Toner for developing electrostatic images, electrostatic image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method

Abstract

To provide a toner for electrostatic charge image development that is not easily affected by environment including temperature and humidity, and prevents the occurrence of fogging, the occurrence of cloud, and a reduction in image density even when images are repeatedly formed over a long period.SOLUTION: A toner for electrostatic charge image development has toner particles, and silica particles externally added to the toner particle, and including a nitrogen element-containing compound including a molybdenum element, in which the ratio (Mo / Si) of the Net intensity of the molybdenum element to the Net intensity of a silicon element measured by fluorescent X-ray analysis is 0.035 or more and 0.35 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In electrophotographic image formation, toner is used as an image forming material, and for example, toner containing toner particles containing a binder resin and a colorant, and an external additive externally added to the toner particles, is often used. Silica particles are often used as the external additive.

[0003] For example, Patent Document 1 discloses "a hydrophobic silica powder, (1) having a hydrophobicity of 50% or more, (2) an extractable amount X of at least one compound selected from the group consisting of quaternary ammonium ions, monoazo complexes, and mineral acid ions in a mixed solvent of methanol and an aqueous methanesulfonic acid solution is 0.1 mass% or more, and (3) the X and the extractable amount Y of the compound in water satisfy the following formula (I): Y / X<0.15."

[0004] Furthermore, Patent Document 2 discloses "silica powder containing a plurality of silica particles in which a quaternary ammonium salt is introduced into a silica structure having an "Si-O" bond as a repeating unit."

[0005] Furthermore, Patent Document 3 discloses "external charge control particles comprising carrier particles made of hydrophobic spherical silica microparticles with an average particle size of 20 to 500 nm obtained by subjecting the surface of hydrophilic spherical silica microparticles obtained by a sol-gel method to a hydrophobic treatment, and a charge control agent adhered to the surface of the carrier particles."

[0006] Furthermore, Patent Document 4 discloses "silica microparticles obtained by treating spherical hydrophobic silica microparticles having an average primary particle size of 0.01 to 5 μm with a compound selected from the group consisting of quaternary ammonium salt compounds, fluoroalkyl group-containing betaine compounds, and silicone oils."

[0007] Furthermore, Patent Document 5 discloses "particles in which silica microparticles having a hydrophobicity of 80% or more are treated with an amphoteric surfactant, and particles in which silica microparticles having a hydrophobicity of 80% or more are treated with a quaternary ammonium salt or a polymer having a quaternary ammonium group." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-073418 [Patent Document 2] Japanese Patent Application Publication No. 2017-039618 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-185998 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-194825 [Patent Document 5] Japanese Patent Application Publication No. 09-166884 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide a toner for developing electrostatic images, which comprises toner particles and silica particles containing a nitrogen-containing compound that contains molybdenum and is externally added to the toner particles, and which is less susceptible to environmental influences such as temperature and humidity than silica particles in which the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by X-ray fluorescence analysis, is less than 0.035 or more than 0.35, and which suppresses the occurrence of fogging, toner scattering (hereinafter also referred to as "cloud"), and reduction in image density even when images are repeatedly formed over a long period of time. [Means for solving the problem]

[0010] Specific means for solving the above problems include the following aspects. <1> toner particles; silica particles that are externally added to the toner particles, contain a nitrogen-containing compound containing molybdenum, and have a ratio (Mo / Si) of net intensity of molybdenum to net intensity of silicon measured by fluorescent X-ray analysis of 0.035 or more and 0.35 or less; A toner for developing electrostatic images comprising: <2> The nitrogen-containing compound in the silica particles is at least one selected from the group consisting of a quaternary ammonium salt containing molybdenum and a mixture of a quaternary ammonium salt and a metal oxide containing molybdenum. <1> 2. The toner for developing electrostatic images according to claim 1. <3> The number average particle diameter of the silica particles is 10 nm or more and 200 nm or less. <1> or <2> 2. The toner for developing electrostatic images according to claim 1. <4> The silica particles are Silica base particles; a silane coupling agent selected from the group consisting of a monofunctional silane coupling agent, a bifunctional silane coupling agent, and a trifunctional silane coupling agent; Fewa structure composed of at least one reaction product, and having a nitrogen-containing compound adsorbed in at least a portion of the pores of the reaction product; have <1> ~ <3> 10. The toner for developing electrostatic images according to claim 9. <5> The hydrophobicity of the silica particles is 10% or more and 60% or less. <1> ~ <4> 10. The toner for developing electrostatic images according to claim 9. <6> In the silica particles, when the pore volumes of pores with diameters of 1 nm or more and 50 nm or less obtained from a pore distribution curve of a nitrogen gas adsorption method before and after baking at 350°C are defined as A and B, respectively, B / A is 1.2 or more and 5 or less, and B is 0.2 cm 3 / g or more 3cm 3 / g or less <1> ~ <5> Toner for developing electrostatic images in any one of the above items. <7> The silica particles were analyzed by polarization / magic angle spinning (CP / MAS) 29 Chemical shifts in Si solid-state nuclear magnetic resonance (NMR) spectra -50 ppm to -75 ppm The integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppm The ratio C / D of the integral value D of the signal observed in the range is 0.10 or more and 0.75 or less. <1> ~ <6> 10. The toner for developing electrostatic images according to claim 9. <8> the amount X of the nitrogen-containing compound extracted from the silica particles by the ammonia / methanol mixed solution is 0.1 mass% or more; The amount X of the nitrogen-containing compound extracted from the silica particles and the amount Y of the nitrogen-containing compound extracted from the silica particles by water satisfy the formula: Y / X<0.3. <1> ~ <7> 10. The toner for developing electrostatic images according to claim 9. <9> The average circularity of the silica particles is 0.60 or more and 0.96 or less. <1> ~ <8> 10. The toner for developing electrostatic images according to claim 9. <10> The number particle size distribution index of the silica particles is 1.1 or more and 2.0 or less. <1> ~ <9> 10. The toner for developing electrostatic images according to claim 9. <11> <1> ~ <10> 10. An electrostatic image developer comprising the toner for developing electrostatic images according to any one of claims 1 to 9. <12> <1> ~ <10> The toner for developing electrostatic images according to any one of the above items is contained, A toner cartridge that is detachably attached to an image forming device. <13> <11> and a developing means for developing an electrostatic image formed on the surface of an image carrier into a toner image by using the electrostatic image developer, A process cartridge is detachably mounted in an image forming apparatus. <14> an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing means containing the electrostatic image developer according to <11> and developing the electrostatic image formed on the surface of the image carrier into a toner image by the electrostatic image developer; a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a cleaning means having a cleaning blade for cleaning the surface of the image carrier; a fixing means for fixing the toner image transferred onto the surface of the recording medium; An image forming apparatus comprising: <15> a charging step of charging the surface of the image carrier; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image carrier; <11> a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to claim 1; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a cleaning step of cleaning the surface of the image carrier with a cleaning blade; a fixing step of fixing the toner image transferred onto the surface of the recording medium; An image forming method comprising the steps of: [Effects of the Invention]

[0011] <1> , or <2> According to the invention, there is provided a toner for developing electrostatic images, which comprises toner particles and silica particles that are externally added to the toner particles and contain a nitrogen-containing compound that contains molybdenum, and which is less susceptible to environmental influences such as temperature and humidity than silica particles in which the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by X-ray fluorescence analysis, is less than 0.035 or exceeds 0.35, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time.

[0012] <3> According to the invention, there is provided a toner for developing electrostatic images, which comprises toner particles and silica particles containing a nitrogen-containing compound that contains molybdenum and is externally added to the toner particles, and which is less susceptible to environmental influences such as temperature and humidity, even when the number-average particle diameter of the silica particles is 10 nm or more and 200 nm or less, compared to silica particles in which the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si) measured by fluorescent X-ray analysis is less than 0.035 or more than 0.35, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time.

[0013] <4> According to the invention, there is provided a toner for developing electrostatic images, which comprises toner particles and silica particles containing a nitrogen-containing compound that contains molybdenum and is externally added to the toner particles, and which, compared to silica particles in which the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si) measured by fluorescent X-ray analysis is less than 0.035 or more than 0.35, comprises silica base particles and a structure that coats at least a portion of the surface of the silica base particles and is composed of at least one reaction product selected from the group consisting of monofunctional silane coupling agents, difunctional silane coupling agents, and trifunctional silane coupling agents, and in which a nitrogen-containing compound is adsorbed in at least a portion of the pores of the reaction product, and is less susceptible to environmental influences such as temperature and humidity, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time.

[0014] <7> According to the present invention, a toner for developing electrostatic images is provided which is less susceptible to environmental influences such as temperature and humidity, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time, compared to toners having a hydrophobicity of less than 10% or more than 60%.

[0015] <6> According to the invention, when the pore volumes of pores having a diameter of 1 nm or more and 50 nm or less obtained from a pore distribution curve of a nitrogen gas adsorption method before and after baking at 350°C are defined as A and B, respectively, B / A is less than 1.2 or B is 0.2 cm 3 / g, the toner for developing electrostatic images is less susceptible to environmental influences such as temperature and humidity, and suppresses the occurrence of fogging, clouding, and reduction in image density even when images are repeatedly formed over a long period of time.

[0016] <7> According to the present invention, when silica particles are heated in a temperature range of 300°C or more and 600°C or less, nitrogen-containing compounds are detected in the silica particles, and the nitrogen-containing compounds are detected by a cross polarization / magic angle spinning (CP / MAS) method. 29 Chemical shifts in Si solid-state nuclear magnetic resonance (NMR) spectra -50 ppm to -75 ppmThe integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppm The present invention provides a toner for developing electrostatic images that is less susceptible to environmental influences such as temperature and humidity, and that suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time, compared to when the ratio C / D of the integral values ​​D of the signals observed in the range is less than 0.10 or more than 0.75.

[0017] <8> According to the invention, a toner for developing electrostatic images is provided which is less susceptible to environmental influences such as temperature and humidity, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time, compared to when the amount X of the nitrogen-containing compound extracted with an ammonia / methanol mixed solution in silica particles is less than 0.1 mass %, or when the ratio of the amount X of the nitrogen-containing compound extracted with the nitrogen-containing compound and the amount Y of the nitrogen-containing compound extracted with water does not satisfy the formula: Y / X<0.3.

[0018] <9> According to the invention, there is provided a toner for developing electrostatic images, which comprises toner particles and silica particles containing a nitrogen-containing compound that contains molybdenum and is externally added to the toner particles, and which exhibits excellent fogging suppression in high-temperature, high-humidity environments even when the average circularity of the silica particles is 0.60 or more and 0.96 or less, compared to silica particles having a ratio (Mo / Si) of the net intensity of molybdenum to the net intensity of silicon measured by X-ray fluorescence analysis of less than 0.035 or more than 0.35.

[0019] <10> According to the present invention, there is provided silica particles that are not easily affected by environmental factors such as temperature and humidity, even when the silica particles have a number particle size distribution index of more than 2.0, and that suppress the occurrence of fogging, cloud formation, and reduction in image density even when images are repeatedly formed over a long period of time.

[0020] <11> , <12> , <13> , <14> , or <15> According to the invention, there is provided an electrostatic image developing toner having toner particles and silica particles containing a nitrogen-containing compound containing molybdenum element, which is externally added to the toner particles, wherein the silica particles have a ratio of the net intensity of molybdenum element to the net intensity of silicon element (Mo / Si) of less than 0.035 or more than 0.35 as measured by fluorescent X-ray analysis, which is less susceptible to environmental influences such as temperature and humidity, and which suppresses the occurrence of fogging, clouding, and a decrease in image density even when images are repeatedly formed over a long period of time. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a process cartridge according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0023] In the present specification, the upper or lower limit of one numerical range may be replaced by the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this disclosure, the upper or lower limit of the numerical range may be replaced by the values ​​shown in the examples.

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

[0025] In this specification, the properties of silica particles are measured after separation from the toner. There is no limitation on the method for separating silica particles from the toner, but for example, the silica particles are separated from the toner by the following separation treatment, and the measurements are performed on the obtained silica particles. -Separation processing- 2 g of toner is dispersed in 50 g of a 0.2 mass % aqueous solution of Triton X-100 (manufactured by Sigma-Aldrich), and the dispersion is subjected to ultrasonic waves using a US-300T ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 20°C and 85 Watts for 30 minutes or more. The dispersion is then centrifuged at high speed, and the supernatant is vacuum dried at 80°C to obtain silica particles.

[0026] The toner for developing electrostatic images according to the present embodiment (also simply referred to as "toner") is Toner particles and an externally added to the toner particles silica particles (hereinafter also referred to as "specific silica particles"). The specific silica particles contain a nitrogen-containing compound containing molybdenum (hereinafter also referred to simply as "nitrogen-containing compound"), and the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less.

[0027] Due to the above-described configuration, the toner according to this embodiment is less susceptible to environmental influences of temperature and humidity (such as the influence of high temperature and high environment (e.g., 30°C and 90% RH) or low temperature and low humidity environment (e.g., 10°C and 10% RH)), and even when images are repeatedly formed over a long period of time, it suppresses the occurrence of fogging (i.e., the phenomenon in which toner adheres to non-image areas), clouding (i.e., toner scattering), and reduction in image density. The reason for this is presumed to be as follows.

[0028] Silica particles have a high negative charge property and can be excessively charged. This results in a wide charge distribution. Toners containing externally added silica particles with a wide charge distribution tend to suffer from fog, clouding, and image density deterioration. In particular, fog, clouding, and image density deterioration are likely to occur in high-temperature, high-humidity environments.

[0029] On the other hand, when a nitrogen-containing compound is adsorbed onto silica particles, excessive negative charging can be suppressed when the silica particles are charged. The nitrogen-containing compound has positive charging properties, and the silica particles to which the nitrogen-containing compound is adsorbed cancel out and suppress excessive negative charging. In particular, by reducing the amount of toner with excessively high charging, which tends to occur in low-temperature, low-humidity environments, the occurrence of fogging, clouding, and a decrease in image density can be easily suppressed.

[0030] However, simply adsorbing a nitrogen-containing compound onto silica particles results in a distribution of charge that is broadened to include negative and positive charges. As described above, particularly in a high-temperature, high-humidity environment (e.g., 30°C, 90% RH) or a low-temperature, low-humidity environment (e.g., 10°C, 10% RH), the toner to which silica particles are externally added has a low charge amount. Therefore, when the charge distribution of silica particles broadens, the amount of toner particles that are difficult to charge increases, which is likely to cause fogging, clouding, and a decrease in image density.

[0031] Therefore, in the toner according to this embodiment, silica particles are used that contain a nitrogen-containing compound containing molybdenum, and the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), as measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less. The nitrogen-containing compound containing molybdenum enhances the activity of the nitrogen element, and even if the nitrogen-containing compound is present inside the pores of silica particles rather than on the outermost surface, it can adequately exhibit the chargeability of the nitrogen element. Furthermore, the interaction with the cationic moiety containing the nitrogen element is enhanced, making the cationic moiety less likely to detach, thereby improving the retention of chargeability. Furthermore, the chargeability can be adjusted according to the requirement, from positive to negative chargeability, depending on the ratio of molybdenum present. Furthermore, by incorporating a nitrogen-containing compound containing molybdenum, which has such properties, into silica particles with a ratio (Mo / Si) of the net strength of molybdenum to the net strength of silicon within the above range, the charge distribution becomes narrow and its maintenance is improved.

[0032] From the above, it is presumed that the toner according to this embodiment is less susceptible to environmental influences such as temperature and humidity, and will suppress the occurrence of fogging, clouding, and reduction in image density even when images are repeatedly formed over a long period of time.

[0033] The silica particles according to this embodiment preferably satisfy either the following aspect (A) or the following aspect (B).

[0034] Aspect (A): When the pore volumes of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before and after firing at 350°C are A and B, respectively, B / A is 1.2 to 5, and B is 0.2 cm 3 / g or more 3cm 3 / g or less. Hereinafter, "pore volume A of pores with diameters of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method before firing at 350°C" will also be referred to as "pore volume A before firing at 350°C". On the other hand, "pore volume B of pores with diameters of 1 nm or more and 50 nm or less obtained from the pore distribution curve of the nitrogen gas adsorption method after firing at 350°C" is also referred to as "pore volume B after firing at 350°C."

[0035] Aspect (B): Cross polarization / magic angle spinning (CP / MAS) 29 Chemical shifts in Si solid-state nuclear magnetic resonance (NMR) spectra (hereinafter also referred to as "Si-CP / MAS NMR spectra") -50 ppm to -75 ppm The integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppm The ratio C / D of the integral value D of the signal observed in the range is 0.10 or more and 0.75 or less.

[0036] When silica particles according to aspect (A) or (B) are used, the toner according to this embodiment is less susceptible to environmental influences such as temperature and humidity, and even when images are repeatedly formed over a long period of time, the occurrence of fogging, clouding, and reduction in image density can be easily suppressed. The reason for this is presumed to be as follows.

[0037] As described above, when a nitrogen-containing compound is adsorbed onto silica particles, excessive negative charging can be suppressed when the silica particles are charged. The nitrogen-containing compound has positive charging properties, and the silica particles having the nitrogen-containing compound adsorbed thereon cancel out the excessive negative charging and suppress the excessive negative charging.

[0038] However, since the nitrogen-containing compound has a positive charge property, if it is adsorbed on the outermost surface of the silica particles, the charge distribution will be spread to negative and positive charges. Therefore, it is preferable that the nitrogen-containing compound is present in the pores of the silica particles rather than coating the surface of the silica particles.

[0039] Therefore, in the silica particles according to the embodiment (A), the pore volume A before firing at 350° C. and the pore volume B after firing at 350° C. are set to have the above-mentioned relationship. The pore volume B after firing at 350°C is the pore volume after firing and evaporation of the nitrogen-containing compound that was adsorbed in the pores of the silica particles and partially blocked the pores. Therefore, B / A is 1.2 or more and 5 or less, and B is 0.2 cm 3 / g or more 3cm 3 / g or less indicates that a sufficient amount of the nitrogen-containing compound is adsorbed in at least some of the pores of the silica particles, thereby improving the narrowing of the charge distribution by the nitrogen-containing compound.

[0040] On the other hand, in the silica particles according to the embodiment (B), the chemical shift in the Si-CP / MAS NMR spectrum -50 ppm to -75 ppm The integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppm The ratio C / D of the integral value D of the signal observed in the range is defined as the above range. The signal integral value satisfying the above range indicates that a sufficient amount of nitrogen-containing compound is adsorbed on the surface of at least a part of the silica particles, and the silica particles have a low density and a structure (e.g., SiO 2 / 3 This shows that a CH3 layer is formed. Structures made from the reaction products of silane coupling agents (especially trifunctional silane coupling agents) have low density and pore shapes that allow nitrogen-containing compounds to easily adsorb. Therefore, the charge distribution can be narrowed more effectively by the nitrogen-containing compound.

[0041] From the above, it is presumed that when silica particles satisfying aspect (A) or (B) are used in the toner according to this embodiment, it is less susceptible to environmental influences such as temperature and humidity, and it is easier to suppress the occurrence of fogging, clouding, and reduction in image density even when images are repeatedly formed over a long period of time.

[0042] The toner according to this embodiment will be described in detail below.

[0043] The toner according to this embodiment includes toner particles and an external additive.

[0044] (toner particles) The toner particles contain a binder resin, and may contain a colorant, a release agent, and other additives, as necessary.

[0045] -Binder resin- Examples of binder resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), and vinyl resins made of copolymers of two or more of these monomers. Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0046] As the binder resin, a polyester resin is preferable. Examples of polyester resins include known polyester resins.

[0047] The polyester resin may be, for example, a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. The polyester resin may be a commercially available product or a synthesized product.

[0048] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. The polycarboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0049] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, preferred polyhydric alcohols are aromatic diols and alicyclic diols, and more preferred are aromatic diols. As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0050] The glass transition temperature (Tg) of the polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0051] The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a Tosoh GPC HLC-8120GPC measuring device and a Tosoh TSKgel SuperHM-M (15 cm) column in THF solvent. The weight-average molecular weight and number-average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0052] The polyester resin can be obtained by a known manufacturing method, for example, by carrying out the reaction at a polymerization temperature of 180°C or higher and 230°C or lower, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation. If the raw material monomers are not soluble or compatible at the reaction temperature, a high-boiling solvent may be added as a solubilizer to dissolve them. In this case, the polycondensation reaction is carried out while distilling off the solubilizer. If a monomer with poor compatibility is present in the copolymerization reaction, it is advisable to first condense the poorly compatible monomer with the acid or alcohol to be polycondensed, and then polycondense it with the main component.

[0053] The content of the binder resin is, for example, preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0054] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, and the like. Examples of the dye include various pigments such as phosphorus blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The colorant may be used alone or in combination of two or more kinds.

[0055] The colorant may be surface-treated as needed, or may be used in combination with a dispersant. Furthermore, a plurality of colorants may be used in combination.

[0056] The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0057] -Mold release agent- Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0058] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" as described in the method for determining the melting temperature in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0059] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0060] -Other additives- Examples of other additives include well-known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0061] -Characteristics of toner particles, etc.- The toner particles may be toner particles of a single layer structure, or may be toner particles of a so-called core-shell structure composed of a core part (core particle) and a coating layer (shell layer) that coats the core part. Here, the toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

[0062] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0063] The various average particle sizes and particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter). For the measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of the electrolyte. The electrolyte solution containing the suspended sample is dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. Based on the particle size distribution measured, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the smallest diameter side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v, the number particle size D16p, the particle size at 50% of the cumulative total as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at 84% of the cumulative total as the volume particle size D84v and the number particle size D84p. Using these, the volumetric particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 , the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 It is calculated as:

[0064] The average circularity of the toner particles is preferably 0.950 or more and 0.990 or less, and more preferably 0.957 or more and 0.980 or less.

[0065] The average circularity of toner particles is measured using a Sysmex FPIA-3000. This device employs a flow image analysis method to measure particles dispersed in water or other liquids. The aspirated particle suspension is introduced into a flat sheath flow cell, where the sheath liquid forms a flat sample flow. By irradiating the sample flow with a strobe light, the particles passing through are captured as still images by a CCD (Charge Coupled Device) camera through an objective lens. The captured particle images are then processed into two-dimensional images, and the circularity is calculated from the projected area and perimeter. The average circularity is determined by statistically processing the images of at least 4,000 particles. Formula: Circularity = Equivalent diameter / Perimeter = [2 × (Aπ)] 1 / 2 ] / PM In the above formula, A represents the projected area and PM represents the perimeter. The measurement is performed in HPF mode (high resolution mode) with a dilution ratio of 1.0. In addition, when analyzing the data, the circularity analysis range is set to 0.40 to 1.00 in order to remove measurement noise.

[0066] (external additives) The external additive contains specific silica particles. The specific silica particles contain a nitrogen-containing compound containing molybdenum, and the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si), measured by X-ray fluorescence analysis, is 0.035 or more and 0.35 or less.

[0067] (Ratio to net strength (Mo / Si)) In the specific silica particles, the ratio of the net intensity of molybdenum element to the net intensity of silicon element (Mo / Si), measured by fluorescent X-ray analysis, is 0.035 or more and 0.35 or less. From the viewpoints of narrowing the charge distribution of the silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, clouding, and image density reduction, the ratio is preferably 0.07 or more and 0.32 or less, and more preferably 0.10 or more and 0.30 or less.

[0068] From the viewpoints of narrowing the charge distribution of the silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, clouding, and image density reduction, the net strength of the molybdenum element is preferably 5 kcps or more and 75 kcps or less, 7 kcps or more and 50 kcps or less, 8 kcps or more and 55 kcps or less, or 10 kcps or more and 40 kcps or less.

[0069] The net intensity of molybdenum element and silicon element is measured as follows.

[0070] Approximately 0.5 g of silica particles is compressed under a load of 6 t for 60 seconds using a compression molding machine to produce a disk with a diameter of 50 mm and a thickness of 2 mm. This disk is used as a sample and qualitative and quantitative elemental analysis is performed using a scanning X-ray fluorescence analyzer (XRF-1500, manufactured by Shimadzu Corporation) under the following conditions to determine the net intensities (unit: kilocounts per second, kcps) of the molybdenum and silicon elements. Tube voltage: 40kV ·Tube current: 90mA ·Measurement area (analysis diameter): Diameter 10mmφ Measurement time: 30 minutes Anticathode: Rhodium

[0071] (pore volume) In the specific silica particles, the ratio B / A of the pore volume B after firing at 350°C to the pore volume A before firing at 350°C is 1.2 or more and 5 or less, but from the viewpoint of narrowing the charge distribution, it is preferably 1.4 or more and 3 or less, and more preferably 1.4 or more and 2.5 or less.

[0072] The pore volume B after firing at 350°C is 0.2 cm 3 / g or more 3cm 3 / g or less, but from the viewpoint of narrowing the charge distribution, 3 / g or more 1.8cm 3 / g or less is preferable, and 0.6cm 3 / g or more 1.5cm 3 / g or less is more preferable.

[0073] Specifically, the 350°C firing is carried out as follows. In a nitrogen environment, the silica particles to be measured are heated to 350°C at a rate of 10°C / min and held at 350°C for 3 hours. After that, they are cooled to room temperature (25°C) at a rate of 10°C / min.

[0074] Pore ​​volume is measured as follows. First, the silica particles to be measured are cooled to liquid nitrogen temperature (-196°C), nitrogen gas is introduced, and the amount of adsorption is determined by constant volume or gravimetric methods. The pressure of the introduced nitrogen gas is gradually increased, and an adsorption isotherm is created by plotting the amount of nitrogen gas adsorbed for each equilibrium pressure. From this adsorption isotherm, a pore size distribution curve, with the vertical axis representing frequency and the horizontal axis representing pore diameter, is calculated using the BJH method formula. Then, from the obtained pore size distribution curve, the cumulative pore volume distribution, where the vertical axis is volume and the horizontal axis is pore diameter, is calculated. From the obtained cumulative pore volume distribution, the pore volume in the pore diameter range of 1 nm to 50 nm is integrated, and this is defined as the "pore volume of pore diameters of 1 nm to 50 nm."

[0075] (CP / MAS NMR spectrum) Chemical shifts in Si-CP / MAS NMR spectra -50 ppm to -75 ppm The integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppm The ratio C / D of the integral value D of the signal observed in this range is 0.10 or more and 0.75 or less, but from the viewpoint of narrowing the charge distribution, it is preferably 0.12 or more and 0.45 or less, and more preferably 0.15 or more and 0.40 or less. The chemical shift when the integral value of all signals is taken as 100% from the viewpoint of narrowing the charge distribution of silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, cloud, and image density reduction. -50 ppm to -75 ppm The signal ratio of the signal integral C observed in this range is preferably 5% or more, and more preferably 7% or more. The upper limit of the signal integral C ratio is, for example, 60% or less.

[0076] The Si-CP / MAS NMR spectrum can be obtained by carrying out measurements by nuclear magnetic resonance spectroscopy under the following conditions. Spectrometer: AVENCE300 (Brunker) ·Resonance frequency: 59.6MHz Measurement nuclei: 29 Si Measurement method: CPMAS method (using Bruker's standard Palk Sequence cp.av) Wait time: 4 seconds Contact time: 8 milliseconds Accumulation count: 2048 times Measurement temperature: Room temperature (actual value 25°C) Observation center frequency: -3975.72Hz MAS rotation speed: 7.0mm-6kHz Reference substance: hexymethylcyclotrisiloxane

[0077] (Composition of specific silica particles) The specific silica particles contain a nitrogen-containing compound. Specifically, the specific silica particles have a structure in which at least a portion of the surface of a silica base particle is coated with at least one reaction product selected from the group consisting of a monofunctional silane coupling agent, a bifunctional silane coupling agent, and a trifunctional silane coupling agent (hereinafter also referred to as a "silane coupling agent reaction product"), and a nitrogen-containing compound is adsorbed onto at least a portion of the reaction product. By forming this structure, the pore volume characteristics and the Si-CP / MAS NMR spectrum characteristics can be controlled. In addition, the hydrophobicity and the amount of OH groups, which will be described later, can also be controlled. Furthermore, the specific silica particles may have a hydrophobic treated structure on the surface of the structure.

[0078] -Silica mother particles- The silica base particles are silica particles on at least a portion of the surface of which a structure is formed in which a nitrogen-containing compound is adsorbed in at least a portion of the pores of the reaction product of the silane coupling agent. Examples of the silica base particles include dry silica particles and wet silica particles. Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound, and deflagration silica obtained by explosively burning metallic silicon powder. Examples of wet silica particles include wet silica particles obtained by the neutralization reaction of sodium silicate and mineral acid (precipitation silica synthesized and agglomerated under alkaline conditions, and gel-process silica particles synthesized and agglomerated under acidic conditions), colloidal silica particles (silica sol particles) obtained by polymerizing acidic silicic acid in an alkaline state, and sol-gel silica particles obtained by hydrolysis of organic silane compounds (e.g., alkoxysilanes). Among these, sol-gel silica particles are preferred as the silica base particles from the viewpoint of narrowing the charge distribution.

[0079] -Reaction products of silane coupling agents- The adsorption structure composed of the reaction product of a silane coupling agent (especially a trifunctional silane coupling agent) has a low density and a high affinity for nitrogen-containing compounds, which allows the nitrogen-containing compounds to be easily adsorbed deep into the pores, resulting in a high adsorption amount (i.e., content) of the nitrogen-containing compounds. The adhesion of the positively charged nitrogen-containing compounds to the negatively charged silica surface effectively counteracts excess negative charge. Furthermore, because the nitrogen-containing compounds are adsorbed within the low-density structure rather than on the outermost surface of the silica particles, they prevent the charge distribution from becoming too strong and widening, and only counteract excess negative charge, further narrowing the charge distribution.

[0080] The reaction product of the silane coupling agent is, for example, a compound represented by the following general formula (TA): R 2 is substituted with an OH group, R 2 a reaction product obtained by polycondensation of two compounds in which the OH group is substituted, R 2The reaction products of silane coupling agents include those in which hydroxyl groups are substituted with OH groups and those in which hydroxyl groups are polycondensed with the SiOH groups of silica particles. R 2 This includes fully or partially substituted reaction products and fully or partially polycondensed reaction products.

[0081] The silane coupling agent is a non-nitrogen element-containing compound that does not contain N (nitrogen element). Specifically, the silane coupling agent is a silane coupling agent represented by the following general formula (TA): Pulling agents are included. General formula (TA):R 1 n -Si(R 2 ) 4-n

[0082] In the general formula (TA), R 1 represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and R 2 represents a halogen atom or an alkoxy group. 2 may be the same group or different groups, and n represents an integer of 1 or more and 3 or less.

[0083] R 1 The aliphatic hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic, but is preferably linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group is preferably 1 to 20, more preferably 1 to 18, even more preferably 1 to 12, and still more preferably 1 to 10. The aliphatic hydrocarbon group may be saturated or unsaturated, but is preferably a saturated aliphatic hydrocarbon group, and more preferably an alkyl group.

[0084] Examples of saturated aliphatic hydrocarbon groups include linear alkyl groups (methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl, and icosyl groups), branched alkyl groups (isopropyl, isobutyl, isopentyl, neopentyl, 2-ethylhexyl, tertiary butyl, tertiary pentyl, and isopentadecyl groups), and cyclic alkyl groups (cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, tricyclodecyl, norbornyl, and adamantyl groups).

[0085] Examples of unsaturated aliphatic hydrocarbon groups include alkenyl groups (vinyl groups (ethenyl groups), 1-propenyl groups, 2-propenyl groups, 2-butenyl groups, 1-butenyl groups, 1-hexenyl groups, 2-dodecenyl groups, pentenyl groups, etc.), and alkynyl groups (ethynyl groups, 1-propynyl groups, 2-propynyl groups, 1-butynyl groups, 3-hexynyl groups, 2-dodecenyl groups, etc.).

[0086] R 1 The aromatic hydrocarbon group represented by the formula (I) preferably has 6 to 20 carbon atoms, more preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, and still more preferably 6 to 10 carbon atoms.

[0087] Examples of the aromatic hydrocarbon group include a phenylene group, a biphenylene group, a terphenylene group, a naphthalene group, and an anthracene group.

[0088] R 2 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. The halogen atom is preferably a chlorine atom, a bromine atom, or an iodine atom.

[0089] R 2Examples of the alkoxy group represented by the formula (I) include alkoxy groups having 1 to 10 carbon atoms (preferably 1 to 8, more preferably 1 to 4). Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, an n-butoxy group, an n-hexyloxy group, a 2-ethylhexyloxy group, and a 3,5,5-trimethylhexyloxy group. The alkoxy group also includes a substituted alkoxy group. Examples of the substituent that can be substituted on the alkoxy group include a halogen atom, a hydroxyl group, an amino group, an alkoxy group, an amide group, and a carbonyl group.

[0090] n is preferably an integer of 1 or 2, and more preferably 1.

[0091] The silane coupling agent represented by the general formula (TA) is R 1 is a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, and R 2 A trifunctional silane coupling agent in which is a halogen atom or an alkoxy group and n is 1 is preferred.

[0092] Examples of trifunctional silane coupling agents include: Vinyltrimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, decyltrichlorosilane, phenyltrichlorosilane (all of the above, R 1 is an unsubstituted aliphatic hydrocarbon group or an unsubstituted aromatic hydrocarbon group); 3-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane (R 1 is a substituted aliphatic hydrocarbon group or a substituted aromatic hydrocarbon group); Examples include: The trifunctional silane coupling agents may be used alone or in combination of two or more.

[0093] Among these, from the viewpoint of narrowing the charge distribution, alkyltrialkoxysilane is preferred as the trifunctional silane coupling agent, and in the general formula (TA), R 1 represents an alkyl group having 1 to 20 carbon atoms (preferably 1 to 15 carbon atoms), and R 2 More preferred is an alkyltrialkoxysilane in which R represents an alkyl group having 1 to 2 carbon atoms.

[0094] The amount of the structure composed of the reaction product of the silane coupling agent attached is preferably 5.5% by mass or more and 30% by mass or less, and more preferably 7% by mass or more and 22% by mass or less, relative to the silica particles, from the viewpoint of narrowing the charge distribution and maintaining the charge distribution.

[0095] -Nitrogen-containing compounds- The nitrogen-containing compound is a nitrogen-containing compound containing molybdenum, excluding ammonia and compounds that are in a gaseous state at temperatures of -200°C or higher and 25°C or lower. Specifically, from the viewpoints of narrowing the charge distribution of silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, cloud, and image density reduction, the nitrogen-containing compound is preferably at least one selected from the group consisting of quaternary ammonium salts containing molybdenum (particularly, quaternary ammonium salts containing molybdenum), and mixtures of quaternary ammonium salts and metal oxides containing molybdenum. In particular, in the case of a quaternary ammonium salt containing molybdenum, the molybdenum anion, which is an anion, is strongly bonded to the quaternary ammonium cation, which is a cation, and therefore the charge distribution maintainability is improved, which makes it easier to achieve and maintain the suppression of fogging, clouding, and image density reduction. The nitrogen-containing compound is preferably adsorbed to at least a portion of the pores of the reaction product of the silane coupling agent. The molybdenum-containing nitrogen-containing compound may be used alone or in combination of two or more. The molybdenum-containing nitrogen-containing compound may also be used in combination with a molybdenum-free nitrogen-containing compound (at least one selected from the group consisting of quaternary ammonium salts, primary amine compounds, secondary amine compounds, tertiary amine compounds, amide compounds, imine compounds, and nitrile compounds, preferably a quaternary ammonium salt).

[0096] The quaternary ammonium salt (quaternary ammonium salt not containing molybdenum element) is not particularly limited, and any known quaternary ammonium salt can be used.

[0097] Quaternary ammonium salts (quaternary ammonium salts that do not contain molybdenum) have a narrow charge distribution. The compounds represented by general formula (AM) may be used singly or in combination of two or more.

[0098] [ka] In the general formula (AM), R 1 , R 2 , R 3 and R 4 each independently represents a hydrogen atom, or an alkyl group, an aralkyl group, or an aryl group which may have a substituent; X - represents an anion, where R 1 , R 2 , R 3 and R 4At least one of R represents an alkyl group, an aralkyl group, or an aryl group which may have a substituent. 1 , R 2 , R 3 and R 4 Two or more of these may be linked to form an aliphatic ring, an aromatic ring, or a heterocycle.

[0099] R 1 ~R 4 Examples of the alkyl group represented by the formula include a linear alkyl group having 1 to 20 carbon atoms and a branched alkyl group having 3 to 20 carbon atoms. Examples of the linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, and an n-hexadecyl group. Examples of branched alkyl groups having 3 to 20 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. Among the above, R 1 ~R 4 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 15 carbon atoms, such as a methyl group, an ethyl group, a butyl group, or a tetradecyl group.

[0100] R 1 ~R 4 Examples of the aralkyl group represented by the formula (I) include aralkyl groups having 7 to 30 carbon atoms. Examples of aralkyl groups having 7 to 30 carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthrathymethyl, and phenylcyclopentylmethyl. Among the above, R 1 ~R 4 The aralkyl group represented by the formula (I) is preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group, a phenylethyl group, a phenylpropyl group, or a 4-phenylbutyl group.

[0101] R 1 ~R 4 Examples of the aryl group represented by the formula include an aryl group having 6 to 20 carbon atoms. Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a pyridyl group, and a naphthyl group. Among the above, R 1 ~R 4 The aryl group represented by the formula (I) is preferably an aryl group having 6 to 10 carbon atoms, such as a phenyl group.

[0102] X - Examples of the anion represented by the formula (I) include organic anions and inorganic anions. Examples of organic anions include polyfluoroalkylsulfonate ions, polyfluoroalkylcarboxylate ions, tetraphenylborate ions, aromatic carboxylate ions, and aromatic sulfonate ions (such as 1-naphthol-4-sulfonate ions). Inorganic anions include OH - , F - , Fe(CN)6 3- , Cl - , Br - , NO2 - , NO3 - , CO3 2- , PO4 3- , SO4 2- etc.

[0103] In the general formula (AM), R 1 , R 2 , R 3 and R 4 Two or more of R may be linked to each other to form a ring. 1 , R 2 , R 3 and R 4 Examples of the ring formed by linking two or more of the above include an alicyclic ring having 2 to 20 carbon atoms, and a heterocyclic amine having 2 to 20 carbon atoms.

[0104] In the compound represented by general formula (AM), R 1 , R 2 , R 3 and R 4 may each independently have a substituent, such as a nitrile group, a carbonyl group, an ether group, an amide group, a siloxane group, a silyl group, or a silane alkoxy group. R 1 , R 2 , R 3 and R 4 each independently preferably represents an alkyl group having 1 to 16 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

[0105] Among these, from the viewpoint of narrowing the charge distribution, the compound represented by general formula (AM) preferably has a total of 18 to 35 carbon atoms, more preferably 20 to 32 carbon atoms.

[0106] X in the compound represented by general formula (AM) - Examples of structures other than those are shown below, but the present embodiment is not limited to these.

[0107] [ka]

[0108] The quaternary ammonium salt containing molybdenum is a compound represented by the general formula (AM), X, from the viewpoint of narrowing the charge distribution of silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, clouding, and image density reduction. - However, the anion is molybdate ion (MoO4 2- , Mo2O7 2- , Mo3O 10 2- , Mo4O 13 2- , Mo7O 24 2- , Mo8O 26 4- Specifically, the quaternary ammonium salt containing molybdenum is preferably a compound represented by the formula: [N(CH 3 ) 2 (C 14 H 29 ) 2 ] 4 Mo 8 O 26 , [N(C 4 H 9 ) 2 (C 6 H 5 ) 2 ] 2 Mo 2 O 7. [N(CH 3 ) 2 (CH 2 C 6 H 5 )(CH 2 ) 17 CH 3 ] 2 MoO 4. [N(CH 3 ) 2 (CH 2 C 6 H 5 )(CH 2 ) 15 CH 3 ] 2 MoO 4, etc. Metal oxides containing molybdenum include molybdenum oxides (molybdenum trioxide, molybdenum dioxide, Mo 8 O 26 ), alkali metal molybdates (lithium molybdate, sodium molybdate, potassium molybdate, etc.), alkaline earth metal molybdates (magnesium molybdate, calcium molybdate, etc.), other composite oxides (Bi2O3·2MoO3, γ-Ce2Mo3O 13 etc.)

[0109] -Detection and content of nitrogen-containing compounds- When the specific silica particles are heated in a temperature range of 300° C. to 600° C., nitrogen-containing compounds are detected. Specifically, for example, the following is true. Nitrogen-containing compounds can be detected, for example, using a heating furnace-type drop-type pyrolysis gas chromatograph mass spectrometer using He as a carrier gas. Nitrogen-containing compounds can be detected under pyrolysis temperature conditions of 300°C to 600°C under inert gas. Specifically, 0.1 mg to 10 mg of silica particles are introduced into the pyrolysis gas chromatograph mass spectrometer, and the presence or absence of nitrogen-containing compounds can be confirmed from the MS spectrum of the detected peak. Examples of components generated by pyrolysis from silica particles containing nitrogen-containing compounds include primary to tertiary amines or aromatic nitrogen compounds represented by the following general formula (N): In the following general formula (N), R N1 ~R N3 each independently represents a hydrogen atom, or an alkyl group, an aralkyl group, or an aryl group which may have a substituent; R N1 ~R N3 is R in general formula (AM) 1 , R 2 , and R 3 is synonymous with. For example, if the nitrogen-containing compound is a quaternary ammonium salt, part of the side chain is eliminated by thermal decomposition at 600°C, and detected as a tertiary amine. [ka]

[0110] From the viewpoint of narrowing the charge distribution, the content of the nitrogen-containing compound is preferably 0.008% by mass or more and 0.45% by mass or less, more preferably 0.015% by mass or more and 0.20% by mass or less, and even more preferably 0.018% by mass or more and 0.10% by mass or less, in terms of N atoms, relative to the silica particles.

[0111] The content of nitrogen-containing compounds calculated as N element is measured as follows. Using an oxygen / nitrogen analyzer (e.g., HORIBA EMGA-920) for 45 seconds, the amount of nitrogen present is measured as the ratio of N (N / Si). As a sample pretreatment, impurities such as ammonia are removed from the silica particles by drying them in a vacuum dryer at 100°C for at least 24 hours.

[0112] -Extraction amount of nitrogen-containing compounds- The amount X of the nitrogen-containing compound extracted by the ammonia / methanol mixed solution is 0.1 mass % or more, and the amount X of the nitrogen-containing compound extracted by the water and the amount Y of the nitrogen-containing compound extracted by the water preferably satisfy the formula: Y / X<0.3.

[0113] That is, the nitrogen-containing compound has a property of being difficult to dissolve in water, that is, it is difficult to adsorb moisture in the air. In silica particles containing a nitrogen-element-containing compound, when the nitrogen-element-containing compound adsorbs moisture, the charge distribution becomes broader and the nitrogen-element-containing compound becomes more likely to separate from the silica particles. However, silica particles containing a nitrogen-containing compound that does not easily adsorb moisture in the air are less likely to have a widening charge distribution and the nitrogen-containing compound is less likely to be released, even when there is a large amount of moisture in the air (even under high humidity conditions), and therefore the charge distribution is more likely to be maintained narrower, which makes it easier to maintain the suppression of fogging, clouding, and image density reduction.

[0114] The extracted amount X of the nitrogen-containing compound is preferably 50% by mass or more, but the upper limit of the extracted amount X of the nitrogen-containing compound is, for example, 95% by mass or less, because the solution is difficult to penetrate into the pores due to surface tension, and a portion of the nitrogen-containing compound remains undissolved. The ratio "Y / X" of the amount of nitrogen-containing compound extracted X to the amount of nitrogen-containing compound extracted Y is preferably less than 0.3, more preferably 0.15 or less. However, the lower limit of the ratio "Y / X" is ideally 0, but since the measurement error range of X and Y is about ±1%, the lower limit is, for example, 0.01 or more.

[0115] Here, the extracted amounts X and Y of the nitrogen-containing compound are measured as follows. First, the silica particles to be measured are analyzed at a constant temperature of 400°C using a thermogravimetric / mass spectrometer (e.g., a gas chromatograph mass spectrometer manufactured by Netsch Japan Co., Ltd.), and the integrated mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to a nitrogen element relative to the silica particles is measured and designated as W1.

[0116] Separately, 1 part by mass of the silica particles to be measured was added to 30 parts by mass of an ammonia / methanol solution (Sigma-Aldrich, ammonia / methanol mass ratio = 1 / 5.2) at 25°C, and after 30 minutes of ultrasonic treatment, the silica powder and the extract were separated. The separated silica particles were dried in a vacuum dryer at 100°C for 24 hours, and the mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to nitrogen atoms was measured with a thermogravimetric-mass spectrometer at a constant temperature of 400°C, and this was designated W2. Then, the extracted amount X of the nitrogen element-containing compound is calculated using the following formula. ·Formula:X=W1-W2

[0117] In addition, 1 part by mass of silica particles to be measured is added to 30 parts by mass of water at 25°C, and after 30 minutes of ultrasonic treatment, the silica particles are separated from the extract. The separated silica particles are dried in a vacuum dryer at 100°C for 24 hours, and the mass fraction of compounds in which hydrocarbons with at least one carbon atom are covalently bonded to nitrogen atoms is measured relative to the silica particles using a thermogravimetric / mass spectrometer at a constant temperature of 400°C, and this is designated as W3. Then, the extracted amount Y of the nitrogen element-containing compound is calculated using the following formula. ·Formula: Y=W1-W3

[0118] (Hydrophobic treated structure) The hydrophobic treated structure is a structure that has been reacted with a hydrophobic treatment agent. As the hydrophobic treatment agent, for example, an organosilicon compound is applied. Examples of organosilicon compounds include: Alkoxysilane compounds or halosilane compounds having a lower alkyl group, such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, and trimethylmethoxysilane; Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane; alkoxysilane compounds having an epoxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane; alkoxysilane compounds having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane; alkoxysilane compounds having an aminoalkyl group, such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; Alkoxysilane compounds having an isocyanate alkyl group, such as 3-isocyanatepropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane; silazane compounds such as hexamethyldisilazane and tetramethyldisilazane; Examples include:

[0119] (Characteristics of specific silica particles) - Hydrophobicity - The hydrophobicity of the specific silica particles is 10% or more and 60% or less, but from the viewpoints of narrowing the charge distribution of the silica particles, maintaining the charge distribution, and maintaining the suppression of fogging, clouding, and image density reduction, it is more preferably 20% or more and 55% or less, and even more preferably 28% or more and 53% or less. If the hydrophobicity of the specific silica particles is 10% or less, the amount of coating on the structure due to the reaction product of the silane coupling agent is low, and the content of the nitrogen element-containing compound is reduced, which makes it easier for the charge distribution to widen. On the other hand, when the hydrophobicity of the specific silica particles exceeds 60%, the density of the structure increases due to the reaction of the silane coupling agent, the number of pores decreases, and the content of the nitrogen-containing compound decreases, which makes the charge distribution more likely to spread.

[0120] The hydrophobicity of silica particles is measured as follows. 0.2% by mass of sample silica particles is placed in 50 ml of ion-exchanged water, and methanol is added dropwise from a burette while stirring with a magnetic stirrer. The mass fraction of methanol in the methanol-water mixed solution at the end point when the entire sample has sunk is determined as the degree of hydrophobicity.

[0121] -Number average particle size and number particle size distribution index- The number average particle size of the specific silica particles is preferably 10 nm or more and 200 nm or less, more preferably 10 nm or more and 80 nm or less, and even more preferably 10 nm or more and 60 nm or less. When the number-average particle diameter of the silica particles is within the above range, the specific surface area is large and excessive charging is likely to occur, but the specific silica particles, even when the number-average particle diameter is within the above range, can narrow the charge distribution and improve the maintainability of the narrow charge distribution, making it easier to maintain the suppression of fogging, clouding, and image density reduction.

[0122] The number particle size distribution index of the specific silica particles is preferably 1.1 or more and 2.0 or less, and more preferably 1.15 or more and 1.6 or less. When the number particle size distribution index of the silica particles is within the above range, the amount of coarse particles, which tend to have a large charge amount, and the amount of fine particles, which tend to have a small charge amount, are reduced, and thus the narrow charge distribution can be easily realized, and as a result, the narrow charge distribution of the silica particles and the maintenance of the charge distribution, as well as the suppression of fogging, clouding, and image density reduction, can be easily realized.

[0123] Here, the number average particle size and number particle size distribution index of the silica particles are measured as follows. Silica particles are observed at 40,000x magnification using a scanning electron microscope (SEM), and the images of the observed silica particles are analyzed using image processing and analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to determine the circular equivalent diameters of at least 200 particles. A cumulative distribution of the number of individual particles is then drawn, starting from the smallest diameter side, and the particle size at 50% of the cumulative diameter from the smallest diameter side, the number-average particle size, is determined. The square root of the particle diameter D84 at 84% cumulative size from the smallest diameter side divided by the particle diameter D16 at 16% cumulative size is defined as the "number particle size distribution index" (GSD). That is, the number particle size distribution index (GSD) = (D84 / D16) 0.5 is.

[0124] -Circularity- The average circularity of the specific silica particles is preferably 0.60 or more and 0.96 or less, more preferably 0.70 or more and 0.92 or less, and even more preferably 0.75 or more and 0.90 or less. When the average circularity of silica particles is within the above range, the specific surface area is large and excessive charging is likely to occur, but the specific silica particles achieve a narrow charge distribution even when the average circularity is within the above range.

[0125] Here, the circularity of the silica particles is measured as follows. Silica particles are observed at 40,000x magnification using a scanning electron microscope (SEM), and the images of the observed silica particles are analyzed using image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.). The circularity of at least 200 particles is determined, and the arithmetic mean is calculated to determine the average circularity. The circularity is calculated by the following formula. Circularity = Equivalent circle diameter / Perimeter = [2 × (Aπ) 1 / 2 ] / PM In the above formula, A represents the projected area and PM represents the perimeter.

[0126] -Volume resistivity- The volume resistivity of a specific silica particle (i.e., the volume resistivity before firing at 350°C) is 1.0 x 10 7 Ωcm or more 1.0×10 11.5 Ωcm or less is preferable, and 1.0×10 8 Ωcm or more 1.0×10 11 Ωcm or less is more preferable. When the volume resistivity of the specific silica particles is within the above range, the content of the nitrogen-containing compound is high, which makes it difficult for excessive charging to occur and facilitates narrowing of the charge distribution, thereby facilitating narrowing of the charge distribution of the silica particles, maintaining the charge distribution, and maintaining suppression of fogging, clouding, and image density reduction.

[0127] In the specific silica particles, when the volume resistivities of the silica particles before and after firing at 350° C. are Ra and Rb, respectively, Ra / Rb is preferably 0.01 or more and 0.8 or less, more preferably 0.015 or more and 0.6 or less. When the Ra / Rb ratio is within the above range, the content of the nitrogen-containing compound is high, which makes it difficult for excessive charging to occur and facilitates narrowing of the charge distribution, thereby facilitating narrowing of the charge distribution of the silica particles, maintaining the charge distribution, and maintaining suppression of fogging, clouding, and image density reduction.

[0128] The 350°C firing is carried out as described above. On the other hand, the volume resistivity is measured as follows: The measurement environment is a temperature of 20°C and a humidity of 50% RH. 20cm 2 The silica particles to be measured are placed on the surface of a circular jig on which the electrode plate is arranged, to a thickness of about 1 mm to 3 mm, forming a silica particle layer. 2 The silica particle layer is sandwiched between two electrode plates. To eliminate gaps between the silica particles, a pressure of 0.4 MPa is applied to the electrode plate placed on the silica particle layer, and the thickness (cm) of the silica particle layer is then measured. Both the top and bottom electrodes of the silica particle layer are connected to an impedance analyzer (Solartron Analytical). -3 Hz over 10 6 Hz or less are measured to obtain a Nyquist plot. This is fitted to an equivalent circuit, assuming the existence of three resistance components: bulk resistance, particle interface resistance, and electrode contact resistance, to determine the bulk resistance R. The formula for calculating the volume resistivity (Ω·cm) of silica particles is shown below. ·Formula:ρ=R / L In the formula, ρ represents the volume resistivity of the silica particles (Ω·cm), R represents the bulk resistance (Ω), and L represents the thickness of the silica particle layer (cm).

[0129] (OH group amount) The amount of OH groups measured by the Sears method for specific silica particles is 0.2 / nm 2 More than 5.5 pieces / nm 2 From the viewpoint of narrowing the charge distribution, 0.2 particles / nm or less is preferable. 2 More than 4 pieces / nm 2 Less than 0.2 particles / nm is more preferable. 2 More than 3 pieces / nm 2 The following is even more preferred: The amount of OH groups measured by the Sears method can be adjusted to fall within the above range by sufficiently forming a structure composed of a reaction product of the silane coupling agent on the silica base particles.

[0130] By reducing the amount of OH groups that inhibit the adsorption of the nitrogen-containing compound to the above range, the nitrogen-containing compound can easily penetrate deep into the pores of the silica particles (for example, the pores of the adsorption layer described below). Then, hydrophobic interactions with the nitrogen-containing compound occur, strengthening its adhesive force to the silica particles. This increases the amount of the nitrogen-containing compound adsorbed. In addition, the nitrogen-containing compound becomes less likely to detach. This improves the narrowing of the charge distribution by the nitrogen-containing compound, and also improves the maintenance of the narrow charge distribution.

[0131] Furthermore, by reducing the amount of OH groups to the above range, the environmental dependency of the charging characteristics becomes low, and it becomes easier to narrow the charge distribution using the nitrogen-containing compound in any environment (particularly in a low-temperature, low-humidity environment where excessive negative charging is likely to occur).

[0132] The amount of OH groups is measured by the Sears method, specifically as follows. 1.5g of silica particles are added to a mixture of 50g of pure water and 50g of ethanol and stirred for 2 minutes with an ultrasonic homogenizer to create a dispersion. While stirring at 25°C, 1.0g of 0.1mol / L hydrochloric acid solution is added dropwise to obtain the test solution. The resulting test solution is placed in an automatic titrator and subjected to potentiometric titration with 0.01mol / L sodium hydroxide solution, and a derivative curve of the titration curve is created. Among the inflection points where the derivative value of the titration curve is 1.8 or greater, the titer E is the one where the titer of 0.01mol / L sodium hydroxide solution is the largest. Using the following formula, the surface silanol group density ρ (particles / nm 2 ) is calculated. Formula: ρ=((0.01×E-0.1)×NA / 1000) / (M×S BET x10 18 ) In the formula, the details of the symbols are as follows: E: Among the inflection points where the derivative of the titration curve is 1.8 or more, the titer of 0.01 mol / L sodium hydroxide solution is the largest. NA: Avogadro's number M: Silica particle amount (1.5g) S BET: specific surface area of ​​silica particles (m 2 / g) The specific surface area of ​​silica particles is measured by the BET nitrogen adsorption three-point method, with the equilibrium relative pressure set to 0.3.

[0133] (Method of manufacturing specific silica particles) An example of a method for producing specific silica particles is a first step of forming a structure composed of a reaction product of a silane coupling agent on at least a portion of the surface of a silica base particle; a second step of adsorbing a nitrogen-containing compound into at least a portion of the pores of the reaction product of the silane coupling agent; It has. The method for producing specific silica particles may further include a third step of hydrophobizing the silica base particles, which have at least a portion of the surface coated thereon and which are composed of a reaction product of a silane coupling agent and have a structure in which a nitrogen-element-containing compound is adsorbed in at least a portion of the pores of the reaction product of the silane coupling agent, after or during the second step.

[0134] The steps of the method for producing the specific silica particles will be described in detail below.

[0135] [Preparation process] First, the step of preparing silica base particles will be described.

[0136] The preparation process includes, for example, (i) A step of preparing a silica base particle suspension by mixing an alcohol-containing solvent with silica base particles. (ii) A step of granulating silica base particles by a sol-gel method to obtain a silica base particle suspension etc. Examples of the silica base particles used in (i) include sol-gel silica particles (silica particles obtained by the sol-gel method), aqueous colloidal silica particles, alcoholic silica particles, fumed silica particles obtained by a gas phase method, and fused silica particles. The alcohol-containing solvent used in (i) above may be a solvent containing alcohol alone, or a mixed solvent containing alcohol and other solvents. Examples of alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Examples of other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

[0137] The step (1-a) is preferably a step of granulating silica base particles by a sol-gel method to obtain a silica base particle suspension. More specifically, step (1-a) may be carried out, for example, by an alkaline catalyst solution preparation step of preparing an alkaline catalyst solution containing an alkaline catalyst in a solvent containing alcohol; a silica base particle producing step of producing silica base particles by supplying tetraalkoxysilane and an alkali catalyst into an alkali catalyst solution; Preferably, the method is a sol-gel method comprising:

[0138] The alkaline catalyst solution preparation step is preferably a step of preparing a solvent containing alcohol and mixing the solvent with an alkaline catalyst to obtain an alkaline catalyst solution.

[0139] The alcohol-containing solvent may be a solvent containing only alcohol, or a mixed solvent containing alcohol and other solvents. Examples of alcohol include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, and butanol. Examples of other solvents include water; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate; and ethers such as dioxane and tetrahydrofuran. In the case of a mixed solvent, the proportion of alcohol is preferably 80% by mass or more, more preferably 85% by mass or more.

[0140] The alkaline catalyst is a catalyst for promoting the reaction (hydrolysis reaction and condensation reaction) of tetraalkoxysilane, and examples thereof include basic catalysts such as ammonia, urea, and monoamine, with ammonia being particularly preferred.

[0141] The concentration of the alkali catalyst in the alkali catalyst solution is preferably 0.5 mol / L or more and 1.5 mol / L or less, more preferably 0.6 mol / L or more and 1.2 mol / L or less, and even more preferably 0.65 mol / L or more and 1.1 mol / L or less.

[0142] The silica base particle production step is a step in which tetraalkoxysilane and an alkali catalyst are supplied to an alkali catalyst solution, and the tetraalkoxysilane is reacted (hydrolysis reaction and condensation reaction) in the alkali catalyst solution to produce silica base particles.

[0143] In the silica base particle generation process, core particles are generated by the reaction of tetraalkoxysilane at the initial stage of supplying tetraalkoxysilane (core particle generation stage), and then these core particles grow (core particle growth stage) to generate silica base particles.

[0144] Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc. From the viewpoint of controllability of the reaction rate and uniformity of the shape of the produced silica base particles, tetramethoxysilane or tetraethoxysilane is preferred.

[0145] Examples of the alkali catalyst supplied to the alkali catalyst solution include basic catalysts such as ammonia, urea, monoamines, and quaternary ammonium salts, with ammonia being particularly preferred. The alkali catalyst supplied together with the tetraalkoxysilane may be of the same type as the alkali catalyst already contained in the alkali catalyst solution, or may be of a different type, but is preferably of the same type.

[0146] The method for supplying the tetraalkoxysilane and the alkali catalyst into the alkali catalyst solution may be a continuous supply method or an intermittent supply method.

[0147] In the silica base particle production step, the temperature of the alkaline catalyst solution (temperature at the time of supply) is preferably 5°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower.

[0148] [First step] In the first step, a structure composed of a reaction product of a silane coupling agent is formed. Specifically, in the first step, for example, a silane coupling agent is added to a silica base particle suspension, and the silane coupling agent is reacted with the surfaces of the silica base particles to form a structure composed of a reaction product of the silane coupling agent. The functional groups of the silane coupling agent react with each other and with OH groups on the surfaces of the silica particles to form a structure composed of the reaction product of the silane coupling agent.

[0149] The reaction of the silane coupling agent is carried out by adding the silane coupling agent to a suspension of silica base particles, and then heating the suspension while stirring. Specifically, for example, the suspension is heated to 40°C to 70°C, the silane coupling agent is added, and then the suspension is stirred. The stirring time is preferably 10 minutes to 24 hours, more preferably 60 minutes to 420 minutes, and even more preferably 80 minutes to 300 minutes.

[0150] [Second process] In the second step, a nitrogen-containing compound is adsorbed into at least some of the pores of the reaction product of the silane coupling agent. Specifically, in the second step, first, for example, a nitrogen-containing compound is added to a silica base particle suspension, and the mixture is stirred at a temperature ranging from 20° C. to 50° C. As a result, the nitrogen-containing compound is adsorbed into at least some of the pores of the reaction product of the silane coupling agent.

[0151] In the second step, for example, an alcohol liquid containing a nitrogen-containing compound may be added to the silica particle suspension. The alcohol may be the same type as the alcohol contained in the silica base particle suspension or may be a different type, but it is more preferable that the alcohol be the same type.

[0152] In the alcohol liquid containing the nitrogen-containing compound, the concentration of the nitrogen-containing compound is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 6% by mass or less.

[0153] [Third step] In the third step, after or during the second step, a hydrophobic treatment is performed on silica base particles having a structure in which a nitrogen-containing compound is adsorbed in at least some of the pores of the reaction product of the silane coupling agent. Specifically, in the third step, for example, a nitrogen-containing compound is added to the silica base particle suspension in which the structures have been formed, and then a hydrophobic treatment agent is added. The hydrophobic treatment agent forms a hydrophobic treatment layer by reacting with its functional groups and with the OH groups of the silica base particles.

[0154] The reaction of the hydrophobic treatment agent is carried out by adding the silane coupling agent to a suspension of silica base particles, and then heating the suspension while stirring. Specifically, for example, the suspension is heated to 40°C to 70°C, the hydrophobic treatment agent is added, and then the suspension is stirred. The stirring time is preferably 10 minutes to 24 hours, more preferably 20 minutes to 120 minutes, and even more preferably 20 minutes to 90 minutes.

[0155] [Drying process] In the method for producing specific silica particles, it is preferable to carry out a drying step of removing the solvent from the suspension after carrying out the second step or the third step. The drying step may be carried out during the second step or the third step.

[0156] The drying method may be, for example, heat drying, spray drying, or supercritical drying. Spray drying can be performed by a conventional method using a commercially available spray dryer (including disk rotation type and nozzle type). For example, spraying the spray liquid into a hot air stream at a rate of 0.2 L / h to 1 L / h is performed. In this case, the hot air temperature is preferably in the range of 70°C to 400°C at the inlet and 40°C to 120°C at the outlet. If the inlet temperature is below 70°C, the solids contained in the dispersion are not sufficiently dried. If the temperature exceeds 400°C, the particle shape is distorted during spray drying. If the outlet temperature is below 40°C, the solids are not sufficiently dried and adhere to the inside of the device. A more preferable inlet temperature is in the range of 100°C to 300°C. The silica particle concentration in the silica particle suspension during spray drying is preferably in the range of 10% by mass or more and 30% by mass or less in terms of solid content.

[0157] In supercritical drying, the solvent is removed using a supercritical fluid, which makes it difficult for surface tension to act between particles, and the primary particles contained in the suspension are dried in a state where aggregation is suppressed, making it easier to obtain silica particles with a highly uniform particle size.

[0158] Examples of substances that can be used as supercritical fluids include carbon dioxide, water, methanol, ethanol, acetone, etc. From the viewpoints of treatment efficiency and suppressing the generation of coarse particles, the solvent removal step is preferably a step that uses supercritical carbon dioxide.

[0159] Specifically, supercritical drying is carried out, for example, by the following procedure. The suspension is placed in a sealed reactor, and then liquefied carbon dioxide is introduced into the reactor. The sealed reactor is then heated and the pressure inside the sealed reactor is increased by a high-pressure pump, thereby bringing the carbon dioxide inside the sealed reactor into a supercritical state. The liquefied carbon dioxide is then flowed into the sealed reactor and the supercritical carbon dioxide is flowed out of the sealed reactor, thereby causing the supercritical carbon dioxide to flow through the suspension inside the sealed reactor. While the supercritical carbon dioxide flows through the suspension, the solvent dissolves in the supercritical carbon dioxide, and the solvent is removed along with the supercritical carbon dioxide flowing out of the sealed reactor. The temperature and pressure in the sealed reactor are those that put carbon dioxide into a supercritical state, i.e., the critical point of carbon dioxide is 31.1°C / 7.38 MPa, and the temperature and pressure are, for example, 40°C to 200°C and 10 MPa to 30 MPa.

[0160] The flow rate of the supercritical fluid in the supercritical drying is preferably 80 mL / sec or more and 240 mL / sec or less.

[0161] The obtained silica particles are preferably crushed or sieved as necessary to remove coarse particles and aggregates. Crushing is performed using, for example, a dry grinding device such as a jet mill, a vibration mill, a ball mill, or a pin mill. Sieving is performed using, for example, a vibration sieve or an air sieving machine.

[0162] The amount (content) of the specific silica particles added externally is, for example, preferably 0.25% by mass or more and 2.0% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less, based on the toner particles.

[0163] -Other external additives- The external additive may be any other external additive other than the specific silica particles. Examples of other external additives include inorganic particles and organic particles other than the specific silica particles. Examples of other inorganic particles include particles of silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, chromium oxide, cerium oxide, magnesium oxide, zirconium oxide, silicon carbide, and silicon nitride.

[0164] The surfaces of the other inorganic particles are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the other inorganic particles.

[0165] Examples of organic particles include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0166] The amount (content) of the other external additives added is, for example, preferably 0.05% by mass or more and 5.0% by mass or less, and more preferably 0.5% by mass or more and 3.0% by mass or less, based on the toner particles.

[0167] (Toner manufacturing method) Next, a method for producing the toner according to this embodiment will be described. The toner according to the exemplary embodiment can be obtained by producing toner particles and then externally adding an external additive to the toner particles, if necessary.

[0168] The toner particles may be produced by any of a dry production method (for example, a kneading and pulverization method) and a wet production method (for example, an aggregation and coalescence method, a suspension polymerization method, a dissolution and suspension method). The method for producing the toner particles is not particularly limited, and any well-known production method may be used. Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

[0169] Specifically, for example, when toner particles are produced by the aggregation and coalescence method, Toner particles are manufactured through the following steps: a step of preparing a resin particle dispersion in which resin particles that will become a binder resin are dispersed (resin particle dispersion preparation step); a step of aggregating the resin particles (and other particles, if necessary) in the resin particle dispersion (in a dispersion after mixing other particle dispersions, if necessary) to form aggregated particles (aggregated particle formation step); and a step of heating the aggregated particle dispersion in which the aggregated particles are dispersed to fuse and coalesce the aggregated particles to form toner particles (fusion and coalescence step).

[0170] Each step will be described in detail below. In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described, but the colorant and the release agent are used as needed. Of course, additives other than the colorant and the release agent may also be used.

[0171] -Resin particle dispersion preparation process- First, a resin particle dispersion in which resin particles serving as a binder resin are dispersed, as well as a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared.

[0172] Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

[0173] Examples of the dispersion medium used in the resin particle dispersion include aqueous media. Examples of aqueous media include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more.

[0174] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactants may be used alone or in combination of two or more.

[0175] In the resin particle dispersion, resin particles can be dispersed in a dispersion medium by a general dispersion method such as a rotary shear homogenizer, a ball mill having a medium, a sand mill, a dyno mill, etc. Depending on the type of resin particles, the resin particles may be dispersed in the resin particle dispersion by, for example, a phase inversion emulsification method. The phase inversion emulsification method involves dissolving the resin to be dispersed in a hydrophobic organic solvent in which the resin is soluble, adding a base to the organic continuous phase (O phase) to neutralize it, and then adding an aqueous medium (W phase), thereby converting the resin from W / O to O / W (so-called phase inversion) and forming a discontinuous phase, and dispersing the resin in particulate form in the aqueous medium.

[0176] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm. The volume average particle size of the resin particles is measured using a particle size distribution obtained by measurement with a laser diffraction particle size distribution analyzer (e.g., LA-700 manufactured by Horiba, Ltd.), and the cumulative distribution for the volume of the divided particle size range (channel) is subtracted from the small particle size side, and the particle size at which the cumulative 50% of all particles is measured is defined as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same way.

[0177] The content of resin particles contained in the resin particle dispersion is, for example, preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass.

[0178] Note that, for example, a colorant particle dispersion and a release agent particle dispersion are also prepared in the same manner as the resin particle dispersion. That is, the volume average particle size, dispersion medium, dispersion method, and particle content of the particles in the resin particle dispersion are the same for the colorant particles dispersed in the colorant particle dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0179] -Agglomerated particle formation process- Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion. Then, in the mixed dispersion, the resin particles, colorant particles, and release agent particles are hetero-aggregated to form aggregated particles containing the resin particles, colorant particles, and release agent particles and having a diameter close to that of the target toner particles.

[0180] Specifically, for example, an aggregating agent is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to be acidic (for example, a pH of 2 or more and 5 or less), and a dispersion stabilizer is added as necessary. After that, the mixed dispersion is heated to the glass transition temperature of the resin particles (specifically, for example, a temperature of the glass transition temperature of the resin particles -30°C or more and the glass transition temperature -10°C or less), and the particles dispersed in the mixed dispersion are aggregated to form aggregated particles. In the aggregate particle formation step, for example, the above-mentioned aggregating agent may be added to the mixed dispersion at room temperature (e.g., 25°C) while stirring with a rotary shear homogenizer, the pH of the mixed dispersion may be adjusted to an acidic value (e.g., pH 2 or more and 5 or less), and a dispersion stabilizer may be added as necessary, followed by the heating.

[0181] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. In particular, when a metal complex is used as the flocculant, the amount of surfactant used can be reduced and the charging characteristics can be improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferably used as this additive.

[0182] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. The chelating agent may be a water-soluble chelating agent, such as hydroxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), etc. The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, per 100 parts by mass of the resin particles.

[0183] -Fusion / unification process- Next, the aggregated particle dispersion liquid in which the aggregated particles are dispersed is heated, for example, to a temperature equal to or higher than the glass transition temperature of the resin particles (for example, a temperature 10 to 30°C higher than the glass transition temperature of the resin particles), to fuse and coalesce the aggregated particles and form toner particles.

[0184] Through the above steps, toner particles are obtained. After obtaining an aggregated particle dispersion in which aggregated particles are dispersed, the toner particles may be produced through the following steps: a step of further mixing the aggregated particle dispersion with a resin particle dispersion in which resin particles are dispersed, and aggregating the aggregated particles so that further resin particles adhere to the surfaces of the aggregated particles to form second aggregated particles; and a step of heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles to form toner particles having a core / shell structure.

[0185] After the fusion and coalescence process, the toner particles formed in the solution are subjected to a known washing process, a solid-liquid separation process, and a drying process to obtain dry toner particles. In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic chargeability. Furthermore, the solid-liquid separation step is not particularly limited, but from the viewpoint of productivity, it is preferable to carry out suction filtration, pressure filtration, etc. Furthermore, in the drying step, there is no particular limitation on the method, but from the viewpoint of productivity, it is preferable to carry out freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc.

[0186] The toner according to the present embodiment is produced by, for example, adding an external additive to the obtained dry toner particles and mixing them. The mixing can be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, or the like. Furthermore, if necessary, coarse particles may be removed from the toner using a vibrating sieve, an air sieve, or the like.

[0187] <Electrostatic image developer> The electrostatic image developer according to this embodiment contains at least the toner according to this embodiment. The electrostatic image developer according to this embodiment may be a one-component developer containing only the toner according to this embodiment, or may be a two-component developer containing the toner mixed with a carrier.

[0188] The carrier is not particularly limited, and examples thereof include known carriers, such as coated carriers in which the surface of a core material made of magnetic powder is coated with a coating resin, magnetic powder dispersion carriers in which magnetic powder is dispersed and blended in a matrix resin, and resin-impregnated carriers in which porous magnetic powder is impregnated with a resin. The magnetic powder dispersion type carrier and the resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and are coated with a coating resin.

[0189] Examples of magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0190] Examples of coating resins and matrix resins include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, and epoxy resins. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0191] Here, the method of coating the surface of the core material with a coating resin includes a method of coating with a solution for forming a coating layer in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent. The solvent is not particularly limited and may be selected taking into consideration the coating resin to be used, its applicability, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer, a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material, a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air, and a kneader coater method in which the core material of the carrier and the solution for forming a coating layer are mixed in a kneader coater and the solvent is removed.

[0192] In the two-component developer, the mixing ratio (mass ratio) of toner to carrier is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0193] <Image forming device / image forming method> An image forming apparatus and an image forming method according to this embodiment will be described. The image forming apparatus according to the present embodiment includes an image carrier, a charging unit for charging the surface of the image carrier, an electrostatic image forming unit for forming an electrostatic image on the surface of the charged image carrier, a developing unit containing an electrostatic image developer and developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer, a transfer unit for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, a cleaning unit having a cleaning blade for cleaning the surface of the image carrier, and a fixing unit for fixing the toner image transferred to the surface of the recording medium. The electrostatic image developer according to the present embodiment is used as the electrostatic image developer.

[0194] The image forming apparatus according to this embodiment carries out an image forming method (the image forming method according to this embodiment) that includes a charging step of charging the surface of an image carrier, an electrostatic image forming step of forming an electrostatic image on the surface of the charged image carrier, a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to this embodiment, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, a cleaning step of cleaning the surface of the image carrier with a cleaning blade, and a fixing step of fixing the toner image transferred to the surface of the recording medium.

[0195] The image forming apparatus according to the present embodiment may be a known image forming apparatus, such as a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; an intermediate transfer type apparatus that primarily transfers a toner image formed on the surface of an image carrier to the surface of an intermediate transfer medium, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer medium to the surface of a recording medium; or an apparatus that includes a discharging means that irradiates the surface of the image carrier with discharging light to discharge it after the toner image is transferred and before it is charged. In the case of an intermediate transfer type device, the transfer means is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0196] In the image forming apparatus according to the present embodiment, for example, a portion including the developing means may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge equipped with developing means that accommodates the electrostatic image developer according to the present embodiment is preferably used.

[0197] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0198] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to this embodiment. The image forming apparatus shown in Figure 1 includes first through fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K (image forming means) that output images in the colors yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side horizontally spaced a predetermined distance apart from one another. Note that these units 10Y, 10M, 10C, and 10K may also be process cartridges that are detachable from the image forming apparatus.

[0199] Above each of the units 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 serving as an intermediate transfer body extends through each unit. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24 that are spaced apart from each other and arranged from left to right in the drawing, and is configured to run in a direction from the first unit 10Y to the fourth unit 10K. A force is applied to the support roll 24 in a direction away from the drive roll 22 by a spring or the like (not shown), thereby applying tension to the intermediate transfer belt 20 wound around them. In addition, an intermediate transfer body cleaning device 30 is provided on the image carrier side of the intermediate transfer belt 20, facing the drive roll 22. In addition, the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with toner including four colors of toner, yellow, magenta, cyan, and black, contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

[0200] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, the first unit 10Y, which forms a yellow image and is disposed upstream in the direction of travel of the intermediate transfer belt, will be described here as a representative. Note that parts equivalent to those of the first unit 10Y are given reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y), and descriptions of the second to fourth units 10M, 10C, and 10K will be omitted.

[0201] The first unit 10Y has a photoreceptor 1Y that acts as an image carrier. Around the photoreceptor 1Y, there are arranged in this order: a charging roll (an example of a charging means) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential; an exposure device (an example of an electrostatic image forming means) 3 that exposes the charged surface to a laser beam 3Y based on a color-separated image signal to form an electrostatic image; a developing device (an example of a developing means) 4Y that supplies charged toner to the electrostatic image to develop it; a primary transfer roll 5Y (an example of a primary transfer means) that transfers the developed toner image onto the intermediate transfer belt 20; and a photoreceptor cleaning device (an example of a cleaning means) 6Y that has a cleaning blade 6Y-1 that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is positioned opposite the photoreceptor 1Y. Furthermore, a bias power supply (not shown) that applies a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power supply varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0202] The operation of forming a yellow image in first unit 10Y will be described below. First, prior to operation, the surface of the photosensitive member 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has conductivity (for example, volume resistivity at 20°C: 1×10 -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate with a resistivity of Ωcm or less. This photosensitive layer normally has a high resistance (the resistance of ordinary resins), but when irradiated with a laser beam 3Y, the resistivity of the irradiated portion changes. Therefore, a laser beam 3Y is output to the charged surface of the photosensitive element 1Y via an exposure device 3 in accordance with image data for yellow sent from a control unit (not shown). The laser beam 3Y is irradiated onto the photosensitive layer on the surface of the photosensitive element 1Y, thereby forming an electrostatic charge image of a yellow image pattern on the surface of the photosensitive element 1Y.

[0203] An electrostatic image is an image formed on the surface of the photosensitive element 1Y by charging it; the laser beam 3Y reduces the resistivity of the irradiated portion of the photosensitive layer, causing the charged charges on the surface of the photosensitive element 1Y to flow, while the charges remain in the portions not irradiated by the laser beam 3Y, forming a so-called negative latent image. The electrostatic image formed on the photoreceptor 1Y is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic image on the photoreceptor 1Y is made visible as a toner image (developed image) by the developing device 4Y.

[0204] The developing device 4Y contains an electrostatic image developer containing, for example, at least yellow toner and a carrier. The yellow toner is frictionally charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoreceptor 1Y. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. The photoreceptor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1Y is transported to a predetermined primary transfer position.

[0205] When the yellow toner image on the photoreceptor 1Y is transported to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y to the primary transfer roll 5Y acts on the toner image, causing the toner image on the photoreceptor 1Y to be transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the (-) polarity of the toner, and in the first unit 10Y, for example, it is controlled to +10 μA by a control unit (not shown). On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

[0206] Furthermore, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K of the second unit 10M and subsequent units is also controlled in accordance with the first unit. In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed sequentially through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are transferred onto the intermediate transfer belt 20 in a superimposed manner.

[0207] The intermediate transfer belt 20, onto which the four-color toner images have been multiplex-transferred through the first to fourth units, reaches a secondary transfer section composed of the intermediate transfer belt 20, a support roll 24 in contact with the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of a secondary transfer means) 26 arranged on the image bearing surface side of the intermediate transfer belt 20. Meanwhile, recording paper (an example of a recording medium) P is fed via a supply mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 at a predetermined timing, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a negative polarity, the same as the negative polarity of the toner. Electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, transferring the toner image on the intermediate transfer belt 20 onto the recording paper P. The secondary transfer bias at this time is determined according to resistance detected by resistance detection means (not shown) that detects resistance in the secondary transfer section, and is voltage-controlled.

[0208] Thereafter, the recording paper P is sent to the pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (an example of fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0209] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, etc. In addition to the recording paper P, examples of the recording medium include overhead projector sheets and the like. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper in which the surface of plain paper is coated with resin or the like, or art paper for printing, is preferably used.

[0210] The recording paper P on which the color image has been fixed is conveyed toward the discharge section, and the series of color image forming operations is completed.

[0211] <Process cartridges / toner cartridges> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that is detachably attached to an image forming apparatus and that contains the electrostatic image developer according to this embodiment and is equipped with a developing means that develops an electrostatic image formed on the surface of an image carrier using the electrostatic image developer into a toner image.

[0212] The process cartridge according to this embodiment is not limited to the above configuration, but may also be configured to include a developing device and, if necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, and a transfer means.

[0213] An example of a process cartridge according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0214] FIG. 2 is a schematic diagram showing the configuration of the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is configured to integrally hold a photosensitive member 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photosensitive member 107, a developing device 111 (an example of a developing means), and a photosensitive member cleaning device 113 (an example of a cleaning means) having a cleaning blade 113-1, all combined together in a cartridge by a housing 117 provided with, for example, a mounting rail 116 and an opening 118 for exposure. In FIG. 2, 109 denotes an exposure device (an example of an electrostatic image forming means), 112 denotes a transfer device (an example of a transfer means), 115 denotes a fixing device (an example of a fixing means), and 300 denotes recording paper (an example of a recording medium).

[0215] Next, the toner cartridge according to this embodiment will be described. The toner cartridge according to the present embodiment is a toner cartridge that contains the toner according to the present embodiment and is detachably attached to an image forming apparatus. The toner cartridge contains replenishment toner to be supplied to a developing unit provided in the image forming apparatus.

[0216] 1 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and developing devices 4Y, 4M, 4C, and 4K are connected to the toner cartridges corresponding to each developing device (color) by toner supply pipes (not shown). When the toner stored in a toner cartridge runs low, the toner cartridge is replaced. [Example]

[0217] The present embodiment will be described in more detail below with reference to examples and comparative examples, but the present embodiment is not limited to these examples. Furthermore, "parts" and "%" are by mass unless otherwise specified.

[0218] <Preparation of toner particles> (Toner particles (1)) -Synthesis of amorphous polyester resin- Bisphenol A ethylene oxide adduct (manufactured by Wako Pure Chemical Industries, Ltd.): 150 parts Bisphenol A propylene oxide adduct (manufactured by Wako Pure Chemical Industries, Ltd.): 250 parts Tetrapropenyl succinic anhydride (Wako Pure Chemical Industries, Ltd.): 130 parts Terephthalic acid (Wako Pure Chemical Industries, Ltd.): 100 parts Trimellitic acid (manufactured by Wako Pure Chemical Industries, Ltd.): 5 parts The above monomer components were charged into a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube, and the atmosphere inside the reaction vessel was replaced with dry nitrogen gas. Then, tin dioctanoate was added in an amount of 0.3% based on the total amount of the monomer components. The temperature was raised to 235°C over 1 hour under a nitrogen gas stream, and the reaction was continued for 3 hours. The pressure inside the reaction vessel was reduced to 10.0 mmHg, and the reaction was continued with stirring until the desired molecular weight was reached. The reaction was terminated when the desired molecular weight was reached. The resulting amorphous polyester resin 1 had a glass transition temperature of 61° C., a weight average molecular weight of 42,000, and an acid value of 13 mgKOH / g.

[0219] -Preparation of amorphous polyester resin dispersion- Amorphous polyester resin: 100 parts Methyl ethyl ketone: 60 parts Isopropyl alcohol: 10 parts The above components were placed in a reaction vessel equipped with a stirrer and dissolved at 60° C. After confirming dissolution, the reaction vessel was cooled to 35° C., and then 3.5 parts of a 10% aqueous ammonia solution was added. Next, 300 parts of ion-exchanged water was added dropwise to the reaction vessel over 3 hours to prepare a polyester resin dispersion. Next, methyl ethyl ketone and isopropyl alcohol were removed using an evaporator to obtain an amorphous polyester resin dispersion.

[0220] -Preparation of colorant particle dispersion- Cyan pigment (Pigment Blue 15:3, manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.) 10 parts Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts 80 parts ion-exchanged water The above components were mixed and dispersed for 1 hour using a high-pressure impact disperser Ultimizer (HJP30006, manufactured by Sugino Machine Co., Ltd.) to obtain a colorant particle dispersion having a volume average particle size of 180 nm and a solid content of 20%.

[0221] -Preparation of release agent particle dispersion- Paraffin wax (HNP 9, manufactured by Nippon Seiro Co., Ltd.) 50 parts Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku) 2 parts 200 parts ion-exchanged water The above components were heated to 120°C, thoroughly mixed and dispersed using an Ultra Turrax T50 manufactured by IKA, and then dispersed using a pressure discharge homogenizer to obtain a release agent particle dispersion liquid with a volume average particle size of 200 nm and a solid content of 20%.

[0222] -Preparation of toner particles (1)- Amorphous polyester resin particle dispersion 210 parts 25 parts of colorant particle water dispersion 30 parts of release agent particle dispersion Polyaluminum chloride 0.4 parts 100 parts ion-exchanged water The above components were placed in a stainless steel flask and thoroughly mixed and dispersed using an Ultra Turrax manufactured by IKA, and then the flask was heated to 48°C while stirring in a heating oil bath. After maintaining at 48°C for 25 minutes, 70 parts of the same polyester resin dispersion as above was slowly added thereto.

[0223] The pH of the system was then adjusted to 8.0 using a 0.5 mol / L aqueous solution of sodium hydroxide. The stainless steel flask was then sealed, the stirring shaft was magnetically sealed, and the mixture was heated to 90°C and maintained at this temperature for 3 hours while continuing to stir. After the reaction was complete, the mixture was cooled at a rate of 2°C / min, filtered, thoroughly washed with ion-exchanged water, and then subjected to solid-liquid separation using Nutsche suction filtration. The mixture was then redispersed in 3 L of ion-exchanged water at 30°C, stirred and washed for 15 minutes at 300 rpm. This washing procedure was repeated six more times, and when the filtrate reached a pH of 7.54 and an electrical conductivity of 6.5 μS / cm, it was subjected to solid-liquid separation using Nutsche suction filtration using No. 5A filter paper. Vacuum drying was then continued for 12 hours to obtain toner particles (1). The toner particles (1) had a volume average particle size (D50v) of 6.1 μm and an average circularity of 0.965.

[0224] <Preparation of external additives> (Preparation of Silica Particles) [Silica particles 1, 3-32, 35] Suspensions containing silica particles 1, 3 to 32, and 35 in each example were prepared as follows.

[0225] -Preparation of alkaline catalyst solution- Methanol, ion-exchanged water, and ammonia water (NH4OH) in the amounts and concentrations shown in Table 1 were placed in a glass reaction vessel equipped with a metal stirring rod, a dropping nozzle, and a thermometer, and the mixture was stirred to obtain an alkaline catalyst solution.

[0226] - Granulation of silica base particles using the sol-gel method - The temperature of the alkaline catalyst solution was adjusted to 40°C, and the alkaline catalyst solution was purged with nitrogen. Next, while stirring the alkaline catalyst solution, tetramethoxysilane (TMOS) in the amounts shown in Table 1 and 124 parts by mass of ammonia water (NH4OH) with a catalyst (NH3) concentration of 7.9% were simultaneously added dropwise to obtain a silica base particle suspension.

[0227] -Addition of silane coupling agent- The silica base particle suspension was heated to 40°C and stirred, while the type and amount of silane coupling agent shown in Table 1 was added to the suspension. Stirring was then continued for 120 minutes to allow the silane coupling agent to react, thereby forming an adsorption structure.

[0228] - Addition of nitrogen-containing compounds - The nitrogen-containing compounds shown in Table 1 were diluted with butanol to prepare alcohol solutions. Next, an alcohol solution prepared by diluting a nitrogen-containing compound with butanol was added to the suspension. The alcohol solution was added so that the number of parts of the nitrogen-containing compound per 100 parts by mass of the solid content of the silica base particle suspension was the amount shown in Table 1. The mixture was then stirred at 30°C for 100 minutes to obtain a suspension containing the nitrogen-containing compound.

[0229] -Drying- Next, 300 parts by mass of the suspension was placed in a reaction vessel, and CO2 was added while stirring, and the temperature and pressure inside the reaction vessel were raised to the temperature and pressure shown in Table 1. CO2 was introduced and discharged at a flow rate of 5 L / min while stirring while maintaining the temperature and pressure. Thereafter, the solvent was removed over 120 minutes, and silica particles 1, 3 to 32, and 35 were obtained.

[0230] [Silica particles 2] Silica particles 2 were obtained in the same manner as silica particles 1, except that spray drying was performed using a Mini Spray Dryer B-290 (manufactured by Nippon Buchi Co., Ltd.) under conditions of the temperature and pressure inside the cylinder shown in Table 1 and the silica particle suspension being fed at a feed rate of 0.2 L / hour.

[0231] [Silica particles 33] After the addition of the nitrogen-containing compound, hexamethyldisilazane (HMDS) was added in an amount of 100 mass% based on the solid content of the silica base particles, and the mixture was stirred at 65°C for 3 hours to hydrophobize the surface of the silica base particles. Except for this, silica particles 37 were obtained in the same manner as silica particles 1.

[0232] [Silica particles 34] Silica particles 38 were obtained in the same manner as silica particles 1, except that 30 g of dry process silica AEROSIL130 (manufactured by Nippon Aerosil) was dispersed in 300 g of methanol to obtain a silica base particle suspension.

[0233] [Silica particles S1-S9] Silica particles S1 to S9 were obtained in the same manner as silica particles 1, except that the types and amounts of the trifunctional silane coupling agent and nitrogen-containing compound added were as shown in Table 1.

[0234] [Silica particles C1, C2, C3] Silica particles C1, C2, and C3 were obtained in the same manner as silica particles 1, except that the types and amounts of the trifunctional silane coupling agent and the nitrogen-containing compound added were changed to those shown in Table 1.

[0235] <Examples 1 to 35, Reference Examples 1 to 9, Comparative Examples 1 to 3> To 100 parts of the toner particles (1), 1.2 parts of an external additive shown in Table 2 was added, and the mixture was mixed in a Henschel mixer at a stirring peripheral speed of 30 m / sec for 15 minutes to obtain the toner of each example.

[0236] Then, each of the obtained toners and carrier was placed in a V blender in a ratio of toner:carrier=8:92 (mass ratio), and stirred for 20 minutes to obtain a developer.

[0237] The carrier used was prepared as follows. Ferrite particles (volume average particle size: 36 μm) 100 parts Toluene 14 parts Styrene-methyl methacrylate copolymer 2 parts (Component ratio: 90 / 10, Mw=80000) Carbon black (R330: manufactured by Cabot Corporation) 0.2 parts First, the above components except for the ferrite particles were stirred with a stirrer for 10 minutes to prepare a dispersed coating liquid. Next, this coating liquid and the ferrite particles were placed in a vacuum degassing kneader and stirred at 60°C for 30 minutes. After that, the pressure was reduced while heating to degas the particles, and the particles were dried to obtain a carrier.

[0238] [Evaluation of silica particles] (Various properties of silica particles) The following properties of the obtained silica particles were measured according to the methods described above. Net strength of molybdenum element (referred to as "Mo Net" in the table) The ratio of the mass % of molybdenum element to the mass % of silicon element (indicated as "Mo / Si" in the table) Number average particle size (referred to as "particle size" in the table) Number particle size distribution index (referred to as "particle size distribution" in the table) Average circularity (referred to as "circularity" in the table) Pore ​​volume A of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method before calcination at 350°C (referred to as "Pore volume A before calcination at 350°C" in the table). Pore ​​volume B of pores with diameters of 1 nm to 50 nm obtained from the pore distribution curve of the nitrogen gas adsorption method after firing at 350°C (referred to as "Pore volume B after firing at 350°C" in the table) Volume resistivity Ra before firing at 350°C (referred to as "volume resistivity Ra before firing" in the table) Volume resistivity Rb after firing at 350°C (referred to as "volume resistivity Rb after firing" in the table) - Amount of OH groups measured by the Sears method (referred to as "Amount of OH groups" in the table) Chemical shift when the integral value of all signals in the Si-CP / MAS NMR spectrum is set to 100% -50 ppm to -75 ppm The ratio of the integral value C of the signal observed in the range (in the table, this is referred to as "(Si-CP / MAS area ratio C")) Chemical shifts in Si-CP / MAS NMR spectra -50 ppm to -75 ppm The integral value C of the signal observed in the range and the chemical shift -90 ppm to -120 ppmThe ratio C / D of the integral value D of the signal observed in the range (in the table, it is written as "(Si-CP / MAS ratio C / D)") Hydrophobicity

[0239] (Charge Dependence of Charge Amount at Low Humidity and Charge Amount at High Humidity / Capacitance) The low humidity charge amount and high humidity charge amount of the silica particles of each example were measured and the environmental dependency of the capacitance was evaluated as follows: Among the criteria, A to B are acceptable. The evaluation method is as follows. 5g of the prepared silica particles added at 2% by mass to the surface of MA1010 manufactured by Nippon Shokubai was mixed with 50g of KNI106GSM manufactured by JFE Chemical Corp. The mixed sample was stirred for 5 minutes using a turbula shaker in a chamber at 10°C and 10% RH, and the charge was measured using a Toshiba TB200. The result was taken as FC, and the result was stirred for 5 minutes using a turbula shaker in a chamber at 30°C and 90% RH, and the charge was measured using a Toshiba TB200. The ratio of these values, FA / FC, was used for evaluation. A(◎): FA / FC is 0.8 or more and less than 1.1 B(〇): FA / FC is 0.65 or more and less than 0.8 C(△): FA / FC is 0.5 or more and less than 0.65 D(×): FA / FC is less than 0.5

[0240] (Charge distribution under normal temperature and humidity conditions) The charge distribution of the silica particles of each example was evaluated in a normal temperature and normal humidity environment (20°C, 50% RH environment) as follows. Five grams of the prepared silica particles were added to the surface of Nippon Shokubai MA1010 at 2% by mass, and mixed with 50 grams of JFE Chemical KNI106GSM. The mixed sample was stirred for 5 minutes using a Turbula shaker in a chamber at 20°C and 50% RH, and evaluated using CSG (charge spectrograph) image analysis. The charge distribution is defined as the difference between the 20% charge Q(20) and the 80% charge Q(80) of the cumulative charge distribution divided by the 50% charge Q(50), i.e., [Q(80) - Q(20)] / Q(50). The evaluation criteria are as follows: A(◎): [Q(80)-Q(20)] / Q(50) value is less than 0.7 B(○): [Q(80)-Q(20)] / Q(50) value is less than 0.8 and 0.7 or more C(△): [Q(80)-Q(20)] / Q(50) value is less than 1.0 and 0.8 or more D(×): [Q(80)-Q(20)] / Q(50) value is 1.0 or more

[0241] (Ability to maintain narrow charge distribution in high temperature and humidity environments) The silica particles of each example were evaluated for their ability to maintain a narrow charge distribution in a high-temperature, high-humidity environment (30°C, 90% RH environment) as follows. Five grams of the prepared silica particles were added to the surface of Nippon Shokubai MA1010 at 2% by mass, and mixed with 50 grams of JFE Chemical KNI106GSM. The mixed sample was stirred for 100 minutes using a Turbula shaker in a 30°C, 90% RH chamber and evaluated using CSG (charge spectrograph) image analysis. The charge distribution is defined as the difference between the 20% charge Q(20) and the 80% charge Q(80) of the cumulative charge distribution divided by the 50% charge Q(50), i.e., [Q(80) - Q(20)] / Q(50). The evaluation criteria are as follows: A(◎): [Q(80)-Q(20)] / Q(50) value is less than 0.75 B(○): [Q(80)-Q(20)] / Q(50) value is less than 0.85 and 0.75 or more C(△): [Q(80)-Q(20)] / Q(50) value is less than 1.0 and 0.85 or more D(×): [Q(80)-Q(20)] / Q(50) value is 1.0 or more

[0242] (Maintaining a narrow charge distribution in low temperature and low humidity environments) The ability of the silica particles of each example to maintain a narrow charge distribution in a low-temperature, low-humidity environment (10°C, 10% RH environment) was evaluated in the same manner as the ability to maintain a narrow charge distribution in a high-temperature, high-humidity environment (30°C, 90% RH environment), except that the evaluation was performed in a low-temperature, low-humidity environment (10°C, 10% RH environment).

[0243] <Toner Evaluation> (Cloud (toner scattering) in a high temperature and humidity environment) Each toner was filled into a toner cartridge, and the toner cartridge was installed in an image forming apparatus (a modified version of ApeosPort-IV C5575 manufactured by Fujifilm Business Innovation Co., Ltd.). The developing device of this image forming apparatus was filled with each developer. It was left in an environment of 30°C temperature and 90% relative humidity for 24 hours. After leaving it, 100,000 images with an image density of 1% were formed on A4 size paper at a speed of one sheet every 120 seconds. After the image formation, the upper cover of the developing machine was transferred onto an OHP sheet using mending tape, and the density of the transferred mending tape was measured at eight points at equal intervals using an X-Rite 938 image densitometer (manufactured by X-Rite). The difference from the density measured using the mending tape alone was quantified as the amount of toner contamination inside the machine. The amount of toner contamination inside the machine was classified as follows based on the maximum density. Grades up to G3 are suitable for practical use. The evaluation criteria are as follows: -Evaluation criteria- G1(◎): 0≦Δconcentration≦0.2 G2(〇): 0.2<Δconcentration≦0.4 G3(△): 0.4<Δconcentration≦0.6 G4(×): 0.6<Δconcentration≦0.8 G5(×): 0.8<Δconcentration

[0244] (Fine line reproducibility under high temperature and humidity conditions) After evaluating cloud (toner scattering) under the above-mentioned high-temperature, high-humidity environment, a 1-on-1-off image (an image in which 1-dot lines are arranged in parallel at 1-dot intervals) at a resolution of 2,400 dpi was printed as a 5 cm x 5 cm chart perpendicular to the development direction at the top left, center, and bottom right of an A4 sheet of paper. The line spacing of each chart printed on the printed sample was observed using a 100x magnification magnifying glass with a scale to see if there were any areas that had narrowed due to toner scattering or any areas that had widened due to thinning of thin lines. The evaluation criteria were as follows: -Evaluation criteria- G1 (◎): Almost no decrease in distance due to toner scattering or increase in distance due to thinning of the line is observed. G2(〇): There is a slight decrease or increase in distance, but a thin line can be seen. G3(△): There is at least one chart where the line spacing is indistinguishable or where thin lines are missing. G4(×): The spacing between thin lines cannot be determined or there are at least two charts where thin lines are missing. G5(×): The spacing between thin lines cannot be determined or there are three or more charts with missing thin lines.

[0245] (Fogging under normal temperature and humidity conditions) After evaluating the fine line reproducibility under the above-mentioned high temperature and high humidity environment, the sample was left in an environment of 20°C temperature and 50% relative humidity for 24 hours. After leaving it, 10 images with an image density of 40% were formed consecutively on A4 size paper. The 10 images were observed with the naked eye and with a 5x magnification loupe, and the state of fogging was classified as follows. The evaluation criteria are as follows. -Evaluation criteria- G1(◎): Duplicates on all 10 cards are not permitted. G2(Good): A slight amount of fogging can be seen on one sheet with a magnifying glass, but it is not enough to cause any problems. G3 (△): Slight fogging can be seen on several sheets with a magnifying glass, but it is minor and does not affect practical use. G4(×): Fog is visible to the naked eye on multiple sheets, making it unsuitable for practical use. G5(×): Fog was visible to the naked eye on all 10 sheets, making them unsuitable for practical use.

[0246] [Fog retention under high temperature and humidity conditions] The toner of each example was filled into a toner cartridge and installed in an image forming apparatus (a modified ApeosPort-IV C5575 manufactured by Fujifilm Business Innovation Co., Ltd.). The developer of each example was filled into the developing device of this image forming apparatus. The test piece was left in an environment with a temperature of 30°C and a relative humidity of 90% for 24 hours. After leaving the test piece, 500,000 images with an image density of 1% were formed on A4 size paper at a speed of one sheet every 120 seconds. Ten images with an image density of 40% were formed consecutively on A4 size paper. The ten images were observed with the naked eye and with a 5x magnification loupe, and the state of fogging was classified as follows. The evaluation criteria are as follows: -Evaluation criteria- G1(◎): Duplicates on all 10 cards are not permitted. G2(Good): A slight amount of fogging can be seen on one sheet with a magnifying glass, but it is not enough to cause any problems. G3 (△): Slight fogging can be seen on several sheets with a magnifying glass, but it is minor and does not affect practical use. G4(×): Fog is visible to the naked eye on multiple sheets, making it unsuitable for practical use. G5(×): Fog was visible to the naked eye on all 10 sheets, making them unsuitable for practical use.

[0247] [Image density maintenance under high temperature and humidity conditions] After evaluating the fog retention under the above-mentioned high temperature and high humidity environment, a halftone image with an area ratio of 90% and an image density of 30% was printed on an A4 size paper under an environment of a temperature of 30°C and a relative humidity of 90%, and the halftone image was visually inspected and classified as follows: A (◎): The entire image has sufficient density and there are no uneven density areas. B (◯): There are some areas of low density, but the density unevenness is slight and does not affect practical use. C(x): The density is low across the entire image, or there is unacceptable density unevenness.

[0248] [Fog retention under low temperature and humidity conditions] After the image density maintenance evaluation under the high temperature and high humidity environment, the image forming apparatus was left in an environment of 10°C temperature and 10% relative humidity for 24 hours. After leaving it, 100,000 images with an image density of 1% were formed on A4 size paper at a speed of one sheet every 120 seconds, and then 10 images were observed with the naked eye and with a 5x magnification loupe, and the state of fogging was classified as follows: G1(◎): No overlapping is permitted on any of the 10 cards. G2 (Good): A slight amount of fogging can be seen on one sheet with a magnifying glass, but it is not enough to cause any problems. G3 (△): Slight fogging was observed on several sheets with a magnifying glass, but it was minor and did not affect practical use. G4 (×): Fog was visible to the naked eye on multiple sheets, and it is not suitable for practical use. G5 (×): Fog was visible to the naked eye on all 10 sheets, and they were unsuitable for practical use.

[0249] [Image density maintenance under low temperature and humidity conditions] After the evaluation of fog retention under the low temperature and low humidity environment, the image forming apparatus was placed in an environment of 10°C temperature and 10% relative humidity to output a halftone image with an area ratio of 90% and an image density of 30% on A4 size paper. The halftone image was visually inspected and classified as follows: A (◎): The entire image has sufficient density and there are no uneven density areas. B (◯): There are some areas of low density, but the density unevenness is slight and does not affect practical use. C(x): The density is low across the entire image, or there is unacceptable density unevenness.

[0250] [Maintainability Post-Cloud] After the image density maintenance test under the above-mentioned low temperature and low humidity environment, the upper cover of the developing unit of the image forming apparatus was transferred onto an OHP sheet using mending tape, and the density of the transferred mending tape was measured at eight points at equal intervals using an X-Rite 938 image densitometer (manufactured by X-Rite). The difference from the density measured with the mending tape alone was quantified as the amount of toner contamination inside the machine. The amount of toner contamination inside the machine was classified as follows according to the maximum density. Grades up to G3 are suitable for practical use. G1(◎):0≦Δconcentration≦0.2 G2(〇):0.2<Δconcentration≦0.4 G3(△):0.4<Δconcentration≦0.6 G4(×):0.6<Δconcentration≦0.8 G5(×):0.8<Δconcentration

[0251] The evaluation results are shown in Table 1. Details of the abbreviations in Table 1 are as follows: MTMS: Methyltrimethoxysilane DTMS: n-dodecyltrimethoxysilane

[0252] TP415: [N(CH 3 ) 2 (C 14 H 29 ) 2 ] 4 Mo 8 O 26 ("TP- 415” manufactured by Hodogaya Chemical Industry Co., Ltd., N,N-Dimethyl-N-tetradecyl-1-tetradecanaminium, hexa-μ-oxotetra-μ3-oxodi -μ5-oxotetradecaoxooctamolybdate(4-) (4:1)

[0253] [Table 1-1]

[0254] [Table 1-2]

[0255] [Table 1-3]

[0256] [Table 2]

[0257] From the above results, it can be seen that the present example is superior in suppressing fogging under a high-temperature and high-humidity environment compared to the comparative example, and is also superior in maintaining the fogging suppression under a high-temperature and high-humidity environment. Furthermore, compared to the comparative example, this example has good stability of toner charging property even when subjected to environmental influences such as temperature and humidity, and even when used for a long period of time, and therefore is also excellent in terms of toner contamination inside the machine, maintenance of fine line reproducibility, and image density maintenance.

[0258] 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K Charging roll (an example of charging means) 3. Exposure device (an example of an electrostatic image forming means) 3Y, 3M, 3C, 3K laser beam 4Y, 4M, 4C, 4K developing device (an example of developing means) 5Y, 5M, 5C, 5K Primary transfer roll (an example of a primary transfer means) 6Y, 6M, 6C, 6K: Photoconductor cleaning device (an example of a cleaning means) 6Y-1, 6M-1, 6C-1, 6K-1 Cleaning Blade 8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K image forming units 20 Intermediate transfer belt (an example of an intermediate transfer body) 22 Drive Roll 26 Secondary transfer roll (an example of a secondary transfer means) 30 Intermediate transfer body cleaning device 107 Photosensitive body (an example of an image carrier) 108 Charging roll (an example of charging means) 109 Exposure device (an example of electrostatic image forming means) 111 Developing device (an example of developing means) 112 Transfer device (an example of transfer means) 113 Photosensitive drum cleaning device (an example of cleaning means) 113-1 Cleaning Blade 115 Fixing device (an example of fixing means) 116 Mounting Rail 118 Exposure opening 117 Cabinet 200 Process Cartridge 300 Recording paper (an example of a recording medium) P Recording paper (an example of a recording medium)

Claims

1. toner particles; silica particles that are externally added to the toner particles, the silica particles containing a nitrogen-containing compound that includes molybdenum, and the ratio of the net intensity of molybdenum to the net intensity of silicon (Mo / Si) measured by fluorescent X-ray analysis is 0.035 or more and 0.35 or less; and The silica particles are Silica base particles; a structure that covers at least a portion of the surface of the silica base particle, and is composed of at least one reaction product selected from the group consisting of a monofunctional silane coupling agent, a bifunctional silane coupling agent, and a trifunctional silane coupling agent, and in which a nitrogen-element-containing compound is adsorbed in at least a portion of the pores of the reaction product; A toner for developing electrostatic images comprising:

2. 2. The toner for developing electrostatic images according to claim 1, wherein the nitrogen-containing compound in the silica particles is at least one selected from the group consisting of a quaternary ammonium salt containing molybdenum and a mixture of a quaternary ammonium salt and a metal oxide containing molybdenum.

3. 3. The toner for developing electrostatic images according to claim 1, wherein the number average particle diameter of the silica particles is 10 nm or more and 200 nm or less.

4. 4. The toner for developing electrostatic images according to claim 1, wherein the silica particles have a hydrophobicity of 10% or more and 60% or less.

5. In the silica particles, when the pore volumes of pores having a diameter of 1 nm or more and 50 nm or less obtained from a pore distribution curve of a nitrogen gas adsorption method before and after baking at 350° C. are defined as A and B, respectively, B / A is 1.2 or more and 5 or less, and B is 0.2 cm ３ / g or more 3cm ３ 5. The toner for developing electrostatic images according to claim 1, wherein the toner has a molecular weight of 1 / g or less.

6. The silica particles were analyzed by polarization / magic angle spinning (CP / MAS) ２９ 6. The toner for developing electrostatic images according to claim 1, wherein a ratio C / D of an integral value C of signals observed in a chemical shift range of −50 ppm to −75 ppm in a Si solid-state nuclear magnetic resonance (NMR) spectrum to an integral value D of signals observed in a chemical shift range of −90 ppm to −120 ppm is 0.10 or more and 0.75 or less.

7. the amount X of the nitrogen-containing compound extracted from the silica particles by the ammonia / methanol mixed solution is 0.1 mass% or more; The amount X of the nitrogen-containing compound extracted from the silica particles and the amount Y of the nitrogen-containing compound extracted from the silica particles by water satisfy the formula: Y / X<0.

3. The toner for developing electrostatic images according to any one of claims 1 to 6.

8. 8. The toner for developing electrostatic images according to claim 1, wherein the silica particles have an average circularity of 0.60 or more and 0.96 or less.

9. 9. The toner for developing electrostatic images according to claim 1, wherein the silica particles have a number particle size distribution index of 1.1 or more and 2.0 or less.

10. An electrostatic image developing method comprising the toner for developing electrostatic images according to any one of claims 1 to 9. Imaging agent.

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

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

13. an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing unit containing the electrostatic image developer according to claim 10 and developing the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer; a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a cleaning means having a cleaning blade for cleaning the surface of the image carrier; a fixing means for fixing the toner image transferred onto the surface of the recording medium; An image forming apparatus comprising:

14. a charging step of charging the surface of the image carrier; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image carrier; a developing step of developing the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer according to claim 10; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a cleaning step of cleaning the surface of the image carrier with a cleaning blade; a fixing step of fixing the toner image transferred onto the surface of the recording medium; An image forming method comprising the steps of:

Images