JP2006317709A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming device which can restrict an excessive temperature rise in a sure manner even when small-sized recording media are fixed continuously or when the drive of the device suddenly stops, in the fixing process of the electromagnetic induction heating system. <P>SOLUTION: The fixing device that fixes a toner image on a recording medium comprises a coil 25 for generating magnetic flux, and heat generating members 22 and 23 for generating heat by magnetic flux. The coil 25 is disposed so as to sandwich the front and back sides of the heat generating members 22 and 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein, and more particularly to an electromagnetic induction heating type fixing device and an image forming apparatus. .

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, many use an electromagnetic induction heating type fixing device for the purpose of reducing the rise time of the apparatus and saving energy (for example, (See Patent Document 1).

  In Patent Document 1 and the like, an electromagnetic induction heating type fixing device includes a support roller (heating roller), a fixing auxiliary roller (fixing roller), a fixing belt stretched between the supporting roller and the fixing auxiliary roller, and a fixing belt on the supporting roller. An induction heating unit that faces the fixing auxiliary roller, a pressure roller that faces the fixing auxiliary roller via a fixing belt, and the like. The induction heating unit includes a coil unit (excitation coil) extending in the width direction (a direction orthogonal to the conveyance direction of the recording medium), a core facing the coil unit, and the like.

The fixing belt is heated at a position facing the induction heating unit. The heated fixing belt heats and fixes the toner image on the recording medium conveyed to the positions of the auxiliary fixing roller and the pressure roller. Specifically, by applying a high-frequency alternating current to the coil portion, a magnetic field is formed around the coil portion, and an eddy current is generated in the vicinity of the support roller surface. When an eddy current is generated in the support roller, Joule heat is generated by the electrical resistance of the support roller itself. The fixing belt wound around the support roller is heated by the Joule heat.
Such an electromagnetic induction heating type fixing device is known as being capable of raising the surface temperature (fixing temperature) of the fixing belt to a desired temperature with a small energy consumption and a short start-up time.

  On the other hand, Patent Document 2 and the like disclose a fixing device using an electromagnetic induction heating method in which a core portion is formed so as to sandwich a fixing belt. That is, the core portion of the induction heating unit is disposed so as to face the outer peripheral surface and the inner peripheral surface of the fixing belt. This technique aims to improve the heat generation efficiency of the fixing belt.

  Further, Patent Document 3 and the like disclose a fixing device that uses an electromagnetic induction heating method and adjusts the Curie point of the core portion (magnetic core) of the induction heating portion in the width direction. Specifically, the curie point of the core part at both ends in the width direction is formed to be smaller than the curie point at the center part in the width direction. This technique is intended to suppress the temperature rise that occurs at both ends in the width direction of the fixing belt when a small-size recording medium is passed.

JP 2002-82549 A JP 2000-214703 A JP 2000-162912 A

  In the conventional fixing device described above, when a small-sized recording medium is continuously fixed, or when the device suddenly stops driving due to a paper jam or the like, a part or all of the fixing belt overheats. was there.

Details are as follows.
A general image forming apparatus is configured to form an image on several types of recording media having different sizes in the width direction. Here, the recording media having different sizes in the width direction include non-standard size recording media in addition to various standard size recording media in the A and B rows of JIS dimensions. Further, even in the case of recording media of the same size (for example, A4 size), the transport direction is the short direction (the direction perpendicular to the longitudinal direction) when the longitudinal direction is the transport direction. In some cases, recording media having different sizes in the width direction are handled.

  When fixing such a recording medium having a different size in the width direction with the fixing device, the heat distribution in the width direction of the fixing belt fluctuates according to the width direction size of the recording medium, resulting in temperature unevenness. was there. For example, when fixing by passing a recording medium having a small size in the width direction, a lot of heat is taken away at the position of the fixing belt corresponding to the size in the width direction of the recording medium (the paper passing area). The fixing temperature is lower than at other positions (non-sheet passing area). Such a phenomenon becomes particularly prominent when a recording medium having a small size in the width direction is continuously fed.

  Therefore, when trying to control the fixing temperature in the entire width direction of the fixing belt with reference to the fixing temperature in the center portion in the width direction of the fixing belt, the fixing temperature in the center portion in the width direction of the fixing belt can be controlled to a desired temperature. The fixing temperature at both ends in the direction will rise (overheated). As described above, when a large recording medium in the width direction is fixed in a state where the fixing temperature at both ends in the width direction of the fixing belt is increased, a hot offset occurs on the recording medium corresponding to the temperature increase position. Furthermore, when the fixing temperature at both ends in the width direction exceeds the heat resistance temperature of the fixing belt, it is considered that the fixing belt is thermally damaged.

  On the other hand, if it is attempted to control the fixing temperature in the entire width direction of the fixing belt based on the fixing temperature at both ends in the width direction of the fixing belt, the fixing temperature at both ends in the width direction of the fixing belt can be controlled to a desired temperature. However, the fixing temperature at the center in the width direction is lowered. As described above, when the recording medium is fixed in a state where the fixing temperature at the center portion in the width direction of the fixing belt is lowered, a cold offset occurs on the recording medium corresponding to the temperature lowered position.

  Further, when a paper jam (jam) occurs in the conveyance path in the image forming apparatus, the driving of the fixing device is suddenly stopped. In such a case, the portion of the fixing belt facing the induction heating unit instantaneously overheats in a short time until the energization to the induction heating unit is cut off. As a result, it is also conceivable that thermal damage occurs to components such as the fixing belt and the coil portion of the induction heating unit.

  On the other hand, the technology disclosed in Patent Document 2 described above improves the heat generation efficiency of the fixing belt by optimizing the shape of the core portion disposed so as to sandwich the fixing belt. Therefore, the effect of suppressing the excessive temperature increase of the fixing belt cannot be expected.

  Moreover, the above-described techniques such as Patent Document 3 adjust the Curie point of the core portion of the induction heating unit in the width direction. However, since the overheating of the fixing member heated by the induction heating unit occurs before the overheating of the core portion occurs, the effect of directly suppressing the overheating of the fixing belt cannot be expected. .

  The present invention has been made to solve the above-described problems. In a fixing process using an electromagnetic induction heating method, when a small-size recording medium is continuously fixed or when the apparatus suddenly stops driving. Therefore, it is an object of the present invention to provide a fixing device and an image forming apparatus in which excessive temperature rise is reliably suppressed.

As a result of repeated researches to solve the above problems, the present inventor has come to know the following matters.
That is, when a material having a Curie point (a material capable of self-temperature control) is used for the heat generating member in order to prevent overheating of the heat generating member, the coil portion that generates magnetic flux is the main surface of the heat generating member. Compared with the case where the heat generating member is disposed opposite to the heat generating member, the self-temperature control ability of the heat generating member is enhanced when the coil portion is disposed so as to sandwich the front and back surfaces of the heat generating member.

  The present invention is based on the above-described matters. That is, the fixing device according to the first aspect of the present invention is a fixing device for fixing a toner image on a recording medium, and a coil portion for generating magnetic flux. And a heat generating member that generates heat by the magnetic flux, and the coil portion is disposed so as to sandwich the front and back surfaces of the heat generating member.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the coil portion is formed in a loop shape, and the heating member is sandwiched in the loop of the coil portion. It is a thing.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, an alternating current is applied to the coil portion.

  The fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the heat generating member is formed so that a Curie point is 300 ° C. or lower. With a layer.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to the fourth aspect, wherein the heat generating layer is made of a magnetic shunt alloy.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the heat generating member is a fixing member that melts a toner image.

  According to a seventh aspect of the present invention, there is provided the fixing device according to the sixth aspect, wherein the fixing member is a fixing belt stretched in a circumferential shape, and the coil portion is the fixing belt. These are disposed so as to face the outer peripheral surface and the inner peripheral surface.

  According to an eighth aspect of the present invention, in the fixing device according to the seventh aspect, the fixing belt is stretched between a support roller and a fixing auxiliary roller, and the fixing auxiliary roller is conveyed. It is disposed so as to abut against a pressure roller for pressing the recording medium via the fixing belt.

  According to a ninth aspect of the present invention, in the fixing device according to the eighth aspect, the coil portion is disposed so as to face the inner peripheral surface of the fixing belt via the support roller. It is a thing.

  According to a tenth aspect of the present invention, in the fixing device according to the sixth aspect, the fixing member is a fixing roller that abuts on a pressure roller that presses a recording medium to be conveyed. The coil portion is disposed so as to face the outer peripheral surface and the inner peripheral surface of the fixing roller.

  The fixing device according to an eleventh aspect of the present invention is the heating device according to any one of the first to tenth aspects, wherein the heating member is a heating member that heats the fixing member that melts the toner image. Is.

  The fixing device according to a twelfth aspect of the present invention is the fixing device according to the eleventh aspect, wherein the fixing member is a fixing belt, and the heating member stretches the fixing belt together with a fixing auxiliary roller. And the coil portion is disposed so as to face the outer peripheral surface of the fixing belt and to face the inner peripheral surface of the fixing belt via the support roller. And a pressure roller that presses the recording medium to be conveyed, and is disposed so as to come into contact with the pressure roller via the fixing belt.

  The fixing device according to a thirteenth aspect of the present invention is the fixing device according to any one of the first to twelfth aspects of the present invention, wherein the heat generating member is driven so that a position sandwiched between the coil portions is displaced. The driving of the heat generating member is stopped for a predetermined time when generation of magnetic flux from the coil portion is started.

  According to a fifteenth aspect of the present invention, in the fixing device according to the thirteenth aspect, the driving of the heat generating member is stopped until the heat generating member reaches a predetermined temperature.

  A fixing device according to a fifteenth aspect of the present invention is the fixing device according to any one of the first to fourteenth aspects, comprising a plurality of the heat generating members.

  According to a fifteenth aspect of the present invention, in the fixing device according to the fifteenth aspect, the plurality of heat generating members are a first heat generating member and a Curie point in the heat generating layer of the first heat generating member. And a second heat generating member having a heat generating layer formed so as to have a larger Curie point.

  According to a fifteenth aspect of the present invention, in the fixing device according to the sixteenth aspect, the heat generating layer of the second heat generating member is formed such that the Curie point is higher than the fixing target temperature. Is.

  The fixing device according to an eighteenth aspect of the present invention is the fixing device according to the sixteenth or seventeenth aspect of the present invention, wherein the heat generating layer of the first heat generating member has a Curie point close to a fixing target temperature. It is formed.

  A fixing device according to a nineteenth aspect of the present invention is the fixing device according to any one of the sixteenth to eighteenth aspects, wherein the fixing device is disposed so as to sandwich only the front and back surfaces of the first heating member. 1 and the second coil part disposed so as to sandwich only the front and back surfaces of the second heat generating member, and the second coil part has a magnetic flux only when the apparatus is started up. It is controlled to generate.

  According to a twentieth aspect of the present invention, in the fixing device according to the nineteenth aspect, the first coil section is controlled so as to generate a magnetic flux only after the apparatus is started up.

  A fixing device according to a twenty-first aspect of the present invention is the fixing device according to any one of the first to twentieth aspects, wherein the toner for forming the toner image includes at least a binder resin, a colorant, A mold release agent is contained, and the mold release agent is formed such that its components are dispersed in islands in the binder resin and the average dispersed particle size is in the range of 0.1 to 1.0 μm. It is a thing.

  According to a twenty-second aspect of the present invention, in the fixing device according to any one of the first to twenty-first aspects, the toner for forming the toner image has a weight average particle diameter (D4). Is formed so that the average circularity is in the range of 0.95 to 0.99.

  An image forming apparatus according to a twenty-third aspect of the present invention includes the fixing device according to any one of the first to twenty-second aspects.

  According to the present invention, in the electromagnetic induction heating type fixing device, the coil portion is disposed so as to sandwich the front and back surfaces of the heat generating member. As a result, the self-temperature control capability of the heat generating member is enhanced, and even if the small-sized recording medium is continuously fixed or the apparatus is suddenly stopped, excessive temperature rise is reliably suppressed. A fixing device and an image forming apparatus can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a laser printer as an image forming apparatus, 3 is an exposure unit that irradiates a photosensitive drum 18 with exposure light L based on image information, and 4 is detachably installed on the apparatus main body 1. A process cartridge as an image forming unit; 7, a transfer unit for transferring a toner image formed on the photosensitive drum 18 to a recording medium P; 10, a paper discharge tray on which an output image is placed; A paper feeding unit containing a recording medium P such as paper, 13 a registration roller for conveying the recording medium P to the transfer unit 7, 15 a manual paper feeding unit, 18 a photosensitive drum as an image carrier, and 20 a recording 1 shows a fixing device that fixes an unfixed image on a medium P;

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, exposure light L such as laser light based on image information is emitted from the exposure unit 3 toward the photosensitive drum 18 of the process cartridge 4. The photosensitive drum 18 rotates counterclockwise in the drawing, and a toner image corresponding to image information is formed on the photosensitive drum 18 through a predetermined electrophotographic process (charging process, exposure process, development process). Is done.
Thereafter, the toner image formed on the photosensitive drum 18 is transferred onto the recording medium P conveyed by the registration roller 13 in the transfer unit 7.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 11, 12, and 15 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 11 is selected). To do.) Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 11 is transported toward the position of the transport path K. Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller 13. Then, the recording medium P that has reached the position of the registration roller 13 is conveyed toward the transfer unit 7 at the same timing in order to align with the toner image formed on the photosensitive drum 18.

After the transfer process, the recording medium P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The recording medium P that has reached the fixing device 20 is fed between the fixing belt and the pressure roller, and the toner image is fixed by the heat received from the fixing belt and the pressure received from the pressure roller. The recording medium P on which the toner image has been fixed is sent from between the fixing belt and the pressure roller, and then is discharged from the image forming apparatus main body 1 as an output image and placed on the paper discharge tray 10.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 in the image forming apparatus main body 1 will be described in detail with reference to FIG.
As shown in FIG. 2, the fixing device 20 mainly includes a fixing auxiliary roller 21, a fixing belt 22, a support roller 23, an induction heating unit 24, a pressure roller 30, a thermistor 38, a guide plate 35, a separation plate 36, and the like. Is done.

  Here, the fixing auxiliary roller 21 is formed by forming an elastic layer such as silicone rubber on the surface of a cored bar made of stainless steel or the like. The elastic layer of the fixing auxiliary roller 21 has a thickness of 3 to 10 mm and an Asker hardness of 10 to 50 degrees. The fixing auxiliary roller 21 is rotationally driven counterclockwise in FIG. 2 by a driving unit (not shown).

  The support roller 23 as a heating member (heat generating member) includes a heat generating layer (cylindrical portion) made of a magnetic conductive material. The cylindrical portion of the support roller 23 is formed so that its thickness (layer thickness) is about 0.6 mm. The support roller 23 rotates counterclockwise in FIG. The coil part 25 is arrange | positioned so as to oppose the front and back (it is an outer peripheral surface and an inner peripheral surface) of the support roller 23 (refer FIG. 3).

Here, as a material of the support roller 23 as a heat generating member, a magnetic conductive material such as nickel, iron, chromium, or an alloy thereof can be used. In the first embodiment, a magnetic shunt alloy having a Curie point that is not less than the fixable temperature and not more than 300 degrees is used as the material of the support roller 23. Specifically, it is an alloy of nickel, iron, and chromium, and a desired Curie point can be obtained by adjusting the amount of each material added and the processing conditions. In this way, by forming the support roller 23 with a magnetic conductive material having a Curie point near the fixing temperature of the fixing belt 22, the support roller 23 is heated without being excessively heated by electromagnetic induction. Become. This will be described in detail later.
In the first embodiment, the support roller 23 is configured by only the heat generating layer, but a reinforcing layer, an elastic layer, a heat insulating layer, or the like may be provided on the heat generating layer of the support roller 23.

Hereinafter, the fixing belt 22 will be described in detail.
Referring to FIG. 2, a fixing belt 22 (fixing member) as a heat generating member is stretched and supported by a support roller 23 and a fixing auxiliary roller 21.
As shown in FIG. 4A, the fixing belt 22 is a multi-layered endless belt in which a heat generating layer 22b, an elastic layer 22c, and a release layer 22d are sequentially formed on a base material 22a. The base material 22a is made of an insulating heat-resistant resin material, and for example, polyimide, polyamideimide, PEEK, PES, PPS, fluorine resin, or the like can be used. The layer thickness of the base material 22a is formed to be 30 to 200 μm from the viewpoint of heat capacity and strength.

The heat generating layer 22b of the fixing belt 22 is made of a magnetic conductive material and has a layer thickness of 1 to 20 μm. The heat generating layer 22b is formed on the base material 22a by plating, sputtering, vacuum deposition or the like.
Here, a magnetic conductive material such as nickel or stainless steel can be used as the material of the heat generating layer 22b. In the first embodiment, a magnetic shunt alloy whose Curie point is higher than the fixable temperature and lower than 300 ° C. is used as the material of the heat generating layer 22b. Specifically, it is an alloy of nickel, iron, and chromium, and a desired Curie point can be obtained by adjusting the amount of each material added and the processing conditions. Thus, by forming the heat generating layer 22b with a magnetic conductive material having a Curie point near the fixing temperature of the fixing belt 22, the heat generating layer 22b is heated without being overheated by electromagnetic induction. Become. This will be described in detail later.

  The elastic layer 22c of the fixing belt 22 is made of silicone rubber, fluorosilicone rubber, or the like, and is formed to have a layer thickness of 50 to 500 μm and an Asker hardness of 5 to 50 degrees. Thereby, a uniform image quality without gloss unevenness can be obtained in the output image.

The release layer 22d of the fixing belt 22 is made of tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP). ), A mixture of these resins, or a dispersion of these resins in a heat resistant resin. The layer thickness of the release layer 22d is 5 to 50 μm (preferably 10 to 30 μm). Thereby, the toner releasability on the fixing belt 22 is ensured and the flexibility of the fixing belt 22 is ensured.
A primer layer or the like may be provided between the layers 22 a to 22 d of the fixing belt 22.

In the first embodiment, the fixing belt 22 as the heat generating member is a four-layer structure (the structure shown in FIG. 4A), but the multilayer structure shown in FIGS. 4B to 4D is used. It can also be a body.
The fixing belt 22 in FIG. 4B includes a heat generating layer 22b, an elastic layer 22c, and a release layer 22d. Here, the heat generating layer 22b may be made of a resin material such as polyimide, polyamideimide, PEEK, PES, PPS, or fluororesin in which magnetic conductive particles are dispersed. In that case, magnetic conductive particles are added within a range of 20 to 90% by weight with respect to the resin material. Specifically, the magnetic conductive particles are dispersed in a resin material in a varnish state using a dispersing device such as a roll mill, a sand mill, or a centrifugal defoaming device. This is adjusted to an appropriate viscosity with a solvent and formed into a desired layer thickness with a mold.

In the fixing belt 22 of FIG. 4C, a plurality of heat generating layers 22b are provided in a base material 22a, and an elastic layer 22c and a release layer 22d are sequentially formed thereon.
In the fixing belt 22 of FIG. 4D, an elastic layer 22c having a plurality of heat generating layers 22b is formed on a base material 22a, and a release layer 22d is further formed as a surface layer.
Also in these cases, the same effect as in the first embodiment can be obtained by configuring the heat generating layer 22b in the same configuration as in the first embodiment.

Referring to FIGS. 2 and 3, the induction heating unit 24 includes a coil unit 25 formed in a loop shape.
Here, the coil portion 25 is an exciting coil disposed so as to sandwich the front and back surfaces (the inner peripheral surface and the outer peripheral surface) of the fixing belt 22 and the support roller 23. In other words, the fixing belt 22 and a part of the support roller 23 are sandwiched in the loop of the loop-shaped coil portion 25. As shown in FIG. 3, the coil portion 25 extends in parallel to the width direction of the fixing belt 22 and the support roller 23. One end in the width direction of the coil portion 25 is a folded portion that connects the inner peripheral surface side and the outer peripheral surface side, and the high-frequency power source portion 40 is connected to the other end. Then, an alternating current of 10 k to 1 MHz (preferably 10 k to 300 kHz) is applied to the coil unit 25 from the high frequency power supply unit 40.

  In the first embodiment, the coil portion 25 is a single loop-shaped excitation coil, but a plurality of loop-shaped coil portions may be used. Here, the plurality of loop-shaped coil portions include a plurality of the coil portions 25 of FIG. 3 installed in the circumferential direction of the support roller 23 and the fixing belt 22, and one excitation coil as the support roller 23 and the fixing belt. 22 that are alternately spirally wound from the inner peripheral surface to the outer peripheral surface.

  Referring to FIG. 2, the pressure roller 30 is formed by forming an elastic layer such as fluororubber or silicone rubber on a cylindrical member made of aluminum, copper or the like. The elastic layer of the pressure roller 30 has a thickness of 1 to 5 mm and an Asker hardness of 20 to 50 degrees. The pressure roller 30 is in pressure contact with the auxiliary fixing roller 21 via the fixing belt 22. Then, the recording medium P is conveyed to a contact portion (a fixing nip portion) between the fixing belt 22 and the pressure roller 30.

A guide plate 35 for guiding the conveyance of the recording medium P is disposed on the entrance side of the contact portion between the fixing belt 22 and the pressure roller 30.
A separation plate 36 that guides the conveyance of the recording medium P and promotes the separation of the recording medium P from the fixing belt 22 is disposed on the exit side of the contact portion between the fixing belt 22 and the pressure roller 30. Yes.

  On the outer peripheral surface of the fixing belt 22 and on the upstream side of the fixing nip portion, a thermistor 38 as a temperature sensitive element having high thermal response is in contact. The thermistor 38 detects the surface temperature (fixing temperature) on the fixing belt 22 and adjusts the output of the induction heating unit 24.

The fixing device 20 configured as described above operates as follows.
By the rotation driving of the auxiliary fixing roller 21, the fixing belt 22 rotates in the arrow direction in FIG. 2, the support roller 23 also rotates counterclockwise, and the pressure roller 30 also rotates in the arrow direction. The fixing belt 22 is heated at a position facing the coil portion 25 (the position of the support roller 23).

  Specifically, the high frequency alternating current of 10 kHz to 1 MHz is allowed to flow from the high frequency power supply unit 40 to the coil unit 25, so that the magnetic field lines are alternately switched in both directions in the loop of the coil unit 25. By forming the alternating magnetic field in this way, when the temperature of the support roller 23 and the heat generation layer 22b is equal to or lower than the Curie point, an eddy current is generated on the surface of the support roller 23 and the heat generation layer 22b of the fixing belt 22, Joule heat is generated by the electrical resistance of the support roller 23 and the heat generating layer 22b, and the support roller 23 and the heat generating layer 22b are heated. In this way, the fixing belt 22 is heated by the heat received from the heat-generating support roller 23 and the heat generated by the heat generating layer 22b.

Thereafter, the surface of the fixing belt 22 that generates heat by the coil unit 25 passes through the position of the thermistor 38 and reaches the contact portion with the pressure roller 30. Then, the toner image T on the conveyed recording medium P is heated and melted.
Specifically, the recording medium P carrying the toner image T through the image forming process described above is fed between the fixing belt 22 and the pressure roller 30 while being guided by the guide plate 35 (indicated by the arrow Y). It is movement in the transport direction.) The toner image T is fixed to the recording medium P by the heat received from the fixing belt 22 and the pressure received from the pressure roller 30, and the recording medium P is sent from between the fixing belt 22 and the pressure roller 30.

  The surface of the fixing belt 22 that has passed through the position of the pressure roller 30 then reaches the position facing the coil portion 25 again. Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

In such a fixing process, when the temperature of the support roller 23 and the heat generating layer 22b exceeds the Curie point, heat generation of the support roller 23 and the heat generating layer 22b is limited.
That is, when the temperature of the support roller 23 and the heat generating layer 22b heated by the induction heating unit 24 exceeds the Curie point, the support roller 23 and the heat generating layer 22b lose their magnetism, so that eddy currents near the surface Occurrence is limited. Thereby, the generation amount of Joule heat in the support roller 23 and the heat generating layer 22b is reduced, and excessive temperature rise is suppressed.

  Such self-temperature control capability is obtained when the coil portion 25 is arranged in a loop shape with respect to the heat generating members 22b and 23 as in the first embodiment (for example, on the outer surface side of the heat generating members 22b and 23). It is particularly high compared to the case where the coil portion 25 is disposed on the surface side. Experimental examples showing such effects will be described later with reference to FIGS.

  As described above, in the first embodiment, in the electromagnetic induction heating type fixing device 20, the front and back surfaces of the heat generating members (the support roller 23 and the heat generating layer 22b) having the Curie point set near the fixing temperature are sandwiched. A coil portion 25 is provided. As a result, the self-temperature control capability of the heat generating members 22b and 23 is increased, and even if the small-size recording medium is continuously fixed or the apparatus is suddenly stopped, the excess of the fixing belt 22 can be obtained. Temperature rise can be reliably suppressed.

  In the first embodiment, the fixing belt 22 having the heat generating layer 22b and the support roller 23 having the heat generating layer are used as the heat generating members. On the other hand, only one of the fixing belt 22 and the support roller 23 can be used as the heat generating member. Also in this case, the same heat generating layer as that of the first embodiment is provided on one member used as the heat generating member, and the heat generating member is inserted into the loop-shaped coil portion 25, so that the same as in the first embodiment. The effect of can be obtained.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a cross-sectional view showing a main part of the image forming apparatus according to the second embodiment. The image forming apparatus of the second embodiment is different from that of the first embodiment in that the image forming apparatus is a tandem color image forming apparatus and the fixing roller 31 is used as a heat generating member.

  The image forming apparatus according to the second embodiment is a tandem color image forming apparatus. As shown in FIG. 5, a plurality of photosensitive drums 18BK, 18Y, 18M, and 18C are arranged in parallel on the transfer belt 8 in the image forming unit. Although not shown, a charging unit, an exposure unit, a developing unit, a cleaning unit, and a charge eliminating unit are disposed on the outer periphery of the plurality of photosensitive drums 18BK, 18Y, 18M, and 18C (process cartridge 4 in FIG. 1). Can be referred to.) Then, a toner image of each color (black, yellow, magenta, cyan) is formed on each photosensitive drum 18BK, 18Y, 18M, 18C.

The transfer unit 7 includes a transfer belt 8 that transports the recording medium P, a bias roller 9 that faces each of the photosensitive drums 18BK, 18Y, 18M, and 18C via the transfer belt 8, and a cleaning roller that cleans the surface of the transfer belt 8. 14, etc.
The transfer belt 8 sequentially conveys the recording medium P conveyed from the direction of the arrow to a position facing each of the photosensitive drums 18Y, 18M, 18C, and 18BK. At this time, the toner images of the respective colors are transferred onto the recording medium P by the transfer bias applied to the bias roller 9. Thus, a full-color toner image is formed on the recording medium P. Thereafter, the recording medium P on which a full-color toner image is formed is separated from the transfer belt 8 and conveyed toward the fixing device 20.

On the other hand, the fixing device 20 of the second embodiment mainly includes a fixing roller 31 (fixing member) as a heat generating member, a pressure roller 30, an induction heating unit 24, and the like.
The fixing roller 31 includes a heat generating layer 22b made of a magnetic conductive material, an elastic layer made of silicone rubber, a release layer made of a fluorine compound, or the like. As in the first embodiment, the heat generating layer 22b of the fixing roller 31 is formed of a magnetic shunt alloy having a Curie point that is higher than the fixable temperature and lower than 300 ° C. The fixing roller 31 has a mechanical strength that resists the pressure applied by the pressure roller 30.

Moreover, the induction heating part 24 is comprised by the coil part 25 formed in loop shape similarly to the said Embodiment 1. FIG. That is, the coil portion 25 is disposed so as to sandwich the front and back surfaces (the inner peripheral surface and the outer peripheral surface) of the fixing roller 31.
When an alternating current of 10 k to 1 MHz is supplied to the coil unit 25, magnetic lines of force are formed in the loop of the coil unit 25, and the fixing roller 31 is heated by electromagnetic induction. In this way, the heated fixing roller 31 heats and melts the toner image on the recording medium P conveyed from the direction of the arrow and fixes the toner image on the recording medium P.

  Also in the second embodiment, when the temperature of the heat generating layer 22b of the fixing roller 31 exceeds the Curie point, the heat generation of the heat generating layer 22b is efficiently limited as in the first embodiment. .

  As described above, in the second embodiment, in the electromagnetic induction heating type fixing device 20, the coil portion 25 is disposed so as to sandwich the front and back surfaces of the fixing roller 31 with the Curie point set near the fixing temperature. Yes. As a result, the self-temperature control capability of the fixing roller 31 is enhanced, and even if the small-size recording medium is continuously fixed or the apparatus suddenly stops driving, the temperature of the fixing roller 31 is excessively high. Can be reliably deterred.

  In the second embodiment, the fixing roller 31 is used as a fixing member facing the induction heating unit 24. However, a cylindrical fixing belt 22 may be used as a fixing member facing the induction heating unit 24. In this case, the holding member that holds the fixing belt 22 in a cylindrical shape is brought into contact with a part of the inner peripheral surface of the fixing belt 22. Further, in order to form an appropriate fixing nip between the fixing belt 22 and the pressure roller 30, a pressure member is brought into contact with a position on the inner peripheral surface of the fixing belt 22 facing the pressure roller 30. Become. Also for such a fixing device 20, the coil unit 25 is disposed so as to sandwich the front and back surfaces of the fixing belt 22 with the Curie point set in the vicinity of the fixing temperature, so that the same effect as in the second embodiment can be obtained. Obtainable.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a cross-sectional view showing the fixing device according to the third embodiment, and corresponds to FIG. 2 of the first embodiment. In the fixing device of the third embodiment, the position of the induction heating unit 24 is different from that of the first embodiment.

The fixing device 20 according to the third embodiment mainly includes a fixing belt 22 (fixing member) as a heat generating member, a heat generating plate 28 (heating member) as a heat generating member, an induction heating unit 24, a support roller 23, and a pressure roller 30. Etc.
Similarly to the heat generation layer 22b of the first embodiment, the heat generation plate 28 is made of a magnetic shunt alloy having a Curie point that is higher than the fixable temperature and lower than 300 ° C. The heat generating plate 28 is in contact with the inner peripheral surface of the fixing belt 22 with a predetermined pressure.

  As shown in FIG. 6, the induction heating unit 24 according to the third embodiment has a loop shape disposed at positions facing the outer peripheral surface and the inner peripheral surface of the fixing belt 22 from the support roller 23 to the auxiliary fixing roller 21. This is a coil portion 25. That is, the coil portion 25 is disposed so as to sandwich the fixing belt 22 and the heat generating plate 28.

In the fixing device 20 configured as described above, an alternating current of 10 k to 1 MHz is supplied to the loop-shaped coil unit 25, so that magnetic lines of force are formed between the fixing belt 22 and the coil unit 25 sandwiching the heat generating plate 28. Thus, the fixing belt 22 and the heat generating plate 28 are heated by electromagnetic induction.
Also in the third embodiment, when the temperature of the heat generating layer of the fixing belt 22 and the heat generating plate 28 exceeds the Curie point, the heat generation of the heat generating layer is efficiently limited as in the first embodiment. become.

  As described above, in the third embodiment, in the electromagnetic induction heating type fixing device 20, the front and back surfaces of the heat generating members (the heat generating layer 22b and the heat generating plate 28) having the Curie point set near the fixing temperature are sandwiched. A coil portion 25 is provided. As a result, the self-temperature control capability of the heat generating members 22b and 28 is increased, and even if the small-size recording medium is continuously fixed or the apparatus is suddenly stopped, the overload of the fixing roller 31 is increased. Temperature rise can be reliably suppressed.

In the third embodiment, the fixing belt 22 having the heat generating layer 22b and the heat generating plate 28 having the heat generating layer are used as the heat generating members. On the other hand, only one of the fixing belt 22 and the heat generating plate 28 can be used as a heat generating member. Also in this case, the same heat generating layer as that of the third embodiment is provided on one member used as the heat generating member, and the heat generating member is sandwiched in the loop-shaped coil portion 25, so that the same as in the third embodiment. The effect of can be obtained.
Further, when the posture of the fixing belt 22 in the loop of the coil unit 25 can be maintained with a certain degree of accuracy, the heat generating plate 28 in the third embodiment can be omitted.

Experimental example.
Examples of experiments for confirming the effects described in the above embodiments will be described with reference to FIGS.
FIG. 7A and FIG. 7B are schematic views showing an experimental apparatus. The experimental apparatus of FIG. 7A is a device in which a loop-shaped coil portion 25 is opposed to the front and back surfaces of a test piece having a heat generating layer 33 (corresponding to the heat generating member in each of the above embodiments). Yes (the configuration of the fixing device in each of the above embodiments). In the experimental apparatus of FIG. 7B, the coil portion 25 is opposed to the main surface of the test piece having the heat generating layer 33 (the configuration of a conventional fixing device).

  That is, the experimental apparatus in FIG. 7A and the experimental apparatus in FIG. 7B have the same configuration of the coil portion 25 and are different only in the direction of the test pieces 33 and 34 facing the coil portion 25. become.

  Here, the test piece includes only the heat generating layer 33, the conductive layer 34 made of aluminum formed on the heat generating layer 33 with a thickness of 0.3 mm, and the conductive layer 34 made of aluminum on the heat generating layer 33. Were prepared in a thickness of 0.8 mm. The heat generation layer 33 of the test piece is made of a magnetic shunt alloy having a front and back size of 25 mm × 50 mm, a thickness of 0.22 mm, and a Curie temperature of 240 ° C. The conductive layer 34 of the test piece also has a front and back size of 25 mm × 50 mm.

  Further, two types of alternating currents having an electric power of 200 to 1200 W and an excitation frequency of 36 kHz and 130 kHz are applied from the high frequency power supply unit 40 to the coil unit 25 of the experimental apparatus. Thereby, magnetic field lines as shown in FIGS. 7A and 7B are formed in the vicinity of the coil portion 25.

8 and 9 are graphs showing the results of experimental examples performed using the above-described experimental apparatus. 8 and 9, the horizontal axis indicates the time from the start of electromagnetic induction, and the vertical axis indicates the temperature on the heat generating layer 33.
FIG. 8 shows the experimental results when using the experimental apparatus of FIG. 7A, and FIG. 9 shows the experimental results when using the experimental apparatus of FIG. 7B.

  FIG. 8A is a graph showing the relationship between time and temperature when the frequency of the alternating current output from the high frequency power supply unit 40 is 36 kHz. FIG. 8B is a graph showing the relationship between time and temperature when the frequency of the alternating current output from the high frequency power supply unit 40 is 130 kHz. Further, in FIG. 8, a solid line R0 is a case where a test piece having only a heat generating layer 33 is used, and a solid line R1 is a case where a test piece in which a conductive layer 34 having a thickness of 0.3 mm is formed on the heat generating layer 33 is used. The solid line R3 is obtained when a test piece in which a conductive layer 34 having a thickness of 0.8 mm is formed on the heat generating layer 33 is used.

  FIG. 9A is a graph showing the relationship between time and temperature when the frequency of the alternating current output from the high frequency power supply unit 40 is 36 kHz. FIG. 9B is a graph showing the relationship between time and temperature when the frequency of the alternating current output from the high frequency power supply unit 40 is 130 kHz. In FIG. 9, a solid line Q0 is a case where a test piece having only a heat generating layer 33 is used, and a solid line Q1 is a case where a test piece in which a conductive layer 34 having a thickness of 0.3 mm is formed on the heat generating layer 33 is used. The solid line Q3 is when a test piece in which a conductive layer 34 having a thickness of 0.8 mm is formed on the heat generating layer 33 is used.

From FIG. 8, it can be seen that, regardless of the presence or absence of the conductive layer 34 and the frequency of the alternating current, when the temperature of the heat generating layer 33 reaches the Curie point, further overheating is prevented.
On the other hand, FIG. 9A shows that when the excitation frequency is set to 36 kHz, overheating of the heat generating layer 33 cannot be prevented unless the conductive layer 34 having a thickness of 0.8 mm or more is provided. Similarly, FIG. 9B shows that when the excitation frequency is set to 130 kHz, excessive heating of the heat generating layer 33 cannot be prevented unless the conductive layer 34 having a thickness of 0.3 mm or more is provided. As described above, when the coil portion 25 is opposed to the main surface of the heat generating member (heat generating layer 33), it is necessary to provide a nonmagnetic and low resistivity conductive layer on the opposite side of the main surface. This is consistent with the contents described in Japanese Patent Application Laid-Open No. 2003-215956.

  From the above, it can be seen that the ability of the heat generating member to control the self-temperature is enhanced by inserting the heat generating member into the loop-shaped coil portion 25. Furthermore, from comparison between FIG. 8 and FIG. 9, it is understood that the heat generation efficiency (rise) of the heat generating member is improved by inserting the heat generating member in the loop-shaped coil portion 25. Moreover, since the above-described effect can be obtained without providing the conductive layer 34 on the heat generating member, the structure of the heat generating member is simplified. Therefore, it is possible to provide a heat generating member that is inexpensive and has no problems due to the provision of a conductive layer such as delamination.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is a graph showing fluctuations in the fixing temperature of the fixing device according to the fourth embodiment. The fixing device of the fourth embodiment is different from that of the first embodiment in which the driving is stopped after the power is turned on in that the driving is stopped for a predetermined time after the power is turned on.

The fixing device according to the fourth embodiment is different only in control at power-on, and the configuration is the same as that of the first embodiment.
As described with reference to FIG. 2, in a normal fixing process, the fixing belt 22 and the support roller 23 as the heat generating members are driven so that the positions sandwiched between the coil portions 25 are displaced. Specifically, as the auxiliary fixing roller 21 is driven to rotate by the drive unit, the fixing belt 22 rotates in the direction of the arrow, and the support roller 23 rotates counterclockwise.

  Here, in the fourth embodiment, the rotation of the auxiliary fixing roller 21 is not started immediately after the power is turned on, but the rotation of the auxiliary auxiliary roller 21 is started after a predetermined time has elapsed since the power was turned on. That is, when an alternating current is applied to the coil unit 25 by turning on the power, generation of magnetic flux from the coil unit 25 is started. The fixing belt 22 and the support roller 23 are stopped for a predetermined time (a part of the fixing belt 22 and the support roller 23 is sandwiched between the coil portions 25). Electromagnetic induction heating is performed. Thereafter, rotation driving of the fixing belt 22 and the support roller 23 is started, and a normal fixing process is performed.

  In FIG. 10, the horizontal axis indicates the time since the power is turned on, and the vertical axis indicates the surface temperature (fixing temperature) of the fixing belt 22. A solid line S1 indicates a change in fixing temperature when the driving is stopped for a predetermined time after the power is turned on and then the driving is started (when the control according to the fourth embodiment is performed), and a broken line S2 indicates the power source. A change in fixing temperature when the driving is started immediately after the charging (when the control of the first embodiment is performed) is shown. In the solid line S1, the driving of the fixing belt 22 is started when the surface temperature of the fixing belt 22 reaches 140 ° after the power is turned on.

  As shown in FIG. 10, the rise time (the time required to reach the desired fixing temperature) is shorter when the drive is stopped for a predetermined time after the start of the temperature rise than when the drive is started immediately after the start of the temperature rise. Recognize. The rise time can be adjusted by the heat capacity depending on the shape and material of the constituent members of the fixing device and the input power.

  Here, such a drive stop after the start of the temperature rise is a control that can be performed by the fixing device with enhanced self-temperature control capability described in the above embodiments. That is, in a fixing device having a low self-temperature control capability, the surface temperature of the fixing belt 22 excessively rises while the driving is stopped. Therefore, it is necessary to start driving immediately after turning on the power.

  As described above, in the fourth embodiment, in addition to the effects described in the above embodiments, the rise time can be shortened by stopping the driving at the time of temperature increase. This further improves energy saving in the fixing device.

Embodiment 5. FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 11 is a cross-sectional view showing the fixing device according to the fifth embodiment. The fixing device of the fifth embodiment is different from that of the first embodiment in that the two heating members 22 and 23 having different Curie points are used and the two induction heating sections 24A and 24B are provided. It is different from the one.

  Referring to FIG. 11, in the fifth embodiment, fixing belt 22 and support roller 23 are used as heat generating members. The Curie point of the heat generating layer of the fixing belt 22 (second heat generating member) is higher than the Curie point of the heat generating layer (the support roller 23 itself) of the support roller 23 (first heat generating member). Is set to Specifically, the support roller 23 has a Curie point in the vicinity of a fixing target temperature (a fixing belt surface temperature intended to ensure stable fixing properties, for example, 180 ° C.). Is formed. On the other hand, the heat generating layer of the fixing belt 22 is formed such that its Curie point is sufficiently larger than the fixing target temperature. Such adjustment of the Curie point can be achieved by selecting a metal material used for the heat generating layer or adjusting the composition of the magnetic shunt alloy.

In the fifth embodiment, the first induction heating unit 24A causes the fixing belt 22 and the support roller 23 to generate heat by electromagnetic induction heating. On the other hand, the second induction heating unit 25B causes only the fixing belt 22 to generate heat by electromagnetic induction heating.
When the belt surface temperature of the fixing belt 22 (detected by a thermistor not shown) reaches the fixing target temperature, the energization to the second induction heating unit 25B is stopped and the first induction heating unit 24A is stopped. Only energizing is performed. As a result, the support roller 23 whose Curie point is set in the vicinity of the fixing target temperature acts as a limiter, and the excessive temperature rise of the fixing belt 22 is suppressed.

  As described above, in the fifth embodiment, since the two heat generating members 22 and 23 having different Curie points are used, the rise time of the apparatus 20 is shortened, the overheating of the fixing belt 22 is prevented, Can be achieved.

Hereinafter, the reason will be described in detail.
The fixing belt 22 is a multilayer structure and has a predetermined temperature gradient. That is, as shown in FIG. 12, when a certain amount of heat is supplied from the heat generating layer (heat source) for a predetermined time unit, the distance from the heat generating layer to the belt surface (the thickness and layer thickness of the belt). The longer the length, the lower the belt surface temperature. Further, such a temperature gradient is caused by the thermal conductivity and specific heat of each layer (base material, elastic layer, release layer, etc.) constituting the fixing belt 22, and further by heat radiation to the peripheral members and the recording medium. Also changes. Therefore, when heat generation and heat dissipation (including heat propagation) are balanced, the Curie point in the heat generation layer of the heat generation member can be determined in consideration of only the temperature gradient shown in FIG.

  However, when the heat generation and the heat dissipation are not balanced, such as when the apparatus is started up, the Curie point in the heat generating layer of the heat generating member cannot be determined only by the temperature gradient shown in FIG. That is, when the apparatus starts up, the temperature of the peripheral members such as the pressure roller 30 and the auxiliary fixing roller 21 is low, and the amount of heat taken by these members increases, so that the heat generation and the heat dissipation are not balanced. A low speed image forming apparatus (small machine) has a relatively small heat capacity of the peripheral members, so that thermal balance is reached in a short time. However, a high speed image forming apparatus (large machine) has a large heat capacity of the peripheral members, The time loss to reach a proper balance will become significant.

  In the fifth embodiment, the heat generating layer of the fixing belt 22 as the second heat generating member is formed so that its Curie point is sufficiently higher than the target fixing temperature. The amount of heat supplied to the member increases and the rise time is shortened. In addition, it is preferable that the positive heat supply using the fixing belt 22 having a high Curie point is performed mainly at the time of start-up. That is, the control temperature at the Curie point at the time of rising (when there is no thermal balance) is set higher than the control temperature at the Curie point after rising (when there is a thermal balance). Thus, both the shortening of the rise time 20 and the prevention of overheating of the fixing belt 22 can be achieved.

  In the fifth embodiment, the Curie point of the support roller 23 is set near the fixing target temperature in consideration of the temperature gradient in FIG. On the other hand, the Curie point of the heat generating layer of the fixing belt 22 is set in the range of 200 to 300 ° C. in consideration of the heat resistance of the base material and the elastic layer.

  As described above, in the fifth embodiment, in addition to the effects described in the first embodiment and the like, the rise time of the fixing device 20 is further shortened and the excessive temperature rise of the fixing belt 22 is prevented. It can be compatible.

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 13 is a cross-sectional view showing the fixing device according to the sixth embodiment. In the fixing device according to the sixth embodiment, the first induction heating unit 24A generates heat only from the support roller 23 as a heating member, and the second induction heating unit 24B generates heat only from the heating plate 28 as a heating member. This is different from that of the fifth embodiment.

  Referring to FIG. 13, in the sixth embodiment, support roller 23 and heat generating plate 28 are used as heat generating members. The Curie point of the heat generating layer of the heat generating plate 28 (second heat generating member) is set to be higher than the Curie point of the heat generating layer of the support roller 23 (first heat generating member). Specifically, the support roller 23 is formed so that its Curie point is close to the fixing target temperature. On the other hand, the heat generating layer (the heat generating plate 28 itself) of the heat generating plate 28 is formed such that its Curie point is sufficiently higher than the fixing target temperature.

  In the sixth embodiment, the first induction heating unit 24A (first coil unit) is disposed so as to sandwich only the support roller 23 among the two heat generating members 23 and 28, and electromagnetic induction heating is performed. As a result, only the support roller 23 generates heat. On the other hand, the second induction heating unit 25B (second coil unit) is disposed so as to sandwich only the heat generating plate 28 among the two heat generating members 23 and 28, and the heat generating plate 28 is obtained by electromagnetic induction heating. Only heat will be generated.

The second induction heating unit 25B (second coil unit) is energized only when the device starts up (generates magnetic flux), and only the heat generating plate 28 generates heat. The first induction heating unit 25A (first coil unit) is energized only after the apparatus is started up, and only the support roller 23 generates heat.
Here, in the two induction heating parts 25A and 25B, the inductance, equivalent series resistance, capacitance, etc. in each coil part 25 and the heat generating members 23 and 28 can be made equal. At this time, since the two induction heating units 25A and 25B are not used at the same time, both the power sources can be shared, and the energization to the two induction heating units 25A and 25 can be switched by switching.

  As described above, also in the sixth embodiment, as in the fifth embodiment, it is possible to achieve both further shortening of the rise time of the fixing device 20 and prevention of excessive temperature rise of the fixing belt 22. it can.

  In each of the above embodiments, the toner used for forming the toner image (the toner accommodated in the developing unit that performs the developing process) includes at least a binder resin, a colorant, and a release agent. Contains. As the release agent in the toner, a component formed such that the components are dispersed in an island shape in the binder resin and the average dispersed particle diameter is in the range of 0.1 to 1.0 μm is used. It is preferable.

  As a result of repeated research, the inventor of the present application uses the toner described above, and in addition to the effects described in the above-described embodiments, the separation of the recording medium P in accordance with the improvement in toner releasability in the fixing device 20. As a result, it has been found that the winding of the recording medium P around the fixing member is suppressed.

  Here, even when the above-described toner is used, when defects occur on the surfaces of the fixing members 22 and 31 of the fixing device 20, the toner releasability is not sufficiently improved. This is because when defects such as cracks, protrusions, and scratches occur on the surface of the fixing member, the toner adheres to the surface of the fixing member starting from the defects. One of the factors causing these defects is an excessive thermal load on the fixing member. When the fixing device 20 is overheated at the time of start-up (overshoot) or a temperature rise occurs at the end of the fixing member by passing a small-sized recording medium P, the surface temperature of the fixing member is 200. May exceed ℃. In such a case, since the heat resistant temperature of the silicone rubber used as the material of the elastic layer of the fixing member is about 200 ° C., the elastic layer is deteriorated. In particular, when the elastic layer is hardened and deteriorated due to oxidation, defects such as cracks are generated in the elastic layer.

  On the other hand, in the fixing device 20 of each of the embodiments described above, the capability of self-temperature control in the heat generating members 22b and 23 is increased, and when the small-size recording medium is continuously fixed, the device suddenly stops driving. Even in such a case, since excessive temperature rise of the fixing belt 22 can be reliably suppressed, an excessive thermal load on the fixing member is reduced to prevent defects on the surface of the fixing member. can do. Therefore, by using the above-described toner, toner releasability and recording medium separability are reliably improved. That is, a toner containing a release agent formed so that the release agent component is dispersed in an island shape in the binder resin and the average dispersed particle diameter is in the range of 0.1 to 1.0 μm. By using it, an appropriate amount of the release agent oozes out on the toner surface during the fixing step, and offset resistance is improved.

Here, as a method of dispersing the toner release agent in a required size, a method of selecting the release agent in consideration of the compatibility between the resin and the wax, or a method of using a dispersion aid for the release agent Alternatively, a method of controlling the amount of the release agent dispersant can be used.
Further, the amount of the release agent in all the components of the toner depends on the average dispersion diameter of the finely divided release agent, but is preferably in the range of 2 to 10% by weight. When the amount of the release agent is less than 2% by weight, sufficient hot offset property cannot be obtained. On the other hand, when the amount of the release agent exceeds 10% by weight, developability and transferability are deteriorated, and filming on the photosensitive drum 18 and the charging unit occurs.

  The average dispersion particle size of the release agent described above is an average of the particle sizes in the maximum direction of the release agent (which is the dispersion diameter). Specifically, the toner is embedded in an epoxy resin and cut into ultrathin sections of about 100 nm. After dyeing with ruthenium tetroxide, observation is performed with a transmission electron microscope (TEM) at a magnification of 10,000 to 50,000 times, and a photograph is taken. Furthermore, this photograph is image-evaluated, the dispersion state of 50 release agents is observed, the dispersion diameter is measured, and this is averaged to obtain the average dispersion diameter.

  As the release agent to be contained in the toner, those having a melting point of 110 ° C. or less are preferable. By using such a low-melting-point release agent, the release agent effectively acts between the fixing member and the toner interface, and high temperature offset can be prevented. When the melting point of the release agent exceeds 110 ° C., sufficient release properties cannot be exhibited. Furthermore, if the melting point of the release agent is 30 ° C. or less, the toner has insufficient blocking resistance and storage stability. The melting point of the release agent is the maximum endothermic peak measured by a differential scanning calorimeter (DSC).

  Here, in each of the above embodiments, examples of the binder resin contained in the toner include styrene such as polyester, polystyrene, poly p-chlorostyrene, and polyvinyltoluene, and a homopolymer of a substituted product thereof; styrene-p -Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene- Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylic acid Methyl copolymer, styrene-acrylonitrile copolymer Styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, Styrene copolymers such as a styrene-maleic acid copolymer and a styrene-maleic acid ester copolymer can be used.

  Examples of the release agent (release agent component) contained in the toner include polyolefin wax (polyethylene wax, polypropylene wax, etc.); long-chain hydrocarbon (paraffin wax, sasol wax, etc.); A carbonyl group-containing wax or the like can be used. Of these, carbonyl group-containing waxes are preferred. Carbonyl group-containing waxes include polyalkanoic acid esters (carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18 -Octadecanediol distearate, etc.); polyalkanol esters (trimellitic acid tristearyl, distearyl maleate, etc.); polyalkanoic acid amides (ethylenediamine dibehenylamide, etc.); polyalkylamides (trimellitic acid tristearylamide, etc.) Dialkyl ketones (such as distearyl ketone) can be used. Among these carbonyl group-containing waxes, polyalkanoic acid esters are preferred.

  Examples of the colorant contained in the toner include carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, and yellow lead. , Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine rake, quinoline yellow rake, anthracene yellow BGL, isoindolinone yellow, bengara, red lead, lead vermilion, cadmium red, cadmium mercury red, antimon vermilion, permanent red 4R, para red, phise red, Parachlor ortho nitroaniline , Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carnmin BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Velcan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo , Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), Indigo, Ultramarine Blue, Bitumen, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, Cobalt Purple, Manganese Purple, Dioxane Violet, Anthraquinone Violet, Chrome Green, Zinc Green, Chrome Oxide, Pyridian, Emerald Green, Pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalocyanine Green, anthraquinone green, titanium oxide, zinc white, lithopone and mixtures thereof can be used. The content of the colorant is desirably 1 to 15% by weight (more preferably 3 to 10% by weight) with respect to the toner.

  The colorant can also be used as a master batch combined with a resin. As the binder resin kneaded with the master batch at the time of producing the master batch, in addition to the modified and unmodified polyester resins, styrene such as polystyrene, poly p-chlorostyrene, polyvinyl toluene, and its substituted polymers; styrene-p- Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic Acid butyl copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate Copolymer, styrene-acrylic Ronitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene copolymers such as copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid Resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax and the like can be used alone or in combination.

  The masterbatch can be formed by mixing and kneading the masterbatch resin and the colorant under high shear. At that time, an organic solvent can be used in order to enhance the interaction between the colorant and the resin. In addition, a method (flushing method) in which an aqueous paste containing water of a colorant is mixed and kneaded together with a resin and an organic solvent, the colorant is transferred to the resin side, and moisture and an organic solvent component are removed. Since the colorant wet cake can be used as it is, there is an advantage that the drying step can be omitted. As a device for mixing and kneading, a high shear dispersion device equipped with a three-roll mill or the like can be used.

The toner used in each of the above embodiments can contain a charge control substance in addition to the binder resin, the colorant, and the release agent. By fixing the charge control substance on the surface of the toner, a high charge amount can be imparted. That is, by fixing the charge control substance on the surface of the toner, the amount and state of presence on the toner surface are stabilized, and the charge amount of the toner can be stabilized.
Examples of the charge control substance include nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (including fluorine-modified quaternary ammonium salts). ), Alkylamide, phosphorus simple substance or compound, tungsten simple substance or compound, fluorine-based activator, salicylic acid metal salt, salicylic acid derivative metal salt, and the like.

  Specifically, Bontron 03 of nigrosine dye, Bontron P-51 of quaternary ammonium salt, Bontron S-34 of metal-containing azo dye, E-82 of oxynaphthoic acid metal complex, E of salicylic acid metal complex -84, phenolic condensate E-89 (above, Orient Chemical Industries), quaternary ammonium salt molybdenum complex TP-302, TP-415 (above, Hodogaya Chemical Co., Ltd.), quaternary Copy charge PSY VP2038 of ammonium salt, copy blue PR of triphenylmethane derivative, copy charge NEG VP2036 of quaternary ammonium salt, copy charge NX VP434 (above, manufactured by Hoechst), LRA-901, LR- which is a boron complex 147 (Nippon Carlit), copper phthalocyanine, perylene, quinacridone Azo pigments, sulfonate group, a carboxyl group, can be used polymer compounds having a functional group such as a quaternary ammonium salt.

  The amount of the charge control substance used is determined by the toner production method including the type of binder resin, the presence or absence of additives used as needed, and the dispersion method, but is not uniquely limited. Preferably, it can be used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. More preferably, it can be used in the range of 0.2 to 5 parts by weight. When the amount of the charge control substance used exceeds 10 parts by weight, the chargeability of the toner becomes too high, and the developing roller (which is a component of the developing unit that carries the developer and faces the photosensitive drum). The electrostatic attraction force increases. As a result, the fluidity of the developer is lowered and the image density is lowered.

  The toner used in each of the above embodiments can contain a fluidity improver for improving the fluidity of the toner in addition to the binder resin, the colorant, and the release agent. As the fluidity improver, silica, titanium oxide, alumina, or the like can be used, and hydrophobized silica is particularly preferable. The fluidity improver can prevent the deterioration of flow characteristics and charging characteristics even under high humidity by performing surface treatment to increase hydrophobicity. Examples of the surface treatment agent used at this time include a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate coupling agent, an aluminum coupling agent, silicone oil, and modified silicone. There is oil.

  In addition to the binder resin, the colorant, and the release agent, the toner used in each of the above embodiments includes a cleaning property improver for improving the removability of the untransferred toner remaining on the photosensitive drum. It can be included. As the cleaning property improver, for example, fatty acid metal salts such as zinc stearate, calcium stearate, stearic acid, for example, polymer fine particles produced by soap-free emulsion polymerization such as polymethyl methacrylate fine particles, polystyrene fine particles, etc. Can do. The polymer fine particles preferably have a relatively narrow particle size distribution and an average particle size of 0.01 to 1 μm.

  The toner used in each of the above embodiments is used as a one-component developer (magnetic toner or non-magnetic toner) in the developing unit, or mixed with a magnetic carrier in the developing unit and used as a two-component developer. it can. The carrier to toner content ratio in the two-component developer is preferably 1 to 10 parts by weight of toner with respect to 100 parts by weight of carrier. As the magnetic carrier, iron powder, ferrite powder, magnetite powder, magnetic resin carrier and the like having a particle size of about 20 to 100 μm can be used.

The magnetic carrier can also be coated with a resin or the like. As the coating material, amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin can be used. Further, as a coating material, polyvinyl and polyvinylidene resins, such as acrylic resin, polymethyl methacrylate resin, polyacrylonitrile resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polystyrene resin, and styrene-acrylic copolymer resin, etc. Polystyrene resins, halogenated olefin resins such as polyvinyl chloride, polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, polycarbonate resins, polyethylene resins, polyvinyl fluoride resins, polyvinylidene fluoride resins, Fluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, copolymer of vinylidene fluoride and vinyl fluoride, tetrafluoroethylene And fluoroterpolymers such as terpolymers of vinylidene fluoride and non-fluoride monomers including, it is also possible to use a silicone resin and the like.
The magnetic carrier can also contain conductive powder or the like in the coating material. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide, or the like can be used. These conductive powders preferably have an average particle diameter of 1 μm or less. When the average particle diameter of the conductive powder is larger than 1 μm, it becomes difficult to control the electric resistance of the carrier.

In each of the above embodiments, the toner is formed such that its weight average particle diameter (D4) is in the range of 2.5 to 5.0 μm, and its average circularity is 0.95 to 0.99. It is preferable to use one formed so as to fall within the range.
As a result of repeated research, the inventor of the present application has found that an output image with uniform gloss can be obtained by using the above-described toner in addition to the effects described in the above embodiments.

The gloss in the output image becomes an especially important image quality in the color image forming apparatus described with reference to FIG. The gloss of the image varies greatly depending on the amount of toner on the recording medium P and the fixing temperature during the fixing process. Therefore, when an end temperature rise or temperature variation occurs in the fixing members 22 and 31, gloss variation occurs on the image. In the fixing device 20 of each of the above embodiments, the excessive temperature rise is suppressed by the self-temperature control in the heat generating member, and an increase in the end temperature of the fixing member can be suppressed even when a small-size recording medium is passed. Local temperature variation is reduced.
Further, the toner on the recording medium P is obtained by using a toner having a weight average particle diameter (D4) of 2.5 to 5.0 μm and an average circularity of 0.95 to 0.99. Since the layers are made uniform, an image with uniform gloss can be reliably obtained.

Here, when the weight average particle diameter (D4) of the toner is smaller than 2.5 μm and the toner is used as a two-component developer together with the magnetic carrier, the surface of the carrier is caused by long-term stirring in the developing unit. Then, the toner is fused and the charging ability of the carrier is lowered. Further, when the toner has a weight average particle diameter (D4) smaller than 2.5 μm and the toner is used as a one-component developer, the toner is filmed on the developing roller or the toner is thinly layered. The toner is fused to the doctor blade or the like.
On the other hand, when the weight average particle diameter (D4) of the toner is larger than 5.0 μm, the toner layer on the recording medium P becomes non-uniform, and the releasability of the toner is deteriorated. The separability of P becomes insufficient.
Further, when the average circularity of the toner is smaller than 0.95, the toner layer on the recording medium P becomes non-uniform, and the releasability of the toner is lowered, so that the separation property of the recording medium P is insufficient. Become. On the other hand, when the average circularity of the toner is larger than 0.99, transfer dust in which the toner is scattered on the recording medium P easily occurs during the transfer process.

Here, the above-mentioned weight average particle diameter (D4) of the toner can be obtained using “Coulter Counter Model TA-II” (manufactured by Coulter Electronics).
Specifically, an interface (manufactured by Nikka Machine Co., Ltd.) that outputs a number distribution and a weight distribution and a PC 9801 personal computer (manufactured by NEC Corporation) are connected to the above-described measuring apparatus. Then, a 1% NaCl aqueous solution is prepared using primary sodium chloride as the electrolytic solution. Thereafter, 0.1 to 5 ml of a surfactant (preferably alkylbenzenesulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. Disperse for 1 to 3 minutes. Further, 100 to 200 ml of the electrolytic aqueous solution is put into another beaker, and the above-mentioned sample dispersion is added therein to a predetermined concentration to prepare a suspension. Then, using the suspension, the particle size distribution of 2 to 40 μm particles is measured by using the aperture (50 μm aperture) with the above-described measuring apparatus on the basis of the number. Then, the weight distribution and the number distribution of particles of 1.58 to 49.18 μm are calculated, and the weight-based weight average particle diameter obtained from the weight distribution (D4: the median value of each channel is set as the representative value of the channel). ).

Further, the average circularity of the toner described above can be obtained as follows.
That is, a suspension containing particles (the same as that prepared in the above-described measurement of the toner weight average particle size) is passed through an imaging unit detection zone on a flat plate, and the particle image is optically detected by a CCD camera. An optical detection band method is used to detect and analyze this. This value is measured as an average circularity by a flow type particle image analyzer “FPIA-1000” (manufactured by Toa Medical Electronics Co., Ltd.). As a specific measuring method, 0.1 to 0.5 ml of a surfactant alkylbenzene sulfonate as a dispersant is added to 100 to 150 ml of water from which impure solids have been removed in advance in a container. Furthermore, about 0.1 to 0.5 g of a measurement sample is added. Then, the suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape of the toner is measured with the above-mentioned apparatus with a dispersion concentration of 3000 to 10000 / μl. Find the degree.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the above-described embodiments can be modified as appropriate in addition to those suggested in the above-described embodiments. Is clear. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiments, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating a fixing device in the image forming apparatus of FIG. 1. FIG. 3 is a perspective view showing the vicinity of a coil portion in the fixing device of FIG. 2. FIG. 3 is a cross-sectional view showing a fixing belt in the fixing device of FIG. 2. It is a block diagram which shows the principal part of the image forming apparatus in Embodiment 2 of this invention. It is sectional drawing which shows the fixing device in Embodiment 3 of this invention. It is the schematic which shows the experimental apparatus for an effect confirmation. It is a graph which shows the experimental result by the experimental apparatus of FIG. It is a graph which shows the experimental result following FIG. It is a graph which shows the fixing temperature fluctuation | variation of the fixing device in Embodiment 4 of this invention. It is sectional drawing which shows the fixing device in Embodiment 5 of this invention. It is a graph which shows the relationship between the distance from a heat generating layer to a belt surface, and belt surface temperature. It is sectional drawing which shows the fixing device in Embodiment 6 of this invention.

Explanation of symbols

1 image forming apparatus main body (apparatus main body), 3 exposure unit,
4 Process cartridge (image forming part), 7 Transfer part,
8 Transfer belt, 9 Bias roller,
18, 18BK, 18Y, 18M, 18C Photosensitive drum,
20 fixing device, 21 fixing auxiliary roller,
22 fixing belt (heating member, fixing member), 22a base material,
22b heating layer, 22c elastic layer, 22d release layer,
23 support roller (heating member), 24, 24A, 24B induction heating unit,
25 coil section, 28 heat generating plate (heat generating member), 30 pressure roller,
31 fixing roller (heating member, fixing member), 33 heating layer (heating member),
34 conductive layer, 40 high frequency power supply.

Claims (23)

A fixing device for fixing a toner image on a recording medium,
A coil section for generating magnetic flux;
A heating member that generates heat by the magnetic flux,
The fixing device, wherein the coil portion is disposed so as to sandwich the front and back surfaces of the heat generating member. The coil portion is formed in a loop shape,
The fixing device according to claim 1, wherein the heat generating member is sandwiched in a loop of the coil portion. The fixing device according to claim 1, wherein an alternating current is applied to the coil portion. The fixing device according to claim 1, wherein the heat generating member includes a heat generating layer formed to have a Curie point of 300 ° C. or lower. The fixing device according to claim 4, wherein the heat generating layer is made of a magnetic shunt alloy. The fixing device according to claim 1, wherein the heat generating member is a fixing member that melts a toner image. The fixing member is a fixing belt stretched around a circumference,
The fixing device according to claim 6, wherein the coil portion is disposed to face an outer peripheral surface and an inner peripheral surface of the fixing belt. The fixing belt is stretched between a support roller and a fixing auxiliary roller,
The fixing device according to claim 7, wherein the fixing auxiliary roller is disposed so as to come into contact with a pressure roller that presses a conveyed recording medium via the fixing belt. The fixing device according to claim 8, wherein the coil portion is disposed so as to face an inner peripheral surface of the fixing belt via the support roller. The fixing member is a fixing roller that contacts a pressure roller that presses a recording medium to be conveyed,
The fixing device according to claim 6, wherein the coil portion is disposed to face an outer peripheral surface and an inner peripheral surface of the fixing roller. The fixing device according to claim 1, wherein the heat generating member is a heating member that heats a fixing member that melts a toner image. The fixing member is a fixing belt,
The heating member is a support roller that stretches the fixing belt together with a fixing auxiliary roller,
The coil portion is disposed to face the outer peripheral surface of the fixing belt and to face the inner peripheral surface of the fixing belt via the support roller,
The fixing device according to claim 11, wherein the fixing auxiliary roller is disposed so as to contact a pressure roller that presses a recording medium to be conveyed via the fixing belt. The heat generating member is driven so that a position between the coil portions is displaced,
The fixing device according to claim 1, wherein when the generation of magnetic flux from the coil portion is started, the driving of the heat generating member is stopped for a predetermined time. The fixing device according to claim 13, wherein the driving of the heat generating member is stopped until the heat generating member reaches a predetermined temperature. The fixing device according to claim 1, comprising a plurality of the heat generating members. The plurality of heat generating members include a first heat generating member and a second heat generating member having a heat generating layer formed to have a Curie point larger than the Curie point in the heat generating layer of the first heat generating member. The fixing device according to claim 15, wherein the fixing device is provided. The fixing device according to claim 16, wherein the heat generating layer of the second heat generating member is formed so that a Curie point is higher than a fixing target temperature. 18. The fixing device according to claim 16, wherein the heat generating layer of the first heat generating member is formed so that a Curie point is close to a fixing target temperature. The first coil portion disposed so as to sandwich only the front and back surfaces of the first heating member;
The second coil portion disposed so as to sandwich only the front and back surfaces of the second heating member,
The fixing device according to claim 16, wherein the second coil unit is controlled so as to generate a magnetic flux only when the device is started up. The fixing device according to claim 19, wherein the first coil unit is controlled to generate a magnetic flux only after the apparatus is started up. The toner for forming the toner image contains at least a binder resin, a colorant, and a release agent,
The mold release agent is formed such that its components are dispersed in an island shape in the binder resin, and an average dispersed particle diameter is in a range of 0.1 to 1.0 μm. The fixing device according to claim 1. The toner for forming the toner image is formed such that its weight average particle diameter (D4) is in the range of 2.5 to 5.0 μm, and its average circularity is in the range of 0.95 to 0.99. The fixing device according to claim 1, wherein the fixing device is formed as follows. An image forming apparatus comprising the fixing device according to any one of claims 1 to 22.

Images