JP6439713B2 - Toner for electrostatic latent image development and external additive - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner and an external additive.

  Patent Document 1 discloses hydrophobic silica as an external additive material for toner particles. In Patent Document 1, hydrophobic silica is surface-treated with aminosilane or the like.

JP 2010-198004 A

  However, when toner is used for continuous printing (especially continuous printing at a high density printing rate), it is considered that the durability (and hence charging stability) of the external additive disclosed in Patent Document 1 is not necessarily sufficient.

  The present invention has been made in view of the above problems, and provides an external additive excellent in positive chargeability, durability, and adhesion resistance, and a toner for developing an electrostatic latent image including such an external additive. With the goal. In addition, the present invention is such that when continuous printing is performed using toner (especially continuous printing at a high density printing rate), the generation of high-quality images is continuously suppressed by suppressing the occurrence of fogging. The purpose.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including toner base particles containing a binder resin and an external additive attached to the surface of the toner base particles. The external additive includes a plurality of external additive particles including alumina particles and a coat layer covering the surface of the alumina particles. The coat layer contains a nitrogen-containing resin. The surface of the coating layer is hydrophobized with one or more isocyanate compounds.

  The external additive according to the present invention includes a plurality of external additive particles. The external additive particles include alumina particles and a coat layer that covers the surfaces of the alumina particles. The coat layer contains a nitrogen-containing resin. The surface of the coating layer is hydrophobized with one or more isocyanate compounds.

  According to the present invention, it is possible to provide an external additive excellent in positive chargeability, durability, and adhesion resistance, and a toner for developing an electrostatic latent image including such an external additive. Further, according to the present invention, in addition to this effect or instead of this effect, when continuous printing is performed using toner (particularly, continuous printing at a high density printing rate), fog is continuously generated. There may be an effect that it is possible to suppress and continue to form high-quality images.

An embodiment of the present invention will be described. Note that the evaluation results (values indicating shape, physical properties, etc.) regarding the powder (more specifically, toner base particles, external additives, toner, etc.) are average values from the powder unless otherwise specified. It is the number average of the values measured for each of these average particles by selecting a significant number of particles. The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. It is. Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. The crystalline polyester resin is described as “crystalline polyester resin”, and the non-crystalline polyester resin is simply described as “polyester resin”.

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner may be used as a one-component developer. Alternatively, a two-component developer may be prepared by mixing toner and carrier using a mixing device (for example, a ball mill). In order to form a high-quality image, it is preferable to use a ferrite carrier as a carrier. In order to form a high-quality image over a long period of time, it is preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. In order to impart magnetism to the carrier particles, the carrier core may be formed of a magnetic material (for example, a ferromagnetic substance such as ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Good. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier.

  The toner according to the exemplary embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

  First, an electrostatic latent image is formed on a photoconductor (for example, a surface layer portion of a photoconductor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing step, toner (for example, toner charged by friction with a carrier or blade) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) is attached to the electrostatic latent image and is applied to the photoreceptor. A toner image is formed. In the subsequent transfer step, the toner image on the photosensitive member is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan.

  The toner according to this embodiment includes a plurality of toner particles. The toner particles include toner base particles containing a binder resin and an external additive. The external additive adheres to the surface of the toner base particles. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, if necessary.

  The toner particles contained in the toner according to the present embodiment may be toner particles not having a shell layer (hereinafter referred to as non-capsule toner particles), or toner particles having a shell layer (hereinafter referred to as capsule toner particles). May be described). In the capsule toner particles, the toner base particles include a core containing a binder resin and a shell layer that covers the surface of the core. The shell layer is substantially composed of a resin. For example, by covering a core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the core, or may partially cover the surface of the core. In the capsule toner particles, toner base particles in non-capsule toner particles described later can be used as a core.

  The toner particles contained in the toner according to the exemplary embodiment include an external additive having the following configuration (hereinafter referred to as a basic configuration).

(Basic composition of external additives)
The external additive includes a plurality of external additive particles (hereinafter referred to as specific external additive particles) including alumina particles and a coating layer that covers the surface of the alumina particles. The coat layer contains a nitrogen-containing resin. The surface of the coat layer is hydrophobized with one or more isocyanate compounds. The nitrogen-containing resin is a resin containing a nitrogen atom in its chemical structure.

  Silica particles tend to exhibit strong negative chargeability. Therefore, the silica particles are difficult to be positively charged. Silica particles have a high moisture adsorptivity. For this reason, the charge amount of the silica particles tends to decrease in a high humidity environment. In order to improve the positive chargeability and charge stability of the silica particles, it is conceivable to treat the silica particles with aminosilane (positive charge agent) and alkylsilane (hydrophobic agent). However, when continuous printing is performed using toner particle powder (toner) having such silica particles, the surface treatment agent (aminosilane and / or alkylsilane) is peeled off from the silica particles and the toner particles are charged. It becomes unstable and fog is likely to occur. Further, when the surface treatment agent is peeled off and the silica particles are exposed, the exposed portion is likely to absorb moisture, so that the chargeability of the toner tends to be insufficient.

  Alumina particles tend to exhibit strong positive chargeability. Therefore, the alumina particles are more positively charged than the silica particles. In the basic configuration, the specific external additive particles include alumina particles, and thus are easily positively charged. By using such specific external additive particles, it becomes easy to ensure sufficient positive chargeability of the toner.

  Further, the nitrogen-containing resin has a moderately strong positive charging property and tends to have excellent charging stability with respect to each of environmental fluctuation and time passage. In the external additive having the above basic structure, the coat layer contains a nitrogen-containing resin. The durability of the external additive particles can be improved by covering the alumina particles (core of the external additive particles) with a coating layer containing a nitrogen-containing resin. It is considered that toner particle powder (toner) having such an external additive is excellent in positive chargeability and charge stability. When continuous printing at a high density printing rate is performed using toner particle powder (toner) having an external additive having the above basic structure, high-quality images can be produced by continuously suppressing the occurrence of fogging. It becomes possible to continue forming. In order to achieve the above effect based on the nitrogen-containing resin, it is preferable that 80% by mass or more of the resins contained in the coat layer is a nitrogen-containing resin, and 90% by mass or more of the resin is a nitrogen-containing resin. More preferably, 100% by mass of the resin is more preferably a nitrogen-containing resin.

  However, nitrogen-containing resins (more specifically, melamine resins and the like) tend to have high adhesion. For this reason, if the nitrogen-containing resin is exposed as it is on the surface of the toner particles, the toner adheres to and is fixed to a member (more specifically, a photosensitive drum) that can be contacted with the toner in the image forming process. It becomes easy to become. In the external additive having the above basic structure, the surface of the coat layer is hydrophobized with an isocyanate compound. The isocyanate compound has high reactivity with the nitrogen-containing resin. By treating (modifying) the surface of the coating layer containing a nitrogen-containing resin with an isocyanate compound (specifically, an isocyanate compound having a hydrophobic functional group) to make it hydrophobic, sufficient external additives (and thus toner) ) Is easily secured.

  In formula (1), phenyl isocyanate is shown as an example of an isocyanate compound.

For example, when the surface of the coating layer containing a melamine resin is hydrophobized with phenyl isocyanate, the phenyl isocyanate and the end group (—NH—CH ₂ —OH) of the melamine resin are represented by the following formula (2). It is thought to be chemically bonded.

  In order to achieve both the adhesion resistance and the positive charging property of the toner, the degree of hydrophobicity of the specific external additive particles by the methanol wettability method is preferably 25% or more, and more preferably 50% or more. .

  The coat layer may cover the entire surface of the alumina particles, or may partially cover the surface of the alumina particles. However, in order to achieve the effect based on the above-mentioned nitrogen-containing resin, it is preferable that the coat layer covers the entire surface of the alumina particles.

In order to improve the fluidity of the toner, the volume median diameter (D ₅₀ ) of the specific external additive particles is preferably 1 nm or more and 25 nm or less.

  In order to impart appropriate positive chargeability to the specific external additive particles and to ensure sufficient durability of the specific external additive particles, the thickness of the coat layer is preferably 1 nm or more and 10 nm or less. The thickness of the coating layer can be measured by analyzing a cross-sectional TEM image of the external additive particles using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). In addition, when the thickness of the coating layer is not uniform in one external additive particle, four equally spaced locations (specifically, two straight lines that are orthogonal to each other at substantially the center of the cross section of the external additive particle are drawn, The thickness of the coat layer is measured at each of these two straight lines intersecting the coat layer, and the arithmetic average of the four measured values obtained is the evaluation value of the external additive particles (of the coat layer). Thickness).

  Next, the configuration of the non-capsule toner particles will be described. Specifically, the toner base particles (binder resin and internal additive) and the external additive will be described in order.

[Toner mother particles]
The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, a colorant, a release agent, a charge control agent, and a magnetic powder).

(Binder resin)
In the toner base particles, generally, the binder resin occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner base particles. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and the binder resin has an amino group or an amide group. In other words, the toner base particles tend to be cationic.

  In order to improve the low-temperature fixability of the toner, it is preferable that the toner base particles contain a thermoplastic resin as the binder resin, and contain the thermoplastic resin in a proportion of 85% by mass or more of the entire binder resin. Is more preferable. Examples of the thermoplastic resin contained in the toner base particles include a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), an olefin resin (more specifically, In particular, polyethylene resin or polypropylene resin), vinyl resin (more specifically, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin), polyester resin, polyamide resin, or urethane resin are preferable. . A copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is also used as a toner. It can be suitably used as a binder resin for base particles.

  In order to improve the low-temperature fixability of the toner, it is particularly preferable that the toner base particles contain a polyester resin as a binder resin. The toner base particles may contain a crystalline polyester resin as a binder resin.

  The thermoplastic resin can be obtained by addition polymerization, copolymerization, or condensation polymerization of one or more thermoplastic monomers. The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization (more specifically, an acrylic acid monomer or a styrene monomer), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, by condensation polymerization). A combination of a polyhydric alcohol and a polyhydric carboxylic acid to be a polyester resin.

  The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. As the alcohol for synthesizing the polyester resin, for example, dihydric alcohols (more specifically, diols or bisphenols) as shown below or trihydric or higher alcohols can be suitably used. As the carboxylic acid for synthesizing the polyester resin, for example, divalent carboxylic acids or trivalent or higher carboxylic acids as shown below can be suitably used.

  Suitable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, Examples include 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, di1,2-propanediol, polyethylene glycol, poly1,2-propanediol, or polytetramethylene glycol.

  Preferable examples of the bisphenol include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferable examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5- Trihydroxymethylbenzene is mentioned.

  As preferable examples of the divalent carboxylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid Succinic acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (more specific Specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.) may be mentioned.

  Preferred examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

(Coloring agent)
The toner base particles may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner base particles may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner base particles may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

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

  The magenta colorant is, for example, selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of the magenta colorant include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be preferably used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66), phthalocyanine blue, C.I. I. Bat Blue, or C.I. I. Acid blue can be preferably used.

(Release agent)
The toner base particles may contain a release agent. The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to improve the fixing property or offset resistance of the toner, the amount of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

(Charge control agent)
The toner base particles may contain a charge control agent. The charge control agent is used, for example, for the purpose of improving the charge stability or charge rising property of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner base particles, the anionicity of the toner base particles can be enhanced. Further, by adding a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner base particles, the cationicity of the toner base particles can be increased. However, if sufficient chargeability is ensured in the toner, it is not necessary to add a charge control agent to the toner base particles.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, etc.) or alloys thereof, ferromagnetic metal oxides (more specifically, ferrite, magnetite, or chromium dioxide). Etc.) or a material subjected to ferromagnetization treatment (more specifically, a carbon material or the like imparted with ferromagnetism by heat treatment) can be suitably used. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

[Production method of toner base particles]
Preferable examples of the method for producing the toner base particles include a pulverization method or an aggregation method. These methods facilitate easy dispersion of the internal additive in the binder resin.

  In an example of the pulverization method, first, a binder resin, a colorant, a charge control agent, and a release agent are mixed. Subsequently, the obtained mixture is melt-kneaded using a melt-kneading apparatus (for example, a single-screw or twin-screw extruder). Subsequently, the obtained melt-kneaded product is pulverized and classified. Thereby, toner mother particles are obtained.

  In an example of the aggregation method, first, these fine particles are aggregated in an aqueous medium containing fine particles of the binder resin, the release agent, and the colorant until a desired particle diameter is obtained. Thereby, aggregated particles containing a binder resin, a release agent, and a colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. Thereby, toner mother particles having a desired particle diameter are obtained.

[External additive]
The toner particles contained in the toner according to the exemplary embodiment include an external additive (and thus a plurality of specific external additive particles) having the above-described basic configuration. For example, the toner base particles (powder) and the external additive (powder) are stirred together, so that the external additive adheres (physically bonds) to the surface of the toner base particles with a physical force. In the basic configuration, the specific external additive particles include alumina particles and a coat layer.

  In order to improve the fluidity and the like of the toner, it is preferable that the toner particles further include one or more inorganic particles as external additive particles in addition to the specific external additive particles. As inorganic particles, particles of silica particles or metal oxides (more specifically, titania, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) can be preferably used. Multiple types of inorganic particles may be used in combination. In order to improve the fluidity of the toner, it is preferable to use silica particles as the inorganic particles. In order to improve the abrasiveness of the toner, it is preferable to use titania particles as inorganic particles. In order to improve the fluidity and polishability of the toner, it is particularly preferable that the toner particles further include silica particles and titania particles as external additive particles in addition to the specific external additive particles.

  In order to improve the fluidity or handleability of the toner, the amount of the external additive (when a plurality of types of external additives are used, the total amount of these external additives) is 100 parts by mass of the toner base particles. On the other hand, it is preferable that they are 0.5 mass part or more and 10 mass parts or less. In order to obtain a toner having excellent chargeability and durability, it is preferable that 20% by mass or more of the external additive particles among all the external additive particles are the specific external additive particles. In order to obtain a toner having excellent fluidity, 20% by mass or more of the external additive particles are preferably silica particles among all the external additive particles. In order to obtain a toner having excellent abrasiveness, it is preferable that 20% by mass or more of the external additive particles among all the external additive particles are titania particles.

  In the specific external additive particles, the coat layer contains a nitrogen-containing resin. In order to impart sufficient positive chargeability to the coat layer, the nitrogen-containing resin contained in the coat layer is a melamine resin, urea resin, sulfonamide resin, guanamine resin, aniline resin, polyimide resin ( More specifically, it is preferably at least one resin selected from the group consisting of a maleimide polymer or a bismaleimide polymer) and a urethane resin, and is a melamine resin and / or a urea resin. Is particularly preferred. Each of the melamine-based resin and the urea-based resin has sufficient strength and is easily bonded firmly to the isocyanate compound.

  In the specific external additive particles, the surface of the coat layer is hydrophobized with one or more isocyanate compounds. The isocyanate compound may be an aromatic isocyanate compound or an aliphatic isocyanate compound. Preferable examples of the aromatic isocyanate compound include monocyclic aromatic isocyanate compounds (more specifically, phenyl isocyanate or benzyl isocyanate). Moreover, as a suitable example of an aliphatic isocyanate compound, the aliphatic isocyanate compound (specifically ethyl isocyanate or octyl isocyanate etc.) which has a C2-C8 alkyl group is mentioned.

[Production method of external additive]
Preferable examples of the method of coating the alumina particles with the coating layer include a coating method or a reaction method. In order to firmly bond the alumina particles and the coating layer, a reaction method is particularly preferable. Hereinafter, the material for forming the coating layer is referred to as a coating material.

  In the case of forming a coat layer by a coating method, for example, a solution in which a coating material is dissolved is applied to alumina particles, and then the solvent is removed. Thereby, a coat layer is formed on the surface of the alumina particles.

  In an example of the reaction method, first, a coating material (for example, a monomer for synthesizing a nitrogen-containing resin) is dissolved in a solvent. By dissolving the coating material in a solvent in advance, the alumina particles and the coating layer are easily bonded firmly by heating described later. The solvent for the coating material is preferably an aqueous medium. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100 ° C.

  Subsequently, alumina particles are dispersed in the coating material solution to obtain a dispersion of alumina particles. Further, the pH of the dispersion is adjusted as necessary.

  Subsequently, the dispersion is heated to cause the coating material in the dispersion to undergo a polymerization reaction on the surface of the alumina particles. While the temperature of the liquid is kept high, the coating material reacts with the alumina particles and is immobilized on the surface of the alumina particles. Subsequently, the dispersion is cooled to room temperature (about 25 ° C.). Thereafter, through post-treatment steps (for example, solid-liquid separation and drying), powder of alumina particles (hereinafter referred to as coated alumina particles) covered with a coating layer is obtained.

  When the nitrogen-containing resin contained in the coating layer is a melamine-based resin or a urea-based resin, a dispersion of alumina particles (more preferably, a dispersion having a pH of 2 or more and 6 or less is used in order to accelerate the polymerization reaction of the coating material. ) Is preferably maintained at 60 ° C. or higher and 100 ° C. or lower by the above heating. By maintaining the temperature of the dispersion at an appropriate temperature, the polymerization reaction of the coating material is facilitated. In addition, the polymerization reaction of the coating material is easily promoted by setting the pH of the dispersion to be more acidic than neutral (pH 7).

(Hydrophobicization process)
For example, the surface of the coated alumina particles (specifically, the surface of the coating layer) can be hydrophobized with the isocyanate compound by mixing the coated alumina particles and the isocyanate compound in a liquid and heating them. For example, the surface of the coat layer is hydrophobized by the reaction between “—OH” on the surface of the coat layer and the isocyanate group “—N═C═O” of the isocyanate compound. After hydrophobization, an external additive (powder) is obtained through post-treatment steps (eg, solid-liquid separation, drying, and pulverization).

[External addition process]
By using a mixing device, the toner base particles and the external additive are mixed under conditions that prevent the external additive from being embedded in the toner base particles, thereby allowing the external additive to adhere to the surface of the toner base particles. . As a mixing apparatus, for example, a V-type mixer, an FM mixer, a Redige mixer, a multi-purpose mixer, or a hybridization system (registered trademark) can be used. As the external additive, only the external additive having the basic structure described above may be used, or other external additives (for example, silica powder and titania powder) may be used in combination.

  Examples of the present invention will be described. Table 1 shows external additives A to I used in the production of toners TA-1 to TA-5 and TB-1 to TB-4 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples. .

  Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of toners TA-1 to TB-4 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with which the error is sufficiently small are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Toner Production Method]
(Preparation of external additive A)
In 500 mL of ion-exchanged water, alumina powder (“AEROXIDE (registered trademark) Alu C” manufactured by Nippon Aerosil Co., Ltd.), content: hydrophilic fumed aluminum oxide particles, number average primary particle size: 13 nm, BET specific surface area: 100 m ² / G) A dispersion of alumina particles was obtained by dispersing 50 g.

  Subsequently, 0.5N-hydrochloric acid (“Wako Class 1 (087-01076)” manufactured by Wako Pure Chemical Industries, Ltd.) was added to the obtained dispersion of alumina particles to adjust the pH of the dispersion of alumina particles. Adjusted to about 3.5.

  Subsequently, 25 g of water-soluble methylol melamine (“Nikaresin (registered trademark) S-260” manufactured by Nippon Carbide Industries Co., Ltd.)) was added and dissolved in the dispersion of alumina particles. Thereafter, the dispersion liquid of alumina particles was put into a 1 L separable flask equipped with a thermometer and a stirring device.

  Subsequently, the flask was placed in a constant temperature water bath ("BK400" sold by Yamato Scientific Co., Ltd.), and the temperature of the constant temperature water bath was raised to 70 ° C at a rate of 1 ° C / 3 minutes while stirring the contents of the flask. And kept at 70 ° C. for 30 minutes. The temperature of the flask contents at the start of the temperature increase was 25 ° C.

  Subsequently, the flask was taken out from the thermostatic water bath, and the flask contents were cooled to room temperature (about 25 ° C.). Subsequently, the precipitate in the flask was filtered (solid-liquid separation) and dried using a square vacuum constant temperature dryer ("DP63" sold by Yamato Scientific Co., Ltd.). As a result, a powder of alumina particles (coated alumina particles) covered with a coating layer was obtained. The coat layer was substantially composed of melamine resin.

  Subsequently, in a three-necked flask equipped with a thermometer and a stirring blade, 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.5 g of sodium perfluorooctane sulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), phenyl isocyanate ( 3 g of Wako Pure Chemical Industries, Ltd.) and 50 g of the coated alumina particle powder obtained as described above were added. Subsequently, while stirring the flask contents, the temperature of the flask contents was increased to 50 ° C. at a rate of 1 ° C./3 minutes and kept at 50 ° C. for 2 hours. The temperature of the flask contents at the start of the temperature increase was 25 ° C.

  Subsequently, the temperature of the flask contents was raised to about 100 ° C., and the flask contents were boiled for 2 hours to remove toluene. As a result, a solid was obtained in the flask. Subsequently, using a supersonic jet pulverizer (“PJM-80SP” manufactured by Nippon Pneumatic Industry Co., Ltd.), the solid (reaction product) was pulverized to obtain external additive A. The surface of the coating layer of the external additive particles contained in the external additive A was hydrophobized with an isocyanate compound (phenyl isocyanate).

(Preparation of external additive B)
The manufacturing method of the external additive B was the same as the manufacturing method of the external additive A except that 3 g of n-octyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 3 g of phenyl isocyanate.

(Preparation of external additive C)
The manufacturing method of the external additive C was an aqueous solution of methylolated urea ("Milben (registered trademark) Resin SU-100" manufactured by Showa Denko KK), solid content concentration instead of 25 g of water-soluble methylolmelamine (Nicaledin S-260) (80% by mass) This was the same as the method for producing external additive A except that 25 g was used.

(Preparation of external additive D)
The manufacturing method of the external additive D was the same as the manufacturing method of the external additive A except that 3 g of ethyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 3 g of phenyl isocyanate.

(Preparation of external additive E)
The manufacturing method of the external additive E was the same as the manufacturing method of the external additive A except that 3 g of benzyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 3 g of phenyl isocyanate.

(Preparation of external additive F)
The manufacturing method of the external additive F was the same as the manufacturing method of the external additive A except that the hydrophobic treatment with phenyl isocyanate was not performed. In the manufacturing method of the external additive F, after obtaining the powder of the coated alumina particles, the pulverization treatment was performed by the supersonic jet pulverizer (PJM-80SP) without performing the hydrophobic treatment with phenyl isocyanate.

(Preparation of external additive G)
In the manufacturing method of the external additive G, the following treatment was performed after obtaining the powder of the coated alumina particles as in the manufacturing method of the external additive A.

  In a three-necked flask equipped with a thermometer and a stirring blade, 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.), 1 g of 3-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), and the procedure described above (“Outside 50 g of the coated alumina particle powder obtained in “Preparation of Additive A” was added. Subsequently, while stirring the flask contents, the temperature of the flask contents was increased to 50 ° C. at a rate of 1 ° C./3 minutes and kept at 50 ° C. for 2 hours. The temperature of the flask contents at the start of the temperature increase was 25 ° C.

  Subsequently, the temperature of the flask contents was raised to about 100 ° C., and the flask contents were boiled for 2 hours to remove toluene. As a result, a solid was obtained in the flask. Subsequently, using an electric furnace, a solid (reaction product) was heated for 3 hours in a nitrogen stream under a set temperature of 200 ° C. Subsequently, the solid after the heat treatment was pulverized using a supersonic jet pulverizer (“PJM-80SP” manufactured by Nippon Pneumatic Kogyo Co., Ltd.) to obtain an external additive G.

(Preparation of external additive H)
The manufacturing method of the external additive H is titania powder (“AEROXIDE P90” manufactured by Nippon Aerosil Co., Ltd.) instead of 50 g of alumina powder (AEROXIDE Alu C), content: untreated dry fumed titanium oxide, BET specific surface area: 90 m ² / g) This was the same as the method for producing external additive A, except that 50 g was used.

(Preparation of external additive I)
In a three-necked flask equipped with a thermometer and a stirring blade, 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.5 g of sodium perfluorooctane sulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and phenyl isocyanate (Wako Pure Chemical Industries, Ltd.) 3 g of Kogyo Co., Ltd. and 50 g of alumina powder (“AEROXIDE Alu C” manufactured by Nippon Aerosil Co., Ltd.) were added. Subsequently, while stirring the flask contents, the temperature of the flask contents was increased to 50 ° C. at a rate of 1 ° C./3 minutes and kept at 50 ° C. for 2 hours. The temperature of the flask contents at the start of the temperature increase was 25 ° C.

  Subsequently, the temperature of the flask contents was raised to about 100 ° C., and the flask contents were boiled for 2 hours to remove toluene. As a result, a solid was obtained in the flask. Subsequently, using a supersonic jet pulverizer (“PJM-80SP” manufactured by Nippon Pneumatic Industry Co., Ltd.), the solid (reaction product) was pulverized to obtain an external additive I.

(Physical properties of external additives A to I)
Regarding the external additives A to I obtained as described above, the degree of hydrophobicity of the external additive particles was measured by the following method. The measurement results were as shown in Table 1. For example, regarding external additive A, the degree of hydrophobicity of the external additive particles was 56.2%.

<Method of measuring the degree of hydrophobicity>
The degree of hydrophobicity of the external additive particles was measured by a methanol wettability method (MW method). Specifically, methanol is added dropwise to 25 mL of pure water charged with a sample (external additive), and the amount of methanol dropped Vm (unit) when the sample (external additive) is all wet and settles (total precipitation). : ML). Based on the following formula, the degree of hydrophobicity MW (unit:%) of the external additive particles was calculated. For example, if the methanol drop amount Vm at the time of total precipitation of the sample is 25 mL, the degree of hydrophobicity MW of the external additive particles is 50%.
MW [%] = 100 × Vm / (Vm + 25)

(External addition process)
100 parts by mass of toner base particles (non-externally added cyan toner for “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Inc.) and external additives (external additives A to I shown in Table 1 defined for each toner) Any) 2 parts by mass were mixed using a multipurpose small-sized mixing and grinding machine (“Multipurpose Mixer” manufactured by Nippon Coke Kogyo Co., Ltd.). As a result, the external additive adhered to the surface of the toner base particles. Thereafter, the obtained powder was sieved using a 300 mesh (aperture 48 μm) sieve. As a result, toners (toners TA-1 to TA-5 and TB-1 to TB-4) containing a large number of toner particles were obtained.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-5 and TB-1 to TB-4) is as follows.

(Preparation of developer for evaluation)
100 parts by mass of a developer carrier (carrier for “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) and 10 parts by mass of a sample (toner) were mixed for 30 minutes using a ball mill. As a result, an evaluation developer was obtained.

(Preparation of evaluation machine)
A color multifunction machine (“TASKalfa 5550ci” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. The evaluation developer prepared as described above was charged into the developing device of the evaluation machine, and the sample (replenishment toner) was charged into the toner container of the evaluation machine.

(Print life test)
A first press life test is performed in which continuous printing is performed on 1000 sheets of paper (A4 size plain paper) at a printing rate of 0.5% using the above-described evaluation machine in an environment of temperature 24 ° C. and humidity 60% RH. It was. After the first printing durability test, in the environment of a temperature of 24 ° C. and a humidity of 60% RH, the above evaluation machine is used to perform continuous printing on 1000 sheets of paper (A4 size plain paper) at a printing rate of 80%. 2 A printing durability test was conducted. After the second printing durability test, in the environment of a temperature of 24 ° C. and a humidity of 60% RH, continuous printing is performed on 100,000 sheets of paper (A4 size plain paper) at a printing rate of 5% using the evaluation machine. 3 A printing durability test was conducted.

(Charge amount)
For the developer for evaluation immediately after the preparation, the charge amount of the toner (initial toner) in the developer was measured by the following method. Further, at each timing after the first printing test, after the second printing test, and after the third printing test, a developer (specifically, it exists on the surface of the developing roller) from the developing device of the evaluation machine. The developer was taken out, and the charge amount of the toner (toner after each printing durability test) in the developer was measured by the following method.

<Measurement method of charge amount of toner in developer>
0.10 g of the developer was put into a measurement cell of a suction type small charge amount measuring device (“MODEL 212HS” manufactured by Trek), and only the toner of the put developer was sucked through a sieve (metal mesh). The toner charge amount (unit: μC / g) was calculated based on the formula “total electricity amount of sucked toner (unit: μC) / mass of sucked toner (unit: g)”.

  When the toner charge amount was 15 μC / g or more and 35 μC / g or less, it was evaluated as “good”, and when the toner charge amount was less than 15 μC / g or more than 35 μC / g, it was evaluated as “poor” (not good).

(Fogging density)
After each of the first printing test, the second printing test, and the third printing test, a sample image including a solid part and a blank part is recorded on a recording medium (evaluation paper) at each timing of printing 5000 sheets. ). Then, using a color reflection densitometer (“R710” manufactured by Ihara Electronics Co., Ltd.), for each of the blank portion of the sample image on the printed recording medium and the base paper (unprinted paper) that is not printed, The reflection density was measured. Then, the fog density (FD) was calculated based on the following equation.
FD = (reflection density of blank area) − (reflection density of unprinted paper)

  The fog resistance of the toner was evaluated based on the highest fog density (maximum fog density) among all the fog densities (FD) measured at each timing. When the maximum fog density (maximum FD) was 0.009 or less, it was evaluated as ◯ (good), and when it exceeded 0.009, it was evaluated as x (not good).

(Dash mark)
For every 5000 sheets printed during the third printing durability test, the formed image was visually observed to check for the presence of a dash mark. If the dash mark was not confirmed, it was evaluated as “good”, and if the dash mark was confirmed, it was evaluated as “x” (not good). The dash mark is an image defect that can be caused by the toner adhering to the surface of the photosensitive drum.

[Evaluation results]
Table 2 shows the results of evaluating the charge amount, the maximum fog density (maximum FD), and the presence or absence of a dash mark for each of toners TA-1 to TA-5 and TB-1 to TB-4. “30,000 sheets” and “60,000 sheets” in Table 2 relating to the evaluation results of the dash marks indicate that the dash marks were observed when 30,000 sheets and 60,000 sheets were printed, respectively.

  Toners TA-1 to TA-5 (toners according to Examples 1 to 5) were each provided with the external additive having the above-described basic configuration. Specifically, in each of the toners according to Examples 1 to 5, the external additive includes a plurality of external additive particles including alumina particles and a coating layer that covers the surface of the alumina particles. The coat layer contained a nitrogen-containing resin (melamine resin or urea resin). The surface of the coat layer was hydrophobized with one or more isocyanate compounds (phenyl isocyanate, benzyl isocyanate, ethyl isocyanate, or octyl isocyanate).

  As shown in Table 2, regarding the toners according to Examples 1 to 5, good evaluation results were obtained for all of the charge amount, the maximum fog density (maximum FD), and the presence or absence of a dash mark. In addition, the toners according to Examples 1 to 5 are excellent in positive chargeability, durability, and adhesion resistance. When used in continuous printing, the toner continuously suppresses the generation of fog over a long period of time. I was able to continue to form high quality images.

  The toner for developing an electrostatic latent image according to the present invention can be used for forming an image in, for example, a copying machine, a printer, or a multifunction machine.

Claims (7)

A plurality of toner particles comprising a toner base particle containing a binder resin and an external additive attached to the surface of the toner base particle;
The external additive includes a plurality of external additive particles comprising alumina particles and a coat layer covering the surface of the alumina particles,
The coat layer contains a nitrogen-containing resin,
The surface of the coat layer is hydrophobized with one or more isocyanate compounds ,
The electrostatic latent image developing toner , wherein the coating layer contains a melamine resin and / or a urea resin as the nitrogen-containing resin .   The electrostatic latent image developing toner according to claim 1, wherein the external additive particles have a hydrophobicity of 25% or more by a methanol wettability method. The isocyanate compound is an aromatic isocyanate compound, an electrostatic latent image developing toner according to claim 1 or 2. The electrostatic latent image developing toner according to claim 3 , wherein the isocyanate compound is a monocyclic aromatic isocyanate compound. The isocyanate compound is an aliphatic isocyanate compound, an electrostatic latent image developing toner according to claim 1 or 2. The electrostatic latent image developing toner according to claim 5 , wherein the isocyanate compound is an aliphatic isocyanate compound having an alkyl group having 2 to 8 carbon atoms. Including a plurality of external additive particles,
The external additive particles include alumina particles and a coat layer that covers the surfaces of the alumina particles,
The coat layer contains a nitrogen-containing resin,
The surface of the coat layer is hydrophobized with one or more isocyanate compounds ,
The coat layer is an external additive containing a melamine resin and / or a urea resin as the nitrogen-containing resin .