Printing method, printing apparatus, and printed matter

Abstract

The degree of wet spreading of the coating material is reduced, which produces a difference. The printing method includes the following steps: a buffer layer forming step of forming a buffer layer on a surface of a printed body that is a printing target, using a buffer material having a surface free energy different from the surface free energy of the printed body or a coating material, in a case where there is a difference between the surface free energy of the printed body and the surface free energy of the coating material coated on the surface of the printed body; and a printing step of performing printing by coating the coating material on the buffer layer.

Description

TECHNICAL FIELD

[0001] The present application relates to a printing method, a printing apparatus, and a printed matter. BACKGROUND

[0002] Patent Documents 1 and 2 disclose a printing apparatus that performs printing by applying ink to a printed object as a printing target.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-14065

[0006] Patent Document 2: Japanese Patent Application Publication No. 2018-187891 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the case where printing is performed using a printing apparatus as described in Patent Documents 1 and 2, depending on the kind of the printed object and the viscosity of the ink as an application material, there are cases where the wet spreading of the application material on the printed object is insufficient, or the wet spreading of the application material is excessive.

[0009] The present application has been achieved in view of the above-described circumstances, and aims to provide a printing method, a printing apparatus, and a printed matter that can reduce cases where the degree of wet spreading of an application material on a printed object varies depending on the kind of the printed object and the viscosity of the application material.

[0010] SOLUTION TO PROBLEM

[0011] The printing method according to the present application includes a buffer layer forming step of forming a buffer layer on a surface of a printed object as a printing target using a buffer material having a surface free energy different from the surface free energy of the printed object or an application material, in a case where there is a difference between the surface free energy of the printed object and the surface free energy of the application material applied to the surface of the printed object, and a printing step of performing printing by applying the application material to the buffer layer.

[0012] The printing device according to the present application includes a droplet ejection section that is capable of ejecting droplets of a coating material toward a surface of a printed object; a buffer layer forming section that is capable of forming a buffer layer for adjusting a disposition state of the coating material on the surface of the printed object; and a control section that causes the buffer layer forming section to form the buffer layer and causes the droplet ejection section to coat the coating material on the buffer layer when an absolute value of a difference between a surface free energy of the printed object and a surface free energy of the coating material is equal to or greater than a threshold value.

[0013] According to the present application, printing is performed by forming a buffer layer on a surface of a printed object using a buffer material having a surface free energy different from that of the printed object or a coating material and performing coating of the coating material on the buffer layer, and thus it is possible to reduce both cases of excessive wet spreading of the coating material and insufficient wet spreading of the coating material. Thus, it is possible to reduce a difference in the degree of wet spreading of the coating material depending on the type of the printed object. Furthermore, in the present application, as a case where there is a difference between the surface free energy of the printed object and the surface free energy of the coating material, it is possible to provide a case where there is a difference of 1 mJ / m2 or more between them.

[0014] The printing method according to the present application further includes a determination process of determining whether to form the buffer layer based on a difference between the surface free energy of the printed object and the surface free energy of the coating material, and forming the buffer layer on the surface of the printed object when it is determined to form the buffer layer. In the determination process, it is determined to form the buffer layer when an absolute value of the difference between the surface free energy of the printed object and the surface free energy of the coating material is equal to or greater than a threshold value. Thus, it is possible to further reduce a case where there is a difference in the degree of wet spreading of the coating material.

[0015] In the printing method according to the present application, at least one of a transparent ink, a primer, and an ink of the same color as the printed object having a surface free energy corresponding to an absolute value of a difference between the surface free energy of the printed object and the surface free energy of the coating material is used as the buffer material to form the buffer layer. Thus, it is possible to appropriately secure a disposition state of the ink on the buffer layer.

[0016] In the printing method according to the present application, the printed object includes the printed object having a surface free energy greater than the surface free energy of the coating material and the printed object having a surface free energy smaller than the surface free energy of the coating material. Thus, in a case where the coating material is coated on a plurality of printed objects having a wide range of surface free energies, it is possible to reduce a case where there is a difference in the degree of wet spreading of the coating material.

[0017] In the printing method according to the present application, the buffer layer is formed over the entire region of the surface of the printed matter where the coating material is applied or over the entire surface of the printed matter. Thus, it is possible to reduce the difference in the degree of wet-spreading over the entire region of the coating material.

[0018] In the printing apparatus according to the present application, the control section further includes a storage section that stores information on the surface free energies of a plurality of printed matters and the surface free energies of a plurality of coating materials; an absolute value calculation section that calculates the absolute value of the difference between the surface free energy of the printed matter to be printed and the surface free energy of the coating material based on the information on the surface free energies of the plurality of printed matters and the surface free energies of the plurality of coating materials; a threshold value determination section that determines whether the absolute value is equal to or greater than a threshold value; and a buffer layer formation determination section that determines whether the buffer layer is formed based on the threshold value. Thus, it is possible to efficiently determine whether the buffer layer is formed.

[0019] The printing method according to the present application includes: ejecting, from a nozzle of a first head, droplets of a first ink to a printed matter while moving the first head in a predetermined main scanning direction; and ejecting, from a nozzle of a second head, droplets of a second ink having a higher viscosity than the first ink to the printed matter, the second head being arranged in parallel with the first head in the main scanning direction and moving integrally with the first head, the droplets of the first ink and the droplets of the second ink being ejected to a target landing position of the droplets of the first ink on the printed matter in a manner that the droplets of the first ink and the droplets of the second ink correspond one-to-one.

[0020] The printing apparatus according to the present application includes: a first head that is capable of moving in a predetermined main scanning direction, the first head ejecting droplets of a first ink from a nozzle to a printed matter; a second head that is arranged in parallel with the first head in the main scanning direction and moves integrally with the first head, the second head ejecting droplets of a second ink having a higher viscosity than the first ink from a nozzle to the printed matter; and a control section that controls the ejection operation of the first head and the second head so that the droplets of the first ink ejected from the nozzle of the first head and the droplets of the second ink ejected from the nozzle of the second head correspond one-to-one at a target landing position of the droplets of the first ink on the printed matter.

[0021] According to the present application, since the droplets of the first ink and the droplets of the second ink correspond one-to-one at the target landing position of the droplets of the first ink on the printed matter, it is possible to make the droplets of the first ink contact the second ink. Thus, it is possible to reduce the wet-spreading of the first ink.

[0022] In the printing method according to the present application, the second ink is at least one of an ink of the same color as the first ink, an ink of the same color as the printed object, and a transparent ink. Thus, the first ink can be selected from a wide range of kinds of inks.

[0023] In the printing method according to the present application, when a droplet of the second ink is ejected to the target landing position before a droplet of the first ink is ejected to the target landing position, the droplet of the first ink is ejected so as to overlap the droplet of the second ink after the droplet of the second ink is ejected to the target landing position. In addition, when a droplet of the first ink is ejected to the target landing position before a droplet of the second ink is ejected to the target landing position, the droplet of the second ink is ejected so as to overlap the droplet of the first ink after the droplet of the first ink is ejected to the target landing position. Thus, whichever of the first ink and the second ink is ejected first, the droplet of the first ink can be caused to contact the second ink.

[0024] In the printing method according to the present application, in one main scanning operation of the first head and the second head, a droplet of the first ink and a droplet of the second ink are ejected to the target landing position so as to overlap the droplet of the first ink and the droplet of the second ink. Thus, the droplet of the first ink can be caused to contact the second ink in one main scanning operation.

[0025] The printing method according to the present application uses the first head and the second head each having nozzle rows each composed of the same number of nozzles arranged in a sub-scanning direction orthogonal to the main scanning direction, and in each main scanning operation, the nozzle rows are divided into regions obtained by equally dividing the nozzle rows in the sub-scanning direction, and the ejection control is performed, where N is a natural number, and in each main scanning operation, the nozzles from which inks are ejected from the first head and the second head are nozzles of regions adjacent in the main scanning direction. Thus, a layer of the first ink and a layer of the second ink can be formed for each region in the sub-scanning direction.

[0026] In the printing method according to the present application, in one main scanning operation of the first head and the second head, droplets of the second ink are ejected to a prescribed region on the print target including the target landing position to form a base layer, and thereafter, in the next main scanning operation which is continuous with the one main scanning operation of the first head and the second head, the first ink is ejected in such a manner that the first ink overlaps the second ink which has been ejected to the target landing position in the base layer. Thus, even in the case where the first ink is ejected onto the base layer, it is possible to cause the droplets of the first ink to contact the second ink. In this case, in the printing method using the first head and the second head each having nozzle rows each of which is composed of the same number of nozzles arranged in a sub-scanning direction orthogonal to the main scanning direction, in each main scanning operation, the nozzle rows are divided into regions obtained by N-division of the nozzle rows in the sub-scanning direction, where N is a natural number, in the one main scanning operation, droplets of the second ink are ejected from the nozzles of the nozzle row of the second head in one of the regions obtained by the N-division, the print target is conveyed in the sub-scanning direction by a distance corresponding to the nozzle row length of the nozzle row obtained by the N-division, and in the next main scanning operation, the first head ejects droplets of the first ink from the nozzles of a region of the first head which is continuous with the region of the second head in which the droplets of the second ink have been ejected. Thus, it is possible to form a layer of the first ink and a layer of the second ink for each region in the sub-scanning direction.

[0027] In the printing method according to the present application, after at least droplets of the first ink are ejected to the target landing position, the second ink is ejected to a prescribed region on the print target including the target landing position to form a coating layer. Thus, it is possible to protect the layer of the first ink by the coating layer in a state where wet spreading of the first ink is reduced.

[0028] In addition, the printed matter according to the present application includes: a print target; droplets of a first ink which are arranged at a target landing position on the print target; and droplets of a second ink which are arranged so as to overlap the droplets of the first ink one-to-one at the target landing position where the droplets of the first ink are arranged, the droplets of the second ink having a higher viscosity than the first ink. Thus, it is possible to provide a printed matter in which wet spreading of a coating material on a print target is reduced.

[0029] Effects of the Invention

[0030] According to the present application, it is possible to provide a printing method, a printing apparatus, and a printed matter which can reduce the occurrence of variations in the degree of wet spreading of a coating material on a print target. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Fig. 1 is a view showing an example of a printing device according to the first embodiment.

[0032] Figure 2 Fig. 2 is a view showing an example of physical property information stored in a physical property information storage section.

[0033] Figure 3 Fig. 3 is a view showing an example of a state of the first ink ejected onto the print object or the buffer layer.

[0034] Figure 4 Fig. 4 is a view showing an example of a state of the first ink ejected onto the buffer layer.

[0035] Figure 5 Fig. 5 is a flowchart showing an example of a printing method in the printing method according to the first embodiment.

[0036] Figure 6 Fig. 6 is a view showing an example of a printing device according to the second embodiment.

[0037] Figure 7 Fig. 7 is a view showing an example of the ejection face side of the first head and the second head.

[0038] Figure 8 Fig. 8 is a view showing an example of an ejection operation in the printing method according to the second embodiment.

[0039] Figure 9 Fig. 9 is a view showing an example of a state of the first ink and the second ink ejected onto the print object in the main scanning operation of the forward path and the return path, respectively.

[0040] Figure 10 Fig. 10 is a view showing an example of a state of the first ink and the second ink on the print object in a case where the printing operation is completed.

[0041] Figure 11 Fig. 11 is a view showing another example of an ejection operation in the printing method according to the second embodiment.

[0042] Figure 12 Fig. 12 is a view showing an example of a state of the first ink and the second ink on the print object in a case where the printing operation is completed.

[0043] Figure 13 Fig. 13 is a view showing another example of an ejection operation in the printing method according to the second embodiment.

[0044] Figure 14 Fig. 14 is a view showing another example of a state of the first ink and the second ink on the print object in a case where the printing operation is completed.

[0045] Figure 15This is a diagram illustrating another example of the ejection action in the printing method according to the second embodiment.

[0046] Figure 16 This is a diagram illustrating another example of the ejection action in the printing method according to the second embodiment. Detailed Implementation

[0047] Preferred embodiments for carrying out the present invention will now be described. However, the present invention is not limited to these embodiments.

[0048] <First Implementation Method>

[0049] Figure 1 Figures (a) and (b) are illustrations of an example of a printing apparatus according to the first embodiment.

[0050] like Figure 1 As shown in (a) and (b), the printing apparatus 100 includes a first droplet ejection unit 10, a second droplet ejection unit 20, and a control unit 30. The first droplet ejection unit 10 and the second droplet ejection unit 20 are mounted on a carriage 40. The carriage 40 is movable along a guide rod 41 in the main scanning direction D1.

[0051] In addition, the printing apparatus 100 also includes a relative moving part (not shown) that moves the first droplet ejection unit 10, the second droplet ejection unit 20, and the printable body M relative to each other in the sub-scanning direction D2. In the first embodiment, the case where the printable body transport unit that moves the printable body M in the sub-scanning direction D2 is used as the relative moving part will be described as an example. Furthermore, the relative moving part may also be a structure that can move the first droplet ejection unit 10 and the second droplet ejection unit 20 in the sub-scanning direction D2.

[0052] The first droplet ejection unit 10 or the second droplet ejection unit 20 can be a mechanism that ejects tiny droplets of ink, such as an inkjet head or an aerosol sprayer, or it can be a mechanism that continuously ejects liquid, such as a dispenser. However, it is not limited to these. The control unit 30 controls the ejection of ink from the first droplet ejection unit 10 and the second droplet ejection unit 20, the movement of the carriage 40 in the main scanning direction D1, and the movement of the printed object M in the sub-scanning direction D2.

[0053] The printing substrate M can be, for example, a non-permeable printing substrate such as a metal or resin that is non-permeable to ink, or a permeable printing substrate such as fabric or paper that is permeable to ink. The printing substrate M can be any material capable of forming an image. Furthermore, the printing substrate M has a surface for forming the image. This surface can be uneven, flat, or curved. The surface simply needs to be shaped to form an image.

[0054] like Figure 1 As shown in (a), within the carriage 40, the first droplet ejection unit 10 and the second droplet ejection unit 20 are arranged side-by-side in the main scanning direction D1. When the carriage 40 moves in the main scanning direction D1, the first droplet ejection unit 10 and the second droplet ejection unit 20 also move integrally in the main scanning direction D1. Alternatively, the carriage 40 can be configured such that the first droplet ejection unit 10 and the second droplet ejection unit 20 are mounted on different carriages 40 for separate scanning.

[0055] The first droplet ejection unit 10 moves along the main scanning direction D1 while ejecting the first ink Q1 from the nozzle toward the printed body M (see reference). Figure 3 The first ink Q1 is composed of a coating material. The first droplet ejection part 10 forms an ink layer on the substrate M.

[0056] The second droplet ejection unit 20 moves along the main scanning direction D1 while ejecting a second ink Q2 from the nozzle toward the printed object M (see reference). Figure 4 The second ink Q2 is composed of a buffer material. The second droplet ejection section 20 forms a buffer layer between the printable body M and the ink layer, as detailed later.

[0057] As the first ink Q1 and the second ink Q2, evaporative drying inks such as solvent inks, water-based inks, or latex inks can be applied.

[0058] As the first ink Q1, examples include colored inks capable of developing a specified color. As the second ink Q2, examples include colorless and transparent inks, primers, and white inks having a surface free energy corresponding to that of the first ink.

[0059] Here, surface free energy is the energy stored per unit area of ​​a surface by external work under constant temperature conditions. Surface free energy is a physical quantity with dimensions equivalent to surface tension (e.g., mJ / m²: millijoules per square meter).

[0060] The first ink Q1, the second ink Q2, and the substrate M each possess inherent surface free energies. For example, when the surface free energy of the substrate M is greater than that of the first ink Q1, droplets of the first ink Q1 readily wet and spread on the substrate M. In this case, the greater the absolute value of the difference between the surface free energy of the first ink Q1 and the surface free energy of the substrate M, the easier it is for the droplets to wet and spread. Conversely, when the surface free energy of the substrate M is less than that of the first ink Q1, droplets of the first ink Q1 do not readily wet and spread on the substrate M. In this case, the greater the absolute value of the difference between the surface free energy of the first ink Q1 and the surface free energy of the substrate M, the less likely it is to wet and spread.

[0061] Similarly, for example, if the surface free energy of the printed body M is greater than the surface free energy of the second ink Q2, the droplets of the second ink Q2 are more likely to wet and spread on the printed body M. Conversely, if the surface free energy of the printed body M is less than the surface free energy of the second ink Q2, the droplets of the second ink Q2 are less likely to wet and spread on the printed body M.

[0062] Furthermore, when the surface free energy of the second ink Q2 is greater than that of the first ink Q1, the droplets of the first ink Q1 are more likely to wet and spread on the buffer layer formed by the second ink Q2. Conversely, when the surface free energy of the second ink Q2 is less than that of the first ink Q1, the droplets of the first ink Q1 are less likely to wet and spread on the buffer layer formed by the second ink Q2.

[0063] Therefore, by providing a buffer layer formed by the second ink Q2 between the first ink Q1 and the printed object M, the wetting and spreading pattern of the first ink Q1 relative to the printed object M can be adjusted.

[0064] Specifically, when the surface free energy of the first ink Q1 is smaller than the surface free energy of the printed body M, it is preferable to provide a buffer layer having a surface free energy equal to or greater than that of the first ink Q1. Furthermore, when the surface free energy of the first ink Q1 is greater than that of the printed body M, it is preferable to provide a buffer layer having a surface free energy equal to or less than that of the first ink Q1.

[0065] The control unit 30 includes a processing device such as a CPU (Central Processing Unit) and a storage device such as RAM (Random Access Memory) or ROM (Read Only Memory).

[0066] like Figure 1 As shown in (b), the control unit 30 includes a printed matter information acquisition unit 31, a storage unit 32, a determination unit 33, a drive control unit 34, and an ejection control unit 35.

[0067] Storage unit 32 stores various types of information. Storage unit 32 includes storage devices such as hard disk drives and solid-state drives. In addition, external storage media such as removable disks can also be used as storage unit 32.

[0068] The storage unit 32 has a physical attribute information storage unit 32a. The physical attribute information storage unit 32a stores physical attribute information that corresponds to the type of the printed body M and the surface free energy of the printed body M.

[0069] Figure 2 Figure (a) is an example of physical attribute information stored in the physical attribute information storage unit 32a. For example... Figure 2 As shown in (a), the type of printed object M and its surface free energy are stored in the physical property information storage unit 32a in a corresponding state. Printed objects M1 to M7 are made of different materials. Printed objects M1 to M7 have different surface free energies. The surface free energy of printed object M1 is E7. The surface free energy of printed object M2 is E6. The surface free energy of printed object M3 is E5. The surface free energy of printed object M4 is E4. The surface free energy of printed object M5 is E3. The surface free energy of printed object M6 is E2. The surface free energy of printed object M7 is E1. Figure 2 Example (a) shows that the surface free energy decreases stepwise from E7 to E1 as the printed body M1 becomes the printed body M7 (E7>E6>E5>E4>E3>E2>E1).

[0070] In addition, Figure 2 In (b), the surface free energies of the first ink Q1 and the second ink Q2 are stored in corresponding states. Figure 2 Example (b) illustrates the case where the first ink Q1 and the second ink Q2 have equal surface free energies E4. Furthermore, it is self-evident that the surface free energies of the first ink Q1 and the second ink Q2 are not limited to E4. Additionally, the surface free energy of the second ink Q2 may be different from that of the first ink Q1.

[0071] The following explanation will use the case where the surface free energy of the first ink Q1 and the second ink Q2 is E4 as an example. Here, since the buffer layer is formed by the second ink Q2, the surface free energy E4 of the second ink Q2 will also be referred to as the surface free energy E4 of the buffer layer in the following explanation.

[0072] The printable information acquisition unit 31 acquires printable information related to the type of printable M. For example, this is done through the input unit 50 (see reference). Figure 1 (b) Inputting the printed material information. The input unit 50 can be an automatic input device that automatically detects the printed material, such as a camera or a light sensor, or a manual input device such as a keyboard or mouse for user input. If it is a manual input device, it can be configured such that multiple options for printed material information are displayed via a display unit (not shown), and the user inputs the printed material information by selecting one or more of the displayed options. In this case, multiple options can be, for example, the printed materials M (M1 to M7) stored in the physical attribute information storage unit 32a of the storage unit 32.

[0073] As Figure 2 As shown in (a) of FIG. 3, the physical property information storage section 32a stores therein a plurality of printed matters Ml to M7.

[0074] The printed matters Ml to M3 have surface free energies E7 to E5 that are larger than the surface free energy E4 of the first ink Ql (refer to (b) of FIG. 3). Figure 2 The printed matter M4 has a surface free energy E4 that is equal to the surface free energy E4 of the first ink Ql (refer to (b) of FIG. 3). Figure 2 The printed matters M5 to M7 have surface free energies E3 to El that are smaller than the surface free energy E4 of the first ink Ql (refer to (b) of FIG. 3). Figure 2 The printed matters M5 to M7 have surface free energies E3 to El that are smaller than the surface free energy E4 of the first ink Ql (refer to (b) of FIG. 3).

[0075] As shown in (a) of FIG. 3, the physical property information storage section 32a stores therein a plurality of printed matters Ml to M7. Figure 2 As shown in (a) of FIG. 3, the physical property information storage section 32a stores therein a plurality of printed matters Ml to M7.

[0076] Specifically, the determination section 33 includes an absolute value calculation section 33a and a threshold value judgment section 33b. The determination section 33 searches for which one of the printed matters Ml to M7 stored in the physical property information storage section 32a the kind of the acquired printed matter M is, and acquires the surface free energy corresponding to the kind of the printed matter. In addition, the determination section 33 acquires the surface free energy of the first ink Ql stored in the physical property information storage section 32a.

[0077] The determination section 33 determines whether or not to form the buffer layer based on the difference between the surface free energy of the acquired printed matter M and the surface free energy of the first ink Ql. For example, in a case where the absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Ql is calculated by the absolute value calculation section 33a and it is judged by the threshold value judgment section 33b that the absolute value is equal to or larger than a threshold value, the determination section 33 determines to form the buffer layer. On the other hand, for example, in a case where the absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Ql is calculated by the absolute value calculation section 33a and it is judged by the threshold value judgment section 33b that the absolute value is smaller than the threshold value, the determination section 33 determines not to form the buffer layer. The threshold value can be set in advance. In the first embodiment, the threshold value can be set, for example, to the difference between two of E1 to E7.

[0078] In this case, in a case where the absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Ql is two or more levels, the determination section 33 determines that the buffer layer is formed. In a case where the absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Ql is less than two levels, the determination section 33 determines that the buffer layer is not formed. Further, regarding the threshold value, in addition to being set to a difference of two levels, in a case where there is a difference between the surface free energy of the first ink Ql and the surface free energy of the printed matter M, it can be set to a difference of, for example, 1 mJ / m2. In this case, "threshold value or more" is 1 mJ / m2or more. "Less than the threshold value" is less than 1 mJ / m2.

[0079] The drive control section 34 controls a drive mechanism that moves the carriage 40 in the main scanning direction Dl. The ejection control section 35 controls the operation of ejecting the droplets of the first ink Ql from the first droplet ejection section 10 and the operation of ejecting the droplets of the second ink Q2 from the second droplet ejection section 20. In a case where it is determined by the determination section 33 that the buffer layer is formed, the ejection control section 35 causes the second droplet ejection section 20 to eject the droplets of the second ink Q2 to form the buffer layer. That is, the second droplet ejection 20 constitutes a buffer layer forming section.

[0080] Figure 3 is a drawing showing an example of the state of the first ink Ql ejected onto the printed matter or the buffer layer. As shown in (a) of Figure 3 As shown in (a) of

[0081] In addition, as shown in (b) of Figure 3 of the first ink Ql to the surface Ma of the printed matter Ml, the first ink Ql wets and spreads on the surface Ma of the printed matter Ml.

[0082] In addition, as shown in (c) of Figure 3 of the first ink Ql to the surface Ca of the buffer layer C, the first ink Ql wets and spreads on the surface Ca of the buffer layer C to a lesser extent than in the case where the first ink Ql is dropped onto the surface Ma of the printed matter Ml and to a greater extent than in the case where the first ink Ql is dropped onto the surface M7a of the printed matter M7. Further, even in a case where the first ink Ql having the surface free energy of E4 is dropped onto the printed matter M4 having the surface free energy of E4, the arrangement state (wetting and spreading state) of the first ink Ql is the same as in the case where the first ink Ql is dropped onto the surface Ca of the buffer layer C.

[0083] Figure 4 This is a diagram showing an example of the state of the first ink Q1 ejected onto the buffer layer C. When forming the buffer layer C, the second ink Q2 is ejected from the nozzles of the second droplet ejection unit 20 over the entire prescribed area R1. The area R1 is an area on the surface of the printing object M1 that includes the portion of the ink layer I formed by the first ink Q1. The buffer layer C is formed over the entire prescribed area R1 including the portion where the ink layer I is formed.

[0084] As Figure 4 shown in (a) of [], in the first embodiment, the surface free energy of the second ink Q2 is E4. When the second ink Q2 with a surface free energy of E4 (<E7) is ejected onto the surface M1a of the printing object M1 with a surface free energy of E7, the droplets of the second ink Q2 are in a state of spreading on the surface M1a of the printing object M1. The buffer layer C1 (C) is formed in this state. When the second ink Q2 has a tendency to wet and spread on the surface M1a of the printing object M1, or when this tendency is significant, the ejection amount of the second ink Q2 can be made less than normal. That is, the control unit 30 normally controls the ejection amount of the droplets to coat one side of the surface M1a of the printing object M1. In contrast, when the second ink Q2 has a tendency to wet and spread on the surface M1a of the printing object M1, droplets with a smaller ejection amount than normal are ejected. Additionally, in this case, not all of the droplets of the ejected second ink Q2 are made to have the same size, and it is also considered to mix and eject droplets with a normal ejection amount and droplets with an ejection amount smaller than normal. Or, the overall ejection amount can be reduced by ejecting at a normal ejection amount and extending the interval.

[0085] Figure 4 This is a diagram showing an example of the state of the first ink Q1 ejected onto the buffer layer C. When forming the buffer layer C, the second ink Q2 is ejected from the nozzles of the second droplet ejection unit 20 over the entire prescribed area R2 respectively. The area R2 is an area on the surface of the printing object M7 that includes the portion of the ink layer I formed by the first ink Q1. The buffer layer C is formed over the entire prescribed area R2 including the portion where the ink layer I is formed.

[0086] As Figure 4When the second ink Q2 having a surface free energy E4 (>E1) is ejected onto the surface M7a of the printed body M7 having a surface free energy E1, the droplets of the second ink Q2 are in a state of not wet-spreading on the surface M7a of the printed body M7 and bulging, as shown in (b). The buffer layer C2 (C) is formed in this state. In the case where the second ink Q2 has a tendency to not wet-spread on the surface M7a of the printed body M7 and expose the surface M7a of the printed body M7, or in the case where the tendency is significant, the amount of the second ink Q2 to be ejected can be increased from the normal. That is, the control section 30 normally controls the amount of the droplets to be ejected so as to coat one side of the surface M7a of the printed body M7. In contrast, in the case where the second ink Q2 has a tendency to not wet-spread on the surface M7a of the printed body M7, droplets are ejected in a larger amount than normal. In this case, the size of the droplets of the second ink Q2 to be ejected is not necessarily uniform, and droplets of the normal amount and droplets of a larger amount than normal can be mixed and ejected.

[0087] As shown in Figure 4 In the case where the first ink Q1 is dropped onto the printed bodies M1, M7 on which the buffer layers C1 (C), C2 (C) are formed, respectively, the first ink Q1 lands on the surfaces C1a, C2a of the buffer layers C1 (C), C2 (C) having the same surface free energy. Thus, regardless of the surface free energy of the printed bodies M1, M7, the degree of wet-spreading of the first ink Q1 on the ink layer I1 (I) formed on the printed body M1 is the same as that on the ink layer I2 (I) formed on the printed body M7. The buffer layer C adjusts the arrangement state of the first ink Q1 on the printed body as such.

[0088] Next, a printing method using the printing apparatus 100 configured as described above will be described. Figure 5 is a flowchart showing an example of the printing method according to the first embodiment. In the case where printing data from the outside is received, the printed body information acquisition section 31 acquires printed body information relating to the kind of the printed body M (step S10). In the case where the printed body information is acquired, the determination section 33 performs a determination as to whether or not to form a buffer layer (step S20: determination process). In step S20, the determination section 33 searches for which of the kinds of the printed bodies M1 to M7 the kind of the printed body M acquired is among the physical property information stored in the physical property information storage section 32a, and acquires the surface free energy corresponding to the kind of the printed body. In addition, the determination section 33 acquires the surface free energy of the first ink Q1 stored in the physical property information storage section 32a.

[0089] For example, as shown in Figure 2As shown, in the case where the surface free energies E1, E2 of the printed bodies M7, M6, and the surface free energies E7, E6 of the printed bodies M1, M2 are acquired, the absolute values of the difference from the surface free energy E4 of the first ink Q1 are respectively as follows, and are equal to or more than the threshold value (2 or more).

[0090] (A) Printed body M7 (E1) - First ink Q1 (E4) = 3

[0091] (B) Printed body M6 (E2) - First ink Q1 (E4) = 2

[0092] (C) Printed body M2 (E6) - First ink Q1 (E4) = 2

[0093] (D) Printed body M1 (E7) - First ink Q1 (E4) = 3

[0094] In these cases, the determination section 33 determines to form the buffer layer C (step S20: "Yes").

[0095] On the other hand, in the case where the surface free energies E5, E4, E3 of the printed bodies M3, M4, M5 are acquired, the absolute values of the difference from the surface free energy E4 of the first ink Q1 are respectively as follows, and are less than the threshold value (less than 2).

[0096] (E) Printed body M3 (E5) - First ink Q1 (E4) = 1

[0097] (F) Printed body M4 (E4) - First ink Q1 (E4) = 0

[0098] (G) Printed body M5 (E3) - First ink Q1 (E4) = 1

[0099] In these cases, the determination section 33 determines not to form the buffer layer C (step S20: "No").

[0100] When it is determined to form the buffer layer C in step S20 (Yes in step S20), the control section 30 causes the second droplet ejection section 20 to eject the second ink Q2 from the nozzles thereof to a prescribed range in the printed body M including the position as the ejection target of the first ink Q1, to form the buffer layer C in the region of the prescribed range (step S30, buffer layer forming process).

[0101] When it is determined not to form the buffer layer C in step S20 (No in step S20), or after the buffer layer C is formed (step S30), the control section 30 causes the first droplet ejection section 10 to eject the first ink Q1 from the nozzles thereof to the position as the ejection target of the first ink Q1 in the printed body M, to form the ink layer I (step S40, printing process).

[0102] In this way, by distinguishing between the case where the buffer layer C is formed and the case where the buffer layer C is not formed in accordance with the surface free energy of both the printed matter M and the first ink Q1, it is possible to reduce the case where the degree of wet-spreading of the first ink Q1 on the printed matter M differs.

[0103] As described above, the printing method according to the first embodiment has the following structure.

[0104] (1) A printing method including the following steps:

[0105] a buffer layer forming step (step S30) of forming a buffer layer C on a surface of a printed matter M that is a printing target using a buffer material having a surface free energy different from the surface free energy of the printed matter M or the first ink Q1, in a case where there is a difference between the surface free energy of the printed matter M and the surface free energy of the first ink Q1 applied to the printed matter M; and

[0106] a printing step (step S40) of performing printing by applying the first ink Q1 to the buffer layer C.

[0107] When configured in this way, it is possible to reduce the case where the degree of wet-spreading of the first ink Q1 differs depending on the type of the printed matter M.

[0108] Specifically, it is possible to form the buffer layer C for adjusting the disposition state of the first ink Q1 on the surfaces of a plurality of printed matters M having different surface free energies, and to form the ink layer I by ejecting droplets of the first ink Q1 onto the buffer layer C.

[0109] Thus, it is possible to reduce both the case where the first ink Q1 excessively wet-spreads and the case where the first ink Q1 does not sufficiently wet-spread, and thereby it is possible to reduce the case where the degree of wet-spreading of the first ink Q1 differs.

[0110] In addition, the printing device 100 according to the first embodiment has the following structure.

[0111] (2) The printing device 100 includes:

[0112] a first droplet ejection section 10 that is capable of ejecting droplets of a first ink Q1 toward a surface of a printed matter M;

[0113] a second droplet ejection section 20 (buffer layer forming section) that is capable of forming a buffer layer C for adjusting the disposition state of the first ink Q1 on the surface of the printed matter M; and

[0114] a control section 30 that, in a case where the absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Q1 is equal to or greater than a threshold value, causes the second droplet ejection section 20 to form the buffer layer C and causes the first droplet ejection section 10 to form an ink layer I on the buffer layer C.

[0115] By providing such a printing device 100, it is also possible to suppress a difference in the degree of wet spreading of the first ink Q1 according to the kind of the printed matter M.

[0116] (3) The printing method further includes a determination process (step S20) in which it is determined whether or not to form the buffer layer C based on a difference between the surface free energy of the printed matter M and the surface free energy of the first ink Q1,

[0117] In a case where it is determined to form the buffer layer C, the buffer layer C is formed on the surface of the printed matter M.

[0118] When configured as such, it is possible to further reduce the case where a difference in the degree of wet spreading of the first ink Q1 occurs.

[0119] (4) In the determination process, in a case where an absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Q1 is equal to or greater than a threshold value, it is determined to form the buffer layer C.

[0120] When configured as such, it is possible to more accurately reduce the case where a difference in the degree of wet spreading of the first ink Q1 occurs.

[0121] (5) In the printing method, at least one of a transparent ink having a surface free energy corresponding to an absolute value of the difference between the surface free energy of the printed matter M and the surface free energy of the first ink Q1, a primer, and an ink of the same color as the printed matter M is used as a buffer material to form the buffer layer C.

[0122] When configured as such, it is possible to appropriately secure the arrangement state of the first ink Q1 on the buffer layer C.

[0123] (6) The plurality of printed matters M include a printed matter M7 to M5 having a surface free energy greater than the surface free energy E4 of the first ink Q1, a printed matter M4 having a surface free energy equal to the surface free energy E4 of the first ink Q1, and a printed matter M3 to M1 having a surface free energy less than the surface free energy E4 of the first ink Q1.

[0124] When configured as such, even in a case where an ink layer I is formed on a plurality of printed matters M having different surface free energies, it is possible to reduce the case where a difference in the degree of wet spreading of the first ink Q1 occurs by forming the buffer layer C.

[0125] (7) In the printing method, the buffer layer C is formed throughout the entire region of the surface of the printed matter M on which the ink layer I is formed or throughout the entire printed matter M.

[0126] When configured as such, it is possible to reduce the case where a difference in the degree of wet spreading of the first ink Q1 occurs throughout the entire ink layer I.

[0127] (8) The control section 30 further has:

[0128] a storage section 32 that stores information of the surface free energies of the plurality of printed bodies M and the surface free energies of the plurality of coating materials;

[0129] an absolute value calculation section 33a that calculates an absolute value of a difference between the surface free energy of the printed body M to be printed and the surface free energy of the coating material, based on the information of the surface free energies of the plurality of printed bodies M and the surface free energies of the plurality of coating materials;

[0130] a threshold value determination section 33b that determines whether the absolute value is equal to or greater than a threshold value; and

[0131] a determination section 33 (buffer layer formation determination section) that determines whether to form the buffer layer C, based on the threshold value.

[0132] When configured as such, determination of whether to form the buffer layer C can be efficiently performed.

[0133] <Second Embodiment>

[0134] Figure 6 is a view that shows an example of a printing device 100A according to the second embodiment.

[0135] Further, in the following description, portions different from the first embodiment are described, and the same portions are described with the same reference numerals.

[0136] As shown in Figure 6 , the printing device 100A has a first head 10A, a second head 20A, and a control section 30A. The first head 10A and the second head 20A are mounted on a carriage 40. The carriage 40 is movable in a main scanning direction D1 along a guide rod 41.

[0137] In addition, the printing device 100A further has a relative movement section (not shown) that relatively moves the first head 10A and the second head 20A with respect to the printed body M in a sub scanning direction D2. In the second embodiment, a case where a printed body conveyance section that conveys the printed body M in the sub scanning direction D2 is used as the relative movement section is described as an example.

[0138] The first head 10A is movable in the main scanning direction D1, and the first head 10A ejects droplets of a first ink Q1A from a nozzle toward the printed body M. The second head 20A is arranged in parallel with the first head 10A in the main scanning direction D1 and moves integrally with the first head 10A. The second head 20A ejects droplets of a second ink Q2A from a nozzle toward the printed body M. The second ink Q2A uses an ink having a higher viscosity than the first ink Q1A.

[0139] As the first ink Q1A and the second ink Q2A, for example, an evaporative drying type ink such as a solvent ink, an aqueous ink, or a latex ink can be applied.

[0140] As the first ink Q1A, for example, a color ink that develops a prescribed color or the like can be listed. In addition, as the second ink Q2A, for example, an ink (white system) whose color is substantially the same as that of the printed matter M, an ink whose color is substantially the same as that of the first ink Q1A, or a transparent ink or the like can be listed. In a case where the second ink Q2A is colorless or transparent, it is possible to cope with almost all kinds of printed matters M or almost all kinds of colors of the first ink Q1A, and it is also possible to cope with various printing methods described later. In a case where the color of the second ink Q2A is substantially the same as that of the printed matter M or the first ink Q1A, it is possible to perform printing without impairing the hue of the original image data or the image quality.

[0141] The control section 30A has a processing device such as a CPU (Central Processing Unit), and a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The control section 30A has a drive control section 31A and an ejection control section 32A. The drive control section 31A controls a drive mechanism that moves the carriage 40 in the main scanning direction D1 and a printed matter conveying section that conveys the printed matter M in the sub scanning direction D2. The ejection control section 32A controls the operation of ejecting the droplets of the first ink Q1A from the first head 10A and the operation of ejecting the droplets of the second ink Q2A from the second head 20A.

[0142] Figure 7 is a view that shows an example of the nozzle face 11, 21 side of the first head 10A and the second head 20A.

[0143] As shown in Figure 7 , the first head 10A has a nozzle face 11 that faces the printed matter M. A plurality of nozzles 12 are formed in the nozzle face 11. The nozzles 12 are arranged in a plurality in the sub scanning direction D2. The plurality of nozzles 12 constitute a nozzle row 13. The nozzle row 13 is arranged in four rows in the main scanning direction D1. In addition, the number of rows of the nozzle row 13 is not limited to four rows, and can be three rows or less or five rows or more. The nozzles 12 eject the droplets of the first ink Q1A. The nozzle row 13 is divided into, for example, n (n is a natural number) ejection regions Al, A2,..., An obtained by equally dividing the nozzle row 13 in the sub scanning direction D2. The number of divisions n can be arbitrarily selected by the user, or can be automatically selected by the control section 30A in accordance with the resolution of the image data to be printed.

[0144] Likewise, the second head 20A has a nozzle face 21 facing the print target M. A plurality of nozzles 22 are formed in the nozzle face 21. The nozzles 22 are formed in the same number as the nozzles 12 of the first head 10A. The nozzles 22 are arranged in the sub-scanning direction D2. The plurality of nozzles 22 constitute a nozzle row 23. The nozzle row 23 is arranged in four rows in the main-scanning direction Dl. Note that the number of rows of the nozzle row 23 is not limited to four, and can be three or less or five or more. The nozzles 22 eject droplets of the second ink Q2A. The nozzle row 23 is divided into n (n is a natural number) ejection regions Bl, B2,..., Bn obtained by equally dividing the nozzle row 23 in the sub-scanning direction D2. The number of divisions n can be arbitrarily selected by the user, or can be automatically selected by the control section 30A in accordance with the resolution of the image data to be printed.

[0145] In the following description, a case where n is set to 2 will be described as an example. That is, the nozzle row 13 of the first head 10A is divided into two regions, the ejection regions Al and A2. In addition, the nozzle row 23 of the second head 20A is divided into two regions, the ejection regions Bl and B2 (see FIG. 4). Figure 8 ).

[0146] Next, a printing method using the printing apparatus 100A will be described. Figure 8 is a view showing an example of the ejection operation in the printing method according to the second embodiment.

[0147] As shown in Figure 8 , the nozzle rows 13 and 23 of the first head 10A and the second head 20A, respectively, are equally divided into two ejection regions (Al and A2, Bl and B2) in the sub-scanning direction D2.

[0148] As shown in Figure 8 , in the main-scanning direction Dl, the ejection region Al of the first head 10A is adjacent to the ejection region Bl of the second head 20A with a gap therebetween. In the main-scanning direction Dl, the ejection region A2 of the first head 10A is adjacent to the ejection region B2 of the second head 20A with a gap therebetween.

[0149] In addition, in the sub-scanning direction D2, the ejection region Al of the first head 10A is arranged in a continuous manner without a gap to the ejection region A2 of the first head 10A. In the sub-scanning direction D2, the ejection region Bl of the second head 20A is arranged in a continuous manner without a gap to the ejection region B2 of the second head 20A.

[0150] The control section 30A controls the operation of the first head 10A and the second head 20A on the basis of the print data from the outside. The control section 30A sets a target landing position on the print target M at which a droplet of the first ink QlA is to land on the basis of the print data.

[0151] When the first ink Q1A is ejected onto the print target M, the carriage 40 is reciprocated in the main scanning direction D1 by the control section 30A.

[0152] In the second embodiment, the following cases are exemplified and described.

[0153] (i) In the forward stroke, the first head 10A is ahead of the second head 20A.

[0154] (ii) In the return stroke, the second head 20A is ahead of the first head 10A.

[0155] Further, the reciprocation of the carriage 40 is not limited to the above (i) and (ii). For example, the carriage 40 can be caused to move in such a manner that the second head 20A is ahead of the first head 10A in the forward stroke and the first head 10A is ahead of the second head 20A in the return stroke.

[0156] First, in the first main scanning operation (forward stroke), the control section 30A causes the nozzles 12 of the nozzle row 13 of the first head 10A disposed in the ejection region A1 to eject droplets of the first ink Q1A (hatched region in FIG. 8). Figure 8

[0157] The control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 12 perform ejection, so that the droplets of the first ink Q1A land on the target landing positions on the print target M.

[0158] Further, in the first main scanning operation (forward stroke), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A disposed in the ejection region B1 to eject droplets of the second ink Q2A (hatched region in FIG. 8). Figure 8

[0159] The control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 22 perform ejection, so that the droplets of the second ink Q2A land on the target landing positions on the print target M. That is, the control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 22 perform ejection, so that the droplets of the second ink Q2A overlap the first ink Q1A which landed on the target landing positions on the print target M one by one.

[0160] ​​After the first main scan operation is completed, the printed matter carrying section carries the printed matter M in the sub-scanning direction D2. The carrying distance at this time is set to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A. The carrying distance is set to half the length of the nozzle rows 13, 23 because the aforementioned discharge region is set to half the nozzle rows 13, 23. Further, in the case where the discharge region is set to a number n other than 2, the carrying distance is set to 1 / n of the length of the nozzle rows 13, 23.

[0161] After the printed matter M is carried in the sub-scanning direction D2, a second main scan operation (return) is performed. In the second main scan operation, the control section 30A causes the nozzles 22 of the second head 20A disposed in the discharge region B1 to discharge droplets of the second ink Q2A. The control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 22 discharge, so that the droplets of the second ink Q2A land on the printed matter M first at the target landing positions of the first ink Q1A discharged from the first head 10A in pursuit.

[0162] Further, in the second main scan operation (return), the control section 30A causes the nozzles 12 of the first head 10A disposed in the discharge region A1 to discharge droplets of the first ink Q1A. At this time, the control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 12 discharge, so that the droplets of the first ink Q1A land on the printed matter M at the target landing positions. That is, the control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 12 discharge, so that the droplets of the first ink Q1A overlap the droplets of the second ink Q2A which landed on the printed matter M first at the target landing positions one-to-one.

[0163] Figure 9 is a view showing an example of the state of the first ink Q1A and the second ink Q2A discharged onto the printed matter M in the main scan operations of the forward and return routes.

[0164] As shown in Figure 9 , in the first main scan operation (forward), the first ink Q1A lands first at the target landing positions P1 on the printed matter M. Next, the second ink Q2A lands on the first ink Q1A in a manner of overlapping one-to-one.

[0165] Here, the viscosity of the second ink Q2A is higher than the viscosity of the first ink Q1A. The first ink Q1A wets and spreads more easily than the second ink Q2A at the time of landing. On the other hand, the second ink Q2A wets and spreads more difficultly than the first ink Q1A at the time of landing. By overlapping the second ink Q2A and the first ink Q1A one-to-one after the first ink Q1A is discharged, the first ink Q1A becomes attached to the second ink Q2A. Thus, the wet and spread of the first ink Q1A is reduced.

[0166] In addition, as shown in FIG. 6, in the second main scanning operation (return path), the second ink Q2A lands first at the target landing position P2 on the print target M. Next, the first ink Q1A lands in a one-to-one overlapping manner on the second ink Q2A. Figure 9

[0167] By causing the first ink Q1A to overlap the second ink Q2A one-to-one after the second ink Q2A is ejected, the first ink Q1A also adheres to the second ink Q2A. Thus, the wet spreading of the first ink Q1A is reduced.

[0168] After the second main scanning operation is completed, the print target conveying section conveys the print target M by a predetermined distance in the sub-scanning direction D2. The conveying distance at this time is set to half the length of one row of nozzles 12, 22, as in the case after the first main scanning operation is completed. After the print target M is conveyed in the sub-scanning direction D2, scanning in the forward path in the main scanning direction D1 is performed. In this way, by repeatedly performing scanning in the main scanning direction D1 by the first head 10A and the second head 20A and conveying the print target M in the sub-scanning direction D2, printing of the print target M based on the print data can be performed.

[0169] Figure 10 FIG. 6 is a view showing an example of the state of the first ink Q1A and the second ink Q2A on the print target M in the case where the printing operation is completed.

[0170] On the print target M after the printing operation is completed, the first ink Q1A is disposed at the target landing position based on the print data, and the first ink Q1A lands in a one-to-one overlapping manner with the second ink Q2A.

[0171] Here, the first ink Q1A and the second ink Q2A are ejected from the first head 10A and the second head 20A, which are in mutually different positions. Therefore, as shown in FIG. 6, the droplets of the ink that are ejected later land in a state in which the top portions of the droplets of the ink that are ejected first on the print target M are slightly offset. Thus, the first ink Q1A becomes a state in which it adheres across the print target M and the second ink Q2A. Figure 10

[0172] In this way, a printed matter W that has droplets of the first ink Q1A and droplets of the second ink Q2A is formed. In the printed matter W, droplets of the first ink Q1A are disposed at the target landing position on the print target M, and the second ink Q2A is disposed in a state in which it overlaps the droplets of the first ink Q1A. Thus, a printed matter W in which the wet spreading of the first ink Q1A is reduced is formed.

[0173] Figure 11 ​​is a view showing another example of the ejection operation in the printing method according to the second embodiment, and is a view showing the case where the number n of the plurality of ejection regions shown in FIG. 8 is set to 2. Figure 7

[0174] As shown in FIG. 9, first, in the first main scanning operation (forward direction), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A disposed in the ejection region B1 to eject droplets of the second ink Q2A (hatched region in FIG. 9). Figure 11 Figure 11

[0175] The control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 22 eject, so that the droplets of the second ink Q2A land on the entire surface of the prescribed region on the print target M including the target landing position. By this first main scanning operation, a base layer C3 is formed on the print target M by the second ink Q2A (see FIG. 10). Figure 12

[0176] After the first main scanning operation is completed, the print target conveyance section conveys the print target M in the sub scanning direction D2 by a distance corresponding to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A. The conveyance distance is set to half the nozzle rows 13, 23 because the aforementioned ejection region is set to half the nozzle rows 13, 23. In the case where the ejection region is set to a number n other than 2, the conveyance distance is set to 1 / n of the length of the nozzle rows 13, 23.

[0177] After the print target M is conveyed in the sub scanning direction D2, in the second main scanning operation (return direction), the control section 30A causes the nozzles 12 of the first head 10A disposed in the ejection region A2 to eject droplets of the first ink Q1A (hatched region in FIG. 11). Figure 11

[0178] The control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 12 eject, so that the droplets of the first ink Q1A land on the target landing position on the print target M. That is, the control section 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing at which the nozzles 12 eject, so that the droplets of the first ink Q1A overlap the second ink Q2A landing on the target landing position one by one among the plurality of second inks Q2A landing on the entire surface of the prescribed region on the print target M.

[0179] After the second main scanning operation is completed, the print target conveyance section conveys the print target M in the sub scanning direction D2 by a distance corresponding to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A, as in the case after the first main scanning operation, to perform scanning in the forward direction in the main scanning direction D1. ​​​​​

[0180] Figure 12 is a view showing an example of a state of the first ink Q1A and the second ink Q2A on the printed matter M in a case where the printing operation shown in Figure 11 is completed. As shown in Figure 12 (c), on the printed matter M, a base layer C3 is formed on the printed matter M by the second ink Q2A. In addition, on the base layer C3, an ink layer is formed by the first ink Q1A. The first ink Q1A constituting the ink layer is in a state of landing in a manner of overlapping the second ink Q2A of the base layer C3 one-to-one. Thus, a state where wet spreading of the first ink Q1A is reduced is obtained. In this way, a printed matter WA in which wet spreading of the first ink Q1A is reduced is formed.

[0181] Here, the state of the second ink Q2A after landing on the printed matter M varies depending on the size or the amount of ejection of the droplets at the time of ejection of the second ink Q2A. For example, there are cases where the droplets of the second ink Q2A after landing do not overlap each other (see Figure 12 (a)), a case where only the peripheral portions of the second ink after landing overlap each other (see Figure 12 (b)), and the like. Since the first ink Q1A and the second ink Q2A are ejected from the first head 10A and the second head 20A which are different heads from each other, the droplets of the ink ejected later do not land on the top of the droplets of the ink landed first on the printed matter M, but land in a state of slightly deviating from the top of each ink. Even in this state, wet spreading of the first ink Q1A is reduced.

[0182] Figure 13 is a view showing another example of the ejection operation in the printing method according to the second embodiment. Figure 13 is a view showing a case where the number n of the plurality of ejection regions shown in Figure 7 is set to 2.

[0183] As shown in Figure 13 , first, in the first main scanning operation (forward), the control section 30A causes the nozzles 12 of the nozzle row 13 of the first head 10A disposed in the ejection region Al to eject droplets of the first ink Q1A (hatched regions in Figure 13 ).

[0184] The control section 30A controls the movement of the carriage 40 in the main scanning direction Dl and the timing at which the nozzles 12 perform ejection, so that the droplets of the first ink Q1A land on the target landing positions on the printed matter M.

[0185] In addition, in the first main scanning operation (forward), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A disposed in the ejection region Bl to eject droplets of the second ink Q2A (hatched regions in Figure 13 ).

[0186] The control unit 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing of the nozzle 22 ejection, so that the droplets of the second ink Q2A fall at the target landing position of the first ink Q1A on the printed body M. In other words, the control unit 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing of the nozzle 22 ejection, so that the droplets of the second ink Q2A overlap one-to-one with the first ink Q1A that first falls at the target landing position on the printed body M.

[0187] After the first main scanning operation is completed, the printable body transport unit transports the printable body M in the sub-scanning direction D2 by a distance corresponding to half the length of the nozzle arrays 13 and 23 of the first head 10A and the second head 20A. The transport distance is set to half the length of the nozzle arrays 13 and 23 because the aforementioned ejection area is set to half the length of the nozzle arrays 13 and 23. Considering that the ejection area is set to a number n other than two equal divisions, the transport distance is set to 1 / n of the length of the nozzle arrays 13 and 23.

[0188] After the printable material M is transported in the sub-scanning direction D2, a second main scan operation (repeated scan) is performed. During the second main scan operation, the control unit 30A ejects droplets of the second ink Q2A through the nozzles 22 arranged in the ejection region B2 of the nozzle array 23 of the second head 20A. Figure 13 (The shaded area in the image).

[0189] The control unit 30A controls the movement of the carriage 40 in the main scanning direction D1 and the timing of nozzle 22 ejection, so that droplets of the second ink Q2A fall onto the entire surface of the printed object M, including the designated area where the target landing position is located. Through this second main scanning action, a coating layer C4 (see reference) is formed on the printed object M. Figure 14 ).

[0190] Figure 14 It is shown Figure 13 The diagram shows an example of the state of the first ink Q1A and the second ink Q2A on the printed body M after the printing operation has been completed.

[0191] like Figure 14 As shown, in the first main scanning operation, at the target landing position on the printed body M, the first ink Q1A lands first. Then, the second ink Q2A lands in a manner that overlaps the first ink Q1A one-to-one. In addition, in the second main scanning operation, a coating layer C4 is formed in a manner that covers the first ink Q1A and the second ink Q2A formed by the first main scanning operation.

[0192] By setting the printing operation in this way, it is possible to reduce the wet-spreading of the first ink Q1A by the second ink Q2A, and it is possible to cover the image formed by the first ink Q1A. Thus, it is possible to obtain a printed matter WB with improved firmness and glossiness.

[0193] Figure 15 and Figure 16 is a view showing another example of the ejection operation in the printing method according to the second embodiment.

[0194] As shown in Figure 15 , in the first main scanning operation (forward), the control section 30A causes the nozzles 12 of the nozzle row 13 of the first head 10A, which are disposed in the ejection region Al, to eject droplets of the first ink Q1A (hatched region in Figure 15 ). In addition, the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A, which are disposed in the ejection region Bl, to eject droplets of the second ink Q2A (hatched region in Figure 15 ).

[0195] After the first main scanning operation is completed, the printed matter conveying section conveys the printed matter M in the sub-scanning direction D2 by a distance corresponding to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A. The conveyance distance is set to half the nozzle rows 13, 23 because the aforementioned ejection regions are set to half the nozzle rows 13, 23. In the case where the ejection regions are set to a number n other than 2, the conveyance distance is set to 1 / n of the length of the nozzle rows 13, 23.

[0196] In the second main scanning operation (return), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A, which are disposed in the ejection region B2, to eject droplets of the second ink Q2A (hatched region in Figure 15 ). In addition, the control section 30A causes the nozzles 12 of the nozzle row 13 of the first head 10A, which are disposed in the ejection region A2, to eject droplets of the first ink Q1A (hatched region in Figure 15 ).

[0197] In the first main scanning operation and the second main scanning operation, the control section 30A causes the droplets of the first ink Q1A and the droplets of the second ink Q2A to be ejected in such a way that the droplets of the first ink Q1A and the droplets of the second ink Q2A overlap one-to-one at the target landing position of the droplets of the first ink Q1A on the printed matter M.

[0198] After the second main scanning operation, the printed matter conveying section feeds back the printed matter M in the sub-scanning direction D2 by a distance corresponding to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A. That is, the printed matter M is fed back to the position at which the first main scanning operation was performed. Thereafter, the third main scanning operation (forward) is performed (refer toFigure 16 ).

[0199] As shown in FIG. 9, in the third main scan operation (outbound), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A, which are arranged in the ejection region B1, to eject droplets of the second ink Q2A (hatched region in FIG. 9). Figure 16 Figure 16

[0200] The control section 30A controls the movement of the carriage 40 in the main scan direction D1 and the timing at which the nozzles 22 eject, so that the droplets of the second ink Q2A ejected from the nozzles 22 land on the entire surface of the prescribed region on the print target M including the target landing position.

[0201] After the third main scan operation is completed, the print target conveyance section conveys the print target M in the sub scan direction D2 by a distance corresponding to half the length of the nozzle rows 13, 23 of the first head 10A and the second head 20A. Thereafter, the fourth main scan operation (inbound) is performed.

[0202] In the fourth main scan operation (inbound), the control section 30A causes the nozzles 22 of the nozzle row 23 of the second head 20A, which are arranged in the ejection region B2, to eject droplets of the second ink Q2A (hatched region in FIG. 10). Figure 16

[0203] The control section 30A controls the movement of the carriage 40 in the main scan direction D1 and the timing at which the nozzles 22 eject, so that the droplets of the second ink Q2A ejected from the nozzles 22 land on the entire surface of the prescribed region on the print target M including the target landing position.

[0204] By the third main scan operation and the fourth main scan operation, a coating layer identical to the coating layer C4 (refer to FIG. 8) is formed on the print target M. Thus, a print in which the wet spreading of the first ink Q1A is reduced is formed. Figure 14 As described above, the print method according to the second embodiment has the following structure.

[0205] (9) The print method includes the following processes:

[0206] the first head 10A in the main scan direction D1 and ejects droplets of the first ink Q1A from the nozzles 12 of the first head 10A toward the print target M; and

[0207] ejects droplets of a second ink Q2A having a higher viscosity than the first ink Q1A from the nozzles 22 of a second head 20A arranged side by side with the first head 10A in the main scan direction D1 and moving integrally with the first head 10A,

[0208]

[0209] ​​​​wherein the droplets of the first ink Q1A and the droplets of the second ink Q2A are ejected to the target landing positions of the droplets of the first ink Q1A on the print target M in a manner that the droplets of the first ink Q1A and the droplets of the second ink Q2A overlap one-to-one.

[0210] When configured as such, it is possible to suppress a difference in the degree of wet-spreading of the first ink Q1A depending on the viscosity of the ink.

[0211] Specifically, by ejecting the droplets of the first ink Q1A and the droplets of the second ink Q2A to the target landing positions of the droplets of the first ink Q1A on the print target M in a manner that the droplets of the first ink Q1A and the droplets of the second ink Q2A overlap one-to-one, it is possible to bring the droplets of the first ink Q1A into contact with the second ink Q2A. Thereby, it is possible to reduce the wet-spreading of the first ink Q1A.

[0212] In addition, the printing device 100A according to the second embodiment has the following structure.

[0213] (10) The printing device 100A includes:

[0214] a first head 10A that is movable in the main scanning direction D1 and that ejects droplets of a first ink Q1A from nozzles 12 toward a print target M;

[0215] a second head 20A that is movable in the main scanning direction D1 and that ejects droplets of a second ink Q2A from nozzles 22 toward the print target M; and

[0216] a control section 30A that controls the ejection actions of the first head 10A and the second head 20A.

[0217] The second head 20A is arranged in parallel with the first head 10A in the main scanning direction D1 and moves integrally with the first head 10A.

[0218] The viscosity of the droplets of the second ink Q2A is higher than the viscosity of the first ink Q1A.

[0219] The control section 30A controls the ejection actions of the first head 10A and the second head 20A so that the droplets of the first ink Q1A and the droplets of the second ink Q2A overlap one-to-one at the target landing positions of the droplets of the first ink Q1A on the print target M.

[0220] With the printing device 100A configured as such, it is also possible to suppress a difference in the degree of wet-spreading of the first ink Q1A.

[0221] (11) In the printing method, when a droplet of the second ink Q2A is ejected to the target landing position before a droplet of the first ink Q1A is ejected to the target landing position, the droplet of the first ink Q1A is ejected so as to overlap the droplet of the second ink Q2A after the droplet of the second ink Q2A is ejected to the target landing position.

[0222] When configured as such, the droplet of the first ink Q1A can be brought into contact with the second ink Q2A when the second ink Q2A is ejected before the first ink Q1A.

[0223] (12) In the printing method, when a droplet of the first ink Q1A is ejected to the target landing position before a droplet of the second ink Q2A is ejected to the target landing position, a droplet of the second ink Q2A, which is a high viscosity droplet, is ejected so as to overlap the droplet of the first ink Q1A after the droplet of the first ink Q1A is ejected to the target landing position.

[0224] When configured as such, the droplet of the first ink Q1A can be brought into contact with the second ink Q2A when the first ink Q1A is ejected before the second ink Q2A.

[0225] (13) In the printing method, in one main scanning operation of the first head 10A and the second head 20A, a droplet of the first ink Q1A and a droplet of the second ink Q2A are ejected to the target landing position so as to overlap the droplet of the first ink Q1A with the droplet of the second ink Q2A.

[0226] When configured as such, the droplet of the first ink Q1A can be brought into contact with the second ink Q2A in one main scanning operation.

[0227] (14) The printing method uses a first head 10A and a second head 20A each having a nozzle row 12, 13 composed of a plurality of nozzles 12, 22 arranged in a sub-scanning direction D2. The number of nozzles 12, 22 is the same.

[0228] In each main scanning operation, the nozzle row 13 of the first head 10A is divided into ejection regions Al, A2 (areas) obtained by 2-division (N-division: N is a natural number) of the nozzle row 13 in the sub-scanning direction D2 to perform ejection control.

[0229] In each main scanning operation, the nozzle row 23 of the second head 20A is divided into ejection regions Bl, B2 (areas) obtained by 2-division (N-division: N is a natural number) of the nozzle row 23 in the sub-scanning direction D2 to perform ejection control.

[0230] In each main scanning operation, the nozzle rows 13, 23 from which ink is ejected from the first head 10A and the second head 20A are nozzles of the ejection regions Al, Bl which are adjacent in the main scanning direction Dl.

[0231] When configured as such, a layer of the first ink QlA and a layer of the second ink Q2A can be formed for each region in the sub-scanning direction D2.

[0232] (15) In a printing method, in one main scanning operation of the first head 10A and the second head 20A, droplets of the second ink Q2A are ejected to a prescribed region on the print target M including a target landing position to form a base layer C3, and thereafter, in the next main scanning operation of the first head 10A and the second head 20A, the first ink QlA is ejected so that the first ink QlA overlaps the second ink Q2A ejected to the target landing position in the base layer C3.

[0233] When configured as such, even in the case where the first ink QlA is ejected onto the base layer C3, the droplets of the first ink QlA can be caused to contact the second ink Q2A.

[0234] (16) A printing method using a first head 10A and a second head 20A each having a nozzle row 12, 13 composed of a plurality of nozzles 12, 22 arranged in a sub-scanning direction D2. The number of nozzles 12, 22 is the same.

[0235] In each main scanning operation, the nozzle row 13 of the first head 10A is divided into ejection regions Al, A2 (areas) obtained by 2-division (N-division: N is a natural number) of the nozzle row 13 in the sub-scanning direction D2 to perform ejection control.

[0236] In each main scanning operation, the nozzle row 23 of the second head 20A is divided into ejection regions Bl, B2 (areas) obtained by 2-division (N-division: N is a natural number) of the nozzle row 23 in the sub-scanning direction D2 to perform ejection control.

[0237] In one main scanning operation, the nozzle 22 of the ejection region Bl from among the regions obtained by 2-division of the nozzle row 23 of the second head 20A, i.e., the nozzle row 23, ejects droplets of the second ink Q2A.

[0238] After the droplets of the second ink Q2A are ejected, the print target M is conveyed in the sub-scanning direction D2 by an amount corresponding to the nozzle row length obtained by 2-division of the nozzle row.

[0239] In the next main scanning operation, the first head 10A ejects droplets of the first ink QlA from the nozzles 12 of the ejection region A2 which is a region continuous with the ejection region Bl of the second head 20A in the sub-scanning direction D2.

[0240] When configured as such, it is possible to form a layer of the first ink Q1A and a layer of the second ink Q2A for each region in the sub-scanning direction D2.

[0241] (17) In the printing method, after at least a droplet of the first ink Q1A is ejected to a target landing position, a second ink Q2A is ejected to a prescribed region on the printed body M including the target landing position to form a coating layer C4.

[0242] When configured as such, it is possible to protect the layer of the first ink Q1A by the coating layer C4 in a state in which wet spreading of the first ink Q1A is reduced.

[0243] In addition, the print W related to the second embodiment has the following structure.

[0244] (18) The print W has:

[0245] a printed body M;

[0246] a droplet of a first ink Q1A disposed on a target landing position on the printed body M; and

[0247] a droplet of a second ink Q2A having a higher viscosity than the first ink Q1A.

[0248] The second ink Q2A is disposed in a state of overlapping the target landing position of the first ink Q1A in one-to-one correspondence with the droplet of the first ink Q1A.

[0249] When configured as such, it is possible to provide a print W in which wet spreading of the first ink Q1A is reduced.

[0250] (19) The second ink Q2A is at least one of an ink of the same color as the first ink Q1A, an ink of the same color as the printed body M, and a transparent ink.

[0251] When configured as such, it is possible to perform printing without impairing the color tone of the original image data and the image quality.

[0252] The technical scope of the present application is not limited to the above-described embodiments, and appropriate changes can be made within the scope of the present application without departing from the gist thereof.

[0253] Explanation of Reference Signs

[0254] 100, 100A: printing device; 10: first liquid droplet ejection section (liquid droplet ejection section); 10A: first head; 12: nozzle; 13: nozzle row; 20: second liquid droplet ejection section (buffer layer forming section); 20A: second head; 22: nozzle; 23: nozzle row; 30, 30A: control section; 33: determination section (buffer layer forming determination section); 33a: absolute value calculation section; 33b: threshold value determination section; 40: carriage; Al, A2: ejection region (zone); Bl, B2: ejection region (zone); C: buffer layer; C3: base layer; C4: coating layer; Dl: main scanning direction; D2: sub scanning direction; I: ink layer; M: printed body; Ql, QlA: first ink; Q2, Q2A: second ink; W, WA, WB: printed matter.

Claims

1. A printing method comprising the following processes: a buffer layer forming process of forming a buffer layer on a surface of a printed object that is a printing target using a buffer material having a surface free energy different from a surface free energy of the printed object or a coating material to be coated on the surface of the printed object, in a case where there is a difference between the surface free energy of the printed object and the surface free energy of the coating material to be coated on the surface of the printed object; and a printing process of performing printing by coating the coating material on the buffer layer, further comprising a determination process of determining whether or not to form the buffer layer based on a difference between the surface free energy of the printed object and the surface free energy of the coating material, in a case where it is determined to form the buffer layer, the buffer layer is formed on the surface of the printed object.

2. The printing method according to claim 1, wherein in the determination process, in a case where an absolute value of the difference between the surface free energy of the printed object and the surface free energy of the coating material is equal to or greater than a threshold value, it is determined to form the buffer layer.

3. The printing method according to claim 2, wherein at least one of a transparent ink, a primer, and an ink of the same color as the printed object having a surface free energy corresponding to the absolute value of the difference between the surface free energy of the printed object and the surface free energy of the coating material is used as the buffer material to form the buffer layer.

4. The printing method according to any one of claims 1 to 3, wherein the printed object includes the printed object having a surface free energy greater than the surface free energy of the coating material and the printed object having a surface free energy smaller than the surface free energy of the coating material.

5. The printing method according to any one of claims 1 to 3, wherein the buffer layer is formed throughout an entire region of the printed object on which the coating material is coated or an entire surface of the printed object.

6. A printing apparatus comprising: a droplet ejection section capable of ejecting droplets of a coating material toward a surface of a printed object; a buffer layer forming section capable of forming a buffer layer for adjusting a disposition state of the coating material on the surface of the printed object; and a control section that causes the buffer layer forming section to form the buffer layer and causes the droplet ejection section to coat the coating material on the buffer layer, in a case where an absolute value of a difference between a surface free energy of the printed object and a surface free energy of the coating material is equal to or greater than a threshold value.

7. The printing apparatus according to claim 6, wherein the control section further comprises: a storage section that stores information of surface free energies of a plurality of printed objects and surface free energies of a plurality of coating materials; an absolute value calculation section that calculates the absolute value of the difference between the surface free energy of the printed object to be printed and the surface free energy of the coating material, from the information of the surface free energies of the plurality of printed objects and the surface free energies of the plurality of coating materials; a threshold value determination section that determines whether or not the absolute value is equal to or greater than a threshold value; and ​ ​ A buffer layer formation determination section determines whether to form the buffer layer using the threshold value.

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