JP6872463B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming device including the fixing device.

So far, an image forming apparatus including a fixing apparatus for fixing a developer image on a medium using a belt has been proposed (see, for example, Patent Document 1). In such a fixing device, the belt is maintained at a predetermined temperature while detecting the temperature of the belt.

Japanese Unexamined Patent Publication No. 2013-250393

In such an image forming apparatus, triboelectric charging on the belt of the fixing apparatus may affect the quality of the formed image.

Therefore, it is desirable to provide a fixing device and an image forming device suitable for realizing a higher quality image.

The fixing device as one embodiment of the present invention includes a belt member having a first insulating layer, a conductive layer, and a second insulating layer in this order, and satisfies the following conditional expression (1).
9.11Ω ≤ logRV1 ≤ 13.34Ω …… (1)
However, RV1 is the volume resistance of the conductive layer when the applied voltage is 100 V.

The image forming apparatus as an embodiment of the present invention includes the fixing apparatus.

In the fixing device and the image forming device as one embodiment of the present invention, since the belt member includes a conductive layer having a predetermined volume resistance, for example, the charging of the belt member caused by friction between the heat transfer member and the belt member. Is relaxed.

According to the fixing device and the image forming device as one embodiment of the present invention, it is suitable for realizing a higher quality image.
It should be noted that this is an example of the effect of the present invention, and the effect of the present invention is not limited to this, and may be any of the effects described below.

It is a block diagram which shows one structural example of the image forming apparatus which concerns on one Embodiment. It is a block diagram which shows one structural example of the fixing part shown in FIG. It is sectional drawing which shows one structural example of the fixing belt shown in FIG. It is a block diagram which shows an example of the control mechanism of the image forming apparatus which concerns on one Embodiment. It is sectional drawing which shows one structural example of the fixing belt as a modification. It is a characteristic figure which shows the relationship between the volume resistance of a conductive layer, and the volume resistance of a fixing belt.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is a specific example of the present invention, and the present invention is not limited to the following aspects. Further, the present invention is not limited to the arrangement, dimensions, dimensional ratio, etc. of each component shown in each figure.

<1. Embodiment>
[Configuration example]
FIG. 1 shows a configuration example of an image forming apparatus (image forming apparatus 1) according to an embodiment of the present invention. The image forming apparatus 1 is an electrophotographic printer that forms an image (for example, a color image) on a medium (also referred to as a printing medium, a recording medium, or a transfer material) PM made of, for example, plain paper.

The image forming apparatus 1 includes a medium tray 11, a pickup roller 12, a separation roller 13, a resist roller 14, a transport roller 15, an ID (Image Drum) unit 20, an exposure head 22, a transfer roller 23, and a fixing unit. 30, a transport roller 16, a transport roller 17, and a discharge roller 18 are provided. These members are arranged in order from upstream to downstream along the transport path 10 in which the medium PM is conveyed.

The medium tray 11 is a container for accommodating the medium PM, and is, for example, detachably provided at the lower part of the image forming apparatus 1. The pickup roller 12 is a member that takes out the medium PM stored in the medium tray 11 one by one from the uppermost portion thereof and sends the taken-out medium PM to the transport path 10. The separation roller 13 is a pair of rollers arranged so as to sandwich the transport path 10, and is a member that sends the medium PM taken out by the pickup roller 12 to the transport path 10 one by one. The resist rollers 14 are a pair of rollers arranged so as to sandwich the transport path 10, and while correcting the skew of the medium PM passing through the transport path 10, the medium PM is matched with the timing of image formation by the ID unit 20. Is a member that conveys. The transfer roller 15 is a pair of rollers arranged so as to sandwich the transfer path 10, and is a member that conveys the medium PM along the transfer path 10.

The ID unit 20 forms a toner image. The ID unit 20 has a photoconductor 21. The photoconductor 21 is a member that supports an electrostatic latent image on the surface (surface layer portion). The exposure head 22 is a member that exposes the photoconductor 21 of the ID unit 20, and is configured by using, for example, a plurality of LED (Light Emitting Diode) elements. An electrostatic latent image is formed on the photoconductor 21 by being exposed by the exposure head 22, and then a toner image is formed by supplying toner. The transfer roller 23 is a member for electrostatically transferring the toner image formed by the ID unit 20 onto the surface to be transferred of the medium PM.

The fixing unit 30 is a member that fixes the toner image transferred on the medium PM to the medium PM by applying heat and pressure to the medium PM. The fixing portion 30 is configured to be replaceable. The fixing unit 30 is a specific example corresponding to the "fixing device" of the present invention.

FIG. 2 shows an example of the configuration of the fixing portion 30. The fixing portion 30 includes a fixing belt 31, a fixing roller 32, a pressure pad 33, a pad support portion 34, a coil spring 35, a temperature sensor 36, a heater 38, a heat transfer member 39, and a heater support portion. It has 40, a coil spring 41, and a pressure roller 43.

The fixing belt 31 is an endless elastic belt, and is stretched (tensioned) by a fixing roller 32, a pressure pad 33, guide members 37A and 37B, and a heat transfer member 39. The fixing belt 31 is provided so as to be rotatable in the direction of arrow A (FIG. 2), for example, about a rotation axis along a direction orthogonal to the transport direction of the medium PM (direction orthogonal to the paper surface of FIGS. 1 and 2). It is a tubular or cylindrical endless belt. FIG. 3 shows the cross-sectional structure of the fixing belt 31. As shown in FIG. 3, the fixing belt 31 includes an inner peripheral surface 31A and an outer peripheral surface 31B. The fixing belt 31 has, for example, a base 61, an elastic layer 62 formed on the base 61, and a release layer 63 formed on the elastic layer 62 from the side of the inner peripheral surface 31A. The substrate 61 has a two-layer structure consisting of an insulating layer 61A exposed on the inner peripheral surface 31A and a conductive layer 61B provided between the insulating layer 61A and the elastic layer 62. The inner peripheral surface 31A is a surface that comes into contact with the heat transfer member 39. Therefore, the insulating layer 61A is located between the conductive layer 61B and the heat transfer member 39. Further, the elastic layer 62 is located on the opposite side of the insulating layer 61A when viewed from the conductive layer 61B. Further, the release layer 63 is located on the opposite side of the conductive layer 61B from the elastic layer 62. Here, the fixing belt 31 is a specific example corresponding to the "belt member" of the present invention, and the insulating layer 61A, The conductive layer 61B and the elastic layer 62 are specific examples corresponding to the “first insulating layer”, the “conductive layer” and the “second insulating layer” of the present invention, respectively.

The substrate 61 is made of a material having excellent heat resistance and strength. The insulating layer 61A is made of a resin having excellent heat resistance and strength, such as polyimide (PI), polyphenylene sulfide (PPS), or polyetheretherketone (PEEK), as the "base material" of the present invention. The conductive layer 61B is made of a material in which the conductive filler is uniformly dispersed in the resin as the base material. As the conductive filler, for example, metals such as Ag, Cu, Al, Mg and Ni, and carbon compounds such as graphite, carbon black, carbon nanofibers and carbon nanotubes are suitable. These conductive fillers are a specific example corresponding to the "conductive agent" of the present invention.

The thickness of the insulating layer 61A is, for example, preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 60 μm or less. When the thickness of the insulating layer 61A is 10 μm or more, it is possible to sufficiently withstand the wear caused by the sliding friction between the fixing belt 31 and other members due to the rotational operation of the fixing belt 31. When the insulating layer 61A is worn, the insulating layer 61A may be broken down and the conductive layer 61B may be exposed. In this case, for example, conduction between the temperature sensor 36 and the conductive layer 61B occurs, that is, conduction between the frame ground (FG) and the primary potential occurs, which is not preferable. On the other hand, if the thickness of the insulating layer 61A is 100 μm or less, the transfer time of the amount of heat transferred from the heater 38 via the heat transfer member 39 in contact with the inner peripheral surface 31A can be shortened, and the fixing portion 30 can be shortened. It is possible to prevent an increase in the time required for startup (startup time).

The volume resistivity of the conductive layer 61B is preferably not more than 10 ⁷ Ω · cm or more 10 ^13.5 Ω · cm, more preferably not more than 10 ⁸ Ω · cm or more 10 ¹¹ Ω · cm. If the volume resistivity of the conductive layer 61B is 10 ⁷ Ω · cm or more, the dielectric breakdown of the insulating layer 61A, i.e., it is possible to prevent a short circuit of the frame ground and (FG) and the primary potential sufficiently. If the volume resistivity of the conductive layer 61B is 10 ^13.5 Ω · cm or less, triboelectric charging between the heat transfer member 39 and the fixing belt 31 and friction charging between the temperature sensor 36 and the fixing belt 31 are performed, as will be described later. It can be relaxed enough. The volume resistivity here is a value measured by a measurement method based on JIS K 6911. For example, a voltage of 100 V is applied for 10 seconds by a high leicester UP MCP HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd. It is a value obtained by measuring in.

Further, the conductive layer 61B satisfies the following conditional expression (1).
9.11Ω ≤ logRV1 ≤ 13.34Ω …… (1)
However, RV1 is the volume resistance of the conductive layer 61B when the applied voltage is 100 V, and is a value measured by a measuring method based on JIS K 6911.

Further, it is desirable that the fixing belt 31 as a whole satisfies the following conditional expression (2).
12.61Ω ≤ logRV2 ≤ 13.19Ω …… (2)
However, RV2 is the volume resistance of the belt member when the applied voltage is 1000 V, and is a value measured by a measuring method based on JIS K 6911.

If logRV1 is 13.34Ω or less, or if logRV2 is 13.19Ω or less, the accumulation of electric charge on the fixing belt 31 is suppressed, and the charged toner TN or the powder of the medium PM adheres to the fixing belt 31. Can be avoided. Further, if logRV1 is 9.11Ω or more, or if logRV2 is 12.61Ω or more, adhesion of toner TN or medium PM powder to the pressure roller 43 can be avoided.

The elastic layer 62 is constructed by using a material having excellent heat resistance and elasticity, for example, a heat-resistant elastomer such as silicone rubber or fluororesin. When the elastic layer 62 is made of, for example, silicone rubber, it preferably has a thickness of 100 μm or more and 300 μm or less.

The release layer 63 is constructed using, for example, a fluororesin such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), or perfluoroethylene propene copolymer (FEP). The release layer 63 has a thickness of, for example, 5 μm or more and 50 μm or less. The fixing belt 31 is stretched so that the release layer 63 is exposed on the outer peripheral surface 31B.

The fixing roller 32 is a member that circulates and rotates the fixing belt 31 and forms a nip portion N2 with the pressure roller 43. The fixing roller 32 has a core metal portion and an elastic layer that covers the periphery of the core metal portion. The core metal portion has, for example, a pipe shape or a shaft shape, and is made of, for example, aluminum, iron, stainless steel, or the like. The elastic layer is constructed by using a rubber material having high heat resistance, such as sponge-like silicone rubber or fluororubber. The configuration of the fixing roller is not limited to this, and the fixing roller 32 may further have a release layer that covers the periphery of the elastic layer in addition to the core metal portion and the elastic layer. The fixing roller 32 rotates clockwise in this example by the power transmitted from the fixing motor 44 (described later). The fixing roller 32 is arranged so as to abut on the inner peripheral surface 31A of the fixing belt 31. As a result, the fixing roller 32 circulates and rotates the fixing belt 31 in the direction of the arrow A in FIG.

The pressure pad 33 is a member that forms a nip portion N1 with the pressure roller 43. The pressure pad 33 is constructed using, for example, a rubber material. The pad support portion 34 is a member that supports the pressure pad 33. The coil spring 35 is a member that is inserted between the support member 42 and the pad support portion 34 and urges the pressure pad 33 in a direction away from the support member 42. As a result, the pressure pad 33 comes into contact with the inner peripheral surface 31A of the fixing belt 31 and is pressed against the pressure roller 43 with the fixing belt 31 sandwiched between them. In this way, the pressure pad 33 forms a nip portion N1 with the pressure roller 43.

The temperature sensor 36 is a sensor that detects the temperature of the fixing belt 31 while abutting against and sliding on the inner peripheral surface 31A of the fixing belt 31, and is configured by using, for example, a thermistor. The temperature sensor 36 is a specific example corresponding to the "temperature detection member" of the present invention.

The heater 38 is a heat source for heating the fixing belt 31, and is configured to include, for example, a resistance wire as a heating element. The heat transfer member 39 is a member that transfers the heat generated in the heater 38 to the fixing belt 31. The heater control unit 581 (later) in the fixing control unit 58 (later) controls the heater 38 so that the temperature of the fixing belt 31 detected by the temperature sensor 36 becomes a predetermined temperature. .. The heater support portion 40 is a member that supports the heater 38. The coil spring 41 is a member that is inserted between the support member 42 and the heater support portion 40 and urges the heater 38 and the heat transfer member 39 in a direction away from the support member 42. As a result, the heat transfer member 39 comes into contact with the inner peripheral surface 31A of the fixing belt 31 and pushes the fixing belt 31 outward to stretch the fixing belt 31. Here, the heater 38 is a specific example corresponding to the "heat generating member" of the present invention, and the heat transfer member 39 is a specific example corresponding to the "heat transfer member" of the present invention.

The pressure roller 43 is a member that forms a nip portion N2 between the fixing roller 32 and the pressure pad 33. The pressurizing roller 43 functions as a "pressurizing member" of the present invention provided so as to be in contact with the outer peripheral surface 31B of the fixing belt 31. The pressurizing roller 43 has, for example, the same configuration as the fixing roller 32. The pressure roller 43 is driven to rotate counterclockwise in this example according to the circulation rotation of the fixing belt 31. The pressure roller 43 may include a halogen heater 45 for raising the temperature of the surface of the pressure roller 43 and accelerating the temperature rise of the fixing belt 31.

With this configuration, when the medium PM on which the toner image is formed is supplied to the nip portions N1 and N2, the toner TN (FIG. 2) on the medium PM is heated, melted, and pressurized. As a result, the toner image is fixed on the medium PM.

The transfer roller 16 (FIG. 1) is a pair of rollers arranged so as to sandwich the transfer path 10, and is a member that conveys the medium PM supplied from the fixing portion 30 along the transfer path 10. The transfer roller 17 is a pair of rollers arranged so as to sandwich the transfer path 10, and is a member that conveys the medium PM along the transfer path 10. The discharge roller 18 is a pair of rollers arranged so as to sandwich the transport path 10, and is a member that discharges the medium PM to the discharge tray 19.

Downstream of the nip portion N2 in the fixing portion 30, a separating member 46 and a guide member 47 which are separated from each other and arranged to face each other are further provided. The separation member 46 separates the fixing belt 31 and the medium PM so that the medium PM that has passed through the nip portions N1 and N2 does not wind around the fixing belt 31. Further, the guide member 47 functions to smoothly guide the medium PM that has passed through the nip portions N1 and N2 toward the transfer roller 16.

FIG. 4 shows an example of the control mechanism in the image forming apparatus 1. The image forming apparatus 1 includes a communication unit 51, an operation unit 52, a display unit 53, a storage unit 54, an exposure control unit 55, a voltage control unit 56, a motor control unit 57, a fixing control unit 58, and the like. It includes an image formation control unit 59.

The communication unit 51 communicates using, for example, USB (Universal Serial Bus) or LAN (Local Area Network), and receives, for example, the print data DP transmitted from the host computer. The operation unit 52 accepts user operations, and is configured by using, for example, various buttons. The display unit 53 displays the operating state of the image forming apparatus 1, and is configured by using, for example, a liquid crystal display or various indicators.

The storage unit 54 stores, for example, print data DP, various setting information of the image forming apparatus 1, and the like. In addition, the storage unit 54 stores the history data 541. The history data 541 is a record of the operation history of the image forming apparatus 1. Specifically, the history data 541 includes, for example, information about the cumulative number of prints printed by the image forming apparatus 1 and the number of prints printed by using the current fixing unit 30. The number of prints is reset when the fixing unit 30 is replaced.

The exposure control unit 55 controls the operation of the exposure head 22 based on an instruction from the image formation control unit 59.

The voltage control unit 56 generates various voltages used in the image forming apparatus 1 based on an instruction from the image forming control unit 59. Specifically, the voltage control unit 56 is adapted to generate a charging voltage and a developing voltage used in the ID unit 20, a transfer voltage applied to the transfer roller 23, and the like.

The motor control unit 57 controls the operation of the main motor or the like used in the image forming apparatus 1 based on the instruction from the image forming control unit 59.

The fixing unit 30 has a fixing motor 44. The fixing motor 44 supplies power to the fixing roller 32. The fixing motor 44 has a rotation unevenness detection unit 441. The rotation unevenness detection unit 441 generates an error signal when the rotation unevenness occurs in the fixing motor 44.

The fixing control unit 58 controls the operation of the fixing unit 30 based on the instruction from the image formation control unit 59 and the detection result of the temperature sensor 36 of the fixing unit 30. The fixing control unit 58 includes a heater control unit 581 and a fixing motor control unit 582. The heater control unit 581 controls the operation of the heater 38 of the fixing unit 30. The fixing motor control unit 582 controls the operation of the fixing motor 44. Further, the fixing control unit 58 also has a function of supplying the error signal to the image formation control unit 59 when an error signal is received from the rotation unevenness detection unit 441 of the fixing motor 44.

The image forming control unit 59 controls the operation of the image forming apparatus 1 by controlling the operation of each of these blocks. Specifically, for example, when the communication unit 51 of the image forming apparatus 1 receives the print data DP, the image forming control unit 59 sets the exposure control unit 55 and the voltage control unit 56 based on the print data DP. , The motor control unit 57, and the fixing control unit 58 are instructed to perform an image forming operation. Further, the image formation control unit 59 also has a function of stopping the processing being executed and causing the display unit 53 to display an error when an error signal is received from the fixing control unit 58. The function of the image formation control unit 59 may be realized by hardware or software, for example.

When performing the image forming operation, the image forming apparatus 1 first performs a warm-up operation so that the belt temperature reaches a predetermined target temperature (for example, 170 [° C.]), and then performs an image forming operation.

[Operation and action]
Subsequently, the operation and operation of the image forming apparatus 1 of the present embodiment will be described.

(Overview of overall operation)
First, an outline of the overall operation of the image forming apparatus 1 will be described with reference to FIGS. 1 and 4. When the communication unit 51 of the image forming apparatus 1 receives the print data DP, the image forming control unit 59 performs processing based on the print data DP. Then, the image formation control unit 59 controls the operations of the exposure control unit 55, the voltage control unit 56, the motor control unit 57, and the fixing control unit 58 based on the processing result. In the warm-up operation, the fixing control unit 58 controls the operation of the fixing unit 30 so that the belt temperature reaches a predetermined target temperature. In the image forming operation, the exposure control unit 55 controls the light emission operation of the exposure head 22, the voltage control unit 56 generates various voltages such as a charging voltage, a developing voltage, and a transfer voltage, and the motor control unit 57 generates an image. The operation of the main motor or the like used in the forming device 1 is controlled, and the fixing control unit 58 controls the operation of the fixing unit 30. As a result, the medium PM supplied from the medium tray 11 is conveyed along the transport path 10, the toner image generated by the ID unit 20 is transferred to the medium PM, and the toner image is transferred to the medium PM in the fixing unit 30. Settle on top. Then, the medium PM on which the toner image is fixed is discharged to the discharge tray 19.

(Electrostatic offset)
By the way, in a general fixing portion, for example, a phenomenon called electrostatic offset in which toner TN electrostatically adheres to the surface of a fixing belt may occur. This electrostatic offset phenomenon is a phenomenon in which a part of the toner TN before the fixing process carried on the medium PM is electrostatically attracted to the surface of the fixing belt, for example, charging of the medium PM itself or with the fixing belt. This is a phenomenon caused by charging of the fixing belt due to friction with other members. Specifically, for example, the toner TN is negatively charged, and the medium PM is positively charged with the opposite polarity to the toner TN. When the medium PM passes through the nip portion in the fixing portion, the fixing belt may be positively charged by the positive charge of the medium PM. Alternatively, the fixing belt may be positively charged due to friction between the fixing belt and the temperature sensor. In such a case, a part of the negatively charged toner TN on the medium PM is electrostatically blown to the surface of the fixing belt by the positive charge on the fixing belt in the vicinity of the inlet of the nip portion of the fixing portion, and as a result, , There is a possibility that streaky unevenness may occur in the printed image.

(Action / effect)
Therefore, in the present embodiment, the fixing belt 31 is on the opposite side of the conductive layer 61B, the insulating layer 61A located between the conductive layer 61B and the heat transfer member 39, and the insulating layer 61A as viewed from the conductive layer 61B. It has an elastic layer 62 located at. The conductive layer 61B has, for example, ^{a volume resistivity of 10 7} Ω · cm or more and 10 ^13.5 Ω · cm or less, and has a volume resistivity satisfying the conditional equation (1). Further, the fixing belt 31 has a volume resistance satisfying the conditional expression (2). When the fixing belt 31 has such a configuration, the charge of the fixing belt 31 caused by the friction between the heat transfer member 39 and the insulating layer 61A of the fixing belt 31 or the friction between the temperature sensor 36 and the insulating layer 61A is alleviated. Will be done. As a result, it is possible to suppress the occurrence of electrostatic offset in which the negatively charged toner TN on the medium PM flies to the fixing belt 31, and it is possible to fix a higher quality image on the medium PM. If carbon black is added to the polyimide, the mechanical durability may decrease. However, in the present embodiment, since the insulating layer 61A in contact with the fixing roller 32 or the like is made of polyimide to which carbon black is not added, the mechanical durability of the insulating layer 61A is sufficiently ensured. Therefore, as in the conventional case, the fixing belt 31 is in close contact with the fixing roller 32 and the like, and good rotational operation is possible.

<2. Experimental example>
As an experimental example, the image forming apparatus 1 according to the above embodiment was evaluated.

(Experimental Examples 1-1-1-11)
The relationship between the thickness (μm) of the insulating layer 61A in the substrate 61, the presence or absence of dielectric breakdown of the insulating layer 61A, and the presence or absence of a delay in the rise time was evaluated. The rise time is the time required for the outer peripheral surface 31B of the fixing belt 31 to reach a predetermined temperature by heating with the heater 38. The results are shown in Table 1. Here, the insulating layer 61A is made of polyimide and has a thickness of 5 μm or more and 115 μm or less. Further, as the conductive layer 61B of the substrate 61, it was used having a volume resistivity of be one obtained by dispersing carbon black as the conductive filler in the polyimide 1.0 × 10 ⁹ Ω · cm. Further, the elastic layer 62 is made of silicone rubber and has a thickness of 200 μm. The release layer 63 was made of PFA.

As shown in Table 1, in Experimental Example 1-1 in which the thickness of the insulating layer 61A was 5 μm, dielectric breakdown of the insulating layer 61A occurred. Further, in Experimental Example 1-11 in which the thickness of the insulating layer 61A was 115 μm, a delay in the rise time was observed. From the results of Experimental Examples 1-1 to 1-11, it was confirmed that the insulating layer 61A preferably has a thickness of 10 μm or more and 100 μm or less.

(Experimental Examples 2-1 to 2-11)
Next, the relationship between the volume resistivity (Ω · cm) of the conductive layer 61B in the substrate 61, the presence or absence of dielectric breakdown of the insulating layer 61A, and the presence or absence of the electrostatic offset phenomenon was evaluated. The results are shown in Table 2. Here, the insulating layer 61A is made of polyimide, and the thickness of the insulating layer 61A is set to 30 μm. Further, the conductive layer 61B is made by dispersing carbon black as a conductive filler in polyimide and having a volume resistivity of ^{1.0 × 10 5} Ω · cm or more and 1.0 × 10 ^{14 Ω · cm or less.} Using. Other conditions are substantially the same as those of Experimental Examples 1-1 to 1-11.

As shown in Table 2, the volume resistivity of the conductive layer 61B is 1.0 × 10 ⁵ Ω · cm in Experimental Example 2-1 and the volume resistivity of the conductive layer 61B is 1.0 × 10 ⁶ Ω · cm. In the case of Experimental Example 2-2, the dielectric breakdown of the insulating layer 61A occurred. Further, in Experimental Example 2-11 in which the volume resistivity of the conductive layer 61B was 1.0 × 10 ¹⁴ Ω · cm, the occurrence of the electrostatic offset phenomenon was observed. From the results of Experimental Examples 2-1 to 2-11, the volume resistivity of the conductive layer 61B, it was confirmed is desirably less 10 ⁷ Ω · cm or more 10 ^13.5 Ω · cm.

(Experimental Examples 3-1 to 2-3)
Next, the relationship between the volume resistance logRV1 (Ω) of the conductive layer 61B and the volume resistance logRV2 (Ω) of the entire fixing belt 31 was investigated. The results are shown in Table 3 and FIG. The measurement of logRV1 (Ω) and logRV2 (Ω) was carried out by a measurement method based on JIS K 6911. Specifically, a URS probe was applied to each sample with a High Leicester UP MCP HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd. for measurement. However, when measuring logRV1 (Ω), a voltage of 100 V is applied to the conductive layer 61B for 10 seconds before measurement, and when measuring logRV2 (Ω), a voltage of 1000 V is applied to the fixing belt 31 for 10 seconds. And then measured.

As shown in Table 3 and FIG. 6, if the logRV1 is 9.11Ω or more and 13.34Ω or less, and the logRV2 is 12.61Ω or more and 13.19Ω or less, the electrostatic offset phenomenon does not occur. It was found (Experimental Examples 3-3 to 3-20). On the other hand, when the sample corresponding to the plot surrounded by the broken line in FIG. 6, that is, logRV1 is out of the range of 9.11Ω or more and 13.34Ω or less, and logRV2 is out of the range of 12.61Ω or more and 13.19Ω or less. The occurrence of the electrostatic offset phenomenon was observed in (Experimental Examples 3-1 and 3-2, 3-21 and 23-23). In particular, in Experimental Examples 3-1, 3-2, adhesion of toner TN, medium PM powder, etc. to the pressure roller 43 occurred. Further, in Experimental Examples 3-23 to 23, electric charges were accumulated on the fixing belt 31, and adhesion of the charged toner TN, medium PM powder, etc. to the fixing belt 31 was observed.

<3. Modification example>
Although the present invention has been described above with reference to embodiments and experimental examples, the present invention is not limited to the above embodiments and can be modified in various ways. For example, in the above embodiment, the image forming apparatus of the primary transfer method (direct transfer method) has been described, but the present invention can also be applied to the secondary transfer method.

Further, in the above-described embodiment and the like, the ID unit 20 that forms a monochrome image has been described as an example, but the image forming apparatus of the present invention may have an ID unit that forms a color image.

Further, in the above embodiment, a plate-shaped heater 38 including a heating element such as a resistance wire is used as the heat source in the fixing portion 30, but in the present invention, for example, a halogen lamp is used as a heat source instead of the heater 38. May be used as. Further, in forming the nip portion, another member such as a pressure pad for urging the inner peripheral surface 31A of the fixing belt 31 may be further provided.

Further, in the above embodiment, the exposure head 22 uses an LED head using a light emitting diode as a light source, but for example, an exposure head using a laser element or the like as a light source may be used.

Further, although the fixing belt 31 of the above embodiment includes an elastic layer 62, the belt member of the present invention is not limited to this. The belt member of the present invention is provided with the release layer 63 as the second insulating layer without providing the elastic layer 62 on the substrate 61 as in the case of the fixing belt 71 as a modification shown in FIG. 5, for example. It may be made like this.

Further, in the above-described embodiment and the like, an image forming apparatus having a printing function has been described as a specific example of the "image forming apparatus" in the present invention, but the present invention is not limited thereto. That is, in addition to such a printing function, the present invention can be applied to, for example, an image forming apparatus that functions as a multifunction device having a scanning function and a fax function.

1 ... image forming apparatus, 11 ... medium tray, 12 ... pickup roller, 13 ... separation roller, 14 ... resist roller, 15 ... transfer roller, 20 ... ID (Image Drum) unit, 21 ... photoconductor, 22 ... exposure head, 23 ... Transfer roller, 16,17 ... Transfer roller, 18 ... Discharge roller, 30 ... Fixing part, 31,71 ... Fixing belt, 32 ... Fixing roller, 33 ... Pressurized pad, 34 ... Pad support part, 35 ... Coil spring , 36 ... Temperature sensor, 38 ... Heater, 39 ... Heat transfer member, 40 ... Heater support, 41 ... Coil spring, 42 ... Support member, 43 ... Pressurizing roller, 45 ... Halogen heater, 46 ... Separation member, 47 ... Guide member, 51 ... Communication unit, 52 ... Operation unit, 53 ... Display unit, 54 ... Storage unit, 55 ... Exposure control unit, 56 ... Voltage control unit, 57 ... Motor control unit, 58 ... Fixing control unit, 59 ... Image Formation control unit, 61 ... substrate, 61A ... insulating layer, 61B ... conductive layer, 62 ... elastic layer, 63 ... mold release layer,
N1, N2 ... Nip part, PM ... Medium.

Claims (13)

A belt member having a first insulating layer, a conductive layer, and a second insulating layer in this order is provided.
A fixing device that satisfies the following conditional expressions (1) and (2).
9.11Ω ≤ logRV1 ≤ 13.34Ω …… (1)
12.61Ω ≤ logRV2 ≤ 13.19Ω …… (2)
However, RV1 is Ri volume resistivity der conductive layer when the applied voltage 100 V, RV2 is the volume resistivity of the belt member when the applied voltage 1000V. The conductive layer, fixing device according to claim 1 having a 10 ⁷ Ω · cm or more 10 ^13.5 Ω · cm or less in volume resistivity. The fixing device according to claim 1 or 2 , wherein the first insulating layer has a thickness of 10 μm or more and 100 μm or less. The fixing device according to any one of claims 1 to 3 , further comprising a temperature detecting member that detects the temperature of the belt member while being in contact with the belt member. The fixing device according to any one of claims 1 to 4 , wherein the second insulating layer is an elastic layer. The fixing device according to claim 5, wherein the belt member further has a release layer located on the side opposite to the conductive layer when viewed from the elastic layer. The fixing device according to any one of claims 1 to 6 , further comprising a heat generating member for generating heat. The fixing device according to claim 7 , further comprising a heat transfer member that transfers the heat generated in the heat generating member to the belt member while contacting the belt member. The belt member is a tubular endless belt that is rotatably provided in a first direction with respect to the heat transfer member and includes an inner peripheral surface and an outer peripheral surface.
The fixing device according to claim 8 , wherein the heat transfer member is in contact with the inner peripheral surface of the endless belt. The fixing device according to claim 9 , further comprising a pressure member provided so as to come into contact with the outer peripheral surface of the belt member. The first insulating layer contains a base material and contains a base material.
The fixing device according to any one of claims 1 to 10 , wherein the conductive layer includes a base material to which a conductive agent is added. The fixing device according to claim 1, wherein the second insulating layer is a release layer. An image forming apparatus including the fixing device according to any one of claims 1 to 12.

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