Endless belt, belt unit and image forming apparatus

Abstract

To provide an endless belt that stably makes a rotary motion for a long period.SOLUTION: An endless belt has a base material layer containing high polymer material and conductive particles. In measurement of the dynamic viscoelasticity of the base material layer at a temperature of 35°C, the value of loss tangent within the measuring frequencies of 0.1 Hz to 10 Hz is smaller than the value of loss tangent within the measuring frequencies of 10 Hz to 100 Hz. The tensile stress when the base material layer is elongated by 5% at a temperature of 24°C is 7 MPa or more, and when the base material layer is elongated by 5% at a temperature of 24°C and held for 10 minutes, the maximum value TSmax and the minimum value TSmin of the tensile stress during that time satisfy {(TSmax-TSmin) / TSmax×100}≤15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure provides an endless belt, a belt unit, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a belt conveying device that includes a circular belt that exhibits viscoelasticity and has a peak frequency in the frequency characteristics of its loss tangent, a drive unit that rotates the circular belt, and a stress applying unit that applies tensile stress to the circular belt, and in which the stress applying frequency, which is the frequency of the tensile stress that is periodically applied to the circular belt as the circular belt rotates, is equal to or lower than the peak frequency of the circular belt. Patent Document 2 discloses an endless belt having a substrate and a surface layer, in which, when the peak temperature of the loss tangent of the surface layer is T (°C), the loss tangent of the surface layer is 0.7 or more and 1.0 or less at a temperature between T°C and T+70°C. Patent Document 3 discloses a semiconductive rubber belt having a tension force attenuation rate of less than 50% calculated by a logarithmic approximation formula obtained from test results in which the belt was stretched by 5% for 30 days using a biaxial tension roll at 25°C±2°C and 55%±5% RH. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-122968 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-197579 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-177802 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide an endless belt that rotates stably over a long period of time, compared to an endless belt that does not satisfy the relationship that, in dynamic viscoelasticity measurement of the base layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz; an endless belt in which the tensile stress when the base layer is stretched by 5% at a temperature of 24°C is less than 7 MPa; or an endless belt in which the difference between the maximum tensile stress TSmax and the minimum tensile stress TSmin when the base layer is stretched by 5% at a temperature of 24°C and maintained for 10 minutes satisfies {(TSmax - TSmin) / TSmax × 100} > 15. [Means for solving the problem]

[0005] Specific means for solving the above problems include the following aspects. <1> a substrate layer containing a polymer material and conductive particles; In a dynamic viscoelasticity measurement of the base material layer at a temperature of 35°C, the loss tangent value at a measurement frequency of 0.1 Hz to 10 Hz is smaller than the loss tangent value at a measurement frequency of 10 Hz to 100 Hz, An endless belt in which the base material layer has a tensile stress of 7 MPa or more when stretched by 5% at a temperature of 24°C, and when the base material layer is stretched by 5% at a temperature of 24°C and held for 10 minutes, the maximum value TSmax and minimum value TSmin of the tensile stress during that period satisfy {(TSmax-TSmin) / TSmax×100}≦15. <2> The tensile stress of the base material layer when stretched by 5% at a temperature of 24°C is 7 MPa or more and 10 MPa or less. <1> The endless belt described in <3> When the base layer is stretched by 5% at a temperature of 24°C and held for 10 minutes, the maximum value TSmax and minimum value TSmin of the tensile stress during that period satisfy {(TSmax-TSmin) / TSmax×100}≦10. <1> or <2> The endless belt described in <4> Further comprising a protective layer provided on at least one of the outer peripheral surface and the inner peripheral surface of the base material layer. <1> ~ <3> 10. The endless belt according to claim 9, <5> <1> ~ <4> and a plurality of roll members around which the endless belt is stretched under tension, at least one of the plurality of roll members being a drive roll that rotates the endless belt, the belt unit being detachably attached to an image forming apparatus. <6> a photoreceptor, charging means for charging the surface of the photoreceptor, electrostatic image forming means for forming an electrostatic image on the charged surface of the photoreceptor, and developing means for containing a developer containing toner and for developing the electrostatic image formed on the surface of the photoreceptor using the developer to form a toner image; <5> and a transfer unit that transfers the toner image onto a recording medium. <7> The transfer means includes an intermediate transfer body, a primary transfer means for transferring the toner image onto the surface of the intermediate transfer body, and a secondary transfer means for transferring the toner image transferred onto the surface of the intermediate transfer body onto a recording medium, and the secondary transfer means <5> a belt unit according to claim 1, <6> 2. The image forming apparatus according to claim 1 . [Effects of the Invention]

[0006] <1> or <4> According to the method described above, an endless belt is provided which rotates stably for a long period of time, compared to an endless belt which does not satisfy the relationship that, in dynamic viscoelasticity measurement of the base layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz, an endless belt in which the tensile stress when the base layer is stretched by 5% at a temperature of 24°C is less than 7 MPa, or an endless belt in which the difference between the maximum value TSmax and the minimum value TSmin of the tensile stress when the base layer is stretched by 5% at a temperature of 24°C and maintained for 10 minutes satisfies {(TSmax-TSmin) / TSmax×100}>15. <2> According to this, an endless belt is provided that rotates stably for a long period of time, compared to an endless belt having a base layer with a tensile stress of less than 7 MPa or more than 10 MPa when stretched by 5% at a temperature of 24°C. <3> According to this, an endless belt that rotates stably for a long period of time is provided, compared to an endless belt that satisfies {(TSmax-TSmin) / TSmax×100}>10. <5> According to the above, a belt unit is provided in which the endless belt rotates stably for a long period of time, compared to an endless belt that does not satisfy the relationship that, in dynamic viscoelasticity measurement of the base layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz, an endless belt in which the tensile stress when the base layer is stretched by 5% at a temperature of 24°C is less than 7 MPa, or an endless belt in which the maximum value TSmax and minimum value TSmin of the tensile stress when the base layer is stretched by 5% at a temperature of 24°C and maintained for 10 minutes satisfy {(TSmax-TSmin) / TSmax×100}>15. <6> or <7> According to the method, an image forming apparatus is provided in which the endless belt rotates stably for a long period of time, compared to an image forming apparatus equipped with an endless belt that does not satisfy the relationship that, in dynamic viscoelasticity measurement of the base layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz, an endless belt in which the tensile stress when the base layer is stretched by 5% at a temperature of 24°C is less than 7 MPa, or an endless belt in which the maximum value TSmax and minimum value TSmin of the tensile stress when the base layer is stretched by 5% at a temperature of 24°C and maintained for 10 minutes satisfy {(TSmax-TSmin) / TSmax×100}>15. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic perspective view illustrating an example of an endless belt according to an embodiment of the present invention. [Figure 2] 10 is a graph showing an example of the results of dynamic viscoelasticity measurement of a base material layer, illustrating the relationship between measurement frequency and loss tangent. [Figure 3] FIG. 2 is a schematic perspective view illustrating an example of a belt unit according to the present embodiment. [Figure 4] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008]

[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.

[0009] 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.

[0010] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0011] 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.

[0012] 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.

[0013] <Endless belt> The endless belt according to the present embodiment has a base layer containing a polymer material and conductive particles. The endless belt according to the present embodiment may have a protective layer on at least one of the outer circumferential surface and the inner circumferential surface of the base layer.

[0014] Fig. 1 is a schematic perspective view showing an example of an endless belt according to the present embodiment. The endless belt 50 shown in Fig. 1 has a base material layer 52, a protective layer 54, and a protective layer 56. The protective layer 54 is provided on the outer peripheral surface of the base material layer 52 and constitutes the outer peripheral surface of the endless belt 50. The protective layer 56 is provided on the inner peripheral surface of the base material layer 52 and constitutes the inner peripheral surface of the endless belt 50.

[0015] The endless belt according to the present embodiment is incorporated into an electrophotographic image forming apparatus as a part of a transfer unit and used as, for example, a secondary transfer belt or an intermediate transfer belt.

[0016] In the dynamic viscoelasticity measurement of the base material layer of the endless belt according to the present embodiment at a temperature of 35°C, the loss tangent value at a measurement frequency of 0.1 Hz to 10 Hz is smaller than the loss tangent value at a measurement frequency of 10 Hz to 100 Hz, The tensile stress when stretched 5% at a temperature of 24°C is 7 MPa or more, and when stretched 5% at a temperature of 24°C ± 3°C and held for 10 minutes, the maximum value TSmax and minimum value TSmin of the tensile stress during that period satisfy {(TSmax - TSmin) / TSmax × 100} ≦ 15.

[0017] FIG. 2 is an example of the results of dynamic viscoelasticity measurement of the substrate layer at a temperature of 35° C., and is a graph showing the relationship between measurement frequency and loss tangent. The solid line graph shows an example of a base material layer of the endless belt according to this embodiment, in which the loss tangent value at measurement frequencies from 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies from 10 Hz to 100 Hz. The dashed line graph shows an example of a base material layer of a conventional endless belt. In this example, the loss tangent values ​​at a measurement frequency of 0.1 Hz and at a measurement frequency of 1 Hz are larger than the loss tangent value at a measurement frequency of 10 Hz. Therefore, this example does not satisfy the requirement that the loss tangent value at a measurement frequency of 0.1 Hz to 10 Hz be smaller than the loss tangent value at a measurement frequency of 10 Hz to 100 Hz.

[0018] The endless belt according to this embodiment identifies the mechanical properties of the base material layer by loss tangent and tensile stress, and rotates stably over a long period by controlling these values. The mechanism is presumed as follows.

[0019] In the dynamic viscoelasticity measurement of the base material layer at a temperature of 35°C, if the requirement that the loss tangent values from a measurement frequency of 0.1 Hz to 10 Hz are smaller than the loss tangent values from a measurement frequency of 10 Hz to 100 Hz is not satisfied (for example, the loss tangent value at a measurement frequency of 0.1 Hz is larger than the loss tangent value at a measurement frequency of 10 Hz; the loss tangent value at a measurement frequency of 1 Hz is larger than the loss tangent value at a measurement frequency of 10 Hz), the endless belt continuously receives an external load due to extensional deformation during rotation, resulting in stress changes (stress relaxation), and residual strain and / or permanent strain tend to increase. Then, the low adhesion of the endless belt in a dynamic state reduces the adhesion to the conveyed medium (i.e., the recording medium) and / or the followability to the surface of the conveyed medium. Also, if the above requirement is not satisfied, the endless belt tends to receive vibrations from the driving device that rotates the endless belt, and the rotation speed of the endless belt tends to fluctuate and the endless belt tends to vibrate. From this perspective, the base material layer of the endless belt of this embodiment shall satisfy the requirement that the loss tangent values from a measurement frequency of 0.1 Hz to 10 Hz are smaller than the loss tangent values from a measurement frequency of 10 Hz to 100 Hz in the dynamic viscoelasticity measurement at a temperature of 35°C.

[0020] In the dynamic viscoelasticity measurement of the base material layer at a temperature of 35°C, it is preferable that the loss tangent value tanδ(0.1) at a measurement frequency of 0.1 Hz, the loss tangent value tanδ(1) at a measurement frequency of 1 Hz, the loss tangent value tanδ(10) at a measurement frequency of 10 Hz, and the loss tangent value tanδ(100) at a measurement frequency of 100 Hz satisfy the relationship of tanδ(0.1) < tanδ(1) < tanδ(10) < tanδ(100).

[0021] If the tensile stress of the base material layer is less than 7 MPa when stretched by 5% at a temperature of 24°C, the desired tension cannot be obtained when the endless belt is tensioned, and the endless belt may not be able to hold the transported medium (i.e., recording medium) well, or the rotation accuracy of the endless belt may not be sufficient. From this perspective, the base material layer of the endless belt of this embodiment has a tensile stress of 7 MPa or more when stretched by 5% at a temperature of 24°C. This value is preferably 10 MPa or less, from the viewpoint of allowing the endless belt to continue stable rotational motion without stretching even when tensioned for a long period of time.

[0022] When the base layer is stretched 5% at 24°C and held for 10 minutes, if the ratio {(TSmax-TSmin) / TSmax×100}, where TSmax is the maximum value and TSmin is the minimum value of the tensile stress during that time, exceeds 15, the endless belt may not be able to hold the conveyed medium (i.e., the recording medium) well, and sufficient conveyance accuracy of the conveyed medium may not be achieved. Furthermore, if {(TSmax-TSmin) / TSmax×100} exceeds 15, excessive tensile stress is generated in the endless belt due to tension changes accompanying rotation of the wrap portion around the roll member on which the endless belt is stretched, and shear forces due to compression and shear deformation in the nip portion between the endless belt and the opposing member when the rotational motion stops and starts (i.e., when mechanical stress occurs), resulting in a decrease in the adhesion of the endless belt to the conveyed medium, a decrease in the mechanical properties of the endless belt, and increased damage to the surface layer of the endless belt. From this viewpoint, the base material layer of the endless belt of the present embodiment has a value of {(TSmax-TSmin) / TSmax×100} equal to or less than 15, preferably equal to or less than 10, and more preferably equal to or less than 5. The value of {(TSmax-TSmin) / TSmax×100} is preferably as low as possible.

[0023] The dynamic viscoelasticity of the substrate layer is measured as follows. A base layer, which is the material used to manufacture an endless belt, is prepared, or the base layer is prepared by peeling off layers other than the base layer from an endless belt. The base layer is cut into a 20 mm x 4 mm rectangle, which is used as a test piece. The long side of the test piece is aligned with the direction of rotation of the endless belt. The test pieces are prepared at 5 equally spaced locations across the width of the endless belt (i.e., evenly from near one end to near the other end) and 4 equally spaced locations around the circumference, for a total of 20 locations. Measurements are taken using a dynamic viscoelasticity measuring device, with the measurement environment temperature at 24°C ± 3°C and relative humidity at 55 ± 5%, and the temperature inside the measuring section of the device maintained at 35°C. Dynamic viscoelasticity measurements are taken in tension mode, with the storage modulus E' and loss modulus E'' measured at frequencies from 0.1 Hz to 100 Hz, and the loss tangent (tanδ = E'' / E') calculated. A graph showing the relationship between measurement frequency (Hz) and loss tangent (tanδ) is drawn, and if, for 18 or more of the 20 test pieces, the loss tangent value at frequencies from 0.1 Hz to 10 Hz is smaller than the loss tangent value at frequencies from 10 Hz to 100 Hz, this requirement is considered to be met. The loss tangent value at a particular measurement frequency is calculated by arithmetically averaging the values ​​of 20 test pieces.

[0024] For the dynamic viscoelasticity of the base layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz can be made smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz by increasing the elastic region of the substrate part of the base layer and improving uniformity. Increasing the elastic region of the substrate part of the base layer and improving uniformity can be achieved, for example, by reducing the amount of granular reinforcing material such as carbon black or inorganic particles added to an elastic material such as rubber when manufacturing the base layer.

[0025] The tensile stress of the substrate layer is measured as follows. A base layer, which is the material used to manufacture an endless belt, is prepared, or the base layer is prepared by peeling off layers other than the base layer from an endless belt. The base layer is cut into a 20 mm x 4 mm rectangle, which is used as a test piece. The long side of the test piece is aligned with the direction of rotation of the endless belt. The test pieces are prepared at 5 equally spaced locations across the width of the endless belt (i.e., evenly from near one end to near the other end) and 4 equally spaced locations around the circumference, for a total of 20 locations. Using a tensile testing machine, the test piece is stretched 5% at a tensile speed of 1 mm / min under a measurement environment temperature of 24°C ± 3°C and a relative humidity of 55 ± 5%. The tensile stress at 5% stretch is the "tensile stress at 5% elongation." The test piece is stretched 5% and held at 5% elongation for 10 minutes; the maximum tensile stress value over the 10 minutes is "TSmax" and the minimum value is "TSmin." A tensile test is performed on 20 test pieces, and the 20 tensile stress measurements are calculated as an arithmetic average.

[0026] The tensile stress of the base layer when stretched 5% at 24°C of 7 MPa or more and {(TSmax-TSmin) / TSmax×100}≦15 can be achieved by increasing the elasticity of the substrate portion of the base layer and increasing the vulcanization density of the substrate portion. Increasing the elasticity of the substrate portion of the base layer can be achieved, for example, by mixing a polymer with an elastic material such as rubber when producing the base layer. Increasing the vulcanization density of the substrate portion of the base layer can be achieved, for example, by adding a larger amount of vulcanizing agent, vulcanization aid, and / or vulcanization accelerator when producing the base layer.

[0027] The layer structure and materials of the endless belt according to this embodiment will be described in detail below.

[0028] [Base material layer] The substrate layer is preferably a film or sheet made of a polymer material containing conductive particles.

[0029] Examples of polymeric materials include rubber and resin, and one type of polymeric material may be used alone, or two or more types may be used in combination.

[0030] Examples of rubber include chloroprene rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber, polyurethane, 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.

[0031] Examples of the resin include polyamide, polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyethersulfone, polyphenylsulfone, polysulfone, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polycarbonate, polyester, and mixed resins thereof.

[0032] Examples of conductive particles 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. Carbon black is preferred as the conductive particles. One type of conductive particle may be used alone, or two or more types may be used in combination.

[0033] The average primary particle size of the conductive particles 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 9 nm or more and 25 nm or less.

[0034] The substrate layer may contain a conductive agent other than conductive particles. Examples of the conductive agent 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. One type of conductive agent may be used alone, or two or more types may be used in combination.

[0035] 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.

[0036] The total content of the conductive particles and conductive agent contained in the base material layer is preferably set based on the volume resistivity of the endless belt. 4 Ω cm or more 1.0×10 12 It is preferable that the resistivity is Ω·cm or less. In this embodiment, the volume resistivity (Ω·cm) is measured as follows. The measurement environment is a temperature of 22°C and a relative humidity of 55%. The sample is left in the measurement environment for at least 24 hours, with the temperature and humidity regulated. The resistance measurement device is a microcurrent meter (R8430A manufactured by Advantest Corporation), and the probe is a UR probe (manufactured by Mitsubishi Chemical Corporation). The applied voltage is 1 kV, the application time is 5 seconds, and the load is 1 kgf. The measurement points are 6 equally spaced points around the circumference of the endless belt, and 3 points in the center and both ends across the width of the endless belt, for a total of 18 points. The measured values ​​at 18 points are arithmetically averaged.

[0037] 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 polymer material.

[0038] The substrate layer may 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.

[0039] From the viewpoint of the durability of the endless 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 bending resistance of the endless belt, it is preferably 1000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less.

[0040] [Protective layer] The endless belt according to the present embodiment may have a protective layer on at least one of the outer peripheral surface and the inner peripheral surface of the base layer, and preferably has a protective layer on the outer peripheral surface and the inner peripheral surface of the base layer. The protective layer provided on the outer peripheral surface of the base layer constitutes the outer peripheral surface of the endless belt. The protective layer provided on the inner peripheral surface of the base layer constitutes the inner peripheral surface of the endless belt.

[0041] The protective layer is preferably a film or sheet containing a polymeric material. Examples of polymeric materials include the rubbers and resins described above for the substrate layer.

[0042] The protective layer preferably contains a urethane resin and fluorine-containing resin particles. Urethane resins (also called polyurethanes or urethane rubbers) are generally synthesized by polymerizing polyisocyanate and polyol. The urethane resin preferably has a hard segment and a soft segment.

[0043] The fluorine-containing resin particles are preferably one or more of particles made of tetrafluoroethylene resin, trifluorochloroethylene resin, hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloroethylene resin, and copolymers thereof. Among these, tetrafluoroethylene resin particles are preferred as the fluorine-containing resin particles.

[0044] The average primary particle size of the fluorine-containing resin particles is preferably 10 nm or more and 500 nm or less, more preferably 50 nm or more and 300 nm or less, and even more preferably 80 nm or more and 200 nm or less.

[0045] The protective layer may contain additives such as antioxidants, crosslinking agents, flame retardants, colorants, and fillers.

[0046] The average thickness of the protective layer on one side of the base material 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 endless 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 bending resistance of the endless belt.

[0047] [Manufacturing method of endless belts] An example of a method for manufacturing an endless belt is a manufacturing method in which a tubular member that will serve as a base layer is prepared, and a protective layer is formed on the outer or inner circumferential surface of the tubular member.

[0048] Methods for producing the tubular member include, for example, extrusion molding, in which a composition containing a polymeric material and conductive particles 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.

[0049] The protective layer can be formed, for example, by applying a liquid composition containing a polymeric material and fluorine-containing resin particles to the outer or inner surface of a tubular member and solidifying it; by applying a liquid composition containing a precursor or monomer of a polymeric material and fluorine-containing 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.

[0050] <Belt unit> FIG. 3 is a schematic perspective view showing an example of a belt unit according to the present embodiment. The belt unit 60 is a schematic perspective view showing an endless belt stretched around a plurality of roll members. The belt unit 60 includes an endless belt 50, a drive roll 62, and a support roll 64, and has a configuration in which the endless belt 50 is stretched around the drive roll 62 and the support roll 64 under tension (also referred to as "tensioned" in this disclosure). The drive roll 62 rotates by the power of a drive unit (not shown) connected to the drive roll 62. The endless belt 50 and the support roll 64 rotate following the rotation of the drive roll 62.

[0051] The belt unit 60 is incorporated into an electrophotographic image forming apparatus as part of a transfer means and is suitable for use as a secondary transfer belt unit. The number of roll members around which the endless belt 50 is stretched in the belt unit 60 is not limited to two, and may be three or more.

[0052] <Image forming device> The image forming apparatus according to the present embodiment includes a photoconductor, a charging unit for charging the surface of the photoconductor, an electrostatic image forming unit for forming an electrostatic image on the charged surface of the photoconductor, a developing unit that contains a developer containing toner and develops the electrostatic image formed on the surface of the photoconductor using the developer to form a toner image, and a transfer unit that has a belt unit according to the present embodiment and transfers the toner image to a recording medium. The transfer unit includes, for example, an intermediate transfer member, a primary transfer member that transfers the toner image to the surface of the intermediate transfer member, and a secondary transfer member 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 embodiment.

[0053] The image forming apparatus according to this embodiment may further include a fixing unit that fixes the toner image transferred onto the surface of the recording medium, a photosensitive member cleaning unit that cleans the surface of the photosensitive member after the toner image is transferred but before it is charged, and a discharging unit that irradiates the surface of the photosensitive member with discharging light to discharge it after the toner image is transferred but before it is charged. The image forming apparatus according to this embodiment may have a cartridge structure (process cartridge) in which the portion including the developing unit is detachably attached to the image forming apparatus.

[0054] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. In the following description, the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0055] FIG. 4 is a schematic diagram showing an example of the configuration of an image forming apparatus according to the present embodiment. 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The first unit 10Y has a photoreceptor 1Y. Around the photoreceptor 1Y, there are arranged in this order: a charging roll (an example of a charging means) 2Y that charges the surface of the photoreceptor 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 an intermediate transfer belt 20; and a photoreceptor cleaning device 6Y that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer.

[0060] 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.

[0061] The belt unit 60 is a belt unit equipped with an endless belt 50 (an example of an endless belt according to this embodiment). The belt unit 60 includes the endless 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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]

[0070] 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.

[0071] Example 1 [Preparation of base layer] After mixing and kneading the rubber material with fillers, plasticizers, softeners, etc., sulfur, vulcanization accelerators, etc., the mixture was extruded into a tube having a predetermined inner circumference and thickness using an extruder to produce a circular belt. Specifically, the rubber composition of the following rubber compounding 1 was prepared.

[0072] -Rubber compound 1- 80 parts of chloroprene rubber (CR) (Tosoh, TSR-61) 20 parts ethylene-propylene-diene rubber (EPDM) (Sumitomo Chemical, Esprene 505) Carbon black (Mitsubishi Chemical, #3030B) 25 parts 1 part sulfur (Bayer, Rhenogran S-80) Zinc oxide (Bayer, Rhenogran ZnO-80) 6 parts Magnesium oxide (Kyowa Chemical Industry, Kyowamag 150) 4 parts Vulcanization accelerator (Ouchi Shinko Chemical Industry, Noccela M) 1 part 0.5 parts stearic acid

[0073] The composition is as described above. More specifically, a conductive rubber material containing carbon black in chloroprene rubber and ethylene-propylene-diene rubber were mixed, and other materials were added and kneaded. The mixture was extruded using a kneading extruder, dried with hot air, and heated for vulcanization to obtain a tubular body with a diameter (outer diameter) of 40 mm and an average thickness of 450 μm. The tubular body was cut to a length of 355 mm to form substrate A.

[0074] [Creating protective layer] A curing agent (Loctite WH-1, Henkel Japan) was added to a urethane resin (Bonderite T862A, Henkel Japan) containing PTFE (polytetrafluoroethylene) in an amount of 1% by mass, and the resin was diluted with water to adjust the PTFE content to 10% by mass, and this was used as the coating solution. The coating liquid was sprayed onto the outer peripheral surface of the substrate A while the substrate A was rotated with its central axis in the horizontal direction. Then, hot air drying was performed at a temperature of 150°C for 35 minutes to form a protective layer. The average thickness of the protective layer on the outer peripheral surface was 6 μm. The same coating liquid was then sprayed onto the inner peripheral surface of the substrate A, and hot air drying was similarly performed to form a protective layer. The average thickness of the protective layer on the inner peripheral surface was 6 μm. In this way, an endless belt was obtained.

[0075] <Example 2> An endless belt was obtained in the same manner as in Example 1, except that the amount of vulcanization accelerator was increased to 5 parts in the preparation of the substrate.

[0076] Example 3 An endless belt was obtained in the same manner as in Example 1, except that the amount of carbon black in the preparation of the substrate was reduced to 15 parts.

[0077] <Comparative Example 1> An endless belt was obtained in the same manner as in Example 1, except that in the preparation of the substrate, the amount of chloroprene rubber was increased to 85 parts and the amount of ethylene-propylene-diene rubber was reduced to 15 parts.

[0078] <Comparative Example 2> An endless belt was obtained in the same manner as in Example 1, except that in the preparation of the substrate, the amount of chloroprene rubber was reduced to 70 parts and the amount of ethylene-propylene-diene rubber was increased to 30 parts.

[0079] <Comparative Example 3> An endless belt was obtained in the same manner as in Example 1, except that the amount of carbon black was increased to 50 parts in the preparation of the substrate.

[0080] <Evaluation of the mechanical properties of the base layer> The dynamic viscoelasticity measurement and tensile test of the substrate layer were carried out according to the methods described above. The results are shown in Table 1.

[0081] <Performance evaluation of endless belts> A secondary transfer unit was fabricated using the endless belt obtained in each example as a secondary transfer belt. The secondary transfer unit was installed in a modified image forming apparatus DocuColor-7171P (Fuji Xerox Co., Ltd.). A guide for conveying the recording medium was attached to the end of the secondary transfer belt, and the conveying speed of the recording medium was adjusted to be constant.

[0082] [Endless belt transport performance] To ensure stable image quality, the endless belt (secondary transfer belt) is required to have excellent transport performance. The transport performance of the endless belt is affected by local tension differences in the endless belt and speed fluctuations that accompany its rotation. The transport performance of the endless belt was evaluated using the following method. The endless belt was continuously rotated while being stretched by a tension roll at a 4% elongation. The rotation speed was 540 mm / s and the drive time was 120 hours. After the rotation was stopped, the state of damage such as scratches on the endless belt ends and scratches on the outer peripheral surface of the endless belt, as well as the position of the endless belt ends, were checked, and belt walk was evaluated based on this.

[0083] The conveying performance of the endless belt was classified as follows, and the results are shown in Table 1. A: Belt walk is within the control target range. B: Belt walk is below the operating limit range. C: Belt walk is above the operating limit range.

[0084] [Cleaning ability and surface properties of endless belts] To ensure stable image quality, the endless belt (secondary transfer belt) is required to maintain the cleaning ability and surface condition of its outer surface even when subjected to changes in elongation due to rotation, fluctuations in external load, and environmental influences.The cleaning ability and changes in surface condition of the outer surface of the endless belt were evaluated using the following method. After 10,000 consecutive image formation and recording medium transport operations, the outer surface of the endless belt was observed at 100x magnification using a CCD camera, and the presence or absence of foreign matter and changes in surface condition were qualitatively evaluated. The ten-point average surface roughness (Rz) of the outer surface of the endless belt was also measured using a contact-type surface roughness measuring device (Surfcom 570A, manufactured by Tokyo Seimitsu Co., Ltd.). The surface roughness was measured using a diamond-tipped contact needle (5 μmR, 90° cone) at a measurement distance of 2.5 mm. The measurement was conducted three times at different locations on the outer surface of the endless belt, and the average value was recorded as the ten-point average surface roughness (Rz).

[0085] The cleaning ability of the endless belt was classified as follows, and the results are shown in Table 1. A: No foreign matter was found to be attached by visual or magnified observation. B: There are foreign objects that cannot be seen with the naked eye but can be seen under magnification. C: Foreign matter is visible to the naked eye.

[0086] The surface properties of the endless belts were classified as follows, and the results are shown in Table 1. A: The fluctuation in the surface roughness value is small, and no abnormalities are observed on the surface under magnification. B: The surface roughness value fluctuates, and minute cracks are observed under magnification. C: The surface roughness value is reduced, and many cracks are observed on the surface under magnification.

[0087] [Image quality uniformity] Recording medium (paper, A3 size, basis weight 82 g / m 2A halftone image with an image density of 20% was continuously printed on 100 sheets of a 97 μm thick endless belt. The final 10 images were visually inspected. The image quality evaluation was carried out after evaluating the initial state, the conveyance performance of the endless belt, and the cleaning ability of the endless belt.

[0088] The image quality uniformity was classified as follows: The results are shown in Table 1. A: No uneven color or color loss is observed. B: Slight color unevenness is observed. C: Partial color unevenness and color loss are observed.

[0089] The "requirements for tan δ" listed in Table 1 state that "in dynamic viscoelasticity measurements of the base material layer at a temperature of 35°C, the loss tangent value at measurement frequencies of 0.1 Hz to 10 Hz is smaller than the loss tangent value at measurement frequencies of 10 Hz to 100 Hz."

[0090] [Table 1]

[0091] The results shown in Table 1 show that, compared to the comparative example, the examples suppressed the variation in contact pressure in the axial direction of the endless belt when a rotating body was brought into contact with the outer peripheral surface of the endless belt, resulting in improved belt walk, cleaning performance, and surface cracking. [Explanation of symbols]

[0092] 50 endless belt 52 Base material layer 54 Protective layer 56 Protective layer 60 Belt unit 62 Drive Roll 64 Support Roll

[0093] 1Y, 1M, 1C, 1K photoconductor 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 60 Belt unit 50 endless belt 62 Drive Roll 64 Support Roll 28 Fixing device (an example of fixing means) 30 Intermediate transfer belt cleaning device P Recording paper (an example of a recording medium)

Claims

1. a substrate layer containing a polymer material and conductive particles; a protective layer provided on the outer peripheral surface of the base material layer; a protective layer provided on the inner circumferential surface of the base material layer, In a dynamic viscoelasticity measurement of the base material layer at a temperature of 35°C, the value of the loss tangent at a measurement frequency of 0.1 Hz to 10 Hz is smaller than the value of the loss tangent at a measurement frequency of 10 Hz to 100 Hz, the tensile stress when the base material layer is stretched by 5% at a temperature of 24°C is 7 MPa or more, and when the base material layer is stretched by 5% at a temperature of 24°C and held for 10 minutes, the maximum value TSmax and the minimum value TSmin of the tensile stress during that period satisfy {(TSmax-TSmin) / TSmax×100}≦15; Endless belt.

2. 2. The endless belt according to claim 1, wherein the base material layer has a tensile stress of 7 MPa or more and 10 MPa or less when stretched by 5% at a temperature of 24°C.

3. 3. The endless belt according to claim 1, wherein when the base material layer is stretched by 5% at a temperature of 24°C and held for 10 minutes, the maximum value TSmax and minimum value TSmin of tensile stress during that period satisfy {(TSmax - TSmin) / TSmax x 100} ≦ 10.

4. An endless belt according to any one of claims 1 to 3; a plurality of roll members around which the endless belt is stretched under tension, At least one of the plurality of roll members is a drive roll that rotates the endless belt, Attached to and detached from the image forming apparatus, Belt unit.

5. A photoreceptor; a charging means for charging the surface of the photoreceptor; an electrostatic image forming means for forming an electrostatic image on the charged surface of the photoreceptor; a developing means for storing a developer containing a toner and developing an electrostatic image formed on the surface of the photosensitive member using the developer to form a toner image; a transfer unit having the belt unit according to claim 4 and transferring the toner image onto a recording medium; Image forming device.

6. 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 according to claim 4. The image forming apparatus according to claim 5 .

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