Decoration of animal skin by inkjet technology

Abstract

A method of decorating an animal skin, comprising the steps of: selecting a digital layout (501), the digital layout (501) comprising a digital profile (110) of the animal skin; a first printed element (551) and a second printed element (552); applying the animal skin on a support (300) of the inkjet printer; adjusting the digital layout (501) to match the digital profile (110) to the applied animal skin; decorating the applied animal skin by printing the adjusted layout with an inkjet printer; and wherein the step of adjusting comprises rotating (600) the first printing element (551) and the second printing element (552) at the same angle.

Description

Technical Field

[0001] The invention relates to the technical field of decorating animal skins by utilizing inkjet printing technology. Background Art

[0002] The manufacture of natural leather products is well known and can be divided into five stages in general. Preparation stage 1 usually occurs partly in slaughterhouses and partly in tanneries, while stages 2 to 4 occur in tanneries. In the first stage (preparation stage), the skin is removed (skinned) from the animal and pretreated for tanning in the second stage. Pretreatment may involve processes such as soaking, liming, dehairing, partitioning and pickling (adjusting pH to help tanning agent penetration). In the tanning stage, the protein of the raw hide or skin is converted into a stable material that will not rot. Chromium is most commonly used as a tanning agent, whereby the tanned product obtains a light blue color, therefore commonly referred to as "wet blue". In the third stage of crusting, the tanned leather is dried and softened. Crusting generally includes processes such as peeling (removing surface-fixed tannic acid), greasing (fixing fats, oils and waxes to leather fibers), dyeing, whitening, physical softening and buffing (abrading the leather surface to reduce grain defects). In the fourth stage, called finishing stage, the leather (also called hide and in irregular shape) is ready to be sold to leather product manufacturers. Therefore, leather product manufacturers receive hides in irregular shapes, which vary in size, thickness and shape each time, which makes the decoration and cutting of the hides into decorative flat leather parts for decorated leather products difficult to automate.

[0003] Leather is already considered a luxury product in its own right, but personalization and customization (e.g., by decoration) can further enhance this sense of luxury. Natural leather has been decorated in the past by screen printing. However, screen printing is labor intensive and requires a separate screen for each color. This is expensive and time consuming, especially when personalization or customization is desired.

[0004] Digital printing techniques for finishing leather have been studied, but many solutions for finishing leather are still of poor quality. Inkjet technology from textile printing using thermal transfer paper has been explored for leather printing. However, just like direct inkjet printing onto natural leather, it has been found that the process of inkjet printing a dye-based image onto a sheet of transfer paper and then transferring the image to tanned leather by heat results in unacceptable quality for many luxury leather products. Examples of such inkjet processes are disclosed in WO01 / 32434A (GILHAM) and US2016067984A (CHUNG). Aspects such as image quality, light fading of the transferred dye and scratch resistance require further improvement.

[0005] Recently, high quality decorated leather has been obtained by printing "into" tanned leather using pigmented ink. WO2013 / 135828A (CODUS) discloses a method of printing into tanned leather, comprising the steps of: a) applying an ink receptor directly to the leather surface; b) applying the ink directly to the receptor by inkjet; c) applying an additive to the ink; d) heating the surface of a substantially ink-impermeable barrier; and e) bringing the heated barrier into direct contact with the ink receptor, additive and ink on the leather surface to soften the additive, ink receptor and ink into the leather, allowing the ink to penetrate into the leather.

[0006] The decoration can be done after the leather product is manufactured, and the animal hide decorated by inkjet technology can be cut into flat leather parts, which are connected (e.g., sewn) together to form leather products, such as shoes or handbags. The shape of the leather product and the method of connection (e.g., sewing) determine the shape and size of the flat leather parts. Rectangular flat leather parts are sometimes called panels, but the flat leather parts can be any shape to construct leather products.

[0007] By inkjet printing on hides, possibilities for decorating leather products before stitching become possible. Due to the differences in shapes and sizes on said hides, several methods for applying leather in inkjet printing devices are studied, such as EP3450574A1 (AGFA NV) and EP3434488A1 (AGFA NV), but there is a need where the layout is printed correctly within the contours of the hide. There is a real need to avoid margins between the printed layout and the supplied hides, which are expensive products. Summary of the invention

[0008] In order to overcome the above described problems, a preferred embodiment of the present invention is implemented using a method for decoration on animal hides by inkjet technology according to claim 1 .

[0009] The decorating method may be part of a method for manufacturing an decorated leather article made from a flat leather portion or preferably a plurality of flat leather portions, which come from one or more animal hides. One of the flat leather portions may be cut from the decorated animal hide.

[0010] Adjusting the layout taking into account the supplied hides ready for decoration results in a more efficient and economical method of manufacturing high quality decorated natural leather products, allowing personalization and customization, with short lead times to the customer, as high lead times reduce the sense of luxury. Wasting of expensive hides due to misregistration of the print layout on the hide is overcome by this embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Several cut types of hides are shown.

[0012] Figure 2 , Figure 3 and Figure 4 A preferred embodiment of this embodiment is shown, with II digital layout (500); it has a digital outline (110) of a whole animal hide, and wherein said digital outline is shown but should not be printed as shown in I.II. A first printing element (551) and a second printing element (552) are arranged within said digital outline (110). In step II, the printing elements (551, 552) are rotated (600) in the adjusted digital layout (502) so that the digital outline matches the whole animal hide (107) applied on the support (300) of the inkjet printing device, which has a movable printing system (305) (as shown by two arrows), which decorates the supported whole animal hide (107) with the adjusted digital layout (502).

[0013] Figure 3 Also shown is the translation (601) of the first print element (551) and the second print element (552) in the adjusted digital layout (502) to match the digital outline to the applied overall hide (107).

[0014] Figure 4 Also shown is the scaling (602) of the first print element (551) and the second print element (552) in the digital layout (502) adjusted to match the digital outline to the entire hide (107) being applied. DETAILED DESCRIPTION

[0015] The present embodiment is a method for decorating animal skins, the method comprising the following steps:

[0016] - selecting a digital layout (501) comprising a digital outline of an animal hide (110); a first printed element (551) and a second printed element (552);

[0017] - applying the hide to a support (300) of an inkjet printer;

[0018] - adjusting the number layout so that the number outline (110) matches the applied hide;

[0019] - decorating the applied hide by printing the adjusted layout using an inkjet printer; and

[0020] The adjustment steps include:

[0021] - Rotating the first printing element (551) and the second printing element (552) at the same angle (600). The hide is preferably selected from the group consisting of belly (100, 101), buttocks (104), double buttocks (105), shoulders (102), double shoulders (103), sides (106), crusted leather and whole hide (107).

[0022] The rotation of two printed elements (551, 552) is an angular displacement about the same point.

[0023] Preferably, the step of adjusting further comprises the step of translating (601) the first printing element (551) and the second printing element (552) by the same distance and / or scaling (602) the first printing element (551) and the second printing element (552) by the same scaling factor (x%).

[0024] How to adjust the digital layout (501) is by digitizing the applied hide for determining the position; angle and / or size of the applied hide, and wherein the determined position; angle and / or size is used to adjust the digital layout (501).

[0025] The digital outline (110) may be determined by applying the hide to another support or to a support on which the hide is digitized. Optionally, the hide is graded into a first digital grade area and a second digital grade area before applying the hide to the support or to another support; and wherein, prior to the step of selection, the digital layout (501) is generated by adding the digital outline (110) and applying a first printing element (551) in the first digital grade area and a second printing element (552) in the second digital grade area.

[0026] The digitization of the hide is preferably performed by a vision system for photographing the applied hide, and wherein the vision system is a line camera.The vision system is preferably configured in a panoramic or by scanning vision system over the applied hide.

[0027] In a preferred embodiment, the steps of applying a base coating and a protective top coating by an inkjet printer are included according to the determined position, angle and size of the applied hide. The base coating and / or the protective top coating may comprise a polyurethane based polymer or copolymer, and preferably, the base coating and / or the protective top coating are preferably applied by one or more valve jet print heads. The position at which the protective top coating is applied by the inkjet printer is preferably calculated according to the determined position, angle and size of the applied hide.

[0028] The digital layout (501) and the adjusted digital layout (502) are preferably in a page description language (such as Adobe TM PDFTM ) and wherein the adjusted digital layout (502) is rendered by a raster image processor (RIP) into a ready-to-print file for printing on the applied hide. In a preferred embodiment, the first print element (551) is used to decorate a first flat leather portion of the decorated leather article, and the second print element (552) is preferably used to decorate a second flat leather portion of the decorated leather article. This embodiment and the preferred embodiment can be steps of a method for manufacturing a leather article having a minimum of the first flat leather portion and the second flat leather portion.

[0029] The inkjet printer is preferably a single-pass inkjet printer having an inkjet head with a nozzle row used in the decorating step, and wherein the hide is applied on a support (300) whereby the back of the hide is parallel to the nozzle row.

[0030] In a preferred embodiment, a plurality of adjusted layouts are generated, wherein for each adjusted layout a different angle is used within a selected range. The range is preferably -10 degrees to 10 degrees; more preferably -5 degrees to 5 degrees. The number of the plurality of adjusted layouts is greater than 3; preferably greater than 4. The plurality of adjusted layouts are each rendered by a raster image processor or other raster image processor, and the rendered adjusted layout that best matches the supplied hide is selected for printing on the supplied hide.

[0031] Animal hides

[0032] During the finishing stage at the tannery, the irregularly shaped hides are ready for sale to leather product manufacturers. Tanneries deliver their hides in several cut types:

[0033] - Whole hide leather or just whole hide (107): Whole hide comprises the entire skinned and tanned hide from an animal.

[0034] - Side leather cut or just side (106): It is actually half of the whole hide (107) in length along the middle part, around the back of the animal.

[0035] - Shoulder leather portion or just shoulder (102): The shoulder section of the whole hide (107) comes from the shoulder area of ​​the animal.

[0036] - Shoulder leather cut or just Shoulder (103): The shoulder section of the whole hide (107) comes from the shoulder area of ​​the animal. It mainly comes from the entire shoulder area of ​​the whole hide (107).

[0037] - Rump leather cut or just rump (104): The rump section of the leather hide comes from the hind leg portion of the whole hide (107).

[0038] - Double hip leather cut or just double hip (105): The double hip section of the whole hide (107) comes from the hind leg part of the whole hide (107). It runs around the hips and up towards the spine on both sides of the whole hide (107).

[0039] - Belly leather cuts or just belly (100, 101): These leather hide sections are long and narrow and come from the belly part of the whole hide (107).

[0040] Therefore, leather product manufacturers receive irregularly shaped hides that vary each time in size; thickness and shape (due to dependency on the original animal size and the methods used in the tannery).

[0041] In a preferred embodiment, the hide to be decorated by inkjet technology is preferably selected from the group consisting of the belly (100, 101), the buttocks, the double buttocks (105), the shoulders (102), the double shoulders (103), the sides (106) and the whole hide (107).

[0042] The hide is more preferably a crusted leather, which means a hide that has been tanned and crusted but not finished. In order to have an optimal image quality commensurate with the luxury aspect of the leather, a base coating is preferably applied to the crusted leather to make it less porous.

[0043] Manufacture of decorated hides

[0044] The image is inkjet printed using one or more pigmented inkjet inks. In contrast to most dyes, pigmented inkjet inks ensure good lightfastness, since leather products are often used in outdoor conditions. The one or more pigmented inkjet inks may be aqueous inkjet inks, but are preferably UV-curable pigmented inkjet inks, since UV curing quickly "freezes" the inkjet printed image. The resulting good image quality further contributes to the luxury aspect of the decorated leather product.

[0045] To enhance scratch resistance, a top coating can be applied to the image and the base coating. In a preferred embodiment of the manufacturing method, the crusted leather, the base coating, the image and the top coating are subjected to heat pressing. Such a method is known from WO 2013 / 135828 A (CODUS) to penetrate and fuse at least part of the interlayer "base coating / decorative inkjet image / top coating" into the leather.

[0046] It was found that by using an inkjet technology (preferably single pass inkjet technology) where the inkjet print head has a nozzle row parallel to the back of the hide, the image quality is much higher than when the nozzle row is not parallel to the back. Possibly, this enhancement is caused by internal structures in the hide. The back of the hide is a 'virtual' line along the back and spine of the original animal.

[0047] The support for carrying the hide in this or the preferred embodiment is preferably flat, such as a flat table, but may also be a conveyor belt or a vacuum belt, onto which the hide is applied.

[0048] Layout for decorative hides or flat leather parts

[0049] There is no real limit to the type of layout that is inkjet printed on the hide (preferably using one or more pigmented inkjet inks). The layout may include text, photographs, decorative patterns, ... The layout may consist of a single color, or it may include multiple colors, such as black, white, cyan, magenta, yellow, red, orange, violet, blue, green and brown. Thereby, the layout is rendered into a printable format for the printing press (such as TIFF format) using a raster image processor, wherein the rendered layout is then transferred to the inkjet printer for printing. Halftoning of the rendered layout may be performed by the raster image processor or by the inkjet printer.

[0050] The layout or adjusted layout in this embodiment is preferably determined in a page description language. The printed elements may be images or may also be determined in a page description language. An example of a page description language is Adobe TM PDF (Portable Document Format). Other page description languages ​​are postscript (PS) and encapsulated postscript (EPS).

[0051] In a preferred embodiment, the supplied hide is digitized so that the outline of the supplied hide is known.

[0052] In a preferred embodiment, one or more portions of an animal hide are decorated by inkjet technology, wherein the one or more portions are cut into flat leather portions for manufacturing leather products. The printed element in the layout then preferably has the same shape / size as the selected flat leather portion of the leather product, but it may include cutting lines to facilitate cutting of leather pieces from the decorated animal hide, and / or bleed areas to overcome unprinted portions in the decorated flat leather portion due to alignment errors in the leather cutting machine.

[0053] Manufacture of upholstered leather goods

[0054] The leather product comprises a plurality of flat leather parts connected (preferably sewn) together. However, the several flat leather parts of the product do not necessarily come from one hide. Depending on the leather product and the position / function of the flat leather parts in the leather product, the position on the hide is preferably determined. This embodiment and preferred embodiments may be steps of a method for manufacturing a decorative leather product.

[0055] The surface of the hide can be scanned for contours, holes, bite marks or other surface defects before decoration, the detected holes and defects can be considered as non-selectable areas for flat leather parts with a certain function for leather products. This is also called a digitization step or grading step on the hide. For example, MIRISYS TM The Phototrace Leather plugin is an example, whereby the contour of the hide is determined and also the detection of defects and quality areas is determined, and the MIRISYS TM CutNest, determines the position of the flat leather part of the leather product. The grading step is completed when the animal hide is applied to a certain support, and the area of ​​the animal hide is divided into one or more grade zones after the step. The grade zone is an area on the animal hide area with animal hide characteristics, which is determined by cutting; printing functions and / or the function of the flat leather part in the leather product (such as support function). In a preferred embodiment, a further step is included: grading the applied animal hide into a first grade zone and a second grade zone. The first printing element (551) can be arranged in the first grade zone, and the second printing element (552) can be arranged in the second grade zone. The arrangement may include a nesting method, and preferably a real shape nesting method.

[0056] After the hide has been decorated, it can be cut into flat leather portions. In a preferred embodiment, the hide is applied on a further support for cutting. The cutting can be performed manually, but is preferably done by using some kind of automation for cutting leather, such as for example in the Versalis from LECTRA. TM Implemented in cutting machines.

[0057] Preferred leather articles include footwear, furniture, upholstery, bags and luggage, gloves, belts, wallets, clothing, automotive leather (e.g., train, airplane, boat and car seats), interiors, books and stationery, packaging, equestrian articles, and the like.

[0058] Base coating

[0059] Because the low viscosity of inkjet inks causes them to quickly penetrate into the leather resulting in poor image quality, the base coating applied to the hide needs to provide a level of image quality commensurate with the luxurious aspect of the leather.

[0060] The base coating preferably comprises a polyurethane based polymer or copolymer as this has been found to improve the flexibility of the printed leather.The base coating preferably also comprises a polyamide polymer or copolymer as polyamides have been found to improve compatibility with crusty leather and to improve the strength of the base coating.

[0061] Suitable polyurethanes include: Urepal from CHEMIPAL SpA TMPU147 and PU181; Melio from STAHL TM Promul 61; Astacin from BASF TM Finish PS; Ecrothan from MICHELMAN TM 4075, 4078 and 4084; Incorez from INCOREZ TM CS8073 and CS065-195. The dry weight of the polyurethane in the base coating is preferably 1 to 6 g / m 2 within the range.

[0062] Suitable polyamides include PA emulsion types ED310 and 161148CX from MICHELMAN. The dry weight of the polyamide in the base coating is preferably less than 7 g / m 2 , more preferably less than 5g / m 2 .

[0063] Although polyurethane and / or polyamide are preferred as polymers for the base coating, other polymers may be preferably used in combination with polyurethane and / or polyamide. Such polymers preferably have an elongation at break of greater than 200%, more preferably 300%. The elongation at break is measured according to ISO 527-2, for example, using an MTS Exceed 1000 from MTS Sustems Corporation. TM Test equipment.

[0064] A suitable polymerized acrylate emulsion is Bioflex from LMF Biokimica TM KGA.

[0065] A crosslinking agent may be incorporated into the base coating to improve the strength of the base coating and adhesion to crusted leather. Preferred crosslinking agents include aldehyde-based crosslinking agents (such as formaldehyde, melamine formaldehyde derivatives, urea formaldehyde resins, glyoxal and glutaraldehyde), epoxides, oxazolines, carbodiimides and isocyanates, with isocyanates being particularly preferred. The dry weight of the crosslinking agent in the base coating is preferably less than 1.4 g / m 2 , more preferably less than 1.0 g / m 2 .

[0066] The base coating may be applied by spraying or by any known coating technique, such as knife coating, extrusion coating, slide hopper coating, and curtain coating.

[0067] Pigmented inkjet inks

[0068] The one or more pigmented inkjet inks that are inkjet printed on the base coating of the hide may be selected from aqueous pigmented inkjet inks, solvent-based pigmented inkjet inks and UV-curable pigmented inkjet inks. In a preferred embodiment, the one or more pigmented inkjet inks are UV-curable inkjet inks.

[0069] The one or more pigmented inkjet inks preferably contain organic color pigments, as they allow a high color gamut to be obtained on natural leather.Carbon black and titanium dioxide are inorganic pigments which can advantageously be used in the present invention to constitute black, respectively white, pigmented inkjet inks.

[0070] Color pigments can be selected from those disclosed in HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications. 3rd edition. Wiley-VCH, 2004. ISBN 3527305769. Suitable color pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548 (AGFA GRAPHICS).

[0071] In a preferred embodiment, the one or more pigmented inkjet inks form a CMYK(W) or CRYL(W) inkjet ink set.

[0072] The pigment particles in the inkjet ink should be small enough to allow the ink to flow freely through the inkjet printing device, especially at the nozzle where it is ejected. It is also desirable to use small particles for maximum color intensity and to slow down sedimentation.

[0073] The numerical average pigment particle size of the organic color pigments and the inorganic black pigment is preferably between 0.050 and 1 μm, more preferably between 0.070 and 0.300 μm, and most preferably between 0.080 and 0.200 μm. The determination of the numerical average particle diameter is best performed by photon correlation spectroscopy of a diluted sample of the pigmented inkjet ink using a 4 mW HeNe laser at a wavelength of 633 nm. A suitable particle size analyzer used is the Malvern Spectroscopy Spectrometer available from Goffin-Meyvis TMnano-S. The sample can be prepared, for example, by adding a drop of ink to a cuvette containing 1.5 mL of ethyl acetate and mixing until a homogenous sample is obtained. The measured particle size is the average of 3 consecutive measurements consisting of 6 runs of 20 seconds.

[0074] White pigments preferably have a numerical average pigment particle size greater than 180 nm in order to have a strong opacify ability. Suitable white pigments are given in Table 2 in

[0116] of WO 2008 / 074548 (AGFA GRAPHICS). White pigments are preferably pigments with a refractive index greater than 1.60. White pigments can be used individually or in combination. Preferably titanium dioxide is used as a pigment with a refractive index greater than 1.60. Suitable titanium dioxide pigments are those disclosed in

[0117] and

[0118] of WO 2008 / 074548 (AGFA GRAPHICS).

[0075] When a UV curable pigmented inkjet ink is used, a polymerizable compound and at least one photoinitiator are present in the inkjet ink.

[0076] Any polymerizable compound known in the art can be used. The polymerizable compound can be any monomer or oligomer found in Polymer Handbook Vol 1+2, 4th edition, edited by J. BRANDRUP et al., Wiley-Interscience, 1999 (Polymer Handbook Volume 1+2, the 4th edition, edited by J. BRANDRUP et al., Wiley-Interscience, 1999). The oligomer in the present invention is understood to contain 2 to 8 repeating monomer units. Preferred monomers and oligomers are those listed in

[0106] to

[0115] in EP 1911814 A (AGFA).

[0077] Preferably, monomers or oligomers capable of free radical polymerization are used as polymerizable compounds. Combinations of monomers, oligomers and / or prepolymers may also be used. Monomers, oligomers and / or prepolymers may have different functionalities, and mixtures of combinations of monomers, oligomers and / or prepolymers comprising mono, di, tri and higher functionality may be used. However, preferably, an amount of at least 60 to 100 wt % of monofunctional polymerizable compounds is used in UV-curable pigmented inkjet inks, wherein the wt % is based on the gross weight of the inkjet ink. The viscosity of the radiation-curable inkjet ink may be adjusted by varying the amounts of specific monomers and oligomers.

[0078] The UV curable inkjet ink comprises one or more photoinitiators, preferably one or more free radical photoinitiators.Free radical photoinitiators are chemical compounds that initiate the polymerization of monomers and oligomers by forming free radicals when exposed to actinic radiation.

[0079] Suitable photoinitiators are disclosed in CRIVELLO, JV, et al. VOLUME III: Photoinitiators for Free Radical Cationic. 2nd edition. Edited by BRADLEY, G.. London, UK: John Wiley and Sons Ltd, 1998. p. 287-294.

[0080] In a particularly preferred embodiment, the one or more photoinitiators include an acylphosphine oxide photoinitiator and a thioxanthone photoinitiator. Such a combination allows for rapid UV curing using UV LEDs emitting above 370 nm. UV LEDs are more economical than mercury lamps in operating inkjet printing.

[0081] To further increase the photosensitivity, the UV-curable inkjet ink may additionally contain a co-initiator. Suitable examples of co-initiators can be classified into three groups: (1) aliphatic tertiary amines, such as methyldiethanolamine and N-methylmorpholine; (2) aromatic amines, such as 2-(dimethylamino)ethylbenzoate; and (3) (meth)acrylated amines, such as dialkylaminoalkyl (meth)acrylates and N-morpholinoalkyl (meth)acrylates. Preferred co-initiators are aminobenzoates.

[0082] The preferred amount of photoinitiator and co-initiator is 0.1-30 wt% and most preferably 5-15 wt% based on the total weight of the UV curable inkjet ink.

[0083] One or more of the pigmented inkjet inks may contain additional additives such as surfactants, polymerization inhibitors and dispersants for the color pigments.

[0084] The preparation of pigmented UV-curable inkjet inks is well known to the skilled person. A preferred preparation method is disclosed in paragraphs

[0076] to

[0085] of WO 2011 / 069943 (AGFA).

[0085] Protective top coating

[0086] The protective top coating may have the same or similar composition as the base coating. Typically, the protective top coating is optimized somewhat depending on the application of the leather. For example, in contrast to leather shoes, flexibility does not play an important role for leather book covers. Therefore, the protective top coating for book covers may be optimized towards scratch resistance.

[0087] To enhance scratch resistance, a protective top coating may be applied over the image and base coating. The top coating preferably comprises a crosslinking agent and a polyurethane and / or polyamide based polymer or copolymer. The protective top coating is preferably applied where the image is inkjet printed, so that less protective top coating is used. The application of the protective top coating is then preferably done by inkjet printing technology.

[0088] The protective top coating preferably comprises a polyurethane based polymer or copolymer as this is beneficial for the flexibility of the printed leather. If the scratch resistance needs to be improved, it preferably comprises a polyamide polymer which has been found to have a high compatibility with the polyurethane adhesive.

[0089] Suitable polyurethanes include: Urepal from CHEMIPAL SpA TM PU147 and PU181; Melio from STAHL TM Promul 61; Astacin from BASF TM Finish PS; Ecrothan from MICHELMAN TM 4075, 4078 and 4084; Incorez from INCOREZ TM CS8073 and CS065-195. The dry weight of the polyurethane in the protective top coating is preferably between 1 and 6 g / m 2 within the range.

[0090] Suitable polyamides include PA emulsion types ED310 and 161148CX from MICHELMAN. The dry weight of the polyamide in the protective top coating is preferably less than 7 g / m 2 , more preferably less than 5g / m 2 .

[0091] Although polyurethane and / or polyamide are preferred as polymers for the protective top coating, other polymers may be preferably used in combination with polyurethane and / or polyamide. Such polymers preferably have an elongation at break of greater than 200% (more preferably 300%). The elongation at break is measured according to ISO 527-2, for example, using an MTS Exceed 1000 from MTS Systems Corporation. TM Test equipment.

[0092] A suitable polymerized acrylate emulsion is Bioflex from LMF Biokimica TM KGA.

[0093] A crosslinking agent may be incorporated into the protective top coating to improve scratch resistance. Preferred crosslinking agents include those mentioned above for the base coating. The dry weight of the crosslinking agent in the protective top coating is preferably less than 1.4 g / m 2 , more preferably less than 1.0 g / m 2 .

[0094] The protective top coating may be applied by spraying or using the same coating techniques mentioned above for the base coating.

[0095] If a matte top surface is desired for inkjet printed leather, a matting agent may be included. Any suitable matting may be used. Preferred matting agents include silica. A preferred commercially available example of a silica dispersion is Euderm® from LANXESS. TM SN2.

[0096] Inkjet printing device

[0097] The image is preferably applied by an inkjet printing device. An inkjet printing device, such as an inkjet printer, is a marking device using an inkjet print head or an inkjet print head assembly having one or more inkjet print heads, which sprays a liquid as droplets or vaporized liquid onto the hide to form an ink layer. The pattern marked on the hide by the spray of the inkjet printing device is preferably an image. The pattern may be in a non-color or color color.

[0098] A preferred embodiment of the inkjet printing device is that the inkjet printing device is an inkjet printer, and more preferably a wide format inkjet printer. A wide format inkjet printer is generally accepted as any inkjet printer having a printing width of more than 17 inches. Inkjet printers having a printing width of more than 100 inches are generally referred to as super wide printers or large format printers. Wide format printers are mostly used to print banners, posters, textiles and general signs, and in some cases may be more economical than short run methods such as screen printing.

[0099] The flatbed in the inkjet printing apparatus may be moved under the inkjet print head, or the stage may move the inkjet print head over the flatbed. These so-called flatbed inkjet printers are most commonly used for printing of flat substrates, ridged substrates and flexible substrate sheets. They may incorporate a drying system (315), such as an IR dryer or a UV dryer, to prevent the prints from sticking to each other as they are produced. An example of a wide format printer and more specifically a flatbed inkjet printer is disclosed in EP1881903B (AGFA GRAPHICS NV). The flatbed may be a vacuum flatbed (400). Flatbed inkjet printers are then referred to as vacuum flatbed inkjet printers.

[0100] Preferably, the inkjet printing device comprises: one or more inkjet print heads, which eject a UV-curable ink onto the marking substrate; and a UV source (=ultraviolet source), as a dryer source, to cure the ink after marking. The spreading of the UV-curable inkjet ink on the substrate can be controlled by a partial curing or "fix-cure" process, wherein the ink droplets are "fixed", i.e. immobile, wherein no further spreading occurs afterwards. For example, WO 2004 / 002746 (INCA) discloses an inkjet printing method for printing an area of ​​a substrate in multiple passes using a curable ink, the method comprising: depositing a first pass of ink on the area; partially curing the ink deposited in the first pass; depositing a second pass of ink on the area; and completely curing the ink on the area.

[0101] A preferred configuration of a UV source is a mercury vapor lamp. In a quartz glass tube containing, for example, charged mercury, energy is added, and the mercury vaporizes and ionizes. Due to vaporization and ionization, the high-energy free disorder of mercury atoms, ions, and free electrons causes many of the mercury atoms and ions to be in an excited state. When they fall back to their ground state, radiation is emitted. By controlling the pressure present in the lamp, the wavelength of the emitted radiation can be accurately controlled to a certain extent, the goal of course being to ensure that much of the emitted radiation falls in the ultraviolet portion of the spectrum and at a wavelength that will be effective for UV-curable ink curing. Another preferred UV source is a UV light emitting diode, also known as a UV-LED.

[0102] As long as part of the emitted light can be absorbed by the photoinitiator or photoinitiator system, any UV light source can be used as the radiation source, such as high-pressure or low-pressure mercury lamps, cold cathode tubes, black light lamps, UV LEDs, UV lasers and flash lamps. Among these, the preferred source is one that exhibits a relatively long wavelength UV contribution, which has a main wavelength of 300-400nm. In particular, a UV-A light source is preferred, resulting in more efficient internal curing due to the reduction of light scattered therewith. UV radiation is generally classified into UV-A, UV-B and UV-C, as follows: UV-A: 400nm to 320nm; UV-B: 320nm to 290nm; UV-C: 290nm to 100nm.

[0103] In a preferred embodiment, the inkjet printing device comprises one or more UV LEDs having a wavelength greater than 360 nm, preferably one or more UV LEDs having a wavelength greater than 380 nm, and most preferably a UV LED having a wavelength of about 395 nm.

[0104] Furthermore, it is possible to use two light sources of different wavelengths or illuminations to cure the image, either sequentially or simultaneously. For example, a first UV source may be selected to be rich in UV-C, particularly in the range of 260nm-200nm. Then, a second UV source may be rich in UV-A, such as a gallium-doped lamp, or a different lamp high in both UV-A and UV-B. It has been found that the use of two UV sources has advantages such as fast curing speed and high degree of curing.

[0105] To facilitate curing, inkjet printing devices typically include one or more oxygen depletion units. The oxygen depletion unit places a blanket of nitrogen or other relatively inert gas (e.g., CO2) with an adjustable position and adjustable inert gas concentration to reduce the oxygen concentration in the curing environment. Residual oxygen levels are typically kept as low as 200 ppm, but generally in the range of 200 ppm to 1200 ppm.

[0106] The inkjet printing device may comprise an IR source (= infrared source) to cure the ink by infrared radiation. The IR source is preferably a NIR source (= near infrared source), such as a NIR lamp, or a SWIR (= short wave infrared source), such as a SWIR lamp. The IR source may comprise a carbon infrared emitter with a very short response time.

[0107] The IR source or UV source in the preferred embodiment above produces a drying zone on the flatbed to immobilize the ejected ink on the substrate. Similar to the drying zone, the inkjet printing device also includes a printing zone on the flatbed, which defines the maximum printing size of the inkjet printing device.

[0108] The inkjet printing apparatus may include a corona discharge device to treat the substrate before the substrate passes through the inkjet print head of the inkjet printing apparatus because some substrates have a chemically inert and / or non-porous top surface resulting in low surface energy which may result in poor print quality.

[0109] The terms "partially dry", "pin dry" and "pin dry" refer to the degree of dryness, i.e., the percentage of functional groups converted, and can be determined, for example, by RT-FTIR (real-time Fourier transform infrared spectroscopy), which is a method well known to those skilled in the art of drying formulations. Partially dry (also called pin dry) is defined as a degree of cure in which at least 5% (preferably at least 10%) of the functional groups in the coating formulation are converted. Pin dry is defined as a degree of dryness in which the increase in the percentage of functional groups converted with increasing exposure (time and / or dose) to radiation is negligible. Pin dry corresponds to a conversion percentage that is within 10% (preferably within 5%) of the maximum conversion percentage defined by the horizontal asymptote in the RT-FTIR graph (conversion percentage versus curing energy or drying time).

[0110] The inkjet printing device may include a heat curing device for removing water and organic solvents in the inkjet printed image. The heat curing device may be composed of different units.

[0111] A preheating device may be included in the inkjet printing device for heating the substrate before jetting. The preheating device may be an infrared radiation source as described herein below, or may be a heat transfer device, such as a hot plate or a heating cartridge. A preferred heating cartridge is an induction heating cartridge.

[0112] The heat curing device may include a dryer. Suitable dryers include devices that circulate hot air, ovens, and devices that use air suction. However, in order to reduce energy consumption, it is preferred to use an infrared radiation source for heat curing.

[0113] Preferred infrared radiation sources include near infrared radiation sources (NIR: 750-1400 nm) and short wave infrared radiation sources (SWIR: 1400-3000 nm). Advantageously, glass lenses (which may be included in the curing device for focusing infrared light on the substrate) transmit in this infrared region, as opposed to medium wavelength infrared light (MWIR: 3000-8000 nm) or long wavelength infrared light (LWIR: 8000-15000 nm).

[0114] The most preferred infrared light source is a SWIR light source, since the absorption of water increases significantly at 1450 nm.

[0115] A commercial example of a SWIR light source is the Carbon Infrared Emitter CIR available from HERAEUSTM , which emits, for example, at a wavelength of about 2000 nm.

[0116] Another preferred thermal curing device is a NIR source that emits near infrared radiation. NIR radiation energy penetrates quickly into the depth of the inkjet ink layer and removes water and solvents from the entire layer thickness, while conventional infrared and hot air energy is mainly absorbed at the surface and slowly conducts into the ink layer, which generally results in slower removal of water and solvents.

[0117] Commercially available NIR emitters are available from ADPHOS TM get.

[0118] The heat curing device can preferably be arranged at least partially in combination with the inkjet print head of the inkjet printer, traveling therewith, so that the curing radiation is applied very shortly after jetting. This allows the aqueous UV free radical curable inkjet ink to be fixed when jetted on the substrate.

[0119] Corona discharge equipment

[0120] The corona discharge equipment consists of a high frequency power generator, a high voltage transformer, a stationary electrode and a processor ground roll. Standard utility electrical power is converted to higher frequency power which is then supplied to the processor station. The processor station applies this power to the surface of the material through a ceramic or metal electrode over an air gap.

[0121] In the present invention, the corona treatment can be applied to the hides and can be applied to the base coated hides.

[0122] Inkjet print head

[0123] The inkjet print head is a component for ejecting a liquid onto a substrate through a nozzle. The nozzle may be included in a nozzle plate attached to the inkjet print head. The inkjet print head preferably has a plurality of nozzles, which may be included in the nozzle plate. A group of liquid channels included in the inkjet print head corresponds to the nozzle of the inkjet print head, which means that the liquid in the group of liquid channels can leave the corresponding nozzle according to the ejection method. The liquid is preferably ink, more preferably UV-curable inkjet ink or water-based inkjet ink, such as water-based resin inkjet ink. The liquid ejected by the inkjet print head is also referred to as an ejectable liquid.

[0124] The manner in which an inkjet print head is incorporated into an inkjet printing device is well known to the skilled person.

[0125] The inkjet print head can be any type of inkjet print head, such as a valve jet print head, a piezoelectric inkjet print head, a thermal inkjet print head, a continuous inkjet print head type, an on-demand electrostatic drop-on-demand inkjet print head type or an on-demand acoustic drop-on-demand inkjet print head type or a page-wide inkjet print head array, also referred to as a page-wide inkjet array.

[0126] The inkjet print head comprises a set of main inlets to provide the inkjet print head with liquid from a set of external liquid supply units. Preferably, the inkjet print head comprises a set of main outlets to perform recirculation of the liquid through the inkjet print head. The recirculation can be done before the droplet forming components, but more preferably, the recirculation is done in the inkjet print head itself, a so-called through-flow inkjet print head. The continuous flow of liquid in the through-flow inkjet print head removes air bubbles and agglomerated particles from the liquid channel of the inkjet print head, thereby avoiding nozzle blockage, which prevents liquid injection. Continuous flow prevents sedimentation and ensures consistent injection temperature and injection viscosity. It also facilitates automatic recovery of blocked nozzles, which minimizes waste of liquid and receivers.

[0127] The number of main inlets in the set of main inlets is preferably 1 to 12 main inlets, more preferably 1 to 6 main inlets, and most preferably 1 to 4 main inlets. The set of liquid channels corresponding to the nozzles is supplemented via one or more main inlets in the set of main inlets.

[0128] The amount of main outlets in the set of main outlets in a through-flow inkjet print head is preferably 1 to 12 main outlets, more preferably 1 to 6 main outlets, and most preferably 1 to 4 main outlets.

[0129] In a preferred embodiment, before the supplementation of a group of liquid channels, a group of liquids is mixed to the jettable liquid that supplements the group of liquid channels. The mixing of the jettable liquid is preferably performed by a mixing component (also referred to as a mixer), which is preferably included in the inkjet print head, wherein the mixing component is attached to the group of main inlets and the group of liquid channels. The mixing component may include a stirring device in a liquid container, such as a manifold in an inkjet print head, wherein the group of liquids is mixed by a mixer. The mixing of the jettable liquid also means the dilution of the liquid to the jettable liquid. The late mixing of a group of liquids for jettable liquids has the following benefits: for the jettable liquid with limited dispersion stability, precipitation can be avoided.

[0130] The droplet forming component causes the liquid to leave the liquid channel through a nozzle corresponding to the liquid channel. The droplet forming component is included in the inkjet print head. The droplet forming component activates the liquid channel to move the liquid out of the inkjet print head through the nozzle corresponding to the liquid channel.

[0131] The amount of liquid channels in the group of liquid channels corresponding to the nozzles is preferably 1 to 12 liquid channels, more preferably 1 to 6 liquid channels, and most preferably 1 to 4 liquid channels.

[0132] The inkjet print head of the present invention is preferably suitable for ejecting liquids having an ejection viscosity of 8 mPa.s to 3000 mPa.s. The preferred inkjet print head is suitable for ejecting liquids having an ejection viscosity of 20 mPa.s to 200 mPa.s; and more preferably suitable for ejecting liquids having an ejection viscosity of 50 mPa.s to 150 mPa.s.

[0133] Valve Jet Print Head

[0134] The preferred inkjet printhead for use in the present invention is a so-called valve jet printhead. The preferred valve jet printhead has a nozzle diameter between 45 and 600 μm. A valve jet printhead comprising a plurality of microvalves allows a resolution of 15 to 150 dpi, which is preferred for having high productivity without compromising image quality. The valve jet printhead is also referred to as a coil pack of microvalves or a dispensing module of microvalves. The manner in which the valve jet printhead is incorporated into an inkjet printing device is well known to the skilled person. For example, US2012105522 (MATTHEWS RESOURCES INC) discloses a valve jet printer comprising a solenoid coil and a plunger rod having a handle susceptible to magnetism. A suitable commercial valve jet printhead is the chromoJET from Zimmer. TM 200, 400 and 800, Printos from VideoJet TM P16 and from Fritz Gyger TM The coil pack of the microvalve SMLD 300's. The nozzle plate of a valve jet printhead is usually called a faceplate and is preferably made of stainless steel.

[0135] The application of the base coat and / or protective top coat is preferably performed by one or more of valve jet print heads for having a uniform layer on the hide.

[0136] The droplet forming component of the valve jet printhead controls each microvalve in the valve jet printhead by electromagnetic actuation to close or open the microvalve so that the medium flows through the liquid channel. The valve jet printhead preferably has a maximum dispensing frequency of at most 3000 Hz.

[0137] In a preferred embodiment of a valve jet print head, the minimum drop size (also called minimum dispense volume) of a single drop is 1 nL (= nanoliter) to 500 μL (= microliter), in a more preferred embodiment the minimum drop size is 10 nL to 50 μL, in a most preferred embodiment the minimum drop size is 10 nL to 300 μL. Larger drop sizes can be achieved by using multiple single droplets.

[0138] In a preferred embodiment, the valve jet print head has a native printing resolution of 10DPI to 300DPI, in a more preferred embodiment, the valve jet print head has a native printing resolution of 20DPI to 200DPI, and in a most preferred embodiment, the valve jet print head has a native printing resolution of 50DPI to 200DPI.

[0139] In preferred embodiments for valve jet print heads, the jetting viscosity is from 8 to 3000 mPa.s, more preferably from 25 to 1000 mPa.s, and most preferably from 30 to 500 mPa.s.

[0140] In preferred embodiments for valve jet print heads, the jetting temperature is 10°C to 100°C, more preferably 20°C to 60°C, and most preferably 25°C to 50°C.

[0141] Piezoelectric inkjet print head

[0142] Another preferred inkjet print head for the present invention is a piezoelectric inkjet print head. A piezoelectric inkjet print head is based on the movement of a piezoelectric ceramic transducer included in the inkjet print head when a voltage is applied thereto. The application of voltage changes the shape of the piezoelectric ceramic transducer to create a gap in the liquid channel, which is then filled with liquid. When the voltage is removed again, the ceramic expands to its original shape, ejecting droplets of liquid from the liquid channel.

[0143] The droplet forming component of the piezoelectric inkjet print head controls a set of piezoelectric ceramic transducers to apply voltage to change the shape of the piezoelectric ceramic transducers. The droplet forming component can be a squeeze mode actuator, a bending mode actuator, a push mode actuator, a shear mode actuator or another type of piezoelectric actuator.

[0144] Suitable commercial piezoelectric inkjet print heads are from TOSHIBA TEC TM TOSHIBA TEC TM CK1 and CK1 L

[0145] (https: / / www.toshibatec.co.jp / en / products / industrial / inkjet / products / cf1 / ) and from XAAR TM XAAR TM 1002 (http: / / www.xaar.com / en / products / xaar-1002).

[0146] The fluid channels in a piezoelectric inkjet print head are also called pressure chambers.

[0147] Between the liquid channels of the piezoelectric inkjet print head and the main inlet, there is a manifold connection to store liquid to supply to the set of liquid channels.

[0148] The piezoelectric inkjet print head is preferably a through-flow piezoelectric inkjet print head. In a preferred embodiment, the recirculation of liquid in the through-flow piezoelectric inkjet print head flows between a set of liquid channels and a nozzle inlet, wherein the set of liquid channels corresponds to the nozzle.

[0149] In a preferred embodiment of the piezoelectric inkjet print head, the minimum drop size of a single ejected drop is 0.1 pL to 300 pL, in a more preferred embodiment, the minimum drop size is 1 pL to 30 pL, and in a most preferred embodiment, the minimum drop size is 1.5 pL to 15 pL. By using grayscale inkjet head technology, multiple single droplets can form larger drop sizes.

[0150] In a preferred embodiment, the piezoelectric inkjet print head has a drop rate of 3 meters per second to 15 meters per second, in a more preferred embodiment, the drop rate is 5 meters per second to 10 meters per second, and in a most preferred embodiment, the drop rate is 6 meters per second to 8 meters per second.

[0151] In a preferred embodiment, the piezoelectric inkjet print head has a native printing resolution of 25DPI to 2400DPI, in a more preferred embodiment, the piezoelectric inkjet print head has a native printing resolution of 50DPI to 2400DPI, and in the most preferred embodiment, the piezoelectric inkjet print head has a native printing resolution of 150DPI to 3600DPI.

[0152] In a preferred embodiment for a piezoelectric inkjet print head, the jetting viscosity is from 8 to 200 mPa.s, more preferably from 25 to 100 mPa.s, and most preferably from 30 to 70 mPa.s.

[0153] In preferred embodiments for piezoelectric inkjet print heads, the jetting temperature is from 10°C to 100°C, more preferably from 20°C to 60°C, and most preferably from 30°C to 50°C.

[0154] The nozzle spacing distance of the nozzle row in the piezoelectric inkjet print head is preferably 10 μm to 200 μm; more preferably 10 μm to 85 μm; and most preferably 10 μm to 45 μm.

Claims

1. A method for decorating animal hides, the method comprising the following steps: - selecting a digital layout (501), said digital layout (501) comprising a digital outline (110) of said hide; a first printed element (551) and a second printed element (552); - applying the hide to a support (300) of an inkjet printer; - adjusting the number layout (501) to match the number outline (110) to the applied hide; - decorating said applied hide by printing the adjusted layout using said inkjet printer; and The adjustment steps include: - Rotating (600) the first printing element (551) and the second printing element (552) by the same angle (Fig. 2).

2. The method according to claim 1, wherein: The step of adjusting further comprises the step of translating (601) said first printing element (551) and said second printing element (552) by the same distance (Fig. 3).

3. The method according to claim 1 or claim 2, wherein: The step of adjusting further comprises the step of scaling (602) said first printing element (551) and said second printing element (552) by the same scaling factor (x%) (Fig. 4).

4. A method according to any one of the preceding claims, wherein: The applied hide is digitized for determining the position; angle and / or size of the applied hide, and wherein the determined position; angle and / or size is used to adjust the digital layout (501).

5. A method according to any one of the preceding claims, wherein: The digital outline (110) is determined by applying the animal hide on another support, wherein the animal hide is digitized and graded into a first digital grade area and a second digital grade area before applying the animal hide on the support (300); and wherein, before the selection step, the digital layout (501) is generated by adding the digital outline (110) and applying the first printing element (551) in the first digital grade area and applying the second printing element (552) in the second digital grade area.

6. The method according to claim 4 or claim 5, wherein: The hide is digitized by a vision system for photographing the applied hide, and wherein the vision system is a line camera.

7. The method of claim 4, comprising the step of applying a base coating and a protective top coating by said inkjet printer according to the determined position, angle and size of said applied hide.

8. The method according to claim 7, wherein: The base coating comprises a polyurethane based polymer or copolymer.

9. The method of claim 8, comprising the step of applying a protective top coating by said inkjet printer according to the determined position, angle and size of said applied hide.

10. The method according to claim 9, wherein: The base coat and protective top coat are applied by one or more valve jet print heads.

11. A method according to any one of the preceding claims, wherein: The digital layout (501) and the adjusted digital layout (502) are defined in a page description language, and wherein the adjusted digital layout (502) is rendered by a raster image processor into a print-ready file for printing on the applied hide.

12. The method according to claim 9, wherein: The first printing element (551) is used to decorate a first flat leather portion of a decorated leather article, and the second printing element (552) is used to decorate a second flat leather portion of the decorated leather article.

13. A method according to any one of the preceding claims, wherein: The hide is crusty leather.

14. A method according to any one of the preceding claims, wherein: The hide is selected from the group consisting of belly (100, 101), buttocks (104), double buttocks (105), shoulders (102), double shoulders (103), sides (106) and whole hide (107).

15. A method according to any one of the preceding claims, wherein: The inkjet printer is a single-pass inkjet printer having an inkjet head with a nozzle row used in the decorating step, and wherein the hide is applied on the support (300) whereby the back of the hide is parallel to the nozzle row.

Images