JPH09146311A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fogging and faulty density by properly changing the DC component of developing bias based on the using circumstances of a photoreceptor drum (film thickness of photoreceptor) and using environment (temperature and humidity). SOLUTION: By applying voltage on an electrifying device 17 arranged in contact with the surface of the photoreceptor drum 16 and detecting the value of a current flowing the drum 16 at this time by a detection means 30, the change of the film thickness of the drum 16 is detected. According to the detection signal, the DC component of the developing bias impressed on the developing roller 21 of a developing device 18 is changed by a controller 31 so as to reduce what is called fogging at the time of developing. Then, output density is made appropriate by changing the DC component of the developing bias by the controller 31 according to output from a temperature and humidity detection means 32.

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 such as an electrophotographic copying machine and a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a drum type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") is generally used as an image bearing member. The photosensitive drum is formed by layering a photosensitive body such as OPC (organic optical semiconductor) on the surface of a cylindrical base body having conductivity such as aluminum, and the characteristics of the photosensitive body are as follows. It is known to change subtly depending on the situation.

For example, when the temperature of the photosensitive drum rises, the sensitivity of the photosensitive member improves and the output density changes. Further, when the film thickness (layer thickness) of the photoconductor is gradually reduced with the use of the photosensitive drum, the charging performance is degraded, the sensitivity is deteriorated, and the density is changed. Further, when the charging performance is remarkably lowered, the phenomenon of toner adhesion to the white background portion, so-called fogging, becomes remarkable. In addition to these, the reproducibility of minute dots changes due to a decrease in the photoconductor film thickness, and a change in output density characteristics at a level that cannot be explained by changes in the charging performance and sensitivity of the photosensitive drum is seen.

The above-mentioned change in the operating environment affects not only the photosensitive drum but also the developing device. In the developing device, when the use environment changes, the charging performance of the toner in the developing device changes, and as a result, the output density characteristics change significantly.

To solve these problems, various measures have hitherto been taken. For example, with respect to the change in the film thickness of the photoconductor of the photosensitive drum, a detection unit for detecting the film thickness is provided, and the charging voltage applied to the charging device is changed according to the detection signal to change the charging performance of the photosensitive drum. There are known methods for compensating for changes in Similarly, there is also known a method of correcting the sensitivity change of the photoconductor by changing the applied voltage to the illumination lamp for irradiating the original to change the illuminance in accordance with the detection signal for detecting the film thickness. Furthermore, regarding the temperature, the temperature around the photosensitive drum is detected,
There is one that corrects the change in the performance of the photoconductor due to the change in temperature by changing the charging voltage applied to the charging device according to the temperature.

[0006]

However, according to the above-mentioned measures, although it is possible to deal with the change of the output density characteristic based on the charging performance of the photoconductor, the output density based on the change of the reproducibility of the minute dot is possible. For changes in characteristics,
There is a problem that we cannot deal with it.

Further, the method of correcting the change in sensitivity due to the change in film thickness by the illuminance of the illumination lamp cannot be applied to a printer or a facsimile which does not have such a lamp.

Further, recent digital copying machines are
Due to its characteristics, it is often commercialized as a complex machine with a printer or a facsimile. Therefore, various images are collectively handled by the same printer unit, and it is very difficult to optimize the printer unit for all image signals. For example, when a printer section optimized for copying is used as a printer, the lines of the image may become thin.

Furthermore, while the facsimile has a resolution of centimeter standard, when the printer unit is designed for copying or printer of inch standard, it becomes necessary to perform resolution conversion on the image signal. When such resolution conversion is performed on the image signal, periodic density unevenness called moire may occur.

Therefore, the present invention responds to changes in the output density characteristics based on changes in the reproducibility of minute dots, optimizes the printer section for various image signals, and further sets the cycle when resolution conversion is performed. An object of the present invention is to provide an image forming apparatus capable of preventing the unevenness of the specific density.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and includes an image carrier having a photosensitive layer on its surface, and a charging unit for uniformly charging the surface of the image carrier. ,
A latent image forming means for forming an electrostatic latent image on the surface of the image bearing member; and a developing means for adhering toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image.
In an image forming apparatus equipped with the above-mentioned image forming apparatus, a usage status detecting means for detecting a usage status of the image carrier, and an electric bias magnitude in the developing means are optimized in accordance with a detection signal from the usage status detecting means. And a control means for controlling the operation.

An image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and a toner is attached to the electrostatic latent image by applying an electric bias. And a developing means for developing the toner image as a toner image, the developing means according to the use environment detecting means for detecting the use environment of the image carrier and the detection signal of the use environment detecting means. And a control means for optimizing the magnitude of the electric bias.

Further, the surface of the image carrier is electrostatically charged by an image carrier having a photosensitive layer on its surface, a charging means for uniformly charging the surface of the image carrier, and a light emitting means modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that develops a toner image by attaching toner to the electrostatic latent image by applying an electric bias. A modulation method detecting means for detecting a modulation method, and a control means for optimizing the magnitude of an electric bias in the developing means according to a detection signal of the modulation method detecting means are provided. .

Furthermore, an image carrier having a photosensitive layer on its surface, a charging means for uniformly charging the surface of the image carrier, and a light emitting means modulated in accordance with an image signal are used to statically charge the surface of the image carrier. An image forming apparatus comprising: a latent image forming unit that forms an electrostatic latent image; and a developing unit that develops a toner image by attaching toner to the electrostatic latent image by applying an electric bias. In response to a usage status detection unit that detects a usage status of the body, a modulation method detection unit that detects a modulation method of the image signal, a detection signal of the usage status detection unit, and a detection signal of the modulation method detection unit Control means for optimizing the magnitude of the electric bias in the developing means.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier by a light emitting unit that is modulated according to an image signal, and an electric bias. In an image forming apparatus including a developing unit that applies toner to the electrostatic latent image to develop it as a toner image by application, a use environment detecting unit that detects a use environment of the image carrier, and an image signal of the image signal. Modulation method detection means for detecting a modulation method, and a detection signal of the use environment detection means,
And a control unit for optimizing the magnitude of the electric bias in the developing unit according to the detection signal of the modulation method detecting unit.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and a toner is attached to the electrostatic latent image by applying an electric bias. And a developing unit for developing the toner image as a toner image, the developing unit according to a use state detecting unit for detecting a use state of the image carrier and a detection signal of the use state detecting unit. It is characterized by comprising a control means for optimizing the magnitude of the electrical bias in the electric field and optimizing the image signal.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and a toner is attached to the electrostatic latent image by applying an electric bias. And a developing means for developing the toner image as a toner image, the developing means according to the use environment detecting means for detecting the use environment of the image carrier and the detection signal of the use environment detecting means. It is characterized by comprising a control means for optimizing the magnitude of the electrical bias in the electric field and optimizing the image signal.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier by a light emitting unit that is modulated according to an image signal, and an electric bias. An image forming apparatus comprising: a developing unit that applies toner to the electrostatic latent image by application to develop the electrostatic latent image as a toner image; and a modulation method detecting unit that detects a modulation method of the image signal, and the modulation method detecting unit. The control means for optimizing the magnitude of the electric bias in the developing means and optimizing the image signal in accordance with the detection signal of 1.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier by a light emitting unit that is modulated according to an image signal, and an electric bias. In an image forming apparatus comprising: a developing unit that applies toner to the electrostatic latent image to develop the electrostatic latent image as a toner image, a use state detecting unit that detects a use state of the image carrier, and an image signal of the image signal. A modulation method detection means for detecting a modulation method, and a detection signal of the usage status detection means,
It is characterized by further comprising control means for optimizing the magnitude of the electric bias in the developing means and optimizing the image signal according to the detection signal of the modulation method detecting means.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier by a light emitting unit that is modulated according to an image signal, and an electric bias. In an image forming apparatus including a developing unit that applies toner to the electrostatic latent image to develop it as a toner image by application, a use environment detecting unit that detects a use environment of the image carrier, and an image signal of the image signal. Modulation method detection means for detecting a modulation method, and a detection signal of the use environment detection means,
It is characterized by further comprising control means for optimizing the magnitude of the electric bias in the developing means and optimizing the image signal according to the detection signal of the modulation method detecting means.

Next, an image carrier having a photosensitive layer on its surface,
A charging unit that uniformly charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier by a light emitting unit that is modulated according to an image signal, and an electric bias. In an image forming apparatus including: a developing unit that applies toner to the electrostatic latent image to develop the electrostatic latent image as a toner image, a usage status detecting unit that detects a usage status of the image carrier, and the image carrier. Environment detecting means for detecting the environment of use, a modulation method detecting means for detecting a modulation method of the image signal, a detection signal of the usage situation detecting means, a detection signal of the usage situation detecting means, and the modulating method. It is characterized by comprising control means for optimizing the magnitude of the electric bias in the developing means and optimizing the image signal in accordance with the detection signal of the detection means.

In these cases, the image bearing member may be a drum type photosensitive member having a photosensitive layer on its surface.

Further, the developing means may be a developing means using a one-component magnetic toner.

Further, the method of modulating the image signal may include means for changing the resolution of the original signal.

Furthermore, the means for optimizing the image signal creates a density signal conversion table in accordance with the detection signal of at least one of the use status detecting means, the use environment detecting means and the modulation method detecting means. It is also possible to have control means for switching.

Next, the use environment detecting means may be means for detecting at least one of temperature and humidity.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

A reader unit is arranged above the image forming apparatus.

The reader unit is provided with a mounting table 11 on which the document is placed with its image surface facing downward, an illumination lamp 12 for illuminating the image surface of the document, and reflected light from the image surface of the document. An optical sensor 13 such as a CCD for reading an image signal is provided.

The image signal read by the optical sensor 13 undergoes a predetermined conversion by the image signal processing device 14, and the image exposure device (latent image forming means) of the next printer section.
15

The printer section includes an image exposure device 15, a photosensitive drum (image carrier) 16, and a primary charging device (charging means) 1.
7, a developing device (developing means) 18, a transfer charging device 19, and a fixing device (not shown) are main components.

The surface of the photosensitive drum 16 has a primary charging device 17
After being uniformly charged by the image exposure device 15, the image exposure device 15 receives the image exposure to form an electrostatic latent image corresponding to the image of the original. The electrostatic latent image on the surface of the photosensitive drum 16 is developed as a toner image with toner attached by the developing device 18. This toner image is transferred onto the transfer material 20 by the transfer charging device 19, and the transfer material 20 after the toner image transfer is
The toner image is fixed by the fixing device and discharged as an output image. On the other hand, the photosensitive drum 16 after the toner image transfer
The transfer residual toner remaining on the surface of the sheet is removed by a cleaning device (not shown), and the sheet is used for the next image formation.

The primary charging device 17 has a contact charging member which is arranged in contact with the surface of the photosensitive drum 16 and to which a high voltage power source (not shown) is connected. By applying a high voltage to the primary charging device (contact charging member) 17 by a high voltage power source, the surface of the photosensitive drum 16 is uniformly charged to a charging potential of −700V.

Further, the above-mentioned image exposure device 15 uses a laser scanner (light emitting means) in the present embodiment. The laser scanner 15 irradiates the surface of the charged photosensitive drum 16 with a laser beam that emits light corresponding to the converted image signal. By the irradiation of the laser beam, charges on the surface of the photosensitive drum 16 corresponding to the image of the original are removed, and an electrostatic latent image is formed.
The image resolution in the printer unit at this time is 600d.
pi.

The developing device 18 performs reversal development by a developing roller (developer carrying body) 21 as a developer carrying body.
The developing roller 21 carries and conveys the developer, to which a negative charge is applied by utilizing the triboelectric charging phenomenon, on its surface. As the developer, for example, a one-component magnetic toner can be used. The developing roller 21 has a developing bias (-600
A voltage in which a DC component of V and an AC component having a peak-to-peak voltage of 1000 V are superimposed) is applied, and thereby a transfer electric field is formed between the developing roller 21 and the surface of the photosensitive drum 16. The toner on the developing roller 21 is attached to the electrostatic latent image on the surface of the photosensitive drum 16 by this transfer electric field to form a toner image.

The toner image thus formed on the surface of the photosensitive drum 16 is transferred onto the transfer material 2 by the transfer charging device 19 described above.
0 is transferred to the upper surface. The transfer material 21 is synchronized with the toner image formed on the surface of the photosensitive drum 16,
It is conveyed to a transfer portion between the photosensitive drum 16 and the transfer charging device 19 by a transfer material conveying device (not shown).

A more specific description will be given below with specific numerical values. <Embodiment 1> In FIG. 2, as the photosensitive drum 16, the film thicknesses of the photosensitive members are 30 μm, 20 μm, 16 μm,
The data on fogging when using a film having a thickness of 13 μm is shown. At this time, the DC component of the developing bias applied to the developing roller 21 is -600V. The fog is a numerical value obtained by subtracting the reflectance of the transfer material after the solid white copy from the reflectance of the transfer material before the copy.

From this figure, it is understood that the fog of the toner increases as the film thickness of the photoconductor becomes thinner.

In this embodiment, as shown in FIG.
As the usage status detecting means, a detecting means 30 for detecting a current value flowing through the photosensitive drum 16 and a control device 31 for optimizing the developing bias according to a detection signal of the detecting means 30 are provided.

That is, a constant voltage is applied to the primary charging device 17 by the above-mentioned high-voltage power supply, and a current is passed through the photosensitive drum 16. At this time, the current value of the current flowing through the photosensitive drum 16 has a correspondence relationship with the film thickness of the photoconductor of the photosensitive drum 16.
Therefore, a detection signal corresponding to the film thickness of the photoconductor can be obtained by detecting the current value by the detection means 30. According to this detection signal, the controller 31 changes the DC component of the developing bias applied to the developing roller 21, thereby reducing fog.

FIG. 3 shows a specific example in which the DC component of the developing bias is changed according to the film thickness of the photoconductor.

Photosensitive film thickness, 30 μm, 20 μm, 16
The DC components of the developing bias are set to -600V, -560V, -550V, -5 corresponding to .mu.m and 13 .mu.m, respectively.
It was set to 30V. The results are 1.20% and 1.2, respectively.
It became 0%, 1.30%, and 1.10%.

From this figure, it is understood that even when the film thickness of the photoconductor is reduced, the deterioration of fog can be prevented by appropriately changing the DC component of the developing bias.

The relationship between the value of the film thickness of the photoconductor and the magnitude of the DC component of the developing bias that eliminates fogging with respect to the film thickness is obtained in advance by experiments or the like, and the result is calculated by the controller 30. It should be stored in a storage device (not shown). <Embodiment 2> An embodiment in which a 600 dpi printer optimized for copying is used as a printer unit to output a facsimile image will be described. In this case, resolution conversion is necessary as described above.

When a facsimile image is output after the resolution is converted by the image signal processing device (resolution converting means) 14, moire may occur at a certain probability due to variations in the printer unit.

However, as a result of the study by the present applicants, the DC component of the developing bias applied to the developing roller 21 is appropriately adjusted by the control device (conversion method detection means) 31 based on the detection signal of the image signal processing device 14. It was found that the probability of occurrence of the above-mentioned moiré can be reduced by changing to.

Referring to FIG. 4, the DC component of the developing bias applied to the developing roller 21 is -600 V optimized for copying.
And the occurrence probability of moire in the case of -550V.

It can be seen that the probability of occurrence of moire at -600V is 30%, whereas at -550V it is significantly reduced to 0%.

The above-mentioned moire occurrence probability refers to the ratio of image forming apparatuses in which moire has occurred to the manufactured image forming apparatuses. <Embodiment 3> As shown in FIG. 1, in this embodiment, a temperature / humidity detecting means (use environment detecting means) 3 is provided around the image forming apparatus.
2 is arranged, and the DC component of the developing bias is changed according to the output.

FIG. 5 shows that the temperature and humidity are 5% RH and 2% at 23 ° C.
The output density characteristics at 60% RH at 3 ° C. and 80% at 30 ° C. are shown in FIG.

At this time, the DC components of the developing bias were all -600V.

On the other hand, at 23 ° C. and 5% RH, −
At 80% RH at 580 V and 30 ° C., it was changed to −630 V. In addition, at 23 ° C. and 60% RH, it is −600 V as it is.

As described above, the control device 31 is responsive to the temperature and humidity around the image forming apparatus detected by the temperature and humidity detecting means 32.
By appropriately changing the DC component of the developing bias, it is possible to obtain good, almost identical output density characteristics.

The relationship between the temperature and humidity and the output density characteristic is as follows.
It is assumed that the data is obtained in advance by experiments and the data is stored in the control device 31.

In the above, depending on both temperature and humidity, D
Although the C component is changed, the DC component may be changed according to either one.

The above-mentioned first and second embodiments and the above-mentioned third embodiment can be carried out independently, but any two or more of them can be combined and carried out at the same time. Of course, it is okay. <Embodiment 4> FIG. 7 shows a photosensitive drum 16 as an image carrier.
The film thickness of the photoconductor is 30 μm, 20 μm, and 16 μm, respectively.
The output density characteristics when using the ones of μm and 13 μm are shown. However, with respect to the DC component of the developing bias, the same control as in the above-described first embodiment is performed. That is,
The DC components are -600V, -580V, -550 in that order.
V and -530V are controlled to eliminate fog.

From the figure, it can be seen that the output density characteristics change as the film thickness of the photosensitive member decreases. This tendency is more remarkable in the case of the present invention in which the DC component of the developing bias is controlled than in the case where the control is not controlled.
In FIG. 8, when the DC component of the developing bias is not controlled (constant at -600 V), the film thickness of the photoconductor is 30 μm.
The changes in the output density characteristics when changing to m, 20 μm, 16 μm, and 13 μm are shown.

In this embodiment, first, the detecting means 30 detects the current value of the current flowing through the photosensitive drum 16 when a constant voltage is applied to the photosensitive drum 16 via the primary charging device 17 by the high voltage power source. Up to this point, the procedure is the same as in the first embodiment.

Next, according to the detection signal of the detecting means 30,
The image signal processing device 14 switches the density signal conversion table so as to correct the change in the output density characteristic according to the change in the film thickness of the photoconductor. A plurality of density conversion tables are stored in the control device 31, and the output density characteristics when the density signal conversion tables are switched are shown in FIG. 19 for film thicknesses of 30 μm, 20 μm, 16 μm, and 13 μm, respectively. Show.

By performing the control as described above, it is possible to obtain a constant output density characteristic, and it is possible to suppress the occurrence of fogging to a low level as in the first embodiment.

[0061]

As described above, according to the present invention,
The usage status of the image carrier, the usage environment, the conversion method of the image signal, etc. are respectively detected by the usage status detection means, the usage environment detection means, the conversion method detection means, etc., and based on these detection signals, by the control device, By optimizing the magnitude of the electric bias in the developing unit or by optimizing the magnitude of the electric bias and the image signal, an image defect, for example, an image caused by a change in output density characteristics based on a change in reproducibility of minute dots It is possible to effectively prevent a defect, an image defect due to the printer section not being optimized for various image signals, and an image defect due to periodical density unevenness when resolution conversion is performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a photoconductor film thickness and fogging when the present invention is not applied.

FIG. 3 is a diagram showing the relationship between the photoconductor film thickness and fogging when the present invention is applied.

FIG. 4 is a diagram showing a moire occurrence probability when the present invention is not applied and when the present invention is applied.

FIG. 5 is a diagram showing output density characteristics under various temperature and humidity environments when the present invention is not applied.

FIG. 6 is a diagram showing output density characteristics under various temperature and humidity environments when the present invention is applied.

FIG. 7 is a diagram showing an output density characteristic with respect to a change in the photoconductor film thickness when the DC component of the developing bias is switched according to the photoconductor film thickness.

FIG. 8 is a diagram showing an output density characteristic with respect to a change in the photoconductor film thickness when the DC component of the developing bias is not switched according to the photoconductor film thickness.

FIG. 9 is a diagram showing an output density characteristic with respect to a change in the photoconductor film thickness when the DC component of the developing bias is switched according to the photoconductor film thickness and the density signal conversion table is switched according to the photoconductor film thickness. .

[Explanation of symbols]

11 Original Plate Glass 12 Illumination Lamp 13 Optical Sensor 14 Means for Changing Resolution (Image Signal Processing Device) 15 Latent Image Forming Means (Image Exposure Device) 16 Image Carrier (Photosensitive Drum) 17 Charging Means (Primary Charging Device) 18 Development Means (developing device) 19 Transfer charging device 20 Transfer material 21 Developer carrier (developing roller) 30 Usage condition detecting means 31 Control means (modulation method detecting means) 32 Usage environment detecting means (temperature and humidity detecting means)

Claims (16)

[Claims] 1. An image carrier having a photosensitive layer on its surface, charging means for uniformly charging the surface of the image carrier, and latent image forming means for forming an electrostatic latent image on the surface of the image carrier. In an image forming apparatus including a developing unit that applies toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image, a use status detecting unit that detects a use status of the image carrier. An image forming apparatus comprising: a control unit that optimizes the magnitude of an electric bias in the developing unit according to a detection signal from the usage status detecting unit. 2. An image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a latent image forming unit for forming an electrostatic latent image on the surface of the image carrier. In an image forming apparatus including: a developing unit that develops a toner image by attaching toner to the electrostatic latent image by applying an electric bias, a use environment detecting unit that detects a use environment of the image carrier. An image forming apparatus comprising: a control unit that optimizes the magnitude of an electrical bias in the developing unit according to a detection signal of the use environment detecting unit. 3. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. A modulation method detecting means for detecting a modulation method; and a control means for optimizing the magnitude of an electric bias in the developing means in accordance with a detection signal of the modulation method detecting means. Image forming apparatus. 4. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Of the usage status detecting means for detecting the usage status of the image signal, a modulation method detecting means for detecting the modulation method of the image signal, a detection signal of the usage status detecting means, and a detection signal of the modulation method detecting means, An image forming apparatus comprising: a control unit that optimizes the magnitude of an electric bias in the developing unit. 5. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit which is modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Use environment detection means for detecting the use environment of, the modulation method detection means for detecting the modulation method of the image signal, the detection signal of the use environment detection means, depending on the detection signal of the modulation method detection means, An image forming apparatus comprising: a control unit that optimizes the magnitude of an electric bias in the developing unit. 6. An image carrier having a photosensitive layer on its surface, charging means for uniformly charging the surface of the image carrier, and latent image forming means for forming an electrostatic latent image on the surface of the image carrier. In an image forming apparatus including a developing unit that applies toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image, a use status detecting unit that detects a use status of the image carrier. An image comprising: a control means for optimizing the magnitude of an electric bias in the developing means and optimizing an image signal in accordance with a detection signal from the usage status detecting means. Forming equipment. 7. An image carrier having a photosensitive layer on its surface, charging means for uniformly charging the surface of the image carrier, and latent image forming means for forming an electrostatic latent image on the surface of the image carrier. In an image forming apparatus including: a developing unit that develops a toner image by attaching toner to the electrostatic latent image by applying an electric bias, a use environment detecting unit that detects a use environment of the image carrier. An image comprising: a control means for optimizing the magnitude of an electric bias in the developing means and optimizing an image signal in accordance with a detection signal of the use environment detecting means. Forming equipment. 8. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Modulation method detection means for detecting the modulation method, and control means for optimizing the magnitude of the electrical bias in the developing means and optimizing the image signal according to the detection signal of the modulation method detection means. An image forming apparatus comprising: 9. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit which is modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Of the usage status detecting means for detecting the usage status of the image signal, a modulation method detecting means for detecting the modulation method of the image signal, a detection signal of the usage status detecting means, and a detection signal of the modulation method detecting means, An image forming apparatus comprising: a control unit that optimizes the magnitude of an electric bias in the developing unit and optimizes an image signal. 10. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Use environment detection means for detecting the use environment of, the modulation method detection means for detecting the modulation method of the image signal, the detection signal of the use environment detection means, depending on the detection signal of the modulation method detection means, An image forming apparatus comprising: a control unit that optimizes the magnitude of an electric bias in the developing unit and optimizes an image signal. 11. An electrostatic latent image is formed on the surface of the image carrier by an image carrier having a photosensitive layer on its surface, a charging unit for uniformly charging the surface of the image carrier, and a light emitting unit modulated according to an image signal. An image forming apparatus comprising: a latent image forming unit that forms a latent image; and a developing unit that attaches toner to the electrostatic latent image by applying an electric bias to develop the electrostatic latent image as a toner image. Status detecting means for detecting the usage status of the image carrier, usage environment detecting means for detecting the usage environment of the image carrier, modulation method detecting means for detecting the modulation method of the image signal, and detection of the usage status detecting means The size of the electric bias in the developing unit is optimized and the image signal is optimized in accordance with the signal, the detection signal of the use state detection unit, and the detection signal of the modulation method detection unit. With control means With the image forming apparatus characterized by. 12. The image forming apparatus according to claim 1, wherein the image bearing member is a drum type photosensitive member having a photosensitive layer on a surface thereof. 13. The image forming apparatus according to claim 1, wherein the developing unit is a developing unit that uses a one-component magnetic toner. 14. The method of modulating the image signal includes means for changing the resolution of the original signal, as claimed in any one of claims 3 to 5 or 8 to 13. The image forming apparatus described. 15. The density signal conversion table is switched in accordance with the detection signal of at least one of the usage status detection means, the usage environment detection means, and the modulation method detection means by the means for optimizing the image signal. The image forming apparatus according to claim 7, further comprising a control unit. 16. The use environment detecting means is a means for detecting at least one of temperature and humidity, wherein the use environment detecting means is a means for detecting at least one of temperature and humidity. Item 16. The image forming apparatus according to any one of items 15.