JP6500739B2 - Toner for developing electrostatic latent image - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner (hereinafter sometimes referred to as "toner").

  From the viewpoint of energy saving and downsizing of the image forming apparatus, a toner having excellent low temperature fixability is desired. By using the toner excellent in low temperature fixability, the toner tends to be fixed to the recording medium without heating the fixing roller as much as possible. However, a toner excellent in low-temperature fixability often contains a binder resin having a low melting point or glass transition temperature, and a release agent having a low melting point. When such a toner is stored at high temperature, toner particles contained in the toner are easily aggregated. When the toner particles are aggregated, the charge amount of the aggregated toner particles tends to be reduced as compared with the charge amount of the non-aggregated toner particles.

  Therefore, toners containing toner particles of a core-shell structure have been studied. The toner particles of core-shell structure comprise a toner core and a shell layer covering the toner core. For example, in the toner described in Patent Document 1, the surface of the toner core is substantially continuously covered with a thin film (shell layer). The thin film (shell layer) contains a thermosetting resin.

Unexamined-Japanese-Patent No. 2004-138985

  However, in the toner described in Patent Document 1, since the toner core is coated with a shell layer of a thermosetting resin, it is difficult to fix the toner to the recording medium at a low temperature.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a toner for electrostatic latent image development which is excellent in low-temperature fixability, hot offset resistance, and heat resistant storage stability.

The electrostatic latent image developing toner of the present invention contains a plurality of toner particles. The toner particles have a toner core and a shell layer covering the toner core. The shell layer contains a thermosetting resin and a thermoplastic resin. The toner core contains at least a polyester resin. The melt viscosity of the toner particles at 80 ° C. is 2.1 × 10 ⁴ Pa · s or more and 2.3 × 10 ⁵ Pa · s or less. The melt viscosity of the toner particles at 90 ° C. is 7.0 × 10 ³ Pa · s or more and 2.3 × 10 ⁴ Pa · s or less.

  According to the present invention, it is possible to provide a toner for developing an electrostatic latent image which is excellent in low temperature fixability, hot offset resistance and heat resistant storage stability.

It is a graph for demonstrating the measuring method of melt viscosity. It is a graph for demonstrating the measuring method of a softening point.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, although description may be suitably abbreviate | omitted about the location where description overlaps, the summary of invention is not limited.

  Hereinafter, embodiments of the present invention will be described. Hereinafter, the term "(meth) acrylic" may be generically inclusive of acrylic and methacrylic. In addition, "system" may be added after the compound name to generically generically refer to the compound and its derivative. Furthermore, when a "system" is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative.

Hereinafter, the average value means the number average value unless otherwise specified. In addition, evaluation values (values indicating the shape, physical properties, etc.) of powder (for example, toner, toner particles, and toner base particles described later) mean the number average value unless otherwise specified. The number average value is a value obtained by dividing the sum of the values measured for a considerable number of measurement targets by the measured number. Furthermore, the particle diameter of the powder is equivalent to the circle equivalent diameter of the primary particles measured using an electron microscope, unless otherwise specified. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle. Volume median diameter D _50, using the Coulter counter method, a median diameter calculated by volume.

  The present embodiment relates to a toner. The toner contains a plurality of toner particles. The toner is an aggregate of a plurality of toner particles (powder). The toner particles have a toner core and a shell layer. A shell layer is provided to cover the toner core.

  The toner according to the exemplary embodiment may substantially include only toner particles, or may include components other than toner particles in addition to the toner particles. Further, the toner according to the exemplary embodiment substantially includes toner particles having a core-shell structure, but may contain toner particles other than the core-shell structure.

The melt viscosity (η 1 t) at 80 ° C. of the toner particles is 2.1 × 10 ⁴ Pa · s or more and 2.3 × 10 ⁵ Pa · s or less. When the melt viscosity at 80 ° C. of the toner particles exceeds 2.3 × 10 ⁵ Pa · s, the low temperature fixability of the toner tends to be deteriorated. On the other hand, when the melt viscosity of the toner particles at 80 ° C. is less than 2.1 × 10 ⁴ Pa · s, the heat resistant storage stability of the toner tends to deteriorate. The melt viscosity of the toner particles at 80 ° C. is 2.3 × 10 ⁴ Pa · s or more and 1.5 × 10 ⁴ or more in order to make it easy to simultaneously achieve the low temperature fixability, the hot offset resistance, and the heat resistant storage stability of the toner. It is preferably ⁵ Pa · s or less, more preferably 2.5 × 10 ⁴ Pa · s or more and 1.0 × 10 ⁵ Pa · s or less.

The melt viscosity (η 2 t) of the toner particles at 90 ° C. is 7.0 × 10 ³ Pa · s or more and 2.3 × 10 ⁴ Pa · s or less. When the melt viscosity at 90 ° C. of the toner particles exceeds 2.3 × 10 ⁴ Pa · s, the low temperature fixability of the toner tends to deteriorate. On the other hand, when the melt viscosity of the toner particles at 90 ° C. is less than 7.0 × 10 ³ Pa · s, the hot offset resistance and the heat resistant storage stability of the toner tend to be deteriorated. The melt viscosity of the toner particles at 90 ° C. is 8.3 × 10 ³ Pa · s or more and 2.1 × 10 2 or more in order to make it easy to simultaneously achieve the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner. It is preferably ⁴ Pa · s or less, more preferably 8.9 × 10 ³ Pa · s or more and 9.8 × 10 ³ Pa · s or less.

  Here, the change in the melt viscosity of the toner particles immediately before the toner particles are completely melted tends to affect the low temperature fixability, the hot offset resistance, and the heat resistant storage stability of the toner. Therefore, by setting the melt viscosity at 80 ° C. and 90 ° C. of the toner particles within a predetermined range, the change in melt viscosity of the toner particles immediately before the toner particles are completely melted (for example, the toner It is believed that the degree to which the melt viscosity of the particles decreases can be controlled. At 80 ° C. and 90 ° C., the melt viscosity tends to be able to be measured for the toner particles in the molten state. When the measurement temperature is too low, the toner particles are difficult to melt and tend to be in a solid state. On the other hand, when the measurement temperature is too high, the toner particles tend to be completely melted to be in a liquid state.

  The melt viscosity of the toner particles at 80 ° C. and 90 ° C. is, for example, the type and amount of polyester resin contained as a binder resin in the toner core, the type and amount of components other than the binder resin contained in the toner core, and the shell layer It is suitably adjusted by changing one or more of the type and amount of resin to form.

(Measuring method of melt viscosity)
The melt viscosity at 80 ° C. and 90 ° C. of the toner particles is measured, for example, as follows. The melt viscosity of the measurement sample (toner particles) is measured using a Koka flow tester ("CFT-500D" manufactured by Shimadzu Corporation). First, 1.2 g of a measurement sample is filled in a mold for preparing the measurement sample. Subsequently, a pressure of 4 MPa is applied to the filled measurement sample. This produces a pellet of a measurement sample (cylindrical pellet of 1 cm in diameter and 2 cm in length). The pellet of the obtained measurement sample is set in a heightening type flow tester. Plunger load: 30 kg / cm ² , die pore diameter: 1 mm, die length: 1 mm, preheating temperature: 70 ° C, preheating time: 300 seconds, temperature rise rate: 4 ° C / min, measurement temperature range: 70 ° C or more and 160 ° C or less Measure the melt viscosity of the measurement sample in Thereby, as shown in FIG. 1, the graph which shows the relationship between temperature and melt viscosity is obtained. In FIG. 1, the horizontal axis shows temperature (° C.), and the vertical axis shows melt viscosity (Pa · s). The melt viscosity at 80 ° C. and 90 ° C. of the measurement sample is read from the graph showing the relationship between the obtained temperature and the melt viscosity.

  In the case where an external additive described later adheres to the surface of toner base particles described later, the melt viscosity (η1 t and η2 t) at 80 ° C. and 90 ° C. of the toner particles are each an external additive as a measurement sample It measures by using the toner base particle (toner particle) which adhered.

  The glass transition point (Tg) of the toner particles is preferably 25 ° C. or more and 55 ° C. or less. When the glass transition point of the toner particles is in such a range, it is easy to improve the low temperature fixability and the heat resistant storage stability of the toner. Furthermore, it is easy to improve the characteristics (offset resistance) capable of suppressing the occurrence of the offset when fixing the toner on the recording medium at high temperature. In order to further improve the low temperature fixability of the toner while suitably maintaining the heat resistant storage stability and the hot offset resistance of the toner, it is more preferable that the glass transition point of the toner particles be 25 ° C. or more and 45 ° C. or less Preferably, the temperature is 34 ° C. or more and 45 ° C. or less. The glass transition point of the toner particles is measured in the same manner as the method of measuring the glass transition point of the non-crystalline polyester resin described later, for example, except that the measurement sample is changed from polyester resin to toner (a plurality of toner particles). .

  The softening point (Tm) of the toner particles is preferably 105 ° C. or less, and more preferably 70 ° C. or more and 100 ° C. or less. When the softening point of the toner particles is in such a range, it is easy to improve the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner. The softening point of the toner particles is more preferably 70 ° C. or more and 95 ° C. or less in order to further improve the low temperature fixability of the toner while suitably maintaining the heat resistant storage stability of the toner and the hot offset resistance. . The softening point of the toner particles is measured, for example, in the same manner as the method for measuring the softening point of the polyester resin described later, except that the measurement sample is changed from polyester resin to toner (a plurality of toner particles).

  The glass transition point and the softening point of the toner particles are adjusted, for example, by changing the type and composition of the polyester resin contained in the toner core. In addition, the glass transition point and the softening point of the toner particles are also adjusted, for example, by changing the type and composition of the releasing agent.

<1. Toner core>
The toner core contains at least a polyester resin as a binder resin. The toner core may further contain one or more of a colorant, a release agent, a charge control agent, and a magnetic powder, as necessary. However, components (for example, a colorant, a release agent, a charge control agent, or a magnetic powder) which are not necessary depending on the use of the toner may be omitted.

The melt viscosity (η 1 c) at 80 ° C. of the toner core is preferably 2.0 × 10 ⁴ Pa · s or more and 1.5 × 10 ⁵ Pa · s or less. When the melt viscosity at 80 ° C. of the toner core exceeds 1.5 × 10 ⁵ Pa · s, the low temperature fixability of the toner tends to deteriorate. On the other hand, when the melt viscosity at 80 ° C. of the toner core is less than 2.0 × 10 ⁴ Pa · s, the heat resistant storage stability of the toner tends to be deteriorated. The melt viscosity of the toner core at 80 ° C. is preferably 2.5 × 10 ⁴ Pa · s or more and 1.0 × 10 ⁵ or more in order to make it easy to simultaneously achieve the low temperature fixability, the hot offset resistance, and the heat resistant storage stability of the toner. More preferably, Pa · s or less.

The melt viscosity (η 2 c) at 90 ° C. of the toner core is preferably 7.0 × 10 ³ Pa · s or more and 1.7 × 10 ⁴ Pa · s or less. When the melt viscosity at 90 ° C. of the toner core exceeds 1.7 × 10 ⁴ Pa · s, the low temperature fixability of the toner tends to deteriorate. On the other hand, when the melt viscosity at 90 ° C. of the toner core is less than 7.0 × 10 ³ Pa · s, the hot offset resistance and heat resistant storage stability of the toner tend to be deteriorated. The melt viscosity of the toner core at 90 ° C. is 8.8 × 10 ³ Pa · s or more and 9.8 × 10 ³ or more in order to make it easy to make the low-temperature fixability, the hot offset resistance, and the heat resistant storage stability of the toner more compatible. More preferably, Pa · s or less.

  The toner core accounts for the majority of the toner particles. Therefore, the characteristics of the toner core tend to affect the low-temperature fixability, the hot offset resistance, and the heat resistant storage stability of the toner (a plurality of toner particles).

  The melt viscosity of the toner core at 80 ° C. and 90 ° C. changes, for example, the type or amount of polyester resin contained as a binder resin in the toner core, or the type or amount of components other than the binder resin contained in the toner core. It adjusts suitably by.

  The melt viscosity at 80 ° C. and 90 ° C. of the toner core is measured, for example, by the same method as the measurement method of melt viscosity at 80 ° C. and 90 ° C. of the toner particles described above except changing the measurement sample from toner particles to toner core Ru.

<1-1. Binder resin>
The toner core contains a polyester resin as a binder resin. Therefore, functional groups (for example, hydroxyl group and carboxyl group) possessed by the polyester resin are exposed on the surface of the toner core. Therefore, when forming the shell layer on the surface of the toner core, the monomer of the thermosetting resin (for example, methylolmelamine) and the functional group (for example, hydroxyl group and carboxyl group) exposed on the surface of the toner core react easily Become. This facilitates formation of a covalent bond between the toner core and the shell layer. As a result, the shell layer and the toner core are likely to be firmly bonded.

  The polyester resin is appropriately selected from polyester resins used as a binder resin for toner. The polyester resin is obtained, for example, by polycondensation or cocondensation polymerization of an alcohol and a carboxylic acid.

  As an alcohol used when synthesize | combining a polyester resin, a dihydric alcohol or alcohol more than trivalence is mentioned, for example. Examples of dihydric alcohols include diols or bisphenols.

  Examples of the diols include aliphatic diols having 2 to 8 carbon atoms, polyethylene glycols, polypropylene glycols, and polytetramethylene glycols. Examples of aliphatic diols having 2 to 8 carbon atoms include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, Examples include 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, or dipropylene glycol.

  Examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-Pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane or 1,3,5-trihydroxyl Methylbenzene is mentioned.

  As a carboxylic acid used when synthesize | combining polyester resin, a bivalent carboxylic acid or the trivalent or more carboxylic acid is mentioned, for example.

  Examples of divalent carboxylic acids include aliphatic divalent carboxylic acids having 2 to 16 carbon atoms, phthalic acid, isophthalic acid, or terephthalic acid. Examples of aliphatic divalent carboxylic acids having 2 to 16 carbon atoms include alkanedicarboxylic acids having 2 to 16 carbon atoms, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, cyclohexanedicarboxylic acid, Adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid, alkyl succinic acid or alkenyl succinic acid can be mentioned. Specific examples of the alkylsuccinic acid include n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid or isododecylsuccinic acid. Specific examples of the alkenyl succinic acid include n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid.

  Examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,3, 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, There may be mentioned 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid or Empol trimer acid.

  The above-mentioned alcohol and carboxylic acid may be used alone or in combination of two or more. Furthermore, the above-mentioned carboxylic acids may be derivatized into ester-forming derivatives and used. Ester-forming derivatives are, for example, acid halides, acid anhydrides or lower alkyl esters. Here, "lower alkyl" means an alkyl group having 1 to 6 carbon atoms.

  The acid value of the polyester resin is preferably 5 mg KOH / g or more and 30 mg KOH / g or less, and more preferably 10 mg KOH / g or more and 18 mg KOH / g or less. The hydroxyl value of the polyester resin is preferably 15 mg KOH / g or more and 80 mg KOH / g or less, and more preferably 27 mg KOH / g or more and 40 mg KOH / g or less. When the acid value and the hydroxyl value of the polyester resin are in such a range, the toner core tends to be well dispersed in the aqueous medium when the shell layer forming step described later is performed using the aqueous medium. As a result, even when no dispersant is used in the shell layer forming step, the formation of the shell layer can be favorably advanced. In addition, when using non-crystalline polyester resin and crystalline polyester resin as a polyester resin, the acid value and hydroxyl value of the whole polyester resin (non-crystalline polyester resin and crystalline polyester resin) are such a range It is preferably inside.

  The acid value and the hydroxyl value of the polyester resin may be, for example, the amount of the dihydric or trivalent or higher alcohol component used when producing the polyester resin, and the used amount of the divalent or trivalent or higher carboxylic acid component, It adjusts by changing each suitably. In addition, when the molecular weight of the polyester resin is increased, the acid value and the hydroxyl value of the polyester resin tend to decrease.

  The acid value and the hydroxyl value of the polyester resin are measured, for example, by the method described in JIS (Japanese Industrial Standard) K0070-1992.

  The toner core preferably contains a non-crystalline polyester resin as the polyester resin. In addition to the non-crystalline polyester resin, the toner core may contain a crystalline polyester resin as the polyester resin. When the toner core contains the crystalline polyester resin in addition to the non-crystalline polyester resin, the low-temperature fixability of the toner tends to be improved.

  Whether the polyester resin is crystalline or noncrystalline is determined based on the crystallinity index of the polyester resin. A polyester resin having a crystallinity index of 0.900 or more and less than 1.100 is referred to as a crystalline polyester resin. A polyester resin having a crystallinity index of less than 0.900 or 1.100 or more is regarded as a non-crystalline polyester resin. In order to improve the low temperature fixability of the toner, it is preferable that the crystallinity index of the crystalline polyester resin is 0.980 or more and 1.050 or less. When the crystallinity index exceeds 1.400, there is a tendency for the noncrystalline portion of the polyester resin to be particularly large. In addition, even when the crystallinity index is less than 0.600, the noncrystalline portion of the polyester resin tends to be particularly large.

  The crystallinity index of the polyester resin is determined from the ratio (Tm / Mp) of the softening point (Tm) of the polyester resin to the melting point of the polyester resin (the temperature of the maximum endothermic peak in the DSC curve, Mp). The softening point (Tm) and the melting point (Mp) of the polyester resin are measured, for example, as follows.

(Measuring method of melting point)
The melting point (Mp) of the polyester resin is measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.). Place a measurement sample (polyester resin) of 10 mg or more and 20 mg or less in an aluminum pan. Subsequently, the aluminum pan is set in the measurement section of the DSC. Use an empty aluminum plate for reference. The measurement start temperature is 30 ° C., and the temperature is raised to 170 ° C. at a rate of 10 ° C./min. The maximum peak temperature of the heat of fusion observed during the temperature rise is taken as the melting point (Mp) of the measurement sample.

(Method of measuring softening point)
The softening point (Tm) of the polyester resin is measured using a Koka flow tester (for example, "CFT-500D" manufactured by Shimadzu Corporation). The measurement sample (polyester resin) is set in a heightening type flow tester. A measurement sample of 1 cm ³ is melted and discharged under the conditions of a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² and a temperature rising rate of 6 ° C./min. Thereby, as shown in FIG. 2, an S-shaped curve is obtained which indicates the relationship between the temperature (° C.) and the stroke (m). In FIG. 2, the horizontal axis represents temperature (° C.), and the vertical axis represents stroke (m). The softening point of the measurement sample is read from an S-shaped curve showing the relationship between the obtained temperature (° C.) and the stroke (m). Specifically, the maximum value of the stroke and S _1, the stroke value of the low-temperature side of the base line and S _2. The temperature at which the stroke value in the S-shaped curve is (S ₁ + S ₂ ) / 2 is taken as the softening point (Tm) of the measurement sample. The softening point (Tm) of the measurement sample corresponds to 1⁄2 outflow temperature (T1 / 2) of the measurement sample.

  The crystallinity index of the polyester resin is adjusted by appropriately changing the type of alcohol as a monomer, and the amount used, and the type and amount of a carboxylic acid. The crystalline polyester resin may be used alone or in combination of two or more. In addition, non-crystalline polyester resins may be used alone or in combination of two or more.

  For the synthesis of the crystalline polyester resin, for example, alcohols and carboxylic acids used in synthesizing the above-described polyester resin are used.

  In order to obtain a crystalline polyester resin, it is preferable to use an aliphatic diol having 2 to 8 carbon atoms as the alcohol used when synthesizing the polyester resin. This is because crystallization of the polyester resin is promoted. Among them, it is more preferable to use an α, ω-alkanediol having 2 to 8 carbon atoms, because crystallization of the polyester resin is easily promoted.

  In order to obtain a crystalline polyester resin, the content of the aliphatic diol having 2 to 8 carbon atoms is 80 mol% or more based on the number of moles of alcohol used in synthesizing the polyester resin. Is preferable, and 90 mol% or more is more preferable. Further, in order to obtain a crystalline polyester resin, the content of the component (single compound) contained in the largest amount in the alcohol used when synthesizing the polyester resin is preferably 70 mol% or more, It is more preferably 90 mol% or more, and most preferably 100 mol%.

  Among the carboxylic acids used in synthesizing the polyester resin, aliphatic dihydric carboxylic acids (dicarboxylic acids) having 2 to 16 carbon atoms are preferable, since the crystallization of the polyester resin is easily promoted. The number 2 or more and 16 or less α, ω-alkanedicarboxylic acids (eg, 1,10-decanedicarboxylic acid) are more preferable.

  In order to obtain a crystalline polyester resin, the content of the aliphatic dicarboxylic acid having 2 to 16 carbon atoms is 70 mol% or more with respect to the number of moles of carboxylic acid used in synthesizing the polyester resin. Is preferably 90 mol% or more. Moreover, in order to obtain a crystalline polyester resin, the content of the component (single compound) contained most in carboxylic acid is preferably 70 mol% or more, and more preferably 90 mol% or more. Preferably, it is 100 mol%.

  The melting point of the crystalline polyester resin is preferably 50 ° C. or more and 100 ° C. or less. When the melting point of the crystalline polyester resin is in such a range, it becomes easy to make the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner compatible with each other. The melting point of the crystalline polyester resin is measured, for example, by the same method as the above-mentioned measuring method of the melting point except that the crystalline polyester resin is used as a measurement sample.

  The ratio (Wc / Wa) of the mass (Wc) of the crystalline polyester resin to the mass (Wa) of the non-crystalline polyester resin (the resin excluding the crystalline polyester resin) in the polyester resin is 1.00 or less Is more preferably 0.01 or more and 0.50 or less, and particularly preferably 0.10 or more and 0.20 or less. When the ratio (Wc / Wa) of the mass (Wc) of the crystalline polyester resin to the mass (Wa) of the noncrystalline polyester resin contained in the toner core is within such a range, the low temperature fixability of the toner, the hot resistance It becomes easy to make offset property and heat resistant storage stability compatible.

  The glass transition point (Tg) of the non-crystalline polyester resin is preferably 30 ° C. or more and 60 ° C. or less, more preferably 35 ° C. or more and 55 ° C. or less, and further preferably 35 ° C. or more and 50 ° C. or less preferable. When the glass transition temperature of the non-crystalline polyester resin is in such a range, it is easy to simultaneously achieve the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner. Furthermore, when the glass transition temperature of the non-crystalline polyester resin is in such a range, toner particles having a desired melt viscosity are easily formed. The glass transition point of the non-crystalline polyester resin is measured, for example, as follows.

(Measurement method of glass transition point)
The glass transition point of the non-crystalline polyester resin is determined from the change point of the specific heat of the non-crystalline polyester resin using a differential scanning calorimeter (DSC). More specifically, a differential scanning calorimeter ("DSC-6220" manufactured by Seiko Instruments Inc.) is used as a measuring device. 10 mg of a measurement sample (noncrystalline polyester resin) is placed in the aluminum pan of the measurement apparatus. Use an empty aluminum pan as a reference. An endothermic curve of the measurement sample is obtained by measurement under the conditions of a measurement temperature range of 25 ° C. or more and 200 ° C. or less and a temperature rising rate of 10 ° C./minute. From the endothermic curve of the obtained measurement sample, the glass transition point of the measurement sample is determined. When the glass transition point is observed in multiple stages, the point observed at the lowest temperature is taken as the glass transition point.

  The softening point (Tm) of the non-crystalline polyester resin is preferably 60 ° C. or more and 150 ° C. or less, more preferably 70 ° C. or more and 140 ° C. or less, and still more preferably 80 ° C. or more and 100 ° C. or less . When the softening point of the non-crystalline polyester resin is in such a range, it becomes easy to make the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner compatible with each other. Furthermore, when the softening point of the non-crystalline polyester resin is in such a range, toner particles having a desired melt viscosity are easily formed. A plurality of non-crystalline polyester resins having different softening points may be used in combination so that the softening point of the non-crystalline polyester resin has a value within such a range.

  The toner core may further contain another binder resin in addition to the polyester resin (one or both of the crystalline polyester resin and the non-crystalline polyester resin). Another binder resin is appropriately selected from known resins used as a binder resin for toner.

  The content of the polyester resin in the binder resin (the total content of the crystalline polyester resin and the non-crystalline polyester resin) is preferably 70% by mass or more based on the mass of the binder resin, and is 80 mass%. % Or more is more preferable, 90% by mass or more is particularly preferable, and 100% by mass is most preferable.

<1-2. Colorant>
As the colorant, known pigments or dyes may be used according to the color of the toner particles. The content of the coloring agent is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. The black colorant includes, for example, a black pigment or a black dye. Carbon black is mentioned as a specific example of a black pigment. A black colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant described later may be used.

  When the toner is a color toner, examples of colorants to be blended into the toner core include colorants such as yellow colorants, magenta colorants, and cyan colorants.

  The toner core may contain a color colorant. Examples of color colorants include yellow colorants, magenta colorants, or cyan colorants.

  Examples of yellow colorants include yellow pigments or yellow dyes, and more specifically include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, or arylamide compounds. . Specific examples of yellow colorants include C.I. I. Pigment yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 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. Bat yellow is mentioned.

  Examples of magenta colorants include magenta pigments or magenta dyes, and more specifically, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazo Long compounds, thioindigo compounds, or perylene compounds may be mentioned. Specific examples of magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 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).

  Examples of cyan colorants include cyan pigments or cyan dyes, and more specifically include copper phthalocyanine, copper phthalocyanine derivatives, anthraquinone compounds, or basic dye lake compounds. Specific 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 is mentioned.

<1-3. Release agent>
The toner core may further contain a release agent. It is considered that the low temperature fixability and the hot offset resistance of the toner are improved by the toner core containing a release agent. In order to improve the low temperature fixability and the hot offset resistance of the toner, the content of the releasing 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, and 3 It is more preferable that it is a mass part or more and 20 mass parts or less.

  Wax is preferred as the release agent. Examples of waxes include ester waxes, polyethylene waxes, polypropylene waxes, fluoroplastic waxes, Fischer-Tropsch waxes, paraffin waxes, or montan waxes. In order to improve the low temperature fixability and the hot offset resistance of the toner, an ester wax is preferred. The ester wax includes natural ester wax (specifically, carnauba wax or rice wax) or synthetic ester wax. These mold release agents may be used alone or in combination of two or more.

  Among ester waxes, synthetic ester waxes are preferred. By appropriately selecting the raw material of the synthetic ester wax, the melting point (the temperature of the maximum endothermic peak in the DSC curve, Mp) measured using a differential scanning calorimeter is adjusted within a suitable range described later It is easy to do.

  The method for producing the synthetic ester wax is not particularly limited as long as it is a chemical synthesis method. For example, synthetic ester waxes are synthesized by reacting an alcohol with a carboxylic acid in the presence of an acid catalyst. In another example, synthetic ester waxes are synthesized by reacting a carboxylic acid halide with an alcohol. The raw material of the synthetic ester wax may be, for example, a raw material derived from a natural product such as a long chain fatty acid produced from a natural fat and oil. Moreover, as synthetic ester wax, you may use ester wax marketed as a synthetic product.

  The release agent is preferably an ester wax having a melting point of 50 ° C. or more and 100 ° C. or less. When the melting point of the releasing agent is in such a range, it is easy to simultaneously achieve the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner. In order to further improve the hot offset resistance and heat resistant storage stability of the toner, an ester wax having a melting point of 60 ° C. or more and 90 ° C. or less is more preferable. The melting point of the release agent is measured, for example, in the same manner as the above-described method of measuring the melting point of the polyester resin except that the measurement sample is changed from the polyester resin to the release agent.

<1-4. Charge control agent>
Charge control agents are used, for example, for the purpose of improving charge level and charge rise characteristics. Moreover, it is used for the purpose of obtaining a toner excellent in durability and stability. The charge rising characteristic is an indicator of whether or not charging can be performed to a predetermined charge level in a short time.

  When developing using positively charged toner, it is preferable to use a positively chargeable charge control agent. On the other hand, when developing using a negatively charged toner, it is preferable to use a negatively chargeable charge control agent. However, when a sufficient charge amount is ensured in the toner, the toner core may not contain the charge control agent.

  The charge control agent is appropriately selected from charge control agents used for toner. Examples of positively chargeable charge control agents include azine compounds, direct dyes comprising azine compounds, nigrosine compounds, acid dyes comprising nigrosine compounds, metal salts of naphthenic acids, metal salts of higher fatty acids, alkoxylated amines, alkylamides Or quaternary ammonium salts.

  Examples of azine compounds include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1,4-thiazine, 1 2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3 , 4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6 -Oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline or quinoxaline can be mentioned.

  Examples of direct dyes consisting of azine compounds include azine fast red FC, azine fast red 12 BK, azine violet BO, azine brown 3 G, azine light brown GR, azine dark green BH / C, azine dark black EW, or There is azine deep black 3RL.

  Examples of nigrosine compounds include nigrosine, nigrosine salts, or nigrosine derivatives.

  Examples of acid dyes consisting of nigrosine compounds include nigrosine BK, nigrosine NB, or nigrosine Z.

  Examples of quaternary ammonium salts include benzyl decyl hexyl methyl ammonium or decyl trimethyl ammonium chloride.

  A quaternary ammonium salt, a carboxylate, or a resin having a carboxyl group as a functional group may be used as a positively chargeable charge control agent. More specifically, styrenic resin having quaternary ammonium salt, acrylic acid resin having quaternary ammonium salt, styrene-acrylic acid resin having quaternary ammonium salt, polyester resin having quaternary ammonium salt, carbonic acid Styrenic resin having acid salt, acrylic acid resin having carboxylic acid salt, styrene-acrylic acid resin having carboxylic acid salt, polyester resin having carboxylic acid salt, styrenic resin having carboxyl group, and carboxyl group Acrylic resin, styrene-acrylic acid resin having a carboxyl group, or polyester resin having a carboxyl group may be mentioned. These resins may be oligomers or polymers.

  Among these positively chargeable charge control agents, nigrosine compounds are particularly preferable in that they can obtain quicker rising properties. One of these positively chargeable charge control agents may be used alone, or two or more thereof may be used in combination.

  Examples of negatively chargeable charge control agents include organometallic complexes or organometallic salts. Examples of organometallic complexes include acetylacetone metal complexes such as aluminum acetylacetonate or iron (II) acetylacetonate; or salicylic acid based metal complexes such as chromium 3,5-di-tert-butylsalicylic acid. Examples of organic metal salts include salicylic acid based metal salts. Among them, salicylic acid metal complexes and salicylic acid metal salts are more preferable. One of these negatively chargeable charge control agents may be used alone, or two or more thereof may be used in combination.

  The use amount of the positively chargeable or negatively chargeable charge control agent is preferably 0.5 parts by mass or more and 20.0 parts by mass or less, and more preferably 1.0 parts by mass or more with respect to 100.0 parts by mass of the toner. More preferably, it is 15.0 parts by mass or less.

<1-5. Magnetic powder>
Examples of the magnetic powder include iron, ferromagnetic metal, alloy containing iron and / or ferromagnetic metal, compound containing iron and / or ferromagnetic metal, ferromagnetic alloy subjected to ferromagnetization treatment, or chromium dioxide Can be mentioned. Examples of iron include ferrite or magnetite. Examples of ferromagnetic metals include cobalt or nickel. An example of the ferromagnetization treatment is heat treatment.

  The particle diameter of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. In the case of using a magnetic powder having a particle diameter in such a range, the magnetic powder can be easily dispersed uniformly in the binder resin.

  A toner containing toner particles produced using a toner core containing magnetic powder is used, for example, as a magnetic one-component developer. When the toner is used as a magnetic one-component developer, the content of the magnetic powder is preferably 35 parts by mass or more and 60 parts by mass or less, and 40 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the toner. It is more preferable that

  A toner containing toner particles produced using a toner core containing magnetic powder may be mixed with a carrier and used in a magnetic two-component developer. When the toner is used in a magnetic two-component developer, the content of the magnetic powder is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less with respect to 100 parts by mass of the toner.

<2. Shell layer>
The shell layer contains a thermosetting resin and a thermoplastic resin. When the shell layer contains only a thermoplastic resin, toner particles contained in the toner are easily fused to each other when the toner is stored at a high temperature. In addition, when an image is formed using toner, hot offset tends to occur. On the other hand, when the shell layer contains only a thermosetting resin, when the toner is heated at the time of fixing, the toner particles contained in the toner are difficult to be destroyed, and the low temperature fixability of the toner tends to be deteriorated. Therefore, when the thermosetting resin and the thermoplastic resin are contained in the shell layer, it is easy to simultaneously achieve the low temperature fixability, the heat resistant storage stability, and the hot offset resistance of the toner.

  The shell layer is formed by mixing or reacting a thermosetting resin raw material (for example, a thermosetting resin monomer or prepolymer) and a thermoplastic resin raw material (for example, a thermoplastic resin). Ru. In the shell layer, the thermosetting resin and the thermoplastic resin are mixed and solidified, and the region formed of the thermosetting resin and the region formed of the thermoplastic resin are mixed in the shell layer. May be In addition, the shell layer may contain a raw material of a thermosetting resin (for example, a monomer or prepolymer of a thermosetting resin which is not polymerized or not polymerized). Furthermore, in the shell layer, at least a part of the substituent of the thermosetting resin and at least a part of the substituent of the thermoplastic resin may be chemically bonded (crosslinked).

  When the substituent that the thermosetting resin has and the substituent that the thermoplastic resin have in the shell layer are chemically bonded (crosslinked), the shell layer has appropriate flexibility due to the thermoplastic resin . Furthermore, due to the three-dimensional crosslinked structure formed by the thermosetting resin, as well as the appropriate flexibility, the shell layer also has an adequate mechanical strength. Toner particles provided with such a shell layer are unlikely to be destroyed during storage and transport. On the other hand, such toner particles tend to be easily broken when temperature and pressure are applied during fixing. As a result, even when the shell layer is thin, it is easy to achieve both the heat resistant storage stability and the low temperature fixability of the toner. The thermosetting resin and the thermoplastic resin contained in the shell layer will be described below.

<2-1. Thermosetting resin>
The thermosetting resin is formed by polycondensation of one or more monomers of the thermosetting resin. The monomer of the thermosetting resin preferably has a functional group capable of reacting with a functional group (for example, a hydroxyl group and a carboxyl group) that the polyester resin in the toner core has. On the surface of the toner core, functional groups (for example, hydroxyl group and carboxyl group) possessed by the polyester resin are exposed. Therefore, when forming the shell layer on the surface of the toner core, the monomer of the thermosetting resin (for example, methylolmelamine) and the functional group (for example, hydroxyl group and carboxyl group) exposed on the surface of the toner core react easily Become. This facilitates formation of a covalent bond between the toner core and the shell layer. As a result, the shell layer and the toner core are likely to be firmly bonded.

  The thermosetting resin contained in the shell layer is preferably one or more resins selected from the group consisting of melamine resins, urea resins, and glyoxal resins. As a raw material of the thermosetting resin contained in a shell layer, the monomer of a melamine resin, the monomer of a urea resin, or the monomer of glyoxal resin is mentioned.

  Melamine resin is a polycondensate of melamine and formaldehyde. The monomer used to form the melamine resin is melamine. Urea resin is a polycondensate of urea and formaldehyde. The monomer used to form the urea resin is urea. Glyoxal resin is a polycondensate of the reaction product of glyoxal and urea with formaldehyde. The monomers used to form the glyoxal resin are the reaction products of glyoxal and urea.

  The urea to be reacted with melamine, urea and glyoxal may be subjected to known modifications. For example, before reacting the thermosetting resin monomer with the thermoplastic resin, it may be made a derivative by methylolizing with formaldehyde.

  The reaction product of melamine, urea, and glyoxal with urea may be used in the form of a prepolymer (which may hereinafter be referred to as an initial polymer). Here, the prepolymer means an intermediate product obtained by stopping the polymerization reaction or polycondensation reaction of the monomer at a stage before the degree of polymerization reaches the degree of polymerization of the polymer.

  When a melamine resin, a urea resin, or a glyoxal resin is used as the thermosetting resin, the shell layer contains a nitrogen atom. Specifically, the nitrogen atom derived from melamine which is a monomer of melamine resin, the nitrogen atom derived from urea which is a monomer of urea resin, the nitrogen atom derived from the reaction product of glyoxal which is a monomer of glyoxal resin and urea 1 or more of these are contained. A toner provided with a shell layer containing nitrogen atoms tends to be positively charged. Therefore, when the toner of this embodiment is positively charged to form an image, it is easy to positively charge toner particles contained in the toner to a desired charge amount. The content of nitrogen atoms in the shell layer is preferably 10% by mass or more, from the viewpoint that it is easy to positively charge the toner particles contained in the toner to a desired charge amount.

2-2. Thermoplastic resin>
The thermoplastic resin has a functional group having reactivity with a functional group (for example, a methylol group or an amino group) possessed by the raw material of the thermosetting resin (for example, one or both of the thermosetting resin monomer and prepolymer). It is preferable to include. The functional group having reactivity with the functional group (for example, methylol group or amino group) possessed by the raw material of the thermosetting resin is a functional group (for example, hydroxyl group, carboxyl group or amino group) containing an active hydrogen atom It can be mentioned. Amino groups may be included in a thermoplastic resin as a carbamoyl group (-CONH _2).

  As the thermoplastic resin, a resin containing a unit derived from (meth) acrylamide is preferable because formation of a shell layer is easy. For the same reason, as the thermoplastic resin, a resin containing a unit derived from a monomer having a functional group such as a carbodiimide group, an oxazoline group or a glycidyl group is also preferable.

  Specific examples of the thermoplastic resin used to form the shell layer include acrylic resin, styrene-acrylic copolymer, silicone- (meth) acrylic graft copolymer, urethane resin, polyester resin, polyvinyl alcohol Or ethylene vinyl alcohol copolymers. These resins may contain units derived from a monomer having a functional group such as a carbodiimide group, an oxazoline group, or a glycidyl group. Among these, in order to improve the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner, an acrylic resin or a silicone- (meth) acrylic graft copolymer is preferable.

  An acrylic resin is formed by polymerizing an acrylic monomer. Examples of acrylic acid monomers include (meth) acrylic acid, (meth) acrylic acid alkyl ester, (meth) acrylic acid aryl ester, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylamide, (meth) acrylic acid And alkyl ethers of ethylene oxide adducts of (meth) acrylic acid esters.

  Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, or n-butyl (meth) acrylate. Examples of (meth) acrylic acid aryl esters include phenyl (meth) acrylate. Examples of (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylic acid, 3-hydroxypropyl (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, or (meth) acrylic acid 4 -Hydroxybutyl is mentioned. Examples of the alkyl ether of ethylene oxide adduct of (meth) acrylic ester include methyl ether, ethyl ether, n-propyl ether or n-butyl ether of ethylene oxide adduct of (meth) acrylic ester.

  Among acrylic monomers, in order to improve the low temperature fixability, hot offset resistance and heat resistant storage stability of toner, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylamide or (meth) acrylic acid Alkyl ethers of ethylene oxide adducts of esters are preferred.

  The acrylic acid monomers may be used alone or in combination of two or more.

  The formation of the shell layer is preferably performed in an aqueous medium because dissolution of the binder resin and elution of the release agent contained in the toner core are difficult to occur. For this reason, it is preferable that the thermoplastic resin used for formation of a shell layer is water-soluble. In particular, in forming the shell layer, it is preferable to use a thermoplastic resin as an aqueous solution.

  When using an aqueous solution of a thermoplastic resin (solid concentration 11 mass%) and an aqueous solution of a raw material of a thermosetting resin (solid concentration 80 mass%) in forming the shell layer, the amount of the aqueous solution of thermoplastic resin ( The ratio (Vs / Vp) of the used amount (Vs, unit: mL) of the aqueous solution of the raw material of the thermosetting resin to Vp, unit: mL is 2.0 / 8.0 or more and 9.0 / 1.0 or less Is preferably 3.0 / 7.0 or more and 7.0 / 3.0 or less, more preferably 3.0 / 7.0 or more and 6.7 / 3.3 or less. preferable.

  The ratio (Ws / Wp) of the mass (Ws) of the thermosetting resin to the mass (Wp) of the thermoplastic resin in the shell layer is preferably 2.0 or more and 65.0 or less, and is 3.0 or more It is more preferably 17.0 or less, and particularly preferably 3.0 or more and 13.0 or less.

  The total content of the thermosetting resin and the thermoplastic resin in the shell layer is preferably 70% by mass or more, more preferably 80% by mass or more, based on the mass of the shell layer, and 90% by mass. % Or more is more preferable, and 100% by mass is particularly preferable.

  The thickness of the shell layer is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 16 nm or less, still more preferably 1 nm or more and 10 nm or less, and particularly preferably 5 nm or more and 10 nm or less. If the thickness of the shell layer of the toner particles is more than 20 nm, the shell layer of the toner particles is unlikely to be broken even if pressure is applied to the toner particles when the toner is fixed to the recording medium. Therefore, the softening and melting of the binder resin contained in the toner core and the softening and melting of the release agent are difficult to progress, and it becomes difficult to fix the toner on the recording medium in a low temperature range. On the other hand, when the thickness of the shell layer of the toner particles is less than 1 nm, the strength of the shell layer tends to be low. If the strength of the shell layer is low, the shell layer of the toner particles is likely to be destroyed by the impact applied to the toner particles during transport. In addition, when the toner is stored at high temperature, toner particles in which at least a part of the shell layer is broken are easily aggregated. Therefore, under high temperature conditions, a component such as a mold release agent easily exudes to the surface of the toner particles through the broken portion of the shell layer.

(Method of measuring thickness of shell layer)
The thickness of the shell layer is measured, for example, by the following method. The toner particles are observed at a magnification of 30,000 and 100,000 using a transmission electron microscope (TEM). As a result, a TEM photograph of the cross section of the toner particles is taken to obtain a TEM taken image. Subsequently, a TEM image of the cross section of the toner particles is analyzed using commercially available image analysis software (for example, "WinROOF" manufactured by Mitani Shoji Co., Ltd.). Two straight lines perpendicular to each other at substantially the center of the cross section of the toner particle are drawn, and the lengths of four points intersecting the two straight shell layers are measured. The average value of the four lengths measured in this manner is taken as the thickness of the shell layer of one toner particle to be measured. Such shell layer thickness measurements are made on ten toner particles. The average value of the thickness of the shell layer provided for each of the ten toner particles to be measured is determined. The sum of the determined average values is divided by the number of measurement targets (10). The obtained value is taken as the thickness of the shell layer provided in the toner.

  When the shell layer is thin (for example, less than 5 nm), it may be difficult to measure the thickness of the shell layer because the interface between the shell layer and the toner core is unclear on the TEM image. In such a case, TEM imaging and electron energy loss spectroscopy (EELS) are combined to perform mapping of an element (for example, nitrogen) characteristic of the material of the shell layer in the TEM image, The interface with the toner core may be clarified to measure the thickness of the shell layer.

The thickness of the shell layer appropriately changes the amount of the raw material of the shell layer used to form the shell layer (for example, monomer of thermosetting resin, prepolymer of thermosetting resin, or thermoplastic resin) It is adjusted by doing. The thickness of the shell layer is calculated according to Formula (1), for example, from the specific surface area of the toner core, the amount of thermosetting resin, and the amount of thermoplastic resin.
Thickness of shell layer = (amount of monomer of thermosetting resin + amount of thermoplastic resin) / specific surface area of toner core (1)

<3. External additive>
An external additive may be attached to the surface of the shell layer-coated toner core, if necessary. The particles (toner core coated with the shell layer) before the external additive is attached may be described as toner base particles.

  The external additive includes silica or metal oxide. Examples of the metal oxide include alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less. The amount of external additive used is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of toner base particles.

<4. Carrier>
The toner may be used in a two-component developer mixed with the desired carrier. When preparing a two-component developer, it is preferable to use a magnetic carrier.

  One example of the carrier is a resin-coated carrier core. The carrier core is formed by magnetic particles. Another example of the carrier is a resin carrier in which magnetic particles are dispersed in a resin.

  Specific examples of magnetic particles are particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel or cobalt; alloys of these materials with metals such as manganese, zinc and aluminum Particles of iron-nickel alloy; particles of iron-cobalt alloy; particles of ceramics; or particles of high dielectric constant material. Examples of ceramics used as particles of ceramics include titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, Lead zirconate or lithium niobate can be mentioned. The high dielectric constant material used as particles of the high dielectric constant material includes, for example, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, or Rochelle salt.

  Examples of the resin covering the carrier core and the resin contained in the resin carrier include acrylic polymers, styrene polymers, styrene-acrylic copolymers, olefin polymers (eg, polyethylene, chlorination) Polyethylene and polypropylene), polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, urethane resin, epoxy resin, silicone resin, fluorine resin (for example, polytetrafluoroethylene, poly Chlorotrifluoroethylene or polyvinylidene fluoride), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, or amino resin can be mentioned. One of these resins may be used alone, or two or more of these resins may be used in combination.

  The particle diameter of the carrier is preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less. The particle size of the carrier is measured, for example, by an electron microscope.

  When the toner is used in a two-component developer, the content of the toner is preferably 3% by mass or more and 20% by mass or less, and is 5% by mass or more and 15% by mass or less based on the mass of the two-component developer Is preferred.

<5. Method of manufacturing toner>
The method of producing the toner is not particularly limited as long as the toner core is coated with the shell layer. Hereinafter, an example of a method for producing a toner will be described.

<5-1. Forming process of toner core>
In the toner core formation step, the toner core is formed by dispersing optional components (for example, one or more of a colorant, a charge control agent, a release agent, and a magnetic powder) in a binder resin. The method for producing the toner core is not particularly limited as long as optional components (for example, one or more of a colorant, a charge control agent, a release agent, and a magnetic powder) are well dispersed in the binder resin. The method for producing the toner core is appropriately selected from known methods. Examples of the method for producing the toner core include a grinding method and an aggregation method.

(Crushing method)
In the pulverization method, first, a binder resin and optional components (for example, one or more of a colorant, a charge control agent, a release agent, and a magnetic powder) are mixed. The resulting mixture is melted and kneaded. The resulting melt-kneaded product is pulverized and then classified to obtain a toner core having a desired particle diameter. The grinding method has the advantage that the preparation of the toner core is easy as compared to the aggregation method described below. On the other hand, in the pulverizing method, since the toner core is obtained through the pulverizing process, it is difficult to obtain a toner core having a high average circularity. However, in the step of forming the shell layer described later, the curing reaction of the shell layer proceeds by heating the raw material of the shell layer. At this time, the slightly softened toner core shrinks due to surface tension, which tends to make the toner core spherical. Therefore, even when the toner core is manufactured by a pulverizing method, the average circularity of toner particles can be easily improved. Therefore, a grinding method is preferable as a method of producing the toner core.

(Aggregation method)
In the aggregation method, first, fine particles of a binder resin and fine particles of each optional component (for example, one or more of a colorant, a charge control agent, a release agent, and a magnetic powder) are aggregated in an aqueous medium To obtain agglomerated particles. The obtained aggregated particles are heated to unite the components contained in the aggregated particles. As a result, an aqueous dispersion containing a toner core is obtained. The resulting aqueous dispersion is washed by removing the dispersant and the like. As a result, a toner core is obtained.

  The zeta potential of the toner core is preferably negative (less than 0 mV) in an aqueous medium adjusted to pH 4, and more preferably -10 mV or less. The zeta potential of the toner core in an aqueous medium adjusted to pH 4 is measured, for example, by the following method.

(Method of measuring zeta potential)
0.2 g of a measurement sample (toner core), 80 mL of ion-exchanged water, and 20 g of a nonionic surfactant (for example, “polyvinylpyrrolidone K-85” manufactured by Nippon Shokubai Co., Ltd., water concentration 5 mass%, solid content concentration 95%) Mix using a magnetic stirrer. Thus, the measurement sample is uniformly dispersed in ion exchange water to obtain a dispersion. Dilute hydrochloric acid is added to the obtained dispersion of the measurement sample to adjust the pH of the dispersion of the measurement sample to 4. Thereby, the dispersion liquid of the measurement sample of pH 4 is obtained. For the dispersion of the measurement sample of pH 4, the zeta potential of the measurement sample in the dispersion is measured. The zeta potential is measured using a zeta potential / particle size distribution analyzer (eg, "Delsa Nano HC" manufactured by Beckman Coulter, Inc.).

  The standard carrier and the 7% by weight toner core with respect to the weight of the standard carrier are mixed using a mixing device for 30 minutes. In this case, the frictional charge amount of the toner core is preferably negative (less than 0 μC / g), and more preferably −10 μC / g or less. The triboelectric charge of the toner core is measured, for example, by the following method.

(Method of measuring triboelectric charge)
Standard Carrier N-01 (Standard Carrier for Negatively Charged Polar Toner) provided by the Japan Imaging Association and a 7% by mass measurement sample (toner core) with respect to the mass of the standard carrier, in a mixing apparatus (for example, WAB Co., Ltd.) Mix for 30 minutes using a "Tabra (R) mixer". The triboelectric charge of the measurement sample in the obtained mixture is measured using a Q / m meter (for example, "Model 210HS-2A" manufactured by Trek Corp.). The triboelectric charge of the measurement sample measured in this manner is an indicator of the ease of charging of the toner core. In addition, it is an indicator of whether the toner core is likely to be charged with positive or negative polarity.

  Usually, in order to form a uniform shell layer on the toner core, the toner core is often highly dispersed in an aqueous medium containing a dispersant. However, when the triboelectric charge amount of the toner core is negative (less than 0 μC / g), in the aqueous medium, the raw material of the shell layer (eg, monomer of thermosetting resin positively charged in aqueous medium) The prepolymer) is electrically attracted. Then, on the surface of the toner core, the reaction between the toner core and the raw material of the thermosetting resin (for example, the monomer or prepolymer of the thermosetting resin) proceeds favorably. Therefore, when a shell layer is formed using a toner core that is negatively charged in an aqueous medium, a uniform shell layer is formed on the surface of the toner core even if the toner core is not highly dispersed in the aqueous medium using a dispersant. It tends to be formed. The same advantage tends to be obtained when the zeta potential in the pH 4 aqueous medium of the toner core is negative (less than 0 mV).

  When at least one of the triboelectric charge with a standard carrier and the zeta potential in an aqueous medium at pH 4 exhibits negative polarity, producing toner particles using such a toner core has the following advantages: it is conceivable that. For example, even when no dispersant is used, the toner core is likely to be coated with a uniform shell layer. Also, for example, even when the waste water is not diluted, the total organic carbon concentration of the waste water discharged when producing the toner particles tends to be maintained at a low level (for example, 15 mg / L or less).

5-2. Shell layer formation process>
In the shell layer forming step, the shell layer is formed by covering the toner core provided with the inorganic oxide particles with the shell layer. Thereby, toner mother particles are obtained.

  As a raw material for forming a shell layer, for example, one or more of melamine, urea, reaction product of glyoxal and urea, and a precursor (methylolated product) formed by addition reaction of these with formaldehyde Is used. A thermoplastic resin is further used as a raw material for forming a shell layer.

  When forming the shell layer, it is preferable to prevent the dissolution of the binder resin and the elution of the component (for example, a release agent) contained in the toner core with respect to the solvent used for forming the shell layer. For this reason, the formation of the shell layer is preferably performed in an aqueous medium.

  The aqueous medium is a medium containing water as a main component. The aqueous medium may function as a solvent or may function as a dispersion medium. Specific examples of the aqueous medium include water or a mixture of water and a polar solvent. Examples of polar solvents contained in an aqueous medium include methanol or ethanol. The content of water in the aqueous medium is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more, based on the mass of the aqueous medium. It is most preferable that it is mass%.

  The formation of the shell layer is performed, for example, by adding the toner core to an aqueous medium containing a raw material for forming the shell layer. After the toner core is added to the aqueous medium, the toner core is dispersed in the aqueous medium.

  Examples of the dispersion method include a method of mechanically dispersing the toner core in an aqueous medium using an apparatus for vigorously stirring the dispersion. As a device for vigorously stirring the dispersion, for example, a mixing device (for example, "Hibismix (registered trademark)" manufactured by Primix, Inc.) is used.

  It is preferable to adjust the pH of the aqueous medium to about 4 with an acidic substance before adding the toner core to the aqueous medium containing the raw material for forming the shell layer. By adjusting the pH of the aqueous medium to the acidic side, the polycondensation reaction of the raw material for forming the shell layer tends to be promoted.

  After adjusting the pH of the aqueous medium as necessary, the raw material for forming the shell layer and the toner core are mixed in the aqueous medium. Thus, an aqueous dispersion of the toner core is obtained. In the obtained aqueous dispersion, the polymerization reaction of the shell material is allowed to proceed on the surface of the toner core.

  The temperature of the aqueous medium at the time of forming the shell layer is preferably 40 ° C. or more and 95 ° C. or less, and more preferably 50 ° C. or more and 80 ° C. or less. If the shell layer is formed at a temperature within such a range, the formation of the shell layer is likely to proceed.

  The temperature at which the shell layer is formed on the surface of the toner core is preferably 40 ° C. or more and 95 ° C. or less, and more preferably 50 ° C. or more and 80 ° C. or less. By forming the shell layer under the temperature in such a range, the formation of the shell layer proceeds well.

  The shell layer is formed to cover the toner core to obtain an aqueous dispersion containing toner base particles. The aqueous dispersion containing toner mother particles is cooled to normal temperature. Thereafter, one or more steps selected from the toner base particle washing step, the drying step, and the external addition step described later are performed as necessary. As a result, a toner containing toner particles is obtained.

5-3. Cleaning process>
The toner mother particles are washed with water as needed. As an example of the washing method, there is a method of recovering a wet cake of toner matrix particles from an aqueous dispersion containing toner matrix particles by solid-liquid separation (for example, filtration), and washing the obtained wet cake with water. It can be mentioned. Another example of the washing method is a method of settling toner mother particles in the dispersion, replacing the supernatant liquid with water, and redispersing the toner mother particles in water after substitution.

5-4. Drying process>
The toner mother particles may be dried as needed. Examples of the method for drying the toner base particles include a method using a dryer. Examples of dryers include spray dryers, fluid bed dryers, vacuum lyophilizers, or vacuum dryers. In order to suppress aggregation of toner base particles during drying, a method using a spray dryer is preferable. When a spray dryer is used, the external additive is adhered to the surface of the toner base particles simultaneously with the drying of the toner base particles by spraying the dispersion of the external additive such as silica together with the dispersion of the toner base particles. May be

5-5. External attachment process>
An external additive may be attached to the surface of the toner base particles, if necessary. As a method of attaching the external additive to the surface of the toner base particle, for example, a mixer (for example, an FM mixer and Nauta Mixer (registered trademark)) under the condition that the external additive is not buried in the surface of the toner base particle. And a method of mixing toner base particles and an external additive.

  The method of producing the toner is arbitrarily changed in accordance with the required characteristics of the toner. Also, unnecessary operations and steps may be omitted. When the external addition process is omitted, toner base particles correspond to toner particles.

  The toner of the present embodiment has been described above. According to the toner of the present embodiment, the low temperature fixability, the hot offset resistance and the heat resistant storage stability of the toner can be improved. Therefore, the electrostatic latent image developing toner of the present invention can be suitably used in various image forming apparatuses.

  Hereinafter, the present invention will be more specifically described using examples. In addition, this invention is not limited at all to the range of an Example.

  Each physical property in an Example and a comparative example was measured with the following method.

(Glass transition point, softening point, and melting point)
The glass transition point (Tg), the softening point (Tm), and the melting point (Mp) of the polyester resin as the binder resin are the method of measuring the glass transition point described in the embodiment, the method of measuring the softening point, and the measurement of the melting point It was measured in the same manner as the method. The glass transition point (Tg) and the softening point (Tm) of the toner particles are the same as in the method for measuring the glass transition point described in the embodiment except that the measurement sample is changed from polyester resin to a plurality of toner particles (toner). It measured by the same method. The melting point (Mp) of the releasing agent was measured by the same method as the measuring method of the melting point described in the embodiment except that the measurement sample was changed from the polyester resin to the releasing agent. The glass transition point (Tg) of the thermoplastic resin was measured by the same method as the method of measuring the glass transition point described in the embodiment, except that the measurement sample was changed from a polyester resin to a thermoplastic resin.

(Crystallinity index)
The crystallinity index of the polyester resin as the binder resin is determined from the ratio (Tm / Mp) of the softening point (Tm) of the polyester resin to the melting point of the polyester resin (the temperature of the maximum endothermic peak in the DSC curve, Mp) The

(Volume median diameter)
The volume median diameter D ₅₀ of the toner core and toner mother particles was measured using a precise particle size distribution measuring apparatus ("Coulter Counter Multisizer 3" manufactured by Beckman Coulter, Inc.).

(Film thickness)
The film thickness (thickness of shell layer) was measured as follows. First, a measurement sample was prepared. The toner was dispersed in a room temperature curable epoxy resin and allowed to stand in an atmosphere of 40 ° C. for 2 days to obtain a cured product. The resulting cured product was dyed with osmium tetroxide. Thereafter, using a microtome (“EM UC6” manufactured by Leica Co., Ltd.) in which a diamond knife is set, a thin film sample for cross-sectional observation of toner particles having a thickness of 200 nm was cut out from the obtained cured product. The obtained thin sample was used as a measurement sample. Using the measurement sample, the thickness of the shell layer was measured by the same method as the method of measuring the thickness of the shell layer described in the embodiment.

(Melt viscosity)
The melt viscosity (η1c) of the toner core at 80 ° C. and the melt viscosity (η2 c) at 90 ° C. of the toner core were measured by the same method as the method of measuring the melt viscosity of the toner core described in the embodiment. The melt viscosity (粘度 1 t) at 80 ° C. of the toner particles after the external addition step and the melt viscosity (η 2 t) at 90 ° C. of the toner particles after the external addition step are the same as the melt viscosity of the toner particles described in the embodiment. It was measured by the same method as the measurement method.

<1. Raw material for preparing toner>
Next, raw materials used to prepare the toners of Examples and Comparative Examples will be described.

<1-1. Amorphous polyester resin 1A to 1I>
Noncrystalline polyester resins 1A to 1I were prepared as binder resins to be contained in the toner core. Specifically, 1575 g of propylene oxide adduct of bisphenol A (BPA-PO), 163 g of ethylene oxide adduct of bisphenol A (BPA-EO), 377 g of fumaric acid, and 4 g of catalyst (dibutyltin oxide) were charged in a reaction vessel. The air in the reaction vessel was replaced with a nitrogen atmosphere. The temperature inside the reaction vessel was raised to 220 ° C. while stirring the contents of the reaction vessel. The contents of the reaction vessel were reacted at 220 ° C. for 8 hours, and then the pressure in the reaction vessel was reduced to 60 mmHg. Subsequently, the contents of the reaction vessel were allowed to react for an additional hour. Thereafter, the contents in the reaction vessel were cooled to 210 ° C. To the contents in the reaction vessel, 336 g of trimellitic anhydride was added. After completion of the reaction, the contents of the reaction vessel were taken out and cooled. Thus, non-crystalline polyester resin 1A was obtained.

  The non-crystalline polyester resins 1B to 1I were prepared in the same manner as the non-crystalline polyester resin 1A, respectively, except that the following points were changed. The amount of propylene oxide adduct of bisphenol A (BPA-PO) was changed from 1575 g in preparation of non-crystalline polyester resin 1A to the amount shown in Table 1. The amount of ethylene oxide adduct of bisphenol A (BPA-EO) used was changed from the amount of 163 g in the preparation of non-crystalline polyester resin 1A to the amount shown in Table 1. The amount of fumaric acid used was changed from 377 g in the preparation of the non-crystalline polyester resin 1A to the amount shown in Table 1. The amount of trimellitic anhydride used was changed from 336 g in the preparation of the non-crystalline polyester resin 1A to the amount shown in Table 1. Table 1 shows the glass transition points (Tg), the softening points (Tm), and the crystallinity indexes of the non-crystalline polyester resins 1A to 1I.

<1-2. Amorphous polyester resin 2A>
A non-crystalline polyester resin 2A was prepared as a binder resin to be contained in the toner core. Specifically, 420 g of a propylene oxide adduct of bisphenol A, 1235 g of an ethylene oxide adduct of bisphenol A, 714 g of terephthalic acid and 4 g of a catalyst (dibutyltin oxide) were charged in a reaction vessel. The air in the reaction vessel was then replaced with a nitrogen atmosphere. The temperature inside the reaction vessel was raised to 220 ° C. while stirring the contents of the reaction vessel. The contents of the reaction vessel were reacted at 220 ° C. for 8 hours, and then the pressure in the reaction vessel was reduced to 60 mmHg. Subsequently, the contents of the reaction vessel were allowed to react for an additional hour. After completion of the reaction, the contents of the reaction vessel were taken out and cooled. Thus, a non-crystalline polyester resin 2A was obtained. Table 2 shows the glass transition point (Tg), the softening point (Tm), and the crystallinity index of the non-crystalline polyester resin 2A.

<1-3. Crystalline polyester resin I and II>
Crystalline polyester resins I and II were prepared as binder resins to be contained in the toner core. Specifically, 132 g of 1,6-hexanediol, 230 g of 1,10-decanedicarboxylic acid, 1 g of a catalyst (dibutyltin oxide), and 0.3 g of hydroquinone were charged in a reaction vessel. Next, the air in the reaction vessel was replaced with a nitrogen atmosphere. The temperature inside the reaction vessel was raised to 200 ° C. while stirring the contents of the reaction vessel. While maintaining the temperature inside the reaction vessel at 200 ° C. and distilling off the by-product water, the contents of the reaction vessel were polymerized for 5 hours. Then, the pressure in the reaction vessel was reduced to 5 mmHg or more and 20 mmHg or less. The polymerization reaction was continued for 1 hour at 200 ° C. under reduced pressure. After completion of the polymerization reaction, the contents of the reaction vessel were taken out and cooled to obtain crystalline polyester resin I. Also, in place of continuing the polymerization reaction at 200 ° C. under reduced pressure for 1 hour, crystalline polyester resin II was prepared in the same manner as the preparation of crystalline polyester resin I, except that the polymerization reaction was continued for 8 hours at 200 ° C. under reduced pressure. I got Table 3 shows the melting points (Mp) of crystalline polyester resins I and II, and the crystallinity index.

<1-4. Measurement of acid value and hydroxyl value of polyester resin>
The acid value and the hydroxyl value of the polyester resin prepared as described above were measured according to JIS (Japanese Industrial Standard) K 0070-1992. First, the acid value and the hydroxyl value of the non-crystalline polyester resins 1A to 1I and 2A were measured. Next, the acid value and the hydroxyl value of the mixture of the non-crystalline polyester resin 1A (85 parts by mass) and the crystalline polyester resin I (15 parts by mass) were measured. This mixture corresponds to the raw material of toner A-25 described later. Next, the acid value and the hydroxyl value of the mixture of the non-crystalline polyester resin 1A (85 parts by mass) and the crystalline polyester resin II (15 parts by mass) were measured. This mixture corresponds to the raw material of toner A-26 described later. The measured acid value (AV) and hydroxyl value (OHV) of the polyester resin are shown in Table 5, Table 7 and Table 9.

<1-5. Release agent>
The following release agents W1 to W3 were prepared as binder resins to be contained in the toner core. In Table 4, melting | fusing point (Mp) of mold release agent W1-W3 is shown.
Releasing agent W1: Carnauba wax ("Carnauba wax No. 1" manufactured by Yoko Yoko Co., Ltd.)
Releasing agent W2: Synthetic ester wax ("Nissan Elector (registered trademark) WEP-2" manufactured by NOF Corporation)
Releasing agent W3: Synthetic ester wax (manufactured by NOF Corporation "Nissan Elector (registered trademark) WEP-3")

<1-6. Thermosetting resin>
Raw materials A to C of the following thermosetting resins were prepared as the raw materials of thermosetting resins to be contained in the shell layer.
Raw material A of thermosetting resin: aqueous solution of hexamethylolmelamine initial polymer ("Milben (registered trademark) resin SM-607" manufactured by Showa Denko KK, solid concentration 80% by mass)
Raw material B of thermosetting resin: aqueous solution of glyoxal monomer ("BECKAMINE (registered trademark) NS-11" manufactured by DIC Corporation, solid content 40% by mass)
Raw material C of thermosetting resin: aqueous solution of methylolated urea ("BECKAMINE (registered trademark) J-300S" manufactured by DIC Corporation, solid concentration 70% by mass)

<1-7. Thermoplastic resin>
The following thermoplastic resins D to F were prepared as thermoplastic resins to be contained in the shell layer.
Thermoplastic resin D: aqueous solution of acrylamide resin ("BECKAMINE (registered trademark) A-1" manufactured by DIC Corporation, solid content concentration 11% by mass, aqueous solution of water-soluble polyacrylamide)
Thermoplastic resin E: aqueous solution of acrylamide copolymer (monomer composition: 2-hydroxyethyl methacrylate / acrylamide / methacrylic acid-methoxypolyethylene glycol = 30/50/20 (molar ratio), solid content concentration 5% by mass , Glass transition point 110 ° C, mass average molecular weight 55000)
Thermoplastic resin F: an aqueous solution of a silicone-acrylic graft copolymer (manufactured by Toagosei Co., Ltd. “Cymac (registered trademark) US-480”, solid content concentration 25 mass%)

<2. Preparation of Toner A-1>
Toner A-1 was prepared as follows.

<2-1. Forming process of toner core>
Amorphous polyester resin 1A (100 parts by mass) as a binder resin, a copper phthalocyanine pigment (CI pigment blue, 5 parts by mass) as a colorant, and a releasing agent W3 (5 parts by mass) The mixture was mixed at a speed of 2400 rpm using an FM mixer ("FM-10B" manufactured by Nippon Coke Industry Co., Ltd.). This gave a mixture.

Then, using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.), the obtained mixture is fed at a material input speed of 5 kg / hour, shaft rotational speed 160 rpm, and a set temperature range of 80 ° C to 130 ° C. It melted and knead | mixed on conditions. Thus, a kneaded material was obtained. The obtained kneaded material was cooled. The cooled kneaded material was pulverized using a mechanical pulverizer ("Turbomill T250" manufactured by Freund Turbo Co., Ltd.) to obtain a pulverized material. The pulverized material was classified using a classifier (Elbow Jet, “EJ-LABO type” manufactured by Nittetsu Kogyo Co., Ltd.). As a result, a toner core was obtained. The volume median diameter D ₅₀ of the obtained toner core was 6.0 μm.

  A part of the obtained toner core (toner core used for preparation of toner A-1) was taken out. The melt viscosity at 80 ° C. and the melt viscosity at 90 ° C. of the removed toner core were measured. The melt viscosity of the toner core at 80 ° C. and the melt viscosity at 90 ° C. of each toner shown in Tables 5, 7 and 9 described later were also measured. The measurement results of the melt viscosity (η1c) at 80 ° C. and the melt viscosity (η2 c) at 90 ° C. of the toner core of each toner are shown in Tables 5, 7 and 9.

  A part of the obtained toner core (toner core used for preparation of toner A-1) was taken out. The removed toner core was used to measure the amount of triboelectricity with a standard carrier and to measure the zeta potential in a pH 4 dispersion. Each measurement was performed as follows. As a result, with respect to the toner core used for preparing the toner A-1, the triboelectric charge amount with the standard carrier was −20 μC / g. The zeta potential in the pH 4 dispersion was -30 mV.

(How to measure the amount of frictional charge with a standard carrier)
Standard carrier N-01 (Standard carrier for negative charge polarity toner) provided by the Japan Imaging Association and 7% by mass of a measurement sample (toner core) with respect to the mass of the standard carrier It mixed for 30 minutes using (trademark) mixer "). The obtained mixture was rubbed with a standard carrier, and the triboelectric charge of the measurement sample in the mixture was measured using a Q / m meter ("MODEL 210HS-2A" manufactured by Trek Co.).

(Method of measuring zeta potential in pH 4 dispersion)
0.2 g of a measurement sample (toner core), 80 mL of ion exchange water, and 20 g of a nonionic surfactant ("polyvinylpyrrolidone K-85" manufactured by Nippon Shokubai Co., Ltd.) were mixed using a magnet stirrer. Thereby, the measurement sample was uniformly dispersed in ion exchange water to obtain a dispersion of the measurement sample. Thereafter, dilute hydrochloric acid was added to the dispersion of the measurement sample to adjust the pH of the dispersion of the measurement sample to 4. About the dispersion of the measurement sample of pH 4, the zeta potential of the measurement sample in the dispersion was measured using a zeta potential and particle size distribution analyzer ("Delsa Nano HC" manufactured by Beckman Coulter, Inc.).

2-2. Shell layer formation process>
In a 1-L three-necked flask equipped with a thermometer and a stirring blade, 300 mL of ion exchanged water was placed. The internal temperature of the flask was maintained at 30 ° C. using a water bath. Next, dilute hydrochloric acid was added to the flask to adjust the pH of the solution in the flask to 4. After pH adjustment, the shell layer material was added to the flask. Specifically, a thermosetting resin raw material A (2.0 mL) and a thermoplastic resin D (2.0 mL) were added to the flask. Then, the contents of the flask were stirred, and the raw material of the shell layer was dissolved in deionized water. Thereby, the aqueous solution of the raw material of shell layer was obtained.

  To the aqueous solution of the raw material of the obtained shell layer, 300 g of a toner core provided with inorganic oxide particles was added. The contents of the flask were stirred at a speed of 200 rpm for 1 hour. Next, 300 mL of ion exchanged water was added to the flask. Thereafter, while the contents of the flask were stirred at a speed of 100 rpm, the temperature inside the flask was raised to 70 ° C. at a rate of 1 ° C./min. After raising the temperature, the contents of the flask were stirred for 2 hours under the conditions of an internal temperature of 70 ° C and a speed of 100 rpm. Thereafter, sodium hydroxide was added to the flask to adjust the pH of the contents of the flask to 7. The contents of the flask were then cooled to ambient temperature. As a result, a shell layer was formed to cover the toner core. Thus, a dispersion of toner base particles was obtained.

<2-3. Cleaning process>
The obtained dispersion of toner mother particles was filtered with a Buchner funnel to obtain a wet cake of toner mother particles. Next, the wet cake of toner mother particles was dispersed in ion exchange water, and the toner mother particles contained in the dispersion were filtered. Thus, the toner base particles were washed. The washing operation of the toner base particles with ion exchange water was repeated 5 times in the same manner. Thus, a wet cake of toner mother particles after washing was obtained.

<2-4. Drying process>
The wet cake of toner base particles after washing was dispersed in an aqueous ethanol solution having a concentration of 50% by mass to prepare a slurry. The toner base particles in the slurry were dried by supplying the obtained slurry to a continuous surface modifying apparatus ("Cotemizer (registered trademark)" manufactured by Freund Corporation). The drying with Coat Mizer (registered trademark) was performed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min.

<2-5. External attachment process>
100 parts by mass of toner mother particles obtained in the drying step and 1 part by mass of silica (dry silica fine particles, "AEROSIL (registered trademark) REA 90" manufactured by Nippon Aerosil Co., Ltd.), an FM mixer (manufactured by Japan Coke Industry Co., Ltd.) The mixture was mixed for 5 minutes using "FM-10B", volume 10 L). Thus, the external additive was attached to the toner base particles. The toner base particles to which the external additive was attached were sieved using a 200 mesh (75 μm mesh) sieve. Thereby, Toner A-1 including a plurality of toner particles was obtained.

  The thickness (film thickness) of the shell layer included in the toner particles was measured for the obtained toner A-1. Further, the glass transition point and the softening point of the obtained toner A-1 were measured. Furthermore, the melt viscosity (η 1 t) at 80 ° C. and the melt viscosity (η 2 t) at 90 ° C. of the obtained toner A-1 were measured. The film thickness, glass transition point, softening point, melt viscosity at 80 ° C. and melt viscosity at 90 ° C. were also measured for each toner shown in Tables 6, 8 and 10 described later. The film thickness, glass transition point (Tg), softening point (Tm), melt viscosity at 80 ° C. (η 1 t) and melt viscosity at 90 ° C. (η 2 t) of each toner are shown in Table 6, Table 8 and Table 10 Shown in.

<3. Preparation of Toners Other than Toner A-1>
Each toner other than the toner A-1 shown in Tables 5 to 10 was prepared by the following method.

(Toners A-2 and A-3)
Toners A-2 and A-3 were obtained in the same manner as in the preparation of toner A-1, except for the following changes. The addition amount of the raw material A of the thermosetting resin was changed from 2.0 mL in preparation of the toner A-1 to the addition amount shown in Table 6. The addition amount of the thermoplastic resin D was changed from 2.0 mL in preparation of the toner A-1 to the addition amount shown in Table 6. Thus, the film thickness was changed from 9 μm of the toner A-1 to the film thickness shown in Table 6.

(Toner A-8 to A-11)
Toners A-8 to A-11 were obtained in the same manner as in the preparation of toner A-1, except for the following changes. The addition amount of the raw material of the thermosetting resin was changed from 2.0 mL in preparation of Toner A-1 to the addition amount shown in Table 6. The addition amount of the thermoplastic resin was changed from 2.0 mL in preparation of Toner A-1 to the addition amount shown in Table 6. Thereby, the ratio (Vs / Vp) of the addition amount (Vs, unit: mL) of the raw material of the thermosetting resin to the addition amount (Vp, unit: mL) of the thermoplastic resin is set to 5 in the preparation of Toner A-1. The ratio shown in Table 6 was changed from .0 / 5.0.

(Toner A-12)
Toner A-12 was obtained in the same manner as in preparation of toner A-1, except for the following changes. The raw material A of the thermosetting resin in the preparation of the toner A-1 was changed to the raw material B of the thermosetting resin. The addition amount of the raw material of the thermosetting resin was changed from 2.0 mL in preparation of Toner A-1 to the addition amount shown in Table 6. Thereby, the ratio (Vs / Vp) of the addition amount (Vs, unit: mL) of the raw material of the thermosetting resin to the addition amount (Vp, unit: mL) of the thermoplastic resin is set to 5 in the preparation of Toner A-1. The ratio shown in Table 6 was changed from .0 / 5.0. Moreover, when adding the raw material B of the thermosetting resin, 2 mL of aqueous solution ("Catalyst GT-3" by DIC Corporation) made of a composite metal salt catalyst was also added.

(Toner A-13)
Toner A-13 was obtained in the same manner as in the preparation of toner A-1, except for the following changes. The raw material A of the thermosetting resin in the preparation of the toner A-1 was changed to the raw material C of the thermosetting resin. The addition amount of the raw material of the thermosetting resin was changed from 2.0 mL in preparation of Toner A-1 to the addition amount shown in Table 6. Thereby, the ratio (Vs / Vp) of the addition amount (Vs, unit: mL) of the raw material of the thermosetting resin to the addition amount (Vp, unit: mL) of the thermoplastic resin is set to 5 in the preparation of Toner A-1. The ratio shown in Table 6 was changed from .0 / 5.0. Further, when the raw material C of the thermosetting resin was added, 2 mL of an aqueous solution of an amine salt catalyst ("Catalyst 376" manufactured by DIC Corporation) was also added.

(Toners A-14 and A-15)
Toners A-14 and A-15 were obtained in the same manner as in the preparation of toner A-1, except for the following changes. The thermoplastic resin D in the preparation of the toner A-1 was changed to a thermoplastic resin of the type shown in Table 6 and Table 8. The addition amount of the thermoplastic resin was changed from 2.0 mL in preparation of Toner A-1 to the addition amount shown in Table 6 and Table 8.

(Toners A-16 to A-19, A-4, and B-1 to B-4)
Toners A-16 to A-19, A-4, and B-1 to B-4 were obtained in the same manner as in the preparation of toner A-1, except for the following changes. The non-crystalline polyester resin 1A in the preparation of the toner A-1 was changed to the non-crystalline polyester resin of the type shown in Table 7 and Table 9.

(Toner A-5)
Toner A-5 was obtained in the same manner as in preparation of toner A-1, except for the following changes. As a binder resin, in place of the non-crystalline polyester resin 1A (100 parts by mass) in the preparation of the toner A-1, the non-crystalline polyester resin 1A (85 parts by mass) and the crystalline polyester resin I (15 parts by mass) Was used.

(Toner A-6)
Toner A-6 was obtained in the same manner as in preparation of toner A-1, except for the following changes. As a binder resin, in place of the non-crystalline polyester resin 1A (100 parts by mass) in preparation of the toner A-1, the non-crystalline polyester resin 1A (85 parts by mass) and the crystalline polyester resin II (15 parts by mass) Was used.

(Toners A-7 and A-20)
Toners A-7 and A-20 were obtained in the same manner as in the preparation of toner A-1, except for the following changes. A mold release agent of the type shown in Table 7 was used in place of the mold release agent W3 in the preparation of the toner A-1.

(Toner B-5)
Toner B-5 was obtained in the same manner as in the preparation of toner A-1, except for the following changes. The thermoplastic resin in the preparation of Toner A-1 was not used in the preparation of Toner B-5.

(Toner B-6)
Toner B-6 was obtained in the same manner as in the preparation of toner A-1, except for the following changes. In the preparation of the toner B-6, the shell layer forming step, the washing step and the drying step were not performed. The external addition step was performed using the toner core obtained in the toner core formation step as toner base particles.

<4. Evaluation>
The low temperature fixability, the hot offset resistance, and the heat resistant storage stability of each of the obtained toners were evaluated.

<4-1. Low temperature fixability>
A two-component developer was prepared by mixing 100 parts by mass of a developer carrier (carrier for FS-C5250DN) and 5 parts by mass of a toner for 30 minutes using a ball mill.

An image was formed on a sheet of paper by the evaluation machine using the two-component developer prepared. As an evaluation machine, a color printer having a roller-roller type heat and pressure fixing device (an evaluation machine capable of changing the fixing temperature by modifying “FS-C5250DN” manufactured by Kyocera Document Solutions Inc.) was used. A 90 g / m ² paper ("C290" manufactured by Fuji Xerox Co., A4 size, 90 g / m ² plain paper evaluation paper) was used as the paper. The prepared two-component developer was loaded into the cyan developing device of the evaluation machine, and the replenishment toner was loaded into the cyan toner container of the evaluation machine.

Using the evaluation machine, a solid image having a size of 25 mm × 25 mm was formed on a portion up to 10 mm from the rear end of the sheet at a linear velocity of 200 mm / sec and a toner loading amount of 1.0 mg / cm ² . Subsequently, the sheet on which the image was formed was passed through the fixing device of the evaluation machine. The fuser nip width was set to 8 mm, and the nip passage time was set to 40 msec.

  In the evaluation of the lowest fixing temperature, the fixing temperature was set in the range of 100 ° C. or more and 200 ° C. or less. Specifically, the fixing temperature of the fixing device was raised from 100 ° C. by 1 ° C., and the minimum temperature (minimum fixing temperature) at which a solid image (toner image) could be fixed to paper was measured. Whether or not the toner could be fixed was confirmed by the following rubbing test. Specifically, the sheet passed through the fixing device was folded in half so that the surface on which the image was formed was inside. The folded paper was rubbed back and forth 10 times on the crease using a 1 kg weight coated with fabric. Subsequently, the paper was unfolded, and the folded part of the paper (the part where the solid image was formed) was observed. Then, the peeling length (peeling length) of the toner at the bent portion was measured. The lowest temperature of the fixing temperatures at which the peeling length is less than 1 mm was taken as the minimum fixing temperature. The toner having the lowest fixing temperature of 155 ° C. or less was evaluated as having a low temperature fixing property of the toner.

<4-2. Hot offset resistance>
With the prepared two-component developer, an unfixed solid image was formed on paper using the same evaluation machine and paper as in the evaluation of low-temperature fixability. In the evaluation of hot offset resistance, the fixing temperature was set in the range of 180 ° C. or more and 230 ° C. or less. The conditions other than the fixing temperature were set in the same manner as the conditions in the evaluation of the low temperature fixability. In the second cycle of the heat roller of the fixing device, the lowest temperature of the temperature at which the toner transferred to the sheet is taken as the hot offset occurrence temperature. The toner having a hot offset occurrence temperature of 200 ° C. or more was evaluated as having a good hot offset resistance of the toner.

<4-3. Heat resistant storage stability>
3 g of the toner was weighed in a 20 mL poly container and allowed to stand in a thermostat set at 60 ° C. for 3 hours. Thus, a toner for evaluating the heat resistant storage stability was obtained. Thereafter, the toner for heat-resistant storage evaluation was sieved using a powder tester (“TYPE PT-E 84810” manufactured by Hosokawa Micron Corporation). Specifically, in accordance with the manual of a powder tester (manufactured by Hosokawa Micron Corporation), a toner for evaluation of heat resistant storage stability was sieved using a sieve of 200 mesh under the condition of rheostat graduation 5 and time 30 seconds. After sieving, the mass of the toner remaining on the sieve was measured. From the mass of the toner before sieving and the mass of the toner remaining on the sieve after sieving, the degree of aggregation [mass%] was determined according to the following formula (2). The toner having a degree of aggregation of 30% by mass or less was evaluated as the heat resistant storage stability of the toner was good.
Cohesion degree [mass%] = 100 × mass of toner remaining on sieve / mass of toner before sieving ... (2)

  Tables 5 to 10 show types and addition amounts of raw materials for preparing the toner for each of the toners A-1 to A-20 and B-1 to B-6. Further, for each toner, the acid value (AV) and the hydroxyl value (OHV) of the polyester resin contained in the toner core are shown in Table 5, Table 7 and Table 9. The melt viscosity (η1c) at 80 ° C. and the melt viscosity (η2 c) at 90 ° C. of the toner core of each toner are shown in Tables 5, 7 and 9. In Tables 5 and 7, Mp indicates the melting point of the crystalline polyester resin.

  The thickness (film thickness) of the shell layer provided in the toner particle of each toner is shown in Table 6, Table 8 and Table 10. The glass transition point (Tg) and the softening point (Tm) of the toner particles of each toner are shown in Table 6, Table 8 and Table 10. The melt viscosity (η 1 t) at 80 ° C. and the melt viscosity (η 2 t) at 90 ° C. of the toner particles (after the external addition step) of each toner are shown in Table 6, Table 8 and Table 10. In Tables 6, 8 and 10, Vs / Vp is the ratio of the addition amount (Vs, unit: mL) of the raw material of the thermosetting resin to the addition amount (Vp, unit: mL) of the thermoplastic resin Show.

  Further, the measurement results of the minimum fixing temperature, the hot offset occurrence temperature, and the aggregation degree of each toner are shown in Table 11. In Table 11, wt% shows mass%.

  The toners A-1 to A-20 are examples. On the other hand, toners B-1 to B-6 are comparative examples.

  As shown in Table 11, the toners A-1 to A-20 were excellent in low-temperature fixability, hot offset resistance, and heat resistant storage stability of the toner.

In the toner B-1, the melt viscosity (η1t) at 80 ° C. of the toner particles was less than 2.1 × 10 ⁴ Pa · s. Therefore, as shown in Table 11, it is considered that Toner B-1 was inferior in heat resistant storage stability.

In the toner B-2, the melt viscosity (η 1 t) at 80 ° C. of the toner particles was over 2.3 × 10 ⁵ Pa · s. Therefore, as shown in Table 11, it is difficult for the toner B-2 to obtain viscosity, and the toner B-2 is considered to be inferior in low-temperature fixability.

In the toner B-3, the melt viscosity (η 2 t) at 90 ° C. of the toner particles was less than 7.0 × 10 ³ Pa · s. Therefore, as shown in Table 11, it is considered that Toner B-3 is inferior in hot offset resistance and heat resistant storage stability.

In the toner B-4, the melt viscosity (η 2 t) of the toner particles at 90 ° C. exceeded 2.3 × 10 ⁴ Pa · s. Therefore, as shown in Table 11, it is difficult to obtain the viscosity of the toner with the toner B-4, and the toner B-4 is considered to be inferior in low-temperature fixability.

  In the toner B-5, the shell layer did not contain a thermoplastic resin. Therefore, as shown in Table 11, when fixing the toner B-5 to the sheet, the shell layer of the toner particles is hard to be destroyed, and the toner B-5 is considered to be inferior in low-temperature fixability.

  In the toner B-6, the toner particles did not have a shell layer. Therefore, as shown in Table 11, it is considered that Toner B-6 was inferior in heat resistant storage stability.

  The toner according to the present invention can be used, for example, to form an image in a copier or printer.

Claims (6)

A toner for developing an electrostatic latent image, comprising a plurality of toner particles, wherein
The toner particles have a toner core and a shell layer covering the toner core,
The shell layer contains a thermosetting resin and a thermoplastic resin,
The toner core contains at least a polyester resin,
The melt viscosity of the toner particles at 80 ° C. is 2.1 × 10 ⁴ Pa · s or more and 2.3 × 10 ⁵ Pa · s or less,
The melt viscosity of the toner particles at 90 ° C. is 7.0 × 10 ³ Pa · s or more and 2.3 × 10 ⁴ Pa · s or less,
As the polyester resin, non-crystalline polyester resin and crystalline polyester resin are contained,
The melting point of the crystalline polyester resin is 50 ° C. or more and 100 ° C. or less,
The thickness of the shell layer is 9 nm,
The electrostatic latent image, wherein the shell layer contains a unit derived from hexamethylolmelamine as the thermosetting resin and a unit derived from a silicone-acrylic graft copolymer as the thermoplastic resin in a ratio of 32 : 5. Developing toner. The glass transition point of the toner particles is 25 ° C. or more and 45 ° C. or less,
The toner for developing an electrostatic latent image according to claim 1, wherein the softening point of the toner particles is 70 ° C. or more and 95 ° C. or less. The acid value of the polyester resin is 5 mg KOH / g or more and 30 mg KOH / g or less,
The toner for developing an electrostatic latent image according to claim 1, wherein a hydroxyl value of the polyester resin is 15 mg KOH / g or more and 80 mg KOH / g or less. The toner core further contains a release agent,
The toner for developing an electrostatic latent image according to any one of claims 1 to 3, wherein the release agent is an ester wax having a melting point of 50 ° C to 100 ° C.   The non-crystalline polyester resin is a polymer of a monomer containing a propylene oxide adduct of bisphenol A as an alcohol component and an ethylene oxide adduct of bisphenol A, and fumaric acid and trimellitic acid as a carboxylic acid component The toner for developing an electrostatic latent image according to any one of claims 1 to 4. The toner for electrostatic latent image development according to any one of claims 1 to 5 , wherein a crystallinity index of the non-crystalline polyester resin is 0.489 or more and 0.548 or less.

Images