JP6583250B2 - Toner for electrostatic latent image development - Google Patents

Description

  The present invention relates to an electrostatic latent image developing toner.

  In the toner described in Patent Document 1, the toner base particles include a binder resin (binder resin), cellulose nanofibers, a colorant, and a release agent. The binder resin contains at least a polyester resin A composed of benzenedicarboxylic acid and disproportionated rosin and glycerin, and a polyester resin B composed of at least benzenedicarboxylic acid and a bisphenol A derivative. In the toner base particles, cellulose nanofibers having a number average fiber length of 50 to 500 μm are internally added.

JP 2013-44886 A

  In the technique described in Patent Document 1, a cellulose nanofiber having a number average fiber length of 50 to 500 μm is placed inside the toner base particle by utilizing the fact that the hydroxyl group of glycol in the binder resin is easily bonded to the cellulose nanofiber. This improves the toner blocking property. However, Patent Document 1 discloses only the use of general cellulose nanofibers having a long fiber length, and there is still room for improvement in the low-temperature fixability and fluidity of the toner. In addition, the fiber length of general cellulose nanofiber is 5 micrometers or more.

  The present invention has been made in view of the above problems, and an object thereof is to provide a toner for developing an electrostatic latent image that is excellent in low-temperature fixability and fluidity.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including toner base particles and an external additive attached to the surface of the toner base particles. The external additive includes nanocellulose powder that is a powder of acicular nanocellulose particles. The nanocellulose particles are one or more types of nanocellulose particles selected from the group consisting of cellulose nanofiber particles and cellulose nanocrystal particles. In the nanocellulose powder, the width of the nanocellulose particles is 5 nm or more and 40 nm or less on the number average, and the length of the nanocellulose particles is 300 nm or more and 1000 nm or less on the number average.

  According to the present invention, it is possible to provide an electrostatic latent image developing toner excellent in low-temperature fixability and fluidity.

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

Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent-circle diameters of primary particles (Haywood diameter: the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Value. Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is measured using a laser diffraction / scattering particle size distribution measuring device (“LA-750” manufactured by Horiba, Ltd.) unless otherwise specified. It is the value.

  The glass transition point (Tg) is a value measured according to “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) at the second temperature rise measured by the differential scanning calorimeter, the change point of the specific heat (outside the extrapolated line of the baseline and the falling line) The temperature (onset temperature) at the intersection with the insertion line corresponds to Tg (glass transition point). Moreover, the measured value of molecular weight (for example, number average molecular weight) is a value measured using gel permeation chromatography unless otherwise specified.

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

  The “main component” of a material means a component most contained in the material on a mass basis unless otherwise specified.

  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. The crystalline polyester resin is described as “crystalline polyester resin”, and the non-crystalline polyester resin is simply described as “polyester resin”.

  In the present specification, both untreated silica particles (hereinafter referred to as silica substrate) and silica particles obtained by subjecting a silica substrate to surface treatment (surface-treated silica particles) are described as “silica particles”. To do. Further, the silica particles hydrophobized with the surface treatment agent may be described as hydrophobic silica particles, and the silica particles positively charged with the surface treatment agent may be described as positively chargeable silica particles, respectively. Both untreated titanium oxide particles (hereinafter referred to as a titanium oxide substrate) and titanium oxide particles in which the titanium oxide substrate is covered with a conductive layer (titanium oxide particles imparted with conductivity by a coating layer) are “titanium oxide particles”. ".

  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. Further, a two-component developer may be prepared by mixing a toner and a carrier using a mixing device (more specifically, a ball mill or the like). In order to form a high-quality image, it is preferable to use a ferrite carrier (ferrite particle powder) 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 impart magnetism to the carrier particles, the carrier core may be formed of a magnetic material (for example, a ferromagnetic substance such as ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Good. 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 contained in the two-component developer is positively charged by friction with the carrier.

  The toner according to this embodiment is a powder containing a plurality of toner particles. The toner particles include toner base particles and an external additive. The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, if necessary. The external additive is attached to the surface of the toner base 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 image forming unit (for example, a charging device and an exposure device) of an electrophotographic apparatus forms an electrostatic latent image on a photosensitive member (for example, a surface layer portion of a photosensitive drum) based on image data. Subsequently, a developing device of the electrophotographic apparatus (specifically, a developing device in which a developer containing toner is set) supplies the toner to the photoconductor to develop the electrostatic latent image formed on the photoconductor. The toner is charged by friction with the carrier, the developing sleeve, or the blade in the developing device before being supplied to the photoreceptor. For example, a positively chargeable toner is positively charged. In the developing process, toner (specifically, charged toner) 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 supplied to the photosensitive member, and the supplied toner is By attaching to the electrostatic latent image on the photoconductor, a toner image is formed on the photoconductor. The consumed toner is replenished to the developing device from a toner container containing replenishment toner.

  In the subsequent transfer process, after the transfer device of the electrophotographic apparatus transfers the toner image on the photosensitive member to an intermediate transfer member (for example, a transfer belt), the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Transcript to. Thereafter, a fixing device (fixing method: nip fixing with a heating roller and a pressure roller) of the electrophotographic apparatus heats and pressurizes the toner 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. After the transfer step, the toner remaining on the photoreceptor is removed by a cleaning member (for example, a cleaning blade). The transfer method may be a direct transfer method in which the toner image on the photosensitive member is directly transferred to the recording medium without using the intermediate transfer member. The fixing method may be a belt fixing method.

  The toner according to the exemplary embodiment is an electrostatic latent image developing toner having the following configuration (hereinafter referred to as a basic configuration).

(Basic toner configuration)
The electrostatic latent image developing toner includes a plurality of toner particles including toner mother particles and an external additive attached to the surface of the toner mother particles. The external additive includes nanocellulose powder that is a powder of acicular nanocellulose particles. The nanocellulose particles are one or more types of nanocellulose particles selected from the group consisting of cellulose nanofiber particles and cellulose nanocrystal particles. In the nanocellulose powder, the width of the nanocellulose particles is 5 nm or more and 40 nm or less on the number average, and the length of the nanocellulose particles is 300 nm or more and 1000 nm or less on the number average. Hereinafter, cellulose nanofiber particles may be referred to as CNF particles, and cellulose nanofiber powder (powder of CNF particles) may be referred to as CNF powder. Cellulose nanocrystal particles may be described as CNC particles, and cellulose nanocrystal powder (CNC particle powder) may be described as CNC powder.

  In the above basic configuration, the “width” and “length” of each particle are values measured based on a two-dimensional projection image (specifically, an SEM photograph) of the particle. The “length” of a particle is the length (major axis diameter) of the long axis of the particle, and more specifically corresponds to the width of the particle that maximizes the interval between two parallel lines that sandwich the particle. . The “width” of a particle is the length (short axis diameter) of the minor axis of the particle, and more specifically, measured on a straight line passing through the midpoint of the major axis and orthogonal to the major axis. This corresponds to the width of the particles to be produced. The “aspect ratio” corresponds to a value obtained by dividing the length (major axis diameter) by the width (minor axis diameter) (= major axis diameter / minor axis diameter).

  When cellulose is hydrogen-bonded and crystallized, it becomes nanocellulose (a fine cellulose fiber having a thickness of 1 nm to 100 nm) and exhibits a very high strength. Cellulose nanofibers are produced from a cellulose raw material (for example, wood), mechanically processed (more specifically, pulverized by a bead mill, etc.) or chemically processed (more specifically, TEMPO catalyzed oxidation, carboxymethylation, or Nanocellulose extracted by cationization or the like. Cellulose nanocrystals use a high concentration of mineral acid (for example, strong acid such as hydrochloric acid, sulfuric acid, or hydrobromic acid) to remove the non-crystalline portion by hydrolyzing the cellulose raw material (for example, wood), It is nanocellulose which isolated only the crystal part.

  The inventor of the present application has found that nanocellulose (specifically, CNF powder and CNC powder) can be used as an external additive for toner particles by adjusting the size of nanocellulose. Then, by using a nanocellulose powder (CNF powder and / or CNC powder) having a particle width and a particle length defined by the above basic configuration as an external additive for toner particles, low temperature fixability is achieved. In addition, the present inventors have succeeded in obtaining a toner for developing an electrostatic latent image having excellent fluidity. Specifically, when the toner base particles are heated and the toner base particles are melted in the fixing process, the CNF particles and / or the CNC particles existing on the surface of the toner base particles promote the melting connection between the toner base particles. Works. By the action of such CNF particles and / or CNC particles, the toner is easily fixed on the paper.

  Each of the cellulose nanofiber particles and the cellulose nanocrystal particles may be subjected to a surface treatment (for example, a hydrophobic treatment).

  In order to improve the fixing property of the toner, in the above-described basic configuration, it is preferable that the toner base particles are non-capsule toner base particles and the toner base particles contain a polyester resin. Cellulose nanofibers and cellulose nanocrystals each have a strong affinity for polyester resins. For this reason, the melting connection between the toner base particles in the fixing step is easily promoted by the CNF particles and / or the CNC particles.

  From the viewpoint of productivity, in the basic configuration described above, it is preferable that the nanocellulose powder contains only cellulose nanofiber particles. In order to obtain a toner suitable for image formation, the main component of the cellulose nanofiber particles is preferably a TEMPO oxide of bleached softwood pulp.

  In order to obtain a toner having excellent fixability, the amount of nanocellulose powder is preferably 0.1 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the toner base particles. Excess nanocellulose powder present on the surface of the toner base particles tends to inhibit toner fixing. In order to obtain a toner having excellent fixability, it is preferable that nanocellulose (nanocellulose as an internal additive) does not exist inside the toner base particles.

  The first method for producing CNF powder includes a chemical method such as a TEMPO catalytic oxidation method. Fine acicular nanocellulose particles with weak external force by oxidizing cellulose fibers with TEMPO (2,2,6,6-TEtraMethylpiperidine-1-Oxyradical) catalyst to generate electrostatic repulsion between particles Can be obtained.

  As a second method for producing the CNF powder, defibration by a physical method is exemplified. As the physical method, for example, a high-pressure homogenizer method, a microfluidizer method, a grinder grinding method, a strong shearing kneading method, or a ball mill grinding method is preferable. For example, the fiber can be defibrated by passing through a gap between media that rub (for example, beads). The fiber can also be defibrated by being pinched with a stone mill rotating at high speed.

  As a third method for producing the CNF powder, an electrical method such as an electrospinning method can be mentioned. For example, a solution in which fibers are dissolved is put into a syringe, and a metal plate (collector electrode) is placed so as to face the needle tip of the syringe. When a high voltage is applied between the needle tip of the syringe and the metal plate, the solution flies from the needle tip of the syringe toward the metal plate, and the acicular nanocellulose particles adhere to the metal plate. The solvent in the solution volatilizes during the flight, and only the acicular nanocellulose particles remain on the metal plate.

  As a fourth method for producing the CNF powder, a biological method using microorganisms can be mentioned. For example, acetic acid bacteria secrete cellulose fibers and create a cellulose gel (pelicle). If acetic acid bacteria are used, a ribbon-like fiber of cellulose can be generated. Moreover, it becomes possible to refine | miniaturize a cellulose fiber by utilizing an enzymatic decomposition.

  As a method for obtaining a CNF powder having a particle width and a particle length defined by the basic configuration described above, a method in which a TEMPO catalytic oxidation method and a ball mill pulverization method are combined is particularly preferable. Specifically, the CNF powder obtained by the TEMPO catalytic oxidation method is finely pulverized by the ball mill pulverization method, thereby obtaining the CNF powder having the particle width and the particle length defined by the basic configuration described above. The particle width of the CNF powder can be easily controlled based on the amount of TEMPO used. In detail, there exists a tendency for the width | variety of acicular nanocellulose particle to become small, so that the usage-amount of TEMPO is increased. Further, the particle length of the CNF powder can be easily controlled based on the amount of media and processing time in ball milling. Specifically, the length of the acicular nanocellulose particles tends to decrease as the amount of media increases and the processing time (grinding time) increases.

  The toner base particles may be toner base particles without a shell layer (hereinafter referred to as non-capsule toner base particles), or toner base particles with a shell layer (hereinafter referred to as capsule toner base particles). It may be. The capsule toner base particles include a toner core containing a binder resin and a shell layer that covers the toner core. Capsule toner base particles can be produced by forming a shell layer on the surface of non-capsule toner base particles (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.

  The non-capsule toner base particles can be produced by, for example, a pulverization method or an aggregation method. In these methods, the internal additive is easily dispersed well in the binder resin of the non-capsule toner base particles. It is well known in the technical field to which the present invention pertains that toner is roughly classified into pulverized toner and polymerized toner (also referred to as chemical toner). The non-capsule toner base particles obtained by the pulverization method belong to the pulverized toner, and the non-capsule toner base particles obtained by the aggregation method belong to the polymerized toner.

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

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

  When the capsule toner base particles are manufactured, the shell layer can be formed by any method. For example, the shell layer can be formed on the surface of the toner core (non-encapsulated toner base particles) by an in-situ polymerization method, a liquid-cured coating method, or a coacervation method.

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

  Next, the non-capsule toner base particles (binder resin and internal additive) and the external additive will be described in order. Depending on the use of the toner, unnecessary components (for example, internal additives) may be omitted. Capsule toner base particles may be produced by forming a shell layer on the surface of the following non-capsule toner base particles (toner core).

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

  Examples of the binder resin include a styrene resin, an acrylic acid resin (more specifically, an acrylate polymer or a methacrylic acid ester polymer), an olefin resin (more specifically, a polyethylene resin or Polypropylene resin, etc.), vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, N-vinyl resin, polyester resin, polyamide resin, or urethane resin. Further, 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 used. May be.

  As the binder resin, a polyester resin is particularly preferable. The toner base particles may contain a crystalline polyester resin. By containing a crystalline polyester resin in the toner base particles, sharp melt properties can be imparted to the toner base particles.

  The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diol, bisphenol, trihydric or higher alcohol as shown below) and one or more polyhydric carboxylic acids (more specifically). Specifically, it can be obtained by polycondensation with a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below. The polyester resin may contain a repeating unit derived from another monomer (a monomer that is neither a polyhydric alcohol nor a polyvalent carboxylic acid).

  Suitable examples of the aliphatic diol include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol (more specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, etc. ), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

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

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

  Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acid (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acid (more specifically, malonic acid). Succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decanedicarboxylic acid), alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid) Acid, n-dodecyl succinic acid, or isododecyl succinic acid), alkenyl succinic acid (specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isodode) Senylsuccinic acid, etc.), maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, or cyclohexanedicarboxylic acid Examples include acids.

  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.

  In order to ensure sufficient toner fixability even during high-speed fixing, a glass of binder resin (the most binder resin on a mass basis when toner base particles contain multiple types of binder resins) is used. The transition point (Tg) is preferably 30 ° C. or higher and 65 ° C. or lower.

  In order to ensure sufficient toner strength and fixability, the number average molecular weight (Mn) of the polyester resin contained in the toner base particles is preferably 1000 or more and 2000 or less.

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

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

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

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

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

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

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

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

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

  By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner base particles, the anionicity of the toner base particles can be enhanced. Further, by adding a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner base particles, the cationicity of the toner base particles can be increased. However, if sufficient chargeability is ensured in the toner, it is not necessary to add a charge control agent to the toner base particles.

(Magnetic powder)
The toner base particles may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, Ferrite, magnetite, chromium dioxide, or the like) or a material subjected to ferromagnetization treatment (more specifically, a carbon material or the like imparted with ferromagnetism by heat treatment) can be 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 base particles under acidic conditions, if the metal ions are eluted on the surface of the toner base particles, the toner base particles are easily fixed to each other. It is considered that fixing of toner mother particles can be suppressed by suppressing elution of metal ions from the magnetic powder.

  As the toner base particles, for example, a non-added cyan toner for “TASKalfa 5551ci” manufactured by Kyocera Document Solutions Inc. can be suitably used.

[External additive]
Unlike the internal additive, the external additive does not exist inside the toner base particles, but selectively exists only on the surface of the toner base particles (surface layer portion of the toner particles). In the toner having the above basic configuration, nanocellulose powder (external additive) is fixed on the surface of the toner base particles. For example, toner base particles (specifically, a powder containing a plurality of toner base particles) and an external additive (specifically, a powder containing a plurality of needle-shaped nanocellulose particles) are stirred together, thereby producing a toner base. Acicular nanocellulose particles (external additive particles) can be attached to the surface of the particles. The toner base particles and the acicular nanocellulose particles (external additive particles) do not chemically react with each other, and are physically bonded instead of chemically. The strength of the bond between the toner base particles and the external additive particles depends on the stirring conditions (more specifically, the stirring time, the rotation speed of the stirring, etc.), the particle diameter of the external additive particles, and the shape of the external additive particles. And the surface condition of the external additive particles.

  In addition to the nanocellulose powder, inorganic particles may be further adhered to the surface of the toner base particles. As inorganic particles (external additive particles), particles of silica particles or metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are suitable. Can be used for In order to improve the fluidity of the toner, it is preferable to use silica particles. In order to improve the abrasiveness of the toner, it is preferable to use titanium oxide particles. One type of inorganic particles may be used alone, or a plurality of types of inorganic particles may be used in combination. For example, in order to improve the chargeability of the toner, it is preferable that the external additive present on the surface of the toner base particles contains silica particles and titanium oxide particles in addition to the nanocellulose powder. By using silica particles with high electrical resistance and titanium oxide particles with low electrical resistance as an external additive in combination, the generated charges are spread over the entire surface of the toner particles by the titanium oxide particles while generating sufficient charges with the silica particles. It becomes possible to disperse uniformly.

  The inorganic particles may be surface treated. For example, when silica particles are used as the inorganic particles, hydrophobicity and / or positive chargeability may be imparted to the surface of the silica particles by a surface treatment agent. Examples of the surface treatment agent include a coupling agent (more specifically, a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent), a silazane compound (for example, a chain silazane compound or a cyclic silazane compound). ) Or silicone oil (more specifically, dimethyl silicone oil or the like) can be preferably used. As the surface treatment agent, a silane coupling agent or a silazane compound is particularly preferable. Preferable examples of the silane coupling agent include silane compounds (more specifically, methyltrimethoxysilane or aminosilane). A preferred example of the silazane compound is HMDS (hexamethyldisilazane).

When the surface of the silica substrate (untreated silica particles) is treated with the 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. Substituted with a functional group. As a result, silica particles having a functional group derived from the surface treating agent (specifically, a functional group that is more hydrophobic and / or positively charged than the hydroxyl group) on the surface can be obtained. For example, when the surface of a silica substrate is treated with a silane coupling agent having an amino group, a hydroxyl group of the silane coupling agent (for example, a hydroxyl group generated by hydrolysis of an alkoxy group of the silane coupling agent with moisture) A dehydration condensation reaction (“A (silica substrate) —OH” + “B (coupling agent) —OH” → “A—O—B” + H ₂ O) occurs with a hydroxyl group present on the surface of the silica substrate. By such a reaction, a silane coupling agent having an amino group and silica are chemically bonded to each other, so that an amino group is imparted to the surface of the silica particles, and positively charged silica particles are obtained. More specifically, the hydroxyl group present on the surface of the silica substrate is substituted with a functional group having an amino group at the end (more specifically, —O—Si— (CH ₂ ) ₃ —NH ₂ or the like). Silica particles provided with amino groups tend to have a positive chargeability stronger than that of a silica substrate. When a silane coupling agent having an alkyl group is used, hydrophobic silica particles are obtained. More specifically, the hydroxyl group present on the surface of the silica substrate may be replaced with a functional group having an alkyl group at the end (more specifically, —O—Si—CH ₃ or the like) by the dehydration condensation reaction. it can. Thus, the silica particle to which the hydrophobic group (alkyl group) was provided instead of the hydrophilic group (hydroxyl group) tends to have a stronger hydrophobicity than the silica substrate.

As the external additive particles, inorganic particles having a conductive layer may be used. The conductive layer is, for example, a metal oxide film (hereinafter, referred to as a doped metal oxide) provided with conductivity by doping (specifically, an Sb-doped SnO ₂ film). The conductive layer may be a layer containing a conductive material other than the doped metal oxide (more specifically, a metal, a carbon material, a conductive polymer, or the like).

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-5 and TB-1 to TB-7 (electrostatic latent image developing toners) according to examples or comparative examples, respectively.

  Hereinafter, a production method, an evaluation method, and an evaluation result of toners TA-1 to TA-5 and TB-1 to TB-7 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

[Preparation of materials]
(External additive: preparation method of CNF powder C-1)
Ion exchange water 1.5 L was put in the container (first container). Thereafter, sulfite bleached softwood pulp equivalent to 200 parts by mass in dry mass, 2.0 parts by mass of TEMPO (2,2,6,6-TEtramethylpiperidine-1-oxyradical), and 25 parts by mass of sodium bromide in a container And dispersed in water. Subsequently, a sodium hypochlorite aqueous solution having a concentration of 13% by mass is added to the container so that the amount of sodium hypochlorite per gram of pulp in the container is 2.5 mmol, and the contents of the container are reacted. I let you. During the reaction, while confirming the pH of the container contents, an aqueous solution of sodium hydroxide having a molar concentration of 0.5 M was dropped into the container according to the amount of change in pH to maintain the pH of the container contents at 10.5. . When the pH of the container contents no longer changes, the reaction is judged to be complete, and the container contents containing the reaction product are solid-liquid separated (filtered) using a glass filter to obtain a solid (reaction product). ) Thereafter, the obtained solid was redispersed in a sufficient amount of ion-exchanged water and washed with water. Dispersion and filtration were repeated a total of 5 times. As a result, a water-impregnated fiber body (solid content concentration: 25% by mass) was obtained.

  Subsequently, the obtained water-impregnated fiber body and ion-exchanged water were placed in a container (second container) different from the first container to prepare a slurry having a solid content concentration of 2% by mass. . Subsequently, the container contents (slurry) were dispersed using a rotary blade mixer. Due to the dispersion treatment, the viscosity of the container contents (slurry) increased. During the dispersion treatment, when ion-exchanged water is added to the container so that the viscosity of the container contents (slurry) is kept substantially constant, the solid content concentration of the container contents (slurry) reaches 0.15% by mass. The distributed processing is finished. As a result, a dispersion containing a cellulose fiber (solid content concentration: 0.15% by mass) was obtained. The dispersion treatment time was about 5 minutes.

  Subsequently, the obtained dispersion was separated into suspended matter and sediment by centrifugation, and the suspended matter was removed. Subsequently, the precipitate was washed with water and then dried to obtain a dried cellulose fiber body. Subsequently, by crushing the dried cellulose fiber body, CNF powder C-1 (cellulose nanofibers) having a particle width (number average fiber diameter) of about 10 nm and a particle length (number average fiber length) of about 1.5 μm Particle powder) was obtained.

(External additive: preparation method of CNF powder C-2)
20 g of the CNF powder C-1 obtained as described above and 500 g of zirconia beads having a diameter of 0.1 mm were placed in a 1 L polyethylene container, and the container was set on a ball mill. And the grinding | pulverization process for 2 hours was performed with respect to the container content on the conditions of the rotational speed of 100 rpm using the ball mill. As a result, CNF powder C-1 was pulverized by pulverization media (zirconia beads), and finer CNF powder C-2 (cellulose nanofiber particle powder) was obtained. By performing media pulverization, the particle length of the CNF powder C-2 became smaller than the particle length of the CNF powder C-1.

(External additive: preparation method of CNF powder C-3)
The production method of CNF powder C-3 was the same as the production method of CNF powder C-1, except that the amount of TEMPO used was changed from 2.0 parts by mass to 3.5 parts by mass. By increasing the amount of TEMPO used, the particle width of the CNF powder C-3 became smaller than the particle width of the CNF powder C-1.

(External additive: CNF powder C-4 production method)
The production method of CNF powder C-4 was the same as the production method of CNF powder C-1, except that the amount of TEMPO used was changed from 2.0 parts by mass to 1.5 parts by mass. By reducing the amount of TEMPO used, the particle width of CNF powder C-4 became larger than the particle width of CNF powder C-1.

(External additive: Method for producing CNF powder C-5)
20 g of CNF powder C-4 and 500 g of zirconia beads having a diameter of 0.1 mm were placed in a polyethylene container having a capacity of 1 L as described above, and the container was set on a ball mill. And the grinding | pulverization process for 5 hours was performed with respect to the container content on the conditions of the rotational speed of 100 rpm using the ball mill. As a result, CNF powder C-4 was pulverized with pulverization media (zirconia beads), and finer CNF powder C-5 (cellulose nanofiber particle powder) was obtained. By performing media pulverization, the particle length of the CNF powder C-5 became smaller than the particle length of the CNF powder C-4.

(External additive: Method for producing CNF powder C-6)
As described above, 20 g of CNF powder C-4 and 1500 g of zirconia beads having a diameter of 0.1 mm were placed in a polyethylene container having a capacity of 1 L, and the container was set on a ball mill. And the grinding | pulverization process for 10 hours was performed with respect to the container content on the conditions of rotational speed 100rpm using the ball mill. As a result, CNF powder C-4 was pulverized by pulverization media (zirconia beads), and finer CNF powder C-6 (cellulose nanofiber particle powder) was obtained. Compared with the production method of CNF powder C-5, the amount of pulverized media was increased and the media was pulverized over a longer time, so that the particle length of CNF powder C-6 was CNF powder. It became smaller than the particle length of C-5.

(External additive: CNF powder C-7 production method)
The production method of CNF powder C-7 was the same as the production method of CNF powder C-1, except that the amount of TEMPO used was changed from 2.0 parts by mass to 0.5 parts by mass. By reducing the amount of TEMPO used, the particle width of CNF powder C-7 became larger than the particle width of CNF powder C-1.

(External additive: CNF powder C-8 production method)
As described above, 20 g of CNF powder C-7 and 500 g of zirconia beads having a diameter of 0.1 mm were placed in a polyethylene container having a capacity of 1 L, and the container was set on a ball mill. And the grinding | pulverization process for 5 hours was performed with respect to the container content on the conditions of the rotational speed of 100 rpm using the ball mill. As a result, CNF powder C-7 was pulverized by pulverization media (zirconia beads), and finer CNF powder C-8 (cellulose nanofiber particle powder) was obtained. By performing media pulverization, the particle length of the CNF powder C-8 became smaller than the particle length of the CNF powder C-7.

(External additive: CNF powder C-9 production method)
The production method of CNF powder C-9 was the same as that of CNF powder except that the amount of TEMPO used was changed from 2.0 parts by mass to 2.7 parts by mass, and the pulverization time was changed from 2 hours to 10 hours. It was the same as the manufacturing method of C-2. By increasing the amount of TEMPO used, the particle width of the CNF powder C-9 is smaller than that of the CNF powder C-2, and the time for the pulverization process is increased, so that the CNF powder C-9 The particle length was smaller than that of CNF powder C-2.

(External additive: CNF powder C-10 production method)
The production method of CNF powder C-10 was the same as that of CNF powder except that the amount of TEMPO used was changed from 2.0 parts by mass to 0.7 parts by mass, and the pulverization time was changed from 2 hours to 12 hours. It was the same as the manufacturing method of C-2. By reducing the amount of TEMPO used, the particle width of the CNF powder C-10 is larger than the particle width of the CNF powder C-2, and the time for the pulverization process is increased, so that the CNF powder C-10 The particle length was smaller than that of CNF powder C-2.

(External additive: Method for producing CNF powder C-11)
The production method of CNF powder C-11 was the same as the production method of CNF powder C-10, except that the pulverization time was changed from 12 hours to 5 hours. By shortening the pulverization time, the particle length of the CNF powder C-11 became larger than the particle length of the CNF powder C-10.

[Method for Producing Toners TA-1 to TA-5 and TB-1 to TB-6]
Using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.), 100 parts by mass of toner base particles (powder), 1.5 parts by mass of silica particles (powder), and titanium oxide particles (powder) ) 1.5 parts by mass and 1.0 part by mass of CNF powder of any of the types shown in Table 1 (any of CNF powders C-1 to C-11 defined for each toner) were mixed for 5 minutes. . For example, in the production of the toner TA-1, CNF powder C-2 was used as the CNF powder (external additive).

The toner base particles are non-externally added non-magnetic toner (production method: pulverization method (pulverized toner), shell layer: none (non-capsule toner particles), binder resin: polyester resin, release agent: ester wax (NOF CORPORATION) "Nissan Electol (registered trademark) WEP-3"), colorant: carbon black ("MA100" manufactured by Mitsubishi Chemical Corporation), charge control agent: quaternary ammonium salt ("BONTRON" (registered by Orient Chemical Industry Co., Ltd.) trademark) P-51 "), the volume median diameter (D _50): was 7.0 .mu.m).
The silica particles are positively charged silica particles (“AEROSIL (registered trademark) REA90” manufactured by Nippon Aerosil Co., Ltd., content: dry silica particles imparted with positive charge by surface treatment, number average primary particle size: 20 nm). there were.
The titanium oxide particles are conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd., substrate: TiO ₂ particles, coating layer: Sb-doped SnO ₂ film, number average primary particle size: about 0.35 μm). there were.

  By the above mixing, external additives (silica particles, titanium oxide particles, and cellulose nanofiber particles) adhered to the surface of the toner base particles. Thereafter, sieving was performed using a 200 mesh sieve (aperture 75 μm). As a result, toners containing a large number of toner particles (toners TA-1 to TA-5 and TB-1 to TB-6 shown in Table 1) were obtained.

[Production Method of Toner TB-7]
The production method of the toner TB-7 was the same as the production method of the toner TA-1, except that the CNF powder was not added. That is, in the production of the toner TB-7, external additives (silica particles and titanium oxide particles) adhered to the surface of the toner base particles by the above-described mixing.

  With respect to the toners TA-1 to TA-5 and TB-1 to TB-6 obtained as described above, the results of measuring the particle width and particle length of the CNF powder are as shown in Table 1. . “Particle width” and “particle length” in Table 1 each represent a number average value (unit: nm). Image analysis software (Mitani Corporation) obtained SEM images obtained by photographing the surface of toner particles using a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.). The particle width and the particle length of the CNF powder existing on the surface of the toner base particles were measured by analyzing using “WinROOF” manufactured by the manufacturer. For example, in the toner TA-1, in the CNF powder existing on the surface of the toner base particles, the width of the CNF particles is 10 nm on the number average, and the length of the CNF particles is 900 nm on the number average.

[Evaluation methods]
The evaluation method of each sample (toners TA-1 to TA-5 and TB-1 to TB-7) is as follows.

(Preparation of developer for evaluation)
100 parts by weight of a developer carrier (carrier for “TASKalfa 5551ci”) and 5 parts by weight of a sample (toner) were mixed for 30 minutes using a ball mill to prepare a developer for evaluation (two-component developer).

(Low temperature fixability)
As an image forming apparatus for evaluation, a multifunction machine (“TASKalfa 5551ci” manufactured by Kyocera Document Solutions Inc.) was used. In addition, the fixing device taken out from the printer having the Roller-Roller type heating and pressing type fixing device (“FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd.) is modified so that the fixing temperature can be changed, and the fixing for evaluation is performed. Used as a device.

The evaluation developer (two-component developer) prepared as described above is charged into the developing device of the composite machine (image forming apparatus for evaluation), and the sample (supplementary toner) is used as the composite machine (image formation for evaluation). Device) in the toner container. Using this multifunction machine, the paper (Fuji Xerox Co., Ltd. “C290”: A4 size, plain paper with a basis weight of 90 g / m ² ) under the environment of temperature 23 ° C. and humidity 60% RH is 10 mm from the rear end. A solid image (specifically, an unfixed toner image) having a size of 25 mm × 25 mm was formed on the portion under the conditions of a linear speed of 200 mm / second and a toner applied amount of 1.0 mg / cm ² .

  Subsequently, the paper on which the unfixed toner image was formed by the above-described multifunction peripheral (evaluation image forming apparatus) was passed through the evaluation fixing apparatus. The evaluation fixing device performed a fixing process on an image on paper (unfixed toner image) at a preset fixing temperature. Subsequently, by performing a rubbing test on the image subjected to the fixing process (specifically, the image formed on the paper), it was confirmed whether or not the toner could be fixed on the paper at the fixing temperature. Fix the solid image (toner image) on the paper at a fixing temperature of 100 ° C. or higher and 200 ° C. or lower while changing the fixing temperature (specifically, by increasing the fixing temperature of the evaluation fixing device by 5 ° C. from 100 ° C.) The lowest possible temperature (minimum fixing temperature) was measured. Whether or not the toner could be fixed was determined based on the fixing rate measured by the rubbing test and the peeling length measured by the rubbing test. Details of each test are as follows.

(Rubbing test)
Using a reflection densitometer (“SpectroEye (registered trademark)” manufactured by X-Rite), the image density (hereinafter referred to as pre-rubbing ID) of the image on the paper passed through the fixing device was measured. Subsequently, the image on the paper was rubbed back and forth 10 times using a 1 kg weight coated with a fabric. Subsequently, using a reflection densitometer (SpectroEye), the image density of the image on the paper (hereinafter referred to as ID after rubbing) was measured. Subsequently, the fixing rate (unit:%) was determined according to the formula “fixing rate = 100 × ID after rubbing / ID before rubbing”. If the fixing rate was 80% or more, it was determined to be acceptable, and if the fixing rate was less than 80%, it was determined to be unacceptable.

(Rubbing test)
The paper passed through the fixing device was folded so that the surface on which the image was formed was on the inside, and a 1 kg weight coated with a fabric was used to rub the image on the fold 5 times. 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. If the peeling length was 1 mm or less, it was determined to be acceptable, and if the peeling length exceeded 1 mm, it was determined to be unacceptable.

  The lowest fixing temperature that passed both the rubbing test and the rubbing test was taken as the minimum fixing temperature. If the minimum fixing temperature is less than 170 ° C, it is evaluated as ◯ (good), if the minimum fixing temperature is 170 ° C, it is evaluated as △ (normal), and if the minimum fixing temperature exceeds 170 ° C, x (not good). evaluated. The evaluation reference value was set based on the minimum fixing temperature (170 ° C.) of toner TB-7 (toner that did not use CNF powder).

(Liquidity)
The apparent density (AD) of the sample (toner) was measured by a method based on Japanese Industrial Standard (JIS K5101-12-1). From the measured apparent density, the fluidity of the sample (toner) was evaluated according to the following evaluation criteria. The higher the apparent density of the toner, the higher the fluidity of the toner.
○ (Good): The apparent density was more than 0.390 g / cm ³ .
Δ (Normal): The apparent density was more than 0.370 g / cm ^{3 and} 0.390 g / cm ³ or less.
X (defect): Apparent density was 0.370 g / cm ³ or less.

[Evaluation results]
Table 2 shows the results of evaluating low-temperature fixability (minimum fixing temperature) and fluidity (apparent density) for each of toners TA-1 to TA-5 and TB-1 to TB-7.

  Toners TA-1 to TA-5 (toners according to Examples 1 to 5) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-5 includes a plurality of toner particles each including toner base particles and an external additive attached to the surface of the toner base particles. The external additive contained nanocellulose powder (specifically, CNF powder) that is a powder of acicular nanocellulose particles (specifically, cellulose nanofiber particles). In the CNF powder existing on the surface of the toner base particles, the width of the cellulose nanofiber particles is 5 nm or more and 40 nm or less on the number average, and the length of the cellulose nanofiber particles is 300 nm or more and 1000 nm or less on the number average (Table). 1).

  In all of toners TA-1 to TA-5, the amount of cellulose nanofiber particles (powder) was 1.0 part by mass with respect to 100 parts by mass of toner base particles (powder).

  As shown in Table 2, the toners TA-1 to TA-5 were excellent in low-temperature fixability and fluidity.

  The same evaluation results were obtained when cellulose nanocrystal particles were used as needle-shaped nanocellulose particles (external additive) instead of cellulose nanofiber particles. That is, in the CNC powder existing on the surface of the toner base particles, the width of the cellulose nanocrystal particles is 5 nm or more and 40 nm or less on the number average, and the length of the cellulose nanocrystal particles is 300 nm or more and 1000 nm or less on the number average. Some toners have better low temperature fixability and fluidity than toners that do not meet these requirements (requirements for particle width and particle length).

  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)

A plurality of toner particles comprising toner mother particles and an external additive attached to the surface of the toner mother particles;
The external additive includes nanocellulose powder that is a powder of acicular nanocellulose particles,
The nanocellulose particles are one or more types of nanocellulose particles selected from the group consisting of cellulose nanofiber particles and cellulose nanocrystal particles,
In the nanocellulose powder, the width of the nanocellulose particles is 5 nm or more and 40 nm or less on the number average, and the length of the nanocellulose particles is 300 nm or more and 1000 nm or less on the number average.   The electrostatic latent image developing toner according to claim 1, wherein the nanocellulose powder contains only cellulose nanofiber particles.   The electrostatic latent image developing toner according to claim 2, wherein a main component of the cellulose nanofiber particles is a TEMPO oxide of bleached softwood pulp.   The amount of the nanocellulose powder is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the toner base particles. Toner for image development.   5. The electrostatic latent image developing toner according to claim 1, wherein the external additive includes silica particles and titanium oxide particles in addition to the nanocellulose powder. 6.   The electrostatic latent image developing toner according to claim 1, wherein the toner base particles are pulverized toner. The toner base particles are non-capsule toner base particles,
The electrostatic latent image developing toner according to claim 1, wherein the toner base particles contain a polyester resin.