Printing method and inkjet recording device

Abstract

A printing method and an inkjet recording device are provided which enable reliably printing on a printing medium surface having a step. In this printing method, which is for discharging ink onto a substrate (S) that has a step portion, the step portion includes three regions: an inclined portion (E) forming the step; an upper adjacent portion (UC), of a prescribed width, adjacent to the inclined portion (E); and a lower adjacent portion (LC), of a prescribed width, adjacent to the inclined portion (E). The printing method involves a discharge amount setting step in which the ink droplet amount per ink discharge period discharged onto at least one selected region of the three regions is increased to greater than the ink droplet amount discharged to outside of the three regions.

Description

[Technical Field]

[0001] The present invention relates to a printing method and an inkjet recording apparatus. [Background technology]

[0002] There is a technology for printing by ejecting ink onto the surface of a printing medium having a three-dimensional structure. Patent Document 1 discloses a technology for ejecting more ink near the center of a convex portion than near the edge thereof in order to prevent ink that has landed on the convex portion from flowing into the concave portion, resulting in a shortage of ink on the convex portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-202635 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when ink flows down the stepped portion of the three-dimensional structure, it is likely to flow down at the corners of the steps, and there are cases where no ink remains and the surface of the printing medium is exposed, which creates the problem that the desired printing cannot be performed reliably.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a printing method and an inkjet recording apparatus that can more reliably print on a printing medium surface having unevenness. [Means for solving the problem]

[0006] In order to achieve the above object, the invention described in claim 1 is as follows: A printing method in which a solder resist ink is ejected onto a base material having a step portion between an insulating substrate and a wiring conductor located on the insulating substrate, the method comprising: the step portion includes three regions: an inclined portion forming a step, an upper adjacent portion of a predetermined width adjacent to the inclined portion, and a lower adjacent portion of a predetermined width adjacent to the inclined portion; the upper adjacent portion is a horizontal flat portion on the upper surface of the wiring conductor, and the lower adjacent portion is a horizontal flat portion on the upper surface of the insulating substrate, At least the upper adjacent portion of the three regions and The method includes a discharge amount setting step of increasing the amount of ink droplets per ink discharge cycle discharged onto the selected area including the lower adjacent portion, compared to the amount of ink droplets discharged onto areas other than the three areas.

[0007] The invention described in claim 2 is the printing method described in claim 1, The aforementioned Solder resist The ink includes a gelling agent.

[0008] The invention described in claim 3 is the printing method described in claim 1 or 2, The distribution of the ink drop volume over the selected area is non-uniform.

[0009] The invention described in claim 4 is the printing method described in claim 3, The selected area Each of the regions The ink droplet volumes for the ink droplets may be different from each other.

[0010] The invention described in claim 5 is the printing method described in any one of claims 1 to 4, The selected area is determined according to the material of the substrate.

[0012] Also, claims 6 The invention described is as follows: 5 In the printing method according to any one of the above items, The aforementioned Solder resist The ink is cured by irradiation with a predetermined energy beam.

[0013] Also, claims 7 The invention described is 6 In the printing method described, The predetermined energy ray is ultraviolet light.

[0014] Also, claims 8 The invention described is as follows: 7 In the printing method according to any one of the above items, The aforementioned Solder resist The ink is thermosetting.

[0015] Also, claims 9 The described invention is a discharge unit that discharges ink; A control unit; Equipped with The control unit A substrate having an insulating substrate and a wiring conductor located on the insulating substrate, A step portion including three regions: an inclined portion forming a step, an upper adjacent portion of a predetermined width adjacent to the inclined portion, and a lower adjacent portion of a predetermined width adjacent to the inclined portion. the upper adjacent portion is a horizontal flat portion on the upper surface of the wiring conductor, and the lower adjacent portion is a horizontal flat portion on the upper surface of the insulating substrate. On the substrate Solder resist When printing by ejecting ink, At least the upper adjacent portion of the three regions and The amount of ink droplets ejected per ink ejection cycle onto the selected region including the lower adjacent portion is increased compared to the amount of ink droplets ejected onto regions other than the three regions. It is an inkjet recording device. [Effects of the Invention]

[0016] According to the present invention, it is possible to more reliably print on a printing medium surface having unevenness. [Brief explanation of the drawings]

[0017] [Figure 1A] 1 is a front view illustrating a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 1B] FIG. 1 is a plan view of an inkjet recording apparatus. [Figure 2] FIG. 2 is a block diagram illustrating a functional configuration of the inkjet printing apparatus. [Figure 3A] FIG. 2 is a diagram illustrating a printing range of a wiring board. [Figure 3B] FIG. 2 is a diagram illustrating a printing range of a wiring board. [Figure 4] Three examples of ink ejection amount distribution are shown. [Figure 5A] FIG. 10 is a diagram illustrating an increase in the amount of ink ejected. [Figure 5B] FIG. 10 is a diagram illustrating an increase in the amount of ink ejected. [Figure 5C] FIG. 10 is a diagram illustrating an increase in the amount of ink ejected. [Figure 6] 10 is a flowchart illustrating a control procedure of a print control process. [Figure 7A] FIG. 10 is a diagram illustrating an example of ink ejection amounts when printing is performed with two scans. [Figure 7B] FIG. 10 is a diagram illustrating an example of ink ejection amounts when printing is performed with two scans. [Figure 8] FIG. 10 is a diagram illustrating a first modification of the ink ejection amount when printing is performed with two scans. [Figure 9] FIG. 10 is a diagram illustrating a second modification of the ink ejection amount when printing is performed with two scans. [Figure 10A] FIG. 10 is a diagram illustrating a third modification of the ink ejection amount when printing is performed with two scans. [Figure 10B] FIG. 10 is a diagram illustrating a third modification of the ink ejection amount when printing is performed with two scans. [Figure 10C] FIG. 10 is a diagram illustrating a third modification of the ink ejection amount when printing is performed with two scans. [Figure 11A] FIG. 10 is a diagram illustrating a fourth modification of the ink ejection amount when printing is performed with two scans. [Figure 11B] FIG. 10 is a diagram illustrating a fourth modification of the ink ejection amount when printing is performed with two scans. [Figure 11C] FIG. 10 is a diagram illustrating a fourth modification of the ink ejection amount when printing is performed with two scans. [Figure 12A] FIG. 10 is a diagram illustrating an example of a driving waveform. [Figure 12B] FIG. 10 is a diagram illustrating an example of a driving waveform. [Figure 12C] FIG. 10 is a diagram illustrating an example of a driving waveform. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1A is a front view illustrating a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention, and Fig. 1B is a plan view of the inkjet recording apparatus 1.

[0019] The inkjet recording apparatus 1 includes an inkjet head 20 (discharge operation unit), a UV irradiation unit 42, a scanning unit 121, a scanning guide unit 122, a transport table 131, a transport guide unit 132, and the like.

[0020] In the inkjet recording apparatus 1 of this embodiment, the target onto which ink is ejected is, for example, a wiring board S (substrate). This wiring board S is placed on a transport table 131. The transport table 131, with the wiring board S placed thereon, is capable of moving in a direction (transport direction, sub-scanning direction) along a transport guide portion 132 such as a rail. The wiring board S has a substantially flat conductor (wiring conductor) that forms signal wiring on an insulating substrate. The conductor is not particularly limited, but may be copper (copper foil), for example. Since this signal wiring is positioned to protrude above the insulating substrate surface, the wiring board S has a stepped portion. Furthermore, the ink that lands does not penetrate into the wiring board S, but rises on the surface, hardens, and becomes fixed. Note that here, the insulating substrate surface is flat, and the direction perpendicular to this flat surface is defined as upward.

[0021] The inkjet head 20 has nozzles N (see FIG. 2) and ejects ink from the nozzles N onto the wiring substrate S. The amount of ink ejected onto each pixel area during each ink ejection cycle can be selected from multiple levels. The UV irradiation unit 42 irradiates ultraviolet light (UV light) onto the wiring substrate S on which the ink has landed. The inkjet head 20 and UV irradiation unit 42 are fixed to the scanning unit 121 and moved (scanned) in a direction along the scanning guide unit 122 (the scanning direction, i.e., a direction intersecting the direction of movement of the conveyance table 131, orthogonal in this case). These movements may be performed using, for example, a linear motor. The nozzles of the inkjet head 20 are aligned across the width of the wiring substrate S. By setting the nozzle spacing to be sufficiently small, printing may be completed in one scan (single pass). Furthermore, by repeatedly scanning the inkjet head 20 multiple times while moving the wiring substrate S, ink ejection in multiple passes (interlaced) is possible.

[0022] FIG. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. As shown in FIG. The inkjet recording device 1 includes a transport unit 10, an inkjet head 20 (ink ejection unit), a head drive control unit 30, a fixing unit 40, a control unit 50, a storage unit 60, an ink heating unit 70, a display unit 81, an operation reception unit 82, and a communication unit 90. The control unit 50 and each unit are connected for communication via a bus or the like.

[0023] The transport unit 10 moves the inkjet head 20 relative to a medium on which an image (coating) is to be formed, in this case, the wiring substrate S. As described above, for example, the inkjet head 20 is movable in a predetermined direction (scanning direction) relative to the wiring substrate S, and the wiring substrate S is movable in a direction perpendicular to the scanning direction of the inkjet head 20.

[0024] The transport unit 10 has a scan driver 12 and a transport driver 13. The scan driver 12 performs scanning by moving the inkjet head 20 via the scanning unit 121. The scan driver 12 has, for example, a linear motor, and moves the inkjet head 20 directly or indirectly via a fixing member for the inkjet head 20, etc.

[0025] The transport drive unit 13 moves a mounting member such as a base (transport table 131) or a belt on which the wiring board S is placed, for example. The transport drive unit 13 is capable of reciprocating the mounting member.

[0026] The inkjet head 20 has a head driver 22 and a plurality of nozzles N, and ejects ink from the nozzles N in response to drive signals output by the head driver 22. The head driver 22 has an ejection selection IC 28 (Integrated Circuit) and an electromechanical conversion element 223. The ejection selection IC 28 performs a switching operation to output a drive signal corresponding to whether or not ink is ejected from each nozzle N and the amount of ink ejected, based on image data, to the electromechanical conversion element 223 corresponding to each nozzle N. The electromechanical conversion element 223 is, for example, a piezoelectric element, which changes shape in response to the input drive signal, and this shape change causes a pressure fluctuation in the ink in an ink flow path communicating with the nozzle N. The electromechanical transducer element 223 and the nozzle N constitute a recording element 26 .

[0027] The head drive control unit 30 includes a head control unit 31 and a drive waveform signal generation circuit 32. Based on the output data (digital data) of the drive waveform signal generation circuit 32, the head drive control unit 30 outputs a drive waveform signal (analog signal) related to ink ejection and other operations to the inkjet head 20 at a predetermined time period (ink ejection period). The drive waveform signal related to ink ejection may be a combination of multiple pulse signals. Alternatively, the head drive control unit 30 may be capable of outputting drive waveform signals with multiple different waveform patterns (including not only waveform but also changes in pulse length, amplitude, voltage value, etc.) according to the ink ejection volume. Alternatively, the head drive control unit 30 may be capable of outputting a number of consecutive drive pulses according to the ink droplet volume per pixel (multi-pulse method). In this case, ink droplets ejected by each drive pulse are caused to coalesce during flight or land within the same pixel range. The ink ejected from each nozzle to each pixel per pass (one cycle) may be an ink droplet volume that will provide a minimum thickness (for example, 15 μm) of an insulating film, which will be described later, taking into consideration the surface characteristics of the wiring substrate S, the temperature (viscosity characteristics) when the ink is ejected, and the time interval between the ink droplet landing and its initial deposition due to UV light irradiation by the UV irradiation unit 42. In addition to ejecting ink, a non-ejection waveform pattern for stirring the ink within the nozzle N may also be output.

[0028] In addition to or instead of the above method, the amount of ink ejected (amount of impact) per pixel can also be controlled by other methods, such as adjusting the state of the ink liquid surface (meniscus) in the nozzle N by adjusting the ink pressure (normally a negative pressure is used to prevent ink leakage) when no drive pulse is applied, or by changing or adjusting the drive frequency. The amount of ink droplets can also be adjusted by applying a drive pulse of an appropriate non-ejection waveform pattern before the ink ejection waveform pattern, causing vibrations in the meniscus, and then applying a drive pulse of a drive waveform pattern.

[0029] The ink ejected by the inkjet recording apparatus 1 of this embodiment is, for example, solder resist ink. The solder resist ink is ink ejected onto the wiring board S to form an insulating film (solder resist) on the wiring board S. Here, the solder resist ink is cured by irradiation with a predetermined energy beam, in this case, ultraviolet (UV) rays. Furthermore, the solder resist ink is thermosetting.

[0030] The solder resist ink contains a compound having a thermosetting functional group. The thermosetting functional group may be any of a variety of well-known groups, including those having an isocyanate group (particularly two or more). Furthermore, a polyfunctional isocyanate compound (blocked isocyanate) in which the isocyanate group is protected with a thermally dissociable blocking agent is preferable from the viewpoint of improving the ink's storability at high temperatures and high humidity. The thermally dissociable blocking agent is not particularly limited, but may be, for example, a compound containing at least one of an oxime compound, a pyrazole compound, and an activated ethylene compound.

[0031] Alternatively, the thermosetting functional group may be, for example, a (meth)acrylic group, particularly a (meth)acrylate compound having an imide group such as imide acrylate. The imide group has high polarity, so it can provide strong adhesion to metal (i.e., wiring on the wiring substrate S). Furthermore, due to its strong cohesive force, it has little effect on metal adhesion even under high humidity conditions.

[0032] On the other hand, the solder resist ink contains, as components involved in curing by irradiation with UV light, a compound having a photopolymerizable functional group and a photopolymerization initiator. The photopolymerizable compound may be any compound that polymerizes or undergoes a crosslinking reaction to form crosslinks and cure the ink when irradiated with active energy rays (UV light), and examples thereof include radically polymerizable compounds and cationically polymerizable compounds. Polymerizable compounds having an imide group, such as the above-mentioned imide acrylate, also have UV curing properties. The photopolymerization initiator is selected according to the type of photopolymerizable functional group (compound) described above.

[0033] The solder resist ink also contains a gelling agent. The ink is in a gel state at room temperature, and undergoes a phase change between a gel state and a sol state depending on the temperature, resulting in a sudden change in viscosity. The gelling agent may be, for example, at least one of compounds represented by the following general formula (G1) or (G2): General formula (G1): R1-CO-R2 General formula (G2): R3-COO-R4 In these formulas, R1 to R4 each independently represent an alkyl chain having a linear portion with 12 or more carbon atoms and which may be branched. Such a gelling agent is dispersed in the cured film without inhibiting the curing of the ink. This improves the moisture resistance of the ink film (solder resist) formed by printing and prevents moisture from penetrating into the cured film. This also improves insulation reliability. Ink containing this gelling agent is also preferable in that it has good pinning properties and is easily able to form a coating that achieves both fine lines and film thickness (i.e., it has excellent fine line reproducibility even when a film thickness is required).

[0034] The fixing unit 40 fixes the ink that has landed on the wiring substrate S. As described above, ink has properties of both heat curing and curing by active energy rays (UV light). Accordingly, the fixing unit 40 includes a UV irradiation unit 42 and a heat fixing unit 43. Although not particularly limited, here, the UV irradiation unit 42 is fixed to the scanning unit 121 together with the inkjet head 20 as described above and scanned to temporarily fix the ink that has landed on the wiring substrate S. The UV irradiation unit 42 includes, for example, a light-emitting diode (LED) that emits ultraviolet light, and irradiates ultraviolet light (UV light) by applying a voltage to the LED to pass a current through it. The UV irradiation unit 42 may also include a light-shielding wall, etc., to prevent the UV light from leaking outside the desired irradiation range, as necessary.

[0035] The configuration for emitting UV light in UV irradiation unit 42 is not limited to an LED. UV irradiation unit 42 may have, for example, a mercury lamp. Furthermore, if the ink has the property of being cured and fixed when exposed to active energy rays other than UV light, UV irradiation unit 42 may have a known emission source (light source) that emits active energy rays that cure the ink, instead of the configuration for emitting UV light described above.

[0036] The heat fixing unit 43 has a heat generating element such as an infrared heater or an electric heater, and directly or indirectly heats the wiring substrate S to permanently fix the temporarily fixed ink. The heat fixing unit 43 is positioned so that, after the ink has landed and temporarily fixed by the inkjet head 20 and the UV irradiation unit 42, the main fixing is performed, for example, after the wiring substrate S is transported downstream in the transport direction. The heat fixing unit 43 may be positioned within a housing that surrounds the wiring substrate S and the transport member on which it is placed, so that the heat generated by the heat generating element is retained within the housing and the curing temperature is efficiently maintained at an appropriate temperature. In this case, it is not necessary to constantly operate the heat generating element during heating; it is sufficient that the temperature is maintained within the set range for the curing temperature.

[0037] It should be noted that heat fixing unit 43 may be provided in a separate heat fixing device, rather than being provided in inkjet recording apparatus 1. Furthermore, the heat fixing device may be a post-processing device of inkjet recording apparatus 1, and conveying unit 10 may be able to feed wiring board S directly into the heat fixing device located on an extension of the direction of movement of conveying table 131, or may have a configuration in which wiring board S removed from conveying table 131 of inkjet recording apparatus 1 is set again in the heat fixing device, or the user may manually move wiring board S.

[0038] The control unit 50 comprehensively controls the operation of each unit of the inkjet recording apparatus 1. The control unit 50 has a CPU 51 (Central Processing Unit) and a RAM 52 (Random Access Memory). The CPU 51 is a hardware processor that performs various arithmetic processing, and executes a program 61 stored in a storage unit 60. The RAM 52 provides the CPU 51 with memory space for control and stores temporary data.

[0039] The storage unit 60 includes at least a nonvolatile memory and stores a program 61 and setting data. Examples of nonvolatile memory include flash memory. Nonvolatile memory may also include a hard disk drive (HDD). The storage unit 60 may also include RAM for temporarily storing image data 62 indicating the area to be coated with the coating to be formed, and drive data for the inkjet head 20 processed and generated based on the image data. The program 61 includes control programs for the ink ejection control process and the coating area adjustment process, which will be described later. The setting data includes thickness correspondence information 63, which includes information regarding the amount of ink ejected according to the thickness of the coating to be formed. The resolution of the information on the coating area (setting area) indicated by the image data 62 is not particularly limited, but may be, for example, 1440 dpi (dots per inch) or higher.

[0040] The ink heating unit 70 heats the ink in the inkjet head 20 and the ink supply path to the inkjet head 20, maintaining it at an appropriate temperature. As described above, ink undergoes a phase change between sol and gel depending on the temperature. If the ink remains in a gel state at room temperature, the ink lacks fluidity and is difficult to supply and eject. The ink heating unit 70 heats the ink to an appropriate temperature, maintaining the ink in a sol state and enabling it to be supplied and ejected properly. The appropriate temperature may be determined so that the ink quickly dissipates heat from the wiring substrate S or the like after landing on the wiring substrate S, and gels within an appropriate time. The ink heating unit 70 includes, for example, an electric heating wire and a sheet member (e.g., rubber) that is heated by the heat generated by the electric heating wire. The sheet member contacts the ink supply path or the like and transfers heat to heat the ink.

[0041] The display unit 81 displays various statuses, menus, and the like on a display screen under the control of the control unit 50. The display unit 81 has, for example, a display screen and LED (Light Emitting Diode) lamps. The display screen is not particularly limited, but is, for example, an LCD (Liquid Crystal Display). The LED lamps are lit (including blinking) by the control unit 50 in positions and colors corresponding to the power supply status, abnormality occurrence status, and the like.

[0042] The operation reception unit 82 receives input operations from an external user or the like and outputs the operations as input signals to the control unit 50. The operation reception unit 82 includes, for example, a touch panel and push button switches. The touch panel may be positioned so as to overlap the display screen of the display unit 81. The operation reception unit 82 may also include various other operation switches and the like.

[0043] The communication unit 90 controls transmission and reception of data (signals) with external devices, etc., in accordance with a predetermined communication standard. The communication unit 90 controls communication in accordance with, for example, a LAN (Local Area Network) standard. The communication unit 90 may also be connectable to peripheral devices, etc., in accordance with the USB (Universal Serial Bus) standard.

[0044] Next, the printing operation of the inkjet recording apparatus 1 of this embodiment will be described. In the inkjet recording device 1, during scanning, ink is ejected from the inkjet head 20 onto pixels on a certain scanning line (including multiple rows of nozzles N if they are arranged in the scanning direction) for each ink ejection cycle, and then the inkjet head 20 is moved by the scan driver 12 so that the nozzles N face pixels on other scanning lines. When ejecting ink in multiple passes, scanning is performed while changing the positional relationship between the wiring substrate S on the transport table 131 and the nozzles N (pixels on the scanning line to which ink is ejected). UV irradiation by the UV irradiation unit 42 is performed for each scan.

[0045] 3A and 3B are diagrams illustrating the printing range of the wiring substrate S. FIG. The solder resist ink is used to provide an insulating film I (solder resist) on the wiring board S. The printing range (i.e., the coverage) of this insulating film I is determined according to the signal wiring C on the insulating substrate R on the wiring board S, and is stored as image data 62. The insulating film I includes circular, annular, rectangular, thin-line, or other openings and notches according to the range of the connection pads P where the signal wiring C located on the insulating substrate R is connected to electronic components, external signal lines, etc. The thickness of the insulating film I is at least as thick as necessary to ensure insulation, and is not particularly limited, but is, for example, in the range of 15 to 30 μm.

[0046] As shown in Figure 3B, the surface of this insulating film I has an uneven surface that corresponds to the unevenness of the wiring substrate S, which depends on the presence or absence of signal wiring C. At the uneven portions of the uneven surface, the ink that lands tends to flow toward the recessed portions before hardening and settling. As a result, if ink is simply ejected uniformly, there may be no ink remaining near the edge (shoulder portion Es) of the upper step (on the convex portion side), causing the printing to stop, exposing the signal wiring C and resulting in a loss of insulation.

[0047] In the inkjet recording device 1 of this embodiment, during scanning (in the case of multi-pass scanning, at least in one of the passes), the ink ejection amount (amount of ink droplets ejected and landed at each pixel position) of at least one of the step portion, the lower flat portion connected to the step portion, and the upper flat portion is increased compared to the ink ejection amount of other flat portions.

[0048] FIG. 4 shows three examples of the distribution of ink ejection amounts. The signal wiring C typically has a slightly inclined region E (slope) on its side, rather than rising perfectly vertically from the insulating substrate R. A lower connection portion LC (lower adjacent portion) of a predetermined width on the insulating substrate R adjacent to the inclined region E and an upper connection portion UC (upper adjacent portion) of a predetermined width on the signal wiring C adjacent to the inclined region E (i.e., forming the inclined region E at both ends) are defined. The ink discharge volume (ejected ink droplet volume) on at least one selected region among the inclined region E, the lower connection portion LC, and the upper connection portion UC (collectively referred to as the three step regions (three regions)) is set (increased) to be larger than the ink discharge volume (ejected ink droplet volume) on the remaining flat portion LF of the insulating substrate R and the central flat portion UF of the signal wiring C (other than the three regions). The inclined region E is not limited to a flat surface, but may be a curved surface or have irregularities relative to the average inclined surface. The width of the inclined region E is not particularly limited, but is typically narrower than its height, so that it can be considered a step. Similarly, the predetermined widths of the upper and lower connecting portions UC and LC are not particularly limited as long as they are approximately one pixel. For example, the predetermined widths of the upper and lower connecting portions UC and LC may be approximately the diameter (although not particularly limited, typically approximately the same as or larger than the width of one pixel, e.g., 10.6 μm at 2400 dpi, and often approximately 1 to 15 times that width) of the landing area of ​​ink droplets (which may be based on the largest (increased) of multiple levels of ink ejection volume) landing on the flat portions UF and LF (if the landing areas differ between the flat portions UF and LF due to differences in material, either one may be used as the reference, or the average value may be used as the reference). In other words, the predetermined widths of the upper and lower connecting portions UC and LC may be approximately the landing area of ​​ink that connects with ink droplets that land on the inclined region E and / or a width that reliably includes ink droplets whose landing areas at least partially span the inclined region E. The predetermined width may be different between the upper connection portion UC and the lower connection portion LC (the predetermined width of the upper connection portion UC may be determined based on the landing range on the flat portion UF, and the predetermined width of the lower connection portion LC may be determined based on the landing range on the flat portion LF). Furthermore, when the wiring width or the wiring spacing is narrow, there may be portions that do not have the flat portion UF or the flat portion LF depending on the situation.

[0049] In the example shown by pattern A, only the ink ejection amount to the inclined region E is made larger than the ink ejection amount to other portions. In the example shown by pattern B, the ink ejection amount to the upper connection portion UC is also increased in addition to the ink ejection amount to the inclined region E. Conversely, in the example shown by pattern C, the ink ejection amount to the lower connection portion LC is also increased in addition to the ink ejection amount to the inclined region E. In this case, the increase in the ink ejection amount may differ between the three step regions where the ink ejection amount increases. Here, the increase in the ink ejection amount to the inclined region E is larger than the increase in the lower connection portion LC. Alternatively, it may be possible to set the increase in the ink ejection amount to a non-uniform (uneven) ink ejection amount independently for each of the three step regions.

[0050] 5A to 5C are diagrams illustrating an increase in the amount of ink ejected. The size of each of the three step regions and which regions to increase the ink ejection amount in may be determined based on the material and surface characteristics of the wiring substrate S. For example, by ejecting more ink onto areas with high wettability, ink shortage due to ink flowing down can be suppressed. As shown in Figure 5A, when the wettability of the insulating substrate R is higher than that of the signal wiring C, more ink is ejected onto the inclined region E and the lower connection portion LC. Here, the size of the three circles indicates the amount of ink ejected directly below.

[0051] As shown in FIG. 5B, if the wettability of the insulating substrate R is lower than that of the signal wiring C, more ink may be ejected onto the inclined region E and the upper connection portion UC. As shown in FIG. 5C, if both the insulating substrate R and the signal wiring C are made of materials with low wettability (here, the level of wettability may be determined, for example, by comparing the spread size of the landed ink with a reference size), only the amount of ink ejected onto the inclined region E may be increased. In this case, the influence of ink droplets joining together with adjacent landed ink droplets and being pulled and spreading may be greater than the spreading characteristics of the ink droplets on the wiring substrate S. Therefore, by not increasing the amount of ink ejected onto the upper connection portion UC and the lower connection portion LC, it may be possible to make it relatively difficult for ink droplets that land on the inclined region E to be pulled to both sides.

[0052] In practice, the boundaries of each pixel often do not exactly coincide with the boundaries of the three-step regions, resulting in some ink droplets landing across multiple regions. In such cases, the corresponding regions may be determined simply based on the impact center position (e.g., center of gravity position; flow due to tilt, etc., need not be taken into account), or the ejection amount may be calculated and adjusted based on the proportion of ink droplets belonging to multiple regions and the ink ejection amount for each region. The widths (predetermined widths) of the upper and lower connecting portions UC and LC may be fixed, or may be determined based on the ink spreading characteristics (material) and the size (height) of the steps in each region. The widths of the upper and lower connecting portions UC and LC may be different.

[0053] 6 is a flowchart showing the control procedure of the print control process by the CPU 51 (control unit 50) of this embodiment. This print control process is started when a print command is acquired together with image data indicating the coverage range from an external device or the like (the timing of acquiring the data and the command may be different).

[0054] When the print control process is started, the CPU 51 (control unit 50) acquires wiring pattern data of the wiring board S (step S101). The CPU 51 identifies the edges of the wiring, that is, step portions, from the wiring pattern data (step S102).

[0055] The CPU 51 acquires image data indicating the printing (ink ejection) range (step S103). The CPU 51 increases the amount of ink ejected to at least one of the three step regions in accordance with a predetermined condition for a portion of the image data range that overlaps with the edge position (step S104).

[0056] The CPU 51 adjusts the position of the wiring substrate S in accordance with the image data (step S105). The adjustment may be performed, for example, by determining an offset value or a rotation amount relative to the normal mounting position of the wiring substrate S. This adjustment may be performed automatically by the CPU 51, or may be performed partially through manual operation (such as input operation) by the user. The CPU 51 causes the inkjet head 20 to eject ink based on the changed image data, thereby printing the coating (insulating film I) (step S106).

[0057] The CPU 51 operates the UV irradiation unit 42 to irradiate the wiring board S with UV light, thereby temporarily curing the ink on the wiring board S (step S107). The CPU 51 heats the wiring board S to harden and fix the coating (insulating film I) (step S108). Then, the CPU 51 ends the print control process.

[0058] The above operation has been described for single-pass printing. However, in multi-pass printing, ink ejection in multiple scans, for example, two scans, is performed at equal intervals and in a complementary manner. In the case of three or more scans, ink ejection may be performed with the phase shifted at equal intervals for each scan. Alternatively, the pattern relating to the position and order of ink ejection in multi-pass printing may be based on other techniques. However, in the inkjet recording apparatus 1 (printing method) of this embodiment, multiple scans are not performed by controlling ink ejection for each pixel based on the number of times corresponding to the ink ejection amount. In other words, scans are performed in which ink is selectively ejected earlier and / or later only at positions where the ink ejection amount is increased, and control is not performed to eject ink uniformly in the remaining scans. In other words, in at least one scan, the ink ejection amount is non-uniform (excluding the presence or absence of ink ejection) depending on the ink droplet volume setting for each pixel.

[0059] 7A and 7B are diagrams illustrating an example of the ink ejection amount when printing is performed with two scans (two passes). FIG. 7A shows an example in which the ink ejection amount is increased in the lower connection portion LC in each of the first and second passes.

[0060] FIG. 7B shows a schematic diagram of the ink ejection amount (landing amount) for each pixel position. In reality, the ink landing area is larger than the pixel area, but for the sake of explanation, the landing area for the normal ink ejection amount is aligned with the pixel area, and pixels for which the ink ejection amount is increased are indicated by circles larger than the pixel area. In FIG. 7B, for example, ink is ejected to the pixels in the top row (horizontally aligned), and the target pixels for ink ejection move row by row to the rows below in accordance with the scan for each ejection cycle. Note that the extension direction of the shoulder and the scanning direction are shown as parallel, and the nozzles for which the ink ejection amount is increased remain fixed during the scan. However, if the extension direction of the shoulder and the scanning direction are not parallel, the nozzles for which the ink ejection amount is increased will move sequentially according to the scanning position.

[0061] In this way, by combining the ejections in two passes, a continuous distribution is obtained in which the amount of ink ejected into the lower connection portion LC is greater than the amount of ink ejected into other portions.

[0062] FIG. 8 is a diagram illustrating a first modification of the ink ejection amount when printing is performed with two scans (two passes). Here, two passes of ink ejection are performed, with the amount of ink ejected to the lower connection portion LC and the inclined region E being set to be greater than the amount of ink ejected to other regions. In this case, the timing may be controlled so that the ink ejection amount is increased only to the lower connection portion LC in the first scan (pass 1), and then the ink ejection to the increased inclined region E is performed in the second scan (pass 2). By first supplying more ink to the lower connection portion LC and temporarily curing it, it is possible to prevent the ink ejected onto the inclined surface in the second scan from easily spreading toward the lower connection portion LC.

[0063] As described above, when the scanning direction and the extension direction of the shoulder portion are not parallel, it is difficult to perfectly align the order of ejection. However, when the three step regions each have a width equivalent to multiple pixels, or when the same amount of ink cannot be ejected from all pixels due to the spread of the ink droplets and the upper limit of the ejection amount per unit area on the wiring substrate S, the pixels for which the ink ejection amount is selectively increased may be set to be ejected as much as possible in the order described above.

[0064] FIG. 9 is a diagram showing a second modification of the ink ejection amount when printing is performed with two scans. In this diagram, the ink ejection amount to the lower connection portion LC and the upper connection portion UC is increased by two-pass ink ejection. In this case, the increased ink ejection to the lower connection portion LC and the upper connection portion UC is performed in the first pass. In cases where the slope of the sloped region E is steep (close to vertical) or the wettability of the conductor surface is high, it may be possible to more reliably prevent shoulder exposure by increasing the ink ejection amount to the lower connection portion LC and the upper connection portion UC rather than increasing the ink ejection amount to the sloped region E itself.

[0065] In this example, the ink ejection amount is uniform during the second scan, meaning that non-uniform ink ejection distribution is sufficient for at least one of the multiple scans.

[0066] 10A to 10C are diagrams showing a third modification of the ink ejection amount when printing is performed with two scans. To adjust the ink ejection amount for the three step regions more flexibly and easily, instead of fixing the ink ejection amount for each region, it is possible to combine multiple types of ink ejection amounts to obtain an average ink ejection amount that corresponds to their ratio.

[0067] In this example of the ink ejection amount distribution in Figure 10A, as shown in Figures 10B and 10C, during the first scan, large ink droplets and small (normal) ink droplets are alternately ejected for each dot at the upper connection portions UC and lower connection portions LC, and on average, an intermediate ink droplet volume between the large and small ink droplets is applied to these upper connection portions UC and lower connection portions LC. The average droplet volume can be changed by appropriately adjusting the ratio of large to small ink droplets within a range that does not cause unevenness in the ink ejection volume. This eliminates the need to finely control the ink ejection waveform pattern to obtain three or more levels of ink ejection volume.

[0068] 11A to 11C are diagrams showing a fourth modification of the ink ejection amount when printing is performed with two scans. To obtain the ink ejection amount distribution shown in Fig. 11A, in the first scan, large ink droplets are ejected for each pixel onto the lower connection portion LC, resulting in a larger droplet amount applied on average than normal, as shown in Fig. 11B. Also, in the second scan, large and small ink droplets are alternately ejected for each pixel onto the inclined region E, resulting in an average droplet amount applied to the inclined region E that is intermediate between the normal ink ejection amount and the ink ejection amount of large ink droplets, as shown in Fig. 11C.

[0069] Note that the timing for ejecting large ink droplets is the same in the two scans, i.e., in Figures 11B and 11C, the odd-numbered ink droplets from the top are large ink droplets. However, this is not limited to this. The timing may be alternated, for example, so that the even-numbered ink droplets from the top are large ink droplets in the second scan.

[0070] The combinations of ink ejection of multiple ink droplet volumes as shown in Modifications 3 and 4 are not limited to ink ejection in the case of multi-pass printing. Similarly, ink ejection of multiple ink droplet volumes may be combined in the case of single-pass printing to provide an average droplet volume. Furthermore, the positioning of large and small ink droplets may be set by various other appropriate timing settings. For example, the size of each ink droplet may be determined stochastically at random, or the timing of large and small ink droplets may be dispersed by dithering or the like.

[0071] 12A to 12C are diagrams showing examples of drive waveforms. For example, the amount of ink droplets ejected by the drive waveform of Fig. 12B is smaller than the amount of ink droplets ejected by the waveform shown in Fig. 12A. Also, in the multi-drop drive waveform pattern shown in Fig. 12C, by removing a portion of the maximum five consecutive pulses that can be output during an ink ejection cycle, for example, a predetermined number from the beginning, it is possible to adjust the amount of ink droplets corresponding to the number of pulses so that they coalesce (or do not coalesce) during flight and land at the same pixel position.

[0072] As described above, the printing method using the inkjet recording apparatus 1 of this embodiment is a printing method in which ink is ejected onto a wiring substrate S having a stepped portion, the stepped portion including three regions: an inclined region E forming a step, an upper connection portion UC of a predetermined width adjacent to the inclined region E, and a lower connection portion LC of a predetermined width adjacent to the inclined region E, and includes a discharge amount setting step of increasing the amount of ink droplets per ink discharge cycle ejected onto at least one selected region out of these three regions compared to the amount of ink droplets ejected onto the other regions. The ink droplet amount referred to here is the average discharge amount for each region, and is not limited to increasing the discharge amount for all pixels. In this way, by ejecting a larger amount of ink droplets near the inclined region E than usual, even if the ink spreads somewhat on the landing surface (wiring substrate S), it is possible to reduce the possibility that the ink covering the inclined region E, particularly the upper corner (shoulder Es), will run out and become exposed. This makes it possible to more reliably print on a printing surface with a step, i.e., to more reliably cover the ink landing area on the printing medium surface with ink.

[0073] The ejected ink also contains a gelling agent, which causes the ink to gel when it lands on the surface and quickly adhere to the surface, preventing the ink from spreading along the surface and enabling more accurate printing.

[0074] Furthermore, the distribution of ink droplet volume in the selected area is uneven. In addition to flowing down the steps, the ink spreads differently depending on the material of the wiring substrate S and the properties of the ink, so by adjusting the distribution of ink droplet volume accordingly, this printing method can more reliably perform printing with less unevenness.

[0075] The selected areas include at least two of the three areas, and the ink droplet volumes for the at least two areas are different from each other. The ink droplet volume distribution may be determined for each of the three stepped areas. Even if the ink droplet volume is set for each of the three stepped areas according to the difference between the flat and inclined portions and the material of each portion, proper printing results can be easily and reliably obtained without causing printing omissions that unnecessarily expose the wiring substrate S.

[0076] The selected area is determined according to the material of the wiring substrate S. As described above, the spreading (wettability) is determined by the combination of the material of the wiring substrate S and the ink characteristics, so by increasing the amount of ink ejected to an appropriate range according to the material of the wiring substrate S, it is possible to avoid ink overcoating and perform printing with higher accuracy.

[0077] The wiring board S includes an insulating substrate R and signal wiring C located on the insulating substrate R, and the ink is a solder resist ink. That is, in the printing operation for forming an insulating film on the wiring board S using solder resist ink, the ink discharge amount is increased and adjusted at the step portion as described above, so that the insulating properties of the coating film can be more reliably obtained.

[0078] The ink is cured by irradiation with a predetermined energy beam. By irradiating the ink that has landed on the wiring substrate S with energy beams, the ink is quickly cured and fixed, particularly by temporarily fixing the ink, which prevents the ink from flowing down over steps and allows the ink to cover the desired area.

[0079] The predetermined energy rays are ultraviolet rays. By irradiating the ink landing surface with ultraviolet rays at an appropriate timing, the ink can be cured in a desired state according to the timing.

[0080] The ink may also be thermosetting, which can prevent the ink from becoming a sol due to temperature changes after fixing, causing it to lose its shape and flow down.

[0081] The inkjet recording apparatus 1 of this embodiment also includes an inkjet head 20 that ejects ink, and a control unit 50. When printing by ejecting ink onto a wiring substrate S having a stepped portion including three regions: an inclined region E forming a step, an upper connection portion UC of a predetermined width adjacent to the inclined region E, and a lower connection portion LC of a predetermined width adjacent to the inclined region E, the control unit 50 (CPU 51) increases the amount of ink droplets per ink ejection cycle ejected onto at least any selected region of these three regions compared to the amount of ink droplets ejected onto regions other than the three regions. By controlling the ink discharge in this way in the inkjet recording apparatus 1, even if the ink spreads somewhat on the landing surface (wiring substrate S), it is possible to reduce the possibility that the ink covering the inclined region E, particularly the upper end corner (shoulder portion Es), will run out and become exposed. This makes it possible to more reliably print on a printing surface having steps.

[0082] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the ink ejection amount is determined individually or uniformly for the three step regions, but the ink ejection amount does not have to be uniform within each region. For example, the ink ejection amount may be gradually reduced from the upper connection portion UC to the upper flat portion UF, gradually approaching and connecting to the normal ink ejection amount in the flat portion UF.

[0083] Furthermore, the ink ejection amount may be increased only in a part of the inclined region E, such as the upper half thereof.

[0084] In addition, in the above embodiment, both the inkjet head 20 and the conveying table 131 are movable, but in the case of single-pass printing only, it is sufficient that only one of them, for example the conveying table 131, is movable, in which case the inkjet head 20 may be fixed.

[0085] Furthermore, in the above embodiment, the ink contains a gelling agent, but the ink may not contain a gelling agent and may be ink whose viscosity can change depending on temperature or other factors.

[0086] Furthermore, in the above embodiment, the ink ejected is described as having both UV curing and heat curing properties, but the ink may have only one of these properties, or may be ink that hardens when exposed to energy rays other than UV light.

[0087] Furthermore, in the above embodiment, an insulating film is printed on the wiring substrate S, but the present invention is not limited to this. For example, it may be a protective film printed on a substrate having other steps (mainly those that do not or only little penetrate ink, such as a resin member or film), and the above technology may be applied to lines, figures, patterns, etc. formed on a substrate, not just coatings, to similarly suppress image quality or structural abnormalities such as discontinuities at the step portions. In these cases, the film thickness (ink discharge amount) may be changed as appropriate depending on the application, etc. In addition, the specific configurations, contents and procedures of the processing operations, etc. shown in the above embodiments can be modified as appropriate without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalents. [Industrial Applicability]

[0088] The present invention can be used in a printing method and an inkjet recording apparatus. [Explanation of symbols]

[0089] 1. Inkjet recording device 10 Conveying section 12 Scanning driver 121 Scanning unit 122 Scanning guide unit 13 Conveyor drive unit 131 Transport Platform 132 Transport guide section 20 Inkjet head 22 Head drive unit 223 Electromechanical transducer 26 Recording element 28 Discharge selection IC 30 Head drive control unit 31 Head control unit 32 Drive waveform signal generation circuit 40 Fixing section 42 UV irradiation section 43 Heat fixing unit 50 control section 60 Storage section 61 Programs 62 Image data 63 Thickness information 70 Ink heating unit 81 Display section 82 Operation reception section 90 Communications Department C Signal wiring E slope area Es Shoulder I. Insulating film LC lower connection N nozzle P Connection pad R insulating substrate S wiring board UC upper connection part

Claims

1. A printing method in which a solder resist ink is ejected onto a substrate having a step between an insulating substrate and a wiring conductor located on the insulating substrate, the step portion includes three regions: an inclined portion forming a step, an upper adjacent portion having a predetermined width adjacent to the inclined portion, and a lower adjacent portion having a predetermined width adjacent to the inclined portion; the upper adjacent portion is a horizontal flat portion on the upper surface of the wiring conductor, and the lower adjacent portion is a horizontal flat portion on the upper surface of the insulating substrate, a discharge amount setting step of increasing the amount of ink droplets per ink discharge cycle discharged onto a selected area of ​​the three areas, including at least the upper adjacent portion and the lower adjacent portion, compared to the amount of ink droplets discharged onto areas other than the three areas, Printing method.

2. The printing method according to claim 1 , wherein the solder resist ink contains a gelling agent.

3. 3. The printing method of claim 1, wherein the distribution of the ink droplet volume over the selected area is non-uniform.

4. the ink droplet volumes for each of the selected regions are different from one another; The printing method according to claim 3.

5. The printing method according to any one of claims 1 to 4, wherein the selected area is determined according to the material of the base material.

6. 6. The printing method according to claim 1, wherein the solder resist ink is cured by irradiation with a predetermined energy ray.

7. 7. The printing method according to claim 6, wherein the predetermined energy ray is ultraviolet light.

8. 8. The printing method according to claim 1, wherein the solder resist ink is thermosetting.

9. a discharge unit that discharges ink; A control unit; Equipped with The control unit A substrate having an insulating substrate and a wiring conductor located on the insulating substrate, the substrate having a step portion including three regions: an inclined portion forming a step, an upper adjacent portion of a predetermined width adjacent to the inclined portion, and a lower adjacent portion of a predetermined width adjacent to the inclined portion, the upper adjacent portion being a horizontal flat portion on the top surface of the wiring conductor, and the lower adjacent portion being a horizontal flat portion on the top surface of the insulating substrate, the amount of ink droplets ejected per ink ejection cycle onto a selected area including at least the upper adjacent portion and the lower adjacent portion of the three areas is increased compared to the amount of ink droplets ejected onto areas other than the three areas; Inkjet recording device.

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