JP2003295535A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that first copying time or first printout time is long and actual image forming efficiency is not good because time for pre- processing performed aiming at the fatigue of a photoreceptor is long in an image forming apparatus having an organic photoreceptor. <P>SOLUTION: The image forming apparatus is provided with a 1st electrifying means and a 1st entire surface exposure means, and a 2nd electrifying means and a 2nd entire surface exposure means at positions where phases are shifted by the half round of the photoreceptor. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and an image forming method for forming an image by an electrophotographic method, and more particularly to a control technique at the start of an image forming process.

[0002]

2. Description of the Related Art As is well known, electrophotography is an image forming method in which an image is formed by using an optical semiconductor, and utilizes a phenomenon in which the conductivity of a photoconductor is changed by carriers generated by light energy. . That is, by charging the photoconductor, a uniform electric potential is formed on the photoconductor, the electric potential is attenuated by the carriers generated by the exposure to form an electrostatic image, and the charged particles are attached according to the electric potential. To form an image.

It is known that the potential of the photoreceptor formed by charging varies depending on various factors, and the variation of the charging potential is mainly caused by defects at the molecular level in the photosensitive layer. That is, defects such as impurities in the photoconductor
As a result of functioning as a carrier trap, the charge holding ability of the photoreceptor changes and the charging potential changes. In many photoreceptors, defects increase and charging potential decreases as the fatigue level increases, that is, as the usage time increases.

In the organic photoreceptor, such a phenomenon of decrease in charging potential is remarkable, and various countermeasures are taken. As one of the countermeasures, carriers are generated by exposure to fill the trap. In the image forming process, this measure is executed as follows.

That is, after the entire surface is exposed at the start of the image forming process to perform a pretreatment for generating carriers in the organic photoconductor and filling the traps, a charging process for image formation is executed. The pretreatment generally consists of charging and overall exposure.

[0006]

The measures as described above are
Although there is some effect, there is a problem in that the decrease in the charging potential cannot be sufficiently corrected by one-time charging and overall exposure. For this reason, it is necessary to carry out the charging and the overall exposure as the pretreatment a plurality of times. However, in this case, it is necessary to rotate the photoconductor 2 times or more, and there is a problem that the pretreatment takes a long time.

In operations such as copying and printing, image formation of a small number of sheets, such as one sheet or a few sheets, occupies a high frequency ratio, so that the first copy time (FCOT) or the first print out time (FPOT) is a machine performance. Although it is an important evaluation item, a device that requires a long time for pretreatment as described above spoils these evaluation items and is not desirable.

The present invention is directed to overcoming the above problems associated with pretreatment of photoreceptors.

[0009]

The above objects of the present invention are achieved by the following inventions.

1. In an image forming apparatus having an organic photoconductor, an image forming charging unit, an image exposing unit, a developing unit, a transferring unit, a separating unit and a cleaning unit, first and second charging units, first and second whole surface exposing units and control. Means for exposing the entire surface of the organic photoconductor charged by the first charging means, the first whole surface exposing means being disposed on the downstream side of the first charging means in the moving direction of the photoconductor, and the second whole surface exposing means. The exposing means is disposed on the downstream side of the second charging means in the moving direction of the photosensitive member, and exposes the entire surface of the organic photosensitive member charged by the second charging means, and the control means, prior to the start of the image forming step. Before the organic photoconductor is rotated at least once and the first and second charging means and the first and second whole surface exposure means are operated to perform two times of charging and whole surface exposure on the organic photoconductor. Characterized by performing processing That the image forming apparatus.

2. 2. The image forming apparatus as described in 1 above, wherein the first charging unit includes the image forming charging unit.

3. 3. The image forming apparatus according to 1 or 2 above, wherein the second charging unit includes the transfer unit.

4. The image forming apparatus according to any one of the items 1 to 3, wherein the second charging unit includes the separating unit.

5. Any one of the above items 1 to 4 is characterized in that the first whole surface exposure means comprises pre-transfer exposure means.
The image forming apparatus according to item.

6. 6. The image forming apparatus according to any one of 1 to 5 above, wherein the first entire surface exposure unit is a transfer simultaneous exposure unit.

7. Any one of the above items 1 to 6 is characterized in that the second whole surface exposure means comprises pre-charging exposure means.
The image forming apparatus according to item.

8. The developing means has a volume average particle diameter of 2 to
8. The image forming apparatus described in any one of 1 to 7 above, which is developed by using a toner of 9 μm.

9. The developing means has a shape factor SF-1 = (Lmax ² / A) × (π / 4) ×
100 Shape factor SF-2 = (Laround ² / A) × (1 /
4π) × 100 (where Lmax is the maximum diameter of toner particles, Larou
nd is the perimeter of the toner particles, A is the projected area of the toner particles), and the spherical coefficient SF-1 represented by
9. The image forming apparatus according to any one of 1 to 8 above, wherein development is performed using a toner having a spherical coefficient SF-2 of 100 to 120.

10. 10. The image forming apparatus according to any one of 1 to 9 above, wherein the developing means performs development using a two-component developer containing toner and carrier as main components.

11. Any one of the above 1 to 10, wherein the developing means develops using a polymerized toner.
The image forming apparatus according to item.

12. The control means includes a first mode in which an image is formed after the pre-processing by the first and second charging means and the first and second whole surface exposure means, and the first and second charging means and the first mode. 12. The second mode, in which one or more of the second whole surface exposure means is not used, or a second mode in which image formation is performed without pretreatment is selected and executed. Image forming apparatus.

13. 13. The image forming apparatus as described in 12 above, further comprising an environment detection sensor, wherein the control unit selects the first mode or the second mode based on an output of the environment detection sensor.

14. The above-mentioned 12 or 13 is characterized in that it has a use history detecting means for the organic photoreceptor, and the control means selects the first mode or the second mode based on the output of the use history detecting means. The image forming apparatus according to item 1.

15. First and second charging steps and first and second
An image forming method, which comprises performing an entire surface exposure step and then performing an image forming step after performing charging and entire surface exposure twice for each of the organic photoreceptors.

16. A second mode in which the image forming step is performed without performing one or more of the first mode in which the image forming step is performed after the first and second charging steps and the first and second whole surface exposure steps are performed. 16. The image forming method as described in 15 above, which is selected and executed.

17. Based on the environment detection result, the first
17. The image forming method as described in 16 above, wherein the mode or the second mode is selected.

18. 18. The image forming method described in 16 or 17, wherein the first mode or the second mode is selected based on a detection result of the usage history of the organic photoconductor.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Image Forming Apparatus> FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. In the figure, 1
Is an organic photoconductor, 2 is an image forming charging means for uniformly charging the organic photoconductor 1, and a scorotron charger, a corotron charger, a contact charger such as a charging roller, or the like is used. Reference numeral 3 denotes an image forming exposure means for exposing the organic photoreceptor 1 imagewise, and a laser exposure device using a laser light source and a rotating polygon mirror, an LED exposure device using a light emitting diode array, and the like are used. Reference numeral 4 denotes a developing unit that develops the electrostatic latent image on the organic photoconductor 1 to form a toner image. A developing unit that uses a one-component developer or a developing unit that uses a two-component developer is used. What is developed by reversal development is used. The image forming charging means, the image forming exposure means 3 and the developing means 4 constitute an image forming means.

The organic photoconductor used in the present invention is an electrophotographic photoconductor which has at least one of a charge generation function and a charge transport function, which are indispensable for the construction of the electrophotographic photoconductor. A photoconductor, a photoconductor composed of a known charge generating substance or charge transporting substance,
It includes all known organic photoreceptors such as a photoreceptor having a charge generation function and a charge transport function of a polymer complex. A typical organic photoreceptor is a function-separated type organic photoreceptor having a charge generation layer and a charge transport layer.

Reference numeral 5 is a transfer means for transferring the toner image onto the recording material P, and a contact type transfer device such as a corotron charger or a roller is used. Reference numeral 6 denotes a separating means, and a corotron static eliminator, a mechanical separating device, or the like is used. 7 is a cleaning means, and as shown in the drawing, the cleaning blade 7
1 and a cleaning roller 72. Reference numeral 8 denotes a transport unit that transports the recording material P after the transfer, and includes a roller and a belt. Reference numeral 9 denotes a fixing unit that fixes the toner image on the recording material. In addition to the heating roller 91 and the pressure roller 92 as shown in the figure, a fixing device using various types of heating members such as a belt and a block is provided. Used. Reference numeral 10 denotes a paper feeding unit that conveys the recording materials P one by one to the transfer unit. Two
Reference numeral 0 is a pre-charging exposure means, and 21 is a pre-transfer exposure means. The pre-charging exposure means 20 and the pre-transfer exposure means 21 are composed of LEDs (light emitting diodes) and uniformly expose the entire surface of the organic photoreceptor 1. The pre-transfer exposure means 21 may be replaced by a simultaneous transfer exposure means. CR is a control unit for controlling the whole, and the control of the image forming exposure unit 3, the transfer unit 5, the pre-charge exposure unit 20, and the pre-transfer exposure unit 21 will be described later. <Control at Start of Image Forming Step> FIG. 2 is a timing chart of control at the start of image formation, and FIG.
FIG. 3 is a diagram showing positions on an organic photoconductor of charging and overall exposure.

Simultaneously with the rotation start T0 of the organic photoconductor PC, the first charging means CH1 and the second charging means CH2 are activated to charge the organic photoconductor PC and form a charging potential on the organic photoconductor PC. In the following, the charging process by the first charging means CH1 is referred to as a first charging step prech1 and a second charging means CH.
The charging process by 2 is referred to as a second charging process prech2.

In the image forming apparatus of FIG. 1, the first charging means CH1 is composed of the image forming charging means 2 and the second charging means CH2 is composed of the transfer means 5. The separating means 6 may be used as the second charging means. First charging step pr
The ech1 and the second charging step prech2 are deviated by a phase corresponding to half the circumference of the organic photoconductor PC which is cyclically moved by rotation or the like. At the same time when the organic photoconductor PC is started, the first charging step pre
It is not essential that the ch1 and the second charging process prech2 are performed, and the first and second charging processes prech1 and prech are performed after a predetermined time elapses after the organic photoconductor PC is started.
Implementation of 2 may be started.

First and second charging steps prech1, pre
After half a rotation of the organic photoconductor PC from the start of ch2, at time t1, the first overall exposure means EX1 and the second overall exposure means EX2 are activated to perform overall exposure steps ex1 and ex2.
Is started. Then, at time T1 when the organic photoconductor PC rotates once, the charging step fch for image formation is started. As described above, since the first charging unit CH1 is composed of the image forming charging unit, the image forming charging process fch is continuously performed after the first charging process. Second charging step prech
2 is carried out by the transfer means 5, and as shown in the drawing, the organic photoconductor PC is started from the end time T1 of the second charging step prech2.
The charging process trch for transfer is started from time t6 when half the time has passed. As shown, the second charging step prech2
The charging polarity in and the charging polarity in the transfer charging step trch are opposite.

The first whole surface exposure means EX1 and the second whole surface exposure means EX2 start to operate at time t1 after the half rotation of the organic photoconductor PC after the start of the operation of the first and second charging means CH1 and CH2. In the image forming apparatus of FIG. 1, the first whole surface exposure means EX1 is composed of a pre-transfer exposure means 21 provided at a downstream portion of the image forming charging means 2 in the photosensitive member moving direction, and the second whole surface exposure means EX2 is transferred. The pre-charging exposure means 20 is provided downstream of the means 5 in the moving direction of the photoconductor. In addition,
The organic photoconductor P is transferred to the first whole surface exposure means EX1 at the same time as the transfer.
Transfer simultaneous exposure means for exposing C or exposure means 3 for image formation
Can also be used.

In the example shown in FIG. 2 and FIG. 3C which will be described later, the first and second charging steps prech1 and
prech2 is started at the same time, and the first and second whole surface exposure steps ex1 and ex2 are performed in the first and second charging steps prech1 and p2.
Although the start is started after about half a round of rech2, it is not limited to such a start timing. That is, the first charging step pr
The ech1 and the second charging step prech2 do not have to start at the same time, and the first overall exposure and the second overall exposure do not have to start at the same time. Further, it is not necessary to start the whole surface exposure process after half the circumference of the charging process. Therefore, the arrangement positions of the first and second charging means CH1 and CH2 and the first and second whole surface exposure means EX1 and EX2 are not limited to the example of FIG. 3C.

The conditions regarding the start timing of these steps are as follows: when the organic photoconductor PC makes one revolution,
In contrast, two charging processes and two overall exposure processes are performed.

The above-described first and second charging means CH1,
The pretreatment by CH2 and the first and second whole surface exposure means EX1 and EX2 is performed on the organic photoconductor PC in the positional relationship shown in FIG.

In the following description, a concrete example of the image forming apparatus shown in FIG. 1, that is, the organic photoconductor 1 is used as the organic photoconductor PC, and the first charging means CH1 is used.
A specific example in which the image forming charging means 2, the second charging means CH2 are the transfer means 5, the first overall exposure means is the pre-charge exposure means 20, and the second overall exposure means is the pre-transfer exposure means 21 will be described.

The phase PH1 in FIG. 3 (c) is the phase in which the organic photoconductor 1 has made a half turn from the start of the first charging process and the second charging process, and the organic photoconductor 1 has the first charging process prech.
In 1 and prech 2, the charging means 2 for image formation and the transfer means 5 are charged half a turn each, so that the entire surface is subjected to one charging process. The phase PH2 indicates a phase obtained by the organic photoconductor 1 being further halved from the phase PH1. Phase P
At the start of H2, the pre-charging exposure means 20 and the pre-transfer exposure means 21 start operating, and the first and second charging steps prech1 and prech2 as well as the first and second whole surface exposure steps ex1 are performed on the organic photoreceptor 1. , Ex2 are performed.

In this way, the organic photoreceptor 1 is subjected to the charging treatment twice and the entire surface exposure treatment twice in the pretreatment,
Image formation is carried out on the organic photoreceptor 1 which has been subjected to this pretreatment. Therefore, the fatigue of the organic photoconductor 1 is sufficiently recovered, and a sufficiently high charging potential is obtained.

The organic photoreceptor 1 according to the present invention described above
The charging potential of (1) will be described in comparison with the conventional example.

FIG. 3A shows a conventional example in which the pretreatment is performed by using only the image forming charging means 2 and the charging pre-exposure means 20, and FIG. 3B shows the image forming charging means 2 and the transfer means. 5 is a conventional example in which the pretreatment is performed by using only No. 5 and pre-charging exposure means 20. 3A is a conventional example 1, FIG. 3B is a conventional example 2,
FIG. 3C is referred to as an example of the present invention in the following. The curve L1 in FIG. 5 represents the charging potential of the organic photoconductor 1 in Conventional Example 1, and the curve L2 represents the organic photoconductor 1 in Conventional Example 2.
And the curve L3 shows the charging potential of the organic photoconductor 1 in the example of the present invention.

FIG. 4 shows the transition of the charging potential of a new organophotoreceptor, that is, an organophotoreceptor which has not been used or has just been used.
FIG. 5 shows changes in the charging potential of the organic photoconductor after long-term use.

As shown in FIG. 4, in the new organic photoconductor, the charging potential of the organic photoconductor reaches the saturation value at the start of charging in a short time. Since the saturation potential VCH is higher than the lower limit value V0 required for image formation, an image-formable state is formed almost at the same time when the rotation of the organic photoconductor is started.

First, Conventional Example 1 will be described. At the start time T0, the image forming charging unit 2 charges the surface potential to rise and reaches the potential V1a at t1 to be saturated. At a time T1 (phase PH1 in FIG. 3A) in which the head of the portion of the organic photoreceptor 1 that has been charged by the image forming charging unit 2 receives the charge of the second rotation after the organic photoreceptor 1 makes one round. As a result of being exposed by the pre-charging exposure means 20 and charged by the image forming charging means 2, the charging potential starts to rise from the potential V1a, and at t5 the potential V is reached.
2a is reached and saturated. Charge potentials V1a to V2
The rise to a is due to the following charging mechanism.

The charge in the first round and the entire surface exposure fill the traps in the organic photoconductor 1 with the carriers and recover the fatigue of the organic photoconductor 1. As a result, the charging performance of the organic photoconductor 1 is improved and the charge potential is increased. To do. The potential V2a is, as shown,
The lower limit potential V0 required for image formation has not yet been reached.

At the third rotation of the organic photoreceptor 1 (starting at time T2, phase PH2 in FIG. 3A), the organic photoreceptor 1 is rotated.
2 by the pre-charging exposure means 20 and the image forming charging means 2.
It has been charged twice and exposed twice. By these processes, the fatigue recovery of the organic photoconductor 1 further progresses, and the charging potential reaches V3a at time t8 and is saturated. Time T2
The increase in the electric potential is due to the fact that the trap of the organic photoconductor is further filled with the carrier by the charging twice and the entire surface exposure twice, and the fatigue recovery progresses. The potential V3a is the lower limit potential V0
Since it has a higher value, image formation becomes possible.

Thus, in Conventional Example 1 indicated by the curve L1,
Since one entire surface exposure means and one charging means are used as the fatigue recovery means for the organic photoreceptor, the charge potential at which the image can be formed becomes the first for the third rotation of the organic photoreceptor 1.

The change in charging potential of the organic photoconductor 1 in Conventional Example 2 is shown by a curve L2 in FIG. FIG. 3B shows a conventional example in which the organic photoreceptor 1 is charged by using the image forming charging means 2 and the transfer means 5, and the entire surface is exposed by using the pre-charging exposure means 20.

At time T0, the image forming charging means 2 and the transfer means 5 are operated to charge the organic photoreceptor 1. By this charging, the charging potential of the organic photoconductor 1 rises at T0 and is saturated at the potential V1b. At the time t2 (phase PH1 in FIG. 3B) when the head of the charging portion of the organic photoreceptor 1 by the transfer means 5 reaches the image forming charging means 2, the pre-charging exposure means 20 is operated. As a result of this exposure, the fatigue of the portion of the organic photoreceptor 1 charged by the transfer means 5 is recovered, and as a result, the charging potential of the organic photoreceptor 1 charged by the image forming charging means 2 rises at t2 and is saturated at the potential V2b. To do. Then, in the first round (phase PH2 in FIG. 3B), the partial potential of the organic photoconductor 1 whose fatigue was further recovered by the second charging by the transfer unit 5 moved to the position of the image forming charging unit 2. It further rises at time t6, saturates at time t1, exceeds the lower limit value V0, and enters a state in which image formation is possible (phase PH3 in FIG. 3B). In Conventional Example 2, the image-formable state is formed when the organic photoconductor 1 rotates one and a half turns.

The transition of the charged state of the organic photoreceptor 1 in the example of the present invention is shown by the curve L3 in FIG. In this embodiment, the image forming charging means 2 charges in the first charging step prech1, and the transfer means 5 charges in the second charging step prech2.

At time T0, charging by the image forming charging means 2 (first charging step prech1) is performed, the potential of the organic photoconductor rises, and at time t1, the potential V
It reaches 1c and becomes saturated. At time t2 (FIG. 3C)
Phase PH1), the charging by the image forming charging means 2 is performed on the portion that has been charged by the transfer means 5 and exposed by the pre-charging exposure means 20, and as a result, the charging potential increases,
At time t3, V2c is reached and saturated. At time T1 when the rotation of the organic photoconductor 1 reaches the second rotation (phase PH2 in FIG. 3C), the organic photoconductor that has been charged twice and exposed twice at the position of the charging means 2 for image formation. Body 1 arrives. As a result, the charging potential of the organic photoconductor 1 further rises from V2c and is saturated at the potential V3c at time t4. Since the potential V3c is higher than the lower limit potential V0 as shown in the figure, the image formation becomes possible from the time t4. As described above, in the present embodiment, an image-formable state is formed at the start time of the second rotation of the organic photoreceptor 1.

In the example in which the organic photoconductor 1 rotates once for 900 msec, in the case of the conventional example 1, the image formation can be started 1800 msec after the rotation of the organic photoconductor 1 is started, but in the case of the conventional example 2, 1350 msec is reached. Image formation can be started, and in the case of the example of the present invention, image formation can be started after 900 msec. Note that, for example, from time T0 to t
The time up to 1, that is, the time between the rise of the potential and the reaching of the saturation potential is exaggerated in the figure, but since it is actually several msec to tens of msec, the saturation potential is almost the same as the rise. Reach

Further, in the figure, V1a <V1b <V
1c, V2a <V2b <V2c, V3a <V3b <V3
It is displayed as c, but this display is the curve L
To avoid the confusion between 1, L2 and L3,
Actually, V1a≈V1b≈V1c, V2a≈V2b≈V
2c and V3a≈V3b≈V3c. <Preferred Embodiment> The preferred embodiment of the present invention is as follows. (1) The toner used in the development is preferably a small particle size toner having a volume average particle size of 2 to 9 μm.

The volume average particle diameter is an average particle diameter on a volume basis, and "Coulter Counter TA" equipped with a wet disperser is used.
-II "or" Coulter Multisizer "(both manufactured by Coulter, Inc.).

With such a small particle size toner, a high quality image having high resolution can be formed. With a toner having a volume average particle size of more than 9 μm, the characteristics of high image quality are weakened.

When a toner having a volume average particle size smaller than 2 μm is used, the image quality is likely to be deteriorated due to fogging or the like. (2) It is desirable that the toner used in the development has a particle shape close to a sphere and that the surface of the particle has few irregularities, and the shape factors SF-1 and SF-2, which are parameters representing the shape, fall within the following range. Is desirable. 100 ≤ SF-1 ≤ 140 100 ≤ SF-2 ≤ 120 For this shape factor, a photograph obtained by magnifying toner particles by 500 times with a scanning electron microscope was taken, and based on this photograph, "SCANNING IMAGE ANALYS
ER "(manufactured by JEOL Ltd.) is used to analyze the photographic image. At this time, the shape factor of the present invention is measured by the following calculation formula using 500 toner particles. Shape factor SF-1 = (Lmax ² / A) × (π / 4) ×
100 Shape factor SF-2 = (Laround ² / A) × (1 /
4π) × 100 where Lmax is the maximum diameter of the toner particles, Laroun
d is the circumference of the toner particles, and A is the projected area of the toner particles. (3) The above condition (2) can be satisfied by using a polymerized toner. In this respect, it is desirable to use a polymerized toner in the present invention.

The polymerized toner means a toner obtained by forming a binder resin for toner and forming a toner shape by polymerizing a raw material monomer or prepolymer of the binder resin and then performing a chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a step of fusing particles with each other. In the case of a polymerized toner, a raw material monomer or prepolymer is uniformly dispersed in an aqueous system and then polymerized to produce a toner, so that a toner having a uniform particle size distribution and shape can be obtained.

Specifically, those produced by the suspension polymerization method or emulsion polymerization of a monomer in a liquid of an aqueous medium to which an emulsion is added to produce fine polymer particles. It can be produced by a method of adding a solvent, a coagulant and the like to cause association. At the time of association, a method of preparing by mixing with a dispersion liquid such as a release agent or a colorant necessary for the constitution of the toner to allow association, or dispersing a toner constituent component such as a release agent or a colorant in a monomer Examples include the method of emulsion polymerization above. Here, the association means that a plurality of resin particles and colorant particles are fused. (4) To charge and expose the organic photoreceptor,
It is desirable to avoid unnecessary charging and exposure as this will shorten the life of the organophotoreceptor. In the preferred embodiment of the present invention, the control system shown in FIG. 6 is used to carry out the control shown in FIG. 7 to form an image in which charging and exposure of the organic photoconductor are restricted.

In FIG. 6, the control means CR is a usage history detection means for counting the operation history from the mounting of the environment sensor AS for detecting the temperature and humidity and the process cartridge incorporating the organic photoconductor to the image forming apparatus. The output of the cartridge counter CC is fetched and used as a control parameter to control the image forming charging unit 2, the transfer unit 5 (or the separating unit 6), the pre-charge exposure unit 20, and the pre-transfer exposure unit 21. The control in the present embodiment will be described with reference to the flowchart of FIG.

Upon receiving the image output command (S1), the rotation of the photoconductor is started (S2). As a result of environment detection (S3), from the output of the environment sensor AS, low humidity, for example, relative humidity 30%
When it is less than (Yes in S4), the process proceeds to step S8, and the preprocessing control shown in FIGS. 2 and 3C is performed. If the humidity is not low (No in S4), the process goes to S5 to read the output of the cartridge counter CC. As a result of the reading, if the drum history, that is, the usage history of the photoconductor has reached a predetermined threshold value (Yes in S6), while the organic photoconductor 1 makes one rotation as shown in FIGS. 2 and 3C. In the pre-processing according to the present invention, in which the charging and the whole surface exposure are performed twice respectively (S8), when the threshold value is not reached, the control of step S7 is performed. The pretreatment control in step S7 is a pretreatment in which the charging and the whole surface exposure are performed once each time the organic photosensitive member 1 is rotated once. In this way, S7 or S8
The fatigue of the organic photoconductor 1 is recovered by executing the following, and in the subsequent step S9, the charging of the image forming charging unit 2, the exposure of the image forming exposure unit 3, and the development of the developing unit 4 are performed. Execute to form an image on the recording material.

[0062]

EXAMPLES Image formation was carried out under the following conditions. -Organic photoconductor: Drum-shaped negatively chargeable organic photoconductor (photosensitive layer thickness: 30 μm) -Photoconductor radius: 40 mm-Photoconductor moving speed (linear velocity): 280 mm / sec-Charging means configuration: Scorotron Wire / grid distance: 7.5 mm Grid / photoconductor distance: 1 mm Wire / back plate distance: 12 mm-Charging current: -800 A-Grid applied voltage: -730 V-Photoconductor charging potential: -750 V-Pre-charging exposure Light source: LED (wavelength: 700 μm, light output: 10 Lux) ・ Image exposure method: laser scanning method (laser wavelength 780 μ
m) -Laser beam diameter: main scanning direction: 50 μm, sub-scanning direction: 80 μm-dot density 600 dpi (600 dots / 24.5 m)
m) ・ Laser power: 300 μW on the surface of the photoconductor ・ Development method: Reversal development using a two-component developer ・ Development sleeve radius: 20 mm ・ Development sleeve moving speed (linear speed): 560 mm / se
c-Developer carrier: ferrite, volume average particle size: 60μ
m Toner: polymerized toner by emulsion polymerization, volume average particle size:
6.5 μm ・ Development bias: −600 V ・ Structure of transfer means: Corotron wire / photoconductor distance: 8 mm Wire / back plate distance: 12 mm ・ Transfer current: 200 μA ・ Pre-charging exposure light source: LED (wavelength: 700 μm, Light output 10 Lux) -Structure of separating means: Corotron wire / photoconductor distance: 8 mm Wire / back plate distance: 12 mm-Separation current: AC component: 1000 μA, DC component: -2
00 μA ・ Fixing means: Continuous 10 on A4 size recording paper in heat roller fixing NN (normal temperature and normal humidity)
Run a running test of 00kc (10 ⁶ copies),
The initial image and the image at the start of image formation after 1000 kc were evaluated.

As a result, in spite of the short-time pretreatment as shown in FIG. 3C, high-quality images were formed through the initial image formation, after 1000 kc, and all tests.

[0064]

According to the invention of any one of claims 1 to 7, the charging potential necessary for image formation can be formed only by making one revolution of the organic photoreceptor, so that the first image can be formed. It is possible to shorten the time required to form the image formation, and it is possible to significantly improve the practical use value of the image forming apparatus in which the ratio of the image formation of a small number of sheets occupies a high rate in the entire image forming operation. it can.

According to the invention of any one of claims 8 to 11,
An image forming apparatus for forming an image with high image quality, which is excellent in image characteristics such as resolution, gradation and sharpness, is realized.

According to the invention of any one of claims 12 to 14 and 16 to 18, an image forming apparatus having a long photoconductor life and a short first copy time or first printout time can be realized.

[Brief description of drawings]

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

FIG. 2 is a timing chart of control at the start of image formation.

FIG. 3 is a diagram showing positions on an organic photoconductor where charging and overall exposure are performed.

FIG. 4 is a diagram showing changes in charging potential of a new organic photoconductor.

FIG. 5 is a diagram showing changes in the charging potential of the organic photoconductor after long-term use.

FIG. 6 is a block diagram of a control system according to a preferred embodiment of the present invention.

FIG. 7 is a flowchart of control in the preferred embodiment of the present invention.

[Explanation of symbols]

1. PC organic photoconductor 2 Image forming charging means 3 Image forming exposure means 4 developing means 5 Transfer means 6 Separation means 7 Cleaning means 8 transport units 9 Fixing means 10 Paper feeder 20 Pre-charging exposure means 21 Pre-transfer exposure means CH1 first charging means CH2 second charging means EX1 First whole surface exposure means EX2 second whole surface exposure means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/08 507 G03G 15/16 15/14 101 102 15/16 21/00 345 102 15/08 507L 21 / 00 345 21/00 342 21/08 9/08 384 (72) Inventor Toru Yamaguchi 2970 Ishikawa-cho, Hachioji, Tokyo Konica Stock Company F-term (reference) 2H005 AA15 AB06 EA05 FA01 2H027 DA13 DA14 DA44 EA01 EA07 EA10 EC14 EC20 EF06 2H035 AA08 AA11 AA24 AB01 AB02 AB04 AC03 AC04 AZ09 BA01 BA07 BA10 CA07 CB01 2H077 AD06 DB14 EA03 2H200 FA01 FA16 GA16 GA23 GA34 GA45 GA66 GA69 GB02 GB03 GB35 HA12 HA28 HA29 HB03 JA02 JA29 KA02 KA07 KA29 PA10 PA17 PA26 PB27 PB28 PB34

Claims (18)

[Claims] 1. An image forming apparatus having an organic photoconductor, an image forming charging means, an image exposing means, a developing means, a transferring means, a separating means and a cleaning means, comprising: first and second charging means, first and second charging means. A first whole surface exposing means and a controlling means, wherein the first whole surface exposing means is disposed on the downstream side of the first charging means in the moving direction of the photosensitive member and exposes the whole surface of the organic photosensitive member charged by the first charging means. The second whole surface exposing means is arranged on the downstream side of the second charging means in the moving direction of the photosensitive body and exposes the whole surface of the organic photosensitive body charged by the second charging means, and the control means comprises an image forming step. Prior to the start of step 1, the organic photoconductor is rotated at least once and the first and second charging means and the first and second whole surface exposure means are operated to charge and charge the organic photoconductor twice. Pretreatment for full exposure An image forming apparatus comprising Ukoto. 2. The image forming apparatus according to claim 1, wherein the first charging unit includes the image forming charging unit. 3. The image forming apparatus according to claim 1, wherein the second charging unit includes the transfer unit. 4. The image forming apparatus according to claim 1, wherein the second charging unit includes the separating unit. 5. The first whole surface exposure means comprises a pre-transfer exposure means.
The image forming apparatus according to item. 6. The image forming apparatus according to claim 1, wherein the first entire surface exposure unit is a transfer simultaneous exposure unit. 7. The second whole surface exposure means comprises a pre-charge exposure means.
The image forming apparatus according to item. 8. The developing means has a volume average particle diameter of 2 to 9
The image forming apparatus according to any one of claims 1 to 7, wherein development is performed using a toner having a size of μm. 9. The developing unit comprises: shape factor SF-1 = (Lmax ² / A) × (π / 4) ×
100 Shape factor SF-2 = (Laround ² / A) × (1 /
4π) × 100 (where Lmax is the maximum diameter of toner particles, Larou
nd is the perimeter of the toner particles, A is the projected area of the toner particles), and the spherical coefficient SF-1 represented by is 100 to 140,
9. The image forming apparatus according to claim 1, wherein development is performed using a toner having a spherical coefficient SF-2 of 100 to 120. 10. The image forming apparatus according to claim 1, wherein the developing unit performs development using a two-component developer containing toner and carrier as main components. 11. The developing device according to claim 1, wherein the developing device develops using polymerized toner.
The image forming apparatus according to item. 12. A first mode in which the control means forms an image after the pre-processing by the first and second charging means and the first and second whole surface exposure means, and the first and second charging means. And a second mode in which an image is formed without using at least one of the first and second whole surface exposure means or without performing a pretreatment, and the second mode is selected and executed. 2. The image forming apparatus according to item 1. 13. An environment detection sensor is provided, and the control means selects the first mode or the second mode based on an output of the environment detection sensor. Image forming apparatus. 14. An organic photoconductor has a usage history detection means, and the control means selects the first mode or the second mode based on an output of the usage history detection means. The image forming apparatus according to claim 12 or 13. 15. The first and second charging steps and the first and second whole surface exposure steps are carried out to form an image after performing two charging and whole surface exposures on the organic photoconductor which makes one turn. An image forming method comprising performing steps. 16. The image forming process is performed without performing at least one of a first mode in which the image forming process is performed after performing the first and second charging processes and the first and second whole surface exposure processes. 16. The image forming method according to claim 15, wherein the second mode for performing is selected and executed. 17. The image forming method according to claim 16, wherein the first mode or the second mode is selected based on a result of environment detection. 18. The image forming method according to claim 16, wherein the first mode or the second mode is selected based on the detection result of the usage history of the organic photoconductor.