CN112824976A - External additive for toner, and image forming apparatus - Google Patents

Abstract

The invention provides an external additive used in a toner of an image forming apparatus capable of stably forming an image with excellent image quality even when the image forming apparatus is repeatedly used in various environmental changes for a long time, a toner using the external additive, and the image forming apparatus using the toner. The external additive for toner of the present invention is formed by having a hydrophobic substance on the surface of metatitanic acid particles having a plurality of uniform primary particle diameters of 10 to 300nm, wherein the hydrophobic substance is formed by using a hydrophobic agent containing an amino silane coupling agent. In addition, the toner of the present invention comprises colored resin particles containing at least a colorant and a resin, and the external additive for toner of the present invention.

Description

External additive for toner, and image forming apparatus

Technical Field

The present invention relates to an external additive for toner (toner), a toner, and an image forming apparatus.

Background

In an electrophotographic image forming method, a surface of a photoreceptor is uniformly charged, and then an electrostatic latent image corresponding to an image is formed by exposure in accordance with the image. A toner having a specific charge is attached to the electrostatic latent image to be developed (developed), and a toner image formed on the photoreceptor is transferred to an image forming support such as paper via an intermediate transfer member or the like as necessary, and fixed to the image forming support by heat or the like to form an image. Examples of an image forming apparatus using the image forming method include a copying machine and a printer.

The photoreceptor used in the image forming apparatus is classified into a negatively charged photoreceptor and a positively charged photoreceptor from the viewpoint of the property of applying a uniform charge to the surface. Further, from the viewpoint of the material constituting the photoreceptor, an inorganic photoreceptor using selenium, amorphous silicon or the like and an organic photoreceptor made of an organic material are classified.

The negatively charged organic photoreceptor generally has a laminated structure of: for example, an undercoat layer for the purpose of imparting adhesiveness or controlling charge transfer is formed on an aluminum substrate as needed, a charge generation layer containing a charge generation substance is formed thereon, and a charge transport layer is further formed thereon.

Positively charged organic photoreceptors can achieve high image quality and are effective for suppressing the generation of ozone. In the positively chargeable organic photoreceptor, since a charge generation layer needs to be formed on the surface layer, for example, a charge transport layer and a charge generation layer are sequentially stacked on an aluminum substrate. In addition, a method of forming a single layer on a substrate by mixing a charge generating substance and a charge transporting substance is also included.

As an inorganic photoreceptor, instead of a photoreceptor using a material such as selenium, a photoreceptor using amorphous silicon is mainly used. Amorphous silicon is preferable because it has a very high hardness and can achieve a long life.

In recent years, it has been desired to print variable information in large quantities because of the convenience of digital data. So-called industrial printers that can provide valuable printed matter by printing variable information, rather than simple copying, can be used. In this case, since the printed matter is valuable, it is necessary that the image quality be stable for a long period of time.

For example, patent document 1 proposes an image forming apparatus that can suppress image flow under a high humidity environment when a photoreceptor having a protective layer containing a crosslinked polymer is used (japanese: image flow れ). In the image forming apparatus, a cleaning effect is exerted by supplying the lubricant, and further, the lubricant removing unit is provided to suppress the lubricant from remaining.

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 condensation diameter. Specifically disclosed is a toner for developing electrostatic latent images, which comprises a toner base particle and conductive fine particles as an external additive, wherein the conductive fine particles have an average primary particle diameter of 90nm or less, an average aggregate particle diameter of 0.5-2.0 [ mu ] m and a BET specific surface area of 15m are formed on the surface of the toner base particle²An aggregate of at least one in a gram of the total amount of the inorganic particles. Titanium oxide is disclosed as the conductive fine particles.

Patent document 3 discloses a hydrophobization-treated resin composition having a crystal grain diameter of 12.0 to 16.0nm and a true density of 2.5 to 3.3g/cm³The metatitanic acid particles of (3) are used as an external additive to be added to a colorant for non-magnetic one-component development from the outside, and can suppress the occurrence of the smudging and realize excellent color reproducibility. Further, patent document 4 discloses a technique of preventing occurrence of white streaks in a toner image by including at least 2 types of silica particles having a volume average particle diameter of 5nm or more and 30nm or less and metatitanic acid particles treated with a silane compound having a volume average particle diameter of 50nm or more and 120nm or less and an aspect ratio of 3 or more and less than 10 as external additives added to a colorant from the outside and setting the coverage of each of the silica particles and the metatitanic acid particles with respect to toner particles.

[ Prior art documents ]

[ patent document ]

Japanese patent laid-open publication No. 2015-114647

Patent document 2 Japanese patent laid-open No. 2009-180890

Patent document 3 Japanese patent laid-open No. 2016-

Patent document 4 jp 2011-154278 a

Disclosure of Invention

(problems to be solved by the invention)

In patent documents 1 and 2, although image flow is suppressed by improving the cleaning effect or the like, it is considered difficult to exert a good cleaning effect for a long period of time. Further, patent document 3 does not disclose that an excellent image can be realized even when the image forming apparatus is repeatedly used for a long period of time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an external additive used for a toner of an image forming apparatus capable of stably forming an image having excellent image quality even when the image forming apparatus is repeatedly used for a long period of time under various environmental changes, a toner using the external additive, and the image forming apparatus using the toner.

(means for solving the problems)

Mode 1 of the present invention is an external additive for toner, which is produced by using a hydrophobizing agent containing an amino silane coupling agent, and has a hydrophobe on the surface of metatitanic acid fine particles having a several uniform primary particle diameter of 10 to 300 nm.

Embodiment 2 of the present invention is the external additive for toner according to embodiment 1, wherein the hydrophobizing agent further contains a modified silicone oil.

Embodiment 3 of the present invention is the external additive for toner according to embodiment 2, wherein the modified silicone oil is an amino-modified silicone oil.

Embodiment 4 of the present invention is the external additive for toner according to embodiment 2 or 3, wherein a mass ratio of the amino silane coupling agent to the modified silicone oil is 20: 1-1: 1.

embodiment 5 of the present invention is the external additive for toner according to any one of embodiments 1 to 4, wherein the proportion of the water repellent agent is 1 to 40% by mass of the content of the metatitanic acid fine particles in the external additive.

Embodiment 6 of the present invention is the external additive for toner according to any one of embodiments 1 to 5, wherein the external additive for toner is positively charged.

Embodiment 7 of the present invention is the external additive for toner according to any one of embodiments 1 to 6, wherein the degree of hydrophobicity of the external additive for toner is 5 to 60%.

Embodiment 8 of the present invention is a toner containing colored resin particles containing at least a colorant and a resin, and the external additive for toner according to any one of embodiments 1 to 7.

Embodiment 9 of the present invention is the toner according to embodiment 8, wherein a ratio of the external additive for toner is 0.05 to 2.0% by mass of a content of the colored resin particles in the toner.

Embodiment 10 of the present invention is the toner according to embodiment 8 or 9, wherein the colored resin particles further include a releasing agent and a charge control agent.

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

Embodiment 12 of the present invention is the toner according to any one of embodiments 8 to 11, further comprising large-particle-diameter inorganic fine particles having a number average primary particle diameter of 25 to 1000nm as an additional external additive.

Mode 13 of the present invention is an image forming apparatus including at least a positively chargeable photoreceptor, 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 embodiments 8 to 12.

An image forming apparatus according to mode 14 of the present invention is the image forming apparatus according to mode 13, wherein the positively chargeable photoreceptor is an amorphous silicon photoreceptor.

An image forming apparatus according to mode 15 of the present invention is the image forming apparatus according to mode 13, wherein the positively chargeable photoreceptor is a positively chargeable organic photoreceptor.

An image forming apparatus according to mode 16 of the present invention is the image forming apparatus according to mode 13, wherein the positively chargeable photoreceptor is a laminated positively chargeable organic photoreceptor having a protective layer on a surface thereof.

(effect of the invention)

According to the present invention, it is possible to provide an external additive used for a toner of an image forming apparatus capable of stably forming an image having excellent image quality even when the image forming apparatus is repeatedly used for a long period of time in various environmental changes, a toner using the external additive, and the image forming apparatus using the toner.

Drawings

FIG. 1 is a photomicrograph showing an example of the external additive and toner of the present invention in examples.

Detailed Description

In an image forming apparatus, after an image forming process, that is, after a toner image formed on a photoreceptor is transferred, a step of cleaning the surface of the photoreceptor with a urethane blade, a brush, or the like is performed to remove residual matters such as residual toner, paper powder, and the like and form a subsequent image. The image forming apparatus is required to sufficiently remove the residue by this cleaning. However, in image formation, for the purpose of imparting a uniform charge to the surface of the photoreceptor, the photoreceptor is charged by corona discharge, a roller charging device, or the like, but there are the following problems: since water is present during the discharge, very small oxides are easily formed on the surface of the photoreceptor as the residue.

In addition, for example, in an office, reduction in running cost of a printer and the like is demanded. In order to reduce the cost, it is effective to extend the maintenance period of component replacement or the like as much as possible. Therefore, it is most effective to suppress deterioration of the photoreceptor, particularly to suppress abrasion of the photoreceptor film, which is the most influential factor thereof. For example, a laminated photoreceptor or an amorphous silicon photoreceptor having a protective layer with high hardness formed on the surface thereof can be used to suppress abrasion.

However, as described above, when the surface of the photoreceptor has high hardness, the following problems occur: the cleaning does not sufficiently remove the oxide, the surface of the photoreceptor is finally electrically conductive, and surface charges are diffused in the surface layer, which is a problem of so-called "image flow". The above-described problem becomes more remarkable by using the image forming apparatus for a long period of time and performing repeated image formation. In addition, in the case of using a positively chargeable organic photoreceptor, the problem of charge diffusion also occurs finally.

In view of the above circumstances, the present inventors have made extensive studies on a toner used in an image forming apparatus and an external additive used in the toner, in order to sufficiently remove a residue containing the oxide in a cleaning stage (hereinafter, this effect is sometimes referred to as "high cleanability"), suppress image flow caused by the residue, and maintain the high cleanability even when the image forming apparatus is repeatedly used for a long period of time in various environmental changes, thereby obtaining an image forming apparatus capable of stably forming an image having excellent image quality.

As a result, they found that: when the external additive used in the toner is an external additive having a hydrophobe on the surface of metatitanic acid particles having a plurality of uniform primary particle diameters of 10 to 300nm, wherein the hydrophobe is prepared by using a hydrophobe containing at least an amino silane coupling agent, the generation of oxides on the surface of a photoreceptor can be suppressed, and the above-mentioned effects can be exhibited. In particular, the first discovery is that: in an image forming apparatus using an amorphous silicon photoreceptor or an organic photoreceptor having a hard protective layer, which is compatible with a long service life, as a photoreceptor, even when the image forming apparatus is repeatedly used for a long period of time in various environmental changes, it is possible to form an image having excellent image quality for a long period of time while maintaining high cleanability.

The external additive for toner, and image forming apparatus of the present invention will be described in order below.

(external additive of the invention)

[ Metatitanic acid fine particles ]

First, the external additive for toner of the present invention uses metatitanic acid fine particles having a number average primary particle diameter of 10 to 300nm as a mother particle. In the present invention, it is considered that the use of fine metatitanic acid particles as the base particles can suppress the generation of oxides formed on the surface of the photoreceptor and suppress the occurrence of image defects. The reason is not clear, but can be considered as follows.

That is, titanium oxide generally has a function of suppressing the influence of environmental fluctuation to stabilize the state. Generally, since titanium oxide has an empty orbit, it is easy to transfer electrons, and as a result, it is presumed that the titanium oxide can exhibit a function of suppressing dispersion of charges in the air or a function of trapping charges, and can suppress influence due to environmental fluctuation to stabilize the state.

However, as described below, it is considered that titanium oxide does not sufficiently exhibit its effect in severe environmental changes. In particular, when a positively chargeable organic photoreceptor is used, a charge generation layer is present in the vicinity of the surface, and electrons are generated. Therefore, leakage of electric charge is likely to occur, and in such a situation, it is presumed that the function of titanium oxide to suppress the fluctuation is insufficient. In contrast, metatitanic acid has a crystal structure with slightly distorted crystallinity, and as a result, it is presumed that the function of transferring and receiving electrons sufficiently functions.

Further, it is considered that peroxides such as ozone generated during charging can be easily captured due to the distorted crystal structure, and as a result, the effect of suppressing the generation of oxides can be sufficiently exhibited on the surface of the organic photoreceptor, for example.

The metatitanic acid fine particles of the present invention have a number average primary particle diameter of 10 to 300 nm. The number average primary particle diameter is preferably 25nm or more, more preferably 50nm or more, preferably 175nm or less, more preferably 150nm or less, and further preferably less than 120 nm.

The number-average primary particle diameter represents an average value of particle diameters in the Feret horizontal direction of 100 particles observed by a transmission electron microscope. The Feret horizontal particle size refers to the length of a side parallel to the x-axis in a rectangle circumscribing a particle located on the x-y plane.

[ production of Metatitanic acid Fine particles ]

In the present invention, the method for producing the fine metatitanic acid particles is not particularly limited. For example, it can be produced by hydrolyzing titanyl sulfate. Further, as a means for controlling the number average primary particle diameter of the fine metatitanic acid particles to be within a range of 10 to 300nm, air-stream pulverization is exemplified.

[ hydrophobizing agent ]

The external additive of the present invention has a hydrophobe on the surface of the fine metatitanic acid particles, and the hydrophobe is produced using a hydrophobe containing at least an amino silane coupling agent. It is considered that the formation of oxides can be sufficiently suppressed by treating the fine metatitanic acid particles with an amino silane coupling agent. Further, by using an amino silane coupling agent, a positively charged (plus) external additive and a toner suitable for a positively chargeable photoreceptor capable of forming an image with excellent image quality can be realized.

Examples of the amino silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -8-aminooctyltrimethoxysilane, and N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane. 1 or 2 or more thereof may be used.

The hydrophobizing agent may also comprise a modified silicone oil. By using the modified silicone oil in combination, the effect of increasing the charging speed can be exerted. As the modified silicone oil, an amino-modified silicone oil is preferably used. By using the amino-modified silicone oil together with the amino silane coupling agent, the external additive and the toner can be sufficiently positively charged. Examples of the amino-modified silicone oil include general-purpose products such as amino-modified organopolysiloxanes, and polymers or copolymers such as dimethyl (aminoethylaminopropyl) methylsiloxane, dimethyl (aminoethylaminopropyl) ethylsiloxane, diaminopropyltetramethyldisiloxane, and dimethyl (aminoethylaminopropyl) methylcyclosiloxane.

The proportion of the water repellent agent is preferably 1 to 40% by mass based on the content of the fine metatitanic acid particles in the external additive of the present invention. The effect can be further improved by setting the proportion of the water repellent agent to 1 mass% or more based on the content of the fine metatitanic acid particles. The proportion of the water repellent is more preferably 5% by mass or more, and still more preferably 8% by mass or more, based on the content of the fine metatitanic acid particles. On the other hand, excessive coverage can be prevented by limiting the proportion of the water repellent agent to 40 mass% or less with respect to the content of the fine metatitanic acid particles. The proportion of the water repellent is more preferably 15% by mass or less based on the content of the fine metatitanic acid particles. In the case of using a plurality of types of hydrophobizing agents, the above ratio can be determined using the total amount of the plurality of types of hydrophobizing agents.

In the case where the amino silane coupling agent and the modified silicone oil are used in combination, the mass ratio of the amino silane coupling agent to the modified silicone oil is preferably 20: 1-1: 1. the effect of the amino silane coupling agent can be sufficiently exerted by setting the amino silane coupling agent to 1 time or more by mass of the modified silicone oil. The amino silane coupling agent may preferably be 1.5 times or more the modified silicone oil in terms of mass ratio. On the other hand, from the viewpoint of exerting the effects of the modified silicone oil described above, the amino silane coupling agent is preferably 20 times or less, more preferably 10 times or less, even more preferably 5 times or less, and even more preferably 3 times or less the modified silicone oil in terms of the mass ratio.

The external additive of the present invention is preferably positively charged. In addition, the hydrophobicity of the external additive is preferably 5-60%.

[ production of external additive of the invention ]

In the present invention, the method for producing the external additive of the present invention is not limited. For example, a method of performing surface treatment of the fine metatitanic acid particles by dropping or spraying a water repellent agent while stirring a solution containing the fine metatitanic acid particles; a method of dissolving a hydrophobizing agent in an organic solvent and adding fine particles of metatitanic acid while stirring the organic solvent to perform surface treatment. In the former method, a water repellent agent may be diluted with an organic solvent or the like and used. It is preferable that the mixture is maintained at 60 to 100 ℃ for 0.5 to 2.0 hours after the addition of the hydrophobizing agent. Then, solid-liquid separation is performed by filtration, and drying is performed, whereby fine particles of metatitanic acid having a hydrophobe prepared using a hydrophobizing agent, that is, the external additive of the present invention can be obtained.

(toner)

(1) External additive of the invention

The toner of the present invention is produced by adding the external additive of the present invention to colored resin particles containing at least a colorant and a resin (hereinafter, may be simply referred to as "colored resin particles") from the outside. Thus, the toner of the present invention can be easily removed when cleaning the photoreceptor, and can maintain good cleaning properties for a long period of time, and can stably obtain an image with excellent image quality.

The proportion of the external additive of the present invention in the toner is preferably 0.05 to 2.0 mass% with respect to the content of the colored resin particles. It is preferable to set the ratio of the external additive to 0.05 mass% or more because the effect of the external additive can be sufficiently exerted. The proportion of the external additive is more preferably 0.1 mass% or more. On the other hand, since the effect is saturated even if the external additive is excessively contained, it is preferable to set the upper limit thereof to 2.0 mass%. The proportion of the external additive is more preferably 1.5% by mass or less.

(2) Colored resin particle

The colored resin particles contain at least a colorant and a resin, and may further contain a release agent (wax) and a charge control agent as internal additives, if necessary. The respective components are explained below.

[ resin ]

Examples of the resin contained in the toner particles constituting the toner of the present invention include known resins such as a vinyl resin such as a styrene resin, an acrylic resin, a styrene-acrylic resin, and an olefin resin, a polyester resin, a polyamide resin, a polycarbonate resin, a polyether, a polyvinyl acetate resin, a polysulfone, an epoxy resin, a polyurethane resin, and a urea resin. One or more of them may be used alone or in combination of 2 or more. In particular, 1 or more of the styrene-acrylic resin and the polyester resin is preferable because a toner having excellent low-temperature fixability can be obtained. The glass transition point of the resin is preferably 35 to 70 ℃, more preferably 45 to 60 ℃. The softening point (T1/2) obtained by the high-viscosity rheometer is preferably 80 to 140 ℃, and more preferably 90 to 135 ℃.

When a styrene resin, (meth) acrylic resin, or a copolymer resin thereof is used as the binder resin, it is preferable to use a resin having a weight average molecular weight Mw of 20000 to 100000 inclusive and a number average molecular weight Mn of 2000 to 30000 inclusive. On the other hand, when a polyester resin is used as the binder resin, it is preferable to use a resin having a weight average molecular weight Mw of 5000 to 40000 and a number average molecular weight Mn of 2000 to 10000. The glass transition temperature of the binder resin is preferably in the range of 40 ℃ to 80 ℃. By setting the glass transition temperature to the above range, the minimum fixed temperature can be easily maintained. The softening point of the resin (T1/2 obtained by a high-viscosity rheometer) is 105 to 160 ℃, and preferably 110 to 140 ℃.

[ coloring agent ]

The colorant contained in the toner particles according to the present invention may use conventionally known dyes and pigments. As a colorant for obtaining a black toner, carbon black such as furnace black and channel black; magnetic materials such as magnetite and ferrite; a dye; and inorganic pigments containing nonmagnetic iron oxide.

As a colorant for obtaining a color toner, a known colorant such as a dye or an organic pigment can be optionally used. Specifically, examples of the organic pigment include c.i. pigment red 5, c.i. pigment red 48: 1. c.i. pigment red 53: 1. c.i. pigment red 57: 1. c.i. pigment red 81: 4. c.i. pigment red 122, c.i. pigment red 139, c.i. pigment red 144, c.i. pigment red 149, c.i. pigment red 166, c.i. pigment red 177, c.i. pigment red 178, c.i. pigment red 222, c.i. pigment red 238, c.i. pigment red 269, c.i. pigment yellow 14, c.i. pigment yellow 17, c.i. pigment yellow 74, c.i. pigment yellow 93, c.i. pigment yellow 94, c.i. pigment yellow 138, c.i. pigment yellow 155, c.i. pigment yellow 180, c.i. pigment yellow 185, c.i. pigment orange 31, c.i. pigment orange 43, c.i. pigment blue 15; 3. examples of the dye include c.i. solvent red 1, c.i. solvent red 49, c.i. solvent red 52, c.i. solvent red 58, c.i. solvent red 68, c.i. solvent red 11, c.i. solvent red 122, c.i. solvent yellow 19, c.i. solvent yellow 44, c.i. solvent yellow 77, c.i. solvent yellow 79, c.i. solvent yellow 81, c.i. solvent yellow 82, c.i. solvent yellow 93, c.i. solvent yellow 98, c.i. solvent yellow 103, c.i. solvent yellow 104, c.i. solvent yellow 112, c.i. solvent yellow 162, c.i. solvent blue 25, c.i. solvent blue 36, c.i. solvent blue 69, c.i. solvent blue 70, c.i. solvent blue 93, and c.i. solvent blue 95. For each color, 1 kind of colorant alone or 2 or more kinds of colorants for obtaining toners of each color may be used in combination.

The content of the colorant is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, based on the content of the resin.

The colored resin particles may further contain a release agent (wax), a charge control agent as an internal additive.

[ Release agent ]

As the release agent, known wax can be used. For example, hydrocarbon-based waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax; ester waxes such as carnauba wax, pentaerythritol behenate, behenyl behenate, and citric acid behenyl behenate. One or more of them may be used alone or in combination of 2 or more. The content of the release agent is preferably 2 to 20% by mass, and more preferably 3 to 10% by mass, based on the resin.

[ Charge control agent ]

As the charge control agent, a known charge control agent can be used. For example, nigrosine dyes, metal salts of naphthenic acids or higher fatty acids, alkoxylated amines, quaternary ammonium compounds, azo metal complexes, metal salicylates or metal complexes thereof, calixarene compounds, and the like can be used. 2 or more of them may be used alone or in combination. The content of the charge control agent is preferably 0.1 to 3.0% by mass, more preferably 0.1 to 1.0% by mass, based on the resin.

Further, a resin-type charge control agent (charge control resin) having a substituent in the resin itself and having a charge imparting ability may be used.

(method for producing colored resin particles)

Examples of the method for producing the resin particles include a kneading and pulverizing method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, an ester extension polymerization method, a dispersion polymerization method, and the like. The colored resin particles may be resin particles obtained by kneading and pulverizing a colorant, a resin, or the like as cores, and a coating layer having a function such as heat resistance may be formed on the surface of the resin particles; colored resin particles in which a covering material monomer is added to resin particles formed by suspension polymerization to form a covering layer; and colored resin particles, which are formed by aggregating polymer fine particles, as cores and further forming a coating layer around the cores with other resin particles.

The size of the colored resin particles (toner particles) obtained by externally adding the external additive of the present invention is preferably 3 to 15 μm, and more preferably 5 to 10 μm in volume average particle diameter. This size is substantially the same as that of the colored resin particles (toner base particles) before the addition of the external additive.

(3) Additional external additives

As for the external additive of the toner of the present invention, in addition to the case where only the external additive of the present invention is used, the following additional external additive may be further used in addition to the external additive of the present invention.

(Small particle size inorganic Fine particles)

In the toner of the present invention, it is preferable to add the external additive of the present invention from the outside and to add inorganic fine particles having a small particle size of 5 to 20nm in number average primary particle size as an additional external additive from the outside, from the viewpoint of imparting chargeability or fluidity.

Examples of the small-particle-size inorganic fine particles include fine particles containing: silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, Diamond carbon lactam (Diamond carbon lactam) and other various carbides, boron nitride, titanium nitride, zirconium nitride and other various nitrides, zirconium boride and other borides, iron oxide, chromium oxide, calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and other various oxides, silica-titania-alumina, calcium titanate, strontium titanate, magnesium titanate and other composite oxides, molybdenum disulfide and other sulfides, magnesium fluoride, carbon fluoride and other fluorides, aluminum stearate, calcium stearate, zinc stearate, magnesium stearate and other various metal soaps, talc, bentonite and other various nonmagnetic inorganic substances. 2 or more of them may be used alone or in combination.

Among them, 1 kind or a combination of 2 or more kinds of small-particle-size inorganic fine particles made of silica, alumina, and a silica-titania-alumina composite oxide is particularly preferably used.

The small-particle-diameter inorganic fine particles are preferably surface-treated by a known method using a conventionally used water repellent agent such as a silane coupling agent, a titanate coupling agent, silicone oil, or silicone based paint, a fluorine-based silane coupling agent, a fluorine-based silicone oil, a coupling agent containing an amino group/quaternary ammonium salt, or a treating agent such as modified silicone oil.

Examples of the hydrophobizing 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, gamma-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane; silicone oils such as dimethylpolysiloxane, polymethylhydrosiloxane, methylphenylpolysiloxane, and dimethylsilicone; etc., 1 or 2 or more thereof may be used. Furthermore, the compound acts as an amine-based hydrophobizing agent. The amino silane coupling agent and the amino-modified silicone oil described above for use in the production of the external additive of the present invention can be used.

When small-particle-size inorganic fine particles are added to the toner from the outside, the proportion of the small-particle-size inorganic fine particles is preferably 0.1 to 2.0 mass% with respect to the content of the colored resin particles. From the viewpoint of sufficiently exhibiting the effect of the small-particle-size inorganic fine particles, that is, the effect of imparting fluidity or the like, the content is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. On the other hand, from the viewpoint of suppressing image defects and the like due to adhesion to a photoreceptor and the like by excessively containing inorganic fine particles having a small particle size, the content is preferably 2.0 mass% or less, and more preferably 1.5 mass% or less. In the case where a plurality of types of small-particle-size inorganic fine particles are used, the ratio can be determined using the total amount of the plurality of types of small-particle-size inorganic fine particles.

(Large particle size inorganic Fine particles)

Further, the incorporation of large-particle-diameter inorganic fine particles having a number average primary particle diameter of 25 to 1000nm into resin fine particles containing at least a colorant and a resin can suppress the embedding of small-particle-diameter inorganic fine particles into the surface of colored resin particles. As the large-particle-diameter inorganic fine particles, the same materials as those of the small-particle-diameter inorganic fine particles described above can be used.

Further, the inorganic fine particles having a large particle diameter of more than 100nm are abrasive, and the effects of polishing the surface of the photoreceptor and cleaning the photoreceptor can be expected.

When the large-particle-diameter inorganic fine particles are added from the outside, the ratio thereof is preferably 0.1 to 2.0 mass% with respect to the content of the colored resin particles. More preferably 0.2 to 1.0 mass%. The effect of the particles can be exerted by setting the proportion of the large-particle-diameter inorganic fine particles to 0.1 mass% or more. Further, by setting the ratio of the large-particle-diameter inorganic fine particles to 2.0 mass% or less, damage to the photoreceptor and image defects caused by excessive large-particle-diameter inorganic fine particles can be suppressed.

The toner of the present invention can be used as a magnetic or non-magnetic one-component developer, and can also be mixed with a carrier to be used as a two-component developer. When a toner is used as a two-component developer, magnetic particles made of conventionally known materials such as metals including iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the carrier, and ferrite particles are particularly preferable. As the carrier, a coated carrier obtained by coating the surface of the magnetic particles with a coating agent such as a resin, a dispersion type carrier obtained by dispersing magnetic fine powder in a binder resin, or the like can be used. As the resin and binder resin forming the covering agent, conventionally used resins can be used. The volume average particle diameter of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

(method for producing toner)

The toner of the present invention can be obtained by adding the above-mentioned small-particle-diameter inorganic fine particles, large-particle-diameter inorganic fine particles, and the like as the external additive of the present invention to the colored resin particles, and adding the external additive as needed. As a method for mixing them, a known mixing device such as a henschel mixer or a V-type mixer can be used.

(image Forming apparatus)

The image forming apparatus of the present invention includes at least a positively chargeable photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit, and the developing unit includes at least a toner to which the external additive of the present invention is added from the outside.

The image forming apparatus of the present invention has a positively chargeable photoreceptor. The positively chargeable photoreceptor is preferably an amorphous silicon photoreceptor, a positively chargeable organic photoreceptor, or a laminated positively chargeable organic photoreceptor having at least a protective layer on the surface thereof. These photoreceptors will be described below.

(amorphous silicon photoreceptor)

Examples of the amorphous silicon (a-Si) photoreceptor include an amorphous silicon photoreceptor in which an amorphous silicon photosensitive layer (a-Si photosensitive layer) is formed on the surface of a conductive substrate formed in a specific shape such as a roll shape. In particular, an amorphous silicon photoreceptor having a thin-film type a-Si photosensitive layer having a thickness of 30 μm or less is preferable because it is excellent in productivity and can form an image with high resolution. The a-Si photosensitive layer may have a carrier blocking layer, a surface protective layer, and the like, which are described in detail below, in addition to a single layer or 2 or more layers that actually function as a photosensitive layer. In the case of having a plurality of layers, the overall layer thickness is preferably 30 μm or less. The a-Si photosensitive layer may be a photosensitive layer containing H or a halogen element, or a photosensitive layer containing an element such as C, N, O on the surface of the conductive substrate. That is, examples of the material constituting the photosensitive layer of a-Si include a-SiC, a-SiO, and a-SiON, in addition to a-Si.

[ Carrier blocking layer ]

A carrier block layer is sandwiched between the a-Si photosensitive layer and the conductive substrate. As such a carrier block layer, an inorganic insulating layer such as a-SiC or the like, an organic insulating layer such as polyethylene terephthalate or the like can be used, and the thickness thereof can be set within a range of 0.01 to 5 μm.

[ surface protective layer ]

The surface protective layer may be made of a conventionally used material, and examples thereof include an organic or inorganic insulating material, and for example, an inorganic insulating layer obtained by adding C, O, N or the like to a-Si is preferably used.

(positively charged organic photoreceptor)

In the positively chargeable organic photoreceptor, an undercoat layer may be formed on the surface of the conductive substrate as necessary, and a photosensitive layer in which a charge transport layer and a charge generation layer are sequentially stacked may be further formed thereon. Alternatively, the positively chargeable organic photoreceptor may be: an undercoat layer may be formed on the surface of the conductive substrate as required, and a photosensitive layer in which a charge generating substance and a charge transporting substance are mixed in the same layer is further formed thereon.

As the conductive substrate, a metal plate such as aluminum, stainless steel, or iron, a conductive substrate obtained by providing a metal layer such as aluminum, palladium, or gold on a surface of a flexible support such as paper or a plastic film by lamination or vapor deposition, a conductive substrate obtained by providing a layer containing a conductive polymer, a conductive compound such as indium oxide, or tin oxide on a surface of a flexible support such as paper or a plastic film by coating or vapor deposition, or the like can be used.

The undercoat layer formed as needed can be used in the case where it is necessary to supplement the adhesiveness between the conductive substrate and the photosensitive layer. The undercoat layer may be made of a material conventionally used, and may have a film thickness of 0.05 to 20 μm.

The charge transport layer is a layer containing a charge transport substance that transports the charge generated by the charge generation layer. The charge transporting substance is not particularly limited, and conventionally used charge transporting substances can be used. The thickness of the charge transport layer may be 5 to 50 μm, preferably 10 to 30 μm.

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

In the case of forming a photosensitive layer in which a charge generating substance and a charge transporting substance are present in a mixed state, the photosensitive layer can be formed by dispersing or dissolving the charge generating substance and the charge transporting substance in a resin. As the resin used in this case, a conventionally used resin can be used. The thickness of the photosensitive layer in which the charge generating substance and the charge transporting substance are mixed may be 5 to 60 μm, and preferably 10 to 40 μm.

(protective layer)

As the positively chargeable organic photoreceptor, a laminated positively chargeable organic photoreceptor having at least a protective layer on the surface thereof can be used. By having the protective layer, the durability of the photoreceptor is further improved. As described above, although the cleaning property of the photoreceptor having high durability is liable to be lowered, the use of the toner containing the external additive of the present invention can exert a rubbing effect and prevent the occurrence of filming, and as a result, an image can be stably output for a long period of time as compared with the conventional one.

As the protective layer, a conventionally used protective layer can be used, and for example, a heat or light curable resin can be used as the binder resin, and if necessary, metal oxide fine particles, lubricant particles, an antioxidant, a resin other than the binder resin, and the like can be contained. The thickness of the protective layer is preferably 0.2 to 10 μm, and more preferably 0.5 to 5 μm.

(Metal oxide Fine particles)

The protective layer may contain, for example, alumina (Al) having a number average primary particle diameter of 1 to 300nm for the purpose of imparting higher durability₂O₃) Tin oxide (SnO)₂) Titanium dioxide (TiO)₂) And the like.

The image forming apparatus of the present invention includes, in addition to the positively chargeable photoreceptor, at least a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit, and the developing unit includes at least the toner of the present invention. The charging unit, the exposure unit, the developing unit such as a magnetic roller or toner supply other than the toner of the present invention, the transfer unit, and the cleaning unit may be conventionally known ones.

As an image forming method using the image forming apparatus, for example, a uniform charge is given to the surface of the photoreceptor, and then an electrostatic latent image corresponding to an image is formed by performing exposure corresponding to the image. The electrostatic latent image is developed (developed) by adhering a toner having a specific charge to the electrostatic latent image, and the toner image formed on the photoreceptor is transferred to an image forming support such as paper via an intermediate transfer member or the like as necessary, and fixed to the image forming support by heat or the like. The toner of the present invention can be preferably used for such an electrostatic latent image developing application, and can be preferably used as a positively charged (i.e., positively chargeable) toner used together with a positively charged photoreceptor.

After the transfer, the toner on the surface of the photoreceptor, which has not been transferred, is removed by static electricity removal and cleaning. According to the present invention, since the toner to which the external additive of the present invention is added is easily removed from the photoreceptor at the time of the cleaning, it is difficult to form a residual material such as an oxide, and as a result, an image having excellent image quality can be stably formed for a long period of time even in various environmental changes such as a change in the moisture content in the atmosphere.

[ examples ]

The present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples, and can be implemented by adding appropriate modifications within the scope conforming to the gist described above and below, and all of them are included in the technical scope of the present invention.

In the present example, the number average primary particle diameter of the metatitanic acid fine particles, the degree of hydrophobicity of the external additive, and the charge amount were measured as shown below as evaluation items.

(number-average primary particle diameter)

The metatitanic acid powder was photographed by a Transmission Electron Microscope (TEM) at a magnification of 10000 times, and 100 particles were subjected to image analysis on the photograph to determine a Feret horizontal average particle size which is an average value of Feret horizontal particle sizes, and the Feret horizontal average particle size was defined as a number average primary particle size.

(degree of hydrophobicity)

50mL of a plurality of ethanol-water mixed solutions were prepared, each of which was changed in 5 steps so that the volume ratio of ethanol/water was 0/100-100/0. While stirring with a magnetic stirrer, 0.20g of the fine particles of metatitanic acid subjected to the hydrophobic treatment was added, and the total amount was wetted for 5 minutes, and the volume ratio of ethanol in the liquid mixture at this time was defined as the degree of hydrophobicity of the sample. In consideration of environmental stability, the degree of hydrophobicity is preferably 5% or more. By setting the water repellency to 5% or more, leakage of charge of the toner can be suppressed and a decrease in charge amount can be suppressed particularly in long-term storage under high temperature and high humidity. The upper limit of the degree of hydrophobicity may be set to, for example, 60%.

(electric quantity)

In a 20mL glass container, 19.5g of an iron powder carrier and 0.5g of an external additive were added, and the mixture was stored at 20 ℃ in a normal temperature and humidity environment at 50% RH for 24 hours. The glass container was removed and capped and shaken for 30 minutes using a paint shaker. After the shaking, 1g of the mixed sample was collected, and a value obtained by blowing nitrogen gas for 10 seconds by a bleed charge amount measuring apparatus (MODEL 230TO, manufactured by TREK JAPAN corporation) was measured as a charge amount.

[ evaluation Using the 1 st image Forming apparatus ]

(preparation of Fine metatitanic acid particles)

An aqueous solution of titanyl sulfate (titanyl sulfate concentration: 10% by mass) was heated to 130 ℃ to cause thermal hydrolysis, thereby obtaining an aqueous sulfuric acid slurry of metatitanic acid. The obtained sulfuric acid aqueous solution slurry of metatitanic acid was subjected to solid-liquid separation by filtration. The filter cake obtained from the water wash was then dried at a temperature of 120 ℃ for 40 hours. The obtained dried product was pulverized by a hammer mill to obtain metatitanic acid fine particles. Wherein the above heating conditions and the like are adjusted to obtain metatitanic acid fine particles having various number average primary particle diameters. The obtained metatitanic acid fine particles are shown in table 1.

As comparative example fine particles, titanium oxide fine particles were prepared as follows. That is, an aqueous solution of titanyl sulfate (titanyl sulfate concentration: 10% by mass) was heated to 130 ℃ to cause thermal hydrolysis, thereby obtaining an aqueous sulfuric acid slurry of metatitanic acid. The obtained sulfuric acid aqueous solution slurry of metatitanic acid was subjected to solid-liquid separation by filtration. Then, the cake obtained by the water washing was dried at a temperature of 120 ℃ for 40 hours, and further dried at a temperature of 500 ℃ for 4 hours. The obtained dried product was pulverized by a hammer mill to obtain titanium oxide fine particles having a number average primary particle diameter of 30 nm. The number average primary particle diameter is measured by the method described above.

[ Table 1]

Metatitanic acid fine particles No.	Number average primary particle diameter
		1	30nm
2	50nm
		3	70nm
4	100nm
		5	300nm

(production of external additive of the invention)

The above-mentioned various metatitanic acid fine particles were treated with various hydrophobizing agents shown in Table 2 (hydrophobizing treatment). As shown in detail below.

First, the external additives 1 to 12 of the present invention shown in Table 2 were obtained in the following manner. That is, the fine metatitanic acid particles were dispersed in water at a solid content concentration of 10 mass% to obtain a slurry, and in the slurry, an amino silane coupling agent shown in table 2 was added as a water repellent in such a ratio that the content of the fine metatitanic acid particles was as shown in table 2, and the slurry was heated to 80 ℃. After reaching 80 ℃, the temperature was maintained for 1 hour, and then solid-liquid separation was performed by filtration and dried to obtain metatitanic acid fine particles having a hydrophobe prepared from a hydrophobizing agent, that is, external additives of the present invention (external additives of the present invention 1 to 12).

In Table 2, as 3-aminopropyltriethoxysilane, an amino silane coupling agent KBE-903 manufactured by shin-Etsu chemical Co., Ltd; as N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, KBM-603 was used.

The external additives 13 to 15 of the present invention shown in Table 2 were obtained in the following manner. That is, the fine metatitanic acid particles were dispersed in water at a solid concentration of 10 mass% to obtain a slurry, and the amino silane coupling agent and the amino modified silicone oil were added to the slurry as a water repellent agent. At this time, the amino silane coupling agent is added to the slurry as described above, solid-liquid separation is performed, and then the amino modified silicone oil is kneaded into the cake before drying by a kneader. Specifically, amino-modified silicone oil KF-862 (main component: amino-modified organopolysiloxane) manufactured by shin-Etsu chemical Co., Ltd was added as amino-modified silicone oil so that the content of the fine particles of metatitanic acid became the ratio shown in Table 2, and the mixture was stirred at room temperature for 1 hour using a pressure kneader, and subjected to surface treatment.

(production of external additive of comparative example)

The titanium oxide fine particles were surface-treated with an amino silane coupling agent as a hydrophobizing agent in the same manner as in the external additive 1 of the present invention, to obtain an external additive of comparative example 1. In addition, as the external additive of comparative example 2, titanium oxide fine particles used as they were without surface treatment were used.

The hydrophobicity and charge amount of the obtained external additive were measured as described above. The results are shown in Table 2.

[ Table 2]

(production of colored resin particles)

Colored resin particles used in the toner are produced. As the resin, the colorant, the release agent, and the charge control agent, substances of the types shown in table 3 were weighed out in amounts shown in table 3, respectively, and dry-premixed, then melt-kneaded by a twin-screw extruder, then pulverized by a mechanical pulverizer, and classified by an air-flow classifier, to obtain colored resin particles (colored resin particle nos. 1 to 5) having volume average particle diameters shown in table 3.

In table 3, the styrene-acrylic resin had Tg of 56 ℃, softening point of 126 ℃, the polyester resin had Tg of 55 ℃ and softening point of 120 ℃. Raven330 manufactured by Cabot was used as carbon black. The melting point of the paraffin wax in Table 3 was 98 ℃. Further, TP-415 produced by Gekko Swinhonis chemical was used as the quaternary ammonium charge control agent, and T-77 produced by Gekko Swinhonis chemical was used as the azo iron complex.

[ Table 3]

(production of toner)

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

Fig. 1 shows a photomicrograph (magnification: 5000 times) obtained by observation with a scanning electron microscope as an example of the obtained toner of the present invention. Therefore, the following steps are carried out: in fig. 1, the external additive of the present invention is uniformly dispersed on the surface of the toner mother particle.

[ Table 4]

(evaluation of characteristics of toner)

The toners 1 to 15 of the present invention and the comparative toners 1 and 2 were used in a multifunction machine having an amorphous silicon photoreceptor (manufactured by Kyocera Document Solutions, TASKalfa 620(62 machines)) as the 1 st image forming apparatus, and 30 ten thousand sheets were printed in a batch mode at a pixel rate of 5% under a high-temperature and high-humidity environment (temperature: 35 ℃ and relative humidity 80% RH), and the image density and the degree of soiling of the 30 th printed matter were evaluated. The image density is measured for 10 positions of a pure black image, the reflection density is subtracted from the reflection density of the paper to obtain the average value of the image density, and the image density is judged to be unqualified if the image density is lower than 1.20; when the concentration is 1.20 or more, the concentration is considered to be practical and judged to be acceptable. The degree of smearing is a phenomenon (scumming) in which non-image portions of the paper after printing are smeared, and is represented by an average value of image densities obtained by measuring reflection densities at 10 positions of a blank paper portion and subtracting the reflection densities of the paper. If the dirty concentration is less than 0.005, the dirty concentration is a practical level, and the dirty concentration is judged to be qualified; if the fouling concentration is 0.005 or more, it is not a practical level and it is judged to be not qualified.

After 30 ten thousand prints were made and left for 1 day and night, the presence or absence of image flow was evaluated based on the image density, the degree of smearing, and the image quality of the 1 st printed matter. The evaluation of the image flow was performed by printing a 30% halftone image and visually observing the reproducibility of the halftone. The case where unevenness occurs in halftone is determined as image flow, and the case where unevenness does not occur in halftone is determined as no image flow. These results are shown in Table 5.

Note that the "standing for 1 day and night" is an operation necessary for evaluating the presence or absence of image flow (image defect). As described above, the photoreceptor having high hardness has low abrasiveness, and an oxide coating film is easily formed on the surface of the photoreceptor by repeated use. The oxide coating absorbs moisture in the air, and the surface of the photoreceptor, which is originally insulating, is conductive, and the electric charge formed on the surface of the photoreceptor diffuses, so that image flow (image defect) is likely to occur. In this evaluation, in order to evaluate the presence or absence of the image flow, the operation of "standing for 1 day and night" was performed to promote moisture absorption.

[ Table 5]

From the results in table 5, it can be seen that: the toner of the present invention does not cause a decrease in image density or a stain even after long-term use, and does not cause image flow, and can stably obtain a good image for a long period of time.

[ evaluation Using the 2 nd image Forming apparatus ]

A Color 1000Press (100 sheets) manufactured by Fuji corporation using a laminated organic photoreceptor having a surface layer formed by a crosslinked structure using a charge transport material having a polyfunctional reactivity as a protective layer is used as the 2 nd image forming apparatus. In this image forming apparatus, 80 ten thousand sheets were printed in a batch mode at a pixel rate of 5% under a high-temperature and high-humidity environment (temperature: 35 ℃ C., relative humidity 80% RH) using the toners shown in Table 6, and the image density and the degree of smearing of the 80 th printed matter were evaluated. After 80 ten thousand prints were printed and left for 1 day and night, the image density, the degree of smearing, and the image quality (presence or absence of image flow) of the printed 1 st printed matter were evaluated. The results are shown in Table 6.

[ Table 6]

From the results in table 6, it can be seen that: the toner of the present invention does not cause a decrease in image density or a stain even when used for a long period of time in an image forming apparatus using a laminated organic photoreceptor, and does not cause image flow, and can stably obtain a good image for a long period of time. In contrast, when the toner of the comparative example is used for a long period of time in an image forming apparatus using a laminated organic photoreceptor, a decrease in image density, a smear phenomenon, and image flow occur, and a good image cannot be obtained for a long period of time.

[ evaluation Using the 3 rd image Forming apparatus ]

A full-color printer HL-L9310CDW (31 sheet machine), manufactured by Brother industries, Inc. using a positively-charged organic photoreceptor, was used as the 3 rd image forming apparatus. In this image forming apparatus, the toner 1 (black) of the present invention, the toner 22 (cyan) of the present invention, the toner 23 (magenta) of the present invention, and the toner 24 (yellow) of the present invention are used in combination. 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 having 5% pixels in yellow, magenta, cyan, and black in full-color mode, 30000 sheets of sheet-fed intermittent printing were performed under high-temperature and high-humidity conditions of 33 ℃ and 80% RH, and the image density and the degree of soiling at the initial stage and after 3 ten thousand sheets were evaluated. After 3 ten thousand prints were made, the sheets were left for 1 day and night, and the image density, the degree of smearing, and the image quality (presence or absence of image flow) of the printed 1 st printed matter were evaluated. The results are shown in Table 7. The image density is measured as the density of a solid black image.

[ Table 7]

From the results in table 7, it can be seen that: the toner of the present invention does not cause decrease in image density and a phenomenon of smearing even when a plurality of toners are used in combination, and does not cause image flow even when used for a long period of time, thereby obtaining a good image for a long period of time. In addition, in the experimental results using the toner of the present invention, the color gamut of the color image was obtained without substantially changing from the initial stage to 3 ten thousand sheets. On the other hand, when the comparative toner is used, the color gamut changes, and the quality of a full-color image is significantly reduced.

Claims (16)

1. An external additive for toner, characterized in that,

the external additive for toner is prepared by having a hydrophobe on the surface of metatitanic acid particles with a plurality of uniform primary particle diameters of 10-300 nm, wherein the hydrophobe is prepared by using a hydrophobe containing an amino silane coupling agent.

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 silane coupling agent to the modified silicone oil is 20: 1-1: 1.

5. the external additive for toners according to any one of claims 1 to 3, wherein,

the proportion of the water repellent agent is 1-40% by mass of the content of the metatitanic acid particles in the external additive.

6. The external additive for toners according to any one of claims 1 to 3, wherein,

the external additive for toner is positively charged.

7. The external additive for toners according to any one of claims 1 to 3, wherein,

the external additive for toner has a hydrophobicity of 5-60%.

8. A toner comprising colored resin particles and the external additive for toner according to any one of claims 1 to 7, wherein the colored resin particles comprise at least a colorant and a resin.

9. The toner according to claim 8, wherein,

the proportion of the external additive for toner is 0.05-2.0% 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-particle-size inorganic fine particles having a number average primary particle size of 5 to 20nm as an additional external additive.

12. The toner according to claim 8 or 9, wherein,

the toner further includes large-sized inorganic fine particles having a uniform number of primary particles of 25 to 1000nm as an additional external additive.

13. An image forming apparatus is characterized in that,

the image forming apparatus has at least a positively chargeable photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit,

the toner according to any one of claims 8 to 12 is provided at least as the developing unit.

14. The image forming apparatus according to claim 13,

the positively charged photoreceptor is an amorphous silicon photoreceptor.

15. The image forming apparatus according to claim 13,

the positively chargeable photoreceptor is a positively chargeable organic photoreceptor.

16. The image forming apparatus according to claim 13,

the positively chargeable photoreceptor is a laminated positively chargeable organic photoreceptor having a protective layer on the surface thereof.

Images