Method for control of nozzles in an ink-jet print module

Abstract

A method for control of a plurality of nozzles (22) in an ink-jet print module (20), the method comprising: forwarding (S1) a paperboard web (10) continuously in a machine direction (MD), printing (S2) a décor layer (30) on a first section (11) of the paperboard web (10) using the ink-jet print module (20), and printing (S3) a control layer (40) on a second section (12) of the paperboard web (10) by activating the plurality of nozzles (22), wherein the first and second sections (11, 12) are distinct from each other.

Description

Technical Field

[0001] The invention relates to a method for control of nozzles of an ink-jet print module, a converting unit, a laminated packaging material, and a package folded from a laminated packaging material.Background Art

[0002] Packaging containers of the single use disposable type for liquid foods are often produced from a laminated packaging material. The laminated packaging material is produced as a continuous web, which is either used in a roll-fed filling machine or cut into separate blanks for use in a blank-fed packaging machine.

[0003] The laminated packaging material is produced using a converting procedure in which multiple materials are joined and processed to form the ready-to-use web of laminated packaging material.

[0004] During the converting process a paperboard web, forming the core layer of the laminated packaging material, may be digitally printed with a décor layer on the outside (i.e. the side intended as the exterior side of the laminated packaging material) for example by ink-jet printing.

[0005] An ink-jet module typically comprises print heads comprising nozzles configured to propel droplets of ink onto a substrate, such as the paperboard web. Depending on the design of the décor layer, not all nozzles are necessarily activated for each converting process. The décor layer may for instance not be designed to comprise all colors available in the print heads, or the width of the décor layer may be smaller than the full width of the assembly of nozzles in the print module.

[0006] When a nozzle is not used for a long period of time, ink comprised in the nozzle may dry to some extent, leading to clogged or blocked nozzles, which in turn may lead to print defects related to misfiring or non-jetting print heads. In order to prevent the ink in the nozzles from drying, it is known to add humectants to the ink formula. However, high levels of humectants may also prevent the ink on the substrate from drying after print, and the increased drying energy needed to overcome this may also dry out the substrate, causing further defects in the laminated packaging material, especially when the substrate is a paperboard web. In addition, ink fog, which refers to an unwanted dispersion of ink particles in the air during the printing process, may also settle on machinery and be accumulated on e.g., the nozzles and / or nozzle plates, leading to increased cleaning and maintenance needs. Ink fog problems may be more frequent on infrequently used nozzles, as the ink fog may cause smudging, blurring, or unintended marks on the printed material.

[0007] As a result, there is a need in the art for improvements of nozzle control in manufacturing techniques for laminated packaging material webs.Summary

[0008] It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to reduce print defects and prolong the lifetime of nozzles in an ink-jet print module. This is at least partly addressed by preventing or reducing drying of ink in the nozzles. By drying, it is meant that carrier fluid of the ink to some extent evaporates. This is an intrinsic feature of the ink, which is normally desired when deposited on a substrate, but less desired when the ink is still in the nozzle. Latency is a term commonly used to describe the negative behavior of ink after periods of sitting idle in the nozzle. Depending on how quickly the fluid evaporates, latency can have adverse effects after days or hours of ink at rest. Minimizing the impact of latency may reduce required maintenance of the print module and mitigate risks related to print defects. Common latency effects caused by local change in ink concentration near the nozzle opening due to carrier evaporation includes abnormally or non-firing ink drops. In printed décor, abnormal or delayed firing may be noticed as ragged edges. It is an object of the present application to reduce latency effects by activating all nozzles of the print module in order to keep them refreshed, and the ink inside recirculated. Recirculation may help to ensure the ink is well mixed within the nozzle, even as the carrier fluid is drying.

[0009] In the present application, the print substrate is described as a paperboard web. The skilled person realizes that the method, converting unit, laminated packaging material and / or package disclosed herein may also be applied to other substrates. The paperboard web is herein sometimes described in relation to a machine direction. The machine direction may be understood as the direction in which the paperboard web would be forwarded in a converting unit but may be referred to even when describing the paperboard web without discussing a converting unit. The transverse direction to the machine direction may be understood as the direction in which nozzles of the converting unit would be arranged. Herein, the width of the paperboard web may be understood as the total distance from an end of the paperboard web to an opposite end in a direction transverse to the machine direction. On the paperboard web, the direction transverse to the machine direction is sometimes used synonymously with the width of the substrate.

[0010] According to an aspect, a method for control of a plurality of nozzles in an ink-jet print module is provided. The method comprises forwarding a paperboard web continuously in a machine direction, preferably at a substantially constant speed. The method further comprises printing a décor layer on a first section of the paperboard web using the ink-jet print module and printing a control layer on a second section of the paperboard web by activating the plurality of nozzles. Although the décor and control layers are referred to as layers, it should be noted that they don't necessarily needs to be arranged on different levels with respect to the paperboard web. The décor layer and the control layer may for instance both be printed immediately on top of the paperboard web. One or both layers may alternatively be printed on top of an intermediate layer or layers, such as a priming layer. The décor layer and the control layer may be printed on the full first and second section respectively, or they may be printed on a subsection of the section, only partly covering the surface of the first and second section. When printing any of the layers, in particular the control layer, the full width of the paperboard web may be printed, and even areas outside the paperboard web may be printed as well. The print area is not limited to the area of the paperboard web. The first and second sections of the paperboard web are distinct from each other, meaning that they do not overlap. By this, printing the control layer on an area of the paperboard web where no décor layer is allowed.

[0011] The control layer is a printed layer which results from controlling the nozzles in the ink-jet module with the purpose of keeping the nozzles refreshed rather than providing a décor to the packaging container. As will be described later, the control layer can also serve other purposes, for example to detect broken nozzles, but the main purpose is to keep the nozzles refreshed though recirculation.

[0012] According to an embodiment, the ink-jet print module comprises a plurality of print heads, and the plurality of print heads comprises the plurality of nozzles. In other words, each print head may comprise a collection of nozzles, and the total number of nozzles of each collection of nozzles together is equal to the total number of nozzles in the plurality of nozzles. The step of printing a control layer may comprise printing from all print heads of the ink-jet print module by activating all nozzles of the plurality of nozzles. By all nozzles of the ink-jet print module being activated, the risk of ink drying in the nozzles is reduced, and the need for modifying the ink to dry slower is reduced. For instance, a lower or no amount of humectants may be added to the ink, facilitating a more efficient drying process of the printed paperboard web with a reduced risk of damaging the paperboard material with excessive drying energy. The terms "printing" and "activating" does not necessarily mean traditional printing or printing in the same way the décor layer is printed. Printing and / or activating may refer to any process where any amount of ink is released from the nozzle, for instance the process known as "spitting", or printing at a lower frequency.

[0013] According to an embodiment, each print head is configured to print a color, and the printed control layer comprises all colors of the plurality of print heads. Each print head may for instance be configured to print a color of the CMYK color model, using the subtractive primary colors of pigment (cyan, magenta, yellow and black). The print heads may be arranged sequentially after each other in the machine direction, for instance in the order cyan, magenta, yellow, black. Each print head may be configured to print a unique color, or more than one print head may be configured to print the same color. The nozzles of each print head may extend in a direction transverse to the machine direction, i.e. over the width of the paperboard web. The total length of the print heads in the transverse direction may be longer than the total width of the paperboard web.

[0014] According to an embodiment, printing the décor layer comprises activating a collection of nozzles out of the plurality of nozzles, the collection of nozzles being a subset of the plurality of nozzles. By this, printing flexibility is increased as for instance the design of the décor layer and / or the paperboard web is allowed to be smaller than the width of the print heads, without compromising the integrity of the nozzles of the print heads. By printing the control layer over the full width of the print heads and activating all nozzles, it is ensured that the ink in each nozzle is recirculated and prevented from drying, even when the décor layer is small or does not comprise all colors available by the print heads.

[0015] According to an embodiment, printing the control layer comprises activating the plurality of nozzles simultaneously, such that the control layer has an elongated extension in a direction transverse to the machine direction after printing. By this, a more efficient printing process is facilitated, as all nozzles may be activated at once. Further, the resulting printed control layer on the paperboard web may be smaller in size, allowing for easier placement on part of the paperboard web that will be removed prior to, or hidden during folding of the resulting packaging product. Beneficially, activating all nozzles at once in an ink-jet print module will result in a similar and predictable control layer each time, which may be used for instance as a test pattern indicative of the status of the print heads and print quality.

[0016] According to an embodiment, the step of printing the décor layer is repeated across the paperboard web in the machine direction during a conversion cycle, and the step of printing the control layer is performed once during the conversion cycle. By this, a more efficient printing process is allowed, while ensuring maintained integrity of the nozzles.

[0017] According to an embodiment, the control layer is printed in the beginning or in the end of the conversion cycle. By this, removal of the sections of the paperboard web comprising the control layer prior to folding the paperboard web into a package is facilitated, ensuring a more material and time efficient process without visual obstructions on the resulting package.

[0018] According to an embodiment, the method further comprises executing a tickling function in the plurality of nozzles. Tickling is a similar function to printing or spitting, but in tickling, when the nozzles fire, the drive voltage or pulse timing is reduced to ensure a drop is not ejected. This allows the ink near the nozzle to be recirculated without leaving the nozzle. Executing a tickling function is on its own not efficient enough to overcome the above-identified limitations of the prior art. This is at least because the fluid is still evaporation, so even when recirculating, the ink is getting thicker and thicker over time. Eventually the ink will be too thick, and the effectiveness is lost. However, tickling in combination with regularly activating the plurality of nozzles may be highly effective in reducing latency effects in the print module.

[0019] According to an embodiment, the method further comprises drying the décor layer and the control layer by exposing the paperboard web to infrared radiation, IR. A drying process utilizing IR is a highly efficient method for drying printed ink. A drawback is the penetration depth of IR that also may dry the paperboard web when used as substrate. In order to ensure an efficient printing and drying process, while mitigating the risks associated with reduced paperboard moisture, it is important to print with a relatively quick drying ink, and not for instance an ink with a high amount of humectants. By activating all nozzles during a conversion cycle, it is enabled to print with a faster drying ink, allowing IR to be used for drying and ensuring an efficient process.

[0020] According to an embodiment, the method further comprises folding the paperboard web into a packaging container. The first section of the paperboard web may correspond to an area of the packaging container which is visible after folding, and the second section may correspond to an area of the packaging container which is non-visible after, and / or is removed prior to the step of folding. By this, it is ensured that the integrity of the nozzles is maintained without obstructing the visual impression of the folded packaging container.

[0021] According to an aspect, a converting unit, configured to continuously manufacture a laminated packaging material, is provided. The converting unit comprises a feeding unit configured to continuously forward a printed paperboard web in a machine direction, preferably at a constant speed. The converting unit further comprises an ink-jet print module comprising a plurality of print heads, wherein the plurality of print heads comprises a plurality of nozzles. The ink-jet print module is configured to print a décor layer on a first section of the paperboard web and is further configured to print a control layer on a second section of the paperboard web by activating the plurality of nozzles. The first and second section are distinct from each other. The converting unit may be configured to perform the continuous in-line method for control of a plurality of nozzles described herein and therefore implies all aspects disclosed with regard to that method.

[0022] According to an embodiment, the plurality of nozzles extends across the paperboard web in a direction transverse to the machine direction.

[0023] The converting unit may further comprise a drying station, preferably an IR drying station and / or a creasing station configured to provide a crease line pattern to the printed paperboard web, and / or at least one lamination station configured to laminate at least a further layer to the printed and creased paperboard web.

[0024] According to an aspect, a laminated packaging material is provided. The laminated packaging material comprises a paperboard web having a décor layer on a first section and a control layer on a second section, the first and second section being distinct from each other. The paperboard web of the laminated packaging material may be printed using the continuous in-line method for control of a plurality of nozzles described herein and therefore implies all aspects disclosed with regard to that method.

[0025] According to an embodiment, the décor layer and the control layer have an extension on the paperboard web in a direction transverse to a machine direction, and the extension of the control layer is larger than the extension of the décor layer.

[0026] According to an embodiment, the control layer extends over the full width of the paperboard web in a direction transverse to a machine direction.

[0027] According to an aspect, a package is provided. The package is folded from a laminated packaging material according to any such material described herein, and the control layer is at least partly hidden in, and / or absent from, the folded package.

[0028] All possible features mentioned above should be assumed as valid for all aspects of the invention, as long as being under the scope of the claims. Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.Brief Description of the Drawings

[0029] Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings. Fig. 1 is a perspective view of a converting unit according to an embodiment. Fig. 2 is a top view of a laminated packaging material according to an embodiment. Fig. 3 is a top view of a paperboard web according to one embodiment moving through a part of the converting unit of Fig. 1 Fig. 4 is a top view of a paperboard web according to one embodiment moving through a part of the converting unit of Fig. 1. Fig. 5 is a flow chart of a method according to an embodiment. Detailed Description

[0030] A package, such as a liquid food or beverage container, is formed by folding blanks or a continuous tube-based forming of a laminated packaging material. The packaging material is typically manufactured in a manufacturing unit, such as a converting unit. By an ink-jet print module of the converting unit, a décor layer is printed onto a substrate which, after a series of process steps, eventually forms part of the laminated packaging material. In the following description, the substrate is referred to as a paperboard material. To maintain the integrity of the nozzles of the print module, an in-line method and system for control of a plurality of nozzles is provided and which will be described in the following.

[0031] With reference to Fig.1, a converting unit 2 configured to manufacture a laminated packaging material is illustrated schematically. The converting unit 2 comprises at least one feeding unit 23, here illustrated as two feeding rolls. The feeding unit(s) 23 is configured to continuously forward a paperboard web 10 in a machine direction MD, as indicated by the arrow markings in Fig. 1, preferably at a substantially constant speed.

[0032] The converting unit 2 further comprises an ink-jet print module 20 comprising a plurality of print heads 21. Each print head 21 of the plurality of print heads 21, illustrated in an enlarged view in Fig.1, may be configured to print an assigned color. Each print head 21 may for instance be configured to print a color of the CMYK color model, using the subtractive primary colors of pigment (cyan, magenta, yellow and black). The print heads 21 may be arranged sequentially after each other in the machine direction MD, for instance in the order cyan, magenta, yellow, black (CMYK), or cyan, magenta, black, yellow (CMKY). Each print head 21 may be configured to print a unique color. Alternately, there may be several print heads 21 for each unique color. It should be noted that the exact configuration of the ink-jet print module 20 may be different depending on the particular application; for example, the ink-jet print module 20 may comprise multiple print heads 21 arranged in the machine direction MD and / or a direction transverse to the machine direction MD. The plurality of print heads 21 may cover the entire area of the paperboard web 10. Each print head 21 of the plurality of print heads 21 comprises a collection of nozzles 22, the collection of nozzles 22 being a subset of a plurality of nozzles 22. The collection of nozzles 22 of each print head 21 may extend in a direction transverse to the machine direction MD, i.e. over the width W of the paperboard web 10. The total length of the print heads 21 in the transverse direction may be longer than the total width W of the paperboard web 10.

[0033] The ink-jet print module 20 is configured to print a décor layer 30 on a first section 11 of the paperboard web 10, as well as a control layer 40, on a second section 12 of the paperboard web 10. The first and second sections 11, 12 are distinct from each other, meaning that they do not overlap. The width of the décor layer 30 may be equal to or smaller than the width W of the paperboard web 10, and the width W of the paperboard web 10 may be smaller than the width of the plurality of print heads 21. Hence, printing S2 the décor layer 30 may comprise activating only a collection of nozzles out of the plurality of nozzles 22, the collection of nozzles 22 being a subset of the plurality of nozzles 22. The control layer 40 is printed by activating all nozzles 22 of the plurality of nozzles 22. Preferably, the plurality of nozzles 22 are activated simultaneously, i.e. at the same time. In the illustrated example, there are two printed décor layers 30 on two first sections 11 of the paperboard web 10, and one control layer 40 printed across the paperboard web 10 in a direction transverse to the machine direction MD. As the plurality of print heads 21 in this case extends outside the width W of the paperboard web 10, the control layer 40 is printed across the paperboard web 10 and extends further outside the paperboard web 10 in a transverse direction. The control layer 40 may alternatively or additionally extend in a parallel direction to the machine direction MD, or in any angle of choice with respect to the machine direction MD. The control layer 40 may extend continuously in the shape of a line, or two or more parallel lines, or dots, square shapes, shorter line sections etc., depending on the arrangement of the plurality of nozzles 22 and the timing of the print S4.

[0034] The décor layer 30 is preferably cyclic in the machine direction MD. This means that a repetitive series of décor layers 30 are printed on the paperboard web 10 in the machine direction MD during printing. The control layer 40 may be cyclic as well, for instance following the cycles of the décor layer, or every other cycle etc. Alternatively, the control layer may be printed a set number of times during each production run, also referred to as conversion cycle. As an example, the control layer 40 may be printed in the beginning of the conversion cycle, before the first décor layer 30, and / or in the end of the conversion cycle, after the last décor layer, and / or in the middle of production, between two sections comprising a printed décor layer 30.

[0035] Although not illustrated, the converting unit 2 may further comprise a drying station configured to dry the décor layer 30, as well as the control layer 40, preferably by exposing the paperboard web 10 to IR, or other drying techniques, such as, NIR, hot air. The drying station may be arranged downstream the ink-jet print module 20 in the machine direction MD. A priming station (not shown) may also be provided in the converting unit 2, before the ink-jet print module 20. Further, the converting unit 2 may comprise a creasing station (not shown) configured to provide a crease line pattern to the printed paperboard web 10, and / or a lamination station (not shown) configured to laminate at least a further layer to the printed and creased paperboard web 10. After printing, drying, creasing, and / or lamination, the so formed web of laminated packaging material 1 may be transferred to a cutting and / or folding station (not shown) to form a package.

[0036] Fig. 2 illustrates a paperboard web 10 moving through a part of the converting unit 2 described above. More specifically, the paperboard web 10 is leaving the ink-jet print module 20 in the machine direction MD where the décor layer 30 and the control layer 40 have been printed onto the web 10. The printed paperboard web 10 is divided into sections, in this case a first section 11 and a second section 12. The first section 11 may be a section later used as a blank from which a package is formed, for instance a section which, if the web of packaging material later is cut into individual sections for a blank-fed packaging machine, will be kept while other sections are discarded. The first section is printed with the décor layer 30. The second section 12 is printed with the control layer 40, and in this example located at an area of the paperboard web 10 which will later be discarded. Alternatively, the second section 12 may represent a section which after folding will be located at least partly hidden in the package. The control layer 40 is illustrated as a straight line, extending in a transverse direction to the machine direction MD. The skilled person realizes that other shapes are feasible.

[0037] The second section 12 on which the control layer 40 is printed extends continuously over the full width W of the paperboard web 10 and the control layer 40 is printed over the full width W of the paperboard web 10 in the second section 12. In this example, the control layer 40 is printed continuously over the full width W, meaning that there are no interruptions or gaps in the printed control layer 40 in the width W direction. However, the control layer 40 could still be printed with gaps in the machine direction MD, for instance if the control layer 40 is printed as a plurality of lines extending continuously over the full width W of the paperboard web 10.

[0038] In other embodiments, for instance if the nozzles are arranged with gaps between them, the resulting control layer 40 may extend non-continuously over the width W, for instance in a pattern.

[0039] The control layer 40 may comprise all colors of the print heads 21 of the ink-jet print module 20 since the control layer 40 is printed by activating the plurality of nozzles 22 of the plurality of print heads 21. The colors may be printed next to each other, for instance in a parallel line pattern, or on top of each other, potentially mixing into other colors.

[0040] Fig. 3 illustrates another example of a paperboard web 10 moving though part of the converting unit 2 described above. More specifically, the paperboard 10 is forwarded in a machine direction MD from the feeding unit 23 through the ink-jet print module 20. The paperboard 10 has multiple lanes 17 along the width W of the paperboard 10. As shown in Fig. 3, each lane 17 may have one or more first sections 11 on which a décor layer 30 is printed. The décor layers 30 printed in the first sections 11 are preferably identical, at least within the same lane 17. The first sections 11 of the lanes 17 may, as illustrated in Fig. 3, be shifted in the machine direction MD between the lanes.

[0041] The lanes 17 may be separated by areas without any decor that may be left for slitting to separate the lanes 17 from each other. Slitting the lanes from each other can make them ready to be fed though a package forming machine to form a plurality packaging containers. Alternatively, each lane may first be cut into individual pieces, where each piece can be used to form a single packaging container. Regardless, each part of a lane 17 configured to form a packaging container may comprise one first section 11 provided with said décor print 30.

[0042] Unlike the first sections 11, the second section 12 extends continuously over the entire width W of the packaging material 10, i.e. continuously across all lanes 17. Accordingly, only a subset of the nozzles may be activated to print the décor layer 30 while all nozzles can be activated to print the control layer 40. This ensures that all nozzles, even those that are not used to provide the décor layer 30, are activated at least now and then to keep them refreshed and ensure that the ink inside them is recirculated. By activating the nozzles to print on a continuous section 12 over the entire width W, a more efficient printing process is facilitated, as all nozzles may be activated simultaneously or close in time. By having the second section 12 extend continuously over the entire width W, it can be easier to remove it from the paperboard later. For example, if a second section 12 is placed in the beginning and / or end of a roll of the packaging material 10 or conversion cycle, the second section 12 may correspond to a section which is naturally removed as part of splicing. Splicing can for instance be performed as part of the lamination or slitting process to join the end of one roll of packaging web 10 to another roll of packaging web 10 without having to stop the machine. Splicing typically involves cutting off some of the paperboard web 10 at one or both ends which are to be joined. Accordingly, by placing the control layer 40 on a second section 12 located at in the beginning or end of a roll (in the machine direction MD), the control layer can be removed as part of the regular manufacturing process.

[0043] Even if all or parts of the second section 12 printed with the control layer 40 is kept during the splicing, this section will be discarded later since packaging containers with splices are not wanted.

[0044] As explained, the main purpose of printing the control layer 40 is to keep the nozzles refreshed. However, as previously mentioned, the control layer 40 could also be used as a test pattern to indicate the status of the print heads and / or the print quality.

[0045] In some embodiments, test patterns 50 which are separate from the control layer 40 could also be printed, as exemplified in Fig. 4. These test patterns 50 can be fixed in relation to the décor layer 140 and thereby also be cyclic in the machine direction MD. Each test pattern 50 can extend at least partially across the décor layer 30 or across the entire décor layer 30. Moreover, the test pattern 50 may extend over the entire décor layer 30 in a continuous or non-continuous manner. The test pattern 50 is typically printed on an area which will be at least partly hidden when a final package is folded. The test patterns 50 can, alternatively or additionally to the control layer 40, be used to inspect the quality of the print and / or nozzles.

[0046] Unlike the test patterns 50, which can extend over the width of a separate lane 17, the control layer 30 is printed, preferably continuously, on a section 12 which extends over the entire width W of the packaging web 10, in this case across all lanes 17.

[0047] Turning now to Fig. 5, an embodiment of a continuous in-line method for control of a plurality of nozzles 22 of an ink-jet print module 20 is illustrated. The method may be performed in the converting unit 2 as described above. Conversely, the converting unit 2 is configured to perform the method as will now be described. Moreover, all aspects disclosed with regard to the method may be implied also for the converting unit 2, as well as the other way around.

[0048] The method includes a step S1 of forwarding a paperboard web 10 continuously in a machine direction MD, preferably at a substantially constant speed. The machine direction MD may be defined as the direction parallel to the movement of the paperboard web 10 through a manufacturing equipment such as a converting unit 2, or as the circumferential direction of a roll of paper used for providing the paperboard web 10. Next, a step of ink-jet printing S2 a décor layer 30 on a first section 11 the paperboard web 10 is performed, using the ink-jet print module 20, and more specifically the nozzles 22 of the print heads 21 included therein. The printing S2 of a décor layer 30 may be performed using application of droplets randomly distributed to the paperboard web 10 during the process. By printing small droplets randomly distributed, and continuously during the of ink-jet printing S2, the printing ink then being continuously exchanged in the nozzles, limiting clogged or blocked nozzles. Clogging of and blocked nozzles could lead to print defects.

[0049] In printing different sizes of droplets may be used. In the waveform there may be three different droplet sizes (named small, medium, and large). The sizes of droplets are connected to how much voltage is needed to fire a drop. The larger a droplet is the more percentage of voltage is needed for the firing the ink. Spitting is for ink printing another term that can be used for the small drops, when they are used to sort of clean the nozzles. Then it is to use the lowest percentage voltage for firing and have a movement of the ink as a "background noise" for the printheads to limit clogging and blockage of the nozzles. This allows for a tickling motion but have every now and then, e.g., every 10 000 cycle of tickling is a little stronger and fire to refresh the nozzle.

[0050] The paperboard web 10 may comprise paper, paperboard or other cellulose-based material. Ink-jet printing is a type of digital printing or computer printing. During ink-jet printing, a digital image is recreated by propelling droplets of ink onto a substrate, such as a paperboard web 10 or a primer layer (not shown). The method may further comprise other printing techniques, such as flexographic printing, and the décor layer 30 may hence be obtained by ink-jet printing only, or by a hybrid approach combining two or more printing techniques. In other words, the décor layer 30 may be ink-jet printed and flexography printed.

[0051] Following the printing of the décor layer 30, a step S3 of printing a control layer 40 onto a second section 12 of the paperboard web 10 is performed by activating the plurality of nozzles 22. The printing 32 of a control layer 40 may be performed using application of droplets randomly distributed to the paperboard web 10 during the process. By printing small droplets randomly distributed, and continuously during the of ink-jet printing S2, the printing ink then being continuously exchanged in the nozzles, limiting clogged or blocked nozzles, which in turn may lead to print defects. The first and second sections 11, 12 being distinct from each other. Printing S3 the control layer 40 may comprise printing from all print heads 21 of the ink-jet print module 20 by activating all nozzles 22 of the plurality of nozzles 22. Preferably, printing S3 the control layer 40 comprises activating the plurality of nozzles 22 simultaneously. Optionally, the step S2 of printing the décor layer 30 and the step S3 of printing the test pattern of the control layer 40 are performed substantially at the same time, for instance by continuously activating print heads 21 of the ink-jet print module 20. The steps S2 and / or S3 of printing a décor layer 30 and a control layer 40 on the paperboard web 10 may be performed repeatedly along the paperboard web 10. In other words, the paperboard web 10, when moving through a converting unit 2 as disclosed herein, may have a print, or coating, which is cyclic along the longitudinal direction of the paperboard web 10. Put differently, the décor layer 30 may be cyclic in the machine direction MD. Also, the control layer 40, which is printed on a distinct section as the décor layer, may be cyclic in the machine direction MD with the same or a different interval. The control layer 40, comprising printed ink from all nozzles 22 of the plurality of nozzles 22 may be used as a test pattern which when inspected may indicate defective nozzles 22, and even location of malfunctioning nozzles 22 among the plurality of nozzles 22.

[0052] In the optional step S4, a tickling function in the plurality of nozzles 22 may be executed. Tickling is performed after and / or during printing, i.e., during and / or after the step S2 of printing the décor layer 30, and during and / or after the step S3 of printing the test pattern of the control layer 40. The tickling function may comprise printing S2 and / or S3 with a reduced drive voltage or pulse timing in order to ensure a drop is not ejected. Within the print module, tickling is included in the wave formation, as a low energy pulsing (background waves) but also when the nozzle is resting (not in a waveform cycle) as the same low energy background wave. Tickling is providing smaller waves within the print module compared to when the printing ink is fired, i.e. the ejection of ink droplets from the printhead nozzles onto the printing surface. To exemplify the tickling may e.g., be performed using only a tenth of the wave height compared to the wave height upon firing the ink.

[0053] Further optionally, the décor layer 30 and control layer 40 may be dried on the paperboard web 10 by e.g., being exposed to infrared radiation, IR. Beneficially, since all nozzles 22 of the plurality of nozzles 22 are continuously activated, a relatively fast drying ink may be selected as the ink used for printing without risking clogged or blocked nozzles 22, and drying S5, e.g., using IR, may be performed at a balanced intensity where the paperboard material is not overexposed and dried out.

[0054] Optionally, at some stage after drying, the second section 12 which is printed with the control layer 40 may be removed from the paper web 10, for instance as part of a splicing process, as explained above.

[0055] The printed paperboard web 10 may be divided into multiple sections which are to be folded S6 into respective packages. The packages may also be referred to as food or beverage containers. The sections are preferably separated by a crease line pattern which may be provided in a step after drying the printed décor layer 30 and the control layer 40. The crease line pattern facilitates the formation of a packaging container from the web of laminated packaging material 1. The crease line pattern is preferably repeated in the machine direction MD. Along the length of the paperboard web 10, the décor layer 30 is printed on the first section(s) 11, and the control layer is printed on the second section(s) 12 of the paperboard web 10. The first and second sections 11, 12 may be comprised in the same section which is to be folded into a package. In this case, the second section 12 is preferably located at a position within the section such that the control layer 40 is at least partly hidden after folding the paperboard web 10 to form the package. Alternatively, or additionally, the second section 12 may at least partly be located outside the section which is to be folded into a package. In this case, at least part of the second section 12 with the printed control layer 40 will be cut off prior to folding the web 10 into a package.

[0056] From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.

Examples

Embodiment Construction

[0030]A package, such as a liquid food or beverage container, is formed by folding blanks or a continuous tube-based forming of a laminated packaging material. The packaging material is typically manufactured in a manufacturing unit, such as a converting unit. By an ink-jet print module of the converting unit, a décor layer is printed onto a substrate which, after a series of process steps, eventually forms part of the laminated packaging material. In the following description, the substrate is referred to as a paperboard material. To maintain the integrity of the nozzles of the print module, an in-line method and system for control of a plurality of nozzles is provided and which will be described in the following.

[0031]With reference to Fig.1, a converting unit 2 configured to manufacture a laminated packaging material is illustrated schematically. The converting unit 2 comprises at least one feeding unit 23, here illustrated as two feeding rolls. The feeding unit(s) 23 is configur...

Technical Field

[0001] The invention relates to a method for control of nozzles of an ink-jet print module, a converting unit, a laminated packaging material, and a package folded from a laminated packaging material.Background Art

[0002] Packaging containers of the single use disposable type for liquid foods are often produced from a laminated packaging material. The laminated packaging material is produced as a continuous web, which is either used in a roll-fed filling machine or cut into separate blanks for use in a blank-fed packaging machine.

[0003] The laminated packaging material is produced using a converting procedure in which multiple materials are joined and processed to form the ready-to-use web of laminated packaging material.

[0004] During the converting process a paperboard web, forming the core layer of the laminated packaging material, may be digitally printed with a décor layer on the outside (i.e. the side intended as the exterior side of the laminated packaging material) for example by ink-jet printing.

[0005] An ink-jet module typically comprises print heads comprising nozzles configured to propel droplets of ink onto a substrate, such as the paperboard web. Depending on the design of the décor layer, not all nozzles are necessarily activated for each converting process. The décor layer may for instance not be designed to comprise all colors available in the print heads, or the width of the décor layer may be smaller than the full width of the assembly of nozzles in the print module.

[0006] When a nozzle is not used for a long period of time, ink comprised in the nozzle may dry to some extent, leading to clogged or blocked nozzles, which in turn may lead to print defects related to misfiring or non-jetting print heads. In order to prevent the ink in the nozzles from drying, it is known to add humectants to the ink formula. However, high levels of humectants may also prevent the ink on the substrate from drying after print, and the increased drying energy needed to overcome this may also dry out the substrate, causing further defects in the laminated packaging material, especially when the substrate is a paperboard web. In addition, ink fog, which refers to an unwanted dispersion of ink particles in the air during the printing process, may also settle on machinery and be accumulated on e.g., the nozzles and / or nozzle plates, leading to increased cleaning and maintenance needs. Ink fog problems may be more frequent on infrequently used nozzles, as the ink fog may cause smudging, blurring, or unintended marks on the printed material.

[0007] As a result, there is a need in the art for improvements of nozzle control in manufacturing techniques for laminated packaging material webs.Summary

[0008] It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to reduce print defects and prolong the lifetime of nozzles in an ink-jet print module. This is at least partly addressed by preventing or reducing drying of ink in the nozzles. By drying, it is meant that carrier fluid of the ink to some extent evaporates. This is an intrinsic feature of the ink, which is normally desired when deposited on a substrate, but less desired when the ink is still in the nozzle. Latency is a term commonly used to describe the negative behavior of ink after periods of sitting idle in the nozzle. Depending on how quickly the fluid evaporates, latency can have adverse effects after days or hours of ink at rest. Minimizing the impact of latency may reduce required maintenance of the print module and mitigate risks related to print defects. Common latency effects caused by local change in ink concentration near the nozzle opening due to carrier evaporation includes abnormally or non-firing ink drops. In printed décor, abnormal or delayed firing may be noticed as ragged edges. It is an object of the present application to reduce latency effects by activating all nozzles of the print module in order to keep them refreshed, and the ink inside recirculated. Recirculation may help to ensure the ink is well mixed within the nozzle, even as the carrier fluid is drying.

[0009] In the present application, the print substrate is described as a paperboard web. The skilled person realizes that the method, converting unit, laminated packaging material and / or package disclosed herein may also be applied to other substrates. The paperboard web is herein sometimes described in relation to a machine direction. The machine direction may be understood as the direction in which the paperboard web would be forwarded in a converting unit but may be referred to even when describing the paperboard web without discussing a converting unit. The transverse direction to the machine direction may be understood as the direction in which nozzles of the converting unit would be arranged. Herein, the width of the paperboard web may be understood as the total distance from an end of the paperboard web to an opposite end in a direction transverse to the machine direction. On the paperboard web, the direction transverse to the machine direction is sometimes used synonymously with the width of the substrate.

[0010] According to an aspect, a method for control of a plurality of nozzles in an ink-jet print module is provided. The method comprises forwarding a paperboard web continuously in a machine direction, preferably at a substantially constant speed. The method further comprises printing a décor layer on a first section of the paperboard web using the ink-jet print module and printing a control layer on a second section of the paperboard web by activating the plurality of nozzles. Although the décor and control layers are referred to as layers, it should be noted that they don't necessarily needs to be arranged on different levels with respect to the paperboard web. The décor layer and the control layer may for instance both be printed immediately on top of the paperboard web. One or both layers may alternatively be printed on top of an intermediate layer or layers, such as a priming layer. The décor layer and the control layer may be printed on the full first and second section respectively, or they may be printed on a subsection of the section, only partly covering the surface of the first and second section. When printing any of the layers, in particular the control layer, the full width of the paperboard web may be printed, and even areas outside the paperboard web may be printed as well. The print area is not limited to the area of the paperboard web. The first and second sections of the paperboard web are distinct from each other, meaning that they do not overlap. By this, printing the control layer on an area of the paperboard web where no décor layer is allowed.

[0011] The control layer is a printed layer which results from controlling the nozzles in the ink-jet module with the purpose of keeping the nozzles refreshed rather than providing a décor to the packaging container. As will be described later, the control layer can also serve other purposes, for example to detect broken nozzles, but the main purpose is to keep the nozzles refreshed though recirculation.

[0012] According to an embodiment, the ink-jet print module comprises a plurality of print heads, and the plurality of print heads comprises the plurality of nozzles. In other words, each print head may comprise a collection of nozzles, and the total number of nozzles of each collection of nozzles together is equal to the total number of nozzles in the plurality of nozzles. The step of printing a control layer may comprise printing from all print heads of the ink-jet print module by activating all nozzles of the plurality of nozzles. By all nozzles of the ink-jet print module being activated, the risk of ink drying in the nozzles is reduced, and the need for modifying the ink to dry slower is reduced. For instance, a lower or no amount of humectants may be added to the ink, facilitating a more efficient drying process of the printed paperboard web with a reduced risk of damaging the paperboard material with excessive drying energy. The terms "printing" and "activating" does not necessarily mean traditional printing or printing in the same way the décor layer is printed. Printing and / or activating may refer to any process where any amount of ink is released from the nozzle, for instance the process known as "spitting", or printing at a lower frequency.

[0013] According to an embodiment, each print head is configured to print a color, and the printed control layer comprises all colors of the plurality of print heads. Each print head may for instance be configured to print a color of the CMYK color model, using the subtractive primary colors of pigment (cyan, magenta, yellow and black). The print heads may be arranged sequentially after each other in the machine direction, for instance in the order cyan, magenta, yellow, black. Each print head may be configured to print a unique color, or more than one print head may be configured to print the same color. The nozzles of each print head may extend in a direction transverse to the machine direction, i.e. over the width of the paperboard web. The total length of the print heads in the transverse direction may be longer than the total width of the paperboard web.

[0014] According to an embodiment, printing the décor layer comprises activating a collection of nozzles out of the plurality of nozzles, the collection of nozzles being a subset of the plurality of nozzles. By this, printing flexibility is increased as for instance the design of the décor layer and / or the paperboard web is allowed to be smaller than the width of the print heads, without compromising the integrity of the nozzles of the print heads. By printing the control layer over the full width of the print heads and activating all nozzles, it is ensured that the ink in each nozzle is recirculated and prevented from drying, even when the décor layer is small or does not comprise all colors available by the print heads.

[0015] According to an embodiment, printing the control layer comprises activating the plurality of nozzles simultaneously, such that the control layer has an elongated extension in a direction transverse to the machine direction after printing. By this, a more efficient printing process is facilitated, as all nozzles may be activated at once. Further, the resulting printed control layer on the paperboard web may be smaller in size, allowing for easier placement on part of the paperboard web that will be removed prior to, or hidden during folding of the resulting packaging product. Beneficially, activating all nozzles at once in an ink-jet print module will result in a similar and predictable control layer each time, which may be used for instance as a test pattern indicative of the status of the print heads and print quality.

[0016] According to an embodiment, the step of printing the décor layer is repeated across the paperboard web in the machine direction during a conversion cycle, and the step of printing the control layer is performed once during the conversion cycle. By this, a more efficient printing process is allowed, while ensuring maintained integrity of the nozzles.

[0017] According to an embodiment, the control layer is printed in the beginning or in the end of the conversion cycle. By this, removal of the sections of the paperboard web comprising the control layer prior to folding the paperboard web into a package is facilitated, ensuring a more material and time efficient process without visual obstructions on the resulting package.

[0018] According to an embodiment, the method further comprises executing a tickling function in the plurality of nozzles. Tickling is a similar function to printing or spitting, but in tickling, when the nozzles fire, the drive voltage or pulse timing is reduced to ensure a drop is not ejected. This allows the ink near the nozzle to be recirculated without leaving the nozzle. Executing a tickling function is on its own not efficient enough to overcome the above-identified limitations of the prior art. This is at least because the fluid is still evaporation, so even when recirculating, the ink is getting thicker and thicker over time. Eventually the ink will be too thick, and the effectiveness is lost. However, tickling in combination with regularly activating the plurality of nozzles may be highly effective in reducing latency effects in the print module.

[0019] According to an embodiment, the method further comprises drying the décor layer and the control layer by exposing the paperboard web to infrared radiation, IR. A drying process utilizing IR is a highly efficient method for drying printed ink. A drawback is the penetration depth of IR that also may dry the paperboard web when used as substrate. In order to ensure an efficient printing and drying process, while mitigating the risks associated with reduced paperboard moisture, it is important to print with a relatively quick drying ink, and not for instance an ink with a high amount of humectants. By activating all nozzles during a conversion cycle, it is enabled to print with a faster drying ink, allowing IR to be used for drying and ensuring an efficient process.

[0020] According to an embodiment, the method further comprises folding the paperboard web into a packaging container. The first section of the paperboard web may correspond to an area of the packaging container which is visible after folding, and the second section may correspond to an area of the packaging container which is non-visible after, and / or is removed prior to the step of folding. By this, it is ensured that the integrity of the nozzles is maintained without obstructing the visual impression of the folded packaging container.

[0021] According to an aspect, a converting unit, configured to continuously manufacture a laminated packaging material, is provided. The converting unit comprises a feeding unit configured to continuously forward a printed paperboard web in a machine direction, preferably at a constant speed. The converting unit further comprises an ink-jet print module comprising a plurality of print heads, wherein the plurality of print heads comprises a plurality of nozzles. The ink-jet print module is configured to print a décor layer on a first section of the paperboard web and is further configured to print a control layer on a second section of the paperboard web by activating the plurality of nozzles. The first and second section are distinct from each other. The converting unit may be configured to perform the continuous in-line method for control of a plurality of nozzles described herein and therefore implies all aspects disclosed with regard to that method.

[0022] According to an embodiment, the plurality of nozzles extends across the paperboard web in a direction transverse to the machine direction.

[0023] The converting unit may further comprise a drying station, preferably an IR drying station and / or a creasing station configured to provide a crease line pattern to the printed paperboard web, and / or at least one lamination station configured to laminate at least a further layer to the printed and creased paperboard web.

[0024] According to an aspect, a laminated packaging material is provided. The laminated packaging material comprises a paperboard web having a décor layer on a first section and a control layer on a second section, the first and second section being distinct from each other. The paperboard web of the laminated packaging material may be printed using the continuous in-line method for control of a plurality of nozzles described herein and therefore implies all aspects disclosed with regard to that method.

[0025] According to an embodiment, the décor layer and the control layer have an extension on the paperboard web in a direction transverse to a machine direction, and the extension of the control layer is larger than the extension of the décor layer.

[0026] According to an embodiment, the control layer extends over the full width of the paperboard web in a direction transverse to a machine direction.

[0027] According to an aspect, a package is provided. The package is folded from a laminated packaging material according to any such material described herein, and the control layer is at least partly hidden in, and / or absent from, the folded package.

[0028] All possible features mentioned above should be assumed as valid for all aspects of the invention, as long as being under the scope of the claims. Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.Brief Description of the Drawings

[0029] Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings. Fig. 1 is a perspective view of a converting unit according to an embodiment. Fig. 2 is a top view of a laminated packaging material according to an embodiment. Fig. 3 is a top view of a paperboard web according to one embodiment moving through a part of the converting unit of Fig. 1 Fig. 4 is a top view of a paperboard web according to one embodiment moving through a part of the converting unit of Fig. 1. Fig. 5 is a flow chart of a method according to an embodiment. Detailed Description

[0030] A package, such as a liquid food or beverage container, is formed by folding blanks or a continuous tube-based forming of a laminated packaging material. The packaging material is typically manufactured in a manufacturing unit, such as a converting unit. By an ink-jet print module of the converting unit, a décor layer is printed onto a substrate which, after a series of process steps, eventually forms part of the laminated packaging material. In the following description, the substrate is referred to as a paperboard material. To maintain the integrity of the nozzles of the print module, an in-line method and system for control of a plurality of nozzles is provided and which will be described in the following.

[0031] With reference to Fig.1, a converting unit 2 configured to manufacture a laminated packaging material is illustrated schematically. The converting unit 2 comprises at least one feeding unit 23, here illustrated as two feeding rolls. The feeding unit(s) 23 is configured to continuously forward a paperboard web 10 in a machine direction MD, as indicated by the arrow markings in Fig. 1, preferably at a substantially constant speed.

[0032] The converting unit 2 further comprises an ink-jet print module 20 comprising a plurality of print heads 21. Each print head 21 of the plurality of print heads 21, illustrated in an enlarged view in Fig.1, may be configured to print an assigned color. Each print head 21 may for instance be configured to print a color of the CMYK color model, using the subtractive primary colors of pigment (cyan, magenta, yellow and black). The print heads 21 may be arranged sequentially after each other in the machine direction MD, for instance in the order cyan, magenta, yellow, black (CMYK), or cyan, magenta, black, yellow (CMKY). Each print head 21 may be configured to print a unique color. Alternately, there may be several print heads 21 for each unique color. It should be noted that the exact configuration of the ink-jet print module 20 may be different depending on the particular application; for example, the ink-jet print module 20 may comprise multiple print heads 21 arranged in the machine direction MD and / or a direction transverse to the machine direction MD. The plurality of print heads 21 may cover the entire area of the paperboard web 10. Each print head 21 of the plurality of print heads 21 comprises a collection of nozzles 22, the collection of nozzles 22 being a subset of a plurality of nozzles 22. The collection of nozzles 22 of each print head 21 may extend in a direction transverse to the machine direction MD, i.e. over the width W of the paperboard web 10. The total length of the print heads 21 in the transverse direction may be longer than the total width W of the paperboard web 10.

[0033] The ink-jet print module 20 is configured to print a décor layer 30 on a first section 11 of the paperboard web 10, as well as a control layer 40, on a second section 12 of the paperboard web 10. The first and second sections 11, 12 are distinct from each other, meaning that they do not overlap. The width of the décor layer 30 may be equal to or smaller than the width W of the paperboard web 10, and the width W of the paperboard web 10 may be smaller than the width of the plurality of print heads 21. Hence, printing S2 the décor layer 30 may comprise activating only a collection of nozzles out of the plurality of nozzles 22, the collection of nozzles 22 being a subset of the plurality of nozzles 22. The control layer 40 is printed by activating all nozzles 22 of the plurality of nozzles 22. Preferably, the plurality of nozzles 22 are activated simultaneously, i.e. at the same time. In the illustrated example, there are two printed décor layers 30 on two first sections 11 of the paperboard web 10, and one control layer 40 printed across the paperboard web 10 in a direction transverse to the machine direction MD. As the plurality of print heads 21 in this case extends outside the width W of the paperboard web 10, the control layer 40 is printed across the paperboard web 10 and extends further outside the paperboard web 10 in a transverse direction. The control layer 40 may alternatively or additionally extend in a parallel direction to the machine direction MD, or in any angle of choice with respect to the machine direction MD. The control layer 40 may extend continuously in the shape of a line, or two or more parallel lines, or dots, square shapes, shorter line sections etc., depending on the arrangement of the plurality of nozzles 22 and the timing of the print S4.

[0034] The décor layer 30 is preferably cyclic in the machine direction MD. This means that a repetitive series of décor layers 30 are printed on the paperboard web 10 in the machine direction MD during printing. The control layer 40 may be cyclic as well, for instance following the cycles of the décor layer, or every other cycle etc. Alternatively, the control layer may be printed a set number of times during each production run, also referred to as conversion cycle. As an example, the control layer 40 may be printed in the beginning of the conversion cycle, before the first décor layer 30, and / or in the end of the conversion cycle, after the last décor layer, and / or in the middle of production, between two sections comprising a printed décor layer 30.

[0035] Although not illustrated, the converting unit 2 may further comprise a drying station configured to dry the décor layer 30, as well as the control layer 40, preferably by exposing the paperboard web 10 to IR, or other drying techniques, such as, NIR, hot air. The drying station may be arranged downstream the ink-jet print module 20 in the machine direction MD. A priming station (not shown) may also be provided in the converting unit 2, before the ink-jet print module 20. Further, the converting unit 2 may comprise a creasing station (not shown) configured to provide a crease line pattern to the printed paperboard web 10, and / or a lamination station (not shown) configured to laminate at least a further layer to the printed and creased paperboard web 10. After printing, drying, creasing, and / or lamination, the so formed web of laminated packaging material 1 may be transferred to a cutting and / or folding station (not shown) to form a package.

[0036] Fig. 2 illustrates a paperboard web 10 moving through a part of the converting unit 2 described above. More specifically, the paperboard web 10 is leaving the ink-jet print module 20 in the machine direction MD where the décor layer 30 and the control layer 40 have been printed onto the web 10. The printed paperboard web 10 is divided into sections, in this case a first section 11 and a second section 12. The first section 11 may be a section later used as a blank from which a package is formed, for instance a section which, if the web of packaging material later is cut into individual sections for a blank-fed packaging machine, will be kept while other sections are discarded. The first section is printed with the décor layer 30. The second section 12 is printed with the control layer 40, and in this example located at an area of the paperboard web 10 which will later be discarded. Alternatively, the second section 12 may represent a section which after folding will be located at least partly hidden in the package. The control layer 40 is illustrated as a straight line, extending in a transverse direction to the machine direction MD. The skilled person realizes that other shapes are feasible.

[0037] The second section 12 on which the control layer 40 is printed extends continuously over the full width W of the paperboard web 10 and the control layer 40 is printed over the full width W of the paperboard web 10 in the second section 12. In this example, the control layer 40 is printed continuously over the full width W, meaning that there are no interruptions or gaps in the printed control layer 40 in the width W direction. However, the control layer 40 could still be printed with gaps in the machine direction MD, for instance if the control layer 40 is printed as a plurality of lines extending continuously over the full width W of the paperboard web 10.

[0038] In other embodiments, for instance if the nozzles are arranged with gaps between them, the resulting control layer 40 may extend non-continuously over the width W, for instance in a pattern.

[0039] The control layer 40 may comprise all colors of the print heads 21 of the ink-jet print module 20 since the control layer 40 is printed by activating the plurality of nozzles 22 of the plurality of print heads 21. The colors may be printed next to each other, for instance in a parallel line pattern, or on top of each other, potentially mixing into other colors.

[0040] Fig. 3 illustrates another example of a paperboard web 10 moving though part of the converting unit 2 described above. More specifically, the paperboard 10 is forwarded in a machine direction MD from the feeding unit 23 through the ink-jet print module 20. The paperboard 10 has multiple lanes 17 along the width W of the paperboard 10. As shown in Fig. 3, each lane 17 may have one or more first sections 11 on which a décor layer 30 is printed. The décor layers 30 printed in the first sections 11 are preferably identical, at least within the same lane 17. The first sections 11 of the lanes 17 may, as illustrated in Fig. 3, be shifted in the machine direction MD between the lanes.

[0041] The lanes 17 may be separated by areas without any decor that may be left for slitting to separate the lanes 17 from each other. Slitting the lanes from each other can make them ready to be fed though a package forming machine to form a plurality packaging containers. Alternatively, each lane may first be cut into individual pieces, where each piece can be used to form a single packaging container. Regardless, each part of a lane 17 configured to form a packaging container may comprise one first section 11 provided with said décor print 30.

[0042] Unlike the first sections 11, the second section 12 extends continuously over the entire width W of the packaging material 10, i.e. continuously across all lanes 17. Accordingly, only a subset of the nozzles may be activated to print the décor layer 30 while all nozzles can be activated to print the control layer 40. This ensures that all nozzles, even those that are not used to provide the décor layer 30, are activated at least now and then to keep them refreshed and ensure that the ink inside them is recirculated. By activating the nozzles to print on a continuous section 12 over the entire width W, a more efficient printing process is facilitated, as all nozzles may be activated simultaneously or close in time. By having the second section 12 extend continuously over the entire width W, it can be easier to remove it from the paperboard later. For example, if a second section 12 is placed in the beginning and / or end of a roll of the packaging material 10 or conversion cycle, the second section 12 may correspond to a section which is naturally removed as part of splicing. Splicing can for instance be performed as part of the lamination or slitting process to join the end of one roll of packaging web 10 to another roll of packaging web 10 without having to stop the machine. Splicing typically involves cutting off some of the paperboard web 10 at one or both ends which are to be joined. Accordingly, by placing the control layer 40 on a second section 12 located at in the beginning or end of a roll (in the machine direction MD), the control layer can be removed as part of the regular manufacturing process.

[0043] Even if all or parts of the second section 12 printed with the control layer 40 is kept during the splicing, this section will be discarded later since packaging containers with splices are not wanted.

[0044] As explained, the main purpose of printing the control layer 40 is to keep the nozzles refreshed. However, as previously mentioned, the control layer 40 could also be used as a test pattern to indicate the status of the print heads and / or the print quality.

[0045] In some embodiments, test patterns 50 which are separate from the control layer 40 could also be printed, as exemplified in Fig. 4. These test patterns 50 can be fixed in relation to the décor layer 140 and thereby also be cyclic in the machine direction MD. Each test pattern 50 can extend at least partially across the décor layer 30 or across the entire décor layer 30. Moreover, the test pattern 50 may extend over the entire décor layer 30 in a continuous or non-continuous manner. The test pattern 50 is typically printed on an area which will be at least partly hidden when a final package is folded. The test patterns 50 can, alternatively or additionally to the control layer 40, be used to inspect the quality of the print and / or nozzles.

[0046] Unlike the test patterns 50, which can extend over the width of a separate lane 17, the control layer 30 is printed, preferably continuously, on a section 12 which extends over the entire width W of the packaging web 10, in this case across all lanes 17.

[0047] Turning now to Fig. 5, an embodiment of a continuous in-line method for control of a plurality of nozzles 22 of an ink-jet print module 20 is illustrated. The method may be performed in the converting unit 2 as described above. Conversely, the converting unit 2 is configured to perform the method as will now be described. Moreover, all aspects disclosed with regard to the method may be implied also for the converting unit 2, as well as the other way around.

[0048] The method includes a step S1 of forwarding a paperboard web 10 continuously in a machine direction MD, preferably at a substantially constant speed. The machine direction MD may be defined as the direction parallel to the movement of the paperboard web 10 through a manufacturing equipment such as a converting unit 2, or as the circumferential direction of a roll of paper used for providing the paperboard web 10. Next, a step of ink-jet printing S2 a décor layer 30 on a first section 11 the paperboard web 10 is performed, using the ink-jet print module 20, and more specifically the nozzles 22 of the print heads 21 included therein. The printing S2 of a décor layer 30 may be performed using application of droplets randomly distributed to the paperboard web 10 during the process. By printing small droplets randomly distributed, and continuously during the of ink-jet printing S2, the printing ink then being continuously exchanged in the nozzles, limiting clogged or blocked nozzles. Clogging of and blocked nozzles could lead to print defects.

[0049] In printing different sizes of droplets may be used. In the waveform there may be three different droplet sizes (named small, medium, and large). The sizes of droplets are connected to how much voltage is needed to fire a drop. The larger a droplet is the more percentage of voltage is needed for the firing the ink. Spitting is for ink printing another term that can be used for the small drops, when they are used to sort of clean the nozzles. Then it is to use the lowest percentage voltage for firing and have a movement of the ink as a "background noise" for the printheads to limit clogging and blockage of the nozzles. This allows for a tickling motion but have every now and then, e.g., every 10 000 cycle of tickling is a little stronger and fire to refresh the nozzle.

[0050] The paperboard web 10 may comprise paper, paperboard or other cellulose-based material. Ink-jet printing is a type of digital printing or computer printing. During ink-jet printing, a digital image is recreated by propelling droplets of ink onto a substrate, such as a paperboard web 10 or a primer layer (not shown). The method may further comprise other printing techniques, such as flexographic printing, and the décor layer 30 may hence be obtained by ink-jet printing only, or by a hybrid approach combining two or more printing techniques. In other words, the décor layer 30 may be ink-jet printed and flexography printed.

[0051] Following the printing of the décor layer 30, a step S3 of printing a control layer 40 onto a second section 12 of the paperboard web 10 is performed by activating the plurality of nozzles 22. The printing 32 of a control layer 40 may be performed using application of droplets randomly distributed to the paperboard web 10 during the process. By printing small droplets randomly distributed, and continuously during the of ink-jet printing S2, the printing ink then being continuously exchanged in the nozzles, limiting clogged or blocked nozzles, which in turn may lead to print defects. The first and second sections 11, 12 being distinct from each other. Printing S3 the control layer 40 may comprise printing from all print heads 21 of the ink-jet print module 20 by activating all nozzles 22 of the plurality of nozzles 22. Preferably, printing S3 the control layer 40 comprises activating the plurality of nozzles 22 simultaneously. Optionally, the step S2 of printing the décor layer 30 and the step S3 of printing the test pattern of the control layer 40 are performed substantially at the same time, for instance by continuously activating print heads 21 of the ink-jet print module 20. The steps S2 and / or S3 of printing a décor layer 30 and a control layer 40 on the paperboard web 10 may be performed repeatedly along the paperboard web 10. In other words, the paperboard web 10, when moving through a converting unit 2 as disclosed herein, may have a print, or coating, which is cyclic along the longitudinal direction of the paperboard web 10. Put differently, the décor layer 30 may be cyclic in the machine direction MD. Also, the control layer 40, which is printed on a distinct section as the décor layer, may be cyclic in the machine direction MD with the same or a different interval. The control layer 40, comprising printed ink from all nozzles 22 of the plurality of nozzles 22 may be used as a test pattern which when inspected may indicate defective nozzles 22, and even location of malfunctioning nozzles 22 among the plurality of nozzles 22.

[0052] In the optional step S4, a tickling function in the plurality of nozzles 22 may be executed. Tickling is performed after and / or during printing, i.e., during and / or after the step S2 of printing the décor layer 30, and during and / or after the step S3 of printing the test pattern of the control layer 40. The tickling function may comprise printing S2 and / or S3 with a reduced drive voltage or pulse timing in order to ensure a drop is not ejected. Within the print module, tickling is included in the wave formation, as a low energy pulsing (background waves) but also when the nozzle is resting (not in a waveform cycle) as the same low energy background wave. Tickling is providing smaller waves within the print module compared to when the printing ink is fired, i.e. the ejection of ink droplets from the printhead nozzles onto the printing surface. To exemplify the tickling may e.g., be performed using only a tenth of the wave height compared to the wave height upon firing the ink.

[0053] Further optionally, the décor layer 30 and control layer 40 may be dried on the paperboard web 10 by e.g., being exposed to infrared radiation, IR. Beneficially, since all nozzles 22 of the plurality of nozzles 22 are continuously activated, a relatively fast drying ink may be selected as the ink used for printing without risking clogged or blocked nozzles 22, and drying S5, e.g., using IR, may be performed at a balanced intensity where the paperboard material is not overexposed and dried out.

[0054] Optionally, at some stage after drying, the second section 12 which is printed with the control layer 40 may be removed from the paper web 10, for instance as part of a splicing process, as explained above.

[0055] The printed paperboard web 10 may be divided into multiple sections which are to be folded S6 into respective packages. The packages may also be referred to as food or beverage containers. The sections are preferably separated by a crease line pattern which may be provided in a step after drying the printed décor layer 30 and the control layer 40. The crease line pattern facilitates the formation of a packaging container from the web of laminated packaging material 1. The crease line pattern is preferably repeated in the machine direction MD. Along the length of the paperboard web 10, the décor layer 30 is printed on the first section(s) 11, and the control layer is printed on the second section(s) 12 of the paperboard web 10. The first and second sections 11, 12 may be comprised in the same section which is to be folded into a package. In this case, the second section 12 is preferably located at a position within the section such that the control layer 40 is at least partly hidden after folding the paperboard web 10 to form the package. Alternatively, or additionally, the second section 12 may at least partly be located outside the section which is to be folded into a package. In this case, at least part of the second section 12 with the printed control layer 40 will be cut off prior to folding the web 10 into a package.

[0056] From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.

Examples

Embodiment Construction

[0030]A package, such as a liquid food or beverage container, is formed by folding blanks or a continuous tube-based forming of a laminated packaging material. The packaging material is typically manufactured in a manufacturing unit, such as a converting unit. By an ink-jet print module of the converting unit, a décor layer is printed onto a substrate which, after a series of process steps, eventually forms part of the laminated packaging material. In the following description, the substrate is referred to as a paperboard material. To maintain the integrity of the nozzles of the print module, an in-line method and system for control of a plurality of nozzles is provided and which will be described in the following.

[0031]With reference to Fig.1, a converting unit 2 configured to manufacture a laminated packaging material is illustrated schematically. The converting unit 2 comprises at least one feeding unit 23, here illustrated as two feeding rolls. The feeding unit(s) 23 is configur...

Claims

1. A method for control of a plurality of nozzles (22) in an ink-jet print module (20), the method comprising: forwarding (S1) a paperboard web (10) continuously in a machine direction (MD), printing (S2) a décor layer (30) on a first section (11) of the paperboard web (10) using the ink-jet print module (20), and printing (S3) a control layer (40) on a second section (12) extending continuously over the full width (W) of the paperboard web (10) in a direction transverse to the machine direction (MD) by activating the plurality of nozzles (22), wherein the first and second sections (11, 12) are distinct from each other.

2. Method according to claim 1, wherein printing (S3) the control layer comprises printing over the full width (W) of the paperboard web (10).

3. Method according to claim 2, wherein printing (S3) the control layer comprises printing continuously over the full width (W) of the paperboard web (10).

4. Method according to any of the preceding claims, wherein the paperboard web (10) is configured to form one or more packaging containers, and the second section (12) corresponds to an area which is configured to be removed prior to forming the one or more packaging containers.

5. Method according to claim 4, further comprising removing the second section (12) of the paperboard web (10).

6. Method according to any previous claim, wherein a lower frequency and / or smaller drop size is used for printing (S3) the control layer (40) than for printing (S2) the décor layer (30).

7. Method according to any one of the preceding claims, wherein the ink-jet print module (20) comprises a plurality of print heads (21), the plurality of print heads (21) comprising the plurality of nozzles (22), and wherein the step of printing (S3) a control layer (40) comprises printing from all print heads (21) of the ink-jet print module (20) by activating all nozzles (22) of the plurality of nozzles (22).

8. Method according to claim 7, wherein each print head (21) is configured to print a color, and wherein the printed control layer (40) comprises all colors of the plurality of print heads (21).

9. Method according to any one of the preceding claims, wherein printing (S2) the décor layer (30) comprises activating a collection of nozzles (22) out of the plurality of nozzles (22), the collection of nozzles (22) being a subset of the plurality of nozzles (22).

10. Method according to any one of the preceding claims, wherein printing (S3) the control layer (40) comprises activating the plurality of nozzles (22) simultaneously, such that the control layer (40) extends continuously in a direction transverse to the machine direction (MD) after printing (S3).

11. Method according to any one of the preceding claims, wherein during a conversion cycle, the step of printing (S2) the décor layer (30) is repeated across the paperboard web (10) in the machine direction (MD), and wherein the step of printing (S3) the control layer (40) is performed fewer times than the step of printing (S2) the décor layer (30) during the conversion cycle.

12. Method according to claim 11, wherein the control layer (40) is printed (S3) in the beginning and / or in the end of the conversion cycle.

13. Method according to any previous claim, wherein the paperboard web (10) has multiple lanes (17) along the width (W) of the paperboard (10), each lane (17) comprising at least one distinct first section (11), and wherein and the step of printing (S2) a décor layer is repeated for the first section (11) of each lane (17) of the paperboard web (10).

14. Method according to any one of the preceding claims, further comprising executing (S4) a tickling function in the plurality of nozzles (22).

15. Method according to any one of the preceding claims, further comprising drying (S5) the décor layer (30) and the control layer (40) by exposing the paperboard web (10) to infrared radiation (IR).

16. Method according to any one of the preceding claims, further comprising folding (S6) the paperboard web (10) into a packaging container, wherein the first section (11) of the paperboard web (10) corresponds to an area of the packaging container which is visible after folding (S6), and wherein the second section (12) corresponds to an area of the packaging container which is non-visible after, and / or is removed prior to the step of folding (S6).

17. A converting unit (2) configured to continuously manufacture a laminated packaging material web, the converting unit (2) comprising a feeding unit (23) configured to continuously forward a paperboard web (10) in a machine direction (MD), and an ink-jet print module (20) comprising a plurality of print heads (21), the plurality of print heads (21) comprising a plurality of nozzles (22), the ink-jet print module (20) being configured to print a décor layer (30) on a first section (11) of the paperboard web (10), and further configured to print a control layer (40) on a second section (12) extending continuously over the full width (W) of the paperboard web (10) in a direction transverse to the machine direction (MD) by activating the plurality of nozzles (22), the first and second section (11, 12) being distinct from each other.

18. The converting unit according to claim 16, wherein the plurality of nozzles (22) extends across the paperboard web (10) in a direction transverse to the machine direction (MD).

19. A laminated packaging material (1), comprising a paperboard web (10) having a décor layer (30) on a first section (11) and a control layer (40) on a second section (12) extending continuously over the full width (W) of the paperboard web (10) in a direction transverse to the machine direction (MD), the first and second section (11, 12) being distinct from each other.

20. The laminated packaging material (1) according to claim 18, wherein the control layer (40) extends over the full width (W) of the paperboard web (10) in a direction transverse to a machine direction (MD).

21. The laminated packaging material (1) according to claim 19, wherein the control layer (40) extends continuously over the full width (W) of the paperboard web (10).

22. The laminated packaging material (1) according to any one of claims 18-20, wherein the paperboard web (10) has décor layers (30) on a plurality of distinct first sections (11) which are repeated across the paperboard web (10) in the machine direction (MD) and / or along the width (W) of the paperboard (10)23. A package, folded from a laminated packaging material (1) according to any one of claims 18-22, wherein the control layer (40) is at least partly hidden in, and / or absent from, the folded package.

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