Inkjet printing method

Abstract

An inkjet printing method on a continuous substrate web (100), the substrate web having a pair of edges (1011, 1021), the method comprising the steps of: a) forming a pair of elongated strips (101, 102) by bending the substrate web (100) along a pair of lines (1010, 1020), wherein each line is parallel to the pair of edges (1011, 1021); and b) supporting the bent substrate web in a support area (201) of a printing press (200), wherein the pair of elongated strips (101, 102) are oriented below the area (201); and printing an image (500) on the supported substrate web by an inkjet print head (202) of the printing press (200).

Description

Field of the Invention

[0001] The present invention relates to an inkjet printing method on a continuous substrate web, in particular a lightweight continuous substrate web, having edge corrugations. Background Art

[0002] For decades, inkjet printing methods on a continuous substrate web (100) have been explored, both by multi-pass printing and by single-pass printing, where the continuous substrate web (100) is transported by a web feed roller pair process or a web feed roller to sheet process. The substrate web (100) is transported by a roller, a so-called input roller (111), that unwinds the substrate web (100) before being supported in a support area (201) of a printing press. After printing, the substrate web can be cut into sheets or can be rewound onto another roller, a so-called output roller (112). The continuous substrate web is typically a lightweight material that can be wound around a roller for printing. It can be easily bent around a core. The printing press has means for supporting the input roller (111) and optionally the output roller (112) and is configured to transport the substrate web (100) under an inkjet printhead (202).

[0003] The method attempts to solve known problems that result in poor print quality when using inkjet printing technology on a continuous substrate web (100):

[0004] - Irregular transport speeds of the substrate web (100);

[0005] - Web swim of the substrate web (100);

[0006] - Tension or contraction of the substrate web (10) due to changes in internal forces in the substrate web (100) during printing, drying, and / or transport.

[0007] Examples of the method are applied in the following printing presses:

[0008] - Agfa Dotrix Modular, manufacturer AGFA NV;

[0009] - KBA Rotajet, manufacturer Koenig & Bauer AG;

[0010] - Rho 312R Plus / LED, manufacturer Durst Phototechnik AG;

[0011] -Gallus Labelfire 340, manufactured by Heidelberg Druckmaschinen Aktiengesellschaft.

[0012] Another problem is the unevenness at the edges (1011, 1021) of the continuous substrate web (100) when transporting the substrate web (100) under the inkjet print head (202) of the printing press (200). The unevenness occurs after the substrate web (100) is unwound and transported towards the support area (201), and is the result of the following: the previous unwinding of the input roller (111), the previous cutting of the large roller into smaller rollers, the storage conditions of the input roller (11), the internal forces in the substrate web (100) that change after unwinding; the internal forces at the substrate edges are lower than those in the middle of the substrate; the humidity of the input roller (111) and / or the humidity of the printing chamber. The unevenness is sometimes referred to as edge waviness.

[0013] US9682573 BB (XEROX CORPORATION) discloses a method in which the unevenness at the edges (1011, 1021) is first calendered before printing to obtain an overall flat substrate web. It has been found that this is not feasible for any type of material of the substrate web.

[0014] The unevenness may also cause the substrate web (100) to be not pressed against the support area (201) of the printing press (200) ideally, which may lead to a collision of the substrate web (100) with the inkjet print head (202) of the printing press (200) and generate wrinkles in the substrate web (100) during the transportation of the substrate web (100) through the printing press (200). Summary of the Invention

[0015] The object of the present invention is to provide a solution for pressing well a substrate web (100) with edge waviness, so that no wrinkles occur in the substrate web (10) during transportation under the inkjet print head (202) of the printing press.

[0016] This object has been achieved by an inkjet printing method as defined in claim 1.

[0017] From the following description, other objects of the present invention will become apparent. Description of the Drawings

[0018] Figures 1 to 5 is a cross-section of an inkjet printing press (200) of a preferred embodiment, with the inlet of the substrate web (100) from the input roller (111) on the left.

[0019] Figure 6is a cross-section of a preferred printing press (200) that shows how a bent substrate web (100) is applied to a support area (201).

[0020] Figures 7 to 9 is a halftone image of a preferred hemming unit (203). Figure 8 and Figure 9 also shows the substrate web (100) bent by the hemming unit (203). The bending is shown by small black arrows. At the other edge of the substrate web (100), there is a similar hemming unit (204) in the printing press (200). It is a mirror version. The mirror version is not shown in the image.

[0021] Figure 10 and Figure 11 shows Figures 7 to 9 the hemming unit of. Figure 11 is an unassembled hemming unit.

[0022] Figure 12 shows how the substrate web (100) is bent in a top view of a preferred printing press (200), i.e., a single-pass inkjet printing press, in which an elongate inkjet printhead (202) is positioned above the substrate web (200).

[0023] Figure 13 shows how the substrate web (100) is bent in a top view of a preferred printing press (200), i.e., a multi-pass inkjet printing press, in which the inkjet printhead (202) is configured to move across the substrate web (100). Detailed Description

[0024] The present invention is an inkjet printing method on a continuous substrate web (100) having a pair of edges (1011, 1021), comprising the steps of:

[0025] a) forming a pair of elongate strips (101, 102) by bending the substrate web (100) along a pair of lines (1010, 1020), wherein each line is parallel to the pair of edges (1011, 1021); and

[0026] b) Support the bent substrate web in the support area (201) of a printing press (200), wherein the pair of elongate strips (101, 102) are oriented below the area (201); and print an image (500) on the supported substrate web by means of an inkjet print head (202) of the printing press (200). Thus, the elongate strips (101, 102) are not supported by the support area (201). Thus, instead of flattening the pair of edges (1011, 1021) before printing as known in the prior art, the pair of edges are bent before printing. In the invention, the material of the substrate web (100) between the pair of lines (1010, 1020) contacts the support area (201).

[0027] As Figure 6 shown, the substrate web (100) is applied to the support area (201), here located on a vacuum belt (250), wherein a vacuum table (253) is used to provide vacuum power in the support area (201) via a vacuum chamber (255). Before being applied to the support area (201), the edges (1011, 1021) are bent and oriented below the support area (201) after being applied to the support area (201). The elongate strips (101, 102) are formed along the lines (1010, 1020) at a defined bending angle (2010). The lines are also referred to as bending lines.

[0028] When the substrate web (100) is supported, the elongate strips (101, 102) are thus also oriented below the substrate web (100) between the strips (101 102). This can be done by bending the substrate web (100) at a bending angle greater than or equal to 90 degrees. Thus, the bending is not a fold resulting in a bending angle of 0 degrees.

[0029] The elongate strips (101, 102) are preferably located on both sides of the support means where the support area is located. The support means is, for example, a conveyor belt or a printing table.

[0030] The elongate strips (101, 102) are applied by bending the substrate web (100) by means of hemming machine units (203, 204) respectively, and when the substrate web is supported on the area (201), the elongate strips will be further oriented below the support area (201). Thereby, the substrate web is positioned more stably on the area (201). The pair of lines (1010, 1020) formed after step a) provides higher stiffness in the substrate web, while the elongate strips (101, 102) act like a pair of flanges located outside the support area and more precisely below the support area.

[0031] The material of the substrate web (100) should of course be flexible, which mainly applies to weights below 150 g / m 2 2, and more preferably below 120 g / m2 and is higher than 10 g / m 2 of the lightweight base web. If the material of the base web includes fibers, such as cellulose fibers, the pair of lines (1010, 1020) is preferably substantially parallel to the orientation of the fibers to facilitate bending and avoid fiber breakage. The base web (100) can of course also be a polymeric base. The width of the base web is preferably greater than 1 m. The width is measured as the shortest distance between the pair of edges (1011, 1021).

[0032] In the present disclosure is a base web between elongated strips (101, 102) supported on a support area (201).

[0033] Preferably, when the continuous base web (100) is supported in the area (201), the minimum angle between the support area (201) and each of the pair of elongated strips (101, 102) is less than 160 degrees. The minimum angle is more preferably between 0.1 and 145 degrees, and most preferably between 2 and 100 degrees. The degrees depend on the material of the base web (100) and how much stiffness is caused by the downwardly directed elongated strips (101, 102) on the support area (201).

[0034] In a preferred embodiment, the width of each of the pair of elongated strips (101, 102) is less than 10 cm. The width is more preferably between 1 mm and 70 mm, and most preferably between 2 mm and 40 mm. The width is selected by the operator of the printing press (200), but is mainly selected according to the material of the base web (100) and / or how much stiffness is caused by the downwardly directed elongated strips (101, 102) on the support area (201). The width is the shortest distance between the lines (1010, 1020) of the elongated strips (101, 102), and the edges (1011, 1021) are part of the elongated strips (101, 102).

[0035] In a preferred embodiment, the inkjet printing method is a single-pass inkjet printing method ( Figure 12 ).

[0036] In a preferred embodiment, step b) includes the following step(s):

[0037] - Applying a vacuum below the support area (201) for holding the pair of elongated strips (101, 102) below the area (201); and

[0038] -Optionally, a vacuum is applied to press the supported substrate web towards the zone (201), for example, by means of a vacuum belt (250) of a preferred printing press (200) that conveys the substrate web (100) under the inkjet printhead (202). Instead of the vacuum belt (250), a vacuum table (253) of the printing press (200) can also be used. Thus, the vacuum belt (250) or the vacuum table (253) is a support device of the printing press (200) where the support zone (201) is located.

[0039] In another preferred embodiment, step b) includes the following steps

[0040] - Blowing air to hold the pair of elongate strips (101, 102) below the support zone (201); or

[0041] - Guiding the pair of elongate strips (101, 102) to hold them below the support zone (201) by means of guiding devices such as rollers or gliders.

[0042] If the support zone (201) is part of the vacuum belt (250), in the support step of step b), a part of each elongate strip (101, 102) can additionally be applied at the opposite side of the support zone (201).

[0043] Figure 11 and Figure 12 The bending of the edges (1011, 1021) of the substrate web (100) is shown as a preferred embodiment of the present disclosure, where the edges (1011, 1020) remain bent (2000) by the hemming units (203, 204) during printing, and thus form lines (1010, 1020) and elongate strips (101, 102), and they (101, 102) can be flattened after printing.

[0044] Aggregate substrate

[0045] Any polymeric substrate with a maximum Tanδ between 40 °C and 110 °C is suitable as the web-shaped polymeric substrate used in the present invention. Polyethylene is the most preferred polymeric substrate used as the web-shaped polymeric substrate in the present invention.

[0046] Polyethylene is produced in various low and high densities. The abbreviations of these materials are well-known to those skilled in the art of manufacturing polyethylene films and foils, such as UHMWPE, HDPE, PEX, MDPE, LLDPE, LDPE, and VLDPE. The latter three are most commonly used for making plastic bags.

[0047] LLDPE consists of 0.915 and 0.925 g / cm 3It is defined by the density between them and is a substantially linear polymer with a large number of short branches, usually made by copolymerizing ethylene with short-chain alpha-olefins (such as 1-butene, 1-hexene, and 1-octene). LLDPE has higher tensile strength than LDPE and exhibits higher impact resistance and puncture resistance than LDPE.

[0048] LDPE is defined by the density between 0.910 and 0.940 g / cm 3 It is defined by the density between them. LDPE has a high degree of short-chain and long-chain branching, which also means that the chains do not stack into a crystal structure. Therefore, it has less strong intermolecular forces because the instantaneous dipole-induced dipole attractions are smaller. This results in lower tensile strength and increased ductility. LDPE is produced by free radical polymerization. The highly long-chain branches give molten LDPE unique and desired flow characteristics.

[0049] VLDPE is defined by the density between 0.880 and 0.915 g / cm 3 It is defined by the density between them and is a substantially linear polymer with a high level of short-chain branches, usually made by copolymerizing ethylene with short-chain alpha-olefins (such as 1-butene, 1-hexene, and 1-octene). VLDPE is most commonly produced using metallocene catalysts because these catalysts exhibit greater comonomer incorporation.

[0050] The polymeric substrate used as the web-like polymeric substrate in the present invention is preferably selected from the group consisting of LLDPE, LDPE, and VLDPE. Most preferably, the polymeric substrate used as the web-like polymeric substrate in the present invention is LDPE.

[0051] The thickness of the polymeric substrate depends on the specific application. For plastic bags, a thickness preferably between 30 and 200 μm, more preferably between 50 and 100 μm, and most preferably between 60 and 80 μm is used.

[0052] Sometimes, a primer layer is applied to the polymeric substrate for producing specific effects such as a gloss or matte finish. As long as the dry thickness is less than 5 μm, preferably less than 3 μm, these primers have no effect on the present invention. The primer can be applied in advance, for example, by coating or flexographic printing as a continuous layer. In a preferred embodiment, the primer is a non-aqueous radiation-curable liquid.

[0053] The present disclosure (printing method) using the polymeric substrate as the substrate web (100) can also be part of manufacturing a decorative plastic bag.

[0054] Edge bend

[0055] In a preferred embodiment, the printing press (200) includes separate hemming units (203, 204) for forming each of the elongated strips (101, 102).

[0056] Each hemming unit (203, 204) is preferably used after the base web (100) is unwound and before the base web (100) is applied to the support area (201) of the printing press (200). Thereby, no wrinkles occur during the conveyance of the base web (100).

[0057] In a preferred embodiment, the inkjet printing method includes steps for controlling the width of one of the pair of elongated strips (101, 102), for example, by:

[0058] - Moving the hemming units of the pair of hemming units (203, 204) through the continuous base web for controlling the width of one of the pair of elongated strips (101, 102). The position of the hemming machine can thus also be adjusted according to the width of the base web. The printing press (200) is configured to enable such movement. Thus, it can be a frame attached to the printing press (200), which is positioned across the continuous base web, and the two hemming units (203, 204) are movably attached to the base web, for example, along tracks in the frame.

[0059] The hemming units (203, 204) preferably include a pair of staggered sliding devices (2031, 2041, 2032, 2042) for bending the continuous base web (100) between the pair of staggered sliding devices (2031, 2042, 2032), which includes support sliding devices (2031, 2041) for supporting the base web (100) and bending sliding devices (2032, 2042) for applying pressure towards the base web (100) along the support sliding devices (2032, 2042). The sliding devices (2031, 2041, 2032, 2042) in the hemming units (203, 204) are preferably rollers, more preferably rotatable rollers that rotate when the edge of the base web (100) passes through the hemming units (203, 204). This minimizes damage to the surface of the base web (100).

[0060] Figures 7 to 11 Such a preferred hemming unit is shown.

[0061] In a preferred embodiment, the inkjet printing method includes steps for controlling the bend angle at one of the pair of elongated strips (101, 102) by the hemming machine:

[0062] - Move the bending slide devices (2042, 2032) in one direction along the support slide devices (2032, 2042) towards the substrate web (100); and / or

[0063] - Move the bending slide devices (2032, 2042) in the other direction towards the support slide devices (2032, 2042).

[0064] By means of a handle (20321) as Figures 7 to 11 shown, the bending slide device (2023) can be moved towards the substrate web (100). This is shown by the white arrow. Here, the hemming unit (203) can also move along a rail or a frame, as shown by the long black arrow.

[0065] Printing press

[0066] The printing press (100) of the present disclosure is a digital printing press in which a non-contact printing technique is used together with an inkjet print head (202). The printing press is also referred to as an inkjet printing press.

[0067] To obtain good image quality, a constant height is required between the inkjet print head and the ink receiver, which is here the continuous substrate web (100). In the present disclosure, the inkjet printing press can be a multi-pass inkjet printing press ( Figure 13 ), but a single-pass inkjet printing press is preferred ( Figure 12 ). A major problem in inkjet printing is that the ink receiver may touch the inkjet print head (202), whereby the inkjet print head is damaged or has nozzles that do not eject and must be restored. If a constant height is required between the inkjet print head and the ink receiver, the ink receiver must be flat, or not warp, or not move up from the support area (201).

[0068] Figures 1 to 5 Several configurations of a preferred printing press are shown, in which the substrate web (100) is applied to the support area of the printing press, and in which the edge (1011) is bent towards the support area by the hemming unit (203). Thereby, the elongated strip (101) is formed and oriented below the support area along the line (1010). The substrate web (100) is unwound from the input roller (111) and, after printing an image by the inkjet print head (202), is rolled up or cut into sheets on the output roller (112), as Figure 2 shown, where the substrate web (100) is cut by a cutting machine (285) and the sheets are collected in the output tray (290).

[0069] Figure 1 and Figure 2Each shows a printing press (200) with a vacuum belt (250) that wraps around two pulleys (270). The support area has a vacuum area that is formed by vacuum power from a vacuum chamber (255) via a vacuum table (253). The vacuum power draws the substrate web (100) towards the support area, as shown by the vertical black arrow. The curved black arrows show the movement of the different rollers in the printing press (200).

[0070] Figure 3 A conveyor belt printing press is shown, whereby after printing an image (500), the bent substrate web (100) is flattened by a flattener (280).

[0071] Figure 4 A web printing press is shown, whereby the substrate web (100) is conveyed past a vacuum table (253) that, together with vacuum power from a vacuum chamber (255), forms a support area. The vacuum power draws the bent substrate web (100) towards the vacuum area before printing.

[0072] The image is preferably printed with one or more colored inkjet inks, which can be selected from water-based colored inkjet inks, solvent-based colored inkjet inks, and radiation-curable colored inkjet inks.

[0073] One or more colored inkjet inks preferably contain organic color pigments because they allow for a high color gamut to be obtained on the substrate web (100). Carbon black and titanium dioxide are inorganic pigments that can be advantageously used in the present disclosure to synthesize black and white colored inkjet inks, respectively.

[0074] In a preferred embodiment, one or more colored inkjet inks form a CMYK(W) or CRYK(W) inkjet ink set. The latest inkjet ink sets are an advantage for printing wood colors, especially when manufacturing decorative surfaces.

[0075] The pigment particles in the inkjet ink should be small enough to allow the ink to flow freely through the inkjet printing device, especially at the ejection nozzles. It is also desirable to use small particles to obtain maximum color intensity and to slow down sedimentation. The number average pigment particle size of the organic color pigments and the inorganic black pigment is preferably between 0.050 and 1 μm, more preferably between 0.070 and 0.300 μm, and most preferably between 0.080 and 0.200 μm.

[0076] In a preferred embodiment, the image is dried after or during printing on a continuous substrate web (100), and the image is dried by an irradiation device. The irradiation can be carried out by using UV bulbs or multiple UV light-emitting diodes or any type of IR dryer.

[0077] The printing press can perform an inkjet printing method on more than one continuous substrate web (100). An example of such a printing press is disclosed in WO2019 / 170456 (AGFA NV), which is part of a production line for manufacturing decorative surfaces.

[0078] The preferred inkjet printhead (202) of the printing press (200) is a piezoelectric printhead. Piezoelectric inkjet printing is based on the movement of piezoelectric ceramic transducers when a voltage is applied to them. The application of the voltage changes the shape of the piezoelectric ceramic transducers in the printhead, creating a void that is then filled with inkjet ink or liquid. When the voltage is removed again, the ceramic expands back to its original shape, ejecting a drop of ink from the inkjet printhead.

[0079] The preferred piezoelectric printhead is a so-called push-mode type piezoelectric printhead, which has a relatively large piezoelectric element that is also capable of ejecting inkjet ink drops of high viscosity. Such an inkjet printhead is available for purchase as a GEN5s printhead from RICOH™.

[0080] The preferred piezoelectric printhead is a so-called through-flow piezoelectric drop-on-demand printhead. Such an inkjet printhead is available for purchase as a CF1ou printhead from TOSHIBA TEC™, and is also available from RICOH™ and XAAR™. In the present invention, through-flow printheads are preferred because they enhance the reliability of inkjet printing.

[0081] The support area (201) is part of the support means of the printing press (200), which is preferably a vacuum table (253) and more preferably a vacuum belt (250). On the said table or belt, a vacuum zone serves as the support area (201) for pressing the ink receiver against it by means of a vacuum from the vacuum chamber (255) of the printing press (200). Details of a printing press with a vacuum belt (250) are disclosed, for example, in WO2016 / 071122 (AGFA GRAPHICS NV).

[0082] The support area (201) can also be formed by a plurality of rollers over which the substrate web (100) is transported for printing, as found, for example, in the Agfa Dotrix Modular from the manufacturer AGFA NV and possibly other single-pass inkjet printing presses. Figure 5 An embodiment of a preferred printing press with the said plurality of rollers (256) is shown.

[0083] After the printed image, the pair of elongate strips (101, 102) can be flattened again for further processing of the printed substrate web (100). Thus, after the substrate web is bent, the substrate web is flattened again, which can be carried out by (thermally) rubbing the elongate strips (101, 102) and / or (thermally) pressing the elongate strips (101, 102), in particular at the lines (1010, 1020). Thereby, the pair of elongate strips (101, 102) unfolds. The flattening is effected by Figures 1 to 5 the flattening device (280) in

[0084] The unfolding of the elongate strips (101, 102) in the present invention means that the bending angle is enlarged back to substantially 180 degrees.

[0085] Manufacturing a decorative surface

[0086] The inkjet printing method according to the present disclosure and all its preferred embodiments are preferably used for manufacturing decorative surfaces:

[0087] - wherein the continuous substrate web (100) is a paper substrate with a weight of less than 150 g / m 2 and an image is printed with one or more aqueous colored inkjet inks; or

[0088] - wherein the continuous substrate web (100) is a thermoplastic substrate with a weight of less than 150 g / m 2 and is based on a material selected from the group consisting of polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET) and thermoplastic polyurethane (TPU) and combinations thereof, and an image is printed with one or more UV-curable inkjet inks.

[0089] For example, the latest type of continuous substrate web is an ideal choice for manufacturing luxury vinyl tiles (LVT). WO2018060189 (AGFA NV) discloses the manufacturing method.

[0090] The one or more aqueous colored inkjet inks are preferably ejected before or after impregnating the substrate web (100) with a thermosetting resin.

[0091] Thereby, the printing press (200) according to the present disclosure is preferably part of a production line for manufacturing decorative surfaces.

[0092] The inkjet printing method preferably comprises the following steps:

[0093] - Before step a), at least one ink-receiving layer containing a polyvinyl alcohol polymer and an inorganic pigment is applied on a paper substrate, wherein more preferably, the outermost ink-receiving layer does not contain an inorganic pigment, or contains an inorganic pigment in an amount less than that of the ink-receiving layer between the paper substrate and the outermost ink-receiving layer.

[0094] The use of a hemming machine (203, 204) in a production line for manufacturing a decorative surface is also an embodiment of the present disclosure, in particular a hemming machine with the pair of staggered sliding devices (2031, 2041, 2032, 2042), as described in the "Edge Bending" section.

[0095] Manufacturing a decorative panel

[0096] The printed paper substrate in the manufacture of a decorative surface preferably becomes the decorative layer of a decorative panel, and as a decorative surface, it is more preferably selected from the group consisting of floors, kitchens, furniture, and wall panels. Here, a continuous printed substrate web, whether cut into sheets or not, is applied on a core layer such as an MDF board and optionally other layers such as a balancing layer, a protective layer, or a sound-absorbing layer, and here, after the entire assembly of the substrate web and the one or more layers, they are hot-pressed together.

[0097] For example, the DPL process (Direct Pressure Laminating) is a known method for manufacturing decorative panels.

[0098] According to the Gurley method (DIN 53120), the porosity of the paper substrate is preferably between 8 and 20 seconds.

[0099] It has been found that the pair of lines (1010, 1020) are no longer visible in the manufactured decorative panel.

[0100] In a preferred embodiment, the elongated strips (101, 102) form part of a tongue and / or groove that is applied in the decorative panel, which allows the decorative panels to fit together. The advantage is easy assembly without glue. In the field of laminate flooring, the tongue and groove shapes necessary to obtain a good mechanical connection are well known, as further illustrated in EP2280130 A (FLOORING IND), WO 2004 / 053258 (FLOORING IND), US 2008010937 (VALINGE), and US 6418683 (PERSTORP FLOORING).

[0101] For floor panels and wall panels, tongue-and-groove profiles are particularly preferred. However, in the case of furniture panels, for aesthetic reasons of furniture doors and drawer fronts, such tongue-and-groove profiles are preferably absent. However, tongue-and-groove profiles can be used to fit other panels of furniture together, as shown in US 2013071172 (UNILIN).

[0102] The image printed on the continuous substrate web (100) is preferably a wood pattern with veins. In a preferred embodiment, the veins of the printed wood pattern are oriented substantially parallel to the pair of lines (1010, 1020).

[0103] The use of edge folding machines (203, 204) in a production line for manufacturing decorative surfaces is also an embodiment of the present disclosure, in particular an edge folding machine with the pair of staggered sliding devices (2031, 2041, 2032, 2042), as described in the "Edge Bending" section.

[0104] Core layer

[0105] The core layer is preferably made of wood-based materials such as particle board, MDF or HDF (medium density fiberboard or high density fiberboard), oriented strand board (OSB), etc. Synthetic material boards or boards hardened by water such as cement boards can also be used. In a particularly preferred embodiment, the core layer is an MDF or HDF board.

[0106] As described in WO 2013 / 050910 (UNILIN), the core layer can also be assembled at least from multiple sheets of paper or other carrier sheets impregnated with a thermosetting resin. Preferred sheets of paper include so-called kraft paper obtained by a chemical pulping process, also known as the kraft process, for example, as described in US 4952277 (BET PAPERCHEM).

[0107] In another preferred embodiment, the core layer is a board material substantially composed of wood fibers, which are bonded by means of a condensation glue, wherein the condensation glue forms 5 to 20% by weight of the board material, and at least 40% by weight of the wood fibers are obtained from recycled wood. Suitable examples are disclosed in EP 2374588 A (UNILIN).

[0108] Instead of a wood-based core layer, a synthetic core layer can also be used, such as those disclosed in US 2013062006 (FLOORING IND). In a preferred embodiment, the core layer includes a foamed synthetic material such as foamed polyethylene or foamed polyvinyl chloride.

[0109] US 2011311806 (UNILIN) and US 6773799 (DECORATIVE SURFACES) disclose other preferred core layers and their manufacture.

[0110] The thickness of the core layer is preferably between 2 and 12 mm, more preferably between 5 and 10 mm.

[0111] An embodiment of the present disclosure is a method for manufacturing a decorative panel, which includes the following steps:

[0112] - Printing a wood pattern on a paper substrate according to the inkjet printing method of the present disclosure and its preferred embodiments;

[0113] - Impregnating the printed paper substrate with a thermosetting resin;

[0114] - Thermally pressing the printed paper substrate impregnated with the thermosetting resin between a core layer and a protective layer, and cutting it into a decorative panel selected from the group consisting of floors, kitchens, furniture, and wall panels.

[0115] Thermosetting resin

[0116] The thermosetting resin is preferably selected from the group consisting of melamine-formaldehyde-based resins, urea-formaldehyde-based resins, and phenol-formaldehyde-based resins.

[0117] Other suitable resins for impregnating paper are listed in

[0028] of EP 2274485 A (HUELSTA).

[0118] Most preferably, the thermosetting resin is a melamine-formaldehyde-based resin, which is commonly referred to as "melamine (based) resin" in the art.

[0119] Manufacturing a decorative corrugated cardboard

[0120] The printed paper substrate in the manufacture of the decorative surface preferably becomes the decorative finish of the facing paperboard of the decorative corrugated cardboard as the decorative surface.

[0121] In the manufacture of decorative corrugated cardboard, the printed continuous substrate web, whether cut into sheets or not, is glued to one or more grooved cardboard sheets (corrugated medium).

[0122] Corrugated cardboard is a preferred packaging material because it is low-cost and lightweight, and has the benefit that corrugated cardboard boxes are stackable, making them easy to store and transport. Corrugated cardboard is a packaging material formed by gluing one or more grooved sheets of cardboard (corrugating medium) to one or more flat liner sheets (referred to as facings). It has four common types: (a) Single-face: One grooved sheet is glued to one facing (a total of two sheets). (b) Single-wall: One grooved sheet is sandwiched between two facings (a total of three sheets); also known as double-face or single-layer. (c) Double-wall: One single-face is glued to one single-wall, so two grooved sheets are alternately sandwiched between three flat sheets (a total of five sheets); also known as double-ply or double-layer. (d) Triple-wall: Two single-faces are glued to one single-wall, so three grooved sheets are alternately sandwiched between four flat sheets (a total of seven sheets); also known as triple-layer.

[0123] The preferred corrugated cardboard in the present invention is single-wall or double-wall, more preferably single-wall corrugated cardboard, because it is strong enough and easy to crease. Single-face corrugated cardboard usually does not have enough strength to hold goods, while triple-wall cardboard is usually more difficult to crease into a packaging box.

[0124] The paper used in corrugated cardboard, such as kraft paper, is usually brown. In a preferred embodiment of manufacturing decorative corrugated cardboard, the paper substrate as the continuous base web (100) is white, for enhancing the color vitality of the inkjet ink printed thereon. The white background helps the customer experience because customers consider it a more luxurious product. Alternatively, before inkjet printing the image, a white background can be applied by coating or printing as a layer.

[0125] An embodiment of the present invention is a method of manufacturing decorative corrugated cardboard, where the continuous base web (100) is a paper substrate; and

[0126] wherein the manufacturing method has an additional step for forming the decorative corrugated cardboard: gluing the printed paper substrate to one grooved sheet of cardboard.

[0127] After printing the image (500) and before gluing to the one grooved sheet of cardboard, the elongated strips (101, 102) can be spread again. More preferably, after printing the image (500) and before gluing to the one grooved sheet of cardboard, the elongated strips (101, 102) are flattened.

[0128] List of reference numerals

[0129] 100 Base web 101 Slender strip 102 Slender strip 1010 Line 1020 Line 1011 Edge of the base web 1021 Edge of the base web 200 Printing press 201 Support area 2011 Edge of the support area 2012 Edge of the support area 202 Inkjet print head 2031 Support sliding device 2041 Support sliding device 2032 Bending sliding device 2042 Bending sliding device 203 Hemming machine unit 204 Hemming machine unit 500 Image

Claims

1. An inkjet printing method on a continuous substrate web (100), the substrate web having a pair of edges (1011, 1021), the method comprising the steps of: a) forming a pair of elongated strips (101, 102) by bending the substrate web (100) along a pair of lines (1010, 1020), each line being parallel to the pair of edges (1011, 1021); and b) supporting the bent substrate web in a support area (201) of a printing press (200), wherein the pair of elongated strips (101, 102) are oriented below the area (201); and printing an image (500) on the supported substrate web by an inkjet print head (202) of the printing press (200).

2. The inkjet printing method according to claim 1, wherein the pair of elongated strips (101, 102) are formed by a pair of hemming machine units (203, 204) of the printing press (200), each hemming machine unit having a pair of interleaved sliding devices, and wherein the continuous substrate web (100) is bent between the pair of interleaved sliding devices, the pair of interleaved sliding devices being a support sliding device for supporting the substrate web (100) and a bending sliding device for applying pressure along the support sliding device towards the substrate web (100).

3. The inkjet printing method according to claim 2, which includes a step for controlling the width of one of the pair of elongated strips (101, 102): - moving the hemming machine unit of the pair of hemming machine units (203, 204) through the continuous substrate web for controlling the width of one of the pair of elongated strips (101, 102).

4. The inkjet printing method according to claim 2, further including a step for controlling the bending angle at one of the pair of elongated strips (101, 102) by the hemming machine unit: - moving the bending sliding device in one direction along the support sliding device towards the substrate web (100); and / or - moving the bending sliding device in the other direction towards the support sliding device.

5. The inkjet printing method according to claim 4, wherein step b) includes the steps of: - applying a vacuum below the support area (201) for holding the pair of elongated strips (101, 102) below the area (201); and - applying a vacuum for pressing the supported substrate web towards the area (201).

6. The inkjet printing method according to claim 1, wherein the support area (201) has a pair of opposite edges; and each of the pair of lines (1010, 1020) is positioned along an edge of the pair of opposite edges.

7. The inkjet printing method according to claim 1, wherein the width of each of the pair of elongated strips (101, 102) is less than 10 cm.

8. The inkjet printing method according to claim 7, wherein the support area (201) is formed on the vacuum belt (250) of the printing press (200).

9. The inkjet printing method according to claim 1, wherein the continuous substrate web (100) is a paper substrate having a weight of less than 150 g / m 2 and the image is printed with one or more aqueous colored inkjet inks.

10. The inkjet printing method according to claim 1, wherein the continuous substrate web (100) is a thermoplastic substrate having a weight of less than 150 g / m 2 , and the thermoplastic substrate is based on materials selected from the group consisting of polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and thermoplastic polyurethane (TPU) and combinations thereof, and the image is printed with one or more UV-curable inkjet inks.

11. The inkjet printing method according to claim 9, wherein the porosity of the paper substrate is between 8 and 20 seconds according to the Gurley method (DIN 53120); comprising the following steps: - Before step a), applying at least one ink receiving layer containing a polyvinyl alcohol polymer and an inorganic pigment on the paper substrate; And printing the image with the one or more aqueous colored inkjet inks before or after impregnating with the thermosetting resin.

12. The inkjet printing method according to claim 11, wherein the outermost ink receiving layer does not contain an inorganic pigment, or contains an inorganic pigment in an amount less than the ink receiving layer between the paper substrate and the outermost ink receiving layer.

13. The inkjet printing method according to claim 1, wherein the printing step is a single-pass printing method.

14. A method for manufacturing a decorative panel, comprising the following steps: - The inkjet printing method according to any one of claims 11 or 12, printing a wood pattern on the paper substrate; - After flattening the strips (101, 102) by spreading a pair of strips (101, 102), impregnating the printed paper substrate with a thermosetting resin; - Thermally pressing the printed paper substrate impregnated with the thermosetting resin between a core layer and a protective layer, and cutting it into the decorative panel selected from the group consisting of floors, kitchens, furniture, and wall panels.

15. A method for manufacturing a decorative corrugated cardboard, comprising the inkjet printing method according to claim 9; and wherein the manufacturing method has additional steps for forming the decorative corrugated cardboard: - Gluing the printed paper substrate to a grooved cardboard.

Images