JP2017223895A - Method for producing toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and properly produce a toner for electrostatic latent image development excellent in all of heat-resistant storage property, low-temperature fixability and charging property.SOLUTION: A method for producing a toner for electrostatic latent image includes: melting and kneading at least nigrosine and a crystalline polyester resin on a condition of a temperature of 120°C or lower; cooling the resultant resin to obtain a first melted and kneaded product; crushing the first melted and kneaded product to obtain first powder; melting and kneading at least the first powder and an amorphous polyester resin on the condition of the temperature of 120°C or lower; cooling the resultant resin to obtain a second melted and kneaded product; crushing the second melted and kneaded product to obtain second powder; subjecting the second powder to annealing treatment; and increasing a degree of crystallization of the crystalline polyester resin in the second powder to 0% at the time of the start of the annealing treatment to 50% or more. The degree of crystallization is a value measured according to X-ray diffraction intensity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a toner for developing an electrostatic latent image.

  Patent Document 1 discloses a method for producing a toner for developing an electrostatic latent image using a crystalline polyester resin and an amorphous polyester resin (amorphous polyester resin) as a binder resin for toner particles.

JP 2006-78707 A

  However, it is difficult to produce a toner for developing an electrostatic latent image that is excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability, depending on the method for producing a toner for developing an electrostatic latent image described in Patent Document 1. It is. By incorporating a crystalline polyester resin into the toner particles, the toner fixability can be improved. However, when a crystalline polyester resin is contained in the toner particles, the chargeability of the toner (particularly, the charging stability in a high temperature and high humidity environment) tends to be insufficient.

  The present invention has been made in view of the above problems, and is an electrostatic latent image developing toner that is excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability (particularly, charge stability in a high-temperature and high-humidity environment). Is intended to be manufactured easily and appropriately.

  The method for producing a toner for developing an electrostatic latent image according to the present invention includes a first melt-kneading step, a first pulverizing step, a second melt-kneading step, a second pulverizing step, and an annealing step. In the first melt-kneading step, at least nigrosine and the crystalline polyester resin are melt-kneaded at a temperature of 120 ° C. or lower, and then cooled to obtain a first melt-kneaded product. In the first pulverization step, the first melt-kneaded product is pulverized to obtain a first powder. In the second melt-kneading step, at least the first powder and the amorphous polyester resin are melt-kneaded at a temperature of 120 ° C. or lower, and then cooled to obtain a second melt-kneaded product. In the second pulverization step, the second melt-kneaded product is pulverized to obtain a second powder. In the annealing step, the second powder is annealed to increase the crystallinity of the crystalline polyester resin in the second powder from 0% at the start of annealing to 50% or more. The crystallinity is a value measured based on the X-ray diffraction intensity.

  According to the present invention, an electrostatic latent image developing toner that is excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability (particularly, charging stability in a high-temperature and high-humidity environment) can be easily and appropriately produced. Is possible.

6 is a graph showing a transition of crystallinity (X-ray diffraction intensity) of a crystalline polyester resin during annealing in an annealing process of a method for producing a toner for developing an electrostatic latent image according to an embodiment of the present invention. 6 is a graph showing changes in toner charge amount in a high-temperature and high-humidity environment for Examples and Comparative Examples of the present invention.

  An embodiment of the present invention will be described. Note that the evaluation results (values indicating shape, physical properties, etc.) regarding the powder (more specifically, toner base particles, external additives, toner, etc.) are average values from the powder unless otherwise specified. It is the number average of the values measured for each of these average particles by selecting a significant number of particles.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-950” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value.

  The glass transition point (Tg) is a value measured according to “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) at the second temperature rise measured by the differential scanning calorimeter, the change point of the specific heat (outside the extrapolated line of the baseline and the falling line) The temperature (onset temperature) at the intersection with the insertion line corresponds to Tg (glass transition point). Moreover, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified. In the S curve (horizontal axis: temperature, vertical axis: stroke) measured with the Koka type flow tester, the temperature that becomes "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point). Equivalent to.

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

  The method for producing a toner for developing an electrostatic latent image according to the present embodiment includes the following steps (first melt-kneading step, first pulverizing step, second melt-kneading step, second pulverizing step, and annealing step). . In the first melt-kneading step, at least nigrosine and the crystalline polyester resin are melt-kneaded at a temperature of 120 ° C. or lower, and then cooled to obtain a first melt-kneaded product. In the first pulverization step, the first melt-kneaded product is pulverized to obtain a first powder. In the second melt-kneading step, at least the first powder and the amorphous polyester resin are melt-kneaded at a temperature of 120 ° C. or lower, and then cooled to obtain a second melt-kneaded product. In the second pulverization step, the second melt-kneaded product is pulverized to obtain a second powder. In the annealing step, the second powder is annealed to increase the crystallinity of the crystalline polyester resin in the second powder from 0% at the start of the annealing process to 50% or more. Hereinafter, the particles contained in the first powder are referred to as first particles, and the particles contained in the second powder are referred to as second particles. In addition, the first melt-kneading step, the first pulverizing step, the second melt-kneading step, the second pulverizing step, and the annealing step may be collectively referred to as “basic steps”.

  The crystallinity of the crystalline polyester resin is determined by setting the crystallinity at the start of annealing to 0% and the crystallinity at the time of annealing until the crystallinity is saturated to 100%. The degree of crystallinity of the crystalline polyester resin is a value measured based on the X-ray diffraction intensity of the target peak (peak derived from the crystalline polyester resin) in the X-ray diffraction spectrum. In one example of the annealing step, the transition of the crystallinity (X-ray diffraction intensity) of the crystalline polyester resin during annealing (specifically, the crystalline polyester resin in the second powder) is shown in FIG. Specifically, FIG. 1 shows the relationship between the annealing time in the annealing step (annealing temperature: 45 ° C.) and the X-ray diffraction intensity of the target peak (X-ray diffraction intensity at a diffraction angle of 21.4 °). ing. In the example of FIG. 1, the X-ray diffraction intensity (vertical axis) of the target peak increases as the annealing time (horizontal axis) becomes longer for a certain period after the annealing process is started, and then is saturated. .

  The second powder annealed in the annealing step may be used as a toner as it is, or the second powder may be externally added after the annealing step. Alternatively, after the second pulverization step, the second powder may be externally added, and the externally added second powder may be annealed. The toner is a powder containing a plurality of toner particles. When the toner particles include an external additive, the toner particles are composed of toner base particles and an external additive. The external additive adheres to the surface of the toner base particles. If not necessary, the external additive may be omitted. When omitting the external additive, the toner base particles correspond to the toner particles.

  When the second particles are used as the toner base particles, the toner base particles contain an amorphous polyester resin as a binder resin. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, if necessary. The internal additive can be contained in the second particles (toner base particles) by, for example, melt-kneading together with the first powder and the amorphous polyester resin in the second melt-kneading step.

  By incorporating a crystalline polyester resin into the toner base particles, the toner fixability can be improved. This is because the crystalline polyester resin imparts sharp melt properties to the toner base particles. However, crystalline polyester resins often do not exhibit good chargeability. The reason is considered to be that the electrical resistance of the crystalline polyester resin is relatively low. For this reason, if a crystalline polyester resin is contained in the toner base particles, it becomes difficult to ensure sufficient chargeability of the toner (particularly, charging stability in a high-temperature and high-humidity environment). It becomes difficult to form an image with high image quality.

  In a toner containing nigrosine as a charge control agent in a binder resin, if nigrosine is finely dispersed in the binder resin, the nigrosine hardly functions as a charge control agent. For example, when the binder resin and nigrosine are melt-kneaded using a twin-screw extruder, it is considered that nigrosine is uniformly dispersed in the binder resin. When nigrosine is uniformly dispersed in the binder resin, nigrosine is dispersed in a wide range (substantially the entire toner base particles), so that nigrosine is considered to be easily finely dispersed in the binder resin. When nigrosine is finely dispersed in the binder resin, it becomes difficult for nigrosine in the binder resin to impart positive chargeability to the toner particles.

  According to the inventor's experiment, nigrosine tends to have higher compatibility with the crystalline polyester resin than the non-crystalline polyester resin. Further, according to the experiments by the inventors, the crystalline polyester resin in the toner base particles tends to move to the surface of the toner base particles by crystallization. Based on these findings, the inventor has retained toner with nigrosine in a crystalline polyester resin, so that toner base particles having excellent chargeability even in a high-temperature and high-humidity environment (specifically, a toner base that is easily positively charged by frictional charging) Particle).

  Specifically, in the method for producing a toner for developing an electrostatic latent image including the basic steps, the first melt-kneaded powder containing nigrosine and the crystalline polyester resin is obtained by the first melt-kneading step and the first pulverizing step ( A first powder) is obtained. Thereby, nigrosine can be dispersed in the crystalline polyester resin in the first particles contained in the first powder. However, in the experiments of the inventor, if the temperature of the melt kneading is set too high to completely dissolve the crystalline polyester resin and nigrosine, nigrosine may not function as a positively chargeable charge control agent. It has been confirmed. Therefore, in the above basic process, the melt kneading temperature in the first melt kneading process is set to 120 ° C. or less, so that the crystalline polyester resin and nigrosine are appropriately mixed. The melt kneading temperature in the first melt kneading step is particularly preferably 90 ° C. or higher and 120 ° C. or lower. The melt kneading temperature is preferably lower than the softening point (Tm) of the crystalline polyester resin. By lowering the temperature of the melt-kneading, it is possible to prevent the resin viscosity from being excessively lowered, so that it becomes easy to apply a sufficient share (shearing force) during the kneading. For the melt-kneading to obtain the first melt-kneaded product, a kneader, a Banbury mixer, an open roll mixer, or a continuous extruder can be used. Among these apparatuses, a kneader or a Banbury mixer is particularly preferable.

  In the first melt-kneading step, the amount of nigrosine is preferably 5 parts by mass or more and 100 parts by mass or less, particularly 10 parts by mass or more and 60 parts by mass or less, with respect to 100 parts by mass of the crystalline polyester resin. preferable. If the amount of nigrosine is too small, it will be difficult to ensure sufficient chargeability and heat-resistant storage stability of the toner. On the other hand, if the amount of nigrosine is too large, a thickening phenomenon tends to occur, and it becomes difficult to stably produce a good first melt-kneaded product. Further, if the amount of nigrosine is too large, the smear resistance of the toner tends to be reduced. For this reason, when an image is formed on paper using toner, the formed image is rubbed (especially due to rubbing between the paper and the roller during automatic document feeding or double-sided backside printing). ) Is likely to occur.

  Further, in the method for producing a toner for developing an electrostatic latent image including the basic step, the first powder obtained as described above by the second melt-kneading step and the second pulverizing step, the non-crystalline polyester resin, A second melt-kneaded powder (second powder) containing Thereby, in the second particles contained in the second powder, the crystalline polyester resin retaining nigrosine can be dispersed in the amorphous polyester resin. In the above basic process, the melt kneading temperature in the second melt kneading process is set to 120 ° C. or lower, and the crystalline polyester resin and nigrosine are prevented from being excessively mixed in the first particles. The melt kneading temperature in the second melt kneading step is particularly preferably 90 ° C. or higher and 120 ° C. or lower. The amount of the crystalline polyester resin in the first melt-kneading step is preferably 20 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the amorphous polyester resin in the second melt-kneading step. If the amount of the crystalline polyester resin is too small, the fixing property (particularly sharp melt property) of the toner may not be sufficiently improved by the crystalline polyester resin. If the amount of the crystalline polyester resin is too large, the heat-resistant storage stability of the toner becomes insufficient, or the toner is liable to be poorly charged.

  In the method for producing a toner for developing an electrostatic latent image including the basic step, the second powder obtained as described above is annealed in the annealing step, so that the crystalline polyester resin in the second powder is obtained. Is increased from 0% at the start of annealing to 50% or more. The crystallinity of the crystalline polyester resin in the second powder may be increased to 100% by the annealing step. However, from the viewpoint of reducing energy required for toner production, the crystallinity at the end of the annealing treatment is particularly preferably, for example, 55% or more and 85% or less. As the crystallization of the crystalline polyester resin in the second powder (specifically, in the first powder) proceeds, the first powder (the crystalline polyester resin and nigrosine) in the second particles becomes the second particles. It is thought to move to the surface. It is considered that nigrosine is exposed on the surface of the second particle by the movement of the first powder to the surface of the second particle. Further, it is considered that nigrosine is unevenly distributed in the surface layer portion of the second particle, and the concentration of nigrosine in the surface layer portion of the second particle is higher than the average nigrosine concentration of the second particle. Nigrosine present in the surface layer portion of the second particles functions as a charge control agent, and improves the chargeability of the toner (particularly, the charge stability in a high-temperature and high-humidity environment). The concentration of nigrosine in the surface layer portion of the second particle can be measured, for example, by eluting nigrosine into ethanol from the surface layer portion of the second particle.

  In order to bring the crystallinity of the crystalline polyester resin in the second powder at the end of the annealing process into an appropriate range, the temperature of the annealing process is preferably 40 ° C. or more and 55 ° C. or less, and the temperature (40 It is particularly preferable that the treatment time of the annealing treatment at a temperature of from 0 ° C. to 55 ° C. is from 20 hours to 30 hours.

  A preferred example of the constitution of toner particles obtained by subjecting the second powder to annealing treatment and external addition treatment will be described. The toner base particles and the external additive will be described in order. Note that unnecessary components (for example, an internal additive or an external additive) may be omitted depending on the use of the toner.

[Toner mother particles]
The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, a colorant, a release agent, a charge control agent, and a magnetic powder). In order to obtain a toner suitable for image formation, it is preferable that the volume median diameter (D ₅₀ ) of the toner base particles is 5 μm or more and less than 10 μm.

(Binder resin)
In the toner base particles, generally, the binder resin occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner base particles. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and when the binder resin has an amino group or an amide group, The toner base particles tend to be cationic.

  The toner base particles contain a crystalline polyester resin and an amorphous polyester resin as a binder resin. By containing a crystalline polyester resin in the toner base particles, sharp melt properties can be imparted to the toner base particles.

  The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. The polyester resin contains an alcohol component and an acid component. As the alcohol for synthesizing the polyester resin, for example, dihydric alcohols (more specifically, diols or bisphenols) as shown below or trihydric or higher alcohols can be suitably used. As the carboxylic acid for synthesizing the polyester resin, for example, divalent carboxylic acids or trivalent or higher carboxylic acids as shown below can be suitably used.

  Preferable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4. -Diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

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

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

  Preferable examples of the divalent carboxylic acid include suberic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid , Malonic acid, succinic acid, alkyl succinic acid (specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (More specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.).

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

  The divalent or trivalent or higher carboxylic acid may be transformed into an ester-forming derivative (for example, an acid halide, an acid anhydride, or a lower alkyl ester). The “lower alkyl” in the lower alkyl ester means an alkyl group having 1 to 6 carbon atoms.

  Preferred examples of the crystalline polyester resin include one or more aliphatic dicarboxylic acids (more specifically, suberic acid, adipic acid, or succinic acid) and one or more aliphatic diols (more specifically, And ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, etc.).

  Preferred examples of the amorphous polyester resin include one or more bisphenols (more specifically, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct) and one or more dicarboxylic acids (more Specific examples include polymers with terephthalic acid, fumaric acid, or alkyl succinic acid.

  In order to ensure sufficient toner fixability even during high-speed fixing, an amorphous polyester resin in the toner base particles (when the toner base particles contain a plurality of types of amorphous polyester resins, the mass ratio The most common non-crystalline polyester resin) has a softening point (Tm) of 60 ° C. or higher and 150 ° C. or lower, and a glass transition point (Tg) of 30 ° C. or higher and 60 ° C. or lower.

(Nigrosine)
The toner base particles contain nigrosine. Nigrosine comprises an aniline compound (more specifically, aniline or aniline hydrochloride) and an aromatic nitro compound (more specifically, nitrobenzene, nitrophenol, nitrocresol, etc.) and a catalyst (more specifically, Is obtained by a redox condensation reaction in the presence of iron, iron chloride, copper or the like. Nigrosine thus obtained is often a mixture containing one or more azine compounds. An azine compound is a compound containing a 6-membered ring having one or more nitrogen atoms in the ring. Preferable examples of nigrosine include azine compounds having a phenazine skeleton.

  As specific examples of nigrosine (CI Solvent Black 5, CI Solvent Black 7, and other nigrosine), commercially available products manufactured by Orient Chemical Industry Co., Ltd. are shown below. One type of commercially available product may be used alone, or two or more types of commercially available products may be mixed and used. Further, instead of or in addition to a commercially available product, nigrosine other than the commercially available product (a custom-made product or an original work) may be used.

<C. I. Solvent Black 5>
・ SPIRIT BLACK: “ABL”
・ NUBIAN (registered trademark) BLACK: “NH-805” / “NH-815”

<C. I. Solvent Black 7>
・ NIGROSINE BASE: “EX” / “EX-BP” / “SAPL”
・ SPECIAL BLACK: “EB”
・ NUBIAN BLACK: “TN-870” / “TN-877” / “TH-807”

<Other nigrosine>
BONTRON (registered trademark): “N-71” / “N-75” / “N-79”

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

  The toner base particles may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

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

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

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

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

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

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

  In order to improve the compatibility between the binder resin and the release agent, a compatibilizing agent may be added to the toner base particles.

(Other charge control agents)
The toner base particles may contain other charge control agents in addition to nigrosine in the first particles. Other charge control agents may be added together with the amorphous polyester resin, for example, in the second melt-kneading step. Other charge control agents are used, for example, for the purpose of improving the charge stability or charge rise characteristics of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time. As the other charge control agent, for example, a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) may be used. As the other charge control agent, for example, a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) may be used. However, if sufficient chargeability is ensured in the toner, it is not necessary to add another charge control agent to the toner base particles.

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

[External additive]
An external additive (specifically, a powder containing a plurality of external additive particles) may be adhered to the surface of the toner base particles. For example, the toner base particles (powder) and the external additive (powder) are stirred together, so that the external additive adheres (physically bonds) to the surface of the toner base particles with a physical force. The external additive is used, for example, to improve the fluidity or handleability of the toner. In order to improve the fluidity or handleability of the toner, the amount of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. In order to improve the fluidity or handleability of the toner, the particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

  The external additive particles may be inorganic particles or resin particles. As the inorganic particles, particles of silica particles or metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are particularly preferable. One type of external additive may be used alone, or a plurality of types of external additives may be used in combination.

  Examples of the present invention will be described. Table 1 shows toners T-1 to T-10 (each toner for electrostatic latent image development) according to Examples or Comparative Examples. Table 2 shows master batches A to E used for manufacturing any of the toners T-1 to T-10.

  Hereinafter, a production method, an evaluation method, and an evaluation result of the toners T-1 to T-10 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Preparation of materials]
(First melt-kneading step and first grinding step: preparation of master batch A)
70 parts by mass of a crystalline polyester resin (sample product manufactured by Kao Corporation) and 30 parts by mass of a charge control agent (Nigrosine dye: “BONTRON (registered trademark) N-71” manufactured by Orient Chemical Co., Ltd.) (Nippon Coke Kogyo Co., Ltd.) was used and premixed under conditions of a rotational speed of 2500 rpm and a processing time of 300 seconds to obtain a premixed mixture. Subsequently, the obtained preliminary mixture was melt-kneaded using a Banbury mixer to obtain a kneaded melt. The temperature in the mixing tank of the Banbury mixer during melt kneading was adjusted to the temperature shown in “melt kneading temperature” in Table 1. By measuring the temperature of the melt before cooling (hereinafter referred to as the first processed product temperature), the temperature in the mixing tank of the Banbury mixer was indirectly measured. For example, in the production of toner T-1, the cylinder temperature of the Banbury mixer was adjusted so that the first processed product temperature was 120 ° C. As a result of such adjustment, the cylinder temperature of the Banbury mixer was 100 ° C. to 110 ° C. during melt kneading.

  Subsequently, the melt obtained as described above is solidified by being cooled to room temperature (about 25 ° C.) while being rolled by a rolling roll belt conveyor type cooling device, so that a sheet-like solid (first melt) is obtained. A kneaded product was obtained. Subsequently, the obtained sheet-like solid is roughly pulverized using a chopper mill, and then a particle having a particle diameter of 1 mm or less is removed by removing particles having a particle diameter of more than 1 mm using a screen having an opening of 1 mm. Batch A (first powder) was obtained. In the preparation method of the master batch A, the amount of nigrosine in the first melt-kneading step was 42.9 parts by mass (≈30 × 100/70 parts by mass) with respect to 100 parts by mass of the crystalline polyester resin.

(First melt-kneading step and first grinding step: preparation of masterbatch B)
The preparation method of the master batch B was the same as the preparation method of the master batch A except that the amount of the charge control agent (BONTRON N-71) was changed from 30 parts by mass to 10 parts by mass. In the preparation method of masterbatch B, the amount of nigrosine in the first melt-kneading step was 14.3 parts by mass (≈10 × 100/70 parts by mass) with respect to 100 parts by mass of the crystalline polyester resin.

(First melt-kneading step and first grinding step: preparation of master batch C)
The preparation method of the master batch C was the same as the preparation method of the master batch A except that the first processed product temperature (the temperature in the mixing tank of the Banbury mixer) was changed from 120 ° C to 110 ° C.

(First melt-kneading step and first grinding step: preparation of master batch D)
The preparation method of the master batch D was the same as the preparation method of the master batch A except that the first processed product temperature (the temperature in the mixing tank of the Banbury mixer) was changed from 120 ° C to 140 ° C.

(First melt-kneading step and first grinding step: preparation of masterbatch E)
The preparation method of the master batch E was the same as the preparation method of the master batch B except that the first processed product temperature (the temperature in the mixing tank of the Banbury mixer) was changed from 120 ° C to 140 ° C.

[Toner Production Method]
(Second melt kneading step)
40 parts by mass of an amorphous polyester resin (sample product manufactured by Kao Corporation), 15 parts by mass of a master batch (any of the master batches A to E shown in Table 1 defined for each toner), and magnetic powder (Fe ₃ O ₄ : “TAROX (registered trademark) synthetic iron oxide BL-100” manufactured by Titanium Industry Co., Ltd.) 40 parts by mass and a release agent (Carnauba wax: “Carnauba wax No. 1” manufactured by Hiroyuki Kato) 5 parts by mass was premixed using an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.) under the conditions of a rotational speed of 2500 rpm and a processing time of 300 seconds to obtain a preliminary mixture. Subsequently, the obtained preliminary mixture was melt-kneaded and kneaded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) under conditions of a material supply speed of 10 kg / hour and a rotation speed of 150 rpm. A melt was obtained. During melt kneading, the temperature in the mixing tank of the twin screw extruder was adjusted to the temperature shown in “melt kneading temperature” in Table 1. By measuring the temperature of the melt before cooling (hereinafter referred to as the second processed product temperature), the temperature in the mixing tank of the twin screw extruder was indirectly measured. For example, in the production of toner T-1, the cylinder temperature of the twin-screw extruder was adjusted so that the second processed product temperature was 120 ° C. As a result of such adjustment, the cylinder temperature of the twin screw extruder was 100 ° C. to 110 ° C. during melt kneading.

  Subsequently, the melt obtained as described above was solidified by cooling with a cooling roll having a temperature of 25 ° C. to obtain a sheet-like solid (second melt-kneaded product).

  The twin screw extruder (PCM-30) controls a cylinder, a hopper with a feeder (quantitative supply device) for supplying material into the cylinder, two screws arranged in the cylinder, and the cylinder temperature. With a heater for. Moreover, the cooling roll (accessory of "PCM-30" made by Ikegai Co., Ltd.) is arranged in the vicinity of the discharge port of the twin-screw extruder, so that the melt discharged from the twin-screw extruder (PCM-30) It was transported by a belt conveyor and immediately passed through a cooling roll.

  In the production method of the toner T-1, the amount of the crystalline polyester resin in the first melt-kneading step is 26.3 parts by mass (≈ ( 100/40) × 15 × (70/100) parts by mass). In the production method of the toner T-2, the amount of the crystalline polyester resin in the first melt-kneading step is 32.8 parts by mass (≈ ( 100/40) × 15 × (70/80) parts by mass).

(Second grinding step)
Subsequently, the obtained sheet-like solid was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark)” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill Type I” manufactured by Nippon Pneumatic Industry Co., Ltd.).

(Classification process)
Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a second powder having a volume median diameter (D ₅₀ ) of 8 μm was obtained.

(Annealing process)
Subsequently, until the crystallinity of the crystalline polyester resin in the second powder obtained as described above becomes a value shown in Table 1 using a constant temperature and temperature chamber ("DKN602" sold by Yamato Scientific Co., Ltd.). The second powder was annealed at 45 ° C. (annealing treatment) to increase the crystallinity of the crystalline polyester resin in the second powder. However, the annealing treatment was not performed in the production of the toners T-9 and T-10. In the production of the toner T-1, the second powder was annealed at a temperature of 45 ° C. for 24 hours, so that the crystallinity of the crystalline polyester resin in the second powder was 60%. In the production of the toner T-3, the second powder was annealed at a temperature of 45 ° C. for 48 hours, so that the crystallinity of the crystalline polyester resin in the second powder was 80%. As a result, toner mother particles (second annealed powder) were obtained. The crystallinity of the crystalline polyester resin in the obtained toner base particles was measured according to the following method.

<Method for measuring crystallinity of crystalline polyester resin>
An X-ray diffraction spectrum (vertical axis: X-ray diffraction intensity, horizontal axis: diffraction angle) was measured using a sample horizontal multipurpose X-ray diffractometer ("Ultima IV" manufactured by Rigaku Corporation). A peak derived from the crystalline polyester resin used in the preparation of the master batches A to E (hereinafter referred to as a target peak) was confirmed at a diffraction angle of 21.4 ° in the X-ray diffraction spectrum.

  The second powder (hereinafter referred to as unannealed powder) immediately before the annealing treatment (at the start of the annealing treatment) and the second powder annealed at a temperature of 45 ° C. for a sufficient time (30 days) ( Hereinafter, the X-ray diffraction spectrum was measured for each of the sample and the completely annealed powder, and the intensity of the target peak (X-ray diffraction intensity at a diffraction angle of 21.4 °) was obtained.

  Further, an X-ray diffraction spectrum was measured for the measurement target (toner mother particles obtained by the above-described annealing step), and the intensity of the target peak (X-ray diffraction intensity at a diffraction angle of 21.4 °) was obtained. And based on the obtained measured value, the crystallinity degree of crystalline polyester resin was calculated | required.

The crystallinity (unit:%) of the crystalline polyester resin in the measurement target (toner base particles) is expressed by the following formula. In the formula, X _A represents the intensity of the target peak measured for the unannealed powder, X _B represents the intensity of the target peak measured for the fully annealed powder, and X _C represents the measurement target (toner base). The intensity of the target peak measured for (particle) is shown.
Crystallinity = 100 × (X _C −X _A ) / (X _B −X _A )

  By the method as described above, the crystallinity of the crystalline polyester resin in the toner base particles was determined for the toner base particles of each toner (toner T-1 to T-10). Table 1 shows the crystallinity of the crystalline polyester resin in the obtained toner base particles. For example, in the production of toner T-1, the crystallinity of the crystalline polyester resin in the toner base particles was 60%.

(External addition process)
100 parts by mass of the toner base particles obtained as described above and 0.3 parts by mass of dry silica particles (“HDK (registered trademark) H3050VP” manufactured by Wacker Chemie) are mixed with an FM mixer (manufactured by Nippon Coke Industries, Ltd.). For 5 minutes. As a result, the external additive (silica particles) adhered to the surface of the toner base particles. Thereafter, sieving was performed using a 200 mesh sieve (aperture 75 μm). As a result, toners (toners T-1 to T-10) containing a large number of toner particles were obtained.

[Evaluation method]
The evaluation method of each sample (toners T-1 to T-10) is as follows.

(Heat resistant storage stability)
3 g of the sample (toner) was put in a 20 mL polyethylene container, and the container was left in an oven set at 58 ° C. for 3 hours. Thereafter, the toner taken out from the oven was allowed to stand at room temperature (about 25 ° C.) for 12 hours to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having an aperture of 106 μm with a known mass. Then, the mass of the sieve containing the toner was measured, and the mass W ₁ of the toner before sieving was determined. Subsequently, the sieve was set on a powder tester (manufactured by Hosokawa Micron Corporation), and the evaluation toner was sieved by vibrating the sieve for 30 seconds under the condition of the rheostat scale 5 according to the manual of the powder tester. After sieving, the mass of the toner that did not pass through the sieve (the toner remaining on the sieve) (the mass W ₂ of the toner after sieving) was measured. Based on the mass W ₁ of the toner before sieving and the mass W ₂ of the toner after sieving, a toner residual ratio W ₀ (unit: mass%) was determined according to the following formula.
W ₀ = 100 × W ₂ / W ₁

  When the toner residual ratio is 20% by mass or less, it is evaluated as ◯ (good), when it is more than 20% by mass and 60% by mass or less, it is evaluated as Δ (normal), and when it is more than 60% by mass, × (bad). It was evaluated.

(Low temperature fixability)
100 parts by mass of a developer carrier (FS-C5250DN carrier) and 5 parts by mass of a sample (toner) were mixed for 30 minutes using a ball mill to prepare a two-component developer.

  As an evaluator, a color printer having a Roller-Roller type heat and pressure type fixing device (nip width: 8 mm) (evaluator capable of changing the fixing temperature by modifying “FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd.) ) Was used. The two-component developer prepared as described above was put into a developing device of an evaluation machine, and a sample (supplementary toner) was put into a toner container of the evaluation machine.

Using the above evaluation machine, under an environment of a temperature of 23 ° C. and a humidity of 50% RH, paper having a basis weight of 90 g / m ² (A4 size plain paper) is conveyed at a linear speed of 200 mm / sec. A solid image (unfixed solid image) was formed under the condition of a toner applied amount of 1.0 mg / cm ² . Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluation machine. The nip passage time was 40 milliseconds. The setting range of the fixing temperature was 100 ° C. or higher and 200 ° C. or lower. Specifically, the fixing temperature of the fixing device was increased from 100 ° C. by 5 ° C. (2 ° C. in the vicinity of the minimum fixing temperature), and the minimum temperature (minimum fixing temperature) at which the toner (solid image) can be fixed on paper was measured. Whether or not fixing was possible was confirmed by a rub test (measurement of toner peeling length of the crease). Specifically, the evaluation paper passed through the fixing device was bent so that the surface on which the image was formed was on the inside, and the image on the crease was rubbed 10 times with a 1 kg weight coated with a cloth. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the length (peeling length) of toner peeling at the bent portion was measured. The lowest temperature among the fixing temperatures at which the peeling length was 1 mm or less was defined as the lowest fixing temperature.

  The evaluation standard of the minimum fixing temperature is based on the minimum fixing temperature (hereinafter referred to as the reference temperature) of the toner manufactured in the same manner as the manufacturing method of the toner T-1, except that the crystalline polyester resin is not added. Set. If the minimum fixing temperature is 20 ° C. or more lower than the reference temperature (that is, “minimum fixing temperature ≦ reference temperature−20 ° C.”), it is evaluated as “good”, and the minimum fixing temperature is lower than the reference temperature. If the temperature is not lower than ° C. (that is, if “reference temperature−20 ° C. <minimum fixing temperature <reference temperature”), it is evaluated as Δ (normal), and if the minimum fixing temperature is not lower than the reference temperature (that is, “ If “reference temperature ≦ minimum fixing temperature”, it was evaluated as x (poor).

(Charge stability)
The sample (toner) is allowed to stand in a high temperature and high humidity environment (temperature 32.5 ° C. and humidity 80% RH) for a predetermined time (0 hour, 2 hours, 10 hours, or 24 hours) and evaluated. Toner was obtained. Note that “0 hour” means that the sample (toner) was not allowed to stand in a high temperature and high humidity environment.

  Subsequently, 5 parts by mass of the obtained toner for evaluation and 100 parts by mass were mixed for 30 seconds using a mixer (“Turbler (registered trademark) mixer T2F” manufactured by Willy et Bacofen (WAB)). The toner for evaluation was triboelectrically charged. Subsequently, the charge amount (unit: μC / g) of the toner for evaluation was measured using a Q / m meter (“MODEL 210HS-1” manufactured by Trek). For each toner (toner T-1 to T-10), four types of evaluation toners (standing time in a high temperature and high humidity environment: 0 hours, 2 hours, 10 hours, 24 hours) were prepared and evaluated. The charge amount of the toner was measured. The measurement results are shown in FIG. In FIG. 2, line L11 is toner T-1, line L12 is toner T-2, line L13 is toner T-3, line L14 is toner T-4, line L21 is toner T-5, and line L22 is toner T-. 6, line L23 shows the measurement result for toner T-7, line L24 shows the measurement result for toner T-8, line L25 shows the measurement result for toner T-9, and line L26 shows the measurement result for toner T-10.

From the charge amount E _A of the evaluation toner having a standing time of 0 hours in a high temperature and high humidity environment and the charge amount E _B of the evaluation toner having a standing time of 24 hours in a high temperature and high humidity environment The charge amount maintenance rate (unit:%) was determined based on the following formula.
Charge amount retention rate = 100 × E _B / E _A

  If the charge amount maintenance rate exceeds 80.0%, it is evaluated as ◯ (good), and if it is 50.0% or more and 80.0% or less, it is evaluated as △ (normal). X (bad).

[Evaluation results]
Table 3 shows the evaluation results (heat-resistant storage stability: toner residual rate, low-temperature fixability: minimum fixing temperature, charge stability: charge amount maintenance rate) for each sample (toners T-1 to T-10).

  The production methods of the toners T-1 to T-4 (the toners according to Examples 1 to 4) are respectively the above-described basic steps (first melt-kneading step, first pulverizing step, second melt-kneading step, second Crushing step and annealing step). Specifically, the melt kneading temperature in the first melt kneading step was 120 ° C. or less (see Tables 1 and 2). The melt kneading temperature in the second melt kneading step was 120 ° C. or lower (see Table 1). In the annealing step, the second powder is annealed, and the crystallinity of the crystalline polyester resin in the second powder is changed from 0% at the start of the annealing process to 50% or more (the crystallinity at the end of the annealing process). (See Table 1).

  As shown in Table 3, each of the toners T-1 to T-4 was excellent in all of heat resistance storage stability, low temperature fixability, and charging stability in a high temperature and high humidity environment.

  The method for producing a toner for developing an electrostatic latent image according to the present invention is suitable for producing a toner for developing an electrostatic latent image that can be used to form an image in, for example, a copying machine, a printer, or a multifunction machine.

Claims (7)

A first melt-kneading step for obtaining a first melt-kneaded product after melt-kneading at least nigrosine and the crystalline polyester resin under a temperature of 120 ° C. or lower;
A first pulverization step of pulverizing the first melt-kneaded product to obtain a first powder;
A second melt-kneading step for obtaining a second melt-kneaded product after melt-kneading at least the first powder and the amorphous polyester resin under a temperature of 120 ° C. or lower;
Crushing the second melt-kneaded product to obtain a second powder;
Annealing the second powder to increase the crystallinity of the crystalline polyester resin in the second powder from 0% at the start of annealing to 50% or more; and
Including
The method for producing a toner for developing an electrostatic latent image, wherein the crystallinity is a value measured based on an X-ray diffraction intensity.   2. The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein in the annealing step, the temperature of the annealing treatment is 40 ° C. or more and 55 ° C. or less.   The method for producing a toner for developing an electrostatic latent image according to claim 2, wherein in the annealing step, a processing time of the annealing process is 20 hours or more and 30 hours or less.   In the said 1st melt-kneading process, the quantity of the said nigrosine is 10 to 60 mass parts with respect to 100 mass parts of said crystalline polyester resins, The static as described in any one of Claims 1-3. A method for producing toner for developing an electrostatic latent image.   The amount of the crystalline polyester resin in the first melt-kneading step is 20 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the amorphous polyester resin in the second melt-kneading step. 5. The method for producing a toner for developing an electrostatic latent image according to claim 4.   6. The electrostatic latent image developing according to claim 1, wherein in the second melt-kneading step, magnetic powder is melt-kneaded together with the first powder and the amorphous polyester resin. Toner manufacturing method.   7. The method according to claim 1, further comprising an external addition step of mixing the second powder and an external additive after the second pulverization step and before the annealing step or after the annealing step. The method for producing a toner for developing an electrostatic latent image according to item 2.

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