JP4813350B2 - Image forming apparatus, process cartridge, and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus that forms an image by an electrostatic copying process such as a copying machine, a facsimile machine, and a printer, a process cartridge provided in the image forming apparatus, and an image forming method applied to the image forming apparatus.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, a uniformly charged image carrier surface is exposed to form a latent image, and the latent image is developed into a toner image. Transferring onto a transfer material such as recording paper is performed. The transfer material carrying the toner image passes through the fixing device, and the toner is fixed on the transfer material by applying heat and pressure.

  In such an image forming apparatus, when developing a latent image on an image carrier, a two-component developer composed of a toner and a carrier is often used because of its excellent developability. In particular, in a color image forming apparatus that forms a full-color or multi-color image, a two-component developer in which a toner and a carrier are mixed is used in most developing apparatuses from the viewpoint of color developability and color mixing.

  In this two-component developer method (two-component development method), the toner and the carrier are agitated in the developing device, and the toner is charged with electric charge from the carrier due to the frictional charge and electrostatically applied to the outer surface of the carrier. It will be in the state which adhered to. The carrier carrying the toner is conveyed to the development area, and under the condition that the development bias is applied, the toner is separated from the carrier and electrostatically adheres to the latent image portion of the image carrier to form a toner image. The

  For this reason, in the two-component development system, in order to provide a highly durable image satisfying high stability, it is important that a stable charge amount is imparted to the toner from the carrier during stirring. For this purpose, it is important that the charge imparting ability of the carrier is stable even before and after long-time use.

  However, in the developing device in the normal two-component developing system, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing tank. For this reason, the carrier stirred together with the toner in the developing tank deteriorates as the stirring frequency increases, such as peeling of the resin coat on the carrier surface and adhesion of the toner to the surface. For example, the resistance value of the carrier In addition, the chargeability of the developer is gradually lowered, the developability of the developer is increased, and problems such as an increase in image density and occurrence of fogging are induced.

  As a solution to this problem, a developing device that suppresses the change in the charge amount and stabilizes the image density by adding a carrier together with the toner consumed by the development and replacing the carrier in the developing unit little by little, A so-called trickle developing device is known (for example, see Patent Document 1).

  However, since the replenished carrier is the same as the carrier accommodated in the developing tank of the developing device, the proportion of the carrier deteriorated in the developing tank increases as it is used for a long time, and the image density It becomes difficult to suppress problems such as a rise.

  On the other hand, it has been proposed that toner is contained in a carrier having a higher resistance value than that of a carrier stored in advance in the developing device to maintain chargeability and suppress deterioration in image quality (see, for example, Patent Document 2). ).

  Further, it has been proposed that toner is contained in a carrier that imparts a higher charge amount to the toner to maintain chargeability and suppress deterioration in image quality (see, for example, Patent Document 3).

  However, in these methods, since the amount of the carrier to be replaced differs depending on the difference in toner consumption, the resistance or charge amount of the developer in the developing machine changes, and the image density tends to fluctuate, which is not satisfactory. There wasn't.

  Further, a method has been proposed in which a plurality of types of replenishment toners containing a carrier having different physical properties from those of carriers stored in advance in the developing device are used, and each toner is replenished sequentially (see, for example, Patent Document 4).

  However, in actuality, the specific gravity of the carrier and the toner is extremely different from the replenishment of the replenishment toner containing a plurality of carriers having different physical properties in one toner replenishing container so that the replenishment toner is not recombined. Therefore, it is very difficult, and since there is much toner relative to the carrier, the carrier is likely to be deteriorated, and a stable image cannot be obtained over a long period of time.

  Further, as described in Patent Document 4, in order to increase the resistance value of the carrier for replenishment, the resistance value can be increased when the coating amount of the silicone coat layer coated on the carrier core material is simply increased. As a result, the charge amount of the carrier is lowered, and as a result, the image reproducibility of the developed image is lowered and the background portion is stained.

  For this reason, in the trickle development method, in order to obtain more stable development characteristics, it is important that the carrier can maintain a stable charge imparting ability even in long-term use.

  The granular carrier used in the two-component development system is for preventing toner filming on the carrier surface, forming a uniform carrier surface, preventing surface oxidation, preventing moisture sensitivity deterioration, extending the life of the developer, and the carrier of the photoreceptor. For the purpose of protecting from scratches or abrasion due to corrosion, controlling the charge polarity or adjusting the charge amount, it is usually coated with an appropriate resin material (see, for example, Patent Document 5), and various additions to the coating layer A method of adding an agent is performed (for example, see Patent Documents 6 to 9).

  Further, Patent Document 9 proposes a material in which an additive is attached to the carrier surface, and also proposes a material in which conductive particles larger than the coating layer thickness are contained in the coating layer (for example, , See Patent Document 10).

  Further, it has been proposed to use a carrier coating material mainly composed of a benzoguanamine-n-butyl alcohol-formaldehyde copolymer (see, for example, Patent Document 11), and a cross-linked product of a melamine resin and an acrylic resin is used as a carrier. It has been proposed to be used as a covering material (for example, see Patent Document 12).

  However, there are still problems with durability or heat resistance, and there are problems of spent toner on the carrier surface, resulting in unstable charge amount, and occurrence of toner fog and the like. Furthermore, it is necessary to improve the environmental resistance.

  In addition, in order to obtain a stable charging characteristic in a developer used in the two-component development method, a resistance adjuster has been conventionally included in a carrier. Black is frequently used.

  However, in color image formation, there are concerns about film smearing on the surface of the carrier and color contamination due to the transfer of carbon black into the color image due to carbon black desorption.

  Various methods have been proposed so far as means for suppressing the occurrence of such a phenomenon.

  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 coating layer (see, for example, Patent Document 13).

  Further, a carrier is proposed in which the coating layer has a carbon black concentration gradient in the thickness direction, the carbon black concentration decreases toward the surface of the coating layer, and there is no carbon black on the surface of the coating layer. (For example, refer to Patent Document 14).

  Further, there has been proposed a two-layer coated carrier in which an inner coating layer containing conductive carbon is provided on the surface of core material particles, and a surface coating layer containing a white conductive material is further provided thereon ( For example, see Patent Document 15).

  However, in recent years, in response to demands from consumers, electrophotographic image forming apparatuses have a tendency to increase the speed, and accordingly, the stress received by the developer has increased dramatically. For this reason, even the proposals of Patent Document 13 to Patent Document 15 cannot cope with the recent increase in stress, and it is difficult to completely prevent the occurrence of color stains.

  Here, in the electrophotographic carrier having at least a surface coating layer made of a resin, the resin has at least an acrylic resin and a silicon resin, and the ratio of the acrylic resin in the coating layer made of the acrylic resin and the silicon resin is 10 to 90 wt%. Therefore, it is possible to provide a carrier for a two-component developer that can form a fine image over a long period of time because there is no toner spent on the carrier surface and the coating resin film is less shaved. There has been proposed a technology that provides a developer with little change with time in the amount of developer pumped up on a roller, a developing device using the developer, and a developing method (see, for example, Patent Document 16).

Further, in an electrophotographic carrier having a coating film composed of at least a binder resin and particles, the relationship between the particle diameter (D) of the particles and the film thickness (h) of the coating film is 1 <[D / h] <10. The particles are surface-treated with an aluminum coupling agent represented by the following general formula (1) alone or in combination of two or more thereof, and / or the coating film is an aluminum represented by the general formula (1). Technology that can provide a highly durable electrophotographic carrier, developer, image forming method, storage container, and image forming apparatus for a two-component developer by containing one or more types of coupling agents Has been proposed (see, for example, Patent Document 17).
Japanese Patent Publication No. 2-21591 Japanese Patent Laid-Open No. 3-145678 Japanese Patent Laid-Open No. 11-223960 JP-A-8-234550 JP 58-108548 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 2003-167389 A JP 2003-345070 A

  The image forming apparatus of the two-component development system is excellent in durability, can suppress the occurrence of carrier adhesion in the solid image portion, has no color stain, and has a stable high image quality over time. An object of the present invention is to provide an image forming apparatus that can be achieved, and to provide a process cartridge provided in the image forming apparatus, and an image forming method applicable to the image forming apparatus.

The above problems are solved by the following inventions (1) to (13) .
(1) At least an image carrier, a latent image forming unit that forms an electrostatic latent image on the image carrier, toner and a carrier (where the carrier is a core material) An image forming apparatus comprising: a developing unit that develops a visible image by developing with a developer including a carrier having a coating layer that covers the core material; and a means for replenishing the carrier; A developer collecting means for collecting the developer of the carrier , wherein the coating layer of the core material of the carrier contains inorganic fine particles, and the inorganic fine particles have a coverage of 70% or more with respect to the core material, The image forming apparatus, wherein the developer collecting means selectively carries out carrier development on at least a low-resistance carrier onto the image carrier , and collects the developed carrier and toner by cleaning.

  (2) The image forming apparatus according to (1), wherein the means for replenishing the carrier is a developer replenishing means for replenishing the developing means with a replenishing developer containing toner and a carrier.

  (3) The image forming apparatus according to (2), wherein the developer replenishing means includes a developer storage container made of a bag-like member that is reduced in volume as the internal pressure decreases.

  (4) The image forming apparatus according to any one of (2) and (3), wherein the replenishment developer has a weight ratio of carrier to toner of 3% by weight to 20% by weight. .

  (5) The image forming apparatus according to any one of (1) to (4), wherein a plurality of the developer collecting units are provided.

  (6) The covering layer of the carrier core material contains at least a binder resin and an ionic liquid or an ionic liquid-derived material, according to any one of (1) to (5) above. Image forming apparatus.

And (7) the particle diameter of the inorganic fine particles (D), the thickness of the coating layer (h) is, 0.5 <[D / h] the above (1), characterized in that <1.5 The image forming apparatus according to any one of (6) .

(8) The volume specific resistance of the carrier is 10 [Log (Ω · cm)] or more and 16 [Log (Ω · cm)] or less, wherein any of the above (1) to (7) The image forming apparatus described.

(9) The image forming apparatus according to any one of (1) to (8) , wherein the carrier core material has a volume average particle diameter of 20 μm to 65 μm.

(10) The covering layer binder resin of the carrier core material contains at least one resin of at least a silicone resin or an acrylic resin, as described in any one of (6) to (9) above Image forming apparatus.

(11) The magnetic moment at 1000 (10 ³ / 4π · A / m) of the carrier is 40 (Am ² / kg) or more and 90 (Am ² / kg) or less. (10) The image forming apparatus according to any one of (10) .

(12) An image bearing member and at least an electrostatic latent image formed on the image bearing member with toner and a carrier (wherein the carrier is a carrier having a core material and a coating layer covering the core material). A developing unit that integrally supports a developing unit that forms a visible image with a developer, and is detachably mounted on the main body of the image forming apparatus, the unit supplying the carrier to the main body of the image forming apparatus, and A developer collecting means for collecting the developer in the developing means, wherein the core coating layer of the carrier contains inorganic fine particles, and the inorganic fine particles have a coverage of 70% or more with respect to the core material. contained, the developer collecting means, carrier developed to at least the low-resistance carrier selectively said image bearing member, and, and collecting the developed carrier and toner by the cleaning process Cartridges.

(13) An electrostatic latent image is formed on an image carrier, and the electrostatic latent image is converted into a toner and a carrier (wherein the carrier is a carrier having a core material and a coating layer covering the core material). An image forming method for developing a visible image by developing with a developing unit containing a developer containing inorganic particles , wherein the coating layer of the carrier core material contains inorganic fine particles, and the inorganic fine particles are applied to the core material. On the other hand, a covering ratio of 70% or more is used, and a means for replenishing the carrier and a developer collecting means for collecting the developer in the developing means are used. The developer collecting means selects at least a low-resistance carrier. An image forming method comprising : developing the carrier on the image carrier and collecting the developed carrier and toner by cleaning.

  According to the image forming apparatus, the process cartridge, and the image forming method of the present invention, the charging property of the developer is stable even in long-term use, the durability is excellent, and the carrier adheres to the solid image portion during running time. A fine image can be formed over a long period of time without being generated, and a high-quality image free from color stains can be provided.

  Hereinafter, an image forming apparatus and the like of the present invention will be described in detail according to embodiments with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, image forming units 2 </ b> A, 2 </ b> B, 2 </ b> C, and 2 </ b> D having four photoreceptors 1 are attached to and detached from the image forming apparatus 100. Wearing is possible. A transfer device in which the transfer belt 8 is rotatably mounted between a plurality of rollers is disposed in the approximate center of the image forming apparatus 100.

  The lower surface of the transfer belt 8 is disposed so that the photoreceptors 1 provided in the image forming units 2A, 2B, 2C, and 2D are in contact with each other. In correspondence with the image forming units 2A, 2B, 2C, and 2D, developing devices 10A, 10B, 10C, and 10D having different toner colors are arranged.

  Each of the image forming units 2A, 2B, 2C, and 2D is a unit having the same configuration. The image forming unit 2A forms an image corresponding to magenta, and the image forming unit 2B displays an image corresponding to cyan. The image forming unit 2C forms an image corresponding to the yellow color, and the image forming unit 2D forms an image corresponding to the black color.

  In each of the developing devices 10A, 10B, 10C, and 10D disposed in the image forming units 2A, 2B, 2C, and 2D, a two-component developer including toner and a carrier is used, and a developer replenishing device 200 described later is used. From the above, trickle development that can replenish toner according to the output of a toner density sensor (not shown) provided in the developer container 14 and also replenish the carrier to discharge the old developer and replace the developer. The method is adopted.

  In the space above the image forming units 2A, 2B, 2C, and 2D, developer replenishing devices 200A, 200B, 200C, and 200D used for the trickle developing method are arranged. The developer replenishing device 200 is a configuration for replenishing the developing device 10 with a new toner different from the toner to be supplied to the photosensitive drum 1 and a new carrier, and the configuration is shown in FIG. .

  As shown in FIG. 1, an exposure device 6 as a writing unit is disposed below the image forming units 2A, 2B, 2C, and 2D.

  The exposure device 6 is arranged in four laser diode (LD) light sources prepared for each color, a set of polygon scanners composed of, for example, a six-sided polygon mirror and a polygon motor, and the route of each light source. Further, it is composed of a lens such as an fθ lens, a long cylindrical lens, or a mirror. Laser light emitted from the laser diode is deflected and scanned by a polygon scanner and is irradiated onto the photosensitive member 1.

  As shown in FIG. 1, a fixing device 9 is provided between the transfer belt 8 and the developer supply device 200 for fixing the image on the transfer paper onto which the image has been transferred. A discharge path 51 is formed on the downstream side of the fixing device 9 in the conveyance direction of the transfer sheet, and the transfer sheet conveyed there can be discharged onto a discharge tray 53 by a discharge roller pair 52.

  A paper feed cassette 7 that can store transfer paper is disposed below the image forming apparatus 100.

  Next, the operation of the image forming apparatus 100 in image formation will be described.

  When the image forming operation is started, each photoconductor 1 rotates in the clockwise direction in FIG. Then, the surface of each photoconductor 1 is uniformly charged by the charging roller 301 of the charging unit 3. Then, laser light corresponding to a magenta image by the exposure device 6 is applied to the photoreceptor 1a of the image forming unit 2A, and laser light corresponding to a cyan image is applied to the photoreceptor 1b of the image forming unit 2B. The 2C photoconductor 1c is irradiated with a laser beam corresponding to a yellow image, and the photoconductor 1d of the image forming unit 2D is irradiated with a laser beam corresponding to a black image, and a latent image corresponding to image data of each color. Are formed respectively. Each latent image reaches the position of the developing devices 10A, 10B, 10C, and 10D by the rotation of the photosensitive member 1, and is developed there by toners of magenta, cyan, yellow, and black. Become.

  On the other hand, the transfer paper is fed from the paper feed cassette 7 by the separation paper feed unit, and the toner image formed on each photoconductor 1 by the registration roller pair 55 provided immediately before the transfer belt 8. It is conveyed at the same timing. The transfer paper is charged to a positive polarity by a paper suction roller 54 disposed near the entrance of the transfer belt 8, and thereby electrostatically attracted to the surface of the transfer belt 8. The transfer paper is conveyed while being adsorbed to the transfer belt 8, and magenta, cyan, yellow, and black toner images are sequentially transferred to form a four-color superimposed full-color toner image. . The transfer paper is melted and fixed by applying heat and pressure by the fixing device 9, and then the transfer paper on which the toner image is fixed passes through the paper discharge system and is discharged from the upper portion of the image forming apparatus 1. The paper is discharged to the tray 53.

  FIG. 2 is a schematic cross-sectional view showing a developing device provided in the image forming apparatus of the present invention and the structure around it. In FIG. 2, a developer replenishing device 200 for replenishing a developer composed of new toner and carrier is provided in the developing device 10 above the developing device 10. Below the developing device 10, a developer collecting device 300 that collects the excess developer in the developing device 10 is provided.

  The developing device 10 includes a housing 15 having a developer accommodating portion 14 that accommodates a two-component developer composed of toner and a carrier, and the photosensitive member 1 serving as an image carrier on the opening side of the housing 15. A developing roller 12 as a developer carrying member disposed so as to rotate; and two conveying screws 11a and 11b as developer stirring and conveying members disposed so as to rotate within the developer container 14. The main part is composed of the layer thickness regulating member 13 disposed in pressure contact with or close to the surface of the developing roller 12.

  Among these, the developing roller 12 is a cylindrical sleeve 121 that rotates and includes a magnet roll 120 fixed inside. Further, the developer accommodating portion 14 is divided into two by a central partition 14c, and is composed of accommodating spaces 14a and 14b that are communicated by communicating portions on both ends, and a conveying screw 11a that rotates in the accommodating spaces 14a and 14b. The developer is circulated and conveyed between the storage spaces 14a and 14b while being agitated by 11b. The layer thickness regulating member 13 has a double structure of a nonmagnetic member and a magnetic member, and is arranged so that the tip thereof faces a predetermined magnetic pole of the magnet roll 120.

  As shown in FIG. 2, the developer supply device 200 includes a developer container 230 that stores a two-component developer for supply, and a two-component developer in the developer container 230 that is sent to the developer container 14. And a developer replenisher 220 to be supplied. The developer replenisher 220 is provided between the developer container 230 and the developing device 10 so as to be connected to each other.

  The detailed configuration of the developer supply device 200 will be described with reference to FIG.

  The developer recovery apparatus 300 sends a recovery container 330 that recovers an excess of the two-component developer in the developer storage unit 14 and a developer that overflows and overflows from the developer storage unit 14 to the recovery container 330. A recovery pipe 331 is used as a developer recovery means. The collection pipe 331 is disposed so that the upper opening 331a is positioned at a predetermined height in the developer accommodating portion 14, and collects the developer that exceeds the upper opening 331a at the predetermined height. It has become.

  The developer recovery device of the present invention is not limited to the above-described configuration. For example, a developer discharge port is opened at a predetermined location of the housing 15 and a developer recovery port is provided instead of the recovery pipe 331. A conveying member such as a collecting screw as a developer discharging means may be installed in the vicinity, and the developer discharged from the developer discharging port may be transferred to the collecting container 330.

  Moreover, it is also possible to provide this collection | recovery screw in the edge part or the inside of the collection | recovery pipe 331 of this embodiment.

  Using such a developing device, development is performed as follows.

  First, as shown in FIG. 2, the two-component developer previously stored in the developer storage portion 14 is stirred and sufficiently mixed by the conveying screws 11a and 11b and frictionally charged. 12 is attached to the surface of the sleeve 121 in layers.

  The developer in the form of a layer adhering to the developing roller 12 is regulated to a predetermined thickness by the layer thickness regulating member 13 to be a uniform layer, and then faces the photoreceptor 1 as the sleeve 121 rotates. To the developing area D to be transported. In the developing area D, the toner of the two-component developer is electrostatically adsorbed and developed on the latent image formed on the photosensitive member 1 according to the image of the original on the image forming apparatus main body 100 (see FIG. 1). And a toner image is formed on the photoreceptor 1.

  The toner image formed on the photoreceptor 1 is transferred and fixed on a transfer material P (not shown) as a recording sheet on the image forming apparatus main body 100 side.

  By repeating this developing operation, the toner contained in the developer in the developer accommodating portion 14 is consumed and gradually decreases. When this toner reduction is detected by the toner concentration sensor, the developer replenishment is performed. The developer replenisher 220 of the apparatus 200 is driven, whereby the two-component developer accommodated in the developer container 230 is replenished. The replenished new two-component developer is agitated by the conveying screws 11a and 11b in the developer accommodating portion 14 and sufficiently mixed with the two-component developer accommodated before replenishment.

  Further, since the two-component developer supplied from the developer supply device 200 is supplied to the developer accommodating portion 14 together with the toner at a predetermined ratio, the amount of developer in the developer accommodating portion 14 is as follows. It becomes gradually excessive. The two-component developer that becomes excessive in the developer accommodating portion 14 overflows beyond the regulated height of the accommodating portion 14 and is accommodated in the collecting container 330 through the collecting pipe 331 of the developer collecting device 300.

  In the trickle developing type developing device 10, most of the deteriorated carrier is recovered by the developer recovery device 300, but some of the carrier may remain in the developer accommodating portion 14 for a long time, In the image forming apparatus 100, when the amount of toner consumption is small, the carrier replacement amount in the developer accommodating portion 14 is small, and the period during which the carrier stays in the developer accommodating portion 14 may become long.

  When the toner and the carrier are mixed by the conveying screws 11a and 11b in the developer accommodating portion 14, the toner and the carrier or the carriers come into contact with each other, and the film is likely to be scraped on the surface of the carrier due to the friction.

  Since the surface film of the carrier is a place where charge is generated, if the phenomenon of film scraping becomes significant, the ability to impart charge to the toner decreases, and stable development characteristics cannot be obtained.

  In the present invention, the carrier accommodated in the developer accommodating portion 14 has a coating layer (coat layer) formed on the surface of the core material as shown in FIG. 8, and the coating layer contains predetermined particles. It is.

  Some of the particles are convex with respect to the coating layer, and the impact on the carrier surface due to contact with the toner and other carrier particles is reduced by the particles. For this reason, the ratio of occurrence of film scraping on the carrier surface is greatly suppressed. In addition, the spent component of the toner adhering to the carrier surface during stirring is scraped off by the particles, thereby preventing the occurrence of toner spent.

  If the film scraping on the carrier surface or the occurrence of toner spent on the carrier surface becomes significant, a decrease in the electrical resistance value of the carrier and the charge amount of the developer is induced, so that stable development characteristics cannot be obtained.

  Further, the carrier resistance value is reduced, so that the phenomenon of carrier adhesion in the solid image portion is likely to occur, image deterioration and durability deterioration due to a decrease in the developer amount in the developer container 14 occur, and on the image. The fineness of the image decreases due to the carrier adhering.

  For this reason, the carrier having a lowered resistance value is selectively subjected to carrier development, and the developed carrier and toner are cleaned and recovered on the photoreceptor without being transferred. There is no particular change in the apparatus, and the control of the background potential is changed from the control during normal printing, and the carrier whose resistance is lowered is selectively developed on the photoconductor. Actually, carrier development is forcibly carried out by increasing the voltage within the range of 100 V to 200 V from the normal background potential. For example, in normal control, printing was performed with an OPC charging potential of −720 V and a developing bias of −600 V (background potential of 120 V), but at the end of printing, the charging potential was −920 V and the developing bias of −600 V (background of the background). The carrier is developed at a potential of 320 V), and this is cleaned and recovered without transferring. The setting for carrier development differs depending on the system (reduction in resistance due to carrier film scraping), but is set according to the coverage (consumed image area) for the number of printed sheets. When there is a large amount of coverage, film removal does not progress (resistance decreases) as a carrier, and no discharge is performed by carrier development. Further, since a large amount of carrier is supplied together with the toner, surplus agent is generated, but it is recovered by overflowing from the developing portion as described above. When the coverage is small (low image area), toner replacement is small and the idle state continues in the developing machine, so that the film scraping progresses (resistance decreases) as the carrier. In this case, carrier development is performed to forcibly discharge (collect) the carrier whose resistance has been lowered.

  The carrier used in the image forming apparatus of the present invention will be described later.

  Hereinafter, the configuration of the developer supply device 200 will be described in detail with reference to FIG.

  FIG. 3 is a schematic configuration diagram of a developer supply device 200 used in the present invention.

  Inside the developer container 230 provided in the developer supply device 200 is provided a developer storage member 231 as a bag-shaped member that can be reduced in volume, and replenishes the developer storage portion 14 of the development device 10. The new toner and carrier are stored in the developer storage member 231. The developer accommodating member 231 is reduced in volume as the internal pressure decreases due to the developer being supplied to the developer accommodating portion 14.

  The developer replenisher 220 includes a screw pump 223 that is connected to the upper end of a replenishing port 15 a provided at a predetermined location of the housing 15, a nozzle 240 that is connected to the screw pump 223, and a nozzle 240. And an air supply means 260 provided in a connected manner, and is driven in accordance with a detection signal from a toner concentration sensor (not shown) installed in the developer accommodating portion 14 so that an appropriate amount of developer is supplied from the developer accommodating unit 230. The developer is supplied to the developer container 14.

  Between the screw pump 223 and the nozzle 240, there is a transport tube 221 as a developer transport passage communicating with the screw pump 223. The transport tube 221 is preferably made of a rubber material such as polyurethane, nitrile rubber, and EPDM (ethylene-propylene-diene rubber) that is flexible and excellent in toner resistance.

  As shown in FIG. 3, the developer supply device 200 has a container holder 222 for supporting a developer container 230 as a developer container. The container holder 222 is made of a rigid material such as resin. Made of high material.

  The developer container 230 includes a developer storage member 231 as a bag-like member formed of a flexible sheet material, and a base portion 232 as a discharge port forming member that forms a developer discharge port.

  As a material of the developer storage member 231, it is preferable to use a plastic sheet such as a polyethylene sheet, a polyester sheet, or a polyurethane sheet.

  Further, the base part 232 is provided with a sealing material 233 formed of sponge, rubber or the like, and the sealing material 233 is provided with a cross-shaped cut. Then, by passing the nozzle 240 of the developer replenisher 220 through this notch, the developer container 230 and the developer replenisher 220 are connected and fixed.

  In the present embodiment, the base portion 232 is provided below the developer container 230. Here, the state where the base part 232 is provided below means that the base part 232 faces downward in the developer container 230 in a state where the developer container 230 is disposed in the developer supply device 200. It shows that it is provided at a position including a vertical component.

  The position where the base 232 is provided in the developer container main body is not limited to the above-described example. In the state where the developer container 230 is disposed in the developer supply device 200, the developer container is accommodated. The main body 230 may be provided in the horizontal direction, or may be provided in an oblique direction.

  In addition, the developer container 230 is appropriately replaced with a new one as the toner is consumed. By adopting these configurations, the developer container 230 can be easily attached and detached, and the toner leakage at the time of replacement and use is effective. To prevent.

  4A is an external view showing a schematic configuration of a nozzle 240 provided in the developer replenisher 220, FIG. 4B is an axial sectional view, and FIG. FIG. 4B is a cross-sectional view taken along line AA in FIG. As shown in FIG. 4B, the nozzle 240 has a double tube structure including an inner tube 241 and an outer tube 242 that accommodates the inner tube 241 therein. The inside of the inner tube 241 serves as a developer flow path 241a as a developer transport path for discharging the developer in the developer container 230. The toner in the developer container 230 is sucked by the suction force of the screw pump 223 and is drawn into the screw pump 223 through the developer flow path 241a.

  FIG. 5 is a cross-sectional view showing a schematic configuration of the screw pump 223. The screw pump 223 employs a configuration called a uniaxial eccentric screw pump. In this configuration, a rotor 224 and a stator 225 are provided inside. The rotor 224 has a shape in which a circular cross section is twisted in a spiral shape, is formed of a hard material, and is fitted inside the stator 225. On the other hand, the stator 225 is formed of a rubber-like flexible material, and has a hole whose elliptical cross section is spirally twisted, and the rotor 224 is fitted into this hole. Further, the helical pitch of the stator 225 is formed to be twice as long as the helical pitch of the rotor 224. The rotor 224 is connected to a drive motor 226 for rotating the rotor 224 via a universal joint 227 and a bearing 228.

  In this configuration, the toner and carrier transported from the developer container 230 through the developer flow path 241 a of the nozzle 240 and the transport tube 221 enter the inside from the toner suction port 223 a of the screw pump 223. Then, it enters the space formed between the rotor 224 and the stator 225 and is sucked and conveyed in the right direction in FIG. 3 as the rotor 224 rotates. The toner that has passed through the space between the rotor 224 and the stator 225 falls downward from the toner dropping port 223b and is supplied into the developing device 10 through the developer supply port 15a of the developing device 10.

  The developer replenisher 220 used in this embodiment includes an air supply unit 260 that supplies air into the developer container 230.

  As shown in FIG. 3, the air flow paths 244a and 244b are respectively connected to air pumps 260a and 260b as separate gas delivery devices via air supply paths 261a and 261b as gas supply paths.

  As shown in FIG. 4B, the air flow path 244 is provided as an air supply passage between the inner tube 241 and the outer tube 242 of the nozzle 240 of the developer replenisher 220. As shown in FIG. 4C, the air flow path 44 is composed of two flow paths 244a and 244b having a semicircular cross section independent from each other.

  Moreover, as shown in FIG. 3, a normal diaphragm type air pump can be used as the air pumps 260a and 260b. The air sent out from these air pumps 260a and 260b is supplied into the toner container 230 from air supply ports 246a and 246b as gas supply ports of the respective air channels through the air channels 244a and 244b, respectively. Each air supply port 246a, 246b is located below the toner outlet 247 as a developer outlet of the toner channel 241a in the figure. As a result, the air supplied from the air supply ports 246a and 246b is supplied to the toner in the vicinity of the toner outlet 247, and is left unused for a long period of time and the toner outlet 247 is clogged. Even in such a state, the toner blocking the toner outlet 247 can be destroyed.

  The air supply passages 261a and 261b are provided with on-off valves 262a and 262b as closing means that are opened and closed by a control signal from a control unit as gas delivery control means (not shown). The on-off valves 262a and 262b operate to open the valve when the ON signal is received from the control unit and allow air to pass therethrough, and when the OFF signal is received from the control unit to close the valve and prevent the passage of air.

  Next, the operation of the developer supply device 220 used in the image forming apparatus of the present invention will be described with reference to FIG.

  The control unit starts a developer replenishing operation by receiving a signal indicating that the toner density is insufficient from the developing device 10. In this developer replenishment operation, first, the air pumps 260a and 260b are driven to supply air into the developer container 230, and the drive motor 226 of the screw pump 223 is driven to suck and convey the developer. .

  When air is sent out from the air pumps 260a and 260b, the air enters the air flow paths 244a and 244b of the nozzle 240 from the air supply paths 261a and 261b, and is supplied into the developer container 230 from the air supply ports 246a and 246b. The The developer in the developer container 230 is agitated by the supplied air, and is in a state in which a large amount of air is contained, and fluidization is promoted.

  Further, when air is supplied into the developer container 230, the internal pressure in the developer container 230 increases. Therefore, a pressure difference is generated between the internal pressure and the external pressure (atmospheric pressure) of the developer container 230, and a force that moves the fluidized developer in the direction in which the pressure is drawn acts. As a result, the developer in the developer container 230 flows out from the pressure drawing direction, that is, from the developer outlet 247.

  In the present embodiment, the suction force by the screw pump 223 also acts, and the developer in the developer container 230 flows out from the developer outlet 247.

  As described above, the developer that has flowed out of the developer container 230 moves from the developer outlet 247 through the developer channel 241 a of the nozzle 240 into the screw pump 223 via the transport tube 221. Then, after moving through the screw pump 223, the developer falls downward from the developer dropping port 223b, and the developer is supplied into the developing device 10 from the developer supply port 15a. When a certain amount of developer supply is completed, the control unit stops driving the air pumps 260a and 260b and the drive motor 226, closes the on-off valves 262a and 262b, and ends the toner supply operation. Thus, by closing the on-off valves 262a and 262b at the end of the toner supply operation, the toner in the toner container 230 is prevented from flowing back to the air pumps 260a and 260b through the air supply passages 244a and 244b of the nozzle 240. is doing.

  The supply amount of air supplied from the air pumps 260 a and 260 b is set to be smaller than the suction amount of toner and air by the screw pump 223. Therefore, as the toner is consumed, the internal pressure of the developer container 230 decreases. Here, since the developer storage member 231 of the developer container 230 used in the present invention is formed of a flexible sheet material, the volume can be reduced as the internal pressure decreases.

  FIG. 6 is a perspective view of the developer containing member 231 filled with the developer.

  FIG. 7 is a front view showing a state where the developer in the developer containing member 231 is discharged and reduced in volume (completely deflated (completely reduced)). Here, it is desirable that the developer accommodating member 231 has, for example, a volume reduction of 60% or more (a volume shrinkage of 60% or more).

  The developer container 230 shown in FIG. 6 contains a developer composed of a novel toner and carrier. The ratio of the toner and carrier in the developer is the weight ratio of the carrier to the toner. 3 wt% or more and 20 wt% or less.

  When the weight ratio of the toner to the carrier in the developer container 230 is less than 3% by weight, the carriers aggregate in the developer container 231 and stable supply to the developing device 10 is obtained. Absent. On the other hand, when the amount exceeds 20% by weight, the amount of carrier supplied to the developing device 10 is insufficient with respect to the amount of toner, and a stable toner charge amount cannot be obtained in the developing device 10.

  Next, the two-component developer containing toner and carrier used in the present embodiment will be described.

[Electrophotographic carrier]
The electrophotographic carrier in the present invention (hereinafter simply referred to as a carrier) has a core material and a coating layer covering the core material, and further has other layers as necessary.

  The coating layer contains at least a binder resin and an ionic liquid or an ionic liquid-derived material, and further contains other components as necessary.

  In a method that requires high image quality such as color images, it is essential to adjust the resistance as a carrier. Carriers with extremely high resistance have abnormalities such as carrier adhesion (background carrier adhesion or edge carrier adhesion) to the non-image area and white spots. An image is generated.

  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 must be added in a large amount in the coating layer. Conductive fine particles are unevenly distributed in the layer. When the unevenly distributed portions of the conductive fine particles are exposed due to the scraping of the coating layer, the portions become electrical leak points from the starting point, and local resistance reduction occurs. Due to the decrease in resistance, carrier adhesion to the image portion occurs, resulting in an abnormal image such as white spots.

  The ionic liquid is a liquid, and is easily finely dispersed with the coating resin at the time of producing the coating layer liquid. As a result, the ionic liquid is present in a finely dispersed state in the carrier coating layer, so that local resistance reduction does not occur. In addition, since the ionic liquid is colorless to cloudy, even if the coating layer is scraped and mixed into the toner, color stains do not occur. In the present invention, such an ionic liquid is used as a raw material. However, this does not mean that the ionic liquid remains as it is in the coating layer of the carrier core material of the obtained toner. In other words, all the ionic liquids exist as ionic groups, exist as ionic groups, or exist as ionic cross-linked products. I mean. Those derived from these ionic liquids can be judged to be derived from the ionic liquid, for example, by extraction or concentration with an aqueous medium, polar solvent, or the like, and with an analyzer such as an ion chromatograph.

  The ionic liquid used in the present invention 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 can be used as long as it has no flammability / flammability and high thermal stability.

  However, in the present invention, it does not decompose in the temperature range used in the production process of electrostatic latent image developing developer (resin thermosetting and desolvation), that is, at least in the temperature range of 100 to 300 ° C. Is preferred.

The ionic conductivity of the ionic liquid is not particularly limited, but is 6.1 × 10 ⁻⁵ S / cm to 1.5 × 10 ⁻² S / cm within a temperature range of 10 to 30 ° C. .

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. It is preferable that physical properties such as ion conduction characteristics are more suitable.
Examples of organic cationium salts include ammonium salts, imidazolium derivatives, pyridinium, phosphonium, etc., and organic acid anions include BF ₄ −, PF ₆ ⁻ , CF ₃ SO ₃ ⁻ (Tf: triflate), and (CF ₃ SO ₂ ). ₂ N ⁻ (TFSI) and the like. 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.

  In addition, the volume specific resistance value of the carrier in the present invention is not particularly limited as long as it is in the range of about 10 to 16 log Ω · cm, and can be adjusted according to the use, and the ionic liquid contained in the coating layer The content of 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.

  As the ionic liquid, it is preferable to use a pyridinium (Formula 1), imidazolium (Formula 2), alicyclic amine (Formula 3), or aliphatic amine (Formula 4) material. Specifically, pyridinium ionic liquids IL-P11, IL-P14, imidazolium ionic liquid IL-IM1, and cycloaliphatic amine ionic liquids IL-C1, IL-C3 manufactured by Guangei Chemical Industry Co., Ltd. IL-C5, and aliphatic amine-based ionic liquids IL-A1, IL-A2, IL-A3, IL-A4, and IL-A5 can be used.

  (R and R ′ in (Formula 1) may be the same or different and each independently represents a hydrogen atom, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or Represents a phenyl group.)

  (In the formula, R and R ′ may be the same or different, and each independently represents a hydrogen atom, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms or a phenyl group. Show.)

  (In (Formula 3), the alicyclic compound described as a 5-membered ring is an alicyclic amine ring which is an alicyclic compound having a nitrogen atom in the ring, and bonded to the amino group of this ring. R and R ′ may be the same or different and each independently represents a hydrogen atom, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a phenyl group. (The carbon number n of the said aliphatic amine is 2 or more.)

  (R, R ′, R ″, R ′ ″ in (Formula 4) may be the same or different, and each independently represents a hydrogen atom, an aliphatic hydrocarbon residue having 1 to 8 carbon atoms, carbon (It represents a cycloalkyl group or a phenyl group of formula 5-7.)

  The carrier coating layer in the present invention contains inorganic fine particles, and the inorganic fine particles are contained in a covering ratio of 70% or more with respect to the core material. The reason for the inclusion of the particles is to create irregularities on the surface of the carrier, and to reduce contact with a strong impact on the binder resin due to friction with the toner or friction between the carriers by agitation for frictionally charging the developer. be able to. As a result, it is possible to prevent spent toner on the carrier.

The coverage in this invention is a coverage with respect to the core material of an inorganic oxide particle, and is represented by following Formula.
Coverage ratio = [(Ds * ρs * W) / (4 * Df * ρf)] * 100
In the above formulas for coverage, Ds is the carrier core particle size, ρs is the true specific gravity of the carrier core material, W is the ratio of the added amount of inorganic oxide particles to the carrier core material, Df is the particle size of inorganic oxide particles, and ρf is inorganic Represents the true specific gravity of oxidized particles.

The true specific gravity ρf and ρs of the inorganic fine particles and the carrier core material were measured using a dry automatic bulk density meter Accupic 1330 (manufactured by Shimadzu Corporation). This measurement method is a gas replacement method using helium. In the measurement method, 4 g of a measurement sample is put in 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 density of the sample (the true specific gravity ρf, ρs of the inorganic fine particles and the carrier core material) is determined from the determined volume and the weight of the sample.

  The carrier core particle diameter Ds (volume average particle diameter) can be measured by 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. Also, 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 particle diameter Df of the inorganic oxide particles is determined by measuring the volume average particle diameter using an automatic particle size distribution analyzer CAPA-700 (manufactured by Horiba Seisakusho). As a pretreatment for 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, 6.0 g of a sample is added, and the mixer rotation speed is set to low and dispersed for 3 minutes. A diluted solution obtained by adding an appropriate amount of a dispersion solution in 500 ml of a toluene solution prepared in advance in a 1000 ml beaker is continuously stirred in a homogenizer and measured with an ultracentrifugal automatic particle size distribution analyzer CAPA-700. The measurement conditions were as follows.
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 inorganic fine particles, a dry automatic bulk density meter Accupic 1330 (manufactured by Shimadzu Corporation) is used, and the true specific gravity value measured as described above is input.

  If the coverage is less than 70%, the probability that the surface of the carrier core material will be exposed due to film scraping with time increases, the resistance decreases locally, and a carrier in which such a state exists is developed in a solid image. As a result, white spots appear in the image.

  Furthermore, the ratio D / h of the particle diameter (D) of the inorganic fine particles contained in the carrier coating layer and the coating layer thickness (h) is 0.5 <[D / h] <1.5. The improvement effect is remarkable. This is because when the ratio D / h between the particle diameter (D) and the coating resin film thickness (h) is 0.5 <[D / h] <1.5, Since the direction becomes convex, the agitation for frictionally charging the developer can relieve the contact with a strong impact on the binder resin due to the friction with the toner or the friction between the carriers. As a result, it is possible to suppress film scraping of the binder resin, which is a place where charging occurs. In addition, since there are many particles on the carrier surface that are more convex than the coating film, it also exhibits a cleaning effect that efficiently scrapes off the spent component of the toner adhering to the carrier surface due to frictional contact between carriers. Can be prevented.

  When the ratio [D / h] is less than 0.5, the inorganic fine particles are buried in the binder resin. When [D / h] exceeds 1.5, the contact area between the particles and the binder resin is small, so that a sufficient restraining force cannot be obtained and the particles are easily detached, which is not preferable. When desorbed, the resistance is lowered.

  As shown in FIG. 8, the coating layer thickness h indicates the thickness from the core material surface to the coating layer surface. The thickness h from the surface of the core material to the surface of the coating layer is observed, for example, using a transmission electron microscope (TEM), and the thickness from the surface of the core material to the surface of the coating layer (like h1 to h4). This is a value obtained by measuring 50 points along the carrier surface at intervals of 0.2 μm and averaging the obtained measurement values.

  As the inorganic fine particles dispersed in the coating layer of the carrier of the present invention, 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 toner particles and causes color stains. The particle diameter (D) of the inorganic fine particles is measured with an ultracentrifugal automatic particle size distribution analyzer CAPA-700 in the same manner as the particle diameter measuring method of the inorganic fine particles described above.

  Furthermore, the improvement effect is remarkable when the volume specific resistance 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 referred to here is 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 × 4 cm as 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, the DC resistance is measured by a high resistance meter 4329A (4329A + LJK5HVLVWDQFH0HWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), electric resistivity R [Ω · cm] is obtained, and LogR is calculated.

  Furthermore, the improvement effect is remarkable because the volume average particle diameter of the carrier core material in the present invention is 20 μm or more and 65 μm or less.

  This is not preferable when the volume average particle size is less than 20 μm, since problems such as carrier adhesion occur due to a decrease in the uniformity of the particles and a lack of sufficient technology on the machine side. On the other hand, if it exceeds 65 μm, the reproducibility of image details is poor and a fine image cannot be obtained, which is not preferable.

  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.). 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.

  Furthermore, at least the binder resin is a silicone resin, so that 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.

  The silicone resin as used herein refers to all generally known silicone resins, and examples include straight silicone consisting only of organosiloxane bonds, and silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, and the like. 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. Further, modified silicone resins include KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicone. , SR2110 (alkyd modified) and the like.

  Further, the improvement effect is remarkable when at least the binder resin includes an acrylic resin or the silicone resin.

  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 particles can be firmly held due to the 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.

Furthermore, 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.

In this range, since the retention force between the carrier particles is properly maintained, the dispersion (mixing) of the toner into the carrier or the developer becomes quick and good, but the magnetic moment at 1 KOe is 40 Am ² / kg. If it is less than 1, 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.

  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 to 3000 oersted (Oe), 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.

  The carrier coating layer in the present invention is prepared by, for example, preparing a coating solution by dissolving inorganic fine particles, a binder resin, etc. in a solvent, and then uniformly coating the coating solution on the surface of the core material by a known coating method. After drying, it can be formed by baking. Examples of the coating method include an immersion method and a spray method.

  There is no restriction | limiting in particular as said solvent, Although it can select suitably according to the objective, For example, toluene, xylene, methyl ethyl ketone (MEK), methyl isobutyl ketone, cersol butyl acetate, etc. are mentioned.

  The baking is not particularly limited, and may be an external heating method or an internal heating method. For example, a stationary electric furnace, a fluid electric furnace, a rotary electric furnace, a burner furnace, etc. The method of using, the method of using a microwave, etc. are mentioned.

(Core material)
As described above, the carrier core material used in the present invention has a volume-average particle diameter of 20 μm or more and 65 μm or less, so that the improvement effect is remarkable. This is not preferable when the volume average particle size is less than 20 μm, since problems such as carrier adhesion occur due to a decrease in the uniformity of the particles and a lack of sufficient technology on the machine side. On the other hand, when the thickness exceeds 65 μm, carrier streaks and the like and reproducibility of image details are poor and a fine image cannot be obtained, which is not preferable. In particular, 25 to 50 μm is more preferable for recent high image quality.

  There is no restriction | limiting in particular as a core material, According to the objective, it can select suitably from what is known as a two-component carrier for electrophotography, For example, a ferrite, magnetite, iron, nickel is mentioned suitably. Considering the environmental impact that has been remarkably advanced in recent years, if it is ferrite, for example, Mn ferrite, Mn—Mg ferrite, Mn—Mg—Sr ferrite, etc. are used instead of conventional copper-zinc ferrite. Is preferred.

[Developer]
The developer used in the image forming apparatus of the present invention comprises the above-described electrophotographic carrier and toner.

  The toner includes at least a binder resin and a colorant, and further includes a release agent, a charge control agent, and other components as necessary. The mixing ratio of the developer toner and the carrier is 1 to 10.0 parts by weight of the toner with respect to 100 parts by weight of the carrier.

[toner]
Here, the toner 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. Further, so-called oilless toner having a releasing 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.

  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, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate 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 of the present invention, known pigments and dyes capable of obtaining yellow, magenta, cyan, and black toners 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 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 preferably used.

  As the resin fine particles, polymethyl methacrylate or polystyrene fine particles having an average particle size 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.

  The above-mentioned inorganic fine particles and resin fine particles are contained (internally added) in the toner, but the effect is reduced as compared with the case of external addition, but the effect of improving transferability and durability can be obtained and the pulverization property of the toner can be improved. Can do. 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, dipentyl-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 a method for producing the toner used in the present invention, a conventionally known method such as a pulverization method or a polymerization method can be applied. 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, coarse pulverization is performed using a hammer mill, a funnel plex, etc. A crusher or the like can be used. The pulverization is desirably performed so that the average particle diameter is 3 to 15 μm. Furthermore, it is preferable that the particle size of the pulverized product is adjusted to 5 to 20 μm by a wind classifier or the like. Next, 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. The 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.

  In addition, since the carrier used in the present invention can adjust its resistance value without containing carbon black as a resistance adjusting agent, even in color image formation, color stain due to carbon black does not occur, A color image with high color reproducibility and fineness can be produced.

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.
Of Examples 1 to 15 shown below, Examples 3 and 11 are test examples corresponding to Reference Examples that do not belong to the scope of the present invention.

(Example 1)
[Carrier coating layer]
Silicone resin solution [solid content 23 wt% (SR2410: manufactured by Toray Dow Corning Silicone)] 432.2 parts Aminosilane [solid content 100 wt% (SH6020: manufactured by Toray Dow Corning Silicone)] 66 parts Inorganic oxide fine particles A Aluminum oxide Particle size: 0.40 μm, True specific gravity: 3.9 [Particle powder specific resistance: 12 Ω · cm] 145 parts ・ Ionic liquid IL-A2 (manufactured by Guangei Chemical Co., Ltd.) 20 Part 300 parts of toluene was dispersed with a homomixer for 10 minutes to obtain a silicone resin coating film forming solution. Average particle diameter as core material: 35 μm sintered ferrite powder (true specific gravity 5.5) MFL-35HS manufactured by Powdertech Co., Ltd., 5000 parts of the above coating film forming solution on the surface of the core material at a liquid flow rate of 40 g / min. It was applied and dried at a coater internal temperature of 40 ° C. with a Spira coater (manufactured by Okada Seiko Co., Ltd.) so as to be 0.35 μm. The carrier obtained at this time was baked in an electric furnace at 200 ° C. for 1 hour. After cooling, the carrier bulk was crushed using a sieve having an aperture of 63 μm, and D / h: 1.1, volume resistivity: 13.9 [Log (Ω · cm)], magnetization: 68 Am ² / kg [carrier 1] was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 93% with respect to the core material.

  FIG. 10 is an explanatory view of an apparatus for measuring the powder specific resistance of the inorganic fine powder in the coating layer.

5 g of a sample is put in a cylindrical vinyl chloride tube having an inner diameter of 1 inch, and the upper and lower sides are sandwiched between electrodes. A pressure of 10 kg / cm ² is applied to these electrodes by a press. Subsequently, measurement with an LCR meter (Yokogawa-HEWLETT-PACKARD 4216A) is performed in this pressurized state to obtain resistance (r). The obtained resistivity can be calculated by the following mathematical formula to obtain the volume resistivity.
Volume resistivity (Ω · cm) = (2.54 / 2) 2 × (π / H × r)
However, in the above formula, H represents the thickness of the sample. r represents a resistance value.

[Career]
For the measurement of the average particle diameter of the core material, an SRA type of Microtrac particle size analyzer (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.

[Toner 1]
(Toner binder synthesis)

  Into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide were placed and reacted at 230 ° C. under normal pressure for 8 hours. Furthermore, after making it react under reduced pressure of 10-15 mmHg for 5 hours, it cooled to 160 degreeC, 32 parts of phthalic anhydride was added to this, and it was made to react 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. 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) (weight ratio), and acetic acid in the toner binder (1). An ethyl / MEK solution was obtained. 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 at 60 ° C. using a TK homomixer, and uniformly dissolved and dispersed. 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. Next, this mixed solution 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) 1OO parts of 10% sodium hydroxide aqueous solution was added to the filter cake of 1), mixed with a TK homomixer (30 minutes at 12,000 rpm), and filtered under reduced pressure.
3): 100 parts of 10% hydrochloric acid was added to the filter cake of 2), 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), 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].

[Filter cake 1] was dried at 45 ° C. for 48 hours with a circulating dryer.
Thereafter, 15 parts of [Filter cake 1] are 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 are 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. Further, 90 parts of [Toner 1] and 10 parts of [Carrier 1] were filled in a developer container to obtain a replenishment developer. Table 2 shows the results of evaluation of toner color stain, carrier adhesion, image density, and durability (charge reduction amount, resistance change amount).

  When coverage (low image area) was low at the time of durability evaluation, a recovery mode was incorporated in which carrier development was performed at a charging potential of −920 V and a developing bias of −600 V (background potential of 320 V) at the end of printing. The carrier and toner developed on the OPC were recovered without cleaning.

  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. A yellow single color image after initial and after 30000 sheets is output, and a ΔE value is obtained according to the following equation. When ΔE is 2 or less, there is no color stain (◯), ΔE
No. 2 to 4 indicate that color stains are not noticeable and no change in color tone is indicated (Δ), and when ΔE is 4 or more, color stains are clearly noticeable and change in color tone is indicated (×).
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 a 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 to calculate a ΔE value.

ΔE = ((initial L *) ² + (initial a *) ² + (initial b *) ² ) ^1/2 − ((L * after run)
² + (after run a *) ² + (after run b *) ² ) ^1/2

[Carrier adhesion]
A developer is set in a commercially available digital full-color printer (Imagio Neo C455 manufactured by Ricoh Co., Ltd.), the charging potential is set to DC-740V, the developing bias is set to -600V (the background potential is fixed to 140V), and the dot forming halftone is developed. The number of carriers adhering to the surface of the photoreceptor was counted by five visual field observations with a magnifying glass, and the average number of adhering carriers per 100 cm ² was used as the edge carrier adhering amount. The evaluation was made in four stages: ◎: 20 or less, ○: 21 to 60, △: 61 to 80, ×: 81 or more, ◎ ○ △ was passed and x was rejected. .

  Also, the white spot (image part) is set to a charging potential of DC-740 V and a developing bias of -600 V (the background potential is fixed to 140 V), a full-color image (A3 size) is output, and the number of white spots on the image is determined. I counted. Evaluation is evaluated as 4 grades: ◎: 5 or less, ○: 6 or more, 10 or less, △: 11 or more, 20 or less, ×: 21 or more, ◎ ○ △ is passed and x is rejected. did.

[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, ◯, when it is 1.2 or more and less than 1.4, △, 1. When it was less than 2, it was displayed in four stages of 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 determination was made based on the charge reduction amount of the developer after the running. The resistance reduction amount 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 refers to an amount obtained by subtracting the charge amount (Q2) of the developer after running from the initial charge amount (Q1), and the target value is within 10.0 (μc / g). It is. The charge amount is a value obtained by measuring the sampled developer by a general blow-off method [manufactured by Toshiba Chemical Co., Ltd .: TB-200].

  Here, the amount of resistance reduction refers to the carrier obtained by removing the toner in the developer after running by the blow-off device from the resistance value (R1) obtained by the resistance measurement method described above for the initial carrier. The value 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. In addition, 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, and the like. By reducing these, the amount of decrease in resistance can be suppressed. .

(Example 2)
D / h: 0.9, volume resistivity: 14.1 [Log (Ω · Ω), in the same manner as in Example 1 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 inorganic oxide particles contained in the resin coating layer at this time had a coverage of 83% 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)] 432.2 parts Aminosilane [100% by weight of solid content (SH6020: manufactured by Toray Dow Corning Silicone)] 3.42 parts ionic liquid IL -A2 (manufactured by Guangei Chemical Industry Co., Ltd.) 20 parts, inorganic oxide fine particles B aluminum oxide particle size: 0.37 μm, true specific gravity 3.9 [particle powder specific resistance: 13 Ω · cm] 97 parts [Carrier 2 ] And [Toner 1] were made into developers by the same method as in Example 1 and evaluated. The results are shown in Table 2.

(Example 3)
[Carrier 3] having a volume resistivity of 15.8 [Log (Ω · cm)] and a magnetization of 68 Am ² / kg, except that inorganic oxide fine particles A were not added in Example 1. Got. [Carrier 3] 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 Table 2.

Example 4
D / h: 1.9, specific volume resistance: 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)], magnetization: 68 Am ² / kg [Carrier 4] was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 83% 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)] 216.2 parts Aminosilane [100% by weight of solid content (SH6020: manufactured by Toray Dow Corning Silicone)] 1.68 parts ionic liquid IL -A2 (manufactured by Guangei Chemical Industry Co., Ltd.) 20 parts-Inorganic oxide fine particles B Aluminum oxide Particle size: 0.37 µm, True specific gravity 3.9 [Particle powder specific resistance: 13 Ω · cm] 97 parts-Toluene 1600 parts Further, [Carrier 4] and [Toner 1] were developed into a developer by the same method as in Example 1 and evaluated. The results are shown in Table 2.

(Example 5)
D / h: 0.4, volume specific resistance: 16.5 [Log (Ω ·····), in the same manner as in Example 2 except that the coating layer formulation was changed in the following ratio of acrylic resin and silicone resin. cm)] and magnetization: 68 Am ² / kg [Carrier 5]. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 83% 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 wt% (SR2410: manufactured by Toray Dow Corning Silicone)] 743.2 parts Aminosilane (solid content: 100 wt% (SH6020: manufactured by Toray Dow Corning Silicone)) 1.68 parts ionic liquid IL -A2 (manufactured by Guangei Chemical Industry Co., Ltd.) 20 parts-Inorganic oxide fine particles B Aluminum oxide Particle size: 0.37 µm, True specific gravity 3.9 [Particle powder specific resistance: 13 Ω · cm] 97 parts-Toluene 1600 parts Further, [Carrier 5] and [Toner 1] were developed into a developer by the same method as in Example 1 and evaluated. The results are shown in Table 2.

(Example 6)
In Example 2, 110 parts by weight of titanium oxide (anatase) C [particle powder specific resistance: 32 Ω · cm, particle size: 0.35 μm, true specific gravity 5.0] was used in place of the inorganic fine powder. Similarly, [Carrier 6] having D / h: 0.9 and volume resistivity: 16.5 [Log (Ω · cm)] was obtained. The fine particles contained in the resin coating layer at this time had a coverage of 73% with respect to the core material.

  [Toner 1] and [Carrier 6] thus obtained were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Table 2.

(Example 7)
D / h: 0.9, volume resistivity: 15. In the same manner as in Example 1 except that the carrier has a weight average particle diameter of 18 μm (true specific gravity 5.7) and the coating layer formulation is as described below. 7 [Log (Ω · cm)] and magnetization: 66 Am ² / kg [Carrier 7] were 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% by weight of solid content (SH6020: manufactured by Toray Dow Corning Silicone)] 0.46 parts ionic liquid IL -A2 (manufactured by Guangei Chemical Industry Co., Ltd.) 20 parts · Inorganic oxide fine particles B Aluminum oxide Particle size: 0.37 µm, True specific gravity 3.9 [Particle powder specific resistance: 13 Ω · cm] 195 parts · Toluene 800 parts [Carrier 7] and [Toner 1] were developed into developers by the same method as in Example 1 and evaluated. The results are shown in Table 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 8)
D / h: 0.6, volume resistivity: 14.5 [except for the carrier having a weight average particle diameter of 71 μm (true specific gravity 5.3) and coating layer formulation as described below. Log (Ω · cm)] and magnetization: 69 Am ² / kg [Carrier 8].
・ 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 wt% (SR2410: manufactured by Toray Dow Corning Silicone)] 292.9 parts Aminosilane [solid content 100 wt% (SH 6020: manufactured by Toray Dow Corning Silicone)] 0.42 parts ionic liquid IL -A2 (manufactured by Guangei Chemical Industry Co., Ltd.) 20 parts ・ Inorganic oxide fine particles B Aluminum oxide Particle size: 0.37 μm, True specific gravity 3.9 [Particle powder specific resistance: 13 Ω · cm] 60 parts ・ Toluene 800 parts [Carrier 8] and [Toner 1] were converted into developers by the same method as in Example 1 and evaluated. The results are shown in Table 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 78% with respect to the core material.

Example 9
In Example 2, 35 μm sintered ferrite (true specific gravity 5.4) having a low magnetization was used and the magnetization was changed to 35 Am ² / kg. D / h: 0.9, volume resistivity: [Carrier 9] of 13.9 [Log (Ω · cm)] was obtained. [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 Table 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 83% with respect to the core material.

(Example 10)
In Example 2, D / h: 0.9, volume resistivity: in the same manner except that 35 μm sintered ferrite (true specific gravity 5.5) having high magnetization was used and the magnetization was changed to 93 Am ² / kg. 14.1 [Log (Ω · cm)] of [Carrier 10] was obtained. [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 Table 2. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 83% with respect to the core material.

(Example 11)
In Example 1, D / h: 1.1, volume resistivity: 13.5 [Log (Ω · cm)] except that the amount of inorganic fine particles added was reduced from 145 parts by weight to 75 parts by weight. [Carrier 11] having a magnetization of 69 Am ² / kg was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 46% 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 Table 2.

(Example 12)
In Example 1, except that the ionic liquid was changed from IL-A2 to IL-P14 (manufactured by Guangei Chemical Industry Co., Ltd.) and increased to 30 parts by weight, D / h: 1.1, volume [Carrier 12] having a specific resistance of 13.8 [Log (Ω · cm)] and a magnetization of 68 Am ² / kg was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 93% 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.

(Example 13)
The developer having a toner concentration of 7% by weight of Example 12 was used. Further, 99 parts of [Toner 1] and 1 part of [Carrier 12] were filled in a developer storage container to obtain a replenishment developer. The results are shown in Table 2.

(Example 14)
The developer having a toner concentration of 7% by weight of Example 12 was used. Further, 75 parts of [Toner 1] and 25 parts of [Carrier 12] were filled in a developer container to obtain a replenishing developer. The results are shown in Table 2.

(Example 15)
In Example 1, the average particle diameter as a core material: 35 μm calcined ferrite powder (true specific gravity 5.5) D / h: 1.1, volume in the same manner except that DFC-400 manufactured by Dowa Iron Powder Industry Co., Ltd. was used. [Carrier 13] having a specific resistance of 13.8 [Log (Ω · cm)] and a magnetization of 71 Am ² / kg was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 93% with respect to the core material. [Carrier 13] 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 1)
[Carrier coating layer]
Silicone resin solution [solid content 23 wt% (SR2410: manufactured by Toray Dow Corning Silicone)] 432.2 parts Aminosilane [solid content 100 wt% (SH6020: manufactured by Toray Dow Corning Silicone)] 66 parts ・ Inorganic oxide fine particles A Aluminum oxide Particle size: 0.40 μm, True specific gravity: 3.9 [Particle powder specific resistance: 12 Ω · cm] 145 parts ・ Carbon black MA100R (Mitsubishi Chemical Industries, Ltd.) 20 parts ・300 parts of toluene was dispersed with a homomixer for 10 minutes to obtain a silicone resin coating film forming solution. Spiral coater (Okada Seiko Co., Ltd.) having an average particle size of 5000 parts by weight as the core material and 35 parts by weight of 35 μm sintered ferrite powder (true specific gravity 5.5), so that the coating film forming solution has a film thickness of 0.35 μm on the surface of the core material. Applied to the coater at a 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, D / h: 1.1, volume resistivity: 12.9 [Log (Ω · cm)], magnetization: 68 Am ² / kg [ Carrier 14] was obtained. The inorganic oxide particles contained in the resin coating layer at this time had a coverage of 93% with respect to the core material. [Carrier 14] 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 2)
The developer of Example 1 having a toner concentration of 7% by weight was used. Further, only [Toner 1] was filled in the developer storage container to obtain a replenishment developer. The results are shown in Table 2.

(Comparative Example 3)
[Carrier 12] and [Toner 1] in Example 12 were converted into developers by the same method as in Example 1 and evaluated. Even when the coverage (low image area) was low at the time of durability evaluation, durability evaluation was carried out without incorporating a recovery mode in which carrier development was performed. The results are shown in Table 2.

  Carrier characteristic values

  Evaluation results

  From Table 2, in Examples 1-15, the favorable carrier without a color stain was obtained. In addition, good results were obtained for all evaluation items of image density, carrier adhesion, charge reduction amount, and resistance reduction amount. In Example 14, it was confirmed that the carrier remained in the developer container when the toner end was reached. Although there was no problem in image quality, the amount of discarded carriers also increased, which is not preferable.

  On the other hand, in Comparative Example 1, color stains occurred, and the results were not usable practically. In Comparative Example 2, the result up to 300,000 sheets was good, but the resistance decreased at 500,000 sheets, and a blank image was generated. Even in Comparative Example 3, the results up to 300,000 sheets were good, but the resistance decreased at 500,000 sheets, and a blank image was generated.

  Although the present invention has been specifically described by way of examples, the present invention is not limited to such specific embodiments, and various modifications can be made within the technical scope of the present invention described in the claims. Deformation / change is possible.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to the present invention. FIG. 2 is a schematic configuration diagram illustrating a structure around a developing unit of a developing device according to an embodiment of the present invention. It is a schematic block diagram of the developer supply part used by this invention. (A) is an external view which shows schematic structure of the nozzle of a developer supply apparatus, (b) is the axial direction sectional drawing, (c) is a code | symbol AA sectional drawing in (b). It is sectional drawing which shows schematic structure of a screw pump. It is a perspective view which shows the state which filled the developer accommodating member with the developer. FIG. 6 is a front view showing a state where the developer inside the developer containing member is discharged and reduced in volume. It is explanatory drawing which shows the coating layer of the core material of the carrier for electrophotography of this invention. It is a perspective view of the resistance measurement cell used for the measurement of the resistivity of a carrier. It is explanatory drawing of the apparatus which measures the powder specific resistance of the inorganic fine powder in a coating layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Apparatus main body 1 Photoconductor 2A, 2B, 2C, 2D Image formation unit 3 Charging unit 6 Exposure apparatus 8 Transfer belt 10A, 10B, 10C, 10D Developing apparatus 11a, 11b Conveying screw 12 Developing roller 13 Doctor blade 14 Developer accommodating part 15a Supply port 200A, 200B, 200C, 200D Developer supply device 220 Developer supply device 221 Conveying tube 223 Screw pump 224 Rotor 225 Stator 226 Drive motor 230 Developer storage device 231 Developer storage member 240 Nozzle 241 Inner tube 241a Developer Flow path 242 Outer pipe 244 Air flow path 246a, 246b Air supply port 247 Developer outlet 260a, 260b Air pump 300 Developer recovery device 330 Recovery container 331 Recovery pipes h1, h2, h3, h4 Covering layer thickness D Particle size of inorganic fine particles

Claims (13)

At least an image carrier;
A latent image forming means for forming an electrostatic latent image on the image carrier;
Developing means for developing the formed electrostatic latent image with a developer including a carrier having a toner, a core material, and a coating layer covering the core material to form a visible image;
Means for replenishing the carrier;
A developer collecting means for collecting the developer in the developing means,
The coating layer of the core material of the carrier contains inorganic fine particles,
The inorganic fine particles contain 70% or more of the coating ratio with respect to the core material,
The image forming apparatus, wherein the developer collecting means selectively collects at least a low resistance carrier on the image carrier and cleans and collects the developed carrier and toner.   2. The image forming apparatus according to claim 1, wherein the means for replenishing the carrier is a developer replenishing means for replenishing the developing means with a replenishing developer containing toner and a carrier.   The image forming apparatus according to claim 2, wherein the developer replenishing unit includes a developer storage container made of a bag-like member that reduces in volume as the internal pressure decreases.   4. The image forming apparatus according to claim 2, wherein the replenishment developer has a carrier to toner weight ratio of 3 wt% to 20 wt%.   The image forming apparatus according to claim 1, wherein a plurality of the developer collecting units are provided.   The image forming apparatus according to claim 1, wherein the coating layer of the carrier core material contains at least a binder resin and an ionic liquid or an ionic liquid-derived material. Wherein the particle size of the inorganic fine particles (D), the thickness of the coating layer (h) is, 0.5 <[D / h] any of claims 1 to 6, characterized in that <1.5 The image forming apparatus described in 1. The volume resistivity of the carrier, 10 [Log (Ω · cm )] or 16 [Log (Ω · cm) ] The image forming apparatus according to any one of claims 1 to 7, characterized in that less. The volume average particle diameter of the carrier core material, the image forming apparatus according to any one of claims 1 to 8, characterized in that at 20μm or 65μm or less. The image forming apparatus according to any one of claims 6 to 9 , wherein the coating resin for the carrier core material contains at least one resin of silicone resin or acrylic resin. Magnetic moment in ^{1000 (10 3 / 4π · A} / m) of the carrier, 40 any one of claims 1 to 10, characterized in that it is (Am ² / kg) or 90 (Am ² / kg) or less The image forming apparatus described in 1. Developing means for converting an electrostatic latent image formed on an image carrier and at least an electrostatic latent image into a visible image with a developer having a core and a coating layer covering the core and a toner. Is a process cartridge that is detachably attached to the main body of the image forming apparatus, the means for supplying the carrier to the main body of the image forming apparatus, and the developer for collecting the developer in the developing means A recovery means,
The coating layer of the core material of the carrier contains inorganic fine particles,
The inorganic fine particles contain 70% or more of the coating ratio with respect to the core material,
The process cartridge is characterized in that the developer collecting means selectively carries out carrier development on at least the low-resistance carrier onto the image carrier , and collects the developed carrier and toner by cleaning. An electrostatic latent image is formed on the image bearing member, and the electrostatic latent image can be developed by developing means containing a developer including a toner, a core material, and a carrier having a coating layer covering the core material. An image forming method for making a visual image,
The coating layer of the core material of the carrier contains inorganic fine particles,
The inorganic fine particles contain 70% or more of the coating ratio with respect to the core material,
Using the means for replenishing the carrier and the developer collecting means for collecting the developer in the developing means, wherein the developer collecting means selectively develops at least a low-resistance carrier on the image carrier , An image forming method comprising cleaning and collecting the developed carrier and toner.

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