Transfer media for transferring sublimation dyes onto three-dimensional surfaces

Abstract

The present invention relates to inkjet printable transfer media for transferring a sublimation dye and/or another functional active ingredient to a surface of an article by means of heat in a thermoformable process, to methods for preparing such inkjet printable transfer media and for providing at least a part of a surface of an article with sublimation dye and/or another functional active ingredient as well as the use of such inkjet printable transfer media in different technical fields.

Claims

1. An inkjet printable transfer medium for transferring a sublimation dye and/or another functional active ingredient to a surface of an article by means of heat in a thermoforming process, wherein the transfer medium comprises: a carrier substrate comprising a thermoplastic polymer; and a sublimation ink receiving coating comprising (a) at least one sublimation ink receiving layer formed over at least a part of one surface of the carrier substrate, the sublimation ink receiving layer comprising at least one of (i) a polyvinyl alcohol and (ii) an N-functional group-containing polymer, or (iii) a polyvinyl alcohol containing N-functional groups; and (b) a topcoat layer formed over at least a part of the sublimation ink receiving layer, the topcoat layer comprising (i) polymeric particles and at least one (ii) binder comprising a material selected from the group consisting of polyvinyl alcohol, modified cellulose, and combinations thereof.

2. The inkjet printable transfer medium according to claim 1, wherein the thermoplastic polymer is selected from the group consisting of poly(methyl methacrylates) (PMMA), thermoplastic polyurethanes (TPU), polyethersulfones (PES), polyethylene terephthalates (PET), amorphous polyethylene terephthalates (APET), polyethylene terephthalates modified by ethylene glycol (PETG), polybutylene terephthalates (PB), cast polypropylenes (cPP), polycarbonates (PC), polyvinylchlorides (PVC), copolymeric polyoxymethylenes (POM-C), acrylonitrile butadiene styrenes (ABS), polystyrenes (PS), polyamides (PA), polylactic acids (PLA), cellulose acetates, copolymers thereof, and mixtures thereof.

3. The inkjet printable transfer medium according to claim 1, wherein the carrier substrate has a thickness in the range of from 75 μm to 500 μm; and/or wherein the sublimation ink receiving layer (a) has a dry coating weight in the range of from 5 g/m.sup.2 to 40 g/m.sup.2.

4. The inkjet printable transfer medium according to claim 1, wherein the N-functional group-containing polymer (a-ii) or the polyvinyl alcohol containing N-functional groups (a-iii) comprises amino groups, amido groups or a combination thereof, and/or wherein the N-functional group-containing polymer (a-ii) is made from a monomer mixture comprising at least a monomer selected from the group consisting of N-vinyl caprolactam, N-vinyl piperidine, N-vinyl pyrrolidone, N-vinyl formamide, alkyl-2-oxazoline, acrylamide, N-vinylacetamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N,N-dimethylaminopropyl acrylamide, diacetone acrylamide, N-hydroxyethyl acrylamide, N-vinyl-imidazole, N-vinyl pyridine, amino-functional (meth)acrylates or combinations thereof, or the polyvinyl alcohol containing N-functional groups (a-iii) is made from a monomer mixture comprising at least a monomer selected from the group consisting of N-vinyl caprolactam, N-vinyl piperidine, N-vinyl pyrrolidone, N-vinyl formamide, acrylamide, N-vinylacetamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-isopropylacrylamide, N,N-dimethylaminopropyl acrylamide, diacetone acrylamide, N-hydroxyethyl acrylamide, N-vinyl-imidazole, N-vinyl pyridine, amino-functional (meth)acrylates, or combinations thereof.

5. The inkjet printable transfer medium according to claim 1, wherein the N-functional group-containing polymer (a-ii) comprises a graft polymer comprising N-functional group-containing side chains.

6. The inkjet printable transfer medium according to claim 1, wherein the mass ratio of the polyvinyl alcohol (a-i) to the N-functional group-containing polymer (a-ii) is from 1:4 to 20:1; or wherein the mass ratio of the polyvinyl alcohol to the N-functional group-containing compound of the polyvinyl alcohol containing N-functional groups (a-iii) is from 1:4 to 20:1.

7. The inkjet printable transfer medium according to claim 1, wherein the polymeric particles (b-i) comprise polyamide, (co)poly(meth)acrylate, (co)polystyrene, polysiloxane, polyurethane, copolymers thereof, or combinations thereof.

8. The inkjet printable transfer medium according to claim 1, wherein the polymeric particles (b-i) have a monomodal particle size distribution; and/or have a mean particle size in the range of from 10 μm to 100 μm imdetermined by confocal laser scanning microscopy.

9. The transfer medium according to claim 1, wherein the topcoat layer (b) comprises 10 to 60 wt.-% of the polymeric particles (i) and/or 40 to 90 wt.-% of the binder (ii), based on the dry weight of said layer.

10. The inkjet printable transfer medium according to claim 1, wherein the modified cellulose is selected from the group consisting of cellulose esters, cellulose ethers, and combinations thereof; and/or wherein the topcoat layer does not include cellulose fibers.

11. The inkjet printable transfer medium according to claim 1, wherein the polymeric particles (b-i) are present as a monolayer in the topcoat layer; or wherein the number of polymeric particles (b-i) in the monolayer of polymeric particles (b-i) having a mean particle size of up to 50 μm is in the range of from 50 polymeric particles per 1 mm.sup.2 of the transfer medium to 300 polymeric particles per 1 mm.sup.2 of the transfer medium; and/or wherein the at least one binder (b-ii) at least partially embeds the polymer particles (b-i) in such a way that the polymeric particles (b-i) protrude at least one third of their diameter on the surface of the topcoat layer.

12. A method for providing at least a part of a surface of an article with a sublimation dye and/or another functional active ingredient comprising: (a) applying at least one sublimation ink comprising a sublimation dye and/or at least another functional active ingredient to the sublimation ink receiving coating of the inkjet printable transfer medium according to claim 1; (b) positioning the transfer medium relative to the article such that the topcoat layer is facing the surface of the article to be provided with a sublimation dye and/or another functional active ingredient; (c) optionally thermoforming the transfer medium to conform with the surface of the article to be provided with the sublimation dye and/or another functional active ingredient; (d) applying heat to the transfer medium to transfer the sublimation dye(s) and/or the functional active ingredient(s) from the sublimation ink receiving coating to at least a part of the surface of the article.

13. The method according to claim 12, wherein the temperature applied in step(s) (c) and/or (d) is independently selected to be in the range of from 100° C. to 220° C.

14. The method according to claim 12, wherein the article is in the field of packaging, including packaging of food; electronics, including consumer electronics; machinery, device and equipment manufacturing; toolmaking; architecture and construction; decoration, including interior decoration; or advertising; or in the domestic or sanitary appliance, automotive, aerospace or textile and clothing industry.

15. A method for preparing an inkjet printable transfer medium according to claim 1, which comprises forming the sublimation ink receiving coating over at least a part of one surface of the carrier substrate by: (a) applying a composition comprising at least (i) a polyvinyl alcohol and (ii) an N-functional group-containing polymer or comprising (iii) a polyvinyl alcohol containing N-functional groups over at least a part of one surface of a carrier substrate to form a sublimation ink receiving layer; (b) optionally drying the coating formed in step (a); (c) applying a composition comprising (i) polymeric particles and at least one (ii) binder comprising a material selected from the group consisting of polyvinyl alcohol, modified cellulose, and combinations thereof over at least a part of the sublimation ink receiving layer to form a topcoat layer; and (d) drying the coating formed in step (c) or steps (a) and (c).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 (not to scale) shows a schematic cross-section of an exemplary embodiment of an inkjet printable transfer medium 10 according to the present invention. The transfer medium comprises a sublimation ink receiving coating 2 over a carrier substrate 1. The sublimation ink receiving coating comprises a sublimation ink receiving layer 3 and a topcoat layer 4 comprising a monolayer of protruding polymeric particles 5.

(2) FIG. 2 shows a scanning electron microscopy (SEM) image of a side view of a transfer medium according to the present invention.

EXAMPLES

Determining Particle Size Distribution by Confocal Laser Scanning Microscopy

(3) The confocal laser scanning microscopy was performed on a Color 3D Laser Microscope VK-9710 available from Keyence Corporation (Osaka) to determine the particle size. The CF IC EPI Plan Apo 50× objective lens available from Nikon is used. A sample of polymeric particles was applied onto a substrate having an adhesive surface (e.g., an adhesive tape) in order to fix the polymer particles and forming a monolayer of the polymer particles on the adhesive surface. The sample was evaluated using a wavelength of 408 nm (violet laser). The sample was investigated in focus planes in steps of 0.02 μm starting from below the bottom of the polymeric particles up to a plane above the polymeric particles. The settings shown in Table 3 were applied.

(4) TABLE-US-00003 TABLE 3 Confocal laser scanning microscopy settings Optical zoom 1x Modus Surface Profile Quality super fine Z-step increment 0.02 μm Brightness 1 834 ND-Filter intensity 100% Filter none

(5) 30 single particles were measured using the software VK-Analyse Modul Plus/Version 3.3.0.0 from Keyence Corporation (Osaka). The average particle size as well as the standard deviation of the particle size was determined.

(6) Alternatively, the particle of a finished coated film can be evaluated by redispersing the topcoat layer and separating the polymer particles for microscopic analysis.

Determining the Number of Polymeric Particles on Transfer Medium

(7) To analyse the number of polymeric particles on a transfer medium, the same device and the same settings were applied as described above for determination of the particle size distribution. A tilt correction function was performed. An area of 200×258 μm.sup.2 was observed in top view (90° angle) onto the surface of the transfer medium on which the sublimation ink receiving coating is applied. The polymeric particles of the topcoat layer were clearly visible on the surface of the transfer medium. The polymer particles were counted, whereby the polymer particles that lie on the edge of the image and were therefore only visible partially were counted in half. Fifteen different areas of a single transfer medium were measured according to this method. The counted number of the polymeric particles was divided by the total area of 15×200×258 μm.sup.2 and related to an area of 1 mm.sup.2.

Protrusion Measurement of Polymeric Particles in Topcoat Layer

(8) To analyse the protrusion of polymeric particles in the topcoat layer of a transfer medium, the same device and the same settings were applied as described above for determination of the particle size distribution. The menu item “Profit” of the analysis software VK-Analyse Modul Plus/Version 3.3.0.0 from Keyence Corporation (Osaka) was used. A virtual cut line was drawn through a single particle, wherein the cut line corresponded to the height of the binder plane on both sides of the single particle.

(9) The distance between the maximum of the protrusion caused by the polymer particle and the binder plane of the topcoat was measured. The distance was measured for fifteen different protrusions/polymer particles of the same transfer medium sample and the average protrusion was determined in p.m. This distance was related to the average particle size of the used polymeric particles to determine the percentage of protrusion from the surface of the topcoat layer.

Preparation of Inkjet Printable Transfer Medium

Example 1

(10) An inkjet printable transfer medium was prepared as follows. The components of the sublimation ink receiving layer formulation 1 as shown in Table 4 were are mixed to provide a dispersion.

(11) TABLE-US-00004 TABLE 4 Sublimation ink receiving layer formulation 1 Parts per Component weight Supplier Water 32.40 — Akucell AF0305 Carboxymethylcellulose 2.60 Nouryon Orgasol 3501 EXD Polyamide particles 2.00 Arkema NAT1 (20 μm) Gasil HP395 Synthetic amorphous 0.40 PQ silicium dioxide Corporation Cationic polyvinyl acetate dispersion in water 2.00 — (40 wt.-% solids) Tanacoat EP 6018 Polyurethane dispersion 2.00 Tanatex in water (37 wt.-% Chemicals solids) Polyvinyl alcohol grafted with N- 54.50 — vinylcaprolactam in water (20 wt.-% solids) Glycerol 0.40 — Defoaming agent 0.20 — Wetting agent 0.20 — Ethanol 3.30 —

(12) The dispersion was applied to an APET polymer film (type PET-A 140, A3 size, having 200 μm thickness) supplied by Folienwerk Wolfen GmbH (Germany) as a carrier substrate using a Mayer rod forming the sublimation ink receiving layer and then dried at 60 ° C. for 3 min in an oven receiving a sublimation ink receiving layer having a dry coating weight of 10 g/m.sup.2. A topcoat layer was prepared by mixing the components of the topcoat layer formulation 1 shown in Table 5 to provide a dispersion.

(13) TABLE-US-00005 TABLE 5 Topcoat layer formulation 1 Parts per Component weight Supplier Water 89.35 — Denka Poval Polyvinyl alcohol 4.00 Denka Company B 33 Ltd. (Japan) Akucell AF0305 Carboxymethylcel- 2.30 Nouryon lulose Dynoadd P 530 Polymethylmethac- 4.00 Dynea rylate particles Defoaming agent 0.20 — Wetting agent 0.15 —

(14) The topcoat layer dispersion was applied onto the sublimation ink receiving layer by using a Mayer rod and dried in an oven at 60° C. for 3 min to provide a topcoat layer having a dry coating weight of 2 g/m.sup.2.

Example 2

(15) The transfer medium was prepared in the same way as described in Example 1 except that the dry coating weight of the sublimation ink receiving layer was increased to 15 g/m.sup.2 and the dry coating weight of the topcoat layer was increased to 3 g/m.sup.2.

Example 3

(16) The transfer medium is prepared in the same way as described in Example 1 except that the sublimation ink receiving layer formulation 2 is used (Table 6).

(17) TABLE-US-00006 TABLE 6 Sublimation ink receiving layer formulation 2 Parts per Component weight Supplier Water 87.70 — Surfynol 440 Wetting agent 0.03 Evonik Triethanolamine 0.17 — Poval 26/88 Polyvinyl alcohol 7.40 Kuraray Poval 4/88 Polyvinyl alcohol 2.40 Kuraray Luvitec K-90 Polyvinylpyrrolidone 1.60 BASF Triethylene glycol 0.70 —

Example 4

(18) The transfer medium was prepared in the same way as described in Example 1 except that the topcoat formulation 2 is used (Table 7).

(19) TABLE-US-00007 TABLE 7 Topcoat layer formulation 2 Component Parts per weight Supplier Water 94.45 — Poval 20/98 Polyvinyl alcohol 5.00 Kuraray Syloid 72 Silica 0.20 Grace Defoaming agent 0.20 — Wetting agent 0.15 —

Printing Onto the Inkjet Printable Transfer Medium

(20) On the topcoat layer of the thus prepared transfer media of Examples 1 to 4, sublimation dyes were printed as color bars in the colors cyan, magenta, yellow, black, red, green and blue with an Epson SureColor T3200 ink jet printer available from Seiko Epson Corporation. An ink limit of 270% was set by profiling with Colorgate software.

(21) After printing, the applied sublimation dyes were dried at 25° C. for 30 sec at ambient conditions. A smear test was performed by smearing by finger with slight pressure over the printed color bars.

(22) The optical density of the cyan, magenta, yellow and black sublimation dyes were measured according to ISO-13655:2017-07 using an X-Rite eXact (Advanced, Standard Basic Plus, Mode D50/2°, M0) available from X-Rite.

(23) A high gloss surface of a white three-dimensional mobile phone cover made of polyester was provided with the sublimation dyes by thermoforming the transfer medium and transferring the sublimation dyes using Elvajet-Opal SB inks from Sun Chemical Corporation (Switzerland). The program shown in Table 8 was used for the thermoforming and sublimation dye transfer in a thermoforming device type SSA3-2 from Technical Image Applications Ltd. (UK).

(24) TABLE-US-00008 TABLE 8 Temperature program Soften time 1 7 sec Soften time 2 6 sec Soften time 3 5 sec SOV Open temperature 100° C. Vacuum time 25 sec Sublimation time 150 sec Sublimation temperature 150° C. Cooling temperature 90° C.

(25) The thermoforming and sublimation dye transfer process was finished after 3 min. After cooling down, the transfer medium was separated by hand from the printed three-dimensional high gloss mobile phone cover.

(26) Subsequently the optical density of the transferred sublimation dye on the high gloss surface of the three-dimensional mobile phone cover (made of polyester) were determined according to ISO-13655:2017-07 as described above. The evaluated properties of the transfer media of Examples 1 to 4 are summarized in Table 9. The particle size distribution, number of polymeric particles on the transfer medium and the protrusion of polymeric particles of Example 4 could not be evaluated as the used silica particles have a broad particle size distribution.

(27) TABLE-US-00009 TABLE 9 Properties of transfer media of Examples 1 to 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Carrier substrate APET [μm] 200 200 200 200 Sublimation ink receiving layer 1 1 2 1 formulation Dry coating weight of 10 15 10 10 sublimation ink receiving layer [g/m.sup.2] Topcoat layer formulation 1 1 1 2 Dry coating weight of topcoat 2 3 2 2 layer [g/m.sup.2] Particle size [μm] 30 30 30 — Particles per mm.sup.2 170 190 180 — Particle protrusion [μm] 18 25 20 — Particle protrusion [%] 60 83 67 — Drying instant instant instant instant Smear test ok ok ok ok Optical density Cyan 1.99 2.37 1.80 1.49 Optical density Magenta 1.95 2.02 1.85 1.84 Optical density Yellow 1.58 1.88 1.67 1.26 Optical density Black 1.85 2.06 1.72 1.68 Print artefacts none none none Inhomo- geneous color bars

(28) The optical density of the colors transferred by the transfer media of Examples 1 to 3 are superior to the optical density of the colors transferred by the transfer medium of comparative Example 4. In addition, the transferred color bars of Example 4 show an inhomogeneous structure, particularly the red, green and blue color bars.