Electrostatic image developing toner, method for producing electrostatic image developing toner, electrostatic image developer, toner cartridge, process cartridge, and image forming apparatus

Abstract

To provide an electrostatic charge image development toner which produces a fixed image with superior color development.SOLUTION: An electrostatic charge image development toner provided herein comprises toner particles containing a binder resin, and exhibits Tg1 of 58-68°C, inclusive, and (Tg1-Tg2) of 20-40°C, inclusive, where Tg1 represents the lowest onset temperature in endothermic change during the first temperature rise in a differential calorimetric curve of the toner particles and Tg2 represents the lowest onset temperature in endothermic change during the second temperature rise.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images, a method for producing a toner for developing electrostatic images, an electrostatic image developer, a toner cartridge, a process cartridge, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a method for producing a toner, which includes a first step of heating a dispersion containing toner base particles, which are produced by aggregating and fusing fine particles of a binder resin containing a crystalline resin in the presence of metal ions, and an aqueous medium, to a temperature equal to or higher than the melting point of the crystalline resin, and a second step of maintaining a temperature T (°C) of the dispersion that satisfies the formula Rc-25≦T≦Rc-5 (Rc is the recrystallization temperature of the crystalline resin) for 30 minutes or more while maintaining the pH of the dispersion at 5.5 or higher and 9.0 or lower.

[0003] Patent Document 2 describes a method for measuring a glass transition temperature of a glass material in which a diffraction peak is present at least at 2θ=20° to 25° in an X-ray diffraction measurement, and the glass transition temperature is measured by using a differential scanning calorimeter (DSC) in which the starting temperature is 20° C., the temperature is raised to 120° C. at 10° C. / min, the temperature is held at 120° C. for 10 minutes, the temperature is lowered to 0° C. at 10° C. / min, there is no holding time at 0° C., and the glass transition temperature observed in the final heating step is compared with the starting temperature of 20° C. The toner is characterized by being heated and cooled under the following temperature rising and cooling conditions: temperature rise to 120°C at 10°C / min, held at 120°C for 10 minutes, cooled to 0°C at 10°C / min, no holding time at 0°C, temperature rise to 45°C at 10°C / min and held for 24 hours, temperature fall to 0°C again at 10°C / min, no holding time at 0°C, and temperature rise to 150°C at 10°C / min, and the difference between the glass transition temperature observed in the final heating step and the temperature rise is within 10°C.

[0004] Patent Document 3 describes a toner containing at least an amorphous polyester and a crystalline polyester as a binder resin, and measuring the glass transition temperature Tg of the toner by a differential scanning calorimeter when a toner sample is heated from 30° C. to 170° C. at a rate of 10° C. / min. 1st is 60 to 70°C, and the Tg 1st and the Tg 1st After measuring the glass transition temperature Tg of the toner, the toner sample is cooled to 30°C at a rate of 100°C / min, and then the toner sample is heated from 30°C to 170°C at a rate of 10°C / min. 2nd The formula "10℃≦Tg 1st -Tg 2nd ≦15°C" relationship, and the content of molecules having a molecular weight of 50,000 or more in the tetrahydrofuran-soluble matter of the toner is 20 to 35 mass %, and the content of molecules having a molecular weight of 10,000 or less is 40 to 55 mass %. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-156505 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-206632 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-076915 Summary of the Invention [Problem to be solved by the invention]

[0006] From the viewpoint of increasing the speed and saving energy of image forming apparatuses, a toner with high low-temperature fixability is required. As a method for obtaining low-temperature fixability of a toner, for example, a method of controlling the glass transition temperature of the toner within a specific range is considered. However, a toner with a controlled glass transition temperature may obtain a fixed image with low color development, although the toner has low low-temperature fixability.

[0007] The present invention aims to provide a toner for developing electrostatic images that can provide fixed images with excellent color development compared to toner particles having a Tg1 of 58°C or higher and 68°C or lower, and a Tg1-Tg2 ratio of less than 20°C. [Means for solving the problem]

[0008] Specific means for solving the above problems include the following aspects.

[0009] <1> The toner particles include a binder resin, a toner for developing electrostatic images, wherein, in a differential scanning calorimetry curve of the toner particles, Tg1 is the lowest onset temperature in the change in the amount of heat absorbed during the first temperature rise, and Tg2 is the lowest onset temperature in the change in the amount of heat absorbed during the second temperature rise, and Tg1 is 58°C or higher and 68°C or lower, and Tg1-Tg2 is 20°C or higher and 40°C or lower. <2> The BET specific surface area of ​​the toner particles is 1.0 m 2 / g or more 2.0m 2 / g or less, <1> 2. The toner for developing electrostatic images according to claim 1.

[0010] <3> The binder resin includes a polyester resin. <1> or <2> 2. The toner for developing electrostatic images according to claim 1. <4> The polyester resin includes a crystalline polyester resin. <3> 2. The toner for developing electrostatic images according to claim 1. <5> The content of the crystalline polyester resin is 5% by mass or more and 25% by mass or less with respect to the total amount of the binder resin. <4> 2. The toner for developing electrostatic images according to claim 1. <6> The binder resin further contains a vinyl resin. <3> ~ <5> 10. The toner for developing electrostatic images according to claim 9, wherein the toner is a toner for developing electrostatic images. <7> The content of the vinyl resin is 1% by mass or more and 30% by mass or less with respect to the total amount of the toner particles. <6> 2. The toner for developing electrostatic images according to claim 1.

[0011] <8> a first cooling step of cooling a toner particle dispersion liquid in which toner particles containing a binder resin are dispersed in a dispersion medium from a fusion temperature of T1°C or higher to a first cooling temperature of lower than T2°C; a holding step of lowering the pH of the toner particle dispersion liquid that has been subjected to the first cooling step and holding the toner particle dispersion liquid at a holding temperature of T3°C or higher and T4°C or lower for 0.5 hours or higher and 3 hours or lower; a second cooling step of cooling the toner particle dispersion liquid that has been subjected to the holding step to a second cooling temperature that is lower than T5°C and is lower than the holding temperature; A method for producing a toner for developing electrostatic images, comprising: T1°C: Tg0°C + 29°C, where Tg0°C is the glass transition temperature of the toner particles before the first cooling step. T2℃: Tg0℃+9℃ T3℃: Tg0℃+4℃ T4℃: Tg0+14℃ T5℃: Tg0℃+9℃

[0012] <9> In the maintaining step, the pH of the toner particle dispersion liquid that has been subjected to the first cooling step is set to 7.0 or more and 9.0 or less. <8> 10. A method for producing the toner for developing electrostatic images according to claim 9. <10> The cooling rate A1 in the first cooling step is 30°C / min or more and 130°C / min or less. <8> or <9> 10. A method for producing the toner for developing electrostatic images according to claim 9.

[0013] <11> The binder resin includes a polyester resin. <8> ~ <10> 10. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 9. <12> The polyester resin includes a crystalline polyester resin. <11> 10. A method for producing the toner for developing electrostatic images according to claim 9. <13> The content of the crystalline polyester resin is 5% by mass or more and 25% by mass or less with respect to the total amount of the binder resin. <12> 10. A method for producing the toner for developing electrostatic images according to claim 9. <14> The binder resin further contains a vinyl resin. <11> ~ <13> 10. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 9. <15> The content of the vinyl resin is 1% by mass or more and 30% by mass or less with respect to the total amount of the toner particles. <14> 10. A method for producing the toner for developing electrostatic images according to claim 9.

[0014] <16> <8> ~ <15> 10. A toner for developing electrostatic images, which is obtained by the method for producing a toner for developing electrostatic images according to any one of 1 to 8.

[0015] <17> <1> ~ <7> and <16> 10. An electrostatic image developer comprising the toner for developing electrostatic images according to any one of claims 1 to 9. <18> <1> ~ <7> and <16> The toner for developing electrostatic images according to any one of the above items is contained, A toner cartridge that is detachably attached to an image forming device. <19> <17> and a developing means for developing an electrostatic image formed on the surface of an image carrier into a toner image by using the electrostatic image developer, A process cartridge is detachably mounted in an image forming apparatus. <20> an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; <17> a developing means for developing the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer; a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing means for fixing the toner image transferred onto the surface of the recording medium; An image forming apparatus comprising: [Effects of the Invention]

[0016] <1> , <3> , or <4> According to the invention, there is provided a toner for developing electrostatic images, which can produce fixed images with excellent color development compared to when the Tg1 of the toner particles is 58°C or higher and 68°C or lower, and Tg1-Tg2 is lower than 20°C. <2> According to the invention, the BET specific surface area is 2.0 m 2 / g, a toner for developing electrostatic images is provided which has excellent color development properties for fixed images both in a high temperature and high humidity environment (temperature 30°C, humidity 85%) and in a low temperature and low humidity environment (temperature 10°C, humidity 15%).

[0017] <5> According to the invention, there is provided a toner for developing electrostatic images that can provide fixed images with excellent color development compared to when the content of the crystalline polyester resin exceeds 25% by mass. <6> According to the invention, there is provided a toner for developing electrostatic images in which dot-like white spots caused by aggregation of toner are suppressed compared to when the binder resin is made of polyester resin. <7> According to the invention, there is provided a toner for developing electrostatic images that can provide fixed images with excellent color development compared to when the vinyl resin content exceeds 30% by mass.

[0018] <8> , <11> , or <12> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can provide a fixed image with excellent color development compared to a case where the holding step and the second cooling step are not carried out. <9> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can provide fixed images with excellent color development compared to when the pH of the toner particle dispersion in the maintaining step is set to more than 9.0. <10> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can provide fixed images with excellent color development compared to when the cooling rate A1 in the first cooling step is less than 30° C. / min.

[0019] <13> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can provide fixed images with excellent color development compared to when the content of the crystalline polyester resin exceeds 25% by mass. <14> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can produce a toner for developing electrostatic images in which spot-like white spots caused by aggregation of the toner are suppressed compared to when the binder resin is made of a polyester resin. <15> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can provide fixed images with excellent color development properties compared to when the content of the vinyl resin exceeds 30% by mass.

[0020] <16> According to the invention, there is provided a toner for developing electrostatic images that can provide fixed images with excellent color development compared to when the toner does not undergo the holding step and the second cooling step.

[0021] <17> , <18> , <19> , or <20> According to the invention, there is provided an electrostatic image developer, a toner cartridge, a process cartridge, or an image forming apparatus, which includes a toner for developing electrostatic images that can provide fixed images with excellent color development, compared to when the toner particles have a Tg1 of 58°C or higher and 68°C or lower and Tg1-Tg2 is lower than 20°C, or when the holding step and second cooling step are not performed. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a process cartridge according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0024] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0025] <Toner for developing electrostatic images> The electrostatic image developing toner according to this embodiment (hereinafter, the electrostatic image developing toner may also be referred to as "toner") has toner particles containing a binder resin, and in a differential scanning calorimetry curve of the toner particles, when Tg1 is the lowest onset temperature in the change in the amount of heat absorbed during the first temperature rise and Tg2 is the lowest onset temperature in the change in the amount of heat absorbed during the second temperature rise, Tg1 is 58°C or more and 68°C or less, and Tg1-Tg2 is 20°C or more and 40°C or less.

[0026] Here, the differential scanning calorimetric curve of the toner particles is obtained by measurement in accordance with ASTM D3418-8. Specifically, 10 mg of toner particles (or toner particles with external additives added) to be measured are placed in a differential scanning calorimeter (Shimadzu Corporation: DSC-60A) equipped with an automatic tangent processing system, and heated from 10°C to 150°C at a heating rate of 10°C / min to obtain a heating spectrum (DSC curve) during the first heating process.Then, the sample is held at 150°C for 5 minutes and cooled to 0°C at a cooling rate of 10°C / min. Next, similarly, the sample is heated from 10°C to 150°C at a rate of 10°C / min, and a temperature rise spectrum (DSC curve) is obtained during the second temperature rise process. After that, the sample is held at 150°C for 5 minutes, and then cooled to 25°C at a rate of 10°C / min. The lowest onset temperature in the change in the amount of heat absorbed in the temperature rise spectrum (DSC curve) during the first temperature rise obtained by the above measurement is designated as Tg1, and the lowest onset temperature in the change in the amount of heat absorbed in the temperature rise spectrum (DSC curve) during the second temperature rise is designated as Tg2.

[0027] The toner according to the present embodiment has the above-described structure, and thus can provide fixed images with excellent color development. The reason for this is presumed to be as follows. Toners with high low-temperature fixability are required from the viewpoint of increasing the speed and saving energy of image forming apparatuses. One method for achieving low-temperature fixability of a toner is, for example, to control the glass transition temperature of the toner within a specific range. Specifically, the low-temperature fixability of a toner can be achieved by adjusting the Tg1 to 58°C or higher and 68°C or lower. However, when a toner having a Tg1 in the above range is used, although low-temperature fixability is obtained, fixed images with low color development may be obtained. The decrease in color development is presumably due to the fact that the resin segments are oriented and crystallized by heating during fixation, which impairs the transparency of the resin and causes the color of the fixed image to become dull.

[0028] In contrast, in this embodiment, Tg1 is 58° C. or higher and 68° C. or lower, and Tg1-Tg2 is 20° C. or higher and 40° C. or lower. Therefore, compared to when Tg1-Tg2 is lower than 20° C., segment orientation of the resin is less likely to occur due to heating, a decrease in transparency due to crystallization of the resin is suppressed, and it is presumed that a fixed image with excellent color development can be obtained. For the above reasons, it is presumed that the toner according to this embodiment can obtain a fixed image with excellent color development while achieving low temperature fixability.

[0029] Furthermore, in this embodiment, since Tg1-Tg2 is 20° C. or more and 40° C. or less, the heat resistance of the fixed image is higher than when Tg1-Tg2 exceeds 40° C. Therefore, image defects (hereinafter also referred to as "print blocking") caused by image transfer when multiple recording media on which fixed images have been formed are stacked are suppressed. Furthermore, in this embodiment, by setting Tg1 to 58°C or higher and 68°C or lower, the resistance to mechanical and thermal loads within the developing unit is improved compared to when Tg1 is lower than 58°C, the toner is less likely to aggregate, and spot-like white spots in the image caused by toner aggregation are suppressed. In addition, in this embodiment, by setting Tg1 to 58°C or higher and 68°C or lower, low-temperature fixability is more easily obtained than when Tg1 exceeds 68°C. Note that, as a method for controlling Tg1 within the above range and controlling Tg1-Tg2 within the above range, for example, a method in which the toner particles undergo a first cooling step, a holding step, and a second cooling step, which will be described later, in the production process of the toner particles, can be mentioned. The toner according to this embodiment will be described in detail below.

[0030] (toner particles) The toner particles are composed of, for example, a binder resin, and, if necessary, a colorant, a release agent, and other additives.

[0031] -Binder resin- Examples of binder resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), and vinyl resins made of copolymers of two or more of these monomers. Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0032] As the binder resin, a polyester resin is preferable. Examples of polyester resins include known amorphous polyester resins. The polyester resin may be used in combination with a crystalline polyester resin. However, the content of the crystalline polyester resin is preferably in the range of 5% by mass to 25% by mass (preferably 5% by mass to 20% by mass) relative to the total binder resin.

[0033] When the content of the crystalline polyester resin relative to the total binder resin is within the above range, the overall crystallinity of the binder resin is lower than when the content is greater than the above range, so that the transparency of the binder resin is improved and a fixed image with excellent color development can be obtained. Furthermore, when the content of the crystalline polyester resin relative to the total binder resin is within the above range, low-temperature fixability can be obtained compared to when the content is less than the above range.

[0034] The "crystalline" nature of a resin refers to the presence of a clear endothermic peak rather than a stepwise change in endothermic heat in differential scanning calorimetry (DSC). Specifically, this refers to the half-width of the endothermic peak being within 10°C when measured at a heating rate of 10°C / min. On the other hand, the term "amorphous" for a resin means that the half-width exceeds 10°C, that the endothermic amount exhibits a stepwise change, or that no clear endothermic peak is observed.

[0035] Amorphous polyester resin Examples of the amorphous polyester resin include a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. Note that, as the amorphous polyester resin, a commercially available product or a synthesized product may be used.

[0036] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. The polycarboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0037] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, preferred polyhydric alcohols are aromatic diols and alicyclic diols, and more preferred are aromatic diols. As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0038] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0039] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a Tosoh GPC HLC-8120GPC measuring device and a Tosoh TSKgel SuperHM-M (15 cm) column in THF solvent. The weight-average molecular weight and number-average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0040] The amorphous polyester resin can be obtained by a known manufacturing method, for example, by carrying out the reaction at a polymerization temperature of 180°C or higher and 230°C or lower, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation. If the raw material monomer is not soluble or compatible at the reaction temperature, a high-boiling solvent may be added as a solubilizer to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the solubilizer. If a monomer with poor compatibility is present, it is advisable to first condense the poorly compatible monomer with the acid or alcohol to be polycondensed, and then polycondense the monomer with the main component.

[0041] Crystalline polyester resin The crystalline polyester resin may be, for example, a polycondensate of a polycarboxylic acid and a polyhydric alcohol. Note that, as the crystalline polyester resin, a commercially available product or a synthesized product may be used. Here, the crystalline polyester resin is preferably a polycondensate using a polymerizable monomer having a linear aliphatic group rather than a polymerizable monomer having an aromatic group, since it easily forms a crystalline structure.

[0042] Examples of polycarboxylic acids 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, and naphthalene-2,6-dicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acid may be a tricarboxylic or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the tricarboxylic 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, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). As the polycarboxylic acid, a dicarboxylic acid having a sulfonic acid group and a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids. The polycarboxylic acids may be used alone or in combination of two or more.

[0043] Examples of polyhydric alcohols include aliphatic diols (for example, straight-chain aliphatic diols having 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols 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, and 1,14-eicosanedecanediol. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols. The polyhydric alcohol may be a trihydric or higher alcohol having a crosslinked or branched structure, such as glycerin, trimethylolethane, trimethylolpropane, or pentaerythritol, in combination with the diol. The polyhydric alcohols may be used alone or in combination of two or more.

[0044] Here, the polyhydric alcohol has an aliphatic diol content of 80 mol % or more, preferably 90 mol % or more.

[0045] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0046] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0047] The crystalline polyester resin can be obtained by a known manufacturing method, for example, in the same manner as the amorphous polyester resin.

[0048] The binder resin preferably further contains a vinyl resin, which suppresses toner aggregation during the toner particle production process and when the toner is stirred in the developing unit, thereby suppressing spot-like white spots caused by toner aggregation. When the binder resin contains a vinyl resin, the content of the vinyl resin relative to the total toner particles is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less. By having the vinyl resin content within the above range, white spots caused by toner aggregation are suppressed compared to when the vinyl resin content is less than the above range. Furthermore, by having the vinyl resin content within the above range, the compatibility between the polyester resin and the vinyl resin is higher, and the transparency of the binder resin is improved, resulting in higher color development of the fixed image compared to when the vinyl resin content is greater than the above range.

[0049] The content of the binder resin is, for example, preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0050] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, and the like. Examples of the dye include various pigments such as phosphorus blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The colorant may be used alone or in combination of two or more kinds.

[0051] The colorant may be surface-treated as needed, or may be used in combination with a dispersant. Furthermore, a plurality of colorants may be used in combination.

[0052] The content of the colorant is, for example, preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner particles.

[0053] -Mold release agent- Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0054] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" as described in the method for determining the melting temperature in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0055] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0056] -Other additives- Examples of other additives include well-known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0057] -Characteristics of toner particles, etc.- The toner particles may be toner particles of a single layer structure, or may be toner particles of a so-called core-shell structure composed of a core part (core particle) and a coating layer (shell layer) that coats the core part. Here, the toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

[0058] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0059] The various average particle sizes and particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter). For the measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of the electrolyte. The electrolyte solution containing the suspended sample is dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. Based on the particle size distribution measured, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the smallest diameter side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v, the number particle size D16p, the particle size at 50% of the cumulative total as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at 84% of the cumulative total as the volume particle size D84v and the number particle size D84p. Using these, the volumetric particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 , the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 It is calculated as:

[0060] The average circularity of the toner particles is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

[0061] The average circularity of toner particles is calculated by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the particle projected image)]. Specifically, this value is measured by the following method. First, the toner particles to be measured are sucked and collected, forming a flat flow, and a still image of the particles is captured by instantaneously activating a strobe light, and the particle image is analyzed using a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation).The number of samples to be sampled when calculating the average circularity is 3,500. When the toner contains external additives, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additives have been removed.

[0062] The Tg1 of the toner particles is 58°C or more and 68°C or less, and from the viewpoint of achieving both low-temperature fixability and suppression of dot-like white spots in the image, it is preferably 60°C or more and 66°C or less, and more preferably 62°C or more and 64°C or less. The Tg1-Tg2 of the toner particles is 20°C or more and 40°C or less, and from the viewpoint of achieving both color development of the fixed image and suppression of print blocking, it is preferably 25°C or more and 38°C or less, and more preferably 30°C or more and 36°C or less. The Tg2 of the toner particles is preferably 15°C or higher and 55°C or lower, more preferably 25°C or higher and 50°C or lower, and even more preferably 30°C or higher and 40°C or lower. When the Tg2 of the toner particles is within this range, the heat resistance of the fixed image is higher than when the Tg2 is higher than this range. Therefore, image defects (i.e., print blocking) caused by image transfer when multiple recording media with fixed images formed thereon are stacked are suppressed. Furthermore, when the Tg2 of the toner particles is within this range, the resistance to mechanical and thermal loads within the developing unit is improved compared to when the Tg2 is lower than this range, and the toner is less likely to aggregate, thereby suppressing spot-like white spots in the image caused by toner aggregation.

[0063] The BET specific surface area of ​​the toner particles is 1.0 m 2 / g or more 2.0m 2 / g or less, and 2 / g or more 1.6m 2 / g or less is more preferable, and 1.3m 2 / g or more 1.5m 2 It is more preferable that the saturation coefficient is 1 / g or less. When the BET specific surface area of ​​the toner particles is within the above range, an increase in charge in a low-temperature, low-humidity environment due to an excessively high surface area is suppressed compared to when the BET specific surface area is greater than the above range, and therefore the difference between the electrical properties in a high-temperature, high-humidity environment and those in a low-temperature, low-humidity environment is reduced, resulting in a fixed image with excellent color development in both high-temperature, high-humidity and low-temperature, low-humidity environments. Furthermore, when the BET specific surface area of ​​the toner particles is within the above range, the resistance to mechanical and thermal loads within the developing unit is higher than when the BET specific surface area is smaller than the above range, the toner is less likely to aggregate, and spot-like white spots in the image caused by the generation of coarse toner powder are suppressed.

[0064] The BET specific surface area of ​​the toner particles is a value measured by the BET method, and is a value measured by a nitrogen substitution method using a BET specific surface area meter (SA3100, manufactured by Beckman Coulter) as a measuring device. Specifically, 1 g of a measurement sample is precisely weighed and placed in a sample tube, and then degassed. The value obtained by automatic measurement using a multipoint method is used as the BET specific surface area (m 2 / g). In addition, when the toner particles to be measured are toners to which external additives have been added on the surface of the toner particles, the external additives may be removed by ultrasonic treatment for 20 minutes with a mixed solution of ion-exchanged water and a surfactant, and the measurement may be performed after the surfactant has been removed and the toner particles have been dried. The external additive removal treatment may be repeated until the external additives have been removed.

[0065] An example of a method for controlling the BET specific surface area of ​​the toner particles within the above range is a method in which the toner particle production process is carried out through a first cooling step, a holding step, and a second cooling step, which will be described later, and the pH of the toner particle dispersion in the holding step is adjusted to a range of 7.0 or more and 9.0 or less.

[0066] (external additives) Examples of external additives include inorganic particles such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, KO, Na2O, ZrO2, CaO·SiO2, KO·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4.

[0067] The surfaces of inorganic particles as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0068] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0069] The amount of the external additive added is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less, based on the toner particles.

[0070] (Toner manufacturing method) Next, a method for producing the toner according to this embodiment will be described. The toner according to this exemplary embodiment is obtained by producing toner particles and then externally adding an external additive to the toner particles.

[0071] The toner particles may be produced by any of a dry production method (for example, a kneading and pulverization method) and a wet production method (for example, an aggregation and coalescence method, a suspension polymerization method, a dissolution and suspension method). The method for producing the toner particles is not particularly limited, and any well-known production method may be used. Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

[0072] Furthermore, the toner particles contained in the toner according to the present embodiment are preferably toner particles that have undergone a first cooling step of cooling a toner particle dispersion in which toner particles containing a binder resin are dispersed in a dispersion medium from a fusion temperature of T1°C or higher to a first cooling temperature of less than T2°C, as described below; a holding step of lowering the pH of the toner particle dispersion that has undergone the first cooling step and holding it at a holding temperature of T3°C or higher and T4°C or lower for 0.5 hours to 3 hours; and a second cooling step of cooling the toner particle dispersion that has undergone the holding step to a second cooling temperature of less than T5°C, as described below, which is lower than the holding temperature.

[0073] T1°C: Tg0°C + 29°C, where Tg0°C is the glass transition temperature of the toner particles before the first cooling step. T2℃: Tg0℃+9℃ T3℃: Tg0℃+4℃ T4℃: Tg0+14℃ T5℃: Tg0℃+9℃

[0074] By undergoing the first cooling step, the holding step, and the second cooling step, it becomes easier to obtain toner particles having Tg1-Tg2 of 20° C. or more and 40° C. or less. The Tg0°C means the lowest onset temperature in the change in heat absorption amount during the first temperature rise in the differential scanning calorimetric curve of the toner particles dispersed in the toner particle dispersion before the first cooling step. The Tg0° C. is, for example, in the range of 20° C. to 60° C., and is preferably 25° C. to 57° C., more preferably 30° C. to 55° C., since low-temperature fixability is easily obtained.

[0075] Specifically, for example, when toner particles are produced by the aggregation and coalescence method, The toner particles are manufactured through the following steps: a step of preparing a resin particle dispersion in which resin particles to be a binder resin are dispersed (resin particle dispersion preparation step); a step of aggregating resin particles (other particles, if necessary) in the resin particle dispersion (in a dispersion after mixing other particle dispersions, if necessary) to form aggregated particles (aggregated particle formation step); a step of heating the aggregated particle dispersion in which the aggregated particles are dispersed to a fusion temperature of T1°C or higher to fuse and coalesce the aggregated particles to form toner particles (fusion and coalescence step); a first cooling step of cooling the toner particle dispersion in which the formed toner particles are dispersed in a dispersion medium from the fusion temperature of T1°C or higher to a first cooling temperature lower than T2°C; a holding step of lowering the pH of the toner particle dispersion that has undergone the first cooling step and holding it at a holding temperature of T3°C or higher and T4°C or lower for 0.5 hours to 3 hours; and a second cooling step of cooling the toner particle dispersion that has undergone the holding step to a second cooling temperature lower than T5°C, which is lower than the holding temperature.

[0076] Each step will be described in detail below. In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described, but the colorant and the release agent are used as needed. Of course, additives other than the colorant and the release agent may also be used.

[0077] -Resin particle dispersion preparation process- First, a resin particle dispersion in which resin particles serving as a binder resin are dispersed, as well as 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.

[0078] Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

[0079] Examples of the dispersion medium used in the resin particle dispersion include aqueous media. Examples of aqueous media include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more.

[0080] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactants may be used alone or in combination of two or more.

[0081] In the resin particle dispersion, resin particles can be dispersed in a dispersion medium by a general dispersion method such as a rotary shear homogenizer, a ball mill having a medium, a sand mill, a dyno mill, etc. Depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion by, for example, a phase inversion emulsification method. The phase inversion emulsification method involves dissolving the resin to be dispersed in a hydrophobic organic solvent in which the resin is soluble, adding a base to the organic continuous phase (O phase) to neutralize it, and then adding an aqueous medium (W phase), thereby converting the resin from W / O to O / W (so-called phase inversion) and forming a discontinuous phase, and dispersing the resin in particulate form in the aqueous medium.

[0082] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm. The volume average particle size of the resin particles is measured using a particle size distribution obtained by measurement with a laser diffraction particle size distribution analyzer (e.g., LA-700 manufactured by Horiba, Ltd.), and the cumulative distribution for the volume of the divided particle size range (channel) is subtracted from the small particle size side, and the particle size at which the cumulative 50% of all particles is measured is defined as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same way.

[0083] The content of resin particles contained in the resin particle dispersion is, for example, preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass.

[0084] Note that, for example, a colorant particle dispersion and a release agent particle dispersion are also prepared in the same manner as the resin particle dispersion. That is, the volume average particle size, dispersion medium, dispersion method, and particle content of the particles in the resin particle dispersion are the same for the colorant particles dispersed in the colorant particle dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0085] -Agglomerated particle formation process- Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion. Then, in the mixed dispersion, the resin particles, colorant particles, and release agent particles are hetero-aggregated to form aggregated particles containing the resin particles, colorant particles, and release agent particles and having a diameter close to that of the target toner particles.

[0086] Specifically, for example, an aggregating agent is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to be acidic (for example, a pH of 2 or more and 5 or less), and a dispersion stabilizer is added as necessary. After that, the mixed dispersion is heated to the glass transition temperature of the resin particles (specifically, for example, a temperature of the glass transition temperature of the resin particles -30°C or more and the glass transition temperature -10°C or less), and the particles dispersed in the mixed dispersion are aggregated to form aggregated particles. In the aggregate particle formation step, for example, the above-mentioned aggregating agent may be added to the mixed dispersion at room temperature (e.g., 25°C) while stirring with a rotary shear homogenizer, the pH of the mixed dispersion may be adjusted to an acidic value (e.g., pH 2 or more and 5 or less), and a dispersion stabilizer may be added as necessary, followed by the heating.

[0087] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. In particular, when a metal complex is used as the flocculant, the amount of surfactant used can be reduced and the charging characteristics can be improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferably used as this additive.

[0088] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. The chelating agent may be a water-soluble chelating agent, such as hydroxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), etc. The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, per 100 parts by mass of the resin particles.

[0089] -Fusion / unification process- Next, the aggregated particle dispersion liquid in which the aggregated particles are dispersed is heated to a fusion temperature of T1° C. or higher to fuse and coalesce the aggregated particles, thereby forming toner particles.

[0090] After obtaining an aggregated particle dispersion in which aggregated particles are dispersed, the toner particles may be produced through the following steps: a step of further mixing the aggregated particle dispersion with a resin particle dispersion in which resin particles are dispersed, and aggregating the aggregated particles so that further resin particles adhere to the surfaces of the aggregated particles to form second aggregated particles; and a step of heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles to form toner particles having a core / shell structure.

[0091] -First cooling process- Next, the toner particle dispersion liquid in which the toner particles formed in the fusion / coalescence step are dispersed in a dispersion medium is cooled from a fusion temperature of T1°C or higher to a first cooling temperature lower than T2°C. The dispersion medium is not particularly limited as long as it is a liquid that disperses toner particles, and the dispersion medium for aggregated particles in the aggregated particle dispersion liquid may be used as is. The fusion temperature is Tg0°C+29°C or higher, and from the viewpoint of the speed at which the inside of the toner fuses, it is preferably Tg0°C+29°C or higher and Tg0°C+40°C or lower, and more preferably Tg0°C+31°C or higher and Tg0°C+38°C or lower. The first cooling temperature is less than Tg0°C + 9°C, and from the viewpoint of maintaining a smooth toner surface and not deteriorating the electrical properties, it is preferably at least Tg0°C - 34°C and less than Tg0°C + 0°C, and more preferably at least Tg0°C - 24°C and less than Tg0°C - 5°C. The difference between the fusion temperature and the first cooling temperature is more than 20°C, and from the viewpoint of keeping the toner surface smooth and not deteriorating the electrical properties, it is preferably more than 20°C and not more than 50°C, more preferably 30°C or more and 40°C or less.

[0092] The cooling rate A1 in the first cooling step is preferably 30°C / min or more and 130°C / min or less, more preferably 35°C / min or more and 110°C / min or less, and even more preferably 40°C / min or more and 100°C / min or less. By keeping the cooling rate A1 within the above range, toner aggregation is suppressed, white spots on the image caused by toner aggregation are suppressed, and crystallization of the binder resin is suppressed, resulting in a fixed image with excellent color development, compared to when the cooling rate A1 is faster than the above range. By keeping the cooling rate A1 within the above range, there is an advantage that the compatibility between resins is increased, improving low-temperature fixability, compared to when the cooling rate A1 is faster than the above range. Examples of methods for setting the cooling rate A1 within the above range include a method using a heat exchanger and a method of adding cooling water to the toner dispersion liquid. The cooling rate A1 is preferably faster than the cooling rate A2 in the second cooling step described below, more preferably 1.5 to 6 times, and even more preferably 2 to 3 times, the cooling rate A2.

[0093] The pH of the toner particle dispersion in the first cooling step (hereinafter referred to as "pH 1From the viewpoint of suppressing coarse powder of the toner and preventing deterioration of the electrical properties of the toner, the particle size distribution (also referred to as "particle size distribution") is preferably 7.5 or more and 10.0 or less, more preferably 8.0 or more and 9.7 or less, and even more preferably 8.3 or more and 9.5 or less.

[0094] -Holding process- Next, the pH of the toner particle dispersion liquid that has been subjected to the first cooling step is lowered, and the dispersion liquid is kept at a holding temperature of T3° C. or more and T4° C. or less for 0.5 hours or more and 3 hours or less. The pH of the toner particle dispersion in the retention process (hereinafter referred to as "pH 2 ") is a pH 1 Lower pH 1 Preferably, the pH is -0.2 or less. 1 pH greater than -2.1 1 It is more preferable that the pH is -0.2 or less. 1 pH greater than -1.1 1 It is more preferable that it is −0.2 or less.

[0095] pH 2 The pH is preferably 7.0 or more and 9.0 or less, more preferably 7.2 or more and 8.8 or less, and even more preferably 7.4 or more and 8.7 or less. 2 When the pH is in the above range, the generation of coarse particles is suppressed, and dot-like white spots on the image caused by the coarse particles are suppressed, compared with when the pH is lower than the above range. 2 When the BET specific surface area is within the above range, toner particles having a low surface area can be easily obtained compared to when the BET specific surface area is higher than the above range. Furthermore, when the BET specific surface area of ​​the toner particles is not too high, an increase in charge in a low-temperature, low-humidity environment is suppressed, and a fixed image having excellent color development can be obtained both in a high-temperature, high-humidity environment and a low-temperature, low-humidity environment.

[0096] The holding temperature in the holding step is Tg0°C + 4°C or more and Tg0 + 14°C or less, and from the viewpoint of promoting smoothing of the toner surface, it is preferably Tg0°C + 6°C or more and Tg0°C + 12°C or less, and more preferably Tg0°C + 7°C or more and Tg0°C + 11°C or less. The holding time in the holding step is 0.5 to 3 hours, and from the viewpoint of improving the smoothness of the toner surface and productivity, it is preferably 0.75 to 2 hours, and more preferably 1.0 to 1.5 hours.

[0097] -Second cooling process- Next, the toner particle dispersion liquid that has been subjected to the holding step is cooled to a second cooling temperature that is lower than T5° C. and is lower than the holding temperature. The second cooling temperature is less than Tg0°C + 9°C, and from the viewpoint of suppressing coarse powder of the toner, it is preferably less than Tg0°C + 4°C, more preferably at least Tg0°C - 30°C but less than Tg0°C - 4°C, and even more preferably at least Tg0°C - 20°C but less than Tg0°C - 9°C. From the viewpoint of improving the smoothness of the toner surface and productivity, the difference between the holding temperature and the second cooling temperature is preferably 10°C or more, more preferably 10°C or more and 25°C or less, and more preferably 15°C or more and 30°C or less. The cooling rate A2 in the second cooling step is, for example, in the range of 10°C / min or more and 50°C / min or less, preferably 15°C / min or more and 40°C / min or less, and more preferably 15°C / min or more and 30°C / min or less.

[0098] After the second cooling step is completed, the toner particles are subjected to a known washing step, a solid-liquid separation step, and a drying step to obtain dry toner particles. In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic chargeability. Furthermore, the solid-liquid separation step is not particularly limited, but from the viewpoint of productivity, it is preferable to carry out suction filtration, pressure filtration, etc. Furthermore, in the drying step, there is no particular limitation on the method, but from the viewpoint of productivity, it is preferable to carry out freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc.

[0099] The toner according to this embodiment is produced by, for example, adding an external additive to the obtained dry toner particles and mixing them. The mixing can be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, or the like. Furthermore, if necessary, coarse particles may be removed from the toner using a vibrating sieve, an air sieve, or the like.

[0100] <Electrostatic image developer> The electrostatic image developer according to this embodiment contains at least the toner according to this embodiment. The electrostatic 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 containing the toner mixed with a carrier.

[0101] The carrier is not particularly limited, and examples thereof include known carriers, such as coated carriers in which the surface of a core material made of magnetic powder is coated with a coating resin, magnetic powder dispersion carriers in which magnetic powder is dispersed and blended in a matrix resin, and resin-impregnated carriers in which porous magnetic powder is impregnated with a resin. The magnetic powder dispersion type carrier and the resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and are coated with a coating resin.

[0102] Examples of magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0103] Examples of coating resins and matrix resins include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, and epoxy resins. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0104] Here, the method of coating the surface of the core material with a coating resin includes a method of coating with a solution for forming a coating layer in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent. The solvent is not particularly limited and may be selected taking into consideration the coating resin to be used, its applicability, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer, a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material, a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air, and a kneader coater method in which the core material of the carrier and the solution for forming a coating layer are mixed in a kneader coater and the solvent is removed.

[0105] In the two-component developer, the mixing ratio (mass ratio) of toner to carrier is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0106] <Image forming device / image forming method> An image forming apparatus and an image forming method according to this embodiment will be described. The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, a developing unit that contains an electrostatic image developer and develops the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic 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. The electrostatic image developer according to the present embodiment is used as the electrostatic image developer.

[0107] The image forming apparatus according to this embodiment carries out an image forming method (the image forming method according to this embodiment) that includes a charging step of charging the surface of an image carrier, an electrostatic image forming step of forming an electrostatic image on the surface of the charged image carrier, a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic 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.

[0108] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; an intermediate transfer type apparatus that primarily transfers a toner image formed on the surface of an image carrier to the surface of an intermediate transfer medium, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer medium to the surface of a recording medium; an apparatus equipped with a cleaning means that cleans the surface of the image carrier after the transfer of the toner image but before charging; and an apparatus equipped with a discharging means that irradiates the surface of the image carrier with discharging light to discharge it after the transfer of the toner image but before charging. In the case of an intermediate transfer type device, the transfer means is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0109] In the image forming apparatus according to the present embodiment, for example, a portion including the developing means may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge equipped with developing means that accommodates the electrostatic image developer according to the present embodiment is preferably used.

[0110] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0111] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to this embodiment. The image forming apparatus shown in Figure 1 includes first through fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K (image forming means) that output images in the colors yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side horizontally spaced a predetermined distance apart from one another. Note that these units 10Y, 10M, 10C, and 10K may also be process cartridges that are detachable from the image forming apparatus.

[0112] Above each of the units 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 serving as an intermediate transfer body extends through each unit. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24 that are spaced apart from each other and arranged from left to right in the drawing, and is configured to run in a direction from the first unit 10Y to the fourth unit 10K. A force is applied to the support roll 24 in a direction away from the drive roll 22 by a spring or the like (not shown), thereby applying tension to the intermediate transfer belt 20 wound around them. In addition, an intermediate transfer body cleaning device 30 is provided on the image carrier side of the intermediate transfer belt 20, facing the drive roll 22. In addition, the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with toner including four colors of toner, yellow, magenta, cyan, and black, contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

[0113] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, the first unit 10Y, which forms a yellow image and is disposed upstream in the direction of travel of the intermediate transfer belt, will be described here as a representative. Note that parts equivalent to those of the first unit 10Y are given reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y), and descriptions of the second to fourth units 10M, 10C, and 10K will be omitted.

[0114] The first unit 10Y has a photoreceptor 1Y that acts as an image carrier. Around the photoreceptor 1Y, there are arranged in this order: a charging roll (an example of a charging means) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential; an exposure device (an example of an electrostatic image forming means) 3 that exposes the charged surface to a laser beam 3Y based on a color-separated image signal to form an electrostatic image; a developing device (an example of a developing means) 4Y that supplies charged toner to the electrostatic image to develop it; a primary transfer roll 5Y (an example of a primary transfer means) that transfers the developed toner image onto an intermediate transfer belt 20; and a photoreceptor cleaning device (an example of a cleaning means) 6Y that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is positioned opposite the photoreceptor 1Y. Furthermore, a bias power supply (not shown) that applies a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power supply varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0115] The operation of forming a yellow image in first unit 10Y will be described below. First, prior to operation, the surface of the photosensitive member 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has conductivity (for example, volume resistivity at 20°C: 1×10 -6The photosensitive layer is formed by laminating a photosensitive layer on a substrate with a resistivity of Ωcm or less. This photosensitive layer normally has a high resistance (the resistance of ordinary resins), but when irradiated with a laser beam 3Y, the resistivity of the irradiated portion changes. Therefore, a laser beam 3Y is output to the charged surface of the photosensitive element 1Y via an exposure device 3 in accordance with image data for yellow sent from a control unit (not shown). The laser beam 3Y is irradiated onto the photosensitive layer on the surface of the photosensitive element 1Y, thereby forming an electrostatic charge image of a yellow image pattern on the surface of the photosensitive element 1Y.

[0116] An electrostatic image is an image formed on the surface of the photosensitive element 1Y by charging it; the laser beam 3Y reduces the resistivity of the irradiated portion of the photosensitive layer, causing the charged charges on the surface of the photosensitive element 1Y to flow, while the charges remain in the portions not irradiated by the laser beam 3Y, forming a so-called negative latent image. The electrostatic image formed on the photoreceptor 1Y is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic image on the photoreceptor 1Y is made visible as a toner image (developed image) by the developing device 4Y.

[0117] The developing device 4Y contains an electrostatic image developer containing, for example, at least yellow toner and a carrier. The yellow toner is frictionally charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoreceptor 1Y. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. The photoreceptor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1Y is transported to a predetermined primary transfer position.

[0118] When the yellow toner image on the photoreceptor 1Y is transported to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y to the primary transfer roll 5Y acts on the toner image, causing the toner image on the photoreceptor 1Y to be transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the (-) polarity of the toner, and in the first unit 10Y, for example, 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 collected by the photoreceptor cleaning device 6Y.

[0119] Furthermore, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K of the second unit 10M and subsequent units is also controlled in accordance with the first unit. In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed sequentially through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are superimposed and transferred.

[0120] The intermediate transfer belt 20, onto which the four-color toner images have been multiplex-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 a secondary transfer means) 26 arranged on the image bearing surface side of the intermediate transfer belt 20. Meanwhile, recording paper (an example of a recording medium) P is fed via a supply mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 at a predetermined timing, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a negative polarity, the same as the negative polarity of the toner. Electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, transferring the toner image on the intermediate transfer belt 20 onto the recording paper P. The secondary transfer bias at this time is determined according to resistance detected by resistance detection means (not shown) that detects resistance in the secondary transfer section, and is voltage-controlled.

[0121] Thereafter, the recording paper P is sent to the pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (an example of fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0122] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, etc. In addition to the recording paper P, examples of the recording medium include overhead projector sheets and the like. 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 in which the surface of plain paper is coated with resin or the like, or art paper for printing, is preferably used.

[0123] The recording paper P on which the color image has been fixed is conveyed toward the discharge section, and the series of color image forming operations is completed.

[0124] <Process cartridges / toner cartridges> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that is detachably attached to an image forming apparatus and that contains the electrostatic image developer according to this embodiment and is equipped with a developing means that develops an electrostatic image formed on the surface of an image carrier using the electrostatic image developer into a toner image.

[0125] The process cartridge according to this embodiment is not limited to the above configuration, but may also be configured to include a developing device and, if necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, and a transfer means.

[0126] An example of a process cartridge according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0127] FIG. 2 is a schematic diagram showing the configuration of the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is configured to integrally combine and hold a photosensitive member 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photosensitive member 107, a developing device 111 (an example of a developing means), and a photosensitive member cleaning device 113 (an example of a cleaning means), which are held by a housing 117 provided with, for example, mounting rails 116 and an opening 118 for exposure, and is made into a cartridge. In FIG. 2, 109 denotes an exposure device (an example of an electrostatic image forming means), 112 denotes a transfer device (an example of a transfer means), 115 denotes a fixing device (an example of a fixing means), and 300 denotes recording paper (an example of a recording medium).

[0128] Next, the toner cartridge according to this embodiment will be described. The toner cartridge according to the present embodiment is a toner cartridge that contains the toner according to the present embodiment and is detachably attached to an image forming apparatus. The toner cartridge contains replenishment toner to be supplied to a developing unit provided in the image forming apparatus.

[0129] 1 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and developing devices 4Y, 4M, 4C, and 4K are connected to the toner cartridges corresponding to each developing device (color) by toner supply pipes (not shown). When the toner stored in a toner cartridge runs low, the toner cartridge is replaced. [Example]

[0130] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0131] [Preparation of particle dispersion] <Preparation of Amorphous Polyester Resin Particle Dispersion> A reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube was charged with 80 moles of polyoxypropylene(2,2)-2,2-bis(4-hydroxyphenyl)propane, 10 moles of ethylene glycol, 10 moles of cyclohexanediol, 80 moles of terephthalic acid, 10 moles of isophthalic acid, and 10 moles of n-dodecenylsuccinic acid, and the atmosphere in the reaction vessel was purged with dry nitrogen gas. Then, 0.25 parts by mass of titanium tetrabutoxide was added as a catalyst per 100 parts by mass of the monomer components. After stirring and reacting for 3 hours at 170°C under a nitrogen gas stream, the temperature was further increased to 210°C over 1 hour, the pressure in the reaction vessel was reduced to 3 kPa, and the reaction was continued under reduced pressure for 13 hours with stirring to obtain an amorphous polyester resin with a weight-average molecular weight of 20,000 and a glass transition temperature of 61°C.

[0132] Next, 200 parts by mass of amorphous polyester resin, 100 parts by mass of methyl ethyl ketone, and 70 parts by mass of isopropyl alcohol were placed in a jacketed 3-liter reaction vessel (Tokyo Rikakikai Co., Ltd.: BJ-30N) equipped with a condenser, thermometer, water dropping device, and anchor blades, and the resin was dissolved by stirring and mixing at 100 rpm while maintaining the temperature at 70°C in a water-circulating thermostatic bath. The stirring speed was then increased to 150 rpm, the water-circulating thermostatic bath was set to 66°C, and 10 parts by mass of 10% ammonia water (reagent) was added over 10 minutes. After that, a total of 600 parts by mass of ion-exchanged water maintained at 66°C was added dropwise at a rate of 5 parts by mass / min to cause phase inversion, yielding an emulsion. 600 parts of the resulting emulsion and 525 parts by mass of ion-exchanged water were placed in a 2-liter recovery flask and placed in an evaporator (manufactured by Tokyo Rikakikai Co., Ltd.) equipped with a vacuum control unit via a trap bulb. While rotating the recovery flask, the pressure was increased to 60°C in a hot water bath, and the pressure was reduced to 7 kPa, taking care to prevent bumping, to remove the solvent. When the amount of recovered solvent reached 825 parts by mass, the pressure was returned to normal, and the recovery flask was cooled with water to obtain a dispersion containing resin particles with a volume average particle size of 160 nm. Ion-exchanged water was added to obtain an amorphous polyester resin particle dispersion with a solids concentration of 20% by mass.

[0133] <Preparation of Crystalline Polyester Resin Particle Dispersion> 1,10-decanedicarboxylic acid: 260 parts by mass 1,6-Hexanediol: 167 parts by mass Dibutyltin oxide (catalyst): 0.3 parts by mass The above materials were placed in a heated and dried three-necked flask, the air in the flask was replaced with nitrogen gas to create an inert atmosphere, and the mixture was stirred and refluxed at 180°C for 5 hours using mechanical stirring. The temperature was then gradually increased to 230°C under reduced pressure and stirred for 2 hours. When the mixture became viscous, it was air-cooled to stop the reaction. This yielded a crystalline polyester resin with a weight-average molecular weight of 12,600 and a melting temperature of 73°C.

[0134] 90 parts of crystalline polyester resin, 1.8 parts of anionic surfactant (TaycaPower, manufactured by Tayca Corporation), and 210 parts of ion-exchanged water were mixed, heated to 120°C, and dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA Corporation), followed by dispersion treatment using a pressure-discharge Gaulin homogenizer for 1 hour to obtain a resin particle dispersion containing dispersed resin particles with a volume average particle size of 160 nm. Ion-exchanged water was added to this resin particle dispersion to adjust the solid content to 20 mass%, thereby obtaining a crystalline polyester resin particle dispersion.

[0135] <Preparation of styrene acrylic resin particle dispersion> Styrene: 375 parts by weight n-Butyl acrylate: 25 parts by mass Acrylic acid: 2 parts by mass Dodecanethiol: 24 parts by mass ·Carbon tetrabromide: 4 parts by mass The mixture obtained by mixing and dissolving the above materials was dispersed and emulsified in a flask with a surfactant solution prepared by dissolving 6 parts by weight of a nonionic surfactant (Nonipol 400, manufactured by Sanyo Chemical Industries) and 10 parts by weight of an anionic surfactant (TaycaPower, manufactured by Tayca Corporation) in 550 parts by weight of ion-exchanged water. Next, an aqueous solution prepared by dissolving 4 parts by weight of ammonium persulfate in 50 parts by weight of ion-exchanged water was added to the flask over a period of 20 minutes while stirring. After nitrogen substitution, the contents of the flask were heated in an oil bath with stirring until the temperature reached 70°C, and the temperature was maintained at 70°C for 5 hours to continue emulsion polymerization. This resulted in a resin particle dispersion containing dispersed resin particles with a volume average particle size of 160 nm and a weight average molecular weight of 56,000. Ion-exchanged water was added to this resin particle dispersion to adjust the solids content to 20% by weight, yielding a styrene-acrylic resin particle dispersion.

[0136] <Preparation of release agent dispersion> Paraffin wax (manufactured by Nippon Seiro Co., Ltd., FNP92, endothermic peak onset 81°C): 45 parts by mass Anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts by mass Ion-exchanged water: 200 parts by weight The above ingredients were mixed and heated to 95°C, and dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA). After that, a dispersion treatment was carried out using a Manton-Gaulin high-pressure homogenizer (Gaulin), and a release agent dispersion liquid (solid content concentration: 20% by mass) in which the release agent was dispersed was prepared. The volume average particle size of the release agent particles was 0.19 μm.

[0137] <Preparation of Colorant Dispersion> Cyan pigment (Dainichi Seikagaku Co., Ltd., Pigment Blue 15:3 (copper phthalocyanine)): 98 parts by mass Anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen R): 2 parts by mass Ion-exchanged water: 400 parts by weight The above ingredients were mixed and dissolved, and dispersed for 10 minutes using a homogenizer (IKA Ultra Turrax), to obtain a colorant dispersion having a median particle size of 0.16 μm and a solid content of 20% by mass.

[0138] <Creating the carrier> <Creating the carrier> 100 parts by mass of ferrite particles (manufactured by Powder Tech Co., Ltd., average particle size 50 μm) and 1.5 parts by mass of polymethyl methacrylate resin (manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 95,000, the proportion of components with a weight average molecular weight of 10,000 or less is 5% by mass) were placed in a pressure kneader together with 500 parts by mass of toluene, stirred and mixed at room temperature (25°C) for 15 minutes, and then heated to 70°C while mixing under reduced pressure to distill off the toluene, then cooled and classified using a 105 μm sieve to obtain a resin-coated ferrite carrier.

[0139] [Preparation of toner and developer] Example 1 (Preparation of Toner Particles (1)) Amorphous polyester resin particle dispersion: 100 parts by weight Crystalline polyester resin particle dispersion: 20 parts by weight Styrene acrylic resin particle dispersion: 7.3 parts by mass Colorant particle dispersion: 10 parts by weight Release agent particle dispersion: 9 parts by weight Anionic surfactant (Tayca Power BN2060, manufactured by Tayca Corporation): 1 part by mass Ion-exchanged water: 200 parts by weight

[0140] The above raw materials were placed in a 2 L cylindrical stainless steel container 1, and 3 parts by mass of a 0.3 M aqueous nitric acid solution was added to adjust the pH to 3.0. Next, 50 parts by mass of a 10% by mass aqueous solution of aluminum sulfate as a flocculant was added dropwise while applying shear force at 6,000 rpm using an Ultraturrax (manufactured by IKA Japan), and the mixture was stirred for 5 minutes. Next, the raw material mixture was heated to 45°C using a mantle heater and held for 30 minutes. After that, a resin particle dispersion for coating, which was a mixture of 25 parts by mass of an amorphous polyester resin dispersion and 10 parts by mass of ion-exchanged water and previously adjusted to pH 3.0, was added and held for 10 minutes. Then, in order to stop the growth of the coated aggregated particles (adhered particles), a 1M aqueous solution of sodium hydroxide was added to adjust the pH of the raw material mixture (pH 1 ) was controlled to 9.0. Next, in order to fuse the aggregated particles, the temperature was raised to a fusion temperature of 80°C at a heating rate of 1°C / min. After reaching 80°C, the average circularity was measured every 30 minutes and maintained until it reached 0.966. Table 1 shows the glass transition temperature Tg0 of the toner particles dispersed in the resulting toner particle dispersion.

[0141] Thereafter, the toner dispersion was cooled to a first cooling temperature of 40° C. at a cooling rate A1 of 60° C. / min using a heat exchanger (first cooling step). Further, a 0.3 M aqueous nitric acid solution was added to adjust the pH (pH 2 ) was measured and found to be 7.5. Thereafter, the temperature was raised to a holding temperature of 57°C and held for a holding time of 1 hour (holding step). Thereafter, the toner dispersion was cooled to a second cooling temperature of 40° C. at a cooling rate A2 of 20° C. / min using a heat exchanger (second cooling step). The mixture was then filtered, redispersed in 3 liters of ion-exchanged water, and subjected to solid-liquid separation using Nutsche suction filtration, which was repeated six times to obtain a wet cake. This was then vacuum dried for 12 hours to obtain toner base particles (1) with a volume average particle size of 6.0 μm and an average circularity of 0.966. The Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (1) are shown in Table 2.

[0142] (Toner production) Next, 1.5 parts by mass of hydrophobic silica (TS720 manufactured by Cabot) was added to 50 parts by mass of the toner base particles, and blended in a sample mill to obtain an externally added toner.

[0143] (Preparation of developer) Next, the externally added toner and the resin-coated ferrite carrier were mixed to prepare a developer with a toner concentration of 7% by mass.

[0144] <Examples 2 and 3> pH during the holding step (pH 2Toner base particles (2) to (3) were obtained in the same manner as in Example 1, except that the values ​​of Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (2) to (3) were set to the values ​​shown in Table 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (2) to (3). Toner with external additives and a developer were prepared in the same manner as in Example 1, except that toner base particles (2) and (3) were used instead of toner base particles (1).

[0145] Example 4 Toner base particles (4) were obtained in the same manner as in Example 1, except that the amount of styrene-acrylic resin particle dispersion added was 1.4 parts by mass. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (4). A toner with external additives and a developer were prepared in the same manner as in Example 1, except that the toner base particles (4) were used instead of the toner base particles (1).

[0146] <Example 5> Toner base particles (5) were obtained in the same manner as in Example 1, except that the amount of styrene-acrylic resin particle dispersion added was 59 parts by mass. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (5). A toner with external additives and a developer were prepared in the same manner as in Example 1, except that the toner base particles (5) were used instead of the toner base particles (1).

[0147] <Examples 6 to 9> Toner base particles (6) to (9) were obtained in the same manner as in Example 1, except that the holding temperature and holding time were set as shown in Table 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (6) to (9). Toners with external additives and developers were prepared in the same manner as in Example 1, except that the toner base particles (6) to (9) were used instead of the toner base particles (1).

[0148] <Examples 10 and 11> Toner base particles (10) to (11) were obtained in the same manner as in Example 1, except that the cooling rate A1 was set as shown in Table 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (10) to (11). Toner with external additives and a developer were prepared in the same manner as in Example 1, except that toner base particles (10) to (11) were used instead of toner base particles (1).

[0149] Example 12 Except for not using the styrene-acrylic resin particle dispersion liquid, toner base particles (12) were obtained in the same manner as in Example 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (12). A toner with external additives and a developer were prepared in the same manner as in Example 1, except that the toner base particles (12) were used instead of the toner base particles (1).

[0150] Example 13 Toner base particles (13) were obtained in the same manner as in Example 1, except that the amount of styrene-acrylic resin particle dispersion added was 75 parts by mass. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (13). A toner with external additives and a developer were prepared in the same manner as in Example 1, except that the toner base particles (13) were used instead of the toner base particles (1).

[0151] <Comparative Examples 1 and 2> Toner base particles (C1) to (C2) were obtained in the same manner as in Example 1, except that the holding temperature and holding time were set as shown in Table 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (C1) to (C2). Toners with external additives and developers were prepared in the same manner as in Example 1, except that the toner base particles (C1) to (C2) were used instead of the toner base particles (1).

[0152] <Comparative Example 3> Except for producing the toner without going through the holding step, toner base particles (C3) were obtained in the same manner as in Example 1. Table 2 shows Tg1, Tg1-Tg2, and BET specific surface area of ​​the toner base particles (C3). A toner with external additives and a developer were prepared in the same manner as in Example 1, except that the toner base particles (C3) were used instead of the toner base particles (1).

[0153] [evaluation] <Print blocking> - Image defect evaluation test for fixed toner images The evaluation sample preparation device used was a DocuCentreColor 450 manufactured by Fuji Xerox Co., Ltd. The resulting developer was filled into a developing unit, and a high image density (density 100% and toner loading amount 110 g / m) was printed on A4 size OS Coated 127 paper (basis weight 127 gsm) manufactured by Fuji Xerox Interfield Co., Ltd. in an environment of 25°C and 50% RH. 2 ) were continuously formed on 100 sheets, and all of the printed matter, which was the recording medium on which the images were formed, was discharged onto the same discharge tray and left in a stacked state for 1 hour. Thereafter, the 51st printed sheet was evaluated for image defects on the fixed image, which is the sheet most susceptible to image defects in terms of latent heat and pressure. The evaluation criteria are shown below, and the results are shown in Table 2. -Evaluation criteria- G1: Image defects are difficult to visually identify. G2: Image defects are inferior to those of G1, but are minor and within the acceptable range. G3: Image loss is worse than G2, but the degradation in image quality is within the acceptable range. G4: There is significant image loss and the degradation in image quality is beyond the acceptable range.

[0154] <Low temperature fixability evaluation> The obtained electrostatic image developer was loaded into the developing unit of an electrophotographic copier (Docu Centre Color 450, manufactured by Fuji Xerox Co., Ltd.) from which the fixing unit had been removed, and an unfixed image was output. Vitality paper was used as the recording medium, and an unfixed image measuring 25 mm x 25 mm and with an image density of 75% was formed on one side. The fixing evaluation device used was a DocuPrint P450 manufactured by Fuji Xerox Co., Ltd., with the fixing unit removed and modified so that the fixing temperature could be changed. The fixing temperature was raised from 110°C to 160°C in 5°C increments, and images were fixed at each temperature. The temperature (minimum fixing temperature) at which offset (a phenomenon in which an image is transferred to the fixing member due to insufficient melting of the toner image) no longer occurred on the low-temperature side was classified as follows. The range up to G2 was considered acceptable. The results are shown in Table 2. G1: Minimum fixing temperature is 130°C or less G2: Minimum fixing temperature is over 130℃ and 150℃ or less G3: Minimum fixing temperature is over 150°C

[0155] <Evaluation of white spots> The resulting electrostatic image developer was loaded into the developing unit of a commercially available electrophotographic copier (Docu Centre Color 450, manufactured by Fuji Xerox Co., Ltd.), and 10,000 sheets of the Imaging Society of Japan Test Chart No. 5-2 were printed on a recording medium, Stone Color White (basis weight 256 gsm), under a high temperature and humidity environment (30°C, 85% RH). Image defects (evaluation of the degree of white space) in the high TMA area (i.e., areas with high toner coverage) of the 10,001st image were evaluated. The evaluation criteria are shown below. Note that up to G3 was considered acceptable. The results are shown in Table 2. G1: No white spots were observed visually or through a magnifying glass. G2: No white spots were visible to the naked eye, but minor white spots of less than three locations per field were observed through magnifying glass observation. G3: No white spots were visible to the naked eye, but minor white spots were observed in 3 to 5 places in one field of view through magnifying glass observation. G4: White spots were confirmed visually or five or more spots were confirmed in one field of view when observed with a magnifying glass. Unacceptable level.

[0156] <Color development evaluation> The resulting electrostatic image developer was loaded into the developing unit of a commercially available electrophotographic copier (Docu Centre Color 450, manufactured by Fuji Xerox Co., Ltd.) and left to stand for one day in a high-temperature, high-humidity environment (30°C, 85% RH). After this, 10,000 images with an image density of 1% were printed consecutively on A4 paper sheets, and the image density of the 10,001st sheet was measured. Image density was measured using an X-Rite 939 (aperture diameter 4 mm) manufactured by X-Rite. The results are shown in Table 2.

[0157] Similarly, the resulting electrostatic image developer was loaded into the developing unit of a commercially available electrophotographic copier (Docu Centre Color 450, manufactured by Fuji Xerox Co., Ltd.) and left to stand for one day in a low-temperature, low-humidity environment (10°C, 15% RH). Then, 10,000 images with an image density of 1% were printed consecutively on A4 paper sheets as recording media, and the image density on the 10,001st sheet was measured. The difference in image density between the high-temperature, high-humidity environment and the low-temperature, low-humidity environment (i.e., environmental dependency) was determined. The evaluation criteria are shown below. Grades up to G3 were considered acceptable. The results are shown in Table 2. G1: Image density (SAD) difference 0.1 or less G2: Image density (SAD) difference 0.2 or less G3: Image density (SAD) difference 0.3 or less G4: Image density (SAD) difference > 0.3

[0158] [Table 1]

[0159] [Table 2]

[0160] From the above results, it can be seen that the toner of this example can obtain fixed images with excellent color development while achieving low temperature fixability, as compared with the toner of the comparative example. [Explanation of symbols]

[0161] 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K Charging roll (an example of charging means) 3. Exposure device (an example of an electrostatic 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 a primary transfer means) 6Y, 6M, 6C, 6K: Photoconductor cleaning device (an example of a cleaning means) 8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K image forming units 20 Intermediate transfer belt (an example of an intermediate transfer body) 22 Drive Roll 24 Support Roll 26 Secondary transfer roll (an example of a secondary transfer means) 30 Intermediate transfer body cleaning device 107 Photosensitive body (an example of an image carrier) 108 Charging roll (an example of charging means) 109 Exposure device (an example of electrostatic image forming means) 111 Developing device (an example of developing means) 112 Transfer device (an example of transfer means) 113 Photosensitive drum cleaning device (an example of cleaning means) 115 Fixing device (an example of fixing means) 116 Mounting Rail 117 Cabinet 118 Exposure opening 200 Process Cartridge 300 Recording paper (an example of a recording medium) P Recording paper (an example of a recording medium)

Claims

1. The toner particles contain an amorphous polyester resin, a crystalline polyester resin, and a styrene-acrylic resin as a binder resin, In a differential scanning calorimetric curve of the toner particles, the toner is heated from 10°C to 150°C at a heating rate of 10°C / min using a differential scanning calorimeter, and Tg1 is the lowest onset temperature in the change in the amount of heat absorbed in the temperature rise spectrum during a first heating run; after the first heating run, the toner is maintained at 150°C for 5 minutes, cooled to 0°C at a heating rate of 10°C / min, and then heated from 10°C to 150°C at a heating rate of 10°C / min. The toner for developing electrostatic images has Tg1 in a range of 58°C to 68°C, and Tg1-Tg2 is in a range of 20°C to 40°C.

2. The BET specific surface area of ​​the toner particles is 1.0 m ２ / g or more 2.0m ２ 2. The toner for developing electrostatic images according to claim 1, wherein the toner has a molecular weight of 1 / g or less.

3. 3. The toner for developing electrostatic images according to claim 1, wherein the binder resin comprises a polyester resin.

4. The toner for developing electrostatic images according to claim 3 , wherein the polyester resin comprises a crystalline polyester resin.

5. 5. The toner for developing electrostatic images according to claim 4, wherein the content of the crystalline polyester resin is 5% by mass or more and 25% by mass or less with respect to the total amount of the binder resin.

6. 6. The toner for developing electrostatic images according to claim 3, wherein the binder resin further contains a vinyl resin.

7. 7. The toner for developing electrostatic images according to claim 6, wherein the content of the vinyl resin is 1% by mass or more and 30% by mass or less based on the total mass of the toner particles.

8. An electrostatic image developer comprising the toner for developing electrostatic images according to any one of claims 1 to 7.

9. A toner for developing electrostatic images according to any one of claims 1 to 7 is contained therein, A toner cartridge that is detachably attached to an image forming device.

10. a developing unit containing the electrostatic image developer according to claim 8 and developing an electrostatic image formed on the surface of an image carrier into a toner image by using the electrostatic image developer, A process cartridge is detachably mounted in an image forming apparatus.

11. an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing unit containing the electrostatic image developer according to claim 8 and developing the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer; a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing means for fixing the toner image transferred onto the surface of the recording medium; An image forming apparatus comprising:

Images