JP4366570B2 - Intermediate transfer medium - Google Patents

Description

  The present invention relates to an intermediate transfer medium used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine that forms an image using electrophotographic technology.

  In general, an image forming apparatus using an electrophotographic technique has a photosensitive member having a photosensitive layer on an outer peripheral surface, a charging unit that uniformly charges the outer peripheral surface of the photosensitive member, and a charging unit that is uniformly charged by the charging unit. An exposure unit that selectively exposes the outer peripheral surface 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 image). Developing means, and transfer means for transferring the toner image developed by the developing means onto a recording material such as paper.

As a transfer unit, an intermediate transfer medium (for example, an intermediate transfer belt) that transfers a toner image formed on the photoreceptor (primary transfer) and further transfers (secondary transfer) the toner image to a recording material such as paper. Are known.
In the conventional intermediate transfer medium, the end portions of the sheet provided with the conductive layer and the resistance layer on one side of the base sheet made of resin are opposed to each other with a gap, and a welding member is brought into contact with the facing portion. A welding member was melted with a welding tool such as an ultrasonic horn, and the ends of the sheet were welded together to form a cylindrical shape (for example, Patent Document 1).

On the other hand, the conventional intermediate transfer medium has a drawback that it is relatively flammable because the base material sheet is made of a resin even though a high-pressure transfer bias is applied. Usually, the conventional intermediate transfer medium has flame retardancy of UL94 VTM-2 or less.
For this reason, conventionally, when an intermediate transfer medium is incorporated into an image forming apparatus, the entire intermediate transfer medium is incorporated by covering it with a cover having flame retardancy.
Therefore, a large installation space is required.

On the other hand, currently, a sheet in which a flame-retardant layer having fire extinguishing properties is sandwiched between resin layers is known.
This sheet has a property that it is very difficult to burn because a flame retardant layer having a fire extinguishing property (a property of depriving oxygen) is provided between the resin layers.
Therefore, if this sheet can be used as a base sheet for an intermediate transfer medium, an intermediate transfer medium that is difficult to burn can be obtained.
However, the fire retardant having fire extinguishing properties does not have adhesiveness.
For this reason, the manufacturing method as described in Patent Document 1, that is, the end portions of the sheet are opposed to each other with a gap, the welding member is brought into contact with the facing portion, and the welding member is contacted with an ultrasonic horn or the like. A cylindrical intermediate transfer medium cannot be obtained by the method of melting and welding the end portions of the sheet. This is because the flame retardant in the vicinity of the bonded portion interferes with the welding of the resin layers and decreases the bonding strength.
JP 11-282260 A

  The problem to be solved is that it is not possible to obtain a cylindrical intermediate transfer medium having a base sheet of a sheet in which a flame retardant layer having fire extinguishing properties is sandwiched between resin layers.

In the intermediate transfer medium of the present invention, the end portions of a sheet provided with a conductive layer and a resistance layer on one side of a base sheet in which a flame retardant layer having fire extinguishing properties is sandwiched between resin layers are made to face each other with a gap between them. The first welding member made of the same material as the layer is melted and pushed into the gap, and the flame retardant near the opposing portions of the sheet ends is melted and extruded while the ends of the sheets are pushed together. welded to form a cylindrical shape, to further end welded portion between said sheet, melting the second welding member Sowase the second weld member made of the resin layer and the same material on the resin layer side In this case, the welding is performed such that the welded portion is pressed into the welded portion between the end portions of the sheet and the welded portion is lined.
Between the gap is preferably set to 50 to 250 [mu] m.

In the intermediate transfer medium of the present invention, the end portions of the sheet provided with the conductive layer and the resistance layer on one side of the base sheet having the fire retardant flame retardant layer sandwiched between the resin layers are opposed to each other, and the vicinity of the facing portion. The flame retardant is welded while being extruded.
That is, since the flame retardant having no adhesiveness is pushed out in the vicinity of the facing portion between the end portions of the sheet, an adhesive state by the resin layer sandwiching the flame retardant layer is obtained.
Therefore, according to the present invention, it is possible to obtain a cylindrical intermediate transfer medium having a base sheet of a sheet in which a fire-retardant flame retardant layer is sandwiched between resin layers, that is, a cylindrical intermediate transfer medium that is difficult to burn.
As a result, according to the intermediate transfer medium of the present invention, it is not necessary to cover it with a cover, and the space for incorporation into the image forming apparatus can be reduced correspondingly, so that the entire image forming apparatus can be reduced in size. it can.
In addition, when the flame retardant layer is a brominated flame retardant layer, a cylindrical intermediate transfer medium that is more difficult to burn can be obtained.
In addition, it is also possible to create an electrically uniform resistor by kneading a conductive material into a material such as polyimide, which itself has flame retardancy, and in this case, an intermediate transfer medium can be created with this resistor. The cost of the material is high and the bending resistance is low, so there is a problem that the durability during running is poor, and when using materials such as silicon rubber, the circumference change due to load fluctuation is large, so the image There arises a problem that the deviation becomes large.
On the other hand, according to the present invention, such a problem does not occur.

FIG. 1 is a schematic side view showing the internal structure of an example of an image forming apparatus using an embodiment of an intermediate transfer medium according to the present invention.
This image forming apparatus is a color image forming apparatus capable of forming a full-color image on both sides of a sheet of A3 size at most, and includes a case 10, an image carrier unit 20 accommodated in the case 10, and an exposure. An image forming unit having a unit 30, a developing unit 40, an intermediate transfer body unit 50, and a fixing unit 60 as a fixing unit, and a sheet on which an image is formed on one side (or both sides as will be described later) by the image forming unit. A transport path 16 that transports toward a paper discharge tray 15 that is a paper discharge section, and the paper transported toward the paper discharge section 15 by the transport path 16 is switched back to form an image on the other side. And a return path 17 for returning the image toward the image forming unit. A paper discharge roller unit 70 is provided in front of the paper discharge tray 15.
A frame (not shown) of the apparatus main body is provided in the case 10, and each unit is attached to the frame.

The image carrier unit 20 includes a photoconductor (image carrier) 21 having a photosensitive layer on the outer peripheral surface, and a charging unit (scorotron charger) 22 for uniformly charging the outer peripheral surface of the photoconductor 21. Then, the outer peripheral surface of the photoconductor 21 uniformly charged by the charging means 22 is selectively exposed with the laser light L from the exposure unit 30 to form an electrostatic latent image. The developing device 40 applies toner as a developer to form a visible image (toner image), and this toner image is primarily transferred to an intermediate transfer belt 51 (an example of an intermediate transfer medium) 51 of the intermediate transfer unit 50 at a primary transfer portion t1. Further, the toner image is transferred and further transferred to the transfer target sheet at the secondary transfer portion t2.
The image carrier unit 20 includes a cleaning unit (cleaning blade) 23 that removes toner remaining on the surface of the photoconductor 21 after the primary transfer, and a waste toner storage that stores the waste toner removed by the cleaning unit 23. A portion 24 is provided.

In the case 10, a sheet from a sheet feeding tray 18 to be described later is conveyed to the secondary transfer unit t <b> 2, and the sheet on which an image is formed on one side by the secondary transfer unit t <b> 2 is a discharge roller unit 70 on the upper surface of the case 10. The transport path 16 transported toward the paper discharge tray section 15 by means of this, and the paper transported halfway toward the paper discharge roller section 70 and the paper discharge tray section 15 by this transport path 16 is switched back to the other side as well. A return path 17 for returning the image to the secondary transfer portion t2 is provided to form an image.
Under the case 10, there are provided a paper feed tray 18 for laminating and holding a plurality of sheets, and a paper feed roller 19 for feeding the sheets one by one toward the secondary transfer portion t2.
A gate roller 10g is provided in the path from the conveyance path 16 and the return path 17 to the secondary transfer portion t2, for controlling the timing of paper supply to the secondary transfer portion t2.

The developing device 40 is a rotary developing device, and a plurality of developing device cartridges each containing toner are detachably attached to the rotating body main body 41. In this embodiment, a yellow developer cartridge 42Y, a magenta developer cartridge 42M, a cyan developer cartridge 42C, and a black developer cartridge 42K are provided (in the drawing, yellow Only the developing device cartridge 42Y is directly drawn), and the rotating body main body 41 is rotated at a pitch of 90 degrees in the direction of the arrow so that the developing roller 43 is selectively brought into contact with the photosensitive body 21 and the photosensitive body 21 The surface can be selectively developed.
The exposure unit 30 is configured to irradiate the photosensitive member 21 with the laser light L from an exposure window 31 made of plate glass or the like.

The intermediate transfer body unit 50 stabilizes the state of the belt 51 at a unit frame (not shown), a driving roller 54, a driven roller 55, a primary transfer roller 56, and a primary transfer portion t1 that are rotatably supported by the frame. A guide roller 57 and a tension roller 58 and an intermediate transfer belt 51 as the intermediate transfer medium stretched around these rollers are provided, and the belt 51 is driven to circulate in the direction of the arrow shown in the figure. The primary transfer portion t1 is formed between the photosensitive member 21 and the primary transfer roller 56, and the secondary transfer portion t2 is in a pressure contact portion between the driving roller 54 and the secondary transfer roller 10b provided on the main body side. It is formed.
The secondary transfer roller 10b can be brought into contact with and separated from the drive roller 54 (and therefore with respect to the intermediate transfer belt 51), and a secondary transfer portion t2 is formed when contacted.
Therefore, when forming a color image, a toner image of a plurality of colors is superimposed on the intermediate transfer belt 51 with the secondary transfer roller 10b being separated from the intermediate transfer belt 51, and then a color image is formed. The secondary transfer roller 10b comes into contact with the intermediate transfer belt 51, and the paper is supplied to the contact portion (secondary transfer portion t2), whereby a color image (toner image) is transferred onto the paper. .
The sheet on which the toner image has been transferred passes through the pressure contact portions of the fixing roller pair 61 and 62 of the fixing unit (fixing device) 60 to melt and fix the toner image, and is conveyed by the conveying roller pair 14 and is conveyed to the discharge roller portion. 70 and the paper discharge tray 15 are discharged.

FIG. 2 is a schematic partially omitted sectional view of the intermediate transfer belt 51 as an embodiment of the intermediate transfer medium according to the present invention.
As shown in FIGS. 3 and 4, the intermediate transfer belt 51 includes a conductive layer 51f and a resistance layer 51g on one side of a base sheet 51d in which a fire-retardant flame retardant layer 51a is sandwiched between resin layers 51b and 51c. Both ends 51i, 51i of the sheet 51h provided with a gap are opposed to each other with a gap C therebetween, and as described later, the flame retardant 51a1 near the facing portion 51i is extruded and welded to form a cylinder.
The flame retardant layer 51a is a flame retardant layer made of a brominated flame retardant, for example, hexabromobenzene (HBB).
As the resin layers 51b and 51c, resin films having high elastic modulus and high bending resistance are used. Thereby, durability can be ensured and a change in circumference due to load fluctuation can also be suppressed. Specifically, for example, a synthetic resin film made of polyethylene terephthalate or the like is used.
The conductive layer 51f is formed by performing metal deposition on the surface of the resin layer 51c.
The resistance layer 51g can be formed, for example, by applying a resin solution in which conductive particles are dispersed onto the conductive layer 51f, and curing and drying.
When the intermediate transfer belt 51 is incorporated in the image forming apparatus as described above to form an image, a transfer bias is applied to the conductive layer 51f, and a toner image is formed on the surface of the resistance layer (medium resistance layer) 51g. 21 is transcribed.

The intermediate transfer belt 51 is manufactured as follows.
(I) As shown in FIG. 4A, on the heat-resistant flat table 80, both end portions 51i and 51i of the sheet 51h are opposed to each other with a gap C therebetween, and the gap C is straddled (closed). The tape-like first welding member 51j that is tape-like and narrow (for example, about 3 mm) is attached. The first welding member 51j is made of the same material as the resin layers 51b and 51c, for example, polyethylene terephthalate.
(Ii) As shown in FIG. 4 (b), a first welding tool (for example, an ultrasonic horn) 81 is applied to the first welding member 51j, and the first welding member 51j and the sheet are joined by the first welding tool 81 and the table 80. 51h, and the first welding tool 81 is moved along the longitudinal direction of the first welding member 51j (the direction perpendicular to the paper surface of FIG. 4 and along the longitudinal direction of the gap C). Then, both end portions 51i of the sheet 51h are welded so as to be pushed into the gap C while melting the first welding member 51j.
At this time, on the first welding tool 81 side, the end portion 51b1 of the resin layer 51b and the end portion 51a1 of the flame retardant layer 51a are melted together with the first welding member 51j, and these are mixed, and this mixture 51k (the surplus part that could not fit in the gap C) protrudes in a burr shape from between both end portions 81a of the first welding tool 81 and the back surface of the sheet 51h. In other words, as the first welding member 51j, a member having a volume larger than that of the gap C is used.
As described above, when the first welding tool 81 is used for welding, the surplus portion 51k protrudes, so that at least both end portions 81a of the welding tool 81 are rounded (R) so as to be easily protruded. As the first welding tool, a tool having a semispherical tip can be used so that the spherical surface is applied to the welded portion.
FIG. 5A shows a cross section of the joint (welded portion) J1 in a state where the first welding is completed.

(Iii) As shown in FIG.5 (b), a cutting tool (for example, a razor-shaped cutter) is run in the direction orthogonal to the paper surface of FIG. 5, and the surplus portion 51k is cut off.
(Iv) As shown to Fig.6 (a), the 2nd welding member 51m of tape shape and wide (for example, about 5 mm) is attached so that the said junction part J1 may be plugged up. The second welding member 51m is made of the same material as the resin layer 51b, for example, polyethylene terephthalate.
(V) As shown in FIG. 6B, a second welding tool (for example, an ultrasonic horn) 83 is applied to the second welding member 51 m, and the second welding member 51 m and the table 80 are combined with the second welding tool 83 and the table 80. The second welding tool 83 is placed along the longitudinal direction of the second welding member 51m (the direction perpendicular to the paper surface of FIG. 6 and along the longitudinal direction of the joint J1) so as to sandwich the joint J1. While moving, the second welding member 51m is melted and welded so as to partially press the joint member J1 into the joint portion J1 so as to line the joint portion J1.
At this time, on the second welding tool 83 side, the end 51b2 (see FIG. 6) (a) of the resin layer 51b and the mixture are partially melted together with the second welding member 51m, and these are mixed. At the same time, a part (excess part) 51n of the second mixing part protrudes from between the both ends 83a of the second welding tool 83 and the back surface of the sheet 51h.
Therefore, burr pressing portions 83a are provided at both ends of the second welding tool 83 so that the protruding excess portion 51n does not protrude in a burr shape. The pressing portion 83a is formed in a step shape at both ends of the second welding tool 83, but the shape thereof can be changed as appropriate, for example, it can be curved.
In FIG. 7, the cross section of the junction part (welding part) J2 of the state which the said 2nd welding was complete | finished is shown.
In this way, the intermediate transfer belt 51 as shown in FIG. 1 is created.

According to the above intermediate transfer medium, the following effects can be obtained.
(A) The above-described intermediate transfer medium 51 includes an end of a sheet 51h in which a fire-retardant flame retardant layer 51a is sandwiched between resin layers 51b and 51c, and a conductive layer 51f and a resistance layer 51g are provided on one surface of a base sheet 51d. The portions 51i are opposed to each other, and the flame retardant 51a1 near the facing portion is welded while being extruded.
That is, since the flame retardant (51a) having no adhesiveness is pushed out in the vicinity of the facing portion between the end portions of the sheet, an adhesion state by the resin layers 51b and 51c sandwiching the flame retardant layer 51a is obtained. Will be.
Therefore, according to this embodiment, a cylindrical intermediate transfer medium having a base sheet of a sheet 51d in which a fire-retardant flame retardant layer 51a is sandwiched between resin layers 51b and 51c, that is, hardly burned (UL94 VTM-0 or more) (A flame-retardant) cylindrical intermediate transfer medium 51 is obtained.
As a result, according to the intermediate transfer medium 51, it is not necessary to cover the intermediate transfer medium 51 with a cover and the space for incorporation into the image forming apparatus can be reduced correspondingly, so that the entire image forming apparatus can be downsized. .
(B) Since the flame retardant layer 51a is a brominated flame retardant layer, a cylindrical intermediate transfer medium that is more difficult to burn can be obtained.
(C) Durability can be ensured by using a resin film having a high elastic modulus and bending resistance, such as polyethylene terephthalate, on the outside of the flame retardant, and a change in circumferential length due to load fluctuation can also be suppressed.
(D) By making the intermediate transfer medium into multiple layers, it is possible to use an optimum material according to the roles of the flame retardant and bending resistant base material and resistor.
(E) Since the welding member 51j is made of the same material as the resin layers 51b and 51c, the strength of the joint portion is improved.
(F) Since the first welding is performed by at least the welding tool 81 rounded at both end portions 81a, the flame retardant 51a near the end portion is smoothly pushed out, so that a stronger bonding state is achieved. Can be obtained.
(G) After the first welding, the flame retardant 51k pushed out on both sides of the first welding part J1 is removed, and then the second welding is performed. Therefore, during the second welding, the second welding part J2 The height of the flame retardant (51n) extruded on both sides can be reduced.
(H) At the time of the second welding, the height of the flame retardant 51n pushed out on both sides of the second welding portion J2 is suppressed by pressing portions 83a provided at both ends of the welding tool 83 that performs the second welding. It is possible to obtain a small joint portion. As a result, the process of removing the surplus portion (burrs) can be omitted, and a smooth running state of the belt can be obtained.
The gap C is preferably 50 to 250 μm. This is because the melted welding member can be solidified flat on the surface of the intermediate transfer medium, the surface resistance layer 51g can be fixed, and the resistance layer 51g can be prevented from being peeled off during operation.
8A and 8B are cross-sectional views showing comparative examples.
As shown in FIG. 8A, the end portions of the sheet 51h are opposed to each other without providing the gap C (see FIG. 3), and welding is performed using the welding members 51j and 51m in the same manner as the above-described welding method. It is possible.
However, when welded in this way, the bonding strength (particularly the bonding strength between the ends of the conductive layer 51f and the resistance layer 51g) at the bonding surface 51p between the ends of the resin layer 51c, the conductive layer 51f, and the resistance layer 51g is obtained. Since almost no image can be obtained, it is not desirable to form a certain number of images because the conductive layer 51f and the resistive layer 51g are likely to be missing as shown in FIG.
On the other hand, according to the embodiment, the welding member 51j enters the gap C, and the end portions of the resin layer 51c, the conductive layer 51f, and the resistance layer 51g are firmly bonded to each other. The problem of missing 51q does not occur.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the gist of the present invention.
For example,
Multiple layers of flame retardant layers may be provided.
The flame retardant layer may be formed of different types of flame retardants (a plurality of flame retardants exhibiting fire-extinguishing properties when both are mixed).

1 is a schematic side view showing an internal structure of an example of an image forming apparatus using an embodiment of an intermediate transfer medium according to the present invention. 1 is a schematic partially omitted cross-sectional view of an intermediate transfer belt which is an embodiment of an intermediate transfer medium according to the present invention. Explanatory drawing of a welding process. (A) and (b) are welding process explanatory drawings. (A) and (b) are welding process explanatory drawings. (A) and (b) are welding process explanatory drawings. The expanded sectional view of a welding part. (A) (b) is sectional drawing which shows a comparative example.

Explanation of symbols

  51: Intermediate transfer belt (intermediate transfer medium), 51a: flame retardant layer, 51b, 51c: resin layer, 51d: substrate sheet, 51f: conductive layer, 51g: resistance layer, 51h sheet, 51i end.

Claims (2)

A first layer made of the same material as that of the resin layer, with the end portions of the sheet provided with the conductive layer and the resistance layer opposed to each other on one side of the base sheet with the fire retardant flame retardant layer sandwiched between the resin layers. The welding member is melted and pushed into the gap while the flame retardant near the facing portion of the sheet is melted and extruded, and the end portions of the sheet are welded to form a cylindrical shape. Further, a second welding member made of the same material as that of the resin layer is attached to the resin layer side with respect to the welding portion between the end portions of the sheet, and the second welding member is melted to be attached to the end of the sheet. An intermediate transfer medium, wherein the welded portion is welded so as to be partially pressed into a welded portion between the portions and the welded portion is lined up. The intermediate transfer medium according to claim 1, wherein between said gap, characterized in that the set to 50 to 250 [mu] m.

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