Toner for electrostatic charge image development, method for manufacturing toner for electrostatic charge image development, and image forming method

Abstract

To provide a toner for electrostatic charge image development with which images can be formed in which image blur and density unevenness are sufficiently reduced even when images are repeatedly formed, while increasing the cleanability of a photoreceptor, a method for manufacturing a toner for electrostatic charge image development, and an image forming method.SOLUTION: A toner for electrostatic charge image development includes a toner base particle including a binder resin, and a mixture in which an antioxidant is dispersed in a fatty acid metal salt.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a toner for electrostatic charge image development, a method for manufacturing the toner for electrostatic charge image development, and an image forming method.

Background Art

[0002] In an electrophotographic image forming apparatus, an electrophotographic photosensitive member (hereinafter, also simply referred to as "photosensitive member") is used to form an electrostatic latent image corresponding to an image to be formed. In an electrophotographic image forming apparatus, first, an electrostatic latent image is formed by irradiating a photosensitive member having a charged surface with light. Next, toner is supplied from a developing device (developing roller) to the photosensitive member to form a toner image corresponding to the electrostatic latent image. Finally, the toner image is transferred onto a recording medium such as paper and fixed. In the step of forming the electrostatic latent image, in order to form the electrostatic latent image, charges opposite to the charges with which the surface of the photosensitive member is charged are generated by irradiating the photosensitive member with light. Therefore, the photosensitive member includes a charge generation layer for generating charges by irradiating with light, and a charge transport layer for transporting the generated charges to the surface of the photosensitive member.

[0003] In the above image forming apparatus, in order to improve the cleanability of the surface of the photosensitive member, a fatty acid metal salt may be applied to the photosensitive member as a lubricant. By applying the fatty acid metal salt to the surface of the photosensitive member, after the transfer of the toner, it becomes difficult for the toner to remain on the surface of the photosensitive member, so the cleanability with respect to the photosensitive member is improved.

[0004] However, it is known that ozone and nitrogen oxides (NOx) are generated by corona discharge performed when charging the photosensitive member, and these oxidize the fatty acid metal salt applied to the surface of the photosensitive member. As a result, the surface of the photosensitive member becomes hydrophilic and water easily adheres thereto, so that image blurring occurs. In addition, since the lubricant oxidizes and deteriorates, the above cleanability deteriorates. Furthermore, since ozone and nitrogen oxides (NOx) also oxidize the charge transport substance in the charge transport layer included in the photosensitive member, it becomes difficult to form a desired electrostatic latent image, and density unevenness occurs in the formed image.

[0005] In order to solve these problems, a photoreceptor containing a compound having an antioxidant function (antioxidant) in the photoreceptor is known (for example, Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, when forming repeated images using the photoreceptors described in Patent Document 1 and Patent Document 2, problems occur in that an image with sufficient suppression of image blur and density unevenness cannot be formed. In response to this, the present inventors focused on the developer toner continuously supplied to the surface of the photoreceptor and considered whether these problems could be solved.

[0008] An object of the present invention is to provide an electrostatic charge image developing toner, a method for manufacturing an electrostatic charge image developing toner, and an image forming method that can form an image with sufficient suppression of image blur and density unevenness even when forming repeated images while enhancing the cleaning property with respect to the photoreceptor.

Means for Solving the Problems

[0009] One aspect of the present invention for achieving the above object relates to an electrostatic charge image developing toner according to the following [1] to [6]. [1] Toner base particles containing a binder resin, A mixture in which an antioxidant is dispersed in a fatty acid metal salt, and An electrostatic charge image developing toner. [2] The antioxidant includes an antioxidant having a piperidine derivative moiety in its molecular structure. [1] The toner for electrostatic charge image development according to [1]. [3] The antioxidant having the piperidine derivative moiety further includes a phenol structure in its molecular structure. [2] The toner for electrostatic charge image development according to [2]. [4] The fatty acid metal salt is zinc stearate. [1] The toner for electrostatic charge image development according to [1]. [5] The content of the antioxidant is 5 mol% or more and 50 mol% or less with respect to the total number of moles of the fatty acid metal salt and the antioxidant. [1] The toner for electrostatic charge image development according to [1]. [6] Further includes a colorant. [1] The toner for electrostatic charge image development according to [1].

[0010] Another aspect of the present invention for achieving the above object relates to a method for manufacturing a toner for electrostatic charge image development according to the following [7] to

[10] . [7] A step of preparing a mixture in which an antioxidant is dispersed in a fatty acid metal salt, A step of preparing toner base particles, A step of mixing the mixture and the toner base particles, A method for manufacturing a toner for electrostatic charge image development, which comprises. [8] In the step of preparing the mixture, the mixture is prepared by producing the mixture. [7] The method for manufacturing a toner for electrostatic charge development according to [7]. [9] The mixture is produced by melt-kneading the fatty acid metal salt and the antioxidant. [8] The method for manufacturing a toner for electrostatic charge image development according to [8].

[10] The mixture is produced by dissolving the fatty acid metal salt and the antioxidant in an organic solvent, mixing them, and then removing the organic solvent. [8] The method for manufacturing a toner for electrostatic latent image development according to [8].

[0011] Another aspect of the present invention for achieving the above object relates to the image forming methods of the following

[11] and

[12] .

[11] An image forming method performed using an image forming apparatus including an electrophotographic photoreceptor and the toner for electrostatic charge image development according to any one of [1] to [6], a step of charging the surface of the electrophotographic photoreceptor; a step of exposing the charged surface of the electrophotographic photoreceptor to form an electrostatic latent image; a step of applying the toner for electrostatic charge image development to the surface of the electrophotographic photoreceptor on which the electrostatic latent image is formed to form a toner image; a step of transferring the formed toner image onto a recording medium; a step of fixing the transferred toner image onto the recording medium; having an image forming method.

[12] The surface of the electrophotographic photoreceptor is composed of a cured product of a polymerizable composition containing a polymerizable compound, the image forming method according to

[11] . [Advantages of the Invention]

[0012] According to the present invention, there are provided a toner for electrostatic charge image development, a method for manufacturing the toner for electrostatic charge image development, and an image forming method, which can enhance the cleaning property with respect to a photoreceptor and form an image in which image blurring and density unevenness are sufficiently suppressed even when repeatedly forming images. [Brief Description of the Drawings]

[0013]

Figure 1

Figure 2

[0014] 1. Toner for Electrostatic Charge Image Development The toner for electrostatic charge image development according to this embodiment (hereinafter simply referred to as toner) includes toner base particles containing a binder resin and a mixture in which an antioxidant is dispersed in a fatty acid metal salt. The above toner may be a one-component developer or a two-component developer having toner base particles and carrier particles.

[0015] As described above, in the photoreceptor having a layer containing the antioxidant described in Patent Document 1 and Patent Document 2, when forming repeated images, it was not possible to form an image with sufficiently suppressed image blur and density unevenness.

[0016] The antioxidant contained in the photoreceptor is consumed to suppress the progress of the oxidation reaction of the fatty acid metal salt and the charge transport material by ozone and nitrogen oxides generated in the charging process. Therefore, as the photoreceptor is used, the amount of the antioxidant contained in the photoreceptor decreases. Further, when forming a photoreceptor functional layer containing an antioxidant, a coating solution containing the antioxidant is applied to a conductive support (the base material of the photoreceptor). Oxygen is dissolved in the above coating solution, and the oxidation reaction of the charge transport material is likely to occur due to the heat applied when drying the applied coating solution. At this time, it is considered that the antioxidant contained in the above coating solution is consumed to suppress the above oxidation reaction.

[0017] For these reasons, when the photoreceptor is used, since the antioxidant is not sufficiently contained in the photoreceptor, it is considered that when the antioxidant is consumed by repeated use, the oxidation suppression of the fatty acid metal salt and the charge transport material is likely to become insufficient. As a result, it is considered that after forming repeated images, it was not possible to form an image with sufficiently suppressed image blur and density unevenness.

[0018] On the other hand, as a result of the inventors' further study, it was found that by using a toner in which a mixture in which an antioxidant is dispersed in a fatty acid metal salt is added to toner base particles, even after forming repeated images, an image with sufficiently suppressed image blur and density unevenness can be formed.

[0019] When the toner is applied to the surface of the photoreceptor, the above mixture containing the fatty acid metal salt is applied to the surface of the photoreceptor together with the toner base particles. Among the applied toner, the toner base particles are transferred to the recording medium during transfer, while the above mixture remains on the surface of the photoreceptor after transfer. In this way, the fatty acid metal salt as a lubricant and the antioxidant are applied to the entire surface of the photoreceptor. At this time, since the above mixture contains an antioxidant, oxidation of the fatty acid metal salt applied to the surface of the photoreceptor by ozone and nitrogen oxides generated during the process of charging the surface of the photoreceptor is suppressed. Also, oxidation of the charge transport material contained in the photoreceptor is suppressed by the above antioxidant. And since the toner is continuously applied to the surface of the photoreceptor, the fatty acid metal salt and the antioxidant contained in the toner are also continuously applied to the surface of the photoreceptor. From these facts, it is possible to suppress a decrease in the amount of the antioxidant on the surface of the photoreceptor even when forming repeated images.

[0020] Also, in the above mixture, since the antioxidant is dispersed at the molecular level in the fatty acid metal salt, the specific surface area of the antioxidant can be increased, and the reactivity of the antioxidant can be sufficiently enhanced. Thereby, it is considered that the progress of the oxidation reaction caused by ozone and nitrogen oxides can be sufficiently suppressed.

[0021] Furthermore, the fatty acid metal salt applied to the surface of the photoreceptor and whose oxidation is suppressed makes it difficult for the toner to remain on the photoreceptor after transfer, so that the cleaning property with respect to the photoreceptor can be enhanced.

[0022] For these reasons, it is considered that the toner according to the present embodiment can form an image in which image blur and density unevenness are sufficiently suppressed while improving the wear resistance of the surface of the photoreceptor and the cleaning property with respect to the photoreceptor by the fatty acid metal salt as a lubricant even when forming repeated images.

[0023] 1-1. Toner Base Particles In the present embodiment, the toner contains toner base particles.

[0024] The toner base particles preferably have a volume-based median diameter (D 50 ) of 1 μm or more and 10 μm or less, more preferably 2 μm or more and 8 μm or less. By setting the median diameter within the above range, the resolution of the formed image can be further enhanced.

[0025] The median diameter of the toner base particles can be measured using a measuring device connected to a computer system equipped with data processing software Software V3.51 and a particle size distribution measuring device (manufactured by Beckman Coulter, Coulter Multisizer 3). Specifically, 0.02 g of a sample (toner base particles) is added to 20 mL of a surfactant solution and allowed to mix, followed by ultrasonic dispersion treatment for 1 minute to prepare a dispersion of the toner base particles. The surfactant solution is, for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10-fold with pure water for the purpose of dispersing the toner base particles. This dispersion is pipetted into a beaker containing an electrolyte solution (manufactured by Beckman Coulter, ISOTON II) in a sample stand until the display concentration of the measuring device reaches 8%. By setting this concentration, reproducible measurement values can be obtained. Then, in the measuring device, the number of measured particles is set to 25,000, the aperture diameter is set to 100 μm, the measurement range of 2 to 60 μm is divided into 256 segments to calculate the frequency values, and based on this, the median diameter (D 50 ) is calculated.

[0026] 1-1-1. Binder resin The toner base particles contain a binder resin. The binder resin is a resin for binding the toner to the recording medium. The binder resin is preferably a thermoplastic resin.

[0027] Examples of the thermoplastic resin include styrene resins, vinyl resins (such as acrylic resins and styrene-acrylic resins), polyester resins, silicone resins, olefin resins, and polyamide resins. Among these, styrene resins, polyester resins, and styrene-acrylic resins are preferred, and styrene-acrylic resins are more preferred.

[0028] The binder resin may be an amorphous resin or a crystalline resin. Alternatively, it may be a composite resin in which a crystalline resin and an amorphous resin are hybridized.

[0029] In this specification, the crystalline resin means a resin in which a melting point is observed in the measurement by differential scanning calorimetry (DSC). Further, the amorphous resin means a resin in which no melting point is observed in the measurement by DSC. In this specification, that a melting point is observed in the resin means that a peak with a half-value width of the endothermic peak within 15 ° C is observed when measured at a heating rate of 10 ° C / min in DSC.

[0030] Examples of the crystalline resin include crystalline polyester resins, crystalline polyurethane resins, crystalline polyurea resins, crystalline polyamide resins, crystalline polyether resins, and the like.

[0031] The content of the binder resin is preferably 1% by mass or more and 40% by mass or less, more preferably 3% by mass or more and 25% by mass or less, based on the total mass of the toner base particles. When the content of the binder resin is 1% by mass or more, the strength of the formed image can be further increased.

[0032] 1-1-2. Other Components The toner base particles may contain a colorant, a release agent, a charge control agent, and the like.

[0033] The colorant may be a dye or a pigment. When the toner is a colored toner that imparts a predetermined color tone to the image, the toner base particles may contain a colorant such as yellow, magenta, cyan, or black according to the color tone to be exhibited by the colored toner. The colorant may be contained alone or in combination of a plurality of kinds in the toner base particles.

[0034] Examples of yellow colorants include yellow dyes and yellow pigments. Examples of the yellow dyes include C.I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162. Examples of the yellow pigments include C.I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180 and 185.

[0035] Examples of magenta colorants include magenta dyes and magenta pigments. Examples of the magenta dyes include C.I. Solvent Red 1, 49, 52, 58, 63, 111 and 122. Examples of the magenta pigments include C.I. Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178 and 222.

[0036] Examples of cyan colorants include cyan dyes such as C.I. Solvent Blue 25, 36, 60, 70, 93 and 95, and cyan pigments such as C.I. Pigment Blue 1, 7, 15, 15:3, 60, 62, 66 and 76.

[0037] Examples of black colorants include carbon blacks such as channel black, furnace black, acetylene black, thermal black and lamp black, and magnetic materials such as ferrite and magnetite.

[0038] The content of the colorant is preferably 0.5% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 10% by mass or less, based on the total mass of the toner base particles. When the toner is a clear toner, it is preferable that the toner base particles substantially do not contain a colorant, and the content of the colorant based on the total mass of the toner base particles is preferably 0.1% by mass or less.

[0039] The release agent can enhance the releasability of the toner from a fixing member or the like. The release agent is preferably wax.

[0040] Examples of release agents that are waxes include hydrocarbon waxes such as polyethylene wax, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax; dialkyl ketone waxes such as distearyl ketone; carnauba wax, montan wax, behenic acid behenate, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, and distearyl maleate; amide waxes such as ethylenediamine dibehenylamide and tristearyl trimellitate amide; and the like.

[0041] The content of the release agent is preferably 1% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on the total mass of the toner base particles. When the content of the release agent is 1% by mass or more, the releasability of the toner can be further improved. When the content of the release agent is 25% by mass or less, a sufficient amount of binder resin can be contained in the toner base particles, so that the fixability of the image is sufficiently enhanced.

[0042] Among these, from the viewpoint of further enhancing low-temperature fixability, the release agent is preferably a hydrocarbon wax or a fatty acid ester wax, more preferably a fatty acid ester wax. Thereby, the release agent can be more finely dispersed in the binder resin, so that the toner base particles can be more sufficiently plasticized and the low-temperature fixability can be further enhanced.

[0043] The charge control agent can adjust the chargeability of the toner base particles.

[0044] Examples of the charge control agent include nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, metal salts of salicylic acid or metal complexes thereof, and the like.

[0045] The content of the charge control agent is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, based on the total mass of the binder resin. Note that if an attempt is made to control the chargeability of the toner by methods such as adding an excessive amount of the charge control agent, other properties of the toner base particles may change significantly. In contrast, in the present embodiment, by adjusting the chargeability of the toner with strontium titanate, the chargeability of the toner can be adjusted to a desired level while satisfying other required properties.

[0046] 1-1-3. Morphology of Toner Base Particles In the present embodiment, the toner base particles containing the above-described components may be used as the toner as they are, or the toner base particles having a core-shell structure having the core particles and a resin shell layer covering the core particles may be used as the toner with the toner base particles as the core particles. At this time, the binder resin constituting the core particles and the resin constituting the shell layer may be the same type of resin or different types of resins.

[0047] 1-2. Mixture The mixture contained in the toner in this embodiment is externally added to the toner base particles. The above mixture is a mixture in which an antioxidant is dispersed in a fatty acid metal salt. That the above mixture is a mixture in which an antioxidant is dispersed in a fatty acid metal salt can be confirmed by performing time-of-flight secondary ion mass spectrometry (Tof-SIMS) on the mixture. Specifically, after fixing the toner particles with a photocurable resin, the particles are cut with a microtome to observe the cross-sections of the toner base particles and the mixture. Then, for the cross-section of the mixture, time-of-flight secondary ion mass spectrometry (Tof-SIMS) is performed, and the distribution of the antioxidant in the fatty acid metal salt is visualized by mapping the mass information of specific atoms or ions derived from the antioxidant. And it can be judged by confirming that the above specific atoms are uniformly distributed inside the mixture.

[0048] The volume-based median diameter (D 50 ) of the mixture is preferably 0.1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 20 μm or less. By the median diameter being within the above range, the cleaning property with respect to the photoreceptor can be further enhanced.

[0049] The content of the mixture is preferably 0.05% by mass or more and 10.00% by mass or less, and more preferably 0.10% by mass or more and 8.00% by mass or less with respect to the total mass of the toner.

[0050] Note that the mixture may contain other components other than the fatty acid metal salt and the antioxidant.

[0051] 1-2-1. Fatty acid metal salt In this embodiment, the fatty acid metal salt functions as a lubricant that adheres to the surface of the photoreceptor to enhance the abrasion resistance of the photoreceptor surface.

[0052] The fatty acid metal salt is not particularly limited in type as long as it has the above functions. Examples of the fatty acid metal salt include lead oleate, zinc oleate, copper oleate, zinc stearate, cobalt stearate, iron stearate, copper stearate, calcium stearate, aluminum stearate, zinc palmitate, copper palmitate, zinc linolenate, and the like. Among these, the fatty acid metal salt is preferably zinc stearate, calcium stearate, and aluminum stearate, more preferably zinc stearate and calcium stearate. Further, the fatty acid metal salt is more preferably aluminum stearate. These fatty acid metal salts have high ductility and are easily applied more uniformly over the entire surface of the photoreceptor. Therefore, these fatty acid metal salts can further enhance the abrasion resistance of the photoreceptor surface and the cleaning property with respect to the photoreceptor.

[0053] The content of the fatty acid metal salt is preferably 50 mol% or more and 95 mol% or less, more preferably 70 mol% or more and 90 mol% or less, based on the total number of moles of the fatty acid metal salt and the antioxidant. It can be measured by quantifying the metal of the fatty acid metal salt contained in the toner by ICP emission spectrometry (Inductively Coupled Plasma).

[0054] 1-2-2. Antioxidant As described above, the antioxidant is dispersed in the fatty acid metal salt.

[0055] Examples of the types of the antioxidant include phenolic compounds, hindered amine compounds, phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, and the like.

[0056] Examples of phenolic compounds include n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, n-octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)-acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, dodecyl β(3,5-di-t-butyl-4-hydroxyphenyl)propionate, ethyl α-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, octadecyl α-(4-hydroxy-3,5-di-t-butylphenyl)isobutyrate, octadecyl α-(4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-(n-octylthio)ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2-(n-octylthio)ethyl 3,5-di-t-butyl-4-hydroxy-phenylacetate, 2-(n-octadecylthio)ethyl 3,5-di-t-butyl-4-hydroxyphenylacetate, 2-(n-octadecylthio)ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2-(2-hydroxyethylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis-(3,5-di-t-butyl-4-hydroxy-phenyl)propionate, 2-(n-octadecylthio)ethyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, stearamide N,N-bis-[ethylene 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], n-butylimino N,N-bis-[ethylene 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2-(2-stearoyloxyethylthio)ethyl 3,5-di-t-butyl-4-hydroxybenzoate, 2-(2-stearoyloxyethylthio)ethyl 7-(3-methyl-5-t-butyl-4-hydroxyphenyl)heptanoate, 1,2-propylene glycol bis-[3-(3,5-Di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis-(3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3-bis-(3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis-[3-(3′,5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,1,1-trimethylolethane-tris-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], sorbitol hexa-[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7-(3-methyl-5-t-butyl-4-hydroxyphenyl) propionate, 2-stearoyloxyethyl 7-(3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis[(3′,5′-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis(3,5-di-t-butyl-4-hydroxyhydrocinnamate), etc. are included.,

[0057] Examples of hindered amine compounds include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl) succinate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis(N-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(N-benzyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-butylmalonate, bis(1-acroyl-2,2,6,6-tetramethyl-4-piperidyl) 2,2-bis(3,5-di-t-butyl-4-hydroxybenzyl)-2-butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) decanedioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-1-[2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl]-2,2,6,6-tetramethylpiperidine, 2-methyl-2-(2,2,6,6-tetramethyl-4-piperidyl)amino-N-(2,2,6,6-tetramethyl-4-piperidyl)propionamide, tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, and the like.Alternatively, a polymer type compound may be used. Specific examples include N,N’,N’’,N’’’-tetrakis-[4,6-bis-[butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino]-triazin-2-yl]-4,7-diazadecane-1,10-diamine, the polycondensate of dibutylamine, 1,3,5-triazine·N,N’-bis(2,2,6,6-tetramethyl-4-piperidyl)-1,6-hexamethylenediamine, and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, the polycondensate of dibutylamine, 1,3,5-triazine, and N,N’-bis(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[{(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], the polycondensate of 1,6-hexanediamine-N,N’-bis(2,2,6,6-tetramethyl-4-piperidyl) and morpholine-2,4,6-trichloro-1,3,5-triazine, poly[(6-morpholino-s-triazine-2,4-diyl)[(2,2,6,6,-tetramethyl-4-piperidyl)imino]-hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]] and other high molecular weight HALS in which a plurality of piperidine rings are bonded via a triazine skeleton, the polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, the mixed esterified product of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and compounds in which piperidine rings are bonded via ester bonds, etc. are included.

[0058] Examples of phosphorus compounds include monophosphite compounds such as triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, tris(dinonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1.3.2]dioxaphosphepine, tridecyl phosphite, diphosphite compounds such as 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis(phenyl-di-alkyl(C12-C15) phosphite), phosphonite compounds such as triphenyl phosphonite, tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite, tetrakis(2,4-di-tert-butyl-5-methylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite, phosphinite compounds such as triphenyl phosphinite, 2,6-dimethylphenyldiphenyl phosphinite, and phosphine compounds such as triphenylphosphine, tris(2,6-dimethoxyphenyl)phosphine.

[0059] Examples of sulfur compounds include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, lauryl stearyl 3,3'-thiodipropionate, pentaerythritol-tetrakis(β-lauryl-thio-propionate), 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and the like.

[0060] The antioxidant preferably contains an antioxidant having a piperidine derivative moiety in its molecular structure. Thereby, an image with more sufficiently suppressed image blurring and density unevenness can be formed. This is considered to be due to the following reasons.

[0061] When a fatty acid metal salt and a charge transport material are oxidized, the molecular chain is cleaved to generate radicals. When oxygen contained in the air is added to this radical, a peroxide radical (ROO·) is generated. The peroxide radical extracts a hydrogen atom contained in another molecular chain to become a hydroperoxide (ROOH). Since hydroperoxide is easily decomposed to generate radicals, the presence of hydroperoxide facilitates the progress of molecular decomposition due to oxidation. On the other hand, the piperidine derivative moiety is particularly likely to release electrons and can react with hydroperoxide to convert hydroperoxide into alcohol (ROH). Therefore, the generation of radicals from hydroperoxide can be suppressed, and the progress of molecular decomposition due to oxidation can be further suppressed. Thereby, an image with more sufficiently suppressed image blurring and density unevenness can be formed.

[0062] In this specification, the "piperidine derivative moiety" refers to a structure represented by the following general formula (1). In general formula (1), * is the bonding position, and R1 represents a hydrogen atom, an alkyl group, or an alkylene group. Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group. Among these, the alkyl group is preferably a methyl group. Examples of the alkylene group include a methylene group, an ethylene group, and a propylene group. Among these, the alkylene group is preferably a methylene group or an ethylene group. The alkylene group may be substituted and may contain a repeating unit via the alkylene group. R2 to R5 represent a hydrogen atom, an alkyl group, or an alkylene group. Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group. Among these, a methyl group is preferable.

[0063]

Chemical formula

[0064] The number of piperidine derivative moieties contained within the molecular structure of the antioxidant having a piperidine derivative moiety is not particularly limited, but is preferably 1 or more and 5 or less, and more preferably 2 or more and 4 or less.

[0065] The antioxidant having a piperidine derivative moiety preferably contains a phenol structure within its molecular structure. The hydroxy group contained in the phenol structure can react with peroxide radicals (ROO·) generated during the oxidation process to produce hydroperoxides (ROOH). Thereby, it is possible to suppress the peroxide radicals from extracting hydrogen atoms contained in other molecular chains, and suppress the decomposition of other molecules. As a result, and since the generated hydroperoxide reacts with the piperidine derivative moiety as described above, it is possible to suppress the generation of radicals and suppress the progress of the oxidation reaction. As a result of these, it is possible to more suppress the oxidation of the fatty acid metal salt and the charge transport material, and form an image in which image blur and density unevenness are more sufficiently suppressed.

[0066] In the present specification, the "phenol structure" refers to a structure represented by the following general formula (2). In general formula (2), * is the bonding position, and R6 to R9 are a hydrogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, or a thioalkyl group.

[0067]

Chemical formula

[0068] The number of phenol structures contained within the molecular structure of the antioxidant containing a piperidine derivative moiety and a phenol structure is not particularly limited, but is preferably 1 or more and 5 or less, and more preferably 2 or more and 4 or less.

[0069] Specific examples of the antioxidant include the following Compounds 1 to 53.

[0070] [Chemistry]

[0071] [Chemistry]

[0072] [Chemistry]

[0073] The oxidation potential of the antioxidant is preferably 2.0 V or less, more preferably 1.5 V or less, and even more preferably 0.6 V or less. When the oxidation potential is 2.0 V or less, the antioxidant is more likely to react with ozone and nitrogen oxides, so the progress of molecular decomposition due to oxidation can be more effectively suppressed. As a result, an image with more sufficiently suppressed image blur and density unevenness can be formed, and the cleaning property of the photoreceptor can be further enhanced. The lower limit value of the oxidation potential is, for example, 0.3 V. Also, the oxidation potential can be measured by the cyclic voltammetry method. Specifically, for example, it is measured according to the following procedure.

[0074] Put the antioxidant and an acetonitrile solution of 0.1 M tetrabutylammonium peroxide salt into a three-electrode cell. After confirming complete dissolution, perform nitrogen bubbling for 10 minutes. Then, measure the oxidation potential under the following conditions. Measuring device: ALS 600E Electrochemical Analyzer (manufactured by BAS Inc.) Scanning speed: 0.1 V / s Sweeping range: -1.2 V on the reduction side and +3.0 V on the oxidation side from the open-circuit potential Working electrode: Glassy carbon (diameter: 3.0 mm) Counter electrode: Platinum wire (outer diameter: 0.5 mm) Reference electrode: Ag / AgNO3 Others: Correct the measured value with the redox potential of ferrocene

[0075] The content of the antioxidant is preferably 5 mol% or more and 50 mol% or less, more preferably 10 mol% or more and 30 mol% or less, based on the total number of moles of the fatty acid metal salt and the antioxidant. When the above content is 5 mol% or more, oxidation of the fatty acid metal salt and the charge transport material due to ozone and nitrogen oxides generated in the charging step can be more sufficiently suppressed, and an image with more sufficiently suppressed image blurring and density unevenness can be formed. When the above content is 50 mol% or less, the content of the fatty acid metal salt can be increased to further enhance the cleaning property.

[0076] 1-3. Externally added agent In addition to the above mixture, the toner may contain an externally added agent added as a post-treatment agent to the surface of the toner base particles in order to enhance the fluidity, chargeability, and cleaning property of the toner.

[0077] The externally added agent preferably contains inorganic particles. Examples of the inorganic particles include silica particles, alumina particles, zirconia particles, titanium oxide particles, strontium titanate particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, tungsten oxide particles, tin oxide particles, and the like. These inorganic particles may be hydrophobically treated with a surface treatment agent such as a silane coupling agent or silicone oil, if necessary.

[0078] The particle size of the inorganic particles preferably has a number average primary particle size of 20 nm or more and 200 nm, more preferably 30 nm or more and 150 nm or less. The number average primary particle size of the externally added agent can be the average value of the horizontal Feret diameters measured for 100 particles by subjecting the image data of the inorganic particles captured by a scanning electron microscope (SEM) to binarization processing using an image processing analyzer.

[0079] Further, the externally added agent may contain organic particles including homopolymers such as styrene and methyl methacrylate, and copolymers thereof. The particle size of the organic particles preferably has a peak top particle size measured by the same method as that for strontium titanate of 10 nm or more and 1000 nm.

[0080] The content of the external additive is preferably 0.05% by mass or more and 5.00% by mass or less, more preferably 0.10% by mass or more and 3.00% by mass or less, based on the total mass of the toner.

[0081] 1-4. Carrier The carrier is mixed with the above-described toner base particles to form a two-component magnetic toner. The carrier may be any known magnetic particles that can be contained in the toner.

[0082] Examples of the magnetic particles include particles containing magnetic substances such as iron, steel, nickel, cobalt, ferrite, and magnetite, and alloys of these with aluminum, lead, etc. The carrier may be a coated carrier in which the surface of the particles composed of the above magnetic substance is coated with a resin or the like, or a resin-dispersed carrier in which the above magnetic substance is dispersed in a binder resin. Examples of the resin for coating include olefin resins, styrene resins, styrene-acrylic resins, silicone resins, polyester resins, and fluororesins. Examples of the binder resin include acrylic resins, styrene-acrylic resins, polyester resins, fluororesins, and phenolic resins.

[0083] The average particle diameter of the carrier is preferably 20 μm or more and 100 μm or less, more preferably 25 μm or more and 80 μm or less, in terms of the volume-based average particle diameter. The average particle diameter of the carrier can be measured by HELOS manufactured by SYMPATEC, a laser diffraction particle size distribution measuring device equipped with a wet disperser.

[0084] The content of the carrier is preferably 2% by mass or more and 10% by mass or less based on the total mass of the toner base particles and the carrier.

[0085] 2. Method for producing an electrostatic charge image developing toner Next, the method for manufacturing the toner described above will be explained. FIG. 1 is a flowchart showing the method for manufacturing the toner for electrostatic charge image development according to the present embodiment. As shown in FIG. 1, the method for manufacturing the toner for electrostatic charge image development according to the present embodiment includes a step of preparing a mixture in which an antioxidant is dispersed in a fatty acid metal salt (step S10), a step of preparing toner base particles (step S20), and a step of mixing the mixture and the toner base particles (step S30).

[0086] 2-1. Step of preparing the mixture (step S10) In this step, the above-described mixture in which an antioxidant is dispersed in a fatty acid metal salt is prepared. In this step, the above mixture may be prepared by producing the above mixture, or the above mixture separately produced may be prepared.

[0087] The method for producing the above mixture is not particularly limited. For example, a method of melt-kneading a fatty acid metal salt and an antioxidant, and a method of dissolving a fatty acid metal salt and an antioxidant in an organic solvent and then mixing them.

[0088] The above melt-kneading method can be performed using, for example, a single-screw kneader, a twin-screw kneader, or the like. The set temperature during melt-kneading may be equal to or higher than the melting points of the fatty acid metal salt and the antioxidant, and equal to or lower than the temperature at which their thermal decomposition can be suppressed. For example, the above set temperature is 40°C or higher and 250°C or lower.

[0089] In the method of dissolving and mixing in the above organic solvent, after mixing the fatty acid metal salt and the antioxidant, the mixture can be obtained by removing the organic solvent.

[0090] The above organic solvent is not particularly limited as long as it can dissolve the fatty acid metal salt and the antioxidant. For example, toluene, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, xylene, ethylbenzene, etc. Among these, the above organic solvent is preferably dimethylacetamide, dimethyl sulfoxide, and toluene, and more preferably toluene.

[0091] The amount of the organic solvent to be used is not particularly limited, but for example, it is preferably 2 times or more and 20 times or less the total mass of the fatty acid metal salt and the antioxidant. Further, when dissolving the fatty acid metal salt and the antioxidant, the temperature of the organic solvent is not particularly limited, but it is preferably a temperature of room temperature (25 ° C) or higher and lower than the boiling point of the above organic solvent.

[0092] When producing the above mixture, a step of pulverizing the produced mixture may be further performed. By the above pulverizing step, the mixture can be adjusted to a desired particle size.

[0093] The method for pulverizing the above mixture is not particularly limited, but for example, a method of manually pulverizing using a mortar and a pestle, a method of mechanically pulverizing using a coffee mill, a mill stardam, etc.

[0094] The volume-based median diameter (D 50 ) of the powder (mixture) obtained by pulverizing the above mixture is preferably 0.1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 30 μm or less.

[0095] Step of preparing toner base particles (Step S20) In this step, the above-mentioned toner base particles are prepared. In this step, the toner base particles may be manufactured, or separately manufactured toner base particles may be prepared.

[0096] When manufacturing the toner base particles, for example, the toner base particles can be manufactured by methods such as a pulverization method, an emulsion polymerization aggregation method, an emulsion aggregation method, a suspension polymerization method, and a dissolution suspension method. Among these, the pulverization method, the emulsion polymerization aggregation method, and the suspension polymerization method are preferable, and from the viewpoints of the uniformity of the particle diameter and the controllability of the shape, the emulsion polymerization aggregation method is more preferable.

[0097] The emulsion polymerization aggregation method is a method for producing toner, which includes a step of preparing a binder resin particle dispersion liquid, and a step of preparing a colorant particle dispersion liquid if necessary, mixing the obtained respective dispersion liquids, and aggregating them until a predetermined particle diameter is obtained. Hereinafter, a method for producing toner base particles by the emulsion polymerization aggregation method will be described.

[0098] (Step of preparing a binder resin particle dispersion liquid) In this step, a dispersion liquid of binder resin particles is prepared. Specifically, monomers used for synthesizing the binder resin are prepared, the prepared monomers and, if necessary, other monomers are introduced into an aqueous medium containing a polymerization initiator, and a polymerization reaction is carried out under heating and stirring to prepare a dispersion liquid of binder resin particles. In this specification, the "aqueous medium" refers to a solvent containing at least 50% by mass of water. Examples of components other than water in the aqueous medium include methanol, ethanol, isopropanol, acetone, dimethylformamide, methyl cellosolve, tetrahydrofuran, and the like.

[0099] Examples of the above polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropanoate, azobiscyanovaleric acid and its salts, hydrogen peroxide, and the like.

[0100] From the viewpoint of enhancing the dispersibility of oil droplets, a surfactant may be previously contained in the aqueous medium. Examples of the above surfactant include anionic surfactants such as sodium polyoxyethylene(2) dodecyl ether sulfate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate.

[0101] Also, when introducing monomers into the aqueous medium, a chain transfer agent may be introduced into the aqueous medium if necessary. Examples of the above chain transfer agent include n-octyl mercaptan, n-octyl-3-mercaptopropionate, and the like.

[0102] The polymerization temperature is preferably in the range of 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower. Also, the polymerization time is preferably 1 hour or longer and 12 hours or shorter.

[0103] In this step, a release agent may be added to the aqueous medium together with the monomer.

[0104] (Step of preparing a colorant particle dispersion) In this step, a colorant is added to an aqueous medium and dispersed into particles to prepare a colorant particle dispersion.

[0105] The method of dispersing the colorant into particles is not particularly limited. For example, the colorant can be dispersed using a homogenizer.

[0106] In the colorant particle dispersion obtained in this step, the volume-based median diameter of the release agent particles is preferably 100 nm or more and 300 nm or less, more preferably 50 nm or more and 200 nm or less. The median diameter of the colorant particles can be measured using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0107] (Step of aggregating resin particles) In this step, a flocculant is added to the binder resin particle dispersion (a mixed solution further added with a colorant particle dispersion as necessary), and the particles are aggregated and fused together while heating and stirring.

[0108] Examples of the above flocculants include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, polyaluminum chloride, copper sulfate, magnesium sulfate, manganese sulfate, aluminum sulfate, etc. These flocculants can be used alone or in combination of two or more.

[0109] The amount of the flocculant used is not particularly limited, but from the viewpoint of controlling the particle size of the toner, it is preferably 2% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on the solid content of the binder resin constituting the toner particles.

[0110] In this step, after adding the flocculant, it is preferable to rapidly raise the temperature by heating, and the rate of temperature increase is preferably 0.05 °C / min or more. The upper limit of the rate of temperature increase is not particularly limited, but from the viewpoint of suppressing the generation of coarse particles due to the rapid progress of fusion, it is preferably 15 °C / min or less. Further, after the dispersion liquid for aggregation reaches the desired temperature, it is preferable to hold the temperature of the dispersion liquid for aggregation for a certain period of time, preferably until the volume-based median diameter becomes 4.5 μm or more and 7.0 μm or less, to continue the fusion.

[0111] When producing toner mother particles having a core-shell structure, after adding the flocculant, heat to a temperature equal to or higher than the softening point of the binder resin particles serving as the core particles, and further add a dispersion liquid of the shell resin particles. Thereby, the core particles and the shell resin particles can be fused.

[0112] After this step, the aggregated particles obtained in this step are aged as necessary, and toner mother particles can be obtained by performing a washing and filtration step and a drying step.

[0113] (Aging step) In this step, the dispersion liquid in which the aggregated particles are dispersed is heated and stirred, and an aging treatment is performed by adjusting the heating temperature, stirring speed, heating time, etc. until the shape of the aggregated particles reaches the desired roundness. The aging treatment is performed as necessary.

[0114] (Washing and filtration step) In this step, the toner particles are separated from the dispersion liquid of the toner particles by solid-liquid separation, and the deposits such as surfactants and flocculants are removed from the toner cake (an aggregate obtained by aggregating the toner particles in a wet state into a cake shape) obtained by the solid-liquid separation and washed.

[0115] The method of solid-liquid separation is not particularly limited. Examples include centrifugal separation, vacuum filtration using a Nutsche filter, etc., and filtration using a filter press, etc.

[0116] (Drying step) In this step, the washed toner cake is dried. The drying method is not particularly limited. Examples include a flash jet dryer, a spray dryer, a vacuum freeze dryer, a vacuum dryer, etc.

[0117] 2-3. Step of mixing the mixture and the toner base particles (Step S30) In this step, the above mixture and the above toner base particles are mixed. In this step, if necessary, the above-mentioned external additive may be mixed together with the above mixture and the above toner.

[0118] The above mixing method is not particularly limited. For example, it is a method of mixing using a mechanical mixing device such as a Henschel mixer, a coffee mill, a sample mill, etc.

[0119] 3. Image forming method and image forming apparatus Another embodiment of the present invention relates to an image forming apparatus having a toner image forming unit that develops an electrostatic charge image with toner to form a toner image, and a fixing device that fixes the toner image on a recording medium by transferring the toner image onto the recording medium, and an image forming method using the image forming layer. In this embodiment, the fixing device fixes the above-mentioned toner on the recording medium.

[0120] The above image forming apparatus may be a four-cycle type image forming apparatus composed of four color developing devices of yellow, magenta, cyan, and black, and one electrophotographic photoreceptor. Further, the above-mentioned image forming apparatus may be a tandem type image forming apparatus composed of four color developing devices of yellow, magenta, cyan, and black, and four electrophotographic photoreceptors provided for each color.

[0121] FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 shown in FIG. 2 includes an image processing unit 30, an image forming unit 40, a paper conveyance unit 50, a fixing device 60, and an image reading unit 70.

[0122] The image forming unit 40 includes image forming units 41Y, 41M, 41C, and 41K that form images using respective color toners of Y (yellow), M (magenta), C (cyan), and K (black). Since these have the same configuration except for the toner to be contained, the symbols representing colors may be omitted hereinafter. The image forming unit 40 further includes an intermediate transfer unit 42 and a secondary transfer unit 43. These correspond to transfer devices.

[0123] The image forming unit 41 includes an exposure device 411, a developing device 412, an electrophotographic photoreceptor 413, a charging device 414, and a drum cleaning device 415. The charging device 414 is, for example, a corona charger. The charging device 414 may be a contact charging device that brings a contact charging member such as a charging roller, a charging brush, or a charging blade into contact with the electrophotographic photoreceptor 413 to charge it. The exposure device 411 includes, for example, a semiconductor laser as a light source and a light deflector (polygon motor) that irradiates the electrophotographic photoreceptor 413 with laser light corresponding to the image to be formed. The electrophotographic photoreceptor 413 is a negatively charged organic photoreceptor having photoconductivity. The electrophotographic photoreceptor 413 is charged by the charging device 414.

[0124] The developing device 412 is a developing device using a two-component developing method. The developing device 412 includes, for example, a developing container that houses a two-component developer, a developing roller (magnetic roller) rotatably disposed at an opening of the developing container, a partition wall that partitions the inside of the developing container so that the two-component developer can communicate, a transfer roller for transferring the two-component developer on the opening side of the developing container toward the developing roller, and a stirring roller for stirring the two-component developer in the developing container. The developing container houses, for example, a two-component developer.

[0125] The electrophotographic photoreceptor 413 has at least a conductive support and a functional layer disposed on the conductive support. The functional layer only needs to have at least a charge generation layer and a charge transport layer, and may further have, for example, an undercoat layer or a protective layer. In the present embodiment, the functional layer has a structure in which an undercoat layer, a charge generation layer, a charge transport layer, and a protective layer are laminated in this order.

[0126] The conductive support is not particularly limited as long as it has conductivity. The conductive support is, for example, a drum or sheet formed of a metal such as aluminum, copper, chromium, nickel, zinc, or stainless steel, or a laminate of a metal foil such as aluminum or copper on a plastic film. Further, examples of the conductive support include those obtained by vapor-depositing aluminum, indium oxide, tin oxide, etc. on a plastic film, metals, plastic films, and papers provided with a conductive layer by applying a conductive substance alone or together with a binder resin.

[0127] The undercoat layer is a layer for suppressing charge injection from the conductive support to the charge generation layer side, improving the adhesiveness of the charge generation layer, and further preventing moiré due to light scattering. The undercoat layer can be a layer containing a binder resin and conductive particles or metal oxide particles. Examples of the binder resin include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, gelatin, etc. Examples of the conductive particles include indium oxide doped with tin, tin oxide doped with antimony, zirconium oxide, etc. Examples of the metal oxide particles include aluminum oxide, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, etc.

[0128] Also, from the viewpoint of adjusting the electrical resistance, the thickness of the undercoat layer is preferably 0.1 μm or more and 15 μm or less, and more preferably 0.3 μm or more and 10 μm or less.

[0129] The charge generation layer is a layer that generates charges upon exposure, and is mainly a layer containing a binder resin and a charge generation material. Examples of binder resins for the charge generation layer include polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymers containing two or more of these resins (e.g., vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer), polyvinyl carbazole resin, etc.

[0130] The charge generation material is not particularly limited. Polycyclic quinone pigments and titanyl phthalocyanine pigments are preferred as the charge generation material. The charge generation material may contain only one of these or may contain two or more of them.

[0131] The thickness of the charge generation layer is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 3 μm or less.

[0132] The charge transport layer is a layer for transporting holes among the charges generated in the charge generation layer to the surface of the electrophotographic photoreceptor 413 (here, the surface of the protective layer). The charge transport layer mainly contains a binder resin and a charge transport material. Examples of binder resins for the charge transport layer include bisphenol A type, bisphenol Z type, dimethyl bisphenol A type, polycarbonate resins of the bisphenol A type-dimethyl bisphenol A type copolymer type, polyacrylate resins, polyester resins, polystyrene resins, styrene-acrylonitrile copolymers, polymethacrylic acid ester resins, styrene-methacrylic acid ester copolymers, etc.

[0133] The type of the charge transport material is not particularly limited, and examples thereof include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds, and the like. When the electrophotographic photoreceptor 413 has a protective layer described later, the charge transport material is preferably a material having high charge transport performance. Examples of such charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, the following compound A, and the like.

[0134] [Chemical formula]

[0135] The thickness of the charge transport layer is preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 40 μm or less.

[0136] The protective layer is a layer for protecting the surface of the electrophotographic photoreceptor 413, improving abrasion resistance and scratch resistance, and reducing the occurrence of toner leakage. When the electrophotographic photoreceptor 413 has a protective layer, the electrophotographic photoreceptor 413, and thus the image forming apparatus 1, can have a longer life. The protective layer can contain, for example, a binder resin, inorganic fine particles, a charge transport material, and the like.

[0137] Examples of the binder resin for the protective layer include polycarbonate resins, polyacrylate resins, polyester resins, polystyrene resins, styrene-acrylonitrile copolymers, polymethacrylic acid ester resins, styrene-methacrylic acid ester copolymers, and the like.

[0138] The protective layer is preferably a cured product of a polymerizable composition containing a polymerizable compound. That is, the surface of the electrophotographic photoreceptor 413 is preferably composed of a cured product of a polymerizable composition containing a polymerizable compound. As a result, the crosslink density of the protective layer is increased, and it is considered that ozone, nitrogen oxides, and oxygen are less likely to penetrate in the depth direction of the protective layer. As a result, oxidation of the charge transport material is further suppressed, and an image with more sufficiently suppressed image blurring can be formed. The above polymerizable composition may further contain inorganic fine particles for the protective layer and a charge transport material for the protective layer, which will be described later.

[0139] Examples of the above polymerizable compounds include polymerizable compounds that polymerize by heat (heat-polymerizable compounds) and polymerizable compounds that polymerize by actinic rays (actinic-ray polymerizable compounds). Among these, actinic-ray polymerizable compounds are preferred. Examples of the above actinic-ray polymerizable compounds include cationic polymerizable compounds and radical polymerizable compounds. Among these, radical polymerizable compounds are preferred. A radical polymerizable compound is a compound having a radical polymerizable functional group. The above radical polymerizable functional group is preferably a (meth)acryloyl group. In this specification, the "(meth)acryloyl group" means an acryloyl group or a methacryloyl group. Examples of actinic rays include electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays. Among these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred.

[0140] The above inorganic fine particles are not particularly limited as long as they are compounds stable in the atmosphere, but are preferably insulating oxide particles from the viewpoint of not hindering the function of the charge transport material. Examples of the inorganic fine particles include silica, alumina, magnesium oxide, zirconium oxide, calcium titanate, and the like. The protective layer 124 may contain only one of these, or may contain two or more of them.

[0141] The content of the inorganic fine particles is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass or less, based on the total mass of the binder resin for the protective layer. When it is 5% by mass or more, the abrasion resistance of the electrophotographic photoreceptor can be easily obtained sufficiently. Also, when it is 50% by mass or less, the strength of the protective layer can be easily obtained sufficiently, and cracks and the like are less likely to occur.

[0142] The charge transport material for the protective layer is the same as the charge transport material contained in the above-described charge transport layer. Also, the content of the charge transport material is preferably 30% by mass or more and 200% by mass or less, more preferably 50% by mass or more and 150% by mass or less, based on the total mass of the binder resin.

[0143] The thickness of the protective layer is preferably 1 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less.

[0144] The intermediate transfer unit 42 includes an intermediate transfer belt (intermediate transfer body) 421, a primary transfer roller 422 that presses the intermediate transfer belt 421 against the electrophotographic photoreceptor 413, a plurality of support rollers 423 including a backup roller 423A, and a belt cleaning device 426. The intermediate transfer belt 421 is looped around the plurality of support rollers 423. When at least one drive roller among the plurality of support rollers 423 rotates, the intermediate transfer belt 421 travels at a constant speed in the direction of arrow A.

[0145] The belt cleaning device 426 has an elastic member 426a. The elastic member 426a abuts against the intermediate transfer belt 421 after secondary transfer and removes the deposits on the surface of the intermediate transfer belt 421. The elastic member 426a is composed of an elastic body and includes a cleaning blade, a brush, and the like.

[0146] The secondary transfer unit 43 has an endless secondary transfer belt 432 and a plurality of support rollers 431 including a secondary transfer roller 431A. The secondary transfer belt 432 is looped by the secondary transfer roller 431A and the support rollers 431.

[0147] The fixing device 60 has, for example, a fixing roller 62, an endless heating belt 10 that covers the outer peripheral surface of the fixing roller 62 and heats and melts the toner constituting the toner image on the paper S, and a pressing roller 63 that presses the paper S toward the fixing roller 62 and the heating belt 10. The paper S corresponds to a recording medium.

[0148] The image forming apparatus 1 further has an image reading unit 70, an image processing unit 30, and a paper conveyance unit 50. The image reading unit 70 has a paper feeding device 71 and a scanner 72. The paper conveyance unit 50 has a paper feeding unit 51, a paper discharging unit 52, and a conveyance path unit 53. In the three paper feeding tray units 51a to 51c constituting the paper feeding unit 51, papers S (standard papers, special papers) identified based on basis weight, size, etc. are stored for each preset type. The conveyance path unit 53 has a plurality of conveyance roller pairs such as a registration roller pair 53a.

[0149] The formation of an image by the image forming apparatus 1 will be described. The scanner 72 optically scans and reads the document D on the contact glass. The reflected light from the document D is read by the CCD sensor 72a and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 30 and sent to the exposure device 411.

[0150] The electrophotographic photoreceptor 413 rotates at a constant peripheral speed. The charging device 414 uniformly charges the surface of the electrophotographic photoreceptor 413 to a negative polarity. In the exposure device 411, the polygon mirror of the polygon motor rotates at high speed, and laser light corresponding to the input image data of each color component is developed along the axial direction of the electrophotographic photoreceptor 413 and irradiated onto the outer peripheral surface of the electrophotographic photoreceptor 413 along the axial direction. Thus, an electrostatic charge image is formed on the surface of the electrophotographic photoreceptor 413.

[0151] In the developing device 412, the toner base particles are charged by stirring and conveying the two-component developer in the developing container, and the two-component developer is conveyed to the developing roller, where a magnetic brush is formed on the surface of the developing roller. The charged toner base particles electrostatically adhere from the magnetic brush to the portion of the electrostatic latent image on the electrophotographic photoreceptor 413. Thus, the electrostatic latent image on the surface of the electrophotographic photoreceptor 413 is visualized, and a toner image corresponding to the electrostatic latent image is formed on the surface of the electrophotographic photoreceptor 413. Note that the "toner image" refers to a state in which toner is aggregated in an image shape.

[0152] The toner image on the surface of the electrophotographic photoreceptor 413 is transferred to the intermediate transfer belt 421 by the intermediate transfer unit 42. The transfer residual toner remaining on the surface of the electrophotographic photoreceptor 413 after transfer is removed by the drum cleaning device 415 having a drum cleaning blade that is in sliding contact with the surface of the electrophotographic photoreceptor 413.

[0153] When the intermediate transfer belt 421 is pressed against the electrophotographic photoreceptor 413 by the primary transfer roller 422, a primary transfer nip is formed for each electrophotographic photoreceptor by the electrophotographic photoreceptor 413 and the intermediate transfer belt 421. In the primary transfer nip, the toner images of each color are sequentially overlapped and transferred to the intermediate transfer belt 421.

[0154] On the other hand, the secondary transfer roller 431A is pressed against the backup roller 423A via the intermediate transfer belt 421 and the secondary transfer belt 432. Thereby, a secondary transfer nip is formed by the intermediate transfer belt 421 and the secondary transfer belt 432. The sheet S passes through the secondary transfer nip. The sheet S is conveyed to the secondary transfer nip by the sheet conveying unit 50. Correction of the inclination of the sheet S and adjustment of the conveyance timing are performed by the registration roller unit provided with the registration roller pair 53a.

[0155] When the paper S is conveyed to the secondary transfer nip, a transfer bias is applied to the secondary transfer roller 431A. By applying this transfer bias, the toner image carried on the intermediate transfer belt 421 is transferred to the paper S (the step of attaching the electrostatic charge image developing toner to the recording medium). The paper S onto which the toner image has been transferred is conveyed toward the fixing device 60 by the secondary transfer belt 432.

[0156] Adhesions such as residual transfer toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer are removed by a belt cleaning device 426 having a cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421. At this time, since the above-described intermediate transfer body is used as the intermediate transfer belt, the dynamic frictional force can be reduced over time.

[0157] The fixing device 60 forms a fixing nip by sandwiching the heating belt 10 between a rotating fixing roller 62 and a pressure roller 63, and heats and presses the conveyed paper S at the fixing nip portion. In this way, the toner image is fixed to the paper S (the step of fixing the electrostatic charge image developing toner to the recording medium). The paper S onto which the toner image has been fixed is discharged outside the machine by a discharging unit 52 provided with a discharging roller 52a.

Example

[0158] Hereinafter, the present invention will be described with reference to examples. The scope of the present invention is not construed as being limited by the examples.

[0159] 1. Preparation of a mixture of an antioxidant and a fatty acid metal salt (Mixture LA-1) 9.5 g (15 mmol) of zinc stearate (manufactured by Kanto Chemical Co., Inc.) and 2.4 g (5 mmol) of an antioxidant (TINUVIN 770, manufactured by BASF Japan Ltd., corresponding to Antioxidant 23) were sequentially charged into the hopper of a small kneading and molding machine (Xplore MC15HT, manufactured by Xplore Instruments), and the powder was fed into the screw. Next, a mixture was prepared by melt-kneading at 180°C and 130 rpm for 5 minutes. Then, the mixture was discharged from the pipe for moving the mixture from the kneading section to the molding section of the above small kneading and molding machine. The obtained mixture was pulverized in a mortar and passed through a sieve with an opening of 25 μm. As a result, a mixed body LA-1 in which an antioxidant was dispersed in a fatty acid metal salt was obtained, and the particle size (D 50 ) at which the cumulative value in the volume-based particle size distribution was 50% was 4.8 μm. That the obtained mixed body LA-1 was a mixed body in which an antioxidant was dispersed in stearic acid was determined by visualizing the distribution of nitrogen atoms contained in the above antioxidant in the mixed body by a time-of-flight secondary ion mass spectrometer (Tof-SIMS TRIFT-V nanoTOF, manufactured by ULVAC-PHI, Inc.) after cutting out a cross-section of the mixed body with a microtome and confirming that the nitrogen atoms were uniformly distributed inside the mixed body.

[0160] (Mixed bodies LA-2 to LA-7, LA-9 to LA-17) Except that the type of fatty acid metal salt, the type, and the amount of the antioxidant were changed as shown in Table 1, mixed bodies LA-2 to LA-7, LA-9 to LA-17 in which an antioxidant was dispersed in a fatty acid metal salt were obtained in the same manner. The numbers of the antioxidants in Table 1 correspond to the numbers of the compounds shown in the above specific examples of the antioxidants. When it is shown in Table 1 that two types of antioxidants were used, it means that they were used in a molar ratio of 1:1. Also, in Table 1, those marked with "Zn" as the fatty acid metal salt mean zinc stearate, those marked with "Al" mean aluminum stearate, and those marked with "Mg" mean magnesium stearate.

[0161] Regarding the blends LA-2 to LA-7, LA-9, and LA-10, that these blends are blends in which an antioxidant is dispersed in a fatty acid metal salt was confirmed by visualizing the distribution of nitrogen atoms in the same manner as for blend LA-1. Regarding blends LA-11 and LA-12, the distribution of C4H9 + was visualized in the same manner, for blends LA-13 and LA-15, the distribution of phosphorus atoms and C4H9 + was visualized, and for blend LA-14, the distribution of C4H9 + and phosphorus atoms was visualized and confirmed. Also, regarding blend LA-16, the distribution of sulfur atoms was visualized, and for blend LS-17, the distribution of C4H9 + and sulfur atoms was confirmed by visualization.

[0162] Further, the oxidation potential [V] of the antioxidant described in Table 1 is measured by the following procedure using cyclic voltammetry.

[0163] An antioxidant and an acetonitrile solution of 0.1 M tetrabutylammonium peroxide salt were placed in a three-electrode cell, and after confirming complete dissolution, nitrogen bubbling was carried out for 10 minutes. Thereafter, the oxidation potential was measured under the following conditions. Measuring device: ALS 600E Electrochemical Analyzer (manufactured by BAS Inc.) Scanning rate: 0.1 V / s Sweeping range: -1.2 V on the reduction side and +3.0 V on the oxidation side from the open circuit potential Working electrode: Glassy carbon (diameter: 3.0 mm) Counter electrode: Platinum wire (outer diameter: 0.5 mm)) Reference electrode: Ag / AgNO3 Others: The measured values were corrected with the redox potential of ferrocene

[0164] (Blend LA-8) Into a 300 ml flask, 9.5 g (15 mmol) of zinc stearate (manufactured by Kanto Chemical Co., Inc.), 2.5 g (5 mmol) of an antioxidant (TINUVIN 765, manufactured by BASF Japan Ltd., corresponding to antioxidant 24), and 120 ml of toluene (manufactured by Kanto Chemical Co., Inc.) were charged, and the mixture was heated and stirred at 100 °C. After confirming that the zinc stearate and the antioxidant were completely dissolved, the mixture was cooled to around 50 °C, and the solvent was distilled off using a rotary evaporator while adjusting the degree of vacuum so as not to cause bumping. Thereafter, the toluene was removed by reducing the pressure at room temperature (25 °C) for 3 hours using a vacuum pump. The obtained mixture was pulverized in a mortar and then passed through a sieve with an opening of 25 μm. As a result, a mixture LA-8 in which an antioxidant was dispersed in a fatty acid metal salt, having a particle size (D 50 ) at which the cumulative value in the volume-based particle size distribution was 50% of 5.1 μm, was obtained.

[0165] 2. Preparation of a non-mixture of an antioxidant and a fatty acid metal salt (LA-18) Zinc stearate (manufactured by Kanto Chemical Co., Inc.) and an antioxidant (TINUVIN 765, manufactured by BASF Japan Ltd., corresponding to antioxidant 24) were weighed so that the ratio of the number of moles of the antioxidant to the total number of moles of both was 25 mol%. No mixing operation was performed on the zinc stearate and the antioxidant weighed here, and the total amount of both was adjusted to be 0.2 mass% with respect to the total mass of the toner base particles to be produced. Then, the general name of the zinc stearate and the antioxidant weighed here was designated as non-mixture LA-18.

[0166] (LA-19) 3 parts by mass of an antioxidant (TINUVIN 765, manufactured by BASF Japan Ltd., corresponding to antioxidant 24) and 35 parts by mass of toluene were added to a 300 mL beaker and stirred to dissolve the antioxidant. This was used as the antioxidant solution. Then, separately, 2.2 parts by mass of a surfactant (E-27C, manufactured by Kao Corporation) and 84 parts by mass of water were added to a 300 mL beaker to prepare an aqueous surfactant solution. Then, the antioxidant solution was added to the aqueous surfactant solution, and dispersion treatment was carried out for 10 minutes using an ultrasonic device (ASU CLEANER ASU-6M, manufactured by AS ONE Corporation) to prepare an antioxidant dispersion solution. Thereafter, the antioxidant dispersion solution was applied to an evaporator to remove toluene and prepare an aqueous antioxidant dispersion solution.

[0167] An aqueous solution of zinc stearate (concentration 10% by mass, solvent: pure water) and an aqueous solution of zinc sulfate (concentration 3% by mass, solvent: pure water) were each weighed at 100 g, and the liquid temperature of each was adjusted to 70°C. Next, a receiving container (capacity 2 L) equipped with a stirring device having a turbine blade with a diameter of 6 cm was prepared, the aqueous solution of zinc stearate was placed in the above receiving container, and the turbine blade was rotated at 350 rpm. Thereafter, the aqueous solution of zinc sulfate was added to the receiving container containing the aqueous solution of zinc stearate over 30 minutes, and stirring was carried out for 1 hour while maintaining the liquid temperature at 70°C. Thereby, a slurry of zinc stearate particles was obtained.

[0168] 100 g of the above aqueous antioxidant dispersion solution was added to the obtained slurry and mixed and dispersed. The cake obtained thereby was washed with water until the conductivity of the filtrate became 300 μS / cm or less, and then the cake was dried in a hot air dryer at 105°C for 12 hours. Thereby, a composite LA-19 in which antioxidant particles were supported on zinc stearate particles was obtained. That the antioxidant particles were supported on the zinc stearate particles was judged by visualizing the distribution of nitrogen atoms contained in the above antioxidant in the composite LA-19 using a time-of-flight secondary ion mass spectrometer (TRIFT-V nanoTOF, manufactured by ULVAC-PHI, Inc.) and confirming that the nitrogen atoms were distributed outside the fatty acid metal salt.

[0169] (LA-20, LA-21) Zinc stearate (manufactured by Kanto Chemical Co., Inc.) was weighed so as to be 0.2% by mass based on the total mass of the toner to be produced.

[0170] 3. Preparation of developer (Preparation of core resin particle dispersion) 201 parts by mass of styrene, 117 parts by mass of butyl acrylate, and 18.3 parts by mass of methacrylic acid were mixed, and the resulting monomer mixture was heated to 80 °C while stirring, and 172 parts by mass of behenyl behenate was gradually added and dissolved. Next, an aqueous surfactant solution prepared by dissolving 11.3 parts by mass of an anionic surfactant (Emal E-27C, manufactured by Kao Corporation, active ingredient 27% by mass) in 1182 parts by mass of pure water was heated to 80 °C, and the above monomer solution was added, followed by high-speed stirring. Thereby, a monomer dispersion was prepared.

[0171] Then, 867.5 parts by mass of pure water was charged into a polymerization apparatus equipped with a stirrer, a condenser, a temperature sensor, and a nitrogen inlet tube, and the internal temperature was set to 80 °C while stirring under a nitrogen stream. The above monomer dispersion was charged into this polymerization apparatus, and an aqueous polymerization initiator solution prepared by dissolving 8.55 parts by mass of potassium persulfate in 162.5 parts by mass of pure water was charged.

[0172] Thereafter, 5.2 parts by mass of n-octyl mercaptan was added over 35 minutes, and polymerization was further carried out at 80 °C for 2 hours. Further, an aqueous polymerization initiator solution prepared by dissolving 9.96 parts by mass of potassium persulfate in 189.3 parts by mass of pure water was added, and a monomer solution obtained by mixing 366.1 parts by mass of styrene, 179.1 parts by mass of butyl acrylate, and 7.2 parts by mass of n-octyl mercaptan was added dropwise over 1 hour. Thereafter, after continuing the polymerization treatment for 2 hours, it was cooled to room temperature to prepare a core resin particle dispersion.

[0173] (Preparation of shell resin particle dispersion) To a reactor equipped with a stirring device, a cooling pipe, a nitrogen introduction pipe, and a temperature sensor, 2948 parts by mass of pure water and 2.3 parts by mass of an anionic surfactant (Emal 2FG, manufactured by Kao Corporation) were added and stirred until dissolved, and then heated to 80 °C under a nitrogen stream.

[0174] Next, a monomer solution obtained by mixing 520 parts by mass of styrene, 184 parts by mass of butyl acrylate, 96 parts by mass of methacrylic acid, and 22.1 parts by mass of n-octyl mercaptan, and an aqueous polymerization initiator solution obtained by dissolving 10.2 parts by mass of potassium persulfate in 218 parts by mass of pure water were prepared. After the prepared aqueous polymerization initiator solution was charged into the reactor, the monomer mixture was added dropwise over 3 hours, and polymerization was further carried out for 1 hour. Thereafter, it was cooled to room temperature to prepare a shell resin particle dispersion. The weight average molecular weight of the shell resin fine particles was 13200, and the mass average particle diameter was 82 nm. The above weight average molecular weight was measured using gel permeation chromatography. Also, the above average particle diameter was measured using a particle size distribution measuring device (manufactured by Beckman Coulter).

[0175] (Preparation of Cyan Colorant Dispersion) 11.5 parts by mass of sodium n-dodecyl sulfate was dissolved in 1600 parts by mass of pure water, and 25 parts by mass of a cyan pigment (C.I. Pigment Blue 15:3) was gradually added. Next, the cyan pigment was dispersed using a precision emulsifying disperser (ClearMix W Motion CLM-0.8, manufactured by M-Technique Co., Ltd.). Thereby, a cyan colorant dispersion having a median diameter of 153 nm based on the number of cyan pigment particles was prepared.

[0176] (Preparation of Toner Particles) 357 parts by mass (in terms of solid content) of the core resin particle dispersion, 68 parts by mass (in terms of solid content) of the fine particle dispersion of polyester ionomer resin (Fine Tech ES-2200, manufactured by DIC Corporation), 900 parts by mass of ion-exchanged water, and 200 parts by mass (in terms of solid content) of the cyan coloring agent dispersion were charged into a reactor equipped with a stirrer, a temperature sensor, and a cooling pipe. Then, while maintaining the temperature inside the container at 30°C, a 5 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 10.

[0177] Next, while stirring an aqueous solution prepared by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water, it was dropped into the above reactor over 10 minutes, and then the temperature inside the container was raised to 75°C to agglomerate and fuse the core resin particles. In this state, the particle size of the agglomerated and fused particles was measured using a particle size distribution measuring device (Coulter Counter 3, manufactured by Beckman Coulter). While referring to the measurement results, heating and stirring were continued until the median diameter (D 50 ) in terms of the number of the above particles reached 6.0 μm.

[0178] When the above median diameter (D50) reached 6.0 μm, 210 parts by mass (in terms of solid content) of the shell resin particle dispersion was added, and stirring was carried out for 1 hour to fuse the shell resin particles onto the surface of the core resin particles. Further, stirring was continuously carried out as it was for 30 minutes until the shell was completely formed, then an aqueous sodium chloride solution prepared by dissolving 40 parts by mass of sodium chloride in 500 parts by mass of ion-exchanged water was added, the internal temperature was raised to 78°C, and stirring was continued for 1 hour. Then, it was cooled to room temperature (25°C) to form particles. The generated particles were repeatedly washed with ion-exchanged water and then dried with warm air at 35°C to produce toner mother particles.

[0179] To the prepared toner base particles, 1 part by mass of hydrophobic silica (number-average primary particle size: 12 nm, degree of hydrophobicity: 68), 1 part by mass of hydrophobic titanium oxide (number-average primary particle size: 20 nm, degree of hydrophobicity: 64), and 0.2 part by mass of mixture LA-1 were added, and mixing treatment was performed using a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Machinery Co., Ltd.). Thereafter, coarse particles were removed using a sieve with an opening diameter of 45 μm to produce toner D-1. The particle size of the obtained toner D-1 was 6.0 μm. Also, the average circularity of the particles was 0.96. The above particle size was a value measured using a particle size distribution measuring device (Coulter Counter 3, manufactured by Beckman Coulter), and the average circularity was a value measured using a measuring device (FPIA-3000, manufactured by Sysmex). Also, the value of the parts by mass of each component added to the toner base particles is a value relative to 100 parts by mass of the toner base particles.

[0180] Toner D-2 to D-17 were produced in the same manner except that mixtures LA-2 to LA-17 were used instead of mixture LA-1. Also, toner D-18 to D-21 were produced in the same manner except that unmixed substances LA-18 to LA-21 were used instead of mixture LA-1.

[0181] (Preparation of Carrier) To a mixture with a composition ratio of Fe2O3 = 60 mol% and MgO = 40 mol%, 0.01 mass% of MgCl2 was added based on the total mass of the above mixture and mixed, and the raw materials were pulverized using a pulverizing and mixing machine.

[0182] Next, an adhesive (polyvinyl alcohol) and water were added to the pulverized product obtained by pulverization to obtain a slurry with a pulverized product concentration of 60 mass%, and then further pulverization treatment was performed using a wet ball mill to produce a slurried dispersion. This slurried dispersion was spray-dried using a spray dryer to produce granulated particles with a particle size (Feret diameter) of 60 μm. The above granulated particles were fired at 1150°C in a drying furnace under an air atmosphere.

[0183] The particles obtained by firing were disintegrated, and after sieving to remove those with large and small particle sizes, particles with a particle size (Feret diameter) of about 50 μm were obtained. Then, these particles were subjected to magnetic separation using a magnetic separator to remove non-magnetic or weakly magnetic particles, and ferrite particles 1 were produced.

[0184] 100 parts by mass of ferrite particles 1 and a copolymer resin of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5 / 5) at 5% by mass based on the total mass of ferrite particles 1 were put into a high-speed stirring mixer with stirring blades. Then, they were stirred and mixed at 120 °C for 30 minutes, and a resin-coated carrier in which a coating layer of the resin was formed on the surface of the ferrite particles using the action of mechanical impact force was produced. The obtained resin-coated carrier was designated as resin-coated carrier 1.

[0185] (Preparation of developer) Toner D-1 and resin-coated carrier 1 were blended so that the toner concentration became 8% by mass, and using a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Machinery Co., Ltd.), mixing treatment was carried out in an environment of 20 °C and 50% RH. Thereby, developer E-1 was obtained.

[0186] Developers E-2 to E-21 were obtained in the same manner except that toners D-2 to D-21 were used instead of toner D-1.

[0187] 4. Preparation of electrophotographic photoreceptor <Electrophotographic photoreceptor CU-1> (Conductive support) The surface of a cylindrical aluminum support with a diameter of 30 mm was machined by cutting to prepare a conductive support with a surface roughness Rz = 1.5 (μm).

[0188] (Undercoat layer (UCL)) The following materials were mixed and dispersed batchwise for 10 hours using a sand mill. After standing overnight, filtration was performed using a filtration filter (Rigid Mesh 5 μm filter manufactured by Nippon Pall Co., Ltd.) to prepare an undercoat layer coating solution. This undercoat layer coating solution was applied onto the above conductive support by dip coating to form an undercoat layer with a dry film thickness of 2 μm. 1 part by mass of polyamide resin CM8000 (manufactured by Toray Industries, Inc.) (binder) 3 parts by mass of titanium oxide SMT500SAS (manufactured by Teika Corporation) 15 parts by mass of methanol 5 parts by mass of tetrahydrofuran

[0189] (Charge generation layer (CGL)) The following materials were mixed and dispersed for 10 hours using a sand mill to prepare a charge generation layer coating solution. This coating solution was applied onto the above-mentioned undercoat layer by the dip coating method to form a charge generation layer with a dry film thickness of 0.3 μm. The following titanyl phthalocyanine pigment has a maximum diffraction peak at least at the position of 27.3° in the Cu-Kα characteristic X-ray diffraction spectrum measurement. Charge generation material: 20 parts by mass of titanyl phthalocyanine pigment 10 parts by mass of polyvinyl butyral resin (#6000-C: manufactured by Electrochemical Industry Co., Ltd.) 700 parts by mass of t-butyl acetate 300 parts by mass of 4-methoxy-4-methyl-2-pentanone

[0190] (Charge transport layer (CTL)) The following materials were mixed to prepare a charge transport layer coating solution. This coating solution was applied onto the above-mentioned charge generation layer by the dip coating method to form a charge transport layer with a dry film thickness of 20 μm. 100 parts by mass of polymer (PC-1) (binder, Upilon FPC-2136, manufactured by Mitsubishi Gas Chemical Company, Inc.) Charge transport material: 50 parts by mass of the following chemical structural formula CTM-1 2 parts by mass of antioxidant (Irganox1010: manufactured by BASF Japan Ltd.) 540 parts by mass of tetrahydrofuran 135 parts by mass of toluene 0.3 parts by mass of silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.)

[0191] [Chemical formula]

[0192] (Overcoat Layer (OCL)) The following materials were mixed to prepare a solution. Next, as inorganic fine particles, 30 parts by mass of silica particles surface-modified with hexamethyldisilazane (AEROSIL (registered trademark) RX50, manufactured by Nippon Aerosil Co., Ltd., number average primary particle diameter 40 nm) were ultrasonically dispersed in 400 parts by mass of tetrahydrofuran, and the resulting dispersion was mixed with the above solution to prepare an overcoat layer coating solution. Then, this overcoat layer coating solution was applied onto the above charge transport layer using a circular slide hopper coater, dried at room temperature for 20 minutes, and then irradiated for 1 minute while rotating the photoreceptor at a position of 100 mm using a metal halide lamp (500 W). Thereafter, an electrophotographic photoreceptor CU-1 was produced by obtaining an overcoat layer with a film thickness of 17 μm. Compound (SA) 50 parts by mass Compound (SB) 50 parts by mass Photopolymerization initiator: Irgacure 819 (manufactured by BASF Japan Ltd.) 2 parts by mass Solvent: 2-butanol 80 parts by mass Solvent: 2-methyltetrahydrofuran 40 parts by mass Silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1 part by mass

[0193] The above compound (SA) is a compound (manufactured by Osaka Organic Chemical Industry Co., Ltd.) having the following structure.

[0194] [Chemical formula]

[0195] Also, the above compound (SB) is a triarylamine group-substituted acrylate compound having the structure shown below, obtained by the synthesis method described in JP-A-2011-099960.

[0196] [Chemical formula]

[0197] <Electrophotographic Photoreceptor TH-1> An electrophotographic photoreceptor TH-1 was fabricated in the same manner as electrophotographic photoreceptor CU-1, except that the protective layer was formed as follows.

[0198] (Protective layer (OCL)) The following materials were mixed to prepare a solution. Next, as inorganic fine particles, 30 parts by mass of silica particles (AEROSIL (registered trademark) RX50, manufactured by Nippon Aerosil Co., Ltd., number average primary particle diameter 40 nm) surface-modified with hexamethyldisilazane were ultrasonically dispersed in 400 parts by mass of tetrahydrofuran, and the resulting dispersion was mixed with the above solution to prepare a protective layer coating solution. Then, this coating solution was applied onto the above charge transport layer using a circular slide hopper type coater and dried at 120 °C for 70 minutes to form a protective layer with a dry film thickness of 17 μm, obtaining electrophotographic photoreceptor TH-1. The following polycarbonate resin A is a polymer of bisphenol AP and has a viscosity average molecular weight of 20,000. Polycarbonate resin A (Yupizeta (registered trademark) FPC-0220, manufactured by Mitsubishi Gas Chemical Company, Inc.) (binder) 100 parts by mass Charge transport material: 50 parts by mass of the above chemical structural formula CTM-1 Antioxidant (Irganox 1010: manufactured by BASF Japan Ltd.) 2 parts by mass Tetrahydrofuran 400 parts by mass Toluene 200 parts by mass Silicone oil (KF-54, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass

[0199] <Electrophotographic photoreceptor CU-2> An electrophotographic photoreceptor CU-2 was fabricated in the same manner as electrophotographic photoreceptor CU-1, except that 25 parts by mass of an antioxidant (TINUVIN 765, manufactured by BASF Japan Ltd.) was added to the protective layer coating solution.

[0200] <Electrophotographic photoreceptor TH-2> An electrophotographic photoreceptor TH-2 was fabricated in the same manner as electrophotographic photoreceptor TH-1, except that 25 parts by mass of an antioxidant (TINUVIN 765, manufactured by BASF Japan Ltd.) was added to the protective layer coating solution.

[0201] 5. Evaluation Using each of the developers E-1 to E-21 and an image forming apparatus (full-color multifunction printer bizhub Pro C353, manufactured by Konica Minolta, Inc.), image formation was performed. In the above image forming apparatus, any one of the electrophotographic photoreceptors CU-1, CU-2, TH-1, and TH-2 with an outer diameter of 60 mm was used. Regarding the charging potential, the surface potential of the photoreceptor was set to -650 V using a scorotron charger. The developing conditions were contact reversal development, and for the developing bias, it was applied with DC superimposed on AC. Under these conditions, Experiments 1 to 21 (Table 1) were conducted for the following evaluations.

[0202] (Image Blur) After the 500,000-sheet printing durability test under environmental conditions of 30°C and 80% RH, the main power supply of the actual machine was immediately stopped. After turning on the power 12 hours later and becoming ready for printing, a halftone image (relative reflection density of 0.4 with a Macbeth densitometer) and a 6-dot grid image covering the entire A3 size were immediately printed on the entire surface of A3 neutral paper. The state of the printed image was observed and the following evaluations were conducted. ◎◎: No image blur occurred in both the halftone and grid images (good) ◎: A very slight decrease in the density of a thin strip in the longitudinal direction of the photoreceptor was observed only in the halftone image (no practical problem) ○: A slight decrease in the density of a thin strip in the longitudinal direction of the photoreceptor was observed only in the halftone image (no practical problem) △: A plurality of slight decreases in the density of thin strips in the longitudinal direction of the photoreceptor were observed only in the halftone image (no practical problem) ×: Defects in the grid image or narrowing of the line width due to image blur occurred (there is a practical problem)

[0203] (Cleanability) After the 500,000-sheet printing durability test under environmental conditions of 30°C and 80% RH, a white solid image was printed on the entire surface of A3 neutral paper, and the cleanability was evaluated based on the presence or absence of streak-like image defects due to poor cleaning. ◎: No streak-like image defects due to poor cleaning were observed at all (good) ○: Streaky image defects due to cleaning defects are observed at low density (no practical problem) △: Multiple streaky image defects due to cleaning defects are observed at low density (no practical problem) ×: Streaky image defects due to cleaning defects are clearly observed (there is a practical problem)

[0204] (Density unevenness) After the halftone printing durability test of 500,000 sheets at environmental conditions of 30°C and 80% RH, the main power supply of the actual machine was immediately stopped. After 12 hours of stopping, the power was turned on to make it printable, and immediately a halftone image (relative reflection density 0.4 with a Macbeth densitometer) was printed on the entire surface of A3 neutral paper. The state of the printed image was visually observed, and the density unevenness was classified as follows ◎◎: No density unevenness is observed (good) ◎: There is density unevenness but it is extremely small (no practical problem) ○: There is density unevenness but it is small (no practical problem) △: There is density unevenness but it is within the practical allowable range (no practical problem) ×: There is density unevenness and it is not practically acceptable (there is a practical problem)

[0205] Each evaluation result is shown in Table 2

[0206]

Table 1

[0207]

Table 2

[0208] From the results of Experiments 1 to 17, it was found that by using a toner containing a mixture in which an antioxidant is dispersed in a fatty acid metal salt, it is possible to enhance the cleaning property with respect to the photoreceptor and form an image in which image blur and density unevenness are sufficiently suppressed

Industrial Applicability

[0209] The toner for electrostatic charge image development of the present invention can enhance the cleaning property with respect to the photoreceptor and form an image in which image blurring and density unevenness are sufficiently suppressed. Therefore, the present invention is effective, for example, in the field of image formation and the like.

Explanation of reference numerals

[0210] 1 Image forming apparatus 10 Heating belt 30 Image processing unit 40 Image forming unit 41Y, 41M, 41C, 41K Image forming units 42 Intermediate transfer unit 43 Secondary transfer unit 50 Paper conveyance unit 51 Paper feeding unit 51a, 51b, 51c Paper feed tray units 52 Paper discharging unit 52a Paper discharge roller 53 Conveying path unit 53a Registration roller pair 60 Fixing device 62 Fixing roller 63 Pressing roller 70 Image reading unit 71 Paper feeding device 72 Scanner 72a CCD sensor D Document S Paper

Claims

1. Toner base particles containing a binder resin, A mixture in which an antioxidant is dispersed in a metal fatty acid salt, and A toner for developing an electrostatic charge image.

2. The antioxidant includes an antioxidant having a piperidine derivative moiety in its molecular structure, The toner for developing an electrostatic charge image according to claim 1.

3. The antioxidant having a piperidine derivative moiety further includes a phenol structure in its molecular structure, The toner for developing an electrostatic charge image according to claim 2.

4. The metal fatty acid salt is zinc stearate, The toner for developing an electrostatic charge image according to claim 1.

5. The content of the antioxidant is 5 mol% or more and 50 mol% or less based on the total number of moles of the metal fatty acid salt and the antioxidant, The toner for developing an electrostatic charge image according to claim 1.

6. Further including a colorant, The toner for developing an electrostatic charge image according to claim 1.

7. A step of preparing a mixture in which an antioxidant is dispersed in a metal fatty acid salt, A step of preparing toner base particles, A step of mixing the mixture and the toner base particles, And a method for manufacturing a toner for developing an electrostatic charge image.

8. In the step of preparing the mixture, the mixture is prepared by producing the mixture, The method for manufacturing a toner for electrostatic development according to claim 7.

9. The mixture is produced by melt-kneading the metal fatty acid salt and the antioxidant, The method for manufacturing an electrostatic charge image developing toner according to claim 8.

10. In the step of preparing, after dissolving and mixing the fatty acid metal salt and the antioxidant in an organic solvent, the mixture is prepared by removing the organic solvent. The method for manufacturing an electrostatic charge image developing toner according to claim 8.

11. An image forming apparatus including an electrophotographic photoreceptor, and an image forming method performed using the electrostatic charge image developing toner according to any one of claims 1 to 6, A step of charging the surface of the electrophotographic photoreceptor; A step of exposing the surface of the charged electrophotographic photoreceptor to form an electrostatic latent image; A step of applying the electrostatic charge image developing toner to the surface of the electrophotographic photoreceptor on which the electrostatic latent image is formed to form a toner image; A step of transferring the formed toner image to a recording medium; A step of fixing the transferred toner image to the recording medium; having An image forming method.

12. The surface of the electrophotographic photoreceptor is composed of a cured product of a polymerizable composition containing a polymerizable compound. The image forming method according to claim 11.

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