Inkjet type image formation device

Abstract

To provide an inkjet type image formation device which can perform corona discharge treatment according to characteristics of a printing base material.SOLUTION: An inkjet type image formation device includes head units 41B, 41C, 41M and 41Y for discharging ink onto a printing base material M conveyed in a predetermined conveyance direction, a corona treatment unit 5 which is arranged on the upstream side in the conveyance direction of the head units 41B, 41C, 41M and 41Y, and performs corona discharge on the printing base material M, and a control part 31 for controlling a discharge amount of the corona discharge performed by the corona treatment unit 5, wherein the control part 31 controls the discharge amount on the basis of glossiness of the printing base material M.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In an inkjet image forming apparatus, corona discharge may be applied to the printing substrate in order to improve adhesion between the printing substrate and the ink.

[0003] The image forming apparatus described in Patent Document 1 sets the amount of corona discharge by referring to a table that associates paper substrates (corresponding to print substrates) with the types of inks and the amount of corona discharge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6950683 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the image forming apparatus described in Patent Document 1 performs corona discharge treatment to compensate for the difference in gloss between printed and non-printed areas, and does not take into consideration 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 ink-jet image forming apparatus capable of performing corona discharge treatment in accordance with the characteristics of a printing substrate. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the inkjet image forming apparatus of the present invention comprises a head unit that ejects ink onto a printing substrate transported along a predetermined transport direction, a corona treatment unit that is arranged upstream of the head unit in the transport direction and performs corona discharge on the printing substrate, and a control unit that controls the amount of discharge of the corona discharge performed by the corona treatment unit, and is characterized in that the control unit controls the amount of discharge based on the glossiness of the printing substrate.

[0008] In the present invention, the control unit may be provided with an input unit for inputting the glossiness of the printing base material.

[0009] In the present invention, the control unit may be configured to control the corona treatment unit to perform the corona discharge when the glossiness of the printing substrate is higher than a predetermined value.

[0010] In the present invention, the control unit may be configured to control the corona treatment unit to perform the corona discharge when the 20 degree gloss of the printing substrate is 25 or more.

[0011] In the present invention, the printing substrate may be a plastic film. Effect of the Invention

[0012] According to the present invention, since corona discharge is applied to a printing substrate having low adhesion to ink, it is possible to improve adhesion between the printing substrate and the ink. [Brief description of the drawings]

[0013] [Figure 1] 1 is a front view showing a schematic diagram of an ink jet type image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating a corona treatment unit in an ink jet image forming apparatus according to one embodiment of the present invention. [Diagram 3]1 is a plan view showing a head unit in an ink jet type image forming apparatus according to an embodiment of the present invention. [Figure 4A] FIG. 4 is a diagram showing the results (Example) of a tape peeling test in an inkjet image forming apparatus according to one embodiment of the present invention. [Figure 4B] FIG. 4 is a diagram showing the results of a tape peeling test (comparative example) in an ink jet image forming apparatus according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet type image forming apparatus according to an embodiment of the present invention will now be described with reference to the drawings.

[0015] The overall configuration of an inkjet 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 inkjet image forming apparatus 1.

[0016] The inkjet type image forming apparatus 1 includes a supply roller 3 around which a long length of printing substrate M is wound, a corona treatment unit 5 that applies corona discharge to the printing substrate M supplied from the supply roller 3, an image forming section 7 that forms an image on the printing substrate M that has been subjected to corona discharge using an inkjet method, a drying section 9 that dries the image formed in the image forming section 7, and a take-up roller 11 that takes up the printing substrate M dried in the drying section 9.

[0017] First, a description will be given of the supply roller 3. The printing substrate M is wound around and attached to the supply roller 3. The printing substrate M is sent out in a predetermined transport direction X as the supply roller 3 rotates.

[0018] Next, the corona treatment unit 5 will be described with reference to FIG. 2. FIG. 2 is a diagram for explaining the corona treatment unit 5. The corona treatment unit 5 is disposed downstream of the supply roller 3 in the conveying direction X. The corona treatment unit 5 includes a corona discharge electrode 21 and an opposing roller 23 disposed at a predetermined interval from the corona discharge electrode 21. The corona discharge electrode 21 is made of, for example, a rod-shaped ceramic or ceramic-coated aluminum cylinder that is long in the width direction Y of the printing substrate M. The opposing roller 23 is made of, for example, a stainless steel cylinder and is grounded. The distance between the corona discharge electrode 21 and the opposing roller 23 is, for example, 0.5 to 2.0 mm. Tension rollers may be disposed upstream and downstream of the opposing roller 23.

[0019] The corona discharge electrode 21 is covered with an electrode cover 25 with an opening on the bottom. The corona discharge electrode 21 is connected to a high-frequency power supply 29 via a high-voltage transformer 27. The high-frequency power supply 29 generates a high-frequency AC current. The high-frequency AC current is, for example, 5.5 kV to 6.5 kV. The higher the discharge power, the higher the discharge voltage (discharge amount). However, the discharge voltage varies depending on the atmospheric pressure, temperature, humidity, etc., and is set according to the environmental conditions when the corona discharge treatment is actually performed. The high-voltage transformer 27 amplifies the generated high-frequency AC current, converts it into discharge power, and applies it to the corona discharge electrode 21. As a result, a corona discharge is generated between the corona discharge electrode 21 and the opposing roller 23.

[0020] The high frequency power supply 29 is electrically connected to the control unit 31 and generates a high frequency alternating current based on an instruction from the control unit 31 .

[0021] Next, the image forming unit 7 will be described with reference to Fig. 1. The image forming unit 7 is disposed downstream in the transport direction X from the corona treatment unit 5. The image forming unit 7 includes four head units 41B, 41C, 41M, and 41Y (collectively referred to as head unit 41) corresponding to four colors (black, cyan, magenta, and yellow) of ink, and a transport plate 43 along whose surface the printing substrate M is transported.

[0022] The head unit 41 will be described with reference to Fig. 3. Fig. 3 is a plan view showing the head unit 41. Each head unit 41 includes three print heads 45 and a plate 47 that supports the three print heads 45.

[0023] 3, the three print heads 45 are arranged in a staggered manner (line head system) along the width direction Y so as to be approximately the same as the width of the printing substrate M, and are supported by a plate 47. The print head 45 is equipped with a large number of nozzles (not shown). The nozzle outlets are open on the bottom surface of the print head 45.

[0024] The four head units 41 are arranged in sequence along the transport direction X, and are supplied with black, cyan, magenta, and yellow ink, respectively. The supplied ink is ejected downward from the ejection openings of the nozzles of each print head 45.

[0025] The transport plate 43 is disposed below the four head units 41, as shown in Fig. 1. The upper surface of the transport plate 43 is formed flat. Also, as shown in Fig. 3, the width of the transport plate 43 is wider than the width of the printing substrate M and all of the head units 41. A heat source (not shown) is provided below the transport plate 43, and heats the transport plate 43 to a predetermined temperature. The transport plate 43 is made of, for example, metal.

[0026] Next, the drying section 9 will be described. The drying section 9 is disposed downstream of the image forming section 7 in the transport direction X. The drying section 9 includes a heat drum 51, and upstream and downstream tension rollers 53, 55 disposed upstream and downstream of the heat drum 51. The printing substrate M that has passed through the image forming section 7 is wound around the heat drum 51 between the upstream and downstream tension rollers 53, 55. The heat drum 51 dries the printing substrate M transported along its surface by being heated.

[0027] Next, the winding roller 11 will be described. The winding roller 11 is disposed downstream of the drying unit 9 in the transport direction X. An end of the printing substrate M is fixed to the winding roller 11. The winding roller 11 is connected to a motor (not shown) and rotates. The winding roller 11 is rotated in a predetermined direction at a predetermined rotation speed by the motor, whereby the printing substrate M is fed from the supply roller 3.

[0028] The sent printing substrate M passes between the corona discharge electrode 21 and the opposing roller 23 of the corona treatment unit 5 and is transported to the image forming section 7. In the image forming section 7, the printing substrate M is transported below the four head units 41 along the upper surface of the transport plate 43 toward the drying section 9. Then, in the drying section 9, the printing substrate M is wound around the heat drum 51 and then taken up by the take-up roller 11.

[0029] Next, the control unit 31 will be described. As shown in Fig. 2, the control unit 31 controls the high-frequency power supply 29 of the corona treatment unit 5 to generate a high-frequency current of a predetermined intensity. Furthermore, the control unit 31 is provided with an input unit 31a such as a display panel. The input unit 31a includes a gloss input unit for inputting the gloss of the printing substrate M (for example, a 20-degree gloss). The control unit 31 is also electrically connected to the head unit 41, and controls the head unit 41 based on the input image data.

[0030] The image forming operation of the inkjet image forming apparatus 1 having the above configuration will be described. During the image forming operation, first, the user inputs the glossiness (20 degree glossiness) of the printing substrate M to the input section 31a of the control section 31. If the input glossiness is 25 or more, the control section 31 controls the corona treatment unit 5 to perform corona discharge treatment.

[0031] Thereafter, the motor is driven to rotate the take-up roller 11, and the printing substrate M is sent from the supply roller 3 to the corona treatment unit 5. In the corona treatment unit 5, corona discharge is generated between the corona discharge electrode 21 and the opposing roller 23, and corona treatment is applied to the upper surface of the printing substrate M. On the other hand, if the input gloss level is lower than 25, the control unit 31 controls the corona treatment unit 5 not to perform corona discharge treatment. In other words, if the input gloss level is lower than 25, corona discharge treatment is not performed.

[0032] Thereafter, the printing substrate M is transported below the head units 41, and ink of a predetermined color is ejected from the corresponding head units 41 based on image data to form an image on the printing substrate M. The printing substrate M on which the image has been formed in this manner is transported to the drying section 9. In the drying section 9, the ink is completely dried. Thereafter, the printing substrate M is taken up by the take-up roller 11.

[0033] As described above, according to the present invention, when the glossiness of the printing substrate M is above a certain level, specifically, when the 20 degree glossiness is 25 or more, corona discharge is applied to the printing substrate M. A printing substrate M with a low glossiness has fine irregularities on its surface, and the ink easily penetrates into these irregularities (anchor effect), improving adhesion between the ink and the printing substrate M. For example, in the case of a printing substrate M such as plain paper with a 20 degree glossiness lower than 25, there is no need to perform corona discharge treatment.

[0034] However, printing substrates M such as plastic films and synthetic papers with a 20-degree gloss of 25 or more have low adhesion to ink. Therefore, by performing a corona discharge treatment, it is possible to improve adhesion to the printing substrate M. In other words, when the printing substrate M is subjected to a corona discharge treatment, fine irregularities are formed on the surface of the printing substrate M, and the above-mentioned anchor effect is obtained. Furthermore, hydrophilic polar groups such as carbonyl groups, carboxyl groups, and nitrides are formed on the surface of the printing substrate M. Such polar groups increase the wettability of the surface of the printing substrate M. Therefore, the compatibility (adhesion) between the printing substrate M and the ink is improved by such physical and chemical actions caused by the corona discharge treatment.

[0035] In addition, in order to improve the compatibility (adhesion) between the printing substrate M and the ink, a precoat process using a precoat liquid may be performed. However, since the precoat process involves applying a liquid, the printing substrate M must be dried, which increases the processing time by the time required for drying and requires the provision of a dryer. Corona discharge treatment can achieve the same effect as the precoat process without using a liquid. However, depending on the type of ink, etc., the precoat process may also be used in combination.

[0036] Next, a test for evaluating the relationship between glossiness and adhesion in the inkjet image forming apparatus 1 of this embodiment will be described. The glossiness was measured by placing the printing substrate M on the white part of a hiding ratio test paper (manufactured by TP Giken Co., Ltd.) and measuring the 20 degree glossiness using a glossmeter (product surface J480T-268, manufactured by Elcometer Co., Ltd.). The adhesion was evaluated by a peeling test.

[0037] The peel test was carried out as follows: First, a cyan solid image was printed at 600 dpi on the printing substrate M. The printing substrate was an OPP film, the width of the printing substrate was 210 mm, and the conveying speed of the printing substrate was 3 m / min.

[0038] A peeling test was conducted on the printed image based on JISK5600 (no cross cuts were formed). The image was firmly rubbed with tape (product surface CT, manufactured by Nichiban Co., Ltd.) with the fingertips, and the tape was peeled off within 5 minutes, or the end of the tape was grasped at an angle close to 60 degrees and securely peeled off within 0.5 to 1.0 seconds. The images after peeling are shown in Figures 4A and 4B. The peeled tape is attached to the right side of the printing substrate on the left. Figure 4A shows an example of the present invention, and Figure 4B shows a comparative example.

[0039] In the example, the printing substrate was subjected to corona discharge by a corona treatment unit. The discharge power was 100 W (discharge voltage was 6.3 kV). In the comparative example, the printing substrate was not subjected to corona discharge. As is clear from Figures 4A and 4B, in the example, the ink was not peeled off from the printing substrate, and the ink did not adhere to the peeled tape. On the other hand, in the comparative example, the ink was peeled off from the printing substrate and adhered to the tape.

[0040] The control unit 31 may control the corona treatment unit 5 so that the higher the gloss level, the higher the voltage applied to the corona discharge electrode. In this case, even if the printing substrate has a high gloss level and low adhesion to the ink, the adhesion to the ink can be improved. The image forming apparatus 1 may also be provided with a measurement unit (not shown) that measures the gloss level of the printing substrate M. In this case, after the printing substrate M is set, the measurement unit measures the gloss level of the printing substrate M. The control unit 31 may control the corona treatment unit 5 to apply corona discharge based on the measured value. In this case, the user does not have to input the gloss level.

[0041] In the above embodiment, four-color head units 41 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 unit 41 is 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 a cut film may also be used.

[0042] 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]

[0043] 1. Inkjet image forming device 5 Corona Treatment Unit 31 Control Unit 31a Input section 41 Head Unit

Claims

1. a head unit that ejects ink onto a printing substrate transported along a predetermined transport direction; a corona treatment unit disposed upstream of the head unit in the transport direction and configured to perform corona discharge on the printing substrate; A control unit for controlling the amount of corona discharge performed by the corona treatment unit, The control unit controls the amount of discharge based on a gloss level of the printing substrate.

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

3. The ink-jet image forming apparatus according to claim 1 , wherein the control unit controls the corona treatment unit to perform the corona discharge when the glossiness of the printing substrate is higher than a predetermined value.

4. 4. The ink-jet image forming apparatus according to claim 3, wherein the control unit controls the corona treatment unit to perform the corona discharge when the 20 degree gloss of the printing substrate is 25 or more.

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

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