JP3695138B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a facsimile, or a copying machine that forms an image using electrophotographic technology. In particular, the present invention relates to the intermediate transfer member.
[0002]
[Prior art]
In general, an image forming apparatus using an electrophotographic technique includes a photosensitive member having a photosensitive layer on the outer peripheral surface of a conductive layer, a charging unit that uniformly charges the photosensitive layer of the photosensitive member, and the charging unit uniformly. An exposure unit that selectively exposes the charged photosensitive layer to form an electrostatic latent image, and a toner that is a developer is applied to the electrostatic latent image formed by the exposure unit to form a visible image (toner And a transfer device for transferring the toner image developed by the developing means onto a recording medium such as paper.
[0003]
As a transfer device for transferring the toner image developed on the photoconductor to a recording medium such as paper, conventionally, the toner image formed on the photoconductor is transferred (primary transfer), and this toner image is further recorded. One having an intermediate transfer body that transfers (secondary transfer) to a medium is known.
[0004]
FIGS. 5A and 5B are views showing an example of an image forming apparatus provided with such an intermediate transfer member, in which FIG. 5A is a schematic perspective view, and FIG. 5B is a partial cross-sectional view along line bb in FIG.
[0005]
In the figure, reference numeral 1 denotes a photoreceptor, which has a conductive layer 1a and a photosensitive layer 1b formed on the conductive layer 1a. The conductive layer 1a is grounded.
[0006]
Reference numeral 2 denotes an intermediate transfer member, which is composed of a dielectric (medium resistance layer) having a resistance value of about 10 ⁷ to 10 ¹⁴ Ωcm, for example. Such an intermediate transfer member 2 can be prepared by kneading conductive carbon in a synthetic resin or the like.
[0007]
The intermediate transfer member 2 is in contact with the photosensitive member 1 at least during image formation, and the contact portion T1 forms a transfer portion (in this case, a primary transfer portion). A primary transfer roller 3 is disposed from the inner side of the intermediate transfer body 2 in the primary transfer portion T1, and a primary transfer voltage is applied to the intermediate transfer medium 2 by the primary transfer roller 3.
[0008]
Further, a secondary transfer roller 4 for applying a secondary transfer voltage is pressed against the intermediate transfer body 2, and the pressure contact portion forms a secondary transfer portion T <b> 2. A backup roller 5 is disposed from the inner side of the intermediate transfer body 2 in the secondary transfer portion T2.
[0009]
At the time of image formation, first, the photosensitive member 1 and the intermediate transfer member 2 are driven to rotate, and the photosensitive layer 1b of the photosensitive member 1 is uniformly charged by a charging unit (not shown), and then an exposure unit (not shown). To selectively form an electrostatic latent image. Next, a toner as a developer is applied to the electrostatic latent image by developing means (not shown) to become a visible image (toner image), and this toner image is transferred onto the intermediate transfer body 2 at the primary transfer portion T1. Then, in the secondary transfer portion T2, the image is transferred to a recording medium such as paper supplied to the secondary transfer portion T2.
[0010]
The recording medium onto which the toner image has been transferred passes through a fixing device (not shown) to fix the toner image.
[0011]
[Problems to be solved by the invention]
The intermediate transfer body 2 in the conventional image forming apparatus described above has a single layer structure formed by kneading conductive particles such as conductive carbon in a synthetic resin or the like, and the conductive particles are uniform in the resin. It was difficult to disperse in the film, and the resistance value was likely to be uneven.
[0012]
Therefore, there is a problem that unevenness is easily generated in the electric field in the transfer portion, and as a result, transfer unevenness is easily generated.
[0013]
In addition, local protrusions on the surface of the intermediate transfer member due to gelling components in the resin and aggregates of conductive particles are likely to occur, and therefore, the contact portion between the photosensitive member and the intermediate transfer member, the intermediate transfer member, and the back surface thereof. At the abutting portion with the arranged roller, the abutting becomes locally unstable, and there is a problem that transfer unevenness is likely to occur.
[0014]
An object of the present invention is to provide an image forming apparatus that solves the above-described problems, is less likely to cause uneven transfer, and can form a good image.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1, wherein a transfer part is formed between a photoreceptor on which an image is formed on the surface of the photosensitive layer formed on the conductive layer and the surface of the photoreceptor. An image forming apparatus having an intermediate transfer member to which the image is transferred in the transfer unit,
The intermediate transfer member is formed on the conductive layer, a resistance layer formed on the conductive layer, and the image is transferred. The intermediate transfer member is exposed on the surface of the end of the intermediate transfer member and supplies a transfer voltage to the conductive layer. And having an electrode part,
The gap between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member in the transfer portion is 20 μm or more, and a gap member for forming the gap includes the end portion of the photosensitive member, the electrode portion, And the gap member has a width that completely covers the surface of the electrode portion in the transfer portion .
[0017]
The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1 , wherein the gap member is made of a material having a resistance value higher than that of the resistance layer of the intermediate transfer medium. .
[0018]
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect , the gap member is made of an insulating material.
[0019]
[Function and effect]
The image forming apparatus according to claim 1, wherein a transfer portion is formed between a photoreceptor on which an image is formed on the surface of the photosensitive layer formed on the conductive layer and the surface of the photoreceptor, and the transfer portion includes the transfer portion. And the intermediate transfer member to which the image is transferred, the image formed on the surface of the photosensitive member is transferred to the intermediate transfer member in the transfer portion.
[0020]
The intermediate transfer member has a multilayer structure including a conductive layer and a resistance layer formed on the conductive layer to which the image is transferred. For example, the resistance layer disperses conductive particles. It is possible to form by applying the cured resin solution, curing and drying. Thus, when conductive particles are dispersed in a resin solution in which a resin is dissolved in a solvent, the dispersibility of the conductive particles becomes better than when conductive particles are kneaded in a heat-melted resin. . Therefore, resistance unevenness of the resistance layer itself can be made difficult to occur. In addition, since the dispersibility of the conductive particles becomes good, local protrusions on the surface of the resistance layer can be hardly generated, and it is possible to stabilize the contact with the photoconductor and prevent transfer defects. It becomes.
[0021]
In addition, since the resistance layer is integrally formed on the conductive layer, when a transfer voltage is supplied to the conductive layer by the electrode portion, the potential on the back side of the resistance layer becomes substantially uniform, and over the entire transfer region. A substantially uniform transfer electric field is formed.
[0022]
Therefore, according to the image forming apparatus of the first aspect, unevenness is hardly generated in the electric field in the transfer portion, and as a result, a good image with little transfer unevenness can be formed.
[0023]
In addition, since the electrode portion for supplying the transfer voltage to the conductive layer is exposed on the surface of the end portion of the intermediate transfer member, the transfer voltage can be easily supplied to the conductive layer.
[0024]
By the way, the intermediate transfer member is configured as described above, that is, a resistance layer is formed on the conductive layer, and an electrode portion for supplying a transfer voltage to the conductive layer is exposed on the surface of the end portion of the intermediate transfer member. It has been found that the following problems occur with this configuration.
[0025]
As shown in FIG. 6A, a pinhole 1c may exist in the photosensitive layer 1b of the photoreceptor 1, and the pinhole 1c exists at the end of the photoreceptor 1 as shown. There is.
[0026]
In such a situation, as shown in FIG. 6B, the structure of the intermediate transfer member 20 is such that the resistance layer 22 is formed on the conductive layer 21 and the electrode for supplying the transfer voltage V1 to the conductive layer 21. If the portion 23 is exposed on the surface of the end portion of the intermediate transfer body 10, it flows from the electrode portion 23 to the conductive layer 1 a of the photoreceptor 1 through the pinhole 1 c unless any measures are taken. It was found that a discharge current E was generated, and transfer voltage V1 was not properly applied, resulting in transfer failure.
[0027]
On the other hand, according to the image forming apparatus of the first aspect, the distance between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member is 20 μm or more in the transfer portion. In spite of the above configuration, even if there is a pinhole at the end of the photoconductor, the discharge current does not occur, and therefore transfer defects do not occur. It has been confirmed by an experiment by the present inventors that the discharge current does not occur at a transfer voltage adopted in this type of image forming apparatus if the distance is 20 μm or more.
[0028]
If the intermediate transfer member has a single-layer structure as in the prior art, the above-described problem occurs even if there is a pinhole 1c at the end of the photosensitive member 1, as shown in FIG. Absent.
[0029]
According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein a gap member for forming the gap is interposed between the end portion of the photoconductor and the electrode portion. Therefore, the gap member reliably forms a gap between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member in the transfer portion, and reliably prevents transfer defects.
[0030]
According to the image forming apparatus of the third aspect, in the image forming apparatus of the second aspect, the gap member is made of a material having a higher resistance value than the resistance layer of the intermediate transfer medium. The generation of the discharged current is more reliably prevented, and the transfer failure is surely prevented.
[0031]
According to the image forming apparatus of the fourth aspect, in the image forming apparatus according to the third aspect, since the gap member is made of an insulating material, the generation of the discharge current is more reliably prevented and the transfer is performed. Defects can be prevented more reliably.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0033]
<First Embodiment>
1A and 1B are diagrams showing a first embodiment of an image forming apparatus according to the present invention. FIG. 1A is a schematic perspective view, and FIG. 1B is a partial cross-sectional view along line bb in FIG.
[0034]
In the figure, reference numeral 10 denotes a photoreceptor, which has a conductive layer 10a and a photosensitive layer 10b formed on the conductive layer 10a. The conductive layer 10a is grounded.
[0035]
Reference numeral 20 denotes an intermediate transfer member, which is exposed on the surface of the conductive layer 21, the resistance layer 22 formed on the conductive layer 21, and the end of the intermediate transfer member, and supplies the transfer voltage V1 to the conductive layer 21. And an electrode part 23 for the purpose. In this embodiment, the conductive layer 21 is formed on an insulating substrate 24 made of a synthetic resin, and the resistance layer 22 is formed on the conductive layer 21. The conductive layer 21 is exposed in a band shape because the resistance layer 22 is removed in a band shape at one side edge of the intermediate transfer body 20 or is not formed in advance in a band shape, and an electrode portion 23 is formed in this exposed portion. . In addition, it is also possible to form an electrode part by the strip | belt-shaped exposed part itself of the conductive layer 21. FIG.
[0036]
The intermediate transfer member 20 is in contact with the photosensitive member 10 at least during image formation, and the contact portion T1 forms a transfer portion (in this case, a primary transfer portion). In the primary transfer portion T1, a primary transfer roller 15 made of an elastic body such as rubber is disposed from the inside of the intermediate transfer body 20, but the primary transfer roller 15 is not necessarily provided.
[0037]
As shown in FIG. 1A, an electrode roller 37 is disposed in contact with the electrode portion 23 of the intermediate transfer body 20, and the conductive layer 21 is interposed via the electrode roller 37 and the electrode portion 23. A primary transfer voltage V1 is applied.
[0038]
Further, a secondary transfer roller 38 to which a secondary transfer voltage V2 is applied is pressed against the intermediate transfer body 20, and this pressure contact portion forms a secondary transfer portion T2. A backup roller 33 is disposed from the inner side of the intermediate transfer body 20 in the secondary transfer portion T2.
[0039]
At least one of the photosensitive member 10 and the intermediate transfer member 20 is configured in a thin cylindrical shape or a belt shape having flexibility.
[0040]
At the time of image formation, first, the photosensitive member 10 and the intermediate transfer member 20 are driven to rotate, the photosensitive layer 10b of the photosensitive member 10 is uniformly charged by a charging unit (not shown), and then an exposure unit (not shown). To selectively form an electrostatic latent image. Next, toner as a developer is applied to the electrostatic latent image by developing means (not shown) to become a visible image (toner image), and this toner image is transferred onto the intermediate transfer body 20 in the primary transfer portion T1. Then, in the secondary transfer portion T2, the image is transferred to a recording medium such as paper supplied to the secondary transfer portion T2.
[0041]
The recording medium onto which the toner image has been transferred passes through a fixing device (not shown) to fix the toner image.
[0042]
Incidentally, as described above, the pinhole 10c may exist in the photosensitive layer 10b of the photoconductor 10, and the pinhole 10c exists at the end of the photoconductor 10 as shown in FIG. There is.
[0043]
In such a situation, as described above, the structure of the intermediate transfer member 20 is such that the resistance layer 22 is formed on the conductive layer 21, and the electrode portion 23 for supplying the transfer voltage V1 to the conductive layer 21 is the intermediate transfer member. If no measures are taken with the structure exposed on the surface of the end of the body 10, a discharge current flows from the electrode portion 23 to the conductive layer 10a of the photoconductor 10 through the pinhole 10c. As described above, the transfer voltage V1 is not properly applied and a transfer failure occurs.
[0044]
Therefore, in this embodiment, at the end portion of the photoconductor 10 such that the gap G between the surface of the conductive layer 10a of the photoconductor 10 and the surface of the electrode portion 23 of the intermediate transfer body 20 in the primary transfer portion T1 is 20 μm or more. The gap member 16 is provided.
[0045]
The gap member 16 is formed by coating the end of the photoconductor 10 with a material having a higher resistance value than the resistance layer 22 of the intermediate transfer medium 20, more preferably with an insulating material.
[0046]
According to the image forming apparatus as described above, the following effects can be obtained.
[0047]
(A) A transfer portion T1 is formed between the photoreceptor 10 on which the image is formed on the surface of the photosensitive layer 10b formed on the conductive layer 10a and the surface of the photoreceptor, and the image is transferred to the transfer portion T1. Therefore, the image formed on the surface of the photoconductor 10 is transferred to the intermediate transfer member at the transfer portion T1.
[0048]
The intermediate transfer body 20 has a multilayer structure including a conductive layer 21 and a resistance layer 22 formed on the conductive layer 21 to which the image is transferred. It can be formed by applying a resin solution in which conductive particles are dispersed, curing, and drying. Thus, when conductive particles are dispersed in a resin solution in which a resin is dissolved in a solvent, the dispersibility of the conductive particles becomes better than when conductive particles are kneaded in a heat-melted resin. . Therefore, resistance unevenness of the resistance layer 22 itself can be made difficult to occur. Further, since the dispersibility of the conductive particles becomes good, local protrusions on the surface of the resistance layer 22 can be hardly generated, and the contact with the photoreceptor 10 and the like can be stabilized to prevent transfer failure. Is possible.
[0049]
Further, since the resistance layer 22 is integrally formed on the conductive layer 21, when a transfer voltage is supplied to the conductive layer 21 by the electrode portion 23, the potential on the back side of the resistance layer 22 becomes substantially uniform, and the transfer region A substantially uniform transfer electric field is formed over the entire surface.
[0050]
Therefore, according to the image forming apparatus of this embodiment, unevenness is hardly generated in the electric field in the transfer portion T1, and as a result, a good image with little transfer unevenness can be formed.
[0051]
In addition, since the electrode portion 23 for supplying the transfer voltage V1 to the conductive layer 21 is exposed on the surface of the end portion of the intermediate transfer body 20, the transfer voltage V1 can be easily set by the electrode roller 37 as shown in the figure, for example. Power can be supplied to the conductive layer 21.
[0052]
Further, since the gap G between the surface of the conductive layer 10a of the photosensitive member 10 and the surface of the electrode portion 23 of the intermediate transfer member 20 in the transfer portion T1 is 20 μm or more, the intermediate transfer member 20 has the above configuration. Regardless, even if there is a pinhole 10c at the end of the photoconductor 10, the above-described discharge current does not occur, and therefore transfer defects do not occur.
[0053]
(B) Since the gap member 16 for forming the gap G is interposed between the end portion of the photosensitive member 10 and the electrode portion 23, the gap member 16 causes the photosensitive portion in the transfer portion T1 to be exposed. A gap G between the surface of the conductive layer 10a of the body 10 and the surface of the electrode portion 23 of the intermediate transfer body 20 is surely formed.
[0054]
(C) Since the gap member 16 is made of a material having a resistance value higher than that of the resistance layer 22 of the intermediate transfer medium 20, the above-described discharge current can be prevented more reliably. When the gap member 16 is made of an insulating material, the generation of the discharge current described above can be prevented more reliably.
[0055]
<Second Embodiment>
2A and 2B are diagrams showing a second embodiment of the image forming apparatus according to the present invention, in which FIG. 2A is a schematic perspective view, and FIG. 2B is a partial cross-sectional view along line bb in FIG. In these drawings, the same reference numerals are given to the same or corresponding parts as those in the first embodiment.
[0056]
This second embodiment differs from the first embodiment described above in that the end of the photoconductor 10 is covered with a material having a higher resistance value than the resistance layer 22 of the intermediate transfer medium 20. The end of the photoconductor 10 and the end of the intermediate transfer body 20 so that the gap G between the surface of the conductive layer 10a of the photoconductor 10 and the surface of the electrode part 23 of the intermediate transfer body 20 in the primary transfer portion T1 is 20 μm or more. The sliding contact member 50 as a gap member is interposed therebetween.
[0057]
The sliding contact member 50 is formed in a band shape with a material having a higher resistance value than the resistance layer 22 of the intermediate transfer medium 20, more preferably with an insulating material, and at least one end 51 holds the frame of the apparatus or the photoreceptor 10. The cartridge case 52 is fixed. Therefore, when the photosensitive member 10 and the intermediate transfer member 20 are driven to rotate, the sliding contact member 50 has one surface 50 a that is in sliding contact with the end portion of the photosensitive member 10, and the other surface 50 b that is in contact with the end portion of the intermediate transfer member 20. It will be in sliding contact.
[0058]
Also according to the second embodiment, the same effects as those of the first embodiment described above can be obtained.
[0059]
Further, unnecessary toner (toner that is not necessary for image formation) may adhere to the end portion of the photoconductor 10, but the unnecessary contact of the unnecessary toner to the electrode portion 23 is caused by the sliding contact member 50. This prevents the contamination of the electrode part 23. If toner adheres across the width direction of the surface of the electrode portion 23, the transfer voltage corresponding to the portion decreases, which is not desirable.
[0060]
<Third Embodiment>
3A and 3B are diagrams showing a third embodiment of the image forming apparatus according to the present invention, in which FIG. 3A is a schematic perspective view, and FIG. 3B is a partial cross-sectional view along line bb in FIG. In these drawings, the same reference numerals are given to the same or corresponding parts as those in the first embodiment.
[0061]
The third embodiment is different from the first embodiment described above in that, instead of providing a gap member at the end of the photoconductor 10, the surface of the conductive layer 10a of the photoconductor 10 in the primary transfer portion T1 is different from the first embodiment. The gap member 25 is provided at the end of the intermediate transfer member 20 so that the gap G between the intermediate transfer member 20 and the surface of the electrode part 23 is 20 μm or more. The gap member 25 is provided in an annular and rib shape, for example, at the boundary between the resistance layer 22 and the electrode part 23 as shown in the figure so as not to cover the entire surface of the electrode part 23 of the intermediate transfer body 20. Further, the intermediate transfer medium 20 is formed of a material having a higher resistance value than that of the resistance layer 22, more preferably an insulating material.
[0062]
Also according to the third embodiment, the same operational effects as those of the first embodiment described above can be obtained.
[0063]
Further, as described above, unnecessary toner may adhere to the end portion of the photoconductor 10, but the unnecessary toner is removed from the electrode portion 23 by the gap member 25 provided on the intermediate transfer body 20 side. It is prevented from coming into direct contact with the electrode portion 23 and strongly adhering to the surface of the electrode portion 23, and the electrode portion 23 is prevented from being soiled.
[0064]
In addition, when the gap member 25 is provided in an annular and rib shape, for example, at the boundary between the resistance layer 22 and the electrode portion 23 as shown in the drawing, the gap member 25 is formed between the resistance layer 22 and the electrode portion 23. Thus, the toner on the resistance layer 22 is prevented from moving to the electrode portion 23.
[0065]
In particular, a cleaning member that collects waste toner remaining on the resistance layer 22 is generally disposed on the resistance layer 22 of the intermediate transfer member 20. Toner may spill or may not be completely recovered.
[0066]
In contrast, according to the third embodiment, the waste toner moves onto the electrode portion 23 by the gap member 25 serving as a partition wall between the resistance layer 22 and the electrode portion 23. Will be prevented.
[0067]
【Example】
FIG. 4 is a schematic diagram showing an example of an image forming apparatus to which the first, second, or third embodiment can be applied. In FIG. 4, the same reference numerals are given to the same or corresponding parts as those in the above-described embodiment.
[0068]
This image forming apparatus is an apparatus capable of forming a full-color image using a developing device using toners of four colors of yellow, cyan, magenta, and black.
[0069]
In FIG. 4, reference numeral 10 denotes a photoconductor, which can be driven to rotate in the direction indicated by the arrow by an appropriate driving means (not shown).
[0070]
A charging roller 11 as a charging unit, a developing roller 17 (Y, M, C, K) as a developing unit, an intermediate transfer device 30, and a cleaning unit 12 are arranged around the photoconductor 10 along the rotation direction. Has been placed.
[0071]
The photoreceptor 10 includes a cylindrical conductive substrate 10a and a photosensitive layer 10b formed on the surface thereof.
[0072]
The charging roller 11 is in contact with the outer peripheral surface of the photoconductor 10, and can uniformly charge the photosensitive layer 10b (for example, can be charged to about -600V). On the outer peripheral surface of the uniformly charged photoconductor 10, selective exposure L corresponding to desired image information is performed by an exposure unit (not shown), and an electrostatic latent image is formed on the photoconductor 10 by this exposure L. The The potential of the exposed portion, that is, the portion where the electrostatic latent image is formed can be set to about −100 V, for example.
[0073]
The electrostatic latent image is developed by the developing roller 17 with toner charged to “−” applied thereto.
[0074]
As the developing rollers, a yellow developing roller 17Y, a cyan developing roller 17C, a magenta developing roller 17M, and a black developing roller 17K are provided. These developing rollers 17Y, 17C, 17M, and 17K can selectively contact the photoreceptor 10, and when contacted, toner of any one of yellow, cyan, magenta, and black is applied to the photoreceptor. The electrostatic latent image on the photoconductor 10 is developed by applying to the surface 10.
[0075]
The developed toner image is transferred onto an intermediate transfer belt 20 as an intermediate transfer member described later.
[0076]
The cleaning unit 12 includes a cleaner blade 13 that scrapes off the toner remaining and adhered to the outer peripheral surface of the photoreceptor 10 after the transfer, and a receiving portion 14 that receives the toner scraped off by the cleaner blade 13. Yes.
[0077]
The intermediate transfer device 30 includes a drive roller 31, four driven rollers 32, 33, 34, and 35, and an intermediate transfer belt 20 that is stretched around each of these rollers.
[0078]
The driving roller 31 is rotationally driven at substantially the same peripheral speed as that of the photosensitive member 10 because a gear (not shown) fixed to the end of the driving roller 31 meshes with a driving gear (not shown) of the photosensitive member 10. Accordingly, the intermediate transfer belt 20 can be driven to circulate in the direction indicated by the arrow at substantially the same peripheral speed as the photoconductor 10.
[0079]
The driven roller 35 is disposed at a position where the intermediate transfer belt 20 is pressed against the photoconductor 10 by its own tension between the driven roller 35 and the primary roller at the press-contact portion between the photoconductor 10 and the intermediate transfer belt 20. A transfer portion T1 is formed. Therefore, the primary transfer roller 15 is not provided. The driven roller 35 is disposed near the primary transfer portion T1 on the upstream side of the intermediate transfer belt 20 in the circulation direction.
[0080]
The driving roller 31 is provided with the electrode roller 37 via the intermediate transfer belt 20. As described above, the conductive layer 21 of the intermediate transfer belt 20 is charged with the photosensitive member 10 via the electrode roller 37. A transfer voltage V1 having a polarity opposite to the polarity (a primary transfer voltage, for example, a voltage of about +500 V) can be applied.
[0081]
The driven roller 32 is a tension roller, and biases the intermediate transfer belt 20 in the tension direction by a biasing means (not shown).
[0082]
The driven roller 33 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 38 is opposed to the backup roller 33 with the intermediate transfer belt 20 interposed therebetween. The secondary transfer roller 38 can be brought into contact with and separated from the intermediate transfer belt 20 by a contact and separation mechanism (not shown). A secondary transfer voltage V2 (a voltage higher than the primary transfer voltage, for example, a voltage of about +1000 V) is applied to the secondary transfer roller 38.
[0083]
The driven roller 34 is a backup roller for the belt cleaner 39. The belt cleaner 39 includes a cleaner blade 39a that contacts the intermediate transfer belt 20 and scrapes off toner adhering to the outer peripheral surface thereof, and a receiving portion 39b that receives the toner scraped off by the cleaner blade 39a. ing. The belt cleaner 39 can be brought into and out of contact with the intermediate transfer belt 20 by a contact and separation mechanism (not shown).
[0084]
In the intermediate transfer belt 20 in this embodiment, the insulating base 24 is made of a sheet-like transparent PET, and an AL layer is deposited thereon to form a conductive layer 21, on which a fluorine-based fine particle based on urethane is formed. In addition, both ends of the belt on which the resistance layer 22 is formed by applying a coating material in which SnO as a conductive agent is dispersed to a thickness of about 10 to 100 μm are welded by ultrasonic fusion so as to be endless. The surface resistance of the resistance layer 22 is about 10 ⁸ to 10 ¹⁵ Ω / □, and the volume resistivity is about 10 ⁷ to 10 ¹⁴ Ωcm. The resistance value of the conductive layer 21 is desirably 10 6 Ωcm or less. The coating material is applied by leaving one end edge of the belt in a belt shape to expose the conductive layer 21 in a belt shape, and the exposed portion forms an electrode portion 23, and an electrode roller 37 is attached to the electrode portion 23. It is made to contact. The gap member 16 or 25 is made of urethane, for example. The gap member 16 or 25 is formed by silk printing or attaching a tape. When formed by silk printing, it is possible to form a pattern without variation in height. When formed by attaching a tape, the intermediate transfer body 20 is not likely to be altered because a process such as heating during manufacturing is unnecessary.
[0085]
When the sliding contact member 50 is used, it is made of a material having a low friction coefficient and excellent abrasion resistance, for example, ETFE (ethylene tetrafluoroethylene copolymer).
[0086]
In the process in which the intermediate transfer belt 20 is circulated, the toner image on the photoconductor 10 is transferred onto the intermediate transfer belt 20 at the primary transfer portion T1, and the toner image transferred onto the intermediate transfer belt 20 is transferred to the secondary transfer belt T20. In the transfer portion T2, the image is transferred to a recording medium S such as paper supplied between the secondary transfer roller 38 and the transfer portion T2. The recording medium S is fed from a sheet feeding device (not shown) and is supplied to the secondary transfer portion T2 by the gate roller pair 40 at a predetermined timing.
[0087]
The basic operation of the entire image forming apparatus as described above is as follows.
[0088]
(I) When a print command signal (image formation signal) from a host computer or the like (not shown) is input to the control unit of the image forming apparatus, the photosensitive member 10, the developing roller 17, and the intermediate transfer belt 20 are Driven by rotation.
[0089]
(Ii) The outer peripheral surface of the photoconductor 10 is uniformly charged by the charging roller 11.
[0090]
(Iii) On the outer peripheral surface of the uniformly charged photoreceptor 10, selective exposure L corresponding to image information of the first color (for example, yellow) is performed by an exposure unit (not shown), and an electrostatic latent image for yellow is formed. It is formed.
[0091]
(Iv) Only the developing roller 17Y for the first color (for example, yellow) is in contact with the photosensitive member 10, whereby the electrostatic latent image is developed, and the first color (for example, yellow) toner image is transferred to the photosensitive member. 10 is formed.
[0092]
(V) A primary transfer voltage V1 having a polarity opposite to the charging polarity of the toner is applied to the intermediate transfer belt 20, and a toner image formed on the photosensitive member 10 is transferred to a primary transfer portion, that is, the photosensitive member 10 and the intermediate transfer belt. Then, the toner image is transferred onto the intermediate transfer belt 20 at the press-contact portion T1 with 20. At this time, the secondary transfer roller 38 and the belt cleaner 39 are separated from the intermediate transfer belt 20.
[0093]
(Vi) After the toner remaining on the photoconductor 10 is removed by the cleaning unit 12, the photoconductor 10 is neutralized by neutralizing light from a neutralizing unit (not shown).
[0094]
(Vii) The operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated according to the content of the print command signal, and the toner images according to the content of the print command signal are superimposed on the intermediate transfer belt 20 to be intermediate. It is formed on the transfer belt 20.
[0095]
(Viii) The recording medium S is supplied at a predetermined timing, immediately before or after the leading end of the recording medium S reaches the second transfer portion T2 (in short, on the intermediate transfer belt 20 at a desired position on the recording medium S). The secondary transfer roller 38 is pressed against the intermediate transfer belt 20 and the secondary transfer voltage V2 is applied to the toner image on the intermediate transfer belt 20 (basically a full-color image). Is transferred onto the recording medium S. Further, the belt cleaner 39 contacts the intermediate transfer belt 20, and the toner remaining on the intermediate transfer belt 20 after the secondary transfer is removed.
[0096]
(Ix) When the recording medium S passes through a fixing device (not shown), the toner image is fixed on the recording medium S, and then the recording medium S is discharged out of the apparatus.
[0097]
According to the image forming apparatus as described above, since the intermediate transfer belt 20 is pressed against the photoreceptor 10 between the rollers 31 and 35, the intermediate transfer belt 20 at the press contact portion (primary transfer portion) T1 is It is pressed against the photoreceptor 10 by its own tension.
[0098]
Therefore, the visible image on the photoconductor 10 is transferred onto the intermediate transfer belt 20 without providing a pressure roller (primary transfer roller) for pressing the intermediate transfer belt 20 against the photoconductor 10 at the pressure contact portion T1. Can do.
[0099]
Further, the intermediate transfer belt 20 is composed of a multilayer belt having a conductive layer 21 and a resistance layer 22 formed on the conductive layer 21 and pressed against the photoconductor 10. The potential on the back side of the resistance layer 22 of the intermediate transfer belt 20 becomes substantially uniform over the entire area of the pressure contact portion (ie, primary transfer portion) T1 with the intermediate transfer belt 20, and as a result, transfer with less toner scattering is obtained. Will be.
[0100]
Therefore, it becomes difficult to be affected by the unevenness of the surface resistance of the intermediate transfer belt 20, and the unevenness of density is further less likely to occur. In addition, since the potential on the back side of the resistance layer 21 of the intermediate transfer belt 20 is substantially uniform over the entire area of the pressure contact portion (that is, the primary transfer portion) T1 between the photosensitive member 10 and the intermediate transfer belt 20, the necessary minimum Transfer with a limited voltage is possible.
[0101]
Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and can be appropriately modified within the scope of the gist of the present invention.
[0102]
For example, in the above embodiment, in order to form the gap G between the conductive layer surface of the photosensitive member and the electrode surface of the intermediate transfer member in the transfer portion, a gap member is provided between the photosensitive member end portion and the electrode portion 23. However, the gap G is not necessarily provided as long as the gap G is 20 μm or more. For example, a guide body may be provided at the end of the intermediate transfer body 20 so that the gap G is formed, or the diameter of the end of the intermediate transfer body 20 may be reduced.
[0103]
【The invention's effect】
According to any one of the image forming apparatuses according to claims 1 to 4, it is difficult for uneven transfer to occur and unevenness in the electric field in the transfer portion, and as a result, it is possible to form a good image with little transfer unevenness. In addition, the transfer voltage can be easily supplied. No transfer failure occurs.
[0104]
Furthermore, according to the image forming apparatus of the second aspect, the gap member reliably forms a gap between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member in the transfer portion, thereby reliably preventing transfer failure. The
[0105]
According to the image forming apparatus of the third aspect, transfer defects can be prevented more reliably.
[0106]
According to the image forming apparatus of the fourth aspect, transfer defects can be prevented more reliably.
[0107]
[Brief description of the drawings]
1A and 1B are diagrams illustrating a first embodiment of an image forming apparatus according to the present invention, in which FIG. 1A is a schematic perspective view, and FIG. 1B is a partial cross-sectional view along line bb in FIG.
2A and 2B are diagrams illustrating a second embodiment of an image forming apparatus according to the present invention, in which FIG. 2A is a schematic perspective view, and FIG. 2B is a partial cross-sectional view along line bb in FIG.
3A and 3B are diagrams showing a third embodiment of the image forming apparatus according to the present invention, in which FIG. 3A is a schematic perspective view, and FIG. 3B is a partial cross-sectional view along line bb in FIG.
FIG. 4 is a schematic diagram showing an example of an image forming apparatus to which the first, second, or third embodiment is applied.
5A and 5B are diagrams illustrating an example of a conventional image forming apparatus, in which FIG. 5A is a schematic perspective view, and FIG. 5B is a partial cross-sectional view taken along line bb in FIG.
6A and 6B are cross-sectional views for explaining a problem.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Photoconductor 10a Conductive layer 10b Photosensitive layer 16 Gap member T1 Primary transfer part T1 (transfer part)
20 Intermediate transfer member 21 Conductive layer 22 Resistive layer 23 Electrode portion G Spacing 25 Gap member 50 Gap member

Claims (3)

A photosensitive member on which an image is formed on the surface of the photosensitive layer formed on the conductive layer, and an intermediate transfer member on which the transfer portion is formed between the photosensitive member surface and the image is transferred at the transfer portion. An image forming apparatus having
The intermediate transfer member is formed on the conductive layer, a resistance layer formed on the conductive layer, and the image is transferred. The intermediate transfer member is exposed on the surface of the end of the intermediate transfer member and supplies a transfer voltage to the conductive layer. And having an electrode part,
The gap between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member in the transfer portion is 20 μm or more, and a gap member for forming the gap includes the end portion of the photosensitive member, the electrode portion, An image forming apparatus , wherein the gap member has a width that completely covers the surface of the electrode portion in the transfer portion . The gap member, an image forming apparatus according to claim 1, characterized in that it is composed of a material having a higher resistivity than the resistive layer of the intermediate transfer medium. The image forming apparatus according to claim 2 , wherein the gap member is made of an insulating material.

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