JP6387951B2 - Toner for electrostatic latent image development - Google Patents

Description

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

  The toner particles contained in the capsule toner include a core and a shell layer (capsule layer) that covers the surface of the core. By covering the core with the shell layer, the heat resistant storage stability of the toner can be improved. In the toner described in Patent Document 1, the core has a Tg (glass transition point) of 60 to 100 ° C., a mass average molecular weight (Mw) of 1000 to 5000, and a ratio of the mass average molecular weight (Mw) to the number average molecular weight (Mn) ( Mw / Mn) 1.0 to 1.3 is contained at a ratio of 10 to 30% by mass.

JP 2006-276307 A

  However, when an image is formed using the toner described in Patent Document 1, the toner may be fused to the developing sleeve, the photosensitive drum, and the like, and an image with high image quality is not always formed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner for developing an electrostatic latent image that is excellent in heat-resistant storage stability, fixing properties, and anti-fusing properties.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles each including a core containing a binder resin and a shell layer covering the surface of the core. The core contains a low molecular weight resin having a number average molecular weight of 1000 or more and 2500 or less and a mass average molecular weight of 1000 or more and 2500 or less at a ratio of 5% by mass or more and 10% by mass or less with respect to the whole binder resin. The softening point of the low molecular weight resin is 50 ° C. or higher and 70 ° C. or lower. The ratio of the weight average molecular weight to the number average molecular weight of the low molecular weight resin is from 1.00 to 1.20.

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

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

  The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . Moreover, the measured value of the volume average particle diameter (MV) of the powder is a laser diffraction / scattering type particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value measured using. In addition, the measurement value of the circularity (= peripheral length of a circle equal to the projected area of the particle / peripheral length of the particle) is not specified, the flow particle image analyzer (“FPIA (registered trademark)” manufactured by Sysmex Corporation) ) -3000 ") is the number average of the values measured for a substantial number (eg 3000) 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 from a magnetic material, or the carrier core may be formed from 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 with respect to 100 parts by mass of the carrier. The positively chargeable toner is positively charged by friction with the carrier.

  The toner particles contained in the toner according to the present embodiment include a core containing a binder resin (hereinafter referred to as a toner core) and a shell layer (capsule layer) that covers the surface of the toner core. The shell layer is substantially composed of a resin. For example, by covering a toner core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. The shell layer may cover the entire surface of the toner core or may partially cover the surface of the toner core. An external additive may be attached to the surface of the toner core and / or the shell layer. A plurality of shell layers may be laminated on the surface of the toner core. If not necessary, the external additive may be omitted. Hereinafter, the toner particles before the external additive adheres are referred to as toner mother particles.

  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 process, toner (toner charged by friction) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is attached to the electrostatic latent image, and then on the photosensitive member. A toner image is formed on the surface. 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 is an electrostatic latent image developing toner having the following basic configuration.

(Basic toner configuration)
The toner core contains a resin having a number average molecular weight (Mn) of 1000 or more and 2500 or less and a mass average molecular weight (Mw) of 1000 or more and 2500 or less in a proportion of 5% by mass or more and 10% by mass or less with respect to the entire binder resin. . Hereinafter, a resin having a number average molecular weight of 1000 or more and 2500 or less and a mass average molecular weight of 1000 or more and 2500 or less is referred to as a low molecular weight resin. The softening point (Tm) of the low molecular weight resin contained in the toner core is 50 ° C. or higher and 70 ° C. or lower. The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the low molecular weight resin contained in the toner core (molecular weight distribution: Mw / Mn) is 1.00 or more and 1.20 or less. Hereinafter, a low molecular weight resin having a softening point of 50 ° C. or more and 70 ° C. or less and a molecular weight distribution (Mw / Mn) of 1.00 or more and 1.20 or less is referred to as a specific low molecular weight resin.

  In the above basic configuration, the method for measuring the softening point (Tm), the number average molecular weight (Mn), and the mass average molecular weight (Mw) is the same method as in Examples described later or an alternative method thereof. The softening point (Tm) of the resin can be adjusted by changing the molecular weight or crosslinkability of the resin, for example. The molecular weight of the resin can be adjusted by changing the polymerization conditions of the resin (more specifically, the amount of polymerization initiator used, the polymerization temperature, or the polymerization time). For example, if the polymerization temperature (reaction temperature during polymerization) is lowered, the amount of solvent used to dissolve the materials used for resin synthesis is reduced, or the amount of polymerization initiator used is reduced, the molecular weight of the resin is reduced. Can do.

  In the toner according to the exemplary embodiment, the toner core contains the specific low molecular weight resin in a ratio of 5% by mass to 10% by mass with respect to the entire toner core. When the toner core contains two or more types of specific low molecular weight resins, the total amount of the specific low molecular weight resins is 5% by mass or more and 10% by mass or less with respect to the entire toner core.

  By including a low molecular weight resin in the toner core, it becomes possible to improve the low-temperature fixability of the toner. Specifically, a toner core containing a low molecular weight resin has a sharp change in viscosity due to heating. That is, when the temperature exceeds a predetermined temperature, the viscosity of the toner core rapidly decreases. However, the inventors have found that when a shell layer is formed on the surface of a toner core produced by a pulverization method, the low molecular weight resin is easily eluted from the toner core in the shell layer forming step. When the low molecular weight resin is eluted from the toner core, the eluted low molecular weight resin is reattached to the surface of the shell layer and remains on the finished toner, and the toner melts on the developing sleeve and the photosensitive drum during image formation. The inventor has found that it causes wearing. The elution of the low molecular weight resin from the toner core is particularly likely to occur when a shell layer containing a heat resistant resin (specifically, a thermosetting resin or a resin having a softening point (Tm) of 100 ° C. or higher) is formed.

  In order to solve the above problems, the inventor has conducted experiments and studies and invented a toner having the above basic configuration. When the toner has the above basic configuration, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner, and to suppress occurrence of toner fusion during image formation. When the molecular weight distribution (Mw / Mn) of the specific low molecular weight resin is sharp (close to 1.0), it is possible to suppress elution of the low molecular weight resin from the toner core in the shell layer forming step. In addition, when the softening point of the specific low molecular weight resin is 50 ° C. or higher and 70 ° C. or lower, it is possible to achieve both heat resistant storage stability and low temperature fixability of the toner.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, it is preferable that the shell layer covers an area of 50% to 99% of the surface area of the toner core. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the maximum thickness of the shell layer is preferably 50 nm or more and 150 nm or less.

  In order to achieve both the heat resistant storage stability and the low-temperature fixability of the toner, the toner preferably has a volume average particle diameter (MV) of 4 μm or more and 9 μm or less.

  Next, a material for forming the toner core (hereinafter referred to as toner core material) and a material for forming the shell layer (hereinafter referred to as shell material) will be described. Resins suitable for forming toner particles are as follows.

<Preferable thermoplastic resin>
Examples of the thermoplastic resin constituting the toner particles (particularly, the toner core and the shell layer) include, for example, a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), Olefin resin (more specifically, 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 is preferred. A copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is also used as a toner. It is preferable as a thermoplastic resin constituting the particles.

  The thermoplastic resin can be 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 acid monomer or a styrene monomer), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, by condensation polymerization). Alcohol and carboxylic acid to be polyester resin).

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid resin, for example, a styrene monomer and an acrylic acid monomer as shown below can be suitably used. By using an acrylic acid monomer, a carboxyl group can be introduced into the styrene-acrylic acid resin. Further, by using a monomer having a hydroxyl group (more specifically, p-hydroxystyrene, m-hydroxystyrene, (meth) acrylic acid hydroxyalkyl ester, or the like), the hydroxyl group can be introduced into the styrene-acrylic acid resin. .

  Preferable examples of the styrene monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), p-hydroxy styrene, m-hydroxy styrene. , Vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Suitable examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic. Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Suitable examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic. The acid 4-hydroxybutyl is mentioned.

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

  Suitable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, Examples include 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, di1,2-propanediol, polyethylene glycol, poly1,2-propanediol, or polytetramethylene glycol.

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

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

  As preferable examples of the divalent carboxylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid Succinic acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (more specific Specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.) may be mentioned.

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

  Hereinafter, the toner core (binder resin and internal additive), shell layer, and external additive will be described in order. Depending on the toner application, unnecessary components (for example, an internal additive or an external additive) may be omitted.

[Toner core]
The toner core contains a binder resin. The toner core may contain internal additives (for example, a colorant, a release agent, a charge control agent, and magnetic powder).

(Binder resin)
In the toner core, the binder resin generally 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 core. 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. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to become anionic, and the binder resin has an amino group or an amide group. The toner core tends to become cationic.

  In order to improve the durability of the toner, the toner core is preferably produced by a pulverization method (one type of dry method). The pulverization method is a method of obtaining a powder (for example, a toner core) through a step of obtaining a kneaded product by melting and kneading a plurality of types of materials (resins and the like) and a step of pulverizing the obtained kneaded product.

  As the binder resin contained in the toner core, for example, the above-described suitable thermoplastic resin is preferable, and a polyester resin is particularly preferable. In order for the toner to have the above-described basic structure, the low molecular weight resin contained in the toner core is preferably a crystalline polyester resin, a crystal containing ethylene glycol as the alcohol component and sebacic acid as the acid component. It is particularly preferable that the polyester resin. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner core is larger than a crystalline polyester resin that is a low molecular weight resin and an amorphous polyester resin that is not a low molecular weight resin (eg, a low molecular weight resin). A non-crystalline polyester resin having Mw).

(Coloring agent)
The toner core 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.

  The toner core 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 core 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 core 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 increase the anionicity of the toner core, it is preferable to produce the toner core using an anionic wax. In order to improve the fixing property or offset resistance of the toner, the amount of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

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

  In order to improve the compatibility between the binder resin and the release agent, a compatibilizer may be added to the toner core.

(Charge control agent)
The toner core 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 core, the anionicity of the toner core can be enhanced. Further, the cationic property of the toner core can be increased by including a positively chargeable charge control agent in the toner core. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Magnetic powder)
The toner core 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.

  In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When a shell layer is formed on the surface of the toner core under acidic conditions, if the metal ions are eluted on the surface of the toner core, the toner cores are easily fixed to each other. It is considered that fixing of the toner cores can be suppressed by suppressing elution of metal ions from the magnetic powder.

[Shell layer]
The shell layer may be a film without graininess or a film with graininess. When resin particles are used as a material for forming the shell layer, if the material (resin particles) is completely melted and cured in a film-like form, it is considered that a film without graininess is formed as the shell layer. It is done. On the other hand, if the material (resin particles) is not completely melted and cured in a film form, a film having a form in which the resin particles are two-dimensionally connected (a film having a granular feeling) is formed as a shell layer. it is conceivable that. The shape of the resin particles constituting the shell layer may be spherical, or the spherical resin particles may be deformed into a flat shape in the course of film formation. Heating in the drying process or physical impact force in the external addition process may cause the resin particles to be formed into a film. The entire shell layer is not necessarily formed integrally. The shell layer may be a single film or an assembly of a plurality of films (islands) that are separated from each other.

  The shell layer may be substantially made of only a thermosetting resin, may be substantially made of only a thermoplastic resin (more specifically, the above-mentioned preferred thermoplastic resin or the like), You may contain both curable resin and thermoplastic resin. When the shell layer contains both a thermosetting resin and a thermoplastic resin, the ratio of the thermoplastic resin and the thermosetting resin in the shell layer is arbitrary. Examples of the ratio of thermoplastic resin to thermosetting resin include 1: 1, 1: 2, 1: 3, 1: 4, 1: 5, 2: 1, 3: 1, 4: 1, or 5 : 1 (each in a mass ratio, thermoplastic resin: thermosetting resin).

  In order to improve the heat resistant storage stability of the toner, the shell layer preferably contains a thermosetting resin or a resin having a softening point (Tm) of 100 ° C. or higher. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, it is particularly preferable to contain an acrylic resin having a softening point of 100 ° C. or higher. In order to uniformly form a shell layer containing a heat-resistant resin (specifically, a thermosetting resin or a resin having a softening point (Tm) of 100 ° C. or higher) on the surface of the toner core, the toner core produced by the pulverization method is used. A shell layer is preferably formed on the surface by a wet method.

The thermosetting resin can be obtained by crosslinking (polymerizing) one or more thermosetting monomers. Moreover, a thermosetting resin can also be synthesize | combined with a thermoplastic monomer by using a crosslinking agent. The thermosetting monomer is a monomer having crosslinkability. For example, when monomers of the same kind are three-dimensionally connected via “—CH ₂ —” to become a thermosetting resin, the monomer corresponds to a “thermosetting monomer”. Examples of the thermosetting resin constituting the shell layer include melamine resin, urea resin, sulfonamide resin, glyoxal resin, guanamine resin, aniline resin, polyimide resin (more specifically, maleimide resin). And a xylene-based resin are preferable. Preferable examples of the thermosetting monomer include methylol melamine, melamine, methylolated urea (more specifically, dimethylol dihydroxyethylene urea), urea, benzoguanamine, acetoguanamine, or spiroguanamine.

  In order to form a good-quality shell layer on the surface of the toner core while suppressing aggregation of the toner core, a surfactant and an aggregating agent are used in the shell layer forming step (as a result, the formed shell layer is used as the surfactant and the aggregating agent). Containing an agent). As the surfactant, for example, sulfate ester salts, sulfonate salts, phosphate ester salts, or soaps can be suitably used. Examples of the flocculant include inorganic metal salts (more specifically, sodium sulfate, sodium chloride, calcium chloride, magnesium chloride, aluminum chloride, or aluminum sulfate, polyaluminum chloride, or polyaluminum hydroxide) or inorganic. An ammonium salt (more specifically, ammonium sulfate, ammonium chloride, ammonium nitrate, or the like) can be preferably used.

[External additive]
An external additive may be attached to the surface of the toner base particles. The external additive is used, for example, to improve the fluidity or handleability of the toner. In order to improve the fluidity or handleability of the toner, the amount of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. In order to improve the fluidity or handleability of the toner, the particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

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

[Toner Production Method]
Hereinafter, an example of a method for producing the toner according to the exemplary embodiment having the above configuration will be described.

(Preparation of toner core)
The toner core is preferably produced by a pulverization method. For example, the binder resin and an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder) are mixed. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is pulverized and classified. As a result, a toner core having a desired particle size can be obtained.

(Formation of shell layer)
First, an aqueous medium (for example, ion exchange water) is prepared. In order to suppress dissolution or elution of the toner core components (particularly the binder resin and the release agent) during the formation of the shell layer, it is preferable to form the shell layer in an aqueous medium. 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). 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. The boiling point of the aqueous medium is about 100 ° C.

  Subsequently, a toner core, a shell material, and a surfactant (for example, sodium lauryl sulfate) are added to the aqueous medium to obtain a dispersion. As the shell material, for example, a dispersion of resin particles (more specifically, heat-resistant resin particles or the like) can be used. The shell material adheres to the surface of the toner core in the liquid. In order to uniformly adhere the shell material to the surface of the toner core, it is preferable to highly disperse the toner core in the liquid containing the shell material, for example, by stirring the liquid.

  Subsequently, the pH of the dispersion is adjusted to a predetermined pH (for example, a pH selected from 7.5 to 9.0). Subsequently, a flocculant (for example, magnesium chloride hexahydrate aqueous solution) is added to the dispersion (for example, alkaline dispersion) whose pH has been adjusted.

  Subsequently, the temperature of the liquid is selected from a predetermined speed (for example, 0.1 ° C./min to 3.0 ° C./min) while stirring the liquid containing the toner core, shell material, surfactant, and aggregating agent. Speed) to a predetermined holding temperature (for example, a temperature selected from 50 ° C. to 85 ° C.). Thereafter, the liquid is cooled to obtain a dispersion of toner base particles. It is considered that the reaction (immobilization of the shell layer) proceeds between the toner core and the shell material while the temperature of the liquid is kept high. It is considered that the surfactant suppresses the aggregation of the toner core, and the aggregating agent adsorbs the shell material on the surface of the toner core. The shell material is combined with the toner core to form a shell layer. In the case where resin particles having heat resistance are used as the shell material, it is considered that the resin particles (shell material) are two-dimensionally connected on the surface of the toner core to form a granular film (shell layer). . Moreover, it is thought that the film formation (unification) of the resin particles (shell material) is promoted by the presence of the flocculant.

(Washing process)
The obtained 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, the drying step and the external addition step described later can be performed simultaneously.

(External addition process)
Thereafter, if necessary, the toner base particles and the external additive are mixed using a mixer (for example, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.), and the external additive is adhered to the surface of the toner base particles. May be. In this way, a toner containing a large number of toner particles is obtained.

  The contents and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, when reacting a material (for example, a shell material) in a liquid, the material may be reacted in the liquid for a predetermined time after the material is added to the liquid, or the material is added to the liquid over a long period of time. Then, the material may be reacted in the liquid while adding the material to the liquid. Further, the shell material may be added to the liquid at once, or may be added to the liquid in a plurality of times. The toner may be sieved after the external addition step. Further, 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. Moreover, even if it does not adjust pH of a liquid, when reaction for forming a shell layer advances favorably, you may omit a pH adjustment process. If an external additive is unnecessary, the external addition process may be omitted. When the external additive is not attached to the surface of the toner base particles (the step of external addition is omitted), the toner base particles correspond to the toner particles. The toner core material and the shell material are not limited to the above-described compounds (such as various monomers for synthesizing the resin). For example, if necessary, a derivative of the aforementioned compound may be used as the toner core material or shell material, or a prepolymer may be used instead of the monomer. Further, in order to obtain the above-mentioned compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-3, TB-1 to TB-2, TC-1 to TC-2, TD-1 to TD-5, and TE-1 to TE according to Examples or Comparative Examples. -2 (each electrostatic toner developing toner).

  Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of toners TA-1 to TE-2 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value. Moreover, the measurement methods of Tm (softening point), number average molecular weight (Mn), and mass average molecular weight (Mw) are as follows unless otherwise specified.

<Tm measurement method>
A sample (for example, resin) is set on a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation), a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² , and a temperature rising rate of 6 ° C./min. Then, a 1 cm ³ sample was melted out and the S curve (vertical axis: stroke, horizontal axis: temperature) of the sample was obtained. Subsequently, the Tm of the sample was read from the obtained S-shaped curve. For example, if the maximum stroke value is S ₁ and the baseline stroke value on the low temperature side is S ₂ , the stroke value in the S curve is “(S ₁ + S ₂ ) / 2”. This temperature corresponds to the Tm (softening point) of the sample.

<Measuring method of Mn and Mw>
The number average molecular weight (Mn) and the mass average molecular weight (Mw) of the resin were measured by gel permeation chromatography (GPC) under the following conditions.

(1) Molecular weight measurement of amorphous resin (1-1) Measurement sample: solution of amorphous resin Eluent: THF (tetrahydrofuran)
Solution concentration: 3.0 mg / mL
Pretreatment: Filtration through a filter with a pore size of 0.45 μm Injection volume: 100 μL
(1-2) GPC measurement conditions Apparatus: HLC-8220 GPC (manufactured by Tosoh Corporation)
Column: TSKgel GMHXL (manufactured by Tosoh Corporation)
Number of columns: 2 (series connection)
Column temperature: 40 ° C
Carrier solvent: THF (tetrahydrofuran)
Carrier flow rate: 1 mL / min Detector: RI (refractive index) detector Calibration curve: Calibration curve prepared using standard polystyrene

(2) Molecular weight measurement of crystalline resin (2-1) Measurement sample: Crystalline resin solution Eluent: THF (tetrahydrofuran)
Solution concentration: 3.0 mg / mL
Pretreatment: Filtration through a filter with a pore size of 0.45 μm Injection volume: 100 μL
(2-2) GPC measurement conditions Apparatus: HLC-8220 GPC (manufactured by Tosoh Corporation)
Column: TSKgel GMHXL-L (manufactured by Tosoh Corporation)
Number of columns: 2 (series connection)
Column temperature: 40 ° C
Carrier solvent: THF (tetrahydrofuran)
Carrier flow rate: 1 mL / min Detector: RI (refractive index) detector Calibration curve: Calibration curve prepared using standard polystyrene

[Toner Production Method]
(Preparation of toner core material A1)
In a 10 L four-necked flask equipped with a thermometer (thermocouple), a dehydrator with a fractionation tube (used with 98 ° C hot water passed through the fractionation tube), a nitrogen inlet tube, and a stirring device A monomer for synthesizing the polyester resin (alcohol component: 2236 g of ethylene glycol, acid component: 7647 g of sebacic acid) was added. Subsequently, the contents of the flask were reacted for 6 hours under conditions of a nitrogen atmosphere and a temperature of 140 ° C. Subsequently, the temperature of the flask contents was raised to 200 ° C. at a rate of 10 ° C./hour in a nitrogen atmosphere. Subsequently, the contents of the flask were reacted in a nitrogen atmosphere and at a temperature of 200 ° C. until the reaction rate reached 80% by mass or more. The reaction rate was calculated according to the formula “reaction rate = 100 × actual amount of reaction product water / theoretical product water amount”.

  Subsequently, 20 g of tin (II) 2-ethylhexanoate was added to the flask, and then the contents of the flask were further reacted for 2 hours in a nitrogen atmosphere and at a temperature of 200 ° C. Subsequently, the contents of the flask were further reacted for 2 hours under the conditions of a reduced pressure atmosphere (pressure 8 kPa) and a temperature of 200 ° C. As a result, a low molecular weight resin was obtained in the flask.

  Subsequently, the low molecular weight resin obtained as described above was pulverized using a mechanical pulverizer (“Turbo Mill T250” manufactured by Freund Turbo Co., Ltd.) under the condition of a set particle diameter of 30 μm to obtain a pulverized product. . Subsequently, 200 g of the obtained pulverized product, 30 g of 1N sodium hydroxide aqueous solution, and 385 g of methanol were mixed to obtain a dispersion. Subsequently, ion-exchanged water was added to the obtained dispersion to prepare a slurry having a total amount of 1000 g.

  Subsequently, 1000 g of the slurry obtained as described above was charged into a 2 L stainless steel round bottom container equipped with a stirrer and a condenser (heat exchanger). Subsequently, the container contents were stirred for 30 minutes under the conditions of a temperature of 50 ° C. and a rotation speed (stirring blade) of 200 rpm. Thereafter, the container contents were rapidly cooled to room temperature (about 25 ° C.). Subsequently, the aqueous phase was separated and removed from the contents of the container using a 300 mesh filter to obtain resin fine particles. Thereafter, the obtained resin fine particles were washed with water and dried to obtain toner core material A1 (crystalline polyester low molecular weight resin powder).

(Preparation of toner core material A2)
The preparation method of the toner core material A2 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of the toner core material A1 except that the addition amount of ethylene glycol was changed from 2236 g to 2190 g.

(Preparation of toner core material A3)
The preparation method of the toner core material A3 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of the toner core material A1 except that the addition amount of ethylene glycol was changed from 2236 g to 2163 g.

(Preparation of toner core material A4)
The preparation method of toner core material A4 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of toner core material A1 except that the addition amount of ethylene glycol was changed from 2236 g to 2240 g.

(Preparation of toner core material A5)
The preparation method of the toner core material A5 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of the toner core material A1 except that the addition amount of ethylene glycol was changed from 2236 g to 2159 g.

(Preparation of toner core material A6)
The preparation method of the toner core material A6 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of the toner core material A1, except that the addition amount of ethylene glycol was changed from 2236 g to 2139 g.

(Preparation of toner core material A7)
The preparation method of the toner core material A7 (crystalline polyester low molecular weight resin powder) was the same as the preparation method of the toner core material A1 except that the addition amount of ethylene glycol was changed from 2236 g to 2160 g.

(Physical properties of toner core materials A1 to A7)
Regarding toner core materials A1 to A7, Tm (softening point), Mw (mass average molecular weight), Mn (number average molecular weight), and Mw / Mn (molecular weight distribution) of the crystalline polyester resin particles are as shown in Table 2. It was.

(Preparation of toner core material B)
25 parts by mass of a bisphenol A-PO (propylene oxide) adduct, 25 parts by mass of a bisphenol A-EO (ethylene oxide) adduct, 46 parts by mass of fumaric acid, and 4 parts by mass of trimellitic acid were added to a catalyst (titanium dioxide). ) To prepare toner core material B (a powder of molecular weight resin in non-crystalline polyester). Regarding the resin particles contained in the obtained toner core material B, Tm was 85 ° C., Mw was 5000, Mn was 2500, and Mw / Mn was 2.

(Preparation of toner core material C)
Reaction of 25 parts by mass of a bisphenol A-PO adduct, 25 parts by mass of a bisphenol A-EO adduct, 44 parts by mass of fumaric acid, and 6 parts by mass of trimellitic acid in the presence of a catalyst (titanium dioxide). Thus, a toner core material C (amorphous polyester high molecular weight resin powder) was prepared. Regarding the resin particles contained in the obtained toner core material C, Tm was 97 ° C., Mw was 6800, Mn was 3400, and Mw / Mn was 2.

(Preparation of shell material)
As a shell material, an acrylic resin dispersion having a solid concentration of 25% by mass was prepared. Regarding the resin particles contained in the prepared dispersion, the number average particle diameter was 110 nm, Tm was 120 ° C., Mw was 15000, Mn was 5000, and Mw / Mn was 3.

(Production of toner core)
Using an FM mixer (“FM-20B” manufactured by Nippon Coke Kogyo Co., Ltd.), 100 parts by mass of a binder resin (low molecular weight resin, medium molecular weight resin, and high molecular weight resin) and a colorant (CI Pigment Blue) 15: 3, component: copper phthalocyanine pigment) 5 parts by mass, release agent (“Nissan Electol (registered trademark) WEP-3” manufactured by NOF Corporation, component: ester wax, melting temperature: 73 ° C.) 5 mass Part. As the low molecular weight resin, any one of toner core materials A1 to A7 shown in Table 1 defined for each toner was used. Further, toner core material B was used as the medium molecular weight resin, and toner core material C was used as the high molecular weight resin. Of 100 parts by mass of binder resin added, each of low molecular weight resin (any of toner core materials A1 to A7), medium molecular weight resin (toner core material B), and high molecular weight resin (toner core material C) ( The mass ratio was as shown in Table 1. For example, in the production of the toner TA-1, 7.5 parts by mass of the toner core material A1, 32.5 parts by mass of the toner core material B, and 60 parts by mass of the toner core material C were added as binder resins.

  Subsequently, the obtained mixture was melt-kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded product was pulverized using a pulverizer (“Turbomill RS type” manufactured by Freund Turbo Co., Ltd.) under the condition of a set particle diameter of 6 μm. Subsequently, the obtained pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core having a volume average particle size (MV) of 6.6 μm and a circularity of 0.931 was obtained.

(Formation of shell layer)
Under a room temperature (about 25 ° C.) environment, in a stainless steel round bottom container having a capacity of 2 L equipped with a stirrer and a condenser (heat exchanger), 100 g of the toner core and the shell material (solid content concentration: 25% by mass) obtained in the above-described procedure. ) 30 g, 3 g of an anionic surfactant (“Emar (registered trademark) 0” manufactured by Kao Corporation, component: sodium lauryl sulfate) and 870 g of ion-exchanged water were added. Subsequently, while stirring the contents of the container at room temperature (about 25 ° C.) and a rotation speed (stirring blade) of 200 rpm, a 1N sodium hydroxide aqueous solution was added to the container to adjust the pH of the container contents to 8. . Thereafter, the contents of the container were continuously stirred at room temperature (about 25 ° C.) and at a rotational speed (stirring blade) of 200 rpm, and after 10 minutes from the end of pH adjustment, a flocculant (magnesium chloride hexahydrate with a solid content concentration of 50 mass%) was obtained. Then, 10 g of the flocculant was dropped into the container over 5 minutes while continuing to stir the contents of the container. Thereafter, the temperature of the container contents was increased to 65 ° C. at a rate of 0.5 ° C./min while continuing to stir the container contents. During this temperature increase, a shell layer was formed on the surface of the toner core. As a result, a dispersion of toner base particles was obtained as the container contents.

(Washing process)
The toner mother particle dispersion obtained as described above was cooled to 25 ° C., and then suction filtered (solid-liquid separation) using a Buchner funnel. As a result, toner base particles in the form of wet cake were obtained. Thereafter, the obtained wet cake-like toner base particles were redispersed in ion-exchanged water. Further, dispersion and filtration were repeated a total of 6 times to wash the toner base particles.

(Drying process)
Subsequently, the obtained toner base particles were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. As a result, a slurry of toner base particles was obtained. Subsequently, the toner base particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. Further, at the time of drying, ethanol containing 0.2 parts by mass of the first external additive (“AEROSIL (registered trademark) REA200” manufactured by Nippon Aerosil Co., Ltd .: silica particles) was sprayed on 100 parts by mass of the toner base particles. As a result, toner mother particles including the first external additive (hereinafter referred to as first external additive toner particles) were obtained. The obtained first externally added toner particles had a volume average particle diameter (MV) of 6.6 μm and a circularity of 0.960.

(External addition process)
After the drying, further external addition was performed on the first externally added toner particles. Specifically, using an FM mixer (“FM-10C / I” manufactured by Nippon Coke Kogyo Co., Ltd.), 100 parts by mass of the first external additive toner particles and the second external additive (silica having a number average primary particle diameter of 20 nm). By mixing 0.4 parts by mass of particles (“AEROSIL90G” manufactured by Nippon Aerosil Co., Ltd., the surface of which is treated with silicone oil and aminosilane) for 5 minutes, a second outer surface is formed on the surface of the toner base particles. Additives (silica particles) were deposited. Thereafter, the obtained powder was sieved using a 300 mesh (aperture 48 μm) sieve. As a result, toner containing a large number of toner particles (toners TA-1 to TA-3, TB-1 to TB-2, TC-1 to TC-2, TD-1 to TD-5, and TE-1 to TE -2) was obtained.

[Evaluation method]
The evaluation method of each sample (toner TA-1 to TE-2) is as follows.

(Heat resistant storage stability)
3 g of a sample (toner) was put in a 20 mL polyethylene container, and the container was tapped for 5 minutes, and then left in an incubator set at 60 ° C. for 8 hours. Thereafter, the toner taken out from the thermostat was cooled to room temperature (about 25 ° C.) to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having a known mass of 300 mesh (aperture 48 μm). Then, the mass of the sieve containing the toner was measured, and the mass of the toner before sieving was determined. Subsequently, a sieve was set on a powder tester (manufactured by Hosokawa Micron Co., Ltd.), and according to the manual of the powder tester, the sieve was vibrated for 30 seconds under the conditions of the rheostat scale 5, and the evaluation toner was sieved. Then, after sieving, the mass of the toner remaining on the sieve was determined by measuring the mass of the sieve containing the toner. From the mass of the toner before sieving and the mass of the toner after sieving (the mass of the toner remaining on the sieving after sieving), the degree of aggregation (% by mass) was determined based on the following formula.
Aggregation degree (% by mass) = 100 × mass of toner after sieving / mass of toner before sieving

  When the degree of aggregation was 10% by mass or less, it was evaluated as “good”, and when the degree of aggregation exceeded 10% by mass, it was evaluated as “poor” (not good).

(Preparation of developer)
39.7 mol% in terms of MnO, 9.9 mol% in terms of MgO, 49.6 mol% calculated as Fe ₂ O _3, each raw material (MnO to be 0.8 mol% in terms of SrO, MgO, Fe ₂ O ₃ and SrO raw materials) were mixed in appropriate amounts, and water was added to the raw materials. Subsequently, the raw materials were ground using a wet ball mill for 10 hours and then mixed. Subsequently, the resulting mixture was dried. Subsequently, the dried mixture was subjected to heat treatment at a temperature of 950 ° C. for 4 hours.

Subsequently, using a wet ball mill, the mixture after the heat treatment was pulverized over 24 hours to prepare a slurry. Subsequently, the obtained slurry was granulated and then dried. Subsequently, the dried granulated product was crushed after being held in an atmosphere at a temperature of 1270 ° C. and an oxygen concentration of 2% for 6 hours. Thereafter, by adjusting the particle size, powder of Mn—Mg—Sr ferrite particles (magnetic carrier core) having a saturation magnetization of 70 Am ² / kg in an applied magnetic field of 3000 (10 ³ / 4π · A / m) ( A number average primary particle size of 35 μm) was obtained.

  Subsequently, a polyamideimide resin (a copolymer of trimellitic anhydride and 4,4'-diaminodiphenylmethane) was diluted with methyl ethyl ketone to prepare a resin solution having a solid content concentration of 10% by mass. Subsequently, FEP (tetrafluoroethylene-hexafluoropropylene copolymer) is dispersed in the obtained resin solution, and silicon oxide is added at a ratio of 2% by mass with respect to the total amount of the resin, and converted to solid content. 150 g of a carrier coating solution was obtained. With respect to the obtained carrier coat solution, the mass ratio of polyamideimide resin to FEP (polyamideimide resin: FEP) was 2: 8.

  Subsequently, 10 kg of the magnetic carrier core (Mn—Mg—Sr ferrite particles) obtained as described above using a rolling fluidized bed coating apparatus (“Spiracoater (registered trademark) SP-25” manufactured by Okada Seiko Co., Ltd.). Was coated with the carrier coating solution. Thereafter, the resin-coated magnetic carrier core was baked at 220 ° C. for 1 hour. As a result, an evaluation carrier was obtained. The resin coating amount was 3% by mass with respect to the entire carrier.

  100 parts by mass of the evaluation carrier prepared as described above and 5 parts by mass of the sample (toner) were mixed for 30 minutes using a ball mill to prepare a two-component developer.

(Preparation of evaluation machine)
As an evaluation machine, a color multifunction machine (“TASKalfa 5551ci” manufactured by Kyocera Document Solutions Co., Ltd.) equipped with a fixing device was used. The surface material of the heating roll of the fixing device was a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) tube having a film thickness of 30 μm ± 10 μm and a surface roughness (Ra: arithmetic average roughness) of 5 μm. 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.

(Fixability)
Using the above-mentioned evaluation machine under the environment of a temperature of 25 ° C. and a humidity of 50% RH, the paper (A4 size plain paper) is subjected to a linear speed of 300 mm / second (paper direction: landscape feed) and a toner loading of 15 mg. A solid image having a size of 25 cm × 25 cm was formed. Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluation machine. The evaluation range of the fixing temperature (heating roll of the fixing device) was 80 ° C to 240 ° C.

  In the evaluation of the minimum fixing temperature, the fixing temperature was increased by 5 ° C. from 80 ° C., and the lowest temperature (minimum fixing temperature) at which a solid image (toner image) can be fixed on paper was measured. Whether or not the toner could be fixed was confirmed by a rubbing test as shown below. Specifically, the evaluation paper passed through the fixing device was bent so that the surface on which the image was formed was on the inside, and the image on the fold was rubbed 5 times with a 1 kg weight coated with a cloth. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the length (peeling length) of toner peeling at the bent portion was measured. The lowest temperature among the fixing temperatures at which the peeling length was 1 mm or less was defined as the lowest fixing temperature.

  In the evaluation of the maximum fixing temperature, the fixing temperature of the fixing device was increased from 150 ° C. by 5 ° C., and the maximum temperature at which no offset occurred (maximum fixing temperature) was measured. With respect to the evaluation paper passed through the fixing device, it was confirmed whether or not an offset was visually observed (toner adhered to the fixing roller).

  Based on the measured maximum fixing temperature and minimum fixing temperature, the fixing width represented by “fixing width = maximum fixing temperature−minimum fixing temperature” was calculated. If the minimum fixing temperature is 100 ° C. or less and the fixing width is 100 ° C. or more, it is evaluated as “good”. If the minimum fixing temperature is higher than 100 ° C., or the fixing width is less than 100 ° C. In some cases, it was evaluated as x (not good).

(Fusion resistance)
A halftone image having a printing rate of 50% was continuously printed on the entire surface of 300,000 sheets of paper (A4 size plain paper) using the above-described evaluation machine in an environment of a temperature of 25 ° C. and a humidity of 50% RH. During continuous printing, the surface of each of the developing sleeve and the photosensitive drum of the evaluator was visually observed for every 1000 sheets to confirm the presence or absence of toner fusion. During continuous printing of 300000 sheets, if the toner does not fuse to either the developing sleeve or the photosensitive drum, it is evaluated as “good”, and the toner is fused to either the developing sleeve or the photosensitive drum. In that case, it was evaluated as x (not good).

[Evaluation results]
Table 3 shows the evaluation results (fixability: minimum fixing temperature and fixing width, heat-resistant storage stability: aggregation degree, fusing resistance: presence / absence of toner fusing) for each sample (toners TA-1 to TE-2). Show. The number of sheets (number in parentheses) in Table 3 relating to the evaluation result of anti-fusing property indicates the timing at which toner fusing occurs (number of sheets printed before toner fusing occurs).

  Toners TA-1 to TA-3, TB-1 to TB-2, and TC-1 to TC-2 (toners according to Examples 1 to 7) each had the above-described basic configuration. Specifically, in the toners according to Examples 1 to 7, as shown in Tables 1 and 2, the toner core has a low molecular weight resin (number average molecular weight (Mn) 1000 to 2500 and mass average molecular weight (Mw)). 1000 or more and 2500 or less resin) in a ratio of 5% by mass or more and 10% by mass or less with respect to the entire binder resin. As shown in Tables 1 and 2, the softening point (Tm) of the low molecular weight resin contained in the toner core was 50 ° C. or higher and 70 ° C. or lower. Further, as shown in Tables 1 and 2, the molecular weight distribution (Mw / Mn) of the low molecular weight resin contained in the toner core was 1.00 or more and 1.20 or less.

  Toners TA-1 to TA-3, TB-1 to TB-2, and TC-1 to TC-2 (toners according to Examples 1 to 7) are respectively heat-resistant storage stability, fixing property, and anti-fusing property. It was excellent.

  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.

Claims (7)

An electrostatic latent image developing toner comprising a plurality of toner particles comprising a core containing a binder resin and a shell layer covering the surface of the core,
The core contains a low molecular weight resin having a number average molecular weight of 1000 or more and 2500 or less and a weight average molecular weight of 1000 or more and 2500 or less in a proportion of 5% by mass or more and 10% by mass or less with respect to the whole binder resin.
The softening point of the low molecular weight resin is 50 ° C. or higher and 70 ° C. or lower,
The toner for developing an electrostatic latent image, wherein a ratio of a mass average molecular weight to a number average molecular weight of the low molecular weight resin is from 1.00 to 1.20.   2. The electrostatic latent image developing toner according to claim 1, wherein the shell layer contains a thermosetting resin or a resin having a softening point of 100 ° C. or higher.   The electrostatic latent image developing toner according to claim 1, wherein the low molecular weight resin is a crystalline polyester resin.   The toner for developing an electrostatic latent image according to claim 3, wherein the crystalline polyester resin contains ethylene glycol as an alcohol component and sebacic acid as an acid component.   The electrostatic latent image developing toner according to claim 1, wherein the shell layer contains an acrylic resin having a softening point of 100 ° C. or higher.   The electrostatic latent image developing toner according to claim 1, wherein the shell layer contains a surfactant and an aggregating agent.   The electrostatic latent image developing toner according to claim 1, wherein the core is manufactured by a pulverization method.