JP2006292850A - Image forming apparatus and image forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method in which the decrease in productivity can be prevented, while maintaining fixing properties and glossiness. <P>SOLUTION: In the image forming method, using the image forming apparatus having, a development means for develop electrostatic latent image on an image carrier 25 with toner; a transfer means for transfer the developed toner image onto a recording medium; a belt-fixing means 1 having a fixing belt 2, a fixing roller 4 and a heating roller 3 supporting the fixing belt 2, and a pressurizing roller 5 that is abutted against the fixing roller 4 via the fixing belt 2; and a temperature detection means 8, 8a for detecting the ambient temperature of a paper feed portion unit of the belt fixing means 1, the paper feed interval to the belt-fixing means 1 in an image forming mode is adjusted or varied, based on the temperature detected by the temperature detection means, disposed near the paper feeding portion of the belt fixing means 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an image forming apparatus employing an electrophotographic process such as a copying machine, a printer, and a facsimile, and an image forming method using the same.

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, facsimile machines, printers, and printing machines are provided with a fixing device that fixes an unfixed image transferred and carried on a recording medium such as paper and prints it out as a copy. Yes. As a fixing device, a configuration in which a pair of rollers are arranged to face each other, one roller is used as a heating roller, and the other roller is used as a pressure roller is known. In the fixing device having such a configuration, the recording medium is sandwiched between nip portions formed between the heating roller and the pressure roller, and the unfixed image is fused to the recording medium by the heat from the heating roller while being conveyed. To be fixed.

On the other hand, apart from the configuration described above, a fixing device having a configuration in which a roller and a belt are combined is known. In this fixing device, instead of a heating roller, a belt wound around a pair of rollers is used. A pressure roller is opposed to one of the rollers around which the belt is wound. The roller that drives the belt in cooperation with the roller on the side facing the pressure roller is provided with a heat source for heating the belt from the back side, and the pressure roller is also usually used to heat the surface of the belt. A heat source is provided. Since the belt has a smaller volume and a smaller heat capacity than the roller, the belt can be increased in temperature for a short time, and has an advantage that the temperature rise is quicker than the configuration using only the heating roller and the pressure roller described above. In addition, by providing a heat source also on the pressure roller, the belt is heated from both the front and back surfaces, thereby speeding up the temperature rise.
As for the configuration of the belt, when aluminum having high thermal conductivity is used as a roller, stainless steel is used as a base in contact with the roller surface, and a belt body having a release layer made of silicon rubber or fluorine-based resin is disposed on the surface. The thing of a 2 layer structure is mentioned.

As a conventional technique related to such a fixing device or an image forming apparatus, Japanese Patent Application Laid-Open No. 2004-133867 discloses a fixing method for the purpose of improving fixing performance while preventing solidification of toner or squealing of a cleaning blade accompanying an increase in apparatus temperature. Image forming in which temperature detecting means is provided on the inlet side and / or outlet side of the apparatus, and the temperature temperature of the nip inlet side is detected by the temperature detecting means, and the sheet passing interval of the recording medium is varied based on the obtained atmosphere temperature. A method is disclosed.
Japanese Patent Application Laid-Open No. 2004-228561 discloses a technique for widening the sheet passing interval at the start of printing and shortening the sheet passing interval for subsequent printing in order to prevent insufficient gloss immediately after start-up.
Further, Patent Document 3 discloses an image forming apparatus in which the fixing temperature of the fixing device is controlled by a pulse width modulation method in order to suppress an excessive increase in the fixing temperature during continuous printing and to stabilize the control. There is disclosed an image forming apparatus that includes a temperature detecting unit that detects a fixing temperature of the fixing device, and controls the pulse width modulation by changing the duty based on the fixing temperature detected by the temperature detecting unit.

Japanese Patent Application Laid-Open No. 09-237013 Japanese Patent Laid-Open No. 2003-066783 JP 2001-051545 A

However, the conventional technique for increasing the sheet passing interval at the start of printing has a problem that if the control is performed to always increase the sheet passing interval at the start of printing, the productivity is unduly lowered. Further, in each of the above conventional techniques, the fixing member is deprived of heat by the transfer paper, and when the next transfer paper passes through the nip portion, a fixing temperature is lowered, so-called a drop phenomenon occurs, causing a fixing failure. It becomes. Such a dip phenomenon occurs frequently when the temperature of the transfer paper is low, and development of a technique for improving this problem has been desired.

The present invention has been made in view of the above-mentioned problems, and its problem is to avoid fixing problems and gloss defects caused by temperature drop in the periphery of the fixing device to ensure fixing characteristics and glossiness, and to produce It is an object of the present invention to provide an image forming apparatus and an image forming method using the same.

In order to solve the above problems, an image forming apparatus according to the present invention includes a developing unit that develops an electrostatic latent image on an image carrier using toner, a transfer unit that transfers the developed toner image to a recording medium, An image forming apparatus comprising: a belt fixing unit that fixes a toner image transferred to the recording medium. The belt fixing unit includes a fixing belt, a fixing roller and a heating roller that support the fixing belt, and the fixing. A pressure roller contacting the roller via the fixing belt, and temperature detecting means for detecting the temperature around the sheet feeding portion of the belt fixing means.
In this case, the fixing belt may have a base and a release layer formed on the base. Moreover, it is preferable that the said base | substrate consists of nickel, stainless steel, or a polyimide, and the thickness is 30-150 micrometers, for example. Furthermore, the release layer is preferably made of silicon rubber, fluorine resin, or a laminate thereof, and the thickness thereof is, for example, 10 to 300 μm.

The cores of the heating roller and the pressure roller may be made of aluminum, iron, copper, or stainless steel, respectively. In this case, the core diameter of the heating roller is preferably 20 to 30 mm, and the thickness of the core metal is preferably 0.3 to 2.0 mm. The pressure roller preferably has a core metal diameter of 30 to 50 mm and a core metal thickness of 0.3 to 1.5 mm.
The toner contains at least a binder resin, a colorant, and a release agent, and has a weight average particle diameter of 2.5 to 5.0 μm and an average circularity of 0. 95-0. 99 is preferred.

The image forming method according to the present invention is the image forming method using the image forming apparatus according to any one of claims 1 to 8, wherein the temperature detecting unit detects a temperature around the sheet feeding unit of the belt fixing unit. The sheet passing interval to the belt fixing unit in the same image forming mode is changed based on the detected temperature.
In this case, when the detected temperature of the temperature detecting means is 15 ° C. or more lower than the predetermined temperature, the sheet passing interval is set larger than the predetermined interval, and when the detected temperature is 25 ° C. higher than the predetermined temperature, It is preferable to make the paper interval smaller than the predetermined interval. Further, the toner contains at least a binder resin, a colorant, and a release agent, has a weight average particle diameter of 2.5 to 5.0 μm, an average circularity of 0. 95-0. It is preferred to use 99 polymerized toner.

According to the present invention, it is possible to efficiently form an image and prevent a reduction in productivity while maintaining the fixing property and glossiness of the image. Further, by using a specific toner, it is possible to improve the releasability of the transfer paper at the time of fixing, to prevent the transfer paper from being wound, and to keep the releasability well.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a device configuration of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the image forming apparatus 20 is opposed to the image forming apparatuses 21Y, 21M, 21C, and 21BK that form an image for each color according to an image signal, and the image forming apparatuses 21Y, 21M, 21C, and 21BK. A sheet feeding cassette 23 serving as a sheet-like medium supply device for supplying various sheet-like media to the transfer device 22 disposed, and a transfer region where each image forming device 21Y, 21M, 21C, 21BK and the transferring device 22 face each other. 24, and a registration roller 30 for supplying the sheet-like medium carried out from the sheet feeding cassettes 23 and 24 in accordance with the timing of image formation by the image forming apparatuses 21Y, 21M, 21C, and 21BK, and a sheet shape after transfer in the transfer region The fixing device 1 mainly performs fixing of the medium.

  Each of the image forming devices 21Y, 21M, 21C, and 21BK performs development of each color of yellow, magenta, cyan, and black, and the configuration of the toner is different, but the configuration is almost the same. For example, in the image forming device 21Y, a charging device, a developing device, a cleaning device, etc. (not shown) are arranged around the photosensitive drum 25Y as an electrostatic latent image carrier along the rotation direction A. . Between the charging device and the developing device, exposure light 29Y is irradiated by a scanning unit having a known polygon mirror, and an electrostatic latent image is formed. The electrostatic latent image carrier is not limited to a drum shape but may be a belt shape. Note that the exposure light 29BK in the image forming device 21BK can be two beams, and the image forming device 21BK can perform faster image forming than the other image forming devices 21Y, 21M, and 21C. .

  An A4 size sheet-like medium, for example, is placed on the paper feed cassette 23, and an A3 size sheet-like medium, for example, is placed on the paper feed cassette 24 so that the horizontal direction in the drawing is the longitudinal direction. The transfer device 22 is disposed along an oblique direction so that the image forming apparatus 20 is small in the left-right direction in the drawing, and the sheet-like medium conveyance direction indicated by an arrow B is obliquely upward. Thus, in the image forming apparatus 20, the width of the apparatus main body 26 in the left-right direction in the drawing is slightly longer than the length in the longitudinal direction of the A3 size sheet-like medium. In other words, the image forming apparatus 20 has a minimum size necessary for accommodating the sheet-like medium therein, and is thereby greatly reduced in size.

The image forming apparatus 20 has a heat capacity higher than that of plain paper and OHP sheets, cards, postcards and other 90K paper used for general copying, thick paper having a basis weight of about 100 g / m ² or more, and envelopes and other paper. Any so-called special sheet (hereinafter referred to as a special sheet) having a large A can be used as a sheet-like medium.
An upper portion of the apparatus main body 26 of the image forming apparatus 20 is a paper discharge tray 27 for stacking a sheet-like medium passing through the fixing device 1 and having a toner image fixed thereon.

  The image forming apparatus 20 also includes pickup rollers 41 and 42 that send out the sheet-like medium from the sheet feeding cassettes 23 and 24, a conveyance roller 43 that inherits and feeds the sheet-like medium from the pickup roller, and the sheet feeding cassette 23. , 24 and a roller 44 that conveys the sheet-like medium conveyed to the registration roller 30 and a discharge roller 45 that discharges the sheet-like medium from the opening 46 to the outside of the apparatus main body 26 toward the paper discharge tray 27. Etc. are provided.

  FIG. 2 is a cross-sectional view showing the fixing device of FIG. The fixing device 1 includes an endless fixing belt 2 as a sheet conveying member for conveying a sheet-like medium on which a toner image is fixed, a heating roller 3 and a fixing roller as a roller pair around which the fixing belt 2 is wound. 4, a pressure roller 5 disposed in contact with and opposed to the fixing roller 4 via the fixing belt 2, heaters 6 and 7 provided inside the heating roller 3 and the pressure roller 5, and heating The thermistor 8 is disposed so as to abut against the roller 3, and detects the surface temperature of the heating roller 3. The thermistor 8 is disposed so as to abut on the pressure roller 5. A thermistor 8a as temperature detecting means for detecting the temperature, a cleaning roller 31 disposed opposite to the fixing roller 4 via the fixing belt 2, and an application roller as a release agent application member 2, a release agent supply means (not shown) for supplying a release agent to the application roller 32, a casing 33, an inlet guide, an outlet guide and a handle fixed to the casing 33, the heating roller 3, and a fixing roller 4. A support body that integrally supports the fixing belt 2 and a support body that supports the casing 33 and the pressure roller 5 are mainly configured.

  In order to give an appropriate tension to the fixing belt 2, the heating roller 3 and the fixing roller 4 are urged away from each other by an elastic body (not shown) such as a spring. The fixing roller 4 includes a cored bar 9 and a heat-resistant elastic body layer 10 that covers the cored bar 9 and forms the surface of the fixing roller. The cored bar 9 is rotationally driven by a driving unit (not shown) by the shaft 11. As a result, the fixing roller 4 is rotationally driven in the direction of arrow C, and the fixing belt 2 is driven in the direction of arrow E by the driven rotation of the heating roller 3 in the direction of arrow D. The roller 5 is rotationally driven in the direction of arrow F, and the application roller 32 is rotationally driven in the direction of arrow G.

  The pressure roller 5 and the fixing roller 4 are urged by an elastic body such as a spring (not shown) in a direction in which they are pressed against each other with a pressure contact force of 10 kgf or more. As clearly shown in FIG. 1, the pressure roller 5 has the axis of the fixing roller 4 as the apex, the axis of the fixing roller 4 and the axis of the heating roller 3, and the axis of the fixing roller 4 and the pressure roller. 5 is in contact with the fixing roller 4 so that the angle between the two straight lines connecting the axes of the 5 forms an acute angle, whereby a pressure roller as a fixing region for fixing the toner on the sheet-like medium A first fixing unit 15 that abuts only on the fixing belt 2 at a portion where 5 does not face the fixing roller 4, and a second fixing unit 16 that the pressure roller 5 abuts on the fixing roller 4 via the fixing belt 2. It is formed.

  In FIG. 1, the fixing device 1 is provided at a position facing the transfer device 22, an opening 34 for receiving a sheet-like medium conveyed by the transfer device 22, the first fixing unit 15, and the second fixing device 15. And an opening 35 for discharging a fixed sheet-like medium provided on the opposite side of the opening 34 with the fixing unit 16 therebetween. The inlet guide 12 has a base portion fixed to the outer surface of the casing below the opening 34, and a distal end entering the inside through the opening 34 and extending toward the first fixing portion 15.

  The fixing belt 2 of the fixing device 1 is formed by forming a release layer made of silicon rubber having a thickness of 200 μm on a substrate having a thickness of 100 μm made of nickel, for example, so that the heat capacity is small and the thermal response is good. Is formed. The length of the fixing belt 2 is such that the diameter is, for example, 60 mm when the belt 2 is circular. The base of the fixing belt 2 may be made of SUS or polyimide, and the thickness thereof may be about 30 to 150 μm in consideration of flexibility.

The silicon rubber as the release layer of the fixing belt 2 desirably has a thickness of about 50 to 300 μm. When using a fluororesin as the release layer, the thickness is preferably about 10 to 50 μm. Further, the release layer may have a structure in which a fluorine-based resin system is stacked on silicon rubber. The fixing belt 2 is desired to have a characteristic that the belt surface is self-cooled in the fixing region to such an extent that it is instantaneously heated and does not cause hot offset. On the other hand, the toner is sufficiently melted and fixed in the fixing region. Must have the necessary heat capacity. The material and thickness of the fixing belt 2 satisfy this condition. The self-cooling is a phenomenon in which the belt cools in the fixing process because there is no heating source on the unfixed image side of the sheet-like medium in the fixing region.

The fixing belt 2 is applied with a tension of 3 kgf / one side by being biased in a direction in which the heating roller 3 and the fixing roller 4 are separated from each other. This tension can be set by adjusting the urging force of an elastic body (not shown), and is preferably set within the range of 1 Kgf (9.8 N) to 3 Kgf (29.4 N) for good fixing.
Each of the heating roller 3 and the pressure roller 5 has a thin cylindrical cored bar, and a reduction in heat capacity is achieved. The core diameter of the heating roller 3 is 20 mm to 30 mm, the thickness of the concentric bar is 0.3 mm to 2.0 mm, the diameter of the core of the pressure roller 5 is 30 mm to 50 mm, and the thickness of the concentric bar is Is 0.3 to 1.5 mm. As a result, the heat capacity of the heating roller 3 is 26 cal / ° C. or less, and the heat capacity of the pressure roller 5 is 36 cal / ° C. or less.

  The cored bar of the heating roller 3 is made of, for example, aluminum and has a diameter of 30 mm and a wall thickness of 0.7 mm. A material having a small specific heat and a high thermal conductivity is preferable, and other metals such as iron, copper, and stainless steel can be used. When the core is made of aluminum and the roller diameter is 30 mm, the wall thickness is in the range of 0.6 to 1.4 mm. When the core is made of iron and the roller diameter is 20 mm, the wall thickness is in the range of 0.3 to 0.9 mm. It is preferable to set. The reason why the wall thickness is reduced as the diameter is increased is that the bending of the roller in the axial direction is taken into consideration.

  These lower limit values of the wall thickness are allowable values in consideration of the deformation of the heating roller 3 due to the tension of the fixing belt 2 described above, and the upper limit value indicates an allowable value for obtaining a desired rise time. The reason why the roller diameter is set to 20 mm or more is to secure the belt tension so that the roller does not bend in the axial direction. Further, the roller diameter is set to 20 to 30 mm because 26 cal for maintaining the temperature of the fixing belt 2 at a constant temperature necessary for fixing even during continuous sheet passing when the sheet-like medium conveyance speed is 200 mm / sec or less. This is to obtain a heat capacity of about / ° C.

  The heater 6 heats the fixing belt 2 via the heating roller 3 and the heating roller 3. The temperature of the heater 6 is input to a control means (not shown) as a detection signal by the thermistor 8 and is compared with a target fixing temperature. When the detected temperature is lower than a predetermined fixing temperature, for example, 110 ° C., the heater 6 is energized. When the detected temperature is higher than the predetermined fixing temperature, for example, 110 ° C., the energization of the heater 6 is stopped. . As described above, the detection temperature of the thermistor 8 is fed back to control the fixing temperature, and the surface temperature of the fixing belt 2 is maintained at 110 ° C. or higher, for example. The thermistor 8 is in contact with the heating roller 3 so as to form an obtuse angle with respect to the rotation direction of the heating roller 3 so as to reduce mutual wear due to the rotation of the heating roller 3.

  The elastic body layer 10 of the fixing roller 4 is a rubber layer. Specifically, the material is silicone sponge rubber. That is, the elastic body layer 10 is a foam, and the bubble diameter is, for example, 500 μm. Particularly, the bubble diameter in the vicinity of the surface, that is, in the vicinity of the peripheral surface of the fixing roller 4 is 300 μm or less. When the elastic layer 10 is a foam, the temperature drop during fixing is suppressed, but because it is a foam, the fixing pressure cannot be obtained, and gloss is not easily generated, and the surface is rough and gloss unevenness occurs. Although problems can occur, problems such as poor gloss and uneven gloss can be avoided by setting the bubble diameter as described above. A non-foamed layer (skin layer) having a thickness of about 1 mm may be provided on the surface of the elastic layer 10.

  The surface hardness of the elastic layer 10 is 20 HS or more in Asuka C. This is because the surface roughness due to the foam of the elastic layer does not affect the image quality regardless of the presence or absence of the skin layer. This is because unevenness can be prevented and good fixing quality can be obtained. The diameter of the fixing roller 4 is, for example, 30 mm, and the material of the elastic body layer 10 is a heat-resistant porous elastic body having a small thermal conductivity and a heat insulation function. The temperature drop is reduced and the pre-rotation time for temperature recovery is shortened. Further, since the elastic layer 10 has a relatively low hardness, a sufficient nip width can be obtained even if the pressure contact force with the pressure roller 5 is small, and good fixing performance is obtained even under relatively low temperature and low pressure conditions. Can be obtained.

  The core metal of the pressure roller 5 is made of, for example, iron, and has a diameter of 40 mm and a wall thickness of 1.0 mm. A material having a small specific heat and a high thermal conductivity is preferable, and other metals such as aluminum, copper, and stainless steel can be used. When the core is made of iron and the roller diameter is 30 mm, the wall thickness ranges from 0.4 to 1.0 mm. When the roller diameter is 50 mm and the roller diameter is 50 mm, the wall thickness ranges from 0.3 to 0.8 mm. When the roller diameter is 30 mm, the wall thickness is preferably set in the range of 1.3 to 1.5 mm. When the roller diameter is 50 mm, the wall thickness is preferably set in the range of 0.6 to 1.2 mm. The larger the diameter is, the thinner the thickness is in consideration of the axial bending of the roller.

These lower limit values of the wall thickness are allowable values in consideration of deformation of the pressure roller 5 due to the surface pressure of 0.6 Kg / cm ² corresponding to the lower limit value of the fixing pressure, and the upper limit value is a desired rise time. The permissible value for obtaining The reason why the roller diameter is set to 30 mm or more is to secure the fixing pressure so that the roller does not bend in the axial direction. Also, the roller diameter is set to 30 to 50 mm in order to keep the temperature of the fixing belt 2 at a constant temperature necessary for fixing even during continuous sheet feeding when the sheet-like medium conveyance speed is 200 mm / sec or less. This is to obtain a heat capacity of about ° C.

  The heater 7 raises the temperature of the pressure roller 5 to shorten the start-up time, and supplies heat from the back surface of the sheet-like medium at the time of fixing to obtain a stable fixing performance.

The pressure roller 5 can have a release layer of 10 to 300 μm on the cored bar. The surface temperature of the pressure roller 5 is detected by the thermistor 8a, and a detection signal from the thermistor 8a is input to the control means (not shown), compared with the target fixing temperature, and when the detected temperature is lower than the fixing temperature, the heater 7 When energization is performed and the detected temperature is higher than the fixing temperature, the energization of the heater 7 is stopped. Thus, the fixing temperature is controlled by feeding back the detection signal of the thermistor 8a, and the surface temperature of the pressure roller 5 is maintained at 110 ° C. or higher, for example. The thermistor 8 a is in contact with the pressure roller 5 so as to form an obtuse angle with respect to the rotation direction of the pressure roller 5 so as to reduce mutual wear due to the rotation of the pressure roller 5.

  The reason why the heat roller 3 and the pressure roller 5 can be made thin to reduce the heat capacity is because the fixing device 1 is a so-called belt fixing device using the fixing belt 2. That is, in the present embodiment, the fixing is performed by a relatively long portion such as the fixing portions 15 and 16, so that the fixing pressure can be reduced, the strength of the pressure roller 5 can be reduced, and the heating roller Since 3 is not pressed against the pressure roller, it can be thinned. Fixing at a relatively long site in distance enables fixing at a relatively low temperature and contributes to shortening the rise time. Further, when the fixing belt 2 is used, there is an advantage that the fixing belt 2 heated by the heater is cooled to a temperature suitable for fixing in the process of being conveyed and is not easily offset. The output of the heaters 6 and 7 is set to 700 W or less in consideration of the inrush current when the power switch is turned on and the flickering phenomenon of the fluorescent lamp when the heater is turned on and off.

  The cleaning roller 31 is disposed at a position via the trace oil application roller 32, and the application roller 32 is positioned downstream of the fixing roller 4 in the moving direction of the fixing belt 2. Further, the cleaning roller 31 moves in the direction of arrow H and the application roller 32 moves in the direction of arrow G in the same moving direction as the fixing belt 2 in the same moving direction as the fixing belt 2 at a portion facing the fixing belt 2 by a driving means (not shown). To be driven. The cleaning roller 31 is in contact with the application roller 32, thereby wiping off the toner transferred from the sheet-like medium to the fixing belt 2 and further to the application roller 32, and refreshing the surface of the transfer belt 2. The application roller 32 applies an appropriate predetermined amount to the fixing belt 2 with a release agent mainly composed of silicone oil.

  The application roller 32 is composed of a metal shaft that is a core metal and a foam of silicon rubber. By re-supplying the release agent to the fixing belt 2, the optimum release property of the sheet-like medium is maintained. Yes. The gloss unevenness and the transmittance non-uniformity with respect to the OHP sheet differ depending on the foaming diameter of the silicon rubber of the coating roller 32. However, when the foaming diameter is 50 μm or less, the hardness of the coating roller 32 is increased, and the coating roller constituted by a foamed body. Therefore, the application roller 32 of this embodiment uses a foaming diameter of about 75 to 150 μm.

The features of the present embodiment will be described with reference to FIGS. FIG. 3 is a diagram showing image signals at normal temperature and low temperature, and FIG. 4 is a table showing a relationship between a temperature difference from a predetermined temperature and a paper passing interval when the paper passing interval is changed according to temperature. FIG. 5 is a graph showing a change in fixability by the smear fixing method, and FIG. 6 is a graph showing a relationship between the number of sheets to be passed and the belt surface temperature. Depending on the temperature detected by the temperature detecting means, the sheet passing interval is changed as shown in FIG. In the present embodiment, when the detected temperature is low, the sheet passing interval is set to be long, and when the detected temperature is high, the sheet passing interval is set to be short. That is, when the temperature detected by the thermistor is lower than a predetermined temperature, for example, 110 ° C. by 15 ° C. or more, the sheet passing interval is made larger than a predetermined interval, for example, standard 67 mm, which will be described later, and the detected temperature is When the temperature is higher by 25 ° C. or more, the sheet passing interval is made smaller than a predetermined interval, for example, a standard 67 mm described later. When the detection temperature is lower than a predetermined temperature, for example, 110 ° C. below 15 ° C. or higher than 25 ° C., the sheet passing interval is set to, for example, a standard 67 mm described later.

In A4 landscape paper with a fixing process speed of 162 mm, the paper interval is 67 mm with respect to 210 mm of paper. However, when the temperature detected by the thermistor is 15 ° C. or more lower than the predetermined temperature 110 ° C., the distance increases to 114 mm. FIG. 6 shows the output result when setting is performed in this way. FIG. 6 shows the case where the control temperature is 160 ° C. As shown in FIG. 6, by increasing the paper interval more than usual, even if the number of transfer papers increases, the belt temperature, which decreases due to heat being taken away by the transfer paper, returns to within the enlarged paper passing interval. It becomes easy to see that the temperature drop is reduced.

In the smear fixing method shown in FIG. 5, a solid image having an image density of 0.75 ± 0.1 is wiped off with a cloth (white cotton cloth = JISL 0803 cotton No. 3) with a predetermined force, and the image density on the wiped cloth is obtained. Is measured. In FIG. 5, it can be seen that the image fixability in this embodiment is superior to the image fixability in the prior art. Therefore, the fixability target is ensured. That is, by adjusting the sheet passing interval in the same image forming mode according to the detected temperature detected by the thermistor that is a temperature detecting means, it is possible to prevent the productivity from being reduced while maintaining the fixing property and the glossiness. be able to. The transfer paper used was Ricoh type 6200.

Detecting the ambient temperature of the fixing device main body and the paper feed unit can obtain information closer to the temperature state of the transfer paper that takes heat away than detecting the temperature of the fixing atmosphere. When the fixing atmosphere temperature is continuously passed, the temperature rises due to heat storage of the fixing unit, and the temperature is not detected low even at low temperatures. However, in reality, the transfer paper waiting in the low temperature paper feed cassette is cold and takes heat of fixing. Therefore, it may be more accurate to change the paper passing interval based on the judgment of the ambient temperature. Therefore, the temperature of the paper feeding unit close to the recording paper standby state may be detected, and the paper passing interval may be adjusted based on the detected temperature.
In this embodiment, examples of the image forming apparatus include a copying machine, a printer, and a facsimile machine that can form a full-color image. The image forming apparatus targets not only an apparatus that targets a color-formed image but also a single-color image. It may be a device.

Next, in recent years, with the demand for higher image quality, image forming apparatuses using a toner manufactured by a polymerization method (hereinafter referred to as a polymerization toner) instead of a toner manufactured by a pulverization method have become widespread. Even when a toner manufactured by a polymerization method is used, the toner may not always be satisfactory in terms of fixability. Hereinafter, problems of the toner produced by the pulverization method will be described.

As dry toners used for electrophotography, electrostatic recording, electrostatic printing and the like, toner binders such as styrene resins and polyesters are melt-kneaded together with colorants and finely pulverized. In order to obtain high-quality, high-quality images, improvements have been made by reducing the particle size of the toner. Even after passing, the ultrafine particles have a drawback that they have strong adhesion and remain attached to the toner having the target particle size and are difficult to classify.

Also, in the machine, when the carrier is agitated with the carrier in the developing unit, or when used as a one-component developer, such a pole is caused by contact stress caused by the developing roller and the toner supply roller, the layer thickness regulating blade, the friction charging blade, or the like. There is a phenomenon in which fine particles adhere to and adhere to carriers and machine parts, and a fluidizing agent is embedded in the toner surface, resulting in a decrease in image quality. Further, due to its shape, the fluidity as a powder is poor, a large amount of fluidization is required, or the filling rate into the toner bottle is low, which is an obstacle to downsizing. Therefore, the current situation is that the merit of reducing the particle size is not utilized. Further, the pulverization method has a particle size limit, making it difficult to cope with further reduction in particle size, and even if possible, productivity and yield are insufficient. Furthermore, in order to create a full-color image, the process of transferring an image formed from multicolor toner from a photoconductor to a transfer medium or paper has become complicated, and due to the poor transferability due to the irregular shape, There have been problems such as missing transferred images and a large amount of toner consumption to compensate for them. It should be noted that there is no sufficient causal relationship between the toner fixability and the toner particle size and shape.

One of the causes of the above-mentioned defects in the toner produced by the pulverization method is that it is difficult to disperse the pigment and the wax. On the other hand, when polymerized toner is used, the fixability can be compensated by adjusting the sheet passing interval.
In this embodiment, polymerized toner is used. The polymerized toner preferably contains at least a binder resin, a colorant, and a release agent, and the weight average particle diameter is preferably in the range of 2.5 to 5.0 μm.

By using such a polymerized toner, the toner layer on the transfer paper is made uniform, the releasability at the time of fixing is improved, the transfer paper becomes more separable, and the winding of the transfer paper can be improved.

When the weight average particle diameter of the toner is smaller than 2.5 μm, in the case of a two-component developer, the toner is fused to the surface of the carrier during a long period of stirring in the developing device, and the charging ability of the carrier is reduced. In this case, the toner filming on the developing roller and the toner fusion to a member such as a blade for thinning the toner are likely to occur. On the contrary, when the toner particle diameter is larger than 5.0 μm, the toner layer on the transfer paper becomes non-uniform, the toner releasability is deteriorated, and the transfer paper may be insufficiently separated. .

Further, as a result of examining the toner shape and the releasability at the time of fixing, in addition to the factor of the toner particle size, the average circularity of the toner is 0. 95-0. 99, preferably 0. When it is smaller than 95, the toner layer on the transfer paper becomes non-uniform, the toner releasability is deteriorated, and the transfer paper may be insufficiently separated. On the other hand, the average circularity is 0. If it is greater than 99, the toner is likely to scatter during transfer, which may cause problems on the image.

Examples of the binder resin used in the toner applied to the exemplary embodiment include those having the following compositions.
For example, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer as a homopolymer of styrene such as polyester, polystyrene, poly p-chlorostyrene, and polyvinyltoluene Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic acid Methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer , Styrene-vinylethyl Ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Examples thereof include styrene copolymers such as copolymers.

  It is presumed that the fixing to the paper in the roller fixing or the belt fixing starts at around 70 ° C. to 100 ° C. in the copying machine, printer, FAX, etc., in which the toner fixing effective temperature is recent energy saving. In order to allow the toner to melt, the toner must start flowing near this temperature, so that the toner should soften and start fixing at least at around 90 to 110 ° C. However, in order to soften at 90 ° C., the glass transition must be 50 ° C. or lower, and the Tg (glass transition point) of such a polymer is also related to the molecular weight. Usually, when the glass transition point is 50 ° C. or lower, the fixability is good, but the storage stability is not satisfied.

In addition, examples of the release agent that can be used for the toner of the exemplary embodiment include the following materials. That is, known waxes can be used, and examples thereof include polyolefin waxes (polyethylene wax, polypropylene wax, etc.), long chain hydrocarbons (paraffin wax, sazol wax, etc.), carbonyl group-containing waxes, and the like. Among these, a carbonyl group-containing wax is more preferable. 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), polyalkanol esters (tristearyl trimellitic acid, distearyl maleate, etc.), polyalkanoic acid amides (ethylenediamine dibehenyl amide, etc.), polyalkylamides (trimellitic acid tristearyl amide, etc.) , And dialkyl ketones (such as distearyl ketone). Of these carbonyl group-containing waxes, polyalkanoic acid esters are more preferred.

The melting point of the wax used in the present embodiment is usually 40 to 160 ° C., preferably 50 to 120 ° C., more preferably 60 to 90 ° C. A wax having a melting point of less than 40 ° C. has an adverse effect on heat resistant storage stability, and a wax having a melting point of more than 160 ° C. tends to cause a cold offset when fixing at a low temperature. Further, the melt viscosity of the wax is preferably 5 to 1000 cps, more preferably 10 to 100 cps as a measured value at a temperature 20 ° C. higher than the melting point. Waxes exceeding 1000 cps have poor effects for improving hot offset resistance and low-temperature fixability. The content of the wax in the toner is usually 0 to 40% by weight, preferably 3 to 30% by weight.

As the toner colorant in the present embodiment, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow. , Yellow iron oxide, ocher, 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 Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Fu Issey Red, Parachlor Ortho Nitroaniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmin Min BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Risor 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, Thioindigo Red B, Thioindigo Maroon, Oil Red, Ki Nacridone Red, Pyrazolone Red, Polyazo Red, 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 A rk, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc white, lithopone and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by weight, preferably 3 to 10% by weight, based on the toner.

The colorant used in this embodiment can also be used as a master batch combined with a resin.
As the binder resin to be kneaded together with the production of the master batch or the master batch, in addition to the above-mentioned modified or unmodified polyester resin, styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene, and its substitution products. Polymer, 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 Chill copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer Styrene copolymers such as styrene-maleic acid ester copolymer; 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, etc. Can be used together.

A masterbatch can be obtained by mixing and kneading a resin for a masterbatch and a colorant under a high shearing force. At this time, an organic solvent can be used in order to enhance the interaction between the colorant and the resin. In addition, a so-called flushing method, which is a wet cake of a colorant, is a method of mixing and kneading an aqueous paste containing water of a colorant together with a resin and an organic solvent, transferring the colorant to the resin side, and removing moisture and organic solvent components. Can be used as it is, so that it is not necessary to dry and is preferably used. For mixing and kneading, a high shear dispersion device such as a three-roll mill is preferably used.

The toner of the exemplary embodiment may contain a charge control substance as necessary. In particular, it is possible to impart a high charge amount by fixing the charge control substance to the surface of the toner. That is, by fixing to the surface of the toner, the amount and state of presence on the toner surface are stabilized, and the charge amount can be stabilized. In particular, the toner having the configuration of the present embodiment increases the stability of the charge amount.

As the charge control substance, all known substances can be used. For example, nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified) Quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives.
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 PSYVP2038 of ammonium salt, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEGVP2036, copy charge NXVP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Japan) Carlit), copper phthalocyanine, perylene, quinacridone, Examples thereof include azo pigments and other polymer compounds having a functional group such as a sulfonic acid group, a carboxyl group, and a quaternary ammonium salt.

In this embodiment, the amount of charge control agent used is determined uniquely by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is uniquely limited. Although it is not a thing, Preferably it is 0. It is used in the range of 1 to 10 parts by weight. Preferably, 0. A range of 2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the main charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the flowability of the developer is reduced, and the image density is reduced. Incurs a decline.

Further, a fluidity improver used for the purpose of improving the fluidity of the toner may be used. Specifically, silica, titanium oxide, alumina and the like are preferable, and silica subjected to hydrophobic treatment is particularly preferable. Such a fluidizing agent can be surface-treated to increase hydrophobicity and prevent deterioration of flow characteristics and charging characteristics even under high humidity. For example, silane coupling agents, silylating agents, silane coupling agents having a fluoroalkyl group, organic titanate coupling agents, aluminum coupling agents, silicone oils, modified silicone oils and the like are preferable surface treatment agents. .

Further, in order to remove the developer after transfer remaining on the photoreceptor or the primary transfer medium, a cleaning property improver may be included. Examples of the cleaning property improver include zinc stearate, calcium stearate, stearic acid. And fatty acid metal salts such as polymer fine particles produced by soap-free emulsion polymerization such as polymethyl methacrylate fine particles and polystyrene fine particles. The polymer fine particles preferably have a relatively narrow particle size distribution and an average particle size of 0.01 to 1 μm.

When the toner of the present embodiment is used for a two-component developer, it may be used by mixing with a magnetic carrier. Part by weight is preferred. As the magnetic carrier, conventionally known ones such as iron powder, ferrite powder, magnetite powder, magnetic resin carrier having a particle diameter of about 20 to 100 μm can be used.

The carrier may be coated with a resin or the like, and examples of the coating material include amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin. Polyvinyl and polyvinylidene resins such as acrylic resins, polymethyl methacrylate resins, polyacrylonitrile resins, polyvinyl acetate resins, polyvinyl alcohol resins, polyvinyl butyral resins, polystyrene resins and polystyrene resins such as styrene-acrylic copolymer 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, polytrifluoroethylene resins, poly Hexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, copolymer of vinylidene fluoride and vinyl fluoride, tetrafluoroethylene and vinyl fluoride Fluoro such as terpolymers of den and non-fluoride monomers including, silicone resins.

Moreover, you may make conductive powder etc. contain in coating resin as needed. 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 is larger than 1 μm, it becomes difficult to control electric resistance.
In addition, the toner of the present exemplary embodiment can be used as a one-component magnetic toner that does not use a carrier, or a non-magnetic toner.

In this embodiment, the weight average particle diameter (D4) of the toner was measured with a Coulter Counter Model TA-II manufactured by Coulter Electronics. That is, using the above measuring device, an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC) that output number distribution and weight distribution are connected, and 1% NaCl aqueous solution is prepared using first grade sodium chloride as the electrolyte. did.

As a measurement method, 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. Dispersion treatment was performed for 1 to 3 minutes, and 100 to 200 ml of an electrolytic aqueous solution was placed in another beaker, and the sample dispersion was added to a predetermined concentration therein to prepare a suspension.

Using this suspension, the particle size distribution of particles of 2 to 40 μm was measured on the basis of the number using a 50 μm aperture as an aperture by the Coulter counter TAII type, and the weight distribution of particles of 1.58 to 49.18 μm The number distribution was calculated, and the weight-based weight average particle diameter (D4: the median value of each channel is the representative value of the channel) determined from the weight distribution.

  Further, the average circularity of the toner was determined as follows. That is, a particle-containing suspension (use the same one prepared in the above-mentioned toner particle size measurement) is passed through the imaging unit detection zone on the flat plate, and the particle image is optically detected and analyzed by a CCD camera. The method of optical detection band to be used. This value can be 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, an alkylbenzene sulfonate as a surfactant was added as a dispersant in 100 to 150 ml of water from which impure solids had been previously removed in a container. 1-0. Add 5 ml and add 0. 1-0. Add about 5g. The suspension in which the sample was dispersed was subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape of the toner was measured with the above apparatus at a dispersion concentration of 3000 to 10,000 / μl.

Hereinafter, the operation of the image forming apparatus having the above-described configuration will be described with reference to FIGS.
Exposure light 29Y, 29M, 29C and 29BK based on image information is irradiated to the photosensitive drums 25Y, 25M, 25C and 25BK as image carriers whose surfaces are uniformly charged by a charging device (not shown). Thus, an electrostatic latent image is formed. The electrostatic latent image is developed with various toners supplied from developing devices (not shown). The toner images of yellow, magenta, cyan, and black developed on each photosensitive drum 25 are sequentially transferred onto a recording sheet as a recording medium supplied between the photosensitive drum 25 and the transfer belt 22 and are then transferred onto the recording sheet. Overlapped as a color toner image.
The recording paper on which the color toner image has been transferred is conveyed to the fixing device 1 and supplied to the nip portion between the fixing belt 2 and the pressure roller 5, where it is heated and the toner image is fixed on the recording paper. . The recording sheet on which the color image is fixed is discharged onto the discharge tray 27 via the discharge roller 45. At this time, the sheet passing interval of the recording paper supplied to the fixing device 1 is adjusted based on the detected temperature of the thermistors 8 and 8a.

According to the present embodiment, since the heating roller 3 is formed with a low heat capacity, even when the fixing belt 2 rotates, the heat is hardly lost, and fixing failure and rise time are not prolonged. Furthermore, even if the temperature is lowered due to continuous fixing or the like, the time until the recovery is shortened.
In addition, according to the present embodiment, the pressure roller 5 has a low heat capacity, so that even when the fixing belt 2 rotates, the heat is hardly taken, and the pressure roller 5 has the heater 7. Therefore, the temperature of the fixing belt 2 is not lowered to adversely affect the fixing, and the rise time is not prolonged. Furthermore, even if the temperature is lowered due to continuous fixing or the like, the time until the recovery can be shortened.

According to the present embodiment, since the sheet passing interval is adjusted based on the temperature around the sheet feeding unit to the fixing device, a decrease in productivity at the start of printing at a low temperature can be minimized. In addition, since the heating roller and pressure roller of the fixing device have a specific diameter or specific thickness depending on a specific material, the heat capacity can be kept small, and good image formation can be achieved while maintaining the fixing property and glossiness. It can be carried out.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram illustrating the fixing device of FIG. 1. It is the figure which showed the image signal at the time of normal temperature and low temperature. It is a figure which shows the relationship between temperature and a paper passing interval. It is a figure which shows the change of the fixing property by a smear fixing method. It is a figure which shows the relationship between the number of paper passing, and belt surface temperature.

Explanation of symbols

1: fixing device 2: fixing belt 3: heating roller 4: fixing roller 5: pressure roller 6, 7: heater 8, 8a: thermistor 9: core metal 10: elastic body layer 11: shaft 12: inlet guide 15: first First fixing unit 16: Second fixing unit 20: Image forming device 21: Image forming device 22: Transfer device (transfer belt)
23, 24: Paper feed cassette 25: Photosensitive drum 26: Apparatus main body 27: Paper discharge tray 29: Exposure light 30: Registration roller 31: Cleaning roller 32: Application roller 33: Casing 34, 35: Opening 41, 42: Pickup Roller 43: Conveyance roller 44: Roller structure 45: Discharge roller 46: Opening

Claims (11)

Developing means for developing an electrostatic latent image on an image carrier using toner, transfer means for transferring the developed toner image to a recording medium, and belt fixing means for fixing the toner image transferred to the recording medium In the image forming apparatus, the belt fixing unit includes a fixing belt, a fixing roller and a heating roller that support the fixing belt, and a pressure roller that contacts the fixing roller via the fixing belt. An image forming apparatus comprising: a temperature detection unit that detects a temperature around the sheet feeding unit of the belt fixing unit.   The image forming apparatus according to claim 1, wherein the fixing belt includes a base and a release layer formed on the base.   The image forming apparatus according to claim 2, wherein the base is made of nickel, stainless steel, or polyimide, and has a thickness of 30 to 150 μm.   The image forming apparatus according to claim 2, wherein the release layer is made of silicon rubber, fluorine-based resin, or a laminate thereof, and has a thickness of 10 to 300 μm.   5. The image forming apparatus according to claim 1, wherein the cores of the heating roller and the pressure roller are made of aluminum, iron, copper, or stainless steel, respectively.   6. The image forming apparatus according to claim 5, wherein the heating roller has a core metal diameter of 20 to 30 mm and a core metal thickness of 0.3 to 2.0 mm. 7. The image forming apparatus according to claim 5, wherein the pressure roller has a core metal diameter of 30 to 50 mm and a core metal thickness of 0.3 to 1.5 mm. The toner contains at least a binder resin, a colorant, and a release agent, has a weight average particle diameter of 2.5 to 5.0 μm, and an average circularity of 0. 95-0. The image forming apparatus according to claim 1, wherein the image forming apparatus is 99. The image forming method using the image forming apparatus according to claim 1, wherein a sheet passing interval of the belt fixing unit in the same image forming mode is changed based on a temperature detected by the temperature detecting unit. An image forming method. When the detected temperature of the temperature detecting means is 15 ° C. or more lower than the predetermined temperature, the sheet passing interval is set larger than the predetermined interval, and when the detected temperature is 25 ° C. higher than the predetermined temperature, the sheet passing interval is set to the predetermined interval. The image forming method according to claim 9, wherein the distance is smaller than the interval. The toner contains at least a binder resin, a colorant, and a release agent, has a weight average particle diameter of 2.5 to 5.0 μm, an average circularity of 0. 95-0. The image forming method according to claim 9 or 10, wherein 99 polymerized toner is used.

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