parts Methyl ethyl ketone: 60 parts Isopropanol: 10 parts 10% ammonia solution: 3.5 parts The above materials were charged into a jacketed reaction vessel equipped with a condenser, a thermometer, a water dropping device, and an anchor blade, and the amorphous polyester resin (1) was dissolved in a water-circulating thermostatic bath while stirring and mixing at 100 rpm while maintaining the liquid temperature at 50° C. Next, the water-circulating thermostatic bath was set to 40° C., and a total of 300 parts of ion-exchanged water maintained at 40° C. was added dropwise at a rate of 3 parts / min to cause phase inversion and produce an emulsion. The resulting emulsion was placed in a recovery flask and placed in an evaporator equipped with a vacuum control unit via a trap bulb. The recovery flask was heated in a 60°C hot water bath while rotating, and the pressure was reduced to 7 kPa while taking care to prevent bumping, to remove the solvent. The pressure was then returned to normal pressure, and the recovery flask was water-cooled to obtain a dispersion. Ion-exchange water was added to the resulting dispersion to obtain an amorphous polyester resin dispersion (1) with a solids content of 20% by mass. The volume average particle size of the amorphous polyester resin particles in the amorphous polyester resin dispersion (1) was 180 nm.

[0110] [Preparation of Crystalline Polyester Resin Particle Dispersion (1)] Dodecanedioic acid: 50 mole parts 1,6-Hexanediol: 50 parts by mole The above materials were charged into a reaction vessel equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column. The temperature was raised to 160°C over 1 hour, and 0.8 parts of dibutyltin oxide was added per 100 parts of the above materials. The temperature was raised to 180°C over 6 hours while distilling off the generated water, and the reaction proceeded under reflux in the vessel while maintaining 180°C and stirring for 5 hours. The temperature was then gradually raised to 230°C under reduced pressure (3 kPa) and maintained at 230°C while stirring for 2 hours. The reaction mixture was then cooled. After cooling, solid-liquid separation was performed, and the solid was dried to obtain crystalline polyester resin (1). The weight-average molecular weight of crystalline polyester resin (1) was 29,000.

[0111] Crystalline polyester resin (1): 100 parts Methyl ethyl ketone: 70 parts Isopropanol: 12 parts 10% ammonia solution: 3 parts The above materials were charged into a jacketed reaction vessel equipped with a condenser, a thermometer, a water dropping device, and an anchor blade, and the crystalline polyester resin (1) was dissolved by stirring and mixing at 100 rpm while maintaining the liquid temperature at 80° C. in a water circulation type thermostatic bath. Next, the water circulation type thermostatic bath was set to 60° C., and a total of 300 parts of ion-exchanged water maintained at 60° C. was added dropwise at a rate of 3 parts / min to cause phase inversion, thereby obtaining an emulsion. The resulting emulsion was placed in a recovery flask and set in an evaporator equipped with a vacuum control unit via a trap bulb. The recovery flask was rotated and heated in a 60°C hot water bath, and the pressure was reduced to 7 kPa while taking care to prevent bumping, to remove the solvent. The pressure was then returned to normal pressure, and the recovery flask was water-cooled to obtain a dispersion. Ion-exchange water was added to the dispersion to obtain a crystalline polyester resin particle dispersion (1) with a solids content of 20 mass%. The volume average particle size of the crystalline polyester resin particles in the crystalline polyester resin particle dispersion (1) was 160 nm.

[0112] [Preparation of Colorant Particle Dispersion] Carbon black (Regal 330, manufactured by Cabot Corporation): 110 parts Anionic surfactant (Neopelex G-65, manufactured by Kao Corporation): 6 parts Ion-exchanged water: 300 parts The above materials were mixed and dispersed for 10 minutes using a homogenizer (Ultra Turrax T50, manufactured by IKA). Ion-exchanged water was added to the resulting dispersion to obtain a colorant particle dispersion with a solid content of 20% by mass. The volume average particle size of the colorant particles in the colorant particle dispersion was 220 nm.

[0113] [Preparation of Release Agent Particle Dispersion] Fischer-Tropsch wax (Sasolwax H1, manufactured by Sasol): 100 parts Anionic surfactant (Neopelex G-65): 6 parts Ion-exchanged water: 300 parts The above materials were mixed and heated to 100°C, and dispersed using a homogenizer (Ultra Turrax T50). The mixture was further dispersed using a Manton-Gaulin high-pressure homogenizer (Gaulin), and ion-exchanged water was added to the dispersion to obtain a release agent particle dispersion with a solid content of 20% by mass. The volume average particle size of the release agent particles in the release agent particle dispersion was 230 nm.

[0114] [Toner Preparation] Amorphous polyester resin dispersion (1) (solid content 20% by mass): 28 parts 7 parts of the obtained styrene-(meth)acrylate copolymer particle dispersion (solid content 30% by mass) Crystalline polyester resin dispersion (solid content 20% by mass): 19 parts Colorant particle dispersion (solid content 20% by mass): 6 parts Release agent particle dispersion (solid content 20% by mass): 8 parts Anionic surfactant (Eleminol MON-2): 0.7 parts Ion-exchanged water: 50 parts The above materials were placed in a reaction vessel equipped with a thermometer, pH meter, and stirrer, and the temperature of the reaction vessel was maintained at 20°C while stirring at 150 rpm for 30 minutes. Next, a 0.3N aqueous nitric acid solution was added to adjust the pH to 5.0, and then a 2% aqueous aluminum sulfate solution was added while dispersing with a homogenizer (Ultra-Turrax T50). The mixture was then heated to 45°C at a rate of 0.4°C / min while stirring, and maintained at this temperature for 30 minutes. Next, 29 parts of amorphous polyester resin particle dispersion (1) was added and held for 30 minutes. Next, a 0.1 N aqueous sodium hydroxide solution was added to adjust the pH to 8.5 and held for 15 minutes, after which the temperature was raised to 80°C at a rate of 1°C / min while continuing to stir, and held at 80°C for 5 hours. Next, the mixture was cooled, solid-liquid separated, the solid matter was washed with ion-exchanged water, and then dried in a vacuum freeze dryer for 24 hours to obtain toner particles (1) with a volume average particle size of 5.5 μm.

[0115] 100 parts of the toner particles (1) and 2.0 parts of hydrophobic silica (manufactured by Nippon Aerosil: trade name RY200) were mixed in a Henschel mixer to obtain toner (1).

[0116] The obtained toner was printed on a DocuCentreColor 400 manufactured by Fujifilm Business Innovation Co., Ltd. at a toner loading of 13.5 g / m 2 The temperature was adjusted so that the unfixed image was output. Film synthetic paper (Yupo paper, manufactured by Yupo Corporation) was used as the recording medium. The output image was a 25mm x 25mm solid image with 100% image density. The fixing evaluation device used was an ApeosPortIV C3370 manufactured by Fujifilm Business Innovation Co., Ltd., with the fixing unit removed and modified so that the fixing temperature could be changed. The nip width of the fixing evaluation device was 6mm and the nip thickness was 1.6kgf / cm 2 The process speed was 175 mm / sec. Unfixed images were fixed at fixing temperatures ranging from 90°C to 180°C in 5°C increments, and good fixed images with no image defects or image disturbances due to poor peeling were bent and a 50 g load was applied to observe the degree of image defects in that area. The fixing temperature at which some image peeling was observed but at a level above which it was determined that there was no practical problem was evaluated as the minimum fixing temperature. A: The minimum fixing temperature is less than 130°C. B: The minimum fixing temperature is 130°C or higher and less than 140°C. C: The minimum fixing temperature is 140°C or higher and lower than 150°C. D: The minimum fixing temperature is 150°C or higher.

[0117] [Table 1]

[0118] As shown in Table 1, the resin particles of the Examples were superior to the resin particles of the Comparative Examples in both suppressing the generation of aggregates over time and in bending resistance.

[0119] ((1)) Resin particles of styrene-(meth)acrylate copolymer, wherein the glass transition temperature determined by the Fox equation from the ratio of constituent monomers of the whole resin particles is Tg1, and when the glass transition temperature determined by the Fox equation from the ratio of constituent monomers calculated from the surface analysis of the resin particles is Tg2, the resin particles satisfy all of the following formulas A, B, and C and have an insoluble content in tetrahydrofuran of 80% by mass or more. Tg1 < 10°C Formula A Tg2 > 10°C Formula B 0°C < Tg2 - Tg1 < 40°C Formula C ((2)) The resin particles according to ((1)), having a volume average particle diameter of 80 nm or more and less than 300 nm. ((3)) The resin particles according to ((1)) or ((2)), having a storage elastic modulus G' at 40°C of 1×10 5 Pa or more and 1×10 7 Pa or less. ((4)) A method for producing resin particles of a styrene-(meth)acrylate copolymer, comprising a step of adding and polymerizing a plurality of emulsions having different ratios of styrene monomer and (meth)acrylate monomer in multiple stages, and the glass transition temperature determined by the Fox equation from the constituent monomer ratio at the time when an emulsion having a monomer amount of 70% by mass with respect to the total amount of constituent monomers of the obtained resin particles is added is Tg3, and the glass transition temperature determined by the Fox equation from the constituent monomer ratio of the emulsion added after that time is Tg4. A method for producing resin particles that satisfy all of the following formulas D, E, and F. -45°C < Tg3 < 10°C Formula D Tg4 > 10°C Formula E 5°C < Tg4 - Tg3 < 60°C Formula F ((5)) In the step of polymerizing, a surfactant is added, and the addition amount of the surfactant is 0.5% by mass or more and less than 3.0% by mass with respect to the total mass of the obtained resin particles. The method for producing resin particles according to ((4)). ((6)) An aqueous dispersion containing the resin particles according to any one of ((1)) to ((3)). (((7))) Powder particles containing resin particles according to any one of (((1))) to (((3))). (((8))) A resin composition comprising the resin particles according to any one of (((1))) to (((3))). (((9))) A toner for developing electrostatic images, comprising the resin particles according to any one of ((1))) to (((3))).

[0120] According to the invention of (((1))), when the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers of the entire resin particle is Tg1 and the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers calculated from the surface analysis of the resin particle is Tg2, resin particles are provided that can achieve both suppression of aggregate formation over time and bending resistance, compared to resin particles that do not satisfy at least one of formula A, formula B, or formula C, or in which the tetrahydrofuran insoluble content is less than 80 mass%. According to the invention (((2))), resin particles are provided which are more excellent in suppressing the formation of aggregates over time than when the volume average particle size is less than 80 nm or 300 nm or more. According to the invention (((3))), the storage modulus G' at 40°C is 1×10 5 Less than Pa or 1×10 7 Compared with a case where the viscosity exceeds Pa, resin particles are provided which are more capable of suppressing the generation of aggregates over time and also having good bending resistance. According to the invention related to (((4))), when the glass transition temperature calculated by the Fox equation from the constituent monomer ratio at the time when an emulsion is added, in which the monomer amount is 70 mass % of the constituent monomer amount of the entire resin particles to be obtained, is Tg3, and the glass transition temperature calculated by the Fox equation from the constituent monomer ratio of an emulsion added after that time is Tg4, a method for producing resin particles is provided that is more capable of suppressing the formation of aggregates over time and improving bending resistance than when at least one of formulas D, E, and F is not satisfied. According to the invention related to (((5))), a surfactant is added in the polymerization step, and a method for producing resin particles is provided which is superior in inhibiting the formation of aggregates over time compared to when the amount of the surfactant added is less than 0.5 mass % or 3.0 mass % or more, relative to the total mass of the obtained resin particles. According to the inventions of (((6))), (((7))), (((8))) or (((9))), when the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers of the entire resin particle is Tg1 and the glass transition temperature calculated by the Fox equation from the ratio of constituent monomers calculated from the surface analysis of the resin particle is Tg2, there is provided an aqueous dispersion, powder particles, resin composition or toner for developing electrostatic images which uses resin particles that can achieve both suppression of aggregate formation over time and bending resistance, compared to when resin particles which do not satisfy at least one of formula A, formula B or formula C or in which the tetrahydrofuran insoluble content is less than 80 mass % are used.

Claims

1. Resin particles of a styrene-(meth)acrylate copolymer, When Tg1 is a glass transition temperature calculated by the Fox equation from the ratio of constituent monomers of the entire resin particle, and Tg2 is a glass transition temperature calculated by the Fox equation from the ratio of constituent monomers calculated from surface analysis of the resin particle, the resin particle satisfies all of the following formulae A, B, and C: The insoluble content of tetrahydrofuran is 80% by mass or more. Resin particles. Tg1<10℃ Formula A Tg2>10℃ Formula B 0℃<Tg2-Tg1<40℃ Formula C

2. 2. The resin particles according to claim 1, wherein the volume average particle size is 80 nm or more and less than 300 nm.

3. The storage modulus G' at 40°C is 1 x 10 ５ Pa or more 1×10 ７ The resin particles according to claim 1, wherein the viscosity is 0.05 Pa or less.

4. A method for producing resin particles of a styrene-(meth)acrylate copolymer, comprising: The method includes a step of adding a plurality of emulsions containing a styrene monomer and a (meth)acrylate monomer at different ratios in multiple stages to polymerize the monomers, When the glass transition temperature calculated by the Fox equation from the constituent monomer ratio at the time when an emulsion is added in an amount of monomers equivalent to 70% by mass of the total amount of constituent monomers in the resulting resin particles is defined as Tg3, and the glass transition temperature calculated by the Fox equation from the constituent monomer ratio of emulsions added after that time is defined as Tg4, the glass transition temperature satisfies all of the following formulae D, E, and F: A method for producing resin particles. -45℃<Tg3<10℃ Formula D Tg4>10℃ Formula E 5℃<Tg4-Tg3<60℃ Formula F

5. In the polymerization step, a surfactant is added, The method for producing resin particles according to claim 4, wherein the amount of the surfactant added is 0.5% by mass or more and less than 3.0% by mass based on the total mass of the resin particles to be obtained.

6. An aqueous dispersion containing the resin particles according to claim 1 .

7. Powder particles comprising the resin particles according to any one of claims 1 to 3.

8. A resin composition comprising the resin particles according to any one of claims 1 to 3.

9. A toner for developing electrostatic images, comprising the resin particles according to claim 1 .

Images