JP2017009794A - Pressure member, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure member that suppresses fracture of a low thermal conductor having a hollow part compared with a case where a pressure member does not include a resin layer with a film thickness of 10 μm or more and 300 μm or less.SOLUTION: There is provided a pressure member 62 sequentially comprising a base material 621, a resin layer 624 with a film thickness of 10 μm or more and 300 μm or less, an elastic layer 622 including a low thermal conductor 625 having a hollow part, and a mold release layer 623.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pressure member, a fixing device, and an image forming apparatus.

  In an image forming apparatus using powdery toner, a toner image is formed by selectively transferring toner to a latent image formed on an image holding member due to a difference in electrostatic potential. Normally, the toner image is transferred directly between the heating member and the pressure member after the toner image is electrostatically transferred directly onto the recording medium, or after first being transferred onto the intermediate transfer member and then transferred onto the recording medium. The medium is sandwiched and the toner image is heated and pressurized to be fixed on the recording medium.

  As a fixing device for fixing a toner image on a recording medium in this way, for example, a fixing roll having a heating element such as a halogen lamp inside a cylindrical metal core and a pressure roll pressed against the fixing roll What is done is widely known. In this fixing device, a recording medium holding an unfixed toner image is fed into a nip portion formed by press-contacting a fixing roll and a pressure roll, and a gap between the rotation-driven fixing roll and the pressure roll is sent. The toner image is heated and pressurized as it passes.

  In addition, a fixing device using an endless belt and a pressure roll instead of the fixing roll as a fixing member has been proposed. The fixing belt includes a type in which the fixing belt is stretched by a plurality of support rolls, and a type in which the fixing belt has a pressing support inside and is rotationally driven by being pressed against the pressure roll in a non-tensioned state. The fixing belt has a thin heat-resistant resin or the like as a base layer, and has a smaller heat capacity than a roll-shaped member, so that warm-up is performed in a short time. Furthermore, the shape of the nip portion can be freely formed by using a fixing belt.

  As a pressure roll used in such a fixing device, a pressure roll containing hollow low thermal conductive particles such as a glass balloon in an elastic layer is known.

  For example, Patent Document 1 includes a core body, a first elastic layer provided around the core body, and a second elastic layer provided around the first elastic layer. The elastic layer is composed of a rubber member, and the second elastic layer is composed of silicone rubber obtained by curing the silicone rubber raw material after mixing the silicone rubber raw material and the glass balloon. Describes a fixing pressure roll including a void formed by breaking a glass balloon by pressurization.

  In Patent Document 2, in a fixing device that includes a heating roller having a low heat capacity having a heat source and a pressure roller that forms a nip by pressure contact with the heating roller, the outer peripheral surface of the pressure roller has at least two or more. A non-foamed elastic material comprising a layer of the above, wherein the layer on the axial core side of the pressure roller is made of glass or resin and has a hollow structure inside or contains low thermal conductive particles containing bubbles And a fixing device in which a layer on the surface side of the pressure roller among the layers is formed of a highly heat conductive material is described.

  Patent Document 3 discloses a sponge roller in which an elastic layer and a release layer are formed on the outer periphery of a metal core in this order from the inside, and the elastic layer includes an inorganic micro hollow body such as a glass balloon. A pressure roller is described.

Japanese Patent Laying-Open No. 2015-022082 JP 2003-177623 A JP 2001-066554 A

  An object of the present invention is to provide a pressure member that suppresses the destruction of a low thermal conductor having a hollow portion as compared with the case where a resin layer having a film thickness of 10 μm to 300 μm is not provided, and fixing using the pressure member An apparatus and an image forming apparatus are provided.

  The invention according to claim 1 is a pressure member that sequentially includes a base material, a resin layer having a thickness of 10 μm or more and 300 μm or less, an elastic layer including a low thermal conductor having a hollow portion, and a release layer.

  The invention according to claim 2 is the pressure member according to claim 1, wherein the low thermal conductor is a hollow glass filler.

  According to a third aspect of the present invention, there is provided a fixing device comprising the pressure member according to the first or second aspect.

  The invention according to claim 4 is an image holding member, a latent image forming unit that forms a latent image on the surface of the image holding member, a developing unit that develops the latent image with toner to form a toner image, and An image forming apparatus comprising: a transfer unit that transfers a toner image to a recording medium; and the fixing device according to claim 3 that fixes the toner image to the recording medium.

  According to the invention which concerns on Claim 1, compared with the case where it does not have a resin layer with a film thickness of 10 micrometers or more and 300 micrometers or less, the pressurization member by which destruction of the low thermal conductor which has a hollow part is suppressed is provided.

  According to the invention which concerns on Claim 2, compared with the case where the said low heat conductor is not a hollow glass filler, the pressurization member with low thermal expansibility is provided.

  According to the invention which concerns on Claim 3, compared with the case where a pressurization member does not have a resin layer with a film thickness of 10 micrometers or more and 300 micrometers or less, the pressurization member by which destruction of the low thermal conductor which has a hollow part is suppressed is provided. A fusing device is provided.

  According to the invention which concerns on Claim 4, compared with the case where a pressurization member does not have a resin layer with a film thickness of 10 micrometers or more and 300 micrometers or less, it is provided with the pressurization member by which destruction of the low thermal conductor which has a hollow part is suppressed. An image forming apparatus is provided.

1 is a schematic configuration diagram illustrating an example of a fixing device according to an embodiment of the present invention. It is a schematic sectional drawing which shows an example of the laminated constitution of the pressurization member which concerns on embodiment of this invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Fixing device and pressure member>
An outline of an example of a fixing device according to an embodiment of the present invention is shown in FIG. Note that a fixing device employing an electromagnetic induction heating method will be described as an example of the fixing device in the present embodiment.

  As shown in FIG. 1, a fixing device 60 according to the present embodiment is disposed in pressure contact with a pressure roll 62 that is a rotatable pressure member, and a pressure roll 62 that is a pressure member. The unfixed toner image is fixed to the recording medium P by the recording medium P holding the unfixed toner image held between the pressurizing portions N (hereinafter also referred to as “nip portion N”) formed between A fixing belt 61 that is a rotatable film tubular body, and a sliding sheet 68 that is interposed between the fixing belt 61 that is a film tubular body and a pressing pad 64 that is a pressing member.

  The fixing device 60 is disposed so as to face the fixing belt 61, a fixing belt 61 that is a film tubular body, a magnetic field generation unit 85 as an example of a heating member that generates heat from the magnetic field generated by an alternating current, and the fixing belt 61. A pressure roll 62 as an example of a pressure member, and a pressing pad 64 that is a pressing member pressed from the pressure roll 62 that is a pressure member via the fixing belt 61 are provided.

  The fixing belt 61 that is a film tubular body is rotatably supported by a pressing pad 64, a belt guide member 63, and edge guide members (not shown) disposed at both ends of the fixing belt 61. Then, it is brought into pressure contact with the pressure roll 62 at the pressure part (nip part) N, and is rotated in the arrow direction following the pressure roll 62.

  The film tubular body described above may be made of resin or metal. Further, when the film tubular body is used as a fixing belt, for example, a single-layer resin film or a single-layer metal film is used, but the resin layer and the metal layer may each be a multilayer, You may combine a resin layer and a metal layer, such as providing a resin-made elastic layer and a mold release layer on a film-made base material.

  The belt guide member 63 is attached to a holder 65 disposed inside the fixing belt 61. The belt guide member 63 is formed of a plurality of ribs (not shown) directed in the rotation direction of the fixing belt 61, and reduces the contact area with the inner peripheral surface of the fixing belt 61. Further, the belt guide member 63 is formed of a heat resistant resin such as PFA (perfluoroalkyl vinyl ether copolymer) or PPS (polyphenylene sulfide) having a low friction coefficient and low thermal conductivity. Thereby, the sliding resistance between the belt guide member 63 and the inner peripheral surface of the fixing belt 61 is reduced, and the heat divergence is reduced.

  The pressure pad 64 is pressed from the pressure roll 62 via the fixing belt 61 to form the pressure portion N. The pressing pad 64 that is a pressing member is supported by a holder 65 that is a holding member so as to press the pressure roll 62 with a load of, for example, 35 kgf by a spring or an elastic body. The pressing pad 64 includes an elastic body such as silicone rubber or fluorine rubber. The pressing pad 64 has a concave portion and a convex portion on the pressure roll 62 side. As a result, when the fixing belt 61 moves away from the surface of the pressing pad 64 on the pressure roll 62 side, a sudden change in curvature occurs, and the recording medium P after fixing is easily peeled off from the fixing belt 61.

  The peeling assisting member 70 disposed in the vicinity of the downstream side of the pressure unit N is held by the baffle holder 72 so that the peeling baffle 71 faces in the direction (counter direction) opposite to the rotation direction of the fixing belt 61. Further, a sliding sheet 68 is disposed between the pressing pad 64 and the fixing belt 61, and sliding resistance between the inner peripheral surface of the fixing belt 61 and the pressing pad 64 is reduced. In the present embodiment, the sliding sheet 68 is configured separately from the pressing pad 64, and at least both ends are fixed to the holder 65.

  A lubricant application member 67 is disposed in the holder 65 serving as a holding member over the longitudinal direction of the fixing device 60. The lubricant application member 67 is brought into contact with the inner peripheral surface of the fixing belt 61, and the lubricant is supplied to the sliding portion between the fixing belt 61 and the sliding sheet 68. Examples of the lubricant include liquid oils such as silicone oil and fluorine oil, grease obtained by mixing a solid substance and liquid, and combinations of these.

  The pressure roll 62 includes a base 621, a resin layer 624, an elastic layer 622, and a release layer 623 in order. Details of the pressure roll 62 will be described later.

  The pressure roll 62 is disposed so as to face the fixing belt 61, and is rotated in the direction of arrow D at a process speed of, for example, 140 mm / sec to drive the fixing belt 61. Further, the fixing belt 61 is held between the pressing roll 62 and the pressing pad 64 to form a pressing portion N, and the recording medium P holding an unfixed toner image passes through the pressing portion N. The unfixed toner image is fixed on the recording medium P by applying heat and pressure.

  The magnetic field generation unit 85 has a cross-sectional shape that is curved along the shape of the fixing belt 61, and is installed with a clearance of, for example, about 0.5 mm to 2 mm from the outer peripheral surface of the fixing belt 61. The magnetic field generation unit 85 includes an excitation coil 851 that generates a magnetic field, a coil support member 852 that holds the excitation coil 851, and an excitation circuit 853 that supplies current to the excitation coil 851.

The exciting coil 851 is formed by, for example, forming litz wires, which are bundled from 16 to 20 copper wires having a diameter of 0.5 mm that are insulated from each other, and wound in a closed ring shape such as an oval shape, an elliptical shape, or a rectangular shape. Use what was done. When an alternating current having a predetermined frequency is applied to the exciting coil 851 by the exciting circuit 853, an alternating magnetic field H is generated around the exciting coil 851. When the alternating magnetic field H crosses the metal layer of the fixing belt 61, an eddy current I is generated so as to generate a magnetic field that hinders the change of the alternating magnetic field H by electromagnetic induction. The frequency of the alternating current applied to the exciting coil 851 is set, for example, from 10 kHz to 50 kHz. When the eddy current I flows through the metal layer of the fixing belt 61, Joule heat is generated by electric power W (W = I ² R) proportional to the resistance value R of the metal layer, and the fixing belt 61 is heated.

  The coil support member 852 is made of a nonmagnetic material having heat resistance, for example. Examples of such a nonmagnetic material include heat resistant resins such as heat resistant glass, polycarbonate, polyethersulfone, and PPS, or heat resistant resins obtained by mixing glass fibers with these.

  In the present embodiment, the electromagnetic induction heating type fixing device 60 including the magnetic field generation unit 85 has been described as an example of a heating member that heats the fixing belt 61. However, as the heating member, a radiation lamp heating element and a resistance heating element can be used. Can also be adopted.

  Examples of the radiant lamp heating element include a halogen lamp. Examples of the resistance heating element include iron-chromium-aluminum, nickel-chromium, platinum, molybdenum, tantalum, tungsten, silicon carbide, molybdenum-silicide, and carbon.

  In the fixing device 60, the fixing belt 61 is driven and rotated by the rotation of the pressure roll 62 in the direction of arrow D, and is exposed to the magnetic field generated by the excitation coil 851. At this time, an eddy current is generated in the metal layer in the fixing belt 61, and the outer peripheral surface of the fixing belt 61 is heated to a temperature at which fixing can be performed. The fixing belt 61 heated in this way moves to the pressure part N with the pressure roll 62. The recording medium P having the unfixed toner image provided on the surface thereof is carried into the fixing device 60 via the fixing inlet guide 56 by the conveying means. When the recording medium P passes through the pressure part N of the fixing belt 61 and the pressure roll 62, the unfixed toner image is heated by the fixing belt 61 and fixed on the surface of the recording medium P. Thereafter, the recording medium P on which the image is formed is conveyed by the conveying unit and is discharged from the fixing device 60. In addition, the fixing belt 61 whose surface temperature on the outer peripheral surface has been lowered after the fixing process in the pressure unit N is rotated in the direction of the exciting coil 851 and is heated again in preparation for the next fixing process.

  FIG. 2 is a schematic cross-sectional view illustrating an example of a layer configuration of a pressure member in the fixing device according to the present embodiment. As shown in FIG. 2, the pressure roll 62 that is a pressure member includes a base material 621, a resin layer 624, an elastic layer 622, and a release layer 623 in order. The resin layer 624 includes a resin, and the thickness of the resin layer 624 is in the range of 10 μm to 300 μm. The elastic layer 622 includes a low thermal conductor 625 having a hollow portion.

  In a fixing device such as a belt-roll system having a fixing belt and a pressure roll for heating in an image forming apparatus, and a roll-roll system having a fixing roll for heating and a pressure roll, etc. It is desirable that the heat is efficiently used for melting the toner, that is, the heat outflow from the pressure member is suppressed as much as possible. Thus, a pressure member having excellent heat insulation properties has been proposed by providing an elastic layer including a low thermal conductor having a hollow portion such as a glass balloon between the substrate and the release layer. However, by including a glass balloon having a hollow portion in the elastic layer, the glass balloon is broken during fixing, and the durability of the elastic layer may be lowered due to the breakage. The present inventor has a resin layer having a thickness of 10 μm or more and 300 μm or less by providing a resin layer having a thickness of 10 μm or more and 300 μm or less between the base material and the elastic layer including the low thermal conductor having a hollow portion. It has been found that the breakage of the low thermal conductor having the hollow portion is suppressed as compared with the case where it is not. By including a low thermal conductor having a hollow portion in the elastic layer of the pressure member, and providing a resin layer not including the low thermal conductor having a hollow portion as a buffer layer between the base material and the elastic layer, It is considered that a local force applied to the elastic layer in the vicinity is suppressed, and breakage of the low thermal conductor having the hollow portion is suppressed. And after the heat | fever outflow from a pressurization member is suppressed and energy saving is achieved, the lifetime improvement of a pressurization member is achieved.

  The film thickness of the resin layer 624 is in the range of 10 μm to 300 μm, and preferably in the range of 10 μm to 150 μm. When the film thickness of the resin layer 624 is less than 10 μm, the low thermal conductor having a hollow portion is broken, and when it exceeds 300 μm, the thermal expansion property of the pressure member is deteriorated.

  The resin contained in the resin layer 624 is not particularly limited as long as it has elastic properties. Examples of the resin include a silicon resin (silicone resin), a fluororesin, and an epoxy resin, and a silicon resin is preferable from the viewpoint of heat resistance.

  For example, the thermal conductivity λ of the elastic layer 622 is preferably 0.5 or less, and more preferably 0.2 or less. When the thermal conductivity λ of the elastic layer 622 exceeds 0.5, it may be difficult to suppress the heat outflow from the pressure member.

  Examples of the elastic material constituting the elastic layer 622 include silicone rubber, fluorinated silicone rubber, and fluorine rubber. Silicone rubber is preferable from the viewpoint of heat resistance, hardness, and the like.

  The low thermal conductor 625 having a hollow portion included in the elastic layer 622 is not particularly limited as long as it has a low thermal conductivity. For example, a spherical shape such as a hollow glass filler, a hollow resin filler, and a hollow ceramic filler is used. And the like, and the like. Among these, hollow glass fillers are preferable from the viewpoints of low thermal conductivity and low thermal expansion coefficient. Since the hollow glass filler is hollow, it is difficult for heat conduction and thermal expansion, and by containing the hollow glass filler in the elastic layer 622, the elastic layer 622 has low thermal conductivity and is difficult to thermally expand.

  The average particle size of the hollow particles such as the hollow glass filler is preferably in the range of 10 μm to 100 μm, and more preferably in the range of 30 μm to 45 μm. If the average particle diameter of the hollow particles is less than 10 μm, the effect of lowering the thermal conductivity may not be obtained, and if it exceeds 100 μm, the hollow glass filler may be broken. Here, the average particle diameter is an accumulated weight average value (D50) in a particle size distribution measuring apparatus by a laser beam diffraction method.

The true density of the hollow particles such as the hollow glass filler is preferably in the range of, for example, 0.1 g / cm ³ or more and 1.1 g / cm ³ or less, and is 0.25 g / cm ³ or more and 0.5 g / cm ^3. The following range is more preferable, and the range of 0.3 g / cm ^{3 to} 0.5 g / cm ³ is more preferable. If the true density of the hollow particles is less than 0.1 g / cm ^{3, the} hollow particles may be broken. If the true density exceeds 1.1 g / cm ³ , the heat insulating property is lowered, and the thermal conductivity of the elastic layer 622 is reduced. May be higher. The true density of the hollow particles is measured, for example, by a gas density substitution method.

  The content of hollow particles such as a hollow glass filler is preferably in the range of 20 vol% or more and 60 vol% or less, more preferably in the range of 30 vol% or more and 45 vol% or less with respect to the elastic layer 622. When the content of the hollow particles is less than 20 vol%, low thermal conductivity may not be obtained, and when it exceeds 60 vol%, the fluidity during molding may be deteriorated.

  The film thickness of the elastic layer 622 is preferably in the range of 200 μm to 5 mm, for example, and more preferably in the range of 450 μm to 2 mm. If the thickness of the elastic layer 622 is less than 200 μm, sufficient heat insulation may not be obtained, and if it exceeds 5 mm, thermal expansion may be too large.

  As the base material 621, for example, a solid columnar metal member or the like can be used. Examples of the metal constituting the metal member include iron and aluminum.

  Examples of the material constituting the release layer 623 include fluorine resins such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA).

  The film thickness of the release layer 623 is, for example, in the range of 5 μm to 300 μm.

  As a manufacturing method of the pressure roll 62, for example, a solid cylindrical shape in which a fluororesin tube in which an adhesion primer is applied to an inner peripheral surface such as a PFA tube (becomes a release layer 623) and a resin layer 624 are applied. A core metal (which becomes the base material 621) is set in a molding die, and an addition-type silicone rubber material containing a hollow glass filler is injected between the fluororesin tube and the solid cylindrical core metal, followed by heat treatment. For example, a method of forming the elastic layer 622 by vulcanizing and foaming silicone rubber by (for example, 100 ° C. or more and 200 ° C. or less, 0.5 hour or more and 4 hours or less) can be used.

  The fixing device 60 according to the present embodiment has been described with respect to a so-called belt-roll type fixing device in which the fixing belt for heating and the pressure roll according to the present embodiment are applied as the pressure member. However, the fixing device may be a so-called roll / roll type fixing device in which the fixing roll for heating and the pressure roll according to the present embodiment are applied as the pressure member.

[Image forming apparatus]
An image forming apparatus according to the present embodiment includes an image holding member, a latent image forming unit that forms a latent image on the surface of the image holding member, a developing unit that develops the latent image with toner to form a toner image, and a toner. Transfer means for transferring an image to a recording medium, and the fixing device for fixing the toner image to the recording medium.

  FIG. 3 shows a schematic configuration of an example of an image forming apparatus to which the pressure member and the fixing device according to the present embodiment are applied. Here, an intermediate transfer type image forming apparatus generally called a tandem type will be described as an example.

  FIG. 3 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus 100 in FIG. 3 is an intermediate transfer type image forming apparatus generally called a tandem type, and a plurality of image forming units 1Y, 1M, 1C, and 1K in which toner images of respective color components are formed by an electrophotographic system. A primary transfer unit 10 that sequentially transfers (primary transfer) the color component toner images formed by the image forming units 1Y, 1M, 1C, and 1K to the intermediate transfer belt 15, and a superimposition transferred on the intermediate transfer belt 15. A secondary transfer unit 20 that batch-transfers (secondary transfer) toner images to a sheet P as a recording medium, and a fixing device 60 that fixes the secondary-transferred image on the sheet P are provided. The fixing device 60 is the fixing device. Further, the image forming apparatus 100 includes a control unit 40 that controls the operation of each device (each unit).

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

  A charging device 12 for charging the photosensitive drum 11 is provided around the photosensitive drum 11 as an example of a charging unit for charging the surface of the image carrier, and a latent image is formed on the surface of the image carrier charged by the charging unit. As an example of a latent image forming means for forming a laser beam, a laser exposure device 13 for writing an electrostatic latent image on the photosensitive drum 11 (the exposure beam is indicated by a symbol Bm in the figure) is provided. Further, around the photosensitive drum 11, each color component toner is accommodated as an example of a developing unit that forms a toner image by developing the latent image formed on the surface of the image holding member with the toner by the latent image forming unit. A developing device 14 is provided that visualizes the electrostatic latent image on the photosensitive drum 11 with toner, and each color component toner image formed on the photosensitive drum 11 is transferred to the intermediate transfer belt 15 by the primary transfer unit 10. A primary transfer roll 16 is provided for transferring the toner.

  Further, a drum cleaner 17 for removing residual toner on the photosensitive drum 11 is provided around the photosensitive drum 11, and a charger 12, a laser exposure device 13, a developing device 14, a primary transfer roll 16, and a drum cleaner are provided. Seventeen electrophotographic devices are sequentially arranged along the rotation direction of the photosensitive drum 11. These image forming units 1Y, 1M, 1C, and 1K are arranged substantially linearly in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15. Is done.

The intermediate transfer belt 15 which is an intermediate transfer member is constituted by a film-like pressure belt containing a resin such as polyimide or polyamide as a base layer and containing an appropriate amount of an antistatic agent such as carbon black. The volume resistivity is formed to be, for example, 10 ⁶ Ωcm or more and 10 ¹⁴ Ωcm or less, and the thickness thereof is configured to be, for example, about 0.1 mm.

  The intermediate transfer belt 15 is circulated (rotated) at a predetermined speed in the direction B shown in FIG. 3 by various rolls. As these various rolls, a drive roll 31 that is driven by a motor (not shown) having excellent constant speed and rotates the intermediate transfer belt 15, and an intermediate transfer that extends substantially linearly along the arrangement direction of the photosensitive drums 11. A support roll 32 that supports the belt 15, a tension roll 33 that functions as a correction roll that applies a predetermined tension to the intermediate transfer belt 15 and suppresses meandering of the intermediate transfer belt 15, and a backup provided in the secondary transfer unit 20. A roll 25 and a cleaning backup roll 34 provided in a cleaning unit that scrapes residual toner on the intermediate transfer belt 15 are provided.

The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 includes a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is, for example, a cylindrical bar made of a metal such as iron or SUS. The sponge layer is formed of, for example, a blend rubber of nitrile rubber (NBR), styrene rubber (SBR), and ethylene propylene rubber (EPDM) containing a conductive agent such as carbon black, and has a volume resistivity of 10 ^7. It is a sponge-like cylindrical roll of ⁵ Ωcm or more and 10 ^8.5 Ωcm or less.

  The primary transfer roll 16 is disposed in pressure contact with the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. Further, the primary transfer roll 16 has a voltage (for example, negative polarity; the same applies hereinafter) having a polarity opposite to that of the toner. (Primary transfer bias) is applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15 so as to form superimposed toner images on the intermediate transfer belt 15.

  The secondary transfer unit 20 is a secondary transfer disposed on the toner image holding surface side of the intermediate transfer belt 15 as an example of a transfer unit that transfers a toner image formed by the backup roll 25 and the developing unit to a recording medium. And a roll 22.

The backup roll 25 is made of, for example, a tube of EPDM and NBR blend rubber having a surface dispersed with carbon, and the inside is made of EPDM rubber. And it is formed so that the surface resistivity may be, for example, 10 ⁷ Ω / □ or more and 10 ¹⁰ Ω / □ or less, and the hardness is, for example, 70 ° (Asker C: manufactured by Kobunshi Keiki Co., Ltd.). Set to The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 to constitute a counter electrode of the secondary transfer roll 22, and a metal power supply roll 26 to which a secondary transfer bias is stably applied is disposed in contact with the backup roll 25. ing.

The secondary transfer roll 22 includes, for example, a shaft and a sponge layer as an elastic layer fixed around the shaft. The shaft is, for example, a cylindrical bar made of a metal such as iron or SUS. The sponge layer is formed of, for example, a blend rubber of NBR, SBR, and EPDM mixed with a conductive agent such as carbon black. For example, the sponge layer has a volume resistivity of 10 ^7.5 Ωcm to 10 ^8.5 Ωcm. It is a cylindrical roll.

  The secondary transfer roll 22 is disposed in pressure contact with the backup roll 25 with the intermediate transfer belt 15 interposed therebetween. Further, the secondary transfer roll 22 is grounded to form a secondary transfer bias between the secondary transfer roll 22 and the secondary transfer roll 25. The toner image is secondarily transferred onto the paper P conveyed to the unit 20.

  On the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15, an intermediate transfer belt cleaner that removes residual toner, paper dust, and the like on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15. 35 is provided detachably.

  On the upstream side of the yellow image forming unit 1Y, a reference sensor (home position sensor) 42 that generates a reference signal serving as a reference for taking image forming timings in the image forming units 1Y, 1M, 1C, and 1K is disposed. Is done. Further, an image density sensor 43 for adjusting image quality is disposed on the downstream side of the black image forming unit 1K. The reference sensor 42 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each image forming unit is instructed by an instruction from the control unit 40 based on the recognition of the reference signal. 1Y, 1M, 1C, and 1K are configured to start image formation.

  In the image forming apparatus 100 according to the present embodiment, as a transport unit that transports the paper P, the paper storage unit 50 that stores the paper P, and the paper P accumulated in the paper storage unit 50 is taken out and transported at a predetermined timing. A paper feed roll 51, a transport roll 52 that transports the paper P fed by the paper feed roll 51, a transport guide 53 that feeds the paper P transported by the transport roll 52 to the secondary transfer unit 20, and the secondary transfer roll 22. A conveyance belt 55 that conveys the sheet P conveyed after the secondary transfer to the fixing device 60 and a fixing entrance guide 56 that guides the sheet P to the fixing device 60 are provided.

  Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described.

  In the image forming apparatus 100 shown in FIG. 3, image data output from an image reading device (not shown) or a personal computer (PC) (not shown) is subjected to predetermined image processing by an image processing device (not shown), and then image formation is performed. Image forming work is executed by the units 1Y, 1M, 1C, and 1K.

  The image processing apparatus performs predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing on the input reflectance data. Is given. The image data that has been subjected to image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the laser exposure unit 13.

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

  The toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 in the primary transfer unit 10 where the photosensitive drums 11 and the intermediate transfer belt 15 are in contact with each other. Transcribed. More specifically, in the primary transfer unit 10, a voltage (primary transfer bias) having a polarity opposite to the charging polarity (for example, negative polarity) of toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16, and the toner Primary transfer is performed by sequentially superimposing images on the surface of the intermediate transfer belt 15.

  After the toner images are sequentially primary transferred onto the surface of the intermediate transfer belt 15, the intermediate transfer belt 15 moves and the toner image is conveyed to the secondary transfer unit 20. When the toner image is transported to the secondary transfer unit 20, the transport unit rotates the paper feed roll 51 in accordance with the timing at which the toner image is transported to the secondary transfer unit 20, so A size paper P is supplied. The paper P supplied by the paper feed roll 51 is transported by the transport roll 52, and reaches the secondary transfer unit 20 through the transport guide 53. Before reaching the secondary transfer unit 20, the paper P is temporarily stopped, and the registration roller (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 on which the toner image is held. And the position of the toner image are aligned.

  In the secondary transfer unit 20, the secondary transfer roll 22 is pressed against the backup roll 25 via the intermediate transfer belt 15. At this time, the sheet P conveyed at the same timing is sandwiched between the intermediate transfer belt 15 and the secondary transfer roll 22. At this time, when a voltage (secondary transfer bias) having the same polarity as the toner charging polarity (for example, negative polarity) is applied from the power supply roll 26, a transfer electric field is generated between the secondary transfer roll 22 and the backup roll 25. It is formed. The unfixed toner image held on the intermediate transfer belt 15 is collectively electrostatically transferred onto the paper P in the secondary transfer unit 20 pressed by the secondary transfer roll 22 and the backup roll 25. The

  Thereafter, the sheet P on which the toner image has been electrostatically transferred is transported as it is while being peeled off from the intermediate transfer belt 15 by the secondary transfer roll 22, and transported downstream of the secondary transfer roll 22 in the sheet transport direction. It is conveyed to the belt 55. The conveyance belt 55 conveys the paper P to the fixing device 60 in accordance with the optimum conveyance speed in the fixing device 60. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 60. Then, the paper P on which the fixed image is formed is conveyed to a paper discharge accommodating portion (not shown) provided in the discharge portion of the image forming apparatus.

  On the other hand, after the transfer to the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and is cleaned by the cleaning backup roll 34 and the intermediate transfer belt cleaner 35. It is removed from the intermediate transfer belt 15.

  Although the embodiments of the present invention have been described above, the present invention is not construed as being limited to the above-described embodiments, and various modifications, changes, and improvements can be made, and a range that satisfies the requirements of the present invention. Needless to say, this is feasible.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
An elastic adhesive DY39-051 A / B (manufactured by Dow Corning Toray, silicone resin) is applied to the outer periphery of a solid cylindrical cored bar (SUS, φ18 mm, 400 mm) as a base material by flow coating. A resin layer having a thickness of 10 μm was formed.

Molding a fluororesin tube with a primer for adhesion (X33-518, manufactured by Shin-Etsu Silicone Co., Ltd.) applied to the inner peripheral surface of a conductive PFA tube (thickness 50 μm) to be a release layer and a base material with a resin layer Set inside, hollow glass filler ("Sphericel" 34P30 manufactured by Potters Barotini, true density = 0.34 g / cm ³ , average particle size = 30 μm between the fluororesin tube and the solid cylindrical cored bar ) Addition-type silicone rubber material (Shin-Etsu Silicone, KE-765) containing 25 volume fraction was injected, and then silicone rubber was added by heat treatment (primary firing: 150 ° C for 1 hour, secondary firing: 200 ° C for 4 hours) The resin layer, the elastic layer, and the release layer were formed in this order on the outer periphery of the base material to obtain a pressure roll. The width of the elastic layer was 350 mm, the thickness of the elastic layer was 5.0 mm, and the pressure roll diameter was 28 mm. The film thickness of the resin layer and the elastic layer was measured by observing the cut surface with a microscope.

<Example 2>
A pressure roll was obtained in the same manner as in Example 1 except that a solid cylindrical metal core having a diameter of 26 mm was used and the thickness of the elastic layer was 1.0 mm.

<Example 3>
A pressure roll was obtained in the same manner as in Example 1 except that the thickness of the resin layer was 150 μm.

<Example 4>
A pressure roll was obtained in the same manner as in Example 1 except that the thickness of the resin layer was 300 μm.

<Example 5>
A pressure roll was obtained in the same manner as in Example 3 except that a resin layer was formed using EW2046 (manufactured by 3M, epoxy resin) instead of the elastic adhesive DY39-051 A / B.

<Comparative Example 1>
A pressure roll was obtained in the same manner as in Example 1 except that the resin layer was not formed.

<Comparative example 2>
A pressure roll was obtained in the same manner as in Example 2 except that the resin layer was not formed.

<Comparative Example 3>
A pressure roll was obtained in the same manner as in Example 1 except that the thickness of the resin layer was 5 μm.

<Comparative example 4>
A pressure roll was obtained in the same manner as in Example 1 except that the thickness of the resin layer was 350 μm.

[Evaluation]
(durability)
While pressing the roll produced as described above against a metal facing roll with a load of 50 kg, a test was performed to check the occurrence of breakage by rotating at a speed of 30 rpm. Evaluation was performed according to the following criteria. The results are shown in Table 1.
○: No failure occurred in repeated durability test of 100,000 times or more. Δ: Failure occurred in repeated durability test of 1000 times or more and less than 100,000 times. ×: Failure occurred in repeated durability test of less than 1000 times.

(Thermal expansion)
The outer diameter R1 of the pressure roll was measured at room temperature (22 ° C.) by laser outer diameter measurement. Next, the outer diameter R2 of the pressure roll when the surface temperature of the roll was raised to 150 ° C. with a halogen lamp was measured while rotating the pressure roll at 30 rpm. The coefficient of thermal expansion (%) was determined by the following formula. The thermal expansibility was determined with a thermal expansion coefficient of 1.3% or less as an acceptance criterion (◯). The results are shown in Table 1.
Thermal expansion coefficient (%) = [(R2-R1) / R1] × 100

(Thermal conductivity)
While rotating the pressure roll at 30 rpm, the thermal conductivity was evaluated by the time taken to raise the surface temperature of the roll to 150 ° C. with a halogen lamp. Regarding the thermal conductivity, the time taken to raise the temperature to 150 ° C. was set to a pass criterion (◯) of 300 seconds or less. The results are shown in Table 1.

  Thus, compared with the pressure roll of the comparative example which does not have a resin layer with a film thickness of 10 micrometers or more and 300 micrometers or less, the pressure roll of the Example suppressed the destruction of the low thermal conductor which has a hollow part.

  1Y, 1M, 1C, 1K Image forming unit, 10 Primary transfer unit, 11 Photosensitive drum, 12 Charger, 13 Laser exposure unit, 14 Developer, 15 Intermediate transfer belt, 16 Primary transfer roll, 17 Drum cleaner, 20 2 Next transfer section, 22 Secondary transfer roll, 25 Backup roll, 26 Feed roll, 31 Drive roll, 32 Support roll, 33 Tension roll, 34 Cleaning backup roll, 35 Intermediate transfer belt cleaner, 40 Control section, 42 Reference sensor (home Position sensor), 43 image density sensor, 50 paper storage unit, 51 paper feed roll, 52 transport roll, 53 transport guide, 55 transport belt, 56 fixing inlet guide, 60 fixing device, 61 fixing belt, 62 pressure roll, 63 Belt guide member, 64 pressure pad 65, 65 holder, 67 Lubricant application member, 68 Sliding sheet, 70 Peeling auxiliary member, 71 Peeling baffle, 72 Baffle holder, 85 Magnetic field generation unit, 100 Image forming apparatus, 621 Base material, 622 Elastic layer, 623 Mold release Layer, 624 resin layer, 625 low thermal conductor, 851 excitation coil, 852 coil support member, 853 excitation circuit.

Claims (4)

  A pressure member comprising a base material, a resin layer having a thickness of 10 μm or more and 300 μm or less, an elastic layer including a low thermal conductor having a hollow portion, and a release layer in this order.   The pressure member according to claim 1, wherein the low thermal conductor is a hollow glass filler.   A fixing device comprising the pressure member according to claim 1. An image carrier,
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for developing the latent image with toner to form a toner image;
Transfer means for transferring the toner image to a recording medium;
The fixing device according to claim 3, wherein the toner image is fixed on the recording medium.
An image forming apparatus comprising:

Images