JPH0361968A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent base fogging due to lowering of photosensibility of a sensitive material from passage of time by making exposing quantity of an exposing lamp greater than the exposing quantity appropriate for the initial photosensibility of the sensitive material. CONSTITUTION:Electric charge is uniformly retained on a surface of the sensitive material 1 by electrifying the surface of the sensitive material 1 with an electrifier 2, and an image of an original 14 on a platen 13 is irradiated and exposed from the exposing part 3 by an exposing lamp 15 on the surface of the sensitive material 1. Here, the exposing quantity by the exposing lamp 15 is made greater than that appropriate for the initial photosensibility of the sensitive material 1. Therefore, even when the sensitivity of the sensitive material 1 is lowered by the change due to the passage of time, since it is the exposing quantity appropriate for the lowered photosensibility, the potential of the part other than an electrostatic latent image of the sensitive material 1 can be made the set value. Thus base fogging can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention involves charging the surface of a sensitive material and then irradiating it with reflected light from an original to form an electrostatic latent image. The present invention relates to an image forming apparatus that develops a visible image using a developing machine and transfers the visible image onto paper.

[Conventional technology]

The following types of image format devices are known.

That is, around the photosensitive material, a charger, an exposure section, a developing machine, a pre-transfer corotron, a transfer corotron, a peeling nail, a cleaner,
Discharge lamps, etc. are arranged one after another, and the surface of the photosensitive material is charged with a charger to maintain the charge uniformly. An electrostatic latent image is formed by exposing one surface to light, and this electrostatic latent image is carried through a developing machine by the rotation of the sensitive material, toner is attached to the electrostatic latent image and a visible image is developed. Ru.

The visible image is transferred to a transfer device by the rotation of the sensitive material and transferred onto paper, and the paper is sent to a fixing device to fix the transferred toner image on the paper, thereby making a copy.

[Problem to be solved by the invention]

In such an image forming apparatus, immediately after the power is turned on first thing in the morning after performing an image forming operation many times or after being stopped for a long time such as during the night, the image forming apparatus is The forming operation may cause background fog, resulting in an unsightly copy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming apparatus capable of solving the above-mentioned problems.

[Means and effects for solving the problems] 1. An image forming apparatus in which the amount of exposure from an exposure lamp is greater than the amount of exposure commensurate with the initial photosensitivity of the photosensitive material.

As a result, even if the photosensitivity of the photosensitive material decreases over time, the amount of exposure will be commensurate with the decreased photosensitivity, and the potential of areas other than the electrostatic latent image on the photosensitive material will be maintained at the set value, resulting in background fog. can be prevented.

2. Immediately after the power is turned on after being stopped for a long period of time, and when no image forming operation is performed for a certain period of time, an image forming apparatus main rotates the photosensitive material for a predetermined period of time and irradiates the photosensitive material with light from each lamp.

As a result, even if the photosensitivity of the photosensitive material changes due to being stopped for a long time, the desired photosensitivity can be recovered quickly, and background fogging can be prevented.

3. Immediately after turning on the power after being stopped for a long time, the developing bias is increased by a certain amount from a preset value, and the developing bias is decreased by a certain amount for each image forming operation to form the same predetermined number of images. An image forming apparatus that is configured to have a preset value after the operation is completed.

Due to this, the toner band of the developing machine may be caused by stopping for a long time. By compensating for the change in 1Sjl, background fogging can be prevented.

4. Immediately after turning on the power after being stopped for a long time, the exposure amount is increased by a certain amount from a preset value, and the exposure amount is decreased by a certain amount for each image forming operation, and the predetermined number of image forming operations are completed. An image forming apparatus that later becomes a preset value.

Thereby, background fog can be prevented by compensating for changes in the toner concentration of the developing machine and changes in the charging characteristics of the photosensitive material due to the long period of stoppage.

5. Immediately after turning on the power after being stopped for a long time, the amount of charge on the sensitive material by the charger is reduced by a certain amount from a preset value,
An image forming system in which the amount of charge is increased by a fixed amount for each image forming operation and reaches a preset value after a predetermined number of image forming operations is completed.As a result, the photosensitive material is charged due to being stopped for a long time. It is possible to compensate for changes in characteristics and prevent background fog.

6. A surface potential detection sensor is provided opposite to the surface of the sensitive material, the potential of the white part of the sensitive material is detected by this surface potential detection sensor, and background fog prevention operation is performed based on the detected potential of the white part. image forming device.

Thereby, the background fog prevention operation can be performed based on the actual potential of the white portion of the sensitive material, so that background fog can be reliably prevented.

〔Example〕

FIG. 1 is a schematic explanatory diagram of an image forming apparatus, in which a photosensitive material 1 is surrounded by a charger 2, an exposure section 3, a developing device 4, a pre-transfer corotron 5, a transfer corotron 6, a peeling claw 7, a cleaner 8, and a static eliminator. Lamps 9 are arranged in sequence, a pre-copy sensitive material fatigue lamp 10 is arranged between the charger 2 and the exposure section 3, an erase lamp 11 is arranged between the exposure section 3 and the developing device 4, An auxiliary static elimination lamp 12 is disposed between the peeling claw 7 and the cleaner 8.

Next, the basic operation of image formation will be explained.

The surface of the photosensitive material 1 is charged with a charger 2, and a second charge is applied to the surface of the photosensitive material 1.
As shown in FIG. 3A, the image of the document 14 on the platen 13 is irradiated onto the surface of the photosensitive material 1 from the exposure section 3 using the exposure lamp 15 while maintaining the charge uniformly.

As a result, as shown in FIG. 2(b), the amount of reflected light 18 from the image portion of the document 14 is small, and the amount of reflected light 17 from the blank portion is large, so that the amount of reflected light 18 from the blank portion is large.
The charge on the portion irradiated with photosensitive material 7 is removed, and the charge remains on the surface of the sensitive material 1 facing the image portion, thereby forming an electrostatic latent image.

This electrostatic latent image is carried to the developing device 4 by the rotation of the photosensitive material 1.

As shown in FIG. 1, the developing device 4 includes a developing roll 19 in a housing 18, and the developing roll 19 conveys a two-component developer 20 consisting of toner and carrier toward the photosensitive material 1. Since the toner is charged with a polarity opposite to that of the electrostatic latent image due to frictional charging within the developing device 4,
As shown in FIG. 2(c), toner 22 adheres to the electrostatic latent image and is developed into a visible image. 21 is a developing bias power supply.

The visible image is transferred to the transfer corotron 6 by the rotation of the photosensitive material 1, and the transfer corotron 6 applies an electric charge of opposite polarity to the visible image to the paper 24 conveyed along the paper conveyance path 23, and transfers it onto the photosensitive material 1. The visible image is transferred to a paper 24 as shown in FIG. 2(d), and the paper 24 is sent to a fixing device 25, where the transferred toner image is fixed on the paper 24.

In FIG. 1, a static elimination lamp 9 is used to eliminate charges remaining on the photosensitive material 1, and a pre-copy photosensitive material fatigue lamp 10 is used to fatigue the photosensitive material 1 by irradiating it with light while idling the photosensitive material 1. The erase lamp 11 is for eliminating unnecessary charges on the sensitive material 1, the pre-transfer corotron 5 is for making it easier for the visible image to peel off from the sensitive material 1, and the auxiliary charge eliminating lamp 12 is for eliminating unnecessary charges on the sensitive material 1. This assists in eliminating the electric charge.

When such an image forming apparatus is stopped for a long period of time or after a predetermined number of image forming operations are performed, the non-image area of the paper 24, that is, the background area may become dark, which is called background fog.

This background fog is caused by toner adhering to portions of the photosensitive material 1 other than the electrostatic latent image during the developing operation shown in FIG. 2(C).

The inventor of the present invention investigated the cause of the above-mentioned background fog, that is, the cause of toner adhering to areas other than the electrostatic latent image on the photosensitive material 1, and as a result discovered that this is the cause.

■Due to changes in the photosensitivity of the photosensitive material 1 over time, the original 14 may
This is because the charge on the photosensitive material 1 is not sufficiently removed by the opposite light 17 from the white part of the photosensitive material 1.

In other words, the photosensitivity of the photosensitive material 1 is the magnitude of the amount of light required to remove the charges.If the photosensitivity is high, the charges can be removed sufficiently even with a small amount of light, but if the photosensitivity is low, the charges can be removed with the same amount of light. When the charge on the photosensitive material 1 decreases and the photosensitivity of the photosensitive material 1 changes with time and becomes lower than the initial photosensitivity, the amount of reflected light 17 from the white portion of the original 14 remains the same during exposure as shown in FIG. 2(b). However, the charge on the photosensitive material 1 is not sufficiently removed and some amount of charge remains, and the toner 22 adheres to areas other than the electrostatic latent image on the photosensitive material 1 during development as shown in FIG. 2(c), resulting in background fog. occurs.

■The photosensitivity of photosensitive material 1 decreases when the image forming apparatus is stopped for a long time, and when the image forming apparatus is turned on and operated first thing in the morning, photosensitive material 1
The photosensitivity of photosensitive material 1 has decreased, and after multiple image forming operations, the photosensitivity of photosensitive material 1 recovers and becomes stable, so it is best to turn on the power first thing in the morning after being stopped for a long time, such as at night. If an image forming operation is performed immediately thereafter, background fog will occur as described above.

■The developing characteristics of the developing machine, that is, the amount of charge on the toner, will be below the value determined by the developing bias when the power is turned on, and will remain close to the value determined by the developing bias for each image forming cycle until multiple image forming cycles are performed thereafter.
After that, the toner charge amount becomes constant determined by the developing bias, so that during the image forming cycle immediately after the power is turned on, the charge on the portion of the photosensitive material 1 other than the electrostatic latent image is reduced during the development shown in FIG. 2(c). Even if it is low, toner will adhere and background fog will occur.

(2) The charging characteristics of the photosensitive material 1 decrease with each image forming cycle until a plurality of image forming cycles are performed after the power is turned on, so that background fogging occurs during the plurality of image forming cycles after the power is turned on.

In other words, if the charging characteristics are good, the amount of charge charged on the photosensitive material 1 during charging as shown in FIG. Some amount of charge remains, and during development as shown in FIG. 2(c), toner 21 adheres to areas other than the electrostatic latent image, causing background fog, and after multiple image forming cycles, the charging characteristics change. Since the value becomes constant at a low value, ground fogging does not occur after that.

Next, the present invention will be explained in detail.

First Example When the above-described image forming apparatus was used to measure the changes in photosensitivity of a plurality of photosensitive materials 1 over time, the results shown in the chart of FIG. 3 were obtained.

From the diagram in FIG. 3, it was found that the photosensitivity decreased by 20±5% of the initial photosensitivity after about 5,000 copies were made, and thereafter became stable.

As a result, if the charge on the photosensitive material 1 is 100% removed during the first image forming operation to make the first copy, then the same amount of charge will be removed during the 5000th image forming operation to make the 5000th copy. Even when the photosensitive material 1 is irradiated with light, 80% of the charge on the photosensitive material 1 is not removed, and 20% of the charge remains on the photosensitive material 1, causing background fog.

Focusing on the above, we determined the amount of exposure that can eliminate the charge on the photosensitive material 1 by the reflected light 17 from the white part of the document to the extent that background fog does not occur during the first image forming operation, that is, the exposure lamp 15. The illuminance was determined experimentally, and the exposure amount was adjusted and set in advance so that it would be a value that was added by 20% of the illuminance.

In this way, the photosensitivity of photosensitive material 1 is 2 times higher than the initial photosensitivity.
Even when the light decreases by about 0%, the reflected light from the white part of the document1
7 can eliminate the charge on the photosensitive material 1 to such an extent that background fog does not occur, so that even if the photosensitivity of the photosensitive material 1 decreases over time, background fog can be prevented from occurring.

Further, a means for arbitrarily varying the exposure amount of the exposure lamp 15 may be provided so that the difference in the exposure amount can be freely varied.

For example, a digital value corresponding to the exposure amount is manually entered into the arithmetic unit from the keyboard, this value is stored, and an analog voltage is supplied to the exposure lamp 15 via a digital/analog converter and an operational amplifier.
The drive circuit is configured to adjust the amount of light from the exposure lamp using this voltage (0 to 3 V).

A more detailed study of the decrease in photosensitivity of the photosensitive material 1 of the second embodiment revealed that the photosensitivity of the photosensitive material slightly decreases after the power is turned off, and recovers when the image forming operation is performed after the power is turned on again. As mentioned above, if the power is turned off and stopped for a long time, then the power is turned on and an image forming operation is performed, or if the time between the previous image forming operation and the current image forming operation is longer than a certain period of time. As mentioned above, the photosensitivity of the photosensitive material 1 decreases, resulting in background fog.

Focusing on the above points, as shown in FIG. 4, a controller 30 is provided to control the operation of each device installed around the photosensitive material 1. When the copy button 32 is not turned on for a certain period of time or more, the controller 30 outputs a signal to cause the photosensitive material 1 to idle for a certain period of time, for example, once, and a signal to turn on each lamp at maximum output, so that the surface of the photosensitive material 1 is irradiated with light. The light sensitivity that decreased when stopped is rapidly restored.

In this way, when the power is turned on and an image forming operation is performed after a long stop, such as first thing in the morning, or when an image forming operation is performed after a certain period of time has elapsed after the previous image forming operation, the photosensitive material 1 can be Since light sensitivity is restored to its original state, background fogging can be prevented.

Note that a means may be provided to freely vary the predetermined time period during which the photosensitive material 1 is rotated idly.

Third Embodiment Focusing on the third cause mentioned above, as shown in FIG.
When the ON signal of the main power switch 31 is input to 0, a signal to increase the developing bias of the developing device 4 by a certain amount is output to the developing bias power supply 21, and each time the copy button 32 is pressed and an image forming operation is performed. A signal for decreasing the power supply bias which has increased by a certain amount by a predetermined amount is applied to the developing bias power supply 2.
1, and after a certain number of image forming operations are performed, the developing bias is predictively controlled so as to return to the preset developing bias value.

In this way, when the power is turned on, the developing bias of the developing device 4 becomes a certain amount larger than a preset value, and the toner charge amount becomes a charge amount lower than the value determined by the large developing bias value. The amount of charge becomes commensurate with the amount of charge determined by the previously set value of the developing bias, and thereafter, each time an image forming operation is performed, the developing bias decreases and approaches the preset value, and at the same time, the amount of toner charge increases. Therefore, when image forming operations are performed multiple times after the power is turned on, the amount of charge on the toner band 11 of the developing device corresponds to the preset developing bias value, and the amount of charge on the photosensitive material 1 during the developing operation is reduced. Since toner does not adhere to areas other than the electrostatic latent image, background fogging can be prevented.

In addition, a preset developing bias value, a developing bias value that increases by a certain amount, a developing bias value that decreases by a specified amount,
A means for freely setting the number of image forming operations may be provided.

Fourth Embodiment Focusing on the third cause and the cause of M4, as shown in FIG. When the signal is manually applied, the voltage controller 33 of the exposure lamp 15
The controller 30 outputs a signal that increases the amount of light by a certain amount over a preset value, and the copy button 32
is pressed to output a signal to the voltage controller 33 to decrease the light amount that has increased by a predetermined amount each time an image forming operation is performed, and when the image forming operation is performed a certain number of times, the preset exposure amount is increased. Predictively controls the exposure amount so that it returns to normal.

In this way, when the power is turned on, the amount of exposure from the exposure lamp 15 will be greater than the preset value, as shown in FIG. 2(b).
Reflected light 17 from the white part of the document during exposure shown in
Since the amount of light becomes larger than the preset amount of light and the charge on the photosensitive material 1 is removed excessively, the amount of charge on the toner becomes at least two times larger than the preset amount of charge due to the third cause mentioned above.
As shown in FIG.
If an extra charge is applied to the surface of the
During the exposure shown in FIG. 1, excess charges on the photosensitive material 1 are removed, so that the charges on the portions of the photosensitive material 1 other than the electrostatic latent image become the set charges, and toner does not adhere to the photosensitive material 1, thereby preventing background fog.

Note that a means may be provided for freely changing the preset exposure amount, the amount of increase in the amount of exposure, the amount of decrease in the amount of exposure, and the number of times of image forming operation.

Fifth Embodiment Focusing on the fourth cause mentioned above, as shown in FIG. At this time, the controller 3 sends a signal to the current controller 34 of the charger 2 to reduce the amount of charge by a certain amount from a preset value.
0 and outputs a signal to the current controller 34 to increase the amount of light, which has decreased by a predetermined amount, by a predetermined amount each time the copy button 32 is pressed and an image forming operation is performed once, and a fixed number of image forming operations are performed. The exposure amount is predictively controlled so that it returns to the preset exposure amount when

In this way, when the power is turned on, the amount of charge by the charger 2 decreases from the preset value, and even if the charging characteristics of the photosensitive material 1 are improved during charging as shown in FIG. The amount of charge given by 2 decreases, and the surface of the photosensitive material 1 is charged with a preset amount of charge, as shown in FIG. 2(b).
During the exposure shown in FIG. 2(c), the electric charge on the sensitive material 1 is sufficiently removed by the reflected light 17 from the white portion of the document.
During the development shown in FIG. 1, the charges on the portions of the photosensitive material 1 other than the electrostatic latent image become the set charges, and toner does not adhere to the photosensitive material 1, thereby preventing the background fog caused by the fourth cause mentioned above.

Note that a means may be provided for freely changing the preset charge amount, the charge amount decrease value, the charge amount increase value, and the number of image forming operations.

Each of the above examples shows a decrease in photosensitivity of photosensitive material 1, a change in charging characteristics,
Although the exposure amount, the charge amount, and the toner charge amount are controlled by predicting the change in the toner charge amount, the following configuration may also be used.

As shown in FIG. 8, a surface potential detection sensor 40 is provided in the developing machine 4 to face the surface of the photosensitive material 1, and this surface potential detection sensor 40 is connected to a sensor 42 in the main body 41 as shown in FIG.
A plurality of sensors 42 are provided at intervals in the longitudinal direction of the sensitive material 1, and each sensor 42 measures the surface potential at a plurality of locations in the longitudinal direction of the sensitive material 1, and the average value of the measured values is detected as the surface potential. be.

Note that the number of the sensor 42 may be one.

As shown in FIG. 10, when a copy signal is manually input to the controller 30 from the copy button 32, the exposure lamp 1
5 is stopped under the white reflective plate 26 provided near the platen 13, and the controller 30 outputs a rotation signal to the photosensitive material 1 to rotate the photosensitive material 1 once, and sends a signal to the current controller 34 of the charger 2. is output and the charger 2 charges the sensitive material 1. At the same time, the voltage controller 33 of the exposure lamp 15
A signal is output to the exposure lamp 15 to expose the surface of the photosensitive material 1. At this time, an original is set on the platen 13, but since the exposure lamp 15 is stopped under a white reflector 26 provided near the platen 13, the state is the same as when a white original is set. From this, the charge on sensitive material 1 is shown in Figure 2 (
The surface potential of the sensitive material 1 becomes the paper output part potential, and the paper output part potential is called the surface potential. It is detected by the detection sensor 40 and input to the controller 30.

In order to detect the potential of the white part, the surface potential of the material 1 at a plurality of locations in the paper feeding direction is measured, and the average value thereof is taken as the potential of the white part.

When the detected paper output part potential is larger than the preset paper output part potential, the voltage shown in FIG. 2(c) occurs during normal image forming operation.
During the development shown in FIG. 1, toner adheres to areas other than the electrostatic latent image on the photosensitive material 1, causing background fog. To prevent background fog, the following control signal is output during the next image forming operation.

(2) Output a voltage increase signal to the voltage controller 34 of the exposure lamp 15 to increase the exposure amount by an amount that compensates for the potential of the paper output section, and increase the exposure amount during the image forming operation as shown in FIG. 2(b). At the time of exposure shown in FIG. 1, the amount of reflected light 17 from the blank portion of the document is increased to set the charge on areas other than the electrostatic latent image portion of the photosensitive material 1 to a set value to prevent toner from adhering.

- A developing bias increase signal is sent to the developing bias power supply 20 of the developing device 4 so that the amount of toner band ts becomes a charging amount such that the toner does not adhere to areas other than the electrostatic latent image on the photosensitive material 1 even at the detected paper output section potential. output to reduce the amount of toner transfer,
Even if the charge on the portion of the photosensitive material 1 other than the electrostatic latent image is larger than the set value during the image forming operation, toner will adhere to the portion of the photosensitive material 1 other than the electrostatic latent image during development as shown in FIG. 2(c). Try not to.

- Outputs a current reduction signal to the current controller 33 of the charger 2 to reduce the amount of charge by an amount that compensates for the potential of the paper output section, and outputs a current reduction signal to the current controller 33 of the charger 2 to reduce the amount of charge on the photosensitive material by the charger 2 during image forming operation.
The amount of charge on the photosensitive material 1 is reduced so that the charge on the portion of the photosensitive material 1 other than the electrostatic latent image becomes a set value, and the toner is prevented from adhering to the portion other than the electrostatic latent image during development.

■ Output a voltage increase signal to the voltage controller of the static elimination lamp 9 or the static elimination lamp 9 and the pre-transfer static elimination lamp 27 to increase the light intensity of the static elimination lamp 9 that eliminates static electricity from the surface of the photosensitive material 1 during image forming operation. The photosensitive material 1 is fatigued early to recover its photosensitivity, thereby achieving a stable state, and by preventing the charge from increasing in areas other than the electrostatic latent image due to the decrease in the photosensitivity of the photosensitive material 1, the toner is transferred to the electrostatic latent image during development. Avoid getting it on other areas.

■ A current or voltage reduction signal is output to the current or voltage controller of the pre-transfer corotron 5 to reduce the amount of charge on the surface of the photosensitive material 1 by the pre-transfer corotron 5 during image forming operation, so that the toner attached to the photosensitive material 1 is By making it difficult for the toner to separate from the material 1, the toner adhering to the photosensitive material 1 is difficult to be transferred to the paper 24 by the transfer corotron 6 during the subsequent transfer process, and the toner adhering to parts of the photosensitive material 1 other than the electrostatic latent image is removed. is paper 24
prevent it from being transferred to

Note that when a lamp is provided in place of the pre-transfer corotron 5, the amount of light from the lamp may be reduced by reducing the current or voltage of the lamp.

■Even if the toner concentration in the developing device 4 is lowered and the toner adheres to areas other than the electrostatic latent image on the photosensitive material 1 during development, it will not be noticeable because the toner concentration is low, thereby preventing background fog. do.

The following methods can be used to reduce the toner concentration within the developing device 4.

■-1 Stop the dispense roller, etc. that replenishes toner into the housing 18 of the developing device 4, and prevent toner from being replenished into the housing 18 to reduce the amount of toner in the developing device 4 compared to the amount of carrier. to reduce toner density.

Note that a means for freely varying the number of operations may be provided.

(2-2) Before starting the image forming operation, the photosensitive material 1 is rotated and charging, exposure, and development are repeated to waste toner and reduce toner density.

(2)-3 A solid black original is set and an image forming operation is performed without feeding paper to uniformly adhere toner to the surface of the photosensitive material 1 and remove it with the cleaner 8 to reduce the toner density. Note that a means for freely varying the number of operations may be provided.

■ Before the image forming operation, each lamp, for example, the exposure lamp 15,
The static eliminating lamp 9, the pre-copy sensitive material fatigue lamp 10, the erase lamp 11, the auxiliary static neutralizing lamp 12, the charger 2, and each corotron, such as the pre-transfer corotron 5 and the transfer corotron 6, are operated in the same manner as in the image forming operation to remove the sensitive material 1. By idling the light-sensitive material 1 and thereby causing the light-sensitive material 1 to become fatigued, the photosensitivity quickly becomes stable, thereby preventing background fogging due to a decrease in photosensitivity.

■ A heater is provided to warm the sensitive material 1, and the heating time and voltage of the heater are controlled to raise the surface temperature of the sensitive material 1.
By quickly bringing the photosensitivity of the photosensitive material 1 into a stable state, background fogging due to a decrease in photosensitivity is prevented.

Note that the operations of ■, ■-1, ■-2, and ■-3 are not based on white part potential detection, but are performed during the image forming operation when the power is turned on after being stopped for a long time as described above, and when the image forming operation is not performed for a certain period of time or more. It may be done if it is not done.

Further, the plurality of operations described above may be combined and performed simultaneously.

〔Effect of the invention〕

(1) Even if the photosensitivity of the photosensitive material 1 decreases below the initial photosensitivity due to changes over time, the amount of exposure is already higher than the amount of exposure that matches the initial photosensitivity, so the electrostatic potential of the photosensitive material 1 Since the potential of parts other than the image can be set to a set value, the photosensitive material 1
It is possible to prevent background fogging caused by a decrease in photosensitivity due to changes over time.

(4) If the photosensitivity of the photosensitive material 1 decreases due to a long stop or no image forming operation for more than a certain period of time, the light sensitivity of the photosensitive material 1 may be reduced by irradiating a piece of the photosensitive material 1 before the next image forming operation. By doing so, the photosensitivity can be recovered to a normal level, so even if the photosensitivity of the photosensitive material 1 decreases due to stopping for more than a certain period of time, it is possible to prevent background fog from occurring when image forming operation is performed again. .

(8) Even if the toner charge amount of the developing device 4 decreases when the power is turned on after being stopped for a long time, the convex image bias can be increased when the power is turned on to bring the toner charge amount to a predetermined charge amount. Toner is prevented from adhering to areas other than the electrostatic latent image on the photosensitive material 1, and background fog due to a decrease in the toner band xi of the developing machine can be prevented.

(12) When the power is turned on after being stopped for a long time, the amount of toner charge in the developing device 4 decreases, and the toner tends to adhere to areas other than the electrostatic latent image on the photosensitive material 1, or the charging characteristics of the photosensitive material 1 deteriorate. Even if the electrostatic latent image on the photosensitive material 1 is changed and an extra charge is generated during charging, the amount of exposure increases when the power is turned on, and the extra charge on the portion of the photosensitive material 1 other than the electrostatic latent image is removed. Toner does not adhere to areas other than the electrostatic latent image No. 1, and background fogging can be prevented.

(17) Even if the charging characteristics of the photosensitive material 1 change when the power is turned on after being stopped for a long time and an extra charge is applied during charging, the amount of charge by the charger 2 decreases when the power is turned on, causing the sensitive material to become sensitive. The material 1 is charged with a predetermined electric charge, thereby preventing background fogging.

(21) Since the surface potential of the sensitive material 1 is actually detected and the background fog prevention operation is performed based on the detected surface potential,
It is possible to reliably prevent ground fogging.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, in which FIG. 1 is a schematic explanatory diagram of an image forming apparatus, FIGS. 2(a) to (d) are explanatory diagrams of image forming operation, and FIG. Diagram showing, Figure 4~
FIG. 7 is a different control circuit diagram, FIG. 8 is an explanatory diagram of the mounting state of the surface potential detection sensor, FIG. 9 is a plan view thereof, and FIG. 10 is a control circuit diagram. 1 is a sensitive material, 2 is a charger, 3 is an exposure section, 4 is a developer, 6 is a transfer corotron, 8 is a cleaner 9 is a static elimination lamp, 15
is an exposure lamp, 4o is a surface potential detection sensor

Claims (1)

[Scope of Claims] (1) A static eliminating lamp 9, a charger 2, an exposure section 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are sequentially arranged around the sensitive material 1, and the surface of the sensitive material 1 is After being charged with a charger 2, the photosensitive material 1 is exposed to light reflected from the original by an exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image using a developing device 4. An image forming apparatus in which the visible image is transferred to paper by a transfer corotron 6, characterized in that the amount of exposure from the exposure lamp 15 is greater than the amount of exposure commensurate with the initial photosensitivity of the photosensitive material 1. . (2) The exposure amount is increased by the difference between the exposure amount that corresponds to the photosensitivity when the photosensitivity of the photosensitive material 1 decreases over time and the exposure amount that corresponds to the initial photosensitivity of the photosensitive material 1. Claim 1
The image forming apparatus described above. (3) The image forming apparatus according to claim 2, further comprising means for freely varying the difference in the exposure amount. (4) A static eliminating lamp 9, a charger 2, an exposure section 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are arranged in order around the photosensitive material 1, and the surface of the photosensitive material 1 is charged with the charger 2. After that, the photosensitive material 1 is exposed to light reflected from the original by the exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image by the developing device 4, and the visible image is transferred. In an image forming apparatus that transfers images onto paper using a corotron 6, immediately after the power is turned on after being stopped for a long period of time, or when no image forming operation is performed for a certain period of time, the photosensitive material 1 is rotated idly for a predetermined period of time and the photosensitive material is transferred using each lamp. 1
An image forming device characterized by irradiating light onto. (5) The image forming apparatus according to claim 4, wherein the light is irradiated onto the photosensitive material 1 by setting the lamp to maximum output. (6) The image formatting device according to claim 4, wherein the predetermined time is one rotation of the material. (7) The image formatting device according to claim 4, further comprising means for freely changing the predetermined time. (8) A static eliminating lamp 9, a charger 2, an exposure section 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are arranged in order around the photosensitive material 1, and the surface of the photosensitive material 1 is charged with the charger 2. After that, the photosensitive material 1 is exposed to light reflected from the original by the exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image by the developing device 4, and the visible image is transferred. In an image forming apparatus that transfers onto paper using a corotron 6, the developing bias is increased by a certain amount from a preset value immediately after the power is turned on after being stopped for a long time, and the developing bias is kept constant for each image forming operation. An image forming apparatus characterized in that the image forming apparatus is configured to decrease the amount in increments so as to reach a preset value after a predetermined number of image forming operations are completed. (9) The image forming apparatus according to claim 4, wherein the developing bias is increased in proportion to the decrease in the amount of toner charge in the developing machine 4 immediately after the power is turned on after being stopped for a long time. (10) means for freely varying the preset value; means for freely varying the fixed amount increase value;
9. The image formatting apparatus according to claim 8, further comprising means for freely varying said predetermined amount reduction value. (11) The image formatting device according to claim 8, further comprising means for freely varying the predetermined number of times. (12) A static elimination lamp 9, a charger 2, an exposure unit 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are arranged in order around the photosensitive material 1, and the surface of the photosensitive material 1 is charged with the charger 2. After that, the photosensitive material 1 is exposed to light reflected from the original by the exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image by the developing device 4, and the visible image is transferred. In an image forming device that transfers onto paper using a Corotron 6, the exposure amount is increased by a certain amount from a preset value immediately after the power is turned on after a long period of stoppage, and the exposure amount is kept constant for each image forming operation. An image forming apparatus characterized in that the amount is decreased to a preset value after a predetermined number of image forming operations are completed. (13) The image forming apparatus according to claim 12, wherein a voltage increase signal is output to a voltage controller of an exposure lamp. (14) The image forming apparatus according to claim 12, wherein the exposure amount is increased by a value commensurate with the amount of toner charge in the developing device immediately after the power is turned on after being stopped for a long time. (15) The image forming apparatus according to claim 12, wherein the exposure amount is increased by a value corresponding to a change in charging characteristics of the photosensitive material immediately after the power is turned on after being stopped for a long time. (18) means for freely varying the preset value; means for freely varying the fixed amount increase value; and
13. The image formatting apparatus according to claim 12, further comprising means for freely varying the fixed amount reduction value. (17) A static elimination lamp 9, a charger 2, an exposure unit 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are arranged in order around the photosensitive material 1, and the surface of the photosensitive material 1 is charged with the charger 2. After that, the photosensitive material 1 is exposed to light reflected from the original by the exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image by the developing device 4, and the visible image is transferred. In an image forming apparatus that transfers onto paper using a corotron 6, the amount of charge on the photosensitive material 1 by the charger 2 is reduced by a certain amount from a preset value immediately after the power is turned on after being stopped for a long time.
An image forming apparatus characterized in that the amount of charge is increased by a fixed amount every time an image forming operation is performed, and the amount of charge is set to a preset value after a predetermined number of image forming operations are completed. (18) The image forming apparatus according to claim 17, wherein a current increase signal is output to the power supply controller of the charger 2. (19) The image forming apparatus according to claim 17, wherein the amount of charge is reduced in proportion to the increase in the amount of charge due to a change in the charging characteristics of the photosensitive material 1 immediately after the power is turned on after being stopped for a long time. (20) means for freely varying the preset value; means for freely varying the fixed amount reduction value; and
18. The image formatting apparatus according to claim 17, further comprising means for freely varying said constant increase value. (21) A static elimination lamp 9, a charger 2, an exposure unit 3, a developing device 4, a transfer corotron 6, a cleaner 8, etc. are arranged in order around the photosensitive material 1, and the surface of the photosensitive material 1 is charged with the charger 1. After that, the photosensitive material 1 is exposed to light reflected from the original by the exposure lamp 15 to form an electrostatic latent image, and the electrostatic latent image is developed into a visible image by the developing device 4, and the visible image is transferred. In an image forming apparatus that transfers images onto paper using a corotron 6, a surface potential detection sensor 40 is provided opposite to the surface of the photosensitive material 1, and this surface potential detection sensor 40 detects the potential of the white portion of the photosensitive material 1. An image forming apparatus characterized in that a background fog prevention operation is performed based on a white part potential. (22) With the document set and the exposure lamp 15
With the photosensitive material 1 stopped under the white reflecting plate 26, the photosensitive material 1 is idle-rotated once to perform charging exposure, and then the surface potential of the photosensitive material 1 is measured by the surface potential detection sensor 40 to detect the potential of the white part. The image forming apparatus according to claim 21. (23) The image forming apparatus according to claim 22, wherein the surface potential at a plurality of locations in the longitudinal direction of the photosensitive material 1 is measured, and the white portion potential is detected based on the average value thereof. (24) The image forming apparatus according to claim 22, wherein the surface potential of the material 1 at a plurality of locations in the paper feeding direction is measured, and the white portion potential is detected based on the average value of three. (25) According to claim 21, background fog is prevented by increasing the exposure amount more than a preset value and increasing the developing bias more than a preset value to reduce the amount of toner transfer. image forming device. (26) The image forming apparatus according to claim 21, wherein the background fog is prevented by reducing the voltage or current of the charger from a set value so that the amount of charge on the photosensitive material 1 is less than the set value. (27) The image forming apparatus according to claim 21, wherein the light intensity of the static elimination lamp is increased during the image forming operation to fatigue the photosensitive material 1, thereby stabilizing the photosensitivity quickly and preventing background fog. (28) The current value or potential value of the pre-transfer corotron is lower than the set value to make it difficult for the visible image to separate from the sensitive material 1, and the voltage value or potential value of the pre-transfer lamp is lower than the set value to make the visible image less likely to separate from the sensitive material 1. Claim 21: The visible image is made more difficult to separate than the material 1.
The image forming apparatus described above. (29) The image forming apparatus according to claim 21, wherein background fog is prevented by controlling the toner concentration in the developing device 4 to be lowered. (30) The image forming apparatus according to claim 21, wherein background fog is prevented by stopping toner supply into the developing device 4 to reduce toner density. (31) The developing device 4 is operated for dry development to reduce the toner concentration to prevent background fog, and the solid black original is developed without paper being fed to reduce the toner density by consuming toner. The image forming apparatus according to claim 21. (32) The image forming apparatus according to claim 31, further comprising means for freely varying the number of operations. (33) The background fog according to claim 21, wherein the light-sensitive material 1 is rotated before the image forming operation, and the lamp and the corotron are operated in the same manner as during the image forming operation to fatigue the light-sensitive material 1. Image forming device. (34) The image forming apparatus according to claim 21, wherein the temperature of the heater that heats the photosensitive material 1 is set such that the surface temperature of the photosensitive material becomes high to prevent fogging.