JP2019124804A - Positively-charged toner, image forming apparatus, and image forming method - Google Patents

Abstract

To provide a positively-charged toner, an image forming apparatus, and an image forming method with which the occurrence of electrostatic offset can be prevented without causing complication of the configuration of the image forming apparatus as much as possible.SOLUTION: A positively charged toner 1 includes toner particles each including a core 2 and a shell layer 3 formed on the surface of the core 2. The core 2 contains a binder resin and a negative charge control agent and does not contain a positive charge control agent. The shell layer 3 contains a positively charged material. The content of the negative charge control agent is preferably 1 pt.mass or more and 10 pts.mass or less based on 100 pts.mass of the binder resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positively chargeable toner, an image forming apparatus and an image forming method.

  In the electrophotographic method, the surface of an electrophotographic photosensitive member (hereinafter sometimes referred to as a photosensitive member) as an image carrier is charged and then exposed to form an electrostatic latent image on the photosensitive member. . Then, the electrostatic latent image is developed as a toner image by a developer, and the toner image is transferred to a recording medium. Next, the transferred toner image is heated and pressed by the fixing device to fix it on the recording medium.

  When the toner image is fixed on the recording medium, a phenomenon (electrostatic offset) in which the toner on the recording medium is electrostatically transferred to the heating unit of the fixing device may occur. In particular, when an image is formed using positively chargeable toner, electrostatic offset tends to occur easily.

  In order to suppress the occurrence of electrostatic offset, the image forming apparatus disclosed in Patent Document 1 adopts a configuration in which a bias is applied to peripheral members of the fixing device.

Unexamined-Japanese-Patent No. 2000-98673

  However, in the image forming apparatus disclosed in Patent Document 1, adopting a configuration in which a bias is applied to the peripheral members of the fixing device leads to complication of the configuration of the image forming apparatus and an increase in cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a positively chargeable toner capable of suppressing the occurrence of electrostatic offset without causing the complication of the configuration of the image forming apparatus as much as possible. An image forming method is provided.

  The positively chargeable toner according to the present invention comprises toner particles comprising a core and a shell layer formed on the surface of the core. The core contains a binder resin and a negative charge control agent, and does not contain a positive charge control agent. The shell layer contains a positively chargeable material.

  An image forming apparatus according to the present invention includes an image carrier, a developing device, a transfer device, and a fixing device. The developing device develops the electrostatic latent image formed on the surface of the image carrier as a toner image with a developer. The transfer device transfers the toner image to a recording medium. The fixing device fixes the transferred toner image on the recording medium. The developer contains the positively chargeable toner of the present invention.

  The image forming method according to the present invention includes development with a developer, transfer of a toner image, and fixing of a toner image. In the development with the developer, the electrostatic latent image formed on the surface of the image carrier is developed as a toner image by the developer containing the positively chargeable toner of the present invention. In the transfer of the toner image, the toner image is transferred to a recording medium. In fixing the toner image, the transferred toner image is fixed on the recording medium.

  According to the positively chargeable toner, the image forming apparatus, and the image forming method of the present invention, the occurrence of electrostatic offset can be suppressed without causing the complication of the configuration of the image forming apparatus as much as possible.

FIG. 2 is a view showing an example of the cross-sectional structure of toner particles contained in the positively chargeable toner according to the first embodiment of the present invention. It is a figure showing an example of composition of an image forming device concerning a 2nd embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described. The toner is an aggregate (for example, powder) of toner particles. The external additive is an aggregate (for example, powder) of external additive particles. If the evaluation results (values indicating shapes, physical properties, etc.) of powder (more specifically, powder of toner particles, etc.) are not specified at all, a considerable number of average particles are selected from the powder. , The number average of the values measured for each of the average particles.

If the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified at all, the Coulter principle (pore electrical resistance method) is made using “Coulter Counter Multisizer 4” manufactured by Beckman Coulter, Inc. It is the median diameter measured based on it. If the number average primary particle diameter of the powder is not specified at all, the number average of the circle equivalent diameter of the primary particles (diameter of a circle having the same area as the projected area of the primary particles) measured using a scanning electron microscope It is a value. The number average primary particle diameter of the powder is, for example, a number average value of circle equivalent diameters of 100 primary particles.

  The chargeability means the chargeability in triboelectric charge, unless specified. The strength of positive chargeability (or the strength of negative chargeability) in the frictional charge can be confirmed by a known charge train or the like. For example, the toner is triboelectrically charged by mixing with a standard carrier (anionic: N-01, cationic: P-01) provided by the Japan Imaging Association and stirring it. Before and after the triboelectric charging, for example, the surface potential of the measuring object is measured with a KFM (Kelvin probe force microscope), and it is shown that the larger the change of the electric potential before and after the triboelectric charging, the stronger the chargeability.

  The negative charge control agent is a component different from the binder resin. For example, the negative charge control agent can be contained in the core to enhance the negative chargeability of the core. The positive charge control agent is a component different from the binder resin. For example, the positive charge control of the core can enhance the positive chargeability of the core.

  The term "main component" of a material means, unless otherwise specified, the component that is most abundant in the material on a mass basis.

  Hereinafter, “system” may be added after the compound name to generically generically refer to the compound and its derivative. When a “system” is added after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacrylic may be generically called "(meth) acrylic" generically. Acrylonitrile and methacrylonitrile may be generically called "(meth) acrylonitrile" generically.

First Embodiment Positively Chargeable Toner
The positively chargeable toner according to the first embodiment (hereinafter, may be simply referred to as toner) may be suitably used, for example, for developing an electrostatic latent image. The toner according to the first embodiment may be used as a one-component developer. Alternatively, the toner and the carrier may be mixed using a mixing device (for example, a ball mill) and used as a two-component developer.

  The toner according to the first embodiment includes toner particles including a core and a shell layer formed on the surface of the core. The core contains a binder resin and a negative charge control agent, and does not contain a positive charge control agent. The core may optionally contain an internal additive other than the negative charge control agent (eg, at least one of a colorant, a release agent, and a magnetic powder). The shell layer contains a positively chargeable material. The positively chargeable material is, for example, a material that positively charges the shell layer (and thus the toner particles) by the friction between the carrier and the shell layer. The shell layer may cover the entire surface of the core or may partially cover the surface of the core, but in order to maintain the positive chargeability of the toner well, the shell layer It is preferred to cover the entire surface. The shell layer may be substantially composed of a thermosetting resin, may be composed substantially of a thermoplastic resin, or may contain both a thermosetting resin and a thermoplastic resin. . In addition, as a constituent material of the shell layer, a resin to which an additive (for example, a positive charge control agent) is added may be used.

  The toner particles contained in the toner according to the first embodiment may include an external additive. When the toner particles include an external additive, the toner particles include toner base particles having a core and a shell layer, and an external additive. The external additive adheres to the surface of the toner base particle (for example, the surface of the shell layer). If necessary, external additives may be omitted. When the external additive is omitted, toner base particles correspond to toner particles.

  By providing the above-described configuration, the toner according to the first embodiment can suppress the occurrence of electrostatic offset without causing complication of the configuration of the image forming apparatus as much as possible. The reason is presumed as follows.

  The toner particles contained in the toner according to the first embodiment have a core containing a negative charge control agent and not containing a positive charge control agent. Therefore, when the fixing device heats and presses the toner image, the negative charge control agent contained in the core of the toner particles is exposed. Since the surface layer portion of the heating unit of the fixing device usually contains a negatively chargeable resin such as a fluorocarbon resin, when the toner according to the first embodiment is fixed, the exposed negative charge control agent and the surface of the heating unit Tends to repel electrostatically. Thus, it is considered that the toner according to the first embodiment can suppress the occurrence of electrostatic offset. Further, by using the toner according to the first embodiment, the occurrence of electrostatic offset can be suppressed without changing the configuration of the image forming apparatus. Therefore, the configuration of the image forming apparatus can be prevented from being complicated. In addition, in the toner according to the first embodiment, since the shell layer contains a positively chargeable material, even when the core contains a negative charge control agent, the positively chargeability can be maintained at the time of formation of the toner image.

  Hereinafter, the details of the toner according to the first embodiment will be described with reference to the drawings as appropriate.

[Toner particle composition]
The configuration of the toner particles contained in the toner according to the exemplary embodiment will be described below with reference to FIG. FIG. 1 is a view showing an example of the cross-sectional structure of toner particles contained in the toner according to the present embodiment. For ease of explanation, the case where the toner particle 1 shown in FIG. 1 is a toner particle without an external additive will be described.

  As shown in FIG. 1, the toner particle 1 includes a core 2 and a shell layer 3 formed on the surface of the core 2. The core 2 contains a binder resin and a negative charge control agent, and does not contain a positive charge control agent. The shell layer 3 contains a positively chargeable material. The shell layer 3 may be composed of only a positively chargeable material, and is composed of a mixture of a positively chargeable material and another material (more specifically, a resin etc. having no positively chargeability). It may be When a mixture of a positively chargeable material and another material is used as a constituent material of the shell layer 3, in order to maintain the positive chargeability of the toner particles 1 well, the positively chargeable material in the mixture material is used. The content is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

  In order to obtain a toner suitable for image formation, the thickness of the shell layer 3 is preferably 1 nm or more and 400 nm or less. The thickness of the shell layer 3 can be measured by analyzing a TEM (transmission electron microscope) image of the cross section of the toner particle 1 using commercially available image analysis software (for example, "WinROOF" manufactured by Mitani Corporation). . When the thickness of the shell layer 3 is not uniform in one toner particle 1, four straight lines are drawn at regular intervals (specifically, two straight lines orthogonal to each other at the approximate center of the cross section of the toner particle 1) The thickness of the shell layer 3 is measured at each of four points where two straight lines intersect the shell layer 3, and the arithmetic mean of the four measured values obtained is the evaluation value of the toner particle 1 (shell layer 3) Thickness). The boundary between the core 2 and the shell layer 3 can be confirmed, for example, by selectively staining only the shell layer 3 among the core 2 and the shell layer 3. When the boundary between the core 2 and the shell layer 3 is unclear in the TEM image, the features included in the shell layer 3 in the TEM image by combining the TEM and electron energy loss spectroscopy (EELS) It is possible to clarify the boundary between the core 2 and the shell layer 3 by performing the elemental mapping.

In order to obtain a toner suitable for image formation, the volume median diameter (D ₅₀ ) of the toner particles 1 is preferably 4 μm or more and 9 μm or less.

  The toner according to the present embodiment may contain toner particles other than the toner particles 1. In the toner according to the exemplary embodiment, in order to further suppress the occurrence of electrostatic offset, the total content of toner particles 1 in all toner particles is preferably 80% by mass or more, and 90% by mass or more Is more preferable, and 100% by mass is particularly preferable.

  As mentioned above, although an example of the toner particle contained in the toner concerning this embodiment was explained, referring to Drawing 1, the present invention is not limited to this. For example, toner particles contained in the toner according to the present invention may be provided with an external additive (not shown). For example, the toner particles 1 shown in FIG. 1 may be used as toner base particles, and toner particles having an external additive attached to the surface of the toner base particles may be used as toner particles contained in the toner according to the present invention.

[Element of toner particle]
Next, elements of toner particles included in the toner according to the exemplary embodiment will be described.

(Binder resin)
In the core, the binder resin occupies most of the components (for example, 70% by mass or more). Therefore, it is considered that the properties of the binder resin greatly affect the properties of the entire core. The properties (more specifically, the acid value etc.) of the binder resin can be adjusted by combining and using a plurality of resins as the binder resin.

  In order to improve the low-temperature fixability of the toner, the core preferably contains a thermoplastic resin as a binder resin, and the thermoplastic resin may be contained in a proportion of 85% by mass or more of the entire binder resin. preferable. Examples of the thermoplastic resin include styrene resins, acrylic ester resins (more specifically, acrylic ester polymers, methacrylic acid ester polymers, etc.), olefin resins (more specifically, polyethylene resins) Polypropylene resin etc., vinyl resin (more specifically, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin etc), polyester resin, polyamide resin, and urethane resin. In addition, copolymers of these resins, that is, copolymers in which an arbitrary repeating unit is introduced into the above resin (more specifically, styrene-acrylate resin, styrene-butadiene resin, etc.) are also included. It can be used as a binder resin.

  The thermoplastic resin is obtained by addition polymerization, copolymerization or condensation polymerization of one or more thermoplastic monomers. The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization (more specifically, an acrylic ester monomer, a styrenic monomer, etc.), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, condensation polymerization) (Combination of polyhydric alcohol and polyhydric carboxylic acid) to become a polyester resin by

  In order to further suppress the occurrence of electrostatic offset, as the binder resin, a polyester resin and a styrene-acrylic acid alkyl ester resin are preferable, and a polyester resin is more preferable.

  The polyester resin is obtained by condensation polymerization of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. Examples of the alcohol for synthesizing the polyester resin include dihydric alcohols (more specifically, diols, bisphenols and the like) and alcohols having a trivalent or higher as shown below. Examples of carboxylic acids for synthesizing a polyester resin include divalent carboxylic acids and trivalent or higher carboxylic acids as shown below. In place of the polyvalent carboxylic acid, polyvalent carboxylic acid derivatives capable of forming an ester bond by condensation polymerization of polyvalent carboxylic acid anhydride, polyvalent carboxylic acid halide and the like may be used.

  Preferred examples of the 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, 2-pentene-1,5-diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, 1,4-benzenediol, polyethylene glycol, polypropylene And glycol and polytetramethylene glycol.

  Preferred examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

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

  Preferred examples of the divalent carboxylic acid include 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 (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, iso dodecyl succinic acid, etc.), and alkenyl succinic acid (more specific) And n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid and the like).

  Preferred examples of trivalent or higher carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylene carboxyl) Methane, 1,2,7,8-octane tetracarboxylic acid, pyromellitic acid, and Empol trimer acid can be mentioned.

  The styrene-acrylic acid alkyl ester resin is a copolymer of one or more styrene monomers and one or more acrylic acid alkyl ester monomers. As a monomer for synthesizing a styrene-acrylic acid alkyl ester-based resin, for example, a styrene-based monomer and an acrylic acid alkyl ester-based monomer as shown below can be suitably used.

  Preferred examples of styrenic monomers include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyl toluene, and p-ethylstyrene.

  Preferred examples of acrylic acid alkyl ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. Can be mentioned.

  In order to further suppress the occurrence of electrostatic offset, a styrene-butyl acrylate copolymer is preferred as the styrene-acrylic acid alkyl ester resin.

(Colorant)
The core may contain a colorant. As the colorant, known pigments or dyes may be used in accordance with 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.

  The core may contain a black colorant. Examples of black colorants include carbon black. The black colorant may be a colorant toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The core may contain a color colorant. Color colorants include yellow colorants, magenta colorants, and cyan colorants.

  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 yellow colorants include C.I. I. Pigment yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 and 194), Naphthol Yellow S, Hansa Yellow G, and C.I. I. Bat yellow is mentioned.

  The magenta colorant is selected, for example, from the group consisting of condensation 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 magenta colorants include C.I. I. Pigment red (2, 3, 5, 6, 7, 19, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 , 184, 185, 202, 206, 220, 221 and 254).

  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 and 66), phthalocyanine blue, C.I. I. Bat blue, and C.I. I. Acid Blue is mentioned.

(Release agent)
The core may contain a release agent. The release agent is used, for example, for the purpose of improving the hot offset resistance of the toner. In order to improve the hot offset resistance of the toner, the amount of the release agent 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.

  Examples of mold release agents include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax and Fischer Tropsch wax; oxidized polyethylene wax, oxidized polyethylene wax Oxides of aliphatic hydrocarbon waxes such as block copolymers; plant waxes such as candelilla wax, carnauba wax, wax wax, jojoba wax, rice wax; animal waxes such as beeswax, lanolin, spermaceti; Mineral waxes such as ozokerite, ceresin, petrolatum, etc .; ester waxes composed mainly of fatty acid esters such as montanic acid ester wax, castor wax; wax from which some or all of the fatty acid esters have been deoxidized Box (e.g., deoxidized carnauba wax) can be preferably used. In the present embodiment, one type of release agent may be used alone, or a plurality of types of release agents may be used in combination.

(Negative charge control agent)
The core contains a negative charge control agent. Examples of negative charge control agents include metal-containing azo dyes, sulfo group-containing resins, oil-soluble dyes, naphthenic acid metal salts, acetylacetone metal complexes, salicylic acid metal complexes, boron compounds, fatty acid soaps, and long chain alkyl carboxylates. Can be mentioned. In the present embodiment, one of these negative charge control agents can be used alone or in combination of two or more. In order to further suppress the occurrence of electrostatic offset, as the negative charge control agent, one or more negative charge control agents selected from the group consisting of metal-containing azo dyes and sulfo group-containing resins are preferable.

  In order to further suppress the occurrence of electrostatic offset, the content of the negative charge control agent is preferably 1 part by mass or more with respect to 100 parts by mass of the binder resin. Further, in order to maintain the positive chargeability of the toner particles favorably, the content of the negative charge control agent is preferably 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Magnetic powder)
The core may contain magnetic powder. As the material of the magnetic powder, for example, ferromagnetic metals (more specifically, iron, cobalt, nickel etc.) and alloys thereof, ferromagnetic metal oxides (more specifically, ferrite, magnetite, chromium dioxide etc.) And materials subjected to a ferromagnetic treatment (more specifically, heat treatment and the like). In the present embodiment, one type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

(Shell layer)
The shell layer contains a positively chargeable material. The positively chargeable material includes, for example, a thermosetting nitrogen-containing resin, a thermoplastic resin containing a quaternary ammonium cation group, and a positive charge control agent. In order to easily form the shell layer while maintaining the positive chargeability of the toner particles well, as the positively chargeable material, a thermosetting nitrogen-containing resin and a thermoplastic resin containing a quaternary ammonium cation group are used. preferable.

  The thermosetting nitrogen-containing resin is a resin containing nitrogen atoms in the chemical structure among thermosetting resins. As a thermosetting nitrogen-containing resin, a urea resin, a melamine resin, and a benzoguanamine resin are mentioned, for example. As the thermosetting nitrogen-containing resin, a melamine resin and a urea resin are preferable, and a urea resin is more preferable, in order to maintain the positive chargeability of the toner particles.

Examples of thermoplastic resins containing quaternary ammonium cation groups include polymers of vinyl compounds containing quaternary ammonium cation groups, and copolymers of vinyl compounds containing quaternary ammonium cation groups with other vinyl compounds. . The vinyl compound is a compound having a vinyl group (CH ₂ CHCH—) or a group in which hydrogen in the vinyl group is substituted (more specifically, ethylene, propylene, butadiene, vinyl chloride, (meth) acrylic) Acid, methyl (meth) acrylate, (meth) acrylonitrile, styrene and the like). A vinyl compound can be added to a polymer (resin) by addition polymerization through a carbon-carbon double bond (C = C) contained in the above-mentioned vinyl group and the like.

  Examples of the vinyl compound containing a quaternary ammonium cation group include vinylbenzyl trialkyl ammonium salt, 2- (acryloyloxy) ethyl trialkyl ammonium salt, and 2- (methacryloyloxy) ethyl trialkyl ammonium salt.

  Examples of the vinylbenzyl trialkyl ammonium salt include vinyl benzyl trimethyl ammonium salt (more specifically, vinyl benzyl trimethyl ammonium chloride and the like), vinyl benzyl triethyl ammonium salt (more specifically, vinyl benzyl triethyl ammonium chloride and the like), Vinyl benzyl dimethyl ethyl ammonium salt (more specifically, vinyl benzyl dimethyl ethyl ammonium chloride etc.), vinyl benzyl dimethyl isopropyl ammonium salt (more specifically, vinyl benzyl dimethyl isopropyl ammonium chloride etc.), vinyl benzyl n-butyl dimethyl Ammonium salts (more specifically, vinyl benzyl n-butyldimethyl ammonium chloride and the like), and vinyl benzyl dimethyl (More specifically, vinylbenzyl dimethylpentyl ammonium chloride and the like) emissions chill ammonium salts.

  Examples of 2- (acryloyloxy) ethyltrialkylammonium salts include 2- (acryloyloxy) ethyltrimethylammonium salts (more specifically, 2- (acryloyloxy) ethyltrimethylammonium chloride etc.), 2- (acryloyloxy) ethyltrimethylammonium salts, etc. ) Ethyldimethylethylammonium salt (more specifically, 2- (acryloyloxy) ethyldimethylethylammonium chloride etc.), 2- (acryloyloxy) ethyltriethylammonium salt (more specifically, 2- (acryloyloxy) Ethyltriethylammonium chloride and the like), and 2- (acryloyloxy) ethyldimethyl n-pentylammonium salt (more specifically, 2- (acryloyloxy) ethyldimethyl n-pentylammonium Roraido, etc.) and the like.

  Examples of 2- (methacryloyloxy) ethyltrialkylammonium salts include 2- (methacryloyloxy) ethyltrimethylammonium salts (more specifically, 2- (methacryloyloxy) ethyltrimethylammonium chloride etc.), 2- (methacryloyloxy) ethyltrialkylammonium salts, etc. ) Ethyldimethylethyl ammonium salt (more specifically, 2- (methacryloyloxy) ethyl dimethyl ethyl ammonium chloride etc.), and 2- (methacryloyloxy) ethyl dimethyl n-pentyl ammonium salt (more specifically (Methacryloyloxy) ethyldimethyl n-pentyl ammonium chloride and the like).

  Examples of other vinyl compounds copolymerizable with the vinyl compound containing quaternary ammonium cation group include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, and the like. , 4-Dimethylstyrene, p-t-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, styrene such as p-n-dodecylstyrene Compound (C): methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate ( T-Butyl acrylate, n-octyl (meth) acrylate, 2-ethyl (meth) acrylate Sil, (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate compounds phenyl acrylate; and (meth) acrylonitrile; (meth) acrylic acid. The vinyl compound containing a quaternary ammonium cation group may be copolymerized with one of these other vinyl compounds, and may be copolymerized with two or more of these other vinyl compounds.

  When the positively chargeable material contained in the shell layer is a positive charge control agent, examples of usable positive charge control agents include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,1 4-oxazine, 1,2-thiazine, 1,3-thiazine, 1,4-thiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,3, 4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2, An azine compound such as 4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline, etc .; Direct dyes such as Stread FC, Adin Fast Red 12 Bk, Azine Violet BO, Azine Brown 3 G, Azine Light Brown GR, Azine Dark Green BH / C, Azine Deep Black EW, Azine Deep Black 3 RL, etc. Nigrosine BK, Nigrosine NB, Acid dyes such as nigrosine Z; metal salts of naphthenic acid; metal salts of higher organic carboxylic acids; alkoxylated amines; alkylamides; benzyl decyl hexyl methyl ammonium chloride, decyl trimethyl ammonium chloride, 2- (methacryloyloxy) ethyl trimethyl ammonium chloride And quaternary ammonium salts such as dimethylaminopropyl acrylamide methyl chloride quaternary salt.

(External additive)
The toner particles may be provided with an external additive. When the toner particles include an external additive, the toner particles include toner base particles having a core and a shell layer, and an external additive. In order to improve the flowability or handleability of the toner, the amount of the external additive is preferably 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles.

  As external additive particles, inorganic particles are preferable, and particles of silica particles and metal oxides (more specifically, particles of alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are more preferable. preferable. In the present embodiment, one type of external additive particles may be used alone, or a plurality of types of external additive particles may be used in combination.

  The external additive particles may be surface treated. For example, when silica particles are used as the external additive particles, the surface treatment agent may impart hydrophobicity and / or positive chargeability to the surface of the silica particles. As the surface treatment agent, for example, a coupling agent (more specifically, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, etc.), a silazane compound (more specifically, a chain silazane compound, Cyclic silazane compounds and the like) and silicone oils (more specifically, dimethyl silicone oils and the like) can be mentioned. As a surface treatment agent, a silane coupling agent and a silazane compound are particularly preferable. Preferred examples of the silane coupling agent include silane compounds (more specifically, methyltrimethoxysilane, aminosilane and the like). Preferred examples of silazane compounds include HMDS (hexamethyldisilazane). When the surface of a silica substrate (untreated silica particles) is treated with a surface treatment agent, a large number of hydroxyl groups (-OH) present on the surface of the silica substrate are partially or entirely derived from the surface treatment agent It is substituted by a functional group. As a result, silica particles having a functional group derived from the surface treatment agent (specifically, a functional group that is more hydrophobic and / or more positively charged than a hydroxyl group) can be obtained.

(Combination of materials)
In order to further suppress the occurrence of electrostatic offset, it is preferable that the binder resin of the core and the constituent material of the shell layer be any one of combination examples 1 to 4 shown in Table 1 below.

[Method of producing toner]
Next, a preferred method of manufacturing the toner according to the first embodiment will be described. The present manufacturing method comprises a core preparation step and a shell layer formation step. In addition, the present manufacturing method may further include an external addition step described later after the step of forming the shell layer.

(Core preparation process)
In the core preparation step, the core is prepared, for example, by a grinding method or an aggregation method.

  In one example of the grinding method, first, a binder resin, a negative charge control agent, and other internal additives, which are optionally added, 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 crushed and classified. This gives the core.

  In one example of the aggregation method, first, in the aqueous medium containing the fine particles of each of the binder resin, the negative charge control agent, and the other internal additives optionally added, Aggregate until it reaches Thereby, aggregated particles containing a binder resin and the like are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. This gives the core.

(Step of forming shell layer)
Then, a shell layer is formed on the surface of the core. Examples of the method for forming the shell layer include in-situ polymerization, in-liquid curing coating, and coacervation. Preferred specific examples include the following methods.

  First, in an aqueous medium, a material for forming a shell layer containing a positively chargeable material (for example, a shell material containing a monomer that forms a positively chargeable material) and the core obtained by the above-described method are placed. Then, the polymerization reaction of the shell material is advanced to form a shell layer on the surface of the core by heating the aqueous medium containing the shell material and the core.

(External addition process)
In this production method, the particles obtained in the shell layer forming step (specifically, the particles including the core and the shell layer formed on the surface of the core) are used as toner base particles, and the toner base particles are You may further comprise the process (external addition process) which makes an additive adhere. As a method of attaching the external additive to the surface of the toner base particles, the external additive is added to the surface of the toner base particles by, for example, mixing the toner base particles and the external additive particles while stirring using a mixing device. The method of making agent particles adhere can be mentioned.

  According to the manufacturing method described above, a positively chargeable toner containing toner particles including a core containing a binder resin and a negative charge control agent and a shell layer containing a positively chargeable material formed on the surface of the core is obtained. Be

Second Embodiment Image Forming Apparatus
Next, an image forming apparatus according to a second embodiment of the present invention will be described. FIG. 2 is a view showing the configuration of an image forming apparatus 100 which is an example of the image forming apparatus according to the second embodiment. The image forming apparatus 100 is a printer that forms an image on a sheet P as a recording medium. The image forming apparatus 100 includes a feeding unit 10, a conveyance unit 20, an image forming unit 30, and a discharge unit 80.

  The feeding unit 10 includes a cassette 11 that accommodates a plurality of sheets P. The sheet P is, for example, a sheet made of paper or synthetic resin. The feeding unit 10 feeds the sheet P to the conveyance unit 20. The conveyance unit 20 conveys the sheet P to the image forming unit 30. The image forming unit 30 forms an image on the sheet P. The transport unit 20 transports the sheet P on which the image is formed to the discharge unit 80. The discharge unit 80 discharges the sheet P to the outside of the image forming apparatus 100.

  The image forming unit 30 includes an exposure unit 32, a first toner image generation unit 34A, a second toner image generation unit 34B, a third toner image generation unit 34C, a fourth toner image generation unit 34D, a first toner cartridge 36A, a second A toner cartridge 36 B, a third toner cartridge 36 C, a fourth toner cartridge 36 D, an intermediate transfer belt 62, a secondary transfer roller 64, and a fixing device 70 are provided. Here, the image forming apparatus 100 is a tandem type, and the first toner image forming unit 34A, the second toner image forming unit 34B, the third toner image forming unit 34C, and the fourth toner image forming unit 34D are linearly arranged. ing.

  In the following description of the present specification, the first to fourth toner image forming units 34A to 34D may be simply referred to as toner image forming units 34A to 34D in order to avoid redundancy. Similarly, the first to fourth toner cartridges 36A to 36D may be simply referred to as toner cartridges 36A to 36D.

  The exposure unit 32 irradiates light based on image data to each of the toner image generation units 34A to 34D, and forms an electrostatic latent image on each of the toner image generation units 34A to 34D.

  The toner image forming unit 34A forms a yellow toner image based on the electrostatic latent image. The toner image forming unit 34B forms a cyan toner image based on the electrostatic latent image. The toner image forming unit 34C forms a magenta toner image based on the electrostatic latent image. The toner image forming unit 34D forms a black toner image based on the electrostatic latent image.

  The toner cartridge 36A has toner for forming a yellow toner image. The toner cartridge 36B has toner for forming a cyan toner image. The toner cartridge 36C has toner for forming a magenta toner image. The toner cartridge 36D has toner for forming a black toner image. The toners included in the toner cartridges 36A to 36D are all toners according to the first embodiment described above.

  The intermediate transfer belt 62 rotates in the arrow R1 direction. The toner images of four colors are sequentially transferred from the toner image forming units 34A to 34D to the outer surface of the intermediate transfer belt 62 (primary transfer step). The secondary transfer roller 64 transfers the toner image formed on the outer surface of the intermediate transfer belt 62 to the sheet P (secondary transfer step). The fixing device 70 heats and presses the sheet P to fix the toner image on the sheet P.

  Each of the toner image forming units 34A to 34D includes a photosensitive drum 40 (image carrier), a charging device 42, a developing device 50, a primary transfer roller 44, a charge removing device 46, and a cleaner 48. In each of the toner image forming units 34A to 34D, the charging device 42, the developing device 50, the primary transfer roller 44, the charge removing device 46, and the cleaner 48 are arranged in order along the circumferential surface of the photosensitive drum 40.

  The photosensitive drums 40 of the toner image forming units 34A to 34D are disposed along the arrow R1 direction, which is the rotational direction of the intermediate transfer belt 62, so as to abut on the outer surface of the intermediate transfer belt 62. The plurality of primary transfer rollers 44 is provided corresponding to each of the plurality of photosensitive drums 40, and faces each of the plurality of photosensitive drums 40 via the intermediate transfer belt 62.

  The photosensitive drum 40 rotates in the direction of arrow R2. The charging device 42 charges the circumferential surface of the photosensitive drum 40. Light is irradiated by the exposure unit 32 on the circumferential surface of the photosensitive drum 40 to form an electrostatic latent image.

  The photosensitive drum 40 is not particularly limited, and, for example, a photosensitive member provided with a photosensitive layer containing amorphous silicon or a photosensitive member provided with a photosensitive layer containing an organic photoconductor can be used.

  The developing device 50 has a two-component developer including, for example, a toner and a carrier. The developing devices 50 in the toner image forming units 34A to 34D are connected to the corresponding toner cartridges 36A to 36D. The toner in each developing device 50 is supplied from the corresponding toner cartridges 36A to 36D. The carrier may be accommodated only in the developing device 50, or may be accommodated in both of the toner cartridges 36A to 36D and the developing device 50. In the latter case, the toner cartridges 36A to 36D may supply both the toner and the carrier to the corresponding developing device 50.

  The developing device 50 includes a developing roller 52. The developing roller 52 carries a two-component developer including, for example, a toner and a carrier. For this reason, the developing roller 52 functions as a developer carrier. The developing roller 52 supplies the toner of the carried developer to the photosensitive drum 40. The developing device 50 causes toner to adhere to the electrostatic latent image on the photosensitive drum 40 to develop the electrostatic latent image and form a toner image on the circumferential surface of the photosensitive drum 40.

  The primary transfer roller 44 transfers the toner image carried on the photosensitive drum 40 to the outer surface of the intermediate transfer belt 62. The charge removing device 46 removes the charge on the circumferential surface of the photosensitive drum 40 after the toner image is transferred to the intermediate transfer belt 62. The cleaner 48 removes the developer remaining on the circumferential surface of the photosensitive drum 40.

  The toner image transferred to the outer surface of the intermediate transfer belt 62 is transferred to the sheet P by the secondary transfer roller 64 (transfer device). The sheet P on which the toner image has been transferred is conveyed by the conveyance unit 20 to the fixing device 70. The fixing device 70 includes a pressure roller 72 for pressing the toner image transferred to the sheet P, and a fixing belt 74 (heating unit) for heating the toner image transferred to the sheet P. As the fixing belt 74, for example, a fixing belt provided with a surface layer portion containing a fluorine resin can be used. Examples of the fluorine resin constituting the surface portion of the fixing belt 74 include polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). A fixing roller may be used instead of the fixing belt 74. The sheet P conveyed to the fixing device 70 is heated and pressed between the pressure roller 72 and the fixing belt 74. Thereby, the toner image (image) is fixed to the sheet P. Thereafter, the sheet P is discharged from the discharge unit 80 to the outside of the image forming apparatus 100. As described above, the image forming apparatus 100 forms an image on the sheet P.

  The image forming apparatus 100 forms an image using the toner according to the first embodiment. As described above, the toner according to the first embodiment can suppress the occurrence of electrostatic offset without causing complication of the configuration of the image forming apparatus as much as possible. Therefore, according to the image forming apparatus 100, the occurrence of electrostatic offset can be suppressed without causing complication of the apparatus configuration as much as possible.

  The example of the image forming apparatus according to the second embodiment has been described above, but the image forming apparatus according to the second embodiment is not limited to the image forming apparatus 100 described above. For example, the image forming apparatus according to the second embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus may have, for example, one toner image generation unit and one toner cartridge. The image forming apparatus according to the second embodiment may adopt a direct transfer method. When the image forming apparatus according to the second embodiment adopts the direct transfer method, the transfer device directly transfers the toner image on the photosensitive drum (image carrier) to the recording medium.

Third Embodiment Image Forming Method
Next, an image forming method according to a third embodiment of the present invention will be described. The image forming method according to the third embodiment is, for example, a method of forming an image using the image forming apparatus according to the second embodiment described above. Hereinafter, a preferable example of the image forming method according to the third embodiment will be described.

  A preferable example of the image forming method according to the third embodiment includes development with a developer, transfer of a toner image, and fixing of a toner image. In the development with the developer, the electrostatic latent image formed on the surface of the image carrier (for example, the photosensitive drum 40 shown in FIG. 2) is developed by the developer containing the toner according to the first embodiment described above. Develop as. In transfer of a toner image, the toner image is transferred to a recording medium (for example, a sheet P shown in FIG. 2). In fixing the toner image, the transferred toner image is fixed on a recording medium (for example, the sheet P shown in FIG. 2).

  A preferred example of the image forming method according to the third embodiment uses the developer containing the toner according to the first embodiment described above, and thus the configuration of the image forming apparatus is complicated for the same reason as the image forming apparatus 100. It is possible to suppress the occurrence of electrostatic offset without causing as much as possible.

  Hereinafter, examples of the present invention will be described.

<Fabrication of core>
[Preparation of core CA-1]
100 parts by mass of a polyester resin ("Mixing Chemical Co., Ltd." XPE 258 ") as a binder resin in an FM mixer (" FM-20B "manufactured by Japan Coke Industry Co., Ltd.) and a polypropylene wax (Sanyo Chemical Co., Ltd.) as a release agent 5 parts by mass of "660P" manufactured by company, 5 parts by mass of carbon black ("REGAL (registered trademark) 330R" manufactured by Cabot) as a colorant, and a sulfo group-containing resin as a negative charge control agent (Fujikura Kasei Co., Ltd. 10 parts by mass of “FCA-1002NS”) was added, and mixed for 3 minutes at a rotation speed of 2400 rpm. Subsequently, the obtained mixture was melt-kneaded using a twin-screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.) at a material supply rate of 5 kg / hour, a shaft rotational speed of 150 rpm, and a cylinder temperature of 150 ° C. . Thereafter, the obtained melt-kneaded product was cooled. Subsequently, the cooled melt-kneaded product was roughly pulverized using a pulverizer (“Rotoplex (registered trademark)” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized material was finely pulverized using a jet mill ("Ultrasonic jet mill I type" manufactured by Nippon Pneumatic Mfg. Co., Ltd.). Subsequently, the obtained pulverized material was classified using a classifier ("Elbow Jet EJ-LABO type" manufactured by Nittetsu Mining Co., Ltd.). As a result, a core CA-1 having a volume median diameter (D ₅₀ ) of 7.0 μm was obtained.

[Preparation of core CA-2]
Core CA-1 except that 100 parts by mass of styrene-butyl acrylate copolymer ("CPR300" manufactured by Mitsui Chemicals, Inc.) was used instead of 100 parts by mass of polyester resin ("XPE258" manufactured by Mitsui Chemicals, Inc.) Core CA-2 was produced by the method similar to production of <1>. The volume median diameter (D ₅₀ ) of core CA-2 was 7.0 μm.

[Preparation of core CA-3]
Metal-containing azo dye ("BONTRON (registered trademark) S-31", negative charge control agent) (Orient Chemical Industry Co., Ltd.) 10 instead of 10 parts by mass of a sulfo group-containing resin ("FCA-1002 NS" manufactured by Fujikura Kasei Co., Ltd.) 10 Core CA-3 was produced by the same method as production of core CA-1 except having used a mass part. The volume median diameter (D ₅₀ ) of core CA-3 was 7.0 μm.

[Preparation of core CA-4]
Metal-containing azo dye ("BONTRON (registered trademark) S-34", negative charge control agent) (Orient Chemical Industry Co., Ltd.) 10 instead of 10 parts by mass of a sulfo group-containing resin ("FCA-1002 NS" manufactured by Fujikura Kasei Co., Ltd.) 10 Core CA-4 was produced by the same method as production of core CA-1 except having used a mass part. The volume median diameter (D ₅₀ ) of core CA-4 was 7.0 μm.

[Preparation of core CA-5]
Core CA-5 was produced by the method similar to production of core CA-1 except having changed the usage-amount of sulfo group containing resin ("FCA-1002NS" by Fujikura Kasei Co., Ltd.) into 1 mass part. The volume median diameter (D ₅₀ ) of core CA-5 was 7.0 μm.

[Preparation of core CA-6]
Core CA-6 was produced by the method similar to production of core CA-1 except having changed the amount of sulfo group containing resin ("FCA-1002NS" by Fujikura Kasei Co., Ltd.) used into 5 mass parts. The volume median diameter (D ₅₀ ) of core CA-6 was 7.0 μm.

[Preparation of core CB-1]
10 quaternary ammonium salt ("BONTRON (registered trademark) P-51", positive charge control agent), instead of 10 parts by mass of a sulfo group-containing resin ("FCA-1002 NS", manufactured by Fujikura Kasei Co., Ltd.) 10 Core CB-1 was produced by the same method as production of core CA-1 except having used a mass part. The volume median diameter (D ₅₀ ) of core CB-1 was 7.0 μm.

[Preparation of core CB-2]
Core CB-2 was produced by the method similar to production of core CA-1, except not having used sulfo group content resin ("FCA-1002NS" by Fujikura Kasei Co., Ltd.). The volume median diameter (D ₅₀ ) of core CB-2 was 7.0 μm.

[Preparation of core CB-3]
Instead of 10 parts by mass of a sulfo group-containing resin ("FCA-1002 NS" manufactured by Fujikura Kasei Co., Ltd.), 5 parts by mass of a quaternary ammonium salt ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Industry Co., Ltd.) Core CB-3 was produced by the method similar to production of core CA-1 except having used 5 mass parts of group content resin ("FCA-1002NS" by Fujikura Kasei Co., Ltd.). The volume median diameter (D ₅₀ ) of core CB-3 was 7.0 μm.

<Production of Toner>
[Production of Toner TA-1]
First, a shell layer was formed on the surface of core CA-1. Specifically, in a three-necked flask (volume: 1 L) equipped with a thermometer and a stirring blade, 100 g of core CA-1, 500 mL of ion exchanged water, and 50 g of sodium polyacrylate (dispersed by Toagosei Co., Ltd. Stabilizer "Jurimer (registered trademark) AC-103") and 1 g of methylolated urea ("Milben (registered trademark) resin SUM-100" manufactured by Showa Denko K. K.) were added. The pH of the contents of the flask was then adjusted to 4 by adding dilute hydrochloric acid to the flask. Next, while maintaining the temperature inside the flask at 70 ° C. using a temperature control tank, stirring was performed for 1 hour under the condition of a rotation speed of 100 rpm. As a result, the material of the shell layer (methylolated urea) undergoes a polymerization reaction on the surface of core CA-1, and a cationic (positively chargeable) shell layer composed of a urea resin is formed on the surface of core CA-1. The As a result, a dispersion containing toner mother particles MA-1 was obtained. Thereafter, the dispersion was cooled to normal temperature (25 ° C.).

  Next, the obtained dispersion liquid of toner base particles MA-1 is filtered (solid-liquid separation) using a Buchner funnel to obtain wet cake toner base particles MA-1. Next, the obtained wet cake toner base particles MA-1 were re-dispersed in ion exchange water and then filtered using a Buchner funnel. Further, redispersion and filtration were repeated five times to wash the toner base particles MA-1.

Subsequently, the obtained toner base particles MA-1 were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. Thereby, a slurry of toner base particles MA-1 was obtained. Subsequently, toner base particles MA in the slurry are produced using a continuous surface reforming apparatus ("Coatmizer (registered trademark)" manufactured by Freund Sangyo Co., Ltd.) at a hot air temperature of 45 ° C and a blower air volume of 2 m ³ / min. -1 was dried. As a result, a powder of toner mother particles MA-1 was obtained.

Then, 100 parts by mass of toner base particles MA-1 and 0.7 parts by mass using an FM mixer ("FM-10B" manufactured by Japan Coke Industry Co., Ltd.) at a rotational speed of 3500 rpm and a jacket temperature of 20 ° C. Silica particles ("AEROSIL (registered trademark) RA-200H" manufactured by Nippon Aerosil Co., Ltd., dry silica particles surface-modified with a trimethylsilyl group and an amino group, number average primary particle diameter: 12 nm), 1.0 part by mass of Conductive titanium oxide particles (Titanium Kogyo Co., Ltd. “EC-100”, base: titanium oxide particles, coating layer: Sb-doped SnO ₂ film, volume median diameter (D ₅₀ ): 0.35 μm), for 5 minutes Mixed. Thereby, the external additive (silica particles and conductive titanium oxide particles) was attached to the surface of the toner base particles MA-1. Subsequently, the obtained powder is sieved using a 300 mesh (48 μm mesh) sieve to obtain a positively chargeable toner TA-1.

[Production of Toner TA-7]
90 g of isobutanol, 100 g of methyl methacrylate, 35 g of butyl acrylate, and 2- (methacryloyloxy) ethyl in a 1 L three-necked flask equipped with a thermometer, a condenser, a nitrogen introduction pipe, and a stirring blade 30 g of trimethyl ammonium chloride (manufactured by Alfa Aesar) and 6 g of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] (“VA-086” manufactured by Wako Pure Chemical Industries, Ltd.) Put. Subsequently, the contents of the flask were reacted for 3 hours while maintaining the temperature in the flask at 80 ° C. under a nitrogen atmosphere. Thereafter, 3 g of 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] ("VA- 086" manufactured by Wako Pure Chemical Industries, Ltd.) is added to the flask, and the flask is The temperature in the flask was maintained at 80 ° C. and the contents of the flask were allowed to react for an additional 3 hours to obtain a polymer solution. The obtained polymer solution was dried under the conditions of a temperature of 150 ° C. and a pressure of 0.1 kPa. Subsequently, the dried polymer was crushed to obtain a positively chargeable resin PR-1.

  Subsequently, 200 g of the positively chargeable resin PR-1 and 184 mL of ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) are contained in a container of a mixing apparatus ("Hibismix (registered trademark) 2P-1 type" manufactured by Primix, Inc.) "Ethyl acetate special grade" was added. Subsequently, the contents of the container were stirred at a rotational speed of 20 rpm for 1 hour to obtain a highly viscous solution. Thereafter, an aqueous solution containing ethyl acetate or the like (specifically, 18 mL of 1 N hydrochloric acid and a cationic surfactant ("Cortamine (registered trademark) 24P" manufactured by Kao Corporation, component: lauryltrimethylammonium chloride in the obtained high viscosity solution) 20 g) and 16 g of ethyl acetate ("ethyl acetate special grade" manufactured by Wako Pure Chemical Industries, Ltd.) in 562 mL of deionized water was added. As a result, a suspension of positively chargeable resin fine particles (thermoplastic resin containing quaternary ammonium cation group) having a solid content concentration of 30% by mass (hereinafter, referred to as positively chargeable suspension) was obtained. The fine resin particles contained in the obtained positively chargeable suspension had a number average primary particle diameter of 35 nm and a zeta potential at pH 4 of 46 mV. The zeta potential was measured using an ultrasonic particle size distribution zeta potential measuring device ("DT-1200" manufactured by Dispersion Technology).

  Subsequently, a 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and 100 mL of deionized water was placed in the flask. Thereafter, while maintaining the temperature in the flask at 30 ° C. using a water bath, dilute hydrochloric acid was added to the flask to adjust the pH of the contents of the flask to 3. Subsequently, 30 g of the positively chargeable suspension obtained in the above-mentioned procedure was added to the flask. Subsequently, 300 g of core CA-1 (core CA-1 prepared in the above-mentioned procedure) was added to the flask, and the contents of the flask were stirred at a rotational speed of 200 rpm for 1 hour. Thereafter, 300 mL of ion exchanged water was added to the flask. Subsequently, the temperature in the flask was raised to 70 ° C. at a rate of 1 ° C./min while stirring the flask contents at a rotational speed of 100 rpm. Subsequently, the contents of the flask were stirred for 2 hours at a temperature of 70 ° C. and a rotational speed of 100 rpm. Subsequently, sodium hydroxide was added to the flask to adjust the pH of the contents of the flask to 7. Subsequently, the contents of the flask were cooled to a temperature of 25 ° C. to obtain a dispersion containing toner mother particles MA-7.

  Next, the obtained dispersion of toner base particles MA-7 is filtered (solid-liquid separation) using a Buchner funnel to obtain wet cake toner base particles MA-7. Next, the obtained wet cake toner base particles MA-7 were re-dispersed in ion exchange water and then filtered using a Buchner funnel. Further, redispersion and filtration were repeated five times to wash the toner base particles MA-7.

Next, the obtained toner base particles MA-7 were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. Thereby, a slurry of toner base particles MA-7 was obtained. Subsequently, toner base particles MA in the slurry are produced using a continuous surface reforming apparatus ("Coatmizer (registered trademark)" manufactured by Freund Sangyo Co., Ltd.) at a hot air temperature of 45 ° C and a blower air volume of 2 m ³ / min. -7 was dried. As a result, a powder of toner mother particles MA-7 was obtained.

Subsequently, 100 parts by mass of toner base particles MA-7 and 0.7 parts by mass using an FM mixer ("FM-10B" manufactured by Japan Coke Industry Co., Ltd.) under the conditions of a rotational speed of 3500 rpm and a jacket temperature of 20 ° C. Silica particles ("AEROSIL (registered trademark) RA-200H" manufactured by Nippon Aerosil Co., Ltd., dry silica particles surface-modified with a trimethylsilyl group and an amino group, number average primary particle diameter: 12 nm), 1.0 part by mass of Conductive titanium oxide particles (Titanium Kogyo Co., Ltd. “EC-100”, base: titanium oxide particles, coating layer: Sb-doped SnO ₂ film, volume median diameter (D ₅₀ ): 0.35 μm), for 5 minutes Mixed. Thereby, the external additive (silica particles and conductive titanium oxide particles) was attached to the surface of the toner base particles MA-7. Subsequently, the obtained powder is sieved using a 300 mesh (48 μm mesh) sieve to obtain a positively chargeable toner TA-7.

[Production of Toner TA-8]
190 g of positively chargeable resin PR-1 and 200 g of positively chargeable resin PR-1 as a resin to be put in a container of a mixing apparatus (Primix Co., Ltd. “Hibismix (registered trademark) 2P-1 type)”, and 190 g of positively chargeable resin PR-1 A positively chargeable toner TA-8 was prepared in the same manner as the preparation of the toner TA-7 except that 10 g of a styrene-butyl acrylate copolymer ("CPR300" manufactured by Mitsui Chemicals, Inc.) was used. .

[Production of Toner TA-9]
140 g of positively chargeable resin PR-1 and 200 g of positively chargeable resin PR-1 as resin to be put in a container of a mixing apparatus (Primix Co., Ltd. “Hibismix (registered trademark) 2P-1 type)” and 140 g of positively chargeable resin PR-1 A positively chargeable toner TA-9 was prepared in the same manner as the preparation of the toner TA-7 except that 60 g of a styrene-butyl acrylate copolymer ("CPR300" manufactured by Mitsui Chemicals, Inc.) was used. .

[Production of Toners TA-2 to TA-6 and Toners TB-1 to TB-3]
Toners TA-2 to TA-6 and toners TA-2 to TA-6 and a method similar to the preparation of toner TA-1 except that the core shown in Table 2 was used instead of core CA-1 as the core when forming the shell layer Toners TB-1 to TB-3 were produced respectively. The toners TA-2 to TA-6 and the toners TB-1 to TB-3 were all positively chargeable toners. In Table 2, "PES" represents a polyester resin. "S-A" represents a styrene-butyl acrylate copolymer. "UF" shows a urea resin. "QA" indicates a thermoplastic resin containing quaternary ammonium cation groups. Further, each value of the content of the charge control agent in the core indicates the content of the charge control agent with respect to 100 parts by mass of the binder resin. Also, the ratio in parentheses in the column of the material of the shell layer indicates the ratio of the mass of QA to the mass of S-A (mass of QA / mass of S-A). Moreover, "-" of the column of a negative charge control agent means that the negative charge control agent was not used. Similarly, "-" in the column of the positive charge control agent means that the positive charge control agent was not used.

<Evaluation method>
[Preparation of developer for evaluation]
A two-component developer was prepared by mixing a ferrite carrier and a toner (each toner prepared in the above procedure) for 30 minutes using a ball mill. The proportion of the toner in the two-component developer was 10% by mass. Ferrite carrier is applied by spraying 230 parts by mass of resin solution (resin: 30 parts by mass of silicone resin, solvent: 200 parts by mass of toluene) to 1000 parts by mass of Mn-Mg ferrite core (powder) having a number average primary particle diameter of 35 μm. After that, heat treatment was performed at a temperature of 200.degree. C. for 60 minutes.

[Measurement of initial charge amount]
Immediately after preparing the developer for evaluation by the above-mentioned procedure, the charge amount (unit: μC / g) of the toner contained in the developer for evaluation obtained in an environment of temperature 23 ° C. and humidity 50% RH is It measured using a / m meter ("TREX company make Model 212 HS"). Hereinafter, the charge amount measured here is described as “initial charge amount E1” (or simply “E1”).

[Measurement of charge amount after printing test]
As an evaluation machine, a color multifunction machine ("TASKalfa 6052ci" manufactured by KYOCERA Document Solutions Inc.) was used. In addition, the said evaluation machine was equipped with the fixing roller (heating part) whose surface layer part contains a fluororesin. The developer for evaluation prepared according to the above-described procedure was loaded into the black developing device of the evaluation machine, and the replenishment toner (toner used for evaluation) was loaded into the black toner container of the evaluation machine. Subsequently, an image (printing rate: 5%) was continuously printed on printing paper (A4 size) in 10,000 sheets continuously using the above-mentioned evaluation machine under an environment of temperature 23 ° C. and humidity 50% RH. Next, after removing the developing device from the evaluation machine, the two-component developer was taken out from the developing device. Using the two-component developer taken out, the charge amount (unit: μC / g) of the toner was measured by the same method as the measurement method of E1 described above. Hereinafter, the charge amount measured here is described as “post-pressing charge amount E2” (or simply “E2”).

[Evaluation of chargeability]
When the initial charge amount E1 and the post-pressing charge amount E2 obtained by the above-described method were each 15 μC / g or more, the chargeability was evaluated as high (good). On the other hand, when at least one of the initial charge amount E1 and the post-pressing charge amount E2 obtained by the above-described method is less than 15 μC / g, the chargeability was evaluated as low (not good). The results are shown in Table 3.

[Evaluation of change in charge amount]
Based on the following equation (1), the charge amount change ΔE (unit: μC / g, hereinafter simply referred to as “ΔE” from the initial charge amount E1 obtained by the above-mentioned method and the charge amount after printing E2 I asked for When ΔE was 5 μC / g or less, it was evaluated that the change of the charge amount could be suppressed (good). On the other hand, when ΔE exceeded 5 μC / g, it was evaluated that the change of the charge amount could not be suppressed (not good). The results are shown in Table 3.
Charge amount change ΔE = | E1-E2 | (1)

[Evaluation of electrostatic offset]
As an evaluation machine, the same one as the evaluation machine used in the above-mentioned printing durability test was used. The developer for evaluation prepared according to the above-described procedure was loaded into the black developing device of the evaluation machine, and the replenishment toner (toner used for evaluation) was loaded into the black toner container of the evaluation machine. Next, after printing 10 sheets of white paper on printing paper (A4 size) continuously using the above evaluation machine under the environment of temperature 23 ° C. and humidity 50% RH, printing paper with 10% printing rate (A4) 1 sheet printed on the size). Subsequently, the printing paper on which the image having a printing rate of 10% was formed was visually observed to determine whether or not electrostatic offset occurred. Specifically, it was determined that electrostatic offset occurred if there was a stain on the printing paper (a stain appearing every rotation cycle of the fixing roller) caused by the toner adhering to the fixing roller. When the electrostatic offset did not occur, it was evaluated as A (the generation of the electrostatic offset can be suppressed). When electrostatic offset occurred, it was evaluated as B (the generation of electrostatic offset could not be suppressed). The results are shown in Table 3.

  As shown in Table 2, in the toners TA-1 to TA-9, the core contained a binder resin and a negative charge control agent. Further, in the toners TA-1 to TA-9, the core did not contain a positive charge control agent. Further, in the toners TA-1 to TA-9, the shell layer contained a positively chargeable material.

  As shown in Table 3, in the toners TA-1 to TA-9, the evaluation of the electrostatic offset was A (the occurrence of the electrostatic offset could be suppressed).

  As shown in Table 2, in the toner TB-1, the core did not contain a negative charge control agent. Further, in the toner TB-1, the core contained a positive charge control agent. In the toner TB-2, the core contained neither a negative charge control agent nor a positive charge control agent. In the toner TB-3, the core contained both a negative charge control agent and a positive charge control agent.

  As shown in Table 3, in the toners TB-1 to TB-3, the evaluation of the electrostatic offset was B (the generation of the electrostatic offset could not be suppressed).

  From the above results, it was shown that the toner according to the present invention can suppress the occurrence of electrostatic offset.

  As to the evaluation of the chargeability and the evaluation of the change of the charge amount, as shown in Table 3, good evaluations were obtained for all of the toners TA-1 to TA-9 and the toners TB-1 to TB-3. .

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

1 positively charged toner 2 core 3 shell layer

Claims (8)

A positively chargeable toner comprising toner particles comprising a core and a shell layer formed on the surface of the core,
The core contains a binder resin and a negative charge control agent, and does not contain a positive charge control agent.
The shell layer is a positively chargeable toner including a positively chargeable material.   The positively chargeable toner according to claim 1, wherein a content of the negative charge control agent is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.   The positively chargeable toner according to claim 1, wherein the binder resin is a polyester resin or a styrene-acrylic acid alkyl ester resin.   The positively chargeable toner according to any one of claims 1 to 3, wherein the positively chargeable material contained in the shell layer is a thermosetting nitrogen-containing resin.   The positively chargeable toner according to any one of claims 1 to 3, wherein the positively chargeable material contained in the shell layer is a thermoplastic resin containing a quaternary ammonium cation group. An image carrier,
A developing device for developing an electrostatic latent image formed on the surface of the image carrier as a toner image by a developer;
A transfer device for transferring the toner image to a recording medium;
A fixing device for fixing the transferred toner image on the recording medium;
The image forming apparatus, wherein the developer comprises the positively chargeable toner according to any one of claims 1 to 5. The fixing device includes a heating unit that heats the toner image transferred to the recording medium.
The image forming apparatus according to claim 6, wherein the surface layer portion of the heating unit includes a fluorine resin. Developing the electrostatic latent image formed on the surface of the image carrier as a toner image with a developer;
Transferring the toner image to a recording medium;
And fixing the transferred toner image on the recording medium.
The image forming method, wherein the developer comprises the positively chargeable toner according to any one of claims 1 to 5.

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