JP7555809B2 - Magnetic carrier, two-component developer, and replenishment developer - Google Patents

Description

The present invention relates to a magnetic carrier, a two-component developer, and a replenishment developer used in an image forming method for visualizing an electrostatic image using electrophotography.

Conventionally, in the electrophotographic image forming method, a method is generally used in which an electrostatic latent image is formed on an electrostatic latent image carrier by using various means, and toner is attached to the electrostatic latent image to develop it. In this development, a two-component development method is widely adopted in which carrier particles called magnetic carrier are mixed with the toner, and the toner is triboelectrically charged to give an appropriate amount of positive or negative charge to the toner, and the charge is used as a driving force for development.
Here, the magnetic carrier (hereinafter also simply referred to as the carrier) is often composed of a core that is magnetized to provide transportability, and a coating resin that coats the core and provides the ability to impart charge to the toner.

In recent years, with the advancement of technology in the field of electrophotography, there is a demand for a longer lifespan of the main body, and the carrier is required to maintain its chargeability even after long-term use. However, it is known that when used for a long period of time, toner components generally adhere to the surface of the carrier, and the chargeability of the carrier decreases due to the decrease in the number of charging sites, resulting in a decrease in the charge amount of the toner and image defects such as changes in color.
As a means for achieving the above-mentioned durability against adhesion of toner components (hereinafter also referred to as contamination resistance), an example has been disclosed in which a silicone resin, which is a material with low surface free energy, is used as a coating resin (Patent Document 1).

JP 2011-191546 A

However, generally, materials with low surface free energy such as silicone resins are capable of suppressing adhesion of toner components, but have weak interactions between molecules and are easily destroyed by external forces. For this reason, when silicone resins are used as the coating resin for the carrier, the coating resin can be worn down by mechanical loads that occur during stirring and transport within the developer, reducing the surface resistance of the carrier and thus reducing the carrier's ability to impart charge. The property of being resistant to wear due to mechanical loads is also called abrasion resistance.

That is, in order to realize a highly stable carrier, it is necessary to simultaneously obtain both contamination resistance to suppress adhesion of toner components and wear resistance to suppress wear of the coating resin due to mechanical loads and the like.
In view of the above, an object of the present invention is to provide a magnetic carrier having excellent contamination resistance and abrasion resistance.

A magnetic carrier having a magnetic core and a coating resin that coats the surface of the magnetic core,
the coating resin contains a silicone-modified acrylic resin having a silicone moiety and an acrylic moiety,
On the surface of the magnetic carrier, the coating resin has a sea-island structure in which islands are dispersed in a sea,
the island portions are mainly composed of the silicone portion, and the number-average diameter of the island portions is 10 nm or more and 100 nm or less;
The magnetic carrier is characterized in that the sea portion is mainly composed of the acrylic portion.

The present invention makes it possible to provide a magnetic carrier with excellent contamination resistance and abrasion resistance.

1 shows an example of a schematic diagram of an image forming apparatus. 1 shows an example of a schematic diagram of a full-color image forming apparatus. An example of a surface treatment apparatus that performs surface treatment on a toner using hot air will be described below. 1 shows an example of a schematic diagram of a resistivity measuring device for a magnetic carrier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the present invention is not limited to the following embodiment.
The magnetic carrier according to the present invention has a magnetic core and a coating resin that coats the surface of the magnetic core.
The coating resin contains a silicone-modified acrylic resin having a silicone moiety and an acrylic moiety.
On the surface of the magnetic carrier, the coating resin has a sea-island structure in which islands are dispersed within a sea.
The island portions are mainly composed of the silicone portion, and the number-average diameter of the island portions is 10 nm or more and 100 nm or less.
The sea portion is mainly composed of the acrylic portion.

The present inventors consider the following regarding the effects of using a magnetic carrier having such a structure.
The silicone modified acrylic resin A used in the present invention is a block polymer, and forms a sea-island structure with a controlled diameter of the island moiety. The sea moiety and the island moiety are chemically bonded to form a strong structure, improving abrasion resistance. The silicone modified portion of the silicone modified acrylic resin A provides contamination resistance. The acrylic portion of the silicone modified acrylic resin A has high adhesion to the carrier core (magnetic core), providing excellent abrasion resistance. Furthermore, by setting the diameter of the island moiety within a specific range, contamination resistance is ensured even during long-term use, while abrasion resistance against external forces is further strengthened.

In the islands-in-sea structure, the islands are mainly composed of the silicone moiety, and the sea is mainly composed of the acrylic moiety, where the main component is 70% by mass or more.
The magnetic carrier preferably has an atomic percentage of silicon (Si) of 1.0 atomic % or more and 8.0 atomic % or less when measured by X-ray photoelectron spectroscopy (XPS). If the percentage of silicon atoms is less than 1.0 atomic %, the percentage of silicone-modified sites is insufficient, and the contamination resistance is reduced. If the percentage of silicon atoms is more than 8.0 atomic %, the adhesion between the acrylic site and the carrier core is insufficient, and the entire coating resin is easily peeled off, and the wear resistance is reduced.

The silicone-modified acrylic resin preferably contains a total of 10% to 40% by mass of moieties represented by the following formulas (1) to (4). Note that when calculating this mass percentage, the alkyl groups located on the boundary between the silicone moiety and the non-silicone moiety are not counted as silicone moieties. Details will be described later.

(In the formula, R ¹ to R ⁶ each independently represent a hydrogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms, or an alkenyloxy group having 2 to 4 carbon atoms. In the formula, -O _1/2 represents that an O is shared with the adjacent Si atom.)

If the total amount of the moieties represented by formulas (1) to (4) is less than 10% by mass, the size and number of islands formed by the silicone-modified moieties will be insufficient, resulting in reduced stain resistance. On the other hand, if the total amount of the moieties represented by formulas (1) to (4) is more than 40% by mass, the acrylic moieties will be insufficient, causing the entire coating resin to peel off easily, resulting in reduced abrasion resistance.
It is preferred that the silicone-modified acrylic resin mainly comprises a structure in which unit B represented by the following formula (5) is continuous and a structure in which unit C represented by the following formula (6) is continuous, in which ^R14 is not included in the calculation of the total content of the units represented by the formulas (1) to (4).

Of the moieties represented by formulae (1) to (4) in the silicone modified acrylic resin, the moiety represented by formula (1) preferably accounts for 90 mol % or more.
When the moiety represented by formula (1) accounts for 90 mol % or more, a structure is easily formed from a plurality of molecules when the island portions are formed, and the toughness is improved due to entanglement of the molecules, thereby improving the wear resistance.

(Wherein,
^R7 is H or CH3 _;
R ⁸ is not particularly limited, but is preferably a hydrocarbon group having 1 to 6 carbon atoms, an alkyl group having 2 to 4 carbon atoms and having a hydroxyl group as a substituent, or an alkyl group having 1 to 3 carbon atoms and having a carboxyl group as a substituent.
R ⁹ and R ¹⁰ are H or a hydrocarbon group having 1 to 6 carbon atoms;
R ¹¹ and R ¹² each represent a hydrogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms, or an alkenyloxy group having 2 to 4 carbon atoms; R ¹³ represents a hydrocarbon group having 1 to 6 carbon atoms, an alkyl group having 2 to 4 carbon atoms and having a hydroxyl group as a substituent, or an alkyl group having 1 to 3 carbon atoms and having a carboxyl group as a substituent; and R ¹⁴ represents a hydrocarbon group having 1 to 6 carbon atoms.
l and m are integers of 1 or more, and n is an integer of 2 or more, and may contain multiple units B and C.

The coating resin layer may further contain a resin D. The resin D preferably contains 75% by mass or more of the unit represented by the formula (5).
By adjusting the content of the resin D, the amount of silicone in the coating resin layer and the number of island portions can be easily controlled.

<Method of Manufacturing Carrier Core>
For the magnetic carrier core of the present invention, known magnetic particles such as magnetite particles, ferrite particles, magnetic material-dispersed resin particles, etc. Among them, magnetic particles obtained by filling the pores of porous magnetic particles with a resin or magnetic material-dispersed resin particles, i.e., magnetic particles containing a magnetic oxide and a resin composition, are preferred from the viewpoint of extending the life since they can reduce the specific gravity of the magnetic carrier.

Lowering the specific gravity of the magnetic carrier reduces the load on the toner in the developer state inside the developing device, prevents the adhesion of toner components to the magnetic carrier surface, and reduces the load between the carriers themselves, leading to further suppression of peeling, chipping, and abrasion of the resin coating layer. It also improves dot reproducibility, making it possible to obtain high-resolution images.

The resin contained in the pores of the porous magnetic particles can be a copolymer resin used as a coating resin, but is not limited to this and can be any known resin. As the thermoplastic resin, the copolymer used as the coating resin is preferable, but other examples include the following: polystyrene, polymethyl methacrylate, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinylpyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester resin such as polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, polyether ketone resin.

Examples of thermosetting resins include the following: phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, acrylic resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid, and polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, glyptal resin, furan resin, silicone resin, polyimide, polyamide-imide resin, polyetherimide resin, polyurethane resin.

A method of filling the voids of ferrite particles having a porous shape with a resin component includes a method of diluting the resin component in a solvent and adding the diluted solution to the porous magnetic core particles. The solvent used here may be any solvent that can dissolve each resin component. In the case of a resin that is soluble in an organic solvent, an organic solvent such as toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, or methanol may be used. In the case of a water-soluble resin component or an emulsion-type resin component, water may be used. A method of adding a resin component diluted with a solvent to the inside of the porous magnetic core particles includes a method of impregnating the resin component by a coating method such as a dipping method, a spraying method, a brushing method, a fluidized bed method, or a kneading method, and then volatilizing the solvent. In the case of filling with a thermosetting resin, after volatilizing the solvent, the temperature is raised to the temperature at which the resin used hardens, and a hardening reaction is carried out.

On the other hand, specific methods for producing magnetic material-dispersed resin particles include the following. For example, submicron magnetic materials such as iron powder, magnetite particles, and ferrite particles are kneaded so as to disperse them in a thermoplastic resin, pulverized to the desired carrier particle size, and, if necessary, subjected to a thermal or mechanical spheronization process to obtain the particles. It is also possible to produce the magnetic material-dispersed resin particles by dispersing the magnetic material in a monomer and polymerizing the monomer to form a resin.

In this case, examples of the resin include vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, silicone resin, acrylic resin, and polyether resin. The resin may be one type or a mixture of two or more types. In particular, phenol resin is preferable in that it increases the strength of the carrier core. The true density and resistivity can be adjusted by adjusting the amount of magnetic material. Specifically, in the case of magnetic particles, it is preferable to add 70% by mass or more and 95% by mass or less to the carrier.

The carrier core preferably has a 50% particle size (D50) based on volume distribution of 20 μm or more and 80 μm or less in order to be uniformly coated with the coating resin, suppress carrier adhesion, and appropriately adjust the density of the developer magnetic brush to obtain a high-quality image.
The specific resistance of the carrier core is preferably from 1.0×10 5 (Ω·cm) to 1.0×10 14 (Ω·cm) at an electric field strength of 1000 (V/cm), since good developability can be obtained.

The method of coating the carrier core surface with the coating resin is not particularly limited, and can be performed by a known method. For example, there is a so-called immersion method in which the carrier core and the coating resin solution are stirred while volatilizing the solvent, and the carrier core surface is coated with the coating resin. Specific examples include a universal mixer (manufactured by Fuji Paudal Co., Ltd.) and a Nauta Mixer (manufactured by Hosokawa Micron Co., Ltd.). There is also a method in which the coating resin solution is sprayed from a spray nozzle while forming a fluidized bed, and the carrier core surface is coated with the coating resin. Specific examples include a Spiracoater (manufactured by Okada Seiko Co., Ltd.) and a Spiraflow (manufactured by Freund Corporation). There is also a method in which the coating resin is coated on the magnetic carrier core in a particle state by a dry method. Specific examples include a treatment method using an apparatus such as a Hybridizer (manufactured by Nara Machinery Co., Ltd.), a Mechanofusion (manufactured by Hosokawa Micron Co., Ltd.), a HighFlex Gral (manufactured by Fukae Powtec Co., Ltd.), and a Theta Composer (manufactured by Tokuju Kogyo Co., Ltd.).
Next, the magnetic carrier will be described.

The magnetic carrier preferably has a magnetization strength of 40 ( ^Am2 /kg) or more and 70 ( ^Am2 /kg) or less under a magnetic field of 5000/4π (kA/m). When the magnetization strength of the magnetic carrier is within the above range, the magnetic binding force to the developing sleeve is appropriate, so that the occurrence of carrier adhesion can be more effectively suppressed. In addition, the stress applied to the toner in the magnetic brush can be reduced, so that the deterioration of the toner and adhesion to other members can be effectively suppressed.

The strength of magnetization of the magnetic carrier can be appropriately adjusted by the amount of resin contained therein.
The residual magnetization of the magnetic carrier is preferably 20.0 ( ^Am2 /kg) or less, and more preferably 10.0 ( ^Am2 /kg) or less. When the residual magnetization of the magnetic carrier is within the above range, particularly good fluidity is obtained as a developer, and good dot reproducibility is obtained.
The magnetic carrier preferably has a 50% particle size (D50) based on volume distribution of 21 μm to 81 μm in terms of the ability to charge the toner, suppression of carrier adhesion to the image area, and high image quality, and more preferably has a D50 of 25 μm to 60 μm.

Next, the preferred toner constitution for achieving the object of the present invention will be described in detail below.

<Binder resin>
The toner particles in the present invention may use the following polymers as the binder resin: homopolymers of styrene and its substitutes, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene-based copolymer resin, polyester resin, a mixture of polyester resin and vinyl resin, or a hybrid resin in which both are partially reacted; polyvinyl chloride, phenol resin, naturally modified phenol resin, naturally modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyethylene resin, polypropylene resin, etc. Among these, those containing polyester resin as the main component are preferred from the viewpoint of low-temperature fixability.

As monomers used in the polyester unit of the polyester resin, polyhydric alcohols (divalent or trivalent or higher alcohols), polyvalent carboxylic acids (divalent or trivalent or higher carboxylic acids), their acid anhydrides or their lower alkyl esters are used. Here, in order to create a branched polymer to express "strain hardening", it is effective to partially crosslink within the molecule of the amorphous resin, and for this purpose, it is preferable to use a polyfunctional compound with a valence of three or more. Therefore, it is preferable to include a trivalent or higher carboxylic acid, its acid anhydride or its lower alkyl ester, and/or a trivalent or higher alcohol as the raw material monomer for the polyester unit.

As the polyhydric alcohol monomer used in the polyester unit of the polyester resin, the following polyhydric alcohol monomers can be used.
The dihydric alcohol component includes the following:
Ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenol represented by formula (A) and its derivatives;

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.)
Diols represented by formula (B);

Examples of trihydric or higher alcohol components include the following: sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Of these, glycerol, trimethylolpropane, and pentaerythritol are preferably used. These dihydric alcohols and trihydric or higher alcohols can be used alone or in combination.

As the polybasic carboxylic acid monomer used in the polyester unit of the polyester resin, the following polybasic carboxylic acid monomers can be used.
Examples of divalent carboxylic acid components include the following: maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids, and lower alkyl esters thereof. Of these, maleic acid, fumaric acid, terephthalic acid, and n-dodecenylsuccinic acid are preferably used.

Examples of trivalent or higher carboxylic acids, their anhydrides, or their lower alkyl esters include the following: 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, their anhydrides, or their lower alkyl esters. Of these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred because it is inexpensive and the reaction is easy to control. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used alone or in combination.

The method for producing the polyester unit of the present invention is not particularly limited, and known methods can be used. For example, the above-mentioned alcohol monomer and carboxylic acid monomer are charged at the same time, and polymerized through an esterification reaction or ester exchange reaction and a condensation reaction to produce a polyester resin. The polymerization temperature is not particularly limited, but is preferably in the range of 180°C to 290°C. When polymerizing the polyester unit, for example, a polymerization catalyst such as a titanium-based catalyst, a tin-based catalyst, zinc acetate, antimony trioxide, or germanium dioxide can be used. In particular, the binder resin of the present invention is more preferably a polyester unit polymerized using a tin-based catalyst.

The acid value of the polyester resin is preferably 5 mgKOH/g or more and 20 mgKOH/g or less, and the hydroxyl value is preferably 20 mgKOH/g or more and 70 mgKOH/g or less. When the acid value of the polyester resin is within the above range, the amount of moisture adsorption in a high-temperature and high-humidity environment can be suppressed, and the anti-electrostatic adhesion can be suppressed to a low level, resulting in excellent fogging properties.
The binder resin may be a mixture of a low molecular weight resin and a high molecular weight resin. When the content ratio of the high molecular weight resin to the low molecular weight resin is 40/60 or more and 85/15 or less by mass, excellent low temperature fixing property and hot offset resistance can be obtained, which is preferable.

<Crystalline Resin>
The toner particles may contain a crystalline resin, which is a resin that exhibits an endothermic peak in differential scanning calorimetry (DSC).
The crystalline resin is not particularly limited, but from the viewpoint of low-temperature fixability, it is preferable that the crystalline resin contains a polyester resin as a main component.
The crystalline polyester is preferably one obtained by polycondensation reaction of a monomer composition containing, as main components, an aliphatic diol having 2 to 22 carbon atoms and an aliphatic dicarboxylic acid having 2 to 22 carbon atoms.

The aliphatic diol having 2 to 22 carbon atoms (more preferably 6 to 12 carbon atoms) is not particularly limited, but is preferably a chain (more preferably a linear) aliphatic diol.
Examples include the following: ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,4-butadiene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, and neopentyl glycol.
Among these, particularly preferred examples are straight-chain aliphatic α,ω-diols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

Of the above alcohol components, preferably 50% by mass or more, more preferably 70% by mass or more, is an alcohol selected from aliphatic diols having 2 to 22 carbon atoms.
Polyhydric alcohol monomers other than the above aliphatic diols can also be used. Among the polyhydric alcohol monomers, examples of dihydric alcohol monomers include aromatic alcohols such as polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A; and 1,4-cyclohexanedimethanol. Among the polyhydric alcohol monomers, examples of trihydric or higher polyhydric alcohol monomers include the following: aromatic alcohols such as 1,3,5-trihydroxymethylbenzene; and aliphatic alcohols such as pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, and trimethylolpropane.

Furthermore, monohydric alcohols may be used to the extent that they do not impair the properties of the crystalline polyester. Examples of such monohydric alcohols include monoalcohols such as n-butanol, isobutanol, sec-butanol, n-hexanol, n-octanol, 2-ethylhexanol, cyclohexanol, and benzyl alcohol.

On the other hand, the aliphatic dicarboxylic acid having 2 to 22 carbon atoms (more preferably 6 to 12 carbon atoms) is not particularly limited, but is preferably a chain (more preferably linear) aliphatic dicarboxylic acid.
Specific examples include the following, including those obtained by hydrolyzing their acid anhydrides or lower alkyl esters: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid.

Of the carboxylic acid components, preferably 50% by mass or more, more preferably 70% by mass or more, is a carboxylic acid selected from aliphatic dicarboxylic acids having 2 to 22 carbon atoms.
Polyvalent carboxylic acids other than the above aliphatic dicarboxylic acids having 2 to 22 carbon atoms can also be used. Among the other polyvalent carboxylic acid monomers, examples of divalent carboxylic acids include the following, including their acid anhydrides and lower alkyl esters: aromatic carboxylic acids such as isophthalic acid and terephthalic acid; aliphatic carboxylic acids such as n-dodecylsuccinic acid and n-dodecenylsuccinic acid; and alicyclic carboxylic acids such as cyclohexanedicarboxylic acid.

Among the other carboxylic acid monomers, examples of trivalent or higher polyvalent carboxylic acids include the following aliphatic carboxylic acids, including their acid anhydrides or derivatives such as lower alkyl esters. Aromatic carboxylic acids such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and pyromellitic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, and 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, etc.

Furthermore, the crystalline polyester may contain a monovalent carboxylic acid to the extent that the properties of the crystalline polyester are not impaired. Examples of monovalent carboxylic acids include monocarboxylic acids such as benzoic acid, naphthalene carboxylic acid, salicylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, phenoxyacetic acid, biphenyl carboxylic acid, acetic acid, propionic acid, butyric acid, and octanoic acid.

From the viewpoint of low-temperature fixability and storage stability, the crystalline polyester resin is preferably a crystalline polyester resin in which one or more aliphatic compounds selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having 10 to 20 carbon atoms are condensed at the ends of the molecular chain.
In general, in the recrystallization of a crystalline polyester, crystals grow from crystal nuclei. Therefore, by condensing one or more aliphatic compounds selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having 10 to 20 carbon atoms at the ends of the molecular chains, the nuclei become crystal nuclei, which can promote recrystallization, thereby improving the storage stability.

Furthermore, when the number of carbon atoms is within the above range, it is easy to condense the molecular chain end and it will not exist as a free monomer, which is preferable from the viewpoint of storage stability. Also, when the number of carbon atoms is within the above range, it is preferable from the viewpoint of low-temperature fixability, since it does not impair the compatibility between the crystalline polyester and the amorphous resin.

Furthermore, the amount of one or more aliphatic compounds selected from the group consisting of aliphatic monocarboxylic acids and aliphatic monoalcohols having 10 to 20 carbon atoms is preferably 1.0 mol% to 10.0 mol% of the raw material monomers of the crystalline polyester resin. Also, it is more preferable that the amount is 4.0 mol% to 8.0 mol%. When the amount of the aliphatic compound is within the above range, it is preferable because an appropriate amount of crystal nuclei can be present without impairing low-temperature fixability.

Aliphatic monocarboxylic acids with 10 to 20 carbon atoms include the following: capric acid (decanoic acid), undecylic acid, lauric acid (dodecanoic acid), tridecylic acid, myristic acid (tetradecanoic acid), pentadecylic acid, palmitic acid (hexadecanoic acid), margaric acid (heptadecanoic acid), stearic acid (octadecanoic acid), nonadecylic acid, and arachidic acid (icosanoic acid).

Aliphatic monoalcohols with 10 to 20 carbon atoms include the following: capryl alcohol (decanol), undecanol, lauryl alcohol (dodecanol), tridecanol, myristyl alcohol (tetradecanol), pentadecanol, palmityl alcohol (hexadecanol), margaryl alcohol (heptadecanol), stearyl alcohol (octadecanol), nonadecanol, and arachidyl alcohol (icosanol).

The content of the crystalline polyester resin is preferably 3 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the amorphous resin from the viewpoint of low-temperature fixability and chargeability in a high-temperature and high-humidity environment.
Crystalline polyester can be produced according to a normal polyester synthesis method. For example, the above-mentioned carboxylic acid monomer and alcohol monomer are subjected to esterification reaction or ester exchange reaction, and then, under reduced pressure or by introducing nitrogen gas, a polycondensation reaction is carried out according to a normal method to obtain a crystalline polyester. Then, the above-mentioned aliphatic compound is further added and an esterification reaction is carried out to obtain a desired crystalline polyester.

The above esterification or transesterification reaction can be carried out, if necessary, using a common esterification catalyst or transesterification catalyst such as sulfuric acid, titanium butoxide, dibutyltin oxide, manganese acetate, magnesium acetate, etc.
The polycondensation reaction can be carried out using a conventional polymerization catalyst, such as titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, germanium dioxide, etc. The polymerization temperature and the amount of catalyst are not particularly limited and may be appropriately determined.
In the esterification or transesterification reaction or polycondensation reaction, all the monomers may be mixed at once in order to increase the strength of the resulting crystalline polyester. In addition, in order to reduce low molecular weight components, a method may be used in which a divalent monomer is first reacted, and then a trivalent or higher monomer is added and reacted.

<Release Agent>
Examples of the release agent used in the toner of the present invention include the following: hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; waxes containing fatty acid esters as the main component such as carnauba wax; and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax. Further examples include the following. Saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassidic acid, eleostearic acid, and valinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid with alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene saturated fatty acid bisamides such as bisstearamide; unsaturated fatty acid amides such as ethylene bisoleamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide; aromatic bisamides such as m-xylene bisstearamide and N,N'-distearyl isophthalamide; fatty metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esters of fatty acids and polyhydric alcohols, such as behenic acid monoglyceride; and methyl ester compounds having a hydroxyl group obtained by hydrogenating vegetable oils and fats.

Among these waxes, from the viewpoint of improving low-temperature fixing property and fixing separation property, preferred are hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax, and fatty acid ester waxes such as carnauba wax. In the present invention, the hydrocarbon waxes are more preferred from the viewpoint of further improving hot offset resistance.
In the present invention, the wax is preferably used in an amount of 3 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the binder resin.
In addition, in an endothermic curve during temperature rise measured by a differential scanning calorimetry (DSC) device, the peak temperature of the maximum endothermic peak of the wax is preferably 45° C. or more and 140° C. or less. If the peak temperature of the maximum endothermic peak of the wax is within the above range, it is preferable because it is possible to achieve both storage stability and hot offset resistance of the toner.

<Wax dispersant>
The toner of the present invention may contain a wax dispersant. The wax dispersant is not particularly limited, but from the viewpoint of wax dispersibility, it is preferably a polymer in which a styrene-acrylic polymer is graft-polymerized to a polyolefin (hereinafter, also referred to as a graft polymer). The polyolefin used in the graft polymer preferably has a peak temperature of the maximum heat peak measured using a differential scanning calorimeter (DSC) of 60° C. or more and 110° C. or less. In addition, the polyolefin preferably has a weight average molecular weight (Mw) of 900 or more and 50,000 or less.

There are no particular limitations on the polyolefin, so long as it is a polymer or copolymer of an unsaturated hydrocarbon having one double bond, and various polyolefins can be used. In particular, polyethylene and polypropylene are preferably used. From the viewpoint of reactivity during the production of the graft polymer, it is more preferable that the polyolefin has a branched structure, such as polypropylene.

The content of the polyolefin in the polymer in which the styrene-acrylic polymer is graft-polymerized onto the polyolefin is preferably 5.0% by mass or more and 20.0% by mass or less, and more preferably 8.0% by mass or more and 12.0% by mass or less.
In the present invention, the method for graft polymerizing the styrene-acrylic polymer onto the polyolefin is not particularly limited, and any conventionally known method can be used.

Preferably, the styrene acrylic polymer has monomer units derived from cycloalkyl (meth)acrylates, where monomer units refer to the reacted form of the monomeric material in the polymer.
As the cycloalkyl(meth)acrylate, for example, the following cycloalkyl(meth)acrylate monomer (a) can be used.

Cyclopropyl acrylate, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, dihydrocyclopentadiethyl acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate.
Among these, from the viewpoint of hydrophobicity, at least one selected from the group consisting of the following is preferred: cyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, and cyclooctyl methacrylate. These may be used alone or in combination.

In addition to the cycloalkyl (meth)acrylate monomer (a), other monomers (b) may be used in the styrene acrylic polymer. Examples include the following: styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, p-methoxystyrene, p-hydroxystyrene, p-acetoxystyrene, vinyltoluene, ethylstyrene, phenylstyrene, and benzylstyrene; alkyl esters of unsaturated carboxylic acids (the alkyl has 1 to 18 carbon atoms) such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate; vinyl ester monomers such as vinyl acetate; vinyl ether monomers such as vinyl methyl ether; halogen-containing vinyl monomers such as vinyl chloride; and diene monomers such as butadiene and isobutylene. A plurality of these may be used.

The acid value of the graft polymer is preferably 5 mgKOH/g to 50 mgKOH/g, more preferably 15 mgKOH/g to 35 mgKOH/g. When the acid value is within the above range, both the affinity with the wax and the hydrophobicity of the graft polymer itself can be achieved, so that the surface is kept hydrophobic and white spots can be easily suppressed.
In the molecular weight distribution of the graft polymer by gel permeation chromatography (GPC), the weight average molecular weight (Mw) is preferably from 5,000 to 70,000, and more preferably from 10,000 to 50,000. When the weight average molecular weight (Mw) is within the above range, the mechanical strength of the toner particle surface is increased and embedding of external additives during durable use is suppressed, so that the effects of charging stability and suppression of white voids are easily obtained.

The content of the graft polymer is preferably 3.0 parts by weight or more and 10.0 parts by weight or less per 100 parts by weight of the amorphous resin. When the content is within this range, the hydrophobicity of the graft polymer is also expressed in the toner, the amount of moisture adsorption in a high-temperature and high-humidity environment is reduced, and the toner is less susceptible to environmental fluctuations.

<Coloring Agent>
The toner particles in the present invention may contain a colorant. Examples of the colorant include the following.
Examples of black colorants include carbon black, and those toned to black using a yellow colorant, a magenta colorant, and a cyan colorant. As the colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity from the viewpoint of the image quality of a full-color image.

Pigments for magenta toner include the following: C.I. C.I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; C.I. Pigment Violet 19; C.I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

Dyes for magenta toner include the following: C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I. Disperse Violet 1; basic dyes such as C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Examples of pigments for cyan toner include C.I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, and 17; C.I. Bat Blue 6; C.I. Acid Blue 45; and copper phthalocyanine pigments having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.
Dyes for cyan toner include C.I. Solvent Blue 70.

Yellow toner pigments include: C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; C.I. Vat Yellow 1, 3, 20.
Yellow toner dyes include C.I. Solvent Yellow 162.

These colorants can be used alone or in combination, or in the form of a solid solution. The colorant is selected in consideration of hue angle, chroma, brightness, light resistance, OHP transparency, and dispersibility in toner.
The content of the colorant is preferably 0.1 parts by mass or more and 30.0 parts by mass or less based on the total amount of the resin components.

<Inorganic fine particles>
The toner preferably contains inorganic fine particles for the main purpose of improving fluidity and chargeability, and the inorganic fine particles are preferably attached to the toner surface.
As inorganic fine particles serving as spacer particles for improving the releasability between the toner and the carrier, silica particles having a maximum peak particle size based on the number distribution of 80 nm to 200 nm are preferred, and in order to function as spacer particles while better suppressing detachment from the toner, a particle size of 100 nm to 150 nm is more preferred.

In order to improve the fluidity of the toner, it is preferable to contain inorganic fine particles having a maximum peak particle size based on the number distribution of 20 nm to 50 nm, and it is also preferable to use them in combination with the silica particles.
Further, in order to improve the fluidity and transferability, other external additives may be added to the toner particles. The external additive added to the surface of the toner particles preferably contains inorganic fine particles such as titanium oxide, alumina oxide, and silica, and a plurality of types may be used in combination.

The total content of the external additives is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.8 parts by mass or more and 4.0 parts by mass or less, relative to 100 parts by mass of toner particles. Among them, the content of silica particles having a maximum peak particle size of 80 nm to 200 nm based on the number distribution standard is 0.1 parts by mass or more and 2.5 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.0 parts by mass or less. If it is within this range, the effect as a spacer particle will be more pronounced.

The surfaces of the silica particles and inorganic fine particles used as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is preferably performed using coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and their metal salts; silicone oils; or combinations thereof.

Examples of titanium coupling agents include the following: tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis(dioctyl pyrophosphate)oxyacetate titanate.

Examples of silane coupling agents include the following: γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane.

Examples of fatty acids include the following: long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid. Examples of metals in the metal salts of these fatty acids include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.
The hydrophobic treatment is preferably carried out by adding a hydrophobic treatment agent to the treated particles in an amount of 1% by mass or more and 30% by mass or less (more preferably 3% by mass or more and 7% by mass or less) relative to the treated particles to coat the treated particles.
The degree of hydrophobization of the external additive that has been subjected to the hydrophobization treatment is not particularly limited, but for example, the degree of hydrophobization after the treatment is preferably from 40 to 98. The degree of hydrophobization indicates the wettability of a sample with respect to methanol, and is an index of hydrophobicity.

<Two-component developer>
When the toner of the present invention is mixed with a magnetic carrier to be used as a two-component developer, good results are usually obtained when the carrier mixing ratio is 2% by mass to 15% by mass, preferably 4% by mass to 13% by mass, in terms of the toner concentration in the developer. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fogging and scattering in the machine tend to occur.

In addition, in a replenishing developer to be replenished to a developing device in response to a decrease in the toner concentration of the two-component developer in the developing device, the amount of toner is 2 parts by mass or more and 50 parts by mass or less per part by mass of the replenishing magnetic carrier.
Next, an image forming apparatus equipped with a developing device using the magnetic carrier, two-component developer and replenishment developer of the present invention will be described by way of example, but the developing device used in the developing method of the present invention is not limited to this.

<Image forming method>
1, an electrostatic latent image carrier 1 rotates in the direction of the arrow (counterclockwise direction) in the figure. The electrostatic latent image carrier 1 is charged by a charger 2, which is a charging means (charging step), and the surface of the charged electrostatic latent image carrier 1 is exposed to light by an exposure device 3, which is an electrostatic latent image forming means, to form an electrostatic latent image (electrostatic latent image forming step).
The developing device 4 has a developing container 5 that contains a two-component developer, a developer carrier 6 that is rotatably arranged, and a magnet 7 that serves as a magnetic field generating means is contained within the developer carrier 6. At least one of the magnets 7 is disposed in a position facing the latent image carrier. The two-component developer is held on the developer carrier 6 by the magnetic field of the magnet 7, and the amount of the two-component developer is regulated by a regulating member 8, and the developer is transported to a developing section that faces the electrostatic latent image carrier 1. In the developing section, a magnetic brush is formed by the magnetic field generated by the magnet 7. Thereafter, a developing bias consisting of an alternating electric field superimposed on a direct current electric field is applied, and the electrostatic latent image is visualized as a toner image (developing process).
The toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to a recording medium (transfer material) 12 by a transfer charger 11 (transfer process).

Here, as shown in FIG. 2, the image may be transferred from the electrostatic latent image carrier 1 to an intermediate transfer body 9, and then electrostatically transferred to a recording medium 12 as a transfer material (transfer process).

Thereafter, the recording medium 12 is conveyed to a fixing device 13 where the toner is fixed onto the recording medium 12 by applying heat and pressure (fixing process).
Thereafter, the recording medium 12 is discharged outside the apparatus as an output image. After the transfer process, the toner remaining on the electrostatic latent image carrier 1 is removed by a cleaner 15. Thereafter, the electrostatic latent image carrier 1 cleaned by the cleaner 15 is electrically initialized by light irradiation from a pre-exposure means 16, and the above image forming operation is repeated.

FIG. 2 is a schematic diagram showing an example of the image forming method of the present invention applied to a full-color image forming apparatus.
The arrangement of the image forming units K, Y, C, M, and arrows indicating the directions of rotation are not limited to those shown in the drawings, and K stands for black, Y for yellow, C for cyan, and M for magenta.

In FIG. 2, electrostatic latent image carriers 1K, 1Y, 1C, and 1M rotate in the direction of the arrow (clockwise direction). Each electrostatic latent image carrier is charged by chargers 2K, 2Y, 2C, and 2M, which are charging means (charging process). The charged surface of each electrostatic latent image carrier is exposed by exposure devices 3K, 3Y, 3C, and 3M, which are electrostatic latent image forming means, to form an electrostatic latent image (electrostatic latent image forming process). After that, the electrostatic latent image is visualized as a toner image by the two-component developer carried on developer carriers 6K, 6Y, 6C, and 6M provided in developing devices 4K, 4Y, 4C, and 4M, which are developing means (developing process). It is then transferred to intermediate transfer body 9 by intermediate transfer chargers 10K, 10Y, 10C, and 10M, which are transfer means. It is then transferred to recording medium 12 by transfer charger 11, which is transfer means (transfer process). The recording medium 12 is heated and pressure-fixed by the fixing device 13, which is a fixing means (fixing process), and output as an image.

The intermediate transfer body cleaner 14, which is a cleaning member for the intermediate transfer body 9, collects the residual toner and the like. Specifically, the development method of the present invention is preferably performed by applying an AC voltage to the developer carrier to form an alternating electric field in the development area while the magnetic brush is in contact with the photosensitive body. The distance (SD distance) between the developer carrier (developing sleeve) 6 and the photosensitive drum is preferably 100 μm or more and 1000 μm or less in order to suppress carrier adhesion and improve dot reproducibility. If it is narrower than 100 μm, the supply of developer is likely to be insufficient, resulting in low image density. If it exceeds 1000 μm, the magnetic field lines from the magnetic pole S1 will spread, the density of the magnetic brush will decrease, and dot reproducibility will decrease, or the force binding the magnetic coated carrier will be weakened, making carrier adhesion more likely to occur.

The peak-to-peak voltage (Vpp) of the alternating electric field is 300V or more and 3000V or less, preferably 500V or more and 1800V or less. The frequency is 500Hz or more and 10000Hz or less, preferably 1000Hz or more and 7000Hz or less, and each can be appropriately selected and used depending on the process. In this case, the waveform of the AC bias for forming the alternating electric field can be a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio. In order to respond to changes in the toner image formation speed, it is preferable to apply a development bias voltage (intermittent AC superimposed voltage) having a discontinuous AC bias voltage to the developer carrier for development. If the applied voltage is lower than 300V, it is difficult to obtain a sufficient image density, and the fogging toner in the non-image area may not be collected well. If it exceeds 3000V, the latent image may be disturbed through the magnetic brush, resulting in a decrease in image quality.

By using a two-component developer with a well-charged toner, the fog removal voltage (Vback) can be lowered, and the primary charge of the photoconductor can be lowered, thereby extending the life of the photoconductor. Vback depends on the development system, but is preferably 200V or less, more preferably 150V or less. A contrast potential of 100V or more and 400V or less is preferably used to produce sufficient image density.

In addition, if the frequency is lower than 500 Hz, the process speed is also affected, but the configuration of the electrostatic latent image bearing photoreceptor may be the same as that of a photoreceptor generally used in an image forming apparatus, for example, a photoreceptor having a configuration in which a conductive layer, an undercoat layer, a charge generating layer, a charge transport layer, and, if necessary, a charge injection layer are provided in this order on a conductive substrate such as aluminum or SUS.
The conductive layer, undercoat layer, charge generating layer and charge transport layer may be layers that are generally used in photoconductors. As the outermost layer of the photoconductor, for example, a charge injection layer or a protective layer may be used.

<Method of Manufacturing Magnetic Carrier>
The magnetic material-dispersed resin particles can be produced, for example, by the method described in the Examples below. For example, first, phenols and aldehydes are stirred in an aqueous medium in the presence of magnetic components such as magnetic iron oxide particles and a basic catalyst. Then, the phenols and aldehydes are reacted and cured to produce magnetic material-dispersed resin particles containing magnetic components such as magnetic iron oxide particles and a phenol resin.

Alternatively, magnetic material-dispersed resin particles can be produced by a method of pulverizing a resin containing a magnetic component such as magnetic iron oxide particles, that is, a so-called kneading and pulverizing method.
From the viewpoint of ease of control of the particle size of the magnetic carrier and sharpening of the particle size distribution of the magnetic carrier, the former method is preferred.
Next, the porous magnetic core particles will be described.

Examples of the material of the porous magnetic core particle include magnetite, ferrite, etc. Among them, ferrite is preferred from the viewpoint of ease of control of the porous structure of the porous magnetic core particle and ease of adjustment of the resistance of the porous magnetic core particle.
Ferrite is a sintered body represented by the following general formula:
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the above general formula, M1 is a monovalent metal, M2 is a divalent metal, and when x+y+z=1.0, 0≦x≦0.8, 0≦y≦0.8, and 0.2<z<1.0.)

In the above general formula, examples of M1 and M2 include Li, Fe, Mn, Mg, Sr, Cu, Zn, Ca, Ni, Co, Ba, Y, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Si, and rare earth elements.
In the case of the porous magnetic core particles, in order to maintain the magnetization amount at an appropriate level and to set the pore size within an appropriate range, it is preferable to appropriately control the surface unevenness of the porous magnetic core particles. In addition, it is preferable that the speed of the ferritization reaction is easily controlled, and the resistivity and magnetic force of the porous magnetic core are easily controlled. From these viewpoints, among ferrites, Mn-based ferrites, Mn-Mg-based ferrites, Mn-Mg-Sr-based ferrites, and Li-Mn-based ferrites containing Mn are more preferable.
The manufacturing process when ferrite is used as the porous magnetic carrier particles will be described in detail below.

<Step 1 (Weighing and Mixing Step)>
The raw materials for the ferrite are weighed and mixed.
Examples of raw materials for ferrite include metal particles of the above-mentioned metal elements, or oxides, hydroxides, oxalates, carbonates, and the like thereof.
Examples of mixing devices include a ball mill, a planetary mill, a Giotto mill, a vibration mill, etc. Among these, a ball mill is preferred from the viewpoint of mixability.
For example, weighed ferrite raw material and balls are placed in a ball mill, and the mixture is pulverized and mixed for a period of 0.1 to 20.0 hours.

<Step 2 (Pre-firing Step)>
The crushed and mixed ferrite raw material is calcined in air or nitrogen atmosphere at a calcination temperature of 700° C. to 1200° C. for 0.5 to 5.0 hours to obtain calcined ferrite. For calcination, a calcination furnace such as a burner type calcination furnace, a rotary type calcination furnace, or an electric furnace can be used.

<Step 3 (Crushing Step)>
The calcined ferrite obtained in step 2 is pulverized in a pulverizer.
Examples of the pulverizer include a crusher, a hammer mill, a ball mill, a bead mill, a planetary mill, and a Giotto mill.
In order to obtain a pulverized ferrite product with a desired particle size, for example, when using a ball mill or a bead mill, it is preferable to control the material of the balls and beads used, the particle size, and the pulverization time. Specifically, in order to reduce the particle size of the calcined ferrite slurry, balls with a heavy specific gravity can be used and the pulverization time can be extended. In addition, in order to widen the particle size distribution of the calcined ferrite, balls or beads with a heavy specific gravity can be used and the pulverization time can be shortened. In addition, calcined ferrite with a wide particle size distribution can be obtained by mixing multiple calcined ferrites with different particle sizes.
Furthermore, when using a ball mill or a bead mill, a wet type is more preferable than a dry type, since the pulverized product does not fly up in the mill and pulverization efficiency is increased.

<Step 4 (granulation step)>
To the pulverized calcined ferrite, water, a binder, and, if necessary, a pore adjusting agent, such as a foaming agent or resin particles, are added.
Examples of the foaming agent include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate.

Examples of the resin fine particles include fine particles of the following resins.
Polyesters, polystyrene, styrene copolymers such as styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-acrylic acid ester copolymers, styrene-methacrylic acid ester copolymers, styrene-α-methyl chloromethacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, and styrene-acrylonitrile-indene copolymers;
Polyvinyl chloride, phenolic resin, modified phenolic resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin;
A polyester resin having, as a structural unit, a monomer selected from an aliphatic polyhydric alcohol, an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, an aromatic dialcohol, and a diphenol;
Polyurethane, polyamide, polyvinyl butyral, terpene resin, coumarone-indene resin, petroleum resin, hybrid resin having polyester units and vinyl polymer units, etc.

An example of the binder is polyvinyl alcohol.
In step 3, when wet pulverization is performed, it is preferable to take into consideration the water contained in the ferrite slurry and to add a binder and, if necessary, a pore regulator.
The obtained ferrite slurry is dried and granulated in a heated atmosphere of 100° C. to 200° C. using a spray dryer to obtain a granulated product. Examples of the spray dryer include a spray drier.

<Step 5 (Main Firing Step)>
The granulated product is fired at a temperature in the range of 800° C. to 1400° C. for 1 hour to 24 hours.
By increasing the sintering temperature and lengthening the sintering time, the sintering of the porous magnetic core particles progresses, resulting in a smaller pore size and a reduced number of pores.

<Step 6 (sorting step)>
After the particles obtained by firing as described above are crushed, they may be classified or sieved to remove coarse particles and fine particles, if necessary.
The volume distribution based 50% particle size (D50) of the magnetic core particles is preferably 18.0 μm or more and 68.0 μm or less from the viewpoint of suppressing adhesion of the carrier to the image and suppressing roughness of the image.

<Process 7 (filling process)>
The physical strength of the porous magnetic core particles may be reduced depending on the internal pore volume. From the viewpoint of increasing the physical strength as a magnetic carrier, at least a part of the pores of the porous magnetic core particles is The amount of resin filled in the porous magnetic core particles is preferably 2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the porous magnetic core particles. The pores may be filled only in part with the resin, or only the pores near the surface of the porous magnetic core particle may be filled with the resin, leaving voids inside, or the pores may be completely filled with the resin. However, it is preferable that there is little variation in the resin content for each magnetic carrier.

Methods for filling the pores of the porous magnetic core particles with resin include, for example, impregnating the porous magnetic core particles with a resin solution by a coating method such as a dipping method, a spraying method, a brush coating method, or a fluidized bed method, and then volatilizing the solvent.
Another method for filling the pores of the porous magnetic core particles with a resin is to dilute the resin in a solvent and add the diluted resin to the pores of the porous magnetic core particles. The solvent used here may be any solvent that can dissolve the resin.

When a resin soluble in an organic solvent is used, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. When a water-soluble resin or an emulsion-type resin is used, water can be used as the solvent.

The amount of resin solids in the resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. If the amount of resin solids is 50% by mass or less, the viscosity of the resin solution does not become too high, and it becomes easier to uniformly penetrate the resin solution into the pores of the porous magnetic core particles. In addition, if the amount of resin solids is 1% by mass or more, a decrease in the adhesion of the resin to the porous magnetic core particles due to a small amount of resin is suppressed.

Examples of resins that can be used to fill the pores of the porous magnetic core particles include thermoplastic resins and thermosetting resins. It is preferable that the resin used to fill the pores has a high affinity for the porous magnetic core particles. When a resin with high affinity is used, the surfaces of the porous magnetic core particles can also be covered with the resin at the same time as the resin is filled into the pores of the porous magnetic core particles.

As the resin to be filled, examples of thermoplastic resins include novolac resin, saturated alkyl polyester resin, polyarylate, polyamide resin, acrylic resin, etc. Examples of thermosetting resins include phenolic resin, epoxy resin, unsaturated polyester resin, silicone resin, etc.

The magnetic carrier used in the present invention is obtained by coating the surface of a magnetic carrier core with a resin to form a resin coating layer. The method of coating the surface of the magnetic carrier core is not particularly limited and can be performed by a known method. For example, there is a so-called immersion method in which the solvent is evaporated while stirring the carrier core and the coating resin solution, and the coating resin is coated on the carrier core surface. Specific examples include a universal mixer (manufactured by Fuji Paudal Co., Ltd.) and a Nauta Mixer (manufactured by Hosokawa Micron Co., Ltd.). There is also a method in which a coating resin solution is sprayed from a spray nozzle while forming a fluidized bed, and the coating resin is coated on the carrier core surface. Specific examples include a Spiracoater (manufactured by Okada Seiko Co., Ltd.) and a Spiraflow (manufactured by Freund Sangyo Co., Ltd.). There is also a method in which the coating resin is applied to the magnetic carrier core in a particle state in a dry coating method. Specifically, examples of processing methods include those using devices such as Hybridizer (manufactured by Nara Machinery Works), Mechanofusion (manufactured by Hosokawa Micron Corporation), Hyflex Gral (manufactured by Fukae Powtec), and Theta Composer (manufactured by Tokuju Machinery Works).

<Toner Manufacturing Method>
The method for producing the toner particles is not particularly limited, and known methods such as a pulverization method and a polymerization method can be used. The pulverization method is preferred. In the pulverization method, a resin component such as an amorphous resin and, if necessary, a crystalline resin, a wax, a wax dispersant, and, if necessary, a colorant are melt-kneaded, and the kneaded product is cooled, and then pulverized and classified.
The procedure for producing the toner by the pulverization method will be described below.

In the raw material mixing process, the materials constituting the toner particles, for example, resin components such as amorphous resin and, if necessary, crystalline resin, wax, wax dispersant, and, if necessary, other components such as colorants and charge control agents, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.).

Next, the mixed materials are melt-kneaded to disperse the wax and the like in the resin components. In the melt-kneading process, a batch-type kneader such as a pressure kneader or a Banbury mixer, or a continuous-type kneader can be used, and single-screw or twin-screw extruders are mainly used because of their advantage of being capable of continuous production.
Examples of the extruder include a KTK type twin screw extruder (manufactured by Kobe Steel, Ltd.), a TEM type twin screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.), a twin screw extruder (manufactured by KCK Corporation), a Co-Kneader (manufactured by Buss Co., Ltd.), and a Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.). Furthermore, the resin composition obtained by melt kneading may be rolled with a twin roll or the like and cooled with water or the like in a cooling step.

The cooled resin composition is then pulverized to a desired particle size in a pulverization process. In the pulverization process, the resin composition is coarsely pulverized using a pulverizer such as a crusher, a hammer mill, or a feather mill. After the coarse pulverization, the resin composition is further pulverized using a pulverizer such as a Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), a Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), a Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.), or an air jet type pulverizer.
Thereafter, the mixture is classified as necessary using a classifier or sieve separator such as the following: Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.) which uses an inertial classification method, Turboplex (manufactured by Hosokawa Micron Corporation) which uses a centrifugal classification method, TSP Separator (manufactured by Hosokawa Micron Corporation), or Faculty (manufactured by Hosokawa Micron Corporation).

The toner particles may then be surface-treated by heating, which can increase the circularity of the toner.
For example, the surface treatment can be performed with hot air using a surface treatment apparatus shown in Fig. 3. The toner particles are preferably heat-treated toner particles.
The mixture supplied by the material supply means 1 is introduced into an introduction pipe 3, which is installed vertically to the material supply means, by compressed gas adjusted by a compressed gas adjustment means 2. The mixture passing through the introduction pipe 3 is uniformly dispersed by a conical protruding member 4 provided in the center of the material supply means, and is introduced into eight supply pipes 5 that radiate outward, and is introduced into a treatment chamber 6 where heat treatment is carried out.

At this time, the flow of the mixture supplied to the treatment chamber is regulated by a regulating means 9 for regulating the flow of the mixture provided in the treatment chamber, so that the mixture supplied to the treatment chamber is heat-treated while swirling in the treatment chamber, and then cooled.
Hot air for heat-treating the supplied mixture is supplied from hot air supplying means 7, and is introduced into the treatment chamber by spirally swirling the hot air using a swirling member 13 for swirling the hot air. In terms of the configuration, the swirling member 13 for swirling the hot air has a plurality of blades, and the swirling of the hot air can be controlled by the number and angle of the blades. The hot air supplied into the treatment chamber preferably has a temperature of 100°C to 300°C at the outlet of the hot air supplying means 7. If the temperature at the outlet of the hot air supplying means is within the above range, it is possible to uniformly spheronize the toner particles while suppressing fusion and coalescence of the toner particles caused by overheating the mixture.

The heat-treated toner particles are then cooled by cold air supplied from cold air supply means 8. The temperature of the cold air supplied from cold air supply means 8 is preferably -20°C to 30°C. If the temperature of the cold air is within the above range, the heat-treated toner particles can be efficiently cooled, and the fusion and coalescence of the heat-treated toner particles can be suppressed without impeding the uniform spheroidization of the mixture. The absolute moisture content of the cold air is preferably 0.5 g/m3 or ^more and 15.0 g/ ^m3 or less.

Next, the cooled heat-treated toner particles are collected by the collecting means 10 at the bottom end of the processing chamber. A blower (not shown) is provided ahead of the collecting means, and the toner particles are sucked and transported by the blower.
In addition, the powder particle supply port 14 is provided so that the swirling direction of the supplied mixture and the swirling direction of the hot air are the same, and the recovery means 10 of the surface treatment device is provided on the outer periphery of the treatment chamber so as to maintain the swirling direction of the swirled powder particles. Furthermore, the cold air supplied from the cold air supply means 8 is configured to be supplied from the outer periphery of the device to the circumferential surface inside the treatment chamber in a horizontal and tangential direction. The swirling direction of the toner particles supplied from the powder particle supply port 14, the swirling direction of the cold air supplied from the cold air supply means 8, and the swirling direction of the hot air supplied from the hot air supply means 7 are all the same direction. Therefore, no turbulence occurs inside the treatment chamber 6, the swirling flow inside the device is strengthened, a strong centrifugal force is applied to the toner particles, and the dispersibility of the toner particles is further improved, so that toner particles with a uniform shape and few coalesced particles can be obtained.

The average circularity of the toner particles is preferably 0.950 or more and 0.980 or less, and more preferably 0.960 or more and 0.980 or less. When the toner particles are in the above range, the transferability is improved and cleaning properties can be achieved at the same time, which is preferable.
The toner particles may be used as they are as a toner, or may be used as a toner by adding an external additive to the surface of the toner particles as necessary. A method for adding an external additive may include a method in which a predetermined amount of a known external additive is mixed with the toner particles and stirred and mixed using a mixer as an external adder. Examples of the mixer include a double con mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, a Nauta mixer, a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), and a Nobilta (manufactured by Hosokawa Micron Corporation).
The methods for measuring various physical properties of the magnetic carrier, toner and raw materials are described below.

<Method of measuring 50% particle size (D50) based on volume distribution of magnetic carrier core>
Particle size distribution measurement is performed using the Microtrac MT, a laser diffraction/scattering particle size distribution measuring device.
The measurements were carried out using a 3300EX (manufactured by Nikkiso Co., Ltd.).
The 50% particle size (D50) based on volume distribution of the magnetic carrier core was measured using a sample supplying machine for dry measurement, "One-shot dry type sample conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.). The supply conditions for the Turbotrac were a dust collector used as a reduced pressure source, with an air volume of about 33 L/sec and a pressure of about 17 kPa. Control was performed automatically on the software. Control and analysis were performed using the attached software (version 10.3.3-202D). The measurement conditions were as follows:

SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81%
Particle shape: non-spherical Upper measurement limit: 1408μm
Measurement lower limit: 0.243μm
Measurement environment: Temperature 23°C, relative humidity 50%

<Separation of magnetic carrier from developer>
When the magnetic carrier is separated from the developer and analyzed, the following method can be adopted.
Put 30 mL of ion-exchanged water into a 100 mL flat-bottom glass beaker, and add 0.3 mL of a dilution of the below-mentioned "Contaminon N" diluted 3 times by mass with ion-exchanged water as a dispersant to prepare a Contaminon N solution.
Contaminon N: a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments, having a pH of 7, which is composed of a nonionic surfactant, an anionic surfactant, and an organic builder; manufactured by Wako Pure Chemical Industries, Ltd.

Prepare an ultrasonic dispersion device "Ultrasonic Dispersion System Tetra150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W. Place 3.3 L of ion-exchanged water in the water tank of the ultrasonic dispersion device, and add 2 mL of Contaminon N to this water tank.
The beaker containing the Contaminon N solution is set in the beaker fixing hole of the ultrasonic disperser, the ultrasonic disperser is operated, and the height of the beaker is adjusted so that the resonance state of the liquid surface of the electrolyte solution in the beaker is maximized.

In a beaker containing the Contaminon N solution, 1.0 g of magnetic carrier is placed in the electrolyte solution and dispersed while ultrasonic waves are being applied to the electrolyte solution. The ultrasonic dispersion process is continued for 10 minutes. During the ultrasonic dispersion process, the water temperature in the water tank is appropriately adjusted to be between 10°C and 40°C.
After that, a magnet is brought close to the beaker containing the magnetic carrier, and the carrier is attracted through the beaker. In this state, the supernatant liquid (Contaminon N solution) in the beaker is removed, and the magnetic carrier can be obtained by repeatedly washing.

<Method of calculating the diameter of the island part of the sea-island structure of the magnetic carrier>
The sea-island structure on the magnetic carrier surface can be identified by observation under a scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) (SEM-EDX) and elemental analysis. For example, observation and elemental mapping are performed in a continuous field of view at a magnification of 40,000 times, the diameters of 20 observed islands of elemental silicon (Si) are calculated, and the average value is taken as the diameter of the island portion. Note that "islands of elemental silicon (Si)" refers to islands in which the presence of Si is observed in elemental mapping.
"Diameter of an island of silicon (Si) element" means the diameter of a circle having an area equal to the area of the island.

<Method of Calculating Si_atom% of Magnetic Carrier by XPS>
Magnetic carrier particles are attached onto an indium foil. At that time, the particles are attached uniformly so that the indium foil portion is not exposed. The measurement conditions for the XPS analysis are as follows.
Equipment: PHI5000VERSAPROBE II (ULVAC-PHI, Inc.)
Irradiation line: Al Kd line Output: 25W 15kV
Pass Energy: 29.35eV
Step size: 0.125eV
XPS peaks: _C2P , _N2P , _O2P , _Fe2P , _Si2D
The atom % of the Si element is calculated from each peak.

<Separation of Resin Coating Layer from Magnetic Carrier and Separation of Resin in Resin Coating Layer>
As a method for separating the resin coating layer from the magnetic carrier, there is a method in which the magnetic carrier is placed in a cup and the coating resin is eluted with toluene.
The eluted resin can be dried and then dissolved in tetrahydrofuran (THF) and separated by high performance liquid chromatography (HPLC).
The composition of the coating resin can be determined by identifying the atomic groups from the absorption wavenumber using a Fourier transform infrared spectrometer (product name: Spectrum One, manufactured by Perkin Elmer).

<Method of measuring the magnetization strength of the carrier core>
The magnetization strength of the carrier core can be determined using a vibrating sample magnetometer or a direct current magnetization characteristic recorder (BH tracer). In the examples described later, the magnetization strength is measured using a vibrating sample magnetometer BHV-30 (manufactured by Riken Denshi Co., Ltd.) according to the following procedure.

A cylindrical plastic container is filled with carrier cores sufficiently densely to prepare a sample. The actual mass of the sample filled in the container is measured. Then, the sample is adhered in the plastic container with instant adhesive so that the sample does not move.
Using a standard sample, the external magnetic field axis and the magnetization moment axis are calibrated at 5000/4π (kA/m).
The magnetization intensity was measured from the loop of the magnetization moment when an external magnetic field of 5000/4π (kA/m) was applied at a sweep speed of 5 (min/loop). The magnetization intensity ( ^Am2 /kg) of the carrier core was calculated by dividing the measured value by the weight of the sample.

<Measurement of specific resistance of magnetic carrier>
The resistivity of the magnetic carrier and the porous magnetic core is measured using a measuring device as shown in Fig. 4. The resistivity of the magnetic carrier is measured at an electric field strength of 2000 (V/cm).
The resistance measurement cell A is composed of a cylindrical container (made of PTFE resin) 17 with a hole having a cross-sectional area of 2.4 ^cm2 , a lower electrode (made of stainless steel) 18, a support base (made of PTFE resin) 19, and an upper electrode (made of stainless steel) 20. The cylindrical container 17 and the lower electrode 18 are placed on the support base 19, a sample (magnetic carrier or porous magnetic core) 21 is filled to a thickness of about 1 mm, and the upper electrode 20 is placed on the filled sample 21 to measure the thickness of the sample. As shown in FIG. 4(a), the gap when there is no sample is d1, and as shown in FIG. 4(b), the gap when the sample is filled to a thickness of about 1 mm is d2, and the thickness d of the sample is calculated by the following formula.
d=d2-d1 (mm)

At this time, the mass of the sample is appropriately changed so that the thickness d of the sample is 0.95 mm or more and 1.04 mm or less.
The resistivity of the sample can be obtained by applying a DC voltage between the electrodes and measuring the current that flows at that time. For the measurement, an electrometer 22 (Kessley 6517A, manufactured by Kessley) and a processing computer 23 for control are used.
A control system and control software (LabVEIW, National Instruments) manufactured by National Instruments were used for the control processing computer.

The measurement conditions are input as follows: contact area S between the sample and the electrode = 2.4 ^cm2 , measured value d of the sample thickness between 0.95 mm and 1.04 mm, load of the upper electrode 270 g, and maximum applied voltage 1000 V.
Specific resistance (Ω·cm)=(applied voltage (V)/measured current (A))×S (cm ² )/d (cm)
Electric field strength (V/cm) = applied voltage (V)/d (cm)
The resistivity of the magnetic carrier and the porous magnetic core at the above electric field strength is read from the graph as the resistivity at the above electric field strength.

<Method of measuring softening point of resin and toner>
The softening point of the resin is measured using a constant load extrusion type capillary rheometer "Flow characteristic evaluation device Flow Tester CFT-500D" (manufactured by Shimadzu Corporation) according to the manual that comes with the device. With this device, a constant load is applied from above the measurement sample by a piston, while the measurement sample filled in a cylinder is heated and melted, and the molten measurement sample is extruded from a die at the bottom of the cylinder, and a flow curve showing the relationship between the piston descent amount and temperature at this time can be obtained.

In the present invention, the "melting temperature in the 1/2 method" described in the manual attached to the "Flow characteristic evaluation device Flow Tester CFT-500D" is taken as the softening point. The melting temperature in the 1/2 method is calculated as follows. First, find 1/2 of the difference between the piston descent amount Smax at the time when the outflow ends and the piston descent amount Smin at the time when the outflow starts (this is called X. X = (Smax - Smin) / 2). Then, the temperature at which the piston descent amount on the flow curve is the sum of Smin and X is the melting temperature in the 1/2 method.

The measurement sample is prepared by compressing approximately 1.0 g of resin at approximately 10 MPa for approximately 60 seconds using a tablet molding machine (e.g., NT-100H, manufactured by NPA Systems) in an environment at a temperature of 25°C to form a cylindrical shape with a diameter of approximately 8 mm.
The measurement conditions for CFT-500D are as follows.
Test mode: Heating method Starting temperature: 50°C
Reached temperature: 200°C
Measurement interval: 1.0°C
Heating rate: 4.0° C./min
Piston cross-sectional area: 1.000 ^cm2
Test load (piston load): 10.0 kgf (0.9807 MPa)
Preheat time: 300 seconds Die hole diameter: 1.0 mm
Die length: 1.0 mm

<Measurement of glass transition temperature (Tg) and melting peak temperature (Tp) of resin and toner>
The glass transition temperature of the resin or toner is measured using a differential scanning calorimeter "Q2000" (manufactured by TA Instruments) in accordance with ASTM D3418-82.
The melting points of indium and zinc are used to correct the temperature of the detector, and the heat quantity is corrected using the heat of fusion of indium.
Specifically, about 3 mg of resin or toner is precisely weighed and placed in an aluminum pan, and an empty aluminum pan is used as a reference, and measurement is performed under the following conditions.
Heating rate: 10° C./min
Measurement start temperature: 30℃
Measurement end temperature: 180°C

Measurements are performed at a temperature rise rate of 10°C/min in the measurement range of 30 to 180°C. The temperature is raised to 180°C once and held for 10 minutes, then cooled to 30°C, and then raised again. During this second temperature rise process, specific heat change is obtained in the temperature range of 30 to 100°C. The temperature at the intersection of the differential thermal curve and a straight line equidistant in the vertical direction from the baseline before the specific heat change appears and the baseline after the specific heat change appears (so-called midpoint glass transition temperature) is taken as the glass transition temperature (Tg) of the resin.
Furthermore, the temperature at which the maximum endothermic peak occurs on the temperature-endothermic curve in the temperature range of 60 to 90° C. is defined as the melting peak temperature (Tp).

<Measurement of Mp and weight average molecular weight (Mw) by GPC>
The molecular weight distribution of the THF-soluble portion of the resin is measured by gel permeation chromatography (GPC) as follows.
First, a sample is dissolved in tetrahydrofuran (THF) at room temperature for 24 hours. The obtained solution is then filtered through a solvent-resistant membrane filter "Maeshori Disk" (manufactured by Tosoh Corporation) with a pore size of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of components soluble in THF is about 0.8 mass%. This sample solution is used to perform measurements under the following conditions.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: 7 columns of Shodex KF-801, 802, 803, 804, 805, 806, and 807 (manufactured by Showa Denko K.K.)
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0mL/min
Oven temperature: 40.0°C
Sample injection volume: 0.10 mL

When calculating the molecular weight of the sample, a molecular weight calibration curve is used that is prepared using standard polystyrene resins (e.g., trade names "TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500" manufactured by Tosoh Corporation).

<Method of measuring acid value>
The acid value is the mass [mg] of potassium hydroxide required to neutralize the acid contained in 1 g of a sample. In other words, the acid value is the mass [mg] of potassium hydroxide required to neutralize the free fatty acids and resin acids contained in 1 g of a sample.
In the present invention, the acid value is measured in accordance with JIS K 0070-1992. Specifically, the acid value is measured according to the following procedure.

(1) Preparation of Reagents 1.0 g of phenolphthalein was dissolved in 90 mL of ethyl alcohol (95% by volume), and ion-exchanged water was added to make up to 100 mL to obtain a phenolphthalein solution.
Dissolve 7 g of special grade potassium hydroxide in 5 mL of water and add ethyl alcohol (95% by volume) to make 1 L. Place in an alkali-resistant container and leave to stand for 3 days, avoiding contact with carbon dioxide gas. After leaving to stand, filter to obtain potassium hydroxide solution. Store the obtained potassium hydroxide solution in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 mL of 0.1 mol/L hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution, and titrating with the potassium hydroxide solution, from the amount of the potassium hydroxide solution required for neutralization. The 0.1 mol/L hydrochloric acid used is prepared in accordance with JIS K 8001-1998.

(2) Procedure (A) Main test 2.0 g of sample is weighed accurately in a 200 mL Erlenmeyer flask, and 100 mL of a mixed solution of toluene/ethanol (2:1) is added and the sample is dissolved over 5 hours. Next, several drops of the above phenolphthalein solution are added as an indicator, and titration is performed using the above potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for 30 seconds.
(B) Blank Test: A blank test is carried out in the same manner as above, except that no sample is added (i.e., only a mixed solution of toluene/ethanol (2:1) is used).

(3) Calculation of Acid Value The obtained results are substituted into the following formula to calculate the acid value.
AV=[(B-A)×f×5.61]/S
In the above formula, AV represents the acid value [mg KOH/g], A represents the amount [mL] of potassium hydroxide solution added in the blank test, B represents the amount [mL] of potassium hydroxide solution added in the main test, f represents the factor of the potassium hydroxide solution, and S represents the mass [g] of the sample.

[Method for measuring hydroxyl value]
The hydroxyl value is the number of milligrams of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl group when 1 g of a sample is acetylated. The hydroxyl value of the binder resin is measured in accordance with JIS K 0070-1992, and specifically, is measured according to the following procedure.
(1) Preparation of the reagent: Place 25 g of special grade acetic anhydride in a 100 mL measuring flask, add pyridine to make the total volume 100 mL, and shake thoroughly to obtain an acetylation reagent. Store the obtained acetylation reagent in a brown bottle to avoid contact with moisture, carbon dioxide, etc.
1.0 g of phenolphthalein is dissolved in 90 mL of ethyl alcohol (95 vol%), and ion-exchanged water is added to make up to 100 mL to obtain a phenolphthalein solution.

Dissolve 35 g of special grade potassium hydroxide in 20 mL of water, and add ethyl alcohol (95 vol%) to make 1 L. Place in an alkali-resistant container to avoid contact with carbon dioxide, etc., leave for 3 days, then filter to obtain potassium hydroxide solution. Store the resulting potassium hydroxide solution in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 mL of 0.5 mol/L hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution, and titrating with the potassium hydroxide solution, from the amount of potassium hydroxide solution required for neutralization. The 0.5 mol/L hydrochloric acid used is prepared in accordance with JIS K 8001-1998.

(2) Procedure (A) Main Test: 1.0 g of sample is accurately weighed into a 200 mL round-bottom flask, and 5.0 mL of the acetylation reagent is accurately added to the sample using a volumetric pipette. If the sample is difficult to dissolve in the acetylation reagent, add a small amount of special grade toluene to dissolve it.
A small funnel is placed on the mouth of the flask, and the flask is heated by immersing about 1 cm of the bottom in a glycerin bath at about 97° C. At this time, it is preferable to cover the base of the neck of the flask with a piece of cardboard with a round hole in it in order to prevent the temperature of the neck of the flask from rising due to the heat of the bath.

After 1 hour, remove the flask from the glycerin bath and allow it to cool. After allowing it to cool, add 1 mL of water from the funnel and shake to hydrolyze the acetic anhydride. To further hydrolyze it completely, heat the flask again in the glycerin bath for 10 minutes. After allowing it to cool, wash the funnel and the walls of the flask with 5 mL of ethyl alcohol.
Add a few drops of the phenolphthalein solution as an indicator and titrate with the potassium hydroxide solution. The end point of the titration is when the light red color of the indicator continues for about 30 seconds.
(B) Blank test: Carry out the same titration procedure as above, except that no sample is used.

(3) The obtained results are substituted into the following formula to calculate the hydroxyl value.
A=[{(B-C)×28.05×f}/S]+D
where A is the hydroxyl value (mgKOH/g), B is the amount of potassium hydroxide solution added for the blank test (mL), C is the amount of potassium hydroxide solution added for the main test (mL), f is the factor of the potassium hydroxide solution, S is the sample (g), and D is the acid value of the sample (mgKOH/g).

The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the following formulations, the number of parts is based on mass unless otherwise specified.
<Production Example of Magnetic Carrier Core 1>
・Process 1 (weighing and mixing process)
_Fe2O3 : 68.3% by _mass
MnCO3 : 28.5% by mass
Mg(OH) ₂ : 2.0% by mass
SrCO ₃ : 1.2% by mass
The ferrite raw material was weighed, and 80 parts of the ferrite raw material was mixed with 20 parts of water and pulverized to prepare a slurry having a solid content of 80 mass %.

Step 2 (pre-firing step)
The slurry was dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.), and then fired in a batch-type electric furnace in a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1,050° C. for 3.0 hours to produce calcined ferrite.

Step 3 (crushing step)
The calcined ferrite was crushed to about 0.5 mm with a crusher, and water was added to prepare a slurry. The solid content of the slurry was 70 mass%. This slurry was placed in a wet ball mill using 1/8 inch stainless steel beads and subjected to a crushing process for 3 hours to obtain a slurry. Furthermore, this slurry was placed in a wet bead mill using zirconia with a diameter of 1 mm and subjected to a crushing process for 4 hours to obtain a calcined ferrite slurry in which the 50% particle size (D50) based on the volume distribution of the calcined ferrite contained therein was 1.3 μm.

・Process 4 (granulation process)
To 100 parts of the calcined ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 1.5 parts of polyvinyl alcohol as a binder were added, and the mixture was dried with a spray dryer (manufactured by Okawara Kakoki Co., Ltd.). The resulting granules were subjected to particle size adjustment, and then heated at 700° C. for 2 hours in a rotary electric furnace to remove organic substances such as dispersants and binders.

Step 5 (firing step)
The material was fired in a nitrogen atmosphere (oxygen concentration: 1.0% by volume) for 2 hours from room temperature (25° C.) to the firing temperature (1100° C.), and then held at 1100° C. for 4 hours. The material was then cooled to 60° C. over 8 hours, returned from the nitrogen atmosphere to the air, and taken out at a temperature of 40° C. or less.

Step 6 (sorting step)
After the aggregated particles were crushed, the particles were sieved through a sieve with an opening of 150 μm to remove coarse particles, air classification to remove fine powder, and magnetic separation to remove low magnetic force particles to obtain porous magnetic core particles. The obtained porous magnetic core particles were porous and had pores.

・Process 7 (filling process)
100 parts of the obtained porous magnetic core particles were placed in a stirring vessel of a mixer (product name: universal stirrer NDMV type, manufactured by Dalton Co., Ltd.), and the temperature was kept at 60° C. and the pressure was reduced to 2.3 kPa. 50 parts of silicone resin (product name: SR2410, manufactured by Dow Corning Toray Co., Ltd.) was mixed with 49.5 parts of toluene and 0.5 parts of γ-aminopropyltriethoxysilane in a multi-blender mixer. The mixture was stirred at 4.00 for 10 minutes and mixed. The obtained resin solution was added dropwise to the porous magnetic core particles. The amount of the resin solution added was 4.0 parts in terms of solid content of the resin component per 100 parts of the porous magnetic core particles. It was adjusted as follows.

After the dropwise addition was completed, stirring was continued for 2.5 hours, the temperature was then raised to 70° C., the solvent was removed under reduced pressure, and the insides of the porous magnetic core particles were filled with the resin composition obtained from the resin solution.
After cooling, the obtained resin-filled magnetic core particles were transferred to a container of a stirrer (mixer) having a spiral blade (product name: drum mixer UD-AT type, manufactured by Sugiyama Heavy Industries Co., Ltd.). Thereafter, the temperature was raised to the set temperature of the stirrer, 220°C, at a heating rate of 2°C/min under a nitrogen atmosphere. Stirring was continued while heating at this temperature for 1.0 hour to harden the resin, and stirring was continued for another 1.0 hour while maintaining the temperature at 200°C.

Then, the mixture was cooled to room temperature (25°C), and the ferrite particles filled with the hardened resin were taken out and non-magnetic materials were removed using a magnetic separator. Furthermore, coarse particles were removed using a vibrating sieve to obtain magnetic carrier core 1 filled with resin. The 50% particle size (D50) based on volume distribution of magnetic carrier core 1 was 38.5 μm.

<Production Example of Silicone Modified Acrylic Resin A1>
37.5 parts by mass of the monomer corresponding to the unit B was added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen suction tube, and a rotary stirrer. Further, 100 parts by mass of dimethylformamide (DMF), 1.0 part by mass of copper bromide, 0.23 parts by mass of ethyl 2-bromoisobutyrate, and 0.8 parts by mass of sparteine were added. The resulting mixture was stirred at 70° C. for 24 hours under a nitrogen stream. This is the first reaction step.
Next, in the second reaction step, 25 parts by mass of a monomer corresponding to the unit C was added, and the mixture was stirred at 70° C. for 5 hours under a nitrogen stream.
In the third reaction step, 37.5 parts by mass of a monomer corresponding to the unit B was added and the mixture was stirred at 70° C. for 24 hours under a nitrogen stream.
After the polymerization reaction was completed and washing was repeated, a toluene solution (solid content: 35% by mass) of silicone-modified acrylic resin A1 was obtained. The molecular weight (Mw) of silicone-modified acrylic resin A1 was 85,000.

The structure of unit B is represented by the above formula (5), and details are shown in Table 1.
The unit C used was represented by the following formula (7): The degree of polymerization, n, of the silicone moiety of unit C is as shown in Table 1.
As for unit B, half of the "total input amount (g)" shown in Table 1 was input in the first reaction step, and the remainder was input in the third reaction step.

<Production Examples of Silicone Modified Acrylic Resins A2 to A10>
Silicone-modified acrylic resins A2 to A10 were obtained in the same manner as in the production method for resin A1, except that the masses of copper bromide, ethyl 2-bromoisobutyrate, and sparteine, the structure and amount of unit B, and the values of n and amount of unit C were changed as shown in Table 1.

<Method of producing macromonomer>
The macromonomer used in the silicone modified acrylic resin A can be synthesized, for example, by reacting methacrylic acid chloride with a polymer having a hydroxyl group at one end.

<Production Example of Silicone Modified Acrylic Resin A11>
57 parts by mass of the monomer corresponding to the unit B used in the silicone-modified acrylic resin A3 shown in Table 1, and 43 parts by mass of the monomer corresponding to the unit C were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen suction tube, and a grinding type stirrer. 100 parts by mass of DMF, 1.72 parts by mass of copper bromide, 0.4 parts by mass of ethyl 2-bromoisobutyrate, and 1.4 parts by mass of sparteine were further added, and the mixture was stirred at 70°C for 48 hours under a nitrogen stream. After the polymerization reaction was completed, washing was repeated to obtain a silicone-modified acrylic resin A11 solution (solid content 35% by mass). The molecular weight of the silicone-modified acrylic resin A11 was 50,000.

<Method of producing resin D>
Two monomers and one macromonomer, as shown below, were added to a four-neck flask equipped with a reflux condenser, thermometer, nitrogen inlet, and ground-wheel stirrer.
Cyclohexyl methacrylate: 74.5% by mass
Methyl methacrylate: 0.5% by mass
Polymethyl methacrylate macromonomer (Mw: 5000)...25.0% by mass

Further, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The resulting mixture was kept at 70°C for 10 hours under a nitrogen stream, and after the polymerization reaction was completed, washing was repeated to obtain a resin D solution (solid content 35% by mass). The weight average molecular weight of this solution measured by gel permeation chromatography (GPC) was 57,000.

<Resin coating process>
- Method for preparing magnetic carrier 1 Magnetic carrier core 1 was placed in a planetary mixer (Nauta Mixer VN type manufactured by Hosokawa Micron Corporation) maintained under reduced pressure (1.5 kPa) at a temperature of 60° C. Then, a resin solution of resin A1 shown in Table 1 was added so that the solid content of the resin component was 2.0 parts by mass per 100 parts by mass of the carrier core, and the solvent was removed and a coating operation was performed for 20 minutes.
Thereafter, the magnetic carrier coated with the coating resin composition was transferred to a mixer (UD-AT type drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) having a spiral blade in a rotatable mixing container. The mixture was heat-treated for 2 hours at a temperature of 120°C in a nitrogen atmosphere while stirring at 10 revolutions per minute. The obtained magnetic carrier 1 was separated into low magnetic products by magnetic separation, passed through a sieve with an opening of 150 μm, and then classified with an air classifier to obtain magnetic carrier 1.

The total mass of the moieties represented by formulas (1) to (4) (total of silicone units) was 24% by mass relative to the total mass of the resin coating the surface of the magnetic carrier 1.
The proportion of formula (1) to the total of the moieties represented by formulas (1) to (4) was 97 mol %.
The diameter of the islands was 20 nm.
When the surface of the magnetic carrier 1 was measured by X-ray photoelectron spectroscopy (XPS), the proportion of silicon (Si) atoms was 4.5 atomic %.

Method for Producing Magnetic Carriers 2 to 13 Magnetic Carriers 2 to 13 were obtained in the same manner as in the method for producing the magnetic carrier 1, except that the type and amount of the coating resin solution were adjusted to the values shown in Table 2.

<Production Example of Low Molecular Weight Polyester Resin E>
Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 76.3 parts (0.19 moles; 100.0 mol% based on the total number of moles of polyhydric alcohol)
・Terephthalic acid:
16.1 parts (0.10 mole; 60.0 mol% based on the total number of moles of polyvalent carboxylic acids)
・Succinic acid:
7.6 parts (0.06 moles; 40.0 mol% based on the total number of moles of polyvalent carboxylic acids)
Titanium tetrabutoxide (esterification catalyst): 0.5 parts

The above materials were weighed and placed in a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the reaction was carried out for 4 hours at a temperature of 200° C. with stirring.
Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained for 1 hour, after which it was cooled to 160° C. and returned to atmospheric pressure (first reaction step).
tert-Butylcatechol (polymerization inhibitor): 0.1 part

The above materials were then added, the pressure in the reaction vessel was lowered to 8.3 kPa, and the reaction was carried out for 1 hour while maintaining the temperature at 180°C. Then, after it was confirmed that the softening point measured according to ASTM D36-86 had reached 90°C, the temperature was lowered to stop the reaction (second reaction step), and Resin E was obtained. The obtained Resin E had a peak molecular weight Mp of 4,500, a softening point Tm of 90°C, and a glass transition temperature Tg of 54°C.

<Production Example of High Molecular Weight Polyester Resin F>
Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 73.8 parts (0.19 moles; 100.0 mol% based on the total number of moles of polyhydric alcohol)
・Terephthalic acid:
12.5 parts (0.08 moles; 48.0 mol% based on the total number of moles of polyvalent carboxylic acids)
Adipic acid:
7.8 parts (0.05 mole; 34.0 mol% based on the total number of moles of polyvalent carboxylic acids)
Titanium tetrabutoxide (esterification catalyst): 0.5 parts

The above materials were weighed and placed in a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the reaction was carried out for 2 hours at a temperature of 200° C. with stirring.
Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained for 1 hour, after which it was cooled to 160° C. and returned to atmospheric pressure (first reaction step).
・Trimellitic acid:
5.9 parts (0.03 moles; 18.0 mole% based on the total number of moles of polyvalent carboxylic acids)
tert-Butylcatechol (polymerization inhibitor): 0.1 part

The above materials were then added, the pressure in the reaction vessel was lowered to 8.3 kPa, and the reaction was carried out for 15 hours while maintaining the temperature at 200°C. Then, after it was confirmed that the softening point measured according to ASTM D36-86 had reached 140°C, the temperature was lowered to stop the reaction (second reaction step), and Resin F was obtained. The obtained Resin F had a peak molecular weight Mp of 10,000, a softening point Tm of 140°C, and a glass transition temperature Tg of 60°C.

<Production Example of Crystalline Resin G>
・Hexanediol:
33.9 parts (0.29 moles; 100.0 mol% based on the total number of moles of polyhydric alcohol)
Dodecanedioic acid:
66.1 parts (0.29 moles; 100.0 mol% based on the total number of moles of polyvalent carboxylic acids)
The above materials were weighed and placed in a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the reaction was carried out for 3 hours at a temperature of 140° C. with stirring.
Then, the above materials were added, the pressure in the reaction vessel was lowered to 8.3 kPa, and the temperature was maintained at 200° C. while reacting for 4 hours to obtain a crystalline resin G (first reaction step). The obtained crystalline resin G had a weight average molecular weight Mw of 10,000 and a melting peak temperature Tp of 71° C.

<Production Example of Wax Dispersant H>
Low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries, Ltd.):
10.0 parts (0.4 mol % based on the total number of moles of constituent monomers)
Xylene: 25.0 parts The above materials were weighed and placed in a reaction vessel equipped with a cooling tube, a stirrer, a nitrogen inlet tube, and a thermocouple. The atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually increased to 175° C. with stirring.
·styrene:
68.0 parts (78.5 mol % based on the total number of moles of constituent monomers)
Cyclohexyl acrylate:
5.0 parts (3.9 mol % based on the total number of moles of constituent monomers)
・Butyl acrylate:
12.0 parts (11.2 mol % based on the total number of moles of constituent monomers)
Methacrylic acid:
5.0 parts (6.0 mol % based on the total number of moles of constituent monomers)
・Xylene: 10.0 parts ・Di-t-butylperoxyhexahydroterephthalate: 0.5 parts The above materials were then dropped over 3 hours and stirred for another 30 minutes. The solvent was then distilled off to obtain a polymer H in which a styrene-acrylic polymer was graft-polymerized onto a polyolefin. The obtained polymer H in which a styrene-acrylic polymer was graft-polymerized onto a polyolefin had a peak molecular weight Mp of 6,000 and a softening point of 125°C.

<Toner 1 Production Example>
Resin E 60 parts Resin F 30 parts Crystalline resin G 10 parts Wax dispersant H 4 parts Fischer-Tropsch wax (peak temperature of maximum endothermic peak 90°C) 4 parts C.I. Pigment Blue 15:3 7 parts The above materials were mixed using a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20s ^-1 and a rotation time of 5 minutes, and then kneaded using a twin-screw kneader (PCM-30 type, manufactured by Ikegai Co., Ltd.) set at a temperature of 130°C. The kneaded product obtained was cooled and coarsely crushed to 1 mm or less using a hammer mill to obtain a coarsely crushed product. The obtained coarsely crushed product was finely crushed using a mechanical crusher (T-250, manufactured by Turbo Kogyo Co., Ltd.). Furthermore, classification was performed using Faculty F-300 (manufactured by Hosokawa Micron Co., Ltd.) to obtain toner particles. The operating conditions were a classifying rotor rotation speed of 130 s ^-1 and a dispersing rotor rotation speed of 120 s ^-1 .

The obtained toner particles were subjected to a heat treatment by the surface treatment device shown in Fig. 3 to obtain heat-treated toner particles. The operating conditions were as follows: feed rate = 5 kg/hr, hot air temperature = 160°C, hot air flow rate = 6 ^m3 /min, cold air temperature = -5°C, cold air flow rate = 4 ^m3 /min, blower air flow rate = 20 ^m3 /min, injection air flow rate = 1 ^m3 /min.
The following materials were mixed using a Henschel mixer (FM-75, manufactured by Mitsui Miike Kakoki Co., Ltd.) at a rotation speed of 30 s ⁻¹ for a rotation time of 10 min to obtain toner 1.
- 100 parts of obtained heat-treated toner particles - 1.0 part of hydrophobic silica (BET: 200 m ² /g) - 1.0 part of titanium oxide fine particles surface-treated with isobutyltrimethoxysilane (BET: 80 m ² /g) The weight average particle size (D4) of Toner 1 was measured using a precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) and found to be 6.5 μm. The average circularity of Toner 1 was measured using a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) and found to be 0.968.

<Production Example of Two-Component Developer 1>
10 parts by mass of toner 1 was added to 90 parts by mass of magnetic carrier 1, and the mixture was shaken using a shaker (product name: YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 300 g of two-component developer 1. The shaking conditions using the shaker were 200 rpm and 5 minutes.

<Production Examples of Two-Component Developers 2 to 13>
In the production example of two-component developer 1, the same operation was carried out except for the changes shown in Table 3, to obtain two-component developers 2 to 13.

Example 1
95 parts by weight of toner 1 was added to 5 parts by weight of magnetic carrier 1, and mixed for 5 minutes in a V-type mixer in a temperature of 23° C./relative humidity of 50% (normal temperature and normal humidity) environment (hereinafter referred to as “N/N environment”) to obtain a replenishment developer.
The above two-component developer and replenishment developer were used for the following evaluations.
As the image forming apparatus, a modified version of a full-color copying machine (product name: imageRUNNER ADVANCE C9075 PRO) manufactured by Canon Inc. was used.
A two-component developer was placed in each color developing device, a refill developer container containing a refill developer for each color was set, and an image was formed. Various evaluations were made while a paper feed durability test was performed.
The paper feed durability test was performed by outputting images on a total of 150,000 sheets in Step 1 and Step 2 while changing the environment and image ratio as follows.

・Step 1 (from 1st to 100,000th)
Temperature 30°C/relative humidity 80% (hereinafter referred to as "H/H environment")
FFH output chart with image ratio of 60% ・Step 2 (100,001st to 150,000th sheets)
Temperature 23°C / Relative humidity 5% (hereinafter referred to as "N/L environment")
FFH output chart with an image ratio of 3% Here, FFH is a value obtained by expressing 256 gradations in hexadecimal, with 00H being the first gradation (white background) of the 256 gradations and FFH being the 256th gradation (solid area) of the 256 gradations.

Other conditions are as follows:
Paper: Laser beam printer paper CS-814 (product name) (81.4 g/m ² ) (Canon Marketing Japan Inc.)
Image forming speed: The printer was modified so that it could output 80 sheets/minute in A4 size and full color.
Development conditions: The development contrast can now be adjusted to any value, and the automatic correction by the camera body has been disabled.
The alternating electric field was modified so that its peak-to-peak voltage (Vpp) could be changed in increments of 0.1 kV from 0.7 kV to 1.8 kV at a frequency of 2.0 kHz.
Each color was modified so that images could be output in monochrome.
The evaluation items are shown below.

(1) Fog After 100,000 sheets were output in Step 1, 10 sheets of 00H output chart (A4 full-white image) with an image ratio of 100% were output, and the whiteness of the white background was measured with a reflectometer (Tokyo Denshoku Co., Ltd.). The fog density (%) was calculated from the difference between the whiteness and the whiteness of the transfer paper, and the one with the highest fog density among the 10 sheets was evaluated. The evaluation criteria are as follows.
A: less than 0.5% B: 0.5% or more and less than 1.0% C: 1.0% or more and less than 1.5% D: 1.5% or more and less than 2.0% E: 2.0% or more The results are shown in Table 4.

(2) Image Density Difference Before and After Durability in Each Step In Step 1 and Step 2, one FFH output chart (A4 full-page solid image) with an image ratio of 100% was output at the beginning and end of each Step. The image density was measured and evaluated using a spectrodensitometer 500 series (manufactured by X-Rite Corporation).
The measurement site is
Three points are placed at 0.5 cm from the leading edge of the image (the side on which the image was formed first), and at 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image (the side on which the image was formed first is considered the top).
7.0 cm from the tip of the image, and 3 points 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image.
At a position 14.0 cm from the tip of the image, and at three points 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image,
A total of 12 points were measured, 20.0 cm from the leading edge of the image, and three points were measured at 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image, and the average value of the 12 points was calculated.

The evaluation was performed by judging the difference between the average value of the first 12 points and the average value of the last 12 points of each step according to the following criteria.
A: 0.00 or more and less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.15 D: 0.15 or more and less than 0.20 E: 0.20 or more

(3) Image Density Difference Between Step 1 and Step 2 One FFH output chart (A4 full-page solid image) with an image ratio of 100% was output at the end of Step 1 and at the end of Step 2. The reflection density of the output image was measured in the same manner as in the density difference described above, and the average value of 12 points was calculated.
The evaluation was performed by judging the difference between the 12-point average value of Step 1 and the 12-point average value of Step 2 according to the following criteria.
A: 0.00 or more and less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.15 D: 0.15 or more and less than 0.20 E: 0.20 or more

(4) Whiteout Immediately after 200 sheets of paper are passed continuously in STEP 2, a chart is output in which halftone horizontal bands (30H, 10 mm wide) and solid black horizontal bands (FFH, 10 mm wide) are alternately arranged in the conveying direction of the transfer paper. The image is read by a scanner and binarized. The luminance distribution (256 gradations) of a line in the conveying direction of the binarized image is taken. A tangent line is drawn to the luminance of the halftone at that time, and the luminance area (area: sum of the luminance numbers) shifted from the tangent line at the rear end of the halftone part until it intersects with the luminance of the solid part is taken as the degree of whiteout, and is evaluated based on the following criteria. The evaluation was performed in monochromatic cyan.
A: Less than 20 B: 20 or more and less than 30 C: 30 or more and less than 40 D: 40 or more and less than 50 E: 50 or more

(5) Overall Judgment The above evaluation ranks were converted into numerical values (A=4, B=3, C=2, D=1, E=0), and the total score was judged according to the following criteria.
A: 17 or more and 20 or less B: 14 or more and 16 or less C: 11 or more and 13 or less D: 7 or more and 10 or less E: 6 or less It was determined that the levels A to C are levels at which the effects of the present invention are obtained.
The results are shown in Table 4.

<Examples 2 to 10 and Comparative Examples 1 to 3>
Evaluation was carried out in the same manner as in Example 1, except that the two-component developer used in the evaluation was changed to the two-component developer shown in Table 3. The evaluation results are shown in Table 4.

1 Electrostatic latent image carrier 2 Charger 3 Exposure device 4 Development device 5 Development container 6 Developer carrier 7 Magnet 8 Regulating member 9 Intermediate transfer body 11 Transfer charger 12 Recording medium (transfer material)
13 Fixing unit 15 Cleaner 16 Pre-exposure means

Claims (6)

A magnetic carrier having a magnetic core and a coating resin that coats the surface of the magnetic core,
the coating resin contains a silicone-modified acrylic resin having a silicone moiety and an acrylic moiety,
On the surface of the magnetic carrier, the coating resin has a sea-island structure in which islands are dispersed in a sea,
the island portions are mainly composed of the silicone portion, and the number-average diameter of the island portions is 10 nm or more and 100 nm or less;
The magnetic carrier is characterized in that the sea portion is mainly composed of the acrylic portion. The magnetic carrier according to claim 1, wherein the proportion of silicon (Si) atoms is 1.0 atomic % or more and 8.0 atomic % or less when measured by X-ray photoelectron spectroscopy (XPS). 3. The magnetic carrier according to claim 1, wherein the silicone-modified acrylic resin contains 10% by mass or more and 40% by mass or less of moieties represented by the following formulas (1) to (4):

(In the formula, R ¹ to R ⁶ each independently represent a hydrogen group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, an alkenyl group having 2 to 4 carbon atoms, or an alkenyloxy group having 2 to 4 carbon atoms. In the formula, -O _1/2 represents that an oxygen (O) atom is shared with adjacent silicon (Si) atoms.) The magnetic carrier according to claim 3, wherein the moiety represented by formula (1) accounts for 90 mol % or more of the moieties represented by formulas (1) to (4) in the silicone-modified acrylic resin. A two-component developer containing a toner and a magnetic carrier,
A two-component developer, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 4. The method includes a charging step of charging an electrostatic latent image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing step of developing the electrostatic latent image with a two-component developer in a developing device to form a toner image, a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer body, and a fixing step of fixing the transferred toner image to the transfer material,
A replenishment developer for use in an image forming method in which the replenishment developer is replenished to a developing device in response to a reduction in a toner concentration of a two-component developer in the developing device, comprising:
The replenishment developer contains a replenishment magnetic carrier and a toner,
5. A refill developer, comprising the refill magnetic carrier according to claim 1.

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