Toner set

Abstract

The present invention provides a toner set and an image forming method which provide excellent gradation and color reproducibility to an image including multiple colors and high printing durability against continuous printing, and which enable printing of full-color images. When a toner having one color, selected from a group of toners having various colors included in the toner set, is defined as a first toner, and a toner having another color is defined as a second toner, the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner satisfy relationships represented by the formulae (1) and (2). Formula (1): θ1<θ2, formula (2): 1°≤θ2-θ1≤3°. An image including multiple colors is formed by transferring a first image developed by using the first toner and a second image developed by using the second toner onto a recording material or a transfer medium in this order.

Description

[Technical field]

[0001] The present disclosure relates to a toner set including a combination of electrostatic image developing toners (hereinafter, sometimes simply referred to as "toners") used for developing electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, and the like, and an image forming method using the toner set. [Background technology]

[0002] 2. Description of the Related Art In image forming apparatuses such as electrophotographic apparatuses, electrostatic recording apparatuses, and electrostatic printing apparatuses, an image forming method in which a desired image is formed by developing an electrostatic latent image formed on a photoconductor with a toner for developing an electrostatic image is widely practiced, and is applied to copiers, printers, facsimiles, and combination machines thereof. For example, in an electrophotographic device 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 an image to be reproduced or a corresponding negative image. The electrostatic latent image is then developed with a 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 a toner for developing an electrostatic image, the original image to be reproduced is separated into the three primary colors of yellow (Y), magenta (M), and cyan (C), or black (K) and each of the four primary colors is added to the three primary colors. An electrostatic latent image of each color component is formed on a separate photoconductor, and developed to form a primary color toner image of each color component. Then, the primary color toner image of each color component is transferred in registration onto a transfer receiving material selected from a recording material and a transfer medium to form a multi-color toner image including multi-colors such as secondary colors and tertiary colors generated by color superposition, and when the multi-color toner image is formed on the transfer medium, it is transferred to the recording material. Thereafter, the multi-color toner image on the recording material is fixed by heating or the like to obtain a full-color image including a gradation region of the multi-colors.

[0004] Patent Document 1 aims to provide a toner for developing electrostatic images that has excellent gradation properties when a multi-color halftone image is formed, and discloses, as a toner that can achieve the aim, an electrostatic image developing toner containing toner particles having a large diameter volume particle size distribution index (GSDv(90 / 50)) of 1.26 or less, a small diameter number particle size distribution index (GSDp(50 / 10)) of 1.28 or less, a GSDv(90 / 50) / GSDp(50 / 10) of 0.96 or more and 1.01 or less, and an average circularity of 0.95 or more and 1.00 or less, and a toner set having toners of different colors, each of which is an electrostatic image developing toner containing the above toner particles. Cited Document 1 describes an experiment in which a printing test was performed using the toner of Cited Document 1. In this experiment, an original image is color-separated to obtain data for each color component, a plurality of single-toner images of different colors are formed based on the data for each color component, these images are transferred sequentially onto a transfer medium, colors are superimposed on the transfer medium to form a full-color image, and then the full-color image is transferred from the transfer medium to a recording material, whereby the printing test is performed.

[0005] Patent Document 2 aims to provide a toner that can provide high-quality output without image defects such as fog and ghosts even when used for a long period of time in a printer using a high-speed one-component development method in a low-temperature, low-humidity environment, and discloses a toner that can achieve this aim, which has toner particles containing a binder resin and a colorant, and fine particles A present on the surfaces of the toner particles, the fine particles A having the following characteristics (i), (ii), and (iii): (i) Adhering or adhering to the surface of toner particles; (ii) fine particles having a charge control agent on the surface thereof, (iii) in the number-based particle size distribution of the fine particles A, the half-value width of the maximum peak in the range of 1 μm or less is 200 nm or less, The toner has a wall surface friction angle θ of 16° or less, as calculated by the following formula (1): The interparticle force Fp of the toner is 2.0×10 -8 N or less, The adhesion rate of the fine particles A on the surface of the toner is 50% by mass or more. Equation (1): θ=τ / 3.0 Equation (1) (where τ represents the shear stress obtained when a circular disk is rotated at (π / 36) rad at (π / 10) rad / min while being inserted with a vertical load of 3.0 kPa into a toner powder layer formed by applying a vertical load of 9.0 kPa.) Cited Document 2 describes the results of an experiment in which an image of a single toner was output on paper, and the resulting image output was evaluated for halftone image density in-plane stability, fog density, and transfer efficiency. In this experiment, a printing test was conducted using a single toner, and a printing test in which a full-color image was formed using toners of multiple colors was not conducted. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-61178 A [Patent Document 2] JP 2018-45004 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present disclosure is to provide a toner set and an image forming method capable of printing full-color images using an electrostatic image development method, which have excellent gradation and color reproducibility of images including multi-color images, and also have excellent printing durability in continuous printing. [Means for solving the problem]

[0008] According to the present disclosure, a toner of a plurality of colors is combined, the toner including colored resin particles including a binder resin, a colorant, and a charge control agent, The combination is a color toner set for developing an electrostatic image, the color toner set including at least a yellow toner, a cyan toner, and a magenta toner, Provided is a color toner set for developing electrostatic images, characterized in that when a toner of one color selected from a group consisting of toners of each color included in the toner set is defined as a first toner and a toner of the other color is defined as a second toner, the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner satisfy the relationship represented by the following formulas (1) and (2). θ1<θ2 Equation (1) 1°≦θ2-θ1≦3° Formula (2)

[0009] In one embodiment of the present disclosure, the color toner set for developing electrostatic images is used in a full-color printer that includes a plurality of developing machines corresponding to the respective color toners included in the toner set, and that sequentially transfers primary color images of the respective colors generated by the respective developing machines onto a transfer receiving material selected from the group consisting of a recording material and a transfer medium, thereby forming an image including multiple colors on the transfer receiving material, the first toner is a top color toner designated for use in a developing machine that produces a primary color image that is transferred first onto the transfer receiving material; The second toner, which is a toner of another color, is a toner defined to be used in a developing machine which produces a primary color image which is transferred second or later onto the transfer receiving material.

[0010] In one embodiment of the present disclosure, the first toner is a toner of one color selected from the group consisting of a yellow toner, a cyan toner, and a magenta toner.

[0011] In one embodiment of the present disclosure, the angle θ1 is equal to or greater than 17° and equal to or less than 20°, and the angle θ2 is equal to or greater than 20° and equal to or less than 23°.

[0012] In one embodiment of the present disclosure, the first toner contains, as an external additive, silicone resin particles having a ratio (BS / TS) of a BET specific surface area (BS) measured by a gas adsorption method to a theoretical specific surface area (TS) calculated by a theoretical formula from a number average particle diameter measured by observation with a scanning electron microscope (SEM) in the range of 3.0 to 30.0, and a number average particle diameter of 0.05 to 1.00 μm; The second toner does not contain the silicone resin particles.

[0013] In one embodiment of the present disclosure, the first toner and the second toner further contain, as an external additive, silica particles A having a number average particle size of 5 nm to 30 nm and having a surface hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil; The content of the silica particles A in the second toner is 1.1 times or more the content of the silica particles A in the first toner.

[0014] In one embodiment of the present disclosure, the first toner and the second toner further contain, as an external additive, silica particles B having a number average particle size of 31 nm to 200 nm and having a surface hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil; The content of the silica particles B in the second toner is 1.1 times or more the content of the silica particles B in the first toner.

[0015] In one embodiment of the present disclosure, the colored resin particles of the first toner and the second toner have an average circularity of 0.97 or more and 1.00 or less.

[0016] According to the present disclosure, the electrostatic image developing color toner set is used to image A method for forming an image by a full-color printer using a development method, comprising the steps of: developing a first image, which is a primary color image formed with the first toner; developing a second image, which is a primary color image of each color formed with the second toner; forming an image including multi-colors on a transfer medium by transferring the first image onto the transfer medium and then transferring the second image onto the transfer medium; A step of transferring the image including the multi-color formed on the transfer medium onto a recording material; and There is provided an image forming method having a step of fixing, on a recording material, an image including multiple colors transferred onto the recording material.

[0017] According to the present disclosure, the electrostatic image developing color toner set is used to image Another method for forming an image by a development type full color printer, comprising the steps of: developing a first image, which is a primary color image formed with the first toner; developing a second image, which is a primary color image of each color formed with the second toner; a step of transferring the first image onto a recording material, and then transferring the second image onto the recording material to form an image including a multi-color image; and There is provided an image forming method having a step of fixing an image including multiple colors formed on a recording material onto the recording material.

[0018] In one embodiment of the present disclosure, paper is used as the recording material. Effect of the Invention

[0019] According to the toner set and image forming method of the present disclosure as described above, when a full-color image is printed by an electrostatic charge image development method, a full-color image having excellent gradation and color reproducibility including multi-colors such as secondary colors and tertiary colors, and also excellent printing durability in continuous printing, can be obtained. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating an example of an image forming apparatus to which an image forming method according to the present disclosure can be applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present disclosure is described in detail below. In this disclosure, a "primary color" is a color obtained when a toner of each color is printed alone, a "secondary color" is a color obtained when two primary color toner images are overlapped, and a "multiple colors" is a color obtained when multiple primary color toner images are overlapped. In addition, in this disclosure, the term "toner image" literally means an image formed from toner, but is used particularly when it is desired to emphasize that the state in which toner is distributed on an image-bearing surface such as a photoconductor, transfer medium, or recording material in accordance with the image to be reproduced is perceived as a visual image. In addition, in this disclosure, "leading color" means the color of the primary color toner image that is transferred first onto a transfer receiving material when multiple toner developing machines are used to form primary color toner images of each color, and then the primary color toner images are transferred sequentially onto a single transfer receiving material (recording material or transfer medium) to form a full-color image by overlaying colors on the transfer receiving material. In addition, in this disclosure, the "leading developer" refers to a developer that develops a primary color toner image of a leading color. When multiple toner developers are arranged in series along the transport path of a transfer receiver (recording material or transfer medium) in a developing device, the developer that the transfer receiver traveling along the transport path encounters first is the "leading developer."

[0022] The methods for forming full-color images using electrostatic image development can be broadly divided into the following two types depending on the transfer process. (1) A method in which an original image is color-separated to obtain data for each color component, multiple single-toner images of multiple colors are formed based on the data for each color component, these images are transferred sequentially onto a transfer medium, colors are layered on the transfer medium to form a full-color image, and then the full-color image is transferred from the transfer medium to a recording material. (2) A method in which an original image is separated into colors to obtain data for each color component, multiple single-color toner images are formed based on the data for each color component, and these images are transferred sequentially onto a single recording material, where they are overlaid to form a full-color image. The present inventor has discovered that in any of the above methods, when the toner forming the primary color image transferred first onto the transfer receiving material (recording material or transfer medium) where the colors are overlaid and the toner forming the primary color image transferred second or thereafter have a certain relationship in terms of the internal friction angle, the color reproducibility, color unevenness, and density unevenness of an image including multi-colors can be improved.

[0023] The toner set of the present disclosure is a combination of toners of multiple colors, each of which includes colored resin particles containing a binder resin and a colorant, The combination is a color toner set for developing an electrostatic image, the color toner set including at least a yellow toner, a cyan toner, and a magenta toner, When a toner of one color selected from a group consisting of toners of each color included in the toner set is defined as a first toner and a toner of the other color is defined as a second toner, the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner satisfy the relationship expressed by the following formulas (1) and (2). θ1<θ2 Equation (1) 1°≦θ2-θ1≦3° Formula (2)

[0024] The present disclosure also includes the following two image forming methods: the former is a method in which colors are superimposed on a transfer medium, and the latter is a method in which colors are superimposed on a recording material. The first method uses the color toner set of the present disclosure to image A method for forming an image by a full-color printer using a development method, comprising the steps of: a step of developing a first image, which is a primary color image formed with the first toner (first image developing step); A step of developing a second image, which is a primary color image of each color formed with the second toner (second image developing step). A step of transferring the first image onto a transfer medium, and then transferring the second image onto the transfer medium to form an image including multi-colors on the transfer medium (a color overlaying step on the transfer medium); A step of transferring the image including the multi-color formed on the transfer medium onto a recording material (a multi-color image transfer step); and The method is characterized by having a step of fixing the image including the multi-color transferred onto the recording material (fixing step).

[0025] The second method uses the color toner set of the present disclosure to remove electrostatic charges. image A method for forming an image by a full-color printer using a development method, comprising the steps of: a step of developing a first image, which is a primary color image formed with the first toner (first image developing step); A step of developing a second image, which is a primary color image of each color formed with the second toner (second image developing step). a step of transferring the first image onto a recording material, and then transferring the second image onto the recording material to form an image including a multi-color image on the recording material (a color overlaying step on the recording material); and The method is characterized by having a step of fixing the image including the multi-color formed on the recording material (fixing step).

[0026] The toner set disclosed herein is suitably applied to a printing method in which multiple primary color toners, such as yellow toner, cyan toner, and magenta toner, are used to develop electrostatic latent images corresponding to the individual primary colors to create individual primary color toner images on a developing machine, and the resulting individual primary color toner images are sequentially transferred onto a transfer receiving material selected from the group consisting of recording materials and transfer media, thereby overlaying colors on the transfer receiving material to form a full-color image. Here, when color overlay is performed on a recording material, the individual primary color toner images are transferred sequentially onto the recording material, either directly or via an intermediate transfer process from the toner image forming surface of the developing machine to a transfer medium, to form a full-color image including multiple colors on the recording material. On the other hand, when color overlay is performed on a transfer medium, each primary color toner image is transferred sequentially from the toner image forming surface of the developing machine onto one transfer medium, either directly or via an intermediate transfer process to another preceding transfer medium, and a full-color image including multi-colors is formed on the transfer medium, and then the full-color image on the transfer medium is transferred onto a recording material, either directly or via an intermediate transfer process to another succeeding transfer medium.

[0027] The first toner included in the toner set of the present disclosure is a primary color toner that is transferred first onto a transfer receiving material selected from the group consisting of recording materials and transfer media, and the second toner included in the toner set is a primary color toner that is transferred second or later onto a transfer receiving material in the process of color overlay on the transfer receiving material. The first toner is typically selected from the group consisting of a yellow toner, a cyan toner, and a magenta toner. The second toner is not limited to yellow toner, cyan toner, and magenta toner, and may be a toner of another color. For example, a black toner may be added as the second toner. In addition to the basic color yellow toner, cyan toner, or magenta toner, a toner of another yellow, cyan, or magenta toner whose color elements such as hue, color density, brightness, or vividness are different from the toner of the yellow, cyan, or magenta set as the basic color may be added as the second toner.

[0028] The reason why the toner set and image forming method of the present disclosure provide the above-mentioned effects is presumed to be as follows. In order to accurately reproduce an original image on a recording material using an electrostatic image development method, it is necessary to appropriately control the amount of toner adhered to each part of the recording material surface. Also, when creating a new image without an original image and expressing it on a recording material as intended, it is necessary to appropriately control the amount of toner adhered to each part of the recording material surface. Generally, the higher the fluidity of a toner for developing an electrostatic image, the more faithfully it can develop an electrostatic latent image on a photoreceptor. Therefore, from the viewpoint of obtaining a natural image with good gradation, it is desirable for the toner to have high fluidity.

[0029] However, the printing method in which an original image is color-separated to obtain data for each color component, an electrostatic latent image is formed based on the data for each color component, developed, and a plurality of primary color toner images are formed, which are then sequentially transferred onto a single transfer receiving material, and a full-color image is formed by overlaying the colors on the transfer receiving material has the following problems: (1) After the first primary color toner image is transferred onto the transfer receiving material, there are areas on the transfer receiving material where toner with high fluidity is already attached and areas where such toner is not attached. When the second or subsequent primary color toner images are transferred onto this transfer receiving material, if toner of another color, which is similarly highly fluid, is transferred onto the areas on the transfer receiving material where toner with high fluidity is already attached, the adhesion between the toners becomes insufficient, making it difficult to attach the toner to the desired position, and the toner attachment position shifts. (2) In a printing method that uses paper (recording paper) as the recording material and forms a full-color image by overlapping colors on the recording paper, paper dust present on the recording paper mixes with the primary color toner image of the leading color transferred to the recording paper, which tends to deteriorate the image quality of the primary color toner image of the leading color. In contrast, most of the paper dust is removed from the recording paper as the recording paper passes through the leading developer, so when the primary color toner images of the second and subsequent colors are transferred to the recording paper, the image quality of the primary color toner images of the second and subsequent colors transferred to the recording paper does not deteriorate due to the inclusion of paper dust. Therefore, it is highly necessary for the primary color toner image of the leading color to have a good image quality after being transferred onto the recording paper, compared with the primary color toner images of the second and subsequent colors. (3) In a printing method in which paper (recording paper) is used as the recording material and a full-color image is formed by overlapping colors on the recording paper, a decrease in electrostatic charge is observed, especially in the leading color, due to the inclusion of paper dust from the paper, which is an obstacle to improving the printing durability of continuous printing.

[0030] The present disclosure solves the above problems (1), (2), and (3) in a printing method for forming a full-color image by sequentially transferring multiple primary color images onto one transfer receiving material (recording material or transfer medium) and overlaying the colors on the transfer receiving material, by using a color toner set for developing electrostatic images, in which the internal friction angle θ1 (°) of the toner (leading color toner) that forms the primary color toner image that is transferred first onto the transfer receiving material and the internal friction angle θ2 (°) of the toner (other toner) that forms the second or subsequent primary color toner images transferred onto the same transfer receiving material satisfy the following relationship expressions (1) and (2). θ1<θ2 Equation (1) 1°≦θ2-θ1≦3° Formula (2)

[0031] The internal friction angle of a toner is an index showing the degree of fluidity of the toner. The smaller the internal friction angle of a toner, the greater the fluidity of the toner, and the greater the internal friction angle of a toner, the smaller the fluidity of the toner. When the internal friction angle θ1 (°) of the leading color toner and the internal friction angle θ2 (°) of the other toners satisfy the relationship of the above formula (1), the fluidity of the leading color toner can be increased because the internal friction angle θ1 (°) of the leading color toner is small, and this improves the image quality of the primary color image that is transferred first onto the transfer receiving material. At the same time, the fluidity of the other toners that are transferred second or later onto the transfer receiving material can be reduced because the internal friction angle θ2 (°) of the other toners is large, and this improves the adhesive force between the leading toner and the following toner, allowing the following toner to adhere to the desired position when the second or later toner is transferred onto the leading color toner image that has already been transferred onto the transfer receiving material. In other words, color overlaying is also improved at the same time. In addition, the smaller the internal friction angle, the better the print durability of the toner. In a printing method that uses paper (recording paper) as the recording material and forms a full-color image by overlapping colors on the recording paper, if the internal friction angle θ1 (°) of the leading color toner and the internal friction angle θ2 (°) of the other toners satisfy the relationship of formula (1) above, the print durability of the leading color toner, which is affected by paper dust, is improved, and therefore the print durability of the entire toner set, which combines toners of multiple colors including the leading color toner, can also be improved. Furthermore, when the internal friction angle θ1 (°) of the leading color toner and the internal friction angle θ2 (°) of the other toners satisfy the relationship of the above formula (2), it is possible to achieve both the printing durability of the leading color toner, which is affected by paper powder, and secondary color reproducibility.

[0032] Therefore, the toner set and image forming method disclosed herein are a printing method in which a full-color image is formed by sequentially transferring multiple primary color images onto a single transfer receiving material and overlaying the colors on the transfer receiving material, and as a result, the image quality of the primary color image of the first color is improved while at the same time the color overlay properties of the primary color images of each color transferred second or thereafter are improved, resulting in a full-color image with excellent gradation and color reproducibility for images including multi-colors. Furthermore, even in a printing method in which paper (recording paper) is used as the recording material and a full-color image is formed by overlaying colors on the recording paper, the toner set and image forming method disclosed herein do not cause deterioration in image quality of the primary color image of the leading color and the print durability of the primary color toner of the leading color due to the inclusion of paper dust, so that a full-color image can be obtained that has excellent gradation and color reproducibility of images including multi-colors, and also has excellent print durability for continuous printing.

[0033] 1. Toner set The toner set of the present disclosure includes at least three toners of yellow, cyan, and magenta, and may further include toners of other colors. Each toner of the colors contains colored resin particles including a binder resin and a colorant, and an external additive. Hereinafter, a method for producing colored resin particles used in the present disclosure, colored resin particles obtained by the production method, a method for producing a toner using the colored resin particles and a toner obtained by the production method, and a toner set of the present disclosure combining these toners will be described in order.

[0034] 1-1. Manufacturing method of colored resin particles In general, 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 the wet methods being preferred because they are more likely to produce toners with excellent printing characteristics such as image reproducibility. Among the wet methods, the emulsion polymerization aggregation methods and polymerization methods such as suspension polymerization methods are more preferred because they are more likely to produce toners with a relatively small particle size distribution on the order of microns, and among the polymerization methods, suspension polymerization is more preferred.

[0035] In the emulsion polymerization aggregation method, an emulsified polymerizable monomer is polymerized to obtain a resin fine particle emulsion, which is then aggregated with a colorant dispersion liquid or the like to produce colored resin particles. In the dissolution suspension method, a solution in which toner components such as a binder resin and a colorant are dissolved or dispersed in an organic solvent is formed into droplets in an aqueous medium, and the organic solvent is removed to produce colored resin particles. Any known method can be used for either method.

[0036] The colored resin particles used in the present disclosure can be produced by adopting a wet method or a dry method. Among the wet methods, the suspension polymerization method is preferably adopted and is carried out by the following process.

[0037] (A) Suspension polymerization method (A-1) Preparation of polymerizable monomer composition First, a polymerizable monomer, a colorant, and optionally other additives such as a charge control agent are mixed to prepare a polymerizable monomer composition. For example, a media type dispersing machine is used for mixing when preparing the polymerizable monomer composition.

[0038] In the present disclosure, the polymerizable monomer refers to a monomer having a polymerizable functional group, and the polymerizable monomer is polymerized to form a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable 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. Of these, styrene, styrene derivatives, and acrylic acid esters or methacrylic acid esters are preferably used as monovinyl monomers.

[0039] In order to improve hot offset and storage stability, it is preferable to use any crosslinkable polymerizable monomer together with the monovinyl monomer. The crosslinkable polymerizable monomer is 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; compounds having three or more vinyl groups; etc. These crosslinkable polymerizable monomers can be used alone or in combination of two or more. In the present disclosure, it is desirable to use the crosslinkable polymerizable monomer in a proportion of usually 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass, based on 100 parts by mass of the monovinyl monomer.

[0040] Furthermore, it is preferable to use a macromonomer as a part of the polymerizable monomer, since the resulting toner has a good balance between storage stability and fixability at low temperature. The macromonomer is a reactive oligomer or polymer having a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and usually has a number average molecular weight of 1,000 to 30,000. The macromonomer is preferably one that gives a polymer having a glass transition temperature (hereinafter sometimes referred to as "Tg") higher than that of a polymer obtained by polymerizing a monovinyl monomer. The macromonomer is preferably used in an amount of 0.03 to 5 parts by mass, and more preferably 0.05 to 1 part by mass, based on 100 parts by mass of the monovinyl monomer.

[0041] Examples of yellow colorants used in yellow toners include compounds such as azo pigments, such as monoazo pigments and disazo pigments, and condensed polycyclic pigments, and examples of such compounds include CI Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 155, 180, 181, 185, 186, and 213.

[0042] Examples of magenta colorants used in magenta toners include compounds such as azo pigments, such as monoazo pigments and disazo pigments, and condensed polycyclic pigments, and examples of such compounds include CI Pigment Red 31, 48, 57:1, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 237, 238, 251, 254, 255, 269, and CI Pigment Violet 19.

[0043] Examples of cyan colorants that can be used in cyan toners include copper phthalocyanine compounds, derivatives thereof, and anthraquinone compounds. Specific examples include CI Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, and 60.

[0044] Examples of black colorants used in black toner include carbon black, titanium black, oil black, etc. The black carbon black preferably has a primary particle size of 20 to 40 nm.

[0045] In the present disclosure, each colorant can be used alone or in combination of two or more kinds. The amount of the colorant is preferably 1 to 10 parts by mass based on 100 parts by mass of the binder resin or 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer).

[0046] In the present disclosure, a charge control agent may be used to improve the chargeability of the toner. As the charge control agent, any charge control agent that has been conventionally used in toners may be used without any restrictions. Among the charge control agents, it is preferable to use a charge control resin. This is because the charge control resin has high compatibility with the binder resin, is colorless, and can provide a toner with stable chargeability even in high-speed continuous color printing. As the positive charge control resin, a quaternary ammonium (salt) group-containing copolymer manufactured in accordance with the descriptions in JP-A-63-60458, JP-A-3-175456, JP-A-3-243954, JP-A-11-15192, etc. can be used. As the negative charge control resin, a sulfonic acid (salt) group-containing copolymer manufactured in accordance with the descriptions in JP-A-1-217464, JP-A-3-15858, etc. can be used.

[0047] The amount of monomer units having a quaternary ammonium (salt) group or a sulfonic acid (salt) group contained in these copolymers is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass. When the content is within this range, the charge amount of the toner is easily controlled, and the occurrence of fog can be reduced. The charge control resin preferably has a weight average molecular weight of 2,000 to 50,000, more preferably 4,000 to 40,000, and most preferably 6,000 to 35,000. If the weight average molecular weight of the charge control resin is less than 2,000, offset may occur, whereas if it exceeds 50,000, fixability may deteriorate. The glass transition temperature of the charge control resin is preferably 40 to 80° C., more preferably 45 to 75° C., and most preferably 45 to 70° C. If the glass transition temperature is less than 40° C., the storage stability of the toner may deteriorate, and if it exceeds 80° C., the fixing property may decrease. The amount of the charge control agent is usually 0.01 to 30 parts by mass, and preferably 0.3 to 25 parts by mass, based on 100 parts by mass of the binder resin or 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer).

[0048] As another additive, a release agent can be added to the polymerizable monomer composition from the viewpoint of improving the releasability of the toner from the fixing roll during fixing. As the release agent, any agent generally used as a toner release agent can be used without any particular limitation. Examples of release agents include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; natural plant waxes such as candelilla, carnauba, rice, Japan wax, and jojoba; petroleum waxes and modified waxes thereof such as paraffin, microcrystalline, and petrolatum; synthetic waxes such as Fischer-Tropsch wax; ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, pentaerythritol tetrabehenate, behenyl behenate, and dipentaerythritol hexamyristate; and mineral waxes such as ozokerite. The release agent is preferably used in an amount of 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, based on 100 parts by mass of the binder resin or 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer).

[0049] As other additives, it is preferable to use a molecular weight modifier when polymerizing the polymerizable monomer that becomes the binder resin by polymerization. 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, and examples thereof include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol; 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; etc. These molecular weight regulators may be used alone or in combination of two or more kinds. In the present disclosure, it is desirable to use the molecular weight modifier in a proportion of usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, per 100 parts by mass of the binder resin or 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer).

[0050] As other additives, the composition may contain a styrene-based thermoplastic elastomer, which refers to a random, block, graft, or other copolymer of a styrene-based monomer and at least one other monomer selected from monoolefins, diolefins, and the like that can be copolymerized with the styrene-based monomer, and a hydrogenated product of such a copolymer. Furthermore, by containing a styrene-based thermoplastic elastomer in the toner, the fixability of the toner can be improved while maintaining the heat resistance temperature of the toner.

[0051] Representative examples of styrene-based thermoplastic elastomers include styrene-butadiene-styrene type block copolymers, styrene-butadiene type block copolymers, styrene-isoprene-styrene type block copolymers, styrene-isoprene type block copolymers, styrene-butadiene-isoprene-styrene type block copolymers, and hydrogenated products thereof; styrene-ethylene-butylene-styrene type block copolymers, styrene-ethylene-propylene-styrene type block copolymers, and styrene-ethylene-ethylene-propylene-styrene type block copolymers. Among these styrene-based thermoplastic elastomers, from the viewpoint of optimizing the balance between the storage stability and low-temperature fixability of the toner, a styrene-isoprene-styrene type block copolymer can be suitably used.

[0052] The styrene content in the styrene-based thermoplastic elastomer is preferably 15 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 20 to 40% by mass. When the styrene content is equal to or more than the lower limit, the proportion of hydrocarbon units is not too high, and the fixed toner is less likely to peel off from the fixing surface, so that a decrease in fixability is suppressed. On the other hand, when the styrene content is equal to or less than the upper limit, the compatibility with the binder resin is not too high, and a decrease in the storage stability of the toner is suppressed.

[0053] The weight average molecular weight Mw of the styrene-based thermoplastic elastomer is not particularly limited, but is preferably 50,000 to 350,000, and more preferably 80,000 to 250,000, from the viewpoint of excellent effect of improving the fixability of the toner while maintaining the heat resistance temperature of the toner.

[0054] The styrene-based thermoplastic elastomer is preferably used in an amount of 0.5 to 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 2 to 6 parts by mass, per 100 parts by mass of the binder resin or 100 parts by mass of the polymerizable monomer (preferably a monovinyl monomer). The styrene-based thermoplastic elastomers may be used alone or in combination of two or more.

[0055] (A-2) Suspension step for obtaining a suspension (droplet formation step) In the present disclosure, it is preferable to disperse a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in an aqueous medium preferably containing a dispersion stabilizer, add a polymerization initiator, and then form droplets of the polymerizable monomer composition. The method of forming droplets is not particularly limited, but may be performed using a device capable of strong stirring, such as an (in-line type) emulsifying disperser (manufactured by Pacific Machinery Works, product name: Milder) or a high-speed emulsifying disperser (manufactured by Primix Corporation, product name: TK Homomixer MARK II type).

[0056] 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-butyl peroxy-2-ethylhexanoate, t-butyl peroxydiethyl acetate, t-hexyl peroxy-2-ethylbutanoate, diisopropyl peroxydicarbonate, di-t-butyl peroxyisophthalate, and t-butyl peroxyisobutyrate. These can be used alone or in combination of two or more. Of these, it is preferable to use organic peroxides, since they can reduce the amount of residual polymerizable monomers and have excellent print durability.

[0057] Among organic peroxides, peroxy esters are preferred because they have good initiator efficiency and can reduce the amount of residual polymerizable monomers, and non-aromatic peroxy esters, i.e., peroxy esters that do not have an aromatic ring, are more preferred.

[0058] As described above, the polymerization initiator may be added after the polymerizable monomer composition is dispersed in an aqueous medium and before droplets are formed, or may be added to the polymerizable monomer composition before it is dispersed in an aqueous medium.

[0059] In the present disclosure, the aqueous medium refers to a medium whose main component is water. 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 above dispersion stabilizers can be used alone or in combination of two or more.

[0060] Among the above dispersion stabilizers, inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides, are preferred. By using an inorganic compound, particularly colloids of poorly water-soluble metal hydroxides, the particle size distribution of the colored resin particles can be narrowed and the amount of the dispersion stabilizer remaining after washing can be reduced, so that the toner obtained can clearly reproduce images and has excellent environmental stability.

[0061] (A-3) Polymerization process Droplets are formed as in the above (A-2), and the resulting aqueous dispersion medium is heated to initiate polymerization, forming an aqueous dispersion of colored resin particles. The polymerization temperature of the polymerizable monomer composition is preferably 50° C. or higher, and more preferably 60 to 95° C. The polymerization reaction time is preferably 1 to 20 hours, and more preferably 2 to 15 hours.

[0062] The colored resin particles may be used as a toner as they are by adding an external additive, but it is preferable to use the colored resin particles as a core layer and to form a shell layer different from the core layer on the outside of the core layer to obtain so-called core-shell type (also called "capsule type") colored resin particles. The core-shell type colored resin particles can achieve a balance between lowering the fixing temperature and preventing aggregation during storage by covering the core layer made of a material having a low softening point with a material having a higher softening point.

[0063] The method for producing the core-shell type colored resin particles using the above-mentioned colored resin particles is not particularly limited, and the core-shell type colored resin particles can be produced by a conventionally known method. In terms of production efficiency, the in situ polymerization method and the phase separation method are preferred.

[0064] A method for producing core-shell type colored resin particles by in situ polymerization will be described below. A polymerizable monomer for forming a shell layer (polymerizable monomer for shell) and a polymerization initiator are added to an aqueous dispersion medium in which colored resin particles are dispersed, and polymerized to obtain core-shell type colored resin particles.

[0065] 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 monomers such as styrene, acrylonitrile, and methyl methacrylate, which can give a polymer with a Tg exceeding 80° C., either alone or in combination of two or more kinds.

[0066] Examples of the polymerization initiator used for 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, based on 100 parts by mass of the shell polymerizable monomer.

[0067] The polymerization temperature for the shell layer is preferably 50° C. or higher, and more preferably 60 to 95° C. The polymerization reaction time is preferably 1 to 20 hours, and more preferably 2 to 15 hours.

[0068] (A-4) Washing, filtering, dehydrating, and drying steps After the polymerization is completed, the aqueous dispersion of the colored resin particles obtained by polymerization is preferably filtered, washed to remove the dispersion stabilizer, dehydrated, and dried in a conventional manner, and if necessary, the operations are repeated several times.

[0069] 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 an alkali to the aqueous dispersion of the colored resin particles to dissolve and remove the dispersion stabilizer in water. When a colloid of a poorly water-soluble inorganic hydroxide 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. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid can be used, but sulfuric acid is particularly preferable because of its high removal efficiency and its small burden on the production equipment.

[0070] The dehydration and filtration methods can be any of various known methods, and are not particularly limited. For example, centrifugal filtration, vacuum filtration, pressure filtration, etc. can be mentioned. The drying method is also not particularly limited, and various methods can be used.

[0071] (B) Crushing method When the colored resin particles are produced by the pulverization method, the process is as follows. First, the binder resin, the colorant, and optionally other additives such as a charge control agent are mixed using a mixer such as a ball mill, a V-type mixer, an FM mixer (product name, manufactured by Nippon Coke and Engineering Co., Ltd.), a high-speed dissolver, an internal mixer, or the like. Next, the mixture obtained above is kneaded while being heated using a pressure kneader, a twin-screw extrusion kneader, a roller, etc. The kneaded product obtained is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, a roller mill, etc. Further, it is finely pulverized using a pulverizer such as a jet mill or a high-speed rotary pulverizer, and then classified into a desired particle size using a classifier such as an air classifier or an airflow classifier to obtain colored resin particles by a pulverization method.

[0072] The binder resin and colorant used in the pulverization method, as well as other additives added as necessary, can be the same as those listed in the suspension polymerization method (A) above. 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, like the colored resin particles obtained by the suspension polymerization method (A) above.

[0073] As the binder resin, resins that have been widely used in toners can also be used. Specific examples of the binder resin used in the pulverization method include polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

[0074] 1-2. Colored resin particles The colored resin particles can be obtained by the above-mentioned production method such as (A) the suspension polymerization method or (B) the pulverization method. The colored resin particles constituting the toner will be described below. The colored resin particles described below include both core-shell type and non-core-shell type particles.

[0075] The volume average particle diameter (Dv) of the colored resin particles is preferably 5.8 to 7.5 μm, more preferably 6.0 to 7.2 μm, and even more preferably 6.2 to 6.8 μm. If Dv is 5.8 μm or more, the toner has high fluidity, excellent transferability can be maintained, and high image density can be maintained. If Dv is 7.5 μm or less, high image resolution can be maintained.

[0076] The colored resin particles preferably have a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of 1.00 to 1.20, more preferably 1.00 to 1.18, and even more preferably 1.00 to 1.15. If Dv / Dn is 1.2 or less, the transferability, image density, and resolution can all be maintained at high levels. The volume average particle diameter and number average particle diameter of the colored resin particles can be measured using, for example, a particle size analyzer (manufactured by Beckman Coulter, product name: Multisizer) or the like.

[0077] From the viewpoint of image reproducibility, the average circularity of the colored resin particles is preferably 0.97 to 1.00, and more preferably 0.98 to 1.00. If the average circularity of the colored resin particles is less than 0.96, the reproducibility of thin lines in printing may be deteriorated.

[0078] The circularity is defined as the perimeter of a circle having the same projected area as the particle image divided by the perimeter 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 colored resin particles. The average circularity indicates 1 when the colored resin particles are perfectly spherical, and the more complex the surface shape of the colored resin particles, the smaller the value becomes. The average circularity (Ca) is a value calculated by the following formula for calculating the average circularity.

[0079]

number

[0080] In the above formula, n is the number of particles for which the circularity Ci is calculated. In the above formula, Ci is the circularity of each particle calculated from the circumference length measured for each particle in the particle group having a circle-equivalent diameter of 0.6 to 400 μm using the following formula for calculating circularity. Circularity calculation formula: Circularity (Ci) = Perimeter of a circle equal to the projected area of ​​a particle / Perimeter of the projected image of a particle In the above formula, fi is the frequency of particles with circularity Ci. The circularity and average circularity can be measured using a flow type particle image analyzer "FPIA-3000" manufactured by Sysmex Corporation.

[0081] 1-3.External additives The colored resin particles described above may be mixed and stirred with an external additive to uniformly adhere (externally added) to the surface of the colored resin particles. The external additive is adhered to the surface of the colored resin particles to form a one-component toner (developer). The one-component toner may be further mixed and stirred with carrier particles to form a two-component developer.

[0082] The stirrer used for the external addition treatment is not particularly limited as long as it is a stirring device capable of adhering an external additive to the surface of colored resin particles. For example, the external addition treatment can be performed using a stirrer capable of mixing and stirring, such as a Henschel Mixer (product name, manufactured by Mitsui Mining Co., Ltd.), an FM Mixer (product name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Super Mixer (product name, manufactured by Kawada Manufacturing Co., Ltd.), a Q Mixer (product name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Mechanofusion System (product name, manufactured by Hosokawa Micron Corporation), and a Mechano Mill (product name, manufactured by Okada Seiko Co., Ltd.).

[0083] As the external additive, one having an appropriate material and particle size can be selected from various inorganic fine particles and resin particles. The number average particle size of the external additive can be measured by a known method, for example, as follows. 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 particle size of the particles. When the shape of the external additive is non-spherical and the major axis and minor axis are confirmed by observation using a TEM or SEM, the major axis and minor axis are measured for each external additive. 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 to take the number-average particle size of the external additive.

[0084] <Silicone resin particles> In the present disclosure, in order to adjust the internal friction coefficient θ1 (°) of the first toner and the internal friction coefficient θ2 (°) of the second toner to satisfy the relationship represented by the above formula (1) and formula (2), it is preferable that the first toner contains, as an external additive, silicone resin particles having a ratio (BS / TS) of the BET specific surface area (BS) measured by a gas adsorption method to the theoretical specific surface area (TS) calculated by a theoretical calculation formula from the number average particle diameter measured by scanning electron microscope (SEM) observation in the range of 3.0 to 30.0 and a number average particle diameter of 0.05 to 1.00 μm, and that the second toner does not contain the silicone resin particles. When the ratio (BS / TS) of the BET specific surface area (BS) to the theoretical specific surface area (TS) is within the above range, the particles are light and flexible, so that the silicone resin particles can be prevented from being crushed during continuous printing. The silicone resin particles contained in the first toner preferably have a ratio (BS / TS) of the BET specific surface area (BS) to the theoretical specific surface area (TS) of 3.5 to 25.0, more preferably 4.0 to 20.0. When the number-average particle diameter of the silicone resin particles is within the above range, the toner can have appropriate charging characteristics under a wide range of temperature and humidity environments. The number-average particle diameter of the silicone resin particles is preferably 0.07 to 0.50 μm, and more preferably 0.08 to 0.30 μm.

[0085] The ratio of the BET specific surface area (BS) to the theoretical specific surface area (TS) (BS / TS) is used as an index of the porosity of silicone resin particles. The BET specific surface area (BS) can evaluate the unevenness of the particle surface, which cannot be evaluated by the theoretical specific surface area (TS), so the higher the BS / TS, the higher the particle's porosity, and the closer it is to 1, the lower the particle's porosity.

[0086] The number-average particle size of the silicone resin particles is measured by observation with a scanning electron microscope (SEM), and the theoretical specific surface area (TS) per unit mass is calculated from the number-average particle size of the silicone resin particles using a theoretical calculation formula. That is, in the present disclosure, regardless of the shape of the silicone resin particles, the theoretical specific surface area (TS) per unit mass is calculated using the following theoretical calculation formula (1), which calculates the specific surface area per unit mass of a sphere, assuming that the silicone resin particles are spherical. Theoretical calculation formula (1): Theoretical specific surface area TS (unit: m 2 / g)=6 / (average density (g / cm 3 ) x number average particle diameter (nm) x 10 3 ) There is no particular limitation on the method for determining the average density used in the above calculation formula, and any known method can be used.

[0087] BET specific surface area (BS) per unit mass measured by gas adsorption method (unit: m 2 / g) can be determined by a method for measuring the amount of a monolayer of nitrogen gas adsorbed on the surface of a silicone resin particle by applying the BET equation. The BET specific surface area (BS) of the silicone resin particles can be measured by a known method. An example of the measurement of the BET specific surface area (BS) of the silicone resin particles includes a method of measuring the BET specific surface area (BS) of the silicone resin particles by a nitrogen adsorption method (BET method) using a BET specific surface area measuring device (product name: Macsorb HM model-1208, manufactured by Mountec Co., Ltd.).

[0088] The silicone resin particles preferably have an adsorbed moisture content of 1.0% by mass or less, more preferably 0.35% by mass or less. If the adsorbed moisture content of the silicone resin particles exceeds 1.0% by mass, there is a risk of fogging due to a decrease in the charge amount under high temperature and high humidity conditions.

[0089] The silicone resin particles are preferably surface-treated with a hydrophobizing agent such as a silane coupling agent. The type of the hydrophobizing agent is not particularly limited, but the hydrophobizing agents used for the silica particles A and silica particles B described later can be used.

[0090] There is no particular limitation on the shape of the silicone resin particles, and they may be amorphous, but they are preferably spherical. The silicone resin particles preferably have a sphericity (Sc / Sr) of 0.970 to 1.000, and more preferably 0.985 to 1.000. If the sphericity (Sc / Sr) exceeds the above range, the resulting toner may be inferior in thin line reproducibility. In this disclosure, sphericity is defined as the area (Sc) of a circle whose diameter is the absolute maximum length of the particle, divided by the actual projected area (Sr) of the particle. The sphericity (Sc / Sr) of silicone resin particles is a value that can be determined by analyzing Sc and Sr in a photograph of silicone resin particles taken with an electron microscope using an image processing analyzer, calculating the sphericity (Sc / Sr), and then taking the arithmetic average. The sphericity can be measured by a known method, for example, by taking an electron microscope photograph of the silicone resin particles and measuring the photograph with an image processing analyzer (trade name: Luzex IID, manufactured by Nireco Corporation).

[0091] <Silica particles A> In the present disclosure, the first toner and the second toner further contain, as an external additive, silica particles A having a number average particle size of 5 nm to 30 nm and having a surface hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil, in addition to the silicone resin particles, and The content of the silica particles A in the second toner is preferably 1.1 times or more the content of the silica particles A in the first toner, and preferably 2.0 times or less the content of the silica particles A in the first toner. A toner having excellent fluidity and good transferability can be obtained by using silica particles A having a number-average particle size in the above range. The number-average particle size of the silica particles A is more preferably 7 to 25 nm, and even more preferably 8 to 20 nm. In addition, when the content of the silica particles A in the second toner is within the above range, the internal friction angle can be controlled within a target range. The content of the silica particles A in the second toner is more preferably 1.15 times or more, even more preferably 1.20 times or more, and even more preferably 1.80 times or less, the content of the silica particles A in the first toner.

[0092] The content of the silica particles A in the first toner is preferably 0.1 to 2.0 parts by mass, more preferably 0.3 to 1.2 parts by mass, per 100 parts by mass of the colored resin particles, and is 1.1 times or more the content of the silica particles A in the first toner. When the content of the silica particles A in the first toner and the second toner is less than the above range, the flowability is decreased, and fogging and transfer failure tend to occur. On the other hand, when the content of the silica particles A is more than the above range, print smears and fixation failure tend to occur due to an increase in the charge amount under low temperature and low humidity.

[0093] The silica particles A have their surfaces hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil. Here, in the present disclosure, the expression that the surface has been hydrophobized with a hydrophobizing agent indicates the state of the surface, thereby specifying the property that the silica particle surface is hydrophobic.

[0094] Among these, examples of hydrophobizing agents having an amino group include silicon compounds having an amino group. As the silicon compound having an amino group, various compounds can be used without being limited to a specific one, and for example, an amino group-containing silane coupling agent, an amino-modified silicone oil, a quaternary ammonium salt type silane, a cyclic silazane shown in the following formula (1), etc. can be used. Among them, from the viewpoint of positive charge imparting ability and fluidity, an amino group-containing silane coupling agent and a cyclic silazane shown in the following chemical formula (1) are particularly preferred. Specific examples of this amino group-containing silane coupling agent include, for example, N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltriethoxysilane, and among them, a coupling agent having an aminoalkyl group is preferred because it has an excellent effect of improving the environmental stability of charging performance.

[0095] [ka]

[0096] (In the formula, R1 and R 2 are independently selected from the group consisting of hydrogen, halogen, alkyl, alkoxy, and aryloxy; R 3 is selected from the group consisting of hydrogen, -(CH2)nCH3, -C(O)(CH2)nCH3, -C(O)NH2, -C(O)NH(CH2)nCH3, and -C(O)N[(CH2)nCH3](CH2)mCH3 (wherein n and m are each an integer of 0 to 3); R 4 is represented by [(CH2)a(CHX)b(CHY)c], where X and Y are independently selected from the group consisting of hydrogen, halogen, alkyl, alkoxy and aryloxy, and a, b and c are integers from 0 to 6, with the condition that a+b+c is equal to an integer between 2 and 6.

[0097] Examples of silane coupling agents (excluding those having an amino group) include disilazanes such as hexamethyldisilazane; alkylsilane compounds such as trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane; and the like. Of the above silane coupling agents, only one may be used, or two or more may be used. Among the silane coupling agents, hexamethyldisilazane (HMDS) is more preferable. Examples of silicone oils (excluding those having an amino group) include dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, and modified silicone oil.

[0098] As described above, the hydrophobic silica particles, the surface of which has been hydrophobized with a hydrophobic treatment agent, have a hydrophobicity measured by the methanol method of usually 30 to 98%, preferably 50 to 95%, and more preferably 60 to 90%. If the hydrophobicity is less than 30%, it is highly susceptible to environmental influences, and particularly at high temperatures and high humidity, the charge may decrease, making fogging more likely to occur, whereas if it is more than 98%, the charge may increase at low temperatures and low humidity, causing a decrease in print density.

[0099] <Silica particles B> In the present disclosure, the first toner and the second toner further contain, as an external additive, silica particles B having a number average particle size of 31 nm to 200 nm and having a surface hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil, in addition to the silicone resin and the silica particles A; The content of the silica particles B in the second toner is preferably 1.1 times or more the content of the silica particles B in the first toner, and the content of the silica particles B in the second toner is preferably 2.0 times or less the content of the silica particles B in the first toner. By using silica particles B having a number-average particle size within the above range, the flowability can be further improved, fogging and smearing of letters can be reduced, and the cleaning properties can be improved. The number average particle size of the silica particles B is more preferably from 35 to 150 nm, and even more preferably from 45 to 100 nm. In addition, when the content of the silica particles B in the second toner is within the above range, the internal friction angle can be controlled within a target range. The content of the silica particles B in the second toner is more preferably 1.15 times or more, even more preferably 1.20 times or more, and even more preferably 1.80 times or less, the content of the silica particles B in the first toner.

[0100] The content of the silica particles B in the first toner is preferably 0.1 to 3.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, per 100 parts by mass of the colored resin particles, and the content of the silica particles B in the second toner is 1.1 times or more the content of the silica particles B in the first toner. When the content of the silica particles B in the first toner and the second toner is less than the above range, the cleaning property tends to be deteriorated, whereas when the content of the silica particles B is more than the above range, print smears and fixing failures tend to occur under low temperature and low humidity conditions.

[0101] The surfaces of the silica particles B are hydrophobized with the same hydrophobizing agent as that of the silica particles A. The hydrophobizing agent used for the silica particles A and the hydrophobizing agent used for the silica particles B may be the same type or different types. The hydrophobizing agent suitable for use in the surface treatment of the silica particles B is the same as that of the silica particles A.

[0102] The hydrophobicity of the hydrophobic-treated silica particles B is usually 10 to 95%, preferably 20 to 90%, and more preferably 30 to 85%. If the hydrophobicity is less than 10%, it is significantly affected by the environment, and the chargeability may decrease, particularly under high temperature and high humidity, making it easier for fogging to occur, whereas if it is more than 95%, the chargeability may increase under low temperature and low humidity, causing a decrease in print density.

[0103] In the present disclosure, in addition to the silicone resin particles, silica particles A, and silica particles B, external additives that have been conventionally used in toners may be further contained. Such external additives include inorganic fine particles and organic fine particles, and examples of inorganic fine particles include aluminum oxide, titanium oxide, zinc oxide, tin oxide, cerium oxide, silicon nitride, calcium carbonate, calcium phosphate, barium titanate, and strontium titanate. Examples of organic fine particles include methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, core-shell type particles in which the core is a styrene polymer and the shell is a methacrylic acid ester polymer, melamine resin particles, and the like.

[0104] 1-4. Internal friction angle of toner In the present disclosure, the internal friction angle θ1 (°) of the first toner transferred first to the transfer receiving material and the internal friction angle θ2 (°) of the second toner transferred second or later satisfy the following relationship: θ1<θ2 Equation (1) 1°≦θ2-θ1≦3° Formula (2)

[0105] By making the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner satisfy the relationship of the above formula (1), when a full-color image is printed using an electrostatic charge image development method, the gradation and color reproducibility of multi-color images such as secondary colors and tertiary colors can be improved. If the internal friction angle θ1 (°) of the first toner is the same as or larger than the internal friction angle θ2 (°) of the second toner, i.e., if the relationship of formula (1) is not satisfied, the print durability of the leading color may decrease. If the difference between the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner is too small, i.e., if the difference represented by θ2-θ1 is smaller than the lower limit of equation (2), the color overlay performance may decrease. If the deviation between the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner is too large, i.e., if the difference expressed by θ2-θ1 is greater than the upper limit of equation (2), the color overlay will be good, but the particle fluidity will be significantly different, and it may not be possible to adjust the print durability of the first color and other colors to an appropriate range within the range of conditions set on the printer.

[0106] From the viewpoint of the balance between color overlay and print durability, it is preferable that the internal friction angle θ1 (°) of the first toner and the internal friction angle θ2 (°) of the second toner are such that θ1 is 17° or more and 20° or less, and θ2 is 20° or more and 23° or less, as long as the relationship between the above formulas (1) and (2) is satisfied. If the internal friction angle θ1 (°) of the first toner is less than 17°, the fluidity is too high, which reduces the supply onto the developing roll, and this may cause smearing. When the internal friction angle θ1 (°) of the first toner exceeds 20°, print durability may decrease. If the internal friction angle θ2 (°) of the second toner is less than 20°, the fluidity is too high, which reduces the supply onto the developing roll, and may cause smearing. When the internal friction angle θ2 (°) of the second toner exceeds 23°, print durability may decrease.

[0107] <Method for measuring internal friction angle> The internal friction angle of the toner can be determined by measuring the shear stress as shown in the following procedure using a powder fluidity analyzer, Powder Rheometer FT4 (manufactured by Freeman Technology). The powder rheometer is a fluidity measuring device that directly determines fluidity by simultaneously measuring the rotational torque and normal load obtained by the spiral rotation of a rotor blade through packed particles. By measuring both the rotational torque and the load, the fluidity, including the properties of the powder itself and the influence of the external environment, can be detected with high sensitivity. A 50 mm x 85 mm vessel attached to the powder rheometer is assembled, and 15 g of toner is uniformly placed in the vessel using a sieve. After placement, measurements are performed using a 48 mm shear stress measurement blade dedicated to the device. The shear load is measured when the vertical load is changed to 1 kPa, 2 kPa, 4 kPa, 10 kPa, 15 kPa, and 20 kPa. Using this measured value, an approximation line passing through the origin (XY=0.0) is calculated with the horizontal axis representing the normal load and the vertical axis representing the shear load, and the angle between the horizontal axis and the approximation line is defined as the internal friction angle of the toner to be measured.

[0108] <How to adjust the internal friction angle> The internal friction angles of the first toner and the second toner can be adjusted by any of the methods described below or a combination of these methods. As one method, the internal friction angle can be adjusted by the amount of silica particles A or silica particles B. With regard to the effect of increasing the amount of added silica particles A, the increase in the internal friction angle is greater when the amount of silica particles A is increased, but if only silica particles A is increased, the amount of silica covering the toner surface increases, and since the particle size is smaller than that of silica particles B, fogging is more likely to occur during printing durability. It is preferable to combine silica particles A and silica particles B in a fixed quantitative ratio in consideration of the overall balance, and increase or decrease silica particles A and silica particles B at the same ratio. As another method, the internal friction angle can be adjusted to a lower value by increasing the amount of silicone resin particles added. However, since the silicone resin particles have a larger particle size than the silica particles A and B, they are more likely to fall off, and increasing the amount may worsen the vertical streaks.

[0109] 2. Image forming method The toner set disclosed herein is suitably applied to a printing method in which multiple primary color toners, such as yellow toner, cyan toner, and magenta toner, are used to develop electrostatic latent images corresponding to the individual primary colors to create individual primary color toner images on a developing machine, and the resulting individual primary color toner images are sequentially transferred from the toner image forming surface of the developing machine onto a transfer receiving material selected from the group consisting of recording materials and transfer media, thereby overlaying colors on the transfer receiving material to form a full-color image. The transfer medium on which the color superposition is performed is, for example, an intermediate transfer belt, an intermediate transfer roll, or the like. In addition, the recording material is not particularly limited and may be plain paper or other recording paper, coated paper, art paper, OHP sheet, etc. In particular, the toner set of the present disclosure is highly effective in improving the gradation and color reproducibility of an image including multi-colors when forming an image on recording paper with a relatively large amount of paper dust, such as plain paper.

[0110] As a printing device capable of carrying out the above-mentioned procedure, for example, a full-color printer can be used in which multiple developing machines 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 machine are transferred onto a single recording material directly from each developing machine or sequentially via a transfer medium, thereby forming 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 diagram showing 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 the one shown in the diagram. In addition, the structure, size and shape of the materials used in the method of the present disclosure are not limited to the structure, size and shape of the various materials in these diagrams.

[0111] The image forming apparatus 100 shown in FIG. 1 is a printer with a tandem arrangement. The image forming apparatus 100 includes a conveying path 4 for the recording material R, four developing machines (1Y, 1M, 1C, 1K) corresponding to the colors of yellow (Y), magenta (M), cyan (C), and black (K), a transfer medium (2Y, 2M, 2C, 2K) and a support roll (3Y, 3M, 3C, 3K) that are paired with each developing machine of each color, an exposure device 5 that irradiates laser light according to primary color image data obtained by color separation of an original image, and a pair of a fixing roll 6 and a support roll 7. The four developing machines (1Y, 1M, 1C, 1K) corresponding to each color are arranged in series along the conveying direction D of the recording material R in the image forming apparatus. The four developing machines are arranged in the order of the yellow developing machine 1Y, the magenta developing machine 1M, the cyan developing machine 1C, and the black developing machine 1K from the upstream side of the conveying direction.

[0112] The configuration of the developing machine will be described by taking the yellow developing machine 1Y as a representative. The developing machine 1Y has a drum-shaped photoconductor 11Y, and around it are arranged a charging roll 12Y that charges the photoconductor surface 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 that transfers the developed toner image, and a cleaning unit 15Y that removes toner remaining on the photoconductor 11Y after the toner image is 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 each include a photoconductor (11M, 11C, 11K), a charging roll (12M, 12C, 12K), a laser light irradiation unit (13M, 13C, 13K), a developing unit (14M, 14C, 14K), a cleaning unit (15M, 15C, 15K), and a toner storage unit (16M, 16C, 16K), and a transfer medium (2M, 2C, 2K) is arranged around the photoconductor together with these components.

[0113] A method of forming an image using the above-mentioned image forming apparatus 100 will be described. In this apparatus, yellow toner is selected as the first toner having an internal friction angle θ1 and is used in the first developing machine 1Y. Also, magenta (M), cyan (C) and black (K) toners are used as second toners having internal friction angles θ2 in the second and subsequent developing machines. First, in the yellow developing unit 1Y, the surface of the photoconductor 11Y is uniformly charged by the charging roll 12Y. The photoconductor is usually highly resistive (the resistance of a typical resin), but when irradiated with a laser beam, the resistivity of the portion irradiated with the laser beam 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 is irradiated onto the photosensitive layer on the surface of the photoconductor 11Y, and an electrostatic latent image corresponding to the yellow primary color image is formed on the surface of the photoconductor 11Y. The electrostatic latent image is a negative latent image because it is formed by residual charges in the areas not irradiated by the laser beam.

[0114] The electrostatic latent image on the photoconductor 11Y moves to the position of the developing unit 14Y by the rotation of the photoconductor, and is developed there, to obtain a yellow primary color toner image. The yellow primary color toner image on the photoconductor moves to the primary transfer position by the rotation of the photoconductor. 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 onto 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 secondarily transferred by the rotation of the transfer medium. 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, the surface of the transfer medium 2Y comes into contact with the image receiving surface of the recording material R, and the yellow primary color toner image on the transfer medium 2Y is secondarily transferred to the recording material R.

[0115] Next, in the magenta developing unit 1M, a procedure similar to the procedure for forming the yellow primary color toner image is performed. That is, in the magenta developing unit 1M, a magenta primary color toner image is formed on the surface of the photoconductor 11M, and is primarily transferred to the surface of the transfer medium 2M, which then moves to a position for secondary transfer of magenta by the rotation of the transfer medium 2M. Meanwhile, from the upstream side of the conveying path 4, a portion of the recording material R on which the yellow primary color toner image is formed moves and reaches 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.

[0116] Next, the cyan developing machine 1C and the black developing machine 1K also carry out a procedure similar to that for forming a yellow primary color toner image. Then, the 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 conveying path, thereby obtaining a full-color image including multi-colors. After the recording material R passes through the developing machines of all colors and an image including multi-colors is formed, the recording material R moves to a position for performing a fixing process. There, the recording material R is sandwiched between the fixing roll 6 and the support roll 7, and the image including multi-colors is fixed onto the recording material. EXAMPLES

[0117] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. Note that parts and % are by weight unless otherwise specified.

[0118] 1. Preparation of external additives 1-1. Production of silicone resin particles 1 A 200 mL recovery flask was charged with 60.0 g of water and 0.01 g of acetic acid as a catalyst, and stirred at 30° C. 70.0 g of methyltrimethoxysilane was added thereto and stirred for 1 hour to obtain a raw material solution. 3.0 g of 25% aqueous ammonia solution, 128.0 g of water, and 390.0 g of methanol were added to a 1000 mL eggplant flask and stirred at 30° C. to prepare an alkaline aqueous medium. The raw material solution was added dropwise to this alkaline aqueous medium over 1 minute. The mixture after the dropwise addition of the raw material solution was stirred for 25 minutes to allow the polycondensation reaction of the fine particle precursor to proceed, thereby obtaining a polycondensation reaction liquid. 3000 g of water was placed in a 5000 mL recovery flask as an aqueous solution, and the polycondensation reaction liquid was added dropwise over 1 minute while stirring at 25° C. As soon as the polycondensation reaction liquid was mixed with the water, it became cloudy, and a dispersion liquid containing silicone particles was obtained. 30.5 g of hexamethyldisilazane was added as a hydrophobizing agent to the silicone particle dispersion liquid, and the mixture was stirred at 25° C. for 48 hours, resulting in a powder suspension in which hydrophobized spherical polymethylsilsesquioxane microparticles floated in the upper layer of the liquid. The powder suspension was left to stand for 5 minutes, and the floating powder was collected by suction filtration and dried under reduced pressure at 100° C. for 24 hours to obtain 32 g of a dry powder of silicone resin particles 1. The properties of the silicone resin particles 1 are shown in Table 1.

[0119] 1-2. Silica particles A1 As the silica particles A1, positively charged silica particles having a number-average particle size of 20 nm (product name: TG7120, manufactured by Cabot Corporation) whose surfaces were hydrophobized with a hydrophobizing agent, hexamethyldisilazane (HDMS) and cyclic silazane, were used. The properties of the silica particles A1 are shown in Table 1.

[0120] 1-3. Silica particles B1 As the silica particles B1, positively charged silica particles having a number-average particle size of 50 nm (product name: H05TA, manufactured by Clariant) whose surfaces had been hydrophobized with aminosilane, a hydrophobizing agent, were used. The properties of the silica particles B1 are shown in Table 1.

[0121] [Table 1]

[0122] 2. Toner set manufacturing A plurality of toners having different internal friction coefficients for each color were produced by the following procedure. 2-1.Yellow toner (1) Manufacturing Example Y1 As polymerizable monomers, 70 parts of styrene, 30 parts of n-butyl acrylate, 0.1 parts of polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Industry Co., Ltd., product name: AA6, Tg = 94 ° C.), and 0.72 parts of divinylbenzene, 1.25 parts of tetraethyl thiuram disulfide as a molecular weight regulator, and 8 parts of CI Pigment Yellow 155 (product name: Toner Yellow 3GP CT, manufactured by Clariant) 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 grinding, 0.5 parts of a charge control resin (styrene acrylic resin containing a quaternary ammonium salt, functional group amount 8% by mass) and 6.0 parts of a synthetic ester wax (pentaerythritol tetrabehenate, melting point 76°C) were added, mixed, and dissolved to prepare a polymerizable monomer composition for a core. Separately, an aqueous solution of 7.3 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added to an aqueous solution of 10.4 parts of magnesium chloride in 280 parts of ion-exchanged water with stirring to prepare a magnesium hydroxide colloidal dispersion. Furthermore, 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 a polymerizable monomer for the shell.

[0123] The above-mentioned core polymerizable monomer composition was added to the above-mentioned magnesium hydroxide colloidal dispersion liquid (magnesium hydroxide amount: 5.3 parts), further stirred, and 6 parts of t-butylperoxy-2-ethylbutanoate was added thereto as a polymerization initiator. The dispersion liquid to which the polymerization initiator was added was dispersed at a rotation speed of 15,000 rpm using an in-line type emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., product name: Milder) to form droplets of the core polymerizable monomer composition. The dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor and heated to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached nearly 100%, 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) was dissolved in the aqueous dispersion of the shell polymerizable monomer and added to the reactor. The temperature was then maintained at 95°C for 4 hours to continue polymerization, and the reaction was stopped by cooling with water to obtain an aqueous dispersion of core-shell type colored resin particles. While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added until the pH became 4.5 or less to perform acid washing (25°C, 10 minutes), and 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. Furthermore, the colored resin particles after the washing and filtration steps were dehydrated and dried to obtain dried colored resin particles.

[0124] The resulting colored resin particles had a volume average particle size Dv of 7.10 μm, a particle size distribution Dv / Dn of 1.12, and an average circularity of 0.990. 0.2 parts of silicone resin particles 1, 0.80 parts of silica particles A1, and 0.80 parts of silica particles B1 were added to 100 parts of the obtained colored resin particles, and mixed using a high-speed mixer (manufactured by Nippon Coke & Engineering Co., Ltd., product name: FM Mixer) and subjected to external addition treatment to prepare yellow toner Y1. The properties of yellow toner Y1 are shown in Table 2.

[0125] (2) Manufacturing Examples Y2 to Y4 Yellow toners Y2 to Y4 were produced in the same manner as in Production Example Y1, except that the amounts of silicone resin particles 1, silica particles A1, and silica particles B1 added in Production Example Y1 were changed as shown in Table 2. The properties of yellow toners Y2 to Y4 are shown in Table 2.

[0126] 2-2. Magenta toner (1) Manufacturing example a1 In a pressure-resistant reactor, 23.2 kg of cyclohexane, 1.5 mmol of N,N,N',N'-tetramethylethylenediamine (TMEDA) and 1.70 kg of styrene were added, and while stirring at 40°C, 99.1 mmol of n-butyllithium was added, and polymerization was carried out for 1 hour while raising the temperature to 50°C. The polymerization conversion rate of styrene was 100% by mass. Subsequently, 6.03 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature to maintain 50 to 60°C. After the addition of isoprene was completed, polymerization was carried out for another 1 hour to form a styrene-isoprene diblock copolymer. The polymerization conversion rate of isoprene was 100% by mass. Next, 15.0 mmol of dimethyldichlorosilane was added as a coupling agent to carry out a coupling reaction for 2 hours, and a styrene-isoprene-styrene triblock copolymer was formed. After this, 198 mmol of methanol was added as a polymerization terminator, and the reaction was stopped by mixing well, to obtain a reaction liquid containing a block copolymer composition. Then, 0.3 parts of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to 100 parts of the reaction liquid thus obtained (containing 30 parts of the polymer component) and mixed, and the mixed solution was dropped little by little into hot water heated to 85 to 95°C to volatilize the solvent and obtain a precipitate, which was then pulverized and dried with hot air at 85°C to recover a block copolymer composition. The content of styrene monomer units in the obtained block copolymer composition (styrene-based thermoplastic elastomer a) was 24% by mass, and the weight average molecular weight Mw was 106,000.

[0127] (2) Manufacturing example M1 74 parts of styrene as a polymerizable monomer, 26 parts of n-butyl acrylate, 0.1 part of polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Industry Co., Ltd., product name: AA6, Tg = 94°C), 0.50 parts of tetraethyl thiuram disulfide as a molecular weight regulator, and 8.0 parts of magenta pigment A (mixed crystal of CI Pigment Red 122 and CI Pigment Violet 19 in a mass ratio of 1:1) 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 grinding, 10.0 parts of a charge control resin (styrene acrylic resin containing a quaternary ammonium salt, functional group amount 1% by mass), 12.0 parts of synthetic ester wax 1 (hexaglycerin octabehenate, melting point 70°C), and 2.0 parts of the styrene thermoplastic elastomer a obtained in Production Example a1 as a styrene thermoplastic elastomer were added, mixed, and dissolved to prepare a polymerizable monomer composition for a core. In addition, a magnesium hydroxide colloidal dispersion was prepared by gradually adding, with stirring, an aqueous solution of 7.3 parts of sodium hydroxide in 50 parts of ion-exchanged water to an aqueous solution of 10.4 parts of magnesium chloride in 280 parts of ion-exchanged water. Furthermore, 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 a polymerizable monomer for the shell.

[0128] The above-mentioned core polymerizable monomer composition was added to the above-mentioned magnesium hydroxide colloidal dispersion liquid (magnesium hydroxide amount: 5.3 parts), further stirred, and 6 parts of t-butylperoxy-2-ethylbutanoate was added thereto as a polymerization initiator. The dispersion liquid to which the polymerization initiator was added was dispersed at a rotation speed of 15,000 rpm using an in-line type emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., product name: Milder) to form droplets of the core polymerizable monomer composition. The dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor and heated to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached nearly 100%, 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) was dissolved in the aqueous dispersion of the shell polymerizable monomer and added to the reactor. The temperature was then maintained at 95°C for 4 hours to continue polymerization, and the reaction was stopped by cooling with water to obtain an aqueous dispersion of core-shell type colored resin particles. While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added until the pH became 4.5 or less to perform acid washing (25°C, 10 minutes), and 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. Furthermore, the colored resin particles after the washing and filtration steps were dehydrated and dried to obtain dried colored resin particles.

[0129] The resulting colored resin particles had a volume average particle size Dv of 7.32 μm, a particle size distribution Dv / Dn of 1.13, and an average circularity of 0.990. 1.0 part of silica particles A1 and 1.0 part of silica particles B1 were added to 100 parts of the obtained colored resin particles, and mixed using a high-speed mixer (manufactured by Nippon Coke & Engineering Co., Ltd., product name: FM Mixer) and subjected to external addition treatment to prepare magenta toner M1. The properties of magenta toner M1 are shown in Table 2.

[0130] (2) Manufacturing example M2~M3 Magenta toners M2 to M3 were produced in the same manner as in Production Example M1, except that the amounts of silicone resin particles 1, silica particles A1, and silica particles B1 added in Production Example M1 were changed as shown in Table 2. The properties of magenta toners M2 to M3 are shown in Table 2.

[0131] 2-3. Cyan toner (1) Manufacturing example C1 As polymerizable monomers, 75 parts of styrene, 25 parts of n-butyl acrylate, 0.1 part of polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Industry Co., Ltd., product name: AA6, Tg = 94°C), 1.95 parts of tetraethyl thiuram disulfide as a molecular weight regulator, and 6 parts of CI Pigment Blue 15:3 as a colorant 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 grinding, 13 parts of a charge control resin (styrene acrylic resin containing a quaternary ammonium salt, functional group amount 1% by mass) and 15 parts of a synthetic ester wax (pentaerythritol tetrabehenate, melting point 76°C) were added, mixed, and dissolved to prepare a polymerizable monomer composition for a core. Separately, an aqueous solution of 7.3 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added to an aqueous solution of 10.4 parts of magnesium chloride in 280 parts of ion-exchanged water with stirring to prepare a magnesium hydroxide colloidal dispersion. Furthermore, 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 a polymerizable monomer for the shell.

[0132] The above-mentioned core polymerizable monomer composition was added to the above-mentioned magnesium hydroxide colloidal dispersion liquid (magnesium hydroxide amount: 5.3 parts), further stirred, and 6 parts of t-butylperoxy-2-ethylbutanoate was added thereto as a polymerization initiator. The dispersion liquid to which the polymerization initiator was added was dispersed at a rotation speed of 15,000 rpm using an in-line type emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., product name: Milder) to form droplets of the core polymerizable monomer composition. The dispersion containing droplets of the core polymerizable monomer composition was placed in a reactor and heated to 90°C to carry out a polymerization reaction. After the polymerization conversion rate reached nearly 100%, 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) was dissolved in the aqueous dispersion of the shell polymerizable monomer and added to the reactor. The temperature was then maintained at 95°C for 4 hours to continue polymerization, and the reaction was stopped by cooling with water to obtain an aqueous dispersion of core-shell type colored resin particles. While stirring the aqueous dispersion of colored resin particles, sulfuric acid was added until the pH became 4.5 or less to perform acid washing (25°C, 10 minutes), and 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. Furthermore, the colored resin particles after the washing and filtration steps were dehydrated and dried to obtain dried colored resin particles.

[0133] The resulting colored resin particles had a volume average particle size Dv of 7.25 μm, a particle size distribution Dv / Dn of 1.13, and an average circularity of 0.992. 1.20 parts of silica particles A1 and 1.20 parts of silica particles B1 were added to 100 parts of the obtained colored resin particles, and mixed using a high-speed mixer (manufactured by Nippon Coke & Engineering Co., Ltd., product name: FM Mixer) and subjected to external addition treatment to prepare cyan toner C1. The properties of cyan toner C1 are shown in Table 2.

[0134] (2) Manufacturing example C2 Cyan toner C2 was produced in the same manner as in Production Example C1, except that the amounts of silicone resin particles 1, silica particles A1, and silica particles B1 added in Production Example C1 were changed as shown in Table 1. The properties of cyan toner C2 are shown in Table 2.

[0135] [Table 2]

[0136] 2-4. Toner Combinations The toner sets were made by combining any one of yellow toners Y1 to Y4 and cyan toner C2 as the top color toner and any one of magenta toners M1 to M3 and cyan toner C1 as the other color toners. Table 3 shows the toner combinations in each toner set.

[0137] [Table 3]

[0138] 3. Physical property testing methods 3-1. Measurement of particle size of colored resin particles The volume average particle diameter Dv, number average particle diameter Dn, and particle size distribution Dv / Dn of the colored resin particles were measured using a particle size measuring instrument (Beckman Coulter, product name: Multisizer). The measurement using this Multisizer was performed under the following conditions: aperture diameter: 100 μm, dispersion medium: Isoton II (product name), concentration: 10%, number of particles measured: 100,000. Specifically, about 0.1 g of colored resin particles were weighed out and placed in a beaker, and 0.1 mL of a surfactant aqueous solution (manufactured by Fujifilm Corporation, product name: Drywell) was added as a dispersant. 10 to 30 mL of Isoton II was further added to the beaker, and the particles were dispersed for 3 minutes using a 20 W (Watt) ultrasonic disperser, after which measurement was performed using the particle size measuring device described above.

[0139] 3-2. Calculation of the average circularity of colored resin particles The average circularity of the colored resin particles was measured in an aqueous dispersion system using a flow particle image analyzer (FPIA-3000; manufactured by Sysmex Corporation). The measurement method was as follows: 10 mL of ion-exchanged water was prepared in a container, and alkylbenzene sulfonate was added as a surfactant to serve as a dispersant. Then, 0.2 g of the measurement sample was added and dispersed uniformly. As a dispersion means, an ultrasonic disperser was used, and dispersion treatment was performed under the conditions of an output of 60 W and 3 minutes. The concentration of the colored resin particles during measurement was adjusted to 3,000 to 10,000 particles / μL. The circularity of 1,000 to 10,000 colored resin particles was measured. The average circularity was calculated using this data.

[0140] 3-3. Measurement of the number-average particle size of silicone resin particles An SEM image was taken using an ultra-high resolution field emission scanning electron microscope (product name: SU9000, manufactured by Hitachi High-Technologies Corporation), and 30 particles were randomly selected from the image. After measuring the particle size of each selected particle, the number-average particle size of the 30 particles was calculated.

[0141] 3-4. Calculation of the theoretical specific surface area (TS) of silicone resin particles The theoretical specific surface area (TS) was calculated from the number-average particle diameter calculated in 3-3 above using the above-mentioned theoretical calculation formula for calculating the specific surface area per unit mass of a sphere.

[0142] 3-5. Measurement of BET specific surface area (BS) of silicone resin particles The BET specific surface area (BS) was measured by the nitrogen adsorption method (BET method) using a fully automatic BET specific surface area measuring device (product name: Macsorb HM model-1208, manufactured by Mountec Co., Ltd.).

[0143] 3-6. Measurement of the number average particle size of silica particles A and silica particles B 0.5 g of each of silica particles A and silica particles B was dispersed in 50 mL of water using an ultrasonic cleaner (product name: BRANSONIC 1510J, manufactured by Branson Corporation, 42 kHz, 90 W, 2 L), and the aqueous dispersion of the particles was measured using a dynamic light scattering particle size distribution measuring device (product name: LB-550, manufactured by Horiba, Ltd.) to determine the number-average particle size.

[0144] 3-7. Measurement of the internal friction angle of toner The internal friction angle was determined by shear stress measurement according to the following procedure using a powder rheometer FT-4 (manufactured by Freeman Technology). A 50 mm x 85 mm vessel attached to the powder rheometer is assembled, and 15 g of toner is uniformly placed in the vessel using a sieve. After placement, measurements are performed using a 48 mm shear stress measurement blade dedicated to the device. The measurements were performed by varying the vertical load from 1 kPa, 2 kPa, 4 kPa, 10 kPa, 15 kPa, and 20 kPa, and measuring the shear load at each vertical load. Using this measured value, an approximation line passing through the origin (XY=0.0) was calculated with the horizontal axis as the vertical load and the vertical axis as the shear load, and the angle between the horizontal axis and the approximation line was determined as the internal friction angle of the toner to be measured.

[0145] 4. Toner performance test method 4-1. Print durability (number of sheets with fogging, vertical streaks, and solid uneven printing) Using a commercially available non-magnetic single-component development printer (resolution 600 dpi, print speed 28 pages / min), print paper was set, and the development device containing the top color toner and the other color toners was set. After leaving it for 24 hours in a normal temperature and humidity (N / N) environment with a temperature of 23°C and a humidity of 50% RH, continuous printing was performed in the same environment for up to 10,000 sheets at 5% print density for each color. Six sets of printing, a total of three sheets, were performed every 1,000 sheets, with a solid white print (0% print density) and a solid print of each color (100% print density), and the condition of the development roll was checked. <Criteria for determining the number of sheets with fogging> Six solid white prints (0% print density) obtained from six sets of printing performed every 1,000 sheets of continuous printing were visually observed, and the number of continuous prints at which fog of the leading color (Y or C) (transfer of toner to non-image areas) was confirmed on one or more solid white prints was determined to be the number of sheets on which fog of the leading color (Y or C) occurred. Similarly, six solid white prints (0% print density) obtained from six sets of printing performed every 1,000 sheets of continuous printing were visually observed, and the number of continuous prints at which fogging of the other color (M or C) (transfer of toner to non-image areas) was confirmed on one or more solid white prints was determined to be the number of sheets on which fogging of the other color (M or C) occurred. <Criteria for determining the number of vertical streaks> Six solid white prints (0% print density) and six solid prints of the leading color (Y or C) (100% print density) obtained from six sets of printing performed every 1,000 sheets of continuous printing were visually observed, and the number of continuous prints at which streaks of the leading color (Y or C) were observed on two or more solid white prints, or the number at which streaks were observed on two or more solid prints of the leading color (Y or C), was determined to be the number of sheets with vertical streaks of the leading color (Y or C). Similarly, six solid white prints (0% print density) and six solid prints of other colors (M or C) (100% print density) obtained from six sets of printing performed every 1,000 sheets of continuous printing were visually observed, and the number of continuous prints at which other color (M or C) streaks were observed on two or more solid white prints, or the number at which other color (M or C) streaks were observed on two or more solid prints of other colors (M or C), was determined to be the number of sheets with vertical streaks of the other color (M or C) occurring, whichever was earlier. <Criteria for determining the number of sheets with solid printing unevenness> Six solid prints (100% print density) of the first color (Y or C) obtained from six sets of printing performed every 1000 sheets of continuous printing are visually observed, and prints with visible density unevenness are selected. For each selected print, three dark areas and three light areas are visually identified, and the reflection density of each of these areas is measured using a reflection densitometer (product name: eXact Basic). For each selected print, the average reflection density of the three dark areas and the average reflection density of the three light areas are calculated, and the ratio of the average reflection density of the three light areas to the average reflection density of the three dark areas is calculated. If one or more of the selected prints do not meet the following conditions, the number of continuous prints at that point is determined to be the number of sheets with solid print unevenness of the first color (Y or C). conditions: (Average of three reflection densities in the light area) / (Average of three reflection densities in the dark area)≧0.85 Similarly, for six solid prints of another color (M or C) obtained from six sets of printing performed every 1,000 sheets of continuous printing, the ratio of the average value of the reflection density of three points in the dark areas to the average value of the reflection density of three points in the light areas was calculated, and if the above condition was not met, the number of continuous prints at that point was determined to be the number of sheets on which solid print unevenness of the other color (M or C) occurred. When any of the above problems occurred, the print durability test was terminated, and the number of sheets at the time of occurrence was determined as the print durability number. If none of the problems occurred, the print durability test was terminated when the maximum number of sheets printed, 10,000, was reached.

[0146] 4-2.Secondary color reproducibility Using a commercially available non-magnetic single-component development printer (resolution 600 dpi, print speed 28 pages / min), print paper was set and each color toner was placed in the development device. After leaving it for 24 hours in a normal temperature and humidity (N / N) environment with a temperature of 23°C and a humidity of 50% RH, overlapping printing was performed in the same environment, and solid printing of the secondary color (print density 100%) was performed. The vertical and horizontal centers of the obtained solid print of the secondary color (print density 100%) were used as the reference point, and the L* [brightness], a*, and b* [color tone] were measured at three points on each side in the horizontal direction from the center of the print, for a total of six points. From these values, the color difference ΔE was calculated using the following formula, and the secondary color reproducibility was evaluated according to the following criteria. <Calculation formula for secondary color reproducibility> ΔE=√((Reference L*-Measurement L*)^2+(Reference a*-Measurement a*)^2+(Reference b*-Measurement b*)^2 <Evaluation criteria> Level 1: When unevenness in secondary colors is clearly visible Level 2: There are points where the unevenness of secondary color formation is not visible to the naked eye, but the maximum ΔE value is 8 or more. Lv.3: When the maximum ΔE value is 4 or more and less than 8 Lv.4: When the maximum ΔE value is 2 or more and less than 4 Lv.5: When the maximum ΔE value is less than 2

[0147] 5. Evaluation Results Table 3 shows the evaluation results of the printing test carried out using the toner set. In Examples 1 to 5, the internal friction coefficient θ1 of the leading color toner and the internal friction coefficient θ2 of the other color toners satisfied the relationships of the following formulas (1) and (2), and θ1 and θ2 were within the following ranges, respectively. Equation (1): θ1<θ2 Formula (2): 1°≦θ2-θ1≦3° 17°≦θ1≦20° 20°≦θ2≦23° The toner sets of Examples 1 to 5 were excellent in print durability, being able to print 7,000 to 9,000 sheets without any problems, without vertical streaks, solid print unevenness, or fogging, both for the top color toner and for the other color toners. In addition, the toner sets of Examples 1 to 3 also had excellent secondary color reproducibility, reaching Level 4.

[0148] In the toner set of Example 1, the leading yellow toner Y1 contained 0.20 parts of silicone resin particles 1 as an external additive relative to 100 parts of colored resin particles, and contained 0.80 parts of silica particles A1 and silica particles B1 relative to 100 parts of colored resin particles, while the other color magenta toner M1 did not contain silicone resin particles 1 as an external additive, and contained 1.00 parts of silica particles A1 and silica particles B1 relative to 100 parts of colored resin particles. The ratio of the amount of silica particles A1 in the other color toners to the amount of silica particles A1 in the leading color toner was 1.25, and the ratio of the amount of silica particles B1 in the other color toners to the amount of silica particles B1 in the leading color toner was 1.25. For the toner set of Example 1, among the items of vertical streaks, solid print unevenness, and fog, the number of sheets with vertical streaks (first color) was over 10,000, and the number of sheets with other items was 9,000. As a result, the print durability number was 9,000 sheets, and the balance of all items related to print durability was the best among the Examples.

[0149] In comparison with Example 1, in the toner set of Example 2, yellow toner Y2 was used as the leading color toner, and magenta toner M1, the same as in Example 1, was used as the other color toner. In the toner set of Example 2, yellow toner Y2 contained 0.40 parts of silicone resin particles 1 per 100 parts of colored resin particles, and the content of silicone resin particles 1 was greater than that of yellow toner Y of Example 1, so the internal friction coefficient θ1 of the leading color toner was smaller. As a result, the number of sheets with solid print unevenness (leading color) and the number of sheets with fog (leading color) improved, but the number of sheets with vertical streaks (leading color) was 7,000 sheets. As a result, the print durability was 9,000 sheets.

[0150] In comparison with Example 1, in the toner set of Example 3, the same yellow toner Y1 as in Example 1 was used as the top color toner, and magenta toner M2 was used as the other color toner. In the toner set of Example 3, magenta toner M2 does not contain silicone resin particles 1 as an external additive, and contains 1.20 parts of silica particles A1 and silica particles B1 per 100 parts of colored resin particles, and the ratio of the amount of silica particles A1 in the other color toner to the amount of silica particles A1 in the top color toner is 1.50, and the ratio of the amount of silica particles B1 in the other color toner to the amount of silica particles B1 in the top color toner is 1.50, so the internal friction coefficient θ2 of the other color toner was increased. Due to this influence, the number of sheets with fog (other colors) was improved, but the number of sheets with vertical streaks (top color) was 9000 sheets, and the number of sheets with vertical streaks (other colors), the number of sheets with solid uneven printing (top color), and the number of sheets with solid uneven printing (other colors) were 7000 sheets. As a result, the print durability reached 7,000 sheets.

[0151] In comparison with Example 1, in the toner set of Example 4, the same yellow toner Y1 as in Example 1 was used as the top color toner, and cyan toner C1 was used as the other color toner. In the toner set of Example 4, the cyan toner C1 does not contain silicone resin particles 1 as an external additive, and contains 1.20 parts of silica particles A1 and silica particles B1 per 100 parts of colored resin particles, and the ratio of the amount of silica particles A1 in the other color toner to the amount of silica particles A1 in the top color toner is 1.50, and the ratio of the amount of silica particles B1 in the other color toner to the amount of silica particles B1 in the top color toner is 1.50, so the internal friction coefficient θ2 of the other color toner is large. Due to this influence, the number of sheets with fog (other colors) was improved, but the number of sheets with vertical streaks (other colors) and the number of sheets with solid printing unevenness (other colors) were 7000 sheets. As a result, the print durability was 7000 sheets.

[0152] In comparison with Example 1, in the toner set of Example 5, cyan toner C2 was used as the leading color toner, and magenta toner M1, the same as in Example 1, was used as the other color toner. In the toner set of Example 5, the material composition of the leading color cyan toner C2 was different from the material composition of the leading color toner Y1 in Example 1, so the internal friction coefficient θ1 of the leading color toner was large. In addition, the leading color cyan toner C2 contains 1.00 parts of silica particles A1 and silica particles B1 per 100 parts of colored resin particles, and the addition ratio of silica particles A1 (other color toner / leading color toner) and the addition ratio of silica particles B1 (other color toner / leading color toner) were 1.00, which was slightly smaller than the addition ratio of silica particles A1 and silica particles B1 in Example 1. Due to this influence, the number of sheets on which fogging occurred (leading color) was 8000 sheets. As a result, the print durability was 8000 sheets.

[0153] On the other hand, in Comparative Examples 1 to 3, the internal friction coefficient θ1 of the leading color toner and the internal friction coefficient θ2 of the other color toners did not satisfy one or both of the relationships of the following formula (1) and formula (2). Furthermore, in Comparative Example 1, the internal friction coefficient θ1 of the leading color toner was outside the following range, and in Comparative Example 2, both the internal friction coefficient θ1 of the leading color toner and the internal friction coefficient θ2 of the other color toners were outside the following range. Equation (1): θ1<θ2 Formula (2): 1°≦θ2-θ1≦3° 17°≦θ1≦20° 20°≦θ2≦23° The toner sets of Comparative Examples 1 to 3 were unable to simultaneously improve print durability and secondary color reproducibility.

[0154] In comparison with Example 1, in the toner set of Comparative Example 1, yellow toner Y3 was used as the top color toner, and magenta toner M1, the same as in Example 1, was used as the other color toner. In the toner set of Comparative Example 1, since yellow toner Y3 does not contain silicone resin particles 1, the internal friction coefficient θ1 of the top color toner was large, and the difference between the internal friction coefficient θ1 of the top color toner and the internal friction coefficient θ2 of the other color toner was less than 1°. As a result, the number of sheets on which solid printing unevenness occurred (top color) and the number of sheets on which fogging occurred (top color) were 6000 sheets. As a result, the print durability was 6000 sheets. In addition, the secondary color reproducibility was also Level 2, which was poor.

[0155] In comparison with Example 1, in the toner set of Comparative Example 2, the same yellow toner Y1 as in Example 1 was used as the leading color toner, and magenta toner M3 was used as the other color toner. In the toner set of Comparative Example 2, the magenta toner M3 of the other color toner contains 0.20 parts of silicone resin particles 1 as an external additive relative to 100 parts of colored resin particles, so that the internal friction coefficient θ2 of the other color toner is smaller than the internal friction coefficient θ1 of the leading color toner, and the two internal friction coefficients θ1 and θ2 do not satisfy the relationship of formula (1). As a result, the number of sheets with solid uneven printing (other colors) and the number of sheets with fog (other colors) improved, but the number of sheets with vertical streaks (other colors) and the number of sheets with solid uneven printing (leading color) were 7000 sheets. As a result, the print durability was 7000 sheets. In addition, the secondary color reproducibility was Level 1, which was the poorest among the comparative examples.

[0156] In comparison with Example 1, in the toner set of Comparative Example 3, yellow toner Y4 was used as the top color toner, and magenta toner M2 was used as the other color toner. In the toner set of Comparative Example 3, the top color toner yellow toner Y4 contained 0.50 parts of silica particles A1 and silica particles B1 per 100 parts of colored resin particles, and the other color toner magenta toner M2 contained 1.20 parts of silica particles A1 and silica particles B1 per 100 parts of colored resin particles, and the ratio of the amount of silica particles A1 in the other color toner to the amount of silica particles B1 in the top color toner was 2.40, and the ratio of the amount of silica particles B1 in the other color toner to the amount of silica particles B1 in the top color toner was 2.40, so the difference between the internal friction coefficient θ1 of the top color toner and the internal friction coefficient θ2 of the other color toner was more than 3°. As a result, the number of sheets with uneven solid printing (leading color) and the number of sheets with fog (other colors) improved, but the number of sheets with vertical streaks (other colors) and the number of sheets with uneven solid printing (other colors) was 7,000 sheets, and the number of sheets with fog (leading color) was 5,000 sheets. As a result, the print durability was 5,000 sheets. Comparative Example 3 was excellent in terms of secondary color reproducibility, being at Level 5, but was the poorest among the comparative examples in terms of print durability. [Explanation of symbols]

[0157] 100 Image forming device R Recording material D Conveying direction 1 developing machine (1Y, 1M, 1C, 1K) 2 Transfer media (2Y, 2M, 2C, 2K) 3 Support rolls (3Y, 3M, 3C, 3K) 4 Transport Path 5 Exposure equipment 6 Fixing roll 7 Support Roll 11 Photoconductor (11Y, 11M, 11C, 11K) 12 Charging roll (12Y, 12M, 12C, 12K) 13 Laser light irradiation unit (13Y, 13M, 13C, 13K) 14 Development section (14Y, 14M, 14C, 14K) 15 Cleaning Section (15Y, 15M, 15C, 15K) 16 Toner storage section (16Y, 16M, 16C, 16K)

Claims

1. A toner of a plurality of colors is combined, the toner including colored resin particles including a binder resin, a colorant, and a charge control agent, The combination is a color toner set for developing an electrostatic image, the color toner set including at least a yellow toner, a cyan toner, and a magenta toner, When a toner of one color selected from a group consisting of toners of each color included in a toner set is defined as a first toner and a toner of the other color is defined as a second toner, an internal friction angle θ1 (°) of the first toner and an internal friction angle θ2 (°) of the second toner satisfy the relationship represented by the following formulas (1) and (2), θ1<θ2 Equation (1) 1°≦θ2−θ1≦3° Formula (2) the first toner contains, as an external additive, silicone resin particles having a ratio (BS / TS) of a BET specific surface area (BS) measured by a gas adsorption method to a theoretical specific surface area (TS) calculated by a theoretical formula from a number average particle diameter measured by observation with a scanning electron microscope (SEM) of 3.0 to 30.0 and a number average particle diameter of 0.05 to 1.00 μm; and the second toner does not contain the silicone resin particles; the first toner and the second toner further contain, as an external additive, silica particles A having a number average particle size of 5 nm to 30 nm and having a surface hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil; The color toner set for developing electrostatic images is characterized in that the first toner and the second toner further contain, as an external additive, silica particles B having a number average particle size of 31 nm to 200 nm and whose surfaces have been hydrophobized with at least one hydrophobizing agent selected from the group consisting of a hydrophobizing agent having an amino group, a silane coupling agent, and a silicone oil.

2. The color toner set for developing electrostatic images is used in a full-color printer that includes a plurality of developing machines corresponding to the respective color toners included in the toner set, and that sequentially transfers primary color images of the respective colors produced by the respective developing machines onto a transfer receiving material selected from the group consisting of a recording material and a transfer medium, thereby forming an image including multiple colors on the transfer receiving material, the first toner being a toner of one color that is a leading color toner designated for use in a developing machine that produces a primary color image that is transferred first onto the transfer receiving material; 2. The color toner set for developing an electrostatic image according to claim 1, wherein the toner of the other color which is the second toner is a toner specified to be used in a developing machine which produces a primary color image which is transferred second or later onto the transfer receiving material.

3. 3. The color toner set for developing an electrostatic image according to claim 1, wherein the first toner is a toner of one color selected from the group consisting of a yellow toner, a cyan toner, and a magenta toner.

4. 4. The color toner set for developing an electrostatic image according to claim 1, wherein the angle θ1 is from 17° to 20°, and the angle θ2 is from 20° to 23°.

5. A color toner set for developing electrostatic images described in any one of claims 1 to 4, wherein the content of silica particles A in the second toner is 1.1 times or more the content of silica particles A in the first toner.

6. A color toner set for developing electrostatic images described in any one of claims 1 to 5, wherein the content of the silica particles B in the second toner is 1.1 times or more the content of the silica particles B in the first toner.

7. 7. The color toner set for developing an electrostatic image according to claim 1, wherein the colored resin particles of the first toner and the second toner have an average circularity of 0.97 or more and 1.00 or less.

8. A method for forming an image by an electrostatic image developing full-color printer using the electrostatic image developing color toner set according to any one of claims 1 to 7, developing a first image, which is a primary color image formed with the first toner; developing a second image, which is a primary color image of each color formed with the second toner; forming an image including multi-colors on a transfer medium by transferring the first image onto the transfer medium and then transferring the second image onto the transfer medium; A step of transferring the image including the multi-color formed on the transfer medium onto a recording material; and An image forming method comprising a step of fixing, on a recording material, an image including multiple colors transferred onto the recording material.

9. A method for forming an image by an electrostatic image developing full-color printer using the electrostatic image developing color toner set according to any one of claims 1 to 7, developing a first image, which is a primary color image formed with the first toner; developing a second image, which is a primary color image of each color formed with the second toner; a step of transferring the first image onto a recording material, and then transferring the second image onto the recording material to form an image including a multi-color image; and An image forming method comprising a step of fixing an image including multiple colors formed on a recording material onto the recording material.

10. 10. The image forming method according to claim 9, wherein the recording material is paper.

Images