Image formation apparatus

Abstract

To provide an inkjet type image formation apparatus that can perform a precoat treatment according to the characteristics of a printing base material.SOLUTION: An image formation apparatus 1 includes: head units 13B, 13C, 13M, 13Y for ink that discharge ink onto a printing base material M conveyed along a predetermined conveyance direction; a head unit 11 for precoat liquid that is arranged on the upstream side in the conveyance direction of the head units 13B, 13C, 13M, 13Y for ink and discharges the precoat liquid to the printing base material; and a control unit 19 that controls the head unit 11 for precoat liquid to discharge the precoat liquid. When surface tension M of the printing base material is lower than a predetermined value, the control unit 19 controls the head unit 11 for precoat liquid to discharge a predetermined amount of precoat liquid.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In an inkjet type image forming apparatus, a precoat process is generally performed in which a precoat liquid is applied to improve adhesion between a printing substrate and ink.

[0003] The image forming apparatus described in Patent Document 1 determines the amount of precoat liquid to be ejected based on the type of ink and the amount of ink deposited per unit area on the printing substrate, which is said to improve the abrasion resistance of the printing substrate on which the image is formed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-172218 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the adhesion between the printing substrate and the ink is thought to depend not only on the type of ink and the amount of ink ejected per unit area as described in Patent Document 1 above, but also on the characteristics of the printing substrate.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In consideration of the above circumstances, an object of the present invention is to provide an inkjet type image forming apparatus capable of performing a precoat process suited to the characteristics of a printing substrate. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the image forming apparatus of the present invention comprises an ink head unit that ejects ink onto a printing substrate transported along a predetermined transport direction, a precoat liquid head unit that is positioned upstream of the ink head unit in the transport direction and ejects precoat liquid onto the printing substrate, and a control unit that controls the precoat liquid head unit to eject the precoat liquid, wherein the control unit controls the precoat liquid head unit to eject a predetermined amount of the precoat liquid when the surface tension of the printing substrate is lower than a predetermined value.

[0008] In the present invention, the control unit may be provided with an input unit for inputting the surface tension of the printing substrate.

[0009] In the present invention, the control unit may be configured to control the precoat liquid head unit to eject a predetermined amount of the precoat liquid when the surface tension of the printing substrate is less than 38 mN / m.

[0010] In the present invention, the printing substrate may be a plastic film. Effect of the Invention

[0011] According to the present invention, by performing a precoat process only when the surface tension of the printing substrate is below a predetermined value, it is possible to increase the adhesion between the ink and the printing substrate, which is not compatible with the ink, and also to perform the precoat process efficiently. [Brief description of the drawings]

[0012] [Figure 1] 1 is a front view showing a schematic diagram of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a plan view showing a head unit in the image forming apparatus according to one embodiment of the present invention. [Diagram 3]5A to 5C are diagrams illustrating the behavior of droplets on printing substrates having different surface tensions in an image forming apparatus according to an embodiment of the present invention. [Figure 4] 5 is a table showing the results of an evaluation test of line width reproducibility and ink drying state in an image forming apparatus according to an embodiment of the present invention. [Figure 5A] FIG. 4 is a diagram showing the results of line width reproducibility (Example 1) in an image forming apparatus according to one embodiment of the present invention. [Figure 5B] FIG. 11 is a diagram showing the results of line width reproducibility (Comparative Example 2) in an image forming apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will now be described with reference to the drawings.

[0014] The overall configuration of the image forming apparatus 1 will be described with reference to Fig. 1. Fig. 1 is a front view showing a schematic internal configuration of the image forming apparatus 1.

[0015] The image forming apparatus 1 includes a supply roller 3 around which a long length of printing substrate M is wound, an image forming section 5 that forms an image on the printing substrate M supplied from the supply roller 3 using an inkjet method, a drying section 7 that dries the image formed in the image forming section 5, and a take-up roller 9 that takes up the printing substrate M dried in the drying section 7.

[0016] The printing substrate M is wound around the supply roller 3. As the supply roller 3 rotates, the printing substrate M is fed in a predetermined transport direction.

[0017] The image forming unit 5 is disposed downstream of the supply roller 3 in the transport direction. The image forming unit 5 includes one precoat liquid head unit 11, four ink head units 13B, 13C, 13M, and 13Y (collectively referred to as 13), and a transport plate 15 along whose surface the printing substrate M is transported.

[0018] One precoat liquid head unit 11 is disposed upstream in the transport direction from the four ink head units 13. The precoat liquid head unit 11 and the four ink head units 13 have the same structure. The head units 11 and 13 are electrically connected to a control unit 19.

[0019] As shown in Fig. 2, each of the precoat liquid head unit 11 and the four ink head units 13 includes three print heads 21 and a plate 23 that supports the three print heads 21. Fig. 2 is a plan view showing each head unit 13.

[0020] 2, the three print heads 21 are arranged in a staggered pattern (line head system) along the width direction Y so that their length is approximately the same as the width of the printing substrate M (the length along the width direction Y intersecting the transport direction X), and are supported by a plate 23. Each print head 21 is equipped with a number of nozzles (not shown). The nozzle outlets open on the bottom surface of the print head 21.

[0021] Precoat liquid is supplied to each print head 21 of the precoat liquid head unit 11. The supplied precoat liquid is discharged downward from the discharge port of each print head 21. The components of the precoat liquid are, for example, 10% polyester resin (product name: Pesresin A-640, manufactured by Takamatsu Resin Co., Ltd.), 0.04% surfactant (product name: Surfynol 440, manufactured by Nissin Chemical Industry Co., Ltd.), 25% propylene glycol, and 64.96% water.

[0022] The four ink head units 13B, 13C, 13M, and 13Y are arranged in sequence along the transport direction X, and supply black, cyan, magenta, and yellow ink, respectively. The supplied ink is ejected downward from the ejection openings of each print head 21.

[0023] 1 again, the transport plate 15 is disposed below one precoat liquid head unit 11 and four ink head units 13. The upper surface of the transport plate 15 is formed flat. As shown in FIG. 2, the width of the transport plate 15 is wider than the width of the printing substrate M and all of the head units 11, 13. A heat source (not shown) is provided below the transport plate 15, and heats the transport plate 15 to a predetermined temperature. The transport plate 15 is made of, for example, metal.

[0024] The printing substrate M sent out from the supply roller 3 is transported along the upper surface of a transport plate 15 below the precoat liquid head unit 11 and the ink head unit 13 .

[0025] The drying section 7 is disposed downstream of the image forming section 5 in the transport direction. The drying section 7 includes a heat drum 31, and upstream and downstream tension rollers 33, 35 disposed upstream and downstream of the heat drum 31. The printing substrate M that has passed through the image forming section 5 is wound around the heat drum 31 between the upstream and downstream tension rollers 33, 35. The heat drum 31 dries the printing substrate M transported along its surface by being heated.

[0026] The winding roller 9 is disposed downstream of the drying unit 7 in the transport direction. One end of the printing substrate M is fixed to the winding roller 9. The winding roller 9 is connected to a motor (not shown) and rotates. The motor rotates the winding roller 9 in a predetermined direction at a predetermined rotation speed, thereby feeding the printing substrate M from the supply roller 3. The fed printing substrate M passes through the image forming unit 5 and the drying unit 7, and is wound up by the winding roller 9.

[0027] The control unit 19 controls the head unit 13 as described above. Furthermore, the control unit 19 is provided with an input unit 19a such as a display panel. The input unit 19a includes a surface tension input unit for inputting the value of the surface tension of the printing substrate M. The value of the surface tension is a value measured in accordance with, for example, "JIS K 6768:1999 Plastics - Films and Sheets - Wetting Tension Test Method."

[0028] An image forming operation of the image forming apparatus 1 having the above configuration will be described. During the image forming operation, first, the user inputs the surface tension of the printing substrate M to the input unit 19a of the control unit 19. If the input value of the surface tension is less than 38 mN / m, the control unit 19 adjusts the surface tension to a predetermined value (for example, 2.0 g / m 2 The precoat liquid head unit 11 is controlled so as to eject the precoat liquid (a).

[0029] Thereafter, the motor is driven to rotate the take-up roller 9, and the printing substrate M is sent from the supply roller 3 to the image forming section 5. In the image forming section 5, the printing substrate M is transported along the upper surface of the transport plate 15. When the printing substrate M is transported below the precoat liquid head unit 11, the control section 19 controls the precoat liquid head unit 11 to eject a predetermined amount of precoat liquid onto the printing substrate M based on the image data. On the other hand, if the input surface tension value is higher than 38 mN / m, the control section 19 controls the precoat liquid head unit 11 not to eject the precoat liquid. In other words, if the input surface tension value is 38 mN / m or more, the precoat process is not performed.

[0030] The printing substrate M is then transported below the ink head units 13, and ink of a predetermined color is ejected from the corresponding head units 13 based on image data. At this time, the ink is dried auxiliarily by the heated transport plate 15. The ink reacts with the precoat liquid and becomes difficult to move from the position where it landed. The printing substrate M on which the image has been formed in this manner is transported to the drying section 7. In the drying section 7, the ink is completely dried. The printing substrate M is then taken up by the take-up roller 9.

[0031] As described above, according to the present invention, the precoat process is performed only when the surface tension of the printing substrate M is less than 38 mN / m. When the surface tension of the printing substrate M is low, the surface energy of the printing substrate M is low and stable, so that the landed ink droplets are easy to move from the landing position on the printing substrate M. As a result, as shown in the left diagram of FIG. 3, two ink droplets may be attracted to each other and become one large droplet after drying. Then, the size of the droplets becomes non-uniform, and as a result, the line width becomes non-uniform. On the other hand, when the precoat process is performed, the adhesion between the ink and the printing substrate M is increased, and the landed ink droplets are difficult to move from the landing position on the printing substrate M. As a result, as shown in the right diagram of FIG. 3, the two ink droplets blend with the printing substrate M and are not attracted to each other. Note that when the surface tension of the printing substrate M is high (for example, 38 mN / m or more), the surface energy of the printing substrate M is high and unstable, so that other objects (such as ink) are easy to attach to the surface. In other words, the ink blends with the printing substrate M easily.

[0032] Therefore, by performing the precoat process only when the surface tension of the printing substrate M is less than 38 mN / m, it is possible to increase the adhesion between the printing substrate M and the ink and to perform the precoat process efficiently. A printing substrate with a surface tension of less than 38 mN / m is, for example, a plastic film made of PET or polypropylene.

[0033] Next, a test for evaluating the relationship between the surface tension of the printing substrate, the line width reproducibility, and the drying state in the image forming apparatus 1 of this embodiment will be described. The precoat liquid used was the above-mentioned components (10% polyester resin (trade name Pesresin A-640, manufactured by Takamatsu Resin Co., Ltd.), 0.04% surfactant (trade name Surfynol 440, manufactured by Nissin Chemical Industry Co., Ltd.), 25% propylene glycol, and 64.96% water).

[0034] The surface tension of the printing substrate to be evaluated was measured in accordance with "JIS K 6768:1999 Plastics - Films and sheets - Wetting tension test method". Printing substrates with different surface tensions were prepared, and precoat treatment was performed by changing the amount of precoat liquid applied. On each printing substrate, a 1-dot line image was printed at 600 dpi using cyan ink, and the line width reproducibility and drying state of the image were evaluated. The results are shown in the table in Figure 4.

[0035] Line width reproducibility was determined from the results of observation using a microscope (product name MM-800 (Nikon Corporation)). Line widths less than 45 μm were rated as ◯, 45 μm or more but less than 50 μm as △, and 50 μm or more as ×. The dry state was evaluated by applying hot air at a temperature of 120°C and a wind speed of 37 m / s to the printed substrate for 10 seconds, and then touching the image with a finger if the ink did not adhere to the finger, and if it did adhere, an × was evaluated.

[0036] In Examples 1 to 5, the surface tension was 22.6 to 38.0 mN / m, and the amount of precoat liquid applied was varied to perform the precoat treatment. In Comparative Examples 1 to 3, the surface tension was 22.6 mN / m, and the amount of precoat liquid applied was less than in the Examples (Comparative Example 1), more than in the Examples (Comparative Example 3), or no precoat treatment was performed (Comparative Example 2). Images of Example 1 and Comparative Example 2 are shown in Figures 5A and 5B, respectively.

[0037] From the table shown in FIG. 4, in Examples 1 to 5, when the surface tension value is 22.6 to 38.0 mN / m, the coating amount is 1.0 to 3.0 g / m 2 By performing the precoat treatment within this range, good results were obtained in terms of line width and drying state. In addition, as shown in Figure 5A, the line width is uniform.

[0038] On the other hand, in Comparative Example 1, the surface tension value is the same as in Examples 1 to 4, but the amount of application is less than that in Examples 1 to 4. Also, for this reason, it is believed that the effect of the precoat treatment is not fully exerted, and good fine line reproducibility is not obtained. Also, in Comparative Example 2, the surface tension value is the same as in Examples 1 to 4, but the precoat treatment is not performed, so as explained above, the landed ink droplets are attracted to each other, the line width becomes wider, and line width reproducibility is not obtained. As shown in FIG. 5B, the line width is non-uniform compared to FIG. 5A. Also, in Comparative Example 3, the surface tension value is the same as in Examples 1 to 4, but the amount of application is greater than that in Examples 1 to 4. Also, for this reason, it is believed that the amount of precoat treatment liquid becomes excessive, and good drying state is not obtained.

[0039] From the evaluation results, it was confirmed that when the surface tension value was less than 38.0 mN / m, good line width reproducibility and a dry state could be obtained by performing a precoat treatment.

[0040] In the above embodiment, four-color head units 13 are used, but the present invention is not limited to four colors, and more or less than four colors may be used. Furthermore, the head units 11 and 13 are not limited to the line head type. However, the line head type is preferable because it can increase the printing speed. Furthermore, a long plastic film (PET film) is used as the printing substrate M, but cut film may also be used. Furthermore, the printing substrate M may be synthetic paper, etc.

[0041] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0042] 1. Image forming device 11 Pre-coat liquid head unit 13 Ink head unit 19 Control section 19a Input section

Claims

1. an ink head unit that ejects ink onto a printing substrate transported along a predetermined transport direction; a precoat liquid head unit disposed upstream of the ink head unit in the transport direction and configured to eject a precoat liquid onto the printing substrate; a control unit that controls the precoat liquid head unit to eject the precoat liquid, The control unit controls the precoat liquid head unit to eject a predetermined amount of the precoat liquid when the surface tension of the printing substrate is lower than a predetermined value.

2. 2. The ink-jet image forming apparatus according to claim 1, wherein the control unit includes an input unit for inputting a surface tension of the printing substrate.

3. 2. The ink-jet image forming apparatus according to claim 1, wherein the control unit controls the precoat liquid head unit to eject a predetermined amount of the precoat liquid when the surface tension of the printing substrate is less than 38 mN / m.

4. 2. The ink-jet image forming apparatus according to claim 1, wherein the printing substrate is a plastic film.

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