JP3727796B2 - Wet electrophotographic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wet electrophotographic apparatus using a liquid toner having a high viscosity and high concentration that exhibits non-volatility, and in particular, removes a carrier without disturbing the toner image on an intermediate transfer member, and forms a toner image of a plurality of colors. The present invention relates to a wet electrophotographic apparatus that can be superimposed.
[0002]
[Prior art]
Electrophotographic apparatuses that generate an electrostatic latent image on a photoconductor (drum), attach toner particles to the photoreceptor, and transfer and fix it on paper or the like are widely used as dry types using powder toner. However, the powder toner has a problem that the toner is scattered and a problem that the resolution is poor because the toner particles are as large as 7 to 10 μm.
[0003]
Therefore, when high resolution is required, a wet type using liquid toner is used. This is because the liquid toner has toner particles as small as about 1 μm and a large charge amount, so that the toner image is hardly disturbed and high resolution can be realized.
[0004]
In a conventional wet electrophotographic apparatus, a low-viscosity liquid toner in which toner particles are mixed in an organic solvent at a ratio of 1 to 2% is used as a developing solution. However, such a developer has a great problem of causing an environmental problem because it uses an organic solvent that is harmful to human bodies and uses a large amount of toner due to its low toner particle concentration.
[0005]
Against this backdrop, wet electrophotography using a high-viscosity and high-concentration developer composed by dispersing high-concentration toner particles in silicone oil or the like under International Publication Number “WO95 / 08792” An apparatus invention has been disclosed. When this liquid toner is used, there is an advantage that there is no problem of harming the human body and there is no need to use a large amount of developer because the toner particle concentration is high.
[0006]
On the other hand, as a method for fixing the toner particles attached to the electrostatic latent image on the photosensitive member to the printing medium, there is also a method in which the toner particles attached to the photosensitive member are directly transferred to the printing medium without using an intermediate transfer member. However, using an intermediate transfer member, the toner particles adhering to the photosensitive member are electrostatically transferred to the intermediate transfer member, and the intermediate transfer member is heated to melt the toner particles and adhesively transfer to the printing medium. It is done to fix. This method has the advantage that the print medium needs to be passed through the intermediate transfer member only once, and is widely used when handling color images.
[0007]
Conventionally, transfer and fixing to a printing medium using an intermediate transfer member in a general electrophotographic apparatus,
1. Electrostatic transfer of toner image from intermediate transfer member to printing medium
2. Thermal pressure fixing by fixing unit
The two steps were generally performed. However, in order to obtain a high-quality image, there has been a concept of a melt transfer method in which fixing is performed at the same time as the transfer because of a desire to reduce the number of times of contact with the image or a simple structure. In this method, transfer and fixing are performed at a time by transferring and fixing a melted toner image from an intermediate transfer member to a printing medium.
[0008]
FIG. 14 shows a conventional configuration of a wet electrophotographic apparatus using a high viscosity and high concentration developer. When this melt transfer method is applied to such a wet electrophotographic apparatus, the process is as follows.
[0009]
1. Primary transfer: electrostatic transfer of toner image from photoconductor 10 to intermediate transfer body 15
2. Carrier removal: removal of carrier oil and pre-wet oil by the carrier removal roller 18
3. Heating and melting: Heat melting of the toner by the heat source inside the intermediate transfer member
4. Melt transfer: Transfer of molten toner from the intermediate transfer body 15 to the printing medium by adhesive force
5. Cleaning: Cleaning of residual toner on the intermediate transfer member
In the case of color printing, for example, printing of yellow, magenta, cyan, and black toner, steps 1 to 3 are repeated four times to superimpose toner images, and then the processes 4 and 5 are performed.
[0010]
In such a configuration, the following is a problem.
[0011]
Since the intermediate transfer member 15 is constantly heated, the photosensitive member 10 is heated, and the photosensitive characteristics are deteriorated.
[0012]
At the time of carrier removal, since the toner image is in a heat-melted state, the toner image is disturbed by the adhesive force to the carrier removal roller 18 and image quality deterioration occurs.
[0013]
When the toner images are superimposed, the toner images that have already been electrostatically transferred are in a heated and melted state, and the images are disturbed and contact with the photoconductor, resulting in deterioration of image quality.
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of such circumstances, and has a configuration in which a liquid toner having high viscosity and high density that exhibits non-volatility is employed, and heating of the intermediate transfer member does not affect the photosensitive member. Therefore, it is an object of the present invention to provide a new wet electrophotographic apparatus that does not cause deterioration of photosensitive characteristics.
[0015]
Another object of the present invention is to provide a new wet electrophotographic apparatus that does not disturb the toner image and cause deterioration in image quality due to carrier removal.
[0016]
It is another object of the present invention to provide a new wet electrophotographic apparatus that does not deteriorate the image quality of toner already electrostatically transferred and cause deterioration in image quality when toner images are superimposed on an intermediate transfer member. And
[0017]
[Means for Solving the Problems]
The image support of the present invention, that is, the photoconductor 10 is charged by a charging device 11 and then exposed by an exposure device 12 to form an electrostatic latent image. The prewetting device 13 applies prewetting oil made of silicone oil or the like to the surface of the photoconductor 10.
[0018]
The developing device 14 is provided in association with yellow / magenta / cyan / black, and uses a high-viscosity, high-concentration liquid toner that exhibits non-volatility as the liquid developer. The developer is supplied by supplying the positively charged toner to the photoconductor 10 in accordance with the electric field between the photoconductor 10 and the toner on the exposed or non-exposed portion of the charged photoconductor 10. Adhere particles.
[0019]
The intermediate transfer belt 24 is biased and transfers the toner attached to the photoconductor 10 in the order of yellow, magenta, cyan, and black according to the electric field between the photoconductor 10 and the intermediate transfer belt 24. A backup roller 20 is provided which rotates while contacting the intermediate transfer belt 24 and conveys the print medium together with the heating roller 25 while applying pressure to the intermediate transfer belt 24. As described above, the intermediate transfer member of the present invention includes the intermediate transfer belt 24.
[0020]
The intermediate transfer belt 24 has a carrier removal roller 18 for removing excess carrier and prewetting liquid at a position after contact with the photoconductor 10 and the intermediate transfer belt 24 at a position before melt transfer to a printing medium. A heating unit (heating roller 25) for heating and melting the toner image on the belt 24 and a cooling unit (cooling roller 23) for cooling the toner image at a position before contacting the photoreceptor are provided. In this way, a cycle for heating and cooling in one rotation of the intermediate transfer belt 24 is established.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail according to embodiments. In the present invention, a high-viscosity and high-concentration liquid toner that exhibits non-volatility is used as a liquid developer. However, the liquid toner contains toner particles such as a thermoplastic resin and a pigment in a liquid carrier (oil). It is dispersed.
[0022]
FIG. 1 illustrates the overall configuration of a wet electrophotographic apparatus including the present invention. As shown in this figure, the wet electrophotographic apparatus of the present invention includes a photoreceptor 10, a charging device 11, an exposure device 12, a prewetting device 13, a developing device 14, an intermediate transfer member (intermediate transfer belt 24). ) And its driving mechanism, a blade 16, a charge eliminating device 17, and a backup roller 20. The charging device 11 charges the photoreceptor 10 to about 700V. The exposure device 12 exposes the photoconductor 10 using laser light having a wavelength of 780 nm, thereby forming an electrostatic latent image on the photoconductor 10 with the potential of the exposed portion being about 100V.
[0023]
The prewetting device 13 applies a silicone oil having a viscosity of about 2.5 cSt to 20 cSt to the surface of the photoreceptor 10 with a thickness of 4 to 5 μm. Here, the prewetting apparatus 13 may execute the prewetting process before the exposure process executed by the exposure apparatus 12, but may also execute the prewetting process after the exposure process.
[0024]
The developing device 14 is provided so as to correspond to yellow / magenta / cyan / black, and is biased to about 400 V to apply liquid toner having a toner viscosity of 400 to 4000 mPa · s and a carrier viscosity of 20 cSt to a plurality of applicators. A toner layer having a thickness of 2 to 3 [mu] m is formed on the developing roller by being conveyed while being thinly extended from the toner reservoir using a roller. The developing roller supplies the positively charged toner particles to the photoconductor 10 in accordance with the electric field between the photoconductor 10 and the exposed or unexposed portion of the photoconductor 10 charged to about 100V. Adhere toner particles. At that time, the toner particles can be prevented from adhering to the non-exposed portion of the photoreceptor 10 in accordance with the prewetting layer applied by the prewetting device 13.
[0025]
The blade 16 removes toner and prewetting liquid remaining on the photoreceptor 10. The neutralization device 17 neutralizes the photoreceptor 10.
[0026]
The intermediate transfer belt 24 is biased to about −500 V, and transfers the toner particles attached to the photoconductor 10 according to the electric field between the photoconductor 10 and the intermediate transfer belt 24. Each of the four color toner particles is transferred from the photoconductor 10 to the intermediate transfer belt 24 a total of four times. For example, first, yellow toner particles attached to the photoreceptor 10 are transferred, then magenta toner particles attached to the photoreceptor 10 are transferred, and then cyan attached to the photoreceptor 10. Next, the black toner particles attached to the photosensitive member 10 are transferred. Thereafter, the toner particles transferred to the intermediate transfer belt 24 are heated and melt-transferred once onto a printing medium such as paper. At this time, the backup roller 20 contacts and heats the heating roller 25 so as to fix the melted toner particles to a medium such as printing paper.
[0027]
The intermediate transfer belt 24 of the present invention is wound around a plurality of tension rollers 26 and 27, a heating roller 25 having a heating mechanism, and a cooling roller 23. The intermediate transfer belt 24 can be driven by any roller, but for example, the heating roller 25 can be provided with a drive mechanism. The heating roller 25 can be constituted by an aluminum roller that can be heated by a heat source such as a halogen lamp provided therein. A carrier removal roller 18 that contacts the surface of the intermediate transfer belt 24 is provided between the contact position of the intermediate transfer belt 24 with the photoconductor 10 and the heating roller 25. The carrier removal roller 18 is biased to +3 KV, for example, to remove not only excess carriers but also the prewetting liquid.
[0028]
A conductive roller 19 that abuts against the carrier removing roller 18 from the inside of the intermediate transfer belt 24 can be provided. By grounding the conductive roller 19, an electric field is formed by the carrier removing roller 18 only on the contact surface of the carrier removing roller 18 and the conductive roller 19 via the intermediate transfer belt 24. A bias can be applied to the carrier removal roller 18 without having an electrical effect on other processes. Further, as shown in FIG. 13, each of the carrier removing roller 18 and the conductive roller 19 can have spacers substantially equal to the roller diameter at both ends of the rollers, and both rollers are positioned by the spacers. Both rollers are engaged by a gear and are driven at a speed equal to the process speed. As a result, the carrier removing roller 18 can obtain stable contact with the intermediate transfer belt 24 and can remove the carrier without disturbing the image.
[0029]
The intermediate transfer belt 24 of the present invention, for example, heats the surface of the intermediate transfer belt to 150 ° C. by its heating mechanism (heating roller 25), while the intermediate transfer belt 24 is cooled by the cooling function of the cooling device (for example, cooling roller). The cycle of cooling to 40 ° C is repeated.
[0030]
FIG. 2 is a diagram illustrating an intermediate transfer process of the intermediate transfer belt 24 of the present invention.
[0031]
Step ST1: A toner image is electrostatically transferred from the photoreceptor 10 onto the intermediate transfer belt 24.
[0032]
Step ST2: The carrier and pre-wet are removed by the carrier removing roller 18 charged to the same polarity as the toner, and at the same time, the toner image is electrically aggregated.
[0033]
Step ST3: The toner image is heated and melted through the belt at the belt winding portion around the heating roller 25. The toner is in a molten state from when the belt contacts the heating roller 25 until it contacts the print medium.
[0034]
Step ST4: In the case of color printing of two or more colors, it is determined whether or not all colors have been completed. When all the colors are completed, the process proceeds to step ST6, and otherwise, the process proceeds to step ST5.
[0035]
Step ST5: The intermediate transfer belt 24 is cooled by the cooling device together with the toner image. The molten toner is solidified in an integrated state, and the remaining carrier is in a state of being raised on the toner image.
[0036]
In this cooled state, the process returns to step ST1 to perform superposition for electrostatic transfer of the next toner image. At this time, since the previous toner image is solidified, the image is not disturbed.
[0037]
Similarly, in step ST2, the carrier from which the previous toner has been lifted and the carrier for the next toner are removed by the carrier removal roller 18.
[0038]
Step ST6: After the above steps are repeated for all colors, the backup roller 20 comes into contact and melt transfer is performed.
[0039]
As shown in FIG. 1, the cooling roller 23 used as a cooling device may be a pipe made of a material having high thermal conductivity such as aluminum. Moreover, as shown in FIG. 3, the cooling effect can be improved by providing an air cooling fan 31 for discharging the air in the pipe. Alternatively, the cooling effect can be enhanced by circulating cooling water inside the pipe-shaped structure.
[0040]
Moreover, as shown in FIG. 4, the cooling fin 32 is provided in the inner surface of a pipe-shaped structure, and the heat dissipation effect of a cooling roller can be improved. Further, by forming the cooling fins 32 in a spiral shape, the cooling roller rotates, thereby creating an air flow and improving the air cooling capacity.
[0041]
Furthermore, the part which the belt of the outer surface of the cooling roller 23 does not wind can be cooled using a cooling fan. Alternatively, as shown in FIG. 5, the intermediate transfer belt 24 can be directly cooled by the cooling fan 33.
[0042]
FIG. 6 illustrates the configuration of the intermediate transfer belt 24 used in the present invention.
[0043]
In the intermediate transfer belt,
-Heat resistance and low coefficient of thermal expansion to prevent image deformation due to thermal expansion and softening of the belt
・ Strength that can withstand belt drive load
・ Electrical properties and toner release properties
These characteristics are required. As an intermediate transfer belt satisfying these characteristics, a conductive resin belt coated with a fluorine-based conductive surface coat, for example, as shown in FIG. 6, a conductive polyimide having a thickness of 50 μm is coated with 20 μm. A film coated with a conductive PTFE having a thickness can be used. The reason for using such a thin belt is to reduce the heat capacity of the intermediate transfer belt and efficiently perform the heating to cooling cycle.
[0044]
FIG. 7 is a diagram illustrating the relationship between the belt contact time with respect to the heating roller 25 and the belt surface temperature. The heating of the intermediate transfer belt 24 by the heating roller 25 needs to be efficiently performed while suppressing the heat generation amount of the heating roller, and it is necessary to obtain a stable heating temperature. This can be achieved by taking a sufficient amount of winding between the intermediate transfer belt and the heating roller until the belt surface temperature is saturated.
[0045]
For example, when it is desired to set the belt temperature to 120 ° C., the heater temperature can be increased sufficiently (for example, 200 ° C.) and the contact time between the belt and the heating roller can be controlled. However, the heating value of the heater is inefficient. Also, the heating temperature depends on the initial temperature and the environmental temperature, and becomes unstable. As shown in FIG. 7, in the case of a 40 μm belt, the wrapping time with the heating roller is set to 60 ms or more, or in the case of a 75 μm belt, the belt temperature is set to 120 ms or more. Becomes saturated, and an efficient and stable belt temperature can be obtained.
[0046]
FIG. 8 is a diagram showing a normal sequence in which the carrier is removed after cooling after heating. c, m, y, and k represent cyan, magenta, yellow, and black, respectively. These four color toners are sequentially transferred from the photosensitive member to the intermediate transfer belt, heated, melted, and cooled. As can be understood from FIG. 1, the carrier removal is performed after the primary transfer and before being melted by heating. The first carrier removal is performed after the primary transfer of the cyan toner. This cyan toner is subsequently heated and melted and cooled. Then, magenta toner is superimposed on this. The second carrier removal is performed in this state, and the same processing is performed thereafter. After the black toner, which is the last color, is heated and melted, the intermediate transfer belt makes one more round in order to cool again and remove the carrier. Then, after removing the last carrier, it is transferred to the printing medium at the same time as the fifth heat melting. In this way, the intermediate transfer belt makes five turns for the four color toners.
[0047]
FIG. 9 is a view similar to FIG. 8, but omits cooling and carrier removal for the final toner image. The black toner, which is the last color, is superposed, and the carrier is removed in that state and heated and melted. Then, the usual cooling and carrier removal are omitted, and the toner is immediately transferred to the printing medium. The omission of the final heat melting and carrier removal can be performed according to the type of print medium. If the print medium has good carrier absorbability, it can be omitted by user selection, for example. Alternatively, a printing medium such as polyester for OHP having particularly poor absorbability can be further cycled one more time or more to be cooled and carrier removed.
[0048]
Further, the omission of the final heat melting and carrier removal can be performed according to the type of print content. It can be determined according to the size of the print duty or whether it is image data or text data. For example, if the print duty is large or a photo or image, it is not to be omitted. it can.
[0049]
For example, when the peripheral length of the intermediate transfer belt 24 is 500 mm and the process speed is 250 mm / sec, when the carrier is removed after heating and cooling for all four colors, the continuous printing sequence is 10 sec / paper, that is, 6 ppm. Become. When carrier removal of the fourth color is omitted, control can be performed at a printing speed of 8 sec / paper, that is, 7.5 ppm.
[0050]
When the black toner, which is the last color, is overlaid, heated and melted, and further cycled, this is done for cooling and carrier removal, and the primary transfer from the photoreceptor is performed. Absent. During this time, a mechanism for retracting the contact between the intermediate transfer belt 24 and the photoreceptor 10 can be provided. This can be performed, for example, by moving the tension roller 27 in FIG. 1 downward in the drawing. Thereby, it is possible to prevent the thermal deterioration of the photoconductor and the disturbance due to the contact of the photoconductor with the image.
[0051]
As described above, the photoconductor 10 is charged by corona charging or the like during the cycle without performing the primary transfer from the photoconductor, and functions in the same manner as the carrier removal roller 18 by the photoconductor 10. In addition, excess carrier on the intermediate transfer belt 24 can be removed, and image deterioration due to contact with the photoreceptor 10 can be minimized.
[0052]
If the heating temperature or cooling temperature is not stable, the quality of the melt transfer cannot be maintained. For this reason, the intermediate transfer belt 24 is driven in a heating / cooling cycle as a pre-printing operation before the first printing. For example, by measuring the temperature of the intermediate transfer belt 24 using a thermistor, the temperature after heating, the temperature after cooling, or both are controlled, and after the predetermined temperature is reached, the first sheet is printed. By doing so, the quality of the melt transfer of each printing can be stably maintained.
[0053]
As described above, since the apparatus of the present invention has a cooling cycle for each rotation of the intermediate transfer belt 24, the thermal load on the photosensitive member 10 is the same as that in normal full-color printing even in monochrome printing. Therefore, by having a process in which the developing device can be switched between the first half and the second half in one cycle of the intermediate transfer belt 24, the thermal deterioration of the photoconductor 10 can be minimized while the intermediate transfer belt 24 is rotated. When printing on a medium half the size of the transfer belt 24, the first half and the second half of the intermediate transfer belt 24 are set as monochrome printing, and only that side is transferred to the printing medium by one development. While performing full color printing on one side, four monochrome prints can be created.
[0054]
FIG. 10 is a diagram illustrating a normal full-color printing sequence for a full-size print medium. Indicate that cyan, magenta, yellow and black are exposed, developed, primary transferred to intermediate transfer belt 24, and transferred to the print medium after all colors are superimposed. Yes.
[0055]
FIG. 11 shows a sequence in which full-color printing is performed in the first half of a medium that is half the size of the intermediate transfer belt 24, and four monochrome printings are mixed in the latter half. . As a result, full-color prints can be printed at 7.5 ppm and monochrome at 30 ppm.
[0056]
Since the apparatus of the present invention can perform mixed printing in this way, when receiving a print command in which color pages and monochrome pages are mixed, the printing order can be changed so as to perform the fastest printing. For example, a monochrome print and a color print can be divided and printed from either one, or can be printed together on four monochrome pages and one color page.
[0057]
If the print request for half-size print media is an odd number, the print sequence of only one fraction, which is a fraction, consumes the pre-wet by not only the development area but also the pre-wet application area as the print image area only. Can be suppressed.
[0058]
A registration reference position on the intermediate transfer belt 24 is provided for each of the first and second half regions, and the accuracy of the registration can be managed separately for each image. This reference position can be detected by a sensor provided with a notch in the intermediate transfer belt 24, a light-reflective marking, a convex portion and the like.
[0059]
FIG. 12 is a diagram illustrating a mixed printing sequence of full color and one-point color. If the medium of the size of the intermediate transfer belt 24 is half the size of the intermediate transfer belt 24 and one of the first half and the second half is a one-point color print using cyan, magenta, or yellow toner, One-point color printed matter can be printed on the intermediate transfer belt 24 by two rotations one by one while printing in this area. In the illustrated example, full-color printing of c, m, y, and k is performed in the first half, while two one-point color printing of c, k, c, and k is performed in the second half. .
[0060]
【The invention's effect】
The present invention is a wet electrophotographic apparatus using a liquid toner having a high viscosity and high concentration that exhibits non-volatility as a liquid developer. The heating means and the cooling means for cooling the toner image are configured so that a cycle of heating and cooling in one rotation of the intermediate transfer belt is established, so that the intermediate transfer member (belt) can be heated. It does not affect the photosensitive member, and therefore does not cause deterioration of photosensitive characteristics.
[0061]
Further, according to the present invention, the toner image is not disturbed and the image quality is not deteriorated by the carrier removal.
[0062]
Further, the present invention produces an effect that, when the toner images are superimposed on the intermediate transfer member, the image quality of the toner already electrostatically transferred is not disturbed and the image quality is not deteriorated.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a wet electrophotographic apparatus according to the present invention.
FIG. 2 is a diagram illustrating an intermediate transfer process of the intermediate transfer belt of the present invention.
FIG. 3 is a diagram illustrating a cooling configuration of an intermediate transfer belt.
FIG. 4 is another diagram illustrating the cooling configuration of the intermediate transfer belt.
FIG. 5 is still another example illustrating the cooling configuration of the intermediate transfer belt.
FIG. 6 is a diagram illustrating a configuration of an intermediate transfer belt used in the present invention.
FIG. 7 is a diagram showing a relationship between a belt contact time with respect to a heating roller and a belt surface temperature.
FIG. 8 is a diagram showing a normal sequence in which carriers are removed after cooling after heating.
FIG. 9 is a view similar to FIG. 8, but omits cooling and carrier removal for the final toner image.
FIG. 10 is a diagram illustrating a normal full-color printing sequence for a full-size print medium.
FIG. 11 is a diagram illustrating a sequence in which full-color printing and four monochrome printing are mixed for a medium having a size half the size of the intermediate transfer belt.
FIG. 12 is a diagram illustrating a mixed printing sequence of full color and one-point color.
FIG. 13 is a diagram illustrating the arrangement of conductive rollers that abut against the carrier removal roller.
FIG. 14 is a diagram showing a conventional configuration of a wet electrophotographic apparatus using a high-viscosity and high-concentration developer.
[Explanation of symbols]
10 Photoconductor (Drum)
11 Charging device
12 Exposure equipment
13 Prewetting device
14 Development device
15 Intermediate transfer member (roller)
16 blades
17 Static eliminator
18 Carrier removal roller
19 Conductive roller
20 Backup roller
23 Cooling roller
24 Intermediate transfer belt
25 Heating roller
26 Tension roller
27 Tension roller
31 Air cooling fan
32 Cooling fins

Claims (7)

A liquid toner having a high viscosity and high concentration that exhibits non-volatility is used as a liquid developer, and
An image support on which an electrostatic latent image is formed, a developing unit that contacts the image support and attaches toner particles to the image support, and a toner particle that adheres to the image support An intermediate transfer member that transfers in accordance with the electric field generated between them and superimposes a plurality of color toner images, and rotates while contacting the intermediate transfer member to convey the print medium while applying pressure to the intermediate transfer member. In a wet electrophotographic apparatus comprising a backup roller that
The intermediate transfer member comprises an intermediate transfer belt,
The intermediate transfer belt includes a carrier removing unit for removing the carrier or the prewetting liquid at a position after contact with the photosensitive member, and a toner image on the intermediate transfer belt at a position before the melt transfer to the printing medium. A heating unit for heating and melting the toner, and a cooling unit for cooling the toner image at a position before contacting the photosensitive member,
A heating / cooling cycle that heats and cools in one rotation of the intermediate transfer belt is established,
The plurality of color toner images primarily transferred from the photoconductor to the intermediate transfer belt are sequentially removed one by one before removing the carrier before heating, melting and cooling, and the last color toner of the plurality of colors is heated and melted. After that, the intermediate transfer belt is further rotated, cooled again, and the means for removing the carrier after heating and cooling, and the removal of the carrier for the last color toner image after cooling and heating and cooling are omitted. The means for shortening the cycle is configured to be selectable,
A wet electrophotographic apparatus characterized by the above. The wet electrophotographic apparatus according to claim 1, further comprising means for further increasing the heating / cooling cycle. 2. The apparatus according to claim 1, further comprising means for driving the intermediate transfer belt in the heating / cooling cycle as an operation before printing, managing a temperature after heating and a temperature after cooling, and printing the first print medium after reaching a predetermined temperature. The wet electrophotographic apparatus as described. 2. The wet method according to claim 1, further comprising means for retracting the contact between the intermediate transfer belt and the photosensitive member during rotation of the intermediate transfer belt without primary transfer for removing the carrier after heating and cooling the toner image of the last color. Electrophotographic device. And a means for removing the carrier of the photosensitive member by charging the photosensitive member during rotation of the intermediate transfer belt without primary transfer for removing the carrier of the last color toner image after heating and cooling. 2. The wet electrophotographic apparatus according to 1. 2. The wet electrophotographic apparatus according to claim 1, wherein the carrier removing means is constituted by a carrier removing roller, and a conductive roller is provided on the back surface of the intermediate transfer belt so as to oppose the carrier removing roller. The carrier removing roller and the conductive roller each have a substantially equal spacers for positioning the roller diameter at each end of the roller, and claim both rollers are engaged by a gear, driven by equal to the process speed fast 6. The wet electrophotographic apparatus according to 6 .

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