JPH11194556A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent defective electrification caused by no toner feed in the outside region of the paper face printing region of a transfer material. SOLUTION: Printing (image formation) C is applied to a margin region B outside a printing region A in the main scanning direction (e) of a transfer material P, in so-called between paper sheets region where an image formed on a photosensitive drum is not transferred on the transfer material P, thus proper toner is fed in the margin region B. Even if a component contained in the transfer material P and causing defective electrification is stuck to the photosensitive drum, it is scraped by the fed toner, and the defective electrification in the margin region B outside the printing region A can be prevented over a long period without selecting the operating environment and the type of the transfer material P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which forms an image by an electrophotographic method.

[0002]

2. Description of the Related Art FIG. 18 is a schematic diagram showing an example of an image forming apparatus using a conventional electrophotographic system.

As shown in FIG. 1, a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 is driven to rotate, and its surface is uniformly charged by a charging roller 2 serving as a charging member. The exposure according to the input image signal is performed to form an electrostatic latent image. This electrostatic latent image is developed by the developing device 4 as a toner image. The toner image formed on the photosensitive drum 1 is transferred to the transfer material P conveyed at a predetermined timing.
Is transferred by a transfer roller 5 as a transfer member. The transfer material P to which the toner image has been transferred is conveyed to the fixing device 7, where the toner image is heated and pressed by the fixing device 7 to be fixed, and then output to the outside.

The transfer residual toner remaining on the photosensitive drum 1 after transferring the toner image is removed by a cleaning device 6.

Here, in the developing step of the electrostatic latent image in the developing device 4, a portion where the photosensitive drum 1 has been exposed is given a potential difference from other portions to thereby provide a potential difference.
The developing device 4 selectively selects the charged toner T as a developer.
Is transferred onto the photosensitive drum 1 to perform development. By this step, the toner T adheres to the exposed portion, and the toner T does not adhere to the unexposed portion.

However, in practice, the toner T is attracted to the unexposed portion because the charged polarity of the developer T is not all the same, and a very small amount of fog, which is originally called fog, also occurs in the white image portion And the toner T was uniformly attached, resulting in an image defect.

Incidentally, a transfer material P such as paper for transferring a toner image developed on the photosensitive drum 1 contains various additives for the purpose of bleaching or the like. Among the additives, some of the additives adhere to the photosensitive drum 1 and cause image defects while the transfer material P repeatedly contacts the photosensitive drum 1. This is because, since this additive is a substance having a relatively high water absorption, the surface of the photosensitive drum 1 is covered with moisture in a high humidity environment, and the resistance of the photosensitive drum 1 is reduced.
This is to disturb the distribution of electric charges on the photosensitive drum 1 formed by the latent image, and cause poor charging.

In order to suppress the occurrence of the charging failure, it is effective to apply a large amount of the toner T onto the photosensitive drum 1. At this time, the toner T In particular, when the level of poor charging is poor, particles having high polishing results are added to the toner T to prevent the occurrence of poor charging. I went.

[0009]

However, in the above-described conventional example, the area of the image formed on the transfer material P is not the entire area of the transfer material P but always has a margin on the peripheral end surface. Of these margins, for example, as shown in FIG.
In the image printing area (image area) A, the toner T of the printed image functions as the above-mentioned abrasive. For this reason, although the occurrence of the charging failure could be suppressed,
In an area (margin area) B from both ends of the image printing area A to the end of the paper with respect to the main scanning direction e of the laser light of the exposure device 3, the toner T reaching the photosensitive drum 1 is the developer T of the fog. Was only.

In recent years, fog has been reduced in order to obtain a good image due to the advancement of technology, and accordingly, poor charging such as image deletion has occurred in a blank area of the transfer material P in the main scanning direction. There was a problem of doing.

In recent years, the use environment of the image forming apparatus has been increased in a high humidity environment where the image forming apparatus was not used before, and further, the type of paper (transfer material) is liable to cause poor charging. In many cases, paper containing such components has been used as a transfer material, and the problem of poor charging has been increasing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing charging failure in a margin area outside an image printing area of a transfer material and performing stable image formation for a long period of time.

[0013]

According to the present invention, there is provided an image forming apparatus for forming an image by transferring a developer image formed on an electrophotographic photosensitive member to a transfer material. Before forming a developer image on the image printing area on the electrophotographic photosensitive member, or after transferring the developer image to the transfer material, outside the image printing area in the main scanning direction on the electrophotographic photosensitive member In which a developer image is formed.

A movable electrophotographic photosensitive member carrying an electrostatic latent image on a surface thereof; a charging means for charging the electrophotographic photosensitive member; and an exposure device for forming an electrostatic latent image on the electrophotographic photosensitive member. Means, a developing means for developing the electrostatic latent image to form a developer image, and a transfer means for transferring the developer image to a transfer material, the image forming apparatus, An image printing area and a developer image formed in an area outside the image printing area in the main scanning direction on the electrophotographic photosensitive member, respectively, and a white background in the developer image formed in an area outside the image printing area. The reflection density of the portion is set higher than the reflection density of a white background portion in the developer image formed in the image printing area.

Further, an area outside the image printing area is
Spot exposure is performed at intervals by the exposure means, and the reflection density of a white background portion in a developer image formed in an area outside the image printing region is determined by a white background portion in a developer image formed in the image printing region. Is higher than the reflection density.

Further, an area outside the image printing area is
Exposure is performed by the exposure unit with a weak light amount to the image printing area, and a developer that forms a reflection density of a white background portion in a developer image formed in an area outside the image printing area in the image printing area It is characterized in that the reflection density is higher than the reflection density of a white background portion in an image.

The developing means has a rotatable developing sleeve in which a developer having a magnetic material on its surface is constrained and a magnet roller is contained inside the developing means, and the electrophotographic photosensitive drum in a region outside the image printing region is provided. The magnitude of the magnetic force of the magnet roller with respect to the main scanning direction of the body is made smaller than the magnitude of the magnetic force in the image printing area, and the white background portion in the developer image formed in the area outside the image printing area is reduced. It is characterized in that the reflection density is higher than the reflection density of a white background portion in the developer image formed in the image printing area.

[0018] Further, the diameter of the magnet roller in a region outside the image printing region is smaller than the diameter of the magnet roller in the image printing region.

Further, the magnetic force pattern of the magnet roller in the area outside the image printing area is a pattern obtained by rotating the magnetic force pattern of the magnet roller in the image printing area.

The developing means has a rotatable developing sleeve having a developer confined on the surface thereof, and the developer on the developing sleeve performs non-contact development with the electrophotographic photosensitive member. The proximity distance from the electrophotographic photosensitive member to the developing sleeve in an area outside the image printing area is smaller than the proximity distance from the electrophotographic photosensitive member to the developing sleeve in the image printing area. Wherein the reflection density of a white background portion in a developer image formed in an area outside the image printing region is higher than the reflection density of a white background portion in a developer image formed in the image printing region. .

Further, the transfer efficiency of the transfer means in the area outside the image printing area is lower than the transfer efficiency of the transfer means in the image print area, and the transfer efficiency of the transfer means in the area outside the image print area is reduced. The reflection density of a white background portion in the developer image to be formed is made higher than the reflection density of a white background portion in the developer image formed in the image printing area.

Further, the transfer means is a transfer roller for pressing the electrophotographic photosensitive member against the electrophotographic photosensitive member to transfer a developer image on the electrophotographic photosensitive member onto a transfer material. The volume resistance of the transfer roller is smaller than the volume resistance of the transfer roller in the image printing area.

The transfer means is a corona transfer device for transferring a developer image on the electrophotographic photosensitive member onto a transfer material without contacting the electrophotographic photosensitive member. A shielding member is provided at a position corresponding to a region outside the image printing region between the photosensitive member and the photosensitive member.

Further, the transfer means is a transfer roller for pressing the electrophotographic photosensitive member against the electrophotographic photosensitive member to transfer a developer image on the electrophotographic photosensitive member onto a transfer material. The diameter of the transfer roller is smaller than the diameter of the transfer roller in the image printing area.

Further, the charging means is a contact charging means for contacting the electrophotographic photosensitive member and charging the electrophotographic photosensitive member, and is provided in contact with the contact charging means in a region outside the image printing area. Providing a cleaning member for cleaning the developer adhering on the contact charging means,
The reflection density of a white background portion in a developer image formed in an area outside the image printing region is set to be higher than the reflection density of a white background portion in a developer image formed in the image printing region.

(Operation) According to the structure of the present invention, the area outside the image printing area in the main scanning direction of the electrophotographic photosensitive member is performed during the process (between sheets) between the previous image formation and the next image formation. By forming a developer image on the image forming area, it is possible to prevent poor charging in an area outside the image printing area in the main scanning direction without affecting the developer image formed in the image printing area.

Further, according to the structure of the present invention, the reflection density of the white background in the developer image formed in the area outside the image printing area is determined by the reflection density of the white background in the developer image formed in the image printing area. By making the density higher than that, it is possible to prevent charging failure in a region outside the image printing region in the main scanning direction without affecting the developer image formed in the image printing region.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention. Note that the same members as those of the conventional image forming apparatus shown in FIG.

This image forming apparatus includes a photosensitive drum 1 as an image carrier. Around the photosensitive drum 1, a charging roller 2, an exposing device 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are provided. Photosensitive drum 1, charging roller 2, exposure device 3, developing device 4, transfer roller 5,
The cleaning device 6 is installed in the housing 8 and is integrated as a process cartridge, and is detachably attached to an apparatus main body (not shown).

The photosensitive drum 1 is a negatively charged organic photosensitive member in the present embodiment, has a photosensitive layer on a drum base (not shown) made of aluminum, and has an arrow at a predetermined peripheral speed (process speed). The charging roller 2 is driven to rotate in the direction a, and receives a uniform negative polarity charging process by the charging roller 2 during the rotation process.

The charging roller 2 comes into contact with the surface of the photosensitive drum 1 with a predetermined pressing force and is driven to rotate. The charging roller 2 applies a predetermined charging bias to the charging roller 2 from a charging bias power source (not shown). 1 is charged to a predetermined polarity and potential.

The exposure device 3 has a scanning optical system (not shown) using a semiconductor laser, and performs exposure L by laser light on the charged photosensitive drum 1 in accordance with input image information. An electrostatic latent image is formed by the difference between the solid potential of the exposed surface of the photosensitive drum 1 and the charged potential of the non-exposed portion.

The developing device 4 includes a fixed developing magnet 10
And a developing sleeve 9 containing the developing container 12.
The developer T is coated on the developing sleeve 9 and the toner T is adhered to the electrostatic latent image formed on the photosensitive drum 1 at the developing position and developed as a toner image (visualization). ). The coating pressure of the toner T carried on the developing sleeve 9 is regulated by the developing blade 11. A predetermined developing bias is applied to the developing sleeve 9 from a developing bias power supply (not shown).

The transfer roller 5 is rotated by being brought into contact with the surface of the photosensitive drum 1 with a predetermined pressing force, and is applied with a predetermined charging bias to the transfer roller 2 from a transfer bias power supply (not shown). The toner image on the surface of the photosensitive drum 1 is transferred onto a transfer material P conveyed to a transfer nip between the photosensitive drum 1 and the transfer drum 5.

The cleaning device 6 has a cleaning blade 13 fixed to a support member 14. The transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer is removed by the cleaning blade 13 and collected in the cleaning container 15. . Reference numeral 16 denotes a squeeze sheet.

Next, the image forming operation of the above-described image forming apparatus will be described.

At the time of image formation, the photosensitive drum 1 is driven to rotate at a predetermined process speed in a direction indicated by an arrow a by a driving means (not shown), and a negative polarity is applied by applying a charging bias from a charging roller 2 rotating in a direction indicated by an arrow b. Receive uniform charging.

Then, an exposure L by a laser beam is given from the exposure device 3 to the charged photosensitive drum 1 surface,
An electrostatic latent image is formed according to the input image signal. Then, the electrostatic latent image is developed by the developing sleeve 9 to which the developing bias is applied, and is visualized as a toner image.

When the toner image on the surface of the photosensitive drum 1 reaches the transfer nip between the transfer roller 5 and the photosensitive drum 1, the transfer material P is transported to the transfer nip at this timing, and a transfer bias is applied. Transfer roller 5
The toner image is transferred. The transfer material P to which the toner image has been transferred is conveyed to a fixing device (not shown), and the transferred toner image is fixed as a permanently fixed image on the transfer material P by heating and pressing by the fixing device and output.

On the other hand, the transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed by the cleaning blade 13 of the cleaning device 6 and collected in the cleaning container 15. Hereinafter, the above process is repeated in the same manner.

The size of the photosensitive drum (image carrier) 1, charging roller 2, developing roller 9, and transfer material (transfer paper) P in the main scanning direction e of the laser light emitted from the exposure device 3 of the image forming apparatus. (Width), an image printing area (hereinafter referred to as a printing area) A in the plane (developing area) of the transfer material (transfer paper) P, and an area (margin area) B from both ends of the printing area A to the end of the paper. Are as shown in FIG. In the present embodiment, the exposure device 3 can also perform exposure on a blank area B outside the image printing area A on the photosensitive drum 1.

As shown in this figure, the relationship between the size (width) of the photosensitive drum (image carrier) 1, charging roller 2, developing roller 9, and transfer material (transfer paper) P in the main scanning direction e is as follows.
The printing area A <the developing area (the width of the transfer material (transfer sheet) P) <the charging roller 2 <the photosensitive drum (image carrier) 1.

For this reason, in the blank area B on the photosensitive drum 1, the transfer material P makes a lot of contact. However, when an image is formed on the transfer material P, the toner T that has reached
The so-called fog toner T alone is very small.

Therefore, in the present embodiment, the toner image formed on the photosensitive drum 1 is transferred onto the transfer material P in the blank area B from the printing area (image area) A to the end of the paper. In this case, no image is formed on the photosensitive drum 1, but an image is formed in a so-called sheet interval in which the image formed on the photosensitive drum 1 is not transferred onto a transfer sheet. .

That is, as shown in FIG. 3, an image for transferring a print (image formation) C from the print area (image area) A to the margin area B from the end of the paper to the transfer material P at all times. It is performed before forming.

As described above, in the present embodiment, an appropriate amount of the toner T is always supplied even in the blank area B from the print area (image area) A to the edge of the paper on the photosensitive drum 1. Even if the component causing the charging failure contained in the transfer material P adheres to the photosensitive drum 1, the component is scraped off by the supplied toner T, and the use environment and the paper type of the transfer material P are selected. Not for a long time,
It is possible to prevent poor charging in the margin area B outside the printing area A.

The printing in the margin area B is determined by the sequence setting of the latent image and the applied voltage for development.
This may always be performed after an image to be transferred onto the transfer material P is formed.

The printing in the margin area B is not always performed every time an image is formed on one transfer material P.
Information obtained by a counter provided in the image forming apparatus, a paper sensor, a temperature / humidity sensor for examining a use environment state, and the like is processed, and printing is performed in a margin area B at an appropriate interval according to the condition. You may.

<Embodiment 2> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In this embodiment, as shown in FIG. 4, in addition to the exposure to the print area A, a blank area B where no image formation is performed from the print area A on the photosensitive drum 1 to the end of the paper is normally performed.
Then, a minute spot exposure D from the exposure device 3 is performed at intervals.

The diameter of the spot exposure D was 70 μm.
This is exposed one spot at a time in an area of 360 μm square on average, and the average area ratio of the exposed portion in the blank area B is about 3%. The amount of the toner T developed on the latent image in the spot exposure D and transferred onto the transfer material P is slightly lower than 3%. If the amount of the toner T is reduced to such an extent, the toner T can be attached to the photosensitive drum 1 without adversely affecting the image. Note that the interval of the spot exposure D is one spot in a 360 μm square area, but the positions are randomly arranged in the main scanning direction e, and the positions in the main scanning direction e when the exposure is repeated are performed. The average exposure amount is uniform.

In this embodiment, the reflection density in the blank area B is 2.3%, while the reflection density in the white background in the printing area A is 1% or less. The measured value of the reflection density in the margin area B is preferably 3% or less, though it depends on the size of one developed spot and its arrangement.

As described above, in the present embodiment, the minute spot exposure D is performed at an interval in the margin area B outside the printing area A on the photosensitive drum 1 so that the printing on the photosensitive drum 1 is performed. Even from the area A to the margin area B outside the area A, an appropriate amount of toner T is always supplied, so that even if a component causing a charging failure contained in the transfer material P adheres to the photosensitive drum 1, It is possible to prevent poor charging in the margin area B outside the print area A for a long time without being scraped off by the supplied toner T and selecting the use environment and the paper type of the transfer material P for a long time.

The minute spot exposure D on the margin area B is not always performed with a repetition cycle.
Information obtained by a counter provided in the image forming apparatus, a paper sensor, a temperature / humidity sensor for examining a use environment state, or the like is processed, and spot exposure is performed on the margin area B at appropriate intervals according to the conditions. It may be.

<Embodiment 3> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, the printing area A on the photosensitive drum 1 and the margin area B outside the area where no image is formed on the photosensitive drum 1 are more exposed than the laser light from the exposure device 3 in the printing area A. Exposure was performed uniformly with a weak light quantity. As shown in FIG. 5, the potential of the latent image on the photosensitive drum 1 in the present embodiment is −650 V in the printing area A, and the potential of the fully exposed black section in the printing area A is −1, as shown in FIG.
30 V, the potential of the blank area B is set to -640.
V, so that the toner T is slightly developed.

As described above, in the present embodiment, the print area A is set in the margin area B outside the print area A on the photosensitive drum 1.
By uniformly exposing with a light amount weaker than the exposure performed in step (1), an appropriate amount of toner T is always supplied even in the margin area B outside the printing area A on the photosensitive drum 1, so that the transfer material P Even if a component causing a charging failure contained in the photoreceptor drum 1 adheres to the photosensitive drum 1, the component is scraped off by the supplied toner T and can be used for a long time without selecting the use environment and the paper type of the transfer material P. Over the print area A
In the margin area B outside the area B can be prevented.

Exposure of the margin area B with a weak light amount is not always performed in a repetitive cycle. Instead, a counter provided in the image forming apparatus, a paper sensor, and a temperature / humidity sensor for checking a use environment state are used. For example, information obtained by such processing may be processed, and the margin area B may be exposed with a small amount of light at appropriate intervals according to the conditions.

As a method of reducing the amount of exposure light to the blank area B, electrical control may be performed. However, as shown in FIG. 6, laser light from the exposure device 3 to the blank area B of the photosensitive drum 1 is used. A filter 21 for reducing the amount of transmitted light is provided on the optical path of L, or a slit 2 for blocking light as shown in FIG.
For example, a part of the laser beam L may be cut by providing the laser beam L.

<Embodiment 4> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, the positions of the developing magnet 10 and the developing sleeve 9 of the developing device 4 with respect to the main scanning direction e of the laser light emitted from the exposure device 3 and the printing area in the plane of the transfer material P FIG. 8 shows the correlation between A and the blank area B from the print area A to the end of the sheet.

In this embodiment, the developing magnet 10
Is smaller in the area corresponding to the blank area B from the print area A to the edge of the paper than in the area corresponding to the print area A. As a result, the magnitude of the magnetic force on the developing sleeve 9 is reduced as shown in FIG.
The magnitude G2 of the magnetic force at the portion corresponding to the margin area B is larger than the magnitude G2 of the magnetic force at the portion corresponding to the print area A of 0.
Is smaller.

Since the force for holding the toner T on the developing sleeve 9 is the size of the magnetic pole facing the photosensitive drum 1 on the developing sleeve 9, the toner T on the developing sleeve 9 in the margin area B is Is weaker than the print area A, and so-called fogging occurs more than the white background portion of the print area A.

As described above, in the present embodiment, the size of the diameter of the developing magnet 10 in the blank area B is made smaller than the size of the diameter of the developing magnet 10 in the printing area A. Of the toner T on the developing sleeve 9 becomes weaker than the printing area A. Accordingly, even in the margin area B outside the printing area A on the photosensitive drum 1, the component causing the charging failure contained in the transfer material P is exposed by the appropriate supply of the toner T at all times. Even if it adheres to the drum 1, it is scraped off by the supplied toner T,
, It is possible to prevent poor charging in the blank area B outside the print area A for a long time without selecting the paper type.

<Embodiment 5> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, in the developing magnet 10 of the developing device 4, the magnetic force pattern G2 in the area corresponding to the blank area B outside the print area A is different from the magnetic force pattern G1 in the area corresponding to the print area A. I did it. That is, in the present embodiment, as shown in FIG. 10, the magnitude of the magnetic force of the developing magnet 10 facing the photosensitive drum 1 is small in an area corresponding to the margin area B outside the printing area A. In this figure, G1 is the magnitude of the magnetic force in the print area A, and G2 is the magnitude of the magnetic force in the margin area B.

As described above, in the present embodiment, the magnitude of the magnetic force of the developing magnet 10 facing the photosensitive drum 1 is
By making the area corresponding to the blank area B smaller than the area corresponding to the print area A, the binding force of the toner T on the developing sleeve 9 in the blank area B becomes weaker than that in the print area A. As a result, even in the margin area B outside the printing area A on the photosensitive drum 1, the appropriate toner T is always supplied, so that the component causing the charging failure contained in the transfer material P is exposed to light. Drum 1
Even if it adheres to the paper, it is scraped off by the supplied toner T, and the charging failure in the margin area B outside the printing area A is prevented for a long time without selecting the use environment and the paper type of the transfer material P. can do.

The developing magnet 10 according to the present embodiment
In FIG. 11, the magnetic force pattern G1 in the print area A and the magnetic force pattern G2 in the blank area B have different patterns. However, as shown in FIG. The same effect can be obtained only by performing the above operation.

<Embodiment 6> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, as shown in FIG.
The gap at a point close to the photosensitive drum 1 of the developing sleeve 9 of the developing device 4, which is kept constant by the pressure in the direction of the arrow f and the developing roller 9a, corresponds to the blank area B outside the printing area A. The area is different from the area corresponding to the print area A. That is, in FIG. 12, the gap K1 between the developing sleeve 9 and the photosensitive drum 1 in the area corresponding to the printing area A is 300 μm, while the gap K1 between the developing sleeve 9 and the photosensitive drum 1 in the area corresponding to the blank area B Photosensitive drum 1
The gap K2 between them is as narrow as 270 μm.

Therefore, the force for holding the toner T on the developing sleeve 9 is the size of the magnetic pole facing the photosensitive drum 1 on the developing sleeve 9, so that the force on the developing sleeve 9 in the margin area B is The binding force of the toner T is weaker than that of the print area A, and so-called fogging occurs more than the white area of the print area A.

As described above, in the present embodiment, the gap K2 between the developing sleeve 9 and the photosensitive drum 1 in the margin area B is larger than the gap K1 between the developing sleeve 9 and the photosensitive drum 1 in the printing area A. As a result, the binding force of the toner T on the developing sleeve 9 in the margin area B is weaker than in the printing area A. Accordingly, even in the margin area B outside the printing area A on the photosensitive drum 1, the component causing the charging failure contained in the transfer material P is exposed by the appropriate supply of the toner T at all times. Drum 1
Even if it adheres to the paper, it is scraped off by the supplied toner T, and the charging failure in the margin area B outside the printing area A is prevented for a long time without selecting the use environment and the paper type of the transfer material P. can do.

<Embodiment 7> This embodiment also uses an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, the transfer roller 5 does not have a uniform resistance value in all areas in the main scanning direction e, but has a margin outside the print area A as shown in FIG. The volume resistance value T2 corresponding to the area B
Has a smaller value than the resistance value T1 in the region corresponding to.

Therefore, the transfer efficiency of transferring the toner T on the photosensitive drum 1 to the transfer material P in the area corresponding to the blank area B of the transfer roller 5 of the present embodiment is higher than the transfer efficiency corresponding to the print area A. Will also be lower.

As described above, in this embodiment, the volume resistance value T2 of the transfer roller 5 corresponding to the blank area B is set to a value smaller than the resistance value T1 of the area corresponding to the print area A. Exposure and development in the region B are less likely to appear on the transfer material P, and a large amount of toner T can be supplied onto the photosensitive drum 1.

Therefore, in the margin area B outside the printing area A on the photosensitive drum 1, even if an appropriate amount of the toner T is supplied, the toner T is not transferred onto the transfer material P. In addition, it is possible to prevent poor charging in the margin area B outside the print area A for a long time without selecting the paper type of the transfer material P.

In this embodiment, the volume resistance value T in the area corresponding to the blank area B on the transfer roller 5 is set.
2 is smaller than the volume resistance value T1 in the area corresponding to the printing area A, but the purpose of the present embodiment is to perform improper transfer in the area corresponding to the margin area B on the transfer roller 5. The volume resistance value T1 of the transfer roller 5 at the portion corresponding to the print area A is usually set so that the most efficient transfer is performed. The volume resistance value T2 in the area corresponding to the blank area B may be high.

<Eighth Embodiment> FIG. 14 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment. In the present embodiment, a corona transfer unit 23 is used as a transfer unit,
Shielding member 24 between photosensitive drum 1 and corona transfer unit 23
Is provided. Other configurations and image forming operations are the same as those of the first embodiment shown in FIG.

As shown in FIG. 15, the shielding member 24 provided between the photosensitive drum 1 and the corona transfer unit 23 has a main scanning direction e.
Are provided at both ends (one end in the figure) of the corona transfer device 23, and this shielding member 24
The blank area B outside the print area A is shielded. The shielding member 24 prevents the toner T on the photosensitive drum 1 from being transferred onto the blank area B of the transfer material P.

As a result, exposure and development in the margin area B are less likely to appear on the transfer material P, and a large amount of toner T can be supplied onto the photosensitive drum 1.

Therefore, in the margin area B outside the printing area A on the photosensitive drum 1, even if an appropriate amount of the toner T is supplied, the toner T is not transferred onto the transfer material P. In addition, it is possible to prevent poor charging in the margin area B outside the print area A for a long time without selecting the paper type of the transfer material P.

The shielding member 24 is installed so as to always be located in the margin area B outside the printing area A according to the size of the transfer material P used.

<Embodiment 9> In this embodiment, an image forming apparatus having the same configuration as that of Embodiment 1 shown in FIG. 1 was used. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, as shown in FIG.
The diameter of the transfer roller 5 in the margin area B outside the printing area A of the transfer material P in the main scanning direction e is made smaller than the diameter in the printing area A. Therefore, the transfer roller 5
Thus, when an image is transferred from the photosensitive drum 1 onto the transfer material P, the pressing force of the transfer material P on the photosensitive drum 1 in the margin area B can be reduced.

As described above, in the present embodiment, the diameter of the margin area B outside the printing area A is made smaller than the diameter of the printing area A, so that the margin area B of the transfer material P Therefore, the component causing the charging failure contained in the transfer material P hardly adheres to the area corresponding to the blank area B of the photosensitive drum 1, and the use environment and the transfer It is possible to prevent poor charging in the margin area B outside the printing area A for a long time without selecting the paper type of the material P.

In the present embodiment, the purpose of the present embodiment is to reduce the pressing force of the transfer roller 5 on the photosensitive drum 1 in the area corresponding to the blank area B on the transfer roller 5. In addition, even when the diameter of the transfer roller 5 is uniform in the longitudinal direction, the hardness of the transfer roller 5 in a region corresponding to the blank region B on the transfer roller 5 is
Even if it is lower than the portion corresponding to the print area A,
Similar effects can be obtained.

<Embodiment 10> This embodiment is also similar to FIG.
An image forming apparatus having the same configuration as that of the first embodiment shown in FIG. The image forming operation is the same as in the first embodiment, and a description thereof will be omitted in the present embodiment.

In the present embodiment, as shown in FIG.
A cleaning member 25 is installed at both ends (one end in the figure) of the charging roller 2, and the cleaning member 25
An area corresponding to a margin area B outside the printing area A of the transfer material P of the charging roller 2 is cleaned. A margin area B on the charging roller 2 by the cleaning member 25
Can be removed.

As described above, according to the present embodiment, it is possible to prevent the toner from adhering to the area corresponding to the blank area B on the charging roller 2, so that the charging failure included in the transfer material P can be prevented. Becomes difficult to adhere to the area corresponding to the blank area B of the photosensitive drum 1 on the charging roller 2, and the printing area A can be used for a long period of time without selecting the use environment or the type of the transfer material P. In the margin area B outside the area B can be prevented.

[0092]

As described above, according to the first aspect, before forming a developer image on an image printing area on an electrophotographic photosensitive member or after transferring the developer image to a transfer material,
By forming the developer image in an area outside the image printing area in the main scanning direction of the electrophotographic photoreceptor, the image printing area in the main scanning direction is not affected without affecting the developer image formed in the image printing area. Since charging failure in the outer region can be prevented, a stable image can be obtained for a long period of time.

According to the second aspect of the present invention, the reflection density of the white background in the developer image formed in the area outside the image printing area is determined by the reflection density of the white background in the developer image formed in the image printing area. By making the density higher than that, it is possible to prevent charging failure in the area outside the image printing area in the main scanning direction without affecting the developer image formed in the image printing area. Images can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between image forming members in a longitudinal direction and a relationship between a print area and a blank area in a transfer material surface according to the first embodiment.

FIG. 3 is a diagram for describing printing in a margin area according to the first embodiment.

FIG. 4 is a diagram for explaining spot exposure on a blank area according to the second embodiment.

FIG. 5 is a diagram illustrating surface potentials in a print area and a margin area on a photosensitive drum according to a third embodiment.

FIG. 6 is a perspective view showing another configuration according to the third embodiment.

FIG. 7 is a perspective view showing another configuration according to the third embodiment.

FIG. 8 is a diagram showing a relationship between a developing magnet and a developing roller and a print area and a margin area in a transfer material surface according to a fourth embodiment.

FIG. 9 is a diagram showing a magnetic force pattern by a developing magnet according to a fourth embodiment.

FIG. 10 is a diagram showing a magnetic force pattern by a developing magnet according to a fifth embodiment.

FIG. 11 is a diagram showing another example of the magnetic force pattern by the developing magnet in the fifth embodiment.

FIG. 12 is a diagram illustrating a relationship between a developing sleeve and a print area and a margin area in a transfer material surface according to a sixth embodiment.

FIG. 13 is a diagram illustrating a relationship between a transfer roller and a print area and a margin area in a transfer material surface according to a seventh embodiment.

FIG. 14 is a schematic configuration diagram showing an image forming apparatus according to Embodiment 8 of the present invention.

FIG. 15 is a diagram illustrating a relationship between a shielding member of a corona charger and a print area and a margin area in a transfer material surface according to an eighth embodiment.

FIG. 16 is a diagram illustrating a relationship between a transfer roller and a print area and a blank area in a transfer material surface according to a ninth embodiment;

FIG. 17 is a diagram illustrating a relationship between a cleaning member of a charging roller and a print area and a margin area in a transfer material surface according to the tenth embodiment.

FIG. 18 is a schematic configuration diagram showing an image forming apparatus according to a conventional example.

FIG. 19 is a diagram illustrating a relationship between a photosensitive drum and a print area and a margin area in a transfer material surface according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (electrophotographic photosensitive body) 2 Charging roller (charging means) 3 Exposure device (exposure means) 4 Developing device (developing means) 5 Transfer roller (transfer means) 6 Cleaning device 9 Developing sleeve 10 Developing magnet 13 Cleaning blade 21 Filter 22 Slit 23 Corona transfer unit (transfer means) 24 Shielding member 25 Cleaning member A Print area B Margin area C Print on margin area B D Spot exposure G1 Magnetic force pattern in print area A G2 Magnetic force pattern in print area A T1 Volume resistance value in print area A T2 Volume resistance value in blank area B

Claims (13)

[Claims] 1. An image forming apparatus for forming an image by transferring a developer image formed on an electrophotographic photosensitive member to a transfer material, wherein a developer image is formed in an image printing area on the electrophotographic photosensitive member. Before forming, or after transferring the developer image to the transfer material, forming a developer image in an area outside the image printing area in the main scanning direction on the electrophotographic photosensitive member, Forming equipment. 2. A movable electrophotographic photosensitive member carrying an electrostatic latent image on a surface thereof, a charging means for charging the electrophotographic photosensitive member, and an exposure for forming an electrostatic latent image on the electrophotographic photosensitive member. Means, a developing means for developing the electrostatic latent image to form a developer image, and a transfer means for transferring the developer image to a transfer material, the image forming apparatus comprising: An image printing area and a developer image formed in an area outside the image printing area in the main scanning direction on the electrophotographic photosensitive member, respectively, and a white background in the developer image formed in an area outside the image printing area. An image forming apparatus, wherein the reflection density of the image forming area is higher than the reflection density of a white background in the developer image formed in the image printing area. 3. An area outside the image printing area is spot-exposed at intervals by the exposure means, and a reflection density of a white background portion in a developer image formed in an area outside the image printing area is determined. 3. The image forming apparatus according to claim 2, wherein the reflection density is higher than a reflection density of a white background portion in the developer image formed in the image printing area. 4. A white background in a developer image formed in an area outside the image printing area by exposing an area outside the image printing area with a light amount weaker than the image printing area by the exposure unit. The image forming apparatus according to claim 2, wherein a reflection density of the portion is set higher than a reflection density of a white background portion in the developer image formed in the image printing area. 5. The electrophotographic photosensitive member in a region outside the image printing area, wherein the developing means has a rotatable developing sleeve which restrains a developer having a magnetic material on a surface and includes a magnet roller inside. The magnitude of the magnetic force of the magnet roller with respect to the main scanning direction of the body is made smaller than the magnitude of the magnetic force in the image printing area, and the white background portion in the developer image formed in the area outside the image printing area is reduced. The image forming apparatus according to claim 2, wherein a reflection density is lower than a reflection density of a white background portion in the developer image formed in the image printing area. 6. The image forming apparatus according to claim 5, wherein a diameter of the magnet roller in an area outside the image printing area is smaller than a diameter of the magnet roller in the image printing area. 7. The image forming apparatus according to claim 5, wherein the magnetic force pattern of the magnet roller in an area outside the image printing area is a pattern obtained by rotating the magnetic force pattern of the magnet roller in the image printing area. apparatus. 8. The non-contact developing means, wherein the developing means has a rotatable developing sleeve whose surface is restrained with a developer, and the developer on the developing sleeve performs development without contacting the electrophotographic photosensitive member. The proximity distance from the electrophotographic photosensitive member to the developing sleeve in a region outside the image printing region is made smaller than the proximity distance from the electrophotographic photosensitive member to the developing sleeve in the image printing region. The reflection density of a white background portion in a developer image formed in an area outside the image printing area is made larger than the reflection density of a white background portion in a developer image formed in the image printing area. Image forming apparatus. 9. The image forming apparatus according to claim 1, wherein a transfer efficiency of the transfer unit in a region outside the image print region is lower than a transfer efficiency of the transfer unit in the image print region, and the transfer unit is formed in a region outside the image print region. The image forming apparatus according to claim 2, wherein a reflection density of a white background portion in the developer image to be formed is higher than a reflection density of a white background portion in the developer image formed in the image printing area. 10. The transfer unit is a transfer roller that presses against the electrophotographic photosensitive member to transfer a developer image on the electrophotographic photosensitive member onto a transfer material. The image forming apparatus according to claim 9, wherein a volume resistance value of the transfer roller is smaller than a volume resistance value of the transfer roller in the image printing area. 11. The corona transfer device for transferring a developer image on the electrophotographic photosensitive member onto a transfer material without contacting the electrophotographic photosensitive member, wherein the corona transfer device and the electrophotographic device The image forming apparatus according to claim 9, wherein a shielding member is provided at a position corresponding to a region outside the image printing region between the photosensitive member and the photosensitive member. 12. The image forming apparatus according to claim 1, wherein the transfer unit is a transfer roller that presses against the electrophotographic photosensitive member to transfer a developer image on the electrophotographic photosensitive member onto a transfer material. The image forming apparatus according to claim 9, wherein a diameter of the transfer roller is smaller than a diameter of the transfer roller in the image printing area. 13. The contact charging means for contacting the electrophotographic photosensitive member to charge the electrophotographic photosensitive member, and contacting the contact charging means in a region outside the image printing area. A cleaning member for cleaning the developer adhering to the contact charging means, and forming a reflection density of a white background portion in a developer image formed in an area outside the image printing area in the image printing area. The image forming apparatus according to claim 2, wherein the density is higher than a reflection density of a white background portion in the developer image.