JPH10698A - Endless belt for image forming apparatus, the image forming apparatus and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an endless belt for an image forming apparatus for obtaining an image of a high image quality with a small step at a connecting part. SOLUTION: A connecting part obtained by superposing both ends of a thermosetting resin sheet such as a polymide resin in which a conductive agent is dispersed is provided. A groove-like uneven part is engraved at both ends of the sheet in its thickness direction and an uneven part formed at one end is adhered to an uneven part formed at the other end. A thickness (t) of the sheet is 50 to 100μm, a depth (d) of a recess is 26 to 90μm, and widths w1 , w2 are in a range of 10μm to 30mm. The recess is preferably engaged with the protrusion. As an adhesive for bonding the recess to the protrusion, a one- pack elastic adhesive, a two-pack elastic adhesive or a sheet-like hot-melt adhesive is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus using an electrophotographic method, such as a laser printer, a facsimile, and a composite device thereof. More specifically, an intermediate transfer belt on which a toner image formed on an image carrier is temporarily transferred once, a transfer material transport belt for transporting a transfer material such as paper on which the toner image has been transferred to a transfer unit, and the like. The present invention relates to an endless belt for an image forming apparatus and a method for manufacturing the same.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic system is a laser in which a uniform charge is formed on an image carrier composed of a photoreceptor made of an inorganic or organic photoconductive material and an image signal is modulated. After forming an electrostatic latent image with light or the like, the electrostatic latent image is developed with charged toner to obtain a visualized toner image. Then, the toner image is transferred onto a transfer material such as paper directly or via an intermediate transfer member to obtain a required reproduced image. As an image forming apparatus adopting a system in which a toner image formed on an image carrier is primarily transferred to a belt-shaped intermediate transfer body, and a toner image on the intermediate transfer body is secondarily transferred to a transfer material, for example, It is disclosed in JP-A-62-206567. Further, as an image forming apparatus adopting a method of sequentially transferring toner images of respective colors formed on a plurality of image carriers to a transfer material on a transport belt, for example, Japanese Patent Application Laid-Open No.
No. 139563. Examples of the belt material used in these image forming apparatuses include polycarbonate (PC) (Japanese Patent Application Laid-Open No. 6-95521), polyalkylene terephthalate (PAT) (Japanese Patent Application Laid-Open No. 6-149081), and PAT and PC. Blend material (JP-A-6-149083), ethylene-
Blend material of tetrafluoroethylene copolymer (ETFE) and PC, blend material of ETFE and PAT,
Blend material of ETFE, PC and PAT
(Japanese Patent No. 149079), a conductive endless belt in which carbon black is blended with a thermoplastic resin has been proposed.

As a method of manufacturing an endless belt, for example,
A method in which a gas is continuously supplied to and removed from the inside of a tubular film extruded from an annular die mounted on an extruder, and is brought into contact with a mandrel to cool and solidify the gas (Japanese Unexamined Patent Publication No.
-228823). As a joining method of the sheet material, for example, a method of joining end faces of a thermoplastic polytetrafluoroethylene (PTFE) sheet and joining them by ultrasonic vibration (Japanese Patent Laid-Open No. 63-1)
No. 34226) and the edges of a sheet having irregularities on the side edges are overlapped, and the edges of the sheets are joined by the action of ultrasonic waves while the tip of the horn of the ultrasonic generating mechanism is brought into contact with the surface of the overlapped sheet. (Japanese Unexamined Patent Publication No. 62-9938), for example, has been proposed. By the way, since the conductive material of the thermoplastic resin such as PC and ETFE has a small Young's modulus among the mechanical characteristics, the deformation of the belt due to the stress applied to the belt at the time of driving is large, so that the intermediate transfer belt and the transfer material are conveyed. When applied to a belt, a high-quality transfer image cannot be stably obtained, and cracks occur at the belt end portion during driving, resulting in poor durability of the belt. On the other hand, as a typical material having a large Young's modulus, a polyimide resin can be given. However, since the polyimide resin is thermosetting, an endless belt cannot be manufactured by the above-described ultrasonic vibration in which the belt material is thermally melted and joined.

[0004]

In the prior art, as a method for manufacturing an endless belt made of a thermosetting resin such as a polyimide resin, i) a method in which both edges of a sheet are overlapped and joined by an adhesive ( FIG. 6A) A method of extending the durability of the joint by covering both ends of the sheet with an adhesive or an adhesive tape so that a step is not generated as much as possible (FIG. 6B), iii) In a puzzle shape A method of engaging both edges of the cut sheet and covering the joined portion with an adhesive or a pressure-sensitive adhesive tape (FIG. 6C) can also be used. In an image forming apparatus of the intermediate transfer belt type, toner remaining on the intermediate transfer belt after the secondary transfer is generally removed by bringing a cleaning blade such as urethane rubber into contact with the intermediate transfer belt. Therefore, in the case where the thickness of the belt is not uniform and there is a step, it becomes difficult to clean the residual toner on the belt. Further, when the step on the belt comes into contact with the belt transport roll or the cleaning blade, there is a problem that the peripheral speed of the belt fluctuates or the position of the belt slightly shifts, which adversely affects the quality of a color image. In order to reduce the adverse effect due to the step, it is desirable that the step at the joint is 25 μm or less. In the above method i), for example, when sheets having a thickness of 25 μm are overlapped, the thickness of the joined portion becomes twice or more the thickness of the belt material, and the step at the boundary between the joined portion and the non-joined portion increases. As a result, the toner remaining on the intermediate transfer belt after the secondary transfer cannot be completely cleaned, and further, the quality of a color image deteriorates. In addition, the above-mentioned method ii), in which both end surfaces of the sheet are butted and covered with an adhesive or a tape and joined.
In iii), the step between the bonded portion and the non-bonded portion is the same as the thickness of the adhesive or the tape. If the adhesive is thinly applied or a thin adhesive tape is used to reduce the step at the joint, there is a problem that a necessary joint strength cannot be obtained at the joint.

As a countermeasure against this problem, there is a method in which both ends of the sheet are cut obliquely to each other and bonded to each other so as to make the thickness of the joint portion as small as possible (FIG. 7). In this method, for example, a thickness of 50 to
It is difficult to accurately and obliquely process a thermosetting resin sheet of about 100 μm, and there is a problem that a predetermined bonding strength cannot be obtained because the bonding area is small. Further, in the case where the belt has a seam portion, a belt-shaped photoreceptor in which the seam portion is hardly destroyed by forming a point contact with each other so as to prevent the seam portion from contacting the cleaning blade at one time is disclosed in JP-A-5-224574 and JP-A-Hei 7
-5701. Normally, since an image is not formed at the seam, a means for separating the cleaning blade from the seam may be provided in order to extend the durability of the seam. There is a problem that occurs.

As described above, in the conventional endless belt for an image forming apparatus, there is a problem that an endless belt having a high joint strength and a small step cannot be manufactured from a thermosetting resin. In view of the above, the present invention is intended to solve the above-described problem, and realizes an endless belt made of a thermosetting resin in which a step generated at a joining portion is made as small as possible to obtain a high-quality image. And an endless belt for the image forming apparatus. Another object of the present invention is to provide an endless belt for an image forming apparatus in which alignment of a joint is easy and breakage or peeling at the joint hardly occurs, and a method of manufacturing the same.

[0007]

Means for Solving the Problems The present inventor has made an attempt to manufacture an endless belt for an image forming apparatus using a thermosetting resin having excellent mechanical properties so that the step at the joining portion does not pose a practical problem. After intensive studies, it has been found that the above-mentioned object is achieved by forming groove-shaped uneven portions at both ends of a film-like thermosetting sheet and joining them with an adhesive. Thus, the present invention has been accomplished. That is, the endless belt for an image forming apparatus of the present invention has a joining portion in which one end of the sheet and the other end of the sheet are overlapped,
The sheet is made of a thermosetting resin, and the joint portion is characterized in that groove-shaped concave and convex portions engraved on both ends of the sheet in the thickness direction are bonded with an adhesive. Further, the image forming apparatus of the present invention is an image carrier that forms an electrostatic latent image according to image information, a developing device that visualizes the electrostatic latent image formed on the image carrier as a toner image with toner, An intermediate transfer belt for temporarily transferring and carrying the toner image carried on the image carrier, a bias roll for secondary transferring the unfixed toner image on the intermediate transfer belt to a transfer material, A back-up roll for supporting the transfer belt from its back surface, wherein the intermediate transfer belt is made of a thermosetting resin sheet, and groove-shaped concave and convex portions engraved in the thickness direction on both ends of the sheet are adhered. It consists of an endless belt having a joining portion superposed via a layer of agent. Further, in the method for producing an endless belt for an image forming apparatus of the present invention, uneven portions are cut into grooves at both ends of a thermosetting resin sheet in the thickness direction, and an adhesive is applied to the surface of the groove-shaped uneven portions. With the interposition, the uneven portion formed at one end of the sheet and the uneven portion formed at the other end of the sheet are overlapped and joined.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail mainly with reference to the drawings. The endless belt of the present invention is applied to an intermediate transfer belt, a transfer material conveying belt, and the like of an image forming apparatus. FIG. 1 is a simplified diagram showing an outline of an arrangement relationship of an intermediate transfer belt in an image forming apparatus having main components.
In FIG. 1, a charging device 2, a developing device 3, a primary transfer device 4, a cleaning device 5, and the like are sequentially arranged on a peripheral surface of an image carrier 1 formed of a photosensitive drum along a rotation direction thereof. In addition, the intermediate transfer belt 6 is
a, 7b, 7c and the backup roll 8. The intermediate transfer belt 6 moves in the direction of the arrow while abutting on the surface of the image carrier 1, and performs primary transfer when passing between the image carrier 1 and the primary transfer device 4 arranged opposite thereto. The unfixed toner image primary-transferred by the device 4 is carried. The bias roll 9 and the belt cleaner 1 are located at positions facing the backup roll 8 and the belt transport roll 7a via the intermediate transfer belt 6, respectively.
0 is disposed, and the backup roll 8 supports the intermediate transfer belt 6 from the back surface. A transfer voltage is applied between the backup roll 8 and the bias roll 9, and the unfixed toner image carried on the intermediate transfer belt 6 is transferred to a transfer material such as paper P (hereinafter, represented by paper P). Next is transferred.

In the present invention, the intermediate transfer belt 6 is constituted by an endless belt in which both ends of a sheet in which a suitable amount of a conductive agent is mixed with various thermosetting resins are joined. The thermosetting resin has the advantage that it has excellent mechanical properties as compared with the thermoplastic resin, and the deformation of the belt during driving is small. As the thermosetting resin, polyimide, epoxy resin or the like is used. Among them, a polyimide resin having a Young's modulus as large as 4 × 10 ⁴ kg / cm ² or more is preferable. The thermosetting resin contains conductive agents such as carbon black, metals or alloys such as aluminum and stainless steel, and metal oxides such as tin oxide, zinc oxide, indium oxide, potassium titanate, and tin oxide-indium oxide solid solution. And its surface resistivity is 1
It is adjusted in the range of 0 ¹⁰ to 10 ¹⁴ Ω / □.

The backup roll 8 forms a counter electrode of the bias roll 9. The layer structure of the backup roll 8 may be either a single layer or a multilayer. For example,
Silicone rubber, urethane rubber, E
It is composed of a roll in which an appropriate amount of the above-mentioned conductive agent such as carbon black is mixed with PDM or the like. In the case of a two-layer structure, the roll in the case of a single layer whose volume resistivity is appropriately adjusted is used as a lower layer,
It is composed of a surface layer whose outer peripheral surface is coated with a conductive resin such as a fluorine resin. FEP (TF
E-hexafluoropropylene copolymer), PFA (perfluoroalkyl vinyl ether resin) and the like. The hardness of the backup roll 8 is asker C
Is preferably in the range of 60 to 75 °.

A bias roll 9 for forming a transfer electrode includes:
While the toner image carried on the image carrier 1 is primarily transferred onto the intermediate transfer belt 6, the toner image is separated from the transfer belt 6;
When the toner image carried on the transfer belt 6 is secondarily transferred onto the sheet P, the toner image is pressed against the transfer belt 6 and pressed against the backup roll 8. The layer structure of the bias roll 9 is not particularly limited. For example, in the case of a two-layer structure, the bias roll 9 includes a core layer and a coating layer covering the surface thereof. The core layer is made of silicone rubber, urethane rubber, EPDM, or the like in which a conductive agent is dispersed, or a foam thereof. The coating layer is preferably made of the above-mentioned fluorine-based resin in which a conductive agent is dispersed. The bias roll 9 generally has a hardness of 30 to 45 with Asker C hardness.
Those in the range of ° are used.

As the primary transfer device 4, a corona transfer device such as a corotron, a transfer roll, a transfer blade or the like is used. A voltage of 1 to 4 kV is applied to the primary transfer device 4, and the toner image carried on the image carrier 1 is transferred to the intermediate transfer belt 6 by the action of an electric field generated between the image carrier 1 and the primary transfer device 4. Is primary-transferred. As described above, a transfer voltage for transferring the toner image carried on the intermediate transfer belt 6 to the paper P is applied between the backup roll 8 and the bias roll 9. Regarding the transfer voltage, a voltage may be applied to the core of the backup roll 8 or an electrically conductive electrode roll pressed against the roll 8, or a voltage may be applied to the bias roll 9. The belt cleaner 10 removes the toner remaining on the intermediate transfer belt 6 after the secondary transfer. In the present invention, there is no step at the junction of the transfer belt 6 or it is so low that it can be ignored. No toner remains on the transfer belt 6 after cleaning.

Although the image forming apparatus of the intermediate transfer belt type has been described above, the endless belt of the present invention can be applied to a transfer material conveying belt of a conventionally known multiple transfer type color image forming apparatus. In the color image forming apparatus, an image carrier including a plurality of photosensitive drums is disposed inside a main body. Around each image carrier, a charging device, a developing device containing toners having different hues, a transfer device,
A cleaning device and the like are arranged. Between each image carrier and the transfer device, a transfer material transport belt that rotates in a predetermined direction while abutting on the surface of the image carrier is stretched around a plurality of belt transport rolls. In such a color image forming apparatus, the electrostatic latent image on the image carrier, which has been photo-decomposed for each color by the laser scanning system, is developed by a developing device and each color (for example, four colors) is developed.
Is formed. The toner images of each color carried on the image carrier are sequentially transferred to the paper conveyed to the transfer section by the transfer material conveyance belt by operating each transfer device,
A superposed multicolor toner image is formed on the paper.

As described above, the endless belt of the present invention is manufactured by overlapping and joining both ends of the thermosetting resin sheet. FIG. 2 is a cross-sectional view showing one end of the thermosetting resin sheet. FIG. 3 is a cross-sectional view of a joint portion of a belt in which both end portions of a sheet are bonded with an adhesive. In FIG. 2, the sheet is generally a film molded to a thickness t of 50 to 100 μm. However, the thickness t is not limited to the above range, and is, for example, 50 to 150 μm.
May be in the range. The dimensions of the groove-shaped concave and convex portions engraved in the thickness direction at one end of the sheet vary depending on the thickness t of the sheet, but the case where the thickness t of the sheet is in the range of 50 to 100 μm is taken as an example. And the depth d of the recess is 26 to 9
It is preferably in the range of 0 μm, especially 30 to 85 μm. That is, in order to reduce the step at the joint portion of the belt, it is desirable to cut the sheet in half or more of the thickness t, and to secure the safety factor of the cutting process and the strength of the joint portion. In addition, the thickness t '(t-d) of the non-engraved portion which is continuous with the sheet portion other than the end portion when the concave portion is formed is 10
It is desirable to leave the thickness of at least μm. The height h of the convex portion adjacent to the concave portion is set so that the step of the joint portion is as low as possible.
It is preferable that the depth is set to be shallower than the depth d in the range of 25 to 80 μm. The width w ₁ , w ₂ of the uneven portion formed in the longitudinal direction of the sheet is not particularly limited, but is 10 μm.
It may be in the range of up to 30 mm. That is, if the width is 10μ
Even if the width is set longer than 30 mm, the joining portion is usually a non-transfer area (in the case of an intermediate transfer belt). Becomes longer than necessary. The height h ′ (ht ′) from the groove bottom surface of the concave portion to the upper surface of the convex portion is 5 to 70.
It is preferably in the range of μm. At the other end of the sheet, a convex portion corresponding to the concave portion formed at the one end portion is formed, and a concave portion is formed adjacent to the convex portion. It is desirable that the concave and convex portions engraved on the other end of the sheet have the same dimensions as the one end for ease of engraving work.

In the present invention, as shown in FIG. 3, d>h> (1/2) so that the convex portion formed at the other end of the sheet fits into the concave portion formed at one end of the sheet. ) It is desirable to satisfy the relationship of t. In this case, dh ≧ 3
μm, the depth d of the recess formed at each end of the sheet
Is preferably set in the range of 25 to 90 μm, particularly 35 to 85 μm, and the height h of the protrusion is preferably set in the range of 25 to 80 μm, particularly 30 to 80 μm. As described above, when the convex portion is fitted into the concave portion, the effect of embedding the convex portion into the concave portion (anchor effect) is exhibited, and the joining strength in the longitudinal direction of the belt is improved. There is no danger of peeling from the recess. Here, the fitting of the concave portion and the convex portion is not a fitting in a strict sense, but is usually in a state where the convex portion is loosely fitted in the concave portion, and in a gap portion other than between the concave portion and the convex portion. The adhesive also intervenes (see FIG. 3). In the loose fit state, the bonding is performed over the entire area between the end faces of both end portions of the sheet and the surface of the uneven portion, so that the bonding area can be increased. Further, the dimensions of the concave portion and the convex portion are such that the width of the concave portion w ₁ > the width of the convex portion w ₂ , and the difference is preferably 2 μm or more in terms of engraving accuracy, and the maximum allowable range is preferably 20%.

In the endless belt of the present invention, when the thickness of the adhesive layer has a relationship of a = dh, it is possible to eliminate the step at the joint. Of course, as t <h + a + t ′,
The thickness of the belt may be greater than the thickness t of the sheet. However, since the step is allowed up to a maximum of 20 μm, the dimensions of the depth d, the height h, and the thickness a of the adhesive layer can be appropriately set within this range. The thickness a of the adhesive layer
As for the thickness a of the adhesive layer, the thickness is preferably in the range of 3 to 25 μm, particularly 5 to 20 μm. A thickness of at least 3 μm is necessary to obtain the required adhesive strength. Even if the thickness is more than 25 μm, the thickness in the thickness direction of the sheet is merely increased and does not lead to much improvement in the adhesive strength. , The required bonding strength increases

Means for engraving the concave and convex portions on both ends of the sheet in a groove shape include an excimer laser, a carbon dioxide laser and the like. In the engraving of these irregularities by laser light, μ
Fine processing of m units (processing tolerance ± 1μm) is possible,
This is preferable because no heat is generated. After the formation of the irregularities, deburring is performed by ultrasonic irradiation or brushing as necessary. In the present invention, the number of uneven portions engraved on both ends of the sheet is not limited to one, and a plurality of uneven portions may exist as shown in FIG. The dimensions of the projections and depressions formed at both ends of the sheet need not necessarily be the same. FIG. 4 shows that d> (1/2) t =
h, the depth d of each concave and convex portion engraved on both ends.
An example is shown in which the widths w ₁ and w ₂ and the height h are set to the same dimensions. If the dimensions (d, w ₁ , w ₂ , h) are standardized as described above, the working conditions for engraving are simplified, which is preferable. This point is the same as described above in the case where there is only one uneven portion formed on both ends of the sheet.

As described above, an adhesive is used to join the concave portion formed at one end of the sheet and the convex portion formed at the other end. The joining portion needs to have a strength of 0.5 N / mm ² or more, and must withstand 500 k cycles or more of repeated deformation by a belt transport roll for supporting and transporting the intermediate transfer belt. Therefore, it is preferable that the adhesive has a high strength and flexibility as a main component so as not to be broken or peeled off at the joint. Specifically, a one-component or two-component silicone-based elastic adhesive, a urethane-based elastic adhesive, a sheet-like hot-melt type silicone-based adhesive, a silane-modified polyimide-based adhesive, or the like is used. The silicone-based and urethane-based adhesives may be modified with various components or functional groups. These adhesives can be used alone or in combination with a high-strength adhesive such as an epoxy-based adhesive. In the case of a one-component or two-component elastic adhesive, the adhesive is applied by spatula coating, spot coating or the like to one or both of the inside of the concave groove at one end of the sheet and the upper surface of the convex portion. In the case of a sheet-like hot-melt adhesive, an adhesive having the same size as the area or slightly smaller than the area may be placed on the uneven portion. Then, depending on the type of the adhesive, the concave portion and the convex portion are joined by curing the adhesive while applying a load to the joining portion at room temperature or under heating.

The operation of the present invention is as follows. In the endless belt for an image forming apparatus according to the present invention, a joining portion of a belt in which groove-shaped concave and convex portions formed on both ends of a thermosetting resin sheet are overlapped is bonded with an adhesive. Since the uneven portion is engraved in the thickness direction thereof, it is possible to eliminate the step at the joint portion or to reduce it to a level of 20 μm or less which does not hinder practical use. Therefore, even if the step comes into contact with the belt transport roll or the cleaning blade, the peripheral speed of the belt does not fluctuate and the position of the belt does not slightly shift, and toner remains on the belt during cleaning. Absent. Therefore, a high-quality color image can be obtained particularly as an endless belt of a color image forming apparatus. According to a second aspect of the present invention, the sheet material forming the belt is made of a polyimide resin in which a conductive agent is dispersed. The thermosetting polyimide has a large Young's modulus among the mechanical properties, so that the deformation of the belt due to the stress at the time of driving is small, and the durability against repeated denaturation by the belt transport roll is excellent. In the endless belt according to the third aspect of the present invention, the thickness of the sheet is 50 to 10 mm.
0 μm, and a depth of 26 to 90 at one end of the sheet.
A concave portion having a width of 10 μm and a width of 10 μm to 30 mm is formed, and a convex portion that fits into a concave portion formed at one end is formed at the other end of the sheet. Therefore, not only is it easy to align the joints during the manufacture of the belt,
It is also possible to completely eliminate the step at the joint. In addition, since the bonding area of the joint can be increased, the bonding strength required for the endless belt can be sufficiently obtained.

The operation of the image forming apparatus according to the present invention is as follows. The electrostatic latent image formed on the image carrier 1 according to the image information is developed by the toner in the developing device 3 and is visualized as an unfixed toner image. This toner image is transferred to the intermediate transfer belt 6 in the primary transfer section while being carried on the image carrier 1. When transferring a multicolor image, the primary transfer is repeated for each color of the toner stored in the developing device 3. When the primary transfer of the toner image from the image carrier 1 onto the intermediate transfer belt 6 is completed, and the intermediate transfer belt 6 carrying the toner image of a desired hue moves to the secondary transfer portion, it is synchronized with this. Then, the paper P is transported to the secondary transfer unit. At this time, the bias roll 9 at the retracted position from the transfer belt 6 is in pressure contact with the transfer belt 6 whose back surface is supported by the backup roll 8. When the paper P passes through the secondary transfer portion while receiving a pressing force between the backup roll 8 and the bias roll 9, by applying a transfer voltage between the rolls 8 and 9,
The toner image carried on the transfer belt 6 is secondarily transferred onto the sheet P from the surface of the intermediate transfer belt 6. The intermediate transfer belt according to a fourth aspect of the present invention has a configuration similar to that of the endless belt according to the first aspect of the invention, and has the same operation as the first aspect of the invention.

According to a fifth aspect of the present invention, there is provided a method for manufacturing an endless belt for an image forming apparatus, wherein a concave and convex portion is engraved on both ends of a thermosetting resin sheet in a thickness direction thereof, and an adhesive is applied to the surface of the concave and convex portion. With the interposition, the concave portion formed at one end of the sheet and the convex portion formed at the other end are overlapped and joined.
According to the method of manufacturing an endless belt, as described in the first aspect of the invention, it is possible to eliminate or significantly reduce the step at the joint, and to obtain a high-quality image. The method for producing an endless belt according to claims 6 to 8 is
The concave portion and the convex portion are joined by using a one-component elastic adhesive, a two-component elastic adhesive, or a sheet-like hot melt type adhesive. These adhesives have the necessary adhesive strength at the joints and are excellent in durability against repeated deformation, so that even when the image forming apparatus is operated for a long period of time, the belt is broken or peeled or deformed. There is no such thing.

[0022]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. (Image Forming Apparatus) FIG. 5 is an overall view of a digital color copying machine provided with an intermediate transfer belt as an image forming apparatus of the present invention. Elements having the same functions as those of the components of the image forming apparatus shown in FIG. 1 are given the same reference numerals in FIG. In FIG. 5, light emitted from a document illumination lamp 12 moving along the lower surface of a document (not shown) placed on a platen 11 and reflected by the document is reflected by a movable mirror unit 13, a lens 14, and a fixed mirror. The light is converged on the CCD of the image reading unit via the line 15. The CCD converts the original image into an electric signal for each color by using a number of photoelectric conversion elements and filters of three colors of blue (B), green (G), and red (R). This electric signal is input to the image processing circuit 16,
The image processing circuit 16 has an image memory that converts a document image reading signal input for each color into a digital signal and stores it.

The optical writing controller 17 reads out the image data of the image processing circuit 16 at a predetermined timing, and outputs the data to the light beam writing device 18. Light beam writing device 18
Writes an electrostatic latent image corresponding to each color on the image carrier 1 composed of a photosensitive drum rotating in the direction of arrow A. Around the image carrier 1, a charger 2 for uniformly charging the surface thereof, a developing unit (developing device) 3 for developing an electrostatic latent image written on the image carrier 1 into a toner image of each color, and each color A transfer corotron (primary transfer device) 4 for transferring the toner image to the intermediate transfer belt 6, a cleaner unit (cleaning device) 5 having a static eliminator and a cleaning blade are arranged. The developing unit 3 has a developing device containing toner of each color of black (K), yellow (Y), magenta (M), and cyan (C), and develops the electrostatic latent image with the toner of each color. And visualize. The intermediate transfer belt 6 is
Backup Roll 8 and Belt Transport Roll 7
a, 7b, and 7c, and moves in the tangential direction while abutting on the surface of the image carrier 1. In this embodiment, of the rolls (7, 8) that stretch the transfer belt 6, the transfer belt 6
The belt transport roll 7a is configured as a drive roll, and the other rolls (7b, 7c, 8) are configured as driven rolls so that moves in the direction of arrow B. In order to prevent the transfer belt 6 from bending, the axis of the transport roll 7c is urged in the direction C by a spring (not shown).

On the back side of the intermediate transfer belt 6, the transfer corotron 4 is disposed at a primary transfer section where the surface of the image carrier 1 and the transfer belt 6 come into contact. On the other hand, on the front side of the transfer belt 6 that carries the unfixed toner image, the bias roll 9 and the belt cleaner 10 are disposed to face the backup roll 8 and the belt transport roll 7a, respectively. An electrode roll 19 connected to a transfer voltage power supply is pressed against the backup roll 8, and a portion where the backup roll 8 and the bias roll 9 face each other forms a secondary transfer portion. Further, between the backup roll 8 and the belt transporting roll 7a, a peeling claw 20 for peeling the paper P carrying the secondary-transferred toner image from the transfer belt 6 is provided.
Is arranged. A cleaning blade 21 made of polyurethane is always in contact with the surface of the bias roll 9 to remove foreign matters such as toner particles and paper powder adhered during secondary transfer or the like.

An extractable paper feed tray 22 is provided below the main body of the image forming apparatus U, and a pickup roller 23 is disposed above the paper feed tray 22. This pickup roller 2
Downstream of 3, a pair of feed rolls 24 for preventing double feeding of the paper P, a paper transport roll 25, a guide member 26 for guiding the paper P, and a registration roll 27 are sequentially arranged. On the downstream side of the secondary transfer section, a transport belt 2 for transporting a sheet P carrying a secondary-transferred toner image sequentially
8, a fixing device 29 for fixing an unfixed toner image on the paper P, a pair of discharge rolls 30 for discharging the paper P on which the fixed image is formed outside the machine, and a paper discharge on which the discharged paper P is placed. A tray 31 is arranged.

(Operation of Image Forming Apparatus) The surface of the image carrier 1 rotating in the direction of arrow A is uniformly charged by the charger 2. An electrostatic latent image is written on the uniformly charged image carrier 1 by a light beam writing device 18. The electrostatic latent image on the image carrier 1 is developed by the developing unit 3 into an unfixed toner image. In the formation of the toner image, a toner image of a first color is formed first, and thereafter, every time the image carrier 1 rotates for a predetermined time, a toner image of a second color to a fourth color is formed. In this embodiment, K, Y, M, and C toner images are sequentially formed. The surface of the image carrier 1 is cleaned by the blade of the cleaner unit 5 after the toner image is transferred to the intermediate transfer belt 1. Here, the optical writing control device 17 first reads out the digital signal of K color of the first color and outputs it to the light beam writing device 18. The writing device 18 writes an electrostatic latent image corresponding to K color on the surface of the image carrier 1. The electrostatic latent image corresponding to the color K is developed by the developing unit K in the developing unit 3 into a visualized toner image of the color K, and moves to the primary transfer unit. In the primary transfer section, an electric field having a polarity opposite to the charging polarity is applied to the toner image from the transfer corotron 4 disposed on the back side of the intermediate transfer belt 6 so that the K color toner image that has reached the primary transfer section is transferred. While being electrostatically attracted to the transfer belt 6, primary transfer is performed by moving the transfer belt 6 in the direction of arrow B.

The intermediate transfer belt 6 moves at the same cycle as the image carrier 1 while adsorbing and carrying the K toner image. When the transfer of the K toner image of the first color is completed, the blue (B) filter is used by the output from the optical writing controller 17 until the transfer start position of the K toner image on the transfer belt 6 reaches the primary transfer portion. Writing of the electrostatic latent image corresponding to the color-separated light image is started. When the transfer start position of the transfer belt 6 carrying the K toner image reaches the primary transfer portion, the transfer corotron 4 transfers the second color Y toner image. Subsequently, the electrostatic latent images corresponding to the light images color-separated by the green (G) and red (R) filters are developed.
The transfer of the M toner image and the C toner image is performed in the same manner as the transfer of the Y toner image. In this way, a multiple toner image superimposed on each color is formed on the intermediate transfer belt 6. Until the toner images of each color are primarily transferred onto the transfer belt 6, the bias roll 9, the peeling claw 20, and the belt cleaner 10 disposed on the surface side of the transfer belt 6 are in the retracted positions separated from the transfer belt 6. Is held.

On the other hand, the paper P stored in the paper feed tray 22
Are picked up one by one by a pickup roller 23 at a predetermined timing, and fed by a pair of feed rolls 24 and a sheet transport roll 25 to form a pair of registration rolls 2.
At 7, the operation is temporarily stopped. The sheet P is then transferred from the registration roll 27 to the secondary transfer section in synchronization with the transfer of the multiple toner images of each color (K, Y, M, C) transferred onto the intermediate transfer belt 6 to the secondary transfer section. Transported to the department. In the secondary transfer section, the bias roll 9 is in pressure contact with the backup roll 8 via the intermediate transfer belt 6. Then, the conveyed sheet P passes through the secondary transfer section by the press-contact conveyance between the rolls 8 and 9 and the movement of the transfer belt 6. At this time, the transfer belt 6 is electrostatically repelled by applying a transfer voltage having the same polarity as the charge polarity of the toner image from the electrode roll 19.
The toner image adsorbed and carried on the sheet P is secondarily transferred onto the sheet P from the surface of the transfer belt 6. When the bias roll 9 is pressed against the backup roll 8, foreign matter such as toner particles attached to the surface of the bias roll 9 is removed by the cleaning blade 21.

While the transfer of a full-color image has been described above, when a single-color image is formed, the intermediate transfer belt 6 is used.
When, for example, a K-color toner image primary-transferred above moves to the secondary transfer section, the toner image is immediately transferred to the paper P. In the case of forming an image of a plurality of colors, the desired hue is selected, and when the multicolor toner image superimposed on those colors moves to the secondary transfer section, the toner image may be transferred to the paper P. . In the case of the transfer of the multicolor image, the rotation of the image carrier 1 and the movement of the intermediate transfer belt 6 are synchronized as described above so that the toner images of the respective colors accurately match without shifting at the primary transfer portion. I have. As described above, the paper P on which the toner image has been transferred to the desired hue is peeled by the operation of the peeling claw 20 and is placed on the transport belt 28 to be fixed.
9. Then, after fixing the unfixed toner image to the permanent image in the fixing device 29, the sheet P is discharged to the discharge tray 31 by the pair of discharge rollers 30. When the secondary transfer is completed, the intermediate transfer belt 6
Since the step at the joining portion is extremely small, the toner remaining on the surface of the belt cleaner 10 is provided downstream of the secondary transfer portion.
Is completely cleaned and ready for the next transfer.

(Intermediate Transfer Belt) The specific structure of the intermediate transfer belt in the image forming apparatus shown in FIG. 5 is as follows. As a sheet constituting the intermediate transfer belt, a thermosetting polyimide having a length of 300 mm, a width of 25 mm, and a thickness of 80 μm was used, and carbon black was added thereto to adjust the surface resistivity to 10 ¹² Ω / □. At both ends of this sheet, a processing energy of 40 mJ and a processing speed of 0.921 were used.
Groove processing was performed with an excimer laser of 6 mm ³ / sec. The dimensions of the uneven portion at one end of the sheet shown in FIG. 2 are depth d: 50 μm, width w _{1 of} the concave portion: 20.05 mm, width w _{2 of the} convex portion: 19.95 mm, and height h: 40 μm. A groove having the same dimensions was formed on the other end of the. Thereafter, a liquid elastic adhesive is applied with a spatula or a sheet-like hot-melt type adhesive is placed on a groove-shaped concave bottom surface and a convex upper surface formed at one end of the thermosetting sheet. The protrusions and recesses formed at the other end of the sheet were aligned. Next, a 1 kg weight was placed on the joint and cured for a predetermined time to produce an endless belt having a step of less than 10 μm at the joint.

(Mechanical Property Test of Intermediate Transfer Belt) Examples 1 and 2 Specially modified silicone (Silex 100; manufactured by Konishi Co., Ltd.) and a specially modified silyl group-containing polymer as a one-part elastic adhesive were used as adhesives. (Super X No. 8008;
Cemedine Co., Ltd.) was used. Then, these adhesives are applied, the adhesive protruding from the joint is wiped off and cured, and the adhesive layer thickness after curing is 15 μm and 1 μm, respectively.
An 8 μm joint was formed. The “tensile bond strength” representing the bonding strength is based on JIS K 6850 (test method for tensile shear bond strength of adhesive), using the carbon black-containing polyimide sheet having a length of 100 mm and a tensile speed of 2 mm.
It was measured at 0 mm / min. In addition, the “repeated deformation” test was conducted by using an endless belt manufactured by the method described above with an outer diameter of 20 mm.
Was stretched between the two belt transport rolls, and the belt was rotated at a belt transport speed of 100 mm / sec. As Reference Examples 1 and 2, an epoxy resin adhesive (EP-170; manufactured by Cemedine Co., Ltd.) and a polycyanoacrylate adhesive (Flexible Aron Alpha # 9)
11P2; manufactured by Toa Gosei Co., Ltd.), and an endless belt was produced in the same manner as described above, and subjected to each test of its tensile adhesive strength and repeated deformation. The curing conditions of the adhesive and the step of the joint are as shown in Table 1 below, and the above test results are summarized in Table 1. The evaluation criteria for the repeated deformation test are as follows. : No visual change after 500k cycles △: Elongated joint after 500k cycles ×: Break within 500k cycles

[0032]

[Table 1]

Examples 3 and 4 As an adhesive, a mixed adhesive (MO) with an epoxy resin containing a specially modified silicone as a two-component elastic adhesive as a main component was used.
S7: manufactured by Konishi Co., Ltd.) and similar mixed adhesives (MOS
1010) was used. As Reference Example 3, an epoxy resin-based adhesive (EP-001; manufactured by Cemedine Co., Ltd.) was used.
The curing conditions of the adhesive and the step of the joint were as shown in Table 2 below, and the joined sheet and endless belt were subjected to the same tensile adhesive strength and repeated deformation tests as in Examples 1 and 2. . Table 2 summarizes the results.

[0034]

[Table 2]

Example 5 As an adhesive, an adhesive mixed with an epoxy resin containing a specially modified silicone as a main component, which is a sheet-like hot-melt type adhesive (Staystick 473; Techno Alpha Co., Ltd.)
Was used. As Reference Examples 4 and 5, an epoxy resin adhesive (Able Stick 551; Techno Alpha Co., Ltd.)
) And polyurethane adhesive (Thermolite 650)
1: Daicel Huls). The curing conditions of the adhesive and the steps of the joints are as shown in Table 3 below.
Each was subjected to the same test for tensile adhesive strength and repeated deformation as in the above. Table 3 summarizes the results.

[0036]

[Table 3]

As shown in Tables 1 to 3, Examples 1, 2 and 2 using a one-component elastic adhesive as an adhesive for joining uneven portions formed on both ends of a thermosetting sheet to each other In Examples 3 and 4 using an elastic elastic adhesive and Example 5 using a sheet-like hot melt type adhesive, 0.5 N / mm ² was used.
The joint strength described above and the durability of 500 k cycles or more are both satisfied. On the other hand, in the case of the epoxy resin-based adhesive (Reference Examples 1, 3, and 4) and the polycyanoacrylate adhesive (Reference Example 2), since the adhesive layer was hard, the belt was repeatedly deformed by the belt transport roll, so that the belt was not bonded at the joint. Broke.
In the case of the polyurethane-based adhesive (Reference Example 5), the joint portion was elongated and remarkably deformed due to repeated deformation with the roll.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope described in the claims.
The endless belt of the present invention is not limited to the color image forming apparatus of the embodiment, but can be applied to a monocolor image forming apparatus.

[0039]

According to the endless belt for an image forming apparatus and the method of manufacturing the same according to the present invention, the belt is formed by bonding a thermosetting resin sheet.
Has excellent durability. In addition, despite the fact that both ends of the sheet are overlapped at the joint of the belt, groove-like irregularities are carved in the thickness direction at both ends of the sheet. It can be made so small that it can be ignored. Therefore, since the peripheral speed of the belt does not fluctuate and the position of the belt does not slightly shift, a high-quality image can be obtained as the intermediate transfer belt or the transfer material conveying belt of the color image forming apparatus. . According to the endless belt of the third aspect of the present invention, the uneven portions formed at both ends of the sheet are fitted to each other, so that the alignment of the joint at the time of manufacturing is easy.
In addition, if the width of the convex portion is formed to be slightly shorter than the width of the concave portion, the bonding area can be increased, so that the bonding strength of the endless belt can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an outline of an arrangement relationship of an intermediate transfer belt in an image forming apparatus including main constituent members.

FIG. 2 is a cross-sectional view showing an end of a thermosetting resin sheet according to the present invention.

FIG. 3 is a cross-sectional view of a joining portion of an endless belt showing one embodiment of the present invention.

FIG. 4 is a cross-sectional view of a joining portion of an endless belt according to another embodiment of the present invention.

FIG. 5 is an overall view of an image forming apparatus shown as one embodiment of the present invention.

FIG. 6 is an explanatory view showing a conventional sheet joining method.

FIG. 7 is another explanatory view showing a sheet joining method.

[Explanation of symbols]

U: image forming apparatus, P: paper (transfer material), 1: image carrier, 3: developing device (developing unit), 6: intermediate transfer belt, 8: backup roll, 9: bias roll.

Claims (8)

[Claims] 1. A sheet having a joined portion in which one end of a sheet and the other end of a sheet are overlapped, the sheet is made of a thermosetting resin, and the joined portion is cut on both ends of the sheet in the thickness direction. An endless belt for an image forming apparatus, wherein the provided groove-shaped uneven portion is bonded with an adhesive. 2. The endless belt for an image forming apparatus according to claim 1, wherein the sheet is made of a polyimide resin in which a conductive agent is dispersed. 3. The thickness of the sheet is in the range of 50 to 100 μm, a recess having a depth of 25 to 90 μm and a width of 10 μm to 30 mm is formed at one end of the sheet, and the sheet is formed at the other end of the sheet. 2. The endless belt for an image forming apparatus according to claim 1, wherein a convex portion that fits into a concave portion formed at one end is formed. 4. An image carrier for forming an electrostatic latent image according to image information, a developing device for visualizing the electrostatic latent image formed on the image carrier as a toner image with toner, and An intermediate transfer belt for carrying the primary transfer of the carried toner image, a bias roll for secondary transfer of the unfixed toner image on the intermediate transfer belt to a transfer material, and The intermediate transfer belt is composed of a thermosetting resin sheet, and groove-shaped concave and convex portions engraved in both ends of the sheet in the thickness direction are provided via an adhesive layer. An image forming apparatus comprising an endless belt having a superposed joint. 5. A thermosetting resin sheet is formed at one end of a sheet with grooves formed at both ends in a thickness direction in the thickness direction thereof, and an adhesive is interposed on the surface of the grooves. A method for manufacturing an endless belt for an image forming apparatus, wherein the uneven portion and the uneven portion formed on the other end of the sheet are overlapped and joined. 6. The method according to claim 5, wherein a one-component elastic adhesive is used as the adhesive. 7. The method according to claim 5, wherein a two-component elastic adhesive is used as the adhesive. 8. The method for producing an endless belt according to claim 5, wherein a sheet-like hot melt adhesive is used as the adhesive.