External additive for toner, toner, and image forming device

Abstract

The present invention provides an external additive for use in a toner of an image forming apparatus that can stably produce high-quality images even when the image forming apparatus is repeatedly used over a long period of time and subjected to various environmental fluctuations, a toner using the external additive, and an image forming apparatus using the toner. The toner external additive of the present invention comprises a hydrophobic substance on the surface of metatitanic acid microparticles having a number average primary particle size of 10 to 300 nm, wherein the hydrophobic substance is produced using a hydrophobic agent containing an amino-based silane coupling agent. Furthermore, the toner of the present invention comprises colored resin particles and the toner external additive of the present invention, wherein the colored resin particles contain at least a colorant and a resin.

Description

Technical Field

[0001] The present invention relates to an external additive for toner, toner, and an image forming apparatus. Background Art

[0002] In electrophotographic image formation methods, a uniform charge is applied to the surface of a photoreceptor, followed by exposure tailored to the image, forming an electrostatic latent image corresponding to the image. A toner with a specific charge is attached to the electrostatic latent image, visualizing it (development). The toner image formed on the photoreceptor is transferred to an image forming support such as paper, optionally via an intermediate transfer member, and fixed to the image forming support by heat, thereby forming an image. Examples of image forming devices using this image forming method include copiers and printers.

[0003] The photoreceptors used in the image forming apparatus are classified into negatively charged photoreceptors and positively charged photoreceptors based on the property of imparting a uniform charge to the surface. Furthermore, based on the material used to form the photoreceptors, they are classified into inorganic photoreceptors using selenium, amorphous silicon, or the like, and organic photoreceptors made of organic materials.

[0004] Negatively chargeable organic photoreceptors generally have the following laminated structure: for example, an undercoat layer is formed on an aluminum substrate as needed to impart adhesion or control charge transfer, a charge generating layer containing a charge generating material is formed thereon, and a charge transport layer is further formed thereon.

[0005] Positively charged organic photoreceptors enable high-quality images and are effective in suppressing ozone generation. Because a charge-generating layer must be formed on the surface of such positively charged organic photoreceptors, a charge transport layer and a charge generating layer are sequentially laminated on an aluminum substrate, for example. Alternatively, a charge-generating material and a charge transport material may be mixed and formed as a single layer on the substrate.

[0006] As inorganic photoreceptors, those using amorphous silicon have become mainstream, replacing those using materials such as selenium. Amorphous silicon is preferred because of its extremely high hardness and long life.

[0007] In recent years, the ease of using digital data has led to a demand for printing large quantities of variable information. Industrial printers are used, which go beyond simple copying and can produce valuable printed materials by printing variable information. Because the printed materials are valuable, stable image quality is required over time.

[0008] For example, Patent Document 1 proposes an image forming apparatus that can suppress image flow (Japanese: 画像流れ) in a high-humidity environment when using a photoreceptor having a protective layer containing a crosslinked polymer. In this image forming apparatus, a lubricant is supplied to exert a cleaning effect, and then a lubricant removing unit is provided to suppress the residue of the lubricant.

[0009] Patent Document 2 is a technique for solving the problem of image flow in an amorphous silicon photoreceptor by using an external additive having a specific aggregation diameter. Specifically, a toner for developing an electrostatic latent image is described, which contains toner master particles and conductive fine particles as an external additive. The average primary particle diameter of the conductive fine particles is 90 nm or less, and an aggregate having an average aggregation diameter of 0.5 to 2.0 μm and a BET specific surface area of 15 m

[0017] , , , ,

[0016] ,

[0018] / g or more is formed on the surface of the toner master particles. Titanium oxide is disclosed as the conductive fine particles.

[0010] Patent Document 3 discloses a technique that by using metatitanic acid particles having a grain diameter of 12.0 to 16.0 nm and being hydrophobized, and having a true density of 2.5 to 3.3 g / cm 3 as an external additive added to a non-magnetic one-component developer coloring agent from the outside, the occurrence of dirtying can be suppressed, and excellent color reproducibility can be achieved. In addition, Patent Document 4 discloses a technique that by at least including two kinds of silica particles having a volume average particle diameter of 5 nm or more and 30 nm or less and metatitanic acid particles having a volume average particle diameter of 50 nm or more and 120 nm or less and an aspect ratio of 3 or more and less than 10 and being treated with a silane compound as external additives added to the coloring agent from the outside, and setting the coverage rate of each of the silica particles and the metatitanic acid particles with respect to the toner particles, white streaks in the toner image can be prevented.

[0011] [Prior Art Documents]

[0012] [Patent Documents]

[0013] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2015-114647

[0014] Patent Document 2 Japanese Unexamined Patent Application Publication No. 2009-180890

[0015] Patent Document 3 Japanese Unexamined Patent Application Publication No. 2016-062082

[0016] Patent Document 4 Japanese Unexamined Patent Application Publication No. 201-154278 Summary of the Invention

[0017] (Problems to be Solved by the Invention) ​It is believed that Patent Documents 1 and 2 suppress image flow by improving the cleaning effect, but it is difficult to achieve a good cleaning effect over a long period of time. In addition, Patent Document 3 does not disclose that excellent images can be achieved even when the image forming apparatus is used repeatedly over a long period of time.

[0019] The present invention has been completed in view of the above situation, and its purpose is to provide an external additive used in the colorant of an image forming device, which can stably form images with excellent image quality even when the image forming device is repeatedly used for a long period of time under various environmental changes, a colorant using the external additive, and the image forming device using the colorant.

[0020] (Technical solutions to solve problems)

[0021] A first embodiment of the present invention is an external additive for toner, comprising a hydrophobic substance on the surface of metatitanic acid fine particles having a number average primary particle size of 10 to 300 nm, wherein the hydrophobic substance is produced using a hydrophobic agent containing an amino-based silane coupling agent.

[0022] A second aspect of the present invention is the external additive for toner according to the first aspect, wherein the hydrophobic agent further contains a modified silicone oil.

[0023] A third aspect of the present invention is the external additive for toner according to the second aspect, wherein the modified silicone oil is an amino-modified silicone oil.

[0024] A fourth aspect of the present invention is the external additive for toner according to the second or third aspect, wherein the mass ratio of the amino-based silane coupling agent to the modified silicone oil is 20:1 to 1:1.

[0025] A fifth aspect of the present invention is the toner external additive according to any one of aspects 1 to 4, wherein the proportion of the hydrophobic agent is 1 to 40% by mass of the content of the metatitanic acid fine particles in the external additive.

[0026] A sixth aspect of the present invention is the external additive for toner according to any one of aspects 1 to 5, wherein the external additive for toner is positively charged.

[0027] A seventh aspect of the present invention is the external additive for toner according to any one of aspects 1 to 6, wherein the external additive for toner has a hydrophobicity of 5 to 60%.

[0028] An eighth aspect of the present invention is a toner comprising colored resin particles and the external additive for toner according to any one of the first to seventh aspects, wherein the colored resin particles contain at least a colorant and a resin.

[0029] A ninth aspect of the present invention is the toner according to the eighth aspect, wherein the ratio of the external additive for toner is 0.05 to 2.0% by mass based on the content of the colored resin particles in the toner.

[0030] A tenth aspect of the present invention is the toner according to the eighth or ninth aspect, wherein the colored resin particles further contain a release agent and a charge control agent.

[0031] Aspect 11 of the present invention is the toner according to any one of aspects 8 to 10, further comprising small-diameter inorganic fine particles having a number average primary particle size of 5 to 20 nm as an additional external additive.

[0032] A twelfth aspect of the present invention is the toner according to any one of aspects 8 to 11, further comprising large-diameter inorganic fine particles having a number average primary particle size of 25 to 1000 nm as an additional external additive.

[0033] A thirteenth aspect of the present invention is an image forming apparatus comprising at least a positively charged photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit.

[0034] The developing unit includes at least the toner according to any one of aspects 8 to 12.

[0035] A fourteenth aspect of the present invention is the image forming apparatus according to the thirteenth aspect, wherein the positively charged photosensitive body is an amorphous silicon photosensitive body.

[0036] A fifteenth aspect of the present invention is the image forming apparatus according to the thirteenth aspect, wherein the positively chargeable photosensitive member is a positively chargeable organic photosensitive member.

[0037] A sixteenth aspect of the present invention is the image forming apparatus according to the thirteenth aspect, wherein the positively chargeable photosensitive member is a laminated positively chargeable organic photosensitive member having a protective layer on its surface.

[0038] (Effects of the Invention)

[0039] According to the present invention, there can be provided an external additive for use in a toner of an image forming apparatus that can stably form images with excellent image quality even when the image forming apparatus is repeatedly used for a long period of time under various environmental fluctuations, a toner using the external additive, and the image forming apparatus using the toner. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a micrograph showing an example of the external additive and toner of the present invention in Examples. DETAILED DESCRIPTION

[0041] In image forming devices, after the image forming process—that is, after the toner image formed on the photoreceptor is transferred—residual toner, paper dust, and other residues are removed to form the next image. This involves cleaning the photoreceptor surface using a polyurethane scraper, brush, or other cleaning method. This cleaning process is required to fully remove these residues. However, during image formation, the photoreceptor surface is charged using methods such as corona discharge and roller charging to impart a uniform charge. However, this process presents a problem: the presence of water during this discharge easily leads to the formation of very small amounts of oxides as residues on the photoreceptor surface.

[0042] Furthermore, in offices, for example, there is a demand for reducing the running costs of printers and other equipment. To reduce these costs, extending maintenance cycles, such as component replacement, is effective. Therefore, suppressing photoreceptor degradation, particularly the wear of the photoreceptor film, which is the most significant factor affecting degradation, is the most effective approach. To suppress wear, for example, laminated photoreceptors or amorphous silicon photoreceptors with a high-hardness protective layer formed on their surfaces can be used.

[0043] However, as mentioned above, when the surface hardness of the photoreceptor is high, the oxide cannot be fully removed by cleaning, resulting in the photoreceptor surface becoming conductive and causing surface charge to diffuse across the surface layer, a phenomenon known as "image flow." This problem becomes more pronounced with long-term use of the image forming apparatus and repeated image formation. Furthermore, when using positively chargeable organic photoreceptors, this charge diffusion problem also eventually arises.

[0044] In view of the above situation, the present inventors have conducted in-depth research on the colorant used in the image forming device and the external additives used in the colorant in order to fully remove the residues containing the oxides in the cleaning stage (hereinafter, this effect is sometimes referred to as "high cleaning performance"), suppress the image flow caused by the residues, and maintain the high cleaning performance even when the image forming device is repeatedly used for a long period of time under various environmental changes, so as to obtain an image forming device that can stably form images with excellent image quality.

[0045] The researchers discovered that when an external additive used in a toner comprises a hydrophobic agent on the surface of metatitanic acid microparticles with a number-average primary particle size of 10 to 300 nm, and the hydrophobic agent is prepared using a hydrophobic agent containing at least an aminosilane coupling agent, the formation of oxides on the photoreceptor surface can be suppressed, achieving the aforementioned effect. In particular, they discovered for the first time that, in image forming devices using amorphous silicon photoreceptors or organic photoreceptors with hard protective layers, which are designed for extended lifespans, high cleanliness can be maintained, enabling the formation of high-quality images over a long period of time, even when the image forming device is repeatedly used over long periods of time and under various environmental fluctuations.

[0046] Hereinafter, the external additive for toner, the toner, and the image forming apparatus of the present invention will be described in order.

[0047] (External additive of the present invention)

[0048] 〔Metatitanate microparticles〕

[0049] First, the toner external additive of the present invention uses metatitanic acid microparticles having a number average primary particle size of 10 to 300 nm as a master particle. It is believed that the use of metatitanic acid microparticles as a master particle in the present invention can suppress the formation of oxides on the photoreceptor surface and thus reduce the occurrence of image defects. The reason for this is not clear, but the following is considered.

[0050] In other words, titanium oxide generally has the function of suppressing the effects of environmental fluctuations and maintaining a stable state. The presence of vacant orbitals in titanium oxide facilitates the transfer of electrons, presumably suppressing the dispersion of charges in the air or trapping charges, thereby suppressing the effects of environmental fluctuations and maintaining a stable state.

[0051] However, as explained below, it's believed that titanium oxide doesn't fully demonstrate its effectiveness under more severe environmental fluctuations. In particular, when using a positively charged organic photoreceptor, a charge-generating layer exists near the surface, generating electrons. This makes charge leakage more likely, and it's speculated that titanium oxide's ability to suppress these fluctuations is insufficient under these conditions. In contrast, metatitanic acid exhibits a slightly distorted crystalline structure, resulting in its electron transfer function being fully utilized.

[0052] Furthermore, due to the distorted crystal structure, peroxides such as ozone generated during charging can be easily captured. As a result, it is considered that the effect of suppressing the generation of oxides can be fully exerted, for example, on the surface of an organic photoreceptor.

[0053] The number average primary particle size of the metatitanic acid fine particles of the present invention is 10 to 300 nm, preferably 25 nm or more, more preferably 50 nm or more, preferably 175 nm or less, more preferably 150 nm or less, and even more preferably less than 120 nm.

[0054] The number average primary particle size represents the average of the Feret horizontal particle sizes of 100 particles observed using a transmission electron microscope. The Feret horizontal particle size refers to the length of the side parallel to the x-axis in a rectangle circumscribing a particle located on the xy plane.

[0055] [Manufacturing of metatitanic acid microparticles]

[0056] In the present invention, the method for producing the metatitanic acid microparticles is not particularly limited. For example, they can be produced by hydrolyzing titanyl sulfate. Airflow milling is an example of a method for controlling the number average primary particle size of the metatitanic acid microparticles to be within the range of 10 to 300 nm.

[0057] 〔Hydrophobic agent〕

[0058] The external additive of the present invention has a hydrophobe on the surface of the metatitanic acid microparticles, and the hydrophobe is produced using a hydrophobic agent containing at least an amino-based silane coupling agent. It is believed that by treating the metatitanic acid microparticles with an amino-based silane coupling agent, the formation of oxides can be fully suppressed. In addition, by using an amino-based silane coupling agent, a positively charged external additive and toner suitable for forming a positively charged photosensitive body with excellent image quality can be achieved.

[0059] Examples of the amino-based silane coupling agent include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-8-aminooctyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane. One or more of these may be used.

[0060] The hydrophobic agent may also include modified silicone oil. By using the modified silicone oil in combination, the effect of improving the charging speed can be exerted. As the modified silicone oil, amino-modified silicone oil is preferably used. By using the amino-modified silicone oil together with the amino-based silane coupling agent, the external additive and the toner can be fully positively charged. As amino-modified silicone oil, for example, general-purpose products such as amino-modified organopolysiloxanes can be cited, such as polymers or copolymers such as dimethyl (aminoethylaminopropyl) methylsiloxane, dimethyl (aminoethylaminopropyl) ethylsiloxane, diaminopropyl tetramethyldisiloxane, and dimethyl (aminoethylaminopropyl) methylcyclosiloxane.

[0061] The ratio of the hydrophobic agent relative to the content of the metatitanic acid microparticles in the external additive of the present invention is preferably 1 to 40% by mass. By setting the ratio of the hydrophobic agent relative to the content of the metatitanic acid microparticles to 1% by mass or more, the effect can be further improved. The ratio of the hydrophobic agent relative to the content of the metatitanic acid microparticles is more preferably 5% by mass or more, and further preferably 8% by mass or more. On the other hand, by limiting the ratio of the hydrophobic agent to 40% by mass or less relative to the content of the metatitanic acid microparticles, excessive coverage can be prevented. The ratio of the hydrophobic agent relative to the content of the metatitanic acid microparticles is more preferably 15% by mass or less. When using multiple types of hydrophobic agents, the above ratio can be calculated using the total amount of the multiple types of hydrophobic agents.

[0062] When the aminosilane coupling agent and the modified silicone oil are used together, the mass ratio of the aminosilane coupling agent to the modified silicone oil is preferably 20:1 to 1:1. By setting the mass ratio of the aminosilane coupling agent to the modified silicone oil to be at least 1:1, the effects of the aminosilane coupling agent can be fully exerted. The mass ratio of the aminosilane coupling agent to the modified silicone oil can preferably be at least 1.5:1. On the other hand, to maximize the effects of the modified silicone oil, the mass ratio of the aminosilane coupling agent to the modified silicone oil is preferably 20:1 or less, more preferably 10:1 or less, even more preferably 5:1 or less, and even more preferably 3:1 or less.

[0063] The external additive of the present invention is preferably positively charged. The hydrophobicity of the external additive of the present invention is preferably 5 to 60%.

[0064] [Manufacturing of the external additive of the present invention]

[0065] In the present invention, the method for producing the external additive of the present invention is not limited. For example, a method of surface treating the metatitanic acid particles by adding or spraying a hydrophobic agent while stirring a solution containing metatitanic acid particles; a method of dissolving a hydrophobic agent in an organic solvent, stirring the organic solvent while adding metatitanic acid particles to perform surface treatment, etc. It should be noted that in the former method, the hydrophobic agent can be diluted with an organic solvent or the like. For example, after adding the hydrophobic agent, the solution is kept at 60 to 100°C for 0.5 to 2.0 hours. Then, solid-liquid separation is performed by filtration, and drying is performed to obtain metatitanic acid particles having a hydrophobic substance produced using a hydrophobic agent, i.e., the external additive of the present invention.

[0066] (Toner)

[0067] (1) External additives of the present invention

[0068] The toner of the present invention is produced by externally adding the external additive of the present invention to colored resin particles (hereinafter sometimes referred to simply as "colored resin particles") containing at least a colorant and a resin. As described above, the toner of the present invention is easily removed during photoreceptor cleaning, maintaining excellent cleaning properties over a long period of time, and stably producing high-quality images.

[0069] The proportion of the external additive of the present invention in the toner is preferably 0.05 to 2.0% by mass relative to the content of the colored resin particles. Setting the proportion of the external additive to 0.05% by mass or greater is preferred because the effects of the external additive can be fully exerted. A more preferred proportion is 0.1% by mass or greater. On the other hand, since the effects become saturated even with excessive inclusion of the external additive, the upper limit is preferably set to 2.0% by mass. A more preferred proportion is 1.5% by mass or less.

[0070] (2) Colored resin particles

[0071] Colored resin particles contain at least a colorant and a resin, and may also contain a release agent (wax) and a charge control agent as internal additives as needed.

[0072] 〔Resin〕

[0073] Examples of the resin contained in the toner particles constituting the toner of the present invention include known resins such as styrene resins, acrylic resins, styrene-acrylic resins, vinyl resins such as olefin resins, polyester resins, polyamide resins, polycarbonate resins, polyethers, polyvinyl acetate resins, polysulfones, epoxy resins, polyurethane resins, and urea resins. One or more of these resins may be used alone or in combination. In particular, one or more of styrene-acrylic resins and polyester resins are preferred because they provide a toner with excellent low-temperature fixability. The glass transition point of the resin is preferably 35 to 70°C, more preferably 45 to 60°C. Furthermore, the softening point (T1 / 2) measured using a high-pressure rheometer is preferably 80 to 140°C, more preferably 90 to 135°C.

[0074] When using styrene resin, (meth) acrylic resin and their copolymer resins as the binder resin, it is preferred to use a resin having a weight average molecular weight Mw in the range of 20,000 to 100,000 and a number average molecular weight Mn in the range of 2,000 to 30,000. On the other hand, when using a polyester resin as the binder resin, it is preferred to use a resin having a weight average molecular weight Mw in the range of 5,000 to 40,000 and a number average molecular weight Mn in the range of 2,000 to 10,000. The glass transition temperature of the binder resin is preferably in the range of 40°C to 80°C. By having the glass transition temperature in the above range, it is easy to maintain the minimum fixing temperature. In addition, the softening point of the resin (T1 / 2 obtained using a high-pressure rheometer) is 105 to 160°C, preferably 110°C to 140°C.

[0075] Colorant

[0076] The colorant contained in the toner particles according to the present invention can be a commonly known dye or pigment. As a colorant for obtaining a black toner, various known colorants can be used, including carbon blacks such as furnace black and channel black; magnetic materials such as magnetite and ferrite; dyes; and inorganic pigments including non-magnetic iron oxide.

[0077] As a colorant for obtaining a color toner, any known colorant such as a dye or an organic pigment can be used. Specifically, examples of organic pigments include CI Pigment Red 5, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 81:4, CI Pigment Red 122, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 222, CI Pigment Red 238, CI Pigment Red 269, CI Pigment Yellow 14, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 155, CI Pigment Yellow 180, CI Pigment Yellow 185, CI Pigment Orange 31, and CI Pigment Orange 4. 3, CI Pigment Blue 15; 3, CI Pigment Blue 60, CI Pigment Blue 76, etc. Examples of dyes include CI Solvent Red 1, CI Solvent Red 49, CI Solvent Red 52, CI Solvent Red 58, CI Solvent Red 68, CI Solvent Red 11, CI Solvent Red 122, CI Solvent Yellow 19, CI Solvent Yellow 44, CI Solvent Yellow 77, CI Solvent Yellow 79, CI Solvent Yellow 81, CI Solvent Yellow 82, CI Solvent Yellow 93, CI Solvent Yellow 98, CI Solvent Yellow 103, CI Solvent Yellow 104, CI Solvent Yellow 112, CI Solvent Yellow 162, CI Solvent Blue 25, CI Solvent Blue 36, CI Solvent Blue 69, CI Solvent Blue 70, CI Solvent Blue 93, and CI Solvent Blue 95. For each color, one colorant can be used alone or two or more can be used in combination to obtain a toner of each color.

[0078] The content of the colorant is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, relative to the content of the resin.

[0079] The colored resin particles may further contain a release agent (wax) and a charge control agent as internal additives.

[0080] 〔Release agent〕

[0081] As release agents, known waxes can be used. For example, hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax; and ester waxes such as carnauba wax, pentaerythritol behenate, behenyl behenate, and behenyl citrate can be used. Any one of these waxes can be used alone or in combination of two or more. The content of the release agent relative to the resin is preferably 2 to 20% by mass, more preferably 3 to 10% by mass.

[0082] 〔Charge control agent〕

[0083] As the charge control agent, known charge control agents can be used. For example, nigrosine dyes, metal salts of cyclohexane acid or higher fatty acids, alkoxylated amines, quaternary ammonium compounds, azo metal complexes, salicylic acid metal salts or their metal complexes, and calixarene compounds can be used. These can be used alone or in combination of two or more. The charge control agent content is preferably 0.1 to 3.0% by mass, more preferably 0.1 to 1.0% by mass, relative to the resin.

[0084] Furthermore, a resin-type charge control agent (charge control resin) in which the resin itself has a substituent and has charge-imparting capability may be used.

[0085] (Method for producing colored resin particles)

[0086] Examples of methods for producing the resin particles include kneading and pulverization, suspension polymerization, emulsion coagulation, dissolution suspension, ester extension polymerization, and dispersion polymerization. Furthermore, the resin particles may be so-called microcapsule-type toners, such as those comprising resin particles obtained by kneading and pulverizing a colorant and a resin as cores, with a coating layer having functions such as heat resistance formed on the surface; colored resin particles obtained by adding a monomer of a coating material to resin particles obtained by suspension polymerization to form a coating layer; and colored resin particles obtained by using particles obtained by agglomerating polymer microparticles as cores, with a coating layer formed of other resin particles surrounding the cores.

[0087] The volume average particle size of the colored resin particles (toner particles) obtained by externally adding the external additives of the present invention is preferably 3 to 15 μm, more preferably 5 to 10 μm, which is substantially the same as that of the colored resin particles (toner base particles) before the addition of the external additives.

[0088] (3) Additional external additives

[0089] Regarding the external additives of the toner of the present invention, in addition to the case of using only the external additives of the present invention, the following additional external additives may be used in addition to the external additives of the present invention.

[0090] (Small-size inorganic particles)

[0091] In the toner of the present invention, from the viewpoint of imparting charging properties or fluidity, it is preferred that small-diameter inorganic fine particles having a number average primary particle size of 5 to 20 nm be added as an additional external additive simultaneously with the external additive of the present invention.

[0092] Examples of the small-diameter inorganic fine particles include fine particles containing the following substances: various carbides such as silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, and diamond carbon lactam; various nitrides such as boron nitride, titanium nitride, and zirconium nitride; borides such as zirconium boride; various oxides such as iron oxide, chromium oxide, calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, and silicon dioxide; composite oxides such as silicon dioxide-titania-alumina, calcium titanate, strontium titanate, and magnesium titanate; sulfides such as molybdenum disulfide; fluorides such as magnesium fluoride and carbon fluoride; various metal soaps such as aluminum stearate, calcium stearate, zinc stearate, and magnesium stearate; and various non-magnetic inorganic substances such as talc and bentonite. These can be used alone or in combination of two or more.

[0093] Among these, it is particularly preferred to use one or a combination of two or more small-diameter inorganic fine particles composed of silica, alumina, and a composite oxide of silica-titania-alumina.

[0094] In addition, these small-particle inorganic fine particles are preferably surface-treated by a known method using a hydrophobic agent such as a silane coupling agent, a titanate coupling agent, silicone oil, or a silicone-based varnish, a fluorinated silane coupling agent or fluorinated silicone oil, an amino group / quaternary ammonium salt-containing coupling agent, or a modified silicone oil.

[0095] Examples of the hydrophobic agent include silane coupling agents such as hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane; and silicone oils such as dimethylpolysiloxane, polymethylhydrogensiloxane, methylphenylpolysiloxane, and dimethyl silicone oil. One or more of these can be used. Amine-based hydrophobic agents are also available. The aforementioned amino-based silane coupling agent and amino-modified silicone oil used in the production of the external additive of the present invention can be used.

[0096] When small-sized inorganic particles are added to the toner from the outside, the ratio of small-sized inorganic particles to the content of the colored resin particles is preferably 0.1 to 2.0% by mass. From the perspective of giving full play to the effect of the small-sized inorganic particles, that is, imparting fluidity, etc., it is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. On the other hand, from the perspective of suppressing image defects caused by adhesion to a photoreceptor, etc. by causing an excessive amount of small-sized inorganic particles, it is preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. When multiple types of small-sized inorganic particles are used, the ratio can be calculated using the total amount of the multiple types of small-sized inorganic particles.

[0097] (Large-size inorganic particles)

[0098] Furthermore, by adding large-diameter inorganic fine particles having a number average primary particle size of 25 to 1000 nm to the resin fine particles containing at least a colorant and a resin, it is possible to suppress the embedding of small-diameter inorganic fine particles into the surface of the colored resin particles. The large-diameter inorganic fine particles can be made of the same materials as those for the small-diameter inorganic fine particles described above.

[0099] In addition, as the aforementioned large-diameter inorganic fine particles, fine particles exceeding 100 nm have abrasive properties and can be expected to polish the surface of the photoreceptor and clean the photoreceptor.

[0100] When the large-diameter inorganic fine particles are added externally, their proportion relative to the content of the colored resin particles is preferably 0.1 to 2.0% by mass. More preferably, it is 0.2 to 1.0% by mass. By setting the proportion of the large-diameter inorganic fine particles to 0.1% by mass or greater, the effects of the particles can be maximized. Furthermore, by setting the proportion of the large-diameter inorganic fine particles to 2.0% by mass or less, damage to the photoreceptor and resulting image defects caused by excessive large-diameter inorganic fine particles can be suppressed.

[0101] The toner of the present invention can also be used as a magnetic or non-magnetic single-component developer, or can be mixed with a carrier and used as a two-component developer. When the toner is used as a two-component developer, as the carrier, magnetic particles containing metals such as iron, ferrite, magnetite, and alloys of these metals with metals such as aluminum and lead can be used, and ferrite particles are particularly preferred. In addition, as the carrier, a coated carrier obtained by covering the surface of the magnetic particles with a covering agent such as a resin, a dispersed carrier obtained by dispersing magnetic fine powder in a binder resin, etc. can also be used. As the resin forming the covering agent and the binder resin, the resins used in the past can be used. The volume average particle size of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

[0102] (Method for producing toner)

[0103] The toner of the present invention can be obtained by adding the aforementioned small-diameter inorganic fine particles, large-diameter inorganic fine particles, and the like as the external additives of the present invention to the colored resin particles, and optionally adding additional external additives. These can be mixed using a known mixing device such as a Henschel mixer or a V-type mixer.

[0104] (Image Forming Apparatus)

[0105] The image forming apparatus of the present invention comprises at least a positively charged photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit. The developing unit comprises at least a toner to which the external additive of the present invention is externally added.

[0106] The image forming apparatus of the present invention includes a positively charged photoreceptor. Preferred examples of the positively charged photoreceptor include an amorphous silicon photoreceptor, a positively charged organic photoreceptor, and a laminated positively charged organic photoreceptor having at least a protective layer on its surface. These photoreceptors are described below.

[0107] (Amorphous silicon photoreceptor)

[0108] As an amorphous silicon (a-Si) photoreceptor, for example, there can be mentioned an amorphous silicon photoreceptor having an amorphous silicon photosensitive layer (a-Si photosensitive layer) formed on the surface of a conductive substrate formed into a specific shape such as a roller shape. In particular, an amorphous silicon photoreceptor having a thin film a-Si photosensitive layer with a thickness of 30 μm or less is excellent in productivity and can form a high-resolution image, so it is preferred. In addition to a single layer or two or more layers that actually function as a photosensitive layer, the a-Si photosensitive layer may also have a carrier blocking layer, a surface protective layer, etc. as described in detail below. Among them, in the case of having multiple layers, the overall layer thickness is preferably 30 μm or less. In addition, as an a-Si photosensitive layer, a photosensitive layer containing H or a halogen element, or a photosensitive layer containing elements such as C, N, and O can be formed on the surface of a conductive substrate. That is, as a material constituting the a-Si photosensitive layer, in addition to a-Si, a-SiC, a-SiO, a-SiON, etc. can be mentioned.

[0109] Carrier blocking layer

[0110] A carrier blocking layer is sandwiched between the a-Si photosensitive layer and the conductive substrate. Examples of such a carrier blocking layer include inorganic insulating layers such as a-SiC and organic insulating layers such as polyethylene terephthalate. Its thickness can be set within a range of 0.01 to 5 μm.

[0111] 〔Surface protective layer〕

[0112] The surface protection layer can be made of conventionally used materials, including organic or inorganic insulating materials. For example, an inorganic insulating layer obtained by adding C, O, N, etc. to a-Si can be preferably used.

[0113] (Positively charged organic photoreceptor)

[0114] For a positively chargeable organic photoreceptor, a primer layer may be formed on the surface of a conductive substrate as needed, and a photosensitive layer may be formed thereon, comprising a charge transport layer and a charge generating layer stacked in this order. Alternatively, a positively chargeable organic photoreceptor may be one in which a primer layer may be formed on the surface of a conductive substrate as needed, and a photosensitive layer may be formed thereon, comprising a charge generating material and a charge transport material mixed in the same layer.

[0115] As a conductive substrate, a metal plate such as aluminum, stainless steel, or iron can be used; a conductive substrate obtained by laminating or vapor-depositing a metal layer of aluminum, palladium, or gold on the surface of a flexible support such as paper or plastic film; a conductive substrate obtained by coating or vapor-depositing a layer containing a conductive compound such as a conductive polymer, indium oxide, or tin oxide on the surface of a flexible support such as paper or plastic film.

[0116] The undercoat layer formed as needed can be used when it is necessary to improve the adhesion between the conductive substrate and the photosensitive layer. The undercoat layer can be made of conventional materials and its film thickness can be 0.05 to 20 μm.

[0117] The charge transport layer contains a charge transport substance that transports the charge generated by the charge generation layer. There are no particular limitations on the charge transport substance, and conventionally used charge transport substances can be used. The thickness of the charge transport layer can be 5 to 50 μm, preferably 10 to 30 μm.

[0118] The charge generating layer is a layer containing a charge generating substance. The charge generating substance is not particularly limited, and conventionally used charge generating substances can be used. The thickness of the charge generating layer can be 0.5 to 15 μm, preferably 0.7 to 10 μm.

[0119] When forming a photosensitive layer containing a mixture of a charge-generating substance and a charge-transporting substance, the photosensitive layer can be formed by dispersing or dissolving the charge-generating substance and the charge-transporting substance in a resin. Conventional resins can be used as the resin used. The thickness of the photosensitive layer containing a mixture of the charge-generating substance and the charge-transporting substance can be 5 to 60 μm, preferably 10 to 40 μm.

[0120] (Protective layer)

[0121] As a positively chargeable organic photoreceptor, a laminated type having at least a protective layer on its surface can also be used. The presence of such a protective layer further enhances the durability of the photoreceptor. As previously mentioned, the cleanability of highly durable photoreceptors tends to decrease. However, using a toner containing the external additive of the present invention can achieve a polishing effect and prevent filming, resulting in longer-term, more stable image output than ever before.

[0122] The protective layer may be any conventionally used protective layer. For example, a heat-curable or photocurable resin may be used as the binder resin. The protective layer may contain metal oxide fine particles, lubricant particles, an antioxidant, or a resin other than the aforementioned binder resin, as needed. The thickness of the protective layer is preferably 0.2 to 10 μm, more preferably 0.5 to 5 μm.

[0123] (Metal oxide microparticles)

[0124] The protective layer may contain metal oxide fine particles such as aluminum oxide (Al2O3), tin oxide (SnO2), and titanium dioxide (TiO2) having a number average primary particle size of 1 to 300 nm for the purpose of imparting higher durability.

[0125] The image forming apparatus of the present invention comprises, in addition to the positively charged photosensitive member, at least a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit. The developing unit comprises at least the toner of the present invention. Conventionally known units may be used for the charging unit, the exposure unit, the developing unit such as a magnetic roller or a toner supply unit other than the toner of the present invention, the transfer unit, and the cleaning unit.

[0126] As an image forming method using the image forming apparatus, for example, a uniform charge is imparted to the surface of the photoreceptor, and then an electrostatic latent image corresponding to the image is formed by exposure corresponding to the image. A colorant having a specific charge is attached to the electrostatic latent image to visualize (develop). The toner image formed on the photoreceptor is transferred to an image forming support such as paper via an intermediate transfer member as needed, and can be fixed to the image forming support by heat or the like. The toner of the present invention can be preferably used for such electrostatic latent image development applications, and can also be preferably used as a positively charged (i.e., positively charged) toner used simultaneously with a positively charged photoreceptor.

[0127] After the transfer, the untransferred toner on the photoreceptor surface is statically neutralized and removed by cleaning. According to the present invention, the toner containing the external additive of the present invention is easily removed from the photoreceptor during the cleaning process, thus less likely to form residues such as oxides. As a result, high-quality images can be stably produced over long periods of time, even under various environmental fluctuations, such as changes in atmospheric moisture content.

[0128] [Example]

[0129] The present invention is described in more detail below with reference to the following examples. The present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope consistent with the aforementioned and subsequent purports, all of which fall within the technical scope of the present invention.

[0130] In this example, as evaluation items, the number average primary particle size of metatitanic acid fine particles, the hydrophobicity of the external additive, and the charge amount were measured as shown below.

[0131] (number average primary particle size)

[0132] The titanate powder was photographed at a magnification of 10,000 times using a transmission electron microscope (TEM), and image analysis was performed on 100 particles in the photograph to determine the average value of the Feret horizontal particle size, i.e., the Feret horizontal average particle size, which was used as the number average primary particle size.

[0133] (Hydrophobicity)

[0134] Prepare a plurality of ethanol-water mixtures 50mL each in which the volume ratio of ethanol / water is changed in 5 levels between 0 / 100 and 100 / 0. While stirring with a magnetic stirrer, add 0.20g of hydrophobized metatitanic acid microparticles and wet the total amount for 5 minutes. The volume ratio of ethanol in the mixed solution at this time is used as the hydrophobicity of the sample. It should be noted that, if environmental stability is considered, the hydrophobicity is preferably 5% or more. By setting the hydrophobicity to 5% or more, particularly in long-term storage under high temperature and high humidity, the leakage of the electric charge of the toner can be suppressed and the reduction of the charge amount can be suppressed. The upper limit of the hydrophobicity can be, for example, set to 60%.

[0135] (Charge)

[0136] Place 19.5 g of the iron powder carrier and 0.5 g of the external additive in a 20 mL glass container and store in a normal temperature and humidity environment at 20°C and 50% RH for 24 hours. Remove the glass container, cover it, and shake it in a paint shaker for 30 minutes. After shaking, take 1 g of the mixed sample and measure it using a degassing charge meter (Model 230TO, manufactured by Trek Japan Co., Ltd.) after purging nitrogen for 10 seconds. The value obtained is the charge.

[0137] [Evaluation Using the First Image Forming Apparatus]

[0138] (Preparation of Metatitanate Microparticles)

[0139] An aqueous solution of titanyl sulfate (titanylic sulfate concentration 10% by mass) was heated to 130° C. to undergo thermal hydrolysis to obtain a slurry of an aqueous solution of metatitanic acid in sulfuric acid. The obtained slurry of an aqueous solution of metatitanic acid in sulfuric acid was subjected to solid-liquid separation by filtration. The filter cake obtained by washing with water was then dried at a temperature of 120° C. for 40 hours. The obtained dried product was crushed using a hammer mill to obtain metatitanic acid microparticles. The above-mentioned heating conditions were adjusted to obtain metatitanic acid microparticles with various number average primary particle sizes. The obtained metatitanic acid microparticles are shown in Table 1.

[0140] As comparative example particles, titanium oxide particles were prepared as shown below. That is, an aqueous solution of titanyl sulfate (titany sulfate concentration 10% by mass) was heated to 130°C to undergo thermal hydrolysis to obtain a slurry of an aqueous solution of sulfuric acid of metatitanic acid. The obtained slurry of an aqueous solution of sulfuric acid of metatitanic acid was subjected to solid-liquid separation by filtration. Then, the filter cake obtained by washing with water was dried at a temperature of 120°C for 40 hours, and further dried at a temperature of 500°C for 4 hours. The obtained dried product was crushed using a hammer mill to obtain titanium oxide particles having a number average primary particle size of 30 nm. The above number average primary particle size was measured using the aforementioned method.

[0141] [Table 1]

[0142] Titanate particles No. Number average primary particle size 1 30nm 2 50nm 3 70nm 4 100nm 5 300nm

[0143] (Manufacturing of the External Additive of the Present Invention)

[0144] The various metatitanic acid fine particles were treated (hydrophobized) with various hydrophobic agents shown in Table 2. The details are as follows.

[0145] First, the external additives 1 to 12 of the present invention listed in Table 2 were prepared as follows. Specifically, the metatitanic acid fine particles were dispersed in water at a solids concentration of 10% by mass to prepare a slurry. The aminosilane coupling agent listed in Table 2 was added to the slurry as a hydrophobizing agent at the ratios shown in Table 2 relative to the content of the metatitanic acid fine particles. The slurry was then heated to 80°C. After reaching 80°C, the slurry was maintained at that temperature for 1 hour, followed by solid-liquid separation by filtration and drying. This yielded metatitanic acid fine particles having a hydrophobic substance produced by the hydrophobizing agent, i.e., the external additives of the present invention (external additives 1 to 12 of the present invention).

[0146] In Table 2, amino-based silane coupling agent KBE-903 manufactured by Shin-Etsu Chemical Co., Ltd. was used as 3-aminopropyltriethoxysilane, and KBM-603 was used as N-2-(aminoethyl)-3-aminopropyltrimethoxysilane.

[0147] In addition, the external additives 13 to 15 of the present invention in Table 2 are obtained as follows. That is, the metatitanic acid microparticles are dispersed in water at a solid concentration of 10% by mass to obtain a slurry. In the slurry, as a hydrophobic agent, while adding the amino-based silane coupling agent, an amino-modified silicone oil is added. At this time, the amino-based silane coupling agent is added to the slurry as described above, and after solid-liquid separation, the amino-modified silicone oil is kneaded into the filter cake before drying using a kneader. In detail, amino-modified silicone oil KF-862 (main component: amino-modified organopolysiloxane) manufactured by Shin-Etsu Chemical Co., Ltd. is added as amino-modified silicone oil in a manner such that the content of the metatitanic acid microparticles becomes the ratio shown in Table 2, and a pressure kneader is used to stir at room temperature for 1 hour, and surface treatment is performed to obtain the result.

[0148] (Manufacturing of External Additives in Comparative Example)

[0149] The titanium oxide fine particles were surface treated with an aminosilane coupling agent as a hydrophobic agent in the same manner as in the external additive 1 of the present invention to obtain the external additive of Comparative 1. In addition, the titanium oxide fine particles were used as they were without surface treatment to form the external additive of Comparative 2.

[0150] The hydrophobicity and charge of the external additive were measured as described above. The results are also shown in Table 2.

[0151] [Table 2]

[0152]

[0153] (Manufacturing of Colored Resin Particles)

[0154] Colored resin particles for use in toners were produced. The resin, colorant, release agent, and charge control agent listed in Table 3 were weighed in the amounts shown in Table 3, premixed dry-type, and then melt-kneaded using a twin-screw extruder. The mixture was then pulverized using a mechanical pulverizer and classified using an airflow classifier to obtain colored resin particles having a volume average particle size shown in Table 3 (colored resin particles Nos. 1 to 5).

[0155] In Table 3, the styrene-acrylic resin has a Tg of 56°C and a softening point of 126°C, and the polyester resin has a Tg of 55°C and a softening point of 120°C. Carbon black was Raven 330 manufactured by Cabot Corporation. The melting point of the paraffin wax in Table 3 is 98°C. Furthermore, TP-415 manufactured by Hodogaya Chemical Co., Ltd. was used as a quaternary ammonium charge control agent, and T-77 manufactured by Hodogaya Chemical Co., Ltd. was used as an azo iron complex.

[0156] [Table 3]

[0157]

[0158] (Manufacturing of Toner)

[0159] The colored resin particles obtained as described above, the external additives 1 to 15 of the present invention in Table 2, the comparative external additives 1 and 2, and the additional external additives (small-particle inorganic fine particles and large-particle inorganic fine particles) shown in Table 4 were mixed in a Henschel mixer in the proportions shown in Table 4 (all ratios relative to the colored resin particles) to obtain toners (toners 1 to 18 of the present invention and comparative toners 1 to 10). As small-particle inorganic fine particles, hydrophobic silica RA-200H (number average primary particle size of 12 nm) and RX200 (number average primary particle size of 12 nm) manufactured by AEROSIL Japan were used. As large-particle inorganic fine particles, NA-50H (number average primary particle size of 30 nm) and NAX-50 (number average primary particle size of 30 nm) manufactured by AEROSIL Japan were used.

[0160] As an example of the obtained toner of the present invention, a micrograph (5000 times magnification) obtained by observation using a scanning electron microscope is shown in FIG. Figure 1 . It can be seen that: Figure 1 In the present invention, the external additive is uniformly dispersed on the surface of the toner mother particle.

[0161] [Table 4]

[0162]

[0163] (Evaluation of Toner Characteristics)

[0164] Inventive toners 1 to 15 and comparative toners 1 and 2 were used in a 62-sheet multifunction printer (TASKalfa 620, manufactured by Kyocera Document Solutions) equipped with an amorphous silicon photoreceptor as the first image forming apparatus. Three hundred thousand sheets were printed in intermittent mode at a 5% pixel ratio in a high-temperature, high-humidity environment (temperature: 35°C, relative humidity: 80%). The image density and scumming of the 300,000th print were evaluated. Image density was determined by measuring the reflection density at 10 locations on a solid black image and subtracting the paper's reflection density. Images with an image density below 1.20 were considered unsuitable for practical use and were rated as unacceptable. Images with a density of 1.20 or higher were considered suitable for practical use and were rated as acceptable. Scumming refers to the appearance of scumming on the non-image portion of the printed paper. This scumming was determined by measuring the reflection density at 10 locations on a white paper and subtracting the paper's reflection density from the average image density. If the dirt concentration is less than 0.005, it is at a practical level and is judged to be qualified; if the dirt concentration is above 0.005, it is not at a practical level and is judged to be unqualified.

[0165] After printing 300,000 sheets and then letting the print sit for a day and night, the first printed sheet was evaluated for image density, smearing, and image quality. Image flow was evaluated by printing a 30% halftone image and visually inspecting the halftone reproducibility. Images were considered to have flow if there was unevenness in the halftones, and to have no flow if there was no unevenness. These results are shown in Table 5.

[0166] It should be noted that the "standing for one day and night" procedure mentioned above is a necessary operation for evaluating the presence or absence of image flow (image defects). As mentioned above, photoreceptors with high hardness have low abrasiveness, and repeated use easily forms an oxide film on the photoreceptor surface. The oxide film absorbs moisture from the air, making the originally insulating surface of the photoreceptor conductive. The charge formed on the photoreceptor surface will diffuse, making image flow (image defects) more likely to occur. In this evaluation, in order to evaluate the presence or absence of such image flow, the "standing for one day and night" operation is performed to promote moisture absorption.

[0167] [Table 5]

[0168]

[0169] The results in Table 5 show that the toner of the present invention does not cause a decrease in image density or smudging even when used for a long period of time, and also does not cause image flow, thereby stably producing good images for a long period of time.

[0170] [Evaluation Using the Second Image Forming Apparatus]

[0171] The second image forming apparatus was a Fuji Xerox Color 1000 Press (100-sheet printer), which uses a laminated organic photoreceptor with a crosslinked surface layer formed from a multifunctional charge transport material as a protective layer. Using the toners listed in Table 6, 800,000 sheets were printed in intermittent mode at a 5% pixel ratio in a high-temperature, high-humidity environment (temperature: 35°C, relative humidity: 80%). The image density and smudging of the 800,000th print were evaluated. Furthermore, after printing 800,000 sheets and allowing them to stand for a day and night, the image density, smudging, and image quality (presence of image flow) of the first print were evaluated. The results are shown in Table 6.

[0172] [Table 6]

[0173]

[0174] The results in Table 6 show that the toner of the present invention does not suffer from a decrease in image density or smudging even when used for a long period in an image forming apparatus using a laminated organic photoreceptor. Furthermore, there is no image flow, and good images can be stably produced over a long period of time. In contrast, the toner of the comparative example suffers from a decrease in image density, smudging, and image flow even when used for a long period of time in an image forming apparatus using a laminated organic photoreceptor, and thus cannot produce good images over a long period of time.

[0175] [Evaluation using the third image forming apparatus]

[0176] A full-color printer, HL-L9310CDW (31-sheet printer), manufactured by Brother Industries, Ltd., using a positively charged organic photoreceptor, was used as the third image forming apparatus. In this image forming apparatus, combinations of the present invention's toner 1 (black), the present invention's toner 22 (cyan), the present invention's toner 23 (magenta), and the present invention's toner 24 (yellow) were used. In addition, combinations of comparative toner 1 and comparative toners 5 to 7, and combinations of comparative toner 1 and comparative toners 8 to 10 were also used. Using evaluation patterns with 5% pixels for each of yellow, magenta, cyan, and black in full-color mode, 30,000 sheets of single-sheet intermittent printing were performed under high temperature and high humidity conditions of 33°C and 80% RH. Image density and smudging were evaluated at the initial stage and after 30,000 sheets had been printed. Furthermore, after printing 30,000 sheets and allowing the printed product to stand for a day and night, the image density, smudging, and image quality (presence of image flow) of the first printed sheet were evaluated. The results are shown in Table 7. It should be noted that the image density measured is the density of a solid black image.

[0177] [Table 7]

[0178]

[0179] The results in Table 7 demonstrate that the toner of the present invention exhibits no decrease in image density or smudging over long-term use, even when multiple toners are used in combination. Furthermore, image flow is absent, resulting in long-term, high-quality images. Furthermore, in experimental results using the toner of the present invention, the color gamut of color images remained essentially unchanged from the initial stage to after 30,000 images were used. In contrast, when the comparative toners were used, color gamut changes occurred in all cases, significantly degrading the quality of full-color images.

Claims

1. An external additive for toner, characterized in that: The toner external additive comprises a hydrophobic substance on the surface of metatitanic acid fine particles having a number average primary particle size of 10 to 300 nm, wherein the hydrophobic substance is prepared using a hydrophobic agent containing an amino-based silane coupling agent. The amino-based silane coupling agent is one or more selected from N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-2-(aminoethyl)-8-aminooctyltrimethoxysilane.

2. The external additive for toner according to claim 1, wherein The hydrophobic agent further comprises modified silicone oil.

3. The external additive for toner according to claim 2, wherein The modified silicone oil is amino-modified silicone oil.

4. The external additive for toner according to claim 2 or 3, wherein The mass ratio of the amino-based silane coupling agent to the modified silicone oil is 20:1 to 1:

1.

5. The external additive for toner according to any one of claims 1 to 3, wherein The ratio of the hydrophobic agent is 1 to 40% by mass of the content of the metatitanic acid fine particles in the external additive.

6. The external additive for toner according to any one of claims 1 to 3, wherein The toner external additive is positively charged.

7. The external additive for toner according to any one of claims 1 to 3, wherein The hydrophobicity of the external additive for toner is 5 to 60%.

8. A toner, characterized in that: The toner comprises colored resin particles and the external additive for toner according to any one of claims 1 to 7, wherein the colored resin particles contain at least a colorant and a resin.

9. The toner according to claim 8, wherein The ratio of the external additive for toner is 0.05 to 2.0% by mass of the content of the colored resin particles in the toner.

10. The toner according to claim 8 or 9, wherein The colored resin particles further contain a release agent and a charge control agent.

11. The toner according to claim 8 or 9, wherein The toner further contains small-diameter inorganic fine particles having a number average primary particle size of 5 to 20 nm as an additional external additive.

12. The toner according to claim 8 or 9, wherein The toner further contains large-diameter inorganic fine particles having a number average primary particle size of 25 to 1000 nm as an additional external additive.

13. An image forming apparatus, characterized in that: The image forming device comprises at least a positively charged photosensitive body, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit. The developing unit includes at least the toner according to any one of claims 8 to 12.

14. The image forming apparatus according to claim 13, wherein The positively charged photosensitive body is an amorphous silicon photosensitive body.

15. The image forming apparatus according to claim 13, wherein The positively charged photosensitive body is a positively charged organic photosensitive body.

16. The image forming apparatus according to claim 13, wherein The positively charged photosensitive body is a laminated positively charged organic photosensitive body having a protective layer on its surface.

Images