IMAGE PRODUCTION EQUIPMENT

Abstract

The invention relates to a device that produces images in which the amount of ultraviolet light emitted by light sources 13 arranged corresponding to the crimson ink nozzle 11M and the black ink nozzle 11K is greater than the amount of ultraviolet light emitted by light sources 13 arranged corresponding to the cyan ink nozzle 11C and the yellow ink nozzle 11Y.

Description

Image forming device

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

[0002] Patent Document 1 discloses a process in which a white layer is formed on the surface of a can body using a white inkjet head, and then ultraviolet light is irradiated using an irradiation lamp.

[0003] JP 2015-83480 A

[0004] When forming an image on a can body, one possible embodiment is to provide a curing device for each image forming device, and irradiate the can body with light such as ultraviolet light each time an image is formed on the can body to harden the image. If the light irradiation amount in each curing device is the same, the amount of light irradiation may be too much for an image that you do not want to harden, or conversely, the amount of light irradiation may be insufficient for an image that you want to harden. An object of the present invention is to make it possible to vary the amount of light irradiation applied to each image formed by the image forming device.

[0005] The image forming device to which the present invention is applicable comprises a plurality of image forming means for forming an image on a can body, and a curing means provided to correspond to each of the plurality of image forming means for irradiating light onto the can body on which an image has been formed by the image forming means to harden the image, wherein the amount of light irradiated onto the can body by one curing means included in the plurality of curing means is different from the amount of light irradiated onto the can body by another curing means included in the plurality of curing means.

[0006] Here, the irradiation time for which the one curing means irradiates the can body with light may be different from the irradiation time for which the other curing means irradiates the can body with light, so that the amount of light irradiated by the one curing means and the amount of light irradiated by the other curing means are different. Furthermore, the output when the one curing means irradiates the can body with light may be different from the output when the other curing means irradiates the can body with light, so that the amount of light irradiated by the one curing means and the amount of light irradiated by the other curing means are different. Furthermore, the multiple image forming means may include an image forming means that forms an image including a character image on the can body and an image forming means that forms an image not including a character image on the can body, and the amount of light irradiated by the curing means provided corresponding to the image forming means that forms the image including the character image may be greater than the amount of light irradiated by the curing means provided corresponding to the image forming means that forms the image not including the character image. Furthermore, the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms the image including the text image may be performed before the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms the image not including the text image. Furthermore, a plurality of sets of the image forming means and the curing means provided corresponding to the image forming means may be provided, and processing by each set may be performed in sequence. Among the sequential irradiations of light onto the can body, the irradiation of light by the curing means provided corresponding to the image forming means that forms the image including the text image may be performed first. Furthermore, the amount of light irradiated onto the can body by the curing means provided corresponding to the image forming means that forms the black image on the can body may be greater than the amount of light irradiated onto the can body by the curing means provided corresponding to the image forming means that forms the image of a color other than black on the can body.

[0007] The curing unit corresponding to the image forming unit that forms the black image may irradiate the can body with light before the curing unit corresponding to the image forming unit that forms the non-black image irradiates the can body with light. The image forming unit and the curing unit corresponding to the image forming unit may be provided in multiple pairs, with each pair performing the process in sequence. The curing unit corresponding to the image forming unit that forms the black image may be the first to irradiate the can body with light. The apparatus may further include a blocking unit that is positioned opposite the curing unit when the can body is not positioned opposite the curing unit and blocks light from the curing unit. The blocking unit may be configured to move in conjunction with the moving can body, and may be positioned opposite the curing unit when the can body is not positioned opposite the curing unit, and may be positioned away from the curing unit when the can body is positioned opposite the curing unit. The curing unit may be positioned on the opposite side of the image forming unit, sandwiching the can body positioned opposite the image forming unit. In addition, when the can body is not positioned opposite the image forming means, a blocking section may be provided that is positioned between the image forming means and the curing means and blocks light from traveling from the curing means to the image forming means.

[0008] According to the present invention, the amount of light irradiated onto an image can be made different for each image formed by the image forming means.

[0009] 1 is a top view of an image forming apparatus; FIG. 2 is a view of the image forming unit as viewed from the direction indicated by arrow II in FIG. 1; FIG. 3 is a view showing a state in which a can body has moved from the state shown in FIG. 2 and is positioned between stop positions; FIG. 4 is a view showing an example of an image formed by the image forming unit; FIG. 5 is a view showing another example of the configuration of the image forming unit; FIG. 6 is a view showing another example of the configuration of the image forming unit; FIG. 7 is a view showing another example of an image formed on a can body; (A) to (D) are views showing another example of an image formed on a can body; (A) to (D) are views showing another example of an image formed on a can body; (A) to (D) are views showing another example of an image formed on a can body.

[0010] An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a top view of an image forming apparatus 1 according to this embodiment. The image forming apparatus 1 according to this embodiment is provided with a can body supply unit 510 to which can bodies 10 are supplied. In this can body supply unit 510, the can bodies 10 are attached (supplied) to a support member 20 that supports the can bodies 10. The support member 20 is formed in a cylindrical shape, and the support member 20 is inserted into the cylindrical can body 10, and the can body 10 is attached to the support member 20.

[0011] The image forming apparatus 1 is also provided with a can body discharge section 520 that discharges the can body 10 after the image has been formed on it. In the can body discharge section 520, the can body 10 is removed from the support member 20 and discharged to the outside of the image forming apparatus 1. In this embodiment, a can body moving mechanism 100 is also provided as an example of a can body moving means that moves the can body 10.

[0012] The can body moving mechanism 100 moves the can body 10 so that the can body 10 moves around a predetermined center 30. The can body moving mechanism 100 also stops the can body 10 at each of a plurality of stopping points 40. More specifically, the can body 10 is stopped below each of a plurality of inkjet heads 11 (details of which will be described later).

[0013] In this embodiment, the can body moving mechanism 100 includes a disk-shaped rotating member 110 that rotates around a center 30. In this embodiment, the rotating member 110 supports a plurality of support members 20 (can bodies 10). More specifically, in this embodiment, connecting members 117 are provided that connect the rotating member 110 and the support members 20, and the support members 20 are supported by the rotating member 110 via the connecting members 117. Each of the connecting members 117 protrudes outward in the radial direction of the rotating member 110 from an outer circumferential surface 110A of the rotating member 110. The connecting members 117 are also arranged radially around the center 30.

[0014] In this embodiment, a support member 20 is attached to the tip of each of the connecting members 117, and further, in this embodiment, the can body 10 is supported by the support members 20. The multiple support members 20 (can bodies 10) are arranged side by side in the circumferential direction of the rotating member 110, as shown in Fig. 1 . The multiple support members 20 (can bodies 10) are also arranged radially around the center 30.

[0015] The can body moving mechanism 100 is provided with a first motor M1 that rotates the rotating member 110. Furthermore, in this embodiment, a second motor (not shown) is provided corresponding to each support member 20 and rotates the support member 20 (can body 10) in the circumferential direction. This second motor is housed, for example, inside the connecting member 117. Note that the second motor may also be provided, for example, inside the rotating member 110. When the second motor is provided inside the rotating member 110, a rotational driving force is transmitted from this second motor provided inside the rotating member 110 to the support member 20 via a driving force transmission member such as a gear.

[0016] In addition, in this embodiment, a control device 60 is provided that controls each part of the image forming apparatus 1. The control device 60 controls the rotation of the first motor M1, causing the rotating member 110 to rotate intermittently. In this embodiment, the intermittent rotation of the rotating member 110 repeatedly moves the can body 10 and stops the can body 10 at the stop points 40. As a result, in this embodiment, the can body 10 stops below each of the inkjet heads 11, which will be described later.

[0017] In this embodiment, the second motor is driven, and the support member 20 is rotated when the can body 10 is positioned at least below the inkjet head 11. As a result, when an image is formed by the inkjet head 11, the can body 10 rotates in the circumferential direction, and an image is formed around the entire circumference of the can body 10.

[0018] In this embodiment, the rotation of the rotating member 110 causes the can body 10 (support member 20) to move along a predetermined circular path R1 (hereinafter referred to as the "can body movement path R1"). In other words, in this embodiment, the rotation of the rotating member 110 causes the can body 10 to move around the center 30. Here, in this embodiment, "the can body 10 moves along the circular path" does not mean that the can body 10 moves around the entire circumference of the circular path, but rather that the can body 10 moves along at least a portion of the circular path.

[0019] An image forming unit 120 is provided downstream of the can body supply unit 510 in the direction of movement of the can body 10. In the image forming unit 120, an image is formed on the can body 10. The image forming unit 120 is provided with a plurality of inkjet heads 11. The inkjet heads 11, which are an example of an image forming means, are provided corresponding to each of the stop locations 40, and form an image on the can body 10 located at the stop location 40. As a result, in this embodiment, an image is formed on the outer peripheral surface 10A of the can body 10.

[0020] In this embodiment, ink is ejected from the inkjet head 11 onto the can body 10 located below, thereby forming an image on the can body 10. In this embodiment, a so-called inkjet printing method is used to form an image on the can body 10, which is located at the stop point 40 and rotating in the circumferential direction.

[0021] In this embodiment, inkjet heads 11 for four colors are provided as the inkjet heads 11. Specifically, an inkjet head 11C that ejects cyan ink, an inkjet head 11M that ejects magenta ink, an inkjet head 11Y that ejects yellow ink, and an inkjet head 11K that ejects black ink are provided.

[0022] In addition, inkjet heads 11 that eject ink of colors other than the above four colors, such as inkjet heads 11 that eject white ink or inkjet heads 11 that eject transparent ink, may be provided. In addition, in this embodiment, an example in which four inkjet heads 11 are provided will be described, but the number of inkjet heads 11 to be installed is not particularly limited, and a number other than four inkjet heads 11 may be provided.

[0023] The four inkjet heads 11, inkjet heads 11C to 11K, form images on the can body 10 using ultraviolet-curable ink. In other words, these four inkjet heads 11 form images on the can body 10 using photocurable ink that hardens when irradiated with light such as ultraviolet light. Here, image formation by inkjet printing refers to image formation performed by ejecting ink from the inkjet heads 11 and depositing the ink on the can body 10. Known methods can be used for image formation by inkjet printing. Specifically, for example, a piezo method, a thermal (bubble) method, a continuous method, or the like can be used.

[0024] Fig. 2 is a diagram of the image forming unit 120 as viewed from the direction indicated by arrow II in Fig. 1. In other words, Fig. 2 is a diagram of the image forming unit 120 as viewed from the side of the image forming apparatus 1. When the image forming unit 120 is viewed from the direction indicated by arrow II in Fig. 1, the side surfaces of the inkjet heads 11 and the like shown in Fig. 1 become visible, but Fig. 2 shows the inkjet heads 11, the can body 10, and the light source 13 as viewed from the axial direction.

[0025] In this embodiment, as shown in Fig. 2, a plurality of light sources 13 are provided as an example of a curing unit. The light sources 13 are provided corresponding to each of the plurality of stop positions 40. In other words, the light sources 13 are provided corresponding to each of the plurality of inkjet heads 11. The light sources 13 are formed, for example, by LEDs (Light Emitting Diodes). However, the light sources 13 may be formed by elements other than LEDs.

[0026] The light source 13 irradiates the can body 10, on which an image has been formed by the inkjet head 11, with ultraviolet light (light with a wavelength in the ultraviolet region) (hereinafter referred to as "ultraviolet light"), which is an example of light, to cure the image formed on the can body 10. In this embodiment, the optical path of the ultraviolet light traveling from the light source 13 to the can body 10 is linear. As a result, in this embodiment, energy consumption can be reduced compared to when the ultraviolet light is diffused, and the ultraviolet light can be prevented from traveling to areas other than the can body 10.

[0027] The light source 13 is provided on the opposite side of the inkjet head 11 across the can body movement path R1, which is the path along which the can body 10 moves. In other words, the light source 13 is located on the opposite side of the inkjet head 11 across the can body 10, which is positioned opposite the inkjet head 11. The light source 13 irradiates the can body 10, which is stopped at the stop point 40 and rotating in the circumferential direction, from below with ultraviolet light, as an example of light. This hardens the image formed on the outer peripheral surface 10A of the can body 10.

[0028] In addition, in this embodiment, as shown in Fig. 2, a blocking portion 14 is provided that blocks ultraviolet light from the light source 13. This blocking portion 14 is disposed between adjacent can bodies 10, as also shown in Fig. 1. In other words, the blocking portion 14 is disposed between adjacent support members 20. The blocking portion 14 is fixed to the rotating member 110 by a connecting member 118 (see Fig. 1). Therefore, in this embodiment, when the can body 10 moves due to rotation of the rotating member 110, this blocking portion 14 also moves. In other words, in this embodiment, the blocking portion 14 moves in conjunction with the can body 10.

[0029] 3 is a diagram showing a state in which the can body 10 has moved from the state shown in FIG. 2 and is now positioned between the stop points 40. As shown in FIG. 3, the blocking portion 14 of this embodiment is positioned in a position facing the light source 13 when the can body 10 is not positioned in this position. This causes the blocking portion 14 to block light from the light source 13. More specifically, when the can body 10 is not positioned in a position facing the inkjet head 11, the blocking portion 14 is positioned between the inkjet head 11 and the light source 13, and blocks light from the light source 13 toward the inkjet head 11.

[0030] In this embodiment, when the can body 10 is not located at the stopping point 40, the blocking portion 14 is located on the path R2 along which the ultraviolet light travels from the light source 13 toward the inkjet head 11 located opposite the light source 13. This prevents the ultraviolet light from the light source 13 from reaching the inkjet head 11, making it less likely that problems such as ink curing will occur in the inkjet head 11.

[0031] In this embodiment, the blocking portion 14 is configured by a plate-like member arranged along the horizontal direction. As described above, the blocking portion 14 moves in conjunction with the moving can body 10. Specifically, as described above, the blocking portion 14 is fixed to the rotating member 110 (see FIG. 1 ) to which the can body 10 is fixed, and therefore the blocking portion 14 moves in conjunction with the can body 10.

[0032] As described above, when the can body 10 is not positioned opposite the inkjet head 11, the blocking portion 14 is positioned opposite this position to block ultraviolet light emitted from the light source 13 toward the inkjet head 11. On the other hand, when the can body 10 is positioned opposite the inkjet head 11, as shown in Fig. 2, the blocking portion 14 is positioned away from this opposing position. This allows ultraviolet light to be irradiated from the light source 13 to the can body 10. In this embodiment, as shown in Fig. 3, a plurality of blocking portions 14 are provided, each corresponding to one of the plurality of inkjet heads 11.

[0033] The light source 13 will be further described with reference to Figure 2. In this embodiment, a plurality of light sources 13 are provided. In this embodiment, the irradiation amount of ultraviolet light irradiated onto the can body 10 from each of the light sources 13 is not the same, and the irradiation amount of ultraviolet light irradiated onto the can body 10 by one light source 13 included in the plurality of light sources 13 is different from the irradiation amount of ultraviolet light irradiated onto the can body 10 by another light source 13 included in the plurality of light sources 13.

[0034] Here, images that should not be blurred, such as character images or code images such as barcodes, may be formed on the can body 10. In addition, in order to widely cover the base surface of the can body 10 with an image, background images may be intentionally blurred before being formed on the can body 10.

[0035] In this case, it is preferable to make the amount of ultraviolet light irradiated by the light source 13 provided corresponding to the inkjet head 11 that forms an image on the can body 10 that you do not want to cause bleeding (hereinafter referred to as the ``first irradiation amount'') greater than the amount of ultraviolet light irradiated by the light source 13 provided corresponding to the inkjet head 11 that forms an image on the can body 10 that you do not want to cause bleeding (hereinafter referred to as the ``second irradiation amount'').

[0036] As described above, when the dose of ultraviolet light irradiated onto the can body 10 by one light source 13 is made different from the dose of ultraviolet light irradiated onto the can body 10 by the other light source 13, the first dose can be made greater than the second dose. By making the first dose greater than the second dose, bleeding can be suppressed for images in which bleeding is undesired, such as character images and code images, and the spread of the dot images constituting the image can be ensured for images in which bleeding and spreading are intentionally desired, such as background images.

[0037] 2, the amount of ultraviolet light emitted by the light sources 13 provided corresponding to the magenta inkjet head 11M and the black inkjet head 11K is greater than the amount of ultraviolet light emitted by the light sources 13 provided corresponding to the cyan inkjet head 11C and the yellow inkjet head 11Y. In this case, it is possible to suppress bleeding of the images formed by the magenta inkjet head 11M and the black inkjet head 11K. Also, bleeding and spreading of the dot images constituting the images formed by the cyan inkjet head 11C and the yellow inkjet head 11Y occurs.

[0038] In order to differentiate the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13, as in the present embodiment, for example, a plurality of light sources 13 with the same output power are provided, and the irradiation time for which one light source 13 irradiates the can body 10 with ultraviolet light is differentiated from the irradiation time for which the other light sources 13 irradiate the can body 10 with ultraviolet light. Specifically, for example, by controlling the light sources 13 on and off and differentiating the lighting time for one light source 13 from the lighting time for the other light sources 13, the irradiation amount of ultraviolet light irradiated onto the can body 10 by one light source 13 is differentiated from the irradiation amount of ultraviolet light irradiated onto the can body 10 by one light source 13. When the light sources 13 are controlled on and off in this way, energy consumption is reduced compared to when the light sources 13 are constantly turned on.

[0039] Alternatively, for example, a retractable shutter member may be provided and moved forward and backward along the optical path of the ultraviolet light, thereby making the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 different from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13. Alternatively, for example, a slit that allows ultraviolet light to pass through may be provided and the width of the slit may be widened or narrowed to make the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 different from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13. Alternatively, for example, the distance between the can body movement path R1 and the light sources 13 may be varied for each light source 13, thereby making the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 different from the amount of ultraviolet light irradiated onto the can body 10 by one light source 13.

[0040] Furthermore, for example, in an image forming apparatus 1 in which each can body 10 moves independently, the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 may be made different from the amount of ultraviolet light irradiated onto the can body 10 by varying the stop time of the can body 10 at the stop point 40. More specifically, for example, the image forming apparatus 1 may be provided with a plurality of moving bodies that each have a drive source and can move independently, and these moving bodies may move each can body 10. In this case, by varying the stop time of the moving bodies at each stop point 40, the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 may be made different from the amount of ultraviolet light irradiated onto the can body 10 by the other light sources 13.

[0041] Furthermore, when the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 is made different from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13, for example, the output when one light source 13 irradiates the can body 10 with ultraviolet light may be made different from the output when another light source 13 irradiates the can body 10 with ultraviolet light. When the output when one light source 13 irradiates the can body 10 with ultraviolet light is made different from the output when another light source 13 irradiates the can body 10 with ultraviolet light, for example, multiple types of light sources 13 with different outputs are prepared. Then, light sources 13 with higher output are installed at stopping locations 40 where it is desired to increase the amount of ultraviolet light irradiated onto the can body 10, and light sources 13 with lower output are installed at stopping locations 40 where it is desired to reduce the amount of ultraviolet light irradiated onto the can body 10.

[0042] Alternatively, for example, the amount of power supplied to each light source 13 may be varied to make the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 different from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13. Alternatively, when the amount of ultraviolet light irradiated onto the can body 10 by one light source 13 is varied from the amount of ultraviolet light irradiated onto the can body 10 by another light source 13, both the irradiation time and output may be varied. Specifically, for example, the irradiation time and output when one light source 13 irradiates the can body 10 with ultraviolet light may be varied from the irradiation time and output when the other light sources 13 irradiate the can body 10 with ultraviolet light.

[0043] The "irradiance amount" can be calculated by multiplying the irradiation time by the output of the light source 13. When the irradiation amount of ultraviolet light irradiated onto the can body 10 by one light source 13 is different from the irradiation amount of ultraviolet light irradiated onto the can body 10 by another light source 13, this can be said to mean that these products are different from each other. Furthermore, the concept of "irradiance amount" also includes zero. When the output or irradiation time of one of the light sources 13 and the other light sources 13 is zero and the output or irradiation time of the other light source 13 is not zero, it can also be said that the irradiation amount of ultraviolet light irradiated onto the can body 10 by the one light source 13 is different from the irradiation amount of ultraviolet light irradiated onto the can body 10 by the other light source 13.

[0044] 2 , a downstream light source 19 is provided downstream of the image forming unit 120 in the direction of movement of the can body 10, which irradiates ultraviolet light onto the can body 10 after an image has been formed by the image forming unit 120. The downstream light source 19 is a light source for finishing, and in this embodiment, the amount of ultraviolet light emitted by the downstream light source 19 is greater than the amount of ultraviolet light emitted by each of the light sources 13. More specifically, in this embodiment, the output of the downstream light source 19 is greater than the output of each of the light sources 13, and as a result, the amount of ultraviolet light emitted by the downstream light source 19 is greater than the amount of ultraviolet light emitted by each of the light sources 13.

[0045] In this embodiment, as indicated by the reference symbol 2X in Fig. 2 , a stop position 40 where no light source 13 is installed is provided between the image forming unit 120 and the downstream light source 19. In other words, a stop position 40 where no ultraviolet light is irradiated is provided between the image forming unit 120 and this downstream light source 19. Note that in this embodiment, there is one stop position 40 where no light source 13 is installed, but there may be two or more stop positions.

[0046] In some cases, it may be desirable to intentionally smear the dot image that constitutes the image on the can body 10 between the time the image is formed by the image forming unit 120 and the time the can body 10 reaches the downstream light source 19, thereby expanding the dot image. In this case, if there are no stop positions 40 where the light source 13 is not installed and ultraviolet light is irradiated by the downstream light source 19 immediately after the image is formed, the extent of expansion of the dot image will be small. In contrast, if there are one or more stop positions 40 where the light source 13 is not installed, as in this embodiment, time is ensured for the dot image to expand, and the dot image will expand more.

[0047] When irradiation of ultraviolet light by the downstream light source 19 is completed, the can body 10 moves to the can body discharge section 520 (see FIG. 1 ). In this embodiment, the can body 10 is removed from the support member 20 at the can body discharge section 520 and discharged to the outside of the image forming apparatus 1. The can body 10 discharged to the outside of the image forming apparatus 1 is sequentially transported to, for example, a coating process in which a clear coating is applied to the outer peripheral surface 10A of the can body 10, and a heating process in which the can body 10 coated with the clear coating is heated. When the clear coating is applied to the outer peripheral surface 10A of the can body 10, a protective layer is formed on the outermost layer of the can body 10. Furthermore, the protective layer is hardened by heating the can body 10 in the heating process.

[0048] FIG. 4 is a diagram showing an example of an image formed by the image forming unit 120. In this embodiment, an image 70 shown in FIG. 4 is formed over the entire outer peripheral surface 10A of the can body 10. Specifically, the image 70 is formed so that a long side 71 of the image 70 shown in FIG. 4 is aligned along the circumferential direction of the can body 10 and a short side 72 of the image 70 shown in FIG. 4 is aligned along the axial direction of the can body 10. The image 70 includes a background image 91 covering the base surface of the can body 10, a character image 92, and a code image 93 formed by a barcode or the like. In this embodiment, the character image 92 includes a vertical character image 92A in which characters are aligned along the axial direction of the can body 10, a horizontal character image 92B in which characters are aligned along the circumferential direction of the can body 10, and a numeric character image 92C in which characters representing numbers are aligned.

[0049] In this embodiment, as shown by reference numeral 4B in Fig. 4, the background image 91 is composed of cyan ink and yellow ink. The ink composition ratio of the background image 91 is 50% cyan and 50% yellow. The vertical character image 92A and horizontal character image 92B included in the character image 92 are composed of black ink. The ink composition ratio of the vertical character image 92A and horizontal character image 92B is 100% black.

[0050] In this embodiment, the code image 93 is also composed of black ink. The ink composition ratio of the code image 93 is 100% black. Furthermore, in this embodiment, the numeric character image 92C included in the character image 92 is composed of magenta ink, cyan ink, and black ink. The ink composition ratio of the numeric character image 92C is 80% magenta, 10% cyan, and 10% black.

[0051] In this embodiment, the irradiation amounts of ultraviolet light at the stopping points 40 where the cyan inkjet head 11C, the magenta inkjet head 11M, the yellow inkjet head 11Y, and the black inkjet head 11K are installed are set to 75%, 100%, 25%, and 100%, respectively, as indicated by the reference symbol 4D. Here, each of these irradiation amounts is the irradiation amount when the irradiation amount of ultraviolet light from the light source 13 corresponding to the black ink, which has the greatest irradiation amount, is set to 100%.

[0052] As described above, in this embodiment, there is a desire to intentionally bleed the ink by reducing the amount of ultraviolet light applied to the background image 91. For this reason, in this embodiment, the amount of ultraviolet light applied to the yellow ink that constitutes the background image 91 is reduced to 25%, as shown by the reference symbol 4D.

[0053] Furthermore, the amount of ultraviolet light exposure for the cyan ink constituting the background image 91 is not set to 100%, but is set to 75%, which is less than 100%. Because cyan ink is also used to form the numeric character image 92C, bleeding is not tolerated to a large extent. For this reason, the amount of exposure for the cyan ink is not set to a small value like the 25% exposure for yellow, but is set to 75%, which is less than 100%.

[0054] Furthermore, in this embodiment, the magenta and black inks are used to form vertical character images 92A, horizontal character images 92B, and numeric character images 92C, which are examples of the character image 92, and therefore the amount of ultraviolet light irradiation is increased to 100%. Furthermore, the magenta and black inks are not used to form the background image 91, so the amount of ultraviolet light irradiation is increased to 100%. Furthermore, in this embodiment, the black ink is also used to form the code image 93. To suppress bleeding of the code image 93, the amount of ultraviolet light irradiation for the black ink is set to 100%.

[0055] In this embodiment, the multiple inkjet heads 11 (see FIG. 2 ) include inkjet heads 11 that form an image including the character image 92 on the can body 10, and inkjet heads 11 that form an image not including the character image 92 on the can body 10. Specifically, magenta, black, and cyan inkjet heads 11M, 11K, and 11C are provided as inkjet heads 11 that form an image including the character image 92 on the can body 10. In addition, a yellow inkjet head 11Y is provided as inkjet head 11 that forms an image not including the character image 92 on the can body 10.

[0056] In this embodiment, the amount of ultraviolet light emitted by the light sources 13 provided corresponding to the magenta, black, and cyan inkjet heads 11M, 11K, and 11C, respectively, that form an image including the character image 92 is set to be greater than the amount of ultraviolet light emitted by the light source 13 provided corresponding to the yellow inkjet head 11Y that forms an image that does not include the character image 92. Specifically, the amounts of ultraviolet light emitted by the light sources 13 provided corresponding to the magenta, black, and cyan inkjet heads 11M, 11K, and 11C, respectively, that form an image including the character image 92 are 100%, 100%, and 75%, as shown by reference numeral 4D in Fig. 4. In contrast, the amount of ultraviolet light emitted by the light source 13 provided corresponding to the yellow inkjet head 11Y that forms an image that does not include the character image 92 is 25%.

[0057] In this embodiment, a black inkjet head 11K is provided as the inkjet head 11 that forms an image including the code image 93 on the can body 10. In this processing example, cyan, magenta, and yellow inkjet heads 11C, 11M, and 11Y are provided as inkjet heads 11 that form an image not including a code on the can body 10.

[0058] In this embodiment, the amount of ultraviolet light emitted by the light source 13 provided corresponding to the black inkjet head 11K that forms an image including the code image 93 is 100%, and the amount of ultraviolet light emitted by the light sources 13 provided corresponding to the cyan and yellow inkjet heads 11C and 11Y that form images that do not include the code image 93 is 75% and 25%, respectively. In other words, the amount of ultraviolet light emitted by the light source 13 provided corresponding to the black inkjet head 11K that forms an image including the code image 93 is greater than the amount of ultraviolet light emitted by the light sources 13 provided corresponding to the cyan and yellow inkjet heads 11C and 11Y that form images that do not include the code image 93.

[0059] Furthermore, in this embodiment, the amount of ultraviolet light irradiated onto the can body 10 by the light source 13 provided corresponding to the inkjet head 11K that forms a black image is greater than the amount of ultraviolet light irradiated onto the can body 10 by the light sources 13 provided corresponding to the inkjet heads 11C and 11Y that form images of colors other than black, cyan and yellow, on the can body 10. Specifically, the amount of ultraviolet light irradiated onto the can body 10 by the light source 13 provided corresponding to the inkjet head 11K that forms a black image is 100%. In contrast, the amount of ultraviolet light irradiated onto the can body 10 by the light sources 13 provided corresponding to the inkjet heads 11C and 11Y that form images of cyan and yellow on the can body 10 is 75% and 25%, respectively.

[0060] In many cases, at least black ink is used to form the character image 92 and the code image 93. Therefore, if the amount of ultraviolet light emitted by the light source 13 provided corresponding to the inkjet head 11K that forms a black image on the can body 10 is made greater than the amount of ultraviolet light emitted by the light source 13 provided corresponding to the inkjet head 11 that forms an image of a color other than black on the can body 10, bleeding of the character image 92 and the code image 93 can be suppressed.

[0061] 5 is a diagram showing another example of the configuration of the image forming unit 120. In this example, the black inkjet head 11K is arranged second from the downstream side in the direction of movement of the can body 10, and the yellow inkjet head 11Y is arranged furthest downstream. In this example, the light source 13 provided corresponding to the black inkjet head 11K, which forms an image including the character image 92 and the code image 93, irradiates the can body 10 with ultraviolet light before the light source 13 provided corresponding to the yellow inkjet head 11Y, which forms an image not including the character image 92 and the code image 93, irradiates the can body 10 with ultraviolet light.

[0062] In the above example, it is preferable to reduce the amount of ultraviolet light irradiated onto the image formed with yellow ink, since yellow is used to form the background image 91. In this case, if the yellow inkjet head 11Y is disposed upstream of the black inkjet head 11K as shown in Fig. 2, when the formed yellow image reaches the black inkjet head 11K, the amount of ultraviolet light irradiated onto the yellow image increases, accelerating the curing of the yellow image.

[0063] More specifically, in a case where it is desired to spread the dot images constituting the yellow image over a longer period of time, if a light source 13 with a large irradiation amount corresponding to the black inkjet head 11K is provided immediately downstream of the yellow inkjet head 11Y as shown in Fig. 2, the hardening of the dot images constituting the yellow image will be promoted by this light source 13. In contrast, if the black inkjet head 11K is provided upstream of the yellow inkjet head 11Y as shown in Fig. 5, the yellow image will not be affected by the light source 13 provided corresponding to the black inkjet head 11K.

[0064] 5, the light source 13 provided corresponding to the inkjet head 11K that forms a black image irradiates the can body 10 with ultraviolet light before the light source 13 provided corresponding to the inkjet head 11Y that forms a yellow image, which is an example of a color other than black, irradiates the can body 10 with ultraviolet light. This suppresses the irradiation of the yellow image with ultraviolet light, making it easier to ensure the spread of the dot images that make up the yellow image.

[0065] FIG. 6 is a diagram showing another example of the configuration of the image forming unit 120. In this example, the black inkjet head 11K is arranged furthest upstream. In this embodiment, a plurality of pairs of inkjet heads 11 and light sources 13 corresponding to the inkjet heads 11 are provided, and processing by each pair is performed in sequence. In this example shown in FIG. 6, among the sequential irradiation of ultraviolet light onto the can body 10, irradiation of ultraviolet light by the light source 13 corresponding to the inkjet head 11K that forms a black image is performed first.

[0066] 6, among the sequential irradiations of ultraviolet light onto the can body 10, the first is irradiation of ultraviolet light by the light source 13 provided corresponding to the black inkjet head 11K, which forms an image including the character image 92. In the embodiment described in FIG. 4, the amount of ultraviolet light emitted by the light source 13 provided corresponding to the black inkjet head 11K is the greatest.

[0067] 6, the light source 13 with the greatest irradiation amount is disposed at the most upstream side in the direction of movement of the can body 10, and is configured to be the first to irradiate ultraviolet light from this light source 13. This prevents images that require a smaller amount of ultraviolet light irradiation than black images, such as yellow and cyan images, from being affected by the light source 13 provided for the black inkjet head 11K.

[0068] 6, the inkjet heads 11 and light sources 13 are arranged in descending order of the amount of ultraviolet light irradiated by the light sources 13. In the embodiment shown in FIG. 4, as indicated by the reference symbol 4D, the order of the amount of ultraviolet light irradiated is black, magenta, cyan, and yellow, or magenta, black, cyan, and yellow.

[0069] In this case, as shown in Fig. 6, for example, the inkjet heads 11 and the light sources 13 provided corresponding to the inkjet heads 11 are preferably arranged in the order of black, magenta, cyan, and yellow from upstream to downstream in the direction of movement of the can body 10. Alternatively, although not shown, the inkjet heads 11 and the light sources 13 provided corresponding to the inkjet heads 11 are preferably arranged in the order of magenta, black, cyan, and yellow. In this case, when two light sources 13 adjacent to each other in the direction of movement of the can body 10 are compared, the irradiation amount of the light source 13 that irradiates first is greater than the irradiation amount of the light source 13 that irradiates second. Alternatively, the irradiation amount of the light source 13 that irradiates first is equal to the irradiation amount of the light source 13 that irradiates second.

[0070] 7 and 8A to 8D are diagrams showing other examples of images formed on the can body 10. Fig. 7 shows the state of image 70 after image formation on the can body 10 by the image forming unit 120 is completed. In other words, Fig. 7 shows the state of image 70 after four color inks have been applied to the can body 10. In image 70 shown in Fig. 7, the contours of each component that makes up the image are clearly defined.

[0071] 8A to 8D respectively show an image formed by the cyan inkjet head 11C, an image formed by the black inkjet head 11K, an image formed by the magenta inkjet head 11M, and an image formed by the yellow inkjet head 11Y. In other words, the images shown in each of Figs. 8A to 8D are images formed based on image data of each color obtained by color separation processing of the image data that is the basis of the image shown in Fig. 7.

[0072] 7 and 8A to 8D, the darker the shaded areas are, the higher the image density and the more ink is applied. In this processing example, as shown by the reference numeral 8X in Fig. 8, the amount of ultraviolet light emitted by the light source 13 is set to 75%, 100%, 75%, and 50% for cyan, black, magenta, and yellow, respectively.

[0073] In this processing example, the character image 92 located in the portion indicated by reference numeral 7A in Fig. 7 is formed primarily with black ink, as shown in Fig. 8B. Furthermore, this character image 92 located in the portion indicated by reference numeral 7A in Fig. 7 is small and detailed. For this reason, in this processing example, the amount of ultraviolet light emitted by the light source 13 corresponding to black is set to 100%, as shown by reference numeral 8X in Fig. 8.

[0074] In this processing example, a text image 92 reading "KOBE BAYSIDE" is formed as shown in Fig. 7. In this processing example, the text image 92 is formed mainly with cyan ink and magenta ink as shown in Figs. 8A and 8C. As shown in Figs. 8A and 8C, the cyan ink and magenta ink are also used to form the background image 91 (see Fig. 7).

[0075] For this reason, in this processing example, the amount of ultraviolet light emitted by the light source 13 corresponding to cyan and magenta is set to 75%, as indicated by reference symbol 8X in Fig. 8. On the other hand, yellow ink is not often used to form the character image 92, as shown in Fig. 8(D). For this reason, the amount of ultraviolet light emitted by the light source 13 corresponding to yellow is set to 50%, as indicated by reference symbol 8X in Fig. 8.

[0076] 9 and 10(A) to 10(D) are diagrams showing other examples of images formed on the can body 10. As described above, FIG. 9 shows the state of the image 70 after the image has been formed by the image forming unit 120. In other words, FIG. 9 shows the state of the image 70 after four colors of ink have been applied to the can body 10. In the image 70 shown in FIG. 9, a background image 91 is present on the top, a sharp image such as an image of a building is present on the bottom, and a text image 92 is present on the left.

[0077] 10A to 10D show, respectively, an image formed by the cyan inkjet head 11C, an image formed by the black inkjet head 11K, an image formed by the magenta inkjet head 11M, and an image formed by the yellow inkjet head 11Y, as described above. In other words, as described above, Figures 10A to 10D show images formed based on image data obtained by color separation.

[0078] In this processing example, as indicated by reference numeral 10X in FIG. 10 , the amount of ultraviolet light emitted by the light source 13 is set to 25%, 100%, 75%, and 50% for cyan, black, magenta, and yellow, respectively. In this processing example, black ink is used to form the character image 92 located in the portion indicated by reference numeral 9A in FIG. 9 , as shown in FIG. 10B. The portion indicated by reference numeral 10B in FIG. 10B has a lighter shade, and this black ink is not used much to form the background image 91 (see FIG. 9 ). Therefore, in this example, as indicated by reference numeral 10X in FIG. 10 , the amount of ultraviolet light emitted by the light source 13 corresponding to black is set to 100%.

[0079] In this processing example, cyan and magenta inks are also used to form the character image 92 (see reference numeral 9A in FIG. 9), as indicated by reference numeral 10E in FIGS. 10A and 10C. These cyan and magenta inks are also used to form the background image 91 (see FIG. 9). For this reason, in this processing example, as indicated by reference numeral 10X in FIG. 10, the amount of ultraviolet light emitted by the light source 13 corresponding to cyan is set to 25%, and the amount of ultraviolet light emitted by the light source 13 corresponding to magenta is set to 75%.

[0080] The amount of ultraviolet light emitted by the light source 13 corresponding to magenta is set to 75% instead of 25% in order to promote the curing of the magenta image. In this processing example, as shown in Figure 10 (C), a large amount of magenta ink is used in the lower part of the image to be formed. Therefore, in order to promote the curing of this ink, the amount of ultraviolet light emitted by the light source 13 corresponding to magenta is set to 75%.

[0081] On the other hand, as shown in FIG. 10(D), the amount of yellow ink used to form the character image 92 (see reference numeral 9A in FIG. 9) is smaller than that of black ink. Therefore, as described above, the amount of ultraviolet light irradiated is reduced for yellow. Note that in this processing example, a large amount of yellow ink is used in the lower portion of the image shown in FIG. 10(D). Therefore, in this processing example, the amount of ultraviolet light irradiated by the light source 13 corresponding to yellow is set to 50% in order to promote curing of this lower portion.

[0082] 11 and 12(A) to 12(D) are diagrams showing other examples of images formed on the can body 10. As described above, FIG. 11 shows the state of the image 70 after the image has been formed by the image forming unit 120. In other words, FIG. 11 shows the state of the image 70 after four colors of ink have been applied to the can body 10. The image 70 shown in FIG. 11 is a halftone image, and in the image 70 shown in FIG. 11, the color of the character image 92 is black.

[0083] 12A to 12D show, as with the above, an image formed by the cyan inkjet head 11C, an image formed by the black inkjet head 11K, an image formed by the magenta inkjet head 11M, and an image formed by the yellow inkjet head 11Y, respectively. In other words, FIGS. 12A to 12D show images formed based on image data obtained by color separation. In this processing example, as indicated by reference numeral 12X in FIG. 12, the irradiation amounts of ultraviolet light from the light source 13 are 25%, 100%, 25%, and 25% for cyan, black, magenta, and yellow, respectively.

[0084] In this processing example, as shown in Fig. 12(B), black ink is used predominantly to form the character image 92 such as "Cocktail" shown in Fig. 11. Furthermore, compared to yellow ink, black ink is used less frequently to form the background image 91. For this reason, in this processing example, the amount of ultraviolet light emitted by the light source 13 corresponding to black is set to 100%, as indicated by the reference symbol 12X in Fig. 12.

[0085] Furthermore, in this processing example, the final image 70 (image 70 shown in FIG. 11) is a halftone image, which is an overall light image. In this case, the density of the image formed by each color of ink is low. In this case, the amount of each color of ink used to form the image 70 is reduced, and accordingly, in this processing example, the amount of ultraviolet light irradiation is set to 25% for each color of ink other than black, as shown by the reference symbol 12X in FIG. 12.

[0086] (Others) In the above, an example of a curing unit has been described in which the light source 13 that emits light with a wavelength in the ultraviolet region is provided, but the curing unit may also be a light source 13 that emits light with a wavelength other than the ultraviolet region. If the ink used by the inkjet head 11 when forming an image is ink that is cured by light with a wavelength other than the ultraviolet region, the curing unit will be a light source 13 that emits light with a wavelength other than the ultraviolet region.

[0087] Furthermore, in the above description, the can body 10 moves along the can body movement path R1 having a curve, but the can body movement path R1 along which the can body 10 moves may be linear, and the can body 10 may move along the linear can body movement path R1. Furthermore, in the above description, an example is given in which the light source 13 is provided on the opposite side of the can body movement path R1 from the inkjet head 11, but the location where the light source 13 is installed is not particularly limited, and the light source 13 may be installed on the side where the inkjet head 11 is installed.

[0088] 1... image forming apparatus, 10... can body, 11... inkjet head, 13... light source, 14... blocking portion, 92... character image

Claims

1. An image forming device comprising: a plurality of image forming means for forming an image on a can body; and a curing means provided corresponding to each of the plurality of image forming means, which irradiates light onto the can body on which an image has been formed by the image forming means, thereby curing the image; wherein the amount of light irradiated onto the can body by one of the plurality of curing means is different from the amount of light irradiated onto the can body by another of the plurality of curing means.

2. An image forming device as described in claim 1, wherein the irradiation time for which the one curing means irradiates the can body with light is different from the irradiation time for which the other curing means irradiates the can body with light, and therefore the irradiation amount of light irradiated by the one curing means to the can body is different from the irradiation amount of light irradiated by the other curing means to the can body.

3. An image forming device as described in claim 1, wherein the output when the one curing means irradiates the can body with light is different from the output when the other curing means irradiates the can body with light, so that the amount of light irradiated by the one curing means onto the can body is different from the amount of light irradiated by the other curing means onto the can body.

4. The image forming device according to claim 1, wherein the plurality of image forming means include an image forming means for forming an image including a character image on the can body and an image forming means for forming an image not including a character image on the can body, and the amount of light irradiated by the curing means provided corresponding to the image forming means for forming the image including the character image is greater than the amount of light irradiated by the curing means provided corresponding to the image forming means for forming the image not including the character image.

5. An image forming apparatus as described in claim 4, wherein the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms an image including the character image is performed before the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms an image that does not include the character image.

6. The image forming device according to claim 4, wherein a plurality of sets of the image forming means and the curing means provided corresponding to said image forming means are provided, and processing by each set is carried out in sequence, and among the sequential irradiation of light onto the can body, the irradiation of light by the curing means provided corresponding to the image forming means that forms the image including the character image is carried out first.

7. An image forming apparatus as described in claim 1, wherein the amount of light irradiated onto the can body by the curing means provided corresponding to the image forming means that forms a black image on the can body is greater than the amount of light irradiated onto the can body by the curing means provided corresponding to the image forming means that forms an image of a color other than black on the can body.

8. An image forming apparatus as described in claim 7, wherein the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms the black image is performed before the irradiation of light onto the can body by the curing means provided corresponding to the image forming means that forms the image of a color other than black.

9. The image forming apparatus according to claim 7, wherein a plurality of sets of the image forming means and the curing means provided corresponding to said image forming means are provided, and processing by each set is carried out in sequence, and among the sequential irradiation of light onto the can body, the irradiation of light by the curing means provided corresponding to the image forming means that forms the black image is carried out first.

10. The image forming apparatus according to claim 1, further comprising a blocking section that is positioned at a position opposite the curing means when the can body is not positioned at the position opposite the curing means and blocks light from the curing means.

11. An image forming apparatus as described in claim 10, wherein the blocking portion is configured to move in conjunction with the moving can body, and is located at the opposing position when the can body is not located at the opposing position, and is located at a location away from the opposing position when the can body is located at the opposing position.

12. An image forming apparatus according to claim 1, wherein said curing means is disposed on the opposite side of said image forming means, with said can body disposed in a position opposite said image forming means.

13. The image forming apparatus according to claim 12, further comprising a blocking section that is positioned between the image forming means and the curing means when the can body is not positioned opposite the image forming means and that blocks light from the curing means toward the image forming means.

Images