Digital overlay

Abstract

A method to form a protective overlay with wear resistant particles applied in well-defined patterns by applying wear resistant particles on a surface, bonding a part of the wear resistant particles with a binder preferably applied with a digital drop application head and removing the non-bonded wear resistant particles from the surface.

Claims

1. A method of forming a transparent or semi-transparent wear resistant layer comprising wear resistant particles on a surface wherein the method comprises the steps of: applying a liquid binder in a pattern on the surface, wherein the surface is a powder layer, applying the wear resistant particles on the surface that has the liquid binder, bonding a part of the wear resistant particles to the surface with the liquid binder, removing non-bonded wear resistant particles from the surface such that the wear resistant layer is formed with evenly distributed wear resistant particles, and pressing the surface with the wear resistant layer under heat for curing the wear resistant layer.

2. The method as claimed in claim 1, wherein the wear resistant particles are applied in a raster pattern with pre-determined distance between the wear resistant particles.

3. The method as claimed in claim 2, wherein the pre-determined distance is between 5 and 10 mm.

4. The method as claimed in claim 1, wherein the surface comprises a printed dcor and the wear resistant particles are spaced from each other and coordinated in register with the printed dcor.

5. The method as claimed in claim 1, wherein the method further comprises embossing the surface with the wear resistant particles under heat and pressure for forming embossed surface portions comprising upper and lower surface portions and wherein the content of wear resistant particles are higher in the upper portions than in the lower portions.

6. The method as claimed in claim 1, wherein the wear resistant particles comprise aluminium oxide.

7. The method as claimed in claim 1, wherein the wear resistant particles are coated or mixed with a thermosetting resin.

8. The method as claimed in claim 7, wherein the pressing is with a continuous or discontinuous laminate press, where the resin cures under heat and pressure.

9. The method as claimed in claim 8, wherein the pressure is in the range of 40-60 bars.

10. The method as claimed in claim 1, wherein the surface is a part of a floor panel.

11. The method as claimed in claim 1, wherein the wear resistant particles are removed by an airstream.

12. The method as claimed in claim 1, wherein the binder is a blank ink comprising a liquid substance that is applied by a digital drop application head.

13. The method as claimed in claim 12, wherein the liquid substance comprises water.

14. The method as claimed in claim 12, wherein the liquid substance is exposed to IR light or heated.

15. The method as claimed in claim 12, wherein the liquid substance is applied with a Piezo ink head.

16. The method as claimed in claim 12, wherein the liquid substance is applied with a thermo ink head.

17. The method as claimed in claim 1, wherein the wear resistant particles are applied by scattering.

18. The method as claimed in claim 1, wherein the wear resistant particles are arranged in a wood grain or a stone pattern.

19. The method as claimed in claim 1, wherein the powder layer is provided on a substrate, and wherein the substrate with the powder layer and the wear resistant particles is pressed under heat.

20. The method as claimed in claim 1, wherein the powder layer is provided on a substrate, and wherein the powder layer is stabilized on the substrate prior to pressing under heat.

21. The method as claimed in claim 20, wherein the substrate is sprayed with an aqueous solution prior to providing the powder layer.

22. The method as claimed in claim 1, further comprising digitally printing on the surface to form a digitally printed surface portion, and applying the liquid binder on the digitally printed surface portion.

23. The method as claimed in claim 22, wherein the liquid binder is applied only on the digitally printed surface portion.

24. The method as claimed in claim 1, wherein an embossed press plate is used for the pressing.

25. A method of forming a panel comprising a transparent or semi-transparent wear resistant layer, wherein the method comprises the steps of: applying a liquid binder in a pattern on a surface of a core, applying wear resistant particles on the surface in a raster pattern with a predetermined distance between the wear resistant particles, bonding a part of the wear resistant particles to the surface with the liquid binder, removing non-bonded wear resistant particles from the surface such that the wear resistant layer is formed with evenly distributed wear resistant particles, and cutting through the wear resistant layer, the surface, and the core along a cutting width to form the panel, wherein the cutting width is equal to the predetermined distance between the wear resistant particles.

26. The method as claimed in claim 25, wherein the predetermined distance is 5 to 10 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure 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-e Illustrate surfaces comprising wear resistant particles;

(3) FIGS. 2a-b Illustrate a sheet and a floor panel having a surface with wear resistant particles;

(4) FIGS. 2c-e Illustrate bonding of wear resistant particles;

(5) FIG. 2f Illustrate a method and equipment to apply wear resistant particles in pre-determined patterns.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) FIG. 1a shows a conventional application of aluminium oxide particles on a paper based overlay surface 2 used in laminate floorings. The particles, which have a size of about 0.1 mm are applied at random and the whole surface, is covered. Some surface portions comprise larger amounts and some smaller amounts. Two to five particles and even more may be connected to each in clusters and some particles may be spaced from each other with a distance D1 of up to about 1 mm.

(7) FIG. 1b shows schematically an embodiment of the disclosure, which is based on a preferred principle where a binder pattern BP is formed digitally by an ink head, hereafter referred to as digital drop application head, that preferably only applies a binder 11, hereafter referred to as blank ink, on a surface 2. Wear resistant particles hereafter referred to as dry overlay 15 that comprises, for example, small aluminium oxide particles, are applied such that they are in contact with the binder pattern BP. The blank ink 11 connects some particles that form the same pattern as the binder 11 and a pattern BP of wear resistant particles is formed on the surface 2 when other non-bonded particles 15 are removed from the surface 2 by, for example, vacuum. This method allows that the surface 2 may be covered with wear resistant dry overlay comprising particles that are evenly distributed on the surface with pre-defined distances D1, D2 between the major parts of the particles. An ideal distance between the particles is about 0.2-0.6 mm and no clusters of connected particles should occur. Such evenly distributed particles of dry overlay provide a high quality surface with high wear resistance and transparency combined with low material costs.

(8) The blank ink 11 and the dry overlay 15 may be applied in many alternative ways. The blank ink may be applied on the dry overlay or the dry overlay may be applied on the blank ink. The surface may point upwards or downwards and the blank and/or the dry overlay particles may be applied from above or from below. A surface with blank ink may, for example, point downwards and may be brought into contact with a dry overlay layer. Non-bonded dry overlay particles may be removed by gravity when the surface is separated from the dry overlay layer. In order to simplify the description, the majority of the preferred embodiments show a surface pointing upwards.

(9) FIG. 1c shows a powder-based surface 2 comprising a base colour 2a and a digital print P applied on the base colour. The base colour may comprise wear resistant particles and a second layer of dry overlay particles 15 is only applied on the printed parts P. The application is made in two steps as described above with blank ink and dry overlay where the dry overlay applied on the non printed portions is removed.

(10) FIG. 1d shows a surface 2 with embossed upper 17a and lower 17b surface portions. The wear resistant particles are preferably only applied on the upper portions 17a, which are exposed to high wear. Surface portions may also be formed with different amounts of particles per cm2. The amount of particles may, for example, be larger in the lower portions than in the upper portions.

(11) FIG. 1e shows a sheet 1 which is after pressing divided into two floor panels 1a, 1b. The wear resistant particles are applied with a distance D1 that corresponds to the part of the surface that is removed when the sheet 1 is cut and the locking systems are formed on the individual panels 1a, 1b. The distance D1 is preferably larger than a few mm, which corresponds to the width of a saw blade SB. The distance may also be about 5-10 mm, which corresponds to the surface portion that is needed to form the major part of the mechanical locking system.

(12) A protective layer of, for example, bleached fibres and melamine resin or only melamine or only fibres may be applied on the wear resistant particles in order to, for example, protect press plates during pressing or to create different gloss levels.

(13) FIG. 2a shows a panel 1a with a core 3, a balancing layer 4 and an embossed surface 2 comprising upper 17a and lower parts 17b. The panel edges are formed with a mechanical locking system comprising a strip 6, with a locking element 8 in one edge that cooperates with a locking groove 14 in an adjacent edge of another panel for horizontal locking of the adjacent edges and a tongue 10 in one edge that cooperates with a tongue groove 9 in another edge for vertical locking of the panels. The panel comprises bevels 5 at the upper edges. The panel may comprise different amounts of dry overlay on the upper and lower surface portions

(14) FIG. 2b shows a sheet 1 which is cut into two individual panels 1a and 1b. The wear resistant particles are applied in patterns with a distance D2 between the particles such that the wear properties of surface portions, which are removed in connection with cutting, and milling of the locking systems and the bevels are lower in such portions than in other parts of the sheet. Preferably such portions should be produced such that the content of wear resistant particles is as small as possible, preferably less than 10% of the average content of the panel surface.

(15) Floor panels may warp in different humidity and the wear on the edges that generally warp upwards in dry conditions is much higher than on the inner part of the panel. Increase amounts of wear resistant particles may be applied at surface portions 2a adjacent to the panel edge.

(16) FIGS. 2c-2e shows how wear resistant particles, preferably aluminium oxide 63, may be bonded and position in well-defined patterns. A binder of blank ink 11 is applied on a surface with preferably a conventional digital ink head. The binder may also be applied with rollers and other similar methods. Water may be sufficient to bond the particles until they are pressed.

(17) FIG. 2c shows that a binder is preferably included in the surface 2 and may react with the liquid pattern of blank ink 11 applied by the digital drop application head.

(18) FIG. 2d shows that aluminium oxide particles 63, may be coated with a thermoplastic or thermosetting resin, for example, melamine 13.

(19) FIG. 2e shows that dry overlay particles 15 may also be mixed with a spray dried binder in powder form such as melamine particles 13 that melt when they are in contact with the blank ink 11.

(20) FIG. 2f shows schematically a digital particle application equipment 40 that may be used to create a digital patter P of wear resistant particles on a panel 1 comprising a surface 2, a core 3 and a backing layer 4. A blank ink application station 36 comprising a digital drop application head 30, that preferably is a Piezo head or a thermal print head, applies a binder pattern with blank ink 11. Several heads 30 may be positioned side by side in order to cover the width of the surface that is printed. The binder pattern is created digitally in the same way as in conventional digital printing. The digital drop application head is connected with a feeding pipe 32 to a container 31 with blank ink. The digital drop application heads 30 are digitally connected with preferably data cables 33 or wireless to a digital control unit 34 that controls the application of the drops, the speed of the conveyor 21, the function of a dry ink application unit 27 and all other equipment that is used to bond and remove particles.

(21) The water based drops of the blank ink 11, which in this embodiment serve as an application binder, should be wet until they pass the dry ink application unit 27 that in this preferred embodiment is a scattering station. Dry overlay 15, that in this preferred embodiment comprises aluminium oxide particles mixed with a resin of spray dried melamine powder, is scattered on the liquid blank ink 11.

(22) The scattering equipment comprises a hopper 45 that contains dry overlay 15, a doctor blade 47 that together with a roller 46, preferably comprising an engraved, embossed, etched or sand blasted roller surface 44, acts as a dispensing device that moves a pre-determined amount of dry overlay 15 from the hopper 45 and to the surface 2. The roller 46 may also have a roller surface 44 that comprise small needles. A material-removing device that may be an oscillating or rotating brush 48 may also be used in some applications together with one or several rotating or oscillating meshes 49 that may oscillate or rotate in different directions.

(23) The doctor blade 47 may be rigid or flexible and may have an edge that is adapted to the structure of the roller surface. The oscillating or rotating meshes 49 may also be formed such that they spread the dry overlay 15 in a pre-defined way and they may be combined with one of several nets that may be used to sieve the particles before they are applied as a layer. The rotation of the roller, the position of the doctor blade and the speed of the surface that is intended to be covered with the dry overlay may be used to control the layer thickness.

(24) The liquid blank ink 11 and the dry overlay is in this embodiment heated and stabilized when it is displaced under preferably a hot IR lamp 23, which is located preferably after the digital drop application head 30 in the feeding direction.

(25) A dry overlay removal station 28, that in this embodiment is based on air streams and vacuum, removes dry overlay particles that are not wet and not bonded by the binder pattern and a perfect dry overlay pattern P is provided. The dry overlay removal station may be located after the IR lights 23 or between the IR lights and the scattering unit 27. This production step may be repeated and several types of wear resistant particles may be applied at different portions of the surface. The removed particles may pass through a sieve or a filter and they may be recycled and reused again several times.

(26) The dry overlay may in addition to wear resistant particles also comprise melamine particles and/or pigments and/or fibres, preferably bleached transparent or semi-transparent wood fibres.

(27) The method to apply wear resistant particles in patterns in order to reach cost saving and increased transparency may also be used together with a conventional overlay paper or decorative paper. Wear resistant particles may be applied in patterns on the overlay prior or after impregnation and the overlay paper with the wear resistant particles applied in patterns may be applied on a decorative paper. Wear resistant particles may be applied in patterns on the decorative paper preferably after impregnation when the decorative paper is positioned on a carrier, preferably a sheet material such as HDF. Impregnation of the decorative paper may be avoided if the paper is applied on a layer comprising thermosetting resin, for example, a powder layer.

(28) A transparent overlay paper without any wear resistant particles or with only small scratch resistant particles may be applied on the wear resistant pattern in order to provide additional properties such as different gloss levels or to provide a layer that protects the press plate against wear during pressing.

(29) Powder based surfaces may be applied with a basic mix that does not include any aluminium oxide particles. Such wear resistant particles may be applied in patterns in a second step and surface portions without any wear resistant particles may be formed even in powder based surfaces in order to reduce tool wear.

(30) All described embodiments may be partly or completely combined.

Example 1Digitally Formed Powder Overlay

(31) A HDF sheet with a thickens of 8 mm was sprayed with deionized water and a powder mix of about 200 g/m.sup.2 of powder comprising wood fibres, melamine particles, brown colour pigments and aluminium particles was applied by scattering equipment on the HDF sheet. The water penetrated into the lower parts of the mix. The upper dry part of the mix was removed by vacuum and a very even powder mix of 150 gr/m.sup.2 was obtained. The mix was cold pressed with a metal roller and a hard stabilized powder based surface with a brown basic colour was obtained. The panel with the stabilized powder surface was put on a conveyer and displaced under a digital Piezo print head that provided a conventional ink jet print on the brown base coloured surface. The digital print covered about 20% of the surface and the basic colour. A digital print head was thereafter used to applied drops of blank ink comprising mainly water on the digitally printed surface portions. A higher intensity of drops was applied on the printed portions that were intended to form upper parts of the surface than on the printed portions that were intended to form lower parts of the surface after the final pressing operation. A dry mix of aluminium particles (85% weight) with an average size of 100 microns and spray dried melamine formaldehyde particles (15% weight) with a similar size was scattered on the whole surface. The sheet was thereafter displaced under a vacuum-sucking pipe where essentially all non-bonded aluminium oxide particles and melamine formaldehyde particles were removed. A protective transparent wear resistant layer or a so-called overlay was formed with aluminium oxide particles applied on essentially only the digitally printed surface portions. The panel was thereafter pressed against an embossed press plate during 15 seconds under a temperature of 170 C. in a 40 bars press. The surface with the protective layer was cured to a hard wear resistant surface with a high quality wear resistant digital print comprising a higher amount of aluminium oxide particles in the upper parts of the printed and embossed surface portions than in the lower surface portions.

Example 2Digitally Formed Paper Overlay

(32) A digital Piezo print head was used to applied drops of blank ink comprising mainly water on a melamine impregnated overlay paper sheet. The drops were applied in a raster pattern with a drop distance of about 1 mm. A higher intensity of drops with a drop distance of 0.5 mm was applied on the surface portions that were intended to form upper parts of the surface. No drops were applied on a 12 mm wide surface portion that extended over the whole length of the overlay paper and that corresponded to the surface portion where a saw blade cuts the pressed sheet and where the locking system is formed. A dry mix of aluminium particles with an average size of 100 microns was scattered on the whole overlay paper surface. The overlay paper was thereafter displaced under a vacuum-sucking pipe where essentially all non-bonded aluminium oxide particles were removed. The bonded aluminium oxide particles formed a pattern, which was essentially identical to the applied drops. The overlay with the aluminium oxide particles was displaced under an IR lamp and applied on a HDF sheet with a decorative melamine impregnated paper. The sheet was thereafter pressed against an embossed press plate during 15 seconds under a temperature of 170 C. in a 40 bars press. The surface with the decorative and overlay papers was cured to a hard wear resistant surface with a high quality wear resistant overlay comprising a base structure with accurately positioned aluminium oxide particles with a pre-defined distances between the particles and with a higher amount of aluminium oxide particles in the upper parts of the printed and embossed surface portions than in the lower surface portions. The sheet was thereafter cut along the surface area without any aluminium oxide particles and the locking system was formed in edge portions, which were almost completely free from aluminium oxide particles. The wear on the saw blade and the milling tool was considerably lower.

Example 3Digital Wear Layer on Decorative Paper

(33) A digital Piezo print head was used to applied drops of blank ink comprising mainly water on a melamine impregnated decorative paper applied on a HDF core. The drops were applied in a raster pattern with a drop distance of about 0.6 mm on surface portions that were intended to form lower parts of the pressed surface. A higher intensity of drops with a drop distance of about 0.3 mm was applied on surface portions that were intended to form upper parts of the pressed surface. No drops were applied on a 12 mm wide surface portion that extended over the whole length of the decorative paper and that corresponded to the surface portion where a saw blade cuts the pressed sheet and where the locking system is formed. A dry mix of aluminium particles with an average size of 100 microns was scattered on the whole surface of the decorative paper. The sheet was thereafter displaced under a vacuum-sucking pipe where essentially all non-bonded aluminium oxide particles were removed. The bonded aluminium oxide particles formed a pattern, which was essentially identical to the applied drops. The sheet with the decorative paper and with the aluminium oxide particles was displaced under an IR lamp. A conventional melamine impregnated overlay without any aluminium oxide particles was applied over the decorative paper and the sheet with the two papers was thereafter pressed against an embossed press plate during 15 seconds under a temperature of 170 C. in a 40 bars pressure. The surface with the decorative and overlay papers was cured to a hard wear resistant surface with a high quality wear resistant surface comprising a base structure with accurately positioned aluminium oxide particles with a pre-defined distances between the particles and with a higher amount of aluminium oxide particles in the upper parts of the embossed surface portions than in the lower surface portions. The sheet was thereafter cut along the surface area without any aluminium oxide particles and a locking system was formed in edge portions, which were almost completely free from aluminium oxide particles. The wear on the saw blade and the milling tool was considerably lower.

EMBODIMENTS

(34) 1. A method of forming a wear resistant layer comprising transparent or semitransparent wear resistant particles (15) on a surface (2) wherein the method comprises the steps of: applying a liquid binder (11) in a pattern (BP) on the surface (2), applying the wear resistant particles (15) on the surface (2), bonding a part of the wear resistant particles (15) to the surface (2) with the liquid binder (11), and removing non-bonded wear resistant particles (15) from the surface (2) such that the wear resistant layer is formed with evenly distributed wear resistant particles (15).

(35) 2. The method as in embodiment 1, wherein the wear resistant particles (15) are applied in a raster pattern with pre-determined distance (D1, D2) between the wear resistant particles (15).

(36) 3. The method as in embodiment 2, wherein the pre-determined distance (D1, D2) essentially corresponds to surface portions where the surface (2) is to be cut and/or where locking systems will be formed.

(37) 4. The method as in embodiments 1-3, wherein the surface (2) comprises a printed dcor (P) and the wear resistant particles (15) are spaced from each other and coordinated in register with the printed dcor (P).

(38) 5. The method as in embodiments 1-4, wherein the surface (2) is formed with embossed surface portions comprising upper (17a) and lower (17b) surface portions and wherein the content of wear resistant particles are higher in the upper portions (17a) than in the lower portions (17b).

(39) 6. The method as in any one of the preceding embodiments, wherein the wear resistant particles (15) comprise aluminium oxide (63) such as corundum.

(40) 7. The method as in any one of the preceding embodiments, wherein the wear resistant particles (15) are coated or mixed with a thermosetting resin.

(41) 8. The method as in any one of the preceding embodiments, wherein the surface (2) is a powder layer, a paper layer or a foil.

(42) 9. The method as in any one of the preceding embodiments, wherein the surface (2) is a part of a floor panel (1).

(43) 10. The method as in any one of the preceding embodiments, wherein the wear resistant particles (15) are removed by an airstream.

(44) 11. The method as in any one of the preceding embodiments, wherein the binder is a blank ink (11) comprising a liquid substance that is applied by a digital drop application head (30).

(45) 12. The method as in embodiment 11, wherein the liquid substance is water based.

(46) 13. The method as in embodiment 11 or 12, wherein the liquid substance is exposed to IR light (23) or hot air.

(47) 14. The method as in embodiment 11, wherein the liquid substance is applied with a Piezo ink head.

(48) 15. The method as in embodiment 11, wherein the liquid substance is applied with a thermo ink head.

(49) 16. The method as in any one of the preceding embodiments, wherein the surface (2) with the wear resistant particles (15) is heated and pressed.

(50) 17. The method as in any one of the preceding embodiments, wherein the wear resistant particles (15) are applied by scattering.

(51) 18. The method as in any one of the preceding embodiments, wherein the wear resistant particles (15) are arranged in a wood grain or a stone pattern.

(52) 19. A panel (1) with a decorative surface (2) comprising a pattern (P) of wear resistant particles (15) wherein the wear resistant particles (15) are applied in a raster pattern with pre-determined distance between the wear resistant particles (15).

(53) 20. The panel as in embodiment 19, wherein the surface (2) comprises a printed dcor (P) and the wear resistant particles (15) are spaced from each other and coordinated with the printed dcor (P).

(54) 21. The panel as in embodiment 19 or 20, wherein the surface (2) comprises a printed and embossed dcor with an upper (17a) and a lower (17b) surface portion and wherein the content of wear resistant particles (15) are higher in the upper surface portion (17a) than in the lower surface portion (17b).

(55) 22. The panel as in embodiments 19-21, wherein an edge portion comprises a higher content of wear resistant particles than an inner surface portion spaced from the edge portion.

(56) 23. The panel as in any one of the preceding embodiments 19-22, wherein the surface (2) is a paper layer or a foil.

(57) 24. The panel as in any one of the preceding embodiments 19-22, wherein the surface (2) comprises a powder layer.

(58) 25. The panel as in any one of the preceding embodiments 19-24, wherein the surface (2) is a part of a building panel (1).

(59) 26. The panel as in any one of the preceding embodiments 19-25, wherein the surface (2) is a part of a floor panel (1).

(60) 27. The panel as in any one of the preceding embodiments 19-26, wherein the wear resistant particles (15) comprise aluminium oxide such as corundum.

(61) 28. The panel as in any one of the preceding embodiments 19-27, wherein the wear resistant particles (15) are arranged in a wood grain or a stone pattern.

(62) 29. The panel as in any one of the preceding embodiments 19-28, wherein the surface (2) is a part of a panel (1) that is a laminate or wood floor, a powder based floor, a tile or a LVT floor.

(63) 30. A sheet (1) with a decorative surface (2) comprising a pattern (P) of wear resistant particles (15) wherein the wear resistant particles (15) are applied in a raster pattern with pre-determined distance (D1, D2) between the wear resistant particles.

(64) 31. The sheet as in embodiment 30, wherein the pre-determined distance (D1, D2) essentially corresponds to surface portions where the sheet (1) is to be cut into several panels (1a, 1b) and/or where locking systems will be formed.

(65) 32. The sheet as in embodiments 30 or 31, wherein the surface (2) comprises a printed dcor (P) and the wear resistant particles (15) are spaced from each other and coordinated in register with the printed dcor (P).

(66) 33. The sheet as in embodiments 30-32, wherein the surface (2) comprises a printed and embossed dcor with upper (17a) and lower (17b) surface portions and wherein the content of wear resistant particles (15) are higher in the upper portions (17a) than in the lower portions (17b).

(67) 34. The sheet as in any one of the preceding embodiments 30-33, wherein the wear resistant particles (15) comprise aluminium oxide (63) such as corundum.

(68) 35. A paper comprising a pattern (P) of wear resistant particles (15) wherein the wear resistant particles (15) are applied in a raster pattern with pre-determined distance between the wear resistant particles (15).

(69) While illustrative embodiments of the invention have been described herein, the present invention is not limited to the various preferred embodiments described herein but includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g. of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to the examples described in the present specification or during prosecution of the application, which examples are to be construed as non-exclusive.