Digital embossed in register surface

Abstract

Building panels, especially floor panels, and a method of forming embossed in register surfaces with a digital ink head that applies a curable ink on the panel surface or on an upper side of a foil as a coating and forms an ink matrix that is used to create a cavity in the surface by applying a pressure on the ink matrix.

Claims

1. A method of forming an embossed surface on a building panel, the method comprising: providing a substrate; applying a curable ink on an upper part of the substrate, thereby forming an ink matrix on the upper part of the substrate; forming a cavity in a surface layer of the building panel by pressing a lower part of the substrate against the surface layer of the building panel, while the ink matrix is located on the upper part of the substrate that does not contact the surface layer of the building panel, thereby forming an embossed surface of the building panel, wherein the lower part of the substrate pressed against the surface layer of the building panel is free of curable ink; and removing the substrate with the ink matrix from the embossed surface.

2. The method according to claim 1, wherein the curable ink is applied by means of a digital ink head.

3. The method according to claim 1, wherein the ink matrix has a horizontal and vertical extension.

4. The method according to claim 1, wherein the surface layer comprises a decorative layer with a print or a digital print.

5. The method according to claim 4, wherein the cavity is in register with the print.

6. The method according to claim 1, wherein the substrate is a foil.

7. The method according to claim 6, wherein the foil comprises a metal.

8. The method according to claim 6, wherein the foil comprises aluminium or wherein the foil is a plastic foil.

9. The method according to claim 1, wherein the substrate is a structured release paper or a film.

10. The method according to claim 1, wherein the surface layer of the building panel comprises a thermosetting resin.

11. The method according to claim 1, wherein the surface layer of the building panel comprises a melamine formaldehyde resin.

12. The method according to claim 1, further comprising curing the curable ink.

13. The method according to claim 1, wherein the curable ink is fixedly connected to the substrate.

14. The method according to claim 1, wherein the substrate is a first basic matrix, and wherein a second basic matrix is pressed against the first basic matrix and against the ink matrix on the first basic matrix.

15. The method according to claim 14, wherein the second basic matrix is a conventional press plate.

16. The method according to claim 1, wherein the building panel is a floor panel.

17. The method according to claim 1, wherein the substrate is a pressing cylinder or a roller.

18. A method of forming an embossed surface on a building panel, the method comprising: providing a substrate, wherein the substrate is a pressing cylinder or a roller; applying a curable ink directly on a surface of the substrate for forming an ink matrix on the surface of the substrate; forming a cavity in a surface layer of the building panel by pressing the surface of the substrate and the ink matrix located on the surface of the substrate against the surface layer of the building panel, thereby forming an embossed surface of the building panel; removing the substrate from the embossed surface such that the ink matrix is transferred from the surface of the substrate to the embossed surface; and removing the ink matrix from the embossed surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will in the following be described in connection to preferred embodiments and in greater detail with reference to the appended exemplary drawings, wherein,

(2) FIGS. 1a-d illustrate known methods to produce a printed and embossed surface;

(3) FIGS. 2a-e illustrate repetition effects in embossed surfaces according to known technology;

(4) FIGS. 3a-f illustrate variable embossed in register according one embodiment of the invention;

(5) FIGS. 4a-c illustrate embodiments of the invention;

(6) FIGS. 5a-d illustrate embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) FIG. 3a-3f shows various production steps that according to the first aspect of the invention may be used to form a variable embossed in register surface in a laminate floor or any other floor where the surface is formed by pressing and preferably also by increased temperature. The method is based on a main principle where a variable embossing is formed by digitally applied curable ink or substance, also referred to as a mat ink, that after application and curing forms an matrix that is pressed against a substrate, hereafter referred to as an ink matrix.

(8) FIG. 3a shows laminate panels 1a, 1b comprising a transparent overlay 18 and a decorative paper 5 having a décor that are applied on a HDF core 3. The laminate panels 1a, 1b comprise a backing layer 4 to balance the panel. A print P1, that may be a part of a wood grain structure, is printed by a digital printer on a first panel 1a and a different print P2 is printed digitally on the second panel 1b.

(9) FIG. 3f shows the panels 1a and 1b after pressing. A part of the surface structure of the two panels, i.e. panel 1a and 1b, is in this embodiment of the invention produced with the same basic matrix 40 (FIG. 3c) that forms a basic embossing 17. This basic embossing is combined with a variable embossing 19a, 19b formed during pressing by an ink matrix 41a, 41b. The ink matrix is formed by a digitally applied curable ink 25a, 25b, also called a mat ink, that prior to the pressing step is cured to a hard substance.

(10) FIG. 3b shows that two different curable ink patterns 25a, 25b are applied in register on the two different prints P1, P2. The curable ink 25a, 25b protrudes vertically upwards from the panel surface. The vertical extension of the curable ink may be in the range of 0.05 to 0.5 mm, for example, about 0.1 mm which corresponds to a normal embossing depth of a wood grain structure.

(11) FIG. 3c shows the curable ink 25a, 25b when it is cured to a hard ink matrix 41a, 41b. The panels are thereafter moved into a press with a press table 24.

(12) FIG. 3d shows that the panels and the ink matrix 41a, 41b is pressed and heated such that the press matrix 41a, 41b is pressed into the panel surface and the panel surface is cured preferably under high heat and pressure similar to the pressing parameters used in laminate and powder based floors or LVT floors. The method may also be used to form structures in wood and ceramic material.

(13) FIG. 3e shows that when the panels leave the press they comprise an ink matrix 41a, 41b above the print P1, P2.

(14) FIG. 3f shows that the ink matrix is thereafter removed and cavities 37a, 37b are formed above the prints P1, P2. The cavities 37a, 37b form a part of a variable embossing 19a, 19b. The panels have an embossed surface comprising a basic embossing 17 and a variable embossing 19a, 19b. The variable embossing is in register with the variable digital prints P1, P2.

(15) Many polymers may be used to produce a curable ink 25 that may form an ink matrix 41. UV curing polymers are preferred. They include a wide range of polymer materials such as acrylics, acrylates, epoxies, polyurethanes, polyesters and silicones. These materials may be applied as ink with a piezo print head. They may be designed such that they do not bond to a thermosetting or thermoplastic surface, such as melamine formaldehyde resin and vinyl, and they have sufficient strength and heat resistance which is needed to form a structured surface in the production steps that are generally used to produces the above mentioned floor types. Release agents may be included in the curable ink, in the surface or as a separate printing application prior to the curable ink coating.

(16) High quality and superior properties may be obtained by water-based UV curing chemistry, which is a preferred embodiment due to environmental reasons.

(17) A wide variety of curable inks may be produced to meet the specific requirements of different surface materials by, for example combining aliphatic- or aromatic, acrylic terminated, polyurethane technology with polyester and/or acrylic materials. Water based UV curing dispersions can be formulated into transparent and/or pigmented low and high gloss curable inks and coatings.

(18) The main principles of a digital curable ink coating method and equipment are shown in FIG. 4a. A digital curable ink coating unit 36, comprising a fixed digital printing head 30, applies a preferably transparent curable ink on the overlay paper 18. The digital application is made without any contact with the overlay and the curable ink 25 is applied as drops, which are fired from the digital print head 30 towards the surface.

(19) A UV curing oven 23 with ultra violet light is located preferably after the digital coating unit 36 in the feeding direction and may provide a practically instant curing within a few seconds of the curable ink 25 into an ink matrix 41, especially if, for example a UV cured polyurethane coating with an appropriate photo polymerization initiator is used. The digital coating head 30, which preferably is a piezo head, has preferably a capacity to fire drops with a drop size of about 50-200 picolitres or more. Several rows of print heads may be used. The drops are preferably positioned such that they overlap or join with each other.

(20) The UV curable ink is preferably a water based UV curable polyurethane substance with a viscosity that is adapted to the digital coating head 30. Water-based polyurethane dispersions are preferred as curable ink used in the digital coating head. They are environmental friendly and technically superior to similar solvent-based coatings. They are, for example free of isocyanate and have a zero or a very low volatile organic content. They have superior properties related to hardness, stain and abrasion resistance, impact strength and temperature.

(21) Polyurethane dispersions are fully reacted polyurethane/polyureas of small and discrete polymer particles and such particles may be produced with a size of about 0.01-5.0 microns and may therefore be handled in a digital Piezo print head or other similar heads. They may have 20-70% solid content and a wide range of layers with different hardness may be produced with a digital coating method. Polyurethane dispersions may be blended with, for example acrylic emulsions and other emulsions in order to reduce costs.

(22) The curable ink is stored in liquid form in a coating container 31, which is connected to the digital ink head 30 with a coat-feeding pipe 32. A digital control unit connected to the ink head and the conveyor with data cables 33 controls the drop size and the speed of a conveyor 21 that displaces the panel 1 in relation to the digital ink head 30. The curable ink application equipment 36 is preferably connected to a digital printer in order to coordinate the curable ink pattern with the desired décor made by the digital printer.

(23) Such a digital coating unit 36 is much more cost efficient than a digital printer since much larger drops may be fired and this gives an increased capacity and less problems with the channels in the head that may be sealed by larger particle in the ink when the printer works with high resolution and small drops. Each ink head may be designed to apply one layer only and there is no need to coordinate different print heads as in conventional digital printing.

(24) The coating line may be very compact and the UV curing oven may be located close to the digital coating unit. The coating may be very precise. Surfaces comprising paper, powder, vinyl, a thermoplastic film and similar may be digitally coated in order form an advanced ink matrix 41. A powder layer is preferably stabilized with IR lamps, hot air or pre-pressing prior to the application of the curable ink and this allows that the curable ink may be applied on a rather hard but still uncured powder surface. The powder may comprise wood fibres or particles, a binder, preferably a thermosetting binder, and preferably also wear resistant particles.

(25) Digital coating equipment may of course have several ink heads and a panel may be displaced under the ink heads several times. The digital coating may be applied on individual panels or on a large sheet that after the coating is divided into several panels.

(26) The ink matrix particles 41 may be removed in many ways, for example by vacuum, air pressure, brushes, increased temperature, chemically, with water, etc. Curable ink may be used that after the initial pressing and heating changes its structure into smaller particles.

(27) Very small amounts may be used to provide an advanced DVEIR surface. Only 5-10% of the surface may be covered to an average depth of 0.05 to 0.5 mm, for example, 0.1 mm and this means that only 5-10 g/m2 may be needed. The removed ink matrix material may be recycled and used as filler in other applications.

(28) The method may be used to form deep embossing with a depth of about 0.5 mm and more especially if several layers of curable ink are applied.

(29) FIG. 4b shows curable ink coating on a substrate such as a structured release paper or film 40 where the curable ink 25 is applied on the substrate 40 and not on the panel surface. This transfer method is preferred when a basic embossing is created by a foil and not by a press plate. The pressure may be applied by a press table 24 as shown or a press cylinder (not shown). FIG. 4c shows that the curable ink may be applied on a pressing cylinder or roller 40. The curable ink 25 may be fixedly connected to the substrate or just transferred to the surface by the substrate where it in a following step is removed from the surface.

(30) FIGS. 5a-5d show a DVEIR method that may be uses to provide embossed structures in practically all type of flooring materials in a very simple and cost efficient way.

(31) FIGS. 5a, b show that a substrate such as a first basic matrix material 40a, that preferably forms a part of the basic microstructure. The first basic matrix material 40a is preferably transported through a press 24 from one in feeding roller 22a to an out feeding roller 22b. The first basic matrix material 40a may be an aluminium or plastic foil, or coated and embossed release paper and similar. Such matrix materials are generally used in the flooring industry and may provide a variety of microstructures with different gloss levels. A second basic matrix 40b may also be used and may be a conventional press plate. A curable ink 25 is applied on the rear side of the first basic matrix 40a by a digital coating unit 36 and may be cured by a UV curing oven 23 to an ink matrix 41. FIG. 5c shows that the second basic matrix 40b on the press table 24 presses against the first basic matrix 40a and against the ink matrix 41 on the first matrix 40a. FIG. 5d shows the surface structure when the first basic matrix 40a with the ink matrix 41 is removed. A variable embossing 19 is formed as a cavity 37 by the ink matrix 41 in the surface 2 and in register with the print P. The surface comprises also a basic microstructure 17a and a basic embossed structure 17b formed by the first and/or the second basic matrix 40a, 40b.

(32) This method may be used to form a basic matrix 40a that may be supplied in roles or sheets and used for forming an embossed surface on a building panel. The basic matrix 40a may be an aluminium or plastic foil or a coated paper as described above. The basic matrix comprises a lower part intended to be pressed and released from a the panel surface and an upper part that is not in contact with the panel surface during pressing and that comprises protrusions 41 that during a pressing operation deforms the basic matrix 40a and created protrusions on the lower parts of the matrix that forms cavities 37 in the panel surface as shown in FIGS. 5b and 5c.

(33) The press and the press plate may be replaced by a hot and preferably pre structured roller. Advanced DVEIR structures may be formed in thermoplastic materials such as floors with a vinyl surface layer.

(34) All the above-described methods may be partly or completely combined.

(35) Embodiments of the invention may also be used to produce conventional pre-embossed release materials such as coated paper or foils that are supplied in rolls or sheets to a flooring factory in order to form an pressing matrix such as a matrix material. A digital ink matrix may be formed on the upper and/or the lower side of the pre embossed materials. Even material of metal may be formed by etching where a digital ink head applies an ink that may be used to etch and form embossed surfaces.

(36) A person skilled in the art appreciates that the embossed structure may be formed only from the ink matrix and that no embossed press plate or first or second basic matrix forming a basic embossed structure has to be used. The ink matrix arranged on a substrate may be used to replace a conventional embossed press plate.

(37) The main principles of embodiments of the invention may also be used to form an embossed surface structure by applying small hard particles on a surface prior to the pressing step and removing the particles after pressing. The particles may be positioned digitally. A binder pattern or image may be formed digitally on a substrate, by an ink head that only applies a binder that may comprise water. The substrate may be a powder layer, an overlay paper, or a thermoplastic foil or similar. The liquid binder may connect the particles directly or indirectly by reacting with a binder such as, for example melamine formaldehyde resin that may be included in the surface or in the hard particles. The small hard particles are scattered randomly by a scattering device over the binder pattern. The binder connects some particles that form the same pattern as the liquid binder while other non-bonded particles are removed by, for example airstreams. The remaining particles form a protruding structure similar to the cured curable ink. The substrate is thereafter pressed and cured and the hard particles are pressed into the surface. The hard particles are thereafter removed, for example mechanically, by heat, air streams, or chemically. The hard particles may be sand, aluminium oxide or other minerals. Even salt or sugar may be used and a final removal may be accomplished by melting the particles with water. The binder may be applied digitally prior or after the scattering of the hard particles.

Example

(38) A digital image was applied in a powder based surface layer of a panel comprising a HDF board material as a core. The powder was a mix of wood fibres (40%), aluminium particles (10%) and melamine formaldehyde resin powder (50%). The image was created and injected into the powder with a single pass printer comprising 5 fixed Piezo print heads. The ink was a water-based ink comprising colour pigments. A piezo print head with a drop size of 30 picolitres was used to apply a matrix pattern with curable ink comprising a water based UV cured polyurethane (PU) on a rear side of an aluminium foil. The PU matrix pattern was the same as the wood grain structure of the digital image. The PU matrix pattern was cured in a UV oven to an ink matrix. The aluminium foil was positioned above the digital print such that the ink matrix and the digital image were in register with each other. The panel and the aluminium foil with the ink matrix were pressed in a press with a pressure of 40 kg/cm2, during 30 seconds and heated to 160 degrees Celsius. The aluminium matrix was removed after pressing. A perfect embossed in register surface design was obtained with a basic gloss level that corresponded to the surface structure of the aluminium foil.

Embodiments

(39) 1. A method of forming an embossed surface (16) in a building panel (1), comprising the steps of: forming an ink matrix (41, 41a, 41b) having a horizontal and vertical extension by applying a curable ink (25, 25a, 25b) on a surface layer (2) of the building panel (1) by means of a digital ink head (30), forming a cavity (37) in the surface layer (2) by pressing the ink matrix (41, 41a, 41b) against the surface layer (2), thereby forming an embossed surface (16) of the building panel (1), and removing the ink matrix (41, 41a, 41b) from the embossed surface (16).

(40) 2. The method as in embodiment 1, wherein the building panel (1) is a floor panel.

(41) 3. The method as in embodiment 1 or 2, wherein the surface layer (2) comprises a decorative layer (5) with a print (P), preferably a digital print (P).

(42) 4. The method as in claimed in embodiment 3, wherein the cavity (37) is in register with the print (P).

(43) 5. The method as in any one of the preceding embodiments, wherein the digital ink head (30) is a Piezo head.

(44) 6. The method as in any one of the preceding embodiments, wherein the curable ink (25) is a polymer material, preferably a UV curing polymer material.

(45) 7. The method as in any one of the preceding embodiments, further comprising curing the curable ink to form the ink matrix (41).

(46) 8. A set of building panels (1) having a surface layer (2) comprising a décor layer (5) and an embossed upper layer (16), characterized in that the décor layer (5) comprises a variable print (P), the embossed upper layer (16) comprises a basic embossing (17) being essentially identical for the set of building panels (1) and a variable embossing (19) being distinguishable for each building panel, wherein the variable embossing (19) is in register with the variable print (P).

(47) 9. The building panels as in embodiment 8, wherein the building panels (1) are floor panels.

(48) 10. The building panels as in embodiment 8 or 9, wherein the variable print (P) is a digital print.

(49) 11. The building panels as in any one of embodiments 8-10, wherein the basic embossing (17) is formed in register with a basic design of the décor layer (5).

(50) 12. The building panels as in embodiment 11, wherein the basic design of the décor layer (5) is a print (P), preferably a digital print.

(51) 13. The building panel as in any one of embodiments 8-12, wherein the building panels are configured with an embossed surface that allows a floor area of more than about 10 m2, preferably more than about 15 m2, to be installed where all building panels have different surface structures.

(52) 14. A method of forming a matrix for forming an embossed surface (16) on a building panel (1), comprising the steps: providing a matrix comprising a foil (40) with a lower part comprising a release surface that during pressing is in contact with a surface of the building panel (1) and that prevents the matrix from bonding to the surface of a building panel, preferably a thermosetting or thermoplastic surface of a building panel, and applying a curable ink (25) by means of a digital ink head (30) on an upper part of the foil (40) that is not in contact with the surface of the building panel (1), thereby forming an ink matrix (41) on the foil (40).

(53) 15. A matrix for forming an embossed surface (16) on a building panel produced according to embodiment 14.

(54) 16. A method of forming an embossed surface (16) on a building panel (1), comprising the steps of: providing a foil (40), forming an ink matrix (41) having a horizontal and vertical extension by applying a curable ink (25) on an upper part of the foil (40) by means of a digital ink head (30); forming a cavity (37) in a surface layer (2) of the building panel (1) by pressing a lower part of the foil and the ink matrix (41) located on the upper part of the foil against the surface layer (2) of the building panel (1), thereby forming an embossed surface (16) of the building panel (1), and removing the foil with the ink matrix (41) from the embossed surface (16).

(55) 17. The method as in embodiment 16, wherein the building panel (1) is a floor panel.

(56) 18. The method as in embodiment 16 or 17, wherein the surface layer (2) comprises a decorative layer (5) with a print (P), preferably a digital print (P).

(57) 19. The method as in embodiment 18, wherein the cavity (37) is in register with the print (P).

(58) 20. The method as in any one of embodiments 16-19, wherein the foil (40) is a metal, such as aluminium, or plastic foil.

(59) 21. The method as in any one of embodiments 16-20, wherein the surface layer (2) of the building panel (1) comprises a thermosetting resin, preferably a melamine formaldehyde resin.

(60) 22. A basic matrix (40a) for forming an embossing on a surface (2) of a building panel (1), wherein the basic matrix is an aluminium or plastic foil or a coated paper, the basic matrix comprising: a lower part intended to be pressed and released from the surface (2) of the building panel (1), an upper part that is intended to not be in contact with the surface (2) of the building panel (1), and protrusions (41) intended during a pressing operation to deform the basic matrix (40a) and to create cavities (37) on the surface (2) of the building panel (1).