Transfer Belt and Electrophotographic Image Forming Apparatus

Abstract

To provide a transfer belt that is provided with transferability, cleanability, and durability without impairing a function to hold a toner image and a transfer material, and an electrophotographic image forming apparatus provided with the transfer belt.SOLUTION: A transfer belt of the present invention is a transfer belt having a base material layer, and a surface layer laminated on the base material layer. The dielectric constant of the base material layer is within a range of 20-100. The dielectric constant of an area from a surface on the side of the surface layer to a depth of 15 μm is within a range of 5-10. The Martens hardness of the surface on the side of the surface layer is within a range of 300-700 N / mm2.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to a transfer belt and an electrophotographic image forming apparatus, and more particularly to a transfer belt having transferability, cleanability, and durability without impairing the function of holding a toner image or a transfer material, and an electrophotographic image forming apparatus including the transfer belt.

Background Art

[0002] In an electrophotographic image forming apparatus, for example, a latent image formed on an image carrier (photoconductor) is developed with toner, and the obtained toner image is transferred (primary transfer) onto an intermediate transfer belt which is a belt-shaped transfer member and temporarily held. Then, the toner image on the intermediate transfer belt is transferred (secondary transfer) onto a transfer material such as paper. At the time of secondary transfer, the transfer material is placed on a secondary transfer belt (also referred to as a "paper conveyance belt" or a "transfer conveyance belt"), conveyed to the position of the intermediate transfer belt, and the transfer (secondary transfer) of the toner image from the intermediate transfer belt to the transfer material is performed on the secondary transfer belt.

[0003] For transfer belts such as the intermediate transfer belt and the secondary transfer belt used in this image forming method, good toner transferability from the electrostatic latent image carrier to the intermediate transfer belt and from the intermediate transfer belt to the transfer material on the secondary transfer belt, and cleanability for removing residual toner after transfer are required.

[0004] In recent electrophotographic image forming apparatuses, various transfer materials are used, and it is required to cope with not only plain paper and OA dedicated paper but also paper types such as thick paper, coated paper, and paper with uneven surfaces. In particular, improvement of transfer belts such as the intermediate transfer belt and the secondary transfer belt is required.

[0005] Here, generally, it is known that a larger capacitance of the transfer belt is advantageous in terms of transfer rate, retention of the transfer material and toner image, etc. However, increasing the capacitance causes a problem that foreign substances such as paper dust and residual toner are likely to adhere to the transfer belt. In response to such a problem, for example, Patent Document 1 describes a technique for reducing the contamination of the transfer belt by reducing the surface energy of the surface of the secondary transfer belt (transfer conveyance belt). However, in the technique described in Patent Document 1, when the charged toner adheres to the surface of the transfer belt, the effect of reducing contamination is insufficient, and means for reducing the electrical force is required.

[0006] Further, Patent Document 2 describes a technique of an intermediate transfer belt in which the relative permittivity of the entire transfer belt is 15 or more, the relative permittivity of the surface layer is 6 or less, and the volume resistivity is within a specific range, based on the technical idea that a lower relative permittivity of the surface layer results in a smaller mirror image force between the toner and the transfer belt. However, in the intermediate transfer belt described in Patent Document 2, a mode in which the hardness of the surface layer is set low is preferable from the viewpoint of durability. In that case, the toner release property is not sufficient.

[0007] Furthermore, Patent Document 3 describes a technique of an intermediate transfer belt having a hard coat layer with high hardness as the surface layer. With this configuration, it is said that the toner is less likely to sink into the intermediate transfer belt and the toner release property is improved. Here, the ultraviolet curable resin, etc., specifically described as the constituent material of the hard coat layer in Patent Document 3, has a lower relative permittivity than the generally used base layer material and is considered to have an effect of reducing the mirror image force. However, in order to obtain the effect of reducing the mirror image force, a hard coat layer with a relative permittivity as low as the toner layer thickness is required. However, problems occur in the durability such as cracking in the hard coat layer made of the above ultraviolet curable resin, etc.

[0008] On the other hand, it is assumed that increasing the toner releasability in the intermediate transfer belt makes it difficult to hold the toner image. Based on such a technical idea, a technique of increasing the relative permittivity of the surface layer of the transfer belt is known from the viewpoint of sufficiently holding the toner image and the transfer material (see, for example, Patent Document 4).

[0009] As described above, in transfer belts such as intermediate transfer belts and secondary transfer belts, there is currently no transfer belt that has a function of sufficiently holding a toner image and a transfer material, while exhibiting transferability of the toner image, cleaning performance for removing paper dust, residual toner, etc., and durability.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide a transfer belt and an electrophotographic image forming apparatus including the transfer belt, which are imparted with transferability, cleaning performance, and durability without impairing the function of holding a toner image and a transfer material.

Means for Solving the Problems

[0012] In order to solve the above problems, the present inventors, in the process of examining the causes of the above problems, regarding a transfer belt having a base material layer and a surface layer laminated on the base material layer, set the relative permittivity of the base material layer and the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm within specific ranges, respectively, and set the Martens hardness of the surface on the surface layer side within a specific range, thereby finding that a transfer belt with transferability, cleanability, and durability can be provided without impairing the function of holding a toner image or a transfer material, and thus arriving at the present invention. That is, the above problems according to the present invention are solved by the following means.

[0013] 1. A transfer belt having a base material layer and a surface layer laminated on the base material layer, wherein the relative permittivity of the base material layer is in the range of 20 to 100, the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm is in the range of 5 to 10, and the Martens hardness of the surface on the surface layer side is in the range of 300 to 700 N / mm 2 A transfer belt characterized by being within the range.

[0014] 2. The transfer belt according to item 1, wherein the surface layer includes a cured product of a composition containing an alkoxysilane.

[0015] 3. Further, an intermediate layer is provided between the base material layer and the surface layer, the intermediate layer contains a resin selected from a polyimide resin, a polyamideimide resin, a polyphenylene sulfide resin, and a polyetheretherketone resin, the total layer thickness of the intermediate layer and the surface layer is in the range of 10 to 20 μm, and the layer thickness of the base material layer is in the range of 40 to 100 μm. The transfer belt according to item 1 or item 2, characterized by being within the range.

[0016] 4. The Martens hardness of the surface on the surface layer side is in the range of 500 to 600 N / mm 2 The transfer belt according to any one of items 1 to 3, characterized by being within the range.

[0017] 5. The transfer belt according to any one of claims 1 to 4, wherein the relative permittivity of the base material layer is in the range of 40 to 100.

[0018] 6. The transfer belt according to claim 3, wherein the relative permittivity of the intermediate layer is in the range of 5 to 10.

[0019] 7. The transfer belt according to any one of claims 1 to 6, wherein the relative permittivity of the surface layer is in the range of 2 to 5.

[0020] 8. An electrophotographic image forming apparatus comprising the transfer belt according to any one of claims 1 to 7.

Advantages of the Invention

[0021] By the above means of the present invention, there is provided a transfer belt having transferability, cleanability, and durability without impairing the function of holding a toner image or a transfer material, and an electrophotographic image forming apparatus including the transfer belt.

[0022] Although the mechanism or action mechanism for the manifestation of the effects of the present invention is not clearly understood, it is presumed as follows.

[0023] The transfer belt of the present invention has a configuration having a base material layer with a relative permittivity of 20 to 100 and a surface layer laminated on the base material layer, and the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm is in the range of 5 to 10. The fact that the relative permittivity of the region is in the range of 5 to 10 means that it has a sufficiently low relative permittivity and a layered region with a sufficient thickness. In the transfer belt of the present invention, the layered region may be composed of only the surface layer or may be composed of the surface layer and the intermediate layer. Further, the surface on the surface layer side has a sufficiently high hardness with a Martens hardness in the range of 300 to 700 N / mm 2 within the range.

[0024] When the transfer belt of the present invention is used as an intermediate transfer belt, on the surface side where primary transfer and secondary transfer of the toner image are performed, there is a layered region having a low relative dielectric constant and a thickness corresponding to the thickness of the toner layer, and further, since the surface has a sufficiently high hardness, the releasability of the toner image in secondary transfer can be improved. Also, due to the same mechanism of action, the cleaning property of the residual toner after secondary transfer is also improved. Furthermore, even without thickening the high-hardness surface layer while the surface on the surface layer side has a high hardness, the transfer belt is excellent in durability because a region with a low relative dielectric constant exists at a thickness of 15 μm from the surface on the surface layer side.

[0025] Also, the transfer belt of the present invention is provided with a base material layer having a sufficiently high relative dielectric constant of 20 to 100 inside the layered region having a low relative dielectric constant. When used as an intermediate transfer belt, the electric field acting on the toner can be strengthened, and even if the force attracting the toner becomes weak due to the existence of the layered region having a low relative dielectric constant, good primary transfer can be performed. Furthermore, polarization charges exist in the base material layer having a high relative dielectric constant, and in the transfer belt of the present invention, it has the ability to sufficiently hold the toner image from primary transfer to secondary transfer. In addition, since a reverse bias is applied during secondary transfer, the above polarization charges disappear promptly and polarize in the reverse polarity, so that secondary transfer from the intermediate transfer belt to the transfer material can also be performed smoothly.

[0026] When the transfer belt of the present invention is used as a secondary transfer belt, by providing a base material layer having a sufficiently high relative dielectric constant of 20 to 100 inside the layered region having a low relative dielectric constant, good secondary transfer can be performed, and due to the secondary transfer bias, the transfer belt can be charged and the transfer material can be sufficiently adsorbed and held. Also, in the secondary transfer belt, excellent cleaning property and durability against paper dust and residual toner are the same as in the case of the intermediate transfer belt.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0028] The transfer belt of the present invention is a transfer belt having a base material layer and a surface layer laminated on the base material layer, wherein the relative permittivity of the base material layer is in the range of 20 to 100, the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm is in the range of 5 to 10, and the Martens hardness of the surface on the surface layer side is in the range of 300 to 700 N / mm 2 within the range. This feature is a technical feature common to or corresponding to each of the following embodiments (forms).

[0029] As an embodiment of the present invention, from the viewpoint of the manifestation of the effects of the present invention, particularly from the viewpoint of making the Martens hardness of the surface on the surface layer side sufficiently high, it is preferable that the surface layer includes a cured product of a composition containing alkoxysilane. More preferably, the surface layer typically consists of a cured product of a composition containing alkoxysilane.

[0030] As an embodiment of the present invention, from the viewpoint of the manifestation of the effects of the present invention, further, an intermediate layer is provided between the base material layer and the surface layer, the intermediate layer contains a resin selected from polyimide resin, polyamideimide resin, polyphenylene sulfide resin, and polyetheretherketone resin, the total layer thickness of the intermediate layer and the surface layer is in the range of 10 to 20 μm, and the layer thickness of the base material layer is preferably in the range of 40 to 100 μm.

[0031] As an embodiment of the present invention, from the viewpoint of the manifestation of the effects of the present invention, the martensite hardness of the surface on the surface layer side is 500 to 600 N / mm 2 and preferably within the range. Further, the relative permittivity of the base material layer is preferably within the range of 40 to 100. The relative permittivity of the intermediate layer is preferably within the range of 5 to 10. Regarding the relative permittivity of the surface layer, it is preferable to satisfy at least one of being within the range of 2 to 5.

[0032] The transfer belt of the present invention can be suitably provided in an electrophotographic image forming apparatus.

[0033] Hereinafter, the present invention, its components, and the forms and embodiments for carrying out the present invention will be described in detail. In the present application, "~" is used in the sense of including the numerical values described before and after as the lower limit value and the upper limit value.

[0034] [Transfer Belt] The transfer belt of the present invention is a transfer belt having a base material layer and a surface layer laminated on the base material layer, and is characterized by satisfying the following requirements (1) to (3). (1) The relative permittivity of the base material layer is within the range of 20 to 100. (2) The relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm is within the range of 5 to 10. (3) The martensite hardness of the surface on the surface layer side is 300 to 700 N / mm 2 and within the range.

[0035] The transfer belt of the present invention has a base material layer and a surface layer laminated on the base material layer. The transfer belt of the present invention may arbitrarily have other layers other than the base material layer and the surface layer as long as the requirements (1) to (3) are satisfied. Examples of other layers include an intermediate layer disposed between the base material layer and the surface layer. When in use, for example, in the case of an intermediate transfer belt, a toner image is transferred to the surface on the surface layer side of the transfer belt of the present invention. Also, in the case of a secondary transfer belt, a transfer material is placed on the surface on the surface layer side during use.

[0036] The shape of the transfer belt of the present invention is preferably an endless structure because it has advantages such as no change in thickness due to superposition, any part can be used as the starting position of the rotation of the transfer belt, and the control mechanism for the rotation starting position can be omitted.

[0037] Hereinafter, with reference to the drawings, embodiments of the transfer belt of the present invention will be described by taking an endless transfer belt as an example. However, the scope of the present invention is not limited to the illustrated examples. FIGS. 1 and 2 are a plan view and a cross-sectional view taken along line II-II of an example of the transfer belt of the present invention (an endless transfer belt) stretched between two conveying rollers. FIG. 3A is an enlarged cross-sectional schematic view of the X portion of the transfer belt shown in FIG. 2. FIG. 3B is an enlarged cross-sectional schematic view of another example of the transfer belt of the present invention.

[0038] In FIGS. 1 and 2, the transfer belt 1A of the present invention is stretched between two conveying rollers R1 and R2 so as to be conveyable in the D direction. The transfer belt 1A is composed of a base material layer 2 and a surface layer 3 laminated on the base material layer 2. In the transfer belt 1A, the inner peripheral surface in contact with the conveying rollers R1 and R2 is the surface S2 on the side of the base material layer 2, and the outer peripheral surface exposed to the outside is the surface S1 on the side of the surface layer 3.

[0039] FIG. 3B shows an enlarged cross-sectional schematic view of a transfer belt 1B having an intermediate layer 4 on the base material layer 2 and a surface layer 3 on the intermediate layer 4. The transfer belt 1B is an endless transfer belt having the same structure as the transfer belt 1A except that the layer structure is a three-layer structure. When the transfer belt 1B is applied to FIGS. 1 and 2 instead of the transfer belt 1A, the inner peripheral surface in contact with the conveying rollers R1 and R2 is the surface S2 on the side of the base material layer 2, and the outer peripheral surface exposed to the outside is the surface S1 on the side of the surface layer 3.

[0040] Referring to FIGS. 3A and 3B, the requirements (1) to (3) of the transfer belt of the present invention will be described. In FIG. 3A, the thickness of the transfer belt 1A, the layer thickness of the base material layer 2, and the layer thickness of the surface layer 3 are denoted by "Tt", "Tb", and "Ts", respectively. In FIG. 3B, the thickness of the transfer belt 1B, the layer thickness of the base material layer 2, the layer thickness of the intermediate layer 4, and the layer thickness of the surface layer 3 are denoted by "Tt", "Tb", "Tm", and "Ts", respectively.

[0041] In the transfer belts 1A and 1B, according to the requirement (1), the relative permittivity of the base material layer 2 is in the range of 20 to 100. When the relative permittivity of the base material layer 2 is within the above range, the transfer belts 1A and 1B are excellent in the retention of toner images and transfer materials, and do not reduce the effects of transferability and cleanability. The relative permittivity of the base material layer 2 is preferably in the range of 40 to 100, and more preferably in the range of 60 to 80. The constituent materials for setting the relative permittivity of the base material layer 2 within the above range will be described later.

[0042] Also, the layer thickness Tb of the base material layer 2 is preferably in the range of 20 to 300 μm, more preferably in the range of 30 to 200 μm, and even more preferably in the range of 40 to 100 μm. When the layer thickness Tb of the base material layer 2 is within the above range, the transfer belts 1A and 1B can easily enjoy the advantage that the base material layer 2 has a high relative permittivity, and can easily achieve the effects of toner image and transfer material retention, transferability, and cleanability.

[0043] In the transfer belts 1A and 1B, according to the requirement (2), the relative permittivity in the region from the surface S1 on the surface layer 3 side to a depth of 15 μm (hereinafter, also referred to as "region L") is in the range of 5 to 10. When the relative permittivity in the region L is within the above range, the transfer belts 1A and 1B are excellent in transferability and cleanability. The relative permittivity in the region L is preferably in the range of 5 to 8, and more preferably in the range of 5 to 6.

[0044] Here, in the embodiment where the transfer belt 1A has a two-layer structure composed of a base material layer and a surface layer, the layer thickness Ts of the surface layer 3 is 15 μm or more, that is, it is an example where all of the region L is composed of the surface layer 3. When the transfer belt of the present invention has a two-layer structure composed of a base material layer and a surface layer, as long as the requirement (2) is satisfied, the ratio of the layer thickness of the surface layer 3 to the thickness of the base material layer 2 in the region L is not particularly limited. For example, a range of 15:0 to 10:5 can be applied. When the layer thickness Ts of the surface layer 3 is 15 μm or more, the thickness of the base material layer 2 in the region L is 0 μm, and the above ratio is 15:0. When the layer thickness Ts of the surface layer 3 is 10 μm, the thickness of the base material layer 2 in the region L is 5 μm, and the above ratio is 10:5.

[0045] Note that as long as all the requirements (1) to (3) are satisfied, an aspect in which all of the base material layer 2 exists within the region L, that is, the total layer thickness of the surface layer 3 and the base material layer 2 is 15 μm, is also included in the present invention. However, considering the thickness Tt of the transfer belt 1A and the layer thickness Tb of the base material layer 2, an aspect in which the base material layer 2 exists while constituting a part of the region L and exceeds the region L or the base material layer 2 exists outside the region of the region L is preferable.

[0046] In the transfer belt 1A, when the layer thickness Ts of the surface layer 3 is 15 μm or more, the relative permittivity in the region L is the same as the relative permittivity of the surface layer 3. When the layer thickness Ts of the surface layer 3 is less than 15 μm, the region L is composed of a part of the surface layer 3 and the base material layer 2. The relative permittivity in the region L in that case corresponds to the relative permittivity of a mixed material composed of the constituent material of the surface layer 3 and a part of the constituent material of the base material layer 2 measured by the following method.

[0047] In order to satisfy the requirement of (2) above, when the transfer belt has a two-layer structure of a base layer and a surface layer like the transfer belt 1A, the relative permittivity of the surface layer 3 is 10 or less, preferably in the range of 2 to 10, and more preferably 2 to 5. Also, the layer thickness Ts of the surface layer 3 is preferably 5 μm or more, more preferably in the range of 5 to 20 μm, and even more preferably in the range of 10 to 20 μm. Since the relative permittivity and the layer thickness of the surface layer 3 are within the above ranges, the surface layer has a low relative permittivity and a layer thickness corresponding to the thickness of the toner layer, and the toner releasability is further improved. The constituent material for setting the relative permittivity of the surface layer 3 within the above range will be described later.

[0048] Also, the transfer belt 1B is an example in which the total layer thickness of the layer thickness Ts of the surface layer 3 and the layer thickness Tm of the intermediate layer 4 is 15 μm in an embodiment where the transfer belt has a three-layer structure including a base layer, an intermediate layer, and a surface layer. When the transfer belt has a two-layer structure including a base layer and a surface layer, the base layer has a high relative permittivity of 20 to 100 according to the requirement of (1), and the surface layer has a low relative permittivity of 10 or less according to the requirement of (2). When the transfer belt has a three-layer structure including a base layer, an intermediate layer, and a surface layer, since the requirement that the base layer has a high relative permittivity of 20 to 100 according to the requirement of (1) remains unchanged, it is preferable that the surface layer and the intermediate layer perform the same functions as the surface layer in the case of the two-layer structure.

[0049] In the transfer belt 1B, as long as the requirement of (2) is satisfied, the layer structure in the region L is not particularly limited. For example, the region L may consist only of the surface layer 3, may consist of the surface layer 3 and the intermediate layer 4, or may consist of the surface layer 3, the intermediate layer 4, and the base layer 2. The region L preferably has an aspect consisting of the surface layer 3 and the intermediate layer 4 or an aspect consisting of the surface layer 3, the intermediate layer 4, and the base layer 2, and more preferably has an aspect consisting of the surface layer 3 and the intermediate layer 4.

[0050] In the transfer belt 1B as well, if all the requirements (1) to (3) are satisfied, an aspect in which all of the base material layer 2 is present within the region L, that is, an aspect in which the total layer thickness of the surface layer 3, the intermediate layer 4, and the base material layer 2 is 15 μm is also included in the present invention. However, considering the thickness Tt of the transfer belt 1B and the layer thickness Tb of the base material layer 2, an aspect in which the base material layer 2 exists while partially constituting the region L and exceeds the region L or the base material layer 2 exists outside the region of the region L is preferable.

[0051] Taking these into consideration, in the transfer belt 1B, the total layer thickness of the layer thickness Ts of the surface layer 3 and the layer thickness Tm of the intermediate layer 4 is preferably in the range of 10 to 20 μm, and more preferably in the range of 15 to 20 μm. When the transfer belt has a three-layer structure of a base material layer, an intermediate layer, and a surface layer like the transfer belt 1B, in order to satisfy the requirement (2) above, an aspect in which the relative dielectric constant and the layer thickness of the surface layer 3 and the intermediate layer 4 are in the following combination is preferable.

[0052] The relative dielectric constant of the surface layer 3 is preferably in the range of 2 to 10, and more preferably 2 to 5. The relative dielectric constant of the intermediate layer 4 is preferably in the range of 5 to 20, and more preferably 5 to 10. Also, the layer thickness Ts of the surface layer 3 is preferably in the range of 1 to 15 μm, and more preferably in the range of 1 to 10 μm. The layer thickness Tm of the intermediate layer 4 is preferably in the range of 5 to 15 μm, and more preferably in the range of 10 to 15 μm. By having the total layer thickness, each relative dielectric constant, and each layer thickness of the surface layer 3 and the intermediate layer 4 within the above ranges, the surface layer 3 and the intermediate layer 4 will have a low relative dielectric constant and a layer thickness corresponding to the thickness of the toner layer, and the toner releasability will be further improved. The constituent materials for setting the relative dielectric constants of the surface layer 3 and the intermediate layer 4 within the above ranges will be described later.

[0053] Also, in the transfer belts 1A and 1B, due to the requirement (3), the Martens hardness of the surface S1 on the surface layer 3 side is in the range of 300 to 700 N / mm 2 . By having the Martens hardness of the surface S1 on the surface layer 3 side within the above range, the transfer belts 1A and 1B are excellent in transferability, cleaning property, and durability. The Martens hardness of the surface S1 on the surface layer 3 side is preferably in the range of 500 to 600 N / mm 2 .

[0054] In order to make the martensitic hardness of the surface S1 on the surface layer 3 side fall within the above range, the constituent material of the surface layer 3 is appropriately selected. The constituent material of the surface layer 3 has a relative dielectric constant that satisfies the requirement of (2) and satisfies the requirement of (3), as will be described later.

[0055] Considering the requirement of (2) above, the thickness Tt of the transfer belts 1A and 1B is 15 μm or more, and can be appropriately determined according to the purpose of use and the like. From the viewpoint of satisfying the requirement of (2) above and generally satisfying mechanical properties such as strength and flexibility, 40 to 400 μm is preferable, and a range of 65 to 300 μm is more preferable. Further, in the transfer belt of the present invention, as long as the above (1) to (3) are satisfied, the relative dielectric constant of the transfer belt itself is not particularly limited, but a range of 20 to 100 is preferable, and a range of 40 to 80 is more preferable.

[0056] The relative dielectric constant of each constituent layer, the region L, and the transfer belt itself in the transfer belt is the relative dielectric constant measured by the following method. In addition, the measurement method of the martensitic hardness of the surface S1 on the surface layer 3 side is also shown below.

[0057] <Relative dielectric constant> In the present invention, the relative dielectric constant of each of the above measurement objects refers to the relative dielectric constant at a frequency of 1 MHz measured in an environment of a temperature of 23 ° C and a humidity of 50% RH. The relative dielectric constant can be calculated, for example, by the following method.

[0058] In order to obtain the relative dielectric constant of the transfer belt, first, dielectric constant measurement is performed on the transfer belt. Specifically, thin film electrodes with a resistance of 1 digit Ω are formed on both sides of the transfer belt by sputtering or the like, cut out with a mold of 10 mmφ to prepare a measurement sample, and using an impedance analyzer "Model 12608W" (manufactured by Solartron Analytical), under the conditions of a frequency of 1 MHz, in an environment of a temperature of 23 ° C and a humidity of 50% RH, the dielectric constant (F / m) is measured by the electrode contact method and converted into the relative dielectric constant.

[0059] For example, the dielectric constants of each layer of the base material layer 2 and the surface layer 3 of the transfer belt 1A shown in FIG. 3A are measured in the same manner as above for the dielectric constant of the transfer belt 1A and the dielectric constant of the base material layer 2 remaining after scraping off the surface layer 3 from the transfer belt 1A, and the dielectric constant of the surface layer 3 is calculated from the difference. The obtained dielectric constant is converted into a relative dielectric constant.

[0060] Also, for example, the transfer belt 1B shown in FIG. 3B has a configuration having an intermediate layer 4 between the base material layer 2 and the surface layer 3. In this case, the dielectric constant of each layer is measured in the same manner as above for the dielectric constant of the transfer belt 1B, the dielectric constant of the laminate of the intermediate layer 4 and the base material layer 2 remaining after scraping off the surface layer 3 from the transfer belt 1A, and further the dielectric constant of the base material layer 2 remaining after scraping off the intermediate layer 4 from the laminate, and the dielectric constants of the base material layer 3 and the intermediate layer 4 are calculated. The obtained dielectric constant is converted into a relative dielectric constant.

[0061] Note that the relationship between the dielectric constant, thickness, and layer thickness of the transfer belt and each layer can be expressed by the following formula (I) in the case of a two-layer structure of the base material layer and the surface layer, and can be expressed by the following formula (II) in the case of a three-layer structure of the base material layer, the intermediate layer, and the surface layer.

[0062]

Equation

[0063] The meanings of the symbols in formula (I) and formula (II) are as follows. ε: Dielectric constant of the transfer belt d: Thickness of the transfer belt (in FIGS. 3A and 3B, "Tt") ε1: Dielectric constant of the surface layer ε2: Dielectric constant of the base material layer ε3: Dielectric constant of the intermediate layer d1: Layer thickness of the surface layer (in FIGS. 3A and 3B, "Ts") d2: Layer thickness of the base material layer (in FIGS. 3A and 3B, "Tb") d3: Layer thickness of the intermediate layer (in FIG. 3B, "Tm")

[0064] Also, the dielectric constant of the region (region L) from the surface S1 on the surface layer 3 side to a depth of 15 μm in the above requirement (2) will be described using the transfer belt 1A shown in FIG. 3A. The dielectric constant of the transfer belt 1A and the dielectric constant of the remaining part obtained by shaving off the region (region L) from the surface S1 on the surface layer 3 side to a depth of 15 μm of the transfer belt 1A are measured in the same manner as above, and the dielectric constant of the region L is calculated from the difference. The obtained dielectric constant is converted to a relative dielectric constant.

[0065] <Martens hardness> In the present invention, the Martens hardness (unit: N / mm 2 ) is obtained by the following formula (III) by pushing a indenter into the measurement object while applying a load. Formula (III) Martens hardness = (test load [N]) / (contact surface area between the indenter and the measurement object under the test load [mm 2 )

[0066] The measurement of Martens hardness can be performed using a commercially available hardness measuring device. For example, it can be measured using a ultra-micro hardness tester "H-100V" (manufactured by Fisher Instruments). In this measuring device, a square pyramid-shaped indenter is pushed into the object to be measured while applying a test load, and the surface area in contact with the object to be measured by the indenter is obtained from the indentation depth when a desired depth is reached. The Martens hardness [N / mm 2 is calculated from the above formula (III).

[0067] (Measurement conditions) Measuring machine: Hardness tester indentation tester "H-100V" (manufactured by Fisher Instruments) Measuring indenter: Vickers indenter Measurement environment: Temperature 23 ° C, humidity 50% RH Measurement sample: A transfer belt is cut into a size of 5 cm × 5 cm to prepare a measurement sample. Maximum test load: 1 mN Load condition: The load is applied in proportion to time at a speed of reaching the maximum test load in 10 seconds. Load creep time: 5 seconds In addition, for each sample, the measurement is randomly taken at 10 points, and the average value is taken as the Martens hardness [N / mm 2 .

[0068] Next, the constituent materials of each layer of the transfer belt of the present invention for the transfer belt of the present invention to satisfy the requirements (1) to (3) will be described.

[0069] (Base material layer) The base material layer 2 satisfies the requirement of (1), that is, the relative permittivity is in the range of 20 to 100. As long as the base material layer 2 satisfies the requirement of (1), its constituent material is not particularly limited.

[0070] In the transfer belts 1A and 1B, the base material layer 2 typically has conductivity. The constituent material of the base material layer 2 contains, for example, a resin serving as a matrix in order to be formed into a belt shape, particularly an endless belt, and contains a conductive agent for imparting conductivity. In the case where the relative permittivity of the conductive agent is higher than that of the resin in the constituent material, the conductive agent has a function of adjusting the conductivity of the base material layer 2 and also has a function of adjusting the relative permittivity. When imparting conductivity to the base material layer 2 using a conductive agent, the volume resistivity of the transfer belts 1A and 1B at an applied voltage of 100 V is 1.0×10 5 ~9.0×10 9 Ω·cm, it is preferable to adjust the conductivity of the base material layer 2.

[0071] In the above, as long as the required conductivity and the requirement of the relative permittivity of (1) are satisfied, the base material layer 2 may be composed of only a resin and a conductive agent. However, in order to impart a high relative permittivity as in (1) to the base material layer 2, it is preferable that the base material layer 2 contains a ferroelectric material having a relative permittivity of 100 or more, preferably 500 or more, in addition to the resin and the conductive agent. Note that a ferroelectric material usually does not have conductivity. In this specification, the relative permittivity refers to the relative permittivity at a frequency of 1 MHz in an environment of a temperature of 23°C and a humidity of 50%RH.

[0072] The base material layer 2 may contain components other than resin, conductive agent, and ferroelectric, as long as the requirement of (1) is satisfied. Examples of other components include inorganic fillers other than conductive agents and ferroelectrics, leveling agents such as silicone oil, and the like.

[0073] <Resin> Examples of the resin used for the base material layer 2 include polyimide resin, polyamide resin, polyamideimide resin, polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride resin, acetate resin, ABS resin, polyester resin, polyamide resin, polyphenylene sulfide resin, polyetheretherketone resin, and the like. These resins may be used alone or in combination of two or more.

[0074] Among these, super engineering plastics having strength and durability such as polyimide resin, polyamideimide resin, polyphenylene sulfide resin, and polyetheretherketone resin are preferable, and polyimide resin and polyamideimide resin are more preferable. Among them, polyimide resin is more preferable because it is excellent in characteristics such as heat resistance, flex resistance, flexibility, and dimensional stability. The polyimide resin (hereinafter, also simply referred to as "polyimide") can be obtained, for example, by synthesizing a polyamic acid (polyimide precursor) from an acid anhydride and a diamine compound, and imidizing the polyamic acid by heat or a catalyst.

[0075] The acid anhydride used for the synthesis of polyimide is not particularly limited. Examples thereof include aromatic tetracarboxylic acid dianhydrides such as biphenyltetracarboxylic acid dianhydride, terphenyltetracarboxylic acid dianhydride, benzophenonetetracarboxylic acid dianhydride, pyromellitic dianhydride, oxydiphthalic acid dianhydride, diphenylsulfonetetracarboxylic acid dianhydride, hexafluoroisopropylidenediphthalic acid dianhydride, and cyclobutanetetracarboxylic acid dianhydride.

[0076] In addition, the diamine compound used for synthesizing the polyimide is not particularly limited. For example, aromatic diamines such as p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,7-diamino-dimethyldibenzothiophene-5,5'-dioxide, 4,4'-diaminobenzophenone, 4,4'-bis(4-aminophenyl)sulfide, 4,4'-diaminobenzanilide, 1,4-bis(4-aminophenoxy)benzene, etc. can be mentioned.

[0077] When producing the base material layer containing polyimide, for example, polyimide varnish mainly composed of polyamic acid which is a polyimide precursor can be used. As commercially available products of polyimide varnish, for example, Upia (registered trademark)-AT (U-varnish-A) and Upia (registered trademark)-ST (U-varnish-S), both manufactured by Ube Industries, Ltd., can be mentioned.

[0078] The polyamide-imide resin (hereinafter, also simply referred to as "polyamide-imide") is a resin having a rigid imide group and an amide group that imparts flexibility in the molecular skeleton, and a polyamide-imide having a generally known structure can be used as the polyamide-imide used in the present invention.

[0079] Generally, as a method for synthesizing a polyamide-imide resin, there are an acid chloride method (a): a known method of producing by reacting a derivative halide of a trivalent carboxylic acid having an acid anhydride group, most typically a chloride compound of the derivative, with a diamine in a solvent (see, for example, Japanese Patent Publication No. 42-15637). Or as another method, an isocyanate method (b): a known method of producing by reacting a trivalent derivative containing an acid anhydride group and a carboxylic acid with an aromatic isocyanate in a solvent (for example, Japanese Patent Publication No. 44-19274), etc. are known, and any of them can be used.

[0080] For example, it is produced by polycondensing trimellitic acid with an aromatic diamine or diisocyanate by a known method. In this case, the same aromatic diamine as the raw material of polyimide can be used. Examples of the diisocyanate include compounds in which the amino group in the above diamine component is substituted with an isocyanate group.

[0081] When producing the base material layer containing polyamideimide, for example, a polyimide varnish mainly composed of a polyamideimide precursor can be used. As commercially available products of polyamideimide varnish, for example, HR-16NN (manufactured by Toyobo Co., Ltd.) etc. can be used.

[0082] The resin according to the present invention is preferably contained in the range of 50 to 95% by volume with respect to the entire base material layer 2. When it is 50% by volume or more, it can have the required mechanical strength. When it is 95% by volume or less, a space for containing a ferroelectric or a conductive agent can be secured.

[0083] <Conductive agent> The conductive agent used for the base material layer 2 is not particularly limited as long as it is a substance having conductivity. Specifically, known electronic conductive substances and ionic conductive substances can be used, and it is preferably carbon black, carbon nanotube, graphite or graphene, and it is more preferable to be carbon black or carbon nanotube in terms of being able to impart conductivity to the base material layer and ease of handling.

[0084] The addition amount of the conductive agent used in the present invention is preferably contained in the range of 0.1 to 20% by volume with respect to the entire base material layer 2. When it is 0.1% by volume or more, it is easy to suppress the occurrence of toner contamination on the surface S1 on the surface layer 3 side of the transfer belts 1A and 1B. When it is 20% by volume or less, a decrease in the strength of the base material layer 2 and the charge amount of the toner is hardly recognized. The addition amount of the conductive agent is more preferably in the range of 0.5 to 15% by volume, and even more preferably in the range of 1 to 10% by volume.

[0085] Among the conductive agents, examples of carbon black include gas black, acetylene black, oil furnace black, thermal black, channel black, ketjen black, and the like. Effective ones for obtaining a desired conductivity with a smaller amount of mixing include ketjen black, acetylene black, and oil furnace black. Note that ketjen black is a contact furnace type carbon black.

[0086] The average primary particle size of the carbon black is preferably in the range of 10 to 50 nm. The average primary particle size can be measured by the method of FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.) using the photon counting method.

[0087] As the carbon black, commercially available products can be used. Examples of commercially available products include carbon black "MA8", "MA11" (both manufactured by Mitsubishi Chemical Corporation), and the like.

[0088] Carbon nanotube (hereinafter abbreviated as CNT) is a single-layer or multi-layer tubular substance without defects having a structure in which a graphite hexagonal network plane is rolled into a cylindrical shape. The average tube diameter of the CNT is preferably in the range of 10 to 150 nm, and the length of the CNT is preferably in the range of 5 to 12 μm. By setting the diameter and length of the CNT within the above ranges, appropriate conductivity can be imparted to the base material layer.

[0089] This CNT may have a functional group covalently bonded thereto as necessary. For example, by subjecting the CNT to strong acid treatment, oxidized CNT with carboxylic acid introduced on the surface is generated. After reacting the oxidized CNT with thionyl chloride and then reacting it with an alkyl alcohol or the like, a chemically decorated CNT that can be dissolved in an organic solvent can be generated. By using such a chemically decorated CNT, the CNT can be uniformly dispersed in the resin. Further, by applying an electric field from the outside in a state where the CNT is dispersed in the resin, the CNT can be oriented in a desired direction, and the relative permittivity of the base material layer can be improved.

[0090] The above average pipe system and the above length can be obtained from a scanning electron microscope (SEM) photograph of the cross-section of the transfer belt, and can be adjusted by cutting (grinding) CNTs or mixing two or more types of CNTs.

[0091] <Ferroelectric> As the ferroelectric used for the base material layer 2, the relative dielectric constant is 20 or more, preferably 100 or more, more preferably 500 or more, and even more preferably 1000 or more. Thereby, it becomes easy to impart a high relative dielectric constant (20 to 100) satisfying the requirement (1) to the base material layer 2.

[0092] The addition amount of the ferroelectric used in the present invention is an amount that can make the relative dielectric constant of the base material layer 2 satisfy the requirement (1), and depends on the type of ferroelectric used. For example, it is preferably contained in the range of 5 to 40% by volume, more preferably in the range of 10 to 30% by volume, and even more preferably in the range of 10 to 20% by volume with respect to the entire base material layer 2.

[0093] As the ferroelectric, ferroelectric ceramics are preferable, and examples include barium titanate (relative dielectric constant: 1200), calcium titanate (relative dielectric constant: 140), strontium titanate (relative dielectric constant: 200), magnesium titanate (relative dielectric constant: 20), and the like.

[0094] Among these, as the ferroelectric according to the present invention, it is preferable to contain at least one compound of barium titanate, calcium titanate, or strontium titanate from the viewpoints of controlling the dielectric constant and durability.

[0095] The form of the ferroelectric is preferably particles. The average primary particle size of the ferroelectric particles according to the present invention is preferably 300 nm or less from the viewpoint of dispersibility. The lower limit value of the average primary particle size is 30 nm, more preferably 50 nm, and the optimal range is within the range of 90 to 110 nm.

[0096] The average primary particle size of the ferroelectric particles can be measured, for example, by analyzing an image obtained using a transmission electron microscope (TEM) (manufactured by Hitachi High-Technologies Corporation). For example, among the particles present in the image, 200 or more particles may be randomly selected, their particle sizes may be measured, and the average value thereof may be determined. Further, when the shape of the particles is not spherical, the average value of the major axis and the minor axis can be calculated as the diameter of each particle.

[0097] As the ferroelectric particles, commercially available products can be used. Examples of commercially available products include barium titanate particles “BT05” (manufactured by Sakai Chemical Industry Co., Ltd.).

[0098] The physical properties of the base material layer 2, such as the relative permittivity and the layer thickness, are as described above.

[0099] (Surface layer) The surface layer 3 preferably has a layer thickness and a relative permittivity as described above so that the transfer belts 1A and 1B satisfy the requirement (2). Further, the surface layer 3 is configured so that the transfer belts 1A and 1B satisfy the requirement (3), that is, the Martens hardness on the surface S1 on the surface layer 3 side is in the range of 300 to 700 N / mm 2 Here, the surface S1 on the surface layer 3 side in the transfer belts 1A and 1B indicates the main surface on the side opposite to the base material layer 2 among the main surfaces of the surface layer 3. Hereinafter, the surface S1 on the surface layer 3 side is also referred to as “the surface S1 of the surface layer 3”.

[0100] The constituent material of the surface layer 3 contains, for example, a film-forming component for maintaining the form of the layer as an essential component, and optionally contains a relative permittivity adjuster. As the film-forming component, a material such that the Martens hardness of the surface S1 of the surface layer 3 is within the above range is appropriately selected. As the film-forming component, for example, a material whose surface Martens hardness is close to the range of 300 to 700 N / mm 2 when formed into a film alone is preferable. Typically, such a film-forming component becomes the main component of the constituent material of the surface layer 3. The surface layer 3 may contain a relative permittivity adjuster having a relative permittivity different from that of the above film-forming component in the constituent material in order to obtain a relative permittivity such that the transfer belts 1A and 1B can satisfy the requirement (2).

[0101] In order for the transfer belts 1A and 1B to satisfy the requirement of (2), when the relative permittivity set for the surface layer 3 is smaller than the relative permittivity of the film-forming component, a material having a relative permittivity smaller than that of the film-forming component is selected as the relative permittivity adjuster. Similarly, when the relative permittivity set for the surface layer 3 is larger than the relative permittivity of the film-forming component, a material having a relative permittivity larger than that of the film-forming component is selected as the relative permittivity adjuster. Note that when the relative permittivity set for the surface layer 3 is the same as the relative permittivity of the film-forming component, it is not necessary to use a relative permittivity adjuster.

[0102] Examples of the film-forming component of the surface layer 3 include organic materials, inorganic materials, and organic-inorganic composite materials whose surface martensitic hardness is close to the above range. The organic material is typically a resin, and examples of the inorganic material and the organic-inorganic composite material include cured products obtained by curing a sol-gel material.

[0103] Examples of the above resin include acrylic resin, polyimide resin, polyamideimide resin, polyphenylene sulfide resin, polyetheretherketone resin, etc. Super engineering plastics having strength and durability such as polyimide resin, polyamideimide resin, polyphenylene sulfide resin, and polyetheretherketone resin are preferable. Among these, polyimide resin and polyamideimide resin are more preferable. Among them, polyimide resin is more preferable because of its excellent properties such as heat resistance, flexural resistance, flexibility, and dimensional stability. As the polyimide resin, the same polyimide resin as described for the base material layer 2 can be used.

[0104] Examples of the sol-gel material serving as a raw material for the inorganic material and the organic-inorganic composite material include metal salts, metal alkoxides, etc. In the present invention, alkoxysilane is preferable for the reason of improving transferability.

[0105] From the viewpoint of obtaining higher martensitic hardness, it is preferable that the alkoxysilane contains a tetrafunctional alkoxysilane (also referred to as "tetraalkoxysilane") or a trifunctional alkoxysilane (also referred to as "trialkoxysilane"). Further, from the viewpoint of making it difficult to generate shrinkage during curing and reducing the occurrence of warping at the ends of the transfer belt, the alkoxysilane may further contain a bifunctional alkoxysilane (also referred to as "dialkoxysilane") or a monofunctional alkoxysilane (also referred to as "monoalkoxysilane").

[0106] When the alkoxysilane contains a tetraalkoxysilane or a trialkoxysilane and a dialkoxysilane or a monoalkoxysilane, it is preferable to contain the tetraalkoxysilane or the trialkoxysilane in the range of 80 to 90% by mass and the monoalkoxysilane or the dialkoxysilane in the range of 10 to 20% by mass with respect to the total alkoxysilane.

[0107] Examples of the alkoxy group in the alkoxysilane include alkoxy groups derived from aliphatic alcohols such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, and alkoxy groups derived from aromatic alcohols such as phenoxy group.

[0108] In addition, examples of the monovalent organic group other than the alkoxy group bonded to the silicon atom in the monofunctional alkoxysilane, bifunctional alkoxysilane, and trifunctional alkoxysilane include aliphatic hydrocarbon groups having 1 to 18 carbon atoms.

[0109] Examples of the alkoxysilane include, as the monofunctional alkoxysilane, trimethylmethoxysilane, triethylmethoxysilane, trimethylethoxysilane, triethylethoxysilane, and the like.

[0110] Examples of the bifunctional alkoxysilane include dimethyldimethoxysilane, diethyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, and the like.

[0111] Examples of the trifunctional alkoxysilane include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isopropyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, n-dodecyltrimethoxysilane, n-tetradecyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane, isopropyltriethoxysilane, n-butyltriethoxysilane, isobutyltriethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, n-decyltriethoxysilane, n-dodecyltriethoxysilane, n-tetradecyltriethoxysilane, n-hexadecyltriethoxysilane, and n-octadecyltriethoxysilane, and the like.

[0112] Examples of the tetrafunctional alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-isopropoxysilane, tetraphenoxysilane, and the like.

[0113] The relative permittivity of the film-forming components exemplified above is, for example, about 3 to 10 in the case of a polyimide resin and about 2 to 5 in the case of a cured product of an alkoxysilane. The constituent material of the surface layer 3 contains a relative permittivity adjuster as appropriate according to the type of the film-forming component based on the set value of the relative permittivity of the surface layer 3.

[0114] As the relative permittivity adjuster, for example, the ferroelectric material and the conductive agent described in the section of the base material layer 2 can be used. Examples of the ferroelectric material include barium titanate, and examples of the conductive agent include carbon black.

[0115] The ratio of the relative permittivity adjuster to the film-forming component in the constituent material of the surface layer 3 is such that the Martens hardness on the surface S1 of the obtained surface layer 3 is 300 to 700 N / mm 2 and the relative permittivity of the surface layer 3 is set within a range where it becomes a predetermined value. Note that the constituent material of the surface layer 3 may contain other components other than the film-forming component and the relative permittivity adjuster, as long as the obtained surface layer 3 does not impair the characteristics of the Martens hardness and the relative permittivity. Examples of the other components include the same components as the other components in the constituent material of the base material layer 2.

[0116] When the surface layer 3 contains a cured product of a sol-gel material as a film-forming component and components such as a relative permittivity adjuster, the surface layer 3 is typically a layer obtained by curing a composition containing the sol-gel material and components such as the relative permittivity adjuster. In this specification, the "cured product of a composition" refers to a cured product obtained by curing the entire composition when the composition contains a curable component and the curable component cures.

[0117] Here, regarding the surface layer for satisfying the requirements (2) and (3) related to the transfer belt of the present invention, in the case of a two-layer structure composed of a base material layer and a surface layer such as the transfer belt 1A, and in the case of a three-layer structure composed of a base material layer, an intermediate layer, and a surface layer such as the transfer belt 1B, preferred embodiments will be described below. In the case of a three-layer structure, the configuration for satisfying the requirement (2) needs to be considered in pairs of the intermediate layer and the surface layer. Therefore, in the case of a three-layer structure, the surface layer and the intermediate layer are described in pairs.

[0118] <Surface layer in the case of a two-layer structure> Taking the transfer belt 1A as an example, in the case of a two-layer structure, the hardness on the surface S1 on the surface layer 3 side satisfies the requirement (3), that is, the Martens hardness is 300 to 700 N / mm 2It satisfies the requirement of being within the range. Also, as described above, in order for the transfer belt 1A to satisfy the requirement of (2), the surface layer 3 preferably has a layer thickness Ts of 5 μm or more, more preferably in the range of 5 to 20 μm, and even more preferably in the range of 10 to 20 μm. Further, the relative permittivity of the surface layer 3 is 10 or less, preferably in the range of 2 to 10, and more preferably 2 to 5.

[0119] Taking these into consideration, the constituent material of the surface layer 3 in the transfer belt 1A is preferably selected from super engineering plastics having strength and durability such as polyimide resin, polyamideimide resin, polyphenylene sulfide resin, polyetheretherketone resin, etc. as the film-forming component, and more preferably polyimide resin. When using polyimide resin, the surface layer 3 can be composed of only polyimide resin. When using polyimide resin, the surface layer 3 may contain a relative permittivity adjuster. For example, depending on the set value of the relative permittivity, carbon black can be contained in the surface layer 3 as a whole in the range of 1 to 15% by volume. Also, when the relative permittivity of the surface layer 3 is set higher than the relative permittivity of the polyimide resin, barium titanate may be used as the relative permittivity adjuster.

[0120] When the film-forming component of the surface layer 3 in the transfer belt 1A is polyimide resin, the martensitic hardness on the surface S1 is 300 to 400 N / mm 2 , the relative permittivity is 3 to 10, and the layer thickness Ts is 10 to 20 μm, which is a preferred embodiment.

[0121] <Surface layer and intermediate layer in the case of a three-layer structure> Taking the transfer belt 1B as an example, in the case of a three-layer structure, the hardness on the surface S1 on the surface layer 3 side satisfies the requirement of (3), that is, the martensitic hardness is in the range of 300 to 700 N / mm 2 In order for the transfer belt 1B to satisfy the requirement of (2), for example, the combination of the relative permittivity and layer thickness of the surface layer 3 and the intermediate layer 4 is appropriately selected.

[0122] Specifically, as described above, the total layer thickness of the surface layer 3 and the intermediate layer 4 is preferably in the range of 10 to 20 μm, more preferably in the range of 15 to 20 μm. Also, the relative permittivity of the surface layer 3 is preferably in the range of 2 to 10, more preferably 2 to 5. The relative permittivity of the intermediate layer 4 is preferably in the range of 5 to 20, more preferably 5 to 10. Further, the layer thickness Ts of the surface layer 3 is preferably in the range of 1 to 15 μm, more preferably in the range of 1 to 10 μm. The layer thickness Tm of the intermediate layer 4 is preferably in the range of 5 to 15 μm, more preferably in the range of 10 to 15 μm.

[0123] The constituent material of the surface layer 3 in the transfer belt 1B may be any cured product obtained by curing the resin and the sol-gel material described above as the film-forming component. As the resin, a polyimide resin, a polyamide-imide resin, a polyphenylene sulfide resin, a polyether ether ketone resin, etc. are preferable, and a polyimide resin is more preferable. These resins may be used alone or in combination of two or more. From the viewpoint of being able to achieve a high range within 300 to 700 N / mm of the Martens hardness 2 the film-forming component is preferably a cured product obtained by curing the sol-gel material, and more preferably a cured product of alkoxysilane.

[0124] In the constituent material of the surface layer 3 in the transfer belt 1B, when the film-forming component is a polyimide resin, the surface layer 3 may be composed of only the polyimide resin, and further, a relative permittivity adjuster may be contained. When the constituent material of the surface layer 3 containing a polyimide resin as the film-forming component contains a relative permittivity adjuster, for example, depending on the set value of the relative permittivity, carbon black can be contained in the range of 1 to 15% by volume with respect to the entire surface layer 3. Also, when the relative permittivity of the surface layer 3 is set higher than the relative permittivity of the polyimide resin, for example, barium titanate may be used as the relative permittivity adjuster in the range of 1 to 15% by volume with respect to the entire surface layer 3.

[0125] When the film-forming component of the surface layer 3 in the transfer belt 1B is a polyimide resin, the Martens hardness at the surface S1 is 300 to 400 N / mm2 、A mode where the relative dielectric constant is 6 to 8 and the layer thickness Ts is 1 to 10 μm is preferable.

[0126] In the constituent material of the surface layer 3 in the transfer belt 1B, when the film-forming component is a cured product of alkoxysilane, the surface layer 3 may be composed only of the cured product of alkoxysilane, and further, a relative dielectric constant adjuster may be contained. When the constituent material of the surface layer 3 containing a cured product of alkoxysilane as the film-forming component contains a relative dielectric constant adjuster, for example, depending on the set value of the relative dielectric constant, barium titanate can be contained in the range of 1 to 15% by volume with respect to the entire surface layer 3. Similarly, carbon black can be contained in the range of 1 to 15% by volume with respect to the entire surface layer 3.

[0127] When the film-forming component of the surface layer 3 in the transfer belt 1B is a cured product of alkoxysilane, the Martens hardness on the surface S1 is 400 to 700 N / mm 2 、A mode where the relative dielectric constant is 2 to 6 and the layer thickness Ts is 1 to 5 μm is preferable.

[0128] The intermediate layer 4 in the transfer belt 1B preferably has a layer thickness and a relative dielectric constant as described above in order for the transfer belt 1B to satisfy the requirement of (2). The constituent material of the intermediate layer 4, similar to the constituent material of the surface layer 3, contains, for example, a film-forming component for maintaining the form of the layer as an essential component, and optionally contains a relative dielectric constant adjuster.

[0129] Examples of the film-forming component of the intermediate layer 4 include the same resins as those used for the base material layer 2, and polyimide resins, polyamideimide resins, polyphenylene sulfide resins, polyetheretherketone resins, etc. are preferable, and polyimide resins are more preferable. These resins may be used alone or in combination of two or more.

[0130] In the intermediate layer 4, in order to obtain the above-mentioned preferable relative permittivity, the constituent material of the intermediate layer 4 may contain a relative permittivity adjusting agent. For example, in the constituent material of the intermediate layer 4 in the transfer belt 1B, when the film-forming component is a polyimide resin, in order to obtain the above-mentioned preferable relative permittivity, the intermediate layer 4 may be composed of only the polyimide resin, and further, it may contain a relative permittivity adjusting agent.

[0131] When the constituent material of the intermediate layer 4 containing a polyimide resin as a film-forming component contains a relative permittivity adjusting agent, for example, depending on the set value of the relative permittivity, carbon black can be contained in the range of 1 to 15% by volume with respect to the entire intermediate layer 4. Further, when the relative permittivity of the intermediate layer 4 is set higher than the relative permittivity of the polyimide resin, for example, barium titanate can be used as the relative permittivity adjusting agent in the range of 1 to 40% by volume with respect to the entire intermediate layer 4.

[0132] Regarding the physical properties such as the relative permittivity and layer thickness of the intermediate layer 4, it is as described above.

[0133] [Manufacturing method of transfer belt] As the manufacturing method of the transfer belt of the present invention, a known method for manufacturing a transfer belt can be applied. For example, when making an endless transfer belt, a cylindrical mold can be used as the molding mold, and each layer can be sequentially formed on the outer peripheral surface or the inner peripheral surface of the mold and then removed from the mold. The film formation is preferably performed by a wet method. That is, first, a coating liquid for forming each layer constituting the transfer belt is prepared, and using the coating liquid, each layer is formed on the outer peripheral surface or the inner peripheral surface of the mold in a predetermined order by coating, drying, and curing.

[0134] Hereinafter, the manufacturing method of the transfer belt of the present invention will be described by taking the three-layer structure transfer belt 1B laminated in the order of the base material layer 2, the intermediate layer 4, and the surface layer 3 as an example. Note that the following manufacturing method is an example, and any method capable of manufacturing a transfer belt can be used.

[0135] (Preparation of coating liquid) As coating liquids, a coating liquid for forming a base material layer, a coating liquid for forming an intermediate layer, and a coating liquid for forming a surface layer, which respectively correspond to the base material layer 2, the intermediate layer 4, and the surface layer 3, are prepared. When the film-forming components of the base material layer 2, the intermediate layer 4, and the surface layer 3 are resins, the coating liquid may contain the resin itself, or may contain a varnish or the like having a resin precursor as a main component, such as a polyimide varnish.

[0136] The coating liquid for forming a base material layer contains a conductive agent in addition to the resin or resin precursor, and optionally contains ferroelectric particles. The content of each component is adjusted, for example, so as to be the above content in the obtained base material layer. The coating liquid for forming a base material layer contains, in addition to the solid content constituting the base material layer, a volatile component that is usually volatilized and removed during drying and curing. Examples of the volatile component include a solvent and the like. The viscosity of the coating liquid for forming a base material layer is set according to the thickness of the coating film, the coating method, the coating conditions, the solution temperature, and the like. The adjustment of the viscosity is performed, for example, by adjusting the type or content of the solvent.

[0137] In addition, in order to make the dispersion state of the conductive agent and the ferroelectric particles in the coating liquid for forming a base material layer good, these components may be prepared in advance as a dispersion liquid dispersed in a dispersion medium, and this may be used in the preparation of the coating liquid for forming a base material layer. The dispersion liquid may contain a dispersant to such an extent that it does not affect the relative dielectric constant and mechanical properties of the base material layer. The dispersion medium is preferably the same as the solvent in the coating liquid for forming a base material layer.

[0138] Regarding the coating liquid for forming an intermediate layer and the coating liquid for forming a surface layer when the film-forming components of the intermediate layer 4 and the surface layer 3 are resins, they can be prepared in the same manner as the coating liquid for forming a base material layer. When a conductive agent or ferroelectric particles are used as the relative dielectric constant adjuster, it is preferable to prepare the coating liquid for forming each layer using a dispersion liquid in the same manner as above. The content of each component is adjusted, for example, so as to be the above content in the obtained intermediate layer and surface layer.

[0139] When the film-forming component of the surface layer 3 is a cured product of a sol-gel material, for example, an alkoxysilane, the coating liquid for forming the surface layer contains alkoxysilane and each component contained in the surface layer as a solid content, and further contains a solvent or the like as a volatile component. The solvent to be used is not particularly limited as long as it can uniformly disperse and dissolve alkoxysilane and organic components. For example, in addition to various alcohols such as methanol and ethanol, acetone, toluene, xylene, etc. can be mentioned. The hydrolysis of alkoxysilane described later can be carried out by moisture in the atmosphere, but the coating liquid for forming the surface layer may contain water for the hydrolysis of alkoxysilane as necessary.

[0140] When containing a relative permittivity adjuster such as a conductive agent and ferroelectric particles in addition to alkoxysilane, it is preferable to prepare the coating liquid for forming the surface layer using a dispersion liquid in the same manner as above.

[0141] After hydrolysis, alkoxysilane forms a cured product by undergoing a dehydration condensation reaction. In order to promote the hydrolysis reaction of alkoxysilane, the coating liquid for forming the surface layer may appropriately contain a catalyst such as hydrochloric acid, phosphoric acid, acetic acid, etc. In addition, the coating liquid for forming the surface layer can also contain alkoxysilane as a hydrolyzate. By using a hydrolyzate, the dehydration condensation reaction may gradually proceed. In addition, the viscosity of the coating liquid for forming the surface layer for smooth coating is preferably in the range of 10 to 100 cP. The degree of hydrolysis when using a hydrolyzate is preferably such that the viscosity of the coating liquid for forming the surface layer can maintain the above range.

[0142] (Formation of each layer) Next, each layer is sequentially formed (film-formed) on the outer peripheral surface or the inner peripheral surface of the cylindrical mold. The following is an example of film-forming using the outer peripheral surface of the mold. When all the film-forming components of each layer are resins, particularly polyimide resins, the order of film-forming each layer on the outer peripheral surface of the mold is the order of the base material layer 2, the intermediate layer 4, and the surface layer 3 or the order of the surface layer 3, the intermediate layer 4, and the base material layer 2. When film-forming is performed in the order of the surface layer 3, the intermediate layer 4, and the base material layer 2, after removing from the mold, the inner peripheral surface and the outer peripheral surface of the obtained laminate are inverted.

[0143] When the film-forming component of the surface layer 3 is a cured product of a sol-gel material such as alkoxysilane, for example, a method of forming films in the order of the base material layer 2, the intermediate layer 4, and the surface layer 3 on the outer peripheral surface of the mold, or forming a laminate in the order of the intermediate layer 4 and the base material layer 2 on the outer peripheral surface of the mold, removing it from the mold, and then inverting the inner peripheral surface and the outer peripheral surface of the obtained laminate, inserting the mold into the laminate, and forming the surface layer 3 on the outer peripheral surface of the laminate, that is, the outer peripheral surface of the intermediate layer 4, can be mentioned.

[0144] Hereinafter, first, an example in which the film-forming components of all layers are resins and films are formed in the order of the surface layer 3, the intermediate layer 4, and the base material layer 2 will be described. When the film-forming components of all layers are resins and films are formed in the order of the base material layer 2, the intermediate layer 4, and the surface layer 3, it is the same except that the order of layer formation is changed.

[0145] The application of the coating liquid for forming the surface layer to the outer peripheral surface of the cylindrical mold can be performed, for example, by the apparatus shown in FIG. 4. FIG. 4 shows an example of a coating apparatus used when producing the transfer belt of the present invention. As shown in FIG. 4, the coating apparatus 1b includes a coating means 2b having a nozzle (for example, a dispenser nozzle) and a metal cylindrical mold 5b.

[0146] The coating means 2b atomizes and sprays the coating liquid 3b for forming the surface layer onto the outer peripheral surface of the cylindrical mold 5b to form a coating film 4b on the cylindrical mold 5b. Specifically, the cylindrical mold 5b is rotated at a desired speed in the direction of arrow 7b, and while moving the coating means 2b in the direction of arrow 6b, a uniform coating film 4b is formed while casting the coating liquid 3b for forming the surface layer from the nozzle. The thickness of the coating film 4b is adjusted so that the thickness of the surface layer obtained after drying and curing becomes a predetermined thickness.

[0147] The rotation speed of the cylindrical mold 5b can be appropriately set according to the viscosity of the coating liquid 3b for forming the surface layer, the size of the cylindrical mold 5b, etc. For example, about 30 to 100 rpm is suitable.

[0148] Next, the coating film made of the coating liquid for forming the surface layer formed on the outer peripheral surface dries and cures to form the surface layer 3. The drying of the coating film is a process of removing volatile components such as solvents in the coating liquid for forming the surface layer. When the coating liquid for forming the surface layer contains the resin itself, curing is performed by drying. When the coating liquid for forming the surface layer contains a resin precursor, curing is a process of causing the resin precursor in the coating liquid for forming the surface layer to undergo a curing reaction to form a resin. The curing reaction of the resin precursor is, for example, imidization of a polyimide precursor or polyamide-imide formation of a polyamide-imide precursor.

[0149] Drying is preferably performed by heating, and curing is performed by heating to the reaction temperature. When both drying and curing are performed by heating, it may be performed by a one-step heat treatment or a multi-step heating method. By using the multi-step heating method, it is possible to prevent the generation of minute voids in the seamless belt caused by the evaporation of the ring-closed water and the solvent generated during the curing reaction.

[0150] The heating in the first stage is low-temperature heating. For example, it is heated at a low temperature of about 50 to 150 °C to remove the solvent. The heating time is appropriately set according to the type, content, and heating temperature of the volatile components such as solvents in the coating liquid for forming the surface layer, but is generally preferably about 30 to 90 minutes. Note that the low-temperature heating is preferably performed until the state of the film after the low-temperature heating can be supported by the film itself, that is, until it has self-supportability. Further, the low-temperature heating is preferably performed while rotating the cylindrical mold around its axis, and the rotation speed is preferably about 30 to 100 rpm, for example. Furthermore, in this step, it is preferable to efficiently circulate and remove the vapor (volatile solvents, etc.) in the atmosphere.

[0151] The heating for curing performed after the low-temperature heating is high-temperature heating, and depending on the temperature of the curing reaction of the resin precursor, for example, the heating temperature can be a high temperature of about 250 to 450 °C. The heating time is appropriately set according to the type of the resin precursor, the thickness of the surface layer, and the heating temperature, etc., but is generally preferably about 30 to 120 minutes. Note that during the heat treatment, in both cases of low-temperature heating and high-temperature heating, it is preferable to raise the temperature step by step.

[0152] Next, an intermediate layer forming coating liquid is applied to the outer peripheral surface of the surface layer 3 formed on the outer peripheral surface of the mold, dried, and cured to form an intermediate layer 4. The application, drying, and curing of the intermediate layer forming coating liquid can be performed in the same manner as forming the surface layer 3 using the above-described surface layer forming coating liquid. Further, a base material layer forming coating liquid is applied to the outer peripheral surface of the intermediate layer 4, on which the surface layer 3 and the intermediate layer 4 are laminated in this order on the outer peripheral surface of the mold, dried, and cured to form a base material layer 2. The application, drying, and curing of the base material layer forming coating liquid can be performed in the same manner as forming the surface layer 3 using the above-described surface layer forming coating liquid.

[0153] In the production of the transfer belt 1B, by omitting the formation (film formation) of the intermediate layer 3, a two-layer transfer belt 1A laminated in the order of the base material layer 2 and the surface layer 3 can be produced.

[0154] Next, the case where the film-forming component of the surface layer 3 is a cured product of a sol-gel material such as alkoxysilane will be described. When forming films on the outer peripheral surface of the mold in the order of the base material layer 2, the intermediate layer 4, and the surface layer 3, the film formation of the base material layer 2 and the intermediate layer 4 can be performed in the same manner as when the film-forming components of the above layers are all resins. Also, in the method of forming a laminate in the order of the intermediate layer 4 and the base material layer 2, removing the laminate from the mold, inverting the inner peripheral surface and the outer peripheral surface of the obtained laminate, and then fitting the mold into the laminate to form a surface layer 3 on the outer peripheral surface of the intermediate layer 4, the method of forming a laminate in the order of the intermediate layer 4 and the base material layer 2 can also be performed in the same manner as when the film-forming components of the above layers are all resins.

[0155] To form a surface layer 3, the film-forming component of which is a cured product of a sol-gel material, for example, alkoxysilane, on the outer peripheral surface of a laminate laminated in the order of the base material layer 2 and the intermediate layer 4 on the outer peripheral surface of the mold, that is, on the outer peripheral surface of the intermediate layer 4, a coating liquid containing the above alkoxysilane or its hydrolyzate is used as the surface layer forming coating liquid for forming the surface layer 3.

[0156] Specifically, a coating solution for forming a surface layer is applied to form a coating film, and the alkoxysilane in the coating film is hydrolyzed and subjected to a dehydration condensation reaction to be cured, whereby the surface layer 3 can be formed.

[0157] As for the method of applying the coating solution for forming the surface layer to the outer peripheral surface of the intermediate layer 4, for example, spray coating is preferable. The coating film of the coating solution for forming the surface layer is then subjected to a drying and curing treatment to become the surface layer 3. The drying of the coating film is a step of removing volatile components such as a solvent in the coating solution for forming the surface layer. The curing treatment is a step of curing the alkoxysilane by a hydrolysis and dehydration condensation reaction.

[0158] The drying of the coating film of the coating solution for forming the surface layer may be performed by natural drying, but typically, it is performed by heat treatment. Here, the heat treatment for drying also promotes the curing by the hydrolysis and dehydration condensation reaction. Therefore, drying and curing can be performed by a single-stage heat treatment. The conditions of the heat treatment are not particularly limited as long as the surface layer 3 having a hardness within a predetermined range can be formed, and for example, they can be set in the range of 60 to 450°C and 20 seconds to 7 hours. The coating step may be performed not only once but also a plurality of times according to the layer thickness of the surface layer 3. That is, the surface layer 3 may be composed of one coat or may be composed of a plurality of coats.

[0159] ≪Use≫ The transfer belt of the present invention is preferably used as an intermediate transfer belt for developing a latent image formed on an image carrier (photoconductor) with toner and transferring the obtained toner image to a transfer material in an electrophotographic image forming apparatus. Further, when transferring the toner image on the intermediate transfer belt to a transfer material such as paper (secondary transfer), it is also preferable to use it as a secondary transfer belt (paper conveyance belt) on which the transfer material is placed.

[0160] [Electrophotographic Image Forming Apparatus] The transfer belt of the present invention described above can be suitably used as an intermediate transfer belt or a secondary transfer belt in various known electrophotographic image forming apparatuses such as monochrome image forming apparatuses and full-color image forming apparatuses.

[0161] FIG. 3 is a cross-sectional view showing an example of the configuration of an image forming apparatus including the transfer belt of the present invention as an intermediate transfer belt.

[0162] This image forming apparatus includes a plurality of sets of image forming units 20Y, 20M, 20C, 20Bk, an intermediate transfer unit 10 that transfers the toner images formed in these image forming units 20Y, 20M, 20C, 20Bk onto a transfer material P, and a fixing device 30 that performs a fixing process of applying pressure while heating the transfer material P to fix the toner image and obtain a toner layer.

[0163] In the image forming unit 20Y, a yellow toner image is formed. In the image forming unit 20M, a magenta toner image is formed. In the image forming unit 20C, a cyan toner image is formed. In the image forming unit 20Bk, a black toner image is formed.

[0164] The image forming units 20Y, 20M, 20C, 20Bk include photoreceptors 11Y, 11M, 11C, 11Bk that are electrostatic latent image carriers, charging means 23Y, 23M, 23C, 23Bk that apply a uniform potential to the surfaces of the photoreceptors 11Y, 11M, 11C, 11Bk, exposure means 22Y, 22M, 22C, 22Bk that form an electrostatic latent image of a desired shape on the uniformly charged photoreceptors 11Y, 11M, 11C, 11Bk, developing means 21Y, 21M, 21C, 21Bk that convey a colored toner onto the photoreceptors 11Y, 11M, 11C, 11Bk to visualize the electrostatic latent image, and cleaning means 25Y, 25M, 25C, 25Bk that recover the residual toner remaining on the photoreceptors 11Y, 11M, 11C, 11Bk after primary transfer.

[0165] The intermediate transfer unit 10 includes an intermediate transfer belt 16 that circulates and moves, primary transfer rollers 13Y, 13M, 13C, and 13Bk as primary transfer means for transferring the toner images formed by the image forming units 20Y, 20M, 20C, and 20Bk to the intermediate transfer belt 16, a secondary transfer roller 13A as secondary transfer means for transferring the full-color toner image transferred onto the intermediate transfer belt 16 by the primary transfer rollers 13Y, 13M, 13C, and 13Bk onto the transfer material P, and a cleaning means 12 for recovering the residual toner remaining on the intermediate transfer belt 16.

[0166] The transfer belt of the present invention is used as the intermediate transfer belt 16. This intermediate transfer belt 16 is an endless belt-like member that is stretched by a plurality of support rollers 16a to 16d and is rotatably supported.

[0167] The toner images of respective colors formed by the image forming units 20Y, 20M, 20C, and 20Bk are sequentially transferred onto the rotating endless intermediate transfer belt 16 by the primary transfer rollers 13Y, 13M, 13C, and 13Bk, and a superimposed color image is formed. The transfer material P accommodated in the paper feed cassette 41 is fed by the paper feed conveying means 42, conveyed through a plurality of intermediate rollers 44a to 44d and the registration roller 46, and conveyed to the secondary transfer roller 13A as secondary transfer means, and the color image is batch-transferred onto the transfer material P. The transfer material P onto which the color image has been transferred is subjected to a fixing process by a fixing device 30 equipped with a heat roller fuser, sandwiched by the paper discharge rollers, and placed on the external paper discharge tray.

[0168] On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 13A, the endless intermediate transfer belt 16 from which the transfer material P has been separated by curvature has the residual toner removed by the cleaning means 12.

[0169] According to the image forming apparatus as described above, since the intermediate transfer belt is composed of the transfer belt of the present invention, the intermediate transfer belt has excellent transferability and cleanability while having high durability, so that an image with high image quality can be formed over a long period.

[0170] [Developer] The developer used in the image forming apparatus of the present invention may be a one-component developer using magnetic or non-magnetic toner, or may be a two-component developer in which toner and carrier are mixed. The toner constituting the developer is not particularly limited, and various known ones can be used. For example, it is preferable to use a so-called polymerization toner having a volume-based median diameter of 3 to 9 μm and obtained by a polymerization method. By using the polymerization toner, high resolution and stable image density can be obtained in the formed image, and the occurrence of image fogging is extremely suppressed.

[0171] As the carrier in the case of constituting a two-component developer, various known ones can be used without particular limitation. For example, a ferrite carrier composed of magnetic particles having a volume-based median diameter of 30 to 65 μm and a magnetization amount of 20 to 70 emu / g is preferable. When a carrier having a volume-based median diameter of less than 30 μm is used, there is a possibility that carrier adhesion occurs and a white-out image is generated. Also, when a carrier having a volume-based median diameter larger than 65 μm is used, a uniform image density image may not be formed.

[0172] [Transfer Material] Examples of the transfer material P used in the image forming apparatus of the present invention include ordinary paper from thin paper to thick paper, coated printing paper such as high-quality paper, art paper, or coated paper, commercially available Japanese paper or postcard paper, plastic film for OHP, cloth, and the like, but are not limited thereto. By using the transfer belt of the present invention, even when uneven paper is used as the transfer material, a high-quality image can be formed without impairing the transferability of the toner image to the transfer material. [Examples]

[0173] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[0174] [Example 1] Using a device similar to that shown in FIG. 4, each layer was formed in order of the surface layer and the base material layer on the outer peripheral surface of a stainless steel cylindrical mold. By inverting the inner peripheral surface and the outer peripheral surface, the transfer belt 1 was manufactured as an endless belt having a two-layer structure composed of a base material layer 2 and a surface layer 3 similar to the transfer belt 1A shown in FIG. 3A.

[0175] <Preparation of Dispersion Liquid> The following dispersion liquids A and B were prepared and used as coating liquids for forming each layer. Dispersion liquid A: A dispersion liquid in which barium titanate particles "BT05" (manufactured by Sakai Chemical Industry Co., Ltd.) are dispersed in a solvent (N-methyl-2-pyrrolidone). Dispersion liquid B: A dispersion liquid in which carbon black "MA11" (manufactured by Mitsubishi Chemical Corporation) is dispersed in a solvent (N-methyl-2-pyrrolidone).

[0176] <Formation of Surface Layer> Dispersion liquid B was added to a polyimide varnish "Upia-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 5% by volume of carbon black with respect to the total solid content components of the surface layer, and mixed using a mixer to prepare a coating liquid for forming a base material layer.

[0177] Next, while rotating the stainless steel cylindrical mold around the cylindrical axis, the dispensing nozzle was moved in the axial direction, and the coating liquid for forming the base material layer was discharged from the nozzle so that the layer thickness after drying was 20 μm, and it was spirally coated on the outer peripheral surface of the mold to form a continuous coating film.

[0178] Next, by heating at 100 °C for 1 hour while rotating the cylindrical mold, most of the solvent was volatilized from the coating film, and then, by heating at 230 °C for 1 hour, an endless belt-shaped surface layer was formed on the outer peripheral surface of the mold.

[0179] <Formation of Base Material Layer> Dispersion liquids A and B were added to the polyimide varnish "Upia-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 10% by volume of barium titanate and 5% by volume of carbon black with respect to the total solid content components of the base material layer, and mixed using a mixer to prepare a coating liquid for forming the base material layer.

[0180] Next, while rotating the mold obtained above with a surface layer formed on its outer peripheral surface around the cylindrical axis, the dispensing nozzle was moved in the axial direction, and the coating liquid for forming the base material layer was discharged from the nozzle so that the layer thickness after drying became 50 μm, and it was applied in a spiral shape on the outer peripheral surface of the surface layer formed on the outer peripheral surface of the mold to form a continuous coating film.

[0181] Next, while rotating the above mold, most of the solvent was volatilized from the coating film by heating at 100 °C for 1 hour, and then, by heating at 360 °C for 1 hour, an endless belt having a two-layer structure was formed. The obtained endless belt was removed from the mold, and the inner peripheral surface and the outer peripheral surface were reversed to obtain Transfer Belt 1.

[0182] [Example 2] Using the same apparatus as in Example 1, each layer was formed in order of the surface layer, the intermediate layer, and the base material layer on the outer peripheral surface of a stainless-steel cylindrical mold, and by reversing the inner peripheral surface and the outer peripheral surface, an endless belt having a three-layer structure composed of a base material layer 2, an intermediate layer 4, and a surface layer 3 similar to Transfer Belt 1B shown in Fig. 3B was manufactured as Transfer Belt 2.

[0183] [Formation of the surface layer] "Upia-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) was applied to a stainless-steel cylindrical mold while rotating it around the cylindrical axis, moving the dispensing nozzle in the axial direction, and discharging the coating liquid from the nozzle so that the layer thickness after drying became 5 μm, and it was applied in a spiral shape on the outer peripheral surface of the mold to form a continuous coating film.

[0184] Next, while rotating the cylindrical mold, most of the solvent was volatilized from the coating film by heating at 100 °C for 1 hour, and then, by heating at 230 °C for 1 hour, an endless belt-shaped surface layer was formed on the outer peripheral surface of the mold.

[0185] <Formation of intermediate layer> Dispersion liquid B was added to the polyimide varnish "UPIA-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 5.5% by volume of carbon black with respect to the total solid component of the intermediate layer, and mixed using a mixer to prepare a coating liquid for forming an intermediate layer.

[0186] While rotating the mold obtained above, on which the surface layer was formed on the outer peripheral surface, the coating liquid for forming the intermediate layer was discharged from the dispensing nozzle while moving the nozzle in the axial direction so that the layer thickness after drying was 10 μm, and it was applied in a spiral shape to the outer peripheral surface of the surface layer formed on the outer peripheral surface of the mold to form a connected coating film.

[0187] Next, while rotating the mold, most of the solvent was volatilized from the coating film by heating at 100 °C for 1 hour, and then, by heating at 230 °C for 1 hour, a laminate in which an endless belt-shaped surface layer and an intermediate layer were formed in that order on the outer peripheral surface of the mold was obtained.

[0188] <Formation of base material layer> Dispersion liquids A and B were added to the polyimide varnish "UPIA-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 10% by volume of barium titanate and 5% by volume of carbon black with respect to the total solid component of the base material layer, and mixed using a mixer to prepare a coating liquid for forming a base material layer.

[0189] While rotating the mold obtained above, on which the surface layer and the intermediate layer were laminated on the outer peripheral surface, the coating liquid for forming the base material layer was discharged from the dispensing nozzle while moving the nozzle in the axial direction so that the layer thickness after drying was 50 μm, and it was applied in a spiral shape to the outer peripheral surface of the intermediate layer formed on the outer peripheral surface of the mold to form a connected coating film.

[0190] Next, the mold was heated at 100°C for 1 hour while rotating to volatilize most of the solvent from the coating film, and then heated at 360°C for 1 hour to form a laminate having an endless belt-shaped surface layer, intermediate layer, and base material layer in that order on the outer peripheral surface of the mold. The obtained endless belt-shaped laminate was removed from the mold, and the inner peripheral surface and the outer peripheral surface were inverted to obtain the transfer belt 2.

[0191] [Example 3] Using the same apparatus as in Example 1, each layer was formed in order of the intermediate layer and the base material layer on the outer peripheral surface of a stainless steel cylindrical mold, and the obtained laminate was removed from the mold. Further, after fitting the mold into the laminate with the inner peripheral surface and the outer peripheral surface inverted, a surface layer was formed on the outer peripheral surface of the intermediate layer to produce the transfer belt 3 as an endless belt having a three-layer structure composed of the base material layer 2, the intermediate layer 4, and the surface layer 3 similar to the transfer belt 1B shown in FIG. 3B.

[0192] [Formation of Intermediate Layer] Dispersion liquid B was added to the polyimide varnish "Upia-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 5.5% by volume of carbon black with respect to the total solid content components of the intermediate layer, and mixed using a mixer to prepare a coating liquid for forming the intermediate layer.

[0193] While rotating a stainless steel cylindrical mold about its cylindrical axis, the coating liquid for forming the intermediate layer was discharged from the dispenser nozzle while moving the nozzle in the axial direction so that the layer thickness after drying was 12 μm, and helically applied onto the outer peripheral surface of the mold to form a continuous coating film.

[0194] Next, most of the solvent was volatilized by heating at 100°C for 1 hour while rotating the cylindrical mold, and then an endless belt-shaped intermediate layer was formed on the outer peripheral surface of the mold by heating at 230°C for 1 hour.

[0195] [Formation of Base Material Layer] Dispersion liquids A and B were added to the polyimide varnish "UPIA-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so that the content of barium titanate was 10% by volume and the content of carbon black was 5% by volume with respect to the total solid components of the base material layer, and they were mixed using a mixer to prepare a coating liquid for forming the base material layer.

[0196] While rotating the mold obtained above, on which the intermediate layer was formed on the outer peripheral surface, around the cylindrical axis, while moving the dispensing nozzle in the axial direction, the coating liquid for forming the base material layer was discharged from the nozzle so that the layer thickness after drying became 50 μm, and it was applied in a spiral shape on the outer peripheral surface of the intermediate layer formed on the outer peripheral surface of the mold to form a continuous coating film.

[0197] Next, while rotating the above mold, most of the solvent was volatilized by heating at 100 °C for 1 hour, and then, by heating at 360 °C for 1 hour, a laminate in which an endless belt-shaped intermediate layer and a base material layer were formed in that order was obtained on the outer peripheral surface of the mold.

[0198] <Formation of the surface layer> 90 g of tetraethoxysilane, 10 g of triethylethoxysilane, and 100 g of butanol were dissolved, and further, barium titanate was added so that the content was 3% by volume with respect to the total solid components of the surface layer to prepare a coating liquid for forming the surface layer.

[0199] The endless belt-shaped laminate in which the intermediate layer and the base material layer were laminated was removed from the mold, the inner peripheral surface and the outer peripheral surface were reversed, and then the mold was inserted into it. The coating liquid for forming the surface layer was spray-coated (spraying device: manufactured by Widy Mechatronics Solutions Co., Ltd.) on the outer peripheral surface of the intermediate layer of the laminate inserted with the mold under the following coating conditions so that the dry layer thickness of the coating layer became 3 μm to form a coating film, and the surface layer was formed by baking at 100 °C for 60 minutes in an air atmosphere to obtain the transfer belt 3.

[0200] <Spray coating conditions> Nozzle scan speed: 1 - 10 mm / sec Nozzle distance: 100 - 150 mm Number of nozzles: 1 Coating liquid supply rate: 1 - 5 mL / min O2 flow rate: 2 - 6 L / min, air atmosphere

[0201] [Example 4] In Example 3, a transfer belt 4 with a three - layer structure was manufactured in the same manner except that the layer thickness of the surface layer was 4 μm and the layer thickness of the intermediate layer was 11 μm.

[0202] [Example 5] In Example 3, a transfer belt 5 with a three - layer structure was manufactured in the same manner except that the addition amount of barium titanate in the base material layer was 20% by volume based on the total solid components of the base material layer, the layer thickness of the surface layer was 4 μm, and the layer thickness of the intermediate layer was 11 μm.

[0203] [Example 6] In Example 3, a transfer belt 6 with a three - layer structure was manufactured in the same manner except that the addition amount of barium titanate in the base material layer was 20% by volume based on the total solid components of the base material layer, the addition amount of carbon black in the intermediate layer was 5% by volume based on the total solid components of the intermediate layer, the layer thickness of the surface layer was 2 μm, and the layer thickness of the intermediate layer was 13 μm.

[0204] [Example 7] In Example 3, a transfer belt 7 with a three - layer structure was manufactured in the same manner except that the addition amount of barium titanate in the base material layer was 20% by volume based on the total solid components of the base material layer, the addition amount of carbon black in the intermediate layer was 5% by volume based on the total solid components of the intermediate layer, the addition amount of barium titanate in the surface layer was 2% by volume based on the total solid components of the surface layer, the layer thickness was 2 μm, and the layer thickness of the intermediate layer was 13 μm.

[0205] [Example 8] In Example 1, a transfer belt 8 with a two - layer structure was manufactured in the same manner except that the addition amount of carbon black in the base material layer was 10% by volume based on the total solid components of the base material layer, the addition amount of barium titanate in the base material layer was 30% by volume based on the total solid components of the base material layer, and the addition amount of carbon black in the surface layer was 3% by volume based on the total solid components of the surface layer.

[0206] [Example 9] In Example 3, a transfer belt 9 having a three-layer structure was produced in the same manner except that the amount of carbon black added to the intermediate layer was 8% by volume, the layer thickness was 10 μm, and barium titanate was not added to the surface layer and the layer thickness was 5 μm.

[0207] [Comparative Example 1] A transfer belt 10 having a two-layer structure was produced by the following method.

[0208] [Formation of Base Material Layer] Dispersion B was added to polyimide varnish "UPIA-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) so as to be 5% by volume of carbon black with respect to the total solid content components of the base material layer, and mixed using a mixer to prepare a coating liquid for forming the base material layer.

[0209] While rotating a stainless steel cylindrical mold around the cylindrical axis, while moving a dispensing nozzle in the axial direction, the coating liquid for forming the base material layer was discharged from the nozzle so that the layer thickness after drying was 50 μm, and it was applied in a spiral shape on the outer peripheral surface of the mold to form a continuous coating film.

[0210] Next, while rotating the cylindrical mold, most of the solvent was volatilized by heating at 100 °C for 1 hour, and then, by heating at 360 °C for 1 hour, an endless belt-shaped base material layer was formed on the outer peripheral surface of the mold.

[0211] [Formation of Surface Layer] The surface layer was formed as follows by the method described in JP-A-2019-197147. That is, 8 parts by volume of 3-acryloxypropyltrimethoxysilane (KBM-5103; Shin-Etsu Chemical Co., Ltd.), which is a surface treatment agent, and 300 parts by volume of a solvent (mixed solvent of toluene:methanol = 1:1 (volume ratio)) were mixed with respect to 100 parts by volume of zinc oxide particles, and dispersed for 45 minutes using a wet media dispersion type apparatus, and then the solvent was removed. Subsequently, it was dried at 150 °C for 10 minutes to obtain surface-treated zinc oxide 1.

[0212] To 100 parts by volume of tin oxide particles, 20 parts by volume of 3-acryloxypropyltrimethoxysilane (KBM-5103; Shin-Etsu Chemical Co., Ltd.), which is a surface treatment agent, and 700 parts by volume of a solvent (a mixed solvent of toluene:isopropyl alcohol = 1:1 (volume ratio)) were mixed, dispersed using a wet media dispersion type apparatus for 40 minutes, and then the solvent was removed. Subsequently, drying was performed at 150°C for 10 minutes to obtain surface-treated tin oxide 1.

[0213] 10 parts by volume of zinc oxide 1 (first particles) subjected to surface treatment, 15 parts by volume of tin oxide 1 (second particles) subjected to surface treatment, 68 parts by volume of monomer 1 (KAYARAD DPEA-12; Nippon Kayaku Co., Ltd.), 5 parts by volume of photoinitiator 1 (Irgacure OXE02; BASF), and 2 parts by volume of reaction accelerator (KAYACURE EPA, Nippon Kayaku Co., Ltd.) were dissolved and dispersed in methyl isobutyl ketone (MIBK), which is a solvent, so that the solid content concentration became 15% by mass to prepare coating liquid 1 for forming a surface layer.

[0214] On the outer peripheral surface of the base material layer, the coating liquid was applied by an immersion coating method using a coating apparatus in an environment of 20°C and a relative humidity of 50% so that the dry layer thickness became 1 μm to form a coating film. Next, the formed coating film was irradiated with ultraviolet rays as actinic rays (active energy rays) under the following irradiation conditions to cure the coating film and form a surface layer on the outer peripheral surface of the base material layer. The irradiation of ultraviolet rays was performed while fixing the light source and rotating the precursor having the coating film formed on the outer peripheral surface of the base material layer at a peripheral speed of 60 mm / s.

[0215] (Irradiation conditions of ultraviolet rays) Type of light source: LED light source (SPX-TA; Eye Graphics Co., Ltd.) Distance from the irradiation port to the surface of the coating film: 50 mm Atmosphere: Nitrogen (oxygen concentration; 600 ppm or less) Irradiation light amount: 3.3 J / cm 2 Irradiation time (rotation time of the precursor): 240 seconds Irradiation wavelength: 365 nm

[0216] [Comparative Example 2] A base material layer forming coating liquid was prepared by adding dispersion liquid A and dispersion liquid B to the entire solid content component of the base material layer such that the amount of barium titanate was 20% by volume and the amount of carbon black was 5% by volume, respectively. Then, a base material layer was formed in the same manner as in Example 2, and the surface layer was formed as follows to produce a transfer belt 11 having a two-layer structure.

[0217] [Formation of Surface Layer] A methyl ethyl ketone solution (solid content 5% by mass) of polyvinylidene fluoride "KYNAR 740" (manufactured by Tokyo Materials Co., Ltd.) was applied to the outer peripheral surface of the obtained base material layer using a coating apparatus by the dipping coating method so that the thickness after drying was 20 μm to form a coating film. After blowing hot air at 60 °C for 10 minutes, it was dried at 120 °C for 20 minutes.

[0218] [Comparative Example 3] A transfer belt 12 having a two-layer structure was produced in the same manner except that no intermediate layer was formed in Example 3, the amount of barium titanate added to the surface layer was 2% by volume with respect to the entire solid content component of the surface layer, and the layer thickness was 1 μm.

[0219] [Comparative Example 4] A transfer belt 13 having a three-layer structure was produced by the following method. [Formation of Base Material Layer] Dispersion liquid B was added to polyimide varnish "UPIA-AT (U-varnish-A)" (manufactured by Ube Industries, Ltd.) such that the amount of carbon black was 5% by volume with respect to the entire solid content component of the base material layer, and the mixture was mixed using a mixer to prepare a coating liquid for forming the base material layer.

[0220] Next, while rotating a stainless steel cylindrical mold around its cylindrical axis and moving a dispensing nozzle in the axial direction, the coating liquid for forming the base material layer was discharged from the nozzle so that the layer thickness after drying was 50 μm, and it was applied in a spiral shape on the outer peripheral surface of the mold to form a continuous coating film.

[0221] Next, while rotating the cylindrical mold, most of the solvent was volatilized by heating at 100 °C for 1 hour, and then, by heating at 360 °C for 1 hour, an endless belt-shaped base material layer was formed on the outer peripheral surface of the mold.

[0222] <Formation of intermediate layer> Dispersion B was adjusted so that the carbon black was 5% by volume with respect to the total solid content of the intermediate layer, 38.5% by volume of acrylonitrile-butadiene rubber "Nipol (registered trademark) 1041" (NBR) (manufactured by Zeon Corporation, Japan), which is an elastic material, and 4% by volume of polychloroprene rubber "Denka Chloroprene DCR (registered trademark) -66" (manufactured by Denka Co., Ltd.), which is an elastic material, 3% by volume of Al2O3, 1% by volume of TiO2, 3% by volume of SiO2, and 10% by volume of sulfur, which is a cross-linking agent, were dissolved and dispersed in toluene so that the solid content concentration became 20% by mass to prepare a coating solution for forming the intermediate layer.

[0223] While rotating the mold obtained above with the base material layer formed on its outer peripheral surface around the cylindrical axis, while moving the dispensing nozzle in the axial direction, the coating solution for forming the intermediate layer was discharged from the nozzle so that the layer thickness after drying was 15 μm, and it was applied in a spiral shape on the outer peripheral surface of the mold to form a continuous coating film.

[0224] Next, while rotating the mold, most of the solvent was volatilized by heating at 50 °C for 1 hour, and then, by performing a heat cross-linking treatment by heating at 170 °C for 20 minutes, a laminate in which an endless belt-shaped base material layer and an intermediate layer were formed in that order was obtained on the outer peripheral surface of the mold.

[0225] <Formation of surface layer> In Comparative Example 2, the surface layer was formed on the outer peripheral surface of the laminate in which the base material layer and the intermediate layer were formed in that order in the same manner except that the amount of barium titanate added to the surface layer was 5% by volume with respect to the total solid content of the surface layer and the layer thickness of the surface layer was 5 μm.

[0226] [Comparative Example 5] In Example 3, the surface layer was formed as follows without forming the intermediate layer, and the transfer belt 14 having a two-layer structure was manufactured.

[0227] <Formation of Surface Layer> Dispersion liquid A was added to a methyl ethyl ketone solution (solid content: 5% by mass) of polyvinylidene fluoride "KYNAR 740" (manufactured by Tokyo Materials Co., Ltd.) so that the addition amount of barium titanate became 10% by volume with respect to the entire solid content component of the surface layer, and the mixture was mixed using a mixer to prepare a coating liquid for forming the surface layer.

[0228] The coating liquid for forming the surface layer was applied to the outer peripheral surface of the obtained base material layer using a coating apparatus by the dip coating method so that the thickness after drying became 20 μm, a coating film was formed, hot air at 60 °C was applied for 10 minutes, and then it was dried at 120 °C for 20 minutes.

[0229] [Comparative Example 6] In Example 1, the transfer belt 15 having a two-layer structure was manufactured in the same manner except that the barium titanate added to the base material layer was changed to 40% by volume.

[0230] [Physical Property Measurement and Evaluation] Using the transfer belts 1 to 15 obtained above, the following physical property measurements and evaluations were performed. The results are shown in Table I together with the configurations of the transfer belts.

[0231] Regarding the abbreviations in Table I, PI represents polyimide resin, NBR represents acrylonitrile butadiene rubber, CR represents polychloroprene rubber, PVDF represents polyvinylidene fluoride, and CB represents carbon black, respectively.

[0232] <Measurement of Relative Permittivity and Layer Thickness> For the transfer belts 1 to 15, the relative permittivity and layer thickness of each layer were measured by the above method. In addition, the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm was measured.

[0233] <Measurement of Martens Hardness> For the transfer belts 1 to 15, the Martens hardness [N / mm2 was measured.

[0234] <Transferability Evaluation> Under the following evaluation conditions, transferability evaluation was performed using embossed paper, and the quality of the image was compared. Using Resac 302g paper, the transfer state of toner to the concave part was ranked. A rank of 3 or higher was considered a pass.

[0235] (Evaluation Conditions) Environment: Temperature 20°C, Relative Humidity 50% Evaluation Machine: bizhub PRESS C1100 (manufactured by Konica Minolta)

[0236] (Evaluation Criteria) Rank 5: Completely transferred. Rank 4: There are several missing parts in the two-layer area. The single-color area has no problems. Rank 3: There are sparse missing parts in the two-layer area. The single-color area has no problems. Rank 2: There are sparse missing parts in the single-color area. Rank 1: The single-color area is completely missing.

[0237] <Cleanability Evaluation> Under the following evaluation conditions, an image with a printing rate of 2.5% for each color of YMCK was subjected to durable printing on A4-sized Konica Minolta J paper. Then, three MC halftone images were printed on the above paper, and the three obtained halftone images were visually observed and evaluated according to the following criteria. △, ○, and ◎ are considered passes.

[0238] (Evaluation Conditions) Environment: Temperature 20°C, Relative Humidity 50% Evaluation Machine: bizhub PRESS C1100 (manufactured by Konica Minolta)

[0239] (Evaluation Criteria) ◎: No cleaning defects after 2 million actual prints (no defects such as streaks on the image) ○: No cleaning defects after 1 million actual prints (no defects such as streaks on the image) △: There are cleaning defects after 1 million actual prints (defects such as streaks occur on the image). ×: There are cleaning defects after 500,000 actual prints (defects such as streaks occur on the image).

[0240] <Durability Evaluation> Under the following evaluation conditions, a paper passing durability test was conducted to compare the damage status of the belt. Those with △ or above were considered qualified. (Evaluation Conditions) Environment: Temperature 20°C, Relative Humidity 50% Evaluation Machine: bizhub PRESS C1100 (manufactured by Konica Minolta) Paper Passing Durability Test: 2 million sheets of paper were passed, and the damage status of the belt at 1 million sheets and 2 million sheets of paper passing was compared.

[0241] (Evaluation Criteria) ◎: No cracks after 2 million sheets of durability. ○: No cracks after 1 million sheets of durability. △: Damage was confirmed at the end after 1 million sheets of durability. ×: Damage was confirmed not only at the end but also at the center after 1 million sheets of durability.

[0242]

Table 1

[0243] From Table I, it can be seen that the transfer belt of the present invention is excellent in transferability, cleaning property and durability.

Explanation of Reference Signs

[0244] 1A, 1B Transfer Belt 2 Base Material Layer 3 Surface Layer 4 Intermediate Layer 10 Intermediate Transfer Part 11Y, 11M, 11C, 11Bk Photoreceptor 12 Cleaning Means 13Y, 13M, 13C, 13Bk Primary Transfer Roller 13A Secondary Transfer Roller 16 Intermediate Transfer Belt 16a to 16d support rollers 20Y, 20M, 20C, 20Bk image forming units 21Y, 21M, 21C, 21Bk developing means 22Y, 22M, 22C, 22Bk exposure means 23Y, 23M, 23C, 23Bk charging means 25Y, 25M, 25C, 25Bk cleaning means 30 fixing device 41 paper feed cassette 42 paper feed conveying means 44a, 44b, 44c, 44d paper feed rollers 46 resist roller N1 fixing nip section P transfer material

Claims

1. A transfer belt having a base material layer and a surface layer laminated on the base material layer, wherein the relative permittivity of the base material layer is in the range of 20 to 100, the relative permittivity in the region from the surface on the surface layer side to a depth of 15 μm is in the range of 5 to 10, and The martensite hardness of the surface on the surface side is in the range of 300 to 700 N / mm ２ The transfer belt is characterized in that it is within the range of.

2. The transfer belt according to claim 1, wherein the surface layer contains a cured product of a composition containing an alkoxysilane.

3. Furthermore, it has an intermediate layer between the base material layer and the surface layer, the intermediate layer contains a resin selected from a polyimide resin, a polyamideimide resin, a polyphenylene sulfide resin, and a polyetheretherketone resin, the total layer thickness of the intermediate layer and the surface layer is in the range of 10 to 20 μm, and The transfer belt according to claim 1 or claim 2, wherein the layer thickness of the base material layer is in the range of 40 to 100 μm.

4. The martensite hardness of the surface on the surface layer side is in the range of 500 to 600 N / mm ２ The transfer belt according to any one of claims 1 to 3, characterized in that it is within the range of

5. The transfer belt according to any one of claims 1 to 4, wherein the relative permittivity of the base material layer is in the range of 40 to 100.

6. The transfer belt according to claim 3, wherein the relative permittivity of the intermediate layer is in the range of 5 to 10.

7. The transfer belt according to any one of claims 1 to 6, wherein the relative permittivity of the surface layer is in the range of 2 to 5.

8. An electrophotographic image forming apparatus comprising the transfer belt according to any one of claims 1 to 7.

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