Pattern formation method and inkjet printing apparatus

Abstract

The present invention addresses the problem of providing a pattern forming method that causes no streaks and has excellent reproducibility, and an inkjet printing device that forms the pattern.　The pattern forming method of the present invention is based on a system in which an ink ejection device having a plurality of nozzle holes or a substrate serving as a printing medium is moved a plurality of times, and liquid droplets of ink are discharged from the nozzles of the ink ejection device onto the substrate serving as the printing medium to form the pattern. The method is characterized in that landing of liquid droplets of the ink that are used to form a film of dots constituting the pattern formed on the substrate occurs a plurality of times, and the positions of the dots at which the liquid droplets are caused to land are controlled so that, in a pattern part other than a boundary part, the dot positions are not in accordance with the orders of rows and columns in which the respective pixels constituting image data are arrayed, and do not have fixed periodicity, and so that, in the boundary part, the dot positions are in accordance with the order in a longitudinal direction in which the respective pixels constituting the image data are arrayed, and have continuity or periodicity.

Description

Technical Field

[0001] The present invention relates to a pattern forming method and an inkjet printing apparatus. More specifically, the present invention relates to a pattern forming method for forming a pattern without streaks and having good reproducibility, and an inkjet printing apparatus for forming the pattern.

Background Art

[0002] In recent years, research and development of a technique for forming a pattern of an electronic device by an inkjet printing method (hereinafter, also simply referred to as "inkjet method") using ink containing a functional material has been advanced.

[0003] Patent Document 1 discloses a method for manufacturing a multilayer wiring board having an interlayer insulating film by a droplet ejection method (inkjet method). However, depending on the combination of the substrate and the ink, problems such as bulges may occur, and when forming a pattern across different substrates, due to differences in the wettability of the ink on each substrate, the ink may flow to the substrate side with high wettability.

[0004] Therefore, Patent Document 2 discloses a method of applying droplets of an insulating film forming material while varying the distance from the peripheral portion based on the wetting characteristics of the base on the substrate. However, when the wetting characteristics of each base are significantly different, problems such as the ink flowing away occur. Also, when forming a pattern across a substrate with irregularities, problems such as the ink flowing away occur.

[0005] In response to this, in Patent Document 3 that discloses the invention of the present inventor, in the pattern formation of an insulating layer by an inkjet method, the viscosity of the ink at the time of ejection and after landing was defined to solve the above problems. However, since the insulating layer forming ink having a phase change mechanism used has high dot fixability after landing, there is room for further improvement in the occurrence of streak-like unevenness in the scan direction.

[0006] Furthermore, Patent Document 4 describes that in an inkjet one-pass printer, by grouping multiple adjacent pixels together and adjusting the amount of droplet ejected by a single pixel within the group, the number of pixels ejected within a group can be reduced, thereby suppressing glossy streaks in the transport direction. However, the inventors' research has shown that when this method is applied to a multi-pass system, streaks perpendicular to the transport direction are observed.

[0007] When high resolution is required for the purpose of printing highly detailed patterns, the multi-pass method is mainly used. However, the time between passes in the multi-pass method is long, which can easily result in streaky unevenness. Furthermore, streaky irregularities are a significant problem not only because they affect the appearance, but also because they result in uneven insulation and conductivity when forming insulating films and conductive films. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2003-309369 [Patent Document 2] Japanese Patent Publication No. 2010-231287 [Patent Document 3] International Publication No. 2015 / 002316 [Patent Document 4] Japanese Patent Publication No. 2012-162057 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention has been made in view of the above-mentioned problems and circumstances, and its objective is to provide a pattern formation method that is free of streaks and has good reproducibility, and an inkjet printing apparatus for forming said pattern. [Means for solving the problem]

[0010] In order to solve the above problems, the inventors investigated the causes of the above problems and, as a result, found that by controlling the position of the dots on which the droplets land to be random in the pattern area excluding the boundaries (a state in which randomness or unpredictability is recognized, lacking overall identity or periodicity), and to have continuity or periodicity in the boundaries, it is possible to form a pattern without streaks and with good reproducibility, leading to the present invention. In other words, the above-mentioned problems according to the present invention are solved by the following means.

[0011] 1. A pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form the pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dots that land the droplets is controlled such that, in the pattern portion excluding the boundary portion, the position is not in the same order as the rows and columns in which the pixels constituting the image data are arranged, and does not have a certain periodicity. In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the longitudinal order in which it is arranged. As the aforementioned ink, use an ink in which the ratio η2 / η1, which is the ratio of viscosity η1 at the temperature of ejection to viscosity η2 at the temperature of impact, is 100 or more. ,and Solder resist ink is used as the aforementioned ink. A pattern forming method characterized by the following.

[0012] 2. A method for forming a pattern using an inkjet printing method based on image data of a pattern, In a method of forming a pattern in which a substrate as an ink ejection device or a printing medium having a plurality of nozzle holes moves a plurality of times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as the printing medium to form the pattern, landing of the ink droplets used for forming a coating film of dots constituting the pattern formed on the substrate occurs a plurality of times, and in the pattern portion excluding the boundary portion, the positions of the dots on which the droplets land are controlled so as not to have continuity or periodicity in the main scanning direction of the ink ejection device, in the boundary portion, control is performed so as to have continuity or periodicity in the order of the longitudinal direction in which each pixel constituting the image data is arranged, as the ink, an ink is used in which the ratio η2 / η1 of the viscosity η1 at the ejection temperature to the viscosity η2 at the landing temperature is 100 or more ,and Solder resist ink is used as the aforementioned ink. A pattern forming method characterized by the above.

[0013] 3. In the pattern portion excluding the boundary portion, the positions of the dots on which the droplets land are further controlled so as not to have continuity or periodicity in the sub-scanning direction of the ink ejection device The pattern forming method according to claim 2, characterized by the above.

[0014] 4. Formation of the coating film of dots in the boundary portion is completed earlier than formation of the coating film of dots in the pattern portion excluding the boundary portion The pattern forming method according to any one of claims 1 to 3, characterized by the above.

[0015] 5. The image data of the pattern is divided into a plurality of parts so that each pixel does not overlap when printed overlaid, and the positions of the dots on which the droplets land do not have continuity or periodicity in the scanning direction of the ink ejection device Lord and the divided image data is printed overlaid sequentially ​A pattern forming method according to any one of paragraphs 2 to 4, characterized by the following:

[0016] 6. The ink ejection device is relative to Main It moves back and forth in the scanning direction, Ink droplets are ejected on both the outbound and return journeys. A pattern forming method according to any one of paragraphs 2 to 5, characterized by the following:

[0018] 7 The ink used is of one of the following types: hot melt type, gel type, or thixotropic type. The first to the second paragraphs characterized by... 6 A pattern formation method described in any one of the items up to item number.

[0020] 8 An inkjet printing apparatus that forms a pattern based on image data of a pattern, Articles 1 through 1 7 A pattern is formed by the pattern formation method described in any one of the items up to item [number]. An inkjet printing apparatus characterized by the following features. [Effects of the Invention]

[0021] The present invention provides a pattern forming method for forming a pattern that is free of streaks and has good reproducibility, and an inkjet printing apparatus for forming said pattern.

[0022] Although the mechanism of action or mechanism of the present invention is not yet clear, it is speculated as follows.

[0023] Through repeated investigations, the inventors have found that in a multi-pass method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form a pattern, the position of the dots where the droplets land is, (I) Control the order of each pixel constituting the image data so that it is not in the same order as the rows and columns in which it is arranged, and does not have a certain periodicity. (II) Control the ink ejection device so that it does not have continuity or periodicity in the main scanning direction. In other words, it was found that by using a random multi-pass method, it is possible to print high-resolution, high-definition patterns.

[0024] The pattern formation method using an inkjet printing method according to the present invention will be explained in comparison with conventional pattern formation methods. For example, this section describes a method of printing image data using an inkjet head with a resolution of 600 dpi, by moving the inkjet head in the direction of the nozzle row in multiple passes, so that the output resolution is 1200 dpi.

[0025] The inkjet printing method shown in Figure 1 is a block method, in which the same nozzle is used for printing during the first scan in the transport direction, and the head is moved in the direction of the nozzle row by a distance of 21.2 μm (the distance required for a 1200 dpi output resolution) for the second scan, completing the 1200 dpi print. In this case, as shown in Figure 1, droplet impact occurs sequentially in "1 scan" and "2 scans" as illustrated, making it easy for streaks to form in the transport direction.

[0026] The inkjet printing method shown in Figure 2 is called the interleaved method. In the first scan in the transport direction, the same nozzle prints every other pixel. In the second scan in the transport direction, the pixels between the parts printed in the first scan are printed. Then the head is moved in the direction of the nozzle row by a distance of 21.2 μm (1200 dpi resolution), and the same process is repeated for the third and fourth scans until printing at an output resolution of 1200 dpi is completed. In this case as well, as shown in the diagram, the order of impact becomes periodic, such as "1 scan" to "4 scans," making it easier for streaks to occur.

[0027] The inkjet printing method shown in Figure 3 is the so-called "random" impact method, or "random multi-pass method," according to the present invention. Printing at 1200 dpi is completed in a total of eight passes, ensuring a random impact order. The number of passes may be increased further. Alternatively, the number of passes may be increased by further reducing the number of transport directions. By using a random multi-pass method, the droplets land randomly, making streaks less noticeable.

[0028] In this invention, "random" refers to a state in a pattern formation method, which is based on the premise of controlling the pattern within the conditions described later, in which randomness or unpredictability is recognized in the relative positions of the dots, where there is no overall identity or regularity such as periodicity. Specifically, it refers to the state shown in Figure 3, for example.

[0029] As can be inferred from the above proportionality, by randomizing the landing locations and order of ink droplets, it is thought that the periodicity between adjacent pixels or dots in the printed image is eliminated, making it less likely for streaks or unevenness to occur overall.

[0030] Further investigation by the inventors revealed that while the random multi-pass method can reduce the occurrence of streaks and unevenness in the patterned areas, it is difficult to reproduce the pattern exactly as it appears in the image data at the boundary between the patterned and non-patterned areas. In other words, even if the pattern boundary in the image data is a straight line, it is difficult to actually form a high-resolution straight line at the pattern boundary, indicating that there is room for further improvement.

[0031] In response to this, the inventors conducted further studies and found that the reproducibility of the pattern can be improved by using the above-mentioned random multipath method mainly for the patterned area, and by controlling the relative positions of the dots near the boundary between the patterned and non-patterned areas to have continuity or periodicity. [Brief explanation of the drawing]

[0032] [Figure 1] Schematic diagram showing a pattern formation method using a block system. [Figure 2] Schematic diagram showing a pattern formation method using the interleaving method. [Figure 3] Schematic diagram showing the pattern formation method using a random multipath method according to the present invention. [Figure 4] Figure showing image data used in the random multipath method (A). [Figure 5] This figure shows an example of a pattern according to the present invention, in which a cutout square is placed inside a square. [Figure 6] This figure shows a 256-level grayscale image with no constant periodicity between adjacent pixels. [Figure 7] This figure shows an example where the direction of the pixel columns and rows in the image data and the main scanning direction and sub-scanning direction in the ink ejection device are not parallel. [Figure 8A] Schematic diagram (front view) showing a multi-pass inkjet printing device. [Figure 8B] Schematic diagram (top view) showing an inkjet printing device using a multi-pass method. [Figure 9] A diagram showing an example of a pattern according to the present invention. [Figure 10] A diagram showing an example of a boundary portion according to the present invention. [Figure 11] This diagram illustrates a method for performing 1200dpi printing with random target placement using a single 600dpi inkjet head. [Figure 12] This figure shows an example of image data used for forming a boundary according to the present invention. [Figure 13] This figure shows an example where the boundary area includes not only the boundary forming area but also the coating of dots located near the boundary between the patterned area and the non-patterned area. [Figure 14] This figure shows image data used to form a boundary when the boundary includes not only the boundary-forming portion but also a coating of dots located near the boundary between the patterned portion and the non-patterned portion. [Figure 15] A diagram showing an example of a pattern and its boundary. [Figure 16] Diagram showing an example of a pattern (rectangle) at the boundary. [Figure 17] Figure showing image data corresponding to example patterns (rectangles) at the boundary. [Figure 18] This diagram shows an example of a printing method (block method) for pattern examples (rectangles) at the boundary. [Figure 19] This diagram shows an example of a printing method (block method) for a rectangular pattern at a boundary (using different nozzles). [Figure 20] Schematic diagram of the nozzles of the ink ejection device used in an example of a printing method (block method) for pattern examples (rectangles) at the boundary (using different nozzles). [Figure 21] This figure shows an example of a printing method (interleaved method) for pattern examples (rectangles) at the boundary. [Figure 22] This figure shows an example of a printing method (interleaved method) for pattern examples (rectangles) at the boundary. [Figure 23] This figure shows an example of a printing method (random multipass method) for pattern examples (rectangles) at the boundary. [Figure 24] This diagram shows an example of a printing method (block method) for a diamond pattern at the boundary. [Figure 25] This figure shows an example of a printing method (random multi-pass method) for a pattern example (diamond shape) at the boundary. [Figure 26] A diagram showing image data used in a pattern formation method by segmented printing. [Figure 27A] Figure (scans 1-8) shows a method (pattern formation method A) in which pattern formation is completed first at the boundary, and then in the patterned area excluding the boundary. [Figure 27B] Figure (9 scans to 12 scans) shows a method (pattern formation method A) in which pattern formation is completed first at the boundary, and then in the patterned area excluding the boundary. [Figure 28]This figure shows a method (pattern formation method B) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. [Figure 29] This diagram illustrates a method for printing at a resolution of 2400 dpi using a single inkjet head with a nozzle resolution of 600 dpi, employing random targeting and segmented printing (image segmentation count: 2). [Figure 30A] This diagram (scans 1-8) illustrates a method for printing at a resolution of 2400 dpi using a single inkjet head with a nozzle resolution of 600 dpi, employing random targeting and segmented printing (4 image divisions). [Figure 30B] This diagram (scans 9-16) illustrates a method for printing at a resolution of 2400 dpi using a single inkjet head with a nozzle resolution of 600 dpi, employing random targeting and segmented printing (4 image divisions). [Figure 31] This diagram illustrates a method for printing at a resolution of 2400 dpi with random targeting using a single inkjet head with a nozzle resolution of 600 dpi. [Figure 32] This diagram illustrates a method for printing at a resolution of 2400 dpi using one inkjet head with a nozzle resolution of 600 dpi, employing random droplet placement and segmented printing (image segmentation count: 2). Specifically, it shows the case where, in scans 1 and 5, the positions of the droplets ejected from the leftmost nozzle and the middle nozzle are identical. [Figure 33] Top view showing a multi-pass inkjet printing apparatus 100. [Figure 34] This diagram shows how to perform printing using an inkjet printer 1 (where the print head moves in the X direction and the substrate moves in the Y direction). [Figure 35] This diagram shows how to perform printing using an inkjet printing device 100 (where the print head moves in the Y direction and the substrate moves in the X direction). [Figure 36] This diagram illustrates a method of printing using an inkjet printer in which the substrate moves in both the X and Y directions. [Figure 37]This diagram illustrates how to perform printing using an inkjet printer whose print head moves in both the X and Y directions. [Figure 38] This diagram illustrates a method of performing bidirectional printing in which an ink ejection device moves back and forth in the main scanning direction relative to the device, ejecting ink droplets in both the forward and return directions. [Figure 39] This diagram illustrates a method of performing mixed forward and reverse printing, in which the ink ejection device moves in a combination of forward and reverse directions relative to the sub-scanning direction. [Figure 40] This diagram illustrates a method of performing split printing at a resolution of 2400 dpi using four inkjet heads with a nozzle resolution of 600 dpi. [Figure 41] This diagram illustrates a printing method when the nozzle row is oriented at an angle, rather than perpendicular or parallel to either the X or Y direction. [Figure 42] This diagram illustrates a printing method when the orientation of the ink ejection device itself is not perpendicular or parallel to either the X or Y direction, but oblique. [Figure 43] This figure shows a method (pattern formation method C) in which pattern formation is started first in the patterned area excluding the boundary, and then the pattern formation in the boundary and the patterned area excluding the boundary are completed simultaneously. [Figure 44] This figure shows a method (pattern formation method D) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started and completed simultaneously. [Figure 45] This figure shows a method (pattern formation method D) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started and completed simultaneously. [Figure 46] This diagram shows a method of forming patterns using a random multi-pass method for both the boundary area and the patterned area excluding the boundary area, without changing the pattern formation method. [Figure 47] This figure shows a method (pattern formation method B) in which pattern formation at the boundary (diamond shape) and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. [Figure 48]This figure shows a method (pattern formation method B) in which pattern formation at the boundary (width of 2 dots) and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. [Figure 49] This figure shows a method (pattern formation method B) in which pattern formation is performed using bidirectional printing, and pattern formation at the boundary and pattern formation in the patterned areas excluding the boundary are started simultaneously, with pattern formation at the boundary being completed first. [Figure 50] This diagram illustrates a method of printing using a block-based printing system, where the pattern area is not distinguished between the boundary area and the pattern area excluding the boundary, and the image data used is treated as a single image file. [Figure 51] An example of a printing method (block method) for a pattern example (gourd shape) at the boundary. [Figure 52] An example of a printing method (block method, divided printing) for a pattern example (gourd shape) at the boundary. [Figure 53] Optical microscope images at 100x magnification of printed materials A and B, which were prepared under the same printing conditions as printed materials 2 and 12, respectively, and have die-cut squares arranged parallel to the main scanning direction and sub-scanning direction. [Modes for carrying out the invention]

[0033] The present invention relates to a pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form the pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dots that land the droplets is controlled such that, in the pattern portion excluding the boundary portion, the position is not in the same order as the rows and columns in which the pixels constituting the image data are arranged, and does not have a certain periodicity. In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the order in the longitudinal direction in which it is arranged. It is characterized by the following:

[0034] Furthermore, a pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form the pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dots that land the aforementioned droplets is controlled so that, in the pattern portion excluding the boundary portion, it does not have continuity or periodicity in the main scanning direction of the ink ejection device. In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the order in the longitudinal direction in which it is arranged. It is characterized by the following: This feature is a technical feature common to or corresponding to the embodiments described below.

[0035] In embodiments of the present invention, from the viewpoint of suppressing the occurrence of streaks in the pattern, it is preferable to control the position of the dots on which the liquid droplets land so that, in the pattern portion excluding the boundary portion, there is no continuity or periodicity even in the sub-scanning direction of the ink ejection device.

[0036] From the viewpoint of obtaining good pattern reproducibility, it is preferable to complete the formation of the coating film on the dots at the boundary before the formation of the coating film on the dots in the pattern area excluding the boundary.

[0037] From the viewpoint of suppressing the occurrence of streaks in the pattern, it is preferable to divide the image data of the pattern into multiple parts such that the pixels do not overlap when printed in layers, and the positions of the dots that land the droplets do not have continuity or periodicity in the main scanning direction of the ink ejection device, and then print the divided image data in order.

[0038] From the viewpoint of shortening the pattern formation time, it is preferable that the ink ejection device moves back and forth relative to the main scanning direction and ejects ink droplets in both the forward and return directions.

[0039] From the viewpoint of improving pattern formation, it is preferable to use an ink in which the ratio η2 / η1 of viscosity η1 at the temperature of ejection to viscosity η2 at the temperature of impact is 100 or more.

[0040] From the viewpoint of improving pattern formation, it is preferable to use an ink of any type, such as a hot-melt type, a gelling type, or a thixotropic type, as the ink.

[0041] From the viewpoint of applications that meet the purpose of the invention, for example, from the viewpoint of solving the problems that arise when protecting a circuit pattern with an insulating film, it is preferable to use solder resist ink as the ink.

[0042] The inkjet printing apparatus of the present invention can form patterns by the pattern forming method of the present invention.

[0043] The present invention, its components, and embodiments and models for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0044] <Summary of the pattern formation method of the present invention> The present invention relates to a pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form a pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dot that causes the aforementioned droplet to land is, In the patterned areas excluding the boundary areas, (I) Control the pixels constituting the image data so that they are not in the same order as the rows and columns in which they are arranged, and do not have a certain periodicity. (II) Control the ink ejection device so that it does not have continuity or periodicity in the main scanning direction, In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the order in the longitudinal direction in which it is arranged. It is characterized by the following:

[0045] In other words, by controlling the position of the dots where the liquid droplets land to be random in the pattern area excluding the boundaries (a state in which randomness or unpredictability is recognized, lacking overall identity or periodicity), and to have continuity or periodicity at the boundaries, it is possible to form a highly detailed pattern that is free from streaks and unevenness and has good reproducibility. Furthermore, when using inks containing functional materials such as insulators and conductors, it is possible to form a pattern with uniform insulating and conductive properties, as well as good adhesion of the coating film.

[0046] In this invention, "having continuity or periodicity" means that when a droplet is dropped onto the surface to form a coating of dots, the coating has a degree of continuity that is visible to the naked eye. If the dots are positioned continuously over a wide area without any gaps, the coating formed by dropping droplets onto those positions will exhibit visible continuity. Furthermore, even if there are gaps between the dots, if the gaps are extremely narrow (for example, 1 to 2 dots) and the pattern is periodic over a wide area, the coating formed by dropping droplets onto those positions will exhibit visible continuity. Conversely, if the gaps are wide, even if the pattern is periodic, visible continuity will not be exhibited.

[0047] Therefore, in the patterned areas excluding the boundaries, even if the positions of the dots where the droplets land are continuous within a range of, for example, 2 to 5 dots without any gaps, it is difficult to visually confirm the continuity of the coating film formed by the droplets landing at those positions. For this reason, within a range that is too narrow to be visually confirmed, sufficient randomness can be obtained even if the positions of the dots where the droplets land are partially continuous. However, the number of dots shown here is just an example and is not necessarily limited to this.

[0048] In this invention, "patterned area" refers to an area where a pattern (in the narrow sense shown below) is formed, and "non-patterned area" refers to an area where no pattern is formed. In this invention, "pattern" in a narrow sense refers to a coating film formed on a substrate using ink, and in a broader sense refers to the entire group of coating films formed on the substrate.

[0049] Furthermore, the term "boundary area" refers to an aggregate of dot coatings located near the boundary between the patterned area and the non-patterned area, and includes at least the dot coatings that contribute to the formation of the boundary between the patterned area and the non-patterned area (hereinafter also referred to as the "boundary-forming area").

[0050] This will be explained in detail using diagrams. Figure 5 shows an example of a pattern according to the present invention in which cutout squares are arranged inside squares, with each square corresponding to one dot of paint film.

[0051] The area indicated by 11 represents the "unpatterned area" where no pattern is formed, the areas indicated by 12, 13, and 14 represent the "patterned area" where a pattern is formed, and the line indicated by 15 represents the "boundary between the patterned area and the unpatterned area." However, in reality, the boundary 15 between the patterned area and the unpatterned area does not have a region.

[0052] The areas indicated by 12 and 13 (the area indicated by 16) located near the boundary 15 between the patterned area and the non-patterned area represent the "boundary area" as defined above, and the area indicated by 14 represents the "patterned area excluding the boundary area".

[0053] The region indicated by 12 represents the "boundary-forming region," which is an aggregate of dot coatings that contribute to the formation of the boundary between the patterned and non-patterned regions, and is essentially included in the boundary region 16. On the other hand, the region indicated by 13 represents the "boundary region excluding the boundary-forming region," but it does not necessarily have to be included in the boundary region 16 and may or may not be included. The boundary region excluding the boundary-forming region 13 is located adjacent to the boundary-forming region 12.

[0054] Furthermore, in this invention, "dot" refers to the smallest unit of pixel that constitutes an ink image formed on a printing medium by the inkjet printing method, and refers to the coating portion formed by a single droplet of ink. Therefore, a pixel in the ink image corresponding to one pixel in the image data to be printed may be formed by multiple dots (droplets).

[0055] [1. Pattern formation method in the patterned area excluding the boundary area] The pattern forming method of the present invention determines the position of the dots on which the droplets land, in the pattern portion excluding the boundary portion according to the present invention. (I) Control the pixels constituting the image data so that they are not in the same order as the rows and columns in which they are arranged, and do not have a certain periodicity. (II) Control the ink ejection device so that it does not have continuity or periodicity in the main scanning direction. It is characterized by the following:

[0056] As mentioned above, in the pattern areas excluding the boundaries, by making the positions of the dots where the droplets land random (a state in which randomness or unpredictability is recognized, lacking overall uniformity or periodicity), that is, by using a random multi-pass method, it is possible to form a highly detailed pattern without streaks or unevenness.

[0057] In this invention, a method that satisfies the above control condition (I) will be referred to as "random multipath method (A)," and a method that satisfies the above control condition (II) will be referred to as "random multipath method (B)."

[0058] Control condition (I) above specifies a condition in which the position of the dots on which the liquid droplets land is randomized, from the perspective of the arrangement of each pixel constituting the image data. Control condition (II) above specifies a condition in which the position of the dots on which the liquid droplets land is randomized, from the perspective of the scanning direction of the ink ejection device. In other words, the control conditions (I) and (II) above define the conditions for making the position of the dots on which the droplets land random, from different perspectives. The random multipath methods (A) and (B) will be explained in detail below.

[0059] [1.1 Random multipath method (A)] In the random multi-pass method (A), the position of the dots that land the droplets is controlled so that it does not follow the order of the rows and columns in which the pixels constituting the image data are arranged, and does not have a constant periodicity.

[0060] The following describes an example of an embodiment of the pattern formation method using the random multipath method (A) according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and any method that satisfies the above control condition (I) is included within the technical scope of the present invention.

[0061] Figure 4 shows image data used in the random multi-pass method (A), where each dot is formed with a uniform amount of liquid. Alternatively, multi-tone random image data, as shown in Figure 6, may be used to form each dot with different amounts of liquid. In this case, the amount of liquid in the dot is changed in accordance with the gradation or density of each pixel. The same image data can also be used in the random multipass (B) method described later.

[0062] The ink placement in this embodiment will be explained from the perspective of the random multi-path method (A). In a single scan, the pixels constituting the image data are not consecutive in the row and column directions, but are spaced apart, forming dots with varying spacing. For subsequent scans, dots are formed in the same manner at positions where no dots have been formed yet, ensuring that the dots do not overlap. The number of dots formed in each scan does not need to be constant. The number of scans may be increased further.

[0063] The printing method in this embodiment will be described below from the perspective of the random multi-pass method (A).

[0064] Figure 11 shows a method for performing 1200 dpi printing with random targeting using one 600 dpi inkjet head. In this embodiment shown in Figure 3, the random multi-pass method (A) for pattern formation is performed by printing with four scans in the Y direction (transport direction), then moving 21.2 μm (equivalent to one pixel at 1200 dpi) in the X direction, and then printing with four more scans in the Y direction, completing the printing in a total of eight moves (passes) (see Figures 8A and 8B for details of the device).

[0065] [1.2 Random multipath method (B)] In the random multi-pass method (B), the position of the dots that land the ink droplets is controlled so that there is no continuity or periodicity in the main scanning direction of the ink ejection device.

[0066] The following describes an example of an embodiment of the pattern formation method using the random multipath method (B) according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and any method that satisfies the above control condition (II) is included within the technical scope of the present invention.

[0067] As mentioned above, the image data used in the random multi-pass method (A) can be used.

[0068] The ink placement in this embodiment will be explained from the perspective of the random multi-path method (B). In a single scan, dots are formed at intervals so as not to have continuity or periodicity in the main scanning direction, and the intervals are not constant. For subsequent scans, dots are formed in the same manner at positions where no dots have been formed, so that the dots do not overlap. The number of dots formed in each scan does not need to be constant. The number of scans may be increased further.

[0069] The printing method in this embodiment will be described below from the perspective of the random multi-pass method (B).

[0070] Figure 11 shows a method for printing at 1200 dpi with random dot placement using a single inkjet head with a resolution of 600 dpi. Here, the Y direction is the primary scanning direction and the X direction is the secondary scanning direction.

[0071] In this embodiment shown in Figure 3, the random multi-pass method (B) for pattern formation is performed by the inkjet head scanning and printing four times in the Y direction, then moving 21.2 μm (equivalent to one pixel at 1200 dpi) in the X direction, and then scanning and printing four more times in the Y direction, completing the printing in a total of eight movements (passes) (see Figures 8A and 8B for details of the device).

[0072] In the method described above, the direction of the pixel columns and rows in the image data is parallel to the main scanning direction and sub-scanning direction in the ink ejection device. However, they do not necessarily have to be parallel, and they may be non-parallel.

[0073] Figure 7 shows an example where the direction of the pixel columns and rows in the image data and the main scanning direction and sub-scanning direction in the ink ejection device are not parallel. For example, the portion indicated by the ellipse in Figure 7 does not have continuity in the direction of the rows and columns of pixels in the image data, but it can be said that it has continuity in the main scanning direction of the ink ejection device. Therefore, the printing method for the portion indicated by the ellipse in Figure 7 corresponds to the random multipass method (A) and does not correspond to the random multipass method (B).

[0074] Furthermore, from the viewpoint of forming a high-definition pattern free from streaks and unevenness, it is preferable to use a printing method that corresponds to both the random multi-pass method (A) and (B).

[0075] Furthermore, in the random multipath method (B), it is preferable to control the sub-scanning direction so that it does not have continuity or periodicity.

[0076] As described in the printing method above, in the multi-pass method, the ink ejector moves in the main scanning direction and deposits droplets in the main scanning direction multiple times, then moves in the sub-scanning direction, and then moves in the main scanning direction and deposits droplets multiple times. Therefore, when droplets are continuously deposited at the positions of two adjacent dots in the main scanning direction, the time difference in the formation of the coating on those two dots becomes extremely short.

[0077] On the other hand, if droplets are to be continuously deposited at the positions of two adjacent dots in the sub-scanning direction, the ink ejector will deposit a droplet at the position of the first dot, then move in the main scanning direction to complete droplet deposition in the main scanning direction, then move in the sub-scanning direction, and then move in the main scanning direction to deposit a droplet at the position of the second dot. As a result, the time difference in the formation of the coating film on these two dots will be longer compared to the main scanning direction. Therefore, when the positions of the dots where the droplets are deposited are continuous in the main scanning direction, streaks and unevenness are more likely to occur compared to when they are continuous in the sub-scanning direction.

[0078] Therefore, in the random multi-pass method (B), by controlling the position of the dots that land the droplets so that they do not have continuity or periodicity in the main scanning direction of the ink ejection device, it is possible to form a high-definition pattern without streaks or unevenness. Furthermore, by controlling them so that they do not have continuity or periodicity in the sub-scanning direction as well, the effect can be enhanced.

[0079] [1.3 Split printing] In embodiments of the present invention, it is also preferable to divide the image data of the pattern into multiple parts such that the pixels do not overlap when printed in layers, and the positions of the dots that land the droplets do not have continuity or periodicity in the main scanning direction of the ink ejection device, and then sequentially print the divided image data in layers.

[0080] In this invention, the printing method that satisfies the above control conditions will be referred to as "split printing."

[0081] The following describes an example of an embodiment of the pattern formation method by divided printing according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and any method that satisfies the above control conditions is included within the technical scope of the present invention. In the following illustrated description, an example is shown in which divided printing is applied to the pattern portion excluding the boundary portion according to the present invention. However, if the above control conditions are satisfied in the boundary portion, the present invention can also be applied to the boundary portion.

[0082] Figure 29 shows a method for printing at a resolution of 2400 dpi using a single inkjet head with a nozzle resolution of 600 dpi, employing random dot placement and segmented printing. In Figure 29, source image data is used in which each dot is formed with a uniform amount of ink. However, as shown in Figure 6, multi-tone random source image data may be used to form each dot with different amounts of ink.

[0083] In split printing, the original image data is divided into two parts, and after creating the split image data, the split image data is printed by sequentially overlapping each part. Therefore, the split image data is created so that each pixel does not overlap when printed. In addition, the split image data is created so that the positions of the dots that will land the ink droplets do not have continuity or periodicity in the main scanning direction of the ink ejection device.

[0084] Split image data can be created using image processing software such as Adobe Photoshop 2020. For example, a grayscale image can be converted to monochrome 2-tone using error diffusion in Photoshop to create a random image of black and white. Next, this image is color-inverted to create an image with inverted black and white. The resulting two images will be split images of solid black data with randomly overlapping impact points.

[0085] The following explains split printing by comparing Figures 29, 30A, 30B, and 31. Figure 31 shows a method for printing at a resolution of 2400 dpi with random bullet placement using a single inkjet head with a nozzle resolution of 600 dpi. In this method, printing is completed for each main scanning direction.

[0086] In Figure 31, printing in the main scanning direction is completed in two consecutive scans, for example, scan 1 and scan 2. On the other hand, in split printing, as shown in Figure 29, it is completed in two non-consecutive scans, scan 1 and scan 5.

[0087] Thus, with split printing, the time required to complete printing in the main scanning direction is relatively long, which allows the ink to set more easily, suppresses ink flow, and reduces the likelihood of streaks and unevenness.

[0088] Figures 30A and 30B show a method of dividing the original image data into four parts and performing divided printing similar to that shown in Figure 29. In this case, printing in the main scanning direction is completed in four non-consecutive scans: scan 1, scan 5, scan 9, and scan 13.

[0089] In this way, increasing the number of divisions in the original image data increases the number of scans required to complete printing in the main scanning direction, which further extends the time required to complete printing, making it less likely for streaks and unevenness to occur and reducing surface roughness.

[0090] Furthermore, since printing in the sub-scanning direction is performed before printing in the main scanning direction is completed, even when using inks with relatively high viscosity at impact or inks with relatively fast phase transition times, the ink is less likely to become fixed in a linear pattern in the main scanning direction, resulting in fewer streaks and unevenness. In addition, increasing the number of scans reduces the likelihood of impact misalignment caused by interaction between adjacent impacts and previously impacted ink droplets (dots), thereby improving pattern formation.

[0091] In this embodiment, "random placement" means controlling the position of the dots that place the liquid droplets so that they do not have continuity or periodicity in the main scanning direction of the ink ejection device.

[0092] Figure 32 shows a method of performing split printing similar to that in Figure 29, but in scan 1 and scan 5, the positions of the dots that land on the droplets ejected from the leftmost nozzle and the middle nozzle are the same.

[0093] The streaks and unevenness that are the problem to be solved in this invention are likely to occur when the position of the dots that land the droplets is continuous or periodic in the main scanning direction, but are less likely to occur even if they are continuous or periodic in the sub-scanning direction. Therefore, as shown in Figure 32, even if the position of the dots that land droplets ejected from different nozzles is the same in some scans, the occurrence of streaks and unevenness can be sufficiently suppressed.

[0094] [1.4 Bidirectional printing] In an embodiment of the present invention, it is also preferable that the ink ejection device moves reciprocally in the main scanning direction relative to the device, and ejects ink droplets in both the forward and return directions.

[0095] In this invention, the printing method that satisfies the above control conditions will be referred to as "bidirectional printing."

[0096] The following describes an example of an embodiment of the pattern formation method by bidirectional printing according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and any method that satisfies the above control conditions is included within the technical scope of the present invention. In the following illustrated description, an example is shown in which bidirectional printing is applied to the pattern portion excluding the boundary portion according to the present invention. However, if the above control conditions are satisfied at the boundary portion, the present invention can also be applied to the boundary portion.

[0097] Figure 38 illustrates a method of performing bidirectional printing in which the ink ejector moves back and forth in the main scanning direction relative to the object, ejecting ink droplets in both the forward and return directions. Although Figure 38 shows split printing, it is not always necessary to perform split printing.

[0098] In the first scan, the ink ejector moves relatively in the direction of the arrow (forward movement) while ejecting ink droplets. Next, in the second scan, the ink ejector moves relatively in the direction of the arrow so that a row of dots is formed to the right of the row of dots formed in the first scan, and moves relatively in the direction of the arrow (return movement) while ejecting ink droplets. This is repeated, and printing is completed in a total of eight scans.

[0099] In this embodiment, "relative movement" means that either the ink ejection device or the substrate as the printing medium may move, or both may move, and that the ink ejection device moves relative to the positional relationship between the ink ejection device and the substrate as the printing medium.

[0100] Therefore, in one scan of Figure 38, the substrate may be fixed and the ink ejector may be moved in the direction of the arrow, or the ink ejector may be fixed and the substrate may be moved in the opposite direction to the arrow.

[0101] As shown in Figure 29, in unidirectional printing, the ink ejector moves back and forth in the relative direction of the main scanning, but ejects ink droplets only on the forward path, and simply moves on the return path. Therefore, by performing bidirectional printing, printing time can be shortened and productivity can be improved.

[0102] [1.5 Forward / reverse mixed printing] In embodiments of the present invention, it is also preferable that the ink ejection device moves in a combination of forward and reverse directions relative to the sub-scanning direction.

[0103] In this invention, the printing method that satisfies the above control conditions will be referred to as "forward and reverse mixed printing."

[0104] The following describes an example of an embodiment of the pattern formation method by forward and reverse mixed printing according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and any method that satisfies the above control conditions is included within the technical scope of the present invention. In the following illustrated description, an example is shown in which forward and reverse mixed printing is applied to the pattern portion excluding the boundary portion according to the present invention. However, if the above control conditions are met at the boundary portion, the present invention can also be applied to the boundary portion.

[0105] Figure 39 shows a method of performing mixed forward and reverse printing in which the ink ejector moves in a combination of forward and reverse directions relative to the sub-scanning direction. Note that although Figure 39 shows split printing, it is not always necessary to perform split printing.

[0106] In the first scan, the ink ejector moves relatively in the main scanning direction and ejects ink droplets. Next, in the second scan, the ink ejector moves relatively in the direction of the arrow so that a row of dots is formed to the right of the row of dots formed in the first scan, with a gap of one dot between them, and then moves again in the main scanning direction and ejects ink droplets. Then, in the third scan, the ink ejector moves relatively in the direction of the arrow so that a row of dots is formed between the row of dots formed in the first scan and the row of dots formed in the second scan, and then moves again in the main scanning direction and ejects ink droplets. This process is repeated, and printing is completed in a total of eight scans.

[0107] In forward printing, as shown in Figure 29, where the relative movement of the ink ejector is in only one direction, dots may be formed adjacent to already formed dots. This can cause streaks and unevenness because adjacent dots are formed before the ink in the dots has set. On the other hand, in forward and reverse mixed printing, dots are formed with a gap between them. This means that adjacent dots are formed after the ink in the dots has set, making streaks and unevenness less likely. Furthermore, in forward and reverse mixed printing, because dots are formed with a gap between them, the interaction between adjacent dots and the previously landed ink (dots) reduces the occurrence of misalignment, improving pattern formation.

[0108] [2. Method for forming patterns at the boundary] The pattern forming method of the present invention determines the position of the dots on which the droplets land, in the boundary portion according to the present invention. The pixels constituting the image data are controlled to have continuity or periodicity in the order they are arranged in the longitudinal direction. It is characterized by the following:

[0109] As mentioned above, by controlling the boundary area to have continuity or periodicity, a pattern with good reproducibility can be formed.

[0110] The following describes an example of an embodiment of the method for forming a pattern at a boundary according to the present invention. However, the invention is not limited to the embodiments and aspects of the example below, and is included in the technical scope of the present invention as long as the above control conditions are met.

[0111] As described above, in the present invention, the term "boundary portion" refers to an aggregate of dot coatings located near the boundary between the patterned portion and the non-patterned portion, and includes at least dot coatings that contribute to the formation of the boundary between the patterned portion and the non-patterned portion (hereinafter also referred to as the "boundary forming portion").

[0112] Figure 9 shows an example of a pattern according to the present invention, and Figure 10 shows an example of its boundary. When the non-patterned portion 11 has an area corresponding to multiple dots, the boundary portion 16 is formed linearly along the boundary between the non-patterned portion and the patterned portion. Figure 12 shows the image data used to form the boundary portion shown in Figure 10. Here, one dot corresponds to one pixel that makes up the image data.

[0113] In the image data corresponding to the boundary 16, each pixel is also arranged linearly. In the present invention, "the longitudinal direction in which each pixel constituting the image data is arranged" refers to the direction along the line formed by connecting each arranged pixel, and is shown by the direction of the arrow in Figure 12.

[0114] Furthermore, as shown in Figure 12, if the area of ​​the non-pattern portion 11 is extremely small, the boundary portion 16 may not be formed in a linear shape. In this case, in the corresponding image data, the direction in which each pixel is adjacent is defined as the "longitudinal direction in which each pixel constituting the image data is arranged," and the order in which each pixel is adjacent is controlled to have continuity or periodicity.

[0115] Figure 9 shows an example of forming a pattern around a non-patterned area. The boundary 16 shown in Figure 10 and the image data corresponding to the boundary 16 shown in Figure 12 are linear with closed ends. However, the boundary and the corresponding image data are not necessarily limited to this shape, and the ends of the lines may not be closed.

[0116] In the example of the boundary shown above, the boundary is shown as being composed only of the boundary forming portion. However, the boundary may also include a coating of dots located near the boundary between the patterned portion and the non-patterned portion. An example of this is shown in Figure 13.

[0117] Figure 13 shows an example where the boundary portion 16 includes, in addition to the boundary forming portion 12, a coating of dots (boundary portion excluding the boundary forming portion) 13 located near the boundary between the patterned portion and the non-patterned portion. Figure 14 shows the image data used to form the boundary portion shown in Figure 13. Here, one dot corresponds to one pixel that makes up the image data.

[0118] The boundary area is preferably a region of uniform width that follows the boundary between the patterned and non-patterned areas. Here, "width" refers to the length (number of dots) perpendicular to the boundary between the patterned and non-patterned areas.

[0119] For example, the boundary section 16 shown in Figure 10 can have a width of one dot, and the boundary section 16 shown in Figure 13 can have a width of two dots.

[0120] Figure 15 shows an example of a pattern and its boundary. In Figure 15, the leftmost column shows each pattern, the middle column shows the boundary of one dot wide within that pattern, and the rightmost column shows the boundary of two dots wide within that pattern.

[0121] The width of the boundary is not particularly limited, but from the viewpoint of pattern reproducibility, it is preferable to create streaks at the boundary, and the number of dots in the width is preferably in the range of 1 to 3.

[0122] The following describes the pattern formation method at the boundary, using the pattern example (rectangle) shown in Figure 16. Figure 17 shows the image data corresponding to the pattern example (rectangle) shown in Figure 16.

[0123] Each pixel constituting the image data is arranged parallel to the row and column directions, and the row and column directions of the pixels in the image data are parallel to the main scanning direction and sub-scanning direction of the ink ejection device. Therefore, in the pattern formation method described below, by continuously or periodically landing ink droplets in the main scanning direction and sub-scanning direction of the ink ejection device, the position of the dots where the droplets land can be controlled to have continuity or periodicity in the order of the pixels constituting the image data in the longitudinal direction in which they are arranged.

[0124] Furthermore, it is not necessarily required that each pixel constituting the image data be arranged parallel to the row and column directions, nor is it necessary for the row and column directions of the pixels in the image data to be parallel to the main scanning direction and sub-scanning direction of the ink ejection device.

[0125] Figure 18 shows an example of a printing method (block method) for a pattern example (rectangle) at the boundary. By continuously (block method) depositing ink droplets in the main scanning direction and sub-scanning direction of the ink ejection device, the position of the dots where the droplets are deposited is controlled to maintain continuity in the longitudinal order in which each pixel constituting the image data is arranged.

[0126] In the first scan, ink droplets are continuously deposited in the main scanning direction. Then, the scanner moves to the sub-scanning direction, and ink droplets are continuously deposited in the sub-scanning direction in the second and third scans. Finally, in the fourth scan, ink droplets are continuously deposited in the main scanning direction, completing the printing process.

[0127] In this printing method, the lines have continuity in the main scanning direction and continuity and periodicity in the sub-scanning direction, making it possible to form highly detailed straight lines.

[0128] In this printing method, droplets are deposited at adjacent dot positions in the sub-scanning direction using the same nozzle, but this may be done using different nozzles.

[0129] Figure 19 shows an example of a printing method (block method) for a pattern example (rectangle) at a boundary (using different nozzles). Similarly, by continuously (block method) depositing ink droplets in the main scanning direction and sub-scanning direction of the ink ejector, the positions of the dots where the droplets land are controlled to maintain continuity in the longitudinal order in which each pixel constituting the image data is arranged. However, in the method shown in Figure 19, droplets landing at the positions of adjacent dots in the sub-scanning direction are performed by different nozzles.

[0130] In the method shown in Figure 19, during the first scan, ink droplets are ejected from nozzles 26, 27, and 28 (see Figure 20) and move in the sub-scanning direction. Then, during the second scan, ink droplets are ejected from nozzles 25, 26, and 27. In this way, the ink droplets ejected from each nozzle land sequentially in the sub-scanning direction.

[0131] While this printing method may increase the number of passes and thus the printing time, it can minimize the impact of nozzle malfunctions such as bullet curvature.

[0132] Figures 21 and 22 show an example of a printing method (interleaved method) for a pattern example (rectangle) at the boundary. By periodically (interleaved method) depositing ink droplets in the main scanning direction and sub-scanning direction of the ink ejection device, the position of the dots where the droplets are deposited is controlled to have periodicity in the longitudinal order in which each pixel constituting the image data is arranged.

[0133] Both printing methods involve splitting the image data into two parts and performing the split printing described above. In the method shown in Figure 21, printing is completed based on the first segmented image data, and then printing is completed based on the second segmented image data. The method shown in Figure 22 involves printing based on the first and second divided image data in parallel. Specifically, one scan is performed based on the first divided image data, followed by one scan based on the second divided image data. This process is repeated until printing is complete.

[0134] In both printing methods, periodicity is present in the main scanning direction and the sub-scanning direction, allowing for the formation of high-resolution straight lines. However, the method shown in Figure 22 allows for a shorter time for the coating film to form on adjacent dots, thus enabling the formation of even higher-resolution straight lines.

[0135] For example, in the linear pattern formed on the left edge, the method shown in Figure 21 completes printing in 1 scan and 5 scans, while the method shown in Figure 22 completes printing in 1 scan and 2 scans. Therefore, the method shown in Figure 22 can shorten the time required for the coating to form on adjacent dots.

[0136] In this invention, the printing method at the boundary may be either a block method or an interleaved method. By using the block method, extremely high-resolution straight lines can be formed in the main scanning direction, and by using the interleaved method, high-resolution straight lines can be formed in both the main scanning direction and the sub-scanning direction.

[0137] For comparison, Figure 23 shows an example of the printing method (random multipass method described above) for a pattern example (rectangle) at the boundary. In other words, Figure 23 shows that the pattern formation method is not changed for the boundary and the patterned area excluding the boundary, and that the entire pattern is formed using the random multipass method.

[0138] While the method shown in Figure 23 can also form straight lines that are practically acceptable, using the block method or interleaving method described above allows for the formation of higher-resolution straight lines.

[0139] Next, we will explain the case where the pixels constituting the image data are not arranged parallel to the row and column directions. However, we will assume that the row and column directions of the pixels in the image data are parallel to the main scanning direction and sub-scanning direction of the ink ejection device.

[0140] Figure 24 shows an example of a printing method (block method) for a pattern example (diamond shape) at the boundary. Even if the pixels constituting the image data are not arranged parallel to the row and column directions, the position of the dots that land the droplets is controlled to have continuity or periodicity in the order of the pixels constituting the image data in the longitudinal direction in which they are arranged.

[0141] After the first scan places an ink droplet in the main scanning direction, the scanner moves to the sub-scanning direction and places an ink droplet in the main scanning direction in the second scan. At this time, the droplet is placed adjacent to the dot where the droplet landed in the first scan. For the third and fourth scans, the droplet is also placed adjacent to the dot where the droplet landed in the previous scan.

[0142] Figure 51 shows an example of a printing method (block method) for a pattern example (gourd shape) at the boundary. In this way, even when the pixels constituting the image data at the boundary are not arranged parallel to the row and column directions and are perceived as curves by the naked eye, it is possible to control the image data to have continuity or periodicity in the order of the longitudinal direction in which the pixels constituting the image data are arranged by landing a droplet at a position adjacent to the position of the dot where the droplet landed in the previous scan.

[0143] Figure 52 also shows an example of a printing method (block method, divided printing) for a pattern example (gourd shape) at the boundary. In this way, divided printing can be used even when the pixels constituting the image data at the boundary are not arranged parallel to the row and column directions and are perceived as curves by the naked eye.

[0144] In this way, even if the pixels constituting the image data are not arranged parallel to the row and column directions, by landing the droplet at a position adjacent to the position where the droplet landed on the dot, it is possible to control the image data so that it has continuity in the order in which the pixels constituting the image data are arranged along the longitudinal direction.

[0145] For comparison, Figure 25 shows an example of a printing method (random multi-pass method) for a pattern example (diamond shape) at the boundary. The position of the dots where the droplets land is randomized in the longitudinal direction of the arrangement of each pixel constituting the image data. While it is possible to form straight lines that are practically acceptable using the method shown in Figure 25, high-resolution straight lines can be formed by using the method shown in Figure 24.

[0146] [3. Pattern Formation Method] The following describes a pattern formation method for the patterned area excluding the boundary area, and a pattern formation method that combines the pattern formation method for the boundary area.

[0147] In the pattern forming method of the present invention, it is preferable that the formation of the coating film of the dots at the boundary portion is completed before the formation of the coating film of the dots in the pattern portion excluding the boundary portion.

[0148] One such pattern formation method is: A method (pattern formation method A) in which pattern formation is completed first at the boundary, and then pattern formation is performed in the patterned area excluding the boundary. A method (pattern formation method B) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. Two methods can be cited.

[0149] In the present invention, from the viewpoint of being able to form highly detailed straight lines at the boundary and having good pattern reproducibility, it is preferable to first complete the pattern formation at the boundary and then perform pattern formation in the patterned area excluding the boundary (pattern formation method A).

[0150] The pattern formation method by divided printing will be explained below using the image data shown in Figure 26. As mentioned above, it is preferable to increase the number of divisions for the pattern areas excluding the boundaries, but it is preferable to decrease the number of divisions for the boundaries.

[0151] In Figure 26, segmented image data α is image data corresponding to pattern formation at the boundary, and segmented image data β and γ are image data obtained by dividing the image data corresponding to pattern formation in the patterned area excluding the boundary into two parts.

[0152] Figures 27A and 27B show a method (pattern formation method A) in which pattern formation is completed first at the boundary, and then in the patterned area excluding the boundary. Segmented image data No. 1 to No. 3 correspond to the above segmented image data α to γ, and printing is completed in the order of segmented image data No. 1 to No. 3.

[0153] Figure 28 shows a method (pattern formation method B) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. The above divided data α and β are designated as a single divided image data No. 1, and the above divided image data γ is designated as divided image data No. 2, and printing is completed in the order of divided image data No. 1 to No. 2.

[0154] For comparison, Figure 43 shows a method (pattern formation method C) in which pattern formation is started first in the pattern area excluding the boundary area, and pattern formation in the boundary area and pattern formation in the pattern area excluding the boundary area are completed simultaneously. The above divided image data β is designated as divided image data No. 1, and the above divided image data α and γ are designated as a single divided image data No. 2, and printing is completed in the order of divided image data No. 1 to No. 2.

[0155] In addition, Figures 44 and 45 show a method (pattern formation method D) in which pattern formation at the boundary and pattern formation in the patterned area excluding the boundary are started and completed simultaneously.

[0156] In all of the pattern forming methods A to D, high-resolution straight lines can be formed at the boundaries, and pattern reproducibility is good. However, from the viewpoint of obtaining a higher effect, it is preferable to use pattern forming method A or B, and more preferable to use pattern forming method A.

[0157] In addition, a method can be considered in which pattern formation is completed in the patterned area excluding the boundary area first, and then pattern formation is performed in the boundary area. Although this method can also form highly detailed straight lines and has good pattern reproducibility, from the viewpoint of obtaining a higher effect, it is preferable to use pattern formation method A or B, and it is more preferable to use pattern formation method A.

[0158] For comparison, Figure 46 shows a method in which the pattern formation method is not changed for the boundary area and the pattern area excluding the boundary area, and the entire pattern is formed using a random multi-pass method. In this method as well, it is possible to form straight lines at the boundary area that do not pose practical problems, but a higher effect can be obtained by using the pattern formation method of the present invention.

[0159] In the pattern formation method described above, the image data (divided image data α) used for pattern formation at the boundary is arranged such that each pixel constituting the image data is parallel to the row and column directions, but this is not always the case. Figure 47 shows a pattern formation method when the pixels constituting the image data corresponding to pattern formation at the boundary are not arranged parallel to the row and column directions.

[0160] Figure 47 shows a method (pattern formation method B) in which pattern formation at the boundary (diamond shape) and pattern formation in the patterned area excluding the boundary are started simultaneously, and pattern formation at the boundary is completed first. As shown in Figure 47, even when each pixel constituting the image data corresponding to the pattern formation at the boundary is not arranged parallel to the row and column directions, a pattern can be formed using the pattern formation method described above.

[0161] In the pattern forming method of the present invention, the amount of liquid droplets to be projected may be the same or different, and the amount of liquid droplets to be projected may be varied between the boundary area and the pattern area excluding the boundary area.

[0162] For example, when forming a pattern on a substrate with uneven surfaces, increasing the amount of liquid droplets deposited in or around the recesses can smooth the pattern formed on the substrate, thereby suppressing variations in functionality such as conductivity and insulation.

[0163] [4 Ink] In the present invention, it is preferable that the ratio η2 / η1 of the viscosity η1 at the temperature of ink ejection to the viscosity η2 at the temperature of impact is 100 or more. By setting η2 / η1 to 100 or higher, bulge formation can be suppressed, and high-resolution patterns can be formed. Furthermore, by setting η2 / η1 to 200 or higher, and even 500 or higher, high-resolution patterns can be formed on substrates made of different materials or on substrates with uneven surfaces.

[0164] Furthermore, in the present invention, it is preferable to use an ink of any of the following types: hot melt type, gel type, or thixotropic type.

[0165] <Viscosity> The viscosity of the ink during ejection and impact is not particularly limited as long as it satisfies the above ratio, but for example, when the ejection temperature is 75°C, the viscosity (η1) is preferably in the range of 3 to 15 mPa·s from the viewpoint of the ejection performance of the inkjet head. On the other hand, the viscosity (η²) when the temperature at impact is room temperature (25°C) is 1 × 10¹⁰, from the viewpoint that the ink will be fixed on the substrate at impact and the formation of bulges and the like will be suppressed. 2 ~1 × 10 4 It is preferable that the range is within mPa·s.

[0166] "Viscosity η2 at the temperature of impact" can be defined as the viscosity of the ink reached before ink flow (not caused by the impact of the projectile) substantially occurs due to the wetting and spreading of the ink on the substrate. Specifically, it is the viscosity reached within 1 second after the ink hits the substrate, but in this invention, it is defined as the temperature of the substrate at the time the ink hits. On the other hand, "viscosity η1 at the ejection temperature" refers to the temperature of the head at the time the ink is ejected from the head.

[0167] Viscosity measurement is performed by setting the ink in a temperature-controllable stress-controlled rheometer (e.g., PhysicaMCR300, manufactured by Anton Paar), heating it to 100°C, and then cooling it to 25°C at a cooling rate of 0.1°C / s before measuring the viscosity. The measurement can be performed using a cone plate with a diameter of 75.033 mm and a cone angle of 1.017° (e.g., CP75-1, manufactured by Anton Paar). Furthermore, temperature control can be performed using a temperature control device, for example, the Peltier element type temperature control device (TEK150P / MC1) included with the PhysicaMCR300.

[0168] <Method for controlling viscosity ratio η2 / η1> The viscosity ratio η2 / η1 of the ink according to the present invention can be appropriately satisfied by, for example, setting the ink composition, the temperature and humidity at the time of ink application, and other physical conditions. The ink according to the present invention preferably has the property of changing viscosity by a phase change mechanism such as hot melt, thixotropy, or gelation. By having the above property, the ink exhibits a phase change function from the time of ink discharge to the time of impact, thereby satisfying the viscosity ratio η2 / η1 condition according to the present invention.

[0169] In this invention, "hot melt" refers to melting by applying heat, and "phase change mechanism by hot melt" refers to the mechanism by which a substance transitions from a state of low viscosity due to heating (melting) (at the time of discharge) to a state of high viscosity (at the time of impact) due to cooling. From the viewpoint of suitably exhibiting the phase change mechanism by hot melt, it is preferable to change the ink temperature at the time of ejection and at the time of impact. For example, one method is to heat the ink at the time of ejection and cool the ink at the time of impact, and it is preferable to perform one or both of these methods.

[0170] In the present invention, when the ink temperature is changed between ejection and impact, it is preferable to appropriately use temperature control means such as a heater (heating means) for heating the ink filled in the inkjet head and a cooling means for cooling the substrate.

[0171] In this invention, "thixotropy" refers to properties intermediate between plastic solids like gels and non-Newtonian liquids like sols, where viscosity changes over time. Furthermore, "thixotropic phase change mechanism" refers to a phase change mechanism in which viscosity transitions from a low viscosity state under the action of shear stress due to stirring or vibration (during discharge) to a high viscosity state (after impact) when the action of shear stress is reduced or stopped. For example, a phase change mechanism due to thixotropy can be brought about by appropriately using means to apply shear stress by stirring or vibrating (micro-vibration) the ink filled in the inkjet head.

[0172] In the present invention, the "phase change mechanism by gelation" refers to a phase change mechanism in which the solute transitions from a low viscosity state (at the time of discharge) due to the independent mobility of the solute to a high viscosity state (at the time of impact) due to the interaction of polymer networks formed by chemical or physical aggregation, or aggregated structures of fine particles, which cause the solute to lose its independent mobility and form aggregated structures. In this case, it is preferable that the ink contains a gelling agent such as an oil gelling agent (details will be described later).

[0173] From the viewpoint of suitably exhibiting the phase change mechanism due to gelation, it is preferable to change the temperature of the ink at the time of ejection and at the time of impact. For example, it is preferable to heat the ink to above the sol-gel phase transition temperature (gelation temperature) at the time of ejection to cause sol formation, and then cool the ink to below the sol-gel phase transition temperature (gelation temperature) at the time of impact to cause gelation.

[0174] [4.1 Thermosetting inkjet inks] The ink used in the present invention is preferably a thermosetting inkjet ink containing a compound having a thermosetting functional group and a gelling agent, and undergoing a sol-gel phase transition depending on temperature. Furthermore, it is even more preferable that the thermosetting inkjet ink contains a compound having a photopolymerizable functional group and a photopolymerization initiator.

[0175] <Thermosetting functional group> Examples of thermosetting functional groups include hydroxyl groups, carboxyl groups, isocyanate groups, epoxy groups, (meth)acrylic groups, maleimide groups, mercapto groups, and alkoxy groups. These may be used individually or in combination of two or more.

[0176] <Gelling agent> The gelling agent is preferably uniformly dispersed within the cured film, which is hardened by light and heat, thereby preventing moisture from penetrating into the cured film.

[0177] Preferably, the gelling agent contains at least one compound represented by the following general formula (G1) or (G2). This allows for uniform dispersion of the gelling agent in the cured film without inhibiting the curing properties of the ink. Furthermore, in inkjet printing, it provides good pinning properties, enables drawing with both fine lines and film thickness, and exhibits excellent fine line reproduction. General formula (G1): R1-CO-R2 General formula (G2): R3-COO-R4 [In the formula, R1 to R4 each independently represent an alkyl chain having a linear portion with 12 or more carbon atoms and which may also be branched.]

[0178] Ketone waxes represented by general formula (G1) or ester waxes represented by general formula (G2) have 12 or more carbon atoms in their linear or branched hydrocarbon groups (alkyl chains), which increases the crystallinity of the gelling agent, improves water resistance, and creates more space in the cardhouse structure described below. As a result, ink media such as solvents and photopolymerizable compounds are more easily encapsulated within this space, and the pinning properties of the ink are improved.

[0179] Furthermore, the number of carbon atoms in the linear or branched hydrocarbon group (alkyl chain) is preferably 26 or less. When it is 26 or less, the melting point of the gelling agent does not rise excessively, so there is no need to excessively heat the ink when ejecting it.

[0180] From the above viewpoint, it is particularly preferable that R1 and R2, or R3 and R4, are linear hydrocarbon groups having 12 to 23 carbon atoms. Furthermore, from the viewpoint of raising the gelation temperature of the ink and allowing the ink to gel more rapidly after impact, it is preferable that either R1 or R2, or either R3 or R4, is a saturated hydrocarbon group having 12 to 23 carbon atoms.

[0181] From the above viewpoint, it is more preferable that both R1 and R2, or both R3 and R4, are saturated hydrocarbon groups with 11 or more carbon atoms and less than 23 carbon atoms.

[0182] The gelling agent content is preferably in the range of 0.5 to 5.0% by mass relative to the total mass of the ink. By keeping the gelling agent content within this range, the solubility and pinning effect of the gelling agent in the solvent component are improved, and furthermore, the water resistance of the cured film is improved. From the above viewpoint, it is even more preferable that the gelling agent content in the inkjet ink be in the range of 0.5 to 2.5% by mass.

[0183] Furthermore, from the following perspectives, it is preferable that the gelling agent crystallizes in the ink at a temperature below the gelation temperature of the ink. The gelation temperature is the temperature at which, when ink that has been solified or liquefied by heating is cooled, the gelling agent undergoes a phase transition from sol to gel, and the viscosity of the ink changes abruptly. Specifically, the gelation temperature of the ink can be determined by cooling the solified or liquefied ink while measuring its viscosity with a viscoelasticity measuring device (for example, MCR300, manufactured by Physica), and the temperature at which the viscosity rapidly increases.

[0184] <Compounds having photopolymerizable functional groups> A compound having a photopolymerizable functional group (also called a photopolymerizable compound) is any compound that reacts with active light to polymerize or crosslink and cure the ink. Examples of photopolymerizable compounds include radical polymerizable compounds and cationic polymerizable compounds. The photopolymerizable compound may be a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof. The inkjet ink may contain only one type of photopolymerizable compound, or two or more types.

[0185] The radical polymerizable compound is preferably an unsaturated carboxylic acid ester compound, and more preferably a (meth)acrylate. Examples of such compounds include the compounds having the (meth)acrylic group mentioned above.

[0186] Cationic polymerizable compounds may include epoxy compounds, vinyl ether compounds, and oxetane compounds. The inkjet ink may contain only one type of cationic polymerizable compound, or two or more types.

[0187] <Photopolymerization initiator> When the photopolymerizable compound is a radical polymerizable compound, it is preferable to use a photoradical initiator as the photopolymerization initiator, and when the photopolymerizable compound is a cationic polymerizable compound, it is preferable to use a photoacid generator.

[0188] The photopolymerization initiator in the ink of the present invention may contain only one type, or two or more types. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator. Photoradical initiators include cleavage-type radical initiators and hydrogen abstraction-type radical initiators.

[0189] <Coloring agent> The ink used in the present invention may further contain a colorant as needed. The colorant may be a dye or a pigment, but a pigment is preferred because it has good dispersibility with the components of the ink and excellent weather resistance.

[0190] The dispersion of the pigment is preferably carried out so that the volume-average particle size of the pigment particles is preferably in the range of 0.08 to 0.5 μm, the maximum particle size is preferably in the range of 0.3 to 10 μm, and more preferably in the range of 0.3 to 3 μm. The dispersion of the pigment is adjusted by selecting the pigment, dispersant, and dispersion medium, the dispersion conditions, and the filtration conditions.

[0191] Furthermore, to improve the dispersibility of the pigment, a dispersant and a dispersing aid may be included. The total amount of the dispersant and dispersing aid is preferably in the range of 1 to 50% by mass relative to the pigment.

[0192] The ink used in the present invention may further contain a dispersion medium for dispersing the pigment, if necessary. A solvent may be included in the ink as the dispersion medium, but in order to suppress the residue of solvent in the formed printed material, it is preferable to use a photopolymerizable compound (particularly a monomer with low viscosity) as described above as the dispersion medium.

[0193] When using dyes, oil-soluble dyes are examples.

[0194] The ink may contain one or more colorants to achieve a desired color. The colorant content is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.4 to 10% by mass, relative to the total amount of ink.

[0195] <Other ingredients> The ink used in the present invention may further contain other components such as polymerization inhibitors, surfactants, curing accelerators, coupling agents, and ion scavengers, to the extent that the effects of the present invention are obtained. These components may be present in the ink alone or in two or more types. Furthermore, while solvent-free inks are preferable from the viewpoint of curability, solvents may be added to adjust the viscosity of the ink.

[0196] <Physical properties> The ink used in the present invention preferably has a phase transition temperature within the range of 40°C to less than 100°C. If the phase transition temperature is 40°C or higher, the ink gels rapidly after landing on the printing medium, resulting in higher pinning properties. If the phase transition temperature is less than 100°C, the ink handling properties improve and the ejection stability increases. From the viewpoint of enabling ink ejection at lower temperatures and reducing the load on the image forming apparatus, it is more preferable that the phase transition temperature of the ink is within the range of 40 to 60°C.

[0197] From the viewpoint of further improving the ejection performance of ink from the inkjet head, the average dispersed particle size of the pigment particles according to the present invention is preferably in the range of 50 to 150 nm, and more preferably in the range of 80 to 130 nm. Furthermore, the maximum particle size is preferably in the range of 300 to 1000 nm. In this invention, the "average dispersed particle size" of the pigment particles refers to the value obtained by dynamic light scattering using a DataSizer Nano ZSP, manufactured by Malvern. For inks containing colorants, the concentration is high and light does not pass through the measuring instrument, so the ink is diluted 200 times before measurement. The measurement temperature is room temperature (25°C).

[0198] [5. Method for forming solder resist patterns] The ink used in this invention is preferably a solder resist ink for forming solder resist patterns used on printed circuit boards. By forming a solder resist pattern using this ink, it is possible to prevent moisture from penetrating the solder resist pattern, resulting in good adhesion between the copper foil and the solder resist pattern interface on the printed circuit board. Furthermore, it is possible to prevent copper migration and suppress the decrease in insulation performance.

[0199] A method for forming a solder resist pattern using the ink used in the present invention preferably includes the following steps: (1) ejecting the ink from the nozzle of an inkjet head and depositing it onto a printed circuit board with a circuit formed on it, and (3) heating the ink to cure it. If the ink used in the present invention contains a compound having a photopolymerizable functional group and a photopolymerization initiator, it is preferable to include a step (step (2)) between steps (1) and (3) above in which the deposited ink is irradiated with active light to pre-cure the ink.

[0200] Step (1): In step (1), droplets of the present invention's ink are ejected from the inkjet head and landed on the printed circuit board, which is the printing medium, at positions corresponding to the solder resist pattern to be formed, thereby performing patterning. The ejection method from the inkjet head may be either on-demand or continuous.

[0201] By heating the ink droplets before ejecting them from the inkjet head, ejection stability can be improved. The ink temperature during ejection is preferably in the range of 40 to 100°C, and more preferably in the range of 40 to 90°C to further improve ejection stability. In particular, it is preferable to perform ejection at an ink temperature such that the ink viscosity is in the range of 7 to 15 mPa·s, more preferably in the range of 8 to 13 mPa·s.

[0202] For sol-gel phase transition type inks, it is preferable that the temperature of the ink when it is filled into the inkjet head is set to (gelation temperature + 10)°C to (gelation temperature + 30)°C in order to improve the ink ejection performance from the inkjet head. If the temperature of the ink in the inkjet head is below (gelation temperature + 10)°C, the ink is likely to gel inside the inkjet head or on the nozzle surface, reducing the ink ejection performance. On the other hand, if the temperature of the ink in the inkjet head exceeds (gelation temperature + 30)°C, the ink becomes too hot, which may cause the ink components to deteriorate.

[0203] The method of heating the ink is not particularly limited. For example, at least one of the ink supply system, such as the ink tanks, supply pipes, and pre-chamber ink tanks immediately before the head, which constitute the head carriage, as well as filtered piping and piezo heads, can be heated by a panel heater, ribbon heater, or warm water. The amount of ink droplets ejected is preferably in the range of 2 to 20 pL from the viewpoint of printing speed and image quality.

[0204] The printed circuit board is not particularly limited, but preferably it is made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, copper-clad laminate for high-frequency circuits using fluorine, polyethylene, PPO, cyanate ester, etc., and is available in all grades (FR-4, etc.), as well as polyimide film, PET film, glass substrate, ceramic substrate, wafer plate, stainless steel plate, etc.

[0205] Step (2): In step (2), the ink that was deposited in step (1) is irradiated with an active light to partially cure the ink. The active light can be selected from, for example, electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays, but ultraviolet rays are preferred. The irradiation with ultraviolet rays can be carried out using, for example, a water-cooled LED manufactured by Phoseon Technology, under conditions of a wavelength of 395 nm. By using an LED as the light source, it is possible to suppress the curing failure of the ink caused by the ink melting due to the radiant heat of the light source.

[0206] The ultraviolet irradiation is performed with ultraviolet light having a wavelength in the range of 370 to 410 nm, and the peak illuminance on the surface of the solder resist pattern is preferably 0.5 to 10 W / cm². 2 Within the range of 1 to 5 W / cm², more preferably 1 to 5 W / cm². 2 The process should be carried out within the specified range. From the standpoint of suppressing radiant heat from irradiating the ink, the amount of light irradiated onto the solder resist pattern should be 500 mJ / cm². 2It is preferable that the time is less than [amount]. Irradiation with active light is preferably performed between 0.001 and 300 seconds after ink impact, and more preferably between 0.001 and 60 seconds in order to form a high-resolution solder resist pattern.

[0207] Step (3): In step (3), after the preliminary curing in (2), the ink is further heated to achieve full curing. The heating method is preferably to place the ink in an oven set to a temperature within the range of 110 to 180°C for a period of 10 to 60 minutes.

[0208] In addition to being used as an ink for forming solder resist patterns as described above, the ink used in this invention can also be used as an adhesive, sealant, or circuit protectant for electronic components.

[0209] In the present invention, the area on which the solder resist pattern is provided is not particularly limited, but as described above, the effects of the present invention are particularly significant when it is formed across different materials or across materials with uneven surfaces.

[0210] Inkjet Printing Equipment The functions of the basic components of the multi-pass inkjet printing apparatus (also referred to as "inkjet printing apparatus" or "inkjet recording apparatus") that can be used in the present invention will be described below.

[0211] Figure 8 is a schematic diagram of a multi-pass inkjet printing apparatus 1, with A being a front view and B being a top view. This inkjet printing apparatus 1 is basically a printing apparatus that ejects ink using a multi-pass method in which the head 3 moves back and forth to perform overlapping printing, and comprises a carriage 2 to which the head is attached, an X-direction linear stage 4 that moves the carriage 2, a table 5 on which the substrate is placed, and a Y-direction linear stage 6 that moves the table 5.

[0212] In the inkjet printing apparatus 1, printing is performed by moving the head 3 in the X direction and moving the table 5 on which the substrate is placed in the Y direction. Although not shown, the inkjet printing apparatus 1 includes a device for controlling the ejection of ink from the head 3 and a computer for controlling the XY stage. The computer for controlling the XY stage controls the operation of the XY stage based on image data. The computer includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.

[0213] As a printing method in the X direction, the carriage 2 to which the head 3 is attached to is mounted on the linear stage 4 in the X direction and is moved to a desired position by a computer that controls the XY stage. As a printing method in the Y direction, the table 5 on which the substrate is placed moves in the Y direction, and ink is ejected from the head when the substrate passes under the head. An encoder installed on the linear stage 6 in the Y direction and a device for controlling the ejection of ink from the head 3 are interlocked, and ink is ejected at the resolution of the image data in response to the encoder signal.

[0214] When printing at a resolution higher than the resolution of the head in the X direction, the head is moved multiple times in the X direction for printing. For example, when printing at 2400 dpi with one inkjet head with a resolution of 600 dpi, after the head performs the first scan in the Y direction, it moves 10.6 μm (equivalent to one pixel of 2400 dpi) in the X direction and performs the second scan in the Y direction. Further, after the head moves 10.6 μm in the X direction and performs the third scan in the Y direction, it moves 10.6 μm in the X direction and performs the fourth scan in the Y direction, and then it is completed.

[0215] In the above description, it is the case of printing in only one direction of the conveyance direction, but there is also a case of printing back and forth (also referred to as "bidirectional printing"). Additionally, if the print area is larger than the print head width, the printer will move the print head by the width of the print head in the X direction before printing.

[0216] Furthermore, the main scanning direction and sub-scanning direction of the ink ejection device do not have to be perpendicular or parallel to the nozzle row, and streaks and unevenness are less likely to occur whether only one of the ink ejection device and the substrate as the printing medium moves to form a pattern, or whether both move to form a pattern.

[0217] The following describes other multi-pass inkjet printing apparatuses that can be used in the present invention. The ink ejection device (synonymous with "head" above) has a plurality of nozzle holes for ejecting ink. While it is preferable that these nozzle holes are arranged in a row, the nozzle row and the main scanning direction (synonymous with "Y direction" above) and sub-scanning direction (synonymous with "X direction" above) of the head do not necessarily have to be perpendicular or parallel, and are not particularly limited.

[0218] Figure 41 shows a printing method when the nozzle row is not perpendicular or parallel to either the X or Y direction, but oblique. An inkjet printing apparatus with an oblique nozzle row can also be used in the pattern formation method of the present invention.

[0219] Figure 42 shows a printing method where the orientation of the ink ejection device itself is not perpendicular or parallel to either the X or Y direction, but oblique. By appropriately changing the angle between the ink ejection device and the main scanning direction, the spacing of the formed dots can be changed, thus increasing the nozzle resolution without adding an additional ink ejection device. Such an inkjet printing device can also be used in the pattern formation method of the present invention.

[0220] Furthermore, in the inkjet printing apparatus 1 described above, printing is performed by the head moving in the X direction and the substrate moving in the Y direction. However, inkjet printing apparatuses in which the head moves in the Y direction and the substrate moves in the X direction, inkjet printing apparatuses in which the substrate moves in both the X and Y directions, and inkjet printing apparatuses in which the head moves in both the X and Y directions can also be used in the pattern forming method of the present invention.

[0221] Figure 34 shows the method of printing with the inkjet printer 1 described above. In the first scan, the head is fixed, and as the substrate moves in the direction of the arrow and passes under the head, ink droplets are ejected from the head, causing the head to move relative to the substrate in the main scanning direction. When printing at a resolution higher than the head's resolution, in the second scan, the head moves in the direction of the arrow, and the substrate moves again in the direction of the arrow to eject ink droplets. This is repeated until printing is complete.

[0222] In the inkjet printing apparatus 100 shown in Figure 33, the carriage 2 to which the head 3 is attached is mounted on a linear stage 6 in the Y direction, and is moved to the desired position by a computer that controls the XY stages. Furthermore, for the X-direction printing method, after printing in the main scanning direction of the Y-direction, the table 5 on which the substrate is placed moves in the X-direction, and the next main scanning direction of the Y-direction is printed. Similar to the inkjet printing apparatus 1, an encoder installed on the linear stage 4 in the X direction and a device that controls the ejection of ink from the head 3 work in conjunction, and ink is ejected at the resolution of the image data according to the encoder signal.

[0223] Figure 35 shows how to perform printing with the inkjet printer 100. In the first scan, the print head moves in the main scanning direction on a fixed substrate and ejects ink droplets. Next, in the second scan, the substrate moves in the direction of the arrow, causing the print head to move in the sub-scanning direction relative to the substrate. Then, the ink ejector moves again in the main scanning direction on the fixed substrate and ejects ink droplets. This is repeated until printing is complete.

[0224] Figure 36 illustrates a printing method using an inkjet printer where the substrate moves in both the X and Y directions. In the first scan, the print head is fixed, and as the substrate moves in the direction of the arrow and passes under the head, ink droplets are ejected from the head, causing the head to move relative to the substrate in the main scanning direction. Next, in the second scan, the substrate moves in the direction of the arrow, causing the head to move relative to the substrate in the sub-scanning direction. Then, the ink ejector moves again in the main scanning direction over the fixed substrate and ejects ink droplets. This process is repeated until printing is complete.

[0225] Figure 37 illustrates how to print using an inkjet printer in which the print head moves in both the X and Y directions. In the first scan, the print head moves in the main scanning direction on a fixed substrate and ejects ink droplets. Next, in the second scan, the print head moves in the direction of the arrow, and the substrate moves again in the direction of the arrow to eject ink droplets. This process is repeated until printing is complete.

[0226] Furthermore, by arranging multiple print heads in a row and mounting them on the carriage, the number of scans can be reduced, shortening the printing time.

[0227] Figure 40 shows a method for performing split printing at a resolution of 2400 dpi using four inkjet heads with a nozzle resolution of 600 dpi. The four inkjet heads are mounted on the carriage with a staggered pitch to achieve a resolution of 2400 dpi.

[0228] As shown in Figures 30A and 30B, when printing at a resolution of 2400 dpi using one inkjet head with a nozzle resolution of 600 dpi and four divided image data, 16 scans are required. However, as shown in Figure 40, if four inkjet heads are mounted with a staggered arrangement, the process of scans 1 to 4 in Figure 30A can be completed in a single scan, allowing printing to be completed in a total of four scans, thus reducing printing time.

[0229] In the present invention, as described above, a multi-gradation random gray image may be used, and the amount of liquid may be controlled in accordance with the gradation or density of each pixel. For example, when forming a pattern on a substrate with uneven surfaces, increasing the amount of liquid droplets that land in the recesses or the area surrounding the recesses can smooth the pattern formed on the substrate, thereby suppressing variations in functionality such as conductivity and insulation.

[0230] For example, by applying a noise filter to a 256-level 30% gray image in Adobe Photoshop, random multi-level gray image data like that shown in Figure 16 can be created. Based on this image data, the ink volume is distributed as follows: for example, 7 pL for the black areas (0-86 levels), 3.5 pL for the gray areas (87-172 levels), and 0 pL for the white areas (173-255 levels).

[0231] The formation of dots with different liquid volumes corresponding to each pixel can be achieved by changing the ejection waveform when ink is ejected from the nozzle, or by forming multiple dots for the same pixel.

[0232] For example, in the case of the liquid volume distribution described above, by using an inkjet head with a liquid volume of 3.5 pL, specifying that two drops are ejected for the black areas (0-86 gradations), one drop for the gray areas (87-172 gradations), and no ejection for the white areas (173-255 gradations), it is possible to form dots with different liquid volumes.

[0233] As a method of printing by the random multipass method in the present invention, there are a method of dividing an original image into a plurality of non-overlapping random images and printing them, a method of randomizing landing by an inkjet ejection control system using a function such as a random number, and the like.

[0234] The divided image data can be produced by the following method. It can be produced by image processing software such as Adobe's image processing software Photoshop 2020. For example, a grayscale image is made into a monochrome two-tone image by the error diffusion method or the like using Photoshop, and a random image of white and black is produced. Next, the image is color-inverted to produce an image with inverted white and black.

Example

[0235] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the display of "parts" or "%" is used, and unless otherwise specified, it represents "parts by mass" or "% by mass". In addition, in the following examples, unless otherwise specified, the operations were carried out at room temperature (25 °C).

[0236] ≪Example 1≫ [Preparation of Ink 1] [Preparation of Pigment Dispersion Liquid] Put the dispersant and dispersion medium shown below into a stainless steel beaker, heat and stir for 1 hour while heating on a hot plate at 65 °C, cool to room temperature, add a pigment thereto, put it into a glass bottle together with 200 g of zirconia beads with a diameter of 0.5 mm, and seal it. This was subjected to dispersion treatment with a paint shaker until the desired particle size was obtained, and then the zirconia beads were removed.

[0237] (Yellow Pigment Dispersion) Dispersant 1: EFKA7701 (manufactured by BASF) 5.6 parts by mass Dispersant 2: Solsperse22000 (manufactured by Nippon Lubrizol Corporation) 0.4 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 80.6 parts by mass Pigment: PY185 (BASF, Paliotol Yellow D1155) 13.4 parts by mass

[0238] (Cyanide pigment dispersion) Dispersant: EFKA7701 (BASF) 7.0 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70.0 parts by mass Pigment: PB15:4 (manufactured by Dainichi Seika, Chromofine Blue 6332JC) 23.0 parts by mass

[0239] The prepared dispersion was mixed according to the following proportions, and then filtered through an ADVATEC Teflon® 3μm membrane filter to prepare ink 1. The viscosity (η1) at the ink ejection temperature of 75°C was 8.5 mPa·s, and the viscosity (η2) at room temperature (25°C), the temperature at impact, was 9.2 mPa·s.

[0240] Yellow pigment dispersion 3.0 parts by mass Cyanide pigment dispersion 1.0 part by mass Epoxy ester (M-600A: manufactured by Kyoei Chemical Co., Ltd.) 30.0 parts by mass Trixene BI7961 (manufactured by LANXESS) 10.0 parts by mass Urethane acrylate (AH-600: manufactured by Kyoei Chemical Co., Ltd.) 10.0 parts by mass M222 (Miwon Corporation) 27.7 parts by mass EM2382 (manufactured by Choko Kagakusha) 10.0 parts by mass Photoinitiator: Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) 3.0 parts by mass Photoinitiator: 2-Isopropylthioxanthone (ITX) 3.0 parts by mass

[0241] [Print Pattern] Using a linear XY stage equipped with one inkjet head (KM1800iSHC-C: Konica Minolta: 600 dpi resolution) and a control system (IJCS-1: Konica Minolta), a print pattern was printed onto an optical PET film substrate under the following conditions, and a UV-LED light source with a wavelength of 395 nm was used to illuminate it at 500 mJ / cm². 2 Printed material 1 was prepared by exposure and curing with the irradiation energy.

[0242] [Split Printing (Image Division Count: 2)] As shown in Figure 28, the image data for the pattern area, excluding the boundary areas, was divided using image processing software so that the pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and so that there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the block method. Then, the divided image data was printed sequentially on top of each other under the following conditions.

[0243] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 28, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 28. Boundary printing method: Block method, see Figure 18. Boundary width in dots: 1 Printing order: Pattern formation method B Liquid distribution: 3.5 pL across the entire surface Print head temperature (ink ejection temperature): Room temperature (25°C) Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0244] Example 2 Printed material 2 of Example 2 was prepared in the same manner as in Example 1, except that ink 1 was changed to ink 2 and the head temperature (during ink ejection) was changed to 75°C.

[0245] [Preparation of Ink 2] The dispersion prepared with Ink 1 was mixed according to the following proportions, and then filtered through an ADVATEC Teflon® 3μm membrane filter to prepare the ink. The viscosity (η1) at the ink ejection temperature of 75°C was 10 mPa·s, and the viscosity (η2) at the impact temperature of room temperature (25°C) was 1 × 10⁻⁶. 4 The viscosity was mPa·s, meaning the viscosity ratio η² / η¹ was 1000.

[0246] Yellow pigment dispersion 3.0 parts by mass Cyanide pigment dispersion 1.0 part by mass Distearyl ketone 1.1 parts by mass Behenyl behenate 1.2 parts by mass Epoxy ester (M-600A: manufactured by Kyoei Chemical Co., Ltd.) 30.0 parts by mass Trixene BI7961 (manufactured by LANXESS) 10.0 parts by mass Urethane acrylate (AH-600: manufactured by Kyoei Chemical Co., Ltd.) 10.0 parts by mass M222 (Miwon Corporation) 27.7 parts by mass EM2382 (manufactured by Choko Kagakusha) 10.0 parts by mass Photoinitiator: Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) 3.0 parts by mass Photoinitiator: 2-Isopropylthioxanthone (ITX) 3.0 parts by mass

[0247] Example 3 Printed material 3 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0248] [Split Printing (Image Division Count: 2)] Regarding the image data, as shown in Figure 44, the image data of the pattern area excluding the boundary area was divided using image processing software so that the individual pixels would not overlap when printed on top of each other, and the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the interleaved method. Then, the divided image data was printed sequentially on top of each other under the following conditions.

[0249] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 44, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 44. Boundary printing method: Interleaved method, see Figure 21. Boundary width in dots: 1 Printing order: Pattern formation method D Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0250] Example 4 Printed material 4 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0251] [Split Printing (Image Division Count: 2)] As shown in Figure 45, the image data for the pattern area, excluding the boundary areas, was divided using image processing software so that the pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and so that there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the interleaved method. Then, the divided image data was sequentially printed on top of each other under the following conditions.

[0252] Printing pattern: A 2mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 45, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 45. Boundary printing method: Interleaved method, see Figure 22. Boundary width in dots: 1 Printing order: Pattern formation method D Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0253] ≪Example 5≫ Printed material 5 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0254] [Split Printing (Image Division Count: 2)] As shown in Figure 43, the image data for the pattern area, excluding the boundary areas, was divided using image processing software so that the pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and so that there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the block method. Then, the divided image data was printed sequentially on top of each other under the following conditions.

[0255] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 43, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 43. Boundary printing method: Block method, see Figure 18. Boundary width in dots: 1 Printing order: Pattern formation method C Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0256] Example 6 Printed material 6 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0257] [Split Printing (Image Division Count: 3)] As shown in Figures 27A and 27B, the image data was divided into a boundary area and a pattern area excluding the boundary area. The image data of the pattern area excluding the boundary area was then divided using image processing software so that the pixels would not overlap when printed on top of each other, and the order of the pixels in rows and columns would not be the same as in which they were arranged, and so that there would be no certain periodicity. For the image data of the boundary area, divided image data No. 1 to No. 3 were created to correspond to a block method. Then, the divided image data was printed on top of each other sequentially under the following conditions.

[0258] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 3 Segmented image data: See Figures 27A and 27B for details on segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 12 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 27. Boundary printing method: Block method, see Figure 18. Boundary width in dots: 1 Printing order: Pattern formation method A Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0259] Example 7 Printed material 7 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0260] [Split Printing (Image Division Count: 2)] Regarding the image data, as shown in Figure 47, the image data of the pattern area excluding the boundary area was divided using image processing software so that the individual pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the order in which they were arranged, and so that there would be no certain periodicity. For the image data of the boundary area, divided image data No. 1 and No. 2 were created to correspond to the block method. Then, the divided image data was printed sequentially on top of each other under the following conditions.

[0261] Printing pattern: A 2mm x 2mm die-cut square (diamond shape) is placed within a 70mm x 70mm square, non-parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 47, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 47. Boundary printing method: Block method, see Figure 24. Boundary width in dots: 1 Printing order: Pattern formation method B Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0262] Example 8 Printed material 8 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0263] [Split Printing (Image Division Count: 2)] As shown in Figure 48, the image data for the pattern area, excluding the boundary areas, was divided using image processing software so that the pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and so that there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the block method. Then, the divided image data was printed sequentially on top of each other under the following conditions. However, the width of the boundary area was set to twice the original width.

[0264] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 48, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 48. Boundary printing method: Block method Boundary width in dots: 2 Printing order: Pattern formation method B Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0265] ≪Example 9≫ Printed material 9 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0266] [Split Printing (Image Division Count: 2)] As shown in Figure 49, the image data for the pattern area, excluding the boundary areas, was divided using image processing software so that the pixels would not overlap when printed on top of each other, and so that the order of the rows and columns in which the pixels were arranged would not be the same as the original order, and so that there would be no constant periodicity. For the boundary area image data, divided image data No. 1 and No. 2 were created to correspond to the block method. Then, the divided image data was printed sequentially on top of each other under the following conditions. However, the printing direction was bidirectional.

[0267] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 49, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Print direction (main scanning direction): Bidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method excluding boundaries: Random multi-pass method, see Figure 49. Boundary printing method: Block method Boundary width in dots: 1 Printing order: Pattern formation method B Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0268] ≪Comparative Example 1≫ Printed material 10 was prepared in the same manner as in Example 1, except that the printing conditions were changed to the following conditions.

[0269] Regarding the image data, as shown in Figure 50, the pattern portion was not distinguished between the boundary portion and the pattern portion excluding the boundary portion. The image data used was treated as a single image file (without split printing), and all were printed using a block method.

[0270] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 4 (600dpi x 4) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method: Block method, see Figure 50. Liquid distribution: 3.5 pL across the entire surface Print head temperature (ink ejection temperature): Room temperature (25°C) Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0271] ≪Comparative Example 2≫ Printed material 11 was prepared in the same manner as in Comparative Example 1, except that ink 1 was changed to ink 2 and the head temperature (during ink ejection) was changed to 75°C.

[0272] ≪Reference example 1≫ Printed material 12 was prepared in the same manner as in Example 2, except that the printing conditions were changed to the following conditions.

[0273] [Split Printing (Image Division Count: 2)] As shown in Figure 46, the image data was divided using image processing software without distinguishing between the boundary area and the pattern area excluding the boundary area. The division was performed so that when printed on top of each other, the individual pixels would not overlap, and the order of the rows and columns in which the pixels were arranged would not be consistent, thus creating divided image data No. 1 and No. 2. These divided image data were then printed sequentially on top of each other under the following conditions.

[0274] Printing pattern: A 3mm x 2mm cutout square is placed within a 70mm x 70mm square, parallel to the main scanning direction and sub-scanning direction. Number of image divisions: 2 Segmented image data: See Figure 46, Segmented image data. Resolution: 2400dpi x 2400dpi (transport direction) Number of passes: 8 (600dpi x 8) Printing direction (main scanning direction): Unidirectional printing Printing direction (sub-scanning direction): Forward printing Inter-pass head nozzle row direction travel distance: 10.6 μm Pattern printing method: Random multi-pass method, see Figure 46. Liquid distribution: 3.5 pL across the entire surface Head temperature (ink ejection temperature): 75℃ Circuit board temperature (temperature at ink impact): Room temperature (25℃)

[0275] [evaluation] <Evaluation of the tendons> The patterns in the resulting printed materials were visually inspected, and the occurrence of streaks was evaluated. ◎: No streaks are observed. ○: There is a slight stringy texture, but it is not noticeable. ×: The texture is noticeable, making it unsuitable for practical use. ××: The lines are very noticeable, making it difficult to use. Furthermore, values ​​of ○ or higher were considered to pose no practical problems.

[0276] <Boundary Linearity (Pattern Reproducibility)> The distance between each of the opposing sides of the pattern-cut rectangles (non-patterned areas) in the obtained printed material was measured at 20 points, and linearity was evaluated based on the deviation from the arithmetic mean. ◎◎: The maximum displacement is 2 μm or less. ◎: The maximum displacement is greater than 2 μm and less than or equal to 3 μm. ○: The maximum displacement is greater than 3 μm and less than or equal to 5 μm. △: The maximum displacement is greater than 5 μm and less than or equal to 10 μm. ×: The maximum displacement is greater than 10 μm. Furthermore, a rating of △ or higher indicates no practical problems.

[0277] The evaluation results are shown in Table I. In the table, "-" indicates that there is no corresponding data. Example 1 is provided as a reference example. Figure 53 also shows optical microscope images at 100x magnification of printed materials A and B, which were prepared under the same printing conditions as printed materials 2 and 12, respectively, and have die-cut squares arranged parallel to the main scanning direction and sub-scanning direction. In the optical microscope images at 100x magnification, some streaks were visible in the pattern areas, excluding the boundaries, in both printed material A (same printing conditions as printed material 2) and printed material B (same printing conditions as printed material 12), but no streaks were visible to the naked eye.

[0278] [Table 1]

[0279] From a comparison of Example 1 and Comparative Example 1, and a comparison of Example 2 and Comparative Example 2, it can be seen that in the pattern portion excluding the boundary portion, the occurrence of streaks can be suppressed by using a random multi-pass method ((I) controlling the order of the rows and columns in which each pixel constituting the image data is arranged and not having a certain periodicity, and (II) controlling the main scanning direction of the ink ejection device so that it does not have continuity or periodicity).

[0280] Furthermore, a comparison of Example 2 and Reference Example 1, as well as Figure 53, shows that the linearity at the boundary is improved by controlling the pixels constituting the image data to have continuity or periodicity in the longitudinal order in which they are arranged.

[0281] A comparison of Examples 2 to 6 shows that by using pattern formation method A or B (completing the formation of the dot coating at the boundary before the formation of the dot coating in the patterned area excluding the boundary), the linearity at the boundary is further improved.

[0282] A comparison of Examples 2 and 9 shows that using bidirectional printing (where the ink ejector moves back and forth in the main scanning direction, ejecting ink droplets in both the forward and return directions) slightly reduces linearity at the boundaries. However, this does not pose a practical problem, and it has the advantage of reducing the movement in the main scanning direction, shortening the printing time, and improving productivity.

[0283] Since the viscosity of ink 1 at 25°C (room temperature) is within the range of suitable viscosity for ink ejection, in Example 1 and Comparative Example 1, the ink was ejected at room temperature without heating. Furthermore, as mentioned above, there is not much difference between the viscosity of ink 1 at 25°C (room temperature) and the viscosity at 75°C, so even when the head temperature was changed to 75°C and the printed material was prepared in the same manner as in Example 1, the same results as in Example 1 (Printed Material 1) were obtained. From a comparison with Example 2, it can be seen that by using an ink in which the ratio η2 / η1 (viscosity η1 at ejection temperature to viscosity η2 at impact temperature) is 100 or more, the linearity at the boundary can be further improved. [Industrial applicability]

[0284] By using the pattern forming method of the present invention, it is possible to form patterns that are free of streaks and have good reproducibility. Therefore, when using inks containing functional materials such as insulators and conductors, it is possible to form patterns with uniform insulating and conductive properties, and the pattern forming method of the present invention can be suitably used for pattern formation on printed circuit boards and the like of electronic devices. [Explanation of Symbols]

[0285] 1. Inkjet printing device 2 carriages 3 heads 4 X-direction linear stage 5 tables 6 Y-direction linear stage 9. Ink ejection device 11 Non-patterned section 12 Boundary forming part 13 Boundary portion excluding boundary forming portion 14 Pattern area excluding boundary area 15. Boundary between patterned and non-patterned areas 16 Boundary 17 Pattern section 21-28 Nozzle 21-28 100 inkjet printing devices

Claims

1. A pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form the pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dots that land the droplets is controlled such that, in the pattern portion excluding the boundary portion, the position is not in the same order as the rows and columns in which the pixels constituting the image data are arranged, and does not have a certain periodicity. In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the longitudinal order in which it is arranged. The ink used is one in which the ratio η2 / η1 of the viscosity η1 at the temperature of ejection to the viscosity η2 at the temperature of impact is 100 or more, and Solder resist ink is used as the aforementioned ink. A pattern forming method characterized by the following.

2. A pattern formation method using an inkjet printing method based on image data of a pattern, In a method in which an ink ejection device having multiple nozzle holes or a substrate as a printing medium moves multiple times, and ink droplets are ejected from the nozzles of the ink ejection device onto the substrate as a printing medium to form the pattern, The ink droplets used to form the coating film of the dots constituting the pattern formed on the substrate are deposited multiple times, The position of the dots that land the aforementioned droplets is controlled so that, in the pattern portion excluding the boundary portion, it does not have continuity or periodicity in the main scanning direction of the ink ejection device. In the boundary portion, each pixel constituting the image data is controlled to have continuity or periodicity in the longitudinal order in which it is arranged. The ink used is one in which the ratio η2 / η1 of the viscosity η1 at the temperature of ejection to the viscosity η2 at the temperature of impact is 100 or more, and Solder resist ink is used as the aforementioned ink. A pattern forming method characterized by the following.

3. The position of the dots that land the aforementioned droplets is controlled so that, in the pattern portion excluding the boundary portion, it does not have continuity or periodicity even in the sub-scanning direction of the ink ejection device. The pattern forming method according to feature 2.

4. The formation of the coating film on the dots at the boundary is completed before the formation of the coating film on the dots in the patterned area excluding the boundary. A pattern forming method according to any one of claims 1 to 3, characterized by the features described herein.

5. The image data of the aforementioned pattern is divided into multiple parts such that when printed in layers, the pixels do not overlap, and the positions of the dots that land the droplets do not have continuity or periodicity in the main scanning direction of the ink ejection device. The divided image data is printed by sequentially overlapping them. The pattern forming method according to any one of claims 2 to 4.

6. The ink ejection device moves back and forth relative to the main scanning direction, Ink droplets are ejected on both the outbound and return journeys. The pattern forming method according to any one of claims 2 to 5, characterized by the features described herein.

7. The ink used is of one of the following types: hot melt type, gel type, or thixotropic type. A pattern forming method according to any one of claims 1 to 6, characterized by the features described above.

8. An inkjet printing apparatus that forms a pattern based on image data of the pattern, A pattern is formed by the pattern forming method described in any one of claims 1 to 7. An inkjet printing apparatus characterized by the following features.

Images