JP2017016057A - Developer for electrostatic image development, and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer for electrostatic image development that can generate high-quality images and be easily manufactured, and a manufacturing method for the developer.SOLUTION: A developer for electrostatic image development comprises a carrier containing multiple carrier particles and a toner containing multiple toner particles. The carrier contains carrier particles of less than 20 μm in particle diameter at a ratio of not less than 10 mass % but not more than 25 mass %. The volume median diameter of all the carrier particles contained in the carrier is not less than 30 μm but not more than 42 μm. The frictional electrification amount Qbetween all the carrier particles contained in the carrier and the frictional electrification amount Qof the carrier particles of less than 20 μm contained in the carrier and the toner satisfies a relational expression "0.5≤Q/Q≤0.8".SELECTED DRAWING: None

Description

  The present invention relates to a developer for developing an electrostatic latent image and a method for producing the same.

  A two-component developer can be prepared by mixing a carrier containing a plurality of carrier particles and a toner containing a plurality of toner particles. When an image is formed using a two-component developer, there is a problem that the image quality of the image is deteriorated due to the occurrence of carrier adhesion (a phenomenon in which carrier particles adhere to the surface of the photosensitive drum). Patent Document 1 discloses a technique for suppressing carrier adhesion (a phenomenon in which carrier particles adhere to the surface of a photoreceptor) by adjusting the particle size distribution of the carrier. In the two-component developer described in Patent Document 1, the carrier has a mass average particle diameter of 22 μm to 32 μm, and the ratio (Dw / Dp) of the mass average particle diameter Dw to the number average particle diameter Dp is 1.0 <. Dw / Dp <1.2. In the carrier, the content of particles having a particle size of 20 μm or less is 7% by mass or less, and the content of particles having a particle size of 36 μm or less is 90% by mass to 100% by mass.

JP 2010-113079 A

  In the two-component developer described in Patent Document 1, the carrier particle size distribution is very sharp. Such carriers are difficult to manufacture and tend to be expensive to manufacture.

  The present invention has been made in view of the above problems, and provides a developer for developing an electrostatic latent image that can form a high-quality image and can be easily manufactured, and a method for manufacturing the same. For the purpose.

The developer for developing an electrostatic latent image according to the present invention includes a carrier including a plurality of carrier particles and a toner including a plurality of toner particles. The carrier includes the carrier particles having a particle diameter of less than 20 μm at a ratio of 10% by mass to 25% by mass. The volume median diameter of all the carrier particles contained in the carrier is 30 μm or more and 42 μm or less. The frictional charge amount Q _A between all the carrier particles contained in the carrier and the toner, and the triboelectric charge amount Q _B between the carrier particles contained in the carrier and the particle diameter of less than 20 μm and the toner are expressed by a relational expression. “0.5 ≦ Q _B / Q _A ≦ 0.8” is satisfied.

The method for producing a developer for developing an electrostatic latent image according to the present invention includes preparation of toner, preparation of a carrier core, and formation of a resin layer. In the toner preparation, a toner including a plurality of toner particles is prepared. In the preparation of the carrier core, a carrier core powder having a volume median diameter of 30 μm or more and 42 μm or less and including a carrier core having a particle diameter of less than 20 μm at a ratio of 10% by mass to 25% by mass is prepared. In the formation of the resin layer, a resin layer having a maximum thickness of 1 μm or less is formed on each surface of the carrier core to obtain carrier particles. Further, in the formation of the resin layer, and the triboelectric charge quantity Q _A and the all of the carrier particles toner, and a triboelectric charge quantity Q _B of the said carrier particles having a particle size of less than 20μm toner relation " In order to satisfy “0.5 ≦ Q _B / Q _A ≦ 0.8”, an additive having a polarity opposite to that of the resin constituting the resin layer is selectively used as the resin of carrier particles having a particle diameter of less than 20 μm. Add in the layer.

  According to the present invention, it is possible to provide a developer for developing an electrostatic latent image that can form a high-quality image and can be easily manufactured, and a method for manufacturing the same.

  Hereinafter, embodiments of the present invention will be described. Note that the evaluation results (values indicating shape, physical properties, etc.) relating to powder (more specifically, toner base particles, external additives, toners, carriers, etc.) are a considerable number of particles unless otherwise specified. Is the number average of the values measured for. Further, the particle diameter of the powder is a circle equivalent diameter of a particle (a diameter of a circle having the same area as the projected area of the particle) unless otherwise specified. 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 developer according to this embodiment includes toner and a carrier. The toner and the carrier are each an aggregate (powder) of a plurality of particles. The toner includes a plurality of toner particles having the configuration described below. The carrier includes a plurality of carrier particles having the configuration described below. The developer according to this embodiment can be suitably used for developing an electrostatic latent image. The toner contained in the developer according to this embodiment is, for example, a positively chargeable toner.

  The developer according to the exemplary embodiment can be suitably used in, for example, the following image forming method. 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 (toner and carrier). In the developing process, a developer is carried on a developing roller (a developing roller having a built-in magnet roll) disposed near the photosensitive drum, and the toner (charged toner) in the developer is converted into an electrostatic latent image on the photosensitive member. Adhere. As a result, a toner image is formed on the photoreceptor. In the subsequent transfer step, the toner image on the photosensitive member is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan.

The developer according to the exemplary embodiment includes toner and a carrier having the following configuration (hereinafter referred to as a basic configuration).
(Basic carrier structure)
The carrier contains carrier particles having a particle diameter of less than 20 μm (hereinafter referred to as small carrier particles) at a ratio of 10% by mass to 25% by mass. The volume median diameter (hereinafter referred to as the total carrier particle diameter) of all carrier particles contained in the carrier is 30 μm or more and 42 μm or less. The triboelectric charge amount between all the carrier particles contained in the carrier and the toner (hereinafter referred to as total carrier charge amount Q _A ), and the triboelectric charge amount Q _B between the small carrier particles contained in the carrier and the toner (hereinafter referred to as small amounts). The carrier charge amount Q _B ) satisfies the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”. The measuring method of each of the volume median diameter (D ₅₀ ) and the triboelectric charge amount (Q _A , Q _B ) is the same method as in the examples described later or an alternative method thereof.

  In order to form a high-quality image, it is preferable that the carrier contains small carrier particles at a ratio of 10% by mass or more and 25% by mass or less so that the total carrier particle diameter is 30 μm or more and 42 μm or less. Small carrier particles have a large specific surface area. When an image is formed using a carrier containing small carrier particles, a large amount of toner can be carried on the carrier, and density unevenness in the formed image can be easily reduced. In addition, carrier particles having a small particle diameter have excellent charge rising characteristics (easy to be charged early). By using a carrier containing small carrier particles at a ratio (10% by mass or more and 25% by mass or less) defined by the above basic configuration, not only a low density image but also a high density image can be easily formed with high image quality. Such a carrier particle size distribution (ratio of small carrier particles: 10% by mass or more and 25% by mass or less) is not too sharp. For this reason, the carrier which has the said basic structure can be manufactured comparatively easily.

As the particle diameter of the carrier particles decreases, the saturation magnetization of the carrier particles tends to decrease. When the saturation magnetization of the carrier particles decreases, carrier adhesion (a phenomenon in which carrier particles adhere to the surface of the photoreceptor) is likely to occur. In the carrier having the above basic configuration, the total carrier charge amount Q _A and the small carrier charge amount Q _B satisfy the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”. By making the small carrier charge amount Q _B sufficiently low, carrier adhesion can be suppressed. The inventor has found that by satisfying the above relational expression in the small carrier charge amount Q _B , toner charging defects can be suppressed while suppressing carrier adhesion.

By forming the resin layer on the surface of the carrier core constituting the carrier particles, the durability or fluidity of the carrier can be improved. In order to adjust the small carrier charge amount Q _B so as to satisfy the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”, among the carrier particles contained in the carrier, the small carrier particles ( It is preferable that only carrier particles having a particle diameter of less than 20 μm contain an additive having a polarity opposite to that of the resin constituting the resin layer in the resin layer. In a negatively chargeable carrier (a carrier for positively charging a toner), it is preferable to use a silicone resin as a resin constituting the resin layer and an aminosilane coupling agent as an additive having a polarity opposite to that of the silicone resin. Preferable examples of the silicone resin include methyl silicone resin, methylphenyl silicone resin, alkyl-modified silicone resin, or fluorine-modified silicone resin. Moreover, as an aminosilane coupling agent, it is especially preferable to use the compound shown below.

  The aminosilane coupling agent is represented by the following general formula (1).

In general formula (1), Y represents a reactive functional group having an amino group at the end. This reactive functional group (Y) reacts and bonds with an organic material (more specifically, an acid, ester, epoxy, ketone, halide, or the like). N represents an integer of 1 to 3. X ₁ each independently represents a hydrolyzable functional group that is hydrolyzed with water or moisture to form silanol. The produced silanol reacts with the inorganic material. X ₂ each independently represents an alkyl group. However, when n represents 3, X ₂ does not exist.

In order to adjust the small carrier charge amount Q _B so as to satisfy the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”, in the general formula (1), the reactive functional group represented by Y The amino group located at the end is “—NH ₂ ”, each X ₁ independently represents an alkoxy group, an acetoxy group, or a chloro group, and each X ₂ independently represents a methyl group. It is preferable to use an aminosilane coupling agent. As an example of such an aminosilane coupling agent, 3-aminopropyltriethoxysilane (Y: aminopropyl group, n: 3, X ₁ : ethoxy group) is represented by formula (2), and 3- (2-aminoethylamino) Propyltrimethoxysilane (Y: aminoethylaminopropyl group, n: 3, X ₁ : methoxy group) is represented by formula (3), and 3- (2-aminoethylamino) propyldimethoxymethylsilane (Y: aminoethylamino) A propyl group, n: 2, X ₁ : methoxy group, X ₂ : methyl group) is shown in Formula (4).

  The toner contained in the developer according to the present embodiment includes a plurality of toner particles. The toner particles may include an external additive. When the toner particles include an external additive, the toner particles include a toner base particle and an external additive. The external additive adheres to the surface of the toner base particles. The toner base particles include a binder resin. If necessary, an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) may be dispersed in the binder resin of the toner base particles. If not necessary, the external additive may be omitted. When omitting the external additive, the toner base particles correspond to the toner particles. The toner particles contained in the toner according to the present embodiment may be toner particles not having a shell layer (hereinafter referred to as non-capsule toner particles), or toner particles having a shell layer (hereinafter referred to as capsule toner particles). May be described). Capsule toner particles can be produced by forming a shell layer on the surface of toner base particles (toner core). The shell layer may consist essentially of only a thermosetting resin (for example, a suitable thermosetting resin described later) or substantially only a thermoplastic resin (for example, a suitable thermoplastic resin described later). It may be included, and both a thermoplastic resin and a thermosetting resin may be contained.

In order to form a high-quality image using the developer according to this embodiment, it is preferable that the volume median diameter (D ₅₀ ) of the toner is 6 μm or more and 9 μm or less. The method for measuring the volume median diameter is the same method as in the examples described later or an alternative method thereof.

  Non-capsule toner particles can be produced, for example, by 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 particles.

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

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

  When producing the capsule toner particles, the method for forming the shell layer is arbitrary. For example, the shell layer may be formed using any of an in-situ polymerization method, a submerged cured coating method, and a coacervation method.

  The types of suitable resins used for each of the toner particles and carrier particles are shown below.

<Preferable thermoplastic resin>
Examples of the thermoplastic resin constituting each of the toner particles (particularly the toner core and shell layer) and the carrier particles (particularly the carrier core) include styrene resins and acrylic resins (more specifically, acrylic esters). Polymer or methacrylic acid ester polymer), olefin resin (more specifically, polyethylene resin or polypropylene resin, etc.), vinyl resin (more specifically, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N -Vinyl resin etc.), a polyester resin, a polyamide resin, or a urethane resin can be used conveniently. In addition, a copolymer (more specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) containing one or more repeating units derived from the same monomer as the repeating unit of any of the above resins, It can be suitably used as a thermoplastic resin constituting each of toner particles and carrier particles.

  The thermoplastic resin can be obtained by condensation polymerization or co-condensation polymerization of one or more thermoplastic monomers (more specifically, an acrylic acid monomer or a styrene monomer). The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization. The polyester resin can be obtained by polycondensation or copolycondensation of alcohol and carboxylic acid. The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers.

<Preferable thermosetting resin>
Examples of the thermosetting resin constituting each of the toner particles (particularly the shell layer) and the carrier particles (particularly the carrier core) include melamine resin, urea resin, sulfonamide resin, glyoxal resin, and guanamine resin. Resins, aniline resins, polyimide resins (more specifically, maleimide polymers or bismaleimide polymers), or xylene resins can be suitably used.

  The thermosetting resin can be obtained by polycondensation or copolycondensation of 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 that becomes a thermosetting resin by homopolymerization.

  Preferable examples of the thermosetting monomer include methylol melamine, melamine, methylolated urea (more specifically, dimethylol dihydroxyethylene urea), urea, benzoguanamine, acetoguanamine, or spiroguanamine.

  Next, preferred examples of the respective configurations of the non-capsule toner particles (toner base particles and external additives) and carrier particles (carrier core and resin layer) will be described.

[Toner mother particles]
The toner base particles contain a binder resin. The toner base particles may contain an internal additive (for example, a colorant, a release agent, a charge control agent, and a magnetic powder).

(Binder resin)
In the toner base particles, generally, the binder resin occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the overall properties of the toner base particles. In order to achieve both heat-resistant storage stability and low-temperature fixability of the non-capsule toner particles, the toner base particles preferably contain the above-mentioned suitable thermoplastic resin as a binder resin, and polyester resin and styrene-acrylic It is particularly preferable to contain at least one of acid resins.

(Coloring agent)
The toner base particles may contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using toner, the amount of the colorant used 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 used is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

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

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

(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 positively chargeable charge control agent to the toner base particles, the cationic property 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 the magnetic powder include iron (more specifically, ferrite or magnetite), ferromagnetic metal (more specifically, cobalt or nickel), an alloy containing iron and / or ferromagnetic metal, ferromagnetic A ferromagnetic alloy or chromium dioxide that has been subjected to a chemical treatment (more specifically, a heat treatment or the like) 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.

[Carrier particles]
In order to improve the durability or fluidity of the carrier, the carrier particles contained in the carrier preferably include a carrier core and a resin layer formed on the surface of the carrier core, and the resin layer is substantially More preferably, it is composed of a silicone resin (more specifically, the aforementioned methyl silicone resin or the like). In order to adjust the small carrier charge amount Q _B so as to satisfy the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”, among the carrier particles contained in the carrier, the small carrier particles ( It is preferable that only the carrier particles having a particle diameter of less than 20 μm contain an aminosilane coupling agent (more specifically, the aforementioned 3-aminopropyltriethoxysilane or the like) in the resin layer.

As a method for producing a developer containing a carrier having the above basic structure, a method including the following steps (preparation of toner, preparation of a carrier core, and formation of a resin layer) is preferable. In the toner preparation, a toner including a plurality of toner particles is prepared. In the preparation of the carrier core, a carrier core powder including a carrier core having a volume median diameter of 30 μm to 42 μm and a particle diameter of less than 20 μm at a ratio of 10% by mass to 25% by mass is prepared. In the formation of the resin layer, a resin layer having a maximum thickness of 1 μm or less is formed on each surface of the carrier core to obtain carrier particles. In forming the resin layer, the resin layer is configured so that the total carrier charge amount Q _A and the small carrier charge amount Q _B satisfy the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”. An additive (for example, an aminosilane coupling agent) having a polarity opposite to that of the resin (for example, a silicone resin) is selectively added to the resin layer of the small carrier particles.

According to the above method, it is possible to easily and suitably produce a developer including a carrier having the above-described basic configuration. As a method other than the above method, for example, the ratio of the small carrier charge amount Q _{B to} the total carrier charge amount Q _{A is} obtained by changing the type of resin constituting the resin layer between the small carrier particles and the other carrier particles. There is a method of adjusting (Q _B / Q _A ).

(Career core)
The carrier core preferably includes a magnetic material. Examples of the magnetic material contained in the carrier core include magnetite, barium ferrite, maghemite, Mn—Zn containing ferrite, Ni—Zn containing ferrite, Mn—Mg containing ferrite, Ca—Mg containing ferrite, Li containing ferrite, or Cu— Metal oxides such as Zn-containing ferrite are preferred, and magnetite is particularly preferred. As a material for each carrier core, one type of magnetic material may be used alone, or two or more types of magnetic materials may be used in combination. A plurality of types of carrier cores made of different materials may be mixed. A commercially available product may be used as the carrier core. Also, the carrier core may be made by pulverizing and firing the magnetic material.

  The magnetic material particles may be dispersed in the binder resin of the carrier core. As the binder resin for the carrier core, for example, one or more resins selected from the group consisting of the above-described suitable thermoplastic resins and suitable thermosetting resins can be used.

(Resin layer)
The resin layer is formed on the surface of the carrier core so as to cover the carrier core. Examples of the resin layer forming method include a method of immersing the carrier core in a liquid containing a resin, or a method of spraying a liquid containing a resin on the carrier core in the fluidized bed.

  The resin constituting the resin layer is preferably an insulating resin. As resin which comprises a resin layer, a thermoplastic resin may be used and a thermosetting resin may be used. Moreover, you may provide crosslinking | crosslinked property to a thermoplastic resin by mixing a thermoplastic resin and a hardening | curing agent.

  When a thermoplastic resin is used as the resin constituting the resin layer, examples of the thermoplastic resin include polystyrene, polymethyl methacrylate, acrylic resin, styrene-acrylic acid copolymer, styrene-butadiene copolymer, ethylene- Vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose or its derivatives (from Specifically, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, or hydroxypropyl cellulose), novolac resin, low molecular weight polyethylene, saturated alkyl polyester Resin, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester resin (more specifically, polyarylate), polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, or polyether ketone Resins can be preferably used.

  When a thermosetting resin is used as the resin constituting the resin layer, examples of the thermosetting resin include phenol resin, modified phenol resin, maleic resin, alkyd resin, epoxy resin, acrylic resin, maleic anhydride and terephthalic acid. Polyester, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin A polyimide resin, a polyamideimide resin, a polyetherimide resin, or a urethane resin is preferable, and a silicone resin is particularly preferable.

  Examples of the present invention will be described. Table 1 shows developers DA-1 to DA-5 and DB-1 to DB-8 (two-component developers for electrostatic latent image development, respectively) according to Examples or Comparative Examples. Table 2 shows carriers A-1 to A-5 and B to I used in the production of developers DA-1 to DB-8. Table 3 shows carrier cores A to I used in the production of carriers A-1 to A-1.

Hereinafter, a production method, an evaluation method, and an evaluation result of developers DA-1 to DB-8 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. The measured value of the mass average molecular weight (Mw) is a value measured using gel permeation chromatography unless otherwise specified. The volume median diameter (D ₅₀ ) is measured as follows unless otherwise specified.

<Measurement method of volume median diameter>
The volume median diameter of the sample was determined from the particle size distribution of the sample measured by the following method. First, 20 mg of a sample (for example, carrier particles), 1 mL of alkyl ether sulfate ester sodium, and 50 mL of an electrolytic solution (“ISOTON-2” manufactured by Beckman Coulter, Inc.) were mixed. Subsequently, the obtained mixture was subjected to ultrasonic irradiation for 3 minutes at a frequency of 20 kHz using an ultrasonic dispersion device ("VS-D100" sold by ASONE Corporation) to obtain a dispersion for evaluation. Subsequently, using a particle size distribution measuring apparatus (“Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc.), the volume particle size distribution of the sample in the dispersion for evaluation was measured under the conditions of an aperture diameter of 100 μm and the number of measured particles of 50000. did. And the volume median diameter of the sample was calculated | required from the measured volume particle size distribution.

Further, the triboelectric charge amount (total carrier charge amount Q _A and small carrier charge amount Q _B ) between the carrier and the toner was measured by the following method.
<Measurement method of triboelectric charge>
100 parts by mass of the carrier and 7 parts by mass of the toner were mixed for 30 minutes under a condition of a rotation speed of 96 rpm using a mixer (“Turbler (registered trademark) mixer T2F” manufactured by Willy et Bacofen (WAB)). Subsequently, the triboelectric charge amount of the toner in the obtained mixture was measured using a Q / m meter (“MODEL 210HS-2A” manufactured by Trek). Specifically, 0.10 g of the mixture (carrier and toner) was charged into a measurement cell of a Q / m meter, and only the toner in the charged mixture was sucked through a sieve (metal mesh) for 10 seconds. Then, the toner charge amount (μC / g) was calculated based on the formula “total amount of sucked toner (μC) / mass of sucked toner (g)”.

[Toner Preparation]
Using a mixer (“FM mixer” manufactured by Nippon Coke Industries, Ltd.), 100 parts by mass of the binder resin, 4 parts by mass of the colorant, 1 part by mass of the charge control agent, and 5 parts by mass of the release agent are mixed. did. As the binder resin, a polyester resin having an acid value of 5.6 mg KOH / g and a melting point of 100 ° C. was used. Examples of the colorant include C.I. I. Pigment Blue 15: 3 (copper phthalocyanine blue pigment) was used. As the charge control agent, a quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Co., Ltd.) was used. As the release agent, a wax (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato Co., Ltd.) was used.

Subsequently, the obtained mixture was kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). Subsequently, the obtained kneaded material was pulverized by using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo). 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, toner mother particles having a volume median diameter (D ₅₀ ) of 6.8 μm were obtained.

  Subsequently, 100 parts by mass of toner base particles and hydrophobic silica particles (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd.) were used using a mixer (“FM mixer” manufactured by Nippon Coke Industries, Ltd.). By mixing with 1 part by mass, an external additive (silica particles) was adhered to the surface of the toner base particles. Thereafter, the obtained toner was sieved using a sieve of 200 mesh (aperture 75 μm). As a result, a toner containing many toner particles was obtained.

[Career preparation]
40 parts by mass in terms of MnO (volume median diameter 0.9 μm), 9 parts by mass in terms of MgO (volume median diameter 0.9 μm), 50 parts by mass in terms of Fe ₂ O ₃ (volume median diameter 0.8 μm) The raw materials (MnO, MgO, and Fe ₂ O ₃ raw materials) were mixed so that Subsequently, the obtained mixture was pulverized for 2 hours at a set particle diameter of 1 μm using a wet ball mill. Thereafter, polyvinyl alcohol was added to the obtained pulverized product, and the pulverized product was granulated using a spray dryer. Subsequently, after the obtained granulated material was put into an electric furnace and fired, carrier cores A to I shown in Table 3 were obtained through a crushing step and a classification step (classification by an airflow type classifier). By changing the carrier core production conditions (more specifically, the conditions of granulation treatment using a spray dryer or the classification process), the volume median diameter of all carrier cores (the total particle diameter of the carrier core) And the ratio of the carrier core having a particle diameter of less than 20 μm (the ratio of small particles of the carrier core) can be adjusted to the values shown in Table 3, respectively.

  Carriers A-1 to A-5 and B to I were produced using the carrier cores A to I obtained as described above. More specifically, the carrier core (any of the carrier cores A to I shown in Table 2) is sieved using a sieve having an opening of 20 μm, and includes only a carrier core having a particle diameter of less than 20 μm (hereinafter referred to as “core core”). And a carrier core including only a carrier core having a particle diameter of 20 μm or more (hereinafter referred to as a large carrier core).

100 parts by mass of a methyl silicone resin having a mass average molecular weight (Mw) of 1.5 × 10 ^{4 and 4} parts by mass of a curing catalyst (octylic acid) were added to a solvent to obtain a carrier coating solution. Subsequently, 3 parts by mass of the carrier coating solution and 100 parts by mass of the large carrier core are set in a rolling fluidized bed coating apparatus (“Spiral Coater (registered trademark) SP-25” manufactured by Okada Seiko Co., Ltd.). The large carrier core was coated with a resin layer (methylsilicone resin layer) so that the methylsilicone resin was 3% by mass relative to the mass of the carrier core. Thereafter, the large carrier core covered with the resin layer was fired at 260 ° C. for 3 hours. Thereafter, the obtained fired product was cooled and crushed to obtain a large carrier.

  In addition, a small carrier was prepared in the same manner as the above large carrier preparation method except for the following. In the preparation of the small carrier, a small carrier core was used instead of the large carrier core. Further, an aminosilane coupling agent (“KBM-602” manufactured by Shin-Etsu Chemical Co., Ltd., component: 3- (2-aminoethylamino) propyldimethoxymethylsilane) is further added to the carrier coating solution, and the mass of the small carrier core is increased. On the other hand, the small carrier core was coated with a resin layer (methylsilicone resin layer) so that the methyl silicone resin was 4.5 mass% and the aminosilane coupling agent was in a predetermined ratio (the ratio shown in Table 2). However, in the production of Carrier A-5, no aminosilane coupling agent was added to the carrier coat solution.

  Subsequently, the large carrier and the small carrier obtained as described above were mixed to obtain carriers A-1 to A-5 and B to I. As shown in Table 2, the total carrier particle diameter (volume median diameter of all carrier particles contained in the carrier) and the ratio of small carrier particles (= 100 × mass of small carrier particles / mass of all carrier particles) Each was substantially the same as the value before forming the resin layer (total particle diameter and ratio of small particles of the carrier core shown in Table 3).

[Manufacture of developer]
100 parts by mass of carriers (carriers defined for each of developers DA-1 to DA-5 and DB-1 to DB-8) shown in Table 1 and 8 parts by mass of toner (toner manufactured by the above procedure) The mixture was stirred for 30 minutes using a powder mixer (“Rocking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd.). As a result, developers DA-1 to DA-5 and DB-1 to DB-8 were obtained.

[Evaluation method]
The evaluation method of each sample (Developers DA-1 to DA-5 and DB-1 to DB-8) is as follows. An image was formed using a sample (developer), and image density (ID), fog density (FD), image roughness, and carrier adhesion were evaluated. As an evaluation machine, a color multifunction machine (an evaluation machine obtained by modifying “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) into a two-component development system was used. The sample (developer) was put into the developing device of the evaluation machine, and the toner (replenishment toner) corresponding to the sample (developer) was put into the toner container of the evaluation machine.

  Using the evaluation machine, a first press life test was performed in which 1000 sheets were continuously printed at a printing rate of 50% in a normal temperature and humidity environment (temperature 23 ° C., humidity 50% RH). Further, after performing the first printing durability test, using the above-mentioned evaluation machine, the second continuous printing is performed for 5000 sheets at a printing rate of 0.1% in a normal temperature and normal humidity environment (temperature 23 ° C., humidity 50% RH). A printing durability test was conducted.

  Before the first printing test (hereinafter referred to as the initial), after the first printing test and before the second printing test (hereinafter described as the first printing test), and after the second printing test At each timing, a sample image including a solid portion and a blank portion was formed on a recording medium (evaluation paper) using the evaluation machine. Thereafter, the image density (ID) of the solid portion of the image formed on the recording medium was measured using a reflection densitometer (“RD914” manufactured by X-Rite). Further, the image density (ID) of the blank portion of the image formed on the recording medium was measured using a reflection densitometer (“RD914” manufactured by X-Rite), and the fog density (FD) was calculated. The fog density (FD) corresponds to a value obtained by subtracting the image density (ID) of the base paper (unprinted paper) from the image density (ID) of the blank portion of the recording medium after printing.

The measured image density (ID) was evaluated according to the following criteria.
A (very good): The image density was 1.4 or more.
○ (good): The image density was 1.3 or more and less than 1.4.
Δ (Normal): The image density was 1.2 or more and less than 1.3.
X (Poor): The image density was less than 1.2.

The measured fog density (FD) was evaluated according to the following criteria.
A (very good): The fog density (FD) was less than 0.004.
○ (Good): The fog density (FD) was 0.004 or more and less than 0.006.
Δ (Normal): The fog density (FD) was 0.006 or more and less than 0.010.
X (Poor): The fog density (FD) was 0.010 or more.

  When evaluating image roughness, a sample image including a solid portion and a blank portion was initially formed on a recording medium (evaluation paper) using the evaluation machine. Thereafter, the image roughness of the solid portion of the image formed on the recording medium is determined by a method defined in “ISO 13660” using a handy image evaluation system (“MODEL PIAS-II” manufactured by QEA (Quality Engineering Associates)). It was measured by. Note that the image blur indicates a degree of granularity due to density unevenness in the solid image (particularly, density fluctuation at a low spatial frequency in the solid image).

The measured image mottle was evaluated according to the following criteria.
A (very good): Image blur was 0.80 or less.
○ (Good): Image roughness was more than 0.80 and 0.95 or less.
X (Poor): Image roughness was more than 0.95.

  When evaluating carrier adhesion, in the initial stage, the evaluator was instructed to print a sample image including a solid portion and a blank portion, and the printing operation of the evaluator was stopped during printing. Thereafter, the photosensitive drum was taken out from the evaluation machine, and the number of carrier particles attached to the photosensitive drum was determined. Specifically, carrier particles attached to the photosensitive drum were collected using a tape, and the number of carrier particles attached per unit area (2 cm × 2 cm) of the surface of the photosensitive drum was determined. The carrier adhesion was evaluated based on the number of carrier particles (hereinafter referred to as “adhered carrier particles”) adhering to the photosensitive drum.

The evaluation criteria for carrier adhesion are as follows.
A (very good): The number of adhered carrier particles was less than 5.
○ (good): The number of the adhered carrier particles was 5 or more and less than 10.
X (Poor): The number of adhering carrier particles was 10 or more.

[Evaluation results]
Tables 4 and 5 show the evaluation results for each of developers DA-1 to DB-8.

Each carrier of developers DA-1 to DA-3 and DB-1 to DB-4 (developers according to Examples 1 to 7) had the above-described basic configuration. Specifically, in each of the developers according to Examples 1 to 7, as shown in Table 2, the carrier contained small carrier particles at a ratio of 10% by mass to 25% by mass. The total carrier particle size was 30 μm or more and 42 μm or less. Further, as shown in Table 1, the total carrier charge amount Q _A and the small carrier charge amount Q _B satisfied the relational expression “0.5 ≦ Q _B / Q _A ≦ 0.8”. As shown in Table 4 and Table 5, in the developers according to Examples 1 to 7, carrier adhesion could be suppressed. In addition, each of the developers according to Examples 1 to 7 can give a stable charge amount to the toner, and excellent developability was maintained both in the initial stage and after the printing durability test. Further, the developers according to Examples 1 to 7 could be manufactured at low cost.

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

Claims (5)

A carrier comprising a plurality of carrier particles and a toner comprising a plurality of toner particles,
The carrier contains the carrier particles having a particle diameter of less than 20 μm at a ratio of 10% by mass to 25% by mass,
The volume median diameter of all the carrier particles contained in the carrier is 30 μm or more and 42 μm or less,
The frictional charge amount Q _A between all the carrier particles contained in the carrier and the toner, and the triboelectric charge amount Q _B between the carrier particles contained in the carrier and the particle diameter of less than 20 μm and the toner are expressed by a relational expression. _A developer for developing an electrostatic latent image that satisfies “0.5 ≦ Q _B / Q _A ≦ 0.8”. The carrier particles include a carrier core and a resin layer formed on the surface of the carrier core,
Only the carrier particles having a particle diameter of less than 20 μm among the carrier particles contained in the carrier contain an additive having an opposite polarity to the resin constituting the resin layer in the resin layer. The developer for electrostatic latent image development of description.   The developer for electrostatic latent image development according to claim 2, wherein the resin constituting the resin layer is a silicone resin, and the additive is an aminosilane coupling agent.   The electrostatic toner image development according to any one of claims 1 to 3, wherein the toner particles are non-capsule toner particles containing at least one of a polyester resin and a styrene-acrylic acid resin as a binder resin. Developer. Preparing a toner comprising a plurality of toner particles;
Preparing a carrier core powder including a carrier core having a volume median diameter of 30 μm or more and 42 μm or less and a particle diameter of less than 20 μm at a ratio of 10% by mass or more and 25% by mass or less;
Forming a resin layer having a maximum thickness of 1 μm or less on each surface of the carrier core to obtain carrier particles;
Including
In the formation of the resin layer, and the triboelectric charge quantity Q _A and the all of the carrier particles toner, and a triboelectric charge quantity Q _B of the said carrier particles having a particle size of less than 20μm toner relationship "0. 5 ≦ Q _B / Q _A ≦ 0.8 ”, an additive having a polarity opposite to that of the resin constituting the resin layer is selectively added to the resin layer of carrier particles having a particle diameter of less than 20 μm. A method for producing a developer for developing an electrostatic latent image, which is added to the above.