Non-magnetic one-component toner and image forming apparatus

Abstract

To provide a non-magnetic one-component toner with which an image with high image density and less thin layer streaks and fogging can be formed even when printing is performed on a large number of sheets.SOLUTION: An external additive contained in a toner particle included in a non-magnetic one-component toner includes alumina particles and fluorine-containing particles. The alumina particles each comprise a substrate and a conductive layer and has a powder specific resistance of 50 Ω cm or less. In predetermined printing, the content Al0 of the alumina particles in the toner particle before the predetermined printing and the content Al1000D of the alumina particles in the toner particle in a developing unit after the predetermined printing satisfy the formula (1) 1.0≤Al1000D / Al0≤1.5. The content F0 of the fluorine-containing particles in the toner particle before the predetermined printing and the content F1000D of the fluorine-containing particles in the toner particle in the developing unit after the predetermined printing satisfy the formula (2) 1.0≤F1000D / F0≤1.5.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-magnetic single-component toner and an image forming apparatus. [Background technology]

[0002] Dry development methods include two-component development methods and one-component development methods. Two-component development methods use a two-component developer containing toner and carrier. One-component development methods use a one-component developer containing toner but not carrier. Because no carrier is used, one-component development methods have the advantage of not causing carrier deterioration or fluctuations in the mixture ratio of toner and carrier. One-component development methods also have the advantage of making image forming apparatuses easier to maintain and more compact. For this reason, various one-component developers for use in one-component development methods are being studied. An external additive is added to the toner base particles of the positively charged toner for non-magnetic one-component development described in Patent Document 1. This external additive has an average particle diameter of 200 nm to 1000 nm and an electrical resistivity of 1×10 15 It contains negatively charged resin particles of Ω·cm or less, silica with an average particle size of 50nm to 300nm, silica with an average particle size of 5nm or more but less than 50nm, and polytetrafluoroethylene particles with an average particle size of 100nm to 1000nm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-180910 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the amount of external additives contained in toner particles in an image forming apparatus gradually changes as a result of printing a large number of sheets. The positively charged toner for non-magnetic one-component development described in Patent Document 1 does not take into consideration this change in the amount of external additives, and is therefore insufficient in terms of stably forming high-quality images when a large number of sheets are printed. Specifically, the toner described in Patent Document 1 is insufficient in terms of forming images with high image density and minimal thin layer streaks and fog when a large number of sheets are printed.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a non-magnetic single-component toner and an image forming apparatus that can form images with high image density and little thin layer streaks and fog, even when printing a large number of sheets. [Means for solving the problem]

[0006] The non-magnetic single-component toner according to the present invention includes toner particles. The toner particles include toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes alumina particles and fluorine-containing particles. The alumina particles include a substrate containing alumina and a conductive layer covering the substrate. The powder resistivity of the alumina particles is 50 Ω·cm or less. In a predetermined printing process in which a standard test page image specified in ISO 19752 is printed on 1,000 sheets of recording medium, the content of the alumina particles in the toner particles before the predetermined printing, Al0, and the content of the alumina particles in the toner particles in a developing unit after the predetermined printing are calculated. 1000D The content rate F0 of the fluorine-containing particles in the toner particles before the predetermined printing and the content rate F of the fluorine-containing particles in the toner particles in the developing unit after the predetermined printing satisfy the following formula (1): 1000D and satisfy the following formula (2). 1.0≦Al 1000D / Al0≦1.5 (1) 1.0≦F 1000D / F0≦1.5 (2)

[0007] The image forming apparatus according to the present invention comprises an image carrier and a developing unit that supplies non-magnetic one-component toner to an electrostatic latent image formed on the surface of the image carrier. The non-magnetic one-component toner includes toner particles. The toner particles include toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes alumina particles and fluorine-containing particles. The alumina particles include a substrate containing alumina and a conductive layer that coats the substrate. The powder resistivity of the alumina particles is 50 Ω·cm or less. In a predetermined printing operation in which a standard test page image defined in ISO 19752 is printed on 1,000 sheets of recording medium, the content of the alumina particles in the toner particles before the predetermined printing, Al0, and the content of the alumina particles in the toner particles in the developing unit after the predetermined printing are calculated. 1000D The content rate F0 of the fluorine-containing particles in the toner particles before the predetermined printing and the content rate F of the fluorine-containing particles in the toner particles in the developing unit after the predetermined printing satisfy the following formula (1): 1000D and satisfy the following formula (2). 1.0≦Al 1000D / Al0≦1.5 (1) 1.0≦F 1000D / F0≦1.5 (2) [Effects of the Invention]

[0008] The non-magnetic single-component toner and image forming apparatus according to the present invention can form images with high image density and little thin layer streaks and fog, even when printing a large number of sheets. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a diagram showing an image forming apparatus according to a second embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the image carrier and the developing unit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described. First, the terms used in this specification will be described. A non-magnetic single-component toner is an aggregate (for example, powder) of toner particles. An external additive is an aggregate (for example, powder) of external additive particles. Unless otherwise specified, evaluation results (for example, values ​​indicating shape and physical properties) of powders (for example, powders of toner particles and powders of external additive particles) are the number averages of values ​​measured for each of a considerable number of particles selected from the powder. Unless otherwise specified, the softening point (Tm) is a value measured using a high-speed flow tester ("CFT-500D" manufactured by Shimadzu Corporation). The volume median diameter (D 50 ) is the median diameter measured using a laser diffraction / scattering particle size distribution analyzer (e.g., Beckman Coulter's "Multisizer 3"). Unless otherwise specified, the number-average primary particle diameter of a powder is the number average of the circle-equivalent diameters of primary particles (Heywood diameter: the diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a scanning electron microscope. Unless otherwise specified, the "major component" of a material refers to the component that is contained in the largest amount in the material by mass. The strength of hydrophobicity can be expressed, for example, by the contact angle of a water droplet (ease of wetting with water). The larger the contact angle of the water droplet, the stronger the hydrophobicity. Each component described in this specification may be used alone or in combination of two or more. The terms used in this specification have been explained above.

[0011] [First embodiment: non-magnetic single-component toner] The first embodiment of the present invention relates to a non-magnetic one-component toner. The non-magnetic one-component toner of the present invention includes toner particles. The toner particles include toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes alumina particles and fluorine-containing particles. The alumina particles include a substrate containing alumina and a conductive layer coating the substrate. The powder resistivity of the alumina particles is 50 Ω·cm or less. In a predetermined printing process in which a standard test page image specified in ISO 19752 is printed on 1,000 sheets of recording medium, the alumina particle content Al0 in the toner particles before the predetermined printing and the alumina particle content Al in the toner particles in the developing unit after the predetermined printing are calculated.1000D The formula (1) "1.0≦Al 1000D / Al0≦1.5". The content of fluorine-containing particles in the toner particles before a predetermined printing F0 and the content of fluorine-containing particles in the toner particles in the developing section after a predetermined printing F 1000D And, the formula (2) "1.0 ≦ F 1000D / F0≦1.5”.

[0012] Hereinafter, "non-magnetic one-component toner" may be referred to as "toner." "The content of alumina particles in toner particles before a predetermined printing Al0" may be referred to as "initial alumina content Al0." "The content of alumina particles in toner particles in the developing section after a predetermined printing Al 1000D " and "Developing section durability alumina content Al 1000D "The content F0 of fluorine-containing particles in toner particles before a predetermined printing" is sometimes referred to as "initial fluorine content F0." "The content F0 of fluorine-containing particles in toner particles in the developing section after a predetermined printing" is sometimes referred to as "initial fluorine content F0." 1000D " to "Development section durability fluorine content F 1000D " in formula (1) 1000D / Al0" is the "ratio (development section durability alumina content Al 1000D The formula (2) "F / initial alumina content Al0" is sometimes written as "F 1000D / F0" and "Ratio (development section durability fluorine content F 1000D / initial fluorine content F0).

[0013] By virtue of the above-described configuration, the toner of the present invention can form images with high image density and little thin layer streaks or fog, even when a large number of sheets are printed. The reason for this is presumed to be as follows. This will be explained below with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing an image forming apparatus 1 according to a second embodiment, which will be described later. FIG. 2 is an enlarged view of the image carrier 23 and the developing unit 22 shown in FIG. 1.

[0014] To facilitate understanding, an overview of the developing unit 22, which employs a non-magnetic single-component development method, will first be described. As shown in FIG. 1, the image forming apparatus 1 includes the developing unit 22 and an image carrier 23. As shown in FIG. 2, the developing unit 22 includes a storage frame 210, a supply roller 220, a developing roller 230, and a regulating blade 240. The storage frame 210 stores toner T therein. The supply roller 220 supplies the toner T stored in the storage frame 210 to the developing roller 230. The developing roller 230 holds the toner T supplied from the supply roller 220 on its surface (circumferential surface) 230a in the form of a toner layer (a so-called thin toner layer). At a nip N2 between the regulating blade 240 and the developing roller 230, the regulating blade 240 regulates the thickness of the toner layer held on the surface 230a of the developing roller 230. Regulating the thickness of the toner layer means adjusting the thickness of the toner layer to a predetermined uniform value. After the thickness is regulated, the toner T contained in the toner layer is supplied from the surface 230a of the developing roller 230 to the electrostatic latent image formed on the surface (circumferential surface) 23a of the image carrier 23. The electrostatic latent image is then developed into a toner image. The above has described an overview of the developing unit 22 that employs a non-magnetic one-component development method.

[0015] Here, at the nip N2, the toner T held by the developing roller 230 may adhere and stick to the regulating blade 240. When the thickness of the toner layer is regulated by the regulating blade 240 to which the toner T has stuck, the thickness of the toner layer becomes uneven. As a result, streaks (thin layer streaks) appear in the formed image.

[0016] Therefore, in the present invention, the external additives contained in the toner particles include fluorine-containing particles. Some of the fluorine-containing particles detached from the toner base particles in the developing unit 22 adhere to the regulating blade 240. The adhered fluorine-containing particles make it difficult for the toner T to adhere to the regulating blade 240. As a result, it is possible to suppress the occurrence of thin layer streaks in the formed image.

[0017] On the other hand, if an excessive amount of fluorine-containing particles adheres to the regulating blade 240, the regulating blade 240 will not be able to adequately regulate the thickness of the toner layer. Therefore, in the present invention, the external additive contained in the toner particles contains alumina particles. The alumina particles detached from the toner base particles in the developing unit 22 scrape off the fluorine-containing particles adhered to the regulating blade 240. This keeps the amount of fluorine-containing particles adhered to the regulating blade 240 appropriate.

[0018] Here, as printing proceeds using the image forming apparatus 1 filled with toner T, the content ratios of fluorine-containing particles and alumina particles change in the developing unit 22. For example, when fluorine-containing particles detached from the toner base particles remain in the developing unit 22, the content ratio of fluorine-containing particles in the toner particles in the developing unit 22 increases. On the other hand, when fluorine-containing particles detached from the toner base particles adhere to the regulating blade 240, the content ratio of fluorine-containing particles in the toner particles in the developing unit 22 decreases. Furthermore, when the fluorine-containing particles detached from the toner base particles are developed onto the image carrier 23 from the developing roller 230 together with the toner T, the content ratio of fluorine-containing particles in the toner particles in the developing unit 22 decreases. Furthermore, when alumina particles detached from the toner base particles remain in the developing unit 22, the content ratio of alumina particles in the toner particles increases. Meanwhile, the alumina particles detached from the toner base particles are developed, together with the toner T, from the developing roller 230 onto the image carrier 23, thereby reducing the alumina particle content in the toner particles in the developing unit 22. As described above, as printing continues, the content of fluorine-containing particles and alumina particles in the developing unit 22 changes. For this reason, controlling the amount of change in the content of fluorine-containing particles and alumina particles in the developing unit 22 during printing is effective for stable toner layer formation and stable image formation during printing.

[0019] Therefore, the toner T of the present invention satisfies the formula (2) "1.0≦F 1000D / F0≦1.5" is satisfied. 1000DIf the initial fluorine content F0) is 1.0 or more, a sufficient amount of fluorine-containing particles remains in the developing unit 22 even after a predetermined amount of printing. Since a sufficient amount of fluorine-containing particles adheres to the regulating blade 240, the toner T is less likely to adhere to the regulating blade 240. As a result, the occurrence of thin layer streaks in the formed image can be suppressed.

[0020] On the other hand, if an excessive amount of fluorine-containing particles adheres to the regulating blade 240, the regulating blade 240 cannot sufficiently regulate the thickness of the toner layer, and the toner layer becomes thick. If the toner layer is thick, only the surface of the toner layer is charged, and it is difficult to charge the entire toner layer uniformly. As a result, fogging occurs in the formed image. Therefore, in the present invention, the ratio of the toner T (development section durability fluorine content F 1000D / initial fluorine content F0) is 1.5 or less. 1000D If the initial fluorine content F0) is 1.5 or less, the amount of fluorine-containing particles in the developing unit 22 will not become excessive after a predetermined amount of printing. Since an excessive amount of fluorine-containing particles will not adhere to the regulating blade 240, the occurrence of fogging in the formed image can be suppressed.

[0021] Furthermore, the toner T of the present invention satisfies the formula (1) "1.0≦Al 1000D / Al0≦1.5" is satisfied. The ratio of toner T (development section durability alumina content Al 1000D If the initial alumina content Al0) is 1.5 or less, the amount of alumina particles in the developing unit 22 will not be excessive after a predetermined amount of printing. Therefore, the fluorine-containing particles adhering to the regulating blade 240 will not be excessively scraped off by the alumina particles. Since a sufficient amount of fluorine-containing particles adheres to the regulating blade 240, the toner T will not easily adhere to the regulating blade 240. As a result, the occurrence of thin layer streaks in the formed image can be suppressed.

[0022] On the other hand, the ratio (development section durability alumina content Al 1000DIf the ratio of the toner T to the initial alumina content Al0 is less than 1.0, the amount of alumina particles in the developing section will be insufficient after a predetermined number of prints. With an insufficient amount of alumina particles, the fluorine-containing particles adhering to the regulating blade 240 cannot be sufficiently scraped off, and an excessive amount of the fluorine-containing particles will adhere to the regulating blade 240. As a result, the regulating blade 240 cannot adequately regulate the thickness of the toner layer, the toner layer becomes thick, and fog will occur in the formed image. Therefore, in the present invention, the ratio of the toner T to the initial alumina content Al0 (developing section durability alumina content Al 1000D The initial alumina content Al0) is set to 1.0 or more, which can prevent fogging from occurring in the formed image.

[0023] Furthermore, in the present invention, the alumina particles comprise a substrate containing alumina and a conductive layer coating the substrate. The powder resistivity of the alumina particles is 50 Ω·cm or less. The conductive layer on the alumina particles can prevent excessive charging of the toner particles. Furthermore, the alumina particles have a relatively low powder resistivity of 50 Ω·cm or less, which allows the toner particles to easily release their electric charge and prevent excessive charging of the toner particles. As a result, the transport of the toner T is stabilized in the nip N2 between the regulating blade 240 and the developing roller 230, allowing for the formation of images with high image density and little fog.

[0024] The reason why the toner of the present invention can form images with high image density and little thin layer streaks and fog even when a large number of sheets are printed has been explained above with reference to FIGS.

[0025] The toner of the present invention is particularly suitable for use as a cartridge-type toner (non-magnetic single-component toner) that does not require replenishment toner. In cartridge-type toner that does not require replenishment toner, small toner particles with high chargeability are preferentially developed over large toner particles with low chargeability. Therefore, the particle size distribution of the toner at the initial stage (e.g., before a predetermined number of prints) differs from the particle size distribution of the toner after printing (e.g., after a predetermined number of prints). Different particle sizes of toner particles also result in different amounts of external additives adhering to the toner base particles. The smaller the particle size of the toner particles, the larger the specific surface area per unit weight of the toner particles, and the greater the amount of external additives that can adhere to the toner base particles. On the other hand, as printing progresses, the particle size of the toner particles increases, the specific surface area per unit weight of the toner particles decreases, and the amount of external additives that can adhere to the toner base particles decreases. When the amount of external additives adhering to the toner base particles decreases, the toner's adhesive force to the regulating blade increases, making the toner more likely to adhere to the regulating blade. Therefore, cartridge-type toners that do not require replenishment are particularly prone to thin layer streaks in formed images. However, as already mentioned, the toner of the present invention can suppress the occurrence of thin layer streaks in formed images. Furthermore, by satisfying formulas (1) and (2), the toner of the present invention can control the amount of external additives attached to the toner base particles initially (e.g., before a predetermined printing) and after printing (e.g., after a predetermined printing). Therefore, the toner of the present invention can be particularly suitably used as a cartridge-type toner that does not require replenishment toner.

[0026] Furthermore, the toner of the present invention is particularly suitable for use as a toner containing a release agent. The aforementioned thin streaks tend to occur particularly when an image is formed using a toner containing a release agent. To reduce the size and cost of the fixing unit of an image forming apparatus, a fixing unit that does not include a fixing oil application mechanism or that applies a reduced amount of fixing oil may be used. To suppress offset to such a fixing unit, a release agent may be incorporated into the toner. However, if a large amount of release agent is incorporated into the toner, the amount of release agent on the toner surface increases, making the toner more likely to adhere to the regulating blade due to mechanical and thermal effects. For these reasons, thin streaks tend to occur particularly when an image is formed using a toner containing a release agent. However, as already mentioned, the toner of the present invention can suppress the occurrence of thin streaks in the formed image. Therefore, the toner of the present invention can be particularly suitable for use as a toner containing a release agent.

[0027] In order to balance the amount of fluorine-containing particles adhering to the regulating blade and the amount of fluorine-containing particles scraped off by the alumina particles, the ratio Al0 / F0 of the initial alumina content Al0 to the initial fluorine content F0 is preferably 0.1 or more and 5.0 or less, and more preferably 0.6 or more and 2.0 or less.

[0028] In order to balance the amount of fluorine-containing particles adhering to the regulating blade and the amount of fluorine-containing particles scraped off by the alumina particles, the development section durability fluorine content F 1000D Durability of the developing section against the alumina content Al 1000D Ratio of Al 1000D / F 1000D is preferably 0.5 or more and 2.3 or less.

[0029] <Measurement method for specified printing and each content> Next, the predetermined printing and the method for measuring each content shown in formulas (1) and (2) will be described. In this specification, "predetermined printing" is defined as printing a standard test page image defined in ISO19752 on 1000 sheets of recording medium. The standard test page image defined in ISO19752 is a monochrome image used to test the number of pages that can be printed by a monochrome printer. The predetermined printing is carried out, for example, using an image forming apparatus to be filled with the toner of the present invention. The initial alumina content Al0, the initial fluorine content F0, and the development section durability alumina content Al 1000D , and the development zone durability fluorine content F 1000D is measured in a predetermined print using the toner (in other words, by performing a predetermined print test on the toner).

[0030] The initial alumina content Al0 and the initial fluorine content F0 are measured using toner before a predetermined printing (for example, toner T before being filled into the developing unit 22 shown in FIG. 2). 1000D , and the development zone durability fluorine content F 1000D In the measurement, the toner in the developing unit after a predetermined printing is the toner (for example, the toner T present inside the storage frame 210 provided in the developing unit 22 shown in FIG. 2, more specifically, the toner T present inside the storage frame 210 provided in the developing unit 22 shown in FIG. 2 and below the developing roller 230) is the measurement target.

[0031] Fluorescent X-ray analysis is performed on the above-mentioned measurement object (more specifically, each of the toner before the specified printing and the toner in the development unit after the specified printing) to obtain a fluorescent X-ray spectrum containing peaks attributable to the measurement elements (Al and F). The X-ray intensity of the peak attributable to the measurement element Al in the obtained fluorescent X-ray spectrum is converted to the alumina particle content (unit: mass%) in the toner particles. The X-ray intensity of the peak attributable to the measurement element F in the fluorescent X-ray spectrum is converted to the fluorine-containing particle content (unit: mass%) in the toner particles. In this way, the alumina particle content in the toner particles and the fluorine-containing particle content in the toner particles are determined for the above-mentioned measurement object.

[0032] <Toner particles> The toner particles comprise toner base particles and an external additive. The external additive is attached to the surface of the toner base particles. The toner base particles may be non-encapsulated toner particles that do not have a shell layer. Alternatively, the toner base particles may be encapsulated toner particles that include a toner core and a shell layer that covers the toner core. The toner particles do not contain magnetic powder and are used as a toner (i.e., a non-magnetic one-component toner) without being mixed with a carrier. A toner containing toner particles is suitably used, for example, as a positively charged toner for developing electrostatic latent images. In the following description of toner particles, the content ratio and amount refer to the content ratio and amount before a predetermined printing, respectively.

[0033] <External additives> The external additive includes alumina particles and fluorine-containing particles. The external additive may include only fluorine-containing particles and alumina particles, or may further include particles other than the fluorine-containing particles and alumina particles (hereinafter, sometimes referred to as "other external additive particles").

[0034] (Fluorine-containing particles) The fluorine-containing particles have fluorine atoms. Examples of the fluorine-containing particles include fluororesin particles. The fluororesin particles contain a fluororesin. The content of the fluororesin in the fluororesin particles is preferably 80% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0035] Examples of fluororesins include polytetrafluoroethylene (PTFE), perfluoroalkoxy fluororesins, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-n-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-ethylene copolymers, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymers, and tetrafluoroethylene-perfluoroalkoxyethylene copolymers. PTFE is preferred as the fluororesin.

[0036] Ratio (development section durability fluorine content F 1000D The number-average primary particle diameter of the fluorine-containing particles is preferably 100 nm or more and 300 nm or less, because this makes it easier to adjust the initial fluorine content (F0) within a desired range. Furthermore, if the number-average primary particle diameter of the fluorine-containing particles is 100 nm or more, the fluorine-containing particles can be prevented from being embedded in the toner base particles. On the other hand, if the number-average primary particle diameter of the fluorine-containing particles is 300 nm or less, the amount of fluorine-containing particles detached from the toner base particles can be optimized.

[0037] When the fluorine-containing particles are fluororesin particles, emulsion polymerization is a preferred method for preparing the fluororesin particles. The fluororesin particles obtained by emulsion polymerization are nearly spherical, making them suitable as external additives for toner. Commercially available fluororesin particles may also be used. Examples of such commercially available products include KTL-500F (Kitamura Corporation, number average primary particle diameter 300 nm), Lubron (registered trademark) L2 (Daikin Industries, Ltd., number average primary particle diameter 300 nm), Lubron (registered trademark) L5 (Daikin Industries, Ltd., number average primary particle diameter 200 nm), Fluon Lubricant L170J (Asahi ICI Fluoropolymers Corporation, number average primary particle diameter 100 nm), and Fluon Lube. Examples of such polymers include Lycant L172J (manufactured by Asahi ICI Fluoropolymers Co., Ltd., number average primary particle diameter 0.1 μm), MP-1100 (manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd., number average primary particle diameter 200 nm), MP-1200 (manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd., number average primary particle diameter 300 nm), and TLP-10F-1 (manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd., number average primary particle diameter 200 nm).

[0038] Ratio (development section durability fluorine content F 1000D Since it is easy to adjust the initial fluorine content F) within a desired range, the content of the fluorine-containing particles before the predetermined printing is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.3 parts by mass or more and 1.0 part by mass or less, relative to 100.0 parts by mass of the toner base particles.

[0039] (alumina particles) As already mentioned, the powder resistivity of the alumina particles is 50 Ω·cm or less. In order to form an image with high image density and little fog, the powder resistivity of the alumina particles is preferably 1 Ω·cm or more and 50 Ω·cm or less, more preferably 10 Ω·cm or more and 45 Ω·cm or less, and even more preferably 15 Ω·cm or more and 35 Ω·cm or less. The powder resistivity of the alumina particles is measured, for example, using an electrical resistance meter.

[0040] The number-average primary particle diameter of the alumina particles is preferably 100 nm or more and 600 nm or less, and more preferably 150 nm or more and 300 nm or less. If the number-average primary particle diameter of the alumina particles is 100 nm or more, the alumina particles can properly polish the fluorine-containing particles adhering to the regulating blade 240, thereby preventing thin layer streaks from occurring in the formed image. On the other hand, if the number-average primary particle diameter of the alumina particles is 600 nm or less, the fluorine-containing particles adhering to the regulating blade 240 can be properly scraped. As a result, the thickness of the toner layer is adequately regulated by the regulating blade 240, preventing the toner layer from becoming too thick and preventing fogging in the formed image.

[0041] Ratio (development section durability alumina content Al 1000D Since it is easy to adjust the initial alumina content Al0) within a desired range, the content of the alumina particles before a predetermined printing is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, more preferably 0.4 parts by mass or more and 1.0 parts by mass or less, and even more preferably 0.6 parts by mass or more and 0.8 parts by mass or less, relative to 100.0 parts by mass of the toner base particles.

[0042] In order to balance the amount of fluorine-containing particles adhering to the regulating blade and the amount of fluorine-containing particles scraped off by the alumina particles, it is preferable that the ratio WAl / WF of the content of fluorine-containing particles per 100.0 parts by mass of toner base particles before the specified printing, WF, to the content of alumina particles per 100.0 parts by mass of toner base particles before the specified printing, is 0.6 or more and 2.0 or less.

[0043] The alumina particles include a substrate and a conductive layer. The conductive layer coats the substrate. The alumina particles may further include a surface treatment layer. The surface treatment layer coats the conductive layer. When the alumina particles include a conductive layer and a surface treatment layer, of the two layers coating the substrate, the inner layer (on the substrate side) is the conductive layer and the outer layer is the surface treatment layer. The alumina particles and the above-mentioned fluorine-containing particles are each independent particles. Therefore, the alumina particles do not need to contain fluorine. The substrate, the conductive layer, and the surface treatment layer will be described below.

[0044] (Base) The substrate contains alumina. Alumina particles tend to be positively charged, so a toner containing alumina particles is easily positively charged. The alumina content in the substrate is preferably 80% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0045] (Conductive layer) The conductive layer is a layer formed from a conductive treatment agent. Since the alumina particles, which are an external additive, have a conductive layer, the electrical resistance of the toner particles is appropriately reduced, thereby suppressing excessive charging of the toner particles. The conductive layer preferably contains a conductive oxide, and more preferably a conductive metal oxide (hereinafter, sometimes referred to as a conductive metal oxide). Examples of conductive metal oxides include metal oxides containing tin oxide (e.g., antimony-doped tin oxide (ATO), indium tin oxide (ITO), and fluorine-doped tin oxide (FTO)), and metal oxides containing zinc oxide (e.g., aluminum-doped zinc oxide (AZO) and gallium-doped zinc oxide (GZO)). To further suppress excessive charging of the toner particles, the conductive layer preferably contains antimony-doped tin oxide. The content of the conductive metal oxide in the conductive layer is preferably 80% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass.

[0046] In order to optimize the electrical resistance of the toner particles, the mass of the conductive layer is preferably 1 part by mass or more and 300 parts by mass or less, and more preferably 100 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the substrate.

[0047] In order to optimize the electrical resistance of the toner particles, in the conductive metal oxide contained in the conductive layer, the ratio (MSn / MSb) of the mass of tin (MSn) to the mass of antimony (MSb) is preferably 0.1 or more and 10.0 or less, more preferably 1.0 or more and 5.0 or less, and even more preferably 3.0 or more and 4.0 or less.

[0048] (Surface treatment layer) The surface treatment layer is a layer formed by a surface treatment agent. The surface treatment layer imparts good charge stability to the toner while suppressing peeling of the conductive layer. The surface treatment agent is, for example, a hydrophobic treatment agent. Specific examples of the surface treatment agent include titanate coupling agents, aluminate coupling agents, and fatty acid metal salts. In order to impart good charge stability to the toner, a titanate coupling agent is preferred as the surface treatment agent. In other words, the surface treatment layer is preferably a titanate coupling agent-treated layer. That is, the surface treatment layer preferably contains a component derived from a titanate coupling agent.

[0049] Examples of titanate coupling agents include isopropyl trialkanoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tridodecyl benzene sulfonyl titanate, isopropyl isostearoyl diacryl titanate, and isopropyl tri (dioctyl phosphate) titanate.As titanate coupling agents, isopropyl trialkanoyl titanate is preferred, and isopropyl triisostearoyl titanate is more preferred.

[0050] The mass of the surface treatment layer is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the substrate. When the mass of the surface treatment layer is within this range, it is possible to impart appropriate hydrophobicity to the toner particles.

[0051] The alumina particles may further include other layers in addition to the conductive layer and the surface treatment layer. The conductive layer may directly or indirectly coat the substrate. The surface treatment layer may directly or indirectly coat the conductive layer. The conductive layer and the surface treatment layer are each preferably a single layer, but may be multilayered.

[0052] (Other external additive particles) Other external additive particles include, for example, silica particles, particles of metal oxides (specifically, magnesium oxide, zinc oxide, etc.), particles of organic acid compounds such as fatty acid metal salts (specifically, zinc stearate, etc.), and resin particles. However, the external additive does not necessarily contain resin particles other than the above-mentioned fluororesin particles. Silica particles that have been surface-treated to impart positive chargeability and / or hydrophobicity are preferred. The number-average primary particle diameter of the silica particles is preferably 10 nm or more and 45 nm or less, more preferably 12 nm or more and 40 nm or less. The content of the silica particles is preferably 0.1 parts by mass or more and 5.0 parts by mass or less relative to 100.0 parts by mass of the toner base particles.

[0053] <Toner base particles> The toner base particles contain, for example, a binder resin as a main component. The toner base particles may further contain an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and other additives) as needed. Methods for producing the toner base particles include a pulverization method and an aggregation method, with the pulverization method being preferred.

[0054] (binder resin) From the viewpoint of providing a toner with excellent low-temperature fixability, the toner base particles preferably contain a thermoplastic resin as a binder resin, and more preferably contain the thermoplastic resin in a proportion of 85% by mass or more of the total binder resin. Examples of thermoplastic resins include styrene resins, acrylic ester resins, olefin resins (e.g., polyethylene resins and polypropylene resins), vinyl resins (e.g., vinyl chloride resins, polyvinyl alcohol, vinyl ether resins, and N-vinyl resins), polyester resins, polyamide resins, and urethane resins. Copolymers of these resins, i.e., copolymers in which any repeating unit is introduced into the above-mentioned resins (e.g., styrene-acrylic ester resins and styrene-butadiene resins), can also be used as binder resins.

[0055] The content of the binder resin in the toner base particles is preferably 60% by mass or more and 95% by mass or less, and more preferably 75% by mass or more and 90% by mass or less.

[0056] From the viewpoint of improving the low-temperature fixability of the toner, polyester resins are preferred as binder resins. Polyester resins are obtained by polycondensation of one or more polyhydric alcohols and one or more polycarboxylic acids. Examples of alcohols used to synthesize polyester resins include dihydric alcohols (e.g., diol compounds and bisphenol compounds) and trivalent or higher alcohols. Examples of carboxylic acids used to synthesize polyester resins include divalent carboxylic acids and trivalent or higher carboxylic acids. Note that instead of polycarboxylic acids, polycarboxylic acid derivatives capable of forming ester bonds by polycondensation (e.g., polycarboxylic acid anhydrides and polycarboxylic acid halides) may be used.

[0057] Examples of diol compounds include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4-diol, 1,5-pentanediol, 2-pentene-1,5-diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, 1,4-benzenediol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0058] Examples of bisphenol compounds include bisphenol A, hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A (for example, polyoxyethylene (2,2)-2,2-bis(4-hydroxyphenyl)propane), and propylene oxide adducts of bisphenol A.

[0059] Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0060] Examples of dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkylsuccinic acids (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid), and alkenylsuccinic acids (more specifically, n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid).

[0061] Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxylpropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

[0062] The polyester resin is preferably a condensation polymer of bisphenol A ethylene oxide adduct, terephthalic acid, and trimellitic anhydride, and more preferably a condensation polymer of polyoxyethylene(2,2)-2,2-bis(4-hydroxyphenyl)propane, terephthalic acid, and trimellitic anhydride.

[0063] (coloring agent) As the colorant, a known pigment or dye can be used in accordance with the color of the toner. From the viewpoint of forming a high-quality image using the toner, the content of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

[0064] The toner base particles may contain a black colorant. Examples of black colorants include carbon black. The black colorant may also be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

[0065] The toner base particles may contain color colorants, such as yellow colorants, magenta colorants, and cyan colorants.

[0066] The yellow colorant may be, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds. Examples of the yellow colorant include CI Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 191, and 194), Naphthol Yellow S, Hansa Yellow G, and CI Vat Yellow.

[0067] Examples of magenta colorants that can be used include one or more compounds selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Examples of magenta colorants include CI Pigment Red (2, 3, 5, 6, 7, 19, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254).

[0068] The cyan colorant may be, for example, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds, including, for example, CI Pigment Blue (1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66), phthalocyanine blue, CI Vat Blue, and CI Acid Blue.

[0069] (mold release agent) The release agent is used, for example, for the purpose of imparting offset resistance to the toner. From the viewpoint of imparting sufficient offset resistance to the toner, the content of the release agent is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

[0070] Examples of release agents include aliphatic hydrocarbon waxes, oxidized aliphatic hydrocarbon waxes, vegetable waxes, animal waxes, mineral waxes, ester waxes primarily composed of fatty acid esters, and waxes in which fatty acid esters have been partially or completely deoxidized. Examples of aliphatic hydrocarbon waxes include low-molecular-weight polyethylene, low-molecular-weight polypropylene, polyolefin copolymers, polyolefin waxes, microcrystalline waxes, paraffin waxes, and Fischer-Tropsch waxes. Examples of oxidized aliphatic hydrocarbon waxes include oxidized polyethylene waxes and block copolymers of oxidized polyethylene waxes. Examples of vegetable waxes include candelilla wax, carnauba wax, Japan wax, jojoba wax, and rice wax. Examples of animal waxes include beeswax, lanolin, and spermaceti. Examples of mineral waxes include ozokerite, ceresin, and petrolatum. Examples of ester waxes primarily composed of fatty acid esters include Montan acid ester wax and castor wax. Examples of waxes in which fatty acid esters have been partially or completely deoxidized include deoxidized carnauba wax. As the release agent, carnauba wax is preferred.

[0071] When the toner base particles contain a release agent, a compatibilizer may be added to the toner base particles in order to improve the compatibility between the binder resin and the release agent.

[0072] (charge control agent) Charge control agents are used, for example, for the purpose of providing a toner having excellent charge stability or excellent charge rise characteristics. The charge rise characteristics of a toner are an index of whether the toner can be charged to a predetermined charge level in a short period of time. By incorporating a positively chargeable charge control agent into the toner base particles, the cationic nature of the toner base particles can be strengthened.

[0073] Examples of positively chargeable charge control agents include azine compounds, direct dyes, acid dyes, alkoxylated amines, alkylamides, quaternary ammonium salts, and resins containing quaternary ammonium cation groups. Quaternary ammonium salts are preferred as charge control agents.

[0074] From the viewpoint of obtaining a toner having excellent charge stability, the content of the charge control agent is preferably 0.1 to 30 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the binder resin.

[0075] <Toner manufacturing method> The toner can be produced, for example, by a production method including a step of preparing toner base particles and a step of adding external additives.

[0076] (Toner base particle preparation process) In the toner base particle preparation step, the toner base particles are prepared by, for example, an aggregation method or a pulverization method.

[0077] The aggregation method includes, for example, an aggregation step and a coalescence step. In the aggregation step, fine particles containing components constituting the toner base particles are aggregated in an aqueous medium to form aggregated particles. In the coalescence step, components contained in the aggregated particles are coalesced in the aqueous medium to form toner base particles.

[0078] Next, the pulverization method will be described. The pulverization method allows toner base particles to be prepared relatively easily and also enables reduction in production costs. When toner base particles are prepared by the pulverization method, the preparation process of the toner base particles includes, for example, a melt-kneading step and a pulverization step. The preparation process of the toner base particles may further include a mixing step before the melt-kneading step. Furthermore, the preparation process of the toner base particles may further include at least one of a fine pulverization step and a classification step after the pulverization step.

[0079] In the mixing step, a binder resin and an internal additive, which is added as needed, are mixed to obtain a mixture. In the melting and kneading step, the toner materials are melted and kneaded to obtain a molten and kneaded product. The mixture obtained in the mixing step, for example, is used as the toner material. In the pulverizing step, the obtained molten and kneaded product is cooled to, for example, room temperature (25°C) and then pulverized to obtain a pulverized product. If it is necessary to reduce the diameter of the pulverized product obtained in the pulverizing step, a step of further pulverizing the pulverized product (fine pulverizing step) may be performed. Furthermore, if the particle size of the pulverized product is to be uniform, a step of classifying the obtained pulverized product (classifying step) may be performed. Through the above steps, toner base particles, which are the pulverized product, are obtained.

[0080] (External addition process) In the external addition step, toner particles are obtained by adhering external additives containing fluorine-containing particles and alumina particles to the surfaces of toner base particles. The method for adhering the external additives to the surfaces of toner base particles is not particularly limited, but examples thereof include a method in which the toner base particles and the external additives are stirred with a mixer or the like.

[0081] When the external additive is attached by stirring, the toner base particles and the external additive particles do not chemically react with each other and are fixed physically, not chemically. The degree of fixation between the toner base particles and the external additive particles can be adjusted by the stirring conditions (more specifically, the stirring time, the stirring rotation speed, etc.), the particle diameter of the external additive particles, the shape of the external additive particles, the surface condition of the external additive particles, etc. Therefore, by changing the stirring conditions, the alumina content Al of the developing section can be adjusted. 1000D / Initial alumina content Al0 and development zone durability fluorine content F 1000D The initial fluorine content F0 can be adjusted appropriately.

[0082] For example, the longer the stirring time for the toner base particles and alumina particles, the more the alumina particles are fixed to the surface of the toner base particles, and the less alumina particles are detached from the toner base particles in the developing section. 1000D The alumina content of Al 1000DThe initial alumina content Al0 also tends to decrease. In addition, the longer the stirring time for the toner base particles and fluorine-containing particles, the more the fluorine-containing particles are fixed to the surface of the toner base particles, and the amount of fluorine-containing particles that detach from the toner base particles in the developing section decreases. As a result, the developing section durability fluorine content F 1000D The fluorine content in the developing area is decreased, and 1000D / The initial fluorine content F0 also tends to decrease.

[0083] The fluorine-containing particles and the alumina particles may be added to the toner base particles simultaneously and stirred. Alternatively, one of the fluorine-containing particles and the alumina particles may be added to the toner base particles and stirred, and then the other may be added and further stirred. By adding the fluorine-containing particles and the alumina particles at different times, the degree of fixation of the alumina particles to the toner base particles and the degree of fixation of the fluorine-containing particles to the toner base particles can be adjusted independently.

[0084] [Second embodiment: image forming apparatus] The second embodiment of the present invention relates to an image forming apparatus. Hereinafter, an image forming apparatus 1, which is one example of the image forming apparatus of the present invention, will be described with reference to FIGS. 1 and 2 again. Note that the same reference symbols in the drawings represent the same or corresponding parts. Dimensional relationships such as length, width, thickness, and depth have been changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[0085] As shown in FIG. 1, the image forming apparatus 1 includes a paper feed section 10, a conveyance section 11, an image forming section 12, a fixing section 13, a discharge section 14, and a control section 15.

[0086] The paper feed unit 10 includes a paper feed cassette 30 and a paper feed roller group 31. The paper feed cassette 30 can accommodate multiple recording media P. The paper feed roller group 31 feeds the recording media P accommodated in the paper feed cassette 30 one by one to the conveyance unit 11. The recording media P are made of, for example, paper or synthetic resin.

[0087] The conveying section 11 extends from the paper feeding section 10 to the discharge section 14. The conveying section 11 conveys the recording medium P from the paper feeding section 10 to the discharge section 14, passing through the image forming section 12 and the fixing section 13.

[0088] The image forming unit 12 includes an exposure unit 20, a charging unit 21, a developing unit 22, an image carrier 23, a cleaning unit 24, and a transfer unit 25. The charging unit 21, the developing unit 22, the transfer unit 25, and the cleaning unit 24 are arranged along the circumferential surface of the image carrier 23 in the order listed from the upstream side in the rotation direction R of the image carrier 23 (clockwise direction in FIG. 1).

[0089] The charging unit 21 uniformly charges the image carrier 23 to a preset polarity.

[0090] The exposure unit 20 irradiates (exposes) light onto the surface 23a of the charged image carrier 23. The exposure unit 20 exposes the surface 23a of the image carrier 23 based on image data input to the image forming apparatus 1. As a result, an electrostatic latent image is formed on the surface 23a of the image carrier 23.

[0091] The developing unit 22 contains toner T. The developing unit 22 supplies the toner T to the electrostatic latent image formed on the surface 23a of the image carrier 23, and develops the electrostatic latent image into a toner image. Details of the developing unit 22 will be described later.

[0092] Toner T is the toner described in the first embodiment. Therefore, for the same reasons as those described in the first embodiment, the image forming apparatus 1 equipped with toner T can form images with high image density and little thin layer streaks and fog. In the second embodiment, predetermined printing is performed using the image forming apparatus 1 of the second embodiment.

[0093] The image carrier 23 carries a toner image on its surface 23a. The image carrier 23 is, for example, a photosensitive drum.

[0094] The transfer unit 25 is disposed opposite the image carrier 23 and transfers the toner image on the image carrier 23 onto the recording medium P.

[0095] The cleaning unit 24 collects the toner T remaining on the surface 23a of the image carrier 23 after transfer from the surface 23a of the image carrier 23.

[0096] The fixing unit 13 includes a heating unit 40 and a pressure unit 41. The heating unit 40 and the pressure unit 41 are arranged opposite each other. The pressure unit 41 presses the heating unit 40 to form a fixing nip. The recording medium P onto which the toner image has been transferred passes through the fixing nip and is heated and pressurized. As a result, the toner T is fixed to the recording medium P. The recording medium P is transported from the fixing unit 13 to the discharge unit 14 by the transport unit 11.

[0097] The discharge section 14 includes a discharge roller pair 60 and a discharge tray 61. The discharge roller pair 60 discharges the recording medium P onto the discharge tray 61.

[0098] The control unit 15 controls the operation of each unit included in the image forming apparatus 1. The control unit 15 is, for example, a processor such as a CPU (Central Processing Unit). The control unit 15 comprehensively controls the operation of the image forming apparatus 1 to realize various functions.

[0099] Next, the details of the developing unit 22 will be described with reference to Fig. 2. As already mentioned, the developing unit 22 includes a storage frame 210, a supply roller 220, a developing roller 230, and a regulating blade 240. The lengths of the supply roller 220 and the developing roller 230 in the axial direction (the direction perpendicular to the paper surface of Fig. 2) are approximately the same as the length of the image carrier 23.

[0100] The storage frame 210 stores toner T therein. The storage frame 210 includes a supply roller 220, a developing roller 230, and a regulating blade 240 therein. The storage frame 210 has an opening 211, which is disposed opposite the image carrier 23. The opening 211 exposes a portion of the developing roller 230 to the outside of the storage frame 210.

[0101] Supply roller 220 is supported so as to be rotatable in the direction of the arrow in FIG. 2 (counterclockwise). Supply roller 220 carries toner T stored inside storage frame 210 on its surface (circumferential surface). A nip N1 is provided between development roller 230 and supply roller 220. In nip N1, supply roller 220 supplies toner T carried on its surface to development roller 230. In addition, in nip N1, toner T on supply roller 220 comes into contact with development roller 230, thereby causing frictional charging of toner T.

[0102] The developing roller 230 is supported so as to be rotatable in the direction of the arrow in FIG. 2 (counterclockwise). The developing roller 230 is disposed opposite the supply roller 220. The developing roller 230 is also disposed opposite the image carrier 23 through the opening 211 of the storage frame 210. The developing roller 230 carries the toner T supplied from the supply roller 220 on its surface (circumferential surface) 230a. More specifically, the toner T is carried on the surface 230a of the developing roller 230 due to the image force acting between the developing roller 230 and the toner T.

[0103] The developing roller 230 includes a conductive support 231, an elastic layer 232, and a coating layer 233. The elastic layer 232 is provided on the conductive support 231 (specifically, on the outer peripheral surface of the conductive support 231). The elastic layer 232 is made of, for example, silicone rubber. The coating layer 233 is provided on the elastic layer 232 (specifically, on the outer peripheral surface of the elastic layer 232). The coating layer is made of, for example, urethane.

[0104] The regulating blade 240 is plate-shaped. One end 241 of the regulating blade 240 is fixed to the containing frame 210, and the other end 242 is a free end. The regulating blade 240 is bent toward the opposite side to the developing roller 230 near the outer edge of the other end 242 (free end). The regulating blade 240 is made of, for example, stainless steel (SUS).

[0105] The regulating blade 240 is flexible and deformable so that the other end 242 approaches the developing roller 230. The developing roller 230 has one or more magnet portions (not shown) therein. The regulating blade 240 is magnetic. The magnetic force generated by the magnet portion of the developing roller 230 urges the other end 242 of the magnetic regulating blade 240 toward the developing roller 230. In this manner, a nip N2 is formed between the regulating blade 240 and the surface 230a of the developing roller 230. In the nip N2, the regulating blade 240 contacts (specifically, makes surface contact with) the toner layer formed on the surface 230a of the developing roller 230 with a predetermined pressure, thereby regulating the thickness of the toner layer. In order to regulate the thickness of the toner layer within a desired range, the pressure (regulating pressure) of the regulating blade 240 against the surface 230a of the developing roller 230 is preferably 15 N / m or more and 40 N / m or less. Furthermore, at the nip N2, the toner T on the developing roller 230 comes into contact with the regulating blade 240, so that the toner T is further triboelectrically charged.

[0106] When a development bias is applied to the development roller 230, the toner T contained in the toner layer is supplied from the development roller 230 to the electrostatic latent image formed on the surface 23a of the image carrier 23 through the opening 211. The details of the development unit 22 have been described above with reference to FIG.

[0107] As described above, the image forming apparatus 1 shown in Fig. 1 has been described as an example of the image forming apparatus of the second embodiment. However, the image forming apparatus of the second embodiment is not limited to the image forming apparatus 1 described above, and can be modified in the following ways, for example.

[0108] For example, in the second embodiment described above, the image forming apparatus 1 is an apparatus that records an image using a single color toner, but is not limited to this. The image forming apparatus 1 may also be an apparatus that records a color image using multiple color toners. [Example]

[0109] Examples of the present invention will be described below, but the present invention is not limited to the scope of the examples. First, methods for measuring physical property values ​​will be described.

[0110] [Number average primary particle size] The number-average primary particle diameter of the external additive particles (specifically, alumina particles and fluorine-containing particles) was determined from particle projection images taken using a scanning electron microscope ("JSM-7600F" manufactured by JEOL Ltd.) Specifically, the external additive particles were observed using the scanning electron microscope, and the number-average circle-equivalent diameter (Heywood diameter: diameter of a circle having the same area as the projected area of ​​a primary particle) of 100 external additive particles was taken as the number-average primary particle diameter.

[0111] [Powder resistivity] Five grams of the object to be measured (alumina particles) was placed in a cylindrical measurement cell of an electrical resistance meter ("R6561" manufactured by Advantest Corporation). The bottom of the measurement cell was a metal electrode, and the cylindrical part was made of fluororesin. The electrodes (superscript: 2, length 25.4 mm) of the electrical resistance meter were then connected to the object to be measured filled in the measurement cell. A load of 1 kg was applied to these electrodes. A DC voltage of 10 V was then applied between the two electrodes, and the electrical resistance of the object to be measured was measured 1 minute after the start of application. The 1 kg load was continuously applied to the electrodes from the start of application to the end of measurement. The measurement was carried out in an environment with a temperature of 25°C and a relative humidity of 50% RH. The powder resistivity of the object to be measured was calculated using the following formula based on the measured electrical resistance value and the dimensions of the object to be measured (more specifically, the object to be measured filled in the measurement cell) during the electrical resistance measurement. Powder resistivity [Ω·cm] = Electrical resistance value × Cross-sectional area of ​​current path / Length of current path

[0112] [Alumina particles] The alumina particles shown in Table 1 were produced by the following method. The production conditions for each alumina particle are shown in Table 1. The number average primary particle diameter and powder resistivity of the measured alumina particles are also shown in Table 1. The "particle diameter" used in Table 1 refers to the number average primary particle diameter.

[0113] [Table 1]

[0114] <Preparation of alumina particles (Al-1)> (Substrate manufacturing process) A high-speed rotary shear mixer (M Technique Co., Ltd., "Clearmix® CLM-2.2S"; rotor diameter: 57 mm, minimum diameter: 25 mm, clearance: 0.3 mm) was installed in a pressure-resistant vessel, which served as the reaction vessel. A mixture of aluminum isopropoxide and isopropyl alcohol (aluminum isopropoxide concentration: 60% by mass) and a mixture of water and isopropyl alcohol (water concentration: 30% by mass) were added to the reaction vessel. Mixtures a and b were continuously added to the reaction vessel while stirring the contents at 70°C for 1.0 hour (hereinafter referred to as reaction time A). The amounts of mixtures a and b added were such that the molar ratio of water to aluminum isopropoxide (water / aluminum isopropoxide) was 2.5. This hydrolysis reaction of the contents of the reaction vessel produced aluminum hydroxide. The resulting aluminum hydroxide was calcined at 800°C for 3 hours to produce alumina. Thereafter, the mixture was pulverized using a pulverizer at a pulverization pressure of 0.9 MPa to obtain an alumina powder, which was used as an alumina substrate.

[0115] (Conductive treatment process) A 2-liter suspension was prepared by dispersing 300 g of alumina substrate in purified water using a PRIMIX Corporation "Homomixer MARK II 2.5." The resulting suspension was heated to 70°C and maintained at 70°C. An acid solution was prepared by dissolving 467 g of stannous chloride pentahydrate (SnCl4·5H2O) (hereinafter, amount B) and 82 g of antimony trichloride (SbCl3) (hereinafter, amount C) in 750 mL of separately prepared 2.4 N hydrochloric acid. A 5 N aqueous ammonia solution and the above acid solution were added dropwise in parallel to the suspension over 1.5 hours. During the parallel addition, the suspension was maintained at 70°C, and the drop rates were adjusted so that the pH of the suspension was maintained between 7 and 8. The suspension was then filtered. Purified water was added to the resulting residue and the mixture was filtered again (washing process). The washing process was repeated until the conductivity of the filtrate reached 50 μS / cm or less. The washed residue was dried at 110°C for 15 hours and then fired in an electric furnace at 700°C for 2 hours. The fired product was then crushed using a crusher at a crushing pressure of 0.8 MPa. This resulted in an alumina substrate whose surface was treated with antimony-doped tin oxide (ATO) to make it conductive.

[0116] (Surface treatment process) 300 g of the conductively treated alumina substrate and 25 g of a titanate coupling agent (Ajinomoto Co., Inc.'s "Plenact® TTS," isopropyl triisostearoyl titanate) were placed in a mixer (Kawata Corporation's "Nanopersion Piccolo") and mixed at 80°C for 1 hour at 6,000 rpm. The resulting mixture was dried at 110°C for 12 hours. The dried mixture was pulverized using a pulverizer at a pulverization pressure of 0.6 MPa. This resulted in alumina particles (Al-1) surface-treated with a titanate coupling agent. The alumina particles (Al-1) comprised an alumina substrate, a conductive layer covering the surface of the alumina substrate, and a surface-treated layer covering the conductive layer. The conductive layer contained ATO, and the surface-treated layer was a titanate coupling agent-treated layer.

[0117] <Preparation of alumina particles (Al-2) to (Al-5)> Alumina particles (Al-2) to (Al-5) were prepared in the same manner as in the preparation of alumina particles (Al-1), except that the reaction time A in the substrate preparation process and the amounts B and C in the conductive treatment process were changed to the values ​​shown in Table 1.

[0118] [Fluorine-containing particles] The fluorine-containing particles shown in Table 2 were prepared by the following method. The preparation conditions for each fluorine-containing particle are shown in Table 2. The measured number-average primary particle diameter of the fluorine-containing particles is also shown in Table 2. The "particle diameter" used in Table 2 refers to the number-average primary particle diameter.

[0119] [Table 2]

[0120] <Preparation of Fluorine-Containing Particles (F-1)> An autoclave equipped with a stainless steel anchor-type stirring blade and a temperature-control jacket was used as the reaction vessel. 3580 mL of deionized water, 3.58 g of ammonium perfluorooctanoate, and 94.1 g of paraffin wax (Nippon Seikoh Co., Ltd., "Paraffin Wax-130") were charged to the reaction vessel. After purging the atmosphere with nitrogen gas and tetrafluoroethylene (TFE), TFE was further pressure-injected into the reaction vessel. The contents of the reaction vessel were stirred at a stirring speed of 250 rpm (hereinafter referred to as the stirring speed X), while the reaction vessel was heated to a temperature of 80°C and maintained at this temperature. While pressure-injecting an aqueous solution of ammonium persulfate (concentration: 0.067% by mass) and an aqueous solution of disuccinic acid peroxide (concentration: 1.61% by mass), TFE was continuously supplied to maintain a constant pressure (0.78 MPa) inside the reaction vessel. The polymerization reaction was carried out for 50 minutes (hereinafter referred to as the polymerization time Y). During the polymerization reaction, the injected amounts of ammonium persulfate aqueous solution, disuccinic acid peroxide aqueous solution, and TFE were 20 mL, 20 mL, and 1735 g, respectively. After the polymerization time Y, the supply of TFE and stirring of the contents of the reaction vessel were stopped, and the polymerization reaction was terminated. 100 mL of ammonium hydroperfluorononanoate aqueous solution (concentration: 10% by mass) was added to the latex-like reaction product obtained by the polymerization reaction. Next, warm water was added to the reaction product and the temperature was adjusted to 50°C. Next, 10 mL of nitric acid (concentration: 60% by mass) was added to the reaction product, and the reaction product was stirred at a stirring speed of 250 rpm. As a result, fluorine-containing particles (FA) began to coagulate from the reaction product. Next, the reaction product was continuously stirred for 1 hour to sufficiently separate the fluorine-containing particles (FA) from the solvent. Next, the solvent was removed from the fluorine-containing particles (FA), and the fluorine-containing particles (F-1) having the number-average primary particle diameter listed in Table 2 were obtained by drying.

[0121] <Preparation of Fluorine-Containing Particles (F-2) to (F-3)> Fluorine-containing particles (F-2) to (F-3) were prepared in the same manner as in the preparation of fluorine-containing particles (F-1), except that the stirring speed X and polymerization time Y were changed to the values ​​shown in Table 2.

[0122] [toner] The toners used in the examples and comparative examples were prepared by the following method, and the details of the toners are shown in Table 3 below.

[0123] [Table 3]

[0124] <Preparation of Toner (T-A1)> (Preparation of Polyester Resin) A polyester resin used as a binder resin for toner was prepared using the following method. 1.0 mol of polyoxyethylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, 4.5 mol of terephthalic acid, 0.5 mol of trimellitic anhydride, and 4 g of dibutyltin oxide were placed in a reaction vessel. The contents of the reaction vessel were reacted at 230°C for 8 hours under a nitrogen atmosphere. Unreacted raw materials were then removed by vacuum distillation at 8.3 kPa. The resulting reaction product was washed and then dried. This yielded a polyester resin with a softening point of 120°C.

[0125] (Preparation of Toner Base Particles) 100 parts by weight of the above-mentioned polyester resin as a binder resin, 5 parts by weight of carbon black ("REGAL® 330R" manufactured by Cabot Specialty Chemicals) as a colorant, 10 parts by weight of carnauba wax ("Carnauba No. 1" manufactured by Kato Yoko Co., Ltd.) as a release agent, and 3 parts by weight of a quaternary ammonium salt compound ("FCA210PS" manufactured by Fujikura Kasei Co., Ltd.) as a charge control agent were mixed using an FM mixer ("FM20B" manufactured by Nippon Coke & Engineering Co., Ltd.). The resulting mixture was melted and kneaded at 150°C using a twin-screw extruder ("TEM45" manufactured by Toshiba Machine Co., Ltd.). The resulting kneaded mixture was cooled. The cooled kneaded mixture was coarsely pulverized using an impact screen-type fine pulverizer ("Feathermill® FM-2S 350 x 600" manufactured by Hosokawa Micron Corporation). The obtained coarsely pulverized material was finely pulverized using a supersonic jet pulverizer ("Jet Mill IDS-2" manufactured by Nippon Pneumatic Mfg. Co., Ltd.). The obtained finely pulverized material was classified using a classifier ("Elbow Jet EJ-LABO" manufactured by Nittetsu Mining Co., Ltd.). This resulted in the production of toner base particles. The volume median diameter (D 50 ) was 8 μm.

[0126] (external attachment) 100.0 parts by mass of toner base particles, 1.5 parts by mass of silica particles (hydrophobic silica particles, "TG-7120" manufactured by Cabot Specialty Chemicals, Inc., number average primary particle diameter 20 nm), and 0.6 parts by mass of alumina particles (Al-1) were mixed using an FM mixer ("FM-10B" manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotation speed of 3500 rpm for 5 minutes (hereinafter referred to as the first mixing time). Next, 0.5 parts by mass of fluorine-containing particles (F-1) were added, and the mixture was mixed at a rotation speed of 3500 rpm for 1.5 minutes (hereinafter referred to as the second mixing time). As a result, toner (T-A1) was obtained.

[0127] <Preparation of Toners (T-A2) to (T-A14) and (T-B1) to (T-B5)> Toners (T-A2) to (T-A14) and (T-B1) to (T-B5) were prepared in the same manner as in the preparation of toner (T-A1), except that in the external addition, the type and amount of alumina particles added, the type and amount of fluorine-containing particles added, the first stirring time, and the second stirring time were as shown in Table 3.

[0128] [Prescribed printing] A predetermined printing was performed for each toner using the following method. A monochrome printer ("PA2000" manufactured by Kyocera Document Solutions Inc.) was used as the test machine for the predetermined printing. This test machine was equipped with a toner container, an image carrier, and a developing unit equipped with a regulating blade. The toner to be measured (either toners (T-A1) to (T-A14) or (T-B1) to (T-B5)) was filled into the toner container of the test machine. Using the test machine, a standard test page image specified in ISO 19752 was printed on 1,000 sheets of recording medium (A4-sized plain paper) under the following printing conditions.

[0129] <Printing conditions> Developing roller material: urethane coated silicone rubber Regulating blade material: SUS - Regulating blade pressure: 40N / m Printing environment: Temperature 23°C and relative humidity 50%RH Printing mode: Intermittent printing, repeating two prints and then pausing for 400 seconds Printing speed: 20 pages / minute when feeding the recording medium in the length direction

[0130] [measurement] <Measurement of initial alumina content Al0 and initial fluorine content F0> The toner before the above-mentioned predetermined printing was performed (i.e., the toner before being filled into the toner container of the test machine) was used as the measurement object. The measurement object was subjected to the following X-ray fluorescence analysis to determine the alumina particle content in the toner particles and the fluorine-containing particle content in the toner particles. The alumina particle content in the toner particles was defined as the initial alumina content Al0. The fluorine-containing particle content in the toner particles was defined as the initial fluorine content F0. The initial alumina content Al0 and the initial fluorine content F0 are shown in Table 4 below.

[0131] <X-ray fluorescence analysis> A 1.5 g sample was pressure-molded under conditions of 20 MPa for 3 seconds to produce a cylindrical pellet with a diameter of 30 mm. X-ray fluorescence analysis was performed on the resulting pellet under the following conditions to obtain a fluorescent X-ray spectrum (horizontal axis: energy, vertical axis: intensity (number of photons)) containing peaks attributable to the measured elements (Al and F). Using a previously prepared calibration curve, the X-ray intensity of the peak attributable to the measured element Al in the obtained fluorescent X-ray spectrum was converted to the alumina particle content (unit: mass%) of the toner particles. Furthermore, using a previously prepared calibration curve, the X-ray intensity of the peak attributable to the measured element F in the fluorescent X-ray spectrum was converted to the fluorine-containing particle content (unit: mass%) of the toner particles. The calibration curve was prepared using samples whose alumina particle content and fluorine-containing particle content in the toner particles were known.

[0132] (X-ray fluorescence analysis conditions) Analytical equipment: Scanning X-ray fluorescence analyzer (Rigaku Corporation "ZSX") X-ray tube (X-ray source): Rh (rhodium) Excitation conditions: Tube voltage 50 kV, tube current 50 mA Measurement area (X-ray irradiation range): 30 mm diameter ·Measurement elements: Al, F

[0133] <Developing section durability Alumina content Al 1000D and development zone durability fluorine content F 1000D Measurement of After the above-mentioned predetermined printing was carried out, the toner was taken out from the developing unit of the test machine and used as the measurement object. The measurement object was subjected to the above-mentioned X-ray fluorescence analysis to determine the content of alumina particles in the toner particles and the content of fluorine-containing particles in the toner particles. The content of alumina particles in the toner particles was determined as the development unit durability alumina content Al 1000D The content of fluorine-containing particles in the toner particles was defined as the development section durability fluorine content F 1000D Durability of the developing section: Alumina content Al 1000D and development zone durability fluorine content F 1000D The formula "ratio Al 1000D / Al0 = Durable alumina content in the developing section Al 1000D Ratio calculated from "initial alumina content Al0" (development section durability alumina content Al 1000D The ratio F / initial alumina content (A10) is shown in Table 4. 1000D / F0 = Durable fluorine content in the developing area F 1000D Ratio calculated from "initial fluorine content F0" (development area durability fluorine content F 1000D / initial fluorine content F0) is shown in Table 4.

[0134] [Table 4]

[0135] The terms used in Table 4 are as follows: "%" indicates mass %. "Al0 / F0" indicates the ratio Al0 / F0 of the initial alumina content Al0 to the initial fluorine content F0. The ratio Al0 / F0 corresponds to the ratio WAl / WF of the content WF of fluorine-containing particles per 100.0 parts by mass of toner base particles before a predetermined printing to the content WAl of alumina particles per 100.0 parts by mass of toner base particles before a predetermined printing. "Al 1000D / F 1000D " is the development zone durability fluorine content F 1000D Durability of the developing section against the alumina content Al 1000D Ratio of Al 1000D / F 1000D Shows.

[0136] [evaluation] Images printed using each of the toners (T-A1) to (T-A14) and (T-B1) to (T-B5) were evaluated for thin layer streaks, image density, and fogging using the following methods. The evaluation results are shown in Table 5 below.

[0137] <Print> After printing 1000 recording media (1st to 1000th sheets) using the above-mentioned predetermined printing method, printing was then performed on another 500 recording media (1001st to 1500th sheets) using the same method as the predetermined printing method.

[0138] <Thin layer streaks> The image printed on the 1500th sheet was visually observed to determine whether thin layer streaks were present. The thin layer streaks were evaluated according to the following criteria.

[0139] (Standard for thin layer streaks) A (good): No thin layer streaks were observed. B (bad): Thin streaks were observed.

[0140] <Image density> The reflection density (ID) of the printed image on the 1500th sheet was measured using a white light meter ("TC-6DX" manufactured by Tokyo Denshoku Co., Ltd.) The image density was judged according to the following criteria.

[0141] (Image density standard) A (Good): ID is 1.20 or higher. B (bad): ID is less than 1.20.

[0142] <Focus> The reflection density A of the non-printed area (white area) of the image printed on the 1500th sheet was measured using a white light meter ("TC-6DX" manufactured by Tokyo Denshoku Co., Ltd.). In addition, the reflection density B of the unprinted recording medium was measured using a white light meter ("TC-6DX" manufactured by Tokyo Denshoku Co., Ltd.). The fog density (FD) was calculated from the formula "Fog density = Reflection density A - Reflection density B". Fog was evaluated according to the following criteria.

[0143] (Fog standard) A (good): FD is 0.010 or less. B (poor): FD is greater than 0.010.

[0144] In addition, if image defects (thin layer streaks, poor image density, or fogging) were found in images printed before the 1,500th sheet, details of the image defects were added to the remarks column of Table 5.

[0145] [Table 5]

[0146] The toners (T-A1) to (T-A14) each contained toner particles, and the toner particles had toner base particles and an external additive attached to the surface of the toner base particles. The external additive contained alumina particles and fluorine-containing particles. The alumina particles had a substrate containing alumina and a conductive layer coating the substrate. The powder resistivity of the alumina particles was 50 Ω·cm or less. These toners were prepared by using the formula (1) "1.0≦Al 1000D These toners satisfied the formula (2) "1.0≦F 1000D The toners (T-A1) to (T-A14) were evaluated as being good in terms of thin layer streaks, image density, and fogging.

[0147] On the other hand, the toner (T-B1) has a ratio (development section durability alumina content Al 1000D / initial alumina content Al0) is greater than 1.5, and the formula (1) "1.0≦Al 1000D The evaluation of thin layer streaks for the toner (T-B1) was poor.

[0148] The toner (T-B2) has a ratio (development section durability alumina content Al 1000D / initial alumina content Al0) is less than 1.0, and the formula (1) "1.0≦Al 1000D The evaluation of the fogging of the toner (T-B2) was poor.

[0149] The powder resistivity of the alumina particles (Al-5) contained in the toner particles contained in toner (T-B3) was greater than 50 Ω·cm. The image density and fogging evaluations of toner (T-B3) were poor.

[0150] The toner (T-B4) has a ratio (development section durability fluorine content F 1000D / initial fluorine content F0) is greater than 1.5, and the formula (2) "1.0≦F 1000D The evaluation of the fogging of the toner (T-B4) was poor.

[0151] The toner (T-B5) has a ratio (development section durability fluorine content F 1000D / initial fluorine content F0) is less than 1.0, and the formula (2) "1.0≦F 1000D The evaluation of thin layer streaks for the toner (T-B5) was poor.

[0152] From the above, it is judged that the toners of the present invention, including the toners (T-A1) to (T-A14), can form images with high image density and little thin layer streaks and fog. [Industrial Applicability]

[0153] The image forming apparatus of the present invention can be used to form images as, for example, a multifunction machine or a printer. [Explanation of symbols]

[0154] 1: Image forming device 22: Development unit 23: Image carrier P: Recording medium T: Toner

Claims

1. A non-magnetic monocomponent toner comprising toner particles, The toner particles include toner base particles and an external additive attached to the surface of the toner base particles, the external additive includes alumina particles and fluorine-containing particles, The alumina particles include a substrate containing alumina and a conductive layer covering the substrate, The alumina particles have a powder resistivity of 50 Ω cm or less, In a predetermined printing operation in which a standard test page image defined in ISO 19752 is printed on 1,000 sheets of recording medium, The content Al of the alumina particles in the toner particles before the predetermined printing 0 and the content Al of the alumina particles in the toner particles in the developing unit after the predetermined printing. 1000D and satisfy the following formula (1), The content F of the fluorine-containing particles in the toner particles before the predetermined printing 0 and the content F of the fluorine-containing particles in the toner particles in the developing unit after the predetermined printing. 1000D and a non-magnetic one-component toner, which satisfies the following formula (2). 1.0≦Al 1000D / Al 0 ≦1.5 ・・・(1) 1.0≦F 1000D / F 0 ≦1.5 ・・・(2)

2. 2. The non-magnetic single-component toner according to claim 1, wherein the content of the fluorine-containing particles relative to 100.0 parts by mass of the toner base particles before the predetermined printing is 0.3 parts by mass or more and 1.0 part by mass or less.

3. 3. The non-magnetic single-component toner according to claim 1, wherein the content of the alumina particles relative to 100.0 parts by mass of the toner base particles before the predetermined printing is 0.4 parts by mass or more and 1.0 part by mass or less.

4. 3. The non-magnetic single-component toner according to claim 1, wherein a ratio WAl / WF of a content WF of the fluorine-containing particles relative to 100.0 parts by mass of the toner base particles before the specified printing to a content WAl of the alumina particles relative to 100.0 parts by mass of the toner base particles before the specified printing is 0.6 or more and 2.0 or less.

5. 3. The non-magnetic one-component toner according to claim 1, wherein the conductive layer of the alumina particles contains antimony-doped tin oxide.

6. the alumina particles further include a surface treatment layer that covers the conductive layer; 3. The non-magnetic one-component toner according to claim 1, wherein the surface treatment layer is a titanate coupling agent treatment layer.

7. an image carrier; an image forming apparatus including a developing unit that supplies a non-magnetic one-component toner to an electrostatic latent image formed on the surface of the image carrier, The non-magnetic single-component toner includes toner particles, The toner particles include toner base particles and an external additive attached to the surface of the toner base particles, the external additive includes alumina particles and fluorine-containing particles, The alumina particles include a substrate containing alumina and a conductive layer covering the substrate, The alumina particles have a powder resistivity of 50 Ω cm or less, In a predetermined printing operation in which a standard test page image defined in ISO 19752 is printed on 1,000 sheets of recording medium, The content Al of the alumina particles in the toner particles before the predetermined printing 0 and the content Al of the alumina particles in the toner particles in the developing unit after the predetermined printing. 1000D and satisfy the following formula (1): The content F of the fluorine-containing particles in the toner particles before the predetermined printing 0 and the content F of the fluorine-containing particles in the toner particles in the developing unit after the predetermined printing. 1000D and the image forming apparatus satisfies the following formula (2): 1.0≦Al 1000D / Al 0 ≦1.5 ・・・(1) 1.0≦F 1000D / F 0 ≦1.5 ・・・(2)

Images