Title of Invention: Image forming apparatus and process cartridge detachably attachable thereto Abstract: To provide an image forming apparatus including: an image bearing member which is movable; an electrifying device which makes contact with the image bearing member and electrifies the image bearing member; a developing device for developing a latent image on the image bearing member by toner; and an abutting member which is provided on a downstream side in a moving direction of the image bearing member with respect to the electrifying device and the contacting portion of the image bearing member and abuts against the image bearing member, in which the image bearing member electrified by the electrifying device is exposed to have the latent image formed, a toner image formed on the image bearing member by the developing device is transferred to a recording material, and the developing device recovers residual toner on the image bearing member after transfer. Summary of Invention: BACKGROUND OF THE INVENTION &lsqb;0001&rsqb; 1. Field of the Invention &lsqb;0002&rsqb; The present invention relates to an image forming apparatus such as a copier and a printer and a process cartridge detachably attachable thereto, and more particularly, to an apparatus for recovering residual toner on an image bearing member by developing means after transfer. &lsqb;0003&rsqb; 2. Related Background Art &lsqb;0004&rsqb; Recently, miniaturization of an image forming apparatus such as an electrophotographic copier, a printer has been proceeding. There have been limits to the miniaturization effected merely by miniaturizing each means in a process of forming an image such as electrifying, exposing, developing, transferring, fixing and cleaning. &lsqb;0005&rsqb; In an image forming apparatus of the transferring type, some transfer residual toner on a photosensitive member (hereinafter referred to a photosensitive drum) as an image bearing member after transfer is collected by a cleaner as waste toner, which is preferably not produced in terms of environmental protection. &lsqb;0006&rsqb; This causes an appearance of an image forming apparatus of a cleaner-less system where a cleaner is removed to carry out cleaning simultaneous with developing of the transfer residual toner by a developing apparatus (developing device). The cleaning simultaneous with developing is a method of recovering some transfer residual toner on the photosensitive drum after the transfer by a fog clearing bias (a potential difference of the fog clearing bias “V back” which is the potential difference between a direct voltage applied on developing means and a surface potential of the photosensitive drum) at the time of developing in and after a next process. &lsqb;0007&rsqb; According to this method, the transfer residual toner is recovered by the developing means to be used in and after the next process, which produces no waste toner and reduces trouble in maintenance. Such a cleaner-less system has a great advantage in space to permit the considerable miniaturization of the image forming apparatus. Further, an electrifying apparatus (electrifying device) of the contact electrifying type permits once recovering the transfer residual toner by an electrifying member which makes contact with the photosensitive drum and discharging the same again onto the photosensitive drum to be recovered by the developing means. &lsqb;0008&rsqb; Moreover, the contact electrifying apparatus, namely the apparatus of a type which effects electrification by abutting a voltage-applied electrifying member against the photosensitive drum, has been in practical use as the electrifying means of the photosensitive drum because of its advantage of low power or the like. &lsqb;0009&rsqb; As such a contact electrifying apparatus, a magnetic brush electrifying apparatus has been preferably used in terms of stability of an electrifying contact. In the magnetic brush electrifying apparatus, the electrification is started by magnetically attracting conductive magnetic particles as a magnetic brush directly on a magnet or a sleeve containing the magnet, stopping or rotating the magnetic brush to be contacted with the photosensitive drum and applying the voltage thereon. &lsqb;0010&rsqb; Conductive fibers in the form of a brush (a fur brush) and a conductive rubber roller which is a rolled conductive rubber have been preferably used as a contact electrifying member. &lsqb;0011&rsqb; Especially, the electrifying apparatus of the magnetic brush type and, as the photosensitive drum, a normal organic photosensitive drum having a surface on which the conductive fine particles are dispersed or an amorphous silicon photosensitive drum are used to make it possible to obtain, on the surface of the photosensitive drum, an electrifying potential substantially the same as a direct component of the bias applied on the magnetic brush as the contact electrifying member. Such an electrifying method is called injecting electrification. This injecting electrification utilizes, in the electrification to the photosensitive drum, no electric discharging phenomenon as in the case of using a corona electrifying device, which permits the electrification of the complete ozone-less and low power consuming type, and attention has been paid thereto. &lsqb;0012&rsqb; In the image forming apparatus using such an injection electrifying method, use of a spherical carrier granulated by polymerizing as the conductive magnetic particle (hereinafter referred to as an injection carrier) narrows an area in contact with the photosensitive drum and prevents reaching a desired potential to cause a defective image such as fog or ghost when passing-sheet enduring is continued. &lsqb;0013&rsqb; This brings the use of a carrier granulated by grinding (hereinafter referred to a ground carrier) instead of the spherical injection carrier. The ground carrier produces a finely powdered carrier, which enlarges the area in contact with the photosensitive drum and thereby increases an electrifying property of the photosensitive drum. Further, the ground carrier is easy to convey and has large friction against the photosensitive drum, which facilitates recovering the transfer residual toner and increases a cleaning property. &lsqb;0014&rsqb; When such injection electrification is used as the electrifying method, the injection carrier is preferably of grounded shape in order to prevent degradation of the image resulting from the poor electrification. &lsqb;0015&rsqb; In the injection electrifying method, the photosensitive drum passes an electrifying portion (electrifying area or electrifying nip) which is a contacting portion with the magnetic brush as the contact electrifying member. If the electrification is carried out merely by applying a DC (direct current) bias, the potential difference between a carrying member for the magnetic brush (hereinafter referred to an injection sleeve) and the photosensitive drum is wide when the photosensitive drum starts contact with the magnetic brush at the electrifying portion so that the resistance of the injection carrier is low to facilitate flow of the current. &lsqb;0016&rsqb; Just before the photosensitive drum is separated from the electrifying portion, however, the potential is on the surface of the photosensitive drum to decrease the potential difference between the injection sleeve and the photosensitive drum and to thereby increase the resistance of the injection carrier. It is known that this causes difficulty in the flow of the current and reduces the electrifying property of the photosensitive drum (FIG. 5). &lsqb;0017&rsqb; For this reason, in the injection electrifying method, often used is applying an AC (alternate bias) at the same time as applying the DC (direct bias applying) as the electrifying bias. Applying the AC decreases the resistance of the injection carrier to facilitate the flow of the current and to increase the electrifying property to the photosensitive drum, which permits the electrification to a desired potential. &lsqb;0018&rsqb; However, the electrification by simultaneously applying the AC causes a micro potential difference between the photosensitive drum and the injection sleeve corresponding to a waveform of the AC. An example of this is shown in FIG. 6. For example, when the electrification is carried out at −500 V by applying the DC and simultaneously by applying the AC at 700 Vpp, there exist locally the potential differences of −150 V at the injection sleeve and −850V at the photosensitive drum. The potentials of the injection sleeve and the photosensitive drum are the same during the time when the photosensitive drum passes the electrifying portion which is the contacting portion with the magnetic brush, and just after the photosensitive drum has passed the electrifying portion, phases of the potentials are shifted between the injection sleeve and the photosensitive drum. The shift of the phase occurs such as the injection sleeve at −150 V and the photosensitive drum at −850 V causes the potential difference at 700 V between the injection sleeve and the photosensitive drum. At this time, between the injection sleeve and the photosensitive drum, a voltage drop between the injection carrier and the photosensitive drum is the largest, so that the injection carrier is attracted to the photosensitive drum. This phenomenon is called “carrier adhesion”. &lsqb;0019&rsqb; When the injection electrification is used as the electrifying method, simultaneously applying the AC is preferable and some occurrence of such carrier adhesion cannot be avoided during the injection electrification. &lsqb;0020&rsqb; When the injection carrier after the carrier adhesion reaches a transferring portion, the injection carrier enters a nip between a transferring member and the photosensitive drum, which results in damaging the photosensitive drum. &lsqb;0021&rsqb; The potential is difficulty in reaching a once damaged portion of the photosensitive drum so that the potential difference between the injection sleeve and the photosensitive drum is increased to acceleratedly increase the carrier adhesion. Repeating a passing-sheet test then further deepens the damage of the photosensitive drum and the potential does not reach the damaged portion so that phenomenon of streak-like developing (hereinafter referred to “streak-like fog”) occurs. &lsqb;0022&rsqb; When the injection carrier is changed in its shape from spherical to ground in order to increase the electrifying property, the particle of the ground carrier has a large number of edges in contact with the photosensitive drum at points, so that pressures thereon are also increased. Accordingly, the use of the ground carrier especially often damages the photosensitive drum to easily cause a defective image by the damage before twenty thousand sheets are passed in the passing-sheet test. &lsqb;0023&rsqb; In the light of the above condition, Japanese Patent Application Laid-Open No. 59-133569 discloses a mechanism of trapping magnetic fine particles which abuts a blade against the photosensitive drum on an downstream side in a rotational direction of the photosensitive drum with respect to a magnetic brush electrifying member to trap and recover the magnetic fine particles separated from a magnetic brush and moved to the photosensitive drum. In this case, when the ground carrier enters a nip between the blade and the photosensitive drum, the carrier is likely to damage the surface of the photosensitive drum, and its influence is much stronger especially in the photosensitive drum which surface is not very hard. At this time, the use of such a blade damages the photosensitive drum and causes the defective image within the passing-sheet test of ten thousand sheets. &lsqb;0024&rsqb; In the cleaner-less system which recovers the transfer residual toner by the magnetic brush electrifying member and discharges the same again onto the photosensitive drum to be recovered again by the developing apparatus, the toner discharged from the magnetic brush is also dammed by the above described blade to cause remarkable contamination from the toner in the electrifying apparatus. This prevents the electrification to the desired potential, resulting in the defective image such as the fog or ghost due to the poor electrification within the passing-sheet test of ten thousand sheets. &lsqb;0025&rsqb; In the above described electrifying apparatus, the transfer residual toner is once recovered in the contact electrifying member and then discharged onto the image bearing member by potential operation to be recovered by the developing apparatus. However, all the transfer residual toner having reached the above described electrifying apparatus is not ideally discharged, with the normal charge maintained, onto the image bearing member and passed on the image bearing member to be recovered by the developing apparatus. The remaining toner is finally accumulated in the electrifying apparatus or spattered from the contact electrifying member or the image bearing member to contaminate the inside of a body of the image forming apparatus. Especially in a system where exposing means such as LED is arranged near the electrifying apparatus, the spattered toner attached to a surface of the LED to thereby shut off exposure will cause an undesirable image lacking. &lsqb;0026&rsqb; Further, the toner, to which the normal charge is not applied, among the toner discharged onto the image bearing member is neither recovered in the developing apparatus in a developing area nor transferred to move around on the image bearing member, thereby causing disadvantages such as spattering or shutting off the exposure when its concentration is increased. SUMMARY OF THE INVENTION &lsqb;0027&rsqb; An object of the present invention is to provide an image forming apparatus and a process cartridge detachably attachable thereto which prevents damage of an image bearing member by a conductive particle and contamination from toner by electrifying means. &lsqb;0028&rsqb; Another object of the present invention is to provide an image forming apparatus and a process cartridge detachably attachable thereto which prevents spattering of the toner from the electrifying means. &lsqb;0029&rsqb; Still another object of the present invention is to provide an image forming apparatus comprising: an image bearing member which is movable; electrifying means which makes contact with the image bearing member and electrifies the image bearing member; developing means for developing a latent image on the image bearing member by toner; and an abutting member which is provided on a downstream side in a moving direction of the image bearing member with respect to the electrifying means and a contacting portion of the image bearing member and abuts against the image bearing member, the image bearing member electrified by the electrifying means being exposed to have the latent image formed, a toner image formed on the image bearing member by the developing means being transferred to a recording material, and the developing means recovering residual toner on the image bearing member after transfer. &lsqb;0030&rsqb; Further object of the present invention is to provide an image forming apparatus and a process cartridge detachably attachable thereto comprising: an image bearing member which is movable; electrifying means which has a carrier for carrying a conductive particle and interposes the conductive particle between the carrier and the image bearing member to electrify the image bearing member; developing means for developing a latent image on the image bearing member by toner; and an abutting member which is provided on a downstream side in a moving direction of the image bearing member with respect to the electrifying means and a contacting portion of the image bearing member and abuts against the image bearing member, the conductive particle of the electrifying means making contact with the image bearing member, the image bearing member electrified by the electrifying means being exposed to have the latent image formed, a toner image formed on the image bearing member by the developing means being transferred to a recording material, the developing means recovering residual toner on the image bearing member after transfer, and a pressure of the abutting member against the image bearing member being 0.3 to 3 kPa. &lsqb;0031&rsqb; Still further object of the present invention is to provide an image forming apparatus and a process cartridge detachably attachable thereto comprising: an image bearing member which is movable; electrifying means which makes contact with the image bearing member and electrifies the image bearing member; developing means for developing a latent image on the image bearing member by toner; and an abutting member which is provided on a downstream side in a moving direction of the image bearing member with respect to the electrifying means and a contacting portion of the image bearing member and abuts against the image bearing member, the image bearing member electrified by the electrifying means being exposed to have the latent image formed, a toner image formed on the image bearing member by the developing means being transferred to a recording material, the developing means recovering residual toner on the image bearing member after transfer, and the abutting member being provided on the electrifying means. &lsqb;0032&rsqb; Yet further object of the present invention is to provide an image forming apparatus and a process cartridge detachably attachable thereto comprising: an image bearing member which is movable; electrifying means which has a carrier for carrying a conductive particle and interposes the conductive particle between the carrier and the image bearing member to electrify the image bearing member; and developing means for developing a latent image on the image bearing member by toner, the image bearing member electrified by the electrifying means being exposed to have the latent image formed, a toner image formed on the image bearing member by the developing means being transferred to a recording material, the developing means recovering residual toner on the image bearing member after transfer, and the electrifying means having a regulating member for regulating amount of the conductive particle on the carrier and a shutting-off member for shutting off spattered toner provided on a downstream side in a moving direction of the carrier with respect to the regulating member. Detailed Description: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS &lsqb;0044&rsqb; Hereinafter, the embodiments of the present invention will be described with reference to the drawings. &lsqb;0045&rsqb; (1) Schematic configuration of the image forming apparatus example. &lsqb;0046&rsqb; FIG. 1 is a schematic configuration view of the image forming apparatus example according to the present invention. The image forming apparatus of the present example is a printer of an electro-photographic process, a magnetic brush electrification system, a LED exposure system, a reverse developing system and a cleaner-less type. Reference symbol A denotes a printer main body and reference symbol B denotes an image reading apparatus (image scanner) mounted on this printer. &lsqb;0047&rsqb; a) Image reading apparatus B &lsqb;0048&rsqb; In the image reading apparatus B, reference numeral 12 denotes an original support glass (platen glass) fixedly disposed on the top surface of the apparatus, and on the top surface of this original support glass, an original G is placed with its surface to be copied put downward and is covered with an original pressure plate (note shown) on it for setting. &lsqb;0049&rsqb; Reference numeral 13 denotes an image reading unit, where an original illumination lamp (original lighting lamp), a short focus lens array, a CCD sensor and the like are disposed. This image reading unit 13 is, when a copy button (not shown) is pushed, driven onward along the under surface of the glass from the right corner side of a home position as shown by a solid line to the left corner side under the original support glass 12 and, upon reaching the last stop, driven back to the initial home position as shown by the sold line. &lsqb;0050&rsqb; In the course of the reciprocating movement of the unit 13, the downward image surface of the original G mounted for setting on the original support glass 12 is scanned in order from the right corner side to the left corner side by the original illumination lamp, and the reflected light on the original surface of the illumination scanning light is imaged and incident upon the CCD sensor by the short focus lens array. &lsqb;0051&rsqb; The CCD sensor is composed of a light receiving region, a transfer region and an output portion. In the CCD light receiving portion, light signals are converted to charged signals and, synchronized with clock pulses in the transfer region are transferred in order to the output portion. In the output portion, the charged signals are converted to voltage signals and amplified, induced to low impedance and outputted. The analogue signals obtained in this way are processed with the known image processing, converted to digital signals and transmitted to the printer A. &lsqb;0052&rsqb; That is, the image information of the original G is read by the image reading apparatus B as time series electrical digital picture element signals (image signals). &lsqb;0053&rsqb; b) Printer A &lsqb;0054&rsqb; In the printer A, reference numeral 1 denotes an electrophotographic sensitive member (photosensitive drum) of a rotary drum type as a movable image bearing member. The photosensitive drum 1 of the present example is a negative charged OPC sensitive member having a charge injecting layer on its surface. The description of this sensitive member will be described in detail in clause (2). &lsqb;0055&rsqb; The photosensitive drum 1 is rotationally driven clockwise in the arrow direction at a predetermined circumferential speed with a central support axis as a center and, when copy signals are input, receives a uniform electrifying processing of −700V at an electrified portion (electrified area, electrified nip portion) in the case of the present example by contact electrifying means 2. The contact electrifying means 2 in the present example is a magnetic brush electrifying device (injecting electrifying device). This magnetic brush electrifying device 2 will be described in detail in clause (3). &lsqb;0056&rsqb; The scanning exposure of the image information is performed in an exposure region b by the LED exposure device 3 as image exposure means against the uniformly electrified surface of the rotary photosensitive drum 1, and on the surface of the rotary photosensitive drum 1, electrostatic latent images corresponding to the image information of the original G read photoelectrically by the image reading apparatus B are formed in order. &lsqb;0057&rsqb; The LED exposure device 3 is a light emitting element array which arranges a number of LEDs in the main scanning direction of the photosensitive drum 1, and the emitted light of each LED of the LED exposure device 3 is selectively controlled ON/OFF corresponding to image signals transmitted to the printer region A side from the image reading apparatus B side. Moreover, the sub scanning by the rotation of the photosensitive drum 1 reduces the electric potential of the exposure portion (light portion potential) through the emitted light of LED in the surface of the rotary photosensitive drum 1, thereby forming electrostatic latent images corresponding to exposure patterns by contrast with the electrical potential (dark portion potential) of non-exposure portions. &lsqb;0058&rsqb; The electrostatic latent images formed in the photosensitive drum 1 surface are developed reversed in order as the toner images in a developing region c by the developing apparatus 4. The developing apparatus 4 of the present example is an apparatus of a two component contact developing system. This developing apparatus 4 will be described in detail in clause (4). &lsqb;0059&rsqb; On the other hand, a transfer material P as a recording medium stored inside a sheet-feeding cassette 7 is drawn out one by one by a sheet-feeding roller 71 and fed inside the printer main body A through a sheet pass 72 and fed to a transfer portion (transfer nip) d which is a contact region between the photosensitive drum 1 and a belt type transfer device 5 as transfer means by a registration roller 73 through a sheet pass 74 with a predetermined control timing. &lsqb;0060&rsqb; On the surface of the transfer material P fed to the transfer region d, a transfer electrified blade 54 disposed inside a transfer belt 51 electrostatically transfers in order toner images of the photosensitive drum 1. This transfer device 5 will be described in detail in Clause (5). &lsqb;0061&rsqb; The transfer material P which received the transfer of the toner images through the transfer region d is separated in order from the surface of the photosensitive drum 1 and carried to a fixing device 8 at the transfer belt extended portion of the transfer device 5 and outputted as an image formed object (copy, print) on a sheet discharging tray 10 outside of the apparatus from a sheet discharging roller 9 upon receipt of a heat fixation of the toner images. &lsqb;0062&rsqb; Reference numeral 6 denotes a conductive brush as supplementary electrifying means and is abutted against the photosensitive drum 1 in the upstream side of the rotational direction of the photosensitive drum rather than the electrified portion a in the downstream side of the rotational direction of the photosensitive drum. Reference symbol e denotes a contact region between this conductive brush 6 and the photosensitive drum 1. In the present example, it is attached and disposed on the magnetic brush electrifying device 2. &lsqb;0063&rsqb; Reference numeral 11 denotes an injecting carrier shielding member which is an abutting member disposed by contacting with the photosensitive drum 1 in the downstream side of the rotational direction of the photosensitive drum rather than the electrified region a. Reference symbol f is a contact portion (contact nip portion) between this injecting carrier shielding member 11 and the photosensitive drum 1. &lsqb;0064&rsqb; The cleaner-less system, the above described conductive brush 6 and the injecting carrier shielding member 11 will be described in detail in clause (6). &lsqb;0065&rsqb; (2) Photosensitive Drum 1 &lsqb;0066&rsqb; For the photosensitive drum 1 as the image bearing member, an organic sensitive member generally used and the like can be used. However, when the organic sensitive member preferably having a surface layer of the material with a resistance of 109 to 1014 &OHgr;·cm or an amorphous silicon sensitive member and the like are used, a charge injecting charge can be realized. This has a strong effect on preventing the generation of ozone and reducing consumption electrical power. Electrostatic property can be also enhanced. &lsqb;0067&rsqb; The photosensitive drum 1 used in the present example is, as shown in a layer structure model view of FIG. 2, the negatively electrified organic sensitive member having a charge injecting layer if disposed on its surface where the following five layers of a first to a fifth layer from 1b to 1f are disposed on a drum substrate (hereinafter referred to as aluminum substrate) 1a made of aluminum having a diameter of 30 mm. &lsqb;0068&rsqb; The first layer 1b: an under coating layer, which is an conductive layer with a thickness of 20 &mgr;m disposed for equalizing defects and the like of the aluminum substrate 1a. &lsqb;0069&rsqb; The second layer 1c: a positive charge injecting prevention layer, which plays a role of preventing a negative charge where the positive charge injected from the aluminum substrate 1a is electrified on the sensitive member surface and is a middle resistance layer having a thickness of 1 &mgr;m adjusted in resistance to a degree of 1×106 &OHgr;·cm by amylene resin and methoxide methylation nylon. &lsqb;0070&rsqb; The third layer 1d: a charge generating layer, which is a layer having a thickness of approximately 0.3 &mgr;m where diazo system pigment is dispersed on resin and generates a pair of positive and negative charges upon receipt of exposure. &lsqb;0071&rsqb; The fourth layer 1e: a charge carrying layer, where hydrazon is dispersed on polycarbonate resin, and which is a p-type semiconductor. Accordingly, the negative charge electrified on the sensitive member surface cannot move on this layer and can only carry the positive charge generated on the charge generating layer 1d on the sensitive member surface. &lsqb;0072&rsqb; The fifth layer 1f: a charge injecting layer, which is a coating layer of the material where SnO2 ultra micro particles as conductive particles 1g are dispersed on the binder of insulated resin, to be concrete, a coating layer of the material where SnO2 particles having a particle size of 0.03 &mgr;m where antimony as a light permeable insulated filler is given a doping on the insulated resin and induced to a low resistance (conduction) are dispersed 70 percent by weight against the resin. &lsqb;0073&rsqb; The coating liquid prepared in this way was coated with a thickness of approximately 3 &mgr;m by a suitable coating method such as a dipping coating method, a spray coating method, a roll coating method, a beam coating method and the like and taken as a charge injecting layer. &lsqb;0074&rsqb; (3) Magnetic brush electrifying device 2 &lsqb;0075&rsqb; FIG. 3 is a schematic configuration view of the magnetic brush electrifying device 2 in the present example. &lsqb;0076&rsqb; Reference numeral 21 denotes an electrifying device housing and reference numeral 22 denotes a magnetic brush electrified member as a contact electrified member disposed inside this housing. The magnetic brush electrified member 22 of the present example is of a rotary sleeve type and comprises a magnet roll 23 fixedly supported non-rotationally, a non-magnetic injecting sleeve (non-magnetic, conductive/electrifying electrode sleeve) 24 having an outer diameter of 16 mm as a conductive particle bearing member which is coaxially freely rotationally engaged circumferentially with the outer periphery of this roller, a magnetic brush 25 of injecting carrier (conductive magnetic particle, magnetic carrier for use of electrification) sucked and held and formed on the outer peripheral surface of this non-magnetic sleeve by the magnetic force of the magnet roller 23 inside the sleeve and the like. Reference numeral 26 denotes a layer thickness control blade of the magnetic brush 25 and disposed fixedly inside the housing 21. &lsqb;0077&rsqb; The electrifying device 2 allows the magnetic brush 25 of the magnetic brush electrified member 22 to contact the photosensitive drum 1 surface and to be disposed approximately in parallel with the photosensitive drum 1. In this case, the contact nip width (width of the electrified region a) of the magnetic brush 25 formed against the photosensitive drum 1 was adjusted and disposed so as to have a predetermined width. In the present embodiment, the nip width formed against the photosensitive drum 1 was adjusted so as to be approximately 6 mm. &lsqb;0078&rsqb; For the injecting carrier constituting the magnetic brush 25, it is preferable that the average particle size (mean particle diameter) is 10 to 100 &mgr;m, saturated magnetization is 20 to 250 kA/m (emu/cm3) and resistance is 1×102 to 1×1010 &OHgr;·cm. Considering that insulation defects such as pin holes exist in the photosensitive drum 1, the carrier having a resistance of more than 1×106 &OHgr;·cm is preferably used. To improve electrification capacity, it is better to use the carrier having a resistance as small as possible. In the present example, magnetic particles having an average particle size of 25 &mgr;m, the saturated magnetization of 200 kA/m and the resistance of 5×106 &OHgr;·cm were used. Note that the injecting carrier is formed by a pulverizing method. &lsqb;0079&rsqb; Here, the resistance value of the injecting carrier is measured in such a manner that the injecting carrier of 2 g is put into a metallic cell having a base area of 228 mm2 and, after that, a weight (load) of 6.6 kg is added and a voltage of 100 V is applied. &lsqb;0080&rsqb; For the injecting carrier, the resin carrier formed by dispersing magnetite in resin as a magnetic material and also by dispersing carbon black for conduction and resistance adjustment, or the carrier which oxidation-reduction-processes the surface of magnetite simple substance such as ferrite and the like and performs a resistance-adjustment on it, or the carrier which coats the surface of magnetite simple substance such as ferrite and the like and performs the resistance-adjustment on it can be used. &lsqb;0081&rsqb; The injecting sleeve 24 of the magnetic brush electrified member 22 was rotated at the electrified region a in the arrow direction of the clockwise direction which is in reverse (counter direction) to the rotational direction of the photosensitive drum 1. In the present embodiment, against the rotational speed of 100 mm/sec of the photosensitive drum 1, the sleeve 24 rotates at the speed of 150 mm/sec. Accompanied by the rotation of this injecting sleeve 24, the magnetic brush 25 of the injecting carrier is also rotationally carried in the same direction and receives the layer thickness control at the position of the layer thickness control blade 26. The photosensitive drum 1 surface is slidably uniformly rubbed by the magnetic brush 25 in the electrified region a. &lsqb;0082&rsqb; By applying a predetermined electrification bias to the injecting sleeve 24 from a bias power source E1, charge is given on the photosensitive drum 1 from the injecting carrier of the magnetic brush 25, which is electrified with a potential corresponding to an electrification voltage. The more faster the rotational speed becomes, the more improved the electrification uniformity becomes. &lsqb;0083&rsqb; In the present example, the direct current voltage DC and the alternating voltage (alternative voltage) AC of −700V were superimposed and applied as the electrification bias. &lsqb;0084&rsqb; In the case of the present example, as described above, because the photosensitive drum 1 is provided with the charge injecting layer 1f on its surface, the electrifying processing of the photosensitive drum 1 is performed by charge injecting electrification. That is, from among the DC&plus;AC bias applied to the injecting sleeve 24, an electrification potential approximately identical to the direct current component DC (−700V) can be obtained on the photosensitive drum surface. &lsqb;0085&rsqb; (4) Developing Apparatus 4 &lsqb;0086&rsqb; FIG. 4 shows a schematic configuration of the developing apparatus 4 used in the present embodiment. The developing apparatus 4 of the present example uses the mixture of non-magnetic negative toner particles and magnetic carrier particles as a developer. It is an apparatus of a two component magnetic brush contact developing system where the developer is held on a developer bearing member as a magnetic brush layer by magnetic force and carried to a developing portion so as to contact the photosensitive drum 1 surface, thereby developing latent images reversed as toner images. &lsqb;0087&rsqb; Reference numeral 41 denotes a developer container, reference numeral 42 a developer sleeve as the developer bearing member, reference numeral 43 a magnet roller as magnetic field generating means fixedly disposed inside the developer sleeve 42, reference numeral 44 a developer layer thickness control blade for forming a thin layer of the developer on the developer sleeve, reference numeral 45 a developer agitation carrying screw, reference numeral 46 a two component developer housed inside the developer container 41, which mixes non-magnetic negative toner particles t and magnetic carrier particles C. &lsqb;0088&rsqb; The two component developer 46 used in the present embodiment uses titanium oxide having an average particle size (mean particle diameter) of 20 nm and externally added with a weight ratio 1% against the negatively electrified toner (hereinafter referred to as pulverized toner) having an average particle size of 6 &mgr;m manufactured by an pulverizing method. For a developing magnetic carrier C, the magnetic carrier having an average particle size of 25 &mgr;m with the saturated magnetization of 205 kA/m was used. The toner t and the developing magnetic carrier were mixed with a weight ratio of 6 to 94. &lsqb;0089&rsqb; The developer sleeve 42 is disposed in such a manner that its closest distance (clearance) to the photosensitive drum 1 becomes approximately 500 &mgr;m at least in the developing time and a developer magnetic brush thin layer 46a borne on the outer surface of the developer sleeve 42 is set so as to contact the surface of the photosensitive drum 1. The contact region between the developer magnetic brush layer 46a and the photosensitive drum 1 is the developing region c. &lsqb;0090&rsqb; The developer sleeve 42 is driven in the arrow direction at a predetermined speed around the outer periphery of the magnet roller 43 fixedly disposed, and a magnetic brush of the developer 46 is formed on the outer surface of the sleeve by magnetic force of the magnet roller 43 inside the developer container 41. The developer magnetic brush is carried with the rotation of the sleeve 42 and, by receiving a thickness control by a blade 44, taken out from the developer container as the developer magnetic brush thin layer 46a having a predetermined layer thickness and carried to the developing region c so as to contact the photosensitive drum 1 surface and then carried back again inside the developer container 41 accompanied by the continuous rotation of the sleeve 42. &lsqb;0091&rsqb; That is, first of all, the developer 46 drawn up on a N3 pole of the magnet roller 43 accompanied by the rotation of the developer sleeve 42 is, in the course of being carried from a S2 pole to a N1 pole, controlled by a control blade 44 disposed vertically against the developer sleeve 42 and a thin layer 46a of the developer 46 is formed on the developer sleeve 42. When the developer layer 46a thinly formed is carried to a developing main pole S1 of the developing portion, ears are formed by the magnetic force. By the developer layer 46a formed in the shape of ears, the latent images of the photosensitive drum 1 are developed as toner images and, after that, by repulsive magnetic field of a N2 pole to N3 pole, the developer on the developer sleeve 42 is returned inside the developer container 41. &lsqb;0092&rsqb; Between the developer sleeve 42 and a conductive drum substrate of the photosensitive drum 1, in the present example, an amplitude voltage superimposed with a negative direct current voltage: −500V, an alternating voltage: amplitude Vpp&equals;1500V and frequency Vf&equals;3000 Hz is applied as a developing bias by a development bias applying power source E2. &lsqb;0093&rsqb; Generally in the two component developing method, when the alternating voltage is applied, developing efficiency is increased and images are highly refined. On the other hand, there is often a risk of causing fog. For this reason, usually by creating a potential difference between the direct current voltage applied to the developing apparatus 4 and the surface potential of the photosensitive drum 1, the prevention of the fog is realized. The potential difference for preventing this fog is referred to as a fog cleaning potential (Vback). By this potential difference, the adhesion of the toner to non-image areas of the photosensitive drum 1 is prevented. &lsqb;0094&rsqb; The toner density (mixing ratio with the carrier) of the developer 46 inside the developer container 41 is gradually reduced as the toner portion is consumed for developing electrostatic latent images. When the toner density of the developer 46 inside the developer container 41 is detected by detecting means (not shown) and reduced to a predetermined permissible low degree, the toner t is supplied to the developer 46 inside the developer container from a toner supply portion 47 and the toner supply is controlled in such a manner that the toner density of the developer 46 inside the developer container 41 is always kept within a predetermined permissible range. &lsqb;0095&rsqb; (5) Transfer apparatus 5 &lsqb;0096&rsqb; The transfer apparatus 5 is, in the present example as described above, a transfer belt type. Reference numeral 51 is an endless type transfer belt and is wound across between a driving roller 52 and a slave roller 53 with a predetermined tensile force and oscillated at the approximately same circumferential speed as the rotational circumferential speed of the photosensitive drum 1 in the forward direction in the rotational direction of the photosensitive drum 1. Reference numeral 54 is a transfer electrified blade disposed inside the transfer belt 51 and forms a transfer region d by pressing the upper moving side belt of the transfer belt 51 against the photosensitive drum 1 and, with the transfer bias applied from the transfer bias applying power source E3, performs the electrification in reverse to the polarity of the toner from the back of the transfer material P. In this way, the toner images on the side of the photosensitive drum 1 are electrostatically transferred in order over the surface of the transfer material P passing through the transfer region d. &lsqb;0097&rsqb; In the present example, a belt comprising polyimide resin having a film thickness of 75 &mgr;m was used as the belt 51. The material of the belt 51 is not limited to polyimide resin, but polycarbonate resin, polyethylene telephthalic resin, polyvinylidene fluoride resin, polyethylene naphtalate resin, polyether etherketone resin, polyether sulfone resin, plastic such as polyurethane resin, rubber of fluorine system, silicon system can be preferably used. The thickness is also not limited to 75 &mgr;m, but a thickness of approximately 25 to 2000 &mgr;m, preferably 50 to 150 &mgr;m can be suitably used. &lsqb;0098&rsqb; Moreover, as the transfer electrified blade 54, a blade having a resistance of 1×105 to 1×107 &OHgr;, a plate thickness of 2 mm and a length of 306 mm which is orthogonal to the moving direction of the belt 51 was used. By applying a bias of &plus;15 &mgr;A to this transfer electrified blade 54 by a constant current control, the transfer was performed. &lsqb;0099&rsqb; (6) Cleaner-less System &lsqb;0100&rsqb; 1) The transfer residual toner remained on the photosensitive drum 1 surface after the toner images are transferred against the transfer material P is, by the continuous rotation of the photosensitive drum 1 surface, carried away by the conductive brush 6 as a supplemental electrifying device disposed by contacting the surface of the photosensitive drum 1 between the transfer region d and the electrified region a. &lsqb;0101&rsqb; To this conductive brush 6, the bias voltage of a predetermined potential, which has a positive polarity in reverse to the negative electrified polarity of the toner, is applied by the power source E4. &lsqb;0102&rsqb; In the transfer residual toner, the toner negatively electrified which is of a normal electrified polarity, the toner having the electrified polarity turned in reverse due to transfer bias, peel discharge and the like at the time of the transfer and the toner in a state where negative electrification is weakened or electrification is rejected are present as a mixture. This transfer residual toner is agitated at the contact portion e between the conductive brush 6 and the photosensitive drum 1. The toner of weak electrification from whichever of the toner negatively electrified as a normal charged polarity, the toner in a state where negative electrification is weakened or electrification is rejected and the toner positively electrified in reverse is actively adhered and mixed with the conductive brush 6 by electrical suction force attributable to the positively applied bias, and the toner positively electrified in reverse is delivered from the conductive brush 6 to the photosensitive drum 1 surface by electrical repulsive force to the positive applied bias against the conductive brush 6 and adhered there again. &lsqb;0103&rsqb; Accordingly, the transfer residual toner is substantially lined up in the positive polarity where the electrified polarity is in reverse to the normal negative electrified polarity and carried to the electrified region a by the continuous rotation of the photosensitive drum 1. &lsqb;0104&rsqb; 2) The transfer residual toner on the photosensitive drum 1 which was carried to the electrified region a is entrapped by the magnetic brush 25 of the magnetic brush electrified member 22 and simultaneously electrified and recovered tentatively. In this case, the transfer residual toner carried to the electrified region a is, as described above, substantially lined up positively in the electrified polarity and therefore effectively tentatively recovered from the photosensitive drum 1 surface in the electrified region a by electrical attractive force against the magnetic brush electrified member 22 applied with negative electrified bias. At this time, when the alternating voltage is applied to the magnetic brush electrified member 22, by virtue of the oscillation effect based on the electrical field between the photosensitive drum 1 and the injecting sleeve 24, the introduction of the transfer residual toner into the magnetic brush 25 can be easily performed. &lsqb;0105&rsqb; The transfer residual toner tentatively recovered by the magnetic brush 25 is effectively restored and electrified from a positive reverse electrified state to a negative electrified state which is the normal electrified polarity by the negative electrified bias applied to the magnetic brush electrified member 22 and also by the friction with the magnetic brush 25. &lsqb;0106&rsqb; The transfer residual toner which is tentatively recovered by the magnetic brush 25 and effectively restored and electrified to the negative electrified state which is the normal charged polarity is delivered from the magnetic brush 25 to the photosensitive drum 1 and adhered there by electrical repulsive force against the negative electrified bias applied to the magnetic brush electrified member 22. &lsqb;0107&rsqb; 3) The toner which was delivered from the magnetic brush 25 to the photosensitive drum 1 and restored and electrified to the negative electrified state which is the normal electrified polarity passes through a contact region f to be described later between the injecting carrier shielding member 11 and the photosensitive drum 1 by the continuous rotation of the photosensitive drum 1 and reaches the developing region c of the developing apparatus 4 through an image exposing region b of an image exposing apparatus 3 for simultaneous developing and cleaning (simultaneous developing and recovery) by the developing member of the developing apparatus 4. &lsqb;0108&rsqb; Here, the delivery of the toner from the magnetic brush of the electrifying device 2 to the photosensitive drum 1 is performed in uniform distribution and small in the amount as well, which substantially does not obstruct the image exposure even if the toner passes through the image exposure region b. &lsqb;0109&rsqb; Simultaneous developing and cleaning is a method where the photosensitive drum 1 is continuously electrified and latent images are formed there by image exposure and at the time of development from the next steps onward, that is, at the time of developing the latent images, the transfer residual toner remained on the photosensitive drum 1 after the transfer is recovered by the fog cleaning bias (potential difference Vback which is the potential difference between the direct current voltage applied to the developing apparatus 4 and the surface potential of the photosensitive drum 1). In the case of the reversal developing, this simultaneous developing and cleaning is performed by the electrical field which recovers the toner to the developing member from the dark portion potential of the photosensitive drum and the electrical field action which adheres the toner to the light portion potential of the photosensitive drum 1. Simultaneous developing and recovery is performed simultaneously with the image forming steps such as other electrification, exposure, developing and transfer when the image area in the rotational direction of the photosensitive drum is longer than the circumferential length of the photosensitive drum 1. &lsqb;0110&rsqb; The above described 1) to 3) cleaner-less system will be described a little bit further. The cleaner-less system, as described above, recovers the transfer residual toner by simultaneous developing and cleaning in the developing region c by the developing apparatus 4. The transfer residual toner on the photosensitive drum 1 after the transfer generates, in the first place, the above described ghost if passed as it is through the electrified region a of the electrifying device 2. That is, even when the transfer residual toner passes through under the magnetic brush which contacts the photosensitive drum 1, almost in all cases, the shapes of the previous images are retained and no case was observed where they are uniformly dispersed under the setting of the magnetic brush in suitable electrifying conditions. &lsqb;0111&rsqb; Thus, it is necessary that the transfer residual toner which reached the electrified region a accompanied by the rotation of the photosensitive drum 1 is entrapped by the magnetic brush 25 so that the history of the previous images is eliminated. At this time, applying the direct current voltage to the magnetic brush electrified member 22 alone is not enough to perform the entrapping of the toner toward the magnetic brush 25, but when the alternating voltage is applied to the magnetic brush electrified member 22, the entrapping of the toner toward the magnetic brush 25 can be relatively easily performed by virtue of vibration effect based on the electrical field between the photosensitive drum 1 and the injecting sleeve 24. &lsqb;0112&rsqb; However, there are some cases where it is extremely difficult to perform the entrapping of the toner toward the magnetic brush 25 depending on the electrified amount of the transfer residual toner which reached the electrified region a. That is, so long as the transfer residual toner is electrified, the potential difference between the magnetic brush 25 and the photosensitive drum 1 and a reflection force between the toner and the photosensitive drum have a great effect on the entrapping property. &lsqb;0113&rsqb; Here, though it is ideal for the surface potential of the photosensitive drum where the toner passes through to be equally electrified against the applied voltage of the magnetic brush electrified member 22, actually there exists a width also in the electrified region a which is the contact region between the magnetic brush 25 and the photosensitive drum 1. Though this will be eventually electrified to the approximately same potential, because the toner is not sufficiently electrified at the initial stage of passing through the electrified portion, there is produced a potential difference between the magnetic brush and the photosensitive drum. In the case of the present embodiment, because Vdc (dark portion potential) of the magnetic brush electrifying device is set at −700 V, in the area where the photosensitive drum surface potential at the initial stage of passing through the electrified portion is smaller than that, the positive electrified toner is easily entrapped in the direction of the magnetic bush, while the negative electrified toner is not entrapped. Moreover, when the electrified amount of the toner is extremely large and even when the reflection force between the toner and the photosensitive drum is large enough, the toner remains on the photosensitive drum. For this reason, though it is a negative electrified toner by nature, the transfer residual toner is preferably positively electrified. However, even when the toner is not positively electrified, if the absolute value
{'app_number': '09816361', 'application_number': None, 'doc_number': '20010041082', 'publication_number': None, 'source_file': './application/2001/pa011115.xml', 'source_data': 'USPTO-Application'}