JP2018136451A - Toner for electrostatic latent image development and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce attenuation in charge of toner while ensuring sufficient low-temperature fixability of the toner.SOLUTION: A toner for electrostatic latent image development includes a plurality of toner particles containing a first resin and a second resin. The first resin includes a repeating unit derived from a styrene-based monomer not having either of an acid radical or a hydroxyl group. The second resin includes a repeating unit having an acid radical and/or a hydroxyl group. The mass Wof a water-soluble component present in a surface layer part of the toner particle measured by a first measuring method, and the mass Wof a water-soluble component present in the entirety of the toner particle measured by a second measuring method satisfy both the formulas (1) and (2). The first resin is a resin soluble in tetrahydrofuran and insoluble in water in the first measuring method and second measuring method. The second resin is a resin soluble in both tetrahydrofuran and water in the first measuring method and second measuring method. (1) W/W≤0.0075; (2) 500 mg≤W.SELECTED DRAWING: None

Description

  The present invention relates to a toner for developing an electrostatic latent image and a manufacturing method thereof, and more particularly to a capsule toner and a manufacturing method thereof.

  Patent Document 1 discloses a technique using a water-soluble resin as a binder resin for toner. In Patent Document 1, a water-soluble resin is insolubilized to increase the hydrophobicity of the water-soluble resin, thereby suppressing a decrease in toner fluidity in a high-humidity environment.

JP-A-4-278960

  It is difficult to obtain a toner having excellent chargeability only by the technique disclosed in Patent Document 1. The toner described in Patent Document 1 is considered to be easily attenuated in electric charge. It is also conceivable to improve the chargeability of the toner by using a resin containing a repeating unit derived from a styrene monomer as the binder resin for the toner. However, when such a binder resin is used, the low-temperature fixability of the toner tends to deteriorate.

  The present invention has been made in view of the above problems, and an object thereof is to suppress toner charge attenuation while ensuring sufficient low-temperature fixability of the toner.

The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles containing a first resin and a second resin. The first resin includes a repeating unit derived from a styrene monomer having neither an acid group nor a hydroxyl group. The second resin includes a repeating unit having an acid group and / or a hydroxyl group. The mass W ₁ of the water-soluble component present in the surface layer portion of the toner particles, measured by the following first measurement method, and the water-soluble component present in the whole of the toner particles, measured by the following second measurement method. The mass W ₂ satisfies both the following formulas (1) and (2). The first resin is a resin that dissolves in tetrahydrofuran but does not dissolve in water in the following first measurement method and second measurement method. The second resin is a resin that is soluble in both water and tetrahydrofuran in the following first measurement method and the following second measurement method.
W ₁ / W ₂ ≦ 0.0075 (1)
500 mg ≦ W ₂ (2)

In the first measurement method, a toner dispersion obtained by adding 5 g of the toner to 10 mL of water is subjected to ultrasonic treatment for 30 minutes at a temperature of 25 ° C., followed by solid-liquid separation, and the obtained aqueous phase. The mass W ₁ of the toner component dissolved in the toner is measured.
In the second measurement method, a toner dispersion obtained by adding 5 g of the toner to 20 mL of tetrahydrofuran is subjected to a stirring process for 30 minutes at a temperature of 25 ° C. and a rotation speed of 300 rpm, followed by solid-liquid separation. A THF solution containing a dissolved toner component is obtained, 200 mL of water is added to the obtained THF solution, tetrahydrofuran is distilled off at a temperature of 98 ° C., and the mass of the toner components dissolved in the remaining aqueous phase. W ₂ is measured.

  The method for producing a toner for developing an electrostatic latent image according to the present invention includes a first step, a second step, and a third step. In the first step, the first resin and the second resin are melt-kneaded to obtain a melt-kneaded product containing the first resin and the second resin. In the second step, the melt-kneaded product is pulverized to obtain a powder. In the third step, ultrasonic treatment is performed on the powder in water. The first resin includes a repeating unit derived from a styrene monomer having neither an acid group nor a hydroxyl group, and is a resin that is soluble in tetrahydrofuran but insoluble in water. The second resin is a resin that contains a repeating unit having an acid group and / or a hydroxyl group and is soluble in both water and tetrahydrofuran.

  According to the present invention, it is possible to suppress toner charge attenuation while ensuring sufficient low-temperature fixability of toner.

  Embodiments of the present invention will be described in detail. Note that the evaluation results (values indicating shape, physical properties, etc.) regarding powders (more specifically, toner base particles, external additives, toners, etc.) are measured for a considerable number of particles unless otherwise specified. The number average of the values obtained.

Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent-circle diameters of primary particles (Haywood diameter: the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Value. The measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value. In addition, the measured value of the circularity of the powder (= peripheral length of a circle equal to the projected area of the particle / peripheral length of the particle) is not specified, the flow particle image analyzer (“FPIA” manufactured by Sysmex Corporation) (Registered trademark) -3000 "), and the number average of values measured for a considerable number (for example, 3000) of particles.

  The glass transition point (Tg) is a value measured according to “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) at the second temperature rise measured with a differential scanning calorimeter, an inflection point (baseline extrapolation line and standing) The temperature (onset temperature) at the intersection of the descending line and the extrapolated line corresponds to Tg (glass transition point). Moreover, the measured value of molecular weight (for example, number average molecular weight) is a value measured using gel permeation chromatography unless otherwise specified.

  The chargeability means the chargeability in frictional charging unless otherwise specified. The strength of positive chargeability (or strength of negative chargeability) in frictional charging can be confirmed by a known charge train or the like.

  The hydrophobic strength (or hydrophilic strength) can be expressed by, for example, the contact angle of water drops (easy to wet water). The larger the contact angle of the water droplet, the stronger the hydrophobicity.

  The “main component” of a material means a component most contained in the material on a mass basis unless otherwise specified.

Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth) acrylonitrile”. Further, acryloyl (CH ₂ ═CH—CO—) and methacryloyl (CH ₂ ═C (CH ₃ ) —CO—) may be collectively referred to as “(meth) acryloyl”.

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The positively chargeable toner is positively charged by friction.

  The toner particles include toner base particles and an external additive. The external additive is attached to the surface of the toner base particles. The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) as necessary. If not necessary, the external additive may be omitted. When omitting the external additive, the toner base particles correspond to the toner particles.

  The toner according to the exemplary embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). The magnetic toner can be suitably used as a one-component developer as it is without being mixed with a carrier. In the magnetic toner, the toner base particles are magnetic particles containing magnetic powder. Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

  First, an image forming unit (for example, a charging device and an exposure device) of an electrophotographic apparatus forms an electrostatic latent image on a photosensitive member (for example, a surface layer portion of a photosensitive drum) based on image data. Subsequently, a developing device of the electrophotographic apparatus (specifically, a developing device in which magnetic toner is set) supplies the toner to the photoconductor to develop the electrostatic latent image formed on the photoconductor. The developing device includes a developing roller (surface layer portion: developing sleeve) and a toner charging member (for example, a blade) for charging toner carried on the surface of the developing roller. The toner charging member may play a role of regulating the amount of toner (the thickness of the toner layer) on the developing roller. The toner is charged by friction with the developing sleeve or the toner charging member in the developing device before being supplied to the photoreceptor. For example, a positively chargeable toner is positively charged. In the development process, toner (specifically, charged toner) on a developing sleeve disposed in the vicinity of the photoreceptor is supplied to the photoreceptor, and the supplied toner adheres to the electrostatic latent image on the photoreceptor, A toner image is formed on the photoreceptor. The consumed toner is replenished to the developing device from a toner container containing replenishment toner.

  In the subsequent transfer process, the transfer device of the electrophotographic apparatus transfers the toner image on the photoreceptor to a recording medium (for example, paper). Thereafter, a fixing device (fixing method: nip fixing with a heating roller and a pressure roller) of the electrophotographic apparatus heats and pressurizes the toner to fix the toner on the recording medium. As a result, an image is formed on the recording medium. After the transfer step, the toner remaining on the photoreceptor is removed by a cleaning member (for example, a cleaning blade).

  A two-component developer may be prepared using toner (for example, non-magnetic toner), and the obtained two-component developer may be set in a developing device. A two-component developer can be obtained by mixing the toner and the carrier using a mixing device (for example, a ball mill). As the two-component developer (toner and carrier) is agitated in the developing device, the toner is charged by friction with the carrier. For example, a positively chargeable toner is positively charged by friction with the carrier. Examples of carriers suitable for image formation include ferrite carriers (ferrite particle powder). In order to form a high-quality image over a long period of time, it is preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. In order to impart magnetism to the carrier particles, the carrier core may be formed of a magnetic material (for example, a ferromagnetic substance such as ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Good. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. Examples of the resin constituting the resin layer include a fluororesin (more specifically, PFA or FEP) or a silicone resin. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The number average primary particle diameter of the carrier is preferably 20 μm or more and 120 μm or less.

  The toner according to the exemplary embodiment is an electrostatic latent image developing toner having the following configuration (hereinafter referred to as a basic configuration).

[Basic toner configuration]
The electrostatic latent image developing toner includes a plurality of toner particles containing the following first resin and the following second resin. Further, the mass W ₁ of the water-soluble component present in the surface layer portion of the toner particle, measured by the following first measurement method, and the water-soluble component present in the whole toner particle, measured by the following second measurement method. The mass W ₂ satisfies both the following formulas (1) and (2).
W ₁ / W ₂ ≦ 0.0075 (1)
500 mg ≦ W ₂ (2)

(First resin)
The first resin includes a repeating unit derived from a styrene monomer having neither an acid group nor a hydroxyl group. The first resin is a resin that dissolves in tetrahydrofuran but does not dissolve in water in each of the following first measurement method and the following second measurement method.

(Second resin)
The second resin includes a repeating unit having an acid group and / or a hydroxyl group. The second resin is a resin that is soluble in both water and tetrahydrofuran in each of the following first measurement method and the following second measurement method.

(First measurement method)
In the first measurement method, a toner dispersion obtained by adding 5 g of toner to 10 mL of water is subjected to ultrasonic treatment for 30 minutes at a temperature of 25 ° C., followed by solid-liquid separation, and dissolved in the obtained aqueous phase. and it is measuring the mass W ₁ of the components of the toner. As for the mass W ₁ of the toner component dissolved in the aqueous phase, solid matter (insoluble matter) is removed by solid-liquid separation. Obtained by measuring the mass of the residue after drying (dehydration).

(Second measurement method)
In the second measurement method, a toner dispersion obtained by adding 5 g of toner to 20 mL of tetrahydrofuran was stirred for 30 minutes under the conditions of a temperature of 25 ° C. and a rotation speed of 300 rpm, followed by solid-liquid separation and dissolution in tetrahydrofuran. A THF solution containing the toner component is obtained. Solid matter (insoluble matter) is removed by solid-liquid separation. 200 mL of water is added to the obtained THF solution, tetrahydrofuran is distilled off under the condition of a temperature of 98 ° C., and the mass W ₂ of the toner component dissolved in the remaining aqueous phase is measured. The mass W ₂ of the toner component dissolved in the aqueous phase can be obtained by measuring the mass of the residue after drying (dehydration).

Hereinafter, in the above basic configuration, the mass W ₁ of the water-soluble component present in the surface layer portion of the toner particles measured by the first measurement method may be referred to as “water-soluble surface layer mass W ₁ ”. In the above basic configuration, the mass W ₂ of the water-soluble component present in the entire toner particles, measured by the second measurement method, may be referred to as “water-soluble total mass W ₂ ”. In addition, the first resin defined by the basic configuration may be referred to as “specific water-insoluble resin”. In addition, the second resin defined by the basic configuration may be described as “specific water-soluble resin”. A styrene monomer having neither an acid group nor a hydroxyl group may be referred to as a “hydrophobic styrene monomer”.

  In general, a toner using a styrene-acrylic acid resin as a binder resin (hereinafter referred to as S-Ac toner) and a toner using a polyester resin as a binder resin (hereinafter referred to as PES toner) are used. Are known. S-Ac toner is superior in chargeability to PES toner, but tends to be inferior in fixability. For this reason, there is a tendency that S-Ac toner is used in an application where chargeability is required, and PES toner is used in an application where fixability is required.

  The inventor of the present application has focused on the fact that the monomer mainly imparting charging property to the styrene-acrylic acid resin is a hydrophobic styrene monomer (first point of focus). Further, the inventor of the present application has the toner fixing property that the affinity between a resin (binder resin) containing a repeating unit derived from a hydrophobic styrenic monomer and paper (recording medium) is poor at the time of toner fixing. Focusing on the inhibition (second point of focus). The inventor of the present application has repeated experiments and studies in order to improve the affinity between the toner and the recording medium.

  The inventor of the present application uses a styrene monomer having at least one of an acid group and a hydroxyl group in place of the hydrophobic styrene monomer as a first measure for improving the affinity between the toner and the recording medium. Thought. However, with this method, the affinity between the toner and the recording medium tends to be improved, but the chargeability of the toner tends to be worse.

  As a second measure for improving the affinity between the toner and the recording medium, the inventor of the present application uses a water-soluble resin as a binder resin in addition to a resin containing a repeating unit derived from a hydrophobic styrenic monomer. I thought about using it. However, even in this method, as in the first countermeasure, the affinity between the toner and the recording medium tends to be improved, but the chargeability of the toner tends to be worse.

  The inventor of the present application analyzed the principle that the affinity between the toner and the recording medium was improved and the cause of the deterioration of the charging property of the toner, and improved the second countermeasure. The present inventors have succeeded in obtaining a toner excellent in both properties and fixing properties (that is, a toner having the above-mentioned basic constitution). The reason why the chargeability of the toner is deteriorated by the second countermeasure is that the present inventor is that water molecules are easily adsorbed on the surface of the toner particles, and the charge amount of the toner particles is easily attenuated. I guessed. Further, the inventor of the present application has thought that the water-soluble component present in the surface layer portion of the toner particles inhibits the chargeability of the toner. The reason why the affinity between the toner and the recording medium is improved is that the binder resin dissolves at the time of toner fixing, so that the water-soluble component present in the entire toner particles flows out onto the recording medium, and the toner and the recording medium. The inventor of the present application considered that the affinity with the above was improved.

The toner having the above-described basic configuration satisfies both the formula (1) “W ₁ / W ₂ ≦ 0.0075” and the formula (2) “500 mg ≦ W ₂ ”. The mass W ₁ corresponds to the mass of the water-soluble component present in the surface layer portion of the toner particles (specifically, the mass per 5 g of toner), and the mass W ₂ represents the mass of the water-soluble component present in the entire toner particle ( Specifically, it corresponds to a mass per 5 g of toner). The amount of the water-soluble component present in the surface layer portion of the toner particles is sufficiently smaller than the amount of the water-soluble component present in the entire toner particles. For this reason, it is considered that water molecules are less likely to be adsorbed on the surface of the toner particles, and the attenuation of the charge amount of the toner particles in a high temperature and high humidity environment is suppressed. Further, the amount of the water-soluble component present in the entire toner particles is sufficiently large. For this reason, it is considered that a sufficient amount of water-soluble components flow out from the toner particles onto the recording medium when the binder resin is melted at the time of fixing the toner, thereby improving the affinity between the toner and the recording medium.

  In the toner having the above basic configuration, the toner particles contain a specific water-insoluble resin and a specific water-soluble resin. For the toner satisfying both the above formulas (1) and (2), for example, a melt kneaded product of a specific water-insoluble resin and a specific water-soluble resin is pulverized to obtain a powder (pulverized product). The obtained powder can be produced by sonication in water. By performing ultrasonic treatment in water, water-soluble components present in the surface layer portion of the toner particles can be removed.

  When a mixture containing a water-insoluble resin and a water-soluble resin that are easily compatible with each other is melt-kneaded, water-soluble components are uniformly finely dispersed throughout the resulting melt-kneaded product. In a pulverized product (toner base particle powder) obtained by pulverizing such a melt-kneaded product, water-soluble components are uniformly finely dispersed throughout each particle (toner base particle). When this pulverized material (toner mother particle powder) is subjected to ultrasonic treatment in water, the surface layer part newly exposed by melting the surface layer part of the toner mother particle (former surface layer part: surface layer part before ultrasonic treatment). (New surface layer portion: surface layer portion after ultrasonic treatment) also contains water-soluble components at the same level as the old surface layer portion. For this reason, even if the surface layer portion of the toner base particles is dissolved, the amount of the water-soluble component present in the surface layer portion of the toner base particles is hardly reduced. In order to reduce the amount of the water-soluble component present in the surface layer portion of the toner base particle by ultrasonic treatment, it is necessary that the water-soluble component is present in the toner base particle in an uneven manner after the melt-kneaded product is pulverized.

  In the toner having the basic configuration described above, the specific water-insoluble resin contains a repeating unit derived from a hydrophobic styrene monomer, so that the specific water-insoluble resin and the specific water-soluble resin are hardly compatible. In the melt-kneaded product of the specific water-insoluble resin and the specific water-soluble resin, it is considered that the water-soluble component becomes a relatively large domain and exists in the toner base particles in a biased manner. After the melt-kneaded product is pulverized, the water-soluble component (water-soluble domain) present in the surface layer portion of the pulverized product (toner base particle) can be easily obtained by subjecting the toner base particle (powder) to ultrasonic treatment in water. Can be removed. By such ultrasonic treatment, the amount of the water-soluble component present in the surface layer portion of the toner base particles can be sufficiently reduced relative to the amount of the water-soluble component present in the entire toner base particles.

  In the toner having the basic configuration described above, the toner particles contain a resin (specific water-insoluble resin and specific water-soluble resin) that is soluble in tetrahydrofuran. Such toner particles tend to have excellent fixability.

  In general, toner base particles are mainly classified into toner base particles not having a shell layer (hereinafter referred to as non-capsule toner base particles) and toner base particles having a shell layer (hereinafter referred to as capsule toner base particles). Separated. From another point of view, toners are roughly classified into pulverized toners and polymerized toners (also called chemical toners). The toner obtained by the pulverization method belongs to the pulverized toner, and the toner obtained by the aggregation method belongs to the polymerized toner. The pulverization method is a method of obtaining a powder through a step of obtaining a kneaded product by melting and kneading a plurality of types of materials (resins and the like) and a step of pulverizing the obtained kneaded product. The toner base particles (powder) of the toner having the basic structure described above are obtained by, for example, a pulverization method using a specific water-insoluble resin, a specific water-soluble resin, and an internal additive (for example, a release agent, a colorant, a charge control agent, And a powder obtained by pulverizing a melt-kneaded product with at least one of magnetic powder and magnetic powder, and subjecting the obtained powder to ultrasonic treatment in water. In such a production method, it is easy to favorably disperse the internal additive in the binder resin (specific water-insoluble resin and specific water-soluble resin). Further, the toner base particles obtained as described above (specifically, powder of non-capsule toner base particles containing a melt-kneaded product of a specific water-insoluble resin, a specific water-soluble resin, and an internal additive) The external additive (for example, silica particle powder) can be mixed to adhere the external additive to the surface of the toner base particles. From the viewpoint of toner productivity (particularly, from the viewpoint of obtaining a toner suitable for image formation at low cost), in the toner having the above-mentioned basic configuration, the toner particles include the specific water-insoluble resin, the specific water-soluble resin, and the internal additive. It is particularly preferable to include non-capsule toner base particles containing a melt-kneaded product with an agent and an external additive attached to the surface of the non-capsule toner base particles.

As the specific water-soluble resin, a resin containing a repeating unit derived from a vinyl alcohol monomer (hereinafter sometimes referred to as a VA unit-containing resin) is preferable. The VA unit-containing resin is likely to have sufficient water solubility, and is likely to have appropriate compatibility with the specific water-insoluble resin. In addition, in order to obtain a specific water-soluble resin having sufficient water-solubility and appropriate compatibility with a specific water-insoluble resin, the specific water-soluble resin is composed of a vinyl alcohol monomer and a vinyl acetate type. A monomer (resin raw material) containing a monomer, and in a specific water-soluble resin, the amount of the vinyl alcohol monomer is 20 mol% or more based on the total amount of the vinyl alcohol monomer and the vinyl acetate monomer. It is particularly preferably 45 mol% or less (more preferably 30 mol% or more and 40 mol% or less). When a vinyl alcohol-vinyl acetate resin containing a vinyl alcohol monomer at such a molar ratio is used as the specific water-soluble resin, the mass W ₂ (mass of the water-soluble component present in the entire toner particles) is 1000 mg to 2000 mg. It is particularly preferred. If the amount of the water-soluble component present in the entire toner particles is too large, the charge retention of the toner particles tends to deteriorate. The reason for this is considered to be that the electrical conductivity of the surface of the toner particles is increased due to adhesion of moisture in the air to the toner particles. Further, if the amount of the water-soluble component present in the entire toner particles is too small, the low-temperature fixability of the toner tends to deteriorate.

  When the specific water-soluble resin is a VA unit-containing resin, the specific water-insoluble resin includes a hydrophobic styrene monomer (a styrene monomer having neither an acid group nor a hydroxyl group), and an ester moiety having 1 or more carbon atoms. It is a polymer of a monomer (resin raw material) containing a (meth) acrylic acid alkyl ester having an alkyl group of 8 or less and a crosslinking agent (hereinafter sometimes referred to as a specific crosslinked S-Ac resin). Is particularly preferred. In order to obtain a specific cross-linked S-Ac resin (specific water-insoluble resin) having sufficient water-insolubility and appropriate compatibility with the VA unit-containing resin (specific water-soluble resin) In the crosslinked S-Ac resin, the amount of repeating units derived from the hydrophobic styrene monomer (styrene monomer having neither acid group nor hydroxyl group) is the total amount of all repeating units contained in the specific crosslinked S-Ac resin. Particularly preferably, the content is 15% by mass or more and 40% by mass or less. If the amount of the repeating unit derived from the hydrophobic styrenic monomer in the specific crosslinked S-Ac resin is too large, the compatibility between the specific crosslinked S-Ac resin and the VA unit-containing resin tends to be insufficient. When the amount of the repeating unit derived from the hydrophobic styrenic monomer in the specific crosslinked S-Ac resin is too small, the specific crosslinked S-Ac resin and the VA unit-containing resin tend to be too compatible.

  In non-capsule toner base particles containing a specific cross-linked S-Ac resin (specific water-insoluble resin) and a VA unit-containing resin (specific water-soluble resin), the amount of the VA unit-containing resin is the same as that of the specific cross-linked S-Ac resin and It is preferable that it is 20 mass% or more and 50 mass% or less with respect to the total amount of VA unit containing resin. When such non-capsule toner base particles are prepared by the above-described methods (specifically, melt kneading, pulverization, and ultrasonic treatment), a specific crosslinked S-Ac resin (specific water-insoluble resin) and a VA unit-containing resin ( In a melt-kneaded product with a specific water-soluble resin, the specific cross-linked S-Ac resin and the VA unit-containing resin tend to be appropriately compatible.

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

  In order to obtain a toner suitable for image formation, it is preferable that the toner contains toner particles containing the first resin and the second resin defined by the above-described basic configuration at a ratio of 80% by number or more. More preferably, it is contained at a rate of several percent or more, more preferably at a rate of 100 percent.

  Next, the toner base particles (binder resin and internal additive) and the external additive will be described in order. Depending on the use of the toner, unnecessary components may be omitted.

[Toner mother particles]
(Binder resin)
In the toner base particles, generally, the binder resin occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner base particles. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and when the binder resin has an amino group, The toner base particles tend to be cationic.

In the toner having the basic configuration described above, the toner base particles contain a specific water-insoluble resin and a specific water-soluble resin as a binder resin. It is particularly preferable that the binder resin is substantially only the specific water-insoluble resin and the specific water-soluble resin. Each of the specific water-insoluble resin and the specific water-soluble resin is preferably a polymer of one or more vinyl compounds. In the polymer of the vinyl compound, it is considered that the repeating unit derived from the vinyl compound is addition-polymerized (“C═C” → “—C—C—”) by the carbon double bond “C═C”. The vinyl compound is a compound having a vinyl group (CH ₂ ═CH—) or a group in which hydrogen in the vinyl group is substituted. Examples of the vinyl compound include ethylene, propylene, butadiene, vinyl chloride, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, or styrene.

(Binder resin: specified water-insoluble resin)
The specific water-insoluble resin includes a repeating unit derived from a hydrophobic styrene monomer (a styrene monomer having neither an acid group nor a hydroxyl group). Examples of hydrophobic styrenic monomers include styrene and alkylstyrene (more specifically, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 4-tert-butylstyrene, etc.) Or halogenated styrene (more specifically, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, or the like).

  As the repeating unit derived from the hydrophobic styrenic monomer, a repeating unit represented by the following formula (1) is particularly preferable.

In formula (1), R ^{11 to} R ¹⁵ each independently represent a hydrogen atom, a halogen atom, an alkyl group that may have a substituent, an alkoxy group that may have a substituent, or a substituent. The aryl group which may have is represented. R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. Each of R ^{11 to} R ¹⁷ does not contain any acid group or hydroxyl group. R ^{11 to} R ¹⁵ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number (specifically, alkoxy and alkyl The total number of carbon atoms) is preferably an alkoxyalkyl group having 2 to 6 carbon atoms. R ¹⁶ and R ¹⁷ are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ¹⁷ represents a hydrogen atom and R ¹⁶ represents a hydrogen atom or a methyl group. In the repeating unit derived from styrene, each of R ^{11 to} R ¹⁷ represents a hydrogen atom.

  In order to improve the fixing property of the toner, in addition to the repeating unit derived from a hydrophobic styrene monomer (a styrene monomer having neither an acid group nor a hydroxyl group), a specific water-insoluble resin, an acrylic acid monomer It is preferable that the repeating unit derived from is included. Examples of acrylic monomers include (meth) acrylic acid, (meth) acrylonitrile, or (meth) acrylic acid alkyl esters. Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic acid n. -Butyl, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate.

  As the repeating unit derived from the acrylic monomer, a repeating unit represented by the following formula (2) is particularly preferable.

In Formula (2), R ²¹ and R ²² each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. R ²³ represents an alkyl group having 1 to 8 carbon atoms which may have a substituent. R ²¹ and R ²² are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ²¹ represents a hydrogen atom and R ²² represents a hydrogen atom or a methyl group. R ²³ is particularly preferably an alkyl group having 1 to 8 carbon atoms. In the repeating unit derived from methyl methacrylate, R ²¹ represents a hydrogen atom, and each of R ²² and R ²³ represents a methyl group.

In order to improve the heat resistant storage stability of the toner, the specific water-insoluble resin is preferably a crosslinked resin. When the specific water-insoluble resin is a polymer of one or more vinyl compounds, the cross-linking agent for crosslinking the specific water-insoluble resin is preferably a compound containing two or more unsaturated bonds. When the specific water-insoluble resin includes a repeating unit derived from a hydrophobic styrene monomer and a repeating unit derived from an acrylic acid monomer, the crosslinking agent for crosslinking the specific water-insoluble resin is unsaturated. Particularly preferred are di (meth) acrylic acid diesters (more specifically, ethylene glycol dimethacrylate, butanediol dimethacrylate, etc.) having functional groups containing bonds at both ends. Examples of the functional group containing an unsaturated bond include a vinyl group (CH ₂ ═CH—) or a functional group in which hydrogen in the vinyl group is substituted.

  In order to achieve both the heat resistant storage stability and the fixing property of the toner, the glass transition point (Tg) of the specific water-insoluble resin is preferably 105 ° C. or higher and 130 ° C. or lower. When the specific water-insoluble resin is a specific cross-linked S-Ac resin, the mass average molecular weight (Mw) of the specific cross-linked S-Ac resin is preferably 10,000 to 15,000. Such a specific cross-linked S-Ac resin tends to have an appropriate melting property.

(Binder resin: Specific water-soluble resin)
The specific water-soluble resin preferably contains a repeating unit derived from a vinyl alcohol monomer. As the repeating unit derived from the vinyl alcohol monomer, a repeating unit represented by the following formula (3) is particularly preferable.

In Formula (3), R ³¹ and R ³² each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. R ³¹ and R ³² are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ³¹ represents a hydrogen atom and R ³² represents a hydrogen atom or a methyl group. In the repeating unit derived from vinyl alcohol, each of R ³¹ and R ³² represents a hydrogen atom.

  In order to prevent the hydrophilicity of the toner from becoming too strong, the specific water-soluble resin preferably contains a repeating unit derived from a vinyl acetate monomer in addition to a repeating unit derived from a vinyl alcohol monomer. As the repeating unit derived from the vinyl acetate monomer, a repeating unit represented by the following formula (4) is particularly preferable.

In formula (4), R ⁴¹ and R ⁴² each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. R ⁵¹ , R ⁵² , and R ⁵³ each independently represent a hydrogen atom, an alkyl group that may have a substituent, or an acetyl group that may have a substituent. R ⁴¹ and R ⁴² are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ⁴¹ represents a hydrogen atom and R ⁴² represents a hydrogen atom or a methyl group. R ⁵¹ , R ⁵² , and R ⁵³ are particularly preferably each independently a hydrogen atom (H—) or an acetyl group (CH ₃ CO—). In the repeating unit derived from vinyl acetate, each of R ⁴¹ , R ⁴² , R ⁵¹ , R ⁵² , and R ⁵³ represents a hydrogen atom.

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

  The toner base particles may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant. You may use the magnetic powder mentioned later as a black coloring agent. That is, the toner base particles may not contain a colorant other than the magnetic powder.

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

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

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

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

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

  In order to obtain a magnetic toner suitable for image formation, the amount of magnetic powder in the toner base particles is preferably 40 parts by mass or more and 120 parts by mass or less with respect to 100 parts by mass of the binder resin.

  In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When metal ions are eluted on the surface of the toner base particles, the toner base particles are easily fixed to each other. It is considered that fixing of toner mother particles can be suppressed by suppressing elution of metal ions from the magnetic powder.

[External additive]
An external additive (specifically, a powder containing a plurality of external additive particles) may be adhered to the surface of the toner base particles. Unlike the internal additive, the external additive does not exist inside the toner base particles, but selectively exists only on the surface of the toner base particles (surface layer portion of the toner particles). For example, by stirring together the toner base particles (powder) and the external additive (powder), the external additive particles can be attached to the surface of the toner base particles. The toner base particles and the external additive particles do not chemically react with each other and are physically bonded instead of chemically. The strength of the bond between the toner base particles and the external additive particles depends on the stirring conditions (more specifically, the stirring time, the rotation speed of the stirring, etc.), the particle diameter of the external additive particles, and the shape of the external additive particles. And the surface condition of the external additive particles.

  In order to improve the fluidity of the toner, it is preferable to use inorganic particles (powder) having a number average primary particle diameter of 5 nm to 30 nm as external additive particles. In order to fully perform the functions of the external additive while suppressing the detachment of the external additive particles from the toner particles, the amount of the external additive (if multiple types of external additive particles are used, The total amount of external additive particles) is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles.

  The external additive particles are preferably inorganic particles such as silica particles or metal oxide particles (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate). Particularly preferred. However, particles of an organic acid compound such as a fatty acid metal salt (more specifically, zinc stearate) or resin particles may be used as the external additive particles. Moreover, you may use the composite particle which is a composite of a multiple types of material as external additive particle | grains. The external additive particles may be surface-treated. One type of external additive particles may be used alone, or a plurality of types of external additive particles may be used in combination.

[Toner Production Method]
Hereinafter, an example of a method for producing a toner having the above-described basic configuration will be described. As a toner manufacturing method, a method including the following first to third steps is particularly preferable.

In the first step, the specific water-insoluble resin and the specific water-soluble resin are melt-kneaded to obtain a melt-kneaded product containing the specific water-insoluble resin and the specific water-soluble resin.
In the second step, the melt-kneaded product is pulverized to obtain a powder.
In the third step, ultrasonic treatment is performed on the powder in water.

(Preparation of pulverized product)
First, a pulverized product is prepared by a pulverization method. Hereinafter, an example of the pulverization method will be described. First, a binder resin and an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder) are mixed. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is pulverized, and the obtained powder (pulverized product) is classified. As a result, a powder having a desired particle size is obtained. Hereinafter, the particles contained in the obtained powder are referred to as pre-treatment particles.

(Sonication)
Subsequently, the pre-treatment particle powder obtained as described above is put into water at a temperature of 25 ° C., for example, and subjected to ultrasonic treatment in water for a predetermined time (for example, a time selected from 15 minutes to 60 minutes or less). ) Apply. By this ultrasonic treatment, water-soluble components present in the surface layer of the pre-treatment particles are dissolved in water. As a result, toner base particles (powder) satisfying both the expressions (1) and (2) in the basic configuration described above are obtained.

(Drying and external addition)
The dispersion of toner base particles obtained as described above is cooled to, for example, room temperature (about 25 ° C.). Subsequently, the dispersion of the toner base particles is filtered using, for example, a Buchner funnel. Thereby, the toner base particles are separated from the liquid (solid-liquid separation), and wet cake-like toner base particles are obtained. Subsequently, the obtained wet cake-like toner base particles are washed. Subsequently, the washed toner base particles are dried. Thereafter, if necessary, the toner base particles and the external additive are mixed using a mixer (for example, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.), and the external additive is adhered to the surface of the toner base particles. May be. When a spray dryer is used in the drying step, the drying step and the external addition step can be performed at the same time by spraying a dispersion of an external additive (for example, silica particles) onto the toner base particles. Thus, a toner containing a large number of toner particles is manufactured.

  The contents and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, the toner may be sieved after the external addition step. Further, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. If an external additive is unnecessary, the external addition process may be omitted. When the external additive is not attached to the surface of the toner base particles (the step of external addition is omitted), the toner base particles correspond to the toner particles. When synthesizing the resin, as a material for synthesizing the resin, a monomer may be used or a prepolymer may be used. In order to obtain a predetermined compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-6 and TB-1 to TB-7 (positively charged toners for developing electrostatic latent images, respectively) according to examples or comparative examples.

  In Table 1, the ratio of water-soluble resin (unit: mass%) indicates the ratio to the total amount of all resins (binder resin) contained in the toner base particles.

In Table 1, the meaning of “type” of the water-soluble resin is as follows.
W-1: Polyvinyl alcohol / polyvinyl acetate copolymer (“GOHSEX (registered trademark) LL-920” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of saponification: about 34.0 mol%)
W-2: Polyvinyl alcohol / polyvinyl acetate copolymer (“GOHSEX (registered trademark) LL-940” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of saponification: about 37.5 mol%)

  The degree of saponification in the polyvinyl alcohol / polyvinyl acetate copolymer is the total amount of all repeating units contained in the resin (polyvinyl alcohol / polyvinyl acetate copolymer). This corresponds to the molar ratio of the amount of the vinyl alcohol monomer to the total amount of the monomer.

  Hereinafter, the production methods, evaluation methods, and evaluation results of the toners TA-1 to TA-6 and TB-1 to TB-7 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Preparation of materials]
In a four-necked flask equipped with a thermometer, a nitrogen introduction tube, a stirring device (stainless blade made of stainless steel), and a flow-down condenser (heat exchanger), 4.9 kg of toluene, 0.9 kg of styrene, methacrylic acid 3.8 kg of methyl acid and 5 mg of azobisisobutyronitrile (AIBN) were added. Subsequently, nitrogen gas was introduced into the flask through the nitrogen introduction tube, and the atmosphere in the flask was changed to a nitrogen atmosphere (inert atmosphere). Subsequently, the flask contents were heated to 70 ° C. while stirring the flask contents in a nitrogen atmosphere, and the flask contents were reacted (condensation polymerization reaction) while stirring the flask contents in a nitrogen atmosphere and a temperature of 70 ° C. ) When 1 hour passed from the start of the reaction, 1 mL of ethylene glycol dimethacrylate was further added to the flask, and the flask contents were reacted for 2 hours. Thereafter, about 5 times as much ethanol as the contents of the flask was added to the flask to precipitate the reaction product. As a result, a polymer (crosslinked styrene-acrylic acid resin) was obtained with a yield of 90%. Regarding the obtained crosslinked styrene-acrylic acid-based resin, the glass transition point (Tg) was 115 ° C., and the mass average molecular weight (Mw) was 11,000.

[Toner Production Method]
(Preparation of pulverized product)
Binder resin (specifically, water-insoluble resin and water-soluble resin) 53 parts by mass, magnetic powder (“EPT-1002” manufactured by Toda Kogyo Co., Ltd.), component: magnetite, particle shape: octahedron, number average primary particles 40 parts by mass of a diameter: 0.23 μm), 2.5 parts by mass of a release agent (high purity solid ester wax: “Nissan Electol (registered trademark) WEP-9” manufactured by NOF Corporation), and a charge control agent ( Nigrosine dye: 2.0 parts by mass of “BONTRON (registered trademark) N-04” manufactured by Orient Chemical Co., Ltd.) was mixed using a super mixer (manufactured by Kawata Corporation). The water-insoluble resin (binder resin) was a water-insoluble resin (cross-linked styrene-acrylic acid resin) prepared by the procedure described above. The water-soluble resin (binder resin) was a resin shown in Table 1 (water-soluble resin W-1 or W-2 determined for each toner). The amount of the water-soluble resin (binder resin) added was such that the ratio of the water-soluble resin to the total amount of the binder resin (water-insoluble resin and water-soluble resin) was the value shown in Table 1. For example, in the production of the toner TA-1, 42.4 parts by mass (= 53 × 0.8) of a water-insoluble resin (cross-linked styrene-acrylic acid resin) and a water-soluble resin W-1 (GOHSEX LL-940) 10.6 parts by mass (= 53 × 0.2), 40.0 parts by mass of magnetic powder (EPT-1002), 2.5 parts by mass of release agent (Nissan Electol WEP-9), and charge control agent (BONTRON N-04) 2.0 parts by mass were mixed. In the production of toner TB-1, no water-soluble resin was used, and the binder resin was only a water-insoluble resin (crosslinked styrene-acrylic acid resin).

Subsequently, the obtained mixture was melt-kneaded using a twin-screw extruder (“TEM-26SS” manufactured by Toshiba Machine Co., Ltd.). Thereafter, the obtained kneaded product was cooled while being rolled. Subsequently, the cooled kneaded material was coarsely pulverized using a hammer mill (impact type screen crusher: manufactured by Hosokawa Micron Corporation). Furthermore, the obtained coarsely pulverized product was finely pulverized using a mechanical pulverizer ("Kriptron Eddy (registered trademark) KTM-EX" manufactured by Earth Technica Co., Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier (wind classifier using the Coanda effect: “Elbow Jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.). As a result, a pulverized product (powder) having a circularity of 0.94 and a volume median diameter (D ₅₀ ) of 8.0 μm was obtained. Hereinafter, the particles contained in the obtained pulverized product are referred to as pre-treatment particles.

  After obtaining the pulverized product (pre-processed particle powder), the following water washing step and drying step were performed. In the production of each of the toners TA-1 to TA-6, the following water washing step A was performed, and in the production of each of the toners TB-5 to TB-7, the following water washing step B was performed. However, in the production of each of the toners TB-1 to TB-4, the water washing step and the drying step described below were not performed, and an external addition step described later was performed following the “preparation of pulverized product”. In the production of each of the toners TB-1 to TB-4, the pulverized product (pre-treatment particles) corresponds to toner base particles.

(Washing process A)
In a room temperature (about 25 ° C.) environment, in a 2 L glass beaker equipped with a thermometer, 500 g of the pulverized product (powder of pre-treated particles) prepared in the above procedure and 1 L of ion-exchanged water at a temperature of 25 ° C. And put. Subsequently, the beaker is output by an ultrasonic cleaning machine ("US-30PS" manufactured by SND Co., Ltd., tank capacity: about 28 L, high frequency output: 480 W, oscillation method: BLT (bolt tightened Langevin type vibrator)) Self-excited oscillation, oscillation frequency: 38 kHz). Subsequently, using the ultrasonic cleaner, ultrasonic treatment was performed for 30 minutes under conditions of a liquid temperature of 25 ° C. and an output of 100%. As a result, a dispersion of pulverized material (toner mother particles) that was ultrasonically treated in water was obtained. Subsequently, the toner mother particle dispersion was taken out of the beaker and suction filtered. Thereafter, reslurry to which 500 mL of ion-exchanged water was added and suction filtration were repeated twice to obtain wet cake-like toner base particles (powder).

(Washing process B)
In a room temperature (about 25 ° C.) environment, in a 2 L glass beaker equipped with a thermometer and a stirring blade, 500 g of the pulverized material (powder of pre-treated particles) prepared in the above-mentioned procedure and ions at a temperature of 25 ° C. 1 L of exchange water was added. Subsequently, the contents of the beaker were stirred for 30 minutes at a rotation speed of 300 rpm. As a result, a dispersion of pulverized material (toner mother particles) stirred in water was obtained. Subsequently, the toner mother particle dispersion was taken out of the beaker and suction filtered. Thereafter, reslurry to which 500 mL of ion-exchanged water was added and suction filtration were repeated twice to obtain wet cake-like toner base particles (powder).

(Drying process)
After the water washing step (water washing step A or B), the wet cake-like toner base particles were put in a vacuum shelf dryer and dried under conditions of a reduced pressure atmosphere (vacuum) and a temperature of 40 ° C. As a result, dried toner base particles (powder) were obtained.

(External addition process)
Subsequently, toner base particles were externally added. Specifically, 100 parts by mass of toner base particles, positively-charged silica particles (“AEROSIL (registered trademark) REA90” manufactured by Nippon Aerosil Co., Ltd.), content: dry-type silica particles imparted with positive charge by surface treatment, number average 1 Next particle size: about 20 nm) 1 part by mass is mixed for 5 minutes using a 10 L capacity FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), so that the external additive (silica particles) is added to the surface of the toner base particles. Attached. Thereafter, sieving was performed using a 200 mesh sieve (aperture 75 μm). As a result, toners TA-1 to TA-6 and TB-1 to TB-7 containing a large number of toner particles were obtained.

With respect to each of the toners TA-1 to TA-6 and TB-1 to TB-7 obtained as described above, the water-soluble surface layer mass W ₁ and the water-soluble total mass W ₂ were measured, respectively. The measurement results were as shown in Table 1. For example, in the toner TA-1, the water-soluble surface layer mass W ₁ is 5 mg (mass per 5 g of toner), the water-soluble total mass W ₂ is 700 mg (mass per 5 g of toner), and W ₁ / W ₂ is 0.0071 (= 5/700). The measuring method of each of the water-soluble surface layer mass W ₁ and the water-soluble total mass W ₂ was as follows.

(Measurement method of water-soluble surface mass W ₁ )
Under a room temperature (about 25 ° C.) environment, in a glass beaker with a capacity of 50 mL equipped with a thermometer, 5 g of toner (measuring object: any of toners TA-1 to TA-6 and TB-1 to TB-7) Then, 10 mL of ion exchange water was added. Subsequently, the beaker was adjusted to an ultrasonic cleaning machine ("US-30PS" manufactured by SND Co., Ltd., tank capacity: about 28 L, high frequency output: 480 W, oscillation method: self-excited oscillation by BLT, oscillation frequency: 38 kHz ). Subsequently, using the ultrasonic cleaner, ultrasonic treatment was performed for 30 minutes under conditions of a liquid temperature of 25 ° C. and an output of 100%. Subsequently, the beaker contents were subjected to solid-liquid separation (suction filtration) using a filter having an opening of 10 μm, and the aqueous phase of the beaker contents was recovered. Subsequently, the container containing the aqueous phase was placed in a hot air circulation oven (“KLO-45M” manufactured by Koyo Thermo System Co., Ltd.) set at a temperature of 80 ° C., and the contents of the container were dried. After completion of drying, the mass of the precipitate was measured. Thus measured mass corresponds to a water-soluble surface weight W _1.

(Measurement method of total water-soluble mass _{W 2)}
In a room temperature (about 25 ° C.) environment, in a glass beaker having a capacity of 50 mL equipped with a thermometer and a stirring blade, toner (measuring object: any of toners TA-1 to TA-6 and TB-1 to TB-7) ) 5 g and 20 mL of tetrahydrofuran were added to obtain a toner dispersion. Subsequently, the contents of the beaker (toner dispersion) were stirred for 30 minutes under the conditions of a temperature of 25 ° C. and a rotation speed of 300 rpm. Subsequently, the beaker contents are subjected to solid-liquid separation (suction filtration) using a filter having an opening of 10 μm, and the liquid phase (specifically, a THF solution containing a toner component dissolved in tetrahydrofuran) is recovered from the beaker contents. did. Subsequently, 200 mL of water was dropped into a container containing the liquid phase (THF solution) to precipitate toner materials (release agent, magnetic powder, charge control agent, and water-insoluble resin) other than the water-soluble resin. . Subsequently, the content of the container was kept at 98 ° C. for 1 hour, and tetrahydrofuran in the container was distilled off. Thereby, tetrahydrofuran in the container was completely removed, and an aqueous phase remained in the container. Thereafter, the remaining aqueous phase was quenched using an ice bath until the temperature reached 25 ° C.

Subsequently, the container containing the aqueous phase was placed in a hot air circulation oven (“KLO-45M” manufactured by Koyo Thermo System Co., Ltd.) set at a temperature of 80 ° C., and the contents of the container were dried. Thereafter, the mass of the solid matter (toner component dissolved in the aqueous phase) remaining in the container was measured. Thus measured mass corresponds to the entire water-soluble mass W _2.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-6 and TB-1 to TB-7) is as follows.

(Low temperature fixability)
As an evaluation machine, a monochrome printer having a Roller-Roller type heat and pressure type fixing device ("ECOSYS (registered trademark) FS-2020D" manufactured by Kyocera Document Solutions Co., Ltd.) has been modified so that the fixing temperature can be changed. ) Was used. A sample (one-component developer: any one of toners TA-1 to TA-6 and TB-1 to TB-7) is put into the developing device of the evaluation machine, and the sample (replenishment toner) is put into a toner container of the evaluation machine. I put it in.

A paper having a basis weight of 90 g / m ² (A4 size) under the conditions of a temperature of 23 ° C. and a humidity of 50% RH, using the above-mentioned evaluation machine under the conditions of a linear speed of 200 mm / second and a toner loading of 1.0 mg / cm ^2. A solid image (specifically, an unfixed toner image) having a size of 25 mm × 25 mm was formed. Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluation machine. The measuring range of the fixing temperature was 150 ° C. or higher and 200 ° C. or lower. Specifically, the fixing temperature of the fixing device is increased from 150 ° C. by 1 ° C. to determine whether fixing is possible for each fixing temperature, and the lowest temperature (minimum fixing temperature) at which a solid image (toner image) can be fixed on paper is measured. did. Whether or not the image could be fixed on the paper was confirmed by a rubbing test as shown below.

  First, the paper was folded so that the surface on which the image was formed was on the inside, and a 1 kg weight covered with a fabric was used to rub the crease 10 times. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the toner peeling length (peeling length) of the bent portion was measured. The lowest temperature among the fixing temperatures at which the peeling length was less than 1 mm was defined as the lowest fixing temperature.

  When the minimum fixing temperature was 180 ° C. or lower, it was evaluated as “good”, and when the minimum fixing temperature exceeded 180 ° C., it was evaluated as “x” (not good).

(Charge decay characteristics)
The charge attenuation constant α of the toner was measured by a method based on JIS (Japanese Industrial Standard) C 61340-2-1-2006 using an electrostatic diffusivity measuring device (“NS-D100” manufactured by Nano Seeds Co., Ltd.). Hereinafter, a method for measuring the charge decay constant of the toner will be described in detail.

  A sample (measuring object: any one of toners TA-1 to TA-6 and TB-1 to TB-7) was put in a measurement cell. The measurement cell was a metal cell in which a recess having an inner diameter of 10 mm and a depth of 1 mm was formed. The toner was pushed in from above using a slide glass, and the concave portions of the cells were filled with the toner. The toner overflowing from the cell was removed by reciprocating the slide glass on the surface of the cell. The filling amount of the object to be measured (toner) was about 0.05 g.

Subsequently, the measurement cell filled with the measurement object was allowed to stand for 12 hours in an environment of a temperature of 32.5 ° C. and a humidity of 80% RH. Subsequently, the grounded measurement cell was placed in an electrostatic diffusivity measuring apparatus, and ions were supplied to the measurement object by corona discharge to charge the measurement object. The probe gap was 1 mm and the discharge time was 0.5 seconds. And after 0.7 second passed after completion | finish of corona discharge, the surface potential of the measuring object was continuously measured on the conditions of sampling frequency 1Hz. A charge decay constant (charge decay rate) α was calculated based on the measured surface potential and the formula “V = V ₀ exp (−α√t)”. In the formula, V represents the surface potential [V], V ₀ represents the initial surface potential [V], and t represents the decay time [second].

  When the charge decay constant was less than 0.0200, it was evaluated as good (good), and when the charge decay constant was 0.0200 or more, it was evaluated as x (not good).

[Evaluation results]
Table 2 shows the results of evaluating low-temperature fixability (minimum fixing temperature) and charge decay characteristics (charge decay constant) for each of toners TA-1 to TA-6 and TB-1 to TB-7. “Insufficient charge” in Table 2 indicates that the chargeability of the toner (measurement target) is insufficient and the toner could not be charged to a level at which the charge attenuation characteristic of the toner can be appropriately measured. means.

The toners TA-1 to TA-6 (toners according to Examples 1 to 6) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-6 includes a plurality of toner particles containing a specific water-insoluble resin and a specific water-soluble resin. In addition, each of the toners TA-1 to TA-6 satisfied both the expressions (1) and (2) (see Table 1).
W ₁ / W ₂ ≦ 0.0075 (1)
500 mg ≦ W ₂ (2)

  As shown in Table 2, each of the toners TA-1 to TA-6 was excellent in both low-temperature fixability and charge decay characteristics (see Table 2).

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

Claims (9)

An electrostatic latent image developing toner comprising a plurality of toner particles containing a first resin and a second resin,
The first resin includes a repeating unit derived from a styrene monomer having neither an acid group nor a hydroxyl group,
The second resin includes a repeating unit having an acid group and / or a hydroxyl group,
The mass W ₁ of the water-soluble component present in the surface layer portion of the toner particles, measured by the following first measurement method, and the water-soluble component present in the whole of the toner particles, measured by the following second measurement method. The mass W ₂ satisfies both the following formulas (1) and (2),
The first resin is a resin that dissolves in tetrahydrofuran but does not dissolve in water in the following first measurement method and the following second measurement method.
The electrostatic latent image developing toner, wherein the second resin is a resin that is soluble in both water and tetrahydrofuran in the following first measurement method and the following second measurement method.
W ₁ / W ₂ ≦ 0.0075 (1)
500 mg ≦ W ₂ (2)
[In the first measurement method, the toner dispersion obtained by adding 5 g of the toner to 10 mL of water was subjected to ultrasonic treatment for 30 minutes at a temperature of 25 ° C., followed by solid-liquid separation, and the obtained water Measuring the mass W ₁ of the toner component dissolved in the phase;
In the second measurement method, a toner dispersion obtained by adding 5 g of the toner to 20 mL of tetrahydrofuran is subjected to a stirring process for 30 minutes at a temperature of 25 ° C. and a rotation speed of 300 rpm, followed by solid-liquid separation. A THF solution containing a dissolved toner component is obtained, 200 mL of water is added to the obtained THF solution, tetrahydrofuran is distilled off at a temperature of 98 ° C., and the mass of the toner components dissolved in the remaining aqueous phase. W ₂ is measured. ]   The electrostatic latent image developing toner according to claim 1, wherein the second resin includes a repeating unit derived from a vinyl alcohol monomer. The second resin is a polymer of monomers including a vinyl alcohol monomer and a vinyl acetate monomer,
3. The electrostatic according to claim 2, wherein in the second resin, the amount of the vinyl alcohol monomer is 20 mol% or more and 45 mol% or less with respect to a total amount of the vinyl alcohol monomer and the vinyl acetate monomer. Latent image developing toner. The electrostatic latent image developing toner according to claim 3, wherein the mass W ₂ is 1000 mg or more and 2000 mg or less.   The first resin includes a styrene monomer having neither an acid group nor a hydroxyl group, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms in the ester portion, and a crosslinking agent. The toner for developing an electrostatic latent image according to any one of claims 2 to 4, which is a polymer of the body.   The amount of the repeating unit derived from the styrenic monomer having neither an acid group nor a hydroxyl group in the first resin is 15% by mass or more and 40% by mass with respect to the total amount of all the repeating units contained in the first resin. The toner for developing an electrostatic latent image according to claim 5, wherein:   The toner particles include a non-capsule toner base particle containing a melt-kneaded product of the first resin, the second resin, and an internal additive, and an external additive attached to the surface of the non-capsule toner base particle. The toner for developing an electrostatic latent image according to claim 5 or 6.   The amount of the second resin contained in the non-capsule toner base particles is 20% by mass or more and 50% by mass or less based on the total amount of the first resin and the second resin contained in the non-capsule toner base particles. The toner for developing an electrostatic latent image according to claim 7. A first step of melt-kneading the first resin and the second resin to obtain a melt-kneaded product containing the first resin and the second resin;
A second step of pulverizing the melt-kneaded product to obtain a powder;
A third step of sonicating the powder in water;
Including
The first resin includes a repeating unit derived from a styrenic monomer having neither an acid group nor a hydroxyl group, and is a resin that is soluble in tetrahydrofuran but not water.
The method for producing a toner for developing an electrostatic latent image, wherein the second resin includes a repeating unit having an acid group and / or a hydroxyl group and is soluble in both water and tetrahydrofuran.