JP4078015B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic system or an electrostatic recording system.
[0002]
[Prior art]
Conventionally, as this type of image forming apparatus, for example, many apparatuses such as a copying machine and a laser printer have been proposed.
[0003]
FIG. 11 is a schematic configuration diagram of an electrophotographic image forming apparatus according to the prior art. The schematic configuration and operation of the image forming apparatus will be briefly described with reference to FIG.
[0004]
In the image forming apparatus shown in FIG. 11, when a copy start signal is inputted, the photosensitive drum 101 is charged by the charger 103 so as to have a predetermined potential.
[0005]
On the other hand, a reader unit 9 including a unit for irradiating a document, a short focus lens array, and a CCD sensor scans the document G placed on the document table 10 while irradiating it. The document surface reflected light is imaged by the short focus lens array and is incident on the CCD sensor.
[0006]
The CCD sensor includes a light receiving unit, a transfer unit, and an output unit. The optical signal is converted into a charge signal in the CCD light receiving unit, and sequentially transferred to the output unit in synchronization with the clock pulse in the transfer unit. The charge signal is converted into a voltage signal in the output unit, amplified and reduced in impedance, and output.
[0007]
The obtained analog signal is subjected to known image processing, converted into a digital signal, and sent to the printer unit. In the printer unit, the surface of the photosensitive drum 101 is scanned by the laser exposure apparatus 102 that receives the image signal converted into the digital signal as described above and scans the light of the solid laser element that is turned ON and OFF by the rotating polygon mirror that rotates at high speed. An electrostatic latent image corresponding to the document image is formed on the top.
[0008]
Next, the electrostatic latent image is developed by a developing device 104 containing a so-called two-component developer having toner particles and carrier particles, and a toner image is obtained on the photosensitive drum 101.
[0009]
In this manner, the toner image formed on the photosensitive drum 101 is electrostatically transferred onto the recording material P by the transfer device 107. Thereafter, the recording material P is electrostatically separated and conveyed to the fixing device 106, where it is thermally fixed and an image is output.
[0010]
On the other hand, untransferred toner remaining without being transferred to the recording material P adheres to the surface of the photosensitive drum 101, and the untransferred toner is collected by the cleaning device 105.
[0011]
By the way, since it has advantages such as low ozone and low power in recent years, a contact charging device, that is, a charging member to which a voltage is applied is brought into contact with a charged body as a charging means of the photosensitive drum 101 described above. Apparatuses for charging the body have been put into practical use.
[0012]
As such a charging means, a magnetic brush type device is preferably used from the viewpoint of the stability of charging contact. In a magnetic brush contact charging device, a charging member is composed of conductive magnetic particles and a magnet as a magnetic particle carrier or a sleeve containing the magnet. Charging is started by magnetically constraining magnetic particles directly on a magnet or sleeve, contacting the object to be charged while stopping or rotating, and applying a voltage thereto.
[0013]
In addition, a conductive rubber roller in which conductive fibers are formed on a brush (fur brush) or a conductive rubber roller in which conductive rubber is formed into a roll shape is also preferably used as the contact charging member.
[0014]
In particular, when such a contact charging member is used and a surface layer in which conductive fine particles are dispersed on an ordinary organic photoreceptor or an amorphous silicon photoreceptor is used as a member to be charged, the contact charging member is applied. It is possible to obtain a charged potential almost equal to the direct current component of the bias on the surface of the member to be charged. Such a charging method is called injection charging. If this injection charging is used, it does not use a discharge phenomenon in which a charged object is charged using a corona charger, so that it is possible to achieve complete ozone-less and low power consumption charging.
[0015]
In recent years, there has also appeared a cleanerless image forming apparatus that performs simultaneous development cleaning by the developing device 4 without providing a dedicated cleaning device, like the image forming device of FIG. 1 shown as an embodiment of the present invention. . The simultaneous development cleaning is a method in which the transfer residual toner remaining on the photosensitive drum 1 after the transfer is collected by the developing device 4 by a fog removal bias at the time of development in the subsequent process. As a result, the transfer residual toner is collected and used in the subsequent steps, so that waste toner can be eliminated. In addition, there is a great advantage in terms of space, and a significant reduction in size is possible.
[0016]
As an exposure means, a linear array type exposure apparatus 2 represented by an LED array writer head as shown in FIG. 2 has been put into practical use. Since the linear array type exposure apparatus has no mechanical drive part, it is highly reliable and safe, and the exposure apparatus can be disposed near the photosensitive drum, so that the image forming apparatus can be miniaturized.
[0017]
Further, in recent years, the color electrophotographic apparatus main body has a photosensitive drum, an exposure device, a magnetic brush charger, a developing device, etc. as one station as in the image forming apparatus of FIG. 10 shown as an embodiment of the present invention. A tandem method has been developed in which stations of four colors are provided in parallel and images of four colors are sequentially superimposed on the recording material P in one pass, which is a single conveyance of the recording material P. This method has an advantage that color recording can be performed at high speed.
[0018]
[Problems to be solved by the invention]
However, in the case of the prior art as described above, the following problems have occurred.
[0019]
In the cleaner-less image forming apparatus having the magnetic brush charger as described above, and performing development simultaneous cleaning, the transfer residual toner once collected by the magnetic brush charger and then discharged after the polarity is aligned is the next step Along with the change in potential distribution on the photosensitive drum caused by the image exposure, there is a problem that the image flies from the photosensitive drum to the exposure light emitting portion and adheres to the exposure device, thereby causing an image defect.
[0020]
In particular, in the tandem method in which four stations are arranged in parallel as described above and image formation is performed independently at each station, toner from the previous station may be mixed in toner discharged from the magnetic brush charger. There is a problem that the above phenomenon appears more remarkably due to the influence of different toner characteristics.
[0021]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus with excellent reliability for preventing image defects due to the influence of residual toner. is there.
[0022]
[Means for Solving the Problems]
In order to achieve the above objective, Tomorrow ,
Movable object to be charged;
Charging means for charging the charged body in contact with the charged body;
Opposes the object to be charged and emits light Out Has a shooting section,
in front Record Out from the shooting section Was Exposure means for forming an electrostatic latent image on the member to be charged by light; and
Developing means for developing the electrostatic latent image with toner;
Transfer means for transferring the toner image on the charged body to a transfer material;
Downstream of the emitting part in the rotation direction of the charged body in front Record Arranged adjacent to the shooting section And For the charging means Applied voltage Voltage of the same polarity as By Create an electric field with the body to be charged First for A conductive member,
The developing means Is Toner remaining on the member to be charged after transfer Recover In the image forming apparatus,
Above first Both ends in the longitudinal direction of the conductive member Are both ends of the emitting portion in the longitudinal direction and both ends of the charging region in the longitudinal direction to be charged by the charging means. Outside Ah The A grounded second conductive member is disposed adjacent to the emission unit downstream of the charging unit and upstream of the emission unit in the rotation direction of the charged body. An image forming apparatus characterized by the above.
[0023]
Accordingly, it is possible to prevent the transfer residual toner from flying to the exposure light emitting portion over the entire exposure area of the exposure means.
[0024]
Furthermore, both ends in the longitudinal direction of the conductive member are opposite to each other with respect to the center of the charging area by the charging means, and both are located outside the end of the charging area. To do.
[0025]
Thereby, it is possible to prevent the transfer residual toner from flying to the exposure light emitting portion over the entire charging area of the charging unit, that is, the entire area where the transfer residual toner is attached.
[0026]
The conductive member may be provided on the downstream side in the moving direction of the charged body with respect to the exposure light emitting portion.
[0027]
A bias having the same polarity as the surface potential after charging of the member to be charged may be applied to the conductive member.
[0028]
The absolute value of the bias applied to the conductive member may be equal to or greater than the absolute value of the surface potential after charging of the object to be charged.
[0029]
A grounding conductive member may be provided adjacent to the exposure light emitting portion on the upstream side in the moving direction of the charged body with respect to the exposure light emitting portion.
[0030]
The charging means includes a charging member including a magnetic particle and a magnetic particle carrier that supports the magnetic particle, and a bias is applied to the charging member to bring the magnetic particle into contact with the member to be charged. The object to be charged is preferably charged.
[0031]
The bias applied to the charging member may be a bias in which an alternating voltage is superimposed on a DC voltage.
[0032]
The power source of the bias applied to the conductive member may be the same power source as the power source of the charging unit.
[0033]
The charged body preferably has a photosensitive layer and a surface layer, and the surface layer preferably has a resin and conductive fine particles.
[0034]
An image forming unit having at least the object to be charged, the charging unit, the exposure unit, the developing unit, and the transfer unit is set as one station, and a plurality of stations are arranged in parallel, and each station forms an image independently. It is characterized by performing.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.
[0036]
(First embodiment)
The image forming apparatus according to the first embodiment will be described with reference to FIGS.
[0037]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
[0038]
Since the reader unit 9 that scans the document G is the same as that shown in FIG. In addition, constituent members and portions that are common to the above-described conventional embodiments are denoted by the same reference numerals, and description thereof is omitted.
[0039]
In FIG. 1, a printer unit of an image forming apparatus includes a magnetic brush charger 3 as a charging unit, an exposure unit 2 as an exposure unit, a developing unit 4 as a developing unit, around a photosensitive drum 1 as a member to be charged. A transfer device 7 as a transfer unit is arranged.
[0040]
FIG. 2 shows a schematic configuration diagram of the charging means according to the embodiment of the present invention.
[0041]
Reference numeral 3 denotes a magnetic brush charger using a magnetic carrier. The charging magnetic carrier has an average particle diameter of 10 to 100 μm and a saturation magnetization of 20 to 250 emu / cm. ^Three (Approximately 0.025 to 0.314 Wb / m ² ), Resistance is 1 × 10 ² ~ 1x10 ^Ten Ω · cm (1-1 × 10 ⁸ Ωm) is preferable, and considering that the photosensitive drum 1 has an insulation defect such as a pinhole, 1 × 10 ⁶ Ω · cm (1 × 10 ^Four It is preferable to use a thing more than (omega | ohm) m). In order to improve the charging performance, it is better to use the one having the smallest possible resistance. Therefore, in this embodiment, the average particle diameter is 25 μm and the saturation magnetization is 200 emu / cm. ^Three (About 0.251 Wb / m ² ), The resistance is 5 × 10 ⁶ Ω · cm (5 × 10 ^Four Ωm) magnetic particles were used. The charging magnetic carrier used in the present embodiment is one in which the resistance is adjusted by oxidizing and reducing the ferrite surface.
[0042]
Here, as the photosensitive drum 1 according to the embodiment of the present invention, a commonly used organic photosensitive member (hereinafter also referred to as an OPC photosensitive member) or the like can be used. Preferably, the resistance is provided on the organic photosensitive member. 10 ² -10 ¹⁴ Ω · cm (1-10 ¹² Using a surface layer having a material of Ωm) or an amorphous silicon (hereinafter also referred to as a-Si) photoreceptor, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. is there. In addition, the chargeability can be improved.
[0043]
FIG. 3 is a schematic sectional view of the photosensitive drum according to the embodiment of the present invention.
[0044]
In the embodiment of the present invention, a photosensitive drum 1 is used, which is a negatively charged organic photoreceptor, in which the following first to fifth layers are provided in order from the bottom on an aluminum drum base having a diameter of 30 mm. .
[0045]
The first layer is an undercoat layer 12 and is a conductive layer having a thickness of 20 μm provided for leveling defects of the aluminum substrate 11.
[0046]
The second layer is a positive charge injection preventing layer 13 which serves to prevent the positive charge injected from the aluminum substrate 11 from canceling the negative charge charged on the surface of the photoreceptor, and is formed by amylan resin and methoxymethylated nylon. 1 × 10 ⁶ Ω · cm (1 × 10 ^Four It is a medium resistance layer having a thickness of 1 μm, whose resistance is adjusted to about Ωm).
[0047]
The third layer is a charge generation layer 14, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.
[0048]
The fourth layer is a charge transport layer 15, which is a P-type semiconductor in which hydrazone is dispersed in a polycarbonate resin. Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer 14 can be transported to the surface of the photoreceptor.
[0049]
The fifth layer is a charge injection layer 16, and SnO is used as a binder of an insulating resin. ₂ It is a coating layer of a material in which ultrafine particles are dispersed. Specifically, SnO having a particle size of about 0.03 μm is obtained by doping an insulating resin with antimony which is a light-transmissive insulating filler to reduce the resistance (conductivity). ₂ It is a coating layer of a material in which particles are dispersed by 70 weight percent with respect to the resin. The thus prepared coating solution was applied to a thickness of about 3 μm by an appropriate coating method such as dipping coating method, spray coating method, roll coating method, beam coating method, etc., to form a charge injection layer 16.
[0050]
Here, the first to fourth layers constitute a photosensitive layer, and the fifth layer constitutes a surface layer. Surface resistance is 10 ¹³ Ω · cm (10 ¹¹ Ωm). By controlling the surface resistance in this way, the direct chargeability is improved and a high-quality image can be obtained. The photoreceptor is not limited to OPC but can be realized by an a-Si drum, and further high durability can be realized.
[0051]
Here, the volume resistance of the surface layer is a value measured by placing metal electrodes at intervals of 200 μm, injecting the surface layer preparation liquid between them to form a film, and applying a voltage of 100 V between the electrodes. The measurement is a value measured under conditions of a temperature of 23 ° C. and a humidity of 50% RH.
[0052]
Next, the development process will be described.
[0053]
In general, a non-magnetic toner is coated on a sleeve with a blade or the like for a non-magnetic toner, and the magnetic toner is coated by a magnetic force and conveyed and developed in a non-contact state with respect to a photosensitive drum (one-component non-contact development). ), A method in which the toner coated as described above is developed in contact with the photosensitive drum (one-component contact development), and a magnetic carrier mixed with toner particles as a developer. There are four main types: a method of transporting by force and developing in contact with the photosensitive drum (two-component contact development) and a method of developing with the above two-component developer in a non-contact state (two-component non-contact development). Separated. A two-component contact development method is often used from the viewpoint of high image quality and high stability.
[0054]
FIG. 4 is a schematic configuration diagram of the developing device 4 for two-component magnetic brush development according to the embodiment of the present invention.
[0055]
In the figure, 41 is a developing sleeve, 42 is a magnet roller fixedly arranged in the developing sleeve 41, 43 and 44 are stirring screws, 45 is a regulating blade arranged to form a thin film of developer on the surface of the developing sleeve 41, Reference numeral 46 denotes a developing container. The developing sleeve 41 is disposed so that a region closest to the photosensitive drum 1 is about 500 μm at least during development, and is set so that development can be performed while the developer is in contact with the photosensitive drum 1. .
[0056]
As the two-component developer used in the present embodiment, a negatively charged toner having an average particle diameter of 6 μm and an external addition of titanium oxide having an average particle diameter of 20 nm in a weight ratio of 1% is used. As a magnetic carrier, saturation magnetization is 205 emu / cm. ^Three (About 0.257 Wb / m ² ) Magnetic carrier having an average particle size of 35 μm. A mixture of this toner and a magnetic carrier for development at a weight ratio of 6:94 was used as a developer. The toner in the developer at this time has a triboelectric charge of about 25 × 10 ^-3 C / kg.
[0057]
Here, a developing process in which the electrostatic latent image formed on the photosensitive drum 1 is visualized by the two-component magnetic brush method using the developing device 4 and a developer circulation system will be described below.
[0058]
First, the developer pumped up at the N2 pole with the rotation of the developing sleeve 41 is regulated by a regulating blade 45 arranged perpendicular to the developing sleeve 41 in the process of being conveyed from the S2 pole to the N1 pole, A thin film is formed on the developing sleeve 41. Here, when the developer formed in a thin film is conveyed to the development main pole S1, a spike is formed by the magnetic force. The electrostatic latent image is developed with the developer formed in a spike shape, and then the developer on the developing sleeve 41 is returned into the developing container 46 by the repulsive magnetic fields of the N3 pole and the N2 pole.
[0059]
A DC voltage and an AC voltage are applied to the developing sleeve 41 from a power supply 47. In this embodiment, -480V is applied as the DC voltage, Vpp = 1500V, and Vf = 3000Hz are applied as the AC voltage. In general, in the two-component development method, when an AC voltage is applied, the development efficiency increases and the image becomes high quality, but conversely, the problem that fogging is likely to occur also arises. For this reason, in general, it is possible to prevent fogging by providing a potential difference between the DC voltage applied to the developing device 4 and the surface potential of the photosensitive drum 1. This potential difference for preventing fogging is referred to as fog removing bias (Vback). This potential difference prevents toner from adhering to the non-image area during development.
[0060]
This toner image is then transferred to the recording material P by the transfer device 7. The transfer device 7 suspends an endless belt 71 between a driving roller 72 and a driven roller 73 and is rotated in the direction of the arrow in FIG. Further, a transfer charging blade 74 is provided in the transfer device 7, and the transfer charging blade 74 is supplied with power from a high voltage power supply (not shown) while generating pressure from the inside of the belt 71 toward the photosensitive drum 1. The toner image on the photosensitive drum 1 is sequentially transferred onto the upper surface of the recording material P by charging from the back side of P with the opposite polarity to the toner.
[0061]
Here, the recording material P is conveyed from the paper feeding / conveying device to a transfer portion formed by the photosensitive drum 1 and the belt 71 with an appropriate timing in synchronization with the rotation of the photosensitive drum 1.
[0062]
In this embodiment, the belt 71 is made of polyimide resin having a film thickness of 75 μm. The material of the belt 71 is not limited to a polyimide resin, but may be a polycarbonate resin, a polyethylene terephthalate resin, a polyvinylidene fluoride resin, a polyethylene naphthalate resin, a polyether ether ketone resin, a polyether sulfone resin, a polyurethane resin, or the like. Plastic, fluorine-based or silicon-based rubber can be preferably used. The thickness is not limited to 75 μm, and a thickness of 25 to 2000 μm, preferably 50 to 150 μm can be suitably used.
[0063]
Further, the transfer charging blade 74 has a resistance of 1 × 10. ^Five ~ 1x10 ⁷ The thing of (omega | ohm) was used. Transfer was performed by applying a bias of +15 μA to the transfer charging blade 74 by constant current control.
[0064]
In this way, the toner image formed on the photosensitive drum 1 is electrostatically transferred onto the recording material P by the transfer charging blade 74. Thereafter, the recording material is conveyed to the fixing device 6 where it is thermally fixed and an image is output.
[0065]
On the other hand, the transfer residual toner remains on the photosensitive drum 1 after the transfer process. Here, the transfer residual toner on the photosensitive drum 1 often has a mixture of positive and negative polarities due to peeling discharge during transfer. The transfer residual toner in which the polarities are mixed is conveyed to the magnetic brush charger 3 and mixed into the magnetic particles in the magnetic brush charger 3, and the polarities are all negatively charged and discharged onto the photosensitive drum 1.
[0066]
At this time, the toner is not sufficiently taken into the magnetic brush charger 3 only by applying a DC voltage to the magnetic brush charger 3, but when an alternating voltage is applied to the magnetic brush charger 3, the photosensitive drum 1 and the magnetic brush charger 3 are magnetically coupled. Due to the vibration effect caused by the electric field between the brush chargers 3, the toner can be easily taken into the magnetic brush charger 3.
[0067]
The transfer residual toner discharged onto the photosensitive drum 1 with the same polarity by the magnetic brush charger 3 is collected in the developing device 4 by the fog removal bias at the time of development.
[0068]
Here, when the image area in the rotation direction is longer than the circumferential length of the photosensitive drum 1, the simultaneous development of these developments is performed simultaneously with other image forming processes such as charging, exposure, development, and transfer. As a result, the transfer residual toner is collected and used in the subsequent steps, so that waste toner can be eliminated. In addition, there is a great advantage in terms of space, and a significant reduction in size is possible.
[0069]
However, as shown in FIG. 5, in the cleanerless image forming apparatus that performs simultaneous development cleaning using the magnetic brush charger 3, the transfer residual toner discharged onto the photosensitive drum 1 after being collected by the magnetic brush charger 3. Is exposed to the exposure light emitting unit 21 by an electric field drawn in the direction of the exposure light emitting unit 21 from the drum surface as the surface potential of the photosensitive drum 1 changes when exposed by the exposure apparatus 2 in the next step. A phenomenon of flying and adhering (hereinafter, exposure scattering phenomenon) occurs. The exposure scattering phenomenon is considered to occur when the surface potential distribution of the photosensitive drum 1 changes due to exposure.
[0070]
Therefore, the present inventor conducted an experiment in which the toner used in the magnetic brush charger 3 was forcedly mixed into the magnetic brush charger 3 by the configuration used in the present embodiment, and the toner was forcibly discharged while performing full-surface exposure. In this experiment, the developing device 4 was set so that no developer was added and the developing device 4 was not driven and biased. Then, the surface potential of the photosensitive drum 1 after charging (hereinafter referred to as Vd) is kept constant at −800 V, and the surface potential (hereinafter referred to as Vl) of the photosensitive drum 1 after exposure is changed to thereby change the latent image contrast that is the difference between Vd and Vl. The experiment was conducted with various changes.
[0071]
As a result of this experiment, it was found that the toner discharged on the photosensitive drum 1 flies perpendicularly to the exposure light emitting portion 21 as the latent image contrast is smaller. As a result, when the latent image contrast is low under actual use conditions, that is, when halftone exposure is performed, the exposure scattering phenomenon occurs remarkably.
[0072]
When the exposure scattering phenomenon occurs, the exposure light emitting unit 21 is shielded by the toner attached thereto. Therefore, an appropriate amount of exposure cannot be given to the photosensitive drum 1 at the portion of the exposure light emitting unit 21 where the toner is attached. The image defect that the image is missing occurs.
[0073]
In order to prevent the exposure scattering phenomenon as described above, in the present embodiment, as shown in FIG. 6, the conductive material is disposed downstream of the photosensitive drum 1 in the rotation direction adjacent to the exposure light emitting portion 21 of the exposure apparatus 2. The conductive member 22 is provided, and a bias is applied to the conductive member 22. The longitudinal direction of the conductive member 22 and the exposure light emitting portion 21 are provided in parallel.
[0074]
FIG. 7 is an explanatory view of the longitudinal end position of the conductive member according to the embodiment of the present invention, and FIG. 7A is a diagram showing the positional relationship between the conductive member 22 and the exposure light emitting region. FIG. 7B is a diagram showing the positional relationship among the conductive member 22, the exposure light emission region, and the magnetic particle coating region.
[0075]
The numerical value in the figure represents the relative distance (unit: mm) from the center of the image (the center of the image forming area on the photosensitive drum 1). Needless to say, the numbers in the figure are merely examples in the present embodiment, and as long as the relative positional relationship between the end of the conductive member 22, the exposure light emitting region, and the magnetic particle coating region is maintained, The scope of the invention is not deviated.
[0076]
As described above, the exposure scattering phenomenon occurs when the residual toner discharged from the magnetic brush charger 3 is present on the photosensitive drum 1 and the area is exposed by the exposure apparatus 2 in the next process. I know that. Therefore, as shown in FIG. 7A, the end of the conductive member 22 provided adjacent to and parallel to the exposure light emitting portion 21 of the exposure apparatus 2 is exposed from the exposure light emitting portion 21. It must be outside the edge of the region.
[0077]
Further, since the untransferred toner is discharged from the magnetic brush charger 3 onto the photosensitive drum 1 in the magnetic particle coating region which is a charging region, as shown in FIG. The end of the conductive member 22 provided adjacent to and parallel to the emission part 21 is outside the end of the exposure light emission region of the exposure light emission part 21 and the magnetic particle coat of the magnetic brush charger 3. It is still desirable if it is outside the region.
[0078]
With the above configuration, the electric field from the surface of the photosensitive drum 1 toward the exposure light emitting unit 21 is weakened, and the electric field in the direction of pressing the toner discharged from the photosensitive drum 1 toward the photosensitive drum 1 works. The occurrence of the exposure scattering phenomenon can be prevented.
[0079]
According to the experiment of the present inventor, the bias applied to the conductive member 22 provided adjacent to and parallel to the exposure light emitting portion 21 of the exposure apparatus 2 has the same polarity as Vd charged by the magnetic brush charger 3. In addition, by making the absolute value greater than that, it was possible to completely prevent the exposure scattering phenomenon.
[0080]
According to the present embodiment, the transfer residual toner discharged from the magnetic brush charger 3 flies from the surface of the photosensitive member due to the fluctuation of the surface potential distribution of the photosensitive drum 1 due to image exposure, and adheres to the exposure device 2, thereby causing an image defect. It is possible to provide a stable image over a long period of time.
[0081]
(Second Embodiment)
FIG. 8 shows a second embodiment. In the present embodiment, a conductive member 23 is provided on the upstream side in the rotation direction of the photosensitive drum 1 adjacent to the exposure light emitting section 21 of the exposure apparatus 2 shown in the first embodiment. Show.
[0082]
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0083]
As shown in FIG. 8, when the conductive member 23 is grounded, the electric field in the direction of pressing the discharged toner on the photosensitive drum 1 toward the photosensitive drum 1 is further strengthened, and the occurrence of the exposure scattering phenomenon is further prevented. Can do.
[0084]
(Third embodiment)
FIG. 9 shows a third embodiment. In the present embodiment, a configuration is shown in which the bias applied to the magnetic brush charger 3 is used as the bias applied to the conductive member 22 shown in the first embodiment.
[0085]
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0086]
As shown in FIG. 9, since the bias applied to the magnetic brush charger 3 can be used as an applied bias to the conductive member 22 provided adjacent to and parallel to the exposure light emitting portion 21, the conventional apparatus is used. Therefore, there is an advantage that it is possible to prevent exposure scattering without increasing the number of power supply devices. Here, the bias applied to the conductive member 22 provided in parallel and adjacent to the exposure light emitting portion 21 of the exposure apparatus 2 is an alternating voltage superimposed on the DC voltage applied to the magnetic brush charger 3. The effect on the exposure scattering phenomenon can be similarly exhibited by applying only a direct current component.
[0087]
(Fourth embodiment)
FIG. 10 shows a fourth embodiment.
[0088]
FIG. 10 is a schematic configuration diagram of a tandem image forming apparatus according to the present embodiment. In FIG. 10, the printer unit of the image forming apparatus is provided with four first to fourth stations in parallel, and the four colors are sequentially formed on the recording material P in one pass, which is one conveyance of the recording material P. By superimposing and transferring the images, color recording can be performed at high speed.
[0089]
The first station includes a photosensitive drum 1a and an exposure device 2a, a magnetic brush charger 3a, a developing device 4a, a transfer charging blade 74a, and the like disposed around the photosensitive drum 1a. Similarly, the second, third, and fourth stations respectively include photosensitive drums 1b, 1c, and 1d, and exposure devices 2b, 2c, and 2d, magnetic brush chargers 3b, 3c, and 3d, and a developing device 4b, respectively. 4c, 4d, transfer charging blades 74b, 74c, 74d and the like are arranged.
[0090]
Since other configurations and operations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0091]
By providing the conductive member described in the above embodiment in each of the exposure apparatuses 2a to 2d, the toner discharged from the magnetic brush chargers 3a to 3d is mixed with the toner of the previous station. However, the occurrence of the exposure scattering phenomenon can be prevented, and a good color image can be obtained.
[0092]
【The invention's effect】
As described above, according to the present invention, the conductive member that prevents the transfer residual toner from flying is provided longer than the width of the exposure region and the charging region. It is possible to completely prevent the transfer residual toner from being scattered and to provide a stable image over a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a charging unit according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of a photosensitive drum according to an embodiment of the present invention.
FIG. 4 is a schematic configuration diagram of a two-component magnetic brush developing device according to an embodiment of the present invention.
FIG. 5 is an explanatory diagram of an exposure scattering phenomenon.
FIG. 6 is a schematic configuration diagram of a conductive member according to the first embodiment of the present invention.
FIG. 7 is an explanatory view of the position in the longitudinal direction of the conductive member according to the embodiment of the present invention, (a) is a diagram showing the positional relationship between the conductive member and the exposure light emitting region; b) is a diagram showing a positional relationship among the conductive member, the exposure light emission region, and the magnetic particle coating region.
FIG. 8 is a schematic configuration diagram of a conductive member according to a second embodiment of the present invention.
FIG. 9 is a schematic configuration diagram of a conductive member according to a third embodiment of the present invention.
FIG. 10 is a schematic configuration diagram of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 11 is a schematic configuration diagram of an electrophotographic image forming apparatus according to a conventional technique.
[Explanation of symbols]
1 Photosensitive drum
11 Aluminum base
12 Underlayer
13 Positive charge injection prevention layer
14 Charge generation layer
15 Charge transport layer
16 Charge injection layer
1a, 1b, 1c, 1d Photosensitive drum
2 Exposure equipment
21 Exposure light exit
22 Conductive members
23 Conductive members
2a, 2b, 2c, 2d exposure apparatus
3 Magnetic brush charger
3a, 3b, 3c, 3d Magnetic brush charger
4 Development device
41 Development sleeve
45 Regulatory blade
46 Developer container
47 Power supply
6 Fixing device
7 Transfer device
71 belt
72 Drive roller
73 Followed roller
74 Transfer charging blade
9 Leader
10 Document table

Claims (4)

Movable object to be charged;
Charging means for charging the charged body in contact with the charged body;
Wherein and a morphism portion out that shines out of the light facing the member to be charged,
An exposure means for forming an electrostatic latent image on the member to be charged by the light emitted from the front Kide morphism unit,
Developing means for developing the electrostatic latent image with toner;
Transfer means for transferring the toner image on the charged body to a transfer material;
Wherein disposed adjacent to the front Kide morphism portion on the downstream side of the emitting portion in the rotational direction of the member to be charged, the at the same polarity as the polarity voltage of the voltage applied to the charging means is applied Rukoto A first conductive member for forming an electric field with the charged body,
In the image forming apparatus wherein the developing means for collecting toner remaining on the member to be charged after the transfer,
Both ends in the longitudinal direction of the first conductive member are outside both ends of the emitting portion in the longitudinal direction and both ends of the charging region in the longitudinal direction charged by the charging means, and are grounded. An image forming apparatus , wherein a second conductive member is disposed downstream of the charging unit and upstream of the emitting unit in the rotation direction of the member to be charged and adjacent to the emitting unit . The image forming apparatus according to claim 1, wherein an absolute value of a voltage applied to the first conductive member is equal to or greater than an absolute value of a charged surface potential of the charged body before exposure . The charging means is a magnetic brush charging member having magnetic particles, and toner remaining on the member to be charged after transfer is recovered by the magnetic brush charging member and discharged, and then recovered by the developing means. the image forming apparatus of any crab according to claim 1 or claim 2, characterized in that. Both end portions in the longitudinal direction of the region where the magnetic brush charging member is coated with the magnetic particles are outside the both end portions of the emitting portion in the longitudinal direction, and the longitudinal direction of the first conductive member is The image forming apparatus according to claim 3, wherein the image forming apparatus is inside the both end portions.

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