JP2011033861A - Magnetic carrier, two-component developer and developer for replenishment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire both high developability and spent resistance, to enhance output speed and enhance durability, and to acquire a superior image, without generating image failure, such as carrier adhesion, even at long-term use or under a low-temperature low-humidity environment. <P>SOLUTION: The magnetic carrier having at least a resin-coating layer formed on a magnetic carrier core surface, the resin coating layer includes, at least a resin composition and carbon black particles, and a particle size Pv of the maximum peak is not less than 0.10 μm and not more than 1.00 μm in the measurement of the particle size distribution of a volume reference of particles, when the resin coating layer is dissolved into toluene; and the full-width at half maximum Hv of the maximum peak is not less than 0.05 μm and not more than 0.40 μm, and frequency ratio Fv, which is the ratio of the maximum peak to the whole peak frequency, is not less than 65% and not more than 95%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic carrier used in a two-component developer for forming an electrostatic latent image on an electrophotographic photosensitive member or an electrostatic latent image carrier that is an electrostatic recording derivative in electrophotography, and two-component development. Agent and replenishment developer.

  In recent years, copying machines and printers have been strictly pursued for higher speed and higher reliability. As a result, the performance required for the developer becomes higher, and if the improvement in the performance of the developer cannot be achieved, a better copying apparatus main body cannot be realized. Of the methods for developing an electrostatic image using toner, a two-component development method using a two-component developer in which toner is mixed with a magnetic carrier is suitable for a full-color copying machine or printer that requires high image quality. It is used.

  There are various characteristics required for the magnetic carrier and toner constituting the above two-component developer, but particularly important characteristics for the magnetic carrier include appropriate chargeability, pressure resistance against alternating voltage, and impact resistance. , Wear resistance, spent resistance, developability and the like. Among them, improvement in performance with respect to developability and spent resistance is required. First, with respect to developability, it is necessary to improve toner separation from the magnetic carrier in order to cope with high speed. In order to solve this problem, studies have been conducted focusing on the dispersion state of conductive fine particles. That is, by adding conductive fine particles to the surface of the magnetic carrier and reducing the surface resistance of the magnetic carrier, toner separation when a developing bias is applied is improved. As an example, a conductive composite particle containing carbon black is contained in a carrier coating layer (Patent Document 1). However, with this method, an effect for improving developability can be obtained, but a problem remains with respect to spent resistance. Furthermore, when it is attempted to obtain a longer life than the conventional case, the conductive composite particles may be detached and an image defect may occur.

  Further, for the purpose of improving spent resistance, a carrier having a coating layer in which conductive powder is present in an aggregated state has been proposed (Patent Document 2). However, in this proposal, a thermosetting silicone resin is used as the coating resin. With a thermosetting resin, the film strength and the dispersion state of the conductive powder vary greatly depending on the curing conditions after coating. Therefore, it is difficult to control the finely dispersed state of the conductive powder, and when used for a long period of time, the external additive tends to adhere to the carrier, and the charge imparting ability is hardly lowered and a good image is difficult to obtain.

  As described above, in the conventional method, examinations on processing conditions, materials, and the like are still insufficient for improving the characteristics of the electrophotographic technology such as developability and prevention of spent.

JP 2005-181935 A JP 2002-278168 A

  An object of the present invention is to obtain a magnetic carrier capable of achieving both high developability and spent resistance by controlling the aggregation state of carbon black particles in the carrier coating layer. Thereby, a two-component developer having high stability and high durability is obtained. In addition, even when used for a long period of time, image defects such as carrier adhesion do not occur and a good image can be obtained.

  Said subject is achieved by the structure of the following this invention.

<1>
A magnetic carrier having a resin coating layer formed on at least the surface of a magnetic carrier core,
The resin coating layer contains at least a resin composition and carbon black particles,
When the resin coating layer is dissolved in toluene, the maximum peak particle size Pv is 0.10 μm or more and 1.00 μm or less in the volume-based particle size distribution measurement, and the maximum peak half-value width Hv is 0.05 μm or more and 0 or less. A magnetic carrier having a frequency ratio Fv of 65% or more and 95% or less that is 40 μm or less and that is occupied by the maximum peak with respect to the total peak frequency.

<2>
<1> The magnetic carrier according to <1>, wherein the resin forming the resin coating layer contains at least a resin obtained by polymerizing a monomer represented by the following formula (A1).

（式中、Ｒ¹は炭素数４以上２２以下の炭化水素基を示し、Ｒ²はＨまたはＣＨ₃を示す。）

(In the formula, R ¹ represents a hydrocarbon group having 4 to 22 carbon atoms, and R ² represents H or CH _3. )

<3>
The resin forming the resin coating layer contains at least a resin obtained by polymerizing the monomer represented by the formula (A1) and occupies the resin of the monomer unit represented by the formula (A1). The magnetic carrier according to <2>, wherein the ratio is 50% by mass or more and 95% by mass or less.

<4>
The resin forming the resin coating layer contains at least a resin obtained by copolymerizing at least a macromonomer and a monomer represented by the formula (A1),
The macromonomer unit is at least one selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. The magnetic carrier according to any one of <1> to <3>, which is a macromonomer obtained by polymerizing the above monomers.

<5>
The resin forming the resin coating layer contains at least a resin obtained by copolymerizing at least a macromonomer and a monomer having a structure represented by the formula (A1),
The magnetic carrier according to <4>, wherein the proportion of the macromonomer unit in the resin is 1% by mass or more and 50% by mass or less.

<6>
The magnetic carrier according to any one of <1> to <5>, wherein the carbon black particles contained in the resin coating layer have an average primary particle diameter of 10 nm to 55 nm.

<7>
The magnetic carrier according to any one of <1> to <6>, wherein the carbon black particles contained in the resin coating layer have a DBP oil absorption of 20 ml / 100 g or more and 500 ml / 100 g or less.

<8>
The magnetic carrier according to any one of <1> to <7>, wherein the true density of the magnetic carrier is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less.

<9>
It is a two-component developer having at least a magnetic carrier having a resin coating layer on the surface of a carrier core and a toner, and the magnetic carrier is the magnetic carrier according to any one of <1> to <8>. Two-component developer characterized.

<10>
Development is performed while supplying a replenishment developer containing at least a toner and a magnetic carrier having a resin coating layer to the developing device, and at least the excess magnetic carrier inside the developing device is discharged from the developing device as necessary. A replenishment developer for use in a component development method,
The replenishment developer includes a toner and a magnetic carrier, and the toner is contained in a mixing ratio of 2 to 50 parts by mass with respect to 1 part by mass of the magnetic carrier.
The replenishment developer, wherein the magnetic carrier is the magnetic carrier according to any one of <1> to <9>.

  According to the present invention, a magnetic carrier capable of achieving both high developability and spent resistance can be obtained. As a result, higher output speed and higher durability became possible. Further, even in long-term use or in a low-temperature and low-humidity environment, a good image can be obtained without causing image defects such as carrier adhesion.

It is a schematic sectional drawing which shows an example of the coating apparatus used for the manufacturing method of the carrier of this invention. It is a schematic diagram which shows an example of the measuring apparatus which measures the specific resistance of the carrier for electrophotography of this invention. It is a schematic explanatory drawing of a color laser printer. It is a schematic explanatory drawing of the image development apparatus which can use this invention suitably.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  In the present invention, it is a magnetic carrier in which a resin coating layer is formed at least on the surface of the magnetic carrier core, and the resin coating layer needs to contain at least a resin composition and carbon black particles. Carbon black particles are added to adjust the resistance of the magnetic carrier. As a general tendency, if the resistance of the magnetic carrier is too low, a leak occurs between the photosensitive drum and the magnetic carrier, and the image quality deteriorates. On the other hand, if the resistance is too high, the separation of the toner from the magnetic carrier is deteriorated during development and the developability is deteriorated.

  Conventionally, resistance is adjusted by adding carbon black particles to a magnetic carrier in order to improve image quality. However, as a result of intensive studies, we have improved the spent resistance of magnetic carriers as well as image quality by controlling the aggregation state of carbon black particles. It was found that there is an effect on accumulation. That is, even if it is durable, the spent on the magnetic carrier is reduced, so that the charge imparting ability of the magnetic carrier is easily maintained even after it has been durable for a long time. Further, since the carbon black particles are appropriately aggregated, it is difficult for charge-up to occur even under low temperature and low humidity. Thus, by controlling the aggregation state of the carbon black particles, it was possible to find a magnetic carrier that can properly charge the toner even under long-term use or under low temperature and low humidity.

  Specifically, in the volume-based particle size distribution measurement of the particles when the magnetic carrier is dissolved in toluene, the maximum peak particle size Pv is 0.10 μm or more and 1.00 μm or less, and the maximum peak half width Hv is 0. It was found that the frequency ratio Fv occupied by the maximum peak with respect to the total peak frequency must be 65% or more and 95% or less.

  First, the method for measuring the particle size distribution of carbon black particles in a magnetic carrier is to dissolve the magnetic carrier in toluene and to elute the resin coating layer from the magnetic carrier. Then, the eluted solution is a method for measuring the particle size distribution of the carbon black particles with a laser diffraction particle size distribution measuring machine.

  In the present invention, the maximum peak particle size Pv in the volume-based particle size distribution of the carbon black particles needs to be 0.10 μm or more and 1.00 μm or less. The present inventors consider that Pv is greatly involved in the resistance in the magnetic carrier. That is, when Pv is less than 0.10 μm, the resistance adjustment effect is small and the resistance of the magnetic carrier is increased, resulting in white spots. Further, in order to adjust the resistance, it is necessary to add a large amount, and when left untreated, the charge is remarkably leaked, and fogging and toner scattering occur. On the other hand, when Pv is larger than 1.00 μm, the carbon black particles are likely to be liberated and an image defect occurs. Pv is preferably 0.20 μm or more and 0.85 μm or less, and more preferably Pv is 0.20 μm or more and 0.75 μm or less.

  In the present invention, the half-value width Hv of the maximum peak in the volume-based particle size distribution of the carbon black particles needs to be 0.05 μm or more and 0.40 μm or less. The present inventors consider that Hv is greatly involved in the charge imparting in the magnetic carrier. That is, when Hv is less than 0.05 μm, the distribution of the carbon black particles is too uniform, so that the magnetic carrier itself is charged up and carrier adhesion occurs. That is, when the magnetic carrier charges the toner, the toner is charged by friction between the two. When the toner is charged, the magnetic carrier also has a charge. If the magnetic carrier does not leak the electric charge, the electric charge of the magnetic carrier is increased and the charge is increased. This makes it difficult for the toner to separate from the magnetic carrier and causes the carrier adhesion to be induced by the deterioration of the fluidity as a developer. On the other hand, when Hv is larger than 0.40 μm, the portion that retains electric charges and the portion that leaks are more distinctly separated on the surface of the magnetic carrier. As a result, the charge imparting ability to the toner also varies, and the charge distribution of the toner becomes broad. As a result, variations in toner development and transfer properties occur, resulting in an image with noticeable graininess. Preferably, Hv is 0.10 μm or more and 0.35 μm or less, and more preferably Hv is 0.15 μm or more and 0.32 μm or less.

  Furthermore, in the present invention, the frequency ratio Fv occupied by the maximum peak with respect to the total peak frequency in the volume-based particle size distribution of the carbon black particles needs to be 65% or more and 95% or less. The present inventors consider that Fv is greatly involved in the accumulation of external additives in the magnetic carrier. That is, the carbon black particles exist in an aggregated state in the resin coating layer on the surface of the magnetic carrier, but the distribution of the aggregated state is plural, and the distribution is a specific ratio. It was found to be important in suppressing accumulation. In general, the external additive has the same polarity as the toner and has a higher resistance than the magnetic carrier. When the external additive adheres to the magnetic carrier, the charge imparting ability of the magnetic carrier is hindered or the developability of the toner is hindered. In order to suppress this, it is necessary to prevent the external additive from adhering to the magnetic carrier, and it is important to control the distribution of the aggregated state of carbon black in the magnetic carrier coat. That is, when Fv is greater than 95%, the ratio of components other than the maximum peak is small and the external additive accumulates, resulting in a decrease in charge and deterioration of developability. When Fv is less than 65%, the ratio of the maximum peak is small and the toner charge distribution becomes broad. As a result, variations in toner development and transfer properties occur, resulting in an image with noticeable graininess. Preferably, Fv is 70% or more and 90% or less, and more preferably Fv is 73% or more and 85% or less.

  The carbon black particles used in the present invention preferably have an average primary particle diameter of 10 nm to 55 nm. More preferably, it is 25 nm or more and 50 nm or less. If the average primary particle size is smaller than 10 nm, uniform dispersion is difficult, and resistance control of the magnetic carrier cannot be performed, and good developability is difficult to obtain. On the other hand, when the average primary particle diameter of carbon black is larger than 55 nm, the carbon black is easily liberated, causing image defects.

  The carbon black particles used in the present invention preferably have a pH of 7 or more, more preferably 7.5 or more and 10.5 or less. A pH smaller than 7 means that many functional groups such as carboxyl groups remain. In this case, the association of carboxyl groups becomes strong and carbon black tends to be unevenly distributed. The tribo-maintaining property at the end will deteriorate. On the contrary, since the carbon black tends to be unevenly distributed even if the pH is extremely high, the pH is more preferably 10.5 or less.

  The carbon black particles used in the present invention preferably have a volatile content of 1% or less, more preferably 0.8% or less. A volatile content greater than 1% means that many functional groups are present on the carbon black surface. When such carbon black is used, carbon black tends to be unevenly distributed on the surface of the magnetic carrier, so that the tribo maintainability under high temperature and high humidity deteriorates.

  In the carbon black particles used in the present invention, the DBP oil absorption is preferably 20 ml / 100 g or more and 500 ml / 100 g or less, more preferably 3020 ml / 100 g or more and 130 ml / 100 g or less. When the amount of oil absorption exceeds 500 ml / 100 g, carbon black tends to be unevenly distributed, and the tribo maintainability under high temperature and high humidity is deteriorated. On the other hand, when the oil absorption is less than 20 ml / 100 g, the dispersibility of the carbon black in the toner particles is not sufficient, and it becomes difficult to adjust the resistance of the magnetic carrier, making it difficult to obtain good developability.

In the carbon black particles used in the present invention, the specific surface area by nitrogen adsorption is preferably 100 m ² / g or less. More preferably 30 m ² / g or more 90m ² / g or less, more preferably 40 m ² / g or more 90m it is good ² / g or less. Further, the toluene extraction amount is preferably 0.1% or less, more preferably 0.05% or less.

  Next, the resin coating layer of the magnetic carrier core used in the present invention will be described.

  The following are mentioned as a thermoplastic resin used for formation of the resin coating layer of a carrier core. Polystyrene, polymethyl methacrylate, styrene-acrylic acid copolymer, acrylic resin, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon Resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose, cellulose acetate, cellulose nitrate, methyl cellulose, hydroxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, novolac resin, low molecular weight polyethylene, saturated alkyl polyester Resin, polyethylene terephthalate, polybutylene terephthalate, polyarylate, aromatic polyester tree , Polyamide resins, polyacetal resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyphenylene sulfide resins, polyether ketone resins. As a resin that can be used more suitably, a resin having a Tg of 70 ° C. or more is preferable because it can prevent toner spent well.

    In the present invention, the resin coating layer preferably contains at least a resin obtained by polymerizing a monomer represented by the following formula (A1).

（式中、Ｒ¹は炭素数４以上２２以下の炭化水素基を示し、Ｒ²はＨまたはＣＨ₃を示す。）

(In the formula, R ¹ represents a hydrocarbon group having 4 to 22 carbon atoms, and R ² represents H or CH _3. )

  By containing the monomer having the structure represented by the formula (A1) as a polymerization component in the magnetic carrier resin coating layer, it is possible to improve the charge imparting property of the magnetic carrier. Thereby, it is easy to maintain the charging stability of the developer for a long period of time. In addition, the Fv tends to increase because the carbon black particles are easily aggregated, and an image with less roughness is easily obtained.

Further, the hydrocarbon group having 4 or more carbon atoms of R ¹ may be a chain hydrocarbon group or a cyclic hydrocarbon group. Examples of the monomer having the structure represented by the above formula (A1) in which R ¹ has a hydrocarbon group having 4 or more carbon atoms include the following. Butyl acrylate, butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, acrylic acid Octadecyl, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate, isobornyl acrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, methacrylic acid Examples include ntadecyl, hexadecyl methacrylate, heptadecyl methacrylate and octadecyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, isobornyl methacrylate, dicyclopentenyl methacrylate, and dicyclopentanyl methacrylate. One or two or more of these monomers may be selected.

  In the resin forming the resin coating layer, the ratio of the monomer unit represented by the formula (A1) to the resin is preferably 50% by mass or more and 95% by mass or less. When the ratio is smaller than 50% by mass, Hv of the carbon black particles tends to increase, and an image with a noticeable graininess tends to be obtained. On the other hand, if it is greater than 95% by mass, Hv tends to be small, and charging tends to charge up. A preferred range is 55 to 85% by mass, and a more preferred range is 60 to 80% by mass.

  The resin forming the resin coating layer contains at least a resin obtained by copolymerizing at least a macromonomer and a monomer represented by the formula (A1). The macromonomer unit is at least one selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. It is preferably a macromonomer obtained by polymerizing the above monomers.

  By copolymerizing the macromonomer and the monomer represented by the formula (A1), it is easy to improve the adhesion between the carrier core and the coating resin layer and to control the Hv of the carbon black particles. The aggregate of carbon black particles is easily dispersed uniformly by the monomer represented by the formula (A1), while the macromonomer has an effect of maintaining the aggregated state. Therefore, by containing both, it is easy to control the dispersion state of the carbon aggregate to a specific state.

  The proportion of the macromonomer unit in the resin is preferably 1% by mass or more and 50% by mass or less. If the ratio is less than 1% by mass, the Hv of the carbon black particles tends to be small. On the other hand, when the ratio is larger than 50% by mass, Hv tends to increase. A preferable range is 55% by mass or more and 85% by mass or less, and a more preferable range is 60% by mass or more and 80% by mass or less.

  An example of a specific macromonomer is shown in the following formula.

（式中、Ａはアクリル酸メチル、メタクリル酸メチル、アクリル酸ブチル、メタクリル酸ブチル、アクリル酸２−ヒドロキシエチル、メタクリル酸２−ヒドロキシエチル、スチレン、アクリロニトリルより選ばれる１種又は２種以上の化合物を重合成分とする重合体を示し、Ｒ³はＨまたはＣＨ₃を示す。）

(In the formula, A is one or more compounds selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, styrene, and acrylonitrile. And R ³ represents H or CH _3. )

  The weight average molecular weight of the macromonomer is preferably 3000 or more and 10,000 or less. In order to improve the adhesion and uniformly disperse the aggregated state of the carbon black particles, the weight average molecular weight is more preferably 4000 or more and 7000 or less.

  Further, in order to improve the triboelectric charging property under high humidity, it is a copolymer obtained by polymerizing a monomer represented by the formula (A1), a monomer represented by the formula (A2), and a methyl methacrylate monomer. It is preferable. Each ratio is a monomer mass ratio when the number of repetitions n of (A2) is 50, and (A1) :( A2) is preferably in the range of 95 to 60: 5 to 40. When the number of repetitions n of (A2) is 50, (A1) :( A2): methyl methacrylate is preferably 95 to 30: 3 to 30: 2 to 40.

  Examples of other resins for forming the resin coating layer include the following. Phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy 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, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin. Of these, silicone resins are preferred because they have releasability. Further, the silicone resin may contain a coupling agent. Examples of the coupling agent include a silane coupling agent, a titanium coupling agent, and an aluminum coupling agent. The following are mentioned as a silane coupling agent preferably used for this invention. γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl)- γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane Hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, γ-chloropropylmethyldimethoxysilane, Tiltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane (manufactured by Torre Silicone), allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3- Divinyltetramethyldisilazane, methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (manufactured by Chisso Corporation).

  The above-mentioned resins can be used alone or in combination. In addition, a curing agent can be mixed with a thermoplastic resin and cured for use.

  The resin coating layer of the carrier may contain fine particles other than carbon black particles.

  As the fine particles, any particles can be used. Specific examples of materials include various metal compounds (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, composite oxides such as titanium-doped silica, etc.) and nitrides ( Silicon nitride, etc.) Carbides (silicon carbide, etc.), metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, wet process silica, dry process silica, etc. Is mentioned. Resin particles (polymethyl methacrylate resin particles, melamine resin particles, and guanamine resin particles) can also be used.

  The fine particles may be treated on the surface in order to improve fluidity and perform uniform mixing with the magnetic carrier.

  Examples of the surface treatment agent include a treatment agent such as a coupling agent, silicone oil, and fatty acid metal salt. By performing the surface treatment, for example, in the case of a coupling agent that is a compound having a hydrophilic group and a hydrophobic group, the hydrophilic group side covers the surface of the inorganic fine particles so that the hydrophobic group side becomes the outer side. As a result, fluctuations in the triboelectric charge amount due to the environment can be suppressed. Further, the triboelectric charge amount can be easily controlled by a coupling agent into which a functional group such as an amino group or fluorine is introduced.

  Examples of the fatty acid metal salt include zinc stearate, sodium stearate, calcium stearate, zinc laurate, aluminum stearate, magnesium stearate and the like, and the same effect can be obtained with stearic acid which is a fatty acid.

  Examples of the treatment method include a wet method in which a surface treatment agent to be treated is dissolved and dispersed in a solvent, inorganic fine particles are added therein, the solvent is removed while stirring, and the treatment is performed. In addition, there may be mentioned a dry method in which a coupling agent, a fatty acid metal salt and inorganic fine particles are directly mixed and treated with stirring.

Silica is a fine powder produced by vapor phase oxidation of a silicon halogen compound, and is called so-called dry silica or fumed silica, and includes those produced by a known technique. For example, the production method uses a thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is the following formula.
SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl

  In the above production method, for example, it is possible to obtain a composite fine powder of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride or titanium chloride together with silicon halogen compounds. .

  Further, as the silica, a known sol-gel method in which the solvent is removed from the silica sol suspension obtained by hydrolyzing and condensing the alkoxysilane with a catalyst in an organic solvent in which water is present, and dried to form particles. Also included are spherical hydrophobic silicas produced by

  Examples of titanium oxide include fine particles of titanium oxide obtained by a low-temperature oxidation method (thermal decomposition, hydrolysis) of a sulfuric acid method, a chlorine method, a volatile titanium compound such as titanium alkoxide, titanium halide, or titanium acetylacetonate. As the crystal system of the titania, any of anatase type, rutile type, mixed crystal type thereof, and amorphous type can be used.

  As the above alumina, the buyer method, improved buyer method, ethylene chlorohydrin method, underwater spark discharge method, organoaluminum hydrolysis method, aluminum alum pyrolysis method, ammonium aluminum carbonate pyrolysis method, aluminum chloride flame decomposition method Examples thereof include fine alumina powder obtained. As the crystal system, α, β, γ, δ, ζ, η, θ, κ, χ, ρ type, mixed crystal type, and amorphous type are used. Α, δ, γ, θ, mixed crystal A mold or an amorphous material is preferably used.

  As a method for granulating the resin fine particles, a method of pulverizing the above polymer, a particle polymerization method such as emulsion polymerization, soap-free emulsion polymerization, suspension polymerization, dispersion polymerization, or the like can be used.

  The number average particle diameter (D1) of the fine particles is preferably 0.01 μm or more and 3.00 μm or less. A more preferable range is 0.01 μm or more and 2.00 μm or less.

  If the number average particle diameter (D1) of the fine particles is less than 0.01 μm, the surface of the magnetic particles coated with at least the resin composition cannot be uneven even if they are fixed. It becomes insufficient. On the other hand, if the number average particle diameter (D1) of the fine particles is larger than 3.00 μm, there are fine particles that are not fixed by the method of the present invention, so that they are released. In addition, the flowability of the developer may be reduced due to the released fine particles, the charge may be uneven, and fogging may occur.

  Moreover, as addition amount of microparticles | fine-particles, it is preferable that microparticles | fine-particles are mixed by the mass ratio of 0.01 mass part or more and 2.00 mass parts or less with respect to 100 mass parts of magnetic particles which coat | covered the surface with the resin composition at least. More preferably, it is mixed at 0.10 parts by mass or more and 1.50 parts by mass or less.

  Further, as the fine particles, those showing reverse polarity to the carbon black particles are preferable. For example, when the pH of the carbon black particles is small, it means that there are more functional groups such as carboxyl groups on the surface of the carbon black particles. In that case, it is preferable to use fine particles having a strong surface cationic property as the fine particles to be added, because the aggregation of the carbon black particles becomes more stable. Conversely, when the pH is high, it is preferable to use a surface having strong anionic properties. By adding fine particles in this way and adsorbing the carbon black particles on the surface, it is possible to form a more stable and uniform agglomeration of carbon black, which has good developability and external addition to the magnetic carrier. Accumulation of the agent can be suppressed.

  As the magnetic carrier core, magnetic particles such as known ferrite particles, magnetite particles, and magnetic material-dispersed resin carrier cores can be used.

  The magnetic carrier core is manufactured, for example, as described below.

  The magnetic carrier core is manufactured using a magnetic material. Magnetic materials include magnetic ferrite particles or magnetite particles containing one or more elements selected from iron, lithium, beryllium, magnesium, calcium, rubidium, strontium, nickel, copper, zinc, cobalt, manganese, and titanium. Can be mentioned. Preferably, it is a magnetite particle, or a magnetic ferrite carrier core having at least one element selected from copper, zinc, manganese, calcium, lithium and magnesium.

  Examples of the magnetic material for ferrite include the following. Ca—Mg—Fe ferrite, Li—Fe ferrite, Mn—Mg—Fe ferrite, Ca—Be—Fe ferrite, Mn—Mg—Sr—Fe ferrite, Li—Mg—Fe ferrite and Li— Ferrite magnetic material of iron oxide such as Rb-Fe ferrite.

  Ferrites of iron-based oxides can be obtained by mixing metal oxides, carbonates and nitrates in a wet or dry manner and pre-firing to obtain a desired ferrite composition. Next, the obtained iron-based oxide ferrite is pulverized to submicron. Water for adjusting the particle size is added to the pulverized ferrite in an amount of 20% by mass to 50% by mass, and, for example, polyvinyl alcohol (molecular weight of 500 to 10,000) is used as a binder resin in an amount of 0.1% by mass to 10% by mass. % Or less is added to prepare a slurry. The slurry is granulated using a spray dryer and fired to obtain a ferrite core.

  When obtaining a porous ferrite core, a pore adjuster such as sodium carbonate or calcium carbonate and various organic substances for controlling the pore density is added during granulation. And it can obtain by forming a slurry, granulating using a spray dryer, and baking. Further, by adding a material that inhibits the particle growth during the ferritization reaction, a complicated void can be formed inside the ferrite. Examples of such materials include tantalum oxide and zirconium oxide.

  In order to produce a magnetic material-dispersed resin carrier core, for example, a vinyl-based or non-vinyl-based thermoplastic resin, a magnetic material, and other additives are sufficiently mixed by a mixer. The obtained mixture is melted and kneaded using a kneader such as a heating roll, a kneader, or an extruder. A magnetic material-dispersed resin carrier core can be obtained by pulverizing and classifying the cooled melt-kneaded product. The obtained magnetic material-dispersed resin carrier core may be further spheroidized thermally or mechanically. As another method, a monomer for forming the binder resin of the magnetic material-dispersed resin carrier core can be obtained by polymerizing in the presence of the magnetic material. Examples of the monomer for forming the binder resin include the following. Vinyl monomers, bisphenols and epichlorohydrin for forming epoxy resins; phenols and aldehydes for forming phenol resins; ureas and aldehydes, melamine and aldehydes for forming urea resins are included.

  A method of synthesizing a phenol resin from phenols and aldehydes is particularly preferable. In this case, a magnetic substance-dispersed resin carrier core is produced by adding a magnetic substance, phenols and aldehydes to an aqueous medium, and polymerizing the phenols and aldehydes in the aqueous medium in the presence of a basic catalyst. can do.

  The phenols for producing the phenol resin may be compounds having a phenolic hydroxyl group in addition to phenol (hydroxybenzene). Examples of the compound having a phenolic hydroxyl group include alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, and bisphenol A; hydrogen of an aromatic ring (for example, benzene ring) or part of hydrogen of an alkyl group Or, halogenated phenols, all of which are substituted with chlorine atoms or bromine atoms.

  Examples of aldehydes for producing a phenol resin include the following. For example, formalin, formaldehyde in any form of paraformaldehyde, and furfural, more preferably formaldehyde.

  The molar ratio of aldehydes to phenols is preferably 1 or more and 4 or less, and more preferably 1.2 or more and 3 or less. If the molar ratio of aldehydes to phenols is less than 1, particles are difficult to produce, and even if they are produced, the resin does not easily cure, and the strength of the particles produced tends to be weak. On the other hand, when the molar ratio of aldehydes to phenols is larger than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

  The condensation of phenols with aldehydes can be performed using a basic catalyst. The basic catalyst may be any catalyst used in the production of ordinary resol type resins. Examples of the basic catalyst include aqueous ammonia, hexamethylenetetramine, dimethylamine, diethyltriamine, and alkylamines such as polyethyleneimine. Is included. The molar ratio of these basic catalysts to phenols is preferably 0.02 or more and 0.3 or less.

  Examples of the solvent used for coating the resin on the carrier core include the following. For example, toluene, methyl ethyl ketone, acetone, ethyl acetate, butyl acetate, xylene, and tetrahydrofuran. These solvents may be used alone or in combination.

  It is preferable to disperse the coating material in this solvent with a disperser using a medium such as beads. Examples of the dispersing machine include a sand mill, a glen mill, a basket mill, a ball mill, a sand grinder, a visco mill, a paint shaker, an attritor, a dyno mill, and a pearl mill. Among them, a paint shaker is preferable as the carbon black particle disperser.

  In order to obtain uniform aggregation of the carbon black particles, a method for dispersing the resin coating layer is important. In order to obtain a more uniform agglomeration state, it is possible to create a better carbon black particle state by selecting a finer bead particle size and using a hard bead material, and performing a longer time. . In the conventional method, the carbon black particles are dispersed using a homogenizer. However, with this method, it is difficult to control the aggregation of the carbon particles as in the present application. Further, if the dispersion time is too long, it takes a very long time for production, which is not preferable. Therefore, in this application, the dispersion of carbon black could be controlled to a good state by devising the resin composition for coating the carrier and the dispersion method.

  The method for coating the copolymer on the surface of the carrier core is not particularly limited, and can be performed by a known method. For example, there is a so-called dipping method in which the solvent is volatilized while stirring the magnetic carrier core and the coating resin solution, and the coating resin is coated on the surface of the magnetic carrier core. Specifically, a universal mixing stirrer (manufactured by Fuji Powder Corporation), a nauter mixer (manufactured by Hosokawa Micron Corporation), and the like can be mentioned. There is also a method in which a coating resin solution is sprayed from a spray nozzle while forming a fluidized bed to coat the coating resin on the surface of the magnetic carrier core. Specific examples include a Spira coater (Okada Seiko Co., Ltd.) and Spiraflow (Freund Sangyo Co., Ltd.). There is also a method in which the coating resin is coated in a dry state on the magnetic carrier core in a particle state. Specifically, a treatment method using an apparatus such as a hybridizer (manufactured by Nara Machinery Co., Ltd.), mechanofusion (manufactured by Hosokawa Micron Co., Ltd.), high flex glal (manufactured by Fukae Powtech) or the like can be mentioned.

  In the present invention, it is important to control the dispersion state of carbon black in the resin coating, and it is also important to produce a magnetic carrier by coating with the dispersion maintained as much as possible. As a coating apparatus for that purpose, a coating treatment method by dipping is more preferable. This is because the coating process using a fluidized bed tends to change the agglomeration state of the carbon black particles because the drying process is performed in a short time after the coating process. In the fluidized bed, since the coating component is sprayed on the magnetic carrier core in a sprayed state, the aggregation of the magnetic carrier particles hardly occurs. On the other hand, however, the coating components are rapidly cooled during coating, and the controlled carbon aggregation tends to be disturbed. On the other hand, the dipping method is preferable because the magnetic carrier core is stirred and coated for a long time in the coating resin so that the aggregated state of the carbon black particles is maintained.

  FIG. 1 is an example of a schematic diagram of an agitation and mixing apparatus using a dipping method in which a rotating shaft having spiral blades arranged along a conical inner peripheral wall surface is configured to be revolved and rotated by a motor.

  A screw-type stirring blade 2 is used as the stirring blade. And the stirring blade 2 is provided in the upper part of the reverse conical stirring mixing container 8, and it is comprised so that this stirring blade 2 may rotate (revolve) along the internal peripheral surface of the container 2, rotating (autorotating). ing. The magnetic material-dispersed resin carrier particles (core) are supplied from the raw material supply port 6 provided on the upper part of the inverted conical stirring and mixing vessel 8 and are moved upward along the inner wall surface of the drying vessel 8 by the rotation of the stirring blade 2. It is carried in the direction, and at the end of the stirring blade 2, it is scattered around by the rotational force. The magnetic material-dispersed resin carrier particles (core) are given a horizontal circular motion by the revolution performed simultaneously with the rotation of the stirring blade 2. Since the magnetic material dispersion type resin carrier particles (core) are carried upward by the stirring blade 2, a space is created in the lower part of the stirring and mixing vessel 8, and the magnetic material dispersion type resin carrier particles (core) fall into the space due to gravity. To go. As described above, stirring and dispersion are repeated while the magnetic material-dispersed resin carrier particles (core) in the stirring and mixing container 8 are lifted upward from below. As a result, the magnetic material-dispersed resin carrier particles (core) are efficiently stirred throughout the stirring and mixing vessel 8 and can be uniformly coated while applying appropriate stress to the particles. Moreover, you may add the process of removing a coarse particle by sinter and a sieve later as needed.

The saturation magnetization of a magnetic carrier with respect to an applied magnetic field of 240 kA / m is 30 Am ² / kg or more and 90 Am ² / kg or less, the residual magnetization is ² Am ² / kg or more and 20 Am ² / kg or less, and the coercive force is 0.4 kA / kg. It is preferable that it is m or more and 4.8 kA / m or less. The saturation magnetization is more preferably in the range of 58 Am ² / kg to 78 Am ² / kg.

When the saturation magnetization exceeds 90 Am ² / kg, the ears on the magnetic brush become hard, and the impact on the developer regulating blade or the like tends to increase during stirring.

Further, when the saturation magnetization is less than 30 Am ² / kg, scattering of magnetic carriers is likely to occur. Further, when the residual magnetization and coercive force deviate from the above values, the transportability of the developer in the developing device tends to be unstable, and the durability tends to be inferior. Further, if the residual magnetization is large, the replenishment developer is not preferable because the magnetic carrier is segregated due to the stirring in the replenishment container, and the discharge performance becomes unstable.

When the residual magnetization is more than ²⁰ Am ² / kg or the coercive force is more than 4.8 kA / m, the fluidity of the developer tends to deteriorate. If the residual magnetization is less than ² Am ² / kg and the coercive force is less than 0.4 kA / m, there is a possibility that a toner that is not sufficiently charged due to the fluidity is too high.

The magnetic carrier obtained by the production method of the present invention has a volume-based 50% particle size (D50) of 15.0 μm to 100 μm and a true specific gravity of 2.5 g / cm ^{3 to} 5.2 g / cm ^3. It is preferable. Since the magnetic carrier of the present invention has a D50 of 15.0 μm or more and 100 μm or less, the density of the magnetic brush at the development pole can be optimized and the toner charge amount distribution can be sharpened. Image quality can be improved. More preferably, D50 is 20.0 μm or more and 80 μm or less.

Further, when the true density is 2.5 g / cm ³ or more and 5.2 g / cm ³ or less, the difference in true density between the toner and the magnetic carrier is in a suitable range, and the charge imparting property to the toner is further improved. be able to. More preferably, it is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less. That is, since the stirring of the toner and the magnetic carrier in the developing device is optimized, the toner can be charged quickly. Thereby, a good image can be obtained over a long period of time.

  In order to suppress the detachment of the particles, it is preferable that the difference in specific gravity between the magnetic carrier and the fine particles is small. If the difference in specific gravity is large, the fine particles are likely to float in the mixing step, and the fine particles are likely to segregate in the upper layer portion in the mixed layer. Accordingly, the fine particles are not uniformly fixed to the magnetic particles whose surfaces are coated with at least the resin composition, and it becomes difficult to obtain high developability.

In addition, the magnetic carrier obtained by the production method of the present invention preferably has a specific resistance value of 1.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ¹⁵ Ω · cm or less at an electric field strength of 5000 V / cm. More preferably, it is 1.0 × 10 ⁷ Ω · cm or more and 1.0 × 10 ¹² Ω · cm or less for improving developability. When the specific resistance value is lower than 1.0 × 10 ⁶ Ω · cm, the possibility of leakage increases, and it is necessary to increase the coating amount of the resin composition, and the magnetic carrier particles are likely to coalesce. If the specific resistance value exceeds 1.0 × 10 ¹⁵ Ω · cm, the developability may be lowered at a low electric field strength.

  Subsequently, as the toner used together with the magnetic carrier of the present invention, a known toner can be used, and any toner manufactured by any method such as a pulverization method, a polymerization method, an emulsion aggregation method, or a dissolution suspension method can be used. Good.

  A known resin can be used as the binder resin for the toner. Specific examples include the following. Polyester; Polystyrene; Polymer compound obtained from styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, Styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrene copolymers such as polymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride; phenol resins; modified phenol resins; maleic resins; acrylic resins; methacrylic resins; Ricone resin; aliphatic polyhydric alcohol; aliphatic dicarboxylic acid, aromatic dicarboxylic acid; polyester resin having monomers selected from aromatic dialcohols and diphenols as structural units; polyurethane resin; polyamide resin; polyvinyl Examples include butyral; terpene resin; coumarone indene resin; petroleum resin; hybrid resin having a polyester unit and a vinyl polymer unit.

  As the mold release agent used in the present invention, known ones can be used, and specific examples include the following.

  Low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax; block of aliphatic hydrocarbon wax Copolymers; waxes based on fatty acid esters such as carnauba wax, montanate wax, candelilla wax, rice wax, ozokerite, beeswax; and part or all of fatty acid esters such as deoxidized carnauba wax And the like.

  Furthermore, the release agent includes saturated linear fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinalic acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, and carnauvir. Saturated alcohols such as alcohol, seryl alcohol, melyl alcohol; polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide; methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis Saturated fatty acid bisamides such as lauric acid amide, hexamethylenebisstearic acid amide; ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N, N′-dioleyl adipic acid amide, N, Unsaturated fatty acid amides such as' -dioleoyl sebacic acid amide; m-xylene bisstearic acid amide, aromatic bisamides such as N, N'-distearylisophthalic acid amide; calcium stearate, calcium laurate, zinc stearate, stearin Fatty acid metal salt such as magnesium acid (generally called metal soap); Graft wax obtained by grafting vinyl monomer such as styrene or acrylic acid to aliphatic hydrocarbon wax; Fatty acid such as behenic acid monoglyceride and polyvalent Examples include partially esterified alcohols; methyl ester compounds having a hydroxyl group obtained by hydrogenating vegetable oils and the like.

  In the molecular weight distribution measured by gel permeation chromatography (GPC) of the release agent, the main peak is preferably in the region of molecular weight 350 or more and 2400 or less, and more preferably in the region of 400 or more and 2000 or less. By giving such a molecular weight distribution, preferable thermal characteristics can be imparted to the toner.

  The addition amount of the release agent used in the present invention is 1 to 10 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin. If the amount is less than 1 part by mass, a sufficient amount of heat and pressure are required because the amount is small in order to come out on the toner surface at the time of melting and to exhibit the releasability. On the other hand, if the amount exceeds 10 parts by mass, the amount of the release agent in the toner is too large and the transparency and charging characteristics are inferior.

  As the colorant of the toner used in the present invention, the following pigments and / or dyes can be used.

  Examples of the color pigment for magenta include C.I. 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, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned.

  Examples of the magenta dye include C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as disperse violet 1, C.I. 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. I. Basic dyes such as basic violet 1,3,7,10,14,15,21,25,26,27,28 are listed.

  These pigments or dyes may be used alone, but it is more preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together.

  Examples of the color pigment for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17, C.I. I. Bat Blue 6, C.I. I. Examples thereof include Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 155, 180, C.I. I. Vat yellow 1, 3, 20 etc. are mentioned.

  In addition, the usage-amount of the said coloring agent is 0.1 to 60 mass parts with respect to 100 mass parts of binder resin, Preferably it is 0.5 to 50 mass parts.

  The toner used in the present invention can also be used in combination with a known charge control agent.

In the present invention, if necessary, an organic metal compound can be used in the toner as a charge control agent. The organometallic compound is preferably a metal compound of an aromatic carboxylic acid derivative selected from aromatic oxycarboxylic acids and aromatic alkoxycarboxylic acids. The metal is preferably a divalent or higher valent metal atom. Examples of the divalent metal include Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , and Cu ²⁺ . Of these, Ca ²⁺ , Mg ²⁺ and Sr ²⁺ are preferable. Examples of the trivalent or higher metal include Al ³⁺ , Fe ³⁺ and Ni ³⁺ , and Al ³⁺ is preferable. Of these metals, Al ³⁺ is particularly preferred.

  The amount of the charge control agent used in the present invention is from 0.3 to 10 parts by weight, preferably from 0.5 to 7 parts by weight, based on 100 parts by weight of the binder resin. is there. If the amount of the charge control agent added is less than 0.3 parts by mass, the effect of charging rise cannot be obtained, and if it is more than 10 parts by mass, the environmental fluctuation becomes large.

  As a method for producing the toner particles used in the present invention, there is a pulverization method in which a binder resin, a colorant, and other internal additives are melt-kneaded, and the kneaded product is cooled and then pulverized and classified. There are also a method of directly producing toner particles using a suspension polymerization method, and a dispersion polymerization method of directly producing toner particles using an aqueous organic solvent which is soluble in monomers and insoluble in the resulting polymer. Alternatively, a method of producing toner particles using an emulsion polymerization method typified by a soap-free polymerization method in which toner particles are directly polymerized in the presence of a water-soluble polar polymerization initiator, and a suspension suspension granulation method can be used.

  A method for producing toner particles by the pulverization method will be described in detail.

  In the raw material mixing step, a predetermined amount of at least a binder resin, a colorant, and a release agent are weighed and mixed as an internal toner additive. Examples of the mixing device include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, and a Nauter mixer.

  The toner particle materials blended and mixed as described above are melt-kneaded to melt the binder resin, and the colorant and the like are dispersed therein. In the melt-kneading step, for example, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used. In recent years, single-screw or twin-screw extruders have become mainstream due to the advantage of being capable of continuous production. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd. In general, a twin-screw extruder manufactured by Kay Sea Kay, a co-kneader manufactured by Buss, or the like is used.

  The colored resin composition obtained by melt-kneading the raw material of the toner particles is melted and kneaded, rolled with a two-roll or the like, and then cooled through a cooling process such as cooling with water.

  In general, the cooled colored resin composition obtained above is then pulverized to a desired particle size in a pulverization step. In the pulverization step, first, coarse pulverization is performed with a crusher, a hammer mill, a feather mill or the like, and further, pulverization is performed with a kryptron system manufactured by Kawasaki Heavy Industries, Ltd., a super rotor manufactured by Nisshin Engineering Co., Ltd. After that, if necessary, classification is performed using a classifier such as an inertia class elbow jet (manufactured by Nippon Steel & Mining Co., Ltd.), centrifugal class turbo plex (manufactured by Hosokawa Micron Co., Ltd.), and the weight average particle size A classified product of 3 μm or more and 11 μm or less is obtained.

  The toner used in the present invention may contain a fluidizing agent.

  For example, a toner having improved fluidity can be obtained by mixing a fluidizing agent or the like with the obtained toner particles with a mixer such as a Henschel mixer after the pulverization / classification step.

  As the fluidizing agent, any fluidizing agent can be used as long as it can be added to toner particles to increase the fluidity before and after the addition. For example, vinylidene fluoride fine powder; fluorine resin powder such as polytetrafluoroethylene fine powder; titanium oxide fine powder; alumina fine powder; fine powder silica such as wet-process silica and dry-process silica, silane compound, and organic Examples include treated silica that has been surface-treated with a silicon compound, a titanium coupling agent, silicone oil, and the like.

  In the case of preparing a two-component developer in the present invention, the mixing ratio is usually 2 to 15% by mass, preferably 4 to 13% by mass, as the toner concentration in the developer. Results are obtained. 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 in-machine scattering tend to occur.

  When adjusting the replenisher in the present invention, a predetermined amount of toner and magnetic carrier are weighed and mixed in a mixer. Examples of the mixing device include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, and a Nauter mixer. Among these, the V-type mixer is preferable in consideration of the dispersibility of the magnetic carrier and the charge rising of the toner.

  The replenishment developer contains 2 to 50 parts by mass of toner per 1 part by mass of the magnetic carrier. The preferable range is 3 to 30 parts by mass of toner with respect to 1 part by mass of the magnetic carrier. A more preferable range is 4 to 20 parts by mass of toner with respect to 1 part by mass of the magnetic carrier. When the blending ratio of the toner is less than 2 parts by mass, the life of the two-component developer is improved. However, since the amount of the magnetic carrier is large, the two-component developer in the developing device is removed. The collecting means for collecting the deteriorated two-component developer is complicated, which is not preferable. Further, the amount of toner in the replenishment developer container is reduced, the replacement frequency of the replenishment developer container is increased, which not only increases the load on the user but also increases the cost. On the other hand, when the blending ratio of the toner exceeds 50 parts by mass, the toner and the magnetic carrier are unevenly distributed in the replenishment developer container, and it is difficult to obtain charging stability.

  The replenishment developer of the present invention can be used in any image forming apparatus. By using the replenishment developer of the present invention, the magnetic carrier replenishment amount from the replenishment developer for auto-refreshing can at least fully exhibit the effects of the present invention such that image quality deterioration can be suppressed. .

  The color laser printer shown in FIG. 3 has a plurality of developing units, and is a quadruple drum system (in-line) that obtains a full-color print image by once continuously transferring multiple images onto an intermediate transfer belt 60 as a second image carrier. ) Printer.

  In FIG. 3, an endless intermediate transfer belt 60 is suspended from a drive roller 36a, a tension roller 36b, and a secondary transfer counter roller 36c, and rotates in the direction of the arrow in the figure. Four developing devices are arranged in series with the intermediate transfer belt 36 corresponding to each color.

  The photosensitive drum 31 disposed in the developing unit for developing the yellow toner is uniformly charged to a predetermined polarity and potential by the primary charging roller 32 in the process of rotation, and then image exposure means (not shown) (color original) Image exposure 33 by image color separation / imaging exposure optical system, scanning exposure system by laser scanning which outputs laser beam modulated in accordance with time series electric digital pixel signal of image information, etc. An electrostatic latent image corresponding to the first color component image (yellow component image) of the color image is formed.

  Next, the electrostatic latent image is developed with yellow toner, which is the first color, by a first developing device (yellow developing device).

  In FIG. 3, the yellow image formed on the photosensitive drum 31 enters the primary transfer nip portion with the intermediate transfer belt 36. In the transfer nip portion, the flexible electrode 63 is brought into contact with the back side of the intermediate transfer belt 36. Each developing device has a primary transfer bias source 63 so that the flexible electrode 63 can be biased independently at each port. The intermediate transfer belt 36 first transfers yellow at the port of the first color, and then performs multiple transfer of each color of magenta, cyan, and black sequentially from the photosensitive drum 31 corresponding to each color through the same process described above.

  The four-color full-color image formed on the intermediate transfer belt 36 is then collectively transferred to the transfer material P by the secondary transfer roller 38 and melted and fixed by a fixing device (not shown) to obtain a color print image.

  The secondary transfer residual toner remaining on the intermediate transfer belt 36 is subjected to blade cleaning by the intermediate transfer belt cleaner 39 to prepare for the next image forming process.

  In selecting the material of the transfer belt 36, in order to improve registration at each color port, a material that expands and contracts is not desirable, and a resin-based or metal cored rubber belt or resin + rubber belt is desirable.

  The auto-refresh development method that can be used in the present invention will be described with reference to FIGS.

In the developing operation of the developing device 4 of FIG. 3 and 4 using the auto-refresh developing system, replenishing developer 48 obtained by mixing the toner and a magnetic carrier, the replenishing developer storage chamber R _3, to the replenishing port 50 Then, the developing device 34 is replenished.

  When the developing operation is repeatedly performed, the excess developer (deteriorated magnetic carrier) overflows from the developer-side developer discharge port 74 provided in the developing device 34, and from the developer intermediate recovery chamber 75, The developer is collected in a developer collection container (not shown) through the developer collection auger 76.

  Below, the measuring method concerning this invention is described in detail.

<Measurement of number average particle diameter (D1) of fine particles>
The particle size distribution of the fine particles was measured in a state where the resin component contained in the resin composition was dissolved in a soluble organic solvent and the fine particles were dispersed in the solution. As a measuring device, a laser diffraction particle size distribution analyzer LS-230 type (manufactured by Beckman Coulter) was used for measurement with a small amount of module attached. The optical model used in the measurement was a real part 1.5 and an imaginary part 0.3, and the refractive index of the organic solvent used was input as the refractive index of the solvent.

<Measurement of 50% particle size (D50) based on volume of magnetic particles and magnetic carrier>
The particle size distribution was measured with Microtrac MT3300II (manufactured by Nikkiso Co., Ltd.). For the measurement, a Turbotrac sample feeder for dry measurement was attached. As the particle size, a volume-based 50% particle size (D50) was obtained. Measurement conditions were as follows.
Number of measurements: 1 time, measurement time: 10 seconds, hardware setting: MT3000 (dry measurement), particle refractive index: 1.81, particle shape: non-spherical, solvent: AIR, solvent refractive index: 1.00

<Measurement of true density of magnetic particles and magnetic carrier>
As a sample preparation, the carrier for electrophotography can be measured as it is, but the magnetic particles need to be separated from the magnetic carrier. Separation was performed by the following method. First, 100 parts by mass of a magnetic carrier was weighed into a glass bottle with a lid, 200 parts by mass of toluene was added, and the mixture was shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.). The amplitude condition of the shaker was 200 rpm for 2 minutes. After shaking, the toluene solution was separated while collecting magnetic particles from the outside of the bottle with a magnet. After repeating this 5 times, dried in a vacuum dryer at 50 ° C. for 8 hours, cooled to room temperature to obtain magnetic particles, while obtaining a resin composition by removing toluene from the toluene solution, These were used as measurement samples.

As a method for measuring the true density, a gas replacement method using helium was used. Accupic 1330 (manufactured by Shimadzu Corporation) was used as the measuring apparatus. Measurement conditions are as follows: 4 g of a measurement sample is put into a stainless steel cell having an inner diameter of 18.5 mm, a length of 39.5 mm, and a capacity of 10 cm ³ . Next, the volume of the sample in the sample cell is measured by changing the pressure of helium, and the true density is obtained from the obtained volume and the mass of the sample.

<Measurement method of BET specific surface area of fine particles>
According to the BET method, a specific surface area measuring device “Gemini 2375 Ver. 5.0” (manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas on the sample surface, and the BET specific surface area (m ² / g ) Is calculated.

<Method for measuring particle size distribution of carbon black particles in magnetic carrier>
Only the magnetic carrier is separated from the two-component developer by the following method.

  The method for separating the magnetic carrier from the developer is performed as follows.

  Separation is performed using a charge separation type charge amount measuring device manufactured by Etowas Co., Ltd. By using the measuring device, the magnetic carrier can be effectively separated from the two-component developer. When separating the toner and the magnetic carrier, 1.5 g of developer was used at a time. When a developer is set on the sleeve and a magnet (1000 gauss) inside the sleeve is rotated at 2000 rpm for 1 minute while applying an applied voltage of −4 kV, only the toner flies inside the cylinder (made of stainless steel). Only the magnetic carrier remains on the sleeve. By collecting the magnetic carrier, the magnetic carrier can be effectively recovered from the developer.

  A desktop ultrasonic washer disperser (for example, “VS-150” (manufactured by Vervocrea, etc.) with an oscillation frequency of 50 kHz and an electric output of 150 W added to 0.5 g of the obtained magnetic carrier. The carbon black particles were eluted by dispersing for 2 minutes using a microtrack particle size distribution measuring device MT3000 (Nikkiso) equipped with a very small sample circulator. The maximum peak particle size Pv (μm), the maximum peak half width Hv (μm), and the frequency ratio Fv (%) occupied by the maximum peak with respect to the total peak frequency were calculated.

<Measurement method of specific resistance of magnetic carrier>
The specific resistance of the electrophotographic carrier is measured using a measuring apparatus outlined in FIG. The resistance measuring cell A includes a cylindrical PTFE resin container 25 having a hole with a cross-sectional area of 2.4 cm ² , a lower electrode (made of stainless steel) 21, a support base (made of PTFE resin) 24, and an upper electrode (made of stainless steel) 22. Composed. A cylindrical PTFE resin container 25 is placed on the support base 24, about 0.7 g of a sample (for example, carrier) 23 is filled, the upper electrode 22 is placed on the filled sample 23, and the thickness of the sample is measured. If the thickness when there is no sample in advance is d ′ (blank), the thickness d ′ of the actual sample when about 0.7 g is filled, and the thickness d ′ (sample) when the sample is filled, the thickness of the sample is expressed by the following formula: It can be expressed as
d = d ′ (sample) −d ′ (blank)

  The specific resistance of the carrier and the carrier core can be obtained by applying a voltage between the electrodes and measuring the current flowing at that time. For the measurement, an electrometer 26 (Kesley 6517, manufactured by Kesley) and a computer 27 are used for control.

The measurement conditions are such that the contact area S between the magnetic component and the electrode is S = 2.4 cm ² and the load of the upper electrode is 240 g.

The voltage application condition uses an internal program of the electrometer. First, the electrometer itself determines whether a maximum of 1000 V can be applied (a range not exceeding the current limiter), and automatically determines the maximum value of the applied voltage. The voltage value obtained by dividing the maximum voltage value into five steps is used as a step, and the current value after being held for 30 seconds is measured. For example, when the maximum applied voltage is 1000 V, 1000 V, 800 V, 600 V, 400 V, and 200 V are applied, and the current value after holding for 30 seconds is measured in each step. By processing it by a computer, the electric field strength and the specific resistance are calculated and plotted on a graph. The specific resistance and the electric field strength are obtained by the following formula.
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)

  As for the specific resistance at 5000 V / cm of the carrier for electrophotography, the specific resistance at 5000 V / cm is read from the graph. The intersection of the vertical line of 5000 V / cm on the graph and the measured specific resistance line is taken as the specific resistance value at 5000 V / cm. If there is no intersection point, extrapolation of the measurement point is performed, and the intersection point of the vertical line of 5000 V / cm is set to a specific resistance value at 5000 V / cm.

<Measurement method of magnetization intensity of magnetic carrier>
The strength of magnetization of the magnetic carrier can be obtained by a vibrating magnetic field measuring device (Vibrating sample magnetometer) or a direct current magnetization characteristic recording device (BH tracer). In the examples described later, the measurement was performed by the following procedure using an oscillating magnetic field type magnetic property measuring apparatus BHV-30 (manufactured by Riken Electronics Co., Ltd.).

A cylindrical plastic container packed with a carrier sufficiently densely was used as a sample, and the magnetization moment in an external magnetic field of 1000 / 4π (kA / m) was measured. In addition, the actual mass of the carrier filled in the container was measured. From these, the magnetization intensity (Am ² / kg), remanent magnetization (Am ² / kg), and coercive force (kA / m) of the carrier were determined.

<Measurement Method of Volume Distribution Standard 50% Particle Size (D50) of Carrier and Resin Composition>
The particle size distribution was measured with Microtrac MT3300EX (Nikkiso Co., Ltd.). For the measurement, a Turbotrac sample feeder for dry measurement was attached.

<Molecular weight measurement of toner binder resin and magnetic carrier coating resin>
The molecular weight distribution of the THF-soluble component of the toner binder resin is measured by gel permeation chromatography (GPC) as follows.

First, the binder resin is dissolved in tetrahydrofuran (THF) at room temperature over 24 hours. The obtained solution is filtered through a solvent-resistant membrane filter “Maescho Disc” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of the component soluble in THF is about 0.8% by mass. Using this sample solution, measurement is performed under the following conditions.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml

  In calculating the molecular weight of the sample, standard polystyrene resin (for example, trade name “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) are used.

<Measurement of DBP oil absorption of carbon black>
The measurement was performed according to JIS 4656/1.

<Method for measuring particle size distribution of carbon black particles in coating resin>
The dispersion for coating the magnetic carrier was measured with a Microtrac particle size distribution measuring apparatus MT3000 (Nikkiso) equipped with a microvolume sample circulator. From this measurement result, the maximum peak particle size Pv (μm), the maximum peak half width Hv (μm), and the frequency ratio Fv (%) occupied by the maximum peak with respect to the total peak frequency were calculated.

  Hereinafter, the present invention will be described in more detail with reference to specific production examples and examples, but the present invention is not limited thereto.

<Example of manufacturing magnetic carrier core 1>
A carrier core was produced using the materials shown below.
-10 parts by weight of phenol-5 parts by weight of formaldehyde solution (37% by weight aqueous solution)-85 parts by weight of magnetite particles (number average particle size 0.3 μm) The above materials, 5 parts by weight of 30% by weight ammonia water, and 25 parts by weight of water The mixture was placed in a flask, heated to 90 ° C. for 30 minutes with mixing, and allowed to cure by polymerization for 3 hours. Then, after cooling to 30 ° C. and further adding water, the supernatant was removed, and the precipitate was washed with water and then air-dried. Subsequently, this was dried under reduced pressure (5 hPa or less) at a temperature of 60 ° C. to obtain a magnetic fine particle dispersed carrier core in which magnetite particles were dispersed in a phenol resin. The volume-based 50% particle size (D50) was 42 μm. This is the carrier core 1.

<Example of production of magnetic carrier core 2 (porous magnetic core)>
Process 1 (weighing / mixing process)
Fe ₂ O ₃ 59.5 mass%
MnCO ₃ 34.5% by mass
Mg (OH) ₂ 4.5% by mass
SrCO ₃ 1.0 mass%
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.

Process 2 (temporary firing process)
After pulverization and mixing, firing was performed in the atmosphere at 950 ° C. for 2 hours using a burner-type firing furnace to prepare calcined ferrite. The composition of the ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.39, b = 0.11, c = 0.01, d = 0.49

  In addition, the said ferrite shows a main element.

Process 3 (Crushing process)
After crushing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using zirconia (φ10 mm) balls, and the mixture was pulverized with a wet ball mill for 2 hours. The slurry was pulverized with a wet bead mill using zirconia beads (φ1.0 mm) for 2 hours to obtain a ferrite slurry. The obtained calcined ferrite pulverized particles had D50 = 1.5 μm and D90 = 3.0 μm.

Process 4 (granulation process)
To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder with respect to 100 parts by mass of calcined ferrite, and granulated into spherical particles of about 36 μm with a spray dryer (manufacturer: Okawahara Chemical).

Process 5 (main firing process)
In order to control the firing atmosphere, firing was performed at 1100 ° C. for 4 hours in an electric furnace under a nitrogen atmosphere (oxygen concentration of 0.01% by volume or less).

Process 6 (screening process)
After the agglomerated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain porous magnetic core particles 1.

  The volume-based 50% particle size (D50) was 39 μm. This is the carrier core 2.

<Example of manufacturing magnetic carrier core 3 (ferrite carrier)>
26.0 mol% of MnO, 3.0 mol% of MgO, 70.0 mol% of Fe ₂ O ₃ and 1.0 mol% of SrCO ₃ were pulverized and mixed for 5 hours in a wet ball mill, dried, and then treated at 900 ° C. for 3 hours. Temporary firing was performed after holding the time. This was pulverized with a wet ball mill for 7 hours to 2 μm or less. A dispersant and a binder (polyvinyl alcohol) were added to the slurry by several weight%, and then granulated and dried by a spray dryer to obtain a granulated product having a volume average particle size (D50) of about 40 μm. This granulated product was put in an electric furnace, and held at 1300 ° C. for 3 hours in a mixed gas in which the oxygen concentration in the nitrogen gas was adjusted to 2.0 vol%, followed by firing. Thereafter, it was crushed and further sieved to obtain a magnetic carrier core 3 having a volume average particle size of 40 μm.

<Production example of copolymer 1>
20 parts by mass of methyl methacrylate macromer (average value n = 50) having a weight average molecular weight of 5,100 having an ethylenically unsaturated group (methacryloyl group) at one end having a structure represented by the following formula (4), 75 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having a structure represented by formula (5) as a unit, and 5 parts by mass of methyl methacrylate monomer are reflux condenser, thermometer, nitrogen suction pipe, and a combination system Add to a four-necked flask with stirrer. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 58,000. Moreover, Tg was 92 degreeC. This is designated as Copolymer 1.

<Production example of copolymer 2>
2 parts by weight of methyl methacrylate macromer (average value n = 50) having a weight average molecular weight of 5,100 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), 5) 75 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having the structure shown in FIG. 5 and 23 parts by mass of methyl methacrylate monomer as reflux condenser, thermometer, nitrogen suction pipe, and mixing type stirring apparatus In a four-necked flask with Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 45,000. Moreover, Tg was 90 degreeC. This is designated as Copolymer 2.

<Production example of copolymer 3>
10 parts by weight of methyl methacrylate macromer (average value n = 40) having a weight average molecular weight of 3900 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), and formula (5) 80 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having a structure represented by the following formula, and 10 parts by mass of methyl methacrylate monomer are provided with a reflux condenser, a thermometer, a nitrogen suction pipe, and a mixing type stirring apparatus. Added to a two-necked flask. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 55,000. Moreover, Tg was 90 degreeC. This is designated as Copolymer 3.

<Production example of copolymer 4>
20 parts by mass of methyl methacrylate macromer (average value n = 50) having a weight average molecular weight of 5,100 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), 5) 50 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having the structure represented by 5) and 30 parts by mass of methyl methacrylate monomer as a reflux condenser, thermometer, nitrogen suction pipe, and a mixing type stirring apparatus Was added to the four-necked flask. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 62,000. Moreover, Tg was 93 degreeC. This is designated as Copolymer 4.

<Production example of copolymer 5>
5 parts by weight of methyl methacrylate macromer (average value n = 50) having a weight average molecular weight of 5,100 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), 5) 95 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having the structure shown in 5) as a unit was added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing type stirring apparatus. . Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 43,000. Moreover, Tg was 89 degreeC. This is designated as Copolymer 5.

<Production example of copolymer 6>
10 parts by weight of a methyl methacrylate macromer (average value n = 40) having a weight average molecular weight of 3900 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), and a stearyl methacrylate monomer 80 parts by mass and 10 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing type stirring apparatus. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 51,000. Moreover, Tg was 89 degreeC. This is designated as Copolymer 6.

<Production example of copolymer 7>
1 part by weight of a methyl methacrylate macromer (average value n = 40) having a weight average molecular weight of 3900 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), and a stearyl methacrylate monomer 80 parts by mass and 19 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a friction stirrer. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 41,000. Moreover, Tg was 88 degreeC. This is designated as Copolymer 7.

<Example of production of copolymer 8>
52 parts by weight of a methyl methacrylate macromer (average value n = 40) having a weight average molecular weight of 3900 having an ethylenically unsaturated group (methacryloyl group) at one end having a structure represented by the formula (4), and a stearyl methacrylate monomer 45 parts by mass and 3 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing type stirring apparatus. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 67,000. Moreover, Tg was 94 degreeC. This is designated as Copolymer 8.

<Production example of copolymer 9>
98 parts by mass of stearyl methacrylate monomer and 2 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a friction stirrer. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 40,000. Moreover, Tg was 88 degreeC. This is designated as Copolymer 9.

<Example of production of copolymer 10>
50 parts by mass of perfluorohexyl methacrylate monomer and 50 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing type stirring apparatus. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 35,000. Moreover, Tg was 85 degreeC. This is referred to as a copolymer 10.

<Production Example of Copolymer 11>
Into a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing-type stirrer, 100 parts by mass of a cyclohexyl methacrylate monomer having an ester moiety as a unit of cyclohexyl having a structure represented by the formula (5) added. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 40,000. Moreover, Tg was 89 degreeC. This is designated as Copolymer 11.

<Example of production of copolymer 12>
20 parts by mass of a methyl methacrylate macromer (average value n = 50) having a weight average molecular weight of 5,100 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by the formula (4), and methacrylic acid 60 parts by mass of perfluorohexyl monomer and 20 parts by mass of methyl methacrylate monomer were added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a mixing type stirring apparatus. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 55,000. Moreover, Tg was 91 degreeC. This is designated as Copolymer 12.

<Example of production of copolymer 13>
52 parts by weight of methyl methacrylate macromer (average value n = 40) having a weight average molecular weight of 3900 having an ethylenically unsaturated group (methacryloyl group) at one end having the structure represented by formula (4), and formula (5) 45 parts by mass of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having a structure represented by the following formula, and 3 parts by mass of methyl methacrylate monomer are provided with a reflux condenser, a thermometer, a nitrogen suction pipe, and a mixing type stirring apparatus. Added to a two-necked flask. Further, 90 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.5 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 12 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 68,000. Moreover, Tg was 94 degreeC. This is referred to as a copolymer 13.

<Carbon black particles>
The method for producing carbon black is not particularly limited, but those produced by a channel method, a furnace method or the like are preferably used. The physical properties of the carbon black particles used this time are summarized in the table.

<Example of manufacturing carrier 1>
-Copolymer 1 (solid content 33% by mass) 100.0 parts by mass-Carbon black particles 1 5.0 parts by mass The above materials are placed in a mayonnaise bottle together with 80 parts by mass of 2 mm glass beads, and dispersed in a paint shaker for 4 hours. (Dispersion condition 1). The glass beads were filtered off with a nylon mesh, and toluene was added so that the dispersion had a solid content of 10% by mass.

  Next, the coating resin composition and the carrier core were placed in the stirring and mixing apparatus shown in FIG. 1 and stirred at 60 ° C. for 1 hour. Then, the magnetic carrier 1 was produced by sintering at 100 degreeC for 2 hours, and also sieving.

The obtained carrier had an average particle size of 40 μm and a true density of 3.6 g / cm ³ . Table 2 shows the physical properties of the obtained carrier.

<Manufacturing example of carriers 4 to 24>
Carriers 2 to 24 were obtained in the same manner as Carrier 1 except that the production method was performed as described in Table 2. Table 2 shows the physical properties of the obtained carrier.

  Incidentally, the carbon black dispersion condition 2 for obtaining the resin composition is the same as the dispersion condition 1 except that the dispersion is performed for 8 hours using a paint shaker.

<Example of toner production>
25 parts by mass of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 25 parts by mass of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 15 parts by mass of terephthalic acid, 3 parts by mass of trimellitic anhydride, 25 parts by mass of fumaric acid and dibutyltin oxide were placed in a 4-liter four-necked flask made of glass. A thermometer, a stirring rod, a condenser, and a nitrogen inlet tube were attached to the four-necked flask, and this four-necked flask was placed in a mantle heater. The reaction was allowed to proceed at 200 ° C. for 3 hours under a nitrogen atmosphere to obtain a polyester resin. The obtained polyester resin had a peak molecular weight Mp of 6000 and a Tg of 62 ° C.

Next, a toner for evaluation was produced using the following materials and production method.
-100 mass parts of said polyester resin-C.I. I. Pigment Blue 15: 3 5.5 parts by mass, paraffin wax (melting point 75 ° C.) 5 parts by mass, aluminum 5,5-di-t-butylsalicylate compound 0.5 part by mass The above materials were mixed with a Henschel mixer (FM-75 type) , Manufactured by Mitsui Miike Chemical Co., Ltd.) and then melt-kneaded in a twin-screw extruder (PCM-30 type, manufactured by Ikegai Seisakusho). The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized toner. The resulting coarsely pulverized toner was finely pulverized using a mechanical pulverizer and then classified by an air classifier to obtain a toner classified product.

1.0 part by mass of anatase-type titanium oxide having a BET specific surface area of 100 m ² / g and 1.0 part by mass of hydrophobic silica having a BET specific surface area of 130 m ² / g are added to 100 parts by mass of the obtained toner classified product. The toner was added and mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.) to obtain a toner for evaluation. The obtained toner had a weight average particle diameter (D4) of 6.5 μm.

[Example 1]
To 91.0 parts by mass of carrier 1, 9.0 parts by mass of toner was added and mixed with a V-type mixer (V-20, manufactured by Seishin Enterprise) to obtain a start developer. To 1.0 part by mass of carrier 1, 7.0 part by mass of toner 1 was added and mixed with a V-type mixer (V-20, manufactured by Seishin Enterprise Co., Ltd.) to obtain developer 1 for replenishment.

  An image of this developer can be formed using a Canon copier iRC5180.

  Table 3 shows the evaluation results of developability. The criteria for evaluating the physical properties and developing properties of the magnetic carrier are shown below.

  A developer having good developability, suppressing accumulation of external additives, and excellent durability stability was obtained.

{Evaluation item}
The developer was placed in a cyan developing device capable of rotation, and used as a developing condition in a room temperature and low humidity (23 ° C., 5% RH) environment. The distance between the developing sleeve and the developing pole of the photosensitive member (between S and D) was 350 μm, and the developing sleeve peripheral speed relative to the photosensitive member was 1.7 times. Further, Vpp is set to 1.0 kV, the contrast potential is set to 350 V, and the fog removal voltage (Vback) is set to 150 V. The image density at that time was determined. Evaluation of the charge amount at that time, carrier adhesion, and leakage (white spots) are evaluated. The items for image evaluation and the evaluation criteria are shown below. The items and evaluation criteria for image output evaluation after 30000 sheets durability using the chart of initial and image duty 5% (area ratio of solid portion on A4 paper) are shown below.

(Image density)
The image density of the fixed image is measured using an X-Rite 500 series. Specifically, an image is output to color laser copier paper under the above conditions, and the image density of the solid image portion is measured. In that case, arbitrary five points are measured, and the average value is used as the image density. The operation procedure is performed according to the “Basic operation guide” attached to the X-Rite 500 series.
A: Δ = 0.05 or less (Δ indicates the absolute value of the difference between before and after endurance)
B: 0.05 <Δ ≦ 0.10
C: 0.10 <Δ ≦ 0.15 (Practical level so far)
D: 0.15 <Δ ≦ 0.20
E: Δ <0.20

(Carrier adhesion)
Only when evaluating carrier adhesion, Vback was changed to 200 V and a solid white image was printed on plain paper. At that time, the portion on the photosensitive drum between the developing unit and the cleaner unit is sampled by attaching a transparent adhesive tape, and the number of magnetic carrier particles adhering to the photosensitive drum in 1 cm × 1 cm is counted. Then, the number of adhered carriers per 1 cm ² is calculated.
A: Less than 10 pieces / cm ² B: 10 or more and less than 20 pieces / cm ² C: 20 or more and less than 50 pieces / cm ² (Practical level so far)
D: 50 or more and less than 100 pieces / cm ² E: 100 pieces / cm ² or more

(White pot)
Five solid black images are continuously output on A4 plain paper, and the number of white spots with a diameter of 1 mm or more is counted in the image, and evaluation is performed from the number of the five out of the five sheets.
A: Less than 1 B: 1 or more and less than 10 C: 10 or more and less than 20
D: 20 or more and less than 100 E: 100 or more

(Charge amount)
As a device for measuring the charge amount, a suction separation type charge amount measuring device Sepasoft STC-1-C1 type (manufactured by Sankyo Piotech) is used. A mesh (metal mesh) with an opening of 20 μm is placed on the bottom of the sample folder (Faraday gauge), and about 0.1 g of developer is placed on the mesh and covered. The mass of the entire sample folder at this time is weighed and is defined as W1 (g). Next, the sample folder is installed in the main body, and the air volume control valve is adjusted so that the suction pressure is 2 kPa. In this state, the toner is removed by suction for 2 minutes. The charge at this time is Q (μC). Further, the mass of the entire sample folder after suction is weighed and is defined as W2 (g). The charge amount (mC / kg) of the developer is calculated as follows. The charge Q is a carrier charge and has a reverse polarity as the toner charge. The measurement was performed in a normal temperature and normal humidity environment (23 ° C., 60%). The developer is sampled from the developing device sleeve.
Charge amount (mC / kg) = Q / (W1-W2)
A: Δ = 1 or less (Δ indicates the absolute value of the difference between before and after endurance)
B: 1 <Δ ≦ 3
C: 3 <Δ ≦ 5 (Practical level so far)
D: 5 <Δ ≦ 7
E: Δ <7

(Measurement method of accumulated amount of external additive on magnetic carrier)
In order to separate the magnetic carrier from the two-component developer, a charge separation type charge amount measuring device manufactured by Etowas Co., Ltd. is used. By using the above measuring device, it is possible to effectively separate the external additives in the toner without leaving them. When separating the toner and the magnetic carrier, 1.5 g of developer was used at a time. A developer is set on the sleeve of the apparatus, and a magnet (1000 gauss) inside the sleeve is rotated at 2000 rpm for 1 minute while applying a voltage of −4 kV. As a result, only the toner flies inside a cylinder (made of stainless steel) arranged at an interval of 5 mm around the sleeve, leaving only the magnetic carrier on the sleeve. The magnetic carrier is sampled and the sample is measured with fluorescent X-rays. At that time, the X-ray intensity of the metal element (in this case, silica) contained in the external additive is measured. This measurement is performed on the two-component developer before and after durability. The fluorescent X-ray intensity (Xa) of the silica obtained by separating the magnetic carrier from the two-component developer before durability, and the silica obtained by separating the magnetic carrier from the two-component developer after durability. The fluorescent X-ray intensity (Xb) is used. The amount of the external additive accumulated on the magnetic carrier was evaluated by (Xb) / (Xa).

[Examples 2 to 18]
Evaluation was performed in the same manner as in Example 1 except that the magnetic carrier particles were changed. The evaluation results are shown in Table 3.

[Comparative Examples 1 to 6]
Evaluation was performed in the same manner as in Example 1 except that the magnetic carrier particles 18 to 23 were changed. The evaluation results are shown in Table 3.

4). Bug filter 6. Raw material supply port Lid 8 8. Stir mixing container Outlet 34. Developing device 48. Replenishment developer

Claims (8)

A magnetic carrier having a resin coating layer formed on at least the surface of a magnetic carrier core,
The resin coating layer contains at least a resin composition and carbon black particles,
In the volume-based particle size distribution measurement when the resin coating layer is dissolved in toluene, the maximum peak particle size Pv is 0.10 μm or more and 1.00 μm or less, and the maximum peak half width Hv is 0.05 μm or more. A magnetic carrier having a frequency ratio Fv of 65% or more and 95% or less, which is 0.40 μm or less and the maximum peak occupies the maximum peak frequency. The magnetic carrier according to claim 1, wherein the resin forming the resin coating layer contains at least a resin obtained by polymerizing a monomer represented by the following formula (A1).

(In the formula, R ¹ represents a hydrocarbon group having 4 to 22 carbon atoms, and R ² represents H or CH _3. )   The resin forming the resin coating layer contains at least a resin obtained by polymerizing the monomer represented by the formula (A1) and occupies the resin of the monomer unit represented by the formula (A1). The magnetic carrier according to claim 2, wherein the ratio is 50% by mass or more and 95% by mass or less. The resin forming the resin coating layer contains at least a resin obtained by copolymerizing at least a macromonomer and a monomer represented by the formula (A1),
The macromonomer unit is at least one selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. 4. The magnetic carrier according to claim 1, wherein the magnetic carrier is a macromonomer obtained by polymerizing the above monomers. The resin forming the resin coating layer contains at least a resin obtained by copolymerizing at least a macromonomer and a monomer having a structure represented by the formula (A1),
The magnetic carrier according to claim 4, wherein a proportion of the macromonomer unit in the resin is 1% by mass or more and 50% by mass or less. 6. The magnetic carrier according to claim 1, wherein a true density of the magnetic carrier is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less.   A two-component developer having at least a magnetic carrier having a resin coating layer on the surface of a carrier core and a toner, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 6. Two-component developer. Development is performed while supplying a replenishment developer containing at least a toner and a magnetic carrier having a resin coating layer to the developing device, and at least the excess magnetic carrier inside the developing device is discharged from the developing device as necessary. A replenishment developer for use in a component development method,
The replenishment developer includes a toner and a magnetic carrier, and the toner is contained in a mixing ratio of 2 to 50 parts by mass with respect to 1 part by mass of the magnetic carrier.
The replenishment developer, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 6.

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