Image forming system

Abstract

To provide an image forming system that, when forming a varnish image superimposed on a toner image formed by using toner including carbon black, can prevent discoloration of the toner image due to heat.SOLUTION: When a black toner image formed by using only black toner is in a superimposition area where a varnish image is formed superimposed on a toner image (Yes in both S3 and S4), a "reference UV condition" is changed (S5). When the black toner image is in the superimposition area, the quantity of irradiation with ultraviolet rays is reduced compared with when the black toner image is not in the area. The reduction in the quantity of irradiation with ultraviolet rays prevents generation of heat resulting from carbon black. However, the reduction in the quantity of irradiation with ultraviolet rays makes the varnish image difficult to be solidified. The conveyance speed of a recording material S is reduced according to the quantity of irradiation with ultraviolet rays so as to secure the integrated light quantity necessary for solidifying the varnish image. The occurrence of discoloration of the toner image can thereby be prevented when the vanish image solidified by ultraviolet rays is formed.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming system including an image forming apparatus that forms a toner image on a recording material, and a varnish application apparatus that forms a varnish image. [Background technology]

[0002] Recently, in order to decorate a toner image formed on a recording material using a developer, a varnish image using a colorless and transparent varnish is formed on the recording material. As a device for forming a varnish image, a varnish application device (called a varnish coater) has been proposed that can form a varnish image by applying a varnish that is hardened by ultraviolet light and then hardening the varnish by irradiating it with ultraviolet light (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-111813 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional devices that form varnish images using varnish that hardens when exposed to light of a specific wavelength, such as ultraviolet light, there was a risk that the color of the toner image would change in the overlapping area where the toner image overlaps the varnish image. This is because, when the toner contains carbon black, in response to irradiation with light, in addition to the heat generated by the varnish, the toner also heats up due to the carbon black, causing the overlapping area to become hot, and the toner discolors due to the heat.

[0005] In view of the above problems, the present invention aims to provide an image forming system that can suppress discoloration of a toner image due to heat when a varnish image is formed using a varnish that solidifies when exposed to light of a predetermined wavelength and is overlaid on a toner image formed using a toner containing carbon black. [Means for solving the problem]

[0006] An image forming system according to one embodiment of the present invention is an image forming apparatus including a first photoreceptor on which an electrostatic latent image is formed, a first developing unit that develops the electrostatic latent image on the first photoreceptor using a first toner containing carbon black, a plurality of second photoreceptors on which electrostatic latent images are formed, a plurality of second developing units that develop the electrostatic latent images on the second photoreceptors using a plurality of different second toners not containing carbon black, respectively, a transfer unit that transfers the toner images on the first photoreceptor and the plurality of second photoreceptors to a recording material, and a fixing unit that fixes the toner images transferred to the recording material to the recording material, and a varnishing unit that includes a conveying unit that conveys the recording material on which the toner image is fixed, a varnish applying unit that applies varnish to the recording material to form a varnish image, and an irradiation unit that irradiates the recording material with light of a predetermined wavelength to solidify the varnish image. The image forming apparatus includes a cloth device, and a control unit which causes the image forming device to form a toner image on a recording material based on first image data relating to a toner image, and causes the varnish application device to form a varnish image on the recording material based on second image data relating to a varnish image, wherein the control unit causes the varnish application device to form a varnish image on the recording material based on the first image data and the second image data, when there is no toner image to be formed using the first toner in an overlapping area where a varnish image is formed by superimposing the toner image on the toner image, by setting the light amount of the irradiation unit to a first light amount and the conveying speed of the conveying unit to a first speed, and when there is a toner image to be formed using the first toner, by setting the light amount to a second light amount which is smaller than the first light amount and the conveying speed to a second speed which is slower than the first speed.

[0007] An image forming system according to one embodiment of the present invention includes an image forming device having a photoconductor on which an electrostatic latent image is formed, a developing unit that develops the electrostatic latent image on the photoconductor into a toner image using a toner containing carbon black, a transfer unit that transfers the toner image on the photoconductor to a recording material, and a fixing unit that fixes the toner image transferred to the recording material to the recording material, a varnish application device having a conveying unit that conveys the recording material on which the toner image is fixed, a varnish application unit that applies varnish to the recording material to form a varnish image, and an irradiation unit that irradiates the recording material with light of a predetermined wavelength to solidify the varnish image, and a toner image forming device that causes the image forming device to form a toner image on the recording material based on first image data related to the toner image. and a control unit that causes the varnish application device to form a varnish image on the recording material based on second image data related to a varnish image, and the control unit causes the varnish application device to form a varnish image on the recording material based on the first image data and the second image data, wherein when there is no toner image to be formed using the toner in an overlapping area where a varnish image is formed by superimposing the toner image on the toner image, the control unit sets the light amount of the irradiation unit to a first light amount and the conveying speed of the conveying unit to a first speed, and when there is a toner image to be formed using the toner, sets the light amount to a second light amount which is smaller than the first light amount and sets the conveying speed to a second speed which is slower than the first speed, causing the varnish application device to form a varnish image. Effect of the Invention

[0008] According to the present invention, when a varnish image is formed using a varnish that solidifies when exposed to light of a specified wavelength and is superimposed on a toner image formed using a toner containing carbon black, discoloration of the toner image due to heat can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a configuration of an image forming system. [Diagram 2] 6 is a graph showing the relationship between the control voltage and the film thickness in forming a varnish image. [Diagram 3] FIG. 2 is a control block diagram of an image formation control system in the image forming system. [Figure 4]Schematic diagram showing an example of a toner image and a varnish image. [Diagram 5] 4 is a flowchart showing an image forming process according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First, the image forming system of this embodiment will be described with reference to 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 application device (called a varnish coater) that forms a varnish image on the recording material S. The varnish coater 200 is a post-process unit that can be freely added to the image forming apparatus 100 for functional expansion, and the image forming apparatus 100 and the varnish coater 200 are connected to be able to transfer the recording material S. In addition, the image forming apparatus 100 and the varnish coater 200 are connected by a data input / output interface (not shown) to be able to transmit and receive control signals and data between them. The recording material S on which the toner image is formed by the image forming apparatus 100 is conveyed to the 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, and the varnish coater 200 forms a varnish image on the recording material S separately from the toner image. The formation of the varnish image by the varnish coater 200 will be described later.

[0011] 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. The finisher device performs, for example, a punching process to make holes in the recording material S, or a stapling process to bundle and staple a plurality of sheets of recording material S, and discharges the punched recording material S or the stapled bundle of recording material S to a discharge tray. In addition to these post-process units, the image forming system 1X may include, for example, a recording material supplying device (not shown) capable of storing a large amount of recording material S therein, and the recording material S may be supplied from the recording material supplying device to the image forming apparatus 100.

[0012] <Image forming device> The image forming apparatus 100 will be described. The image forming apparatus 100 is a tandem-type full-color printer of an electrophotographic system. The image forming apparatus 100 has image forming units Pa, Pb, Pc, and Pd that form images of yellow, magenta, cyan, and black, respectively. The image forming apparatus 100 forms a toner image on a recording material S based on data relating to the toner image included in image data sent from an external device 1000 such as a document reading device (not shown) connected to the image forming apparatus 100 or a personal computer. Examples of the recording material S include sheet materials such as plain paper, thick paper, rough paper, textured paper, and coated paper.

[0013] The conveying process of the recording material S of the image forming apparatus 100 will be described. The recording material S is stored in a cassette 10 in a stacked form, and is sent out from the cassette 10 by a supply roller 13 in accordance with the image formation timing. The recording material S sent out by the supply roller 13 is conveyed to a registration roller 12 arranged in the middle of a conveying path 114. Then, after the registration roller 12 performs skew correction and timing correction on the recording material S, the recording material S is sent to a secondary transfer portion T2. ​​The secondary transfer portion T2 is a transfer nip portion formed by a secondary transfer inner roller 14 and a secondary transfer outer roller 11 as a transfer portion, and a toner image is transferred onto the recording material in response to the application of a secondary transfer voltage to the secondary transfer outer roller 11.

[0014] The process of forming an image sent to the secondary transfer portion T2 at the same timing as the process of conveying the recording material S to the secondary transfer portion T2 described above will be described. First, the image forming portion will be described. The image forming portions Pa, Pb, Pc, and Pd of each color are configured almost the same except that the color of the toner used in the developing devices 1a, 1b, and 1c as the multiple second developing portions is yellow (Y), magenta (M), and cyan (C), and the color of the toner used in the developing device 1d as the first developing portion is black (K). Therefore, the following will describe the black image forming portion Pd as a representative, and the description of the other image forming portions Pa, Pb, and Pc will be omitted. In this embodiment, the photosensitive drums 3a, 3b, and 3c correspond to the multiple second photosensitive bodies, and the photosensitive drum 3d corresponds to the first photosensitive body.

[0015] The image forming section Pd is mainly composed of a developing device 1d, a charging device 2d, a photosensitive drum 3d, a photosensitive drum cleaner 4d, and an exposure device 5d. The surface of the photosensitive drum 3d as a photosensitive member is uniformly charged in advance by the charging device 2d, and then an electrostatic latent image is formed on the surface of the photosensitive drum 3d by the exposure device 5d, which is driven based on a signal of image information. Next, the electrostatic latent image formed on the photosensitive drum 3d is developed into a toner image by the developing device 1d using a developer. Then, the toner image formed on the photosensitive drum 3d is primarily transferred onto the intermediate transfer belt 80 in response to a primary transfer voltage being applied to a primary transfer roller 6d, which is disposed with the image forming section Pd and the intermediate transfer belt 80 sandwiched therebetween. A small amount of primary transfer residual toner remaining on the photosensitive drum 3d is collected by the photosensitive drum cleaner 4d.

[0016] The intermediate transfer belt 80 is stretched by the inner secondary transfer roller 14 and tension rollers 15 and 16, and is driven in the direction of the arrow R2. In this embodiment, the tension roller 16 also serves as a drive roller for driving the intermediate transfer belt 80. The image forming processes of each color, which are processed in parallel by the image forming units Pa to Pd, are performed at a timing when the images are sequentially superimposed on the toner images of the upstream colors that have 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 is conveyed to the secondary transfer unit T2. Note that the secondary transfer residual toner after passing through the secondary transfer unit T2 is removed from the intermediate transfer belt 80 by the transfer cleaner 22.

[0017] Through the above-described conveying process and image forming process, the timing of the recording material S and the full-color toner image coincides in the secondary transfer section T2, and the secondary transfer is performed. After that, the recording material S is conveyed to the fixing device 50, where heat and pressure are applied to fix the toner image on the recording material. The fixing device 50 as a fixing section pinches and conveys the recording material S on which the toner image has been formed, and heats and presses the conveyed recording material S to fix the toner image on the recording material S. That is, the toner of the toner image formed on the recording material S is melted and mixed, and is fixed on the recording material S as a full-color image. In this way, a series of image forming processes is completed. In the case of this embodiment, the recording material S on which the toner image has been fixed is conveyed from the image forming device 100 to the varnish coater 200.

[0018] <Developer> In this embodiment, a two-component developer containing a toner and a carrier is used. The toner contains a binder resin, a colorant, and a release agent (wax). The binder resin can be a known one. For example, a vinyl copolymer such as a styrene-(meth)acrylic copolymer, a polyester resin, a hybrid resin in which a vinyl copolymer unit and a polyester unit are chemically bonded, an epoxy resin, a styrene-butadiene copolymer, or other resin can be used. The colorants can be known for yellow (Y), magenta (M), cyan (C), and black (K), but the black toner (first toner) contains carbon black, and the yellow, magenta, and cyan toners (second toners) do not contain carbon black.

[0019] Examples of the release agent include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight olefin copolymer wax, microcrystalline wax, Fischer-Tropsch wax, and paraffin wax, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, and block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax and montan acid ester wax, ester waxes which are synthetic reaction products of higher fatty acids and higher alcohols such as behenyl behenate and behenyl stearate, and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax.

[0020] In the case of this embodiment, the image data also includes data relating to the varnish image to be formed by the varnish coater 200. That is, the varnish image data (second image data) relating to the varnish image is set separately from the toner image data (first image data) relating to the four colors of toner images YMCK formed by the image forming apparatus 100. The data relating to the varnish image included in the image data is similar to the data relating to the toner image, in that each varnish image is associated with the coordinates of the image formation area on the recording material S for each page.

[0021] <Varnish coater> Next, the varnish coater 200 will be described with reference to Figures 1 and 2. The varnish coater 200 is an inkjet type varnish application device that can eject varnish onto the surface of a recording material S on which a toner image has been formed, and form a varnish image such as a user-desired character, line drawing, or figure separately from the toner image. In the case of the inkjet type, the varnish is ejected as droplets toward the recording material S, and the varnish is adhered to the recording material S to form a varnish image. Note that various types of varnish, such as water-based varnish, oil-based varnish, or UV varnish, may be used as the varnish, and the following description will be given taking as an example the varnish coater 200 that forms a varnish image using an ultraviolet-curing UV varnish that is cured by exposure to ultraviolet light.

[0022] The varnish coater 200 includes a sheet conveying section 241, a position detection section 245, a varnish discharge section 246, and a varnish solidification section 247. The sheet conveying section 241 conveys the recording material S while adsorbing it to the belt conveying surface by an air suction device (not shown) through holes formed in the conveying belt 242. Along the sheet conveying path of the sheet conveying section 241, the position detection section 245, the varnish discharge section 246, and the varnish solidification section 247 are arranged in this order from the upstream side to the downstream side in the conveying direction (arrow X direction) of the recording material S. The position detection section 245 is a detection section using, for example, a CCD, and detects the position of the leading end of the recording material S in the conveying direction and the positions of both ends in the width direction intersecting with the conveying direction, as well as the position of the toner image on the recording material S, with respect to the recording material S adsorbed and conveyed on the belt conveying surface. By detecting the position of the toner image by the position detection section 245, the varnish coater 200 can overprint the varnish image on the toner image.

[0023] The varnish discharge section 246 as a varnish application section discharges UV varnish onto one side of the recording material S transported by the sheet transport section 241, thereby applying varnish to the recording material S and forming a varnish image. 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 discharge ports (not shown) are arranged in a line in a width direction intersecting the transport direction of the recording material S so as to cover a range covering the maximum width of the recording material S on which an image can be formed by the varnish coater 200. The varnish discharge method of the print head may be a method using a heating element, a method using a piezoelectric element, a method using an electrostatic element, a method using a MEMS element, or the like. Although not shown, the UV varnish is supplied to the print head from a tank via a tube.

[0024] The thickness of the varnish image depends on the amount of UV varnish applied per unit area of ​​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 piezoelectric element, as shown in FIG. 2, the amount of varnish discharged changes according to the adjustment of the control voltage, and the thickness of the varnish image is adjusted by increasing or decreasing the amount of varnish discharged per unit area. In this embodiment, the thickness of the varnish image is adjusted to a range of, for example, "5 to 100 μm," preferably "10 to 70 μm."

[0025] Furthermore, the resolution of the varnish image that can be formed by the varnish coater 200 is, for example, "600 dpi," in which case the line width of the varnish image is adjusted in units of "600 dpi." Note that the above-mentioned range of varnish image thickness, and the adjustment range of the resolution and line width of the varnish image 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.

[0026] Returning to FIG. 1, the recording material S, on one side of which a varnish image has been formed by the varnish discharge section 246, is sent by the sheet transport section 241 to the varnish solidification section 247 downstream in the transport direction, where the UV varnish on the recording material S is solidified. The varnish solidification section 247, which serves as an irradiation section, has an ultraviolet lamp, which irradiates light (ultraviolet rays) of a predetermined wavelength corresponding to the UV varnish to solidify the varnish image formed on the recording material S. The ultraviolet lamp is disposed so as to be able to irradiate ultraviolet rays over almost the entire width of the recording material S, and is turned on only when the recording material S passes by. In this manner, the varnish image is overprinted on the toner image formed on the recording material S.

[0027] The UV varnish used in this embodiment contains photosensitive resin, photosensitive monomer, photoinitiator, additives, etc. as main components. Examples of photosensitive resins 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 photoinitiators include acetophenone, benzoin ethyl ether, 1-hydroxycyclohexyl phenyl ketone, etc. Examples of additives include wax, plasticizer, leveling agent, solvent, polymerization inhibitor, antiaging agent, photosensitizer, defoamer, etc. The UV varnish may contain one of these, or two or more of them. The content of each component is not particularly limited, but it is preferable that the UV varnish contains, for example, "1 to 20% by mass" of photosensitive resin, "30 to 70% by mass" of photosensitive monomer, "5 to 15% by mass" of photoinitiator, and "5% by mass" or less of additives. 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)" and the like (manufactured by T&K TOKA Corporation) can be used.

[0028] Next, the control configuration of the image formation control system in the image forming system 1X will be described using Fig. 3 with reference to Fig. 1. In this embodiment, an example has been given in which the image forming apparatus 100 centrally manages and controls operation commands for the varnish coater 200. Note that various devices such as motors and power supplies are connected to the main control unit 101 and varnishing control unit 330 described below in addition to those shown in Fig. 3, but illustration and description of these will be omitted here as they are not the main point of the invention.

[0029] In the image forming system 1X of this embodiment, as shown in Fig. 3, the varnish processing control unit 330 is connected to the main control unit 101 as a control unit via communication units 501 and 502 so as to be able to communicate operation commands and various data. The varnish processing control unit 330 operates the varnish coater 200 according to operation commands from the main control unit 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. At this time, the main control unit 101 can function as an acquisition unit that acquires image data including data related to the toner image and varnish image to be formed on the recording material S.

[0030] The main control unit 101 and the varnishing control unit 330 may have the same configuration. For example, each of them has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory).

[0031] The main control unit 101 has a CPU 102, a ROM 103, and a RAM 104. The ROM 103 stores various programs such as "image forming processing" (see FIG. 5) described later. The RAM 104 stores various data such as image data acquired from the operation unit 110 or the external device 1000 (see FIG. 1). The RAM 104 can also temporarily store the results of calculations associated with the execution of the various programs.

[0032] The image forming apparatus 100 includes an operation unit 110 having, for example, a liquid crystal display unit 111 (see FIG. 1), and the operation unit 110 is connected to the main control unit 101. The operation unit 110 serving as an input unit is, for example, a touch panel. The operation unit 110 is capable of displaying various screens presenting various programs and various data on the liquid crystal display unit 111, and accepts inputs for starting various programs and inputting various data in response to a user's touch operation on the screen. A screen including various buttons, switches, and the like as software keys is displayed on the touch panel.

[0033] A user can input the start of an image forming job from the operation unit 110. When the start of an image forming job is input, the CPU 102 executes an "image forming process (program)" (see FIG. 5) stored in the ROM 103. In response to this, the image forming apparatus 100 and the varnish coater 200 are operated, and a toner image and a varnish image are formed on the recording material S.

[0034] The varnish processing control unit 330 has a CPU 331, a ROM 332, and a RAM 333. The CPU 331 operates the sheet transport unit 241, the position detection unit 245, the varnish discharge unit 246, and the varnish solidification unit 247 of the varnish coater 200 based on a control program stored in the ROM 332. When the varnish processing control unit 330 receives 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.

[0035] As already mentioned, in the conventional device that forms a varnish image using UV varnish that is solidified by ultraviolet rays, there was a risk that the color of the toner image would change at the point where the toner image and the varnish image were superimposed. In particular, when the toner image was a black toner image formed only with black toner containing carbon black, the change in color was remarkable. Figure 4 is a diagram showing an example of a toner image and a varnish image, which shows a schematic representation of a square toner image 601 and a water droplet-shaped varnish image 602 formed on a recording material S.

[0036] The toner image data and the varnish image data each include coordinate positions of a large number of dots (pixels) constituting the toner image 601 and the varnish image 602 on the recording material S. In FIG. 4, based on the toner image data, the left region 601a of the left half of the toner image 601 is formed using only black toner, and the right region 601b of the right half is formed using at least one of yellow toner, magenta toner, and cyan toner other than black toner. Also, based on the varnish image data, the varnish image 602 is formed superimposed on the toner image 601. In the example shown in FIG. 4, the overlapping region in which the varnish image 602 is formed superimposed on the toner image 601 is the entire area (first region 602a and second region 602b) of the varnish image 602. The first region 602a of the left half of the varnish image 602 overlaps with the left region 601a formed using only black toner, and the second region 602b of the right half overlaps with the right region 601b formed using toners of each color other than black toner.

[0037] Conventionally, when a varnish image 602 is formed by superimposing a toner image 601 using UV varnish, there was a risk that the toner would discolor in part of the left region 601a, causing a change in the color of the toner image 601. This is because both the UV varnish and the carbon black generate heat due to the influence of ultraviolet rays irradiated when solidifying the UV varnish, and the region of the left region 601a that overlaps with the first region 602a of the varnish image 602 becomes hotter than the other regions. Therefore, in this embodiment, when a varnish image 602 is formed by superimposing a toner image 601, the toner is prevented from generating heat due to the carbon black in order to prevent the color of the toner image 601 from changing. This will be described below.

[0038] <Image formation process> The "image forming process" of this embodiment will be described with reference to Fig. 5 along with Fig. 3 and Fig. 4. 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 image forming job is completed.

[0039] As shown in FIG. 5, the main control unit 101 acquires image data stored in the RAM 104 when an image forming job starts (S1). The main control unit 101 refers to the acquired image data and determines whether the image data includes varnish image data and is image data for spot varnish coating (S2). In the example shown in FIG. 4, the image data includes varnish image data related to the varnish image 602 together with toner image data related to the toner image 601. If the image data does not include varnish image data (No in S2), the main control unit 101 performs image formation processing to cause the image forming apparatus 100 to form a toner image based on the toner image data (S6). In this case, the main control unit 101 does not cause the varnish coater 200 to form a varnish image. After that, the main control unit 101 proceeds to the processing of step S7.

[0040] If the image data includes varnish image data (Yes in S2), the main control unit 101 judges whether or not there is a toner image formed using only black toner in the overlapping area where the varnish image is formed by superimposing the toner image (S3). The main control unit 101 compares the toner image data with the varnish image data, and judges that there is a black toner image in the overlapping area when both a varnish image and a toner image using only black toner (hereinafter referred to as a black toner image) are present at the same coordinates. In the example shown in FIG. 4, in the overlapping area (first area 602a and second area 602b) between the toner image 601 and the varnish image 602, the coordinates of the first area 602a and part of the coordinates of the left area 601a of the black toner image are the same coordinates, so it is judged that there is a black toner image in the overlapping area.

[0041] If there is no black toner image in the overlapping area (No in S3), the main control unit 101 performs image formation processing in which the image forming apparatus 100 forms a toner image based on the toner image data, and also forms a varnish image based on the varnish image data (S6). In this case, the main control unit 101 causes the varnish coater 200 to form a varnish image in accordance with predetermined "reference UV conditions" pre-stored in the ROM 103 or the like (see FIG. 3). As the "reference UV conditions", for example, the amount of ultraviolet light irradiated by the varnish solidification unit 247 is set to "97 mJ / cm2 " (first light amount), and the conveying speed of the recording material S by the sheet conveying unit 241 is set to "11.7 m / min" (first speed). After the toner image and the varnish image are formed, the main control unit 101 proceeds to the process of step S7.

[0042] On the other hand, if there is a black toner image in the overlapping area (Yes in S3), the main control unit 101 judges whether the condition change function for changing the "reference UV condition" is enabled or disabled (S4). The user can arbitrarily input the setting of the condition change function enabled / disabled from the operation unit 110, and the main control unit 101 judges whether the condition change function is enabled or disabled according to the user input from the operation unit 110. If the condition change function is enabled, the image forming system 1X is set to the "image quality priority mode". If the condition change function is disabled, the image forming system 1X is set to the "productivity priority mode". If the image forming system 1X is set to the "productivity priority mode", a varnish image is formed according to the "reference UV condition". If the image forming system 1X is set to the "image quality priority mode", a varnish image is formed according to the "changed UV condition" in which the "reference UV condition" is changed, as described later. Note that the main control unit 101 is not limited to obtaining and judging the "condition change function enabled / disabled" input by the user from the operation unit 110, but may also read and judge the setting of the "condition change function enabled / disabled" stored in advance in the RAM 104 or the like (see FIG. 3).

[0043] If the condition change function is disabled (No in S4), the main control unit 101 performs image formation processing in which the image forming apparatus 100 forms a toner image based on the toner image data, and the varnish coater 200 forms a varnish image based on the varnish image data (S6). In this case, the image forming system 1X is set to the "productivity priority mode," and the main control unit 101 forms a varnish image according to the above-mentioned "reference UV conditions." After that, the main control unit 101 proceeds to the processing of step S7.

[0044] If the condition change function is enabled (Yes in S4), the main control unit 101 changes the "reference UV conditions" (S5). Then, the main control unit 101 performs image formation processing in which a toner image is formed by the image forming apparatus 100 based on the toner image data, and the varnish coater 200 forms a toner image based on the varnish image data (S6). In this case, the image forming system 1X is set to the "image quality priority mode," and the main control unit 101 forms a varnish image according to the "changed UV conditions" that are the changed versions of the above-mentioned "reference UV conditions." After that, the main control unit 101 proceeds to the processing of step S7.

[0045] When the "reference UV condition" is changed, the "changed UV condition" has a lower irradiation light amount and an extended irradiation time of ultraviolet light compared to the "reference UV condition". In this embodiment, in order to extend the irradiation time of ultraviolet light, the conveying speed of the recording material S by the sheet conveying unit 241 is slowed down. That is, if the irradiation light amount of ultraviolet light irradiated by the varnish solidifying unit 247 is a first light amount in the "reference UV condition", and the conveying speed of the recording material S by the sheet conveying unit 241 is a first speed, in the "changed UV condition", the irradiation light amount of ultraviolet light is a second light amount smaller than the first light amount, and the conveying speed of the recording material S is a second speed slower than the first speed. Note that it is preferable that the integrated light amount (= irradiation light amount x irradiation time) based on the irradiation light amount (first light amount) and the conveying speed (first speed) in the "reference UV condition" is the same as the integrated light amount based on the irradiation light amount (second light amount) and the conveying speed (second speed) in the "changed UV condition".

[0046] In the process of step S7, the main control unit 101 determines whether or not the image formation job has been completed (S7). If the image formation job has been completed (Yes in S7), the main control unit 101 ends the "image formation process". If the image formation job has not been completed (No in S7), the main control unit 101 returns to the process of S2 and executes the processes of steps S2 to S5 described above.

[0047] Table 1 shows the results of an experiment conducted by the inventors to examine whether or not discoloration of a toner image occurs due to heat generation caused by irradiation of carbon black with ultraviolet rays. [Table 1]

[0048] The experiment was carried out as follows. First, a toner image is formed on a recording material S based on predetermined image data. The predetermined image data here refers to toner image data for forming a black toner image using only black toner (K ​​toner) so that the area ratio is "100%", and toner image data for forming a toner image using CMY toner so that the area ratio is "0%". The toner image formed using CMY toner is a pseudo black toner image that expresses the same black color as a black toner image using only black toner, and the predetermined image data specifies the area ratios of each of cyan (C), magenta (M), and yellow (Y) toners. In this embodiment, when the maximum toner amount per unit area of ​​each toner image is "100%, the ratio of the toner amount per unit area of ​​the toner image that is actually formed is called the "area ratio".

[0049] Next, a varnish image with a thickness of 40 μm was formed on both the black toner image and the toner image formed using CMY toners by using UV varnish with "DDC-810" (manufactured by Duplo Co., Ltd.). Then, ultraviolet rays were irradiated onto the recording material S on which the toner image and the varnish image were formed, to solidify the UV varnish. For the recording material S on which the toner image was formed using CMY toners, a varnish image was formed according to the "standard UV conditions". In contrast, for the recording material S on which the black toner image was formed, a varnish image was formed according to each of the "standard UV conditions" and the "changed UV conditions". Finally, the inventors visually confirmed whether or not the toner image on the recording material S had changed color.

[0050] As shown in Table 1, when a varnish image was formed under the "standard UV conditions" on a toner image formed using CMY toner, no discoloration occurred in the toner image. This is because heat is generated as the UV varnish solidifies in response to irradiation with ultraviolet light, but because CMY toner does not contain carbon black, no heat is generated due to carbon black.

[0051] On the other hand, when a varnish image was formed on a black toner image under the "standard UV conditions" (productivity priority mode), discoloration occurred in the toner image. This is because heat may be generated due to the solidification of the UV varnish in response to irradiation with ultraviolet light, as well as heat generated due to carbon black. In contrast, when a varnish image was formed on a black toner image under the "changed UV conditions" (image quality priority mode), discoloration did not occur in the toner image. In the "changed UV conditions," when the "standard UV conditions" are set to "100%," the amount of irradiation light is reduced to "50%" (second amount of light), while the irradiation time is increased to "200%," that is, the conveying speed of the recording material S is slowed to half the speed (second speed). In other words, the integrated light amount under the "changed UV conditions" is maintained at the integrated light amount under the "standard UV conditions". However, in the "image quality priority mode", the conveying speed of the recording material S is slowed to half the speed, so the number of sheets of recording material S on which images are formed per unit time is reduced compared to the "productivity priority mode". That is, in the "image quality priority mode", the productivity of the image forming system 1X may decrease.

[0052] As described above, in this embodiment, when there is a black toner image in the overlapping area between the toner image and the varnish image, the amount of ultraviolet light irradiation for solidifying the varnish image is reduced compared to when there is no black toner image in the overlapping area. By reducing the amount of ultraviolet light irradiation, heat generation caused by carbon black is suppressed. However, since reducing the amount of ultraviolet light irradiation makes it difficult for the varnish image to solidify, the conveying speed of the recording material S is slowed down to extend the irradiation time according to the reduced amount of ultraviolet light irradiation in order to ensure the integrated light amount required to solidify the varnish image. That is, when the conveying speed of the recording material S is reduced to extend the irradiation time, the instantaneous amount of heat generated by the toner image tends to decrease compared to when the amount of irradiation light is not reduced. This is thought to be because, although the total amount of heat applied to the toner image does not change, the heat is dissipated through the recording material S or the air, so that the temperature of the toner image does not continue to increase. Therefore, when the conveying speed is reduced and the irradiation time is extended, the varnish image can be sufficiently cured while suppressing discoloration of the toner image. In this way, when a varnish image is formed using UV varnish that hardens when exposed to ultraviolet light, overlaying a toner image formed using a toner containing carbon black, discoloration of the toner image can be suppressed.

[0053] <Other embodiments> When changing the "reference UV conditions" (see S5 in FIG. 5), the main control unit 101 may determine the amount of irradiated light based on the above-mentioned "area ratio." The inventors conducted an experiment to investigate whether or not discoloration of the toner image occurs due to heat generation caused by UV irradiation of carbon black when the amount of irradiated light is changed based on the "area ratio." Table 2 shows the experimental results. The experimental results for the first to third rows from the left in Table 2 are the same as those in Table 1 described above. [Table 2]

[0054] As shown in Table 2, when a varnish image was formed under "standard UV conditions" on a black toner image formed with an area ratio of "95%," discoloration occurred in the toner image (fourth from the left). In contrast, when a varnish image was formed under "changed UV conditions" on a black toner image formed with an area ratio of "95%," no discoloration occurred in the toner image (fifth from the left). Here, the mass of the black toner image present on the recording material when the area ratio is "100%, " is 0.50 mg / cm 2 " and the mass of the black toner present on the recording material when the area ratio is "95%" is "0.475 mg / cm 2 " It was.

[0055] For a black toner image formed with an area ratio of "100%," when the "changed UV conditions" were set to an irradiation amount of "50%" and an irradiation time of "200%," the toner image did not discolor (third from the left). In contrast, for a black toner image formed with an area ratio of "95%," when the "changed UV conditions" were set to an irradiation amount of "80%" and an irradiation time of "125%,", the toner image did not discolor (fifth from the left). That is, when the area ratio is the first area ratio, the main control unit 101 sets the irradiation amount to be smaller and the conveying speed to be slower as the "changed UV conditions" compared to when the area ratio is the second area ratio which is smaller than the first area ratio. When the area ratio is "100%," the mass of the black toner image is larger than when the area ratio is "95%," as described above, and the black toner image is more likely to generate heat due to the effect of the irradiation amount. Therefore, the irradiation amount is reduced to suppress heat generation caused by carbon black.

[0056] As described above, it is preferable to change the amount of irradiation light and the irradiation time (conveying speed) under the “changed UV conditions” according to the area ratio, since this makes it possible to both prevent discoloration of the toner image and prevent a decrease in the productivity of the image forming system 1X.

[0057] In the above embodiment, the varnish coater 200 is used as a spot varnish coater, but the present embodiment may be applied even if the varnish coater 200 is used as an overcoat. In the above embodiment, the varnish image is formed according to the "changed UV conditions" when there is a black toner image in the overlapping area, but the present embodiment is not limited to this. The varnish image may be formed by changing the UV conditions, not only in the case of a black toner image, but also in the case of a toner image formed by mixing black toner with toner of another color. Furthermore, the above embodiment can be applied to an image forming system 1X equipped with a monochrome image forming device capable of forming a toner image using only black toner.

[0058] The present technology can also be configured as follows. (1) a first photoconductor on which an electrostatic latent image is formed; a first developing section for developing the electrostatic latent image on the first photoreceptor using a first toner including carbon black; A plurality of second photoconductors on which electrostatic latent images are formed; a plurality of second developing units each developing an electrostatic latent image on the second photoconductor using a plurality of different second toners each not including carbon black; a transfer section that transfers the toner images on the first photoconductor and the plurality of second photoconductors onto a recording material; a fixing section for fixing the toner image transferred onto the recording material; an image forming apparatus having a conveying section that conveys the recording material on which the toner image is fixed; a varnish application section for applying varnish onto the recording material to form a varnished image; an irradiation unit that irradiates the recording material with light of a predetermined wavelength to solidify the varnish image; A varnishing device having a control unit that causes the image forming device to form a toner image on a recording material based on first image data relating to a toner image, and causes the varnish application device to form a varnish image on the recording material based on second image data relating to a varnish image, The control unit, in an overlapping area where a varnish image is formed by superimposing the toner image on the first image data and the second image data, When there is no toner image to be formed using the first toner, the light amount of the irradiation unit is set to a first light amount, the conveying speed of the conveying unit is set to a first speed, and a varnish image is formed in the varnish application device; When there is a toner image to be formed using the first toner, the light amount is set to a second light amount smaller than the first light amount, and the conveying speed is set to a second speed slower than the first speed, causing the varnish application device to form a varnish image. 1. An image forming system comprising: (2) The control unit is When an area ratio of a toner image formed using the first toner with respect to the varnish image in the overlapping region is a first area ratio, the light amount is set to be smaller and the conveying speed is set to be slower than when the area ratio is a second area ratio smaller than the first area ratio. 4. The image forming system according to claim 1, (3) the control unit sets the light amount and the conveying speed such that an integrated light amount based on the first light amount and the first speed is equal to an integrated light amount based on the second light amount and the second speed. 3. The image forming system according to claim 1, wherein the first and second components are arranged in a first direction. (4) an input unit that is provided in the image forming apparatus and that is capable of inputting whether or not to perform a change process for changing the amount of light and the conveying speed depending on whether or not a toner image formed by using the first toner is present in the overlapping area and whether or not a toner image formed by using the first toner is present in the overlapping area, When an input that does not perform the change process is made by the input unit, even if there is a toner image formed using the first toner in the overlapping area, the control unit sets the light amount of the irradiation unit to a first light amount, sets the conveying speed of the conveying unit to a first speed, and causes the varnish application device to form a varnish image, in the same manner as when there is no toner image formed using the first toner in the overlapping area. 4. The image forming system according to claim 1, wherein the image forming system comprises: (5) The first toner is a black toner. 5. The image forming system according to claim 1, wherein the image forming system comprises: (6) The varnish is an ultraviolet curing type UV varnish, The irradiation unit irradiates ultraviolet light to solidify the UV varnish. 6. The image forming system according to claim 1, wherein the image forming system comprises: (7) a photoreceptor on which an electrostatic latent image is formed; a developing section for developing the electrostatic latent image on the photoconductor into a toner image using a toner containing carbon black; a transfer section for transferring the toner image on the photoreceptor to a recording material; a fixing section for fixing the toner image transferred onto the recording material; an image forming apparatus having a conveying section that conveys the recording material on which the toner image is fixed; a varnish application section for applying varnish onto the recording material to form a varnished image; an irradiation unit that irradiates the recording material with light of a predetermined wavelength to solidify the varnish image; A varnishing device having a control unit that causes the image forming device to form a toner image on a recording material based on first image data relating to a toner image, and causes the varnish application device to form a varnish image on the recording material based on second image data relating to a varnish image, The control unit, in an overlapping area where a varnish image is formed by superimposing the toner image on the first image data and the second image data, When there is no toner image to be formed using the toner, the light amount of the irradiation unit is set to a first light amount, the conveying speed of the conveying unit is set to a first speed, and a varnish image is formed in the varnish application device; When there is a toner image to be formed using the toner, the light amount is set to a second light amount smaller than the first light amount, and the conveying speed is set to a second speed slower than the first speed, causing the varnish application device to form a varnish image. 1. An image forming system comprising: [Explanation of symbols]

[0059] 1a, 1b, 1c... second developing section (developing device), 1d... first developing section (developing section, developing device), 1X... image forming system, 3a, 3b, 3c... second photoconductor (photosensitive drum), 3d... first photoconductor (photoconductor, photosensitive drum), 11, 14... transfer section (secondary transfer outer roller, secondary transfer inner roller), 50... fixing section (fixing device), 100... image forming apparatus, 101... control section (main control section), 110... input section (operation section), 200... varnish application device (varnish coater), 241... conveying section (sheet conveying section), 246... varnish application section (varnish discharge section), 247... irradiation section (varnish solidification section), S... recording material

Claims

An image forming apparatus including an image forming unit that forms a toner image on a recording material using a first toner containing carbon black, and a fixing unit that fixes the toner image on the recording material, a conveying unit that conveys the recording material on which the toner image is fixed, a sizing coating unit that applies a sizing agent on the recording material to form a sizing agent image, and an irradiation unit that irradiates the recording material on which the sizing agent image is formed with a light beam having a predetermined wavelength to solidify the sizing agent image, and a control unit, wherein the control unit, when the toner image formed using the first toner and the sizing agent image do not overlap, sets the light amount of the irradiation unit to a first light amount and the conveying speed of the conveying unit to a first speed, and causes the sizing coating apparatus to form a sizing agent image, when the toner image formed using the first toner and the sizing agent image overlap, sets the light amount of the irradiation unit to a second light amount and the conveying speed of the conveying unit to a second speed, and causes the sizing coating apparatus to form a sizing agent image, wherein the second light amount is smaller than the first light amount and the second speed is slower than the first speed, characterizing an image forming system.

2. The control unit sets the light amount of the irradiation unit and the conveying speed of the conveying unit so that the integrated light amount based on the first light amount and the first speed is the same as the integrated light amount based on the second light amount and the second speed. The image forming system according to claim 1, characterized in that.

3. An input unit capable of inputting whether or not to perform a changing process of changing the light amount of the irradiation unit and the conveying speed of the conveying unit is provided, wherein when an input not to perform the changing process is made by the input unit, even when the toner image formed using the first toner and the sizing agent image overlap, the light amount of the irradiation unit is set to the first light amount and the conveying speed of the conveying unit is set to the first speed in the same manner as when the toner image formed using the first toner and the sizing agent image do not overlap, and the sizing coating apparatus is caused to form a sizing agent image. The image forming system according to claim 1, characterized in that.

4. The first toner is a black toner. The image forming system according to claim 1, characterized in that.

5. The sizing agent is an ultraviolet-curable UV sizing agent, and the irradiation unit irradiates ultraviolet rays to solidify the UV sizing agent. The image forming system according to claim 1, characterized in that. **Claim 6**: An image forming apparatus including an image forming unit configured to form a toner image on a recording material using a first toner containing carbon black, and a fixing unit configured to fix the toner image on the recording material, a conveyance unit configured to convey the recording material on which the toner image is fixed, a sizing agent application unit configured to apply a sizing agent on the recording material to form a sizing agent image, and an irradiation unit configured to irradiate the recording material on which the sizing agent image is formed with a light beam having a predetermined wavelength to solidify the sizing agent image, and a control unit, wherein the control unit when the area ratio of the toner image in an overlapping region where the toner image formed using the first toner and the sizing agent image overlap is a first value, sets the light amount of the irradiation unit to a first light amount and the conveyance speed of the conveyance unit to a first speed, and causes the sizing agent application apparatus to form a sizing agent image, when the area ratio of the toner image in the overlapping region is a second value, sets the light amount of the irradiation unit to a second light amount and the conveyance speed of the conveyance unit to a second speed, and causes the sizing agent application apparatus to form a sizing agent image, wherein the second value is larger than the first value, the second light amount is smaller than the first light amount, and the second speed is slower than the first speed, characterizing an image forming system. **Claim 7**: The control unit sets the light amount and the conveyance speed such that an integrated light amount based on the first light amount and the first speed is the same as an integrated light amount based on the second light amount and the second speed. The image forming system according to claim 6, characterized by the above. **Claim 8**: An input unit provided in the image forming apparatus and capable of inputting whether to perform a change process of changing the light amount and the conveyance speed when there is no toner image formed using the first toner in the overlapping region and when there is a toner image formed using the first toner in the overlapping region, wherein when an input not to perform the change process is made by the input unit, the control unit sets the light amount of the irradiation unit to the first light amount and the conveyance speed of the conveyance unit to the first speed, and causes the sizing agent application apparatus to form a sizing agent image even when there is a toner image formed using the first toner in the overlapping region, in the same manner as when there is no toner image formed using the first toner in the overlapping region. The image forming system according to claim 6, characterized by the above. **Claim 9**: The first toner is a black toner. The image forming system according to claim 6, characterized by the above. **Claim 10**: The sizing agent is an ultraviolet curable UV sizing agent. The irradiation unit irradiates ultraviolet rays to cure the UV varnish. The image forming system according to claim 6, characterized in that.

Images