JPH096159A - Image forming device - Google Patents

Abstract

PURPOSE: To enable an inexpensive material whose heat resistant temperature is low to be used by lowering the thermostatic temperature of a fixing means. CONSTITUTION: The image forming device provided with a photoreceptor 1 provided with a photoconductive layer on the surface of a conductive body, a means 3 for successively forming plural electrostatic latent images on the photoreceptor 1, a means 4 for successively developing the electrostatic latent images on the photoreceptor 1 by using toner in plural colors, an intermediate transfer body 5 which is rotated in contact with the photoreceptor 1 so as to execute the multiple transfer of plural toner images, and a 2nd transfer means 6 for transferring the toner image on the intermediate transfer body 5 to a transfer material P, is provided with a heat source 6a for supplying a heat to the transfer material P and the toner T at a position where the toner image is transferred from the intermediate transfer body 5 to the transfer material P, besides, a fixing means 10 equipped with a heat source 10a, so that the stable fixation and the uniform glossiness (gloss value) on an image part can be maintained. Especially, even in the case where the transfer material P is left at a low temperature and even in the case where the material P is made longer in the carrying direction, satisfactory results can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to fixing of a color image forming apparatus using an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an intermediate transfer member as shown in FIG. 13 has been proposed for the purpose of obtaining a color image without color shift.

In FIG. 13, reference numeral 101 denotes a photosensitive drum as a first image bearing member which is rotationally driven in the direction of the arrow shown in the figure. First, the surface of the photosensitive drum is uniformly negatively charged by the charging roller 102.

Next, according to the first image information, ON / OF
The F-controlled exposure unit 103 performs scanning to form a first electrostatic latent image on the photosensitive drum 101. The first electrostatic latent image is developed by the first developing unit 104a containing the first color negatively charged developer, and is visualized as a first toner image.

The visualized first toner image is electrostatically transferred (primary transfer) onto the surface of the intermediate transfer member 105 at a portion facing the intermediate transfer member 105 as the second image carrier which is rotationally driven. ) Will be done.

The above steps are repeated a plurality of times, and the second developing means 104b and the third developing means 104 are carried out each time.
c, the toner images formed by the developers of different colors contained in the fourth developing means 104d are sequentially electrostatically transferred and laminated on the surface of the intermediate transfer member 105. Of course, at that time, the transfer roller 10
6 and the blade 110a of the cleaning unit 110 are separated from the surface of the intermediate transfer member 105.
After the color image is formed in this way, the intermediate transfer member 105
And a transfer material P which is conveyed to a nip portion with a transfer roller 106 as a transfer means which is brought into contact with and rotated.
The color image is collectively transferred (secondary transfer) to the surface of the. still,
The transfer residual toner remaining on the surface of the photosensitive drum 101 at the time of primary transfer and the transfer residual toner remaining on the surface of the intermediate transfer member 105 at the time of secondary transfer are intermediate with the blade of the cleaning unit 109 which is always in contact with the photosensitive member. The cleaning unit 110 that has moved to the surface of the transfer body removes the residual toner from the surface of the photosensitive drum 101 in the former and from the surface of the intermediate transfer body 105 in the latter.

The batch-transferred transfer material P is sent to a fixing device 108 composed of a fixing roller 108b containing a halogen heater 108a and a pressure roller 108c in pressure contact with the roller to fix the toner image. After receiving it, it is discharged to the outside of the aircraft.

[0008]

However, in the apparatus as shown in the above-mentioned conventional example, it is difficult to maintain stable fixability and uniform glossiness (gloss) of the image portion. In particular, the above problem may occur when the transfer material is left at a low temperature or when the transfer material is long in the transport direction.

An object of the present invention is to solve the above problems, to lower the temperature control temperature of the fixing means, and to use an inexpensive material having a low heat resistant temperature such as a resin on each fixing means side. To do.

[0010]

The present invention employs the following means to solve the above-mentioned problems.

1. A photoreceptor having a photoconductive layer on the surface of the conductor, a means for sequentially forming a plurality of electrostatic latent images on the photoreceptor, and the electrostatic latent images are sequentially developed on the photoreceptor with toner of a plurality of colors. And an intermediate transfer member that rotates in contact with the photosensitive member to multiple-transfer the plurality of toner images, and a second transfer unit that transfers the toner images on the intermediate transfer member to a transfer material. A heat source for supplying heat to the transfer material and the toner at a position where the toner image is transferred from the intermediate transfer body to the transfer material, and a fixing unit having the heat source.

2. The image forming apparatus according to the above 1, wherein a heat source for supplying heat to the transfer material and the toner at a position where the toner image is transferred from the intermediate transfer body to the transfer material is inside the intermediate transfer body.

3. The image forming apparatus according to the above 1, wherein a heat source for supplying heat to the transfer material and the toner at a position where the toner image is transferred from the intermediate transfer body to the transfer material is outside the intermediate transfer body.

4. 4. The image forming apparatus according to any one of 1 to 3 above, wherein one of the fixing devices has a pressure roller that does not include a heat source, and the peripheral length of the pressure roller is shorter than the peripheral length of the intermediate transfer member. It is a device.

5. The heat source for supplying heat to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer member to the transfer material is set to be lower than the glass transition point of the toner used at the position where the transfer material comes into contact. The image forming apparatus according to any one of 1 to 4.

6. At the position where the toner image is transferred from the intermediate transfer body to the transfer material, the temperature control temperature of the heat source for supplying heat to the transfer material and the toner is constant during transfer from the front end of the transfer material sheet to the rear end 6. The image forming apparatus as described in any one of 1 to 5 above, wherein the rear end has a higher temperature control temperature than the front end.

[0017]

According to the present invention, heat is supplied to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer member to the transfer material, and heat is mainly applied to the transfer material to stabilize the fixing process. Heat can be supplied to the transfer material, and stable fixing and desired gloss of the image area can be obtained.

[0018]

【Example】

 [Embodiment 1] FIG. 1 shows an embodiment according to the present invention.

Here, a laser beam printer will be described as an example with reference to FIG.

Reference numeral 1 designates a photosensitive member (a cylindrical substrate of aluminum or the like on which organic photoconductor, selenium, amorphous silicon, zinc oxide, CdS, etc. are formed) which is a drum or belt shape. is there. Here, a photosensitive drum will be described.

Reference numeral 5 denotes an intermediate transfer member, which is a pipe-shaped aluminum core metal 5
On a, fine carbon or metal powder is uniformly dispersed in an elastic body made of EPDM or the like to obtain a volume resistivity of 10 ⁵ to 10 ¹¹
An elastic body 5b adjusted to Ω · cm is coated. The peripheral length of the intermediate transfer member is set to be slightly larger than the length of the transfer material. In this embodiment, A3 or Ledger is used.
In order to vertically feed a transfer material of a size, the outer diameter of the intermediate transfer body 5 is set to 140 mm, the peripheral length is set to 439.8 mm, the thickness of the elastic body 5b is 8 mm, and the Asker C hardness is 30 degrees to 50 degrees.
Is set in degrees. Further, a bias power source 11 for applying a voltage to the intermediate transfer member 5, and the bias power source 11 is configured so that the voltage polarity can be changed.

In this embodiment, the process speed is 90 m.
m / sec, the outer diameter of the photosensitive drum is set to 70 mm.

On the other hand, transfer means and means 6 for supplying heat to the transfer material.
Is a film on the outside, and is rotated by rotation of the intermediate transfer member.

A film guide 6d has a function of supporting the core 6e having a high magnetic permeability and the coil 6f.

The high-permeability core 6e is preferably made of a material such as ferrite or permalloy that is used for the core of a transformer, and more preferably ferrite with a low loss even at 100 KHz or more.

An exciting circuit (not shown) is connected to the coil 6f, and this circuit can generate a high frequency of 20 KHz to 500 KHz by the switching power supply.

The transfer material passes through the nip formed by the intermediate transfer member 5 and the transfer means 6 which can be heated.

Since the principle of heating in this nip is the same as that of the fixing device 10 of this embodiment, it will be described with reference to the fixing device of FIG.

The magnetic flux generated by the current applied to the coil by the exciting circuit (not shown) is guided to the high magnetic permeability core to generate the magnetic flux 13 and the eddy current 14 in the heat generating layer 10a of the film in the nip. Heat is generated by the eddy current 14 and the specific resistance of the heat generating layer 10a.

The structure of the film is as shown in FIG.
a), 10b (6b) and 10c (6c) are integrated. Reference numeral 10a (6a) is a base layer which is a conductive layer of the film, which is a heat generating layer made of a metal film, and more preferably a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, or nickel-cobalt alloy is used. .

The thickness is preferably thicker than the skin depth expressed by the following equation and not more than 200 μm. The skin depth σ (m) is expressed as σ = 503 × (ρ / fμ) ^1/2 by the frequency f (Hz) of the excitation circuit, the magnetic permeability μ and the specific resistance ρ (Ω · m).

This shows the depth of absorption of electromagnetic waves used for electromagnetic induction. At deeper points, the intensity of electromagnetic waves is 1 / e or less. Conversely, most energy is at this depth. It is absorbed by now. Shown in FIG.

The thickness of the heating layer 10a (6a) is preferably 1 to 100 μm. If the thickness of the heat generating layer is less than 1 μm, most of the electromagnetic energy cannot be absorbed, resulting in poor efficiency. On the other hand, if the heat generating layer exceeds 100 μm, the rigidity becomes too high and the flexibility deteriorates, which is not practical for use as a rotating body.

10b (6b) is an elastic layer made of silicone rubber,
Fluorine rubber, fluorosilicone rubber, etc. have good heat resistance,
It is a material having good thermal conductivity, a thickness of 50 μm, and a hardness of 45 degrees (JIS-A).

Numeral 10c (6c) is a semiconductive releasing layer, which is made of fluororesin, silicone resin, fluororesin silicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP, etc. mixed with carbon or the like, and has a resistance of 1 × 10 ⁶ Ω / It is semi-conductive and has a thickness of 5 μm.

A brush 7 made conductive by carbon or the like is arranged in contact with the outermost conductive release layer 6c of the film at the transfer site, and is connected to a power source 8.

The photosensitive drum 1 is rotationally driven in the direction of the arrow shown in the drawing at a peripheral speed of 90 mm / sec. First, the surface of the photosensitive drum 1 is darkened by a charging roller 2 as a charging device.
D is uniformly charged to -700V. Next, the surface of the photosensitive drum 1 is turned on / off according to the first image information.
Scan exposure is performed by the F-controlled laser beam 3, and a first electrostatic latent image of −100 V is formed on the photosensitive drum 1 as the bright portion VL.

The first electrostatic latent image thus formed is developed and visualized by the developing means 4. The developing means 4 contains the yellow toner as the first color toner. No. 1 developing device 4a, and second developing device 4 containing magenta toner as the second color toner.
b, a third developing device 4c containing cyan toner as a third color toner, and a fourth developing device 4d containing black toner as a fourth color toner are integrated. First, the first electrostatic latent image is developed by the first developing device 4a containing the yellow toner as the toner of the first color and is visualized as the first toner image.

As the developing method, image exposure and reversal development are often used in combination.

Thus, the visualized first toner image is
It is brought into pressure contact with the photosensitive drum 1 with a predetermined pressing force, and comes into contact with an intermediate transfer member 5 as a second image carrier which is rotationally driven in the direction of the arrow in the drawing at a speed substantially equal to the peripheral speed of the photosensitive drum 1. Electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer member 5 at the first transfer portion N ₁ . Here, the intermediate transfer body 5 has a peripheral length slightly longer than the length of the transfer material, and the toner image formed on the surface of the photosensitive drum 1 is charged on the intermediate transfer body 5 from the bias power supply 11 with the toner charging polarity. Primary transfer is performed by applying a voltage having a polarity opposite to that of.

Subsequently, the above steps are repeated three times, and each time, the second toner image developed with magenta toner,
The third toner image developed with the cyan toner and the fourth toner image developed with the black toner are sequentially transferred onto the surface of the intermediate transfer member 5 and laminated to form a color image.

By the way, when the toner image on the photosensitive drum 1 is transferred to the intermediate transfer member 5, the potential of the non-image portion is different from the potential of the toner image portion. Since the potential difference from the image portion is larger than the potential difference from the toner image portion, the transfer current flows more in the non-image portion.

The above tendency is remarkable when the resistance of the intermediate transfer member 5 is low. For example, when the current value to the non-image portion is more than twice the current value to the toner image portion, the non-image The electric field in the area affects the toner image, and the toner image is scattered around.

That is, it is not suitable for an intermediate transfer member having a low resistance. On the contrary, in the high resistance intermediate transfer member, the electric field that can be formed by the bias power source 11 becomes too small, and the function itself of the intermediate transfer member is impaired. Therefore, 10 ⁵ to 10 ¹¹ Ω
cm, and preferably an intermediate transfer member having a medium resistance in the range of 10 ⁷ to 10 ⁹ Ω · cm.

After that, the transfer means 6 which was in a separated state from the surface of the intermediate transfer body 5 is pressed against the surface of the intermediate transfer body 5 with a predetermined pressing force, and the film is driven and rotated by the intermediate transfer body which is driven to rotate. The color image is collectively transferred (secondary transfer) onto the surface of the transfer material P conveyed to the second transfer portion N ₂ at a predetermined timing.

In this secondary transfer, in order to transfer from the intermediate transfer member 5 to the transfer material P, a power source 8 which is a bias power source having a polarity opposite to that of the toner T is supplied to the conductive brush 7, and the toner is transferred to the back surface of the transfer material. At the same time that the toner image on the intermediate transfer member is transferred to the transfer material by applying electric charges of opposite polarities, the transfer means 6 having a heating means detects the temperature with the thermistor 18 and controls the current value applied to the coil. Thus, the temperature of the transfer material is constantly controlled to a predetermined temperature control temperature, and when the transfer material passes through the nip, the transfer material is heated at the previous transfer site. Although not attached to this example, when the temperature of the transfer material was measured with a thermistor 17, the results shown in FIG. 5 were obtained. The transfer material used at that time was A3 size 64 g / m ² PP.
The C paper was left in an environment of 5 ° C. for a long time.

The transfer material P was conveyed to the fixing device 10 whose temperature was controlled at 160 ° C. at the 15 thermistors, and the transfer means fixed the color image as a permanent image by the same heating principle as described above. After that, it is discharged to the outside of the machine.
To clean the toner remaining on the surface of the intermediate transfer body 5 after the secondary transfer, the cleaning unit 12 in the separated state comes into contact with the intermediate transfer body at a predetermined timing.
It is cleaned by the cleaning blade 12a. Under the conditions at this time, the glossiness (gloss) of the image portion when printed in A3 size was measured from the leading edge to the trailing edge of the transfer material, and the result of FIG. 4 was obtained.

The size of the transfer material can be detected by the information from the frame of the known cassette.

FIG. 6 shows the glossiness (gloss) of the image portion in the conventional example.
Here, L is the circumference of the pressure roller, and it can be seen that the gloss is reduced in this circumference cycle. That is, since the transfer material removes the heat of the pressure roller 16, the gloss value is low in the circumferential cycle of the pressure roller.

FIG. 9 shows the relationship between the surface temperature of the fixing roller of the conventional example and the glossiness (gloss value) of the image at the front end of the transfer material after fixing. As a gloss measuring method, a gloss meter (GLOSS GARD2 / GARDNER) 75
The method of measuring the amount of reflected light in the degree direction was used. As the fixing conditions, a pair of a fixing roller and a pressure roller is used, the HTV rubber of the fixing roller is about 0.3 mm, the HTV rubber of the pressure roller is about 2 mm, and the fluorine coating layer thickness is about 50 mm.
μm, the outer diameter of the fixing roller and the pressure roller is 26.7.
mm and contacted with a linear pressure of 1.0 kg / cm. Also,
The sheet passing speed was 90 mm / sec. The glossiness increases with temperature, but when it is 181 ° C or higher, hot offset (a phenomenon in which toner of the transfer material adheres to the fixing roller side) is caused on the fixing roller side, and the toner surface of the image surface becomes uneven, resulting in glossiness. Tend to go down. If the temperature is 158 ° C. or lower, cold offset (a phenomenon in which toner of the transfer material adheres to the fixing roller side) will occur.

Generally, an image having a gloss of 10 to 20% is preferred. However, it was difficult to maintain the stable fixing property and the uniform glossiness (gloss value) of the image area in the conventional example. In particular, FIG. 6 shows that the above problem occurs when the transfer material is left at a low temperature or when the transfer material is long in the conveying direction. A shake with a glossiness of 8 to 30% occurs.

As described above, the results obtained in the present embodiment are as shown in FIG. 4 under the condition of FIG.
It was able to be suppressed to%.

[Modification 1] Here, a color laser beam printer using yellow, magenta, cyan, and black toners is used. The measurement of the inflection point Tg of the endothermic change graph with black toner will be described. In the present invention, the Tg of the toner is calculated by differential scanning calorimetry according to ASTM (American Society of Materials Standards). Figure 12
It is explanatory drawing of the calculation method of Tg by a differential scanning calorimetry. That is, 10 to 15 mg of toner is heated in a N ₂ atmosphere to raise the temperature. Drawing a graph of the change in the amount of heat absorbed by the toner during the process of raising the temperature, the amount of heat absorbed is constant up to temperature T1, and the amount of heat absorbed is also constant above temperature T2.

The inflection point of the endothermic change graph corresponding to 1 / 2h of the difference in the amount of heat absorbed between T1 and T2 is Tg.

By way of example, styrene-acrylic resin (MW 250,000) 100 parts by weight Magnetic powder 50 parts by weight Low molecular weight polypropylene 5 parts by weight Black toner produced with 2 parts by weight of charge control agent had Tg of 70 ° C. .

When the other three types of color toners containing no magnetic powder were measured with the same measuring device, Tg was 70 ° C.

Therefore, in this modification, the toner at the transfer portion is heated, but as shown in FIG. 5, since the toner is heated at a temperature lower than Tg, the toner becomes soft and sticks to the surface of the intermediate transfer member. Is gone.

[Embodiment 2] The difference between Embodiment 2 and Embodiment 1 is that, as shown in FIG. 8, Embodiment 1 has a transfer means 6 having a heating means.
Was constantly controlled to a predetermined controlled temperature,
In the second embodiment, the transfer means 6 having a heating means is the thermistor 1.
When the temperature of the transfer material passes through the nip, the temperature is detected in step 8 and the current value applied to the coil is controlled to control the controlled temperature so that the temperature of the transfer material sheet rises from the leading edge to the trailing edge. , It is different that it is heated at the transcription site.

The operation is the same as that of the first embodiment, and will be omitted. As a result, as shown in FIG.
It can be reduced to within 20%.

[Embodiment 3] The difference between Embodiment 3 and Embodiment 1 is that, as shown in FIG. 10, the intermediate transfer member is changed from a drum shape to a belt shape, a transfer roller 313 is used, and a transfer portion is used. There is a transfer unit 306 having a heating unit in the intermediate transfer belt 314, and the transfer unit 306 faces the transfer roller 307.
There is. This transfer roller is a plated iron core
EPDM rubber is wound with foamed semiconductive rubber whose resistance is adjusted with carbon or paraffin oil.

The fixing device 308 is a fixing roller 308b in which a heater 308a is included on the non-image side of the transfer material, and the pressure roller 308c does not include a heat source.

In operation, the primary transfer is transferred by the transfer roller 313 connected to the bias power source 311, and the secondary transfer is the transfer roller 30 connected to the bias power source 310.
Transcribed at 7. Further, the heating of the transfer portion is performed from the inside of the intermediate transfer belt. The other operations are the same as those in the first embodiment and will not be described.

[Embodiment 4] The difference between Embodiment 4 and Embodiment 3 is that, as shown in FIG. 11, the intermediate transfer belt 213 is a heating layer made of a metal belt, more preferably nickel.
It is a ferromagnetic metal such as iron, ferromagnetic SUS, or nickel-cobalt alloy.

In operation, the primary transfer is transferred by the transfer belt 213 connected to the bias power supply 211, and the secondary transfer is the transfer roller 20 connected to the bias power supply 210.
Transcribed at 7. The transfer belt is heated from the inside of the intermediate transfer belt. The other operations are the same as those in the third embodiment, and will be omitted.

[0065]

As described above, the first embodiment according to the present application is described.
According to the present invention, it becomes possible to maintain stable fixability and uniform glossiness (gloss) of the image area. In particular, good results were obtained even when the transfer material was left at a low temperature or when the transfer material was long in the conveying direction. Furthermore, the temperature control temperature of the fixing means is lowered, and it becomes possible to use an inexpensive material having a low heat resistant temperature such as a resin used in each fixing means side.

According to the second and third inventions of the present application, in addition to the effect of the first invention, heat is supplied to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer body to the transfer material. Since the heat source for heating is arranged at a convenient place, it is advantageous in terms of space structure.

According to the fourth invention of the present application,
In addition to the effect of the invention of 3, the glossiness (gloss value) of the image area
There is an effect that the change can be reduced from the front end to the rear end of the transfer material.

According to the fifth invention of the present application,
In addition to the effect of the invention of 4, there is an effect that the glossiness of the image portion can be selected within an appropriate range.

According to the sixth invention of the present application,
In addition to the effect of the invention of 5, the effect that the glossiness of the image portion can be made substantially constant from the front end to the rear end of the transfer material is exhibited.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a film in the first embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between electromagnetic wave intensity and conductive layer depth.

FIG. 4 is a gloss value from the leading edge to the trailing edge of the transfer material according to the first embodiment of the present invention.

FIG. 5 shows temperature control and transfer material temperature in the first embodiment of the present invention.

FIG. 6 is a gloss value from a front end to a rear end of a transfer material in a conventional example.

FIG. 7 is a gloss value from the front end to the rear end of the transfer material according to the second embodiment of the present invention.

FIG. 8 shows temperature control and transfer material temperature in the second embodiment of the present invention.

FIG. 9 shows the relationship between the gloss value at the tip of the transfer material and the surface temperature of the fixing roller in the conventional example.

FIG. 10 is a schematic vertical sectional view of an image forming apparatus according to a third embodiment of the invention.

FIG. 11 is a schematic vertical sectional view of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 12 is an explanatory diagram for obtaining Tg of toner.

FIG. 13 is a schematic vertical sectional view of a conventional image forming apparatus.

[Explanation of symbols]

1, 101, 201, 301 ... Photosensitive drum 2, 102, 202, 302 ... Charging roller 3, 103, 203, 303 ... Exposure means 4, 104, 204, 304 ... Developing means 5, 105, 213, 314 ... Intermediate transfer Body 6 ... Transfer means 6a, 10a, 306a ... Exothermic layer 6b, 10b, 306b ... Elastic layer 6c, 10c, 306c ... Release layer 6d, 10d, 206d, 306d ... Film guide 6e, 10e, 206e, 306e ... Core 6f , 10f, 206f, 306f ... Coil 7, 107 ... Conductive brushes 8, 11, 210, 211, 310, 311 ... Power supply 9, 12, 109, 110, 212, 312 ... Cleaning means 10, 108, 208, 308 ... Fixing Container 13 ... Magnetic flux 14 ... Eddy current 15, 17, 18, 19 ... Thermistor 16 ... Pressure roller 1 6,207,307,313 ... transfer roller 204a, 304a ... first yellow which the toner is contained
Developing device 204b, 304b ... second containing magenta toner
Developing device 204c, 304c ... third developing device containing cyan toner 204d, 304d ... fourth developing device containing black toner
Developing device 208a ... Halogen heater 208b ... Fixing roller 208c ... Pressing roller L ... Perimeter of pressing roller P ... Transfer material T ... Toner

Claims (6)

[Claims] 1. A photoreceptor having a photoconductive layer on the surface of the conductor,
A unit for sequentially forming a plurality of electrostatic latent images on the photoconductor, a unit for sequentially developing the electrostatic latent images on the photoconductor with toner of a plurality of colors, and a unit for rotating the plurality of electrostatic latent images in contact with the photoconductor. In an image forming apparatus having an intermediate transfer member that multiple-transfers toner images and a second transfer unit that transfers the toner images on the intermediate transfer member to a transfer material, a position at which the toner image is transferred from the intermediate transfer member to the transfer material. 2. An image forming apparatus comprising: a heat source for supplying heat to the transfer material and the toner; and a fixing unit having the heat source. 2. The heat source for supplying heat to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer body to the transfer material is inside the intermediate transfer body.
The image forming apparatus as described in the above. 3. The heat source for supplying heat to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer body to the transfer material is outside the intermediate transfer body.
The image forming apparatus as described in the above. 4. The fixing device according to claim 1, wherein one of the fixing devices has a pressure roller that does not include a heat source, and the peripheral length of the pressure roller is shorter than the peripheral length of the intermediate transfer member. An image forming apparatus according to claim 2. 5. The heat source for supplying heat to the transfer material and the toner at the position where the toner image is transferred from the intermediate transfer member to the transfer material is set to a position lower than the glass transition point of the toner used at the position where it contacts the transfer material. The image forming apparatus according to any one of claims 1 to 4, wherein: 6. A temperature control temperature of a heat source for supplying heat to the transfer material and the toner at a position where the toner image is transferred from the intermediate transfer member to the transfer material, while the rear end from the front end of the transfer material sheet is being transferred,
The image forming apparatus according to any one of claims 1 to 5, wherein the temperature is constant or higher at the rear end than at the front end of the transfer material sheet.