Toner set and image forming method

Abstract

Provided is a toner set making it possible to suppress peeling of a toner layer when forming a full-color image, hardly generating ultrafine particles when fixing the toner, and hardly causing ejection of toner when performing continuous printing in a high-temperature and high-humidity environment. The toner set comprises at least a yellow toner, a magenta toner, and a cyan toner, wherein these toners include an ester wax having a molecular weight of 600-3000 as a softener and include a specific external additive A as an external additive, the loss tangent of the yellow toner at 100°C, the loss tangent of the magenta toner at 100°C, and the loss tangent of the cyan toner at 100°C are each 0.840 or more, and the absolute value of the difference in loss tangent at 100°C between toners of each color is 0.140 or less.

Description

Toner set and image forming method

[0001] The present disclosure relates to a toner set that combines multiple electrostatic image developing toners (hereinafter, sometimes simply referred to as "toners") used to develop electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, and the like, and an image forming method that uses the toner set.

[0002] In image forming devices such as electrophotographic devices, electrostatic recording devices, and electrostatic printing devices, an image forming method is widely used in which a desired image is formed by developing an electrostatic latent image formed on a photoconductor with an electrostatic image developing toner, and this method is applied to copiers, printers, facsimiles, and combination machines thereof. For example, in electrophotographic devices using electrophotography, the surface of a photoconductor made of a photoconductive material is generally uniformly charged by various means, and then a laser beam is irradiated onto the photoconductor to change the electrostatic charge distribution, thereby forming an electrostatic latent image having an electrostatic charge distribution that produces the image to be reproduced or a corresponding negative image. The electrostatic latent image is then developed with toner to form a toner image, which is then transferred to a recording material such as printing paper directly or via a transfer member, and then fixed by heating or the like to obtain a copy.

[0003] When forming a full-color image using electrostatic image developing toners, the original image to be reproduced is separated into the three primary colors of yellow (Y), magenta (M), and cyan (C), or four additional colors, including black (K), and electrostatic latent images of each color component are formed on separate photoreceptors and developed to form primary color toner images of each color component. The primary color toner images of each color component are then registered and transferred onto a transfer receiving material selected from a recording material and a transfer medium, forming a multi-color toner image including multi-colors such as secondary and tertiary colors resulting from color superposition. If the multi-color toner image is formed on the transfer medium, it is then transferred to the recording material. The multi-color toner image on the recording material is then fixed by heating or other means to obtain a full-color image including multi-color gradation regions.

[0004] Patent Literature 1 discloses a toner set that is excellent in gradation and color reproducibility of images including multi-colors and also in print durability in continuous printing, and that includes at least a yellow toner, a cyan toner, and a magenta toner, and in which the internal friction angle of the leading color toner and the internal friction angles of the other toners satisfy a specific relational expression. The internal friction angle of a toner is an index that indicates the degree of fluidity of the toner.

[0005] On the other hand, Patent Document 2 discloses a toner that achieves both the releasability of the printed paper from the fixing member and the suppression of multi-layer peeling, and the absorbance I derived from the binder resin, which is determined by total reflection absorption infrared spectroscopy, is Ｂ Absorbance I from the release agent ｗ Peak intensity ratio (I ｗ / I Ｂ ) and adhesive strength are set within specific ranges. ｗ / I Ｂ is used as an index of the amount of release agent present in the depth region up to 0.4 μm from the printing surface of the toner.

[0006] Patent Document 3 discloses a magenta toner that exhibits brighter colors than conventional magenta toners, has a high reflection density, an excellent balance between low-temperature fixability and heat-resistant storage stability, and also has excellent print durability, and contains a magenta pigment obtained by surface-treating a pigment having a specific structure, such as C.I. Pigment Red 48:3, with a metal rosinate.

[0007] International Publication No. 2021 / 172517 International Publication No. 2018 / 181131 International Publication No. 2020 / 066700

[0008] Problems with conventional toner sets include the tendency for peeling to occur between toner layers of different colors superimposed on top of each other in the formed full-color image, the tendency for ultrafine particles (UFPs) to be generated, and the tendency for toner to spray out of the cartridge when printing continuously in a high-temperature, high-humidity environment.

[0009] The object of the present disclosure is to provide a toner set that can suppress peeling of the toner layer when a full-color image is formed, that is less likely to generate ultrafine particles when the toner is fixed, and that is less likely to cause toner ejection when continuous printing is performed in a high-temperature, high-humidity environment.

[0010] That is, the present disclosure provides the following toner set: [1] A toner set including toners of multiple colors each including a binder resin, colorant, colored resin particles including a softener and a charge control agent, and an external additive, wherein the toners of multiple colors include at least a yellow toner, a magenta toner, and a cyan toner, and the yellow toner, magenta toner, and cyan toner each include, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one kind selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, and titanium oxide fine particles; A toner set, wherein the loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and satisfy the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (III).

[0011] [2] The toner set according to [1], wherein the yellow toner, magenta toner, and cyan toner further contain an external additive B which is silica fine particles as the external additive, and in each of the yellow toner, magenta toner, and cyan toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of the external additive A relative to 100% by mass of the total amount of the external additive A and the external additive B is 16% by mass or more and 51% by mass or less.

[0012] The present disclosure also provides the following image forming method: [3] An image forming method using the toner set according to [1] or [2].

[0013] The present disclosure further provides the following toner set: [4] A toner set including toners of multiple colors each containing a binder resin, colorant, colored resin particles containing a softener and a charge control agent, and an external additive, wherein the toners of multiple colors include at least a yellow toner, a magenta toner, and a cyan toner, and the yellow toner, magenta toner, and cyan toner each contain, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, titanium oxide fine particles, aluminum oxide fine particles, and aluminum hydroxide fine particles; A toner set, wherein the loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and the following formulas (I), (II), and (III) are satisfied: |tan δ(M, 100°C) - tan δ(Y, 100°C) | ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (III) [5] The toner set according to [4], wherein the external additive A contains metal titanate fine particles and aluminum oxide fine particles. [6] The toner set according to [4] or [5], wherein the yellow toner, magenta toner, and cyan toner further contain an external additive B which is silica fine particles as the external additive, and in each of the yellow toner, magenta toner, and cyan toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of the external additive A relative to 100% by mass of the total amount of the external additive A and the external additive B is 16% by mass or more and 51% by mass or less.

[0014] The present disclosure also provides the following image forming method: [7] An image forming method using the toner set according to any one of [4] to [6].

[0015] The present disclosure further provides the following toner set: [8] A toner set including toners of multiple colors each containing a binder resin, colorant, colored resin particles containing a softener and a charge control agent, and an external additive, wherein the toners of multiple colors include a yellow toner, a magenta toner, a cyan toner, and a black toner, and the yellow toner, magenta toner, cyan toner, and black toner each contain, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, titanium oxide fine particles, aluminum oxide fine particles, and aluminum hydroxide fine particles; The loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and satisfy the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (III) A toner set in which the loss tangent at 100°C (tan δ(K, 100°C)) of the black toner is higher than each of tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C), and the following formula (IV) is satisfied: 0.10<|{tan δ(C, 100°C)+tan δ(M, 100°C)+tan δ(Y, 100°C)}-tan δ(K, 100°C)×3| / 3<0.30 (IV) [9] The toner set according to [8], in which the external additive A contains metal titanate fine particles and aluminum oxide fine particles.

[10] The toner set according to [8] or [9], wherein the yellow toner, magenta toner, cyan toner, and black toner further contain an external additive B, which is silica fine particles, as the external additive, and in each of the yellow toner, magenta toner, cyan toner, and black toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of the external additive A relative to 100% by mass of the total amount of the external additive A and the external additive B is 16% by mass or more and 51% by mass or less.

[0016] The present disclosure also provides the following image forming method.

[11] An image forming method using the toner set according to any one of [8] to

[10] .

[12] The image forming method according to

[11] , wherein a multi-color image formed by overlaying colors in the order of the yellow toner, magenta toner, cyan toner and black toner, or the magenta toner, yellow toner, cyan toner and black toner, is fixed to a recording material so that the black toner is on the outermost surface.

[0017] According to the toner set of the present disclosure as described above, it is possible to form full-color images in which peeling of the toner layer is suppressed, the generation of ultrafine particles when the toner is fixed can be suppressed, and toner spraying can be suppressed when continuous printing is performed in a high-temperature, high-humidity environment.

[0018] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus that can be used to form an image using a toner set of the present disclosure.

[0019] In this disclosure, the use of "to" in a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. Furthermore, among the values ​​described to explain this disclosure, values ​​that may contain decimal places are values ​​obtained by rounding off the digit that is one place lower than the lowest digit included in the value, unless otherwise specified.

[0020] 1. Toner Set The toner set of the present disclosure includes at least three colors of toner: yellow toner, cyan toner, and magenta toner, and may further include toners of other colors. The toner set of the present disclosure also includes a black toner, which tends to improve charge buildup. Each color of toner contains colored resin particles including a binder resin, a colorant, a softener, and a charge control agent, as well as external additives. Below, the colored resin particles contained in each color of toner, the external additives further contained in each color of toner, the toner set of the present disclosure, and an image forming method using the toner set of the present disclosure will be described in order.

[0021] 1-1. Colored Resin Particles The colored resin particles contained in the toner of each color contain a binder resin, a colorant, a softener, and a charge control agent, and may further contain other additives such as a polar resin, as necessary. Furthermore, the colored resin particles may be core-shell type colored resin particles having a core layer containing a binder resin and a shell layer made of a resin different from the binder resin.

[0022] Generally, methods for producing colored resin particles are roughly divided into dry methods such as pulverization methods, and wet methods such as emulsion polymerization aggregation methods, suspension polymerization methods, and dissolution suspension methods, with wet methods being preferred because they are more likely to produce toners with excellent printing properties such as image reproducibility. Among the wet methods, polymerization methods such as emulsion polymerization aggregation methods and suspension polymerization methods are preferred because they are more likely to produce toners with a relatively small particle size distribution on the order of microns, and among polymerization methods, suspension polymerization is more preferred.

[0023] The emulsion polymerization aggregation method involves polymerizing an emulsified polymerizable monomer to obtain a resin fine particle emulsion, which is then aggregated with a colorant dispersion or the like to produce colored resin particles. The solution suspension method involves forming droplets of a solution in which toner components such as a binder resin and a colorant are dissolved or dispersed in an organic solvent in an aqueous medium, and then removing the organic solvent to produce colored resin particles. Any known method can be used for either method.

[0024] The colored resin particles used in the present disclosure can be produced by employing a wet method or a dry method, and are not particularly limited. For example, the colored resin particles can be produced by employing a suspension polymerization method, which is preferred among wet methods, through the following process.

[0025] (A) Suspension Polymerization Method (A-1) Preparation of Polymerizable Monomer Composition First, a polymerizable monomer, a colorant, a softener, a charge control agent, and, if necessary, other additives such as a polar resin and a molecular weight modifier are mixed to prepare a polymerizable monomer composition. For example, a media-type disperser is used for mixing when preparing the polymerizable monomer composition.

[0026] [Polymerizable Monomer] In the present disclosure, a polymerizable monomer refers to a monomer having a polymerizable functional group, and the polymerizable monomer polymerizes to form a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable monomer. That is, the binder resin contained in the colored resin particles is preferably a polymer of a polymerizable monomer containing a monovinyl monomer. Examples of monovinyl monomers include styrene; styrene derivatives such as vinyltoluene and α-methylstyrene; acrylic acid and methacrylic acid; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and dimethylaminoethyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and dimethylaminoethyl methacrylate; 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, styrene derivatives, and acrylic acid esters or methacrylic acid esters are preferably used as the monovinyl monomer. Furthermore, from the viewpoint of achieving a good balance between the low-temperature fixability and heat-resistant storage stability of the toner, the monovinyl monomer may be a combination of at least one selected from the group consisting of styrene and styrene derivatives with at least one selected from the group consisting of acrylic acid esters and methacrylic acid esters, or a combination of styrene with at least one selected from the group consisting of acrylic acid esters and methacrylic acid esters. The acrylic acid ester may be, for example, an alkyl acrylate ester having an alkyl group having 1 to 12 carbon atoms, an alkyl acrylate ester having an alkyl group having 1 to 10 carbon atoms, or an alkyl acrylate ester having an alkyl group having 1 to 8 carbon atoms.The methacrylic acid ester may be, for example, an alkyl methacrylate ester having an alkyl group having 1 to 12 carbon atoms, an alkyl methacrylate ester having an alkyl group having 1 to 10 carbon atoms, or an alkyl methacrylate ester having an alkyl group having 1 to 8 carbon atoms.

[0027] The content of the monovinyl monomer in 100% by mass of the polymerizable monomer is preferably 95% by mass or more, more preferably 98% by mass or more, and even more preferably 99% by mass or more. The polymerizable monomer may consist of a monovinyl monomer, but the content of the monovinyl monomer in 100% by mass of the polymerizable monomer may be 99.5% by mass or less.

[0028] To improve hot offset and storage stability, it is preferable to use any crosslinkable polymerizable monomer 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 having carbon-carbon double bonds are ester-bonded to alcohols 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 can be used alone or in combination of two or more. Of these, aromatic divinyl compounds are preferably used as the crosslinkable polymerizable monomer, and divinylbenzene is particularly preferably used. When the polymerizable monomer contains the crosslinkable polymerizable monomer, the content of the crosslinkable polymerizable monomer is usually 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass, and more preferably 0.5 to 1 part by mass, relative to 100 parts by mass of the monovinyl monomer.

[0029] Furthermore, using a macromonomer as part of the polymerizable monomer is preferable because it provides a good balance between the storage stability and low-temperature fixability of the resulting toner. The macromonomer is a reactive oligomer or polymer having a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, typically having a number-average molecular weight of 1,000 to 30,000. Examples of the macromonomer include styrene macromonomers, styrene-acrylonitrile macromonomers, polyacrylic acid ester macromonomers, and polymethacrylic acid ester macromonomers. Among these, at least one selected from the group consisting of polyacrylic acid ester macromonomers and polymethacrylic acid ester macromonomers is preferably used. Examples of the acrylic acid esters used in the polyacrylic acid ester macromonomers include the same acrylic acid esters usable as the monovinyl monomers described above. Examples of the methacrylic acid esters used in the polymethacrylic acid ester macromonomers include the same methacrylic acid esters usable as the monovinyl monomers described above. As the macromonomer, it is preferable to appropriately select and use one that, when incorporated into the polymerizable monomer, results in a binder resin with a higher glass transition temperature (Tg) than when not incorporated. Commercially available macromonomers may be used. Examples of commercially available macromonomers include the macromonomer series AA-6, AS-6, AN-6S, AB-6, and AW-6S manufactured by Toagosei Co., Ltd. These macromonomers may be used alone or in combination of two or more. When the polymerizable monomer contains the macromonomer, the content of the macromonomer is not particularly limited, but is preferably 0.03 to 5 parts by mass, more preferably 0.05 to 2 parts by mass, even more preferably 0.1 to 1.5 parts by mass, and even more preferably 0.3 to 1 part by mass, per 100 parts by mass of the monovinyl monomer.

[0030] [Colorant] The colorant can be selected from colorants conventionally used in toners and is not particularly limited.The colorant used in magenta toner can be, for example, condensed polycyclic pigments such as quinacridone pigments, magenta pigments such as monoazo pigments, disazo pigments and azo pigments such as condensed azo pigments, and magenta dyes.Specific examples include C.I. 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, 237, 238, 251, 254, 255, 269; C.I. Pigment Violet 19; C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I. Disperse Violet 1; C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28, etc.

[0031] The magenta toner preferably contains a pigment containing a quinacridone skeleton (sometimes referred to as a "quinacridone pigment" in the present disclosure) as a colorant. This allows for the production of a toner with excellent saturation and print density in printed matter, and also makes it easier for the toner to have the desired viscoelasticity. Examples of quinacridone pigments that are preferably used include C.I. Pigment Red 122, 192, 202, 206, 207, 282, and C.I. Pigment Violet 19. Among these, the quinacridone pigment is preferably at least one selected from the group consisting of C.I. Pigment Red 122 and C.I. Pigment Violet 19. It is more preferable to use C.I. Pigment Red 122 and C.I. Pigment Violet 19 in combination, and a mixed crystal of C.I. Pigment Violet 19 and C.I. Pigment Red 122 is particularly preferred. Mixed crystals of C.I. Pigment Violet 19 and C.I. Pigment Red 122 can be produced, for example, by the method described in U.S. Pat. No. 3,160,510, in which the mixed crystal components are simultaneously recrystallized from sulfuric acid or other suitable solvent, and if necessary, salt-milled and then treated with a solvent, or by the method described in German Patent Application Publication No. 1,217,333, in which a substituted diaminoterephthalic acid mixture is cyclized and then treated with a solvent. When the magenta toner contains C.I. Pigment Violet 19 and C.I. Pigment Red 122 as colorants, the mass ratio of C.I. Pigment Violet 19 to C.I. Pigment Red 122 is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60.

[0032] The magenta toner preferably contains, as colorants, a quinacridone pigment and a pigment that does not contain a quinacridone skeleton. This can suppress the generation of coarse particles and facilitate the toner to have the desired viscoelasticity. As the pigment that does not contain a quinacridone skeleton, an azo pigment is preferably used from the viewpoints of the saturation and print density of the printed matter and the viscoelasticity of the toner. Among azo pigments, a monoazo pigment is preferred, and a pigment represented by the following formula (1) and a pigment represented by the following formula (1) treated with a metal rosinate are more preferred. In the present disclosure, the pigment represented by the following formula (1) treated with a metal rosinate is referred to as "magenta pigment A." Magenta pigment A is, in other words, the pigment represented by the following formula (1) that has been surface-treated with a metal rosinate. In a magenta toner, as an azo pigment to be used in combination with a quinacridone pigment, the magenta pigment A is particularly preferred.

[0033] (In formula (1), Me represents a divalent metal.)

[0034] The pigment represented by the above formula (1) is classified as a so-called lake pigment. Lake pigments are pigments insolubilized by the action of a metal salt on a dye. Because lake pigments are less expensive than other pigments, their use has the advantage of reducing toner production costs. Magenta Pigment A, in which the pigment represented by the above formula (1) is surface-treated with a metal rosinate, is superior in suppressing the generation of coarse particles during magenta toner production compared to pigments that have not been surface-treated. Furthermore, the use of this magenta Pigment A allows for the production of a magenta toner that exhibits vivid color and high reflection density even with a small amount of toner, has an excellent balance of low-temperature fixability and heat-resistant storage stability, and further has excellent print durability.

[0035] Examples of the pigment represented by the formula (1) include Me in the formula (1). ＋＋ Ba ＋＋ C.I. Pigment Red 48:1, Me in the above formula (1) ＋＋ is Ca ＋＋ C.I. Pigment Red 48:2, Me in the above formula (1)＋＋ is Sr ＋＋ C.I. Pigment Red 48:3, Me in the above formula (1) ＋＋ is Mn ＋＋ C.I. Pigment Red 48:4, Me in the above formula (1) ＋＋ is Mg ＋＋ Pigment Red 48:5, and Me in the above formula (1) ＋＋ is Cd ＋＋ Among them, C.I. Pigment Red 48:6, etc., which is represented by the formula (1) above, ＋＋ is Sr ＋＋ Preferably, the magenta pigment A is C.I. Pigment Red 48:3 (CAS No. 15782-05-5), which is a pigment classified as C.I. Pigment Red 48:3. That is, it is preferred that the magenta pigment A is a pigment classified as C.I. Pigment Red 48:3, and that the C.I. Pigment Red 48:3 has been surface-treated with a metal rosinate.

[0036] The magenta pigment A can be a commercially available product, or a product synthesized in advance. Examples of commercially available magenta pigment A include Daido Kasei Co., Ltd.'s product name: NO. 5500 ST-RED (pigment classification: C.I. Pigment Red 48:3, content of metal rosinate per 100 parts by mass of magenta pigment A: 5.0 parts by mass) and Daido Kasei Co., Ltd.'s product name: S-7014 RED (pigment classification: C.I. Pigment Red 48:3, content of metal rosinate per 100 parts by mass of magenta pigment A: 3.0 parts by mass). When synthesizing the magenta pigment A, for example, when synthesizing a dye to be used in the pigment (lake pigment) represented by formula (1) above, the magenta pigment A can be obtained by synthesizing the dye by a coupling reaction using a coupler component containing a metal rosinate, and then converting the resulting dye into a lake. The magenta pigment A can also be produced by, for example, contacting the pigment represented by formula (1) with a metal rosin acid. The rosin acid may be any known or commonly used rosin acid, including abietic acid-based rosin acid, disproportionated rosin acid, partially hydrogenated rosin acid, fully hydrogenated rosin acid, maleic acid-modified rosin acid, fumaric acid-modified rosin acid, and polymerized rosin acid. A low-acid-value rosin acid having an acid value of 170 mg KOH / g or less, preferably 100 mg KOH / g or less, is preferably used. The use of such a low-acid-value rosin acid reduces the acid value of the magenta pigment A, thereby suppressing the generation of coarse particles. The metal rosin acid is a salt composed of rosin acid and a divalent, trivalent, or tetravalent polyvalent metal, such as a Ca salt, a Ba salt, a Sr salt, an Al salt, or a Zn salt. As the metal salt of rosin acid, it is preferable to include a Sr salt of rosin acid, for example, in view of the high effect of improving flushing properties in the toner production process.

[0037] The content of the metal rosinate is typically 1 to 7 parts by mass, preferably 2 to 6 parts by mass, and more preferably 2.5 to 5.5 parts by mass, per 100 parts by mass of magenta pigment A. By limiting the content of the metal rosinate to 1 to 7 parts by mass, liberation of the metal rosinate is suppressed. As a result, the liberated metal rosinate or its derivatives do not interfere with toner production, resulting in a toner with fewer coarse particles. The content of magenta pigment A can be calculated as the total content of the pigment represented by formula (1) above, which serves as a raw material, and the metal rosinate, which serves as a surface treatment agent.

[0038] The acid value of magenta pigment A is not particularly limited and is typically 3 mgKOH / g or less. However, in order to suppress the generation of coarse particles, it is preferably 2.4 mgKOH / g or less, more preferably 0.1 to 2.0 mgKOH / g, and even more preferably 0.4 to 1.8 mgKOH / g. The acid value of magenta pigment A can be adjusted, for example, by the type and amount of rosin acid metal salt added. Note that, in the present disclosure, the acid value is a value measured in accordance with JIS K 0070, a standard method for analyzing fats and oils established by the Japanese Industrial Standards Committee (JICS).

[0039] When magenta pigment A is used as the colorant, the content of magenta pigment A is preferably 1 to 10 parts by mass, more preferably 1.5 to 7 parts by mass, and even more preferably 2 to 5 parts by mass, per 100 parts by mass of the monovinyl monomer. The content of magenta pigment A in the magenta toner is preferably 1 to 10 parts by mass, more preferably 1.5 to 7 parts by mass, and even more preferably 2 to 5 parts by mass, per 100 parts by mass of the binder resin. When the content of magenta pigment A is equal to or greater than the lower limit, a toner exhibiting brighter colors than conventional toners, a high reflection density, an excellent balance between low-temperature fixability and heat-resistant storage stability, and excellent print durability can be easily obtained, even with a small amount of toner. When the content of magenta pigment A is equal to or less than the upper limit, excess magenta pigment A does not inhibit toner production, and a toner with fewer coarse particles can be easily obtained.

[0040] When the magenta toner contains a combination of a quinacridone pigment and a pigment not containing a quinacridone skeleton as a colorant, the mass ratio of the quinacridone pigment to the pigment not containing a quinacridone skeleton is not particularly limited. However, from the viewpoints of obtaining a brighter color and a higher reflection density, suppressing the generation of coarse particles, improving print durability and low-temperature fixability, and the viscoelasticity of the toner, the total amount of these components is 100 mass%, i.e., the content of the quinacridone pigment relative to 100 mass% of the colorant contained in the magenta toner is preferably 25 to 70 mass%, more preferably 30 to 60 mass%, and even more preferably 35 to 50 mass%. The quinacridone pigments described above can be used alone or in combination of two or more. The pigments not containing a quinacridone skeleton described above can also be used alone or in combination of two or more.

[0041] Examples of colorants used in yellow toners include azo pigments such as monoazo pigments, disazo pigments, and condensed azo pigments, and yellow pigments such as condensed polycyclic pigments, as well as yellow dyes.Specific examples include C.I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 155, 180, 181, 185, 186, 213, and 214; C.I. Solvent Yellow 98 and 162; and the like.Among these, from the viewpoint of the viscoelasticity of the toner and the saturation and print density of the printed matter, examples of yellow colorants include C.I. Pigment Yellow 74, C.I. Pigment Yellow 120, C.I. Pigment Yellow 151, C.I. Pigment Yellow 155, and C.I. Disazo pigments such as C.I. Pigment Yellow 180, C.I. Pigment Yellow 185, and C.I. Pigment Yellow 213 are preferred, with C.I. Pigment Yellow 155 being particularly preferred.

[0042] Examples of colorants used in cyan toners include phthalocyanine pigments such as copper phthalocyanine pigments and their derivatives, cyan pigments such as anthraquinone pigments, and cyan dyes. Specific examples include C.I. Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, and 60; C.I. Solvent Blue 70, and the like. Among these, from the viewpoint of the viscoelasticity of the toner and the saturation and print density of the printed matter, copper phthalocyanine compounds and derivatives thereof such as C.I. Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, and 60 are preferred as cyan colorants, with C.I. Pigment Blue 15:3 and 15:4 being particularly preferred.

[0043] Examples of colorants used in black toner include carbon black, titanium black, and magnetic powders such as iron zinc oxide and iron nickel oxide. Among these, carbon black is preferred as a colorant used in black toner from the viewpoints of the viscoelasticity of the toner and print density.

[0044] The content of the colorant in the toner is preferably 1 to 15 parts by mass, more preferably 5 to 12 parts by mass, per 100 parts by mass of the monovinyl monomer, from the viewpoints of print density and viscoelasticity of the toner. From the same viewpoints as above, the content of the colorant in the toner is preferably 1 to 15 parts by mass, more preferably 5 to 12 parts by mass, per 100 parts by mass of the binder resin. In the present disclosure, 100 parts by mass of the binder resin corresponds to 100 parts by mass of the polymerizable monomer described above. In the case of core-shell type colored resin particles, it corresponds to 100 parts by mass of the polymerizable monomer used to obtain the core layer. In each color toner, the colorants can be used alone or in combination of two or more types.

[0045] [Charge Control Agent] As the charge control agent, any charge control agent that has been used in conventional toners can be used without any restrictions. Among the charge control agents, it is preferable to use a charge control resin. The charge control resin is preferred because it has high compatibility with the binder resin, is colorless, and can provide a toner with stable chargeability even in high-speed continuous color printing, and is also preferred from the viewpoint of the viscoelasticity of the toner.

[0046] Positively or negatively chargeable charge control resins can be, for example, copolymers containing functional group-containing monomer units (sometimes simply referred to as "functional group-containing copolymers" in this disclosure). Positively chargeable charge control resins can be, for example, functional group-containing copolymers containing structural units containing functional groups such as pyridinium groups, amino groups, quaternary ammonium groups, or quaternary ammonium salt-containing groups, including polyamine resins, quaternary ammonium group-containing copolymers, and quaternary ammonium base-containing copolymers. Negatively chargeable charge control resins can be, for example, functional group-containing copolymers containing structural units containing functional groups such as sulfonic acid groups, sulfonate salt-containing groups, carboxyl groups, or carboxylate salt-containing groups, including sulfonic acid group-containing copolymers, sulfonate salt group-containing copolymers, carboxyl group-containing copolymers, and carboxylate salt group-containing copolymers.

[0047] The glass transition temperature (Tg) of the charge control resin is not particularly limited, but is preferably in the range of 50°C to 110°C, and more preferably in the range of 60°C to 100°C. When the glass transition temperature (Tg) of the charge control resin is within the above range, a toner having desirable viscoelasticity is easily obtained, and the storage stability of the toner can be improved. Since the charge control resin is likely to localize near the surface of the colored resin particles and function like a shell, it is presumed that when the Tg of the charge control resin is within the above range, the toner storage stability is improved due to the sufficiently high Tg. In the present disclosure, the glass transition temperature (Tg) of the charge control resin can be determined, for example, in accordance with ASTM D3418-82. Specifically, a sample is heated at a heating rate of 10°C / min using a differential scanning calorimeter (e.g., SSC5200 manufactured by Seiko Electronics Co., Ltd.), and the temperature showing the maximum endothermic peak in the DSC curve obtained during this process can be determined as the glass transition temperature.

[0048] The weight-average molecular weight (Mw) of the charge control resin is not particularly limited, but is preferably in the range of 5,000 to 30,000, and more preferably in the range of 10,000 to 25,000. When the weight-average molecular weight (Mw) is equal to or greater than the lower limit, deterioration in the storage stability and print durability of the toner can be suppressed, while when it is equal to or less than the upper limit, deterioration in the fixability of the toner can be suppressed. Furthermore, when the weight-average molecular weight (Mw) is within the above range, the charge control resin can be suitably dispersed in the colored resin particles, making it easier to obtain a toner imparted with a stable charge amount over time. In this disclosure, the weight-average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF).

[0049] As the charge control resin, a functional group-containing copolymer having a content ratio of functional group-containing monomer units (sometimes simply referred to as "functional group amount" in the present disclosure) of 0.4 to 10% by mass is preferably used from the viewpoint of imparting the desired chargeability and viscoelasticity to the toner. The lower limit of the functional group amount of the functional group-containing copolymer is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 6% by mass or more, and the upper limit is preferably 10% by mass or less, more preferably 9% by mass or less.

[0050] Furthermore, each color toner included in the toner set of the present disclosure preferably contains a positively charged charge control agent, more preferably contains a positively charged charge control resin, and even more preferably contains a positively charged functional group-containing copolymer, in view of the fact that charging is likely to be stabilized when combined with an external additive described below.

[0051] The functional group contained in the positively chargeable functional group-containing copolymer is preferably a functional group that provides positive charging, such as a pyridinium group, an amino group, a quaternary ammonium group, or a quaternary ammonium salt-containing group. Among these, from the viewpoints of imparting the desired charging property to the toner, improving the dispersibility of the colorant, and imparting the desired viscoelasticity to the toner, quaternary ammonium groups and quaternary ammonium salt-containing groups are preferred, and quaternary ammonium salt-containing groups are more preferred. The quaternary ammonium salt-containing group is a group represented by the formula -NR ３ ＋ ・X － In this ionic structure, the three R's are each independently a hydrogen atom or a substituent such as an alkyl group, and among these, a hydrogen atom or a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms is preferred. X － represents a halogen ion, an alkyl group in which one hydrogen atom is substituted with a halogen ion, or —SO ３ － , -PO ３ － Or -BO ３ －Examples of the hydrocarbon group include an alkyl group, an aromatic hydrocarbon group, and a substituted aromatic hydrocarbon group. X － Among these, —SO 2 in which at least one hydrogen atom may be substituted with a halogen atom is preferred, in that the charge amount of the toner is easily maintained during continuous printing and printing defects are less likely to occur. ３ － Preferably, the anion is a hydrocarbon group having the formula:

[0052] The functional group-containing copolymer is preferably a styrene-acrylic copolymer from the viewpoints of compatibility with the polymerizable monomer and viscoelasticity of the toner. The styrene-acrylic copolymer may be a copolymer of an aromatic vinyl hydrocarbon monomer and a (meth)acrylate monomer. The functional group-containing copolymer is more preferably a copolymer containing a functional group-containing monomer unit, an aromatic vinyl monomer unit, and a (meth)acrylate monomer unit. Here, the aromatic vinyl monomer unit and the (meth)acrylate monomer unit do not contain a functional group that imparts chargeability. Such a copolymer has excellent compatibility with the binder resin, and therefore tends to produce a uniform charge amount in the toner. In this disclosure, (meth)acrylate refers to both acrylate and methacrylate, and (meth)acrylic refers to both acrylic and methacrylic. Furthermore, the functional group-containing copolymer is preferably one that dissolves in the aromatic vinyl monomer from the viewpoint of dispersibility in the polymerizable monomer composition.

[0053] The functional group-containing copolymer may be, for example, a copolymer obtained by copolymerizing a monomer containing a functional group with another monomer copolymerizable therewith, or may be a copolymer obtained by polymerizing a monomer not containing a functional group and then introducing a functional group by modification treatment. A copolymer containing a monomer unit containing a quaternary ammonium salt-containing group, an aromatic vinyl monomer unit, and a (meth)acrylate monomer unit, which is preferably used as a positively chargeable functional group-containing copolymer, is not particularly limited, and can be obtained, for example, by the following method. The polymerization method is not limited, and known polymerization methods such as emulsion polymerization, dispersion polymerization, suspension polymerization, and solution polymerization can be used.

[0054] (i) A method in which an aromatic vinyl monomer, a (meth)acrylate monomer, and an N,N-disubstituted aminoalkyl (meth)acrylate monomer are copolymerized in the presence of a polymerization initiator, and then the amino group is quaternized using a quaternizing agent such as a halogenated organic compound or an acid ester compound. (ii) A method in which an aromatic vinyl monomer, a (meth)acrylate monomer, and an N,N-disubstituted aminoalkyl (meth)acrylate monomer are copolymerized in the presence of a polymerization initiator with a monomer obtained by converting the monomer into a quaternary ammonium salt using a quaternizing agent such as a halogenated organic compound or an acid ester compound.

[0055] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-propylstyrene, 3-propylstyrene, 4-propylstyrene, 2-isopropylstyrene, 3-isopropylstyrene, 4-isopropylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-butylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2-methyl-α-methylstyrene, 3-methyl-α-methylstyrene, 4-methyl-α-methylstyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, and vinylnaphthalene. Among these, styrene and α-methylstyrene are preferred. These may be used alone or in combination of two or more.

[0056] As the (meth)acrylate monomer, for example, an alkyl (meth)acrylate monomer which may have a hydroxyl group is preferably used. Examples of the alkyl (meth)acrylate monomer which may have a hydroxyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxypropyl (meth)acrylate, and dodecyl (meth)acrylate. These may be used alone or in combination of two or more. In the alkyl (meth)acrylate monomer, the number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 6. Furthermore, alkyl (meth)acrylate monomers which do not have a substituent are particularly preferred.

[0057] Examples of the N,N-disubstituted aminoalkyl (meth)acrylate monomer include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, dipropylaminomethyl (meth)acrylate, diisopropylaminomethyl (meth)acrylate, ethylmethylaminomethyl (meth)acrylate, methylpropylaminomethyl (meth)acrylate, dimethylamino-1-ethyl (meth)acrylate, diethylamino-1-ethyl (meth)acrylate, and dipropylamino-1-ethyl (meth)acrylate. These can be used alone or in combination of two or more. In the N,N-disubstituted aminoalkyl (meth)acrylate monomer, the number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 3.

[0058] Examples of halogenated organic compounds used as quaternizing agents include linear, branched, or cyclic alkyl halides having 1 to 6 carbon atoms, such as chloromethane, dichloromethane, and trichloromethane; and aromatic halides, such as chlorobenzene, 4-chlorotoluene, and 1-chloronaphthalene. Examples of acid ester compounds used as quaternizing agents include alkyl sulfonates, such as methyl methylsulfonate and ethyl methylsulfonate; alkyl benzenesulfonates, such as methyl benzenesulfonate; alkyl paratoluenesulfonates, such as methyl paratoluenesulfonate; phosphoric acid esters, such as trimethylphosphate; and boric acid esters, such as trimethoxyborane. These quaternizing agents can be used alone or in combination of two or more.

[0059] The monomer unit containing a quaternary ammonium salt-containing group contained in the functional group-containing copolymer is preferably a structural unit represented by the following formula [I]:

[0060] [In the above formula [I], R １ is a hydrogen atom or a methyl group, and R ２is a linear or branched alkylene group having 1 to 3 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, and R ３ ~R ５ are each independently a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms; X － may have at least one substituent selected from the group consisting of a halogen ion, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, and a halogen atom; —SO ３ － , -PO ３ － Or -BO ３ － Benzene or naphthalene having either of the following:

[0061] X － is a halogen ion or may have at least one substituent selected from the group consisting of a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms and a halogen atom; —SO ３ － , -PO ３ － Or -BO ３ － The toner is preferably benzene or naphthalene having either of the following: X － is more preferably an aromatic sulfonate anion which may have the above-mentioned substituent. Examples of the aromatic sulfonate anion include a benzenesulfonate anion and a paratoluenesulfonate anion.

[0062] Specific examples of the structural unit represented by formula [I] include structural units corresponding to monomers containing a quaternary ammonium salt-containing group, such as N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride (DMC; methacrylic acid dimethylaminoethyl methyl chloride), 2-(methacryloyloxy)-N-benzyl-N,N-dimethylethane ammonium chloride (DML; methacrylic acid dimethylaminoethyl benzyl chloride), and N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium paratoluenesulfonate, 2-(methacryloyloxy)ethyltrimethylammonium paratoluenesulfonate, and 2-(methacryloyloxy)-N-benzyl-N,N-dimethylethane ammonium paratoluenesulfonate. Among these, a structural unit corresponding to N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium paratoluenesulfonate is preferred.

[0063] In the functional group-containing copolymer, the copolymerization ratio of the aromatic vinyl monomer and the (meth)acrylate monomer is not particularly limited, but from the viewpoints of solubility in the polymerizable monomer and dispersibility in the binder resin, the mass ratio of the (meth)acrylate monomer unit to the aromatic vinyl monomer unit ((meth)acrylate monomer unit / aromatic vinyl monomer unit) is preferably 0.05 to 0.35, more preferably 0.10 to 0.30, and even more preferably 0.15 to 0.25.

[0064] The charge control resin can be used alone or in combination of two or more types. There are no particular limitations on the type. However, from the viewpoint of improving print density, a combination of copolymer A and copolymer B may be used as the charge control resin. Here, copolymer A and copolymer B are functional group-containing copolymers with different amounts of functional groups, with copolymer A having a greater amount of functional groups than copolymer B. In particular, in a magenta toner containing the preferred magenta colorant described above, using a combination of copolymer A and copolymer B as the charge control resin is preferred because it facilitates improving print density. When the colored resin particles contain a combination of copolymer A, which has a relatively high amount of functional groups, and copolymer B, which has a relatively low amount of functional groups, as the charge control resin, the toner can be provided with the desired chargeability while improving the dispersibility of the colorant. Therefore, the colorant can be incorporated at a high concentration, resulting in improved print density. When copolymer A and copolymer B are used in combination as charge control agents, the difference in functional group amount is thought to result in a distribution in which copolymer B is unevenly distributed relatively toward the center of the colored resin particles, and copolymer A is unevenly distributed toward the surface of the colored resin particles. Copolymer A has a larger amount of functional groups than copolymer B, and therefore has a stronger charge-imparting effect, and is unevenly distributed toward the surface of the colored resin particles. Therefore, it is believed that the chargeability of the toner is mainly influenced by copolymer A. On the other hand, copolymer B not only exhibits a charge-imparting effect, but also has a strong effect of dispersing the colorant within the colored resin particles. It is presumed that the action of copolymer A and copolymer B imparts the desired chargeability to the toner and improves the dispersibility of the colorant.

[0065] The amount of functional groups in the copolymer A is preferably 5% by mass or more, more preferably 6% by mass or more, from the viewpoint of imparting a desired chargeability to the toner, improving the dispersibility of the colorant, and imparting a desired viscoelasticity to the toner, as a lower limit, and is preferably 10% by mass or less, and more preferably 9% by mass or less. The amount of functional groups in the copolymer B is preferably 0.4% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of imparting a desired chargeability to the toner, improving the dispersibility of the colorant, and imparting a desired viscoelasticity to the toner, as a lower limit, and is preferably less than 5% by mass, more preferably 4% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of imparting a desired chargeability to the toner, improving the dispersibility of the colorant, and imparting a desired viscoelasticity to the toner.

[0066] The difference between the amount of functional groups in the copolymer A and the amount of functional groups in the copolymer B (amount of functional groups in copolymer A - amount of functional groups in copolymer B) is preferably 1 to 9% by mass, more preferably 2 to 8% by mass, and even more preferably 3 to 7% by mass, from the viewpoints of imparting the desired chargeability to the toner, improving the dispersibility of the colorant, and imparting the desired viscoelasticity to the toner.

[0067] In addition, from the viewpoint of imparting the desired chargeability to the toner, improving the dispersibility of the colorant, and imparting the desired viscoelasticity to the toner, it is preferable that the functional group contained in the copolymer A and the functional group contained in the copolymer B have the same structure, and it is more preferable that they are the same and are quaternary ammonium groups or quaternary ammonium salt-containing groups. From the same viewpoint, it is preferable that each of the copolymers A and B consists of a copolymer having the same monomer unit composition. Note that, copolymers having the same monomer unit composition mean that the types and copolymerization ratios of the monomers used in the synthesis of the copolymers are the same. In other words, when the copolymers A and B are contained in combination, it is preferable that only one type of the copolymer A and only one type of the copolymer B are contained.

[0068] In a toner containing a combination of copolymer A and copolymer B, the ratio of the content of copolymer A to the content of copolymer B (copolymer A content / copolymer B content) is not particularly limited, but from the viewpoints of imparting the toner with desired chargeability, improving the dispersibility of the colorant, improving the heat resistance of the toner, and imparting the toner with desired viscoelasticity, the lower limit is preferably 0.5 or more, more preferably 0.8 or more, even more preferably 1.0 or more, and still more preferably 1.5 or more, and the upper limit is preferably 15 or less, more preferably 10 or less, even more preferably 5 or less, and still more preferably 3 or less. When the ratio is equal to or greater than the lower limit, toner quality can be easily controlled, and when the ratio is equal to or less than the upper limit, the dispersibility of the colorant in particular is improved, making it possible to easily improve print density.

[0069] Each color toner included in the toner set of the present disclosure may contain a relatively low molecular weight charge control compound as a charge control agent. Examples of positively chargeable charge control compounds include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds, and imidazole compounds. Examples of negatively chargeable charge control compounds include azo dyes containing metals such as Cr, Co, Al, and Fe, salicylic acid metal compounds, and alkylsalicylic acid metal compounds. These charge control compounds may be used alone or in combination.

[0070] The content of the charge control agent is preferably 0.01 to 15 parts by mass, more preferably 0.1 to 8 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the monovinyl monomer. Furthermore, the content of the charge control agent in the magenta toner is particularly preferably 1 to 5 parts by mass, per 100 parts by mass of the monovinyl monomer. Among the toners of each color other than the magenta toner, the content of the charge control agent in the yellow toner and the cyan toner is particularly preferably 0.5 to 1 part by mass, per 100 parts by mass of the monovinyl monomer. The content of the charge control agent in the black toner is particularly preferably 0.3 to 13 parts by mass, per 100 parts by mass of the monovinyl monomer. Furthermore, the content of the charge control agent in each color toner included in the toner set of the present disclosure is preferably 0.01 to 15 parts by weight, more preferably 0.1 to 8 parts by weight, and even more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the binder resin. Furthermore, in the magenta toner, the content of the charge control agent is particularly preferably 1 to 5 parts by weight, per 100 parts by weight of the binder resin. Among the color toners other than the magenta toner, the content of the charge control agent in the yellow toner and the cyan toner is particularly preferably 0.5 to 1 part by weight, per 100 parts by weight of the binder resin. The content of the charge control agent in the black toner is particularly preferably 0.3 to 13 parts by weight, per 100 parts by weight of the binder resin. When the content of the charge control agent is equal to or greater than the lower limit, the occurrence of fogging can be suppressed. When the content of the charge control agent is equal to or less than the upper limit, print smearing can be suppressed. Furthermore, adjusting the content of the charge control agent can adjust the viscoelasticity of the toner. In each color toner, the content of the charge control resin in 100% by mass of the charge control agent is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0071] [Softener] The softener contains an ester wax having a molecular weight of 600 to 3000. The inclusion of a softener can improve the releasability of the toner from the fixing roll during fixing. Among the softeners, the inclusion of an ester wax having a molecular weight of 600 to 3000 can improve the fixability of the toner while suppressing the generation of UFP during fixation. If the molecular weight of the ester wax is less than 600, UFP is more likely to occur during fixation of the toner, while if it exceeds 3000, the fixability of the toner deteriorates. The softener has the effect of lowering the melt viscosity of the binder resin. However, if the molecular weight of the softener is too high, the effect of lowering the melt viscosity of the binder resin is weakened, making the toner less soluble, resulting in poor fixability. Furthermore, if the molecular weight of the softener is too high, the bleeding properties of the softener are also reduced. In other words, the softener is less likely to migrate from the interior of the toner to the surface of the toner. This makes it difficult for the softener to exert its adhesion effect. The molecular weight of the ester wax has a lower limit of preferably 800 or more, more preferably 1000 or more, and an upper limit of preferably 2800 or less, more preferably 2700 or less. In the present disclosure, the yellow toner, magenta toner, and cyan toner contained in the toner set may contain an ester wax having a molecular weight of 600 to 3000 as a softener. However, it is preferable that all toners contained in the toner set contain an ester wax having a molecular weight of 600 to 3000 as a softener, from the viewpoint of improving the fixability of the toner while suppressing the occurrence of UFP during fixation of the toner. When the toner set of the present disclosure contains a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that each of the yellow toner, magenta toner, cyan toner, and black toner contains an ester wax having a molecular weight of 600 to 3000 as a softener.

[0072] Ester wax is a product of an esterification reaction between an alcohol and a fatty acid. The alcohol may be at least one alcohol selected from the group consisting of monohydric alcohols and polyhydric alcohols. Examples of monohydric alcohols include saturated monohydric aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, octanol, 2-ethyl-1-hexanol, nonyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, and behenyl alcohol; unsaturated monohydric aliphatic alcohols such as allyl alcohol, methallyl alcohol, crotyl alcohol, and oleyl alcohol; monohydric alicyclic alcohols such as cyclohexanol; and monohydric aromatic alcohols such as phenol, phenylmethanol (benzyl alcohol), methylphenol (cresol), p-ethylphenol, dimethylphenol (xylenol), nonylphenol, dodecylphenol, phenylphenol, and naphthol. Examples of polyhydric alcohols include dihydric saturated aliphatic alcohols such as ethylene glycol and propylene glycol, dihydric aromatic alcohols such as catechol and hydroquinone, and trihydric or higher saturated aliphatic alcohols such as glycerin, pentaerythritol, dipentaerythritol, hexaglycerol, and polyglycerin. Among these monohydric and polyhydric alcohols, polyhydric saturated aliphatic alcohols are preferred, trihydric or higher saturated aliphatic alcohols are more preferred, trihydric to octahydric saturated aliphatic alcohols are even more preferred, and hexaglycerol and pentaerythritol are particularly preferred, from the viewpoints that an ester wax having a molecular weight of 600 to 3,000 can be easily obtained and that the low-temperature fixability of the toner can be easily improved while suppressing the generation of UFP.

[0073] The fatty acid used as a raw material for the ester wax may be at least one fatty acid selected from the group consisting of saturated fatty acids and unsaturated fatty acids. The lower limit of the number of carbon atoms in the fatty acid used as a raw material for the ester wax is preferably 12 or more, more preferably 14 or more, and even more preferably 16 or more, and the upper limit is preferably 24 or less, more preferably 22 or less, and even more preferably 18 or less. When the carbon number of the fatty acid is equal to or greater than the lower limit, the generation of UFP and bleeding out of the ester wax are likely to be suppressed. When the carbon number of the fatty acid is equal to or less than the upper limit, a decrease in the heat resistance of the toner is suppressed. Furthermore, saturated fatty acids with a carbon number within the above range are particularly preferred because an ester wax having a molecular weight of 600 to 3000 can be easily obtained.

[0074] The saturated fatty acid is not particularly limited, but examples thereof include lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), pentadecylic acid (15 carbon atoms), palmitic acid (16 carbon atoms), margaric acid (17 carbon atoms), stearic acid (18 carbon atoms), arachidic acid (20 carbon atoms), and behenic acid (22 carbon atoms). Of these, palmitic acid (16 carbon atoms), behenic acid (22 carbon atoms), and stearic acid (18 carbon atoms) are preferred.

[0075] The unsaturated fatty acids are not particularly limited, but examples thereof include: Palmitoleic acid (CH ３ (CH ２ ) ５ CH=CH(CH ２ ) ７ COOH) oleic acid (CH ３ (CH ２ ) ７ CH=CH(CH ２ ) ７ COOH) ・Vaccenic acid (CH ３ (CH ２ ) ５ CH=CH(CH ２ ) ９ COOH) Linoleic acid (CH ３ (CH ２ ) ３ (CH ２ CH=CH) ２ (CH ２ )７ COOH) (9,12,15)-linolenic acid (CH ３ (CH ２ CH=CH) ３ (CH ２ ) ７ COOH) (6,9,12)-linolenic acid (CH ３ (CH ２ ) ３ (CH ２ CH=CH) ３ (CH ２ ) ４ COOH) Eleostearic acid (CH ３ (CH ２ ) ３ (CH=CH) ３ (CH ２ ) ７ COOH) and arachidonic acid (CH ３ (CH ２ ) ３ (CH ２ CH=CH) ４ (CH ２ ) ３ COOH). The above fatty acids can be used either alone or in combination of two or more.

[0076] The esterification rate of the ester wax is preferably 92% or more, more preferably 95% or more, and even more preferably 97% or more, from the viewpoint of improving the low-temperature fixability of the toner due to the sharp melting properties of the ester wax. The esterification rate of the ester wax is the ratio of the number of hydroxyl groups ester-bonded to a carboxylic acid (e.g., a fatty acid) to the total number of hydroxyl groups possessed by the raw material alcohol of the ester wax. The esterification rate of the ester wax can be calculated by measuring the saponification value (SV), hydroxyl value (OHV), and acid value (AV) of the ester wax, respectively, and using the following formula: Esterification rate (%) = [(SV - AV) / (SV - AV + OHV)] × 100. The saponification value (SV) and acid value (AV) of the ester wax are measured in accordance with JIS K 0070, and the hydroxyl value (OHV) of the ester wax is measured in accordance with JIS K 1557.

[0077] The ester wax may be either a monoester or a polyfunctional ester such as a diester, triester, tetraester or polyester. However, from the viewpoint of improving the low-temperature fixability of the toner while suppressing the generation of UFP, a polyfunctional ester is preferred, and a trifunctional to octafunctional polyfunctional ester, i.e., a polyfunctional ester having 3 to 8 ester bonds in the structure of one molecule, is more preferred.

[0078] The ester wax having a molecular weight of 600 to 3000 is not particularly limited, but for example, hexaglycerin octabehenate, pentaglycerol heptabehenate, tetraglycerol hexabehenate, triglycerol pentabehenate, diglycerol tetrabehenate, glycerol tribehenate, pentaerythritol tetrastearate, pentaerythritol tetrapalmitate, pentaerythritol tetramyristate, stearyl stearate, behenyl behenate, pentaerythritol tetrapalmitate, pentaerythritol tetrabehenate, dipentaerythritol hexalaurate, dipentaerythritol hexamyristate, dipentaerythritol hexapalmitate, dipentaerythritol hexastearate, dipentaerythritol hexabehenate, and dipentaerythritol hexanonacosanate can be preferably used. The ester waxes having a molecular weight of 600 to 3000 may be used alone or in combination of two or more.

[0079] The toner may further contain a softener other than the ester wax having a molecular weight of 600 to 3000, provided that the object of the present disclosure is not impaired. Examples of softeners other than the ester wax include hydrocarbon waxes such as ester waxes having a molecular weight of less than 600, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, and petroleum waxes; natural waxes such as jojoba; and mineral waxes such as ozokerite. When each color toner contains a softener other than the ester wax having a molecular weight of 600 to 3000 as a softener, the content of the ester wax having a molecular weight of 600 to 3000 in 100% by mass of the softener is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0080] In addition, from the viewpoint of the viscoelasticity of the toner and improving the balance between the storage stability and low-temperature fixability of the toner, the melting point of the softener is preferably in the range of 50°C or higher and 90°C or lower, more preferably in the range of 60°C or higher and 85°C or lower, and even more preferably in the range of 70°C or higher and 80°C or lower.

[0081] The content of the softener is not particularly limited, but from the viewpoint of the viscoelasticity of the toner and from the viewpoint of improving the balance between the storage stability and low-temperature fixability of the toner while suppressing the generation of UFP, the lower limit is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and the upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the monovinyl monomer. From the same viewpoint as above, the content of the softener in the toner is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and the upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0082] [Polar Resin] The polymerizable monomer composition may contain a polar resin. This makes it easier to control the particle size of the colored resin particles and to suppress the generation of coarse particles. In the present disclosure, the polar resin is selected from the group consisting of polymers containing repeating units containing heteroatoms. Specific examples of the polar resin include acrylic resins, polyester resins, and vinyl resins containing heteroatoms. The polar resin may be a homopolymer or copolymer of a heteroatom-containing monomer, or a copolymer of a heteroatom-containing monomer and a non-heteroatom-containing monomer. When the polar resin is a copolymer of a heteroatom-containing monomer and a non-heteroatom-containing monomer, the proportion of the heteroatom-containing monomer unit is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, of all repeating units constituting the copolymer (100% by mass), from the viewpoints of easier control of the particle size of the colored resin particles and easier suppression of the generation of coarse particles.

[0083] Examples of heteroatom-containing monomers used in the polar resin include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, sec-pentyl (meth)acrylate, and isopentyl (meth)acrylate. acrylate, alkyl (meth)acrylates such as neopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, neohexyl (meth)acrylate, sec-hexyl (meth)acrylate, tert-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate, as well as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate Examples of suitable monomers include (meth)acrylic acid esters such as 4-hydroxybutyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and 4-hydroxybutyl acrylate glycidyl ether, as well as monomers having a (meth)acryloyl group such as (meth)acrylic acid, i.e., (meth)acrylic monovinyl monomers; aromatic vinyl monomers containing heteroatoms such as halogenated styrenes and styrene sulfonic acids; vinyl carboxylic acid ester monomers such as vinyl acetate; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinylpyridines; carboxyl group-containing monomers such as ethylenically unsaturated carboxylic acid monomers such as crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; and epoxy group-containing monomers such as allyl glycidyl ether. These heteroatom-containing monomers can be used alone or in combination of two or more.The polar resin used for the positively chargeable toner preferably has a copolymerization ratio of 0.1% by mass or less of a monomer containing a functional group that imparts positive chargeability and is selected from a pyridinium group, an amino group, a quaternary ammonium group, and a quaternary ammonium salt-containing group, and the polar resin used for the negatively chargeable toner preferably has a copolymerization ratio of 0.1% by mass or less of a monomer containing a functional group that imparts negative chargeability and is selected from a sulfonic acid group, a sulfonate-containing group, a carboxyl group, and a carboxylate-containing group, which can improve the charge stability of the toner.

[0084] Examples of heteroatom-free monomers used in the polar resin include aromatic vinyl monomers that do not contain heteroatoms, such as styrene, vinyltoluene, α-methylstyrene, and p-methylstyrene; monoolefin monomers, such as ethylene, propylene, and butylene; and diene monomers, such as butadiene and isoprene. These heteroatom-free monomers can be used alone or in combination of two or more.

[0085] In the polar resin, it is preferable that the heteroatom-containing monomer contains a polar group-containing monomer unit containing at least one polar group selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, an amino group, a polyoxyethylene group, and an epoxy group, from the viewpoints of easy control of the particle size of the colored resin particles and easy suppression of the generation of coarse particles. Among these, the polar group is preferably at least one selected from the group consisting of a carboxyl group and a hydroxyl group. Examples of polar group-containing monomers include carboxyl group-containing monomers such as ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid; amino group-containing monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; polyoxyethylene group-containing monomers such as methoxypolyethylene glycol (meth)acrylate; and epoxy group-containing monomers such as glycidyl (meth)acrylate, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether. These polar group-containing monomers can be used alone or in combination of two or more.

[0086] When the polar resin does not contain the polar group-containing monomer unit, the heteroatom-containing monomer unit contained in the polar resin preferably contains a monomer unit derived from an alkyl(meth)acrylate, from the viewpoints of high compatibility with the polymerizable monomer, ease of control of the particle size of the colored resin particles, and ease of suppressing the generation of coarse particles. In particular, from the viewpoint of high polarity, it is more preferable to contain a monomer unit derived from an alkyl(meth)acrylate having an alkyl group having 3 or less carbon atoms, still more preferable to contain a monomer unit derived from at least one selected from the group consisting of methyl(meth)acrylate and ethyl(meth)acrylate, and even more preferable to contain a monomer unit derived from methyl(meth)acrylate.

[0087] The weight average molecular weight (Mw) of the polar resin is preferably 8,000 to 45,000, more preferably 9,000 to 45,000, and even more preferably 10,000 to 40,000. When the weight average molecular weight (Mw) of the polar resin is at least the lower limit, the heat-resistant storage stability and durability of the toner can be improved, and when it is at most the upper limit, an increase in the fixing temperature of the toner can be suppressed.

[0088] The glass transition temperature (Tg) of the polar resin is preferably 60 to 95°C, more preferably 65 to 90°C, and even more preferably 70 to 80°C. When the glass transition temperature of the polar resin is equal to or higher than the lower limit, the heat-resistant storage stability of the toner can be improved, and when the glass transition temperature is equal to or lower than the upper limit, the low-temperature fixability of the toner can be improved. The glass transition temperature (Tg) of the polar resin can be measured in the same manner as the glass transition temperature (Tg) of the charge control resin.

[0089] The polar resin may be commercially available, or may be produced by polymerizing a monomer containing the heteroatom-containing monomer by a known method such as solution polymerization, aqueous solution polymerization, ionic polymerization, high-temperature high-pressure polymerization, or suspension polymerization. When the polar resin is a copolymer, the copolymer may be a random copolymer, a block copolymer, or a graft copolymer, but is preferably a random copolymer. The polar resin is preferably pulverized to improve solubility.

[0090] When the polar resin is contained, the content thereof is preferably 0.5 to 2.5 parts by mass, more preferably 0.8 to 2.2 parts by mass, and even more preferably 1.0 to 2.0 parts by mass, per 100 parts by mass of the monovinyl monomer. When the polar resin is contained in the toner, the content thereof is preferably 0.5 to 2.5 parts by mass, more preferably 0.8 to 2.2 parts by mass, and even more preferably 1.0 to 2.0 parts by mass, per 100 parts by mass of the binder resin. When the content of the polar resin is equal to or greater than the lower limit, it is easy to control the particle size of the colored resin particles and to suppress the generation of coarse particles. On the other hand, when the content of the polar resin is equal to or less than the upper limit, it is possible to suppress an increase in the fixing temperature of the toner.

[0091] [Molecular Weight Regulator] It is preferable to use a molecular weight regulator as an additive when polymerizing the polymerizable monomer that becomes the binder resin. The molecular weight regulator is not particularly limited as long as it is one that is generally used as a molecular weight regulator 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 regulators may be used alone or in combination of two or more. In the present disclosure, in order to impart the desired viscoelasticity to the toner, the molecular weight modifier is used in an amount of usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, relative to 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer).

[0092] (A-2) Suspension step for obtaining a suspension (droplet formation step) In the present disclosure, it is preferable to disperse the polymerizable monomer composition in an aqueous medium containing a dispersion stabilizer, add a polymerization initiator, and then form droplets of the polymerizable monomer composition. The method for forming droplets is not particularly limited, but may be performed using an apparatus capable of strong stirring, such as an (in-line type) emulsifying disperser (manufactured by Pacific Machinery Works, trade name: Milder) or a high-speed emulsifying disperser (manufactured by Primix Corporation, trade name: T.K. Homomixer MARK II type).

[0093] Examples of the polymerization initiator 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-butylperoxydiethylacetate, t-hexylperoxy-2-ethylbutanoate, diisopropyl peroxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate. These may be used alone or in combination of two or more. Among these, it is preferable to use organic peroxides, since they can reduce the amount of residual polymerizable monomers and the resulting toner has excellent print durability.

[0094] 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.

[0095] As described above, the polymerization initiator may be added after the polymerizable monomer composition is dispersed in an aqueous medium and before droplet formation, or may be added to the polymerizable monomer composition before it is dispersed in an aqueous medium.

[0096] In the present disclosure, the aqueous medium refers to a medium containing water as a main component. It is preferable that the aqueous medium contains a dispersion stabilizer. Examples of the dispersion stabilizer include inorganic compounds such as sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; and organic compounds such as water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants; nonionic surfactants; and amphoteric surfactants. The dispersion stabilizers can be used alone or in combination of two or more.

[0097] Among the dispersion stabilizers, inorganic compounds, particularly colloidal metal hydroxides with poor water solubility, are preferred. By using an inorganic compound, particularly colloidal metal hydroxide with poor water solubility, the particle size distribution of the colored resin particles can be narrowed and the amount of dispersion stabilizer remaining after washing can be reduced, so that the resulting toner can clearly reproduce images and has excellent environmental stability.

[0098] (A-3) Polymerization Step As described in (A-2) above, a suspension is prepared by forming droplets of the polymerizable monomer composition in an aqueous medium, and the resulting suspension is heated to polymerize the polymerizable monomer, thereby obtaining an aqueous dispersion of colored resin particles. The polymerization temperature of the polymerizable monomer composition is preferably 50°C or higher, more preferably 60 to 95°C. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

[0099] Although the colored resin particles obtained by polymerization of the polymerizable monomer may be used as a toner by adding an external additive as they are, it is preferable to use so-called core-shell type (also called "capsule type") colored resin particles obtained by forming a core layer made of the colored resin particles obtained by polymerization of the polymerizable monomer and a shell layer different from the core layer on the outside of the core layer. The core-shell type colored resin particles can achieve a balance between lowering the fixing temperature and preventing aggregation during storage by coating the core layer made of a material having a low softening point with a material having a higher softening point.

[0100] The method for producing the core-shell type colored resin particles using the above-mentioned colored resin particles is not particularly limited, and they can be produced by a conventionally known method. In terms of production efficiency, an in situ polymerization method or a phase separation method is preferred.

[0101] A method for producing core-shell type colored resin particles by in situ polymerization is described below. A polymerizable monomer for forming a shell layer (shell polymerizable monomer) and a polymerization initiator are added to an aqueous dispersion medium in which colored resin particles are dispersed, and polymerization is then carried out to obtain core-shell type colored resin particles. In this case, the shell layer of the core-shell type colored resin particles is composed of a polymer of the shell polymerizable monomer.

[0102] 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, alone or in combination, monomers that can give polymers with a Tg of more than 80°C, such as styrene, acrylonitrile, and methyl methacrylate.

[0103] Examples of the polymerization initiator used in the polymerization of the shell polymerizable monomer include water-soluble polymerization initiators such as metal persulfates, such as potassium persulfate and ammonium persulfate; and azo initiators, 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). These can be used alone or in combination of two or more. The amount of the polymerization initiator is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the shell polymerizable monomer.

[0104] The polymerization temperature for the shell layer is preferably 50° C. or higher, more preferably 60 to 95° C. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

[0105] (A-4) Washing, Filtration, Dehydration, and Drying Steps After the polymerization is completed, the aqueous dispersion of colored resin particles obtained by polymerization is preferably subjected to washing, filtration, dehydration, and drying operations for removing the dispersion stabilizer according to a conventional method, which are repeated several times as necessary.

[0106] As for the above-mentioned washing method, when an inorganic compound is used as the dispersion stabilizer, it is preferable to add an acid or alkali to the aqueous dispersion of the colored resin particles to dissolve and remove the dispersion stabilizer in water. When a poorly water-soluble metal hydroxide colloid is used as the dispersion stabilizer, it is preferable to add an acid to adjust the pH of the aqueous dispersion of the colored resin particles to 6.5 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 of its high removal efficiency and small burden on the production equipment.

[0107] The dehydration and filtration methods can be any of various known methods, 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.

[0108] (B) Pulverization Method When colored resin particles are produced using the pulverization method, the process is as follows. First, a binder resin, a colorant, a softener, a charge control agent, and optionally other additives are mixed using a mixer such as a ball mill, a V-type mixer, an FM mixer (trade name, manufactured by Nippon Coke & Engineering Co., Ltd.), a high-speed dissolver, or an internal mixer. Next, the mixture obtained above is kneaded while heating using a pressure kneader, a twin-screw extrusion kneader, a roller, or the like. The resulting kneaded product is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, or a roller mill. The resulting mixture is then finely pulverized using a pulverizer such as a jet mill or a high-speed rotary pulverizer, and then classified to the desired particle size using a classifier such as an air classifier or an airflow classifier to obtain colored resin particles produced by the pulverization method.

[0109] The binder resin, colorant, softener, and charge control agent used in the pulverization method, as well as other additives added as needed, can be the same as those listed in the (A) suspension polymerization method. The colored resin particles obtained by the pulverization method can also be made into core-shell type colored resin particles by a method such as in situ polymerization, similar to the colored resin particles obtained by the (A) suspension polymerization method.

[0110] As the binder resin, resins that have been widely used in toners can also be used. Specific examples of binder resins used in the pulverization method include polystyrene, styrene-butyl acrylate copolymers, polyester resins, and epoxy resins.

[0111] 1-2. External Additives Colored resin particles are obtained by a manufacturing method such as the above-mentioned (A) suspension polymerization method or (B) pulverization method. The colored resin particles may or may not be core-shell type. A toner is obtained by mixing and stirring the colored resin particles with an external additive, and uniformly adhering (externally adding) the external additive to the surface of the colored resin particles. A one-component toner (developer) may be obtained by adhering the external additive to the surface of the colored resin particles, or the one-component toner may be further mixed and stirred with carrier particles to form a two-component developer.

[0112] [External Additive A] The external additive includes at least one external additive A selected from the group consisting of metal titanate salt microparticles, zinc oxide microparticles, and titanium oxide microparticles, or at least one external additive A selected from the group consisting of metal titanate salt microparticles, zinc oxide microparticles, titanium oxide microparticles, aluminum oxide microparticles, and aluminum hydroxide microparticles. This suppresses toner from being ejected from the cartridge when continuous printing is performed using the toner set of the present disclosure. Toner ejection can occur when toner particle aggregates are formed and the heat from the sliding of the developing roller locally melts the toner particle aggregates, causing the molten toner to spill from the developing roller. Toner ejection can also occur when the toner fluidity is unstable when the toner particles are released from the aggregated state. Unstable toner fluidity can prevent the toner from generating sufficient triboelectric charge, resulting in inability to support the toner on the developing roller or excessive toner transport, causing toner to spill. This type of toner ejection is particularly likely to occur in high-temperature, high-humidity environments. During continuous printing, the toner is agitated inside the developing machine, and the toner particles may compress and aggregate, forming aggregates that can cause toner to spurt out. In contrast, when the toner contains the external additive A, the abrasive effect periodically breaks down the toner particle aggregates, thereby preventing toner from spurting out. Furthermore, when the toner particle aggregates continue to be compressed, the toner particles may be crushed, causing the softener to be liberated from the broken toner particles, which can deteriorate the toner fixability and make the toner layer more likely to peel off when a full-color image is formed. In contrast, when the toner contains the external additive A, the toner particle aggregates are broken down and the toner particle crushing is suppressed, thereby preventing the toner fixability from deteriorating and preventing toner layer peeling. Furthermore, typically, the higher the loss tangent (tan δ) of the toner at 100°C, the more likely to be toner particles fusing together during toner compression. However, when the toner contains the external additive A, the abrasive effect suppresses fusion between toner particles, so that a toner having a high loss tangent (tan δ) at 100° C. can be used.In the present disclosure, it is sufficient that the yellow toner, magenta toner, and cyan toner contained in the toner set contain the external additive A as an external additive, but it is preferable that all toners contained in the toner set contain the external additive A as an external additive, since this makes it easier to achieve the above-mentioned effects when printing a full-color image using the toner set. When the toner set of the present disclosure contains a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that each of the yellow toner, magenta toner, cyan toner, and black toner contains the external additive A as an external additive. Furthermore, it is preferable that each color toner contained in the toner set of the present disclosure is a positively charged toner, since this makes it easier to achieve the effects of the external additive A.

[0113] The external additive A is not particularly limited as long as it is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, and titanium oxide fine particles, or at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, titanium oxide fine particles, aluminum oxide (alumina) fine particles, and aluminum hydroxide fine particles. Aluminum oxide includes aluminum oxide hydrate (boehmite (AlOOH)). Examples of metal titanates include strontium titanate, barium titanate, calcium titanate, magnesium titanate, neodymium titanate, lanthanum titanate, and zinc titanate. Strontium titanate is particularly preferred as the external additive A. External additives A can be used alone or in combination of two or more. For example, external additive A containing metal titanate fine particles and aluminum oxide fine particles is preferred from the viewpoint of the polishing effect of preventing aggregation of toner particles. External additive A can also be used in a composite state.

[0114] The external additive A may be surface-treated. Examples of the surface treatment include hydrophobic treatment using a hydrophobic treatment agent such as a silane coupling agent, silicone oil, fatty acid, or fatty acid metal salt. Furthermore, various surface treatments such as triethanolamine treatment can be used to adjust the chargeability of the fine particles.

[0115] The number-average particle size of the external additive A is not particularly limited and is appropriately selected depending on the type of the external additive A. The number-average particle size of the metal titanate fine particles and titanium oxide fine particles has a lower limit of preferably 0.03 μm or more, more preferably 0.05 μm or more, from the viewpoint of toner chargeability and suppressing deterioration of toner fixability, and an upper limit of preferably 2 μm or less, more preferably 1 μm or less, from the viewpoint of improving toner fluidity. The number-average particle size of the zinc oxide fine particles has a lower limit of preferably 0.1 μm or more, more preferably 0.2 μm or more, from the viewpoint of toner chargeability and suppressing deterioration of toner fixability, and an upper limit of preferably 2 μm or less, more preferably 1 μm or less, from the viewpoint of improving toner fluidity.

[0116] The particle size of the aluminum oxide microparticles and aluminum hydroxide microparticles is preferably 10 nm or more, more preferably 15 nm or more, from the viewpoint of the toner charging property and preventing deterioration of the toner fixing property, and is preferably 100 nm or less, more preferably 50 nm or less, from the viewpoint of improving the toner fluidity.

[0117] The content of the external additive A is not particularly limited, but the lower limit is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the colored resin particles. The upper limit is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.5 parts by mass or less. When the content of the external additive A is equal to or greater than the lower limit, the polishing effect of the external additive A is fully exerted, which makes it easier to suppress toner aggregation, thereby further suppressing toner ejection and peeling of the toner layer. On the other hand, when the content of the external additive A is equal to or less than the upper limit, toner deterioration can be suppressed, thereby suppressing deterioration of toner fixability, etc. In the present disclosure, "100 parts by mass of the colored resin particles" refers to the mass of the colored resin particles in a dry state. The colored resin particles in a dry state may have a moisture content of 0.30% or less. The moisture content can be determined by the following method. First, approximately 1 g of the measurement sample is sampled, and the sampled measurement sample is weighed to the nearest 0.1 mg, and this weight is designated as W1 [g]. Next, the precisely weighed measurement sample is placed in a 105°C dryer (with a temperature error of 1°C or less at each location within the dryer) and dried for 1 hour. After cooling, it is weighed again, and this weight is designated as W2 [g]. These measured values ​​are then used to calculate the moisture content using the following formula: Moisture content (%) = [(W1 - W2) / W1] x 100

[0118] [External Additive B] The external additive preferably further contains external additive B, which is silica microparticles. When the toner contains external additive B (i.e., silica microparticles) together with external additive A as an external additive, the fluidity of the toner is improved, damage to the colored resin particles caused by external additive A is suppressed, and therefore toner deterioration is suppressed, the effects of external additive A are fully exhibited, and deterioration of the toner storage stability is suppressed. In the present disclosure, since the above-mentioned effects are easily obtained when printing full-color images using the toner set, it is preferable that the yellow toner, magenta toner, and cyan toner included in the toner set contain the external additive B as an external additive, and it is more preferable that all toners included in the toner set contain the external additive B as an external additive. When the toner set of the present disclosure includes yellow toner, magenta toner, cyan toner, and black toner, it is preferable that each of the yellow toner, magenta toner, cyan toner, and black toner contains the external additive B as an external additive.

[0119] The external additive B may be any silica fine particles, and is not particularly limited, but is preferably hydrophobized silica fine particles. Examples of the hydrophobizing agent used in the external additive B include a silane coupling agent, silicone oil, fatty acid, and fatty acid metal salt.

[0120] The external additive B preferably contains one or more selected from the group consisting of silica fine particles (a) having a number-average primary particle size of 36 to 100 nm, silica fine particles (b) having a number-average primary particle size of 15 to 35 nm, and silica fine particles (c) having a number-average primary particle size of 6 to 14 nm, more preferably two or more selected from this group, and particularly preferably contains all of the silica fine particles (a), silica fine particles (b), and silica fine particles (c). It is preferable that the silica fine particles (a), silica fine particles (b), and silica fine particles (c) are all hydrophobically treated silica fine particles.

[0121] The number-average primary particle diameter of the silica fine particles (a) is not particularly limited as long as it is 36 to 100 nm, but the lower limit is preferably 40 nm or more, more preferably 45 nm or more, and the upper limit is preferably 80 nm or less, more preferably 70 nm or less. If the number-average primary particle diameter of the silica fine particles (a) is less than 36 nm, the spacer effect may be reduced, which may adversely affect printing performance, such as the occurrence of fogging. On the other hand, if the number-average primary particle diameter of the silica fine particles (a) exceeds 100 nm, the toner fluidity may be reduced, and the silica fine particles (a) may be more likely to be liberated from the surface of the toner particles, which may reduce their function as an external additive and adversely affect printing performance.

[0122] The content of the silica fine particles (a) is preferably 0.50 parts by mass or more, more preferably 0.80 parts by mass or more, and even more preferably 0.95 parts by mass or more, relative to 100 parts by mass of the colored resin particles, as a lower limit, and is preferably 2.50 parts by mass or less, more preferably 2.00 parts by mass or less, and even more preferably 1.50 parts by mass or less, as an upper limit. When the content of the silica fine particles (a) is equal to or greater than the above lower limit, the function as an external additive can be fully exhibited, thereby suppressing deterioration of printing performance or storage stability. On the other hand, when the content of the silica fine particles (a) is equal to or less than the above upper limit, liberation of the silica fine particles (a) from the surface of the toner particles is suppressed, thereby suppressing deterioration of printing performance. The silica fine particles (a) can be used alone or in combination of two or more types.

[0123] The number-average primary particle diameter of the silica fine particles (b) is not particularly limited as long as it is 15 to 35 nm, but the lower limit is preferably 17 nm or more, more preferably 20 nm or more, and the upper limit is preferably 30 nm or less, more preferably 25 nm or less. If the number-average primary particle diameter of the silica fine particles (b) is less than 15 nm, the silica fine particles (b) tend to be embedded from the surface to the interior of the colored resin particles, which may result in insufficient fluidity being imparted to the toner particles, which may adversely affect printing performance. On the other hand, if the number-average primary particle diameter of the silica fine particles (b) exceeds 35 nm, the proportion of the toner particle surface occupied by the silica fine particles (b) (coverage) decreases, which may result in insufficient fluidity being imparted to the toner particles.

[0124] The content of the silica fine particles (b) is preferably 0.40 parts by mass or more, more preferably 0.50 parts by mass or more, and even more preferably 0.70 parts by mass or more, relative to 100 parts by mass of the colored resin particles, as a lower limit, and is preferably 2.00 parts by mass or less, more preferably 1.50 parts by mass or less, and even more preferably 1.00 parts by mass or less. When the content of the silica fine particles (b) is equal to or greater than the above lower limit, the function as an external additive can be fully exhibited, thereby suppressing a decrease in fluidity and a deterioration in storage stability or durability. On the other hand, when the content of the silica fine particles (b) is equal to or less than the above upper limit, the release of the silica fine particles (b) from the surface of the toner particles is suppressed, thereby suppressing a deterioration in charging characteristics and thus suppressing the occurrence of fogging. The silica fine particles (b) can be used alone or in combination of two or more types.

[0125] The number-average primary particle diameter of the silica fine particles (c) is not particularly limited as long as it is 6 to 14 nm, but the lower limit is preferably 6.5 nm or more, more preferably 7.0 nm or more, and the upper limit is preferably 12 nm or less, more preferably 10 nm or less. If the number-average primary particle diameter of the silica fine particles (c) is less than 6 nm, the silica fine particles (c) tend to be embedded from the surface to the interior of the colored resin particles, which may result in insufficient fluidity being imparted to the toner particles, which may adversely affect printing performance. On the other hand, if the number-average primary particle diameter of the silica fine particles (c) exceeds 14 nm, the proportion of the toner particle surface occupied by the silica fine particles (c) (coverage) decreases, which may result in insufficient fluidity being imparted to the toner particles.

[0126] The content of the silica fine particles (c) is preferably 0.10 parts by mass or more, more preferably 0.15 parts by mass or more, and even more preferably 0.20 parts by mass or more, relative to 100 parts by mass of the colored resin particles, as a lower limit, and is preferably 1.50 parts by mass or less, more preferably 1.00 parts by mass or less, even more preferably 0.80 parts by mass or less, and even more preferably 0.60 parts by mass or less. When the content of the silica fine particles (c) is equal to or greater than the above lower limit, the function as an external additive can be fully exhibited, thereby suppressing a decrease in fluidity and a deterioration in storage stability. On the other hand, when the content of the silica fine particles (c) is equal to or less than the above upper limit, the release of the silica fine particles (c) from the surface of the toner particles is suppressed, thereby suppressing a deterioration in charging characteristics and thus suppressing the occurrence of fogging. The silica fine particles (c) can be used alone or in combination of two or more types.

[0127] As the silica fine particles (a), various commercially available silica fine particles can be used, for example, VPNA50H (trade name, number average primary particle diameter: 40 nm) manufactured by Nippon Aerosil Co., Ltd.; H05TA (trade name, number average primary particle diameter: 50 nm) manufactured by Clariant; etc. As the silica fine particles (b), various commercially available silica fine particles can be used, for example, NA50Y (trade name, number average primary particle diameter: 35 nm) manufactured by Nippon Aerosil Co., Ltd.; MSP-012 (trade name, number average primary particle diameter: 16 nm) manufactured by Teica Corporation; TG-7120 (trade name, number average primary particle diameter: 20 nm) manufactured by Cabot Corporation; etc. As the silica fine particles (c), various commercially available silica fine particles can be used, and examples thereof include HDK2150 (trade name, number average primary particle diameter: 12 nm) manufactured by Clariant; R504 (trade name, number average primary particle diameter: 12 nm) and RA200HS (trade name, number average primary particle diameter: 12 nm) manufactured by Nippon Aerosil Co., Ltd.; MSP-013 (trade name, number average primary particle diameter: 12 nm) manufactured by Teica Corporation; and TG-820F (trade name, number average primary particle diameter: 7 nm) manufactured by Cabot Corporation.

[0128] The content of the external additive B is not particularly limited, but the lower limit is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 1.9 parts by mass or more, and even more preferably 2.0 parts by mass or more, relative to 100 parts by mass of the colored resin particles. The upper limit is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. When the content of the external additive B is equal to or greater than the lower limit, sufficient fluidity can be imparted to the toner particles. As a result, printing performance is improved and toner deterioration is suppressed, thereby suppressing deterioration of the toner storage stability and suppressing toner ejection and peeling of the toner layer. When the content of the external additive B is equal to or less than the upper limit, liberation of the external additive B from the surface of the toner particles is suppressed, thereby suppressing deterioration of printing performance or the occurrence of fogging.

[0129] The yellow toner, magenta toner, and cyan toner included in the toner set of the present disclosure preferably contain both the external additive A and the external additive B as external additives, and it is more preferable that all toners included in the toner set of the present disclosure contain both the external additive A and the external additive B as external additives. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is more preferable that each of the yellow toner, magenta toner, cyan toner, and black toner contains both the external additive A and the external additive B as external additives. In toners that include the external additive A and the external additive B as external additives, the content of the external additive A relative to the total amount of the external additive A and the external additive B (100% by mass) is preferably 16% by mass or more and 51% by mass or less. When the content of the external additive A relative to the total amount of the external additives A and B (100% by mass) is within the above range, the effects of the external additive A and the effects of the external additive B described above are both likely to be exerted, so the toner has good fluidity and is less likely to form aggregates. As a result, the storage stability and printing performance are improved, and toner spraying and peeling of the toner layer are further suppressed.

[0130] Furthermore, when the toner set of the present disclosure contains a yellow toner, a magenta toner, and a cyan toner, the yellow toner, the magenta toner, and the cyan toner contain both the external additive A and the external additive B. Alternatively, when the toner set of the present disclosure contains a yellow toner, a magenta toner, a cyan toner, and a black toner, the yellow toner, the magenta toner, the cyan toner, and the black toner contain both the external additive A and the external additive B. This reduces the difference in the initial charge amount between the color toners, achieving a balanced charge amount, and thus improving the charge initial charge of the toner set of the present disclosure. The reason why the charge initial charge of the toner set is good when the difference in the initial charge amount between the color toners is small is thought to be because charge interference between the color toners is less likely. In conventional toner sets, large differences in the initial charge amount between the color toners can result in insufficient charge initial charge and poor formation of a toner layer on the paper surface. In contrast, small differences in the initial charge amount between the color toners of a toner set can suppress such printing defects. Furthermore, in a high-temperature, high-humidity environment, the high moisture content in the air causes the external additives present on the surface of the toner particles to absorb moisture, which tends to decrease the charge amount of each color toner. However, because the rate at which the charge amount decreases varies among the color toners, the difference in charge amount between the color toners tends to be large under a high-temperature, high-humidity environment. In a low-temperature, low-humidity environment, the charge amount of each color toner tends to increase. However, because the rate at which the charge amount increases varies among the color toners, the difference in charge amount between the color toners tends to be large even under a low-temperature, low-humidity environment. Therefore, the charge buildup property of a toner set tends to deteriorate under both a high-temperature, high-humidity environment and a low-temperature, low-humidity environment. However, by including both the external additive A and the external additive B in each color toner constituting a toner set, it is believed that charge interference between the color toners can be suppressed even under a high-temperature, high-humidity environment and a low-temperature, low-humidity environment. In a toner containing the external additive A and the external additive B, the content of the external additive A relative to the total amount of the external additive A and the external additive B (100% by mass) is preferably within the above-mentioned range, from the viewpoint of charge buildup property.Furthermore, since the difference in the amount of charge at start-up between the toners of different colors is small, the adhesion between the toner layers of different colors is improved, and peeling of the toner layers when a full-color image is formed can also be suppressed.

[0131] [External Additive C] The external additive preferably further contains external additive C, which is silicone resin particles. When the toner contains the external additive C, the toner tends to have good fluidity, is less likely to film on the photoreceptor, and provides the toner particles with stable chargeability over time, making it less likely to cause deterioration in image quality due to fogging or the like even when printing a large number of sheets continuously. In the present disclosure, since the above-mentioned effects are more easily obtained when printing full-color images using a toner set, it is preferable that the yellow toner, magenta toner, and cyan toner contained in the toner set contain the external additive C as an external additive, and it is more preferable that all toners contained in the toner set contain the external additive C as an external additive. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that each of the yellow toner, magenta toner, cyan toner, and black toner contains the external additive C as an external additive.

[0132] Furthermore, the external additive C is preferably silicone resin particles that have been hydrophobized. Examples of the hydrophobizing agent used in the external additive C include the same hydrophobizing agent as that used in the external additive B.

[0133] The silicone resin particles used as the external additive C are fine particles made of organopolysiloxane having a three-dimensional network structure, and polyorganosilsesquioxane having a structural unit of the following formula (2) is particularly preferred.

[0134]

[0135] In formula (2), R represents an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, or a propyl group, or a phenyl group. In formula (2), R is preferably a methyl group due to its high heat resistance. That is, the silicone resin particles are preferably silicone resin particles having a polymethylsilsesquioxane structure. Polymethylsilsesquioxane can be obtained by hydrolyzing and condensing methyltrialkoxysilane or methyltrihalosilane in an aqueous solution of ammonia or amines, as described in JP-A-2008-208158 and JP-A-2004-99630. Alternatively, commercially available silicone resin particles may be used.

[0136] The silicone resin particles are preferably spherical in shape, since this minimizes the decrease in toner fluidity. The number-average primary particle size of the silicone resin particles is preferably 50 to 1,000 nm, more preferably 100 to 800 nm, and even more preferably 140 to 500 nm. When the number-average primary particle size of the silicone resin particles is equal to or greater than the lower limit, the effect of suppressing filming and fogging is high, and when it is equal to or less than the upper limit, the decrease in fluidity is suppressed and toner ejection is also suppressed.

[0137] The content of the external additive C is not particularly limited, but the lower limit is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the colored resin particles, and the upper limit is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less. When the content of the external additive C is equal to or greater than the lower limit, the toner fluidity is likely to be improved, so that toner ejection is likely to be suppressed, and the occurrence of filming or fogging is suppressed. When the content of the external additive C is equal to or less than the upper limit, the release of the external additive C from the surface of the toner particles is suppressed, so that deterioration of printing performance or the occurrence of fogging is suppressed. The external additives C can be used alone or in combination of two or more.

[0138] [External Additive D] The external additive may further contain external additive D, which is organic fine particles different from silicone resin particles. When the toner contains external additive D, the toner is likely to have good fluidity, is less likely to film on the photoreceptor, and provides the toner particles with stable chargeability over time, making it less likely that image quality will deteriorate due to fogging or the like even when printing a large number of sheets continuously. In the present disclosure, it is preferable that the yellow toner and cyan toner contained in the toner set contain external additive D as an external additive, since this makes it easier to achieve the above-mentioned effects when printing full-color images using the toner set. Each color toner other than the yellow toner or cyan toner may also contain external additive D as an external additive.

[0139] The number average primary particle diameter of the organic fine particles used as the external additive D is not particularly limited, but the lower limit is preferably 0.3 μm or more, more preferably 0.4 μm or more, and even more preferably 0.5 μm or more, and the upper limit is preferably 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. When the number average primary particle diameter of the organic fine particles is equal to or greater than the lower limit, the effect of suppressing filming and fogging is high, and when it is equal to or less than the upper limit, a decrease in fluidity is suppressed and toner ejection is also suppressed.

[0140] As the external additive D, fatty acid metal salt particles are preferably used. － The fatty acid (R-COOH) from which the above-mentioned carboxylic acid is derived may be a monocarboxylic acid containing only one carboxyl group (-COOH), and is preferably a monocarboxylic acid having a chain structure, more preferably a saturated monocarboxylic acid having a chain structure, and even more preferably a linear saturated monocarboxylic acid.

[0141] In addition, the fatty acid moiety (R—COO) contained in the fatty acid metal salt particles －) is preferably derived from a higher fatty acid having a large number of carbon atoms in the alkyl group (R-). The number of carbon atoms in the alkyl group of the fatty acid moiety is not particularly limited, but is preferably 12 to 24, more preferably 14 to 22, and even more preferably 16 to 20. Preferred higher fatty acids used as raw materials for fatty acid metal salt particles include, for example, lauric acid (CH ３ (CH ２ ) １０ COOH), tridecanoic acid (CH ３ (CH ２ ) １１ COOH), myristic acid (CH ３ (CH ２ ) １２ COOH), pentadecanoic acid (CH ３ (CH ２ ) １３ COOH), palmitic acid (CH ３ (CH ２ ) １４ COOH), heptadecanoic acid (CH ３ (CH ２ ) １５ COOH), stearic acid (CH ３ (CH ２ ) １６ COOH), arachidic acid (CH ３ (CH ２ ) １８ COOH), behenic acid (CH ３ (CH ２ ) ２０ COOH), lignoceric acid (CH ３ (CH ２ ) ２２ COOH). Among these, stearic acid and behenic acid are preferred, and stearic acid is more preferred. These fatty acids used as raw materials for the fatty acid metal salt particles can be used alone or in combination of two or more kinds, but it is preferable to use one kind of fatty acid alone in order to obtain uniform properties.

[0142] The metal contained in the fatty acid metal salt particles may be an alkali metal, an alkaline earth metal, or a metal element of Group 12 of the periodic table, such as Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Zn, etc. Among these, an alkaline earth metal or a metal element of Group 12 of the periodic table is preferred, at least one selected from the group consisting of Mg and Zn is more preferred, and Zn is even more preferred.

[0143] As the fatty acid metal salt particles, various commercially available products can be used, and examples thereof include SPZ-100F (trade name, zinc stearate particles, number average primary particle size: 0.5 μm) and SPX-100F (trade name, magnesium stearate particles, number average primary particle size: 0.72 μm), manufactured by Sakai Chemical Industry Co., Ltd.

[0144] The content of the external additive D is not particularly limited, but the lower limit is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.03 parts by mass or more, and even more preferably 0.04 parts by mass or more, relative to 100 parts by mass of the colored resin particles. The upper limit is preferably 0.25 parts by mass or less, more preferably 0.23 parts by mass or less, and even more preferably 0.20 parts by mass or less. When the content of the external additive D is equal to or greater than the lower limit, the toner fluidity is likely to be improved, so that toner ejection is likely to be suppressed, and the occurrence of filming or fogging is suppressed. When the content of the external additive C is equal to or less than the upper limit, the release of the external additive C from the surface of the toner particles is suppressed, so that deterioration of printing performance or the occurrence of fogging is suppressed. The external additives D can be used alone or in combination of two or more.

[0145] Each color toner included in the toner set of the present disclosure may further contain other external additives different from the external additives A to D described above, as long as the object of the present disclosure is not impaired. Examples of other external additives include inorganic fine particles such as aluminum oxide, tin oxide, calcium carbonate, calcium phosphate, and cerium oxide; and organic fine particles such as polymethyl methacrylate resin and melamine resin. The number-average primary particle size of the other external additives is not particularly limited and may be, for example, 0.3 to 500 nm. The other external additives may be used alone or in combination of two or more.

[0146] The number average particle size and number average primary particle size of an external additive can be measured using known methods, for example, as follows. The number average particle size can be measured using a particle size distribution measuring device (such as Multisizer, manufactured by Beckman Coulter) using the Coulter Counter method. To determine the number average primary particle size, first, the particle size of each particle of the external additive is measured using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). The particle sizes of 30 or more external additive particles are measured, and the average value is taken as the number average primary particle size of the particle. Note that when the shape of the external additive is non-spherical and the major axis and minor axis can be confirmed by observation using a TEM or SEM, the major axis and minor axis of each external additive are first measured. In this way, the major axis and minor axis of 30 or more external additives are measured, and the average value is taken as the average major axis or average minor axis of the external additive. The sum of the calculated average major axis and average minor axis is divided by 2, and the value obtained is taken as the number-average primary particle size of the external additive.

[0147] The external addition treatment of adhering the external additive to the surface of the colored resin particles can be performed by a known method, and is not particularly limited. The external addition treatment can be performed using a mixer capable of mixing and stirring, such as a Henschel Mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), an FM Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Super Mixer (trade name, manufactured by Kawada Manufacturing Co., Ltd.), a Q Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Mechanofusion System (trade name, manufactured by Hosokawa Micron Corporation), and a Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.).

[0148] Alternatively, the external addition treatment method may include a first-stage external addition treatment in which a portion of the external additive to be added is mixed and stirred with colored resin particles and dried to obtain intermediate particles, followed by a second-stage external addition treatment in which the remaining external additive is mixed and stirred with the intermediate particles. By performing the external addition treatment in two stages in this manner, the external additive added before the colored resin particles are dried is relatively easily embedded in the surface of the colored resin particles, while the external additive added after the colored resin particles are dried is relatively less likely to be embedded in the surface of the colored resin particles. This makes it easier to obtain a toner with the desired fluidity. In the first-stage external addition treatment, it is preferable to dry the wet colored resin particles with the external additive while mixing and stirring them, i.e., it is preferable to perform mixing and drying simultaneously. The drying method for the first-stage external addition treatment is not particularly limited, and can be, for example, reduced-pressure drying, vacuum drying, or heat drying. The second-stage external addition treatment is not particularly limited, and can be performed, for example, using a stirrer capable of the above-mentioned mixing and stirring.

[0149] The method of performing the external addition treatment in two stages is particularly preferred when adding the external additive D. The external additive added in the first stage of the external addition treatment preferably contains the silica fine particles (c). The external additive added in the second stage of the external addition treatment preferably contains the external additive D, and more preferably contains the silica fine particles (a) and (b), the external additive A, and the external additive C.

[0150] In each of the yellow toner, magenta toner, and cyan toner included in the toner set of the present disclosure, the content of the external additive per 100 parts by mass of the colored resin particles is preferably 2.0 parts by mass or more and 6.0 parts by mass or less. Here, when the toner contains multiple types of external additives, the content of the external additives refers to the total content of the multiple types of external additives. In all toners included in the toner set of the present disclosure, the content of the external additives is preferably within the above range. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, the content of the external additives is preferably within the above range for each of the yellow toner, the magenta toner, the cyan toner, and the black toner. When the content of the external additive is equal to or greater than the above lower limit, the toner fluidity is improved, and toner ejection and peeling of the toner layer are easily suppressed. When the content of the external additive is equal to or less than the above upper limit, deterioration of printing performance or the occurrence of fogging, etc. are suppressed. Furthermore, the content of the external additive is appropriately adjusted so that the toner has the desired viscoelasticity.

[0151] 1-3. Toner Set The toner set of the present disclosure includes toners of multiple colors each containing the colored resin particles and an external additive, and includes at least a yellow toner, a magenta toner, and a cyan toner. The toner set of the present disclosure may also include a yellow toner, a magenta toner, a cyan toner, and a black toner. Each color toner included in the toner set of the present disclosure is an aggregate of toner particles formed by adding the external additive to the surface of the colored resin particles.

[0152] [Toner particle size and shape] The volume average particle size (Dv) of each color toner is preferably 3 to 15 μm, more preferably 4 to 12 μm. When Dv is 3 μm or more, the fluidity of the toner can be improved, and deterioration of transferability and reduction in image density can be suppressed. When Dv is 15 μm or less, reduction in image resolution can be suppressed.

[0153] Furthermore, the ratio (Dv / Dp) of the volume average particle diameter (Dv) to the number average particle diameter (Dp) of each color toner is preferably 1.0 to 1.3, and more preferably 1.0 to 1.2. By having Dv / Dp of 1.3 or less, it is possible to suppress deterioration in transferability, image density, and resolution. The volume average particle diameter and number average particle diameter of the toner can be measured, for example, using a particle size distribution measuring device (manufactured by Beckman Coulter, product name: Multisizer, etc.) using the Coulter Counter method.

[0154] From the viewpoint of image reproducibility, the average circularity of each color toner is preferably 0.97 to 1.00, and more preferably 0.98 to 1.00. Circularity is defined as the circumferential length of a circle having the same projected area as the particle image divided by the circumferential length of the projected image of the particle. The average circularity in the present disclosure is used as a simple method for quantitatively expressing the shape of a particle, and is an index showing the degree of unevenness of the toner particles. The average circularity is 1 when the toner particles are perfectly spherical, and the more complex the surface shape of the toner particles, the smaller the value becomes. The average circularity (Ca) is a value calculated using the following formula for calculating average circularity:

[0155]

[0156] In the above formula, n is the number of particles for which the circularity Ci is determined. In the above formula, Ci is the circularity of each particle calculated using the following formula for calculating circularity based on the circumferential length measured for each particle in a particle group having a circle-equivalent diameter of 0.6 to 400 μm. Formula for calculating circularity: Circularity (Ci) = Circumferential length of a circle equal to the projected area of ​​the particle / Circumferential length of the projected image of the particle In the above formula, fi is the frequency of particles with circularity Ci. The above circularity and average circularity can be measured using a flow particle image analyzer "FPIA-3000" manufactured by Sysmex Corporation.

[0157] [Viscoelasticity] In the toner set of the present disclosure, the loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)) are all 0.840 or more, and the toner has viscoelasticity that satisfies the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (III) Here, the loss tangent (tan δ) is defined as the ratio (G" / G') of the storage modulus (G') to the loss modulus (G") measured by dynamic viscoelasticity measurement. In the present disclosure, the value of tan δ is rounded to three decimal places in accordance with Rule B of JIS Z8401:1999. The loss tangent (tan δ) of the toner at each temperature is determined from the temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement. In the present disclosure, the temperature dependency curve of loss tangent (tan δ) obtained by dynamic viscoelasticity measurement may be referred to as a "temperature-tan δ curve."

[0158] In the present disclosure, dynamic viscoelasticity measurements are performed using a rotating plate rheometer (ARES-G2, manufactured by TA Instruments) with a parallel plate or crosshatch plate under the following conditions: Frequency: 24 Hz Sample set: A test specimen (2 to 4 mm thick) is sandwiched between 8 mmφ plates with a load of 20 g, and the temperature is raised to 80°C to fuse the test specimen to the jig, and then the temperature is returned to 45°C and heating begins. Heating rate: 5°C / min Temperature range: 45°C to 190°C The test specimen can be produced, for example, by pouring 0.2 g of the toner of the present disclosure into an 8 mmφ cylindrical molding machine and applying pressure at 1.0 MPa for 30 seconds to form a cylindrical molded body with a thickness of 2 to 4 mm and a diameter of 8 mm.

[0159] In the toner set of the present disclosure, the yellow toner, magenta toner, and cyan toner have the above-described viscoelasticity, and these toners contain an ester wax with a molecular weight of 600 to 3,000 as a softener and the above-described external additive A as an external additive, thereby suppressing peeling of the toner layers when a full-color image is formed, and improving multi-layer fixing of the toner layers. Peeling of the toner layers when a full-color image is formed includes, for example, peeling at the interface between the toner layer and the paper surface, peeling between toner layers, and peeling within the toner layer. To suppress peeling of the toner layers and improve multi-layer fixing of the toner layers, it is necessary that (i) the heat of the fixing roll is transmitted to the toner layer and the paper surface layer, causing the toner to melt to the extent that it adheres to the paper surface, and (ii) the softener contained in the toner oozes out of the toner and contributes to adhesion between the layers. Item (ii) above is achieved by the external additive A suppressing the crushing of toner particles and by the toner containing an ester wax with a molecular weight of 600 to 3,000 as a softener. Item (i) above is achieved by each color toner having the above-described viscoelasticity. More specifically, when the loss tangents at 100°C (tan δ(100°C)) of the yellow toner, magenta toner, and cyan toner are all high above a certain value, the toners melt and spread easily. Furthermore, when the difference in tan δ(100°C) between the color toners is small below a certain value, toners with relatively low tan δ(100°C) also melt, resulting in good adhesion between toner layers and between the toner layer and the paper surface, thereby achieving item (i). When the difference in tan δ(100°C) between the color toners is large, toners with relatively low tan δ(100°C) do not melt completely, resulting in insufficient adhesion between toner layers or between the toner layer and the paper surface. On the other hand, when the toner set of the present disclosure further contains a black toner, the difference between the tan δ (100° C.) of the black toner and the tan δ (100° C.) of each of the yellow, magenta, and cyan toners may be more than 0.140. When a full-color image is formed using the toner set of the present disclosure further containing a black toner, the black toner is usually fixed on the surface side of the yellow, magenta, and cyan toners.The toner layer of black toner formed on the outermost surface (i.e., the uppermost layer when the recording material side is placed downward) is less likely to peel off because the tan δ(100°C) of the black toner is sufficiently large. Therefore, the multi-layer fixation of the yellow, magenta, and cyan toners formed first is good as described above, and the sufficiently large tan δ(100°C) of the black toner results in good multi-layer fixation of the full-color image. From the viewpoint of the fixability of the black toner, and ultimately from the viewpoint of the multi-layer fixation of the full-color image, it is preferable that the difference between the tan δ(100°C) of the black toner and the tan δ(100°C) of each of the yellow, magenta, and cyan toners satisfies the formula (IV) described below.

[0160] In the toner set of the present disclosure, the absolute value of the difference between the tan δ(Y, 100°C) and the tan δ(M, 100°C), the absolute value of the difference between the tan δ(C, 100°C) and the tan δ(M, 100°C), and the absolute value of the difference between the tan δ(Y, 100°C) and the tan δ(C, 100°C) may be 0.140 or less, and is not particularly limited. However, the upper limit of each is preferably 0.120 or less, and more preferably 0.100 or less. The difference in loss tangent at 100°C (tan δ(100°C)) between the respective color toners is preferably as small as possible from the viewpoint of suppressing peeling between the toner layers and peeling within the toner layers. However, from the viewpoint of ease of production, the difference may be, for example, 0.0001 or more, or 0.001 or more. Furthermore, it is preferable that the absolute value of the difference in loss tangent at 100°C (tan δ(100°C)) between all toners included in the toner set of the present disclosure is not more than the above upper limit value. Furthermore, from the viewpoint of suppressing peeling between toner layers and peeling within a toner layer, it is preferable that the absolute value of the difference in loss tangent at 100°C (tan δ(100°C)) between toners preceding and succeeding in the order of overprinting is not more than the above upper limit value. On the other hand, when the toner set of the present disclosure further contains a black toner, since the black toner is usually fixed to the outermost surface of the paper during printing, as described above, the difference between the loss tangent at 100°C (tan δ(100°C)) of the black toner and the tan δ(100°C) of each of the yellow, magenta, and cyan toners may be more than 0.140. Furthermore, the difference between the tan δ(100° C.) of the toner of the other color in contact with the black toner and the loss tangent at 100° C. (tan δ(100° C.)) of the black toner may also exceed 0.140.

[0161] In the toner set of the present disclosure, the tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C) may be 0.840 or more, but are preferably 0.850 or more, more preferably 0.860 or more, from the viewpoint of suppressing peeling of the toner layer and improving the fixability of the toner. The upper limits of the tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C) are not particularly limited, but are preferably 0.960 or less, more preferably 0.950 or less, and even more preferably 0.940 or less, from the viewpoint of hot offset resistance, suppressing deterioration in storage stability, and suppressing deterioration in image gloss. Furthermore, it is preferable that the loss tangent at 100°C (tan δ(100°C)) of all toners included in the toner set of the present disclosure is within the above range. On the other hand, when the toner set of the present disclosure further contains a black toner, it is preferable that the tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C) are within the above ranges, and that the loss tangent at 100°C of the black toner (tan δ(K, 100°C)) is 1.000 or more and 1.200 or less. Since black toner is usually fixed to the outermost surface of paper during printing, if tan δ(K, 100°C) is equal to or greater than the above lower limit, the toner fixed to the outermost surface is easily melted, resulting in excellent fixability, and peeling of not only the black toner layer but also the other color toner layers is suppressed. On the other hand, if tan δ(K, 100°C) is equal to or less than the above upper limit, printing defects can be suppressed. The viscoelasticity of each color toner can be adjusted, for example, by the type or amount of a molecular weight modifier, colorant, charge control agent, polar resin, or external additive.

[0162] When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that the loss tangent at 100°C (tan δ(K, 100°C)) of the black toner is higher than each of the tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C). Since black toner is usually fixed to the outermost surface of paper during printing, when tan δ(K, 100°C) is highest, the toner fixed to the outermost surface melts most easily and has excellent fixability, thereby suppressing peeling of not only the toner layer of the black toner but also the toner layers of each color, thereby making it possible to suppress peeling of the toner layers when a full-color image is formed and printed. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that the following formula (IV) be satisfied: 0.10<|{tan δ(C, 100°C)+tan δ(M, 100°C)+tan δ(Y, 100°C)}-tan δ(K, 100°C)×3| / 3<0.30 (IV) As described above, the difference between the tan δ(100°C) of the black toner and the tan δ(100°C) of each of the yellow, magenta, and cyan toners may exceed 0.140. However, it is preferable that the difference between the average of the loss tangents at 100°C of the three color toners (yellow, magenta, and cyan) and the loss tangent at 100°C of the black toner satisfy the above formula (IV). This results in a good balance of fluidity between the color toners, thereby reducing the difference in charge buildup between the color toners and improving the charge buildup performance of the toner set. Furthermore, the small difference in charge buildup between the color toners improves the adhesion between the color toner layers, resulting in good multilayer fixing and the formation of a uniform multilayer fixing structure. Furthermore, in the toner set that satisfies the above formula (IV), the difference between the average loss tangent at 100°C of the three color toners, yellow, magenta, and cyan, and the loss tangent at 100°C of the black toner is not too small, and therefore the loss tangent at 100°C of the black toner is sufficiently large, so that the black toner fixed to the outermost surface melts most easily and has excellent fixability, thereby suppressing peeling of not only the toner layer of the black toner but also the toner layers of each color.From the above-mentioned viewpoint, the value of "|{tan δ(C, 100°C) + tan δ(M, 100°C) + tan δ(Y, 100°C)} - tan δ(K, 100°C) × 3| / 3" in the above formula (IV) is preferably more than 0.15 and less than 0.20.

[0163] [Toner Density] The compacted bulk density of each color toner included in the toner set of the present disclosure, as determined using a powder fluidity analyzer, is preferably 0.525 g / mL or more and 0.560 g / mL or less, more preferably 0.527 g / mL or more and 0.558 g / mL or less, and even more preferably 0.530 g / mL or more and 0.555 g / mL or less. Here, the compacted bulk density simulates the bulk density of densely packed toner in a toner pool formed during toner development and can be used as an index of the strength of the toner pool (i.e., the hardness of the toner mass). If the compacted bulk density is below the upper limit, the toner tends to crumble even when retained, making it difficult for the toner to aggregate. If the compacted bulk density is below the lower limit, toner leakage from the toner pool is likely to occur. If the compacted bulk density is within the above range, toner leakage is unlikely to occur even when the toner is retained. Note that toner near the seal portion of the developing unit is particularly difficult to circulate, making toner leakage more likely. In the present disclosure, toner leakage from the seal portion of the developing unit is sometimes referred to as "seal leakage." Such seal leakage is less likely to occur when the compacted bulk density is within the above range. Furthermore, when the compacted bulk density is within the above range, the toner has good fluidity during continuous printing, and aggregates are less likely to form, making toner ejection less likely. Note that in the present disclosure, the compacted bulk density of the yellow toner, magenta toner, and cyan toner contained in the toner set is preferably within the above range, and it is more preferable that the compacted bulk density of all toners contained in the toner set is within the above range. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that the compacted bulk density of each of the yellow toner, magenta toner, cyan toner, and black toner is within the above range.

[0164] As the powder fluidity analyzer (hereinafter sometimes referred to as the analyzer), for example, Powder Rheometer FT4 (trade name, manufactured by Freeman Technology) can be used.

[0165] When measuring the compacted bulk density of a toner, reference can be made to known literature related to powder fluidity analyzers, such as "Powder Fluidity Analyzer Powder Rheometer FT-4 Academic Materials" (published by Sysmex Corporation, Scientific Measurement Division, first edition published September 1, 2007) (particularly pages 6-7 and 10). However, the compacted bulk density in the present disclosure is not necessarily limited to the contents described in the known literature.

[0166] The compacted bulk density of the toner can be determined, for example, by dividing the mass of the toner, which has been conditioned by three cycles of the following steps (Step 1) and then the following steps (Steps 2 to 5), by its volume. (Step 1) 100 g of toner is filled into a conditioning container with an inner diameter of 50 mm and a total height of 140 mm, and the toner is allowed to stand for 10 minutes to form a toner layer. (Step 2) The tip speed of the blade of the analyzer is set to 60 mm / sec, and the blade is rotated clockwise at an angle of 5°. While stirring the toner layer, the blade is passed from the surface of the toner layer to the interior of the toner layer, reaching a position 10 mm from the bottom of the conditioning container. The blade angle refers to the angle at which the spiral path of the blade intersects with the surface of the toner layer. (Step 3) Without changing the tip speed of the blade, the blade is lowered to a position 1 mm from the bottom of the conditioning container by changing the blade approach angle to 2° clockwise, and stirring the toner layer. (Step 4) Without changing the tip speed of the blade, the blade approach angle is changed to 5° counterclockwise, and while stirring the toner layer, the blade is raised to a position 100 mm from the bottom of the conditioning container. (Step 5) The blade is lifted from the surface of the toner layer. If Step 2 is performed after Step 5, excess toner adhering to the blade lifted from the surface of the toner layer in Step 5 is brushed off.

[0167] The conditioning container preferably comprises a measuring container having a bottom and sides, and an accessory container having only sides stacked on top of the measuring container. An example of such a conditioning container is a cylindrical measuring container having a bottom with a clamp attached, and another cylindrical accessory container having only sides stacked on top of the measuring container and connected with a splitter. By using such a conditioning container, the accessory container can be removed after toner conditioning. By simultaneously removing the accessory container and scraping off the toner above the edge of the measuring container, a toner cake having the same volume as the measuring container can be produced. The compacted bulk density of the toner can be calculated by dividing the mass of the toner cake thus obtained by the volume of the measuring container.

[0168] The toner contained in the toner set of the present disclosure preferably has a loose bulk density of 0.512 g / mL or more and 0.530 g / mL or less. Here, loose bulk density refers to the bulk density in a loosely packed state. The loose bulk density of the toner can be calculated, for example, by pouring the toner into a 100 mL SUS cylindrical container, leaving it for 30 seconds, smoothing off any toner that has risen above the container's top surface, and then dividing the weight of the toner in the container by the volume (100 mL) of the toner. When the toner contains the external additive A, the loose bulk density of the toner tends to fall within the above range. When the loose bulk density of the toner is within the above range, the toner's fluidity tends to be stable during continuous printing, thereby suppressing toner spillage and leakage. Furthermore, when the loose bulk density of the toner is within the above range, the toner's fluidity tends to be good when printing from an intermittent state. In the present disclosure, the loose bulk density of the yellow toner, magenta toner, and cyan toner contained in the toner set is preferably within the above range, and it is more preferable that the loose bulk density of all toners contained in the toner set is within the above range. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that the loose bulk density of each of the yellow toner, magenta toner, cyan toner, and black toner is within the above range.

[0169] For the toner included in the toner set of the present disclosure, the difference between the compacted bulk density and the loose bulk density (compacted bulk density - loose bulk density) is preferably 0.036 g / mL or less, more preferably 0.035 g / mL or less, and even more preferably 0.033 g / mL or less. When the difference between the compacted bulk density and the loose bulk density is equal to or less than the above upper limit, the fluidity of the toner is likely to be stable during continuous printing. Furthermore, since the shear stress applied to the toner tends to be constant, the toner particles are less likely to crack, the toner charge buildup is stable, and the toner transport amount is also likely to be stable. As a result, toner ejection and toner leakage are also suppressed. Meanwhile, the lower limit of the difference between the compacted bulk density and the loose bulk density is preferably 0.001 g / mL or more, more preferably 0.004 g / mL or more, and even more preferably 0.008 g / mL or more. When the difference between the compacted bulk density and the loose bulk density is equal to or greater than the lower limit, sufficient shear stress is applied to the toner, leading to suppression of toner ejection. In the present disclosure, it is preferable that the difference between the compacted bulk density and the loose bulk density of the yellow toner, magenta toner, and cyan toner contained in the toner set is within the above range, and it is more preferable that the difference between the compacted bulk density and the loose bulk density of all toners contained in the toner set is within the above range. When the toner set of the present disclosure includes a yellow toner, a magenta toner, a cyan toner, and a black toner, it is preferable that the difference between the compacted bulk density and the loose bulk density of each of the yellow toner, magenta toner, cyan toner, and black toner is within the above range.

[0170] 2. Image Forming Method The toner set of the present disclosure is a color toner set for electrostatic image development, typically used to form a full-color image using an electrostatic image development method. Methods for forming full-color images using an electrostatic image development method can be broadly divided into the following two types based on the difference in the transfer process: (1) A method in which an original image is color-separated to obtain data for each color component, multiple single-color toner images are formed based on the data for each color component, these images are sequentially transferred onto a single transfer medium, and a full-color image is formed by color superposition on the transfer medium, and the full-color image is then transferred from the transfer medium to a recording material. (2) A method in which an original image is color-separated to obtain data for each color component, multiple single-color toner images are formed based on the data for each color component, these images are sequentially transferred onto a single recording material, and a full-color image is formed by color superposition on the recording material. The toner set of the present disclosure can suppress peeling of the toner layer and the generation of ultrafine particles in both of the above methods.

[0171] The present disclosure also includes the following two image forming methods. The former is a method of overlaying colors on a transfer medium, and the latter is a method of overlaying colors on a recording material. The first method is a method of forming an image using an electrostatic charge development type full-color printer with the toner set of the present disclosure, and is characterized by including the steps of: developing a first image, which is a primary color image formed with a first toner (first image developing step); developing a second image, which is a primary color image of each color formed with a second toner (second image developing step); transferring the first image onto the transfer medium and then transferring the second image onto the transfer medium to form an image including multi-colors on the transfer medium (color overlaying step on transfer medium); transferring the image including multi-colors formed on the transfer medium onto a recording material (multi-color image transfer step); and fixing the image including multi-colors transferred onto the recording material (fixing step).

[0172] The second method is a method of forming an image using an electrostatic charge development type full-color printer with the toner set of the present disclosure, and is characterized by having a step of developing a first image which is a primary color image formed with a first toner (first image developing step), a step of developing a second image which is a primary color image of each color formed with a second toner (second image developing step), a step of transferring the first image onto a recording material, and then transferring the second image to form an image including multi-colors on the recording material (color overlaying step on recording material), and a step of fixing the image including multi-colors formed on the recording material onto the recording material (fixing step).

[0173] In this disclosure, a "primary color" refers to a color obtained when a toner of each color is printed alone; a "secondary color" refers to a color obtained when two primary color toner images of different colors are superimposed; and a "multi-color" refers to a color obtained when primary color toner images of multiple colors are superimposed. In this disclosure, the term "toner image" literally refers to an image formed with toner, but is used particularly to emphasize that it is a visual image of the state in which toner is distributed on an image-bearing surface such as a photoreceptor, transfer medium, or recording material in accordance with the image to be reproduced. In this disclosure, a "leading color" refers to the color of the primary color toner image transferred first onto a transfer receiving material when a full-color image is formed by color superposition on a transfer receiving material by forming primary color toner images of each color using multiple toner developing machines and sequentially transferring them onto a single transfer receiving material (recording material or transfer medium). In this disclosure, a "leading developing machine" refers to a developing machine that develops the primary color toner image of the leading color. When multiple toner developing units are arranged in series along the transport path of the transfer receiving material (recording material or transfer medium) in a developing device, the first developing unit encountered by the transfer receiving material moving along the transport path is the "leading developing unit."

[0174] The toner set disclosed herein is suitable for a printing method in which electrostatic latent images corresponding to the individual primary colors are developed using multiple primary color toners, such as yellow, cyan, and magenta toners, to form individual primary color toner images on a developing machine, and the resulting individual primary color toner images are then sequentially transferred onto a transfer receiving material selected from the group consisting of a recording material and a transfer medium, thereby forming a full-color image by color superposition on the transfer receiving material. When color superposition is performed on the recording material, the individual primary color toner images are sequentially transferred onto the recording material, either directly or via an intermediate transfer process from the toner image forming surface of the developing machine to the transfer medium, to form a full-color image including multiple colors on the recording material. When color superposition is performed on the transfer medium, the individual primary color toner images are sequentially transferred onto one transfer medium, either directly or via an intermediate transfer process from the toner image forming surface of the developing machine to another transfer medium, to form a full-color image including multiple colors on the transfer medium, and then the full-color image on the transfer medium is subsequently transferred onto the recording material, either directly or via an intermediate transfer process to another transfer medium.

[0175] The first toner included in the toner set of the present disclosure is the primary color toner that is transferred first onto a transfer receiving material selected from the group consisting of recording materials and transfer media during the color overlay process on the transfer receiving material. The second toner included in the toner set is the primary color toner that is transferred second or later during the color overlay process on the transfer receiving material. The first toner is typically selected from the group consisting of yellow toner, cyan toner, and magenta toner. The second toner is typically selected from the group consisting of yellow toner, cyan toner, and magenta toner so that the relationship between adjacent toners in the color overlay process satisfies the above-mentioned formula (I), (II), or (III). Note that, in the image forming method using the toner set of the present disclosure, toners other than the above-mentioned colors, such as black toner, may also be used. Furthermore, in addition to the basic colors of yellow toner, cyan toner, and magenta toner, yellow, cyan, or magenta toners that differ in some color element, such as hue, color density, brightness, or vividness, may also be used.

[0176] When the toner set of the present disclosure includes a black toner, it is preferable to fix the multi-color image to the recording material so that the black toner is on the outermost surface, in terms of suppressing peeling of the toner layer and improving the charge build-up property of the toner set. When an image is formed using the toner set of the present disclosure including yellow, magenta, cyan, and black toners, for example, a multi-color image formed by overlaying colors in the order of yellow toner, magenta toner, cyan toner, and black toner, or magenta toner, yellow toner, cyan toner, and black toner, may be fixed to the recording material so that the black toner is on the outermost surface.

[0177] Examples of the transfer medium on which color superposition is performed include an intermediate transfer belt, an intermediate transfer roll, etc. In addition, examples of the recording material include recording paper such as plain paper, as well as coated paper, art paper, OHP sheet toner, etc., and are not particularly limited.

[0178] A printing apparatus capable of carrying out the above-described procedure may be, for example, a full-color printer in which multiple developing units corresponding to the respective colors of toner contained in a toner set are arranged in series, and primary color images (color separation images) of each color generated by each developing unit are transferred onto a single recording material, either directly from the individual developing units or sequentially via a transfer medium, to form an image including secondary or higher colors on the recording material. This is a type of printer with a so-called tandem arrangement. FIG. 1 is a schematic diagram illustrating an example of the structure of an image forming apparatus to which the toner set of the present disclosure can be applied. Note that the image forming method of the present disclosure is not limited to that shown in the figure. Furthermore, the structure, dimensions, and shape of the materials used in the method of the present disclosure are not limited to those shown in these figures.

[0179] The image forming apparatus 100 shown in FIG. 1 is a tandem printer. The image forming apparatus 100 includes a conveyance path 4 for the recording material R, four developing units (1Y, 1M, 1C, and 1K) corresponding to the colors yellow (Y), magenta (M), cyan (C), and black (K), pairs of transfer media (2Y, 2M, 2C, and 2K) and support rolls (3Y, 3M, 3C, and 3K) for each developing unit, an exposure device 5 that irradiates laser light in accordance with primary color image data obtained by color separation of an original image, and pairs of fixing rolls 6 and support rolls 7. The four developing units (1Y, 1M, 1C, and 1K) corresponding to each color are arranged in series along the conveyance direction D of the recording material R within the image forming apparatus. The four developing units are arranged in the following order from the upstream side of the conveyance direction: yellow developing unit 1Y, magenta developing unit 1M, cyan developing unit 1C, and black developing unit 1K.

[0180] The configuration of the developing machine will be described using the yellow developing machine 1Y as an example. The developing machine 1Y has a drum-shaped photoconductor 11Y, and is surrounded by a charging roll 12Y that charges the surface of the photoconductor to a predetermined potential, a laser light irradiation unit 13Y that irradiates the photoconductor 11Y with laser light generated by an exposure device to form an electrostatic image, a developing unit 14Y that supplies charged toner to the electrostatic image to develop it, a roll-shaped transfer medium 2Y to which the developed toner image is transferred, and a cleaning unit 15Y that removes toner remaining on the photoconductor 11Y after the toner image has been transferred to the transfer medium. The developing unit 14Y is also connected to a toner storage unit 16Y by a yellow toner supply path. Similarly, the developing machines for the other colors are equipped with photosensitive members (11M, 11C, 11K), charging rolls (12M, 12C, 12K), laser light irradiation units (13M, 13C, 13K), developing units (14M, 14C, 14K), cleaning units (15M, 15C, 15K), and toner storage units (16M, 16C, 16K), and transfer media (2M, 2C, 2K) are arranged around the photosensitive members together with these components.

[0181] A method for forming an image using the image forming apparatus 100 described above will be described. In this apparatus, yellow toner is selected as the first toner and used in the first developing unit 1Y. Magenta (M), cyan (C), and black (K) toners are used as second toners in the second and subsequent developing units. First, in the yellow developing unit 1Y, the surface of the photoconductor 11Y is uniformly charged by the charging roll 12Y. Photoconductors typically have high resistance (the resistance of ordinary resins), but when irradiated with laser light, the resistivity of the irradiated portion changes. Therefore, the exposure device 5 generates a laser beam according to the yellow primary color image data, and the laser beam irradiation unit 13Y irradiates the charged surface of the photoconductor 1Y. The laser beam irradiates the photosensitive layer on the surface of the photoconductor 11Y, thereby forming an electrostatic latent image corresponding to the yellow primary color image on the surface of the photoconductor 11Y. The electrostatic latent image is a negative latent image because it is formed by the residual charge in the areas not irradiated with the laser beam.

[0182] The electrostatic latent image on the photoconductor 11Y moves to the position of the developing unit 14Y as the photoconductor rotates, where it is developed to obtain a yellow primary color toner image. The yellow primary color toner image on the photoconductor moves to the primary transfer position as the photoconductor rotates. At the primary transfer position, the surface of the photoconductor 11Y and the surface of the transfer medium 2Y come into contact, where the yellow primary color toner image on the photoconductor is primarily transferred to the surface of the transfer medium 2Y. The yellow primary color toner image on the transfer medium 2Y moves to a position where the yellow is secondary transferred as the transfer medium rotates. At the secondary transfer position, the recording material R on the conveying path 4 is sandwiched between the transfer medium 2Y and the support roll 3Y, where the surface of the transfer medium 2Y comes into contact with the image receiving surface of the recording material R, where the yellow primary color toner image on the transfer medium 2Y is secondary transferred to the recording material R.

[0183] Next, the magenta developing unit 1M performs a procedure similar to that for forming the yellow primary color toner image. That is, in the magenta developing unit 1M, a magenta primary color toner image is formed on the surface of the photoreceptor 11M, and is primarily transferred to the surface of the transfer medium 2M. The rotation of the transfer medium 2M moves the magenta primary color toner image to a position for secondary transfer. Meanwhile, from the upstream side of the conveying path 4, the portion of the recording material R on which the yellow primary color toner image has been formed moves to a position for secondary transfer of magenta. There, the magenta primary color toner image on the transfer medium 2M is aligned with the yellow primary color toner image on the recording material R and is secondary transferred to the recording material R.

[0184] Next, the cyan developing unit 1C and the black developing unit 1K perform a procedure similar to that for forming a yellow primary color toner image. Then, primary color toner images of yellow (Y), magenta (M), cyan (C), and black (K) are superimposed in this order on the recording material R moving along the conveyance path, thereby obtaining a full-color image including multiple colors. After the recording material R passes through the developing units of all colors and an image including multiple colors is formed, the recording material R moves to a position where a fixing process is performed. There, the recording material R is sandwiched between the fixing roll 6 and the support roll 7, where the image including multiple colors is fixed onto the recording material.

[0185] The present disclosure will be further described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. Note that parts and percentages are by mass unless otherwise specified. The weight-average molecular weight Mw of the polymer was determined in polystyrene equivalent by GPC. The sample for measurement was prepared by dissolving the polymer in tetrahydrofuran (THF) to a concentration of 2 mg / mL, sonicating for 10 minutes, and then passing the solution through a 0.45 μm membrane filter. The measurement conditions were: temperature: 40°C, solvent: tetrahydrofuran, flow rate: 1.0 mL / min, concentration: 0.2 wt%, sample injection volume: 100 μL, and a GPC TSKgel Multipore HXL-M (30 cm x 2 columns) manufactured by Tosoh Corporation was used. The measurement was also carried out under the condition that the linear correlation equation between Log(Mw) and elution time for weight average molecular weights Mw of 1,000 to 300,000 was 0.98 or more.

[0186] [Production Example 1: Production of Magenta Pigment Mixed Crystal] 2,9-dimethylquinacridone (C.I. Pigment Red 122) was synthesized by cyclization of 2,5-di-(4-methylphenylamino)terephthalic acid in phosphoric acid. Water was added to the resulting phosphoric acid dispersion of 2,9-dimethylquinacridone, which was then filtered and washed with water. Water was added again to the washed 2,9-dimethylquinacridone to prepare an aqueous dispersion with a 20% solids content. Similarly, an aqueous dispersion of quinacridone (C.I. Pigment Violet 19) with a 20% solids content was prepared using 2,5-diphenylaminoterephthalic acid. 250 parts of ethanol were added to 250 parts of the aqueous dispersion of dimethylquinacridone (C.I. Pigment Red 122) with a 20% solids content and 250 parts of the aqueous dispersion of quinacridone (C.I. Pigment Violet 19) with a 20% solids content to prepare a pigment mixture. This mixture was transferred to a vessel equipped with a condenser, and the pigment was reacted for 5 hours under heating and reflux while being ground. After the reaction was completed, the pigment was filtered out from the reaction mixture, washed, dried, and then pulverized to obtain a magenta pigment mixed crystal (i.e., a mixed crystal of C.I. Pigment Red 122 (PR122) and C.I. Pigment Violet 19 (PV19)). The mass ratio of the pigments contained in the mixed crystal was C.I. Pigment Red 122:C.I. Pigment Violet 19=1:1.

[0187] [Production Example 2: Production of CCR-A1] A total of 92 parts of styrene and n-butyl acrylate were copolymerized with 8 parts of N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium p-toluenesulfonate to produce a copolymer (CCR-A1). In CCR-A1, the copolymerization ratio of the monomer containing a quaternary ammonium salt-containing group was 8 mass%.

[0188] [Production Example 3: Production of CCR-B1] A total of 98 parts of styrene and n-butyl acrylate were copolymerized with 2 parts of N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium p-toluenesulfonate to produce a copolymer (CCR-B1). In CCR-B1, the copolymerization ratio of the monomer containing a quaternary ammonium salt-containing group was 2 mass%.

[0189] [Production Example 4: Production of barium titanate fine particles] A 0.92N NaOH aqueous solution was kept at about 90°C, and TiCl ４ Aqueous solution (TiCl ４ concentration of 0.485 mol / L) and BaCl 2 which had been previously removed of undissolved matter and heated and maintained at approximately 95°C. ２ / NaOH aqueous solution (BaCl ２ A solution of 0.265 mol / L of HCl and 2.73 mol / L of NaOH was continuously fed into the reaction vessel. After the temperature of the mixed aqueous solution was kept constant at approximately 90°C, 10.0 mass% isobutyltrimethoxysilane was added relative to the solid content, and the mixture was stirred for 1 hour to produce particulate barium titanate. After aging, the mixture was decanted to separate the supernatant and precipitate, which were then washed and recovered. The recovered solid reactant was dried by heating at 100°C in an air atmosphere. The mixture was further heated to 900°C for 30 minutes to obtain barium titanate microparticles. The resulting barium titanate microparticles had a number-average particle size of 100 nm.

[0190] The details of the external additive A shown in Tables 1 to 3 are as follows: Titanium oxide: titanium oxide fine particles treated with triethanolamine and surface-treated for hydrophobicity, having a number-average particle size of 40 nm Strontium titanate: strontium titanate fine particles having a number-average particle size of 35 nm, the surface of which has been hydrophobized with aminosilane Barium titanate: barium titanate fine particles obtained in Production Example 4 above, which have not been surface-treated and have a number-average particle size of 100 nm Aluminum oxide: Nippon Aerosil Co., Ltd., trade name: VP-Alu-RK, aluminum oxide fine particles surface-treated with alkylsilane, having a particle size of 18 nm Zinc oxide: Sakai Chemical Industry Co., Ltd., trade name: XZ-300, zinc oxide fine particles with a number-average particle size of 0.3 μm

[0191] <Magenta Toner> [Production of Magenta Toner M-1] 1. Production of Colored Resin Particles 1-1. Preparation of Core Polymerizable Monomer Composition: 74 parts of styrene, 26 parts of n-butyl acrylate, 0.74 parts of divinylbenzene, 1.0 part of tetraethylthiuram disulfide (TET), and 4.2 parts of Magenta Pigment A1 (manufactured by Daido Kasei Co., Ltd., product name: NO. 5500 ST-RED, pigment classification: C.I. Pigment Red 48:3, content of rosin acid metal salt (Sr salt) per 100 parts of Magenta Pigment A1: 5.0 parts) as a magenta colorant, and 2.8 parts of the magenta pigment mixed crystal obtained in Production Example 1 above were wet-pulverized using a media-type disperser (manufactured by Asada Iron Works Co., Ltd., product name: Picomil). To the mixture obtained by the wet pulverization, 2.0 parts of CCR-A1 obtained in Production Example 2 above and 1.0 part of CCR-B1 obtained in Production Example 3 above were added as charge control resins, and further 2.0 parts of Ester Wax 1 (hexaglycerin octabehenate, molecular weight: 2649) and 7.0 parts of Ester Wax 3 (pentaerythritol tetrapalmitate, molecular weight: 1088) were added as softeners, and the mixture was mixed and dissolved to prepare a polymerizable monomer composition.

[0192] 1-2. Preparation of aqueous dispersion medium: On the other hand, an aqueous solution prepared by dissolving 9.9 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 14.1 parts of magnesium chloride in 280 parts of ion-exchanged water to prepare a magnesium hydroxide colloidal dispersion.

[0193] 1-3. Preparation of polymerizable monomer for shell: Separately, 2 parts of methyl methacrylate and 130 parts of water were subjected to a fine dispersion treatment using an ultrasonic emulsifier to prepare an aqueous dispersion of polymerizable monomer for shell.

[0194] 1-4. Droplet formation step: The core polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion (magnesium hydroxide amount: 7.2 parts), and the mixture was further stirred, followed by the addition of 4.4 parts of t-butylperoxy-2-ethylhexanoate as a polymerization initiator. The dispersion to which the polymerization initiator had been added was dispersed using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., trade name: Milder) at a rotation speed of 15,000 rpm to form droplets of the polymerizable monomer composition.

[0195] 1-5. Polymerization step: A dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor, and the temperature was raised to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached approximately 100%, a solution prepared by dissolving 0.1 parts of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide] (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble initiator) as a shell polymerization initiator in the aqueous dispersion of the shell polymerizable monomer was added to the reactor. The temperature was then maintained at 95°C for 4 hours to further continue polymerization, after which the reaction was stopped by water cooling to obtain an aqueous dispersion of core-shell type colored resin particles.

[0196] 1-6. Washing, Filtration, and Dehydration Steps: While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added to the dispersion until the pH reached 6.0 or less, followed by acid washing (25°C, 10 minutes). The colored resin particles were filtered out, washed with water, and the washing water was filtered. The electrical conductivity of the filtrate was 20 μS / cm. The colored resin particles after the washing and filtration steps were then dehydrated and dried to obtain dried colored resin particles (water content: 0.25%).

[0197] 2. Toner Production 2-1. External Addition Treatment Step: To 100 parts of the dried colored resin particles obtained above, 1.0 part of strontium titanate microparticles as external additive A, 1.28 parts of hydrophobized silica microparticles having an average particle size of 50 nm (manufactured by Clariant, product name: H05TA) as silica microparticles (a), 1.01 parts of hydrophobized silica microparticles having an average particle size of 22 nm (manufactured by Cabot Corporation, product name: TG-7120) as silica microparticles (b), 0.20 parts of hydrophobized silica microparticles having an average particle size of 7 nm (manufactured by Cabot Corporation, product name: TG-820F) as silica microparticles (c), and 0.25 parts of silicone resin particles (number-average primary particle size 145 nm) as external additive C were added, and mixed using a high-speed mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name: FM Mixer) to prepare magenta toner M-1.

[0198] [Production of Magenta Toners M-2 to M-9 and M-14] Magenta toners M-2 to M-9 and M-14 were obtained in the same manner as in the production of magenta toner M-1, except that in the above "Production of Toner", the type or amount of external additive A was changed according to Table 1.

[0199] [Production of Magenta Toners M-10 to M-11] Magenta toners M-10 to M-11 were obtained in the same manner as in the production of magenta toner M-1, except that in the above "Production of Toner", the amounts of silica fine particles (a) and (b) added were changed according to Table 1.

[0200] [Production of Magenta Toner M-12] Magenta toner M-12 was obtained in the same manner as in the production of magenta toner M-1, except that in the above "production of toner", strontium titanate fine particles were not added.

[0201] [Production of Magenta Toner M-13] Magenta toner M-13 was obtained in the same manner as in the production of magenta toner M-1, except that in the above "Preparation of polymerizable monomer composition for core", ester wax 1 was not added, and further, in the above "Production of toner", strontium titanate fine particles were not added.

[0202] <Yellow Toner> [Production of Yellow Toner Y-1] 1. Production of Colored Resin Particles 1-1. Preparation of Core Polymerizable Monomer Composition: 72 parts of styrene, 28 parts of n-butyl acrylate, 0.1 parts of polymethacrylic acid ester macromonomer (manufactured by Toagosei Chemical Industry Co., Ltd., trade name: AA-6, Tg = 94 ° C.) and 0.71 parts of divinylbenzene as binder resins, 1.25 parts of tetraethyl thiuram disulfide (TET) as a molecular weight modifier, and 7 parts of C.I. Pigment Yellow 155 (trade name: Toner Yellow 3GP CT, manufactured by Clariant) as a colorant were wet-pulverized using a media-type disperser (manufactured by Asada Iron Works, trade name: Picomil). To the mixture obtained by the wet grinding, 0.8 parts of CCR-A1 obtained in Production Example 2 above was added as a charge control resin, and 6.0 parts of Ester Wax 2 (pentaerythritol tetrastearate, molecular weight: 1200) as a softener were further added, mixed, and dissolved to prepare a polymerizable monomer composition for a core.

[0203] 1-2. Preparation of aqueous dispersion medium: On the other hand, an aqueous solution prepared by dissolving 7.3 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 10.4 parts of magnesium chloride in 280 parts of ion-exchanged water to prepare a magnesium hydroxide colloidal dispersion.

[0204] 1-3. Preparation of polymerizable monomer for shell: Separately, 2 parts of methyl methacrylate and 130 parts of water were subjected to a fine dispersion treatment using an ultrasonic emulsifier to prepare an aqueous dispersion of polymerizable monomer for shell.

[0205] 1-4. Droplet formation step: The core polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion (magnesium hydroxide amount: 5.3 parts), and the mixture was further stirred. 6 parts of t-butylperoxy-2-ethylbutanoate was added as a polymerization initiator. The dispersion with the added polymerization initiator was dispersed using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., trade name: Milder) at a rotation speed of 15,000 rpm to form droplets of the core polymerizable monomer composition.

[0206] 1-5. Polymerization step: A dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor, and the temperature was raised to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached approximately 100%, a solution prepared by dissolving 0.1 parts of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide] (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble initiator) as a shell polymerization initiator in the aqueous dispersion of the shell polymerizable monomer was added to the reactor. The temperature was then maintained at 95°C for 4 hours to further continue polymerization, after which the reaction was stopped by water cooling to obtain an aqueous dispersion of core-shell type colored resin particles.

[0207] 1-6. Washing, Filtration, and Dehydration Steps: While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added to the dispersion until the pH reached 4.5 or less, followed by acid washing (25°C, 10 minutes). The colored resin particles were filtered out, washed with water, and the washing water was filtered. The electrical conductivity of the filtrate was 20 μS / cm. The washed and filtered colored resin particles were then dehydrated to obtain wet colored resin particles.

[0208] 2. Toner Production 2-1. First-Stage External Addition Treatment Step: The moisture content of wet colored resin particles was measured, and the dry weight of the colored resin particles was calculated from the moisture content. Colored resin particles were sampled in an amount that would be 100 parts when the moisture content was set to 0%. 0.20 parts of hydrophobized silica fine particles (manufactured by Cabot Corporation, product name: TG-820F) having a number-average primary particle size of 7 nm were added as silica fine particles (c) to the wet colored resin particles sampled in this way. The colored resin particles were then placed in a mixer (manufactured by Hosokawa Micron Corporation, product name: LABOMIXER, MODEL: LV-1) placed in a constant temperature and humidity chamber at 35°C, and dried for 24 hours while mixing at 180 rpm to obtain intermediate particles.

[0209] 2-2. Second external addition treatment step: To the intermediate particles, 1.0 part of strontium titanate microparticles as external additive A, 1.35 parts of hydrophobized silica microparticles (manufactured by Clariant, product name: H05TA) having a number average primary particle size of 50 nm as silica microparticles (a), 0.54 parts of hydrophobized silica microparticles (manufactured by Cabot Corporation, product name: TG-7120) having a number average primary particle size of 20 nm as silica microparticles (b), and silicone resin as external additive C were added. To the resulting mixture were added 0.25 parts of the above-mentioned particles (number-average primary particle diameter of 145 nm) and 0.13 parts of fatty acid metal salt particles (zinc stearate particles, manufactured by Sakai Chemical Industry Co., Ltd., product name: SPZ-100F) having a number-average primary particle diameter of 0.5 μm as external additive D, and the resulting mixture was mixed and stirred using a high-speed mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name: FM Mixer) under conditions of a stirring blade peripheral speed of 46.6 m / s and an external addition treatment time of 8.0 minutes, thereby preparing yellow toner Y-1.

[0210] [Production of Yellow Toners Y-2 to Y-4 and Y-7] Yellow toners Y-2 to Y-4 and Y-7 were obtained in the same manner as in the production of yellow toner Y-1, except that in the above "Production of toner", the type or amount of external additive A was changed according to Table 2.

[0211] [Production of Yellow Toner Y-5] Yellow toner Y-5 was obtained in the same manner as in the production of yellow toner Y-1, except that in the above "production of toner", strontium titanate fine particles were not added.

[0212] [Production of Yellow Toner Y-6] Yellow toner Y-6 was obtained in the same manner as in the production of yellow toner Y-1, except that in the above "Preparation of polymerizable monomer composition for core", the amounts of styrene, n-butyl acrylate, divinylbenzene, and C.I. Pigment Yellow 155 (PY155) added were changed according to Table 2, and further, in the above "Production of toner", strontium titanate fine particles were not added.

[0213] <Cyan Toner> [Production of Cyan Toner C-1] 1. Production of Colored Resin Particles Colored resin particles were obtained in the same manner as in Yellow Toner Y-1, except that in the above "Preparation of Core Polymerizable Monomer Composition", 5.0 parts of Ester Wax 1 (hexaglycerin octabehenate, molecular weight: 2649) was used as the softener instead of 6.0 parts of Ester Wax 2, and 7.0 parts of C.I. Pigment Blue 15:3 (PB15:3) was used instead of 7.0 parts of C.I. Pigment Yellow 155 (PY155).

[0214] 2. Toner Production Cyan toner C-1 was obtained by subjecting 100 parts of the obtained colored resin particles to the same external addition treatment step as in yellow toner Y-1.

[0215] [Production of Cyan Toners C-2 to C-4 and C-6] Cyan toners C-2 to C-4 and C-6 were obtained in the same manner as in the production of cyan toner C-1, except that in the above "Production of toner", the type or amount of external additive A was changed according to Table 2.

[0216] [Production of Cyan Toner C-5] Cyan toner C-5 was obtained in the same manner as in the production of cyan toner C-1, except that in the above "production of toner", strontium titanate fine particles were not added.

[0217] <Black Toner> [Production of Black Toner K-1] 1. Production of Colored Resin Particles 1-1. Preparation of Core Polymerizable Monomer Composition: 72 parts of styrene, 28 parts of n-butyl acrylate, 0.25 parts of polymethacrylic acid ester macromonomer (manufactured by Toagosei Chemical Industry Co., Ltd., product name: AA-6, Tg = 94°C), and 0.13 parts of divinylbenzene as binder resins, 0.40 parts of tetraethylthiuram disulfide (TET) as a molecular weight modifier, and 8 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, #25BS) as a colorant were wet-pulverized using a media-type disperser (manufactured by Asada Iron Works, product name: Picomil). To the mixture obtained by the wet pulverization, 11.20 parts of CCR-A1 obtained in Production Example 2 above was added as a charge control resin, and 20.0 parts of Ester Wax 2 (pentaerythritol tetrastearate, molecular weight: 1200) as a softener were further added, mixed, and dissolved to prepare a polymerizable monomer composition for a core.

[0218] 1-2. Preparation of aqueous dispersion medium: On the other hand, an aqueous solution prepared by dissolving 7.3 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 10.4 parts of magnesium chloride in 280 parts of ion-exchanged water to prepare a magnesium hydroxide colloidal dispersion.

[0219] 1-3. Preparation of polymerizable monomer for shell: Separately, 2 parts of methyl methacrylate and 130 parts of water were subjected to a fine dispersion treatment using an ultrasonic emulsifier to prepare an aqueous dispersion of polymerizable monomer for shell.

[0220] 1-4. Droplet formation step: The core polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion (magnesium hydroxide amount: 5.3 parts), and the mixture was further stirred. 6 parts of t-butylperoxy-2-ethylbutanoate was added as a polymerization initiator. The dispersion with the added polymerization initiator was dispersed using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., trade name: Milder) at a rotation speed of 15,000 rpm to form droplets of the core polymerizable monomer composition.

[0221] 1-5. Polymerization step: A dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor, and the temperature was raised to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached approximately 100%, a solution prepared by dissolving 0.1 parts of 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide] (manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble initiator) as a shell polymerization initiator in the aqueous dispersion of the shell polymerizable monomer was added to the reactor. The temperature was then maintained at 95°C for 4 hours to further continue polymerization, after which the reaction was stopped by water cooling to obtain an aqueous dispersion of core-shell type colored resin particles.

[0222] 1-6. Washing, Filtration, and Dehydration Steps: While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added to the dispersion until the pH reached 4.5 or less, followed by acid washing (25°C, 10 minutes). The colored resin particles were filtered out, washed with water, and the washing water was filtered. The electrical conductivity of the filtrate was 20 μS / cm. The washed and filtered colored resin particles were then dehydrated to obtain wet colored resin particles.

[0223] 2. Toner Production 2-1. First-Stage External Addition Treatment Step: The moisture content of wet colored resin particles was measured, and the dry weight of the colored resin particles was calculated from the moisture content. Colored resin particles were sampled in an amount that would be 100 parts when the moisture content was set to 0%. 0.20 parts of hydrophobized silica fine particles (manufactured by Cabot Corporation, product name: TG-820F) having a number-average primary particle size of 7 nm were added as silica fine particles (c) to the wet colored resin particles sampled in this way. The colored resin particles were then placed in a mixer (manufactured by Hosokawa Micron Corporation, product name: LABOMIXER, MODEL: LV-1) placed in a constant temperature and humidity chamber at 35°C, and dried for 24 hours while mixing at 180 rpm to obtain intermediate particles.

[0224] 2-2. Second-stage external addition treatment step: To the intermediate particles, 1.0 part of strontium titanate microparticles as external additive A, 0.96 parts of hydrophobized silica microparticles (manufactured by Clariant, product name: H05TA) having a number-average primary particle size of 50 nm as silica microparticles (a), 0.58 parts of hydrophobized silica microparticles (manufactured by Cabot Corporation, product name: TG-7120) having a number-average primary particle size of 20 nm as silica microparticles (b), and 0.58 parts of silicone resin as external additive C were added. To the resulting mixture were added 0.25 parts of the above-mentioned particles (number-average primary particle diameter of 145 nm) and 0.13 parts of fatty acid metal salt particles (zinc stearate particles, manufactured by Sakai Chemical Industry Co., Ltd., product name: SPZ-100F) having a number-average primary particle diameter of 0.5 μm as external additive D, and the mixture was mixed and stirred using a high-speed mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name: FM Mixer) under conditions of a stirring blade peripheral speed of 46.6 m / s and an external addition treatment time of 8.0 minutes, thereby preparing black toner K-1.

[0225] [Production of Black Toner K-2] Black toner K-2 was obtained in the same manner as in the production of black toner K-1, except that in the above "production of toner", the type of external additive A was changed according to Table 3.

[0226] [Production of Black Toners K-3 to K-5] Black toners K-3 to K-5 were obtained in the same manner as in the production of black toner K-1, except that in the above "Preparation of polymerizable monomer composition for core", the amounts of styrene, n-butyl acrylate, divinylbenzene, TET, and CCR-A1 added were changed according to Table 3, and further, the type or amount added of external additive A and the amounts added of silica particles (a), (b), and (c) added were changed according to Table 3.

[0227] [Evaluation] 1. Toner Particle Size Measurement (Multisizer) The volume average particle size Dv of the toner was measured using a particle size distribution analyzer (manufactured by Beckman Coulter, Inc., trade name: Multisizer). Measurement using this Multisizer was performed under the following conditions: aperture diameter: 100 μm, dispersion medium: Isoton II (trade name), concentration: 10%, and number of particles measured: 100,000. Specifically, 0.2 g of a toner sample was placed in a beaker, and an aqueous surfactant solution (manufactured by Fujifilm Corporation, trade name: Drywell) was added as a dispersant. 2 ml of dispersion medium was further added to wet the toner, and then 10 ml of dispersion medium was added. The mixture was dispersed in an ultrasonic disperser for 1 minute, and then measurement was performed using the particle size distribution analyzer.

[0228] 2. Viscoelasticity Measurements For each toner, a temperature dependency curve of loss tangent (tan δ) was obtained by dynamic viscoelasticity measurement, and the loss tangent tan δ (100°C) of each toner at 100°C was determined from the obtained temperature-tan δ curve. Dynamic viscoelasticity measurements were performed using a rotating plate rheometer (TA Instruments, ARES-G2) with a crosshatch plate under the following conditions. Test specimens were prepared by pouring 0.2 g of toner into an 8 mmφ cylindrical molding machine, applying pressure at 1.0 MPa for 30 seconds, and molding a 3 mm thick, 8 mmφ cylindrical body. (Conditions for Dynamic Viscoelasticity Measurement) Frequency: 24 Hz Sample set: A test specimen (3 mm thick) was sandwiched between 8 mmφ plates with a load of 20 g. The temperature was raised to 80°C to fuse the test specimen to the jig, and then the temperature was lowered to 45°C, and the temperature increase was initiated. Heating rate: 5°C / min Temperature range: 45°C to 190°C

[0229] 3. UFP (ultrafine particle) generation temperature A predetermined amount of toner was heated on a heater installed in a chamber. The ultrafine particles discharged into this chamber were continuously measured using a particle counter (TSI, model: CPC3007). Next, the heater temperature was raised from 160°C, and the total count number of ultrafine particles in the particle size range of 10 to 1,000 nm observed during the measurement was read in 5°C increments. The temperature at which the total count number exceeded 10,000 particles was taken as the toner's emission start temperature (UFP (ultrafine particle) generation temperature).

[0230] 4. Packed Bulk Density The following measurements were performed using a powder fluidity analyzer (trade name: Powder Rheometer FT4, manufactured by Freeman Technology). The conditioning container used was a container with an inner diameter of 50 mm and a total height of 140 mm, which was constructed by stacking an auxiliary container (inner diameter: 50 mm, volume: 85 mL) on top of a clamp-attached measuring container (inner diameter: 50 mm, volume: 160 mL) and connecting them with a splitter. Toner conditioning was performed by carrying out the following first step, followed by three cycles of the following series of steps from step 2 to step 5. (Step 1) 100 g of toner was filled into the conditioning container, and the toner was allowed to stand for 10 minutes to form a toner layer. The amount of toner filled exceeded the capacity of the measuring container. (Step 2) The measurement container was set in an analyzer equipped with a propeller-type blade. The blade tip speed was set to 60 mm / sec, and the blade entry angle was set to 5° clockwise. While stirring the toner layer with the blade, the blade was passed from the surface of the toner layer into the interior of the toner layer, reaching a position 10 mm from the bottom of the measurement container. (Step 3) The blade tip speed was not changed, but the blade entry angle was changed to 2° clockwise. While stirring the toner layer, the blade was lowered to a position 1 mm from the bottom of the measurement container. (Step 4) The blade tip speed was not changed, but the blade entry angle was changed to 5° counterclockwise. While stirring the toner layer, the blade was raised to a position 100 mm from the bottom of the measurement container. (Step 5) The blade was lifted from the surface of the toner layer. When the second step was performed after the fifth step, the blade that had been lifted from the surface of the toner layer in the fifth step was rotated alternately in small clockwise and counterclockwise directions to remove excess toner adhering to the blade before the second step was performed. After toner conditioning, the attached container was removed, and the toner above the edge of the measurement container was scraped off with a splitter to produce a toner cake with the same volume as the measurement container. The value obtained by dividing the mass of the obtained toner cake by the volume of the measurement container was taken as the packed bulk density (g / mL).

[0231] 5. Loose Bulk Density The toner was poured into a 100 mL SUS cylindrical container, left to stand for 30 seconds, and any toner that had risen above the top surface of the container was scraped off. The weight of the toner in the container was then divided by the volume of the toner (100 mL) to determine the loose bulk density (g / mL).

[0232] For each toner, the difference between the compacted bulk density and the loose bulk density obtained above (compacted bulk density - loose bulk density) was calculated.

[0233] 6. Storage Stability 20 g of toner was placed in a 100 mL polyethylene container and sealed. The container was then submerged in a thermostatic water bath set at a predetermined temperature and removed after 8 hours. The toner was transferred from the removed container onto a 42-mesh sieve while minimizing vibration and set in a powder measuring instrument (manufactured by Hosokawa Micron Corporation, product name: Powder Tester (registered trademark) PT-R). The sieve amplitude was set to 1.0 mm, and the sieve was vibrated for 30 seconds. The mass of the toner remaining on the sieve was measured and defined as the mass of the aggregated toner. The maximum temperature at which the mass of the aggregated toner became 1.0 g or less was defined as the heat-resistant temperature of the toner. The higher the heat-resistant temperature, the less likely the toner is to block during storage and the better the storage stability. The storage stability of the toner was evaluated based on the heat-resistant temperature of the toner. (Evaluation Criteria) A: Toner has a heat resistance temperature of 54°C or higher B: Toner has a heat resistance temperature of 53°C or higher but lower than 54°C C: Toner has a heat resistance temperature of 52°C or higher but lower than 53°C D: Toner has a heat resistance temperature of 51°C or higher but lower than 52°C

[0234] 7. Spouting after Printing Durability Using a commercially available non-magnetic single-component development printer (HL-3040CN), toner was filled into the toner cartridge of the developing device, and then printing paper was set. The printer was left in a high-temperature, high-humidity environment (temperature: 32.5°C, humidity: 80% RH) for 24 hours, and then a durability test was conducted in which 10,000 sheets were continuously printed at 5% print density under the same environment. After that, the toner in the cartridge was extracted, and it was confirmed whether or not the toner spilled (spouted) from the developing roller of the cartridge, and evaluated according to the following evaluation criteria. (Evaluation Criteria) A: No toner spillage from the developing roller was observed even when the cartridge was tilted. B: Toner spillage was observed from part of the developing roller when the cartridge was tilted. C: Toner spillage was observed from part of the developing roller even without tilting the cartridge. D: Toner spillage was observed from the entire developing roller even without tilting the cartridge.

[0235] The measurement and evaluation results for the magenta toner are shown in Table 1 together with the toner composition, the measurement and evaluation results for the yellow toner and cyan toner are shown in Table 2 together with the toner composition, and the measurement and evaluation results for the black toner are shown in Table 3 together with the toner composition.

[0236]

[0237]

[0238] Magenta toners M-1 to M-11 and M-14, yellow toners Y-1 to Y-4 and Y-7, and cyan toners C-1 to C-4 and C-6 contained an ester wax with a molecular weight of 600 to 3000 as a softener and the external additive A as an external additive. Therefore, the UFP generation temperature was high, i.e., UFP generation was suppressed. Furthermore, among these toners, toners with a tan δ (100°C) of 0.950 or less had a particularly high heat resistance temperature and excellent storage stability. On the other hand, magenta toners M-12 to M-13, yellow toners Y-5 to Y-6, and cyan toner C-5 did not contain the external additive A as an external additive. Therefore, they were prone to toner ejection from the cartridge when continuously printing in a high-temperature, high-humidity environment. Furthermore, all of the toners shown in Tables 1 and 2 had a tan δ (100° C.) of 0.840 or more.

[0239]

[0240] Black toners K-1 to K-5 contained an ester wax with a molecular weight of 600 to 3000 as a softener and the external additive A as an external additive, and therefore had a high UFP generation temperature, i.e., UFP generation was suppressed. Furthermore, even when continuously printed in a high-temperature, high-humidity environment, the toners were less likely to eject toner from the cartridge. Furthermore, black toners K-1 to K-5 had excellent storage stability, although their tan δ (100°C) exceeded 0.950. This is presumably due to the large amount of macromonomer added.

[0241] <Toner Sets> [Examples 1 to 6 and Comparative Examples 1 to 3] The toner sets of Examples 1 to 6 and Comparative Examples 1 to 3 were prepared by combining the leading color toner and the other color toners according to Table 4. Table 4 shows the absolute value of the difference between the tan δ (100°C) of the leading color toner and the tan δ (100°C) of the other color toners in each toner set.

[0242] [Peeling Evaluation] A commercially available non-magnetic single-component development printer (printing speed: 20 sheets / min) was modified to allow the temperature of the fuser roll to be changed. Print paper was loaded, and a developing device containing the leading color toner and other color toners was set according to Table 4. Solid secondary color printing (100% print density) was performed by overlapping the transfer paper to form a 5 cm x 20 cm rectangle 0.5 cm from the leading edge in the paper feed direction. The temperature of the fuser roll was changed from 200°C to 150°C in 5°C increments, and solid secondary color printing was performed in the same manner. Peeling at the interface between the toner layer and the paper surface, peeling between overlapping printed toner layers, or peeling within the toner layer was visually confirmed. The temperature of the fuser roll during printing of the print that exhibited peeling was recorded as the peeling temperature. The evaluation method was graded into three categories: A, B, and F. The lower the peeling temperature, the better the multilayer fixing of the toner layers can be evaluated, so the order of excellent multilayer fixing is A, B, and F, which is a failure. The evaluation results are shown in Table 4. <Evaluation criteria> A: Peeling temperature is 160°C or less B: Peeling temperature is over 160 to 170°C F: Peeling temperature is over 170°C

[0243] [UFP Generation] A developing device filled with the leading color toner and other color toners according to Table 4 was set in a full-color printer (HL-L3230CDW manufactured by Brother Industries, Ltd., print speed: 24 pages / min), and then print paper was set. Continuous printing of secondary color images was performed for 5 minutes at 5% print density using the full-color printer in a chamber at 160°C. Immediately after the 5-minute continuous printing, the number of ultrafine particles (UFPs) with a particle size range of 10 to 1,000 nm present in the chamber was measured using a particle counter (TSI, model: CPC3007). This continuous printing and UFP measurement were performed at each temperature, with the chamber temperature being increased in increments of 5°C from 160°C, to identify the lowest temperature at which the UFP count reached 10,000. The toner set was evaluated for its resistance to UFP generation based on the lowest temperature at which the UFP count reached 10,000 when multicolor images (secondary color images in the toner set of Table 4) were continuously printed. <Evaluation criteria> A: The lowest temperature at which the UFP count reached 10,000 was 190°C or higher B: The lowest temperature at which the UFP count reached 10,000 was 170°C or higher and lower than 190°C C: The lowest temperature at which the UFP count reached 10,000 was 160°C or higher and lower than 170°C D: The lowest temperature at which the UFP count reached 10,000 was lower than 160°C

[0244] [Spouting after Printing Durability] A developing device filled with the leading color toner and other color toners according to Table 4 was set in a commercially available non-magnetic single-component development printer (HL-3040CN), and then printing paper was set. The printer was left in a high-temperature, high-humidity environment (temperature: 32.5°C, humidity: 80% RH) for 24 hours, and then a durability test was conducted in which secondary color images were continuously printed up to 10,000 sheets at 5% print density under the same environment. After that, the toner in each of the leading color toner cartridge and other color toner cartridges was removed from the cartridge, and it was confirmed whether or not the toner spilled (spouted) from the developing roller of the cartridge, and the evaluation was performed according to the following evaluation criteria. (Evaluation criteria) A: For all cartridges, toner spillage from the developing roller was not observed even when the cartridge was tilted. B: For at least one cartridge, toner spillage from part of the developing roller was observed when the cartridge was tilted. C: For at least one cartridge, toner spillage from part of the developing roller was observed even when the cartridge was not tilted. D: For at least one cartridge, toner spillage from the entire surface of the developing roller was observed even when the cartridge was not tilted.

[0245]

[0246] In the toner sets of Examples 1 to 6, the absolute value of the difference between the tan δ (100°C) of the top color toner and the tan δ (100°C) of the other color toners was 0.140 or less, so the temperature at which peeling occurs during overprinting was low, i.e., peeling of the toner layers was suppressed. The results of the peeling evaluation of Examples 1 to 6 showed that if the difference in tan δ (100°C) between toners used in overprinting of secondary colors is 0.140 or less, peeling at the interface between the toner layer and the paper surface, peeling between toner layers, and peeling within the toner layer are suppressed. The above-mentioned peeling evaluation is the result of performing overlapping printing of secondary colors, but according to the toner set of the present disclosure that satisfies the above formulas (I), (II), and (III), by performing overlapping printing using yellow toner, magenta toner, and cyan toner, the difference in tan δ (100°C) between the overlapping toners is 0.140 or less, so even when printing tertiary or higher colors, peeling at the interface between the toner layer of the first color and the paper surface is suppressed, and further, peeling between subsequently printed toner layers and peeling within the toner layers is suppressed. Furthermore, the toners contained in the toner sets of Examples 1 to 6 are toners that are unlikely to cause UFP and are unlikely to spray out of the cartridge when continuously printing in a high-temperature, high-humidity environment, so even when performing overlapping printing of secondary colors using these toner sets, UFP was unlikely to occur and spraying out was unlikely to occur when continuously printing in a high-temperature, high-humidity environment. The reason why the toner sets of Examples 1 and 3 to 6 were particularly unlikely to cause ejection when continuously printing in a high-temperature, high-humidity environment is presumed to be because the difference between the compacted bulk density and the loose bulk density (compacted bulk density - loose bulk density) was particularly small for each toner included in the toner set. Note that although the toner sets of Examples 1 to 6 consist of two-color toner, even in toner sets containing yellow toner, magenta toner, and cyan toner, if these toners are unlikely to cause UFP and ejection from the cartridge when continuously printing in a high-temperature, high-humidity environment, it is clear from the evaluation results of Examples 1 to 6 that when a full-color image is printed using the toner set, UFP is unlikely to occur and ejection is unlikely to occur when continuously printing in a high-temperature, high-humidity environment.

[0247] On the other hand, in the toner sets of Comparative Examples 1 and 2, the absolute value of the difference between the tan δ (100°C) of the leading color toner and the tan δ (100°C) of the other color toners exceeded 0.140, and therefore the temperature at which peeling occurred during overprinting was high, i.e., peeling of the toner layers was likely to occur. In the toner set of Comparative Example 3, although the absolute value of the difference between the tan δ (100°C) of the leading color toner and the tan δ (100°C) of the other color toners was 0.140 or less, peeling of the toner layers was likely to occur because magenta toner M-12 was a toner that did not contain external additive A. This is presumably due to the poor fixability of magenta toner M-12 that does not contain external additive A. Furthermore, in the toner sets of Comparative Examples 1 to 3, at least one toner was prone to ejection from the cartridge when continuous printing was performed in a high-temperature, high-humidity environment, and therefore, when the toner sets were used to continuously print overlapping secondary colors in a high-temperature, high-humidity environment, toner ejection was also prone to occur.

[0248] [Examples 7 to 14 and Comparative Examples 4 to 5] The toner sets of Examples 7 to 14 and Comparative Examples 4 to 5 were prepared by combining the top color toner and the other color toners according to Table 5. The toner sets were prepared by overlaying the top color toner, the second other color toner, the third other color toner, and the fourth other color toner in this order, with the black toner being the outermost toner. For each toner set, the tan δ (100°C) of each of the yellow, magenta, cyan, and black toners, the absolute value of the difference in tan δ (100°C) between the yellow, magenta, and cyan toners, and the value of "|{tan δ(C, 100°C) + tan δ(M, 100°C) + tan δ(Y, 100°C)} - tan δ(K, 100°C) × 3| / 3" in the above formula (IV) are shown in Table 5.

[0249] The toner sets of Examples 7 to 14 and Comparative Examples 4 to 5 were evaluated in the same manner as the peeling evaluation, UFP occurrence evaluation, and post-printing ejection evaluation conducted for Examples 1 to 6 and Comparative Examples 1 to 3. For the peeling evaluation, a solid print of a quaternary color was performed, and for the durability tests for the evaluation of UFP occurrence and post-printing ejection evaluation, continuous printing of a quaternary color image was performed. The evaluation results are shown in Table 5. The toner sets of Examples 7 to 14 and Comparative Examples 4 to 5 were also evaluated for the following charge buildup property.

[0250] [Charge Rise] The blow-off charge of each color toner constituting the toner set was measured in a high-temperature, high-humidity (HH) environment (32.5°C, 80% RH) and a low-temperature, low-humidity (LL) environment (10°C, 20% RH) using the following procedure. 0.25 g of toner and 9.75 g of uncoated spherical Mn-Mg-Sr-Fe ferrite carrier with an average particle diameter of 60 μm were placed in a glass container with a volume of 30 cc (internal bottom diameter of 30 mm, height of 50 mm). Two glass containers were prepared. Triboelectric charging was performed by stirring the mixture using a roller stirrer at 160 rpm for a predetermined period of time. One glass container was stirred for 3 minutes, and the other was stirred for 30 minutes. 0.2 g of the mixture of the toner and the ferrite carrier after the triboelectric charging treatment was placed in a Faraday cage and blown off for 30 seconds using a blow-off powder charge measurement device under a nitrogen gas pressure of 0.098 MPa to measure the blow-off charge (μC / g) of the toner. For each toner, the blow-off charge of the toner stirred for 3 minutes and the blow-off charge of the toner stirred for 30 minutes were determined, and the initial charge was calculated using the following formula: Initial charge (%) = "Blow-off charge of toner stirred for 3 minutes" / "Blow-off charge of toner stirred for 30 minutes" x 100. The minimum and maximum initial charge values ​​of each color toner constituting the toner set measured under a high-temperature, high-humidity (HH) environment were used to determine the difference between them, and this was used as the initial charge difference under a high-temperature, high-humidity (HH) environment. Based on this initial charge difference, the charge initial property under a high-temperature, high-humidity (HH) environment was evaluated according to the following evaluation criteria. Furthermore, the difference between the minimum and maximum values ​​of the charge-up amount of each color toner constituting the toner set in a low-temperature, low-humidity (LL) environment was calculated, and this difference was taken as the charge-up amount difference in a low-temperature, low-humidity (LL) environment. Based on this charge-up amount difference, the charge-up performance in a low-temperature, low-humidity (LL) environment was evaluated according to the following evaluation criteria. (Evaluation criteria) A: Charge-up amount difference is 10% or less B: Charge-up amount difference is less than 10% and 20% or less C: Charge-up amount difference is more than 20% and less than 40% D: Charge-up amount difference is 40% or more

[0251]

[0252] The toner sets of Examples 7 to 14 contained a yellow toner, a magenta toner, a cyan toner, and a black toner, and satisfied the above formulas (I), (II), (III), and (IV). Tan δ(K, 100°C) was higher than tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C). Therefore, the temperature at which peeling occurs during overprinting was low, i.e., peeling of the toner layers was suppressed. Furthermore, in the toner sets of Examples 7 to 14, each color toner had the above-described viscoelasticity, and each color toner contained both the external additive A and the external additive B. Therefore, the balance between fluidity and hydrophobicity between the color toners was good, and thus the charge buildup was excellent in both high-temperature, high-humidity environments and low-temperature, low-humidity environments. Furthermore, the toners contained in the toner sets of Examples 7 to 14 were less likely to cause UFP and less likely to eject from the cartridge when continuously printed in a high-temperature, high-humidity environment. Therefore, even when these toner sets were used to perform quaternary color overprinting, UFP was less likely to occur and ejection was less likely to occur when continuously printed in a high-temperature, high-humidity environment. On the other hand, the toner sets of Comparative Examples 4 and 5 had an absolute value of the difference between the tan δ (100°C) of the top color toner and the tan δ (100°C) of the other color toners that exceeded 0.140, resulting in a high peeling temperature during overprinting, i.e., a tendency for peeling of the toner layers to occur. Furthermore, in the toner sets of Comparative Examples 4 and 5, the yellow toner and cyan toner did not contain external additive A, and the tan δ (100°C) of the black toner was either too high or too low, resulting in an imbalance between the fluidity and hydrophobicity of the individual color toners. As a result, the charge buildup was poor in both high-temperature, high-humidity and low-temperature, low-humidity environments. Furthermore, in the toner sets of Comparative Examples 4 and 5, at least one toner was prone to ejection from the cartridge when continuous printing was performed in a high-temperature, high-humidity environment, and therefore, when continuous printing of overlapping quaternary colors was performed using the toner sets in a high-temperature, high-humidity environment, toner ejection was also prone to occur.

[0253] 100 Image forming apparatus R Recording material D Conveying direction 1 Developing unit (1Y, 1M, 1C, 1K) 2 Transfer medium (2Y, 2M, 2C, 2K) 3 Support roll (3Y, 3M, 3C, 3K) 4 Conveying path 5 Exposure device 6 Fixing roll 7 Support roll 11 Photosensitive member (11Y, 11M, 11C, 11K) 12 Charging roll (12Y, 12M, 12C, 12K) 13 Laser light irradiation unit (13Y, 13M, 13C, 13K) 14 Developing unit (14Y, 14M, 14C, 14K) 15 Cleaning unit (15Y, 15M, 15C, 15K) 16 Toner storage unit (16Y, 16M, 16C, 16K)

Claims

1. A toner set including toners of multiple colors each containing colored resin particles including a binder resin, a colorant, a softener, and a charge control agent, and an external additive, wherein the toners of multiple colors include at least a yellow toner, a magenta toner, and a cyan toner, and the yellow toner, magenta toner, and cyan toner each contain, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, and titanium oxide fine particles, A toner set, wherein the loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and satisfy the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (III).

2. The toner set according to claim 1, wherein the yellow toner, magenta toner and cyan toner further contain external additive B, which is silica microparticles, as the external additive, and in each of the yellow toner, magenta toner and cyan toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of external additive A relative to 100% by mass of the total amount of external additive A and external additive B is 16% by mass or more and 51% by mass or less.

3. An image forming method using the toner set according to claim 1 or 2.

4. A toner set including toners of multiple colors each containing colored resin particles including a binder resin, a colorant, a softener, and a charge control agent, and an external additive, wherein the toners of multiple colors include at least a yellow toner, a magenta toner, and a cyan toner, and the yellow toner, magenta toner, and cyan toner each contain, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, titanium oxide fine particles, aluminum oxide fine particles, and aluminum hydroxide fine particles, A toner set, wherein the loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and satisfy the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C)| ≦ 0.140 (III).

5. The toner set according to claim 4, wherein the external additive A contains metal titanate fine particles and aluminum oxide fine particles.

6. The toner set according to claim 4 or 5, wherein the yellow toner, magenta toner and cyan toner further contain external additive B, which is silica microparticles, as the external additive, and in each of the yellow toner, magenta toner and cyan toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of external additive A relative to 100% by mass of the total amount of external additive A and external additive B is 16% by mass or more and 51% by mass or less.

7. An image forming method using the toner set according to claim 4 or 5.

8. A toner set including toners of multiple colors each containing colored resin particles including a binder resin, a colorant, a softener, and a charge control agent, and an external additive, wherein the toners of multiple colors include a yellow toner, a magenta toner, a cyan toner, and a black toner, and the yellow toner, magenta toner, cyan toner, and black toner each contain, as the softener, an ester wax having a molecular weight of 600 to 3000, and as the external additive, external additive A which is at least one selected from the group consisting of metal titanate fine particles, zinc oxide fine particles, titanium oxide fine particles, aluminum oxide fine particles, and aluminum hydroxide fine particles, The loss tangent at 100°C of the yellow toner (tan δ(Y, 100°C)), the loss tangent at 100°C of the magenta toner (tan δ(M, 100°C)), and the loss tangent at 100°C of the cyan toner (tan δ(C, 100°C)), which are specified from a temperature dependency curve of the loss tangent (tan δ) of the toner obtained by dynamic viscoelasticity measurement at a measurement frequency of 24 Hz, are all 0.840 or more, and satisfy the following formulas (I), (II), and (III): |tan δ(M, 100°C) - tan δ(Y, 100°C)| ≦ 0.140 (I) |tan δ(M, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (II) |tan δ(Y, 100°C) - tan δ(C, 100°C) | ≦ 0.140 (III) A toner set in which the loss tangent at 100°C (tan δ(K, 100°C)) of the black toner is higher than each of the tan δ(Y, 100°C), tan δ(M, 100°C), and tan δ(C, 100°C), and the following formula (IV) is satisfied: 0.10<|{tan δ(C, 100°C)+tan δ(M, 100°C)+tan δ(Y, 100°C)}-tan δ(K, 100°C)×3| / 3<0.30 (IV) 9. The toner set according to claim 8, wherein the external additive A contains metal titanate fine particles and aluminum oxide fine particles.

10. The toner set according to claim 8 or 9, wherein the yellow toner, magenta toner, cyan toner and black toner further contain external additive B, which is silica microparticles, as the external additive, and in each of the yellow toner, magenta toner, cyan toner and black toner, the content of the external additive relative to 100 parts by mass of the colored resin particles is 2.0 parts by mass or more and 6.0 parts by mass or less, and the content of external additive A relative to 100% by mass of the total amount of external additive A and external additive B is 16% by mass or more and 51% by mass or less.

11. An image forming method using the toner set according to claim 8 or 9.

12. The image forming method according to claim 11, wherein a multi-color image formed by overlaying colors in the order of yellow toner, magenta toner, cyan toner and black toner, or in the order of magenta toner, yellow toner, cyan toner and black toner, is fixed to a recording material so that the black toner is on the outermost surface.

Images