JP2005257795A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a developer image carrying belt capable of deterring deformation. <P>SOLUTION: The image forming apparatus 100 which has the developer image carrying belt 1 which carries developer images formed by image forming means Pa, Pb, Pc and Pd is so constituted that the developer image carrying belt 1 has at least one layer 10, and a center part 12 and an end part 11 in a thrust direction of at least the layer 10 have a difference in Young's modulus in the surface moving direction of the image carrying belt 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system or an electrostatic recording system, and more specifically, a recording material carrier or an intermediate transfer transfer body. The present invention relates to an image forming apparatus including a developer image conveying belt.

  2. Description of the Related Art Conventionally, for example, an image forming apparatus using an electrophotographic system is configured to uniformly charge an electrophotographic photosensitive member (hereinafter simply referred to as “photosensitive member”) as an image carrier and then perform exposure according to image information. By doing so, an electrostatic image is formed on the surface of the photoreceptor. The electrostatic image formed on the photoreceptor is visualized as a developer image (toner image) by the developer (toner) by the developing means, and the toner image is transferred to a recording material and fixed to form a recorded image. The

  In an image forming apparatus using such an electrophotographic system, a toner image formed sequentially on a single photosensitive member by a plurality of developing units, or a toner image formed by a developing unit on each of a plurality of photosensitive members, A toner image composed of a plurality of types of toners, for example, yellow, magenta, cyan, and black toners that are sequentially superimposed and transferred onto a recording material or intermediate transfer member carried on a recording material carrier is formed. There is something. As such a recording material carrier or intermediate transfer member as a developer image carrier for conveying a toner image formed on the recording material carried directly by the image forming means or directly on the recording material, a photosensitive material has been conventionally used. A belt (developer image conveying belt) such as a seamless belt that moves endlessly through a position facing the body is used.

  For example, in a color image forming apparatus capable of forming a full-color image using a belt-shaped intermediate transfer member (hereinafter referred to as “intermediate transfer belt”), for example, a plurality of belts are provided along the moving direction of the intermediate transfer belt. The process of primary transfer of toner images formed with toners of different colors (yellow, magenta, cyan, and black) onto the arranged photoreceptor is repeated on the intermediate transfer belt, and this intermediate transfer is repeated. A full-color image can be formed on the recording material by collectively transferring the toner image on the belt to a recording material such as recording paper.

  Further, for example, in a color image forming apparatus capable of forming a full-color image using a belt-shaped recording material carrier (hereinafter referred to as “recording material carrier belt”), for example, movement of the recording material carrier belt Toner images formed with toners of different colors (yellow, magenta, cyan, black) on a plurality of photoconductors arranged in the direction are sequentially transferred onto a recording material carried on a recording material carrying belt. Thus, a full color image can be formed on the recording material.

  Conventionally, an elastic belt having at least one elastic layer having excellent flexibility is used as the recording material carrying belt and the intermediate transfer belt as described above.

  However, when the elastic layer of the elastic belt is a rubber composition, it is a rubber, and therefore, distortion or the like occurs due to elongation. When distortion occurs, a difference in phase occurs between both ends of the elastic belt, that is, both ends in the direction perpendicular to the belt surface movement direction (conveying direction) (hereinafter referred to as “thrust direction”), thereby improving the conveyance performance. affect.

  Thus, for example, when the elastic belt is an intermediate transfer belt onto which the toner image is transferred, the toner image is disturbed when the toner image is formed on the elastic belt, and the electrostatic image is placed on the printing medium. It will not be possible to reproduce accurately. In particular, in a color image forming apparatus, toners of four colors of yellow, magenta, cyan, and black are used. Therefore, the relative positions of the toners are displaced due to the distortion of the elastic belt, and an image such as color misregistration or image unevenness is generated. Disturbance will occur.

  In addition, if a large distortion occurs at the end of the elastic belt, even if the belt transportability is maintained by a conveyance assisting member such as a rib, the rib may run on a tension roller or the like, and the elastic belt may come to one side. is there. This phenomenon not only detracts from the conveyance of the belt, but in some cases may lead to a belt breakage or a failure of the image forming apparatus.

  The same applies to the case where the elastic belt is a recording material carrying belt that carries and conveys the recording material thereon.

  For this reason, in order to prevent distortion of an elastic belt, it is necessary to raise rigidity.

  By the way, Patent Document 1 discloses that a layer structure of a transfer belt that carries and conveys a recording material has an elastic layer and a reinforcing layer. It is understood that the reinforcing layer is intended to reduce permanent elongation even in long-term use.

However, although the rigidity of the entire belt is certainly increased by using the reinforcing layer, in order to obtain a stable rigidity over the entire belt longitudinal direction (perpendicular to the belt traveling direction: thrust direction), the reinforcing layer It may be necessary to choose a material with a fairly high Young's modulus or to make it a very thick layer. For this reason, it becomes a high cost or it becomes a belt body which is difficult to handle.
JP 2000-10417 A

  The present invention has been made in view of the above-described problems. In other words, an object of the present invention is to provide an image forming apparatus having a developer image conveying belt capable of suppressing distortion.

  Another object of the present invention is to suppress the occurrence of image distortion such as color misregistration and image unevenness caused by distortion of a developer image conveying belt used as a recording material carrier or an intermediate transfer member even in long-term use. An image forming apparatus is provided.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus having a developer image transport belt for transporting a developer image formed by an image forming means, wherein the developer image transport belt has at least one layer, and The image forming apparatus is characterized in that there is a difference in Young's modulus between a central portion and an end portion of the at least one layer in a direction perpendicular to the surface movement direction of the agent transport belt.

  According to an embodiment of the present invention, the end portion has a higher Young's modulus than the central portion. In one embodiment, the central portion corresponds to an image portion, and the end portion corresponds to a non-image portion.

  According to an embodiment of the present invention, the developer image transport belt has a plurality of layers, and among the plurality of layers, the Young's modulus of an end portion of a layer serving as a base layer is equal to that of the developer image transport belt. The highest Young's modulus of all layers.

  According to one embodiment of the present invention, the end portion has a Young's modulus higher than that of the central portion by allowing isocyanate to permeate the end portion of the base material forming the layer. In one embodiment, the substrate is formed of a fluorine-based rubber.

  According to another embodiment of the present invention, the end portion is irradiated with ultraviolet rays at the end portion of the base material forming the layer, so that its Young's modulus is made higher than that of the central portion. In one embodiment, the substrate comprises epichlorohydrin rubber impregnated with a radiation sensitive acrylic monomer.

  According to another embodiment of the present invention, the end portion is irradiated with an electron beam at the end portion of the base material forming the layer, so that its Young's modulus is made higher than that of the central portion. In one embodiment, the substrate is formed of silicone rubber.

  In the present invention, the developer image conveying belt may be a seamless belt. The developer image conveying belt is formed on the recording material carrier for carrying and conveying the recording material on which the developer image is formed by the image forming means, or on the image forming means. It may be an intermediate transfer member that carries and conveys a developer image. In one embodiment, each of the image forming units includes a plurality of image carriers on which developer images to be transferred to the developer image conveying belt are formed.

  According to the present invention, the developer image transport belt provided in the image forming apparatus can suppress distortion. Therefore, the image forming apparatus of the present invention can suppress the occurrence of image distortion such as color misregistration and image unevenness caused by distortion of the developer image conveying belt used as a recording material carrier or an intermediate transfer member even during long-term use. Can do.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings. Note that the dimensions, materials, shapes, relative positions, and the like of the components of the image forming apparatus are not intended to limit the scope of the present invention only to those unless otherwise specified.

Example 1
[Overall Configuration and Operation of Image Forming Apparatus]
First, an overall configuration and operation of an example of an image forming apparatus to which the present invention can be applied will be described with reference to FIG. The image forming apparatus 100 of the present embodiment is connected to a host such as a personal computer connected to an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 100A, or connected to the apparatus main body. A laser beam printer capable of forming a full-color image of four colors such as a recording material, for example, a recording sheet, an OHP sheet, a cloth, etc., using an electrophotographic method in accordance with an image information signal from a document reading device to be converted into It is.

  The image forming apparatus 100 includes a belt-like intermediate transfer member that travels in the direction of arrow X in the drawing, that is, an endless intermediate transfer belt 1A, in the apparatus main body 100A. The intermediate transfer belt 1A is wound around a driving roller 13, a tension roller 14 and a backup roller 15 as a support. Four image forming portions Pa, Pb, Pc, and Pd are arranged in series as image forming means along a horizontal portion that runs on the upper side of the intermediate transfer belt 1A in the figure. A toner image is formed on the intermediate transfer belt 1A by the portions Pa, Pb, Pc, and Pd.

  Hereinafter, the operations of the image forming units Pa, Pb, Pc, and Pd will be further described. In this embodiment, the image forming units Pa, Pb, Pc, and Pd perform the same operation with substantially the same configuration except that the color of the toner to be used is different. Is a general description, omitting the suffixes a, b, c, and d given to the reference numerals in the drawing to indicate that they belong to an image forming unit for any color.

  The image forming unit P includes a drum-shaped photoconductor (hereinafter referred to as “photosensitive drum”) 21 as an image carrier disposed rotatably. Around the photosensitive drum 21, process devices such as a charging roller 22 as a charging unit, a developing device 24 as a developing unit, and a cleaning device 26 as a cleaning unit are arranged. The developing devices 24a, 24b, 24c, and 24d disposed in the image forming portions Pa, Pb, Pc, and Pd respectively store yellow toner, magenta toner, cyan toner, and black toner as developers.

  The photosensitive drum 21 is uniformly charged by the charging roller 22, and as exposure means (image writing means), from the exposure device 23, which is a laser scanner device in this embodiment, among the image information of the color-separated document. Laser light is projected onto the photosensitive drum 21 via a polygon mirror or the like according to the image signals of the component colors corresponding to the image forming portions Pa, Pb, Pc, and Pd, and an electrostatic image is formed on the photosensitive drum 21. It is formed.

  Next, the electrostatic image on the photosensitive drum 21 is developed as a toner image by supplying toner from the developing device 24. When the toner image arrives at the primary transfer portion T1 where the photosensitive drum 21 and the intermediate transfer belt 1A come into contact with the rotation of the photosensitive drum 21, the primary transfer bias from the primary transfer roller 25 serving as a primary transfer unit. Is applied and transferred to the intermediate transfer belt 1A.

  For example, when a four-color full-color image is formed, the above-described steps are performed at predetermined timings in the image forming units Pa, Pb, Pc, and Pd. That is, first, the intermediate transfer belt 1A carrying the yellow toner image transferred by the yellow image forming unit Pa is conveyed to the next magenta image forming unit Pb, and by this time, the magenta image forming unit Pb has the above-described state. In this process, the magenta toner image formed on the photosensitive drum 1b is superimposed and transferred onto the yellow toner image on the intermediate transfer belt 1A. Similarly, as the intermediate transfer belt 1A advances to the image forming portions Pc and Pd along the arrow X direction in the drawing, the cyan toner image and the black toner image are transferred onto the intermediate transfer belt 1A in each primary transfer portion T1. Is superimposed and transferred onto the toner image already transferred.

  In this embodiment, the image forming units Pa, Pb, Pc, and Pd that form toner images on the intermediate transfer belt 1 through the charging, exposure, development, and transfer steps constitute image forming means.

  On the other hand, in synchronization with the formation of the toner image on the intermediate transfer belt 1A as described above, the secondary transfer roller 16 as the secondary transfer unit and the backup roller 15 are opposed to each other from the recording material supply unit 30. It is conveyed to the transfer part T2. That is, the recording material S sent out by the pickup roller 32 from the cassette 31 serving as a recording material storage unit is timed by the conveying roller 33 and the registration roller 34 and reaches the secondary transfer unit T2. The four-color toner images on the intermediate transfer belt 1A are collectively transferred onto the recording material S by the secondary transfer bias applied to the secondary transfer member 16 in the secondary transfer portion T2.

  The recording material S to which the toner image has been transferred is then conveyed to the fixing unit 40. In the fixing unit 40, the toner image is fixed on the recording material S by heat and pressure. Thereafter, the recording material S on which the toner image is fixed is discharged out of the apparatus main body 100A.

  The surface of the photosensitive drum 21 after the toner image is primarily transferred to the intermediate transfer belt 1A is cleaned by a cleaning device 26 including a cleaning blade disposed in contact with the photosensitive drum 21, and used for subsequent image formation. Is done. Further, the surface of the intermediate transfer belt 1A after the toner image is secondarily transferred to the recording material S is cleaned by a belt cleaner 17 provided with a cleaning blade or the like disposed in contact with the intermediate transfer belt 1A. Served for formation.

[Intermediate transfer belt]
In this embodiment, as shown in FIG. 2, the endless intermediate transfer belt 1A is composed of one elastic (resin) layer (belt body). That is, the elastic layer (belt main body) 10A can be provided with ribs 18A as a conveyance auxiliary member. In this embodiment, the belt member as a functional member as an intermediate transfer member is substantially a single layer. It is formed of an elastic layer (belt body) 10A.

  According to the present invention, the Young's modulus of the elastic layer 10A of the intermediate transfer belt 1A corresponds to the substantially non-image portion on the edge side in the thrust direction from the central portion 10A1 corresponding to the substantially image portion on the inner side in the thrust direction. The ends 10A2 and 10A2 are higher. In other words, according to the present invention, the intermediate transfer belt 1A is configured to have a difference in Young's modulus between the central portion 10A1 and the end portions 10A2 and 10A2 in the thrust direction of the elastic layer 10A.

  More specifically, in the present embodiment, the Young's modulus of the central portion 10A1 is 20 MPa, and the Young's modulus of the end portions 10A2, 10A2 is 1,500 MPa. That is, apparently, the central portion 10A1 side has higher rigidity than the end portions 10A2 and 10A2 side.

  Thereby, the central portion 10A1 of the intermediate transfer belt 1A maintains the original flexibility of rubber (described later) constituting the elastic layer 10A, and the end portions 10A2 and 10A2 have higher rigidity than the central portion 10A1. Accordingly, the intermediate transfer belt 1A is less likely to be distorted as a whole belt, and image disturbance caused by the distortion can be suppressed. Further, the intermediate transfer belt 1A is provided with a rib 18A as a conveyance auxiliary member, and a conveyance regulating member for guiding the rib 18A includes the apparatus main body 100A or the drive roller 13, the tension roller 14, the backup roller 15, the intermediate transfer belt 1, and the like. Even when it is provided on the frame of the unitized belt unit, since the distortion of the elastic layer 10A of the intermediate transfer belt 1A is greatly suppressed, the transportability of the belt by the transport regulating member is sufficiently ensured. The Accordingly, high image quality can be stably maintained even during long-term use.

  The rib 18A as the conveyance auxiliary member can be the same as the conventional one. For example, the rib 18A is formed of the same or different material as the elastic layer 10A, and is formed on the inner side of the intermediate transfer belt 1 (the side opposite to the contact side of the photosensitive drum) ), The elastic layer 10A can be provided, for example, by adhering in the vicinity of one edge in the thrust direction. Further, for example, by restricting the movement of the rib 18A in the thrust direction by the conveyance restricting member using a guide member, a roller or the like, it is possible to improve the conveyability of the intermediate transfer belt 1.

  Here, the central portion 10A1 of the elastic layer 10A having a relatively low Young's modulus does not need to correspond strictly only to the image portion that is the region to which the toner image is transferred. Similarly, the end portions 10A2 and 10A2 of the elastic layer 10A having a relatively high Young's modulus do not need to correspond exactly to the non-image portion that is a region where the toner image is not transferred. However, the end portions 10A2 and 10A2 whose Young's modulus is relatively high are set so that the intermediate transfer belt 1A is in contact with the secondary transfer roller 16 substantially uniformly to ensure good transfer performance without white spots. It is preferable to dispose in the non-image area (the same applies to Examples 2 and 3 below).

  The Young's modulus of the central portion 10A1 and the end portions 10A2 and 10A2 of the intermediate transfer belt 1A was measured according to JIS K7127. That is, the Young's modulus was measured with strip-shaped test pieces (width 6 mm, length 130 mm), dumbbell No. 1 and a test speed of 500 mm / min. However, the thickness of the intermediate transfer belt 1A was calculated based on the thickness of only the elastic layer 10A.

  Next, with reference to FIG. 3, a method for giving the elastic layer 10 </ b> A a gradient of Young's modulus in the thrust direction perpendicular to the belt conveyance direction will be described in the present embodiment. In this example, the method includes any one or combination of the following steps. As will be readily appreciated by those skilled in the art, it will be appreciated that other steps may be included that are generally required or desirable to produce the belt member.

  (I) First, a seamless belt constituting the elastic layer 10A is produced. In this embodiment, the seamless belt (base material) constituting the elastic layer 10A is a fluorine-based rubber such as vinylidene fluoride-hexafluoropropene, vinylidene fluoride-chlorotrifluoroethylene, vinylidene fluoride-pentafluoro. Propene-based and tetrafluoroethylene-propylene-based ones can be suitably produced, but tetrafluoroethylene-propylene-based ones are more preferable in terms of surface smoothness.

  The manufacturing method of the seamless belt is the same as the conventional one. Such a method is well known to those skilled in the art and will not be described in detail, but may be manufactured by a centrifugal molding method.

  (II) Next, as shown in FIG. 3, the end portion 10A2 of the elastic layer 10A is immersed in a polyisocyanate compound bath for a predetermined time to perform “curing treatment”. In this example, tetrafluoroethylene-propylene was used for the elastic layer 10A.

  As the polyisocyanate compound, 4,4-diphenylmethane diisocyanate (MDI), 1,6-diisocyanatohexane (HDI), 2-methylpentamethylene diisocyanate-1,5 (MPDI) or the like is preferably used, but high elongation is used. MDI is more preferred in that a high rate reaction product is obtained.

  The method for reacting the fluorinated rubber with the polyisocyanate compound is not particularly limited, but the fluorinated rubber, the polyisocyanate compound and other components added as necessary may be added to an appropriate solvent such as methyl ethyl ketone, A method of dissolving in toluene and xylene and allowing this solution to penetrate into the rubber member forming the elastic layer 10A and reacting and curing at room temperature or under heating is preferable in that a curing reaction can be performed at room temperature.

  The time for performing the “curing treatment” by immersing the end portion 10A2 of the elastic layer 10A in the polyisocyanate compound can be appropriately selected so that the end portion 10A2 has a desired Young's modulus. However, if the processing time is too long during the curing process, the processing unit may be pulled, and the rubber may be locally torn, which may affect the belt transportability. Also, as shown in FIG. 4, the Young's modulus of the curing processing portion reaches almost saturation when the curing processing time exceeds a certain time according to the configuration of the elastic layer 10A. On the other hand, if the processing time is too short, the curing process becomes inadequate and there is a possibility that desired rigidity cannot be obtained. Therefore, the time for the curing treatment is suitably from 3 minutes to 10 minutes, more preferably from 5 minutes to 7 minutes.

  In addition, when the end portion 10A2 is immersed in the isocyanate compound bath, the central portion 10A1 may be masked with a silane coupling material, polyethylene glycol, or the like so that the isocyanate compound does not enter the central portion 10A1.

  (III) Next, after wiping off the excess isocyanate compound, it is left (cured) at room temperature for 72 hours, for example. Of course, the curing time is not limited to the above, and can be arbitrarily set as long as the purpose of relatively increasing the Young's modulus of the end portions 10A2 and 10A2 can be achieved.

  In this example, as shown in FIG. 5, in the above manufacturing method, the curing time is 5 minutes, and the Young's modulus of the end portion 10A2 is changed from 20 MPa in the untreated portion (center portion 10A1) to 1500 MPa. It was. Thereby, the rigidity of end part 10A2 was able to be improved.

  FIG. 3 schematically shows the curing process for only one end 10A2 in the thrust direction of the elastic layer 10A, but the other end 10A2 can be similarly cured.

  Here, the principle of the curing process of the end portion 10A2 of the elastic layer 10A in the present embodiment will be described. The reaction between the fluorinated rubber of the seamless belt constituting the elastic layer 10A and the polyisocyanate compound is carried out by reacting the functional group of the fluorinated rubber with an isocyanate group, and the fluorinated rubber is bonded by an allophanate bond. After a long time, a reaction product having excellent mechanical properties such as strength and elongation can be obtained. The method of this embodiment is based on this principle.

  From the viewpoint of transferability as described above, the Young's modulus of the central portion 10A1 substantially corresponding to the image portion is preferably 10 to 1000 MPa, and more preferably 20 to 700 MPa. On the other hand, in order to achieve the object of the present invention, the Young's modulus of the end portions 10A2 and 10A2 substantially corresponding to the non-image portions is preferably 1000 to 1500 MPa, more preferably 1300 to 1500 MPa.

  In addition, it is preferable that the Young's moduli of both end portions 10A2 and 10A2 match in the thrust direction of the elastic layer 10A. However, the present invention is not limited to the case where they strictly match. Furthermore, there may be a Young's modulus gradient (transition part) in which the Young's modulus gradually changes (decreases) from the end 10A2 of the elastic layer 10A to the central part 10A1 (the same applies to Examples 2 and 3 below). .

  Actually, when an endurance test of full-color image formation was performed in the image forming unit 100 on which the intermediate transfer belt 1A of this embodiment is mounted, it is considered that the distortion of the intermediate transfer belt 1A is caused throughout the endurance life of the image forming apparatus 100. Image disturbance such as color misregistration and image unevenness did not occur. The intermediate transfer belt 1A is provided with a rib 18A as a conveyance auxiliary member by a conventional method and guided by a conveyance regulating member (not shown). However, the conveyance performance of the intermediate transfer belt 1A by the rib 18A and the conveyance regulating member is It was sufficiently guaranteed that the rib 18A did not ride on the tension roller 14 and the intermediate transfer belt 1A did not approach one side in the thrust direction.

  As described above, according to the present embodiment, the center portion 10A1 and the end portion 10A2 in the thrust direction of the elastic layer 10A are caused by the reaction between the fluorine rubber material of the seamless belt constituting the elastic layer 10A of the intermediate transfer belt 1A and the isocyanate compound. 10A2 is different in Young's modulus. Accordingly, even if the elastic layer 10A is not provided with a reinforcing layer in order to impart rigidity to the intermediate transfer belt 1A, the intermediate transfer belt 1A can have both flexibility and rigidity, and distortion can be suppressed. Accordingly, it is possible to suppress the occurrence of image disturbance such as color misregistration and image unevenness even in long-term use.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus according to the present exemplary embodiment are substantially the same as those of the first exemplary embodiment, and the intermediate transfer belt manufacturing method is different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

[Intermediate transfer belt]
In this embodiment, as shown in FIG. 1, the endless intermediate transfer belt 1B is composed of a single elastic layer 10B. According to this embodiment, the Young's modulus of the elastic layer 10B of the intermediate transfer belt 1B corresponds to the substantially non-image portion on the edge side in the thrust direction from the central portion 10B1 corresponding to the substantially image portion on the inner side in the thrust direction. The end portions 10B2 and 10B2 to be higher are higher. That is, the intermediate transfer belt 1B is configured to have a difference in Young's modulus between the central portion 10B1 and the end portions 10B2 and 10B2 in the thrust direction of the elastic layer 10B, similarly to the intermediate transfer belt 1A of the first embodiment.

  More specifically, in the present embodiment, the Young's modulus of the central portion 10B1 is 70 MPa, and the Young's modulus of the end portions 10B2, 10B2 is 2,000 MPa. That is, apparently, the central portion 10B1 side has higher rigidity than the end portions 10B2 and 10B2 side. Thereby, the central portion B of the intermediate transfer belt 1B maintains the original flexibility of rubber (described later) constituting the elastic layer 10B, and the end portions 10B2, 10B2 have higher rigidity than the central portion 10B1. Accordingly, the intermediate transfer belt 1B is less likely to be distorted as a whole belt, and image disturbance caused by the distortion can be suppressed. Even when the rib 18B is provided on the intermediate transfer belt 1B as a conveyance auxiliary member, and a conveyance regulating member for guiding the rib 18B is provided on the apparatus main body 100A or the frame of the belt unit, the elastic layer 10B of the intermediate transfer belt 1B is provided. Since the distortion is greatly suppressed, the transportability of the belt by the transport regulating member is sufficiently ensured. Accordingly, high image quality can be stably maintained even during long-term use.

  The Young's modulus of the central portion 10B1 and the end portions 10B2, 10B2 of the intermediate transfer belt 1B is a value measured and calculated in the same manner as in the first embodiment.

  Next, with reference to FIG. 6, a method of giving the elastic layer 10 </ b> B a gradient of Young's modulus in the thrust direction perpendicular to the belt conveyance direction will be described in the present embodiment. In this example, the method includes any one or combination of the following steps. As will be readily appreciated by those skilled in the art, it will be appreciated that other steps may be included that are generally required or desirable to produce the belt member.

  (I) First, a seamless belt constituting the elastic layer 10B is produced. In this embodiment, the seamless belt constituting the elastic layer 10B is mainly composed of epichlorohydrin rubber impregnated with a radiation-sensitive acrylic monomer.

  The radiation-sensitive acrylic monomer is not particularly limited as long as it has sensitivity to ultraviolet rays. For example, an acrylic acid ester derivative or a methacrylic acid ester derivative can be suitably used, but in terms of stability of the curing reaction. Acrylic ester derivatives are more preferred.

  The method of impregnating the epichlorohydrin rubber with the radiation-sensitive acrylic monomer is not particularly limited, but a method of dispersing the acrylic monomer in the molten epichlorohydrin rubber can be used.

  In this embodiment, if the material constituting the seamless belt contains epichlorohydrin rubber impregnated with a radiation-sensitive acrylic monomer (preferably 0.1 to 20% by weight), other than that, tertiary amine, alkyl It may contain a phosphine photopolymerization accelerator, a thioether photopolymerization accelerator, and the like.

  The manufacturing method of the seamless belt can be the same as that described in the first embodiment.

  (II) Next, as shown in FIG. 6, the end portions 10B2 and 10B2 of the elastic layer 10B were irradiated with ultraviolet rays to perform “curing treatment”.

The light source may be any light source that can generate ultraviolet rays having the following wavelengths, such as a high-pressure mercury lamp, an ultra-high pressure mercury lamp, or a xenon lamp. The wavelength may be in the range of 200 nm to 400 nm, but a wavelength of 350 nm or more is desirable in order to allow the ultraviolet rays to reach the inside of the irradiated object and obtain a desired hardness. The ultraviolet irradiation time (curing treatment time) can be appropriately selected so that the end portions 10B2 and 10B2 of the elastic layer 10B have a desired Young's modulus, but according to the study of the present inventors, the end portion 10B2 of the elastic layer 10B. In order to obtain a desired Young's modulus of 10B2, it is preferably 7 minutes or more, more preferably 10 minutes or more. However, even if the ultraviolet irradiation time is longer than 20 minutes, the curing reaction is in an equilibrium state, so that the Young's modulus does not change and is preferably within 20 minutes from the viewpoint of productivity. As shown in FIG. 7, the Young's modulus of the curing processing portion reaches almost saturation when the ultraviolet irradiation time exceeds a certain time according to the configuration of the elastic layer 10 </ b> B. Accordingly, the ultraviolet irradiation time is 7 minutes to 15 minutes, more preferably 10 minutes to 15 minutes. The illuminance may be appropriately selected according to the type and content of the ultraviolet curable material, but in the present invention, about 200 to 700 mW / cm ² is appropriate so as not to cause a curing failure. If the illuminance is lower than this, the curing treatment is insufficient and the desired rigidity may not be obtained, and if it exceeds this, curing may be poor (hardness varies).

  When the end portions 10B2 and 10B2 are irradiated with ultraviolet rays, the central portion 10B1 is covered with a shielding member such as paper so that the central portion 10B1 is not irradiated with ultraviolet rays.

In this embodiment, in the above-described manufacturing method, a mercury lamp is used as the light source, the ultraviolet irradiation conditions are such that the wavelength is 365 nm, the irradiation time is 10 minutes, the illuminance is 500 mW / cm ² , and the end portions 10B2, 10B2 The Young's modulus was changed from 70 MPa in the untreated part (central part 10B1) to 2,000 MPa, and the rigidity of the end parts 10B2 and 10B2 could be improved.

  Here, the principle of the curing process of the end portions 10B2 and 10B2 of the elastic layer 10B in the present embodiment will be described. When the radiation-sensitive acrylic monomer is irradiated with ultraviolet rays by the photopolymerization reaction, it approaches the polymerizable double bond (unsaturated group) of the prepolymer and monomer, and the double bond portion is activated one after another. Bonded in a chain to obtain the desired hardness. The ultraviolet irradiation method used in this example is based on such a principle.

  Actually, when an endurance test of full-color image formation was performed in the image forming unit 100 on which the intermediate transfer belt 1B of this embodiment is mounted, it is considered that the distortion of the intermediate transfer belt 1B occurs throughout the endurance life of the image forming apparatus 100. Image disturbance such as color misregistration and image unevenness did not occur. The intermediate transfer belt 1B is provided with a rib 18B as a conveyance auxiliary member by a conventional method and guided by a conveyance regulating member (not shown). However, the conveyance performance of the intermediate transfer belt 1B by the rib 18B and the conveyance regulating member is as follows. It was sufficiently ensured that the rib 18B did not ride on the tension roller 14 and the intermediate transfer belt 1B did not approach one side in the thrust direction.

  As described above, according to the present embodiment, ultraviolet rays are applied to the end portions 10B2 and 10B2 of the seamless belt of the elastic layer 10B of the intermediate transfer belt 1B mainly composed of epichlorohydrin rubber impregnated with a radiation-sensitive acrylic monomer. By curing, a difference in Young's modulus is provided between the central portion 10B1 and the end portions 10B2 and 10B2 in the thrust direction of the elastic layer 10B. As a result, the intermediate transfer belt 1B can have both flexibility and rigidity without providing a reinforcing layer in order to impart rigidity to the intermediate transfer belt 1B, and distortion can be suppressed. Accordingly, it is possible to suppress the occurrence of image disturbance such as color misregistration and image unevenness even in long-term use.

Example 3
Next, still another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the first embodiment, and the method for manufacturing the intermediate transfer belt is different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

[Intermediate transfer belt]
In this embodiment, as shown in FIG. 1, the endless intermediate transfer belt 1C is composed of one elastic layer 10C. According to the present embodiment, the Young's modulus of the elastic layer 10C of the intermediate transfer belt 1C corresponds to the substantially non-image portion on the edge side in the thrust direction from the central portion 10C1 corresponding to the substantially image portion on the inner side in the thrust direction. The end portions 10C2 and 10C2 to be higher are higher. That is, the intermediate transfer belt 1C is configured to have a difference in Young's modulus between the central portion 10C1 and the end portions 10C2, 10C2 in the thrust direction of the elastic layer 10C, as in the first and second embodiments.

  More specifically, in the present embodiment, the Young's modulus of the central portion 10C1 is 100 MPa, and the Young's modulus of the end portions 10C2, 10C2 is 2,500 MPa. That is, apparently, the central portion 10C1 side has higher rigidity than the end portions 10C2 and 10C2 side. Thereby, the central portion 10C1 of the intermediate transfer belt 1C maintains the original flexibility of rubber (described later) constituting the elastic layer 10C, and the end portions 10C2, 10C2 have higher rigidity than the central portion 10C1. Therefore, the intermediate transfer belt 1 </ b> C is less likely to be distorted as a whole belt, and image disturbance caused by the distortion can be suppressed. Even when the rib 18C is provided on the intermediate transfer belt 1C as a conveyance auxiliary member and a conveyance regulating member for guiding the rib 18C is provided on the apparatus main body 100A or the frame of the belt unit, the elastic layer 10C of the intermediate transfer belt 1C is provided. Since distortion is greatly suppressed, belt transportability by the transport regulating member is sufficiently ensured. Accordingly, high image quality can be stably maintained even during long-term use.

  The Young's modulus of the central portion 10C1 and the end portions 10C2, 10C2 of the intermediate transfer belt 1C is a value measured and calculated by the same method as in the first embodiment.

  Next, with reference to FIG. 8, a method of giving the elastic layer 10C a gradient of Young's modulus in the thrust direction perpendicular to the belt conveying direction will be described in the present embodiment. In this example, the method includes any one or combination of the following steps. As will be readily appreciated by those skilled in the art, it will be appreciated that other steps may be included that are generally required or desirable to produce the belt member.

  (I) First, a seamless belt constituting the elastic layer 10C is manufactured. In this embodiment, the seamless belt constituting the elastic layer 10C is made of silicone rubber. In addition, the material of the elastic layer used by this invention will not be specifically limited if it has the sensitivity with respect to an electron beam. In addition to the above silicone rubber, for example, chloroprene rubber, fluorine-based rubber, epichlorohydrin rubber can be suitably used, but it has excellent environmental durability against temperature and humidity, and has little environmental dependency on electrical resistance. Silicone rubber is more preferable.

  The manufacturing method of the seamless belt can be the same as that described in the first embodiment.

  (II) Next, as shown in FIG. 8, the ends 10C2 and 10C2 of the elastic layer 10C were irradiated with an electron beam to perform “curing treatment”.

  If the acceleration voltage is less than 100 kV, it is difficult to reach the inside of the irradiated object deeply. On the other hand, if the acceleration voltage is higher than 300 kV, it may be cured to a desired hardness or more, and cracks may occur on the surface. Accordingly, the acceleration voltage is preferably 100 kV to 300 kV, but is preferably 250 kV or more in order to obtain a desired hardness. When the absorbed dose is 20 Mrad or more, the unevenness of the surface becomes high, and when the absorbed dose is 150 Mrad or less, the curing of the irradiated object hardly proceeds. Therefore, in order to obtain a desired hardness while maintaining the smoothness of the surface, a range of 100 Mrad to 150 Mrad is preferable, and a range of 120 Mrad to 150 Mrad is more preferable.

  When the end portions 10C2 and 10C2 are irradiated with the electron beam, the central portion 10C1 is covered with a shielding member such as a thin aluminum plate so that the central portion 10C1 is not irradiated with the electron beam.

  In this example, in the above-described manufacturing method, a curtain type electron beam irradiation apparatus is used as the electron beam, and the electron beam irradiation conditions are as follows: the acceleration voltage is 350 kV, the absorbed dose is 150 Mrad, and the Young's modulus of the end portions 10C2 and 10C2 is set. The rigidity of the end portions 10C2 and 10C2 could be improved by changing the untreated portion (center portion 10C1) from 100 MPa to 2,500 MPa.

  Here, the principle of the curing treatment of the end portions 10C2 and 10C2 of the elastic layer 10C in the present embodiment will be described. According to the electron beam irradiation method used in this example, the vulcanization of the silicone rubber can be promoted, and thereby the desired hardness of the end portions 10C2 and 10C2 can be obtained. The method of this embodiment is based on this principle.

  Actually, when an endurance test of full-color image formation was performed in the image forming unit 100 on which the intermediate transfer belt 1C of this embodiment is mounted, it is considered that the distortion of the intermediate transfer belt 1C is caused throughout the endurance life of the image forming apparatus 100. Image disturbance such as color misregistration and image unevenness did not occur. The intermediate transfer belt 1C is provided with ribs 18C as a conveyance auxiliary member by a conventional method and guided by a conveyance restriction member (not shown). However, the conveyance performance of the intermediate transfer belt 1C by the ribs 18C and the conveyance restriction member is as follows. The rib 18C rides on the tension roller 14 and the intermediate transfer belt 1C does not approach one side in the thrust direction.

  As described above, according to this embodiment, the end portions 10C and 10C2 of the seamless belt of the elastic layer 10C of the intermediate transfer belt 1C made of silicone rubber are irradiated with an electron beam to be cured, and the elastic layer 10C in the thrust direction. There is a difference in Young's modulus between the central portion 10C1 and the end portions 10C2, 10C2. As a result, the intermediate transfer belt 1C can have both flexibility and rigidity without providing a reinforcing layer in order to impart rigidity to the intermediate transfer belt 1C, and distortion can be suppressed. Accordingly, it is possible to suppress the occurrence of image disturbance such as color misregistration and image unevenness even in long-term use.

Example 4
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the first embodiment, and the intermediate transfer belt is different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

[Intermediate transfer belt]
In this embodiment, as shown in FIG. 9, the endless intermediate transfer belt 1D is composed of three elastic layers (belt main bodies). That is, the base layer 10D of the belt body 1D can be provided with a rib 18D as a conveyance assisting member, but in this embodiment, the belt member as a functional member as an intermediate transfer member has substantially three layers of elasticity. A layer (belt body), that is, a base layer 10D, an intermediate layer 11D, and a surface layer 12D are formed.

  The function of each of the three layers will be described. Among the three elastic layers, the Young's modulus of the intermediate layer 11D is very soft as 70 MPa, so that processing may be difficult when performing a polishing or cutting process in order to improve surface properties. Therefore, a base layer 10D that can easily perform surface processing is provided below the intermediate layer 11D. In this embodiment, the base layer 10D is not intended for reinforcement, but for improving the surface properties of the back surface of the intermediate transfer belt 1D. The surface layer 12D is provided to improve the releasability of the toner image.

  According to the present invention, the Young's modulus of the base layer 10D of the intermediate transfer belt 1D has an end corresponding to the substantially non-image portion on the edge side in the thrust direction from the central portion 10D1 corresponding to the substantially image portion on the inner side in the thrust direction. The portions 10D2 and 10D2 are higher. Further, the Young's modulus of the base layer 10D of the intermediate transfer belt 1D is higher than the Young's modulus of the intermediate layer 11D and the surface layer 12D of the intermediate transfer belt 1D. That is, according to the present invention, the intermediate transfer belt 1D is configured to have a difference in Young's modulus between the central portion 10D1 in the thrust direction of the base layer 10D and the end portions 10D2 and 10D2, and includes three elastic layers. Among them, the Young's modulus of the end portions 10D2 and 10D2 of the base layer 10D is the highest.

  More specifically, in this example, the Young's modulus of the central portion 10D1 of the base layer 10D is 900 MPa, and the Young's modulus of the end portions 10D2 and 11D2 is 2,800 MPa. The Young's modulus of the intermediate layer 11D is 70 MPa, and the Young's modulus of the surface layer 12D is 30 MPa. Before the following curing treatment, the Young's modulus of the base layer 10D is the highest among the three elastic layers.

  That is, the intermediate transfer belt 1D apparently has higher rigidity on the end portions 10D2 and 10D2 side than the central portion 10D1 side, and among the three layers, the Young's modulus of the end portions 10D2 and 10D2 of the base layer 10D is the highest. Get higher.

  Thereby, the central part of the intermediate transfer belt 1D maintains the original flexibility of rubber (described later) constituting the elastic layers (base layer, intermediate layer, surface layer) 10D, 11D, 12D, and the end part is the central part. Higher rigidity. Therefore, the intermediate transfer belt 1D is less likely to be distorted as a whole belt, and image disturbance caused by the distortion can be suppressed. Further, the intermediate transfer belt 1D is provided with a rib 18D as a conveyance auxiliary member, and a conveyance regulating member for guiding the rib 18D is provided integrally with the apparatus main body 100A or the drive roller 13, the tension roller 14, the backup roller 15, and the intermediate transfer belt 1. Even when it is provided on the frame of the unitized belt unit, since the distortion of the intermediate transfer belt 1D is greatly suppressed, the belt transportability by the transport regulating member is sufficiently ensured. Accordingly, high image quality can be stably maintained even during long-term use.

  As the rib 18D serving as a conveyance auxiliary member, the same rib as described in the first embodiment can be used. The rib 18D is formed of the same or different material as that of the base layer 10D, and the inner side of the intermediate transfer belt 1D (the contact of the photosensitive drum). It can be provided on the base layer 10D by, for example, bonding in the vicinity of one edge in the thrust direction on the side opposite to the contact side.

  Here, as described in the first embodiment, the central portion 10D1 of the base layer 10D having a relatively low Young's modulus needs to correspond strictly only to the image portion that is the region to which the toner image is transferred. Absent. Similarly, the end portion 10D2 of the base layer 10D having a relatively high Young's modulus does not need to correspond exactly to the non-image portion, which is a region where the toner image is not transferred. However, the end portion 10D2 of the base layer 10D having a relatively high Young's modulus is ensured so that the intermediate transfer belt 1D is in contact with the secondary transfer roller 16 substantially uniformly to ensure good transfer performance without white spots. Are preferably arranged in the non-image area.

  The Young's modulus of the central portion 10D1 and the end portion 10D2 of the base layer 10D of the intermediate transfer belt 1D, the Young's modulus of the intermediate layer 11D, and the Young's modulus of the surface layer (outermost layer) 12D are the same as described in the first embodiment. It is the value measured and calculated by the method. However, the Young's modulus of the base layer 10D, the intermediate layer 11D, and the surface layer 12D was calculated as the thickness of each of the layers 10D, 11D, and 12D.

  Next, with reference to FIG. 3, a method for providing the base layer 10D with a gradient of Young's modulus in the thrust direction perpendicular to the belt conveyance direction will be described in the present embodiment. Such a method is the same as the method of giving the elastic layer 10A in Example 1 a gradient of Young's modulus in the thrust direction. In this example, the method includes any one or combination of the following steps. As will be readily appreciated by those skilled in the art, it will be appreciated that other steps may be included that are generally required or desirable to produce the belt member.

  (I) First, a seamless belt constituting the base layer 10D is produced. In this embodiment, the seamless belt (base material) constituting the base layer 10D is a fluorine rubber, such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropene, vinylidene fluoride-chlorotrifluoroethylene, vinylidene fluoride. Ride-pentafluoropropene-based and tetrafluoroethylene-propylene-based ones can be suitably produced, but polyfluorinated in terms of maintaining the performance as rubber, easy surface treatment, and low production costs. A vinylidene type is more preferable. The manufacturing method of the seamless belt is the same as the conventional one. Such a method is well known to those skilled in the art and will not be described in detail, but may be manufactured by a centrifugal molding method.

  (II) Next, as shown in FIG. 3, the end portion 10D2 of the base layer 10D is immersed in a polyisocyanate compound bath for a predetermined time to perform “curing treatment”. In this example, polyvinylidene fluoride was used for the base layer 10D.

  As the polyisocyanate compound, 4,4-diphenylmethane diisocyanate (MDI), 1,6-diisocyanatohexane (HDI), 2-methylpentamethylene diisocyanate-1,5 (MPDI) or the like is preferably used, but high elongation is used. MDI is more preferred in that a high rate reaction product is obtained.

  The method for reacting the fluorinated rubber with the polyisocyanate compound is not particularly limited, but the fluorinated rubber, the polyisocyanate compound and other components added as necessary may be added to an appropriate solvent such as methyl ethyl ketone, A method of dissolving in toluene and xylene and allowing this solution to penetrate into the rubber member forming the base layer 10D and reacting and curing at room temperature or under heating is preferable in that a curing reaction can be performed at room temperature.

  The time for performing the “curing treatment” by immersing the end 10D2 of the base layer 10D in the polyisocyanate compound can be appropriately selected so that the end 10D2 has a desired Young's modulus. However, if the processing time is too long during the curing process, the processing unit may be pulled, and the rubber may be locally torn, which may affect the belt transportability. Further, as described above, the Young's modulus of the curing processing portion reaches almost saturation when the curing processing time exceeds a certain time according to the configuration of the base layer 10D. On the other hand, if the processing time is too short, the curing process becomes inadequate and there is a possibility that desired rigidity cannot be obtained. Therefore, the time for the curing treatment is suitably from 3 minutes to 10 minutes, more preferably from 5 minutes to 7 minutes.

  Note that when the end portion 10D2 is immersed in the isocyanate compound bath, the central portion 10D1 may be masked with a silane coupling material, polyethylene glycol, or the like so that the isocyanate compound does not enter the central portion 10D1.

  (III) Next, after wiping off the excess isocyanate compound, it is left (cured) at room temperature for 72 hours, for example. Of course, the curing time is not limited to the above, and can be arbitrarily set as long as the purpose of relatively increasing the Young's modulus of the end portion 10D2 can be achieved.

  In this example, the Young's modulus of the end portion 10D2 was changed from 900 MPa of the untreated portion (central portion 10D1) to 2,800 MPa with the curing time being 5 minutes in the above-described manufacturing method. Thereby, the rigidity of end part 10D2 was able to be improved.

  FIG. 3 schematically shows the curing process for only one end 10D2 in the thrust direction of the elastic layer 10D, but the other end 10D2 can be similarly cured.

  The principle of the curing process of the end portion 10D2 of the base layer 10D in the present embodiment is the same as that described as the principle of curing the end portion 10A2 of the elastic layer 10A in the first embodiment.

  Here, in the configuration of the present embodiment, from the viewpoint of transferability as described above, the Young's modulus of the central portion 10D1 substantially corresponding to the image portion is preferably 100 to 900 MPa, more preferably 700 to 900 MPa. It is. On the other hand, in order to achieve the object of the present invention, the Young's modulus of the end portion 10D2 corresponding to the substantially non-image portion is preferably 2000 to 2800 MPa, more preferably 2500 to 2800 MPa.

  In addition, as described in the first embodiment, it is preferable that the Young's moduli of both end portions 10D2 and 10D2 match in the thrust direction of the base layer 10D, but the present invention strictly matches. The case is not limited. Furthermore, there may be a Young's modulus gradient (transition portion) in which the Young's modulus gradually changes (decreases) from the end portions 10D2 and 10D2 of the base layer 10D to the central portion 10D1.

  (IV) Next, the intermediate layer 11D is formed on the upper layer of the base layer 10D. In this embodiment, the intermediate layer is made of a fluorine-based rubber such as vinylidene fluoride-hexafluoropropene, vinylidene fluoride-chlorotrifluoroethylene, vinylidene fluoride-pentafluoropropene, tetrafluoroethylene-propylene. 11D can be suitably produced, but a tetrafluoroethylene-propylene system is more preferable in terms of surface smoothness. The manufacturing method of the intermediate layer 11D is the same as the conventional method. Such a method is well known to those skilled in the art and will not be described in detail, but can be manufactured by an injection molding method.

(V) Next, the surface layer 12D is formed on the upper layer of the intermediate layer 11D. In this embodiment, the surface layer can be suitably produced from a fluororesin, an acrylic resin, a urethane resin, or the like, but a fluororesin is preferred in terms of toner releasability and durability (crack). The manufacturing method of the surface layer 12D is not different from the conventional one. Such a method is well known to those skilled in the art and will not be described in detail, but can be manufactured by coating.

  Actually, when an endurance test of full-color image formation was performed in the image forming unit 100 on which the intermediate transfer belt 1D of this embodiment is mounted, it is considered that it is caused by distortion of the intermediate transfer belt 1D throughout the endurance life of the image forming apparatus 100. Image disturbance such as color misregistration and image unevenness did not occur. The intermediate transfer belt 1D is provided with a rib 18D as a conveyance auxiliary member by a conventional method and guided by a conveyance regulating member (not shown). However, the conveyance performance of the intermediate transfer belt 1D by the rib 18D and the conveyance regulating member is as follows. The rib 18D climbed onto the tension roller 14 and the intermediate transfer belt 1D did not come to one side in the thrust direction.

  As described above, according to this embodiment, the central portion 10D1 and the end portions 10D2 and 10D2 in the thrust direction of the base layer 10D are caused by the reaction between the fluororubber material of the seamless belt constituting the base layer 10D of the intermediate transfer belt 1D and the isocyanate compound. And make a difference in Young's modulus. That is, when there are a plurality of layers 10D, 11D, 12D of the intermediate transfer belt 1D, the strength of at least one layer end is increased. Thus, even if the base layer 10D is not provided with a reinforcing layer in order to impart rigidity to the intermediate transfer belt 1D, the intermediate transfer belt 1D can have both flexibility and rigidity, and distortion can be suppressed. Accordingly, it is possible to suppress the occurrence of image disturbance such as color misregistration and image unevenness even in long-term use.

  In the present embodiment, the base layer 10D having increased rigidity in the thrust direction is used similarly to the elastic layer 10A of the intermediate transfer belt 1A described in the first embodiment, and the intermediate layers 11D and 12D are formed thereon. However, the elastic layers 10A and 10B of the intermediate transfer belts 1B and 1C described in Examples 2 and 3 are used as the base layer 10D in this embodiment, and the intermediate layer 11D and the surface layer 12D are formed thereon. It can also be formed.

Example 5
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the first embodiment, and the intermediate transfer belt is different. Accordingly, elements having substantially the same or corresponding functions and configurations as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here.

[Intermediate transfer belt]
In this embodiment, as shown in FIG. 10, the endless intermediate transfer belt 1E is composed of three elastic layers (belt bodies). That is, the base layer 10E of the belt main body 1E can be provided with ribs 18E as a conveyance auxiliary member, but in this embodiment, the belt member as a functional member as an intermediate transfer member has substantially three layers of elasticity. It is formed of layers (belt main bodies) 10E, 11E, and 12E. The functions of the three layers, that is, the base layer 10E, the intermediate layer 11E, and the surface layer 12E are the same as those in the fourth embodiment.

  According to the present invention, the Young's modulus of the base layer 10E of the intermediate transfer belt 1E has an end corresponding to the substantially non-image portion on the edge side in the thrust direction from the central portion 10E1 corresponding to the substantially image portion on the inner side in the thrust direction. The portions 10E2 and 10E2 are higher. Further, the Young's modulus of the base layer 10E of the intermediate transfer belt 1E is higher than the Young's modulus of the central portion 11E1 and the end portion 11E2 of the intermediate layer 11E of the intermediate transfer belt 1E and the central portion 12E1 and the end portion 12E2 of the surface layer 12E. . That is, according to the present invention, the intermediate transfer belt 1E is configured to have a difference in Young's modulus between the central portion 10E1 in the thrust direction of the base layer 10E and the end portions 10E2, 10E2, and includes three elastic layers. Among them, the Young's modulus of the end portions 10E2 and 10E2 of the base layer 10E is the highest. In the present embodiment, the Young's modulus of the end portions 11E2 and 12E2 of the intermediate layer 11E and the surface layer 12E is additionally higher than the central portions 11E1 and 12E1 by the manufacturing method described later.

  More specifically, in this embodiment, the Young's modulus of the central portion 10E1 of the base layer 10E is 900 MPa, and the Young's modulus of the end portions 10E2 and 10E2 is 2,800 MPa. The Young's modulus of the central portion 11E1 of the intermediate layer 11E is 70 MPa, and the Young's modulus of the end portions 11E2 and 11E2 of the intermediate layer 11E is 1500 MPa. Further, the Young's modulus of the central portion 12E1 of the surface layer 12E is 30 MPa, and the Young's modulus of the end portions 12E2 and 12E2 of the surface layer 12E is 1000 MPa.

  That is, apparently, the intermediate transfer belt 1E has higher rigidity on the end portions 10E2 and 10E2 side than the central portion 10E1 side, and among the three layers, the Young's modulus of the end portions 10E2 and 10E2 of the base layer 10E is the highest. Get higher.

  Thereby, the central portion of the intermediate transfer belt 1E maintains the original flexibility of rubber (described later) constituting the elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, and 12E, and the end portion from the central portion. High rigidity. Accordingly, the intermediate transfer belt 1E is less likely to be distorted as a whole belt, and image disturbance caused by the distortion can be suppressed. Further, a rib 18E is provided on the intermediate transfer belt 1E as a conveyance auxiliary member, and a conveyance regulating member for guiding the rib 18E is provided integrally with the apparatus main body 100A or the drive roller 13, the tension roller 14, the backup roller 15, and the intermediate transfer belt 1. Even when it is provided on the frame of the unitized belt unit, since the distortion of the intermediate transfer belt 1E is greatly suppressed, the transportability of the belt by the transport regulating member is sufficiently ensured. Accordingly, high image quality can be stably maintained even during long-term use.

  As the rib 18E serving as the conveyance auxiliary member, the same material as that described in the first embodiment can be used. In the vicinity of one edge in the thrust direction on the side opposite to the contact side, the base layer 10E can be provided, for example, by bonding.

  Here, as described in the first embodiment, the central portions 10E1, 11E1, and 12E1 of the elastic layers (base layer, intermediate layer, and surface layer) 10E, 11E, and 12E that have relatively low Young's modulus are toner images. It is not necessary to strictly correspond only to an image portion that is a region to which is transferred. Similarly, the end portions 10E2, 11E2, and 12E2 of the elastic layers 10E, 11E, and 12E having relatively high Young's modulus do not need to correspond strictly to non-image portions that are regions where toner images are not transferred. However, the end portions 10E2, 11E2, where the Young's modulus is relatively increased so that the intermediate transfer belt 1E is in contact with the secondary transfer roller 16 substantially uniformly to ensure good transfer performance without white spots. 12E2 is preferably arranged in the non-image area.

  The Young's modulus of the central portions 10E1, 11E1, 12E1 and the end portions 10E2, 11E2, 12E2 of the elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, 12E of the intermediate transfer belt 1E is as described in the first embodiment. It is the value measured and calculated by the same method. However, the Young's modulus of the base layer 10E, the intermediate layer 11E, and the surface layer 12E was calculated as the thickness of each of the layers 10E, 11E, and 12E.

  Next, in this embodiment, a method of giving Young's modulus gradient in the thrust direction perpendicular to the belt conveying direction to the elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, 12E will be described. In the fourth embodiment, the intermediate layer 11D and the surface layer 12D are provided after increasing the Young's modulus of the end portion 10D2 in the thrust direction of the base layer 10D, whereas in this embodiment, after forming three layers, the end in the thrust direction of each layer is formed. The Young's modulus of the portions 10E2, 11E2, and 12E2 is increased. In this example, the method includes any one or combination of the following steps. As will be readily appreciated by those skilled in the art, it will be appreciated that other steps may be included that are generally required or desirable to produce the belt member.

  (I) First, a seamless belt constituting the base layer 10E is produced. In this embodiment, the seamless belt (base material) constituting the base layer 10E is a fluorine-based rubber such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropene, vinylidene fluoride-chlorotrifluoroethylene, vinylidene fluoride. Ride-pentafluoropropene-based and tetrafluoroethylene-propylene-based ones can be suitably produced, but polyfluorinated in terms of maintaining the performance as rubber, easy surface treatment, and low production costs. A vinylidene type is more preferable. The manufacturing method of the seamless belt is the same as the conventional one. Such a method is well known to those skilled in the art and will not be described in detail, but may be manufactured by a centrifugal molding method.

(II) Next, the intermediate layer 11E is formed on the upper layer of the base layer 10E. In this embodiment, the intermediate layer is made of fluorine rubber, for example, vinylidene fluoride-hexafluoropropene, vinylidene fluoride-chlorotrifluoroethylene, vinylidene fluoride-pentafluoropropene, tetrafluoroethylene-propylene. 11E can be suitably produced, but a tetrafluoroethylene-propylene system is more preferable in terms of surface smoothness. The manufacturing method of the intermediate layer 11E is the same as the conventional method. Such a method is well known to those skilled in the art and will not be described in detail, but can be manufactured by an injection molding method.

(III) Next, the surface layer 12E is formed on the upper layer of the intermediate layer 11E. In this embodiment, the surface layer can be suitably produced from a fluororesin, an acrylic resin, a urethane resin, or the like, but a fluororesin is preferred in terms of toner releasability and durability (crack). The manufacturing method of the surface layer 12E is not different from the conventional method. Such a method is well known to those skilled in the art and will not be described in detail, but can be manufactured by coating.

  (IV) Next, the respective end portions 10E2, 11E2, and 12E2 of the elastic layers (base layer, intermediate layer, and surface layer) 10E, 11E, and 12E of the intermediate transfer belt 1E are immersed in a polyisocyanate compound bath for a predetermined time. Process. Such a curing process is similar to that described above with reference to FIG. In this example, the single elastic layer 10A (Example 1) or the base layer 10D (Example 4) in FIG. 3 becomes three elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, and 12E. . Similarly, the central portions 10A1, 10D1 in FIG. 3 become the central portions 10E1, 11E1, 12E1, and the end portions 10A2, 10D2 become the end portions 10E2, 11E2, 12E2. Please refer to each of them.

  As the polyisocyanate compound, 4,4-diphenylmethane diisocyanate (MDI), 1,6-diisocyanatohexane (HDI), 2-methylpentamethylene diisocyanate-1,5 (MPDI) or the like is preferably used, but high elongation is used. MDI is more preferred in that a high rate reaction product is obtained.

  The method for reacting the fluorinated rubber with the polyisocyanate compound is not particularly limited, but the fluorinated rubber, the polyisocyanate compound and other components added as necessary may be added to an appropriate solvent such as methyl ethyl ketone, The method of dissolving in toluene and xylene and allowing this solution to penetrate into the rubber members forming the elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, and 12E and react and cure at room temperature or under heating is cured at room temperature. It is preferable at the point which can be made to react.

  The end 10E2 is desired for the time during which the end portions 10E2, 11E2, and 12E2 of the elastic layers (base layer, intermediate layer, and surface layer) 10E, 11E, and 12E of the intermediate transfer belt 1E are immersed in the polyisocyanate compound to perform “curing treatment”. The Young's modulus can be appropriately selected. However, if the processing time is too long during the curing process, the processing unit may be pulled, and the rubber may be locally torn, which may affect the belt transportability. Further, as described above, the Young's modulus of the curing processing portion reaches almost saturation when the curing processing time exceeds a certain time according to the configuration of the base layer 10E. On the other hand, if the processing time is too short, the curing process becomes inadequate and there is a possibility that desired rigidity cannot be obtained. Accordingly, the time for the curing treatment is suitably 5 minutes to 12 minutes, more preferably 7 minutes to 9 minutes.

  When the end portions 10E2, 11E2, and 12E2 of the elastic layers (base layer, intermediate layer, and surface layer) 10E, 11E, and 12E are immersed in the isocyanate compound bath, the center portion 10E1 of the base layer 10E and the center portion 12E1 of the surface layer 12E The central portion 10E1 of the base layer 10E and 12E1 of the surface layer 12E may be masked with a silane coupling material, polyethylene glycol, or the like so that the isocyanate compound does not enter.

(V) Next, after wiping off the excess isocyanate compound, it is left (cured) at room temperature for 72 hours, for example. Of course, the curing time is not limited to the above, and can be arbitrarily set as long as the purpose of relatively increasing the Young's modulus of the end portion 10E2 can be achieved.

  In this example, the Young's modulus of the end portion 10E2 of the base layer 10E was changed from 900 MPa of the untreated portion (center portion 10E1) to 2,800 MPa with the curing time being 5 minutes in the above-described manufacturing method. Thereby, the rigidity of the end portion 10E2 of the base layer 10E could be improved. Moreover, the Young's modulus of end part 11E2 of intermediate | middle layer 11E improved from 70 MPa to 1500MP by the said process, and the Young's modulus of end part 12E2 of surface layer 12E improved from 30 MPa to 1000 MPa.

  FIG. 3 schematically shows the curing treatment of only one end 10E2, 11E2, 12E2 in the thrust direction of the elastic layers (base layer, intermediate layer, surface layer) 10E, 11E, 12E, but the other end 10E2, 11E2, and 12E2 can be similarly cured.

  The principle of the curing process of the end portion 10E2 of the base layer 10E in the present embodiment is the same as that described as the principle of curing the end portion 10A2 of the elastic layer 10A in the first embodiment.

  Here, in the configuration of the present embodiment, from the viewpoint of transferability as described above, the Young's modulus of the central portion 10E1 of the base layer 10E substantially corresponding to the image portion is preferably 100 to 900 MPa, more preferably, 700 to 900 MPa. On the other hand, in order to achieve the object of the present invention, the Young's modulus of the end portion 10E2 substantially corresponding to the non-image portion is preferably 2000 to 2800 MPa, more preferably 2500 to 2800 MPa.

  Further, as described in the first embodiment, it is preferable that the Young's moduli of both end portions 10E2 and 10E2 are in the thrust direction of the base layer 10E, but the present invention strictly matches. The case is not limited. Furthermore, there may be a Young's modulus gradient (transition portion) in which the Young's modulus gradually changes (decreases) from the end 10E2 to the central portion 10E1 of the elastic layer 10E.

  Actually, when an endurance test for full-color image formation was performed in the image forming unit 100 on which the intermediate transfer belt 1E of this embodiment is mounted, it is considered that the distortion of the intermediate transfer belt 1E occurs throughout the endurance life of the image forming apparatus 100. Image disturbance such as color misregistration and image unevenness did not occur. The intermediate transfer belt 1E is provided with a rib 18E as a conveyance auxiliary member by a conventional method and guided by a conveyance regulating member (not shown). However, the conveyance performance of the intermediate transfer belt 1E by the rib 18E and the conveyance regulating member is as follows. The rib 18E climbs on the tension roller 14 and the intermediate transfer belt 1E does not approach one side in the thrust direction.

  As described above, according to this embodiment, the central portion 10E1 and the end portions 10E2 and 10E2 in the thrust direction of the base layer 10E are caused by the reaction between the fluororubber material of the seamless belt constituting the base layer 10E of the intermediate transfer belt 1E and the isocyanate compound. And make a difference in Young's modulus. That is, when there are a plurality of layers 10E, 11E, 12E of the intermediate transfer belt 1E, the strength of at least one layer end is increased. Accordingly, even if the base layer 10E is not provided with a reinforcing layer in order to impart rigidity to the intermediate transfer belt 1E, the intermediate transfer belt 1E can have both flexibility and rigidity, and distortion can be suppressed. Accordingly, it is possible to suppress the occurrence of image disturbance such as color misregistration and image unevenness even in long-term use. In this embodiment, the intermediate layer 11E and the surface layer 12E are formed on the base layer 10E, and then the curing treatment is performed by the above reaction. At this time, the Young's modulus of the end portions 11E2 and 12E of the intermediate layer 11E and the surface layer 12E is additionally set. Is higher than the central portions 11E1 and 12E1. Accordingly, the intermediate transfer belt 1E has flexibility and further rigidity.

  In Examples 4 and 5 described above, the case where the developer image transport belt has a plurality of layers has been described as having a base layer, an intermediate layer, and a surface layer, but the present invention is not limited to this. For example, a release layer (surface layer) may be simply provided on the base layer (outermost layer). In this case, as the at least one layer, the Young's modulus at the end in the thrust direction of the base layer may be set higher than that at the center, and the Young's modulus at the end in the thrust direction of the surface layer is also increased relative to the center. Also good.

  In the above embodiments, the present invention has been described by taking the intermediate transfer belt 1 as an example of the developer image transport belt having at least one layer, but the present invention is not limited to this. The present invention is equally applicable to the recording material carrier belt as the recording material carrier described above. The developer conveying belt according to the present invention can be applied to all belt materials that require rigidity and flexibility, such as a transfer belt and a recording material carrying belt, used in an image forming apparatus. For example, FIG. 11 shows a schematic configuration of an image forming apparatus 200 including a recording material carrying belt 201 as a developer image conveying belt. The illustrated image forming apparatus 200 includes a plurality of image forming portions Pa, Pb, Pc, and Pd as in the above-described embodiment. In FIG. 11, elements having substantially the same or corresponding configuration and function as those of the image forming apparatus 100 shown in FIG. The recording material carrying belt 201 is provided with a difference in Young's modulus between the central portion and the end portion in the thrust direction in the same manner as described in the above embodiments according to the present invention. All the other features described for the intermediate transfer belt can be applied to the recording material carrying belt 201, and the same effects as described above can be obtained.

  When the developer image conveying belt according to the present invention is used as a recording material carrier, the image portion corresponds to an image area on the carried recording material S (or a carrying area of the recording material S) and is a non-image. The portion corresponds to a non-image area (or outside the recording material S carrying area) on the carried recording material S. However, in this case as well, as described above, the central portion and the end portion do not need to correspond exactly to the image portion and the non-image portion, respectively, but in view of transferability, the end portion corresponds to the non-image portion. It is preferable.

  In each of the above embodiments, the image forming apparatus has been described as having a plurality of image forming units as image forming means, but the present invention is not limited to this. For example, in an image forming apparatus that has a single image forming unit and forms an image, typically a monochrome image, using a single type of developer, the recording material is placed between the image carrier and the transfer unit. The present invention can be equally applied to the transfer belt even if it has a transfer belt that sandwiches the recording material and conveys the recording material. In this case, since it may be considered that the image forming unit 100 or 200 shown in FIG. 1 or FIG. 11 has the image forming unit alone, the above description is used here.

  Further, as an image forming apparatus capable of forming an image using a plurality of types of developers, a developer having a plurality of developing units for one image carrier and sequentially formed on the one image carrier. An image, typically an image, typically transferred onto a recording material carried on a recording material carrier, or sequentially transferred onto an intermediate transfer body and then secondary transferred onto a recording material at a time. The present invention is equally applicable to image forming apparatuses that form full-color images. FIG. 12 shows a schematic configuration of an example of this type of image forming apparatus. The illustrated image forming apparatus 300 includes a developing device 24 in which four developing devices 24a, 24b, 24c, and 24d are mounted on a rotating body 24A as a plurality of developing units. By rotating the rotating body 24A, a desired developing means is opposed to the photosensitive drum 21 as an image carrier, and a toner image can be sequentially formed on the photosensitive drum 21 by the desired developing means. The toner images sequentially formed on the photosensitive drum 21 are primarily transferred to the intermediate transfer belt 301 as an intermediate transfer member, and then collectively transferred to the recording material S. In FIG. 12, elements having substantially the same or corresponding configurations and functions as those of the image forming apparatus 100 shown in FIG. In this case, the image has a photosensitive drum 21, a charging roller 22, an exposure device 23, a developing device 24, and a transfer roller 25 that form a toner image on the intermediate transfer belt 301 through the steps of charging, exposure, development, and primary transfer. Forming means are configured. Also in such an image forming apparatus 300, substantially the same intermediate transfer belt 301 as that described in the above embodiments can be used, and the same operational effects as described above can be obtained.

1 is a schematic configuration diagram of an example of an image forming apparatus to which the present invention can be applied. FIG. 3 is a schematic cross-sectional view in the thrust direction of an embodiment of an intermediate transfer belt according to the present invention. It is explanatory drawing for demonstrating one Example of the manufacturing method of the intermediate transfer belt according to this invention. It is a graph which shows the relationship between the immersion time to the isocyanate compound of an elastic layer, and Young's modulus. FIG. 6 is a graph showing the Young's modulus distribution at the center and end of the intermediate transfer belt. It is explanatory drawing for demonstrating the other Example of the manufacturing method of the intermediate transfer belt according to this invention. It is a graph which shows the relationship between the ultraviolet irradiation time to an elastic layer, and a Young's modulus. It is explanatory drawing for demonstrating the other Example of the manufacturing method of the intermediate transfer belt according to this invention. It is a cross-sectional schematic diagram of the thrust direction of the other Example of the intermediate transfer belt according to this invention. FIG. 10 is a schematic cross-sectional view in the thrust direction of still another embodiment of the intermediate transfer belt according to the present invention. It is a schematic block diagram of the other example of the image forming apparatus which can apply this invention. It is a schematic block diagram of further another example of the image forming apparatus to which the present invention can be applied.

Explanation of symbols

1A-1E Intermediate transfer belt (intermediate transfer member)
10A-10E Elastic layer (layer, base layer)
10A1-10E1 Center part (image part)
10A2-10E2 end (non-image part)
11E1, 12E1 Central part (image part)
11E2, 12E2 edge (non-image part)
11D, 11E Intermediate layer 12D, 12E Surface layer 16 Secondary transfer roller (secondary transfer means)
21a, 21b, 21c, 21d Photosensitive drum (image carrier)
22a, 22b, 22c, 22d Charging roller (charging means)
23a, 23b, 23c, 23d Exposure apparatus (exposure means)
24a, 24b, 24c, 24d Developing device (developing means)
25a, 25b, 25c, 25d Primary transfer roller (primary transfer means)

Claims (13)

In an image forming apparatus having a developer image conveying belt for conveying a developer image formed by an image forming unit,
The developer image transport belt has at least one layer, and has a difference in Young's modulus between a central portion and an end portion of the at least one layer in a direction perpendicular to the surface movement direction of the developer image transport belt. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the end portion has a higher Young's modulus than the center portion.   3. The image forming apparatus according to claim 1, wherein the central portion corresponds to an image portion, and the end portion corresponds to a non-image portion.   The developer image transport belt has a plurality of layers, and among the plurality of layers, the Young's modulus at the end of the base layer is the highest among the Young's moduli of all the layers of the developer image transport belt. The image forming apparatus according to claim 1, 2 or 3.   The said edge part makes the Young's modulus higher than the said center part by making isocyanate penetrate | invade into the edge part of the base material which forms the said layer, The claim in any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus described.   The image forming apparatus according to claim 5, wherein the base material is made of fluorine-based rubber.   The said edge part makes the Young's modulus higher than the said center part by irradiating an ultraviolet-ray to the edge part of the base material which forms the said layer, The Claim 1 characterized by the above-mentioned. Image forming apparatus.   The image forming apparatus according to claim 7, wherein the base material includes epichlorohydrin rubber impregnated with a radiation-sensitive acrylic monomer.   The said edge part makes the Young's modulus higher than the said center part by irradiating the electron beam to the edge part of the base material which forms the said layer, The claim in any one of Claims 1-4 characterized by the above-mentioned. The image forming apparatus described.   The image forming apparatus according to claim 9, wherein the base material is formed of silicone rubber.   The image forming apparatus according to claim 1, wherein the developer image conveying belt is a seamless belt.   The developer image conveying belt is a recording material carrier that carries and conveys a recording material on which a developer image is formed by the image forming means, or a developer formed thereon by the image forming means. The image forming apparatus according to claim 1, wherein the image forming apparatus is an intermediate transfer member that carries and conveys an image.   13. The image forming unit according to claim 1, wherein the image forming unit includes a plurality of image carriers on which developer images to be transferred to the developer image conveying belt are formed. The image forming apparatus described.

Images