JP2015055657A - Pressure member, image heating device using the same, image forming apparatus, and manufacturing method of pressure member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both prevention of paper jam and suppression of damage to the edge of paper due to separation failure, even when an elongated pressure member (pressure pad) 27 for an image heating device is brought close to a separation roller 26 up to a point where an icicle-like glossiness unevenness does not occur, the pressure member being stationary disposed and having an elastic layer 27b that forms, with a heating member 20, a nip N for holding and conveying a recording material P carrying an image T and heating the recording material P.SOLUTION: An elastic layer 27b has anisotropy in terms of an elasticity modulus in which the elasticity modulus in a short direction is larger than the elasticity modulus in a thickness direction.

Description

  The present invention relates to a pressure member, an image heating apparatus using the same, an image forming apparatus, and a method for manufacturing the pressure member.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a recording material (hereinafter referred to as paper), and this is fixed by heating and pressing with a fixing device as an image heating apparatus. Thus, an image is formed. As such a fixing device, a fixing nip is formed by pressing a pressure roller against a fixing roller having a heater (heating source) therein, and a sheet carrying a toner image is nipped and conveyed by the fixing nip for fixing. A roller fixing method has been conventionally employed.

  By the way, in order to increase the glossiness of the image and increase the speed of image formation, it is preferable to lengthen the paper passing through the fixing nip and sufficiently melt the toner. In the case of the roller fixing method, in order to achieve this, the roller diameter has to be increased, and the fixing device becomes large.

  Therefore, a belt fixing method has been proposed that can obtain a sufficient nip width (nip length in the paper conveyance direction) while achieving a reduction in size and speed of the apparatus as compared with the roller fixing method.

  Here, in the belt fixing method, a belt fixing device employing a pressure pad which is a fixed pressure member has been put into practical use. In the pressure pad method, a fixing nip is formed between the fixing member and the pressure belt by bringing a pressure pad made of an elastic body into pressure contact with the fixing member via a pressure belt having a low heat capacity.

  Increasing the nip width is effective for speeding up the device, but in order to obtain a sufficient nip width with the pressure roller, a large-diameter roll must be used and the device is large. It will become. In this respect, the pressure pad, which is a fixed pressure member, only needs to have a length in the paper conveyance direction as large as the nip width, so that a wide fixing nip can be obtained without increasing the size of the apparatus. Is possible.

  In many cases, a belt-fixing nip employing a pressure pad is composed of two nips, a nip by a pressure pad and a nip by a separation roller. The nip by the separation roller drives the pressure belt and forms a nip with a high peak pressure on the nip outlet side, so that the fixing member can be deformed to separate the paper from the nip from the fixing member. It becomes.

  However, on paper with a resin coating on the surface, if there is a place where the nip pressure decreases between the nip by the pressure pad and the nip by the separation roller, icicle-shaped gloss unevenness is formed on the surface of the fixed image and output. Image quality may be degraded.

  This is because the water vapor generated at the time of fixing cannot be suppressed in the portion where the nip pressure is reduced. For this reason, the contact state between the toner image and the surface of the fixing roller is different between the portion where the air or water vapor is accumulated and the portion where the air or water vapor is not accumulated in the width direction of the paper (direction perpendicular to the conveyance direction) of the portion where the nip pressure is reduced. Due to gloss unevenness. Gloss unevenness is particularly likely to occur on paper with low air permeability such as coated paper.

  On the other hand, Patent Document 1 discloses an image heating apparatus in which a belt member is brought into contact with a roller member. Here, a wedge-shaped pressure pad is disposed in a wedge-shaped gap formed between the roller member on the outlet side of the heating nip and the inner surface of the belt member, and the roller member and The nip pressure of the heating nip is prevented from decreasing between the pressure pads.

JP 2006-146156 A

  However, when the roller member and the pressure pad are brought close to each other as described in Patent Document 1, the wedge-shaped pressure pad bites into the nip formed by the separation roller, so that it is formed by the separation roller. It was found that the nip pressure was reduced.

  This is because the pressure pad is a fixed member and rubs against the pressure belt, and the elastic layer portion is pulled downstream in the rotation direction of the pressure belt, so that the elastic layer portion is deformed so as to approach the separation roller. It is. If the nip pressure at the exit of the nip formed by the separation roller is reduced, the paper curvature separation at the exit of the nip is hindered, and jamming due to poor paper separation is likely to occur. It has also been found that the rotational resistance of the belt member increases and the power consumption of the driving means increases, and the rotational speed becomes uneven and the fixed image is affected.

  If the separation roller and the pressure pad are separated to prevent this, icicle-shaped gloss unevenness, which is the original problem, occurs. In addition, increasing the hardness of the pressure pad to reduce deformation of the pressure pad is effective in preventing uneven gloss and poor separation. However, when the hardness of the pressure pad is increased, the pressure is concentrated on the sheet passing area of the nip, particularly when a small size sheet having a width smaller than the maximum width sheet usable in the apparatus is passed. There has been a case where a paper edge scratch or a paper edge sharpening becomes noticeable.

  Accordingly, there is a demand for both preventing jamming due to poor separation and scratching the paper edge even if the pressure pad is brought close to the separation roller until the icicle-shaped gloss unevenness does not occur.

  The present invention meets this need. The purpose is to provide a pressure member for an image heating apparatus, an image heating apparatus using the same, which can achieve both prevention of jamming due to poor separation and suppression of paper edge scratches, even if the setting is such that gloss unevenness does not occur, An object of the present invention is to provide an image forming apparatus and a pressure member manufacturing method.

  In order to achieve the above object, a typical configuration of the pressure member according to the present invention includes an elastic layer, which forms a nip that heats a recording material carrying an image while nipping and conveying the recording material. The elastic layer is characterized in that the elastic layer has a characteristic that the elastic modulus in the short direction is larger than the elastic modulus in the thickness direction.

  According to the present invention, it is possible to provide a pressure member capable of achieving both prevention of jamming due to poor separation and suppression of paper edge damage, and an image heating apparatus including the pressure member, even when setting is performed so that gloss unevenness does not occur.

Schematic configuration diagram of an image forming apparatus in an embodiment Schematic configuration diagram of a fixing device in an embodiment Overhead view of pressure pad as pressure member FIG. 3 is an enlarged perspective view of a cut sample of the elastic layer of the pressure pad of FIG. (A) is an enlarged view of a cross section of the cut-out sample of FIG. Schematic diagram of needle filler Explanatory diagram of nip pressure distribution Explanatory drawing showing the positional relationship between the pressure pad and the separation roller Explanatory drawing of needle-like filler orientation of the pressure pad in the second embodiment Explanatory drawing of thermal conductivity measurement of cut sample of elastic layer Schematic of another configuration of the fixing device (part 1) Schematic of another configuration of the fixing device (part 2) Schematic of other configuration of fixing device (part 3)

  Hereinafter, although the form for implementing this invention is demonstrated based on the pressurization member used for an image heating apparatus, the range of this invention is not limited only to this form, and the meaning of this invention was impaired. Those modified within a range not included are also included in the present invention.

<< First Embodiment >>
(1) Image Forming Unit FIG. 1 is a schematic longitudinal sectional view showing a schematic configuration of an electrophotographic printer 100 which is an example of an image forming apparatus in which an image heating apparatus according to the present invention is mounted as a fixing device 110. First, an outline of the image forming unit will be described. The printer 100 performs an image forming operation based on image information input from a host device 200 (FIG. 2) such as a personal computer to a control unit (control circuit unit: CPU) 50 to transfer a toner image onto a recording material P. Then, the toner image is thermally fixed by the fixing device 110.

  The recording material P is a sheet-like recording medium on which a toner image is formed by an image forming apparatus. For example, regular or irregular plain paper, cardboard, thin paper, envelope, postcard, seal, resin sheet, OHT sheet, glossy paper Etc. are included. Hereinafter referred to as paper. In the following description, for the sake of convenience, the recording material will be described using terms such as passing paper, paper discharge, paper feeding, paper passing portion, and non-paper passing portion, but the recording material is limited to paper. is not.

  In the printer 100, a charging roller 102, an exposure device 103, a developing device 104, a transfer roller 105, and a cleaning device 109 are disposed around the photosensitive drum 101. The photosensitive drum 101 is formed by applying a negatively charged OPC photosensitive material to the outer peripheral surface of an aluminum cylindrical base, and rotates in the direction of arrow R1 at a process speed of 300 mm / sec.

  The charging roller 102 is driven to rotate in contact with the photosensitive drum 101 and is applied with an oscillating voltage obtained by superimposing an AC voltage on a DC voltage from a power source (not shown), so that the surface of the photosensitive drum 101 has a uniform negative polarity. Charge to dark part potential VD. The exposure device 103 scans a laser beam that is ON-OFF modulated in accordance with an image signal obtained by developing the image data, and forms an electrostatic image of the image on the surface of the photosensitive drum 101. In the exposed portion, the charging is released by the laser beam, and the dark portion potential VD is lowered to the bright portion potential VL.

  The developing device 104 magnetically carries the one-component developer charged to a negative polarity on the developing sleeve 104 a and conveys it to a portion facing the photosensitive drum 101. By applying an oscillating voltage obtained by superimposing an AC voltage on a negative DC voltage Vdc from a power source (not shown) to the developing sleeve 104a, the portion of the bright portion potential VL having a relatively positive polarity is negatively charged. The toner adheres and the electrostatic image is reversely developed.

  The transfer roller 105 is in pressure contact with the photosensitive drum 101 to form a transfer portion T1 that sandwiches and conveys the paper P. By applying a positive voltage to the transfer roller 105 from a power source (not shown), the toner image charged to the negative polarity and carried on the photosensitive drum 101 is transferred to the paper P that is nipped and conveyed across the transfer portion T1.

  The paper P is taken out from the cassette 106 by the paper feed roller 107, waits at the registration roller 108, and is fed to the transfer portion T1 by the registration roller 108 in synchronization with the toner image on the photosensitive drum 101. The paper P from which the toner image is transferred by the transfer unit T1 and separated from the photosensitive drum 101 is conveyed to the fixing device 110.

  The fixing device 110 heats and presses the paper P carrying an unfixed toner image, and fixes the toner image on the paper P to form a fixed image. The paper P on which the image is fixed is discharged and stacked on a paper discharge tray 112 on the printer housing by a paper discharge roller 111. The cleaning device 109 rubs the photosensitive drum 101 with a cleaning blade to remove the transfer residual toner remaining on the photosensitive drum 101 after passing through the transfer portion T1.

(2) Fixing Device FIG. 2 is a schematic cross-sectional view of the main part of the fixing device 110 in the present embodiment. The fixing device 110 is a roller heating-belt pressure type image heating device.

  Here, regarding the fixing device 110 of this example or its constituent members, the front side is the surface of the fixing device 110 viewed from the paper inlet side, and the back side is the opposite surface (paper outlet side). Left and right are left (one end side) or right (the other end side) when the fixing device 110 is viewed from the front side. Further, the upstream side and the downstream side are the upstream side and the downstream side with respect to the paper conveyance direction (recording material conveyance direction, recording material traveling direction) c. The longitudinal direction (width direction) and the paper width direction are directions substantially parallel to the direction orthogonal to the paper transport direction c on the paper transport path surface. The short side direction is a direction substantially parallel to the conveyance direction c of the paper P on the paper conveyance path surface. The thickness direction is a direction perpendicular to the sheet surface.

  In the fixing device 110 of this example, the conveyance of the paper P is performed by so-called central reference conveyance centered on the paper width. It may be made by so-called one-side reference conveyance. Hereinafter, the maximum width paper that can be used in the apparatus is referred to as a large size paper, and a paper having a smaller width is referred to as a small size paper.

  The fixing device 110 of this example includes a fixing roller (heating roller: heating rotator) 20 as a heating member, and a pressure belt unit 30 that forms a nip N with the fixing roller 20.

(2-1) Fixing roller 20
The fixing roller 20 includes a cored bar 20a that is a cylindrical base, an elastic layer 20b formed on the outer peripheral surface of the cored bar 20a, and a surface release layer 20c formed on the outer peripheral surface of the elastic layer 20b. It is an elastic hollow roller having a composite layer structure.

  In this example, the cored bar 20a is an aluminum cylindrical body having an outer diameter of 60 mm and a thickness of 1.5 mm. The elastic layer 20b is made of silicon rubber and has a thickness of 500 μm, a JIS Asuka hardness of 20 degrees, and a thermal conductivity of 0.8 W / (m · K). As a material of the elastic layer 20b, a known elastic material such as fluoro rubber can be used in addition to silicon rubber. The surface release layer 20c is a layer for ensuring separation from the image surface of the paper P, and is a fluororesin layer (for example, PFA or PTFE) having a thickness of 30 μm in this example.

  Both ends of the fixing roller 20 are rotatably supported by bearings between left and right support members of an apparatus frame (not shown), and are counterclockwise indicated by an arrow R20 by a drive motor 36 controlled by the control unit 50. Are rotated at a predetermined peripheral speed.

  A halogen heater 22 as a heating source is disposed inside the hollow cored bar 20 a of the fixing roller 20. The heater 22 generates heat by the power supplied from the power supply unit 52 controlled by the control unit 50, and the fixing roller 20 is heated from the inside by the generated heat. The surface temperature of the fixing roller 20 is detected by a contact type thermistor 11 which is a temperature detection member. Information regarding the temperature detected by the thermistor 11 is input to the temperature adjustment circuit of the control unit 50. The temperature adjustment circuit controls the power supplied from the power supply unit 52 to the heater 22 so that the detected temperature information input from the thermistor 11 is raised to and maintained at a predetermined fixing temperature (temperature for melting the toner).

(2-2) Pressure belt unit 30
The pressure belt unit 30 includes a separation roller (pressure roller) 26 that also serves as a driving roller, a tension roller 25, a pressure pad 27 as a pressure member between the rollers 26 and 25, and these three members. And a pressure belt 21 suspended around 25-27.

  The separation roller 26 and the tension roller 25 are rotatably supported by bearings between left and right support members of a unit frame (not shown) of the pressure belt unit 30. The pressure pad 27 is fixed (non-rotated) between the separation roller 26 and the tension roller 25 at a position adjacent to the separation roller 26. The tension roller 25 is disposed upstream of the separation roller 26 in the sheet movement direction c, and is urged to move in a direction in which the pressure belt 21 is tensioned.

  The pressure belt unit 30 is switched between a pressure position with respect to the fixing roller 20 and a separated position where the pressure is released by the pressure mechanism 40 controlled by the control unit 50. The pressurizing mechanism 40 is a mechanism having, for example, a pressurizing spring, a pressurizing lever, a pressurizing cam, a motor as a drive source, and an electromagnetic solenoid.

  When the state of the pressure belt unit 30 is switched to the pressure position, the separation roller 26 and the pressure pad 27 are respectively set to the fixing roller 20 via the pressure belt 21 as shown in FIG. It comes into pressure contact with the pressing force. As a result, a wide nip N is formed in the sheet conveyance direction c by pressing against the belly pad so that the pressure belt 21 is wound around the outer peripheral surface of the fixing roller 20. That is, a wide nip N in which two nips of the nip by the separation roller 26 and the nip by the pressure pad 27 are adjacent to each other is formed.

  When the pressure belt unit 30 is switched to a separation position (not shown), the pressure belt unit 30 moves away from the fixing roller 20 and the pressure belt 21 is separated from the fixing roller 20 in a non-contact manner. Then, the nip N is released.

  The separation roller 26 is a low-sliding hollow rigid roller made of an iron alloy having an outer diameter of 20 mm and an inner diameter of 16 mm. A halogen heater 23 as a heating source is disposed in the hollow inside of the separation roller 26. The heater 23 generates heat by the power supplied from the power supply unit 53 controlled by the control unit 50, and the separation roller 26 is heated from the inside by the generated heat. When the separation roller 26 is heated, the pressure belt 21 is heated at the belt suspension portion of the separation roller 26.

  Then, the surface temperature of the pressure belt 21 is detected by the contact type thermistor 12 which is a temperature detecting member in the belt suspension portion of the separation roller 26. Information regarding the temperature detected by the thermistor 12 is input to the temperature adjustment circuit of the control unit 50. The temperature adjustment circuit controls the power supplied from the power supply unit 53 to the heater 23 so that the detected temperature information input from the thermistor 12 is maintained at a predetermined pressure belt temperature.

  The tension roller 25 is provided with a silicon rubber sponge layer on the outer peripheral surface of an iron alloy cylindrical base body (core metal) having an outer diameter of 20 mm and an inner diameter of 16 mm to reduce the thermal conductivity of the surface, thereby reducing the pressure belt 21. The heat conduction from is reduced.

  The pressure belt 21 is an endless belt having flexibility. The inner layer is 50 mm and the thickness is 75 μm, and the surface is provided with a PFA tube made of a fluororesin as a release layer with a thickness of 30 μm. ing. The pressure pad 27 which is a pressure member for the image heating apparatus will be described in detail in the section (3).

(2-3) Fixing Operation During standby (standby) of the printer 100, the pressure belt unit 30 of the fixing device 110 is switched to the separated position. In this state, the fixing roller 20 and the pressure belt 21 are individually heated at a predetermined speed and heated to a predetermined temperature. In this example, the surface temperature of the fixing roller 20 is adjusted to 170 ° C., and the surface temperature of the pressure belt 21 is adjusted to 120 ° C.

  The rotation of the pressure belt 21 when the pressure belt unit 30 is located at the separation position is performed by the separation roller 26 receiving the driving force of the driving motor 36 via a drive transmission mechanism (not shown). The rotation direction of the pressure belt 21 is the counterclockwise direction indicated by the arrow R21 in both the separated position and the pressure position.

  Based on the image formation start signal, the image forming unit performs an image forming operation, and the state of the pressure belt unit 30 of the fixing device 110 is switched from the separated position to the pressure position. As a result, a nip N is formed between the fixing roller 20 and the pressure belt 21. The fixing roller 20 is adjusted to a predetermined fixing temperature. In a state where the pressure belt unit 30 is switched to the pressure position (during image formation), the pressure belt 21 rotates following the rotational driving of the fixing roller 20.

  The circumferential speed of the fixing roller 20 forms a loop on the paper P between the nip N and the transfer portion T1 of the image forming portion, so that it is slightly lower than the transport speed of the paper P transported from the transfer portion T1. Slow peripheral speed. In this embodiment, the process speed is 300 mm / sec, the peripheral speed of the fixing roller 20 is slightly less than 300 mm / sec, and A4 size full-color images can be fixed 70 sheets per minute.

  A sheet P carrying an unfixed toner image T is introduced from the image forming unit side to the fixing device 110 with the image surface facing the fixing roller 20. Then, the unfixed toner image T on the sheet P is nipped and conveyed while being in close contact with the outer peripheral surface of the fixing roller 20, so that heat is mainly applied from the fixing roller 20 and the pressure of the sheet P is received by the applied pressure. Fixed on the surface. The sheet P on which the image has been fixed is separated by the separation roller 26 at the exit of the nip N and is discharged from the fixing device 20.

  That is, the elastic layer 20 b of the fixing roller 20 is deformed along the outline of the separation roller 26 in the rotation direction at the separation roller pressure contact portion of the fixing roller 20. Due to the deformation of the elastic layer 20 b along the circumferential surface of the separation roller 26, the paper P is forcibly separated from the fixing roller 20 at the exit of the nip N, and the paper P is prevented from being wound around the fixing roller 20. .

(3) Pressure pad 27
In order to form a continuous wide nip N up to the upstream side of the separation roller 26, a pressure pad 27 is disposed at a position adjacent to the separation roller 26 and the inner surface of the pressure belt 21 faces the fixing roller 20. Pressurized. In the pressure pad 27, an elastic layer 27b made of silicon rubber is formed on a base 27a made of iron, aluminum or the like. The elastic layer 27b is made of heat-resistant silicone rubber and has a thickness of 3 mm and a width (short direction) of 15 mm.

  The separation roller 26 supports the inner surface of the pressure belt 21 on the outlet side of the nip N. The pressure pad 27 is disposed in a wedge-shaped gap formed between the separation roller 26 and the inner surface of the pressure belt 21 so as to extend the nip N upstream in the rotation direction of the pressure belt 21. The inner surface of the pressure belt 21 is pressurized.

  As shown in FIG. 7, the pressure distribution in the sheet conveyance direction of the nip N is set such that the pressure in the nip N becomes a maximum value in a region where the pressure is suspended by the separation roller 26. As described above, since the fixing roller 20 is an elastic roller having the elastic layer 20 b and the separation roller 26 in the pressure belt 21 is a rigid roller made of iron alloy, the nip N between the fixing roller 20 and the pressure belt 21. At the outlet, the deformation on the fixing roller 20 side is large. As a result, the sheet P carrying the toner image T is separated from the fixing roller 20 by its own curvature.

  FIG. 3 is a bird's-eye view of the pressure pad 27. The pressure pad 27 is an elongate horizontally long member having a rigid base 27a made of iron, aluminum or the like and an elastic layer 27b made of silicone rubber supported by the base 27a and having a longitudinal direction in the left-right direction. The elastic layer 27b faces and abuts against the inner surface of the pressure belt 21. In the rotating state of the pressure belt 21, the belt inner surface slides and moves on the elastic layer 27b.

  The elastic layer 27b has needle-like fillers (fillers and additives with a thin and long stick shape and little elongation) 53b1 and voids 53b2 that are oriented in the short direction (paper conveyance direction) of the elastic layer in the elastic layer. (FIG. 5). The elastic layer 27b will be described in more detail with reference to FIGS.

  FIG. 6 is an enlarged perspective view of a needle-like filler 53b1 having a diameter D and a length L. The acicular filler 53b1 is oriented in the short direction of the elastic layer in the elastic layer 27b. In addition, the physical property etc. of the acicular filler 53b1 are mentioned later.

  4 is an enlarged perspective view of a cut sample 53bs obtained by cutting the elastic layer 27b of FIG. The cut sample 53bs is cut along the longitudinal direction and the short direction of the elastic layer 27b as shown in FIG.

  In the cut sample 53bs, if the longitudinal section (a section) and the short section (b section) of the elastic layer 27b are observed, the section a is the acicular filler 53b1 as shown in FIG. A cross section of diameter D can be observed mainly. Further, in the b cross section, as shown in FIG. 5B, the length L portion of the needle-like filler 53b1 can be mainly observed. Moreover, the space | gap 53b2 distributed uniformly can be observed also in (a) and (b) of FIG.

  If the needle-like filler 53b1 is oriented in the elastic layer 27b, the elastic modulus is reduced because the needle-like filler 53b1 hinders deformation when trying to deform the elastic layer 27b in the orientation direction of the needle-like filler 53b1. Get higher. In the direction where the needle-like filler 53b1 is not oriented, the elastic modulus is low because the deformation is not hindered. Accordingly, the elastic modulus is high in the short direction of the elastic layer 27b and low in the longitudinal direction and the thickness direction. Further, when the needle-like filler 53b1 is put in the elastic layer 27b, the elastic modulus tends to increase. However, by providing the elastic layer 27b with the gap 53b2, it is possible to prevent the elastic modulus from being excessively increased.

  Since the pressure pad 27 is a fixed member, the upper part of the elastic layer 27b of the pressure pad 27 is pulled and deformed by rubbing against the pressure belt 21. FIG. 8A shows the positional relationship between the pressure pad 27, the separation belt 21, and the separation roller 26 when the pressure belt 21 is stationary.

  When the pressure belt 21 moves, the upper portion of the elastic layer 27b of the pressure pad 27 is pulled by sliding with the pressure belt 21 and deformed in the direction of the separation roller 26 as shown in FIG. When the deformation is large, the wedge-shaped portion 27b-a of the elastic layer 27b of the pressure pad 27 bites into the nip formed by the separation roller 26, and the nip pressure formed by the separation roller 26 is reduced.

  When the nip pressure at the exit of the nip N is reduced, the paper sheet curvature separation at the exit of the nip N is hindered, and jamming due to poor paper separation is likely to occur. In addition, the rotational resistance of the pressure belt 21 may increase to increase the power consumption of the driving unit, or the rotational speed may become uneven and affect the fixed image.

  In order to prevent this, as shown in FIG. 8C, when the separation roller 26 and the pressure pad 27 are arranged apart from each other, the icicle-shaped gloss unevenness is improved in normal times. However, when the conveying speed of the pressure belt 21 is set low or when the pressing force is set low, the separation roller 26 and the pressure pad 27 are separated as shown in FIG. As shown by the solid line C in FIG. When the pressure-out portion is formed, icicle-shaped gloss unevenness, which is the original problem, occurs.

  Further, in order to reduce the deformation of the pressure pad 27, making the pressure pad 27 high in hardness is effective in preventing uneven gloss and poor separation. However, when the pressure pad 27 is made harder, especially when a small-size sheet is passed, the deformation amount of the pressure pad 27 is small, so that the pressure concentrates on the sheet passing area of the nip N. In some cases, the edge crack or the paper edge scraping becomes noticeable.

  When the elastic modulus of the pressure pad 27 in the short direction (paper conveyance direction) is high, the deformation of the pressure pad 27 in the short direction is small as shown in FIG. The pad 27 can be disposed close to the separation roller 26. Since the pressure pad 27 is arranged close to the separation roller 26, no pressure relief portion is generated even when the conveyance speed of the pressure belt 21 is set to be low or the pressure is set to be low.

  Further, in the case of the pressure pad 27 having a low elastic modulus in the thickness direction of the elastic layer 27b, the pressure pad 27 can be sufficiently deformed when passing through a small size sheet, so that the pressure concentration in the sheet passing area is alleviated. The occurrence of paper edge scratches and paper edge scraping is suppressed. If the pressure pad 27 has a high modulus of elasticity in the short direction of the elastic layer 27b of the pressure pad 27 and a low modulus of elasticity in the thickness direction, it prevents jamming due to poor separation even if it is set so that uneven gloss does not occur. And the suppression of paper edge scratches.

  Since the elastic modulus in the short-side direction of the elastic layer 27b is 1.5 times or more than the elastic modulus in the thickness direction, the characteristics of the pressure pad 27 as the pressure member of the present invention appear more suitably.

  Next, as a characteristic expression of the elastic layer 27b of the pressure pad 27 in FIG. 3, there are a base polymer, a gap 53b2, and a needle-like filler 53b1. The following will be described in order.

<Base polymer>
The base polymer of the elastic layer 27b is obtained by crosslinking and curing an addition-curable liquid silicone rubber. That is, the elastic layer 4b contains a mixture of addition-curable silicone rubber.

  The addition-curable liquid silicone rubber is an uncrosslinked silicone rubber having an organopolysiloxane (A) having an unsaturated bond such as a vinyl group and an organopolysiloxane (B) having a Si—H bond (hydride). Crosslinking and hardening proceeds by the addition reaction of Si—H to an unsaturated bond such as a vinyl group by heating or the like. As a catalyst for promoting the reaction, (A) generally contains a platinum compound. This addition-curable liquid silicone rubber can adjust the fluidity within a range that does not impair the object of the present invention.

<Cavity 53b2>
In the elastic layer 27b, oriented needle fillers 53b1 and voids 53b2 coexist. Therefore, it is important that the needle-like filler 53b1 and the gap 53b2 can be arranged in a state where they do not interfere with each other.

  As a result of investigations by the present inventors, depending on the void forming means such as void formation with a foaming agent or void formation with hollow particles, the orientation of the needle-like filler may be inhibited during void formation. Since the orientation state of the needle-like filler dominates the elastic modulus in the orientation direction, if the orientation is hindered, the effect of suppressing the temperature rise in the non-sheet passing portion is undesirably reduced.

  On the other hand, when the voids are formed using a water-containing material in which water is contained in the water-absorbing polymer, it is possible to reduce the inhibition of orientation of the coexisting needle-like filler. It is not clear about the mechanism that can achieve both the orientation of the needle-like filler 53b1 in the short direction of the elastic layer 27b and the formation of the void 53b2. Due to the thixotropy developed in the uncrosslinked addition-curable liquid silicone rubber in which the needle-like filler 53b1 and the water-containing material are dispersed (hereinafter, this liquid is referred to as a liquid composition), the viscosity is lowered when the liquid composition flows. Therefore, it is assumed that the orientation of the needle-like filler 53b1 is not likely to be hindered.

  The porosity of the elastic layer 27b is preferably 10% by volume or more and 70% by volume or less. By setting the porosity within the above range, not only the necessary elastic modulus can be obtained, but also the elastic modulus can be prevented from changing due to durability.

<Needle filler 53b1>
As the acicular filler used in the present invention, as shown in FIG. 6, a material having a large ratio of the length L to the diameter D, that is, a high aspect ratio can be used. The shape of the bottom surface of the filler may be circular or square, and can be applied as long as the material is oriented by the molding method described later.

  An example of such a material is pitch-based carbon fiber (carbon fiber: CF). When this pitch-based carbon fiber is needle-shaped, it is possible to provide a pressure pad 27 as a more preferable pressure member. As a more specific shape of the acicular pitch-based carbon fiber, one having a diameter D of 5 μm to 11 μm and a length L (average length) of about 50 μm to 1000 μm in FIG. It is easy to obtain.

  Since acicular (bar-shaped) carbon fibers have high tensile strength and little elongation, when carbon fibers are oriented, they are difficult to deform in the oriented direction. Therefore, by increasing the orientation of the carbon fibers in the short direction of the elastic layer 27b of the pressure pad 27, the elastic layer 27b is not easily deformed in the short direction, which is the paper conveying direction, and in the thickness direction or the long direction. It becomes easy to deform. Since it is difficult to deform in the short direction, good separation can be realized as will be described later. Since it is easily deformed in the thickness direction and the longitudinal direction, paper edge damage can be reduced as will be described later.

  In addition, the orientation direction of the carbon fiber (longitudinal direction thereof) is not only in a form that coincides with the short direction of the elastic layer 27b, but also in a relationship that intersects the short direction within a range that satisfies the relationship of elastic modulus described later. It doesn't matter.

  Here, it is desirable that 5 to 40% by volume of the needle-like filler 53b1 is contained in the elastic layer 27b. By setting the content of the acicular filler within the above range, the elastic modulus of the elastic layer 27b according to the present invention can be more reliably improved. In addition, the moldability of the elastic layer 27b due to the inclusion of the needle filler 53b1 is hardly affected.

  In the present invention, unless the range of the features of the invention is exceeded, the elastic layer 27b includes fillers, fillers and compounding agents not described in the present invention as means for solving known problems. It doesn't matter.

(4) Pressure pad manufacturing method <Liquid composition formulation>
The above-mentioned acicular filler 53b1 and the above-mentioned water-containing material are blended with the uncrosslinked addition-curable liquid silicone rubber. The blending can be performed by weighing a predetermined amount of uncrosslinked addition-curing liquid silicone rubber, needle-like filler 53b1, and water-containing material, and dispersing the mixture by a known filler mixing and stirring means such as a planetary universal mixing and stirring machine. is there.

<Liquid composition layer formation>
The liquid composition is cast by a known method. A liquid composition is cast on a substrate 27a in a mold in which a substrate 27a that has been subjected to a known primer treatment is placed, while flowing in the lateral direction of the substrate 27a. By this flow, the needle-like filler 53b1 is oriented in the short direction of the elastic layer, and the elastic modulus in the short direction of the elastic layer can be increased. That is, the elastic layer 27b has anisotropy in which the elastic modulus in the short direction is greater than the elastic modulus in the thickness direction with respect to the elastic modulus.

  Note that there is no particular limitation as long as it is a method capable of forming a layer while applying a flow of the liquid composition in the short direction of the substrate 27a.

<Silicon rubber component cross-linking cure>
The mold filled with the liquid composition is sealed and heat treated at a temperature below the boiling point of water for 5 to 120 minutes to crosslink and cure the silicone rubber component. As heat processing temperature, 60-90 degreeC is desirable. Since it is under sealing, the silicone rubber component in the layer of the liquid composition can be cross-linked and cured while keeping the moisture in the water-containing material.

<Demolding>
After appropriately cooling the mold with water or air, the substrate 27a on which the liquid composition layer after crosslinking and curing is laminated is removed from the mold.

<Dehydration>
The liquid composition layer laminated on the base body 27a is dehydrated by evaporating moisture in the water-containing material by heat treatment, thereby forming the gap 53b2. As heat processing conditions, 100 to 250 degreeC and 1 to 5 hours are desirable. By forming the gap 52b2, the thermal conductivity in the thickness direction of the pressure pad 27 is reduced.

(5) Example The base body 27a was an elongated iron sheet metal having a thickness of 2 mm, a length of 320 mm in the longitudinal direction, and a length of 20 mm in the short direction. The water-containing material is obtained by adding water to Rheosic 250H (manufactured by Toa Gosei Co., Ltd.). The amount of Rheological 250H was adjusted to 1 wt% with respect to the water-containing material. The needle-like filler 53b1 used the pitch-based carbon fiber shown below.

<Product Name: XN-100-01Z (Nippon Graphite Fiber Co., Ltd.)>
Average fiber diameter D: 10 μm
Average fiber length L: 1mm
Thermal conductivity 900W / (m · K)
This acicular filler is hereinafter referred to as 100-01.

  In the present embodiment, the elastic layer 27b and the base 27a are bonded together with the liquid A and liquid B of “DY39-051” (trade name, manufactured by Toray Dow Corning Co., Ltd.).

  In the liquid composition blending step, a universal mixing stirrer was used, and in the silicone rubber component curing step, heat treatment was performed in a hot air oven at 90 ° C. for 1 hour. In the formation process of the elastic layer 4b, the pipe-shaped cylindrical shape having the inner diameter of 30 (mm) was used. Furthermore, in the dehydration process, heat treatment was performed in a hot air oven at 200 ° C. for 4 hours.

Example 1
7% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer was poured into a mold in which a base 27a had been installed, and an elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. In this way, a pressure pad of Example 1 was obtained.

(Example 2)
10% by volume of needle-shaped filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer was poured into a mold in which a base 27a had been installed, and an elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. In this way, a pressure pad of Example 1 was obtained.

(Comparative Example 1)
A water-containing material was mixed in an amount of 10% by volume with an uncrosslinked addition-curable liquid silicone rubber containing no needle-like filler. Next, a liquid composition for forming an elastic layer was poured into a mold in which a base 27a had been installed, and an elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. Thus, the pressurizing pad of Comparative Example 1 was obtained.

(Comparative Example 2)
2% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer was poured into a mold in which a base 27a had been installed, and an elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. Thus, the pressure pad of this comparative example 2 was obtained.

(Comparative Example 3)
5% by volume of needle-shaped filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer was cast in a mold having a base 27a installed therein so as to minimize the flow, and the elastic layer 27b was formed through the steps of crosslinking, demolding and dehydration. . Thus, the pressure pad of this comparative example 3 was obtained.

(Comparative Example 4)
An uncrosslinked addition-curing liquid silicone rubber containing no acicular filler and a water-containing material is cast, and a liquid composition for forming an elastic layer is cast into a mold in which a base 27a is already installed, and crosslinking, demolding and dehydration are performed. The elastic layer 27b was formed through the process. In this way, a pressure pad of Comparative Example 5 was obtained.

(Evaluation method)
<Elastic modulus in thickness direction and longitudinal direction>
The elastic modulus of the cut sample 53bs of the elastic layer 27b of the pressure pad 27 was measured as follows.

  In this measurement example, first, the elastic modulus was measured in the longitudinal direction. A sample of the elastic layer 27b is cut out from the pressure pad 27 in the short direction (5 mm) × longitudinal direction (15 mm) × thickness (3 mm), and after measuring the thickness, a tensile tester (Tensilon RTC-1250A, Orientec Co., Ltd.) ) To be pulled in the longitudinal direction. The thickness is the average of 5 points in the sample. Tensile test is performed with a measurement interval of 5 mm and a test speed of 0.025 mm / min. Elongation and stress are recorded with a recorder, and when the elongation is 0.2% and 0.5%, the stress is read. Calculate the rate. This measurement is performed 5 times, and the average value is the elastic modulus of the present invention.

Elastic modulus = (f2−f1) / (20 × t) × 1000 [MPa]
(In the formula, f1 represents a stress [N] of 0.2% elongation, f2 represents a stress [N] of 0.5% elongation, and t represents a thickness [mm] of the sample.)
Regarding the thickness direction, the measurement was performed in the same manner as described above except that it was attached to a tensile tester so as to be pulled in the thickness direction.

<Separation evaluation>
For the evaluation of separability, the fixing device 110 shown in FIG. 2 on which the pressure pads of Examples 1 and 2 and Comparative Examples 1 to 4 manufactured by the above method were mounted was used. The rotational peripheral speed of the fixing roller 20 mounted on the fixing device 110 was adjusted to be 234 mm / sec, and the fixing roller temperature was set to 180 ° C. The separation roller 26 and the pressure pad 27 were arranged close to each other so that a pressure relief portion was formed and icicle-shaped gloss unevenness did not occur.

The paper that has passed through the nip N of the fixing device 110 as paper P is 52.3 g / m ² (manufactured by Oji Paper) of OK Prince Quality Eco G100. An unfixed toner image having the maximum density was placed on the paper and fixed, and it was judged whether or not a jam or a corner break occurred.

<Edge crack>
First, 1000 sheets of high-quality color laser copier paper 80 g / m ² (manufactured by Canon) is passed through the fixing device 110 by A4R feeding (conveyed in the longitudinal direction), and the surface of the fixing roller 20 is placed horizontally. The edge part of a direction (direction orthogonal to a conveyance direction) is damaged by the edge part. Next, coated paper OK top coat 128 g / m ² (manufactured by Oji Paper Co., Ltd.) is A4 fed (conveyed in the short direction) to form a cyan halftone uniform image. Judgment was made based on whether gloss unevenness caused by scratches on the fixing roller (edge scratches) due to the edge portion was observed at a position corresponding to the A4R width paper edge on the image.

<Evaluation results>
Table 1 shows the evaluation results of thermal conductivity ratio α, separability, and edge scratches. In Example 1, the elastic modulus in the thickness direction of the elastic layer 27b was low, the elastic modulus in the short direction was high, and α was 1.5. Since the elastic modulus in the thickness direction is low, edge cracks do not occur, and since the elastic modulus in the short direction is high, the separability is also good. From this, it was found that if α is 1.5, both separability and edge scratches can be achieved. In Example 2, α was 1.9, and both edge cracks and separability were good.

  In Comparative Example 1 in which the elastic layer 27b did not contain the needle filler, α was 1.0, and the elastic modulus in the short direction of the elastic layer 27b was low, resulting in insufficient separation.

  In Comparative Example 2 in which the elastic layer 27b contained less acicular filler, α was 1.3. Since the separability is insufficient, it can be determined that the elastic layer 27b has a low elastic modulus in the short direction and the deformation amount is too large. Therefore, when α is 1.3, it has been found that there is a case where the separability and the edge scratch may not be compatible.

  In Comparative Example 3 where the elastic layer 27b contains a needle-like filler but the orientation is not good, α is 1.1 and the separability is insufficient. From this, it was found that the orientation of the filler increases the elastic modulus in the short direction of the elastic layer 27b, so that both separability and edge damage can be achieved.

  In Comparative Example 4 in which the elastic layer 27b did not contain acicular fillers and did not have voids, α was 1.0 and the level of edge damage was not good. Since the elastic layer 27b has a high elastic modulus in the short direction, the separability is good, but since α is small, it can be determined that the elastic modulus is also high in the thickness direction and the level of edge scratches is not good.

  As described above, the elastic layer 27b of the pressure member 27 has a characteristic (anisotropy) in which the elastic modulus in the short side direction is larger than the elastic modulus in the thickness direction. Preferably, the elastic layer 27b is configured such that the elastic modulus in the short direction is 1.5 times or more the elastic modulus in the thickness direction. More specifically, the elastic layer includes a needle-like filler, and the needle-like filler is oriented so that the elastic modulus in the short direction of the elastic layer is larger than the elastic modulus in the thickness direction.

  Thereby, even if it is set so that gloss unevenness does not occur, it is possible to provide a pressure pad that can both prevent jamming due to poor separation and paper edge damage, and a fixing device including the pressure pad.

<< Second Embodiment >>
In the present embodiment, the pressure pad of the first embodiment and the fixing device including the pressure pad can further obtain the effect of suppressing the temperature rise of the non-sheet passing portion and the effect of shortening the startup time. It is a thing.

  In a fixing device that uses a pressure pad, the non-passage area when a large amount of small size paper that is smaller than the maximum width of paper that can be used in the device is passed or when a small size paper that is thick is passed. There is a problem that the so-called non-sheet passing portion temperature rise increases. In the case of a fixing device using a pressure pad, the pressure pad has a small heat capacity and easily rises in temperature.

  Further, since the pressure pad is a fixed member that does not rotate, it constantly exists in the nip. Therefore, the pressure pad type fixing device which is constantly present in the nip and does not relax the temperature rise of the non-sheet passing portion is not heated against the pressure roller in which the temperature rise at the end portion is mitigated outside the nip. It gets bigger.

  On the other hand, there is generally known a technique for reducing the temperature increase of the non-sheet passing portion by not heating the non-sheet passing portion by having a plurality of heating sources corresponding to the paper size. However, having a plurality of heating elements increases the size, complexity, and cost of the apparatus. Also, it is difficult to cope with all paper sizes.

  A method of increasing the thermal conductivity of the pressure roller is generally known as a means for reducing the temperature rise of the non-sheet passing portion. This is because, by positively improving the heat transfer property of the elastic layer, it is possible to obtain the effect of lowering the temperature rise temperature of the non-sheet passing portion, that is, reducing the difference in heat in the longitudinal direction.

  Japanese Patent No. 4508692 discloses that 12 vol% to 26 vol% of acicular pitch-based carbon fibers having an average length of 100 μm to 500 μm and a thermal conductivity of 300 W / m · K or more are dispersed in the elastic layer of the pressure member. To do. Thus, a pressure member having an elastic body with low hardness and high thermal conductivity is described. In this case, if the thermal conductivity of the elastic layer of the pressurizing member is increased, the amount of heat transferred from the fixing member to the pressurizing member at the time of start-up increases. The raising time tends to be longer.

  Japanese Patent Application Laid-Open No. 2002-351243 integrally forms a high thermal conductive rubber composite layer on a pressure member. The thermal conductivity of the pressure member surface is such that the thermal conductivity of the high thermal conductive rubber composite layer has anisotropy and the heat flow in the direction intersecting the recording material conveyance direction is greater than the heat flow in the other direction. Causes anisotropy in the flow of water. Thus, a method for reducing the temperature increase in the non-sheet passing portion is described. Further, it is described that a rise time can be shortened by providing a porous elastic layer below the elastic layer and reducing the thermal conductivity in the elastic layer thickness direction.

  In this pressurizing member, the high thermal conductive rubber composite and the heat insulating rubber are formed in separate steps, and the manufacturing process may be complicated. In addition, even a member having high thermal conductivity requires a certain thickness in order to obtain a sufficient amount of heat transfer. When the elastic layer is composed of a plurality of layers, the elastic layer may be thick. When the elastic layer becomes thick, the amount of deformation of the elastic layer increases, and it may be difficult to adjust the thickness distribution.

  Therefore, the present embodiment also provides the effect of suppressing the temperature rise of the non-sheet passing portion and the effect of shortening the startup time for the pressure pad of the first embodiment and the fixing device including the pressure pad. It is intended to be.

(1) Pressure pad In contrast to the second embodiment described above, this embodiment differs from the above-described second embodiment only in the orientation of the needle-like filler 27b1 in the elastic layer of the pressure pad 27. Since the apparatus configuration and the pressure pad configuration are the same, a repetitive description thereof will be omitted.

  In the present embodiment, the elastic layer 27b of the pressure pad 27 has a characteristic (anisotropy) in which the elastic modulus in the short direction is larger than the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is higher than the thermal conductivity in the thickness direction. It has large characteristics (anisotropy). Preferably, the elastic modulus in the short direction of the elastic layer 27b is 1.5 times or more the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is 6 times or more and 900 times or less than the thermal conductivity in the thickness direction. It is. More specifically, the elastic layer 27b includes a needle-like filler, the elastic modulus in the short direction of the elastic layer is larger than the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is higher than the thermal conductivity in the thickness direction. Oriented to be larger.

  In the pressure pad 27 of this embodiment, needle-like fillers 53b1 are present in the elastic layer in the short-side direction and the long-side direction. That is, in the cut sample 53bs cut out from the elastic layer 27b in FIG. 4, the longitudinal section (a section) and the short section (b section) are observed. As shown in FIG. 8A, both the cross section of the diameter D of the acicular filler 53b1 and the length L of the acicular filler 53b1 can be observed in the a cross section. Similarly, as shown in FIG. 8B, both the cross section of the needle filler 53b1 having the diameter D and the length L of the needle filler 53b1 can be observed in the b cross section.

  However, neither of them has a portion with a length L facing in the vertical direction (thickness direction of the elastic layer 27b). This can be determined that the orientation of the needle-like filler 53b1 is the short direction and the long direction, and is not oriented in the thickness direction. Moreover, the space | gap 53b2 distributed uniformly can be observed also in (a) and (b) of FIG.

  As described above, when the needle-like filler 53b1 is oriented in the elastic layer 27b, the needle-like filler 53b1 hinders deformation when attempting to deform the elastic layer 27b in the orientation direction of the needle-like filler 53b1. Therefore, the elastic modulus is increased. In the direction where the needle-like filler 53b1 is not oriented, the elastic modulus is low because the deformation is not hindered.

  Therefore, in this embodiment, the elastic modulus is high in the short and long directions of the elastic layer 27b, and the elastic modulus is low in the thickness direction. Further, when the needle-like filler 27b is put into the elastic layer 27b, the elastic modulus tends to increase. However, by providing the void 53b2 in the elastic layer 27b, it is possible to prevent the elastic modulus from becoming too high. Further, by forming the gap 52b2, the thermal conductivity in the thickness direction of the pressure pad 27 is reduced.

  On the other hand, regarding the thermal conductivity in the longitudinal direction and the short direction of the elastic layer 27b, the needle-like filler 53b1 oriented in the longitudinal direction and the short direction serves as a heat conduction path, and the thermal conductivity is maintained higher than that in the thickness direction. Is done.

  By forming the gap 53b2, the thermal conductivity in the thickness direction of the elastic layer 27b is reduced. On the other hand, for the thermal conductivity in the longitudinal direction of the elastic layer 27b, the needle-like filler 53b1 oriented in the longitudinal direction of the elastic layer 27b serves as a thermal conduction path, and the thermal conductivity is maintained higher than that in the thickness direction.

  In addition, the orientation direction of the acicular filler (longitudinal direction) is not only in the form matching the short direction and the long direction of the elastic layer 27b, but also short in the range satisfying the relationship between the elastic modulus and the thermal conductivity. It does not matter if the relationship intersects the direction or the longitudinal direction.

  The elastic layer 27b preferably has a ratio λ1 / λ2 of the thermal conductivity λ1 in the longitudinal direction and the thermal conductivity λ2 in the thickness direction (hereinafter referred to as α) of 6 to 900. If the thermal conductivity ratio α is less than 6, the effect of suppressing the temperature rise of the non-sheet passing portion may not be sufficiently obtained. Moreover, in order to make it larger than 900 times, the amount of acicular fillers and voids increase, and it is difficult to process and mold.

  The thermal conductivity in the thickness direction is preferably 0.08 W / (m · K) or more and 0.4 W / (m · K) or less. When the thickness direction thermal conductivity is lower than 0.08 W / (m · K), it may be difficult to process or the strength as a pressurizing rotating body mounted on a heating device may not be obtained due to the large amount of voids. . In the thickness direction thermal conductivity higher than 0.4 W / (m · K), the effect of shortening the rise time may not be sufficiently obtained.

  By including, for example, pitch-based carbon fiber having a thermal conductivity λ of 500 W / (m · K) or more as the needle-like filler 53b1, the features of the pressure pad 27 as the pressure member of the present invention are suitably implemented. it can. Furthermore, when the pitch-based carbon fiber has a needle shape, the characteristics of the pressure pad 27 as the pressure member of the present invention more appropriately appear.

  When needle-like (rod-like) carbon fibers are oriented, a heat path is formed in the oriented direction, so that heat conduction is improved. Further, as described above, since the carbon fiber has a high tensile strength and little elongation, when the carbon fiber is oriented, it is difficult to be deformed in the oriented direction.

  Therefore, the elastic layer 27b of the pressure pad 27 is increased in the longitudinal direction by increasing the orientation of the carbon fibers in the short direction and the longitudinal direction of the elastic layer 27b of the pressure pad 27 and decreasing the orientation of the carbon fibers in the thickness direction. In the short direction, heat conduction is large, and in the thickness direction, heat conduction is small. Therefore, as will be described later, it is possible to achieve both relaxation of the temperature rise of the non-sheet passing portion and reduction of the startup time. Moreover, since it is hard to deform | transform in a transversal direction, favorable separability can be implement | achieved so that it may mention later. Since it easily deforms in the thickness direction, it is possible to reduce paper edge scratches as will be described later.

  That is, in the case of the pressure pad 27 of this embodiment, the elastic modulus in the short direction of the elastic layer 27b is high and the elastic modulus is low in the thickness direction due to the orientation of the needle-like filler 53b1 in the short direction of the elastic layer 27b. For this reason, as described with reference to FIG. 8 for the pressure pad 27 of the first embodiment, even if the setting is such that gloss unevenness does not occur, the pressure pad that can simultaneously prevent jamming due to poor separation and paper edge damage, A fixing device having a pressure pad can be provided.

  In the case of the pressure pad 27 of the present embodiment, the needle-like filler 53b1 is also oriented in the longitudinal direction of the elastic layer 27b. Therefore, for the thermal conductivity in the longitudinal direction and the short direction of the elastic layer 27b, the needle-like filler 53b1 oriented in the longitudinal direction and the short direction becomes a thermal conduction path, and the thermal conductivity is higher than that in the thickness direction. Maintained. Thereby, the effect of suppressing the temperature rise of the non-sheet passing portion and shortening the rise time can be obtained.

(2) Method for Manufacturing Pressure Pad The method for manufacturing the pressure pad 27b is the same as the method for manufacturing the pressure pad 27b described in the first embodiment. However, in the case of this embodiment, in the step of <liquid composition layer formation>, the liquid composition is applied to the substrate 27a on the substrate 27a in the mold in which the substrate 27a subjected to a known primer treatment is placed in advance. Cast while giving flow in the short and long direction. By this flow, the needle-like filler 53b1 can be oriented in the short and long directions of the elastic layer, and the elastic modulus and thermal conductivity in the short and long directions of the elastic layer can be increased. There is no particular limitation as long as the layer can be formed while applying a flow in the lateral direction and the longitudinal direction of 27a.

(3) Example The base body 27a was a long and thin iron sheet metal having a thickness of 2 mm, a length of 320 mm in the longitudinal direction, and a length of 20 mm in the short direction. The water-containing material is obtained by adding water to Rheosic 250H (manufactured by Toa Gosei Co., Ltd.). The amount of Rheological 250H was adjusted to 1 wt% with respect to the water-containing material. The needle-like filler 53b1 used the pitch-based carbon fiber shown below.

<Product Name: XN-100-01Z (Nippon Graphite Fiber Co., Ltd.)>
Average fiber diameter D: 10 μm
Average fiber length L: 1mm
Thermal conductivity 900W / (m · K)
This acicular filler is hereinafter referred to as 100-01.

  In the present embodiment, the elastic layer 27b and the base 27a are bonded together with the liquid A and liquid B of “DY39-051” (trade name, manufactured by Toray Dow Corning Co., Ltd.).

  In the liquid composition blending step, a universal mixing stirrer was used, and in the silicone rubber component curing step, heat treatment was performed in a hot air oven at 90 ° C. for 1 hour. In the formation process of the elastic layer 4b, the pipe-shaped cylindrical shape having the inner diameter of 30 (mm) was used. Furthermore, in the dehydration process, heat treatment was performed in a hot air oven at 200 ° C. for 4 hours.

Example 1
7% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, after casting the liquid composition for forming an elastic layer in a mold in which the base 27a has been installed while applying a flow in the short direction of the base 27a, vibration is applied in the longitudinal direction of the base 27a. The elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. In this way, a pressure pad of Example 1 was obtained.

(Example 2)
10% by volume of needle-shaped filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, after casting the liquid composition for forming an elastic layer in a mold in which the base 27a has been installed while applying a flow in the short direction of the base 27a, vibration is applied in the longitudinal direction of the base 27a. The elastic layer 27b was formed through casting, cross-linking, demolding, and dehydration processes. Thus, a pressure pad of Example 2 was obtained.

(Comparative Example 1)
A water-containing material was mixed in an amount of 10% by volume with an uncrosslinked addition-curable liquid silicone rubber containing no needle-like filler. Next, a liquid composition for forming an elastic layer was poured into a mold in which a base 27a had been installed, and an elastic layer 27b was formed through the steps of crosslinking, demolding, and dehydration. Thus, the pressurizing pad of Comparative Example 1 was obtained.

(Comparative Example 2)
7% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer is poured into a mold in which the base body 27a has been installed in the mold 27 by flowing in the longitudinal direction of the base body 27a, and the elastic layer 27b is subjected to crosslinking, demolding and dehydration processes. Formed. Thus, the pressure pad of this comparative example 2 was obtained.

(Comparative Example 3)
7% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer is poured into a mold in which the base body 27a has been installed in the mold so as to flow in the short direction of the base body 27a, and the elastic layer is subjected to crosslinking, demolding, and dehydration processes. 27b was formed. Thus, the pressure pad of this comparative example 3 was obtained.

(Comparative Example 4)
7% by volume of acicular filler “100-01” and 10% by volume of water-containing material were mixed with uncrosslinked addition-curable liquid silicone rubber. Next, a liquid composition for forming an elastic layer is poured over a mold in which a base body 27a has been installed in a mold so as not to flow as much as possible, and the elastic layer 27b is subjected to crosslinking, demolding, and dehydration processes. Formed. Thus, the pressure pad of this comparative example 4 was obtained.

(4) Evaluation method <Elastic modulus in thickness direction and longitudinal direction>
This is the same as the measuring method of <elasticity in thickness direction and longitudinal direction> in the first embodiment.

<Thermal conductivity in the thickness direction and longitudinal direction>
The thermal conductivity of the cut sample 53bs of the elastic layer 27b of the pressure pad 27 was measured as follows. In this measurement example, first, thermal conductivity measurement in the longitudinal direction was performed. The measurement of the thermal conductivity in the longitudinal direction and the thickness direction of the elastic layer 27b of the pressure pad 27 will be described with reference to FIG. FIG. 10 shows the thermal conductivity evaluation of the elastic layer 27b created by superimposing the sample 53bs cut in the short direction (15 mm) × longitudinal direction (15 mm) × thickness (set thickness) to have a thickness of about 15 mm. Sample.

  When measuring the thermal conductivity, as shown in FIG. 10, the sample to be measured was fixed with a tape TA having a thickness of 0.07 mm and a width of 10 mm. Next, in order to make the measured surface flat, the measured surface and the measured surface back surface are cut with a razor. Then, two sets of the sample to be measured are prepared, the sensor S is sandwiched between the samples to be measured, and measurement is performed. For the measurement, a hot disk method thermophysical property measuring apparatus TPA-501 (manufactured by Kyoto Electronics Industry Co., Ltd.) was used.

  When measuring the thermal conductivity in the thickness direction, the direction of the sample to be measured was changed by the same method as described above. In this measurement example, the ratio α between the longitudinal thermal conductivity λ1 and the thicknesswise thermal conductivity λ2 was calculated using an average value of five thermal conductivity measurements in the longitudinal direction and the thickness direction.

  <Separation evaluation> and <edge scratch> are the same as <Separation evaluation> and <edge scratch> in the first embodiment.

<Non-paper passing part temperature rise>
The fixing device 110 shown in FIG. 2 on which the pressure pads of Examples 1 and 2 and Comparative Examples 1 to 4 manufactured by the above method were mounted was used for the non-sheet passing portion temperature rise. The speed of the fixing roller 20 mounted on the fixing device 110 was adjusted to be 234 mm / sec, and the fixing roller temperature was set to 180 ° C. The paper that passed through the nip N of the fixing device 110 as paper P is A4 vertical size paper (GF-C081 manufactured by Canon Inc.). The temperature of the surface of the fixing roller in a non-sheet-passing region (a region where A4 vertical size paper does not pass) when 500 sheets are continuously fed was measured. Judgment was made based on whether or not the durable fracture temperature of 230 ° C was exceeded.

<Rise time>
For the evaluation of the rise time, the time from when the heater switch was turned on until the surface temperature of the fixing roller 20 reached 180 ° C. was measured in the idling state where no paper is passed through the fixing device 110. The rise time was judged by whether it was 23 seconds or less.

<Evaluation results>
The specifications of each pressure pad in Examples 1-2 and Comparative Examples 1-4 are summarized in FIG. Table 3 shows the evaluation results of separability, edge scratches, non-sheet passing portion temperature rise, and start-up time of each pressure pad in Examples 1-2 and Comparative Examples 1-4.

  In Example 1, since the elastic modulus in the thickness direction of the elastic layer 27b was low and the elastic modulus in the short side direction was high, edge cracks did not occur and the separability was good. In addition, since the thermal conductivity in the longitudinal direction was high and the thermal conductivity in the thickness direction was low, the temperature rise at the non-sheet passing portion was good and the startup time was short.

  Similarly in Example 2, since the elastic modulus in the thickness direction of the elastic layer 27b is low and the elastic modulus in the short-side direction is high in Example 1, the edge damage does not occur and the separability is good. In addition, since the thermal conductivity in the longitudinal direction was high and the thermal conductivity in the thickness direction was low, the temperature rise at the non-sheet passing portion was good and the startup time was short.

  In the comparative example 1 which does not contain an acicular filler, since the elastic modulus in the short direction of the elastic layer 27b was low, the separability was not good. Further, since the thermal conductivity in the longitudinal direction is low, the temperature rise in the non-sheet passing portion becomes remarkable.

  In Comparative Example 2 in which the needle-like filler is oriented in the longitudinal direction of the elastic layer 27b, the thermal conductivity in the longitudinal direction is high and the thermal conductivity in the thickness direction is low. The raising time was short. However, since the elastic modulus in the short direction was low, the separability was not good.

  In Comparative Example 3 in which the needle-like filler is oriented in the short direction of the elastic layer 27b, the elastic modulus in the thickness direction is low, and the elastic modulus in the short direction is high. there were. However, since the thermal conductivity in the longitudinal direction is low, the temperature rise at the non-sheet passing portion becomes remarkable.

In Comparative Example 4 in which the needle-like filler is not oriented in the elastic layer 27b, the elastic modulus is increased in the thickness direction, so that the flaws become conspicuous. In addition, since the thermal conductivity in the thickness direction has increased, the startup time has become longer. As described above, the elastic layer 27b of the pressure pad 27 has a greater elastic modulus in the short direction than in the thickness direction. The characteristics and the thermal conductivity in the longitudinal direction are larger than the thermal conductivity in the thickness direction. Preferably, the elastic modulus in the short direction of the elastic layer 27b is 1.5 times or more the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is 6 times or more and 900 times or less than the thermal conductivity in the thickness direction. It is. More specifically, the elastic layer 27b includes a needle-like filler, the elastic modulus in the short direction of the elastic layer is larger than the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is higher than the thermal conductivity in the thickness direction. Oriented to be larger.

  Thereby, even if it is set so that gloss unevenness does not occur, it is possible to achieve both the prevention of jamming due to poor separation and paper edge scratches, and the pressure pad that achieves both non-sheet passing portion temperature rise and startup time, and the pressure pad Can be provided.

<< Third Embodiment >>
The configuration of the image heating apparatus 110 is not limited to the roller heating-belt pressure type image heating apparatus as in the first and second embodiments. 11, 12, and 13 are schematic views of other device configuration examples, respectively.

  (1) FIG. 11 shows a twin belt type device. This apparatus includes a heating belt unit 60 using a flexible endless belt (heating belt: heating member) 61, and a pressure belt unit 30 using a flexible endless belt (pressure belt) 21. Have

  The heating belt unit 60 includes a fixing roller 62 having an elastic layer, a tension roller 63, a pressure pad 27A, a heating belt 61 that is stretched around these and is heated by electromagnetic induction, and the heating belt 61. A coil 64 for induction heating. The pressure belt unit 30 is the same as the pressure belt unit 30 of the fixing device of FIG.

  The separation roller 26 is in pressure contact with a fixing roller 62 having an elastic layer with the pressure belt 27 and the heating belt 61 interposed therebetween. The pressure pad 27 is in pressure contact with the pressure pad 27 </ b> A across the pressure belt 27 and the heating belt 61. Thus, a wide nip N is formed between the heating belt 61 of the heating belt unit 60 and the pressure belt 27 of the pressure belt unit 30 in the paper conveyance direction c. The heating belt 61 and the pressure belt 21 are rotationally driven in the directions of arrows R61 and R21, respectively. The heating belt 61 is raised to a predetermined fixing temperature by a coil 64 and is temperature-controlled. The paper P is nipped and conveyed by the nip N and heated.

  (2) The apparatus shown in FIG. 12 supports a flexible endless belt (heating belt) 61 as a heating member by applying tension between the plurality of support members 71 to 73. Then, the belt 61 is rotationally driven in the clockwise direction of the arrow R61 by a support roller 71 as a driving member driven by the motor M.

  A fixed heater (heating source) 74 supported by a fixed stay 72 as a heater support member is disposed inside the belt 61 so as to contact the inner surface of the belt 61. An apparatus configuration in which a pressure pad 27 as a fixed pressure member that forms a nip N together with the heater 74 is pressed through the belt 61 may be used. The paper P is nipped and conveyed by the nip N and heated.

  The heater 74 can be, for example, a ceramic heater, a nichrome wire heater, or an electromagnetic induction heating member. Further, the belt 61 may be provided with an energization heat generating layer to generate heat. The surface of the pressure pad 27 on which the belt 61 and the paper P are rubbed can be provided with a surface layer having a small friction coefficient with the belt 61 and the paper P, or covered with a sheet material.

  (3) The apparatus shown in FIG. 13 uses a flexible web-shaped belt 61A having flexibility and traveling as a heating member from the feeding portion 81 to the winding portion 82. A fixed heater (heating source) 74 supported by a fixed support member 83 inside the belt 61A is disposed between the feeding portion 81 and the winding portion 82 in contact with the inner surface of the belt 61A. It is also possible to adopt an apparatus configuration in which a pressure pad 27 as a pressure member that forms a nip N together with the heater 74 is pressed through the belt 61A. The paper P is nipped and conveyed by the nip N and heated.

  In each apparatus of FIGS. 11 to 13, the pressure pads 27 and 27A as pressure members are configured in the same manner as the pressure pad 27 described in the apparatus 110 of the first or second embodiment.

《Other matters》
(1) In the image heating apparatus according to the present invention, in addition to an apparatus that heats an unfixed toner image (developer image, developer image) and fixes or presupposes it as a fixed image, the fixed toner image is reproduced again. An apparatus for modifying the surface properties such as gloss by heating is also included.

  (2) The image forming unit of the image forming apparatus is not limited to the electrophotographic system. The image forming unit may be an electrostatic recording system or a magnetic recording system. Further, the toner image is not limited to the transfer method, and a toner image may be formed directly on the recording material.

  (3) In the embodiment, the fixing device 110 may be implemented by a mono-color or full-color image forming apparatus other than the electrophotographic printer of the embodiment, a copying machine, a facsimile, a printer, a complex machine of these, or the like. That is, the fixing device and the electrophotographic printer according to the embodiment are not limited to the combination of the above-described constituent members, and may be realized by another embodiment in which a part or all of the replacement members are replaced.

  115 ·· Image heating device (fixing device), 20 · · Heating member, 30 · · Pressure belt unit, N · · Nip, 27 · · Pressure member (pressure pad), 27a · · Base, 27b · · Elastic layer, P ... Recording material, T ... Toner image

Claims (33)

An elongate pressure member for an image heating apparatus that has an elastic layer and is fixedly formed, together with a heating member, a nip that heats the recording material carrying the image while nipping and conveying the recording material,
The pressure member, wherein the elastic layer has a characteristic that an elastic modulus in a short side direction is larger than an elastic modulus in a thickness direction.   The pressure member according to claim 1, wherein an elastic modulus in a short direction of the elastic layer is 1.5 times or more of an elastic modulus in a thickness direction.   The said elastic layer contains an acicular filler, The said acicular filler is orientated so that the elastic modulus of the transversal direction of the said elastic layer may become larger than the elastic modulus of the thickness direction. 2. A pressing member according to 2.   The pressure member according to claim 3, wherein the needle-like filler has an average length of 50 μm to 1000 μm.   The pressure member according to claim 3 or 4, wherein the elastic layer contains 5 to 40% by volume of the acicular filler.   The pressure member according to any one of claims 3 to 5, wherein the needle-like filler is carbon fiber.   The pressure member according to claim 1, wherein the elastic layer includes a mixture of addition-curable silicone rubber.   The pressure member according to any one of claims 1 to 7, wherein the elastic layer is porous.   The pressure member according to claim 8, wherein the elastic layer has a porosity of 10 volume% or more and 70 volume% or less.   The pressure member according to any one of claims 1 to 9, wherein the elastic layer is supported by a rigid base.   An image heating apparatus comprising the pressure member according to claim 1.   The image heating apparatus according to claim 11, wherein the heating member is a rotating body that is rotationally driven.   The image heating apparatus according to claim 12, wherein the rotating body is a heating roller or a heating belt.   14. A belt having a nip formed with the rotating body, wherein the pressure member applies pressure from the inside of the belt toward the rotating body at the nip. The image heating apparatus described in 1.   An image forming apparatus comprising the image heating apparatus according to claim 12. It is a manufacturing method of the pressurization member according to any one of claims 1 to 10,
1) A composition of an uncrosslinked addition-curable liquid silicone rubber in which a water-containing material in which water is contained in a water-absorbing polymer and a needle-like filler is dispersed, and a short of the substrate is placed in a mold in which an elongated substrate of a pressure member is set. A casting process for casting while giving flow in the hand direction;
2) A cross-linking and curing step in which the mold filled with the composition is sealed and heat-treated at a temperature below the boiling point of water to cross-link and cure the silicone rubber component;
3) a demolding step of demolding the substrate on which the composition has been cast from the mold, cross-linked and cured, and laminated;
4) a dehydration step in which the composition laminated on the demolded substrate is heat-treated to evaporate water in the water-containing material and dehydrate to form voids;
A method for producing a pressure member, comprising: An elongate pressure member for an image heating apparatus that has an elastic layer and is fixedly formed, together with a heating member, a nip that heats the recording material carrying the image while nipping and conveying the recording material,
The elastic layer is characterized in that the elastic modulus in the short direction is greater than the elastic modulus in the thickness direction and the thermal conductivity in the longitudinal direction is greater than the thermal conductivity in the thickness direction. Element.   The elastic modulus in the short direction of the elastic layer is 1.5 times or more of the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is 6 times or more and 900 times or less than the thermal conductivity in the thickness direction. The pressure member according to claim 17.   The pressure member according to claim 17 or 18, wherein a thermal conductivity in a thickness direction of the elastic layer is 0.08 W / (m · K) or more and 0.4 W / (m · K) or less.   The elastic layer includes a needle-like filler, and is oriented so that the elastic modulus in the short direction of the elastic layer is larger than the elastic modulus in the thickness direction, and the thermal conductivity in the longitudinal direction is larger than the thermal conductivity in the thickness direction. The pressurizing member according to any one of claims 17 to 19, wherein the pressurizing member is provided.   The pressure member according to claim 20, wherein the needle-like filler has an average length of 50 µm to 1000 µm.   The pressure member according to claim 20 or 21, wherein the elastic layer contains 5 to 40% by volume of the acicular filler.   The pressurizing member according to any one of claims 20 to 22, wherein the needle-like filler is carbon fiber.   The pressure member according to any one of claims 17 to 23, wherein the elastic layer includes a mixture of addition-curable silicone rubber.   The pressurizing member according to any one of claims 17 to 24, wherein the elastic layer is porous.   The pressure member according to claim 25, wherein the elastic layer has a porosity of 10% by volume or more and 70% by volume or less.   The pressure member according to any one of claims 17 to 26, wherein the elastic layer is supported by a rigid base.   An image heating apparatus comprising the pressure member according to any one of claims 17 to 27.   The image heating apparatus according to claim 28, wherein the heating member is a rotating body that is rotationally driven.   30. The image heating apparatus according to claim 29, wherein the rotating body is a heating roller or a heating belt.   31. A belt having a nip formed with the rotating body, wherein the pressure member applies pressure from the inside of the belt toward the rotating body at the nip. The image heating apparatus described in 1.   An image forming apparatus comprising the image heating apparatus according to any one of claims 28 to 31. A method for producing a pressure member according to any one of claims 17 to 27,
1) A composition of an uncrosslinked addition-curable liquid silicone rubber in which a water-containing material in which water is contained in a water-absorbing polymer and a needle-like filler is dispersed, and a short of the substrate is placed in a mold in which an elongated substrate of a pressure member is set. A casting process for casting while giving flow in the hand direction and the longitudinal direction;
2) A cross-linking and curing step in which the mold filled with the composition is sealed and heat-treated at a temperature below the boiling point of water to cross-link and cure the silicone rubber component;
3) a demolding step of demolding the substrate on which the composition has been cast from the mold, cross-linked and cured, and laminated;
4) a dehydration step in which the composition laminated on the demolded substrate is heat-treated to evaporate water in the water-containing material and dehydrate to form voids;
A method for producing a pressure member, comprising: