EP3124279A1

EP3124279A1 - Method to produce wallpaper with minimum side effects

Info

Publication number: EP3124279A1
Application number: EP15178656.3A
Authority: EP
Inventors: Patrick MOLEMANS; Herman VAN DER PLAETSEN
Original assignee: Grandeco Wallfashion Group - Belgium
Current assignee: Grandeco Wallfashion Group - Belgium
Priority date: 2015-07-28
Filing date: 2015-07-28
Publication date: 2017-02-01
Anticipated expiration: 2035-07-28
Also published as: EP3124279B1; EP3328656A1; LT3124279T; ES2684100T3; PL3124279T3; WO2017017226A1

Abstract

The current invention concerns an automated method to produce digitally printed wall coverings, such as wallpaper, which can be produced with high quality in a flexible and cost effective manner with minimum side effects due to cutting occurring on the edges of the wall covering.

Description

TECHNICAL FIELD

The invention pertains to the technical field of methods to produce wall coverings, preferably wallpaper. In particular, it pertains to methods to produce digitally printed wall coverings.

BACKGROUND

A wall covering, like wallpaper, is typically applied to the walls or ceiling of a room to improve the overall appearance of the room. Different types of wall coverings and methods to produce them are known in the art. These methods often consist in providing a substrate and applying a desired coloured print pattern onto it. Recently, digital printing techniques are being used to apply the coloured print pattern to the substrate, such as for example disclosed in WO 2010 070 367 , US 7 588 381 or US 6 354 212 . The advantage of using digital printing techniques over analogue printing techniques, such as intaglio printing or screen printing, is that the print patterns applied using digital printing techniques often comprise a higher resolution and print quality than using analogue printing techniques and may be applied in a more accurate and controlled manner. Furthermore, the different types of print patterns that may be provided are much more elaborate than the ones that may be applied using analogue printing techniques.
In general, a wall covering is positioned against a ceiling or wall in the form of strips which are hung, often using an adhesive, side-by-side to form a coherent piece of decoration against the wall or ceiling. It is hereby detrimental that the print pattern of one strip of wall covering correctly corresponds to the print pattern of the strip of wall covering hanging adjacent thereof, else the appearance of the wall or ceiling decoration may be significantly disturbed. Typically, when applying the print pattern on the substrate, the substrate has larger dimensions than the print pattern provided thereon, especially when using digital printing techniques, resulting in unprinted selvage edges on the substrate which are typically cut off to obtain the wall covering. However, it may occur that during the cutting of the substrate into its correct dimensions, cutting errors occur, which may result in the appearance of unprinted areas on the edges of the final wall covering or may result in the print pattern of one strip of wall covering no longer correctly corresponding to the print pattern of the strip of wall covering which is to be hung adjacent thereof. In such a case, when hanging the wall coverings, the different strips will no longer form a nice coherent piece of decoration at the wall or ceiling and hence, the wall coverings thus produced are typically disposed of in large quantities, significantly decreasing the efficiency of the production process and increasing its overall cost.
Using analogue printing techniques, a few methods have been developed in the art to overcome such cutting errors, such as for example disclosed in US 4 111 124 . However, these correction methods are often not applicable when using digital printing techniques. Moreover, due to the higher degree of accuracy of the digital printing device, the cutting device often cannot cut the wall covering with the same amount of accuracy as the print pattern applied thereon.
The present invention aims to resolve at least some of the problems mentioned above.
The invention thereto aims to provide a method to produce digitally printed wall coverings, such as wallpaper, which can be produced with high quality in a flexible and cost effective manner with minimum side effects due to cutting occurring on the edges of the wall covering.

SUMMARY OF THE INVENTION

The present invention provides a method to produce wall coverings, such as wallpaper, as provided for in claim 1. By providing an additional print pattern on the at least one selvage edge of the substrate layer using a digital printing device, which additional print pattern is substantially continuous with the main print pattern, cutting errors that may occur during cutting of the substrate layer can be masked and camouflaged, thereby minimizing side effects due to cutting occurring on the edges of the final wall covering.
In a preferred embodiment, a marker is further provided on the at least one selvage edge, which marker can be detected by the cutting device and which marker provides a guiding means for the cutting device to cut the substrate layer along a transition border between the main print pattern and the at least one selvage edge. The combination of providing an additional print pattern on the at least selvage edge with the provision of a marker, allows to significantly reduce problems that may occur due to cutting, thereby avoiding that unprinted side edges are formed on the final wall covering or that the print pattern of one strip of wall covering may no longer correctly correspond to the print pattern of the strip of wall covering which is to be hung adjacent thereof.

DESCRIPTION OF FIGURES

Figure 1 provides a schematic top view of a coated substrate layer according to an embodiment of the current invention provided with a main print pattern and comprising two unprinted selvage edges.
Figure 2A and 2B provides schematic side views of the coated and printed substrate layer of figure 1, according to two different embodiments of the present invention.
Figure 3 provides a schematic top view illustration of a cutting error made by a cutting device according to the prior art.
Figure 4 provides a schematic top view of a coated substrate layer of figure 1 which is provided with additional print patterns and a marker according to an embodiment of the current invention.
Figure 5A and 5B provides a schematic top view of a coated substrate layer provided with a main print pattern whereby two additional print patterns are provided on the two selvage edges on opposing sides of the main print pattern according to an embodiment of the present invention, whereby the additional print pattern is provided substantially discontinuous (5A) and substantially continuous (5B) with the main print pattern.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.
As used herein, the following terms have the following meanings:

"A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a marker" refers to one or more than marker.

"About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/-20% or less, preferably +/-10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and still more preferably +/-0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.
"Comprise," "comprising," and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.
The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.
The expression "weight percent", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.
With the term "automated" as used herein, a method or process is meant that is partially or completely executed and guided by machinery, hereby limiting the input of humans. Preferably, the term "automated" also refers to a process or method that can be performed in a continuous or substantially continuous manner.
"m²" as used in the current invention corresponds to "square meter".
The term "polymer" as used herein generally includes, but is not limited to, homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and random symmetries. Examples of polymers include, but are not limited to, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, etc.
The term "colour", as used in the present invention, may refer to any possible colour such as white, black, red, orange, yellow, green, blue, indigo, violet, brown, and/or any other colour or combination of colours.
The term "wall covering" as used herein refers to any type of wall covering known in the art, such as wallpaper, decorative panels, etc. Preferably, the term wall covering refers to wallpaper.
In a first aspect, the invention provides an automated method to produce wall coverings, such as wallpaper, which method comprises the following steps:

a. providing a substrate layer, which substrate layer has a top side and a back side and which substrate layer is essentially endless along a longitudinal dimension and which comprises a substrate layer width along a transverse dimension;
b. providing a coating on the top side of said substrate layer;
c. optionally providing said coating with an embossed pattern;
d. providing a main print pattern on top of the coating using a digital printing device, which print pattern has a main print pattern width which is smaller than the width of the substrate layer, thereby resulting in at least one unprinted selvage edge on the coated substrate layer; and
e. cutting of the substrate layer with printed coating using a cutting device, thereby reducing the width of the substrate layer to a desired width of the wall covering.

In particular, the method according to the current invention will, simultaneously during or directly after providing the main print pattern to the coated substrate layer, provide the at least one unprinted selvage edge at least partly with an additional print pattern using a digital printing device, which additional print pattern is substantially continuous with the main print pattern.
The substrate layer according to the present invention has a top side and a back side, is essentially endless along a longitudinal dimension and comprises a substrate layer width along a transverse dimension. The longitudinal dimension of the substrate layer preferably corresponds to a longitudinal direction and the transverse dimension preferably corresponds to a transverse direction whereby the transverse direction is preferably substantially perpendicular to the longitudinal direction. The substrate layer width is preferably determined by the distance between two opposing side edges of the substrate layer as measured along the transverse direction, which two opposing side edges are substantially parallel to each other and run substantially along the longitudinal direction of the substrate layer. The plane of the substrate layer created by the longitudinal and the transverse dimension of the substrate layer hereby preferably provides two surfaces, i.e. the top side and the back side of the substrate layer, whereby the coating is preferably provided on the top side surface of the substrate layer.
In a preferred embodiment, the coating is provided on the entire top side of the substrate layer, i.e. on the entire top side surface created by the longitudinal dimension and the transverse dimension of the substrate layer. Preferably, the coating according to the current invention has a bottom surface, which bottom surface is in contact with the top side of the substrate layer, and a top surface, onto which top surface an embossed pattern optionally may be provided. When it is referred to that a main print pattern is provided on top of the coating, it is preferably meant that the print pattern is applied on the top surface of the coating, or, if the top surface of the coating is provided with an embossed pattern, it is preferably meant that the print pattern is applied on the embossed top surface of the coating.
The main print pattern according to the present invention has a main print pattern width which is smaller than the width of the substrate layer, thereby resulting in at least one unprinted selvage edge on the coated substrate layer. The width of the main print pattern, provided on the coated substrate layer, is preferably measured along the transverse direction between two opposing side edges of the main print pattern, which two opposing side edges substantially run parallel to each other and substantially run along the longitudinal direction. The two opposing side edges of the main print pattern should not necessarily be interpreted as being substantially continuous edges on both sides of the main print pattern, but may be interrupted in some parts on the coating due to e.g. the irregularity of the main print pattern, i.e. the print pattern does not necessarily need to be applied to the entire top surface of the coating and some parts of the coating may e.g. not be provided with the main print pattern and hence lead to interruptions in the side edges of the main print pattern. This is for example illustrated in figure 1. Because the width of the main print pattern is smaller than the width of the substrate layer, at least one unprinted selvage edge is created on the coated substrate layer. In a preferred embodiment, two unprinted selvage edges are created on the coated substrate layer, preferably along the two opposing side edges of the substrate layer.
When the main print pattern is provided on the coated substrate layer, whereby at least one unprinted selvage edge is created on the coated substrate layer, preferably there is a transition border between the main print pattern and the at least one unprinted selvage edge, which transition border preferably coincides with the side edge of the main print pattern which is adjacent to the the at least one unprinted selvage edge. Similar as for the side edges of the main print pattern, this transition border should not necessarily be interpreted as being a substantially continuous border between the main print pattern and the at least one unprinted selvage edge, but may be interrupted in some parts on the coating due to e.g. the irregularity of the main print pattern, i.e. the print pattern does not necessarily need to be applied to the entire top surface of the coating and some parts of the coating may e.g. not be provided with the main print pattern and hence lead to interruptions in the transition border between the main print pattern and the at least one unprinted selvage edge. This is for example illustrated in figure 1. When used herein, when it is referred to that the additional print pattern is substantially continuous with the main print pattern, it is preferably meant that the additional print pattern is provided at the transition border between the main print pattern and the at least one unprinted selvage edge, whereby the additional print pattern extends the main print pattern from the transition border at least partly into the at least unprinted selvage edge, preferably whereby the additional print pattern extends the main print pattern in such a manner that the transition between the main print pattern and the additional print pattern is not distinguishable to the human eye, i.e. does not comprise any discontinuities.
In an ideal situation, the cutting device, when cutting the substrate layer, should preferably cut off the at least one selvage edge from the coated substrate layer at the transition border between the main print pattern and the at least one selvage edge. However, due to cutting errors, the cutting device may not exactly cut the substrate layer at this border, but may, for example, cut the substrate layer partly in the selvage edge, which would result in unprinted areas appearing on the edges of the final wall covering, or it may cut the substrate layer partly in the main print pattern whereby the print pattern of the wall covering would no longer correctly correspond to the print pattern of the wall covering which is to be hung adjacent thereof. Because an additional print pattern is provided at least partly on the at least one unprinted selvage edge, which additional print pattern is substantially continuous with the main print pattern, the cutting device, if it would diverge from the transition border and, for example, cut in the at least one unprinted selvage, will in such a case cut in the additional print pattern, and hence cutting errors can be masked and camouflaged, thereby minimizing side effects due to cutting occurring on the edges of the wall covering. Because a digital printing device is used to apply the additional print pattern, the exact additional print pattern that is to be provided along the main print pattern and the location where it needs to be provided on the at least unprinted selvage edge can be pre-calculated and controlled allowing a smooth and continuous transition between the main print pattern and the additional print pattern.
In a preferred embodiment, when it is referred to that the additional print pattern is substantially continuous with the main print pattern, it is meant that the additional print pattern is provided at the transition border between the main print pattern and the at least one unprinted selvage edge, whereby the additional print pattern extends the main print pattern from the transition border at least partly into the at least unprinted selvage edge in such a manner that the transition between the main print pattern and the additional print pattern is not distinguishable to the human eye, i.e. does not comprise any discontinuities, and whereby the additional print pattern will correspond with the print pattern provided at the side edge of a wall covering which is to be hung adjacent of the wall covering that is being produced. This is for example illustrated in figure 5. This way, the print pattern will thus be able to better correspond with the print pattern of the strip of wall covering that is to be hung adjacent of the strip of wall covering that is produced, even if cutting errors are made during the synthesis of the wall covering.
In a preferred embodiment, two opposing selvage edges will be created when the main print pattern is provided on the coated substrate, preferably one on each side edge of the substrate layer, whereby an additional print pattern is provided at least partly on both unprinted selvage edges using a digital printing device, whereby the additional print patterns are substantially continuous with the main print pattern. In such a case, preferably there will be two transition borders between the main print pattern and the two unprinted selvage edges, preferably each transition border corresponding to one of the opposing side edges of the main print pattern. If the cutting device would diverge from the transition border on one side edge of the main print pattern, for example if it would cut the substrate layer partly in the selvage edge, the cutting device, typically having a fixed cutting width, would also diverge on the other transition border and would there cut the substrate layer partly in the main print pattern. In such a case, on one side this would result in an unprinted area appearing on the side edge of the final wall covering, and on the other side the print pattern of the wall covering would no longer correctly correspond to the print pattern of the wall covering which is to be hung adjacent thereof. Because an additional print pattern is provided at least partly on both unprinted selvage edge, which additional print patterns are substantially continuous with the main print pattern, cutting errors made by the cutting device on both sides can be masked and camouflaged, thereby minimizing side effects due to cutting occurring on the edges of the final wall covering.
In a preferred embodiment, the additional print pattern is simultaneously provided during the provision of the main print pattern. The additional print pattern may be provided with the same or a different digital printing device as the one used to provide the main print pattern on the coating. In a preferred embodiment, the additional print pattern is provided using the same digital printing device as the one used to provide the main print pattern on the coating. In a most preferred embodiment, the additional print pattern is simultaneously provided during the provision of the main print pattern using the same digital printing device. This will allow to more correctly tune and adapt the additional print pattern to the main print pattern so that it can be rendered substantially continuous therewith.
In a preferred embodiment, the at least one unprinted selvage edge comprises a width with a value corresponding to maximum 5% of the substrate layer width, more preferably corresponding to maximum 4% of the substrate layer width, even more preferably corresponding to maximum 3% of the substrate layer width, even more preferably corresponding to maximum 2% of the substrate layer width, most preferably, corresponding to maximum 1% of the substrate layer width. The at least one selvage edge thus only comprises a small part of the side edge of the substrate layer, thus allowing excessive loss of substrate layer during cutting to be limited and hence, optimizing the production costs for the wall covering. The width of the at least one unprinted selvage edge is hereby preferably measured along the transverse direction, preferably between the side edge of the substrate layer where the selvage edge is located and the transition border between the selvage edge and the main print pattern.
In a preferred embodiment, the width of the substrate layer comprises a value which ranges between about 40 and about 150 cm, more preferably between about 50 and about 120 cm, most preferably between about 53 and 107 cm. In one preferred embodiment, the substrate layer has a substrate layer width between about 53 cm and about 54 cm. In another preferred embodiment, the substrate layer has a substrate layer width between about 106 cm and about 107 cm. The width of the at least one selvage edge has a value between about 0.1 and 10 mm, more preferably between about 0.5 and 5 mm, even more preferably between about 1.0 and about 4 mm, even more preferably between about 1.5 and about 3 mm, most preferably between about 2.0 and about 3.0 mm. It should be noted that the values provided here for the width of the unprinted selvage edge, constitute values for one unprinted selvage edge. When two unprinted selvage edges are present on the coated substrate, each unprinted selvage edge will preferably comprise an unprinted selvage edge width ranging along the values as provided herein.
The at least one unprinted selvage edge according to the present invention is at least partly provided with an additional print pattern using a digital printing device. Because the additional print pattern is substantially continuous with the main print pattern, the additional print pattern preferably starts from the transition border between the at least one unprinted selvage edge and the main print pattern and extends towards the side edge of the substrate layer, i.e. the side edge of the substrate layer where the selvage edge is located, and thus may extend in part or entirely the width of the unprinted selvage edge. In a preferred embodiment, the additional print pattern extends from the transition border to maximum 99 % of the unprinted selvage edge width, more preferably maximum 90 % of the unprinted selvage edge width, even more preferably maximum 80 % of the unprinted selvage edge width, most preferably maximum 70 % of the unprinted selvage edge width. The additional print pattern is preferably not extended along the entire width of the unprinted selvage edge as it is difficult to digitally print the additional print pattern at or near the side edge of the substrate layer and because this would result in an overall increase of the printing costs, but on the other hand it is still significantly extended over the width of the unprinted selvage edge in order to camouflage and mask cutting errors created by the cutting device.
In a preferred embodiment, the at least one selvage edge is provided with a marker, which marker can be detected by the cutting device and which marker provides a guiding means for the cutting device to cut the substrate layer at a transition border between the main print pattern and the at least one unprinted selvage edge.
Preferably, the marker runs substantially parallel to the transition border between the main print pattern and the at least one unprinted selvage edge, preferably at a fixed position thereof when looking along the transverse direction. Said marker may be any type of marker that can be detected by the cutting device and may be a visual marker, i.e. a marker that can be detected in the visible light spectrum and preferable is visible for the human eye, or a non-visual marker, i.e. that cannot be detected in the visible light spectrum and is not visible for the human eye. The marker may also be a combination of a visual and non-visual marker. Examples of non-visual markers include for example markers that can be detected by the cutting means using UV light, infrared light, fluorescent light, etc. In a preferred embodiment, the marker is a visual marker. Said visual marker may comprise any form or configuration such as dots, full or interrupted lines, text, letters, numbers, polygons, colors, textures, patterns, opacity, reflectivity, sheen, etc.
Preferably, the marker is printed on the at least one selvage edge. More preferably, the marker is a line printed on the at least one selvage edge, which line runs substantially parallel to the transition border between the main print pattern and the at least one unprinted selvage edge, preferably at a fixed position thereof when looking along the transverse direction. Preferably, the marker is printed on the at least one selvage edge using the same digital printing device which provides the additional print pattern to the at least one unprinted selvage edge. In a preferred embodiment, the main print pattern, the additional print pattern and the marker are provided using the same digital printing device. In a most preferred embodiment, the marker comprises a printed two pixel line on the at least one selvage edge, which line runs substantially parallel to the transition border between the main print pattern and the at least one unprinted selvage edge at a fixed position thereof when looking along the transverse direction.
When two unprinted selvage edges are present on the coated substrate, the marker is preferably only provided on one of the two unprinted selvage edges as one marker usually suffices to effectively guide the cutting means. However, if required, a marker may be provided on both unprinted selvage edges.
In a preferred embodiment, the at least one selvage edge is provided with a marker which marker runs substantially parallel to the transition border between the main print pattern and the at least one unprinted selvage edge, whereby the marker is positioned from the transition border at a fixed position thereof when looking along the transverse direction, preferably the marker is positioned from the transition border when looking along the transverse direction over a distance of between about 50% and about 100% of the unprinted selvage edge width, more preferably of between about 60% and about 100% of the unprinted selvage edge width, even more preferably of between about 70% and about 100% of the unprinted selvage edge width, even more preferably of between about 80% and about 100% of the unprinted selvage edge width, most preferably of between about 85% and about 99% of the unprinted selvage edge width.
The combination of providing an additional print pattern on the at least selvage edge with the provision of a marker, allows on the one hand to more accurately guide and control the cutting means to cut the substrate layer in the desired width of the wall covering due to the presence of the marker, i.e. preferably it allows the cutting means to cut along the transition border between the main print pattern and the at least one unprinted selvage edge. On the other hand, if cutting errors were to occur, the presence of the additional print pattern allows to camouflage and mask these errors. The combination thus allows to almost completely eliminate unwanted side effects occurring due to cutting on the side edges of the final wall covering.
The cutting device according to the present invention may comprise any cutting device known in the art to cut wall coverings into their desired dimensions. The cutting device may for example comprise cutting knives or cutting lasers to cut the substrate layer.
The substrate layer according to the present invention may be any substrate layer known in the art for the production of wall coverings. Preferably, the substrate layer comprises paper, a non-woven, plastic, cellulose and/or cardboard. According to a preferred embodiment, the substrate layer comprises paper. According to another preferred embodiment, the substrate layer comprises a non-woven.
According to a preferred embodiment, the substrate layer has a weight between about 40 and about 200 g per m² of substrate layer, more preferably between about 50 and about 150 g per m² of substrate layer, most preferably between about 60 and about 130 p per m² of substrate layer. Such weights allow to produce a firm and robust wall covering without the wall covering being too heavy or too difficult to be applied to a wall, ceiling, etc. by a user or a craftsman.
The embossed pattern, which optionally may be provided on the coating, may be provided on the coating using any type of embossing technique known in the art such as mechanical embossing techniques or chemical embossing techniques. Preferably, the embossing pattern is provided to the coating using a mechanical embossing technique. In such mechanical embossing technique, an embossed pattern is preferably applied in the coating by means of an embossing element which is pressed into the coating, optionally using heat to aid the pressure process. The embossing element typically comprises a pattern which is the negative/positive of the embossing pattern that is to be applied to the coating. If an embossed pattern is provided to the coating, it is preferably provided to the coating prior to applying a print pattern, either a main print pattern or an additional print pattern, and optionally a marker, to the coating. The print patterns and optionally the marker will thus be provided on the embossed coating.
The digital printing device may be any type of digital printing device known in the art such as a digital inkjet printing device, a digital laser printing device, etc. In a preferred embodiment, the digital printing device is a digital inkjet printing device. In such inkjet printing devices, tiny drops of ink are typically projected directly onto an ink receptor surface, for example a coating, without physical contact between the printing device and the receptor. Typically one or more printheads are used to deposit the droplets on the coating. The printing device typically stores the printing data electronically and controls a mechanism for ejecting the drops image-wise. Printing may be accomplished by moving e.g. a print head across the receptor or vice versa. Preferably, the provision of the main print pattern, the additional print pattern and/or optionally the marker, if present and if printed, on the coating according to the present invention occurs by moving the substrate layer, comprising the coating, relative to the printing device and not by moving the printing device, e.g. print head(s), relative to the substrate layer.
Inkjet printing devices generally are of two types which are known in the art: continuous stream and drop-on-demand. Preferably, the digital printing device is a digital drop-on demand inkjet printing device, preferably comprising at least one print head. Preferably, said one print head is piezoelectrically controlled. Early patents on inkjet printers include US 3739393 (MEAD CORP), US 3805273 (MEAD CORP) and US 3891121 (MEAD CORP). Digital inkjet printing devices that may be used according to the present invention include, but are not limited to, printing devices disclosed in WO 2010/150012 , WO 2010/125129 , EP 2 055 490 or WO 2008/065411 , which are incorporated herein as a reference.
In a more preferred embodiment the printheads are recirculating printheads, more preferably recirculating piezo-drop-on-demand print heads. The recirculation keeps constantly ink flowing through the printhead, thereby preventing the printhead to dry out and getting blocked. An extra advantage is that shorter drying times can be achieved as solvents in the ink can be used with a higher vapour pressure without blocking the printhead due to evaporation.
Any type of ink known in the art may be used in the digital printing device of the current invention. Preferably, the ink according to the current invention is suitable for application in a digital inkjet printing device. Ink compositions for inkjet printing devices typically include following ingredients: dyes or pigments, water and/or organic solvents, humectants such as glycols, detergents, thickeners, polymeric binders, preservatives, etc. It will be readily understood that the optimal composition of such ink is dependent on the inkjet printing device used and on the nature of the ink-receiver to be printed. The ink compositions can be roughly divided in: water-based inks, the drying mechanism involving absorption, penetration and evaporation; oil-based inks, the drying involving absorption and penetration; solvent-based inks, the drying primarily involving evaporation; hot melt or phase change, in which the ink is liquid at the ejection temperature but solid at room temperature and wherein drying is replaced by solidification; UV-curable, in which drying is replaced by polymerization. Any of these ink-types may be used separately or combined in order to provide the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, on the coating according to the present invention. Preferably, the main print pattern and/or additional print pattern is provided on the coating by applying between about 5 and about 20 g/m² of ink, more preferably between about 6 and about 18 g/m² of ink, even more preferably between about 7 and about 16 g/m² of ink, even more preferably between about 8 and about 14 g/m² of ink, even more preferably between about 9 and about 12 g/m² of ink, most preferably between about 10 and about 11 g/m² of ink.
In a preferred embodiment, the main print pattern and/or additional print pattern is provided on the coating using a solvent-based ink. Optionally the marker, if present and printed, may also be provided using a solvent-based ink. Such solvent-based inks are usually more compatible with the coating of the substrate layer, for example when it comprises a thermoplastic material such as polyvinyl chloride, as compared to e.g. water-based inks and hence will result in a better print quality.
In a preferred embodiment, the print pattern is provided on top of the embossed coating by a wet-on-wet printing technique, preferably in a single pass, meaning that all the different inks are deposited on the coating in one single movement of the printheads. Providing the printing pattern in a single pass has the advantage that the printing process in more time efficient, especially when it's done wet-on-wet. A wet-on-wet printing process does not require drying time for the ink before the next ink can be deposited.
A wet-on wet printing technique has the advantage that the printheads can be placed close to each other because no drying or curing time is required between the depositions of different inks. This has the advantage that the overall printing array can be kept small and compact. During drying or curing of certain types of ink, gasses can be released from that ink. These gasses can get in contact with the print heads, disturbing the working of said printheads. The smaller the print array, the less contact between the gasses released by drying or curing and the array and the less problems that the gasses can cause.
In a preferred embodiment the gasses caused by drying or curing of ink are extracted during printing. Extracting the gasses causes the less interference of the gasses with the printing array and printheads.
In a preferred embodiment the print pattern is provided by colour inks and special effects inks. Preferably the colour inks comprise the, in the art standard colours for printing, namely cyan, magenta, yellow and black, also known as CMYK. Additionally other colour inks can be included. The special effect inks are inks that provide optical or mechanical properties to a substrate when printed that is not possible by colour inks alone.
The term "special effect" refers to glitter, metallic, magnetic, ceramic, polymeric, odour and flavour, glossy, matt, pearl, fluorescent, phosphorescent, electroluminescent, electrical or thermal conductive, transparent, anti-static, adhesive, anti-bacterial, anti-corrosive, scratch resistant, anti-graffiti, anti-climb, or sound-absorbing effect.
In a preferred embodiment the ink is deposited on the coating in a thin layer, this layer has a maximum thickness when wet of 0.0 to 60.0 µm, more preferably 5.0 to 40.0 µm, even more preferably 10.0 to 20.0 µm. A thin wet ink layer results in a high resolution when dried or cured. Ink deposited by inkjet printing has a low viscosity, causing the ink to flow easily. Especially on an embossed surface, where parts of the surface are sloped, gravity will cause ink to flow. The thinner the layer of ink, the less the ink has the tendency to flow, resulting in a higher resolution after drying or curing.
In a preferred embodiment the printing device comprises colour ink printheads and special ink printheads. In a more preferred embodiment the printing device comprises 4 colour ink printheads, one for cyan ink, one for magenta ink, one for yellow ink and one for black ink.
In a preferred embodiment the special effect ink comprises particles. These particles provide the special effect. Preferably, the particles are rounded, with have a diameter between 2.00 and 100.00 µm, preferably 4.00 to 70.00 µm, more preferably 6.00 to 25.00 µm, even more preferably 7.50 to 15.00 µm and most preferably 10.00 to 12.50 µm. The larger the particle, the larger the special effect but also the larger the tendency for the special effect ink to block the printhead. The use of a recirculating printhead prevents the blocking of the printhead, especially when a larger than standard nozzle is used, like a nozzle with a diameter of 15 to 150 µm, preferably 25 to 100 µm, more preferably 35 to 45 µm. The constant movement of the ink in the printhead prevents the particles to precipitate. When the particle size becomes too large, hence the upper limit, even the use of a recirculating printhead can't prevent the printhead from blocking. As previously stated, the larger the particles, the larger the special effect. This implies that a less concentrated ink can be used when using large particles to obtain the same special effect as when an ink is used with smaller particles. Eventually, larger particles will allow the ink to be deposited in a thinner layer than ink with smaller particles and still lead to the same special effect.
In a preferred embodiment the special effect ink comprises rounded but flatted shape, the particles have a diameter between 2.00 and 100.00 µm, preferably 4.00 to 70.00 µm, more preferably 6.00 to 25.00 µm, even more preferably 7.50 to 15.00 µm and most preferably 10.00 to 12.50 µm and a height of 0.01 to 1.20 µm, preferably 0.05 to 0.80 µm, more preferably 0.09 to 0.50 and most preferably 0.13 to 0.20 µm. When deposited, these particles will orient themselves in the still wet ink layer and form a less thick layer then when spherical particles are used.
In a preferred embodiment the particles are metallic particles. These metallic particles result in a metallic effect. The ink provides after drying or curing, a metal like appearance. The metal particles can also be used to print electrical conductor or even and electrical circuit. In a more preferred embodiment, the metallic particles is said special effect ink are aluminium filings. The advantage of aluminium is that when aluminium oxidises, on the surface a layer of aluminium oxide is formed and this layer stops the further oxidation of aluminium. Even with this aluminium oxide layer on the surface, the look of aluminium remains metallic. The aluminium filings provide a metallic silver appearance. The colour of the metallic effect can be changed by applying transparent colour ink on top of the metallic ink. In the art, metallic inks are available, but these have metallic particles with a diameter below 2 µm in an effort to stop blockage of a non-recirculating printhead.
In a preferred embodiment the particles are sparkling particles, glitter particles, pearl particles, glossy particles, matt particles, magnetic particles, ceramic particles, polymeric particles, particles with a high refractive index or zeolite particles. All these kind of particles can cause an effect that is not possible to achieve with colour inks, and hence these particles cause a special effect.
In a more preferred embodiment the particles are glitter particles, metallic particles or ceramic particles.
After providing of the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, on top of the coating, the print pattern is preferably subjected to a post-treatment in order for it to properly adhere to the coating. Such post-treatment may be for example a heat treatment, a UV-curing treatment, etc. In a preferred embodiment, the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, is subjected to a heat treatment after its application to the coating. If a solvent-based ink is used to apply the print pattern on the coating, such heat treatment will result in the evaporation of the solvent of the ink and hence in its adherence to the coating. Preferably, a temperature between about 110 and about 160 °C is used during the heat treatment, more preferably a temperature between about 120 and about 150 °C, most preferably between about 125 and about 145 °C. Preferably, said heat treatment comprises an infrared heat treatment.
In a preferred embodiment, the post-treatment is performed in a different zone, a post-treatment zone, from the printing itself, in a printing zone. The zones are separated from each other in a way that gasses released during post treatment are not entering the printing zone. This has the advantage that the printheads are exposes to less gasses caused by drying or curing of the ink.
In one embodiment, the main print pattern and/or additional print pattern comprises glitter particles, metallic particles and/or ceramic particles. Such particles may influence the optical appearance of the print pattern and provide additional decorative elements in the wall covering. Preferably, the particles comprise a particle size between about 0.1 and about 100 µm, more preferably between about 0.5 and about 75 µm, most preferably between about 1 and about 50 µm. Particles of such size are more readily applicable on a coating using a digital printing device. Such particles may also provide additional surface texture to the coating, i.e. in addition to the embossed pattern, when present.
As mentioned before, the provision of the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, on the coating according to the present invention occurs by moving the substrate layer, comprising the coating, relative to the printing device and not by moving the printing device, e.g. print head(s), relative to the substrate layer. Preferably, when the print pattern, i.e. the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, is provided on top of the coating, the substrate layer is provided at a relative speed, as compared to the digital printing device, of between about 15 and about 60 meters of substrate layer per minute along the longitudinal dimension. More preferably, the substrate layer is provided at a relative speed, as compared to the digital printing device, of between about 18 and about 55 meters of substrate layer per minute, even more preferably between about 20 and about 50 meters of substrate layer per minute, most preferably between about 24 and about 48 meters of substrate layer per minute along the longitudinal dimension. The speed of the substrate layer is optimized in order to allow the substrate layer, with the coating provided thereon, to be printed at a sufficient high rate, allowing an optimal production efficiency of the wall covering, while still maintaining a high print quality and print efficiency of the digital printing device on the coating.
Preferably, when a print pattern, i.e. the main print pattern, the additional print pattern and/or optionally the marker, if present and printed, is provided on top of the coating, the substrate layer is provided with a carrier means which is essentially endless along the longitudinal dimension of the substrate layer, whereby the carrier means has a contact surface, which contact surface is in contact with the back side of the substrate layer. The contact surface hereby preferably comprises a width as measured along the transverse direction which is larger than the substrate layer width of the substrate layer. Preferably, the relative speed between the contact surface of the carrier means and the substrate layer is essentially zero. Preferably, the contact surface of the carrier means has a relative speed, as compared to the digital printing device, of between about 15 and about 60 meters of contact surface per minute along the longitudinal dimension of the substrate layer. More preferably, the contact surface of the carrier means is provided at a relative speed, as compared to the digital printing device, of between about 18 and about 55 meters of contact surface per minute, even more preferably between about 20 and about 50 meters of contact surface per minute, most preferably between about 24 and about 48 meters of contact surface per minute along the longitudinal dimension of the substrate layer.
The surface of the coating may be modified prior to and/or during the provision of a print pattern, i.e. the main print pattern, the additional print pattern and optionally the marker, if present and printed, thereon. For example, the surface energy of the coating may be modified in such a manner that the surface energy difference between the surface energy of the coating and the surface energy of the ink which is e.g. used to provide the print pattern to the coating, may be altered and controlled. By altering this surface energy difference, the tendency of the ink to spread over the surface of the coating when applied thereon can be tuned, and hence, the print quality and resolution of the print pattern can be controlled. Surface treatments that may be used according to the present invention include a flame treatment, a corona treatment, a plasma treatment, and/or a liquid treatment. In a preferred embodiment, the coating is subjected to a corona treatment and/or a humidification treatment before and/or during the application of the print pattern, preferably to alter the surface energy of the coating. Further, the above described surface treatments may also be used in order to allow a stronger adherence of the print pattern to the coating.
It should be noted that, when used herein, surface tension and surface energy refer to equivalent parameters. The surface tension of a liquid is defined as the force acting on a unit length of the surface and is expressed in mN/m, whereas surface energy of a solid is the energy needed to create a unit area of interface and is expressed in mJ/m². These dimensions are equivalent: mN/m x m/m = mJ/m². For consistency in disclosing the present invention, the term surface energy of an ink will be used instead of the term surface tension of an ink.
The coating preferably comprises a thermoplastic material. The thermoplastic material can be any thermoplastic polymer material known in the art that can be used as coating material in wall coverings and includes, but is not limited to, vinyl containing thermoplastics such as polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, and other vinyl and vinylidene resins and copolymers thereof; polyethylenes such as low density polyethylenes and high density polyethylenes and copolymers thereof; styrenes such as ABS, SAN, and polystyrenes and copolymers thereof, polypropylene and copolymers thereof; saturated and unsaturated polyesters; acrylics; polyamides such as nylon containing types; engineering plastics such as acetyl, polycarbonate, polyimide, polysulfone, and polyphenylene oxide and sulfide resins and the like. In a preferred embodiment, the thermoplastic material comprises polyvinyl chloride. The term "polyvinyl chloride" as used in present invention does not only refer to the polymer polyvinyl chloride, but also to derivatives of polyvinyl chloride, such as polyvinylidene chloride, polyvinyl acetate, polyacrylate, polymethacrylate and/or combinations thereof. Preferably, the term "polyvinyl chloride" refers to the polymer polyvinyl chloride.
In a preferred embodiment, the coating is applied to the substrate layer by providing between about 50 and about 400 g of a coating composition per m² substrate layer to the top side of the substrate layer, more preferably between about 100 and about 300 g of a coating composition per m² substrate layer, even more preferably between about 125 and about 275 g of a coating composition per m² substrate layer, most preferably between about 150 and about 250 g of a coating composition per m² substrate layer. Preferably, the coating composition is applied in a substantially uniform manner to the substrate layer, meaning that the coating composition is applied to substantially the entire top side surface of the substrate layer.
Preferably, the coating composition comprises polyvinyl chloride, a blowing agent, a plasticizer, a dispersing agent, a diluent, a filler and/or a stabilizer.
In a preferred embodiment, the coating composition comprises polyvinyl chloride. Preferably, the coating composition comprises between about 20 to about 80 weight percent of polyvinyl chloride. In a more preferred embodiment, the coating composition comprises between about 20 to about 75 weight percent of polyvinyl chloride, even more preferably between about 20 and about 70 weight percent polyvinyl chloride, most preferably between about 25 and about 65 weight percent of polyvinyl chloride. Polyvinyl chloride is preferably used in the coating composition because it offers many advantages such as for example its easy processability and applicability as a coating material to a substrate layer. Further it is known for its isolating properties, both for heat and sound, and because it makes the final wall covering more readily washable compared to other polymer materials.
The coating composition preferably comprises a blowing agent, more preferably comprises between about 0 to about 5 weight percent of a blowing agent. As used herein, the term "blowing agent", also sometimes referred to as "foaming agent", refers to a compound that is capable of forming a cellular structure in a wide variety of materials, such as a coating, through a foaming process. The formation of such cellular structure typically results in an expansion of the material, thereby decreasing the density of the material. The blowing agent used in the present invention may include at least one selected from a chemical blowing agent, a physical blowing agent, or a mixture thereof.
Examples of physical blowing agents include carbon dioxide, nitrogen, argon, water, air, helium, or the like, and/or an organic blowing agent such as aliphatic hydrocarbons containing 1 to 9 carbon atoms, such as methane, ethane, propane, n-butane, isobutene, n-pentane, isopentane, neopentane, etc.; aliphatic alcohols containing 1 to 3 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, etc.; and halogenated aliphatic hydrocarbons containing 1 to 4 carbon atoms, such as methyl fluoride, perfluoromethane, ethyl fluoride, 1,1-difluoroethane, pentafluoroethane, difluoromethane, perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane, methyl chloride, methylene chloride, ethyl chloride, etc., and/or combinations and/or derivatives thereof.
Preferably, the blowing agent comprises a chemical blowing agent. As the chemical blowing agent, any compound is not particularly limited as long as the compound may be decomposed at a specific temperature or more to generate gas and thus form a cellular structure, and an example thereof may include azodicarbonamide, azodi-isobutyro-nitrile, benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semicarbazide, barium azodicarboxylate, N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trihydrazino triazine, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, and/or combinations and/or derivatives thereof.
The blowing agent preferably becomes "active", i.e. starts forming a cellular structure in the coating, when it is exposed to heating. Depending on the amount and type of blowing agent in the coating composition, the density of the resulting coating will be larger of smaller. In a preferred embodiment, the coating composition comprises between about 0.1 and about 4.5 weight percent of blowing agent, more preferably between about 0.2 and about 4 weight percent of blowing agent, even more preferably between about 0.5 and about 3 weight percent of blowing agent, most preferably between about 1 and about 2 weight percent of blowing agent.
The coating composition preferably comprises a plasticizer, more preferably comprises between about 5 to about 40 weight percent of a plasticizer. The term "plasticizer," as used herein refers to a compound that will increase the plasticity or fluidity of a material, typically a polymer. This will cause the coating composition to be more readily applicable to a substrate layer. The plasticizer can be any conventional plasticizer known in the art and comprises, but is not limited to, phtalate-based plasticizers, trimellitate-based plasticizers, adipate-based plasticizers, sebacate-based plasticizers, maleate-based plasticizers, benzoate-based plasticizers, dibenzoate-based plasticizers, terephtalate-based plasticizers, hydrogenated derivatives of the previous and/or any combination of the previous. In preferred embodiment, the composition comprises between about 8 and about 38 weight percent of a plasticizer, more preferably between about 15 and about 35 weight percent of a plasticizer, most preferably between about 20 and about 30 weight percent of a plasticizer.
The coating composition preferably comprises a dispersing agent, more preferably comprises between about 0.01 to about 5 weight percent of a dispersing agent. The term "dispersing agent" as used herein refers to a component that improves the dispersion of solids in a composition. Preferably, the dispersing agent will improve the dispersion of polyvinyl chloride, and of pigments and the filler in the composition, when present. A better dispersion and stabilization will increase the covering properties of the coating on the substrate layer. Dispersing agents are typically surfactants and comprise, but are not limited to alcohol ethoxylates, oxo-alcohol ethoxylates, alcohol ethoxysulphates, alkylphenol-ethoxylates, amine- and - amide-ethoxylates, alkyl polyglucosides and/or combinations thereof. In a preferred embodiment, the coating composition comprises between about 0.05 and about 4 weight percent of a dispersing agent, more preferably between about 0.1 and about 3 weight percent of a dispersing agent, most preferably between about 0.2 and about 2 weight percent of a dispersing agent.
The coating may comprise at least one diluent, more preferably may comprise between about 0 to about 5 weight percent of at least one diluent. With the term "diluent" as used herein, a component is meant which reduces the viscosity of a composition. This further contributes to a better applicability of the composition to the substrate layer in order to form a coating. Non-limiting examples of diluents include water, alkanes, toluene, xylene, methyl isobutyl ketone, isopropyl alcohol, acetone, isobutyl alcohol, butanone, turpentine, fatty acid esters and/or combinations thereof. In a preferred embodiment, the coating composition comprises between about 0 and about 4 weight percent of a diluent, more preferably between about 0 and about 3 weight percent of a diluent, most preferably between about 0 and about 2 weight percent of a diluent.
The coating composition preferably comprises a filler, more preferably comprises between about 0.01 to about 40 weight percent of a filler. The term "filler" as used herein refers to a component that can improve the properties of the composition by improving the structure or texture of the composition and/or by reducing the overall cost of the composition. Fillers may thus reduce the overall cost to produce the coating and/or enhance the covering properties of the coating. Examples of suitable fillers include calcium/magnesium carbonate, talc, kaolin, silica, alumina, magnesium hydroxide, clay and/or combinations thereof. In a preferred embodiment, the coating composition comprises between about 0.02 and about 38 weight percent of a filler, more preferably between about 0.05 and about 35 weight percent of a filler, most preferably between about 0.1 and about 30 weight percent of a filler.
The coating composition preferably comprises a stabilizer, more preferably comprises between about 0.1 to about 5 weight percent of a stabilizer. The term "stabilizer" as used herein refers to a component that can increase the stability of a polymer, preferably of polyvinyl chloride, and/or that can increase the activity of the blowing agent, when present. The stabilizer can for example inhibit that HCl is liberated from polyvinyl chloride and form polyenes. Further, it can result in an increased foaming activity of the blowing agent, when present, and thus simultaneously influence the density of the coating. A suitable stabilizer includes, but is not limited to, Ca-Zn based compounds, K-Zn based compounds, Ba-Zn based compounds, organic Tin based compounds, metallic soap based compounds, phenolic compounds, phosphoric acid ester based compounds, and phosphorous acid ester based compounds. In a preferred embodiment, the coating composition comprises between about 0.2 and about 4 weight percent of a stabilizer, more preferably between about 0.3 and about 3 weight percent of a stabilizer, most preferably between about 0.5 and about 2 weight percent of a stabilizer.
In a preferred embodiment, the coating composition according to the present invention, used to provide a coating to the substrate layer, comprises the following components:

20-80 weight percent of polyvinyl chloride;
0-5 weight percent of a blowing agent;
5-40 weight percent of a plasticizer;
0.01-5 weight percent of a dispersing agent;
0-5 weight percent of a diluent;
0.01-40 weight percent of a filler; and
0.1-5 weight percent of stabilizer,

According to a more preferred embodiment, the coating composition comprises the following components:

20-75 weight percent of polyvinyl chloride;
0.2-4 weight percent of a blowing agent;
8-38 weight percent of a plasticizer;
0.05-4 weight percent of a dispersing agent;
0-4 weight percent of a diluent;
0.02-38 weight percent of a filler; and
0.2-4 weight percent of stabilizer,

According to an even more preferred embodiment, the coating composition comprises the following components:

20-70 weight percent of polyvinyl chloride;
0.5-3 weight percent of a blowing agent;
15-35 weight percent of a plasticizer;
0.1-3 weight percent of a dispersing agent;
0-3 weight percent of a diluent;
0.05-35 weight percent of a filler; and
0.3-3 weight percent of stabilizer,

According to a most preferred embodiment, the coating composition comprises the following components:

25-65 weight percent of polyvinyl chloride;
1-2 weight percent of a blowing agent;
20-30 weight percent of a plasticizer;
0.2-2 weight percent of a dispersing agent;
0-2 weight percent of a diluent;
0.1-30 weight percent of a filler; and
0.5-2 weight percent of stabilizer,

It is possible that the top side of the substrate layer may be provided with one or more additional layers prior to providing the coating to the top side of the substrate layer, the one or more layers thus being positioned between the substrate layer and the coating. Such additional layers may, for example, improve the adherence between the coating and the substrate layer, provide better isolating properties to the final wall covering, etc.
The coating according to the present invention may also comprise components or additives other than the ones described above. For example, the coating may comprise one or more pigments. With the term "pigment", as used in the current invention, a compound is meant that can change the colour of reflected or transmitted light as the result of wavelength-selective absorption. This way, the coating can be provided with a certain colour, depending on the desired wall covering. The pigment may comprise any type of pigment known in the art and may comprise inorganic pigments, metal-based pigments and/or organic pigments. In a preferred embodiment, the coating comprises titanium dioxide as pigment. This component provides the coating with a substantially white colour and improves the opacity of the coating, i.e. it will cause the coating to be less transparent, which influences the colour perception of the print pattern. Further, the coating may comprise fire retarding agents such as, but not limited to antimony(III)oxide, aluminium trihydrate, magnesium hydroxide, etc. and/or combinations thereof. Such fire retardant agents provide the eventual wall covering with fire retardant properties and thus also the room, i.e. wall, ceilings, etc. where the wall covering is provided.
After providing a coating on the top side of the substrate layer, the substrate layer with coating can be used as such to provide it with a print pattern and, optionally, an embossed pattern, or the substrate layer with coating can optionally undergo additional steps prior to providing a print pattern and optionally an embossed pattern to the coating. The coating can for example be gelled after application of the coating, for example at a temperature between about 100 and about 200 °C, whereby the coating is typically brought from a viscous, semi-liquid condition into a solid, non-sticky condition under the influence of heat which enables plasticizer absorption of polyvinyl chloride. Further, preferably when the coating composition used to apply the coating to the substrate layer comprises a blowing agent, the coating can undergo a foaming step, whereby the blowing agent is activated under the influence of heat to form a cellular structure in the coating. Typically, the coating will hereby expand and increase in thickness. This foaming step is preferably performed at a temperature between about 150 and about 250 °C. In one embodiment, after application of the coating, the substrate layer with the coating will be gelled and/or will undergo a foaming step prior to applying a print pattern and optionally an embossed pattern to the coating.
The invention is further described by referring to the figures which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.
Figures 1 provides a top view of a substrate layer (1), which is essentially endless along a longitudinal dimension, which longitudinal dimension corresponds with a longitudinal direction (L). The substrate layer is preferably a paper substrate layer or a non-woven. The substrate layer has two opposing side edges (2) which are substantially parallel to each other and which run along the longitudinal direction (L). The substrate layer (1) has a substrate layer width (T₁) along a transverse dimension, which transverse dimension corresponds with a transverse direction (T), which transverse direction is substantially perpendicular to the longitudinal direction (L). The substrate layer width (T₁) is determined by the distance between the two opposing side edges (2) of the substrate layer (1) measured along the transverse direction (T). The longitudinal dimension and the transverse dimension of the substrate layer define a plane comprising two surfaces, a back side and a top side. The substrate layer of figure 1 is displayed with its top side facing the viewer. On the top side of the substrate layer, a coating (3) is provided. On the coating (3) a main print pattern (4) is provided using an inkjet printing device whereby 5 g/m² of a solvent-based ink was provided on top of the coating. The main print pattern has two opposing side edges (5, indicated by the striped line). Due to the irregularity of the main print pattern, whereby a print pattern is only provided on selected parts of the coating, these side edges (5) are only visible on the coating on the parts where the print pattern is provided and interrupted where no print pattern is provided. By connecting these parts with an imaginary line (as indicated by (5)), these side edges become apparent. The main print pattern has a main print pattern width (T₄) which is measured along the transverse direction (T) between the two opposing side edges (5) of the main print pattern (4).
Because the main print pattern width (T₄) is smaller than the substrate layer width (T₁), two unprinted selvage edges (6) are created along the side edges (2) of the coated substrate layer. Between each unprinted selvage edge (6) and the main print pattern (4), a transition border (7) is created, which border coincides with the side edges (5) of the main print pattern (4). In figure 1, the two unprinted selvage edges (6) are depicted as having the same unprinted selvage edge width (T₆), which width is measured along the transverse direction (T) between the side edge of the substrate layer (2) where each selvage edge (6) is located and the transition border (7) between the selvage edge and the main print pattern. It should be noted, though, that when two unprinted selvage edges are present, the widths of the two selvage edges do not necessarily have to comprise the same value and can be larger or smaller on one side as compared to the other side, or can be equal in size, as e.g. is depicted in figure 1.
The selvage edges (6) of figure 1 are significantly enlarged, are not in proportion and have been exaggerated for better illustration of the invention. Preferably, the substrate layer has a width of about 535 mm, whereby the main print pattern has a width of 530 mm and the unprinted selvage edges have a width of 2.5 mm, hence, in reality, each unprinted selvage edge comprises a width (T₆) with a value corresponding to 0.47% of the substrate layer width (T₁).
Figure 2A and 2B provides schematic side views of the coated and printed substrate layer of figure 1, according to two different embodiments of the present invention. It should be noted that the dimensions of the various layers are exaggerated and enlarged for better understanding and are not in proportion. The substrate layer (1) is displayed having a top side (12) and a bottom side (11), whereby a coating (3) is provided on the top side (12) of the substrate layer (1). The coating according to these embodiments is preferably provided on top of the substrate layer by applying 180 g of a coating composition per m² of substrate layer to the top side of the substrate layer. The coating composition hereby preferably comprises the following components:

40 weight percent of polyvinyl chloride;
1.5 weight percent of a blowing agent;
25 weight percent of a plasticizer;
1 weight percent of a dispersing agent;
1 weight percent of a diluent;
15 weight percent of a filler;
1 weight percent of a stabilizer;
5.5 weight percent of titanium dioxide.

After applying the coating composition to the top side of the substrate layer, it was preferably allowed to undergo a foaming step by subjecting it to a temperature of 180 °C during 15 seconds in order to activate the blowing agent in the coating composition and form a foamed coating on the top side of the substrate layer. After the foaming step, for the embodiment in figure 2A, a main print pattern (4) was provided to the coating (3), whereas according to the embodiment of figure 2B, an embossed pattern (13) was first provided in the foamed coating using a mechanical embossing technique, after which the main print pattern (4) was provided to the embossed coating using an inkjet printing device. The coatings according to these embodiments have a bottom surface (15), which bottom surface is in contact with the top side (12) of the substrate layer (1), and a top surface (14), onto which top surface an embossed pattern (13) optionally may be provided (Fig. 2B) and onto which the main print pattern (4) is provided.
After the main print pattern is provided to the coated substrate layer, the substrate layer is preferably cut into the desired width of the wall covering using a cutting device. Figure 3 illustrates the coated substrate layer of figure 1, whereby the cutting means have cut the substrate layer with a cutting error and displays the effect of this cutting error if a production method according to the prior art were to be used. The cutting device typically cuts the substrate layer with a fixed width. However, the substrate layer is not cut along the transition border between the main print pattern and the unprinted selvage edges, but is cut diverging from said border (cutting lines indicated with reference number (8)). The cutting error is exaggerated in order to better illustrate the effect of the cutting error on the side edges of the final wall covering. On one side, the cutting device has partly cut in the main print pattern, e.g. as illustrated in the area A, whereas on the opposing side, an unprinted side edge is created, e.g. as illustrated in the area B. Similarly, due to the diverging angle alpha (a) of the cutting line from the transition border made by cutting device, in the area B' an unprinted side edge is created, whereas in the opposing area A', the cutting device has partly cut in the main print pattern. This results in the appearance of unprinted areas on the edges of the final wall covering and in that the print pattern of this strip of wall covering will no longer correctly correspond to the print pattern of the strips of wall covering which are to be hung adjacent thereof.
Figure 3 illustrates a substrate layer (1) with printed coating according to a preferred embodiment of the current invention, whereby on the unprinted selvage edges (6) of figure 1, additional print patterns (9) are provided. These additional print patterns are preferably simultaneously provided during the application of the main print pattern using the same inkjet printer as the one used to provide the main print pattern. The additional print patterns (9) are substantially continuous with the main print pattern (4) on both side edges (5) of the main print pattern, whereby each additional print pattern (9) is provided at the transition border (7) between the main print pattern (4) and the unprinted selvage edge (6), whereby the additional print pattern (9) extends the main print pattern (4) from the transition border (7) into the unprinted selvage edge (6) in such a manner that the transition between the main print pattern and the additional print pattern is not distinguishable to the human eye, i.e. does not comprise any discontinuities. In this embodiment, the additional print pattern (9) will extend from the transition border (7) towards the side edge (2) of the substrate layer to 80 % of the unprinted selvage edge width, i.e. the additional print pattern (7) extends over a distance T₉ from the transition border (7) towards the side edge (2) of the substrate layer, which distance T₉ in this embodiment comprises a value of 2 mm and thus will not extend over the entire width of the selvage edge (6). Besides the additional print patterns, a marker (10) is also provided on one of the two selvage edges (6), which marker is a two pixel black line which runs substantially parallel to the transition border (7) between the main print pattern (4) and the selvage edge (6) on which the marker is provided, whereby the marker is positioned from the transition border when looking along the transverse direction (T) over a distance (T₉) of about 80% of the unprinted selvage edge width (T₆). In this embodiment, the positioning of the marker from the transition border (T₉) corresponds to the distance T₉ over which the additional print pattern (9) extends from the transition border (7) towards the side edge (2) of the substrate layer. The positioning of the marker from the transition border and the distance over which the additional print pattern extends from the transition border towards the side edge of the substrate layer do not necessarily have to correspond to each other. The marker can for example be positioned over a larger distance from the transition border than the distance over which the additional print pattern extends from the transition border, or can be less far positioned thereof, i.e. the marker would then partly overlap with the additional print pattern.
The marker (10) according to this embodiment is provided using an inkjet printing device which is the same as the one which is used to provide the main print pattern (4) and the two additional print patterns (9).
After the provision of the main print pattern, the additional print patterns and the marker on the coated substrate layer, the print patterns are preferably first dried and adhered to the coating by subjecting it to an infrared heat treatment at 135 °C, making the print pattern 'touch-dry'. The substrate layer, with coating and print patterns, is then cut into the desired width of the wall covering using a cutting device. Due to the presence of the marker (10), the cutting device will cut the substrate layer with the printed coating substantially along the transition border between the main print pattern and the selvage edges, even though the transition border is an imaginary line and in some parts of the coated substrate layer cannot really be distinguished where there is no main print pattern provided. Furthermore, if a cutting error were to occur, the presence of the additional print pattern (9) provided on the selvage edges would camouflage and mask these errors on both transition borders (7).
Figure 5A and 5B provide schematic top views of a substrate layer (1), which is essentially endless along a longitudinal dimension, which longitudinal dimension corresponds with a longitudinal direction (L). The substrate layer has two opposing side edges (2) which are substantially parallel to each other which run along the longitudinal direction (L). The substrate layer (1) has a substrate layer width along a transverse dimension, which transverse dimension corresponds with a transverse direction (T), which is substantially perpendicular to the longitudinal direction (L). The substrate layer is displayed with its top side facing the viewer. On the top side of the substrate layer, a coating (3) is provided. On the coating (3) a main print pattern (4) is provided using an inkjet printing device. The main print pattern has two opposing side edges (5, indicated by the striped line). Because the main print pattern width is smaller than the substrate layer width, two unprinted selvage edges (6) are created along the side edges (2) of the coated substrate layer. Between each unprinted selvage edge (6) and the main print pattern (4), a transition border (7) is created, which border coincides with the side edges (5) of the main print pattern (4). On the two selvage edges, two additional print patterns (9'/9) are provided. However, the additional print patterns provided in Fig. 5A are not continuous with the main print pattern, i.e. there are discontinuities at the transition border (7) between the main print pattern (4) and the additional print pattern (9') provided on the selvage edge (6). If cutting errors were to occur is such a case, the discontinuities at the transition border (7) would become apparent in the final wall decoration, which is not desirable. In Fig. 5B, the additional print patterns are continuous with the main print pattern. The additional print pattern hereby corresponds with the print pattern provided at the side edge of a wall covering which is to be hung adjacent of the wall covering that is being produced. This way, when cutting errors were to occur, they can be masked and camouflaged so as to not appear on the side edges on the final wall covering.
It is supposed that the present invention is not restricted to any form of realization described previously and that some modifications can be added to the presented example of fabrication without reappraisal of the appended claims.

Claims

Automated method to produce wall coverings, such as wallpaper, which method comprises the following steps:
a. providing a substrate layer, which substrate layer has a top side and a back side and which substrate layer is essentially endless along a longitudinal dimension and which comprises a substrate layer width along a transverse dimension;

b. providing a coating on the top side of said substrate layer;

c. optionally providing said coating with an embossed pattern;

d. providing a main print pattern on top of the coating using a digital printing device, which print pattern has a main print pattern width which is smaller than the width of the substrate layer, thereby resulting in at least one unprinted selvage edge on the coated substrate layer; and

e. cutting of the substrate layer with printed coating using a cutting device, thereby reducing the width of the substrate layer to a desired width of the wall covering;
characterized in that simultaneously during or directly after providing the main print pattern to the coated substrate layer, the at least one unprinted selvage edge is at least partly provided with an additional print pattern using a digital printing device, which additional print pattern is substantially continuous with the main print pattern.
Automated method according to claim 1, whereby the at least one unprinted selvage edge comprises a width with a value corresponding to maximum 5% of the substrate layer width.
Automated method according to claim 1 or 2, whereby two opposing selvage edges are created when the main print pattern is provided on the coated substrate, whereby an additional print pattern is provided at least partly on both unprinted selvage edges using a digital printing device, whereby the additional print patterns are substantially continuous with the main print pattern.
Automated method according to any of the previous claims, whereby the additional print pattern is simultaneously provided during the provision of the main print pattern using the same digital printing device.
Automated method according to any of the previous claims, whereby the at least one selvage edge is provided with a marker, which marker can be detected by the cutting device and which marker provides a guiding means for the cutting device to cut the substrate layer along a transition border between the main print pattern and the at least one selvage edge.
Automated method according to claim 5, whereby the marker is printed on the at least one selvage edge, preferably using the same digital printing device which provides the additional print pattern to the at least one unprinted selvage edge.
Automated method according to claim 5 or 6, whereby the marker runs substantially parallel to the transition border between the main print pattern and the at least one unprinted selvage edge, whereby the marker is positioned from the transition border at a fixed position thereof when looking along the transverse dimension of the substrate layer.
Automated method according to any of the previous claims, whereby when the main print pattern and/or additional print pattern is provided on top of the coating, the substrate layer is provided at a relative speed, as compared to the digital printing device, of between about 15 and about 60 meters of substrate layer per minute along the longitudinal dimension.
Automated method according to any of the previous claims, whereby the coating is subjected to a corona treatment and/or a humidification treatment before and/or during the application of the main print pattern and/or additional print pattern.
Automated method according to any of the previous claims, whereby said digital printing device is a digital inkjet printing device.
Automated method according to any of the previous claims, whereby said digital printing device is a digital inkjet printing device comprising recirculating printheads.
Automated method according to any of the previous claims, whereby the main print pattern and/or additional print pattern is provided on the coating using a solvent-based ink.
Automated method according to any of the previous claims, whereby at least part of the main print pattern and/or additional print pattern is provided by ink comprising particles, with a particle size between about 0.1 and about 100 µm.
Automated method according to claim 13, whereby the particles are metallic particles, glitter particles or ceramic particles.
Automated method according to any of the previous claims, whereby the coating comprises a thermoplastic material, preferably polyvinyl chloride.
Automated method according to any of the previous claims, whereby the coating is applied to the substrate layer by providing between about 50 and about 400 g of a coating composition per m² substrate layer on the top side of the substrate layer.
Automated method according to any of the previous claims, whereby the substrate layer comprises paper, a non-woven, plastic, cellulose and/or cardboard.