Ink-jet image forming device

Abstract

To provide an ink-jet image forming device capable of accurately adjusting an image forming position on the basis of a position adjustment mark on an elastic printing base material.SOLUTION: This ink-jet image forming device 1 comprises: an image forming unit 9; a precoat processing unit 5 that is disposed on the upstream side of the image forming unit 9 and that discharges precoat liquid having UV light absorption property; a fluorescent screen 15a disposed between the image forming unit 9 and the precoat processing unit 5; UV light 33 applied to a printing base material M passed on the fluorescent screen 15a; and a camera 35 that photographs the printing base material M irradiated with the UV light 33. A position adjustment mark is formed on the printing base material M by the precoat processing unit 5, the formed position adjustment mark is irradiated with the UV light 33, the irradiated position adjustment mark is photographed by the camera 35, and the image forming unit 9 forms an image on the basis of the photographed position adjustment mark.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet type image forming apparatus that forms an image on a printing substrate by an inkjet method.

Background Art

[0002] In an inkjet type image forming apparatus, in order to enhance the adhesion between a printing substrate and ink, precoat treatment may be performed on the printing substrate. Further, in such an image forming apparatus, as described in Patent Document 1, position adjustment marks called fleas that have been printed on the surface of a medium (printing substrate) are read by an optical sensor, and based on the read fleas, adjustment of the image forming position and color registration during color printing are performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when fleas are pre-printed on a printing substrate, if the printing substrate has a certain degree of stretchability like a plastic film, the printing substrate may stretch during conveyance, and the positions of the fleas may shift. Then, there are problems such as the image forming position shifting or color mixing occurring during color printing.

[0005] Therefore, in consideration of the above circumstances, an object of the present invention is to provide an inkjet type image forming apparatus that can accurately adjust the image forming position based on position adjustment marks even in a printing substrate having stretchability.

Means for Solving the Problems

[0006] To achieve the above object, the inkjet type image forming apparatus of the present invention includes an image forming unit that forms an image by discharging ink onto a printing substrate conveyed along a predetermined conveyance direction, a precoat processing unit that is disposed upstream of the image forming unit in the conveyance direction and discharges a precoat liquid having a property of absorbing UV light onto the printing substrate, a fluorescent paint coating surface disposed between the image forming unit and the precoat processing unit through which the upper surface of the printing substrate passes, a UV light that irradiates the printing substrate passing on the fluorescent paint coating surface with UV light, and a camera that photographs the printing substrate irradiated with the UV light. The precoat processing unit forms a position adjustment mark on the printing substrate using the precoat liquid, irradiates the formed position adjustment mark with UV light from the UV light, photographs the irradiated position adjustment mark with the camera, and the image forming unit forms an image based on the photographed position adjustment mark.

[0007] In the present invention, the precoat liquid may contain a dispersant, and the dispersant may have a property of absorbing UV light.

[0008] In the present invention, the image forming unit includes a head unit that discharges ink, the precoat processing unit includes a head unit that discharges the precoat liquid, and the two head units may have the same structure.

[0009] In the present invention, the printing substrate may be a plastic film.

Effect of the Invention

[0010] According to the present invention, since the position adjustment mark and the image are formed on the printing substrate under the same conditions (elongated state), the position adjustment accuracy is improved, and a good image without ink color mixing or the like can be formed.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Mode for Carrying Out the Invention

[0012] Hereinafter, an inkjet type image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0013] With reference to FIG. 1, the overall configuration of the inkjet type image forming apparatus 1 will be described. FIG. 1 is a front view schematically showing the internal configuration of the inkjet type image forming apparatus 1.

[0014] The inkjet type image forming apparatus 1 includes, in order along the conveyance direction of the printing substrate M, a supply roller 3, a precoat processing unit 5, an imaging unit 7, an image forming unit 9, a drying unit 11, and a take-up roller 13. Further, the inkjet type image forming apparatus 1 includes a conveyance plate 15 disposed below the precoat processing unit 5, the imaging unit 7, and the image forming unit 9 between the supply roller 3 and the drying unit 11.

[0015] First, the supply roller 3 will be described. A long printing substrate M is wound around the supply roller 3. By rotating the supply roller 3, the printing substrate M is sent out in a predetermined conveyance direction X.

[0016] Next, the precoat processing unit 5 will be described. The precoat processing unit 5 performs precoat processing on the printing substrate M sent out from the supply roller 3. The precoat processing unit 5 includes a precoat head unit 21 that discharges a precoat liquid. The precoat head unit 21 is electrically connected to the control unit 61.

[0017] Referring to FIG. 2, the precoat head unit 21 will be described. FIG. 2 is a plan view showing the precoat head unit 21. The precoat head unit 21 includes three print heads 23 and a plate 25 that supports the three print heads 23. The three print heads 23 are arranged in a staggered manner along the width direction Y (in a line head method) so as to be approximately the same as the width of the printing substrate M (the length along the width direction Y intersecting the conveyance direction X), and are supported by the plate 25. The precoat liquid is supplied from a precoat liquid supply source to the three print heads 23.

[0018] The print head 23 includes a large number of nozzles and a piezoelectric element provided in each nozzle. The discharge port of the nozzle opens on the lower surface of the print head 23. By applying a voltage to the piezoelectric element, the piezoelectric element deforms, and the precoat liquid in the nozzle is discharged downward from the discharge port.

[0019] The components of the precoat liquid are, for example, 10% of an aqueous dispersion of polyester resin (trade name: Pesresin A-640, manufactured by Takamatsu Resin Co., Ltd.), 0.04% of a surfactant (trade name: Surfynol 440, manufactured by Nissin Chemical Industry Co., Ltd.), 25% of propylene glycol, and 64.96% of water. Among these, the surfactant contains a component having an acetylene bond that has the property of absorbing UV light.

[0020] Next, the imaging unit 7 will be described with reference to FIG. 1. The imaging unit 7 includes a light-shielding box 31 with an open lower surface, and a UV light 33 and a camera 35 arranged inside the light-shielding box 31. The light-shielding box 31 is arranged such that the open lower surface faces the printing substrate M that has passed through the precoat processing unit 5.

[0021] The UV light 33 irradiates the printed base material M that has passed through the precoat processing unit 5 with UV light inside the light-shielding box 31. The camera 35 images the printed base material M irradiated by the UV light 33. The camera 35 is electrically connected to the control unit 61.

[0022] Next, the image forming unit 9 will be described. The image forming unit 9 forms an image on the printed base material by an inkjet method. The image forming unit 9 includes four image forming head units 41B, 41C, 41M, and 41Y (collectively referred to as the image forming head unit 41) corresponding to four colors (black, cyan, magenta, and yellow) of ink. The four image forming head units 41 are arranged in order along the conveyance direction X. The four image forming head units 41 are electrically connected to the control unit 61.

[0023] The image forming head unit 41 has the same configuration as the precoat head unit 21 of the precoat processing unit 5 shown in FIG. 2, and includes three print heads 43 and a plate 45 that supports the three print heads 43. Black, cyan, magenta, and yellow inks are supplied to the three print heads 43 of the four image forming head units 41, respectively.

[0024] The print head 43 includes a large number of nozzles and piezoelectric elements provided in each nozzle. The discharge port of the nozzle opens on the lower surface of the print head 43. By applying a voltage to the piezoelectric element, the piezoelectric element deforms, and the ink in the nozzle is discharged downward from the discharge port.

[0025] Next, the drying unit 11 will be described with reference to FIG. 1. The drying unit 11 dries the image formed on the printing substrate M in the image forming unit 9. The drying unit 11 includes a heat drum 51, and upstream and downstream tension rollers 53 and 55 disposed on the upstream side and the downstream side of the heat drum 51. The printing substrate M that has passed through the image forming unit 9 is wound around the heat drum 51 between the upstream and downstream tension rollers 53 and 55. The heat drum 51 is heated to dry the printing substrate M conveyed along its surface.

[0026] Next, the take-up roller 13 will be described. An end of the printing substrate M is fixed to the take-up roller 13. The take-up roller 13 is connected to a motor (not shown) and rotates. By rotating the take-up roller 13 in a predetermined direction at a predetermined rotational speed by the motor, the printing substrate M is fed out from the supply roller 3. The fed-out printing substrate M passes through the precoat processing unit 5, the imaging unit 7, the image forming unit 9, and the drying unit 11, and is wound around the take-up roller 13.

[0027] Next, the conveying plate 15 will be described. As shown in FIG. 1, the conveying plate 15 is disposed below the precoat processing unit 5, the imaging unit 7, and the image forming unit 9. The upper surface of the conveying plate 15 is formed flat. Also, as shown in FIG. 2, the width of the conveying plate 15 is wider than the width of the printing substrate M and all the image forming head units 41. A heat source (not shown) is provided below the conveying plate 15 to heat the conveying plate 15 to a predetermined temperature. The conveying plate 15 is made of, for example, metal.

[0028] A fluorescent paint is applied to a portion of the upper surface of the conveying plate 15 that faces the imaging unit 7. The surface to which the fluorescent paint is applied (fluorescent paint application surface) is defined as the fluorescent surface 15a.

[0029] Next, the control unit 61 will be described. As shown in FIG. 1, the control unit 61 controls the precoat head unit 21 of the precoat processing unit 5 and the four image forming head units 41 of the image forming unit 9. Further, the image data captured by the camera 35 of the imaging unit 7 is input to the control unit 61.

[0030] The image forming operation of the inkjet type image forming apparatus 1 having the above configuration will be described with reference to FIG. 3. FIG. 3 is a diagram for explaining the operation of the imaging unit 7.

[0031] During the image forming operation, the motor is driven to rotate the take-up roller 13, and the printing substrate M is fed out from the supply roller 3. When the printing substrate M reaches below the precoat processing unit 5, the control unit 61 controls the precoat processing unit 5 to form a position adjustment mark T using a precoat liquid at a predetermined position outside the image forming area R1 of the printing substrate M as shown in the lower diagram of FIG. 3. The position adjustment mark T is, for example, an arrow. Note that the precoat processing unit 5 performs a precoat process of discharging the precoat liquid in the normal manner in the image forming area R2.

[0032] When the printed substrate M is conveyed and the formed position adjustment mark T reaches below the imaging unit 7, the position adjustment mark T is irradiated with UV light by the UV light 33. When the position adjustment mark T is irradiated with visible light, since the printing substrate M and the precoat liquid are transparent, only the fluorescent surface 15a of the conveyance plate 15 can be seen, and the position adjustment mark T and other parts cannot be distinguished.

[0033] However, when the position adjustment mark T is irradiated with UV light, as shown in the lower diagram of FIG. 3, the portion T' (printing substrate M) other than the position adjustment mark T allows the UV light to pass through. As shown in the upper left diagram of FIG. 3, the transmitted UV light irradiates the fluorescent surface 15a of the transport plate 15, causing the fluorescent surface 15a to fluoresce. On the other hand, as shown in the upper right diagram of FIG. 3, since the position adjustment mark T is formed of a precoat liquid having the property of absorbing UV light, the UV light is absorbed. Therefore, the fluorescent surface 15a below the position adjustment mark T is not irradiated with UV light and does not fluoresce. As a result, as shown in the lower diagram of FIG. 3, the position adjustment mark T becomes darker than the other portion T' and is visualized. Also, since the periphery of the UV light 33 is surrounded by the light-shielding box 31, external light is shielded, and the position adjustment mark T can be seen more clearly.

[0034] The visualized position adjustment mark T is photographed by the camera 35. The photographed position adjustment mark T is transmitted to the control unit 61. The control unit 61 adjusts the printing position of the formed image based on this mark T. The image forming unit 9 discharges ink of a predetermined color from the print head 43 of the image forming head unit 41 based on the image data at the adjusted printing position, and forms an image on the printing substrate M. The printing substrate M on which the image is thus formed is conveyed to the drying unit 11. In the drying unit 11, the ink is completely dried. Thereafter, the printing substrate M is wound up by the winding roller 13.

[0035] As described above, according to the present invention, based on the position adjustment mark T formed by the precoat processing unit 5, the printing position of the image by the image forming head unit 41 of the image forming unit 9 is adjusted (alignment). When the printing substrate M is made of a material having a certain degree of elasticity, such as a plastic film, it may be stretched and elongated when the printing substrate M is conveyed by the two rollers 3 and 13. For this reason, for example, when a position adjustment mark is previously marked on the printing substrate M, the position of the position adjustment mark may move.

[0036] However, in the present embodiment, the position adjustment mark T is formed by the precoat process immediately before image formation. Therefore, the position adjustment mark T and the image are formed on the printing substrate M under the same conditions (extended state). Accordingly, the position adjustment accuracy is improved, and a good image without ink color mixing or the like can be formed.

[0037] With reference to FIGS. 4A and 4B, the effects of the present invention will be described. A test image in which four different color images are adjacent to each other was printed at 600 dpi. FIG. 4A shows a test image of an example in which the position adjustment of the present embodiment is performed, and FIG. 5B shows a test image of a comparative example in which normal position adjustment is performed.

[0038] As shown in FIG. 4A, in the example, the boundary portions of the images of different colors are clear. On the other hand, as shown in FIG. 4B, in the comparative example, it can be seen that the boundary portions of the images of different colors are blurred and color mixing has occurred.

[0039] In the present embodiment, since the printing substrate M is conveyed along the upper surface of the conveying plate 15, there is a possibility that the fluorescent surface 15a comes into contact with the printing substrate M and peels off. Therefore, it is preferable to convey the printing substrate M while slightly floating it from the upper surface of the conveying plate 15.

[0040] In the above embodiment, the four-color head unit 41 is used, but the present invention is not limited to four colors, and may be more or less than four colors. Further, the head unit 41 is not limited to the line head method. However, the line head method is preferable because the printing speed can be increased. Further, although a long plastic film (PET film) is used as the printing substrate M, a cut film may also be used.

[0041] Although the present invention has been described with respect to specific embodiments, the present invention is not limited to the above embodiments. Those skilled in the art can modify the above embodiments without departing from the scope and gist of the present invention.

Description of Reference Numerals

[0042] 1 Inkjet type image forming apparatus 5 Precoat Processing Unit 9 Image Forming Unit 15a Fluorescent Surface (Fluorescent Paint Coated Surface) 21 Precoat Head Unit 33 UV Light 35 Camera 41 Image Forming Head Unit

Claims

1. An image forming unit that discharges ink onto a printing substrate conveyed along a predetermined conveyance direction to form an image, A precoat processing unit that is disposed upstream of the image forming unit in the conveyance direction and discharges a precoat liquid having a property of absorbing UV light onto the printing substrate, A fluorescent paint coating surface disposed between the image forming unit and the precoat processing unit, through which the upper surface of the printing substrate passes, A UV light that irradiates the printing substrate passing through the fluorescent paint coating surface with UV light, A camera that photographs the printing substrate irradiated with the UV light, and comprising, In the precoat processing unit, a position adjustment mark is formed on the printing substrate using the precoat liquid, the formed position adjustment mark is irradiated with UV light by the UV light, the irradiated position adjustment mark is photographed by the camera, and the image forming unit forms an image based on the photographed position adjustment mark. An inkjet type image forming apparatus characterized by the above.

2. The inkjet type image forming apparatus according to claim 1, wherein the precoat liquid contains a dispersant, and the dispersant has a property of absorbing UV light.

3. The image forming unit includes a head unit that discharges ink, The precoat processing unit includes a head unit that discharges the precoat liquid, and the two head units have the same structure. The inkjet type image forming apparatus according to claim 1.

4. The inkjet type image forming apparatus according to claim 1, wherein the printing substrate is a plastic film.

Images