JP2018136471A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both low-temperature fixability and heat-resistant storage property of toner, and form a high-quality image (particularly, image excellent in gradation of colors) with the toner.SOLUTION: A toner particle includes a core and a shell layer. The shell layer contains a thermosetting resin and a thermoplastic resin. In a storage modulus temperature dependence curve of toner, at least within a temperature range of 80°C or more and 120°C or less, the storage modulus becomes smaller as the temperature increases; the storage modulus at a temperature of 80°C is 1.00×10Pa or less; the storage modulus at a temperature of 120°C is 2.00×10Pa or more; the ratio of the storage modulus at a temperature of 80°C to the storage modulus at a temperature of 120°C is 5 or less. In a loss tangent temperature dependence curve of the toner, at least within a temperature range of 80°C or more and 120°C or less, the loss tangent becomes smaller as the temperature increases; the loss tangent at a temperature of 80°C is 1.000 or less; the loss tangent at a temperature of 120°C is 0.100 or more.SELECTED DRAWING: Figure 1

Description

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

  Patent Document 1 discloses that the heat-resistant storage stability of the toner is improved by covering the core of the toner particles with a shell layer, and the low-temperature fixability of the toner is improved by adjusting the storage elastic modulus of the toner to a predetermined range. Technology is disclosed.

Japanese Patent Laying-Open No. 2006-48336

  With the technology disclosed in Patent Document 1, it is possible to achieve both low-temperature fixability and heat-resistant storage stability of the toner. However, there is still room for improvement in forming a high-quality image (especially an image with excellent color gradation) with the toner while achieving both low-temperature fixability and heat-resistant storage stability of the toner. ing.

  The present invention has been made in view of the above problems, and while achieving both low-temperature fixability and heat-resistant storage stability of a toner, a high-quality image (especially an image excellent in color gradation) with the toner. The purpose is to form.

The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles each including a core and a shell layer covering the surface of the core. The shell layer contains a thermosetting resin and a thermoplastic resin. In the storage elastic modulus temperature dependency curve of the toner, at least in the range of 80 ° C. or higher and 120 ° C. or lower, the storage elastic modulus decreases as the temperature increases, and the storage elastic modulus at the temperature of 80 ° C. is 1.00 × 10 6. ⁴ Pa or less, the storage elastic modulus at a temperature of 120 ° C. is 2.00 × 10 ³ Pa or more, and the ratio of the storage elastic modulus at the temperature of 80 ° C. to the storage elastic modulus at the temperature of 120 ° C. is 5 or less. In the loss tangent temperature dependency curve of the toner, at least in the range of 80 ° C. or higher and 120 ° C. or lower, the loss tangent decreases as the temperature increases, and the loss tangent at a temperature of 80 ° C. is 1.000 or lower. The loss tangent at 120 ° C. is 0.100 or more.

  According to the present invention, it is possible to form a high-quality image (particularly, an image excellent in color tone) with the toner while achieving both low-temperature fixability and heat-resistant storage stability of the toner.

It is a graph which shows an example of the G 'temperature dependence curve of the toner for electrostatic latent image development concerning an embodiment of the present invention. 6 is a graph showing an example of a tan δ temperature dependency curve of the toner for developing an electrostatic latent image according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described. Note that the evaluation results (values indicating shape, physical properties, etc.) regarding the powder (more specifically, the toner core, toner base particles, external additive, toner, etc.) are a considerable number of particles unless otherwise specified. Is the number average of the values measured for.

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. Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified, and the “Coulter counter multisizer 3” manufactured by Beckman Coulter Co., Ltd. is used. ) Measured based on. Moreover, the measured value of molecular weight (for example, a number average molecular weight or a mass average molecular weight) is a value measured using gel permeation chromatography unless otherwise specified.

  In the present specification, both untreated silica particles (hereinafter referred to as silica substrate) and silica particles obtained by subjecting a silica substrate to surface treatment (surface-treated silica particles) are described as “silica particles”. To do. In addition, silica particles hydrophobized with a surface treatment agent may be referred to as “hydrophobic silica particles”. Both untreated titanium oxide particles (hereinafter referred to as a titanium oxide substrate) and titanium oxide particles obtained by subjecting a titanium oxide substrate to surface treatment (surface-treated titanium oxide particles) are oxidized with a conductive layer on the surface. Titanium particles are also referred to as “titanium oxide particles”. Titanium oxide particles having a titanium oxide substrate covered with a conductive layer (titanium oxide particles imparted with conductivity by a coating layer) may be referred to as “conductive titanium oxide particles”.

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

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner may be used as a one-component developer. Alternatively, a two-component developer may be prepared by mixing toner and carrier using a mixing device (for example, a ball mill). 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 ensure a sufficient charge imparting property of the carrier to the toner for a long period of time, the resin layer must completely cover the surface of the carrier core (that is, there is no surface area of the carrier core exposed from the resin layer). preferable. 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 are 1 selected from the group consisting of a fluororesin (more specifically, PFA or FEP), a polyamideimide resin, a silicone resin, a urethane resin, an epoxy resin, and a phenol resin. More than one type of resin may be mentioned. 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 positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier. The negatively chargeable toner contained in the two-component developer is negatively charged by friction with the carrier.

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

  First, an 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 a developer containing toner is set) supplies the toner to the photoconductor to develop the electrostatic latent image formed on the photoconductor. The toner is charged by friction with the carrier, the developing sleeve, or the blade in the developing device before being supplied to the photoreceptor. For example, a positively chargeable toner is positively charged. In the developing process, toner (specifically, charged toner) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is supplied to the photosensitive member, and the supplied toner is By attaching to the electrostatic latent image on the photoconductor, a toner image is formed on the photoconductor. The consumed toner is replenished to the developing device from a toner container containing replenishment toner.

  In the subsequent transfer process, after the transfer device of the electrophotographic apparatus transfers the toner image on the photosensitive member to an intermediate transfer member (for example, a transfer belt), the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Transcript to. 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. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan. After the transfer step, the toner remaining on the photoreceptor is removed by a cleaning member (for example, a cleaning blade). The transfer method may be a direct transfer method in which the toner image on the photosensitive member is directly transferred to the recording medium without using the intermediate transfer member. The fixing method may be a belt fixing method.

  Toner particles (capsule toner particles) contained in the toner according to the present embodiment include a core (hereinafter referred to as a toner core) and a shell layer (capsule layer) formed on the surface of the toner core. The shell layer is substantially composed of a resin. For example, by covering a toner core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the toner core or may partially cover the surface of the toner core. An external additive may be attached to the surface of the shell layer (or the surface region of the toner core not covered with the shell layer). If not necessary, the external additive may be omitted. Toner particles mainly including toner particles including a shell layer (for example, 80% by number or more) may be mixed with toner particles not including a shell layer. Hereinafter, the toner particles before the external additive adheres are referred to as toner mother particles. A material for forming the shell layer is referred to as a shell material.

  By dispersing the toner core in a solution in which the shell material is dissolved, a toner core dispersion liquid (hereinafter referred to as toner core dispersion liquid) can be obtained. When the shell material is polymerized in the toner core dispersion, it is preferable that the toner core has an anionic property and the shell material has a cationic property. In the toner core dispersion, the cationic shell material is electrically attracted to the anionic toner core, so that a shell layer is easily formed on the surface of the toner core by in-situ polymerization. Further, a uniform shell layer can be easily formed on the surface of the toner core without using a surfactant (or only with a small amount of surfactant).

  As an indicator of anionic or cationic magnitude, zeta potential can be used. For example, when the zeta potential of a particle measured in an aqueous medium at 25 ° C. adjusted to pH 4 exhibits negative polarity (less than 0 V), the particle has an anionic property. Moreover, when the zeta potential of the particle measured in an aqueous medium at 25 ° C. adjusted to pH 4 exhibits positive polarity (over 0 V), the particle has a cationic property. The higher the pH of the aqueous medium, the smaller the zeta potential of particles (eg, toner core or toner particles) measured in the aqueous medium. As the aqueous medium used for measuring the zeta potential, ion-exchanged water having a conductivity of 10 μS / cm or less is preferable. In order to accurately measure the zeta potential of the particles in the aqueous medium, it is desirable that bubbles do not adhere to the surface of the particles in the aqueous medium and the surface of the particles is sufficiently wetted. Examples of the method for improving the wettability of the particles include a method of sonicating an aqueous medium containing the particles, or a method of adding a surfactant to the aqueous medium. Since ions in the aqueous medium easily affect the measured value of the zeta potential, it is preferable to use a nonionic surfactant when adding the surfactant to the aqueous medium.

  In order to strengthen the bond between the toner core and the shell layer, the zeta potential of the toner core at pH 4 is less than 0V (more preferably, −5 mV or less), and the zeta potential of the toner particles at pH 4 is greater than 0V (more Preferably, it is +5 mV or more. When the toner core contains a polyester resin, the zeta potential of the toner core at pH 4 tends to be smaller than 0V. When the shell material contains a nitrogen atom, the zeta potential at pH 4 of the toner particles having a shell layer formed of the shell material tends to be larger than 0V.

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

(Basic toner configuration)
The electrostatic latent image developing toner includes a plurality of toner particles including a toner core and a shell layer covering the surface of the toner core. The shell layer contains a thermosetting resin and a thermoplastic resin. In the storage elastic modulus temperature dependency curve (vertical axis: storage elastic modulus, horizontal axis: temperature) of the toner measured with a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz, the temperature is at least 80 ° C. or higher. In the range of ℃ or lower, the storage elastic modulus decreases as the temperature increases, the storage elastic modulus at a temperature of 80 ℃ is 1.00 × 10 ⁴ Pa or lower, and the storage elastic modulus at a temperature of 120 ℃ is 2.00 × and at 10 3 ^Pa or more, the ratio of the storage modulus temperature 80 ° C. for storage modulus temperature 120 ° C. is 5 or less. In the loss tangent temperature dependence curve (vertical axis: loss tangent, horizontal axis: temperature) of the toner measured with a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz, at least the temperature is 80 ° C. or higher and 120 ° C. or lower. In this range, the loss tangent decreases as the temperature increases, the loss tangent at a temperature of 80 ° C. is 1.000 or less, and the loss tangent at a temperature of 120 ° C. is 0.100 or more. The measuring method of each of the storage elastic modulus temperature dependency curve and the loss tangent temperature dependency curve of the toner is the same method as in the examples described later or an alternative method thereof.

Hereinafter, the storage elastic modulus temperature dependency curve measured with a rheometer under the conditions of a temperature increase rate of 2 ° C./min and a frequency of 0.01 Hz is referred to as “G ′ temperature dependency curve”, and a temperature increase rate of 2 ° C./min with a rheometer. The loss tangent temperature dependence curves measured under the condition of frequency 0.01 Hz are described as “tan δ temperature dependence curves”, respectively. Further, the storage elastic modulus at a temperature of 80 ° C. is “storage elastic modulus G ′ ₈₀ ”, the storage elastic modulus at a temperature of 120 ° C. is “storage elastic modulus G ′ ₁₂₀ ”, and the storage elastic modulus at a temperature of 120 ° C. The ratio of the storage elastic modulus is described as “ratio G ′ ₈₀ / G ′ ₁₂₀ ”. Further, the loss tangent at a temperature of 80 ° C. is described as “loss tangent tan δ ₈₀ ”, and the loss tangent at a temperature of 120 ° C. is described as “loss tangent tan δ ₁₂₀ ”.

  FIG. 1 shows an example of a G ′ temperature dependency curve (vertical axis: storage elastic modulus, horizontal axis: temperature) of the toner having the above basic configuration. FIG. 1 shows the temperature dependence of the storage elastic modulus of the toner in the temperature range of 40 ° C. or more and 200 ° C. or less. Specifically, FIG. 1 shows the storage elasticity of toner at each temperature under the condition of a frequency of 0.01 Hz while using a rheometer to raise the toner temperature from 40 ° C. at a constant rate (temperature increase rate 2 ° C./min). It is the result of measuring the rate. In the G ′ temperature dependency curve shown in FIG. 1, the storage elastic modulus decreases as the toner temperature increases. In addition, a shoulder S exists in the G ′ temperature dependency curve. When the temperature of the toner rises to the temperature of the shoulder S, the storage elastic modulus of the toner begins to rapidly decrease. After the storage elastic modulus of the toner decreases with a large change rate for a certain period of time, the change rate gradually increases. Is getting smaller. At the temperature of the shoulder S, the change rate of the storage elastic modulus of the toner (corresponding to the slope of the G ′ temperature dependency curve) changes abruptly. In the G ′ temperature dependency curve shown in FIG. 1, the shoulder S exists at a temperature lower than 80 ° C. Specifically, the temperature of the shoulder S is 56 ° C. In addition, in the G ′ temperature dependence curve, when the point (one point) where the slope changes suddenly cannot be clearly determined, the tangent of the curve before the slope changes suddenly and after the slope changes suddenly The intersection with the tangent of the curve is the shoulder.

In the G ′ temperature dependence curve shown in FIG. 1, the storage elastic modulus G ′ ₈₀ is 8.57 × 10 ³ Pa, and the storage elastic modulus G ′ ₁₂₀ is 2.28 × 10 ³ Pa. Therefore, the ratio G ′ ₈₀ / G ′ ₁₂₀ is 3.76 (= (8.57 × 10 ³ ) / (2.28 × 10 ³ )).

  FIG. 2 shows an example of a tan δ temperature dependency curve (vertical axis: loss tangent, horizontal axis: temperature) of the toner having the above basic configuration. FIG. 2 shows the temperature dependence of the loss tangent of the toner in the temperature range of 40 ° C. or higher and 200 ° C. or lower. Specifically, FIG. 2 shows the loss tangent of the toner at each temperature under the condition of a frequency of 0.01 Hz while increasing the toner temperature from 40 ° C. at a constant rate (temperature increase rate 2 ° C./min) using a rheometer. It is the result of having measured. In the tan δ temperature dependency curve shown in FIG. 2, the loss tangent decreases as the toner temperature increases. A peak P exists in the tan δ temperature dependency curve. In the tan δ temperature dependence curve shown in FIG. 2, a peak P exists at a temperature lower than 80 ° C. Specifically, the temperature of the peak P is 65 ° C.

In the tan δ temperature dependence curve shown in FIG. 2, the loss tangent tan δ ₈₀ is 0.725 and the loss tangent tan δ ₁₂₀ is 0.265.

  The inventor of the present application has found that the spread of the toner after fixing can be predicted from the characteristics in the temperature range of 80 ° C. to 120 ° C. of the G ′ temperature dependency curve and the tan δ temperature dependency curve of the toner. The G ′ temperature dependency curve and the tan δ temperature dependency curve are curves measured by a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz. The lower the frequency in the rheometer measurement conditions, the more difficult the storage elastic modulus of the toner decreases at a low temperature (temperature 80 ° C.). The temperature range of 80 ° C. to 120 ° C. generally corresponds to the fixing temperature of the toner.

At a temperature of 80 ° C., the storage elastic modulus of the toner is 1.00 × 10 ⁴ Pa or less, and the loss tangent of the toner is 1.000 or less. The toner ratio G ′ ₈₀ / G ′ ₁₂₀ (ratio of storage elastic modulus at a temperature of 80 ° C. to storage elastic modulus at a temperature of 120 ° C.) is 5 or less. That is, at a temperature of 80 ° C., the toner is sufficiently melted, but the toner has a sufficiently strong viscosity.
At a temperature of 120 ° C., the storage elastic modulus of the toner is 2.00 × 10 ³ Pa or more, and the loss tangent of the toner is 0.100 or more. That is, at a temperature of 120 ° C., the toner has a sufficiently strong elasticity.

  The toner having the temperature characteristics as described above is excellent in low-temperature fixability and hardly spreads even when fixed. The inventor of the present application has found that by forming an image using such toner, the spread of the toner after fixing can be suppressed, and an image excellent in color gradation (specifically, an image having a small dot gain) can be formed. It was.

  When the shell layer is formed with only one type of resin, high-quality images (especially images with excellent color gradation) are formed as described above while achieving both low-temperature fixability and heat-resistant storage stability of the toner. It is not easy to do. For example, heat-resistant storage stability can be imparted to the toner by including a thermosetting resin in the shell layer. However, such toners do not melt sufficiently at low temperatures. On the other hand, low temperature fixability can be imparted to the toner by including a thermoplastic resin in the shell layer. However, with such a toner, it is difficult to ensure sufficient sharp melt properties, and elasticity at high temperatures (120 ° C.) tends to be insufficient.

  The inventor of the present application uses both the thermosetting resin and the thermoplastic resin in an appropriate ratio (mass ratio) in the shell layer to achieve both low-temperature fixability and heat-resistant storage stability of the toner. Succeeded in forming high-quality images (particularly images with excellent color gradation).

  A particularly preferable toner configuration from the viewpoint of toner productivity and performance is the following configuration (hereinafter referred to as “preferable core-shell configuration”).

(Preferable core shell configuration)
The toner core contains an amorphous polyester resin having a number average molecular weight of 2,000 to 5,000 and a weight average molecular weight of 5,000 to 30,000, and does not contain a crystalline polyester resin. The shell layer contains a melamine resin and an acrylamide resin. A shell layer covers the entire surface of the toner core.

  The toner having the preferred core-shell structure can be produced without using a crystalline polyester resin. The amorphous polyester resin having the molecular weight is easily melted at a low temperature. By including such an amorphous polyester resin in the toner core, it becomes easy to ensure sufficient low-temperature fixability of the toner even during high-speed printing. Further, the shell layer contains a melamine resin and an acrylamide resin and covers the entire surface of the toner core, so that sufficient positive chargeability of the toner can be easily secured. And, by making the thickness of the shell layer appropriate, and by making the ratio (mass ratio) of melamine resin and acrylamide resin appropriate, the toner has sufficient heat storage stability and sufficient Sharp melt properties and sufficient elasticity at high temperatures (120 ° C.) can be imparted. Specifically, the thickness of the shell layer is 5 nm or more and 15 nm or less, and the ratio of the mass of the melamine resin contained in the shell layer to the mass of the acrylamide resin contained in the shell layer is 0.20 or more and 0. It is preferable to make it .50 or less. If the thickness of the shell layer is too thin, the loss tangent of the toner tends to be too large.

  Whether or not the shell layer covers the entire surface of the toner core is determined by, for example, toner particles (previously dyed toner particles) photographed with a field emission scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.). This can be determined by analyzing the image. The covered area and the other area (non-covered area) on the surface of the toner core can be distinguished by, for example, a difference in luminance value.

  The thickness of the shell layer can be measured by analyzing a TEM (transmission electron microscope) image of the cross section of the toner particles using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). If the thickness of the shell layer is not uniform in one toner particle, four equally spaced locations (specifically, two straight lines that are perpendicular to each other at the approximate center of the cross section of the toner particle are drawn. The thickness of the shell layer is measured at each of the four points where the straight line intersects the shell layer, and the arithmetic average of the four measured values obtained is taken as the evaluation value of the toner particles (shell layer thickness). The boundary between the toner core and the shell layer can be confirmed, for example, by selectively dyeing only the shell layer of the toner core and the shell layer. When the boundary between the toner core and the shell layer is unclear in the TEM photographed image, a characteristic element contained in the shell layer in the TEM photographed image is formed by combining TEM and electron energy loss spectroscopy (EELS). By performing the mapping, the boundary between the toner core and the shell layer can be clarified.

  In particular, in order to obtain a toner suitable for image formation, it is preferable that the toner having the preferable core-shell configuration further has the following temperature characteristics.

(Preferred temperature characteristics)
The glass transition point of the toner is 38.0 ° C. or higher and 46.0 ° C. or lower. The storage elastic modulus of the toner at 80 ° C. is 8.50 × 10 ³ Pa or more and 1.00 × 10 ⁴ Pa or less. The storage elastic modulus of the toner at a temperature of 120 ° C. is 2.00 × 10 ³ Pa or more and 4.00 × 10 ³ Pa or less. The loss tangent of the toner at 80 ° C. is 0.700 or more and 0.750 or less. The loss tangent of the toner at 120 ° C. is not less than 0.200 and not more than 0.300.

  The toner core is preferably a pulverized core (so-called pulverized toner). In general, the toner core is roughly classified into a pulverized core and a polymerized core (also called a chemical toner). The toner core obtained by the pulverization method belongs to the pulverization core, and the toner core obtained by the aggregation method belongs to the polymerization core. The pulverization method is a method of obtaining a powder (for example, a toner core) 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 pulverized core containing the polyester resin contains one or more polyester resins melt-kneaded.

The shoulder temperature in the G ′ temperature dependency curve of the toner is preferably 45 ° C. or higher and 65 ° C. or lower, and particularly preferably 50 ° C. or higher and 60 ° C. or lower. The peak temperature in the tan δ temperature dependency curve of the toner is preferably 55 ° C. or higher and 75 ° C. or lower, and particularly preferably 60 ° C. or higher and 70 ° C. or lower. The toner ratio G ′ ₈₀ / G ′ ₁₂₀ is particularly preferably 2.00 or more and 4.00 or less.

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

  Hereinafter, the toner core (binder resin and internal additive), shell layer, and external additive will be described in order. An unnecessary component (for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder) may be omitted depending on the use of the toner.

[Toner core]
(Binder resin)
In the toner core, the binder resin generally 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 core. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to be anionic, and when the binder resin has an amino group, the toner core The tendency to become cationic becomes stronger.

  As the binder resin, an amorphous polyester resin is preferable. The toner core may contain a crystalline polyester resin. By containing a crystalline polyester resin in the toner core, sharp melt properties can be imparted to the toner core.

  The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diol, bisphenol, trihydric or higher alcohol as shown below) and one or more polyhydric carboxylic acids (more specifically). Specifically, it can be obtained by polycondensation with a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below. The polyester resin is a repeating unit derived from another monomer (a monomer that is neither a polyhydric alcohol nor a polyvalent carboxylic acid: more specifically, a styrene monomer or an acrylic acid monomer as shown below). May be included.

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

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

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

  Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acid (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acid (more specifically, malonic acid). , Succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decanedicarboxylic acid), α, ω-alkanedicarboxylic acid with a side chain added (more specifically, Alkyl succinic acid or alkenyl succinic acid), unsaturated dicarboxylic acid (more specifically, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, etc.), or cycloalkane dicarboxylic acid (more specifically, Are cyclohexanedicarboxylic acid and the like.

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

  As the binder resin, an amorphous polyester resin containing bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) as an alcohol component is particularly preferable. Such an amorphous polyester resin is easily available and has a temperature characteristic suitable for fixing a toner.

  As a first preferred example of the non-crystalline polyester resin, the alcohol component contains bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) and does not contain a trivalent or higher alcohol. Examples of the acid component include an amorphous polyester resin containing an aromatic dicarboxylic acid (for example, terephthalic acid) and an unsaturated dicarboxylic acid (for example, fumaric acid) and not containing a trivalent or higher carboxylic acid.

  As a second preferred example of the non-crystalline polyester resin, the alcohol component contains bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) and does not contain a trihydric or higher alcohol. Examples of the acid component include an amorphous polyester resin containing an aromatic dicarboxylic acid (for example, terephthalic acid) and containing neither an unsaturated dicarboxylic acid nor a trivalent or higher carboxylic acid.

  If the shell layer covers the entire surface of the toner core, it becomes easy to ensure sufficient heat-resistant storage stability of the toner. For this reason, in the toner having such a configuration, the degree of freedom in selecting the binder resin is increased.

(Coloring agent)
The toner core 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 core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

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

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

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

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

(Release agent)
The toner core 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 core 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 core, the anionicity of the toner core 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 core, the toner core can be made more cationic. In order to form a high-quality image (especially an image with excellent color gradation) with the toner while achieving both low-temperature fixability and heat-resistant storage stability of the toner, a polymer-type positively chargeable charge control agent is used. Particularly preferred. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Magnetic powder)
The toner core 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.

[Shell layer]
In the toner having the basic configuration described above, the shell layer contains both a thermoplastic resin and a thermosetting resin.

  The thermosetting resin contained in the shell layer is at least one selected from the group consisting of melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, aniline resins, and polyimide resins. The thermosetting resin is preferable.

  In order to improve the heat resistant storage stability and positive chargeability of the toner, the shell layer contains one or more thermosetting resins produced by condensation polymerization of a compound having an amino group and an aldehyde (for example, formaldehyde). It is preferable. The melamine resin is a condensation polymer of melamine and formaldehyde. The urea resin is a condensation polymer of urea and formaldehyde. Glyoxal resin is a polycondensation product of a reaction product of glyoxal and urea and formaldehyde.

  The thermoplastic resin contained in the shell layer is preferably a polymer of one or more acrylic acid monomers. Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Suitable examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic. Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Suitable examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic. The acid 4-hydroxybutyl is mentioned.

  In order to form a high-quality image (especially an image with excellent color tone) with the toner while achieving both low-temperature fixability and heat-resistant storage stability of the toner, the shell layer is made of a melamine resin (details) It is particularly preferable to contain a polymer of one or more melamine monomers) and an acrylamide resin (specifically, a polymer of one or more acrylamide monomers). In the shell layer, a strong bond such as a covalent bond is not formed between the melamine resin and the acrylamide resin, and a weak bond such as a hydrogen bond tends to be formed. For this reason, the melamine-based resin and the acrylamide-based resin are likely to exist by being bonded with an appropriate strength. Such a structure of the shell layer is considered to improve the fixing property of the toner. A preferred example of a resin raw material (melamine monomer) for synthesizing a melamine resin is methylol melamine. Preferable examples of the resin raw material (acrylamide monomer) for synthesizing the acrylamide resin include acrylamide or methacrylamide.

[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. The toner base particles include a toner core and a shell layer. Unlike the internal additive, the external additive does not exist inside the toner core, 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.

As the external additive particles, inorganic particles having a conductive layer on the surface may be used. The conductive layer is, for example, a metal oxide film (hereinafter referred to as a doped metal oxide) provided with conductivity by doping (more specifically, an Sb-doped SnO ₂ film or the like). The conductive layer may be a layer containing a conductive material other than the doped metal oxide (more specifically, a metal, a carbon material, a conductive polymer, or the like). For example, by forming a conductive layer on the surface of a titanium oxide substrate (untreated titanium oxide particles), external additive particles (conductive titanium oxide particles) having low electrical resistance can be obtained.

[Toner Production Method]
Hereinafter, an example of a method for producing a toner having the above-described basic configuration will be described.

(Preparation of toner core)
In order to easily obtain a good quality toner core, the toner core is preferably produced by an agglomeration method or a pulverization method, and more preferably produced 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 pulverized product is classified. As a result, a toner core having a desired particle size can be obtained.

  Hereinafter, an example of the aggregation method will be described. First, the fine particles of the binder resin, the release agent, and the colorant are aggregated in an aqueous medium to obtain aggregated particles containing the binder resin, the release agent, and the colorant. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. As a result, a toner core dispersion is obtained. Thereafter, an unnecessary substance (such as a surfactant) is removed from the dispersion liquid of the toner core to obtain the toner core.

(Formation of shell layer)
Next, a shell layer is formed on the surface of the obtained toner core. Hereinafter, a suitable example of the method for forming the shell layer will be described. In order to suppress dissolution or elution of the toner core components (particularly, the binder resin and the release agent) when forming the shell layer, it is preferable to form the shell layer in an aqueous medium. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100 ° C.

  First, an acidic substance (for example, hydrochloric acid or p-toluenesulfonic acid aqueous solution) is added to ion-exchanged water to prepare a weakly acidic (for example, pH selected from 3 to 5) aqueous medium. Subsequently, the toner core and the shell material are added to the aqueous medium whose pH is adjusted. As a shell material, a shell material (hereinafter referred to as a first shell material) for forming a portion made of a thermosetting resin in the shell layer, and a portion made of a thermoplastic resin substantially as a shell. A shell material to be formed in the layer (hereinafter referred to as a second shell material) is added. In order to form a homogeneous shell layer, the first shell material and the second shell material are preferably water-soluble. The first shell material is particularly preferably a methylol melamine polymer (for example, a methylol melamine initial polymer). The second shell material is particularly preferably a polymer of acrylamide monomers (for example, polyacrylamide or polymethacrylamide). Each of the first shell material and the second shell material is polymerized separately in advance, so that the shell layer is substantially composed of a portion made of a thermosetting resin and substantially made of a thermoplastic resin. It can suppress that a site | part couple | bonds too strongly with each other.

  In order to form a homogeneous shell layer, it is preferable to dissolve or disperse the shell material in the liquid by, for example, stirring the liquid containing the shell material. In order to suppress dissolution or elution of the toner core components (particularly, the binder resin and the release agent) when forming the shell layer, it is preferable to form the shell layer in an aqueous medium.

  Subsequently, while stirring the liquid containing the toner core and the shell material, the liquid temperature is set at a predetermined holding temperature (for example, a speed selected from 0.05 ° C./min to 3.50 ° C./min). And a temperature selected from 50 ° C. to 85 ° C.). Furthermore, the temperature of the liquid is maintained at the above holding temperature for a predetermined time (for example, a time selected from 30 minutes to 4 hours) while stirring the liquid. While the temperature of the liquid is kept high (or during the temperature increase), the shell material (first shell material and second shell material) adheres to the surface of the toner core and bonds between the toner core and the shell material ( It is considered that the fixation of the shell layer proceeds and the hardening of the shell layer also proceeds. By such heating, a hardened shell layer is formed on the surface of the toner core. The formed shell layer contains a thermosetting resin and a thermoplastic resin.

(Solid-liquid separation, washing, external addition)
By forming a shell layer on the surface of the toner core in the liquid as described above, a dispersion of toner base particles can be obtained. Subsequently, the toner mother particle dispersion is neutralized using, for example, sodium hydroxide. Subsequently, the toner mother particle dispersion 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, for example, the dispersion of the toner base particles in water and the filtration of the obtained dispersion liquid are repeated to wash the toner base particles. Subsequently, the washed toner base particles are dried. For drying the toner base particles, for example, a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, or a vacuum dryer can be used. 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.) under the condition that the external additive is not buried in the toner base particles. An external additive may be attached to the surface of the toner base particles. 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. In this way, a toner containing a large number of toner particles is obtained.

  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, when reacting a material (for example, a shell material) in a liquid, the material may be reacted in the liquid for a predetermined time after the material is added to the liquid, or the material is added to the liquid over a long period of time. Then, the material may be reacted in the liquid while adding the material to the liquid. Moreover, a material (for example, shell material) may be added to the liquid at once, or may be added to the liquid in a plurality of times. After obtaining the powder, classification and / or sieving may be performed. 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. Moreover, even if it does not adjust pH of a liquid, when reaction for forming a shell layer advances favorably, you may omit a pH adjustment process. 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. 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-3 and TB-1 to TB-4 (each positively charged toner for developing an electrostatic latent image) according to Examples or Comparative Examples.

  “Mass ratio M / A” in Table 1 means the ratio of the mass of the melamine resin contained in the shell layer to the mass of the acrylamide resin contained in the shell layer.

  Hereinafter, a production method, an evaluation method, and an evaluation result of toners TA-1 to TA-3 and TB-1 to TB-4 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. Moreover, the measuring method of Tg (glass transition point) is as follows, if not specified at all.

<Measurement method of Tg>
As a measuring device, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) was used. The Tg (glass transition point) of the sample was determined by measuring the endothermic curve of the sample using a measuring device. Specifically, about 10 mg of a sample (for example, toner) was placed in an aluminum dish (aluminum container), and the aluminum dish was set in the measurement unit of the measurement apparatus. In addition, an empty aluminum dish was used as a reference. In the measurement of the endothermic curve, the temperature of the measurement part was increased from the measurement start temperature of 25 ° C. to 200 ° C. at a rate of 10 ° C./min (RUN1). Thereafter, the temperature of the measurement part was lowered from 200 ° C. to 25 ° C. at a rate of 10 ° C./min. Subsequently, the temperature of the measurement part was again raised from 25 ° C. to 200 ° C. at a rate of 10 ° C./min (RUN 2). An endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of the sample was obtained by RUN2. The Tg of the sample was read from the obtained endothermic curve. In the endothermic curve, the temperature (onset temperature) of the inflection point (intersection of the extrapolation line of the base line and the extrapolation line of the falling line) due to the glass transition corresponds to the Tg (glass transition point) of the sample. .

[Preparation of materials]
(Production of toner core)
Using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.), 87 parts by mass of an amorphous polyester resin (“CBC500” manufactured by Kao Corporation) and a colorant (carbon black: “REGAL” manufactured by Cabot Corporation) (Registered trademark) 330R ") 5 parts by mass, mold release agent (Carnauba wax:" Carnauba wax No. 1 "manufactured by Hiroyuki Kato Co., Ltd.), and polymer type positive charge control agent (Fujikura Kasei Co., Ltd.) 3 parts by mass of “Acrybase (registered trademark) FCA-201-PS”, component: styrene-acrylic acid resin containing a repeating unit derived from a quaternary ammonium salt, was mixed.

  The non-crystalline polyester resin (CBC500) has a number average molecular weight (Mn) of 2000 or more and 5000 or less and a mass average molecular weight (Mw) of 5000 or more and 30000 or less.

Subsequently, the obtained mixture was melt-kneaded using a twin screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) under conditions of a material supply speed of 5 kg / hour, a shaft rotation speed of 150 rpm, and a cylinder temperature of 150 ° C. . Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark)” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill Type I” manufactured by Nippon Pneumatic Industry Co., Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core (powder) having a volume median diameter (D ₅₀ ) of 6 μm was obtained.

(External additive: Preparation of silica particles)
Using a supersonic jet pulverizer (“Jet Mill IDS-2” manufactured by Nippon Pneumatic Industry Co., Ltd.), silica particles (hydrophilic fumed silica particles having a number average primary particle size of 12 nm: “AEROSIL” manufactured by Nippon Aerosil Co., Ltd. (Registered trademark) 200 "). The crushed silica particles (powder) are put in a closed FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.) and sprayed toward 100 parts by mass of silica particles with a hydrophobizing agent (3-aminopropyltriethoxysilane and 20 parts by mass of a solution containing dimethyl silicone oil in a mass ratio of 1: 1 was sprayed uniformly. Subsequently, the surface of the silica particles was hydrophobized by reacting at 110 ° C. for 2 hours while mixing the silica particles and the hydrophobizing agent using a closed FM mixer. Subsequently, after the side reaction product was removed by a reduced pressure treatment, a heat treatment at 200 ° C. was further performed for 1 hour to obtain hydrophobic silica particles (powder).

(External additive: Preparation of titanium oxide particles)
A mixture of titanium tetrachloride and oxygen gas produced by the chlorine method was introduced into the gas phase oxidation reactor. Subsequently, titanium oxide (bulk) was obtained by performing a gas phase oxidation reaction of the mixture at a temperature of 1000 ° C. in the reactor. The obtained titanium oxide (bulk) was pulverized using a hammer mill. Subsequently, the obtained pulverized titanium oxide was washed and then dried at a temperature of 110 ° C. Furthermore, the dried pulverized titanium oxide was pulverized using a jet mill. As a result, fine titanium oxide particles (titanium oxide by a vapor phase method) were obtained.

Subsequently, using an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), 100 parts by mass of the obtained titanium oxide fine particles and 2.6 parts by mass of isopropyl triisostearoyl titanate are subjected to a coupling reaction at a temperature of 130 ° C. Thus, the titanium oxide fine particles were surface-treated. Subsequently, the surface-treated titanium oxide fine particles were dried and then crushed. As a result, fine titanium oxide particles having an electric resistivity of 1.0 × 10 ⁹ Ω · cm and a methanol hydrophobization degree of 35% were obtained. Since the electrical resistivity of the titanium oxide fine particles is likely to vary depending on the manufacturing conditions, the titanium oxide fine particles were repeatedly produced until titanium oxide fine particles having a desired electrical resistivity were obtained.

Subsequently, the obtained titanium oxide fine particles were subjected to tin antimony treatment. Specifically, the obtained titanium oxide fine particles were dispersed in water to prepare a 100 g / L suspension of titanium oxide fine particles. Subsequently, the obtained titanium oxide suspension was heated to 70 ° C. Further, a solution prepared by dissolving 2 g of tin chloride (SnCl ₄ .5H ₂ O) and 0.1 g of antimony chloride (SbCl ₂ ) in 50 mL of a 2N hydrochloric acid aqueous solution and an aqueous sodium hydroxide solution having a concentration of 10% by mass were oxidized. It was added over 1 hour to the titanium oxide suspension so that the pH of the titanium suspension was maintained at 2-3. As a result, a conductive layer composed of each hydrate of tin oxide and antimony oxide was formed on the surface of the titanium oxide fine particles in the titanium oxide suspension.

  Thereafter, the titanium oxide suspension was filtered (solid-liquid separation), and the resulting titanium oxide fine particles were washed. Subsequently, the washed titanium oxide fine particles were fired at a temperature of 600 ° C. Subsequently, the fired titanium oxide fine particles were crushed using a jet mill (manufactured by Nippon Pneumatic Industry Co., Ltd.). As a result, conductive titanium oxide particles (powder) having an electrical resistivity of 50 Ω · cm and a hydrophilic property were obtained.

(Preparation of developer carrier)
2 kg of an epoxy resin (“jER (registered trademark) 1004” manufactured by Mitsubishi Chemical Corporation) was dissolved in 20 L of acetone to obtain a solution. Subsequently, 100 g of diethylenetriamine and 150 g of phthalic anhydride were added to the resulting solution to obtain a mixed solution. Subsequently, the obtained mixed liquid and 10 kg of a Mn—Mg—Sr ferrite core (“EF-35” manufactured by Powder Tech Co., Ltd., number average primary particle size: about 35 μm) are mixed with a fluidized bed coating apparatus (Freund Sangyo). ("Spiraflow (registered trademark) SFC-5" manufactured by Co., Ltd.). Subsequently, the surface of the ferrite particles (Mn—Mg—Sr ferrite core) was coated with an epoxy resin using a coating device while sending hot air of 80 ° C. into the coating device. The obtained resin-coated particles were heated at 180 ° C. for 1 hour using a dryer. As a result, a developer carrier (powder) was obtained.

[Toner Production Method]
In the production of each of toners TA-1 to TA-3 and TB-1 to TB-3, a shell layer was formed on the toner core produced by the above-described procedure. In the production of the toner TB-4, the above-described toner core was directly used as toner base particles without performing the following shell layer forming step, washing step, and drying step (see Table 1).

(Shell layer forming process)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and 300 mL of ion-exchanged water was placed in the flask. Thereafter, the temperature in the flask was kept at 30 ° C. using a water bath. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 4.

  Subsequently, the first shell material (aqueous solution of hexamethylol melamine initial polymer having a solid content concentration of 80% by mass: “Milben (registered trademark) Resin SM-607” manufactured by Showa Denko KK) and the second shell material (solid content) An aqueous solution of polyacrylamide having a concentration of 11% by mass: “BECKAMINE (registered trademark) A-1” manufactured by DIC Corporation) was added to the flask. The addition amount of each of the first shell material (milben resin SM-607) and the second shell material (BECKAMINE A-1) was such that the mass ratio M / A was a value shown in Table 1. The total amount of the first shell material (Milben Resin SM-607) and the second shell material (BECKAMINE A-1) was such that the thickness of the shell layer of each toner was the same (about 10 nm).

  For example, in the production of the toner TA-1, 1.25 mg of the first shell material (Milben Resin SM-607) and 0.0409 g of the second shell material (BECKAMINE A-1) were added. The amount of the melamine resin contained in the shell layer after curing was 0.001 g (= 0.80 × 0.00125 g). The amount of acrylamide resin contained in the shell layer after curing was 0.0045 g (= 0.11 × 0.0409 g). The mass ratio M / A was 0.22 (= 0.001 / 0.0045).

  Subsequently, 300 g of the toner core (powder) prepared by the above procedure was added to the flask, and the flask contents were stirred for 1 hour under the conditions of a rotation speed of 200 rpm and a temperature of 40 ° C. Subsequently, 300 mL of ion exchange water was added to the flask, and the temperature in the flask was increased to 70 ° C. at a rate of 1.0 ° C./min while stirring the flask contents at a rotation speed (stirring blade) of 100 rpm. The flask contents were stirred for 2 hours under the conditions of 70 ° C. and rotation speed (stirring blade) of 100 rpm. As a result, a shell layer was formed on the surface of the toner core, and a dispersion of toner base particles was obtained. Thereafter, the pH of the dispersion of the toner base particles was adjusted to 7 (neutralized) using sodium hydroxide, and the dispersion of the toner base particles was cooled to room temperature (about 25 ° C.).

(Washing process)
The dispersion of toner base particles obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, toner base particles in the form of wet cake were obtained. Thereafter, the obtained wet cake-like toner base particles were dispersed again in ion-exchanged water. Dispersion and filtration were repeated a total of 5 times to wash the toner base particles.

(Drying process)
Subsequently, the washed toner base particles (powder) were dispersed in an aqueous ethanol solution having a concentration of 50% by mass to obtain a slurry of toner base particles. Subsequently, the toner base particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. As a result, dried toner base particles (powder) were obtained.

(External addition process)
Using an FM mixer ("FM-10B" manufactured by Nippon Coke Kogyo Co., Ltd.), 100 parts by mass of toner base particles and 1 mass of hydrophobic silica particles (powder) prepared by the above procedure under the condition of a rotational speed of 3500 rpm. Part and 1 part by mass of conductive titanium oxide particles (powder) prepared by the procedure described above were mixed for 5 minutes. As a result, the external additive adhered to the surface of the toner base particles. Then, sieving was performed using a 300 mesh sieve (aperture 48 μm). As a result, toners (toners TA-1 to TA-3 and TB-1 to TB-4) containing a large number of toner particles were obtained.

Regarding the toners TA-1 to TA-3 and TB-1 to TB-4 obtained as described above, characteristics of G ′ temperature dependency curves (storage elastic modulus G ′ ₈₀ and G ′ ₁₂₀ , and ratio G ′ ₈₀ / G ′ ₁₂₀ ), the characteristics of the tan δ temperature dependence curve (loss tangent tan δ ₈₀ and tan δ ₁₂₀ ), and the Tg (glass transition point) of the toner are as shown in Table 2. .

For example, regarding toner TA-1, Tg (glass transition point) was 41.2 ° C. In the G ′ temperature dependency curve of the toner TA-1, the storage elastic modulus G ′ ₈₀ is 8.57 × 10 ³ Pa, the storage elastic modulus G ′ ₁₂₀ is 2.28 × 10 ³ Pa, and the ratio G ′. ₈₀ / G ′ ₁₂₀ (ratio of storage elastic modulus at a temperature of 80 ° C. to storage elastic modulus at a temperature of 120 ° C.) was 3.76 (= (8.57 × 10 ³ ) / (2.28 × 10 ³ )). It was. In the tan δ temperature dependency curve of the toner TA-1, the loss tangent tan δ ₈₀ was 0.725 and the loss tangent tan δ ₁₂₀ was 0.265.

  The method for measuring the Tg (glass transition point) of the toner was the above-described method using a differential scanning calorimeter. The measurement methods of the G ′ temperature dependency curve and the tan δ temperature dependency curve of the toner were as follows.

<Method for Measuring G ′ Temperature Dependency Curve and Tan Tan Temperature Dependency Curve>
Under an environment of a temperature of 25 ° C. and a humidity of 50% RH, 0.1 g of toner (measuring object: any of toners TA-1 to TA-3 and TB-1 to TB-4) is set in a pellet molding machine, and the toner A load of 4 kN was applied for 1 minute to obtain a disk-shaped pellet having a diameter of 10 mm and a thickness of 1 mm. Subsequently, the obtained pellets were set in a measuring device. As a measuring device, a rheometer (“ARES” manufactured by TA Instruments Japan Co., Ltd.) was used. A measuring jig (parallel plate) was attached to the tip of the shaft of the measuring device (specifically, a shaft driven by a motor). Thereafter, using a measuring apparatus, the G ′ temperature dependency curve (vertical axis: storage elastic modulus, horizontal axis: temperature) and tan δ temperature dependency curve (vertical axis: loss tangent, horizontal axis) under the following conditions: : Temperature).

(Measurement condition)
Measurement temperature range: 40 ° C to 200 ° C
Temperature rising rate: 2 ° C / min Frequency: 0.01Hz
Measurement interval: 15 seconds Applied strain: Automatic measurement mode (initial value: 1%)
Extension compensation: Automatic measurement mode

'From the temperature dependence curve, the storage modulus G' obtained G was read ₈₀ and G _'120. Further, loss tangent tan δ ₈₀ and tan δ ₁₂₀ were read from the obtained tan δ temperature dependency curve. For any of the toners TA-1 to TA-3 and TB-1 to TB-4, a G ′ temperature dependency curve is obtained in which the storage elastic modulus decreases as the temperature increases. There was a shoulder in the region of the temperature below 80 ° C. For any of the toners TA-1 to TA-3 and TB-1 to TB-4, a tan δ temperature dependency curve in which the loss tangent decreases as the temperature rises is obtained, and the temperature 80 in the tan δ temperature dependency curve is obtained. There was a peak in the region below ° C.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-3 and TB-1 to TB-4) is as follows.

<Method for preparing developer for evaluation>
Using a ball mill, 100 parts by mass of the developer carrier prepared by the above-described procedure and 10 parts by mass of toner (evaluation target: toners TA-1 to TA-3 and TB-1 to TB-4) are used. The developer for evaluation was obtained by mixing for 30 minutes.

(Low temperature fixability)
As an evaluator, a printer having a Roller-Roller type heat and pressure type fixing device (nip width: 8 mm) (evaluator that modifies "FS-C5300DN" manufactured by Kyocera Document Solutions Co., Ltd., and can change the fixing temperature) Was used. The evaluation developer (two-component developer) prepared in the above-described procedure is charged into the developing device of the evaluation machine, and toner for replenishment (evaluation objects: toners TA-1 to TA-3 and TB-1 to TB-4) Any) was put into the toner container of the evaluation machine.

In an environment of a temperature of 23 ° C. and a humidity of 50% RH, a paper of 90 g / m ² (ordinary A4 size paper) was used with the above evaluation machine under the conditions of a linear speed of 240 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 on the paper. Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluation machine. The nip passage time was 30 milliseconds. The measuring range of the fixing temperature was 80 ° C. or higher and 160 ° C. or lower. Specifically, the fixing temperature of the fixing device is increased from 80 ° C. by 5 ° 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 120 ° C. or lower, it was evaluated as “good”, and when the minimum fixing temperature exceeded 120 ° C., it was evaluated as “poor” (not good).

(Tone)
As an evaluation machine, a multifunction machine (“TASKalfa 5501i” manufactured by Kyocera Document Solutions Inc.) was used. Using this evaluation machine, 90 g / m ² paper (A4 size plain paper) under the conditions of a temperature of 23 ° C. and a humidity of 50% RH under conditions of a linear speed of 240 mm / sec and a toner loading of 1.0 mg / cm ^2. ) Was formed. Nine images with different printing rates (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%) on one sheet of paper Formed. The size of each image was 10 mm × 10 mm. Nine images were arranged with sufficient space between the images.

Of each of the nine images formed as described above, an image having a printing rate of 50% and an image having a printing rate of 100% are each measured using a reflection densitometer ("SpectroEye (registered trademark)" manufactured by X-Rite). The image density (ID) was measured, and the dot area ratio (unit:%) was determined from the measured image density according to the Murray Davis equation. Further, the dot gain (unit:%) was determined from the obtained halftone dot area ratio and the image printing ratio (50%) according to the following equation.
Dot gain = (halftone dot area ratio)-(printing ratio)

  When the dot gain was 32% or less, it was evaluated as ◯ (good), and when the dot gain exceeded 32%, it was evaluated as x (not good).

[Evaluation results]
Table 3 shows the evaluation results of the toners TA-1 to TA-3 and TB-1 to TB-4. Table 3 shows measured values of low-temperature fixability (minimum fixing temperature) and gradation (dot gain).

  The toners TA-1 to TA-3 (toners according to Examples 1 to 3) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-3 includes a plurality of toner particles each including a toner core and a shell layer covering the surface of the toner core (see Table 1). The shell layer contained a thermosetting resin and a thermoplastic resin. Specifically, the shell layer contained a melamine resin (thermosetting resin) and an acrylamide resin (thermoplastic resin) at a mass ratio M / A of 0.20 or more and 0.50 or less (Table). 1).

For any of the toners TA-1 to TA-3, the G ′ temperature dependency curve of the toner (storage elastic modulus temperature dependency curve measured with a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz). In at least the temperature range of 80 ° C. or higher and 120 ° C. or lower, the storage elastic modulus decreases as the temperature increases, the storage elastic modulus at a temperature of 80 ° C. is 1.00 × 10 ⁴ Pa or lower, and the temperature of 120 ° C. The storage elastic modulus was 2.00 × 10 ³ Pa or more, and the ratio of the storage elastic modulus at a temperature of 80 ° C. to the storage elastic modulus at a temperature of 120 ° C. was 5.00 or less (see Table 2).

  For any of the toners TA-1 to TA-3, in the tan δ temperature dependency curve of the toner (loss tangent temperature dependency curve measured by a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz), At least in the range of 80 ° C. or more and 120 ° C. or less, the loss tangent decreases as the temperature increases, the loss tangent at 80 ° C. is 1.000 or less, and the loss tangent at 120 ° C. is 0.100 or more. (See Table 2).

  When the surface of the toner particles was observed using a scanning electron microscope (SEM), the shell layer covered the entire surface of the toner core in any of the toners TA-1 to TA-3. Further, when the cross section of the toner particles was confirmed using a TEM (transmission electron microscope), the thickness of the shell layer in each of the toners TA-1 to TA-3 was 5 nm to 15 nm.

  In each of toners TA-1 to TA-3 (toners according to Examples 1 to 3), the surface of the toner core is covered with a shell layer (specifically, a shell layer containing a thermosetting resin and a thermoplastic resin). Sufficient heat-resistant storage stability of the toner could be secured. In addition, the toners TA-1 to TA-3 were excellent in low-temperature fixability (see Table 3). In addition, each of the toners TA-1 to TA-3 was able to form a high-quality image (particularly, an image excellent in color gradation) (see Table 3).

  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.

S shoulder P peak

Claims (6)

An electrostatic latent image developing toner comprising a plurality of toner particles each having a core and a shell layer covering the surface of the core,
The shell layer contains a thermosetting resin and a thermoplastic resin,
In the storage elastic modulus temperature dependence curve of the toner measured with a rheometer at a temperature rising rate of 2 ° C./min and a frequency of 0.01 Hz, at least in the temperature range of 80 ° C. to 120 ° C., the temperature increases. The storage elastic modulus decreases, the storage elastic modulus at a temperature of 80 ° C. is 1.00 × 10 ⁴ Pa or less, the storage elastic modulus at a temperature of 120 ° C. is 2.00 × 10 ³ Pa or more, and the temperature of 120 ° C. The ratio of the storage elastic modulus at the temperature of 80 ° C. to the storage elastic modulus is 5 or less,
In the loss tangent temperature dependency curve of the toner measured with a rheometer at a temperature rise rate of 2 ° C./min and a frequency of 0.01 Hz, at least in the temperature range of 80 ° C. to 120 ° C., the loss increases as the temperature increases. A toner for developing an electrostatic latent image, wherein the loss tangent at a temperature of 80 ° C. is 1.000 or less and the loss tangent at a temperature of 120 ° C. is 0.100 or more. The core contains an amorphous polyester resin having a number average molecular weight of 2,000 to 5,000 and a weight average molecular weight of 5,000 to 30,000, and does not contain a crystalline polyester resin.
The shell layer covers the entire surface of the core;
The electrostatic latent image developing toner according to claim 1, wherein the thermosetting resin is a melamine resin, and the thermoplastic resin is an acrylamide resin. The thickness of the shell layer is 5 nm or more and 15 nm or less,
The static ratio according to claim 2, wherein a ratio of a mass of the melamine resin contained in the shell layer to a mass of the acrylamide resin contained in the shell layer is 0.20 or more and 0.50 or less. Toner for developing electrostatic latent image. The glass transition point of the toner is 38.0 ° C. or higher and 46.0 ° C. or lower,
The storage elastic modulus of the toner at a temperature of 80 ° C. is 8.50 × 10 ³ Pa or more and 1.00 × 10 ⁴ Pa or less,
The storage elastic modulus of the toner at 120 ° C. is 2.00 × 10 ³ Pa or more and 4.00 × 10 ³ Pa or less,
The loss tangent of the toner at a temperature of 80 ° C. is 0.700 or more and 0.750 or less,
The electrostatic latent image developing toner according to claim 3, wherein a loss tangent of the toner at a temperature of 120 ° C. is 0.200 or more and 0.300 or less.   The electrostatic latent image developing toner according to claim 2, wherein the core is a pulverized core.   The electrostatic latent image developing toner according to claim 5, wherein the core contains a polymer-type positively chargeable charge control agent.

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