JP2001188420A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent soiling of an intermediate transfer body and a secondary transfer roller due to a patch image on a photoreceptor drum formed for image density control. SOLUTION: In the image forming device provided with developing devices 53 to 55 for developing a latent image on the photoreceptor drum 51 with toner of negative polarity into toner images and an intermediate transfer body 50 onto which the toner image is transferred by having its surface electrified to positive polarity, a part corresponding to an image forming range of the photoreceptor drum 51 and a part corresponding to a non image forming range in the intermediate transfer body 50 are each made to be a paper passing range and a paper non passing range. When a non transfer toner image of negative polarity that is not transferred as the toner image to the intermediate transfer body 50, is formed the surface potential of at least a part corresponding to the patch image in the non paper passing range is electrified to the positive surface potential with a smaller absolute value than the surface potential of the positive polarity in the paper passing range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system or an electrostatic recording system such as a copying machine or a printer, and more particularly, to a method for converting a visible image formed on an image carrier into an intermediate image. The present invention relates to an image forming apparatus that transfers an image to a transfer body to form an image.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional color image forming apparatus provided with an intermediate transfer member. The color image forming apparatus of the present embodiment includes an intermediate transfer member 150 and a photosensitive drum adjacent to the intermediate transfer member 150. 151, a charging roller 157, laser scanning units 152,
Two developing units, namely, a yellow developing unit 153, a magenta developing unit 154, a cyan developing unit 155, a black developing unit 156, and a photosensitive drum cleaner 159 are provided.
1. Corona charger 158 and intermediate transfer member cleaner 16
0 is provided. The secondary transfer roller 161 and the intermediate transfer member cleaner 160 can be separated from and contacted with the intermediate transfer member 150. Further, a registration roller pair 163 is installed on the upstream side of the secondary transfer roller 161 in the recording material conveyance direction, and the fixing device 1 is installed on the downstream side of the corona charger 158 in the recording material conveyance direction.
62 are provided.

The intermediate transfer member 150 of this embodiment is formed as a hollow cylindrical member made of a resin sheet 170 as a transfer sheet, and a primary transfer roller 165 is provided inside the hollow member at a position facing the photosensitive drum 151. Secondary transfer roller 16
1 and a backup roller 167 at a position facing the intermediate transfer member cleaner 160, respectively. Further, the inner charger 180 and the outer charger 18 sandwich the resin sheet 170 therebetween.
1 are installed facing each other.

[0004] An image forming operation in the apparatus having the above configuration will be described.

First, prior to image formation, an intermediate transfer member 15 is formed.
The zero resin sheet 170 is uniformly charged by, for example, 4 kV by the inner charger 180 and the outer charger 181.

The surface of the photosensitive drum 151 is uniformly charged by the charging roller 157. A laser scanning unit 152 is provided for the uniformly charged photosensitive drum 151.
Irradiates a laser beam L based on image data output from a controller (not shown) to form a first-color electrostatic latent image on the surface of the photosensitive drum 151. This latent image is developed by, for example, a yellow developing unit 153 for the first color,
A first color yellow toner image is formed on the photosensitive drum 151.

The intermediate transfer member 151 also serves as a transfer means, and the yellow toner image on the photosensitive drum 151 is primarily transferred to the intermediate transfer member 150 by a transfer bias applied to a primary transfer roller 165 from a high-voltage power supply (not shown). Is done. The toner remaining on the photosensitive drum 151 without being transferred by this transfer is cleaned by the photosensitive drum cleaner 159.

Thereafter, in the same manner as described above, latent images are formed for the second, third, and fourth colors, and the respective latent images are developed by the corresponding magenta developing device 154, cyan developing device 155, and black developing device 156. The obtained magenta toner image, cyan toner image and black toner image are transferred onto the intermediate transfer member 150 in a superimposed manner, and a color in which four toner images of yellow, magenta, cyan and black are superimposed on the intermediate transfer member 150 Images are obtained.

In order to control the image density, the photosensitive drum 151 and the intermediate transfer member 150 are separated from each other during continuous image formation, and a patch image (non-transfer toner) of a fixed density is formed in a non-image forming area on the photosensitive drum 151. Image) is developed, the density of the patch image is read by a sensor (not shown), and the amount of toner is calculated based on the density by a CPU (not shown). And the image density is maintained constant.

The four color toner images formed on the intermediate transfer member 150 are supplied from a paper supply unit (not shown), and are timed by a pair of registration rollers 163.
The secondary transfer is collectively transferred onto the recording material 164 sent to the nip portion between the recording material 164 and the secondary transfer roller 161.

At this time, the secondary transfer roller 161 is brought into contact with the intermediate transfer member 150 immediately before the recording material 164 comes to the nip. At the time of this contact, the secondary transfer roller 161
, A transfer bias is applied from a high-voltage power supply (not shown),
As a result, the toner images of four colors are collectively transferred from the intermediate transfer member 150 to the recording material 164. Thereafter, the recording material 164 is subjected to a fixing process in a fixing device 162, and is discharged outside the apparatus.

After the completion of the transfer process, the intermediate transfer member 150 is replaced with an intermediate transfer member cleaner 160 and a backup roller 16.
7 is cleaned.

[0013]

However, in the above-mentioned conventional example, the patch image developed on the photosensitive drum 151 is electrostatically transferred onto the intermediate transfer body 150 by the potential difference between the patch image and the surface of the intermediate transfer body in the primary transfer section. And the intermediate transfer body 150 is stained, and further, the secondary transfer roller 161 and then the recording material 164 are stained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus for preventing contamination of an intermediate transfer member and a secondary transfer member due to a non-transferred toner image on an image carrier.

[0015]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image carrier on which a latent image is formed; developing means for developing the latent image on the image carrier with a negative polarity toner to form a toner image; and transferring the toner image by charging the surface to a positive polarity. In the image forming apparatus having the intermediate transfer member, a portion corresponding to the image forming region and a portion corresponding to the non-image forming region of the image carrier of the intermediate transfer member are respectively formed in a paper passing region and a non-passing region. When a non-transfer toner image having a negative polarity that is not transferred as a toner image on the intermediate transfer member is formed in a non-image forming region of the image carrier as a paper region, at least the non-transfer toner in the non-sheet passing region is formed. An image forming apparatus is characterized in that a surface potential of a portion corresponding to an image is charged to a plus surface potential having an absolute value smaller than a plus polarity surface potential in the paper passing area.

According to another aspect of the present invention, an image carrier on which a latent image is formed, developing means for developing the latent image on the image carrier with a negative polarity toner to form a toner image, An image forming apparatus having an intermediate transfer body on which the toner image is transferred by being charged to a positive polarity,
In the intermediate transfer member, a portion corresponding to the image forming region of the image carrier and a portion corresponding to the non-image forming region are defined as a paper passing region and a non-paper passing region, respectively. When a non-polarity non-transferred toner image that is not transferred as a toner image on the intermediate transfer body is formed in the area, the surface potential of at least a portion corresponding to the non-transferred toner image in the non-sheet passing area is set to the non-transferred area. An image forming apparatus is provided which is charged to a negative surface potential having the same polarity as a transfer toner image.

According to another aspect of the present invention, there is provided an image carrier on which a latent image is formed, and developing means for developing the latent image on the image carrier with a toner having a positive polarity to form a toner image.
In an image forming apparatus having an intermediate transfer member onto which the toner image is transferred by charging the surface to a negative polarity, a portion of the intermediate transfer member corresponding to an image forming area of the image carrier and a non-image A portion corresponding to the formation area is defined as a paper passing area and a non-paper passing area, respectively, and a non-transferred toner image having a positive polarity that is not transferred as a toner image on the intermediate transfer body is formed in a non-image forming area of the image carrier. In this case, the surface potential of at least the portion corresponding to the non-transferred toner image in the non-paper passing area is charged to a negative polarity surface potential having an absolute value smaller than the negative polarity surface potential in the paper passing area. An image forming apparatus is provided.

Further, according to another aspect of the present invention, there is provided an image carrier on which a latent image is formed, and developing means for developing the latent image on the image carrier with a toner having a positive polarity to form a toner image;
In an image forming apparatus having an intermediate transfer member onto which the toner image is transferred by charging the surface to a negative polarity, a portion of the intermediate transfer member corresponding to an image forming area of the image carrier and a non-image A portion corresponding to the formation area is defined as a paper passing area and a non-paper passing area, respectively, and a non-transferred toner image having a positive polarity that is not transferred as a toner image on the intermediate transfer body is formed in a non-image forming area of the image carrier. Wherein the surface potential of at least a portion of the non-sheet passing area corresponding to the non-transferred toner image is charged to a positive surface potential having the same polarity as the non-transferred toner image. Is provided.

In the above invention, it is preferable that the non-transferred toner is a patch image formed for adjusting an image density. According to another aspect, it is preferable that the non-transferred toner image is formed other than at the time of image formation.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

First, the image forming apparatus of this embodiment will be described with reference to FIGS. The image forming apparatus according to the present embodiment includes:
It has a configuration substantially similar to that of the conventional example, and includes a photosensitive drum 51 serving as an image carrier and an intermediate transfer member 50 adjacent to the photosensitive drum 51. Around the photosensitive drum 51, a charging roller 57, a laser scanning unit 52, and four Developing devices, that is, a yellow developing device 53, a magenta developing device 54, a cyan developing device 55, a black developing device 56, and a cleaner 59 are provided.
Around the intermediate transfer body 50, a transfer roller 61, a corona charger 58, and a cleaner 60 are provided. The transfer roller 61 and the cleaner 60 can be separated from and brought into contact with the intermediate transfer body 50. Further, a registration roller 63 is provided upstream of the secondary transfer roller 61 in the recording material transport direction, and a fixing device 62 is provided downstream of the corona charger 58 in the recording material transport direction.

FIG. 2 shows the structure of the intermediate transfer member 50. The intermediate transfer member 50 includes a pair of rings 68, 68, a connecting member 69 connecting the two rings, and a resin sheet 70 wound around an opening area thereof. As shown in FIG. At a position facing the primary transfer roller 65, a facing roller 66 is provided at a position facing the secondary transfer roller 61, and a backup roller 67 is provided at a position facing the cleaner 60. Further, the inner charger 80 and the outer charger 8 sandwich the resin sheet 70 therebetween.
1 are installed facing each other.

An image forming operation in the apparatus having the above configuration will be described.

First, prior to image formation, the resin sheet 70 of the intermediate transfer body 50 is charged with the inner charger 8 in order to initialize the potential of the resin sheet 70 charged during the previous image formation.
It is uniformly charged by 0 and the outer charger 81.

The surface of the photosensitive drum 51 is uniformly charged by the charging roller 57. A laser scanning unit 52 irradiates the uniformly charged photosensitive drum 51 with a laser beam L based on image data output from a controller (not shown) to form a first-color electrostatic latent image on the surface of the photosensitive drum 51. Form. This latent image is developed by the first color, for example, the yellow developing device 53, and a first color yellow toner image is formed on the photosensitive drum 51.

Next, the yellow toner image on the photosensitive drum 51 is transferred to the intermediate transfer body 50 by a transfer bias applied to a primary transfer roller (first transfer means) 65 from a high-voltage power supply (not shown) (1). Next transfer). The toner remaining on the photosensitive drum 51 without being transferred by this transfer is
The cleaning is performed by the cleaner 60.

Thereafter, in the same manner as described above, latent images are formed for the second, third, and fourth colors, and the respective latent images are developed by the corresponding magenta developing unit 54, cyan developing unit 55, and black developing unit 56. The obtained magenta toner image, cyan toner image and black toner image are superimposed and transferred on the intermediate transfer member 50, and yellow,
A color image is obtained in which four color toner images of magenta, cyan and black are superimposed.

In order to control the image density, the photosensitive drum 51 and the intermediate transfer member 50 are separated (450 μm in this embodiment) during continuous image formation, and a predetermined density is formed in a non-image forming area on the photosensitive drum 1. Of the patch image (test toner image), the density of the patch image is read by a sensor (not shown), and the amount of toner is determined based on the density.
The calculation is performed by a PU (not shown). If the calculation is insufficient, the toner is supplied to the developing devices 53 to 56, and the image density is maintained constant.

The four color toner images formed on the intermediate transfer body 50 are fed from a paper feed unit (not shown), and the nip between the intermediate transfer body 50 and the secondary transfer roller 61 is timed by a registration roller 63. (Secondary transfer nip), the image is collectively transferred onto paper 64 as a recording material (secondary transfer).

At this time, the secondary transfer roller 61 is brought into contact with the intermediate transfer member 50 immediately before the paper 64 comes to the nip portion. At the time of this contact, a transfer bias is applied to the secondary transfer roller (second transfer means) 61 from a high-voltage power supply (not shown), whereby the four-color toner images are transferred from the intermediate transfer body 50 to the paper 64 at a time. Is done.

Thereafter, the recording material 64 is subjected to a fixing process in a fixing device 62, and is discharged outside the apparatus. On the other hand, the intermediate transfer body 50 after the transfer step is cleaned by the action of the intermediate transfer body cleaner 60 and the backup roller 167.

Next, features of the present invention will be described.

Toner image (image density control patch image) formed at a position on photosensitive drum 51 not facing recording material 64
The present inventors have found that even when the surface of the photosensitive drum 51 and the surface of the intermediate transfer body 50 are separated from each other via an air layer, the airplane flies in the air layer and transfers to the intermediate transfer body 51. Have been observed in experiments.

Therefore, the potential difference between the patch image and the surface of the intermediate transfer member required for toner transfer with respect to the distance between the surface of the photosensitive drum 51 and the intermediate transfer member 50 was confirmed by experiments.

In the above experiment, the distance between the photosensitive drum 51 and the intermediate transfer member 50 was set to 0 using the image forming apparatus of this embodiment.
The measurement was performed by changing the potential between the patch image required for toner transfer and the surface of the intermediate transfer member corresponding to the change every 50 μm between 500 μm and 500 μm.

The results are shown in Table 1 below.

[0038]

[Table 1] From Table 1, for example, as in this embodiment, the photosensitive drum 51
When the distance between the intermediate transfer member 50 and the intermediate transfer member 50 is 450 μm, the potential difference between the patch image necessary for toner transfer and the surface of the intermediate transfer member is 3.5 kV.

FIG. 3 shows the surface potential of the intermediate transfer member at the start of image formation in this embodiment and the surface potential of the intermediate transfer member in the conventional example.

In the above-described conventional example, as shown by the broken line in FIG. 3, the intermediate transfer member, that is, the transfer sheet 70 was uniformly charged to 4 kV prior to image formation. In the example, in the charging of the intermediate transfer member 150 performed prior to image formation, by controlling the inner charger 80 and the outer charger 81, as shown by the solid line in FIG. 51 recording materials 6
The surface potential of the region formed opposite to the image formed at a position not opposed to No. 4, ie, the image density control patch image, is 3 kV in comparison with the surface potential (4 kV) of the other region of the intermediate transfer body 50.
It is charged to a low 1 kV. On the other hand, the surface potential of the patch image for image density control on the photosensitive drum 51 is about -2 kV. That is, the surface potential difference between the patch image and the corresponding intermediate transfer member is 3 kV.

In this embodiment, this value is determined with a sufficient margin based on the experimental results shown in Table 1 because the photosensitive drum 51 and the intermediate transfer member 50 are separated from each other by about 450 μm at the time of forming a patch image. It is a thing.

With the above arrangement, the potential difference between the patch image for image density control and the surface of the intermediate transfer member is reduced, and the phenomenon in which the patch image for image density control electrostatically adheres to the surface of the intermediate transfer member 50 can be prevented. The patch image developed on the photosensitive drum 51, which is a conventional problem, is electrostatically attracted onto the intermediate transfer body 50 by the potential difference between the patch image and the surface of the intermediate transfer body in the transfer unit, and the intermediate transfer body 50 This solves the problem of soiling and further soiling the secondary transfer roller 61 and the recording material 64.

It is desirable that the surface of the intermediate transfer member 50 is charged to the same polarity as the image density control patch image on the photosensitive drum 51 (for example, -1 kV). This is because an electric repulsion acts between the patch image for image density control and the surface of the intermediate transfer member. As a result, the potential difference between the patch image for image density control and the surface of the intermediate transfer member is reduced, and the phenomenon that the patch image for image density control is electrostatically attached to the transfer sheet surface can be prevented. It is possible to solve the contamination of the intermediate transfer member, the secondary transfer roller, and the recording material.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIGS.

The image forming apparatus of this embodiment has substantially the same structure as that of the first embodiment, but has an endless belt made of a resin sheet stretched over a plurality of rollers 65, 66, 67 as an intermediate transfer member. (Hereinafter, referred to as an “intermediate transfer belt”) 250. The rollers 65, 66 and 67 are the same as those described in the first embodiment.
They correspond to the next transfer roller 65, the opposing roller 66, and the backup roller 67, respectively.

Further, the configuration of the present embodiment is more suitable for a more compact apparatus since the arrangement of the intermediate transfer belt as the intermediate transfer member is more flexible than the image forming apparatus of the first embodiment.

The operation of the image forming apparatus according to this embodiment is substantially the same as that described in the first embodiment.
Here, a description will be omitted, and a characteristic portion relating to charging of the intermediate transfer belt performed prior to image formation will be described below.

In the conventional example, prior to image formation, the intermediate transfer member was uniformly charged to 4 kV. However, in the present embodiment, by controlling the inner charger 80 and the outer charger 81 in charging the intermediate transfer belt 250 prior to image formation, the intermediate transfer belt 250 is charged as shown by the solid line in FIG. The photosensitive drum 5 of the belt 250
The surface potential of an image formed at a position not opposed to the first recording material, that is, an area opposed to the image density control patch image is:
The intermediate transfer belt 250 is charged to 0 kV, which is 4 kV lower than the surface potential in other areas. The surface potential of the image density control patch image on the photosensitive drum 51 is charged to about -2 kV. That is, the surface potential difference between the patch image and the intermediate transfer belt 250 corresponding to the patch image is 4 kV. In this embodiment, this value is
When forming a patch image, the photosensitive drum 51 and the intermediate transfer belt 2
Since the reference numerals 50 are separated from each other by about 300 μm, they are determined with a sufficient margin based on the experimental results shown in Table 1 above.

As a result, the potential difference between the patch image for image density control and the surface of the intermediate transfer belt 250 is reduced, and the phenomenon that the patch image for image density control is electrostatically attached to the surface of the intermediate transfer belt 250 is prevented. The patch image developed on the photosensitive drum 51, which has been a problem in the related art, is electrostatically attracted to the intermediate transfer belt 250 by the potential difference between the patch image and the surface of the intermediate transfer belt in the transfer unit, and the intermediate transfer belt 250 This can solve the problem that the recording material is stained and the recording material is stained.

As described in the first embodiment, it is desirable that the intermediate transfer belt 250 is charged to the same polarity as the image density control patch image on the photosensitive drum 51 (for example, -1 kV). This is because an electric repulsion acts between the intermediate transfer belt and the surface of the intermediate transfer belt. This reduces the potential difference between the image density control patch image and the surface of the intermediate transfer belt, thereby preventing the image density control patch from electrostatically adhering to the intermediate transfer belt surface. The dirt on the intermediate transfer belt which was caused was able to be solved.

Embodiment 3 Next, a third embodiment of the present invention will be described.

In this embodiment, in the image forming apparatus of the second embodiment, a sequence for independently forming an image density control patch image on a photosensitive drum other than at the time of image formation is adopted.

In this embodiment, the same effect as in the second embodiment can be obtained.

In the above embodiment, the potential of the patch image for image density adjustment has a negative polarity, but the same effect can be obtained when the potential is positive.

In the above embodiment, a patch image for adjusting image density is used as a non-transferred toner image. However, similar effects can be obtained when the image is formed for other purposes.

[0056]

As is apparent from the above description, according to the image forming apparatus of the present invention, the non-transferred toner image formed in the non-image forming area of the image carrier is brought into contact with the image carrier at the transfer section. The non-transferred toner image is transferred to the intermediate transfer body by reducing the surface potential difference between the surface of the intermediate transfer body and the portion corresponding to the non-transferred toner image, or by giving a potential of the opposite polarity. It is difficult to perform the transfer, or it is possible to prevent the transfer, so that it is possible to prevent the intermediate transfer member from being stained and the secondary transfer unit from being stained. Therefore, the stain on the recording material can be prevented, and a high-quality image 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 perspective view showing an intermediate transfer member in the image forming apparatus of FIG.

FIG. 3 is an explanatory diagram showing a surface potential of a transfer sheet in a conventional example and a first embodiment.

FIG. 4 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment.

FIG. 5 is an explanatory diagram showing a surface potential of a transfer sheet in a conventional example and a second embodiment.

FIG. 6 is a schematic configuration diagram illustrating an example of an image forming apparatus provided with a conventional intermediate transfer member.

[Explanation of symbols]

50, 250 Intermediate transfer member 51 Photosensitive drum (image carrier) 53 Yellow toner developing device (developing device) 54 Magenta toner developing device (developing device) 55 Cyan toner developing device (developing device) 56 Black toner developing device (developing device)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takao Ogata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masahiro Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Koichi Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) 2H027 DA10 EA01 EA03 EB04 EC03 ED03 ED24 EF12 ZA07 2H032 AA05 AA15 BA05 BA08 BA09 BA11 BA23 BA26 BA30 CA02 CA12 DA03

Claims (6)

[Claims] An image carrier on which a latent image is formed; developing means for developing the latent image on the image carrier with a negative polarity toner to form a toner image; An image forming apparatus having an intermediate transfer member onto which a toner image is transferred, wherein a portion of the intermediate transfer member corresponding to an image forming region of the image carrier and a portion corresponding to a non-image forming region are respectively passed. When a non-transferred toner image having a negative polarity that is not transferred as a toner image on the intermediate transfer member is formed in a non-image forming area of the image carrier, a non-paper passing area is defined as a paper area and a non-paper passing area. An image forming apparatus configured to charge at least a surface potential of a portion corresponding to the non-transferred toner image to a positive surface potential having an absolute value smaller than a positive polarity surface potential in the paper passing area. . 2. An image carrier on which a latent image is formed; developing means for developing the latent image on the image carrier with a negative polarity toner to form a toner image; An image forming apparatus having an intermediate transfer member onto which a toner image is transferred, wherein a portion of the intermediate transfer member corresponding to an image forming region of the image carrier and a portion corresponding to a non-image forming region are respectively passed. When a non-transferred toner image having a negative polarity that is not transferred as a toner image on the intermediate transfer member is formed in a non-image forming area of the image carrier, a non-paper passing area is defined as a paper area and a non-paper passing area. An image forming apparatus, wherein at least a surface potential of a portion corresponding to the non-transferred toner image is charged to a negative surface potential having the same polarity as the non-transferred toner image. 3. An image carrier on which a latent image is formed, developing means for developing the latent image on the image carrier with a toner having a positive polarity to form a toner image, and charging the surface to a negative polarity to form the toner image. An image forming apparatus having an intermediate transfer member onto which a toner image is transferred, wherein a portion of the intermediate transfer member corresponding to an image forming region of the image carrier and a portion corresponding to a non-image forming region are respectively passed. When a non-transferred toner image having a positive polarity that is not transferred as a toner image on the intermediate transfer body is formed in a non-image forming area of the image carrier, the non-paper passing area is defined as a paper area and a non-paper passing area. At least a surface potential of a portion corresponding to the non-transferred toner image is charged to a negative polarity surface potential having an absolute value smaller than a negative polarity surface potential in the paper passing area. Forming apparatus. 4. An image carrier on which a latent image is formed, developing means for developing the latent image on the image carrier with a toner having a positive polarity to form a toner image, and charging the surface to a negative polarity to form the toner image. An image forming apparatus having an intermediate transfer member onto which a toner image is transferred, wherein a portion of the intermediate transfer member corresponding to an image forming region of the image carrier and a portion corresponding to a non-image forming region are respectively passed. When a non-transferred toner image having a positive polarity that is not transferred as a toner image on the intermediate transfer body is formed in a non-image forming area of the image carrier, the non-paper passing area is defined as a paper area and a non-paper passing area. An image forming apparatus, wherein at least a surface potential of a portion corresponding to the non-transferred toner image is charged to a positive surface potential having the same polarity as the non-transferred toner image. 5. The image forming apparatus according to claim 1, wherein the non-transferred toner is a patch image formed for adjusting an image density. 6. The image forming apparatus according to claim 1, wherein the non-transferred toner image is formed other than when the image is formed.