JP6919454B2 - Carrier, carrier manufacturing method, and two-component developer - Google Patents

Description

The present invention relates to a carrier, a method for producing the carrier, and a two-component developer.

Resin coated carriers are known. Each of the plurality of carrier particles contained in the resin-coated carrier includes a carrier core and a resin layer that coats the surface of the carrier core. Patent Document 1 described later describes that a single resin layer is formed by using two or more kinds of resins having different compositions.

JP-A-2009-98348

If the composition of the resin is different, the curing temperature of the resin is likely to be different. Therefore, if an attempt is made to form a single-layer resin layer using two or more types of resins having different compositions, the thickness of the obtained resin layer may become non-uniform. This may reduce the durability of the resin layer. For example, when the carrier is used for a long period of time, the resin layer may peel off from the surface of the carrier core. Further, when the carrier is used for a long period of time, the toner or the external additive may adhere to the surface of the carrier particles. When the durability of the resin layer is lowered, the charging ability of the carrier may be lowered when the carrier is used for a long period of time.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a carrier capable of maintaining a charging ability even when used for a long period of time, and a method for producing the same. Another object of the present invention is to provide a two-component developer containing such a carrier.

The carrier according to the present invention includes a plurality of carrier particles. The carrier particles each include a carrier core and a first coat layer and a second coat layer that cover the surface of the carrier core. The first coat layer and the second coat layer have a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. The first coat layer contains a melamine resin. The second coat layer contains a fluororesin. The melamine resin and the fluororesin are bonded to each other by a covalent bond represented by the following formula (1-1).

In the above formula (1-1), X ¹ represents the first terminal portion and X ² represents the second terminal portion. The first terminal portion is connected to the atoms constituting the melamine resin. The second terminal portion is connected to the atoms constituting the fluororesin.

The method for producing a carrier according to the present invention is a method for producing a carrier containing a plurality of carrier particles. Specifically, the method for producing a carrier according to the present invention includes a step of supplying a first resin to the surface of a carrier core, a step of supplying a second resin to the surface of the first resin, and the first resin and the first resin. 2 Includes a step of heat-treating the carrier core supplied with the resin on the surface at a predetermined temperature. The first resin contains a melamine resin or a precursor of a melamine resin. The second resin contains at least one selected from the group consisting of a fluororesin containing a hydroxyl group in the molecule and a fluororesin containing a functional group capable of generating a hydroxyl group in the molecule by a hydrolysis reaction. The predetermined temperature is equal to or higher than the temperature at which the methylol group contained in the molecule of the melamine resin or the methylol group contained in the molecule of the precursor of the melamine resin reacts with the hydroxyl group.

The two-component developer according to the present invention includes a carrier having the above-mentioned structure and a positively charged toner that is positively charged by friction with the carrier.

According to the present invention, the charging ability of the carrier can be maintained even when the carrier is used for a long period of time.

An embodiment of the present invention will be described. Unless otherwise specified, the evaluation result (value indicating the shape or physical properties) of the powder is the average number of values measured for a considerable number of particles. The powder includes, for example, carriers, toner, and toner matrix particles.

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

Unless otherwise specified, the measured values of the acid value and the hydroxyl value are the values measured according to "JIS (Japanese Industrial Standards) K0070-1992". The glass transition point (Tg) is a value measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. The softening point (Tm) is a value measured using an heightened flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified.

The strength of chargeability corresponds to the ease of triboelectric charging, unless otherwise specified. For example, the toner can be triboelectrically charged by mixing it with a standard carrier (anionic: N-01, cationic: P-01) provided by the Imaging Society of Japan and stirring it. The surface potential of the toner particles is measured with, for example, KFM (Kelvin probe force microscope) before and after triboelectric charging, and the larger the change in potential before and after triboelectric charging, the stronger the chargeability.

A compound and its derivatives may be generically referred to by adding "system" after the compound name. When the polymer name is represented by adding "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacryl may be collectively referred to as "(meth) acrylic". Acryloyl and methacryloyl may be collectively referred to as "(meth) acryloyl".

The carrier according to the present embodiment is an electrostatic latent image developing carrier that can be suitably used for developing an electrostatic latent image. The carrier according to the present embodiment positively charges the toner by rubbing against the toner in the developing apparatus.

The carrier-containing two-component developer according to this embodiment can be used, for example, in forming an image in an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

First, an electrostatic latent image is formed on the photosensitive layer of the photoconductor drum based on the image data. Next, the formed electrostatic latent image is developed using the toner contained in the two-component developer (development step). Specifically, first, the toner is positively charged by friction between the toner and the carrier in the developing apparatus. Next, the developing device supplies the toner on the developing sleeve to the photosensitive layer of the photoconductor drum and attaches it to the electrostatic latent image by an electric force. In this way, the electrostatic latent image is developed, and a toner image is formed on the photosensitive layer of the photoconductor drum. Subsequently, the toner image is transferred to a recording medium (for example, paper), and then the unfixed toner image is fixed to the recording medium by heating. As a result, an image is formed on the recording medium.

[Basic career structure]
The carrier according to this embodiment includes a plurality of carrier particles. The carrier particles each include a carrier core and a first coat layer and a second coat layer that cover the surface of the carrier core. The first coat layer and the second coat layer have a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. More specifically, the first coat layer covers at least a part of the surface of the carrier core, and the second coat layer covers at least a part of the surface of the first coat layer. Preferably, the coverage of the first coat layer in the surface region of the carrier core is 100%. Preferably, the coverage of the second coat layer in the surface region of the first coat layer is 100%.

The first coat layer contains a melamine resin. The second coat layer contains a fluororesin. The melamine resin and the fluororesin are bonded to each other by a covalent bond represented by the following formula (1-1). In the following formula (1-1), X ¹ represents the first terminal portion and X ² represents the second terminal portion. The first terminal portion is connected to the atoms constituting the melamine resin. The second terminal portion is connected to the atoms constituting the fluororesin. Hereinafter, the "covalent bond represented by the formula (1-1)" will be referred to as a "specific covalent bond".

In the carrier according to the present embodiment, the first coat layer contains a melamine resin. Melamine resins generally have a relatively high hardness. Therefore, even when the carrier according to the present embodiment is used for a long period of time, it is possible to prevent the first coat layer from peeling off from the surface of the carrier core. Therefore, it is possible to prevent the second coat layer from peeling off together with the first coat layer.

Further, in the carrier according to the present embodiment, the melamine resin and the fluororesin are bonded to each other by a specific covalent bond. Therefore, even when the carrier according to the present embodiment is used for a long period of time, it is possible to prevent the second coat layer from peeling off from the surface of the first coat layer.

Summarizing the above, peeling of the second coat layer can be prevented even when the carrier according to the present embodiment is used for a long period of time. As a result, even when the carrier according to the present embodiment is used for a long period of time, the charging ability of the carrier can be maintained.

Fluororesin also generally has a relatively low surface free energy. Therefore, if the peeling of the second coat layer can be prevented, it is possible to prevent the toner or the external additive from adhering to the surface of the carrier particles even when the carrier according to the present embodiment is used for a long period of time. This also makes it possible to prevent a decrease in the charging ability of the carrier when the carrier according to the present embodiment is used for a long period of time.

As described above, even when the carrier according to the present embodiment is used for a long period of time, the charging ability of the carrier can be maintained. Therefore, even when the carrier according to the present embodiment is used for a long period of time, it is possible to prevent the toner charge amount from being out of the desired range. For example, even when the carrier according to the present embodiment is used for a long period of time, it is possible to prevent the toner charge amount from being significantly reduced. Further, even when the carrier according to the present embodiment is used for a long period of time, it is possible to prevent the back-charged toner from scattering, so that the fog resistance of the toner can be maintained.

Fluororesin generally exhibits a relatively strong negative charge. Therefore, the carrier according to the present embodiment tends to positively charge the toner by friction. As the amount of the fluororesin in the second coat layer increases, the toner charge amount tends to increase while maintaining a state not exceeding a desired range. In the examples described later, three types of fluororesins having different compositions (more specifically, copolymers A to C described later) are used. Then, in the examples described later, the larger the amount of each of the copolymers A to C in the second coating liquid, the higher the toner charge amount tends to be while maintaining a state not exceeding a desired range. Therefore, the present inventor considers that the copolymers A to C have different compositions, but do not have a large difference in charging ability.

When the surface layer of the carrier particles is composed of a melamine resin layer, it is difficult to positively charge the toner. This is because the melamine resin exhibits a relatively strong positive charge (see Comparative Examples 2 and 3 described later).

Further, when only the fluororesin layer covers the surface of the carrier core, the fluororesin layer is easily peeled off from the surface of the carrier core. Therefore, when the carrier is used for a long period of time, the charging ability of the carrier tends to decrease (for example, Comparative Example 4 described later). When the fluororesin contained in the fluororesin layer contains a hydroxyl group in the molecule, a path through which the electric charge is released (more specifically, a path through which the electric charge charged in the toner is released from the toner) is likely to be formed. Therefore, when the carrier is used for a long period of time, the toner charge amount tends to fall below the desired range (see Comparative Example 4 described later).

Further, when the melamine resin layer and the fluororesin layer coat the surface of the carrier core in this order, but the melamine resin and the fluororesin are not bonded to each other by a specific covalent bond, the fluororesin layer is a melamine resin layer. Easy to peel off from the surface of the resin. Therefore, when the carrier is used for a long period of time, the charging ability of the carrier tends to decrease (see Comparative Example 1 described later).

Further, when a single coat layer containing a melamine resin and a fluororesin covers the surface of the carrier core, the surface of the coat layer has a region having a relatively high surface free energy and a surface free energy. Relatively low regions are likely to exist. Therefore, when the carrier is used for a long period of time, the toner or the external additive tends to adhere to the region of the surface of the coat layer where the surface free energy is relatively high. Therefore, when the carrier is used for a long period of time, the charging ability of the carrier tends to decrease (see Comparative Example 5 described later).

[Preferable manufacturing method of carrier]
The carrier manufacturing method according to the present embodiment includes a first supply step, a second supply step, and a heat treatment step. Hereinafter, the steps will be described in order.

<First supply process>
In the first supply step, the first resin is supplied to the surface of the carrier core. Preferably, the first resin is supplied to the surface of the carrier core so that the surface of the carrier core is completely covered with the first resin.

More specifically, first, the first coating liquid is prepared. Preferably, the melamine resin or the precursor of the melamine resin (hereinafter, "the precursor of the melamine resin or the melamine resin used for forming the first coat layer" is collectively referred to as "the melamine resin for forming"). Is dispersed or dissolved in the first solvent. In this way, the first coating liquid is prepared. The amount of the forming melamine resin in the first coating liquid is preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the first solvent.

The forming melamine resin is preferably methylol melamine. By changing the type or number of functional groups contained in methylolmelamine, the solubility of methylolmelamine in water can be changed. The forming melamine resin may be a commercially available product. For example, "Milben (registered trademark) resin SM-607" or "Milben resin SM-850" manufactured by Showa Denko KK can be used. "Milben Resin SM-607" manufactured by Showa Denko KK is an aqueous solution of an initial polymer of hexamethylolmelamine (solid content concentration: 75% by mass). "Milben Resin SM-850" manufactured by Showa Denko KK is an aqueous solution (solid content concentration: 70% by mass) of an trimethylolpropane initial polymer.

The first solvent is preferably ion-exchanged water or pure water. More preferably, the first solvent is ion-exchanged water containing an acidic substance or pure water containing an acidic substance. As the acidic substance, for example, hydrochloric acid can be used.

Next, the first coating liquid is attached to the surface of the carrier core. The carrier core may be immersed in the first coating liquid, or the first coating liquid may be sprayed on the carrier core in the fluidized bed. For example, a rolling fluidized bed coating granulator (more specifically, "Spiracoater" manufactured by Okada Seiko Co., Ltd.) can be used to spray the first coating liquid onto the carrier core in the fluidized bed.

It is preferable to adjust the supply amount of the first coating liquid so that the amount of the forming melamine resin contained in the first coating liquid is 10 parts by mass or more and 50 parts by mass or less with respect to 1000 parts by mass of the carrier core. As a result, the coverage of the forming melamine resin in the surface region of the carrier core tends to be 100%. In addition, it is easy to prevent the first coat layer from peeling off in the obtained carrier. In addition, it is easy to prevent the carrier particles from agglutinating with each other in the obtained carriers. More preferably, the supply amount of the first coating liquid is adjusted so that the amount of the forming melamine resin contained in the first coating liquid is 20 parts by mass or more and 40 parts by mass or less with respect to 1000 parts by mass of the carrier core. In this way, a carrier core (first coated carrier core) to which the first resin is supplied to the surface is obtained.

<Second supply process>
In the second supply step, the second resin is supplied to the surface of the first coated carrier core. Preferably, the second resin is supplied to the surface of the first coated carrier core so that the surface of the first coated carrier core is completely covered with the second resin.

More specifically, first, a second coating liquid is prepared. Preferably, a fluororesin (hereinafter, "fluororesin used for forming the second coat layer" is referred to as "formation fluororesin") is dispersed or dissolved in a second solvent. In this way, the second coating liquid is prepared. The amount of the fluororesin for formation in the second coating liquid is preferably 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the second solvent. The second solvent is preferably an organic solvent, for example, toluene.

The fluororesin for forming includes at least one selected from the group consisting of a fluororesin containing a hydroxyl group in the molecule and a fluororesin containing a functional group capable of generating a hydroxyl group in the molecule by a hydrolysis reaction. Hereinafter, "fluororesin containing a hydroxyl group in the molecule" will be referred to as "hydroxyl-fluororesin". Further, a "functional group capable of generating a hydroxyl group by a hydrolyzing reaction" is described as a "hydrolyzable functional group". Further, "fluororesin containing a hydrolyzable functional group in the molecule" is described as "hydrolyzable functional group-fluororesin".

The hydroxyl group-fluororesin is composed of a vinyl compound containing a hydroxyl group in the molecule (hereinafter referred to as "hydroxyl compound-containing vinyl monomer") and a vinyl compound containing a fluorine atom in the molecule (hereinafter referred to as "fluoroolefin"). It is preferably a polymer of the monomer containing. The hydroxyl group-fluororesin may be, for example, a copolymer of a hydroxyl group-containing vinyl monomer and a fluoroolefin, or a copolymer of a hydroxyl group-containing vinyl monomer, a fluoroolefin, and another vinyl monomer. The hydroxyl value of the hydroxyl group-fluororesin is preferably 40.0 mgKOH / g or more, and more preferably 40.0 mgKOH / g or more and 80.0 mgKOH / g or less.

The fluoroolefin is, for example, a group consisting of vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene, and hexafluoropropylene. It is preferably at least one that is more selected. The fluoroolefin may be a (perfluoroalkyl) (perfluorovinyl) ether. The (perfluoroalkyl) (perfluorovinyl) ethers are, for example, (trifluoromethyl) (trifluorovinyl) ethers, (pentafluoroethyl) (trifluorovinyl) ethers, and (heptafluoropropyl) (trifluorovinyl) ethers. ) It is preferable that it is at least one selected from the group consisting of ether.

The hydroxyl group-containing vinyl monomer is preferably a vinyl ether containing a hydroxyl group in the molecule. The vinyl ethers containing a hydroxyl group in the molecule include, for example, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 3-hydroxypropyl vinyl ether, 3-hydroxybutyl vinyl ether, 4-hydroxybutyl vinyl ether, and 2-hydroxy-. It is preferably at least one selected from the group consisting of 2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether, and 6-hydroxyhexyl vinyl ether.

The hydroxyl group-fluororesin may be a commercially available product. For example, "Fluoronate (registered trademark) K-700" manufactured by DIC Corporation, "Lumiflon (registered trademark) LF200" manufactured by Asahi Glass Co., Ltd., or "Zefle (registered trademark) GK-510" manufactured by Daikin Industries, Ltd. can be used. can. "Fluoronate K-700" manufactured by DIC Corporation contains a hydroxyl group-containing fluoroolefin copolymer having a main chain protected by fluorine (hydroxyl value: 42.0 mgKOH / g or more and 54.0 mgKOH / g or less) (solid content concentration). : 50% by mass). "Lumiflon LF200" manufactured by Asahi Glass Co., Ltd. contains an alternating copolymer of vinyl ether containing a hydroxyl group in the molecule and fluoroethylene (hydroxyl value: 55.0 mgKOH / g or more and 65.0 mgKOH / g or less) (solid content concentration: 60% by mass). "Zeffle GK-510" manufactured by Daikin Industries, Ltd. contains a copolymer (hydroxyl value: 52.0 mgKOH / g) of tetrafluoroethylene and a hydroxyl group-containing vinyl monomer (solid content concentration: 50% by mass).

The hydrolyzable functional group-fluororesin is preferably a polymer of a monomer containing a vinyl compound containing a hydrolyzable functional group in the molecule and a fluoroolefin. The hydrolyzable functional group-fluorine resin may be a copolymer of a vinyl compound containing a hydrolyzable functional group in the molecule and a fluoroolefin, or a vinyl compound containing a hydrolyzable functional group in the molecule. It may be a copolymer of a fluoroolefin and another vinyl monomer.

The vinyl compound containing a hydrolyzable functional group in the molecule is preferably, for example, a vinyl compound containing a hydrolyzable silyl group in the molecule. Vinyl compounds containing a hydrolyzable silyl group in the molecule include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinylmethyldiethoxysilane, and vinyltris (β-methoxyethoxy) silane. , Allyltrimethoxysilane, trimethoxysilylethylvinyl ether, methyldimethoxysilylethylvinyl ether, trimethoxysilylpropylvinyl ether, triethoxysilylpropylvinyl ether, methyldimethoxysilylpropylvinyl ether, γ- (meth) acryloyloxy. It is preferably at least one selected from the group consisting of propyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, and γ- (meth) acryloyloxypropylmethyldimethoxysilane.

The other vinyl monomer means a vinyl compound excluding a fluoroolefin, a hydroxyl group-containing vinyl monomer, and a vinyl compound containing a hydrolyzable functional group in the molecule. Other vinyl monomers include, for example, alkyl vinyl ethers which may contain substituents, cycloalkyl vinyl ethers, carboxylic acid vinyl esters, α-olefins, halogenated olefins (excluding fluoroolefins), and the like. It is preferably at least one selected from the group consisting of aromatic vinyl compounds, methacrylic acid esters, and acrylic acid esters.

Next, the second coating liquid is attached to the surface of the first coating carrier core. The first coating carrier core may be immersed in the second coating liquid, or the second coating liquid may be sprayed onto the first coating carrier core in the fluidized bed. For example, the second coating liquid can be sprayed onto the first coating carrier core in the fluidized bed by using the above-mentioned rolling fluidized bed coating granulation apparatus.

It is preferable to adjust the supply amount of the second coating liquid so that the amount of the fluororesin for formation contained in the second coating liquid is 5 parts by mass or more and 40 parts by mass or less with respect to 1000 parts by mass of the carrier core. As a result, it is easy to obtain a carrier having an excellent charging ability. In addition, it is easy to prevent the carrier particles from agglutinating with each other in the obtained carriers. More preferably, the supply amount of the second coating liquid is adjusted so that the amount of the fluororesin for formation contained in the second coating liquid is 10 parts by mass or more and 30 parts by mass or less with respect to 1000 parts by mass of the carrier core. In this way, a carrier core (second coated carrier core) in which the first resin and the second resin are supplied to the surface is obtained.

<Heat treatment process>
The second coated carrier core is heat treated at a predetermined temperature. The predetermined temperature is equal to or higher than the temperature at which the methylol group reacts with the hydroxyl group. This heat treatment forms a specific covalent bond.

Generally, the melamine resin is obtained by polycondensation of melamine and formaldehyde, and has a three-dimensional network structure. Specifically, first, melamine or a melamine derivative and formaldehyde undergo an addition reaction. Melamine derivatives include, for example, methylated melamine and butylated melamine. By this addition reaction, methylol melamine (precursor of melamine resin) is obtained. Next, methylolmelamines undergo a condensation reaction with each other. As a result, the methylol group of one methylol melamine and the methylol group of another methylol melamine react with each other, and water and formaldehyde are desorbed. In this way, the melamine resin is synthesized. Therefore, melamine resins generally contain one or more unreacted methylol groups in the molecule. Therefore, the forming melamine resin tends to contain one or more unreacted methylol groups in the molecule.

As described above, the forming melamine resin tends to contain one or more unreacted methylol groups in the molecule. The fluororesin for forming is at least one selected from the group consisting of a hydroxyl group-fluororesin and a hydrolyzable functional group-fluororesin. From these facts, when the second coated carrier core is heat-treated at a predetermined temperature, the methylol group and the hydroxyl group react (dehydration reaction) to form a specific covalent bond. As described above, by using at least one selected from the group consisting of the hydroxyl group-fluororesin and the hydrolyzable functional group-fluororesin as the fluororesin for formation, the carrier according to the present embodiment can be easily obtained.

The predetermined temperature is preferably a temperature selected from a temperature range of 150 ° C. or higher and 300 ° C. or lower. The heat treatment time is preferably a time selected from a time range of 60 minutes or more and 180 minutes or less.

The method of adhering the first coating liquid to the surface of the carrier core and the method of adhering the second coating liquid to the surface of the first coating carrier core may be the same or different from each other. ..

Further, the carrier according to the present embodiment may be manufactured by the following method. Specifically, after the first coating liquid is adhered to the surface of the carrier core, the first coating liquid is cured on the surface of the carrier core. The second coating liquid is adhered to the surface of the obtained carrier core. After that, the above-mentioned heat treatment step is performed. Even in such a case, in the heat treatment step, the methylol group reacts with the hydroxyl group to form a specific covalent bond.

[Examples of materials that make up carriers]
<Career core>
The carrier core preferably contains a magnetic material. More specifically, the carrier core may be particles made of a magnetic material (magnetic material particles). The magnetic material particles may be dispersed in the resin to form a carrier core.

The magnetic material contained in the carrier core is preferably, for example, a ferromagnetic metal or a ferromagnetic metal oxide. The ferromagnetic metal is preferably, for example, iron, cobalt, or nickel. The ferromagnetic metal may be, for example, a metal material containing at least one selected from the group consisting of iron, cobalt and nickel (hereinafter, referred to as "iron and the like"). The metal material may be an alloy or a mixture. The alloy is preferably an alloy of iron or the like and another metal. The mixture is preferably a mixture containing iron or the like and another metal. The other metals mentioned above shall be at least one selected from the group consisting of copper, zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese, magnesium, selenium, tungsten, zirconium, and vanadium, respectively. Is preferable. The ferromagnetic metal oxide is preferably ferrite, for example.

The magnetic material contained in the carrier core may be a mixture of at least one selected from the group consisting of metal oxides, metal nitrides, and carbides and the above-mentioned ferromagnetic metal oxides. The metal oxide is preferably, for example, iron oxide, titanium oxide, or magnesium oxide. The metal nitride is preferably, for example, chromium nitride or vanadium nitride. The carbide may be silicon carbide or a metal carbide typified by tungsten carbide.

More preferably, the magnetic material contained in the carrier core is ferrite. Ferrites include, for example, spinel ferrite (magnetite), barium ferrite, Mn ferrite, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, Cu-Zn ferrite, or Mn-Mg-. It is preferably Sr ferrite.

As the material of each carrier core, one kind of magnetic material may be used alone, or two or more kinds of magnetic materials may be used in combination. Commercially available carrier cores may be used. You may make your own carrier core by crushing and firing the magnetic material. By changing the amount of the magnetic material added (particularly, the amount of the ferromagnetic material added), the saturation magnetization of the carrier can be adjusted. The circularity of the carrier can be adjusted by changing the firing temperature (firing temperature) of the magnetic material.

More preferably, the carrier core is particles composed of ferrite (ferrite particles). Ferrite particles tend to have sufficient magnetism for image formation. Further, the ferrite particles produced by a general manufacturing method do not become true spheres and tend to have appropriate irregularities on the surface. Specifically, the arithmetic mean roughness of the surface of the ferrite particles (specifically, the arithmetic mean roughness Ra defined by JIS (Japanese Industrial Standards) B0601-2013) tends to be 0.3 μm or more and 2.0 μm or less.

The volume median diameter (D ₅₀ ) of the carrier core is preferably 30 μm or more and 100 μm or less. Thereby, better developability can be obtained. The volume median diameter (D ₅₀ ) of the carrier core is a value measured using a laser diffraction / scattering type particle size distribution measuring device (“LA-700” manufactured by HORIBA, Ltd.).

<First coat layer>
The first coat layer contains a melamine resin. The first coat layer is preferably a melamine resin layer formed by the method described above.

<Second coat layer>
The second coat layer contains a fluororesin. The second coat layer is preferably a fluororesin layer formed by the method described above.

More preferably, the fluororesin contained in the second coat layer does not contain a hydroxyl group in the molecule. As a result, it is possible to prevent the formation of a path through which the electric charge escapes, and thus it is possible to prevent the toner charge amount from falling below a desired range.

[Examples of carrier applications]
As described above, the carrier according to the present embodiment tends to positively charge the toner by friction. Therefore, a two-component developer can be provided by using the carrier according to the present embodiment and a toner that can be positively charged by friction with the carrier.

A two-component developer according to the present embodiment is obtained by mixing and stirring the carrier according to the present embodiment and the positively charged toner using a mixer (for example, a ball mill, a nouter mixer, a locking mixer, etc.). Can be done. The blending amount of the toner particles with respect to 100 parts by mass of the carrier particles is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 15 parts by mass or less.

The composition of the toner contained in the two-component developer is not particularly limited. For example, it is preferable that each of the plurality of toner particles contained in the toner includes a toner mother particle and an external additive. The toner mother particles may be capsule toner or non-capsule toner. The external additive preferably contains a plurality of external additive particles that adhere to the surface of the toner matrix particles. Hereinafter, the positively charged toner will be specifically described by taking the case where the toner mother particles are non-capsule toner as an example.

[Example of materials constituting positively charged toner]
<Toner mother particles>
The toner mother particles contain a binder resin. The toner mother particles may further contain at least one of a colorant, a wax, and a charge control agent.

(Bundling resin)
In toner mother particles, the binder resin usually occupies most of the components (for example, 85% by mass or more). Therefore, it is considered that the properties of the binder resin have a great influence on the properties of the entire toner matrix particles.

Further, by using a plurality of types of resins in combination as the binder resin, the properties of the binder resin (specifically, the hydroxyl value, the acid value, the glass transition point, or the softening point) can be adjusted. For example, when the binder resin has an amino group or an amide group, the toner matrix particles tend to be cationic.

The binder resin preferably contains a thermoplastic resin. As the thermoplastic resin, for example, a polyester resin, a styrene resin, an acrylic acid resin, an olefin resin, a vinyl resin, a polyamide resin, or a urethane resin can be used. As the acrylic acid-based resin, for example, an acrylic acid ester polymer or a methacrylic acid ester polymer can be used. As the olefin resin, for example, a polyethylene resin or a polypropylene resin can be used. As the vinyl resin, for example, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin can be used. Further, a copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the above-mentioned resin can also be used as the thermoplastic resin constituting the toner particles. For example, a styrene-acrylic acid-based resin or a styrene-butadiene-based resin can also be used as the thermoplastic resin constituting the binder resin. In the following, a polyester resin, which is an example of a binder resin, will be described in detail.

(Bundling resin: polyester resin)
The polyester resin is a copolymer of one or more alcohols and one or more carboxylic acids. As the alcohol for synthesizing the polyester resin, for example, the following divalent alcohol or trihydric or higher alcohol can be used. As the dihydric alcohol, for example, diols or bisphenols can be used. As the carboxylic acid for synthesizing the polyester resin, for example, the following divalent carboxylic acid or trivalent or higher carboxylic acid can be used.

Preferred examples of diols include aliphatic diols. Preferable examples of aliphatic diols are diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol, 2-butene-1,4-diol, 1,4-cyclohexanedi. Examples thereof include methanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol. The α, ω-alkanediol is, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1, It is preferably 8-octanediol, 1,9-nonanediol, or 1,12-dodecanediol.

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

Preferable examples of trihydric or higher alcohols are 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, trimethylolethane, or 1,3,5- Trihydroxymethylbenzene can be mentioned.

Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acids, α, ω-alkanedicarboxylic acids, unsaturated dicarboxylic acids, or cycloalkanedicarboxylic acids. The aromatic dicarboxylic acid is preferably, for example, phthalic acid, terephthalic acid, or isophthalic acid. The α, ω-alkanedicarboxylic acid is preferably, for example, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decandicarboxylic acid. The unsaturated dicarboxylic acid is preferably, for example, maleic acid, fumaric acid, citraconic acid, itaconic acid, or glutaconic acid. The cycloalkanedicarboxylic acid is preferably, for example, a cyclohexanedicarboxylic acid.

Preferable examples of trivalent or higher valent carboxylic acids are 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-Butantricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimeric acid.

(Colorant)
As the colorant, a pigment or dye known according to the color of the positively charged toner can be used. In order to form a high-quality image using the positively charged toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

The toner mother particles may contain a black colorant. An example of a black colorant is carbon black. Further, the black colorant may be a colorant that has been adjusted to black by using a yellow colorant, a magenta colorant, and a cyan colorant.

The toner matrix 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. Bat yellow can be used.

The magenta colorant is selected from the group consisting of, for example, 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).

As the cyan colorant, for example, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and base dye lake compounds can be used. Examples of the cyan colorant 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 used.

(wax)
The wax is used, for example, for the purpose of improving the fixability or high temperature offset resistance of the positively charged toner. In order to enhance the cationic property of the toner matrix particles, it is preferable to prepare the toner matrix particles using a wax having a cationic property.

The wax is preferably, for example, an aliphatic hydrocarbon wax, a vegetable wax, an animal wax, a mineral wax, a wax containing a fatty acid ester as a main component, or a wax obtained by deoxidizing a part or all of the fatty acid ester. .. The aliphatic hydrocarbon wax is preferably, for example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or Fishertropch wax. Aliphatic hydrocarbon waxes also include these oxides. The vegetable wax is preferably, for example, candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax. The animal wax is preferably, for example, beeswax, lanolin, or whale wax. The mineral wax is preferably, for example, ozokerite, ceresin, or petrolatum. The waxes containing the fatty acid ester as a main component are preferably, for example, montanic acid ester wax or caster wax. One type of wax may be used alone, or a plurality of types of wax may be used in combination.

(Charge control agent)
The charge control agent is used, for example, for the purpose of improving the charge stability or charge rise characteristics of the positively chargeable toner. The charge rising characteristic of the positively charged toner is an index of whether or not the positively charged toner can be charged to a predetermined charging level in a short time. By incorporating a positively charged charge control agent (positive charge control agent) into the toner mother particles, the cationic property of the toner mother particles can be strengthened.

Examples of the positive charge control agent include an azine compound, a direct dye composed of an azine compound, a niglosin compound, an acid dye composed of a niglocin compound, and a quaternary ammonium salt. Examples of the azine compound include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1,4-thiazine, 1 , 2,3-Triazine, 1,2,4-Triazine, 1,3,5-Triazine, 1,2,4-Oxaziazine, 1,3,4-Oxaziazine, 1,2,6-Oxaziazine, 1,3 , 4-Triazine, 1,3,5-Triazine, 1,2,3,4-Tetrazine, 1,2,4,5-Tetrazine, 1,2,3,5-Tetrazine, 1,2,4,6 -Oxatorazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, or quinoxalin. Examples of the direct dye composed of the azine compound include azine fast red FC, azine fast red 12BK, azine violet BO, azine brown 3G, azine light brown GR, azine dark green BH / C, azine deep black EW, and azine. Deep black 3RL can be mentioned. Examples of the niglosin compound include niglosin, niglosin salt, and niglosin derivative. Examples of the acid dye composed of the niglosin compound include niglosin BK, niglocin NB, and niglosin Z. Examples of the quaternary ammonium salt include benzyldecylhexylmethylammonium chloride or decyltrimethylammonium chloride. As the positive charge control agent, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines, or alkyl amides can also be used. One kind of positive charge control agent may be used alone, or a plurality of kinds of positive charge control agents may be used in combination.

<External agent>
For the purpose of improving the fluidity of the toner particles or the handleability of the toner, it is preferable to externally add the external additive particles to the toner mother particles. The external additive particles preferably contain at least one selected from the group consisting of silica particles, metal oxide particles, and resin particles. The metal oxide constituting the metal oxide particles is preferably, for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate. The resin constituting the resin particles may be a melamine resin or a crosslinked styrene-acrylic acid-based resin. The particle size of the external additive particles is preferably 0.01 μm or more and 1.00 μm or less. The amount of the external additive particles is preferably 0.5 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the toner mother particles.

[Example of manufacturing method of positively charged toner]
The method for producing a positively charged toner according to the present embodiment preferably includes a process for producing toner mother particles and an external addition step. In the step of producing the toner matrix particles, it is preferable to produce the toner matrix particles by a known aggregation method or a known pulverization method. As a result, toner mother particles can be easily produced. Further, in the external addition step, it is preferable to mix the toner matrix particles and the external addition agent using a mixer (for example, an FM mixer manufactured by Nippon Coke Industries Co., Ltd.). As a result, a plurality of external additive particles adhere to the surface of the toner mother particles. In this way, a positively charged toner containing a plurality of toner particles can be obtained.

Examples of the present invention will be described. Table 1 shows carriers C-01 to C-03 and C-11 to C-15 (carriers for electrostatic latent image development, respectively) according to Examples or Comparative Examples.

In Table 1, "precursor A" and "precursor B" mean precursors of melamine resin, respectively. More specifically, "precursor A" means "Milben Resin SM-607" (solid content concentration: 75% by mass) manufactured by Showa Denko KK. Further, "precursor B" means "Milben Resin SM-850" (solid content concentration: 70% by mass) manufactured by Showa Denko KK.

In Table 1, "copolymer A" to "copolymer C" each mean a hydroxyl group-fluororesin. More specifically, "copolymer A" means "Fluonate K-700" (solid content concentration: 50% by mass) manufactured by DIC Corporation. "Copolymer B" means "Lumiflon LF200" (solid content concentration: 60% by mass) manufactured by Asahi Glass Co., Ltd. "Copolymer C" means "Zeffle GK-510" (solid content concentration: 50% by mass) manufactured by Daikin Industries, Ltd. "PTFE resin" means polytetrafluoroethylene. The PTFE resin does not contain a hydroxyl group in the molecule.

In the carriers C-01 to C-03 and C-11 to C-13, the coat layer had a laminated structure, respectively. On the other hand, in the carriers C-14 and C-15, the coat layer had a single-layer structure, respectively.

Hereinafter, the manufacturing method, the evaluation method, and the evaluation result of the carriers C-01 to C-03 and C-11 to C-15 will be described in order. In the evaluation in which an error occurs, a considerable number of measured values in which the error is sufficiently small are obtained, and the arithmetic mean of the obtained measured values is used as the evaluation value.

[Manufacturing method of carrier]
<Manufacturing of carrier C-01>
First, hydrochloric acid was added to the ion-exchanged water to adjust the pH of the ion-exchanged water to 4.0. To 100 parts by mass of the obtained ion-exchanged water (pH: 4.0), 40 parts by mass of precursor A (“Milben Resin SM-607” manufactured by Showa Denko KK, solid content concentration: 75% by mass) was added. In this way, the first coating liquid was prepared. Then, using a rolling fluidized bed coating granulator (“Spiracoater” manufactured by Okada Seiko Co., Ltd.), 1000 parts by mass of carrier core (“EF-35” manufactured by Powdertech Co., Ltd., particle size: 35 μm) in the fluidized bed. , Component: Mn-Mg-Sr ferrite) was sprayed with the first coating liquid.

Next, in 100 parts by mass of toluene, 60 parts by mass of copolymer A (“Fluoronate K-700” manufactured by DIC Corporation, hydroxyl value: 42.0 mgKOH / g or more and 54.0 mgKOH / g or less, solid content concentration: 50% by mass) was added. In this way, the second coating liquid was prepared. Then, the second coating liquid was sprayed onto the carrier core on which the first coating liquid was sprayed using the above-mentioned rolling fluidized bed coating granulation apparatus.

Subsequently, the fluidized bed in the above-mentioned rolling fluidized bed coating granulation apparatus was heat-treated at a temperature of 200 ° C. for 2 hours. In this way, carrier C-01 containing a plurality of carrier particles was obtained.

<Manufacturing of carrier C-02>
To 100 parts by mass of ion-exchanged water (pH: 4.0), 66 parts by mass of precursor A (“Milben Resin SM-607” manufactured by Showa Denko KK, solid content concentration: 75% by mass) was added. In this way, the first coating liquid was prepared. Further, in 100 parts by mass of toluene, 67 parts by mass of copolymer B (“Lumiflon LF200” manufactured by Asahi Glass Co., Ltd., hydroxyl value: 55.0 mgKOH / g or more and 65.0 mgKOH / g or less, solid content concentration: 60% by mass) ) Was added. In this way, the second coating liquid was prepared. Except for these, carrier C-02 was manufactured according to the method for manufacturing carrier C-01.

<Manufacturing of carrier C-03>
To 100 parts by mass of ion-exchanged water (pH: 4.0), 14 parts by mass of precursor B (“Milben Resin SM-850” manufactured by Showa Denko KK, solid content concentration: 70% by mass) was added. In this way, the first coating liquid was prepared. Further, 10 parts by mass of copolymer C (“Zefle GK-510” manufactured by Daikin Industries, Ltd., hydroxyl value: 52.0 mgKOH / g, solid content concentration: 50% by mass) was added to 100 parts by mass of toluene. .. In this way, the second coating liquid was prepared. Except for these, carrier C-03 was manufactured according to the method for manufacturing carrier C-01.

<Manufacturing of carrier C-11>
To 100 parts by mass of toluene, 40 parts by mass of PTFE resin (“TLP10F-1” manufactured by Mitsui-DuPont Fluorochemical Co., Ltd.) was added. In this way, the second coating liquid was prepared. Except for these, carrier C-11 was manufactured according to the method for manufacturing carrier C-02.

<Manufacturing of carrier C-12>
To 100 parts by mass of toluene, 40 parts by mass of PTFE resin (“TLP10F-1” manufactured by Mitsui-DuPont Fluorochemical Co., Ltd.) was added. In this way, the first coating liquid was prepared. Further, 66 parts by mass of precursor A (“Milben Resin SM-607” manufactured by Showa Denko KK, solid content concentration: 75% by mass) was added to 100 parts by mass of ion-exchanged water (pH: 4.0). In this way, the second coating liquid was prepared. Except for these, carrier C-12 was manufactured according to the method for manufacturing carrier C-01.

<Manufacturing of carrier C-13>
80 parts by mass of copolymer A (“Fluoronate K-700” manufactured by DIC Corporation, hydroxyl value: 42.0 mgKOH / g or more and 54.0 mgKOH / g or less, solid content concentration: 50% by mass) in 100 parts by mass of toluene. ) Was added. In this way, the first coating liquid was prepared. Further, 71 parts by mass of precursor B (“Milben Resin SM-850” manufactured by Showa Denko KK, solid content concentration: 70% by mass) was added to 100 parts by mass of ion-exchanged water (pH: 4.0). In this way, the second coating liquid was prepared. Except for these, carrier C-13 was manufactured according to the method for manufacturing carrier C-01.

<Manufacturing of carrier C-14>
80 parts by mass of copolymer A (“Fluoronate K-700” manufactured by DIC Corporation, hydroxyl value: 42.0 mgKOH / g or more and 54.0 mgKOH / g or less, solid content concentration: 50% by mass) in 100 parts by mass of toluene. ) Was added. In this way, the coating liquid was prepared. Then, using the above-mentioned rolling fluidized bed coating granulator, 1000 parts by mass of carrier core (“EF-35” manufactured by Powdertech Co., Ltd., particle size: 35 μm, component: Mn-Mg-Sr) in the fluidized bed. The coating liquid was sprayed on the ferrite).

Next, the fluidized bed in the above-mentioned rolling fluidized bed coating granulation apparatus was heat-treated at a temperature of 200 ° C. for 2 hours. In this way, carrier C-14 containing a plurality of carrier particles was obtained.

<Manufacturing of carrier C-15>
80 parts by mass of copolymer A (“Fluoronate K-700” manufactured by DIC Corporation, hydroxyl value: 42.0 mgKOH / g or more and 54.0 mgKOH / g or less, solid content concentration: 50% by mass) in 100 parts by mass of toluene. ) Was added. In this way, the first liquid was obtained. Further, 53 parts by mass of precursor B (“Milben Resin SM-850” manufactured by Showa Denko KK, solid content concentration: 70% by mass) was added to 100 parts by mass of ion-exchanged water (pH: 4.0). In this way, the second liquid was obtained. The first liquid and the second liquid were mixed to obtain a coating liquid. Except for these, carrier C-15 was manufactured according to the method for manufacturing carrier C-14.

[Career evaluation method]
<Preparation of evaluation target>
An evaluation target (two-component developer) was obtained by the method shown below.

(Synthesis of binding resin)
In a reaction vessel, 1.0 mol of polyoxyethylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, 4.5 mol of terephthalic acid, and 0.5 mol of trimellitic anhydride. And put in. Further 4 g of dibutyl tin oxide was added to the reaction vessel. The air in the reaction vessel was replaced with nitrogen gas. After raising the temperature inside the reaction vessel to 230 ° C. under a nitrogen atmosphere, the temperature inside the reaction vessel was maintained at 230 ° C. for 8 hours. The contents of the reaction vessel reacted while the temperature inside the reaction vessel was kept at 230 ° C. The pressure in the reaction vessel was reduced to 8.3 kPa. The unreacted material remaining in the reaction vessel was distilled off while the pressure in the reaction vessel was maintained at 8.3 kPa. The solid matter (reaction product) in the reaction vessel was washed and then dried. In this way, a polyester resin (softening point: 120 ° C.) was obtained.

(Preparation of toner matrix particles)
Using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries Co., Ltd.), 100 parts by mass of polyester resin (obtained polyester resin) and 5 parts by mass of carbon black (“REGAL®” manufactured by Cabot Co., Ltd.) 330R ”), 10 parts by mass of carnauba wax (“Carnauba wax No. 1” manufactured by Hiroyuki Kato Co., Ltd.), and 3 parts by mass of positive charge control agent (“Acribeth (registered trademark) FCA” manufactured by Fujikura Kasei Co., Ltd. -201-PS ”, component: styrene-acrylic acid-based resin containing a repeating unit derived from a quaternary ammonium salt) was mixed. The obtained mixture was subjected to a twin-screw extruder (“TEM-45” manufactured by Toshiba Machine Co., Ltd.) under the conditions of a material supply speed of 6 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 150 ° C. , Melt kneaded. The resulting kneaded product was cooled. The cooled kneaded product was roughly pulverized using a pulverizer (“Feather Mill (registered trademark)” 350 × 600 type manufactured by Hosokawa Micron Co., Ltd.). The obtained coarsely pulverized product was finely pulverized using a supersonic jet crusher (“Jet Mill IDS-2” manufactured by Nippon Pneumatic Industries Co., Ltd.). The obtained finely pulverized product was classified using a classification machine (“Elbow Jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.). As a result, toner mother particles having a volume median diameter (D ₅₀ ) of 7.0 μm were obtained.

(External processing)
Using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries Co., Ltd.), under the conditions of stirring speed of 3500 rpm and processing time of 5 minutes, 100.0 parts by mass of toner matrix particles and 1.5 parts by mass of hydrophobic silica Particles (“AEROSIL® RA-200H” manufactured by Nippon Aerosil Co., Ltd.) and 1.0 parts by mass of conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) were mixed. In this way, toner T-1 was obtained.

(Mixing process)
Using a powder mixer (“Locking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd.), 100 parts by mass of carriers (more specifically, carriers C-01 to C-03 and C-11) over 30 minutes. ~ C-15) and 10 parts by mass of toner T-1 were mixed. In this way, a two-component developer (evaluation target) was obtained.

<Preparation of evaluation machine>
The evaluation target was put in the housing part of the developing device of the multifunction device (“TASKalfa 3252ci” manufactured by Kyocera Document Solutions Co., Ltd.). Further, the toner T-1 was placed in the toner container of the multifunction device. In this way, the evaluation machine was prepared.

<Evaluation of toner charge amount and fog concentration>
First, 200,000 sheets of images (printing rate: 5%) were continuously printed on plain paper (A4 size) using an evaluation machine in an environment of a temperature of 23 ° C. and a humidity of 50% RH. After continuous printing, the evaluation image was printed on plain paper (A4 size) using an evaluation machine in an environment of a temperature of 23 ° C. and a humidity of 50% RH. The evaluation image included a solid image portion and a blank paper portion (area without printing). Then, the toner charge amount was measured by the method shown below. In addition, the fog concentration was measured by the method shown below.

(Measurement method and evaluation criteria for toner charge)
The method of measuring the toner charge amount is shown. Specifically, first, the evaluation target was taken out from the developing device of the evaluation machine. Next, 0.10 g of an evaluation target was placed in a measurement cell of a Q / m meter (“MODEL 210HS-1” manufactured by Trek Co., Ltd.), and only the toner among the evaluation targets was sucked through a sieve (wire mesh) for 10 seconds. Then, the toner charge amount (unit: μC / g) was calculated based on the following formula.
Toner charge amount (unit: μC / g) = total electric energy of sucked toner (unit: μC) / mass of sucked toner (unit: g)

The evaluation criteria for the amount of toner charged are shown below. The evaluation results are shown in Table 2.
Good: The toner charge amount was 20 μC / g or more and 40 μC / g or less.
Defective: The toner charge amount was less than 20 μC / g or more than 40 μC / g.

(Measurement method and evaluation criteria for fog concentration)
Using a Macbeth reflection densitometer (“RD914” manufactured by X-Rite), the reflection density of the blank portion of the evaluation image was measured. Then, the fog concentration (FD) was calculated based on the following formula.
FD = (reflection density of blank paper)-(reflection density of unprinted paper)

The evaluation criteria for the fog concentration (FD) are shown below. The evaluation results are shown in Table 2.
Good: The fog concentration (FD) was 0.007 or less.
Defective: The fog concentration (FD) was more than 0.007.

[Evaluation results]
Table 2 shows the evaluation results of the toner charge amount and the fog concentration.

The carriers C-01 to C-03 (more specifically, the carriers according to Examples 1 to 3) each had the above-mentioned basic configuration. Specifically, carriers C-01 to C-03 each contained a plurality of carrier particles. The carrier particles each included a carrier core and a first coat layer and a second coat layer covering the surface of the carrier core. The first coat layer and the second coat layer had a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core. The first coat layer contained a melamine resin. The second coat layer contained a fluororesin. The melamine resin and the fluororesin were bonded to each other by a specific covalent bond.

The carriers C-01 to C-03 were each manufactured by the following methods. Specifically, first, the first resin was supplied to the surface of the carrier core. The first resin was supplied to the surface of the carrier core in a state of being contained in the first coating liquid, and contained a melamine resin for forming. Next, the second resin was supplied to the surface of the first coated carrier core. The second resin was supplied to the surface of the first coating carrier core in a state of being contained in the second coating liquid, and contained a hydroxyl group-fluororesin. Subsequently, the second coated carrier core was heat-treated at a predetermined temperature. The predetermined temperature was equal to or higher than the temperature at which the methylol group contained in the molecule of the forming melamine resin reacts with the hydroxyl group, and more specifically, it was 200 ° C.

As shown in Table 2, when an image is formed using a two-component developer containing each of carriers C-01 to C-03, the toner charge amount is maintained within a desired range even after printing 200,000 sheets. It was possible to suppress the fog concentration below the desired value.

On the other hand, the carriers C-11 to C-15 (more specifically, the carriers according to Comparative Examples 1 to 5) did not have the above-mentioned basic configuration. Specifically, in the carrier C-11, a coat layer was formed by using the first coating liquid and the second coating liquid. The second coating liquid contained a PTFE resin. When an image was formed using a two-component developer containing carrier C-11, the toner charge amount was below the desired range and the fog density exceeded the desired value after printing 200,000 sheets.

In the carrier C-12, a coat layer was formed by using the first coating liquid and the second coating liquid. The first coating liquid contained a PTFE resin. The second coating liquid contained a precursor of a melamine resin. When an image was formed using a two-component developer containing carrier C-12, the toner charge amount was below the desired range and the fog density exceeded the desired value after printing 200,000 sheets.

In the carrier C-13, a coat layer was formed by using the first coat liquid and the second coat liquid. The first coating liquid contained a hydroxyl group-fluororesin. The second coating liquid contained a precursor of a melamine resin. When an image was formed using a two-component developer containing carrier C-13, the toner charge amount was below the desired range and the fog density exceeded the desired value after printing 200,000 sheets.

In the carrier C-14, a coating layer was formed using only one type of coating liquid. The coating liquid contained a hydroxyl group-fluororesin. When an image was formed using a two-component developer containing carrier C-14, the toner charge amount was below the desired range and the fog density exceeded the desired value after printing 200,000 sheets.

In the carrier C-15, a coating layer was formed using only one type of coating liquid. The coating liquid contained a hydroxyl group-fluororesin and a precursor of a melamine resin. When an image was formed using a two-component developer containing carrier C-15, the toner charge amount was below the desired range and the fog density exceeded the desired value after printing 200,000 sheets.

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

Claims (5)

A carrier containing multiple carrier particles
The carrier particles each include a carrier core and a first coat layer and a second coat layer that cover the surface of the carrier core.
The first coat layer and the second coat layer have a laminated structure in the order of the first coat layer and the second coat layer from the surface of the carrier core.
The first coat layer contains a melamine resin and contains
The second coat layer contains a fluororesin and contains
A carrier in which the melamine resin and the fluororesin are bonded to each other by a covalent bond represented by the following formula (1-1).

In the above formula (1-1), X ¹ represents the first terminal portion and X ² represents the second terminal portion. The first terminal portion is connected to the atoms constituting the melamine resin. The second terminal portion is connected to the atoms constituting the fluororesin. A method for producing a carrier containing a plurality of carrier particles.
The process of supplying the first resin to the surface of the carrier core and
The step of supplying the second resin to the surface of the first resin and
A step of heat-treating a carrier core in which the first resin and the second resin are supplied to the surface at a predetermined temperature, and
Including
The first resin contains a melamine resin or a precursor of a melamine resin, and contains a melamine resin or a precursor of the melamine resin.
The second resin contains at least one selected from the group consisting of a fluororesin containing a hydroxyl group in the molecule and a fluororesin containing a functional group capable of generating a hydroxyl group in the molecule by a hydrolysis reaction.
A method for producing a carrier, wherein the predetermined temperature is equal to or higher than a temperature at which the methylol group contained in the molecule of the melamine resin or the methylol group contained in the molecule of the precursor of the melamine resin reacts with the hydroxyl group. The method for producing a carrier according to claim 2 , wherein the hydroxyl value of the fluororesin containing the hydroxyl group in the molecule is 40.0 mgKOH / g or more. The method for producing a carrier according to claim 3 , wherein the fluororesin containing a hydroxyl group in the molecule is a polymer of a monomer containing a vinyl compound containing a hydroxyl group in the molecule and a vinyl compound containing a fluorine atom in the molecule. The carrier according to claim 1 and
Positively charged toner that is positively charged by friction with the carrier, and
A two-component developer containing.