Abstract
A method is provided for manufacturing a printed paper layer. The method may involve providing the paper layer with a printed pattern. Providing the printed pattern may involve depositing water based inks using a digital inkjet printer. The water based inks may be pigment containing inks. The dry weight of the deposited pigment containing inks may be lower than 9 grams per square meter. The paper layer may include an inkjet receiver coating, such that the inks are deposited on the inkjet receiver coating. The paper layer may have a mean air resistance according to the Gurley method (Tappi T460) of below 30 seconds.
Claims
1. A method for manufacturing a printed paper layer, the method comprising: providing the paper layer with a printed pattern; wherein providing the printed pattern involves depositing water based inks using a digital inkjet printer; wherein the water based inks are pigment containing inks; wherein the dry weight of the deposited pigment containing inks is lower than 9 grams per square meter; wherein the paper layer at least includes an inkjet receiver coating, such that the inks are deposited on the inkjet receiver coating; and wherein the paper layer has a mean air resistance according to the Gurley method (Tappi T460) of below 30 seconds.
2. The method according to claim 1, wherein the inkjet receiver coating includes a binder or a polymer and a pigment.
3. The method according to claim 2, wherein the binder is selected from the group consisting of polyvinyl alcohol, starch, gelatin, cationic additives, precipitated calcium carbonate, polymer latex, vinylacetate/ethylene copolymer, and carboxymethylcellulose.
4. The method according to claim 2, wherein the pigment to binder ratio in the inkjet receiver coating is between 10:90 and 90:10.
5. The method according to claim 2, wherein the polymer is a hydrophilic polymer.
6. The method according to claim 2, wherein the pigment/polymer ratio in the inkjet receiver coating is at least 2.
7. The method according to claim 2, wherein the pigment of the inkjet receiver coating is silica.
8. The method according to claim 2, wherein the pigment of the inkjet receiver coating has a mean particle size of 0.01 to 40 micrometer.
9. The method according to claim 1, wherein the inkjet receiver coating has a weight of 0.5 to 10 grams per square meter.
10. The method according to claim 1, wherein the paper layer is a colored, pigmented and/or dyed base paper.
11. The method according to claim 1, wherein the paper layer is suitable for rotogravure.
12. The method according to claim 11, wherein the paper layer has a weight between 60 and 90 grams per square meter.
13. The method according to claim 1, wherein the paper layer comprises titanium oxide as a whitening agent.
14. The method according to claim 1, wherein the pigment containing inks include organic pigments.
15. The method according to claim 1, wherein the pigments of the pigment containing inks have an average particle size of less than 250 nanometer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) With the intention of better showing the characteristics according to the invention, in the following, as an example without limitative character, an embodiment is described, with reference to the accompanying drawings, wherein:
(2) FIG. 1 shows an embodiment of a paper layer that has been printed in accordance with the method of the invention;
(3) FIG. 2 illustrates some steps of a method in accordance with the invention;
(4) FIGS. 3 and 4 show a decorative panel obtainable by means of the method of FIG. 2, wherein FIG. 3 is a perspective view of said panel, and FIG. 4 is a cross section at a larger scale along the line Iv-Iv in FIG. 3;
(5) FIG. 5 on a larger scale shows a view on the area F5 indicated on FIG. 2 for a variant, wherein said sixth measure is put to practice.
DESCRIPTION OF NON-LIMITING EMBODIMENTS
(6) FIG. 1 illustrates a decorative layer 1 for incorporation in a decorative panel, obtainable by means of a method in accordance with the invention. The decorative layer 1 comprises a paper sheet 2 provided with thermosetting resin 3. The thermosetting resin 3 satisfies or fills the paper core 4. The paper layer has been provided with a digitally printed ink layer 5 on the basis of pigment containing inks, wherein for these inks use is made of water based pigment containing inks and an ink load lower than 9 grams per square meter area of the paper sheet 2. The printed ink layer 5 covers the entire surface of the paper sheet 2, or at least the majority thereof.
(7) FIG. 1 also clearly shows that at least at the side opposite the digitally printed ink layer the decorative layer 1 comprises a resin layer 6A outside the paper core 4. At the side that contains said digitally printed ink layer 5 a similar resin layer 6B is available. Possibly such resin layer 6B can be dispensed with, or the available resin layer 6B may be thinner, for example less than half the thickness of the resin layer 6A.
(8) From FIG. 1 it is clear that the digitally printed ink layer 5 covers the majority of the papers surface. Such print might for example represent a wood pattern, a stone pattern or a fantasy pattern.
(9) FIG. 2 illustrates a method for manufacturing decorative panels 7 of the type shown in FIGS. 3 and 4. The obtained decorative panels 7 at least comprise a substrate 8 and a top layer 9. The top layer comprises a paper layer 2 with a printed pattern or a digitally printed ink layer 5 representing a wood pattern, as is the case here. The method comprises at least the step S1 of providing said paper layer 2 with thermosetting resin 3. Hereto the paper layer 2 is taken from a roll 10 and transported to a first impregnation station 11 where said paper layer is immersed in a bath 12 of said resin 3, more particularly a mixture of water and resin 3. The paper layer 2 is then allowed to rest while in this case being transported upwards. The resting allows for the resin 3 to penetrate the paper core 4. The paper layer 2 then comes into a second impregnation station 13 where the paper layer 2 is, in this case, again immersed in a bath 14 of resin 3, more particularly a mixture of water and resin 3. A set of squeezing rollers 15 allows to dose the amount of resin 3 applied to the paper layer 2.
(10) In the example several doctor blades 16 are available for partially removing resin at the surface of the treated paper layer 2.
(11) In a second step S2 the resin provided paper layer 2 is dried and its residual humidity level is brought to below 10%. In the example hot air ovens 17 are used, but alternatively other heating equipment can be used, such as microwave drying equipment.
(12) FIG. 2 also illustrates that the method at least comprises the step S3 of providing said resin provided paper layer 2 with a printed pattern, in this case a digitally printed ink layer representing a wood pattern. Use is made of pigment containing inks, that are deposited on the paper layer 2 by means of a digital inkjet printer 18, in this case a single pass inkjet printer having print heads extending over the width of the paper layer 2. The dry weight of the total volume of pigment containing inks deposited on said paper layer 2 is lower than 9 grams per square meter. The inkjet printer is preferably a drop on demand printer that allows to dry the deposited droplets of pigmented ink, e.g. by means of infrared or near infrared light. Preferably a further drying station 19 is provided downstream of the printer 18. After printing and drying the inks the continuous paper layer 2 is cut to sheets 20 and stacked. The obtained sheets 20 resemble the decorative layer 1 illustrated in FIG. 1.
(13) According to a non illustrated variant the step of the printing S3 and/or the curing of the ink might be carried out after the resin provided paper layer 2 is already cut to sheets 20.
(14) According to still another non illustrated variant, the resin provided paper layer 2 might be rolled up again before cutting it to sheets and/or before printing.
(15) FIG. 2 further illustrates that in a subsequent step S4 the obtained sheets 20 or the decorative layer 1 is taken up in a stack to be pressed in a short daylight press 21 between upper and lower press plates 22-23. Said stack comprises from bottom to top a counter layer 24, a plate shaped substrate 8, the abovementioned decorative layer 1 and a protective layer 25, wherein the counter layer 24 and the protective layer 25 both comprise a paper layer 2 and resin 3. The stack is then pressed and the press treatment results in a mutual connection between the constituent layers 1-8-24-25, including the substrate 8, of the stack, as well as in a hardening or curing of the available resin 3. More particularly here a polycondensation reaction of the melamineformaldehyde resin 3 takes place, having water as a by-product.
(16) The upper press plate 22 is a structured press plates that provides a relief in the melamine surface of the panel 1 during the same press treatment of the step S4, by bringing the structured surface 26 of the upper press plate 22 into contact with the melamine of the protective layer 25.
(17) FIGS. 3 and 4 illustrate that the obtained decorative panel 7 can have the shape of a rectangular and oblong laminate floor panel, with a pair of long sides 27-28 and a pair of short sides 29-30 and having an HDF or MDF substrate 8. In this case the panel 7 is at long at least the long sides 27-28 with coupling means 31 allowing to lock the respective sides 27-28 together with the sides of a similar panel both in a direction R1 perpendicular to the plane of the coupled panels, as in a direction R2 perpendicular to the coupled sides and in the plane of the coupled panels. As illustrated in FIG. 4 such coupling means or coupling parts can basically have the shape of a tongue 32 and a groove 33, provided with additional cooperating locking means 34 allowing for said locking in the direction R2.
(18) Referring again to FIG. 1, it becomes clear that the printed paper layer 2 illustrated there has been provided with an inkjet receiver coating 35, thereby illustrating the sixth measure mentioned in the introduction.
(19) FIG. 5 shows that, in accordance with a preferred embodiment, the inkjet receiver coating 35, is obtained by coating a liquid substance 36 to the resin provided paper layer 2. In this case a device 37 comprising reverse metering rollers 38 is applied. Such device 37 may initially apply an excess of the liquid substance 36, which is squeezed off to the desired weight by means of the rollers 38, which also may provide for a smooth coating surface.
(20) From FIG. 2 it can be gleaned that the device 37 is present on the impregnation line, more particularly in this case after a drying operation, here performed by means of a hot air oven 17. Preferably, the resin provided paper layer possesses a residual humidity of below 10% by weight, or even lower than 6%, when the liquid substance 36, which is preferably a water based suspension of at least a polymer, is applied thereto. Preferably, and as is the case in FIG. 2, the treated paper layer 2 is then dried again, here again by means of a hot air oven 17, to reach once more a residual humidity level of below 10%, or of about 7%. The obtained treated paper comprises an inkjet receiver coating which is free from thermosetting resin.
(21) The present invention is in no way limited to the above described embodiments, but such methods, equipment and treated paper layers may be realized according to several variants without leaving the scope of the invention.
