JP7206766B2 - toner - Google Patents

Description

The present invention relates to toner.

In toners (especially toners for electrostatic latent image development), an external additive may be adhered to the surface of the toner base particles for the purpose of imparting fluidity and desired charging properties (for example, positive charging properties). As such an external additive, silica particles formed by surface-treating a silica substrate with a silane coupling agent or silicone oil have been proposed (for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2005-321690 JP 2010-198004 A

However, the present inventors have found that the toners using the silica particles described in Patent Documents 1 and 2 have room for improvement in charging stability, anti-fogging properties and anti-filming properties.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner excellent in charging stability, anti-fogging property and anti-filming property.

The toner of the present invention is a positively charged toner, and contains toner particles comprising toner base particles and an external additive adhering to the surface of the toner base particles. The external additive includes external additive particles having a substrate containing lanthanum atoms and a coating layer covering the surface of the substrate. The coating layer contains a nitrogen-containing resin and is hydrophobized on the surface with an isocyanate compound having a hydrophobic group.

The toner of the present invention is excellent in charging stability, anti-fogging property and anti-filming property.

1 is a schematic cross-sectional view showing an example of toner according to an embodiment of the invention; FIG.

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.) regarding powder (more specifically, powder of toner particles, powder of external additive particles, etc.) are the It is the number average of the values measured for each of the selected particles.

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 circle-equivalent diameter of the primary particles measured using a scanning electron microscope (Heywood diameter: a circle having the same area as the projected area of the primary particles diameter). The number average primary particle diameter of the powder is, for example, the number average value of equivalent circle diameters of 100 primary particles. The number average primary particle size of particles refers to the number average primary particle size of particles in powder unless otherwise specified.

Chargeability means chargeability in triboelectrification unless otherwise specified. The strength of positive chargeability (or the strength of negative chargeability) in triboelectrification can be confirmed by a known electrification series or the like. For example, toner is mixed with a standard carrier provided by the Imaging Society of Japan (standard carrier for negatively charged toner: N-01, standard carrier for positively charged toner: P-01) and stirred to rub the object to be measured. electrify. Before and after triboelectrification, the charge amount of the object to be measured is measured with, for example, a charge amount measuring device (Q/m meter). indicates that

A "major component" of a material means, by mass, the component that is the most abundant in the material, unless otherwise specified.

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.

Hereinafter, compounds and derivatives thereof may be collectively referred to by adding "system" to the name of the compound. When the polymer name is expressed by adding "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

<Toner>
Embodiments of the present invention relate to toners. The toner according to the present embodiment is positively charged toner and includes toner particles having toner base particles and an external additive adhering to the surfaces of the toner base particles. The external additive includes external additive particles having a substrate containing lanthanum atoms and a coating layer covering the surface of the substrate. The coating layer contains a nitrogen-containing resin, and the surface is hydrophobized with an isocyanate compound having a hydrophobic group.

The toner according to the exemplary embodiment can be suitably used as a positively charged toner for developing an electrostatic latent image. The toner according to this embodiment may be used as a one-component developer. The toner according to the exemplary embodiment may be mixed with a carrier using a mixing device (for example, a ball mill) and used as a two-component developer. When used as a one-component developer, the toner according to the exemplary embodiment is positively charged by friction with a developing sleeve or a toner charging member in the developing device. Examples of the toner charging member include a doctor blade. When forming a two-component developer, the toner according to the present embodiment is positively charged by friction with the carrier in the developing device. The details of the toner will be described below with appropriate reference to the drawings.

[Toner particles]
FIG. 1 shows an example of toner particles 1 contained in the toner according to this embodiment. The toner particles 1 shown in FIG. The external additive includes external additive particles 3 having a substrate 3a containing lanthanum atoms and a coating layer 3b covering the surface of the substrate 3a.

However, the toner particles contained in the toner according to the exemplary embodiment may have a structure different from that of the toner particles 1 shown in FIG. Specifically, the toner particles may further include external additive particles other than the external additive particles 3 described above. Further, the toner particles may be toner particles provided with a shell layer (hereinafter sometimes referred to as capsule toner particles). In the capsule toner particles, the toner base particles comprise, for example, a toner core containing a binder resin and a shell layer covering the surface of the toner core. The details of the toner particles 1 contained in the toner according to the present embodiment have been described above with reference to FIG.

The toner according to the present exemplary embodiment has the above-described structure, and is therefore excellent in charging stability, anti-fogging property, and anti-filming property. The reason is explained below. Both the lanthanum atom-containing substrate and the nitrogen-containing resin-containing coating layer tend to exhibit strong positive electrification and relatively high hardness. Moreover, since the substrate containing lanthanum atoms is covered with the coating layer, deliquescence is suppressed. Since the external additive particles have such a substrate and coating layer, they can continue to impart excellent positive chargeability to the toner over a long period of time. Therefore, the toner has excellent charging stability. Furthermore, since the external additive particles have a high dielectric constant due to the substrate containing lanthanum atoms, it is possible to suppress variations in the charge amount of each toner particle. Therefore, the toner can suppress image fogging caused by variations in the charge amount of each toner particle. Furthermore, the surface of the coating layer of the external additive particles is hydrophobized with an isocyanate compound having a hydrophobic group. Generally, nitrogen-containing resins tend to have high adhesiveness, but the adhesiveness is suppressed when functional groups on the surface are reduced by hydrophobizing treatment. Since the surface of the coating layer is hydrophobized by the isocyanate compound, which has excellent reactivity with the nitrogen-containing resin, the external additive particles included in the toner particles are less likely to adhere to other members. Therefore, the toner can suppress filming caused by adhesion of toner particles to the photoreceptor drum.

Details of the toner particles are further described below. Unless otherwise specified, each component described below may be used singly or in combination of two or more.

[External additive particles]
The external additive particles comprise a substrate containing lanthanum atoms and a coating layer covering the surface of the substrate. The content of the external additive particles in the toner particles is preferably 0.1 parts by mass or more and 10.0 parts by mass or less, and 0.5 parts by mass or more and 4.0 parts by mass or less with respect to 100 parts by mass of the toner base particles. more preferred.

The degree of hydrophobicity of the external additive particles measured by the methanol wettability method is preferably 20% or more and 70% or less, more preferably 40% or more and 60% or less. By setting the degree of hydrophobicity of the external additive particles to 20% or more and 70% or less, the adhesion of the toner particles to the photoreceptor can be further reduced, and the filming resistance of the toner can be further improved. The degree of hydrophobicity of the external additive particles is adjusted, for example, by adjusting the type of nitrogen-containing resin contained in the coating layer, or by adjusting the amount or type of isocyanate compound used for hydrophobizing the surface of the coating layer. can do.

The degree of hydrophobicity of the external additive particles is a value measured by the following measuring method. First, 0.1 g of the external additive particles are dispersed in 25 mL of pure water at room temperature (23° C.) to prepare a dispersion (dispersion preparing step). Next, while the dispersion is being stirred, methanol is added dropwise to the dispersion to cause the total amount of the external additive particles in the dispersion to settle (total precipitation) (dropping step). The degree of hydrophobicity of the external additive particles is obtained from the following formula based on the amount of methanol dropped [mL] required for the total precipitation of the external additive in the dispersion in the dropping step. In addition, the stirring speed in the dropping step can be, for example, a rotation speed of 150 rpm.
Hydrophobicity [%] = 100 x methanol drop amount [mL] / (methanol drop amount [mL] + 25 mL)

(substrate)
The substrate is not particularly limited as long as it contains lanthanum atoms, but a substrate containing at least one of lanthanum oxide and lanthanum hydroxide is preferred, and lanthanum oxide particles are more preferred. The content of the lanthanum compound in the substrate is preferably 70% by mass or more, more preferably 90% by mass or more. Note that lanthanum oxide may react with water or the like to produce lanthanum hydroxide during the production stage of the external additive particles. Therefore, when lanthanum oxide particles are used as the base of the external additive particles, the base may contain lanthanum hydroxide.

The number average primary particle diameter of the substrate is preferably 15 nm or more and 100 nm or less, more preferably 15 nm or more and 35 nm or less.

(coating layer)
The coating layer contains a nitrogen-containing resin, and the surface is hydrophobized with an isocyanate compound having a hydrophobic group. The coating layer preferably covers the entire surface of the substrate, but may cover only part of the surface of the substrate. Here, the term "hydrophobic group" refers to a group that is more hydrophobic than a hydroxy group.

The thickness of the coating layer in the external additive particles is proportional to the content of nitrogen atoms (more specifically, nitrogen atoms derived from the nitrogen-containing resin) in the external additive particles. The content of nitrogen atoms in the external additive particles is preferably 5.00% by mass or more and 15.00% by mass or less, more preferably 7.00% by mass or more and 12.00% by mass or less. By setting the content of nitrogen atoms in the external additive particles to 5.00% by mass or more and 15.00% by mass or less, the deliquescence of the substrate is sufficiently reduced while maintaining a high dielectric constant and excellent positive chargeability of the substrate. It is possible to further improve the charging stability and anti-fogging property of the toner. The content of nitrogen atoms in the external additive particles can be measured by CHN analysis using an elemental analyzer (for example, "2400II CHNS/O" manufactured by PerkinElmer).

[Nitrogen-containing resin]
Examples of nitrogen-containing resins include amino resins (particularly melamine resins and urea resins), polyamide resins, polyimide resins, polyamideimide resins, aniline resins, guanamine resins, and polyurethane resins. As the nitrogen-containing resin, a melamine resin or a urea resin is preferable from the viewpoint of improving the adhesion between the substrate and the coating layer.

The content of the nitrogen-containing resin in the coating layer is preferably 70% by mass or more, preferably 90% by mass or more.

[Isocyanate compound]
Examples of the hydrophobic group possessed by the isocyanate compound include an alkyl group having 2 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, and an aralkyl group having 7 to 15 carbon atoms.

Alkyl groups having 2 to 8 carbon atoms are unsubstituted and may be branched or linear. Examples of alkyl groups having 2 to 8 carbon atoms include ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, sec-butyl, isobutyl, linear or branched linear or branched pentyl groups, linear or branched hexyl groups, linear or branched heptyl groups, and linear or branched octyl groups.

Aryl groups having 6 to 14 carbon atoms are unsubstituted. Examples of the aryl group having 6 to 14 carbon atoms include phenyl group, naphthyl group and anthracenyl group.

Examples of the aralkyl group having 7 to 15 carbon atoms include an alkyl group having 1 to 5 carbon atoms substituted with an aryl group having 6 to 14 carbon atoms. Examples of specific aralkyl groups having 7 or more and 15 or less carbon atoms include a benzyl group, a phenylethyl group and a naphthylmethyl group.

The isocyanate compound having a hydrophobic group is preferably an aromatic isocyanate compound or an aliphatic isocyanate compound having an alkyl group having 2 to 8 carbon atoms, and an aromatic isocyanate having an aryl group having 6 to 14 carbon atoms. compound, an aromatic isocyanate compound having an aralkyl group having 7 to 15 carbon atoms, or an aliphatic isocyanate compound having an alkyl group having 2 to 8 carbon atoms, ethyl isocyanate, octyl isocyanate, phenyl isocyanate or benzyl Isocyanates are more preferred. In making the coating layer hydrophobic, the isocyanate compound having a hydrophobic group may be used alone or in combination of two or more.

A group represented by the following general formula (I) (hereinafter sometimes referred to as group (α)) is preferably present on the surface of the coating layer. The group (α) is derived from an isocyanate compound having a hydrophobic group and a terminal group (eg --NH--CH ₂ --OH) of the nitrogen-containing resin. The group (α) can be confirmed, for example, by FT-IR analysis as a peak at 1515 cm ⁻¹ or more and 1650 cm ⁻¹ or less (C═O stretching peak of amide).

In general formula (I), R ¹ represents an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 15 carbon atoms, or an alkyl group having 2 to 8 carbon atoms. * represents a bonding site with a nitrogen-containing resin. R ¹ preferably represents an ethyl group, an octyl group, a phenyl group or a benzyl group.

[Toner base particles]
The toner base particles are not particularly limited, and toner base particles in known toners can be used. The toner base particles contain, for example, a binder resin as a main component. The toner base particles may further contain an internal additive (for example, at least one of a colorant, release agent, charge control agent, and magnetic powder), if necessary. Examples of the method for producing the toner base particles include a pulverization method and an aggregation method, with the pulverization method being preferred.

From the viewpoint of forming good images, the volume median diameter (D ₅₀ ) of the toner base particles is preferably 4 μm or more and 9 μm or less.

(Binder resin)
From the viewpoint of providing a toner excellent in low-temperature fixability, the toner base particles preferably contain a thermoplastic resin as a binder resin, and the thermoplastic resin is contained at a rate of 85% by mass or more of the total binder resin. is more preferable. 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-based resins, styrene-butadiene-based resins, etc.) Can be used as a binder resin.

(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. From the viewpoint of forming a high-quality image using the toner, the content 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.

(Release agent)
The toner core may contain a release agent. A release agent is used, for example, for the purpose of imparting anti-offset properties to the toner.

(shell layer)
When the toner base particles are encapsulated toner particles, the shell layer is substantially composed of resin. The shell layer may be substantially composed of a thermosetting resin, may be substantially composed of a thermoplastic resin, or may contain both a thermosetting resin and a thermoplastic resin. good. 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.

(other external additives)
The toner preferably comprises only the above-described external additive particles as an external additive, but may further comprise other external additive particles. Examples of other external additive particles include silica particles, particles of metal oxides (specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.), and fatty acid metal salts. (specifically, zinc stearate, etc.) and resin particles. The content of the other external additive particles in the toner particles is preferably 5.0 parts by mass or less, more preferably 1.0 parts by mass or less, relative to 100 parts by mass of the toner base particles.

[Toner manufacturing method]
For the toner according to the present embodiment, for example, the surface of a substrate containing lanthanum atoms is coated with a coating layer containing a nitrogen-containing resin to obtain coated particles (coating step); A step of obtaining external additive particles by hydrophobizing the surface of the coating layer of the coated particles with a compound (hydrophobizing step), and a step of adhering the external additive particles to the surface of the toner base particles (external addition step). It can be manufactured by the method of providing. Each step will be described below.

(Coating process)
In this step, coated particles are obtained by coating the surface of a substrate containing lanthanum atoms with a coating layer containing a nitrogen-containing resin. Specifically, for example, a nitrogen-containing resin or a precursor thereof is added to a dispersion obtained by dispersing a substrate in an aqueous medium, and curing treatment is performed as necessary. As a result, coated particles in which the surface of the substrate is coated with the coating layer are obtained. When the curing treatment is performed, the conditions may be, for example, a reaction temperature of 60° C. or higher and 100° C. or lower, a reaction time of 10 minutes or longer and 1 hour or shorter, and a pH of 2 or higher and 6 or lower. The obtained coated particles may be dried by a vacuum drying treatment or the like, if necessary. For example, methylolmelamine or methylolated urea can be used as a precursor of the nitrogen-containing resin.

(Hydrophobic process)
In this step, the surface of the coating layer of the coated particles is hydrophobized with an isocyanate compound having a hydrophobic group to obtain the external additive particles. Specifically, for example, the coated particles obtained in the coating step are reacted with an isocyanate compound having a hydrophobic group in an organic solvent (eg, toluene). As a result, external additive particles in which the surface of the coating layer is hydrophobized are obtained. As the reaction conditions, for example, the reaction temperature can be 30° C. or higher and 70° C. or lower, and the reaction time can be 30 minutes or longer and 6 hours or shorter. After the reaction, the organic solvent can be removed by boiling the reaction solution. Moreover, the solid content obtained by removing the organic solvent may be pulverized with a pulverizer, if necessary.

(External addition process)
In this step, external additive particles are adhered to the surfaces of the toner base particles. As a result, toner particles comprising the toner base particles and the external additive particles adhering to the surfaces of the toner base particles are obtained. A method for adhering the external additive particles to the surface of the toner base particles is not particularly limited, but an example thereof includes a method of stirring the toner base particles and the external additive particles with a mixer or the like.

EXAMPLES Hereinafter, the present invention will be described more specifically using examples. However, the present invention is in no way limited to the scope of the examples.

(Preparation of External Additive Particles A)
External additive particles A used in the production of toner were prepared by the following method. First, lanthanum oxide particles L were prepared as a substrate containing lanthanum atoms.

(Preparation of substrate)
A powder of lanthanum oxide (La ₂ O ₃ ) (manufactured by Wako Pure Chemical Industries, Ltd.) is pulverized using a pulverizer ("Jet Mill I-2" manufactured by Nippon Pneumatic Industry Co., Ltd.) to obtain lanthanum atoms. Lanthanum oxide particles L as a substrate containing were obtained. In addition, in the pulverization by the pulverizer, a flat plate made of ceramic was used as a collision plate, and the pulverization pressure was set to 0.6 MPa. The lanthanum oxide particles L were photographed with a scanning electron microscope ("JSM-7600F" manufactured by JEOL Ltd.) at a magnification of 100,000. Based on the obtained image, the number average value of the projected area of 100 lanthanum oxide particles L was calculated, and the equivalent circle diameter was calculated from this number average value. The obtained equivalent circle diameter was taken as the number average primary particle diameter of the lanthanum oxide particles L. The number average primary particle size of the lanthanum oxide particles L was 21 nm.

(coating treatment)
Lanthanum oxide particles L (50 g) were dispersed in 500 mL of ion-exchanged water. To the resulting dispersion, 0.5N hydrochloric acid (“Wako First Grade 087-01076” manufactured by Wako Pure Chemical Industries, Ltd.) was added to adjust the pH to 5-6. 25 g of water-soluble methylol melamine (melamine resin precursor) (“Nika Resin (registered trademark) S-260” manufactured by Nippon Carbide Industry Co., Ltd.) as a nitrogen-containing resin precursor was added to the dispersion after pH adjustment and dissolved. let me The resulting reaction solution was put into a 1 L separable flask and reacted at 70° C. for 30 minutes using a constant temperature bath (“Constant temperature water bath BK400” manufactured by Yamato Scientific Co., Ltd.). After the reaction, the precipitate was filtered, and the resulting filter cake was dried with a vacuum dryer (“Square Vacuum Constant Temperature Dryer DP43/63” manufactured by Yamato Scientific Co., Ltd.). As a result, coated particles comprising lanthanum oxide particles L and a coating layer coating the surface of the substrate were obtained.

(Hydrophobic treatment)
500.0 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.5 g of sodium perfluorooctylsulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 3.0 g of phenyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) as an isocyanate compound having a hydrophobic group and 50.0 g of the coated particles described above were added. The mixture was reacted at 50° C. for 2 hours and then boiled at 90-110° C. for 2 hours to remove toluene. External additive particles A were obtained by pulverizing the resulting product with a pulverizer (“Supersonic jet pulverizer PJM-80SP” manufactured by Nippon Pneumatic Industry Co., Ltd.).

External additive particles B to K were prepared in the same manner as for external additive particle A, except for the following changes.

(Preparation of external additive particles B)
In the preparation of the external additive particles B, octyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as an isocyanate compound having a hydrophobic group in the hydrophobic treatment.

(Preparation of External Additive Particles C)
In the preparation of the external additive particles C, an aqueous solution of methylolated urea (precursor of urea resin) (“Milben Resin SU-100” manufactured by Showa Denko KK) was used as a nitrogen-containing resin precursor in the coating treatment.

(Preparation of external additive particles D)
In the preparation of the external additive particles D, ethyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as an isocyanate compound having a hydrophobic group in the hydrophobic treatment.

(Preparation of External Additive Particles E)
In the preparation of the external additive particles E, benzyl isocyanate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as an isocyanate compound having a hydrophobic group in the hydrophobic treatment.

(Preparation of external additive particles F)
In the preparation of the external additive particles F, no hydrophobic treatment was performed. That is, in the preparation of the external additive particles F, the coated particles obtained by the coating treatment are pulverized with a pulverizer (“Supersonic jet pulverizer PJM-80SP” manufactured by Nippon Pneumatic Co., Ltd.) to obtain the external additive particles F. got

(Preparation of external additive particles G)
In the preparation of the external additive particles G, the following treatments were performed in the hydrophobic treatment. That is, in the preparation of the external additive particles G, 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.) and octyltriethoxysilane (Shin-Etsu Chemical Co., Ltd.) were placed in a 1 L three-necked flask equipped with a thermometer and stirring blades. and 50 g of the coated particles described above were added. The resulting mixture was reacted at 50° C. for 2 hours and then boiled at 90-110° C. for 2 hours to remove toluene. Next, the obtained product was subjected to heat treatment at 200° C. for 3 hours under a nitrogen stream using an electric furnace. Furthermore, external additive particles G were obtained by pulverizing the heat-treated product with a pulverizer (“Supersonic jet pulverizer PJM-80SP” manufactured by Nippon Pneumatic Co., Ltd.).

(Preparation of external additive particles H)
In the preparation of the external additive particles H, instead of the lanthanum oxide particles L, fumed alumina particles (“AEROXIDE (registered trademark) Alu C” manufactured by Nippon Aerosil Co., Ltd.) were used as a substrate in the coating treatment.

(Preparation of External Additive Particles I)
In the preparation of the external additive particles I, fumed titania particles (“AEROXIDE (registered trademark) TiO ₂ 90” manufactured by Nippon Aerosil Co., Ltd.) were used as a substrate instead of the lanthanum oxide particles L in the coating treatment.

(Preparation of external additive particles J)
In the preparation of the external additive particles J, no coating treatment was performed. That is, in the preparation of the external additive particles J, the lanthanum oxide particles L were used instead of the coated particles in the hydrophobic treatment.

(Preparation of external additive particles K)
In the preparation of the external additive particles K, instead of the lanthanum oxide particles L, fumed silica particles ("AERSIL (registered trademark) 90" manufactured by Nippon Aerosil Co., Ltd.) were used as the substrate in the coating treatment.

(Measurement of hydrophobicity)
The degree of hydrophobicity of the external additive particles A to K was measured by the methanol wettability method described below. A dispersion was prepared by dispersing 0.1 g of the external additive particles in 25 mL of pure water at room temperature (23° C.). Next, methanol was added dropwise to the dispersion liquid until all the external additive particles were wet and precipitated (total sedimentation). Based on the dropping amount of methanol [mL] required for the total precipitation of the external additive particles, the degree of hydrophobicity of the external additive particles was obtained from the following formula.
Hydrophobicity [%] = 100 x methanol drop amount [mL] / (methanol drop amount [mL] + 25 mL)

(Measurement of nitrogen atom content)
The nitrogen atom content of the external additive particles A to K was analyzed using a fully automatic elemental analyzer ("2400II CHNS/O" manufactured by PerkinElmer). Specifically, 2 mg of a sample (any one of the external additive particles A to K) was set in a tin vial and measured under the following conditions. Measurement was performed three times for each sample, and the average value was adopted.
・Measurement mode: CHN mode ・Combustion temperature (combustion tube): 950℃
・Reduction temperature (reduction tube): 600°C

Specifically, a tin vial was put into the combustion tube of the analyzer, and the sample was burned at 1800° C. or higher due to the highly exothermic reaction of the tin vial. This caused complete combustion of the sample, producing CO ₂ , H ₂ O and NO _x (nitrogen oxides) from the carbon, hydrogen and nitrogen atoms in the sample, respectively. Next, the generated combustion gas was introduced into a reduction pipe to reduce NOx in the combustion gas to _N2 .

Furthermore, the amounts of CO ₂ , H ₂ O and N ₂ in the reduced combustion gas were measured by frontal chromatography (detector: thermal conductivity detector). As a result, the masses of carbon element, hydrogen element and nitrogen element in the combustion gas after reduction were quantified.

From the obtained measured value (the mass of nitrogen atoms in the combustion gas after reduction), the content ratio [% by mass] of the nitrogen element in the sample was obtained based on the following formula.
Content ratio of nitrogen atoms [mass%] = 100 x mass of nitrogen atoms in combustion gas after reduction [mg] / mass of sample [mg]

Table 1 below shows the production method, degree of hydrophobicity, and nitrogen atom content of each of the external additive particles A to K.

<Toner manufacturing>
As shown in Table 2 below, 2 parts by mass of an external additive (any one of external additive particles A to K) and 100 parts by mass of toner base particles are mixed with a multi-purpose small mixing pulverizer (manufactured by Nippon Coke Kogyo Co., Ltd.). "Multi-Purpose Mixer") to produce toners of Examples 1-5 and Comparative Examples 1-6. As the toner base particles, a cyan toner for "TASKalfa5550ci" manufactured by Kyocera Document Solutions Co., Ltd. was used. This toner base particle was a non-externally added non-magnetic toner, was produced by a pulverization method (pulverized toner), did not have a shell layer (non-encapsulated toner base particle), and contained a polyester resin as a binder resin. .

<Evaluation>
The toners of Examples 1 to 5 and Comparative Examples 1 to 6 were evaluated for charging stability, anti-fogging property and anti-filming property by the following methods. The evaluation was performed under conditions of a temperature of 24° C. and a humidity of 60% RH.

[Preparation of developer]
100 parts by mass of developer carrier (carrier for "TASKalfa5550ci" manufactured by Kyocera Document Solutions Co., Ltd.) and 10 parts by mass of toner (one of the toners of Examples 1 to 5 and Comparative Examples 1 to 6) were mixed in a ball mill. A two component developer was prepared by mixing for 30 minutes. Immediately after the adjustment, the charge amount of the toner contained in the two-component developer was measured using a compact suction-type charge amount measuring device ("Model 212HS" manufactured by Trek Japan Co., Ltd.). The measured charge amount was taken as the initial charge amount of the toner.

[Preparation of evaluation machine]
A developer (developer containing any of the toners of Examples 1 to 5 and Comparative Examples 1 to 6) was put into the cyan developing device of the evaluation machine ("TASKalfa5550ci" manufactured by Kyocera Document Solutions Co., Ltd.). Further, replenishment toner (the same toner as the toner contained in the developer) was put into the cyan toner container of the evaluation machine.

[First printing endurance test]
The evaluation machine was used to continuously print 100,000 sheets of evaluation paper (printing paper of A4 size) at a coverage rate of 5% (first printing durability test). In the first printing endurance test, the evaluation paper was observed every 5,000 printed sheets to confirm the presence or absence of dash marks caused by toner filming. Further, after the first printing endurance test, the magnet roller was taken out from the evaluation machine, and the charge amount (charge amount in the first printing endurance test) of the toner collected from the magnet roller was measured. Furthermore, after the first printing durability test, the reflection density A of the blank part of the last printed evaluation sheet and the reflection density B of the evaluation sheet before printing were measured, and the fogging density (FD) was obtained based on the following formula. (fogging density in the first printing endurance test).
FD = reflection density A - reflection density B

[Second printing endurance test]
The evaluation machine was used to continuously print 1,000 sheets of evaluation paper (printing paper of A4 size) at a coverage rate of 0.5% (second printing durability test). After the second printing durability test, the magnet roller was taken out from the evaluation machine, and the charge amount of the toner collected from the magnet roller (charge amount in the second printing durability test) was measured. After the second printing test, the reflection density A of the blank portion of the last printed evaluation paper was measured, and the fogging density (FD) was obtained based on the above formula (fogging density in the second printing test).

[Third printing endurance test]
The evaluation machine was used to continuously print 1,000 sheets of evaluation paper (printing paper of A4 size) at a coverage rate of 80% (third printing endurance test). After the third printing durability test, the magnet roller was taken out from the evaluation machine, and the charge amount of the toner collected from the magnet roller was measured (charge amount in the third printing durability test). After the third printing test, the reflection density A of the blank portion of the last printed evaluation paper was measured, and the fogging density (FD) was calculated based on the above formula (fogging density in the third printing test).

[Electrification stability]
The initial charge amount, the charge amount in the first endurance printing test, the charge amount in the second endurance printing test, and the charge amount in the third endurance printing test of each toner are shown in Table 2 below. If the charge amount of the toner was 15 μC/g or more and 35 μC/g or less, it was evaluated as pass (A), and otherwise it was evaluated as fail (B). The charge stability of the toner can be evaluated as good when all of the initial charge amount, the charge amount in the first printing test, the charge amount in the second printing test, and the charge amount in the third printing test are passed. , can be evaluated as defective when any one of them fails.

[Fog resistance]
Among the fog densities in the first endurance printing test, the second endurance printing test, and the third endurance printing test for each toner, the highest fog density FD _MAX is shown in Table 2 below. The fogging resistance of the toner was evaluated as good (A) when FD _MAX was 0.009 or less, and was evaluated as bad (B) when it exceeded 0.009.

[Filming resistance]
For each toner, Table 2 below shows the number of printed sheets at the time when a dash mark due to toner filming was first observed on the evaluation paper in the first printing endurance test. In Table 2 below, "None" in "Occurrence of dash marks" indicates that no dash marks were generated even after printing 100,000 sheets. The anti-filming property of the toner was evaluated as good (A) when dash marks did not occur even after printing 100,000 sheets, and as bad (B) otherwise.

Each of the toners of Examples 1 to 5 was a positively charged toner, and contained toner particles having toner base particles and an external additive adhering to the surface of the toner base particles. The external additive contained external additive particles (any of external additive particles A to E) having a substrate containing lanthanum atoms and a coating layer covering the surface of the substrate. The coating layer contained a nitrogen-containing resin and had its surface hydrophobized with an isocyanate compound having a hydrophobic group. As shown in Table 2, each of the toners of Examples 1 to 5 was excellent in charging stability, anti-fogging property and anti-filming property.

On the other hand, the toners of Comparative Examples 1 to 6, which did not have the above-described structure, were inferior in at least one of charging stability, anti-fogging property, and anti-filming property.

Specifically, the surface of the coating layer of the external additive particles F used in the toner of Comparative Example 1 was not hydrophobized. External additive particles G used in the toner of Comparative Example 2 did not use an isocyanate compound to hydrophobize the surface of the coating layer. As a result, the toners of Comparative Examples 1 and 2 had poor filming resistance.

External additive particles H, I and K used in the toners of Comparative Examples 3, 4 and 6 did not contain lanthanum atoms in the substrate. As a result, the toners of Comparative Examples 3, 4 and 6 were inferior in at least one of charging stability and anti-fogging properties.

External additive particles J used in the toner of Comparative Example 5 did not have a coating layer. As a result, the toner of Comparative Example 5 had poor charging stability and anti-fogging properties.

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

1 Toner Particle 2 Toner Base Particle 3 External Additive Particle 3a Substrate 3b Coating Layer

Claims (6)

A toner that is positively charged and non-magnetic ,
including toner particles comprising toner base particles and an external additive adhering to the surface of the toner base particles;
The external additive comprises external additive particles comprising a substrate containing lanthanum atoms and a coating layer covering the surface of the substrate,
The coating layer contains a nitrogen-containing resin and the surface is hydrophobized with an isocyanate compound having a hydrophobic group ,
The toner , wherein the isocyanate compound having a hydrophobic group is octyl isocyanate or benzyl isocyanate . 2. The toner of claim 1, wherein the substrate is lanthanum oxide particles. 3. The toner according to claim 1, wherein the hydrophobicity of the external additive particles measured by a methanol wettability method is 20% or more and 70% or less. The toner according to any one of claims 1 to 3, wherein the nitrogen-containing resin is melamine resin or urea resin. The toner according to any one of claims 1 to 4 , wherein a group represented by the following general formula (I) is present on the surface of the coating layer.

(In the general formula (I), R ¹ represents an octyl group or a benzyl group, and * represents a bonding site with the nitrogen-containing resin.) The toner according to any one of claims 1 to 5 , wherein the nitrogen atom content ratio in the external additive particles is 5.00% by mass or more and 15.00% by mass or less.

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