Printing method and inkjet recording device

Abstract

To provide a printing method and an inkjet recording device which enable reliably printing on a printing medium surface having a step.SOLUTION: 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.SELECTED DRAWING: Figure 4

Description

Technical Field

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[0001] This invention relates to a printing method and an inkjet recording apparatus.

Background Art

[0002] There is a technique of performing a printing operation by discharging ink onto a printing medium surface having a three-dimensional structure. In Patent Document 1, a technique is disclosed in which, in order to suppress the ink landing on the convex portion from flowing out to the concave portion and the ink amount on the convex portion from being insufficient, more ink is discharged near the center than at the edge of the convex portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the ink flows down at the stepped portion of the three-dimensional structure, the ink is likely to flow down at the corner of the step, and there is a problem that the printing medium surface may be exposed without remaining ink, and the desired printing cannot be surely performed.

[0005] An object of this invention is to provide a printing method and an inkjet recording apparatus capable of more surely performing printing on a printing medium surface having a step.

Means for Solving the Problems

[0006] To achieve the above object, the invention according to claim 1 is a printing method of discharging a solder resist ink onto a base material having a stepped portion between an insulating substrate and a wiring conductor located on the insulating substrate and having a wettability higher than that of the insulating substrate, <s The stepped portion includes three regions: a stepped inclined portion, 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 the upper surface of the wiring conductor and is a horizontal flat portion, and the lower adjacent portion is the upper surface of the insulating substrate and is a horizontal flat portion. The method includes a discharge volume setting step in which the amount of ink droplets discharged per ink discharge cycle to the upper adjacent portion and the inclined portion of the three regions is increased compared to the amount of ink droplets discharged to the lower adjacent portion. fruit, The distribution of ink droplet volume in the upper adjacent portion and the inclined portion is non-uniform within their respective regions.

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

[0009] Furthermore, the invention described in claim 4 is the printing method described in claim 3, The amount of ink droplets on the upper adjacent portion and the inclined portion are different from each other.

[0010] Furthermore, the invention described in claim 5 relates to the printing method described in any one of claims 1 to 4, The solder resist ink is cured by irradiation with a predetermined energy ray.

[0011] Furthermore, the invention described in claim 6 is the printing method described in claim 5, The aforementioned predetermined energy ray is ultraviolet light.

[0012] Furthermore, the invention described in claim 7 relates to the printing method described in any one of claims 1 to 6, The solder resist ink is thermosetting.

[0013] Furthermore, claims 7 The invention described is, The ejection unit that ejects ink, Control unit and Equipped with, The control unit, A base material having a step portion between an insulating substrate and a wiring conductor located on the insulating substrate and having a wettability higher than that of the insulating substrate, the base material having 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. When performing printing by discharging solder resist ink onto the base material, 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. Increase the amount of ink droplets per ink discharge cycle discharged to the upper adjacent portion and the inclined portion among the three regions compared to the amount of ink droplets discharged to the lower adjacent portion. The distribution of the amount of ink droplets in the upper adjacent portion and the inclined portion is non-uniform within each respective region. An inkjet recording apparatus.

Advantages of the Invention

[0014] According to the present invention, there is an effect that printing can be more reliably performed on a printing medium surface having a step.

Brief Description of the Drawings

[0015] [Figure 1A] It is a front view for explaining the schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 1B] It is a plan view of an inkjet recording apparatus. [Figure 2] It is a block diagram showing the functional configuration of an inkjet recording apparatus. [Figure 3A] It is a diagram for explaining the printing range of a wiring board. [Figure 3B] It is a diagram for explaining the printing range of a wiring board. [Figure 4] Three types of examples of the distribution of ink discharge amounts are shown. [Figure 5A] It is a diagram for explaining the increase in ink discharge amount. [Figure 5B] It is a diagram for explaining the increase in ink discharge amount. [Figure 5C]This diagram illustrates the increase in ink ejection volume. [Figure 6] This flowchart shows the control procedure for the print control process. [Figure 7A] This diagram illustrates an example of ink ejection volume when printing with two scans. [Figure 7B] This diagram illustrates an example of ink ejection volume when printing with two scans. [Figure 8] This figure illustrates a modified example of ink ejection volume when printing with two scans. [Figure 9] This figure illustrates a modified example of ink ejection volume when printing with two scans. [Figure 10A] This figure illustrates a third variation of the ink ejection amount when printing with two scans. [Figure 10B] This figure illustrates a third variation of the ink ejection amount when printing with two scans. [Figure 10C] This figure illustrates a third variation of the ink ejection amount when printing with two scans. [Figure 11A] This figure illustrates a modified example of ink ejection volume when printing with two scans (part 4). [Figure 11B] This figure illustrates a modified example of ink ejection volume when printing with two scans (part 4). [Figure 11C] This figure illustrates a modified example of ink ejection volume when printing with two scans (part 4). [Figure 12A] This figure shows an example of a drive waveform. [Figure 12B] This figure shows an example of a drive waveform. [Figure 12C] This figure shows an example of a drive waveform. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the present invention will be described based on the drawings. Figure 1A is a front view illustrating the schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. Figure 1B is a plan view of the inkjet recording apparatus 1.

[0017] The inkjet recording device 1 includes an inkjet head 20 (ejection 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.

[0018] In the inkjet recording apparatus 1 of this embodiment, the target of ink ejection is, for example, a wiring board S (substrate). This wiring board S is placed on a transport table 131. The transport table 131 can move along a transport guide section 132, such as a rail, in the direction of transport (transport direction, sub-scanning direction) while the wiring board S is placed on it. The wiring board S has substantially flat conductors (wiring conductors) that form signal wiring on an insulating substrate. The conductors are not particularly limited, but for example, copper (copper foil). Because these signal wirings protrude from the insulating substrate surface, the wiring board S has stepped portions. Furthermore, the deposited ink does not penetrate into the interior of the wiring board S, but rises up on the surface, hardens, and is fixed. Here, the insulating substrate surface is flat, and the direction perpendicular outward to this plane is considered upward.

[0019] The inkjet head 20 has nozzles N (see Figure 2) and ejects ink from these nozzles N onto the wiring board S. The amount of ink ejected to each pixel area in each ink ejection cycle can be selected from multiple levels. The UV irradiation unit 42 irradiates the wiring board S onto which the ink has landed with ultraviolet light (UV light). The inkjet head 20 and the UV irradiation unit 42 are fixed to the scanning unit 121 and are moved (scanned) in a direction along the scanning guide unit 122 (scanning direction; that is, a direction that intersects with the direction of movement of the transport table 131, in this case, a perpendicular direction). For example, a linear motor may be used for these movements. The nozzles of the inkjet head 20 are arranged across the width of the wiring board S, and by setting the nozzle spacing to be sufficiently small, it may be possible to complete printing in a single scan (single pass). Alternatively, by repeatedly scanning the inkjet head 20 multiple times while moving the wiring board S, ink ejection in multi-pass (interlaced) mode is possible.

[0020] Figure 2 is a block diagram showing the functional configuration of the inkjet recording device 1. The inkjet recording device 1 includes a transport unit 10, an inkjet head 20 (ink ejection unit), a head drive control unit 30, a fuser unit 40, a control unit 50, a storage unit 60, an ink heating unit 70, a display unit 81, an operation reception unit 82, a communication unit 90, and the like. The control unit 50 and each unit are connected by communication via a bus or the like.

[0021] The transport unit 10 moves the inkjet head 20 relative to the medium on which the image (film) is to be formed, in this case the wiring board S. As described above, for example, the inkjet head 20 is movable in a predetermined direction (scanning direction) relative to the wiring board S, and the wiring board S is movable in a direction perpendicular to the scanning direction of the inkjet head 20.

[0022] The transport unit 10 includes a scanning drive unit 12 and a transport drive unit 13. The scanning drive unit 12 performs scanning by moving the inkjet head 20 with the scanning unit 121. The scanning drive unit 12 has, for example, a linear motor and moves the inkjet head 20 directly or indirectly via a fixing member of the inkjet head 20.

[0023] The transport drive unit 13 moves, for example, a base (transport table 131) on which the wiring board S is placed, or a mounting member such as a belt. The transport drive unit 13 is capable of moving the mounting member back and forth.

[0024] The inkjet head 20 has a head drive unit 22 and a plurality of nozzles N, and ejects ink from the nozzles N in accordance with the drive signals output by the head drive unit 22. The head drive unit 22 has an ejection selection IC 28 (Integrated Circuit) and an electromechanical conversion element 223, etc. The ejection selection IC 28 switches operations to output drive signals to the electromechanical conversion element 223 corresponding to each nozzle N, according to whether or not ink is ejected from each nozzle N and the amount of ink ejected, based on image data. The electromechanical conversion element 223 is, for example, a piezoelectric element, which changes shape in accordance with the input drive signal, and this change in shape causes pressure fluctuations in the ink in the ink flow path communicating with the nozzles N. The recording element 26 is composed of the electromechanical conversion element 223 and the nozzle N.

[0025] The head drive control unit 30 includes a head control unit 31 and a drive waveform signal generation circuit 32, and outputs a drive waveform signal (analog signal) related to ink ejection, etc., to the inkjet head 20 at a predetermined time period (ink ejection period) based on the output data (digital data) of the drive waveform signal generation circuit 32. The drive waveform signal related to ink ejection may be a combination of multiple pulse signals. In addition, it may be possible to output drive waveform signals of multiple different waveform patterns (including not only waveforms, but also changes in pulse length, amplitude, voltage value, etc.) according to the amount of ink ejected. Alternatively, it may be possible to output a number of continuous drive pulses corresponding to the amount of ink droplets per pixel (multi-pulse method). In this case, the ink droplets ejected by each drive pulse are brought together in flight or land within the same pixel range. The amount of ink ejected from each nozzle to each pixel per pass (one cycle) may be such that the minimum thickness of the insulating film (e.g., 15 μm) described later is obtained, taking into consideration the surface characteristics of the wiring substrate S, the temperature (viscosity characteristics) at the time of ink ejection, and the time interval from the impact of the ink droplet to the temporary adhesion due to UV light irradiation from the UV irradiation unit 42. Furthermore, it may be possible to output a non-ejection waveform pattern not only for ejecting ink, but also for stirring the ink within the nozzle N.

[0026] In addition to or instead of the above method, the amount of ink ejected (impact amount) per pixel can also be controlled by other methods, such as adjusting the state of the ink level (meniscus) in the nozzle N by adjusting the ink pressure (usually set to negative pressure to prevent ink leakage) when no drive pulse is applied, or by changing and adjusting the drive frequency. Furthermore, the amount of ink droplets can also be adjusted by applying a suitable non-ejection waveform pattern drive pulse beforehand to vibrate the meniscus, and then applying the drive pulse of the drive waveform pattern.

[0027] The ink ejected by the inkjet recording device 1 of this embodiment is, for example, solder resist ink. Solder resist ink is ink ejected onto a wiring substrate S to form an insulating film (solder resist) on the wiring substrate S. Here, the solder resist ink is cured by irradiation with a predetermined energy ray, in this case ultraviolet (UV) light. Furthermore, the solder resist ink is thermosetting.

[0028] Solder resist ink contains a compound having a thermosetting functional group. The thermosetting functional group may be any known type, for example, one having an isocyanate group (especially two or more). Furthermore, a polyfunctional isocyanate compound (blocked isocyanate) in which the isocyanate group is protected with a thermally dissociable blocking agent is preferred from the viewpoint of improving the resistance to high temperature and high humidity and thus improving the shelf life of the ink. The thermally dissociable blocking agent is not particularly limited, but for example, it is a compound containing at least one of an oxime compound, a pyrazole compound, and an active ethylene compound.

[0029] Alternatively, the thermosetting functional group may be, for example, a (meth)acrylic group, particularly an imide group-containing (meth)acrylate compound such as imide acrylate. Because the imide group has high polarity, strong adhesion to metal (i.e., wiring on the wiring substrate S) can be obtained. Furthermore, due to its strong cohesive force, the effect on metal adhesion is minimal even under high humidity.

[0030] On the other hand, the components involved in curing solder resist ink by UV light irradiation include a compound having a photopolymerizable functional group and a photopolymerization initiator. The photopolymerizable compound can be any compound that polymerizes or undergoes a crosslinking reaction upon irradiation with active energy rays (UV light) and has the effect of curing the ink, such as radical polymerizable compounds and cationic polymerizable compounds. Polymerizable compounds having an imide group, such as the above-mentioned imide acrylate, also have UV curability. The photopolymerization initiator is selected according to the above-mentioned type of photopolymerizable functional group (compound).

[0031] Furthermore, solder resist ink contains a gelling agent. The ink is in a gel state at room temperature, and undergoes a phase change between a gel and a sol state depending on the temperature, causing a rapid change in viscosity. The gelling agent may be, for example, at least one of the compounds represented by the following general formulas (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 also be branched. Such gelling agents are dispersed in the cured film without inhibiting the curing properties of the ink. This improves the moisture resistance of the printed ink film (solder resist) and prevents moisture from penetrating into the cured film. This also improves insulation reliability. Furthermore, inks containing this gelling agent are preferable because they have good pinning properties, making it easy to form a film that balances fine lines and film thickness (i.e., excellent fine line reproducibility even when film thickness is required).

[0032] The fixing unit 40 performs the operation of fixing the ink that has landed on the wiring board S. As described above, the ink has thermosetting and curing properties with active energy rays (UV light), so corresponding to these, the fixing unit 40 has a UV irradiation unit 42 and a heating fixing unit 43. Although not particularly limited, in this case, the UV irradiation unit 42 is fixed to the scanning unit 121 together with the inkjet head 20 as described above and is scanned to fix the ink that has landed on the wiring board S. The UV irradiation unit 42 has, for example, a light-emitting diode (LED) that emits ultraviolet light, and by applying a voltage to the LED and passing a current through it, it emits light and irradiates with ultraviolet light (UV light). The UV irradiation unit 42 may be equipped with a light-shielding wall or the like to block the leakage of UV light outside the desired irradiation range as needed.

[0033] Furthermore, the configuration for emitting UV light in the UV irradiation unit 42 is not limited to LEDs. The UV irradiation unit 42 may, for example, have a mercury lamp. Also, if the ink has the property of curing and fixing upon exposure to active energy rays other than UV light, the UV irradiation unit 42 may have a well-known emission source (light source) that emits active energy rays to cure the ink, instead of the above-described configuration for emitting UV light.

[0034] The heating and fixing unit 43 has a heating element, such as an infrared heater or an electric heating element, and directly or indirectly heats the wiring board S to permanently fix the temporarily deposited ink. The heating and fixing unit 43 is positioned so that permanent fixing occurs after the ink has been deposited and temporarily fixed by the inkjet head 20 and the UV irradiation unit 42, for example, after the wiring board S has been transported downstream in the transport direction. The heating and fixing unit 43 may be located within a housing that surrounds the wiring board S and the portion of the transport member on which it is placed, so that the heat generated by the heating element is retained inside the housing and efficiently maintained at an appropriate curing temperature. In this case, it is not necessary to operate the heating element at all times during heating, and it is sufficient as long as the temperature is maintained within the set range related to the curing temperature.

[0035] The heating and fixing unit 43 is not provided by the inkjet recording device 1, but may be provided by a separate heating and fixing device. Alternatively, the heating and fixing device may be a post-processing device for the inkjet recording device 1, and the transport unit 10 may be able to directly feed the wiring board S to the heating and fixing device located on the extension of the direction of movement of the transport table 131, or the device may have a configuration that allows the wiring board S removed from the transport table 131 of the inkjet recording device 1 to be set again in the heating and fixing device, or the user may manually move the wiring board S.

[0036] The control unit 50 provides overall control over the operation of each part of the inkjet recording device 1. The control unit 50 has a CPU 51 (Central Processing Unit) and RAM 52 (Random Access Memory). The CPU 51 is a hardware processor that performs various calculations and executes the program 61 stored in the memory unit 60. The RAM 52 provides the CPU 51 with memory space for control and stores temporary data.

[0037] The storage unit 60 includes at least non-volatile memory and stores the program 61 and setting data. Examples of non-volatile memory include flash memory. HDDs (Hard Disk Drives) may also be included in the non-volatile memory referred to here. The storage unit 60 may also include RAM for temporarily storing image data 62 indicating the formation (coating) range of the film to be formed, and drive data for the inkjet head 20 that is processed and generated based on this image data. The program 61 includes control programs related to the ink ejection control process and the coating range adjustment process described later. The setting data includes thickness-corresponding information 63, which includes information related to the ink ejection amount according to the thickness of the film to be formed. The resolution of the information of the coating range (setting range) indicated by the image data 62 is not particularly limited, but may be, for example, 1440 dpi (dots per inch) or higher.

[0038] The ink heating unit 70 heats the ink in the inkjet head 20 and the ink supply path to the inkjet head 20 to maintain an appropriate temperature. As described above, the ink undergoes a phase change between sol and gel depending on the temperature, so if it remains in a gel state at room temperature, the fluidity of the ink will be insufficient, making it difficult to supply and eject the ink. The ink heating unit 70 heats the ink to an appropriate temperature, keeping the ink in a sol state and enabling supply and proper ejection. The appropriate temperature should be set so that the ink is quickly cooled by the wiring board S after it lands on the wiring board S, and gels in an appropriate amount of time. The ink heating unit 70, for example, has a heating element and a sheet member (such as rubber) that is heated by the heat generated by the heating element, and the sheet member contacts the ink supply path, etc., to transfer heat and heat the ink.

[0039] The display unit 81 displays various statuses, menus, etc., on its display screen based on the control of the control unit 50. The display unit 81 includes, for example, a display screen and LED (Light Emitting Diode) lamps. The display screen is not particularly limited, but for example, it is an LCD (Liquid Crystal Display). The LED lamps are illuminated (including blinking) by the control unit 50 in positions and colors corresponding to each situation, for example, the power supply status or the occurrence of an abnormality.

[0040] The operation reception unit 82 receives input operations from external users and outputs them as input signals to the control unit 50. The operation reception unit 82 may have, for example, a touch panel and push-button switches. The touch panel may be positioned overlapping with the display screen of the display unit 81. The operation reception unit 82 may also have various other operation switches.

[0041] The communication unit 90 controls the transmission and reception of data (signals) with external devices in accordance with a predetermined communication standard. For example, the communication unit 90 controls communication in accordance with the LAN (Local Area Network) standard. The communication unit 90 may also be able to connect peripheral devices in accordance with the USB (Universal Serial Bus) standard.

[0042] Next, the printing operation in the inkjet recording device 1 of this embodiment will be described. In the inkjet recording device 1, during scanning, ink is ejected from the inkjet head 20 to a pixel on a certain scanning line (including multiple rows if multiple rows of nozzles N are arranged in the scanning direction) at each ink ejection cycle. Then, the inkjet head 20 is moved by the scanning drive unit 12 to bring the nozzles N opposite to pixels on other scanning lines. When performing multi-pass ink ejection, scanning is performed in each pass while changing the positional relationship between the wiring board S on the transport table 131 and the nozzles N (the pixels on the scanning line from which ink is ejected). UV irradiation by the UV irradiation unit 42 is performed with each scan.

[0043] Figures 3A and 3B illustrate the printing area of ​​the wiring board S. Solder resist ink is used to provide an insulating film I (solder resist) on a wiring board S. The printing area (i.e., the covering area) 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, and fine-line openings and cutouts, depending on the area that forms a connection pad P where the signal wiring C located on the insulating substrate R is connected to electronic components or external signal lines. The thickness of the insulating film I is not particularly limited, but is at least the thickness necessary to ensure insulation, for example, in the range of 15 to 30 μm.

[0044] As shown in Figure 3B, the surface of this insulating film I has irregularities according to the irregularities of the wiring substrate S, depending on the presence or absence of signal wiring C. At the stepped portions of the irregularities, the ink that lands tends to flow to the recessed side before it can harden and fix. As a result, if the ink is ejected uniformly, the ink may not remain near the edge (shoulder Es) of the upper step (convex side), causing the printing to be interrupted, exposing the signal wiring C, and resulting in a loss of insulation.

[0045] In the inkjet recording device 1 of this embodiment, during scanning (in the case of multi-pass scanning, at least one of the passes), the amount of ink ejected from at least one of the stepped portion, the lower flat portion connected to the stepped portion, and the upper flat portion (the amount of ink droplets ejected and landed at each pixel position) is increased compared to the amount of ink ejected from the other flat portions.

[0046] Figure 4 shows three examples of ink ejection volume distributions. The signal wiring C typically does not rise perfectly vertically from the insulating substrate R on its sides, but has a slight inclined region E (inclined portion). A predetermined width lower connection portion LC (lower adjacent portion) on the insulating substrate R adjacent to this inclined region E and a predetermined width upper connection portion UC (upper adjacent portion) on the signal wiring C adjacent to the inclined region E (i.e., forming an inclined region E at both ends) are defined, and the amount of ink ejected (amount of ink droplets ejected) to at least one selected region from these inclined region E, lower connection portion LC, and upper connection portion UC (collectively known as the three stepped regions) is set to be greater than (increased) the amount of ink ejected (amount of ink droplets ejected) to the remaining flat portion LF of the insulating substrate R and the central flat portion UF (other than the three stepped regions) of the signal wiring C. Note that the inclined region E is not limited to a flat surface, but may be a curved surface, and may have irregularities relative to the average inclined surface. The width of the inclined region E is not particularly limited, but is usually narrow in proportion to its height to the extent that it can be called a step. Similarly, the predetermined width of the upper connection part UC and the lower connection part LC is not particularly limited as long as it is about the width of one pixel. For example, the predetermined width of the upper connection part UC and the lower connection part LC may be about the diameter of the landing area of ​​ink droplets that land on the flat parts UF and LF (the largest (enlarged) of the multiple stages of ink ejection may be used as the basis) (although not particularly limited, it is usually about the same as or larger than the width of one pixel, for example, 10.6 μm at 2400 dpi, and is often about 1 to 15 times that) (if the landing area differs between the flat parts UF and LF depending on the difference in material, either one may be used as the basis, or the average value may be used as the basis). In other words, the predetermined width of the upper connection part UC and the lower connection part LC may be about the width of the landing area of ​​ink connected to ink droplets that land on the inclined region E, and / or ink droplets whose landing area spans at least a part of the inclined region E. Furthermore, the predetermined widths of the upper connection section UC and the lower connection section LC may differ (the predetermined width of the upper connection section UC may be determined based on the range of impact on the flat section UF, and the predetermined width of the lower connection section LC may be determined based on the range of impact on the flat section LF). Also, if the wiring width is narrow or the wiring spacing is narrow, there may be parts without flat sections UF or LF, depending on the situation.

[0047] In the example shown in Pattern A, only the ink discharge amount to the inclined region E is greater than the ink discharge amount to the other parts. In the example shown in Pattern B, the ink discharge amount to the upper connection part UC is increased in addition to the inclined region E. Conversely, in the example shown in Pattern C, the ink discharge amount to the lower connection part LC is increased in addition to the inclined region E. In this case, the amount of increase in ink discharge amount may differ from that of the other three stepped regions where the ink discharge amount is increased. Here, the amount of increase in the inclined region E is greater than the amount of increase in the lower connection part LC. In addition, it may be possible to independently set the amount of increase in ink discharge amount for each of the three stepped regions to be non-uniform (non-equivalent) ink discharge amounts.

[0048] Figures 5A to 5C illustrate the increase in ink ejection volume. Of the three stepped regions, the size of each region and which region's ink discharge amount is increased may be determined according to the material and surface characteristics of the wiring board S. For example, discharging more ink to the highly wettable areas suppresses ink shortage due to flow. As shown in Figure 5A, if the wettability of the insulating substrate R is higher than that of the signal wiring C, more ink is discharged to the inclined region E and the lower connection section LC. Here, the sizes of the three circles indicate the relative amounts of ink discharged directly below.

[0049] As shown in Figure 5B, if the wettability of the insulating substrate R is lower than that of the signal wiring C, more ink may be ejected to the inclined region E and the upper connection part UC. As shown in Figure 5C, if both the insulating substrate R and the signal wiring C are made of materials with low wettability (the degree of wettability here may be determined, for example, by comparing the spread size of the deposited ink with a reference size), only the amount of ink ejected to the inclined region E may be increased. In this case, the effect of the ink droplet being pulled and spread together with adjacent ink droplets may be greater than the spread characteristics of the ink droplet on the wiring substrate S, so it is also possible to avoid increasing the amount of ink ejected to the upper connection part UC and the lower connection part LC so that the ink droplets deposited in the inclined region E are less likely to be pulled to both sides.

[0050] In reality, the boundaries of each pixel often do not precisely coincide with the boundaries of the three stepped regions, and some ink droplets will land across multiple regions. In such cases, the corresponding region may be determined simply based on the center of impact position (such as the center of gravity; it is not necessary to consider flow due to incline, etc.), or the discharge amount may be calculated and adjusted based on the proportion belonging to multiple regions and the amount of ink discharged for each region. Furthermore, the widths (predetermined widths) of the upper connection section UC and the lower connection section LC may be fixed, or they may be determined according to the characteristics of ink spread in each region (material) or the size (height) of the step. Also, the widths of the upper connection section UC and the lower connection section LC may be different.

[0051] Figure 6 is a flowchart showing the control procedure by the CPU 51 (control unit 50) for the print control process in this embodiment. This print control process is started when a print command is received from an external device or the like along with image data indicating the coverage area (the timing of data acquisition and command acquisition may differ).

[0052] When the print control process is started, the CPU 51 (control unit 50) acquires the wiring pattern data of the wiring board S (step S101). From the wiring pattern data, the CPU 51 identifies the edges of the wiring, i.e., the stepped portions (step S102).

[0053] The CPU 51 acquires image data indicating the printing (ink ejection) area (step S103). The CPU 51 increases the ink ejection amount for at least one of the three step areas in the portion of the image data that overlaps with the position of the edge mentioned above, according to predetermined conditions (step S104).

[0054] The CPU 51 adjusts the position of the wiring board S according to the image data (step S105). This adjustment may be performed, for example, by determining an offset value or rotation amount relative to the normal mounting position of the wiring board S. This adjustment may be performed automatically by the CPU 51 or through some manual operation (such as input operation) by the user. The CPU 51 ejects ink based on the modified image data using the inkjet head 20 and prints the coating (insulating film I) (step S106).

[0055] The CPU 51 operates the UV irradiation unit 42 to irradiate the wiring board S with UV light, pre-curing the ink on the wiring board S (step S107). The CPU 51 heats the wiring board S to cure and fix the coating (insulating film I) (step S108). Then, the CPU 51 terminates the printing control process.

[0056] The above description concerns single-pass printing. However, in multi-pass printing, ink ejection occurs multiple times, for example, through two scans, at equal intervals and complementaryly. Even in the case of three or more scans, ink ejection should occur with each scan while shifting the phase at equal intervals. Alternatively, the pattern relating to the position and order of ink ejection in multi-pass printing may be based on other methods. However, in the inkjet recording device 1 (printing method) of this embodiment, multiple scans are not performed by a control that causes each pixel to eject ink a number of times corresponding to the amount of ink ejected. That is, there is no control that selectively ejects ink only at positions where the amount of ink ejection is increased, and then ejects ink uniformly in the remaining scans. In other words, in at least one scan, the amount of ink ejected is non-uniform (excluding the presence or absence of ink ejection) according to the setting of the amount of ink droplets to each pixel.

[0057] Figures 7A and 7B illustrate examples of ink ejection amounts when printing with two scans (two passes). Figure 7A shows an example where the ink ejection volume is increased in the lower LC connection section during the first and second passes, respectively.

[0058] Figure 7B schematically shows the ink ejection amount (impact amount) for each pixel position. In reality, the ink impact area is larger than the pixel area, but here, for illustrative purposes, the impact area with normal ink ejection is shown to be the same as the pixel area, and pixels with increased ink ejection are shown as larger circles than the pixel area. In Figure 7B, for example, ink is ejected to the top row (horizontally arranged) pixels, and with each ejection cycle, the target pixels move down one row according to the scan. Here, it is assumed that the extension direction of the shoulder and the scanning direction are parallel, and the nozzles with increased ink ejection are fixed during scanning. However, if the extension direction of the shoulder and the scanning direction are not parallel, the nozzles with increased ink ejection will move sequentially according to the scanning position.

[0059] In this way, by combining the ejection in each of the two passes, a continuous distribution is obtained in which the amount of ink ejected into the LC in the lower connection section is greater than the amount of ink ejected into other parts.

[0060] Figure 8 illustrates a modified example of ink ejection volume 1 when printing with two scans (2 passes). Here, by using two ink ejection passes, the amount of ink ejected to the lower connection section LC and the inclined region E is set to be greater than in other regions. In this case, the timing may be controlled so that the amount of ink ejected only to the lower connection section LC increases during the first scan (pass 1), and then the increased amount of ink is ejected to the inclined region E during the second scan (pass 2). By supplying more ink to the lower connection section LC first and pre-curing it, it is possible to suppress the tendency for the ink ejected to the inclined surface during the second scan to spread towards the lower connection section LC.

[0061] As described above, when the scanning direction and the extension direction of the shoulder portion are not parallel, it is difficult to perfectly synchronize the ejection order. However, if each of the three stepped regions has a width equivalent to multiple pixels, or if it is not possible to eject the same amount to all pixels due to the spread of the ink droplets and the upper limit of the ejection amount per unit area on the wiring board S, the pixels that selectively increase the ink ejection amount may be set to eject as much as possible in the order described above.

[0062] Figure 9 shows a modified example of ink ejection volume 2 when printing is performed with two scans. In this diagram, the ink ejection volume at the lower connection LC and upper connection UC is increased by two-pass ink ejection. In this case, the increased ink ejection to both the lower connection LC and upper connection UC is performed in the first pass. In cases where the slope of the inclined region E is steep (almost 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 volume to the lower connection LC and upper connection UC rather than increasing the ink ejection volume to the inclined region E itself.

[0063] Furthermore, in this example, the ink ejection amount is assumed to be uniform during the second scan. In other words, a non-uniform ink ejection distribution only needs to occur at least once during multiple scans.

[0064] Figures 10A to 10C show a modified example of ink ejection volume 3 when printing with two scans. To adjust the ink discharge amount for three stepped areas more flexibly and easily, instead of fixing the ink discharge amount for each area, it is possible to obtain an average ink discharge amount corresponding to the ratio of multiple types of ink discharge amounts by combining them.

[0065] In this example relating to the ink ejection volume distribution in Figure 10A, as shown in Figures 10B and 10C, during the first scan, large ink droplets and small (normal) ink droplets are ejected alternately for each dot from the upper connection section UC and the lower connection section LC. On average, these upper connection section UC and lower connection section LC are given an intermediate droplet volume between large and small ink droplets. 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.

[0066] Figures 11A to 11C show a modified example of ink ejection volume 4 when printing with two scans. To obtain the ink ejection distribution shown in Figure 11A, as shown in Figure 11B, in the first scan, a large ink droplet is ejected to each pixel in the lower connection section LC, resulting in an average increase in the amount of droplets applied compared to normal. Furthermore, as shown in Figure 11C, in the second scan, large and small ink droplets are ejected alternately to each pixel in the inclined region E, resulting in an average amount of droplets applied to the inclined region E that is intermediate between the normal ink ejection amount and the ink ejection amount with large ink droplets.

[0067] In this case, the timing of ejecting large ink droplets is the same for both scans; that is, in Figures 11B and 11C, the odd-numbered ink droplets from the top are large ink droplets. However, this is not the only option. The timing may be alternating; for example, in the second scan, the even-numbered ink droplets from the top may be large ink droplets.

[0068] The combinations of multiple ink droplet amounts shown in Modification 3 and Modification 4 are not limited to ink ejection in the case of multi-pass ink ejection. Similarly, in the case of single-pass ink ejection, it is also possible to combine ink ejection with multiple ink droplet amounts to average out to an intermediate droplet amount. Furthermore, the position setting of the size of the ink droplets may be done by various other appropriate timing settings. For example, the size of each ink droplet may be determined randomly and probabilistically, or the timing of the size of the ink droplets may be dispersed by dithering or the like.

[0069] Figures 12A to 12C show examples of drive waveforms. For example, the amount of ink droplets ejected with the waveform shown in Figure 12A is smaller with the drive waveform shown in Figure 12B. Also, with the multi-drop drive waveform pattern shown in Figure 12C, by removing some of the five consecutive pulses that can be output at maximum output during the ink ejection cycle, for example, a predetermined number of pulses from the beginning, it is possible to adjust the amount of ink droplets corresponding to the number of pulses so that they converge (or do not converge) during flight and land at the same pixel position.

[0070] As described above, the printing method using the inkjet recording device 1 of this embodiment is a printing method performed by ejecting ink onto a wiring board S having a stepped portion, wherein the stepped portion includes three areas: a stepped inclined region E, 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 an ejection amount setting step in which the amount of ink droplets ejected per ink ejection cycle to at least one selected area of ​​these three areas is increased compared to the amount of ink droplets ejected to areas other than the three areas. The amount of ink droplets referred to here is the average ejection amount for each area and is not limited to cases where the ejection amount for all pixels is increased. In this way, by increasing the amount of ink droplets ejected near the inclined region E compared to normal, even if the ink spreads somewhat on the landing surface (wiring board S), the possibility of the ink covering the upper corner (shoulder Es) of the inclined region E running out and becoming exposed can be reduced. This makes it possible to print more reliably on printing surfaces with steps, that is, to more reliably cover the ink landing area on the printing medium surface with ink.

[0071] Furthermore, the dispensed ink contains a gelling agent. By causing the ink to gel upon impact and quickly adhere to the surface, it prevents the ink from spreading along the impact surface, enabling more precise printing.

[0072] Furthermore, the distribution of ink droplet volume in the selected area is uneven. In addition to flowing down steps, the way the ink spreads differs depending on the material of the wiring board S and the characteristics of the ink. By adjusting the distribution of ink droplet volume accordingly, this printing method can more reliably produce prints with less unevenness.

[0073] Furthermore, the selected area includes at least two of the three areas, and the ink droplet amounts for each of the at least two areas are different from each other. The distribution of ink droplet amounts may be determined for each of the three stepped areas. Even if the ink droplet amounts for each of the three stepped areas are set according to the differences between flat and inclined areas, and the differences in the materials of each part, it is possible to easily and more reliably obtain proper printing results without causing printing defects such as unnecessary exposure of the wiring board S.

[0074] Furthermore, the selected area is determined according to the material of the wiring board S. As described above, the way the ink spreads (wettability) is determined by the combination of the material of the wiring board S and the characteristics of the ink. By increasing the amount of ink dispensed in an appropriate range according to the material of the wiring board S, it is possible to avoid ink leakage and perform more accurate printing.

[0075] Furthermore, the wiring board S includes an insulating substrate R and signal wiring C located on the insulating substrate R, and the ink is solder resist ink. In other words, in the printing operation in which an insulating film is formed on the wiring board S with solder resist ink, by adjusting the amount of ink ejected at the stepped portion as described above, insulation by the coating film can be obtained more reliably.

[0076] Furthermore, the ink hardens upon irradiation with a predetermined energy ray. By rapidly hardening and fixing the ink that has landed on the wiring board S by irradiation with an energy ray, particularly by temporarily fixing it, it is possible to suppress the flow of ink down at steps and cover the desired area.

[0077] Furthermore, the specified energy ray is ultraviolet light. By irradiating the ink-impacted surface with ultraviolet light at the appropriate timing, the ink can be cured to the desired state in accordance with that timing.

[0078] Furthermore, the ink may be thermosetting. This prevents the ink from becoming sol-like and losing its shape due to temperature changes after fixing, thus preventing it from flowing or running down.

[0079] Furthermore, the inkjet recording device 1 of this embodiment includes an inkjet head 20 for ejecting ink and a control unit 50. When printing by ejecting ink onto a wiring board S having a stepped portion including three areas: a stepped inclined region E, 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 ejected per ink ejection cycle to at least one of these three selected areas compared to the amount of ink droplets ejected to areas other than the three. By performing this ink ejection control in the inkjet recording device 1, even if the ink spreads somewhat on the landing surface (wiring board S), the possibility of the ink covering the inclined region E, especially the upper corner (shoulder Es), running out and becoming exposed can be reduced. This makes it possible to print more reliably on printing surfaces with steps.

[0080] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the above embodiment, the ink discharge amount is determined for each of the three stepped regions, either individually or uniformly. However, the ink discharge amount does not have to be uniform even within each region. For example, the ink discharge amount may be gradually reduced from the upper connection section UC to the upper flat section UF, asymptotically approaching and connecting to the normal ink discharge amount in the flat section UF.

[0081] Furthermore, with respect to the inclined region E, the ink ejection amount may be increased only in a portion of it, such as the upper half.

[0082] Furthermore, in the above embodiment, both the inkjet head 20 and the transport table 131 are movable. However, in the case of single-pass printing only, it is sufficient if only one of them, for example, the transport table 131, is movable, and in this case, the inkjet head 20 may be fixed.

[0083] Furthermore, although the above embodiments were described as including a gelling agent, it may not necessarily be a gelling agent, but rather an ink whose viscosity can change significantly in response to temperature changes or other factors.

[0084] Furthermore, although the above embodiment was described as dispensing an ink that has both UV curing and thermosetting properties, the ink may have only one of these properties, or it may be an ink that hardens by irradiation with energy rays other than UV light.

[0085] Furthermore, although the above embodiment describes the case in which an insulating film is printed on a wiring board S, it is not limited to this. For example, it may be a protective film printed on a substrate having other steps (mainly those in which ink does not penetrate or does not penetrate much, such as resin members or films), and the above technology may also be applied to lines, figures, patterns, etc. formed on the substrate, not limited to coatings, in order to suppress the occurrence of abnormalities in image quality and structure, such as breaks at the steps. In these cases, the film thickness (ink ejection amount) may be appropriately changed depending on the application. Furthermore, the specific configurations, processing operations, and procedures 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]

[0086] This invention can be used in printing methods and inkjet recording devices. [Explanation of Symbols]

[0087] 1. Inkjet recording device 10 Conveying section 12 Scanning drive unit 121 Scanning Unit 122 Scanning guide section 13. Transport drive unit 131 Transport platform 132 Conveyor guide section 20 inkjet heads 22 Head drive unit 223 Electromechanical Conversion Element 26 Recording 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 section 50 Control Unit 60 Storage section 61 Programs 62 Image Data 63 Thickness Compatibility Information 70 Ink heating section 81 Display section 82 Operation Reception Section 90 Communications Department C Signal wiring E slope area Es Shoulder I insulating film LC lower connection section N Nozzle P Connection Pad R Insulating substrate S Wiring board UC upper connection section

Claims

1. A printing method in which solder resist ink is ejected onto a substrate having a stepped portion between an insulating substrate and a wiring conductor located on the insulating substrate and having a higher wettability than the insulating substrate, The stepped portion includes three regions: a stepped inclined portion, 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 the upper surface of the wiring conductor and is a horizontal flat portion, and the lower adjacent portion is the upper surface of the insulating substrate and is a horizontal flat portion. The process includes a discharge volume setting step in which the amount of ink droplets discharged per ink discharge cycle to the upper adjacent portion and the inclined portion among the three regions is increased to the amount of ink droplets discharged to the lower adjacent portion. The distribution of the amount of ink droplets in the upper adjacent portion and the inclined portion is non-uniform within each respective region. Printing method.

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

3. The amount of ink droplets on the upper adjacent portion and the inclined portion are different from each other. The printing method according to claim 2.

4. The printing method according to any one of claims 1 to 3, wherein the solder resist ink is cured by irradiation with a predetermined energy ray.

5. The printing method according to claim 4, wherein the predetermined energy ray is ultraviolet light.

6. The solder resist ink is thermosetting, according to the printing method according to any one of claims 1 to 5.

7. The ejection unit that ejects ink, Control unit and Equipped with, The control unit, A substrate having a stepped portion between an insulating substrate and a wiring conductor located on the insulating substrate and having a higher wettability than the insulating substrate, wherein the substrate has three regions: an inclined portion forming the 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 the upper surface of the wiring conductor and a horizontal flat portion, and the lower adjacent portion being the upper surface of the insulating substrate and a horizontal flat portion, when solder resist ink is ejected onto the substrate for printing, The amount of ink droplets discharged per ink discharge cycle to the upper adjacent portion and the inclined portion among the three regions is increased to be greater than the amount of ink droplets discharged to the lower adjacent portion. The distribution of the amount of ink droplets in the upper adjacent portion and the inclined portion is non-uniform within each respective region. Inkjet recording device.

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