JP7351137B2 - Toner for developing electrostatic latent images - Google Patents

Description

The present invention relates to a toner for developing electrostatic latent images, and particularly to a toner for developing electrostatic latent images that has excellent charging stability during high coverage printing and can suppress image fogging and image quality deterioration.

In recent years, there has been an increasing demand for high-definition, high-quality images at high speeds, and it is desired that toners for forming images have stable charging properties even under such conditions. In particular, during high-coverage printing at high speeds, it is necessary for the supplied toner and carrier to be instantly tribo-electrified to reach a desired amount of charge. For this purpose, it is necessary that the toner and carrier mix easily and that the charge of the toner that comes into contact with the carrier is immediately diffused.
In order to play these roles, external additives are added to the toner surface, and generally fine powder of inorganic oxide, often silica, titania, or alumina, is used.
Although silica particles are effective in improving fluidity, they have high electrical resistance and are insufficient for charge diffusion. On the other hand, titania particles with low resistance are effective in charge diffusion, but titania Due to the low resistance, when the carrier moves to the surface of the carrier, the charge movement of the carrier is promoted, resulting in a decrease in the amount of toner charge.

In Patent Document 1, silica fine particles containing a specific amount of Na are proposed as a means for improving toner charging stability and transport amount stability. Although not specified in the text, this is thought to be because the resistance was lowered due to the influence of water molecules coordinated to the Na ions, making it easier for the charge to diffuse.
On the other hand, when the resistance is lowered by such means, the amount of charge under high temperature and high humidity is reduced due to the influence of the coordinated water molecules, and image fogging is worsened due to the low charge amount component.

Patent No. 6477688

The present invention was made in view of the above-mentioned problems and circumstances, and the object of the present invention is to provide an electrostatic latent image developing device that has excellent charging stability during high coverage printing and can suppress image fogging and image quality deterioration. toner.

In order to solve the above problem, the present inventor used silica particles that have been hydrophobized as an external additive in the process of investigating the causes of the above problems, and discovered that the silica particles contain SO ₄ and that the content of The present inventors have discovered that by setting the toner within a specific range, it is possible to provide a toner for developing electrostatic latent images that has excellent charging stability during high coverage printing and can suppress image fogging and image quality deterioration, leading to the present invention.
That is, the above-mentioned problems related to the present invention are solved by the following means.

1. A negatively charged electrostatic latent image developing toner comprising toner particles containing an external additive on at least the surface,
The external additive contains silica particles whose surfaces have been subjected to a hydrophobization treatment,
The silica particles contain SO ₄ and the content is within the range of 10 to 30,000 ppm by mass,
The silica particles contain Na, and the content is within the range of 3 to 2000 ppm by mass, and
A toner for developing an electrostatic latent image , wherein the content of SO ₄ and Na in the silica particles satisfies the following relational expression (1A).
0.3≦SO4 _content (mass ppm)/Na content (mass ppm)...(1A)

2 . 2. The toner for developing an electrostatic latent image according to item 1, wherein the silica particles contain SO ₄ and the content thereof is within a range of 50 to 15,000 ppm by mass.

3 . The toner for developing an electrostatic latent image according to item 1 or 2, wherein the content of SO ₄ and Na in the silica particles satisfies the following relational expression (1).
0.3 ≦ _SO4 content (mass ppm)/Na content (mass ppm)≦20...(1)

4 . The toner for developing an electrostatic latent image according to any one of Items 1 to 3 , wherein the surface of the silica particles is coated with alumina particles and further subjected to a hydrophobic treatment.

5 . 5. The toner for developing electrostatic latent images according to item 4 , wherein the amount of alumina covered in the silica particles coated with the alumina particles is within a range of 4 to 40% by mass.

6 . 6. The toner for developing electrostatic latent images according to item 4 or 5 , wherein the silica particles are hydrophobized with any one of silazane, alkoxysilane, and silicone oil.

7 . The toner for developing an electrostatic latent image according to any one of Items 4 to 6 , wherein the hydrophobized silica particles have a degree of hydrophobization of 30 or more.

8 . According to any one of items 1 to 7 , wherein the content of the silica particles is within a range of 0.1 to 2.0 parts by mass based on 100 parts by mass of the toner particles. The described toner for developing electrostatic latent images.

By means of the above means of the present invention, it is possible to provide a toner for developing electrostatic latent images that has excellent charging stability during high coverage printing and can suppress image fogging and image quality deterioration.
Although the mechanism of expression or action of the effects of the present invention is not clear, it is speculated as follows.
SO ₄ ions have the property of being easily stabilized by resonance and attracting electrons, and can enhance the charge diffusion ability of negatively charged toner without attracting moisture unlike Na ions. That is, in the present invention, the silica particles contain SO ₄ and the content is within the range of 10 to 30,000 ppm by mass, thereby suppressing a decrease in the charge amount of the negatively charged toner in a high temperature and high humidity environment. Charging stability can be maintained during high coverage. As a result, image fogging and image deterioration can be suppressed.
In addition, from the viewpoint of ease of mixing, silica, which is effective in improving fluidity, is preferred. In addition, when SO ₄ ions form a salt with Na ions, the charge diffusion ability is higher, and since Na ions also coordinate with SO ₄ ions rather than water molecules, hydration due to coordination is suppressed. It is possible to suppress a decrease in the amount of charge under high temperature and high humidity conditions.
It is preferable that Na ions be contained in a specific amount because they easily coordinate with SO ₄ ions and have weak coordination power with water. In addition, in order to suppress the coordination of Na ions and water molecules, it is preferable to perform hydrophobic treatment by surface treatment. Furthermore, by coating the silica surface with alumina, it becomes more densely hydrophobic. Coordination of molecules can be suppressed.

The toner for developing electrostatic latent images of the present invention is a negatively charged toner for developing electrostatic latent images comprising toner particles containing an external additive on at least the surface, wherein at least the surface of the toner is hydrophobic as the external additive. It is characterized in that it contains silica particles that have been subjected to chemical treatment, and that the silica particles contain SO ₄ and the content thereof is in the range of 10 to 30,000 ppm by mass.
This feature is a technical feature common to or corresponding to each of the embodiments described below.

In an embodiment of the present invention, the silica particles contain Na, and the content is in the range of 3 to 2000 mass ppm, so that SO ₄ ions can stably exist in the silica particles, and , is preferable in that it can suppress the coordination bond of water molecules to Na ions.

The silica particles contain SO ₄ and the content is in the range of 50 to 15,000 ppm by mass, since charge diffusion is sufficiently performed, image fog is suppressed, and dot reproducibility is excellent. preferable.
The content of SO ₄ and Na in the silica particles satisfying the above relational expression (1) eliminates the influence of water molecules coordinating with Na ions, resulting in excellent image stability and dot reproducibility. It is preferable in that it is also excellent.

It is preferable that the surface of the silica particles be coated with alumina particles and further subjected to a hydrophobic treatment in order to obtain the effect of reducing hygroscopicity.
The coating amount of alumina in the silica particles coated with the alumina particles is within the range of 4 to 40% by mass, so that the surface treatment of the silica particles can be uniformly performed, and the hygroscopicity does not increase, and the coating amount of alumina is within the range of 4 to 40% by mass. This is preferable in that it is possible to suppress deterioration of image quality and occurrence of fogging due to large fluctuations in the amount of charge under high humidity. Further, the shape of the silica particles does not change, and the fluidity deteriorates, thereby suppressing the deterioration of image quality stability during durability.

It is preferable that the silica particles are hydrophobized with any one of silazane, alkoxysilane, or silicone oil, since they generally exhibit negative chargeability and can provide the effect of charge diffusion.
It is preferable that the degree of hydrophobization of the hydrophobized silica particles is 30 or more, since the surface of the silica particles can be sufficiently hydrophobized and the effect of reducing hygroscopicity can be obtained.
The content of the silica particles is within the range of 0.1 to 2.0 parts by mass based on 100 parts by mass of the toner particles, so that charge diffusion is sufficiently performed and charging stability is excellent. This is preferable in that image fogging and image deterioration can be suppressed. In addition, highly negatively charged parts are not locally generated, and as a result, the adhesive force does not increase and dot reproducibility does not deteriorate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, its constituent elements, and forms and aspects for carrying out the present invention will be described below. In this application, "~" is used to include the numerical values described before and after it as a lower limit value and an upper limit value.

[Overview of toner for developing electrostatic latent images of the present invention]
The toner for developing electrostatic latent images of the present invention is a negatively charged toner for developing electrostatic latent images comprising toner particles containing an external additive on at least the surface, wherein at least the surface of the toner is hydrophobic as the external additive. The silica particles contain SO ₄ and the content is within the range of 10 to 30000 ppm by mass, and the silica particles contain Na and the content is within the range of 10 to 30000 ppm by mass. is within the range of 3 to 2000 ppm by mass, and the content of SO ₄ and Na in the silica particles satisfies the following relational expression (1A).
0.3≦SO4 _content (mass ppm)/Na content (mass ppm)...(1A)

<Silica particles>
The external additive according to the present invention contains silica particles whose at least surfaces have been subjected to hydrophobization treatment.
The silica particles contain SO ₄ , and the content is preferably in the range of 10 to 30,000 ppm by mass, particularly preferably in the range of 50 to 15,000 ppm by mass. When it is 10 mass ppm or more, charge diffusion is sufficiently performed, charging stability is excellent, and image fogging and image deterioration can be suppressed. Moreover, if it is 30,000 mass ppm or less, a highly negatively charged portion will not be locally generated due to SO ₄ . As a result, the adhesion force increases and dot reproducibility does not deteriorate.

Further, the silica particles preferably contain Na (sodium), and the content thereof is preferably in the range of 3 to 2000 ppm by mass. If it is 3 mass ppm or more, SO ₄ is stably present, and if it is 2000 mass ppm or less, there will be fewer water molecules coordinating with Na ions, and due to the influence of water molecules, SO 4 will be present in a stable manner at the initial stage and in high humidity and high temperature environments. The image stability is excellent without widening environmental differences.

It is preferable that the contents of SO ₄ and Na in the silica particles satisfy the following relational expression (1).
0.3 ≦ _SO4 content (ppm)/Na content (ppm)≦20...(1)
In the above relational expression (1), when it is 0.3 or more, the influence of water molecules coordinating to Na ions is small, and the environmental difference between the initial stage and the high-humidity, high-temperature environment does not widen due to the influence of water molecules. , excellent image stability. Moreover, when it is 20 or less, a highly negatively charged portion will not be locally generated due to SO ₄ . As a result, the adhesion force increases and dot reproducibility does not deteriorate.

(Measurement method for SO ₄ and Na ion content)
The amount of SO ₄ and Na ions contained in the silica particles is determined by dissolving the silica particles in hydrofluoric acid, volatilizing the generated silicon fluoride by heating, and dipping the resulting dry solid with ultrapure water. After dissolving, it is measured by analysis using ion chromatography.
Specifically, first, 100 mg of silica is dispersed in 10 mL of hydrofluoric acid and sufficiently heated using a hot plate. The obtained dried product was diluted by appropriately adding ultrapure water, and then analyzed using an ion chromatography device (manufactured by Nippon Dionex Co., Ltd., model number ICS-5000) under the following conditions to determine the SO ₄ and Na ions in the toner. Find the content of.

(Analysis conditions)
Ion separation column: Nippon Dionex Co., Ltd. IonPacAS12A, IonPacCS12A
Ion guard column: Nippon Dionex Co., Ltd. IonPacAG12A, IonPacCG12A
Eluent: _Na2CO3 ( _2.7mM )/ _NaHNO3 (0.3mM)
Flow rate: 1.5mL/min
Detection method: Electric conductivity method (suppressor method)

It is preferable that the surface of the silica particles be coated with alumina particles and further subjected to a hydrophobizing treatment, since the effect of reducing hygroscopicity can be obtained.
A wet method is preferable as the method for coating with alumina particles, since it enables more uniform coating. For example, an aluminum hydroxide raw material is added dropwise to a predetermined aqueous dispersion of silica particles in a basic environment, and the system is stirred for a predetermined period of time. As a result, silica particles can be obtained in which fine alumina particles are precipitated and formed on the surface and chemically bonded with alumina.

The amount of alumina covered in the silica particles coated with the alumina particles is preferably within the range of 4 to 40% by mass. When the content is 4% by mass or more, the surface treatment of the silica particles can be uniformly performed, hygroscopicity does not increase, and fluctuations in the amount of charge are suppressed under high temperature and high humidity conditions, and image quality deteriorates due to deterioration of fluidity. It is possible to prevent the occurrence of fog and fog. When the amount is 40% by mass or less, the shape of the silica particles does not change, and deterioration of image quality stability during durability due to deterioration of fluidity can be suppressed.
Note that impurities other than alumina may be included as long as the alumina content is within the above range.

(Measurement method of alumina content)
In silica particles coated with alumina particles, the alumina content can be measured using an X-ray fluorescence analyzer "XRF-1700" (manufactured by Shimadzu Corporation). As a specific measurement method, 3 g of the sample is pressurized to pelletize it, and qualitative analysis is performed under the following conditions. In addition, for the measurement, the Kα peak angle of the element to be measured was determined from the 2θ table and used.
・X-ray generator conditions/target Rh, tube voltage 40 kV, tube current 95 mA, no filter ・Spectroscopic system conditions/slit standard, attenuator none, spectroscopic crystal (Al = PET) Alumina content is Al Kα in alumina alone It was calculated as the value of the net intensity of the analytical line divided by the value of the net intensity of the Al Kα analytical line with silica particles coated with alumina particles.

The number average particle diameter of the primary particles of the silica particles is preferably within the range of 7 to 150 nm, particularly preferably within the range of 10 to 70 nm. When it is 7 nm or more, it is difficult to be buried in the toner base particles, and when it is 150 nm or less, fluidity does not deteriorate and stability against coverage dependence can be obtained.
In order to ensure fluidity, the silica particles are preferably spherical, disc-shaped, or needle-shaped without corners.

(Method for measuring number average particle diameter)
The number average particle diameter is determined by taking a SEM photograph of the toner magnified 30,000 times using a scanning electron microscope (SEM) "JSM-7401F" (manufactured by JEOL Ltd.), and observing the SEM photograph. The particle size (Ferret diameter) of the primary silica particles is measured, and the average particle size is determined by dividing the total value by the number of particles. The particle size is measured by selecting an area in the SEM image where the total number of particles is about 100 to 200.

It is preferable that the silica particles be hydrophobized with any one of silazane, alkoxysilane, or silicone oil, from the viewpoint of obtaining the effect of charge diffusion.

Specific examples of silazane and alkoxysilane include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, and diphenyldimethoxysilane. , tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, tert-butyldimethylchlorosilane , vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ Typical examples include -glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane.

Specific examples of silicone oil include dimethyl silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, carboxyl-modified silicone oil, epoxy-modified silicone oil, fluorine-modified silicone oil, alcohol-modified silicone oil, polyether-modified silicone oil, Methylphenyl silicone oil, methyl hydrogen silicone oil, mercapto-modified silicone oil, higher fatty acid-modified silicone oil, phenol-modified silicone oil, methacrylic acid-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, etc. can be used. Moreover, among these, it is preferable to use dimethyl silicone oil as the silicone oil from the viewpoint of cost and ease of handling.
Furthermore, dimethyl silicone oil, these modified silicone oils, and other surface treatment agents may be mixed or treated in combination. Examples of the processing agent used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esterified products thereof, rosin acid, etc. .

Surface treatment methods include, for example, a dry method such as a spray drying method in which a treatment agent or a solution containing a treatment agent is sprayed onto particles suspended in a gas phase, and a dry method in which particles are immersed in a solution containing a treatment agent. Examples include a wet method in which the treatment agent is dried and a mixing method in which the processing agent and particles are mixed using a mixer.

It is preferable that the degree of hydrophobization of the hydrophobized silica particles is 30 or more. When it is 30 or more, surface hydrophobization becomes sufficient and the effect of reducing hygroscopicity is obtained.

(Method for measuring degree of hydrophobicity)
In a laboratory environment, put a stirrer chip with a length of 20 mm and 60 mL of ion-exchanged water in a 100 mL tall beaker, irradiate it with ultrasonic waves for 5 minutes to degas it, and use the powder wettability tester WET-100P (Resca Co., Ltd.). (manufactured by). 25 mg of the toner sample was floated on the ion-exchanged water, and then the lid and methanol supply nozzle were immediately set, and the measurement was started at the same time as stirring by the stirrer was started. The methanol supply rate was 1.6 mL/min, and the measurement time was 30 min. The stirring speed of the stirrer was adjusted to 350 to 450 rpm. Initially, the toner floats on the ion-exchanged water interface, but as the methanol concentration increases, the toner gradually gets wet with the mixture of ion-exchanged water and methanol and is dispersed in the liquid, reducing the light transmittance of the liquid. The wettability is evaluated based on the appearance of this decrease.
Specifically, from the obtained data, the methanol concentration (voL%) calculated from Flow (mL) is plotted on the horizontal axis, and the light transmittance (voltage ratio (%)) is plotted on the vertical axis. The methanol concentration between the maximum and minimum values was defined as the "degree of hydrophobicity."

The content of the silica particles is preferably within a range of 0.1 to 2.0 parts by mass based on 100 parts by mass of toner particles. When the amount is 0.1 part by mass or more, charge diffusion is sufficiently performed, and charging stability is excellent, and image fogging and image deterioration can be suppressed. Further, if the amount is 2.0 parts by mass or less, a highly negatively charged portion will not be locally generated due to SO ₄ . As a result, the adhesion force increases and dot reproducibility does not deteriorate.

(Method for manufacturing silica particles)
Although the silica particles according to the present invention can be produced by a known method, it is preferable to produce them by a wet method, particularly by a precipitation method in order to adjust the SO ₄ content.
In the precipitation method, silica is generally synthesized by a neutralization reaction of sodium silicate and sulfuric acid. The content of SO ₄ is mainly adjusted by the pH of this reaction field, but it can also be adjusted by the conditions of subsequent filtration and water washing (pH adjustment, additional addition of ions, etc.).

Specifically, the precipitation method will be explained.
First, wet-process synthetic silica, which is a raw powder, is pretreated by adding a strong acid, strong base type, neutral salt compound, such as sodium sulfate (Na ₂ SO ₄ ) component, which is a substance that serves as a catalyst.
In addition to sodium sulfate, examples of strong acid/strong base type neutral salt compounds include sodium chloride, potassium sulfate, potassium chloride, and mixtures thereof. The amount of the strong acid/strong base type neutral salt compound present on the surface of the wet-process synthetic silica is, for example, suitably in the range of 0.3 to 3.0% by mass.
The pretreatment method is not particularly limited, but when the silica synthesis reaction is completed, sodium sulfate (Na ₂ SO ₄ ), a reaction by-product, is washed with water until it reaches a predetermined amount, and then the pH is adjusted and used. Alternatively, after thorough washing with water, add a predetermined amount of sodium sulfate (Na ₂ SO ₄ ) in a slurry state, and adjust the pH with an alkali such as sodium hydroxide (NaOH) as necessary. Examples include a method in which only a predetermined amount of sulfuric acid (H ₂ SO ₄ ) is added to the silica slurry, and the pH is adjusted later using sodium hydroxide (NaOH).

Thereafter, it undergoes drying, pulverization, and classification steps to become wet-process synthetic silica having the desired particle size. The Na component and S component contained in the wet-process synthetic silica, which is the raw powder at this time, are approximately 0.3 to 1.4 mass% in terms of Na ₂ O and 0.36 to 1.44 in terms of SO ₃ , respectively. Adjust to the desired range around mass%. These values indicate the amount of impurities in the raw powder, and tend to be slightly different from the amount of impurities contained in the final product, hydrophobic silica. If the amount of Na ₂ O is too small, the catalytic effect will be low, and even if it is too large, not only will the catalytic effect not be significantly improved, but the silica will contain a large amount of salts, which is not preferable. Moreover, S and SO ₃ are acidic components for suppressing basicity due to Na, and by setting them within the above range, it is possible to suppress bias toward basicity.

When the raw powder, wet-process synthetic silica, is pretreated with only an alkaline component such as sodium hydroxide (NaOH), or only with an acidic component such as sulfuric acid (H ₂ SO ₄ ), The wet method synthetic silica component is undesirable because it becomes alkaline and acidic, respectively, and it is necessary that both components exist in a well-balanced manner and that the pH is around neutral. Considering the use and purpose, the pH of the raw powder, wet-process synthetic silica, is preferably in the range of 5.5 to 8.0, which is near neutrality.

In addition, in the case of wet-process synthetic silica, it may contain aluminum-based impurities derived from natural ores as raw materials, but if there is a large amount of aluminum as an impurity in wet-process synthetic silica, the catalytic effect tends to decrease. The amount of aluminum contained in the wet-process synthetic silica, which is the raw powder, is preferably less than 0.5% by mass in terms of Al ₂ O ₃ .

<Other external additives>
In addition to silica particles, other known external additives may be included as external additives, but silica particles with high negative chargeability are particularly preferred because they facilitate the effect of charge diffusion.
In addition, other known external additives may be further included. As known external additives, for example, inorganic fine particles, organic fine particles, and lubricants can be used.

Examples of inorganic fine particles include inorganic oxide fine particles such as aluminum oxide fine particles and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, or inorganic fine particles such as strontium titanate and zinc titanate. Examples include titanic acid compound fine particles. These inorganic fine particles are subjected to gloss treatment, hydrophobization treatment, etc. using silane coupling agents, titanium coupling agents, higher fatty acids, silicone oil, etc. in order to improve heat-resistant storage properties and environmental stability. You can.

As the organic fine particles, for example, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, organic fine particles made of homopolymers such as styrene or methyl methacrylate or copolymers thereof can be used.

The lubricant is used for the purpose of further improving cleaning properties and transfer properties. As the lubricant, for example, metal salts of higher fatty acids can be used. Specific examples of metal salts of higher fatty acids include stearic acid salts of zinc, aluminum, copper, magnesium, calcium, etc., oleic acid salts of zinc, manganese, iron, copper, magnesium, etc., zinc palmitic acid, Examples include salts of copper, magnesium, calcium, etc., salts of linoleic acid such as zinc and calcium, salts of ricinoleic acid such as zinc and calcium, and the like.

<Toner base particles>
The toner base particles according to the present invention contain at least a binder resin.
Further, the toner base particles according to the present invention may contain other constituent components such as a release agent (wax), a colorant, and a charge control agent, if necessary.

In the present invention, toner base particles to which an external additive is added are referred to as toner particles, and an aggregate of toner particles is referred to as a toner. Generally, toner base particles can be used as toner particles as they are, but in the present invention, toner base particles to which an external additive is added are used as toner particles.

(Binder resin)
As the binder resin constituting the toner base particles, a known amorphous resin can be used. Specific examples thereof include vinyl resin, urethane resin, urea resin, polyester resin, and the like. Among these, polyester resins having an acid value are preferred because their OH groups have electron-donating properties, making it easier to obtain the effect of charge diffusion by SO ₄ .

The polyester resin according to the present invention is produced by a polycondensation reaction using polycarboxylic acid monomers (derivatives) and polyhydric alcohol monomers (derivatives) as raw materials in the presence of an appropriate catalyst.

As polyhydric carboxylic acid monomer derivatives, alkyl esters, acid anhydrides, and acid chlorides of polyhydric carboxylic acid monomers can be used, and as polyhydric alcohol monomer derivatives, ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acids can be used. can be used.
Examples of polycarboxylic acid monomers include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, and fumaric acid. Acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucinic acid, phthalic acid, Isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylene diacetic acid, m-phenylene diglycolic acid, p-phenylene diglycolic acid, o-phenylene diglycolic acid, Divalent acids such as diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, dodecenylsuccinic acid, etc. Carboxylic acids of trivalent or higher valence such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid. As the polycarboxylic acid monomer, it is preferable to use unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and mesaconic acid. Further, in the present invention, dicarboxylic acid anhydrides such as maleic anhydride can also be used.

Examples of polyhydric alcohol monomers include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. Dihydric alcohols such as trihydric or higher hydric alcohols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine.

The weight average molecular weight (Mw) of the polyester resin is preferably within the range of 10,000 to 100,000.

The method for producing polyester resin is not particularly limited, and any polymerization initiator such as peroxide, persulfide, persulfate, or azo compound commonly used in the polymerization of the above monomers is used, and bulk polymerization, solution polymerization, etc. Examples include polymerization methods using known polymerization methods such as polymerization, emulsion polymerization method, miniemulsion method, and dispersion polymerization method. Furthermore, a commonly used chain transfer agent can be used for the purpose of adjusting the molecular weight. The chain transfer agent is not particularly limited, and examples include alkyl mercaptans such as n-octyl mercaptan, mercapto fatty acid esters, and the like.

The glass transition temperature (Tg) of the resin is not particularly limited, but is within the range of 30 to 70°C from the viewpoint of ensuring fixing properties such as low-temperature fixing properties, and heat resistance such as heat-resistant storage property and blocking resistance. It is preferable that

Moreover, regardless of the above-mentioned amorphous resin, it is preferable to use a crystalline resin in combination from the viewpoint of low-temperature fixability. In particular, it is preferable to use a crystalline polyester resin from the viewpoint of compatibility with the above-mentioned amorphous resin and manufacturability.

The binder resin according to the present invention preferably contains an amorphous resin in a range of 80 to 99.9% by mass, and a crystalline polyester resin in a range of 0.1 to 20% by mass based on the entire binder resin. The content is preferably within the range of .

(Release agent)
As the mold release agent according to the present invention, various known waxes can be used.
Examples of waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long-chain hydrocarbon waxes such as paraffin wax and Sasol wax, and dialkyl waxes such as distearyl ketone. Ketone wax, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol dibehenate Examples include ester waxes such as stearate, tristearyl trimellitate, and distearyl maleate, and amide waxes such as ethylenediamine behenylamide and tristearyl trimellitate. From the viewpoint of fixing properties, hydrocarbon waxes are preferred.
The content of the release agent is preferably in the range of 0.1 to 30 parts by weight, more preferably in the range of 1 to 10 parts by weight, based on 100 parts by weight of the binder resin.
These can be used alone or in combination of two or more. Further, the melting point of the release agent is preferably within the range of 50 to 95° C. from the viewpoint of low-temperature fixing properties and release properties of the toner in electrophotography.

(colorant)
As the coloring agent according to the present invention, carbon black, magnetic material, dye, pigment, etc. can be arbitrarily used. As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, etc. are used. be done.
As the magnetic material, ferromagnetic metals such as iron, nickel, or cobalt, alloys containing these metals, ferrite, or compounds of ferromagnetic metals such as magnetite can be used.
As a dye, C. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C. I. Solvent Blue 25, Solvent Blue 36, Solvent Blue 60, Solvent Blue 70, Solvent Blue 93, Solvent Blue 95, etc. can be used, and mixtures thereof can also be used. As a pigment, C. I. Pigment Red 5, 48:1, 48:3, 53:1, 57:1, 81:4, 122, 139, 144, 149, 166, 177, 178, 222, C. I. Pigment Orange 31, Pigment Orange 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C. I. Pigment Green 7, C. I. Pigment Blue 15:3, Pigment Blue 15:4, or Pigment Blue 60 can be used, and mixtures thereof can also be used.
The content of the colorant is preferably in the range of 1 to 10 parts by weight, more preferably in the range of 2 to 9 parts by weight, based on 100 parts by weight of the binder resin.

(Charge control agent)
As the charge control agent according to the present invention, various known ones that can be dispersed in an aqueous medium can be used. Specific examples include nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts, or metal complexes thereof.
The content of the charge control agent is preferably in the range of 0.01 to 30 parts by weight, more preferably in the range of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder resin.

<Form of toner base particles>
The toner base particles may have a so-called single-layer structure or a core-shell structure (a form in which a resin forming a shell layer is aggregated and fused on the surface of a core particle). It is preferable that the toner has a core-shell structure, since it has good properties and low-temperature fixability.
Note that the core-shell structure is not limited to a structure in which the shell layer completely covers the core particle; for example, the shell layer does not completely cover the core particle and the core particle is exposed in some places. Including those who are present.

The above-mentioned morphology of the toner base particles (core-shell cross-sectional structure) can be confirmed using known means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM), for example. .

<Average circularity of toner particles>
The average circularity of the toner particles is preferably within the range of 0.935 to 0.995, more preferably within the range of 0.945 to 0.990, and more preferably within the range of 0.955 to 0.980. It is more preferable that the range is within If the average circularity falls within this range, individual toner particles will be less likely to be crushed, the amount of charge will be stable, and the image quality will be high.
Note that the average circularity can be measured using, for example, a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex).

[Toner manufacturing method]
The method for producing the toner of the present invention is not particularly limited, and includes known methods such as a kneading and pulverization method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, a polyester stretching method, and a dispersion polymerization method. Among these, it is preferable to employ the emulsion aggregation method from the viewpoint of particle size uniformity and shape controllability.

<Emulsification aggregation method>
The emulsion aggregation method is a method in which a dispersion of binder resin particles (hereinafter also referred to as "binder resin particles") dispersed with a surfactant or dispersion stabilizer is mixed with colorant particles ( (Hereinafter, also referred to as "colorant particles"), the toner particles are mixed with a dispersion liquid, agglomerated until the desired toner particle size is reached, and the shape of the toner particles is controlled by fusing the binder resin particles. This is a method of manufacturing. Here, the binder resin particles may optionally contain a release agent, a charge control agent, and the like.
As a preferred method for producing the toner according to the present invention, an example of obtaining toner particles having a core-shell structure using an emulsion aggregation method will be shown below.

(1) A step of preparing a colorant particle dispersion liquid in which colorant particles are dispersed in an aqueous medium. (2) A process in which binder resin particles containing an internal additive are dispersed in an aqueous medium as necessary. Step of preparing a resin particle dispersion (resin particle dispersion for core/shell) (3) Mixing a colorant particle dispersion and a resin particle dispersion for core to obtain a resin particle dispersion for aggregation, A step of agglomerating and fusing colorant particles and binder resin particles in the presence of a flocculant to form agglomerated particles as core particles (aggregation/fusing step)
(4) A shell resin particle dispersion containing binder resin particles for the shell layer is added to the dispersion containing the core particles, and the particles for the shell layer are aggregated and fused on the surface of the core particles to form a core.・Process of forming shell-structured toner base particles (agglomeration/fusion process)
(5) Step of filtering toner base particles from a dispersion of toner base particles (toner base particle dispersion) and removing surfactant, etc. (washing step)
(6) Step of drying toner base particles (drying step)
(7) Step of adding external additives to toner base particles (external additive treatment step)

Toner particles having a core-shell structure are produced by first aggregating and fusing binder resin particles for the core particles and colorant particles to prepare core particles, and then adding particles for the shell layer to a dispersion of the core particles. It can be obtained by adding binder resin particles for a shell layer to the surface of the core particle and agglomerating and fusing the binder resin particles for the shell layer to form a shell layer covering the surface of the core particle. However, for example, in the step (4) above, toner particles formed from single-layer particles can be similarly produced without adding the shell resin particle dispersion.

<External addition treatment>
A mechanical mixing device can be used to perform the external addition mixing process on the toner base particles.
As the mechanical mixing device, a Henschel mixer, a Nauta mixer, a turbular mixer, etc. can be used. Among these, a mixing device such as a Henschel mixer that can apply shearing force to the particles to be treated may be used to perform the mixing process by lengthening the mixing time or increasing the rotational speed of the stirring blade. In addition, when using multiple types of external additives, either all of the external additives are mixed with the toner base particles at once, or the mixture is divided into multiple batches depending on the external additives. It's okay.
The external additive mixing method uses the mechanical mixing device described above to control the mixing intensity, that is, the circumferential speed of the stirring blade, the mixing time, the mixing temperature, etc., to control the degree of crushing and adhesion strength of the external additive. can be controlled.

[Two-component developer]
Although the toner of the present invention can be used as a magnetic or nonmagnetic one-component developer, it is preferable to mix it with a carrier and use it as a two-component developer.
When the toner is used as a two-component developer, the carrier preferably includes carrier particles whose surfaces are coated with a coating resin.

(core material particles)
Examples of the core particles (magnetic particles) used in the present invention include iron powder, magnetite, various ferrite particles, or those dispersed in a resin. Preferred are magnetite and various ferrite particles. As the ferrite, ferrites containing heavy metals such as copper, zinc, nickel, and manganese, and light metal ferrites containing alkali metals and/or alkaline earth metals are preferable.
Further, it is preferable that the core material particles contain Sr (strontium). By containing Sr, the unevenness on the surface of the core particle can be increased, and even when coated with a coating resin, the surface is easily exposed, making it easier to adjust the resistance of the carrier.

(Particle size of core material particles)
The volume average particle diameter of the core material particles is preferably within the range of 10 to 100 μm, more preferably within the range of 20 to 80 μm.
The volume average particle diameter of the core material particles can be typically measured using a laser diffraction particle size distribution analyzer "HELOS" (manufactured by SYMPATEC) equipped with a wet disperser.

(Coating resin)
Coating resins suitable for forming the carrier coating layer include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polystyrene, polyacrylates such as polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, Polyvinyl and polyvinylidene resins such as polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polybiliketone; copolymers such as vinyl chloride-vinyl acetate copolymer and styrene-acrylic acid copolymer; consisting of organosiloxane bonds Silicone resins or modified resins thereof (for example, modified resins such as alkyd resins, polyester resins, epoxy resins, and polyurethanes); Fluororesins such as polytetrachloroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyamides; These include polyester; polyurethane; polycarbonate; amino resin such as urea-formaldehyde resin; and epoxy resin.

Particularly preferred is a polyacrylate resin, which contains a resin formed from an alicyclic methacrylate monomer with low hygroscopicity, thereby suppressing fluctuations in the amount of charge due to environmental differences and preventing embedding of silica particles due to collisions between toner and carrier. It is preferable because it is suppressed.
Alicyclic methacrylate monomers have a cycloalkyl group having 5 to 8 carbon atoms from the viewpoints of mechanical strength, environmental stability of charge amount (small environmental difference in charge amount), ease of polymerization, and availability. It is preferable. The alicyclic methacrylate monomer is at least one selected from the group consisting of cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. is preferred. Among these, it is preferable to include cyclohexyl (meth)acrylate from the viewpoint of mechanical strength and environmental stability of charge amount.
The copolymer ratio of the alicyclic methacrylate monomer is preferably 50% or more, more preferably 75% or more.

Specific methods for producing the coating layer include a wet coating method and a dry coating method. Each method will be described below, but the dry coating method is a particularly desirable method for application to the present invention, and will be described in detail in .
Wet coating methods include the following.
(1) Fluidized bed spray coating method A method in which a coating solution in which a coating resin is dissolved in a solvent is sprayed onto the surface of core particles using a fluidized bed, and then dried to produce a coating layer. (2) Dip coating method A method in which the core material particles are dipped into a coating solution in which the coating resin is dissolved in a solvent, and then dried to form a coating layer. (3) Polymerization method A reactive compound is dissolved in a solvent. Examples include a method in which core material particles are immersed in a dissolved coating liquid for coating treatment, and then heat or the like is applied to perform a polymerization reaction to produce a coating layer.

In the dry coating method, resin particles are applied to the surface of the core material particles to be coated, and then mechanical impact force is applied to melt or melt the resin particles adhered to the surface of the core material particles to be coated. This is a method of softening and fixing to create a covering layer.
Using a high-speed stirring mixer that can apply mechanical impact force to the core material particles, resin, low-resistance fine particles, etc. without heating or under heating, high-speed stirring is used to repeatedly apply impact force to the mixture. A carrier is prepared by dissolving or softening and fixing the particles onto the surface of the particles.
When heating, the coating conditions are preferably within the range of 80 to 130°C, and the wind speed that causes the impact force is preferably 10 m/s or more during heating, and 5 m/s or more during cooling to suppress aggregation of carrier particles. /s or less is preferable. The time for applying impact force is preferably 20 to 60 minutes.

A method of peeling off the resin on the convex portions of the core particles by applying stress to the carrier in the resin coating step or the post-coating step described above to expose the core particles will be described.
In the resin coating step using the dry coating method, resin peeling can be caused by lowering the heating temperature to 60° C. or lower and setting the wind speed during cooling to high shear. The post-coating process can be carried out using any device that can perform forced stirring, such as stirring and mixing using a turbulator, ball mill, vibration mill, or the like.
Next, as described above, the method of applying heat and shock to the coat resin to move the resin on the surface of the convex part to the concave part side and expose the core material particles is to take a long time to apply the impact force. becomes effective. Specifically, it is preferable to set the time period to one and a half hours or more.

[Image forming method]
The image forming method according to the present invention includes forming an image forming layer on a recording medium using the toner of the present invention.
The image forming method according to the present invention is a method using the toner of the present invention, and can be suitably used in a full-color image forming method. A full-color image forming method requires four types of color developing devices for each of yellow, magenta, cyan, and black, and one electrostatic latent image carrier (also referred to as an "electrophotographic photoreceptor" or simply "photoreceptor"). A method using a 4-cycle type image forming apparatus consisting of Any image forming method can be used, such as the method used.
In addition, when clear toner is further used, five types of developing devices for each of yellow, magenta, cyan, black, and clear, and one electrostatic latent image carrier ("electrophotographic photoreceptor" or simply "photoreceptor") are required. A method using a 5-cycle image forming device consisting of a 5-cycle image forming device (also referred to as a “body”), and an image forming unit equipped with a developing device for each color including clear toner and an electrostatic latent image carrier for each color. An image forming method such as a method using a tandem type image forming apparatus can be used.

Preferred examples of the image forming method include an image forming method including a fixing step using a heat-pressure fixing method that can apply pressure and heat.
Specifically, in this image forming method, the above toner is used to develop an electrostatic latent image formed on a photoconductor to obtain a toner image, and this toner image is transferred to an image support. By transferring the toner image onto the image support and then fixing the toner image transferred onto the image support by heat-pressure fixing, a printed matter on which a visible image is formed can be obtained.
The application of pressure and heating in the fixing step are preferably performed at the same time, and pressure may be applied first and then heating may be performed.

Further, the image forming method according to the present invention is suitably used in a heat-pressure fixing type image forming method. As the heat-pressure fixing type fixing device used in the image forming method according to the present invention, various known fixing devices can be employed. Hereinafter, a heat roller type fixing device and a belt heating type fixing device will be described as the heat pressure fixing device.

(i) Heat Roller Type Fixing Device A heat roller type fixing device generally includes a roller pair including a heating roller and a pressure roller that comes into contact with the heating roller. In the fixing device, when the pressure roller is deformed by the pressure applied between the heating roller and the pressure roller, a so-called fixing nip portion is formed in this deformed portion.
A heating roller is generally a hollow metal roller made of aluminum or the like, with a heat source such as a halogen lamp disposed inside a core metal. The heating roller has a core metal heated by the heat source. At this time, the temperature is adjusted by controlling the power supply to the heat source so that the outer peripheral surface of the heating roller is maintained at a predetermined fixing temperature.
The fixing device has the ability to sufficiently heat and melt a toner image consisting of four toner layers (yellow, magenta, cyan, and black) or five toner layers (yellow, magenta, cyan, black, and clear) to mix colors. When used in an image forming apparatus that forms required full-color images, it is preferable to have the following configuration.
That is, the fixing device includes a core metal having a high heat capacity as a heating roller, and an elastic layer formed on the outer peripheral surface of the core metal for uniformly melting the toner image. preferable.

Further, the pressure roller has an elastic layer made of soft rubber such as urethane rubber or silicone rubber.
As the pressure roller, one having a core made of a hollow metal roller made of aluminum or the like and having an elastic layer formed on the outer peripheral surface of the core may be used.
Furthermore, when the pressure roller has a core metal, a heat source such as a halogen lamp may be provided inside the core metal, similar to the heating roller. The core metal may be heated by the heat source, and the temperature may be adjusted by controlling power supply to the heat source so that the outer circumferential surface of the pressure roller is maintained at a predetermined fixing temperature.
The outermost layer of these heating rollers and pressure rollers is a release layer made of a fluororesin such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). It is preferable to use one formed by the following methods.
In such a heat roller type fixing device, the image support on which a visible image is to be formed is conveyed in the fixing nip by rotating a pair of rollers, thereby controlling the heating by the heating roller and the pressure in the fixing nip. This fixes the unfixed toner image to the image support.

The image forming method according to the present invention also has good low-temperature fixability. Therefore, in the heat roller type fixing device, the temperature of the heat roller can be made relatively low, specifically, 150° C. or less. Further, the temperature of the heating roller is preferably 140°C or lower, more preferably 135°C or lower. From the viewpoint of excellent low-temperature fixing properties, the lower the temperature of the heating roller, the more preferable it is, and the lower limit thereof is not particularly limited, but is substantially about 90°C.

(ii) Belt heating type fixing device A belt heating type fixing device generally consists of a heating body made of, for example, a ceramic heater, a pressure roller, and a heat-resistant belt between the heating body and the pressure roller. The fixing belt is sandwiched between the fixing belt and the pressure roller is deformed by the pressure applied between the heating body and the pressure roller, so that a so-called fixing nip is formed in this deformed part. It is.

As the fixing belt, a heat-resistant belt or sheet made of polyimide or the like is used. Furthermore, the fixing belt has a heat-resistant belt or sheet made of polyimide or the like as a base, and a fluorine-containing material such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is coated on the base. It may have a structure in which a mold release layer made of resin or the like is formed, and further, it may have a structure in which an elastic layer made of rubber or the like is provided between the base body and the mold release layer. .

In such a belt heating type fixing device, an image support carrying an unfixed toner image is sandwiched and conveyed together with the fixing belt between a fixing belt and a pressure roller that form a fixing nip. As a result, the unfixed toner image is fixed to the image support by heating by the heating body via the fixing belt and applying pressure at the fixing nip.
According to such a belt heating type fixing device, the heating body may be heated to a predetermined fixing temperature by energizing the heating body only during image formation. Therefore, it is possible to shorten the waiting time from when the power of the image forming apparatus is turned on until it reaches a state where image formation can be performed. Further, the power consumption of the image forming apparatus during standby is extremely small, and there are advantages such as power saving can be achieved.

As described above, the heating body, pressure roller, and fixing belt used as the fixing member in the fixing step preferably have a plurality of layers.
In the above-mentioned belt heating type fixing device, the temperature of the heating body can be made relatively low, and specifically, it can be kept at 150° C. or less. Further, the temperature of the heating body is preferably 140°C or lower, more preferably 135°C or lower. From the viewpoint of excellent low-temperature fixing properties, the lower the temperature of the heating element, the better, and the lower limit thereof is not particularly limited, but is substantially about 90°C.

<Recording medium>
The recording medium (also referred to as recording material, recording paper, recording paper, etc.) may be one that is commonly used, such as one that holds a toner image formed by a known image forming method using an image forming apparatus or the like. However, it is not particularly limited. Usable image supports include, for example, plain paper from thin paper to thick paper, high-quality paper, art paper, coated printing paper such as coated paper, commercially available Japanese paper, postcard paper, OHP paper, etc. Examples include plastic films, cloth, various resin materials used in so-called flexible packaging, resin films formed from these materials, and labels.
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various changes can be made.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In addition, in the following examples, unless otherwise specified, operations were performed at room temperature (25° C.). Further, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[Toner base particles]
<Preparation of amorphous polyester resin particle dispersion>
<<Preparation of amorphous polyester resin (A1)>>
- Bisphenol A ethylene oxide 2.2 mole adduct 62 parts by mass - Bisphenol A propylene oxide 2.2 mole adduct 381 parts by mass - Dimethyl terephthalate 85 parts by mass - Dimethyl fumarate 18 parts by mass - Dodecenylsuccinic anhydride 80 parts by mass - 10 parts by mass of trimellitic anhydride In a reaction vessel equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas introduction tube, among the above monomers, the monomers other than dimethyl fumarate and trimellitic anhydride and dioctylic acid were added. 0.25 parts by mass of tin was added to 100 parts by mass of the above monomers in total. After reacting at 235° C. for 6 hours under a nitrogen gas stream, the temperature was lowered to 200° C., dimethyl fumarate and trimellitic anhydride were added, and the mixture was reacted for 1 hour. The temperature was raised to 220° C. over 5 hours and polymerized under a pressure of 10 kPa until a desired molecular weight was reached, yielding a pale yellow transparent amorphous polyester resin (A1).
The amorphous polyester resin (A1) had a weight average molecular weight of 35,000, a number average molecular weight of 8,000, and a glass transition temperature (Tg) of 56°C.

<<Preparation of amorphous polyester resin particle dispersion (a1)>>
Next, 200 parts by mass of the amorphous polyester resin, 100 parts by mass of methyl ethyl ketone, 35 parts by mass of isopropyl alcohol, and 7.0 parts by mass of a 10% by mass ammonia aqueous solution were placed in a separable flask, thoroughly mixed and dissolved, and then While heating and stirring at 40° C., ion-exchanged water was added dropwise at a feeding rate of 8 g/min using a liquid feeding pump, and the dropping was stopped when the amount of liquid fed reached 580 parts by mass. Thereafter, the solvent was removed under reduced pressure to obtain an amorphous polyester resin particle dispersion. Ion-exchanged water was added to the above dispersion to adjust the solid content to 25% by mass to prepare an amorphous polyester resin particle dispersion (a1). The volume-based median diameter (D ₅₀ ) of this dispersion was measured using Microtrack UPA-150 (manufactured by Nikkiso Co., Ltd.) and was found to be 156 nm.

<Preparation of crystalline polyester resin particle dispersion>
[Preparation of crystalline polyester resin particle dispersion (b1)]
<<Preparation of crystalline polyester resin (B1)>>
- 315 parts by mass of 1,10-dodecanedioic acid - 133 parts by mass of 1,6-hexanediol The above monomers were placed in a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas introduction tube, and the inside of the reaction vessel was flushed with dry nitrogen. Replaced with gas. Next, 0.25 parts by mass of titanium tetrabutoxide (Ti(O-n-Bu) ₄ ) was added to the total of 100 parts by mass of the above monomers. After stirring and reacting at 170°C for 3 hours under a nitrogen gas stream, the temperature was further raised to 210°C over 1 hour, the pressure inside the reaction vessel was reduced to 3 kPa, and the mixture was stirred and reacted under reduced pressure for 13 hours. , a crystalline polyester resin (B1) was obtained.
The crystalline polyester resin (B1) had a weight average molecular weight of 25,000, a number average molecular weight of 8,500, and a melting point of 71.8°C.

<<Preparation of crystalline polyester resin particle dispersion (b1)>>
Next, 200 parts by mass of the crystalline polyester resin, 120 parts by mass of methyl ethyl ketone, and 30 parts by mass of isopropyl alcohol were placed in a separable flask, and after thoroughly mixing and dissolving at 60°C, 8 parts by mass of 10 mass% ammonia aqueous solution was added. part was instilled. The heating temperature was lowered to 67°C, and while stirring, the ion exchange water was added dropwise at a delivery rate of 8 g/min using an ion exchange water delivery pump, and when the amount of delivered liquid reached 580 parts by mass, the dropping of ion exchange water was stopped. . Thereafter, the solvent was removed under reduced pressure to obtain a crystalline polyester resin particle dispersion. Ion-exchanged water was added to the above dispersion to adjust the solid content to 25% by mass to prepare a crystalline polyester resin particle dispersion (b1). The volume-based median diameter (D ₅₀ ) of this dispersion was measured using Microtrack UPA-150 (manufactured by Nikkiso Co., Ltd.) and was found to be 198 nm.

<Preparation of release agent particle dispersion (W1)>
・Paraffin wax (Nippon Seiro HNP0190, melting temperature 85°C)
270 parts by mass, anionic surfactant (Neogen RK manufactured by Daiichi Kogyo Seiyaku) 13.5 parts by mass (60% active ingredient, 3% based on mold release agent)
・Ion-exchanged water 21.6 parts by mass Mix the above materials, dissolve the mold release agent using a pressure discharge homogenizer (Gorlin Homogenizer, manufactured by Gorlin) at an internal liquid temperature of 120°C, and then apply a dispersion pressure of 5 MPa for 120 minutes. , followed by dispersion treatment at 40 MPa for 360 minutes and cooling to obtain a dispersion. Ion-exchanged water was added to adjust the solid content to 20%, and this was used as a release agent particle dispersion (W1). The volume average particle diameter of the particles in the release agent particle dispersion (W1) was 215 nm.

<Preparation of colorant particle dispersion>
[Preparation of black colorant particle dispersion (1)]
・Carbon black (manufactured by Cabot, Regal (registered trademark) 330) 100 parts by mass ・Anionic surfactant (Neogen SC manufactured by Daiichi Kogyo Seiyaku) 15 parts by mass ・Ion exchange water 400 parts by mass Mix the above components and homogenize (Ultra Turrax, manufactured by IKA Corporation) for 10 minutes, and then a high-pressure impact dispersion machine Ultimizer (manufactured by Sugino Machine) was used for dispersion treatment at a pressure of 245 MPa for 30 minutes to obtain an aqueous dispersion of black colorant particles. Obtained. A black colorant particle dispersion (1) was prepared by further adding ion-exchanged water to the obtained dispersion to adjust the solid content to 15% by mass. The volume-based median diameter (D ₅₀ ) of the colorant particles in this dispersion was measured using Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 110 nm.

<Preparation of toner base particles>
[Preparation of toner base particles (1)]
≪Agglomeration/fusion process and ripening process≫
・Amorphous polyester resin particle dispersion (a1) 1040 parts by mass ・Crystalline polyester resin particle dispersion (b1) 160 parts by mass ・Release agent particle dispersion (W1) 200 parts by mass ・Black colorant particle dispersion ( 1) 187 parts by mass of anionic surfactant (Dowfax2A1 20% aqueous solution)
40 parts by mass / 1500 parts by mass of ion-exchanged water The above materials were placed in a 4-liter reaction vessel equipped with a thermometer, pH meter, and stirrer, and the pH was adjusted to 3 by adding 1.0% nitric acid at a temperature of 25°C. Adjusted to .0. Thereafter, 100 parts by mass of an aqueous solution of aluminum sulfate (flocculant) having a concentration of 2% was added over 30 minutes while dispersing at 3000 rpm using a homogenizer (Ultra Turrax T50 manufactured by IKA). After the dropwise addition was completed, the mixture was stirred for 10 minutes to thoroughly mix the raw material and the flocculant.
After that, a stirrer and a mantle heater were installed in the reaction vessel, and while adjusting the rotation speed of the stirrer so that the slurry was sufficiently stirred, the heating rate was 0.2 °C/min until the temperature reached 40 °C. After the temperature exceeded 0.05°C, the temperature was increased at a rate of 0.05°C/min, and the particle size was measured every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, manufactured by Beckman Coulter). When the volume-based median diameter reached 3.9 μm, the temperature was maintained and the mixture was mixed in advance. - 400 parts by mass of amorphous polyester resin particle dispersion (a1) - Anionic surfactant (Dowfax 2A1 20% aqueous solution) )
15 parts by mass of the liquid mixture was added over 20 minutes.
Next, after maintaining the temperature at 50°C for 30 minutes, 8 parts of 20% EDTA (ethylenediaminetetraacetic acid) solution was added to the reaction vessel, and then 1 mol/L aqueous sodium hydroxide solution was added to adjust the pH of the raw material dispersion to 9. It was controlled to 0. Thereafter, while adjusting the pH to 9.0 every 5°C, the temperature was raised to 85°C at a temperature increase rate of 1°C/min, and maintained at 85°C.

≪Cooling process≫
Thereafter, when the shape factor reached 0.970, the mixture was cooled using "FPIA-3000" at a cooling rate of 10° C./min to obtain toner base particle dispersion (1).

≪Filtration/washing process and drying process≫
Thereafter, it was filtered and thoroughly washed with ion-exchanged water. Next, it was dried at 40° C. to obtain toner base particles (1). The obtained toner base particles (1) had a volume-based median diameter of 6.0 μm and an average circularity of 0.972.

≪Preparation of external additive 1≫
(Preparation of silica particles)
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 7.8. Thereafter, an aqueous sodium silicate solution and an aqueous sulfuric acid solution were gradually added while maintaining the pH, and then an aqueous sulfuric acid solution was added to adjust the pH to 3.0 and the mixture was left to stir, thereby synthesizing silica with a BET of 150 m ² /g. The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles.

(Alumina coating)
The suspension of silica particles was heated and maintained at 70 ° C., a 5N aqueous sodium hydroxide solution was added dropwise to adjust the pH to 8.0, and 20% of sodium aluminate was added as alumina based on the mass of the silica. The pH of the slurry was neutralized to 5.0, and the slurry was maintained at a temperature of 80° C. for 30 minutes with stirring to age. After this dispersion was distilled under reduced pressure and dried, the fine particles were crushed to obtain external additive particles 1.
When the number average primary particle size of the external additive particles 1 obtained by the above method was measured, the number average primary particle size (D ₅₀ ) was 20 nm.

(Surface hydrophobization treatment)
The external additive particles 1 obtained above were placed in a reaction container, and while stirring the powder with a rotary blade under a nitrogen atmosphere, 20 g of isobutyltrimethoxysilane, a hydrophobizing agent, was added to 100 g of the external additive particle powder. A mixture diluted with 60 g of hexane was added, heated and stirred at 200° C. for 120 minutes, cooled with cooling water, and dried under reduced pressure to obtain external additive 1.

≪Preparation of external additive 2≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 5.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g.
The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles. Thereafter, External Additive 2 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 3≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 7.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g.
The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles. Further, sodium sulfate was added so that the concentration was 0.8% by mass in terms of Na ₂ O and 0.96% by mass in terms of SO ₃ , and an aqueous sulfuric acid solution was added so that the pH was 5.5. Thereafter, External Additive 3 was obtained in the same manner as External Additive 1 except that the hydrophobic treating agent shown in Table I was used as the hydrophobic treating agent.

≪Preparation of external additive 4≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 7.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles. Further, sodium sulfate was added so that the concentration was 0.9% by mass in terms of Na ₂ O and 1.08% by mass in terms of SO ₃ , and an aqueous sulfuric acid solution was added so that the pH was 3.5. Thereafter, External Additive 4 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 5≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 5.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica is filtered, and then a NaOH aqueous solution is added to the pH to 7.8, a sulfuric acid aqueous solution is added to the pH to 3.5, and after thorough washing with ion-exchanged water, it is repulped with water to remove silica particles. It was made into a suspension. Thereafter, External Additive 5 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 6≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 7.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles. Further, sodium sulfate was added so that the concentration was 1.2% by mass in terms of Na ₂ O and 1.44% by mass in terms of SO ₃ , and an aqueous sulfuric acid solution was added so that the pH was 3.5. Thereafter, External Additive 6 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 7≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 5.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, followed by stirring to synthesize silica with a BET of 150 m ² /g.
The synthesized silica is filtered, and then a NaOH aqueous solution is added to the pH to 7.8, a sulfuric acid aqueous solution is added to the pH to 3.0, and after thorough washing with ion-exchanged water, it is repulped with water to remove the silica particles. It was made into a suspension. Thereafter, External Additive 7 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 8≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, pH and thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80 ° C. The pH was adjusted to 7.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica was filtered, thoroughly washed with ion-exchanged water, and then repulped with water to obtain a suspension of silica particles. Further, sodium sulfate was added so that the concentration was 0.5% by mass in terms of Na ₂ O and 0.6% by mass in terms of SO ₃ , and an aqueous sulfuric acid solution was added so that the pH was 6.5. Thereafter, External Additive 8 was obtained using the same procedure as External Additive 1.

≪Preparation of external additive 9≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 5.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica was filtered and thoroughly washed with ion-exchanged water, and then an aqueous sulfuric acid solution was added to adjust the pH to 5.5, followed by repulping with water to obtain a suspension of silica particles. Thereafter, External Additive 9 was obtained in the same manner as External Additive 1.

≪Preparation of external additive 10≫
A sodium silicate aqueous solution with a SiO ₂ concentration of 27% by mass and a Na ₂ O concentration of 8% by mass was placed in a reaction vessel equipped with a stirrer, a pH meter, and a thermometer, and a 60% by mass sulfuric acid aqueous solution was added at a temperature of 80°C. was added to adjust the pH to 5.8. Thereafter, a sodium silicate aqueous solution and a sulfuric acid aqueous solution were gradually added while maintaining the pH, and then a sulfuric acid aqueous solution was added to adjust the pH to 3.0, and the mixture was left stirring to synthesize silica with a BET of 150 m ² /g. .
The synthesized silica was filtered and thoroughly washed with ion-exchanged water, and then an aqueous NaOH solution was added to adjust the pH to 7.5, followed by repulping with water to obtain a suspension of silica particles. Thereafter, the same procedure as for external additive 1 was followed to obtain external additive 10.

≪Preparation of external additives 11 to 14≫
In preparing the above-mentioned external additive 1, as shown in Table I, external additives 11 to 13 were prepared by changing the hydrophobizing agent. External additive 14 was an external additive that had not been subjected to hydrophobization treatment.

≪Preparation of external additives 15 to 18≫
In preparing the above-mentioned external additive 1, external additives 15 to 18 were prepared by changing the alumina content as shown in Table I.

≪Preparation of external additives 19-20≫
In preparing the above-mentioned external additive 1, the hydrophobizing agent isobutyltrimethoxysilane was changed to 8 g to prepare external additive 19. Further, external additive 20 was prepared by changing the hydrophobizing agent isobutyltrimethoxysilane to 15 g.

<<Preparation of toner particles 1>>
(External additive addition process)
0.8 parts by mass of external additive 1 and 0.5 parts by mass of hydrophobic silica 1 "RY50 (manufactured by Nippon Aerosil Co., Ltd.)" were added to toner base particles 1 (median diameter on a volume basis 6.0 μm), Toner particles 1 were prepared by mixing for 20 minutes using a Henschel mixer.

<<Preparation of toner particles 2 to 23>>
In the production of toner particles 1, toner particles 2 to 23 were produced by changing the external additives and the number of parts added as shown in Table II.

≪Preparation of carrier particles≫
(Preparation of core material particles 1)
The raw materials were weighed so that MnO: 35 mol%, MgO: 14.5 mol%, Fe ₂ O ₃ : 50 mol% and SrO: 0.5 mol% were mixed with water, and then ground in a wet media mill for 5 hours. Got slurry.
The obtained slurry was dried with a spray dryer to obtain perfectly spherical particles. After adjusting the particle size of the particles, they were heated at 950° C. for 2 hours and pre-calcined in a rotary kiln. After grinding with a dry ball mill for 1 hour using stainless steel beads with a diameter of 0.3 cm, 0.8% by mass of PVA was added as a binder based on the solid content, water and a dispersant were further added, and a ball with a diameter of 0.5 cm was ground. It was ground for 25 hours using zirconia beads.
Next, the mixture was granulated and dried using a spray dryer, and main firing was performed in an electric furnace at a temperature of 1050° C. for 20 hours.
Thereafter, it was crushed, further classified to adjust the particle size, and then low-magnetic products were separated by magnetic separation to obtain core material particles 1. The volume average particle diameter of core material particles 1 was 28.0 μm.

(Preparation of coating resin 1)
100 parts by mass of cyclohexyl methacrylate monomer and 1 part by mass of dodecanethiol were mixed and dissolved, and 0.5 parts by mass of an anionic surfactant (Neogen SC manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was dissolved in 400 parts by mass of ion-exchanged water. Emulsion polymerization was carried out in a flask, and while slowly mixing for 10 minutes, 50 parts by mass of ion-exchanged water in which 0.5 parts by mass of ammonium persulfate was dissolved as an initiator was added. After purging with nitrogen, the flask was heated in an oil bath while stirring until the contents reached 70°C, and emulsion polymerization was continued for 5 hours to obtain a resin dispersion. Thereafter, coating resin 1 was obtained by drying the resin dispersion by spray drying. The weight average molecular weight of the resin particles 1 for forming a coating layer was 350,000.

(Preparation of carrier particles 1)
100 parts by mass of the core material particles 1 prepared above as core material particles and 4.5 parts by mass of the coating resin 1 were put into a high-speed stirring mixer with horizontal stirring blades, and the peripheral speed of the horizontal rotary blade was 8 m/ After mixing and stirring at 22° C. for 15 minutes under conditions such that After that, it was cooled to room temperature to produce "carrier particles 1".

<<Preparation of developer 1>>
Toner particles 1 and carrier particles 1 prepared as described above were mixed so that the toner concentration was 9% by mass to prepare developer 1. A V-type mixer (manufactured by Tokuju Kosho Co., Ltd.) was used as a mixer, and the mixture was mixed at 25° C. for 30 minutes.

≪Preparation of developers 2 to 23≫
Developers 2 to 23 were produced in the same manner as in the production of Developer 1, except that toner particles 1 were replaced with toner particles 2 to 23.

[evaluation]
Using a commercially available color multifunction device "bizhub PRO C6500" (manufactured by Konica Minolta Business Technologies), images were printed on A4-sized high-quality paper (65 g/m ² ) in a room temperature and normal humidity environment (temperature 20°C, humidity 50% RH). 1,000 sheets were printed to form a band-like solid image with a printing rate of 5% as a test image (denoted as "after initial printing" in Table II).
Next, we moved to a high-temperature, high-humidity environment (temperature: 30°C, humidity: 80% RH), and printed 100,000 test images to form a band-like solid image with a printing rate of 5% (in Table II, it is indicated as "after HH printing"). ), 50,000 sheets were printed to form a band-like solid image with a printing rate of 40% (in Table II, it is expressed as "after HH high coverage printing").
After printing 1,000 sheets, after printing 100,000 sheets, and after printing 50,000 sheets, the following evaluations were performed.

(Charge amount)
The amount of charge of the toner in this sample was measured using a charge amount measuring device "Blow-off type TB-200" (manufactured by Toshiba Corporation).
A 400-mesh stainless steel screen is attached to the apparatus, and nitrogen gas is blown for 10 seconds at a blowing pressure of 0.5 kgf/cm ² . The amount of charge [μC/g] was calculated by dividing the measured charge by the mass of the flying toner.

(fogging)
Absolute image densities at 20 locations on a blank sheet of unprinted paper are measured using a Macbeth reflection densitometer "RD-918" and averaged to determine the white paper density. Next, regarding the white background portion of the evaluation image, the absolute image density was similarly measured at 20 locations and averaged, and the value obtained by subtracting the white paper density from this average density was evaluated as the fog density.
○: Fog density is 0.007 or less △: Fog density is 0.008 or more and 0.010 or less ×: Fog density is 0.011 or more

(dot reproducibility)
A gradation pattern with a 32-step gradation rate is output, and this gradation pattern is subjected to Fourier transformation processing that takes into account MTF (Modulation Transfer Function) correction to the read value by the CCD, and a GI value ( Graininess Index) was measured to determine the maximum graininess. The smaller the GI value, the better, and the smaller the GI value, the less grainy the image. Note that this GI value is a value published in the Journal of the Imaging Society of Japan 39(2), 84/93 (2000). The graininess of the gradation pattern in the above image was evaluated according to the following evaluation criteria.
○: The maximum GI value (GIi) in the image is 0.170 or less. △: The maximum GI value (GIi) in the image is 0.171 or more and 0.180 or less. ×: The maximum GI value (GIi) in the image is 0.171 or more and 0.180 or less. , 0.181 or more

As is clear from the above results, when the toner of the present invention is used, compared to the toner of the comparative example, it has excellent charging stability during high coverage printing, can suppress image fogging, and has excellent dot reproducibility and high It can be seen that high-quality images can be formed.

Claims (8)

A negatively charged electrostatic latent image developing toner comprising toner particles containing an external additive on at least the surface,
The external additive contains silica particles whose surfaces have been subjected to a hydrophobization treatment,
The silica particles contain SO ₄ and the content is within the range of 10 to 30,000 ppm by mass,
The silica particles contain Na, and the content is within the range of 3 to 2000 ppm by mass, and
A toner for developing an electrostatic latent image , wherein the content of SO ₄ and Na in the silica particles satisfies the following relational expression (1A).
0.3≦SO4 _content (mass ppm)/Na content (mass ppm)...(1A) The toner for developing an electrostatic latent image according to claim 1 , wherein the silica particles contain SO ₄ and the content thereof is within a range of 50 to 15,000 ppm by mass. 3. The toner for developing an electrostatic latent image according to claim 1 , wherein the content of SO ₄ and Na in the silica particles satisfies the following relational expression (1).
0.3 ≦ _SO4 content (mass ppm)/Na content (mass ppm)≦20...(1) 4. The toner for developing electrostatic latent images according to claim 1 , wherein the surface of the silica particles is coated with alumina particles and further subjected to a hydrophobic treatment. The toner for developing electrostatic latent images according to claim 4 , wherein the amount of alumina covered in the silica particles coated with the alumina particles is within a range of 4 to 40% by mass. 6. The toner for developing electrostatic latent images according to claim 4 , wherein the silica particles are hydrophobized with any one of silazane, alkoxysilane, and silicone oil. 7. The toner for developing an electrostatic latent image according to claim 4 , wherein the hydrophobized silica particles have a hydrophobization degree of 30 or more. According to any one of claims 1 to 7 , the content of the silica particles is within a range of 0.1 to 2.0 parts by mass based on 100 parts by mass of the toner particles. The described toner for developing electrostatic latent images.