Toner manufacturing method

Abstract

To provide a method for producing a toner capable of obtaining the toner in which an existence ratio of fine particles and a volume average particle diameter (Dv) are controlled within appropriate ranges while lowering the existence ratio of coarse particles.SOLUTION: Provided is a method for producing a toner which includes: a colloidal dispersion liquid preparation step; a liquid droplet formation step; and a polymerization step. The total content of the second water-soluble polyvalent metal salt (a2), which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1), and the boron-containing compound (a3) is 2000 to 4000 ppm by weight when the content of the first water-soluble polyvalent metal salt (a1) as the main component is 100% by weight as an aqueous solution (A) of the water-soluble polyvalent metal salt used for preparing the colloidal dispersion liquid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a toner. [Background technology]

[0002] In image forming devices such as electrophotographic devices, electrostatic recording devices, and electrostatic printing devices, developers are used to visualize electrostatic latent images formed on photoconductors. Developers are primarily composed of colored particles (toner) in which colorants, charge control agents, release agents, etc. are dispersed in a binder resin.

[0003] Toner manufacturing methods can be broadly divided into pulverization methods and polymerization methods. In the pulverization method, a binder resin, a colorant, and other additive components are melted and kneaded, and the molten material is pulverized and classified to produce a toner (pulverized toner) made of colored resin particles. In the polymerization method, a polymerizable composition containing a polymerizable monomer, a colorant, and other additive components is polymerized by a suspension polymerization method, an emulsion polymerization aggregation method, a dispersion polymerization method, a solution suspension method, or the like to produce a toner made of colored resin particles.

[0004] For example, Patent Document 1 discloses a method for producing toner particles, which includes a preparation step of preparing an aqueous medium containing poorly water-soluble inorganic fine particles and polyvalent metal ions, a granulation step of adding a polymerizable monomer composition containing a polymerizable monomer and a colorant to the aqueous medium to form particles of the polymerizable monomer composition in the aqueous medium, and a polymerization step of polymerizing the polymerizable monomer contained in the particles of the polymerizable monomer composition to produce toner particles, wherein the content of the polyvalent metal ions in the aqueous medium prepared in the preparation step is 4 mmol / L or more and 120 mmol / L or less, and when D1 is the number average particle diameter of the poorly water-soluble inorganic fine particles, D1 satisfies the relationship 50 nm≦D1≦250 nm. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-060009 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, in order to improve the functionality of toner, there has been a demand for technology that can obtain toner with a highly controlled particle size distribution. Specifically, if the proportion of coarse particles in the toner is too high, there is a risk of developing roll abrasion, vertical streaks, uneven solid printing, etc., so the proportion of coarse particles must be low. Furthermore, if the proportion of fine particles (especially particles with a particle size of less than 5 μm) in the resulting toner is too high, the toner tends to deteriorate over time, while if the proportion of fine particles is too low, there is a risk of insufficient fixation to printing paper. Therefore, it is necessary to control the proportion of fine particles within an appropriate range.

[0007] An object of the present invention is to provide a method for producing a toner that can produce a toner in which the proportion of fine particles and the volume average particle size (Dv) are controlled within appropriate ranges while the proportion of coarse particles is reduced. [Means for solving the problem]

[0008] The present inventors have conducted studies to achieve the above-mentioned object, and have found that the above-mentioned problems can be solved by a toner manufacturing method comprising a colloidal dispersion preparation step, a droplet formation step, and a polymerization step, in which the aqueous solution (A) of a water-soluble multivalent metal salt used in preparing the colloidal dispersion contains, when the content of the first water-soluble multivalent metal salt (a1) as the main component is taken as 100% by weight, a second water-soluble multivalent metal salt (a2) which is a water-soluble multivalent metal salt other than the first water-soluble multivalent metal salt (a1), and a boron-containing compound (a3), in a total amount of 2000 to 4000 ppm by weight, thereby completing the present invention.

[0009] That is, according to the present invention, there is provided a method for preparing a colloidal dispersion of a poorly water-soluble metal compound by mixing an aqueous solution (A) of a water-soluble polyvalent metal salt with an aqueous solution (B) of a water-soluble alkali metal compound; (2) a droplet forming step of mixing a polymerizable monomer composition containing a polymerizable monomer and a colorant with a colloidal dispersion of the poorly water-soluble metal compound to obtain a suspension containing droplets of the polymerizable monomer composition; and (3) a polymerization step of subjecting the suspension to a polymerization reaction to obtain colored resin particles; A toner manufacturing method comprising: The method for producing a toner provides the following: when the water-soluble polyvalent metal salt contained as a main component in the aqueous solution (A) of the water-soluble polyvalent metal salt is a first water-soluble polyvalent metal salt (a1), the aqueous solution (A) of the water-soluble polyvalent metal salt contains at least one of a second water-soluble polyvalent metal salt (a2) which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1) and a boron-containing compound (a3), and when the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution (A) of the water-soluble polyvalent metal salt is taken as 100% by weight, the total content of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​is 2000 to 4000 ppm by weight.

[0010] In the toner manufacturing method of the present invention, it is preferable that the aqueous solution of the water-soluble polyvalent metal salt (A) contains the second water-soluble polyvalent metal salt (a2), and that the second water-soluble polyvalent metal salt (a2) contains a polyvalent metal sulfate or a polyvalent metal chloride. In the toner manufacturing method of the present invention, it is preferable that the content of the boron-containing compound (a3) ​​in the aqueous solution of the water-soluble polyvalent metal salt (A) is 3 to 60 ppm by weight, when the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) is taken as 100% by weight. In the toner production method of the present invention, the first water-soluble polyvalent metal salt (a1) preferably contains magnesium chloride. In the toner production method of the present invention, the second water-soluble polyvalent metal salt (a2) preferably contains magnesium sulfate. In the toner production method of the present invention, the second water-soluble polyvalent metal salt (a2) preferably contains calcium chloride. In the toner production method of the present invention, the boron-containing compound (a3) ​​preferably contains boric acid. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for producing a toner that can produce a toner in which the proportion of fine particles and the volume average particle size (Dv) are controlled within appropriate ranges while the proportion of coarse particles is reduced. DETAILED DESCRIPTION OF THE INVENTION

[0012] The toner manufacturing method of the present invention is a toner manufacturing method comprising a colloidal dispersion preparation step, a droplet formation step, and a polymerization step, which will be described later, and in which, when the content of the first water-soluble polyvalent metal salt (a1) as the main component in the aqueous solution (A) of the water-soluble polyvalent metal salt used in the preparation of the colloidal dispersion is taken as 100% by weight, the total content of the second water-soluble polyvalent metal salt (a2), which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1), and the boron-containing compound (a3) ​​is 2000 to 4000 ppm by weight.

[0013] (1) Colloidal dispersion preparation process In the present invention, the colloidal dispersion preparation step is a step of preparing a colloidal dispersion of a poorly water-soluble metal compound by mixing an aqueous solution (A) of a water-soluble polyvalent metal salt with an aqueous solution (B) of a water-soluble alkali metal compound.

[0014] <Water-soluble polyvalent metal salt solution (A)> The aqueous solution of water-soluble polyvalent metal salt (A) contains a water-soluble polyvalent metal salt and water. When the water-soluble polyvalent metal salt contained as a main component in the aqueous solution of water-soluble polyvalent metal salt (A) is designated as a first water-soluble polyvalent metal salt (a1), the aqueous solution of water-soluble polyvalent metal salt (A) contains at least one of a second water-soluble polyvalent metal salt (a2) which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1) and a boron-containing compound (a3). When the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of water-soluble polyvalent metal salt (A) is taken as 100% by weight, the total content of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​is 2000 to 4000 ppm by weight.

[0015] The water-soluble polyvalent metal salt may be any polyvalent metal salt that is water-soluble, and examples thereof include magnesium metal salts such as magnesium chloride, magnesium phosphate, magnesium sulfate, etc.; calcium metal salts such as calcium chloride, calcium nitrate, calcium acetate, calcium sulfate, etc.; aluminum metal salts such as aluminum chloride, aluminum sulfate, etc.; barium salts such as barium chloride, barium nitrate, barium acetate, etc.; zinc salts such as zinc chloride, zinc nitrate, zinc acetate, etc. The water-soluble polyvalent metal salts may be used alone or in combination of two or more.

[0016] The first water-soluble polyvalent metal salt (a1) is a water-soluble polyvalent metal salt contained as a main component in the aqueous solution of the water-soluble polyvalent metal salt (A). In this specification, the term "water-soluble polyvalent metal salt contained as a main component" specifically refers to a water-soluble polyvalent metal salt that accounts for 30% by weight or more of the total content of all water-soluble polyvalent metal salts in the aqueous solution of the water-soluble polyvalent metal salt (A).

[0017] In the aqueous solution (A) of the water-soluble polyvalent metal salt, the first water-soluble polyvalent metal salt (a1) is preferably a single water-soluble polyvalent metal salt. In this case, the first water-soluble polyvalent metal salt (a1) is the water-soluble polyvalent metal salt with the highest content in the aqueous solution (A) of the water-soluble polyvalent metal salt. On the other hand, the first water-soluble polyvalent metal salt (a1) may contain two or three water-soluble polyvalent metal salts, as long as each of them accounts for 30% by weight or more of the total content of all the water-soluble polyvalent metal salts.

[0018] When the content of all water-soluble polyvalent metal salts in the aqueous solution of water-soluble polyvalent metal salts (A) is taken as 100% by weight, the content of the first water-soluble polyvalent metal salt (a1) is not particularly limited as long as it is 30% by weight or more, but is preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 95% by weight or more, and particularly preferably 99% by weight or more. By setting the content of the first water-soluble polyvalent metal salt (a1) within the above range, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the obtained toner within more preferred ranges, which will be described later.

[0019] The concentration of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, even more preferably 6 to 22% by weight, and particularly preferably 10 to 20% by weight. By adjusting the concentration of the first water-soluble polyvalent metal salt (a1) within the above range, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0020] The first water-soluble polyvalent metal salt (a1) may be any of the water-soluble polyvalent metal salts described above. Among these, magnesium metal salt, calcium metal salt, and aluminum metal salt are preferred, magnesium metal salt and calcium metal salt are more preferred, magnesium chloride and calcium chloride are even more preferred, and magnesium chloride is particularly preferred.

[0021] The aqueous solution of water-soluble polyvalent metal salt (A) contains at least one of a second water-soluble polyvalent metal salt (a2) which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1) and a boron-containing compound (a3).

[0022] The aqueous solution of the water-soluble polyvalent metal salt (A) preferably contains a second water-soluble polyvalent metal salt (a2) other than the first water-soluble polyvalent metal salt (a1). The second water-soluble polyvalent metal salt (a2) is a water-soluble polyvalent metal salt that accounts for less than 30% by weight of the total content of all water-soluble polyvalent metal salts in the aqueous solution of the water-soluble polyvalent metal salt (A).

[0023] The second water-soluble polyvalent metal salt (a2) may be any of the water-soluble polyvalent metal salts described above. Among these, preferred are sulfates, chlorides, phosphates, nitrates, and acetates of polyvalent metals, more preferred are sulfates and chlorides of polyvalent metals, and even more preferred are magnesium sulfate and calcium chloride. By using these compounds as the second water-soluble polyvalent metal salt (a2), it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below. The second water-soluble polyvalent metal salt (a2) may be used alone or in combination of two or more.

[0024] The aqueous solution of the water-soluble polyvalent metal salt (A) preferably contains a boron-containing compound (a3).

[0025] The boron-containing compound (a3) ​​may be any compound containing boron, but is preferably a water-soluble compound, such as boric acid, sodium borate, sodium tetraborate, sodium tetraborate decahydrate, sodium peroxoborate, sodium peroxoborate tetrahydrate, metaboric acid, sodium metaborate, sodium metaborate tetrahydrate, hypoboric acid, sodium tetrahydroborate, and potassium tetrahydroborate. Among these, boric acid and sodium tetraborate decahydrate are preferred, with boric acid being more preferred. Using these compounds as the boron-containing compound (a3) ​​makes it easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within the preferred ranges described below. The boron-containing compounds (a3) ​​may be used alone or in combination of two or more.

[0026] When the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of water-soluble polyvalent metal salt (A) is taken as 100% by weight, the total content of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​[{(a2) + (a3)} / (a1)] is 2000 to 4000 ppm by weight. By using the aqueous solution of water-soluble polyvalent metal salt (A) having the above composition, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the obtained toner within more preferred ranges, as described below.

[0027] The raw material for the water-soluble polyvalent metal salt may contain, in addition to the first water-soluble polyvalent metal salt (a1) as the main component, the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​as trace components. In this case, the contents of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​may be adjusted to fall within the above ranges, taking into consideration the contents of the trace components contained in the raw material for the water-soluble polyvalent metal salt.

[0028] When the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of water-soluble polyvalent metal salt (A) is taken as 100% by weight, the content of the second water-soluble polyvalent metal salt (a2) [(a2) / (a1)] is not particularly limited, but is preferably 1200 to 3999.5 ppm by weight, more preferably 1600 to 3999 ppm by weight, even more preferably 1900 to 3998 ppm by weight, and particularly preferably 1960 to 3997 ppm by weight. By setting the content of the second water-soluble polyvalent metal salt (a2) [(a2) / (a1)] within the above range, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the obtained toner within more preferred ranges, as described below.

[0029] When the second water-soluble polyvalent metal salt (a2) contains magnesium sulfate, the content of magnesium sulfate [MgSO4 / (a1)], where the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) is taken as 100% by weight, is not particularly limited, but is preferably 600 to 2500 ppm by weight, more preferably 700 to 2000 ppm by weight, even more preferably 800 to 1800 ppm by weight, and particularly preferably 900 to 1500 ppm by weight. By setting the magnesium sulfate content [MgSO4 / (a1)] within the above range, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0030] When the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) is taken as 100% by weight, the content of the boron-containing compound (a3) ​​[(a3) / (a1)] is not particularly limited, but is preferably 0.5 to 800 ppm by weight, more preferably 1 to 500 ppm by weight, even more preferably 2 to 200 ppm by weight, particularly preferably 3 to 100 ppm by weight, and most preferably 3 to 60 ppm by weight. By setting the content of the boron-containing compound (a3) ​​[(a3) / (a1)] within the above range, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0031] When the boron-containing compound (a3) ​​contains boric acid, the content of the boric acid [B(OH)3 / (a1)], where the content of the first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) is taken as 100% by weight, is not particularly limited, but is preferably 0.5 to 800 ppm by weight, more preferably 1 to 400 ppm by weight, even more preferably 2 to 100 ppm by weight, and particularly preferably 3 to 40 ppm by weight. By controlling the content of boric acid [B(OH)3 / (a1)] within the above range, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0032] The weight ratio [(a2) / (a3)] of the content of the second water-soluble polyvalent metal salt (a2) to the content of the boron-containing compound (a3) ​​in the aqueous solution of the water-soluble polyvalent metal salt (A) is not particularly limited, but is preferably 5 to 2000, more preferably 20 to 1500, even more preferably 40 to 1000, particularly preferably 45 to 800, and most preferably 50 to 700. By setting the weight ratio [(a2) / (a3)] of the content of the second water-soluble polyvalent metal salt (a2) to the content of the boron-containing compound (a3) ​​within the above range, it becomes easier to control the proportion of coarse particles and the proportion of fine particles in the resulting toner, as well as the volume average particle size (Dv) of the resulting toner, within more preferred ranges, as described below.

[0033] When the second water-soluble polyvalent metal salt (a2) contains magnesium sulfate, the weight ratio of the content of magnesium sulfate to the content of boron-containing compound (a3) ​​in the aqueous solution of the water-soluble polyvalent metal salt (A) [MgSO4 / (a3)] is not particularly limited, but is preferably 2 to 390, more preferably 5 to 375, even more preferably 10 to 360, particularly preferably 18 to 350, and most preferably 25 to 340. By setting the weight ratio of the content of magnesium sulfate to the content of boron-containing compound (a3) ​​[MgSO4 / (a3)] within the above range, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the obtained toner within more preferred ranges, which will be described later.

[0034] <Water-soluble alkali metal compound solution (B)> The aqueous solution of a water-soluble alkali metal compound (B) contains a water-soluble alkali metal compound and water.

[0035] The water-soluble alkali metal compound may be any alkali metal compound that is water-soluble, and examples thereof include hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; phosphates such as trilithium phosphate, dilithium phosphate, monolithium phosphate, trisodium phosphate, disodium phosphate, monosodium phosphate, tripotassium phosphate, dipotassium phosphate, and monopotassium phosphate; etc. Among these, lithium hydroxide, sodium hydroxide, potassium hydroxide, trisodium phosphate, disodium phosphate, and monosodium phosphate are preferred, sodium hydroxide and trisodium phosphate are more preferred, and sodium hydroxide is even more preferred.

[0036] In the colloidal dispersion preparation step, a colloidal dispersion of a poorly water-soluble metal compound is prepared by mixing an aqueous solution (A) of a water-soluble polyvalent metal salt with an aqueous solution (B) of a water-soluble alkali metal compound. During this process, a first water-soluble polyvalent metal salt (a1) in the aqueous solution of the water-soluble polyvalent metal salt (A) reacts with the water-soluble alkali metal compound in the aqueous solution of the water-soluble alkali metal compound (B) in the aqueous medium, producing a colloid of the poorly water-soluble metal compound in the aqueous medium as the reaction product.

[0037] For example, when a water-soluble magnesium metal salt is used as the first water-soluble polyvalent metal salt (a1) and an alkali metal hydroxide is used as the water-soluble alkali metal compound, magnesium hydroxide is produced as the poorly water-soluble metal compound.

[0038] Furthermore, for example, when a water-soluble calcium metal salt is used as the first water-soluble polyvalent metal salt (a1) and an alkali metal phosphate is used as the water-soluble alkali metal compound, tricalcium phosphate is produced as the poorly water-soluble metal compound.

[0039] Examples of poorly water-soluble metal compounds include metal hydroxides such as aluminum hydroxide and magnesium hydroxide; sulfates such as barium sulfate and calcium sulfate; and phosphates such as tricalcium phosphate. Among these, magnesium hydroxide and tricalcium phosphate are preferred, with magnesium hydroxide being more preferred. By using these compounds as the poorly water-soluble metal compound, the amount of poorly water-soluble metal compound remaining in the resulting toner can be reduced, and further, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0040] When mixing the aqueous solution (A) of the water-soluble polyvalent metal salt with the aqueous solution (B) of the water-soluble alkali metal compound, a preferred method is to mix the aqueous solution (A) of the water-soluble polyvalent metal salt by gradually adding the aqueous solution (B) of the water-soluble alkali metal compound to the aqueous solution while stirring the aqueous solution, from the viewpoint of being able to suitably control the particle size of the colloid of the resulting poorly water-soluble metal compound.

[0041] The ratio of the amount of the aqueous solution of water-soluble multivalent metal salt (A) to the amount of the aqueous solution of water-soluble alkali metal compound (B) is not particularly limited, but the weight ratio of the water-soluble alkali metal compound in the aqueous solution of water-soluble alkali metal compound (B) to the first water-soluble multivalent metal salt (a1) in the aqueous solution of water-soluble multivalent metal salt (A) (weight of water-soluble alkali metal compound / weight of first water-soluble multivalent metal salt (a1)) is preferably 0.2 to 1.0, more preferably 0.3 to 0.8. By setting the weight ratio of the water-soluble alkali metal compound in the aqueous solution of water-soluble alkali metal compound (B) to the first water-soluble multivalent metal salt (a1) in the aqueous solution of water-soluble multivalent metal salt (A) within the above ranges, it becomes easier to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0042] (2) Droplet formation process In the present invention, the droplet forming step is a step of mixing a polymerizable monomer composition containing a polymerizable monomer and a colorant with the colloidal dispersion of the poorly water-soluble metal compound obtained above to obtain a suspension containing droplets of the polymerizable monomer composition.

[0043] The polymerizable monomer composition used in the droplet forming step contains a polymerizable monomer and a colorant.

[0044] In the present invention, the polymerizable monomer refers to a polymerizable compound, and the polymerizable monomer is polymerized to form a binder resin. The monomer composition of the obtained binder resin is approximately the same as the composition of the polymerizable monomer to be polymerized in the polymerization step described below.

[0045] As the polymerizable monomer, it is preferable to use a monovinyl monomer as the main component constituting the polymerizable monomer. Examples of the monovinyl monomer include styrene-based monomers such as styrene, vinyltoluene, α-methylstyrene, and ethylstyrene; (meth)acrylate-based monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and dimethylaminoethyl methacrylate; acrylic acid and methacrylic acid; nitrile compounds such as acrylonitrile and methacrylonitrile; amide compounds such as acrylamide and methacrylamide; and olefins such as ethylene, propylene, and butylene. These monovinyl monomers can be used alone or in combination of two or more. Among these, styrene-based monomers and (meth)acrylate-based monomers are preferred, and styrene and butyl acrylate are more preferred. Furthermore, it is preferable to use at least a styrene-based monomer and a (meth)acrylate-based monomer as the monovinyl monomer, since this can further improve the low-temperature fixability of the resulting toner.

[0046] The content of styrene-based monomers in the polymerizable monomer composition (the content of styrene-based monomer units in the resulting binder resin) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 68% by mass or more, and particularly preferably 70% by mass or more, with an upper limit of preferably 85% by mass or less, more preferably 83% by mass or less, even more preferably 81% by mass or less, and particularly preferably 80% by mass or less. The content of (meth)acrylate-based monomers is preferably 15% by mass or more, more preferably 17% by mass or more, even more preferably 19% by mass or more, and particularly preferably 20% by mass or more, with an upper limit of preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 32% by mass or less, and particularly preferably 30% by mass or less. By setting the content of styrene-based monomer units and (meth)acrylate-based monomers within the above ranges, the resulting toner can have excellent storage stability and low-temperature fixability.

[0047] In the present invention, any crosslinkable polymerizable monomer may be used together with the monovinyl monomer. A crosslinkable polymerizable monomer refers to a monomer having two or more polymerizable functional groups. Examples of crosslinkable polymerizable monomers include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; ester compounds in which two or more carboxylic acids are ester-bonded to an alcohol having two or more hydroxyl groups, such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; other divinyl compounds such as N,N-divinylaniline and divinyl ether; and compounds having three or more vinyl groups. These crosslinkable polymerizable monomers may be used alone or in combination of two or more. The amount of the crosslinkable polymerizable monomer used is preferably 0.1 to 5 parts by mass, more preferably 0.15 to 2 parts by mass, and even more preferably 0.2 to 0.7 parts by mass, relative to 100 parts by mass of the monovinyl monomer, and the content of the crosslinkable polymerizable monomer unit in the binder resin used in the present invention is preferably 0.1 to 5% by mass, more preferably 0.15 to 2% by mass, and even more preferably 0.2 to 0.7% by mass.

[0048] Furthermore, any macromonomer may be used as part of the polymerizable monomer. A macromonomer is a reactive oligomer or polymer having a polymerizable carbon-carbon unsaturated bond at the end of the molecular chain and typically having a number average molecular weight (Mn) of 1,000 to 30,000. Preferably, the macromonomer gives a polymer having a higher Tg (glass transition temperature) than the Tg of a polymer obtained without polymerizing the macromonomer. The amount of macromonomer used is preferably 0.03 to 5 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the monovinyl monomer.

[0049] In the present invention, when producing color toner (usually, four types of toner are used: black toner, cyan toner, yellow toner, and magenta toner), a black colorant, a cyan colorant, a yellow colorant, and a magenta colorant can be used as the colorant.

[0050] As the black colorant, for example, pigments and dyes such as carbon black, titanium black, and magnetic powders such as iron zinc oxide and iron nickel oxide can be used.

[0051] Examples of cyan colorants include copper phthalocyanine pigments, their derivatives, and anthraquinone pigments and dyes, etc. Specific examples include CI Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, 60, etc.

[0052] Examples of yellow colorants that can be used include azo pigments such as monoazo pigments and disazo pigments, condensed polycyclic pigments, and dyes. Specific examples include CI Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 151, 155, 180, 181, 185, 186, 214, and 219, and CI Solvent Yellow 98 and 162.

[0053] Examples of magenta colorants that can be used include azo pigments such as monoazo pigments and disazo pigments, condensed polycyclic pigments, and dyes. Specific examples include CI Pigment Red 31, 48, 57:1, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 251, CI Solvent Violet 31, 47, 59, and CI Pigment Violet 19.

[0054] The colorant may be used alone or in combination of two or more kinds. The amount of the colorant used is preferably 1 to 10 parts by mass relative to 100 parts by mass of the polymerizable monomer (100 parts by mass of the resulting binder resin).

[0055] The polymerizable monomer composition preferably contains a charge control agent. The charge control agent is not particularly limited as long as it is one that is generally used as a charge control agent for toner, but among the charge control agents, a positively or negatively chargeable charge control resin is preferred from the viewpoint of having high compatibility with the polymerizable monomer and being able to impart stable chargeability (charge stability) to the toner particles, thereby improving the dispersibility of the colorant, and further, from the viewpoint of obtaining a negatively chargeable toner, a negatively chargeable charge control resin is more preferably used.

[0056] Examples of positively chargeable charge control agents include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds, and imidazole compounds, as well as polyamine resins, quaternary ammonium group-containing copolymers, and quaternary ammonium base-containing copolymers, which are preferably used as charge control resins.

[0057] Examples of negatively chargeable charge control agents include azo dyes containing metals such as Cr, Co, Al, and Fe, metal salicylate compounds, and metal alkylsalicylate compounds, as well as sulfonic acid group-containing copolymers, sulfonate salt group-containing copolymers, carboxylic acid group-containing copolymers, and carboxylic acid salt group-containing copolymers, which are preferably used as charge control resins.

[0058] The weight average molecular weight (Mw) of the charge control resin is in the range of 5,000 to 30,000, preferably 8,000 to 25,000, and more preferably 10,000 to 20,000, in terms of polystyrene, measured by gel permeation chromatography (GPC) using tetrahydrofuran.

[0059] Furthermore, the copolymerization ratio of the monomer having a functional group such as a quaternary ammonium group or a sulfonate group in the charge control resin is preferably in the range of 0.5 to 12 mass%, more preferably in the range of 1.0 to 6 mass%, and even more preferably in the range of 1.5 to 3 mass%.

[0060] The amount of the charge control agent added is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 8 parts by mass, relative to 100 parts by mass of the polymerizable monomer (100 parts by mass of the resulting binder resin). By setting the amount of the charge control agent added within the above range, it is possible to appropriately increase the dispersibility of the colorant while effectively suppressing the occurrence of fog and print smears.

[0061] The polymerizable monomer composition preferably contains a release agent. Any release agent commonly used as a toner release agent can be used without particular limitation, but a release agent having a number average molecular weight (Mn) of 500 to 1500 is preferred, and a fatty acid ester compound having a number average molecular weight (Mn) of 500 to 1500 is preferred. The term "fatty acid ester compound" refers to a product of an ester reaction between a monohydric alcohol and / or a polyhydric alcohol and a saturated fatty acid and / or an unsaturated fatty acid.

[0062] As the monohydric alcohol and / or polyhydric alcohol, monohydric to tetrahydric saturated aliphatic alcohols are preferred, stearyl alcohol, behenyl alcohol and pentaerythritol are more preferred, stearyl alcohol and behenyl alcohol are more preferred, and behenyl alcohol is particularly preferred.

[0063] The saturated fatty acid and / or unsaturated fatty acid used is preferably a saturated fatty acid and / or unsaturated fatty acid having a carbon number of 12 to 22, more preferably a carbon number of 14 to 18. Among these, saturated fatty acids having the above carbon numbers are particularly preferred because they make it easy to obtain a fatty acid ester compound having a number average molecular weight (Mn) of 500 to 1500.

[0064] In the present invention, instead of or together with the fatty acid ester compound, a release agent other than a fatty acid ester compound may be used as the release agent, and examples thereof include low-molecular-weight polyolefin waxes and modified waxes thereof, natural plant waxes such as jojoba, petroleum waxes such as paraffin, mineral waxes such as ozokerite, synthetic waxes such as Fischer-Tropsch wax, and polyhydric alcohol esters such as dipentaerythritol esters. These may be used alone or in combination of two or more.

[0065] The number average molecular weight (Mn) of the release agent is preferably 500 to 1500, more preferably 550 to 1200, and even more preferably 550 to 1100. The number average molecular weight (Mn) of the release agent can be measured, for example, as a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran.

[0066] The amount of the release agent used is preferably 1 to 30 parts by mass, more preferably 8 to 28 parts by mass, and even more preferably 12 to 25 parts by mass, relative to 100 parts by mass of the polymerizable monomer (100 parts by mass of the resulting binder resin). By setting the amount of the release agent used within the above range, it is possible to further improve the low-temperature fixability while making the particle size distribution of the resulting toner relatively uniform.

[0067] The polymerizable monomer composition may contain an acrylic resin as another additive to suppress bleeding out of the release agent. The acrylic resin is a copolymer (acrylate copolymer) whose main components are at least one of an acrylic acid ester and a methacrylic acid ester and at least one of an acrylic acid and a methacrylic acid. The acid monomer is preferably acrylic acid.

[0068] Furthermore, the polymerizable monomer composition may contain a molecular weight modifier as another additive. The molecular weight modifier is not particularly limited as long as it is one generally used as a molecular weight modifier for toners. Examples include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol; and thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N,N'-dimethyl-N,N'-diphenylthiuram disulfide, and N,N'-dioctadecyl-N,N'-diisopropylthiuram disulfide. These molecular weight modifiers may be used alone or in combination of two or more. The amount of the molecular weight modifier used is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the polymerizable monomer (100 parts by mass of the resulting binder resin).

[0069] The polymerizable monomer composition is prepared by mixing and dissolving the polymerizable monomer, the colorant, and other additives used as needed. The mixing when preparing the polymerizable monomer composition is carried out using, for example, a media-type disperser.

[0070] Next, the polymerizable monomer composition obtained above and the colloidal dispersion of the poorly water-soluble metal compound obtained above are mixed to obtain a suspension containing droplets of the polymerizable monomer composition. In the production method of the present invention, the colloid of the poorly water-soluble metal compound contained in the colloidal dispersion of the poorly water-soluble metal compound acts as a dispersion stabilizer when obtaining the suspension.

[0071] The mixing ratio of the polymerizable monomer composition and the colloidal dispersion of the poorly water-soluble metal compound is preferably such that the amount of the poorly water-soluble metal compound in the colloidal dispersion of the poorly water-soluble metal compound is 0.1 to 20 parts by mass, and more preferably 0.2 to 10 parts by mass, per 100 parts by mass of the polymerizable monomer in the polymerizable monomer composition (100 parts by mass of the resulting binder resin). By using such a mixing ratio, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, as described below.

[0072] It is preferable to disperse the polymerizable monomer composition in a colloidal dispersion of a poorly water-soluble metal compound, add a polymerization initiator, and then form droplets of the polymerizable monomer composition.

[0073] Here, "suspension" means forming droplets of the polymerizable monomer composition in an aqueous medium. The dispersion treatment for forming droplets can be carried out using a device capable of strong stirring, such as an in-line emulsifying disperser (manufactured by Pacific Machinery Works, trade name: Milder) or a high-speed emulsifying / dispersing machine (manufactured by Primix Corporation, trade name: TK Homomixer MARK II type).

[0074] The polymerization initiator may be added after dispersing the polymerizable monomer composition in a colloidal dispersion of a poorly water-soluble metal compound and before forming droplets, or may be added in advance to the colloidal dispersion of a poorly water-soluble metal compound.

[0075] Examples of polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobisisobutyronitrile; and organic peroxides such as di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylbutanoate, diisopropyl peroxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate. These can be used alone or in combination of two or more. Among these, organic peroxides are preferred because they can reduce the amount of residual polymerizable monomers and provide excellent print durability. Among organic peroxides, peroxyesters are preferred because they have good initiator efficiency and can reduce the amount of residual polymerizable monomers, and non-aromatic peroxyesters, i.e., peroxyesters without an aromatic ring, are more preferred.

[0076] The amount of polymerization initiator used in polymerizing the polymerizable monomer composition is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and particularly preferably 1 to 10 parts by mass, relative to 100 parts by mass of polymerizable monomer (100 parts by mass of the resulting binder resin). By setting the amount of polymerization initiator added within the above range, it becomes easy to control the proportion of coarse particles, the proportion of fine particles, and the volume average particle size (Dv) of the resulting toner within more preferred ranges, which will be described later.

[0077] In the present invention, dispersion stabilizers other than the poorly water-soluble metal compound may be used. Examples of other dispersion stabilizers include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants; nonionic surfactants; and organic compounds such as amphoteric surfactants. The above dispersion stabilizers may be used alone or in combination of two or more.

[0078] (3) Polymerization process In the present invention, the polymerization step is a step of subjecting the suspension obtained above to a polymerization reaction to obtain colored resin particles.

[0079] The preferred method for subjecting the suspension to the polymerization reaction is to heat the suspension to initiate polymerization. The polymerization temperature is preferably 50° C. or higher, more preferably 60 to 95° C. The polymerization time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

[0080] From the viewpoint of carrying out polymerization in a state in which droplets of the polymerizable monomer composition are stably dispersed, in the (3) polymerization step, the polymerization reaction may be allowed to proceed while carrying out a dispersion treatment by stirring following the (2) droplet formation step.

[0081] Toner may be produced by adding an external additive directly to the colored resin particles thus obtained, but so-called core-shell type (also called "capsule type") colored resin particles may also be obtained by using the colored resin particles obtained by the polymerization process as a core layer and forming a shell layer different from the core layer on the outside of the core layer. Core-shell type colored resin particles have a core layer made of a material with a low softening point, and by coating it with a material with a higher softening point, the storage stability and low-temperature fixability of the resulting toner can be further improved.

[0082] The method for producing the core-shell type colored resin particles is not particularly limited and can be any conventionally known method, but in situ polymerization or phase separation is preferred from the viewpoint of production efficiency. The method for producing the core-shell type colored resin particles by in situ polymerization is described below.

[0083] In the in situ polymerization method, a polymerizable monomer for forming a shell layer (shell polymerizable monomer) and a shell polymerization initiator are added to an aqueous dispersion medium in which colored resin particles are dispersed, and polymerization is carried out to obtain core-shell type colored resin particles.

[0084] As the polymerizable monomer for the shell, the same polymerizable monomers as those described above can be used. Among them, it is preferable to use a monomer that can give a polymer with a Tg exceeding 80°C, such as styrene or methyl methacrylate, either alone or in combination of two or more.

[0085] Examples of the shell polymerization initiator used in the polymerization of the shell polymerizable monomer include metal persulfates such as potassium persulfate and ammonium persulfate; and water-soluble azo compounds such as 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) and 2,2'-azobis(2-methyl-N-(1,1-bis(hydroxymethyl)2-hydroxyethyl)propionamide). The amount of the shell polymerization initiator used is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the shell polymerizable monomer.

[0086] The polymerization temperature for the shell layer is preferably 50° C. or higher, more preferably 60 to 95° C. The polymerization time for the shell layer is preferably 1 to 20 hours, more preferably 2 to 15 hours.

[0087] In this manner, colored resin particles containing a binder resin and a colorant can be obtained in the form of a dispersion in an aqueous medium.

[0088] <Washing, filtering, dehydration, and drying processes> In the production method of the present invention, it is preferable to subject the aqueous medium dispersion of colored resin particles obtained above to a series of operations of washing, filtering, dehydrating and drying in a conventional manner, and if necessary, repeat the series of operations several times.

[0089] Specifically, first, in order to remove the poorly water-soluble metal compound remaining in the aqueous medium dispersion of the colored resin particles, it is preferable to add an acid or an alkali to the aqueous medium dispersion of the colored resin particles and wash it. If the poorly water-soluble metal compound is soluble in acid, it is preferable to add an acid to the aqueous medium dispersion of the colored resin particles and wash it, while if the poorly water-soluble metal compound is soluble in alkali, it is preferable to add an alkali to the aqueous medium dispersion of the colored resin particles and wash it.

[0090] Furthermore, when the poorly water-soluble metal compound is soluble in acid, it is preferable to add an acid to the aqueous medium dispersion of colored resin particles to adjust the pH to preferably 6.5 or less, more preferably 6 or less. The acid to be added may be an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid such as formic acid or acetic acid, but sulfuric acid is particularly preferred because it has a high efficiency in removing the poorly water-soluble metal compound and places a small burden on the production equipment.

[0091] The dehydration and filtration methods can be any known method, and are not particularly limited. Examples include centrifugal filtration, vacuum filtration, pressure filtration, etc. The drying method is also not particularly limited, and various methods can be used.

[0092] In this manner, colored resin particles containing a binder resin and a colorant can be obtained. The obtained colored resin particles can be used as a toner as is, or by mixing the colored resin particles with carrier particles (ferrite, iron powder, etc.). However, in order to adjust the chargeability, fluidity, storage stability, etc. of the toner, an external additive can be added and mixed with the colored resin particles using a high-speed mixer (for example, FM Mixer (trade name, manufactured by Nippon Coke & Engineering Co., Ltd.)) to form a one-component toner, or the colored resin particles, external additives, and carrier particles can be mixed to form a two-component toner.

[0093] The agitator used for the external addition treatment is not particularly limited as long as it is an agitator that can adhere an external additive to the surface of the colored resin particles. For example, the external addition treatment can be performed using an agitator that is capable of mixing and stirring, such as FM Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), Super Mixer (trade name, manufactured by Kawada Manufacturing Co., Ltd.), Q Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), Mechanofusion System (trade name, manufactured by Hosokawa Micron Corporation), or Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.).

[0094] Examples of external additives include inorganic fine particles made of silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, calcium carbonate, calcium phosphate, cerium oxide, etc.; and organic fine particles made of polymethyl methacrylate resin, silicone resin, melamine resin, etc. Among these, inorganic fine particles are preferred, silica and titanium oxide are more preferred, and silica is particularly preferred. It is also preferred to use two or more types of fine particles in combination as external additives. These external additives can be used alone, but it is preferred to use two or more types in combination.

[0095] The external additive is preferably used in an amount of 0.3 to 6 parts by mass, more preferably 1.2 to 3 parts by mass, relative to 100 parts by mass of the colored resin particles.

[0096] As described above, the toner can be produced by the production method of the present invention.

[0097] From the viewpoint of image reproducibility, the volume average particle diameter (Dv) of the toner is preferably 6.1 to 10 μm. If the volume average particle diameter (Dv) of the toner is less than the above range, the fluidity of the toner may decrease, and deterioration of image quality due to fogging or the like may easily occur. On the other hand, if the volume average particle diameter (Dv) of the toner exceeds the above range, the resolution of the obtained image may decrease. From the viewpoint of image reproducibility, the volume average particle diameter (Dv) of the toner is more preferably 6.3 to 9.5 μm, even more preferably 6.5 to 9 μm, and particularly preferably 6.7 to 8.5 μm.

[0098] The proportion of coarse particles in the toner, specifically the proportion of coarse particles with a particle size of more than 20 μm relative to the total toner, is preferably 1% by volume or less, more preferably 0.8% by volume or less, and even more preferably 0.6% by volume or less. The lower limit of the proportion of coarse particles is usually 0.1% by volume or more. By keeping the proportion of coarse particles within the above range, the resulting toner can suppress the occurrence of scraping of the developing roll, the occurrence of vertical streaks, and the occurrence of uneven solid printing.

[0099] The smaller the volume average particle diameter (Dv) of the toner, the more likely defects caused by the presence of coarse particles, such as scraping of the developing roll, the occurrence of vertical streaks, and uneven solid printing, tend to occur. Therefore, when the volume average particle diameter (Dv) of the toner is relatively small (for example, 7.5 μm or less), it is particularly preferable that the proportion of coarse particles be 0.5 volume % or less.

[0100] The proportion of microparticles in the toner, specifically the proportion of microparticles with a particle size of less than 5 μm relative to the total toner, is preferably 5 to 38% by volume from the viewpoint of stability of printing performance. If the proportion of microparticles is less than this range, the fixing ability of the toner tends to be insufficient, while if the proportion of microparticles is greater than this range, the toner physical properties tend to change significantly over time, and the printing performance also tends to change significantly over time. From the viewpoint of stability of printing performance, the proportion of microparticles is more preferably 7 to 36% by volume, even more preferably 9 to 34% by volume, and particularly preferably 11 to 32% by volume.

[0101] Furthermore, the particle size distribution (Dv / Dn), which is the ratio of the volume average particle size (Dv) to the number average particle size (Dn) of the toner, is preferably 1.00 to 1.30, more preferably 1.00 to 1.20, from the viewpoint of image reproducibility. If the particle size distribution (Dv / Dn) of the toner exceeds the above range, the fluidity of the toner may decrease, and image quality may be easily deteriorated due to fogging or the like. The volume average particle size (Dv), the proportion of coarse particles, the proportion of fine particles, and the number average particle size (Dn) of the toner can be measured, for example, using a particle size analyzer (trade name: Multisizer, manufactured by Beckman Coulter) or the like.

[0102] Furthermore, from the viewpoint of image reproducibility, the average circularity of the toner is preferably from 0.960 to 1.000, more preferably from 0.970 to 1.000, and even more preferably from 0.980 to 1.000. [Example]

[0103] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that "parts" and "%" are by mass unless otherwise specified. The test methods used in these examples and comparative examples are as follows.

[0104] <Volume average particle size of toner (Dv)> Approximately 0.1 g of toner was weighed and placed in a beaker, followed by the addition of 0.1 mL of a surfactant solution (Fujifilm Corporation, product name: Drywell) as a dispersant. 10-30 mL of Isoton II was then added to the beaker, and the mixture was dispersed for 3 minutes using a 20 W ultrasonic disperser. The volume average particle size (Dv) of the toner was then measured using a particle size analyzer (Beckman Coulter, product name: Multisizer) under the following conditions: aperture diameter: 100 μm, medium: Isoton II, particle number: 100,000.

[0105] <Ratio of coarse particles and fine particles> The particle size distribution was determined in the same manner as in the measurement of the volume average particle size (Dv) of the toner, except that the aperture diameter was changed to 200 μm. The volume ratio of particles with a particle size of more than 20 μm was calculated as the proportion of coarse particles. The volume ratio of particles with a particle size of less than 5 μm was calculated as the proportion of fine particles.

[0106] <Influence index of coarse particles> The coarse particle influence index was calculated by dividing the proportion of coarse particles (unit: volume %) calculated as described above by the volume average particle diameter (Dv) (unit: μm) of the toner. When comparing multiple toners with similar volume average particle diameters (Dv), a smaller coarse particle influence index is preferable, as it tends to suppress the occurrence of problems caused by the presence of coarse particles (for example, scraping of the developing roll, vertical streaks, and uneven solid printing).

[0107] Example 1 (1) Colloidal dispersion preparation process An aqueous solution of water-soluble polyvalent metal salt (A-1) was prepared, containing magnesium chloride as the first water-soluble polyvalent metal salt (a1), magnesium sulfate and calcium chloride as the second water-soluble polyvalent metal salt (a2), and boric acid as the boron-containing compound (a3). Specifically, magnesium sulfate, calcium chloride, and boric acid were added to an aqueous solution containing magnesium chloride at a concentration of 25 wt% so that the magnesium sulfate content [MgSO4 / (a1)], calcium chloride content [CaCl2 / (a1)], and boric acid content [B(OH)3 / (a1)], respectively, when the magnesium chloride content was taken as 100 wt%, were as shown in Table 1. Next, the solution was diluted with ion-exchanged water to a magnesium chloride concentration of 16 wt%, thereby preparing an aqueous solution of water-soluble polyvalent metal salt (A-1). Table 1 shows the weight ratio of the magnesium sulfate content to the boron-containing compound (a3) ​​content [MgSO4 / (a3)] ([MgSO4 / B(OH)3]) and the weight ratio of the second water-soluble polyvalent metal salt (a2) content to the boron-containing compound (a3) ​​content [(a2) / (a3)] ([(MgSO4+CaCl2) / B(OH)3]) in the obtained aqueous solution (A) of the water-soluble polyvalent metal salt.

[0108] Also, an aqueous solution (B) of a water-soluble alkali metal compound containing sodium hydroxide at a concentration of 10% by weight was prepared by dissolving sodium hydroxide in ion-exchanged water.

[0109] Then, at room temperature, the aqueous solution of a water-soluble alkali metal compound (B) was gradually added under stirring to the aqueous solution of a water-soluble polyvalent metal salt (A-1) in a weight ratio of magnesium chloride:sodium hydroxide of 3:1, and after mixing, a colloidal dispersion of magnesium hydroxide (colloidal dispersion of a poorly water-soluble metal compound) was prepared.

[0110] (2) Droplet formation process 78 parts of styrene as polymerizable monomers, 22 parts of n-butyl acrylate, and 5 parts of carbon black (trade name: #25B, manufactured by Mitsubishi Chemical Corporation) as a black colorant were dispersed using an in-line emulsifying disperser (trade name: Milder, manufactured by Pacific Machinery Works, Ltd.) to obtain a polymerizable monomer mixture.

[0111] Next, to the polymerizable monomer mixture obtained above, 1.0 part of a charge control resin (a styrene acrylic resin containing a quaternary ammonium group) as a charge control agent, 5.0 parts of a fatty acid ester wax (behenyl behenate) as a release agent, 0.3 parts of a polymethacrylic acid ester macromonomer (trade name: AA6, manufactured by Toa Gosei Chemical Industry Co., Ltd.) as a macromonomer, 0.6 parts of divinylbenzene as a crosslinkable polymerizable monomer, and 1.6 parts of t-dodecyl mercaptan as a molecular weight adjuster were added, mixed, and dissolved to prepare a polymerizable monomer composition.

[0112] The polymerizable monomer composition prepared above was then added to the magnesium hydroxide colloidal dispersion prepared above and stirred until the droplets stabilized. The mixing ratio of the magnesium hydroxide colloidal dispersion to the polymerizable monomer composition was such that 6.0 parts of magnesium hydroxide in the magnesium hydroxide colloidal dispersion was mixed with 100 parts of the polymerizable monomer in the polymerizable monomer composition. Next, 6 parts of t-butyl peroxyisobutyrate (manufactured by NOF Corporation, product name: Perbutyl IB) as a polymerization initiator was added to the stirred mixture, and the mixture was then subjected to high-shear stirring at 15,000 rpm using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, product name: Milder) to circulate and disperse the mixture, thereby obtaining a suspension in which droplets of the polymerizable monomer composition were dispersed.

[0113] The suspension obtained above was then placed in a reactor equipped with a stirring blade and heated to 90°C to initiate the polymerization reaction. When the polymerization conversion rate reached nearly 100%, 1 part of methyl methacrylate as a shell polymerizable monomer and 0.3 parts of 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)-propionamide) (trade name: VA-086, manufactured by Wako Pure Chemical Industries, Ltd., water-soluble) as a shell polymerization initiator dissolved in 10 parts of ion-exchanged water were added. The reaction was continued at 90°C for 4 hours, and then the reaction was stopped by water cooling to obtain an aqueous dispersion of colored resin particles having a core-shell structure.

[0114] Dilute sulfuric acid was added to the aqueous dispersion of the colored resin particles to adjust the pH to 4.5 or less. Next, the water was separated by filtration, and 200 parts of ion-exchanged water was added to re-slurry the mixture. The water washing process (washing, filtration, dehydration) was repeated several times at room temperature (25°C). The resulting solid matter was separated by filtration and then vacuum dried to obtain dried colored resin particles.

[0115] To 100 parts of the colored resin particles obtained above, 0.5 parts of silica fine particles hydrophobized with cyclic silazane and having a number-average primary particle size of 7 nm, and 1 part of silica fine particles hydrophobized with amino-modified silicone oil and having a number-average primary particle size of 35 nm were added as external additives, and the mixture was mixed and stirred using a high-speed mixer (manufactured by Nippon Coke & Engineering Co., Ltd., product name: FM Mixer) to prepare a toner. The volume-average particle size (Dv), the proportion of coarse particles, and the proportion of fine particles were determined for the obtained toner according to the methods described above. The results are shown in Table 1.

[0116] Using the obtained toner, continuous printing (print density 5%) was performed as evaluation printing, followed by solid printing (print density 100%) and solid white printing (print density 0%). In the continuous printing (print density 5%) and solid printing (print density 100%), the print was beautiful and no print defects were observed. Furthermore, in the solid white printing (print density 0%), no print defects such as vertical streaks were observed. Therefore, it was confirmed that the obtained toner has excellent printing performance.

[0117] <Examples 2 to 7, Comparative Examples 1 to 6> Aqueous solutions of water-soluble polyvalent metal salts (A-2) to (A-7) and (A'-8) to (A'-13) were prepared by adding magnesium sulfate, calcium chloride, and boric acid to an aqueous solution containing magnesium chloride at a concentration of 25% by weight so that the respective contents of magnesium sulfate, calcium chloride, and boric acid, when the magnesium chloride content was taken as 100% by weight, were as shown in Table 1. Toners were then produced in the same manner as in Example 1, and measurements were performed in the same manner as in Example 1, except that the aqueous solutions of water-soluble polyvalent metal salts obtained were used. The results are shown in Table 1.

[0118] Using the toners obtained in each of Examples 2 to 7, evaluation printing was performed in the same manner as in Example 1. In continuous printing (print density 5%) and solid printing (print density 100%), the print was beautiful and no print defects were observed. Furthermore, in solid white printing (print density 0%), no print defects such as vertical streaks were observed. Therefore, it was confirmed that the obtained toners have excellent printing performance. [Table 1]

[0119] As shown in Table 1, a toner manufacturing method including a colloidal dispersion preparation step, a droplet formation step, and a polymerization step, in which the aqueous solution (A) of a water-soluble multivalent metal salt used in preparing the colloidal dispersion has a total content [{(a2) + (a3)} / (a1)] of the second water-soluble multivalent metal salt (a2), which is a water-soluble multivalent metal salt other than the first water-soluble multivalent metal salt (a1), and the boron-containing compound (a3) ​​of 2000 to 4000 ppm by weight, when the content of the first water-soluble multivalent metal salt (a1) as the main component is taken as 100% by weight, made it possible to obtain a toner manufacturing method in which the proportion of fine particles and the volume average particle size (Dv) were controlled within appropriate ranges while the proportion of coarse particles was reduced (Examples 1 to 7).

[0120] On the other hand, when the content of the first water-soluble polyvalent metal salt (a1) is taken as 100% by weight, whether the total content of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​[{(a2) + (a3)} / (a1)] is too high or too low, it was not possible to obtain a toner in which the proportion of coarse particles was reduced while the proportion of fine particles and the volume average particle size (Dv) were controlled within appropriate ranges (Comparative Examples 1 to 6).

Claims

1. (1) a colloidal dispersion preparation step of mixing an aqueous solution (A) of a water-soluble polyvalent metal salt with an aqueous solution (B) of a water-soluble alkali metal compound to prepare a colloidal dispersion of a poorly water-soluble metal compound; (2) a droplet forming step of mixing a polymerizable monomer composition containing a polymerizable monomer and a colorant with a colloidal dispersion of the poorly water-soluble metal compound to obtain a suspension containing droplets of the polymerizable monomer composition; and (3) a polymerization step of subjecting the suspension to a polymerization reaction to obtain colored resin particles; A toner manufacturing method comprising: When the water-soluble polyvalent metal salt contained as a main component in the aqueous solution (A) of a water-soluble polyvalent metal salt is designated as a first water-soluble polyvalent metal salt (a1), the aqueous solution (A) of a water-soluble polyvalent metal salt contains a second water-soluble polyvalent metal salt (a2) which is a water-soluble polyvalent metal salt other than the first water-soluble polyvalent metal salt (a1), and a boron-containing compound (a3), the first water-soluble polyvalent metal salt (a1) contains magnesium chloride; the second water-soluble polyvalent metal salt (a2) comprises magnesium sulfate and calcium chloride; The method for producing a toner, wherein the total content of the second water-soluble polyvalent metal salt (a2) and the boron-containing compound (a3) ​​in the aqueous solution of the water-soluble polyvalent metal salt (A) is 2000 to 4000 ppm by weight, relative to the content of the first water-soluble polyvalent metal salt (a1) taken as 100% by weight.

2. 2. The method for producing a toner according to claim 1, wherein a content of the boron-containing compound (a3) ​​in the aqueous solution of the water-soluble polyvalent metal salt (A) is 3 to 60 ppm by weight, relative to a content of the first water-soluble polyvalent metal salt (a1) taken as 100% by weight.

3. The method for producing a toner according to claim 1 or 2, wherein the boron-containing compound (a3) ​​contains boric acid.

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