JPH1195565A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of hardly causing a failure in transfer, even if a substance with low resistance generated by an electric discharge is stuck to the rear surface of a carrying/transferring belt, further, providing excellent cleanability for the surface of the carrying/ transferring belt and moreover, detecting/correcting a deviation in an image position caused by the fluctuations of temperature and humidity in environment where a device is installed, a changes with the lapse of time, etc., so as to minimize the deviation in the image position and stably obtain high image quality over a long period of time. SOLUTION: In the image forming device provided with plural photoreceptors 1Y, 1M, 1C and 1Bk and the carrying/transferring belt 9 which is arranged to face these photoreceptors and for sucking/carrying a transfer paper P, the inner peripheral side (rear surface) of the belt 9 is made rougher than the outer peripheral side (front surface) for sucking/carrying the transfer paper P. Further, in detail, the surface roughness Ra of the front surface of the belt 9 is set to be Ra<0.5 μm and the surface roughness Ra of the rear surface of the belt 9 is set to be 0.5 μm<=Ra<=5.0 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to an image forming apparatus for forming an image using an image carrier by an electrophotographic method, or a plurality of image carriers. The present invention relates to an image forming apparatus that forms a full-color image using a body.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a full-color image from four colors of yellow (Y), magenta (M), cyan (C), and black (Bk), when an image misregistration of each color occurs on a transfer paper, the image is shifted. In order to impair the quality, it is necessary to precisely superpose the four color toner images on the transfer paper.

In particular, a full-color image is formed by having photoconductors for each color of yellow (Y), magenta (M), cyan (C), and black (Bk), and sequentially transferring toner images of each color to transfer paper. In such a tandem type image forming apparatus, strict component accuracy and assembly accuracy are required to prevent image displacement. Even so, fine image position shifts occur due to temperature / humidity fluctuations in the installation environment of the apparatus, changes over time, and the like. For example, in Japanese Patent Application Laid-Open No. 6-106779, image position shifts between colors are detected and correction is performed. A technique for adjusting the position of each color image is disclosed.

In such an image forming apparatus, since the image misregistration detection pattern is formed on the transfer belt, if the cleaning of the transfer belt is insufficient, the toner remaining on the transfer belt causes the toner on the back of the transfer paper to be removed. Smears occur and degrade image quality. According to the technique described in Japanese Patent Application Laid-Open No. 9-68900, it is shown that good cleaning properties can be obtained by setting the surface roughness of the surface of the transfer belt and the average particle size of the toner in an appropriate relationship.

[0005] Such a transfer belt as a transfer means is often processed into a belt shape by joining sheet-like materials. Conventionally, the belt is formed on the outer peripheral surface side and the inner peripheral surface side of the belt. Generally, the surface roughness of a certain back surface is equivalent. Japanese Patent Application Laid-Open No. 9-15993 discloses that the surface roughness of the back surface of the transfer belt is increased. The purpose is to prevent abrasion and chatter, the purpose is different from the present invention, the surface roughness of the belt surface is not mentioned at all, and there is no description suggesting the operation and effect of the present invention described later. .

[0006]

However, in the tandem-type image forming apparatus as described above, when the transfer sheet is shifted with respect to the transfer belt during transfer of the transfer sheet by the transfer belt. Also, since the image position shift occurs, the transfer paper needs to be firmly electrostatically attracted to the transfer belt. Therefore, a dielectric material having high electric resistance is used as the material of the transfer belt. In a transfer belt having such a dielectric property, for example, low-resistance ozone or NOx generated by a transfer unit such as a corotron is used.
Such discharge products adhere to the back surface of the transfer belt, and these discharge products cannot be easily removed even if a cleaning member is provided, so that the surface resistance of the back surface of the transfer belt gradually decreases. If the surface resistance of the back surface of the transfer belt is reduced in this way, the charge provided by the transfer means is not retained and diffuses along the back surface of the belt, so that the charge escapes to the driving roller and the driven roller. In some cases, the image quality may be degraded due to the transfer or adversely affecting the transfer of other adjacent colors.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances and has been made in order to solve those problems. In particular, even if a low-resistance substance generated by discharge adheres to the rear surface of a transfer belt, transfer is performed. Defects are less likely to occur, and the surface of the transfer belt has good cleaning properties.Furthermore, it detects and corrects image misalignment caused by fluctuations in temperature and humidity in the installation environment of the device and changes over time, and corrects images. An object of the present invention is to provide an image forming apparatus capable of obtaining high image quality stably over a long period while minimizing positional deviation. In addition, it is an object of the present invention to provide an image forming apparatus having one image carrier and a transfer unit and having the above-described problems.

[0008]

In order to achieve the above-mentioned object, the present invention provides an image bearing member comprising: an image carrier;
An image forming apparatus having a transfer unit disposed to face the image carrier and supporting and transferring the transfer material, wherein the transfer unit has a surface roughness greater than the surface roughness of the outer peripheral surface of the transfer unit that supports the transfer material. Is characterized in that it is roughened on the inner peripheral side.

According to the first aspect of the present invention, the surface roughness of the inner peripheral surface side (hereinafter referred to as "back surface") of the transfer means is reduced by the surface roughness of the outer peripheral surface side (hereinafter referred to as "front surface") supporting the transfer material. By making the surface rougher than that, the contact area with the member disposed in contact with the back surface of the transfer unit is reduced, and the surface area per unit length is increased as compared with a case where the transfer unit is smooth. The effective surface resistance increases, and even if a low-resistance substance adheres to the back surface over time, it becomes difficult for the charge to escape. On the other hand, since the surface of the transfer means is smooth, the contact area with the transfer material is increased, and the transfer material is firmly
It can be securely carried and transported. Further, since the surface of the transfer means is smooth, the cleaning property is good.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the surface roughness Ra on the outer peripheral surface side is R
a <0.5 μm, and the surface roughness Ra on the inner peripheral surface side is 0.5 μm ≦ Ra ≦ 5.0 μm. The surface roughness of the back surface of the transfer means is the center line average roughness R
If the value of a exceeds 5.0 μm, the transfer electric field does not act uniformly, and a side effect of uneven transfer may occur.
By setting the surface roughness of the front surface and the back surface of the transport transfer unit in the above-described ranges by the center line average roughness Ra, a good image can be obtained without causing the above-mentioned side effects.

[0011] The invention according to claim 3 is the invention according to claim 1 or 2.
The image forming apparatus according to claim 1, further comprising a transfer unit configured to transfer a toner image formed on the image carrier to a transfer material on the transfer unit, wherein the transfer unit is configured to transfer the toner image onto the inner peripheral surface of the transfer unit. The contact transfer means is in contact with the contact transfer means.

According to the third aspect of the present invention, since the transfer means is of the contact transfer type, the amount of generated discharge products is greatly reduced as compared with the corona transfer type. Low resistance of the back surface of the transfer means is less likely to occur.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second or third aspect, the transport transfer unit is arranged to face the image carrier and transports the transfer material by suction. It is a belt.

According to the fourth aspect of the present invention, the surface roughness of the inner peripheral surface side (hereinafter referred to as “back surface”) of the transfer belt is reduced by the outer peripheral surface side (hereinafter referred to as “front surface”) supporting the transfer material. By making the surface rougher, the contact area with the drive roller and the driven roller arranged to come into contact with the back surface of the transfer belt is reduced, and the surface area per unit length is increased as compared to the case where the transfer belt is smooth. The effective surface resistance of the back surface of the transfer belt increases, and even if a low-resistance substance adheres to the back surface over time, it becomes difficult for charges to escape. On the other hand, since the surface of the transfer belt is smooth, the contact area with the transfer material is increased, and the transfer material can be firmly and surely adsorbed and carried to be transferred. Further, since the surface of the transfer belt is smooth, the cleaning property is improved.

If the surface roughness of the back surface of the transfer belt is more than 5.0 μm in center line average roughness Ra, the transfer electric field does not act evenly and a side effect of uneven transfer may occur. The surface roughness Ra of the surface of the transfer belt is set to Ra <0.5 μm, and the surface roughness Ra of the back surface is set to 0.5.
By setting ≦ Ra ≦ 5.0 μm, a good image can be obtained without causing the above-mentioned side effects.

The invention according to claim 5 is the invention according to claim 1 or 2.
The image forming apparatus according to the above, further comprising a plurality of the image carriers, wherein the transport transfer unit is a transport transfer belt that is disposed to face the plurality of image carriers and suctions and transports a transfer material. I do.

According to the fifth aspect of the present invention, the surface roughness of the back surface of the transfer belt is made larger than the surface roughness of the transfer belt. Since the contact area with the roller is reduced and the surface area per unit length is increased as compared to the case where the roller is smooth, the effective surface resistance of the back surface of the transfer belt is increased, and a low-resistance substance adheres to the back surface over time. Even if the charge is hard to escape. Similarly, other colors adjacent to each other are unlikely to have the above-described influence. On the other hand, since the surface of the transfer belt is smooth, the contact area with the transfer material is increased, and the transfer material can be firmly and surely adsorbed and carried to be transferred. Therefore, it is possible to prevent the transfer material from being shifted with respect to the transfer belt or the transfer material and the transfer belt from being shifted during transfer of the transfer material, thereby causing an image position shift. In addition, since the surface of the transfer belt is smooth, the cleaning property is improved.

Further, if the surface roughness of the back surface of the transfer belt is too rough with a center line average roughness Ra of more than 5.0 μm, the side effect of uneven transfer may not be obtained because the transfer electric field does not act uniformly. , Surface roughness Ra of the transfer belt surface
Is set to Ra <0.5 μm, and the surface roughness Ra of the back surface is set to 0.
By setting 5 μm ≦ Ra ≦ 5.0 μm, respectively,
Good images can be obtained without causing the above-mentioned side effects.

According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, there is provided transfer means for transferring the toner images formed on the plurality of image carriers to a transfer material on the transfer belt. The transfer unit is a contact transfer unit that is in contact with the inner peripheral surface of the transfer belt.

According to the sixth aspect of the present invention, since the transfer means is of the contact transfer type, the amount of generated discharge products is greatly reduced as compared with the corona transfer type. Low resistance of the back surface of the belt hardly occurs.

The invention according to claim 7 is the invention according to claim 5 or 6.
In the image forming apparatus described above, a position shift detecting unit that detects an image position shift detection pattern formed on the transfer belt, and the image on the transfer belt based on an output signal from the position shift unit Correction means for correcting the displacement; the transfer belt has a light-transmitting property; and the displacement detection means includes a light source and a light-receiving element opposed to each other across the transfer belt. It is characterized by being.

According to a seventh aspect of the present invention, an image misregistration detection pattern formed on a light-transmissive transfer belt is provided with a light source and a light-receiving element disposed to sandwich the transfer belt. The image position deviation is detected by the position deviation detection unit, and the image position deviation is corrected by well-known mechanical or electrical means in accordance with the position deviation detection unit, thereby minimizing the image position deviation caused by temperature fluctuation or temporal change. be able to.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention including embodiments with reference to the drawings (hereinafter, simply referred to as "embodiments").
Will be described. Throughout the embodiments and the like, components having the same function, shape, and the like are denoted by the same reference numerals, and description thereof is omitted as much as possible. Components that are configured as a pair and do not need to be specifically distinguished and described in the drawings will be replaced with the description by appropriately describing one of them for the sake of simplification of description.

FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 shows a schematic overall configuration of an image forming apparatus according to a first embodiment of the present invention and an operation during full-color image formation.

In FIG. 1, reference numeral 25 denotes the image forming apparatus according to the first embodiment, and reference numeral 26 denotes the image forming apparatus 25.
Are shown, respectively. In the apparatus main body 26 of the image forming apparatus 25, four photoconductors 1Y, 1
M, 1C, and 1Bk are arranged horizontally in this order from right to left in the figure. Each photoconductor 1Y, 1M,
1C and 1Bk include image forming units 22Y, 22M, 22C, and 22Bk for forming four-color images of yellow (Y), cyan (C), magenta (M), and black (Bk).
Is arranged. These image forming units 22Y and 22
A full-color image is formed by M, 22C, and 22Bk. Image forming units 22Y, 22M, 22C, 22B of each color
Since k has the same configuration and operation, only the yellow (Y) image forming unit 22Y disposed at the rightmost part will be described, and the other image forming units 2Y will be described.
For 2M, 22C, and 22Bk, the same parts are given the same Arabic numerals, and the letters representing the colors are added, so that the description is omitted.

The image forming section 22Y includes a drum-shaped photosensitive member 1
Y, and yellow (Y) disposed around the photoconductor 1Y.
The image forming apparatus includes a charging device 2Y, an exposure device 21Y, a developing device 3Y, a cleaning device 4Y, and the like for repeatedly forming an image.

The photoreceptor 1Y is disposed rotatably clockwise in FIG. The exposure device 21Y has a laser light scanning optical system including a laser diode (LD) (not shown) that generates and irradiates laser light in accordance with an image signal, and a polygon mirror 5 that scans the laser light emitted from this LD. I have.

Each of the image forming units 22Y, 22M, 22C, 2
In FIG. 1, the transfer paper P as an example of a transfer material is located below the arrangement positions of the photoconductors 1Y, 1M, 1C, and 1Bk of 2Bk.
A transfer belt 9 for adsorbing and transporting the paper is stretched to face each other. The transfer belt 9 is stretched between a driving roller 15 and a driven roller 17 to travel and convey in a counterclockwise direction.

As shown in detail in FIG. 2, the surface of the transfer transfer belt 9 has an outer peripheral surface whose surface roughness is within a range of Ra <0.5 μm in center line average roughness Ra, The surface roughness of the back surface is 0.5 μm ≦ in center line average roughness Ra.
It is formed by manufacturing means described later so as to satisfy the range of Ra ≦ 5.0 μm. As described above, the transport transfer belt 9 is greatly characterized in that the rear surface thereof is formed to be coarser than the surface roughness of the front surface of the transport transfer belt 9 that electrostatically attracts and carries and transports the transfer paper P. .

The transfer belt 9 is made of a material that transmits visible light, for example, polyethylene terephthalate resin (PET).
And a dielectric resin such as polyvinylidene fluoride resin (PVdF) or a material in which transparent conductive particles such as tin oxide are dispersed in these resins. The thickness of the transfer belt 9 is in the range of 30 to 300 μm, and more preferably 50 to 200 μm.

Means for making the surface roughness of the rear surface of the transfer belt 9 rough as described above include sandblasting one side of the sheet material before being processed into a belt shape, or JP-A-9-15993. As shown in the publication, it is of course possible to roughen one side during the process of forming the sheet of material. The manufacturing method for roughening the back surface of the transfer belt 9 described above is merely an example of the means for manufacturing the transfer belt 9 of the present invention, and is limited to these manufacturing methods. is not.

In FIG. 1, opposite to the photoconductors 1Y, 1M, 1C, and 1Bk, a transfer device 8 provided with a transfer roller as a contact transfer unit with a transfer belt 9 interposed therebetween.
Y, 8M, 8C, and 8Bk are provided. Each transfer device 8Y, 8M, 8C, 8Bk is provided with a corresponding one of the photoconductors 1Y, 1M, 1
It has a well-known function of transferring the toner images of the respective colors formed on C and 1Bk onto transfer paper P conveyed by being electrostatically attracted to and conveyed by the conveyance transfer belt 9 by the action of an electric field. The transfer paper P is
The sheet is fed onto the transfer belt 9 at a predetermined timing by a sheet feeding unit 19 provided at a lower portion of the apparatus main body 26.

The paper supply unit 19 includes a paper supply cassette 6 for stacking and storing the transfer papers P, and a transfer material supply roller disposed above the paper supply cassette 6 and for feeding the uppermost transfer papers P one by one. 2
0, and a pair of registration rollers 7 for sending out the transfer paper P fed by the transfer material supply roller 20 at a predetermined timing. A transfer material guide plate (not shown) is provided in a transfer material transport path between the transfer material supply roller 20 and the registration roller pair 7.

In FIG. 1, which is on the downstream side of the transfer material conveyance path, at the left side of the apparatus main body 26, a separation device 10 for separating the transfer paper P from the conveyance transfer belt 9 is provided via the conveyance transfer belt 9. It is provided to face the drive roller 15.
On the left side of the separation device 10, a fixing device 11 including a fixing roller and a pressure roller for fusing and pressing the toner images of each color transferred to the transfer paper P is further provided.
A pair of paper discharge rollers 24 is disposed above the paper discharge guide plate (not shown) via a paper discharge guide plate (not shown), and a lower right portion of the paper discharge roller pair 24 for discharging the transfer paper P on which the toner image is formed. Discharge trays (not shown) are provided respectively.

A position shift detection for detecting an image position shift detection pattern (not shown) formed on the transfer belt 9 is provided below the drive roller 15 on the downstream side in the rotational transfer direction of the transfer belt 9. A displacement detecting unit 18 having means is provided. The position shift detecting means includes a light emitting element 12 and a light receiving element 13 as light sources which are opposed to each other with the transfer belt 9 interposed therebetween. As the light emitting element 12, an LED (light emitting diode) or the like that generates, emits, and irradiates light in a visible light region is used.

The configuration of the displacement detecting unit 18 and the shape of the image displacement detecting pattern include, for example, those described in JP-A-6-106779.
This may be used. In addition, the image forming apparatus is configured such that the position shift detecting unit 18 described above uses the output signal (detection result) from the light receiving element 13 of the position shift detecting unit to detect
A well-known correction unit for correcting the image position deviation of each color on the transfer belt 9 is provided. This correction means is provided by the light-receiving element 1
Based on the output signal from the optical writing device 3, the writing start timing of each color in each of the exposure devices 2121Y, 21M, 21C, and 21D as the optical writing device is changed, or the mirror or lens in the optical path in each optical writing device is finely moved. And the like, which have a well-known configuration in which image position deviation is corrected by an electrical or mechanical correction unit (not shown).

Next, the operation at the time of forming a full-color image will be described with reference to FIGS. When a signal for full-color image formation is transmitted by a key operation of an operation panel (not shown) or the like, each of the image forming units 22Y and 22 for yellow (Y), cyan (C), magenta (M), and black (Bk) is transmitted.
M, 22C, and 22Bk operate at predetermined timings, and toner images of respective colors are formed on the photoconductors 1Y, 1M, 1C, and 1Bk. When this is exemplified in the image forming section 22Y, the photosensitive member 1Y rotates clockwise in FIG. 1, and the outer surface thereof is uniformly charged by the charging device 2Y, and then, in response to the image signal from the LD of the exposure device 3Y. Then, the laser beam is irradiated to form an image on the photoreceptor 1Y while being scanned by the polygon mirror 5, and an electrostatic latent image is formed. Then, when the photoconductor 1Y on which the electrostatic latent image is formed faces the developing device 3Y, toner is supplied and developed, and a yellow (Y) toner image is formed on the photoconductor 1Y.

In the image forming units 7M, 7C and 7Bk of other colors, toner images are formed in the same manner as in the image forming unit 22Y.

On the other hand, the transfer paper P set in the paper feed cassette 6 is taken out by the transfer material supply roller 20, sent to the registration roller pair 7 along the transfer material conveyance path, and then transferred by the registration roller pair 7. The leading end of the paper P is sent to the transfer unit of the photoconductor 1Y in time with the first color yellow (Y) toner image formed on the photoconductor 1Y.

At the first yellow (Y) toner image transfer position, the yellow (Y) toner image is transferred to the transfer paper P by the action of the electric field formed by the transfer device 8Y.
At the same time as the transfer is performed, the transfer paper P is electrostatically attracted to the transfer belt 9 and is transferred by the transfer belt 9. The transfer paper P on which the yellow (Y) toner image has been transferred in this manner is transferred to a transfer device 8 provided in order for each color.
M, 8C, 8Bk and the respective photoconductors 1M, 1C, 1Bk are sequentially conveyed to a transfer position between the photoconductors 1M, 1C, 1Bk.
The cyan (C) toner image, the magenta (M) toner image, and the black (Bk) toner image formed on the transfer paper P are sequentially transferred onto the transfer paper P. By transferring the toner images of all colors onto the transfer paper P in this manner, a full-color toner image is formed on the transfer paper P.

The transfer paper P on which the full-color toner image has been formed is separated from the transfer belt 9 by the separation device 10 and then sent to the fixing device 11, where the full-color toner image is fused and pressed by the fixing device 11. As a result, a full-color image is completed, and is discharged onto a discharge tray (not shown) via the discharge roller pair 24 of the discharge section 23.

On the other hand, the photoconductors 1Y, 1M, 1C and 1Bk after the transfer of the respective toner images are directly driven to rotate, and the residual toner and paper dust are cleaned by the cleaning devices 4Y, 4M, 4C and 4Bk. You.

Next, the operation for detecting the displacement of the image and correcting it will be described. In the tandem type image forming apparatus used in the first embodiment,
Even if you adjust the image registration for each color at the time of shipment,
Since a slight image position shift occurs due to a temperature change or a temporal change in the use environment, detection of the image position shift and its correction are required to obtain a good image over a long period of time.

Therefore, the detection of the image position deviation and the correction thereof are performed as follows when the power is turned on or at a predetermined required time. The photoconductors 1Y, 1M, 1C, and 1D of each color are uniformly charged by the charging devices 2Y, 2M, 2C, and 2D in the same manner as in image formation, and the exposure devices 2121Y, 21M, and 21C, which are optical writing devices, are used. 21D, an electrostatic latent image of an image misregistration detection pattern similar to that described in, for example, JP-A-6-106779
Y, 1M, 1C, and 1D, respectively, and are developed by the developing devices 3Y, 3M, 3C, and 3D. Thus,
The image misregistration detection patterns of the respective colors formed from the toner particles on the photoconductors 1Y, 1M, 1C, and 1D are sequentially transferred onto the transfer belt 9, and are rotationally conveyed by the transfer belt 9 to perform the misalignment. The detection unit 18 is reached. The image misregistration detection pattern of each color formed from the toner particles does not transmit visible light regardless of the color of the toner because light is scattered on the surface of the particles. Therefore, as described above, the image misregistration detection pattern is detected by the light receiving element 13 of the misregistration detection means arranged opposite to the conveyance transfer belt 9 therebetween. Then, based on the output signal from the light receiving element 13 of the position shift detecting means in the position shift detecting unit 18, the correcting means changes the writing start timing of each color, or a mirror in the optical path of each optical writing device. The image position shift is corrected by an electrical or mechanical correction method (not shown) such as fine movement of the lens or the lens.

On the other hand, the image misregistration detection pattern that has passed through the misregistration detecting section 18 is transmitted to the belt cleaning device 14.
As a result, the toner is removed from the transfer belt 9 and cleaned. At this time, since the surface of the transfer belt 9 is smooth as described above, the cleaning property is good, and each toner does not remain on the transfer belt 9.
The belt cleaning device 14 is in contact with the transfer belt 9 not only during the image position deviation detection operation but also during the image formation operation as described above, and the paper dust and toner adhering to the transfer belt 9 are removed. Remove and clean.

Here, with respect to the change with time when the tandem type image forming apparatus is continuously used, a transfer apparatus using a transfer roller as a contact transfer method in the first embodiment shown in FIGS. The black (Bk) transfer is performed between the image forming apparatus using the simple transfer belt 9 and the transfer apparatus using the corona transfer method shown in FIG. 4 and the conventional image forming apparatus using the conventional transfer belt 9 ′. A description will be given while taking the periphery of the part as an example and comparing appropriately.

The dielectric resin such as polyethylene terephthalate resin used for the transfer belts 9 ′ and 9 is a substance having a high electric resistance and a high surface resistance, and is used by each of the transfer devices 8 Bk and 28 Bk during use. The generated low-resistance discharge product gradually accumulates on the back surface of the transfer belt 9 and lowers the resistance to form the low-resistance layer 16. FIG.
As shown in the figure, when the conventional transfer belt 9 'is used, the back surface of the transfer belt 9' is smooth, so that the transfer belt 9 'and the driving roller 15 or a driven roller (not shown) And the contact resistance between the transfer belt 9 'and the driving roller 15 or the driven roller is low, so that the positive charge (positive charge) given by the transfer device 28Bk is applied to the smooth back surface of the transfer belt 9'. To spread the low-resistance layer 16 along the transfer device 28B.
Positive charges given by k escape to the driving roller 15 (or the driven roller), or adversely affect the transfer of other adjacent colors, thereby easily causing a problem of deteriorating image quality.

On the other hand, when a new transfer belt 9 as shown in FIG. 2 is used, the surface roughness Ra of the back surface of the transfer belt 9 is rough as described above. Since the roller 15 or the driven roller does not adhere, the contact resistance between the transfer belt 9 and the driving roller 15 or the driven roller increases, and the positive charge (plus charge) given by the transfer device 8Bk is transferred to the transfer belt. Since the low-resistance layer 16 flows along the uneven surface on the back surface of the transfer belt 9, the path to the drive roller 15 (or the driven roller) is longer than that in the case where the back surface of the transfer belt 9 ′ is smooth, and the effective transfer path is effective. Resistance increases, and the positive charge given by the transfer device 8Bk is hardly diffused.
It is less likely that the positive charge given by Bk escapes to the driving roller 15 (or the driven roller) or adversely affects the transfer of another adjacent color, thereby causing a problem of deteriorating the image quality.

In the first embodiment, transfer devices 8Y, 8M, 8C, 8C each having a transfer roller as a contact transfer unit are provided.
Since Bk is used and the contact transfer method is used, the amount of generated discharge products is significantly reduced as compared with the corona transfer method according to the second embodiment described later (the thickness of the low resistance layer 16 in FIG. 2). And the like, the transfer belt 9 for simplicity of illustration.
Is exaggerated with respect to the thickness of the transfer transfer belt 9 compared to the corona transfer method.

Note that the contact transfer means is not limited to the transfer roller of the first embodiment, and the same effects as those of the first embodiment can be obtained even when another contact transfer means such as a transfer brush or a transfer blade is used. Needless to say, this is obtained.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, instead of the transfer devices 8Y, 8M, 8C, and 8Bk of the image forming apparatus in the first embodiment, for example, a corona transfer type transfer device 28 having a corotron is used.
The only difference is that they have Y, 28M, 28C and 28Bk. FIG. 3 shows only the transfer device 28Bk around the black (Bk) transfer portion, the transport transfer belt 9, and the like.

According to the second embodiment, low-resistance discharge products such as ozone and NOx generated in the corona transfer type transfer devices 28Y, 28M, 28C and 28Bk accumulate on the back surface of the transfer belt 9, Since the surface resistance of the back surface of the transfer belt 9 is reduced, the remarkable effect when the transfer devices 8Y, 8M, 8C, and 8Bk are used in the first embodiment is the same as in the first embodiment. A similar effect is obtained.

Needless to say, the first and second embodiments can be applied to each tandem type image forming apparatus as described in the background art.

The transfer means of the present invention is not limited to the transfer belt 9 of the first and second embodiments described above, but is an example of the transfer means of the present invention.
The present invention is also applicable to a transfer drum 8 which is a recording material carrier shown in FIG. 1 and FIG. Incidentally, the transfer drum 8 described in the publication is made of the same material as the transfer belt 9 in the first and second embodiments.
For example, a dielectric resin film such as a polyethylene terephthalate resin (PET) or a polyvinylidene fluoride resin (PVdF) is formed into a drum shape by joining two rings in accordance with a frame connected by a connecting member, and is also transferred. As the means, the transfer charging means 4 or the contact type transfer charging member 80
Is used.

That is, the first and second image forming apparatuses according to the first to fourth aspects of the present invention, each having one image bearing member and a transfer / transfer means, are also provided. It will be apparent to those skilled in the art that the present invention can be easily applied according to the embodiments and the like.

As described above, the present invention has been described with respect to the specific embodiments including the examples.
The present invention is not limited to the above-described embodiments, and may be configured by appropriately combining them. Within the scope of the present invention, various embodiments and examples are described according to the necessity, purpose, application, and the like. It is obvious to those skilled in the art that the configuration can be made.

[0057]

As described above, according to the present invention, it is possible to provide an image forming apparatus which can solve the above-mentioned conventional problems. The specific effects of each claim are as follows. According to the first aspect of the present invention, the outer peripheral surface side (front surface) of the transport transfer unit that supports the transfer material.
By making the inner surface (rear surface) of the transfer unit rougher than the surface roughness of the transfer unit, the contact area with a member disposed in contact with the back surface of the transfer unit is reduced, and the surface is further smoothed. Since the surface area per unit length is greater than in the case, the effective surface resistance of the back surface of the transfer means is increased, and transfer failure is less likely to occur even if a low-resistance substance adheres to the back surface over time, and Since the surface of the transfer means is smooth, the contact area with the transfer material is increased, and the transfer material and the transfer means are not displaced during transfer of the transfer material. In addition, since the surface of the transfer unit is smooth and the cleaning property is improved, the back contamination of the transfer material by the toner adhered to the surface of the transfer unit can be prevented. Therefore, high image quality can be obtained over a long period.

According to the second aspect of the present invention, the surface roughness Ra of the outer peripheral surface (front surface) of the transfer means is less than 0.5 μm.
m, and the surface roughness Ra on the inner peripheral surface side (rear surface) is 0.1 mm.
When 5 μm ≦ Ra ≦ 5.0 μm, the surface roughness of the back surface of the transfer means is 5.0 μm in center line average roughness Ra.
When the surface roughness is too large, the transfer electric field does not act uniformly, and a side effect of uneven transfer may occur. However, the surface roughness of the front and back surfaces of the transfer means may fall within the above range by the center line average roughness Ra. By setting each, it is possible to prevent the above-mentioned side effects from occurring, and to obtain a better image over a long period of time.

According to the third aspect of the present invention, since the transfer means is a contact transfer means which is in contact with the inner peripheral side (back side) of the transfer means, the discharge product of the discharge product can be compared with the corona transfer method. Since the amount of generation is greatly reduced, it is difficult for the resistance of the back surface of the conveyance transfer unit to be reduced due to the adhesion of the discharge product, and a stable and high quality image can be obtained for a long period of time.

According to the fourth aspect of the present invention,
In the image forming apparatus described in the item 2 or 3, the transfer effect is achieved by the transfer transfer belt which is disposed to face the image carrier and adsorbs and transfers the transfer material.

The inner surface (back surface) of the transfer belt is made rougher than the outer surface (front surface) supporting the transfer material so as to contact the back surface of the transfer belt. The contact area with the drive roller and the driven roller arranged decreases, and the surface area per unit length increases as compared to the case where the roller is smooth. Even if a low-resistance substance adheres to the back surface, transfer defects are less likely to occur, and the surface of the transfer belt is smooth, so that the contact area with the transfer material increases, and the transfer material and the transfer transfer belt are separated. The occurrence of image position shift due to shift during conveyance is eliminated. Further, the cleaning property is improved by the smooth surface of the transfer belt, so that the back surface of the transfer material due to the toner adhered to the surface of the transfer belt can be prevented. Therefore, high image quality can be obtained over a long period.

If the surface roughness of the rear surface of the transfer belt is too coarse, with a center line average roughness Ra exceeding 5.0 μm, the transfer electric field does not work uniformly, and a side effect of uneven transfer may occur. The surface roughness Ra of the surface of the transfer belt is set to Ra <0.5 μm, and the surface roughness Ra of the back surface is set to 0.5.
By setting ≦ Ra ≦ 5.0 μm, it is possible to prevent the above-mentioned side effects from occurring, and to obtain a better image over a long period of time.

According to the fifth aspect of the present invention, the image forming apparatus includes a plurality of image carriers, and the transport transfer unit is a transport transfer belt that is arranged to face the plurality of image carriers and sucks and transports a transfer material. Thereby, the surface roughness of the back surface of the transfer belt is made larger than the surface roughness of the front surface, so that the contact area with the driving roller and the driven roller disposed to contact the back surface of the transfer belt is reduced, Further, since the surface area per unit length is increased as compared with the case where the surface is smooth, the effective surface resistance of the back surface of the transfer belt is increased, and even if a low-resistance substance adheres to the back surface over time, it becomes difficult for electric charges to escape. Similarly, other colors adjacent to each other are unlikely to have the above-described influence. On the other hand, since the surface of the transfer belt is smooth, the contact area with the transfer material is increased, and the transfer material can be firmly and surely adsorbed and carried to be transferred. Therefore, it is possible to prevent the transfer material from being shifted with respect to the transfer belt or the transfer material and the transfer belt from being shifted during transfer of the transfer material, thereby causing an image position shift. Further, since the surface of the transfer belt is smooth, the cleaning property is improved, so that the back surface of the transfer material due to the toner adhered to the surface of the transfer belt can be prevented. Therefore, high image quality can be obtained over a long period.

If the surface roughness of the back surface of the transfer belt is too coarse, with a center line average roughness Ra exceeding 5.0 μm, the transfer electric field does not act uniformly, and the side effect of uneven transfer may occur. The surface roughness Ra of the surface of the transfer belt is set to Ra <0.5 μm, and the surface roughness Ra of the back surface is set to 0.5.
By setting μm ≦ Ra ≦ 5.0 μm, it is possible to prevent the above-mentioned side effects from occurring, and to obtain a better image over a long period of time.

According to the sixth aspect of the present invention, since the transfer unit is a contact transfer unit that is in contact with the back surface of the transfer belt, the amount of generated discharge products is significantly reduced as compared with the corona transfer system. Therefore, it is difficult for the resistance of the back surface of the transport transfer belt to be reduced due to the adhesion of the discharge product, and stable high image quality can be obtained over a long period of time.

According to the seventh aspect of the present invention, a misregistration detecting means for detecting an image misregistration detection pattern formed on the conveyance transfer belt, and the conveyance transfer belt based on an output signal from the misregistration detection means. Correction means for correcting the above image position shift, the transport transfer belt has a light transmitting property, and the position shift detecting means includes a light source and a light receiving element which are opposed to each other with the transport transfer belt interposed therebetween. This allows the light receiving element to receive the light emitted and emitted from the light source disposed between the transfer belt and the image misalignment detection pattern formed on the transfer belt having optical transparency. , And mechanical and electrical correction means correct the image position deviation based on the output signal from the light receiving element, so that the image position deviation caused by temperature fluctuation, temporal change, etc. It can be suppressed to a small limited, it is possible to obtain a more stable image quality.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram when a full-color image is formed according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a main part in an exaggerated manner showing a surface roughness state of the front and back surfaces of the transport transfer belt and a state in which a low-resistance substance adheres to the rear surface of the transport transfer belt in the first embodiment. .

FIG. 3 is a schematic view of a main part in an exaggerated manner showing a surface roughness state of a front surface and a back surface of the transfer belt and a state where a low-resistance substance adheres to the back surface of the transfer belt in the second embodiment. .

FIG. 4 is a schematic view of a main part showing a state where a low-resistance substance adheres to the back surface of a conventional transfer belt.

[Explanation of symbols]

Reference Signs List 1Y, 1M, 1C, 1Bk Photoreceptor as image carrier 9 Conveyance transfer belt 8Y, 8M, 8C, 8Bk Transfer device with transfer roller as contact transfer means 12 Light emitting element as light source 13 Light receiving element 15 Drive roller 16 Low resistance layer 22Y, 22M, 22C, 22Bk Image forming unit 28Y, 28M, 28C, 28Bk Transfer device P Transfer paper as an example of transfer material

Claims (7)

[Claims] An image forming apparatus comprising: an image carrier; and a transfer unit arranged to face the image carrier and configured to support and transfer a transfer material, wherein an outer peripheral surface of the transfer unit that supports the transfer material is provided. An image forming apparatus characterized in that the inner surface of the transfer unit is made rougher than the surface roughness of the transfer device. 2. The image forming apparatus according to claim 1, wherein the surface roughness Ra on the outer peripheral surface side is Ra <0.5 μm, and the surface roughness Ra on the inner peripheral surface side is 0.5 μm ≦ Ra ≦.
An image forming apparatus having a thickness of 5.0 μm. 3. The image forming apparatus according to claim 1, further comprising a transfer unit that transfers the toner image formed on the image carrier to a transfer material on the transfer unit. An image forming apparatus, wherein the transfer unit is a contact transfer unit that is in contact with the inner peripheral surface of the transfer unit. 4. The image forming apparatus according to claim 1, wherein the transfer unit is a transfer belt that is arranged to face the image carrier and sucks and transfers a transfer material. Image forming apparatus. 5. The image forming apparatus according to claim 1, further comprising a plurality of said image carriers, wherein said transfer means is arranged to face said plurality of image carriers and adsorbs and transports a transfer material. An image forming apparatus comprising: 6. The image forming apparatus according to claim 5, further comprising a transfer unit that transfers the toner images formed on the plurality of image carriers to a transfer material on the transfer belt. An image forming apparatus comprising: a contact transfer unit that contacts the inner peripheral surface of the transfer belt. 7. An image forming apparatus according to claim 5, wherein a position shift detecting means for detecting an image position shift detecting pattern formed on said transport transfer belt, and an output signal from said position shift detecting means. Correction means for correcting the image position shift on the transfer belt based on the transfer transfer belt, wherein the transfer transfer belt has light transmissivity, and the position shift detection means is disposed opposite to the transfer transfer belt. An image forming apparatus comprising: a light source and a light receiving element.