JP2017082148A - Resin powder and toner for electrostatic latent image developing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form high-resolution images by fixing toner at low temperature while preventing toner scattering and toner adhesion (specifically photoreceptor drum adhesion).SOLUTION: Resin powder contains plural resin particles 12 including core (thermoplastic core 12a) and coat layer 12b formed on the surface of the core. The core of the resin particle 12 consists of thermoplastic substantially. The number average first particle size of the core of the multiple resin particles 12 is 50-120 nm. The coat layer 12b consists of melamine-based resin substantially. Toner particle 10 contained in toner for electrostatic latent image developing comprises the resin powder as an external additive.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resin powder and a toner for developing an electrostatic latent image.

  Patent Document 1 discloses a technique for suppressing toner deterioration by causing organic fine particles to be present on the surface of colored particles (toner particles) contained in a toner. Patent Document 1 describes polystyrene, polymethyl methacrylate, styrene- (meth) acrylate copolymer, benzoguanamine, and melamine resin as materials for organic fine particles.

JP 2008-14999 A

  However, with the technique disclosed in Patent Document 1 alone, it is difficult to form a high-quality image by fixing toner at a low temperature while suppressing toner scattering and toner adhesion. For example, when organic fine particles composed only of a thermosetting resin (for example, melamine resin) are used as the external additive, the low-temperature fixability of the toner tends to be insufficient. Further, when organic fine particles made only of a thermoplastic resin (for example, polystyrene) are used as the external additive, toner adhesion (more specifically, photosensitive drum adhesion or the like) is likely to occur.

  The present invention has been made in view of the above problems, and by fixing toner at a low temperature while suppressing toner scattering and toner adhesion (more specifically, photosensitive drum adhesion, etc.), a high-quality image can be obtained. The purpose is to form.

  The resin powder according to the present invention includes a plurality of resin particles including a core and a coat layer formed on the surface of the core. The core is substantially composed of a thermoplastic resin. The number average primary particle diameter of the core in the plurality of resin particles is 50 nm or more and 120 nm or less. The coat layer is substantially composed of a melamine resin.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including toner base particles and an external additive attached to the surface of the toner base particles. The toner particles include the resin powder according to the present invention as the external additive.

  According to the present invention, it is possible to fix a toner at a low temperature and form a high-quality image while suppressing toner scattering and toner adhesion (more specifically, adhesion to a photosensitive drum).

FIG. 4 is a diagram illustrating toner particles (external additive: resin powder according to an embodiment of the present invention) included in a toner according to an embodiment 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. Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”.

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner may be used as a one-component developer. Alternatively, a two-component developer may be prepared by mixing toner and carrier using a mixing device (for example, a ball mill). In order to form a high-quality image, it is preferable to use a ferrite carrier as a carrier. In order to form a high-quality image over a long period of time, it is preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. In order to produce magnetic carrier particles, the carrier core may be formed of a magnetic material (for example, ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less, and 8 parts by mass or more and 12 parts by mass with respect to 100 parts by mass of the carrier. The following is more preferable.

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

  First, an electrostatic latent image is formed on a photoconductor (for example, a surface layer portion of a photoconductor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing step, toner (charged toner) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) is attached to the electrostatic latent image to form a toner image on the photoreceptor. In the subsequent transfer step, the toner image on the photosensitive member is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan.

  The toner according to this embodiment includes a plurality of toner particles. The toner particles include toner base particles and an external additive. The external additive adheres to the surface of the toner base particles. The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, if necessary.

  The toner particles contained in the toner according to the present embodiment may be toner particles not having a shell layer (hereinafter referred to as non-capsule toner particles), or toner particles having a shell layer (hereinafter referred to as capsule toner particles). May be described). In the capsule toner particles, the toner base particles include a core and a shell layer formed on the surface of the core. In order to improve the fixing property of the toner, it is preferable that the core of the capsule toner particle is substantially composed of a thermoplastic resin. The shell layer may be substantially composed of a thermosetting resin, may be substantially composed of a thermoplastic resin, or may contain both a thermoplastic resin and a thermosetting resin. Good. As the thermoplastic resin, for example, a styrene resin, an acrylic acid resin, or a styrene-acrylic acid resin can be used. Examples of the thermosetting resin include melamine resin, urea resin, sulfonamide resin, glyoxal resin, guanamine resin, aniline resin, polyimide resin (more specifically, maleimide polymer or bismaleimide resin). A xylene-based resin can be used.

The toner particles contained in the toner according to the present embodiment include, as an external additive, a resin powder having the following configuration (hereinafter referred to as a basic configuration) (hereinafter referred to as the resin powder according to the present embodiment). To be described).
(Basic composition of resin powder)
The resin powder includes a plurality of resin particles each including a core (hereinafter referred to as a thermoplastic core) and a coat layer formed on the surface of the thermoplastic core. The thermoplastic core is substantially composed of a thermoplastic resin. The number average primary particle diameter of the thermoplastic core in the plurality of resin particles is 50 nm or more and 120 nm or less. The coat layer is substantially composed of a melamine resin. The method for measuring the particle size (number average primary particle size) of the thermoplastic core is the same method as in Examples described later or an alternative method thereof. When producing a thermoplastic core in a liquid containing a surfactant, the number average primary particle size of the thermoplastic core can be adjusted by changing the amount of the surfactant.

  FIG. 1 shows an example of toner particles contained in the toner according to this embodiment. A toner particle 10 shown in FIG. 1 includes toner base particles 11 and a plurality of resin particles 12 (resin powder). The resin particles 12 are attached to the surface of the toner base particles 11 and correspond to external additives. The resin particle 12 includes a thermoplastic core 12a and a coat layer 12b. The coat layer 12b is formed on the surface of the thermoplastic core 12a. The thermoplastic core 12a is substantially composed of a thermoplastic resin. Additives may be dispersed in the thermoplastic resin constituting the thermoplastic core 12a. The coat layer 12b is substantially composed of a melamine resin. Additives may be dispersed in the melamine-based resin constituting the coat layer 12b.

  By using the resin powder according to the present embodiment (resin powder having the above basic configuration) as an external additive for toner particles, toner scattering and toner adhesion (more specifically, photosensitive drum adhesion, etc.) can be achieved. The inventors have found that it is possible to form a high-quality image by fixing toner at a low temperature while suppressing it.

  In the resin particles (external additive), the thermoplastic core is covered with the coating layer, so that it is possible to suppress toner adhesion (more specifically, photosensitive drum adhesion and the like). Further, since the resin particles function as spacers between the toner particles, toner aggregation can be suppressed. It is considered that the heat-resistant storage stability of the toner is improved by suppressing toner aggregation.

  The resin particles (external additive) include a thermoplastic core (particles substantially composed of a thermoplastic resin) and a coat layer substantially composed of a melamine-based resin, so that the heat resistant storage stability of the toner is increased. In addition, it is possible to improve both the low-temperature fixability and the toner chargeability. It is considered that the melamine resin contributes to the improvement of low-temperature fixability and chargeability of the toner. In order to improve the chargeability of the toner, a melamine resin is particularly preferable as a material for the coat layer among thermosetting resins.

  In the above basic configuration, when the number average primary particle diameter of the thermoplastic core in the plurality of resin particles is 50 nm or more and 120 nm or less, it is possible to form a high-quality image while suppressing toner scattering. If the particle diameter of the resin powder is too small, the resin powder is easily embedded in the toner base particles. If the resin powder is buried, it is considered that the chargeability of the toner particles is lowered and the charge amount of the toner is likely to be insufficient when the toner is replenished. Insufficient charge amount of toner can cause replenishment fog or toner scattering. Specifically, when the amount of reversely charged toner increases, replenishment fog tends to occur. Further, when the amount of low-charged toner increases, toner scattering tends to occur easily. On the other hand, if the particle diameter of the resin powder is too large, the resin powder tends to be detached from the toner particles. When the resin powder is detached, it is considered that the toner particles are likely to be excessively positively charged due to the absence of the resin powder (spacer) between the toner particles. Such excessive charging (charge-up) of the toner is considered to reduce the developability of the toner. For this reason, when the particle diameter of the resin powder is too large, it is considered difficult to form a high-quality image (more specifically, an image having a sufficient image density). In addition, even when the degree of resin powder embedding is large, the resin powder does not function as a spacer, and thus a high-quality image (more specifically, an image having sufficient image density) can be formed. It will be difficult.

  In order to achieve both heat resistant storage stability and low-temperature fixability of the toner, the thickness of the coat layer is preferably 1 nm or more and 12 nm or less, and more preferably 3 nm or more and 8 nm or less. The method for measuring the thickness of the coat layer is the same method as in the examples described later or an alternative method thereof.

The thermoplastic core can be obtained by polycondensation or copolycondensation of one or more thermoplastic monomers (more specifically, an acrylic acid monomer or a styrene monomer). In order to improve the adhesion between the thermoplastic core and the coating layer, the thermoplastic resin constituting the thermoplastic core is at least one of a repeating unit derived from a hydroxyl group-containing monomer and a repeating unit derived from an amide group-containing monomer. It is preferable to contain. By improving the adhesion between the thermoplastic core and the coating layer, the durability of the toner is improved, and there is a tendency that a high-quality image can be formed over a long period of time. The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization. The thermosetting monomer is a monomer that becomes a thermosetting resin by homopolymerization. For example, when monomers of the same type are connected to each other through “—CH ₂ —” to become a thermosetting resin, the monomer corresponds to a “thermosetting monomer”.

  It is considered that the repeating unit derived from the hydroxyl group-containing monomer and the repeating unit derived from the amide group-containing monomer are likely to react (and thus bond) with the melamine resin constituting the coat layer. As the hydroxyl group-containing monomer, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate is particularly preferable. The thermoplastic resin constituting the thermoplastic core may contain two or more repeating units derived from a hydroxyl group-containing monomer. Examples of the amide group-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N- [3- (dimethylamino) propyl] (meth) acrylamide, or N- (hydroxymethyl) (meth) acrylamide. Particularly preferred. The thermoplastic resin constituting the thermoplastic core may contain two or more repeating units derived from the amide group-containing monomer.

  Next, the configuration of the non-capsule toner particles will be described. Specifically, the toner base particles (binder resin and internal additive) and the external additive will be described in order.

[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).

(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, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner base particles tend to be anionic, and when the binder resin has an amino group or an amide group. The toner base particles tend to be cationic.

  In order to improve the storage stability or durability of the toner while maintaining excellent low-temperature fixability of the toner, the glass transition point (Tg) of the binder resin contained in the toner base particles is 45 ° C. or higher and 65 ° C. or lower. It is preferable that

  The glass transition point (Tg) can be measured using, for example, a differential scanning calorimeter. More specifically, the specific heat in the endothermic curve obtained by measuring the endothermic curve of the sample (for example, binder resin) using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.). The Tg of the binder resin can be obtained from the change point.

  In order to improve the storage stability or durability of the toner while maintaining excellent low-temperature fixability of the toner, the softening point (Tm) of the binder resin contained in the toner base particles is 80 ° C. or higher and 150 ° C. or lower. Preferably there is.

The softening point (Tm) can be measured using, for example, a Koka flow tester. More specifically, a sample (for example, a binder resin) is set in a Koka type flow tester (for example, “CFT-500D” manufactured by Shimadzu Corporation), and the sample is melted and discharged under predetermined conditions. Then, an S-shaped curve (horizontal axis: temperature, vertical axis: stroke) of the sample is measured. The Tm of the sample can be read from the obtained S-shaped curve. In the obtained S-curve, if the maximum stroke value is S ₁ and the low-temperature baseline stroke value is S ₂ , the stroke value in the S-curve is “(S ₁ + S ₂ ) / 2”. Is equivalent to the Tm of the sample.

  In order to improve the low-temperature fixability of the toner, it is preferable that the toner base particles contain a thermoplastic resin as the binder resin, and contain the thermoplastic resin in a proportion of 85% by mass or more of the entire binder resin. Is more preferable. Examples of the thermoplastic resin contained in the toner base particles include a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), an olefin resin (more specifically, In particular, polyethylene resin or polypropylene resin), vinyl resin (more specifically, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin), polyester resin, polyamide resin, or urethane resin are preferable. . Further, a copolymer of the above resin, that is, a copolymer containing one or more repeating units derived from the same monomer as any one of the repeating units of the resin (more specifically, a styrene-acrylic acid resin or styrene). -Butadiene resin and the like are also preferable as the thermoplastic resin contained in the toner base particles.

  The polyester resin is an alcohol (more specifically, a diol such as 1,2-propanediol, a bisphenol such as bisphenol A ethylene oxide adduct, or a trihydric or higher alcohol such as trimethylolethane). And a carboxylic acid (more specifically, a divalent carboxylic acid such as fumaric acid or succinic acid, or a trivalent or higher carboxylic acid such as 1,2,4-benzenetricarboxylic acid). Obtained by condensation polymerization.

  The styrene-acrylic acid resin is composed of one or more styrene monomers (more specifically, styrene, hydroxystyrene, vinyltoluene, chlorostyrene, methylstyrene, or ethylstyrene) and one or more acrylic monomers. More specifically, it is a copolymer with (meth) acrylic acid, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester).

(Coloring agent)
The toner base particles may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using 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. It is more preferable that the amount is not more than part by mass.

  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. More preferably, it is 15 parts by mass or less.

  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.

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

  By adding a negatively chargeable charge control agent to the toner base particles, the anionicity of the toner base particles can be enhanced. Further, by adding a positively chargeable charge control agent to the toner base particles, the cationic property of the toner base particles can be enhanced. However, if sufficient chargeability is ensured in the toner, it is not necessary to add a charge control agent to the toner base particles.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, etc.) or alloys thereof, ferromagnetic metal oxides (more specifically, ferrite, magnetite, or chromium dioxide). Etc.) or a material subjected to a ferromagnetization treatment (more specifically, a heat treatment etc.) can be suitably used. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

[External additive]
The toner particles contained in the toner according to this embodiment include the resin powder according to this embodiment (resin powder having the above-described basic configuration) as an external additive. In order to improve the fluidity and the like of the toner, it is preferable that the toner particles further include one or more inorganic particles as an external additive in addition to the resin powder according to the present embodiment. As inorganic particles, particles of silica particles or metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) can be suitably used. Multiple types of inorganic particles may be used in combination. In order to improve the fluidity of the toner, it is preferable to use silica particles as the inorganic particles. In order to improve the abrasiveness of the toner, it is preferable to use titanium oxide particles as inorganic particles. In order to improve the fluidity and abrasiveness of the toner, it is particularly preferable that the toner particles further include silica particles and titanium oxide particles as external additives in addition to the resin powder according to the present embodiment.

  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 addition, when the resin powder according to the present embodiment is used as an external additive together with inorganic particles, in order to adjust the chargeability of the toner to an appropriate level, among the external additives contained in the toner, 10 The external additive having a mass% of 50% by mass or less is preferably the resin powder according to this embodiment, and the external additive having a mass of 20% by mass to 35% by mass is the resin powder according to this embodiment. Is more preferable. For example, when three types of external additives (resin powder, silica powder, and titanium oxide powder according to this embodiment) are used, the ratio of the resin powder according to this embodiment described above is The mass of the resin powder can be calculated by dividing the mass of the resin powder by the total mass of the three types of external additives. When expressed as a percentage (mass%), the calculated value may be multiplied by 100. For example, in the case of using 1 part by mass of silica powder, 1 part by mass of titanium oxide powder, and 0.5 part by mass of the resin powder according to this embodiment, the above-described embodiment is used. The ratio of the resin powder is 20% by mass (= 100 × 0.5 / (1 + 1 + 0.5)).

[Production method of resin powder]
The resin powder is obtained, for example, by emulsion polymerization of an unsaturated monomer in an aqueous medium and drying the obtained emulsion. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). In order to suitably manufacture the resin powder, it is preferable to use pure water (for example, ion-exchanged water) to which an additive (for example, a surfactant) is added as an aqueous medium. The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. A surfactant and / or protective colloid may be dissolved or dispersed in the aqueous medium. As the surfactant, a reactive surfactant may be used, or a non-reactive surfactant may be used. Surfactants may be used as emulsifiers. Preferable examples of the surfactant having reactivity include a propenyl group-containing surfactant having radical polymerization properties (more specifically, an anionic surfactant or a nonionic surfactant). As the protective colloid, a water-soluble polymer (more specifically, polyvinyl alcohol or the like) can be preferably used. Two or more surfactants and protective colloids may be used.

  Preferable examples of the unsaturated monomer used in the production of the resin powder include ethylene, propylene, vinyl acetate, vinyl propionate, acrylonitrile, methacrylonitrile, (meth) acrylic acid alkyl ester (more specifically, Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate), a styrene monomer (more specific) Specifically, styrene, α-methylstyrene, tert-butylstyrene, vinyltoluene, etc.) may be mentioned. Two or more unsaturated monomers may be used.

[Toner Production Method]
Preferable examples of the method for producing the toner base particles include a pulverization method or an aggregation method. These methods facilitate easy dispersion of the internal additive in the binder resin.

  In an example of the pulverization method, first, a binder resin, a colorant, a charge control agent, and a release agent are mixed. Subsequently, the obtained mixture is melt-kneaded using a melt-kneading apparatus (for example, a single-screw or twin-screw extruder). Subsequently, the obtained melt-kneaded product is pulverized and classified. Thereby, toner mother particles are obtained. When the pulverization method is used, the toner base particles can often be produced more easily than when the aggregation method is used.

  In an example of the aggregation method, first, these fine particles are aggregated in an aqueous medium containing fine particles of the binder resin, the release agent, and the colorant until a desired particle diameter is obtained. Thereby, aggregated particles containing a binder resin, a release agent, and a colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. Thereby, toner mother particles having a desired particle diameter are obtained.

(Washing process)
The toner base particles may be washed. As a method for cleaning the toner base particles, for example, the dispersion containing the toner base particles is solid-liquid separated to collect the wet cake-like toner base particles, and the collected wet cake-like toner base particles are washed with water. Is preferred. As a method for cleaning the toner base particles, a method is preferred in which the toner base particles in the dispersion containing the toner base particles are settled, the supernatant liquid is replaced with water, and the toner base particles are redispersed in water after the replacement.

(Drying process)
After the cleaning step, the toner base particles may be dried. For example, the toner base particles can be dried using a dryer (more specifically, a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, a vacuum dryer, or the like). In order to suppress aggregation of the toner base particles during drying, it is preferable to dry the toner base particles using a spray dryer. In the case of using a spray dryer, for example, by spraying a dispersion liquid in which an external additive is dispersed onto the toner base particles, a drying step and an external addition step described later can be performed simultaneously.

(External addition process)
External additives (for example, resin powder, silica powder, and titanium oxide powder according to the present embodiment) are attached to the surface of the toner base particles obtained as described above. By using a mixer, the toner base particles and the external additive are mixed under conditions that prevent the external additive from being embedded in the toner base particles, thereby allowing the external additive to adhere to the surface of the toner base particles. .

  Through the above process, a toner containing a large number of toner particles can be produced. Note that unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. In order to produce the toner efficiently, it is preferable to produce a large number of toner particles simultaneously.

  Examples of the present invention will be described. Table 1 shows resin powders A-1, A-2, B-1 to B-B used in the production of toners A to J according to Examples or Comparative Examples (respectively, electrostatic latent image developing toners: see Table 2). -4 and C to F are shown. “Amount of surfactant” in Table 1 indicates the amount of surfactant (unit: parts by mass) when the amount of monomer for forming the core of the resin particles is 100 parts by mass. The “particle diameter” of the core in Table 1 indicates the number average primary particle diameter of the thermoplastic core. In Table 1, the thermoplastic monomer A was methyl methacrylate and n-butyl acrylate. Thermoplastic monomer B was methyl methacrylate, n-butyl acrylate, and acrylamide. Thermoplastic monomer C was methyl methacrylate, n-butyl acrylate, and 2-hydroxyethyl methacrylate. In the production of the resin powder E, methylol melamine was used as a thermosetting monomer (core material of resin particles). The resin particles contained in the resin powder E were melamine resin particles (particles substantially composed of melamine resin).

Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of toners A to J (see Table 2 described later) will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with which the error is sufficiently small are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value. Unless otherwise specified, the measured volume median diameter (D ₅₀ ) is a value measured using “Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc.

  In addition, for each of the resin particles A-1, A-2, B-1 to B-4, and C to F, the core particle diameter (number average primary particle diameter) and the thickness of the coating layer The thickness was measured by the following method.

<Measuring method of particle diameter of core of resin particle and thickness of coat layer>
A sample (resin powder) was dispersed in a room temperature curable epoxy resin and cured in an atmosphere at 40 ° C. for 2 days to obtain a cured product. The obtained cured product was dyed using osmium tetroxide and then cut out using an ultramicrotome (“EM UC6” manufactured by Leica Microsystems Co., Ltd.) equipped with a diamond knife to obtain a flake sample. Then, the cross section of the obtained thin piece sample was image | photographed using the transmission electron microscope (TEM) (The JEOL Co., Ltd. product "JSM-6700F").

  The obtained TEM image was analyzed using image analysis software ("WinROOF" manufactured by Mitani Corporation), thereby measuring the particle diameter of the core and the thickness of the coating layer. Specifically, two straight lines are drawn on the two straight lines with respect to one resin particle by drawing two straight lines that are orthogonal to each other at the approximate center of the cross section of the resin particles (or the center of gravity if the cross section is not circular). The particle diameter of the core in the (two orthogonal directions) and the thickness of the four coat layers were measured. The arithmetic average value of the measured particle diameters (two measured values) of two types of cores was defined as the primary particle diameter of the core of one resin particle to be measured. In addition, the arithmetic average value of the measured thicknesses of the four coat layers was defined as the thickness of the coat layer of one resin particle as the measurement target. For the 10 resin particles contained in the sample (resin powder), the particle diameter of the core and the thickness of the coating layer were measured, respectively, and the 10 number average value was used as the evaluation value (resin particle size) of the sample (resin powder). The particle diameter of the core and the thickness of the coating layer).

  When the coat layer is thin, the boundary between the resin particle core and the coat layer on the TEM image becomes unclear, which may make it difficult to measure the thickness of the coat layer. In such a case, the thickness of the coat layer was measured by combining TEM and electron energy loss spectroscopy (EELS) to clarify the boundary between the core and the coat layer. Specifically, in the TEM image, mapping of an element (for example, nitrogen element) contained in the coat layer was performed using EELS.

[Production Method of Toner A]
(Preparation of toner base particles)
86 parts by mass of a polyester resin (“Toughton (registered trademark) NE-410” manufactured by Kao Corporation), 3 parts by mass of carbon black (“REGAL (registered trademark) 330R” manufactured by Cabot), and polypropylene wax (Sanyo Chemical Industries Co., Ltd.) 5 parts by mass of “Biscol (registered trademark) 660P” manufactured by the company, 2 parts by mass of quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Industry Co., Ltd.), and styrene-acrylic acid resin ( 4 parts by mass of “FCA-201-PS” manufactured by Fujikura Chemical Co., Ltd. was mixed for 180 seconds at a rotational speed of 2400 rpm using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.).

  Subsequently, the obtained mixture was melt-kneaded using a twin screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) under conditions of a material supply speed of 5 kg / hour, a shaft rotation speed of 150 rpm, and a cylinder temperature of 150 ° C. . Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rotoplex (registered trademark) 16/8 type” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a pulverizer (“Turbo Mill RS Model” manufactured by Freund Turbo Co., Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner mother particles having a volume median diameter of 6.5 μm were obtained.

(Production of resin powder A-1)
In the production of toner A, resin powder A-1 produced by the following method was used as an external additive.
Ion-exchanged water and sodium lauryl sulfate were placed in a glass container equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube, and a stirring device. Subsequently, the temperature of the container contents was raised to 80 ° C. in a nitrogen atmosphere. While stirring the contents of the container, ammonium persulfate was added to the container. Subsequently, a mixture of methyl methacrylate and n-butyl acrylate was dropped into the container over 1 hour. Subsequently, the container contents were stirred for 1 hour to obtain an emulsion. Subsequently, the obtained emulsion was dried to obtain a thermoplastic core. The addition amount of each material was as follows with respect to 200 parts by mass of the ion exchange water.
Sodium lauryl sulfate: 3 parts by mass Ammonium persulfate: 1 part by mass Methyl methacrylate: 70 parts by mass n-butyl acrylate: 30 parts by mass

  Subsequently, a three-necked flask equipped with a thermometer and a stirring blade was prepared, and the flask was set in a water bath. Subsequently, 500 mL of ion-exchanged water was put in the flask, and the temperature in the flask was kept at 30 ° C. using a water bath. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 4.

  Subsequently, an aqueous solution of hexamethylolmelamine initial polymer (“Milben (registered trademark) Resin SM-607” manufactured by Showa Denko KK, solid content concentration 80% by mass) was added to the flask, and the flask contents were stirred. Methylol melamine was dissolved. The amount of milben resin SM-607 added was such that a coat layer having a predetermined thickness (see Table 1) was formed. As the amount of milben resin SM-607 added was increased, a thicker coating layer tended to be formed.

  Subsequently, 30 g of a resin particle core (thermoplastic core produced by the above-described procedure) was added to the flask, and the contents of the flask were sufficiently stirred. Subsequently, 500 mL of ion-exchanged water was added to the flask, the temperature in the flask was increased to 75 ° C. at a rate of 1 ° C./min while stirring the flask contents at a rotation rate of 100 rpm, and the temperature was 75 ° C. and the rotation rate was 100 rpm. The contents of the flask were stirred for 2 hours under the following conditions. As a result, a coat layer was formed on the surface of the core in the flask, and a dispersion of resin powder was obtained. Thereafter, the pH of the dispersion of the resin powder was adjusted to 7 (neutralized) using sodium hydroxide. Subsequently, the resin powder dispersion was cooled to room temperature (about 25 ° C.).

  The dispersion of the resin powder obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, a wet cake-like resin powder was obtained. Thereafter, the obtained wet cake-like resin powder was redispersed in ion-exchanged water. Furthermore, dispersion and filtration were repeated 5 times to wash the resin powder. Thereafter, the resin powder was dried to obtain resin powder A-1. The number average primary particle diameter of the resin particle core (thermoplastic core) in the resin powder A-1 was 86 nm. Moreover, the resin particle contained in resin powder A-1 was provided with the coating layer comprised from a melamine resin substantially. The thickness of the coat layer was 3 nm.

(External addition process)
100 parts by mass of toner base particles, 0.8 parts by mass of resin powder (resin powder A-1 produced by the above procedure), and hydrophobic silica powder (“AEROSIL (registered trademark) RA-” manufactured by Nippon Aerosil Co., Ltd. 200H ") and 1.0 part by mass of conductive titanium oxide powder (" EC-100 "manufactured by Titanium Industry Co., Ltd.) using an FM mixer (manufactured by Nippon Coke Industries Co., Ltd.). Mix for 5 minutes at a speed of 3500 rpm. As a result, the external additive adhered to the surface of the toner base particles. Then, sieving was performed using a 300 mesh sieve (aperture 48 μm). As a result, Toner A containing a large number of toner particles was obtained. In toner A, 28.6% by mass (= 100 × 0.8 / (1 + 1 + 0.8)) out of all external additives (resin powder A-1, silica powder, and titanium oxide powder). The additive was resin powder A-1.

[Production Method of Toners B to J]
As shown in Table 2 to be described later, each of the manufacturing methods of the toners B to J is any one of the resin powders A-2, B-1 to B-4, and C to F instead of the resin powder A-1. Was the same as the production method of the toner A except that was used. Regarding the resin particles of resin powders A-2, B-1 to B-4, and C to F, the particle diameter of the core and the thickness of the coat layer were values as shown in Table 1, respectively. .

  The production method of the resin powder A-2 was the same as the production method of the resin powder A-1, except that the addition amount of milben resin SM-607 was changed so that the thickness of the coat layer was 8 nm.

  The production methods of the resin powders B-1 to B-4 were respectively resin powder A except that the amount of sodium lauryl sulfate (surfactant) used was changed from 3 parts by mass to the amount shown in Table 1. It was the same as the manufacturing method of -1.

  The manufacturing method of the resin powder C is the manufacturing method of the resin powder A-1, except that 20 parts by mass of acrylamide is added to the aforementioned 70 parts by mass of methyl methacrylate and 30 parts by mass of n-butyl acrylate. Was the same. The resin powder D was produced in the same manner as the resin powder A except that 20 parts by mass of 2-hydroxyethyl methacrylate was added to 70 parts by mass of methyl methacrylate and 30 parts by mass of n-butyl acrylate. It was the same as the manufacturing method of -1.

  The production method of the resin powder E does not use a thermoplastic core, but polymerizes methylol melamine under the same conditions (reaction temperature: 75 ° C., reaction time: 2 hours) as in the above-mentioned coating layer forming step, thereby producing melamine resin particles. Was the same as the manufacturing method of the resin powder A-1. Resin powder E contained a large number of melamine resin particles.

  The manufacturing method of the resin powder F was the same as the manufacturing method of the resin powder A-1, except that the coat layer was not formed.

[Evaluation method]
The evaluation method of each sample (toners A to J) is as follows.

(Image density, toner adhesion, and toner scattering)
The sample (toner) and the ferrite carrier were mixed for 30 minutes using a ball mill to prepare a developer for evaluation (two-component developer). The ratio of the sample (toner) in the developer for evaluation was 10% by mass.

  A color multifunction machine (“TASKalfa 500ci” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. The evaluation developer prepared as described above was put into the developing device of the evaluation machine, and the sample (replenishment toner) was put into the toner container of the evaluation machine.

  Printing durability for continuous printing on 200,000 sheets of paper (A4 size printing paper) at a printing rate of 5.0% using the above-mentioned evaluation machine in a normal temperature and humidity environment (temperature 20 ° C., humidity 50% RH). A test was conducted.

  After the printing durability test, a sample image including the solid portion is formed on a recording medium (evaluation paper) using the evaluation machine, and the solid portion is measured using a reflection densitometer (“RD914” manufactured by X-Rite). Image density (ID) was measured. When the measured image density was 1.0 or more, it was evaluated as ◯ (good), and when it was less than 1.0, it was evaluated as x (not good).

After the printing durability test, the photosensitive drum was taken out from the evaluation machine, and the adhesion state of the sample (toner) to the photosensitive drum was visually evaluated according to the following criteria.
○ (good): No toner adhered to the surface of the photosensitive drum.
X (not good): Toner adhered to the surface of the photosensitive drum.

  After the printing durability test, the entire sample (toner) scattered in the developing unit of the evaluation machine was collected. Then, the mass of the collected toner was measured, and the measured mass of toner (toner scattering amount) was evaluated according to the following criteria. When the toner scattering amount was less than 400 mg, it was evaluated as ◯ (good), and when it was 400 mg or more, it was evaluated as x (not good).

(Minimum fixing temperature)
The sample (toner) and the ferrite carrier were mixed for 30 minutes using a ball mill to prepare a developer for evaluation (two-component developer). The ratio of the sample (toner) in the developer for evaluation was 10% by mass.

  An image was formed using the two-component developer prepared as described above, and the minimum fixing temperature was evaluated. As an evaluator, a color printer having a Roller-Roller type heat and pressure type fixing device (an evaluator in which “FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd. was modified to change the fixing temperature) was used. The two-component developer prepared as described above was put into the developing device of the evaluation machine, and the sample (supplementary toner) was put into the toner container of the evaluation machine.

After the paper (Fuji Xerox Co., Ltd. “C ² 90”: A4 size, 90 g / m ² plain paper) using the above evaluation machine under normal temperature and humidity environment (temperature 20 ° C., humidity 50% RH) A solid image having a size of 25 mm × 25 mm was formed in a portion from the end to 10 mm under conditions of a linear speed of 200 mm / second and a toner applied amount of 1.0 mg / cm ² . Subsequently, the paper on which the image was formed was passed through a fixing device (nip width: 8 mm) 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 gradually increased from 100 ° C., and the lowest temperature (minimum fixing temperature) at which the solid image (toner image) can be fixed on the paper was measured. Whether or not the toner could be fixed was confirmed by a rubbing test as shown below.

  In the folding test, the paper passed through the fixing device was folded so that the surface on which the image was formed was on the inside, and the image on the fold was rubbed back and forth 10 times using a 1 kg weight coated with a fabric. 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 minimum fixing temperature is the lowest fixing temperature at which three or more strips (offset portions) are not visually confirmed and the peeling length of each strip is 1 mm or less. When the minimum fixing temperature was 155 ° C. or lower, it was evaluated as “good”, and when it exceeded 155 ° C., it was evaluated as “poor” (not good).

[Evaluation results]
Table 2 shows the evaluation results for each sample (toners A to J). Table 2 shows the evaluation results of the image density, toner scattering, toner adhesion, and minimum fixing temperature.

  The toner particles contained in each of the toners A to D, G, and H (the toners according to Examples 1 to 6) were each provided with the resin powder having the above-described basic configuration as an external additive. Specifically, the resin particles contained in each of the resin powders A-1, A-2, B-1, B-2, C, and D are thermoplastic cores (particles substantially composed of a thermoplastic resin). ) And a coating layer formed on the surface of the thermoplastic core. For resin powders A-1, A-2, B-1, B-2, C, and D, the number average primary particle diameter of the thermoplastic core in the plurality of resin particles is 50 nm or more and 120 nm or less, respectively. (See Table 1). The coat layer was substantially composed of a melamine resin. For toners A to D, G, and H, good results were obtained in all evaluations of image density, toner scattering, toner adhesion (specifically, toner adhesion to the photosensitive drum), and minimum fixing temperature. .

  In the toner E (toner according to Comparative Example 1), the evaluation results of the image density and the toner scattering were worse than those of the toners according to Examples 1 to 6. In the toner E, it is presumed that the charge amount of the toner at the time of toner replenishment is insufficient because the resin powder B-3 (external additive) is embedded in the toner base particles and the chargeability of the toner particles is reduced. In addition, since the resin powder does not function as a spacer, the toner particles are likely to be excessively charged (charged up), and it is assumed that the developability of the toner is lowered. As the particle diameter of the resin powder becomes smaller, the resin powder tends to be embedded in the toner base particles.

  In the toner F (toner according to Comparative Example 2), the evaluation result of the image density was poor as compared with the toners according to Examples 1 to 6. This is because in the toner F, the resin powder B-4 (external additive) is detached from the toner particles, the toner particles are easily charged excessively (charged up), and the developability of the toner is lowered. It is guessed. As the particle diameter of the resin powder increases, the resin powder tends to be detached from the toner particles.

  In the toner I (toner according to Comparative Example 3), resin powder E was used as an external additive, and the resin particles contained in the resin powder E were melamine resin particles. Toner I was inferior in low-temperature fixability as compared with toners according to Examples 1-6. The reason for this is presumed that in toner I, the external additive (melamine resin particles) substantially composed of a thermosetting resin hindered toner fixing (more specifically, deformation and melting of the toner). Is done.

  In the toner J (toner according to Comparative Example 4), the evaluation result of toner adhesion (specifically, toner adhesion to the photosensitive drum) was worse than the toner according to Examples 1 to 6. It is assumed that heat and pressure are applied to the resin powder F (external additive) by the movement (slip motion) of the cleaning blade on the photosensitive drum, and the resin powder F (external additive) adheres to the photosensitive drum. Is done. The resin particles contained in the resin powder F used in the toner J were not provided with a coat layer (resin film formed on the surface of the core), and thus are considered to have insufficient resistance to heat and pressure.

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

DESCRIPTION OF SYMBOLS 10 Toner particle 11 Toner mother particle 12 Resin particle 12a Thermoplastic core 12b Coat layer

Claims (6)

A resin powder comprising a plurality of resin particles comprising a core and a coating layer formed on the surface of the core,
The core is substantially composed of a thermoplastic resin;
The number average primary particle diameter of the core in the plurality of resin particles is 50 nm or more and 120 nm or less,
The coating layer is a resin powder substantially composed of a melamine resin.   The resin powder according to claim 1, wherein the thermoplastic resin constituting the core includes at least one of a repeating unit derived from a hydroxyl group-containing monomer and a repeating unit derived from an amide group-containing monomer.   The resin powder according to claim 1 or 2, wherein the coat layer has a thickness of 1 nm or more and 12 nm or less. An electrostatic latent image developing toner comprising a plurality of toner particles comprising toner mother particles and an external additive attached to the surface of the toner mother particles,
The toner for developing an electrostatic latent image, wherein the toner particles include the resin powder according to claim 1 as the external additive.   The electrostatic latent image developing toner according to claim 4, wherein the toner particles further include inorganic particles as the external additive.   The electrostatic additive according to claim 5, wherein 10 wt% or more and 50 wt% or less of the external additive is the resin powder according to claim 1. Latent image developing toner.

Images