JP2004345099A - Annular die for manufacturing seamless belt and seamless belt manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an annular die capable of efficiently manufacturing a seamless belt, wherein a surface layer and a rear surface layer are formed of a low hardness material and an intermediate layer is formed of a high hardness material, by the reduced number of processes. <P>SOLUTION: The annular die 1 is used for manufacturing the seamless belt having a three-layered structure comprising the surface layer, the intermediate layer and the rear surface layer and equipped with a first supply part 2 for supplying the low hardness material from a first extruder, a second supply part 3 for supplying the high hardness material from a second extruder, an annular discharge port 6 from which the belt formed of the low/high hardness materials is extruded in a molten state, a first annular route 21 for guiding the low hardness material to the discharge port 6 from the supply part 2, a second annular route 22 for allowing the route 21 to branch on the way thereof and meeting with the route 21 at a first confluent position X1 and a third annular route 31 meeting with the route 21 at a second confluent position X2 provided on this side of the confluent position X1 from the supply part 3. The belt, wherein the intermediate layer is formed of the high hardness material and the surface layer and the rear surface layer are formed of the low hardness material, is extruded in a molten state from the discharge port 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

次に成型方法を説明する。２層式押出装置にてφ４０ｍｍの押出機側に第２ベルト形成材料であるＰＢ−５６０に導電剤で導電調整されたペレット（押し出し温度２６５℃）を、また、φ３０ｍｍの押出機側に第１ベルト形成材料であるＥＮ−２０３４に導電剤で導電調整されたペレット（押し出し温度２２５℃） を同時に押出機からギヤーポンプを経て、φ２７５ｍｍの２層共押し出し環状ダイへ送り込み、同時に溶融押し出しする。溶融押し出しされた樹脂は、φ２６０ｍｍの冷却マンドレルに接触させ、冷却・固化し、シームレスベルトとする。環状ダイの温度制御には、外側にバンドヒーターを、 環状ダイの内側にプレートヒーターを取り付けて制御する。
第１供給部２より、第１ベルト形成材料のＥＮ−２０３４が第１押出機４により溶融され、ギヤーポンプを経て環状ダイに送られ、第１環状経路２１の途中で一旦分岐する。一方、第２供給部３より、 第２ベルト形成材料のＰＢ−５６０が第２押出機５により溶融され、 ギヤーポンプを経て環状ダイに送られる。
【００３２】
第１環状経路２１で分岐した第１ベルト形成材料のＥＮ−２０３４は、第１合流位置Ｘ１で再び合流するが、その前に第２供給部３より溶融押し出しされた第２ベルト形成材料のＰＢ−５６０が第３環状経路３１を通り、第１合流位置Ｘ１よりも上流の第２合流位置Ｘ２にて、第１環状経路２１より溶融押し出しされた第１ベルト形成材料のＥＮ−２０３４と合流する。その際、第１供給部２から第２合流位置Ｘ２までの距離をＤ１とし、第２供給部３から第２合流位置Ｘ２までの経路の距離をＤ２とし、Ｌ１＝Ｄ１−Ｄ２とした場合、Ｌ１＝３０〜３００ｍｍに設定する。
【００３３】
すなわち、 Ｌ１＜３０ｍｍの場合は、構造的に不可能であり、Ｌ１＞３００ｍｍの場合は、第２ベルト形成材料のＰＢ−５６０が十分に溶融しない、あるいは、第１ベルト形成材料のＥＮ−２０３４に余計な熱を与えてしまい、成分が熱分解する怖れがある。
【００３４】
第２合流位置Ｘ２で合流した第１ベルト形成材料ＥＮ−２０３４は、第２ベルト形成材料ＰＢ−５６０と合わさり、２層又は硬度が傾斜された状態になる。（傾斜とは、硬度が段階的に変化している状態をいう。）
この２層もしくは傾斜した第１ベルト形成材料のＥＮ−２０３４と、第２ベルト形成材料のＰＢ−５６０が、再び第１合流位置Ｘ１で、第２環状経路２２を流れる第１供給部から一旦分岐した第１ベルト形成材料のＥＮ−２０３４と合流する。そして、２層もしくは傾斜した２つのベルト形成材料を挟み込む形で、更に積層もしくは傾斜した状態となる。すなわち、 真中に第２ベルト形成材料のＰＢ−５６０が、その両側に第１ベルト形成材料のＥＮ−２０３４が形成された状態で環状ダイ１の環状吐出口６から溶融押し出しされる。これにより、硬度の高い材料を硬度の低い材料で両面を被覆したようなシームレスベルトが連続的に成型可能になる。
【００３５】
ここで第１合流位置Ｘ１と第２合流位置Ｘ２の経路の差をＬ２とした場合、Ｌ２＝５ｍｍ〜１５０ｍｍにするのが好ましい。すなわち、 Ｌ２＜５ｍｍの場合、３つの樹脂材料が混ざり合ってしまい層が形成されない。また、Ｌ２＞１５０ｍｍの場合は、安定した均一な厚み分布にならないという問題がある。したがって、３つの層の厚み分布を均一なものにするためには、Ｌ２＝５ｍｍ〜１５０ｍｍにするのが好ましい。
【００３６】
上記のようなＥＮ−２０３４とＰＢ−５６０は同種の材料であるので、上記実施例に基づいて溶融押し出しすると、硬度が傾斜した状態になる。これにより得られたシームレスベルトは、表面層Ｓ１，中間層Ｓ２，裏面層Ｓ３からなり、表面層Ｓ１と裏面層Ｓ３は、同じ材料ＥＮ−２０３４で形成され、中間層Ｓ２はＰＢ−５６０で形成される。このことにより、表面層Ｓ１のＥＮ−２０３４は、トナーが転写される面であり、又トナー以外の異物をクッションとして受け止める機能を有する。又、 裏面層Ｓ３も硬度の低いＥＮ−２０３４であり、裏面側が駆動シャフトにより駆動させられる関係から、駆動シャフトとシームレスベルトの間で滑りが生じなくなる。
【００３７】
また、中間層Ｓ２のＰＢ−５６０については硬度の高い（剛性の高い）材料であるために、ベルト長手方向に沿って伸びない。これにより、カラー画像を形成する場合は、トナーを同じ場所に４回転写させることが可能になる。
【００３８】
本発明によれば、３層構造のシームレスベルトを１層づつ順番に形成していくのではなく、一度に成形するようにしているので、工程を少なくすることができ、コストを下げることができる。
【図面の簡単な説明】
【図１】シームレスベルト製造用環状ダイの縦断面図
【図２】シームレスベルト製造用環状ダイの平面図
【図３】シームレスベルトの断面構造
【符号の説明】
１ 環状ダイ
２ 第１供給部
３ 第２供給部
４ 第１押出機
５ 第２押出機
６ 環状吐出口
２０ 水平経路
２１ 第１環状経路
２２ 第２環状経路
３１ 第３環状経路
Ｘ１ 第１合流位置
Ｘ２ 第２合流位置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an annular die for manufacturing a seamless belt used for a copying machine, a printer, and the like, and a method for manufacturing a seamless belt.
[0002]
[Prior art]
2. Description of the Related Art Copiers and printers use a conductive belt wound around a plurality of support rollers as an intermediate transfer unit for transferring an image formed on the surface of a photosensitive drum or the like to a transfer material (paper or the like). Can be This belt is required to clean the toner adhered to the surface and to make the electric resistance uniform over the entire belt. Therefore, an endless belt having no joint, that is, a so-called seamless belt is preferably used. On the other hand, in a copying machine, a printer, and the like, an image to be formed is also shifting from monochrome to color, and a required quality level is also increasing. In the case of color, it is necessary to transfer the toner accurately to the same location four times. However, it is difficult to satisfy the quality required for color with a seamless belt having a single layer structure.
[0003]
That is, the surface of the belt is preferably elastic because it is necessary to increase the transfer efficiency of the toner and to receive foreign substances other than the toner as a cushion. Also, it is necessary to prevent the back surface of the belt from slipping with the drive shaft, and from this point, it is preferable that the belt has elasticity. On the other hand, if the belt is elongated in the longitudinal direction, color shift occurs when a color image is formed. Therefore, from this point, it is preferable that the belt has higher rigidity. As described above, in order to provide the belt with the contradictory properties, it cannot be realized with a seamless belt having a single-layer structure. Therefore, techniques disclosed in the following patent applications 1 and 2 are known.
[0004]
Patent Document 1 discloses a conductive belt having a two-layer structure and a three-layer structure of a rubber layer and an elastomer layer. Further, it is described that the belt may be formed after forming the rubber layer and then forming the elastomer layer, or may be formed in the reverse order.
[0005]
Patent Literature 2 discloses a seamless belt having a multilayer structure having at least an inner layer and an outer layer. The inner layer material and the outer layer material are obtained by co-extrusion molding.
[0006]
[Patent Document 1]
JP-A-2000-167991 (FIG. 1, paragraph 0038, etc.)
[Patent Document 2]
Patent No. 3322842 (Claims, paragraphs 0040 to 0045)
[0007]
[Problems to be solved by the invention]
However, the above prior art has problems as described below. That is, Patent Document 1 employs a method of sequentially forming each layer when manufacturing a seamless belt having a three-layer structure of a rubber layer and an elastomer layer. Therefore, the number of steps is large and the cost is high.
[0008]
In addition, Patent Literature 2 only describes a two-layer structure in the embodiment of the invention. Although there is disclosure that the inner layer and the outer layer are coextruded, no specific structure of the annular die is disclosed. Further, different materials are used for the inner layer and the outer layer, and a seamless belt having the structure intended in the present application is not manufactured.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to form a front layer and a back layer with a material having a first hardness, and to form an intermediate layer having a second hardness higher than the first hardness. It is an object of the present invention to provide an annular die capable of efficiently manufacturing a seamless belt made of a material having a hardness of 1 with a small number of man-hours, and a method of manufacturing a seamless belt using the annular die.
[Means for Solving the Problems]
To solve the above problems, the annular die for producing a seamless belt according to the present invention is:
A second hardness having a three-layer structure of a surface layer, an intermediate layer and a back surface layer, wherein the surface layer and the back surface layer are formed of a material having a first hardness, and the intermediate layer has a higher hardness than the first hardness; An annular die for producing a seamless belt formed of a material having
A first supply unit to which a first belt forming material having a first hardness is supplied from a first extruder;
A second supply unit to which a second belt forming material having a second hardness higher than the first hardness is supplied from the second extruder;
An annular discharge port from which the seamless belt formed of the first belt forming material and the second belt forming material is melted and extruded;
A first annular path for guiding the first belt forming material from the first supply unit to the annular discharge port;
A second annular path that once branches off the first annular path on the way and then joins the first annular path again at a first junction position;
A third belt that guides the second belt forming material from the second supply section to the first annular path and merges with the first annular path at a second junction position located closer to the front than the first junction position. With an annular path,
The intermediate belt is formed from the second belt-forming material, and the seamless belt, in which the front surface layer and the back surface layer are formed from the first belt-forming material, is melt-extruded from the annular discharge port. It is assumed that.
The operation and effect of the annular die with this configuration are as follows.
From the first supply unit, a first belt forming material having a first hardness (lower hardness) is supplied. A second belt-forming material having a second hardness (higher hardness) is supplied from the second supply unit. An annular discharge port is provided, from which a seamless belt is melt-extruded. The low-hardness material supplied from the first supply unit is guided by the first annular path. The first annular path branches on the way and merges again at the first merging position. That is, the first belt forming material once branches and splits into two hands, and then merges again.
[0010]
On the other hand, the material having high hardness supplied from the second supply unit is guided by the third annular path, and joins the first annular path at the second junction position closer to the front than the first junction position. That is, they merge before the first merging position. Therefore, the flow of the second belt forming material forming the intermediate layer merges with the first belt forming material forming the back surface layer at the second merging position. Thereafter, the first belt forming material forming the surface layer joins the intermediate layer at the first joining position. Thereby, the desired seamless belt having a three-layer structure can be melt-extruded from the annular discharge port. As a result, it is possible to provide an annular die capable of efficiently manufacturing a seamless belt with a small number of steps.
[0011]
As a preferred embodiment of the present invention, a distance of a path from the first supply unit to the second junction is D1, a distance of a path from the second supply unit to the second junction is D2, and L1 = D1-D2 (where D1 and D2 are distances measured by cutting on a plane including the center axis of the annular die)
L1 = 30 mm to 300 mm
Is set.
[0012]
That is, when L1 <30 mm, there is a problem that it is structurally impossible. When L1> 300 mm, D2 is much shorter than D1, so that the second belt forming material is not sufficiently melted. There is. Therefore, in order for the first belt forming material and the second belt forming material to form two layers and to flow uniformly toward the first merging position, L1 is preferably 30 mm to 300 mm.
[0013]
As another preferred embodiment of the present invention, when the distance difference between the path of the first junction position and the path of the second junction position is L2,
L2 = 5mm-150mm
Is set.
[0014]
That is, when L2 <5 mm, there is a problem that the resins are mixed, and when L2> 150 mm, there is a problem that a stable and uniform thickness distribution is not obtained. Therefore, in order to make the thickness distribution of the three layers uniform, L2 is preferably 5 mm to 150 mm.
[0015]
In order to solve the above-mentioned problems, a seamless belt manufacturing method according to the present invention includes:
A second hardness having a three-layer structure of a surface layer, an intermediate layer and a back surface layer, wherein the surface layer and the back surface layer are formed of a material having a first hardness, and the intermediate layer has a higher hardness than the first hardness; A method for producing a seamless belt formed of a material having
Supplying a first belt forming material having a first hardness from a first extruder;
Supplying a second belt-forming material having a second hardness higher than the first hardness from the second extruder;
Melt extruding a seamless belt formed from the first belt forming material and the second belt forming material from an annular discharge port;
Guiding the first belt forming material from the first supply section to the annular discharge port through a first annular path;
Guiding the first belt forming material by a second annular path that once branches off the first annular path in the middle and then joins the first annular path again at a first junction position;
Guiding the second belt-forming material from the second supply section by a third annular path that merges with the first annular path at a second merging position located closer to the front than the first merging position;
Forming the intermediate layer with the second belt-forming material and melting and extruding the seamless belt formed with the first and second belt-forming materials from the annular discharge port. It is assumed that.
The operation and effect of this configuration are as described above.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the annular die for producing a seamless belt according to the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of the annular die (a cross section cut along a vertical plane including a central axis), and FIG. 2 is a plan view of the annular die.
[0017]
<Structure of annular die>
FIG. 3 shows a sectional structure of a seamless belt manufactured by the annular die 1 according to the present invention. The seamless belt has a three-layer structure, and includes a surface layer S1, an intermediate layer S2, and a back layer S3. The surface layer S1 and the back surface layer S3 are formed of the same material. The surface layer S1 is a surface to which the toner is transferred. Further, it has a function of receiving foreign matter G other than toner as a cushion. Therefore, the surface layer S1 is formed of a material having low hardness. In addition, since the back surface side of the back surface layer S3 is driven by the drive shaft, it is necessary to prevent slippage between the drive shaft and the seamless belt. Therefore, the back surface layer S3 is also formed of a material having the same low hardness as the surface layer S1, that is, the same material as the surface layer S1.
[0018]
The intermediate layer S2 is formed of a material having high hardness (high rigidity) so that the belt does not extend in the longitudinal direction. When a color image is formed, it is necessary to transfer the toner to the same location four times, so that rigidity is required.
[0019]
If the back layer and the surface layer are formed of different materials, the seamless belt will warp due to the difference in the shrinkage of the materials. According to the present invention, since the back layer and the front layer sandwiching the intermediate layer are made of the same material, the occurrence of warpage can be suppressed.
[0020]
The annular die 1 is used for melting and extruding a seamless belt. The annular die 1 has a substantially cylindrical shape as a whole shape. The annular die 1 is arranged so that the cylindrical axis is oriented in the vertical direction, a material is supplied from the upper portion of the annular die 1, and a seamless belt is melt-extruded from the lower bottom surface. A first supply unit 2 and a second supply unit 3 are provided above the annular die 1. In FIG. 2, the first supply unit 2 and the second supply unit 3 are provided at positions separated by 90 ° in the circumferential direction. However, it is not limited to this.
[0021]
A first extruder 4 is connected to the first supply unit 2, and a low-hardness material (corresponding to a first belt forming material) is melted and extruded and supplied. The first extruder 4 is provided with a hopper 4a for supplying the material in the form of pellets or the like. A second extruder 5 is connected to the second supply unit 3, and a high hardness material (corresponding to a second belt forming material) is melted and extruded and supplied. The second extruder 5 is also provided with a hopper 5a.
[0022]
As shown in FIG. 1, the first supply unit 2 is located at a position slightly higher than the second supply unit 3. At the bottom of the annular die 1, an annular discharge port 6 is provided, from which a seamless belt having a three-layer structure is melt-extruded. A path for guiding the low-hardness material supplied from the first supply unit 2 to the annular discharge port 6 is provided. After being guided from the first supply unit 2 to the horizontal path 20 first, it is guided to the first annular path 21 facing upward and downward. Also, the horizontal path 20 is branched on the way. It is also connected to a second annular path 22 that is oriented vertically. The second annular path 22 joins the first annular path 21 again at the first junction position X1. That is, the low-hardness material supplied to the first supply unit 2 is guided to both the first annular path 21 and the second annular path 22.
[0023]
In addition, the second supply unit 3 is also guided to the horizontal path 30 first, and then to the third annular path 31 that faces upward and downward. The third annular path 31 is located outside the first annular path 21 and inside the second annular path 22. The third annular path 31 merges with the first annular path 21 at the second merging position X2. The second merging position X2 is located on the front side (upward in FIG. 1) of the first annular path X1.
By arranging such an annular path, first, at the second merging position X2, the high-hardness material as the intermediate layer merges with the outside of the low-hardness material contributing to the formation of the back surface layer. Further, at the first merging position X1, low-hardness materials contributing to the formation of the surface layer merge. Thereby, a seamless belt having a three-layer structure in which the front surface layer and the back surface layer are formed of a low-hardness material and the intermediate layer is formed of a high-hardness material can be melt-extruded from the annular discharge port 6. The seamless belt melt-extruded and formed from the annular discharge port 6 is sequentially taken up by a known mandrel (not shown) and a take-up machine.
[0024]
Heaters (not shown) are provided on the outer peripheral surface and inside of the annular die 1, and the annular die 1 is set to an appropriate temperature to melt the material flowing in the path. Specifically, a band heater is provided outside the annular die 1, and a plate heater is provided inside the annular die 1.
[0025]
Next, a description will be given of an appropriate setting value of the path length for the annular path. First, let D1 be the distance of the path from the first supply unit 2 to the second merging position X2. The distance of the horizontal path 20 and D _11, the distance along the path from a height of the horizontal path 20 is disposed to the second merging position X2 and D _12. D1 ₌ the _D 11 ₊ D _12. Similarly, the distance of the path from the second supply unit 3 to the second merging position X2 is D2. The distance of the horizontal path 30 and D _21, the distance along the route from the position of the height to the second merging position X2 and D _22. And D2 _{= D} 21 ₊ D _22. Then, if L1 = D1-D2,
L1 = 30 mm to 300 mm
It is preferable to set so that If L1 <30 mm, there is a problem that it is structurally impossible. This will be described in detail. From the above _{equation, L1 = D1-D2 = (} D 11 + D 12) - is a _{(D 21 + D 22) =} (D 11 -D 21) + (D 12 -D 22). Diameter here _{D 11} is generally about Fai30～fai40mm. If the horizontal path 20 and the horizontal path 30 are at the same height and depth, the annular paths will collide with each other. Therefore, it is necessary to put a step _(D 12 _{-D 22)} and the depth difference _(D 11 _{-D 21).} D ₁₁ and _{D 21} Datosuruto both diameter .phi.30 mm, becomes 30mm required minimum in this step. Further, since the annular path is very narrow (about several millimeters), the difference in depth (D ₁₁ -D ₂₁ ) becomes several millimeters, and if this numerical value is not considered, L1 <30 mm is structurally impossible.
[0026]
Further, if L1> 300 mm, D2 is much shorter than D1, so that there is a problem that the second belt forming material is not sufficiently melted. Therefore, in order for the first belt forming material and the second belt forming material to have two layers and to flow uniformly toward the first merging position, it is preferable to set as described above.
[0027]
Also, assuming that the distance difference between the routes of the first merging position X1 and the second merging position X2 is L2,
L2 = 5mm-150mm
It is preferable to set so that If L2 <5 mm, there is a problem that the resins are mixed.
If L2> 150 mm, there is a problem that a stable and uniform thickness distribution is not obtained. Therefore, in order to make the thickness distribution of the three layers uniform, it is preferable to set as described above.
[0028]
<About materials>
The belt forming material used for manufacturing the seamless belt according to the present invention will be described. It is preferable to use the same kind of material as the high hardness material and the low hardness material, but the material is not limited thereto. As the material, a thermoplastic resin is preferable, and the following materials can be used.
[0029]
That is, PBN (polybutylene naphthalate), thermoplastic polyurethane, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, polystyrene, AS resin, ABS resin, methacrylic resin, polycarbonate, polyphenylene oxide, polysulfone, celluloid, plastic polyethylene, Examples include polypropylene, fluororesin, polyamide, polyacetal, and saturated polyester.
[0030]
<Example>
Next, examples will be described. First, a material whose conductivity was adjusted based on Pelprene EN-2034 (a thermoplastic polyester elastomer manufactured by Toyobo Co., Ltd.) was used as the first belt forming material, and a conductive agent was added to PB-560 to adjust the conductivity. Using the material as a second belt forming material, melt extrusion is performed with an annular die. Examples of the type of the conductive agent include ionic conductivity and carbon conductivity. Table 1 shows the characteristics of each material alone.
[0031]
[Table 1]

Next, a molding method will be described. Pellets (extrusion temperature: 265 ° C.) of which conductivity has been adjusted with a conductive agent to PB-560, which is a second belt forming material, are placed on the extruder side of φ40 mm in the extruder side of φ40 mm by the two-layer type extruder. Pellets (extrusion temperature: 225 ° C.), the conductivity of which has been adjusted with a conductive agent, are simultaneously fed to a belt forming material EN-2034 via a gear pump from an extruder, into a two-layer co-extrusion die having a diameter of 275 mm, and simultaneously melt-extruded. The melt-extruded resin is brought into contact with a cooling mandrel of φ260 mm, cooled and solidified to form a seamless belt. To control the temperature of the annular die, a band heater is installed outside and a plate heater is installed inside the annular die.
From the first supply unit 2, EN-2034 of the first belt forming material is melted by the first extruder 4, sent to an annular die via a gear pump, and branched once in the first annular path 21. On the other hand, PB-560 of the second belt forming material is melted by the second extruder 5 from the second supply unit 3 and sent to the annular die via the gear pump.
[0032]
EN-2034 of the first belt forming material branched in the first annular path 21 joins again at the first merging position X1, but before that, the PB of the second belt forming material melt-extruded from the second supply unit 3 before. -560 passes through the third annular path 31 and joins EN-2034 of the first belt forming material melt-extruded from the first annular path 21 at a second joining position X2 upstream of the first joining position X1. . At this time, if the distance from the first supply unit 2 to the second junction position X2 is D1, the distance of the path from the second supply unit 3 to the second junction position X2 is D2, and L1 = D1-D2, L1 is set to 30 to 300 mm.
[0033]
That is, when L1 <30 mm, it is structurally impossible, and when L1> 300 mm, PB-560 of the second belt forming material does not melt sufficiently, or EN-2034 of the first belt forming material. May give excess heat, and the components may be thermally decomposed.
[0034]
The first belt forming material EN-2034 that has merged at the second merging position X2 is combined with the second belt forming material PB-560, and is in a two-layer or state in which the hardness is inclined. (The term “inclination” refers to a state in which the hardness changes stepwise.)
The two layers or the slanted first belt forming material EN-2034 and the second belt forming material PB-560 are once again branched from the first supply section flowing through the second annular path 22 at the first junction position X1. Merges with the first belt forming material EN-2034. Then, two layers or two inclined belt forming materials are sandwiched between the layers, and the belt is further laminated or inclined. That is, PB-560 of the second belt forming material is melted and extruded from the annular discharge port 6 of the annular die 1 in a state where EN-2034 of the first belt forming material is formed on both sides thereof. This makes it possible to continuously mold a seamless belt in which a high-hardness material is coated on both sides with a low-hardness material.
[0035]
Here, when the difference between the paths of the first junction position X1 and the second junction position X2 is L2, it is preferable that L2 = 5 mm to 150 mm. That is, when L2 <5 mm, the three resin materials are mixed and no layer is formed. When L2> 150 mm, there is a problem that a stable and uniform thickness distribution is not obtained. Therefore, in order to make the thickness distribution of the three layers uniform, it is preferable that L2 = 5 mm to 150 mm.
[0036]
Since EN-2034 and PB-560 as described above are the same type of material, when melt-extruded based on the above-described embodiment, a state in which the hardness is inclined is obtained. The seamless belt thus obtained is composed of a surface layer S1, an intermediate layer S2, and a back layer S3. The surface layer S1 and the back layer S3 are formed of the same material EN-2034, and the intermediate layer S2 is formed of PB-560. Is done. Thus, EN-2034 of the surface layer S1 is a surface to which the toner is transferred, and has a function of receiving foreign substances other than the toner as a cushion. In addition, the back surface layer S3 is also EN-2034 having a low hardness, and since the back surface is driven by the drive shaft, no slippage occurs between the drive shaft and the seamless belt.
[0037]
Further, since PB-560 of the intermediate layer S2 is a material having high hardness (high rigidity), it does not extend along the longitudinal direction of the belt. Thus, when forming a color image, it is possible to transfer toner four times to the same location.
[0038]
According to the present invention, the seamless belt having a three-layer structure is formed at once instead of being formed one by one in order, so that the number of steps can be reduced and the cost can be reduced. .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an annular die for producing a seamless belt. FIG. 2 is a plan view of an annular die for producing a seamless belt. FIG. 3 is a sectional structure of a seamless belt.
Reference Signs List 1 annular die 2 first supply section 3 second supply section 4 first extruder 5 second extruder 6 annular discharge port 20 horizontal path 21 first annular path 22 second annular path 31 third annular path X1 first junction position X2 Second merging position

Claims (4)

A second hardness having a three-layer structure of a surface layer, an intermediate layer and a back surface layer, wherein the surface layer and the back surface layer are formed of a material having a first hardness, and the intermediate layer has a higher hardness than the first hardness; An annular die for producing a seamless belt formed of a material having
A first supply unit to which a first belt forming material having a first hardness is supplied from a first extruder;
A second supply unit to which a second belt forming material having a second hardness higher than the first hardness is supplied from the second extruder;
An annular discharge port from which the seamless belt formed of the first belt forming material and the second belt forming material is melted and extruded;
A first annular path for guiding the first belt forming material from the first supply unit to the annular discharge port;
A second annular path that once branches off the first annular path on the way and then joins the first annular path again at a first junction position;
A third belt that guides the second belt forming material from the second supply section to the first annular path and merges with the first annular path at a second junction position located closer to the front than the first junction position. With an annular path,
The intermediate belt is formed from the second belt-forming material, and the seamless belt, in which the front surface layer and the back surface layer are formed from the first belt-forming material, is melt-extruded from the annular discharge port. Annular die for seamless belt production. When the distance of the path from the first supply unit to the second junction is D1, the distance of the path from the second supply unit to the second junction is D2, and L1 = D1-D2, However, D1 and D2 are distances measured by cutting on a plane including the center axis of the annular die.
L1 = 30 mm to 300 mm
The annular die for producing a seamless belt according to claim 1, wherein the annular die is set to: When the distance difference between the route of the first junction position and the route of the second junction position is L2,
L2 = 5mm-150mm
The annular die for producing a seamless belt according to claim 1, wherein the annular die is set to: A second hardness having a three-layer structure of a surface layer, an intermediate layer and a back surface layer, wherein the surface layer and the back surface layer are formed of a material having a first hardness, and the intermediate layer has a higher hardness than the first hardness; A method for producing a seamless belt formed of a material having
Supplying a first belt forming material having a first hardness from a first extruder;
Supplying a second belt-forming material having a second hardness higher than the first hardness from the second extruder;
Melt extruding a seamless belt formed from the first belt forming material and the second belt forming material from an annular discharge port;
Guiding the first belt forming material from the first supply section to the annular discharge port through a first annular path;
Guiding the first belt forming material by a second annular path that once branches off the first annular path in the middle and then joins the first annular path again at a first junction position;
Guiding the second belt-forming material from the second supply section by a third annular path that merges with the first annular path at a second merging position located closer to the front than the first merging position;
Forming the intermediate layer with the second belt-forming material and melting and extruding the seamless belt formed with the first and second belt-forming materials from the annular discharge port. And a seamless belt manufacturing method.

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