KR102180848B1 - Digital binder printing - Google Patents

Abstract

The present disclosure relates to a method and equipment for forming a digital image on a surface by applying a powder layer comprising color pigments to the surfaces, bonding a portion of the powder and removing the unbonded powder from the surface.

Description

Digital binder printing {DIGITAL BINDER PRINTING}

The present disclosure relates generally to the field of digitally generated decorative surfaces, preferably building panels such as floor and wall panels. The present disclosure relates to methods and equipment for making such decorative surfaces.

Embodiments of the present invention are particularly suitable for use in floors that can be formed of floor panels comprising a core, a decorative layer and a transparent wear-resistant structured layer over the decorative layer. The following technical description, the problems of the known technology and the objects and features of the embodiments of the present invention are therefore, among other things, by way of non-limiting example, in this field of application and in particular with conventional laminated floors or elastic surface layers. We will be targeting floors similar to floors.

Embodiments of the present invention are digital to any surface but flat panels, such as building panels, generally wall panels, ceilings, furniture components and similar ones with large surfaces where generally advanced decorative patterns are desirable. It should be emphasized that it can be used to produce images. This method may be flat, curved, structured or similar on paper, foils, textiles, metal, wood veneer, cork, polymer material and similar surfaces. It can also be used to apply to prints on the surface of.

Most of all laminated floors are manufactured according to a manufacturing method commonly referred to as Direct Pressed Laminated (DPL). These laminated floors comprise a laminate of plastic, paper or similar material consisting of a core of 6 to 12 mm fiber board, a 0.2 mm thick upper decorative surface layer and a lower residual layer 0.1 to 0.2 mm thick.

The superficial layer of the laminated floor is characterized in that the decorative and wear properties are generally obtained by two separate layers of paper, one on top of the other. The decorative layer is usually printed paper and the wear layer is a transparent overlay paper, which overlay paper contains small aluminum oxide particles.

Printed decorative papers and overlays are immersed in melamine formaldehyde resins with large discontinuous or continuous lamination presses and laminated to the HDF core, the resin is cured under high heat and pressure and the papers are laminated to the core material. Embossed press plates or steal belts form the surface structure. Sometimes structured paper is used as the press matrix.

Laminated floors can also be manufactured by printing technology. One advantage is that the pressing operation can be avoided and printed papers are not required to provide a decorative wear-resistant surface.

Floor panels with direct-print laminated surfaces contain the same type of HDF core as DPL. The decoration is printed directly on the core. The manufacturing process is quite complex and is only cost effective in ultra-high volume productions. Hydroprinting inks are used to print the decoration by a multicolor printing press with rollers that print directly on a pre-sealed core.

Direct printing technology can be replaced by Digital Printing Technology, which is more variable and can be produced economically in small volumes. The difference between these two methods is mainly the printing step, in which the printing rollers are replaced by a digital non-contact printing process and the desired image is applied directly to the pre-finished core.

Digital printing is used in conventional additive manufacturing and can also be used to print on paper sheets that are laminated under heat and pressure. Printing can be done before or after immersion.

Paper and plastic foils are also used as surface layers at the bottom and these materials can also be digitally printed.

Recently, new "paperless" floor types have been developed with solid surfaces comprising a substantially homogeneous powder mixture of fibers, binders and wear resistant particles.

The powder mixture may include aluminum oxide particles, melamine formaldehyde resins and wood fibers. In most applications decorative particles such as color pigments are included in the mixture. In general, all these materials are applied in dry form as mixed powders on the HDF core and cured under heat and pressure to a solid layer of 0.1 to 1.0 mm. The powder is stabilized by moisture and UV lamps prior to pressing so that the powder forms an upper skin layer similar to a paper layer, which prevents the powder from flying away during pressing. Melamine formaldehyde resin and wood fibers can be replaced with thermoplastic particles.

Several advantages over the known technology and especially over conventional laminated floors can be obtained, such as increased abrasion and impact resistance, deep relief, increased manufacturing variability and lower costs.

The powder technique is very suitable for making decorative surface layers, which are replicas of rock and ceramics. However, it is even more difficult to create designs such as wooden decorations. However, recently digital powder printing has been developed and it is possible to create very advanced designs of any type by spraying ink onto the powder and to create a digital print on the powder prior to pressing. The surface structure is made in the same way as in the laminate floor by a structured press plate, steel belt or embossed matrix paper that is pressed against the powder.

Floors with wooden surfaces are manufactured in many different ways. Conventional solid wood floors have been developed with wood lamellas, processed floors with wood layers applied to a core made of HDF or plywood. Most of these floors are delivered at the factory as pre-finished floors with a wooden surface coated with several transparent layers. Recently, wood floors are also manufactured with digitally printed patterns that improve the design of the wood grain structure of wood species that do not have sufficient surface quality.

Digital printing is used on several floor types to create the decoration. However, the amounts are still very small, mainly because of the high cost of the ink and the high investment cost for industrial printers. There would be great advantages if ink costs could be reduced and more cost-effective equipment could be used on an industrial scale.

In the following description, the visible surface of the installed floor panel is called "front side", while the opposite side of the floor panel facing the bottom floor is called "back side". "Surface layer" means all layers that give the panel its decorative properties and its abrasion resistance.

"Print" means decoration or image. "Up" means facing the front side and "down" means facing the back side. "Vertically" means perpendicular to the surface and "horizontally" means parallel to the surface.

"Pigments" means a very fine powder of solid colorant particles.

"Pigment ink" means an ink comprising pigments suspended or diffused over a carrier fluid.

“Dye ink” refers to a substance having a color that is completely soluble in the carrier fluid and the resulting ink is a true solution that is completely soluble, such as sugar in water.

"Aqueous or water-based ink" means an ink in which water is used as the liquid substance of the ink. Water-based liquids carry pigments.

"Solvent based ink" generally means an ink containing three main parts: a fluid carrier, pigments and resins. Technically, solvent inks generally represent only the oil-based carrier portion of the ink that retains the other constituents in a liquid form and evaporates once applied to the surface via jetting.

“UV curable inks or coatings” means an ink or coating that is cured after application by exposure to the intense UV-light of a UV oven.

"Binder" means a substance that connects or contributes to connecting two particles or materials. The binder may be a liquid, powder based, thermoset or thermoplastic resin and the like.

The general technique used by the industry to provide digital prints is described below. The methods described below may be used separately or in combinations to create a digital application or digital print of a material in embodiments of the present disclosure.

High-resolution digital printers use non-impact printing processes. Printers have print heads that "fire" droplets of ink from the print heads to the substrate in a very precise manner.

Multipass printing, also called scanning printing, is a printing method in which the print head moves multiple times across a substrate to generate an image.

These printers are slow, but one small printhead can produce a larger image.

Industrial printers are generally based on a single pass printing method, which uses fixed printer heads and has a width corresponding to the width of the printed medium. The printed substrate moves under the heads. These printers have a high capacity and they are equipped with fixed print heads that are aligned side by side in the transport direction. Each print head prints one color. These printers can be customized for each application.

Fig. 1A shows a single pass printer 35 comprising five digital print heads 30a to 30e connected by ink pipes 32 to ink containers 31 filled with ink of different colors. The print heads are digital to a digital control unit 34 that controls the speed of the conveyor 21 displacing the panel under the print heads with high precision to ensure a high quality image including several colors and application of ink droplets. It is connected by data cables 33. 1B shows a wood grain print P provided on the panel surface 2. The surface of the floor panel is often embossed by a standard structure 17, which is the same as some of the basic decorations, as shown in Fig. 1C. Advanced floors use embossing 17 that matches the printed pattern P as shown in Fig. 1D.

A typical width of an industrial print head is about 6 cm and any lengths can be printed. Large areas of 1 to 2 m can be printed by digital printers containing several rows of print heads arranged side by side.

The number of dots per inch or DPI is used to define the printing quality and resolution of a digital printer. 300DPI is generally sufficient to print structures of wood grains of the same quality as currently used, for example in conventional laminated floors. Industrial printers are capable of printing patterns with a resolution of 300 to 600 DPI and even higher and speeds in excess of 60 m/min.

The print may be "full print". This means that the visible printed decoration is mainly produced by ink pixels applied to the surface. The color of the powder layer or the basic color of the paper has a limited effect on the generally visible pattern or decoration in this embodiment.

The print can also be a "part print". The color of the layer below the other is one of the colors seen in the final decoration. The area covered by the printed pixels and the amount of ink used can be reduced and cost savings can be obtained due to the increased printing capacity and reduced ink usage when compared to a full print design. However, partial prints are not as variable as full prints because it is more difficult to change the base colors than when full prints are used.

Printing can be based on the CMYK color principle. This is a four-color setup that includes cyan, magenta, yellow and black. Mixing them together will give you a relatively small color space/gamut. Spot colors can be added to increase a specific color or the overall gamut. The spot color can be any color. The colors are mixed and controlled by a combination of software and hardware (print engine/print heads).

A new technology was developed by Valinge Innovation AB, which made it possible to spray digital prints onto a powder layer. This new type of "Digital Injection Print" or DIP is obtained due to the fact that the printing takes place in a powder that hardens after it has been printed. The print is embedded in the cured layer and is not applied to the layer as when conventional printing methods are used. The print can be positioned in several dimensions horizontally and vertically at different depths. This can be used to create 3D effects and increase wear resistance when transparent fibers are used. No protective layers are required to interfere with the original design.

The DIP method can be used for all powder-based materials that can be cured after printing. However, the DIP method is particularly suitable for use when the powder comprises a mixture of wood fibers, small hard wear-resistant particles and melamine formaldehyde resin. The surface layer may also comprise a thermoplastic material, for example vinyl particles applied in powder form to the substrate. This makes it possible that the print can be sprayed with vinyl powder particles. Improved design and increased wear resistance can even be reached in these materials.

A suitable printer head must be used to obtain high printing quality and speed in powder-based layers and other layers as described above. The print head has several small nozzles that can fire droplets of inks in a controlled manner (Drop on Demand (DOD)), the size of each droplet is usually 1 depending on the ink type and head type. It can vary between to 100 picoliters. It is possible to design print heads that can fire larger droplets of more than 200 picoliters up to a maximum. Some printer heads can fire different droplet sizes and they have a gray tone ( gray scale), other heads can only fire one fixed droplet size.

Different techniques can be used to shoot droplets out of the nozzle.

Thermal printer head technology uses print cartridges with a series of small chambers each with a heater, all of which are constructed by photolithography. In order to eject droplets from each chamber, a pulse of current passes through a heating element which causes rapid vaporization of the ink in the chamber to form bubbles, causing a large pressure increase, causing ink droplets to the substrate through the nozzle. Promote. Most consumer inkjet printers from companies including Canon, Hewlett-Packard and Lexmark use thermal printer heads.

Most commercial and industrial inkjet printer heads and some consumer printers, such as those manufactured by Epson, use piezoelectric printer head technology. The piezoelectric material of the ink-filled chamber behind each nozzle is used instead of the heating element. When voltage is applied, the piezoelectric material changes shape, which generates a pressure pulse of the fluid that forces droplets of ink from the nozzle. Piezoelectric (also called Piezo) inkjets allow for a wider variety of inks than thermal inkjets because there is no demand for volatile components and no problems with kogation. Many ink types can be used such as dye inks, solvent based inks, latex inks or UV curable inks.

Pigment based inks are generally mixed together individually by using color pigments and several chemicals. Pigments are very fine powders of solid colorant particles that are suspended or diffused through a liquid carrier. Pigments used in digital ink have an average particle size of about 0.1 micron. The common size of the nozzles is about 20 microns, which means that the pigment particles have enough space to pass through the nozzle channels of the print head. The nozzles may still be clogged by the ink itself and pigments forming clusters of particles. High quality pigmented inks must keep the pigments suspended in the carrier fluid for a long period of time. This is particularly difficult at the low viscosities required for good functioning of the print heads. Pigments have a natural tendency to settle and settle in the liquid carrier. In high quality pigment inks, the settling of the pigment should not usually occur.

Water based inks containing color pigments are particularly suitable and can provide a high quality printing method in many different materials. Pigment inks generally have greater light resistance and greater fade resistance than dye based inks.

Pigments do not stick to the surface. They are similar to sand particles and can be easily removed from most dry surfaces. Water-based carrier fluids are therefore generally intended to provide adhesion of pigments to the surface, dot gain, pH level, droplet formation, corrosion of the print head, fade resistance, etc. to provide special ink and print properties. It is mixed with a small amount of several other additives such as binders.

The color pigments themselves are quite cost competitive, but the manufacture of pigment based inks and other inks for digital printers is very complex and expensive, which leads to a very high cost for the ink, which can usually be in the range of about 100 EUR/liter. A floor of about 100 m2 can be printed by 1 liter if a sufficiently high quality print is applied, which pays a cost of 1 EUR/m2. The costs for conventional printed floor surfaces in which printing cylinders are used are only 10% of the cost for digitally printed floor surfaces.

Digital inkjet printers use a non-contact method to apply ink to a surface. However, laser printing is based on a contact method in which a laser beam projects an image onto a charged rotating drum. Dry ink particles, commonly referred to as toners, are then electrostatically picked up by the charged areas of the drum. The ink contains fine particles of dry plastic powder mixed with carbon black or coloring agents. Thermosetting plastic material acts as a binder. The drum prints the image on the paper by direct contact and heat fusing the ink on the paper by bonding the plastic powder to the paper. Color laser printers use the CMYK principle with dry inks with colors that are typically cyan, magenta, yellow and black, which are mixed to provide a high quality colored image.

Laser technology by the impact method is not used for the printing of flat panel surfaces such as floor panel surfaces.

The above description of various known aspects is itself a feature of the present application, and is not an admission that any above description is prior art. Some of the techniques described above are known and used individually, but not in all manners and combinations as described above.

As a summary, it can be mentioned that digital printing is a highly variable method, but it cannot be fully utilized due to the high cost for the ink. The costs are mainly caused by the need to mill down the color pigments into well formed very small particles and diffuse the particles through the carrier fluid. It would be a great advantage if digital images were created by color pigments or ink without color materials.

The digital application technique is only used to obtain the benefits associated with the possibility to generate high-resolution images in a variable manner. However, other aspects of the technique, which are primarily concerned with the possibility of applying liquid substances with high precision by non-impact methods, have not been fully utilized or developed.

It is known that powder applied to a liquid substance can be used mainly to create a raised portion or image on a paper substrate and the liquid substance can be applied digitally by inkjet.

US 3,083,116 describes an elevated printing powder and an elevated printing process, which includes dusting freshly printed sheets of powdery resin, removing excess powder from them that did not stick to wet ink, and And applying heat to the retained powder to fuse it so that its particles flow together and adhere to the sheet. The powder may contain a phenolic resin.

US 3,446,184 describes a method for forming a viscous image copy. The toner powder is applied to the liquid forming portion and the portion of the powder is held by the liquid coating, forming a visible image. The loose powder is removed and the sheet passes through a heating unit where the retained powder is fused to form a permanent image.

US 4,312,268 describes a method in which a water based ink is digitally applied to a continuous web and a fusible single color powder material is applied to the web and to the ink. A portion of the powdered material is bonded to the liquid and the unbonded powdered material is removed from the web prior to heating of the web to fuse the powdered material to the web by drying the liquid and melting the powder. It is mentioned that the powdered material may have a particle size of 5 to 1000 microns and may have a melting point or fusion point of 50 to 300°C. The powdered material may be prepared by dissolving or diffusing the dyes or pigments of the resin or resin formation, respectively, followed by grinding, spray chilling, etc. to reduce the material to a fine powder. The powder material can provide abrasion resistance qualities for inks that may contain phenolic resins. The liquid material applied through the jets can be clear and colorless water.

US 6,387,457 describes a printing method using dry pigments. The binder material is applied uniformly or in a pattern to the surface of the substrate. The dry pigment is applied uniformly or in a pattern to the binder material. The dry pigment material includes flakes of non-metallic material having a particle size of less than about 100 microns. The flakes are aligned in a direction parallel to the surface of the substrate.

EP 0 403 264 A2 describes a transfer method of forming a multicolored image on a drum that transfers the image to paper. The fluid digital latent image is then developed at a development station where a colored powder is applied and fixed to the fluent latent image to produce a visible and permanent image. Several digital print heads may be used that print with dye-free fluids including mixtures of water with polyhydric alcohols and their ethylene glycol, glycerol, diethylene glycol and sub-sets of polyethylene glycol and water. Powder toner is applied across the surface of the paper and a voltage is applied during this phenomenon. The voltage is then reversed to remove the toner from the background areas. Fixation is achieved by conventional copier fusion methods.

EP 0 657 309 A1 describes a multi-color transfer method using a transfer paper carrying a pattern formed by powder and ink jet similar to the methods described above. The transfer method is for decorating ceramics.

WO 2011/107610 describes a method of creating a raised portion or relief in a floor panel in order to avoid the use of expensive press plates. This method is the same as known methods for creating an elevated print. This describes a method of manufacturing a floor board by printing a curable material to create a raised portion on the panel. The elevation can be printed directly on the panel or applied to a basic decorative pattern that is laminated. The curable material may include wear resistant particles. The curable material can be digitally printed on the panel by first printing the liquid in a predefined pattern and then providing an intermediate material that may contain powder. The curable material can be cured or varnished by UV irradiation.

Known methods are not suitable for producing high quality multicolor images of building panels, especially for floor panels where UV resistant pigments must be used and the image must be incorporated into a wear resistant surface. It is not known whether known principles can be used to create images on the floor surface being pressed, and in particular the principles allow powder, ink and application methods to form a high quality multi-colored surface of abrasion resistance, impact resistance and stain resistance in a cost effective manner. It is not known how it should be adapted for the printing of floor surfaces similar to Lamination and Wood Fiber Floors (WFF), which must be adapted to the specific resins, materials and pressing parameters required for it.

The object of at least certain embodiments of the present invention is a digitally printed building panel, preferably a floor, which can be produced in a more cost-effective manner without inks comprising colored substances, e.g. without complex color pigments to handle in a digital printing head. It is to provide a method and equipment for manufacturing a panel.

The above objects are exemplary, and the embodiments of the present invention can achieve different or additional embodiments.

A first aspect of the invention is a method of forming a digitally printed image with color pigments on the surface of a building panel, the method comprising:

-Dispersing dry color pigments on the surface,

-Bonding some of the dry color pigments to the surface, and

-Removing unbonded dry color pigments from the surface such that a digitally generated image is formed by the bonded color pigments.

According to the first principle of the first aspect, a pattern or image can be formed digitally by means of a digital coating head only applying a binder to the surface. Pigments are randomly dispersed by a second device over the pattern. The binder connects some pigments to form the same pattern as the binder while other unbonded pigments are removed.

This two-step process, in which pigments and liquid binder are applied separately, can provide comparable images with comparable quality, such as 300 DPI or higher, as conventional digital printing techniques.

According to the second principle of the first aspect, the pigments can be dispersed on the surface in a first step and then the digital coating head, which only applies a binder to the dispersed mixture, forms a pattern or image digitally. The digitally applied binder may comprise water, for example melting melamine formaldehyde particles which may be mixed with the pigments, preferably substantially homogeneously mixed with the pigments. The binder connects some pigments forming the same pattern as the binder while the unbonded pigments are removed.

According to the third principle of the first aspect, pigments can be dispersed on the surface in the first step and mixed with the pigments or by melting or curing a binder that can be incorporated into the surface underneath the pigments in a binder pattern or image. It is then formed digitally by a laser beam bonding some pigments. Digitally generated prints are obtained when unbonded pigments are removed.

Dry color pigments can be bonded to the binder on the surface of the building panel. The binder can be applied separately to the surface of the building panel.

Dry color pigments can be mixed with a binder.

The binder can be a powder, preferably a dry powder or a liquid substance.

The binder may include a thermosetting or thermoplastic resin. The surface of the building panel may comprise a thermosetting resin, preferably a melamine formaldehyde resin.

The surface can be a paper layer, a foil, a wood or wood based layer, or a powder layer. The powder layer may comprise a mixture comprising lignocellulosic or cellulose particles, a binder and optionally resistant particles such as aluminum oxide. The binder is preferably a thermosetting binder such as melamine formaldehyde resin.

The building panel may have a surface of a resin impregnated paper, a thermoplastic film or foil, a powder layer comprising wood cellulose or cellulose particles, and a binder. Building panels can be formed by applying heat and pressure.

The building panel can be a floor panel. The surface can be part of the floor panel.

The floor panel can include a mechanical locking system for vertical and horizontal locking.

Building panels can be wall panels or furniture components. The surface can be a wall panel or part of a furniture component.

Pigments can be removed by airflow.

Bonding some of the dry color pigments to the surface may include applying a liquid substance by a digital coating head. The liquid substance may be applied to the surface before the dry color pigments are applied to the surface, or may be applied to the surface after the dry color pigments are applied to the surface.

The liquid substance can be water based.

Liquid substances can be exposed to UV light.

The liquid material may be a water based UV curable polyurethane.

The liquid material may include a binder such as a thermosetting or thermoplastic binder.

The liquid substance can be applied by the piezo ink head.

Bonding some of the dry color pigments to the surface may include applying a laser beam to bond the dry color pigments to the surface.

The method may further include applying heat and pressure to the surface of the building panel. The surface of the building panel can be pressed after the digitally generated image is formed by the bonded color pigments. The final bonding of the dry color pigments to the surface of the building panel can occur by applying heat and pressure to the surface of the building panel. For example, a binder that bonds dry color pigments to the surface of a building panel can be cured by applying heat and pressure to the surface of the building panel. A binder that bonds dry color pigments to the surface of a building panel, such as a thermosetting resin such as melamine formaldehyde resin, may be cured simultaneously with a binder on the surface of the building panel, such as a thermosetting resin such as melamine formaldehyde resin. Curing can occur by applying heat and pressure to the surface of the building panel.

A second aspect of the present invention is to provide an equipment for forming a digital image on a building panel, which equipment includes a digital coating head, a powder dispersing unit and a powder removal system. The digital coating head is configured for applying a liquid substance to the surface of a building panel or to a powder layer comprising color pigments and/or a binder to the surface of the building panel. The powder dispersion unit is configured to apply a powder layer comprising color pigments to the surface of the building panel. The liquid material is configured to bond a portion of the powder to the surface of the building panel, and the powder removal unit is configured to remove the unbonded powder from the surface of the building panel. The digital image is formed by the color pigments joined thereby.

The powder may contain a thermosetting resin.

The liquid substance can be water based. Liquid substances can be exposed to UV light.

The surface of the building panel comprises a thermosetting resin, preferably a melamine formaldehyde resin.

The equipment may further comprise a pressing unit configured to apply heat and pressure to the surface of the building panel. The surface of the building panel can be pressed after the digital image is formed by the bonded color pigments.

The manufacturing method and equipment according to the embodiments of the present invention makes it possible to manufacture very advanced decorative patterns in a variable and very cost-effective manner, which allows the digital equipment to generate the pattern only by a binder that does not have any color pigments. Because it is only used for.

Embodiments and details of various aspects may be combined with embodiments and details of other aspects. Mixed color pigments of a liquid binder are not excluded and this can be used to apply smaller amounts of pigments, for example by means of a digital coating head that may require a specific color combination.

The invention will be described in more detail hereinafter with reference to exemplary embodiments and with reference to the accompanying exemplary drawings.

1A-1D illustrate known methods of manufacturing printed and embossed surfaces;
2A-2D illustrate a first aspect of the present invention;
3A-3D illustrate a second aspect of the present invention;
4A-4D illustrate a third aspect of the present invention;
5A-5H illustrate the digital application of pigments according to the first aspect of the invention;
6A-6C illustrate embodiments of the present invention.

2A to 2D illustrate an embodiment of the present invention based on the first principle in which a binder pattern BP or an image is digitally formed by a digital coating head that applies a binder 11 in the form of a liquid material. do. A digital print head or digital ink head, which is mainly used to apply liquid substances without any colorants, and is not intended to print an image with color, is hereinafter referred to as a "digital coating head". The pigments 12 are randomly dispersed on the binder pattern BP by the second device. The binder connects some pigments to form the same pattern as the binder while other unbonded pigments are removed.

This two-step process in which pigments and liquid binder are applied separately can provide an image with the same quality as conventional digital printing techniques. This method is particularly suitable in applications where a significant amount of pigments must be applied to the large flat panel 1 in order to form an advanced large image or decorative pattern. In contrast to known methods, digital coating heads are typically not used to apply any type of conventional ink with color pigments. This is a major advantage because expensive inks containing pigment diffusions are not handled by the digital coating head.

FIG. 2A shows that the binder pattern BP is formed on the surface 2 of the building panel 1 by the digital coating head 30 as shown in FIG. 2D. The surface 2 can be, for example, a paper layer, a stabilized powder layer, a foil or a basic color applied to a material, preferably a wood or plastic based core material. The binder 11 is water based in this preferred embodiment and contains primarily water, such as preferably at least 50% water. The binder 11 may further include additives such as release agents, surface tension agents, wetting agents, and viscosity increasing agents. The pigment layer 12 is applied by dispersing it as a dry powder on the wet binder pattern BP, for example as shown in FIG. 2B. The pigment layer may include, for example, melamine formaldehyde powder particles that melt when in contact with the water-based pattern BP. The dry pigments and melamine formaldehyde powder that do not come into contact with the water-based pattern (BP) are removed, for example, by airflow, and the remaining color pigments (12) form a print (P) as shown in Fig. 2c, which is essentially It is the same as the binder pattern BP.

The print P can be dried and stabilized by exposure to IR or UV lights which bond the color pigments to the surface 2, for example by heating the wet melamine formaldehyde resin and drying the wet melamine formaldehyde resin. A second bonded pattern can be coated on the surface 2 and a second layer of pigments and melamine formaldehyde powder can be applied to the surface and over and/or adjacent to the first print. Advanced decoration can be created by several colors.

The binder may contain wet melamine formaldehyde in this embodiment and may be applied in two steps, first applied from the digital coating head 30 as a liquid material such as water, and secondly the dispersing unit 27 as a powder. Is applied from The powder can be mixed with dry color pigments. This simplifies the function of the digital coating head having to apply water droplets only without any binders and color pigments, or with a limited amount of binders and color pigments.

The binder may be included as a powder in dry form and activated by a liquid material applied by the coating head as described above, or the binder may only be included in a liquid material applied by the digital coating head.

This method, in which liquid substances and powders are applied directly to the panel, is suitable for forming digital images on building panels. A method comprising the following steps is particularly suitable for forming an image on a floor surface having high impact resistance and abrasion resistance. A liquid material compatible with thermosetting resins is applied and the material must have certain chemical properties so that defects are not caused during curing of the thermosetting resins. This can be achieved, for example, with a liquid material comprising water and/or glycols. The material must be applied to the surface of the building panel to eliminate problems associated with the positioning of the panel's print. Thermosetting resins such as melamine formaldehyde resins are preferably included in the surface layer of the panel and/or in the powder applied to the panel, which can react with liquid substances and apply powder to the panel surface so that unbonded powder can be removed. Bonding. The powder preferably comprises UV stable color pigments. The advantages are that materials of this combination can be pressed and cured by high pressures in excess of 40 bar and heated to temperatures in excess of 160°C. The surface and digitally formed images can be cured to a hard wear-resistant surface without the so-called bleeding of the pigments during the pressing and heating steps, and the pigments can produce UV stable abrasion-resistant images similar to those of conventional laminated floors. It can be incorporated into a hardened surface so as to be.

Many different thermosetting and thermoplastic materials can be used as particles of dispersed powder or liquid substances or diffusions of a binder applied by a digital coating head. Most of these materials can be made in dry powder form or as liquid diffusions.

As an alternative to thermosetting materials such as melamine formaldehyde, or to thermoplastic materials such as PVC powder, for example, UV curable polyurethane can be used in powder form or as a diffuser.

A UV curable polyurethane material having a viscosity adapted to the digital coating head 30 may be used. Water-based polyurethane diffusions are preferred as the liquid material for the digital coating head because they do not cure until exposed to UV light. Polyurethane diffusions are fully reacted polyurethane/polyureas of small and discrete polymer particles and these particles can be manufactured to a size of about 0.01 to 5.0 microns and thus can be handled in a digital print head or other similar heads. They can have a solids content of 20 to 70%. Polyurethane diffusions can be mixed, for example, with acrylic emulsions and other emulsions to reduce cost.

The digital coating head 30, which is preferably a piezo head, preferably has a capacity to fire droplets having a droplet size of about 1 to 200 picoliters or more. The droplet size can be varied and this can be used to change the intensity of the color and create a gray tone by the same base color.

Water based binders such as soluble binders or water diffusion binders may also be used.

Other UV curable materials such as acrylates of epoxy, urethane, polyester, polyether, amine modified polyether acrylic acid and various types of acrylate oligomers can be used as a powder for or as diffusions.

2D shows one "binder printing" station of a binder printing equipment that can be used to create a digital print by the digital "binder print" method. The digital coating head 30, which may be a piezo head, applies a binder pattern BP. Several coating heads 30 may be placed side by side to cover the width of the surface to be printed. The binder pattern is digitally created in the same way as in conventional digital printing. The colors are separated and each coating unit 36 mainly applies the same material used to bond one particular color in each coating step. The digital coating head is connected by means of a transfer pipe 32 to a container 31 containing a binder or one component of the binder, preferably a water-based material, which may be primarily distilled or deionized water in this embodiment. do. The digital coating heads are connected to digital data cables 33 to a digital control unit 34 that controls the application of droplets, the speed of the conveyor 21, the function of the powder application unit, and all other equipment used to bond and remove pigments. Connected by

Water droplets serving as binder 11 should remain wet until they pass through dispersing station 27 applying a powder mixture comprising color pigments 12 and melamine formaldehyde powder 13 in this preferred embodiment. do. The melamine formaldehyde particles of the powder mixture in contact with the wet water-based binder pattern (BP) melt and the water/melamine formaldehyde solution is a binder that connects part of the pigment/melamine formaldehyde mixture to the surface (2) of the panel (1). Acts as When the powder mixture is displaced under a hot UV curing oven 23, which is preferably placed after the digital coating unit 36 in the transport direction, preferably with ultraviolet light, a practically immediate bonding or curing can take place within seconds. have.

In this embodiment, a powder removal system 28 based on airflow and vacuum removes pigments and melamine formaldehyde particles that are not bonded by the binder pattern BP, and a perfect color print P is provided. This manufacturing step can be repeated and different colors can be applied by means of a second dispersing unit 27 comprising different colors. The dried pigments and melamine formaldehyde particles removed can be passed through a sieve or filter and they can be recycled and reused again several times.

Melamine formaldehyde or other binders may also be included in the surface layer 2 as a dry layer when, for example, a melamine formaldehyde impregnated paper layer or a stabilized powder layer is used as the base surface. The water based bonding pattern will melt some of this melamine formaldehyde layer and only pigments can be applied and reused as a powder by the spraying unit 27. This method can also be used when the complete binder material is incorporated into the liquid material applied by the digital coating head.

The powder mixture may also comprise, in addition to pigments and melamine formaldehyde particles, preferably wood fibers comprising wear-resistant particles and fibers, such as small aluminum oxide particles, preferably bleached transparent or translucent fibers. have. Such a mixture can be used to create a solid print with binders and pigments one above the other and abrasion resistant particles above and below the pigments. Water based materials without any pigments can penetrate deeper into the powder mixture than pigments applied as a diffuser in conventional digital printing and a very wear resistant print can be obtained.

Several layers of prints can be placed one on top of the other, which further increases wear resistance and can be used to create 3D decorative effects.

An electrostatic device can be used to apply and/or remove unbonded powder particles. Vacuums and air streams that blow away and/or suck up particles can be combined by means of brushes. All dry and wet methods generally used to remove dust can be used separately or in various combinations to remove pigments and unbonded portions of the dispersed powder mixture. However, dry and non-impact methods are preferred.

Controlled complete or partial removal of unbonded pigments is essential for high quality prints with predefined decorative images. Advanced removal systems can also be used that only remove color pigments while an essential part of the transparent melamine formaldehyde powder particles can remain on the surface. This can be achieved, for example, by a two-step dispersion wherein the first layer is sprayed with water and dried by IR, hot air, UV and similar methods, only melamine form which is connected to the surface prior to application of the binder. It contains aldehyde particles. This separate melamine formaldehyde layer can replace pre-soaked paper in some applications, for example, and unsoaked paper with or without only basic color can be used as the surface layer 2.

The moisture content of the surface layer must be precisely controlled to facilitate the removal of unbonded powder particles. A moisture content of less than 6% is preferred. The surface layer 2 can be dried, for example by IR or UV lamps or hot air, prior to application of the pigments. The upper part or surface of the color pigments bonded to create a sealing or release layer that can prevent the color pigments from sticking to certain parts of the surface layer to which the binder is not applied by special chemicals such as water and release agents ( 2) can be applied to seal.

The print is made by transparent protective layers of a paper-based or powder-based overlay comprising a UV curable coating, which can be applied digitally, for example by aluminum oxide and melamine formaldehyde resins or rollers or by piezo coating heads, for example. Can be covered.

Figures 3a to 3d are shown digitally by a digital coating head in which pigments 12 are dispersed on the surface 2 in a first step and the pattern or image thereafter only applies a binder pattern BP to the dispersed mixture. It shows an embodiment of the invention based on the second principle to be formed. The digitally applied binder may for example comprise water to melt the melamine formaldehyde particles 13 mixed with the pigments 12 or applied under the pigments. The binder connects some pigments to form the same pattern as the binder pattern BP while other unbonded pigments are removed. FIG. 3a shows a substantially homogeneous mixture of melamine formaldehyde powder 13 and pigment 12 dispersed on the surface 2. 3B shows a digitally applied binder pattern BP applied to the mixture. 3C shows all unconjugated pigments and in this example also melamine formaldehyde particles 13 have been removed. 3D shows a binder printing station comprising a dispersion unit 27, a digital coating unit 36, a UV oven 23 and a powder removal system 28 based on airflow and vacuum.

The first and second principles can be combined. The binder pattern can be applied prior to and after the application of the pigment mixture, which can be used to create a solid print with a larger vertical size and higher abrasion resistance.

4A to 4C show that the pigments 12 are dispersed on the surface 2 in the first step and the binder pattern BP or the image can then be mixed with the pigments 12 or included in the surface 2. An embodiment of the invention is shown, based on the third principle, which is formed digitally by a laser beam 29 that melts or cures a binder. A digitally generated print (P) is obtained when the unbonded pigments are removed.

4D shows a binder printing station comprising a dispersion unit 27, a laser 29 and a powder removal system 28 based on airflow and vacuum. The laser can be replaced by heating lamps that can be used to create images containing fairly large areas of the same color as in some rock designs. Even a conventional laser system based on the impact method described above can be used to apply a digital print to a floor panel partially or completely, or can be used in combination with the binder printing methods described above.

All of the above-described principles may be partially or completely combined and the manufacturing line may include several digital binder printing stations according to the first, second or third principles.

5A-5H show the application of two different colors according to the first principle. In this embodiment a first binder 11a, which is essentially water, is applied by means of a digital piezo head to the surface 2, which may be a stabilized powder layer or paper as shown in Fig. 5A. A first powder layer comprising color pigments 12a and melamine formaldehyde particles 13a is applied to the surface 2 and the binder 11a. Melamine formaldehyde particles 13a in contact with the wet water droplets will melt. The first UV oven 23a dries wet melamine formaldehyde as shown in FIG. 5C and bonds the pigments to the surface, and the unbonded melamine formaldehyde and pigment particles are applied to the pigment image corresponding to the applied binder 11a. It is removed to obtain 12a). 5E to 5H show melamine formaldehyde particles 13b and a new binder 11b so that a two-color image is obtained by two types of color pigments 12a, 12b, as shown in FIG. 5H. It shows that the same application can be repeated with different pigment colors 12b mixed.

6A shows an embodiment in which digital binder printing equipment including a digital coating unit 36, a dispersion unit 27, a UV curing unit 23 and a powder removal vacuum system 28 is combined with a conventional inkjet printer 35 Shows. The binder printing method can use these combinations to produce most digital images, although some parts of the final print can be produced by an inkjet printer. This can significantly reduce the ink cost, since, for example, a cost effective binder printing method in which pigments are not handled by a digital coating head can apply e.g. 90% of the pigments required to create a fully printed ornament or pattern. to be.

6B shows a binder printing equipment in which pigments 12 and melamine formaldehyde powder 13 are applied by means of a dispersion unit 27, preferably comprising a relief roller 22 and a vibrating brush 42. The unconjugated pigments and melamine formaldehyde particles are removed by a powder removal system 28 that recycles the mixtures 12 and 13 to the dispersion unit 27. The pigment/melamine formaldehyde dust cloud may be created by air currents and only the pigments that come into contact with the wet binder 11 and melamine formaldehyde powder will bond to the surface 2.

Figure 6c shows that the method has a paper-based or powder-based surface (2), a core (3), a residual layer (4), comprising a strip (6), locking of adjacent edges of another panel for horizontal locking of adjacent edges. Bottom with a mechanical locking system with a locking element 8 on one edge cooperating with the groove 14 and a tongue 10 on one edge cooperating with a tongue groove 9 on the other edge for vertical locking of the panels It shows what is particularly suitable for applying a digital binder print to the panel 1. These floor panels generally have advanced wood or rock decorations that require a large amount of different colored pigments and decorations that must be accurately positioned relative to the panel edges with embossed structures and a mechanical locking system.

In all embodiments, the surface of the building panel may comprise a thermosetting resin, such as melamine formaldehyde resin. The building panel may preferably be formed by applying heat and pressure after the digitally generated image is formed by the bonded color pigments. In one embodiment, the binder mixed with the dry color pigments is a binder on the surface of a building panel, preferably cured simultaneously by applying heat and pressure.

All of the above-described methods may be partially or completely combined.

Yes

A powder mixture of 300 g/m2 comprising wood fibers, melamine formaldehyde particles, brown pigments and aluminum oxide particles such as corundum was applied to an 8 mm HDF core by means of dispersing equipment. The mixture was sprayed with deionized water and dried by UV oven to obtain a hard, stabilized powder based surface with a brown base color. A panel with a stabilized powder surface was placed on a conveyor and displaced under a digital piezo coating head that applied droplets of water to the stabilized surface and printed a transparent wood grain pattern on the surface. Melamine formaldehyde under the transparent pattern melted when the digital coated piezo head applied water droplets. Black pigments were dispersed over the entire surface and transparent pattern in the second step. The panels were then displaced by a conveyor under the UV oven. The melamine formaldehyde in the transparent pattern was dried again and the pigments on the transparent pattern were bonded to the surface. The panel was then displaced under a vacuum suction pipe from which all unbonded pigments and melamine formaldehyde particles were removed. A wood grain pattern with a brown base color and a structure of black wood grains were obtained. A protective layer comprising melamine formaldehyde and aluminum oxide particles was dispersed over the entire surface. The layer was sprayed with water and dried under a UV oven. The panel with the print and protective layer was then pressed for 20 seconds under a temperature of 170° C. at a pressure of 40 bar and the powder base surface with the grain structure and protective layer was cured to a hard wear-resistant surface with a high quality print.

Claims (27)

A method of forming a digitally printed image P with color pigments 12 on the surface 2 of a building panel 1,
-Dispersing dry color pigments 12 on the surface 2,
-Bonding some of the dry color pigments to the surface (2),
-Removing unbonded dry color pigments from the surface such that a digitally generated image P is formed by the bonded color pigments 12, and
-Applying heat and pressure to the surface (2) of the building panel (1),
How to form a digitally printed image.
The method of claim 1,
The dry color pigments 12 are bonded to the binder of the surface 2 of the building panel 1,
How to form a digitally printed image.
The method of claim 1,
The dry color pigments 12 are mixed with a binder,
How to form a digitally printed image.
The method according to claim 2 or 3,
The binder comprises a thermosetting resin,
How to form a digitally printed image.
The method according to claim 2 or 3,
The binder comprises a thermoplastic resin,
How to form a digitally printed image.
The method according to claim 2 or 3,
The binder is a powder,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
The surface (2) of the building panel (1) comprises a thermosetting resin,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
The surface 2 of the building panel 1 comprises a powder layer,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
The building panel 1 is a floor panel,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
The building panel 1 is a wall panel or a furniture component,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
The dry color pigments 12 are removed by airflow,
How to form a digitally printed image.
The method according to any one of claims 1 to 3,
Bonding the part of the dry color pigments to the surface (2) comprises applying a liquid substance (11) by a digital coating head (30),
How to form a digitally printed image.
The method of claim 12,
The liquid substance 11 is water based,
How to form a digitally printed image.
An equipment for providing a digital image (P) to a building panel (1), comprising a digital coating head (30), a powder dispersing unit (27) and a powder removal system (28),
The digital coating head 30 is configured to apply a liquid material 11 to a panel, and the powder dispersion unit 27 is configured to apply a powder layer including color pigments 12 to the panel, and the liquid material (11) is configured to bond a portion of the powder to the panel, the powder removal system (28) is configured to remove the unbonded powder from the panel (1),
The equipment further comprises a pressing unit configured to apply heat and pressure to the panel 1,
Equipment for providing images to building panels.

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