UA124420C2 - Method for the manufacture of embossed and digitally printed substrates - Google Patents

Abstract

The present invention relates to a method for the manufacture of wood fiber based decorative substrates, comprising the steps of: a) mechanical embossing a substrate (2) so as to form an embossed surface; b) applying a primer on the embossed surface of the substrate; c) drying or curing the primer coated on the embossed surface so as to form a base layer (3); d) digitally printing a decor (4) onto the base layer (3) using a liquid ink; and e) drying or curing the liquid ink forming the digitally printed decor.

Description

The field of technology to which the invention belongs

The invention relates to a method of manufacturing embossed decorative substrates, especially panels and boards, in particular, based on wood fibers, for example, substrates in the form of medium-density fiberboard (MDF) or high-density fiberboard (HDF), on which a decor is formed by digital printing .

The invention further relates to substrates, for example panels and slabs, especially for floors suitable for laying, which are obtained in this way.

Technical level

Digital printing refers to methods of printing a digital image directly on a substrate. It usually refers to professional printing, in which small-run works from desktop publishing and other digital sources are printed using large-format printers and/or high-volume laser or inkjet printers. With the use of digital printing, the cost of one printed object is higher than with the use of traditional offset printing methods, but this higher cost is usually compensated by the cost savings achieved by eliminating all the intermediate technical steps required for the production of printing forms. When using digital printing, it is also possible to print one copy of the product at the customer's request, shorten the production cycle, and even modify the image during the production of each printed copy. The labor savings and increased capacity of digital presses means that when using digital printing, a point is reached where digital printing can compete with or exceed the technological capabilities of offset printing in the production of larger print runs of several thousand copies at low cost.

However, when using digital printing on substrates such as high-density fiberboard, the decor is usually still printed on a separate medium in the form of a paper or fiber web that is placed over the substrate. Indeed, since a base layer may be applied to ensure sufficient adhesion of applied printing inks, these base layers may adversely affect print quality. Indeed, the porous layer can absorb the printing ink, which can lead to insufficient coverage, while the use of

A non-porous base layer can cause drops to stick together and also adversely affect the quality of painting. However, using a separate print media makes the process more expensive and complicated.

Usually, the production of floors or similar products includes an embossing step, carried out after printing (for example, after digital printing) the decoration on wood-based panels and boards, for example, on chipboard, MDF or HDF. In this way, embossed reliefs are directly transferred to the top coating (varnish, liquid...) using engraved rollers or to the top layer (melamine, paper, foil.) using a short-cycle press. That is, the embossed reliefs are not transferred directly to the substrate, but rather to the top coating/top layer.

Therefore, known floors, for example standard laminates, contain embossed reliefs with a maximum depth limited by the thickness of said topcoat/top layer, which is about 30-300 µm thick.

Thus, there is a need for alternative processes that would provide the possibility of obtaining floors that contain surfaces with deeper embossing.

The purpose of the present invention is to provide a method of manufacturing substrates that contain a decor formed by digital printing, which has deep embossed reliefs / embossed images.

Also, the purpose of the present invention is to create a method of manufacturing such substrates, on which the possibility of reproducing images of good quality is ensured.

In addition, the purpose of the present invention is to create a method of manufacturing such substrates that have an improved natural appearance.

Disclosure of the invention

This invention relates to the method of manufacturing decorative substrates on a wood fiber basis, which includes the following steps: a) mechanical embossing of the substrate to form an embossed surface; p) applying a primer to the embossed surface of the substrate; c) drying or thermosetting of the primer on the pressed surface to form the base layer; a) digital printing of the decor on the base layer using liquid printing ink; and bo f) drying or thermosetting of liquid printing ink of digital printing decor.

Substrates can be, in particular, selected from the group consisting of panels and plates.

Wood-based boards, in particular, wood-fiber boards, are mainly used.

In one embodiment, the substrates are selected from the group consisting of HDF, MDF, cardboard, and wood-plastic composite (DPC). In particular, the substrate is HDF.

In the case of the production of panels for flooring, wood fiber boards with printed decor obtained according to the proposed method are cut to form a finished panel for flooring, the surface area of which is preferably less than 0.5 m? or even less than 0.3 m". Before applying the method according to the invention, the surface of the substrates can be filled with a layer of material that contains a filler to obtain a flat surface.

According to the method according to the invention, stage a) can be carried out using engraved embossing cylinders or pressing plates.

In one embodiment, the embossing step (a) is carried out using hot or cold embossing cylinders. In particular, hot embossing cylinders are cylinders that are heated to a temperature ranging from 120 "C to 170 "C, preferably up to 1506.

In particular, cold pressing cylinders are cylinders used at a temperature of

C to 3576.

Advantageously, with the help of both hot and cold embossing cylinders to form a relief on the substrate without reverse deformation of the substrate. 20 Usually embossing cylinders can be engraved embossing cylinders, with the help of which it is possible to transfer the relief of said cylinders to the substrate. Stamping cylinders can have a relief of the surface structure, the depth of which is up to 12 mm, preferably up to 1.5 mm.

When using embossing cylinders, it is preferable that the mechanical embossing stage (a) is carried out at a substrate transport speed of 5 m/min. up to 20 m/min., mostly - 8 m/min.

In one embodiment, step (a) is carried out using press plates, for example, in a short-cycle press.

The press with a short cycle is preferably heated to a temperature in the range from 30 "C to 300 "C, preferably in the range from 120 "C to 250 "C.

The heating period is preferably from 2 seconds to 10 minutes, preferably from 2 seconds to 30 seconds, which is sufficient.

According to the method according to the invention, the embossing step (a) is advantageously carried out directly on the substrate and not on any top coating/top layer present on the substrate. In this way, the embossed surface is advantageously directly applied to the substrate.

Thus, according to the method according to the invention, the embossing step (a) is carried out before the digital printing step.

In one embodiment, step (a) is performed on at least one side of the substrate.

In particular, the embossed surface is at least on one side of the substrate.

In one embodiment, the primer is selected from the group consisting of clear or colored UV varnish, clear or colored UV oil, water-based dyes, and mixtures thereof. UV primer consists mainly, in fact, of varnish that hardens under the influence of UV radiation, pigments, hardener, reactive thinners or radical generators, which are used as initiators of chain formation.

The water-based pigment primer preferably contains at least one pigment of a bright color, in particular, preferably at least one white pigment. The primer is mostly a white colored UV varnish.

In particular, the primer is a transparent UV varnish, known under the trade name OM VAZE SOAT (UV

BASIC COATING), which is industrially produced by AKlo Mobei; or the primer is a colored UV varnish, known under the trade name SHM VABE SOAT UUNITE (UV BASIC

WHITE COATING), which is industrially produced by AK?20o Mobei company.

In particular, the primer is a water-based dye known under the trade name AOSHA

RISMEMT5 5TAIM MOVOIS MNITE (AQUEOUS PIGMENT DYE, NORDIC, WHITE), which is industrially produced by AKlo Mobei company; or a clear UV oil known as OI VASE

SOAT (OIL-BASED COATING), which is industrially produced by O5to Roiukh.

The applied amount of primer used according to the method according to the invention can be from 5 g/m2 to 50 g/m2, preferably from 25 g/m2 to 30 g/m2.

Favorably, by means of priming, the possibility of a good transfer of the decor inside the embossed image, for example, holes in the embossed surface, is ensured.

In addition, with the help of priming, adhesion between the embossed surface and the digital printed decor is also achieved in a favorable way.

In one embodiment, in step (c), the substrate covered with UV primer is subjected to preliminary gelatinization by UV irradiation.

In one embodiment, the substrate covered with a water-based pigment primer is dried in a convection dryer by heating the coated substrate to a temperature in the range from 50 "C to 90 "C, preferably in the range from 60 "C to 80 "C.

In one embodiment, the substrate coated with a water-based pigment primer is dried in an infrared dryer.

At stage (4), the substrate covered with the base layer is subjected to digital printing to form the decor.

Usually, printed decor is a wood pattern. However, other designs are also possible, for example, stone designs, parquet imitations or fantastic designs. Since digital printing is very versatile, any design can be printed, even with a small number of copies, within a short period of time and without the need for an external provider, such as a printing company.

In step (4), the liquid printing ink may be a water-based printing ink or

Ugh printing ink. Water-based printing inks are cheaper than solvent-based printing inks. Thus, water-based printing inks are more preferable for said digital printing.

The mentioned digital printing technologies are mainly those that can apply drops of printing ink in the form of dots, for example, as is the case with Ohor-op-Oetapa (drop-on-demand) inkjet printing systems.

In a preferred embodiment, the substrate during printing has a speed that exceeds 10 m/min., and preferably exceeds 80 m/min.; or, in particular, reaches 150 m/min.

In another embodiment, the substrate lies still in place, and the print heads of the inkjet printer system are moved over the substrate.

At stage (e), the printing ink of the printed decoration is dried or heat-fixed. Water-based printing ink can be dried at room temperature

From the environment or (optionally) it can be accelerated using conventional means such as a heater, fan or infrared dryer. The period of time required for printing ink to dry depends on a number of factors, for example, on the composition of the printing ink, the water content in it, the size of the droplet and, of course, on the temperature of the surface, the temperature and humidity of the surrounding air, and the degree of air circulation in the space around the printed decoration

In particular, UV printing inks are heat-fixed by UV irradiation.

The amount of printing ink used for digital printing can be from 5 g/m2 to 15 g/m-, preferably from 6 g/m: to 8 g/m".

Digital printing is mainly direct digital printing, and its implementation does not require the use of a separate medium in the form of paper or a fibrous web, which is superimposed on the substrate.

According to the invention, the decor is performed in the form of digital printing on the base layer, and the mentioned base layer lies on the embossed surface of the substrate. In particular, the resulting decorative substrates contain an embossed surface formed directly on the substrate, and said embossed surface is located under the base layer and the decorative layer (digitally printed decoration).

In one embodiment, the method according to the invention additionally includes a step that consists in: 7) covering the digital printed decor with a top coating or a finishing layer.

The top coating is preferably selected from the group consisting of varnishes, oils and resins.

Among the oils, we should mention, for example, UV or oxidizing oils.

The topcoat is preferably based on an amino resin, such as melamine, which is provided as a resin or sheet. As an alternative, you can use translucent or transparent varnishes.

The top coating is preferably applied to the plate in a liquid state, for example, with the help of one or more rollers. Alternatively, the top coating is applied to the plate using melamine sheets.

The mentioned top coating can additionally contain solid particles, for example, aluminum oxide, which increase the wear resistance of the surface of the finished substrate. This top coating has a higher wear resistance than varnish. Such particles are preferably introduced into the still liquid top coating.

The final thickness of the top coating is usually from 30 μm to 300 μm, preferably from 50 μm to 220 μm.

According to one variant of the implementation, to increase the wear resistance of the upper smooth surface (the surface on which people walk), a top coating of polyurethane is applied according to the technology

KiIviregii NoiSoaiipofF, and apply UV varnish, in particular, with the help of a sponge shaft, in the deep area of embossing. According to this embodiment, the hot coating is not applied to the embossed areas so as not to lose the embossed structure.

The technology of KiIeibegiya NoiSoaiyyipde consists in applying the substance KI EEIIVEKIT ROK NS 717 to the surface. KI EIVEKIT ROK NS 717 is a solid at room temperature.

In one embodiment, the method according to the invention additionally includes a step consisting in: d) drying or thermosetting of the top coating.

In particular, the top coating made of UV material is heat-fixed by UV irradiation.

The conditions required to ensure thermal fixation of the top coating, especially the coating based on melamine sheets, include, in particular, ensuring the temperature range, duration of exposure and pressure. The appropriate temperature range, duration of action and pressure for thermosetting the top coating can be varied, as they are parameters dependent especially on the specifically used polymer and hardener. However, usually the temperature range from 100 "C to 300 "C, preferably from 120 "C to 250 "C, is suitable.

Heating for 2 seconds to 10 minutes, preferably 2 seconds to 30 seconds, is usually sufficient. Additional pressure from 20 kg/cm? up to 60 kg/sme is preferred.

In one embodiment, the method according to the invention additionally includes a step consisting in:

P) providing the back side of the substrate with balancing paper or a layer of varnish.

In particular, the varnish layer is selected from the group consisting of: colored UV varnish, transparent

UV varnish, colored UV oil, transparent UV oil, water-based dyes and their mixtures.

According to the variant of implementation according to the method according to the invention, step n) consists in providing

On the back side of the substrate, needle-punched polyester (PE) fiber felt with a woven polypropylene (PP) fiber backing. This stage is carried out to increase surface strength and water resistance.

Currently, when laying standard laminate and/or parquet, a foil is placed between the "ground" and the floor covering. According to this embodiment, the needle-punched PE felt with a woven backing is replaced by foil.

In one embodiment, the embossed surface contains embossed images that extend to a maximum depth through the thickness of the substrate, for example, up to 12 mm, in particular, when the substrate is xHDF.

Embossed images are preferably selected from the group consisting of holes, cracks, pores, and combinations thereof.

According to the invention, the decor is performed in the form of digital printing on an embossed surface covered with a base layer.

In one embodiment, the digital printed decor is performed in exact combination with embossed images. In particular, during the digital printing stage, the embossed surface is placed under the print heads in order to apply the digital printed decor in exact accordance with the positions of the embossed images.

The authors established that with the help of the method according to the invention, it is advantageously possible to lay floors with surfaces with deep embossing, and more specifically - with surfaces with deeper embossing than on known floors.

More specifically, the use of the method according to the invention advantageously provides the possibility of forming an embossed surface directly on the substrate, and not on the top coating or top layer, as is done, for example, according to a typical known method.

Thus, embossed images of a substrate with an embossed surface have a maximum depth limited by the thickness of the substrate and not limited by the thickness of the top coating. In particular, the use of the method according to the invention provides the possibility of obtaining a substrate with embossed images that have a maximum depth of up to 12 mm (equal to the thickness of HDF), preferably from 0.8 mm to 12 mm, more preferably from 1 mm to 12 mm.

The use of the method also advantageously provides the possibility of obtaining floors with good image quality that look more natural than existing products. In particular, 60 when using the method, the possibility of good transfer of the decor to or inside the embossed images of the embossed surface is ensured. A high degree of realistic imitation of wood pattern is achieved in a favorable way.

The present invention also relates to a panel or slab for flooring which is obtained according to the method disclosed above.

The present invention relates to a panel or slab for flooring, which contains: i) an embossed, wood-fibrous substrate; ii) the base layer applied to the embossed substrate; ii) digital printed decor applied to the base layer; and im) the top covering layer applied to the digital printed decor.

In the context of this document, the words "embossed, wood-fiber substrate" mean a wood-fiber substrate containing an embossed surface, in which said embossed surface contains at least one embossed image.

In particular, the embossed surface is located directly on the surface of the substrate and not on the topcoat/top layer.

In one embodiment, the substrate is pressed to the maximum depth through the thickness of the substrate. In particular, the substrate is pressed to a maximum depth of 12 mm.

The substrate with an embossed surface preferably contains at least one embossed image having a depth of between 1 mm and 12 mm, preferably 1 mm or 1.5 mm.

Preferably, according to this invention, the substrate, in the location of the embossed images, is subjected to embossing to a depth of at least 0.5 mm, preferably to a depth of 0.8 mm. In particular, the substrate at the location of the embossed images is subjected to embossing to a depth of 1 mm to 12 mm, preferably to a depth of 1 mm or 1.5 mm.

Brief description of the drawings

In Fig. 1 schematically presents a substrate made using a preferred embodiment of the method according to the invention.

The primer can be applied as a filler, both to cover and to fill the embossed images on the embossed surface, as shown in particular in Fig. 1. Indeed, in Fig. 1, the base layer 3 covers the entire embossed surface 5 and, in particular, filled embossed images E,

For example, holes, cracks, pores and their connections.

In Fig. 2 schematically presents a substrate made using another preferred embodiment of the method according to the invention. In this Fig. 2, the base layer C is preferably covered, but not filled, with the embossed images E of the embossed surface 5. The primer is preferably applied using a roller with a soft rubber coating (with a hardness of 25 Shore units, on the A scale).

According to the preferred embodiment of the method according to the invention, shown in fig. 1, the panel is made 1 as follows.

Substrate 2, made of high density fiberboard (HDF), was subjected to embossing, in particular using engraved cylinders or a short cycle press, to form an embossed surface on the substrate. The printed surface was covered with a reactive liquid, for example, transparent or colored UV varnish, transparent or colored Ufoil, water-based dyes and their mixtures, from which the base layer 3 was formed.

More specifically, the reactive liquid was applied in one application step to the substrate 2 using appropriate means, for example, using a roller.

The applied amount of primer used according to the method according to the invention can be from 5 g/m2 to 50 g/m2, preferably from 25 g/m2 to 30 g/m2. In one embodiment, the substrate coated with UV primer is subjected to preliminary thickening by UV irradiation. In one embodiment, the substrate coated with a water-based pigment primer is dried in a convection dryer by heating the coated substrate to a temperature in the range from 50 "C to 90 "C, preferably to a temperature in the range from 60 "C to 80 "C. In one embodiment, the substrate coated with a water-based pigment primer is dried in an infrared dryer.

The embossed surface of the substrate 2, covered in this way with the base layer 3, is then provided with the decor 4, using digital printing and water-based printing ink or UV printing ink, using, for example, a Yugor-opretap jet printer system (drop on demand) . Due to the special properties of the base layer C, increased adhesion of the printing ink to the substrate 2 is ensured, but at the same time, the layer prevents excessive absorption or, on the contrary, sticking together of the drops of the printing ink of the decor 4.

In one embodiment, after printing the decor 4 using a water-based printing ink, the panel 1 is introduced into a thermal chamber and heated to a temperature of 70 "C to 2507 for 2 seconds to 30 seconds to dry and/or heat-fix the droplets of the printing ink of the decor 4. In one embodiment, the UV printing inks are heat-set by UV radiation.

Later, the decor applied to the panel 1 is protected by applying a top coating 5, especially based on amino resin, in particular, melamine resin. Such a resin can be applied to the panel 1 in a liquid state, especially with the help of one or more rollers.

Alternatively, the top coating can be applied to the panel 1 in a solid state, especially in the form of one or more sheets. The dimensions of the top cover sheet are chosen according to the dimensions of the panel. As an example, a sheet of top coating has a length of 2620 mm, a width of 2070 mm and a weight of 1 m: 150 g.

When using resin, after drying, the top coating is subjected to a pressing operation under a pressure of about 60 kg/cm2 at a temperature from 100 "C to 300 "C for 10 seconds. If necessary, the water-based printing ink can also be heat-set during this step. After thermosetting, the base layer C has significant adhesive properties, however, it retains its elasticity and flexibility. Thus, the adhesion between different layers of panel 1 is strengthened, and the risk of delamination, especially under load, is reduced.

In particular, the top coating made of UV material is heat-fixed by UV irradiation.

The final thickness of the top coating is usually from 2 μm to 100 μm, preferably from 5 μm to 50 μm. In the case of manufacturing panels for flooring, the panels can have profiled edge regions before or after applying the method according to the invention.

The back side of the panel can be additionally protected by applying a suitable protective layer 6, for example, from balanced paper or from a suitable varnish.

Claims (13)

FORMULA OF THE INVENTION 1. The method of manufacturing decorative substrates on a wood fiber basis, which includes the following three stages: a) mechanical embossing of the substrate to form an embossed surface; p) applying a primer to the embossed surface of the substrate; c) drying or thermosetting of the primer applied to the embossed surface to form the base layer; a) applying decor by digital printing on the base layer using liquid printing ink; and f) drying or thermosetting of liquid printing ink of digital printed decor, while step a) is performed directly on the substrate without any top coating or top layer present on it. 2. The method according to claim 1, according to which the substrates are selected from the group consisting of panels and plates. C. The method according to claim 1, according to which the substrates are selected from the group consisting of HDF, MDF, cardboard and DPK. 4. The method according to claim 1, according to which stage a) is carried out using engraved embossing cylinders or pressing plates. 5. The method according to claim 1, according to which the primer is selected from the group consisting of transparent or colored UV varnish, transparent or colored UV oil, water-based dyes and their mixtures. b. The method according to claim 1, according to which the digital printing at stage 4) is carried out using an Ohor-op-betapa jet printer system (drop on demand). 7. The method according to claim 1, according to which stage a) is carried out using UV printing ink or water-based printing ink. 8. The method according to claim 1, which additionally includes the stage of Her), which consists in covering the digital printed decor with a top coating. 9. The method according to claim 8, according to which the top coating is selected from the group consisting of varnishes, oils and resins. 10. The method according to claim 8, which additionally includes step 4), which consists in: e) drying or heat-fixing the top coating. 11. The method according to claim 1, additionally includes stage P), which consists in providing the back side of the substrate with balancing paper or a layer of varnish. 12. The method according to claim 1, according to which the embossed surface contains embossed images that pass to the maximum depth through the thickness of the substrate. 13. The method according to claim 1, according to which digital printed decor is performed in exact combination with embossed images. Z SKK 4 III III III IEE ShK Ky E y