JP2024016348A - image forming system - Google Patents

Abstract

The present invention provides an image forming system capable of suppressing image defects in a varnish image formed over a toner image. SOLUTION: When the toner image is fixed on the varnish image forming surface (S3), the recording material is conveyed again to the secondary transfer section (S4, S5). A voltage higher than the discharge voltage is applied to the secondary transfer outer roller forming the secondary transfer portion (S6). Then, discharge occurs on the varnish image forming surface side, positive ions and negative ions appear in the toner, and the surface of the toner image is coated with a film of these ions. In the case of water-based varnish, the adhesion between the toner image and the water-based varnish can be reduced by creating a film made of positive ions, and the adhesion between the toner and the water-based varnish can be improved by creating a film made of negative ions. In the case of oil-based varnish or UV varnish, a voltage of the opposite polarity to that of water-based varnish is applied to generate a discharge. By performing such discharge treatment, it is possible to suppress image defects such as "bleeding" and "repelling" from occurring in the varnish image formed over the toner image. [Selection diagram] Figure 4

Description

The present invention relates to an image forming system that includes an image forming apparatus that forms a toner image on a recording material and a varnish coating apparatus that forms a varnish image on the recording material.

Recently, in addition to the toner image formed on the recording material using a developer, in order to decorate the surface of the recording material, a varnish image using transparent varnish is superimposed on the toner image. formed on top. As a device for forming a varnish image, for example, an inkjet type varnish coating device (referred to as a varnish coater) is used. A varnish coater can partially apply varnish to a recording material after a toner image has been fixed to form a varnish image desired by the user (Patent Document 1).

JP 2019-111813 Publication

However, conventionally, when a varnish image is formed over a toner image, there is a risk that the varnish may be repelled or smeared due to the wettability of the toner. In this specification, the wettability of the toner indicates the affinity of the varnish to the toner surface, in other words, the ease with which the varnish adheres. When the wettability of the toner is low, that is, when the toner is difficult to wet, the varnish is repelled and deviates from a predetermined landing position, and an image defect called "repelling" may occur in the varnished image. On the other hand, if the toner has high wettability, that is, it is easily wetted, the shape of the varnish, which is a droplet, is not maintained and spreads, which can cause an image defect called "bleeding" in the varnished image.

In view of the above problems, the present invention provides an image forming system that can suppress image defects in the varnish image due to the wettability of the toner when forming the varnish image on a recording material overlapping the toner image. With the goal.

An image forming system according to an embodiment of the present invention includes an image forming apparatus capable of forming a toner image on a recording material using toner containing wax, and a varnish image forming on one side of the recording material using a water-based varnish. an endless image-bearing belt that rotates while carrying a toner image; a first rotating body that comes into contact with an inner circumferential surface of the image-bearing belt; a second rotating body that is provided to sandwich the first rotating body and the image bearing belt and forms a transfer nip portion that transfers the toner image from the image bearing belt to the recording material while nipping and conveying the recording material; A voltage applying means capable of applying a voltage to a rotating body; and a voltage applying means capable of heating a recording material at a plurality of fixing temperatures, the toner image being fixed on the recording material by applying heat and pressure to the recording material on which the toner image has been formed. a fixing means; a reversing conveyance means capable of reversing the recording material that has passed through the fixing means and conveying it to the transfer nip; and a control means controlling the voltage application means and the reverse conveyance means; When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and When passing through the transfer nip portion with one surface facing toward the second rotating body, the voltage applying means applies a voltage equal to or higher than the discharge start voltage and of positive polarity when the fixing temperature is equal to or lower than a threshold value. is applied, and when the fixing temperature is higher than a threshold, a voltage of negative polarity that is equal to or higher than the discharge start voltage is applied, and then discharged to the varnish coating device so that a varnish image is formed on the one surface side. It is characterized by:

An image forming system according to an embodiment of the present invention includes an image forming apparatus capable of forming a toner image on a recording material using toner containing wax, and varnishing one side of the recording material using an oil-based varnish or a UV varnish. An image forming system comprising a varnish coating device capable of forming an image, the system comprising: an endless image carrying belt that rotates while carrying a toner image; and a first rotating body that comes into contact with an inner circumferential surface of the image carrying belt. and a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material. a voltage applying means capable of applying a voltage to the second rotating body; and a voltage applying means capable of heating the recording material at a plurality of fixing temperatures, applying heat and pressure to the recording material on which the toner image is formed to form a toner image on the recording material. a fixing means for fixing the recording material, a reversing conveying means capable of reversing the front and back of the recording material that has passed through the fixing means and conveying it to the transfer nip portion, and a control means controlling the voltage applying means and the reversing conveying means; When printing on one side of a recording material, a toner image is transferred to the one side of the recording material, the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section. When passing through the transfer nip portion with the one surface side facing the second rotating body, the voltage applying means causes the fixing temperature to be higher than the discharge starting voltage and negative electrode when the fixing temperature is below the threshold value. the varnish applying device such that when a voltage of positive polarity is applied and the fixing temperature is higher than a threshold value, a voltage of positive polarity that is equal to or higher than the discharge start voltage is applied, and then a varnish image is formed on the one surface side; It is characterized by being discharged to.

An image forming system according to an embodiment of the present invention includes an image forming apparatus capable of forming a toner image on a recording material using toner containing wax, and a varnish image forming on one side of the recording material using a water-based varnish. an endless image-bearing belt that rotates while carrying a toner image; a first rotating body that comes into contact with an inner circumferential surface of the image-bearing belt; a second rotating body that is provided to sandwich the first rotating body and the image bearing belt and forms a transfer nip portion that transfers the toner image from the image bearing belt to the recording material while nipping and conveying the recording material; A voltage applying means capable of applying a voltage to a rotating body; and a voltage applying means capable of heating a recording material at a plurality of fixing temperatures, the toner image being fixed on the recording material by applying heat and pressure to the recording material on which the toner image has been formed. a fixing means, a reversing conveyance means capable of reversing the recording material that has passed through the fixing means and conveying it to the transfer nip portion, and a control means controlling the voltage application means and the reversing conveyance means, When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and The sheet passes through the transfer nip portion with one side facing the second rotating body and no voltage is applied by the voltage applying means, and is further reversed by the reversing conveyance means to reach the transfer nip portion. When being re-transported and passing through the transfer nip portion with the one surface side facing the first rotating body, the voltage applying means causes the fixing temperature to be equal to or higher than the discharge starting voltage when the fixing temperature is equal to or lower than the threshold value. When the fixing temperature is higher than a threshold value, a voltage of negative polarity that is equal to or higher than the discharge start voltage is applied, and then the varnish is applied such that a varnish image is formed on the one surface side. It is characterized by being discharged to a coating device.

An image forming system according to an embodiment of the present invention includes an image forming apparatus capable of forming a toner image on a recording material using toner containing wax, and varnishing one side of the recording material using an oil-based varnish or a UV varnish. An image forming system comprising a varnish coating device capable of forming an image, the system comprising: an endless image carrying belt that rotates while carrying a toner image; and a first rotating body that comes into contact with an inner circumferential surface of the image carrying belt. and a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material. a voltage applying means capable of applying a voltage to the first rotating body; and a voltage applying means capable of heating the recording material at a plurality of fixing temperatures, applying heat and pressure to the recording material on which the toner image is formed to form a toner image on the recording material. a fixing means for fixing the recording material, a reversing conveying means capable of reversing the front and back of the recording material that has passed through the fixing means and conveying it to the transfer nip portion, and a control means controlling the voltage applying means and the reversing conveying means; When printing on one side of a recording material, a toner image is transferred to the one side of the recording material, the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section. is passed through the transfer nip portion with the one surface side facing the second rotating body and no voltage is applied by the voltage applying means, and is further reversed by the reversing conveyance means to transfer the transfer material. When being re-transported to the nip section and passing through the transfer nip section with the one surface side facing the first rotating body, the voltage applying means applies a discharge starting voltage when the fixing temperature is below a threshold value. If the voltage is above and has a negative polarity and the fixing temperature is higher than the threshold, a voltage that is equal to or higher than the discharge start voltage and has a positive polarity is applied, and then a varnish image is formed on the one surface side. The varnish coating device is then discharged to the varnish coating device.

According to the present invention, when forming a varnish image superimposed on a toner image on a recording material, it is possible to prevent image defects from occurring in the varnish image due to the wettability of the toner.

FIG. 1 is a schematic diagram showing the configuration of an image forming system. 5 is a graph showing the relationship between control voltage and film thickness regarding the formation of a varnish image. FIG. 1 is a block diagram showing a control configuration of an image forming system. 2 is a flowchart showing image forming processing during single-sided printing in which a toner image is formed on one side and varnish is applied on one side in an external power supply method. FIG. 2 is a schematic diagram illustrating a recording material conveyance flow for explaining discharge control during single-sided printing using an external power feeding method; (a) from toner image formation on one side (one side) to a double-sided conveyance unit; (b) double-sided conveyance; FIG. from the secondary transfer section to the reversal discharge section. 2 is a flowchart showing image forming processing during double-sided printing in which toner images are formed on both sides and varnish is applied to one side in an external power feeding method. FIG. 2 is a schematic diagram illustrating the conveyance flow of a recording material to explain discharge control during double-sided printing using an external power supply method, in which (a) from toner image formation on two sides to a duplex conveyance unit; (b) from a duplex conveyance unit; (c) From the reverse discharge section to the reverse discharge section via the double-sided transport section and the secondary transfer section via the secondary transfer section (no discharge). A graph showing the relationship between voltage and current applied to the secondary transfer section. 2 is a flowchart showing image forming processing during single-sided printing in which a toner image is formed on one side and varnish is applied on one side in the internal power feeding method. FIG. 3 is a schematic diagram illustrating the conveyance flow of a recording material to explain discharge control during single-sided printing using an internal power feeding method; (a) from toner image formation on one side (one side) to a double-sided conveyance unit; (b) double-sided conveyance; FIG. (c) From the reversal ejection section to the reversal ejection section via the double-sided conveyance section and the secondary transfer section. 2 is a flowchart showing image forming processing during double-sided printing in which toner images are formed on both sides and varnish is applied to one side in an internal power feeding method. FIG. 2 is a schematic diagram showing the conveyance flow of a recording material to explain discharge control during double-sided printing using an internal power feeding method; Via the secondary transfer section to the reversal discharge section.

[First embodiment]
First, the image forming system of this embodiment will be explained using FIG. 1. The image forming system 1X shown in FIG. 1 includes an image forming apparatus 100 that forms a toner image on a recording material S, and a varnish coater 200 that forms a varnish image on the recording material S. The varnish coater 200 is a post-processing unit that can be retrofitted to the image forming apparatus 100 for functional expansion, and the image forming apparatus 100 and the varnish coater 200 are connected so that the recording material S can be transferred thereto. Further, the image forming apparatus 100 and the varnish coater 200 are connected by a data input/output interface (not shown) so that control signals, data, etc. can be transmitted and received between them. The recording material S on which a toner image has been formed by the image forming apparatus 100 is conveyed to a varnish coater 200 for the purpose of improving the gloss, water resistance, abrasion resistance, etc. of the toner image formed on the recording material S. A varnish image is formed on the recording material S by the varnish coater 200 separately from the toner image. Formation of a varnish image by the varnish coater 200 will be described later.

Although not shown, the image forming system 1X may include other post-process units such as a relay device and a finisher device. The relay device is disposed between the image forming apparatus 100 and the varnish coater 200, and reverses the recording material S conveyed from the image forming apparatus 100 and sends it to the varnish coater 200, or temporarily stacks it and sends it to the varnish coater 200. or The finisher device performs, for example, a punching process to make holes in the recording material S, a stapling process to bundle a plurality of recording materials S and close the staples, etc. Eject to the output tray. In addition to such a post-processing unit, for example, a recording material supply device (not shown) capable of storing a large amount of recording material S therein is provided, and the recording material S is supplied from the recording material supply device to the image forming apparatus 100. Good too.

<Image forming device>
The image forming apparatus 100 will be explained. The image forming apparatus 100 is an electrophotographic tandem full-color printer. The image forming apparatus 100 includes image forming sections Pa, Pb, Pc, and Pd that form yellow, magenta, cyan, and black images, respectively. The image forming apparatus 100 forms a toner image on the recording material S based on image data sent from, for example, a document reading device (not shown) connected to the image forming apparatus 100 or an external device 1000 such as a personal computer. Examples of the recording material S include sheet materials such as plain paper, cardboard, rough paper, textured paper, and coated paper.

The image data includes toner image data regarding the toner image formed by the image forming apparatus 100 and data regarding the varnish image formed by the varnish coater 200. In the varnish image data, each varnish image is associated with the coordinates of the image forming area on the recording material S for each page, similarly to the toner image data.

The conveyance process of the recording material S of the image forming apparatus 100 will be described. The recording materials S are stored in a stacked manner in a cassette 10, and are sent out from the cassette 10 by a supply roller 13 in accordance with the image forming timing. The recording material S sent out by the supply roller 13 is conveyed to the registration roller 12 disposed in the middle of the conveyance path 114. After the recording material S is corrected for skew and timing by the registration roller 12, the recording material S is sent to the secondary transfer section T2. The secondary transfer portion T2 is a transfer nip portion formed by the inner secondary transfer roller 14 and the outer secondary transfer roller 11.

In contrast to the process of conveying the recording material S to the secondary transfer section T2 described above, a process of forming an image that is conveyed to the secondary transfer section T2 at a similar timing will be described. First, the image forming sections will be explained. In the image forming sections Pa, Pb, Pc, Pd, and Pe of each color, the toner used in the developing devices 1a, 1b, 1c, and 1d is yellow (Y), magenta (M), The configuration is almost the same except that cyan (C) and black (K) are different. Therefore, below, the black image forming section Pd will be explained as a representative, and the explanation of the other image forming sections Pa, Pb, and Pc will be omitted.

The image forming section Pd mainly includes a developing device 1d, a charging device 2d, a photosensitive drum 3d, a photosensitive drum cleaner 4d, an exposure device 5d, and the like. The surface of the rotated photosensitive drum 3d is uniformly charged in advance by a charging device 2d, and then an electrostatic latent image is formed by an exposure device 5d driven based on an image information signal. Next, the electrostatic latent image formed on the photosensitive drum 3d is developed into a toner image using a developer by the developing device 1d. Then, in response to a primary transfer voltage being applied to the primary transfer roller 6d disposed with the image forming portion Pd and the intermediate transfer belt 80 in between, the toner image formed on the photosensitive drum 3d is transferred to the intermediate transfer belt 80. Primary transfer is performed on top. A small amount of primary transfer residual toner remaining on the photosensitive drum 3d is collected by a photosensitive drum cleaner 4d.

The intermediate transfer belt 80 serving as an image bearing belt is an endless belt member, and is stretched by the secondary transfer inner roller 14 and tension rollers 15 and 16, and is driven in the direction of arrow R2. In the case of this embodiment, the tension roller 16 also serves as a drive roller that drives the intermediate transfer belt 80. The image forming process of each color, which is processed in parallel by the image forming units Pa to Pd, is performed at the timing of sequentially superimposing the toner image of the upstream color that has been primarily transferred onto the intermediate transfer belt 80. As a result, a full-color toner image is finally formed on the intermediate transfer belt 80, and as the intermediate transfer belt 80 rotates while carrying the toner image, the toner image is conveyed to the secondary transfer section T2. . Note that the secondary transfer residual toner after passing through the secondary transfer portion T2 is removed from the intermediate transfer belt 80 by the transfer cleaner 22.

A power source 403 that can be applied with variable polarity and voltage is connected to the secondary transfer outer roller 11 as the second rotating body, and the secondary transfer inner roller 14 as the first rotating body is connected to the ground potential (0V). connected (called external power supply method). When a secondary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer outer roller 11 by the power supply 403 as a voltage applying means, a transfer electric field is generated in the secondary transfer portion T2, and the intermediate transfer belt 80 is The carried toner image is transferred to the recording material S. For example, when a secondary transfer voltage of "1 to 7 kV" is applied by the power source 403, a current of "40 to 120 μA" flows through the secondary transfer portion T2.

For example, the secondary transfer outer roller 11 has an elastic layer made of, for example, ion conductive foam rubber (NBR rubber) on the outer periphery of a core metal, and is formed to have an outer diameter of 20 to 25 mm. Further, the secondary transfer outer roller 11 is set to have a resistance value of, for example, 1×10 ⁵ to 1×10 ⁸ Ω (environmental temperature 23° C., relative humidity 50% RH, 2 kV applied). ing.

Through the transport process and image forming process described above, the timings of the recording material S and the full-color toner image match in the secondary transfer portion T2, and the secondary transfer is performed. After that, the recording material S is conveyed to the fixing device 50. The fixing device 50 has a fixing roller 51 and a pressure roller 52, and a halogen heater 53 is arranged inside the fixing roller 51. The fixing roller 51 as a fixing rotating body is heated by a halogen heater 53 as a heating means. The halogen heater 53 can heat the fixing roller 51 by changing the temperature by being supplied with power from a heater power supply 54 serving as a power supply means. The pressure roller 52 as a pressure rotating body is moved by a contact/separation mechanism (not shown) between a pressure position where it contacts the fixing roller 51 and applies pressure, and a separated position where it does not contact the fixing roller 51. The fixing roller 51 is provided so as to be able to approach and separate from the fixing roller 51. When the pressure roller 52 comes into contact with the fixing roller 51, a fixing nip portion having a predetermined width is formed in the conveying direction of the recording material S.

A fixing device 50 serving as a fixing means nip and convey a recording material S on which a toner image has been formed in a fixing nip formed by a fixing roller 51 and a pressure roller 52, and applies heat and pressure to the recording material S. As a result, the toner image is fixed on the recording material S. That is, the toner of the toner image formed on the recording material S by heating and pressurization is melted and mixed, and fixed on the recording material S as a full-color image.

Although details will be described later, in this embodiment, when printing on one or both sides of the recording material S, after the toner image is fixed on the "varnished image forming surface", the recording material (as shown) to a switchback section 32 having a A switchback section 32 serving as a switchback unit performs switchback conveyance in which the leading edge and the trailing edge of the recording material S are exchanged to change the conveyance direction of the recording material S in order to exchange the front surface and the back surface of the recording material S. The recording material S is selectively sent from the switchback section 32 to either the double-sided conveying section 33 or the reversing and discharging section 31 . In this embodiment, the varnish coater 200 is capable of forming a varnish image only on one side of a predetermined recording material S, and one side of the recording material S on which a varnish image is to be formed is designated as "varnish image forming It is called "men".

When the recording material S is sent to the double-sided conveyance section 33, it is conveyed again toward the secondary transfer section T2 by the double-sided conveyance section 33, which serves as a double-sided conveyance means having conveyance rollers (not shown). When the recording material S passes through the secondary transfer section T2, it passes through the switchback section 32 and the double-sided conveyance section until the varnished image forming surface on which the toner image is formed faces the secondary transfer outer roller 11 side (second rotating body side). 33, it is repeatedly conveyed one or more times. On the other hand, when the recording material S is sent to a reversing and discharging section 31 as a reversing and discharging means, it is discharged to the varnish coater 200 by the reversing and discharging section 31 . The reversing and discharging section 31, the switchback section 32, and the double-sided conveying section 33 constitute a reversing conveying means that can reverse the front and back sides of the recording material S that has passed through the fixing device 50 and convey it to the secondary transfer section T2.

In this embodiment, when the recording material S passes through the secondary transfer portion T2 with the varnish image forming surface facing the secondary transfer outer roller 11 side, a predetermined voltage of a predetermined polarity is applied by the power source 403. Thereafter, the recording material S that has passed through the fixing device 50 is conveyed again depending on the case, so that the varnish image forming surface is directed toward the position detection section 245, varnish discharge section 246, and varnish solidification section 247 side of the varnish coater 200. and is discharged to the varnish coater 200.

The intermediate transfer belt 80 has, for example, a volume resistivity of "5 x 10 ⁸ to 1 x 10 ¹⁴ Ωcm" (23°C, 50% RH), a hardness of MD-1 hardness of "60 to 85°" (23°C , 50%RH). Further, the static friction coefficient is set to "0.15 to 0.6" (23° C., 50% RH). The intermediate transfer belt 80 is formed into a three-layer structure including a base layer, an elastic layer, and a surface layer from the back surface side that the secondary transfer inner roller 14 comes into contact with.

The base layer is made of a material such as a resin such as polyimide or polycarbonate, or a resin made of various rubbers containing carbon black as an antistatic agent, and is formed to have a thickness of 0.05 to 0.15 mm. The elastic layer is made of a material made of various rubbers such as urethane rubber and silicone rubber containing an ion conductive agent, and is formed to have a thickness of 0.1 to 0.5 mm. The surface layer is made of a resin material such as fluororesin, and is formed to have a thickness of 0.0002 to 0.02 mm. The base material of the surface layer is one type of material such as polyurethane, polyester, or epoxy resin, or two or more types of elastic materials such as elastic material rubber, elastomer, butyl rubber, etc. In order to reduce surface energy and improve lubricity, a surface layer is formed on this base material by dispersing one or more types of powder or particles such as fluororesin, or with different particle sizes. be done.

<Developer>
In this embodiment, a two-component developer containing toner and carrier is used. The toner contains a binder resin, a colorant, and a release agent. A known binder resin can be used. For example, vinyl copolymers such as styrene-(meth)acrylic copolymers, polyester resins, hybrid resins in which vinyl copolymers and polyesters are chemically bonded, epoxy resins, and styrene-butadiene copolymers. Other resins can be used. As the colorant, known colorants can be used for yellow (Y), magenta (M), cyan (C), and black (K).

Examples of mold release agents include aliphatic hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight olefin copolymer wax, microcrystalline wax, Fischer-Tropsch wax, and paraffin wax, and aliphatic hydrocarbon waxes such as oxidized polyethylene wax. Wax oxides or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax and montanic acid ester wax; synthetic reactions between higher fatty acids and higher alcohols such as behenyl behenate and behenyl stearate. Examples include ester waxes, which are natural products, and fatty acid esters that have been partially or completely deoxidized, such as deoxidized carnauba wax.

<varnish coater>
Next, the varnish coater 200 will be explained using FIGS. 1 and 2. The varnish coater 200 is an inkjet type varnish coating device that can eject varnish onto the surface of the recording material S to form a varnish image such as characters, line drawings, and figures desired by the user in addition to the toner image. In the case of the inkjet method, by ejecting droplets of varnish toward the recording material S, the varnish is adhered to the recording material S and a varnish image is formed. The varnish coater 200 can form a varnish image on the recording material S based on varnish image data included in the image data.

The varnish coater 200 includes a sheet conveyance section 241, a position detection section 245, a varnish discharge section 246, and a varnish solidification section 247. The sheet conveyance unit 241 conveys the recording material S while adsorbing it to the belt conveyance surface using an air suction device (not shown) that passes through holes formed in the conveyance belt 242 . Along the sheet conveying path of the sheet conveying section 241, a position detecting section 245, a varnish discharging section 246, and a varnish solidifying section 247 are installed in order from the upstream side to the downstream side in the conveying direction of the recording material S (arrow X direction). It is arranged. The position detection unit 245 is a detection unit using, for example, a charge-coupled device (CCD), and detects the position of the leading edge of the recording material S in the conveyance direction and the conveyance direction with respect to the recording material S attracted onto the belt conveyance surface and conveyed. The positions of both ends in the width direction intersecting with the recording material S and the position of the toner image on the recording material S are detected. By detecting the position of the toner image by the position detection unit 245, the varnish coater 200 can overprint the varnish image on the toner image.

The varnish discharge section 246 forms a varnish image on the recording material S by discharging varnish onto one side of the recording material S transported by the sheet transport section 241 . The varnish discharge section 246 has a plurality of print heads (not shown). The print head is, for example, a line type head, and a plurality of ejection ports (not shown) intersect with the conveyance direction of the recording material S over a range that covers the maximum width of the recording material S on which an image can be formed by the varnish coater 200. They are arranged side by side in the width direction. As the varnish ejection method of the print head, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS element, etc. may be adopted. Although not shown, varnish is supplied from the tank to the print head via tubes.

The film thickness of the varnish image depends on the amount of varnish applied per unit area to the recording material. The amount of varnish applied can be varied by adjusting the amount of varnish discharged from the print head. For example, in the case of a method using a piezo element, as shown in Figure 2, the amount of varnish discharge changes as the control voltage is adjusted, and the varnish image changes as the amount of varnish discharge per unit area increases or decreases. The film thickness is adjusted. In the case of this embodiment, the film thickness of the varnish image is adjusted to a range of, for example, "5 to 100 μm", preferably "10 to 70 μm".

Further, the resolution of the varnish image that can be formed by the varnish coater 200 is, for example, "600 dpi", and in that case, the line width of the varnish image is adjusted in units of "600 dpi". Note that the range of the film thickness of the varnish image, the resolution of the varnish image, and the adjustment range of the line width may be changed as appropriate depending on the varnish ejection method of the print head in the varnish coater 200, the type of varnish, etc.

In the case of this embodiment, water-based varnish, oil-based varnish, or the like is used as the varnish. Aqueous varnish, for example, has a latex emulsion as its main component and contains water, amino alcohol, a conditioning agent, and the like. Examples of latex emulsions include styrene/acrylic emulsions, acrylic emulsions, and polyester emulsions. Amino alcohols are used to adjust the pH of varnishes and are mixed in varnish compositions to adjust the varnish to "pH 8 to pH 10." Amino alcohol refers to a compound having an amino group(s) bonded to, for example, an alkyl alcohol or an aryl alcohol. Examples of the adjusting agent include surfactants that adjust the surface tension of the varnish. Examples include anionic surfactants, nonionic surfactants, silicone surfactants, and fluorosurfactants. The content of each of these components is not particularly limited, but water-based varnishes include, for example, latex emulsion of "40 to 95% by weight", water of "5 to 30%", ammonia of "1 to 5% by weight", and "0.1% by weight" of ammonia. Contains ~5% of conditioning agents. As the water-based varnish, for example, "Aqua Pack Varnish (trade name)" (manufactured by T&K TOKA Co., Ltd.) is used.

Oil-based varnish contains resin, solvent, drying oil, etc. as its main ingredients. Examples of the resin include rosin-modified phenol resin, rosin-modified maleic acid resin, and the like. Examples of the solvent include mineral oils such as light oil, petroleum solvents such as paraffin solvents, and the like. Drying oils include, for example, vegetable oils such as linseed oil. The oil-based varnish only needs to contain one kind of these, and may contain two or more kinds. The content of each of these components is not particularly limited, but the oil-based varnish contains, for example, "20 to 30% by mass" of resin, "10 to 20% by mass" of solvent, and "30 to 40% by mass" of drying oil. As the oil-based varnish, for example, "Best Dry OP Varnish (trade name)" or "Best One Matte OP Varnish (trade name)" (manufactured by T&K TOKA Co., Ltd.) can be used.

Returning to FIG. 1, the recording material S on which a varnish image has been formed on one side by the varnish discharge section 246 is sent by the sheet conveying section 241 to the varnish solidifying section 247 on the downstream side in the conveying direction. Hardening of the varnish on S takes place. The varnish solidifying unit 247 solidifies the varnish image formed on the recording material S by emitting infrared rays (infrared light) of a wavelength corresponding to the varnish using, for example, an infrared lamp. Alternatively, the varnish solidification unit 247 solidifies the varnish image by blowing hot air onto the recording material S to dry the varnish. In this way, the varnish image can be overprinted over the toner image.

Next, the control configuration of the image forming system 1X will be described using FIG. 3 while referring to FIG. 1. In this embodiment, an example will be given in which the image forming apparatus 100 centrally manages and controls operation commands to the varnish coater 200. Note that various devices such as a motor and a power source are connected to the main control section 101 and varnishing control section 330, which will be described later, in addition to those shown in FIG. Omitted.

In the image forming system 1X of this embodiment, as shown in FIG. 3, the varnishing control unit 330 can communicate operation commands, various data, etc. to the main control unit 101 as a control means via communication units 501 and 502. It is connected. The varnish processing control section 330 operates the varnish coater 200 according to the operation command from the main control section 101. That is, the main control unit 101 can control the entire image forming system 1X including the varnish coater 200 by transmitting operation commands and various data to the varnish coater 200 while controlling the operation of the image forming apparatus 100.

The main control section 101 and the varnishing control section 330 described above may have the same configuration. For example, each has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory).

The main control unit 101 includes a CPU 102, a ROM 103, and a RAM 104. The ROM 103 stores various programs such as "image forming processing" (for example, see FIGS. 4 and 6), which will be described later. The RAM 104 stores various data such as image data obtained from the operation unit 110 or the external device 1000 (see FIG. 1), for example. Note that the RAM 104 can also temporarily store the results of arithmetic processing associated with the execution of various programs.

The image forming apparatus 100 includes, for example, an operation section 110 having a liquid crystal display section 111 (see FIG. 1), and the operation section 110 is connected to the main control section 101. The operation unit 110 is, for example, a touch panel. The operation unit 110 is capable of displaying various screens presenting various programs and data on the liquid crystal display unit 111, and accepts inputs to start various programs, input various data, etc. in response to a screen touch operation by the user. A screen including various buttons, switches, etc. as software keys is displayed on the touch panel.

The user can input the start of various programs such as an image forming job from the operation unit 110. At this time, the user can input the type (plain paper, coated paper, etc.) and size (A3 landscape, A4 portrait, etc.) of the recording material S, and whether to perform single-sided printing or double-sided printing. When the start of an image forming job is input, the CPU 102 executes an "image forming process (program)" (see FIGS. 4 and 6 described later) stored in the ROM 103.

The main control unit 101 also includes a power supply 403, a voltage detection sensor 403a that detects the output voltage of the power supply 403, and a current detection sensor 403b that detects the output current flowing between the power supply 403 and the secondary transfer outer roller 11. is connected. The main control unit 101 controls the power supply 403 according to the detection results of the voltage detection sensor 403a and the current detection sensor 403b during an image forming job. Further, a heater power supply 54 is connected to the main control unit 101, and the main control unit 101 determines that the surface temperature of the fixing roller 51 is, for example, “140 to 190° C.” as a fixing temperature at which the toner image can be fixed to the recording material S. The heater power source 54 can be controlled so that the desired temperature is within the range of . The fixing temperature is set to a predetermined temperature that is predetermined according to the basis weight of the recording material S in order to achieve both the fixability of the toner on the recording material S and the gloss of the toner image after fixing. The main control unit 101 heats the recording material S at a fixing temperature based on the basis weight corresponding to the type of the recording material S inputted from the operation unit 110, for example, among a plurality of fixing temperatures stored in the ROM 103 in advance. Controls the heater power supply 54.

The varnishing control unit 330 includes a CPU 331, a ROM 332, and a RAM 333. The CPU 331 operates the sheet conveyance section 241, position detection section 245, varnish discharge section 246, and varnish solidification section 247 of the varnish coater 200 based on a control program stored in the ROM 332. When the varnish processing control unit 330 receives the varnish image data from the main control unit 101, it stores the received varnish image data in the RAM 333, and controls the varnish coater 200 to form a varnish image on the recording material S based on this varnish image data. control.

By the way, as already mentioned, conventionally, when a varnish image is formed on a recording material overlapping a toner image, there is a risk that image defects called "repelling" or "bleeding" may occur in the varnish image. The reason why ``repelling'' and ``bleeding'' occur in varnish images is due to the wettability of the toner that overlays the varnish images. In general, wettability indicates the ease with which a liquid (here, varnish) adheres to a solid surface (here, the toner surface) (affinity), and is evaluated by the magnitude of the contact angle between the liquid and the recording material S.

The larger the above contact angle, the lower the wettability and the easier the varnish will be repelled. "Repelling" of varnish is a phenomenon that occurs when varnish is discharged at a location where wettability is low, that is, the contact angle is greater than 90 degrees, and the varnish deviates from a predetermined landing position (coordinates). On the other hand, the smaller the above contact angle is, the higher the wettability is, and the more easily the varnish bleeds. The "bleeding" of varnish is caused by the fact that when varnish is discharged onto an area where wettability is high, i.e. where the contact angle is smaller than 90 degrees, the varnish cannot maintain its shape as a droplet and the shape collapses. . As mentioned above, the toner contains wax as a release agent, and the wax can be precipitated on the toner surface by heat during fixing. The wettability of the toner can be lowered or increased depending on the degree of wax precipitation.

<Image formation processing>
Therefore, in this embodiment, it is possible to suppress the occurrence of image defects such as the above-mentioned "repelling" and "bleeding" in the varnish image. First, the "image forming process" in the case of the external power feeding method will be described using FIGS. 4 to 8 while referring to FIGS. 1 and 3. FIG. 4 is a flowchart showing an image forming process during single-sided printing in which a toner image is formed only on one side and varnish is applied to the other side in the external power supply method. The "image forming process" is started by the main control unit 101 in response to an input to start an image forming job, and is repeated until the end of the image forming job. In the following description, an example will be explained in which one side of the recording material S on which the toner image M1 is formed is a "varnish image forming surface."

As shown in FIG. 4, the main control unit 101 transfers the toner image M1 to the intermediate transfer belt 80 to be transferred onto one side (one side) of the recording material S based on the image data stored in the RAM 104 upon the start of the image forming job. (S1). The main control unit 101 secondarily transfers the toner image M1 from the intermediate transfer belt 80 to the recording material S at the secondary transfer unit T2 (S2). When transferring the toner image M1 from the intermediate transfer belt 80 to the recording material S, the main control unit 101 causes the power supply 403 to apply a secondary transfer voltage having a polarity opposite to the charging polarity of the toner to the secondary transfer outer roller 11. For example, when the charging polarity of the toner is negative, a positive secondary transfer voltage is applied to the secondary transfer outer roller 11 .

The main control unit 101 applies heat and pressure to the recording material S by the fixing device 50 to fix the toner image M1 on one side of the recording material S (S3), and then transfers the toner image M1 to the double-sided conveyance unit via the switchback unit 32. 33 (S4). Conventionally, after the toner image M1 is fixed, the recording material S is delivered to the varnish coater 200. On the other hand, in this embodiment, after the toner image M1 is fixed, the recording material S is conveyed to the double-sided conveyance section 33 via the switchback section 32, as shown in FIG. 5(a).

Then, the main control unit 101 transports the recording material S again to the secondary transfer unit T2 using the double-sided transport unit 33 (S5). The recording material S is reversed by the switchback section 32 and passes through the secondary transfer section T2 with one side on which the toner image M1 is formed facing the secondary transfer outer roller 11 side, as shown in FIG. 5(b). . The main control unit 101 causes the power supply 403 to apply a predetermined voltage to the secondary transfer outer roller 11 when the recording material S passes through the secondary transfer section T2, so that the secondary transfer outer roller 11 and the recording material S are connected to each other. In the meantime, a discharge process is performed to generate a discharge (S6). The discharge treatment is performed to form a film on the surface of the toner by electrical discharge and change the wettability of the toner, that is, the adhesion force with the varnish on the surface of the toner. The voltage applied to perform the discharge treatment will be described later (see Tables 1 and 2).

The main control unit 101 transports the recording material S that has been subjected to the discharge treatment to the fixing device 50 . The main control unit 101 sets the pressure roller 52 in the fixing device 50 to a non-pressure state by separating it from the fixing roller 51 in order to pass the recording material S after the discharge treatment (S7). In other words, the recording material S passes through the fixing device 50 without being subjected to heat or pressure. The main control unit 101 transports the recording material S that has passed through the fixing device 50 to the varnish coater 200 (S8). At that time, as shown in FIG. 5(b), the one side on which the toner image M1 has been fixed is transported through the varnish coater 200 with the side facing the position detection unit 245, varnish discharge unit 246, and varnish solidification unit 247. After the recording material S is reversed by the switchback section 32, the recording material S is delivered to the varnish coater 200 by the reverse discharge section 31.

FIG. 6 is a flowchart showing an image forming process during double-sided printing in which toner images are formed on both the first side and the second side and varnish is applied to the first side in the external power supply method. In order to make the explanation easier to understand, FIG. 6 shows the subsequent steps of fixing the toner image M1 on one side of the recording material S and then forming the toner image M2 on the second side.

As shown in FIG. 6, after fixing the toner image M1 on one side, the main control unit 101 forms a toner image M2 on the intermediate transfer belt 80 to be transferred to the second side of the recording material S (S11). The main control unit 101 secondarily transfers the toner image M2 from the intermediate transfer belt 80 to the recording material S at the secondary transfer unit T2 (S12). When transferring the toner image M2 from the intermediate transfer belt 80 to the recording material S, the main control unit 101 causes the power supply 403 to apply a secondary transfer voltage having a polarity opposite to the charged polarity of the toner to the secondary transfer outer roller 11.

The main control unit 101 applies heat and pressure to the recording material S using the fixing device 50 to fix the toner image M2 on two sides of the recording material S (S13), and then transports both sides through the switchback unit 32. The recording material S is conveyed to the section 33 (S14). In this embodiment, after the toner image M2 is fixed, the recording material S is conveyed to the double-sided conveyance section 33 via the switchback section 32, as shown in FIG. 7(a).

Then, the main control unit 101 transports the recording material S again to the secondary transfer unit T2 using the double-sided transport unit 33 (S15). As shown in FIG. 7B, the recording material S on which toner images (M1, M2) are formed on both sides is rotated with the second side on which the toner image M2 is formed facing the secondary transfer outer roller 11 side. It passes through the next transfer section T2. At this time, the main control unit 101 is in a non-applying state in which no voltage is applied to the secondary transfer outer roller 11 by the power source 403 (S16). That is, the above-described discharge treatment is not performed. Further, the main control unit 101 sets the pressure roller 52 in a non-pressure state by separating it from the fixing roller 51 so that the recording material S passes through the fixing device 50 without applying heat or pressure (S17). .

The main control unit 101 transports the recording material S that has passed through the fixing device 50 to the double-sided transport unit 33 via the switchback unit 32 (S18), and transports the recording material S again to the secondary transfer unit T2 by the double-sided transport unit 33 (S18). S19). Here, the second re-conveyance is performed by passing through the secondary transfer section T2 with one side on which the toner image M1 is formed facing the secondary transfer outer roller 11 side, as shown in FIG. 7(c). It's for a reason. The main control unit 101 causes the power supply 403 to apply a predetermined voltage to the secondary transfer outer roller 11 when the recording material S passes through the secondary transfer section T2, so that the secondary transfer outer roller 11 and the recording material S are connected to each other. In the meantime, a discharge process is performed to generate a discharge (S20).

The main control unit 101 transports the recording material S that has been subjected to the discharge treatment to the fixing device 50 (S21). The main control unit 101 maintains the fixing device 50 in a non-pressurized state (S21) in order to allow the recording material S to pass through the fixing device 50 without applying heat or pressure to the recording material S after the discharge treatment. The recorded recording material S is conveyed to the varnish coater 200 (S22). At that time, as shown in FIG. 7(c), the one side on which the toner image M1 is fixed is conveyed through the varnish coater 200 with the side facing the position detection unit 245, varnish discharge unit 246, and varnish solidification unit 247. After the recording material S is reversed by the switchback section 32, the recording material S is delivered to the varnish coater 200 by the reverse discharge section 31.

The polarity of the predetermined voltage applied to the secondary transfer outer roller 11 for the above-mentioned discharge processing (see S6 in FIG. 4 and S20 in FIG. 6) will be described. In this embodiment, as shown in Table 1, the polarity of the voltage applied to the secondary transfer outer roller 11 by the power source 403 is controlled depending on whether "repelling" or "bleeding" is suppressed depending on the type of varnish. change.

Poor toner wettability can cause water-based varnish to "repel". In order to suppress "repelling" of the water-based varnish, a negative voltage is applied to the secondary transfer outer roller 11 to perform a discharge process. In this case, a film of negative ions is generated on the surface of the toner, and the wettability of the toner can be increased compared to before performing the discharge treatment. That is, the energy due to the discharge that occurs when a predetermined voltage is applied acts on the toner, increasing the surface energy of the toner, and the surface of the toner becomes activated, that is, becomes a radical. In that case, since polar groups are generated on the toner surface, the adhesion force with the water-based varnish becomes greater than before the discharge treatment.

On the other hand, high wettability of the toner can result in "bleeding" of the water-based varnish. In order to suppress "bleeding" of the water-based varnish, a positive voltage is applied to the secondary transfer outer roller 11 to perform a discharge process. In this case, a film of positive ions is generated on the surface of the toner and radicals are suppressed, so that the wettability of the toner can be lowered than before the discharge treatment. That is, the polar groups on the surface of the toner react with each other due to the discharge, and the surface energy of the toner decreases, so that the wettability of the toner can be lowered.

On the other hand, in the case of oil-based varnish, a voltage of the opposite polarity is applied as in the case of water-based varnish. That is, in order to suppress "repelling" of the oil-based varnish, a voltage of negative polarity is applied to the secondary transfer outer roller 11, and in order to suppress "bleeding" of the oil-based varnish, a voltage of positive polarity is applied to the outer secondary transfer roller 11. A voltage is applied to the roller 11.

Furthermore, the "repellency" and "bleeding" of water-based varnishes and oil-based varnishes are affected by the wax contained in the toner. Wax may be deposited on the toner surface due to the heat generated by the fixing device 50, and whether "bleeding" or "repelling" occurs depends on the degree of wax deposition. If the degree of wax precipitation is small, water-based varnishes tend to bleed, while oil-based varnishes tend to splatter. On the other hand, if the degree of wax precipitation is large, water-based varnishes tend to "repel" and oil-based varnishes tend to "bleed". This is because oil-based varnishes have properties (water repellency) that are more similar to wax than water-based varnishes.

The degree of wax precipitation in such a toner is determined by the fixing temperature at which the toner image is fixed. In the toner, when the fixing temperature is below a threshold value (for example, 140 to 190° C.), the degree of wax precipitation is small, and when the fixing temperature is higher than the threshold value, the degree of wax precipitation is large.

From the above point of view, in the case of water-based varnish, "bleeding" is likely to occur when the fixing temperature is below the threshold value. is applied to In addition, in the case of water-based varnish, "repelling" is likely to occur when the fixing temperature is higher than a threshold value, so in order to suppress "repelling" of the water-based varnish, a voltage of negative polarity is applied to the secondary transfer outer roller 11. Ru.

On the other hand, in the case of oil-based varnish, "repelling" is likely to occur when the fixing temperature is below the threshold value, so in order to suppress "repelling" of the oil-based varnish, a voltage of negative polarity is applied to the secondary transfer outer roller 11. be done. In addition, in the case of oil-based varnish, "bleeding" is likely to occur when the fixing temperature is higher than a threshold value, so in order to suppress "bleeding" of oil-based varnish, a positive voltage is applied to the secondary transfer outer roller 11. Ru.

Next, the voltage applied to the secondary transfer outer roller 11 for the above-mentioned discharge process will be described. FIG. 8 shows the applied voltage (V) of the power source 403 detected by the voltage detection sensor 403a and the current detection sensor 403b when the secondary transfer outer roller 11 with a resistance value of 5×10 ⁶ (Ω) is used. The relationship between the amount of current (μA) detected by is shown.

The inventors conducted experiments to determine whether "repelling" or "bleeding" occurs in varnish images using water-based varnish and oil-based varnish. In the experiment, the recording material S on which the monochromatic black solid toner image was fixed was re-transported, different voltages were applied for discharge treatment, and the recording material S was passed through the secondary transfer section T2. When processing was performed on the toner image, it was visually confirmed whether "repelling" or "bleeding" occurred on the varnish image. Table 2 shows the experimental results. As the recording material S, an A3 size "OK Top Coat + 127.9 g/m ² (manufactured by Oji Paper)" was used.

As shown in Table 2, for both the water-based varnish and the oil-based varnish, "repelling" and "bleeding" occurred in the varnish image when "no application" was applied, that is, when no discharge treatment was performed. On the other hand, in the case of water-based varnish, when a negative polarity voltage with a current amount of "-60 to -40 μA" is applied, "repelling" does not occur, and when a positive polarity voltage with a current amount of "40 to 60 μA" is applied. No "bleeding" occurred when voltage was applied. On the other hand, in the case of oil-based varnish, no "bleeding" occurs when a negative polarity voltage with a current amount of "-60 to -40 μA" is applied, and a positive polarity voltage with a current amount of "40 to 60 μA" is applied. When the voltage was applied, "repelling" did not occur.

In view of the above experimental results, in this embodiment, when performing the above discharge process, the power supply 403 applies a voltage higher than the discharge start voltage through which a current of "40 μA" or more and "60 μA" or less in absolute value flows. As shown in FIG. 8, the voltage value at which a current of "40 μA" or more and "60 μA" or less flows in absolute value is, for example, "2200 V" or more and "2800 V" or less in absolute value. In this way, by applying a voltage that causes a current with an absolute value of 40 μA or more to flow, it is possible to change the wettability of the toner as described above, thereby suppressing the occurrence of "repelling" or "bleeding" on the varnish image. can. Note that it is not preferable to apply a voltage that causes a current larger than the absolute value "60 μA" to flow, since deterioration of the secondary transfer outer roller 11 may be accelerated due to discharge and the life of the secondary transfer outer roller 11 may be shortened.

As described above, in the present embodiment, the recording material S on which the toner image is fixed to the varnish image forming surface on which the varnish image is formed is transferred to the secondary transfer outer roller 11 by applying a voltage higher than the discharge voltage to the recording material S. It is conveyed again to section T2, and discharge is generated on the varnish image forming surface side on which the toner image has been formed. In the toner image formed on the varnish image forming surface side, positive ions and negative ions appear in the toner due to discharge, and the surface of the toner image is coated with a film of these ions. In the case of water-based varnish, if the fixing temperature is below a threshold value and "bleeding" is likely to occur, a film of positive ions is formed to reduce the adhesion between the toner image and the water-based varnish. On the other hand, if the fixing temperature is higher than the threshold value and "repelling" due to wax is likely to occur, a film of negative ions is formed to improve the adhesion between the toner image and the water-based varnish. In the case of oil-based varnish, a voltage of the opposite polarity to that of the water-based varnish described above is applied to cause discharge to occur on the varnish image forming surface on which the toner image is formed. By performing this discharge treatment, it is possible to suppress image defects such as "bleeding" and "repelling" from occurring in the varnish image when forming the varnish image on the recording material overlapping the toner image.

[Second embodiment]
In the above-described first embodiment, an example has been described of an external power supply method in which a secondary transfer voltage is applied to the secondary transfer outer roller 11 to form a transfer electric field in the secondary transfer portion T2, but the present invention is not limited to this. The embodiment described above uses a method (internal power feeding method) in which a secondary transfer voltage is applied to the inner secondary transfer roller 14 that contacts the inner peripheral surface of the intermediate transfer belt 80 in order to form a transfer electric field in the secondary transfer portion T2. ) may also be applied. Below, regarding the second embodiment of the internal power supply system, mainly the points different from the above-described first embodiment will be described.

First, an internal power feeding type image forming apparatus will be briefly described. In the case of the internal power feeding method, a power source 403 with variable polarity and voltage is connected to the secondary transfer inner roller 14, and the secondary transfer outer roller 11 is connected to the ground potential (0V) (see FIG. 10(a) described later). reference). When a secondary transfer voltage having the same polarity as the charged polarity of the toner is applied to the secondary transfer inner roller 14 by the power source 403, a transfer electric field is generated in the secondary transfer portion T2, and the toner carried on the intermediate transfer belt 80 is The image is transferred to the recording material S. Note that the inner secondary transfer roller 14 may have the same configuration as the outer secondary transfer roller 11 described above. The main control unit 101 also includes a power supply 403, a voltage detection sensor 403a that detects the output voltage of the power supply 403, and a current detection sensor 403b that detects the output current flowing between the power supply 403 and the secondary transfer inner roller 14. It is connected.

Next, the "image forming process" in the internal power supply system will be explained using FIGS. 9 to 12(b) while referring to FIG. 3. FIG. 9 is a flowchart showing an image forming process during double-sided printing in which toner images are formed on both the first side and the second side and varnish is applied to the first side in the internal power feeding method. In order to make the explanation easier to understand, FIG. 9 shows the subsequent steps of fixing the toner image M1 on one side of the recording material S and then forming the toner image M2 on the second side. Here, a case where one side of the recording material S on which the toner image M1 is formed is the "varnish image forming surface" will be described as an example. Note that in the image forming process of the second embodiment shown in FIG. 9, the same steps as the image forming process of the first embodiment described above (see FIG. 6) are given the same step numbers, and the explanation will be simplified or omitted. .

As shown in FIG. 9, the main control unit 101 forms a toner image M1 on the intermediate transfer belt 80 to be transferred to one side of the recording material S (S41). The main control unit 101 secondarily transfers the toner image M1 from the intermediate transfer belt 80 to the recording material S at the secondary transfer unit T2 (S12). When transferring the toner image M1 from the intermediate transfer belt 80 to the recording material S, the main control unit 101 causes the power supply 403 to apply a secondary transfer voltage having the same polarity as the charging polarity of the toner to the secondary transfer inner roller 14.

The main control unit 101 applies heat and pressure to the recording material S by the fixing device 50 to fix the toner image M1 on one side of the recording material S (S13), and then transfers the toner image M1 to the double-sided conveyance unit via the switchback unit 32. 33 (S14). In this embodiment, after the toner image M1 is fixed, the recording material S is conveyed to the double-sided conveyance section 33 via the switchback section 32, as shown in FIG. 10(a).

Then, the main control unit 101 transports the recording material S again to the secondary transfer unit T2 using the double-sided transport unit 33 (S15). As shown in FIG. 10(b), the recording material S with the toner image M1 formed on the first surface is placed at the secondary transfer section with the first surface side on which the toner image M1 is formed facing the secondary transfer outer roller 11 side. Pass T2. At this time, the main control unit 101 is in a non-applying state in which no voltage is applied to the secondary transfer inner roller 14 by the power source 403 (S16). In other words, the above-described discharge treatment is not performed. Further, the main control unit 101 sets the pressure roller 52 in a non-pressure state by separating it from the fixing roller 51 so that the recording material S passes through the fixing device 50 without applying heat or pressure (S17). .

The main control unit 101 transports the recording material S that has passed through the fixing device 50 to the double-sided transport unit 33 via the switchback unit 32 (S18), and transports the recording material S again to the secondary transfer unit T2 by the double-sided transport unit 33 (S18). S19). As a result, as shown in FIG. 10C, the recording material S passes through the secondary transfer portion T2 with one side on which the toner image M1 is formed facing the inner secondary transfer roller 14 side. The main control unit 101 causes the power source 403 to apply a predetermined voltage to the secondary transfer inner roller 14 when the recording material S passes through the secondary transfer portion T2, so that the secondary transfer inner roller 14 and the recording material S are connected to each other. In the meantime, a discharge process is performed to generate a discharge (S20). Note that the polarity of the predetermined voltage applied to the secondary transfer inner roller 14 by the power source 403 is determined based on whether the varnish is water-based or oil-based, and whether the fixing temperature is below the threshold value or above the threshold value in the first embodiment described above. The voltage value is the same as in the first embodiment described above.

The main control unit 101 transports the recording material S that has been subjected to the discharge treatment to the fixing device 50 (S21). The main control unit 101 maintains the fixing device 50 in a non-pressurized state (S21) in order to allow the recording material S to pass through the fixing device 50 without applying heat or pressure to the recording material S after the discharge treatment. The recorded recording material S is conveyed to the varnish coater 200 (S22). In the case of the internal power feeding method, as shown in FIG. 10C, the recording material S is delivered to the varnish coater 200 by the reversing and discharging section 31 without being reversed by the switchback section 32. This is because the one side on which the toner image M1 is fixed faces the position detection section 245, varnish discharge section 246, and varnish solidification section 247 side by the second re-transport (see S19).

FIG. 11 is a flowchart showing an image forming process during double-sided printing in which toner images are formed on both the first side and the second side and varnish is applied to the first side in the internal power feeding method. In order to make the explanation easier to understand, FIG. 11 shows the subsequent steps of fixing the toner image M1 on one side of the recording material S and then forming the toner image M2 on the second side.

As shown in FIG. 11, after fixing the toner image M1 on one side, the main control unit 101 forms a toner image M2 on the intermediate transfer belt 80 to be transferred to the second side of the recording material S (S31). The main control unit 101 secondarily transfers the toner image M2 from the intermediate transfer belt 80 to the recording material S at the secondary transfer unit T2 (S2).

The main control unit 101 applies heat and pressure to the recording material S by the fixing device 50 to fix the toner image M2 on two sides of the recording material S (S3), and then transports both sides through the switchback unit 32. The recording material S is conveyed to the section 33 (S4). After the toner image M2 is fixed, the recording material S is conveyed to the double-sided conveyance section 33 via the switchback section 32, as shown in FIG. 12(a).

Then, the main control unit 101 transports the recording material S again to the secondary transfer unit T2 using the double-sided transport unit 33 (S5). As shown in FIG. 12(b), the recording material S on which toner images (M1, M2) are formed on both sides is subjected to secondary transfer with one side on which the toner image M1 is formed facing the secondary transfer inner roller 14 side. It passes through the transfer section T2. The main control unit 101 causes the power source 403 to apply a predetermined voltage to the secondary transfer inner roller 14 when the recording material S passes through the secondary transfer portion T2, so that the secondary transfer inner roller 14 and the recording material S are connected to each other. In the meantime, a discharge process is performed to generate a discharge (S6). Note that the polarity of the predetermined voltage applied to the secondary transfer inner roller 14 by the power source 403 is determined based on whether the varnish is water-based or oil-based, and whether the fixing temperature is below the threshold value or above the threshold value in the first embodiment described above. The voltage value is the same as in the first embodiment described above.

The main control unit 101 transports the recording material S that has been subjected to the discharge treatment to the fixing device 50 . The main control unit 101 sets the pressure roller 52 in the fixing device 50 to a non-pressure state by separating it from the fixing roller 51 in order to pass the recording material S after the discharge treatment (S7). The main control unit 101 transports the recording material S that has passed through the fixing device 50 to the varnish coater 200 (S8). In the case of the internal power feeding method, as shown in FIG. 12(b), the recording material S is delivered to the varnish coater 200 by the reversing and discharging part 31 without being reversed by the switchback part 32. This is because the one side on which the toner image M1 has been fixed faces the position detection section 245, varnish discharge section 246, and varnish solidification section 247 due to the re-conveyance described above (see S5).

As described above, in the case of the internal power feeding method, it is necessary to direct the side on which the toner image M1 is formed toward the secondary transfer inner roller 14 side instead of the secondary transfer outer roller 11 side. Compared to the case of the power feeding method, the procedure for re-conveying the recording material S is different. On the other hand, the discharge process associated with voltage application by the power source 403 is the same as in the case of the external power supply method. Therefore, even in the case of the internal power supply system, by performing the discharge process in the same way as in the case of the external power supply system, it is possible to suppress the occurrence of image defects such as "bleeding" and "repelling" in the varnish image.

[Other embodiments]
Note that in the first and second embodiments described above, when the recording material S is conveyed again, the fixing device 50 is placed in a non-pressurized state to allow the recording material S to pass, but the present invention is not limited to this. For example, the recording material S may be allowed to pass in a non-heating state in which power supply to the halogen heater 53 by the heater power supply 54 is stopped, that is, in a state in which the fixing roller 51 is not heated by the halogen heater 53. Although not shown in the drawings, an evacuation route may be provided in the image forming apparatus 100 that does not pass through the fixing device 50, and the recording material S may be routed through the evacuation route when being conveyed again.

In addition, in the first and second embodiments described above, a case has been described in which a water-based varnish or an oil-based varnish is used as the varnish, but the varnish is not limited to this, and the varnish may be an ultraviolet curing type UV varnish. UV varnish contains a photosensitive resin, a photosensitive monomer, a photoinitiator, an additive, etc. as main components. Examples of the photosensitive resin include acrylic resins having (meth)acryloyl groups. Examples of photosensitive monomers include monomers and oligomers having at least one (meth)acryloyl group in the molecule. Examples of the photoinitiator include acetophenone, benzoin ethyl ether, and 1-hydroxycyclohexylphenyl ketone. Examples of additives include waxes, plasticizers, leveling agents, solvents, polymerization inhibitors, antiaging agents, photosensitizers, antifoaming agents, and the like. The UV varnish may contain one kind or two or more kinds of these. The content of each component is not particularly limited, but for example, in UV varnish, the photosensitive resin is 1 to 20% by mass, the photosensitive monomer is 30 to 70% by mass, and the photoinitiator is 5 to 15% by mass. It is preferable that the amount of additives is 5% by mass or less. As the UV varnish, for example, "UV L Carton OP Varnish (product name)", "UV L Gloss OP Varnish (product name)", "UV Matte OP Varnish (product name)" (manufactured by T&K TOKA Co., Ltd.) are used. be able to. When using such a UV varnish, in order to prevent image defects such as "repelling" and "bleeding" from occurring in the varnish image, the toner image is subjected to the same discharge treatment as when using the above-mentioned oil-based varnish before applying the varnish. All you have to do is

1X... Image forming system, 11... Second rotating body (secondary transfer outer roller), 14... First rotating body (secondary transfer inner roller), 31... Reversing conveyance means (reversing discharge means, reverse discharge unit), 32 ...Reversing conveyance means (switchback means, switchback section), 33... Reversing conveyance means (double-sided conveyance means, double-sided conveyance section), 50... Fixing means (fixing device), 51... Fixing rotary body (fixing roller), 52... Pressure rotating body (pressure roller), 53... heating means (halogen heater), 54... power supply means (heater power supply), 80... image bearing belt (intermediate transfer belt), 100... image forming apparatus, 101... control means (Main control unit), 200... Varnish coating device (varnish coater), 403... Voltage application means (power supply), S... Recording material, T2... Transfer nip section (secondary transfer section)

Claims (28)

An image forming system comprising an image forming device capable of forming a toner image on a recording material using toner containing wax, and a varnishing device capable of forming a varnish image on one side of the recording material using a water-based varnish. There it is,
an endless image carrying belt that rotates while carrying a toner image;
a first rotating body that comes into contact with the inner circumferential surface of the image carrying belt;
a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material;
Voltage applying means capable of applying a voltage to the second rotating body;
a fixing unit capable of heating the recording material at a plurality of fixing temperatures and applying heat and pressure to the recording material on which the toner image is formed to fix the toner image on the recording material;
a reversing conveyance means capable of reversing the front and back sides of the recording material that has passed through the fixing means and conveying it to the transfer nip portion;
comprising a control means for controlling the voltage application means and the reversal conveyance means,
When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and When passing through the transfer nip portion with one surface facing toward the second rotating body, the voltage applying means applies a voltage equal to or higher than the discharge start voltage and of positive polarity when the fixing temperature is equal to or lower than a threshold value. is applied, and when the fixing temperature is higher than a threshold, a voltage of negative polarity that is equal to or higher than the discharge start voltage is applied, and then discharged to the varnish coating device so that a varnish image is formed on the one surface side. Ru,
An image forming system characterized by: The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the one surface side, to a non-pressure state in which the pressure rotating body is separated from the fixing rotating body. pass in condition,
The image forming system according to claim 1, characterized in that: The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing unit is configured to control the recording material, which is re-conveyed to the transfer nip portion by the reversal conveyance unit after fixing the toner image on the one surface side, to a non-operating device in which power supply to the heating unit by the power supply unit is stopped. pass it through in a heated state,
The image forming system according to claim 1, characterized in that: During double-sided printing on a recording material, after a toner image is fixed on the one side of the recording material, when the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, the recording material is transferred to the second side opposite to the one side. The toner image is transferred to the surface side,
After fixing the toner image on the second side, the toner image is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and with the second side facing toward the second rotating body, and by the voltage application means. The sheet passes through the transfer nip section in a state where no voltage is applied, is further reversed by the reversing conveyance means, and is conveyed again to the transfer nip section, with the one surface side facing the second rotating body side. When passing through the transfer nip portion, the voltage applying means applies a voltage of positive polarity that is equal to or higher than the discharge start voltage when the fixing temperature is below the threshold value, and when the fixing temperature is higher than the threshold value, After a voltage of negative polarity that is equal to or higher than a discharge start voltage is applied, the discharged material is discharged to the varnish coating device so that a varnish image is formed on the one surface side.
The image forming system according to claim 1, characterized in that: The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the second surface side, to a non-pressure state where the pressure rotating body is separated from the fixing rotation body. Pass it under pressure,
The image forming system according to claim 4, characterized in that: The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing means stops supplying power to the heating means by the power supply means, so that the recording material is conveyed again to the transfer nip portion by the reversal conveyance means after fixing the toner image on the second surface side. Pass it in an unheated state,
The image forming system according to claim 4, characterized in that: The reversing conveyance means includes a switchback means for changing the conveyance direction of the recording material by changing the leading edge and the trailing edge of the recording material that has passed through the fixing means, and a switchback means for conveying the recording material from the switchback means to the transfer nip portion. comprising a double-sided conveying means and a reversing discharge means for discharging the recording material from the switchback means to the varnish coating device in an inverted state;
The recording material is discharged to the varnish coating device in a reversed state by the reverse discharge means.
The image forming system according to any one of claims 1 to 6. An image comprising an image forming device capable of forming a toner image on a recording material using toner containing wax, and a varnishing device capable of forming a varnish image on one side of the recording material using oil-based varnish or UV varnish. A formation system,
an endless image carrying belt that rotates while carrying a toner image;
a first rotating body that comes into contact with the inner circumferential surface of the image carrying belt;
a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material;
Voltage applying means capable of applying a voltage to the second rotating body;
a fixing unit capable of heating the recording material at a plurality of fixing temperatures and applying heat and pressure to the recording material on which the toner image is formed to fix the toner image on the recording material;
a reversing conveyance means capable of reversing the front and back sides of the recording material that has passed through the fixing means and conveying it to the transfer nip portion;
comprising a control means for controlling the voltage application means and the reversal conveyance means,
When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and When passing through the transfer nip portion with one surface facing toward the second rotating body, the voltage applying means applies a voltage of negative polarity that is equal to or higher than the discharge start voltage when the fixing temperature is equal to or lower than a threshold value. is applied, and when the fixing temperature is higher than a threshold, a voltage of positive polarity that is equal to or higher than the discharge start voltage is applied, and then the varnish is discharged to the varnish coating device so that a varnish image is formed on the one surface side. Ru,
An image forming system characterized by: The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the one surface side, to a non-pressure state in which the pressure rotating body is separated from the fixing rotating body. pass in condition,
9. The image forming system according to claim 8. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing unit is configured to control the recording material, which is re-conveyed to the transfer nip portion by the reversal conveyance unit after fixing the toner image on the one surface side, to a non-operating device in which power supply to the heating unit by the power supply unit is stopped. pass it through in a heated state,
9. The image forming system according to claim 8. During double-sided printing on a recording material, after a toner image is fixed on the one side of the recording material, when the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, the recording material is transferred to the second side opposite to the one side. The toner image is transferred to the surface side,
After fixing the toner image on the second side, the toner image is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and with the second side facing toward the second rotating body, and by the voltage application means. The sheet passes through the transfer nip section in a state where no voltage is applied, is further reversed by the reversing conveyance means, and is conveyed again to the transfer nip section, with the one surface side facing the second rotating body side. When passing through the transfer nip, when the fixing temperature is below a threshold value, the voltage applying means applies a voltage that is equal to or higher than the discharge start voltage and has a negative polarity, and when the fixing temperature is greater than the threshold value, the After a voltage of positive polarity that is equal to or higher than a discharge start voltage is applied, the material is discharged to the varnish coating device so that a varnish image is formed on the one surface side.
9. The image forming system according to claim 8. The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the second surface side, to a non-pressure state where the pressure rotating body is separated from the fixing rotation body. Pass it under pressure,
The image forming system according to claim 11. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing means stops supplying power to the heating means by the power supply means, so that the recording material is conveyed again to the transfer nip portion by the reversal conveyance means after fixing the toner image on the second surface side. Pass it in an unheated state,
The image forming system according to claim 11. The reversing conveyance means includes a switchback means for changing the conveyance direction of the recording material by changing the leading edge and the trailing edge of the recording material that has passed through the fixing means, and a switchback means for conveying the recording material from the switchback means to the transfer nip portion. comprising a double-sided conveying means and a reversing discharge means for discharging the recording material from the switchback means to the varnish coating device in an inverted state;
The recording material is discharged to the varnish coating device in a reversed state by the reverse discharge means.
The image forming system according to any one of claims 8 to 13. An image forming system comprising an image forming device capable of forming a toner image on a recording material using toner containing wax, and a varnishing device capable of forming a varnish image on one side of the recording material using a water-based varnish. There it is,
an endless image carrying belt that rotates while carrying a toner image;
a first rotating body that comes into contact with the inner circumferential surface of the image carrying belt;
a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material;
Voltage applying means capable of applying a voltage to the first rotating body;
a fixing unit capable of heating the recording material at a plurality of fixing temperatures and applying heat and pressure to the recording material on which the toner image is formed to fix the toner image on the recording material;
a reversing conveyance means capable of reversing the front and back sides of the recording material that has passed through the fixing means and conveying it to the transfer nip portion;
comprising a control means for controlling the voltage application means and the reversal conveyance means,
When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and It passes through the transfer nip section with one side facing the second rotating body and no voltage is applied by the voltage application means, and is further reversed by the reversing conveyance means and reaches the transfer nip section. When being re-transported and passing through the transfer nip portion with the one surface side facing the first rotating body, the voltage applying means causes the fixing temperature to be equal to or higher than the discharge starting voltage when the fixing temperature is equal to or lower than the threshold value. When the fixing temperature is higher than a threshold value, a voltage of negative polarity that is equal to or higher than the discharge start voltage is applied, and then the varnish is applied so that a varnish image is formed on the one surface side. discharged to coating equipment,
An image forming system characterized by: The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the one surface side, to a non-pressure state in which the pressure rotating body is separated from the fixing rotating body. pass in condition,
The image forming system according to claim 15. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing unit is configured to control the recording material, which is re-conveyed to the transfer nip portion by the reversal conveyance unit after fixing the toner image on the one surface side, to a non-operating device in which power supply to the heating unit by the power supply unit is stopped. pass it through in a heated state,
The image forming system according to claim 15. During double-sided printing on a recording material, after the toner image is fixed on the one side of the recording material, the recording material is reversed by the reversing conveyance means, and the recording material is passed through the transfer nip portion with the one side facing the second rotating body. When passing, a predetermined transfer voltage is applied by the voltage applying means, so that a toner image is transferred to the second side opposite to the first side,
After the toner image is fixed on the second surface side, the toner image is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and passes through the transfer nip section with the first surface side facing the first rotating body. In this case, when the fixing temperature is below a threshold value, the voltage applying means applies a voltage which is equal to or higher than the discharge starting voltage and has a positive polarity, and when the fixing temperature is higher than the threshold value, the voltage is applied when the voltage is equal to or higher than the discharge starting voltage. a negative voltage is applied to the varnish, and then the varnish is discharged to the varnish coating device so that a varnish image is formed on the one surface side.
The image forming system according to claim 15. The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the second surface side, to a non-pressure state where the pressure rotating body is separated from the fixing rotation body. Pass it under pressure,
The image forming system according to claim 18. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing means stops supplying power to the heating means by the power supply means, so that the recording material is conveyed again to the transfer nip portion by the reversal conveyance means after fixing the toner image on the second surface side. Pass it in an unheated state,
The image forming system according to claim 18. The reversing conveyance means includes a switchback means for changing the conveyance direction of the recording material by changing the leading edge and the trailing edge of the recording material that has passed through the fixing means, and a switchback means for conveying the recording material from the switchback means to the transfer nip portion. comprising a double-sided conveying means and a reversing discharge means for discharging the recording material from the switchback means to the varnish coating device in an inverted state;
The recording material is discharged to the varnish coating device in a reversed state by the reverse discharge means.
The image forming system according to any one of claims 15 to 20. An image comprising an image forming device capable of forming a toner image on a recording material using toner containing wax, and a varnishing device capable of forming a varnish image on one side of the recording material using oil-based varnish or UV varnish. A formation system,
an endless image carrying belt that rotates while carrying a toner image;
a first rotating body that comes into contact with the inner circumferential surface of the image carrying belt;
a second rotating body that is provided to sandwich the first rotating body and the image carrying belt and forms a transfer nip portion that transfers the toner image from the image carrying belt to the recording material while nipping and conveying the recording material;
Voltage applying means capable of applying a voltage to the first rotating body;
a fixing unit capable of heating the recording material at a plurality of fixing temperatures and applying heat and pressure to the recording material on which the toner image is formed to fix the toner image on the recording material;
a reversing conveyance means capable of reversing the front and back sides of the recording material that has passed through the fixing means and conveying it to the transfer nip portion;
comprising a control means for controlling the voltage application means and the reversal conveyance means,
When printing on one side of a recording material, a toner image is transferred to the one side of the recording material and the toner image is fixed by the fixing means, and then the recording material is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and It passes through the transfer nip section with one side facing the second rotating body and no voltage is applied by the voltage application means, and is further reversed by the reversing conveyance means and reaches the transfer nip section. When being re-transported and passing through the transfer nip portion with the one surface side facing the first rotating body, the voltage applying means causes the fixing temperature to be equal to or higher than the discharge starting voltage when the fixing temperature is equal to or lower than the threshold value. When the fixing temperature is higher than a threshold value, a voltage of positive polarity that is equal to or higher than the discharge start voltage is applied, and then the varnish is applied so that a varnish image is formed on the one surface side. discharged to coating equipment,
An image forming system characterized by: The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the one surface side, to a non-pressure state in which the pressure rotating body is separated from the fixing rotating body. pass in condition,
23. The image forming system according to claim 22. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing unit is configured to control the recording material, which is re-conveyed to the transfer nip portion by the reversal conveyance unit after fixing the toner image on the one surface side, to a non-operating device in which power supply to the heating unit by the power supply unit is stopped. pass it through in a heated state,
23. The image forming system according to claim 22. During double-sided printing on a recording material, after the toner image is fixed on the one side of the recording material, the recording material is reversed by the reversing conveyance means, and the recording material is passed through the transfer nip portion with the one side facing the second rotating body. When passing, a predetermined transfer voltage is applied by the voltage applying means, so that a toner image is transferred to the second side opposite to the first side,
After the toner image is fixed on the second surface side, the toner image is reversed by the reversing conveyance means and conveyed again to the transfer nip section, and passes through the transfer nip section with the first surface side facing the first rotating body. In this case, when the fixing temperature is below a threshold value, the voltage applying means applies a voltage which is equal to or higher than the discharge starting voltage and has a negative polarity, and when the fixing temperature is higher than the threshold value, the voltage is applied when the voltage is equal to or higher than the discharge starting voltage. After a positive voltage is applied to the varnish, the varnish is discharged to the varnish coating device so that a varnish image is formed on the one surface side.
23. The image forming system according to claim 22. The fixing means includes a fixing rotary body, and a pressure rotary body that is provided so as to be able to approach and separate from the fixing rotary body, and that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body. and has
The fixing unit is configured to transfer the recording material, which is re-conveyed to the transfer nip portion by the reversing conveyance unit after fixing the toner image to the second surface side, to a non-pressure state where the pressure rotating body is separated from the fixing rotation body. Pass it under pressure,
The image forming system according to claim 25. The fixing means includes a fixing rotary body, a pressure rotary body that forms a fixing nip portion that pinches and conveys the recording material while in contact with the fixing rotary body, and a heating means that heats the fixing rotary body. have,
comprising a power supply means for supplying electric power to the heating means to heat the heating means,
The fixing means stops supplying power to the heating means by the power supply means, so that the recording material is conveyed again to the transfer nip portion by the reversal conveyance means after fixing the toner image on the second surface side. Pass it in an unheated state,
The image forming system according to claim 25. The reversing conveyance means includes a switchback means for changing the conveyance direction of the recording material by changing the leading edge and the trailing edge of the recording material that has passed through the fixing means, and a switchback means for conveying the recording material from the switchback means to the transfer nip portion. comprising a double-sided conveying means and a reversing discharge means for discharging the recording material from the switchback means to the varnish coating device in an inverted state;
The recording material is discharged to the varnish coating device in a reversed state by the reverse discharge means.
The image forming system according to any one of claims 22 to 27.

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