JPH07261554A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the toner fog on a non-image section when the image formation is started by delaying the applying timing of the developing bias to a developing roller and/or the rotation starting timing of the developing roller until the tip section of an electrostatic latent image formed on a photoreceptor drum reaches the front of the developing roller. CONSTITUTION:When a user pushes the copy button of a laser printer, the copying of the first document is started. A photoreceptor drum starts rotating immediately after the copy button is turned on, and electrification charges are put on it immediately after that. The applying timing t4 of the developing bias to a developing roller and/or the rotation starting timing t4 of the developing roller is delayed until the tip section of an electrostatic latent image (image section) formed on the photoreceptor drum reaches the front of the developing roller (t4-t5) at t1 after the photoreceptor drum starts rotating. The toner is hardly stuck to the non-image section when the image formation is started, and the photographic fog on the non-image section of the printing paper can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an improvement of an image forming apparatus for visualizing an electrostatic latent image having a potential distribution corresponding to image data by applying a developing material (toner) to the electrostatic latent image. Regarding In particular, the present invention relates to a technique for preventing a so-called “fogging”, which is a phenomenon in which a print paper is soiled by toner adhering to a non-image portion where an electrostatic latent image is not formed.

[0002]

2. Description of the Related Art An image forming method using an electrostatic latent image is applied to a copying machine or the like. In particular, the charge on the uniformly charged photoconductor is partially removed by light corresponding to the image data to form an electrostatic latent image on the photoconductor, and the electrostatic latent image part is formed according to the residual charge distribution. A copying machine utilizing reversal development in which a large amount of toner (carbon or the like) is attached to make an electrostatic latent image visible is generally used. Laser printers, liquid crystal printers, LED printers and the like are practical examples.

Now, let us consider a case where image formation (copying) is performed by a laser printer, for example. When the user presses the copy button to start the printing operation, the photosensitive drum inside the printer starts rotating. While rotating, this drum is first neutralized to a potential of 0 V by a static elimination lamp, and then charged to -600 by a charging charger.
It is uniformly charged to about V to -700V. When the charged and rotating photosensitive drum is exposed with laser light modulated according to print data, a potential distribution (electrostatic latent image) corresponding to the print data is formed on the drum.

To the photosensitive drum having this electrostatic latent image, a developing roller facing the drum supplies negatively charged carbon toner by a developing bias of about -400V. Then, the amount of toner corresponding to the potential distribution of the electrostatic latent image adheres to the surface of the photosensitive drum by the force of static electricity. As a result, the electrostatic latent image (invisible image) on the drum corresponding to the print data is developed into a visible image.

An image of print data (toner density distribution) visualized on the photoconductor drum is transferred to a printing paper, and the transferred image is then fixed on the printing paper to form an image once. (Copying) is completed.

[0006]

When image formation (printing / printing) is started, the photosensitive drum starts to rotate, and an electric potential is applied to the rotating photosensitive drum that has been discharged by the discharging lamp, and the drum is charged. To do. At this time, before the electrostatic latent image is formed, the potential of the photosensitive drum in the section from the position of the charging charger to the position of the developing roller of the developing device is almost 0 V as a result of the charge removal. For this reason, when the 0V section passes in front of the developing biased developing roller, the negatively strongly charged toner (-400V) adheres to the drum in the 0V section. This toner causes "fog" on the non-image area.
As a result, the non-image part of the printing paper is stained black.

Even when the 0V portion of the photosensitive drum passes in front of the developing roller before the developing bias is applied, if the developing roller to which the toner is attached rotates at that time, the toner is slightly charged. Toner (or floating toner around the developing roller) is attracted to the photosensitive drum to some extent and is entrained in the airflow accompanying the rotation of this drum / roller, and this toner is scattered in the rotating direction of the photosensitive drum. (Toner scattering phenomenon). This causes dirt inside the printer.

The "fog" and the "toner stain" inside the printer cause waste of toner, leading to an increase in toner consumption. An object of the present invention is to provide an image forming apparatus capable of preventing toner fogging on a non-image portion at the start of image formation.

[0009]

According to the present invention, after the photosensitive drum 1 starts to rotate, the leading portion of the electrostatic latent image (image portion) formed on the photosensitive drum 1 is in front of the developing roller 4a. Until this time, the application timing of the developing bias to the developing roller 4a and / or the rotation start timing of the developing roller 4a are delayed.

[0010]

The photosensitive drum 1 from the position of the non-image portion to the position of the leading portion of the electrostatic latent image is created by making the above timing delay.
The developing roller 4a is not rotating (the continuous supply of toner is prohibited) or the developing bias is not applied to the developing roller 4a (the strong charging of the toner is prohibited) while the potential 0V area of the developing roller 4a passes in front of the developing roller 4a. ).

If the developing roller 4a does not rotate even if the developing bias is applied (prohibition of continuous toner supply), the developing roller 4 facing the photosensitive drum 1
Since only a part of the toner on the surface of a is attracted to the photosensitive drum 1 side, “fog” on the non-image portion occurs only in a very small portion at the beginning.

If the developing bias is not applied even if the developing roller 4a is rotated (prohibition of strong toner charging), the potential difference between the toner on the surface of the developing roller 4a and the photosensitive drum 1 is small. The amount of toner attracted from the developing roller 4a to the photosensitive drum 1 side is small, and the degree of "fog" on the non-image portion can be reduced to a level that does not pose a practical problem.

The developing roller 4a until the leading portion of the electrostatic latent image formed on the photoconductor drum 1 comes before the developing roller 4a.
When neither the rotation nor the application of the developing bias is performed (prohibition of continuous toner supply and prohibition of strong toner charge), the above "fog" can be prevented more completely.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, it is assumed that a two-component developer composed of toner (carbon C or the like) and carrier (iron Fe or the like) is used for developing the electrostatic latent image.

FIG. 2 shows the internal structure of a laser printer according to an embodiment of the present invention (electrophotographic process unit section of a digital image forming apparatus). The photoconductor drum 1 as an image carrier has a conductive support, a photoconductive layer and an insulating layer as a basic structure, and rotates in the direction of arrow a in the drawing during operation. Around the photosensitive drum 1, a charging charger 2 for uniformly charging the surface of the photosensitive drum 1 along the rotation direction of the drum 1 and a laser beam LB corresponding to image data are applied to the charged drum surface and statically charged there. A laser unit 12 that forms an electrostatic latent image, a developing device 4 that applies toner to the photosensitive drum 1 to develop the electrostatic latent image formed thereon, and a transfer unit that transfers the developed image to the printing paper P. 15, a cleaning device 7 that removes the toner remaining on the surface of the photoconductor drum 1 after the transfer, and a destaticizing lamp 8 that sets the surface potential of the photoconductor drum 1 after cleaning to 0V are provided.

On the upper side of the main body of the laser printer, a fluorescent lamp carriage 22 for illuminating the original D set on the original table glass 9 and a laser beam corresponding to the image information of the original D illuminated by a fluorescent lamp. An optical system movable exposure device 10 for exposing the surface of the photosensitive drum 1 charged by LB is provided. A control panel 110 for the user to perform a copy operation is also provided on the upper part of the main body.

Inside the main body of the laser printer, the printing paper P loaded in the paper cassette 11 is passed through the image transfer section 15 between the transfer device 5 and the photosensitive drum 1 to receive a copy receiver 1.
A sheet conveying path 17 leading to the sheet 6 is formed. The printing paper P on which the toner image is formed is peeled from the surface of the photosensitive drum 1 by the peeling device 6, passes on the paper conveyance path 17, and is thermally fixed in the fixing device 19.

A pair of registration rollers 18 as an aligning unit is arranged upstream of the image transfer section 15 in the sheet conveying path 17, and a fixing device 19 is provided downstream of the image transfer section 15. , And a discharge roller pair 20 are provided. A paper feed roller pair 21 that conveys the print paper P is arranged on the downstream side of the cassette mounting portion 11.

FIG. 3 shows an example of a rotational driving force transmission system for the photosensitive drum 1 and the developing roller 4a in the internal structure of the laser printer of FIG. Here, the rotational driving force of the photosensitive drum motor 1b is applied to the idler / pulley mechanism 1
It is transmitted to the drum drive gear 1e via c and the belt 1d, and thereby the photosensitive drum 1 is rotated at a predetermined angular velocity in the direction of arrow a in FIG.

Similarly, the rotational driving force of the developing roller motor 4b is transmitted to the developing roller 4a via the belt 4d so that the developing roller 4a rotates at a predetermined angular velocity in the rotational direction opposite to the photosensitive drum 1. Has become.

In the configuration of FIG. 3, the photosensitive drum motor 1b
And the developing roller motor 4b are independent. For this reason,
By individually controlling the drive of these motors (1b, 4b), the rotation timing of the photosensitive drum 1 and the rotation timing of the developing roller 4a can be freely controlled.

FIG. 4 shows another example of the rotational driving force transmission system for the photosensitive drum 1 and the developing roller 4a in the internal structure of the laser printer of FIG. Here, the rotational driving force of the photosensitive drum motor 1b is applied to the idler / pulley mechanism 1
It is transmitted to the drum drive gear 1e via c and the belt 1d, and thereby the photosensitive drum 1 is rotated at a predetermined angular velocity in the direction of arrow a in FIG.

The rotational driving force of the photosensitive drum motor 1b is further transmitted to the electromagnetic clutch mechanism 3 via the idler / pulley mechanism 1c, the belt 1d, the pulley mechanism 1f and the pulley mechanism 1g. The electromagnetic clutch mechanism 3 appropriately transmits the transmitted driving force of the motor 1b to the developing roller 4a,
The developing roller 4a is rotated at a predetermined angular velocity in the rotation direction opposite to the photosensitive drum 1.

In the structure shown in FIG. 4, the electromagnetic clutch mechanism 3 applies the driving force of the photosensitive drum motor 1b to the developing roller 4a.
You can freely control whether or not to tell. Therefore, the delay amount of the rotation timing of the developing roller with respect to the rotation start timing of the photosensitive drum 1 can be freely controlled depending on when the electromagnetic clutch mechanism 3 is turned on.

The image forming process in the laser printer having such a configuration will be described below focusing on the functions of the photosensitive drum 1 and the developing roller 4a. 5 is shown in FIG.
3 is a block diagram showing a schematic configuration of an electric system used in the laser printer of FIG. FIG. 6 is a flowchart showing the operation of the laser printer controlled by the central processing unit (hereinafter referred to as CPU) 100 when the driving force transmission mechanism of FIG. 3 is used.

The CPU 100 has a control panel 11
A command (copy start, etc.) based on a user operation from 0 is received, and various controls according to the command content are performed. For example, when the user presses the copy button of the control panel 110 (step ST10), the CPU 100 starts the rotation of the photoconductor drum motor 1b via the driver (external device interface) 130 to turn on the discharge lamp 8, and The operation of the charging charger 2 is started (step ST12). Then, the surface of the photoconductor drum 1, which is once discharged to 0 V by the charge removing lamp 8, is charged by the charging charger 2.
Is charged to a uniform potential of about -700V.

At the same time, the document D set on the document table glass 9 in FIG. 2 is illuminated by the fluorescent lamp of the carriage 22, and the reflected light from the document D is exposed through the respective mirrors to the exposure device 10.
The light is focused on the CCD sensor 14 of. The light information collected on the CCD sensor 14 in this way is given to the laser unit 12 as an image signal obtained by reading the document D.

A laser oscillator (laser diode) 12a in the laser unit 12 is provided with a CCD sensor 14
The laser beam LB modulated in accordance with the image signal given from is output. This laser beam LB is a polygon mirror 12c that is rotationally driven by a mirror motor 12b.
Is scanned by the collimator lens, condensed by the collimator lens, and irradiated onto the photosensitive drum 1 through the f-θ lens, the mirror and the like. As a result, an electrostatic latent image having a potential distribution corresponding to the image signal of the document D is formed on the surface of the photosensitive drum 1 uniformly charged to about −700V (step S).
T14).

On the other hand, in response to the copy button on the control panel 110 being pressed, the CPU 100 causes the timer counter 120 to start counting. As a result, the elapsed time after the start of rotation of the photosensitive drum 1 is checked (step ST16).

When a predetermined time (for example, 0.4 seconds) determined according to the radius of the photosensitive drum 1 and its rotational angular velocity elapses, the CPU 100 develops the head of the electrostatic latent image (the portion of the first line of the laser scan). It is determined that it has come just before the roller 4a (step ST18, Yes).

When this judgment is made, the CPU 100
The driver 130 is instructed to turn on the drive motor 4b of the developing roller 4a, and the developing bias source 40 is instructed to apply a developing bias of about -400 V to the developing roller 4a (step ST20). (If the mechanism of FIG. 4 is adopted instead of the mechanism of FIG. 3, step ST2
In the processing of 0, the electromagnetic clutch mechanism 3 is turned on, the rotational driving force of the drum motor 1b is transmitted to the developing roller 4a,
The rotation of the developing roller 4a will be started. ) The surface potential of the electrostatic latent image portion formed on the photoconductor drum 1 is attenuated by light, and has a potential (average of about −150 V) according to the density pattern of the image data. Then, the toner charged to −400V adheres to the surface of the photoconductor drum 1 with a density corresponding to the electrostatic latent image potential distribution having a potential relatively higher than that of the toner. The part where the laser beam does not hit is -7
It has a potential of about 00V, and toner charged to -400V does not adhere to it. In this way, the electrostatic latent image on the photosensitive drum 1 is developed into a toner image (visible image).

Thereafter, the toner image is transferred onto the paper P by applying a + polarity corona to the printing paper (transfer paper) P supplied from the paper cassette 11 from the transfer device 5. The paper P on which the toner image is transferred is peeled off from the surface of the photosensitive drum 1 by the peeling device 6, and the paper conveyance path 17
After passing through the upper part, it is thermally fixed in the fixing device 19 (step ST22).

The developing device 4 has a developing roller 4a arranged so as to face the photosensitive drum 1, and the developing material 4x is constantly supplied to the developing roller 4a. The two-component developer 4x has iron as a carrier, and this carrier is magnetically attached to the developing roller 4a. Further, this carrier is positively charged (+ Fe), and the negative toner (-C) clings to the periphery of the carrier by this charging.

The developing roller 4a continuously conveys the supplied developing material 4x to the surface facing the photosensitive drum 1 while rotating. The toner component (negatively charged carbon) in the carried developer 4x is sucked to the drum 1 side in accordance with the potential distribution of the electrostatic latent image formed on the photosensitive drum 1, and development is performed. . Although the toner on the developing roller 4a is consumed more and more by this development, since the developing material 4x is constantly supplied to the developing roller 4a, the electrostatic latent image on the photosensitive drum 1 should be continuously developed. You can

When the user of the laser printer makes a continuous copy of a plurality of originals (step ST24, Yes), the next original is continuously illuminated with fluorescent lamps, and the laser scanning of the image data of the original is performed ( Step ST26). This image data is converted into an electrostatic latent image on the photosensitive drum 1 and then subjected to processing such as development / transfer / fixing (step ST22).

During the continuous copying, both the photosensitive drum 1 and the developing roller 4a are continuously rotated, and the developing bias is continuously applied to the developing roller 4a. The reason is that, during the continuous copying process, the surface area of the photosensitive drum between the electrostatic latent image of one original document and the electrostatic latent image of the next original document is charged to −700V, and the toner is This is because the "fogging" does not occur because the dust does not adhere.

If the user's operation is not continuous copying (step ST24, No) but intermittent copying one by one (step ST28, Yes), as in the case of the first copying, the cause of "fog" There is a possibility that the section of the potential 0 V that would become is generated on the photosensitive drum 1. In this case, the processes of steps ST10 to ST24 are performed. When the copy process is completed (NO in step ST28), the state before step ST10 is restored, and the laser printer in FIG. 2 shifts to the standby state.

Next, the operation of the laser printer according to the embodiment of the present invention will be described with reference to the timing chart of FIG. Before time t0, the laser printer of FIG. 2 is in the standby state. In this case, the photosensitive drum 1
And the developing roller 4a is not rotating,
No developing bias is applied to a (developing roller 4
The potential of a is 0V). The photosensitive drum 1 is not yet charged, and the surface area of the photosensitive drum from the position of the charging charger 2 to the position of the developing roller 4a is almost 0V.

Since this 0V area is a portion which causes "fog", this 0V area is the developing roller 4 in the present invention.
The developing bias is applied to the developing roller 4a until it passes past a.
Is applied to the developing material 4 by the rotation of the developing roller 4a.
The continuous supply of x has been refused. Since the application timing of the developing bias and the rotation timing of the developing roller 4a are extremely important in the present invention, this point will be described in detail below with reference to FIGS.

Now, when the user of the laser printer presses the copy button (step ST10; t0), the first original D
Will start copying. Immediately after the copy button is turned on (within 0.1 second), first the rotation of the photosensitive drum 1 is started (step ST12; t1), and immediately after that (within 0.1 second), the charging charger 2 is turned on (step ST12). ; T
2). When this is turned on (t2), immediately below (t1), the portion directly below the charging charger 2 of the photosensitive drum 1 which has begun to be charged is charged to -700V, and at the same time, the portion directly below the discharge lamp 8 of the photosensitive drum 1 is discharged to 0V. It

At this time (t2), laser scanning has not started yet. Further, the developing roller 4a is also stopped and the developing bias is not applied to the developing roller 4a (the developing bias changeover switch 40a is 0V).
side). FIG. 7 shows this state.

Along with the rotation of the photosensitive drum 1, the drum portion charged to -700 V by the charging charger 2 is a region where laser scanning is performed (electrostatic latent image forming region).
When it comes to, the polygon mirror 12c rotates and laser scanning is started (step ST14; t3).

The period T1 from the start of the rotation of the photosensitive drum 1 (t1) to the start of the charging / discharging of the photosensitive drum 1 (t2) is measured by the timer counter 120 of FIG. Further, the timer counter 120 also measures the period T2 from (t2) to (t3) after the charging of the photoconductor drum 1 starts by charging the photosensitive drum 1 by -700V and (t2) starts the laser scan by rotating the polygon mirror 12c. (Step ST1
6).

Even after the laser scan is started,
Until the first line of this laser scan (the leading portion of the electrostatic latent image formed by the laser scan) arrives just before the developing roller 4a (step ST18, No), the developing roller 4a remains stopped and the developing bias is applied. Is not applied (development bias 0V). FIG. 8 shows this state.

Immediately before the first line (leading portion of the electrostatic latent image) of the laser scan arrives at the developing roller 4a (step ST18, YES; t4), the developing roller 4a starts rotating and the developing roller 4a. The application of the developing bias to is also started. That is, the bias switch 40a is switched, and the bias potential to the developing roller 4a changes from 0V to -400V (step ST20).

Immediately after that (about several tens of milliseconds from t4),
The first line of the laser scan comes just before the developing roller 4a (t5). At this point, the toner on the developing roller 4a is charged to -400V and the developing roller 4a
The continuous supply operation of the developing material 4x by the rotation of is also started. Therefore, the electrostatic latent image formed on the photoconductor drum 1 is reliably developed from the leading portion thereof. FIG. 9 shows this state.

As shown in FIG. 9, after the non-image portion having a surface potential of 0 V on the photosensitive drum 1 has finished passing in front of the developing roller 4a, the developing bias is applied to start the toner development. “Fogging” on the non-image portion of the drum 1 is prevented.

Here, from the start of laser scanning (t3)
The period T3 until the developing bias is turned on (t4) and the period T4 from the start of the laser scan (t3) until the leading portion of the electrostatic latent image is located just before the developing roller 4a (t5),
It is measured by the timer counter 120 (step ST16).

After the development is started from the state shown in FIG. 9, the image forming process similar to the normal laser printer operation is performed. FIG. 10 shows this state. If only one sheet is to be copied, after a predetermined time T5 has elapsed (t7) after the laser scanning of the first document D is completed (t6),
The rotation of the photosensitive drum 1 is stopped, the charging and the charge removal of the photosensitive drum 1 are stopped, the laser scanning is stopped, the developing bias is returned to 0V, and the rotation of the developing roller 4a is stopped. After that (t10), the copying process for the second sheet is performed in the same manner as the first sheet.

In the case of a continuous copying process of two or more sheets, even after the laser scanning of the first original D is completed (t6), the rotation, charging and charge removal of the photosensitive drum 1 are continued and the laser scanning is also continuously performed. The development bias is -40.
The voltage is maintained at 0V, and the rotation of the developing roller 4a is also continued.

In FIG. 1, the present invention can be put to practical use even if the timing t5 when the leading portion of the electrostatic latent image comes just before the developing roller 4a coincides with the developing bias application timing t4.

In the above-mentioned one embodiment, the case of using the two-component type developer is explained, but the operation of the present invention is the one-component type developer (for example, carrier such as iron surrounded by carbon toner). It does not change even when is used.

[0053]

According to the present invention, after t1 when the photosensitive drum 1 starts rotating, the leading portion of the electrostatic latent image (image portion) formed on the photosensitive drum 1 comes to the front of the developing roller 4a at t4.
From t5 to t5, the developing bias to the developing roller 4a (-40
0V) application timing t4 and / or development roller rotation start timing t4 are delayed. Therefore, the amount of toner adhered to the non-image portion at the start of image formation is almost eliminated (toner adhesion can be substantially removed), and “fog” on the non-image portion of the printing paper P can be prevented. Become.

[Brief description of drawings]

FIG. 1 is a timing chart explaining the operation of a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an internal configuration of a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a rotational driving force transmission system for a photosensitive drum and a developing roller in an internal configuration of a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing another example of a rotational driving force transmission system for a photosensitive drum and a developing roller in an internal configuration of a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 5 is a block diagram illustrating a schematic configuration of an electric system used in a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 6 is a flowchart illustrating the operation of a laser printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a developing operation of the laser printer of FIG. 2, showing a state before the photosensitive drum starts rotating.

FIG. 8 is a diagram illustrating a developing operation of the laser printer of FIG. 2, showing a state immediately after the photosensitive drum starts rotating.

FIG. 9 is a diagram for explaining a developing operation of the laser printer of FIG. 2, showing a state in which the head of the electrostatic latent image formed is located immediately before the developing roller after the photosensitive drum starts rotating. Fig.

FIG. 10 is a diagram for explaining the developing operation of the laser printer of FIG. 2, in which after the photosensitive drum starts to rotate, the head of the electrostatic latent image formed passes through the front of the developing roller to form an electrostatic charge. FIG. 6 is a diagram showing a process in which a latent image is developed.

[Explanation of symbols]

1 ... Photosensitive drum (image bearing member), 1b ... Photosensitive drum motor (moving means), 1c ... Idler / pulley mechanism, 1d
... belt, 1e ... drum drive gear, 1f ... pulley mechanism,
1 g ... pulley mechanism, 2 ... electrification charger (charging means),
3 ... Electromagnetic clutch mechanism, 4 ... Developing device, 4a ... Developing roller (developing material supply means), 4b ... Developing roller motor, 4d ...
Belt, 4x ... Developer (toner / carrier), 5 ... Transfer device, 6 ... Peeling device, 7 ... Cleaning device, 8 ... Eliminating lamp, 9 ... Original plate glass, 10 ... Exposure device, 11 ... Paper cassette, 12 ... Laser unit (electrostatic latent image forming means), 12a ... Laser oscillator, 12b ... Polygon mirror motor, 12c ... Polygon mirror, 14 ... CCD sensor, 15 ... Transfer unit, 16 ... Copy receiver, 17 ... Paper transport path, 18 ... Registration roller pair, 19 ... Fixing device, 20 ...
Paper discharge roller pair, 21 ... Paper feed roller pair, 22 ... Fluorescent lamp carriage, 40 ... Development bias source (development bias means),
40a ... Development bias changeover switch, 100 ... Central processing unit (CPU; detecting means / developing material supply starting means), 110 ... Control panel, 120 ... Timer counter, 130 ... Driver, D ... Original, LB ... Laser beam, P … Printing paper.

Claims (4)

[Claims] 1. An electrostatic latent image having a potential distribution corresponding to image data, which is visualized by applying a developing agent to the electrostatic latent image, wherein the electrostatic latent image is carried on an image carrier. A developer supplying means arranged to face the image carrier and supplying the developer; a charging means for charging the image carrier; and an electrostatic latent image formed on the charged image carrier. Electrostatic latent image forming means, moving means for moving the electrostatic latent image formed on the image carrier to the position of the developing material supplying means, and the leading position of the electrostatic latent image by the moving means for developing the electrostatic latent image. Detecting means for detecting that the developer supply means has arrived, and the developer supply means when the detecting means detects that the leading position of the electrostatic latent image has arrived at the developer supply means. Supply of the developing material from the means to the image carrier is started. An image forming apparatus comprising the developing material supply starting means. 2. A photosensitive drum, which is made visible by applying a developing material to the electrostatic latent image having a potential distribution corresponding to image data. And a developing roller for supplying the developing material, a charging unit for charging the photosensitive drum, an electrostatic latent image forming unit for forming the electrostatic latent image on the charged photosensitive drum, A drum motor that rotates a body drum to move an electrostatic latent image formed on the body drum to an opposing position where the photosensitive drum and the developing roller face each other; and the electrostatic latent image is rotated by rotation of the photosensitive drum. Detection means for detecting that the leading position of the image has come to the facing position of the photosensitive drum and the developing roller; and the leading position of the electrostatic latent image is the facing position of the photosensitive drum and the developing roller. Before coming The rotation of the developing roller is prohibited, and the rotation of the developing roller is stopped when the detection unit detects that the leading position of the electrostatic latent image has come to a position where the photosensitive drum and the developing roller face each other. An image forming apparatus comprising: a developer supply starting unit that starts the supply of the developer to the photosensitive drum. 3. A photosensitive drum, which opposes the photosensitive drum, wherein the electrostatic latent image is visualized by applying a developing material to the electrostatic latent image having a potential distribution corresponding to image data. Developing means for charging the photosensitive drum, a developing bias means for applying a developing bias potential to the developing material supply means, and a charged photosensitive drum An electrostatic latent image forming unit that forms the electrostatic latent image on the photosensitive drum, and the photosensitive drum is rotated to make the electrostatic latent image formed on the photosensitive drum face the developing material supply unit. And a detection unit that detects that the leading position of the electrostatic latent image has come to the opposing position of the photosensitive drum and the developer supply unit by the rotation of the photosensitive drum. , The The application of the developing bias potential to the developer supplying means is prohibited until the leading position of the electrostatic latent image comes to the position where the photosensitive drum and the developer supplying means face each other, and the electrostatic latent image is detected by the detecting means. When it is detected that the leading position of the image has come to the position where the photoconductor drum and the developer supply unit face each other, the application of the developing bias potential by the developing bias unit is started, and the photosensitive drum is started. An image forming apparatus comprising: a developer supply starting unit that starts supplying the developer to the developer. 4. A photosensitive drum, which opposes the photosensitive drum, wherein the electrostatic latent image is visualized by applying a developing material to the electrostatic latent image having a potential distribution corresponding to image data. Developing roller for supplying the developer, charging means for charging the photosensitive drum, developing bias means for applying a developing bias potential to the developing roller, and electrostatic charging for the charged photosensitive drum. An electrostatic latent image forming unit that forms a latent image and the photosensitive drum are rotated to move the electrostatic latent image formed there to a facing position where the photosensitive drum and the developing roller face each other. A drum motor; detection means for detecting that the leading position of the electrostatic latent image has come to a position where the photosensitive drum and the developing roller face each other due to rotation of the photosensitive drum; Rank The application of the developing bias potential to the developing roller and the rotation of the developing roller are prohibited until the photosensitive drum and the developing roller are opposite to each other, and the leading position of the electrostatic latent image is detected by the detecting means. When it is detected that the photosensitive drum and the developing roller have come to face each other, the application of the developing bias potential by the developing bias means is started, the rotation of the developing roller is started, and An image forming apparatus comprising: a developer supply starting unit that starts supplying the developer to the photosensitive drum.