Toner for electrostatic charge image development, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method

Abstract

To provide an electrostatic charge image development toner which suppresses image omission that may occur when an image with a large amount of applied toner is formed on a rugged recording medium at high speed.SOLUTION: An electrostatic charge image development toner provided herein comprises toner particles containing a binder resin and a mold release agent and satisfying the following condition (A1) in a cross-sectional observation of a toner particle. Condition (A1): domain diameters to the maximum diameter of the toner particle are 8-30%, inclusive; domain centroids are present within a depth of R / 2 from a surface of the toner particle, where R represents a distance from a centroid of the toner particle to the surface of the toner particle, and the entire domain has one or more domains of the mold release agent present inside at a depth of 50nm or more from the surface of the toner particle.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Methods for visualizing image information, such as electrophotography, are currently used in various fields. In electrophotography, an electrostatic charge image is formed as image information on the surface of an image carrier by charging and electrostatic charge image formation. Then, a toner image is formed on the surface of the image carrier by a developer containing toner, and after transferring this toner image to a recording medium, the toner image is fixed to the recording medium. Through these steps, the image information is visualized as an image.

[0002] For example, Patent Document 1 discloses "a toner containing at least a binder resin, a crystalline polyester resin, a colorant, and a release agent, wherein the volume average particle diameter of the toner is in the range of 4 to 8 μm, a release agent domain exists in a toner cross-sectional image in which the equivalent circle diameter of the toner cross-section is in the range of 4 to 8 μm, and when the ratio (distance A / equivalent circle diameter) of the distance A between the center of gravity of the release agent domain and the center of gravity of the toner cross-section to the equivalent circle diameter of the toner cross-section is divided into regions at intervals of 0.05 from 0, the number frequency of the release agent domain is the highest in the region where the ratio (distance A / equivalent circle diameter) is 0.25 or more and 0.3 or less, and the number frequency of the release agent domain in the region where the ratio (distance A / equivalent circle diameter) is 0.25 or more and 0.3 or less is 20% or more."

[0003] Further, Patent Document 2 discloses "an electrostatic charge image developing toner containing toner particles having a release agent domain containing a release agent and satisfying the following conditions (1) to (4). Condition (1): The length in the major axis direction of the release agent domain is 300 nm or more and 1500 nm or less. Condition (2): The ratio (length in the major axis direction / length in the minor axis direction) of the length in the major axis direction of the release agent domain to the length in the minor axis direction is 3.0 or more and 15.0 or less. Condition (3): The angle formed by a tangent passing through the contact point between the circumference of a circle inscribed in the outer edge of the toner particle with the center of gravity of the release agent domain as the center and the outer edge, and a line extending in the major axis direction of the release agent domain passing through the center of gravity of the release agent domain is 0° or more and 45° or less. Condition (4): The ratio of the equivalent circle diameter of the toner particles to the distance A between the center of gravity of the release agent domain and the contact point (distance A / equivalent circle diameter) is 0.03 or more and 0.25 or less.」 has been proposed.

[0004] Further, Patent Document 3 proposes 「A toner containing toner particles containing a binder resin and a wax, and organosilicon polymer particles, wherein the wax is an ester wax, and the average major axis of the domain of the wax is 0.03 μm or more and 2.00 μm or less, and the SP value SPw of the wax is 8.59 or more and 9.01 or less.」

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem of the present invention is to provide an electrostatic charge image developing toner that suppresses image dropout, which occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness, as compared with an electrostatic charge image developing toner having only toner particles that do not satisfy the following condition (A1) when observing the cross section of the toner particles, which contains a binder resin and a release agent.

Means for Solving the Problems

[0007] Means for solving the above problems include the following aspects. <1> An electrostatic charge image developing toner containing a binder resin and a release agent, having toner particles that satisfy the following condition (A1) when observing the cross section of the toner particles. Condition (A1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particles, and the entire domain exists within the interior at a depth of 50 nm or more from the surface of the toner particles. There is one or more domains of the release agent. <2> When observing the cross-section of the toner particles, the toner for electrostatic charge image development satisfies the following condition (A2). Condition (A2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particles, and the entire domain exists within the interior at a depth of 50 nm or more from the surface of the toner particles. There are a plurality of domains of the release agent. <3> When observing the cross-section of the toner particles, the toner for electrostatic charge image development according to <1> satisfies the following condition (B1). Condition (B1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particles, and the entire domain exists within the interior at a depth of 50 nm or more from the surface of the toner particles. There is one or more domains of the release agent. <4> When observing the cross-section of the toner particles, the toner for electrostatic charge image development according to <2> satisfies the following condition (B2). Condition (B2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particles, and the entire domain exists within the interior at a depth of 50 nm or more from the surface of the toner particles. There are a plurality of domains of the release agent. <5> When observing the cross-section of the toner particles, the electrostatic charge image developing toner according to any one of <1> to <4> below, wherein the toner particles satisfy the following condition (C). Condition (C): The circularity of the domain of the release agent is 0.92 or more and 1.00 or less. <6> The electrostatic charge image developing toner according to any one of <1> to <5> below, wherein the melting temperature of the release agent is 65°C or more and 95°C or less. <7> The electrostatic charge image developing toner according to <6>, wherein the release agent having a melting temperature of 65°C or more and 95°C or less is an ester wax. <8> The electrostatic charge image developing toner according to any one of <1> to <7> below, wherein the toner particles contain an amorphous resin having a polyester resin segment and a styrene acrylic resin segment as the binder resin. <9> The electrostatic charge image developing toner according to <8>, wherein the toner particles further contain a crystalline polyester resin as the binder resin. <10> The electrostatic charge image developing toner according to any one of <1> to <9> below, wherein the content of the toner particles is 30% or more by number based on all the toner particles. <11> The electrostatic charge image developing toner according to <10>, wherein the content of the toner particles is 70% or more by number based on all the toner particles. <12> An electrostatic charge image developer containing the electrostatic charge image developing toner according to any one of <1> to <11>. <13> A toner cartridge that houses the electrostatic charge image developing toner according to any one of <1> to <11>, and is detachable from an image forming apparatus. <14> A process cartridge that houses the electrostatic charge image developer according to <12>, and has developing means for developing an electrostatic charge image formed on the surface of an image carrier as a toner image with the electrostatic charge image developer, and is detachable from an image forming apparatus. <15> An image carrier, and Charging means for charging the surface of the image carrier, Electrostatic charge image forming means for forming an electrostatic charge image on the charged surface of the image carrier, Developing means for accommodating the electrostatic charge image developer according to <12> and developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer, Transferring means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, Fixing means for fixing the toner image transferred to the surface of the recording medium, An image forming apparatus comprising the above. <16> A charging step of charging the surface of the image carrier, An electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image carrier, A developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to <12>, A transferring step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, A fixing step of fixing the toner image transferred to the surface of the recording medium, An image forming method having the above.

Advantages of the Invention

[0008] According to the invention according to <1>, compared with an electrostatic charge image developing toner containing a binder resin and a release agent and having only toner particles that do not satisfy condition (A1) when observing the cross section of the toner particles, an electrostatic charge image developing toner is provided that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with irregularities. According to the invention according to <2>, compared with an electrostatic charge image developing toner having toner particles that satisfy condition (A1) but do not satisfy condition (A2), an electrostatic charge image developing toner is provided that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with irregularities. According to the invention according to <3>, compared with an electrostatic charge image developing toner having toner particles that satisfy condition (A1) but do not satisfy condition (B1), an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided. According to the invention according to <4>, compared with an electrostatic charge image developing toner having toner particles that satisfy condition (A1) but do not satisfy condition (B2), an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided. According to the invention according to <5>, compared with an electrostatic charge image developing toner having toner particles that satisfy condition (A1) but do not satisfy condition (C), an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided.

[0009] According to the invention according to <6>, compared with the case where the melting temperature of the release agent exceeds 95°C, an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided. According to the invention according to <7>, compared with the case where the release agent having a melting temperature of 65°C or higher and 95°C or lower is a release agent other than an ester wax, an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided.

[0010] According to the invention according to <8>, including a binder resin and a release agent, when observing the cross-section of the toner particles, compared with an electrostatic charge image developing toner having only toner particles that do not satisfy condition (A1), even if the toner particles contain an amorphous resin having a polyester resin segment and a styrene acrylic resin segment as the binder resin, an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with unevenness is provided. According to the invention according to <9>, compared with an electrostatic charge image developing toner having only toner particles that do not satisfy condition (A1) when observing the cross-section of the toner particles, which contains a binder resin and a release agent, even if the toner particles contain a crystalline polyester resin as the binder resin, there is provided an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with irregularities.

[0011] According to the invention according to <10> or <11>, compared with the case where the content of toner particles satisfying the above condition (A1) and condition (B1) is less than 30% by number or less than 70% by number, there is provided an electrostatic charge image developing toner that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with irregularities.

[0012] According to the invention according to <12>, <13>, <14>, <15>, or <16>, compared with the case where an electrostatic charge image developing toner having only toner particles that do not satisfy condition (A1) when observing the cross-section of the toner particles, which contains a binder resin and a release agent, is applied, there is provided an electrostatic charge image developer, a toner cartridge, a process cartridge, an image forming apparatus, or an image forming method that suppresses image dropout that occurs when forming an image with a high toner loading amount at high speed on a recording medium with irregularities.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments that are examples of the present invention will be described in detail. In a numerical range described step by step, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in a numerical range, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. The amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. The term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved.

[0015] <Electrostatic charge image developing toner> The electrostatic charge image developing toner (hereinafter referred to as "toner") according to the present embodiment contains a binder resin and a release agent, and has toner particles that satisfy the following condition (A1) when observing the cross section of the toner particles. Condition (A1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particles, and there is one or more domains of the release agent in which the entire domain exists inside the toner particles at a depth of 50 nm or more from the surface of the toner particles.

[0016] The toner according to the present embodiment suppresses image dropout that occurs when forming an image with a large toner loading amount at high speed on a recording medium with unevenness due to the above configuration. The reason is presumed as follows.

[0017] Conventionally, a technique of disposing a release agent domain near the surface layer of toner particles is known. When the release agent domain is disposed near the surface layer of the toner particles, the bleeding property of the release agent from the toner particles is improved when the toner particles are crushed during fixing, and the releasability with respect to the fixing member is improved. However, if the diameter of the release agent domain is small, when forming an image with a large toner loading amount (for example, an image with a toner loading amount of 10.0 g / m 2 or more) at high speed (for example, a high speed of 300 mm / sec or more for the conveyance speed of the recording medium) on a recording medium with unevenness (for example, embossed paper), image dropout may occur. This is because when fixing an image with a large toner loading amount at high speed, the amount of toner on the recording medium increases, so the adhesive force between the toners is insufficient. In that state, if the amount of release agent oozing out from the toner is insufficient, the peelability becomes weak and toner peeling occurs, which becomes a factor of image dropout. Furthermore, heat is difficult to transfer to the toner, making it difficult for the toner to melt sufficiently, because the exudability of the release agent present near the center of the toner particles is insufficient. That is, due to the insufficient exudability of the release agent, the peelability with respect to the fixing member decreases and image dropout occurs. In particular, when fixing at high speed and low temperature on a recording medium with unevenness, it is likely that the amount of heat for sufficiently melting the toner with respect to the toner that has entered the unevenness will be insufficient, and the exudability of the release agent from the toner will be significantly insufficient, so image dropout is likely to occur.

[0018] Therefore, in the toner according to this embodiment, toner particles that satisfy condition (A1) are employed. Condition (A1) indicates that a large release agent domain exists near the surface of the toner particles without being exposed (see FIG. 3). When the release agent domain is large and exists near the surface of the toner particles, compared to the case where a large release agent domain exists near the center of the toner particles or when a small release agent domain exists near the surface of the toner particles, the exudability of the release agent from the toner particles during fixing increases even with a small amount of heat. Furthermore, since the presence of a large release agent domain near the surface of the toner particles improves the thermal conductivity to the center of the toner particles, the meltability of the entire toner is improved. Therefore, image density unevenness is also suppressed for images with a large toner loading amount.

[0019] Accordingly, even when forming an image with a large toner loading amount at high speed on a recording medium with unevenness, the bleeding of the release agent is likely to occur, and the releasability with respect to the fixing member is also improved. As a result, image dropout is suppressed. And, even when a large release agent domain exists near the surface of the toner particles but is not exposed from the toner particles, destabilization of the toner fluidity, reduction in transferability, and in-machine contamination are suppressed, and basic toner performance is also ensured.

[0020] From the above, it is presumed that the toner according to the present embodiment suppresses image dropout that occurs when forming an image with a large toner loading amount at high speed on a recording medium with unevenness. Furthermore, density unevenness in an image with a large toner loading amount is also suppressed.

[0021] Note that, simply when the release agent domain is enlarged near the surface of the toner particles, the release agent domain is exposed from the toner particles, and deterioration of fluidity and transfer failure due to selective adhesion of the external additive, as well as in-machine contamination of the toner, occur. Therefore, conventionally, when enlarging the release agent domain, in order to ensure basic toner performance, the release agent domain is enlarged near the center of the toner particles, and it has been difficult to enlarge the release agent domain near the surface of the toner particles.

[0022] Here, each reference numeral shown in FIG. 3 indicates the following matters. TN: Toner particle Amo: Binder resin L T : Maximum diameter of the toner particle Lw: Domain diameter of the release agent Tcg: Center of gravity of the toner particle Wcg: Center of gravity of the release agent domain R T : Distance from the center of gravity of the toner particle to the surface of the toner particle

[0023] Hereinafter, the toner according to the present embodiment will be described in detail.

[0024] The toner according to the present embodiment has toner particles. The toner may have an external additive.

[0025] (Toner particles) The toner particles contain a binder resin and a release agent. Note that the toner particles may contain a colorant and other additives.

[0026] -(Morphology of the release agent domain in toner particles)- When observing the cross-section of the toner particles, the release agent domain satisfies condition (A1). The more the number of large release agent domains and the closer they are to the toner particle surface, the more the image dropout is suppressed. Therefore, it is preferable that the release agent domain satisfies condition (A2), more preferably satisfies condition (B1), and even more preferably satisfies condition (B2). From the viewpoint of suppressing image dropout, it is preferable that the release agent domain further satisfies condition (C).

[0027] Here, the toner particles satisfying condition (A1) are preferably 30% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more, based on the total number of toner particles, from the viewpoint of suppressing image dropout. Ideally, the proportion of toner particles satisfying each of the above conditions is 100% by number. The more toner particles satisfy each of the above conditions, the easier it is to suppress image dropout.

[0028] Note that the proportion of toner particles satisfying at least one of condition (A2), condition (B1), condition (B2), and condition (C) is also preferably 30% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more, based on the total number of toner particles, from the viewpoint of suppressing image dropout, as described above. Ideally, the proportion of toner particles satisfying each of the above conditions is 100% by number.

[0029] · Condition (A1) Condition (A1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particle to the surface of the toner particle is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particle, and there is one or more domains of the release agent in which the entire domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle.

[0030] · Condition (A2) Condition (A2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particle to the surface of the toner particle is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particle, and there are a plurality of domains of the release agent in which the entire domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle.

[0031] · Condition (B1) Condition (B1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particle to the surface of the toner particle is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particle, and there is one or more domains of the release agent in which the entire domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle.

[0032] · Condition (B2) Condition (B2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particle to the surface of the toner particle is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particle, and there are a plurality of domains of the release agent in which the entire domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle.

[0033] Here, in Conditions (A1) to (B2), specifically, the domain diameter of the release agent is, for example, 0.5 μm or more and 1.5 μm or less. The "domain diameter of the release agent" means the maximum diameter of the release agent domain (that is, the maximum length of a straight line drawn between any two points on the contour line of the cross-section of the release agent). The "maximum diameter of toner particles" means the maximum length of a straight line drawn between any two points on the contour line of the cross-section of the toner particles. The "distance from the center of gravity of the toner particle to the surface of the toner particle" means the straight-line distance between the point where the straight line passing through the center of gravity of the release agent domain and the center of gravity of the toner particle intersects the outer edge of the toner particle, and the center of gravity of the toner particle (in Fig. 3, R T See reference). "The release agent domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle" means that when observing the cross-section of the toner particle, the shortest distance between the release agent domain existing in the toner particle and the surface (i.e., the outer edge) of the toner particle is 50 nm or more. In other words, "the release agent domain exists inside the toner particle at a depth of 50 nm or more from the surface of the toner particle" means that the release agent domain is not exposed on the surface of the toner particle.

[0034] ·Condition (C) Condition (C): The circularity of the release agent domain (the release agent domain satisfying condition (A1), condition (A2), condition (B1), or condition (B2)) is 0.92 or more and 1.00 or less. Since the release agent domain is large and circular, the bleeding property of the release agent is enhanced. Therefore, when condition (C) is satisfied, it becomes easier to suppress image dropout. The circularity of the domain is the circularity defined by the following formula. Formula: Circularity (100 / SF2) = 4π×(A / I 2 ) Formula (1) In formula (1), I represents the perimeter of the domain, and A represents the area of the domain.

[0035] ·Method for observing the cross-section of toner particles The method for observing the cross-section of toner particles to determine whether the toner particles satisfy each condition is as follows. Mix toner particles (or toner particles with an external additive attached) with an epoxy resin, embed them, and solidify the epoxy resin. Cut the obtained solidified product with an ultramicrotome (Leica Ultracut UCT) to prepare a thin sample with a thickness of 80 nm or more and 130 nm or less. Next, stain the obtained thin sample with ruthenium tetroxide in a desiccator at 30 °C for 3 hours. Then, obtain a STEM observation image in the transmission image mode (acceleration voltage: 30 kV, magnification: 20,000 times) of the stained thin sample with a high-resolution field emission scanning electron microscope (FE-SEM, S-4800 manufactured by Hitachi High-Technologies Corporation). In the toner particles, determine the crystalline polyester resin and the release agent from the contrast and shape. In the SEM image, the ruthenium-stained crystalline resin has more double bond parts than the amorphous resin, release agent, etc., and is stained by ruthenium tetroxide, so the release agent part and the resin part other than the release agent can be distinguished. That is, by ruthenium staining, it is the domain where the release agent is stained the thinnest, and then the crystalline resin (for example, crystalline polyester resin) is stained, and the amorphous resin (for example, amorphous polyester resin) is stained the darkest. By adjusting the contrast, the release agent can be judged as a domain that is observed as white, the amorphous resin as black, and the crystalline resin as light gray.

[0036] Then, image-analyze the region of the ruthenium-stained crystalline resin to determine whether the toner particles meet each condition. Also, when obtaining the ratio of toner particles that meet each of the above conditions, observe 100 toner particles and calculate the ratio of toner particles that meet each of the above conditions.

[0037] Note that since the SEM image includes toner particle cross-sections of various sizes, select a toner particle cross-section whose diameter is 85% or more of the volume average particle diameter of the toner particles as the toner particles to be observed. Here, the diameter of the toner particle cross-section refers to the maximum length of a straight line drawn between any two points on the contour line of the toner particle cross-section (so-called major axis).

[0038] -Binder resin- Examples of the binder resin include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers obtained by combining two or more of these monomers. Vinyl resins composed of such materials are included. Examples of the binder resin also include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, mixtures of these with the aforementioned vinyl resins, or graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0039] In particular, it is preferable to apply an amorphous resin and a crystalline resin as the binder resin. However, the mass ratio of the crystalline resin to the amorphous resin (crystalline resin / amorphous resin) is preferably 3 / 97 or more and 50 / 50 or less, more preferably 7 / 93 or more and 30 / 70 or less. When an amorphous resin and a crystalline resin are applied, even when forming an image with a large toner loading amount at high speed on a recording medium with unevenness, the meltability of the toner during fixing increases, and the bleeding property of the release agent also increases. Therefore, image dropout is more suppressed.

[0040] Here, an amorphous resin refers to a resin that, in thermal analysis measurements using differential scanning calorimetry (DSC), has only a stepwise endothermic change rather than a distinct endothermic peak, is a solid at room temperature, and is thermoplastically softened at a temperature above the glass transition temperature. On the other hand, a crystalline resin refers to a resin that has a distinct endothermic peak in differential scanning calorimetry (DSC) rather than a stepwise change in the endothermic amount. Specifically, for example, a crystalline resin means that the half-width of the endothermic peak measured at a heating rate of 10 °C / min is within 10 °C, and an amorphous resin means a resin with a half-width exceeding 10 °C or a resin for which no distinct endothermic peak is observed.

[0041] An amorphous resin will be described. Examples of amorphous resins include known amorphous resins such as amorphous polyester resins, amorphous vinyl resins (e.g., styrene-acrylic resins, etc.), epoxy resins, polycarbonate resins, and polyurethane resins. Among these, amorphous polyester resins and amorphous vinyl resins (especially styrene-acrylic resins) are preferred, and amorphous polyester resins are more preferred. In addition, it is also a preferred embodiment to use an amorphous polyester resin and a styrene-acrylic resin in combination as the amorphous resin. Further, it is also a preferred embodiment to apply an amorphous resin having an amorphous polyester resin segment and a styrene-acrylic resin segment as the amorphous resin. In particular, when applying an amorphous resin having an amorphous polyester resin segment and a styrene-acrylic resin segment as the amorphous resin, if the above-mentioned resins are bonded by an ester bond, it is easier to be compatible with an ester-based release agent, so it has better toner meltability. Therefore, even when forming an image with a large toner loading amount at high speed on a recording medium with unevenness, image dropout is more suppressed.

[0042] · Amorphous polyester resin Examples of the amorphous polyester resin include condensation polymers of polyvalent carboxylic acids and polyhydric alcohols. As the amorphous polyester resin, commercially available products may be used, or those synthesized may be used.

[0043] Examples of the polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. Among these, aromatic dicarboxylic acids are preferred as the polyvalent carboxylic acids. The polyvalent carboxylic acid may be used in combination with a trivalent or higher carboxylic acid having a crosslinked structure or a branched structure together with the dicarboxylic acid. Examples of the trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, anhydrides thereof, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0044] Examples of the polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), aromatic diols (e.g., ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc.). Among these, aromatic diols and alicyclic diols are preferred as the polyhydric alcohols, and aromatic diols are more preferred. As the polyhydric alcohol, a polyhydric alcohol having a crosslinked structure or a branched structure with a diol may be used in combination. Examples of the polyhydric alcohol having three or more hydroxyl groups include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohol may be used alone or in combination of two or more.

[0045] The amorphous polyester resin is obtained by a known production method. Specifically, for example, it can be obtained by a method in which the polymerization temperature is set to 180°C or higher and 230°C or lower, the inside of the reaction system is depressurized as necessary, and the reaction is carried out while removing water and alcohol generated during condensation. When the raw material monomer does not dissolve or is not compatible at the reaction temperature, a high-boiling solvent may be added as a dissolution aid to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the dissolution aid. When a monomer with poor compatibility exists in the copolymerization reaction, it is advisable to first condense the monomer with poor compatibility with the acid or alcohol intended for polycondensation and then carry out polycondensation with the main component.

[0046] Examples of the amorphous polyester resin include not only an unmodified amorphous polyester resin but also a modified amorphous polyester resin. The modified amorphous polyester resin is an amorphous polyester resin having a bonding group other than an ester bond, or an amorphous polyester resin in which a resin component different from polyester is bonded by a covalent bond or an ionic bond. Examples of the modified amorphous polyester resin include a resin obtained by reacting an amorphous polyester resin having a functional group such as an isocyanate group introduced at the terminal with an active hydrogen compound to modify the terminal.

[0047] The proportion of the amorphous polyester resin in all the binder resins is preferably 60% by mass or more and 98% by mass or less, more preferably 65% by mass or more and 95% by mass or less, and still more preferably 70% by mass or more and 90% by mass or less.

[0048] · Styrene acrylic resin Styrene acrylic resin is a copolymer obtained by copolymerizing at least a styrene monomer (a monomer having a styrene skeleton) and a (meth)acrylic monomer (a monomer having a (meth)acrylic group, preferably a monomer having a (meth)acryloxy group). Styrene acrylic resin includes, for example, a copolymer of a styrene monomer and a (meth)acrylate monomer. Note that the acrylic resin portion in the styrene acrylic resin is a partial structure formed by polymerizing either an acrylic monomer or a methacrylic monomer, or both. Also, “(meth)acrylic” is an expression that includes both “acrylic” and “methacrylic”.

[0049] Examples of the styrene monomer include styrene, α-methylstyrene, metachlorostyrene, parachlorostyrene, parafluorostyrene, paramethoxystyrene, meta-tert-butoxystyrene, para-tert-butoxystyrene, paravinylbenzoic acid, paramethyl-α-methylstyrene, and the like. The styrene monomer may be used alone or in combination of two or more.

[0050] Examples of the (meth)acrylic monomer include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)methacrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. The (meth)acrylic monomer may be used alone or in combination of two or more.

[0051] The polymerization ratio of the styrene monomer and the (meth)acrylic monomer is preferably styrene monomer:(meth)acrylic monomer = 70:30 to 95:5 on a mass basis.

[0052] The styrene acrylic resin may have a crosslinked structure. The styrene acrylic resin having a crosslinked structure can be produced, for example, by copolymerizing a styrene monomer, a (meth)acrylic monomer, and a crosslinkable monomer. The crosslinkable monomer is not particularly limited, but a bifunctional or higher (meth)acrylate compound is preferable.

[0053] The method for producing the styrene acrylic resin is not particularly limited, and for example, solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization are applicable. Known operations (for example, batch, semi-continuous, continuous, etc.) are applicable to the polymerization reaction.

[0054] The proportion of the styrene acrylic resin in the total binder resin is preferably 0% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less.

[0055] · An amorphous resin having an amorphous polyester resin segment and a styrene acrylic resin segment (hereinafter also referred to as "hybrid amorphous resin") The hybrid amorphous resin is an amorphous resin in which the amorphous polyester resin segment and the styrene acrylic resin segment are chemically bonded. The hybrid amorphous resin includes a resin having a main chain made of a polyester resin and a side chain made of a styrene acrylic resin chemically bonded to the main chain; a resin having a main chain made of a styrene acrylic resin and a side chain made of a polyester resin chemically bonded to the main chain; a resin having a main chain formed by chemical bonding of a polyester resin and a styrene acrylic resin; a resin having a main chain formed by chemical bonding of a polyester resin and a styrene acrylic resin, and at least one side chain of a side chain made of a polyester resin chemically bonded to the main chain and a side chain made of a styrene acrylic resin chemically bonded to the main chain; and the like.

[0056] Regarding the amorphous polyester resin and styrene acrylic resin of each segment, it is as described above, and the description is omitted.

[0057] The total amount of the polyester resin segment and the styrene acrylic resin segment in the whole hybrid amorphous resin is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 100% by mass.

[0058] In the hybrid amorphous resin, the proportion of the styrene acrylic resin segment in the total amount of the polyester resin segment and the styrene acrylic resin segment is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 55% by mass or less, and still more preferably 30% by mass or more and 50% by mass or less.

[0059] The hybrid amorphous resin is preferably produced by any one of the following methods (i) to (iii). (i) After producing a polyester resin segment by polycondensation of a polyhydric alcohol and a polyvalent carboxylic acid, monomers constituting the styrene acrylic resin segment are subjected to addition polymerization. (ii) After producing a styrene acrylic resin segment by addition polymerization of an addition polymerizable monomer, a polyhydric alcohol and a polyvalent carboxylic acid are subjected to polycondensation. (iii) Polycondensation of a polyhydric alcohol and a polyvalent carboxylic acid and addition polymerization of an addition polymerizable monomer are carried out in parallel.

[0060] The proportion of the hybrid amorphous resin in all the binder resins is preferably 60% by mass or more and 98% by mass or less, more preferably 65% by mass or more and 95% by mass or less, and still more preferably 70% by mass or more and 90% by mass or less.

[0061] The properties of the amorphous resin will be described. The properties of the amorphous resin will be described. The glass transition temperature (Tg) of the amorphous resin is preferably 50°C or higher and 80°C or lower, more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC). More specifically, it is determined by the "extrapolated glass transition start temperature" described in the method for determining the glass transition temperature in JIS K 7121-1987 "Method for Measuring the Transition Temperature of Plastics".

[0062] The weight average molecular weight (Mw) of the amorphous resin is preferably 5,000 or higher and 1,000,000 or lower, more preferably 7,000 or higher and 500,000 or lower. The number average molecular weight (Mn) of the amorphous resin is preferably 2,000 or higher and 100,000 or lower. The molecular weight distribution Mw / Mn of the amorphous resin is preferably 1.5 or higher and 100 or lower, more preferably 2 or higher and 60 or lower. The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using Tosoh's GPC·HLC-8120GPC as the measurement device, Tosoh's column·TSKgel SuperHM-M (15 cm), and THF solvent. The weight average molecular weight and the number average molecular weight are calculated using the molecular weight calibration curve prepared from the measurement results with a monodisperse polystyrene standard sample.

[0063] The crystalline resin will be described. Examples of the crystalline resin include known crystalline resins such as crystalline polyester resins and crystalline vinyl resins (for example, polyalkylene resins, long-chain alkyl (meth)acrylate resins, etc.). Among these, crystalline polyester resins are preferred from the viewpoints of the mechanical strength and low-temperature fixability of the toner.

[0064] · Crystalline polyester resin Examples of the crystalline polyester resin include polycondensates of polyvalent carboxylic acids and polyhydric alcohols. As the crystalline polyester resin, commercially available products may be used, or synthesized products may be used. Since crystalline polyester resins can easily form a crystalline structure, polycondensates using linear aliphatic polymerizable monomers are preferred over polymerizable monomers having aromatic rings.

[0065] Examples of the polyvalent carboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, etc.), anhydrides thereof, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. As the polyvalent carboxylic acid, a carboxylic acid having a trivalent or higher valence that forms a crosslinked structure or a branched structure may be used in combination with the dicarboxylic acid. Examples of the trivalent carboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), anhydrides thereof, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. As the polyvalent carboxylic acid, a dicarboxylic acid having a sulfonic acid group or a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids. The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0066] Examples of the polyhydric alcohol include aliphatic diols (e.g., linear aliphatic diols having 7 to 20 carbon atoms in the main chain portion). Examples of the aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,14-eicosanedecanediol, and the like. Among these, as the aliphatic diol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferable. The polyhydric alcohol may be used in combination with a trivalent or higher alcohol having a crosslinked structure or a branched structure together with the diol. Examples of the trivalent or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and the like. The polyhydric alcohol may be used alone or in combination of two or more.

[0067] The content of the aliphatic diol in the polyhydric alcohol is preferably 80 mol% or more, and more preferably 90 mol% or more.

[0068] The crystalline polyester resin can be obtained by a known production method, for example, in the same manner as the amorphous polyester resin.

[0069] As the crystalline polyester resin, a polymer of an α,ω-linear aliphatic dicarboxylic acid and an α,ω-linear aliphatic diol is preferable. Since the polymer of an α,ω-linear aliphatic dicarboxylic acid and an α,ω-linear aliphatic diol has high compatibility with the amorphous polyester resin, even when an image with a large toner loading amount is formed at high speed on a recording medium with irregularities, the meltability of the toner during fixing is enhanced, and the bleeding property of the release agent is also enhanced. Therefore, image dropout is more suppressed.

[0070] As the α,ω-linear aliphatic dicarboxylic acid, an α,ω-linear aliphatic dicarboxylic acid in which the number of carbon atoms of the alkylene group connecting two carboxy groups is 3 or more and 14 or less is preferable, the number of carbon atoms of the alkylene group is more preferably 4 or more and 12 or less, and the number of carbon atoms of the alkylene group is still more preferably 6 or more and 10 or less. Examples of the α,ω-linear aliphatic dicarboxylic acid include succinic acid, glutaric acid, adipic acid, 1,6-hexanedicarboxylic acid (common name suberic acid), 1,7-heptanedicarboxylic acid (common name azelaic acid), 1,8-octanedicarboxylic acid (common name sebacic acid), 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc. Among them, 1,6-hexanedicarboxylic acid, 1,7-heptanedicarboxylic acid, 1,8-octanedicarboxylic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid are preferable. The α,ω-linear aliphatic dicarboxylic acid may be used alone or in combination of two or more.

[0071] As the α,ω-linear aliphatic diol, an α,ω-linear aliphatic diol in which the number of carbon atoms of the alkylene group connecting two hydroxy groups is 3 or more and 14 or less is preferable, the number of carbon atoms of the alkylene group is more preferably 4 or more and 12 or less, and the number of carbon atoms of the alkylene group is still more preferably 6 or more and 10 or less. Examples of the α,ω-linear aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, etc. Among them, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol are preferable. The α,ω-linear aliphatic diol may be used alone or in combination of two or more.

[0072] As the polymer of an α,ω-linear aliphatic dicarboxylic acid and an α,ω-linear aliphatic diol, from the viewpoint of suppressing image dropout, at least one selected from the group consisting of 1,6-hexanedicarboxylic acid, 1,7-heptanedicarboxylic acid, 1,8-octanedicarboxylic acid, 1,9-nonanedicarboxylic acid, and 1,10-decanedicarboxylic acid, and at least one selected from the group consisting of 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred. Among them, a polymer of 1,10-decanedicarboxylic acid and 1,6-hexanediol is more preferred.

[0073] The proportion of the crystalline polyester resin in all the binder resins is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and still more preferably 3% by mass or more and 10% by mass or less. The properties of the crystalline resin will be described. The melting temperature of the crystalline resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and still more preferably 60°C or higher and 85°C or lower. The melting temperature is determined by the "melting peak temperature" described in the method for obtaining the melting temperature of JIS K7121-1987 "Method for Measuring the Transition Temperature of Plastics" from the DSC curve obtained by differential scanning calorimetry (DSC).

[0074] The weight average molecular weight (Mw) of the crystalline resin is preferably 6,000 or more and 35,000 or less.

[0075] The content of the binder resin is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and still more preferably 60% by mass or more and 85% by mass or less with respect to the total toner particles.

[0076] -Colorant- Examples of colorants include pigments such as carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, Watchung red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, resorcin red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, malachite green oxalate; dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, thiazole-based; etc. The colorant may be used alone or in combination of two or more.

[0077] As the colorant, a surface-treated colorant may be used as necessary, and it may be used in combination with a dispersant. Also, a plurality of types of colorants may be used in combination.

[0078] The content of the colorant is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 15% by mass or less, based on the total toner particles.

[0079] - Release agent -

[0080] Examples of release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester waxes such as fatty acid esters, montanic acid esters; etc. The release agent is not limited thereto.

[0081] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, more preferably 60°C or higher and 100°C or lower. The melting temperature of the release agent is determined from the DSC curve obtained by differential scanning calorimetry (DSC) according to the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121:1987 "Method for Measuring the Transition Temperature of Plastics".

[0082] In particular, the melting temperature of the release agent is preferably 65°C or higher and 95°C or lower, more preferably 67°C or higher and 91°C or higher. When a release agent with a melting temperature of 65°C or higher and 95°C or lower is applied, the release agent domain is likely to increase in diameter and become spherical, and the toner particles are likely to satisfy the above conditions.

[0083] Also, as the release agent with a melting temperature of 65°C or higher and 95°C or lower, an ester wax is preferred. The ester wax also makes it easier for the release agent domain to increase in diameter and become spherical, and the toner particles are likely to satisfy the above conditions.

[0084] The ester wax is a wax having an ester bond. As the ester wax, any of monoester, diester, triester, and tetraester may be used, and known natural or synthetic ester waxes can be adopted. Examples of the ester wax include ester compounds of higher fatty acids (such as fatty acids having 10 or more carbon atoms) and monovalent or polyvalent aliphatic alcohols (such as aliphatic alcohols having 8 or more carbon atoms). Examples of ester waxes include ester compounds of higher fatty acids (such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, etc.) and alcohols (monohydric alcohols such as methanol, ethanol, propanol, isopropanol, butanol, capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, etc.; polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, sorbitol, pentaerythritol, etc.). Specifically, carnauba wax, rice wax, candelilla wax, jojoba oil, wood wax, beeswax, ibota wax, lanolin, montanic acid ester wax, etc. can be mentioned.

[0085] The content of the release agent is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, based on the total toner particles.

[0086] -Other Additives- Examples of other additives include known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as internal additives.

[0087] -Properties of Toner Particles, etc.- The toner particles may be single-layer structured toner particles or so-called core-shell structured toner particles composed of a core part (core particles) and a coating layer (shell layer) covering the core part. Here, the core-shell structured toner particles are preferably composed of a core part containing a binder resin and other additives such as a colorant and a release agent as necessary, and a coating layer containing a binder resin.

[0088] The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 15 μm or less, more preferably 4 μm or more and 8 μm or less.

[0089] In addition, various average particle sizes and various particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and the electrolyte used is ISOTON-II (manufactured by Beckman Coulter, Inc.). When measuring, as a dispersant, 0.5 mg or more and 50 mg or less of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (sodium alkylbenzene sulfonate is preferred). This is added to 100 ml or more and 150 ml or less of the electrolyte. The electrolyte in which the sample is suspended is subjected to a dispersion treatment for 1 minute with an ultrasonic disperser, and the particle size distribution of particles having a particle size in the range of 2 μm or more and 60 μm or less is measured using an aperture with an aperture diameter of 100 μm by the Coulter Multisizer II. The number of particles to be sampled is 50,000. For the particle size ranges (channels) divided based on the measured particle size distribution, cumulative distributions of volume and number are drawn from the smaller diameter side, respectively, and the particle size at which the cumulative value becomes 16% is defined as the volume particle size D16v, the number particle size D16p, the particle size at which the cumulative value becomes 50% is defined as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at which the cumulative value becomes 84% is defined as the volume particle size D84v and the number particle size D84p. Using these, the volume particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 , and the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 and is calculated as such.

[0090] As the average circularity of the toner particles, 0.94 or more and 1.00 or less is preferable, and 0.95 or more and 0.98 or less is more preferable.

[0091] The average circularity of the toner particles is obtained by (circumference equivalent to a circle) / (circumference) [(circumference of a circle having the same projected area as the particle image) / (circumference of the particle projection image)]. Specifically, it is a value measured by the following method. First, toner particles to be measured are aspirated and collected, a flat flow is formed, and stroboscopic light emission is instantaneously performed to capture a particle image as a still image, which is obtained by a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation). Then, the number of samplings when obtaining the average circularity is set to 3500. When the toner has an external additive, toner particles (developer) to be measured are dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additive has been removed.

[0092] (External additive) Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO 2 , TiO 2 , Al 2 O 3 , CuO, ZnO, SnO 2 , CeO 2 , Fe 2 O 3 , MgO, BaO, CaO, K 2 O, Na 2 O, ZrO 2 , CaO·SiO 2 , K 2 O·(TiO 2 )n, Al 2 O 3 ·2SiO 2 , CaCO 3 , MgCO 3 , BaSO 4 , MgSO 4 and the like.

[0093] The surface of the inorganic particles as the external additive is preferably subjected to a hydrophobization treatment. The hydrophobization treatment is performed, for example, by immersing the inorganic particles in a hydrophobization treatment agent. The hydrophobization treatment agent is not particularly limited, and examples thereof include silane-based coupling agents, silicone oils, titanate-based coupling agents, aluminum-based coupling agents, and the like. These may be used alone or in combination of two or more. The amount of the hydrophobization treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

[0094] Examples of external additives include resin particles (such as resin particles of polystyrene, polymethyl methacrylate (PMMA), melamine resin, etc.), cleaning agents (for example, metal salts of higher fatty acids represented by zinc stearate, particles of fluorine-based high molecular weight substances), etc.

[0095] As the addition amount of the external additive, for example, with respect to the toner particles, it is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less.

[0096] (Method for manufacturing toner) Next, the method for manufacturing the toner according to the present embodiment will be described. The toner according to the present embodiment can be obtained by externally adding an external additive to the toner particles after manufacturing the toner particles.

[0097] The toner particles may be manufactured by any of a dry method (for example, a kneading and grinding method, etc.) or a wet method (for example, an aggregation and unification method, a suspension polymerization method, a dissolution and suspension method, etc.). The manufacturing method of the toner particles is not particularly limited to these methods, and well-known manufacturing methods are adopted. Among these, from the viewpoint of making the domain of the crystalline resin satisfy the above conditions, it is preferable to obtain toner particles by the aggregation and unification method.

[0098] Specifically, for example, when manufacturing toner particles by the aggregation and unification method, a step of preparing a resin particle dispersion liquid in which resin particles are dispersed and a release agent particle dispersion liquid in which release agent particles are dispersed (particle dispersion liquid preparation step), and a step of aggregating resin particles (and coloring agents, etc. if necessary) in the resin particle dispersion liquid (in the dispersion liquid after mixing a coloring agent dispersion liquid if necessary) to form first aggregated particles (first aggregated particle formation step), and After obtaining an aggregated particle dispersion in which the first aggregated particles are dispersed, the aggregated particle dispersion is mixed with a resin particle dispersion and a release agent particle dispersion (or the aggregated particle dispersion is mixed with a mixture of a resin particle dispersion and a release agent particle dispersion), and the operation of aggregating so that resin particles and release agent particles further adhere to the surface of the first aggregated particles is repeated one or more times to form second aggregated particles (second aggregated particle forming step). After obtaining an aggregated particle dispersion in which the second aggregated particles are dispersed, the aggregated particle dispersion is mixed with a resin particle dispersion, and aggregation is performed so that resin particles adhere to the surface of the second aggregated particles to form third aggregated particles (third aggregated particle forming step). The aggregated particle dispersion in which the third aggregated particles are dispersed is heated, and the third aggregated particles are fused and united to form toner particles (fusing and uniting step), and toner particles are produced through these steps.

[0099] Here, in the second aggregated particle forming step, examples of the surfactant used in the release agent particle dispersion to increase the hydrophobicity of the release agent particle dispersion include highly hydrophilic surfactants (sodium octanesulfonate, sodium octylbenzenesulfonate, sodium benzenoxybistetrapolypropylene sulfonate, etc.). Then, in the fusing and uniting step, by maintaining the temperature at a temperature equal to or higher than the melting temperature of the release agent, the size of the release agent domain is increased. Thereby, the coating property by the resin particles mixed in the second and third aggregated particle forming steps is improved, and while suppressing the exposure from the toner particles, the size of the release agent domain can be increased near the surface of the toner particles. In addition, by adding the highly hydrophilic surfactant as a dispersant for the release agent particles to the release agent dispersion, in the fusing and uniting step, the surfactant separates from the release agent particles and the release agent particles become hydrophobic. Therefore, since the release agent particles are buried inside the toner particles, while suppressing the exposure from the toner particles, the size of the release agent domain can be increased by the hydrophobicity of the release agent near the surface of the toner particles. Therefore, toner particles satisfying each condition such as condition (A1) can be obtained by the above method.

[0100] The details of each process will be described below. In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described. However, the colorant is used as needed. Of course, other additives other than the colorant may be used.

[0101] - Resin particle dispersion preparation process - First, together with each resin particle dispersion (amorphous resin particle dispersion and crystalline resin particle dispersion) in which each resin particle serving as a binder resin is dispersed, for example, a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared.

[0102] Here, the resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium with a surfactant.

[0103] Examples of the dispersion medium used for the resin particle dispersion include aqueous media. Examples of the aqueous medium include water such as distilled water and ion-exchanged water, and alcohols. These may be used alone or in combination of two or more.

[0104] Examples of the surfactant include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, in particular, anionic surfactants and cationic surfactants are mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant. The surfactant may be used alone or in combination of two or more.

[0105] In a resin particle dispersion, as a method for dispersing resin particles in a dispersion medium, for example, general dispersion methods such as a rotary shear type homogenizer, a ball mill having media, a sand mill, a dyno mill, etc. can be mentioned. Further, depending on the type of resin particles, for example, the resin particles may be dispersed in the resin particle dispersion by using a phase inversion emulsification method. The phase inversion emulsification method is a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) and neutralized, and then an aqueous medium (W phase) is added, whereby the resin is converted from W / O to O / W (so-called phase inversion), becomes a discontinuous phase, and the resin is dispersed in the aqueous medium in a particulate form.

[0106] As the volume average particle diameter of the resin particles dispersed in the resin particle dispersion, for example, 0.01 μm or more and 1 μm or less is preferable, 0.08 μm or more and 0.8 μm or less is more preferable, and 0.1 μm or more and 0.6 μm or less is even more preferable. The volume average particle diameter of the resin particles is obtained by using the particle size distribution obtained by measurement with a laser diffraction type particle size distribution measuring device (for example, LA-700 manufactured by Horiba, Ltd.). For the divided particle size range (channel), the cumulative distribution is subtracted from the small particle size side with respect to the volume, and the particle diameter at which the cumulative value becomes 50% with respect to all particles is measured as the volume average particle diameter D50v. The volume average particle diameter of the particles in other dispersions is also measured in the same manner.

[0107] As the content of the resin particles contained in the resin particle dispersion, for example, 5% by mass or more and 50% by mass or less is preferable, and 10% by mass or more and 40% by mass or less is more preferable.

[0108] In the same manner as the resin particle dispersion, for example, a colorant particle dispersion and a release agent particle dispersion are also prepared. That is, regarding the volume average particle diameter of the particles, the dispersion medium, the dispersion method, and the content of the particles in the resin particle dispersion, the same applies to the colorant particles dispersed in the colorant particle dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0109] -First Aggregated Particle Formation Step- Next, a colorant particle dispersion is mixed with the resin particle dispersion. Then, in the mixed dispersion, the resin particles and the colorant particles are hetero-aggregated to form first aggregated particles containing the resin particles and the colorant particles, which have a diameter close to the diameter of the target toner particles.

[0110] Specifically, for example, a flocculant is added to the mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (for example, the pH is 2 or more and 5 or less), and a dispersion stabilizer is added as necessary. Then, after heating to the glass transition temperature of the resin particles (specifically, for example, the glass transition temperature of the resin particles - 30°C or more and the glass transition temperature of the resin particles - 10°C or less), the particles dispersed in the mixed dispersion are aggregated to form first aggregated particles. In the first aggregated particle formation step, for example, the flocculant may be added to the mixed dispersion at room temperature (for example, 25°C) while stirring with a rotary shear homogenizer, the pH of the mixed dispersion is adjusted to be acidic (for example, the pH is 2 or more and 5 or less), and a dispersion stabilizer is added as necessary, and then the above heating may be performed.

[0111] Examples of the flocculant include surfactants with opposite polarities to the surfactants used as dispersants added to the mixed dispersion, inorganic metal salts, and metal complexes with a valence of 2 or more. In particular, when a metal complex is used as the flocculant, the amount of surfactant used is reduced and the charging characteristics are improved. An additive that forms a complex or a similar bond with the metal ions of the flocculant may be used as necessary. As this additive, a chelating agent is preferably used.

[0112] Examples of the inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, aluminum sulfate, and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. As the chelating agent, a water-soluble chelating agent may be used. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), and the like. As the addition amount of the chelating agent, for example, 0.01 part by mass or more and 5.0 parts by mass or less, preferably 0.1 part by mass or more and less than 3.0 parts by mass, is preferable with respect to 100 parts by mass of the amorphous resin particles.

[0113] -Second Agglomerated Particle Formation Step- Next, after obtaining an agglomerated particle dispersion in which the first agglomerated particles are dispersed, the agglomerated particle dispersion is mixed with a resin particle dispersion and a release agent resin particle dispersion. The agglomerated particle dispersion may be mixed with a mixture of the resin particle dispersion and the release agent resin particle dispersion.

[0114] Then, in the dispersion in which the first agglomerated particles, resin particles, and release agent resin particles are dispersed, the resin particles and the release agent resin particles are agglomerated on the surface of the first agglomerated particles. Specifically, for example, in the first agglomerated particle formation step, when the first agglomerated particles reach the target particle size, a resin particle dispersion and a release agent resin particle dispersion are added to the first agglomerated particle dispersion, and this dispersion is heated below the glass transition temperature of the resin particles. This agglomeration operation is repeated one or more times to form second agglomerated particles.

[0115] -Third Agglomerated Particle Formation Step- After obtaining an agglomerated particle dispersion in which the second agglomerated particles are dispersed, the agglomerated particle dispersion is mixed with a resin particle dispersion.

[0116] Then, in the dispersion in which the second agglomerated particles and the resin particles are dispersed, the resin particles are agglomerated on the surface of the second agglomerated particles. Specifically, for example, in the third agglomerated particle formation step, when the second agglomerated particles reach the target particle size, a resin particle dispersion is added to the second agglomerated particle dispersion, and this dispersion is heated below the glass transition temperature of the resin particles. Then, the pH of the dispersion is adjusted to stop the progress of agglomeration.

[0117] -Fusion and Unification Process- Next, with respect to the third aggregated particle dispersion liquid in which the third aggregated particles are dispersed, for example, it is heated to a temperature equal to or higher than the glass transition temperature of the resin particles (for example, a temperature equal to or higher than 10 to 30 °C higher than the glass transition temperature of the resin particles) to fuse and unify the aggregated particles and form toner particles.

[0118] Here, after the completion of the fusion and unification process, the toner particles formed in the solution are obtained as toner particles in a dried state through known cleaning processes, solid-liquid separation processes, and drying processes. In the cleaning process, it is preferable to perform substitution cleaning sufficiently with ion-exchanged water from the viewpoint of chargeability. Also, in the solid-liquid separation process, although there is no particular limitation, it is preferable to perform suction filtration, pressure filtration, etc. from the viewpoint of productivity. Also, in the drying process, although there is no particular limitation on the method, it is preferable to perform freeze drying, airflow drying, fluidized drying, vibration-type fluidized drying, etc. from the viewpoint of productivity.

[0119] And the toner according to this embodiment is manufactured, for example, by adding and mixing an external additive to the obtained toner particles in a dried state. The mixing may be performed, for example, by a V blender, a Henschel mixer, a Lodige mixer, etc. Further, if necessary, coarse particles of the toner may be removed using a vibration sieve, an air classifier, etc.

[0120] <Electrostatic Charge Image Developer> The electrostatic charge image developer according to this embodiment includes at least the toner according to this embodiment. The electrostatic charge image developer according to this embodiment may be a one-component developer containing only the toner according to this embodiment, or may be a two-component developer in which the toner and a carrier are mixed.

[0121] There is no particular limitation on the carrier, and known carriers can be mentioned. Examples of the carrier include a coated carrier in which a coating resin is coated on the surface of a core material made of magnetic powder; a magnetic powder dispersion type carrier in which magnetic powder is dispersed and blended in a matrix resin; a resin impregnated type carrier in which porous magnetic powder is impregnated with resin; etc. The magnetic powder-dispersed carrier and the resin-impregnated carrier may be carriers in which the constituent particles of the carrier are used as a core material and coated with a coating resin thereon.

[0122] Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0123] Examples of the coating resin and the matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic ester copolymer, straight silicone resin containing an organosiloxane bond or a modified product thereof, fluororesin, polyester, polycarbonate, phenol resin, epoxy resin, and the like. Note that the coating resin and the matrix resin may contain other additives such as conductive particles. Examples of the conductive particles include metals such as gold, silver, and copper, and particles such as carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0124] Here, to coat the coating resin on the surface of the core material, methods of coating with a coating layer-forming solution in which the coating resin and various additives as necessary are dissolved in an appropriate solvent can be mentioned. The solvent is not particularly limited and may be selected in consideration of the coating resin to be used, coating suitability, and the like. Specific resin coating methods include an immersion method in which the core material is immersed in the coating layer-forming solution, a spray method in which the coating layer-forming solution is sprayed onto the surface of the core material, a fluidized bed method in which the coating layer-forming solution is sprayed in a state where the core material is suspended by flowing air, and a kneader coater method in which the core material of the carrier and the coating layer-forming solution are mixed in a kneader coater and the solvent is removed.

[0125] In the two-component developer, the mixing ratio (mass ratio) of toner to carrier is preferably from toner:carrier = 1:100 to 30:100, more preferably from 3:100 to 20:100.

[0126] <Image forming apparatus / Image forming method> The image forming apparatus / image forming method according to this embodiment will be described. The image forming apparatus according to this embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic charge image forming unit that forms an electrostatic charge image on the charged surface of the image carrier, a developing unit that stores an electrostatic charge image developer and develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer, a transfer unit that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing unit that fixes the toner image transferred to the surface of the recording medium. And, as the electrostatic charge image developer, the electrostatic charge image developer according to this embodiment is applied.

[0127] In the image forming apparatus according to this embodiment, an image forming method (the image forming method according to this embodiment) having a charging step of charging the surface of the image carrier, an electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image carrier, a developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to this embodiment, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing step of fixing the toner image transferred to the surface of the recording medium is implemented.

[0128] The image forming apparatus according to this embodiment is a direct transfer type apparatus that directly transfers the toner image formed on the surface of the image carrier to a recording medium; an intermediate transfer type apparatus that first transfers the toner image formed on the surface of the image carrier to the surface of an intermediate transfer member and then secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium; an apparatus provided with cleaning means for cleaning the surface of the image carrier after transfer of the toner image and before charging; an apparatus provided with discharging means for discharging by irradiating the surface of the image carrier with discharging light after transfer of the toner image and before charging, etc., and well-known image forming apparatuses are applicable. In the case of an apparatus using an intermediate transfer method, the transfer means includes, for example, an intermediate transfer member onto which a toner image is transferred on the surface, a primary transfer means for primarily transferring the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer member, and a secondary transfer means for secondarily transferring the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium. A configuration having these components is applied.

[0129] In the image forming apparatus according to the present embodiment, for example, a portion including the developing means may be a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including developing means that houses the electrostatic charge image developer according to the present embodiment is preferably used.

[0130] Hereinafter, an example of the image forming apparatus according to the present embodiment is shown, but the present invention is not limited thereto. Note that the main parts shown in the drawings will be described, and the description of the other parts will be omitted.

[0131] FIG. 1 is a schematic configuration diagram showing the image forming apparatus according to the present embodiment. The image forming apparatus shown in FIG. 1 includes electrophotographic first to fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) that output images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter, may be simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side at a predetermined distance from each other in the horizontal direction. Note that these units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

[0132] Above each of the units 10Y, 10M, 10C, and 10K in the drawings, an intermediate transfer belt 20 as an intermediate transfer member extends through each unit. The intermediate transfer belt 20 is provided by being wound around a driving roll 22 and a support roll 24 that is in contact with the inner surface of the intermediate transfer belt 20 and is arranged at intervals in the left-to-right direction in the drawing, and is adapted to travel in the direction from the first unit 10Y to the fourth unit 10K. Note that a force is applied to the support roll 24 in a direction away from the driving roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around both of them. Further, an intermediate transfer member cleaning device 30 is provided on the side surface of the image holding body of the intermediate transfer belt 20 so as to face the driving roll 22. Also, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K is supplied with toner including four colors of toner, namely yellow, magenta, cyan, and black, stored in toner cartridges 8Y, 8M, 8C, and 8K.

[0133] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, here, the first unit 10Y that forms a yellow image disposed on the upstream side in the traveling direction of the intermediate transfer belt will be described as a representative. Note that for parts equivalent to the first unit 10Y, reference numerals with magenta (M), cyan (C), and black (K) attached instead of yellow (Y) are used, and the description of the second to fourth units 10M, 10C, and 10K is omitted.

[0134] The first unit 10Y has a photoreceptor 1Y that acts as an image holding member. Around the photoreceptor 1Y, there are a charging roll (an example of charging means) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential, an exposure device (an example of electrostatic charge image forming means) 3 that exposes the charged surface with a laser beam 3Y based on the color-separated image signal to form an electrostatic charge image, a developing device (an example of developing means) 4Y that supplies toner charged to the electrostatic charge image to develop the electrostatic charge image, a primary transfer roll 5Y (an example of primary transfer means) that transfers the developed toner image onto the intermediate transfer belt 20, and a photoreceptor cleaning device (an example of cleaning means) 6Y that removes the toner remaining on the surface of the photoreceptor 1Y after primary transfer, which are arranged in order. Note that the primary transfer roll 5Y is arranged inside the intermediate transfer belt 20 and provided at a position facing the photoreceptor 1Y. Further, each of the primary transfer rolls 5Y, 5M, 5C, 5K is connected to a bias power source (not shown) that applies a primary transfer bias. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0135] Hereinafter, the operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of -600 V to -800 V by the charging roll 2Y. The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (for example, volume resistivity at 20 °C: 1 × 10 -6 Ωcm or less). This photosensitive layer is usually of high resistance (resistance of a general resin), but has the property that the specific resistance of the portion irradiated with the laser beam 3Y changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output via the exposure device 3 according to the yellow image data sent from a control unit (not shown) to the charged surface of the photoreceptor 1Y. The laser beam 3Y is irradiated onto the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of the yellow image pattern is formed on the surface of the photoreceptor 1Y.

[0136] The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y due to charging. By the laser beam 3Y, the specific resistance of the irradiated portion of the photosensitive layer decreases, and the charged charges on the surface of the photoreceptor 1Y flow. On the other hand, a so-called negative latent image is formed by the remaining charges in the portion not irradiated by the laser beam 3Y. The electrostatic charge image formed on the photoreceptor 1Y is rotated to a predetermined development position according to the travel of the photoreceptor 1Y. And at this development position, the electrostatic charge image on the photoreceptor 1Y is visualized as a toner image (developed image) by the developing device 4Y.

[0137] Inside the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, has the same polarity (negative polarity) as the charged charges on the photoreceptor 1Y, and is held on a developer roll (an example of a developer holding member). And as the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the discharged latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed by the yellow toner. The photoreceptor 1Y on which the yellow toner image is formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

[0138] When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and the electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y acts on the toner image, and the toner image on the photoreceptor 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has the opposite polarity (+) to the polarity (-) of the toner. For example, in the first unit 10Y, it is controlled to +10 μA by a control unit (not shown). On the other hand, the toner remaining on the photoreceptor 1Y is removed and recovered by the photoreceptor cleaning device 6Y.

[0139] Also, the primary transfer biases applied to the primary transfer rolls 5M, 5C, 5K after the second unit 10M are also controlled according to the first unit. In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred in the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and toner images of each color are superimposed and multi-transferred.

[0140] The intermediate transfer belt 20 onto which four-color toner images have been multi-transferred through the first to fourth units reaches a secondary transfer section composed of the intermediate transfer belt 20, a support roll 24 in contact with the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of secondary transfer means) 26 disposed on the image holding surface side of the intermediate transfer belt 20. On the other hand, the recording paper (an example of a recording medium) P is fed at a predetermined timing into the gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact via a supply mechanism, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a (-) polarity that is the same polarity as the polarity of the toner (-), and an electrostatic force directed from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the toner image on the intermediate transfer belt 20 is transferred onto the recording paper P. Note that the secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) that detects the resistance of the secondary transfer section and is voltage-controlled.

[0141] Thereafter, the recording paper P is fed into the pressure contact section (nip section) of a pair of fixing rolls in the fixing device (an example of fixing means) 28, and the toner image is fixed onto the recording paper P, forming a fixed image.

[0142] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copiers, printers, etc. Examples of the recording medium other than the recording paper P also include OHP sheets. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper obtained by coating the surface of plain paper with resin or the like, art paper for printing, etc. are preferably used.

[0143] The recording paper P on which the fixing of the color image has been completed is carried out toward the discharge section, and a series of color image forming operations are terminated.

[0144] <Process cartridge / Toner cartridge> A process cartridge according to this embodiment will be described. The process cartridge according to this embodiment contains the electrostatic charge image developer according to this embodiment, and includes developing means for developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer, and is a process cartridge that is detachable from the image forming apparatus.

[0145] Note that the process cartridge according to this embodiment is not limited to the above configuration, and may be configured to include a developing device and at least one selected from other means such as, for example, an image carrier, charging means, electrostatic charge image forming means, and transfer means as necessary.

[0146] Hereinafter, an example of the process cartridge according to this embodiment is shown, but it is not limited thereto. Note that the main parts shown in the figure will be described, and the description of the others will be omitted.

[0147] FIG. 2 is a schematic configuration diagram showing the process cartridge according to this embodiment. The process cartridge 200 shown in FIG. 2 is configured by integrally combining and holding, for example, a photosensitive member 107 (an example of an image carrier), a charging roll 108 (an example of charging means) provided around the photosensitive member 107, a developing device 111 (an example of developing means), and a photosensitive member cleaning device 113 (an example of cleaning means) with a housing 117 having an attachment rail 116 and an opening 118 for exposure, and is made into a cartridge. Note that in FIG. 2, 109 indicates an exposure device (an example of electrostatic charge image forming means), 112 indicates a transfer device (an example of transfer means), 115 indicates a fixing device (an example of fixing means), and 300 indicates a recording paper (an example of a recording medium).

[0148] Next, the toner cartridge according to this embodiment will be described. The toner cartridge according to this embodiment is a toner cartridge that houses the toner according to this embodiment and is detachable from the image forming apparatus. The toner cartridge houses replenishing toner for supplying to developing means provided in the image forming apparatus.

[0149] Note that the image forming apparatus shown in FIG. 1 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K are detachable, and the developing devices 4Y, 4M, 4C, and 4K are connected by toner supply pipes (not shown) to the toner cartridges corresponding to the respective developing devices (colors). Further, when the amount of toner housed in the toner cartridge becomes small, the toner cartridge is replaced.

Example

[0150] Hereinafter, examples and comparative examples will be given to describe this embodiment in more specific detail, but this embodiment is not limited to these examples in any way. Note that "parts" and "%" indicating amounts are based on mass unless otherwise specified.

[0151] <Preparation of amorphous resin> (Preparation of amorphous polyester resin (A)) ·Terephthalic acid: 70 parts ·Fumaric acid: 30 parts ·Ethylene glycol: 41 parts ·1,5-Pentanediol: 48 parts The above materials were charged into a 5-liter flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column, and the temperature was raised to 220°C over 1 hour under a nitrogen gas stream. 1 part of titanium tetraethoxide was added to 100 parts of the above materials. The temperature was raised to 240°C over 0.5 hour while distilling off the generated water, and after continuing the dehydration condensation reaction at this temperature for 1 hour, the reaction product was cooled. Thus, an amorphous polyester resin (A) having a weight average molecular weight of 96,000 and a glass transition temperature of 61°C was synthesized.

[0152] <Preparation of amorphous resin particle dispersion> (Preparation of Amorphous Polyester Resin Particle Dispersion (A1)) Into a container equipped with temperature control means and nitrogen replacement means, 40 parts of ethyl acetate and 25 parts of 2-butanol were charged to form a mixed solvent. Then, 100 parts of amorphous polyester resin (A) was gradually charged and dissolved. Here, a 10% aqueous ammonia solution (equivalent to 3 times the molar amount based on the acid value of the resin) was added and stirred for 30 minutes. Next, the inside of the container was replaced with dry nitrogen, the temperature was maintained at 40 °C, and while stirring the mixed solution, 400 parts of ion-exchanged water was dropped at a rate of 2 parts / minute for emulsification. After the dropping was completed, the emulsion was returned to 25 °C to obtain a resin particle dispersion in which resin particles with a volume average particle diameter of 190 nm were dispersed. Ion-exchanged water was added to the resin particle dispersion to adjust the solid content to 20% to obtain an amorphous polyester resin particle dispersion (A1).

[0153] <Preparation of Crystalline Resin> (Preparation of Crystalline Polyester Resin (B)) ·1,10-Decanedicarboxylic acid: 265 parts ·1,6-Hexanediol: 168 parts ·Dibutyltin oxide (catalyst): 0.3 parts by mass Into a heated and dried three-necked flask, the above components were put in. Then, by a vacuum operation, the air in the container was made into an inert atmosphere with nitrogen gas, and stirring and refluxing were carried out at 180 °C for 5 hours with mechanical stirring. Thereafter, the temperature was gradually raised to 230 °C under reduced pressure and stirred for 2 hours. When it became viscous, it was air-cooled to stop the reaction. By molecular weight measurement (in terms of polystyrene conversion), the weight average molecular weight (Mw) of the obtained "crystalline polyester resin (B)" was 12700, and the melting temperature was 73 °C.

[0154] <Preparation of Crystalline Polyester Resin Particle Dispersion> (Preparation of Crystalline Polyester Resin Particle Dispersion (B1)) 90 parts by mass of a crystalline polyester resin (B), 1.8 parts by mass of an ionic surfactant Neogen RK (Daiichi Kogyo Seiyaku Co., Ltd.), and 210 parts by mass of ion-exchanged water were used. The mixture was heated to 120 °C and sufficiently dispersed with an Ultra Turrax T50 manufactured by IKA, and then subjected to a dispersion treatment with a pressure discharge type Gorin homogenizer for 1 hour to obtain a crystalline polyester resin particle dispersion (B1) having a volume average particle diameter of 190 nm and a solid content of 20 parts by mass.

[0155] <Preparation of a hybrid resin (an amorphous resin having an amorphous polyester resin segment and a styrene acrylic resin segment) particle dispersion (SPE1)> The inside of a four-necked flask equipped with a nitrogen inlet tube, a dehydrating tube, a stirrer, and a thermocouple was purged with nitrogen. 5,670 parts of polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, 585 parts of polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, 2,450 parts of terephthalic acid, and 44 parts of tin(II) bis(2-ethylhexanoate) were put in, and the temperature was raised to 235 °C while stirring under a nitrogen atmosphere and maintained for 5 hours. Then, the pressure inside the flask was further reduced and maintained at 8.0 kPa for 1 hour. After returning to atmospheric pressure, it was cooled to 190 °C, 42 parts of fumaric acid and 207 parts of trimellitic acid were added, and after maintaining at a temperature of 190 °C for 2 hours, the temperature was raised to 210 °C over 2 hours. Further, the pressure inside the flask was reduced and maintained at 8.0 kPa for 4 hours to obtain an amorphous polyester resin A (polyester segment). Next, 800 parts of the amorphous polyester resin A was added to a four-necked flask equipped with a condenser, a stirring device, and a thermocouple, and stirring was carried out at a stirring speed of 200 rpm under a nitrogen atmosphere. Then, as an addition polymerizable monomer, 40 parts of styrene, 142 parts of ethyl acrylate, 16 parts of acrylic acid, 2 parts of 1,10-decanediol diacrylate, and 1000 parts of toluene were added, and further mixed for 30 minutes. Furthermore, 6 parts of polyoxyethylene alkyl ether (nonionic surfactant, trade name: Emulgen 430, manufactured by Kao Corporation), 40 parts of 15% aqueous sodium dodecylbenzenesulfonate solution (anionic surfactant, trade name: Neopelex G-15, manufactured by Kao Corporation), and 233 parts of 5% potassium hydroxide were added, and while stirring, the temperature was raised to 95 °C to melt, and mixed at 95 °C for 2 hours to obtain a resin mixture solution. Next, while stirring the resin mixture solution, 1,145 parts of deionized water was dropped at a rate of 6 parts / minute to obtain an emulsion. Next, the obtained emulsion was cooled to 25 °C, passed through a 200-mesh wire net, and deionized water was added to adjust the solid content to 20% to obtain a hybrid resin particle dispersion (SPE1). In addition, the content of the structural unit derived from styrene in the synthesized hybrid resin was 4% by mass based on the total mass of the hybrid resin.

[0156] (Preparation of Colorant Particle Dispersion) · Carbon black (Cabot Corporation, Regal 330): 50 parts · Ionic surfactant Neogen RK (Daiichi Kogyo Seiyaku Co., Ltd.): 5 parts · Ion-exchanged water: 193 parts The above components were mixed and treated at 240 MPa for 10 minutes with an Altimizer (manufactured by Sugino Machine Limited) to prepare a colorant particle dispersion (solid content concentration: 20%).

[0157] <Preparation of Release Agent Particle Dispersion> (Preparation of Release Agent Particle Dispersion (W1)) · Ester wax (WEP-5 manufactured by NOF Corporation, melting temperature 85 °C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed and heated to 100 °C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin) to obtain a release agent particle dispersion (W1) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed.

[0158] (Preparation of Release Agent Particle Dispersion (W2)) · Ester wax (WEP-9 manufactured by NOF Corporation, melting temperature 67 °C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100 °C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W2) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0159] (Preparation of Release Agent Particle Dispersion (W3)) · Ester wax (WEP-2 manufactured by NOF Corporation, melting temperature 60 °C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100 °C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W3) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0160] (Preparation of Release Agent Particle Dispersion (W4)) · Paraffin wax (HNP-9 manufactured by Nippon Seiro Co., Ltd., melting temperature 75 °C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100 °C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W4) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0161] (Preparation of Release Agent Particle Dispersion (W5)) · Polyethylene wax (PW600 manufactured by Toyo Adrees Co., Ltd., melting temperature 91°C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gorin high-pressure homogenizer (manufactured by Gorin). A release agent particle dispersion (W5) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0162] (Preparation of Release Agent Particle Dispersion (W6)) · Paraffin wax (FT-100 manufactured by Nippon Seiro Co., Ltd., melting temperature 98°C): 100 parts · Sodium octylbenzenesulfonate (manufactured by Wako Pure Chemical Industries, Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gorin high-pressure homogenizer (manufactured by Gorin). A release agent particle dispersion (W5) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0163] (Preparation of Release Agent Particle Dispersion (W7)) · Ester wax (WEP-5 manufactured by NOF Corporation, melting temperature 85°C): 100 parts · Sodium benzenoxybistetrapolypropylene sulfonate (manufactured by Dow Chemical): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gorin high-pressure homogenizer (manufactured by Gorin). A release agent particle dispersion (W1) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0164] (Preparation of Release Agent Particle Dispersion (W8)) · Paraffin wax (HNP-9 manufactured by Nippon Seiro Co., Ltd., melting temperature 75°C): 100 parts · Sodium benzenedioxybistetrapropylenesulfonate (manufactured by Dow Chemical): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W1) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0165] (Preparation of Release Agent Particle Dispersion (WC1)) · Ester wax (WEP-5 manufactured by NOF Corporation, melting temperature 85°C): 100 parts · Anionic surfactant (Neogen RK manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W2) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0166] (Preparation of Release Agent Particle Dispersion (WC2)) · Paraffin wax (HNP-9 manufactured by Nippon Seiro Co., Ltd., melting temperature 75°C): 100 parts · Anionic surfactant (Neogen RK manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.): 3 parts · Ion-exchanged water: 350 parts The above materials were mixed, heated to 100°C, dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin). A release agent particle dispersion (W2) (solid content 20%) in which release agent particles with a volume average particle diameter of 220 nm were dispersed was obtained.

[0167] <Example 1> - Preparation of Toner Particles - · Amorphous polyester resin particle dispersion (A1): 230 parts (solid content 20%) · Crystalline polyester resin particle dispersion (B1): 60 parts (solid content 20%) · Colorant dispersion: 20 parts (solid content 20%) · Anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.: Neogen RK, 20%): 2.0 parts · Ion-exchanged water: 215 parts The above components were placed in a 3-liter reaction vessel equipped with a thermometer, a pH meter, and a stirrer, and while controlling the temperature with a mantle heater from the outside, they were held at a temperature of 30°C and a stirring rotation speed of 150 rpm for 30 minutes. Then, a 0.3N nitric acid aqueous solution was added to adjust the pH to 3.0 in the aggregation step.

[0168] While dispersing with a homogenizer (Ultra Turrax T50 manufactured by IKA Japan), an aqueous PAC solution in which 0.7 part of PAC (powder product, 30% manufactured by Oji Paper Co., Ltd.) was dissolved in 7 parts of ion-exchanged water was added. Then, while stirring, the temperature was raised to 50°C, and the particle size was measured with a Coulter Multisizer II (aperture diameter: 50 μm, manufactured by Coulter), and the volume average particle size was set to 4.5 μm. Next, a mixed solution of 30 parts of the amorphous polyester resin particle dispersion (A1) adjusted to pH 4.0 and 40 parts of the mold release agent dispersion (W1) was additionally added and held for 30 minutes. Further, 75 parts of the amorphous polyester resin particle dispersion (A1) adjusted to pH 4.0 was additionally added to set the volume average particle size to 5.0 μm. Subsequently, 20 parts of a 10% aqueous solution of an NTA (nitrilotriacetic acid) metal salt (Krest 70: manufactured by Krest Co., Ltd.) was added, and then the pH was adjusted to 9.0 using a 1N aqueous sodium hydroxide solution. Then, the temperature was heated to 80°C all at once, held for 60 minutes, cooled to 30°C, and filtered to obtain coarse toner particles. This was further redispersed in ion-exchanged water and filtered repeatedly until the electrical conductivity of the filtrate became 20 μS / cm or less, and then vacuum dried in an oven at 40°C for 5 hours to obtain toner particles.

[0169] -Production of Toner- To 100 parts of the obtained toner particles, 1.5 parts of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd., RY50) was mixed at 10,000 rpm for 30 seconds using a sample mill. Then, the toner was obtained by sieving with a vibrating sieve having an aperture of 45 μm.

[0170] <Examples 2 to 40, Comparative Examples 1 and 2> Toner particles were obtained in the same manner as in Example 1, except that the conditions of the amount and type of the dispersion liquid and the coalescence temperature of the coalesced particles were changed according to Table 1.

[0171] <Properties> For the toner of each example, the following properties were measured according to the method described above. ·Maximum diameter of toner particles ·Domain diameter of release agent ·Number of release agent domains having a domain diameter of 8% or more and 30% or less with respect to the maximum diameter of toner particles (denoted as "number of large domains" in the table) ·Shortest distance between the release agent domain and the surface of the toner particle (denoted as "WT shortest distance" in the table)

[0172] ·Ratio (number %) of toner particles A1 satisfying condition (A1) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles A2 satisfying condition (A2) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles B1 satisfying condition (B1) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles B2 satisfying condition (B2) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles AC1 satisfying condition (A1) and condition (C) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles AC2 satisfying condition (A2) and condition (C) with respect to all toner particles (100 particles measured) ·Ratio (number %) of toner particles BC1 satisfying condition (B1) and condition (C) with respect to all toner particles (100 particles measured) · The ratio (number %) of toner particles BC2 satisfying condition (B2) and condition (C) with respect to all toner particles (100 particles measured)

[0173] Note that Table 2 shows the forms of the release agent domains of typical toner particles. Specifically, it is as follows.

[0174] <Evaluation> (Preparation of developer) Using the toner of each example, a developer was obtained as follows. Spherical magnetite powder particles (volume average particle diameter: 0.55 μm): 500 parts were sufficiently stirred with a Henschel mixer, then 5.0 parts of a titanate coupling agent was added, the temperature was raised to 100 °C, and the mixture was mixed and stirred for 30 minutes to obtain titanate coupling agent-coated spherical magnetite particles. Subsequently, 6.25 parts of phenol, 9.25 parts of 35% formalin, 500 parts of the above magnetite particles, 6.25 parts of 25% aqueous ammonia, and 425 parts of water were placed in a four-necked flask and mixed and stirred. Next, after reacting at 85 °C for 120 minutes while stirring, it was cooled to 25 °C, 500 parts of water was added, the supernatant was removed, and the precipitate was washed with water. This was dried under reduced pressure at 150 °C or higher and 180 °C or lower to obtain a carrier with an average particle diameter of 35 μm. Then, the toner of each example and the obtained carrier were put into a V blender at a ratio of toner:carrier = 5:95 (mass ratio) and stirred for 20 minutes to obtain a developer.

[0175] (Image dropout) Using the obtained developer, image dropout was evaluated as follows. The developers obtained in each example and comparative example were respectively filled into the developing machine of a modified image forming apparatus "DocuCentrecolor 400 manufactured by Fuji Xerox Co., Ltd.". With this image forming apparatus, in an environment of a temperature of 28 °C and a humidity of 85% RH, a solid image (toner loading amount (TMA) 10.0 g / m 2 of the image) with a length of 100 mm and a width of 100 mm was output 100 sheets on embossed paper (manufactured by Tokai Pulp Co., Ltd., trade name: Rezac 66, 203 gsm). As an evaluation of image dropout of the solid image at the 1,000th output, the solid image was visually checked and checked with a magnifying glass (area magnification 10 times), and the grade was determined according to the following criteria. The evaluation was up to E as the allowable range. A: In the embossed paper, the image dropout part cannot be visually confirmed. B: In the embossed paper, the image dropout part cannot be visually confirmed, but the number of image dropout parts is within 10 points with a magnifying glass. C: In the embossed paper, image dropout exists in the range where the image area is 2% or less. D: In the embossed paper, image dropout exists in the range where the image area is 5% or less. E: In the embossed paper, image dropout exists in the range where the image area is 10% or less. F: In the embossed paper, image dropout exists in the range where the image area is larger than 10%, which is not an acceptable level.

[0176]

Table 1-1

[0177]

Table 1-2

[0178]

Table 1-3

[0179] From the above results, it can be seen that this example suppresses image dropout that occurs when forming an image with a large toner loading amount at high speed on a thin recording medium compared to the comparative example.

Explanation of Signs

[0180] 1Y, 1M, 1C, 1K Photoconductor (an example of an image holding member) 2Y, 2M, 2C, 2K Charging Roll (an example of a charging means) 3 Exposure Device (an example of an electrostatic charge image forming means) 3Y, 3M, 3C, 3K Laser Beam 4Y, 4M, 4C, 4K Developing Device (An Example of Developing Means) 5Y, 5M, 5C, 5K Primary Transfer Roll (An Example of Primary Transfer Means) 6Y, 6M, 6C, 6K Photoconductor Cleaning Device (An Example of Cleaning Means) 8Y, 8M, 8C, 8K Toner Cartridge 10Y, 10M, 10C, 10K Image Forming Unit 20 Intermediate Transfer Belt (An Example of Intermediate Transfer Medium) 22 Driving Roll 24 Supporting Roll 26 Secondary Transfer Roll (An Example of Secondary Transfer Means) 30 Intermediate Transfer Medium Cleaning Device 107 Photoconductor (An Example of Image Holding Body) 108 Charging Roll (An Example of Charging Means) 109 Exposure Device (An Example of Electrostatic Charge Image Forming Means) 111 Developing Device (An Example of Developing Means) 112 Transfer Device (An Example of Transfer Means) 113 Photoconductor Cleaning Device (An Example of Cleaning Means) 115 Fixing Device (An Example of Fixing Means) 116 Mounting Rail 118 Aperture for Exposure 117 Housing 200 Process Cartridge 300 Recording Paper (An Example of Recording Medium) P Recording Paper (An Example of Recording Medium)

Claims

Claim 1: An electrostatic charge image developing toner containing a binder resin containing an amorphous resin having a polyester resin segment and a styrene acrylic resin segment, or an amorphous polyester resin, and a release agent, wherein the proportion of the binder resin in the amorphous resin having the polyester resin segment and the styrene acrylic resin segment is 60% by mass or more and 98% by mass or less, the proportion of the binder resin in the amorphous polyester resin is 60% by mass or more and 98% by mass or less, and having toner particles satisfying the following condition (A1) when observing a cross section of the toner particles. Condition (A1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particles, and the entire domain exists within the interior of the toner particles at a depth of 50 nm or more from the surface of the toner particles, and having one or more domains of the release agent. Claim 2 The electrostatic charge image developing toner according to claim 1, wherein when observing a cross section of the toner particles, the toner particles satisfy the following condition (A2). Condition (A2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 2 from the surface of the toner particles, and the entire domain exists within the interior of the toner particles at a depth of 50 nm or more from the surface of the toner particles, and having a plurality of domains of the release agent. Claim 3 The electrostatic charge image developing toner according to claim 1 or claim 2, wherein when observing a cross section of the toner particles, the toner particles satisfy the following condition (B1). Condition (B1): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particles, and the entire domain exists within the interior of the toner particles at a depth of 50 nm or more from the surface of the toner particles, and having one or more domains of the release agent. Claim 4 The electrostatic charge image developing toner according to claim 3, wherein when observing a cross section of the toner particles, the toner particles satisfy the following condition (B2). Condition (B2): The domain diameter with respect to the maximum diameter of the toner particles is 8% or more and 30% or less. When the distance from the center of gravity of the toner particles to the surface of the toner particles is R, the center of gravity of the domain exists within a depth of R / 3 from the surface of the toner particles, and the entire domain exists inside the toner particles at a depth of 50 nm or more from the surface of the toner particles. There are a plurality of domains of the release agent.

5. The electrostatic charge image developing toner according to any one of claims 1 to 4, wherein when the cross-section of the toner particles is observed, the toner particles satisfy the following condition (C). Condition (C): The circularity of the domain of the release agent is 0.92 or more and 1.00 or less.

6. The electrostatic charge image developing toner according to any one of claims 1 to 5, wherein the melting temperature of the release agent is 65°C or more and 95°C or less.

7. The electrostatic charge image developing toner according to claim 6, wherein the release agent having a melting temperature of 65°C or more and 95°C or less is an ester wax.

8. The electrostatic charge image developing toner according to any one of claims 1 to 7, wherein the toner particles contain, as the binder resin, the amorphous resin having the polyester resin segment and the styrene acrylic resin segment.

9. The electrostatic charge image developing toner according to claim 8, wherein the toner particles further contain a crystalline polyester resin as the binder resin.

10. The electrostatic charge image developing toner according to any one of claims 1 to 9, wherein the content of the toner particles is 30% by number or more based on all the toner particles.

11. The electrostatic charge image developing toner according to claim 10, wherein the content of the toner particles is 70% by number or more based on all the toner particles.

12. An electrostatic charge image developer containing the electrostatic charge image developing toner according to any one of claims 1 to 11.

13. A toner cartridge that houses the electrostatic charge image developing toner according to any one of claims 1 to 11, and is detachable from an image forming apparatus.

14. A process cartridge that houses the electrostatic charge image developer according to claim 12, and includes developing means for developing an electrostatic charge image formed on the surface of an image carrier as a toner image with the electrostatic charge image developer, and is detachable from an image forming apparatus.

15. An image carrier, charging means for charging the surface of the image carrier, electrostatic charge image forming means for forming an electrostatic charge image on the charged surface of the image carrier, Developing means for accommodating the electrostatic charge image developer according to claim 12 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer; Transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; Fixing means for fixing the toner image transferred to the surface of the recording medium; An image forming apparatus comprising the above.

16. A charging step of charging the surface of the image carrier; An electrostatic charge image forming step of forming an electrostatic charge image on the charged surface of the image carrier; A developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to claim 12; A transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; A fixing step of fixing the toner image transferred to the surface of the recording medium; An image forming method having the above steps.

Images