Image forming method

Abstract

To provide an image forming method which can elongate lifetime of a photoreceptor and improve image quality.SOLUTION: An image forming method disclosed herein comprises forming a toner image on a surface of a charged photoreceptor using electrostatic image developing two-component developer comprising a carrier and toner, and transferring the formed toner image, where the carrier includes strontium titanate particles on an outermost surface or in a surface layer, and the photoreceptor contains a polyarylate resin in a surface layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming method. [Background technology]

[0002] In a photoreceptor used in general electrophotographic image formation, after electrostatic image developing toner (hereinafter also simply referred to as "toner") is transferred to a recording medium, the toner remaining on the surface of the photoreceptor is removed by a cleaning blade. Even if the toner adheres firmly to the surface of the photoreceptor, the cleaning blade can remove the toner by scraping off a very small area of ​​the surface of the photoreceptor.

[0003] In order to extend the life of photoreceptors used in this way, the use of resins with high mechanical strength in the photoreceptor has been considered. By using a photoreceptor containing a resin with high mechanical strength, wear is suppressed and durability is improved.

[0004] For example, Patent Document 1 discloses an electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer, the photosensitive layer being a single layer, the photosensitive layer containing a binder resin having a polyarylate resin with a specific structure, and the hole transport agent having one nitrogen atom. Such an electrophotographic photoreceptor is said to be capable of forming a good photosensitive layer, suppressing transfer memory, and having excellent abrasion resistance, filming resistance, and scratch resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-181419 Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to the findings of the present inventors, the electrophotographic photosensitive member described in Patent Document 1 leaves something to be desired in terms of achieving both a long life of the photosensitive member and good image quality.

[0007] SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming method that can extend the life of a photoreceptor and improve image quality. [Means for solving the problem]

[0008] One aspect of the present invention for solving the above problems relates to an image forming method described in the following [1] to [8].

[0009] [1] A step of forming a toner image on a surface of a charged photoreceptor using a two-component developer for developing electrostatic images, the two-component developer including a carrier and a toner; and transferring the formed toner image. the carrier contains strontium titanate particles on the outermost surface or in a surface layer thereof, The photoreceptor contains a polyarylate resin in a surface layer. Image forming method.

[0010] [2] The carrier contains magnetic particles; The carrier may include a resin coating layer made of a resin that coats the surfaces of the magnetic particles, the carrier contains the strontium titanate particles attached to the surface of the magnetic particles or the resin coating layer; [1] The image forming method according to [1].

[0011] [3] The carrier includes magnetic particles and a resin coating layer made of a resin that coats the surfaces of the magnetic particles, The resin coating layer contains the strontium titanate particles. [1] The image forming method according to [1].

[0012] [4] The carrier includes magnetic particles, a resin coating layer made of resin that coats the surfaces of the magnetic particles, and the strontium titanate particles that are attached to the surface of the resin coating layer, The resin coating layer contains the strontium titanate particles. [1] The image forming method according to [1].

[0013] [5] The toner is applied to the surface of the photoreceptor via a developing roller to which a developing bias in which an AC component is superimposed on a DC component is applied. The image forming method according to any one of [1] to [4].

[0014] [6] The toner contains wax, the amount of the wax added is 2.0% by mass to 30.0% by mass with respect to the total mass of the toner; The image forming method according to any one of [1] to [5].

[0015] [7] The polyarylate resin contains a structural unit represented by the following general formula (1) and / or a structural unit represented by the following general formula (2): The image forming method according to any one of [1] to [6].

[0016] [ka]

[0017] [ka]

[0018] [8] The strontium titanate particles are lanthanum-doped strontium titanate. The image forming method according to any one of [1] to [7]. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide an image forming method that can extend the life of a photoreceptor and improve image quality. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic cross-sectional view illustrating an example of a photoreceptor. [Figure 2] FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus. [Figure 3] FIG. 2 is a cross-sectional view showing a part of the structure of the imaging unit. [Figure 4] FIG. 3 is a cross-sectional view showing the arrangement of magnetic poles in a magnet roller included in the developing roller. DETAILED DESCRIPTION OF THE INVENTION

[0021] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0022] 1. Image forming method The image forming method according to this embodiment includes: forming a toner image on the surface of a charged photoreceptor using a two-component developer for developing an electrostatic image, the two-component developer including a carrier and a toner; and transferring the formed toner image. the carrier contains strontium titanate particles on the outermost surface or in a surface layer thereof, The photoreceptor contains a polyarylate resin in the surface layer.

[0023] Polyarylate resins contain a rigid aromatic ring structure in the main chain, which tends to increase hardness. Therefore, in photoreceptors containing polyarylate resins in the surface layer, the cleaning blade is more likely to be prevented from penetrating too deeply, as described above, and wear is suppressed when scraping off extremely small areas on the surface of the photoreceptor. This is thought to result in a longer life for the photoreceptor.

[0024] However, when toner or the like adheres firmly to the surface of the photoreceptor due to the suppression of photoreceptor wear, there are cases where the cleaning blade is unable to scrape off the photoreceptor surface (toner). In such cases, the adhered matter on the photoreceptor may be transferred to a recording medium, cause poor charging of the photoreceptor, or cause a thin layer of toner to adhere to the surface of the photosensitive layer (hereinafter also referred to as "filming"), which can result in a deterioration in image quality.

[0025] The reason why the above-mentioned image forming method, using a photoreceptor containing a polyarylate resin in the surface layer, can achieve both a longer photoreceptor life and improved image quality is not entirely clear, but is thought to be as follows.

[0026] In an image forming method using a two-component developer for developing electrostatic images, an electrostatic image formed on the surface of a photoconductor is developed into a toner image, for example, as follows. In the development process, the two-component developer for developing electrostatic images is supplied to the outer peripheral surface of a developing roller arranged near the photoconductor. A magnet is built into the developing roller, and the carrier forms a magnetic brush on the developing roller. The toner adhering to the magnetic brush adheres to the electrostatic image formed on the surface of the photoconductor, thereby developing the toner image on the photoconductor.

[0027] At this time, when the magnetic brush formed by the carrier on the developing roller comes into contact with the surface of the photosensitive member, it abrades the photosensitive member, causing an abrasive action that removes deposits on the photosensitive member.

[0028] Furthermore, when the toner is charged, the toner and the carrier are mixed and stirred. If the toner and the carrier come into contact with each other, components contained in the toner may adhere to the carrier, contaminating it. Furthermore, if contaminated carriers come into contact with each other, an abrasive action occurs between the carriers, removing the contaminants, such as the components of the toner, that have adhered to the carrier. If the toner contamination and the carrier abrasion are repeated and the toner contamination becomes dominant, the electrical properties of the carrier change, resulting in problems such as variations in the electrical properties within the carrier or failure to obtain the desired electrical properties.

[0029] The effects of the above-mentioned abrasive action of the carrier on the surface of the photoreceptor and the abrasive action of the carrier particles themselves vary greatly depending on the type of carrier used.

[0030] The image forming method uses a carrier containing strontium titanate particles. Strontium titanate particles have a perovskite crystal structure and tend to have a cubic or rectangular parallelepiped shape. A cubic or rectangular parallelepiped shape provides a larger surface area per volume than a spherical shape, significantly increasing the abrasive action on the photoreceptor surface when contacting the surface, as well as the abrasive action between carrier particles. This is thought to facilitate the abrasion and removal of adhesion areas on the photoreceptor that could not be completely removed by a cleaning blade, as well as suppressing contamination adhering to the carrier surface, improving the carrier's charging stability, and facilitating improved image quality.

[0031] It is believed that the above-mentioned factors contribute to achieving both a longer life of the photosensitive member and high image quality.

[0032] Furthermore, as image forming devices have become smaller in recent years, each component has been densely packed, resulting in a narrower heat dissipation area and a narrower heat dissipation path. Furthermore, as image forming devices become faster, the processing speed of elements and motors increases, which tends to increase the amount of heat generated. This can lead to heat buildup within the image forming device, which can easily increase the temperature near the photoreceptor, making it easier for toner to fuse to the photoreceptor. Therefore, in image forming devices that are smaller and / or faster, significant degradation in image quality can occur. The image forming method according to this embodiment has the remarkable effect of improving image quality even in such image forming devices that are smaller and / or faster.

[0033] 1-1. Two-component developer for electrostatic image development The two-component developer for developing electrostatic images according to this embodiment contains a carrier and a toner.

[0034] 1-1-1. Toner The toner according to the present embodiment contains a binder resin, and may also contain a colorant, a release agent, other additives, and external additives.

[0035] 1-1-1-1. Binder resin The binder resin according to this embodiment preferably contains an amorphous polyester resin and a crystalline polyester resin.

[0036] The term "crystalline resin" refers to a resin that has a clear endothermic peak when measured by differential scanning calorimetry (DSC). A "clear endothermic peak" refers to an endothermic peak whose half-width is within 10°C when measured by DSC at a heating rate of 10°C / min.

[0037] On the other hand, "the resin is amorphous" means that the half-width of the endothermic peak measured under the above conditions exceeds 10°C, or no clear endothermic peak is observed.

[0038] 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, relative to the total mass of the toner. In this specification, the term "total mass of the toner" refers to the total mass of the toner particles, not including external additives, and the same applies hereinafter.

[0039] 1-1-1-1-1.Amorphous polyester resin The content of the amorphous polyester resin is preferably in the range of 50% by mass to 88% by mass (more preferably 60% by mass to 80% by mass) relative to the total binder resin.

[0040] Examples of the amorphous polyester resin include a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. Note that, as the amorphous polyester resin, a commercially available product or a synthesized product may be used.

[0041] Examples of polycarboxylic acids include: aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.); Alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), Aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), Anhydrides of these or lower (e.g., carbon number 1 to 5) alkyl esters of these Among these, the polycarboxylic acid is preferably, for example, an aromatic dicarboxylic acid.

[0042] 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 (e.g., C1 to C5) alkyl esters thereof.

[0043] The polycarboxylic acids may be used alone or in combination of two or more.

[0044] 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.), Aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.) Examples include:

[0045] 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.

[0046] The polyhydric alcohols may be used alone or in combination of two or more.

[0047] The glass transition temperature (Tg) of the amorphous polyester resin is preferably from 50°C to 80°C, more preferably from 50°C to 65°C.

[0048] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K-7121:1987 "Method for measuring transition temperature of plastics."

[0049] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 to 1,000,000, and more preferably 7,000 to 500,000.

[0050] The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 to 100,000.

[0051] The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5-100, more preferably 2-60.

[0052] 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.

[0053] In this embodiment, two or more types of amorphous polyester resins may be used in combination. In this case, the absolute value of the difference in SP value between the amorphous polyester resin showing the largest SP value and the amorphous polyester resin showing the smallest SP value is preferably 0.25 or less, more preferably 0.01 to 0.25, and even more preferably 0.10 to 0.25. If the absolute value of the difference in SP value is 0.25 or less, it is possible to adjust the compatibility between the crystalline polyester resin and the amorphous polyester resin within an appropriate range.

[0054] The amorphous polyester resin can be obtained by a known manufacturing method, for example, by carrying out the reaction at a polymerization temperature of 180°C to 230°C, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation.

[0055] 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.

[0056] In this embodiment, an example of a method for adjusting the SP value of the amorphous polyester resin is to select the types of polycarboxylic acid and polyhydric alcohol that constitute the amorphous polyester resin so that the SP value of the amorphous polyester resin becomes a desired value.

[0057] 1-1-1-1-2.Crystalline polyester resin The crystalline polyester resin may be, for example, a polycondensate of a polycarboxylic acid and a polyhydric alcohol. Note that, as the crystalline polyester resin, a commercially available product or a synthesized product may be used.

[0058] Here, the crystalline polyester resin is preferably a polycondensate using a polymerizable monomer having a linear aliphatic group rather than a polymerizable monomer having an aromatic group, since it easily forms a crystalline structure.

[0059] Examples of polycarboxylic acids include: aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.); Aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalene-2,6-dicarboxylic acid), Anhydrides of these or lower (e.g., carbon number 1 to 5) alkyl esters of these etc.

[0060] The polycarboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid.

[0061] Examples of tricarboxylic acids include: aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.); Anhydrides of these or lower alkyl esters (e.g., having 1 to 5 carbon atoms) of these Examples include:

[0062] As the polycarboxylic acid, a dicarboxylic acid having a sulfonic acid group and a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids.

[0063] The polycarboxylic acids may be used alone or in combination of two or more.

[0064] Examples of polyhydric alcohols include aliphatic diols (for example, straight-chain aliphatic diols having 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol. Among these, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols.

[0065] The polyhydric alcohol may be a trihydric or higher alcohol having a crosslinked or branched structure, such as glycerin, trimethylolethane, trimethylolpropane, or pentaerythritol, in combination with the diol.

[0066] The polyhydric alcohols may be used alone or in combination of two or more.

[0067] Here, the polyhydric alcohol has an aliphatic diol content of 80 mol % or more, preferably 90 mol % or more.

[0068] The melting temperature of the crystalline polyester resin is preferably 60 to 80°C, more preferably 62 to 78°C, and even more preferably 64 to 76°C.

[0069] If the melting temperature of the crystalline polyester resin is 60° C. or higher, the thermal storage stability is further improved. If the melting temperature of the crystalline polyester resin is 80° C. or lower, the low-temperature fixability is further improved.

[0070] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining melting temperature in JIS K7121:1987 (Method for measuring transition temperatures of plastics).

[0071] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 10,000 to 45,000.

[0072] The crystalline polyester resin can be obtained by a known manufacturing method, for example, in the same manner as the amorphous polyester resin.

[0073] In this embodiment, a method for adjusting the SP value of the crystalline polyester resin includes selecting the types of polycarboxylic acid and polyhydric alcohol that constitute the crystalline polyester resin so that the SP value of the crystalline polyester resin becomes a desired value.

[0074] 1-1-1-1-3. Other resins In this embodiment, resins other than amorphous polyester resins and crystalline polyester resins may be used as the binder resin. Examples of other binder resins include vinyl resins made of 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.), or copolymers of two or more of these monomers.

[0075] Examples of binder resins include: Non-vinyl resins such as epoxy resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosins, a mixture of these with the vinyl resin; or a graft polymer obtained by polymerizing a vinyl monomer in the presence of these. Other examples include:

[0076] These other binder resins may be used alone or in combination of two or more.

[0077] In this embodiment, a styrene-(meth)acrylic copolymer resin may be used as the other binder resin. By using a styrene-(meth)acrylic copolymer resin as the other binder resin, fixing properties such as hot offset and heat storage properties are further improved.

[0078] When a styrene-(meth)acrylic copolymer resin is used as the other binder resin, the proportion of the styrene-(meth)acrylic copolymer resin in the binder resin is preferably 5% by mass to 25% by mass. The proportion of the styrene-(meth)acrylic copolymer resin in the binder resin is more preferably 5% by mass to 20% by mass, and even more preferably 10% by mass to 15% by mass. If the proportion of the styrene-(meth)acrylic copolymer resin in the binder resin is 5% by mass or more, fixing properties such as hot offset and heat storage stability are further improved. If the proportion of the styrene-(meth)acrylic copolymer resin in the binder resin is 25% by mass or less, low-temperature fixing properties are further improved.

[0079] In this embodiment, (meth)acrylic means acrylic or methacrylic.

[0080] The styrene-(meth)acrylic copolymer resin can be synthesized by various polymerization methods, such as solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. The polymerization reaction can be carried out by known procedures such as batch, semi-continuous, and continuous polymerization.

[0081] 1-1-1-2. Coloring agents 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.

[0082] The colorant may be used alone or in combination of two or more kinds.

[0083] 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.

[0084] The content of the colorant is, for example, preferably 1% by mass to 30% by mass, and more preferably 3% by mass to 15% by mass, relative to the total mass of the toner.

[0085] 1-1-1-3. Release agent Examples of the release agent include: hydrocarbon waxes; Natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; Ester waxes such as fatty acid esters and montanic acid esters; The release agent is not limited to these.

[0086] The melting temperature of the release agent is preferably 50 to 110°C, more preferably 60 to 100°C.

[0087] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) using the "melting peak temperature" described in the method for determining melting temperature in JIS K-7121:1987 (Method for measuring transition temperatures of plastics).

[0088] The content of the release agent is, for example, preferably 2.0% by mass to 30.0% by mass, and more preferably 5.0% by mass to 15.0% by mass, relative to the total mass of the toner. If the content is 2.0% by mass or more, the toner is more likely to separate from the photoreceptor, etc., and image quality (white voids) is more likely to improve. If the content is 30.0% by mass or less, the wax particles tend to aggregate, which makes it easier to prevent dirt from adhering to the photoreceptor, and dirt on the photoreceptor is more likely to be removed, and image quality (white voids) is more likely to improve.

[0089] 1-1-1-4. Other additives Examples of other additives include magnetic materials, charge control agents, inorganic powders, etc. These additives may be contained in the toner particles as internal additives, or may be attached to the surfaces of the toner particles as external additives.

[0090] 1-1-1-5.External additives Examples of external additives include inorganic particles, such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc.

[0091] The surfaces of inorganic particles as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more.

[0092] The amount of the hydrophobic treatment agent is usually, for example, 1% by mass to 10% by mass with respect to 100% by mass of the inorganic particles.

[0093] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0094] The amount of the external additive is, for example, preferably 0.01% by mass to 5% by mass, and more preferably 0.01% by mass to 3% by mass, relative to the total mass of the toner. As mentioned above, in this specification, the term "total mass of the toner" refers to the total mass of the toner particles, and means the mass excluding the external additive.

[0095] 1-1-1-6. Toner characteristics 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.

[0096] 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.

[0097] The volume average particle size (D50v) of the toner particles is preferably from 2 μm to 10 μm, and more preferably from 4 μm to 8 μm.

[0098] 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).

[0099] 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.

[0100] The electrolyte solution containing the suspended sample was dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles in the range of 2 μm to 60 μm was measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled was 50,000.

[0101] 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 particle size side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v and number particle size D16p. Similarly, the particle size at 50% of the cumulative total is defined 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 number particle size D84p.

[0102] Using these, the volume average particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 The number average particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 It is calculated as:

[0103] The shape factor SF-1 of the toner particles is preferably 110 to 150, and more preferably 120 to 140.

[0104] The shape factor SF-1 is calculated by the following formula. Formula: SF-1 = (ML 2 / A)×(π / 4)×100 In the above formula, ML represents the absolute maximum length of the toner, and A represents the projected area of ​​the toner.

[0105] Specifically, the shape factor SF-1 is primarily quantified by analyzing a microscope image or a scanning electron microscope (SEM) image using an image analyzer, and is calculated as follows: an optical microscope image of particles scattered on the surface of a glass slide is captured by a video camera into a Luzex image analyzer, the maximum length and projected area of ​​100 particles are determined, and the average value is calculated using the above formula.

[0106] 1-1-1-7. Toner manufacturing method The toner according to this exemplary embodiment is obtained by producing toner particles and then externally adding an external additive to the toner particles.

[0107] 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.

[0108] Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

[0109] Specifically, for example, when toner particles are produced by the aggregation and coalescence method, (a) a step of preparing a resin particle dispersion in which resin particles to be a binder resin are dispersed (a resin particle dispersion preparation step); (b) a step of aggregating resin particles (and other particles, if necessary) in a resin particle dispersion (in a dispersion after mixing other particle dispersions, if necessary) to form aggregated particles (aggregated particle forming step); (c) 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 (a fusion and coalescence step); Toner particles are produced through the above steps.

[0110] Each step will be described in detail below.

[0111] However, the coloring agent and the releasing agent are used as needed. Of course, additives other than the coloring agent and the releasing agent may also be used.

[0112] 1-1-1-7-1. (a) Resin particle dispersion liquid 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.

[0113] Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

[0114] Examples of the dispersion medium used in the resin particle dispersion include aqueous media.

[0115] 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.

[0116] As surfactants, For example, anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soap-based surfactants; Cationic surfactants such as amine salts and quaternary ammonium salts; Non-ionic surfactants such as polyethylene glycol, alkylphenol ethylene oxide adducts, and polyhydric alcohols etc.

[0117] Among these, anionic surfactants and cationic surfactants are particularly preferred. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants.

[0118] The surfactants may be used alone or in combination of two or more.

[0119] 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.

[0120] The phase inversion emulsification method is as follows: The resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize it, and then an aqueous medium (W phase) is added. This causes the resin to change from W / O to O / W (so-called phase inversion), forming a discontinuous phase, and the resin is dispersed in the aqueous medium in the form of particles.

[0121] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm to 1 μm, more preferably 0.08 μm to 0.8 μm, and even more preferably 0.1 μm to 0.6 μm.

[0122] The volume average particle size of the resin particles is determined by the particle size distribution obtained by measurement using a laser diffraction particle size distribution analyzer (e.g., HORIBA, Ltd. LA-700). For each divided particle size range (channel), the cumulative distribution is calculated from the smallest 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.

[0123] The content of the resin particles contained in the resin particle dispersion is, for example, preferably 5% by mass to 50% by mass, and more preferably 10% by mass to 40% by mass.

[0124] 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.

[0125] 1-1-1-7-2. (b) Aggregate particle formation process Next, the colorant particle dispersion and the release agent particle dispersion are mixed together with the resin particle dispersion.

[0126] 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.

[0127] Specifically, for example, an aggregating agent is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to an acidic value (for example, a pH of 2 to 5) as needed, and a dispersion stabilizer is added as needed. Thereafter, the mixed dispersion is heated to the glass transition temperature of the resin particles (specifically, for example, the glass transition temperature of amorphous polyester resin particles −30°C to −10°C), and the particles dispersed in the mixed dispersion are aggregated to form aggregated particles.

[0128] In the aggregated 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 to 5), and a dispersion stabilizer may be added as necessary, followed by the heating.

[0129] Examples of the flocculant include surfactants having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, such as inorganic metal salts and divalent or higher metal complexes. 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.

[0130] 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.

[0131] 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; Inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide etc.

[0132] 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.

[0133] The amount of the chelating agent added is, for example, preferably 0.01% by mass to 5.0% by mass, and more preferably 0.1% by mass to 3.0% by mass, relative to 100% by mass of the resin particles.

[0134] 1-1-1-7-3. (c) Fusion / coalescence 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°C or higher than the glass transition temperature of the amorphous polyester resin particles) to fuse and coalesce the aggregated particles, thereby forming toner particles.

[0135] Through the above steps, toner particles are obtained.

[0136] a step of further mixing the aggregated particle dispersion liquid with a resin particle dispersion liquid in which resin particles are dispersed, after obtaining the aggregated particle dispersion liquid in which the aggregated particles are dispersed, and aggregating the resin particles so that the resin particles are further attached to the surfaces of the aggregated particles to form second aggregated particles; a step of heating the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, thereby forming toner particles having a core / shell structure; The toner particles may be produced through the above steps.

[0137] 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.

[0138] In the washing step, it is preferable to carry out sufficient displacement washing with ion-exchanged water from the viewpoint of chargeability. 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. The drying step is also not particularly limited, but from the viewpoint of productivity, it is preferable to carry out freeze drying, flash jet drying, fluidized bed drying, vibration fluidized bed drying, etc.

[0139] In this embodiment, after the toner particles are prepared, the toner particles may be subjected to an annealing treatment under predetermined temperature and heating time conditions. As a result, the storage modulus G' (after thermal storage) at a temperature of X'°C may be increased to 1.0 x 10 8 Pa ~ 5.0 × 10 8 The physical properties of the toner particles may be adjusted so that the Pa is equal to or greater than the predetermined value.

[0140] The toner according to this embodiment is produced by, for example, adding an external additive to the obtained dry toner particles and mixing them. The mixing can be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, or the like. Furthermore, if necessary, coarse particles may be removed from the toner using a vibrating separator, an air separator, or the like.

[0141] 1-1-2. Career The carrier according to the present embodiment may include magnetic particles and a resin layer (hereinafter simply referred to as a "resin coating layer") that coats the magnetic particles. The carrier may also have fine particles attached to the outermost surface of the carrier (hereinafter, the fine particles attached to the outermost surface of the carrier may also be referred to as "external particles"). For example, when the carrier is composed of magnetic particles and external particles (when a resin coating layer is not included), inorganic particles may be attached to the surface of the magnetic particles. When the carrier is composed of magnetic particles, a resin coating layer, and external particles, inorganic particles may be attached to the surface of the resin coating layer.

[0142] The carrier according to this embodiment contains strontium titanate particles on the outermost surface or in the surface layer.

[0143] In this specification, the phrase "containing strontium titanate particles on the outermost surface" means that the external particles contain strontium titanate particles.

[0144] In this specification, the phrase "containing strontium titanate particles in the surface layer" refers to the presence of strontium titanate particles in the components constituting the outermost layer of the carrier, excluding externally added particles. For example, when the resin coating layer has a multi-layer structure of two or more layers, it is sufficient that the strontium titanate particles are contained in at least the outermost layer of the resin coating layer.

[0145] The strontium titanate particles may be contained in either the external particles or the resin coating layer. When the strontium titanate particles are contained in either the external particles or the resin coating layer, the carrier particles are more likely to exhibit a polishing effect with each other, which reduces the occurrence of variations in the electrical properties of the carrier, facilitates stable transfer of the toner to the photoreceptor, etc., and makes it easier to suppress toner scattering.

[0146] The externally added particles preferably contain strontium titanate particles, since the abrasive action of the carrier on the photoreceptor surface and the abrasive action of the carriers themselves are more likely to be exerted at the beginning of continuous printing, thereby improving image quality at the beginning of continuous printing. Furthermore, the resin coating layer preferably contains strontium titanate particles, since the abrasive action of the carrier on the photoreceptor surface and the abrasive action of the carriers themselves are more likely to be exerted even after a certain amount of continuous printing, thereby improving image quality after a certain amount of continuous printing. Alternatively, only the externally added particles may contain strontium titanate particles, which makes it easier to improve image quality at the beginning of continuous printing, and also makes the abrasive action of the photoreceptor surface milder after a certain amount of continuous printing, thereby improving the durability of the photoreceptor.

[0147] From the viewpoint of easily improving both the image quality at the beginning of continuous printing and the image quality after a certain amount of continuous printing, it is more preferable that the strontium titanate particles are contained in both the external additive particles and the resin coating layer.

[0148] 1-1-2-1.Magnetic particles The magnetic particles are not particularly limited, and known magnetic particles used as a core material of a carrier can be used. Specific examples of the magnetic particles include particles of magnetic metals such as iron, nickel, and cobalt; particles of magnetic oxides such as ferrite and magnetite; resin-impregnated magnetic particles in which porous magnetic powder is impregnated with resin; and magnetic powder-dispersed resin particles in which magnetic powder is dispersed in resin.

[0149] In this embodiment, ferrite particles are suitable as the magnetic particles.

[0150] In this embodiment, the ferrite particles preferably contain at least one selected from calcium oxide and strontium oxide. Calcium oxide and strontium oxide are easily contained on the surface of ferrite particles. Therefore, the presence of calcium element or strontium element on the surface of ferrite particles suppresses charge leakage from the ferrite particles, making it easier for the carrier surface to be relatively highly charged. This carrier suppresses low charge of the toner in the developer, thereby further suppressing fogging and improving thin line reproducibility (e.g., suppressing thickening, crushing, or blurring of thin lines). This effect is particularly noticeable when forming a low-density image of the same color after repeatedly forming a high-density, monochromatic image at a higher speed.

[0151] The ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of calcium and strontium is preferably 0.1% by mass to 2.0% by mass relative to the total mass of the ferrite particles. When the total content of calcium and strontium is 0.1% by mass or more relative to the total mass of the ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the total content of calcium and strontium is 2.0% by mass or less relative to the total mass of the ferrite particles, the crystal structure of the ferrite particles is well-ordered, and the resistivity and magnetic susceptibility fall within appropriate ranges. As a result, fogging is further suppressed, and thin line reproducibility is improved (for example, thickening, crushing, or blurring of thin lines is suppressed).

[0152] The contents of calcium and strontium contained in the ferrite particles are measured by X-ray fluorescence analysis. The X-ray fluorescence analysis of the ferrite particles is performed by the following method.

[0153] Qualitative and quantitative analysis is performed using an X-ray fluorescence analyzer (Shimadzu Corporation, XRF1500) under the following conditions: X-ray output: 40 V / 70 mA, measurement area: 10 mm diameter, measurement time: 15 minutes. The elements to be analyzed are selected based on the elements detected in the qualitative analysis. The main elements selected are iron (Fe), manganese (Mn), magnesium (Mg), calcium (Ca), strontium (Sr), oxygen (O), and carbon (C). The mass percentage (%) of each element is calculated by referring to separately prepared calibration curve data.

[0154] The volume average particle size of the magnetic particles is, for example, 10 μm to 500 μm, preferably 20 μm to 180 μm, and more preferably 25 μm to 60 μm.

[0155] The magnetic force of the magnetic particles is, for example, 50 emu / g or more, preferably 60 emu / g or more, in terms of saturation magnetization in a magnetic field of 3000 oersteds. The saturation magnetization is measured using a vibrating sample magnetometer VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.). The measurement sample is placed in a cell with an inner diameter of 7 mm and a height of 5 mm and set in the instrument. The measurement is performed by applying a magnetic field and sweeping up to a maximum of 3000 oersteds. The applied magnetic field is then reduced, and a hysteresis curve is created on recording paper. The saturation magnetization, remanent magnetization, and coercive force are determined from the curve data.

[0156] The volume resistivity of the magnetic particles is, for example, 10 5 Ω·cm~10 9 Ω cm, 10 7 Ω·cm~10 9 Ω·cm is preferred.

[0157] The volume resistivity (Ω·cm) of magnetic particles is measured as follows: 2 The object to be measured is placed flat on the surface of the circular jig on which the electrode plate is arranged, so that the thickness of the object to be measured is 1 mm to 3 mm, and a layer is formed on top of this. 2 The layer is sandwiched between two electrode plates. To eliminate any gaps between the objects being measured, a 4 kg load is placed on the electrode plates placed on the layer, and then the layer thickness (cm) is measured. The electrodes above and below the layer are connected to an electrometer and a high-voltage power supply generator. A high voltage is applied to both electrodes so that the electric field becomes 103.8 V / cm, and the current value (A) that flows at this time is read. The measurement environment is a temperature of 20°C and a humidity of 50% RH. The formula for calculating the volume electrical resistivity (Ω·cm) of the object being measured is as shown below. R=E×20 / (I-I0) / L

[0158] In the above formula, R represents the volume electrical resistance (Ω·cm) of the object to be measured, E represents the applied voltage (V), I represents the current value (A), I0 represents the current value (A) at an applied voltage of 0 V, and L represents the layer thickness (cm). The coefficient 20 is the area of ​​the electrode plate (cm 2 )

[0159] 1-1-2-2.Resin coating layer Examples of resins that make up the resin coating layer include styrene-acrylic acid copolymers; polyolefin resins such as polyethylene and polypropylene; polyvinyl or polyvinylidene resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymers; straight silicone resins or modified silicone resins consisting of organosiloxane bonds; fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; and epoxy resins.

[0160] The resin coating layer may contain inorganic particles for the purpose of controlling charging, resistance, abrasive action of the carrier on the photoreceptor surface, and abrasive action between carriers.

[0161] Examples of inorganic particles include: strontium titanate particles, as described below; Carbon black; Metals such as gold, silver, copper, etc.; metal compounds such as barium sulfate, aluminum borate, potassium titanate, titanium oxide, zinc oxide, tin oxide, antimony-doped tin oxide, tin-doped indium oxide, and aluminum-doped zinc oxide; metal-coated resin particles; Examples include:

[0162] Methods for forming a resin coating layer on the surface of magnetic particles include, for example, a wet method and a dry method. The wet method is a method that uses a solvent to dissolve or disperse the resin that constitutes the resin coating layer. On the other hand, the dry method is a method that does not use the solvent.

[0163] Examples of wet manufacturing methods include: A dipping method in which magnetic particles are dipped into a resin liquid for forming a resin coating layer to coat them; A spray method in which a resin liquid for forming a resin coating layer is sprayed onto the surface of magnetic particles; A fluidized bed method in which magnetic particles are fluidized in a fluidized bed and a resin liquid for forming a resin coating layer is sprayed onto the particles; a kneader-coater method in which magnetic particles and a resin liquid for forming a resin coating layer are mixed in a kneader-coater and the solvent is removed; Examples include:

[0164] The resin liquid for forming the resin coating layer used in the wet manufacturing method is prepared by dissolving or dispersing the resin and other components in a solvent.

[0165] The solvent is not particularly limited as long as it dissolves or disperses the resin, and examples thereof include: Aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; Alcohols such as methanol etc. are used.

[0166] An example of a dry manufacturing method is a method in which a mixture of magnetic particles and a resin for forming a resin coating layer is heated in a dry state to form a resin coating layer. Specifically, for example, the magnetic particles and the resin for forming the resin coating layer are mixed in a gas phase and heated to melt, thereby forming a resin coating layer.

[0167] The thickness of the resin coating layer is preferably 0.1 μm to 10 μm, and more preferably 0.3 μm to 5 μm.

[0168] The exposed surface ratio of the magnetic particles on the resin-coated magnetic particles is preferably 2% to 20%, more preferably 2% to 10%, and even more preferably 3% to 8%.

[0169] The exposed ratio of the magnetic particles on the surface of the resin-coated magnetic particles is determined by X-ray photoelectron spectroscopy (XPS) using the following method.

[0170] The target resin-coated magnetic particles and magnetic particles obtained by removing the resin coating layer from the target resin-coated magnetic particles are prepared. Methods for removing the resin coating layer from the resin-coated magnetic particles include, for example, a method of removing the resin coating layer by dissolving the resin component in an organic solvent, and a method of removing the resin coating layer by heating at about 800°C. The resin-coated magnetic particles and the magnetic particles from which the resin coating layer has been removed are each used as measurement samples, and Fe (atomic %) is quantified using XPS. (Fe in resin-coated magnetic particles) ÷ (Fe in magnetic particles) × 100 is calculated and used as the exposed ratio (%) of magnetic particles.

[0171] The exposed ratio of the magnetic particles on the surface of the resin-coated magnetic particles can be controlled by the amount of resin used to form the resin coating layer, and the greater the amount of resin relative to the amount of magnetic particles, the smaller the exposed ratio.

[0172] 1-1-2-3. Externally added particles Examples of the external particles include inorganic particles, such as strontium titanate particles, SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc.

[0173] The surfaces of inorganic particles as externally added 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, but 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.

[0174] The amount of the hydrophobic treatment agent is usually, for example, 1% by mass to 10% by mass with respect to 100% by mass of the inorganic particles.

[0175] Examples of externally added 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).

[0176] 1-1-2-4. Strontium titanate particles The content of strontium titanate particles contained in the carrier according to this embodiment is preferably 0.01% by mass to 0.8% by mass, more preferably 0.01% by mass to 0.5% by mass, even more preferably 0.02% by mass to 0.2% by mass, and even more preferably 0.04% by mass to 0.1% by mass, relative to the mass of the resin-coated magnetic particles. When the content of strontium titanate particles is 0.01% by mass or more relative to the mass of the resin-coated magnetic particles, the carrier can more easily abrade the photoreceptor surface and the carrier particles themselves, thereby improving image quality. When the content of strontium titanate particles is 0.8% by mass or less relative to the mass of the resin-coated magnetic particles, the photoreceptor surface is not excessively abraded, thereby extending the life of the photoreceptor. The content of strontium titanate particles contained in the carrier refers to the sum of the content of strontium titanate particles contained in the resin coating layer and the content of strontium titanate particles contained in the external additive particles.

[0177] When the resin coating layer contains strontium titanate particles, the content of the strontium titanate particles is preferably 0.1 mass % to 30 mass %, more preferably 0.1 mass % to 10 mass %, relative to the total mass of the resin coating layer.

[0178] When the external particles contain strontium titanate particles, the content of the strontium titanate particles is preferably 20% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, based on the total mass of the external particles.

[0179] 1-1-2-4-1. Characteristics of strontium titanate particles In this embodiment, the strontium titanate particles preferably have an average primary particle size of 10 nm to 100 nm. If the average primary particle size of the strontium titanate particles is 10 nm or more, when the strontium titanate particles are contained in a resin coating layer, embedding of the resin-coated magnetic particles in the resin coating layer is easily suppressed, and when the strontium titanate particles are contained as externally added particles, highly uniform dispersion on the surface of the resin-coated magnetic particles is easily achieved. If the average primary particle size of the strontium titanate particles is 100 nm or less, separation from the carrier is suppressed, and the electrical properties of the strontium titanate particles can relatively highly charge the carrier surface, making it easier to improve image quality.

[0180] From the same viewpoint, the average primary particle size of the strontium titanate particles is more preferably 20 to 90 nm, even more preferably 30 to 80 nm, and most preferably 30 to 60 nm. By setting the particle size to 60 nm or less, the electrical properties of the carrier tend to be stable, and the migration of the toner to the photoreceptor and the like tends to be stable, which tends to improve not only the image quality but also toner scattering.

[0181] In this embodiment, the primary particle size of the strontium titanate particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of the strontium titanate particles is the particle size that is the cumulative 50% from the smallest diameter side in the number-based distribution of primary particle sizes. The primary particle size of the strontium titanate particles is determined by image analysis of at least 300 strontium titanate particles.

[0182] The average primary particle size of the strontium titanate particles can be controlled, for example, by adjusting various conditions when producing the strontium titanate particles by a wet process.

[0183] In this embodiment, the strontium titanate particles preferably have an average circularity of primary particles of 0.82 to 0.94, and a circularity of cumulative 84% of the primary particles of more than 0.92.

[0184] In this embodiment, the circularity of the primary particles of the strontium titanate particles is expressed as 4π × (area of ​​the primary particle image) ÷ (perimeter of the primary particle image). 2 The average circularity of primary particles is the circularity that is 50% cumulative from the smallest side in the circularity distribution, and the circularity that is 84% ​​cumulative from the smallest side in the circularity distribution of primary particles is the circularity that is 84% ​​cumulative from the smallest side in the circularity distribution. The circularity of strontium titanate particles is determined by image analysis of at least 300 strontium titanate particles.

[0185] For strontium titanate particles, the cumulative 84% circularity of the primary particles is one of the shape indicators. Cubic or rectangular strontium titanate particles have a cumulative 84% circularity of the primary particles of 0.92 or less. Rounded strontium titanate particles have a cumulative 84% circularity of the primary particles of more than 0.92.

[0186] In this embodiment, the average circularity of primary particles of the strontium titanate particles is preferably 0.82 to 0.94, more preferably 0.84 to 0.94, and even more preferably 0.86 to 0.92, from the viewpoint of suppressing the occurrence of fogging.

[0187] In this embodiment, the standard deviation of the circularity of the primary particles of the strontium titanate particles is preferably 0.04 to 2.0, more preferably 0.04 to 1.0, and even more preferably 0.04 to 0.50.

[0188] In this embodiment, the strontium titanate particles preferably have a half-width of the peak of the (110) plane obtained by X-ray diffraction of 0.2° to 2.0°, more preferably 0.2° to 1.0°.

[0189] The (110) plane peak obtained by X-ray diffraction of strontium titanate particles appears at a diffraction angle of approximately 2θ = 32°. This peak corresponds to the (110) plane peak of perovskite crystals.

[0190] In this embodiment, the half width of the peak of the (110) plane of the strontium titanate particles is preferably 0.2° to 2.0°, more preferably 0.2° to 1.0°, and even more preferably 0.2° to 0.5°.

[0191] X-ray diffraction of strontium titanate particles is measured using an X-ray diffractometer (e.g., Rigaku Corporation, trade name: RINT Ultima-III). Measurement settings are as follows: radiation source: CuKα, voltage: 40 kV, current: 40 mA, sample rotation speed: no rotation, divergence slit: 1.00 mm, divergence vertical limiting slit: 10 mm, scattering slit: open, receiving slit: open, scanning mode: FT, counting time: 2.0 seconds, step width: 0.0050°, scanning axis: 10.0000° to 70.0000°. In this disclosure, the half-width of a peak in an X-ray diffraction pattern is the full width at half maximum.

[0192] 1-1-2-4-2.Dopants In this embodiment, the strontium titanate particles are preferably doped with a metal element other than titanium and strontium (hereinafter also referred to as a dopant). By including a dopant, the strontium titanate particles can be easily shaped and can easily stabilize image quality.

[0193] The dopant for the strontium titanate particles is not particularly limited as long as it is a metal element other than titanium and strontium. A metal element having an ionic radius that can be incorporated into the crystal structure of the strontium titanate particles when ionized is preferred. From this perspective, the dopant for the strontium titanate particles is preferably a metal element having an ionic radius of 40 pm to 200 pm when ionized, more preferably a metal element having an ionic radius of 60 pm to 150 pm.

[0194] Specific examples of dopants for strontium titanate particles include lanthanoids, silica, aluminum, magnesium, calcium, barium, phosphorus, sulfur, calcium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, yttrium, zinc, niobium, molybdenum, ruthenium, rhodium, palladium, silver, indium, tin, antimony, barium, tantalum, tungsten, rhenium, osmium, iridium, platinum, and bismuth. Lanthanoids are preferably lanthanum and cerium. Among these, lanthanum is preferred from the viewpoints of ease of doping, ease of shape control of strontium titanate particles, ease of stable transfer of toner to a photoreceptor, stabilization of image quality, and ease of suppression of white spots.

[0195] As a dopant for the strontium titanate particles, a metal element having an electronegativity of 2.0 or less is preferred, and a metal element having an electronegativity of 1.3 or less is more preferred, from the viewpoint of preventing the strontium titanate particles from being excessively negatively charged. In this embodiment, the electronegativity is the Allred-Rochow electronegativity. Metal elements with an electronegativity of 2.0 or less include lanthanum (electronegativity 1.08), magnesium (1.23), aluminum (1.47), silica (1.74), calcium (1.04), vanadium (1.45), chromium (1.56), manganese (1.60), iron (1.64), cobalt (1.70), nickel (1.75), copper (1.75), zinc (1.66), gallium (1.82), yttrium (1.11), zirconium (1.22), niobium (1.23), silver (1.42), indium (1.49), tin (1.72), barium (0.97), tantalum (1.33), rhenium (1.46), and cerium (1.06).

[0196] The amount of dopant in the strontium titanate particles is preferably in the range of 0.1 mol% to 20 mol% per 100 mol of strontium, from the viewpoints of easy shape control, the ability to control the rate of wear of the photoreceptor by adjusting the contact area with the photoreceptor, and stabilizing image quality, more preferably in the range of 0.1 mol% to 15 mol%, and even more preferably in the range of 0.1 mol% to 10 mol%.

[0197] 1-1-2-4-3. Hydrophobic treatment In this embodiment, the strontium titanate particles are preferably strontium titanate particles having a hydrophobic surface, from the viewpoint of improving the function of the strontium titanate particles. It is presumed that the hydrophobic strontium titanate particles repel each other on the resin-coated magnetic particles, facilitating highly uniform dispersion.

[0198] In this embodiment, the strontium titanate particles are preferably strontium titanate particles having surfaces that have been hydrophobized with a silicon-containing organic compound. Compared with strontium titanate particles that have been hydrophobized with a treatment agent with a strong positive charge, such as a fatty acid metal salt, the strontium titanate particles are less likely to be liberated to non-image areas on the photoreceptor, and are less likely to cause image defects.

[0199] The strontium titanate particles preferably have a surface containing 1% by mass to 50% by mass (preferably 5% by mass to 40% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 10% by mass to 25% by mass) of a silicon-containing organic compound relative to the mass of the particles.

[0200] In other words, the amount of hydrophobic treatment with the silicon-containing organic compound is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, even more preferably 5% by mass to 30% by mass, and even more preferably 10% by mass to 25% by mass, relative to the mass of the strontium titanate particles.

[0201] When the amount of hydrophobic treatment is within the above range, the occurrence of fogging is easily suppressed. When the amount of hydrophobic treatment is 30 mass % or less, the occurrence of aggregates due to the hydrophobic treated surface is suppressed.

[0202] The surface of the strontium titanate particles that has been hydrophobized with a silicon-containing organic compound preferably has a mass ratio (Si / Sr) of silicon (Si) to strontium (Sr) of 0.025 to 0.25, more preferably 0.05 to 0.20. By keeping the mass ratio within this range, the function of the strontium titanate particles is easily improved. The mass ratio (Si / Sr) of silicon (Si) to strontium (Sr) is a value calculated from qualitative and quantitative analysis by X-ray fluorescence analysis.

[0203] X-ray fluorescence analysis of the hydrophobized surface of strontium titanate particles is performed using the following method. Qualitative and quantitative analysis is performed using an X-ray fluorescence analyzer (Shimadzu Corporation, XRF1500) under the following conditions: X-ray output: 40 V / 70 mA, measurement area: 10 mm diameter, measurement time: 15 minutes. The elements analyzed are oxygen (O), silicon (Si), titanium (Ti), strontium (Sr), and other metal elements (Me). The mass percentage (%) of each element is calculated by reference to separately prepared calibration curve data. The mass ratio Si / Sr is calculated from the mass percentage (%) of silicon (Si) and the mass percentage (%) of strontium (Sr) obtained from this measurement.

[0204] 1-1-2-4-4. Physical properties of strontium titanate particles In this embodiment, the strontium titanate particles preferably have a volume resistivity R (Ω·cm) of 11 to 14, more preferably 11 to 13, and even more preferably 12 to 13, in common logarithm logR.

[0205] The specific volume resistivity R of the strontium titanate particles can be controlled by, for example, the type and amount of dopant, the type and amount of hydrophobic treatment agent, the amount of hydrophobic treatment, the drying temperature and drying time after the hydrophobic treatment, and the like.

[0206] The specific volume resistivity R of the strontium titanate particles is measured as follows.

[0207] A pair of 20cm electrodes connected to an electrometer (KEYTHLEY, KEITHLEY610C) and a high voltage power supply (FLUKE, FLUKE415B) 2 Strontium titanate particles are placed on the lower electrode of the measurement jig, which is a circular electrode (made of steel), so as to form a flat layer with a thickness of 1 mm to 2 mm. The test is then conditioned for 24 hours in an environment of 22°C temperature and 55% relative humidity. Next, an upper electrode is placed on the strontium titanate particle layer in an environment of 22°C temperature and 55% relative humidity. A 4 kg weight is placed on the upper electrode to eliminate voids within the strontium titanate particle layer, and the thickness of the strontium titanate particle layer is measured in this state. A voltage of 1000 V is then applied to both electrodes to measure the current, and the specific volume resistivity R is calculated using the following formula (1): Formula (1): Volume resistivity R (Ω cm) = V × S ÷ (A1-A0) ÷ d In equation (1), V is the applied voltage of 1000 (V), S is the electrode plate area of ​​20 (cm 2 ), A1 is the measured current value (A), A0 is the initial current value (A) when the applied voltage is 0 V, and d is the thickness (cm) of the strontium titanate particle layer.

[0208] In this embodiment, the strontium titanate particles preferably have a water content of 1.5% to 10% by mass. When the water content is 1.5% to 10% by mass (more preferably 2% to 5% by mass), the resistance of the strontium titanate particles is controlled within an appropriate range, and uneven distribution due to electrostatic repulsion between the strontium titanate particles is effectively suppressed. The water content of the strontium titanate particles can be controlled, for example, by producing the strontium titanate particles by a wet method and adjusting the temperature and time of a drying treatment. When the strontium titanate particles are subjected to a hydrophobic treatment, the water content of the strontium titanate particles can be controlled by adjusting the temperature and time of a drying treatment after the hydrophobic treatment.

[0209] The moisture content of strontium titanate particles is measured as follows: 20 mg of a measurement sample is left to stand in a chamber at 22°C and 55% relative humidity for 17 hours to condition the humidity. Then, in a room at 22°C and 55% relative humidity, the sample is heated from 30°C to 250°C in a nitrogen gas atmosphere at a temperature increase rate of 30°C / min using a thermobalance (Shimadzu TGA-50) to measure the loss on heating (mass lost due to heating). The moisture content is calculated based on the measured loss on heating using the following formula: Moisture content (mass%) = (heat loss from 30°C to 250°C) ÷ (mass after humidity control before heating) × 100

[0210] 1-1-2-4-5.Method for producing strontium titanate The strontium titanate particles may be strontium titanate particles themselves, or may be strontium titanate particles (sometimes referred to as mother particles) whose surfaces have been subjected to a hydrophobic treatment. The method for producing the strontium titanate particles (mother particles) is not particularly limited, but a wet method is preferred from the viewpoint of controlling the particle size and shape.

[0211] A wet method for producing strontium titanate particles is, for example, a method in which a mixture of a titanium oxide source and a strontium source is reacted while adding an alkaline aqueous solution, followed by an acid treatment. In this production method, the particle size of the strontium titanate particles can be controlled by the mixing ratio of the titanium oxide source and the strontium source, the concentration of the titanium oxide source at the start of the reaction, the temperature and addition rate of the alkaline aqueous solution, etc.

[0212] The titanium oxide source is preferably a mineral acid peptized product of a hydrolyzed titanium compound, and the strontium source may include strontium nitrate and strontium chloride.

[0213] The mixing ratio of the titanium oxide source and the strontium source is preferably an SrO / TiO2 molar ratio of 0.9 to 1.4, more preferably 1.05 to 1.20. The concentration of the titanium oxide source in terms of TiO2 at the initial stage of the reaction is preferably 0.05 mol / L to 1.3 mol / L, more preferably 0.5 mol / L to 1.0 mol / L.

[0214] From the viewpoints of easily controlling the shape of strontium titanate particles, easily controlling the wear rate of the photoreceptor by adjusting the contact area with the photoreceptor, and easily stabilizing image quality, it is preferable to add a dopant source to a mixture of a titanium oxide source and a strontium source. Examples of dopant sources include oxides of metals other than titanium and strontium. The metal oxide used as the dopant source is added as a solution dissolved in, for example, nitric acid, hydrochloric acid, or sulfuric acid. The amount of dopant source added is preferably an amount such that the metal contained in the dopant source is 0.1 mol % to 20 mol %, more preferably 0.5 mol % to 10 mol %, per 100 mol of strontium contained in the strontium source.

[0215] The alkaline aqueous solution is preferably a sodium hydroxide aqueous solution. The higher the temperature of the reaction solution when the alkaline aqueous solution is added, the better the crystallinity of the strontium titanate particles obtained. The temperature of the reaction solution when the alkaline aqueous solution is added is preferably in the range of 60°C to 100°C, from the viewpoint of obtaining a rounded shape while maintaining a perovskite-type crystal structure. The slower the addition rate of the alkaline aqueous solution, the larger the particle size of the strontium titanate particles obtained, and the faster the addition rate, the smaller the particle size of the strontium titanate particles obtained. The addition rate of the alkaline aqueous solution is, for example, 0.001 equivalent / h to 1.2 equivalent / h relative to the charged raw materials, and 0.002 equivalent / h to 1.1 equivalent / h is appropriate.

[0216] After the addition of the alkaline aqueous solution, an acid treatment is carried out to remove unreacted strontium source. The acid treatment is carried out by adjusting the pH of the reaction solution to 2.5 to 7.0, more preferably 4.5 to 6.0, using, for example, hydrochloric acid. After the acid treatment, the reaction solution is subjected to solid-liquid separation, and the solid content is dried to obtain strontium titanate particles.

[0217] The surface treatment of strontium titanate particles is carried out, for example, by preparing a treatment liquid by mixing a silicon-containing organic compound, which is a hydrophobic treatment agent, with a solvent, and then mixing the strontium titanate particles with the treatment liquid under stirring, and continuing to stir. After the surface treatment, a drying treatment is carried out to remove the solvent from the treatment liquid.

[0218] Examples of the silicon-containing organic compound used for the surface treatment of the strontium titanate particles include alkoxysilane compounds, silazane compounds, and silicone oils.

[0219] Examples of alkoxysilane compounds used for the surface treatment of strontium titanate particles include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxy ... Examples include ethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; trimethylmethoxysilane, trimethylethoxysilane.

[0220] Examples of the silazane compound used for the surface treatment of strontium titanate particles include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, and hexamethyldisilazane.

[0221] Examples of silicone oils used for the surface treatment of strontium titanate particles include: Silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and phenylmethylpolysiloxane; reactive silicone oils such as amino-modified polysiloxanes, epoxy-modified polysiloxanes, carboxyl-modified polysiloxanes, carbinol-modified polysiloxanes, fluorine-modified polysiloxanes, methacryl-modified polysiloxanes, mercapto-modified polysiloxanes, and phenol-modified polysiloxanes; etc.

[0222] The solvent used to prepare the treatment liquid is preferably an alcohol (e.g., methanol, ethanol, propanol, or butanol) when the silicon-containing organic compound is an alkoxysilane compound or a silazane compound, or a hydrocarbon (e.g., benzene, toluene, normal hexane, or normal heptane) when the silicon-containing organic compound is a silicone oil.

[0223] In the treatment liquid, the concentration of the silicon-containing organic compound is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, and even more preferably 10% by mass to 30% by mass.

[0224] The amount of the silicon-containing organic compound used for the surface treatment is preferably 1 to 50 mass %, more preferably 5 to 40 mass %, and even more preferably 5 to 30 mass %, relative to 100 mass % of the strontium titanate particles.

[0225] 1-1-2-5. Carrier characteristics The volume average particle size of the carrier is preferably 15 μm to 510 μm, more preferably 20 μm to 180 μm, and even more preferably 25 μm to 60 μm.

[0226] The magnetic force of the carrier is, for example, 40 emu / g or more, preferably 50 emu / g or more, in terms of saturation magnetization in a magnetic field of 1000 oersted. The saturation magnetization is measured in the same manner as in the measurement of the saturation magnetization of magnetic particles, except that the saturation magnetization is swept up to 1000 oersted. The volume resistivity (25°C) of the carrier is, for example, 1×10 7Ω·cm~1×10 15 Ω cm, 1×10 8 Ω·cm~1×10 14 Ω·cm is preferred, 1×10 8 Ω·cm~1×10 13 Ω·cm is more preferable. The volume resistivity of the carrier is measured in the same manner as the volume resistivity of the magnetic particles.

[0227] 1-2.Photoreceptor The photoreceptor according to the present embodiment includes at least a conductive support and a photosensitive layer, and may include a surface protective layer, and at least one of the photosensitive layer and the surface protective layer contains a polyarylate resin. In this application, the term "surface layer of the photoreceptor" refers to a layer such as the photosensitive layer or the surface protective layer formed on the conductive support, and the term "outermost layer of the photoreceptor" refers to the outermost layer among the layers formed on the conductive support.

[0228] The photosensitive layer has the function of absorbing light to generate charges and the function of transporting charges. The photosensitive layer may be a multilayer structure including a charge generation layer and a charge transport layer, or may be a single layer structure. In particular, when the photosensitive layer has a two-layer structure consisting of a charge generation layer and a charge transport layer, the order of the charge generation layer and the charge transport layer from the conductive support side is preferably arranged.

[0229] The polyarylate may be contained in the surface layer of the photoreceptor, but is not necessarily contained in the outermost layer of the photoreceptor. Even when the polyarylate is contained in a layer (inner layer) closer to the conductive support than the outermost layer of the photoreceptor, it is thought that the photoreceptor will have a longer life because the hard polyarylate layer is less likely to be abraded after the outermost layer is abraded during long-term use.

[0230] From the viewpoint of easily extending the life of the photoreceptor, the polyarylate resin is preferably contained in the outermost surface layer of the photoreceptor. That is, when a surface protective layer is included, the polyarylate resin is preferably contained in the surface protective layer, when there is no surface protective layer and the photosensitive layer has a two-layer structure, the polyarylate resin is preferably contained in the charge transport layer, and when there is no surface protective layer and the photosensitive layer has a single-layer structure, the polyarylate resin is preferably contained in the photosensitive layer. By including the polyarylate resin in the outermost surface layer of the photoreceptor, the hardness of the outermost surface layer that comes into direct contact with the cleaning blade is increased, which makes it easier to suppress wear of the photoreceptor by the cleaning blade.

[0231] Furthermore, the photoreceptor may further have an intermediate layer between the conductive support and the photosensitive layer, if necessary.

[0232] From the viewpoint of simplifying the layer structure of the photoreceptor (simplifying production), preferred structures include those not including the surface protective layer shown in the following (A) to (D). These structures shown in the following (A) to (D) will be explained below, but the present embodiment is not limited to the following structures.

[0233] (A) A layer structure in which a "two-layer photosensitive layer consisting of a charge generating layer containing a charge generating agent and a charge transport layer containing a charge transport agent and a polyarylate resin" is sequentially laminated on a conductive support. (B) A layer structure in which an "intermediate layer" and a "two-layer photosensitive layer consisting of a charge generating layer containing a charge generating agent and a charge transport layer containing a charge transport agent and a polyarylate resin" are sequentially laminated on a conductive support. (C) A layer structure in which a "single-layer photosensitive layer containing a charge generating material, a charge transport material, and a polyarylate resin" is sequentially laminated on a conductive support. (D) A layer structure in which an "intermediate layer" and a "single-layer photosensitive layer containing a charge generating material, a charge transport material, and a polyarylate resin" are sequentially laminated on a conductive support.

[0234] The layer structure of the photoreceptor may be any of the above (A) to (D), but (B) is more preferred.

[0235] The photoreceptor according to the present embodiment is preferably an organic photoreceptor. The organic photoreceptor refers to a photoreceptor in which at least one of the charge generating function and the charge transporting function, which are essential for the photoreceptor's configuration, is realized by an organic compound. Examples of organic photoreceptors include a photoreceptor having a photosensitive layer containing an organic charge generating agent or an organic charge transporting agent, and a photoreceptor having a photosensitive layer containing an organic polymer complex that realizes the charge generating function and the charge transporting function.

[0236] Fig. 1 is a schematic cross-sectional view showing the layer structure (B) of the photoreceptor of the present invention. In the photoreceptor 210 shown in Fig. 1, an intermediate layer 212 and a photosensitive layer 213 are laminated on a conductive support 211. The photosensitive layer 213 is composed of a charge generation layer 213a laminated on the intermediate layer 212, and a charge transport layer 213b laminated on the charge generation layer 213a.

[0237] 1-2-1.Conductive support The conductive support 211 may be any support that is conductive. Examples of the conductive support 211 include a drum or sheet formed from a metal such as aluminum, copper, chromium, nickel, zinc, or stainless steel. The conductive support 211 may be a plastic film laminated with a metal foil made of a metal such as aluminum or copper. The conductive support 211 may be a plastic film onto which aluminum, indium oxide, tin oxide, or the like is vapor-deposited. The conductive support 211 may be a metal, plastic film, paper, or the like, on which a conductive layer is provided by applying a conductive substance alone or together with a binder resin.

[0238] 1-2-2. Photosensitive layer 1-2-2-1. Two-layer photosensitive layer When the photosensitive layer has a two-layer structure, it preferably includes a charge generation layer and a charge transport layer, preferably arranged in this order from the conductive support side.

[0239] 1-2-2-1-1. Charge generation layer The charge generating layer 213a preferably contains a charge generating agent and a binder resin for the charge generating layer.

[0240] Examples of charge generating agents include azo pigments, quinone pigments, indigo pigments, polycyclic quinone pigments, phthalocyanine pigments, etc. Examples of azo pigments include Sudan Red and Diane Blue. Examples of quinone pigments include pyrenequinone and anthanthrone. Examples of indigo pigments include quinocyanine pigments, perylene pigments, indigo, and thioindigo. Examples of polycyclic quinone pigments include pyranthrone and diphthaloylpyrene. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferred. The charge generating agents may be used alone or in combination of two or more.

[0241] Known resins can be used as the binder resin for the charge generating layer. Examples of binder resins for the charge generating layer include polystyrene resins, polyethylene resins, polypropylene resins, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, polyvinyl butyral resins, epoxy resins, polyurethane resins, phenolic resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl acetate-maleic anhydride copolymer resins), polyvinyl carbazole resins, etc. Among these, polyvinyl butyral resins are preferred.

[0242] The content of the charge generating agent in the charge generating layer 213a is preferably 1% to 600% by mass, and more preferably 50% to 500% by mass, relative to 100% by mass of the binder resin for the charge generating layer.

[0243] The thickness of the charge generating layer 213a depends on the characteristics of the charge generating material and the characteristics of the binder resin for the charge generating layer. Although it differs depending on the content ratio, it is preferably 0.01 μm to 5 μm, and more preferably 0.05 μm to 3 μm.

[0244] 1-2-2-1-2.Charge transport layer The charge transport layer 213b contains a charge transport material and a binder resin for the charge transport layer, and the binder resin for the charge transport layer preferably contains a polyarylate resin.

[0245] The content of the charge transport material in the charge transport layer 213b is preferably 10% by mass to 500% by mass, and more preferably 20% by mass to 250% by mass, relative to 100% by mass of the binder resin for the charge transport layer.

[0246] The thickness of the charge transport layer 213b varies depending on the characteristics of the charge transport material, the characteristics and content of the binder resin for the charge transport layer, etc., but is preferably 5 μm to 40 μm, and more preferably 10 μm to 30 μm.

[0247] The charge transport layer 213b may contain, in addition to the charge transport material and binder resin for the charge transport layer described below, an antioxidant, an electron conductive agent, a stabilizer, silicone oil, etc. The antioxidant is preferably one disclosed in JP-A-2000-305291. The electron conductive agent is preferably one disclosed in JP-A-50-137543 or JP-A-58-76483.

[0248] 1-2-2-1-2-1. Charge transport material Examples of the charge transport agent include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, triphenylamine derivatives, etc. The charge transport agents may be used alone or in combination.

[0249] 1-2-2-1-2-2. Electron transport layer binder resin containing polyarylate resin The binder resin for the charge transport layer preferably contains a polyarylate resin.

[0250] Examples of polyarylate resins include polyester resins having structural units derived from dicarboxylic acids (hereinafter simply referred to as "dicarboxylic acid units") and structural units derived from diols (hereinafter simply referred to as "diol units"), in which at least one of the dicarboxylic acid units and the diol units has an aromatic ring. The polyarylate resin may be one in which only the dicarboxylic acid units have an aromatic ring, one in which only the diol units have an aromatic ring, or one in which both the dicarboxylic acid units and the diol units have aromatic rings. From the viewpoint of the abrasion resistance of the photoreceptor, the polyarylate resin is preferably one in which both the dicarboxylic acid units and the diol units have aromatic rings, and more preferably an aromatic polyester resin in which an aromatic dicarboxylic acid and an alcohol compound containing an aromatic ring are ester-bonded.

[0251] The terminals of the polyarylate resin may be blocked or modified with a terminal blocking agent or a molecular weight modifier used during production. Examples of the terminal blocking agent or the molecular weight modifier include a monohydric phenol, a monovalent acid chloride, a monohydric alcohol, and a monovalent carboxylic acid.

[0252] Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include o-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane.

[0253] Examples of the monovalent acid chloride include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions thereof.

[0254] Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol.

[0255] Examples of the monocarboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0256] The weight-average molecular weight of the polyarylate resin is preferably 30,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The weight-average molecular weight of the polyarylate resin is a weight-average molecular weight measured by GPC (gel permeation chromatography) in terms of polystyrene. GPC uses tetrahydrofuran as an eluent.

[0257] Examples of methods for producing polyarylate resins include interfacial polymerization, solution polymerization, and melt polymerization.

[0258] The polyarylate resin preferably contains a dicarboxylic acid unit (A) represented by the following general formula (A).

[0259] [ka]

[0260] In formula (A), X is an organic group. Examples of the organic group represented by X include an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, an ether group, a thioether group, and a combination thereof.

[0261] X preferably contains an aromatic ring, more preferably two or more aromatic rings. In particular, it is more preferable that the dicarboxylic acid unit (A) contains a structural unit represented by the following general formula (1) and / or a structural unit represented by the following general formula (2). By containing the structural unit represented by the general formula (1) and / or the structural unit represented by the general formula (2), the hardness of the photoreceptor surface is improved, which tends to increase the abrasion resistance of the photoreceptor and further tends to improve image quality after continuous printing.

[0262] The dicarboxylic acid unit (A) contained in the polyarylate resin may be of one type or two or more types.

[0263] [ka]

[0264] [ka]

[0265] The molar proportion of aromatic ring-containing dicarboxylic acid units in the total molar amount of dicarboxylic acid units is preferably 50 mol% to 100 mol%. When the mass proportion of aromatic ring-containing dicarboxylic acid units is 50 mol% or more, the abrasion resistance of the photosensitive layer is good. From the same viewpoint, the mass proportion of dicarboxylic acid units is more preferably 75 mol% or more, further preferably 90 mol% or more, and most preferably 97 mol%. The polyester resin may contain one or more types of dicarboxylic acid units.

[0266] The mass proportion of the dicarboxylic acid units (A) in the polyarylate resin is preferably 15% by mass to 60% by mass. When the mass proportion of the dicarboxylic acid units is 15% by mass or more, the abrasion resistance of the photosensitive layer is good. From this viewpoint, the mass proportion of the dicarboxylic acid units is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the mass proportion of the dicarboxylic acid units is 60% by mass or less, peeling of the photosensitive layer can be suppressed. From this viewpoint, the mass proportion of the dicarboxylic acid units is more preferably 55% by mass or less, and even more preferably 50% by mass or less. The dicarboxylic acid units contained in the polyester resin may be of one type or two or more types.

[0267] Other dicarboxylic acid units include, for example, aliphatic dicarboxylic acid (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid) units, alicyclic dicarboxylic acid (e.g., cyclohexanedicarboxylic acid) units, and lower (e.g., carbon number 1 to 5) alkyl ester units thereof The dicarboxylic acid units contained in the polyarylate resin may be of one type or two or more types. The dicarboxylic acid units (A) contained in the polyarylate resin may be of one type or two or more types.

[0268] The polyarylate resin preferably contains a diol unit (B) represented by the following general formula (B).

[0269] [ka]

[0270] In formula (B), Ar B1 and Ar B2 each independently represents an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or —C(Rb1)(Rb2)—, and n B1is 0, 1, or 2. Rb1 and Rb2 each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb1 and Rb2 may be bonded to form a cyclic alkyl group.

[0271] Ar B1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0272] Ar B1 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B1 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0273] Ar B2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0274] Ar B2 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B2 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0275] The alkyl group having 1 to 20 carbon atoms for Rb1 and Rb2 may be linear, branched, or cyclic. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 14 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0276] The aryl group having 6 to 12 carbon atoms related to Rb1 and Rb2 may be either monocyclic or polycyclic. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 carbon atoms.

[0277] The alkyl group in the aralkyl group having 7 to 20 carbon atoms related to Rb1 and Rb2 may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2.

[0278] The aryl group in the aralkyl group having 7 to 20 carbon atoms related to Rb1 and Rb2 may be either monocyclic or polycyclic. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 carbon atoms.

[0279] The diol unit (B) contained in the polyarylate resin may be one type or two or more types.

[0280] The mass proportion of the diol units (B) is preferably 25% by mass to 80% by mass relative to the total mass of the polyarylate resin. When the mass proportion of the diol units is 25% by mass or more, peeling of the photosensitive layer can be suppressed. From the same viewpoint, the mass proportion of the diol units is more preferably 30% by mass or more, and even more preferably 35% by mass or more. When the mass proportion of the diol units is 80% by mass or less, solubility in the coating liquid for forming the photosensitive layer can be maintained, and abrasion resistance can be improved. From this viewpoint, the mass proportion of the diol units is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0281] Examples of other diol units include: aliphatic diol (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) units, Alicyclic diol (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A) units The polyester resin may contain one or more types of these diol units.

[0282] The binder resin for the charge transport layer may contain a known resin other than a polyarylate resin, such as a polycarbonate resin, a polyacrylate resin, a polystyrene resin, a styrene-acrylonitrile copolymer resin, a polymethacrylate resin, or a styrene-methacrylate copolymer resin.

[0283] 1-2-2-2. Single-layer photosensitive layer When the photosensitive layer has a single layer structure, the photosensitive layer contains a charge generating material, a charge transport material, and a binder for the photosensitive layer, and the binder for the photosensitive layer preferably contains a polyarylate resin.

[0284] The charge generating material, charge transport material, and polyarylate resin used in the case of a single layer structure are the same as the materials that can be used in the case of a two-layer structure.

[0285] 1-2-3. Middle class The intermediate layer 212 has a function of enhancing the barrier property or adhesiveness between the conductive support 211 and the photosensitive layer 213. Although the intermediate layer 212 is not an essential component of the photoreceptor 210, it is preferable to provide the intermediate layer 212 in consideration of preventing various failures and the like.

[0286] The intermediate layer 212 contains, for example, an intermediate layer binder resin and, if necessary, conductive particles or metal oxide particles.

[0287] Examples of binder resins for the intermediate layer include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, gelatin, etc. Among these, alcohol-soluble polyamide resins are preferred.

[0288] The intermediate layer may contain various conductive particles or metal oxide particles for the purpose of adjusting resistance. Examples of the metal oxide particles that can be used include alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, and zirconium oxide. Particles of composite metal oxides such as tin-doped indium oxide and antimony-doped tin oxide may also be used. Particles of composite oxides having a perovskite structure, such as strontium titanate, may also be used.

[0289] The number average primary particle size of the metal oxide particles that can be contained in the intermediate layer is preferably 10 nm to 300 nm, and more preferably 20 nm to 100 nm.

[0290] The conductive particles or metal oxide particles may be used alone or in combination of two or more kinds. When two or more kinds are mixed, they may be in the form of a solid solution or fused particles.

[0291] The content of the conductive particles or metal oxide particles is preferably 20% by mass to 400% by mass, and more preferably 50% by mass to 350% by mass, relative to 100% by mass of the binder resin.

[0292] The thickness of the intermediate layer is preferably 0.1 μm to 15 μm, more preferably 0.3 μm to 10 μm. The intermediate layer may have a laminated structure of two or more layers depending on the function. The intermediate layer may contain an electron transport agent.

[0293] 1-2-4. Photoconductor manufacturing method The photoreceptor 210 can be manufactured, for example, by sequentially forming each layer constituting the photoreceptor 210 on a conductive support 211. Each layer is formed by a process of forming a coating film made of a coating liquid containing a solvent and solid components (or raw material components thereof) constituting each layer, and a process of curing the coating film. A specific method for manufacturing the photoreceptor 210 will be described below using the case of manufacturing the photoreceptor 210 shown in FIG. 1 as an example.

[0294] The photoreceptor 210 can be manufactured, for example, through the following steps. Step (1): A step of applying a coating liquid for forming an intermediate layer to the surface of a conductive support 211 and drying it to form an intermediate layer 212. Step (2): A step of applying a coating liquid for forming a charge generating layer to the surface of the intermediate layer 212 and drying it to form the charge generating layer 213a. Step (3): A step of applying a coating liquid for forming a charge transport layer to the surface of the charge generation layer 213a and drying it to form the charge transport layer 213b.

[0295] 1-2-4-1. Step (1) Formation of the intermediate layer The intermediate layer 212 can be formed, for example, by the following procedure. A coating liquid for forming an intermediate layer is prepared by dissolving a binder resin for the intermediate layer in a solvent. Conductive particles or metal oxide particles are dispersed in the coating liquid for forming an intermediate layer as needed. The coating liquid for forming an intermediate layer is applied to the conductive support 211 to a certain thickness to form a coating film. The coating film is then dried.

[0296] As a means for dispersing the conductive particles or metal oxide particles in the coating liquid for forming the intermediate layer, an ultrasonic disperser, a ball mill, a sand mill, a homomixer, or the like can be used.

[0297] Examples of methods for applying the coating liquid for forming an intermediate layer include dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper, and circular slide hopper methods. The circular slide hopper method is a method used for coating the outer peripheral surface of a cylindrical or columnar article as the coating surface. The circular slide hopper method can be used as a method for applying the coating liquid for forming an intermediate layer to the outer peripheral surface of a drum-shaped conductive support.

[0298] The method for drying the coating film can be appropriately selected depending on the type of solvent and the thickness of the coating film, but heat drying is preferred.

[0299] The solvent used in the process of forming the intermediate layer 212 may be any solvent that can disperse the conductive particles or metal oxide particles well and dissolve the binder resin for the intermediate layer. Specifically, alcohol solvents having 1 to 4 carbon atoms, such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, and sec-butanol, are preferred because they have excellent binder resin solubility and coating performance. Furthermore, examples of co-solvents that can be used in combination with the above solvents to improve storage stability and particle dispersibility and that provide favorable effects include benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

[0300] The concentration of the binder resin for the intermediate layer in the coating liquid for forming the intermediate layer is appropriately selected according to the thickness of the intermediate layer 212 and the production speed.

[0301] 1-2-4-2. Step (2) Formation of charge generation layer The charge generation layer 213a can be formed, for example, by the following procedure. A coating liquid for forming the charge generation layer is prepared by dispersing a charge generation agent in a solution prepared by dissolving a binder resin for the charge generation layer in a solvent. The coating liquid for forming the charge generation layer is applied to a certain thickness on the intermediate layer 212 to form a coating film. The coating film is then dried.

[0302] As a means for dispersing the charge generating agent in the coating liquid for forming the charge generating layer, for example, an ultrasonic disperser, a ball mill, a sand mill, a homomixer, or the like can be used.

[0303] Examples of methods for applying the coating liquid for forming the charge generating layer include dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper coating, and circular slide hopper coating.

[0304] The method for drying the coating film can be appropriately selected depending on the type of solvent and the thickness of the coating film, but heat drying is preferred.

[0305] Examples of solvents used in forming the charge generating layer 213a include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, t-butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, 4-methoxy-4-methyl-2-pentanone, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine, 3-methyl-2-butanone, cyclohexanone, etc. These solvents may be used alone or in combination of two or more.

[0306] 1-2-4-3. Step (3) Formation of charge transport layer The charge transport layer 213b can be formed, for example, by the following procedure: A coating solution for forming the charge transport layer is prepared by dissolving a binder resin for the charge transport layer and a charge transport agent in a solvent. The coating solution for forming the charge transport layer is applied to a certain thickness on the charge generation layer 213a to form a coating film. The coating film is then dried.

[0307] Examples of methods for applying the coating solution for forming the charge transport layer include dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper coating, and circular slide hopper coating.

[0308] The method for drying the coating film can be appropriately selected depending on the type of solvent and the thickness of the coating film, but heat drying is preferred.

[0309] Examples of solvents used to form the charge transport layer 213b include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

[0310] 1-2-5. Configuration including surface protection layer As described above, the photoreceptor may include a surface protective layer, and the polyarylate resin may be used as the binder resin used in the surface protective layer.

[0311] The surface protection layer can be formed using known materials and manufacturing methods, for example, the materials and manufacturing methods described in paragraphs

[0081] to

[0120] of JP 2021-170059 A can be used.

[0312] 1-3. Image forming method The image forming method according to this embodiment includes: forming a toner image on the surface of a charged photoreceptor using a two-component developer for developing an electrostatic image, the two-component developer including a carrier and a toner; and transferring the formed toner image. Includes:

[0313] The image forming method according to this embodiment preferably includes a fixing step of fixing the toner image transferred onto the surface of the recording medium and / or a cleaning step of the surface of the photoreceptor.

[0314] 1-3-1. Charging process In the charging step, the photoreceptor is charged. The charging method is not particularly limited, and a known method such as a charging roller method in which the electrophotographic photoreceptor is charged by a charging roller can be used.

[0315] 1-3-2. Electrostatic image formation process In the electrostatic image forming process, an electrostatic image is formed on the photoreceptor according to this embodiment.

[0316] The electrostatic image is formed, for example, by uniformly charging the surface of the photoreceptor with a charging means and then exposing the surface of the photoreceptor to light in an imagewise manner with an exposing means.

[0317] The term "electrostatic image" refers to an image formed on the surface of a photoreceptor by such a charging means.

[0318] The charging means and the exposure means are not particularly limited, and known methods in the electrophotographic system can be used.

[0319] 1-3-3.Developing process In the developing step, the electrostatic image is developed using the two-component developer for developing electrostatic images according to this embodiment to form a toner image.

[0320] The toner image is formed using a two-component developer for developing electrostatic images, using a developing means comprising a stirrer that charges the toner by frictional stirring, and a rotatable developing roller.

[0321] Specifically, in the developing unit, for example, toner and carrier are mixed and stirred, and the toner is charged by friction during this process. The carrier is held on the surface of a developing roller that has a built-in magnet, forming a magnetic brush. Because the developing roller is positioned near the photosensitive member, some of the toner adhering to the magnetic brush formed on the surface of the developing roller is moved to the surface of the photosensitive member by electrical attraction. As a result, the electrostatic image is developed with the toner, and a toner image is formed on the surface of the photosensitive member.

[0322] 1-3-4. Transfer process In the transfer step, the toner image is transferred.

[0323] As the transfer means, for example, a corona transfer device using corona discharge, a transfer belt, a transfer roller, or the like can be used.

[0324] The transfer step can be carried out, for example, by using an intermediate transfer body, performing primary transfer of a toner image onto the intermediate transfer body, and then secondary transfer of this toner image onto a recording medium, or by directly transferring a toner image formed on a photosensitive body onto a recording medium.

[0325] The toner image is transferred onto the recording medium by peeling and charging the toner image onto the recording medium.

[0326] The recording medium is not particularly limited, and examples thereof include: Papers such as plain paper from thin paper to thick paper, high-quality paper, coated printing paper such as art paper or coated paper, commercially available Japanese paper, postcard paper, etc.; Resin films such as polypropylene (PP) film, polyethylene terephthalate (PET) film, and triacetyl cellulose (TAC) film; cloth The color of the recording medium is not particularly limited, and recording media of various colors can be used.

[0327] 1-3-5. Fixing process In the fixing process, the recording medium onto which the unfixed image (toner image) formed using toner has been transferred is passed between a heated fixing belt or fixing roller and a pressure member, thereby fixing the unfixed image (toner image) to the recording medium.

[0328] Examples of the fixing process include a belt fixing method and a roller fixing method, which are configured with a fixing belt or a fixing roller as a fixing rotating body and a pressure roller as a pressure member that is placed in pressure contact with the fixing belt or the fixing roller so as to form a fixing nip portion.

[0329] 1-3-6. Cleaning process In the cleaning step, developer that has not been used for image formation or that has not been transferred and remains on a developer carrier such as a photoreceptor or intermediate transfer member is removed from the developer carrier.

[0330] The cleaning method is not particularly limited, and examples thereof include a method using a blade whose tip is in contact with the object to be cleaned, such as a photoreceptor, and which scrapes the surface of the photoreceptor.

[0331] 2. Image forming equipment The image forming apparatus according to this embodiment includes the above-described photoreceptor 210, The developing device includes a developing means for developing the electrostatic image formed on the surface of the photosensitive member into a toner image using the two-component developer for developing electrostatic images.

[0332] The image forming apparatus according to this embodiment preferably includes a first charging unit, an exposure unit, the developing unit, a transfer unit, a second charging unit, and a cleaning unit.

[0333] The first charging means is a means for charging the surface of the photoreceptor 210 .

[0334] The exposure means is a means for irradiating the surface of the photoreceptor 210 with light to form an electrostatic latent image.

[0335] The developing means is a means for developing the electrostatic latent image with toner to form a toner image.

[0336] The transfer means is a means for transferring the toner image onto a transfer material. A support is, for example, plain paper, a transparent sheet, or the like.

[0337] The second charging means is a means for charging the surface of the photosensitive member 210 after the toner image is transferred onto the transfer material. be.

[0338] The cleaning means is a means for removing residual toner from the photoreceptor 210 .

[0339] 2-1. Main components of image forming device 2 is a schematic diagram of an example of an image forming apparatus that can be used in the image forming method. The image forming apparatus 1 shown in FIG.

[0340] The document reading unit 100 uses an automatic document feeder (ADF) to transport a document placed on a document tray, and optically reads the document to generate image data. The image data is stored in the control unit 112.

[0341] Image forming unit 110 includes imaging units 111Y to 111K, control unit 112, intermediate transfer belt 113, secondary transfer roller pair 114, timing roller pair 115, cleaner 116, fixing unit 117, paper discharge roller pair 118, paper discharge tray 119, density sensor 102, and primary transfer rollers 103Y to 103K. Toner cartridges 101Y to 101K for the respective colors of Y (yellow), M (magenta), C (cyan), and K (black) are installed in image forming unit 110.

[0342] Receiving toner supply from toner cartridges 101Y-101K, imaging units 111Y-111K form toner images of the respective colors YMCK under the control of control unit 112. Primary transfer rollers 103Y-103K electrostatically transfer (primary transfer) these toner images onto intermediate transfer belt 113 so that they overlap. Intermediate transfer belt 113 is an endless rotating body that rotates in the direction of arrow A and transports the primarily transferred toner images to a secondary transfer position. The intermediate transfer belt 113 can be made of a semiconductive material such as polycarbonate, polytetrafluoroethylene (PTFE), or polyimide with dispersed carbon as the main ingredient.

[0343] The paper feed unit 120 includes a paper feed cassette 121 that stores recording media P by paper size. The paper feed unit 120 supplies the recording media P one by one to the image forming unit 110. The supplied recording media P are conveyed out in parallel with the intermediate transfer belt 113 conveying the toner image, and are conveyed to the secondary transfer roller pair 114 via the timing roller pair 115.

[0344] The timing roller pair 115 is made up of a pair of rollers. The timing roller pair 115 adjusts the timing at which the recording medium P reaches the secondary transfer roller pair 114.

[0345] The secondary transfer roller pair 114 consists of a pair of rollers to which a transfer voltage is applied. The secondary transfer roller pair 114 are pressed against each other to form a transfer NIP section. In this transfer NIP section, the toner image on the intermediate transfer belt 113 is electrostatically transferred (secondary transfer) onto the recording medium P. The recording medium P onto which the toner image has been transferred is transported to a fixing section 117. After the secondary transfer, the residual toner remaining on the intermediate transfer belt 113 is further transported in the direction of arrow A, and then scraped off by a cleaner 116 and discarded.

[0346] The fixing unit 117 heats and melts the toner image carried on the recording medium P, and presses it onto the recording medium P. The recording medium P with the fused toner image is discharged onto a discharge tray 119 by a pair of discharge rollers 118.

[0347] The control unit 112 controls the operation of the image forming apparatus 1. The control unit 112 also transmits and receives image data to and from other devices such as a personal computer, and receives print jobs.

[0348] The image forming apparatus 1 may perform image stabilization processing to stabilize the image quality to be formed. The density sensor 102 is a reflective density sensor that illuminates an object and measures the density based on the amount of reflected light, and optically detects the test pattern formed on the intermediate transfer belt 113 during the image stabilization processing.

[0349] A transfer charger or a transfer belt may be used instead of the transfer roller. A cleaning brush, a cleaning roller, or the like may be used instead of the cleaner 116 (cleaning blade). As for the fixing unit 117, instead of the electromagnetic induction heating system, a halogen lamp, a resistance heating element, or the like may be used as the heat source. The fixing heating element may be in the form of a roller or a belt.

[0350] Next, the configuration of the image forming units 111Y to 111K will be described, focusing particularly on the developing means. Note that since the image forming units 111Y to 111K all have the same configuration, in the following description they will be simply referred to as 111, omitting the letters YMCK that represent the toner colors.

[0351] Fig. 3 is a cross-sectional view showing a part of the image forming unit 111. The image forming unit 111 has a photoconductor 210, a charging unit, an exposure unit, a developing unit 200, and a cleaning unit, which are arranged in this order along the outer circumferential surface of the photoconductor 210. Of these, the photoconductor 210 and the developing unit 200 are shown in Fig. 3.

[0352] The photoreceptor 210 is driven to rotate in the direction of arrow B by a driving means (not shown). The photoreceptor 210 is a photoreceptor according to this embodiment, and is, for example, a laminated photoreceptor in which a two-layer photoreceptor consisting of an intermediate layer, a charge generation layer containing a charge generation agent, and a charge transport layer containing a charge transport agent and a polyarylate resin are sequentially laminated on a conductive support. The charge transport layer has a thickness of, for example, about 25 μm. The outer peripheral surface of the photoreceptor 210 is uniformly charged by a charging means, and then an electrostatic charge image is formed by irradiating the surface with laser light by an exposure means.

[0353] The developing means 200 has a developing housing 201 that opens toward the photosensitive member 210. A developing roller 202 is disposed in this opening. A regulating blade 203 that regulates the layer thickness of the developer carried on the outer peripheral surface of the developing roller 202 is also provided on one edge of the opening.

[0354] The developing roller 202 has a structure in which a fixedly arranged magnet roller is enclosed in a rotatable sleeve roller. The developing roller 202 rotates, for example, in the counter direction (the direction of arrow C) relative to the photoconductor 210.

[0355] 4 is a cross-sectional view showing the arrangement of magnetic poles in the magnet roller of the developing roller 202. The magnet roller shown in FIG. 4 has five magnetic poles, N1, S1, N2, S2, and S3, arranged in that order along the circumferential direction. Of these five magnetic poles, the developing magnetic pole N1 is positioned opposite the photosensitive member 210.

[0356] Downstream of the developing magnetic pole N1, there are arranged a transport magnetic pole S1 and repulsion magnetic poles S2 and S3. The regulating magnetic pole N2 is arranged in a position facing the regulating blade 203. The repulsion magnetic poles S and S3 generate a repulsive magnetic field to separate the developer from the sleeve roller, and in particular, the magnetic pole S3 also functions as a pickup pole.

[0357] The developing means 200 is supplied with the two-component developer for developing electrostatic images according to the present embodiment (hereinafter also simply referred to as "developer") from the toner cartridge 101 via a toner hopper (not shown). The supplied developer is stirred by the stirring screw 204 and the supply screw 205, and is given a predetermined charge, after which it is guided onto the outer circumferential surface of the developing roller 202 by the action of the supply magnetic pole S2 of the developing roller 202.

[0358] The developer carried on the outer peripheral surface of developing roller 202 is transported in the direction of arrow C by the rotation of developing roller 202 and the action of the magnetic field between supply magnetic pole S2 and regulating magnetic pole N2. On the outer peripheral surface of developing roller 202, the developer is regulated to a predetermined layer thickness by regulating blade 203, and then transported to the development region where photoreceptor 210 and developing roller 202 face each other. Regulating blade 203 regulates the height of the developer spikes to prevent toner fogging and scattering.

[0359] The peripheral speed of the developing roller 202 is not particularly limited, but is preferably in the range of 200 mm / s to 800 mm / s. As the peripheral speed of the developing roller 202 increases, the toner tends to break down, so the peripheral speed is preferably 800 mm / s or less. On the other hand, the toner according to the present invention has high resistance to breaking down, and therefore does not easily break down even when the peripheral speed of the developing roller 202 is 200 mm / s or more.

[0360] A DC bias and / or AC bias voltage is applied to the developing roller 202 as a developing bias from a power supply (not shown). This developing bias creates an electrostatic attraction between the developing roller 202 and the photoconductor 210 in the development area. As a result, the toner in the developer is supplied from the developing roller 202 to the outer circumferential surface of the photoconductor 210, thereby visualizing the electrostatic latent image. The developing bias is preferably a DC voltage superimposed with an AC voltage. By applying a developing bias voltage in which an AC component is superimposed on a DC component to the developing roller 202, a predetermined potential difference required for development is generated between the developing roller 202 and the photoconductor 210 at the development position. This causes the toner to reciprocate between the developing roller 202 and the photoconductor 210 due to the AC component, facilitating the toner to move from the developing roller 202 to the electrostatic latent image on the photoconductor 210, facilitating the toner to move as intended, and reducing toner migration to white areas, which tends to improve image quality.

[0361] The developer that has passed through the development zone is further transported in the direction of arrow C on the outer peripheral surface of the development roller 202. The developer is then separated from the development roller 202 by the action of the repulsive magnetic poles S2 and S3 and returned to the supply screw 205 side. The regulating blade 203 is made of, for example, a magnetic material. Therefore, the regulating blade 203 can form effective spikes of the developer between the regulating magnetic pole N2 of the development roller 202 and the regulating blade 203, and can stably regulate the layer thickness.

[0362] A toner concentration sensor 220 is disposed along the outer peripheral surface of photoconductor 210, immediately downstream of the development area in the direction of rotation of photoconductor 210 (the direction of arrow B). Toner concentration sensor 220 detects the density of the toner image formed on the outer peripheral surface of photoconductor 210.

[0363] The outer peripheral surface of the photoreceptor 210 is in contact with the intermediate transfer belt 113, which is pressed by the primary transfer roller 103. The toner image formed on the outer peripheral surface of the photoreceptor 210 is transferred onto the intermediate transfer belt 113 by a transfer electric field formed by a primary transfer bias applied to the primary transfer roller 103.

[0364] The cleaning unit mechanically scrapes off and cleans the toner remaining on the outer peripheral surface of the photoreceptor 210 after the primary transfer by bringing a cleaning blade into contact with the outer peripheral surface of the photoreceptor 210. The scraped off toner is discharged as waste toner by a screw.

[0365] The eraser lamp exposes the outer peripheral surface of the photoconductor 210, from which the residual toner has been cleaned, through the gap between the cleaning blade and the charging means. This eliminates the charge on the outer peripheral surface of the photoconductor 210, setting it to a uniform potential of, for example, about -30V.

[0366] Thereafter, the above-described operations are repeated to form images one after another.

[0367] The drum-shaped photoreceptor 210 may be replaced by a photoreceptor belt.

[0368] The charging means applies a uniform potential to the photoreceptor 210. It may be a corona discharge type, a roller charging type, or a charging type using a charging blade, a charging brush, a proximity charging member, or the like.

[0369] The exposure unit exposes the photoconductor 210, to which a potential has been applied by the charging unit, based on an image signal to form an electrostatic image. The exposure unit may be, for example, a unit consisting of an LED in which light-emitting elements are arranged in an array in the axial direction of the photoconductor 210 and an imaging element, or a laser optical system.

[0370] The cleaning means may be a brush, a roller, etc. instead of a cleaning blade. The developing means 200 may be used to collect the residual toner.

[0371] Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for purposes of illustration and example only, and not for purposes of limitation. The scope of the present invention should be interpreted by the following claims.

[0372] For example, the image forming apparatus according to this embodiment A direct transfer device that transfers a toner image formed on the surface of a photoreceptor directly to a recording medium; An apparatus including a static elimination means for irradiating the surface of the photoreceptor with static elimination light to eliminate static electricity after the toner image is transferred and before the surface is charged; The two-component developer for developing electrostatic images according to the present embodiment and a photoconductor may be used in a known image forming apparatus such as the above.

[0373] 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 that contains the two-component developer for developing electrostatic images according to the present embodiment and is equipped with the developing means is preferably used. [Example]

[0374] The present invention will be described below with reference to examples, which should not be construed as limiting the scope of the present invention.

[0375] <Toner Production> [Preparation of Resin Particle Dispersion (1)] The following materials were charged into a flask, and the temperature was raised to 200°C over 1 hour. After confirming that the reaction system was uniformly stirred, 1.2 parts of dibutyltin oxide was added. The temperature was raised to 240°C over 6 hours while distilling off the generated water, and stirring was continued at 240°C for 4 hours to obtain amorphous polyester resin (1) (acid value 9.4 mgKOH / g, weight average molecular weight 13,000, glass transition temperature 62°C).

[0376] -Composition of polyester resin (1)- Ethylene glycol (Wako Pure Chemical Industries) 37 parts by mass Neopentyl glycol (Wako Pure Chemical Industries) 65 parts by mass 1,9-nonanediol (Wako Pure Chemical Industries) 32 parts by mass Terephthalic acid (Wako Pure Chemical Industries) 96 parts by mass

[0377] The polyester resin (1) was transferred in a molten state to an emulsifying / dispersing machine (Cavitron CD1010, Eurotech) at a rate of 100 g / min. Separately, diluted ammonia water with ion-exchanged water to a concentration of 0.37% was placed in a tank so as to achieve the resin concentration described below. The diluted ammonia water was heated to 120°C in a heat exchanger and transferred to the emulsifying / dispersing machine at a rate of 0.1 liters / min simultaneously with the polyester resin. The emulsifying / dispersing machine was operated at a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm. 2 The operation was carried out under the conditions of (a) and (b) to obtain a resin particle dispersion (1) having a volume average particle size of 160 nm and a resin concentration of 20%.

[0378] [Preparation of Resin Particle Dispersion (2)] The following materials were charged into a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide was added. The temperature was raised to 200°C over 6 hours while distilling off the produced water, and stirring was continued at 200°C for 4 hours. The reaction liquid was then cooled, solid-liquid separation was performed, and the solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (2) (melting point 64°C, weight average molecular weight 15,000).

[0379] -Composition of polyester resin (2)- Sebacic acid (Tokyo Kasei Kogyo) 81 parts by mass Hexanediol (Wako Pure Chemical Industries) 47 parts by mass

[0380] The following materials were heated to 120°C and thoroughly dispersed using a homogenizer (Ultra Turrax T50, IKA), and then dispersed using a pressure discharge homogenizer. When the volume average particle size reached 180 nm, the particles were collected to obtain a resin particle dispersion (2) with a resin concentration of 20%.

[0381] -Composition of resin particle dispersion (2)- Polyester resin (2) 50 parts by mass Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku) 2 parts by mass Ion-exchanged water 200 parts by mass

[0382] [Preparation of Colorant Particle Dispersion (1)] The following materials were mixed and dispersed for 1 hour using a high-pressure impact disperser (Ultimizer HJP30006, Sugino Machine Co., Ltd.) to obtain a colorant particle dispersion (1) with a volume average particle size of 180 nm and a pigment concentration of 20%.

[0383] -Preparation of Colorant Particle Dispersion (1)- Cyan pigment (Pigment Blue 15:3, Dainichiseika Color & Chemicals Mfg. Co., Ltd.) 20 parts by weight Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku) 2 parts by mass Ion-exchanged water 80 parts by mass

[0384] [Preparation of Release Agent Particle Dispersion (1)] The following materials were heated to 120°C and thoroughly dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA), and then dispersed using a pressure discharge homogenizer. When the volume average particle size reached 200 nm, the particles were collected to obtain a release agent particle dispersion (1) with a release agent concentration of 20%.

[0385] -Composition of release agent particle dispersion (1)- Paraffin wax (HNP-9, Nippon Seiro) 50 parts by weight Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku) 2 parts by mass Ion-exchanged water 200 parts by mass

[0386] [Preparation of Toner (1)] The following materials were placed in a round stainless steel flask and thoroughly mixed and dispersed using a homogenizer (Ultra Turrax T50, IKA). The flask was then heated to 48°C in an oil bath while stirring. The reaction system was maintained at 48°C for 60 minutes. The pH was then adjusted to 8.0 using a 0.5 mol / L aqueous sodium hydroxide solution. The flask was then sealed, the stirring shaft was magnetically sealed, and the mixture was heated to 90°C with continued stirring and maintained for 30 minutes. The mixture was then cooled at a rate of 5°C / min, solid-liquid separated, and thoroughly washed with ion-exchanged water. The solid-liquid separated product was then redispersed in ion-exchanged water at 30°C and washed with stirring for 15 minutes at 300 rpm. This washing procedure was repeated six more times. When the pH of the filtrate reached 7.54 and the electrical conductivity reached 6.5 μS / cm, solid-liquid separation was performed. The mixture was then vacuum dried for 24 hours to obtain toner particles with a volume average particle size of 5.7 μm.

[0387] - Composition of Toner (1) - Resin particle dispersion (1) 150 parts by mass Resin particle dispersion (2) 50 parts by mass Colorant particle dispersion (1) 25 parts by mass Release agent particle dispersion (1) 35 parts by mass Polyaluminum chloride 0.4 parts by mass Ion-exchanged water 100 parts by mass

[0388] 100 parts of the above toner particles and 2.5 parts of silica particles (surface hydrophobized with hexamethyldisilazane, average primary particle size 40 nm) were mixed in a Henschel mixer to obtain toner (1).

[0389] [Preparation of Toners (2) to (5)] Toners (2) to (5) were obtained in the same manner as toner (1), except that the amount of release agent particle dispersion (1) added (35 parts by mass) in the composition of toner (1) was changed so that the content ratio of the release agent to the total mass of the toner particles was the addition ratio shown in Table 1.

[0390] [Table 1]

[0391] <Creating the carrier> [Strontium titanate particles (1)] Commercially available strontium titanate particles (SW-360 manufactured by Titanium Kogyo Co., Ltd.) were prepared and subjected to a surface treatment similar to the i-BTMS treatment used to prepare strontium titanate particles (1), producing strontium titanate particles (1). SW-360 manufactured by Titanium Kogyo Co., Ltd. is a strontium titanate particle that is not doped with a metal element and has an untreated surface.

[0392] [Strontium titanate particles (2)] 0.7 moles of desulfurized and peptized metatitanic acid, the titanium source, was collected and placed in a reaction vessel. Next, 0.77 moles of strontium chloride aqueous solution was added to the reaction vessel to achieve a SrO / TiO molar ratio of 1.1. Next, a solution of lanthanum oxide dissolved in nitric acid was added to the reaction vessel in an amount equivalent to 2.5 moles of lanthanum per 100 moles of strontium. The initial TiO concentration in the mixture of the three materials was adjusted to 0.75 moles / L. The mixture was then stirred and heated to 90°C. While maintaining the temperature at 90°C, 153 mL of 10N aqueous sodium hydroxide solution was added over 4 hours. Stirring was continued for another hour while maintaining the temperature at 90°C. The reaction mixture was then cooled to 40°C, and hydrochloric acid was added until the pH reached 5.5, followed by stirring for 1 hour. The precipitate was then washed by repeated decantation and redispersion in water. Hydrochloric acid was added to the slurry containing the washed precipitate to adjust the pH to 6.5, and the solids were filtered off and dried. An ethanol solution of i-butyltrimethoxysilane (i-BTMS) was added to the dried solids in an amount of 20 parts i-BTMS per 100 parts solids, and the mixture was stirred for 1 hour. The solids were filtered off and dried in air at 130°C for 7 hours to obtain strontium titanate particles (2).

[0393] [Strontium titanate particles (3)] Strontium titanate particles (3) were prepared in the same manner as in the preparation of strontium titanate particles (2), except that the dropwise addition time of the 10N aqueous sodium hydroxide solution was changed to 11 hours.

[0394] [X-ray diffraction of strontium titanate particles] Using each of the strontium titanate particles (1) to (3) as a sample, crystal structure analysis was performed using an X-ray diffractometer (Rigaku Corporation, product name RINT Ultima-III) under the conditions described above. The strontium titanate particles (1) to (3) had a peak at a diffraction angle 2θ of approximately 32°, which corresponded to the peak of the (110) plane of the perovskite crystal.

[0395] [Measurement of the shape of strontium titanate particles] Separately prepared resin particles and one of strontium titanate particles (1) to (3) were mixed using a Henschel mixer at a stirring peripheral speed of 30 m / s for 15 minutes. The mixture was then sieved using a vibrating sieve with 45 μm mesh size, allowing the strontium titanate particles to adhere to the resin particles. Images of the resin particles with the strontium titanate particles attached were taken at 40,000x magnification using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, S-4700). The image information of 300 randomly selected strontium titanate particles was analyzed via an interface using image processing and analysis software WinRoof (Mitani Corporation). The circle-equivalent diameter, area, and perimeter of each primary particle image were determined, and the circularity was calculated using the formula: 4π × (area) ÷ (perimeter). 2 The average primary particle size was determined as the equivalent circle diameter at 50% cumulative from the smallest diameter in the distribution of equivalent circle diameters, and the average circularity was determined as the circularity at 50% cumulative from the smallest diameter in the distribution of circularity. The average primary particle size and average circularity of the strontium titanate particles (1) were 0.89.

[0396] [Table 2]

[0397] [Preparation of resin-coated ferrite particles (1)] The following materials and glass beads (1 mm diameter, same amount as toluene) were placed in a sand mill (Kansai Paint Co., Ltd.) and stirred at a rotation speed of 1200 rpm for 30 minutes to prepare coating liquid (1).

[0398] -Composition of coating solution (1)- Cyclohexyl acrylate resin (weight average molecular weight 50,000) 30 parts by mass Polyisocyanate (Coronate L, Tosoh) 6 parts by mass Carbon black (VXC72, Cabot) 4 parts by mass Toluene 250 parts by mass Methanol 50 parts by mass

[0399] 200 parts of ferrite particles (1) (Mn-Mg-Sr ferrite particles (average particle size 40 μm)) were placed in a vacuum degassing kneader, and 36 parts of coating liquid (1) were added. The mixture was heated and reduced pressure with stirring, and then stirred and dried for 30 minutes in an atmosphere of 90°C / -720 mHg. Next, the mixture was sieved through a 75 μm mesh sieve to obtain resin-coated ferrite particles (1).

[0400] [Preparation of resin-coated ferrite particles (2) and (3)] Resin-coated ferrite particles (2) and (3) were prepared in the same manner as resin-coated ferrite particles (1), except that the coating liquid was changed to that shown in Table 3. Coating liquids (2) and (3) were prepared in the same manner as coating liquid (1), except that the strontium titanate particles shown in Table 3 were added in the mass ratio shown in Table 3 relative to 100% by mass of the total mass of the resin-coated ferrite particles.

[0401] [Table 3]

[0402] [Preparation of carrier (1)] 100 parts by mass of the resin-coated ferrite particles (1) and 0.05 parts by mass of strontium titanate particles (2) as external additive particles were charged into a V-blender and mixed with stirring for 20 minutes to obtain a carrier (1).

[0403] [Preparation of carriers (2) to (7)] Carriers (2) to (7) were obtained in the same manner as carrier (1), except that the type of resin-coated ferrite particles and the type and amount of externally added strontium titanate particles (mass ratio relative to 100 mass% of the total mass of the resin-coated ferrite particles) were changed as shown in Table 4.

[0404] [Table 4]

[0405] The amount of externally added particles shown in Table 4 indicates the mass ratio relative to the total mass of the resin-coated ferrite particles, 100 mass %.

[0406] <Preparation of two-component developer for electrostatic image development> [Preparation of two-component developer 1 for electrostatic image development] 100 parts by mass of carrier (1) and 6 parts by mass of toner (1) were placed in a V-blender and stirred for 20 minutes, then sieved through a sieve with 212 μm openings to obtain a cyan two-component developer 1 for developing electrostatic images.

[0407] [Preparation of two-component developers 2 to 23 for developing electrostatic images] As shown in Table 9, two-component developers 2 to 23 for developing electrostatic images were obtained in the same manner as two-component developer 1 for developing electrostatic images, except that the type of toner and the type of carrier were changed.

[0408] <Preparation of photoreceptor> [Preparation of binder resin for charge transport layer] Polyarylate resins PAR1 to PAR3 and polycarbonate resin PC1 (Z300, manufactured by Mitsubishi Gas Chemical Company, Inc.) were prepared as binder resins for the charge transport layer. Polycarbonate resin (PC1) was prepared. Table 5 shows the structural units and compositions constituting polyarylate resins PAR1 to PAR3. The structures of the dicarboxylic acid units and diol units are as shown in Tables 6 and 7.

[0409] [Table 5]

[0410] [Table 6]

[0411] [Table 7]

[0412] [Preparation of conductive support] The surface of the cylindrical aluminum support was machined to form a conductive support.

[0413] [Creating the intermediate layer] The components of the composition below were mixed and dispersed batchwise for 10 hours using a sand mill as a disperser to obtain a coating liquid for forming an intermediate layer.

[0414] -Composition of coating solution for forming intermediate layer- Polyamide resin X1010 (manufactured by Daicel Degussa Co., Ltd.) 10 parts by mass Titanium oxide SMT500SAS (manufactured by Teika Co., Ltd.) 11 parts by mass Ethanol 200 parts by mass

[0415] The coating solution for forming the intermediate layer was applied onto the conductive support by dip coating, and the resulting coating was dried at 110°C for 20 minutes to form an intermediate layer having a thickness of 2 µm after drying.

[0416] [Preparation of charge generation layer] The following components were mixed and dispersed using a circulation ultrasonic homogenizer "RUS-600TCVP (manufactured by Nippon Seiki Seisakusho Co., Ltd.)" to prepare a coating solution for forming a charge generating layer under the following dispersion conditions: 19.5 kHz, 600 W, circulation flow rate of 40 L / H, and 0.5 hours.

[0417] -Composition of coating liquid for forming charge generating layer- Charge generating material 1 24 parts by mass Polyvinyl butyral resin 1 12 parts by mass Mixed solvent 1 400 parts by mass

[0418] The charge generating material 1, polyvinyl butyral resin 1, and mixed solvent 1 used were as follows. Charge-generating material 1: A mixed crystal of a 1:1 adduct of titanyl phthalocyanine and (2R,3R)-2,3-butanediol, and unadducted titanyl phthalocyanine, which has clear peaks at 8.3°, 24.7°, 25.1°, and 26.5° in Cu-Kα characteristic X-ray diffraction spectrum measurement. Polyvinyl butyral resin 1: S-LEC BL-1, manufactured by Sekisui Chemical Co., Ltd. Mixed solvent 1: 3-methyl-2-butanone / cyclohexanone = 4 / 1 (V / V)

[0419] The coating solution for forming the charge generating layer was applied onto the intermediate layer by dip coating, and the resulting coating was dried to form a charge generating layer having a thickness of 0.3 μm after drying.

[0420] [Preparation of Coating Solution for Forming Charge Transport Layer] The components shown below were mixed and dissolved to prepare a coating solution 1 for forming a charge transport layer.

[0421] -Composition of Coating Solution 1 for Forming Charge Transport Layer- Charge transport agent 1 (compound represented by general formula CTM-1) 60 parts by mass Polyarylate resin PAR1 100 parts by mass Antioxidant 1 4 parts by mass Tetrahydrofuran (appropriate amount)

[0422] The structural formula of the charge transport agent 1 and antioxidant 1 used are as follows: Antioxidant 1: Irganox 1010, manufactured by Ciba Specialty Chemicals

[0423] [ka]

[0424] [Preparation of Photoreceptor 1] Charge transport layer-forming coating liquid 1 was applied onto the charge generation layer by dip coating. The resulting coating film was dried at 120°C for 70 minutes to form a charge transport layer with a dry thickness of 24 μm, thereby obtaining photoreceptor 1 in which an intermediate layer, charge generation layer, and charge transport layer were formed in this order on the conductive support.

[0425] [Preparation of Photoreceptors 2 to 4] Photoreceptors 2 to 4 were obtained in the same manner as above, except that the polyarylate resin PAR1 used in the coating liquid for forming the charge transport layer was changed to the binder resin for the charge transport layer shown in Table 8.

[0426] [Table 8]

[0427] <Evaluation> [Image forming device] The two-component developer for electrostatic image development prepared above and a photoreceptor were installed in the cyan position of a commercially available full-color multifunction printer, the "bizhub C650i" (manufactured by Konica Minolta), which uses a contact roller charging system, in the combinations shown in Table 9, to produce configurations Nos. 1 to 23. The evaluation of each image forming apparatus is described below. The "bizhub C650i" used had been modified so that the DC and / or AC bias voltage could be stopped from being applied to the developing roller. In Table 9, a "○" in the "Development Bias Superposition" column indicates that the developing bias supplied to the developing roller was a DC voltage with an AC voltage superimposed thereon. In Table 9, a "-" in the "Development Bias Superposition" column indicates that the developing bias supplied to the developing roller was a DC voltage with an AC voltage not superimposed thereon.

[0428] [White Out] For whiteout, a vertically written English chart image was printed on an A4 size sheet in a normal temperature and humidity (20°C, 50%RH) printing environment at the beginning of continuous printing (after 10,000 sheets of transfer paper were printed) and at the end of continuous printing (after 20,000 sheets of transfer paper were printed) as a halftone image, and the presence or absence of whiteout in the halftone part of the paper was visually inspected and ranked according to the following evaluation criteria. Note that at least one of the evaluations for whiteout after 10,000 sheets of printing and whiteout after 20,000 sheets of printing was deemed acceptable if it was rated B or higher.

[0429] (Judgment criteria) A: No white spots B: A small amount of white spots occurs, but it is at an acceptable level. C: White spots occur

[0430] [Cover] Fog was evaluated in a printing environment of normal temperature and humidity (20°C, 50% RH) by printing a text image with a 5% coverage rate on 10,000 sheets of A4 transfer paper, then printing a blank sheet of paper, and measuring the density of the blank sheet of the transfer material. The density of the blank sheet of the transfer material was measured at 20 points on the A4 sheet, and the average value was taken as the blank sheet density. Density measurements were performed using a reflection densitometer "RD-918" (manufactured by Macbeth). A and B were deemed acceptable.

[0431] (Judgment criteria) A: Fog density is less than 0.003 B: Fog density is 0.003 or more and less than 0.010 C: Fog density is 0.010 or more

[0432] [Toner scattering] Before printing began, double-sided tape was attached to the top of the developing means, and a character image with a 5% print rate was printed on 10,000 sheets of A4-sized transfer paper. The toner contamination caused by toner scattering inside the machine was then measured using a reflection densitometer (RD-918: Macbeth Co.). The difference in reflection density between the start of printing and after 10,000 sheets had been printed was determined. A and B were deemed acceptable.

[0433] (Judgment criteria) A: The difference in reflection density is 0.1 or less B: Reflection density difference is more than 0.1 and 0.8 or less C: The difference in reflection density is more than 0.8

[0434] [Wear resistance] In a low-temperature, low-humidity environment (temperature 20°C, humidity 50%), a horizontal band chart with an image area ratio of 5% was printed on an A4 sheet. A durability test was conducted in which 100,000 sheets were continuously printed on one side of each sheet in a transverse feed. The thickness of the photosensitive layer of the photoreceptor was measured before and after the durability test, and the amount of thickness loss was calculated. The thickness of the photosensitive layer was measured at 10 mm intervals in the width direction between a position 10 mm from one end and a position 10 mm from the other end, and the average value was taken as the thickness of the photosensitive layer. The thickness was measured using an eddy current film thickness measuring device (Fisher film thickness meter FMP30). The evaluation criteria were set as follows, with A to C being acceptable.

[0435] (Judgment criteria) A: Depletion amount ≦0.2μm B:0.2μm<wearing amount≦0.3μm C: 0.3μm<decreased amount≦0.5μm D:0.5μm<decreased amount

[0436] <Evaluation results> Table 9 shows the results of the evaluations of the compositions Nos. 1 to 24.

[0437] [Table 9]

[0438] It was found that configurations Nos. 1 to 22, which use a carrier containing strontium titanate particles and a photoreceptor containing polyarylate resin, can extend the life of the photoreceptor and improve image quality compared to configuration No. 23, which does not use either of these. Image forming method. [Industrial Applicability]

[0439] According to the image forming method of the present invention, the life of the photoreceptor can be extended and the image quality can be improved, and therefore the present invention is useful in the field of image forming. [Explanation of symbols]

[0440] 210 Photoreceptor 211 Conductive support 212 Middle Class 213 Photosensitive layer 213a Charge generation layer 213b Charge transport layer 1. Image forming device 100 Document reading unit 110 Image forming unit 111, 111Y~111K Imaging section 112 Control section 113 Intermediate transfer belt 114 Secondary transfer roller pair 115 Timing Roller Pair 116 Cleaner 117 Fixing section 118 Paper ejection roller pair 119 Paper output tray 101Y~101K Toner Cartridge 102 Concentration sensor 103Y~103K Primary transfer roller 200 Developing means 202 Developing roller 203 Regulatory Blade 204 stirring screw 205 supply screw 220 Toner density sensor S1 Carrying pole S2, S3 repulsive magnetic poles N1 developing magnetic pole N2 Regulatory Pole 120 Paper feed section 121 Paper cassette P Recording medium

Claims

1. forming a toner image on the surface of a charged photoreceptor using a two-component developer for developing an electrostatic image, the two-component developer including a carrier and a toner; and transferring the formed toner image. the carrier contains strontium titanate particles on the outermost surface or in a surface layer thereof, The photoreceptor contains a polyarylate resin in a surface layer. Image forming method.

2. the carrier comprises magnetic particles; The carrier may include a resin coating layer made of a resin that coats the surfaces of the magnetic particles, the carrier contains the strontium titanate particles attached to the surface of the magnetic particles or the resin coating layer; The image forming method according to claim 1 .

3. the carrier includes magnetic particles and a resin coating layer made of a resin that coats the surfaces of the magnetic particles; The resin coating layer contains the strontium titanate particles. The image forming method according to claim 1 .

4. the carrier includes magnetic particles, a resin coating layer made of resin that coats the surfaces of the magnetic particles, and the strontium titanate particles that are attached to the surface of the resin coating layer, The resin coating layer contains the strontium titanate particles. The image forming method according to claim 1 .

5. The toner is applied to the surface of the photosensitive member via a developing roller to which a developing bias in which an AC component is superimposed on a DC component is applied. The image forming method according to claim 1 .

6. the toner contains wax, the amount of the wax added is 2.0% by mass to 30.0% by mass with respect to the total mass of the toner; The image forming method according to claim 1 .

7. The polyarylate resin contains a structural unit represented by the following general formula (1) and / or a structural unit represented by the following general formula (2): The image forming method according to claim 1 . 【Chemistry 1】 【Chemistry 2】

8. the strontium titanate particles are lanthanum-doped strontium titanate; The image forming method according to any one of claims 1 to 7.

Images