JP2008058463A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method in which an abrasive used is inorganic powder abrasive particles having such a small particle diameter as a number average particle diameter of 0.03-0.30 μm, and in which even when a cleaning blade 10a is disposed above an image carrier 1, image deletion and the influence of contamination of a charging member on an output image are suppressed and excellent durability performance free of image degradation can be retained over a long period of time. <P>SOLUTION: The image forming method includes an auxiliary cleaning step using a magnetic brush 10f of magnetic particles borne on a magnet roller 10e before a cleaning step and after a transfer step, wherein the formulae: 7≤B×M/100≤23 and 60≤B×M×D≤320 are satisfied, wherein B is a maximum magnetic flux density (mT) of the magnet roller in a photoreceptor surface position; M is a saturation magnetization (Am<SP>2</SP>/kg) of the magnetic particles; and D is an average diameter (μm) of the inorganic powder abrasive particles being 0.03-0.30 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention forms a toner image on the surface of an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, transfers the toner image to a recording medium, and the image carrier is repeatedly used for image formation. The present invention relates to an image forming method.

  In the electrophotographic image forming method, an electrophotographic photosensitive member using a photoconductive substance is used as an image carrier. After the photoreceptor is uniformly charged to a required polarity and potential, an exposure corresponding to the image pattern is performed to form an electrical latent image, and the latent image is visualized as a toner image. In general, the toner image is transferred to a recording medium such as paper, and the transferred toner image is fixed on the recording medium to form an image formed product. The photoreceptor is repeatedly used for image formation. In the above, the toner image formed on the photoconductor is primarily transferred to an intermediate recording medium such as an intermediate transfer drum or a belt, and the toner image on the intermediate recording medium is secondarily transferred to a recording medium such as paper. There is also a system in which an image formed product is obtained by fixing a transfer toner image on a recording medium.

  In the electrostatic recording image forming method, an electrostatic recording dielectric using a dielectric substance is used as the image carrier. After the electrostatic recording dielectric is uniformly charged to a required polarity and potential, an electric latent image is formed by performing charge removal corresponding to the image pattern. Thereafter, as in the case of the above-described electrophotographic image forming method, an image formed product is obtained by a development / transfer / fixing process or by a development / primary transfer / secondary transfer / fixing process. The electrostatic recording dielectric is repeatedly used for image formation.

  In recent years, image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses using the transfer-type image forming method as described above have all output terminals such as copiers, printers, and facsimiles, and are compatible with networks. The machine is widely accepted in the market.

  One of the performances required for such an image forming apparatus as a network-compatible output terminal is the duty cycle of the apparatus body.

  The duty cycle is a limit number of sheets in which the apparatus main body continues to operate normally without requiring maintenance by an operator.

  One of the greatest dominating factors of the duty cycle is the life of the image carrier that is used repeatedly. If the life of the image carrier can be extended, it is possible to reduce waste, that is, reduce consumables, extend the life of consumables, and improve reliability. From the viewpoint of environmental protection, development of such a technology is required.

  Under such circumstances, as an image carrier in an image forming apparatus of an electrophotographic system, an abrasion-resistant photoconductor such as an amorphous silicon (a-Si) photoconductor or an organic photoconductor having a protective layer on the outermost layer has been gradually used. ing. Such a highly durable photoconductor has become indispensable particularly in a high-speed machine that requires high reliability (for example, see Patent Document 1).

  However, according to the knowledge of the present inventors, in such an image forming apparatus, it is not limited to toner that adheres to the surface of an image carrier (hereinafter referred to as a photoreceptor) and affects the image quality. That is, it is attached to the surface of the photosensitive member and affects the image quality that fine paper dust generated from paper that is often used as a recording medium (hereinafter referred to as recording material) and organic components precipitated from the paper. Or a corona product generated due to the presence of a high-pressure member in the apparatus.

  These fine paper powders, organic components, and corona products adhere to the surface of the photoconductor to form foreign matter, and particularly reduce resistance in a high humidity environment, thereby preventing the formation of a clear electrostatic latent image. This is considered to be a factor causing image quality degradation.

  A corona charger (corona discharger) is often used as a charging device that uniformly charges a photosensitive member to a required polarity and potential (including charge removal processing). The corona charger is a non-contact type charging device, and includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and is disposed in a non-contact manner with the discharge opening facing the photoreceptor. Then, the image bearing member surface is exposed to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode, whereby the surface of the photoreceptor is charged to a predetermined level.

  In recent years, many contact charging devices have been proposed and put to practical use because of their advantages such as low ozone and low power compared with corona chargers as charging devices for photoreceptors.

  The contact charging device brings a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type into contact with the photoreceptor. Then, a predetermined charging bias is applied to the contact charging member to charge the photoreceptor surface to a predetermined polarity and potential. Here, the charging member does not necessarily need to be in contact with the surface of the photosensitive member that is a member to be charged. That is, if a dischargeable area determined by the voltage between the gap and the correction Paschen curve is ensured between the charging member and the photosensitive member, for example, a gap (gap) of several tens of μm exists and is arranged in a non-contact manner. (Proximity charging).

  Whether the photosensitive member is charged by a non-contact type charging device such as a corona charger or by a contact type (including proximity charging) charging device, the discharge product adheres to the surface of the photosensitive member. For this reason, in an image forming apparatus using a highly durable photoconductor that is difficult to be refreshed by shaving the surface, the discharge product adheres to the surface of the photoconductor and the surface resistance is reduced. The resulting image flow phenomenon may occur. Further, the discharge product is generated not only in the charging device for charging the photoconductor but also in a high voltage application site such as a development site, a pre-transfer charging site, and a transfer site.

  In addition, when fine paper dust generated from toner or paper used as a recording material in most cases adheres to the surface of the photoreceptor, it is easily altered by discharge products, which absorbs moisture and lowers resistance, resulting in image flow. Will occur.

In order to solve this problem, a method has been proposed in which the photosensitive member is heated by a heater to remove moisture and prevent a reduction in resistance. In addition, a method that eliminates the need for a heater from the viewpoint of energy saving has also been proposed (see, for example, Patent Document 2). In other words, the photosensitive member is refreshed and used by polishing it by rubbing various abrasives against the photosensitive member in the cleaning step.
JP 60-67951 A JP-A-10-63157

  However, in an image forming apparatus using a contact charging device (including a proximity charging device) as a charging device for the photosensitive member, if the surface of the photosensitive member is polished and refreshed with an abrasive during the cleaning process, The charging member is contaminated.

  That is, an elastic blade is generally used for the cleaning member, and the residual toner on the photoconductor after the transfer process is scraped off and removed by bringing the rade into contact with the photoconductor against the counter in the rotational direction. ing. When small particle size abrasive particles are used as the abrasive, the abrasive often slips from the contact portion between the photoreceptor and the cleaning blade.

  As a result of studies by the present inventors, in the design of the image forming apparatus, when the cleaning blade is disposed above the photosensitive member, the abrasive layer deposited on the blade edge is likely to be packed by its own weight. More specifically, as will be described later, when the blade arrangement angle θ is set in a range of −20 degrees to +100 degrees, packing of the abrasive layer is likely to occur. Further, the movement of the abrasive layer is delayed due to the packing, and the abrasive slips from the cleaning blade becomes uneven. It has been found that if image formation is continued as it is, contamination of the charging member in contact with (adjacent to) the photosensitive member becomes non-uniform, and charging streaks occur in the output image.

  In particular, damage to the photoconductor due to contact charging directly attacks the surface of the photoconductor, so image flow often occurs during image formation rather than after leaving the device, and the type of abrasive and polishing conditions are selected appropriately. Otherwise, the image flow cannot be sufficiently prevented.

  The present invention has been made in view of such technical problems. The purpose is to reduce image degradation by suppressing the occurrence of image flow and the influence on the output image due to contamination of the charging member even when the abrasive has a small particle size and the cleaning blade is placed above the image carrier. It is an object of the present invention to provide an image forming method capable of maintaining excellent durability performance over a long period of time.

A typical configuration of the image forming method according to the present invention for achieving the above object is as follows:
A charging step for charging the image carrier by bringing a charging member to which a voltage is applied into contact with or approaching a rotating drum-type image carrier, and an information writing step for forming an electrostatic latent image on the charging surface of the image carrier A developing step of developing the electrostatic latent image as a toner image with a developer, a transfer step of transferring the toner image to a recording medium, and a cleaning in which the image carrier is brought into contact with a counter with respect to the rotation direction. A cleaning step of removing residual toner on the image carrier after the transfer step by a blade, and in a cross section of the image carrier, a vertical line extending upward through the rotation center of the image carrier The angle formed by the line connecting the contact point between the cleaning blade and the image carrier and the rotation center of the image carrier is defined as the blade position angle θ, and the angle downstream of the image carrier rotation direction from the vertical line is + , The angle of the opposite - when the side, in the image forming method of the blade position angle θ is set in a range of -20 degrees to + 100 degrees,
Inorganic powder abrasive particles having a number average particle size of 0.03 μm to 0.30 μm are externally added to the developer,
The surface of the image carrier after the transfer process is a magnet roller on the upstream side in the rotation direction of the image carrier relative to the contact point between the cleaning blade and the image carrier, and on the downstream side in the rotation direction of the image carrier relative to the position of the transfer process. It has a cleaning auxiliary step of rubbing with the magnetic brush of the supported magnetic particles, and the following formula 7 ≦ B × M / 100 ≦ 23
60 ≦ B × M × D ≦ 320
B: Magnet roller maximum magnetic flux density (mT) at the surface of the image carrier
M: saturation magnetization of magnetic particles (Am ² / kg)
D: Average diameter of inorganic powder abrasive particles of 0.03 μm to 0.30 μm (μm)
It is characterized by satisfying.

  According to the image forming method of the present invention, it is possible to prevent high-quality image output for a long period of time while preventing image flow and preventing image failure due to contamination of the contact or proximity charging member.

<Image forming process>
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus using an image forming method according to the present invention. This image forming apparatus is a digital electrophotographic copying machine.

  Reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum) as an image carrier. The drum 1 is, for example, an amorphous silicon (a-Si) photosensitive member, and is driven to rotate at a predetermined speed in a clockwise direction indicated by an arrow by a driving mechanism unit (not shown) around a central shaft portion 1a.

  A charging device 2 uniformly charges the drum surface uniformly to a predetermined polarity and potential. The charging device 2 in this example is a contact charging device using a charging roller 2a as a charging member. The charging roller 2a is a conductive elastic roller having a basic configuration of a cored bar 2b and a conductive elastic layer 2c formed concentrically around the cored bar. The charging roller 2a is arranged substantially parallel to the drum 1. They are pressed against each other with a predetermined pressing force against the elasticity. A pressure contact portion between the drum 1 and the charging roller 2a is a charging portion a of the drum. The charging roller 2a rotates in the counterclockwise direction indicated by the arrow following the rotation of the drum 1. A predetermined charging voltage is applied to the cored bar 2b of the charging roller 2a from the power supply unit 2d at a predetermined control timing. As a result, the rotating drum surface is uniformly contact-charged to a predetermined polarity / potential by the charging roller 2a. In this embodiment, the negative charge is charged to a predetermined potential.

  Reference numeral 3 denotes a laser scanner (exposure means) as image information writing means, laser emitting means for emitting light modulated in accordance with a time-series electric digital pixel signal of image information inputted from the image processing section 3a, a rotating polygon mirror, etc. It consists of The image processing unit 3 a performs predetermined processing on electrical image information input from a document image photoelectric reading device (not shown) or an external host device (personal computer, facsimile, etc.) and outputs the processed information to the scanner 3. The scanner 3 scans and exposes the uniformly charged surface of the rotating drum 1 with the modulated laser beam L at the exposure part b. As a result, the charge on the laser beam irradiated portion of the drum surface is removed, and an electrostatic latent image corresponding to the scanned and exposed image pattern is formed on the drum surface.

  A developing device 4 develops the electrostatic latent image formed on the drum surface as a toner image. The developing device 4 in this example is a developing device using magnetic toner as a developer. 4a is a developing container, 4b is a non-magnetic developing sleeve as a developing member disposed in the developing container, 4c is a magnet roller (magnetizing means) inserted into the developing sleeve, and 4d is a predetermined edge portion on the developing sleeve 4b. 2 is a developer layer thickness regulating blade disposed close to the blade. Reference numerals 4e and 4f denote developer stirring and conveying screw shafts arranged in the developing container so as to be substantially parallel to the developing sleeve 4b. A magnetic toner T is accommodated as a developer in the developing container 4a. The magnetic toner T is externally added with inorganic powder abrasive particles (abrasive, cleaning aid) Z at a predetermined ratio.

  The developing sleeve 4b is arranged substantially in parallel with the drum 1 and faces the drum 1 with a predetermined slight gap. The magnet roller 4c is a non-rotating fixed member, and the developing sleeve 4b is driven to rotate around the magnet roller 43 in a counterclockwise direction indicated by an arrow by a drive mechanism unit (not shown) at a predetermined speed. The magnetic toner T (+ Z) in the developing container 4a is agitated while being cyclically conveyed in the developing container 4a along the length of the screw shaft by rotating the developer stirring and conveying screw shafts 4e and 4f. Triboelectrically charged to polarity. A part of the magnetic toner T is adsorbed and carried as a magnetic brush by the magnetic force of the magnet roller 4c on the outer surface of the developing sleeve 4b, conveyed along with the rotation of the developing sleeve 4b, and the layer thickness is regulated to a predetermined value by the blade 4d. The Then, the magnetic brush of the magnetic toner T conveyed by the subsequent rotation of the developing sleeve 4b comes into contact with the drum surface at the developing portion c which is the opposed portion between the drum 1 and the developing sleeve 4b. A predetermined developing voltage is applied to the developing sleeve 4b at a predetermined control timing from the power supply unit 4g. Thereby, the electrostatic latent image on the drum surface is developed as a toner image. The toner image formed on the drum surface also includes abrasive particles Z externally added to the magnetic toner T. There are two methods for developing an electrostatic latent image: a regular development method and a reversal development method. The regular development method is a method in which a charged drum surface is exposed corresponding to a background portion of image information (background exposure method), and a portion other than the background portion is developed. In the reverse development method, conversely, exposure is performed corresponding to the image information portion (image exposure method), and the non-exposed portion is developed. It is used by taking advantage of each feature. In this example, image exposure and reversal development are performed.

  Reference numeral 5 denotes a corona charger as a pre-transfer charger. The charger 5 applies a charge-removing current that weakens the electrical attraction force of the toner on the drum surface and the toner image to the drum at a pre-transfer site d between the development site c and the transfer site e. The transfer efficiency of the toner image to the recording medium at the transfer site e is improved.

  A transfer device 6 transfers the toner image formed on the drum surface to a recording material (transfer material) P such as paper as a recording medium. The transfer device 6 in this example is a contact transfer device using a transfer roller 6a as a transfer member. The transfer roller 6a is a conductive elastic roller having a basic configuration of a cored bar 6b and a conductive elastic layer 6c formed concentrically around the cored bar. The transfer roller 6a is arranged substantially parallel to the drum 1. They are pressed against each other with a predetermined pressing force against the elasticity. A pressure contact portion between the drum 1 and the transfer roller 6a is a transfer portion e of the drum. The transfer roller 6a rotates in the counterclockwise direction of the arrow following the rotation of the drum 1.

  On the other hand, one sheet of recording material P as a recording medium is fed from a sheet feeding mechanism (not shown) at a predetermined sheet feeding timing and is sent to the registration roller pair 7. The registration roller pair 7 feeds the recording material P so that the leading end of the recording material P also reaches the transfer portion e at a predetermined timing in accordance with the timing when the leading end of the toner image on the rotating drum 1 reaches the transfer portion e. Transport timing. The recording material P introduced into the transfer site e is nipped between the drum 1 and the transfer roller 6a and conveyed through the transfer site e. From the power supply unit 6d to the cored bar 6b of the transfer roller 6a from the time when the leading end of the recording material P reaches the transfer site e until the trailing end of the recording material P passes through the transfer site e. A transfer voltage having a predetermined potential opposite to the charging polarity is applied. As a result, the toner image on the drum surface side is electrostatically transferred sequentially onto the surface of the recording material P being conveyed through the transfer site e.

  Reference numeral 8 denotes a corona charger as a post-transfer charger (recording material separating charger). This charging device 8 has an electrical attraction force with the drum surface on the back surface of the recording material P that comes out of the transfer site e and is in electrostatic contact with the drum surface at the post-transfer site f next to the transfer site e. The recording material P is separated from the drum surface by applying a neutralizing current that weakens.

  The recording material P leaving the transfer site e and separated from the drum surface is conveyed to the fixing device 9. The fixing device 9 in this example is a heat fixing device having a basic configuration of a pressure roller pair of a rotating heating roller (fixing roller) 9a and a pressure roller 9b. The recording material P is introduced into a fixing nip portion that is a pressure contact portion of the roller pair 9a and 9b, and is nipped and conveyed so that the unfixed toner image is fixed on the recording material surface as a fixed image by being heated and pressurized. Then, it is sent out to a paper discharge section (not shown) as an image formed product.

  The drum surface after the toner image transfer to the recording material P (after the recording material separation) is cleaned by the cleaning device 10 and repeatedly used for image formation.

  The cleaning device 10 is means for collecting and removing post-transfer residues such as transfer residual toner and paper powder remaining on the drum surface after the toner image transfer. For example, the cleaning blade 10a having elasticity mainly made of polyurethane rubber is brought into contact with the rotation of the drum 1 by a counter to scrape off post-transfer residues such as transfer residual toner and paper dust on the drum surface. Done.

  In this example, the cleaning blade 10a is disposed above the drum. More specifically, the cleaning blade 10a is arranged with respect to the drum 1 so that the blade position angle θ defined below is approximately +20 degrees.

  Here, in the drum cross section, a vertical line extending upward through the rotation center O of the drum 1 is defined as C. A line connecting the contact point h between the cleaning blade 10a and the drum 1 and the drum center O is defined as D. An angle formed by the connection D with respect to the vertical line C is defined as a blade position angle θ. For the angle θ, the angle downstream from the vertical line C in the drum rotation direction is the plus (+) side, and the angle from the vertical line C upstream in the drum rotation direction is the minus (−) side.

  As described above, when the cleaning blade 10a is arranged with respect to the drum 1 so that the blade position angle θ is within a range of −20 degrees to +100 degrees, the abrasive layer deposited on the blade edge Packing due to its own weight is likely to occur.

  Residues after transfer such as toner and paper dust scraped off by the blade 10a are received by a scooping sheet, and the rotary transport member 10b such as a toner feed blade, a brush roller, and a screw is rotated in the cleaning container 10c in the longitudinal direction. Is conveyed to one end side. Further, it is discharged and conveyed from the cleaning container 10c to a waste toner box (not shown).

  10d is a cleaning auxiliary member (rubbing auxiliary member), which acts on the drum surface after the transfer process and before the cleaning process by the cleaning blade 10a, scraping off the toner from the drum surface, recoating, The surface of the drum is rubbed and polished. In this example, the cleaning auxiliary member 10d is a magnet roller (magnet generation means) 10e and a magnetic brush 10f of magnetic particles carried on the magnet roller. And this is arrange | positioned in the cleaning container 10c in the site | part g of the drum rotation direction upstream from the blade contact point h.

  The magnet roller 10e is arranged substantially in parallel with the drum 1 with a predetermined slight gap (gap) between the magnet roller 10e and the drum 1. A magnetic brush 10f of magnetic particles is formed and supported by magnetically adsorbing magnetic particles on the outer peripheral surface of the magnet roller. The magnetic brush 10f is in contact with the drum surface. The magnet roller 10e is rotationally driven at a predetermined speed in the clockwise direction indicated by an arrow by a drive mechanism (not shown). As the magnet roller 10e rotates, the magnetic brush 10f also rotates in the clockwise direction of the arrow together with the magnet roller 10e. At the drum contact portion g of the magnetic brush 10f, the rotation direction of the magnetic brush 10f is opposite to the drum rotation direction, and the drum surface is rubbed well by the magnetic brush 10f.

  Part of the transfer residual toner (including paper dust) on the drum carried to the cleaning device 10 by the subsequent rotation of the drum 1 after the transfer process is partially applied by the magnetic brush 10f that rubs the drum surface. It reaches the edge of the cleaning blade 10a while being scraped off. That is, it reaches the contact point h between the cleaning blade 10a and the drum 1, and is scraped off from the drum surface like canna waste in the flow shown by the arrow A in FIG. The transfer residual toner thus scraped off is conveyed by the magnetic brush 10f and passes through the line of the arrow B to the upper surface side of the cleaning blade 10a. Then, the inside of the cleaning container 10c is transported to the one end side in the longitudinal direction of the rotational transport member by the rotational transport member 10b. Further, the toner is discharged and conveyed from the cleaning container 10c to a waste toner box (not shown).

  The magnetic brush 10f acts to uniformly re-apply the transfer residual toner scraped off from the drum surface and reach the cleaning blade 10a. In addition, the surface of the drum is rubbed and polished with the abrasive particles contained in the magnetic brush 10f, and the abrasive particles are uniformly reapplied to the drum surface to reach the cleaning blade 10a. The drum surface is also rubbed by the abrasive particles that have reached the contact point h between the cleaning blade 10 a and the drum 1.

  As described above, the abrasive particles are externally added to the developer contained in the developing device 4, and adhere to the drum surface together with the toner when developing the electrostatic latent image on the drum surface. In the transfer step, toner mainly moves to the recording material P, and most of the abrasive particles remain on the drum surface and are carried to the cleaning device 10 so that they are mixed and replenished in the magnetic brush 10f.

  As the magnetic particles constituting the magnetic brush 10f, for example, a magnetic carrier such as iron powder used in the magnetic brush charging device can be used. When the magnetic toner is used as the developer as in the image forming apparatus of this example, the magnetic brush is used as the magnetic particles constituting the magnetic brush 10f, so that the high durability of the magnetic brush due to toner replacement is achieved. Can be realized. In this example, magnetic toner is used as magnetic particles constituting the magnetic brush 10f.

  In the drum surface rubbing with the magnetic brush 10f, if the strength of the magnetic brush is high, scraping lines are generated and the blade slip of the abrasive particles tends to be uneven.

  In particular, when the blade position angle θ is in the range of −20 degrees to +100 degrees, the toner flow A becomes dull due to the weight of the waste toner, and the influence of non-uniform abrasive particles becomes large.

  The magnetic brush 10f applies uniform abrasive particles, which are cleaning aids, to the photoreceptor to achieve uniform cleaning along the length of the photoreceptor. If the application of the abrasive particles is not uniform, the load on the cleaning blade 10a is locally concentrated and develops into a blade chip. In addition, the external additive having a lubricating action for sliding the blades becomes streaks, and particularly the contact charging member 2a is also contaminated with streaks and easily causes image defects.

  In particular, the abrasive particles in the present invention have a number average particle size of 30 nm to 300 nm and are appropriately small as viewed from the toner. This particle size has the property that slipping through the blade is gradually performed and it is easy to pass through in a streak shape. When the average particle size is smaller than 30 nm, the blade is hardly blocked, and when it is larger than 300 nm, it is difficult to come off. In order to prevent streaking, it is necessary to make contact with the drum like a fluid and supply abrasive particles without streaking.

  As a result of intensive studies, the present inventors have found a condition in which abrasive particles can be supplied without contact by contacting the photoconductor like a fluid while having an appropriate photoconductor rubbing force.

That is, the following formula 7.0 ≦ B × M / 100 ≦ 23.0
60 ≦ B × M × D ≦ 320
It has been found that by satisfying the above, it is possible to form an image with less streaking.

However,
B: Maximum magnetic flux density (mT) of the mag roller at the photosensitive member surface position
M: saturation magnetization of magnetic particles (Am ² / kg)
D: It is an average particle diameter of the inorganic powder abrasive particles at 30 nm to 300 nm.

  By performing cleaning and rubbing polishing with a magnetic brush containing an abrasive on the surface of the high durability image bearing member under appropriate conditions, it is possible to form a high-quality and long-life image without causing an image flow. That is, a configuration in which abrasive particles having an average diameter of 30 to 300 nm are included in the magnetic brush, and the strength of the magnetic brush is appropriately set to behave fluidly on the surface of the image bearing member and rub with an abrasive without unevenness. Therefore, image flow can be prevented. At the same time, the charging member can be uniformly soiled, and image formation with high image quality and long life can be performed.

<Electrophotographic photoreceptor>
An electrophotographic photosensitive member (drum) 1 that is an image bearing member is preferably a durable photosensitive member that is less worn by a contact member such as a cleaning blade. In particular, the amorphous silicon (a-Si) photoreceptor has a very high Vickers hardness of 500 or more (500 Kg / m ² or more, JIS standard), and is excellent in durability, heat resistance, and environmental stability. In this example, an amorphous silicon photoreceptor is used.

  FIGS. 3A and 3B are schematic views showing an example of the layer structure of an amorphous silicon electrophotographic photosensitive member.

  The photoconductor 1 (a) is obtained by sequentially laminating a photoconductive layer 12 and a surface protective layer 13 on a base 11 made of a conductive material such as Al or stainless steel.

  In addition to these layers, various functional layers such as a lower charge injection blocking layer, an upper charge injection blocking layer, a charge injection layer, and an antireflection layer can be provided as necessary.

  The photosensitive member 1 of (b) is further provided with a lower charge injection blocking layer 14 and an upper charge injection blocking layer 15. By selecting a group 13 element or a group 15 element in the periodic table as a dopant, it is possible to control the charging polarity such as positive charging and negative charging.

  The shape of the substrate 11 may be as desired according to the driving method of the electrophotographic photosensitive member. As the base material, it is common to use conductive materials such as Al and stainless steel. For example, these conductive materials are deposited on non-conductive materials such as various plastics and ceramics. In addition, those imparted with conductivity can also be used.

  A typical example of the photoconductive layer 12 is an amorphous material containing silicon atoms and hydrogen atoms or halogen atoms (abbreviated as “a-Si (H, X)”). The thickness of the layer is not particularly limited, but about 15 to 50 μm is appropriate in consideration of manufacturing costs. Further, the photoconductive layer 12 may have a plurality of layer structures such as a lower photoconductive layer 16 and an upper photoconductive layer 17 as shown in FIG.

  The surface protective layer 13 is generally formed of the following exemplary materials 1) to 3).

1) Non-single-crystal (preferably amorphous) material a-SiC (H, X) containing a silicon atom as a base and containing a carbon atom and, if necessary, a hydrogen atom or a halogen atom
2) Non-single crystal (preferably amorphous) material a-SiN (H, X) containing a silicon atom as a base and containing a nitrogen atom and, if necessary, a hydrogen atom or a halogen atom
3) Non-single crystal carbon (preferably amorphous carbon) aC (H, X) containing a carbon atom as a base and containing a hydrogen atom or a halogen atom as necessary
Further, the interface between the photoconductive layer 12 and the surface protective layer 13 may be continuously changed, an antireflection layer may be provided, and control may be performed so as to suppress interface reflection of the portion.

<Charging device 2>
As described above, the charging method in this example is a contact charging method in which a roller-type charging member (charging roller) 2a is used, brought into contact with the photoreceptor 1, and a voltage is applied to charge the surface of the photoreceptor. is there.

  The contact charging device contacts a charged object such as an image carrier with a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Let Then, a predetermined charging bias is applied to the contact charging member to charge the surface to be charged to a predetermined polarity / potential.

  Although a roller-type charging member is widely used as a simple and inexpensive charging member, it is weak against streaky dirt such as toner or abrasive that passes through the cleaning blade, and this often determines the life of the charging member. As a condition for causing streak-like dirt, it is remarkable when particles having a particle size that is easily released from the toner particles and easily removed from the blade are used.

  Also, the roller-type contact charging member is difficult to ensure a close contact with the photosensitive member as compared with the brush type and the like, and is disadvantageous to the injection charging mechanism.

  The discharge charging mechanism is a mechanism in which the surface of the charged body is charged by a discharge phenomenon that occurs in a minute gap between the contact charging member and the charged body. Since the discharge charging mechanism has a constant discharge threshold value for the contact charging member and the member to be charged, it is necessary to apply a voltage larger than the charging potential to the contact charging member. Moreover, although the amount of generation is much smaller than that of a corona charger, the generation of discharge products is unavoidable in principle, so that harmful effects due to active ions such as ozone are unavoidable.

  The voltage applied to the charging member may be only a DC voltage or a DC / AC component superimposed voltage. As the AC component, in the case of the injection charging method, although depending on the process speed of the apparatus, the peak-to-peak voltage of the applied AC component is preferably about 1000 V or less at a frequency of about 100 Hz to 10 kHz. When the voltage exceeds 1000 V, the photosensitive member potential is obtained with respect to the applied voltage, so that the latent image surface may be wavy in terms of potential, causing fogging and density thinning.

  In the case of a charging method using discharge, the AC component has a frequency of about 100 Hz to 10 kHz depending on the process speed of the apparatus, and the peak-to-peak voltage of the applied AC component is about 1000 V or more, which is twice the discharge start voltage. The above is preferable. As the waveform of the alternating current component to be applied, a sine wave, a rectangular wave, a sawtooth wave or the like can be used.

  The contact charging member is not particularly selected as long as it is a member that makes contact with a photosensitive member such as a roller, brush, or plate type, and among them, the roller type charging member secures a wide area for charging. It is more preferable because it is possible.

The contact charging member used in this example is the flexible conductive elastic roller (charging roller) 2a disposed in contact with the photoreceptor 1 with a predetermined pressing force as described above. It is important that the charging roller 2a which is a contact charging member functions as an electrode. In other words, it is necessary to obtain sufficient contact with the photosensitive member 1 that is a member to be charged by providing elasticity, and at the same time, have a sufficiently low resistance to charge the moving photosensitive member. On the other hand, it is necessary to prevent voltage leakage when there is a low breakdown voltage defect portion such as a pinhole in the photoreceptor. When an electrophotographic photoreceptor is used as the member to be charged, a resistance of 10 ⁴ to 10 ⁷ Ω is desirable in order to obtain sufficient chargeability and leakage resistance.

  If the hardness of the charging roller 2a is too low, the shape is not stable, and the contact property with the photosensitive member is deteriorated. If it is too high, a charging nip portion cannot be secured between the photosensitive member and the micro contact property to the surface of the photosensitive member is deteriorated. The hardness of the charging roller 2a is preferably in the range of 25 to 50 degrees in terms of Asker C hardness.

  The material of the elastic layer 2c is not limited to an elastic foam. Examples of elastic materials include EPDM, urethane, NBR, silicone rubber, rubber materials in which conductive materials such as carbon black and metal oxide are dispersed for resistance adjustment in IR, and the like, and those obtained by foaming these materials. can give. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance.

  Charging in this example is performed by setting a DC voltage value so that the photosensitive member has a desired potential and applying it, and superimposing an alternating voltage on the surface of the photosensitive member as an energy for charging. For example, when a potential of −400 V is applied to the surface of the photoreceptor, a −400 V DC voltage is applied, and an AC voltage of about 0.1 to 3.0 kV is superimposed depending on the charging means and the resistance of the photoreceptor. To do.

  In the contact charging, it is necessary to cause some discharge between the charging member and the photosensitive member in order to ensure sufficient chargeability by applying the charge. In particular, when charging is performed by applying an AC voltage having excellent charging uniformity, stabilization of the potential by discharging is indispensable. If this discharge is insufficient, charging unevenness will occur and unevenness will occur in halftone, or a charging failure that will cause black spots on the white background of the image, such as sandy fog, will occur. The image quality is greatly changed and the influence on the image is likely to occur. However, even if the discharge amount is too large, an increase in abrasion due to deterioration of the surface of the photoreceptor, a cleaning failure due to a decrease in slipperiness, and the like may occur.

<Toner T>
The production method of the toner T is not particularly limited, and a suspension polymerization method, an emulsion polymerization method, an associative polymerization method, a kneading pulverization method, or the like is used.

  In the production method of a polymerized toner, components necessary for a toner such as a magnetic substance, a release agent, a plasticizer, a charge control agent, a cross-linking agent, and, in some cases, a colorant are generally added to a polymerizable monomer. In addition, other additives, for example, an organic solvent, a high molecular weight polymer, a dispersing agent and the like which are added in order to reduce the viscosity of the polymer produced by the polymerization reaction are appropriately added. Then, the compound (monomer system) in which the blend is uniformly dissolved or dispersed by a disperser such as a homogenizer, a ball mill, a colloid mill, or an ultrasonic disperser is added to an aqueous medium containing a dispersion stabilizer. Suspend.

  At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Further, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added immediately after granulation and before starting the polymerization reaction.

  As the dispersion stabilizer, known surfactants and organic / inorganic dispersants can be used. Among them, inorganic dispersants are unlikely to produce harmful ultrafine powders, and because of their steric hindrance, dispersion stability is obtained, so even if the reaction temperature is changed, stability is not easily lost, and cleaning is easy and does not adversely affect the toner. Can be preferably used.

  In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent or wax to be sealed inside is precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, it is possible to raise the reaction temperature to 90 to 150 ° C. at the end of the polymerization reaction.

  Furthermore, it can also be produced by a dispersion polymerization method in which a toner is produced directly using an aqueous organic solvent that is soluble in the monomer and insoluble in the resulting polymer. Alternatively, a toner is produced using an emulsion polymerization method represented by a soap-free polymerization method in which a toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator, and polymer particles obtained by emulsion polymerization are associated and aggregated. The method can also be manufactured.

  The polymerized toner particles are filtered, washed, and dried by a known method after the polymerization is completed, and the toner can be obtained by mixing and adhering the inorganic fine powder to the surface. Moreover, it is also one of desirable forms that a classification process is included in the manufacturing process to cut coarse powder and fine powder.

  When the toner is manufactured by a pulverization method, a known method is used. For example, a binder resin, a magnetic material, a release agent, a charge control agent, and optionally a component such as a colorant and other additives necessary for the toner and other additives are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill. This is melt-kneaded using a heat kneader such as a heating roll, kneader, extruder, etc., and other toner materials such as a magnetic material are dispersed or dissolved in the resin, and cooled and solidified. After pulverization, the toner particles can be obtained by classification and, if necessary, surface treatment. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier in terms of production efficiency.

  The pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a toner having a specific degree of circularity, it is preferable to perform a process of further pulverizing by applying heat or applying a mechanical impact in an auxiliary manner. Further, a hot water method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  Examples of means for applying a mechanical impact force include a method using a mechanical impact pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry. Moreover, a method using a device such as a mechano-fusion system manufactured by Hosokawa Micron Corporation or a hybridization system manufactured by Nara Machinery Co., Ltd. can be mentioned. This is a method in which the toner is pressed against the inside of the casing by centrifugal force with high-speed rotating blades, and mechanical impact force is applied to the toner by force such as compression force and friction force.

  In the case of using the mechanical impact method, a thermomechanical impact in which the processing temperature is a temperature in the vicinity of the glass transition point Tg (Tg ± 10 ° C.) of the toner is preferable from the viewpoint of preventing aggregation and productivity. More preferably, it is particularly effective to improve the transfer efficiency to carry out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner.

<Average circularity of toner>
The circularity of the particle toner is used as a simple method for quantitatively expressing the shape of the particle. In the present invention, measurement is performed using a flow type particle image analyzer FPIA-3000 manufactured by Toa Medical Electronics, It calculated using the following formula.

Circularity = (perimeter of the same circle as the particle projection area) / (perimeter of the particle projection image)
Here, the “particle projected area” is the binarized toner particle area, and “perimeter of the same circle as the particle projected area” is the contour line obtained by connecting the edge points of the toner particle image. Define length.

  The circularity in the present invention is an index of the degree of unevenness of the particles constituting the toner, and is 1.000 when the toner is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated.

  The average circularity C is calculated from the following equation where Ci is the circularity at the dividing point i of the number-based particle size distribution and fi is the frequency fi.

As a specific measurement method, 10 ml of ion-exchanged water from which impure solids in the container have been removed in advance is prepared, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant therein, followed by further measurement. Add 0.02 g of sample and disperse uniformly. As a means for dispersion, an ultrasonic disperser UH-50 type (manufactured by SMT Corporation) equipped with a 5Φ titanium alloy chip as a vibrator is used and subjected to a dispersion treatment for 5 minutes to obtain a dispersion for measurement. In that case, it cools suitably so that the temperature of a dispersion liquid may not become 40 degreeC or more.

  To measure the shape of the toner particles, the flow type particle image analyzer is used, the concentration of the dispersion is readjusted so that the toner particle concentration at the time of measurement is 3000 to 10,000 / μl, and 1000 toner particles are obtained. Measure above. After the measurement, the circularity of the toner is obtained using this data.

  In the present invention, the circularity of the toner is preferably 0.950 or more and 0.990 or less. Below 0.950, the movement of the toner layer in the vicinity of the blade edge slows down especially in the blade arrangement of the present case, and packing becomes easy, and conversely, when it exceeds 0.990, it becomes difficult to clean the toner with a rubber blade.

<Saturation magnetization of toner>
The magnetization intensity of the magnetic toner was measured using a vibration magnetometer VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) at a room temperature of 25 ° C. and an external magnetic field of 796 kA / m. Note that the value of the saturation magnetization was obtained by measuring the toner value of the initial developer in the developing device.

<Abrasive particles Z>
As a result of intensive studies by the present inventors, the surface of the photoreceptor, the magnetic brush, and the inorganic fine powder having an average particle size (number average particle size) of 30 nm to 300 nm (0.03 μm to 0.30 μm) as abrasive particles are used. Between them. As a result, it has been found that deposits such as discharge generation substances, paper dust, and toner on the high-hardness photoconductor can be effectively removed, and image flow and foreign matter fusion on the photoconductor can be prevented.

  It is desirable that the abrasive particles Z have an appropriate circularity. Moreover, what has a rectangular parallelepiped crystal | crystallization is preferable. Among the rectangular parallelepiped abrasive particles, more preferable are strontium titanate, barium titanate, and calcium titanate, and strontium titanate is particularly preferable.

  The rectangular parallelepiped abrasive particles used in the present invention preferably have an average particle size of 30 nm to 300 nm. When the average particle size of the rectangular parallelepiped abrasive particles is less than 30 nm, the abrasive particles are liable to adhere to the toner or the photoreceptor surface, and the polishing effect is insufficient. On the other hand, if the thickness exceeds 300 nm, the external additive is removed in a streak form when it is sandwiched between the blade edge and the photoconductor, which is liable to cause charging roller streaks, photoconductor fusing and scratches.

  The particle size of the abrasive particles Z was determined by measuring 100 particle sizes from a photograph taken with an electron microscope at a magnification of 50,000 times. The particle diameter was determined by (a + b) / 2, where a is the longest side and b is the shortest side.

  Abrasive particles suitably used in the present invention are prepared by adding strontium hydroxide to a titania sol dispersion obtained by adjusting the pH of a hydrous titanium oxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution, for example. It can be synthesized by heating to temperature. By setting the pH of the hydrous titanium oxide slurry to 0.5 or more and 1.0 or less, a titania sol having a good crystallinity and a particle size can be obtained.

  For the purpose of removing ions adsorbed on the titania sol particles, it is preferable to add an alkaline substance such as sodium hydroxide to the titania sol dispersion. At this time, it is preferable that the pH of the slurry is not 7 or higher so that sodium ions and the like are not adsorbed on the surface of the hydrous titanium oxide. The reaction temperature is preferably about 60 ° C. to 100 ° C., the temperature rising rate is preferably 30 ° C./hour or less in order to obtain a desired particle size distribution, and the reaction time is 3 hours or more and 7 hours or less. preferable.

  The inorganic particles thus prepared have a circularity of 0.89 to 0.91, and can be obtained as perovskite crystals having a cubic or rectangular parallelepiped shape. Since the degree of circularity is small, it is possible to prevent particle rolling at the blade edge, and good scraping properties can be obtained. Moreover, the scraping property by the ridgeline is obtained when it is a cube shape or a rectangular parallelepiped shape.

  FIG. 4 is an electron micrograph (magnification of 20,000 times) of an example of a rectangular parallelepiped abrasive particle.

<Average circularity of abrasive particles Z>
The circularity of the abrasive particles Z in this case is obtained by capturing an enlarged image of the abrasive taken with an electron microscope into a computer. Then, the circumference of the same circle as the particle projection area and the circumference of the particle projection image were calculated by software “analySIS” of Soft Imaging System, and the circularity was calculated by the following equation.

Circularity = (perimeter of the same circle as the particle projection area) / (perimeter of the particle projection image)
For the target data, 100 samples randomly extracted from 30 nm or more and 300 nm or less abrasive images obtained from the images were used, and the average value was calculated.

<Example of photoconductor preparation>
Using an apparatus for manufacturing a photoreceptor for an electrophotographic apparatus using a high frequency plasma CVD method using a VHF band, a charge injection blocking layer, a photoconductive layer, a surface are formed on a φ30 aluminum cylinder which has been roughened by cutting the surface. An a-Si photosensitive member 1 composed of layers was produced. The obtained photoreceptor had a Vickers hardness (JIS standard) of 1200 kg / m ² .

<Production example of charging member>
A charging roller 2a as a charging member was prepared with the following specifications.

(Elastic layer)
Epichlorohydrin rubber 100 parts Quaternary ammonium salt 2 parts Calcium carbonate 30 parts Zinc oxide 5 parts Fatty acid 5 parts The above materials were kneaded for 10 minutes in a closed mixer adjusted to 60 ° C.

  Thereafter, 15 parts of an ether ester plasticizer was added to 100 parts of epichlorohydrin rubber, and the mixture was further kneaded for 20 minutes in a closed mixer cooled to 20 ° C. to prepare a raw material compound.

  To 100 parts of the raw material epichlorohydrin rubber, 1 part of sulfur as a vulcanizing agent, 1 part of Noxeller DM as a vulcanization accelerator and 0.5 part of Noxeller TS are added to this compound, and the two roll machine cooled to 20 ° C is added. And kneaded for 10 minutes.

  The resulting compound is molded around an φ6mm stainless steel support (core metal) with an extruder so as to form a roller, heat vulcanized, and then polished to an outer diameter of φ8.5mm. Thus, an elastic layer was obtained.

(Surface layer)
A surface layer as shown below was formed on the elastic layer.

As a material for the surface layer,
Acrylic polyol solution (active ingredient 70% by mass, diluted solvent xylene 30% by mass)
.... 100 parts Isocyanate A (IPDI) 40 parts (active ingredient 60% by mass; diluted solvent n-butyl acetate 15% by mass, xylene 25% by mass)
... 40 parts Isocyanate B (HDI) 30 parts (containing 80% by weight of active ingredient and 20% by weight of diluted solvent ethyl acetate)
... 30 parts Surface-treated conductive tin oxide 90 parts (Treatment agent: fluoroalkylalkoxysilane)
... 90 parts Polymethylmethacrylate (PMMA) resin particles (particle size 8μm)
... 35 parts Methyl isobutyl ketone ... 340 parts were stirred using a mixer to prepare a mixed solution.

  Next, the mixed solution was subjected to dispersion treatment (treatment speed 500 ml / min) using a circulation type bead mill disperser to prepare a coating solution of conductive tin oxide.

  Next, the stainless steel support was held in a state perpendicular to the surface of the coating solution and immersed in the coating solution to form a surface layer. At this time, a masking cap made of polyacetal was put on the lower stainless steel support 2a. Then, it was dried with a hot air dryer at 80 ° C. for 1 hour and further at 160 ° C. for 1 hour to obtain a roller-shaped charging member having a surface layer formed thereon.

<Developer production example>
Into 709 g of ion-exchanged water, 451 g of a 0.1 M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then 67.7 g of a 1.0 M CaCl ₂ aqueous solution was gradually added to obtain Ca ₃ (PO _{4 2} ) An aqueous medium containing ₂ was obtained.

Styrene ... 80 parts n-Butyl acrylate ... 20 parts Unsaturated polyester resin ... 2 parts Saturated polyester resin ... 3 parts Negative charge control agent (monoazo dye-based Fe compound) ... 1 part Surface treated hydrophobized magnetic material ( [sigma] s = 83Am < ² > / kg) ... 20-100 parts The said prescription was uniformly disperse-mixed using the attritor (Mitsui Miike Chemical Co., Ltd.).

  This monomer composition was heated to 60 ° C., and 6 parts of ester wax (maximum value of endothermic peak in DSC 72 ° C.) mainly composed of behenyl behenate was added and dissolved therein. Into this, 5 g of a polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) [t1 / 2 = 140 minutes, at 60 [deg.] C.] was dissolved.

The polymerizable monomer system was charged into the aqueous medium and granulated by stirring at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at 60 ° C. in an N ₂ atmosphere. . Then, it was made to react at 60 degreeC for 6 hours, stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C. and stirring was continued for 4 hours. After completion of the reaction, distillation was further performed at 80 ° C. for 2 hours, and then the suspension was cooled and hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ .

Then, it is filtered, washed and dried to obtain a magnetic toner having a weight average particle diameter of 6.5 μm and a saturation magnetization of 14, 15, 24, 25, 30, 31, 35, 36 Am ² / kg in an external magnetic field of 796 kA / m. It was.

These magnetic toners: 100 parts Silica with a primary particle size of 8 nm is treated with hexamethyldisilazane and the BET value after treatment is 250 m ² / g hydrophobic silica fine powder
... 1.2 parts Strontium titanate abrasive particles produced as follows A, B, C, D, E, F, G
... 1 part was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare a developer.

<Production example of rectangular parallelepiped abrasive particles Z>
Production Example 1
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, hydrochloric acid was added to the hydrous titanium oxide slurry to adjust the pH to 0.65 to obtain a titania sol dispersion. NaOH was added to the titania sol dispersion, the pH of the dispersion was adjusted to 4.5, and washing was repeated until the electrical conductivity of the supernatant reached 70 μS / cm.

0.97-fold molar amount of Sr (OH) ₂ .8H ₂ O was added to the hydrous titanium oxide, and the mixture was placed in a SUS reaction vessel and purged with nitrogen gas. Further, distilled water was added so as to be 0.1 mol / liter or more and 2.0 mol / liter or less in terms of SrTiO ₃ .

  The slurry was heated to 83 ° C. at a rate of 5 to 30 ° C./hour in a nitrogen atmosphere, and reacted for 3 to 7 hours after reaching 83 ° C. After the reaction, the mixture was cooled to room temperature, the supernatant was removed, and washing was repeated with pure water.

  Various strontium titanates A, B, and C having different average particle diameters were obtained by changing the temperature increase rate and reaction time of the slurry.

  The obtained strontium titanates had average diameters of 50, 120, and 180 nm, respectively.

  When the circularity of the particles was measured, they were 0.910, 0.895, and 0.900, respectively.

Production Example 2
After strontium titanate A was sintered at 1000 ° C., it was pulverized until the primary average particle size became 110 nm to obtain strontium titanate particles D through a sintering process. The circularity of the particles was measured and found to be 0.860. The circularity of the strontium titanate particles E that had been subjected to the two crushing steps with the spraying pressure in the crushing step set to 50% was 0.870.

Production Example 3
In 300 ml of an aqueous solution of titanium hydroxide 100 g / l (TiCl ₄ ), strontium carbonate (SrCO ₃ ) equivalent to Ti was dissolved, and potassium hydroxide (KOH) equivalent to chlorine ions in the solution was added under a nitrogen atmosphere. The mixture was stirred for 2 hours at 120 ° C. in an autoclave.

  The product was filtered, washed and dried to obtain strontium titanate particles F having a primary average particle size of 120 nm. The circularity of the particles was measured and found to be 0.930. Similarly, the strontium titanate particles G having a stirring temperature of 140 ° C. had a circularity of 0.940.

<Cleaning auxiliary member 10d>
A 14Φ 4-pole symmetric magnet roller 10e having a 6Φ cored bar with a plastic magnet attached thereto was produced.

  Magnets A, B, C, and D were obtained by changing the magnet so that the maximum magnetic flux density on the surface of the photoconductor was 76 (mT), 62 (mT), 48 (mT), and 35 (mT), respectively. .

  The magnet roller was installed so that the counter rotation peripheral speed ratio was 50% and the gap was 800 μm with respect to the photoreceptor.

  Then, the magnetic brush 10f was formed and supported on each of the magnet rollers by magnetically adsorbing magnetic toner as magnetic particles.

<Evaluation method>
1) Evaluation of image flow In an environment of 30 ° C. and humidity 85% RH, Canon digital copier iR4570 is used for an amorphous silicon photoconductor with a charging device, exposure device, and cleaning device modified image forming device. To produce 100,000 images. After displaying 1,000 and 100,000 images, turn off the power and leave it in the same environment for 48 hours, then output A100 digital halftone images and 100 5-point character images for a total of 200 images each for evaluation. did. The evaluation results were ranked as follows.

◎: 1 to 200 images with no image flow ○: Halftone highlight skipping of images after 50 sheets is slight, but characters are good △: Halftone highlight skipping of images is slightly from the first image 2) Charging streak evaluation Under a temperature of 30 ° C and humidity of 85% RH, Canon digital color copier iR4570 was charged for an amorphous silicon photoconductor. Then, the image forming apparatus in which the exposure apparatus and the cleaning apparatus are remodeled performs 100,000 images with 5% image.

  Further, after printing 100 images with a 5% image, 1000 solid white images are printed.

  In the above two cases, after endurance of the paper passing, each image was printed in an environment of a temperature of 23 ° C. and a humidity of 5% RH, and the streaks caused by the charging roller contamination of the halftone image at that time were evaluated.

◎: No streaks ○: Slight streaks are hardly visible △: Streaks are inconspicuous ×: Streaks are conspicuous 3) Evaluation of cleaning performance Canon digital under an environment of 30 ° C and humidity 85% RH The color copier iR4570 is used for an amorphous silicon photoconductor, and an image forming apparatus obtained by modifying a charging device, an exposure device, and a cleaning device outputs 500,000 sheets with a 5% image. The presence or absence and level of cleaning failure that occurred for all the output images was evaluated.

◎: No cleaning failure ○: Some sheets have streak stains due to poor cleaning, but they are not noticeable ×: One or more sheets have noticeable cleaning failure <Evaluation Result>
Tables 1 to 7 show the evaluation results of “image flow”, “charging streak stain”, and “toner cleaning property” according to the evaluation methods 1), 2), and 3).

As can be seen from the results in Tables 1-7,
B × M / 100 ≦ 23
By satisfying the above, image defects due to streaks on the charging member can be suppressed.

7 ≦ B × M / 100
By satisfying the above, it is possible to secure a sufficient scraping force of the waste toner by the magnet roller and to clean the toner satisfactorily.

60 ≦ B × M × D
By satisfying the above, it is possible to suppress the image flow during the paper passing by the rubbing of the waste toner magnet roller and the abrasive particles.

B × M × D ≦ 320
By satisfying the above, it is possible to suppress image defects due to charging member streak stains during solid white durability by rubbing between the magnet roller of the waste toner and the abrasive particles.

  By using abrasive particles having an abrasive particle circularity of 0.870 or more and 0.930 or less, the effect of suppressing image flow is further enhanced. This is because the abrasive particles A, B, C, E, and F have a circularity of 0.870 to 0.930 or more and the image flow evaluation is ◯ or more after satisfying the formula of claim 1. Since D and G have circularity of 0.860 and 0.940, respectively, it is concluded from Δ in the image flow evaluation.

When the saturation magnetization strength of the magnetic powder constituting the magnetic brush is 15 Am ² / kg or more and 35 Am ² / kg or less at a magnetic field of 796 kA / m, the ears of the magnetic brush become dense and better prevent charging roller streak stains. it can. This is because, when satisfying the formula of claim 1 and when the magnetic particle (toner) saturation magnetization is 15, 24, 25, 30, 31, 35, the charged streak stain is ◎, and when the saturation magnetization is 14 or 36, It is concluded from the fact that the charged streak stain is ○.

<Special notes>
1) In the above examples, strontium titanate was used as the abrasive particles, but the same effect can be obtained with barium titanate and calcium titanate.

  2) Although the a-Si electrophotographic photoreceptor is used as the image carrier, other electrophotographic photoreceptors such as an OPC electrophotographic photoreceptor can be used. The image carrier may be an electrostatic recording dielectric.

  3) Although the charging roller is used as the contact charging member, other types of charging members such as a brush type and a plate type may be used.

  4) The charging member is not necessarily in contact with the image carrier surface. If a dischargeable area determined by the voltage between the gap and the correction Paschen curve is guaranteed between the charging member and the image carrier surface, for example, a gap (gap) of several tens of μm exists and is arranged close to the non-contact. (Proximity charging).

  5) The information writing means when the image carrier is an electrophotographic photosensitive member is not limited to the laser scanner of the embodiment. Other digital exposure means corresponding to a combination of a light source such as an LED array or a fluorescent lamp and a liquid crystal shutter may be used, or analog exposure means for imaging and projecting a document image.

  When the image carrier is an electrostatic recording dielectric, the dielectric surface is uniformly charged, and then selectively neutralized by a neutralizing means such as a static elimination needle array or an electron gun, so that an electrostatic latent image of image information is obtained. It is formed.

  6) The transfer means is not limited to the contact system using the transfer roller of the embodiment, but may be a non-contact system using a corona charger.

  7) The recording medium may be an intermediate transfer member such as an intermediate transfer drum or an intermediate transfer belt. In this case, the toner image is transferred again from the intermediate transfer member to a secondary recording medium such as paper.

  8) The cleaning auxiliary member 10d has a nonmagnetic or magnetic thruve fitted on the magnet roller 10e, magnetic particles are magnetically adsorbed on the outer circumferential surface of the thruve to form and carry a magnetic brush, and the thruve or the magnet roller is rotated. It can also be configured.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is the elements on larger scale of a cleaning device. It is a layer structure model figure of an amorphous silicon photoconductor. It is an electron micrograph of an example of a rectangular parallelepiped abrasive particle.

Explanation of symbols

  1 .... photosensitive member (image carrier), 2a ... charging roller, 3 .... exposure device, 4 .... developing device, 6a ... transfer member, 9 .... fixing device, 10 .... cleaning device, ... Substrate 12... Photoconductive layer 13.. Surface protection layer 14.. Lower charge injection blocking layer 15 upper charge injection blocking layer 16 lower photoconductive layer 17 upper photoconductive layer 10a ... Cleaning blade, 10b ... Waste toner feed blade, 10d ... Cleaning auxiliary member (rubbing auxiliary member), 10e ... Magnet roller, 10f ... Magnetic brush

Claims (8)

A charging step for charging the image carrier by bringing a charging member to which a voltage is applied into contact with or approaching a rotating drum-type image carrier, and an information writing step for forming an electrostatic latent image on the charging surface of the image carrier A developing step of developing the electrostatic latent image as a toner image with a developer, a transfer step of transferring the toner image to a recording medium, and a cleaning in which the image carrier is brought into contact with a counter with respect to the rotation direction. A cleaning step of removing residual toner on the image carrier after the transfer step by a blade, and in a cross section of the image carrier, a vertical line extending upward through the rotation center of the image carrier The angle formed by the line connecting the contact point between the cleaning blade and the image carrier and the rotation center of the image carrier is defined as the blade position angle θ, and the angle downstream of the image carrier rotation direction from the vertical line is + , The angle of the opposite - when the side, in the image forming method of the blade position angle θ is set in a range of -20 degrees to + 100 degrees,
Inorganic powder abrasive particles having a number average particle size of 0.03 μm to 0.30 μm are externally added to the developer,
The surface of the image carrier after the transfer process is a magnet roller upstream of the contact point between the cleaning blade and the image carrier in the rotation direction of the image carrier and downstream of the transfer process in the rotation direction of the image carrier. It has a cleaning auxiliary step of rubbing with the magnetic brush of the supported magnetic particles, and the following formula 7 ≦ B × M / 100 ≦ 23
60 ≦ B × M × D ≦ 320
B: Magnet roller maximum magnetic flux density (mT) at the surface of the image carrier
M: saturation magnetization of magnetic particles (Am ² / kg)
D: Average diameter of inorganic powder abrasive particles of 0.03 μm to 0.30 μm (μm)
An image forming method characterized by satisfying   The image forming method according to claim 1, wherein the circularity of the inorganic powder abrasive particles is 0.870 or more and 0.930 or less.   The image forming method according to claim 1, wherein the shape of the inorganic powder abrasive particles is a cubic shape or a rectangular parallelepiped shape.   4. The image forming method according to claim 1, wherein the inorganic powder abrasive particles are strontium titanate, barium titanate, or calcium titanate.   The image forming method according to claim 1, wherein the toner is a magnetic toner, and the magnetic particles are a magnetic toner.   6. The image forming method according to claim 1, wherein the toner has a circularity of 0.950 to 0.990.   7. The image forming method according to claim 1, wherein the image carrier has a photoconductive layer made of a non-single crystal material having a silicon atom as a base. 8. The image forming method according to claim 1, wherein a saturation magnetization intensity of the magnetic particles is 15 to 35 Am ² / kg at a magnetic field of 796 kA / m.