JP7281043B2 - toner - Google Patents

Description

The present invention relates to toner.

Patent Document 1 discloses a toner containing two types of hydrophobized silica powder (positively charged silica powder and negatively charged silica powder) as an external additive.

JP-A-11-231571

However, it is difficult to obtain a toner capable of continuously forming high-quality images only with the technique disclosed in Patent Document 1.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner capable of continuously forming high-quality images.

The toner according to the present invention comprises toner particles. The toner particles include toner base particles containing a binder resin and an external additive adhering to the surface of the toner base particles. The external additive contains silica particles and composite particles as external additive particles. The composite particles include substrate particles and conductive particles attached to the surfaces of the substrate particles. The substrate particles are titania particles, alumina particles or crosslinked resin particles. The amount of the conductive particles is 2.0 parts by mass or more and 13.0 parts by mass or less with respect to 100 parts by mass of the substrate particles. The silica particles have a number average primary particle diameter of 20 nm or less. The number average primary particle diameter of the substrate particles is 100 nm or more and 250 nm or less. The number average primary particle diameter of the conductive particles is 10 nm or more and 40 nm or less. The area ratio of the area covered with the silica particles in the surface area of the toner base particles is 40% or more and 80% or less. In the surface area of the toner base particles, the area ratio of the area covered with the composite particles is 5% or more and 20% or less.

According to the toner of the present invention, high-quality images can be continuously formed.

FIG. 2 is a diagram showing an example of a cross-sectional structure of toner particles contained in the toner according to the embodiment of the invention;

Preferred embodiments of the present invention are described below. Note that the toner is an aggregate (for example, powder) of toner particles. The external additive is an aggregate (for example, powder) of external additive particles. Evaluation results (values indicating shape, physical properties, etc.) of powder (more specifically, powder of toner particles, powder of base particles, powder of conductive particles, powder of external additive particles, etc.) is the number average of the values measured for each of a number of selected particles from the powder, unless otherwise specified.

The measured value of the volume median diameter (D ₅₀ ) of the powder was measured using a laser diffraction/scattering particle size distribution analyzer ("LA-950" manufactured by Horiba, Ltd.) unless otherwise specified. is the median diameter. Unless otherwise specified, the number average primary particle diameter of the powder is the equivalent circle diameter of 100 primary particles (Haywood diameter: having the same area as the projected area of the primary particles) measured using a scanning electron microscope. circle diameter). Unless otherwise specified, the number average primary particle size of particles refers to the number average primary particle size of particles in powder (the number average primary particle size of powder).

The electrification strength is the ease of triboelectrification, unless otherwise specified. For example, a standard carrier provided by the Imaging Society of Japan (standard carrier for negatively charged polarity toner: N-01, standard carrier for positively charged polarity toner: P-01) and an object to be measured (for example, toner) are mixed and stirred. to triboelectrically charge the object to be measured. Before and after triboelectrification, the charge amount of the object to be measured is measured by, for example, a small suction type charge amount measuring device (“MODEL 212HS” manufactured by Trek). A measurement object with a greater change in charge amount before and after triboelectrification indicates a stronger electrification property.

Unless otherwise specified, the softening point (Tm) is a value measured using a Koka flow tester ("CFT-500D" manufactured by Shimadzu Corporation). In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured with a Koka flow tester, the temperature at which "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point) Equivalent to.

The strength of hydrophobicity (or the strength of hydrophilicity) can be represented, for example, by the contact angle of a water droplet (easiness of wetting with water). The greater the contact angle of water droplets, the stronger the hydrophobicity. Hydrophobic treatment refers to treatment for enhancing hydrophobicity.

“Conductive particles” are particles made of a conductive material, and for example, particles having a volume resistivity of 100,000 Ω·cm or less. In this specification, the volume resistivity of the conductive particles refers to a compact of conductive particles (for example, a compact obtained by compressing the powder of conductive particles at a pressure of 10 MPa) as "JIS (Japanese Industrial Standard) K7194-1994" is the volume resistivity measured according to.

Hereinafter, compounds and derivatives thereof may be collectively referred to by adding "system" to the name of the compound. When the polymer name is indicated by adding "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acryl and methacryl may be collectively referred to as "(meth)acryl". Acrylonitrile and methacrylonitrile may be collectively referred to as "(meth)acrylonitrile".

Silica substrate refers to untreated silica particles. Titania substrate refers to untreated titania particles. Alumina substrate refers to untreated alumina particles. A crosslinked resin refers to a resin having a crosslinked structure. Crosslinked resin particles refer to resin particles whose constituent resin is a crosslinked resin.

In this specification, both a silica substrate and silica particles obtained by surface-treating a silica substrate may be referred to as "silica particles". Both a titania substrate and titania particles obtained by subjecting a titania substrate to a surface treatment are sometimes referred to as "titania particles." Both an alumina substrate and alumina particles obtained by subjecting an alumina substrate to a surface treatment are sometimes referred to as "alumina particles."

<Toner>
The toner according to the exemplary embodiment can be suitably used for developing electrostatic latent images, for example, as a positively charged toner. The toner according to the present embodiment is an aggregate (for example, powder) of toner particles (particles each having a configuration to be described later). The toner may be used as a single component developer. Alternatively, a two-component developer may be prepared by mixing toner and carrier using a mixing device (eg, ball mill).

The toner particles contained in the toner according to the exemplary embodiment include toner base particles containing a binder resin and an external additive adhering to the surface of the toner base particles. The external additive contains silica particles and composite particles as external additive particles. The composite particles include substrate particles and conductive particles attached to the surfaces of the substrate particles. The substrate particles are titania particles, alumina particles or crosslinked resin particles. The amount of the conductive particles is 2.0 parts by mass or more and 13.0 parts by mass or less with respect to 100 parts by mass of the base particles. The silica particles have a number average primary particle size of 20 nm or less. The number average primary particle diameter of the substrate particles is 100 nm or more and 250 nm or less. The number average primary particle size of the conductive particles is 10 nm or more and 40 nm or less. The area ratio of the area covered with the silica particles in the surface area of the toner base particles is 40% or more and 80% or less. The area ratio of the area covered with the composite particles in the surface area of the toner base particles is 5% or more and 20% or less.

Hereinafter, the area ratio of the area covered by the silica particles in the surface area of the toner base particles may be referred to as the first coverage. In addition, the ratio of the area covered by the composite particles to the surface area of the toner base particles may be referred to as a second coverage. The method for measuring the first coverage and the method for measuring the second coverage are the same as or similar to those in the examples described later.

According to the toner according to the present embodiment, since it has the above-described configuration, it is possible to continuously form high-quality images. The reason is presumed as follows.

Generally, the use of silica particles as an external additive imparts excellent fluidity and charge stability to the toner. However, when only silica particles are used as an external additive for toner particles, the silica particles are buried in the toner base particles due to collisions between the toner particles or between the toner particles and the carrier particles in the developing device. becomes easier. As a result, the fluidity and charging stability of the toner particles may deteriorate. Further, when only silica particles are used as the external additive for the toner particles, the charged silica particles on the surfaces of the toner particles adhere to the toner base particles, and the members (more specifically, may adhere to the photosensitive drum, transfer belt, etc.). Therefore, when a toner containing only silica particles as an external additive is used to continuously print a large number of sheets (for example, 10,000 sheets), the fluidity and charging stability of the toner particles are lowered, and the toner particles are By adhering to members in the image forming apparatus, the density of the printed image tends to gradually decrease.

In the toner according to the present embodiment, the external additive contains silica particles and composite particles, and the composite particles contain base particles and conductive particles adhering to the surfaces of the base particles. Moreover, in the composite particles, the amount of the conductive particles is 2.0 parts by mass or more with respect to 100 parts by mass of the base particles. In this way, the composite particles are less likely to be charged because they are imparted with conductivity. Therefore, the composite particles tend to be less likely to adhere to members in the image forming apparatus. Further, in the toner according to the exemplary embodiment, the silica particles have a number average primary particle size of 20 nm or less, the base particles have a number average primary particle size of 100 nm or more, and the conductive particles have a number average primary particle size of 10 nm. That's it. Furthermore, in the toner according to the exemplary embodiment, the first coverage is 80% or less, and the second coverage is 5% or more. Therefore, in the toner according to the present embodiment, the composite particles are composed of silica particles adhering to the toner base particles and other elements in the image forming apparatus (more specifically, other toner base particles, carriers, image forming apparatus). It functions as a spacer that suppresses contact with the inner member, etc.).

Further, in the toner according to the exemplary embodiment, the base particles are titania particles, alumina particles, or crosslinked resin particles. Titania particles, alumina particles and crosslinked resin particles have relatively hard surfaces among particles used as external additive particles. Therefore, the composite particles containing titania particles, alumina particles, or crosslinked resin particles function as spacers that prevent the silica particles from being embedded in the toner base particles.

Further, in the toner according to the exemplary embodiment, the amount of the conductive particles is 13.0 parts by mass or less with respect to 100 parts by mass of the base particles. Further, in the toner according to the exemplary embodiment, the number average primary particle size of the base particles is 250 nm or less, and the number average primary particle size of the conductive particles is 40 nm or less. Furthermore, in the toner according to the exemplary embodiment, the first coverage is 40% or more and the second coverage is 20% or less. As described above, in the toner according to the present embodiment, the upper limit of the amount of the conductive particles and the number average primary particle diameter of the base particles are such that the silica particles do not impair the fluidity-imparting function and the charging stability-imparting function. An upper limit, an upper limit of the number average primary particle size of the conductive particles, a lower limit of the first coverage, and an upper limit of the second coverage are set.

Therefore, in the toner according to the exemplary embodiment, the silica particles impart excellent fluidity and charge stability to the toner, the composite particles suppress contact between the silica particles and other elements, and the silica particles Since the toner functions as a spacer that suppresses burying in the base particles, the toner according to the exemplary embodiment can continuously form high-quality images.

In the toner according to the present embodiment, in order to continuously form images of higher quality, the amount of the conductive particles should be 3.0 parts by mass or more and 11.5 parts by mass with respect to 100 parts by mass of the base particles. The following are preferable.

In the toner according to the exemplary embodiment, the number average primary particle diameter of the silica particles is preferably 7 nm or more and 20 nm or less, more preferably 7 nm or more and 15 nm or less, in order to continuously form higher quality images. More preferably, it is 10 nm or more and 15 nm or less.

In the toner according to the exemplary embodiment, the number average primary particle diameter of the conductive particles is preferably 20 nm or more and 30 nm or less in order to continuously form images of higher quality.

The toner particles contained in the toner according to the exemplary embodiment may be toner particles without a shell layer, or toner particles with a shell layer (hereinafter sometimes referred to as capsule toner particles). good. In capsule toner particles, toner mother particles comprise a toner core containing a binder resin and a shell layer covering the surface of the toner core. The shell layer contains resin. For example, by covering a toner core that melts at a low temperature with a shell layer that has 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 forming the shell layer. The shell layer may cover the entire surface of the toner core, or may partially cover the surface of the toner core.

In order to obtain a toner suitable for image formation, the volume median diameter (D ₅₀ ) of the toner base particles is preferably 4 μm or more and 9 μm or less.

The toner base particles may optionally contain an internal additive (for example, at least one of a colorant, release agent, charge control agent, and magnetic powder) in addition to the binder resin.

Details of the toner according to the present embodiment will be described below with reference to the drawings as appropriate. It should be noted that FIG. 1 to be referred to schematically shows each component mainly for ease of understanding. may differ from the actual product.

[Structure of Toner Particles]
Hereinafter, the configuration of toner particles contained in the toner according to the exemplary embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an example of the cross-sectional structure of toner particles contained in the toner according to this embodiment.

Toner particles 10 shown in FIG. 1 include toner base particles 11 containing a binder resin and external additives adhering to the surfaces of toner base particles 11 . The external additive contains silica particles 12 and composite particles 13 as external additive particles. Composite particles 13 include substrate particles 14 and conductive particles 15 adhered to the surfaces of substrate particles 14 . For example, a plurality of conductive particles 15 are attached to the surface of one substrate particle 14 . The substrate particles 14 are titania particles, alumina particles, or crosslinked resin particles.

The amount of the conductive particles 15 is 2.0 parts by mass or more and 13.0 parts by mass or less with respect to 100 parts by mass of the base particles 14 . The number average primary particle diameter of the silica particles 12 is 20 nm or less. The number average primary particle diameter of the substrate particles 14 is 100 nm or more and 250 nm or less. The number average primary particle diameter of the conductive particles 15 is 10 nm or more and 40 nm or less.

The area ratio of the area covered with the silica particles 12 in the surface area of the toner base particles 11 is 40% or more and 80% or less. The area ratio of the area covered with the composite particles 13 in the surface area of the toner base particles 11 is 5% or more and 20% or less.

In FIG. 1, composite particles 13 are attached to toner base particles 11 in a state of being bitten, but composite particles 13 may not be attached to toner base particles 11 in a state of being bitten. However, in order to improve the adhesiveness between the composite particles 13 and the toner base particles 11 , it is preferable that the composite particles 13 adhere to the toner base particles 11 while biting into them.

An example of the configuration of the toner particles contained in the toner according to the exemplary embodiment has been described above with reference to FIG.

[Elements of Toner Particles]
Next, the elements of the toner particles contained in the toner according to this exemplary embodiment will be described.

(Binder resin)
The binder resin accounts for, for example, 70% by mass or more of the total components of the toner base particles. Therefore, it is considered that the properties of the binder resin have a great influence on the properties of the toner base particles as a whole. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the glass transition point, etc.) can be adjusted.

In order to obtain a toner excellent in low-temperature fixability, the toner base particles preferably contain a thermoplastic resin as a binder resin, and the thermoplastic resin should be contained at a rate of 85% by mass or more of the total binder resin. is more preferred. Examples of thermoplastic resins include styrene-based resins, acrylic acid ester-based resins, olefin-based resins (more specifically, polyethylene resins, polypropylene resins, etc.), vinyl resins (more specifically, vinyl chloride resins, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, etc.), polyester resin, polyamide resin, and urethane resin. In addition, copolymers of these resins, that is, copolymers in which arbitrary repeating units are introduced into the above resins (more specifically, styrene-acrylic acid ester resins, styrene-butadiene resins, etc.) Can be used as a binder resin.

Thermoplastic resins are 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 ester-based monomer, a styrene-based monomer, etc.), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, polycondensation A combination of a polyhydric alcohol and a polycarboxylic acid resulting in a polyester resin).

In order to obtain a toner excellent in low-temperature fixability, the toner base particles preferably contain a polyester resin as a binder resin, and the polyester resin is contained at a rate of 80% by mass or more and 100% by mass or less based on the total binder resin. is more preferable. A polyester resin is obtained by condensation polymerization of one or more polyhydric alcohols and one or more polycarboxylic acids. Alcohols for synthesizing the polyester resin include, for example, dihydric alcohols (more specifically, aliphatic diols, bisphenols, etc.) and trihydric or higher alcohols as shown below. Carboxylic acids for synthesizing the polyester resin include, for example, divalent carboxylic acids and trivalent or higher carboxylic acids as shown below. Instead of the polycarboxylic acid, a polycarboxylic acid derivative capable of forming an ester bond by polycondensation, such as an anhydride of a polycarboxylic acid or a polycarboxylic acid halide, may be used.

Suitable examples of aliphatic diols include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α,ω-alkanediol (more specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, etc.) , 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Suitable examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

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

Suitable examples of dicarboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, and malonic acid. , 1,10-decanedicarboxylic 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.), and alkenylsuccinic acid (more specifically, n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, etc.).

Preferable examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl) Methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol 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 the 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. Examples of black colorants include carbon black. Alternatively, the black colorant may be a colorant toned black using a yellow colorant, a magenta colorant, and a cyan colorant.

The toner base particles may contain a colorant. Color colorants include yellow colorants, magenta colorants, and cyan colorants.

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 yellow colorants 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, and 194), Naphthol Yellow S, Hansa Yellow G, and C.I. I. Bat yellow is mentioned.

Examples of magenta colorants include 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 magenta coloring agents 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, and 254).

As the cyan colorant, for example, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds can be used. Cyan colorants include, for example, C.I. I. pigment blue (1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66), phthalocyanine blue, C.I. I. bat blue, and C.I. I. acid blue.

(Release agent)
The toner base particles may contain a releasing agent. A release agent is used, for example, to obtain a toner having excellent anti-offset properties. In order to obtain a toner excellent in offset resistance, the amount of the release agent 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.

Release agents include, for example, ester wax, polyolefin wax (more specifically, polyethylene wax, polypropylene wax, etc.), microcrystalline wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, candelilla wax, montan wax, and castor wax. Ester waxes include natural ester waxes (more specifically, carnauba wax, rice wax, etc.) and synthetic ester waxes. In this embodiment, one type of release agent may be used alone, or multiple types of release agents may be used in combination.

A compatibilizer may be added to the toner base particles in order to improve compatibility between the binder resin and the release agent.

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

The cationic property (positive chargeability) of the toner base particles can be strengthened by including the positively chargeable charge control agent in the toner base particles. In addition, the anionicity (negative chargeability) of the toner base particles can be enhanced by incorporating a negatively chargeable charge control agent into the toner base particles.

Examples of positive charge control agents include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1, 4-thiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6- oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1, azine compounds such as 2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast red FC, azine fast red 12BK, azine violet BO, azine brown 3G, azine light Direct dyes such as Brown GR, Azin Dark Green BH/C, Azin Deep Black EW, Azin Deep Black 3RL; Acid dyes such as Nigrosine BK, Nigrosine NB, and Nigrosine Z; Alkoxylated amines; Alkylamides; Benzyldecylhexylmethyl quaternary ammonium salts such as ammonium chloride, decyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride, dimethylaminopropylacrylamide methyl chloride quaternary salt; and resins containing quaternary ammonium cationic groups. One of these charge control agents may be used alone, or two or more charge control agents may be used in combination.

Examples of negative charge control agents include organometallic complexes that are chelate compounds. Preferred organic metal complexes are acetylacetone metal complexes, salicylic acid metal complexes, and salts thereof.

In order to obtain a toner excellent in charging stability, the content of the charge control agent is preferably 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, etc.) and their alloys, and ferromagnetic metal oxides (more specifically, ferrite, magnetite, chromium dioxide, etc.). , and materials subjected to ferromagnetization treatment (more specifically, carbon materials and the like to which ferromagnetism is imparted by heat treatment). In this embodiment, one type of magnetic powder may be used alone, or multiple types of magnetic powder may be used together.

(external additive)
The toner particles contained in the toner according to the exemplary embodiment include an external additive adhering to the surface of the toner base particles. The external additive contains silica particles and composite particles as external additive particles. The composite particles include substrate particles and conductive particles attached to the surfaces of the substrate particles. As the silica particles, the substrate particles and the conductive particles, commercially available products may be used, or they may be produced, for example, by known methods.

[Silica particles]
The silica particles are not particularly limited as long as they are silica particles having a number average primary particle diameter of 20 nm or less. For example, the silica particles may be silica particles produced by a dry method (more specifically, a combustion method, a deflagration method, etc.), or a wet method (more specifically, a precipitation method, a gel method, Silica particles produced by a sol-gel method or the like) may also be used. The silica particles may be a silica substrate, or may be silica particles obtained by subjecting a silica substrate to surface treatment using a surface treatment agent. Examples of surface treatment agents include coupling agents (more specifically, silane coupling agents, titanate coupling agents, aluminate coupling agents, etc.), silazane compounds (more specifically, chain silazane compounds, cyclic silazane compounds, etc.), and silicone oils (more specifically, dimethyl silicone oil, etc.). Silane coupling agents and silazane compounds are particularly preferred as surface treatment agents. Suitable examples of silane coupling agents include silane compounds (more specifically, methyltrimethoxysilane, aminosilane, etc.). Suitable examples of silazane compounds include HMDS (hexamethyldisilazane).

When the surface of the silica substrate is treated with the surface treatment agent, many hydroxyl groups (--OH) present on the surface of the silica substrate are partially or wholly replaced with functional groups derived from the surface treatment agent. As a result, silica particles having on the surface functional groups derived from the surface treatment agent (specifically, functional groups that are more hydrophobic and/or more positively charged than hydroxyl groups) are obtained. When the toner according to the exemplary embodiment is used as a positively charged toner, the silica particles are preferably silica particles having functional groups (for example, amino groups) with higher positive chargeability than hydroxyl groups on the surface.

[Composite particles]
The composite particles include substrate particles and conductive particles attached to the surfaces of the substrate particles. In order to continuously form images of higher quality, the composite particles are preferably composed of base particles and conductive particles.

First, the substrate particles will be described. The substrate particles are not particularly limited as long as they satisfy the following conditions (1) and (2).
(1) Titania particles, alumina particles or crosslinked resin particles.
(2) The number average primary particle size is 100 nm or more and 250 nm or less.

When titania particles are used as the substrate particles, the titania particles may be titania substrates or titania particles obtained by surface-treating the titania substrates. However, in order to increase the adhesion between the titania particles and the conductive particles, the titania particles before forming the composite particles are preferably titania substrates (titania particles that are not surface-treated).

When alumina particles are used as the substrate particles, the alumina particles may be an alumina substrate, or may be alumina particles obtained by subjecting an alumina substrate to a surface treatment. However, in order to increase the adhesion between the alumina particles and the conductive particles, the alumina particles before forming the composite particles are preferably alumina substrates (alumina particles that are not surface-treated).

When crosslinked resin particles are used as the substrate particles, in order to easily adjust the number average primary particle size in the range of 100 nm or more and 250 nm or less, the crosslinked resin particles include a styrene-based monomer, an acrylic acid-based monomer, Resin particles containing a polymer (hereinafter sometimes referred to as a specific crosslinked polymer) with a crosslinker having two or more unsaturated bonds (eg, carbon-carbon double bonds) are preferred. In order to continuously form images of higher quality, it is preferable that the crosslinked resin particles contain only a specific crosslinked polymer as a constituent resin. The number average primary particle size of the crosslinked resin particles is, for example, at least one of the type of cross-linking agent, the amount of cross-linking agent used, the type of surfactant used during polymerization, and the amount of surfactant used during polymerization. It can be adjusted by changing

Styrenic monomers for synthesizing the specific crosslinked polymer include, for example, styrene, alkylstyrene, hydroxystyrene, and halogenated styrene. Alkylstyrenes include, for example, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, and 4-t-butylstyrene. Hydroxystyrenes include, for example, p-hydroxystyrene and m-hydroxystyrene. Halogenated styrenes include, for example, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. Styrene is preferable as the styrenic monomer for easily synthesizing the specific crosslinked polymer.

Examples of acrylic acid-based monomers for synthesizing the specific crosslinked polymer include (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid alkyl esters, and (meth)acrylic acid hydroxyalkyl esters. is mentioned. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, Examples include isobutyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxypropyl (meth)acrylate. Hydroxybutyl may be mentioned. In order to easily synthesize the specific crosslinked polymer, the acrylic acid-based monomer is preferably a (meth)acrylic acid alkyl ester, and more preferably methyl methacrylate.

Examples of cross-linking agents having two or more unsaturated bonds for synthesizing the specific cross-linked polymer include N,N'-methylenebisacrylamide, divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, Tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate , 1,4-butanediol dimethacrylate, and 1,6-hexanediol dimethacrylate.

Divinylbenzene is preferable as the cross-linking agent having two or more unsaturated bonds in order to continuously form images of higher quality.

Furthermore, in order to continuously form high-quality images, the crosslinked resin particles preferably contain a polymer of styrene, (meth)acrylic acid alkyl ester, and divinylbenzene as constituent resins. For the same reason, it is more preferable that the crosslinked resin particles contain only a polymer of styrene, a (meth)acrylic acid alkyl ester, and divinylbenzene as the constituent resins, and the crosslinked resin particles contain styrene as the constituent resins. , methyl methacrylate and divinylbenzene.

Next, the conductive particles will be explained. The conductive particles are not particularly limited as long as the number average primary particle size is 10 nm or more and 40 nm or less.

In order to continuously form images of higher quality, the conductive particles are antimony-doped tin oxide particles (hereinafter sometimes referred to as ATO particles) or aluminum-doped zinc oxide particles. (hereinafter sometimes referred to as AZO particles).

In order to continuously form images of higher quality, the volume resistivity of the conductive particles is preferably 1 Ω·cm or more and 100,000 Ω·cm or less, and 1 Ω·cm or more and 20,000 Ω·cm or less. and more preferably 3 Ω·cm or more and 10,000 Ω·cm or less.

Composite particles, for example, using a mixer (more specifically, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.), by mixing the base particles and the conductive particles, conductive on the surface of the base particles Obtained by adhering particles. The amount of the conductive particles with respect to 100 parts by mass of the base particles can be adjusted, for example, by changing the amount of the conductive particles added with respect to the weight of the base particles during mixing.

When titania particles or alumina particles are used as the base particles, the surfaces of the composite particles are preferably hydrophobized in order to easily maintain the charging stability of the toner particles.

Hydrophobizing agents for hydrophobizing the surfaces of composite particles include, for example, silane coupling agents and titanate coupling agents. agents are preferred.

Examples of titanate coupling agents suitable as hydrophobizing agents include titanate coupling agents having an organic group containing an alkyl group (hydrophobic group) and an alkoxy group. In addition, an alkoxy group is not contained in the organic group containing the said alkyl group.

Titanate coupling agents having an organic group containing an alkyl group and an alkoxy group include, for example, isopropyl triisostearoyl titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacryl titanate, titanium diacryl titanate, isopropoxybis(acetylacetonate), and titanium di-2-ethylhexoxybis(2-ethyl-3-hydroxyhexoxide).

Isopropyltriisostearoyl titanate is preferred as the titanate coupling agent in order to continuously form images of higher quality.

When the surface of the composite particles is hydrophobized using a titanate coupling agent, for example, the hydroxyl groups generated by hydrolyzing the alkoxy groups of the titanate coupling agent with moisture undergo dehydration condensation with the hydroxyl groups present on the surfaces of the composite particles. react. Through such a reaction, the surfaces of the composite particles are provided with alkyl groups (hydrophobic groups) derived from the titanate coupling agent.

[Combination of materials]
Furthermore, in order to continuously form high-quality images, it is preferable that the base particles and the conductive particles contained in the composite particles are any of Combination Examples 1 to 4 shown in Table 1 below.

Further, in order to continuously form particularly high-quality images, it is preferable that the base particles and the conductive particles contained in the composite particles are combination example 1 shown in Table 1, and the base material contained in the composite particles More preferably, the particles and the conductive particles are Combination Example 1 shown in Table 1, and the surfaces of the composite particles are hydrophobized with isopropyltriisostearoyl titanate.

[Other external additive particles]
The external additive may contain only silica particles and composite particles as external additive particles, or may contain other external additive particles in addition to the silica particles and composite particles. However, in order to continuously form images of higher quality, the external additive preferably contains only silica particles and composite particles as external additive particles.

In order to sufficiently exhibit the function of the external additive while suppressing detachment of the external additive from the toner base particles, the amount of the external additive (when other external additive particles are used, silica particles , composite particles, and other external additive particles) is preferably 3.0 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the toner base particles.

<Toner manufacturing method>
Next, a preferred method of manufacturing the toner according to the embodiment described above will be described. Hereinafter, descriptions of components that overlap with those of the toner according to the above-described embodiment will be omitted.

[Step of preparing toner base particles]
First, toner base particles are prepared by an aggregation method or a pulverization method.

Aggregation methods include, for example, aggregation and coalescence steps. In the aggregating step, fine particles containing components constituting toner base particles are aggregated in an aqueous medium to form aggregated particles. In the coalescing step, components contained in the aggregated particles are coalesced in an aqueous medium to form toner base particles.

Next, the pulverization method will be explained. According to the pulverization method, the toner base particles can be prepared relatively easily, and the manufacturing cost can be reduced. When the toner base particles are prepared by the pulverization method, the preparation process of the toner base particles includes, for example, a melt-kneading process and a pulverization process. The step of preparing the toner base particles may further include a mixing step before the melt-kneading step. Further, the step of preparing the toner base particles may further include at least one of a fine pulverization step and a classification step after the pulverization step.

In the mixing step, a mixture is obtained by mixing the binder resin and an internal additive added as necessary. In the melt-kneading step, the toner material is melted and kneaded to obtain a melt-kneaded product. As the toner material, for example, a mixture obtained in a mixing step is used. In the pulverization step, the obtained melt-kneaded material is cooled to room temperature (25° C.), for example, and then pulverized to obtain a pulverized material. If it is necessary to reduce the diameter of the pulverized material obtained in the pulverization step, a step of further pulverizing the pulverized product (fine pulverization step) may be carried out. Further, when the particle size of the pulverized material is uniform, a step of classifying the obtained pulverized material (classification step) may be carried out. Through the above steps, toner base particles, which are pulverized products, are obtained.

[External addition process]
After that, using a mixer, the obtained toner base particles and the external additive are mixed to adhere the external additive to the surfaces of the toner base particles. The external additive contains at least silica particles and composite particles. Examples of the mixer include FM mixer (manufactured by Nippon Coke Industry Co., Ltd.). The first coverage and the second coverage are, for example, the number average primary particle size of silica particles, the number average primary particle size of substrate particles, the number average primary particle size of conductive particles, and the number of silica particles to be introduced into the mixer. It can be adjusted by changing at least one of the amount and the amount of composite particles fed into the mixer. Thus, a toner containing toner particles is produced.

Examples of the present invention will be described below, but the present invention is not limited to the scope of the examples. A scanning electron microscope "JSM-7401F" manufactured by JEOL Ltd. was used to measure the number average primary particle size of the powder.

<Synthesis of polyester resin>
A 5-liter four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen inlet tube, rectifying column, and stirring device was set in an oil bath, and 1,2-propanediol 1,200 g and 1,2-propanediol were placed in the flask. , 1700 g of terephthalic acid and 3 g of tin(II) dioctoate were charged. Subsequently, the contents of the flask were reacted (specifically, a condensation reaction) for 15 hours under a nitrogen atmosphere at a temperature of 230°C. Subsequently, the pressure in the flask is reduced, and under the conditions of a reduced pressure atmosphere (pressure of 8.0 kPa) and a temperature of 230° C., the contents of the flask are evacuated until the Tm of the reaction product (polyester resin) reaches a predetermined temperature (90° C.). reacted. As a result, a polyester resin having a Tm of 90° C. was obtained.

<Preparation of toner base particles M1>
80 parts by weight of the polyester resin obtained by the synthesis method described above, a release agent ("Nissan Elector (registered trademark) WEP-3" manufactured by NOF Corporation, component: synthetic ester wax) 9 parts by weight, and a coloring agent ("MA100" manufactured by Mitsubishi Chemical Corporation, component: carbon black) 9 parts by mass, and a charge control agent ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Industry Co., Ltd., component: quaternary ammonium salt) 2 mass After these parts were put into an FM mixer (“FM-20B” manufactured by Nippon Coke Kogyo Co., Ltd.), these materials were mixed for 4 minutes at a rotation speed of 2000 rpm.

Subsequently, the obtained mixture was extruded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) at a material feed rate of 5 kg/h, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 100 ° C. was melt-kneaded with After that, the obtained kneaded product was cooled. Subsequently, the cooled kneaded material was pulverized using a mechanical pulverizer ("Turbo Mill T250" manufactured by Freund Turbo Co., Ltd.). Subsequently, the obtained pulverized material was classified using a classifier ("Elbow Jet EJ-LABO type" manufactured by Nittetsu Mining Co., Ltd.). As a result, toner base particles M1 having a volume median diameter (D ₅₀ ) of 6.7 μm were obtained.

<Preparation of silica particles>
Silica particles S1 and silica particles S2 were prepared as external additive particles. The silica particles S1 were hydrophobic dry silica particles (“AEROSIL (registered trademark) REA200” manufactured by Nippon Aerosil Co., Ltd., number average primary particle diameter: 12 nm) to which positive chargeability was imparted by surface treatment. The silica particles S2 were hydrophobic silica particles (“AEROSIL (registered trademark) RX50” manufactured by Nippon Aerosil Co., Ltd., number average primary particle size: 40 nm). The number-average primary particle diameter of the silica particles is the same when the powder of silica particles separated from the toner particles after the toner is produced by the method described later is measured. rice field. The same applies to the number-average primary particle size of base particles and conductive particles, which will be described later.

<Preparation of composite particles>
Methods for preparing composite particles C1 to C12 are described below.

[Preparation of Composite Particle C1]
(Preparation step of substrate particles B1)
After adding 475.0 g of anhydrous ethanol and 14.7 g of titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) into a flask equipped with a stirrer, hydrochloric acid (concentration of hydrogen chloride: 3.0 mass% ) and 1.8 g of deionized water were added. In the resulting mixture (flask contents), the molar ratio of titanium tetraisopropoxide, hydrogen chloride and water (titanium tetraisopropoxide:hydrogen chloride:water) was 1:0.01:2.

Then, the resulting mixture was stirred for 2 hours under conditions of a flask internal temperature of 25° C. and a rotation speed of 160 rpm. Then, the obtained product was subjected to suction filtration (solid-liquid separation) using a Buchner funnel to obtain wet cake-like particles (powder). Subsequently, the obtained wet cake-like particles were dispersed in ion-exchanged water, and then subjected to suction filtration using a Buchner funnel. Further, the dispersion and suction filtration were repeated three times to wash the particles. Then, the washed particles were dried to obtain substrate particles B1 (number average primary particle diameter: 130 nm) which were titania particles.

(Step of attaching conductive particles)
Next, 400 g of base particles B1 and 30 g of ATO particles (manufactured by Ishihara Sangyo Co., Ltd. "SN-100P", number average primary particle diameter: 20 nm, volume resistivity: 3 Ω cm) are combined with an FM mixer (Nippon Coke Kogyo Co., Ltd.) and mixed for 10 minutes at a rotational speed of 4000 rpm using an FM mixer. As a result, the ATO particles (conductive particles) were adhered to the surfaces of the substrate particles B1 to obtain composite particles.

(Hydrophobic treatment step)
Next, 300 g of the obtained composite particles are put into an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), and while stirring at a rotation speed of 3000 rpm, in an atmosphere at a temperature of 25 ° C., isopropyl triisostearoyl titanate ( 5 g of “Plenact (registered trademark) TTS” manufactured by Ajinomoto Fine-Techno Co., Inc. was sprayed. Next, the composite particles with isopropyl triisostearoyl titanate adhering thereto were stirred at a rotation speed of 3000 rpm for 10 minutes in an atmosphere at a temperature of 25° C., and then dried in an atmosphere at a temperature of 105° C. for 24 hours. As a result, composite particles C1, which are composite particles hydrophobized with isopropyl triisostearoyl titanate (titanate coupling agent), were obtained. In the obtained composite particles C1, the amount of ATO particles was 7.5 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of composite particles C2]
Composite particles except that 400 g of base particles B2 (number average primary particle diameter: 100 nm) were used instead of 400 g of base particles B1, and that the amount of ATO particles added to the FM mixer was changed to 40 g. Composite particles C2 were obtained in the same manner as in the preparation of C1. Substrate particles B2 were obtained in the same manner as for substrate particles B1, except for the following changes.

(change point)
In the preparation of substrate particles B2, the amount of hydrochloric acid put into the flask was changed to 6.0 g. In the preparation of substrate particles B2, the stirring time was changed to 1 hour when the mixture was stirred under the conditions of a flask internal temperature of 25° C. and a rotation speed of 160 rpm.

In the obtained composite particles C2, the amount of ATO particles was 10.0 parts by mass with respect to 100 parts by mass of the base particles B2.

[Preparation of Composite Particle C3]
Composite particles except that 400 g of base particles B3 (number average primary particle diameter: 250 nm) were used instead of 400 g of base particles B1, and that the amount of ATO particles added to the FM mixer was changed to 12 g. Composite particles C3 were obtained in the same manner as in the preparation of C1. Substrate particles B3 were obtained in the same manner as in the preparation of substrate particles B1, except for the following changes.

(change point)
In the preparation of substrate particles B3, the amount of hydrochloric acid put into the flask was changed to 16.0 g.

In the obtained composite particles C3, the amount of ATO particles was 3.0 parts by mass with respect to 100 parts by mass of base particles B3.

[Preparation of Composite Particle C4]
Composite particles C4 were obtained in the same manner as in the preparation of composite particles C1, except that the amount of ATO particles charged into the FM mixer was changed to 45 g. In the obtained composite particles C4, the amount of ATO particles was 11.3 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of composite particles C5]
Composite particles C5 were obtained in the same manner as in the preparation of composite particles C1, except that the amount of ATO particles charged into the FM mixer was changed to 15 g. In the resulting composite particles C5, the amount of ATO particles was 3.8 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of Composite Particle C6]
The same method as for preparing composite particles C1, except that 400 g of base particles B4 (number average primary particle diameter: 120 nm) were used instead of 400 g of base particles B1, and that the hydrophobization treatment step was not performed. to obtain composite particles C6. The steps for preparing the substrate particles B4 were as follows.

(Preparation step of substrate particles B4)
A glass container equipped with a stirrer, cooling tube, thermometer, and nitrogen inlet tube was set in a water bath at a temperature of 80°C. Subsequently, 200 parts by mass of ion-exchanged water and 3 parts by mass of a surfactant (sodium lauryl sulfate) were put into the container. Subsequently, while stirring the contents of the container, 1 part by mass of ammonium persulfate and 100 parts by mass of the monomer mixture were added dropwise into the container at a constant rate over 1 hour under conditions of a nitrogen atmosphere and a temperature of 80°C. The monomer mixture was a mixture of methyl methacrylate, styrene and divinylbenzene. In the above monomer mixture, the mass ratio of methyl methacrylate, styrene and divinylbenzene (methyl methacrylate:styrene:divinylbenzene) was 3:1:1.

Subsequently, while stirring the contents of the container, the contents of the container were allowed to react for 1 hour under the conditions of a nitrogen atmosphere and a temperature of 80°C. As a result, an emulsion was obtained. Subsequently, the obtained emulsion was cooled and then dried at a temperature of 80° C. for 18 hours to obtain base particles B4. Base particle B4 had a structure in which the constituent resin was crosslinked using divinylbenzene as a crosslinker. That is, the substrate particles B4 were crosslinked resin particles.

In the resulting composite particles C6, the amount of ATO particles was 7.5 parts by mass with respect to 100 parts by mass of base particles B4.

[Preparation of Composite Particle C7]
Composite particles except that 400 g of base particles B5 (number average primary particle diameter: 80 nm) were used instead of 400 g of base particles B1, and that the amount of ATO particles added to the FM mixer was changed to 50 g. Composite particles C7 were obtained in the same manner as the preparation of C1. Substrate particle B5 was obtained in the same manner as substrate particle B1, except for the following changes.

(change point)
In the preparation of substrate particles B5, the amount of hydrochloric acid put into the flask was changed to 4.0 g. In the preparation of substrate particles B5, the stirring time was changed to 1 hour when the mixture was stirred under the conditions of a flask internal temperature of 25° C. and a rotation speed of 160 rpm.

In the obtained composite particles C7, the amount of ATO particles was 12.5 parts by mass with respect to 100 parts by mass of the base particles B5.

[Preparation of Composite Particle C8]
Composite particles except that 400 g of base particles B6 (number average primary particle diameter: 270 nm) were used instead of 400 g of base particles B1, and that the amount of ATO particles added to the FM mixer was changed to 10 g. Composite particles C8 were obtained in the same manner as the preparation of C1. Substrate particle B6 was obtained in the same manner as substrate particle B1, except for the following changes.

(change point)
In the preparation of substrate particles B6, the amount of hydrochloric acid put into the flask was changed to 20.0 g.

In the obtained composite particles C8, the amount of ATO particles was 2.5 parts by mass with respect to 100 parts by mass of base particles B6.

[Preparation of Composite Particle C9]
Composite particles C9 were obtained in the same manner as in the preparation of composite particles C1, except that the amount of ATO particles charged into the FM mixer was changed to 55 g. In the obtained composite particles C9, the amount of ATO particles was 13.8 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of Composite Particle C10]
Composite particles C10 were obtained in the same manner as in the preparation of composite particles C1, except that the amount of ATO particles charged into the FM mixer was changed to 4 g. In the obtained composite particles C10, the amount of ATO particles was 1.0 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of Composite Particle C11]
Instead of 30 g of ATO particles (“SN-100P” manufactured by Ishihara Sangyo Co., Ltd., number average primary particle diameter: 20 nm, volume resistivity: 3 Ω cm), 30 g of AZO particles (“Pazet CK” manufactured by Hakusui Tech Co., Ltd., Composite particles C11 were obtained in the same manner as in the preparation of composite particles C1, except that a number average primary particle diameter of 30 nm and a volume resistivity of 10,000 Ω·cm were used. In the obtained composite particles C11, the amount of AZO particles was 7.5 parts by mass with respect to 100 parts by mass of base particles B1.

[Preparation of composite particles C12]
Composite particles C12 were obtained in the same manner as composite particles C1 except that 400 g of base particles B7 (number average primary particle diameter: 250 nm) were used instead of 400 g of base particles B1. As the substrate particles B7, alumina particles (“AO-502” manufactured by Admatechs Co., Ltd.) were used. In the obtained composite particles C12, the amount of ATO particles was 7.5 parts by mass with respect to 100 parts by mass of base particles B7.

Table 2 shows the details of the obtained composite particles C1 to C12. In Table 2, "particle size" is the number average primary particle size. In Table 2, "Amount" in the column of conductive particles is the amount (unit: parts by mass) of conductive particles with respect to 100 parts by mass of base particles.

<Preparation of Toner>
Methods for producing toners TA-1 to TA-12 and TB-1 to TB-9 are described below.

[Preparation of Toner TA-1]
100 parts by mass of toner base particles M1 and 2.0 parts by mass of composite particles C1 are added to an FM mixer (“FM-10B” manufactured by Nippon Coke Kogyo Co., Ltd.), and the FM mixer is used to rotate at a rotational speed of 4000 rpm. In addition, the powder in the FM mixer was mixed for 10 minutes at a jacket temperature of 35°C. Subsequently, 2.0 parts by mass of silica particles S1 were put into the FM mixer, and the powder in the FM mixer was mixed for 3 minutes at a rotation speed of 4000 rpm and a jacket temperature of 35°C. As a result, the external additives (silica particles S1 and composite particles C1) were adhered (externally added) to the surfaces of the toner base particles M1. The obtained powder (powder of toner base particles M1 to which external additives are attached) was sieved using a 200-mesh (75 μm mesh) sieve. As a result, a positively chargeable toner TA-1 was obtained.

[Production of Toners TA-2 to TA-12 and TB-1 to TB-9]
Positively chargeable toner TA-2 was prepared in the same manner as toner TA-1, except that the type and amount of silica particles and the type and amount of composite particles were as shown in Table 3. ~TA-12 and TB-1 to TB-9 were produced respectively. In Table 3, the "input amount" in the column for silica particles and the "input amount" in the column for composite particles are both It is the amount of agent particles (unit: parts by mass). Also, the first coverage and the second coverage shown in Table 3 were measured by the following methods.

[Method for measuring first coverage and second coverage]
Using a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.), the toner particles contained in the toner to be measured were observed to determine the first coverage and the second coverage. rate and were measured. Specifically, after obtaining a backscattered electron image (surface photographed image) of the toner particles using FE-SEM, image analysis of the surface photographed image obtained using image analysis software (“WinROOF” manufactured by Mitani Shoji Co., Ltd.) is performed. By performing, the first coverage and the second coverage were obtained. The first coverage corresponds to the area ratio of the area covered with the silica particles in the surface area of the toner base particles. Further, the second coverage corresponds to the area ratio of the area covered by the composite particles in the surface area of the toner base particles. With respect to the portion where a plurality of types of external additive particles overlap on the surface of the toner base particle, the outermost external additive particle (more specifically, the highest position with respect to the surface of the toner base particle) It was determined that the external additive particles) covered the site. For example, on the surface of the toner base particles, it was determined that the portions where the composite particles and the silica particles overlapped in this order were covered with the outermost silica particles.

As for the measurement procedure, first, the first coverage and the second coverage were measured in 10 fields per toner particle (size of one field: 2 µm × 2 µm), and 10 measurements were obtained. The arithmetic mean of the values was used as the evaluation value of the toner particles (hereinafter referred to as first coverage CA and second coverage CB). Further, the first coverage CA and the second coverage CB were measured for 10 toner particles contained in the measurement object (toner), and the arithmetic mean of the 10 measured values obtained was calculated as the measurement object ( Toner) was used as an evaluation value (first coverage and second coverage shown in Table 3).

<Evaluation method>
[Preparation of two-component developer]
100 parts by mass of developer carrier (carrier for "TASKalfa5550ci" manufactured by Kyocera Document Solutions Co., Ltd.) and 8 parts by mass of toner (evaluation object: toner TA-1 to TA-12 or TB-1 to TB-9) were mixed for 30 minutes using a ball mill to prepare a two-component developer.

[Transfer efficiency]
A multi-function machine (“TASKalfa5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) was used as an evaluation machine for evaluating the transfer efficiency. The two-component developer prepared as described above was put into the black developing device of the evaluation machine, and a replenishing toner (evaluation object: any of toners TA-1 to TA-12 and TB-1 to TB-9). was put into the black toner container of the evaluation machine. Subsequently, an image with a coverage rate of 5% was printed on 10,000 sheets of printing paper (A4 size) using the evaluation machine under an environment of a temperature of 20° C. and a humidity of 50% RH. Then, the mass of the consumed toner and the mass of the collected toner were measured, and the transfer efficiency (unit: %) was calculated from the following formula. Note that the consumed toner is the toner discharged from the toner container among the samples (toner) set in the toner container. The collected toner is the toner that is not transferred to the printing paper among the consumed toner.
Transfer efficiency=100×(consumed toner mass−collected toner mass)/(consumed toner mass)

A transfer efficiency of 90% or more was evaluated as A (good), and a transfer efficiency of less than 90% was evaluated as B (poor).

[Image Density]
A multifunction machine ("TASKalfa5550ci" manufactured by Kyocera Document Solutions Co., Ltd.) was used as an evaluation machine for evaluating the image density. The two-component developer prepared as described above was put into the black developing device of the evaluation machine, and a replenishing toner (evaluation object: any of toners TA-1 to TA-12 and TB-1 to TB-9). was put into the black toner container of the evaluation machine. Subsequently, in an environment of a temperature of 20° C. and a humidity of 50% RH, 100,000 sheets of printing paper (A4 size) were continuously printed with an image with a print ratio of 5% using the evaluation machine. Subsequently, under an environment of a temperature of 20° C. and a humidity of 50% RH, 10,000 sheets of printing paper (A4 size) were continuously printed with an image with a print ratio of 1% using the evaluation machine. Thus, a continuous printing test was conducted.

During the continuous printing test, before printing an image with a printing rate of 5% (hereinafter referred to as "initial"), after printing 100,000 sheets of an image with a printing rate of 5% and printing an image with a printing rate of 1%. before printing (hereinafter referred to as "after printing 100,000 sheets") and after printing 10,000 sheets of an image with a coverage rate of 1% (hereinafter referred to as "after printing 10,000 sheets"). , image density was evaluated. Specifically, at the initial stage, after printing 100,000 sheets, and after printing 10,000 sheets, a solid image with a size of 25 mm × 25 mm was obtained using the above evaluation machine under an environment of a temperature of 20°C and a humidity of 50% RH. , was formed on a sheet of printing paper (A4 size). Next, the image density (ID) of the solid image formed on the printing paper was measured using a reflection densitometer (“RD914” manufactured by X-Rite).

Of the obtained image densities (ID), if both the image densities (ID) of the solid images printed after printing 100,000 sheets and after printing 10,000 sheets are 1.00 or more, it is determined that "high-quality images can be continued." It has been effectively formed,” he said. On the other hand, among the obtained image densities (ID), if at least one of the image densities (ID) of the solid images printed after printing 100,000 sheets and after printing 10,000 sheets is less than 1.00, "high image quality Images cannot be formed continuously." Also, the higher the image density (ID), the higher the quality of the image.

Table 4 shows the transfer efficiency evaluation results and the image density (ID) evaluation results for each of the toners TA-1 to TA-12 and TB-1 to TB-9. In Table 4, ID _A is the image density (ID) of the initially printed solid image, ID _B is the image density (ID) of the solid image printed after printing 100,000 sheets, and ID _C is the image density (ID) of the 10,000 printed solid image. This is the image density (ID) of a solid image printed after printing one sheet.

In toners TA-1 to TA-12, the external additive contained silica particles and composite particles as external additive particles. In toners TA-1 to TA-12, the composite particles contained substrate particles and conductive particles attached to the surfaces of the substrate particles. In toners TA-1 to TA-12, the base particles were titania particles, alumina particles or crosslinked resin particles.

As shown in Tables 2 and 3, in the toners TA-1 to TA-12, the amount of the conductive particles was 2.0 parts by mass or more and 13.0 parts by mass or less with respect to 100 parts by mass of the base particles. rice field. In toners TA-1 to TA-12, the number average primary particle size of silica particles was 20 nm or less. In the toners TA-1 to TA-12, the number average primary particle diameter of the base particles was 100 nm or more and 250 nm or less. In the toners TA-1 to TA-12, the number average primary particle diameter of the conductive particles was 10 nm or more and 40 nm or less. For toners TA-1 to TA-12, the first coverage was 40% or more and 80% or less. For toners TA-1 to TA-12, the second coverage was 5% or more and 20% or less.

As shown in Table 4, with the toners TA-1 to TA-12, both the image density (ID) of the solid images printed after printing 100,000 sheets and after printing 10,000 sheets were 1.00 or more.

As shown in Tables 2 and 3, in toner TB-1, the number average primary particle diameter of the base particles was less than 100 nm. In toner TB-2, the number average primary particle diameter of the base particles exceeded 250 nm. In toner TB-3, the amount of the conductive particles exceeded 13.0 parts by mass with respect to 100 parts by mass of the base particles. In toner TB-4, the amount of the conductive particles was less than 2.0 parts by weight with respect to 100 parts by weight of the base particles. For toner TB-5, the second coverage was less than 5%. For toner TB-6, the second coverage exceeded 20%. For toner TB-7, the first coverage was less than 40%. For toner TB-8, the first coverage exceeded 80%. In toner TB-9, the number average primary particle diameter of silica particles exceeded 20 nm.

As shown in Table 4, with the toners TB-1 to TB-9, the image density (ID) of the solid image printed after printing 10,000 sheets was less than 1.00.

From the above results, it was shown that high-quality images can be continuously formed with the toner according to the present invention.

The toner according to the present invention can be used, for example, to form images in multifunction devices or printers.

10: Toner Particles 11: Toner Base Particles 12: Silica Particles 13: Composite Particles 14: Base Particles 15: Conductive Particles

Claims (3)

A toner comprising toner particles,
The toner particles comprise toner base particles containing a binder resin and an external additive adhering to the surface of the toner base particles,
The external additive contains silica particles and composite particles as external additive particles,
The composite particles include substrate particles and conductive particles attached to the surfaces of the substrate particles,
The substrate particles are crosslinked resin particles,
The amount of the conductive particles is 2.0 parts by mass or more and 13.0 parts by mass or less with respect to 100 parts by mass of the base particles,
The number average primary particle diameter of the silica particles is 20 nm or less,
The number average primary particle diameter of the substrate particles is 100 nm or more and 250 nm or less,
The number average primary particle diameter of the conductive particles is 10 nm or more and 40 nm or less,
The area ratio of the area covered with the silica particles in the surface area of the toner base particles is 40% or more and 80% or less,
In the surface area of the toner base particles, the area ratio of the area covered with the composite particles is 5% or more and 20% or less,
The toner, wherein the crosslinked resin particles include a polymer of a styrene-based monomer, an acrylic monomer, and a cross-linking agent having two or more unsaturated bonds. 2. The toner of claim 1, wherein the conductive particles are antimony-doped tin oxide particles or aluminum-doped zinc oxide particles. 3. The toner according to claim 1 , wherein the cross-linking agent having two or more unsaturated bonds is divinylbenzene.

Images