Process cartridge

Abstract

To provide a process cartridge that can prevent the occurrence of fogging and developing streaks throughout the life of the process cartridge, and can form a high-quality image even in a high-speed, long-life electrophotographic image forming apparatus.SOLUTION: A process cartridge has toner and a developing roller. The toner has an aggregate containing silica fine particles and a binder resin present on a surface of a toner particle. A number% ratio of toner particles having the aggregate before and after being subjected to treatment with specific supersonic conditions is within a predetermined range. The Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a process cartridge used in an image forming method such as an electrophotographic method.

Background Art

[0002] In recent years, electrophotographic image forming apparatus main bodies such as printers and copiers and process cartridges have been required to be further speeded up and have a longer life. Along with the speeding up of the apparatus, the rotation speeds of electrophotographic members such as developing rollers and photoreceptors used in the electrophotographic process also increase, so that the toner receives a stronger frictional load from these electrophotographic members. In addition, due to the longer life of the apparatus, the number of times the toner is rubbed increases. Thus, along with the speeding up and the longer life, the toner receives a stronger and more frictional load, so that the deterioration of the toner is promoted. Examples of image defects associated with toner deterioration include the so-called "fogging" problem in which toner adheres to non-image areas. When the toner repeatedly receives a frictional load, the external additives of the toner are embedded in the toner particles or transferred to the electrophotographic member that is the rubbing partner, so that the amount of the external additives present on the surface of the toner particles gradually decreases. The decrease in the amount of the external additives causes a decrease in the chargeability of the toner, and the amount of toner having a charge amount of zero or toner having an opposite-polarity charge increases, so that fogging deteriorates. In a high-speed and long-life electrophotographic image forming apparatus, there is a problem that fogging easily deteriorates because the deterioration of the toner is promoted. Regarding such problems of toner deterioration, for example, Patent Document 1 shows that a shell can be firmly adhered to the toner surface to prevent the shell from coming off, so that the toner can ensure high chargeability and durability. Further, Patent Document 2 discloses that silica aggregates are mixed with the toner and the aggregates are gradually crushed in the developing machine, whereby the aggregates are supplied as external additives to the toner.

Prior Art Documents

Patent Documents

[0003] Patent Document 1 Japanese Patent Application Laid-Open No. 2013-76996 Patent Document 2 Japanese Patent Application Laid-Open No. 2016-65963 Summary of the Invention Problems to be Solved by the Invention

[0004] However, due to the more severe frictional load associated with further speeding up and extending the life of electrophotographic image forming apparatuses, it is difficult to completely prevent the shell from detaching even in the case of toner designed to prevent shell detachment as shown in Patent Document 1, for example, and the fogging may gradually deteriorate throughout the life of the process cartridge. Also, even in the case of toner designed to gradually crush aggregates as shown in Patent Document 2, the crushing may progress more than expected due to the more severe frictional load, and the aggregates may be consumed, resulting in the loss of the effect of the aggregates and the deterioration of fogging in the latter half of the life of the process cartridge. If the amount of aggregates is increased to prevent this, there is a concern about a so-called "development streak" defect in which excessive aggregates adhere to the developing roller, the developing blade, etc., and streak-like density unevenness occurs in the toner coat on the developing roller due to this adhered matter. In view of these problems, an object of the present disclosure is to provide a process cartridge that can suppress the occurrence of fogging and development streaks throughout the life of the process cartridge and can form high-quality images even in a high-speed and long-life electrophotographic image forming apparatus. Means for Solving the Problems

[0005] The present inventors conducted intensive studies to solve the above problems. As a result, they found that the above problems can be solved by the following configuration. That is, the present invention is a process cartridge that is detachable from an electrophotographic apparatus main body, and the process cartridge has at least toner and a developing roller. (I) The toner has at least toner particles, and agglomerates containing silica fine particles and a binder component are present on the surface of the toner particles. The arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less, when the number ratio of toner particles having the agglomerates is defined as CI (number %), the CI is 1% or more and 15% or less, when the number ratio of toner particles having the agglomerates in the toner after being processed under the following ultrasonic condition A is defined as Ca (number %), and the number ratio of toner particles having the agglomerates in the toner after being processed under the following ultrasonic condition B is defined as Cb (number %), the CI, the Ca, and the Cb satisfy the formulas (1) and (2), · Ultrasonic condition A: Output frequency 30 kHz, output power 0.75 W, irradiation time 300 s · Ultrasonic condition B: Output frequency 30 kHz, output power 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2) (II) The developing roller has a conductive shaft body and at least one elastic layer on the conductive shaft body, and the Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less. A process cartridge characterized by the above.

Advantages of the Invention

[0006] The process cartridge of the present invention suppresses fogging and the occurrence of development streaks throughout its life, and can form high-quality images even in a high-speed and long-life electrophotographic image forming apparatus.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in detail, but it is not limited to these descriptions.

[0009] In the present disclosure, the description of "○○ or more and ×× or less" or "○○ to ××" representing a numerical range means a numerical range including the lower limit and the upper limit which are the endpoints, unless otherwise specified. Further, in the following description, the toner particles before the agglomerates are present on the surface of the toner particles may be referred to as "toner core particles".

[0010] 〔Features of the Present Invention〕 The present invention is a process cartridge that is detachable from an electrophotographic apparatus main body, and the process cartridge has at least toner and a developing roller. (I) The toner has at least toner particles, and agglomerates containing silica fine particles and a binding component are present on the surface of the toner particles. The arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less. When the number ratio of the toner particles having the agglomerates is defined as CI (number %), the CI is 1 number % or more and 15 number % or less. When the number ratio of the toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition A is defined as Ca (number %), and the number ratio of the toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition B is defined as Cb (number %), the CI, the Ca, and the Cb satisfy formulas (1) and (2). · Ultrasonic condition A: Output frequency 30 kHz, output power 0.75 W, irradiation time 300 s · Ultrasonic condition B: Output frequency 30 kHz, output power 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Equation (1) 0.05 ≦ Cb / CI ≦ 0.25 Equation (2) (II) The developing roller has a conductive shaft body and at least one elastic layer on the conductive shaft body, and the Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less. It is characterized by this.

[0011] The inventors have found that by adopting the above configuration, it is possible to suppress the occurrence of fogging and development streaks throughout its life, and to form high-quality images even in a high-speed and long-life electrophotographic image forming apparatus. Although the details of this reason are unknown, it is presumed as follows.

[0012] First, by setting the CI to 1% by number or more and 15% by number or less, it is considered possible to avoid the problem of development streaks caused by excessive agglomerates adhering to the developing roller, the developing blade, etc.

[0013] In addition, the agglomerates are defined in terms of the ease of being crushed by these three values, with the abundance after treatment under ultrasonic condition A being Ca and the abundance after treatment under ultrasonic condition B being Cb, in addition to the value of the CI. In the process cartridge container, there are considered to be two main types of frictional loads that the toner undergoes. The first is the weak frictional load by the toner agitation mechanism provided in the container. The second is the strong frictional load due to friction with various electrophotographic members such as the developing roller, the toner supply roller, the developing blade, and the photoreceptor.

[0014] Ca is an index indicating the ease of fragmentation under the above-mentioned weak rubbing load, and Cb is an index indicating the ease of fragmentation under the above-mentioned strong rubbing load. In a high-speed and long-life electrophotographic apparatus, in order to suppress the occurrence of fog throughout its life, it is considered necessary that agglomerates are continuously fragmented throughout its life and the amount of externally added agent reduced due to toner deterioration is compensated. In order to achieve such a state, the inventors have conducted intensive studies. As a result, the following directions were found. (i) By setting the value of Ca / CI within the range of formula (1), design so that almost no agglomerates are fragmented under the weak rubbing load by the toner agitation mechanism. (ii) By setting the value of Cb / CI within the range of formula (1), a certain amount of agglomerates are fragmented under the strong rubbing load due to rubbing with various electrophotographic members.

[0015] It was found that by satisfying the above (i) and (ii), the occurrence of fog can be suppressed to some extent throughout the life. However, this alone is insufficiently effective, and fog may occur at the end of the life. Therefore, the inventors further studied and found that when the following condition (iii) is satisfied in addition to (i) and (ii), the occurrence of fog is specifically suppressed. (iii) The Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less.

[0016] Regarding the specific suppression of the occurrence of fog when the condition of the above (iii) is satisfied, the inventors speculate as follows.

[0017] In the process cartridge container, toner is supplied onto the developing roller by a toner supply roller. The toner on the developing roller is regulated by a developing blade into a toner coat layer of a certain thickness and is conveyed to the contact portion with the photoreceptor. At the contact portion with the photoreceptor, a latent image previously formed on the photoreceptor is developed by the toner. After development, the toner remaining on the developing roller without transferring onto the photoreceptor is scraped off the developing roller at the contact portion with the toner supply roller. In the toner of the present invention, agglomerates on the surface of toner particles are gradually crushed by rubbing against various electrophotographic members such as the developing roller, the toner supply roller, the developing blade, and the photoreceptor. Among the generated crushed materials, those remaining on the developing roller without transferring onto the photoreceptor are scraped off the developing roller together with the toner at the contact portion with the toner supply roller. This scraped-off crushed material is supplied to the toner, and by compensating for the decrease in the amount of external additives caused by toner deterioration, the occurrence of fogging is suppressed.

[0018] However, if the Asker C hardness of the developing roller is too low, the adhesion of the crushed material to the developing roller increases, and it becomes difficult to scrape off the crushed material at the contact portion with the toner supply roller. Therefore, it is considered that the effect of suppressing the occurrence of fogging cannot be sufficiently exerted. Conversely, when the Asker C hardness of the developing roller is too high, the adhesion of the crushed material to the developing roller decreases, but on the other hand, the rate of toner deterioration increases. Therefore, in some cases, it is considered that the rate of decrease in the amount of external additives due to toner deterioration exceeds the rate of supply of the crushed material, and fogging occurs. For these reasons, when the Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less, the adhesion of the crushed material to the developing roller is low, and it is possible to suppress the rate of toner deterioration, and it is considered that the occurrence of specific fogging is suppressed.

[0019] Hereinafter, preferred embodiments of the process cartridge of the present invention will be described. Note that the preferred embodiments are not limited to the present content.

[0020] 〔Toner〕 Hereinafter, each component constituting the toner and the method for manufacturing the toner will be described.

[0021] The toner of the present disclosure has at least toner particles, and agglomerates containing silica fine particles and a binder component are present on the surface of the toner particles. The arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less. When the number ratio of the toner particles having the agglomerates is defined as CI (number %), the CI is 1 number % or more and 15 number % or less. When the number ratio of the toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition A is defined as Ca (number %), and the number ratio of the toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition B is defined as Cb (number %), the CI, the Ca, and the Cb satisfy formulas (1) and (2). · Ultrasonic condition A: Output frequency 30 kHz, output capacity 0.75 W, irradiation time 300 s · Ultrasonic condition B: Output frequency 30 kHz, output capacity 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2)

[0022] <Agglomerates and toner particles> FIG. 4 is a representative view of a toner in which agglomerates are present on the surface of toner particles.

[0023] Specific examples of the agglomerates containing silica fine particles and a binder component include particles mainly composed of silica and a binder component capable of binding these particles to each other.

[0024] As the particles mainly composed of silica, for example, both dry silica fine particles called so-called dry method or fumed silica produced by vapor phase oxidation of silicon halide, and so-called wet silica fine particles produced from water glass or the like can be used. These particles may be subjected to a hydrophobization treatment. Examples of the treatment agent used for the hydrophobization treatment include silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, and organotitanium compounds. These may be used alone or in combination of two or more kinds.

[0025] The number average particle diameter of the primary particles of the silica fine particles is preferably 10 nm or more and 200 nm or less (more preferably 15 nm or more and 150 nm or less). The number average particle diameter of the primary particles of the silica fine particles is preferably measured using a photograph of the toner taken at an enlarged scale with a scanning electron microscope.

[0026] As the binder component capable of binding the particles mainly composed of silica, it is required to be able to fix the particles with appropriate strength and not cause any adverse effects even when subjected to environmental changes such as mechanical stress, temperature, and humidity in the development process. Examples of such materials include organic resins. In particular, vinyl resins and polyester resins can be preferably used. These can hold the particles mainly composed of silica with appropriate fixing strength, and as the toner is used, it becomes possible to continuously supply the particles mainly composed of silica into the development process. Also, although the binder component itself is simultaneously supplied into the development process, by appropriately selecting the responsiveness of the binder component to environmental changes such as hardness, temperature, and humidity, it is possible to suppress member contamination and changes in development characteristics. Specific materials will be described in the section on the manufacturing method described later.

[0027] For the toner according to the present invention, when the percentage of the number of toner particles having the agglomerates is defined as CI (number %), the CI is 1% or more and 15% or less by number. If the CI is too low, since the number of agglomerates contained is too small, the effect of suppressing fogging may not be sufficiently exhibited. Further, if the CI is too high, excessive agglomerates may adhere to the developing roller, the developing blade, etc., and developing streaks may occur. The value of CI is preferably 2% or more and 14% or less by number, more preferably 3% or more and 12% or less by number.

[0028] Furthermore, for the toner according to the present invention, when the percentage of the number of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition A is defined as Ca (number %), and the percentage of the number of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition B is defined as Cb (number %), the above CI, the Ca, and the Cb satisfy the formulas (1) and (2). · Ultrasonic condition A: Output frequency 30 kHz, output power 0.75 W, irradiation time 300 s · Ultrasonic condition B: Output frequency 30 kHz, output power 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2)

[0029] That is, the range of Ca / CI needs to be 0.90 or more and 1.00 or less. The fact that Ca / CI is smaller than 0.90 means that the agglomerates are easily crushed even by weak rubbing by the toner stirring mechanism provided in the container. For this reason, the agglomerates are quickly consumed, the effect does not last long, and fogging may occur in the latter half of the life. The preferable range of Ca / CI is 0.95 or more and 1.00 or less.

[0030] The range of Cb / CI needs to be 0.05 or more and 0.25 or less. If Cb / CI is larger than 0.25, the agglomerates are difficult to be crushed even when receiving a strong rubbing load due to rubbing with various electrophotographic members, and the effects of the present disclosure are difficult to obtain. The preferable range of Cb / CI is 0.05 or more and 0.15 or less.

[0031] Furthermore, the arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less. If Ag is less than 500 nm, the consumption rate of the agglomerates becomes high and the effect does not last long, and fogging may occur in the latter half of the life. Also, if Ag is greater than 8000 nm, development streaks are likely to occur due to the adhesion of the agglomerates to the development roller or the development blade. The value of Ag is preferably 1000 nm or more and 4000 nm or less.

[0032] Furthermore, on the surface of the toner having the agglomerates observed with a scanning electron microscope, the area ratio of the binder component of the agglomerates is preferably 5% or more and 50% or less with respect to the entire aggregate. As described above, when the agglomerates appropriately contain the binder component, the migration property of the agglomerates is appropriately controlled, and the effects of the present disclosure can be obtained at a high level. If it is smaller than this range, the agglomerates are likely to migrate, and development streaks are likely to occur due to the adhesion of the agglomerates to the development roller or the development blade. If it is larger than this range, the agglomerates are difficult to migrate, and it is difficult to obtain the effect of suppressing fogging.

[0033] Furthermore, among the toner particles having the agglomerates, it is preferable to contain 50% by number or more, more preferably 60% by number or more, and still more preferably 80% by number or more of the toner particles having the agglomerates that satisfy the following (a).

[0034] (a) In the binary image of the backscattered electron image of the agglomerates taken by a scanning electron microscope, when 18 straight lines are drawn at 10° intervals passing through the midpoint of the image of the agglomerates as a reference point, the number A of straight lines having a line segment with a continuous dark part length of 100 nm or more on the straight line is 12 or more with respect to the total 18 straight lines.

[0035] Satisfying the above (a) means that resin particles are uniformly contained in the agglomerates. When resin particles are uniformly contained in the agglomerates, there is no bias in the composition of the agglomerates, so there is little bias when migrating from the toner particles, and the effects of the present invention are easily obtained.

[0036] The toner particles contain a binder resin. The content of the binder resin is preferably 50% by mass or more based on the total amount of the resin components in the toner particles.

[0037] The binder resin is not particularly limited, and examples thereof include styrene acrylic resins, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, mixed resins and composite resins thereof. Styrene acrylic resins and polyester resins are preferred in terms of low cost, easy availability and excellent low-temperature fixability.

[0038] Examples of the styrene acrylic resin include polymers composed of the following monofunctional polymerizable monomers or polyfunctional polymerizable monomers, copolymers obtained by combining two or more of these, and mixtures thereof.

[0039] Examples of the monofunctional polymerizable monomers include the following.

[0040] Styrene; styrene derivatives such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene; acrylic polymerizable monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl acrylate dimethyl phosphate, ethyl acrylate diethyl phosphate, ethyl acrylate dibutyl phosphate, 2-benzoyloxyethyl acrylate; methacrylic polymerizable monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, ethyl methacrylate diethyl phosphate, ethyl methacrylate dibutyl phosphate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl formate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropyl ketone.

[0041] Examples of the polyfunctional polymerizable monomers include the following.

[0042] Diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6 - hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 2,2'-bis(4-(acryloxy diethoxy)phenyl)propane, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3 - butylene glycol dimethacrylate, 1,6 - hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis(4-(methacryloxy diethoxy)phenyl)propane, 2,2'-bis(4-(methacryloxy polyethoxy)phenyl)propane, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, divinylbenzene, divinylnaphthalene, divinyl ether, etc.

[0043] As the polyester resin, those obtained by condensation polymerization of the following carboxylic acid component and alcohol component can be used. Examples of the carboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, fumaric acid, maleic acid, cyclohexanedicarboxylic acid, and trimellitic acid. Examples of the alcohol component include bisphenol A, hydrogenated bisphenol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane, and pentaerythritol.

[0044] Also, the polyester resin may be a polyester resin containing a urea group. It is preferable not to cap the carboxy groups such as at the ends as the polyester resin.

[0045] The toner particles may contain a colorant. As the colorant, known pigments and dyes can be used. From the viewpoint of excellent weather resistance, a pigment is preferred as the colorant.

[0046] Examples of cyan-based colorants include copper phthalocyanine compounds and their derivatives, anthraquinone compounds, and basic dye lake compounds.

[0047] Specifically, the following can be mentioned. C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.

[0048] Examples of magenta-based colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds.

[0049] Specifically, the following can be mentioned. C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254, and C.I. Pigment Violet 19.

[0050] Examples of yellow-based colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds.

[0051] Specifically, the following can be mentioned. C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185, 191, and 194.

[0052] Examples of the black colorant include carbon black and those toned to black using the above yellow colorant, magenta colorant, and cyan colorant.

[0053] These colorants can be used alone, as a mixture, or even in a solid solution state.

[0054] It is preferable to use the colorant in an amount of 1.0 to 20.0 parts by mass based on 100.0 parts by mass of the binder resin.

[0055] The toner can also contain a magnetic material to be a magnetic toner.

[0056] In this case, the magnetic material can also serve as a colorant.

[0057] Examples of the magnetic material include iron oxides typified by magnetite, hematite, and ferrite; metals typified by iron, cobalt, and nickel; or alloys and mixtures thereof with metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium.

[0058] The toner particles may contain a release agent. As the release agent, conventionally known waxes may be used without particular limitation. Specifically, the following are examples.

[0059] Petroleum waxes typified by paraffin wax, microcrystalline wax, and petrolactam and their derivatives; montan wax and its derivatives; hydrocarbon waxes obtained by the Fischer-Tropsch method and their derivatives; polyolefin waxes typified by polyethylene and their derivatives; natural waxes typified by carnauba wax and candelilla wax and their derivatives.

[0060] The derivatives include oxides, block copolymers with vinyl monomers, and graft-modified products.

[0061] Also, alcohols such as higher aliphatic alcohols; fatty acids such as stearic acid and palmitic acid, or their acid amides, esters, and ketones; hydrogenated castor oil and its derivatives, vegetable waxes, and animal waxes. These can be used alone or in combination.

[0062] Among these, when polyolefins, hydrocarbon waxes obtained by the Fischer-Tropsch process, or petroleum waxes are used, the developability and transferability tend to improve, which is preferable.

[0063] In addition, antioxidants may be added to these waxes as long as the above effects are not affected.

[0064] The content of the release agent is preferably 1.0 part by mass or more and 30.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin or the polymerizable monomer forming the binder resin.

[0065] The melting point of the release agent is preferably 30°C or higher and 120°C or lower, more preferably 60°C or higher and 100°C or lower.

[0066] By using a release agent having the above thermal properties, the release effect is efficiently exhibited, and a wider fixing area is ensured.

[0067] <External additive> Various organic or inorganic fine powders can be externally added to the toner particles as necessary within a range that does not impair the effects of the present case. The organic or inorganic fine powder preferably has a particle size of 1 / 10 or less of the weight average particle size of the toner particles in terms of durability when added to the toner particles.

[0068] As the organic or inorganic fine powder, for example, the following are used. (1) Fluidity imparting agents: silica, alumina, titanium oxide, carbon black, and carbon fluoride. (2) Abrasive: Metal oxides (e.g., strontium titanate, cerium oxide, alumina, magnesium oxide, chromium oxide), nitrides (e.g., silicon nitride), carbides (e.g., silicon carbide), metal salts (e.g., calcium sulfate, barium sulfate, calcium carbonate). (3) Lubricant: Fluorine-based resin powder (e.g., vinylidene fluoride, polytetrafluoroethylene), fatty acid metal salts (e.g., zinc stearate, calcium stearate). (4) Charge control particles: Metal oxides (e.g., tin oxide, titanium oxide, zinc oxide, silica, alumina), carbon black, hydrotalcite.

[0069] The organic or inorganic fine powder may have its surface hydrophobized for improving the fluidity of the toner and equalizing the charging of toner particles. Examples of the treating agent for hydrophobizing the organic or inorganic fine powder include unmodified silicone varnish, various modified silicone varnishes, unmodified silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, and organic titanium compounds. These treating agents may be used alone or in combination.

[0070] Among them, it is preferable to contain hydrotalcite, which is a layered composite compound, as an external additive. By containing hydrotalcite having an opposite-polarity charge property with respect to silica, which is the main component constituting the agglomerates, the charging property of the toner, specifically, the charging rise property under a severe high-temperature and high-humidity environment, is improved. Furthermore, it is more preferable that the hydrotalcite is fluorine-treated. This is considered to obtain a higher effect because the inclusion of fluorine with a high electronegativity in hydrotalcite promotes the transfer of charges more.

[0071] 〔Method for manufacturing toner〕 Hereinafter, an example of the method for obtaining the above toner particles will be described, but it is not limited to the following.

[0072] The method for manufacturing toner particles is not particularly limited, and suspension polymerization method, dissolution suspension method, emulsion aggregation method, grinding method, etc. can be used. As an example, the method for obtaining toner particles by the emulsion aggregation method will be described below.

[0073] <Method for manufacturing toner particles (toner core particles) by emulsion aggregation method> (Preparation step of resin fine particle dispersion) The resin fine particle dispersion can be prepared by known methods, but is not limited to these methods. For example, emulsion polymerization method, self-emulsification method, phase inversion emulsification method in which an aqueous medium is added to a resin solution dissolved in an organic solvent to emulsify the resin, or forced emulsification method in which the resin is forcibly emulsified by heat treatment in an aqueous medium without using an organic solvent can be mentioned.

[0074] As an example, the method for preparing a resin fine particle dispersion by the phase inversion emulsification method will be described below.

[0075] Dissolve the resin component in an organic solvent in which these are soluble, and add a surfactant or a basic compound. At this time, if the resin component is a crystalline resin having a melting point, it may be heated to a temperature above the melting point and dissolved. Subsequently, while stirring with a homogenizer or the like, an aqueous medium is slowly added to precipitate resin fine particles. Then, the solvent is removed by heating or reducing the pressure to prepare an aqueous dispersion of resin fine particles.

[0076] Here, the organic solvent used for dissolving the resin component may be any one that can dissolve these. Specifically, toluene, xylene, etc. can be mentioned.

[0077] Examples of the surfactant used during the preparation step include anionic surfactants such as sulfate ester salts, sulfonate salts, carboxylate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols.

[0078] Examples of the basic compound used in the preparation process include inorganic bases such as sodium hydroxide and potassium hydroxide; and organic bases such as ammonia, triethylamine, trimethylamine, dimethylaminoethanol, and diethylaminoethanol. The basic compound may be used alone or in combination of two or more kinds.

[0079] (Preparation of Colorant Dispersion) For the preparation of the colorant dispersion, known dispersion methods can be used. For example, general dispersion means such as a homogenizer, a ball mill, a colloid mill, and an ultrasonic disperser can be used, and there is no particular limitation. Examples of the surfactant used during dispersion include the surfactants described above.

[0080] (Preparation of Wax Dispersion) In the preparation of the wax dispersion, the wax is dispersed in water together with a surfactant, a basic compound, etc., and then heated to a temperature equal to or higher than the melting point of the wax, and dispersion treatment is performed using a homogenizer or a disperser that applies a strong shearing force. By undergoing such treatment, a wax dispersion is obtained. Examples of the surfactant used during dispersion include the surfactants described above. Examples of the basic compound used during dispersion include the basic compounds described above.

[0081] (Agglomerated Particle Formation Step) In the agglomerated particle formation step, first, a resin fine particle dispersion, a colorant dispersion, a wax dispersion, etc. are mixed to obtain a mixed liquid. Next, while heating at a temperature equal to or lower than the melting point of the resin fine particles, the pH is made acidic to cause agglomeration, and agglomerated particles containing resin fine particles, colorant particles, and release agent particles are formed to obtain an agglomerated particle dispersion.

[0082] (First Fusion Step) In the first fusion step, under stirring conditions similar to those in the agglomerated particle formation step, the pH of the agglomerated particle dispersion is increased to stop the progress of agglomeration, and heating is performed at a temperature equal to or higher than the melting point of the resin component to obtain a fused particle dispersion.

[0083] (Amorphous resin fine particle adhesion step) In the amorphous resin fine particle adhesion step, an amorphous resin particle dispersion liquid is added to the fused particle dispersion liquid, and the pH is decreased, so that amorphous resin particles are adhered to the surface of the fused particles to obtain a dispersion liquid of resin-adhered particles. Here, this coating layer corresponds to the shell layer formed through the shell layer formation step described later. Note that the amorphous resin fine particle dispersion liquid can be manufactured according to the preparation step of the resin fine particle dispersion liquid described above.

[0084] (Second fusion step) In the second fusion step, in accordance with the first fusion step, the progress of aggregation is stopped by increasing the pH of the resin-adhered particle dispersion liquid, and heating is performed at a temperature equal to or higher than the melting point of the resin component to fuse the adhered resin aggregated particles to obtain a toner core particle dispersion liquid in which toner core particles with a shell layer formed are dispersed.

[0085] (Manufacturing method of toner particles having agglomerates) As a manufacturing method of toner particles having agglomerates including silica fine particles and a binder component, from the viewpoint of uniformly aggregating the silica fine particles and the binder component, it is preferable to externally add them to the toner core particles in a wet manner. When obtaining toner particles having agglomerates containing silica fine particles and a binder component in a wet manner, (Step 1) A step of obtaining a toner core particle dispersion liquid in which toner core particles are dispersed in an aqueous medium, and (Step 2) A step of mixing silica fine particles and a polymerizable monomer (monomer) serving as a binder resin component into the toner core particle dispersion liquid and polymerizing the monomer in the toner core particle dispersion liquid to form agglomerates having silica fine particles and a binder resin on the toner core particles are preferably included.

[0086] In Step 1, as a method for obtaining the toner core particle dispersion liquid, there are mentioned a method of directly using a dispersion liquid of toner core particles manufactured in an aqueous medium, and a method of charging dried toner core particles into an aqueous medium and mechanically dispersing them. When dispersing dried toner core particles in an aqueous medium, a dispersion aid may be used.

[0087] As the dispersion aid, known dispersion stabilizers, surfactants, etc. can be used. Specifically, the following can be mentioned as the dispersion stabilizers.

[0088] Inorganic dispersion stabilizers such as tricalcium phosphate, hydroxyapatite, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina; organic dispersion stabilizers such as polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salt of carboxymethylcellulose, starch.

[0089] Also, the following can be mentioned as the surfactants. Anionic surfactants such as alkyl sulfate esters, alkylbenzene sulfonates, fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers; cationic surfactants such as alkylamine salts, quaternary ammonium salts.

[0090] In step 1, it is preferable to adjust the solid content concentration of the toner core particle dispersion to 10 mass% or more and 50 mass% or less.

[0091] In step 2, the silica fine particles and the monomer serving as the binder component may be added directly to the toner core particle dispersion, or a dispersion obtained by previously dispersing the silica fine particles and the monomer may be added to the toner core particle dispersion. As the means for dispersing the silica fine particles and the monomer, the dispersion aids exemplified in the section of step 1 can be used.

[0092] Examples of the binder component include polymers composed of monofunctional polymerizable monomers or polyfunctional polymerizable monomers, copolymers obtained by combining two or more of these, and mixtures thereof.

[0093] Examples of the above-mentioned polymerizable monomers include the following.

[0094] Styrene; styrene derivatives such as α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene; acrylic polymerizable monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, ethyl acrylate dimethyl phosphate, ethyl acrylate diethyl phosphate, ethyl acrylate dibutyl phosphate, 2-benzoyloxyethyl acrylate; methacrylic polymerizable monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, ethyl methacrylate diethyl phosphate, ethyl methacrylate dibutyl phosphate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl formate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropyl ketone; trifunctional silane compounds having a methacryloxyalkyl group as a substituent such as γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxyoctyltrimethoxysilane, γ-methacryloxypropyldiethoxymethoxysilane, γ-methacryloxypropylethoxydimethoxysilane; Trifunctional silane compounds having an acryloxyalkyl group as a substituent, such as γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxyoctyltrimethoxysilane, γ-acryloxypropyldiethoxymethoxysilane, γ-acryloxypropylethoxydimethoxysilane, etc.

[0095] Among them, from the viewpoint of high affinity with silica, it is preferable to use a trifunctional silane compound. Further, the following may be used in combination with the trifunctional silane compound. An organosilicon compound having four reactive groups in one molecule (tetrafunctional silane), an organosilicon compound having two reactive groups in one molecule (bifunctional silane), or an organosilicon compound having one reactive group (monofunctional silane). For example, the following can be mentioned.

[0096] Trifunctional vinyl silanes such as dimethyldiethoxysilane, tetraethoxysilane, hexamethyldisilazane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-(2-aminoethyl)aminopropyltriethoxysilane, vinyltriisocyanatosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyldiethoxymethoxysilane, vinylethoxydimethoxysilane, vinylethoxydihydroxysilane, vinyldimethoxyhydroxysilane, vinylethoxymethoxyhydroxysilane, vinyldiethoxyhydroxysilane.

[0097] In step 2, silica fine particles and a monomer as a binder component are added to and mixed with the toner core particle dispersion. At this time, it is preferable to adjust the temperature of the toner core particle dispersion to a temperature suitable for the polymerization reaction. Then, while mixing the toner core particles, the silica fine particles, and the monomer, a polymerization initiator is added to polymerize the added monomer, and aggregates containing the silica fine particles and the binder component are externally added to the toner core particles to obtain a dispersion of toner particles.

[0098] As the polymerization initiator, known polymerization initiators can be used without particular limitation. Specifically, the following can be mentioned.

[0099] Hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxydicarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, tert-hydroperoxide of pertrifluoroacetic acid, tert-butyl peroxyformate, tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, tert-butyl N-(3-toluoyl)palmitate benzoyl peroxide, t-butyl peroxy 2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyisobutyrate, t-butyl peroxyneodecanoate, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide and other peroxide-based polymerization initiators; 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and other azo-based or diazo-based polymerization initiators; etc.

[0100] (Filtration step, washing step, drying step, classification step, external addition step) Thereafter, a filtration step for filtering out the solid content of the toner particles, a washing step if necessary, a drying step, and a classification step for adjusting the particle size are performed to obtain toner particles. The toner particles may be used as toner as they are. If necessary, the toner particles and an external additive such as inorganic fine powder are mixed and adhered using a mixer to obtain toner.

[0101] 〔Characteristics and Configuration of Developing Roller〕 The developing roller of the present disclosure has an Asker C hardness of 56 degrees or more and 75 degrees or less as measured on its surface. By setting the Asker C hardness to 56 degrees or more, the adhesion of the crushed aggregates present on the toner surface can be reduced, and it becomes possible to efficiently scrape off the crushed aggregates from the developing roller. Further, by setting the Asker C hardness to 75 degrees or less, the frictional load on the toner can be suppressed, and it becomes possible to reduce the deterioration rate of the toner. The details of the method for measuring the Asker C hardness will be described later.

[0102] Next, each component constituting the developing roller of the present disclosure and the manufacturing method of the developing roller will be described in more detail.

[0103] As shown in FIG. 1, the developing roller 1 has a conductive shaft body 2 and at least one layer of elastic layer 3 on the conductive shaft body. The developing roller 1 may be provided with a surface layer 4 as necessary.

[0104] <Conductive Shaft Body> The conductive shaft body has a function of supporting the elastic layer provided thereon. Examples of the material of the conductive shaft body include metals such as iron, copper, aluminum, and nickel; alloys such as stainless steel, duralumin, brass, and bronze containing these metals. These may be used alone or in combination of two or more. The surface of the conductive shaft body can be plated within a range that does not impair conductivity for the purpose of imparting scratch resistance. Further, a shaft body in which the surface of a resin shaft body is coated with a metal to make the surface conductive or a shaft body manufactured from a conductive resin composition can also be used.

[0105] <Elastic Layer> The elastic layer is disposed on the conductive shaft body and can have a single-layer structure or a laminated structure of two or more layers.

[0106] The elastic layer can contain elastic materials such as resins and rubbers. Specific examples of resins and rubbers include polyurethane resin, polyamide, urea resin, polyimide, melamine resin, fluororesin, phenol resin, alkyd resin, silicone rubber, polyester, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, epichlorohydrin rubber, hydrogenated NBR, urethane rubber, and the like. Among these materials, from the viewpoints of flexibility and deformation recovery, it is preferable to contain polyurethane resin or silicone rubber.

[0107] These resins and rubbers can be used alone or in combination of two or more as needed. Also, when laminating two or more elastic layers, elastic layers made of the same kind of resin and rubber may be laminated, or elastic layers made of different kinds of resin and rubber may be laminated.

[0108] The materials of the resin and rubber can be identified by measuring the elastic layer of the developing roller using a Fourier transform infrared-visible spectrophotometer.

[0109] Specific examples of the polyurethane resin used for the elastic layer include ether-based polyurethane resin, ester-based polyurethane resin, acrylic-based polyurethane resin, and carbonate-based polyurethane resin. These polyurethane resins include those obtained by the reaction of known polyols and isocyanate compounds.

[0110] Specific examples of the polyol include, for example, polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyester polyols such as polyethylene succinate diol, polybutylene succinate diol, polyethylene adipate diol, and polybutylene adipate diol; and polycarbonate polyols such as polyethylene carbonate diol and polybutylene carbonate diol.

[0111] The isocyanate component that reacts with these polyol components is not particularly limited. Examples include aliphatic polyisocyanates such as ethylene diisocyanate and 1,6 - hexamethylene diisocyanate (HDI); alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane 1,3 - diisocyanate, and cyclohexane 1,4 - diisocyanate; aromatic isocyanates such as 2,4 - tolylene diisocyanate, 2,6 - tolylene diisocyanate (TDI), 4,4’ - diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate, and copolymers, isocyanurate forms, TMP adduct forms, biuret forms, and blocked forms thereof. Among these, aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and polymeric diphenylmethane diisocyanate are more preferably used.

[0112] Examples of the silicone rubber used for the elastic layer include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these siloxanes.

[0113] The elastic layer preferably contains a conductive agent. Examples of the conductive agent include various ionic conductive agents and electronic conductive agents such as carbon black. From the perspective of preventing bleeding, it is preferable to use an electronic conductive agent, and among them, inexpensive carbon black is preferably used. The volume resistivity of the elastic layer is usually 3 1.0×10 11 Ω·cm or more and 1.0×10

[0114] Specific examples of carbon black include conductive carbon blacks such as "Ketjen Black" (trade name, manufactured by Lion Corporation) and acetylene black; carbon blacks for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT. In addition, as carbon black, carbon black for color ink subjected to oxidation treatment, pyrolytic carbon black, etc. can be used.

[0115] The addition amount of carbon black is preferably 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total of the resin and rubber in the elastic layer. The content of carbon black in the elastic layer can be measured using an analysis method such as thermogravimetric analysis.

[0116] In addition to the above carbon black, examples of electronic conductive agents that can be used in the elastic layer include the following. Graphite such as natural graphite and artificial graphite; metal powders such as copper, nickel, iron, and aluminum; metal oxide powders such as titanium oxide, zinc oxide, and tin oxide; conductive polymers such as polyaniline, polypyrrole, and polyacetylene. These can be used alone or in combination of two or more as required. Also, the addition amount of these conductive agents can be set appropriately.

[0117] In the elastic layer, roughness control particles can be contained as needed. As the roughness control particles, fine particles such as polyurethane resin, polyester resin, polyether resin, polyamide resin, acrylic resin, and polycarbonate resin can be used. The volume average particle diameter of the roughness control particles is preferably 3 μm or more and 20 μm or less. Also, the amount of the particles contained in the elastic layer is preferably 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass in total of the resin and rubber in the elastic layer. The content of the particles in the elastic layer can be measured using an analysis method such as thermogravimetric analysis.

[0118] In addition, the elastic layer can contain various additives such as a charge control agent, a lubricant, a filler, an antioxidant, and an anti-aging agent, as long as the functions of the above resin, rubber, and conductive agent are not inhibited. The addition amounts of these additives can be set as appropriate.

[0119] <Surface layer> In the developing roller of the present disclosure, a surface layer is formed as needed. As the material of the surface layer, various resins, rubbers, etc. similar to those used for the elastic layer can be used. In particular, from the viewpoint of excellent triboelectrification performance to toner and having abrasion resistance, polyurethane resin is preferably used. Specific examples of the polyurethane resin are the same as those of the polyurethane resin used for the elastic layer.

[0120] In addition, the surface layer can contain a conductive agent, roughness control particles, and various other additives as needed, and the same ones as those used for the elastic layer can be used.

[0121] <Manufacturing method of developing roller> The manufacturing method of the developing roller is not particularly limited, and known methods such as a casting method using liquid rubber and an extrusion method using millable rubber can be used.

[0122] Also, as a method of forming the surface layer, there is a method of coating a previously prepared coating liquid on the elastic layer by dipping coating, spray coating, or the like.

[0123] 〔Process Cartridge〕 The process cartridge of the present invention is characterized by having the above toner and developing roller according to the present disclosure. FIG. 2 is a schematic cross-sectional view of an example of the process cartridge of the present invention.

[0124] The process cartridge 100 shown in FIG. 2 is configured to be detachable from the main body of the electrophotographic apparatus. The process cartridge 100 includes a developing chamber 102 having an opening at a portion facing the photoreceptor 101, and a toner container 104 for storing toner 103 is arranged on the back surface of the developing chamber 102. A toner stirring mechanism 107 is arranged in the toner container 104 as necessary. The opening communicating the developing chamber 102 and the toner container 104 is partitioned by a seal member 105, and this seal member 105 is removed at the start of use of the process cartridge 100. Further, a developing roller 106, a toner supply roller 108, a developing blade 109, and a toner ejection prevention sheet 110 are provided in the developing chamber 102.

[0125] The toner 103 is applied to the developing roller 106 by the toner supply roller 108. The developing roller 106 is rotated in the direction indicated by the arrow in the figure, and the toner 103 carried on the developing roller 106 is regulated to a predetermined layer thickness by the developing blade 109 and then sent to the developing area facing the photoreceptor 101.

[0126] In addition to the above configuration, the process cartridge 100 includes a charging roller 111. Further, a cleaning blade 112 and a waste toner container 119 are arranged as necessary.

[0127] 〔Electrophotographic Image Forming Apparatus〕 FIG. 3 is a schematic cross-sectional view of an electrophotographic apparatus equipped with the process cartridge of the present invention. This electrophotographic apparatus can be used by mounting the process cartridge 100 shown in FIG. 2.

[0128] The printing operation of the electrophotographic apparatus will be described below. The photoreceptor 101 is uniformly charged by a charging roller 111 connected to a bias power supply (not shown). Next, an electrostatic latent image is formed on the surface of the photoreceptor 101 by exposure light 113 for writing the electrostatic latent image. As the exposure light 113, either LED light or laser light can be used.

[0129] Next, toner charged negatively by a developing roller 106 built in a process cartridge 100 configured to be detachable from the electrophotographic apparatus main body is applied (developed) to the electrostatic latent image. Next, a toner image is formed on the photoreceptor 101, and the electrostatic latent image is converted into a visible image. At this time, a voltage is applied to the developing roller 106 by a bias power supply (not shown).

[0130] The toner image developed on the photoreceptor 101 is primarily transferred to an intermediate transfer belt 114. A primary transfer member 115 is in contact with the back surface of the intermediate transfer belt 114, and by applying a voltage to the primary transfer member 115, the negatively charged toner image is primarily transferred from the photoreceptor 101 to the intermediate transfer belt 114. The primary transfer member 115 may be in the shape of a roller or a blade.

[0131] In the electrophotographic apparatus shown in FIG. 3, a total of four process cartridges 100 each containing toner of each color of yellow, cyan, magenta, and black are detachably mounted on the electrophotographic apparatus main body. Then, the above-described charging, exposure, development, and primary transfer steps are sequentially executed with a predetermined time difference, and a state is created in which four toner images for expressing a full-color image are superimposed on the intermediate transfer belt 114.

[0132] The toner image on the intermediate transfer belt 114 is conveyed to a position facing the secondary transfer member 116 as the intermediate transfer belt 114 rotates. At this time, a recording sheet, which is a transfer material, is being conveyed along the conveyance route 117 of the recording sheet between the intermediate transfer belt 114 and the secondary transfer member 116 at a predetermined timing. Then, by applying a secondary transfer bias to the secondary transfer member 116, the toner image on the intermediate transfer belt 114 is transferred onto the recording sheet. The recording sheet onto which the toner image has been transferred by the secondary transfer member 116 is conveyed to the fixing device 118. After melting the toner image on the recording sheet and fixing it onto the recording sheet, the recording sheet is discharged outside the electrophotographic apparatus, thereby completing the printing operation. Note that the toner image remaining on the photoreceptor 101 without being transferred to the intermediate transfer belt 114 is scraped off by the cleaning blade 112 and stored in the waste toner container 119.

[0133] [Measurement Methods for Various Physical Properties] The measurement methods for various physical properties according to the present invention will be described below.

[0134] [Measurement Method for Weight-Average Particle Diameter (D4) and Number-Average Particle Diameter (D1)] The weight-average particle diameter (D4) and number-average particle diameter (D1) of the toner are calculated as follows. As the measuring device, a precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. For setting the measurement conditions and analyzing the measurement data, the attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) is used. Note that the measurement is performed with an effective number of measurement channels of 25,000 channels.

[0135] The electrolytic aqueous solution used for the measurement is prepared by dissolving special grade sodium chloride in ion-exchanged water so that the concentration becomes approximately 1 mass%. For example, "ISOTON II" (manufactured by Beckman Coulter, Inc.) can be used.

[0136] Before performing measurement and analysis, the dedicated software was set as follows.

[0137] On the "Change Standard Measurement Method (SOMME)" screen of the dedicated software, set the total count number in the control mode to 50,000 particles, the number of measurements to 1 time, and set the Kd value to the value obtained using "Standard Particle 10.0μm" (manufactured by Beckman Coulter). By pressing the "Measurement Button for Threshold / Noise Level", the threshold and noise level are automatically set. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check "Flash of the Aperture Tube after Measurement".

[0138] On the "Conversion Setting from Pulse to Particle Size" screen of the dedicated software, set the bin interval to logarithmic particle size, the particle size bins to 256 particle size bins, and the particle size range to 2 μm to 60 μm. The specific measurement method is as follows. (1) Pour about 200 ml of the electrolytic aqueous solution into a 250 ml round-bottom glass beaker dedicated to Multisizer 3, set it on the sample stand, and stir with a stirrer rod counterclockwise at 24 rotations per second. Then, use the "Flash of the Aperture" function of the dedicated software to remove dirt and bubbles in the aperture tube. (2) Pour about 30 ml of the electrolytic aqueous solution into a 100 ml flat-bottom glass beaker. Add about 0.3 ml of a dilution obtained by diluting "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for precision measuring instrument cleaning with pH 7 composed of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) about 3 times by mass with ion-exchanged water as a dispersant. (3) Prepare an ultrasonic disperser "Ultrasonic Dispension System Tetra150" (manufactured by Nikkaki Bios Co., Ltd.) with an electrical output of 120 W and built-in two oscillators with an oscillation frequency of 50 kHz and a 180-degree phase shift. Pour about 3.3 l of ion-exchanged water into the water tank of the ultrasonic disperser, and add about 2 ml of Contaminon N to this water tank. (4) Set the beaker of (2) in the beaker fixing hole of the ultrasonic disperser and operate the ultrasonic disperser. Then, adjust the height position of the beaker so that the resonance state of the liquid level of the electrolytic aqueous solution in the beaker is maximized. (5) While irradiating the electrolytic aqueous solution in the beaker of (4) with ultrasonic waves, add about 10 mg of toner little by little to the electrolytic aqueous solution and disperse it. Then, continue the ultrasonic dispersion treatment for another 60 seconds. In ultrasonic dispersion, appropriately adjust so that the water temperature in the water tank is 10°C or higher and 40°C or lower. (6) Dropwise add the electrolyte aqueous solution of (5) in which the toner is dispersed to the round-bottom beaker of (1) installed in the sample stand using a pipette, and adjust so that the measurement concentration becomes about 5%. Then, perform the measurement until the number of measured particles reaches 50,000. (7) Analyze the measurement data using the dedicated software attached to the device, and calculate the weight average particle size (D4) and the number average particle size (D1). When setting to graph / volume% in the dedicated software, the "average diameter" on the "Analysis / Volume Statistical Value (Arithmetic Mean)" screen is the weight average particle size (D4), and when setting to graph / number% in the dedicated software, the "average diameter" on the "Analysis / Number Statistical Value (Arithmetic Mean)" screen is the number average particle size (D1).

[0139] <Method for Obtaining Reflection Electron Image of Toner Surface> The matrix exposure rate of the toner is calculated using the reflection electron image of the toner particle surface.

[0140] The reflection electron image of the toner surface was obtained by a scanning electron microscope (SEM).

[0141] The reflection electron image obtained from the SEM is also called a "composite image", and the smaller the atomic number, the darker it is detected, and the larger the atomic number, the brighter it is detected.

[0142] Toner particles are generally resin particles mainly containing a composition mainly composed of carbon such as a resin component and a release agent. When silica fine particles or metal oxides are present on the surface of the toner particles, in the reflected electron image obtained from SEM, the silica fine particles or metal oxides are observed as bright parts, and the resin part mainly composed of carbon is observed as a dark part.

[0143] The SEM apparatus and observation conditions are as follows. Apparatus used: ULTRA PLUS manufactured by Carl Zeiss Microscopy GmbH Acceleration voltage: 1.0 kV WD: 2.0 mm Aperture Size: 30.0 μm Detection signal: EsB (energy-selective backscattered electrons) EsB Grid: 800 V Observation magnification: 50,000 times Contrast: 63.0 ± 5.0% (reference value) Brightness: 38.0 ± 5.0% (reference value) Resolution: 1024 × 768 Pretreatment: Sprinkle toner particles on carbon tape (no vapor deposition) The contrast and brightness are appropriately set according to the state of the apparatus used. Also, the acceleration voltage and EsB Grid are set so as to achieve items such as acquisition of the outermost surface structure information of the toner particles, prevention of charge-up of the non-vapor-deposited sample, and selective detection of high-energy backscattered electrons. The observation field of view is selected near the apex where the curvature of the toner particles is the smallest.

[0144] <Method for confirming that the dark part in the backscattered electron image is derived from carbon atoms> That the dark part in the observed backscattered electron image is derived from the resin is confirmed by superimposing the elemental mapping image obtained by energy-dispersive X-ray spectroscopy (EDS) that can be acquired with a scanning electron microscope (SEM) and the backscattered electron image. The SEM / EDS apparatus and observation conditions are as follows. Apparatus used (SEM): ULTRA PLUS manufactured by Carl Zeiss Microscopy GmbH Energy Dispersive Spectrometer (EDS): NORAN, manufactured by Thermo Fisher Scientific K.K. System 7, Ultra Dry EDS Detecter Accelerating voltage: 5.0 kV WD: 7.0 mm Aperture Size: 30.0 μm Detected signal: SE2 (secondary electron) Magnification: 50,000 times Mode: Spectral Imaging Pretreatment: Sprinkle toner particles on carbon tape and perform platinum sputtering Overlay the elemental mapping image obtained by this method with the backscattered electron image, and confirm that the carbon atom part of the mapping image coincides with the dark part of the backscattered electron image.

[0145] <Method for Confirming the Dispersion State of the Binder Component Contained in the Agglomerate> The dispersion state of the binder component contained in the agglomerate is calculated using the backscattered electron image of the agglomerate on the toner surface. The backscattered electron image of the agglomerate on the toner surface is obtained in the same manner as the method for obtaining the backscattered electron image of the toner surface.

[0146] For the obtained backscattered electron image, use the image processing software ImageJ (developed by Wayne Rashand) to calculate the dispersion state of the resin particles contained in the agglomerate. The procedure is shown below.

[0147] First, convert the backscattered electron image to be analyzed to 8-bit from the Type in the Image menu. Next, set the Median diameter to 2.0 pixels from the Filters in the Process menu to reduce image noise. Estimate the center of the image excluding the observation condition display part displayed at the bottom of the backscattered electron image, and select a range of 1.5 μm square from the center of the backscattered electron image using the rectangle tool in the toolbar.

[0148] Next, select Threshold from Adjust in the Image menu. In manual operation, select all pixels corresponding to luminance B1 and click Apply to obtain a binary image. By this operation, the pixels corresponding to A1 are displayed in black (pixel group A1), and the pixels corresponding to A2 are displayed in white (pixel group A2). Again, estimate the image center excluding the observation condition display section shown at the bottom of the backscattered electron image, and select a range of 1.5 μm square from the image center of the backscattered electron image using the Rectangle Tool in the toolbar.

[0149] Next, use the Straight Line in the toolbar to select the scale bar in the observation condition display section shown at the bottom of the backscattered electron image. In this state, select Set Scale in the Analyze menu, and a new window will open, and the pixel distance of the selected straight line will be input in the Distance in Pixels column.

[0150] Input the value of the scale bar (for example, 100) in the Known Distance column of the window, input the unit of the scale bar (for example, nm) in the Unit of Measurement column, and click OK to complete the scale setting.

[0151] Subsequently, select Set Measurements in the Analyze menu and check Area and Feret’s diameter. Select Analyze Particles in the Analyze menu, check Display Result and click OK to perform domain analysis.

[0152] Subsequently, perform an Erode process for 10 pixels on the obtained analysis image using ImageJ, and then perform a Dilate process for 10 pixels using ImageJ. Note that the Erode process and the Dilate process are performed from the Binary item in the Process menu. FIG. 5 illustrates an image obtained by performing the above process.

[0153] For the analyzed image obtained after the above processing, using the Straight Line tool in the toolbar, with the midpoint of the analyzed image as the reference point, draw a total of 18 straight lines at 10° intervals from one end of the image to the other end so that they pass through the reference point. An image with line segments drawn is illustrated in FIG. 6.

[0154] Subsequently, measure the length L of a line segment where bright portions are continuous on the straight line, count the number of straight lines having a line segment with a length L of 100 nm or more, and check whether the number of straight lines in the agglomerate is 12 or more.

[0155] <Method for checking the ratio of toner particles containing an agglomerate with 12 or more straight lines> For 30 toner particles having agglomerates contained in the toner to be evaluated, perform the above procedure on the agglomerates, count the number of toner particles having an agglomerate with 12 or more straight lines, and calculate the ratio A of toner particles containing an agglomerate with 12 or more straight lines from the following formula. A = {(the number of toner particles containing an agglomerate with 12 or more straight lines) / 30}

[0156] <Method for checking the area ratio of the binder component contained in the agglomerate> The area ratio of the binder component is calculated based on the domain D1 of the binder component and the domain D2 that is not the binder component using a backscattered electron image of the agglomerate on the toner surface. The backscattered electron image of the agglomerate on the toner surface is obtained in the same manner as the method for obtaining the backscattered electron image of the toner surface.

[0157] The analysis of domains D1 and D2 is performed using the image processing software ImageJ (developed by Wayne Rashand) on the outermost backscattered electron image of the toner particles obtained by the above method. The procedure is shown below.

[0158] First, convert the reflected electron image to be analyzed to 8-bit from the Type in the Image menu. Next, set the Median diameter to 2.0 pixels from the Filters in the Process menu to reduce image noise. Estimate the image center excluding the observation condition display part shown at the bottom of the reflected electron image, and select a range of 1.5 μm square from the image center of the reflected electron image using the Rectangle Tool in the toolbar.

[0159] Next, use the Freehand selections function in the Image menu to select only the part where the carbon atom part of the mapping image coincides with the dark part of the reflected electron image and fill it all in black. Also, fill in all parts other than the part where the carbon atom part of the mapping image coincides with the dark part of the reflected electron image in white. Next, select Threshold from Adjust. In manual operation, select 128, which is the middle tone between black and white in an 8-bit image, as the threshold value, and click Apply to obtain a binary image.

[0160] By this operation, the pixels corresponding to domain D1 (binder component) are displayed in black (pixel group A1), and the pixels corresponding to domain D2 (other than the binder component) are displayed in white (pixel group A2).

[0161] Again, estimate the image center excluding the observation condition display part shown at the bottom of the reflected electron image, and select a range of 1.5 μm square from the image center of the reflected electron image using the Rectangle Tool in the toolbar.

[0162] Next, use the Straight Line in the toolbar to select the scale bar in the observation condition display part shown at the bottom of the reflected electron image. When Set Scale in the Analyze menu is selected in that state, a new window opens and the pixel distance of the selected straight line is input in the Distance in Pixels column.

[0163] Enter the value of the scale bar (e.g., 100) in the Known Distance column of the window, enter the unit of the scale bar (e.g., nm) in the Unit of Mesurement column, and click OK to complete the scale setting.

[0164] Subsequently, select Set Mesurements in the Analyze menu and check Area and Feret’s diameter. Select Analyze Particles in the Analyze menu, check Display Result and click OK to perform domain analysis.

[0165] From the newly opened Results window, obtain the area (Area) of each domain corresponding to the domain D1 formed by the pixel group A1 and the domain D2 formed by the pixel group A2.

[0166] Let the sum of the areas of the domains D1 derived from the binder component be S1 (μm 2 ), and let the sum of the areas of the domains D2 derived from other than the binder component be S2 (μm 2 ). Calculate the area ratio S of the binder component from the obtained S1 and S2 using the following formula. S (area %) = {S1 / (S1 + S2)} × 100

[0167] Perform the above procedure for 10 fields of view of the toner particles to be evaluated, and use the additive average value as the area ratio.

[0168] <Method for observing toner and method for calculating the number of toner particles> The toner is observed using a scanning electron microscope (SEM).

[0169] The SEM apparatus and observation conditions are as follows. Apparatus used: ULTRA PLUS manufactured by Carl Zeiss Microscopy GmbH Acceleration voltage: 1.0 kV WD: 2.0 mm Aperture Size: 30.0μm Detection Signal: SE2 (Secondary Electron) Magnification: 2,000x Contrast: 45.0 ± 5.0% (Reference Value) Brightness: 38.0 ± 5.0% (Reference Value) Resolution: 1024 × 768 Pretreatment: Sprinkle toner particles on carbon tape (No evaporation) The contrast and brightness are appropriately set according to the state of the equipment used. Also, the acceleration voltage is set to achieve items such as obtaining the surface structure information of the outermost surface of the toner particles and preventing charge-up of the un-evaporated sample.

[0170] The number of observation fields of view is observed until the number of fields of view reaches the number where the number of toner particles whose entire particles are within the observation field of view in the obtained secondary electron image is counted, and when the number is set as Tall (pieces), Tall is 300 pieces or more.

[0171] <Calculation Method for the Number CI of Toner Particles with Agglomerates> In all secondary electron images of the number of fields of view obtained in the above observation, count the number of toner particles containing agglomerates among the toner particles whose entire particles are within the observation field of view, and set it as Tagg (pieces). For the toner containing agglomerates, count the number of toner as shown in Figure 4.

[0172] From the obtained Tall (pieces) and Tagg (pieces), calculate CI (number %) by the following formula. CI (number %) = Tagg / Tall × 100

[0173] <Method for Measuring the Size of Agglomerates and Method for Counting Toner with Agglomerates> In the above scanning electron microscope observation, photograph and save the entire toner at an appropriate magnification (5k - 10k). The image resolution is 1024 × 768 pixels.

[0174] From the obtained SEM images, the portions determined to be agglomerates are selected on the image using Image J (developed by Wayne Rasband), which is image analysis software. The size of the agglomerates is defined by the maximum Feret diameter of this selected area. The calculation procedure is shown below. a) Set the scale by selecting [Analyze] - [Set Scale]. i) Select [Analyze] - [Set Measurements] - [Feret’s diameter]. iii) Select [Freehand Selections] and manually select the agglomerates on the image. iv) Select [Analyze] - [Measure] to obtain the maximum Feret diameter (Feret) of the selected portion. v) If there are multiple agglomerates on the image, repeat steps iii) and iv). vi) Perform the same analysis on the remaining 9 images of the toner observed where the agglomerates have a maximum Feret diameter of 500 nm or more and 8000 nm or less. vii) Take the maximum value of the Feret (Feret diameter) of the obtained analysis results as the maximum Feret diameter. Consider those with a maximum Feret diameter of 500 nm or more and 8000 nm or less as agglomerates.

[0175] Arbitrarily observe the toner with a scanning electron microscope, and let Ag be the arithmetic mean value of the maximum Feret diameters of a total of 100 agglomerates.

[0176] Also, let CI be the percentage of the number of toner particles having agglomerates among the arbitrarily observed toner particles.

[0177] <Evaluation method for the presence of silica and binder components in agglomerates> Regarding the confirmation of the presence of silica and binder components in the agglomerates, it is carried out using STEM - EDX and a scanning electron microscope.

[0178] First, for the toner having agglomerates, evaluate the cross - sectional structure and composition of the agglomerates using STEM - EDX.

[0179] Using an osmium plasma coater (Filgen, OPC80T), an Os film (5 nm) and a naphthalene film (20 nm) were applied to the toner as a protective film, and after embedding with a photocurable resin D800 (JEOL Ltd.), a cross-section of toner particles with a film thickness of 100 nm was prepared at a cutting speed of 1 mm / s using an ultrasonic ultramicrotome (Leica, UC7). At this time, a plurality of toners may be processed collectively to obtain 300 to 500 toner cross-sections. A schematic diagram of the cross-section of the toner having agglomerates is shown in Fig. 7.

[0180] For the obtained cross-section, STEM-EDX observation is performed using the STEM function of TEM-EDX (TEM: JEOL, JEM2800 (200 keV), EDX detector: JEOL, dry SD 100GV, EDX system: Thermo Fisher, NORAN SYSTEM7). The probe size of STEM is 1.0 nm, the observation magnification is 50 to 300k, the image size of EDX is 256×256 pixels, and 50 frames are acquired by adjusting the storage rate to 10,000 cps and integrating them. The observation location is set so that the field of view includes the agglomerates present in the outer periphery of the toner particles.

[0181] The presence of particles mainly composed of silica and a binder component in the agglomerates can be determined by confirming that a portion where a large amount of silicon and oxygen are observed and a portion where a large amount of elements derived from the binder component are observed exist separately at the same location. When a resin is used as the binder component, a large amount of carbon is observed.

[0182] Next, for the toner having agglomerates, observation of the backscattered electron image is performed using a scanning electron microscope. The image shooting conditions are as follows.

[0183] (1) Sample preparation A carbon tape is attached to a sample stage (aluminum sample stage 12.5 mmφ×6 mmt), and the toner is placed thereon. Further, air is blown to remove excess sample from the sample stage. The sample stage is set in a sample holder and then set in a scanning electron microscope (Zeiss UltraPlus).

[0184] (2) Electron microscope observation condition setting To confirm the presence of agglomerates containing silica particles and the binding component, it is carried out using the image obtained by observing the backscattered electron image of Ultra Plus. In the backscattered electron image, since the image contrast changes according to the elemental composition, the presence of silica particles and the binding component in the agglomerates can be judged. The acceleration voltage is 0.7 kV, the ECB Grid is 500 V, and the WD is 3.0 mm.

[0185] (3) Focus adjustment Set the observation magnification to 30,000 (30k) times and adjust the Alignment and Stigma. Next, align the field of view with the area having a form considered to be an agglomerate at an appropriate observation magnification. From the obtained backscattered electron image, it can be judged that it is the same as the agglomerate for which the composition observation was performed by STEM-EDX, having two types of contrasts, one considered to correspond to silica and the other considered to be the binding component.

[0186] <Calculation method of the number of toner particles Ca, Cb having agglomerates when ultrasonic treatment is performed> Put about 10 ml of ion-exchanged water from which impurities and the like have been removed in advance into a glass container. Add about 0.5 ml of a dilution obtained by diluting "Contaminon N" (a 10 mass% aqueous solution of a neutral detergent for precision measuring instrument cleaning with pH 7 composed of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) about 3 mass times with ion-exchanged water as a dispersant. Further add about 0.02 g of the measurement sample, and while stirring, perform the following dispersion treatment using an ultrasonic disperser to obtain a dispersion for measurement. At that time, appropriately cool so that the temperature of the dispersion becomes 10°C or higher and 40°C or lower. As the ultrasonic disperser, use an ultrasonic homogenizer ("VP-050" (manufactured by TAITEC)) with an oscillation frequency of 30 kHz, insert the vibrating part 1.0 cm into the dispersion, and vibrate it under the following ultrasonic condition A or ultrasonic condition B. Ultrasonic condition A: Output frequency 30 kHz, output capacity 0.75 W, irradiation time 300 s Ultrasonic condition B: Output frequency 30 kHz, output capacity 30 W, irradiation time 300 s

[0187] The dispersion obtained by the above procedure is filtered using Kiriyama filter paper (No. 5C: pore diameter 1 μm) to separate the particles and the filtrate. The obtained particles are further washed with 100 parts by mass of ion-exchanged water and vacuum dried at 25°C for 24 hours to obtain a powder for measuring the number Ca and Cb of toner particles containing agglomerates.

[0188] For the obtained powder, Ca and Cb are calculated by the same procedure as the “method for calculating the number CI of toner particles containing agglomerates”, and it is confirmed whether the relationships of the following formulas (1) and (2) are satisfied. 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2)

[0189] <Asker C hardness of the developing roller> The measurement of the Asker C hardness can be performed using a type C hardness tester (Asker C type spring rubber hardness tester, manufactured by Kobunshi Keiki Co., Ltd.) described in JIS K 7312-1996 in an environment of a temperature of 23°C and a relative humidity of 55%. For a developing roller left in an environment of a temperature of 23°C and a relative humidity of 55% for 12 hours or more, after bringing the above hardness tester into contact with it with a force of 10 N, the value after 2 seconds is taken as the measured value. The measurement positions are three positions at the center in the longitudinal direction of the developing roller and at positions 90 mm from the center toward both end portions, respectively, at three positions in the circumferential direction (at intervals of 120°), for a total of nine positions. The arithmetic mean value of the measured values at these nine positions is taken as the Asker C hardness.

[0190] 〔Constitutions included in the embodiments of the present invention〕 The disclosure of this embodiment includes the following constitutions. (Constitution 1) A process cartridge that is detachable from the electrophotographic apparatus main body, the process cartridge having at least toner and a developing roller, (I) The toner has at least toner particles, and agglomerates containing silica fine particles and a binder component are present on the surface of the toner particles, The arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less, When the number ratio of toner particles having the agglomerates is defined as CI (number %), the CI is 1% by number or more and 15% by number or less, when the number ratio of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition A is defined as Ca (number %), and the number ratio of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition B is defined as Cb (number %), the CI, the Ca, and the Cb satisfy formulas (1) and (2), · Ultrasonic condition A: output frequency 30 kHz, output power 0.75 W, irradiation time 300 s · Ultrasonic condition B: output frequency 30 kHz, output power 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2) (II) The developing roller has a conductive shaft body and at least one layer of elastic layer on the conductive shaft body, and the Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less. A process cartridge characterized by the above. (Configuration 2) The process cartridge according to Configuration 1, wherein the developing roller has a conductive shaft body and an elastic layer on the conductive shaft body, and further has a surface layer covering the surface of the elastic layer. (Configuration 3) The process cartridge according to Configuration 2, wherein the elastic layer contains a urethane resin or a silicone rubber. (Configuration 4) The process cartridge according to Configuration 2, wherein the surface layer contains a urethane resin. (Configuration 5) The process cartridge according to any one of Configurations 1 to 4, wherein the toner contains a layered composite compound as an external additive.

Examples

[0191] Specific examples and comparative examples of the process cartridge of the present invention are shown below, but the present disclosure is not limited to the configurations described in the examples. In addition, "parts" in the production examples and examples are all based on mass unless otherwise specified.

[0192] <Preparation of Resin Particle Dispersion Liquid 1> 78.0 parts of styrene, 20.7 parts of butyl acrylate, 1.3 parts of acrylic acid as a carboxyl group - imparting monomer, and 3.2 parts of n - lauryl mercaptan were mixed and dissolved. To this solution, an aqueous solution prepared by dissolving 2.0 parts of sodium linear alkylbenzene sulfonate (product name: Neogen RK, manufactured by Dai - Ichi Kogyo Seiyaku Co., Ltd.) in 150 parts of ion - exchanged water was added in its entirety and dispersed.

[0193] While stirring slowly for another 10 minutes, an aqueous solution of 0.3 part of potassium persulfate and 10 parts of ion - exchanged water was added. After nitrogen substitution, emulsion polymerization was carried out at 70 °C for 6 hours. After the polymerization was completed, the reaction solution was cooled to room temperature, and by adding ion - exchanged water, a resin particle dispersion liquid 1 with a solid content concentration of 12.5 mass% and a median diameter of 0.2 μm based on volume was obtained.

[0194] <Preparation of Release Agent Dispersion Liquid 1> 100 parts of a release agent (behenyl behenate, melting point: 72.1 °C) and 15 parts of an aliphatic alcohol alkylene oxide adduct were mixed in 385 parts of ion - exchanged water, and dispersed using a wet jet mill JN100 (manufactured by Tsunehikari Co., Ltd.) for about 1 hour to obtain release agent dispersion liquid 1. The concentration of release agent dispersion liquid 1 was 20 mass%.

[0195] <Preparation of Colorant Dispersion Liquid 1> 100 parts of carbon black "Nipex 35 (manufactured by Orion Engineered Carbons Co., Ltd.)" as a colorant and 15 parts of an aliphatic alcohol alkylene oxide adduct were mixed in 885 parts of ion - exchanged water, and dispersed using a wet jet mill JN100 for about 1 hour to obtain colorant dispersion liquid 1.

[0196] <Preparation of Toner Core Particle Dispersion Liquid 1> (Dispersion Step) Resin particle dispersion 1: 265 parts, mold release agent dispersion 1: 10 parts, colorant dispersion 1: 10 parts, aliphatic alcohol alkylene oxide adduct: 2.9 parts, sodium linear alkylbenzene sulfonate (Neogen RK): 0.6 part were dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA). While stirring, the temperature inside the container was adjusted to 30 °C, and a 1 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 8.0.

[0197] (Aggregation step) As a flocculant, an aqueous solution prepared by dissolving 0.08 part of aluminum chloride in 10 parts of ion-exchanged water was added over 10 minutes with stirring at 30 °C. After leaving it standing for 3 minutes, the temperature was raised, and the temperature was raised to 50 °C to form associated particles. In that state, the particle size of the associated particles was measured using a "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter). When the weight average particle size reached 7.0 μm, 0.9 part of sodium chloride and 5.0 parts of aliphatic alcohol were added to stop particle growth.

[0198] A 1 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 9.0, and then the temperature was raised to 95 °C to sphericalize the aggregated particles. When the average circularity reached 0.980, the temperature was lowered, and it was cooled to room temperature to obtain toner core particle dispersion 1.

[0199] <Preparation of monomer dispersion 1 having silica and a binder component> Styrene: 100 parts, methacryloxypropyltrimethoxysilane: 20 parts, colloidal silica: 100 parts were dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA), the temperature inside the container was adjusted to 25 °C, and it was stirred for 1 hour to obtain monomer dispersion 1 having silica and a binder component.

[0200] <Preparation of monomer dispersions 2 to 8 having silica and a binder component> In the preparation of monomer dispersion 1 having silica and a binder component, monomer dispersions 2 to 8 having silica and a binder component were obtained in the same manner except that the number of parts and the types of materials were changed as described in Table 1.

[0201]

Table 1

[0202] <Manufacture of Toner 1> To 100 parts of the toner core particle dispersion, 2.75 parts of the monomer dispersion obtained by the above method and 0.005 part of potassium persulfate were added. The temperature inside the container was adjusted to 90°C, and stirring was carried out for 2 hours using a full-zone stirring blade to obtain toner particle dispersion 1.

[0203] Hydrochloric acid was added to the obtained toner particle dispersion 1 to adjust the pH to 1.5 or less, and it was stirred and left for 1 hour, then solid-liquid separation was carried out using a pressure filter to obtain a toner cake. This was reslurried with ion-exchanged water to make it a dispersion again, and then solid-liquid separation was carried out using the aforementioned filter. Reslurrying and solid-liquid separation were repeated until the electrical conductivity of the filtrate became 5.0 μS / cm or less, and finally solid-liquid separation was carried out to obtain a toner cake. The obtained toner cake was dried and further classified using a classifier to obtain toner particles 1. The weight average particle diameter of toner particles 1 was 6.9 μm.

[0204] 100 parts of toner particles 1 and 0.4 part of hydrotalcite “DHT-4A (manufactured by Kyowa Chemical Industry Co., Ltd.)” were put into an FM mixer (FM10C type manufactured by Nippon Coke & Engineering Co., Ltd.) through which water at 7°C was passed in the jacket. After the water temperature in the jacket was stabilized at 7°C ± 1°C, mixing was carried out at a peripheral speed of the rotating blade of 38 m / sec for 5 minutes to obtain toner mixture 1. At this time, the water flow rate in the jacket was appropriately adjusted so that the temperature inside the tank of the FM mixer did not exceed 25°C. The obtained toner mixture 1 was sieved with a mesh having an opening of 75 μm to obtain toner 1.

[0205] For the obtained toner 1, CI, Ca, Cb, and Ag values were measured. These physical properties are shown in Table 2.

[0206] <Manufacture of Toners 2 to 7, 9 to 13> Toners 2 to 7, 9 to 13 were obtained in the same manner as the production of Toner 1, except that the monomer dispersion used was changed as shown in Table 2. The physical properties of the obtained Toners 2 to 7, 9 to 13 are shown in Table 2.

[0207] <Production of Toner 8> The toner particles 1 obtained in the production of Toner 1 were used as Toner 8 without subjecting them to the external addition treatment of hydrotalcite. The physical properties of the obtained Toner 8 are shown in Table 2.

[0208]

Table 2

[0209] <Fabrication of Developing Roller 1> (Molding of Elastic Layer) As the conductive shaft body, a primer (trade name "DY39-012"; manufactured by Toray Dow Corning) was applied to a 6-mm-diameter core metal made of stainless steel: SUS304 to a thickness of 10 μm, and it was placed in a hot air vulcanizing furnace at 150 °C for 15 minutes and baked. This conductive shaft body was placed in a mold, and an addition-type silicone rubber composition in which the materials shown in "Elastic Roller 1" in Table 3 below were mixed was injected into the cavity formed in the mold.

[0210]

Table 3

[0211] Subsequently, the mold was heated at 130 °C for 5 minutes to cure the addition-type silicone rubber composition, and then demolded from the mold. Thereafter, it was further heated at 180 °C for 1 hour to complete the curing reaction of the silicone rubber layer, thereby fabricating an elastic roller 1 having an elastic layer with a thickness of 3 mm on the outer periphery of the shaft core body.

[0212] (Formation of Surface Layer) The materials shown below were mixed, methyl ethyl ketone was added so that the total solid content ratio became 30% by mass, and then mixed with a sand mill. ·Polytetramethylene ether glycol (Product Name: PTMG2000; manufactured by Mitsubishi Chemical Corporation) 100.0 parts · Polymeric MDI (Product Name: Millionate MR-200; manufactured by Tosoh Corporation) 20.0 parts · Carbon black (Product Name: MA100; manufactured by Mitsubishi Chemical Corporation) 30.0 parts · Urethane resin fine particles (Product Name: Art Pearl C-400; manufactured by Kao Corporation) 1.0 part · Polyether-modified silicone oil (Product Name: TSF4445; manufactured by Momentive Performance Materials Inc.) 1.0 part

[0213] Subsequently, methyl ethyl ketone was added and the viscosity was adjusted to 10 - 12 cps (mPa·s) to prepare a coating liquid.

[0214] This coating liquid was applied to the elastic roller 1 by the dipping method to a film thickness of 15 μm. In the dipping method, the longitudinal direction of the elastic roller 1 was set vertically, and the upper end of the conductive shaft body was gripped and immersed in the coating liquid. The obtained coated object was dried at room temperature (23°C) for 30 minutes and then subjected to a curing reaction in an oven at 150°C for 2 hours to produce a developing roller 1 having a surface layer on the outer peripheral surface of the elastic layer.

[0215] (Measurement of Asker C hardness) The Asker C hardness of the developing roller 1 was measured using a Type C hardness tester (Asker C type spring rubber hardness tester, manufactured by Kobunshi Keiki Co., Ltd.) described in JIS K 7312 - 1996 in an environment of 23°C and 55% relative humidity. For the developing roller 1 left in an environment of 23°C and 55% relative humidity for 12 hours or more, the value 2 seconds after the hardness tester was brought into contact with it with a force of 10 N was taken as the measured value. The measurement positions were three positions each at the central part in the longitudinal direction of the developing roller and at positions 90 mm from the central part toward both end parts, and for each of these three positions, three positions at intervals of 120° in the circumferential direction, for a total of nine positions. The arithmetic mean value of the measured values at these nine positions was taken as the Asker C hardness. The Asker C hardness of the developing roller 1 was 65 degrees.

[0216] <Fabrication of Developing Rollers 2 and 3> Developing rollers 2 and 3 were fabricated in the same manner as developing roller 1, except that the material of the addition type silicone rubber used for forming the elastic layer was changed to the materials shown in "Elastic Roller 2" and "Elastic Roller 3" in Table 3. The Asker C hardness of developing roller 2 was 56 degrees, and the Asker C hardness of developing roller 3 was 75 degrees.

[0217] <Fabrication of Developing Roller 4> The conductive shaft body was placed in a mold, and a thermosetting polyurethane resin composition obtained by mixing the following materials was injected into the cavity formed in the mold. · Polypropylene glycol (Trade name: Excenol 3020; manufactured by AGC Inc.) 100.0 parts · Isocyanate compound (Trade name: Takenate 500; manufactured by Mitsui Chemicals, Inc.) 12.0 parts · Carbon black (Trade name: MA100; manufactured by Mitsubishi Chemical Corporation) 30.0 parts

[0218] Subsequently, the mold was heated at 120 °C for 30 minutes to cure the thermosetting polyurethane resin composition, and then demolded from the mold. Thereafter, further aging was performed at room temperature for 24 hours to fabricate an elastic roller 4 having an elastic layer with a thickness of 3 mm on the outer periphery of the shaft body.

[0219] For the obtained elastic roller 4, the same procedure as the formation procedure of the surface layer of developing roller 1 was performed to fabricate developing roller 4. The Asker C hardness of developing roller 4 was 70 degrees.

[0220] <Fabrication of Developing Roller 5> An elastic roller 5 was fabricated by the same fabrication procedure as the above elastic roller 4.

[0221] (Formation of Surface Layer) Each of the following types and amounts of materials was mixed with a pressure kneader to obtain an A kneaded rubber composition. · NBR (Product Name: Nipol DN219; manufactured by Zeon Corporation, Japan) 100.0 parts · Carbon black (Product Name: Tokablack #4300; manufactured by Tokai Carbon Co., Ltd.) 40.0 parts · Calcium carbonate (Product Name: Nanox #30; manufactured by Maruo Calcium Co., Ltd.) 20.0 parts · Stearic acid (Product Name: Stearic acid S; manufactured by Kao Corporation) 1.0 part

[0222] Furthermore, for the above-mentioned A kneaded rubber composition, the following respective materials were mixed with an open roll to prepare an unvulcanized rubber composition. · Sulfur (Product Name: Sulfax 200S; manufactured by Tsurumi Chemical Industry Co., Ltd.) 1.2 parts · Tetrabenzylthiuram disulfide (Product Name: TBZTD; manufactured by Sanshin Chemical Industry Co., Ltd.) 4.5 parts

[0223] The above unvulcanized rubber composition was formed into a sheet shape, charged into a press mold with an inner diameter of 13 mm in a state of being wound around the outer peripheral surface of the previously prepared elastic roller 5, pressed at 160 °C for 1 hour to be formed and crosslinked, and integrated with the elastic roller 5. After further cooling, it was polished so that the outer diameter of the roller became 12.1 mm to form a surface layer, and the developing roller 5 was produced. The Asker C hardness of the developing roller 5 was 72 degrees.

[0224] <Production of Developing Roller 6> The following materials were mixed with a pressure kneader to obtain an A kneaded rubber composition. · NBR rubber (Product Name: Nipol DN219; manufactured by Zeon Corporation, Japan) 100.0 parts · Carbon black (Product Name: Tokablack #4300; manufactured by Tokai Carbon Co., Ltd.) 40.0 parts · Calcium carbonate (Product Name: Nanox #30; manufactured by Maruo Calcium Co., Ltd.) 20.0 parts · Stearic acid (Product Name: Stearic acid S; manufactured by Kao Corporation) 1.0 part

[0225] Furthermore, for the above-mentioned kneaded rubber composition A, the following respective materials were mixed on an open roll to prepare an unvulcanized rubber composition. · Sulfur (trade name: Sulfax 200S; manufactured by Tsurumi Chemical Industry Co., Ltd.) 1.2 parts · Tetrabenzylthiuram disulfide (trade name: TBZTD; manufactured by Sanshin Chemical Industry Co., Ltd.) 4.5 parts

[0226] A crosshead extruder having a supply mechanism for the conductive shaft body and a discharge mechanism for the unvulcanized rubber roller was prepared. A die with an inner diameter of 16.5 mm was attached to the crosshead. The extruder and the crosshead were adjusted to 80°C, and the conveying speed of the conductive shaft body was adjusted to 60 mm / sec. As the conductive shaft body, a mandrel with a diameter of 6 mm made of stainless steel: SUS304 was prepared. Under these conditions, the unvulcanized rubber composition was supplied from the extruder, and the unvulcanized rubber composition was coated as an elastic layer on the conductive shaft body in the crosshead to obtain an unvulcanized rubber roller. Next, the unvulcanized rubber roller was put into a hot air vulcanizing furnace at 170°C and heated for 60 minutes to obtain an unpolished conductive roller. Thereafter, the ends of the elastic layer were cut off and removed, and the surface of the elastic layer was polished with a rotary grinding wheel. Thereby, an elastic roller 6 having an elastic layer with a thickness of 3 mm on the outer periphery of the shaft core body was manufactured.

[0227] For the obtained elastic roller 6, the same procedure as the formation procedure of the surface layer of the developing roller 1 was performed to manufacture a developing roller 6. The Asker C hardness of the developing roller 6 was 75 degrees.

[0228] <Manufacture of Developing Roller 7> An elastic roller 7 having an elastic layer with a thickness of 3 mm on the outer periphery of the shaft core body was manufactured by the same manufacturing procedure as the above-mentioned elastic roller 4. This elastic roller 7 was used as a developing roller 7 as it was without providing a surface layer. The Asker C hardness of the developing roller 7 was 70 degrees.

[0229] <Manufacture of Developing Roller 8> The developing roller 8 was produced in the same manner as the developing roller 1, except that the material of the addition type silicone rubber used for forming the elastic layer was changed to the material shown in Table 3. The Asker C hardness of the developing roller 8 was 55 degrees.

[0230] <Fabrication of the developing roller 9> The developing roller 9 was produced in the same manner as the developing roller 6, except that the material of the kneaded rubber composition A was changed to the material shown below. ·NBR rubber (Product name: Nipol DN219; manufactured by Zeon Corporation, Japan) 100.0 parts ·Carbon black (Product name: Tokablack #4300; manufactured by Tokai Carbon Co., Ltd.) 40.0 parts ·Calcium carbonate (Product name: Nanox #30; manufactured by Maruo Calcium Co., Ltd.) 25.0 parts ·Stearic acid (Product name: Stearic acid S; manufactured by Kao Corporation) 1.0 part

[0231] The Asker C hardness of the developing roller 9 was 76 degrees.

[0232] 〔Example 1〕 As an electrophotographic apparatus, a laser printer (product name: HP Color Laser jet Enterprise M653dn, manufactured by HP) was prepared. The process cartridge dedicated to this electrophotographic apparatus was filled with toner 1. Further, as the developing roller, the produced developing roller 1 was mounted. These electrophotographic apparatus and process cartridge were left in each evaluation environment described below for 24 hours or more to be well adapted to the environment, and then the process cartridge was mounted on the electrophotographic apparatus for evaluation. As the evaluation paper, A4 color laser copy paper (manufactured by Canon, 80 g / m 2 ) was used.

[0233] <Fogging evaluation> The fogging evaluation was carried out in a high temperature and high humidity environment of 30 °C and 80% relative humidity.

[0234] First, using a reflection densitometer (product name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.), the reflection density of the evaluation paper was measured with an amber light filter. Subsequently, a solid white image was output onto this evaluation paper, and the reflection density after output was measured. The difference in reflection density before and after image output was taken as the initial fog value.

[0235] Subsequently, a durability test was conducted in which an image in which the letter "E" of the alphabet was printed so that the coverage rate was 1% with respect to the area of A4 paper (hereinafter referred to as the "E-character image") was repeatedly output. The conditions of the durability test were such that after outputting two E-character images, the rotation of the photosensitive drum was completely stopped for about 5 seconds, and an intermittent image formation operation of restarting image output was repeated to output 50,000 electrophotographic images.

[0236] After outputting 50,000 sheets, a solid white image was output onto the evaluation paper whose reflection density had been measured in advance, and the difference in reflection density before and after image output was taken as the fog value after the durability test.

[0237] Regarding the initial fog value and the fog value after the durability test, evaluation was performed based on the following criteria. The evaluation results are shown in Table 4. Rank A: Less than 1% Rank B: 1% or more and less than 2.5% Rank C: 2.5% or more and less than 5% Rank D: 5% or more and less than 10%

[0238] <Developing streak evaluation> The developing streak evaluation was carried out in a low-temperature and low-humidity environment with a temperature of 15°C and a relative humidity of 10%.

[0239] The above durability test of repeatedly outputting the E-character image was conducted. The conditions of the durability test were such that after outputting two E-character images, the rotation of the photosensitive drum was completely stopped for about 5 seconds, and an intermittent image formation operation of restarting image output was repeated to output 50,000 electrophotographic images.

[0240] After outputting 50,000 sheets, a halftone image was output, and the occurrence of vertical streaks on the image was evaluated based on the following criteria. The evaluation results are shown in Table 4. Rank A: No occurrence of vertical streaks Rank B: One vertical streak occurs Rank C: Two to four vertical streaks occur Rank D: Five or more vertical streaks occur

[0241] 〔Examples 2 to 14, Comparative Examples 1 to 7〕 Evaluation was performed in the same manner as in Example 1, except that the toner filled in the process cartridge and the developing roller to be mounted were set as the combinations shown in Table 4. The evaluation results are shown in Table 4.

[0242]

Table 4

[0243] As shown in Table 4, by using the process cartridges according to Examples 1 to 14, it was found that the occurrence of fogging can be suppressed even when used for a long time under high temperature and high humidity, and the occurrence of developing streaks can also be suppressed when used for a long time under low temperature and low humidity environments.

[0244] On the other hand, in Comparative Example 1 where the CI value is 0.7%, the fogging suppression deteriorated due to long-term use in a high temperature and high humidity environment, and in Comparative Example 2 where the CI value is 16%, the developing streak suppression deteriorated due to long-term use in a low temperature and low humidity environment. Also, in Comparative Examples 3 to 5 where any of Ag, Ca / CI, and Cb / CI does not satisfy the specified range of the present invention, the fogging suppression deteriorated due to long-term use in a high temperature and high humidity environment. For Comparative Example 6 where the Asker C hardness of the developing roller is 55 degrees and Comparative Example 7 where the Asker C hardness of the developing roller is 76 degrees, the fogging suppression also deteriorated due to long-term use in a high temperature and high humidity environment.

Explanation of Signs

[0245] 1 ‥‥ Developing roller, 2 ‥‥ Conductive shaft body, 3 ‥‥ Elastic layer, 4 ‥‥ Surface layer, 100 ‥‥ Process cartridge, 101 ‥‥ Photoconductor, 102 ‥‥ Developing chamber, 103 ‥‥ Toner, 104 ‥‥ Toner container, 105 ‥‥ Seal member, 106 ‥‥ Developing roller, 107 ‥‥ Toner agitation mechanism, 108 ‥‥ Toner supply roller, 109 ‥‥ Developing blade, 110 ‥‥ Toner ejection prevention sheet, 111 ‥‥ Charging roller, 112 ‥‥ Cleaning blade, 113 ‥‥ Exposure light, 114 ‥‥ Intermediate transfer belt, 115 ‥‥ Primary transfer member, 116 ‥‥ Secondary transfer member, 117 ‥‥ Conveying route, 118 ‥‥ Fixing device, 119 ‥‥ Waste toner container

Claims

1. A process cartridge that is detachable from an electrophotographic apparatus main body, the process cartridge having at least toner and a developing roller, (I) The toner has at least toner particles, and agglomerates containing silica fine particles and a binder component are present on the surface of the toner particles, The arithmetic mean value Ag of the Feret diameter of the agglomerates is 500 nm or more and 8000 nm or less, When the number ratio of toner particles having the agglomerates is CI (number %), the CI is 1 number % or more and 15 number % or less, Taking the number ratio of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition A as Ca (number %), and taking the number ratio of toner particles having the agglomerates in the toner after being treated under the following ultrasonic condition B as Cb (number %), the CI, the Ca, and the Cb satisfy the formulas (1) and (2), ・Ultrasonic condition A: Output frequency 30 kHz, output capacity 0.75 W, irradiation time 300 s ・Ultrasonic condition B: Output frequency 30 kHz, output capacity 30 W, irradiation time 300 s 0.90 ≦ Ca / CI ≦ 1.00 Formula (1) 0.05 ≦ Cb / CI ≦ 0.25 Formula (2) (II) The developing roller has a conductive shaft body and at least one layer of elastic layer on the conductive shaft body, and the Asker C hardness of the developing roller is 56 degrees or more and 75 degrees or less A process cartridge characterized by the above.

2. The process cartridge according to claim 1, wherein the developing roller has a conductive shaft body, an elastic layer on the conductive shaft body, and a surface layer covering the surface of the elastic layer.

3. The process cartridge according to claim 2, wherein the elastic layer contains a urethane resin or silicone rubber.

4. The process cartridge according to claim 2, wherein the surface layer contains a urethane resin.

5. The process cartridge according to claim 1 or 2, wherein the toner contains a layered composite compound as an external additive.

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