JP2618929B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus applicable to, for example, a laser printer or the like, and particularly to a developing step and a cleaning step for an image carrier. The present invention relates to an image forming apparatus that is simultaneously performed by the same apparatus.

(Prior Art) As shown in FIG. 12, a conventional image forming apparatus includes a corona charger b, a laser, around a drum-shaped photoconductor a as an image carrier along the rotation direction of the photoconductor a. The exposure means c, the developing device d, the transfer charger e, the peeling charger f, the blade-type cleaning device (cleaner) g, the static eliminator h, and the like are sequentially arranged.

Further, a sheet conveyance path j for conveying a sheet P as a recording medium is formed in a state of passing through an image transfer portion i between the transfer charger e and the photoconductor a. Reference numeral k denotes an aligning roller pair provided slightly upstream of the image transfer section i of the paper transport path j.

After the photoconductor a is charged by the charger b, an electrostatic latent image is formed on the photoconductor a by irradiating the laser beam 1 with the laser exposure unit c. Next, the electrostatic latent image is developed by a colored powder (hereinafter, referred to as toner) in a developer by being opposed to the developing device d to be visualized.

On the other hand, in synchronization with the operation of forming the developer image, the sheet P taken out from the sheet feeding cassettes m and n and the manual sheet feeding table 0 is fed through the aligning roller pair k and is formed on the photosensitive member a in advance. The transferred developer image is transferred onto the sheet P by the action of the transfer charger e.

Next, the paper P is sent to the fixing device q through the paper transport path j, where the developer image is fused and fixed on the paper P, and then discharged to the paper discharge unit s via the paper discharge roller pair r. Will be done.

After the developer image is transferred onto the paper P, the residual developer remaining on the photoconductor a is cleaned by the cleaning device g, the latent image is erased by the neutralizer h, and one process is completed. The configuration is such that the next image can be formed.

(Problems to be Solved by the Invention) However, conventionally, the photoconductor a
Since the toner remaining on the cleaning device g is collected inside the cleaning device g, the cleaning device g becomes full of toner and becomes unusable after recording 2000 to 3000 sheets.

In some devices, the cleaning device g discards the photoconductor a together with the photoconductor a. However, the cost of consumables increases, and the frequently used device such as a printer is used during replacement work. It is not preferred because it becomes impossible.

Therefore, normally, a collected toner carrying screw (toner auger) t is provided in the cleaning device g, and the toner is sent to and collected from a toner collection box (not shown) provided outside the cleaning device g. .

However, since the collection box occupies a place in the apparatus, a large one cannot be attached, and it is necessary to replace the thousands of records, which is not preferable. Also, when the collection box is removed, part of the toner spills, and the hands and clothes of the exchanger,
It is not preferred because it may stain the floor. Further, since the cleaning device g makes the blade u abut on the surface of the photoconductor a, the photoconductor a is easily damaged and is safe and harmless like the OPC photoconductor, but the soft photoconductor a has an extremely long life. Since the photoconductor a has a small diameter, the exchange cycle is short in the case of the photoconductor a, which is not preferable.

Therefore, a process for solving the above-mentioned problem is being developed by configuring a process in which the cleaning device g is removed, but the following problem occurs, and this is a major obstacle in practical use.

That is, when toner of opposite polarity adheres to the photosensitive member a due to charge injection during development, that is, reverse adhesion to a non-image portion occurs, the toner that has not been transferred at the time of transfer is used in the next cycle. In exposure, it functions as a filter and occurs as an image memory, which is a problem.

The present invention has been made based on the above circumstances, and it is an object of the present invention to provide an image forming apparatus in which a developing step and a cleaning step for an image carrier are simultaneously performed by the same apparatus,
An object of the present invention is to provide an image forming apparatus capable of performing good image formation without generating an image memory by eliminating reverse adhesion toner (colored powder) during development.

[Constitution of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a charging unit for charging a photoconductor to a specific polarity, and the photoconductor charged by the charging unit. Exposure means for forming an electrostatic latent image by exposing the photosensitive member, a developer conveying member for supplying a developer charged to the specific polarity to the photosensitive member, and a photosensitive member for the developer conveying member. The residual developer adhering to the unexposed portion of the photoconductor moves toward the developer transport member, and the electric field to which the developer travels from the developer transport member to the exposed portion of the photoconductor is generated by the developer transport member and the photoconductor. A voltage applying means for applying a bias voltage having a difference between the charged potential of the photoconductor and the charged potential of the photoconductor of 100 to 300 v. To visualize the charged latent image and simultaneously A reversal-developing-type developing / cleaning unit for collecting the residual developer adhering to the unexposed portion of the photoconductor to the developer conveying member; and transferring a developer image on the photoconductor developed by the developing / cleaning unit. Transfer means for transferring to the material, and a memory removing means for disturbing the residual developer remaining on the photoreceptor after the transfer is performed on the transfer material by the transfer means, and the developer is ,
The dynamic resistance value when the developer is transported by the developer transport member is 2 × 10 ¹⁰ to 2 × 10 ¹¹ Ωcm, and the charging unit, the exposure unit, the developing cleaning unit,
The transfer unit and the memory removing unit are operated to form one image forming process, and the image forming process is repeated by rotation of the photoconductor. When a developer charged to a polarity opposite to the specific polarity is attached to the unexposed portion of the photoconductor, the photoreceptor is charged with a charge generating layer so that the unexposed portion attenuates to a predetermined potential in the next image forming process. And a light-transmissive charge transport layer provided on the charge generation layer.

(Effect) That is, in the present invention, a developer having a dynamic resistance of 2 × 10 ¹⁰ to 2 × 10 ¹¹ Ω · cm is used as the developer contained in the developing means. Adhesion of reverse polarity colored powder on image carrier generated by injection Does not occur so-called reverse adhesion to non-image area, and also maintains image density etc., so that coloring that reversely adheres in the exposure process in the next cycle The filter effect of the powder can be removed, and therefore, an image memory, a ghost image and the like can be prevented. Further, in the present invention, even if a filter effect occurs due to the opposite polarity toner adhering to the photoreceptor, the photoreceptor has a charge generation layer and a light-transmissive charge transport layer provided on the charge generation layer. Therefore, the light reliably reaches the charge generation layer due to the diffraction and reflection of the light generated in the charge transport layer, and it is possible to eliminate insufficient light exposure.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 11.

FIG. 2 shows an overall configuration of an electrophotographic image forming apparatus using a semiconductor laser, and FIG. 1 shows a configuration of a main part thereof.

The image forming apparatus (laser beam printer) is connected to a host system (not shown) which is an external output device such as an electronic computer or a word processor via a transmission controller such as an interface circuit.

When a print start signal is received from the host system, an image recording operation is started, and the image is recorded on paper P as a recording medium and output.

This image forming apparatus has the following configuration. That is, in the figure, reference numeral 1 denotes an apparatus main body, in which a drum-shaped photosensitive member 2 as an image carrier is arranged. Around the photoreceptor 2, a charging unit 3 composed of a scorotron, an exposure unit 4a of a laser exposure unit 4 described later as an electrostatic latent image forming unit, a developing process and a cleaning (cleaning) process are arranged along the rotation direction. A magnetic brush type developing means 5, a transfer means 6 composed of a scorotron, and a memory removing means 7 composed of a brush member are sequentially provided.

An image transfer unit 11 between the photosensitive member 2 and the transfer unit 6 transfers a sheet P as a recording medium fed from a sheet cassette 9 via a sheet feeding unit 10 to a lower portion inside the apparatus main body 1. A paper transport path 15 is formed to lead to a paper discharge tray 12 provided on the upper surface side of the apparatus main body 1 through the apparatus.

Further, an aligning roller pair 16 is disposed on the upstream side of the image transfer section 11 of the paper transport path 15, and a fixing device 17 and a paper discharge roller pair 18 are disposed on the downstream side.

The laser exposure means 4 includes a semiconductor laser oscillator (not shown), a polygon scanner 22 including a polygon mirror 20 and a mirror motor 21, an fΘ lens 23, a correction lens 24,
It is composed of reflection mirrors 25 and 26 for scanning the scanned laser beam to a predetermined position. 2 in FIG.
7 are control boards that constitute control means for controlling the present apparatus.

The photoreceptor 2 is made of an organic photoconductor. As shown in FIG. 3, a double-sided aluminum cylinder 30 having an outer diameter of 30 mm and a wall thickness of 0.8 mm, and a charge formed on the surface of the cylinder 30 are formed. Shipping layer
31 and a charge transport layer 32 that covers the charge generation layer 31.

When the printing start signal is received by the host system, the drum-shaped photoconductor 2 rotates and the photoconductor 2 is charged by the charging unit 3. Next, the laser beam 1 modulated by receiving the dot image data from the host system is scanned and exposed on the photosensitive member 2 by using a laser exposure means 4 including a polygon mirror scanner 20, and an image signal is formed on the photosensitive member 2. A corresponding electrostatic latent image is formed.

The electrostatic latent image on the photoreceptor 2 is developed by the developing means 5 and visualized.

On the other hand, in synchronization with the operation of forming the developer image, the sheet P taken out from the paper feed cassette 9 is fed through the pair of aligning rollers 16 and the developer image previously formed on the photosensitive member 2 is transferred. The image is transferred onto the sheet P by the operation of the means 6.

Next, the paper P is sent to the fixing unit 17 through the transport path 15, where the developer image is melted and fixed on the paper P, and then discharged onto the paper discharge tray 12 via the paper discharge roller pair 18. Is done.

After the transfer of the developer image onto the paper P, the residual toner remaining on the photoreceptor 2 is diffused by the memory removing means 7 composed of a conductive brush to remove the memory, and the next copying operation is possible. State.

The developing means 5 has a configuration as shown in FIG. In the figure, reference numeral 35 denotes a casing having a developer accommodating portion 36 accommodating therein a two-component developer D composed of colored powder (hereinafter referred to as toner) t and magnetic powder (hereinafter referred to as carrier) c. In the casing 35, a developing roller 37 is provided so as to face the photoconductor 2, and a developer magnetic brush D 'formed on the surface of the developing roller 37 is in sliding contact with the photoconductor 2. That is, a doctor 39 that regulates the thickness of the developer magnetic brush D ′ is provided upstream of the developing position 38 in the rotation direction of the photoconductor 2. Further, the first and second developer stirring bodies 4 are stored in the developer accommodating section 36.
0,41 are accommodated.

Further, the developing means 5 is provided with a toner replenishing device 42 so that the toner t is supplied to the developer accommodating portion 36 as appropriate.

The photosensitive member 2 is built in the casing 35, and the developing roller 37 passes through the rotation center of the photosensitive member 2 and has an angle α (about 50 °) with respect to a horizontal line L.
It is provided so that the center is located on the line which becomes.

The developing roller 37 is composed of a magnetic roll 48 having three magnetic pole portions 45, 46, 47, and a non-magnetic sleeve 49 fitted around the magnetic roll 48 and rotating counterclockwise in the drawing.

Of the three magnetic pole portions 45, 46, 47 of the developing roller 37, the developing position
The magnetic pole part 46 facing the element 38 is an N pole, and the other magnetic pole parts 45, 47
Are S poles. The angle theta ₁ is 150 ° between the magnetic pole disconnect 45 and the magnetic pole portion 46, the angle theta ₂ between the magnetic pole portion 46 and the magnetic pole portion 47 is 120 ° set.

By the way, in the present invention, in order to simplify the process of the electrophotographic method, a reversal development method is adopted, and a method of removing the toner t remaining after transfer simultaneously with the development is adopted. At this time, the change in the surface potential of the photoconductor 2 and the state of the toner on the photoconductor 2 are as shown in FIGS. 4 and 5.

That is, as shown in FIG. 4 (a) and FIG. 5 (a), the photoreceptor 2
Is charged. At this time, the toner t on the photoconductor 2 that has not been completely transferred in the previous image forming operation is also charged, and the photoconductor 2 under the toner t is also charged. This means that even if the toner t is removed with a urethane blade or the like,
Experimental results show that the surface potential of the photoreceptor 2 is maintained at about 80 to 90%.

In the apparatus of this embodiment, since the surface potential is made uniform by using a scorotron charger as the transfer unit 3, the potential of the portion of the photoconductor 2 below the toner t is equal to the inner portion of the toner t as described above. This potential difference is practically not a problem at all.

As described above, the surface potential of the photoconductor 2 is attenuated by the laser beam 1 scanned by the laser optical unit 4 modulated by receiving the dot image data from the host system. As shown in FIG. 5B and FIG. 5B, an electrostatic latent image is formed.

The electrostatic latent image is developed by the developing unit 5, and at this time, unnecessary toner t for the image adhered to the photoreceptor 2 as a transfer residue is simultaneously generated by the developing unit 5.
Will be cleaned by The electrostatic latent image on the photoreceptor 2 is visualized after the toner t is supplied by the developing means 5 and then, as shown in FIG. 4 (d) and FIG. The image is transferred by the transfer means 6.

A high voltage having a polarity opposite to that of the negatively charged toner t is applied to the transfer unit 6, a positive corona discharge is performed from the back of the paper P, the paper P is positively charged, and the negative toner t is transferred to the paper P. It has a role to attract to. After the image is thus transferred, as shown in FIGS. 4 (e) and 5 (e), the toner t remaining on the photoreceptor 2 is transferred to the memory removing means 7 comprising a brush. Thus, the toner t is diffused.

Next, the principle, conditions, and the like, including experimental data, will be described.

The process of simultaneous cleaning and development of the present invention (CD
P) has a point in performing reversal development. Because the polarity of the toner t and the polarity of the charge are the same,
This is because the polarity of the toner t by the charging unit 3 is not reversed.

However, in order to obtain good image quality, certain process conditions are required in the present system CDP.

FIG. 6 is an explanatory diagram of terms used herein. The potential when the photosensitive member 2 reaches the developing position without being exposed by being charged by the charging means 3 is defined as a charged potential V ₀ , The attenuated potential is the post-exposure potential Ver, the potential applied to the developing roller 37 of the developing means 5 is the development bias Vb, and the difference between the post-exposure potential Ver and the development bias Vb is the cleaning potential (cleaning potential) Vcl = V ₀ − Vb. In this embodiment, the photosensitive member 2 uses OPC for negative charging, but V ₀ , Vb, Ver, Vb−Ver, and V ₀ −Vb are absolute values in consideration of the positive charging type.

FIG. 7 is a plot of the measured data with the developing bias on the horizontal axis and the photoconductor charging potential on the vertical axis. The cleaning potential Vcl is required to be 100 V or more. Since there is no cleaning, poor cleaning is likely to occur as an image memory in the next cycle, and uneven charging, fogging, and the like are likely to occur due to the fluctuation margin of the charging potential.

Conversely, if the cleaning potential is set to 300 V or more, the charge is reversely injected from the developing roller 37 into the toner t, and the non-transferred injected toner t of the opposite polarity is generated at the time of development, and is generated as an image memory described later. Problems such as adhesion also occur, and it is not easy to go.

Therefore, a relationship of 100V <Vcl <300V is necessary in this process.

Here, an outline in which the toner t of the opposite polarity is generated as an image memory will be described.

Referring to FIGS. 8 and 9, in FIG. 9A, the toner remaining without being transferred in the non-image portion, that is, the reversely attached toner t 'is the transfer residual toner t in the image portion.
However, the toner is negatively charged by the negative corona during charging.

In (b), a dot image of the next cycle is written by laser exposure to form a latent image. here,
The transfer residual toner t has a small absolute amount as described above, and the transfer residual image, which is a dot image in the previous cycle, is diffused by the memory removing means 7. This is not a problem. 7, the laser beam 1 is filtered more strongly than the transfer residual toner portion at the time of exposure, so that the latent image pattern of the photoreceptor potential of the transfer residual toner portion is low and the reverse adhesion toner portion is high. Is formed as shown in FIG.

When the latent image proceeds to the development shown by (c) in the figure, the transfer residual toner portion develops to a high density, and further develops to the reverse adhesion toner portion to a low density due to its development potential relationship.

At this time, at the time of development, the toner t on the charged potential portion of the photoconductor 2 is cleaned, but at the same time, the reversely adhered toner t 'is attached to this charged potential portion.

The reversely attached toner t ′ is a positive toner into which positive charges are injected from the developing roller 37 due to a potential difference between the charging potential of the photosensitive member 2 and the developing bias voltage.

Therefore, the toner remains on the photoconductor 2 without being transferred even in the transfer process shown in FIG.

When the reversely adhered toner 5 'is generated from the above process, it is generated as an image memory due to its effect as an optical filter.

 The following experiment was conducted to eliminate these problems.

The resistance values of the toner t and the carrier c are varied randomly in the composition or particle size, and the mixture of the toner t and the carrier c are variously changed, and are randomly selected using the developer dynamic resistor 5 'shown in FIG. It was measured.

The developer dynamic resistance measuring device 5 'has substantially the same configuration as the developing means 5 shown in detail in FIG. Further, a gap d ₂ between the doctor 39 and the developing roller 37 is set to 1.85 mm, and
Distance d ₁ of the developing position 38 of the developing roller 37 and the photoreceptor 2 is 2.0m
is set to m.

The developing roller 37 has a diameter of 35 mm and a rotation speed of 14 mm.
It is set to rotate at 0 rpm.

With these configurations, the sample is put into the measuring device 5 ', and the developing roller 37 is rotated while applying a voltage of -100 V to the developing roller 37, and the current value from the aluminum cylinder 30 of the photoreceptor 2 is measured. The dynamic resistance value of the agent D was calculated.

 FIG. 11 shows the dynamic resistance values of some developers.

The horizontal axis shows the developer dynamic resistance value, and the vertical axis shows the reverse adhesion reflection density and the image reflection density.

The reverse adhesion reflection density is measured by collecting a tape from the photosensitive member 2 described later, and the photosensitive member potential is set as a process condition.
The test was performed at V ₀ = −500 V and developing bias Vb = −300 V. Table 1 shows the physical properties of the developer.

As can be seen from the graph of FIG. 11, when the density is 2 × 10 ¹⁰ Ω · cm or less, the reverse adhesion reflection density is increased, and the image memory of the previous cycle is actually generated due to the image quality of the paper P. On the other hand, conversely, 2 × 10 ¹¹
If it exceeds Ω · cm, satisfactory image density cannot be obtained.
Therefore, from the relationship between the image density and the reverse adhesion density, 2 × 10 ¹⁰
It can be seen that the process does not match the process from which the cleaner is removed by the present process unless it is within the range of Ω · cm to 2 × 10 ¹¹ Ω · cm.

At this time, the photosensitive member 2 and the sleeve 49 of the developing roller 37 are used.
The gap between the doctor 39 and the sleeve 49 (Dc-Sl) is 0 <(Dr-Sl)-(Dc-Sl) <0.3.
If the dynamic resistance is the same, there is no significant change.

Here, as an example of the composition of the toner t used, a resin is a styrene-n-butyl methacrylate copolymer (Sanyo Chemical: Hymer SBM-73), a carbon black (Mitsubishi Chemical: MA-100), It is composed of colloidal silica (Nippon Felodil: R972), charge control agent and the like.

The toner t used had a volume resistivity of about 2 × 10 ¹⁰ Ω · cm.

The carrier c is made of Cu-Zn ferrite, Mn-Cu-Zn
A ferrite carrier such as ferrite or Zu ferrite, or a carrier provided with an acrylic resin coating as the case may be mainly used as a magnet carrier.

On the other hand, in the simultaneous development cleaning method, the characteristics of the toner t are affected. Here, the following experiment was performed in order to examine the characteristics of the toner t.

First, an electrostatic latent image is formed by performing charging and exposure on the photoreceptor 2 to which the toner t does not adhere, and reversal development is formed thereon.

At this time, the toner image on the photoreceptor 2 is taken on a mending tape (manufactured by 3M), pasted on white paper, and the reflection density is measured.

Next, an image is formed on the photoreceptor 2 in the same manner as described above, and the image is not transferred, but is subjected to light elimination and recharge. After passing through the developing means 5 without exposure, the toner image is taken on a mending tape (manufactured by 3M) and the density is measured on a white paper. The density at this time is defined as Dcl. Then, the cleaning efficiency ξ can be expressed as ξ = 1−Dcl / Dd.

Normally, the case where the amount of the transfer residual toner t is large is a case where the image density is high and the transfer density is about 1.6.
The transfer efficiency is about 75 to 90%. Here, assuming that the transfer efficiency is a low method value of 75%, the untransferred toner concentration remaining on the photoreceptor 2 (mending tape method) is as follows: Dp / (Dd + Dp) = η 1,6 / (Dd + 1.6 ) = 0.75 (Dp: transfer density, Dd: transfer residual density, η: transfer efficiency), it is about 0.53. If this amount is on the photoreceptor 2, the memory will be used if it is not cleaned.
If l can be reduced to 0.1 by simultaneous cleaning with development, there is no problem on the transferred image.

Here, when Dcl = 0.1 and Dd = 0.53 are substituted into the equation of cleaning efficiency ξ, ξ = 1-Dcl / Dd 1-0.1 / 0.53 ≒ 0.81, which indicates that a cleaning efficiency of approximately 80% or more is sufficient. .

The transfer residual toner is removed by a conductive brush (about 10 ³ Ω · cm) as a memory removing unit 7 installed before recharging.
, The cleaning can be performed without any problem of simultaneous cleaning.

Further, in the present process, as described above with reference to FIG. 3, a double-cut aluminum cylinder 30, a charge generation layer 31 formed on the surface of the cylinder 30, and a surface of the charge generation layer 31 A function-separated organic photoconductor constituted by the applied charge transport layer 32 is used.

This is characterized in that since the charge transport layer 32 is translucent and located above the charge generation layer 31, when the photoreceptor 2 is exposed, underexposure is easily reduced by diffracted light or reflected scattered light. In addition, due to a problem in the production of the toner t, the positive polarity toner easily absorbs moisture in a humid environment and its volume specific resistance changes, so that the above-mentioned reverse adhesion easily occurs.

Therefore, it is necessary to use a negatively charged toner having excellent stability. In the case of performing reversal development, a negatively charged corona is required, so that the above-described organic photoconductor must be used.

It is needless to say that the present invention can be variously modified and implemented without changing the gist.

[Effects of the Invention] As described above, according to the present invention, the colored powder remaining on the image carrier is electrically suctioned and removed simultaneously with the development by the developing means. Since a collection box is not required, the size, weight, and cost can be reduced, and there is no risk of contamination. Further, since the cleaning blade does not contact the image carrier, the life of the image carrier is reduced. Can be longer. Further, a two-component developer composed of a colored powder (toner) and a magnetic powder (carrier) is used as a developer, and 2 × 10 ¹⁰
Since a material exhibiting a dynamic resistance value of ~ 2 × 10 ¹¹ Ω · cm is used, there is no problem due to reverse adhesion, which has been regarded as a conventional problem, and good image quality without an image memory, a ghost image, etc. can be obtained. This has the effect. Even if a filter effect occurs due to the opposite polarity toner adhering to the photoconductor, the photoconductor has a charge generation layer and a light-transmissive charge transport layer provided on the charge generation layer. Therefore, light reaches the charge generation layer reliably due to diffraction and reflection of light generated in the charge transport layer, and it becomes possible to eliminate insufficient exposure.

[Brief description of the drawings]

1 to 11 show an embodiment of the present invention.
FIG. 1 is a view schematically showing the structure of a main part, FIG. 2 is a longitudinal sectional side view schematically showing the whole structure, FIG. 3 is a view showing the structure of a photoreceptor, and FIG. Illustrated illustration, fifth
FIG. 6 is an explanatory diagram showing a change in the surface potential of the photosensitive member during the image forming process. FIG. 6 is a diagram showing various potentials. FIG. 7 is a diagram showing the relationship between the photosensitive member charging potential and the developing bias.
FIG. 9 is an explanatory diagram showing an image forming process when reversely adhered toner is generated. FIG. 9 is an explanatory diagram showing a change in the surface potential of the photoconductor during the image forming process when reversely adhered toner is generated. Is an illustration of a developer dynamic resistance measuring instrument, the eleventh
FIG. 12 is a diagram showing reverse adhesion characteristics and image characteristics when the dynamic resistance value of the developer is changed, and FIG. 12 is a schematic configuration diagram showing a conventional example. 2 ... image carrier (photoreceptor), 3 ... charging means, 4 ... laser exposure means, 5 ... development means, 6 ... transfer means, 7
... Memory removal means, P... Paper, D... Developer, t.
... Colored powder (toner), c ... Magnetic powder (carrier).

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Katsuhide Sano, Inventor Toshiba Automatic Equipment Engineering Co., Ltd. 70, Yanagicho, Saitama-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-59-133573 (JP, A) JP-A Sho 59-121350 (JP, A)

Claims (1)

(57) [Claims] A charging unit configured to charge the photoconductor to a specific polarity; an exposure unit configured to expose the photoconductor charged by the charging unit to form an electrostatic latent image; A developer transport member that supplies a developer charged to a specific polarity, and, for this developer transport member, the residual developer attached to the unexposed portion of the photoconductor faces the developer transport member; In order to form an electric field in which the developer travels from the developer transport member to the exposed portion of the photoconductor between the developer transport member and the photoconductor, the difference between the charged potential of the photoconductor and the electric potential is 100 to 300 v. A voltage application unit for applying a bias voltage, and supplying the developer from the developer conveying member to an exposed portion of the photoconductor to visualize the electrostatic latent image, and simultaneously exposing the photoconductor to an unexposed portion. The residual developer adhering to the portion is transferred to the developer transport member. A reversal developing type developing and cleaning unit, a transferring unit for transferring a developer image on the photoreceptor developed by the developing and cleaning unit to a transfer material, and the transfer unit performs transfer on the transfer material. And a memory removing unit that disturbs the residual developer remaining on the photoconductor after the developer is transferred, and the developer has a dynamic resistance value of 2 × 10 ¹⁰ to when the developer is transported by the developer transport member. a 2 × 10 ¹¹ Ω · cm, the the photosensitive member, the charging unit, the exposing unit, the developing cleaning means, and said transfer means, said memory removing means is operated to first image forming process, the photosensitive member While repeating this image forming process by the rotation of, after the residual developer is disturbed by the memory removing unit,
When a developer charged to a polarity opposite to the specific polarity is attached to the unexposed portion of the photoreceptor, the photoreceptor is attenuated to a predetermined potential in the next image forming process. An image forming apparatus comprising: a charge generation layer; and a light-transmissive charge transport layer provided on the charge generation layer.