Image forming apparatus

Abstract

Even when the density of multilayer images is high, this suppresses the decrease in fixing strength of multicolor images using varnish. [Solution] An image forming apparatus comprising: an image processing unit that acquires image information for forming an image on a medium, and when the area of ​​a multilayer region in which toner images of multiple colors overlap in the image information is larger than a predetermined size, it performs image processing to form a small-layer region in a part of the multilayer region in which toner images are formed with fewer layers than the number of layers in the multilayer region; an image forming unit that forms a toner image on a medium using the image information from which the image processing has been performed; and a varnish application unit that applies varnish to the toner image formed on the medium.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an image manufacturing method characterized by forming an image of ISO / IEC 15775:1999 compliant test chart No. 4 using an image forming apparatus with an oil-less fixer, and then applying an overcoat layer to the image, which has image defects of up to 3 to 25 μm in the areas with the highest density of red, green, and blue in the formed image, and in which the area ratio of the defect is 2 to 6%. Patent Document 2 describes an image forming method for obtaining a printed object in which an adhesive layer made of a gel-like adhesive is laminated on an image support substrate, and a toner image is held in the adhesive layer, comprising the steps of: forming an electrostatic latent image by exposing a uniformly charged photoreceptor to light; developing the electrostatic latent image with toner to form a toner image; electrostatically transferring the toner image onto the adhesive layer of a substrate sheet, which is made of an adhesive layer made of a gel-like adhesive laminated on an image support substrate; and holding the toner image by pressing the substrate sheet that carries the electrostatically transferred toner image to embed the toner particles constituting the toner image in the adhesive layer, and when an electrostatic latent image formed based on original image data is developed, one or more of the multiple image regions, each having a unit area, formed by dividing the obtained toner image, have an average toner adhesion amount of 2.5 g / m². 2 When it is assumed that the high-density image region exceeds a certain area, the original image data is defined as having an area of ​​6 × 10 per unit in the high-density image region. -11 m 2 The above 1000 x 10 -11 m 2 An image forming method is disclosed, characterized by obtaining corrected image data by performing image processing to form a minute toner-non-adhered area, and forming an electrostatic latent image based on this corrected image data. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-52537 [Patent Document 2] Japanese Patent Publication No. 2013-25207 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] A multi-layered image of multiple colors is formed on a medium, and then varnish is applied to the formed multi-layered image to create a printed image. However, if the density of this multi-layer image is high, the varnish may not penetrate the medium easily, which can reduce the fixing strength of the multi-color image. The present invention aims to suppress the decrease in fixing strength of multicolor images using varnish, even when the density of the multilayer image is high. [Means for solving the problem]

[0005] The invention described in claim 1 is an image forming apparatus comprising: an image processing unit that acquires image information for forming an image on a medium, and when the area of ​​a multilayer region in which toner images of multiple colors overlap on the image information is larger than a predetermined size, it performs image processing to form a small-layer region in a part of the multilayer region in which toner images are formed with fewer layers than the number of layers in the multilayer region; an image forming unit that forms a toner image on the medium using the image information from which the image processing has been performed; and a varnish application unit that applies varnish to the toner image formed on the medium. The invention described in claim 2 is an image forming apparatus according to claim 1, characterized in that the position in which the thin layer region is formed is determined according to the toner concentration in the multilayer region. The invention described in claim 3 is an image forming apparatus according to claim 2, characterized in that the thin layer region is formed in a region with a relatively low toner density within the multilayer region. The invention described in claim 4 is an image forming apparatus according to claim 2, characterized in that the thin layer region is formed in a region with a relatively high toner density within the multilayer region. The invention described in claim 5 is an image forming apparatus according to claim 1, characterized in that the color of the toner forming the thin layer region is selected based on the color of the area surrounding the region in which the thin layer region is formed. The invention described in claim 6 is an image forming apparatus according to claim 5, characterized in that the color of the toner forming the thin layer region is selected to be a color close to the surrounding color. The invention described in claim 7 is such that the number of toner layers forming the small layer region is one. The image forming apparatus according to any one of claims 1 to 6, characterized by the above. The invention described in claim 8 is an image forming apparatus according to claim 7, characterized in that the small layer region is formed in a region within the multilayer region in which there are two toner layers. The invention described in claim 9 comprises a non-contact fixing unit that heats the toner image formed on the medium without contacting it to fix the toner image on the medium, The image forming apparatus according to claim 1 is characterized in that the varnish coating section applies varnish after fixing the toner image formed on the medium with the non-contact fixing section. The invention described in claim 10 further comprises a pressurized fixing unit that heats the toner image formed on the medium under pressure to fix the toner image on the medium, The image forming apparatus according to claim 9, characterized in that it acquires fixing information regarding a method for fixing a toner image formed on the medium, and performs the image processing based on the fixing information. The invention described in claim 11 is an image forming apparatus according to claim 10, characterized in that when the toner image formed on the medium is fixed by the pressurized fixing unit, the amount of toner removed in the thin layer region is increased compared to when it is fixed by the non-contact fixing unit. The invention described in claim 12 is an image forming apparatus according to claim 11, characterized in that when the toner image formed on the medium is fixed by the pressurized fixing unit, the thin layer region is formed in a region with a relatively high toner density within the multilayer region. The invention described in claim 13 is an image forming apparatus according to claim 11, characterized in that when a toner image formed on the medium is fixed by the non-contact fixing unit, the thin layer region is formed in a region with a relatively low toner density within the multilayer region. The invention described in claim 14 is an image forming apparatus according to claim 1, characterized in that the image processing unit acquires lamination information regarding the presence or absence of a lamination process for bonding laminates, and performs the image processing based on the acquired lamination information. The invention described in claim 15 is an image forming apparatus according to claim 14, characterized in that, when the lamination process is present, the amount of toner in the thin-layer region is reduced compared to when the lamination process is absent. The invention described in claim 16 is an image forming apparatus according to claim 15, characterized in that, if there is a lamination step, the thin layer region is formed in a region with a relatively high toner density within the multilayer region. The invention described in claim 17 is an image forming apparatus according to claim 15, characterized in that, in the absence of the lamination process, the thin layer region is formed in a region with a relatively low toner density within the multilayer region. [Effects of the Invention]

[0006] According to the invention of claim 1, even when the density of the multilayer image is high, it is possible to suppress the decrease in the fixing strength of a multicolor image using varnish. According to the invention of claim 2, it is possible to increase adhesive strength while suppressing deterioration of image quality. According to the invention of claim 3, the color difference from the original image can be suppressed. According to the invention of claim 4, the adhesive strength of areas with weak adhesive strength can be increased. According to the invention of claim 5, it is possible to suppress the deterioration of image quality. According to the invention of claim 6, the color difference from the original image can be suppressed. According to the invention of claim 7, the fixing strength can be increased. According to the invention of claim 8, the load of image processing can be suppressed. According to the invention of claim 9, the adhesive strength between the toner image and the substrate can be increased. According to the invention of claim 10, the deterioration of the image can be suppressed. According to the invention of claim 11, the deterioration of the image can be suppressed. According to the invention of claim 12, when the varnish applied to the toner image easily penetrates, the deterioration of the image can be suppressed. According to the invention of claim 13, when the varnish applied to the toner image easily penetrates, the deterioration of the image can be suppressed. According to the invention of claim 14, the amount of varnish corresponding to the laminate can be made to penetrate. According to the invention of claim 15, the adhesive strength with the substrate can be increased. According to the invention of claim 16, while increasing the adhesive strength with the substrate, the deterioration of the image quality can be suppressed. According to the invention of claim 17, while increasing the adhesive strength with the substrate, the deterioration of the image quality can be suppressed.

Brief Description of the Drawings

[0007] [Figure 1] It is a diagram showing the hardware configuration of the image forming apparatus to which this embodiment is applied. [Figure 2] It is a diagram showing the hardware configuration of the transfer unit. [Figure 3] It is a diagram showing the hardware configuration of the control unit. [Figure 4] It is a diagram showing the functional configuration of the control unit. [Figure 5] It is a diagram showing an example of the relationship between the setting information and conditions of a print job. [Figure 6] It is a table showing an example of the contents of conditions 1 to 4 shown in FIG. 5. [Figure 7] It is a flowchart showing an example of the processing executed by the control unit. [Figure 8] It is a diagram showing the verification result. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the attached drawings. [Overall structure] Figure 1 shows the hardware configuration of the image forming apparatus 1 to which this embodiment is applied. In this embodiment, various media with different thicknesses and shapes, such as metal, glass, and tiles, are assumed to be the objects to be printed on. In the example in Figure 1, a metal can is shown as the medium. The image forming apparatus 1 comprises a control unit 10, a receiving unit 20, a transfer unit 30, a fixing unit 40, a varnishing unit 50, and a transport unit 60.

[0009] The control unit 10 controls the entire image forming apparatus 1. The configuration of the control unit 10 will be described later. The reception unit 20 receives instructions from the user for the image forming apparatus 1. The reception unit 20 is, for example, composed of a touch panel. The transfer unit 30 is a unit that transfers an image formed with particles such as toner onto the medium 2. The transfer unit 30 will be described later.

[0010] The fixing unit 40 is a unit that fixes the toner image transferred by the transfer unit 30 onto the medium 2 by heating the medium 2. The fixing unit 40 comprises a non-contact fixing unit 41 and a pressure fixing unit 42. The fixing unit 40 heats the toner image transferred onto the medium 2 using either the non-contact fixing unit 41 or the pressure fixing unit 42. The non-contact fixing unit 41 includes a heat source 411 that heats the toner image formed on the medium 2 without contacting it. Various existing heat sources such as halogen lamps, ceramic heaters, and infrared lamps can be used as the heat source 411. The pressurized fixing unit 42 includes a pressurized roll 421 that heats and pressurizes the toner image formed on the medium 2 to fix the toner image. The pressurized roll 421 is a rotatable cylindrical roll. The pressurized roll 421 has a heat source inside and is heated. The pressurized roll 421 rotates while in contact with the toner image formed on the medium 2, heating the toner image and fixing it to the medium 2. The pressurized roll 421 is provided to be movable in the vertical direction. The pressurized roll 421 moves vertically to contact mediums 2 of different shapes and thicknesses.

[0011] The varnish section 50 comprises a coating section 51 and a post-treatment section 52. The coating unit 51 is an apparatus for applying varnish to the toner image formed on the medium 2, and is an example of a varnish coating unit. The post-processing unit 52 is an apparatus for performing post-processing on the varnish applied to the medium. The coating section 51 comprises a varnish tank 511, a fountain roll 512, and an anilox roll 513. The varnish tank 511 stores and supplies varnish. The varnish tank 511 has recesses for storing varnish. The fountain roll 512 is cylindrical in shape. The fountain roll 512 is immersed in the varnish stored in the recess of the varnish tank 511 and draws up the varnish. The material of the fountain roll 512 is, for example, rubber. The anilox roll 513 receives varnish from the fountain roll 512 and applies a fixed amount of varnish to the medium 2. The anilox roll 513 is cylindrical in shape. The anilox roll 513 and the fountain roll 512 are positioned so that their cylindrical extensions are parallel. The anilox roll 513 and the fountain roll 512 are also positioned so that their sides are in contact with each other. The anilox roll 513 has countless depressions of a certain volume engraved on its side surface. Any varnish supplied to the side of the anilox roll 513 is scraped off by a blade (not shown) that is in contact with the side of the anilox roll 513.

[0012] The post-processing unit 52 is a unit that performs post-processing on the varnish applied in the coating unit 51. The specific unit configuration of the post-processing unit 52 differs depending on the type of varnish applied in the coating unit 51. For example, if a water-based varnish is used, the post-processing unit 52 becomes a device for heat drying. In this case, a halogen lamp is an example of the post-processing unit 52. Also, if a UV varnish is used, the post-processing unit 52 becomes a device for curing the varnish with ultraviolet light. In this case, an ultraviolet irradiation lamp is an example of the post-processing unit 52.

[0013] The transport unit 60 is provided throughout the transfer unit 30, the fixing unit 40, and the varnishing unit 50. The transport unit 60 is provided with a holding unit 61 for holding the printing medium 2. In Figure 1, the holding unit 61 for rotatably holding a cylindrical can is shown. The transport unit 60 transports the medium 2 held by the holding unit 61 in the order of transfer unit 30, fixing unit 40, and varnishing unit 50. The holding unit 61 is detachably attached to the transport unit 60 in order to hold media 2 of different shapes. When the media 2 is a flat metal plate, the holding unit 61 is removed. The flat metal plate is placed on the transport unit 60 and transported.

[0014] [Configuration of the transfer section 30] Figure 2 shows the hardware configuration of the transfer unit 30. The transfer unit 30 forms an image with charged particles and generates an electric field to transfer the image to the medium 2. The transfer unit 30 comprises a developing device 310, a primary transfer roll 320, and an intermediate transfer belt 331. The intermediate transfer belt 331 is stretched by rollers 332, 333 and a backup roll 340. The intermediate transfer belt 331 is stretched between the developing device 310 and the position where the transfer to the medium 2 takes place. The transfer unit 30 also includes a cleaning device 350 for removing particles adhering to the intermediate transfer belt 331.

[0015] The developing unit 310 is a unit that forms an electrostatic latent image of the image to be transferred onto a photoreceptor and develops the image by attaching charged particles to this electrostatic latent image on the photoreceptor. Existing devices used in electrophotographic image forming apparatuses can be used as the developing unit 310. Figure 2 shows an example configuration for color image forming processing using four colors: yellow, magenta, cyan, and black. A separate developing unit 310 is provided for each of these colors, and in Figure 2, the developing units 310 for yellow, magenta, cyan, and black are indicated with the subscripts Y, M, C, and K, respectively, to represent the corresponding color. In the following description, when distinguishing between the colors in relation to the developing unit 310, the subscripts Y, M, C, and K are added to the symbols; however, when it is not necessary to distinguish between the colors, the subscripts are omitted. In this embodiment, a color image is formed using four colors, but the number of toner colors is not particularly limited. For example, orange and green may be added to form a six-color image. Alternatively, spot colors such as gold or silver may be added to form a color image.

[0016] The primary transfer roll 320 is a unit used to transfer (primary transfer) the image formed in the developing unit 310 to the intermediate transfer belt 331. The primary transfer roll 320 is positioned opposite the photoreceptor of the developing unit 310, and the intermediate transfer belt 331 is positioned between the developing unit 310 and the primary transfer roll 320. The primary transfer rolls 320 are provided in correspondence to each of the developing units 310Y, 310M, 310C, and 310K. In Figure 2, each primary transfer roll 320 corresponding to the developing unit 310Y, 310M, 310C, and 310K for each color is indicated with the subscripts Y, M, C, and K to indicate the corresponding color. In the following description, when distinguishing each color with respect to the primary transfer roll 320, the subscripts Y, M, C, and K are added to the symbols, but when it is not necessary to distinguish each color, the subscripts are omitted.

[0017] The intermediate transfer belt 331, rollers 332 and 333, and backup roll 340 are units used to transfer the image formed in the developing apparatus 310 to the medium 2. As shown in Figure 2, the intermediate transfer belt 331 is stretched over the rollers 332 and 333 and the backup roll 340 and rotates in the direction of the arrow in Figure 2 (counterclockwise in the illustrated example). The rotation of the intermediate transfer belt 331 is achieved, for example, by using a roller that rotates one or both of the rollers 332 and 333, and pulling the intermediate transfer belt 331 with the rotation of this roller.

[0018] In the configuration example shown in Figure 2, the outer surface of the intermediate transfer belt 331 is the surface that holds the image (hereinafter referred to as the "transfer surface"). As the intermediate transfer belt 331 passes between the developing device 310 and the primary transfer roll 320, the image is transferred from the photoreceptor of the developing device 310 to the transfer surface of the intermediate transfer belt 331. In the configuration example shown in Figure 2, the developing devices 310Y, 310M, 310C, 310K and the primary transfer rolls 320Y, 320M, 320C, 320K superimpose the toner images of each color onto the transfer surface to form a multi-colored toner image.

[0019] The backup roll 340 brings the transfer surface of the intermediate transfer belt 331 into contact with the medium 2, transferring the image to the medium (secondary transfer). When transferring the image, a predetermined voltage is applied to the backup roll 340. This generates an electric field (hereinafter referred to as the "transfer electric field") in the area including the backup roll 340 and the medium 2, and the image formed by the charged particles is transferred from the intermediate transfer belt 331 to the medium 2. Thus, in order to transfer the image from the intermediate transfer belt 331 to the medium 2, current must flow from the backup roll 340 through the intermediate transfer belt 331 to the medium 2. If the medium 2 is a conductor such as a metal, the transfer electric field is generated by the flow of current through the medium 2 itself, and the image is transferred to the surface of the medium 2. On the other hand, if the medium 2 is not a conductor, no current flows through the medium, and therefore the image cannot be transferred as is. For this reason, when the medium 2 is a non-conductor, measures are taken in advance, such as forming a conductive material on at least the area on the surface of the medium 2 where the image is to be formed, so that current can flow through the medium 2.

[0020] The procedure for transferring an image using the intermediate transfer belt 331 will now be described. As the intermediate transfer belt 331 rotates, the developing units 310Y, 310M, 310C, 310K and the primary transfer rolls 320Y, 320M, 320C, 320K sequentially superimpose images of each color onto the transfer surface of the intermediate transfer belt 331 (the outer surface in Figure 2). Once the images of each color are superimposed, a multicolor image is formed on the transfer surface of the intermediate transfer belt 331. The formed multicolor image reaches the position where the intermediate transfer belt 331 contacts the medium 2 (hereinafter referred to as the "transfer position"). At this point, as described above, a voltage is applied to the backup roll 340 to generate a transfer electric field, and the image is transferred from the intermediate transfer belt 331 to the medium 2.

[0021] The cleaning device 350 is a unit that removes particles adhering to the transfer surface of the intermediate transfer belt 331. The cleaning device 350 is located downstream of the transfer position in the rotational direction of the intermediate transfer belt 331 and upstream of the developing device 310Y and the primary transfer roll 320Y. As a result, after the image is transferred from the intermediate transfer belt 331 to the medium 2, any particles remaining on the transfer surface of the intermediate transfer belt 331 are removed by the cleaning device 350. Then, in the next operation cycle, a new image is transferred to the transfer surface from which the particles have been removed.

[0022] [Hardware configuration of the control unit 10] Figure 3 shows the hardware configuration of the control unit 10. The control unit 10 includes a CPU (Central Processing Unit) 11, RAM (Random Access Memory) 12, ROM (Read Only Memory) 13, and a storage device 14. The control unit 10 also includes a network interface 15. The CPU 11 controls the entire image forming apparatus 1. When the control program is executed by the CPU 11, each functional part of the image forming apparatus 1 is controlled. The RAM 12 is used as a work area when the CPU 11 performs calculations. The ROM 13 is a memory that stores various programs executed by the CPU 11. The storage device 14 stores various settings used to control the image forming apparatus 1, as well as image information used for printing. This storage device 14 can use an HDD (Hard Disk Drive) or semiconductor memory. The network interface 15 connects to an information and communication terminal via a network and acquires various information.

[0023] [Functional configuration of the control unit 10] Figure 4 shows the functional configuration of the control unit 10. The control unit 10 includes a job reception unit 110 and a rasterization unit 120. The control unit 10 also includes a layer number detection unit 130, a specific region detection unit 140, a small layer region determination unit 150, and a small layer region conversion processing unit 160.

[0024] The job reception unit 110 receives print jobs from users via the reception unit 20 (see Figure 1) or the network interface 15 (see Figure 3). Here, a print job includes image information for forming an image on the medium 2 and print setting information. The print setting information includes, for example, the number of prints to be performed and information on the type and size of the medium 2 to be printed on. The print setting information may also include information on whether or not to apply varnish, fixing information, and lamination information.

[0025] Here, fixing information refers to information about the method for fixing the toner image formed on the medium 2. Fixing information, for example, indicates whether or not pressure is applied to the toner image when fixing the toner image formed on the medium 2. More specifically, it is information indicating whether or not to use the non-contact fixing unit 41 (see Figure 1) or the pressurized fixing unit 42 (see Figure 1) of the fixing unit 40 (see Figure 1) when performing fixing. Note that when fixing is done using the pressurized fixing unit 42, pressure is applied to the toner image.

[0026] Here, information regarding lamination refers to information indicating whether or not there is a lamination process in which a laminate film is bonded after the varnishing process. The apparatus for bonding the laminate film may be located outside the image forming apparatus 1 or may be included within the image forming apparatus 1.

[0027] The rasterization unit 120 interprets the acquired image information and creates bitmap data for each CMYK color. In the following explanation, the bitmap data for each CMYK color output from the rasterization unit 120 will be referred to as CMYK raster data.

[0028] The layer number detection unit 130 detects the number of overlapping toner layers in the CMYK raster data using the CMYK raster data before printing. Here, the number of overlapping toner layers means the number of layers where different color toner layers overlap when an image is formed on the medium 2. For example, at a position where the cyan density is 60 and the magenta density is 60, the number of toner layers is 2. Also, for example, at a position where the cyan density is 60, the magenta density is 30, and the yellow density is 30, the number of toner layers is 3. The position where the image is formed may be specified, for example, for each pixel, or for a region of a predetermined size (for example, 0.1 mm 2 ). Hereinafter, in this specification, a region where the number of toner layers is at least 2 or more in a region specified by the position of the image is referred to as a multi-layer region.

[0029] The specific region detection unit 140 detects a region as a specific region when the area of a multi-layer region where toner images of a plurality of colors overlap in the image information is wider than a predetermined size. Here, the area of the multi-layer region is the area where the image is formed on the medium. This predetermined size is determined, for example, in consideration of the adhesive force of the varnish to be applied and the ease of penetration of the varnish into the toner. Examples of the predetermined size include 2 cm 2 , 1.5 cm 2 and the like.

[0030] As a method for detecting a specific region, for example, when the area of a region where the multi-layer regions are continuous is larger than a predetermined size, the multi-layer region may be determined as a specific region. Also, as a method for detecting a specific region, for example, with a position within the multi-layer region as the center, an area of a predetermined size (for example, 2 cm 2A virtual circle is assumed. If there is no area with 1 or 0 toner layers within the virtual circle, the position at the center of the virtual circle may be determined to be a specific area. Alternatively, if there is no area with 1 or 0 toner layers within the virtual circle, the area within that virtual circle may be determined to be a specific area.

[0031] The small-layer area determination unit 150 comprises a position determination unit 151 and a layer selection unit 152. The small-layer area determination unit 150 refers to predetermined conditions based on information regarding the fixing method and information regarding the presence or absence of a lamination process in the print job settings. These conditions are determined, for example, by the manufacturer of the image forming apparatus 1 or by the user of the image forming apparatus 1. These predetermined conditions are stored, for example, in the storage device 14 (see Figure 3) of the control unit 10. These predetermined conditions may also be stored on an external server other than the storage device 14. In this case, the predetermined conditions are referenced from the external server via the network interface 15 (see Figure 3).

[0032] Here, a "low-layer region" refers to a region within a specific area where a toner image is formed with fewer layers than the total number of layers in that specific area. For example, in a region where an image is formed with 3 layers, this region may be defined as a region where 1 layer is deleted and an image is formed with 2 layers. Alternatively, in a region where an image is formed with 3 layers, this region may be defined as a region where 2 layers are deleted and an image is formed with 1 layer.

[0033] In this embodiment, the size of the small layer region is 0.1 cm. 2 The following is defined. The size of the thin layer area refers to the area when printed on medium 2. From the perspective of the print quality of the printed image, it is desirable for the thin layer area to be small so that it is not noticeable. On the other hand, from the perspective of how easily the varnish penetrates, it is desirable for the thin layer area to be large. The size of this thin layer area is determined from various perspectives. For example, the size of the thin layer area may be determined according to the level of image quality desired by the user or the strength of the varnish desired by the user. Furthermore, the number of sub-layers provided in a specific region can be determined, for example, according to the size of the area of ​​the specific region. More specifically, for example, if the area of ​​the specific region is 2 cm² 2 We may also set a condition that n small layers are provided for each layer (where n is a natural number).

[0034] The position determination unit 151 determines the position for forming the low-layer region. The layer selection unit 152 determines the layers to remain in the low-layer region. In other words, it determines the layers to be deleted from the low-layer region. Here, a low-layer region is defined as a region from which at least one toner layer has been deleted from a specific region. The number of layers to be deleted is predetermined; for example, a region with three layers may be reduced to a region with two layers by deleting one layer, or a region with three layers may be reduced to a region with one layer. Alternatively, a region with two layers may be reduced to a region with one layer by deleting one layer.

[0035] The position determination unit 151 determines the position for forming the sub-layer region based on predetermined conditions referenced by the sub-layer region determination unit 150. The conditions for determining the position where the sub-layer region is provided can, for example, be determined using the number of layers in a specific region. For example, the sub-layer region may be formed in a region with three or more layers within a specific region. Alternatively, the sub-layer region may be formed in a region with two layers within a specific region.

[0036] Furthermore, as a predetermined condition, for example, the position where the thin-layer region is formed may be determined according to the toner concentration within the multi-layer region. As a condition according to toner concentration, for example, the thin-layer region may be formed in the region with a higher toner concentration compared within a specific region. Alternatively, for example, the thin-layer region may be formed in the region with a lower toner concentration compared within a specific region. For example, if there is a lamination process, a thin layer region may be formed in areas with relatively high toner density within a specific area, and if there is no lamination process, a thin layer region may be formed in areas with relatively low toner density within a specific area. In other words, if there is a lamination process, the amount of toner in the thin layer region may be reduced compared to the case without a lamination process.

[0037] Furthermore, for example, when fixing a toner image formed on medium 2 using a pressurized fixing unit 42, a thin layer region may be formed in a region with a relatively high toner density within a specific area. Moreover, when fixing a toner image formed on medium 2 using a non-contact fixing unit 41, a thin layer region may be formed in a region with a relatively low toner density within a specific area. In other words, when fixing a toner image formed on medium 2 using a pressurized fixing unit 42, the amount of toner removed in the thin layer region may be greater than when fixing using a non-contact fixing unit 41. Here, "higher toner density" within a specific area means, for example, that the sum of the toner densities of each layer at a certain location is greater than the sum of the toner densities of each layer at the location being compared.

[0038] Furthermore, the layer selection unit 152 selects toner layers that form a sub-layer region according to predetermined conditions referenced by the sub-layer region determination unit 150. Here, one example of predetermined conditions is a condition based on the color of the toner forming the sub-layer region and the color of the area surrounding the region in which the sub-layer region is formed. More specifically, the sub-layer region is selected such that the color of the toner forming the sub-layer region is close to the surrounding color. Here, "close color" can be determined, for example, based on the distance in the L*a*b* color space. The smaller the distance in the L*a*b* color space, the closer the color is considered to be. Alternatively, for example, a distance in a color space based on CIEDE2000, which has been modified based on the characteristics of the color discrimination range of the human eye in the L*a*b* color space, may be used.

[0039] Furthermore, predetermined conditions may include conditions based on the toner concentration of each toner layer. For example, the toner layer with the lowest toner concentration among multiple layers at the location where the thin-layer region is formed may be designated as the toner layer forming the thin-layer region.

[0040] The low-layer region conversion processing unit 160 performs image processing on the CMYK raster data to form low-layer regions. The low-layer region conversion processing unit 160 deletes the image of the low-layer region in toner layers other than the toner layer selected by the layer selection unit 152 as the layer to form the low-layer region. When printing using the CMYK raster data after this processing, the low-layer region will have an image formed only from the selected toner layer.

[0041] [Non-contact fixing method and pressure fixing method] Here, we will explain the difference in varnish penetration between the non-contact fixing method and the pressure fixing method. In the pressure fixing method, the toner particles are crushed during fixing, and the gaps between the toner particles are filled. As a result, when varnish is applied after the fixing process, the varnish has difficulty penetrating into the gaps between the toner particles, and therefore has difficulty penetrating into the substrate. On the other hand, in the non-contact fixing method, the toner is not compressed, and the gaps between the toners are larger compared to the pressure fixing method, allowing the varnish to penetrate more easily. Therefore, in the non-contact fixing method, the varnish penetrates more easily compared to the pressure fixing method.

[0042] Figure 5 shows an example of the relationship between print job settings and conditions. In the example shown in Figure 5, four conditions 1 to 4 are associated with two types of fixing methods and two types of lamination (with or without). This association is stored in the memory device 14 (see Figure 3). Condition 1 is stored in association with a setting where the fixing method is non-contact fixing and lamination is not performed. Condition 2 is stored in association with a setting where the fixing method is pressure fixing and lamination is not performed. Condition 3 is stored in association with a setting where the fixing method is non-contact fixing and lamination is performed. Condition 4 is stored in association with a setting where the fixing method is pressure fixing and lamination is performed.

[0043] Figure 6 is a table showing an example of the contents of conditions 1 to 4 shown in Figure 5. For each of conditions 1 to 4, the conditions for defining the low-layer area are stored. In the example in Figure 6, the conditions for defining the low-layer area are stored as: "the number of layers in which the low-layer area is preferentially placed within a specific area," "the conditions for determining the toner layers that form the low-layer area," and "the number of toner layers that form the low-layer area."

[0044] Condition 1 stores "prioritize 2-layer regions" as the "number of layers at which a low-layer region is preferentially placed within a specific region." This condition means, for example, that if a specific region contains both a 2-layer region and a region with 3 or more layers, the low-layer region will be preferentially placed in the 2-layer region. Furthermore, under Condition 1, the condition for determining the toner layer that forms the smallest region is stored as "retain the toner layer with the smaller color difference." This condition means that the toner layer with the smaller color difference between the color of the smallest region and the color of the surrounding region is selected. The smallest region is then formed using this selected toner layer. Furthermore, the number of toner layers forming the low-layer region is stored as "1 layer". This condition determines the number of toner layers in the low-layer region; if it is "1 layer", the low-layer region is formed by one toner layer. If it is, for example, "2 layers", the low-layer region is formed by two toner layers. In this case, a two-layer low-layer region is formed in a location with at least three toner layers.

[0045] Condition 2 stores "the number of layers in the location where a low-layer region is preferentially placed within a specific region," which is set to "prioritize regions with a large number of layers." This condition means that low-layer regions are preferentially placed in regions with a large number of layers within a specific region. For example, if a specific region contains both a 2-layer region and a 3-layer region, the low-layer region will be placed in the 3-layer region. Furthermore, under Condition 2, the condition for determining the toner layer forming the small-layer area is stored as "retain the toner layer with the lower density." This condition means that among the multiple toner layers in the area where the small-layer area is to be placed, the toner layer with the lower toner density is retained. For example, if the area to be designated as the small-layer area is formed by a layer with a cyan density of 80 percent and a layer with a yellow density of 60 percent, the yellow toner layer with the lower density is retained, and the cyan toner layer is removed. Furthermore, condition 2 stores that the "number of toner layers forming the low-layer region" is "1 layer".

[0046] Condition 3 is the same as Condition 1. Condition 3 stores "prioritize areas with 2 layers" as the "number of layers in the position where low-layer areas are preferentially placed within a specific area." Condition 3 also stores "leave the toner layer with the smaller color difference" as the "condition for determining the toner layers that form the low-layer areas." Furthermore, it stores "1 layer" as the "number of toner layers that form the low-layer areas."

[0047] Condition 4 is the same as Condition 2. Condition 4 stores "prioritize areas with more layers" as the "number of layers in the position where fewer layers are preferentially placed within a specific area." Condition 4 also stores "leave the toner layer with the lower density" as the "condition for determining the toner layer that forms the fewest layers." Furthermore, Condition 4 stores "1 layer" as the "number of toner layers that form the fewest layers."

[0048] [Process flow for executing printing] Figure 7 is a flowchart showing an example of a process performed by the control unit 10, illustrating the flow of the process in which the CPU 11 of the control unit 10 shown in Figure 3 controls the image forming apparatus 1 to perform printing.

[0049] First, the job reception unit 110 receives a print job from the user (step 201). Next, the control unit 10 checks the print settings of the print job to detect whether or not there is a varnishing process (step 202). If the result in step 202 is NO, the control unit 10 causes the image forming apparatus 1 to perform printing according to the normal printing process (step 210), and the process ends.

[0050] Furthermore, if the answer in step 202 is YES, the layer detection unit 130 detects the number of layers relative to the position of the print image in the print job (step 203). Next, the specific area detection unit 140 detects whether or not there is a specific area in the multilayer area (step 204). If the answer in step 204 is NO, the process does not proceed to the step for forming the low-layer area, and the control unit 10 causes the image forming apparatus 1 to perform printing according to the normal printing process (step 210), and the process ends.

[0051] Furthermore, if the answer in step 204 is YES, the process proceeds to the step for forming the sub-layer area. First, the sub-layer area determination unit 150 refers to the conditions for defining the sub-layer area according to the print job settings (step 205). The conditions for defining the sub-layer area are stored in the storage device 14 (see Figure 3). Next, using the referred conditions for defining the sub-layer area, the position determination unit 151 determines the position where the sub-layer area will be formed (step 206). Furthermore, using the referred conditions for defining the sub-layer area, the layer selection unit 152 determines the toner layer that will form the sub-layer area (step 207).

[0052] Furthermore, based on the information of the determined position for forming the thin layer region and the toner layer, the thin layer region conversion processing unit 160 performs image processing to create a thin layer region in the print image included in the print job (step 208). Using the print image after image processing, the control unit 10 causes the image forming apparatus 1 to execute printing (step 209), and the process ends.

[0053] 〔verification〕 By using different image formation and fixing methods, attaching a counter substrate, and then peeling off the counter substrate, we verified the difference in varnish strength due to the image formation method and fixing method. [Verification Method] As the first step, an image was formed on an OHP (Overhead projector) sheet, which is a transparent material used in overhead projectors. As the second step, the image formed on the OHP sheet was fixed. In the third step, varnish was applied to the image that had been fixed onto the OHP sheet. In the fourth step, the opposing substrate was attached to the image coated with varnish. During this attachment process, a portion of the edges of the opposing substrate was left unattached to allow for gripping. This opposing substrate is a so-called laminate film. In the fifth step, the OHP sheet was positioned horizontally with the spreading surface facing the back, and then fixed in place. The grippable portion of the edge of the opposing substrate was then grasped, and the substrate was pulled vertically. The damage to the opposing substrate caused by this pulling was observed, and the strength of the varnish was evaluated.

[0054] Figure 8 shows the verification results. In this verification, three types of images were formed on the OPH sheet. The first type of image was a solid image 501 with the density of CMY each set to 80%. The second type of image was a tonerless image 502, in which a tonerless area was formed in part of the first image where no toner layer was formed. The third type of image was a single-layer image 503, in which a single-layer area with a cyan density of 80% was formed in the area that was designated as a tonerless area in the second image. Then, for each of these three types of images, two samples were created using different fixing methods. One of these fixing methods was pressure fixing, and the other was non-contact fixing.

[0055] In this test, color difference and intensity were each evaluated on a three-point scale from 1 to 3. A higher number on this scale indicates better quality. In this test, solid image 501 was used as the original image with no toner removed, resulting in no color difference and a color difference rating of 3. The tonerless image 502, which had missing areas, showed the background of the medium, and its color difference in the L*a*b* color space was ΔE2.0. The single-layer image 503, which had 80% cyan in one layer, had a color difference of ΔE1.4 in the L*a*b* color space. The single-layer image 503 had less color difference than the tonerless image 502. Therefore, the color difference evaluation for the single-layer image 503 was set to 2, and the color difference evaluation for the tonerless image 502 was set to 1.

[0056] The strength was evaluated by observing the condition of the opposing substrate after pulling it up. A strength rating of 1 indicates that delamination has occurred between the OHP substrate and the toner layer, resulting in complete detachment of the opposing substrate. In other words, the varnish of the image has not penetrated to the OHP substrate. The varnish has hardened on the surface of the image and has not penetrated between the toner particles, resulting in weak strength between the toner particles. The images that received a strength rating of 1 were the solid image 501 with a pressure fixing method and the solid image 501 with a non-contact fixing method.

[0057] In cases where the strength rating was 2, delamination occurred between the OHP substrate and the toner layer, but a portion of the opposing substrate remained bonded to the OHP substrate. The image that received a strength rating of 2 was the single-layer image 503, which uses a pressure fixing method. In the single-layer image 503, which uses a pressure fixing method, the opposing substrate and the OHP substrate remained bonded in the single-layer portion, but delamination occurred between the OHP substrate and the toner layer.

[0058] In cases where the strength rating was 3, the image did not peel off, but the opposing substrate fractured. In other words, the varnish penetrated the toner image and then the OHP substrate, bonding with it and protecting the toner image. The images that received a strength rating of 3 were the single-layer image 503 with a non-contact fixing method, the tonerless image 502 with a pressure fixing method, and the tonerless image 502 with a non-contact fixing method.

[0059] As shown in the verification results in Figure 8, in the single-layer image 503, which has a single-layer area, the degree of intensity differed depending on whether the fixing method was pressure fixing or non-contact fixing. Specifically, the intensity was 3 when using non-contact fixing and 2 when using pressure fixing. In the single-layer area, the varnish intensity was stronger when using non-contact fixing. In the case of non-contact fixing, the toner particles are less crushed compared to pressure fixing, and the gaps between toner particles are larger. Therefore, it was confirmed that in the case of non-contact fixing, the varnish penetrates between the toner images more easily than in the case of pressure fixing, and the varnish reaches the OHP substrate more easily.

[0060] In this embodiment, the conditions for forming a thin layer region are determined based on the fixing method. This makes it easier to determine conditions that suppress the reduction in varnish strength while maintaining the image quality of the thin layer region, compared to cases where the conditions for forming a thin layer region are not determined based on the fixing method.

[0061] 〔others〕 In this embodiment, the fixing unit 40 includes a non-contact fixing unit 41 and a pressure fixing unit 42, but an image forming apparatus may also include only one of these units.

[0062] (Note) (((1))) An image processing unit acquires image information for forming an image on a medium, and when the area of ​​a multilayer region where toner images of multiple colors overlap in the image information is larger than a predetermined size, it performs image processing to form a small-layer region in a part of the multilayer region where toner images are formed with fewer layers than the number of layers in the multilayer region. An image forming unit that forms a toner image on the medium using the image information that has undergone the aforementioned image processing, A varnish coating unit for applying varnish to the toner image formed on the aforementioned medium, An image forming apparatus equipped with the following features. (((2))) The position where the thin layer region is formed is determined according to the toner concentration within the multilayer region. The image forming apparatus described in (((1))) characterized by the following. (((3))) The thin layer region is formed in the region with a lower toner density within the multilayer region. The image forming apparatus described in (((2))) characterized by the following. (((4))) The thin layer region is formed in the region with a relatively high toner density within the multilayer region. The image forming apparatus described in (((2))) characterized by the following. (((5))) The color of the toner forming the aforementioned thin layer region is selected based on the color of the area surrounding the region in which the thin layer region is formed. The image forming apparatus described in (((1))) characterized by the following. (((6))) The toner color used to form the aforementioned thin layer region is selected to be a color close to the surrounding color. The image forming apparatus described in (((5))) characterized by the following. (((7))) The number of toner layers forming the aforementioned small-layer region is one. An image forming apparatus according to any one of (((1))) to (((6))) characterized by the above. (((8))) The small layer region is formed in the region within the multilayer region where there are two toner layers. The image forming apparatus described in (((7))) characterized by the following: (((9))) A non-contact fixing unit heats the toner image formed on the medium without contacting it, thereby fixing the toner image to the medium. Equipped with, The varnish coating section applies varnish after the toner image formed on the medium has been fixed by the non-contact fixing section. An image forming apparatus according to any one of (((1))) to (((8))) characterized by the above. (((10))) Pressurized fixing unit heats the toner image formed on the medium under pressure to fix the toner image to the medium. Furthermore, Fixing information is obtained regarding a method for fixing a toner image formed on the aforementioned medium, and the aforementioned image processing is performed based on said fixing information. The image forming apparatus described in (((9))) characterized by the following. (((11))) When fixing the toner image formed on the medium by the pressurized fixing unit, the amount of toner removed in the thin layer region is increased compared to when fixing by the non-contact fixing unit. The image forming apparatus described in (((10))) characterized by the following. (((12))) When fixing the toner image formed on the medium by the pressurized fixing unit, the thin layer region is formed in the region with a relatively high toner concentration within the multilayer region. The image forming apparatus described in (((11))) is characterized by the following. (((13))) When the toner image formed on the medium is fixed by the non-contact fixing unit, the thin layer region is formed in the region with a relatively low toner density within the multilayer region. The image forming apparatus described in (((11))) is characterized by the following. (((14))) The image processing unit acquires lamination information regarding the presence or absence of a lamination process in which laminates are bonded together, and performs the image processing based on the acquired lamination information. An image forming apparatus according to any one of (((1))) to (((13))) characterized by the above. (((15))) If the lamination process is performed, the amount of toner in the thin-layer region should be reduced compared to the case where the lamination process is not performed. The image forming apparatus described in (((14))) characterized by the following. (((16))) If the lamination process is performed, the thin layer region is formed in the region with a relatively high toner concentration within the multilayer region. The image forming apparatus described in (((15))) characterized by the following. (((17))) If the lamination process is absent, the thin layer region is formed in the region with a relatively lower toner density within the multilayer region. The image forming apparatus described in (((15))) characterized by the following.

[0063] According to the invention of (((1))), even when the density of the multilayer image is high, it is possible to suppress the decrease in the fixing strength of a multicolor image using varnish. According to the invention of (((2))), it is possible to increase adhesive strength while suppressing the deterioration of image quality. According to the invention of (((3))), the color difference from the original image can be suppressed. According to the invention of (((4))), the adhesive strength of areas with weak adhesive strength can be increased. According to the invention of (((5))), it is possible to suppress the deterioration of image quality. According to the invention of (((6))), the color difference from the original image can be suppressed. According to the invention of (((7))), the fixing strength can be increased. According to the invention of (((8))), the load on image processing can be suppressed. According to the invention of (((9))), the adhesive strength between the toner image and the substrate can be increased. According to the invention of (((10))), image degradation can be suppressed. According to the invention of (((11))), image degradation can be suppressed. According to the invention of (((12))), when the varnish applied to the toner image is easily penetrated, image degradation can be suppressed. According to the invention of (((13))), when the varnish applied to the toner image is easily penetrated, image degradation can be suppressed. According to the invention of (((14))), the amount of varnish can be impregnated according to the laminate. According to the invention of (((15))), the adhesive strength with the substrate can be increased. According to the invention of (((16))), it is possible to suppress the deterioration of image quality while increasing the adhesive strength with the substrate. According to the invention of (((17))), it is possible to suppress the deterioration of image quality while increasing the adhesive strength with the substrate. [Explanation of Symbols]

[0064] 1…Image forming apparatus, 2…Medium, 10…Control unit, 11…CPU, 12…RAM, 13…ROM, 14…Storage device, 30…Transfer unit, 40…Fixing unit, 50…Varnish unit, 51…Coating unit, 52…Post-processing unit, 60…Transport unit, 110…Job reception unit, 120…Rasterization unit, 130…Layer detection unit, 140…Specific area detection unit, 150…Small layer area determination unit, 160…Small layer area conversion processing unit

Claims

1. An image processing unit acquires image information for forming an image on a medium, and when the area of ​​a multilayer region where toner images of multiple colors overlap in the image information is larger than a predetermined size, it performs image processing to form a small-layer region in a part of the multilayer region where toner images are formed with fewer layers than the number of layers in the multilayer region. An image forming unit that forms a toner image on the medium using the image information that has undergone the aforementioned image processing, A varnish coating unit for applying varnish to the toner image formed on the aforementioned medium, An image forming apparatus equipped with the following features.

2. The position where the thin layer region is formed is determined according to the toner concentration within the multilayer region. The image forming apparatus according to claim 1, characterized by the following:

3. The thin layer region is formed in the region with a lower toner density within the multilayer region. The image forming apparatus according to claim 2, characterized by the following:

4. The thin layer region is formed in the region with a relatively high toner density within the multilayer region. The image forming apparatus according to claim 2, characterized by the following:

5. The color of the toner forming the aforementioned thin layer region is selected based on the color of the area surrounding the region in which the thin layer region is formed. The image forming apparatus according to claim 1, characterized by the following:

6. The toner color used to form the aforementioned thin layer region is selected to be a color close to the surrounding color. The image forming apparatus according to claim 5, characterized by the following:

7. The number of toner layers forming the aforementioned small-layer region is one. An image forming apparatus according to any one of claims 1 to 6, characterized by the following:

8. The small layer region is formed in the region within the multilayer region where there are two toner layers. The image forming apparatus according to claim 7, characterized by the following:

9. A non-contact fixing unit heats the toner image formed on the medium without contacting it, thereby fixing the toner image to the medium. Equipped with, The varnish coating section applies varnish after the toner image formed on the medium has been fixed by the non-contact fixing section. The image forming apparatus according to claim 1, characterized by the following:

10. Pressurized fixing unit heats the toner image formed on the medium under pressure to fix the toner image to the medium. Furthermore, Fixing information is obtained regarding a method for fixing a toner image formed on the aforementioned medium, and the aforementioned image processing is performed based on said fixing information. The image forming apparatus according to claim 9, characterized by the following:

11. When fixing the toner image formed on the medium by the pressurized fixing unit, the amount of toner removed in the thin layer region is increased compared to when fixing by the non-contact fixing unit. The image forming apparatus according to claim 10, characterized by the following:

12. When fixing the toner image formed on the medium by the pressurized fixing unit, the thin layer region is formed in the region with a relatively high toner concentration within the multilayer region. The image forming apparatus according to claim 11, characterized by the following:

13. When the toner image formed on the medium is fixed by the non-contact fixing unit, the thin layer region is formed in the region with a relatively low toner density within the multilayer region. The image forming apparatus according to claim 11, characterized by the following:

14. The image processing unit acquires lamination information regarding the presence or absence of a lamination process in which laminates are bonded together, and performs the image processing based on the acquired lamination information. The image forming apparatus according to claim 1, characterized by the following:

15. If the lamination process is performed, the amount of toner in the thin-layer region should be reduced compared to the case where the lamination process is not performed. The image forming apparatus according to claim 14, characterized by the following:

16. If the lamination process is performed, the thin layer region is formed in the region with a relatively high toner concentration within the multilayer region. The image forming apparatus according to claim 15, characterized by the following:

17. If the lamination process is absent, the thin layer region is formed in the region with a relatively lower toner density within the multilayer region. The image forming apparatus according to claim 15, characterized by the following:

Images