Belt for transfer, belt unit, and image forming apparatus

Abstract

To provide a belt for transfer that is excellent in image transfer performance.SOLUTION: A belt for transfer has three layers: a front face layer; a base material layer including at least one elastic material selected from the group consisting of rubber and an elastomer; and a rear face layer. The relationship between the volume resistivity R1 of the front face layer, the volume resistivity R2 of the base material layer, and the volume resistivity R3 of the rear face layer, in an environment of 25°C and 55%RH satisfies the formula 1: R1>R2>R3, or the formula 2: R1<R2<R3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a transfer belt, a belt unit, and an image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus, a belt having a resin layer laminated on a base material layer is used as a belt for transferring an image onto a recording medium.

[0003] For example, Patent Document 1 discloses an intermediate transfer belt having a base layer on which a primer layer and a coating layer are provided in this order, in which the base layer contains a resin having a carbonyl group, the primer layer contains a silane coupling agent containing a nitrogen atom, and the coating layer contains a compound having a structure represented by the following general formula (1): Patent Document 2 discloses a transfer belt that is configured by stacking an elastic layer and a surface layer in this order, and the surface layer has a breaking elongation of 7 to 60% and a tensile modulus of elasticity of 100 to 1000 MPa. Furthermore, Patent Document 3 discloses a transfer belt for an image forming apparatus, which is characterized by having a surface layer formed from a resin composition containing a silicone-acrylic copolymer resin and a urethane resin as main components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-086013 [Patent Document 2] Patent No. 6241270 [Patent Document 3] Patent No. 6929767 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present disclosure is to provide a transfer belt having superior image transfer performance compared to a transfer belt in which the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer do not satisfy either Formula 1 or Formula 2, a belt unit including the transfer belt, and an image forming apparatus. [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> The cushion has three layers: a surface layer, a base layer containing at least one elastic material selected from the group consisting of rubber and elastomer, and a back layer; A transfer belt, wherein the relationship between the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer in an environment of 25°C and 55% RH satisfies the following formula 1 or 2: Formula 1: R1>R2>R3 Formula 2: R1 <R2<R3 <2> the volume resistivity of the entire transfer belt under an environment of 25°C and 55% RH is 8.0 log Ω or more and 11.0 log Ω or less; <1> The transfer belt according to claim 1. <3> the volume resistivity of the entire transfer belt under an environment of 25°C and 55% RH is 8.5 log Ω or more and 10.0 log Ω or less; <2> The transfer belt according to claim 1. <4> a difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and a difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back surface layer are both 0.1 log Ω or more; <1> ~ <3> 10. The transfer belt according to claim 9, wherein the transfer belt is a belt for transferring a transfer signal. <5> a difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and a difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back surface layer, each being 0.2 log Ω or more and 1.0 log Ω or less; <4> The transfer belt according to claim 1. <6> The surface layer and the back layer each contain a conductive filler in a range of 0.1% by mass to 8.0% by mass. <1> ~ <5> 10. The transfer belt according to claim 9, wherein the transfer belt is a belt for transferring a transfer signal. <7> The surface layer and the back layer each contain a conductive filler in a range of 0.5% by mass to 4.0% by mass. <6> The transfer belt according to claim 1. <8> the surface layer and the back surface layer contain a conductive filler, the content of the conductive filler in the layer having a higher volume resistivity out of the front surface layer and the back surface layer is 0.1% by mass or more and 2.0% by mass or less, and the content of the conductive filler in the layer having a lower volume resistivity is 1.0% by mass or more and 8.0% by mass or less; <1> ~ <7> 10. The transfer belt according to claim 9, wherein the transfer belt is a belt for transferring a transfer signal. <9> the content of the conductive filler in the layer having a higher volume resistivity out of the front surface layer and the back surface layer is 0.3% by mass or more and 1.8% by mass or less, and the content of the conductive filler in the layer having a lower volume resistivity is 1.5% by mass or more and 4.0% by mass or less; <8> The transfer belt according to claim 1. <10> the base material layer contains, as the elastic material, at least one selected from the group consisting of chloroprene rubber, epichlorohydrin rubber, and urethane elastomer; <1> ~ <9> 10. The transfer belt according to claim 9, wherein the transfer belt is a belt for transferring a transfer signal. <11> the surface layer contains a base resin and particles of a resin having a siloxane bond, the content of the resin particles having a siloxane bond relative to the base resin is 1.0% by mass or more and 20.0% by mass or less; <1> ~ <10> 10. The transfer belt according to claim 9, wherein the transfer belt is a belt for transferring a transfer signal. <12> the content of the resin particles having a siloxane bond relative to the base resin is 2.0% by mass or more and 15.0% by mass or less; <11> The transfer belt according to claim 1. <13> <1> ~ <12> a transfer belt according to any one of the above items; a plurality of rolls around which the transfer belt is stretched under tension; Equipped with At least one of the plurality of rolls is a drive roll that rotates the transfer belt, A belt unit that is detachably attached to an image forming apparatus. <14> an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing means for storing a developer containing a toner and developing an electrostatic image formed on the surface of the image carrier using the developer to form a toner image; <13> and a transfer unit that transfers the toner image onto a recording medium. <15> The transfer means is The image forming apparatus includes an intermediate transfer member, a primary transfer unit that transfers a toner image onto the surface of the intermediate transfer member, and a secondary transfer unit that transfers the toner image transferred onto the surface of the intermediate transfer member onto a recording medium, the secondary transfer unit has the belt unit; <14> 2. The image forming apparatus according to claim 1 . [Effects of the Invention]

[0007] <1> According to the invention, a transfer belt is provided that has superior image transfer performance compared to a transfer belt in which the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer do not satisfy either Formula 1 or Formula 2. <2> or <3> According to the invention, a transfer belt is provided that has superior image transfer performance compared to a transfer belt whose entire volume resistivity in an environment of 25°C and 55% RH is less than 8.0 log Ω or more than 11.0 log Ω. <4> or <5> According to the present invention, a transfer belt is provided that has superior image transfer performance compared to a transfer belt in which at least one of the difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer and the difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer is less than 0.1 log Ω. <6> or <7> According to the present invention, a transfer belt is provided that has superior image transfer performance compared to a transfer belt having a conductive filler content of less than 0.1 mass % or more than 8.0 mass % in at least one of the front layer and the back layer. <8> or <9> According to the invention, a transfer belt is provided that has superior image transfer performance compared to a transfer belt in which the conductive filler content in the layer having a higher volume resistivity out of the front and back layers is less than 0.1 mass % or more than 2.0 mass %, and a transfer belt in which the conductive filler content in the layer having a lower volume resistivity is less than 1.0 mass % or more than 8.0 mass %. <10> According to the invention, a transfer belt is provided which has superior image transfer performance compared to a transfer belt whose base layer contains only EPDM rubber or polyamide as an elastic material. <11> or <12> According to the present invention, a transfer belt is provided in which contamination on the back surface of a recording medium is suppressed compared to a transfer belt in which the content of resin particles having siloxane bonds relative to the base resin in the surface layer is less than 1.0 mass % or more than 20.0 mass %. <13> According to the present invention, a belt unit is provided that has superior image transfer performance compared to a transfer belt having a surface layer volume resistivity R1, a base layer volume resistivity R2, and a back layer volume resistivity R3 that do not satisfy either formula 1 or formula 2. <14> or <15> According to the present invention, an image forming apparatus is provided that has superior image transfer performance compared to a case where the transfer belt has a surface layer volume resistivity R1, a base layer volume resistivity R2, and a back layer volume resistivity R3 that do not satisfy either formula 1 or formula 2. [Brief explanation of the drawings]

[0008] [Figure 1]1A and 1B are diagrams showing an example of a circular electrode, in which FIG. 1A is a schematic plan view and FIG. 1B is a schematic cross-sectional view. [Figure 2] 1 is a schematic perspective view illustrating an example of a transfer belt according to the present disclosure. [Figure 3] FIG. 2 is a schematic perspective view illustrating an example of a belt unit according to the present disclosure. [Figure 4] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0010] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these. In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified.

[0011] <Transfer belt> The transfer belt according to the embodiment of the present disclosure has three layers: a surface layer, a base layer containing at least one elastic material selected from the group consisting of rubber and elastomer, and a back layer. The relationship between the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer in an environment of 25° C. and 55% RH satisfies the following formula 1 or 2. Formula 1: R1>R2>R3 Formula 2: R1 <R2<R3 In the following description, the transfer belt according to the embodiment of the present disclosure will also be simply referred to as the "belt according to the present disclosure."

[0012] The belt according to the present disclosure is a belt that is involved in both transporting a recording medium such as paper and transferring a toner image onto the recording medium. Specifically, the belt according to the present disclosure is used as a belt disposed opposite the intermediate transfer belt and transporting the recording medium to a secondary transfer unit in an image forming apparatus that performs primary transfer of a toner image formed on the surface of an image carrier (specifically, an electrophotographic photosensitive member, also referred to as a photosensitive member) to an intermediate transfer belt, and then secondary transfer of the toner image from the intermediate transfer belt to a recording medium.Furthermore, the belt according to the present disclosure is used as a belt disposed opposite the image carrier and transporting the recording medium to a transfer unit in an image forming apparatus that directly transfers a toner image formed on the surface of the image carrier to a recording medium.

[0013] As described above, the transfer belt used in an electrophotographic image forming apparatus transports a recording medium while electrostatically attracting the recording medium to its surface in the transfer section, and also contributes to the transfer of a toner image onto the transported recording medium. Therefore, the transfer belt is required to have good image transfer performance. Image transfer performance is often affected, for example, when abnormal discharge occurs in the transfer section (e.g., the transfer section between the intermediate transfer belt and the image carrier) or when transfer conditions are changed depending on the type of recording medium, environment, etc. Therefore, as a result of the inventor's investigation, it has been found that by having a three-layer structure including a surface layer, a base material layer containing an elastic material, and a back surface layer, and satisfying the relationship of Formula 1 (R1>R2>R3) or Formula 2 (R1<R2<R3) for the volume resistivity of these three layers, the transfer performance of an image can be improved.

[0014] When the belt according to the present disclosure satisfies the relationship of Formula 1, the volume resistivity increases in the order of the surface layer, the base material layer, and the back surface layer. In this case, the surface layer with the highest resistance maintains the charging performance, and the transfer current flowing from the surface layer side has a configuration that easily passes from the surface layer through the base material layer and the back surface layer to the back side of the belt. That is, while maintaining the required charging performance, the configuration is such that the charge of the transfer current does not remain too much in the belt. On the other hand, when the belt according to the present disclosure satisfies the relationship of Formula 2, the volume resistivity decreases in the order of the surface layer, the base material layer, and the back surface layer. In this case, the back surface layer with the highest resistance maintains the charging performance, and the transfer current flowing from the surface layer side has a configuration that easily flows from the surface layer to the base material layer and the back surface layer side. That is, similar to the case where the relationship of Formula 1 is satisfied, while maintaining the required charging performance, the configuration is such that the charge of the transfer current does not remain too much in the belt. In this way, by having a configuration that maintains the required charging performance while the charge of the transfer current does not remain too much in the belt, the transferability of the toner image to the recording medium is improved, that is, the transfer performance is improved.

[0015] Hereinafter, embodiments of the present disclosure will be described in detail.

[0016] ·Volume resistivity of the surface layer, base material layer, and back surface layer For the belt according to the present disclosure, the relationship between the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base material layer, and the volume resistivity R3 of the back surface layer under the environment of 25°C and 55%RH satisfies the following Formula 1 or the following Formula 2. Formula 1: R1>R2>R3 Formula 2: R1<R2<R3 By satisfying Formula 1 or Formula 2, the transferability of the toner image to the recording medium can be improved.

[0017] In addition, from the viewpoint of further improving the transferability of the toner image to the recording medium, the difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and the difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are preferably 0.1 log Ω or more, and more preferably 0.2 log Ω or more. On the other hand, from the viewpoint of maintaining high transfer efficiency during high-speed transfer, the upper limit values ​​of the difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and the difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are preferably 1.0 log Ω or less, and more preferably 0.8 log Ω or less.

[0018] An example of a method for adjusting the relationship between the volume resistivities of the surface layer, the base layer, and the back surface layer is to adjust the amount of conductive filler contained in the surface layer and the back surface layer in each layer.

[0019] -Volume resistivity of the entire belt The belt according to the present disclosure preferably has a volume resistivity of 8.0 log Ω or more and 11.0 log Ω or less, and more preferably 8.5 log Ω or more and 10.0 log Ω or less, in an environment of 25° C. and 55% RH throughout the entire belt. By having the overall volume resistivity of 8.0 log Ω or more, the charging performance of the belt is maintained and the transferability of the toner image to the recording medium is improved. Also, by having the overall volume resistivity of 11.0 log Ω or less, the transfer current flowing through the belt is easily transmitted to the back side of the belt, which also improves the transferability of the toner image to the recording medium.

[0020] [Volume resistivity measurement method] The method for measuring the volume resistivity will be described below. In each of the belt, surface layer, base layer, and back layer according to the present disclosure, the measurement points are 6 equally spaced around the circumference of the belt or layer, and 3 points at the center and both ends in the width direction of the belt or layer, for a total of 18 points. The arithmetic mean value of the measurements at these 18 points is used.

[0021] The volume resistivity of the belt, surface layer, base layer, and back layer according to the present disclosure is measured as follows. Measurements are made using a circular electrode (for example, a UR probe for a Hirester IP manufactured by Mitsubishi Petrochemical Co., Ltd.) in accordance with JIS K6911:1995. The volume resistivity measurement method will be described with reference to FIG. 1. FIG. 1 is a schematic plan view (A) and a schematic cross-sectional view (B) showing an example of a circular electrode. The circular electrode shown in FIG. 1 includes a first voltage-applying electrode A and a second voltage-applying electrode B. The first voltage-applying electrode A includes a cylindrical electrode portion C and a cylindrical ring-shaped electrode portion D that has an inner diameter larger than the outer diameter of the cylindrical electrode portion C and surrounds the cylindrical electrode portion C at a fixed interval. A belt T is then clamped between the cylindrical electrode portion C and ring-shaped electrode portion D of the first voltage-applying electrode A and the second voltage-applying electrode B. A voltage V (V) is applied between the cylindrical electrode portion C of the first voltage-applying electrode A and the second voltage-applying electrode B. The current I (A) that flows when the voltage V (V) is applied between the cylindrical electrode portion C of the first voltage-applying electrode A and the second voltage-applying electrode B is measured, and the volume resistivity ρv (Ωcm) of the belt T is calculated using the following formula: In the following formula, t represents the thickness of the measurement sample (that is, the belt, the surface layer, the base layer, or the back layer). Formula: ρv = 19.6 × (V / I) × t The volume resistivity is calculated by measuring the current value after applying a voltage of 500 V for 10 seconds in an environment of 22°C / 55% RH using a circular electrode (UR probe of Hirester IP manufactured by Mitsubishi Petrochemical Co., Ltd.: cylindrical electrode part C with an outer diameter of Φ16 mm, ring-shaped electrode part D with an inner diameter of Φ30 mm and an outer diameter of Φ40 mm).

[0022] The 19.6 in the above formula is the electrode coefficient for converting to resistivity. From the outer diameter d (mm) of the cylindrical electrode part and the thickness t (cm) of the measurement sample, πd 2 It is calculated as / 4t. The thicknesses of the measurement samples, namely the belt, surface layer, base layer, and back layer, are all measured using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics Co., Ltd. The thickness is measured at one arbitrary position. As mentioned above, since the number of measurement points (i.e., the number of measurement samples) is 18, the arithmetic mean value of the thicknesses of the 18 measurement samples can also be used as the total thickness of the belt, the thickness of the surface layer, the thickness of the base material layer, or the thickness of the back layer. When determining the thickness of the surface layer, base layer, and back layer from the belt, one of the surface layer, base layer, or back layer is polished and removed with a polishing means such as an extra-fine or finer file, with reference to the thickness of each layer measured in the cross section by cross-sectional observation, to obtain a measurement sample. Then, the thickness, volume resistivity, etc. of the obtained measurement sample (measurement sample of the surface layer, base layer, or back layer) can be measured by the above-mentioned method.

[0023] The volume resistivity of the belt according to the present disclosure and the surface layer, base layer, and back layer that constitute it are all controlled by the type of conductive particles, the type of conductive agent, and the amounts thereof added, etc.

[0024] Belt configuration Next, a belt according to the present disclosure will be described with reference to Fig. 2. Here, Fig. 2 is a schematic perspective view showing an example of a belt according to the present disclosure. 2, the belt 50 has a base layer 52, a surface layer 54, and a back layer 56. The surface layer 54 is provided on the outer peripheral surface of the base layer 52 and constitutes the outer peripheral surface of the belt 50. The back layer 56 is provided on the inner peripheral surface of the base layer 52 and constitutes the inner peripheral surface of the belt 50. The outer peripheral surface of the belt 50 is also called the belt surface, and corresponds to the conveying surface of the recording medium.

[0025] (base material layer) The base layer contains at least one elastic material selected from the group consisting of rubber and elastomer. The base layer may further contain conductive particles (conductive filler) and other additives. The elastic material may be used alone or in combination of two or more.

[0026] Examples of rubbers and elastomers in the elastic material include chloroprene rubber (CR), epichlorohydrin rubber (ECO rubber), urethane elastomer, isoprene rubber, butyl rubber, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber (NBR), ethylene propylene rubber, ethylene-propylene-diene terpolymer rubber (EPDM), natural rubber, and mixed rubbers thereof. Among these, it is preferable to contain at least one selected from the group consisting of chloroprene rubber (CR), epichlorohydrin rubber (ECO rubber), and urethane elastomer, from the viewpoints of excellent ionic conductivity, reducing the voltage dependency of the volume resistivity of the belt, and improving the transferability of the toner image to the recording medium.

[0027] Examples of the conductive particles (conductive filler) contained in the base layer include carbon black such as ketjen black, oil furnace black, channel black, and acetylene black; metal particles such as aluminum and nickel; and metal oxide particles such as indium tin oxide, tin oxide, zinc oxide, titanium oxide, and yttrium oxide. Of these, carbon black is preferred as the conductive particles. The conductive particles may be used alone or in combination of two or more kinds.

[0028] The average primary particle size of the conductive particles (preferably carbon black) is preferably 1 nm or more and 500 nm or less, more preferably 5 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0029] The substrate layer may contain a conductive agent other than the conductive particles. Examples of conductive agents include ion-conductive substances such as potassium titanate, potassium chloride, sodium perchlorate, and lithium perchlorate; and ion-conductive polymers such as polyaniline, polyether, polypyrrole, polysulfone, and polyacetylene. The conductive agent other than the conductive particles may be used alone or in combination of two or more kinds.

[0030] The substrate layer is preferably a conductive elastic layer containing rubber and conductive particles, and more preferably a conductive elastic layer containing at least one of chloroprene rubber and epichlorohydrin rubber, and carbon black.

[0031] The total content of the conductive particles and conductive agent contained in the substrate layer is preferably set based on the volume resistivity of the entire belt as described above. When the substrate layer contains carbon black, the content of carbon black is preferably 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the elastic material.

[0032] The substrate layer may further contain additives such as a vulcanizing agent, a vulcanization aid, a vulcanization accelerator, a crosslinking agent, an antioxidant, a flame retardant, a colorant, a surfactant, a dispersant, and a filler. The resistivity can be adjusted by using an insulating or semiconductive filler such as zinc oxide or magnesium oxide as an additive.

[0033] From the viewpoint of the durability of the belt, the average thickness of the base material layer is preferably 50 μm or more, more preferably 75 μm or more, and even more preferably 100 μm or more, and from the viewpoint of the flexibility and flex resistance of the belt, it is preferably 1000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less.

[0034] <Surface layer and back layer> The surface layer is provided on the outer peripheral surface of the base material layer and constitutes the outer peripheral surface of the belt, and the back layer is provided on the inner peripheral surface of the base material layer and constitutes the inner peripheral surface of the belt.

[0035] Both the front and back layers are preferably layers containing a resin (base resin). Examples of the base resin include urethane resin, polyamide, polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyethersulfone, polyphenylsulfone, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polycarbonate, polyester, and mixed resins thereof.

[0036] However, from the viewpoint of improving adhesion to the base layer, it is preferable that the front surface layer and the back surface layer each contain a urethane resin. The urethane resin is generally synthesized by polymerizing a polyisocyanate and a polyol. The urethane resin preferably has a hard segment and a soft segment.

[0037] The front and back layers preferably contain a conductive filler. For example, by adjusting the amount of conductive filler contained in the surface layer and the back layer in each layer, the relationship between the volume resistivities of the surface layer, the base layer, and the back layer can be adjusted to fall within the above-mentioned range.

[0038] The conductive filler contained in the front and back layers may be the conductive particles (conductive filler) described above for the base layer. One type of conductive filler may be used alone, or two or more types may be used in combination. The average primary particle size of the conductive filler is also preferably within the range described above for the base layer.

[0039] The content of the conductive filler in each of the front and back layers is preferably 0.1% by mass to 8.0% by mass, and more preferably 0.5% by mass to 4.0% by mass. By setting the content of the conductive filler in each of the front and back layers within the above range, it is easy to control the volume resistivity of the entire belt within the above range, and image transfer performance is excellent.

[0040] The content of the conductive filler in the layer having the higher volume resistivity out of the front and back layers is preferably 0.1% by mass to 2.0% by mass, more preferably 0.3% by mass to 1.8% by mass. Furthermore, the content of the conductive filler in the layer having the lower volume resistivity out of the front and back layers is preferably 1.0% by mass or more and 8.0% by mass or less, and more preferably 1.5% by mass or more and 4.0% by mass or less. The content of the conductive filler in the layer having the higher volume resistivity out of the front and back layers is preferably less than the content of the conductive filler in the layer having the lower volume resistivity. By setting the conductive filler content in the layer with the higher volume resistivity of the front layer or back layer and the conductive filler content in the layer with the lower volume resistivity within the above ranges, the volume resistivity R1 of the front layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer can be set to satisfy the relationship in formula 1 or formula 2, resulting in excellent image transfer performance.

[0041] The front and back layers may contain a conductive agent other than the conductive filler, such as the conductive agents already described for the substrate layer.

[0042] The surface layer preferably contains particles of a resin having a siloxane bond (siloxane resin particles). The content of the resin particles having siloxane bonds in the surface layer is preferably 1.0% by mass or more and 20.0% by mass or less, and more preferably 2.0% by mass or more and 15.0% by mass or less, relative to the base resin. By including the resin particles having siloxane bonds in the surface layer at the above content, the transfer of residual toner (toner that remains on the intermediate transfer belt or image carrier without being transferred to the recording medium) to the surface of the transfer belt is suppressed, thereby suppressing contamination of the back surface of the recording medium.

[0043] Examples of the siloxane resin particles include resins having a polysiloxane structure in the main chain or side chain. Specific examples of siloxane resin particles include thermosetting silicone resin particles, silicone oil gum, silicone elastomer, and siloxane-modified polyetherimide particles.

[0044] Among these, the siloxane resin particles are preferably thermosetting silicone resin particles, as this component reduces the sliding resistance of the sliding surface and makes it easier to improve the maintenance of sliding resistance.

[0045] Here, the thermosetting silicone resin particles are silicone resin particles that are cured by heat to have rubber-like elasticity. The thermosetting silicone resin particles are preferably unmodified, since they have a high affinity with the lubricant and are therefore more likely to suppress an increase in the rotational torque of the belt. Silicone rubber is made by molding silicone oil with a molecular weight of 300,000 or more into pellets.

[0046] The average particle size of the siloxane resin particles is, for example, 0.1 μm to 10 μm, and from the viewpoint of improving the maintenance of sliding resistance, the average particle size is preferably 0.5 μm to 4 μm, and more preferably 1 μm to 3 μm.

[0047] The average particle size of the resin particles is measured as follows. A sample having a cut surface cut along the thickness direction of the belt to be measured is obtained. The cut surface of the sample is observed under an electron microscope, and the area value of the resin particles is determined by image analysis, and the circle-equivalent diameter is calculated from the area value. This calculation of the circle-equivalent diameter is performed for 100 resin particles. The 50% diameter (D50) of the volume-based cumulative frequency of the obtained circle-equivalent diameters is then taken as the average particle size of the resin particles.

[0048] The back surface layer also preferably contains particles of a resin having a siloxane bond (siloxane resin particles). The content of the particles of a resin having a siloxane bond in the back surface layer is preferably in the same range as the content in the front surface layer. When the back layer contains the resin particles having siloxane bonds at the above content, friction with the roll member that contacts the inside of the transfer belt is reduced.

[0049] The front and back layers may each further contain additives such as an antioxidant, a crosslinking agent, a flame retardant, a colorant, and a filler.

[0050] The average thickness of the front layer and the back layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, from the viewpoint of the durability of the belt, and is preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less, from the viewpoint of the flexibility and flex resistance of the belt.

[0051] The compositions of the front and back layers may be the same or different. The thickness of the front layer and the back layer may be the same or different.

[0052] [Belt manufacturing method] As a method for manufacturing a belt according to the present disclosure, for example, a manufacturing method may be mentioned in which a tubular member that will serve as a base layer is prepared, and a surface layer and a back layer are formed on the outer peripheral surface of the tubular member.

[0053] Methods for manufacturing tubular members include, for example, extrusion molding, in which a composition containing a polymeric material that serves as an elastic material and conductive particles (conductive filler) is melted and extruded through a die into a belt-like shape to solidify; injection molding, in which a composition containing a polymeric material and conductive particles is melted and placed in a belt-shaped mold to solidify; and coating molding, in which a composition containing a precursor or monomer of a polymeric material and conductive particles is applied to a core and solidified. Heating for the purpose of vulcanizing the rubber may be performed at an appropriate time during the molding process.

[0054] Methods for forming the surface layer and the back layer include, for example, applying a liquid composition containing a polymeric material that serves as a resin (base resin) and a conductive filler (which may further contain siloxane resin particles) to the outer or inner surface of a tubular member and solidifying it; applying a liquid composition containing a precursor or monomer of a polymeric material and a conductive filler (which may further contain siloxane resin particles) to the outer or inner surface of a tubular member and solidifying it; etc. To solidify the liquid composition, drying, heating, electron beam irradiation, or ultraviolet irradiation may be performed depending on the types of components.

[0055] <Belt unit> The belt unit according to the present disclosure includes a transfer belt and a plurality of rolls around which the transfer belt is stretched under tension, at least one of which is a drive roll that rotates the transfer belt, and is detachable from an image forming apparatus. Here, the belt according to the present disclosure described above is used as the transfer belt.

[0056] 3 is a schematic perspective view showing an example of a belt unit according to the present disclosure, in which a transfer belt is stretched over a plurality of roll members. As shown in FIG. 3, the belt unit 60 includes a transfer belt 50, a drive roll 62, and a support roll 64, and the transfer belt 50 is stretched across the drive roll 62 and the support roll 64 under tension (also referred to as "stretched" in this disclosure). The drive roll 62 is rotated by the power of a drive unit (not shown) connected to the drive roll 62. The transfer belt 50 and the support roll 64 are rotated by the rotation of the drive roll 62.

[0057] The belt unit 60 is incorporated into an electrophotographic image forming apparatus as a part of a transfer means and is suitable for use as a secondary transfer belt unit. In the belt unit, the number of roll members around which the transfer belt is stretched is not limited to two, but may be three or more.

[0058] <Image forming device> The image forming apparatus according to the present disclosure includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the charged surface of the image carrier, a developing unit that contains a developer containing toner and develops the electrostatic image formed on the surface of the image carrier using the developer to form a toner image, and a transfer unit that has a belt unit according to the present disclosure and transfers the toner image to a recording medium. The transfer unit has, for example, an intermediate transfer member, a primary transfer unit that transfers the toner image to the surface of the intermediate transfer member, and a secondary transfer unit that transfers the toner image transferred to the surface of the intermediate transfer member to a recording medium, the secondary transfer unit having the belt unit according to the present disclosure.

[0059] The image forming apparatus according to the present disclosure may further include a fixing unit that fixes the toner image transferred onto the surface of the recording medium, an image carrier cleaning unit that cleans the surface of the image carrier after the toner image is transferred but before it is charged, a discharging unit that irradiates the surface of the image carrier with discharging light after the toner image is transferred but before it is charged, etc. The image forming apparatus according to the present disclosure may have a cartridge structure (process cartridge) in which a portion including the developing unit is detachably attached to the image forming apparatus.

[0060] An example of an image forming apparatus according to the present disclosure will be described below, but the present disclosure is not limited to this example. In the following description, the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0061] FIG. 4 is a schematic diagram illustrating an example of an image forming apparatus according to the present disclosure. The image forming apparatus shown in Figure 4 includes first through fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K (image forming means) that output images in the colors yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side horizontally spaced apart by predetermined distances. These units 10Y, 10M, 10C, and 10K may be process cartridges that are detachably attached to the image forming apparatus.

[0062] An intermediate transfer belt (an example of an intermediate transfer body) 20 extends above each of the units 10Y, 10M, 10C, and 10K and passes through each unit. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24, which are in contact with the inner surface of the intermediate transfer belt 20, and runs in a direction from the first unit 10Y to the fourth unit 10K. A force is applied to the support roll 24 by a spring or the like (not shown) in a direction away from the drive roll 22, and tension is applied to the intermediate transfer belt 20 wound around them. An intermediate transfer belt cleaning device 30 is provided on the image bearing surface side of the intermediate transfer belt 20, facing the drive roll 22.

[0063] The developing devices (examples of developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with yellow, magenta, cyan, and black toner contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

[0064] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration and operation, we will explain here the first unit 10Y, which forms a yellow image and is arranged upstream in the direction of travel of the intermediate transfer belt.

[0065] The first unit 10Y has a photoconductor (an example of an image carrier) 1Y. Around the photoconductor 1Y, there are arranged in this order: a charging roll (an example of a charging means) 2Y that charges the surface of the photoconductor 1Y to a predetermined potential; an exposure device (an example of an electrostatic image forming means) 3 that exposes the charged surface to a laser beam 3Y based on a color-separated image signal to form an electrostatic image; a developing device (an example of a developing means) 4Y that supplies charged toner to the electrostatic image to develop it; a primary transfer roll (an example of a primary transfer means) 5Y that transfers the developed toner image onto the intermediate transfer belt 20; and a photoconductor cleaning device 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer.

[0066] The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is provided at a position facing the photosensitive member 1Y. A bias power supply (not shown) that applies a primary transfer bias is connected to the primary transfer rolls 5Y, 5M, 5C, and 5K of each unit.

[0067] The belt unit 60 is a belt unit equipped with a transfer belt 50 (one example of a belt according to the present disclosure). The belt unit 60 includes the transfer belt 50, a drive roll 62, and a support roll 64. The belt unit 60 is disposed outside the intermediate transfer belt 20, and is provided at a position facing the support roll 24. A bias power supply (not shown) that applies a secondary transfer bias is connected to the belt unit 60.

[0068] The operation of forming a yellow image in the first unit 10Y will be described below. First, prior to operation, the surface of the photosensitive member 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has conductivity (for example, a volume resistivity of 1×10 at 20°C). -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate with a resistivity of Ωcm or less. This photosensitive layer normally has a high resistance (the resistance of ordinary resins), but when irradiated with a laser beam, the resistivity of the irradiated portion changes. Therefore, the exposed surface of the photosensitive element 1Y is irradiated with a laser beam 3Y from the exposure device 3 in accordance with image data for yellow sent from a control unit (not shown). This forms an electrostatic charge image of a yellow image pattern on the surface of the photosensitive element 1Y.

[0069] An electrostatic image is an image formed on the surface of the photosensitive element 1Y by charging it; the laser beam 3Y reduces the resistivity of the irradiated portion of the photosensitive layer, causing the charged charges on the surface of the photosensitive element 1Y to flow, while the charges remain in the portions not irradiated by the laser beam 3Y, forming a so-called negative latent image. The electrostatic image formed on the photoreceptor 1Y rotates to a predetermined development position as the photoreceptor 1Y moves, and at this development position, the electrostatic image on the photoreceptor 1Y is developed into a toner image by the developing device 4Y and made visible.

[0070] The developing device 4Y contains an electrostatic image developer containing, for example, at least yellow toner and a carrier. The yellow toner is frictionally charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoreceptor 1Y. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. The photoreceptor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1Y is transported to a predetermined primary transfer position.

[0071] When the yellow toner image on the photoreceptor 1Y is transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y acts on the toner image, causing the toner image on the photoreceptor 1Y to be transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the (-) polarity of the toner, and is controlled to, for example, +10 μA by a control unit (not shown) in the first unit 10Y.

[0072] The primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K of the second unit 10M and subsequent units is also controlled in accordance with the first unit. In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed sequentially through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are superimposed and transferred.

[0073] The intermediate transfer belt 20, onto which the four color toner images have been multiplex-transferred through the first to fourth units, reaches a secondary transfer section made up of the intermediate transfer belt 20, a support roll 24, and a belt unit 60. Meanwhile, recording paper (an example of a recording medium) P is fed at a predetermined timing via a supply mechanism into the gap between the belt unit 60 and the intermediate transfer belt 20, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a negative polarity, the same as the negative polarity of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, causing the toner image on the intermediate transfer belt 20 to be transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) that detects the resistance of the secondary transfer section, and is voltage-controlled.

[0074] The recording paper P onto which the toner image has been transferred is sent to the pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (an example of a fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image. After the color image has been fixed, the recording paper P is conveyed toward the discharge portion, and the series of color image forming operations is completed.

[0075] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copiers, printers, etc. In addition to the recording paper P, examples of the recording medium include overhead projector sheets and the like. [Example]

[0076] The present embodiment will be described in more detail below by way of examples, but the present embodiment is not limited to the following examples. Synthesis, processing, production, etc. were carried out at room temperature (24°C ± 3°C) unless otherwise specified. In the following description, all "parts" and "%" are by mass unless otherwise specified.

[0077] Example 1 [Preparation of base layer] Chloroprene rubber (CR) (Tosoh Corporation, TSR-61) 100 parts Carbon black (Mitsubishi Chemical Corporation, #3030B) 25 parts 1 part sulfur (Bayer, Rhenogran S-80) Zinc oxide (Bayer, Rhenogran ZnO-80) 6 parts Magnesium oxide (Kyowa Chemical Industry Co., Ltd., Kyowamag 150) 4 parts Vulcanization accelerator (Ouchi Shinko Chemical Industry Co., Ltd., Noccela M) 1 part 0.5 parts stearic acid The above materials were mixed, placed in a kneading extruder, extrusion-molded, dried with hot air, and further heated for vulcanization to obtain a tubular member with a diameter (outer diameter) of 40 mm and an average thickness of 450 μm. The tubular member was cut to a length of 355 mm to form the base layer A.

[0078] [Preparation of surface layer and back layer] 1% by mass of a curing agent (Loctite WH-1, Henkel Japan) was added to a PTFE (polytetrafluoroethylene)-containing urethane resin (Bonderite T862A, Henkel Japan), and the mixture was diluted with water to adjust the PTFE content to 10% by mass. To this, 0.5% by mass of a conductive agent (carbon black, Mitsubishi Chemical Corporation, #3030B) and 10.0% by mass of silicone resin particles (Shin-Etsu Chemical Co., Ltd., KMP-590, average particle size = 2 μm) were added and kneaded to form a coating liquid for the surface layer. Furthermore, the amount of conductive agent (carbon black, Mitsubishi Chemical Corporation, #3030B) in the surface layer coating liquid was changed to 2.0 mass %, and this was used as the back layer coating liquid.

[0079] While rotating the base layer A with its central axis oriented horizontally, the surface layer coating liquid was sprayed onto the outer circumferential surface of the base layer A. The surface layer was then dried with hot air at 150°C for 35 minutes to form a surface layer with an average thickness of 15 μm. Next, the back surface layer coating liquid was sprayed onto the inner peripheral surface of the base layer A, and similarly dried with hot air to form a back surface layer. The average thickness of the back surface layer was 15 μm. In this way, an endless belt was obtained.

[0080] <Examples 2 to 4> An endless belt was obtained in the same manner as in Example 1, except that the amount of conductive agent (carbon black) in the surface layer and back layer was changed to the amount shown in Table 1, and the amount of conductive agent (carbon black) in the base layer was changed so that the volume resistivity R2 in the base layer was the value shown in Table 1.

[0081] <Example 5> An endless belt was obtained in the same manner as in Example 4, except that silicone resin particles were not added to the front and back layers.

[0082] <Comparative Example 1> [Preparation of base layer] 100 parts EPDM rubber (Mitsui Chemicals, Inc., product name: EPM3045) Carbon black (Mitsubishi Chemical Corporation, #3030B) 20 parts The above materials were mixed with various additives, placed in a kneading extruder, extruded, dried with hot air, and further heated for vulcanization to obtain a tubular member with a diameter (outer diameter) of 40 mm and an average thickness of 450 μm. The tubular member was cut to a length of 355 mm to form the base layer B.

[0083] [Preparation of surface layer and back layer] In Example 1, the surface layer and the back layer were formed in the same manner as in Example 1, except that the amount of conductive agent (carbon black) in the surface layer and the back layer was the amount shown in Table 1 and no silicone resin particles were added. In this way, an endless belt of Comparative Example 1 was obtained.

[0084] <Comparative Example 2> [Preparation of base layer] 100 parts polyamide resin (UBE Corporation, product name: UBESTA) Carbon black (Mitsubishi Chemical Corporation, #3030B) 15 parts The above materials were mixed and subjected to hot-melt tubular extrusion using an extruder at an extrusion temperature of 220° C. to obtain a tubular member having a diameter (outer diameter) of 40 mm and an average thickness of 450 μm. The tubular member was cut to a length of 355 mm to form a base layer C.

[0085] [Preparation of surface layer and back layer] In Example 1, the surface layer and the back layer were formed in the same manner as in Example 1, except that the amount of conductive agent (carbon black) in the surface layer and the back layer was the amount shown in Table 1 (i.e., no conductive agent was added) and silicone resin particles were not added. In this way, an endless belt of Comparative Example 2 was obtained.

[0086] <Comparative Examples 3 and 4> An endless belt was obtained in the same manner as in Example 1, except that the amount of conductive agent (carbon black) in the surface layer and back layer was changed to the amount shown in Table 1, and the amount of conductive agent (carbon black) in the base layer was changed so that the volume resistivity R2 in the base layer was the value shown in Table 1.

[0087] <Volume resistivity> The volume resistivity [log Ω] of the entire endless belt, the surface layer, the base layer, and the back layer was measured according to the method described above. The results are shown in Table 1.

[0088] <Evaluation> The endless belt obtained in each example was used as a transfer belt to prepare a secondary transfer belt unit. This secondary transfer belt unit was installed as a secondary transfer means in a modified image forming apparatus DocuColor-7171P (FUJIFILM Business Innovation Co., Ltd.), to obtain an image forming apparatus.

[0089] [Transferability] Using the above-mentioned image forming apparatus, in an environment of 10°C temperature and 10% humidity, and at an applied voltage of 8 kV, a recording medium (paper, A3 size, basis weight 82 g / m 2 A halftone image with an image density of 20% was continuously printed on 100 sheets of a 97 μm thick paper. The final 10 images were visually observed, and the transfer performance was evaluated according to the following criteria. -Evaluation index (transferability / density)- A (◎): No unevenness in transfer density was observed, and the density of the transferred image was 95% or more of the required image density. B (◯): No unevenness in transfer density was observed, and the density of the transferred image was 90% or more but less than 95% of the required image density. C(×): Uneven transfer density (i.e., an area where the transfer image density is lower than the surrounding area relative to the required image density) is confirmed, and the area where the transfer density is uneven is 5% or more and 20% or less of the image area. D(xx): Uneven transfer density is confirmed, and the area where the uneven transfer density occurs is more than 20% of the image area.

[0090] -Evaluation index (transferability / image history)- A (◎): Image history (i.e., the image from the previous cycle remaining on the intermediate transfer body as an afterimage on the image from the next cycle due to toner remaining on the intermediate transfer body from the previous cycle) is not observed either visually or with a CCD camera (100x magnification). B (〇): The image history can be observed with a CCD camera (100x magnification), but not with the naked eye. C(×): The image history is visually observed, and the visually observable image history area is 5% to 20% of the image area. D(xx): Image history is visually observed, and the area of ​​the image history that can be visually observed is more than 20% of the image area.

[0091] [Paper backside soiling] In addition, in the transferability test, the occurrence of stains on the back surface of the paper (recording medium) was visually confirmed and evaluated according to the following criteria. -Evaluation indicators- A (◎): No stains observed B (Good): Slight staining is observed, but the stained area is less than 5% of the image area. C (×): Staining is observed, and the stained area is 5% to 20% of the image area. D(xx): Stains are observed, and the stained area is more than 20% of the image area.

[0092] [Durability] Using the above-mentioned image forming apparatus, a recording medium (paper, A3 size, basis weight 82 g / m) 2 After forming half-tone images with an image density of 5% on a recording medium (97 μm thick) and transporting the recording medium 10,000 times in succession, 10 half-tone images with an image density of 20% were formed on the recording medium and the 10th image was visually observed. In addition, the endless belt after image formation was removed from the image forming apparatus, and the outer surface of the endless belt was observed visually or at 100x magnification using a CCD camera to check the surface condition (presence or absence of foreign matter). Based on these, the maintainability was evaluated according to the following indexes. -Evaluation indicators- A (◎): No abnormalities were found in the image or on the outer surface of the endless belt. B (〇): Irregularities are observed on the outer surface of the endless belt, but no abnormalities are seen in the image. C (×): Abnormalities are observed in the image, and irregularities are observed in an area of ​​5% to 20% of the outer surface of the endless belt. D(xx): Abnormalities are observed in the image, and irregularities are observed in more than 20% of the area of ​​the outer surface of the endless belt.

[0093] [Table 1]

[0094] The results shown in Table 1 show that the examples have superior transfer performance compared to the comparative examples.

[0095] Preferred aspects of the present disclosure will be described below. (((1))) The cushion has three layers: a surface layer, a base layer containing at least one elastic material selected from the group consisting of rubber and elastomer, and a back layer; A transfer belt, wherein the relationship between the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer in an environment of 25°C and 55% RH satisfies the following formula 1 or 2: Formula 1: R1>R2>R3 Formula 2: R1 <R2<R3 (((2))) The transfer belt according to (((1))), wherein the volume resistivity of the entire transfer belt in an environment of 25° C. and 55% RH is 8.0 log Ω or more and 11.0 log Ω or less. (((3))) The transfer belt according to (((2))), wherein the volume resistivity of the entire transfer belt in an environment of 25° C. and 55% RH is 8.5 log Ω or more and 10.0 log Ω or less. (((4))) The transfer belt according to any one of (((1))) to (((3))), wherein the difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and the difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are both 0.1 log Ω or more. (((5))) The transfer belt according to (((4))), wherein a difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and a difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are both 0.2 log Ω or more and 1.0 log Ω or less. (((6))) The transfer belt according to any one of (((1))) to (((5))), wherein the surface layer and the back layer each contain a conductive filler in the range of 0.1% by mass to 8.0% by mass. (((7))) The transfer belt according to (((6))), wherein the surface layer and the back layer each contain a conductive filler in the range of 0.5% by mass to 4.0% by mass. (((8))) the surface layer and the back surface layer contain a conductive filler, The transfer belt according to any one of (((1))) to (((7))), wherein the content of the conductive filler in the layer having a higher volume resistivity out of the front layer and the back layer is 0.1% by mass or more and 2.0% by mass or less, and the content of the conductive filler in the layer having a lower volume resistivity is 1.0% by mass or more and 8.0% by mass or less. (((9))) The transfer belt according to (((8))), wherein the content of the conductive filler in the layer having a higher volume resistivity out of the front layer and the back layer is 0.3% by mass or more and 1.8% by mass or less, and the content of the conductive filler in the layer having a lower volume resistivity is 1.5% by mass or more and 4.0% by mass or less. (((10))) The transfer belt according to any one of (((1))) to (((9))), wherein the base material layer contains at least one material selected from the group consisting of chloroprene rubber, epichlorohydrin rubber, and urethane elastomer as the elastic material. (((11))) the surface layer contains a base resin and particles of a resin having a siloxane bond, The transfer belt according to any one of (((1))) to (((10))), wherein the content of the resin particles having siloxane bonds relative to the base resin is 1.0% by mass or more and 20.0% by mass or less. (((12))) The transfer belt according to (((11))), wherein the content of the resin particles having siloxane bonds relative to the base resin is 2.0% by mass or more and 15.0% by mass or less. (((13))) The transfer belt according to any one of (((1))) to (((12))), a plurality of rolls around which the transfer belt is stretched under tension; Equipped with At least one of the plurality of rolls is a drive roll that rotates the transfer belt, A belt unit that is detachably attached to an image forming apparatus. (((14))) an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing means for storing a developer containing a toner and developing an electrostatic image formed on the surface of the image carrier using the developer to form a toner image; An image forming apparatus including the belt unit according to (((13))) and a transfer means for transferring the toner image onto a recording medium. (((15))) The transfer means is The image forming apparatus includes an intermediate transfer member, a primary transfer unit that transfers a toner image onto the surface of the intermediate transfer member, and a secondary transfer unit that transfers the toner image transferred onto the surface of the intermediate transfer member onto a recording medium, the secondary transfer unit has the belt unit; The image forming apparatus according to (((14))).

[0096] According to the invention (((1))), a transfer belt is provided that has superior image transfer performance compared to a transfer belt in which the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer do not satisfy either Formula 1 or Formula 2. According to the inventions (((2))) or (((3))), a transfer belt is provided that has superior image transfer performance compared to a transfer belt whose overall volume resistivity in an environment of 25°C and 55% RH is less than 8.0 log Ω or more than 11.0 log Ω. According to the inventions (((4))) or (((5))), a transfer belt is provided which has superior image transfer performance compared to a transfer belt in which at least one of the difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer and the difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer is less than 0.1 log Ω. According to the inventions (((6))) or (((7))), a transfer belt is provided which has superior image transfer performance compared to a transfer belt in which the content of conductive filler in at least one of the front layer and the back layer is less than 0.1 mass % or more than 8.0 mass %. According to the inventions (((8))) or (((9))), a transfer belt is provided which has superior image transfer performance compared to a transfer belt in which the conductive filler content in the layer having a higher volume resistivity out of the front and back layers is less than 0.1 mass % or more than 2.0 mass %, and a transfer belt in which the conductive filler content in the layer having a lower volume resistivity is less than 1.0 mass % or more than 8.0 mass %. According to the invention (((10))), a transfer belt is provided which has superior image transfer performance compared to a transfer belt whose base layer contains only EPDM rubber or polyamide as an elastic material. According to the invention of (((11))) or (((12))), a transfer belt is provided in which contamination on the back surface of a recording medium is suppressed compared to a transfer belt in which the content of resin particles having siloxane bonds relative to the base resin in the surface layer is less than 1.0 mass % or more than 20.0 mass %. According to the invention (((13))), a belt unit is provided that has superior image transfer performance compared to a transfer belt having a surface layer volume resistivity R1, a base layer volume resistivity R2, and a back layer volume resistivity R3 that do not satisfy either formula 1 or formula 2. According to the inventions (((14))) or (((15))), an image forming apparatus is provided that has superior image transfer performance compared to a case where the transfer belt has a surface layer volume resistivity R1, a base layer volume resistivity R2, and a back layer volume resistivity R3 that do not satisfy either formula 1 or formula 2. [Explanation of symbols]

[0097] 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K Charging roll (an example of charging means) 3. Exposure device (an example of an electrostatic image forming means) 3Y, 3M, 3C, 3K laser beam 4Y, 4M, 4C, 4K developing device (an example of developing means) 5Y, 5M, 5C, 5K Primary transfer roll (an example of a primary transfer means) 6Y, 6M, 6C, 6K Photoconductor Cleaning Device 8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K image forming units 20 Intermediate transfer belt (an example of an intermediate transfer body) 22 Drive Roll 24 Support Roll 28 Fixing device (an example of fixing means) 30 Intermediate transfer belt cleaning device 50 Transfer belt 52 Base material layer 54 Surface layer 56 Back layer 60 Belt unit 62 Drive Roll 64 Support Roll P Recording paper (an example of a recording medium)

Claims

1. The cushion has three layers: a surface layer, a base layer containing at least one elastic material selected from the group consisting of rubber and elastomer, and a back layer; A transfer belt, wherein the relationship among the volume resistivity R1 of the surface layer, the volume resistivity R2 of the base layer, and the volume resistivity R3 of the back layer in an environment of 25°C and 55% RH satisfies the following formula 1 or 2: Formula 1: R1>R2>R3 Formula 2: R1<R2<R3

2. 2. The transfer belt according to claim 1, wherein the volume resistivity of the entire transfer belt in an environment of 25° C. and 55% RH is 8.0 log Ω or more and 11.0 log Ω or less.

3. 3. The transfer belt according to claim 2, wherein the volume resistivity of the entire transfer belt in an environment of 25° C. and 55% RH is 8.5 log Ω or more and 10.0 log Ω or less.

4. 2. The transfer belt according to claim 1, wherein a difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and a difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are both 0.1 log Ω or more.

5. 5. The transfer belt according to claim 4, wherein a difference between the volume resistivity R1 of the surface layer and the volume resistivity R2 of the base layer, and a difference between the volume resistivity R2 of the base layer and the volume resistivity R3 of the back layer are both 0.2 log Ω or more and 1.0 log Ω or less.

6. 2. The transfer belt according to claim 1, wherein the surface layer and the back layer each contain a conductive filler in a range of 0.1% by mass to 8.0% by mass.

7. 7. The transfer belt according to claim 6, wherein the surface layer and the back layer each contain a conductive filler in the range of 0.5% by mass to 4.0% by mass.

8. the surface layer and the back surface layer contain a conductive filler, 2. The transfer belt according to claim 1, wherein the conductive filler content in the layer having a higher volume resistivity out of the front layer and the back layer is 0.1% by mass or more and 2.0% by mass or less, and the conductive filler content in the layer having a lower volume resistivity is 1.0% by mass or more and 8.0% by mass or less.

9. 9. The transfer belt according to claim 8, wherein the conductive filler content in the layer having a higher volume resistivity out of the front layer and the back layer is 0.3% by mass or more and 1.8% by mass or less, and the conductive filler content in the layer having a lower volume resistivity is 1.5% by mass or more and 4.0% by mass or less.

10. 2. The transfer belt according to claim 1, wherein the base layer contains, as the elastic material, at least one selected from the group consisting of chloroprene rubber, epichlorohydrin rubber, and urethane elastomer.

11. the surface layer contains a base resin and particles of a resin having a siloxane bond, 2. The transfer belt according to claim 1, wherein the content of the resin particles having siloxane bonds relative to the base resin is 1.0% by mass or more and 20.0% by mass or less.

12. 12. The transfer belt according to claim 11, wherein a content of the resin particles having a siloxane bond relative to the base resin is 2.0% by mass or more and 15.0% by mass or less.

13. The transfer belt according to any one of claims 1 to 12, a plurality of rolls around which the transfer belt is stretched under tension; Equipped with At least one of the plurality of rolls is a drive roll that rotates the transfer belt, A belt unit that is detachably attached to an image forming apparatus.

14. an image carrier; a charging means for charging the surface of the image carrier; an electrostatic image forming means for forming an electrostatic image on the charged surface of the image carrier; a developing means for storing a developer containing a toner and developing an electrostatic image formed on the surface of the image carrier using the developer to form a toner image; An image forming apparatus comprising the belt unit according to claim 13 and a transfer unit that transfers the toner image onto a recording medium.

15. The transfer means is The image forming apparatus includes an intermediate transfer member, a primary transfer unit that transfers a toner image onto the surface of the intermediate transfer member, and a secondary transfer unit that transfers the toner image transferred onto the surface of the intermediate transfer member onto a recording medium, the secondary transfer unit has the belt unit; The image forming apparatus according to claim 14.

Images