Printing method and ink set

Abstract

To provide a printing method and an ink set capable of suppressing differences in the degree of wet spreading of a coating material depending on the type of print target.SOLUTION: A printing method that performs printing by using a printing device provided with a droplet ejection unit that ejects first ink for forming an image on a print target and second ink for forming a buffer layer between at least a part of the print target and an image formed by the first ink, includes: a buffer layer forming step of forming a buffer layer on a surface of the print target using the second ink; and a printing step of performing printing by applying the first ink on the buffer layer. In the buffer layer forming step, an ejection amount calculated such that one surface of the surface of the print target is painted over with the second ink is defined as a normal ejection amount, and the buffer layer is formed by changing the ejection amount of the second ink discharged onto the surface of the print target according to the type of the print target.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a printing method and an ink set. [Background technology]

[0002] BACKGROUND ART As a printing device that prints on a printing medium as a printing target, for example, an inkjet printing device that ejects droplets from a head onto the printing medium is known (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-14065 Summary of the Invention [Problem to be solved by the invention]

[0004] When printing using a printing device such as that described in Patent Document 1, depending on the type of substrate, the coating material such as ink may not wet and spread sufficiently or may wet and spread too much. For this reason, there is a need for a technology that can prevent differences in the degree of wetting and spreading of the coating material depending on the type of substrate.

[0005] The present invention has been made in consideration of the above, and aims to provide a printing method and printing device that can suppress differences in the degree of wetting and spreading of coating material depending on the type of printing substrate. [Means for solving the problem]

[0006] The printing method of the present invention includes a buffer layer formation step of forming a buffer layer on the surface of the substrate using a buffer material having a surface free energy different from that of the substrate or the coating material when there is a difference between the surface free energy of the substrate to be printed and the surface free energy of the coating material to be applied to the surface of the substrate, and a printing step of applying the coating material onto the buffer layer to perform printing.

[0007] The printing device of the present invention comprises a droplet ejection unit capable of ejecting droplets of coating material toward the surface of a substrate to be printed, a buffer layer formation unit capable of forming a buffer layer on the surface of the substrate to adjust the placement of the coating material, and a control unit that, when the absolute value of the difference between the surface free energy of the substrate to be printed and the surface free energy of the coating material is equal to or greater than a threshold value, causes the buffer layer formation unit to form the buffer layer and causes the droplet ejection unit to apply the coating material onto the buffer layer.

[0008] According to the present invention, a buffer layer is formed on the surface of a substrate using a buffer material having a surface free energy different from that of the substrate or the coating material, and printing is performed by applying the coating material onto the buffer layer, so that it is possible to prevent both the coating material from spreading too much and the coating material from spreading insufficiently. This makes it possible to prevent differences in the degree of wetting and spreading of the coating material depending on the type of substrate. In addition, in the present invention, when there is a difference between the surface free energy of the substrate and the surface free energy of the coating material, for example, there is a difference of 1 mJ / m between the two. 2 This can be the case when there is a difference of more than this.

[0009] The printing method according to the present invention further includes a determination step of determining whether or not to form the buffer layer based on the difference between the surface free energy of the substrate and the surface free energy of the coating material. If it is determined that the buffer layer should be formed, the buffer layer is formed on the surface of the substrate. Furthermore, the determination step determines that the buffer layer should be formed if the absolute value of the difference between the surface free energy of the substrate and the surface free energy of the coating material is equal to or greater than a threshold value. This more reliably prevents differences in the degree of wetting and spreading of the coating material.

[0010] In the printing method according to the present invention, the buffer layer is formed using at least one of a clear ink, a primer, and an ink of the same color as the substrate, which has a surface free energy corresponding to the absolute value of the difference between the surface free energy of the substrate and the surface free energy of the coating material, thereby ensuring an appropriate ink distribution state on the buffer layer.

[0011] In the printing method according to the present invention, the substrates include substrates having a surface free energy greater than that of the coating material, and substrates having a surface free energy less than that of the coating material. This makes it possible to prevent differences in the degree of wetting and spreading of the coating material when coating the coating material on multiple types of substrates having a range of surface free energies.

[0012] In the printing method according to the present invention, the buffer layer is formed over the entire area on the surface of the substrate to which the coating material is applied or over the entire surface of the substrate, thereby preventing variations in the degree of wetting and spreading of the coating material across the entire surface.

[0013] In the printing device according to the present invention, the control unit further includes a storage unit that stores information on the surface free energies of a plurality of substrates and a plurality of coating materials, an absolute value calculation unit that calculates the absolute value of the difference between the surface free energies of the substrates to be printed and the surface free energies of the coating materials based on the information on the surface free energies of the plurality of substrates and the plurality of coating materials, a threshold determination unit that determines whether the absolute value is equal to or greater than a threshold, and a buffer layer formation determination unit that determines whether the buffer layer is to be formed based on the threshold, thereby enabling an efficient determination of whether the buffer layer is to be formed. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a printing method and a printing device that can suppress differences in the degree of wetting and spreading of the coating material depending on the type of printing medium. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example of a printing apparatus according to this embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the physical property information stored in the physical property information storage unit. [Figure 3] FIG. 3 is a diagram showing an example of the state of the first ink ejected onto the printing medium or the buffer layer. [Figure 4] FIG. 4 is a diagram showing an example of the state of the first ink ejected onto the buffer layer. [Figure 5] FIG. 5 is a flowchart showing an example of the printing method according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of a printing method and a printing device according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0017] FIGS. 1A and 1B are diagrams illustrating an example of a printing apparatus according to the present embodiment. As shown in FIGS. 1A and 1B, the printing apparatus 100 includes a first droplet ejection unit 10, a second droplet ejection unit (buffer layer forming unit) 20, and a control unit 30. The printing apparatus 100 also includes a relative movement unit (not shown) that moves the first head 10, the second head 20, and the printing medium M relative to each other in the sub-scanning direction D2. In the present embodiment, a printing medium drive unit that moves the printing medium M in the sub-scanning direction D2 is used as the relative drive unit. Note that the relative drive unit may also be configured to move the first droplet ejection unit 10 and the second droplet ejection unit 20 in the sub-scanning direction D2. The first droplet ejection unit 10 or the second droplet ejection unit 20 may be a mechanism that ejects fine droplets, such as an inkjet head or a spray, or a mechanism that continuously ejects liquid, such as a dispenser. However, the present embodiment is not limited to these.

[0018] The printing substrate M can be, for example, an impermeable printing substrate made of metal, resin, or the like that is impermeable to ink, or a permeable printing substrate made of cloth, paper, or the like that is permeable to ink, and any material can be used as long as it is a printing substrate on which an image can be formed. Furthermore, the printing substrate M has a surface on which an image is to be formed, and this surface may be uneven, flat, or curved in shape, and can be applied to any shape as long as it is a shape on which an image can be formed.

[0019] The first droplet ejecting unit 10 is movable in the main scanning direction D1 and applies a coating material from a nozzle to the print substrate M, i.e., ejects droplets of the first ink to form an ink layer. The second droplet ejecting unit 20 is arranged alongside the first head 10 in the main scanning direction D1 and moves integrally with the first droplet ejecting unit 10. The first droplet ejecting unit 10 and the second droplet ejecting unit 20 may be controlled to scan separately as necessary. The second droplet ejecting unit 20 is capable of forming a buffer layer on the surface Ma of the print substrate M, which adjusts the positioning of the first ink after it lands on the print substrate M. The second droplet ejecting unit 20 ejects droplets of the second ink that form the buffer layer.

[0020] The first ink and the second ink may be, for example, evaporation-drying inks such as solvent ink, aqueous ink, or latex ink. The first ink may be, for example, a color ink capable of producing a predetermined color. The second ink may be, for example, a colorless, transparent clear ink, a primer, or a white ink having a surface free energy corresponding to the surface free energy of the first ink.

[0021] In this embodiment, the surface free energy is the energy per unit area stored on a surface by work performed from the outside under a constant temperature condition. The surface free energy has a dimension equivalent to the surface tension (for example, mJ / m 2 : millijoules per square meter). For example, if the surface free energy of the substrate M is greater than the surface free energy of the first ink, the first ink will more easily 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 and the surface free energy of the substrate M, the more easily the first ink will spread. Also, if the surface free energy of the substrate M is smaller than the value of the surface free energy of the first ink, the more difficult it will be for the first ink to 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 and the surface free energy of the substrate M, the more difficult it will be for the first ink to spread on the substrate M.

[0022] Similarly, for example, if the surface free energy of the buffer layer is greater than the surface free energy of the first ink, the first ink will be more likely to wet and spread on the buffer layer. Furthermore, if the surface free energy of the buffer layer is less than the surface free energy of the first ink, the first ink will be less likely to wet and spread on the buffer layer. Therefore, if the surface free energy of the first ink is less than the surface free energy of the substrate M, it is preferable that the surface free energy of the second ink constituting the buffer layer be the same as or greater than the surface free energy of the first ink. Furthermore, if the surface free energy of the first ink is greater than the surface free energy of the substrate M, it is preferable that the surface free energy of the second ink constituting the buffer layer be the same as or less than the surface free energy of the first ink.

[0023] The first droplet ejection unit 10 and the second droplet ejection unit 20 are mounted on a carriage 40. The carriage 40 is movable in the main scanning direction D1 along a guide bar 41. When the carriage 40 moves in the main scanning direction D1, the first droplet ejection unit 10 and the second droplet ejection unit 20 move integrally in the main scanning direction D1.

[0024] The control unit 30 includes 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).

[0025] As shown in FIG. 1(b), the control unit 30 includes a print medium information acquisition unit 31, a storage unit 32, a determination unit 33, a drive control unit , and a discharge control unit .

[0026] The storage unit 32 stores various types of information. The storage unit 32 has storage such as a hard disk drive, a solid state drive, etc. Note that an external storage medium such as a removable disk may also be used as the storage unit 32.

[0027] The storage unit 32 includes a physical property information storage unit 32a. The physical property information storage unit 32a stores physical property information that associates the type of the printing medium M with the surface free energy of the printing medium M.

[0028] FIG. 2(a) is a diagram showing an example of physical property information stored in the physical property information storage unit 32a. As shown in FIG. 2(a), the physical property information storage unit 32a stores the material of the print substrate M and the surface free energy in a correlated state. The print substrates M1 to M7 are formed using different materials. The print substrate M1 has a surface free energy of E7. The print substrate M2 has a surface free energy of E6. The print substrate M3 has a surface free energy of E5. The print substrate M4 has a surface free energy of E4. The print substrate M5 has a surface free energy of E3. The print substrate M6 has a surface free energy of E2. The print substrate M7 has a surface free energy of E1. However, E1 <E2<E3<E4<E5<E6<E7である。

[0029] In addition, in FIG. 2(b), the types of the first ink and the second ink are stored in association with the surface free energy. In the example shown in FIG. 2(b), the first ink and the second ink (buffer layer) have surface free energies equal to E4. Note that the surface free energy of the second ink may differ from the surface free energy of the first ink. Below, an example will be described in which the surface free energy of the first ink and the second ink (buffer layer) is E4. Note that in the following description, since the buffer layer is formed from the second ink, the surface free energy of the buffer layer can be set to E4, the same as the surface free energy of the second ink.

[0030] The print substrate information acquisition unit 31 acquires print substrate information related to the type of print substrate M. The print substrate information is input, for example, via the input unit 50. The input unit 50 may be an automatic input device, such as a camera or optical sensor, that automatically detects the print substrate, or a manual input device, such as a keyboard or mouse, through which the user inputs information. For example, a configuration may be adopted in which multiple print substrate information options are displayed on a display unit (not shown), and the print substrate information is input by selecting one or more print substrate information options from the displayed options. In this case, the multiple options may be, for example, print substrates M1 to M7 stored in the physical property information storage unit 32a of the storage unit 32. The multiple types of print substrates M1 to M7 include print substrates having a surface free energy greater than that of the first ink and print substrates having a surface free energy less than that of the first ink.

[0031] The determination unit 32 determines whether or not to form a buffer layer on the printing material M based on the printing material information acquired by the printing material information acquisition unit 31 and the information stored in the physical property information memory unit 32a of the memory unit 32.

[0032] Specifically, the determination unit 33 includes an absolute value calculation unit 33a and a threshold determination unit 33b. The determination unit 33 searches for which of the print substrates M1 to M7 of the physical property information stored in the physical property information storage unit 32a the acquired type of print substrate M corresponds to, and obtains the surface free energy value corresponding to the corresponding type of print substrate. The determination unit 33 also obtains the surface free energy value of the first ink stored in the physical property information storage unit 32a. The determination unit 33 determines whether or not to form a buffer layer based on the difference between the acquired surface free energy and the surface free energy of the first ink. For example, the absolute value calculation unit 33a calculates the absolute value of the difference between the surface free energy of the print substrate M and the surface free energy of the first ink, and the threshold determination unit 33b determines that the absolute value is equal to or greater than the threshold, and then determines that a buffer layer should be formed. On the other hand, the determination unit 33 determines that a buffer layer should not be formed when, for example, the absolute value calculation unit 33a calculates the absolute value of the difference between the surface free energy of the print substrate M and the surface free energy of the first ink, and the threshold determination unit 33b determines that the absolute value is less than the threshold. The threshold can be set in advance. In this embodiment, the threshold can be set to two levels, for example, E1 to E7. In this case, if the absolute value of the difference between the surface free energy of the print substrate M and the surface free energy of the first ink is two levels or more, the determination unit 33 determines that a buffer layer should be formed. If the absolute value of the difference between the surface free energy of the print substrate M and the surface free energy of the first ink is less than one level, the determination unit 33 determines that a buffer layer should not be formed.

[0033] The drive control unit 34 controls a drive mechanism that moves the carriage 40 in the main scanning direction D1. The ejection control unit 35 controls the operation of ejecting droplets of the first ink from the first droplet ejection unit 10 and the operation of ejecting droplets of the second ink from the second droplet ejection unit 20. When the determination unit 33 determines that a buffer layer should be formed, the ejection control unit 35 causes the second droplet ejection unit 20 to eject droplets of the second ink to form the buffer layer.

[0034] FIG. 3 is a diagram showing an example of the state of the first ink ejected onto the object to be printed or the buffer layer. As shown in FIG. 3(a), when the first ink Q1 with a surface free energy of E4 (<E7) is dropped onto the surface M1a of the object to be printed M1 with a surface free energy of E7, the first ink Q1 spreads on the surface M1a of the object to be printed M1.

[0035] Also, as shown in FIG. 3(b), when the first ink Q1 with a surface free energy of E4 (>E1) is dropped onto the surface M7a of the object to be printed M7 with a surface free energy of E1, the first ink Q1 does not spread on the surface M7a of the object to be printed M7 and assumes a bulged state.

[0036] Also, as shown in FIG. 3(c), when the first ink Q1 with a surface free energy of E4 is dropped onto the surface Ca of the buffer layer C with a surface free energy of E4, the spreading of the first ink Q1 on the surface Ca of the buffer layer C is smaller than when the first ink Q1 is dropped onto the surface M1a of the object to be printed M1, and larger than when the first ink Q1 is dropped onto the surface M7a of the object to be printed M7. Note that, regarding the case where the first ink Q1 with a surface free energy of E4 is dropped onto the object to be printed M4 with a surface free energy of E4, the arrangement state (spreading state) of the first ink Q1 is the same as when the first ink Q1 is dropped onto the surface Ca of the buffer layer C.

[0037] FIG. 4 is a diagram showing an example of the state of the first ink ejected onto the buffer layer. When forming the buffer layer, the second ink Q2 is ejected from the nozzles of the droplet ejection unit 20 over the entire predetermined regions R1 and R2 including the portion where the ink layer I is formed by the first ink Q1 on the surface of the object to be printed M. Therefore, the buffer layers C1 and C2 are formed over the entire predetermined regions R1 and R2 including the portion where the ink layer I is formed.

[0038] As shown in FIG. 4(a), in the present embodiment, the surface free energy of the second ink Q2 is E4. When forming the buffer layer C1 on the surface M1a of the printing object M1 with a surface free energy of E1 using the second ink Q2 with a surface free energy of E4 (<E7), the buffer layer C1 is formed in a state of spreading on the surface M1a of the printing object M1. When the second ink Q2 has a tendency to spread and wet on the surface M1a of the printing object M1, or when this tendency is significant, the discharge amount of the second ink Q2 may be reduced compared to normal. Reducing it compared to normal means discharging droplets (small dots) with an amount less than the discharge amount calculated by the control unit 30 so as to cover one surface of the surface M1a of the printing object M1. Also, in this case, instead of making all the droplets of the second ink Q2 discharged have the same size, it is also conceivable to discharge a mixture of droplets with a normal discharge amount and droplets with a discharge amount less than the normal droplets. Or, the overall discharge amount may be reduced by thinning out while discharging at the normal discharge amount.

[0039] Also, as shown in FIG. 4(b), when forming the buffer layer C2 on the surface M7a of the printing object M7 with a surface free energy of E1 using the second ink Q2 with a surface free energy of E4 (>E1), the buffer layer C2 does not spread and wet on the surface M7a of the printing object M7 and becomes a raised state. When the second ink Q2 has a tendency not to spread and wet on the surface M1a of the printing object M1 and the surface of the surface M7a of the printing object M7 is exposed, or when this tendency is significant, the discharge amount of the second ink Q2 may be increased compared to normal. Increasing it compared to normal means discharging droplets (large dots) with an amount more than the discharge amount calculated by the control unit 30 so as to cover one surface of the surface M1a of the printing object M1. Also, in this case, instead of making all the droplets of the second ink Q2 discharged have the same size, it is also conceivable to discharge a mixture of droplets with a normal discharge amount and droplets with a discharge amount more than the normal droplets.

[0040] When the first ink Q1 is dropped onto the printing substrates M1 and M7 on which the buffer layers C1 and C2 are formed, the first ink Q1 lands on the surfaces C1a and C2a of the buffer layers C1 and C2, which have the same surface free energy. Therefore, the ink layers I1 and I2 formed on the printing substrates M1 and M7 have the same degree of wetting and spreading of the first ink Q1.

[0041] Next, a printing method using the printing device 100 configured as described above will be described. FIG. 5 is a flowchart illustrating an example of the printing method according to this embodiment. When printing data is received from an external source, the print substrate information acquisition unit 31 acquires print substrate information regarding the type of print substrate M (step S10). When the print substrate information has been acquired, the determination unit 33 determines whether or not to form a buffer layer (step S20). In step S20, the determination unit 33 searches for which of the print substrates M1 to M7 in the physical property information storage unit 32a corresponds to the acquired type of print substrate M, and acquires a surface free energy value corresponding to the corresponding type of print substrate. For example, when the surface free energies E1 and E2 of print substrates M7 and M6 and the surface free energies E7 and E6 of print substrates M1 and M2 are acquired, the absolute value of the difference from the surface free energy E4 of the first ink is equal to or greater than a threshold (by two or more levels), so the determination unit 33 determines that a buffer layer should be formed. On the other hand, when the surface free energies E5, E4, and E3 of the printing bodies M3, M4, and M5 are obtained, the absolute value of the difference from the surface free energy E4 of the first ink is less than the threshold value (two levels), so the judgment unit 33 determines that a buffer layer will not be formed.

[0042] If it is determined in step S20 that a buffer layer is to be formed (Yes in step S20), the control unit 30 ejects the second ink Q2 from the nozzles of the second head 20 into a predetermined range on the printing medium M that includes the position that is the target for ejection of the first ink Q1, thereby forming a buffer layer C in the area of ​​that predetermined range (step S30).

[0043] If it is determined in step S20 that a buffer layer will not be formed (No in step S20), or after forming the buffer layer, the control unit 30 ejects the first ink Q1 from the nozzles of the first head 10 onto a position on the printing medium M that is the ejection target of the first ink Q1, thereby forming an ink layer I (step S40).

[0044] As described above, the printing method of this embodiment includes a buffer layer formation process in which, when there is a difference between the surface free energy of the printing substrate M, which is the object to be printed, and the surface free energy of the first ink Q1, which is the coating material to be applied onto the printing substrate M, a buffer layer C is formed using a buffer material having a surface free energy different from that of the surface of the printing substrate M, the printing substrate M, or the first ink Q1, and a printing process in which printing is performed by applying the first ink Q1 onto the buffer layer C.

[0045] Furthermore, the printing device 100 according to this embodiment includes a first droplet ejection unit 10 capable of ejecting droplets of the first ink Q1 toward the surface of the substrate M, a second droplet ejection unit 20 capable of forming a buffer layer C on the surface of the substrate M to adjust the positioning state of the first ink Q1, and a control unit 30 that, when the absolute value of the difference between the surface free energy of the substrate 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 unit 20 to form the buffer layer C and causes the first droplet ejection unit 10 to form an ink layer I on the buffer layer C.

[0046] According to this embodiment, a buffer layer C that adjusts the arrangement of the first ink Q1 is formed on the surface of multiple types of print substrates M with different surface free energies, and droplets of the first ink Q1 are ejected onto the buffer layer C to form an ink layer I, thereby preventing the first ink Q1 from wetting and spreading too much or insufficiently. This makes it possible to prevent differences in the degree of wetting and spreading of the first ink Q1 depending on the type of print substrate M.

[0047] The printing method according to this embodiment further includes a determination step of determining whether or not to form a buffer layer C based on the difference between the surface free energy of the substrate M and the surface free energy of the first ink Q1, and if it is determined that the buffer layer C should be formed, the buffer layer C is formed on the surface of the substrate M. Furthermore, the determination step determines that the buffer layer C should be formed if the absolute value of the difference between the surface free energy of the substrate M and the surface free energy of the first ink Q1 is equal to or greater than a threshold value. This more reliably prevents differences in the degree of wetting and spreading of the first ink Q1.

[0048] In the printing method according to this embodiment, the buffer layer C is formed using at least one of a clear ink having a surface free energy corresponding to the absolute value of the difference between the surface free energy of the print substrate M and the surface free energy of the first ink Q1, a primer, and an ink of the same color as the print substrate M. This makes it possible to ensure that the first ink Q1 is appropriately positioned on the buffer layer C.

[0049] In the printing method according to this embodiment, the multiple types of substrates M include substrates M with a surface free energy greater than that of the first ink Q1 and substrates M with a surface free energy less than that of the first ink Q1. This makes it possible to prevent differences in the degree of wetting and spreading of the first ink Q1 when forming an ink layer I on multiple types of substrates with a range of surface free energies.

[0050] The printing method according to this embodiment forms a buffer layer C over the entire area on the surface of the print medium M where the ink layer I is formed, or over the entire print medium M. This makes it possible to prevent differences in the degree of wetting and spreading of the first ink Q1 across the entire ink layer I.

[0051] Furthermore, in the printing device 100 according to this embodiment, the control unit 30 further includes a memory unit 35 that stores information on the surface free energies of the plurality of substrates M to be printed and the surface free energies of the plurality of coating materials, an absolute value calculation unit 33a that calculates the absolute value of the difference between the surface free energy of the substrate M to be printed and the surface free energy of the coating material from the information on the surface free energies of the plurality of substrates M to be printed and the surface free energy of the coating material, a threshold determination unit 33b that determines whether the absolute value is equal to or greater than a threshold, and a determination unit 33 that determines whether or not to form a buffer layer C based on the threshold. This allows for efficient determination of whether or not to form a buffer layer.

[0052] The technical scope of the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0053] C, C1, C2... buffer layer, Ca, C1a, C2a, Ma, M1a, M7a... surface, D1... main scanning direction, D2... sub-scanning direction, I, I1, I2... ink layer, M, M1 to M7... printing substrate, Q1... first ink, Q2... second ink, R1, R2... area, 10... first head, 20... second head, 30... control unit, 31... printing substrate information acquisition unit, 32... storage unit, 32a... physical property information storage unit, 33... determination unit, 33a... absolute value calculation unit, 33b... threshold value determination unit, 34... drive control unit, 35... ejection control unit, 40... carriage, 41... guide bar, 50... input unit, 100... printing device

Claims

1. A printing method for performing printing using a printing device including a droplet ejecting unit that ejects a first ink for forming an image on a printing medium and a second ink for forming a buffer layer between at least a portion of the printing medium and the image formed by the first ink, a buffer layer forming step of forming a buffer layer on the surface of the printing medium using the second ink; a printing step of printing by applying the first ink onto the buffer layer, In the buffer layer forming step, a discharge amount calculated to fill one surface of the print medium with the second ink is set as a normal discharge amount, and the buffer layer is formed by changing the discharge amount of the second ink discharged onto the surface of the print medium depending on the type of the print medium. Printing method.

2. The printing device further includes a storage unit in which information about the printing medium and information about the second ink are stored. The printing method according to claim 1 .

3. The information on the printing substrate includes a plurality of types of the printing substrate and surface free energy according to the type of the printing substrate. The printing method according to claim 2 .

4. The information about the second ink includes the surface free energy of the second ink. The printing method according to claim 2 .

5. In the buffer layer forming step, when the surface free energy of the printing medium is greater than the surface free energy of the second ink, the second ink is discharged with a larger discharge amount than the normal discharge amount. The printing method according to any one of claims 1 to 4.

6. In the buffer layer forming step, when the surface free energy of the printing medium is smaller than the surface free energy of the second ink, droplets of the second ink are discharged in an amount smaller than the normal discharge amount. The printing method according to any one of claims 1 to 4.

7. In the buffer layer forming step, when the surface free energy of the printing medium is smaller than the surface free energy of the second ink, droplets of the second ink are ejected by thinning out the droplets of the normal ejection amount. The printing method according to any one of claims 1 to 4.

8. The second ink is a colorless and transparent clear ink, a primer, white, or a color similar to that of the printing substrate on which the image is to be formed. The printing method according to claim 1 .

9. a first ink to be ejected from the droplet ejecting unit to form an image on a printing medium; a second ink having a surface free energy corresponding to the surface free energy of the first ink; An ink set comprising:

10. The second ink is a colorless and transparent clear ink, a primer, white, or a color similar to that of the printing medium on which the image is to be formed. The ink set according to claim 9.

Images