JP2019061144A - Tubular body for image forming apparatus, tubular body unit, transfer device, and image forming apparatus - Google Patents

Abstract

To provide a tubular body for an image forming apparatus that prevents a variation in contact pressure in the axial direction of the tubular body when a rotating body is brought into contact with the outer peripheral surface of the tubular body.SOLUTION: A tubular body 15A for an image forming apparatus has an elastic substrate 152, an intermediate protective layer 154B on the elastic substrate 152, and a surface protective layer 154A on the intermediate protective layer 154B. In the tubular body 15A for an image forming apparatus, the tubular body 15A has the largest thickness at both ends in the axial direction and the smallest thickness at the center in the axial direction, and has, on at least both end sides in the axial direction, a thickness changing area where the thickness continuously changes from both ends toward the direction to the center.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a tubular body for an image forming apparatus, a tubular body unit, a transfer device, and an image forming apparatus.

  In an electrophotographic image forming apparatus (such as a copying machine, a facsimile, or a printer), a toner image formed on the surface of an image carrier is transferred to the surface of a recording medium, and the toner image transferred onto the recording medium is transferred. The image is formed by fixing on a recording medium by heating or the like. A tubular body is used as a belt member or the like in a transfer device or the like for transferring such a toner image to a recording medium.

  For example, Patent Document 1 discloses “a laminated endless belt having at least a surface layer and an inner layer, the inner layer being lower in hardness than the surface layer, and the surface layer being molded in a state in which a tensile stress is applied”. There is.

  Further, in Patent Document 2, “an intermediate transfer belt provided in an electrophotographic image forming apparatus, and an elastic layer and a surface layer are laminated in this order on a base material, and the surface layer is made of JIS K7161 An intermediate transfer belt is disclosed which has an elastic limit of 5% or more and a stress of 5 MPa or more of the elastic limit obtained from the stress-strain curve measured in accordance with the above.

  Further, in Patent Document 3, “an endless form of multilayer structure having a plurality of belt layers consisting of at least an outer peripheral layer and an inner peripheral layer, and in which the stretch rates of the respective belt layers in a stretched state are different from each other In a belt device having a belt and a plurality of stretching rollers for stretching the endless belt rotatably, the belt width of the belt layer having the smallest elongation rate of the endless belt is set to the plurality of tensions. There is disclosed a belt device having a belt width equal to or less than the width of the stretching roller having the shortest roller width among the bridge rollers.

JP, 2009-069455, A JP, 2017-016049, A JP 2002-189353 A

Conventionally, in an image forming apparatus, a tubular body is used for various applications such as an intermediate transfer member (intermediate transfer tubular body) in a transfer device adopting an intermediate transfer method, and a rotating body such as an image carrier It is arranged in contact and used in a manner arranged to form a nip (contact area) with the rotating body. As such a tubular body, a laminated tubular body in which a protective layer is formed on an elastic base material is used, and the thickness in the axial direction of the tubular body is generally equal, that is, the thickness in the axial direction It is common to use a tubular body that does not change.
However, since the tubular body is used by being tensioned and applied to a plurality of rolls, the contact pressure generated between the tubular body and the rotating body due to the extension of the tubular body ends more than the axial central portion. A phenomenon may occur in which the size of the part is smaller.

  Therefore, an object of the present invention is a tubular body for an image forming apparatus having an elastic base and a protective layer, wherein the outer peripheral surface of the tubular body is greater than when the axial thickness of the tubular body is generally equal. It is an object of the present invention to provide a tubular body for an image forming apparatus in which the variation of the contact pressure in the axial direction of the tubular body when the rotating body is brought into contact with the above is suppressed.

  The above-mentioned subject is solved by the following means. That is,

The invention according to claim 1 is
An elastic base, an intermediate protective layer on the elastic base, and a surface protective layer on the intermediate protective layer,
The thickness of the tubular body is thickest at both ends in the axial direction and thinnest at the center in the axial direction,
And a tubular body for an image forming apparatus having variable thickness regions in which the thickness continuously changes in the direction from the both ends toward the center on at least both axial end sides.

The invention according to claim 2 is
The variable thickness region is a region in which the rate of change of the thickness from the both ends toward the center changes by more than 0% and 5% or less with respect to the thickness of the both ends every 15 mm. The tubular body according to claim 1, which is

The invention according to claim 3 is
The difference in thickness at the same distance from the center toward the one end and the other end with respect to the center in the axial direction is 1% at all the positions at the one end and the other end. The tubular body according to claim 1 or claim 2, which is as follows.

The invention according to claim 4 is
The tubular body according to any one of claims 1 to 3, wherein the variable thickness area occupies an area of 15% or more from each of the both ends with respect to the axial length of the tubular body.

The invention according to claim 5 is
The intermediate protective layer is thickest at both ends in the axial direction and thinnest at the center in the axial direction, and continuously at least on both axial ends toward the central direction from the both ends continuously The tubular body according to any one of claims 1 to 4, having a variable thickness area which changes.

The invention according to claim 6 is
The elastic modulus [Ms] of the surface protective layer, the elastic modulus [Mm] of the intermediate protective layer, and the elastic modulus [Mb] of the elastic base material have a relationship of [Ms <Mm <Mb]. A tubular body according to any one of the preceding claims.

The invention according to claim 7 is
The tubular body according to claim 6, wherein the ratio [Ms / Mm] of the elastic modulus [Ms] of the surface protective layer to the elastic modulus [Mm] of the intermediate protective layer is 1/8 or more and 1/2 or less.

The invention according to claim 8 is
The ratio [Mm / Mb] of the elastic modulus [Mm] of the intermediate protective layer to the elastic modulus [Mb] of the elastic base is 1/7 or more and 1/2 or less. Tubular body.

The invention according to claim 9 is
The tubular body according to any one of claims 1 to 8, wherein the surface protective layer and the intermediate protective layer are a fluorine-based resin layer, a silicone-based resin layer, or a fluorine-containing urethane resin layer.

The invention according to claim 10 is
The elastic base material is chloroprene rubber (CR), urea rubber, silicone rubber, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), epichlorohydrin rubber (ECO), styrene-butadiene copolymer The rubber according to any one of claims 1 to 9, comprising at least one rubber selected from rubber (SBR), chlorinated polyisoprene rubber, isoprene rubber, acrylonitrile-butadiene rubber, hydrogenated polybutadiene rubber, urethane rubber, butyl rubber, and fluororubber. The tubular body according to any one of the preceding claims.

The invention according to claim 11 is
The tubular body according to any one of claims 1 to 10, wherein the total thickness of the surface protective layer and the intermediate protective layer at the center in the axial direction is 3 μm or more and 25 μm or less.

The invention according to claim 12 is
The tubular body according to claim 11, wherein a thickness ratio (surface protective layer / intermediate protective layer) at the center in the axial direction between the surface protective layer and the intermediate protective layer is 3/7 or more and 7/3 or less. .

The invention according to claim 13 is
The tubular body according to any one of claims 1 to 12, wherein a thickness of the elastic base at the center in the axial direction is 200 μm or more and 1000 μm or less.

The invention according to claim 14 is
When the tubular body is sandwiched by two rotating bodies from the inner peripheral surface side and the outer peripheral surface side, the pressing force [Pe] on the outer peripheral surface of the both ends in the axial direction and the pushing on the central outer peripheral surface in the axial direction The tubular body according to any one of claims 1 to 13, wherein the ratio [Pe / Pc] to the pressure [Pc] is not less than 1.25 / 1 and not more than 1.6 / 1.

The invention according to claim 15 is
The tubular body according to any one of claims 1 to 14, and
A plurality of rolls over which the tubular body is tensioned;
A tubular unit that comprises a unit that is detachable from the image forming apparatus.

The invention according to claim 16 is
It has a tubular body unit according to claim 15,
A transfer device for transferring a toner image formed on the surface of an image carrier to the surface of a recording medium.

The invention according to claim 17 is
An image carrier,
Toner image forming means for forming a toner image on the surface of the image carrier;
A transfer unit comprising the transfer device according to claim 16, for transferring the toner image to the surface of a recording medium.
An image forming apparatus comprising:

According to the invention as claimed in claim 1, 9, 10, 11, 12, or 13, it is a tubular body for an image forming apparatus having an elastic base and a protective layer, and the thickness of the tubular body in the axial direction is Provided is a tubular body for an image forming apparatus in which the variation in the contact pressure in the axial direction of the tubular body is suppressed when the rotating body is brought into contact with the outer peripheral surface of the tubular body as compared with the case of the entire case.
According to the second aspect of the present invention, in the variable thickness region, the ratio of the change in thickness from both ends in the axial direction toward the center in the variable thickness region exceeds 5% with respect to the thickness of both ends at intervals of 15 mm. Provided is a tubular body for an image forming apparatus in which the variation in contact pressure in the axial direction of the tubular body is suppressed when the rotating body is brought into contact with the outer circumferential surface of the tubular body as compared with the tubular body having the tubular body.
According to the third aspect of the present invention, the difference in thickness at the position where the distance from the center to the one end and the other end are equal to each other with the border in the center in the axial direction exceeds 1%. Provided is a tubular body for an image forming apparatus in which the variation in contact pressure in the axial direction of the tubular body is suppressed when the rotating body is brought into contact with the outer peripheral surface of the tubular body as compared with the tubular body.
According to the invention as set forth in claim 4, the outer surface of the tubular body is rotated compared to the tubular body in which the area occupied by the variable thickness area is less than 15% from both axial ends with respect to the axial length of the tubular body. Provided is a tubular body for an image forming apparatus in which variation in contact pressure in the axial direction of the tubular body when contacting is suppressed.
According to the invention as set forth in claim 5, the contact pressure in the axial direction of the tubular body when the outer circumferential surface of the tubular body is brought into contact with the rotating body as compared with the tubular body having the same overall thickness in the axial direction of the intermediate protective layer. There is provided a tubular body for an image forming apparatus in which the variation of
According to the sixth, seventh, or eighth aspect of the present invention, the elastic modulus [Ms] of the surface protective layer, the elastic modulus [Mm] of the intermediate protective layer, and the elastic modulus [Mb] of the elastic base material satisfy [Ms> Mm]. Variation in contact pressure in the axial direction of the tubular body when the rotating body is brought into contact with the outer peripheral surface of the tubular body is suppressed as compared to a tubular body having a relationship of [Mm> Mb]. A tubular body for an imaging device is provided.
According to the invention of claim 14, when the tubular body is sandwiched by the two rotating bodies from the inner peripheral surface side and the outer peripheral surface side, the pressing force [Pe] at the outer peripheral surfaces of both ends in the axial direction and the central outer peripheral surface Contact pressure in the axial direction of the tubular body when the rotating body is brought into contact with the outer peripheral surface of the tubular body as compared to the tubular body having a ratio [Pe / Pc] of less than 1.25 / 1 There is provided a tubular body for an image forming apparatus in which the variation of

  According to the invention as claimed in claim 15, 16 or 17, a tubular body for an image forming apparatus having an elastic base and a protective layer, wherein the tubular body has the same overall thickness in the axial direction. A tubular unit, a transfer device, or an image forming apparatus is provided in which the variation in contact pressure in the axial direction of the tubular body is suppressed when the rotating body is brought into contact with the outer peripheral surface of the tubular body as compared with the case of including.

It is a schematic perspective view which shows an example of the tubular body which concerns on this embodiment. It is sectional drawing which expands and shows the cross section of the tubular body shown in FIG. It is sectional drawing which expands and shows the cross section of another example tubular body which concerns on this embodiment. It is sectional drawing which expands and shows the cross section of another example tubular body which concerns on this embodiment. It is sectional drawing which shows the state which pressed the tubular body shown in FIG. 2 on the rotary body. It is sectional drawing which shows the state which pressed the conventional tubular body on the rotary body. (A) is a schematic plan view which shows an example of a circular electrode, (B) is the schematic sectional drawing. FIG. 1 is a schematic configuration view showing an example of an image forming apparatus according to the present embodiment. FIG. 6 is a schematic configuration view showing another example of the image forming apparatus according to the present embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described.

[Tubular body for image forming apparatus]
The tubular body for an image forming apparatus according to the present embodiment has an elastic base, an intermediate protective layer on the elastic base, and a surface protective layer on the intermediate protective layer.
And, the thickness of the tubular body is thickest at both ends in the axial direction and thinnest at the center in the axial direction. Furthermore, at least both axial end sides, there is a variable thickness area whose thickness continuously changes from both ends toward the center.

  Here, the tubular body according to the present embodiment will be specifically described by way of an example with reference to the drawings. 1 and 2 are a schematic perspective view showing an example of a tubular body according to the present embodiment, and a cross-sectional view showing an enlarged cross section along the axial direction of the tubular body.

As shown in FIG. 1, the tubular body 15 is formed endlessly. The endless tubular body 15 may be bridged across multiple rolls (rolls 131, 132 in FIG. 1) under tension to form a tubular body unit 150.
The tubular body 15 (15A) has, as shown in FIG. 2, an elastic base 152 and a protective layer 154 disposed on the outer peripheral side of the elastic base 152, and the protective layer 154 is an elastic base. It comprises the intermediate protective layer 154B disposed on the side 152 and the surface protective layer 154A disposed on the outer peripheral surface side.

The thickness of the tubular body 15A shown in FIG. 2 is the thickest at both ends in the axial direction (left and right direction in FIG. 2) and the thinnest at the center in the axial direction.
Here, the “axial direction” in the tubular body refers to a direction in which the tubular body is in the axial direction of the rolls when the tubular body is bridged in a tensioned state.

In addition, the thickness of the tubular body 15A continuously changes from both ends in the axial direction to the entire central region, that is, the entire axial direction corresponds to a variable thickness region.
In addition, although the aspect which thickness changed continuously over the axial whole area is shown in FIG. 2, it is not limited to this aspect. That is, it has a variable thickness area in which the thickness continuously changes from both ends toward the center on both end sides in the axial direction, and the thickness is substantially equal to the central area between the variable thickness areas on both ends Equal thickness area (specifically, the area where the rate of change in thickness is 1% or less of the thickness at the center in the axial direction even if the thickness changes) It may be
However, as shown in FIG. 2, it is more preferable that it is a tubular body in which the entire axial direction corresponds to the variable thickness region.

Further, in the tubular body 15A shown in FIG. 2, the layer responsible for the change in thickness is the intermediate protective layer 154B. That is, in the tubular body 15A, the thickness of the intermediate protective layer 154B is the thickest at both ends in the axial direction and the thinnest at the center in the axial direction, and the thickness is at least at both axial ends toward the central direction from both ends It has a continuously changing variable thickness region. On the other hand, the elastic base material 152 and the surface protection layer 154A in the tubular body 15A have substantially the same thickness in the axial direction.
In addition, although the layer which bears the change of thickness shows the aspect which is the intermediate | middle protective layer 154B in FIG. 2, it is not limited to this aspect.
For example, as in a tubular body 15B shown in FIG. 3, the layer responsible for the change in thickness may be the elastic base 152. That is, in the tubular body 15B, the thickness of the elastic base 152 is the thickest at both ends in the axial direction, the thinnest at the center in the axial direction, and the thickness at least at both axial ends toward the central direction from both ends It has a continuously changing variable thickness region. The surface protective layer 154A and the intermediate protective layer 154B in the tubular body 15B are in a mode in which the thickness is substantially equal in the axial direction.
Further, as in a tubular body 15C shown in FIG. 4, the layer responsible for the change in thickness may be the surface protective layer 154A. That is, in the tubular body 15C, the thickness of the surface protection layer 154A is the thickest at both ends in the axial direction and the thinnest at the center in the axial direction, and the thickness is at least at both axial ends toward the central direction from both ends It has a continuously changing variable thickness region. The elastic base material 152 and the intermediate protective layer 154B in the tubular body 15C have a substantially equal thickness in the axial direction.
However, as shown in FIG. 2, it is more preferable that the layer responsible for the change in thickness is the intermediate protective layer 154B, and the thickness in the axial direction of the elastic base 152 and the surface protective layer 154A is substantially equal.

The tubular body according to the present embodiment includes the elastic base, the intermediate protective layer on the elastic base, and the surface protective layer on the intermediate protective layer, and the thickness of the tubular is at both ends in the axial direction. Is thickest, and has a configuration in which the center in the axial direction is the thinnest, and at least both end sides in the axial direction have a variable thickness region in which the thickness changes continuously from both ends toward the center. The variation in the contact pressure in the axial direction of the tubular body when the rotor is brought into contact with the outer peripheral surface of the body is suppressed.
The reason is presumed as follows.

Conventionally, in a transfer device adopting an intermediate transfer method in an image forming apparatus, a toner image formed on an image carrier is primarily transferred onto an intermediate transfer member, and then the toner image transferred onto the intermediate transfer member is further recorded. A configuration for secondary transfer to a medium is employed. In this configuration, for example, a tubular body is applied to the intermediate transfer member under tension in a plurality of rolls. Then, at the primary transfer portion, a tubular member is brought into contact with the image carrier, and a transfer member such as a primary transfer roll is disposed at a position opposite to the image carrier via the tubular member, thereby forming the image carrier and the tubular member. A configuration in which a nip (contact area) is formed between the body (intermediate transfer member) is taken.
Further, in a transfer device in an image forming apparatus adopting a direct transfer method, a configuration is adopted in which a toner image formed on an image carrier is directly transferred to a recording medium. In this configuration, for example, a tubular body is applied, in which a plurality of rolls are tensioned on a recording medium transport member for transporting a recording medium. Then, at the transfer portion, the image carrier and the tubular body are brought into contact by disposing a transfer member such as a transfer roll at a position facing the image carrier with a tubular body in contact with the image carrier via the tubular body of the image carrier. A configuration in which a nip (contact area) is formed between the recording medium conveyance member and the recording medium conveyance member) is taken.
Like these configurations, in an image forming apparatus, a tubular body is used for various applications, is disposed in contact with a rotating body such as an image carrier, and forms a nip (contact area) with the rotating body. It is used in a manner arranged to

Here, as such a tubular body, a laminated tubular body in which a protective layer is formed on an elastic base material has been conventionally used. And, the tubular body used in the image forming apparatus is a tubular body in which the thickness in the axial direction of the tubular body is generally equal, that is, the thickness does not change in the axial direction (but the thickness change due to manufacturing error is excluded). Is generally used.
Temporarily, as shown in FIG. 6, it is a laminated structure provided with the intermediate protective layer 254B and the surface protective layer 254A on the elastic base material 252, and the thickness in the axial direction is generally equal, ie, in the axial direction. It is assumed that a tubular body 250 whose thickness does not change is used. The tubular body 250 having the same overall thickness has substantially the same pressing force at any position in the axial direction, and the pressing force (arrow A) at the axially central portion of the tubular body 250 as shown in FIG. The pressure (arrow B) at is approximately equal. Therefore, in the nip between the tubular body 250 and the rotating body 110, the contact pressure between the tubular body 250 and the rotating body 110 also seems to be substantially equal at the axial center and the end. However, since the tubular body 250 is under tension, the contact pressure generated between the tubular body 250 and the rotating body 110 by the extension of the tubular body 250 is smaller at the end than at the axial center. Phenomenon may occur.
There is a difference in the contact pressure applied from the tubular body 250 to the rotating body 110 at the axial center portion and the end portion, that is, the contact pressure in the axial direction varies when the rotating body 110 contacts the outer peripheral surface of the tubular body 250 As a result, a phenomenon (belt walk) in which the tubular body 250 moves on the side where the contact pressure is low may occur, and as a result, a shift may occur in the formed image. In addition, when the contact pressure in the axial direction varies between the tubular body 250 and the rotating body 110, the difference in extension force generated in the tubular body 250 is further increased in the axial direction, and higher stress is generated at the end. . As a result, the difference in extension force makes it difficult for the protective layer (intermediate protective layer 254B and surface protective layer 254A) to follow deformation of the elastic base at the end, resulting in surface defects such as cracks in the protective layer. I had something to do.

In contrast, as shown in FIGS. 2, 3 and 4, the tubular body 15 (15A, 15B, 15C) according to the present embodiment has the largest thickness at both ends in the axial direction, and the center in the axial direction. Is the thinnest, and at least on both axial end sides, there is a variable thickness region in which the thickness changes continuously from both ends toward the center.
In the tubular body 15 according to the present embodiment, as shown in FIG. 5, the pressing force (arrow B) at the end is larger than the pressing force (arrow A) at the axial center. Therefore, when the tubular body 15 is tensioned across a plurality of rolls and a nip is formed with the rotary body 110, the contact pressure generated between the tubular body 15 and the rotary body 110 is controlled by an axial central portion A difference between the end and the end is suppressed, that is, the axial variation of the contact pressure is suppressed.
And, by suppressing the variation in the axial direction of the contact pressure, the phenomenon (belt walk) in which the tubular body 15 moves to the side where the contact pressure is low is also suppressed, and the occurrence of the shift in the image is also suppressed. Further, the increase in the difference in extension force in the axial direction of the tubular body 15 is also suppressed, and surface defects such as cracks are generated in the protective layer (intermediate protection layer 154B, surface protection layer 154A) due to the difference in extension force. Is also suppressed.

  As described above, according to the present embodiment, the variation in the contact pressure in the axial direction of the tubular body when the rotating body is in contact with the outer peripheral surface of the tubular body is suppressed.

-Change in thickness As shown in FIG. 2, FIG. 3 and FIG. 4, the tubular body 15 (15A, 15B, 15C) according to the present embodiment has an aspect in which the thickness changes from the both axial ends to the central region. That is, the entire area in the axial direction may be a variable thickness region, and the variable thickness region has a thickness continuously changing from both ends toward the center on both end sides in the axial direction, and each variable thickness on both ends It may be a mode which has an equal thickness area of approximately equal thickness in a central area between the areas.

The variable thickness region is a region of 10% or more (more preferably 15% or more) from both axial ends with respect to the axial length of the tubular body 15 from the viewpoint of suppressing the variation in the contact pressure in the axial direction. It is more preferable that the entire axial direction corresponds to the variable thickness region.
When the range of the variable thickness region in the tubular body 15 is confirmed, the thickness is measured at intervals of 15 mm in the axial direction of the tubular body 15 from both ends toward the center.

The thickness change in the axial direction of the tubular body 15 does not change the thickness rapidly in part from the viewpoint of suppressing the variation in the axial direction of the contact pressure, and the thickness gradually changes over the entire variable thickness region It is preferable to do.
From this point of view, in the variable thickness region of the tubular body 15, the rate of change in thickness from both ends in the axial direction toward the center exceeds 0% with respect to the thickness of the both ends at intervals of 15 mm. It is preferable to change 5% or less (more preferably 1% or more and 5% or less, more preferably 1% or more and 3% or less).

The change in thickness in the axial direction of the tubular body 15 is preferably a change close to the left-right symmetry with respect to the axial center, from the viewpoint of suppressing the variation in the contact pressure in the axial direction.
From this point of view, the thickness difference (hereinafter also referred to as "left-right symmetry") at the same distance from the center toward the one end side and the other end bordering on the center in the axial direction is the one end side And 1% or less (more preferably 0.7% or less) at all positions on the other end side.

Here, the method of confirming the above-mentioned left-right symmetry will be described in detail.
With respect to the tubular body 15, the region at one end and the region at the other end are divided at intervals of 15 mm, respectively, bordering on the center in the axial direction. The thickness at each divided position is measured, and the difference in thickness at divided positions where the distance is equal from the center toward one end and the other end (that is, from the center toward one end and the other end) Calculate the nth division position (the difference of thickness between n = 1 or more), and check whether the thickness difference satisfies the above numerical range at all the divided positions. Is done.

  Here, the thickness (average thickness) at each position in the axial direction of the tubular body 15 is measured by an eddy current film thickness meter ISOSCOPE MP30 manufactured by Fisher Instruments. In addition, it measures at fixed intervals in the circumferential direction of the tubular body 15, and makes the average value the average thickness in each position of an axial direction.

· Pressing force at both ends in the axial direction and in the center In the tubular body 15 according to the present embodiment, from the viewpoint of suppressing variation in the contact pressure in the axial direction, pressing force in the axial center (for example, arrow A shown in FIG. 5) Preferably, the pressure at the end (for example, the arrow B shown in FIG. 5) is larger.
Specifically, when the tubular body is sandwiched by the two rotating bodies from the inner peripheral surface side and the outer peripheral surface side, the pressing force [Pe] on the outer peripheral surfaces of both ends in the axial direction and the central outer peripheral surface in the axial direction The ratio [Pe / Pc] to the pressing force [Pc] is preferably 1.25 / 1 to 1.6 / 1 (more preferably 1.3 / 1 to 1.5 / 1).

Here, when the tubular body 15 is sandwiched by the two rotating bodies from the inner circumferential surface side and the outer circumferential surface side, the measurement of the pressing force at the axial center and the pressing force at the end is performed by the following method. .
Using a film-type pressure distribution measurement system manufactured by NITTA Corporation, the pressure distribution is measured while being applied to the film-like sensor sheet. In the measurement, the sensor size is 1 mm, the pressure applied to each of the axially distributed sensors is measured, and the pressure per 1 mm width obtained is converted into a load value.

-Elastic modulus of each layer From the viewpoint of suppressing variation in the axial direction of the contact pressure, the tubular body 15 further suppresses the occurrence of belt walk, and surface defects such as cracks in the protective layer 154 (intermediate protective layer 154B, surface protective layer 154A) It is preferable that the elastic base material 152, the intermediate protective layer 154B, and the surface protective layer 154A have a relationship in which the elastic modulus decreases in this order from the viewpoint of generation suppression of the above.
That is, it is preferable that the elastic modulus [Ms] of the surface protective layer, the elastic modulus [Mm] of the intermediate protective layer, and the elastic modulus [Mb] of the elastic base material have a relationship of [Ms <Mm <Mb].

The elastic modulus [Ms] of the surface protective layer and the intermediate protective layer from the viewpoint of suppressing the variation in the contact pressure in the axial direction, and further suppressing the generation of the belt walk and the generation of surface defects such as cracks in the protective layer 154. The ratio [Ms / Mm] to the elastic modulus [Mm] of is preferably 1/8 or more and 1/2 or less (more preferably 1/6 or more and 1/4 or less).
From the same point of view, the ratio [Mm / Mb] of the elastic modulus [Mm] of the intermediate protective layer to the elastic modulus [Mb] of the elastic base is 1/8 or more and 1/2 or less (more preferably 1/0). It is preferable that it is 7 or more and 1/2 or less, more preferably 1/6 or more and 1/4 or less.

  In addition, adjustment of the elastic modulus in each layer can be performed by selection of the material used for each layer.

-Thickness of each layer In the tubular body 15 according to the present embodiment, from the viewpoint of suppressing variation in the contact pressure in the axial direction, and further from the viewpoint of suppressing the occurrence of belt walk and the occurrence of surface defects such as cracks in the protective layer 154, The thickness (average thickness) at the axial center in each layer is preferably in the following relationship.
The total thickness at the axial center of the surface protective layer and the intermediate protective layer is preferably 1 μm to 25 μm (more preferably 3 μm to 25 μm, still more preferably 3 μm to 13 μm).
The ratio of the thickness at the center in the axial direction between the surface protective layer and the intermediate protective layer (surface protective layer / intermediate protective layer) is 3/7 to 7/3 (more preferably 4/6 to 6/7). It is preferably 4 or less, more preferably 4.5 / 5.5 or more and 5.5 / 4.5 or less).
The thickness at the center in the axial direction of the elastic base is preferably 200 μm to 1000 μm (more preferably 350 μm to 750 μm).
In addition, the measurement of the thickness (average thickness) in the axial direction center of each layer is performed by the above-mentioned method.

  Next, the composition of each layer constituting the tubular body according to the present embodiment will be described.

The tubular body 15 which concerns on this embodiment is formed in endless form, as shown in FIG. The endless tubular body 15 may be bridged across multiple rolls (rolls 131, 132 in FIG. 1) under tension to form a tubular body unit 150.
The tubular body 15 (15A) has, as shown in FIG. 2, an elastic base 152 and a protective layer 154 disposed on the outer peripheral side of the elastic base 152, and the protective layer 154 is an elastic base. It comprises the intermediate protective layer 154B disposed on the side 152 and the surface protective layer 154A disposed on the outer peripheral surface side.

  In the tubular body 15A shown in FIG. 2, the thickness of the intermediate protective layer 154B changes in the axial direction, and the elastic base material 152 and the surface protective layer 154A have substantially the same thickness in the axial direction. However, the present invention is not limited to this aspect, and, for example, as in the tubular body 15B shown in FIG. 3, even in the aspect in which the thickness of the elastic base 152 changes in the axial direction, the tubular shown in FIG. As in the case of the body 15C, the thickness of the surface protective layer 154A may be changed in the axial direction.

It is preferable that the elastic base 152 and the intermediate protective layer 154B be disposed so as to be in direct contact with each other at the interface or be disposed only via an adhesive layer (not shown) therebetween. Further, it is preferable that the intermediate protective layer 154B and the surface protective layer 154A be disposed so as to be in direct contact with each other at the interface or be disposed only via an adhesive layer (not shown) therebetween.
That is, it is preferable that no layer other than the adhesive layer be formed between the elastic base 152 and the intermediate protective layer 154B and between the intermediate protective layer 154B and the surface protective layer 154A.

(Elastic substrate)
The elastic substrate is configured to include an elastic material (elastic material), and preferably includes a rubber material. In addition, the elastic substrate may contain a conductive agent from the viewpoint of imparting conductivity, and may be configured to contain other well-known additives.

-Elastic material-
As an elastic material used for an elastic base material, for example, chloroprene rubber (CR), urea rubber, silicone rubber, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), epichlorohydrin rubber (ECO) Rubber materials such as styrene-butadiene copolymer rubber (SBR), chlorinated polyisoprene rubber, isoprene rubber, acrylonitrile-butadiene rubber, hydrogenated polybutadiene rubber, urethane rubber, butyl rubber, and fluoro rubber; Materials obtained by mixing types or two or more types can be mentioned.
Among these, urethane rubber, ethylene-propylene-diene copolymer rubber (EPDM), epichlorohydrin rubber (ECO), and chloroprene rubber (CR), from the viewpoint of the formation of the nip and the followability to the roll over the tubular body. Materials composed of a mixture of ethylene and propylene-diene copolymer rubber (EPDM) are preferable, and chloroprene rubber (CR) and ethylene-propylene- from the point that flame retardancy is improved and ozone deterioration resistance is improved. A material obtained by mixing with a diene copolymer rubber (EPDM), and a urethane rubber are more preferable.

-Conductive agent-
The elastic base material may contain a conductive agent from the viewpoint of imparting conductivity.
The conductive agent may be conductive (for example, volume resistivity less than 10 ⁷ Ω · cm, the same applies hereinafter) or semiconductive (for example, volume resistivity 10 ⁷ Ω · cm or more and 10 ¹³ Ω · cm or less, or the like) (1) powder of particles having a primary particle size of less than 10 μm, and preferably powder of particles having a primary particle size of 1 μm or less.

The conductive agent is not particularly limited, but, for example, carbon black (for example, ketjen black, acetylene black, carbon black whose surface has been oxidized, etc.), carbon fiber, carbon nanotube, carbon-based material such as carbon nanotube, metal or Alloys (eg, aluminum, nickel, copper, silver etc.), metal oxides (eg, yttrium oxide, tin oxide, indium oxide, antimony oxide, SnO ₂ -In ₂ O ₃ complex oxide etc.), ion conductive substances (eg titanium) Acid potassium, LiCl, etc.).

  The conductive agent is selected according to the purpose of use, but carbon black is preferable, and in particular, pH 5 or less (preferably pH 4) from the viewpoint of the stability of the electrical resistance over time and the electric field dependency to suppress the electric field concentration due to the transfer voltage. .5 or less, more preferably pH 4.0 or less oxidation treated carbon black (for example, carbon black obtained by giving a carboxyl group, a quinone group, a lactone group, a hydroxyl group etc. to the surface) is preferable.

The average primary particle diameter of carbon black is, for example, 10 nm or more and 50 nm or less, and more preferably 15 nm or more and 30 nm or less.
The average primary particle size of carbon black is measured by the following method.
First, a tubular sample to be measured is cut with a microtome, a measurement sample with a thickness of 100 nm is collected, and this measurement sample is observed by a TEM (transmission electron microscope). The diameter of a circle equal to the projected area of each of the 50 carbon black particles is taken as the particle diameter, and the average value is taken as the average primary particle diameter.

Although the content of the conductive agent in the elastic base material is selected according to the target resistance, for example, 20 mass% or more and 35 mass% or less is preferable with respect to the total mass of the elastic base material, and further 25 mass% or more 30 mass% or less is more preferable.
The conductive agent may be used alone or in combination of two or more.

-Other additives-
As other additives other than the conductive agent, for example, a dispersant for improving the dispersibility of the conductive agent (carbon black etc.), various fillers for giving various functions such as mechanical strength, catalysts, film formation The leveling agent for quality improvement etc. are mentioned.

(Surface protective layer and intermediate protective layer)
The surface protective layer and the intermediate protective layer are preferably formed of a material having releasability. The intermediate protective layer is preferably a layer having a higher elastic modulus than the elastic base, and the surface protective layer is preferably a layer having a higher elastic modulus than the intermediate protective layer.

  The surface protective layer and the intermediate protective layer are preferably a fluorine-based resin layer, a silicone-based resin layer, or a fluorine-containing urethane resin layer, and more preferably a fluorine-containing urethane resin layer.

-Urethane resin having a fluorine atom-
The urethane resin having a fluorine atom, which is used when at least one of the surface protective layer and the intermediate protective layer is a fluorine-containing urethane resin layer, polymerizes, for example, polyisocyanate, a polyol and, if necessary, other monomers, It is synthesized by using a material having a fluorine atom as at least one of them.

Polyol As the polyol, for example, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, dodecanediol, tridecanediol, tetradecanediol, octadecanediol , Eicosan diol and the like.

Polyisocyanate As the polyisocyanate, for example, 4,4′-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), hexane diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), 3,3 '-Dimethylbiphenyl-4,4'-diisocyanate (TODI) etc. are mentioned.

-Fluorinated resin-
The fluorine-based resin used for the surface protective layer and the intermediate protective layer represents a resin containing a fluorine atom. For example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride co-weight Examples include coalescent (THV), polyvinylidene fluoride (PVDF), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), polychlorotrifluorinated ethylene (PCTFE), polyvinyl fluoride (PVF) and the like.

-Silicone resin-
The silicone-based resin used for the surface protective layer and the intermediate protective layer represents a resin having a silanol group. For example, unmodified silicone resin (thermosetting silicone resin, photocurable silicone resin, etc.), modified silicone resin (polyester modified silicone resin, urethane modified silicone resin, acrylic modified silicone resin, polyimide modified silicone resin, olefin modified silicone resin And ether-modified silicone resins, alcohol-modified silicone resins, fluorine-modified silicone resins, amino-modified silicone resins, mercapto-modified silicone resins, carboxy-modified silicone resins, and the like.

Various well-known additives may be blended in the protective layer (surface protective layer and intermediate protective layer). Examples of the additive include a conductive agent (for example, the conductive agent listed in the section of the elastic substrate described above), a softener, a processing aid, an antiaging agent, and the like.
When a urethane resin having fluorine atoms is used in both the surface protective layer and the intermediate protective layer, the amount of the curing component may be increased or decreased as a method of providing a difference in elastic modulus between the surface protective layer and the intermediate protective layer. The method of adjusting by is mentioned.

(Adhesive layer)
In the tubular body according to the present embodiment, an adhesive layer may be formed on at least one of the elastic base and the intermediate protective layer, and between the intermediate protective layer and the surface protective layer. The adhesive used for the adhesive layer is not particularly limited, and any known adhesive may be used, and examples thereof include silane coupling agents, silicone adhesives, urethane adhesives and the like.

(Method of manufacturing tubular body)
Here, a method of manufacturing the tubular body according to the present embodiment will be described. In addition, the method of manufacturing a tubular body is not particularly limited, and for example, a manufacturing method including the following respective steps may be mentioned.

· (Preparation process of coating solution for forming surface protective layer and intermediate protective layer)
A coating liquid for forming a surface protective layer and an intermediate protective layer, that is, a coating liquid for forming a surface protective layer and an intermediate protective layer in which the above-mentioned resin material or the like is dissolved or dispersed in a solvent is prepared.
· (Formation process of elastic base material)
An additive such as a conductive agent (carbon black etc.) is mixed and dispersed into the above-mentioned elastic material (CR, NBR, EPDM, ECO etc.) if necessary, and then it is kneaded by a kneader such as a pressure kneader Furthermore, a vulcanizing agent, a vulcanization accelerator, etc. are added and extrusion processing is performed. In the case of extruding the kneaded elastic material, a condition defined in advance in a state where the kneaded elastic material is covered with a metal cylinder having an outer diameter of the same size as the inner diameter of the tubular body called a vulcanizing mandrel For example, the method of vulcanizing at 170 ° C. for 1 hour may be mentioned.

  When an elastic base having a thickness change in the axial direction as shown in FIG. 3 is formed as the elastic base, known methods such as adjusting the shape of the extrusion opening for extrusion molding, adjusting the extrusion speed, etc. The shape can be controlled by the method.

· (Step of forming intermediate protective layer and surface protective layer)
A coating liquid for forming an intermediate protective layer is applied on the elastic base of the cylinder on which the elastic base is formed. The cylinder on which the coating solution is applied is dried while being rotated, and if necessary, is heated (baked) to form an intermediate protective layer.
Next, a coating liquid for forming a surface protective layer is applied onto the intermediate protective layer of the cylinder on which the intermediate protective layer is formed. The surface protection layer is formed by drying while rotating the cylinder on which the coating liquid is applied, and further heating (baking) if necessary.
After applying and drying the coating liquid for forming the intermediate protective layer and then coating and drying the coating liquid for forming the surface protective layer, heating (baking) to both layers may be performed in one step. Good.

  Examples of the coating method include known methods such as spray coating, spiral coating (flow coating), blade coating, wire bar coating, dip coating, bead coating, air knife coating and curtain coating. It can be mentioned.

  When an intermediate protective layer having a thickness change in the axial direction is formed as the intermediate protective layer as shown in FIG. 2, and a surface having the thickness change in the axial direction as shown in FIG. In the case of forming a protective layer, a method of controlling the thickness by changing the application amount of the coating liquid for forming an intermediate protective layer or the coating liquid for forming a surface protective layer in the axial direction (for example, the spray coating method) The shape can be controlled by a method such as changing the discharge amount of the coating liquid from the nozzle in the axial direction).

・ (Demolding process)
Thereafter, the solidified tubular body is removed from the cylinder (demolding) to obtain the tubular body.
Furthermore, surface treatment such as polishing and etching may be performed on the outer peripheral surface and the inner peripheral surface of the tubular body. Further, the obtained tubular body may be further subjected to drilling, ribbing and the like.
Alternatively, an adhesive may be applied to form an adhesive layer before forming each layer.

(Characteristics of tubular body)
The surface resistivity of the outer peripheral surface of the tubular body according to the present embodiment is, for example, 9 (common logarithmic value) from the viewpoint of transferability if it is used as an intermediate transfer belt, a recording medium transport belt, etc. Log Ω / □) or more and 13 (Log Ω / □) or less is preferable, and 10 (Log Ω / □) or more and 12 (Log Ω / □) or less is more preferable.
The common logarithm value of the surface resistivity is controlled by the type of the conductive agent and the addition amount of the conductive agent.

Here, the measuring method of surface resistivity is performed as follows. It measures according to JIS-K6911 using a circular electrode (for example, "UR probe" of Hirestar IP made by Mitsubishi Yuka Chemical Co., Ltd.). The method of measuring the surface resistivity will be described with reference to the drawings. FIG. 7 is a schematic plan view (A) and a schematic cross-sectional view (B) showing an example of a circular electrode. The circular electrode shown in FIG. 7 includes a first voltage application electrode A and a plate-like insulator B. The first voltage application electrode A has a cylindrical electrode portion C and an inner diameter larger than the outer diameter of the cylindrical electrode portion C, and a cylindrical ring-shaped electrode surrounding the cylindrical electrode portion C at a constant interval. And D. The belt T is held between the cylindrical electrode portion C and the ring electrode portion D in the first voltage application electrode A and the plate insulator B, and the cylindrical electrode portion C and the ring electrode in the first voltage application electrode A The current I (A) flowing when a voltage V (V) is applied between the part D and the part D is measured, and the surface resistivity ss (Ω / □) of the transfer surface of the belt T is calculated by the following equation. Here, in the following formula, d (mm) indicates the outer diameter of the cylindrical electrode portion C, and D (mm) indicates the inner diameter of the ring-shaped electrode portion D.
Formula: ss = π × (D + d) / (D−d) × (V / I)
The surface resistivity is a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .: outer diameter 16 16 mm of cylindrical electrode portion C, inner diameter 30 30 mm, outer diameter 40 40 mm of ring electrode D The current value after application of voltage 500 V for 10 seconds in an environment of 22 ° C./55% RH is obtained and calculated.

  The volume resistivity of the entire tubular body according to the present embodiment is, for example, 8 (Log Ω cm) as a common logarithm value from the viewpoint of transferability if it is used as an intermediate transfer belt, a recording medium conveyance belt or the like in an image forming apparatus. Or more and 13 (Log Ω cm) or less. In addition, the common logarithm value of volume resistivity is controlled by the kind of electroconductive agent, and the addition amount of an electroconductive agent.

Here, the measurement of the volume resistivity is measured according to JIS-K6911 using a circular electrode (for example, UR probe of Hilyster IP manufactured by Mitsubishi Yuka Co., Ltd.). The method of measuring the volume resistivity will be described with reference to FIG. The measurement is performed with the same device as the surface resistivity. However, in the circular electrode shown in FIG. 7, a second voltage application electrode B ′ is provided in place of the plate-like insulator B at the time of measuring the surface resistivity. Then, the belt T is held between the cylindrical electrode portion C and the ring electrode portion D in the first voltage application electrode A and the second voltage application electrode B ′, and the cylindrical electrode portion C in the first voltage application electrode A. The current I (A) flowing when a voltage V (V) is applied between the second voltage application electrode B and the second voltage application electrode B is measured, and the volume resistivity vv (Ωcm) of the belt T is calculated by the following equation. Here, in the following formula, t represents the thickness of the belt T.
Formula vv = 19.6 × (V / I) × t
The volume resistivity is a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .: outer diameter Φ 16 mm of cylindrical electrode portion C, inner diameter 30 30 mm, outer diameter 外 40 mm of ring electrode portion D) The current value after application of voltage 500 V for 10 seconds in an environment of 22 ° C./55% RH is obtained and calculated.

Further, the numerical value of 19.6 shown in the above equation is an electrode coefficient for converting into resistivity, and from the outer diameter d (mm) of the cylindrical electrode portion and the thickness t (cm) of the sample, πd ² Calculated as / 4t. The thickness of the belt T is measured using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics Co., Ltd.

  The thickness of the tubular body according to the present embodiment is, for example, preferably 350 mm or more and 700 mm or less, more preferably 400 mm or more and 600 mm or less in total thickness (average thickness) at the axial center.

(Use)
The tubular body according to the present embodiment is a tubular body in an image forming apparatus, for example, an intermediate transfer belt in which a toner image on an image carrier is transferred (primary transfer) and then transferred again onto a recording medium (secondary transfer) A secondary transfer belt which transports the recording medium in contact with the back surface (non-transfer surface) of the recording medium and applies a voltage for the secondary transfer when the toner image held on the transfer body is secondarily transferred onto the recording medium It is used as a recording medium conveyance belt or the like which conveys the recording medium and applies a voltage for transfer in a mode in which the toner image on the image carrier is directly transferred onto the surface of the recording medium.

<Image forming apparatus>
The image forming apparatus according to this embodiment includes an image carrier, a charging unit that charges the image carrier, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the charged image carrier, and a toner. An electrostatic charge image developer containing the developer, and developing means for developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer, and formed on the surface of the image carrier And transfer means for transferring the toner image to the surface of the recording medium.
And the said transfer means has a tubular body unit provided with the above-mentioned tubular body which concerns on this embodiment, and the several roll over which the said tubular body is tensioned.

  For example, in a mode in which the tubular body according to the present embodiment is provided as an intermediate transfer belt, an electrostatic latent image is formed on the surface of the image carrier, charging means for charging the image carrier, and the charged image carrier. An electrostatic charge image forming unit to be formed, a developing unit to develop an electrostatic charge image formed on the surface of the image carrier as a toner image by an electrostatic charge image developer containing toner, and formed on the surface of the image carrier An intermediate transfer belt (a tubular body according to the present embodiment) to which the transferred toner image is transferred, and a primary transfer means for primarily transferring the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer belt And second transfer means for secondarily transferring the toner image transferred to the surface of the intermediate transfer belt to a recording medium, and fixing means for fixing the toner image transferred to the recording medium. apparatus And the like. Furthermore, a cleaning device may be provided which cleans the outer peripheral surface of the intermediate transfer belt by bringing a cleaning member (for example, a cleaning blade) into contact with the intermediate transfer belt.

  In the image forming apparatus according to the present embodiment, for example, a normal mono-color image forming apparatus containing only a single color toner in the developing device, primary transfer of the toner image held on the image carrier to the intermediate transfer member in order. Examples include a color image forming apparatus to be repeated, and a tandem type color image forming apparatus in which a plurality of image carriers provided with developing devices for each color are arranged in series on an intermediate transfer member.

  Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings.

· Configuration of image forming apparatus (first aspect)
FIG. 8 is a schematic configuration view showing the configuration of an example of the image forming apparatus according to the present embodiment.

  The image forming apparatus 100 according to the present embodiment is, for example, an intermediate transfer type image forming apparatus generally called tandem type, as shown in FIG. 8, and a plurality of toner images of respective color components are formed by electrophotography. And a primary transfer portion 10 for sequentially transferring (primary transfer) each color component toner image formed by each of the image forming units 1Y, 1M, 1C and 1K and each of the image forming units 1Y, 1M, 1C and 1K onto the intermediate transfer belt 15 A secondary transfer unit 20 for collectively transferring (secondary transfer) the superimposed toner images transferred onto the intermediate transfer belt 15 onto a sheet K serving as a recording medium, and fixing the image transferred onto the sheet K onto the sheet K And a device 60. The image forming apparatus 100 also includes a control unit 40 that controls the operation of each device (each unit).

  The intermediate transfer belt 15 is a tubular body according to the embodiment described above.

  Each of the image forming units 1Y, 1M, 1C, and 1K of the image forming apparatus 100 includes a photosensitive member 11 that rotates in the direction of arrow A as an example of an image carrier that holds a toner image formed on the surface.

  A charger 12 for charging the photosensitive member 11 is provided around the photosensitive member 11 as an example of a charging unit, and a laser exposure unit for writing an electrostatic latent image on the photosensitive member 11 as an example of a latent image forming unit 13 (the exposure beam is indicated by a symbol Bm in the figure) is provided.

  In addition, a developing device 14 is provided around the photosensitive member 11, as an example of a developing unit, for storing each color component toner to visualize the electrostatic latent image on the photosensitive member 11 with the toner. A primary transfer roll 16 is provided to transfer the color component toner images formed thereon onto the intermediate transfer belt 15 at the primary transfer portion 10.

  Furthermore, a photosensitive body cleaner 17 is provided around the photosensitive body 11, from which residual toner on the photosensitive body 11 is removed, and the charger 12, the laser exposure unit 13, the developing unit 14, the primary transfer roll 16 and the photosensitive body cleaner Seventeen electrophotographic devices are sequentially disposed along the rotational direction of the photosensitive member 11. The image forming units 1Y, 1M, 1C, and 1K are arranged substantially linearly in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15. It is done.

  The intermediate transfer belt 15 is circularly driven (rotated) at various speeds in the direction B shown in FIG. 8 by various rolls. As the various rolls, a drive roll 31 driven by a motor (not shown) to rotate the intermediate transfer belt 15, and a support roll 32 supporting the intermediate transfer belt 15 extending substantially linearly along the arrangement direction of the photosensitive members 11. The tension applying roll 33 functions as a correction roll that applies tension to the intermediate transfer belt 15 and suppresses the meandering of the intermediate transfer belt 15. The back roll 25 provided on the secondary transfer portion 20 and the residual on the intermediate transfer belt 15. It has a cleaning back roll 34 provided in a cleaning unit for scraping off the toner.

The primary transfer portion 10 is configured of a primary transfer roll 16 as an opposing member disposed opposite to the photosensitive member 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 is composed of a core and a sponge layer as an elastic layer fixed around the core. The core is a cylindrical rod made of metal such as iron or SUS. The sponge layer is formed of a blend rubber of NBR, SBR and EPDM blended with a conductive agent such as carbon black, and is a sponge-like cylindrical roll having a volume resistivity of 10 ^7.5 Ωcm or more and 10 ^8.5 Ωcm or less.

  The primary transfer roll 16 is disposed so as to be in pressure contact with the photosensitive member 11 with the intermediate transfer belt 15 interposed therebetween, and the primary transfer roll 16 further has a voltage (primary) opposite to the charging polarity (negative polarity) of the toner. Transfer bias is applied. As a result, the toner images on the respective photosensitive members 11 are electrostatically attracted to the intermediate transfer belt 15 sequentially, and a superimposed toner image is formed on the intermediate transfer belt 15.

  The secondary transfer unit 20 is configured to include a back surface roll 25 and a secondary transfer roll 22 disposed on the toner image holding surface side of the intermediate transfer belt 15.

The back roll 25 is a tube of a blend rubber of EPDM and NBR in which the surface has carbon dispersed, and the inside is made of EPDM rubber. The surface resistivity is formed to be 10 ⁷ Ω / sq or more and 10 ¹⁰ Ω / sq or less, and the hardness is set to, for example, 70 ° (Asker C: manufactured by Kobunshi Keiki Co., Ltd., the same applies hereinafter). Ru. The back roll 25 is disposed on the back side of the intermediate transfer belt 15 to constitute a counter electrode of the secondary transfer roll 22, and a metal feed roll 26 to which a secondary transfer bias is stably applied is disposed in contact. ing.

On the other hand, the secondary transfer roll 22 is composed of a core and a sponge layer as an elastic layer fixed around the core. The core is a cylindrical rod made of metal such as iron or SUS. The sponge layer is formed of a blend rubber of NBR, SBR and EPDM blended with a conductive agent such as carbon black, and is a sponge-like cylindrical roll having a volume resistivity of 10 ^7.5 Ωcm or more and 10 ^8.5 Ωcm or less.

  The secondary transfer roll 22 is press-contacted to the back roll 25 with the intermediate transfer belt 15 interposed therebetween, and the secondary transfer roll 22 is grounded to form a secondary transfer bias with the back roll 25. The toner image is secondarily transferred onto the sheet K conveyed to the transfer unit 20.

  Further, on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, an intermediate transfer belt for removing the residual toner and paper powder on the intermediate transfer belt 15 after the secondary transfer and cleaning the surface of the intermediate transfer belt 15. A cleaner 35 is provided so as to be freely attachable and detachable.

  The intermediate transfer belt 15, the primary transfer portion 10 (primary transfer roll 16), and the secondary transfer portion 20 (secondary transfer roll 22) correspond to an example of the transfer unit.

  On the other hand, on the upstream side of the yellow image forming unit 1Y, a reference sensor (home position sensor) 42 that generates a reference signal serving as a reference for setting the image forming timing in each of the image forming units 1Y, 1M, 1C, and 1K. It is arranged. Further, an image density sensor 43 for adjusting the image quality is disposed downstream of the black image forming unit 1K. The reference sensor 42 recognizes a mark provided on the back side of the intermediate transfer belt 15 to generate a reference signal, and each image forming unit 1Y, 1 Y,... According to an instruction from the control unit 40 based on the recognition of the reference signal. 1M, 1C, 1K are configured to start image formation.

  Further, in the image forming apparatus according to the present embodiment, the sheet storage unit 50 for storing the sheet K and the sheet K stacked in the sheet storage unit 50 are taken out at a predetermined timing as the transport means for transporting the sheet K. Transport roller 52 for transporting the sheet K, the transport roll 52 for transporting the sheet K fed by the feed roll 51, the transport guide 53 for feeding the sheet K transported by the transport roll 52 to the secondary transfer unit 20, secondary transfer The conveyance belt 55 conveys the sheet K conveyed after being secondarily transferred by the roll 22 to the fixing device 60, and a fixing inlet guide 56 which guides the sheet K to the fixing device 60.

Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described.
In the image forming apparatus according to the present embodiment, image data output from an image reading apparatus (not shown) or a personal computer (PC) (not shown) is subjected to image processing by an image processing apparatus (not shown), and then image forming unit 1Y. , 1M, 1C, and 1K perform an imaging operation.

  The image processing apparatus performs image processing such as shading correction, positional deviation correction, lightness / color space conversion, gamma correction, various types of image editing such as border deletion, color editing, movement editing etc. on the inputted reflectance data. Be done. The image data subjected to the image processing is converted into color material tone data of four colors of Y, M, C, and K, and is output to the laser exposure device 13.

  The laser exposure device 13 irradiates, for example, the exposure beams Bm emitted from the semiconductor laser to the respective photosensitive members 11 of the image forming units 1Y, 1M, 1C, and 1K according to the input color material gradation data. . In each of the photosensitive members 11 of the image forming units 1Y, 1M, 1C, and 1K, the surface is charged by the charger 12, and then the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of Y, M, C and K by each of the image forming units 1Y, 1M, 1C and 1K.

  The toner images formed on the photosensitive members 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 at the primary transfer portion 10 where the respective photosensitive members 11 and the intermediate transfer belt 15 contact. Ru. More specifically, in the primary transfer portion 10, the primary transfer roller 16 applies a voltage (primary transfer bias) opposite to the charging polarity (minus polarity) of the toner to the base material of the intermediate transfer belt 15, thereby forming a toner image Are sequentially superimposed on the surface of the intermediate transfer belt 15 to perform primary transfer.

  After the toner image is sequentially primarily transferred to the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 is moved to convey the toner image to the secondary transfer portion 20. When the toner image is conveyed to the secondary transfer unit 20, the conveyance unit rotates the paper feed roll 51 in accordance with the timing at which the toner image is conveyed to the secondary transfer unit 20, and the paper storage unit 50 A size sheet K is supplied. The sheet K supplied by the sheet supply roll 51 is conveyed by the conveyance roll 52, passes through the conveyance guide 53, and reaches the secondary transfer unit 20. Before reaching the secondary transfer portion 20, the sheet K is temporarily stopped, and the sheet K is rotated by rotation of a positioning roll (not shown) in accordance with the movement timing of the intermediate transfer belt 15 holding the toner image. The position of the toner image and the position of the toner image are aligned.

  In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the back roll 25 via the intermediate transfer belt 15. At this time, the sheet K conveyed at the same timing is nipped between the intermediate transfer belt 15 and the secondary transfer roll 22. At that time, when a voltage (secondary transfer bias) having the same polarity as the charging polarity (minus polarity) of the toner is applied from the feeding roll 26, a transfer electric field is formed between the secondary transfer roll 22 and the back roll 25. Be done. Then, the unfixed toner images held on the intermediate transfer belt 15 are collectively electrostatically transferred onto the sheet K at the secondary transfer portion 20 pressurized by the secondary transfer roll 22 and the back roll 25. Ru.

  Thereafter, the sheet K on which the toner image has been electrostatically transferred is conveyed as it is in a state of being separated from the intermediate transfer belt 15 by the secondary transfer roll 22 and conveyed on the downstream side of the secondary transfer roll 22 in the sheet conveyance direction. It is conveyed to the belt 55. The conveyance belt 55 conveys the sheet K to the fixing device 60 in accordance with the optimum conveying speed of the fixing device 60. The unfixed toner image on the sheet K conveyed to the fixing device 60 is fixed on the sheet K by receiving a fixing process by heat and pressure by the fixing device 60. Then, the sheet K on which the fixed image has been formed is conveyed to a discharge storage unit (not shown) provided in the discharge unit of the image forming apparatus.

  On the other hand, after the transfer to paper K is completed, the residual toner remaining on intermediate transfer belt 15 is conveyed to the cleaning section as the intermediate transfer belt 15 rotates, and is cleaned by cleaning back roll 34 and intermediate transfer belt cleaner 35. The intermediate transfer belt 15 is removed.

  As mentioned above, although this embodiment was described, it can not be interpreted limitedly to the said embodiment, and various modification, change, improvement are possible.

· Configuration of image forming apparatus (second aspect)
Next, an image forming apparatus using the tubular body according to the present embodiment as a recording medium transport belt will be described as an example.
FIG. 9 is a schematic configuration view showing another example of the image forming apparatus according to the present embodiment.

  In the image forming apparatus 200 shown in FIG. 9, the units Y, M, C, and BK are respectively provided with the photosensitive drums (image carriers) 201Y, 201M, 201C, and 201BK so as to rotate counterclockwise in the direction of arrow C. Be Around the photosensitive drums 201Y, 201M, 201C and 201BK, charging devices (charging means) 202Y, 202M, 202C and 202BK, exposing devices (electrostatic charge image forming means) 214Y, 214M, 214C and 214BK, and each color development Devices (Developer: yellow developing device 203Y, magenta developing device 203M, cyan developing device 203C, black developing device 203BK) and photosensitive drum cleaning members (image carrier cleaning device) 204Y, 204M, 204C, 204BK are respectively arranged It is done.

  The units Y, M, C, BK are arranged in parallel in the order of the units BK, C, M, Y in parallel to the sheet conveying belt (tubular body) 207, but the units BK, Y, C, M An appropriate order is set according to the image forming method, such as the order of.

  The sheet conveying belt 207 is supported from the inner surface side by the four belt support rolls 206 and forms an intermediate transfer belt unit. The sheet conveying belt 207 is configured to rotate in the counterclockwise direction indicated by arrow A at the same peripheral speed as the photosensitive drums 201Y, 201M, 201C, and 201BK, and a portion thereof located between the belt support rolls 206 is a photosensitive member. The drums 201Y, 201M, 201C, and 201BK are disposed in contact with each other.

  The cleaning blade 212 in the sheet conveying belt 207 is arranged to be in contact with the surface (outer peripheral surface) on the sheet conveying side. In addition, a cleaning opposing roll 213 as a conductive opposing member is disposed in contact with the surface on the opposite side of the cleaning blade 212 via the sheet conveying belt 207, and forms a sheet conveying belt cleaning device 220. There is.

In addition to the cleaning blade 212, the sheet conveying belt cleaning device 220 may further include brush cleaning, roll cleaning, scraper cleaning, and the like.
Further, as the cleaning opposing roll 213, one having the same configuration as that of the cleaning back roll 34 used in the image forming apparatus 100 shown in FIG. 8 described above can be applied as it is.

  The transfer rolls (transfer means) 205Y, 205M, 205C, and 205BK are located inside the sheet conveying belt 207 and face the portions where the sheet conveying belt 207 and the photosensitive drums 201Y, 201M, 201C, and 201BK are in contact with each other. The transfer areas are formed on the photosensitive drums 201Y, 201M, 201C, and 201BK, and the transfer image on the sheet (recording medium) 215 via the sheet conveyance belt 207.

  The fixing device (fixing unit) 210 is disposed so as to be conveyed after passing through the transfer areas of the sheet conveying belt 207 and the photosensitive drums 201Y, 201M, 201C, and 201BK.

  The sheet conveying roll 208 conveys the sheet 215 to the sheet conveying belt 207.

  In the image forming apparatus shown in FIG. 9, in the unit BK, the photosensitive drum 201BK is rotationally driven. In conjunction with this, the charger 202BK is driven to charge the surface of the photosensitive drum 201BK to a target polarity and potential. Next, the photosensitive drum 201BK whose surface is charged is imagewise exposed by the exposing unit 214BK, and an electrostatic latent image is formed on the surface.

  Subsequently, the electrostatic latent image is developed by the black developing device 203BK. Then, a toner image is formed on the surface of the photosensitive drum 201BK. The developer at this time may be a one-component system or a two-component system.

  The toner image passes through the transfer area of the photosensitive drum 201BK and the sheet conveying belt 207, and the sheet 215 is electrostatically attracted to the sheet conveying belt 207, conveyed to the transfer area, and applied from the transfer roll 205BK. The electric field formed by the transfer bias sequentially transfers the sheet 215 to the surface.

  Thereafter, the toner remaining on the photosensitive drum 201BK is cleaned and removed by the photosensitive drum cleaning member 204BK. Then, the photosensitive drum 201BK is used for the next image transfer.

  The above image transfer is also performed in units C, M and Y by the above method.

  The sheet 215 to which the toner image has been transferred by the transfer rolls 205BK, 205C, 205M, and 205Y is further conveyed to the fixing device 210, and fixing is performed.

Photosensitive drum cleaning members 204Y, 204M, 204C, and 204BK remove residual toner on the photosensitive drums 201Y, 201M, 201C, and 201BK after transfer. On the other hand, after the recording medium 215 is conveyed, the residual toner is removed by the cleaning blade 212 in the sheet conveying belt cleaning device 220, and the sheet conveying belt 207 prepares for the next image forming process.
Thus, an image is formed on the sheet.

  EXAMPLES Hereinafter, the present invention will be described using examples, but the present invention is not limited to these examples. In the following, "parts" and "%" are based on mass unless otherwise noted.

Example 1
On a metal cylinder, an elastic base was formed into a belt shape by chloroprene rubber (CR).
The coating liquid for forming an intermediate protective layer (fluorine-containing urethane resin solution) was applied onto the elastic base of the cylinder on which the elastic base was formed using a spray coating apparatus. The thickness of the intermediate protective layer was changed in the axial direction by changing the discharge amount of the coating liquid from the nozzle in the axial direction. Thereafter, the cylinder coated with the coating liquid for forming an intermediate protective layer was dried while rotating.
Subsequently, on the said intermediate protective layer of the cylinder in which the intermediate protective layer was formed, the coating liquid for surface protective layer formation (fluorine-containing urethane resin solution) was apply | coated using the spray coating apparatus. The cylinder on which the coating liquid for forming a surface protective layer was applied was dried while rotating.
Thereafter, heating (baking) was performed on both layers to form an intermediate protective layer and a surface protective layer, to obtain a tubular body.

Comparative Example 1
In Example 1, when the surface protective layer and the intermediate protective layer are formed, the discharge amount of the coating liquid from the nozzle is not changed in the axial direction, that is, the thicknesses of the surface protective layer and the intermediate protective layer are not changed in the axial direction. A tubular body was obtained in the same manner as Example 1 except for the following.

Comparative Example 2
In Example 1, at the time of formation of the intermediate protective layer, the discharge amount of the coating liquid from the nozzle is not changed in the axial direction, and then, from the nozzle on the intermediate protective layer of the cylinder on which the intermediate protective layer is formed. The thickness of the surface protective layer was changed in the axial direction by changing the discharge amount of the coating solution in the axial direction.

For the tubular body obtained in each example, the thickness of each layer (surface protective layer, intermediate protective layer, elastic base material) and total thickness of the tubular body were measured at intervals of 15 mm from the axial center to both end directions did.
The results are shown in Table 1, Table 2 and Table 3.

Further, the pressing force at the axial center and at both axial ends of the tubular body was measured when the tubular body was sandwiched between the two rotating bodies from the inner circumferential surface side and the outer circumferential surface side.
The results are shown in Table 4.

-Evaluation test-
The following evaluation tests were performed using the tubular body obtained in each example.
The results are shown in Table 4.

・ Belt Walk The following method was evaluated for the occurrence of belt walk.
The tubular body is cyclically driven (rotated) by various rolls, and as the various rolls, tension is applied to the tubular body and the tubular body is continuously rotated by the circulation driving means by a motor, and constant rotation is performed. After the operation, the operation was stopped to check the condition of the tubular body such as a flaw on the end of the tubular body or a surface flaw, and the position of the tubular body at the end to confirm the presence or absence of occurrence of belt walk. The case where the belt walk occurred was evaluated as "B (x)", and the case where the belt walk was suppressed was evaluated as "A (o)".

-Cleanability, surface cracking The following methods were evaluated for the cleaning performance and the presence or absence of surface cracking.
The evaluation is carried out by observing the surface condition of the tubular body after being operated for a fixed period of time by incorporating the prototype tubular body into an image forming apparatus using as a recording medium transport belt, repeating the operations of image formation and paper transport. The The surface condition was observed by enlarging the surface by 200 times using a CCD camera, and the adhesion state of foreign matter and the presence or absence of surface cracking were qualitatively evaluated in three stages (A (○ from the excellent results in order) , B (.DELTA.), C (x) in this order).

  From the results shown in Table 4, the phenomenon of belt walk is suppressed as a result of suppressing the variation in the contact pressure in the axial direction of the tubular body when the rotating body is brought into contact with the outer peripheral surface of the tubular body in the present embodiment as compared with the comparative example. It can be seen that the cleaning property and the surface cracking are improved.

1Y, 1M, 1C, 1K Image forming unit 11 Photoreceptor (image carrier)
12 charger 13 laser exposure unit 14 developing unit 15, 15A, 15B, 15C, 250 tubular body (intermediate transfer belt)
16 Primary Transfer Roll 17 Photosensitive Material Cleaner 20 Secondary Transfer Unit 22 Secondary Transfer Roll 25 Back Roll 26 Power Feed Roll 31 Drive Roll 32 Support Roll 33 Tension Roll 34 Cleaning Back Roll 35 Intermediate Transfer Belt Cleaner 40 Control Unit 42 Reference Sensor 43 Image density sensor 50 sheet storage unit 51 sheet supply roll 52 conveyance roll 53 conveyance guide 55 conveyance belt 56 fixation entrance guide 60 fixing device 100 image formation device 110 rotary body 131, 132 roll 150 tubular unit 152, 252 elastic base 154 protection Layers 154A, 254A Surface protection layer 154B, 254B Intermediate protection layer 200 Image forming devices 201BK, 201C, 201M, 201Y Photosensitive drums 202BK, 202C, 202M, 202Y Charger 203BK Black developing device 203 Cyan developing device 203M Magenta developing device 203Y Yellow developing device 204BK, 204C, 204M, 204Y Photosensitive drum cleaning member 205BK, 205C, 205M, 205Y Transfer roll 206 Belt support roll 207 Paper conveying belt 208 Paper conveying roll 210 Fixing device 212 Cleaning blade 213 Countering rolls for cleaning 214BK, 214C, 214M, 214Y Exposure unit 215 Paper (recording medium)
220 Paper Transport Belt Cleaning Device

Claims (17)

An elastic base, an intermediate protective layer on the elastic base, and a surface protective layer on the intermediate protective layer,
The thickness of the tubular body is thickest at both ends in the axial direction and thinnest at the center in the axial direction,
And a tubular body for an image forming apparatus having variable thickness regions in which the thickness continuously changes in the direction from the both ends toward the center on at least both axial end sides.   The variable thickness region is a region in which the rate of change of the thickness from the both ends toward the center changes by more than 0% and 5% or less with respect to the thickness of the both ends every 15 mm. The tubular body according to claim 1, which is   The difference in thickness at the same distance from the center toward the one end and the other end with respect to the center in the axial direction is 1% at all the positions at the one end and the other end. The tubular body according to claim 1 or claim 2, which is as follows.   The tubular body according to any one of claims 1 to 3, wherein the variable thickness area occupies an area of 15% or more from each of the both ends with respect to the axial length of the tubular body.   The intermediate protective layer is thickest at both ends in the axial direction and thinnest at the center in the axial direction, and continuously at least on both axial ends toward the central direction from the both ends continuously The tubular body according to any one of claims 1 to 4, having a variable thickness area which changes.   The elastic modulus [Ms] of the surface protective layer, the elastic modulus [Mm] of the intermediate protective layer, and the elastic modulus [Mb] of the elastic base material have a relationship of [Ms <Mm <Mb]. A tubular body according to any one of the preceding claims.   The tubular body according to claim 6, wherein the ratio [Ms / Mm] of the elastic modulus [Ms] of the surface protective layer to the elastic modulus [Mm] of the intermediate protective layer is 1/8 or more and 1/2 or less.   The ratio [Mm / Mb] of the elastic modulus [Mm] of the intermediate protective layer to the elastic modulus [Mb] of the elastic base is 1/7 or more and 1/2 or less. Tubular body.   The tubular body according to any one of claims 1 to 8, wherein the surface protective layer and the intermediate protective layer are a fluorine-based resin layer, a silicone-based resin layer, or a fluorine-containing urethane resin layer.   The elastic base material is chloroprene rubber (CR), urea rubber, silicone rubber, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), epichlorohydrin rubber (ECO), styrene-butadiene copolymer The rubber according to any one of claims 1 to 9, comprising at least one rubber selected from rubber (SBR), chlorinated polyisoprene rubber, isoprene rubber, acrylonitrile-butadiene rubber, hydrogenated polybutadiene rubber, urethane rubber, butyl rubber, and fluororubber. The tubular body according to any one of the preceding claims.   The tubular body according to any one of claims 1 to 10, wherein the total thickness of the surface protective layer and the intermediate protective layer at the center in the axial direction is 3 μm or more and 25 μm or less.   The tubular body according to claim 11, wherein a thickness ratio (surface protective layer / intermediate protective layer) at the center in the axial direction between the surface protective layer and the intermediate protective layer is 3/7 or more and 7/3 or less. .   The tubular body according to any one of claims 1 to 12, wherein a thickness of the elastic base at the center in the axial direction is 200 μm or more and 1000 μm or less.   When the tubular body is sandwiched by two rotating bodies from the inner peripheral surface side and the outer peripheral surface side, the pressing force [Pe] on the outer peripheral surface of the both ends in the axial direction and the pushing on the central outer peripheral surface in the axial direction The tubular body according to any one of claims 1 to 13, wherein the ratio [Pe / Pc] to the pressure [Pc] is not less than 1.25 / 1 and not more than 1.6 / 1. The tubular body according to any one of claims 1 to 14, and
A plurality of rolls over which the tubular body is tensioned;
A tubular unit that comprises a unit that is detachable from the image forming apparatus. It has a tubular body unit according to claim 15,
A transfer device for transferring a toner image formed on the surface of an image carrier to the surface of a recording medium. An image carrier,
Toner image forming means for forming a toner image on the surface of the image carrier;
A transfer unit comprising the transfer device according to claim 16, for transferring the toner image to the surface of a recording medium.
An image forming apparatus comprising: