JP5327500B2 - Electrophotographic developer carrier, electrophotographic developer, image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent carrier for electrophotography which is excellent in durability, forms a fine image having no edge effect for a long period of time, and does not cause color contamination, and to provide a developer using the carrier. <P>SOLUTION: The carrier has a coating layer, which includes a binding resin and conductive microparticles, on a carrier core material. In addition, at least the form coefficients SF-1 of the conductive microparticles are 160 or larger, and the ratio (Df/h) of the volume average particle size Df of the conductive microparticles to the thickness h of the coating layer satisfies an inequality 0.5&lt;[Df/h]&lt;1.5, and the coating rate (%) of the conductive microparticles to the core material, which is represented by an equation (1) ((Ds&times;&rho;s&times;W)/(4&times;Df&times;&rho;f))&times;100, is 70% or larger, wherein Ds represents the volume average particle size of the carrier core material, &rho;s represents the true specific gravity of the carrier core material, W represents the ratio of the amount of the added conductive microparticles to the carrier core material, Df represents the volume average particle size of the conductive microparticles, and &rho;f represents the true specific gravity of the conductive microparticles. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a carrier and a developer used for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like, and an image forming method and an image forming apparatus using the developer.

  In electrophotographic image formation, a latent image is formed by an electrostatic charge on an image carrier such as a photoconductive substance, and charged toner particles are attached to the electrostatic latent image to form a visible image (toner The toner image is transferred to a recording medium such as paper and fixed to form an output image. In recent years, the technology of copiers and printers using an electrophotographic system has been rapidly expanding from monochrome to full color, and the full color market tends to expand.

  By the way, color image formation by full-color electrophotography generally reproduces all colors by laminating three color toners of three primary colors, yellow, magenta and cyan, or four color toners with black added thereto. It is. Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the fixed toner image surface to some extent to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines or the like is often 10 to 50% of medium to high gloss.

  In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated and pressed against the toner is frequently used. This method has high thermal efficiency and high-speed fixing, and is advantageous in that it can give gloss and transparency to the color toner. However, the surface of the heat-fixing member is brought into contact with the molten toner under pressure. Since the toner image is peeled off later, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the fixing roller or the like and retransfers to another image. For the purpose of preventing this offset phenomenon, there is a method in which the surface of a fixing roller or the like is formed of silicone rubber or fluorine resin having excellent releasability, and further, a release oil such as silicone oil is applied to the surface of the fixing roller or the like. It was generally adopted.

  However, this method is extremely effective in preventing toner offset, but a device for supplying release oil is necessary, and the fixing device becomes large and unsuitable for downsizing the machine. For this reason, in a monochrome toner, by adjusting the molecular weight distribution of the binder resin so that the melted toner does not break internally, the viscoelasticity at the time of melting of the toner is increased, and a release agent such as wax is further included in the toner. There is a tendency to employ a method in which the release oil is not applied to the fixing roller (oilless) or the amount of oil applied is very small.

  On the other hand, in the case of color toners, as in the case of monochrome toners, there is a tendency toward oil-less for the purpose of downsizing the machine and simplifying the configuration. However, as described above, in order to improve the color reproducibility of the color toner, it is necessary to smooth the surface of the fixed image. Therefore, the viscoelasticity at the time of melting must be lowered, and therefore, offset from the monochromatic toner having no gloss. It is easy to make the fixing device less oil-free and to apply a small amount. In addition, when a release agent is contained in the toner, the adhesion of the toner is increased and the transfer property to the transfer paper is lowered. Further, the release agent in the toner contaminates the frictional charging member such as a carrier, thereby improving the charging property. This causes a problem that the durability is lowered.

  On the other hand, regarding the carrier, prevention of filming of toner components on the carrier surface, formation of a uniform carrier surface, prevention of surface oxidation, prevention of moisture sensitivity deterioration, extension of developer life, prevention of carrier adhesion to the surface of the photoreceptor, photoreceptor For the purpose of protection from scratches or abrasion due to the carrier, control of the charge polarity, or adjustment of the charge amount, a hard and high-strength coating layer is usually provided by coating the carrier surface with an appropriate resin material. For example, those coated with a specific resin material (for example, see Patent Documents 1 and 17), and further, various additives are added to the coating layer (for example, Patent Documents 2, 3, 4, 5, 6, 7, and 8), those using an additive added to the carrier surface (see, for example, Patent Document 9), and further containing conductive particles larger than the coating layer thickness in the coating layer Those using those obtained (e.g., see Patent Document 10) have been proposed. In addition, a benzoguanamine-n-butyl alcohol-formaldehyde copolymer as a main component is used for a carrier coating material (see, for example, Patent Document 11), or a cross-linked product of a melamine resin and an acrylic resin is used as a carrier coating material (for example, , See Patent Document 12).

  However, durability and carrier adhesion suppression are still insufficient. Concerning durability, there are problems such as spent toner on the carrier surface, destabilization of the charge amount associated therewith, reduction of the coating layer due to film removal of the coating resin and concomitant decrease in resistance, etc. Even if it can be obtained, there is a problem that the image quality of the copied image decreases as the number of copies increases.

  Furthermore, while the demand for faster and more beautiful is increasing, the speed of machines in recent years is remarkable. Along with this, the stress received by the developer has also increased dramatically, and it has become impossible to obtain a sufficient life even with a carrier that has been long-lived in the past. In addition, carbon black has been used as a carrier resistance adjusting agent in the past, but there is a concern about color stains caused by film removal or / and migration of carbon black into a color image due to carbon black detachment. As a countermeasure, various methods have been proposed and demonstrated their effects.

  For example, a carrier has been proposed in which a conductive material (carbon black) is present on the surface of the core material and no conductive material is present in the resin coating layer (see, for example, Patent Document 13). In addition, a carrier is proposed in which the coating resin layer has a carbon black concentration gradient in the thickness direction, the carbon black concentration decreases toward the surface of the coating resin layer, and carbon black is not present on the surface of the coating layer. (For example, see Patent Document 14). In addition, a two-layer coated carrier has been proposed in which an inner coating resin layer containing conductive carbon is provided on the surface of core material particles, and a surface coating resin layer containing a white conductive material is further provided thereon. (For example, refer to Patent Document 15). However, it cannot cope with the recent increase in stress, and color stains have become a problem.

  As a drastic measure against color stains, it is obvious that the most effective method is to eliminate carbon black that causes color stains. However, when carbon black is simply pulled out, the resistance of the carrier increases because carbon black has the property of low electrical resistance as described above. In general, when a carrier having a high resistance is used as a developer, on the image surface of a large area of a copy image, the image density at the center is very thin and only the edges are expressed deeply, so-called edge effect is sharply used. It becomes the image that was. In addition, when the image is a character or a thin line, the image is clear due to the edge effect. However, when the image is halftone, there is a defect that the image is very reproducible.

  Generally, as a resistance adjuster other than carbon black, for example, titanium oxide, zinc oxide, etc. are known, but as an effect of lowering resistance, an effect sufficient to replace carbon black cannot be obtained, and there is a problem Has not yet been resolved. In order to prevent an increase in resistance, the coating layer may be made as thin as possible to reduce the resistance. There is no particular problem in the short term, but in the present situation where a long life is required, the resin and the resistance modifier (conductive fine particles) forming the coat layer are detached due to stress, and the core material surface is exposed. As a result, the resistance decreases. It is necessary to improve the life by adjusting resistance and stress.

  In addition, in Patent Document 16, there is no toner spent on the carrier surface, and at least an acrylic resin and a silicone resin are used as the resin of the coating layer in order to reduce film scraping of the coating layer, and the ratio of the acrylic resin is 10 to 90 wt. Patent Document 17 discloses that a quaternary ammonium salt compound in which the resin coating layer is positively charged with respect to the binder resin and iron powder and an aminosilane coupling agent in order to control the toner charge amount to a desirable level. In order to obtain a highly durable carrier, Patent Document 18 includes a coating layer containing at least a binder resin and particles, and a particle diameter (D) of the particles. The film thickness (h) of the coating layer has a relationship of 1 <(D / h) <10, and it is proposed that the particles be surface-treated with a specific aluminum coupling agent. To have. However, although these Patent Documents 16 to 18 have a study on spent properties, the film strength has not been studied.

JP 58-108548 A JP 54-1555048 A JP 57-40267 A JP 58-108549 A JP 59-166968 A Japanese Patent Publication No. 1-19584 Japanese Examined Patent Publication No. 3-628 JP-A-6-202381 JP-A-5-273789 JP-A-9-160304 JP-A-8-6307 Japanese Patent No. 2683624 Japanese Unexamined Patent Publication No. 7-140723 JP-A-8-179570 JP-A-8-286429 JP 2002-229325 A JP 2003-167389 A Japanese Patent No. 3879838

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to form a fine image with excellent durability and no edge effect over a long period of time, and color stains. It is an object to provide a good electrophotographic carrier in which no toner is generated and a developer using the carrier, and to provide an image forming method and an image forming apparatus using the developer.

In order to solve the above problem, the invention according to claim 1 is a carrier having a coating layer containing a binder resin and conductive fine particles on a carrier core material,
The ratio (Df) between the volume average particle diameter Df of the conductive fine particles and the thickness h of the resin part existing between the core material surface and the particles, at least the shape factor SF-1 of the conductive fine particles is 160 or more. / h) is 0.5 <a [Df / h] <1.5, Ri der coverage of 70% or more of the conductive fine particles to the core material represented by the following formula (1),
The conductive fine particles are characterized in that the surface of inorganic fine particles is conductively treated with an ionic liquid .

[Equation 1]
Formula (1)
Coverage (%) = ((Ds × ρs × W) / (4 × Df × ρf)) × 100
(Wherein, Ds: volume average particle diameter of carrier core material, ρs: true specific gravity of carrier core material, W: ratio of addition amount of conductive fine particles to carrier core material, Df: volume average particle diameter of conductive fine particles, ρf: represents the true specific gravity of the conductive fine particles.

According to a second aspect of the present invention, in the carrier for an electrophotographic developer according to the first aspect , the ionic liquid is an ionic organic compound containing an organic cationium salt and an organic acid anion.

According to a third aspect of the present invention, in the carrier for an electrophotographic developer according to the second aspect , any one of ammonium, imidazolium, pyridinium, and phosphonium is used as the organic cationium salt. .

According to a fourth aspect of the present invention, in the carrier for an electrophotographic developer according to the second aspect , the organic acid anion includes tetrafluoroboron, hexafluorophosphate, trifluorocarbon sulfonyl, and di (fluorocarbon sulfonyl). Any of the above is used.

According to a fifth aspect of the present invention, in the carrier for an electrophotographic developer according to any one of the first to fourth aspects, the volume specific resistance of the carrier is 10 [Log (Ω · cm)] or more and 16 [Log ( Ω · cm)] or less.

The invention according to claim 6 is the carrier for an electrophotographic developer according to any one of claims 1 to 5 , wherein the volume average particle diameter of the carrier is 20 μm or more and 65 μm or less.

The invention according to claim 7 is the carrier for an electrophotographic developer according to any one of claims 1 to 6 , wherein the binder resin contains at least a silicone resin.

The invention according to claim 8 is the carrier for an electrophotographic developer according to any one of claims 1 to 7 , wherein the binder resin contains at least an acrylic resin and a silicone resin.

The invention according to claim 9 is the carrier for an electrophotographic developer according to any one of claims 1 to 8 , wherein the magnetic moment at 1000 ((10 ³ / 4π) A / m) is 40 (Am ² / kg) or more and 90 (Am ² / kg) or less.

A tenth aspect of the invention is an electrophotographic developer containing a toner including at least a binder resin and a pigment, and the carrier according to any one of the first to ninth aspects. .

According to the eleventh aspect of the present invention, as the image forming process, the image carrier and at least one means selected from the charging means, the developing means, and the cleaning means are integrally supported and detachably attached to the main body of the image forming apparatus. An image forming method using a cartridge, wherein the developer according to claim 10 is used for the developing unit.

According to a twelfth aspect of the present invention, an image carrier, an electrostatic latent image forming unit for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image with a developer are visible. Developing means for forming an image; transfer means for transferring the visible image to a recording medium; fixing means for fixing the transferred image transferred to the recording medium; and transfer residual toner on the image carrier after the transfer An image forming apparatus comprising at least a cleaning unit for cleaning the image forming apparatus, wherein the image forming method according to claim 11 is performed.

According to the carrier of the present invention and the developer using the carrier, it is possible to obtain a high-definition image with no carrier adhesion and good image density reproducibility. In addition, image quality deterioration such as color smearing that occurs as the number of copies increases is greatly improved. Further, since the amount of charge and resistance change are small, a good image can be maintained over a long period of time.
Furthermore, it is possible to provide an image forming method and an image forming apparatus in which a good image is formed over a long period of time with the developer of the present invention.

The present invention is described in detail below.
The present invention is an electrophotographic development carrier having a coating layer containing a binder resin and conductive fine particles on a carrier core material, and at least SF-1 of the conductive fine particles is 160 or more, and the conductive The ratio (Df / h) between the volume average particle diameter Df of the fine particles and the film thickness h of the coating layer is 0.5 <[Df / h] <1.5, and further represented by the above formula (1). When the coverage of the conductive fine particles with respect to the core material is 70% or more, a carrier capable of forming a good image over a long period of time with excellent durability and no edge effect is obtained. .

As described above, the conductive fine particles contained in the coating layer preferably have SF-1 of 160 or more. This shape factor SF-1 indicates the degree of sphericity. The conductive fine particles are fixed to the core material using a resin to be coated as an adhesive. When SF-1 of the conductive fine particles is less than 150 , an adhesion area between the core material and the resin that adheres the conductive fine particles cannot be obtained, and the conductive fine particles are easily detached due to stress, and the core material surface is exposed. easy. As a result, resistance is lowered. When SF-1 is 160 or more, a sufficient adhesion area between the core material and the conductive fine particles is obtained, and the detachment of the conductive fine particles against the stress is suppressed. However, when SF-1 exceeds 250, fine irregularities are formed on the surface of the coat layer, and small particles of toner and additives released from the toner tend to accumulate in the recesses. When it accumulates in the recess, the charging performance of the carrier is hindered.

  SF-1 in the present invention uses a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) to randomly sample 100 conductive fine particle images, and image information of the image information is manufactured by Nicole via an interface. This is a value obtained by introducing into (Luxex3), performing analysis, and calculating from the following equation (2).

[Equation 2]
Formula (2)
SF-1 = {(MXLNG) ² / AREA} × (100π / 4)
(MXLNG: absolute maximum length, AREA: projected area of conductive fine particles)

  The coating layer contains conductive fine particles in a covering ratio of 70% or more with respect to the core material. The reason for the inclusion of the conductive fine particles is to create irregularities on the carrier surface and to agitate the developer to frictionally charge, thereby relieving contact with a strong impact on the binder resin due to friction with toner or friction between carriers. This makes it possible to prevent toner spent on the carrier.

  The coverage in this invention is a coverage with respect to the core material of electroconductive fine particles, and is represented by following Formula (1).

[Equation 3]
Formula (1)
Coverage (%) = ((Ds × ρs × W) / (4 × Df × ρf)) × 100
(Wherein, Ds: volume average particle diameter of carrier core material, ρs: true specific gravity of carrier core material, W: ratio of addition amount of conductive fine particles to carrier core material, Df: volume average particle diameter of conductive fine particles, ρf: represents the true specific gravity of the conductive fine particles.

  The true specific gravity of the conductive fine particles ρf and the carrier core material ρs was measured using a dry automatic bulk density meter Accupic 1330 (manufactured by Shimadzu Corporation). The volume average particle diameter Ds (volume average particle diameter) of the carrier core material can be measured using an SRA type of a microtrack particle size analyzer (manufactured by Nikkiso Co., Ltd.). What was performed by the range setting of 0.7 micrometer or more and 125 micrometers or less was used. Further, methanol is used for the dispersion, and the refractive index is set to 1.33, and the refractive indexes of the carrier and the core material are set to 2.42. The volume average particle diameter Df of the conductive fine particles is measured by an automatic particle size distribution analyzer CAPA-700 (manufactured by Horiba, Ltd.). As a pretreatment for the measurement, 300 ml of a toluene solution is added to 30 ml of aminosilane (SH6020: manufactured by Toray Dow Corning Silicone) in a juicer mixer. Add 6.0 g of sample, set the mixer rotation speed to low and disperse for 3 minutes. An appropriate amount of the dispersion is added to 500 ml of a toluene solution prepared in advance in a 1000 ml beaker and diluted. The diluting solution is continuously stirred with a homogenizer. This diluted solution is measured with an ultracentrifugal automatic particle size distribution analyzer CAPA-700.

Measurement conditions Rotational speed: 2000rpm
Maximum particle size: 2.0 μm
Minimum particle size: 0.1 μm
Particle size interval: 0.1 μm
Dispersion medium viscosity: 0.59 mPa · s
Dispersion medium density: 0.87 g / cm ³
Particle density: For the density of conductive fine particles, enter the true specific gravity value measured using a dry automatic bulk density meter Accupic 1330 (manufactured by Shimadzu Corporation).

  If the coverage is less than 70%, there is a high probability that the surface of the carrier core material will be exposed due to film scraping over time, and a decrease in resistance occurs locally. Carriers in such a state are present in the solid image. It develops and white spots occur in the image.

  Furthermore, the volume average particle diameter (Df) of the conductive fine particles contained in the carrier coating layer and the coating layer film thickness (h) are improved by 0.5 <[Df / h] <1.5. The effect is remarkable. When [Df / h] is 0.5 or less, since the fine particles are buried in the binder resin, convex particles are reduced on the surface of the carrier, so that they adhere to the surface of the carrier due to frictional contact between the carriers. The cleaning effect of efficiently scraping off the spent component of the toner is reduced, and the effect of preventing the toner spent is significantly reduced, which is not preferable. When [Df / h] is 1.5 or more, the contact area between the particles and the binder resin is small, so that a sufficient binding force cannot be obtained and the particles are easily detached, which is not preferable. When desorbed, the resistance is lowered.

  The thickness h of the carrier coating layer was obtained from an average value by observing the cross section of the carrier using a transmission electron microscope (TEM), measuring the thickness of the resin portion of the coating layer covering the carrier surface. Specifically, as shown in FIG. 3, only the thickness of the resin part existing between the core material surface and the particles is measured. The thickness of the resin part existing between the particles and the thickness of the resin part on the inorganic fine particles are not included in the measurement. The average of 50 arbitrary measurements on the carrier cross section was determined and defined as the thickness h (μm). The measurement of the volume average particle diameter (Df) of the conductive fine particles is as described above.

Next, further preferable points in the present invention will be described.
[1] The conductive fine particles are preferably conductive fine particles obtained by treating the surface of inorganic fine particles with an ionic liquid.
As the inorganic fine particles, any one of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfate and zirconium oxide may be used alone or in combination. However, when it comes off from the coating layer, it is mixed with the toner particles and causes color stains.
In addition, the ionic liquid has general physical properties as an ionic liquid, that is, a liquid state in a wide temperature range of about −100 ° C. to 200 ° C., a high ionic conductivity, and a non-volatile property. Any material that is not flammable or combustible and has high thermal stability can be used. However, it is preferable not to decompose in the temperature range used in the production process of electrophotographic developer (thermosetting and solvent removal of the resin), that is, at least in the temperature range of 100 to 300 ° C.
Moreover, although the ion conduction characteristic of an ionic liquid is not specifically limited, It is preferable that it is 1.0 * 10 < ^-3 > (S / cm) or more in a 10 thru | or 30 degreeC temperature range. If it is less than 1.0 × 10 ⁻³ (S / cm), the effect of reducing the resistance as a carrier cannot be expected. When the carrier resistance is high, abnormal images such as carrier adhesion (edge carrier adhesion) and white spots on non-image portions occur.

  The specific composition of the ionic liquid used in the present invention is not particularly limited as long as it has physical properties as a general ionic liquid, and the temperature at which the ionic liquid can be maintained as described above. In addition, it is preferable that physical properties such as ion conduction characteristics are more suitable, for example, an ionic organic compound including an organic cationium salt and an organic acid anion is preferable.

Examples of organic cationium salts include ammonium salts, imidazolium derivatives, pyridinium, phosphonium, and the like, and examples of organic acid anions include BF ⁴⁻ , PF ⁶⁻ , CF ₃ SO ₃ — (Tf: triflate), and (CF ₃ SO ₂ ). ) ₂ N- (TFSI). Of these, salts of ethylmethylimidazolium (EMI) and butylmethylimidazolium (BMI) are preferably used. In this invention, you may use the ionic substance containing the component melt | dissolved in an ionic liquid besides these.

  Further, preferable materials for the ionic liquid include pyridinium-based (the following structural formula 1), imidazolium-based (the following structural formula 2), alicyclic amine-based (the following structural formula 3) or aliphatic amine-based (the following structure Using the material of formula 4). Specifically, pyridinium-based ionic liquids IL-P11 and IL-P14 manufactured by Guangei Chemical Industry Co., Ltd., imidazolium-based ionic liquid IL-IM1, and alicyclic amine-based ionic liquids IL-C1 and IL- C3, IL-C5, and aliphatic amine-based ionic liquids IL-A1, IL-A2, IL-A3, IL-A4, IL-A5 can be used.

(R and R ′ in the formula may be the same or different and each represents a hydrogen element, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a phenyl group. X ^- represents a halogen).

(R and R ′ in the formula may be the same or different and each represents a hydrogen element, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a phenyl group. X ^- represents a halogen).

(R and R ′ in the formula may be the same or different and each represents a hydrogen element, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a phenyl group. X ^- represents a halogen).

(In the formula, R, R ′, R ″, and R ′ ″ may be the same or different, and each is a hydrogen element, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, or a cyclohexane having 5 to 7 carbon atoms. .X represents an alkyl group or a phenyl group ^- represents a halogen).

  In the present invention, as a method for measuring the ionic conductivity of the ionic liquid, measurement is performed at a frequency of 10 kHz and 25 ° C. using a closed conductivity measuring cell and an AC impedance meter (CM-40S, manufactured by Toa Denpa Kogyo Co., Ltd.).

  The resistance value of the carrier of the present invention is not particularly limited as long as it is measured by the carrier resistance measuring device of FIG. 4 and is in the range of about 10 to 16 (log Ω · cm), and can be adjusted according to the application. The content of the ionic liquid contained in the coating layer is not particularly limited, and can be determined in consideration of a desired resistance value and ionic conductivity of the ionic liquid to be used.

  In systems that require high image quality such as color images, it is essential to adjust resistance as a carrier. Carriers with extremely high resistance generate abnormal images such as carrier adhesion (edge carrier adhesion) or white spots on non-image areas. . When resistance adjustment is performed as a carrier, conventionally, resistance is improved by adding conductive fine particles such as carbon black, titanium oxide, zinc oxide, indium oxide and fine particles surface-treated with indium oxide as a resistance adjusting agent to the carrier coating layer. It is adjusted. However, if the conductive fine particles are mixed in the toner due to the scraping of the coating layer and the conductive fine particles are not colorless or white, it causes color stains in the color image. Carbon black, indium oxide, and the like have an effect of reducing carrier resistance in a small amount, but cannot be used due to the problem of color stains. In addition, zinc oxide and indium oxide treated fine particles are white, but the effect of reducing the resistance cannot be obtained in a small amount like carbon black, and it must be added in a large amount to the coating layer, so it is a very expensive material. It is not preferable in terms of cost.

  The ionic liquid is a liquid and can easily be impregnated into the surface layer of the inorganic fine particles and can be conductively treated in a small amount. Fine particles that have been conductively treated with an ionic liquid dispersed in the coating layer also have the effect of lowering the resistance. Since the ionic liquid is colorless to cloudy, the coating layer is scraped and mixed into the toner. Even if it does not stain the color. Thus, the present invention has a remarkable improvement effect by including the fine particles subjected to the conductive treatment with the ionic liquid.

[2] The volume resistivity of the carrier is preferably 10 [Log (Ω · cm)] or more and 16 [Log (Ω · cm)] or less.
The improvement effect is remarkable when the volume resistivity of the carrier is 10 [Log (Ω · cm)] or more and 16 [Log (Ω · cm)] or less. This is not preferable because, when the volume resistivity is less than 10 [Log (Ω · cm)], carrier adhesion occurs in the non-image area. On the other hand, if the volume resistivity exceeds 16 [Log (Ω · cm)], the edge effect is deteriorated to an unacceptable level. In addition, when it falls below the measurable lower limit of the high resist meter, the volume specific resistance value is not substantially obtained, and it will be treated as a breakdown.

  The volume specific resistance mentioned here means that a carrier 33 is filled in a cell 31 made of a fluororesin container containing an electrode 32a and an electrode 32b having an interelectrode distance of 2 mm and a surface area of 2 cm × 4 cm shown in FIG. Manufactured: Using a tapping machine PTM-1 type, a tapping operation is performed for 1 minute at a tapping speed of 30 times / min. A DC voltage of 1000 V is applied between the two electrodes, a DC resistance is measured by a high resistance meter 4329A (4329A + LJK5HVLVWDQFH0HWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), an electric resistivity RΩ · cm is obtained, and LogR is calculated.

[3] The volume average particle diameter of the carrier is preferably 20 μm or more and 65 μm or less.
The improvement effect is remarkable because the volume average particle diameter of the carrier is 20 μm or more and 65 μm or less. This is not preferable when the volume average particle diameter is less than 20 μm, since the uniformity of the particles is lowered and a technique for sufficiently using on the machine side has not been established. On the other hand, if it exceeds 65 μm, the reproducibility of image details is poor and a fine image cannot be obtained.

  The volume average particle diameter of the carrier can be measured using an SRA type of a microtrack particle size analyzer (manufactured by Nikkiso Co., Ltd.). In this invention, what was performed by the range setting of 0.7 micrometer or more and 125 micrometers or less was used. Further, methanol is used for the dispersion, and the refractive index is set to 1.33, and the refractive indexes of the carrier and the core material are set to 2.42.

[4] Since the binder resin is at least a silicone resin, the improvement effect is remarkable.
This is because the silicone resin has a low surface energy, so that it is difficult to spend the toner component, and it is difficult to accumulate the spent component due to film scraping.

  Silicone resin here refers to all commonly known silicone resins, including straight silicone consisting only of organosilosan bonds and silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, etc. However, it is not limited to this. Examples of commercially available straight silicone resins include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicone. In this case, it is possible to use the silicone resin alone, but it is also possible to simultaneously use other components that undergo a crosslinking reaction, charge amount adjusting components, and the like. Furthermore, as modified silicone resins, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd., SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicone Co., Ltd. ), SR2110 (alkyd modified), and the like.

[5] The improvement effect is remarkable when the binder resin uses a silicone resin and an acrylic resin in combination.
This is because acrylic resin has strong adhesion and low brittleness, so it has very excellent properties in abrasion resistance, and it is difficult for deterioration such as coating film scraping and film peeling, so the coating layer can be maintained stably. In addition, the particles contained in the coating layer such as conductive fine particles can be firmly held due to strong adhesiveness. In particular, a powerful effect can be exhibited in holding particles having a particle size larger than the coating layer thickness.

  The acrylic resin here refers to all resins having an acrylic component, and is not particularly limited. In addition, it is possible to use the acrylic resin alone, but it is also possible to use at least one other component that undergoes a crosslinking reaction at the same time. Examples of other components that undergo a crosslinking reaction include amino resins and acidic catalysts, but are not limited thereto. The amino resin here refers to guanamine, melamine resin and the like, but is not limited thereto. Moreover, what has a catalytic action can be used with an acidic catalyst here. For example, it has a reactive group such as a fully alkylated type, a methylol group type, an imino group type, and a methylol / imino group type, but is not limited thereto.

  Acrylic resin has excellent adhesion properties and low brittleness, so it has excellent wear resistance. On the other hand, its surface energy is high, so when it is combined with easily spent toner, toner component spent accumulates. In some cases, problems such as a decrease in charge amount due to the occurrence of charging. In this case, this problem can be solved by using together a silicone resin that has an effect that it is difficult to spend the toner component due to the low surface energy and the accumulation of the spent component is difficult to progress due to film scraping. However, since the silicone resin has weak adhesiveness and high brittleness, it also has a weak point that it has poor wear resistance. Therefore, it is important to obtain a good balance between the properties of these two resins. It is possible to obtain a coating film having wear characteristics.

[6] Further, when the magnetic moment at 1000 (10 ³ / 4π · A / m) is 40 (Am ² / kg) or more and 90 (Am ² / kg) or less, the improvement effect is remarkable.
This is because, within this range, the retention force between the carrier particles is appropriately maintained, so that the dispersion (mixing) of the toner into the carrier or developer is quickly and favorably improved. However, the magnetic moment at 1 KOe is 40 Am ^2. If it is less than / kg, carrier adhesion occurs due to insufficient magnetic moment, which is not preferable. On the other hand, when the magnetic moment at 1 KOe exceeds 90 Am ² / kg, the ears of the developer formed at the time of development become too hard, so that the reproducibility of image details is poor and a fine image cannot be obtained, which is not preferable.

  The magnetic moment can be measured as follows. Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1.0 g of carrier core particles are packed in a cylindrical cell (inner diameter 7 mm, height 10 mm) and set in an apparatus. The magnetic field is gradually increased and changed to 3000 Oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 Oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.

[7] Further, if the toner is a color toner as well as a monochrome toner, the improvement effect is more remarkable.
This is because the carrier of the present invention does not contain carbon black in the coating layer, and therefore does not cause image color staining due to carbon black due to film scraping or the like. Therefore, it is very suitable for a color developer in which color reproducibility is regarded as important. The color toner referred to here includes not only a color toner generally used for a single color but also a black toner in addition to yellow, magenta, cyan, red, green, blue and the like used for full color.

<Toner>
Here, the toner used in the present invention will be described in detail. The toner in the present invention includes all the general toners regardless of whether they are monochrome toner, color toner or full color toner. For example, conventionally kneaded and pulverized toners and various polymerized toners that have been used in recent years can be used. Furthermore, so-called oilless toner having a release agent can also be used. Since the carrier of the present invention has excellent spent resistance, good quality can be maintained over a long period of time. In particular, oilless full color toners are generally said to be spent easily because the binder resin is soft, but it can be said that the carrier of the present invention is very suitable for oilless without such anxiety.

As the binder resin used in the toner of the present invention, known resins can be used. For example, styrene such as polystyrene, poly-p-styrene, and polyvinyltoluene, and homopolymers thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene- Methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid copolymer Corp., Styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid Butyl copolymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene-isopropyl copolymer, styrene-male Styrene copolymers such as acid ester copolymer, polythyme methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified Rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, or the like can be used alone or in combination.

  And as a binder resin for pressure fixing, a well-known thing can be mixed and used. For example, polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-chlorinated Vinyl copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin, epoxy resin, polyester resin, styrene-butadiene copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride, maleic acid modified phenol resin Phenol-modified terpene resins and the like can be used alone or in combination, but are not limited thereto.

  Further, the toner used in the present invention may contain a fixing aid in addition to the binder resin, the colorant, and the charge control agent. Accordingly, it can be used in a fixing system in which toner fixing prevention oil is not applied to the fixing roll, so-called oilless system. Known fixing aids can be used. For example, polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin waxes, amide waxes, polyhydric alcohol waxes, silicone varnishes, carnauba waxes and ester waxes can be used, but are not limited thereto.

  As the colorant used in the toner such as the color toner used in the present invention, known pigments and dyes capable of obtaining toners of each color of yellow, magenta, cyan, and black can be used, and are not limited to those listed here. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, and Tartrazine Lake. Can be mentioned.

  Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

  Examples of purple pigments include fast violet B and methyl violet lake.

  Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC.

  Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides.

  Moreover, these colorants can use 1 type (s) or 2 or more types.

  A toner such as a color toner used in the present invention can contain a charge control agent in the toner as necessary. For example, nigrosine, an azine dye containing an alkyl group having 2 to 16 carbon atoms (Japanese Patent Publication No. 42-1627), a basic dye (for example, CI Basic Yellow 2 (CI 41000), CI Basic Yellow 3, C.I.Basic Red 1 (C.I. 45160), C.I.Basic Red 9 (C.I. 42500), C.I.Basic Violet 1 (C.I. 42535), C I. Basic Violet 3 (C.I. 42555), C. I. Basic Violet 10 (C.I. 45170), C.I.Basic Violet 14 (C.I. 42510), C.I.Basic Blueet 1 (C.I. 42025), C.I.Basic Blue 3 (C.I.51005), C.I. ascii blue 5 (C.I. 42140), C.I.Basic Blue 7 (C.I.42595), C.I.Basic Blue 9 (C.I.522015), C.I.Basic Blue 24 (C. CI Basic Blue 25 (C.I.52025), C.I.Basic Blue 26 (C.I.44045), C.I.Basic Green 1 (C.I.42040), Lake pigments of these basic dyes, such as CI Basic Green 4 (CI 42000), CI Solvent Black 8 (CI 26150), benzoylmethyl hexadecyl ammonium chloride, decyltrimethyl chloride Quaternary ammonium salts such as dibutyl or dioctyl Dialkyl tin compounds, dialkyl tin borate compounds, guanidine derivatives, vinyl polymers containing amino groups, polyamine resins such as condensation polymers containing amino groups, Japanese Patent Publication No. 41-20153, Japanese Patent Publication No. 43-27596 A metal complex salt of a monoazo dye described in JP-B-44-6397 and JP-B-45-26478, salicylic acid described in JP-B-55-42752, JP-B-59-7385, Examples include dialkyl salicylic acid, naphthoic acid, dicarboxylic acid metal complexes such as Zn, Al, Co, Cr, and Fe, sulfonated copper phthalocyanine pigments, organic boron salts, fluorine-containing quaternary ammonium salts, calixarene compounds, and the like. . Naturally, color toners other than black should avoid the use of charge control agents that impair the target color, and white metal salts of salicylic acid derivatives are preferably used.

  As for the external additive, transferability and durability are further improved by externally adding inorganic fine particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride and resin fine particles to the base toner particles. This effect can be obtained by covering the wax that lowers transferability and durability with these external additives and reducing the contact area due to the toner surface being covered with fine particles. The surface of these inorganic fine particles is preferably subjected to a hydrophobic treatment, and metal oxide fine particles such as silica and titanium oxide subjected to the hydrophobic treatment are suitably used.

  As the resin fine particles, polymethyl methacrylate or polystyrene fine particles having an average particle diameter of about 0.05 to 1 μm obtained by a soap-free emulsion polymerization method are suitably used.

  In addition, the combination of hydrophobized silica and hydrophobized titanium oxide increases the amount of hydrophobized titanium oxide externally added compared to the amount of hydrophobized silica externally charged. The toner can also be excellent in stability.

  In combination with the above inorganic fine particles, external additives conventionally used such as silica having a specific surface area of 20 to 50 m / g and resin fine particles having an average particle diameter of 1/100 to 1/8 of the average particle diameter of the toner. The durability can be improved by externally adding an external additive having a particle size larger than that of the agent to the toner. This is because the metal oxide particles externally added to the toner tend to be embedded in the base toner particles in the process where the toner is mixed and stirred with the carrier in the developing device, charged, and used for development. This is because it is possible to prevent the metal oxide fine particles from being embedded by externally adding an external additive having a particle size larger than that of the oxide fine particles to the toner.

  Although the above-mentioned inorganic fine particles and resin fine particles are contained (internally added) in the toner, the effect is reduced as compared with the case of external addition, but the effect of improving transferability and durability is obtained and the pulverizing property of the toner is improved. be able to. In addition, since external addition and internal addition can be used together to suppress embedding of externally added fine particles, excellent transferability can be stably obtained and durability can be improved.

  In addition, the following are mentioned as a typical example of the hydrophobization processing agent used here. Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyl-tris (β-methoxyethoxy) ) Silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyl Trichlorosilane, decyl-trichlorosilane, nonyl-trichlorosilane, (4-t-propylphenyl) -trichlorosilane, (4-t-butylphenyl) -trichlorosilane, diventyl-dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl -Dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, dihexadecyl-dichlorosilane, (4-t-butylphenyl) -octyl-dichlorosilane, dioctyl-dichlorosilane, didecenyl-dichlorosilane, dinonenyl-dichlorosilane, di-2-ethylhexyl-dichlorosilane, di- 3,3-dimethylbenthyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-chlorosilane, tridecyl-chlorosilane Dioctyl-methyl-chlorosilane, octyl-dimethyl-chlorosilane, (4-t-propylphenyl) -diethyl-chlorosilane, octyltrimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilazane, hexaphenyldisilazane , Hexatolyl disilazane and the like. In addition, titanate coupling agents and aluminum coupling agents can also be used. In addition, as an external additive for the purpose of improving cleaning properties, a lubricant such as a fatty acid metal salt or a fine particle of polyvinylidene fluoride can be used in combination.

  As the carrier core material in the present invention, those known as two-component carriers for electrophotography, such as ferrite, Cu-Zn ferrite, Mn ferrite, Mn-Mg ferrite, Mn-Mg-Sr ferrite, magnetite, iron, What is necessary is just to select suitably according to the use and intended purpose of carriers, such as nickel, and it is not restricted to these examples.

Conventionally known methods such as a pulverization method and a polymerization method can be applied to the toner production method of the present invention. For example, in the case of the pulverization method, as a device for kneading the toner, a batch type two roll, a Banbury mixer or a continuous twin screw extruder, for example, KTK type twin screw extruder manufactured by Kobe Steel, TEM manufactured by Toshiba Machine Co., Ltd. Type twin screw extruder, KCK twin screw extruder, Ikegai Iron Works PCM type twin screw extruder, Kurimoto Iron Works KEX type twin screw extruder, continuous single screw kneader, for example Buss Co-kneader is preferably used. The melt-kneaded product obtained as described above is cooled and then pulverized. For pulverization, for example, coarsely pulverized using a hammer mill, a funnel plex, etc. A machine can be used. The pulverization is desirably performed so that the average particle diameter is 3 to 15 μm. Further, the pulverized product is preferably adjusted in particle size to 5 to 20 μm by a wind classifier or the like. Subsequently, the external additive is externally added to the base toner. The base toner and the external additive are mixed and stirred using a mixer, and the external additive is crushed and coated on the toner surface. At this time, it is important in terms of durability that external additives such as inorganic fine particles and resin fine particles are uniformly and firmly attached to the base toner. The above is only an example, and the present invention is not limited to this.

<Image forming apparatus, process cartridge>
FIG. 1 shows a schematic configuration of an image forming apparatus provided with a process cartridge using the developer of the present invention. FIG. 2 shows the entire process cartridge, which includes a photosensitive member, a charging unit, a developing unit, and a cleaning unit.

  In the present invention, among the constituent elements such as the above-described photoreceptor, charging means, developing means, and cleaning means, the developing means using the developer of the present invention and one or more other means are used as a process cartridge. The process cartridge is configured so as to be integrally connected, and is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer.

  In the image forming apparatus equipped with the process cartridge 2 (2A, 2B, 2C, 2D) using the developer of the present invention shown in FIG. 1, the photoreceptor 1 (1a, 1b, 1c, 1d) is at a predetermined peripheral speed. Driven by rotation. In the rotation process, the photosensitive member 1 is uniformly charged at a predetermined positive or negative potential on the peripheral surface thereof by the charging unit 3, and then receives image exposure light from the image exposure unit 6 such as slit exposure or laser beam scanning exposure. Thus, electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor 1, and the formed electrostatic latent images are then developed with toner by the developing means 10 (10A, 10B, 10C, 10D), and the developed toner images are developed. Are sequentially transferred by the transfer unit 8 to the transfer material fed in synchronization with the rotation of the photoconductor 1 between the photoconductor 1 and the transfer unit 8 from the paper feeding unit. The transfer material that has received the image transfer is separated from the surface of the photosensitive member, introduced into the image fixing unit 9, and fixed, and printed out as a copy (copy). The surface of the photoconductor 1 after the image transfer is cleaned by receiving the toner remaining after the transfer by the cleaning unit 5, and after being further neutralized, it is repeatedly used for image formation.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these. Parts are based on weight.

Example 1
[Carrier coating layer]
・ Silicone resin solution [solid content: 23% by weight
(SR2410: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 432.2 parts, aminosilane [solid content: 100% by weight
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 0.66 parts, conductive fine particles EC-500 (ITO-treated titanium dioxide): manufactured by Titanium Industry Co., Ltd.
[Particle size: 0.43 μm, true specific gravity: 4.6, SF-1: 165] 145 parts and 300 parts of toluene were dispersed with a homomixer for 10 minutes to obtain a silicone resin coating film forming solution.
Volume average particle size: 5000 parts of 35 μm calcined ferrite powder (true specific gravity 5.5) is used as the core material, and the above-mentioned coating film forming solution is spired on the surface of the core material so that the film thickness after drying is 0.35 μm. A coater (manufactured by Okada Seiko Co., Ltd.) was applied at a coater temperature of 40 ° C. and dried.
The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm, Df / h: 1.2, volume resistivity: 12.9 [Log (Ω · cm)], magnetization: 68 Am ² / kg [ Carrier 1] was obtained. At this time, the conductive fine particles contained in the resin coating layer had a coverage of 71% with respect to the core material.

  In addition, the particle powder specific resistance of inorganic oxide fine particles was measured using the apparatus of FIG.

  For the measurement of the volume average particle diameter of the core material, the SRA type of Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) was used, and the measurement was performed with a range setting of 0.7 μm or more and 125 μm or less.

  The thickness of the binder resin was measured by observing the cross section of the carrier with a transmission electron microscope so that the coating film covering the carrier surface could be observed.

  For the magnetization measurement, VSM-P7-15 manufactured by Toei Kogyo Co., Ltd. was used. About 0.15 g of the sample was weighed, and the sample was filled in a cell having an inner diameter of 2.4 mmφ and a height of 8.5 mm, and 1000 Oersted (Oe ) Measured under a magnetic field.

[Toner 1]
(Toner binder synthesis)
724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide were placed in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, and reacted at 230 ° C. for 8 hours at normal pressure. The reaction was further carried out at a reduced pressure of 10 to 15 mmHg for 5 hours, followed by cooling to 160 ° C., and 32 parts of phthalic anhydride was added thereto and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and reacted with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the isocyanate containing prepolymer (1) was obtained. Next, 267 parts of the prepolymer (1) and 14 parts of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester (1) having a weight average molecular weight of 64,000. In the same manner as above, 724 parts of bisphenol A ethylene oxide 2-mole adduct and 276 parts of terephthalic acid were polycondensed at 230 ° C. for 8 hours under normal pressure, and then reacted for 5 hours at a reduced pressure of 10 to 15 mmHg to give a peak molecular weight of 5000. An unfinished polyester (a) was obtained. 200 parts of urea-modified polyester (1) and 800 parts of unmodified polyester (a) are dissolved and mixed in 2000 parts of a mixed solvent of ethyl acetate / MEK (1/1), and an ethyl acetate / MEK solution of toner binder (1) is mixed. Got. Part of the mixture was dried under reduced pressure to isolate toner binder (1). Tg was 62 ° C.

(Production of toner)
In a beaker, 240 parts of an ethyl acetate / MEK solution of the toner binder (1), 20 parts of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), C.I. I. 4 parts of raw pigment of Pigment Yellow 154 was added and stirred at 12000 rpm with a TK homomixer at 60 ° C. to uniformly dissolve and disperse. In a beaker, 706 parts of ion-exchanged water, 294 parts of hydroxyapatite 10% suspension (Superite 10 manufactured by Nippon Chemical Industry Co., Ltd.) and 0.2 part of sodium dodecylbenzenesulfonate were uniformly dissolved. Next, the temperature was raised to 60 ° C., and the toner material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer. Subsequently, this mixed liquid was transferred to a Kolben equipped with a stirring bar and a thermometer, and the temperature was raised to 98 ° C. to remove the solvent. After the dispersion slurry was filtered under reduced pressure, a filter cake was obtained.

(Washing / drying / fluorine treatment)
1: 100 parts of ion-exchanged water was added to the filter cake, mixed with a TK homomixer (rotation speed: 12,000 rpm for 10 minutes), and then filtered.
2: 100 parts of a 10% aqueous sodium hydroxide solution was added to the filter cake of 1 above, mixed with a TK homomixer (30 minutes at 12,000 rpm), and then filtered under reduced pressure.
3: 100 parts of 10% hydrochloric acid was added to the filter cake of 2 above, mixed with a TK homomixer (rotation speed: 12,000 rpm for 10 minutes), and then filtered.
4: 300 parts of ion-exchanged water was added to the filter cake of 3 above and mixed with a TK homomixer (rotation speed: 12,000 rpm for 10 minutes) and then filtered twice to obtain a cake. This is designated as [Filter cake 1].

  The above [Filter cake 1] was dried at 45 ° C. for 48 hours in a circulating dryer.

  Thereafter, 15 parts of [Filter cake 1] is added to 90 parts of water, and 0.0005 part of the fluorine compound is dispersed therein, thereby attaching the fluorine compound (2) to the toner particle surface, and then circulating air. It dried for 48 hours at 45 degreeC with the dryer. Thereafter, the mixture was sieved with a 75 μm mesh to obtain toner base particles. This is designated as [toner base particle 1].

  To 100 parts of [Toner Base Particle 1] obtained above, 1.5 parts of hydrophobic silica and 0.7 parts of hydrophobized titanium oxide as external additives were added at 2000 rpm × 30 seconds, 5 cycles using a Henschel mixer. Was mixed to obtain a toner. This is referred to as [Toner 1].

  7 parts of [Toner 1] and 93 parts of [Carrier 1] thus obtained were mixed and stirred to obtain a developer having a toner concentration of 7% by weight. Color stain, carrier adhesion, image density, durability (charge reduction amount, resistance) Change). The results are shown in Tables 1 and 2.

The evaluation methods and conditions in the examples are shown below.
[Color stains]
Evaluation of the ΔE value of a yellow monochromatic image after running up to 30,000 image charts having a 0.5% image area with a commercially available digital full-color printer (image Neo Neo C455 manufactured by Ricoh Co., Ltd.) was performed. The initial and 30,000 sheets of yellow single color image are output, and the ΔE value is obtained according to the following equation. When ΔE is 2 or less, there is no color stain (◯), when ΔE is 2 to 4, color stain is not noticeable (Δ), no change in color tone is indicated, and when ΔE is 4 or more, color stain is clearly noticeable (×) be pointed out.

  After image output, the image density was measured with X-RITE 938 (manufactured by x-rite). Three points of CIE L *, CIE a *, and CIE b * at the point where the yellow image density is 1.4 ± 0.5 are measured, an average value is obtained, and is substituted into the following equation (3) to calculate ΔE value.

[Equation 4]
Formula (3)
ΔE = √ ((initial L *) ² + (initial a *) ² + (initial b *) ² ) −√ ((post-run L *) ² + (post-run a *) ² + (post-run b *) ² )

[Carrier adhesion]
The developer is set on a commercially available digital full-color printer (Imagio Neo C455 manufactured by Ricoh), and the surface of the photosensitive member is developed with a charged potential of DC740V and a developing bias of 600V (fixed to a ground potential of 140V), and the dot formation halftone is developed. The number of carriers adhering to the substrate was counted by five visual field observations with a magnifier, and the average number of adhering carriers per 100 cm ² was taken as the edge carrier adhering amount. The evaluation was as follows: ◎: 20 or less, ○: 21 or more and 60 or less, Δ: 61 or more and 80 or less, ×: 81 or more, ◎ ○ △ was passed and × was rejected.

  Further, white spots (image part) were set to a charging potential of DC 740 V and a developing bias of 600 V (the background potential was fixed to 140 V), a full-color image (A3 size) was output, and the number of white spots on the image was counted. The evaluation was as follows: ◎: 5 or less, ◯: 6 or more and 10 or less, △: 11 or more and 20 or less, ×: 21 or more, ◎ ○ △ was accepted and x was rejected.

[Image density]
After running 300,000 image charts with 50% image area in monochrome mode, the solid image is output to 6000 paper manufactured by Ricoh, and the image density is measured by X-Rite (manufactured by X-Rite). It was. In Table 2, when the measured value is 1.8 or more and less than 2.2, it is ◎, when it is 1.4 or more and less than 1.8, it is ◯, when it is 1.2 or more and less than 1.4, it is △, And when less than 1.2, it displayed by x.

[durability]
The developer was set in a commercially available digital full-color printer (image Neo Neo C455 manufactured by Ricoh Co., Ltd.), and a running evaluation of 300,000 sheets was performed with an image chart of 50% image area in a single color mode. The judgment was made based on the amount of charge reduction of the carrier after the running. The amount of decrease in resistance was evaluated by running 300,000 sheets with an image chart of 0.5% image area in the monochromatic mode. And it judged with the amount of resistance fall of the career which finished this running.

  The amount of charge reduction here is a room temperature and humidity room (temperature: 23.5 ° C., humidity: 60% RH), and the humidity is adjusted in an opening system for 30 minutes or more, and 6.000 g of initial carrier and 0.452 g of toner are added. After adding to a stainless steel container, the sample was sealed, and YS-LD (manufactured by Yayoi Co., Ltd., shaker) was operated on a scale 150 for 5 minutes, and the sample was frictionally charged with an amplitude of about 1100 times. Carrier obtained by removing toner in the developer after running from the charge amount (Q1) measured by a typical blow-off method [manufactured by Toshiba Chemical Co., Ltd .: TB-200] with the blow-off device. This is the amount obtained by subtracting the charge amount (Q2) measured by the same method as above, and the target value is within 10.0 (μc / g).

  Here, the amount of resistance change refers to the carrier from which the toner in the developer after running can be removed by the blow-off device from the resistance value (R1) obtained by the resistance measurement method described above for the initial carrier. It means an amount obtained by subtracting the value (R2) measured by the same method as the resistance measuring method, and the target value is 3.0 [Log (Ω · cm)] in absolute value. Further, the cause of the resistance change is scraping of the binder resin film of the carrier, spent toner component, particle detachment in the carrier coating film, etc., and reducing these can suppress the resistance change amount. .

(Example 2)
Df / h: 1.1, volume resistivity: 13.1 [Log (Ω), except that the coating layer formulation was changed to the mixed system of acrylic resin and silicone resin described below. Cm)], magnetization: 68 Am ² / kg [Carrier 2] was obtained. The conductive fine particles contained in the resin coating layer at this time had a coverage of 71% with respect to the core material.

・ Acrylic resin solution (solid content 50 wt%) 34.2 parts ・ Guanamine solution (solid content 70 wt%) 9.7 parts ・ Acid catalyst (solid content 40 wt%) 0.19 parts ・ Silicone resin solution [solid content 20% by weight
(SR2410: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 432.2 parts ・ Aminosilane [solid content: 100% by weight
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 3.42 parts • Conductive fine particles EC-500 (ITO-treated titanium dioxide): manufactured by Titanium Industry Co., Ltd. [particle size: 0.43 μm, true specific gravity: 4.6 SF-1: 165] 145 parts [Carrier 2] and [Toner 1] thus obtained were developed into a developer by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Example 3)
[Conductive fine particles]
200 g of rutile titanium oxide JR (manufactured by Teika Co., Ltd., average primary particle size 0.27 μm, true specific gravity 4.2, SF-1: 172) was dispersed in 2.5 liters of toluene to obtain a suspension. This suspension was kept warm at 80 ° C. 50 g of ionic liquid IL-P14 (manufactured by Guangei Chemical Industry Co., Ltd., aromatic amine) prepared separately was added and stirred while heating at 80 ° C. The treated suspension was filtered and the resulting treated pigment cake was dried at 120 ° C. Next, the obtained dry powder was pulverized to obtain white conductive fine particles A having SF-169 of 169.

  In Example 2, instead of the conductive fine particles EC-500, 100 parts of the white conductive fine particles A [particle size: 0.31 μm, true specific gravity: 4.0, SF-1: 169] obtained as described above were used. [Carrier 3] having Df / h: 0.8 and volume resistivity: 13.8 [Log (Ω · cm)] was obtained in the same manner except that it was used. The conductive fine particles contained in the resin coating layer at this time had a coverage of 78% with respect to the core material.

  [Carrier 3] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

Example 4
In Example 2, Df / h: 1.1, volume resistivity: 9.5 [Log (Ω · cm), except that the amount of conductive fine particles: EC-500 was increased from 145 parts to 210 parts. [Carrier 4] was obtained. The conductive fine particles contained in the resin coating layer at this time had a coverage of 102% with respect to the core material.

  [Toner 1] and [Carrier 4] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Example 5)
In Example 2, in place of conductive fine particles: EC-500, rutile type titanium oxide: JR (manufactured by Teika Co., Ltd.) (average primary particle size 0.27 μm, true specific gravity 4.2, SF-1: 172) was 110. [Carrier 5] having Df / h: 0.7 and volume resistivity: 16.5 [Log (Ω · cm)] was obtained in the same manner except that the part was used. At this time, the conductive fine particles contained in the resin coating layer had a coverage of 93% with respect to the core material.

  [Toner 1] and [Carrier 5] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Example 6)
Df / h: 1.1, volume resistivity: 13.7, except that the carrier had a volume average particle size of 18 μm (true specific gravity of 5.7) and the coating layer formulation was as follows: [Carrier 6] with [Log (Ω · cm)] and magnetization: 66 Am ² / kg was obtained.

・ Acrylic resin solution (solid content 50 wt%) 68.4 parts ・ Guanamine solution (solid content 70 wt%) 19.4 parts ・ Acid catalyst (solid content 40 wt%) 0.38 parts ・ Silicone resin solution [solid content 20% by weight
(SR2410: manufactured by Toray Dow Corning Silicone)] 864.4 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 0.46 parts-Conductive fine particles EC-500 (ITO-treated titanium dioxide): manufactured by Titanium Industry Co., Ltd. [particle size: 0.43 [mu] m, true specific gravity: 4.6 , SF-1: 165]
275 parts Toluene 800 parts [Carrier 6] and [Toner 1] thus obtained were converted into a developer by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2. At this time, the conductive fine particles contained in the resin coating layer had a coverage of 71% with respect to the core material.

(Example 7)
Df / h: 0.7, volume resistivity: 12.5 except that the carrier had a volume average particle diameter of 71 μm (true specific gravity 5.3) and the coating layer formulation was as follows: [Carrier 7] having [Log (Ω · cm)] and magnetization of 69 Am ² / kg was obtained.

・ Acrylic resin solution (solid content 50 wt%) 34.2 parts ・ Guanamine solution (solid content 70 wt%) 9.7 parts ・ Acid catalyst (solid content 40 wt%) 0.19 parts ・ Silicone resin solution [solid content 20% by weight
(SR2410: manufactured by Toray Dow Corning Silicone)] 292.9 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 0.42 parts ・ Conductive fine particles EC-500 (ITO-treated titanium dioxide): manufactured by Titanium Industry Co., Ltd., particle size: 0.43 μm, true specific gravity: 4.6 [SF-1: 165] 85 parts Toluene 800 parts [Carrier 7] and [Toner 1] thus obtained were converted into a developer by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 81% with respect to the core material.

(Example 8)
In Example 2, Df / h: 1.1, volume resistivity: 13.9 [same] except that sintered ferrite having a volume average particle size of 36 μm (true specific gravity 5.4) having a low magnetization was used. Log (Ω · cm)] and magnetization: 35 Am ² / kg [Carrier 8].
[Carrier 8] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 71% with respect to the core material.

Example 9
In Example 2, Df / h: 1.1, volume resistivity: 14.1 [Log] except that 35 μm sintered ferrite (true specific gravity 5.5) with high magnetization and volume average particle diameter was used. (Ω · cm)] and magnetization: 93 Am ² / kg [Carrier 9].
[Carrier 9] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 71% with respect to the core material.

(Comparative Example 1)
[Carrier coating layer]
・ Silicone resin solution [solid content: 23% by weight
(SR2410: manufactured by Toray Dow Corning Silicone)] 432.2 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone Co.)] 0.66 parts Aluminum oxide: AKP-30, manufactured by Sumitomo Chemical Co., Ltd.
[Particle size: 0.31 μm, true specific gravity: 4.4, SF-1: 132] 145 parts Carbon black MA100R (Mitsubishi Chemical Industry Co., Ltd.) 20 parts Toluene 300 parts are dispersed with a homomixer for 10 minutes, A silicone resin coating film forming solution was obtained.
Using 5,000 parts of a sintered ferrite powder (true specific gravity 5.5) having a volume average particle size of 35 μm as a core material, the film thickness after drying the coating film forming solution on the core material surface is 0.35 μm. It was applied and dried at a coater internal temperature of 40 ° C. using a Spira coater (Okada Seiko Co., Ltd.) The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm, Df / h: 0.9, volume resistivity: 12.9 [Log (Ω · cm)], magnetization: 68 Am ² / kg [ Carrier 10] was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 102% with respect to the core material.
[Carrier 10] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 2)
[Carrier coating layer]
・ Silicone resin solution [solid content: 23% by weight
(SR2410: manufactured by Toray Dow Corning Silicone)] 432.2 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone)] 0.66 parts-Conductive fine particles: EC-700 manufactured by Titanium Industry Co., Ltd.
[Particle size: 0.41 μm, true specific gravity: 4.3, SF-1: 151] 145 parts-300 parts of toluene was dispersed with a homomixer for 10 minutes to obtain a silicone resin coating film forming solution.
Using 5,000 parts of a sintered ferrite powder (true specific gravity 5.5) having a volume average particle size of 35 μm as a core material, the film thickness after drying the coating film forming solution on the core material surface is 0.35 μm. It was applied and dried at a coater internal temperature of 40 ° C. using a Spira coater (Okada Seiko Co., Ltd.) The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm, Df / h: 0.9, volume resistivity: 12.9 [Log (Ω · cm)], magnetization: 68 Am ² / kg [ Carrier 11] was obtained. The conductive fine particles contained in the resin coating layer at this time had a coverage of 79% with respect to the core material.
[Carrier 11] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 3)
In Example 1, Df / h: 1.2, volume resistivity: 15.3 [Log (), except that the amount of conductive fine particles EC-500 was reduced from 145 parts by weight to 75 parts by weight. Ω · cm)] and magnetization: 68 Am ² / kg [Carrier 12]. The coverage of the conductive fine particles contained in the resin coating layer at this time was 41% with respect to the core material.
[Carrier 12] and [Toner 1] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Table 2.

(Comparative Example 4)
Df / h: 1.9, volume resistivity: 13.1 [Log (Ω), except that the coating layer formulation described below was changed in the formulation ratio of acrylic resin and silicone resin. Cm)] and magnetization: 68 Am ² / kg [Carrier 13]. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 71% with respect to the core material.

・ Acrylic resin solution (solid content 50 wt%) 17.1 parts ・ Guanamine solution (solid content 70 wt%) 4.85 parts ・ Acid catalyst (solid content 40 wt%) 0.10 parts ・ Silicone resin solution [solid content 20% by weight
(SR2410: manufactured by Toray Dow Corning Silicone Co.)] 216.2 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.) 1.68 parts. Conductive fine particles EC-500: manufactured by Titanium Industry Co., Ltd. [particle diameter: 0.43 μm, true specific gravity: 4.6, SF-1: 165] 145 Part 1600 parts of toluene [Carrier 13] and [Toner 1] obtained in this way were developed into a developer by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 5)
Df / h: 0.4, volume resistivity: 16.5 [Log (Ω), except that the coating layer formulation described below was changed in the formulation ratio of acrylic resin and silicone resin. Cm)] and magnetization: 68 Am ² / kg [Carrier 14]. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 71% with respect to the core material.

・ Acrylic resin solution (solid content 50 wt%) 158.8 parts ・ Guanamine solution (solid content 70 wt%) 49.6 parts ・ Acid catalyst (solid content 40 wt%) 0.88 parts ・ Silicone resin solution [solid content 20% by weight
(SR2410: manufactured by Toray Dow Corning Silicone)] 743.2 parts Aminosilane [100 wt% solid content
(SH6020: manufactured by Toray Dow Corning Silicone Co., Ltd.)] 1.68 parts-Conductive fine particles EC-500: manufactured by Titanium Industry Co., Ltd. [particle size: 0.43 μm, true specific gravity: 4.6, SF-1: 165] 145 parts ・ Toluene 1600 parts
[Carrier 14] and [Toner 1] thus obtained were developed into a developer by the same method as in Example 1 and evaluated. The results are shown in Tables 1 and 2.

  From Tables 1 and 2, it can be seen that according to the present invention, no carrier adhesion occurs even during long-term running, an image with good image density reproducibility can be obtained, and no color smearing occurs. The reason why white spots occurred after long-term running in Example 4 is that the volume resistivity of the carrier was less than 10 [Log (Ω · cm)] because the amount of conductive fine particles was increased.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus equipped with a process cartridge that uses a developer of the present invention. It is a schematic block diagram which shows an example of the process cartridge which uses the developing agent of this invention. It is explanatory drawing for demonstrating the measuring method of the thickness h of a carrier coating layer. It is a schematic perspective view of the resistance measurement apparatus of the carrier used by this invention.

Explanation of symbols

(About Figure 1)
DESCRIPTION OF SYMBOLS 100 Device body 1 Photoconductor 2A, 2B, 2C, 2D Process cartridge 3 Charging unit 4 Primary transfer roller 5 Cleaning unit 6 Exposure unit 7 Paper feed cassette 8 Transfer belt 9 Fixing unit 10A, 10B, 10C, 10D Development unit 51 Paper discharge Guide 52 Paper discharge roller 53 Paper discharge part 54 Secondary transfer 55 Paper feed roll 200A, 200B, 200C, 200D Developer replenisher (About FIG. 3)
h1 to h4 thickness of each resin part D particle diameter (about FIG. 4)
31 cell 32a, 32b electrode 33 carrier

Claims (12)

A carrier having a coating layer containing a binder resin and conductive fine particles on a carrier core material,
The ratio (Df) between the volume average particle diameter Df of the conductive fine particles and the thickness h of the resin part existing between the core material surface and the particles, at least the shape factor SF-1 of the conductive fine particles is 160 or more. / h) is 0.5 <a [Df / h] <1.5, Ri der coverage of 70% or more of the conductive fine particles to the core material represented by the following formula (1),
The carrier for an electrophotographic developer, wherein the conductive fine particles are obtained by subjecting inorganic fine particles to a conductive treatment with an ionic liquid .
[Equation 1]
Formula (1)
Coverage (%) = ((Ds × ρs × W) / (4 × Df × ρf)) × 100
(Wherein, Ds: volume average particle diameter of carrier core material, ρs: true specific gravity of carrier core material, W: ratio of addition amount of conductive fine particles to carrier core material, Df: volume average particle diameter of conductive fine particles, ρf: represents the true specific gravity of the conductive fine particles. The carrier for an electrophotographic developer according to claim 1 , wherein the ionic liquid is an ionic organic compound containing an organic cationium salt and an organic acid anion. The carrier for an electrophotographic developer according to claim 2 , wherein any one of ammonium salt, imidazolium, pyridinium, and phosphonium is used as the organic cationium salt. The carrier for an electrophotographic developer according to claim 2 , wherein any one of tetrafluoroboron, hexafluorophosphate, trifluorocarbon sulfonyl, and di (fluorocarbon sulfonyl) is used as the organic acid anion. The volume resistivity of the carrier, 10 [Log (Ω · cm )] or 16 [Log (Ω · cm) ] electrophotographic developer according to any one of claims 1 to 4, characterized in that less is For carrier. Electrophotographic developer carrier according to any one of claims 1 to 5, characterized in that the volume average particle diameter of the carrier is 20μm or more 65μm or less. Electrophotographic developer carrier according to any one of claims 1 to 6 wherein the binder resin is characterized in that it comprises at least silicone resin. The carrier for an electrophotographic developer according to any one of claims 1 to 7 , wherein the binder resin contains at least an acrylic resin and a silicone resin. ^{1000 ((10 3 / 4π)} A / m) Magnetic moment in the, 40 ^(Am 2 / kg) or 90 according to any one of claims 1 to 8, characterized in that a ^(Am 2 / kg) or less Carrier for electrophotographic developer. A toner containing at least a binder resin and a pigment, an electrophotographic developer, wherein the carrier is contained according to any one of claims 1 to 9. An image forming method in which an image carrier and at least one means selected from a charging means, a developing means, and a cleaning means are integrally supported as an image forming process, and a process cartridge that is detachable from the main body of the image forming apparatus is used. The image forming method according to claim 10 , wherein the developer according to claim 10 is used for the developing unit. An image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier, a developing unit that develops the electrostatic latent image using a developer to form a visible image, and Transfer means for transferring a visible image to a recording medium, fixing means for fixing the transferred image transferred to the recording medium, and cleaning means for cleaning the transfer residual toner on the image carrier after the transfer. An image forming apparatus provided with at least the image forming method according to claim 11 .

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