JP2015152715A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development, which has excellent heat-resistant storage property and low-temperature fixability and can suppress occurrence of offset at high temperature.SOLUTION: The toner for electrostatic latent image development comprises a plurality of toner particles. Each toner particle comprises a toner core containing a binder resin and a shell layer covering a surface of the toner core. The binder resin comprises a crystalline polyester resin and a non-crystalline polyester resin. The crystalline polyester shows a melting point Mpof 30°C or higher and 100°C or lower measured by use of a differential scanning calorimeter; and a difference (Mp-Tg) between the above Mpand a glass transition temperature Tgof the non-crystalline polyester resin is 10°C or more and 80°C or less. The shell layer is formed from a resin containing a unit derived from a thermosetting resin monomer and a unit derived from a thermoplastic resin; and the thermosetting resin is one or more resins selected from melamine resin, urea resin, and glyoxal resin.

Description

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

  Regarding toners, capsule toners are known. The capsule toner includes a toner core and a shell layer (capsule layer) formed on the surface of the toner core.

  Patent Document 1 describes a capsule toner in which a shell layer contains a thermosetting resin. In this toner, the softening temperature of the toner core before the shell layer is formed is 40 ° C. or higher and 150 ° C. or lower.

JP 2004-138985 A

  The toner described in Patent Document 1 has insufficient low-temperature fixability. Further, when an image is formed using the toner described in Patent Document 1, if the fixing temperature is high, offset is likely to occur due to fusion of the melted toner particles to a heated fixing roller.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an electrostatic latent image developing toner that is excellent in heat-resistant storage stability and low-temperature fixability and can suppress the occurrence of offset at high temperatures. And

The electrostatic latent image developing toner of the present invention includes a plurality of toner particles. Each of the plurality of toner particles includes a toner core containing a binder resin and a shell layer covering the surface of the toner core. The binder resin includes a crystalline polyester resin and an amorphous polyester resin. Is measured using a differential scanning calorimeter, the melting point Mp ^c of the crystalline polyester resin is not more 100 ° C. or less 30 ° C. or higher, Mp difference between the glass transition point Tg ^{nc c} and non-crystalline polyester resin (Mp ^c - Tg ^nc ) is 10 ° C. or higher and 80 ° C. or lower. The shell layer is made of a resin including a unit derived from a monomer of a thermosetting resin and a unit derived from a thermoplastic resin, and the thermosetting resin is an amino resin group consisting of a melamine resin, a urea resin, and a glyoxal resin. One or more kinds of resins selected from the above.

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

Softening point Tm ^c of the crystalline polyester resin, and is a diagram for explaining a method of reading a softening point Tm ^nc of the amorphous polyester resin. From the endothermic curve, it is a diagram for explaining a method of measuring the melting point Mp ^c of the crystalline polyester resin. It is a figure explaining the method of measuring the glass transition point ^Tgnc of an amorphous polyester resin from an endothermic curve.

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

  The electrostatic latent image developing toner (also simply referred to as toner) according to the present embodiment is a powder containing a plurality of toner particles. The toner according to the exemplary embodiment can be used in an image forming apparatus, for example.

  In the image forming apparatus, an electrostatic image is developed using a developer containing toner. As a result, charged toner adheres to the electrostatic latent image formed on the photoreceptor. Then, after the adhered toner is transferred to the transfer belt, the toner image on the transfer belt is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated and fixed on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be obtained by superimposing toner images formed using four color toners of black, yellow, magenta, and cyan.

  Each of the plurality of toner particles includes a toner core and a shell layer that covers the toner core. The toner core includes a binder resin as an essential component, and may further include an optional component such as a colorant, a release agent, a charge control agent, or magnetic powder in the binder resin as necessary. A shell layer consists of resin containing the unit derived from the monomer of a thermosetting resin.

  The surface of the toner particles (toner mother particles) may be treated with an external additive as necessary. The toner particles before being treated with the external additive may be referred to as toner mother particles. A plurality of shell layers may be laminated on the surface of the toner core.

  It is preferable that the toner core has an anionic property and the shell layer has a cationic property. Since the toner core has an anionic property, the material of the cationic shell layer can be attracted to the surface of the toner core when the shell layer is formed. Specifically, for example, a toner core material that is negatively charged in an aqueous medium and a shell layer material that is positively charged in an aqueous medium are electrically attracted to each other. For example, the shell layer is formed on the surface of the toner core by in-situ polymerization. Is formed. This makes it easy to form a uniform shell layer on the surface of the toner core without excessively dispersing the toner core in the aqueous medium using a dispersant.

  In the toner core, the binder resin occupies most of the core component (for example, 85% by mass or more). For this reason, the polarity of the binder resin greatly affects the polarity of the entire toner core. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core has a strong tendency to become anionic, for example, the binder resin has an amino group, an amine, or When it has an amide group, the toner core has a strong tendency to become cationic.

  In this embodiment, an indicator that the toner core is anionic is that the zeta potential of the toner core measured in an aqueous medium having a pH adjusted to 4 exhibits negative polarity. In order to strengthen the bond between the toner core and the shell layer, it is preferable that the zeta potential of the toner core at pH 4 is smaller than 0V and the zeta potential of the toner particles at pH 4 is larger than 0V. In this embodiment, pH 4 corresponds to the pH of the aqueous medium when the shell layer is formed.

  Examples of the zeta potential measurement method include an electrophoresis method, an ultrasonic method, and an ESA (electroacoustic) method.

  In the electrophoresis method, an electric field is applied to the particle dispersion to cause electrophoresis of charged particles in the dispersion, and the zeta potential is calculated based on the electrophoresis speed. As an example of the electrophoresis method, there is a laser Doppler method (a method in which an electrophoretic velocity is obtained from the amount of Doppler shift of the obtained scattered light by irradiating the electrophoretic particles with laser light). The laser Doppler method has the advantage that the particle concentration in the dispersion does not need to be high, the number of parameters necessary for calculating the zeta potential is small, and the electrophoresis speed can be detected with high sensitivity.

  The ultrasonic method is a method of irradiating a particle dispersion with ultrasonic waves to vibrate charged particles in the dispersion and calculating a zeta potential based on a potential difference caused by the vibration.

  In the ESA method, a high frequency voltage is applied to the particle dispersion to vibrate charged particles in the dispersion to generate ultrasonic waves. Then, the zeta potential is calculated from the magnitude (intensity) of the ultrasonic waves.

  The ultrasonic method and the ESA method have an advantage that the zeta potential can be measured with high sensitivity even in a particle dispersion having a high particle concentration (for example, exceeding 20% by mass).

  The toner may be used as a one-component developer, or mixed with a desired carrier and used as a two-component developer.

  The toner core that constitutes the toner particles contains a binder resin. The binder resin includes a crystalline polyester resin and an amorphous polyester resin. For this reason, hydroxyl groups and carboxyl groups are exposed on the surface of the toner core. As will be described later, the shell layer includes a resin containing a unit derived from a monomer of a thermosetting resin (one or more resins selected from an amino resin group consisting of a melamine resin, a urea resin, and a glyoxal resin). The shell layer is formed using a precursor obtained by reacting such a thermosetting resin monomer with formaldehyde, or using a precursor obtained by methylating the thermosetting resin monomer with formaldehyde.

  The toner core and the shell layer are made of the above materials. For example, when the shell layer is formed by a method described later, a hydroxyl group or a carboxyl group exposed on the surface of the toner core, and a methylol group included in an intermediate of the shell layer material Is selected from a polyester resin having a hydroxyl group constituting the toner core (crystalline polyester resin and non-crystalline polyester resin) and a thermosetting resin (melamine resin, urea resin, and glyoxal resin) contained in the shell layer. Since a covalent bond is formed with the resin), the shell layer and the toner core are firmly bonded.

  Furthermore, since the toner particles are protected by a hard shell layer made of a thermosetting resin, even if the toner particles are stressed for a long time in the developing device, the toner particles are not easily crushed. Furthermore, the shell layer is firmly bonded to the toner core, and peeling from the toner core hardly occurs. Therefore, the toner of this embodiment is excellent in heat resistant storage stability.

  The toner of this embodiment is excellent in low-temperature fixability because the binder resin contains a crystalline polyester resin. Hereinafter, the crystalline polyester resin and the amorphous polyester resin will be described in order.

  The crystalline polyester resin is obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component. A divalent or trivalent or higher alcohol can be used as the alcohol component. Specific examples of the divalent or trivalent or higher alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol; Bisphenols such as A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, or polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1, -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 trivalent or higher alcohols such as 1,3,5-trihydroxymethylbenzene.

  Among these alcohol components, aliphatic diols having 2 to 8 carbon atoms are preferable and α, ω-alkanediols having 2 to 8 carbon atoms are more preferable because crystallization of the polyester resin is easily promoted. .

  In order to obtain a crystalline polyester resin, the proportion of the aliphatic diol having 2 to 10 carbon atoms in the alcohol component is preferably 80 mol% or more, and more preferably 90 mol% or more. Similarly, the content of the component (single compound) contained in the largest amount in the alcohol component is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%. Most preferred.

  As the carboxylic acid component, a divalent or trivalent or higher carboxylic acid can be used. Specific examples of the divalent or trivalent or higher carboxylic acid component include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, Sebacic acid, azelaic acid, malonic acid, alkyl or alkenyl succinic acid (e.g., n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n- Divalent carboxylic acids such as dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid or isododecenyl succinic acid); 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5 -Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4- Phthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Examples thereof include trivalent or higher carboxylic acids such as acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, or lower alkyl esters. Here, “lower alkyl” means an alkyl group having 1 to 6 carbon atoms.

  Among these carboxylic acid components, an aliphatic dicarboxylic acid having 2 to 16 carbon atoms is preferable and an α, ω-alkanedicarboxylic acid having 2 to 16 carbon atoms is preferable because it facilitates crystallization of the polyester resin. Acid is more preferred.

  In order to obtain a crystalline polyester resin, the aliphatic dicarboxylic acid having 2 to 16 carbon atoms in the carboxylic acid component is preferably 70 mol% or more, and more preferably 90 mol% or more. Similarly, the content of the component (single compound) contained in the largest amount in the carboxylic acid component is preferably 70 mol% or more, more preferably 90 mol% or more, and 100 mol%. Is most preferred.

  “Crystallinity” as shown in the above “crystalline polyester resin” means that it has a clear endothermic peak rather than a stepwise endothermic change in differential scanning calorimetry (DSC). Specifically, “crystallinity” means that the half-value width of the endothermic peak when measured at a heating rate of 10 ° C./min is 15 ° C. or less. On the other hand, a polyester resin in which the half-value width of the endothermic peak exceeds 15 ° C. or a polyester resin in which no clear endothermic peak is observed means that it is amorphous (amorphous).

For measurement of the softening point (Tm ^c ) of the crystalline polyester resin, an elevated flow tester (for example, “CFT-500D” manufactured by Shimadzu Corporation) is used. A measurement sample (crystalline polyester resin) is set in an elevated flow tester, and a 1 cm ³ sample is melted and flowed under conditions of a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² , and a heating rate of 6 ° C./min. Thus, an S-shaped curve (S-shaped curve related to temperature (° C.) / Stroke (mm)) as shown in FIG. 1 is obtained. The temperature at the first shoulder portion of the S-curve is the softening point (Tm ^c ) of the crystalline polyester resin.

How to determine the melting point of the crystalline polyester resin (Mp ^c), it will be described with reference to FIG. The crystalline polyester resin melting point (Mp ^c) is, for example, can be measured using a differential scanning calorimeter (Seiko Instruments Co., Ltd. "DSC6220"). Specifically, 10 mg or more and 12 mg or less of toner is put in an aluminum dish and set in the measurement unit. Starting from 30 ° C., the temperature is raised to 170 ° C. at 10 ° C./min. At this time, a heat of fusion curve as shown in FIG. 2 is obtained. In this heat of fusion curve, the maximum peak temperature of heat of fusion is observed and the melting point of the crystalline polyester resin (Mp ^c).

Melting point of the crystalline polyester resin (Mp ^c) is 100 ° C. or less 30 ° C. or higher.
Toner using a melting point (Mp ^c) is 30 ° C. or higher 100 ° C. or less crystalline polyester resin is excellent in heat resistant storage stability and low-temperature fixability. Specifically, the melting point (Mp ^c) is (less than 30 ° C.) too low toner using a crystalline polyester resin, easily easily deformed under a high temperature environment, poor heat-resistant storage stability. Mp (Mp ^c) is (greater than 100 ° C.) too high toner comprising toner particles prepared using the toner core comprising a crystalline polyester resin, since the toner core is hardly melted when fixing the toner on a recording medium Inferior in low-temperature fixability.

  An amorphous polyester resin may be used independently and may be used in combination of 2 or more type.

The glass transition point of the amorphous polyester resin (Tg ^nc), the melting point of the crystalline polyester resin and (Mp ^c), the difference between the Tg ^nc of the non-crystalline polyester resin (Mp ^c -Tg ^nc) is 10 ° C. or higher 80 As long as it is below ℃, it is not particularly limited. Tg ^nc is preferably 50 ° C. or higher and 70 ° C. or lower, and more preferably 60 ° C. or higher and 65 ° C. or lower. When a plurality of types of amorphous polyester resins are used, Tg ^nc is a glass transition point of a resin obtained by uniformly melting and kneading a plurality of amorphous polyester resins. The measurement of tg ^nc, according to the same method as the measuring method of Mp ^c, using a differential scanning calorimeter.

How to read the glass transition point (Tg ^nc ) of the amorphous polyester resin will be described with reference to FIG. A differential scanning calorimeter (DSC) can be used to measure the endothermic curve of the amorphous polyester resin and determine the specific heat change point in the endothermic curve. Specifically, 10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, and the measurement temperature range is 25 ° C. or more and 200 ° C. or less and the temperature increase rate is 10 ° C./min. An endothermic curve of the amorphous polyester resin is obtained, and the glass transition point (Tg ^nc ) of the amorphous polyester resin is obtained based on the endothermic curve.

The method for reading the softening point (Tm ^nc ) of the amorphous polyester resin will be described with reference to FIG. The maximum value of the stroke obtained by elevated type flow tester and S _1, the stroke value of the low-temperature side of the base line and S _2. In S-shaped curve, the temperature at which the stroke value is _{(S 1 + S 2) /} 2, the melting point of the non-crystalline polyester resin which is a measurement sample (Mp ^c).

As described above, the melting point of the crystalline polyester resin (Mp ^c), the difference between the glass transition point of the amorphous polyester resin ^{(Tg nc) (Mp c -Tg} nc) is located at 10 ° C. or higher 80 ° C. or less . A toner including toner particles composed of a toner core including a crystalline polyester resin and an amorphous polyester resin is excellent in heat-resistant storage stability and low-temperature fixability, and can suppress the occurrence of offset at a high temperature. When an image is formed using toner containing such toner particles, the crystalline polyester resin and the non-crystalline polyester resin are mutually softened or melted when the toner particles are heated at the time of fixing to the recording medium. As a result, the toner particles are rapidly melted. Therefore, the toner comprising toner particles the value of (Mp ^c -Tg ^nc) is too large (crystalline polyester resin and amorphous toner particles constituted by using a toner core comprising a polyester resin) is the low-temperature fixability Inferior.

  The mass average molecular weight (Mw) of the amorphous polyester resin is preferably 10,000 or more and 50,000 or less in order to improve the strength or fixability of the core. The molecular weight distribution (Mw / Mn) of the amorphous polyester resin, which is the ratio of the mass average molecular weight (Mw) of the amorphous polyester resin to the number average molecular weight (Mn) of the amorphous polyester resin, is preferably 8 or more and 50 or less. . The mass average molecular weight (Mw) and the number average molecular weight (Mn) of the amorphous polyester resin can be measured using gel permeation chromatography.

  The acid value of the amorphous polyester resin is preferably 5 mgKOH / g or more and 30 mgKOH / g or less because it has sufficient anionic property. For the same reason, the hydroxyl value of the amorphous polyester resin is preferably 15 mgKOH / g or more and 80 mgKOH / g or less.

  The acid value and the hydroxyl value of the amorphous polyester resin can be adjusted by appropriately changing the amounts of the alcohol component and the carboxylic acid component used when the amorphous polyester resin is produced. Moreover, when the molecular weight of the amorphous polyester resin is increased, the acid value and the hydroxyl value of the amorphous polyester resin tend to decrease.

  In the binder resin, the ratio (P / Q, mass ratio) of the content (P) of the crystalline polyester resin to the content (Q) of the amorphous polyester resin is excellent in heat-resistant storage and low-temperature fixability, and high temperature In order to suppress the offset in the case, it is preferably 0.01 or more and 1 or less.

  The binder resin may contain other thermoplastic resins (hereinafter, other thermoplastic resins) other than the crystalline polyester resin and the non-crystalline polyester resin. The other thermoplastic resin is appropriately selected from thermoplastic resins conventionally used as a binder resin for toner.

  The total of the content of the crystalline polyester resin (P) in the binder resin and the content (Q) of the amorphous polyester resin is preferably 70% by mass or more, more preferably 80% by mass or more, and 90% by mass. The above is particularly preferable, and 100% is most preferable.

  As the colorant, a known pigment or dye can be used in accordance with the color of the toner particles. Specific examples of suitable colorants include the following colorants. The amount of the colorant used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the black colorant include carbon black. As the black colorant, a colorant that is toned to black using a colorant such as a yellow colorant, a magenta colorant, and a cyan colorant, which will be described later, can also be used.

  When the toner is a color toner, examples of the colorant contained in the toner core include a colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  Examples of yellow colorants include colorants such as condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, or allylamide compounds. Specifically, C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, or 194); Nephthol Yellow S, Hansa Yellow G, or C.I. I. Bat yellow is mentioned.

  Examples of magenta colorants include colorants such as condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, or perylene compounds. Specifically, C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254).

  Examples of cyan colorants include colorants such as copper phthalocyanine compounds, copper phthalocyanine derivatives, anthraquinone compounds, or basic dye lake compounds. Specifically, 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.

  The release agent is used for the purpose of improving the toner fixing property and offset resistance. The amount of the release agent used is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

As the release agent, wax is preferable. Examples of the wax include ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, or montan wax. Among these release agents, ester wax is more preferable. Examples of the ester wax include synthetic ester wax or natural ester wax (carnauba wax or rice wax). As the ester wax, a synthetic ester wax is preferred because it is easy to adjust the melting point (Mp _r ) of the release agent measured using a differential scanning calorimeter by selecting a synthetic raw material as appropriate. These release agents can be used in combination of two or more.

  The method for producing the synthetic ester wax is not particularly limited as long as it is a chemical synthesis method. For example, a synthetic ester wax can be produced using a well-known method (reaction of alcohol and carboxylic acid in the presence of an acid catalyst, or reaction of carboxylic acid halide and alcohol). In addition, the raw material of synthetic ester wax may be derived from a natural product such as a long-chain fatty acid produced from natural fat or oil, or may be commercially available as a synthetic product.

The melting point (Mp _r ) of the release agent is preferably 50 ° C. or higher and 100 ° C. or lower. The melting point (Mp _r ) of the release agent is the temperature of the maximum endothermic peak in the DSC curve measured using a differential scanning calorimeter. The toner Mp _r was used release agent is 100 ° C. or less than 50 ° C. is excellent in low-temperature fixability can be further suppress the occurrence of offset at high temperatures.

  In the toner core or the shell layer, a charge control agent may be used for adjusting the acid value of the binder resin in the toner core or adjusting the charging property of the shell layer.

  The toner core may contain magnetic powder in the binder resin as necessary. The toner including toner particles manufactured using the toner core including the magnetic powder manufactured as described above is used as a magnetic one-component developer. Suitable magnetic powders include iron such as ferrite or magnetite; ferromagnetic metals such as cobalt or nickel; alloys containing iron and / or ferromagnetic metals; compounds containing iron and / or ferromagnetic metals A ferromagnetic alloy subjected to a ferromagnetization treatment such as heat treatment; chromium dioxide.

  The particle size 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. When magnetic powder having a particle diameter in such a range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

  The amount of magnetic powder used is preferably 35 parts by weight or more and 60 parts by weight or less, more preferably 40 parts by weight or more and 60 parts by weight or less when the toner is used as a one-component developer and the total amount of toner is 100 parts by weight. preferable.

Softening point Tm ^t of the toner core is measured using the elevated type flow tester. Softening point Tm ^t of the toner core is excellent in fixability, in order to suppress the offset at high temperatures, preferably 70 ° C. or higher 100 ° C. or less. To adjust the softening point Tm ^t of the toner core, the crystalline polyester resin in the toner core, non-crystalline polyester resin, or composition of the release agent may be appropriately adjusted.

[Shell layer]
The resin constituting the shell layer includes a unit derived from a monomer of a thermosetting resin and a unit derived from a thermoplastic resin. For example, a unit derived from a thermoplastic resin is crosslinked with a unit derived from a monomer or prepolymer of a thermosetting resin. The shell layer constituted by such a resin has both moderate flexibility based on the thermoplastic resin and moderate mechanical strength based on the three-dimensional crosslinked structure formed by the monomer or prepolymer of the thermosetting resin. . For this reason, a toner composed of toner particles having such a shell layer is excellent in heat-resistant storage stability and low-temperature fixability. Specifically, the shell layer is not easily destroyed during storage or transportation. On the other hand, at the time of fixing, the toner core is easily broken by applying temperature and pressure, and the softening or melting of the toner core proceeds rapidly. For this reason, the toner can be fixed to the recording medium at a low temperature.

  Units derived from thermoplastic resins (hereinafter referred to as thermoplastic units) significantly change the structure or properties of the thermoplastic resin matrix such as introduction of functional groups, oxidation, reduction, or atom replacement. Units with some degree of modification are included. In addition, a unit derived from a thermosetting resin monomer or prepolymer (hereinafter referred to as a thermosetting unit) includes a thermosetting resin monomer such as introduction of a functional group, oxidation, reduction, or atom replacement. Alternatively, units that have been modified to the extent that they do not significantly change the structure or properties of the prepolymer matrix are included.

  The monomer used to introduce the thermosetting unit into the resin is a monomer used to form one or more thermosetting resins selected from the amino resin group consisting of melamine resin, urea resin, and glyoxal resin, or It is a prepolymer.

  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 a reaction product of glyoxal and urea with formaldehyde. The monomer used to form the glioxal resin is a reaction product of glyoxal and urea. Urea reacted with melamine, urea and glyoxal may have undergone well-known modification. Thermosetting resin monomers can be used as derivatives methylolated with formaldehyde prior to the formation of the shell layer.

  The shell layer contains nitrogen atoms derived from melamine, urea or glyoxal. For this reason, the toner of this embodiment having a shell layer containing nitrogen atoms is easily positively charged. Therefore, when an image is formed by positively charging the toner of this embodiment, the toner particles included in the toner are easily positively charged 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 the toner particles contained in the toner are easily positively charged to a desired charge amount.

The thermoplastic resin preferably has a functional group having reactivity with the functional group of the monomer of the thermosetting resin. For example, the thermoplastic resin preferably has a functional group containing an active hydrogen atom such as a hydroxyl group, a carboxyl group, or an amino group. The amino group may be contained in the thermoplastic resin as a carbamoyl group (—CONH ₂ ). Since the formation of the shell layer is easy, the thermoplastic resin includes a thermoplastic resin containing a unit derived from (meth) acrylamide; a thermoplastic resin having a functional group such as a carbodiimide group, an oxazoline group, or a glycidyl group. preferable.

  Specific examples of the thermoplastic resin include (meth) acrylic resin, styrene- (meth) acrylic copolymer resin, silicone- (meth) acrylic graft copolymer, polyurethane resin, polyester resin, polyvinyl alcohol, or ethylene. A vinyl alcohol copolymer is mentioned. These resins may contain a unit derived from a monomer having a functional group such as a carbodiimide group, an oxazoline group, or a glycidyl group. Among these, as the thermoplastic resin, (meth) acrylic resin, styrene- (meth) acrylic copolymer resin, or silicone- (meth) acrylic graft copolymer is preferable, and (meth) acrylic resin is preferable. More preferred.

  Examples of (meth) acrylic monomers that can be used to prepare (meth) acrylic resins include (meth) acrylic acid; (meth) acrylic acid alkyl esters (for example, methyl (meth) acrylate, (meth ) Ethyl acrylate, n-propyl (meth) acrylate, or n-butyl (meth) acrylate); (meth) acrylic acid aryl esters (eg, phenyl (meth) acrylate); hydroxyalkyl (meth) acrylate Esters (eg, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or 4-hydroxybutyl (meth) acrylate); (meth) acrylamide Ethylene oxide adducts of (meth) acrylic acid; alkyl ethers (for example, Meth) methyl ether of ethylene oxide adduct of acrylic acid esters, ethyl ether, n- propyl ether, or n- butyl ether) and the like.

  Since dissolution of the binder resin or elution of the release agent component in the toner core is unlikely to occur, the shell layer is preferably formed in an aqueous medium. Therefore, the thermoplastic resin used for forming the shell layer is preferably water-soluble, and it is particularly preferable to use the thermoplastic resin as an aqueous solution.

  In the resin constituting the shell layer, the ratio (Ws / Wp) (mass ratio) of the content (Ws) of the unit derived from the monomer of the thermosetting resin to the content (Wp) of the unit derived from the thermoplastic resin. Is preferably from 3/7 to 8/2, more preferably from 4/6 to 7/3.

  The thickness of the shell layer is preferably 1 nm to 20 nm, and more preferably 1 nm to 10 nm. If the shell layer is too thick, the shell layer is not easily destroyed even if pressure is applied when fixing the toner to the recording medium. In this case, the softening or melting of the binder resin or the release agent contained in the toner core does not proceed quickly, and it is difficult to fix the toner on the recording medium in a low temperature range. On the other hand, a shell layer that is too thin has low strength, and the shell layer may be destroyed by an impact in a situation such as transportation. Here, when the toner is stored at a high temperature, the toner particles in which at least a part of the shell layer is broken easily aggregate. This is because a component such as a release agent tends to ooze out to the surface of the toner particles through the broken portion in the shell layer at a high temperature.

  The thickness of the shell layer can be measured by analyzing a cross-sectional TEM image of the toner particles using commercially available image analysis software. As commercially available image analysis software, software such as WinROOF (manufactured by Mitani Corporation) can be used. Specifically, two straight lines that are orthogonal to each other at the approximate center of the cross section of the toner are drawn, and the lengths of four points on the two straight lines that intersect the shell layer are measured. The average value of the four lengths thus measured is taken as the thickness of the shell layer of one toner particle to be measured. Such a measurement of the thickness of the shell layer is performed on 10 or more toner particles, and an average value of the thicknesses of the shell layers included in each of the plurality of toner particles to be measured is obtained. The obtained average value is taken as the film thickness of the shell layer provided in the toner particles.

  If the shell layer is too thin, 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, a combination of TEM imaging and energy dispersive X-ray spectroscopic analysis (EDX) is performed to perform mapping of elements (for example, nitrogen) characteristic of the material of the shell layer in the TEM imaging image, The thickness of the shell layer may be measured by clarifying the interface with the toner core.

In order to adjust the thickness of the shell layer, the amount of materials (thermosetting resin monomer and thermoplastic resin) used to form the shell layer is adjusted. The thickness of the shell layer can also be obtained using the following formula.
Shell layer thickness = (mass of thermosetting monomer in shell layer + mass of thermoplastic resin in shell layer) / specific surface area of toner core

  An external additive may be attached to the surface of the toner particles as necessary. Examples of the external additive include fine particles of silica or metal oxide (for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or 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 the external additive used is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner base particles.

  The toner of this embodiment is mixed with a desired carrier and used as a two-component developer. When preparing a two-component developer, it is preferable to use a magnetic carrier.

  Suitable carriers include those in which a carrier core material is coated with a resin. Specific examples of carrier core materials include iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, or cobalt particles; these materials and metals such as manganese, zinc, or aluminum. Alloy particles; iron-nickel alloy or iron-cobalt alloy particles; ceramics (titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, titanate Particles of lithium, lead titanate, lead zirconate or lithium niobate; particles of high dielectric constant material (ammonium dihydrogen phosphate, potassium dihydrogen phosphate or Rochelle salt); Resin carriers.

  Examples of the resin for coating the carrier core material include (meth) acrylic polymer, styrene polymer, styrene- (meth) acrylic copolymer, olefin polymer (polyethylene, chlorinated polyethylene, or polypropylene). , Polyvinyl chloride, polyvinyl acetate, polycarbonate resin, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluorine resin (polytetrafluoroethylene, polychlorotrifluoroethylene, or (Polyvinylidene fluoride), phenol resin, xylene resin, diallyl phthalate resin, polyacetal resin, or amino resin. These resins can be used in combination of two or more.

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

  When the toner is used as a two-component developer, the toner content is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to the mass of the two-component developer.

[Toner Production Method]
The method for producing the toner is not particularly limited as long as the method can coat the toner core with the shell layer made of the predetermined material. Hereinafter, a preferred method for producing the electrostatic latent image developing toner of this embodiment will be described. This manufacturing method includes a step of manufacturing a toner core (toner core manufacturing step) and a step of forming a shell layer on the surface of the toner core (shell layer forming step).

  The toner core production process is not particularly limited as long as an arbitrary component (a component such as a colorant, a charge control agent, a release agent, or a magnetic powder) can be satisfactorily dispersed in the binder resin. It can be adopted as appropriate. In the toner core manufacturing process, for example, a pulverization method or an aggregation method is employed.

  In the pulverization method, a binder resin and an optional component (colorant, release agent, charge control agent, or magnetic powder) are mixed (mixing step), and the mixture is further melt-kneaded (kneading step) to obtain kneading. In this method, the product is pulverized (pulverization step) and classified (classification step) to obtain a toner core having a desired particle size. According to the pulverization method, the preparation of the toner core is relatively easy. However, in order to obtain a toner core through the pulverization step, it is difficult to obtain a toner core having a high sphericity as compared with the aggregation method. However, in the shell layer forming process described later, before the hardening reaction of the shell layer proceeds, the toner core is spheroidized by being contracted or slightly softened by surface tension. Accordingly, when the toner of the present embodiment is manufactured, there is no significant disadvantage even if the sphericity of the toner core is somewhat low.

  The aggregation method includes, for example, an aggregation process and a coalescence process. The aggregating step is a step of aggregating fine particles containing components constituting the toner core in an aqueous medium to form agglomerated particles. The coalescence process is a process in which the components contained in the aggregated particles are coalesced in an aqueous medium to form a toner core. When the aggregation method is used as a method for preparing the toner core, it is easy to obtain a toner core having a uniform shape and a uniform particle diameter.

  The triboelectric charge amount of the toner core is preferably negative and more preferably −10 μC / g or less. A method for measuring the triboelectric charge amount will be described below. A standard carrier (standard carrier for negatively charged polarity toner “N-01”) provided by the Imaging Society of Japan and a toner core are mixed for 30 minutes using a turbula mixer. At this time, the usage amount of the toner core is 7% by mass with respect to the mass of the standard carrier. After mixing, the triboelectric charge amount of the toner core is measured using a QM meter (“MODEL 210HS-2A” manufactured by TREK). The triboelectric charge amount of the toner core measured in this manner is an index of whether the toner core is easily charged to a positive or negative polarity and an index of the ease of charging of the toner core.

  The toner core preferably has a negative zeta potential measured in an aqueous medium adjusted to pH 4 and more preferably -10 mV or less. The method for measuring the zeta potential in the pH 4 dispersion is described below. Toner core 0.2 g, 80 mL of ion-exchanged water, and 20 g of nonionic surfactant (polyvinylpyrrolidone, “K-85” manufactured by Nippon Shokubai Co., Ltd., concentration 1 mass%) are mixed using a magnetic stirrer. Is uniformly dispersed in a solvent to obtain a dispersion. Thereafter, dilute hydrochloric acid is added to adjust the pH of the dispersion to 4. Using this dispersion as a measurement sample, the zeta potential of the toner core in the dispersion is measured using a zeta potential / particle size distribution measuring device (“Delsa Nano HC” manufactured by Beckman Coulter, Inc.).

  Usually, when a uniform shell layer is formed on the surface of the toner core, the toner core needs to be sufficiently dispersed in an aqueous medium containing a dispersant. However, for the toner core, when the triboelectric charge amount with the standard carrier measured under the above specific conditions is within a predetermined range, the toner core and the nitrogen-containing compound in the aqueous medium are positive in the aqueous medium. The monomer of the thermosetting resin that is charged is electrically attracted to each other. On the surface of the toner core, the reaction between the thermosetting resin monomer adsorbed on the toner core and the thermoplastic resin proceeds favorably. For this reason, even if it does not use a dispersing agent, a shell layer can be formed uniformly. By not using a dispersant with a very high drainage load, when producing toner particles without diluting the wastewater, it is possible to reduce the total organic carbon concentration of the discharged wastewater to a low level of 15 mg / L or less. It becomes.

  Even when the zeta potential of the toner core in an aqueous medium having a pH of 4 is within a predetermined range, the same effect can be obtained when the shell layer is formed on the surface of the toner core in the aqueous medium.

  In the shell layer forming step, a shell layer is formed so as to cover the toner core. The shell layer is formed using a melamine, urea, or a reaction product of glyoxal and urea, or a precursor (methylolated product) generated by addition reaction of these with formaldehyde, and a thermoplastic resin. In addition, since it is necessary to prevent the binder resin from dissolving in the solvent used for forming the shell layer or to prevent elution of components such as a release agent contained in the toner core, the shell is not dissolved in a solvent such as water. It is preferred that a layer is formed.

  The shell layer is formed by adding a toner core to an aqueous solution of a material for forming the shell layer. In order to satisfactorily disperse the toner core in the aqueous medium, it is preferable to mechanically disperse the toner core using an apparatus (for example, “Hibismix” manufactured by Primix Co., Ltd.) capable of stirring the dispersion strongly.

  The pH of the aqueous solution is preferably adjusted to about 4 using an acidic substance before adding the toner core. By adjusting the pH of the dispersion to the acidic side, the polycondensation reaction of the material for forming the shell layer described later is promoted.

  After adjusting the pH of the aqueous solution as necessary, the material for forming the shell layer and the toner core are mixed in an aqueous medium. Thereafter, the reaction between the materials for forming the shell layer on the surface of the toner core is advanced in the aqueous dispersion to form the shell layer so as to cover the surface of the toner core.

  The temperature at which the shell layer is formed on the surface of the toner core is preferably 40 ° C. or higher and 95 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower so that the formation of the shell layer proceeds well.

  After forming the shell layer as described above, the aqueous dispersion containing the toner core covered with the shell layer is cooled to room temperature to obtain a dispersion of toner particles (toner mother particles). After that, if necessary, it is selected from a step of cleaning the toner particles (cleaning step), a step of drying the toner particles (drying step), and a step of attaching an external additive to the surface of the toner base particles (external addition step). Through one or more steps, the toner is recovered from the toner particle dispersion.

  In the washing step, the toner particles (toner mother particles) are washed with water. As a suitable washing method, a method of recovering toner particles as a wet cake from an aqueous dispersion containing toner particles by solid-liquid separation, and washing the resulting wet cake with water; in a dispersion containing toner particles The toner particles are allowed to settle, the supernatant liquid is replaced with water, and the toner particles are redispersed in water after the replacement.

  In the drying step, the toner particles (toner mother particles) are dried. A suitable method for drying the toner particles includes a method using a dryer (for example, a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, or a vacuum dryer). Among these methods, a method using a spray dryer is preferable in order to suppress aggregation of toner particles during drying. In the case of using a spray dryer, the external additive can be attached to the surface of the toner particles by spraying a dispersion of the external additive such as silica together with the dispersion of the toner particles.

  In the external addition step, an external additive is attached to the surface of the toner particles (toner base particles). As a preferred method for attaching the external additive, the toner particles and the external additive are mixed using a mixer (for example, a Henschel mixer or a Nauter mixer) under the condition that the external additive is not buried in the surface of the toner particles. The method of mixing is mentioned.

  The electrostatic latent image developing toner of the present invention described above is excellent in heat-resistant storage and low-temperature fixability, and can suppress the occurrence of offset at a high temperature. 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 described more specifically with reference to examples. The present invention is not limited to the scope of the examples.

[Crystalline polyester resins A to E]
Crystalline polyester resins A to E having physical properties as shown in Table 1 were prepared. The half width (unit: ° C) of the endothermic peak was measured using a differential scanning calorimeter (DSC). Specifically, 10 mg of a measurement sample is put in an aluminum pan, an empty aluminum pan is used as a reference, and an endothermic peak is obtained under the conditions of a measurement temperature range of 25 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min. The full width at half maximum based on this endothermic peak was determined.

[Amorphous polyester resins A to G]
Amorphous polyester resins A to G having physical properties as shown in Table 2 were prepared. In addition, as for the non-crystalline polyester resins A to G, since no clear endothermic peak was observed, the half width of the endothermic peak could not be obtained.

[Release agents A to C]
The following release agents A to C were prepared.
The releasing agent A: ester wax (NOF Co., Ltd. "WEP-3", Mp _r: 75 ℃)
The releasing agent B: ester wax (NOF Co., Ltd. "WEP-2", Mp _r: 50 ℃)
Mold release agent C: ester wax (NOF Co., Ltd. "WEP-8", Mp _r: 100 ℃)

The following thermoplastic resins a to d were prepared.
Thermoplastic resin a: Water-soluble polyacrylamide (DIC Corporation [BECKAMINE A-1], aqueous solution with a solid content of 11% by mass)
Thermoplastic resin b: acrylamide copolymer (monomer composition: 2-hydroxyethyl methacrylate / acrylamide / methacrylic acid-methoxypolyethylene glycol = 30/50/20, molar ratio) (aqueous solution having a solid content concentration of 5% by mass Glass transition point: 110 ° C., mass average molecular weight: 55,000)
Thermoplastic resin c: Silicone-acrylic graft copolymer (“Saimac US-480” manufactured by Toagosei Co., Ltd., aqueous solution having a solid concentration of 25% by mass)
Thermoplastic resin d: Water-soluble urethane resin ("Superflex 170" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., aqueous solution with a solid content of 30% by mass)

Example 1
[Preparation of toner core]
As binder resin, 22.5 parts by mass of crystalline polyester resin A, 67.5 parts by mass of amorphous polyester resin A, 5 parts by mass of a colorant (CI Pigment Blue 15: 3, copper phthalocyanine), And 5 parts by mass of release agent A were mixed using a mixer (Henschel mixer) to obtain a mixture.

Subsequently, the obtained mixture was melt-kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The kneaded product was pulverized using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo Co., Ltd.) to obtain a pulverized product. The pulverized product was classified using a classifier (“Elbow Jet” manufactured by Nippon Steel Mining Co., Ltd.) to obtain a toner core having a volume average particle diameter (D ₅₀ ) of 6.0 μm. The volume average particle size of the toner core was measured using a Coulter Counter Multisizer 3 (manufactured by Beckman Coulter). A part of this toner core was taken out and used for measurement of triboelectric charge with a standard carrier and measurement of zeta potential in a pH 4 dispersion.

  Regarding the toner core used for the preparation of the toner of Example 1, the triboelectric charge amount with the standard carrier was −20 μC / g, and the zeta potential in the dispersion at pH 4 was −30 mV.

Shell layer forming step After putting 300 mL of ion-exchanged water into a 1 L three-necked flask equipped with a thermometer and a stirring blade, the temperature inside 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 aqueous medium in the flask to 4. After the pH adjustment, 3.2 mL of an aqueous methylol melamine solution (“Milben 607” manufactured by Showa Denko KK, solid content concentration 80% by mass) as a raw material for the shell layer and an aqueous solution (solid content concentration) of the thermoplastic resin a are used. 11 mL of an aqueous solution of 11% by weight water-soluble polyacrylamide) was added. Next, the contents of the flask were stirred, and the shell layer raw material was dissolved in an aqueous medium to obtain an aqueous solution (A) of the shell layer raw material.

  To the three-necked flask containing the aqueous solution (A), 300 g of the toner core was added, and 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, and the temperature inside the flask was increased to 70 ° C. at a rate of 1 ° C./min while stirring at 100 rpm. After the temperature increase, the contents of the flask were continuously stirred for 2 hours at 70 ° C. and 100 rpm. Thereafter, sodium hydroxide was added to adjust the pH of the contents of the flask to 7. Next, the contents of the flask were cooled to room temperature to obtain a dispersion containing toner mother particles.

Washing Step Using a Buchner funnel, a wet cake of toner base particles was filtered from the dispersion containing the toner base particles. The wet cake was dispersed in ion exchange water to wash the toner base particles. The same washing was repeated 5 times.

  Here, the filtrate of the dispersion liquid containing the toner mother particles and the washing water subjected to the washing step were collected as waste water. The amount of the collected waste water was 97 parts by mass with respect to 100 parts by mass of the toner obtained after the drying step. The concentration of total organic carbon (TOC) contained in the collected waste water was 8 mg / L. The total organic carbon concentration in the waste water was measured using a TOC meter (“TOC-4200” manufactured by Shimadzu Corporation).

Drying Step A wet cake of toner base particles was dispersed in an aqueous ethanol solution (concentration: 50% by mass) to prepare a slurry. The resulting slurry was supplied to a continuous surface reformer (“Coatmizer (registered trademark)” manufactured by Freund Turbo) to dry the toner base particles in the slurry (drying conditions were hot air temperature) 45 ° C., blower air flow 2 m ³ / min).

External Addition Step 100 parts by mass of toner base particles after drying and 1.0 part by mass of silica (“REA90” manufactured by Nippon Aerosil Co., Ltd.) as an external additive were added to a 10 L Henschel mixer (manufactured by Nippon Coke Industries, Ltd.). And mixed for 5 minutes to adhere silica to the surface of the toner base particles. Thereafter, the mixture was sieved using a 200 mesh sieve (aperture 75 μm) to obtain the toner of Example 1.

[Examples 2-3]
Except that the amount of methylolmelamine aqueous solution used and the amount of thermoplastic resin a (polyacrylamide aqueous solution) used were changed as shown in Table 3, the procedure was substantially the same as in Example 1 except that 3 toner was obtained.

[Example 4]
The aqueous solution of 3.2 mL of methylolmelamine was changed to 4.0 mL of an aqueous solution of glyoxal monomer (“BECKAMINE NS-11” manufactured by DIC Corporation, solid concentration 40% by mass), and 2 mL of the aqueous solution of glyoxal monomer was added. A mixed metal catalyst aqueous solution (“CATALIST GT-3” manufactured by DIC Corporation) was added, and the procedure was substantially the same as in Example 1 except that the amount of the thermoplastic resin a used was 2.0 mL. The toner of Example 4 was obtained.

[Example 5]
3.2 mL of methylol melamine aqueous solution was changed to 4 mL of methylolated urea aqueous solution (DIC Corporation, “BEKKAMINE J-300S”, solid content concentration 70% by mass). An organic amine catalyst aqueous solution (manufactured by DIC Corporation, “CATALIST 376”) was added, and the amount of the thermoplastic resin a was changed to 2.0 mL. No toner was obtained.

[Examples 6 to 8]
Toners of Examples 6 to 8 were obtained in the same manner as in Example 2 except that the thermoplastic resin a was changed to the thermoplastic resins b, c, or d, respectively.

[Examples 9 to 10]
The amount of the methylol melamine aqueous solution and the amount of the thermoplastic resin a (polyacrylamide aqueous solution) were changed in the same manner as in Example 1 except that the amounts were changed as shown in Table 3, respectively. 9 and 10 toners were obtained.

[Example 11]
A toner of Example 11 was obtained in the same manner as in Example 11 except that the crystalline polyester resin and the kind of the amorphous polyester resin were changed as shown in Table 3, respectively.

[Example 12]
A toner of Example 12 was obtained in substantially the same manner as in Example 2, except that the kind of the crystalline polyester resin was changed as described in Table 3.

[Examples 13 to 14]
Except for changing the addition amount of the crystalline polyester resin and the addition amount of the non-crystalline polyester resin as described in Table 3, the methods of Examples 13 to 14 were substantially the same as in Example 2. A toner was obtained.

[Examples 15 to 18]
Toners of Examples 15 to 18 were obtained in the same manner as in Example 2 except that the type of the amorphous polyester resin was changed as described in Table 3.

[Examples 19 to 20]
Except that the type of release agent was changed as described in Table 3, toners of Examples 19 to 20 were obtained in substantially the same manner as in Example 2.

[Comparative Example 1]
A toner of Comparative Example 1 was obtained in substantially the same manner as in Example 1 except that the amount of methylolmelamine aqueous solution added was changed to 4.0 mL and an aqueous thermoplastic resin solution was not used.

[Comparative Example 2]
A toner of Comparative Example 2 was obtained in substantially the same manner as in Example 1 except that the aqueous methylol melamine solution was not used and the amount of the aqueous solution of the thermoplastic resin a was changed to 4.0 ml.

[Comparative Example 3]
A toner of Comparative Example 3 was obtained in the same manner as in Example 2 except that the type of crystalline polyester resin and the type of amorphous polyester resin were changed as shown in Table 4.

[Comparative Examples 4 to 5]
Toners of Comparative Examples 4 to 5 were obtained in the same manner as in Example 2 except that the type of the crystalline polyester resin was changed as described in Table 4.

[Comparative Example 6]
The toner core was used as toner base particles without performing the shell layer forming step. The toner base particles were externally added in the same manner as in Example 1 to obtain a toner of Comparative Example 6.

[Comparative Example 7]
A toner of Comparative Example 7 was obtained in the same manner as in Example 2 except that the crystalline polyester resin was not used as the binder resin.

[Comparative Example 8]
A toner of Comparative Example 8 was obtained in the same manner as in Example 2 except that the amount of the crystalline polyester resin and the type of the amorphous polyester resin were changed as shown in Table 4.

[Comparative Example 9]
A toner was obtained in substantially the same manner as in Example 2 except that the non-crystalline polyester resin was not used as the binder resin. However, sufficient melt-kneading could not be performed, and a toner core could not be produced.

  The evaluation methods of the toners obtained in Examples 1 to 20 and Comparative Examples 1 to 8 are as follows.

(1) Toner core softening point Tm ^t
Measurement was performed using an elevated flow tester.

(2) Thickness of Shell Layer TEM photographs of cross sections of toner particles contained in the toners of Examples 1 to 20, Comparative Examples 1 and 3 to 5, and Comparative Examples 7 to 8 were taken according to the following method. Since the toner of Comparative Example 2 used only the thermoplastic resin when forming the shell layer, and the toner of Comparative Example 6 was not subjected to the shell layer forming step, both had the thickness of the shell layer. The thickness could not be measured. From the TEM photograph of the cross section of the toner particles, the thickness of the shell layer was measured according to the following method.

<Method for Taking TEM Photo of Cross Section of Toner Particle>
First, 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 obtained cured product was dyed with osmium tetroxide. Thereafter, a thin sample for cross-sectional observation of toner particles having a thickness of 200 nm was cut out from the obtained cured product using a microtome (“EM UC6” manufactured by Leica Corporation). The obtained flake sample was observed with a transmission electron microscope (TEM, “JSM-6700F” manufactured by JEOL Ltd.) at a magnification of 3000 times and 10,000 times, and a TEM photograph of a cross section of the toner particles was taken.

(3) Heat-resistant storage stability The toners of Examples 1 to 20 and Comparative Examples 1 to 8 were evaluated for heat-resistant storage stability according to the following method.

2 g of toner was weighed into a 20 mL capacity plastic container and allowed to stand in a thermostat set at 60 ° C. for 3 hours to obtain a toner for heat resistant storage stability evaluation. Thereafter, the toner for heat-resistant storage stability evaluation was sieved using a 200 mesh (75 μm mesh) sieve under the conditions of rheostat scale 5 and time 30 seconds according to the manual of a powder tester (manufactured by Hosokawa Micron Corporation). . After sieving, the mass of toner remaining on the sieve was measured. From the mass of the toner before sieving and the mass of the toner remaining on the sieving after sieving, the degree of aggregation (%) was calculated according to the following formula. From the calculated degree of aggregation, heat resistant storage stability was evaluated according to the following criteria. The evaluation of ○ was set as a pass.
Aggregation degree (%) = (mass of toner remaining on sieve / mass of toner before sieving) × 100
○ (Good): The degree of aggregation is 30% or less.
X (not good): the degree of aggregation exceeds 30%.

[Preparation of two-component developer]
The toners of Examples 1 to 20 and Comparative Examples 1 to 8 were evaluated for low-temperature fixability and high-temperature offset resistance according to the following methods. For the evaluation of the low-temperature fixability and the high-temperature offset resistance, a two-component developer prepared according to the following method and the toners of Examples 1 to 20 and Comparative Examples 1 to 8 were used.

  Carrier for developer (carrier for TASKalfa 5550 manufactured by Kyocera Document Solutions Co., Ltd.) and 10% by mass of toner (one of toners of Examples 1 to 20 and Comparative Examples 1 to 8) based on the mass of the carrier Were mixed for 30 minutes using a ball mill to prepare a two-component developer for evaluation.

(4) Low-temperature fixability A printer (“FSC-5250DN” manufactured by Kyocera Document Solutions Inc.) remodeled so that the fixing temperature can be adjusted was used as an evaluation machine. Any two-component developer prepared as described above was put into the developing section of the evaluation machine, and the toner corresponding to the two-component developer was put into the toner container of the evaluation machine. In the evaluation machine, the linear velocity was set to 200 mm / second, and the applied toner amount was set to 1.0 mg / cm ² , and an unfixed solid image was formed on the recording medium. The fixing temperature of the fixing device of the evaluator was increased by 5 ° C. from 100 ° C. in the range of 100 ° C. to 200 ° C. to fix the unfixed solid image. The recording medium on which the solid image was fixed was folded in half so that the surface on which the image was formed was on the inside, and a 1 kg weight covered with a cloth was used to rub the reciprocation on the crease 5 times. Next, the recording medium was expanded, and the case where toner peeling at the bent portion was 1 mm or less was determined to be acceptable, and the case where the toner exceeded 1 mm was determined to be unacceptable. The lowest fixing temperature at which toner peeling was determined to be acceptable was defined as the minimum fixing temperature. The low temperature fixability was evaluated according to the following criteria.
○ (Good): The minimum fixing temperature is 140 ° C. or lower.
X (not good): The minimum fixing temperature exceeds 140 ° C.

(5) High-temperature offset resistance An unfixed solid image was formed on a recording medium under the same conditions using the same evaluation machine and recording medium as those for evaluation of low-temperature fixability. The fixing temperature of the fixing device of the evaluation machine was increased from 170 ° C. by 10 ° C., and the lowest temperature (first offset generation temperature) at which an offset occurred every 10 ° C. was confirmed. Next, the fixing temperature of the fixing device of the evaluator was increased by 1 ° C. from a temperature 10 ° C. lower than the first offset generation temperature, and the lowest temperature at which an offset occurred every 1 ° C. was confirmed. When the fixing temperature of the fixing device of the evaluation machine was increased by 1 ° C., the lowest temperature at which the offset occurred was defined as the offset generation temperature. The high temperature offset resistance was evaluated according to the following criteria.
○ (Good): Offset generation temperature is 190 ° C. or higher.
X (not good): Offset generation temperature is less than 190 ° C.

Tables 3 to 5 show the evaluation results of the toners obtained in Examples 1 to 20 and Comparative Examples 1 to 8. In Tables 3 to 5, “P / Q” indicates the ratio (mass ratio) of the usage amount P of the crystalline polyester to the usage amount Q of the amorphous polyester. In Table 5, “-” indicates that no addition was made.

As is apparent from Examples 1 to 20, the toner of this embodiment (including toner particles including a toner core containing a binder resin and a shell layer covering the surface of the toner core. The shell layer is a monomer of a thermosetting resin. The thermosetting resin is at least one resin selected from the group of amino resins consisting of melamine resin, urea resin, and glyoxal resin. there. a binder resin is a crystalline polyester resin, and a non-crystalline polyester resin. is measured using a differential scanning calorimeter, the melting point of the crystalline polyester resin (mp ^c) is at 30 ° C. or higher 100 ° C. or less and some .mp ^c, the difference between the glass transition point of the amorphous polyester resin ^{(Tg nc) (Mp c -Tg} nc) is, at 10 ° C. or higher 80 ° C. or less.) the heat-resistant storage stability and It can be understood that it has excellent low-temperature fixability and can suppress the occurrence of offset at high temperatures.

  From Comparative Example 1, it can be understood that the toner including toner particles made of a resin whose shell layer does not contain a unit derived from a thermoplastic resin is inferior in low-temperature fixability. The reason is estimated as follows. A resin including a unit derived from a monomer of a thermosetting resin and a unit derived from a thermoplastic resin has flexibility due to the unit derived from the thermoplastic resin. On the other hand, the shell layer consisting only of units derived from the monomer of the thermosetting resin is too hard because it is highly crosslinked. For this reason, the toner of Comparative Example 1 is difficult to be fixed because the shell layer is not easily broken even when temperature and pressure are applied to the toner particles during fixing.

  According to Comparative Example 2, when the toner contains toner particles whose shell layer is formed of a resin that does not contain a unit derived from a monomer of a thermosetting resin, the toner is inferior in heat resistant storage stability and suppresses offset at high temperature. I can understand that it is difficult. The reason is estimated as follows. When the resin contained in the shell layer contains only the thermoplastic resin, since the crosslinking reaction between the molecules of the thermoplastic resin does not occur, the toner particles contained in the toner of Comparative Example 2 have a shell layer in a desired state. Not prepared. For this reason, in Comparative Example 2, a component such as a release agent contained in the toner core easily oozes out to the surface of the toner particles, and is inferior in heat resistant storage stability and high temperature offset property.

Comparative Example 3, as a toner binder resin, if it contains toner particles prepared using the toner core comprising (Mp ^c -Tg ^nc) is too large crystalline polyester resin, and a non-crystalline polyester resin, It can be understood that the low-temperature fixability is inferior.

Comparative Example 4, the toner is, if the crystalline polyester resin melting point (Mp ^c) is too low, containing toner particles comprising a toner core as contained in the binder resin has poor heat-resistant storage stability, offset at high temperatures It can be understood that it is difficult to suppress. The reason is presumed that the toner particles contained in the toner of Comparative Example 2 are easily deformed in a high temperature environment.

Comparative Example 5, when the toner contains toner particles comprising a toner core containing the crystalline polyester resin melting point (Mp ^c) is too high in the binder resin may be understood to be inferior in low-temperature fixability.

  From Comparative Example 6, it can be understood that when the toner contains toner particles in which the shell layer is not formed, the heat resistant storage stability is poor and it is difficult to suppress the offset at a high temperature. This is presumably because the toner particles contained in the toner of Comparative Example 6 easily exudes components such as a release agent contained in the toner core to the surface of the toner particles.

  From Comparative Example 7, it can be understood that when the toner contains toner particles having a toner core that does not contain a crystalline polyester resin in the binder resin, the low-temperature fixability is poor.

Comparative Example 8, when the toner is a value of (Mp ^c -Tg ^nc) comprises toner particles comprising a toner core comprising a crystalline polyester resin, and the non-crystalline polyester resin is too small, poor heat-resistant storage property, high temperature It can be understood that it is difficult to suppress the offset at.

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

Claims (6)

An electrostatic latent image developing toner containing a plurality of toner particles,
Each of the plurality of toner particles includes a toner core containing a binder resin, and a shell layer that covers a surface of the toner core. The binder resin includes a crystalline polyester resin and an amorphous polyester resin.
Is measured using a differential scanning calorimeter, the melting point Mp ^c of the crystalline polyester resin is not higher than 100 ° C. 30 ° C. or higher,
The difference between the glass transition point Tg ^nc of the non-crystalline polyester resin and the Mp ^c (Mp ^c -Tg ^nc) is, and at 10 ° C. or higher 80 ° C. or less,
The shell layer is made of a resin including a unit derived from a monomer of a thermosetting resin and a unit derived from a thermoplastic resin,
An electrostatic latent image developing toner, wherein the thermosetting resin is at least one resin selected from the group of amino resins consisting of melamine resin, urea resin, and glyoxal resin.
The electrostatic latent image developing toner according to claim 1, wherein a zeta potential of the toner core measured in an aqueous medium adjusted to pH 4 is negative.
The toner for developing an electrostatic latent image according to claim 1, wherein the content of nitrogen atoms in the shell layer is 10% by mass or more.
The ratio (Ws / Wp) of the content (Ws) of the unit derived from the monomer of the thermosetting resin to the content (Wp) of the unit derived from the thermoplastic resin in the resin constituting the shell layer. The toner for developing an electrostatic latent image according to any one of claims 1 to 3, which is 3/7 or more and 8/2 or less.
The electrostatic latent image developing toner according to claim 1, wherein the thermoplastic resin contains a unit derived from (meth) acrylamide.
  The acid value of the non-crystalline polyester resin is from 5 mgKOH / g to 30 mgKOH / g, and the hydroxyl value of the non-crystalline polyester resin is from 15 mgKOH / g to 80 mgKOH / g. Item 2. The toner for developing an electrostatic latent image according to item 1.

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