THERMAL SUBLIMATION PAPER, METHOD FOR THE PRODUCTION THEREOF AND USE THEREOF

Abstract

The invention relates to a thermal sublimation paper which can be printed with inks containing a sublimatable dye, in particular ink-jet inks, in which paper a hydrophilic thermal transfer layer to be printed is formed on a porous base paper. Thermoplastic particles with an average particle size of between 0.3 and 5 μm and a melting point of between 35° C. and 190° C. are present in the thermal transfer layer. This thermal sublimation paper can be advantageously produced as follows: an aqueous coating slip is applied to a porous base paper having a Cobb value of between 55 and 150 g/m.sup.2, in particular between 70 and 150 g/m.sup.2, in a paper-making or coating machine, online or offline, said aqueous coating slip containing thermoplastic particles and constituents suitable for forming a hydrophilic thermal transfer layer, and a drying step is subsequently carried out in order to obtain the thermal sublimation paper. The thermal sublimation paper can be used advantageously to mint flat materials, in particular films and textiles.

Claims

1. A thermal sublimation paper for printing with inks containing a sublimable dye, wherein a hydrophilic thermal transfer layer for printing is formed on a porous base paper, characterized in that in the thermal transfer layer there are thermoplastic particles with a particle size of 0.3 to 5 μm and a melting point of 35° C. to 190° C. and also hydrophilic monomers, oligomers or polymers, wherein the thermal transfer layer contains 5 to 65 wt % of thermoplastic particles.

2. A thermal sublimation paper according to claim 1, characterized in that the thermoplastic particles have a melting point of 120° C. to 190° C.

3. A thermal sublimation paper according to claim 1, characterized in that the thermal transfer layer contains 10 to 45 wt %, of thermoplastic particles.

4. (canceled)

5. A thermal sublimation paper according to claim 1, characterized in that the thermoplastic particles are based on polyolefins, a copolymer of ethylene and propylene, polyacrylates, polymethacrylates, acrylonitrile-butadiene-styrene polymers, polylactates, polycarbonates, polyethylene terephthalate, polystyrene, polyvinyl chloride, polyether ketone, celluloid or polyamides.

6. A thermal sublimation paper according to claim 1, characterized in that the thermoplastic particles have hydrophilic groups on their surface, in the form of carboxylate, hydroxyl, sulfonate and/or amino groups.

7. A thermal sublimation paper according to claim 1, characterized in that the Cobb value of the base paper measured on the reverse side of the composite material is 45 to 165 g/m.sup.2 and the Cobb value of the thermal transfer layer measured in the composite material on the top side is 30 to 120 g/m.sup.2.

8. A thermal sublimation paper according to claim 1, characterized in that the base paper has a wire side and a felt side, and the thermal transfer layer is on the wire side of the base paper.

9. A thermal sublimation paper according to claim 1, characterized in that the thermal sublimation paper has a porosity of at most 200 ml/min, and/or at least 25 ml/min (measured according to ISO-5636-3).

10. A thermal sublimation paper according to claim 1, characterized in that the thermal transfer layer is made hydrophilic by incorporation of water-soluble monomers, oligomers or polymers, selected from polyvinyl alcohol, carboxyalkylcellulose, starch, starch degradation products, dextrins, modified starch, cellulose derivatives, polyhydric alcohols, pentahydric alcohols (pentitols) and also hexahydric alcohols (hexitols), sorbitol, alginates and/or gelatin.

11. A thermal sublimation paper according to claim 1, characterized in that the thermal transfer layer contains 0.3 to 60 wt % of a filler selected from kaolin, calcined kaolin, precipitated CaCO.sub.3 and/or silica.

12. A thermal sublimation paper according to claim 1, characterized in that it contains surface-active substances in amphoteric, cationic, anionic or nonionic form.

13. A thermal sublimation paper according to claim 1, characterized in that the layer thickness of the thermal transfer layer is 1.5 to 20 μm.

14. A thermal sublimation paper according to claim 1, characterized in that the layer thickness of the base paper is 45 to 165 μm.

15. A thermal sublimation paper according to claim 1, characterized in that the base paper contains inorganic constituents in the form of CaCO.sub.3, kaolin or talc.

16. A method for producing a thermal sublimation paper according to claim 1, characterized in that an aqueous coating slip which contains thermoplastic particles and hydrophilic monomers, oligomers or polymers for forming a hydrophilic thermal transfer layer is applied to a porous base paper with a Cobb value of 55 to 150 g/m.sup.2, on- or offline in a paper machine or coating machine, followed by drying to give the thermal sublimation paper.

17. A method according to claim 16, characterized in that between the thermal transfer layer and the base paper, in a separate operation or simultaneously on- or offline, one or more layers are formed which correspond to the thermal transfer layer but contains no thermoplastic particles.

18. A method according to claim 16, characterized in that between the thermal transfer layer and the base paper, in a separate operation or simultaneously on- or offline, one or more layers are formed which do not correspond to the composition of the thermal transfer layer.

19. A method according to claim 16, characterized in that between the thermal transfer layer and the base paper, in a separate operation or simultaneously on- or offline, an interlayer is formed which corresponds to the thermal transfer layer.

20. (canceled)

21. A method according to claim 16, characterized in that an unsized base paper is used which contains sizing agent in the form of resin size, alkenylsuccinic anhydride (ASA), alkyl ketene dimer (AKD) and/or a synthetic sizing agent based on styrene-acrylate (SA).

22. A method according to claim 16, characterized in that the coating slip for forming the thermal transfer layer is applied in the form of a curtain coating, as roll or nozzle application with roller doctor or doctor knife, with a film press, by means of a printing process, or with an engraved roll.

23. A method according to claim 16, characterized in that on the reverse side of the thermal sublimation paper, on- or offline, one or more further layers are formed as protective layer.

24. A method according to claim 23, characterized in that a reverse side coating is formed which contains binders and/or surface-active substances, and/or pigments.

25. (canceled)

26. (canceled)

27. (canceled)

Description

EXAMPLES

[0042] A thermal transfer layer was formed on each of two different untreated papers (base paper); in a comparative example, no thermoplastic particles were incorporated, whereas in the inventive example, a modified coating was applied which additionally contains an aqueous polyolefin dispersion (water content about 55 wt %). A coat weight of 7.5 to 8 g/m.sup.2 was applied in each case. The applied thermal transfer layer on the base paper was subsequently dried in a drying cabinet and thereafter conditioned for 24 h at 21° C. and 53+/−3% relative humidity. The resultant thermal sublimation paper specimens were subsequently subjected to performance evaluations. In these evaluations, the specimens were printed with the commercial inkjet ink J-next Subly (sold by J-Teck3 SRL) and also with the commercial inkjet ink Sawgrass ArTainium UV+ (sold by Sawgrass Europe), using a commercial inkjet printer (EPSON STYLUS PRO4450). The printer settings were selected here as follows: medium: photo quality inkjet paper, quality level: level 4, quality: superfine 1440×720 dpi, bidirectional: on, colour: colour/BW photo, colour matching: ICM, mode: driver ICM (standard). Transfer printing in the transfer press was performed for 40 s at 204° C.; the textile selected here was a cloth of polyester having a basis weight of 250 g/m.sup.2 and a wetting angle of 56-58°/2; on an uncoated protective paper with a basis weight ≦60 g/m.sup.2, the piece of textile, with the side for printing upward, and subsequently the thermal sublimation paper, with the printed thermal transfer layer downward, followed by a further uncoated protective paper with a basis weight <60 g/m.sup.2, were placed. The transfer press used was a Qubeat transfer press (Model No. HP 3802 1400 W).

TABLE-US-00001 TABLE I (Materials data) Comparative Inventive example 1 example 1 Base paper Basis weight [g/m.sup.2] 72 Cobb value* [g/m.sup.2] 114 Air permeability* [ml/min.] 1118 acc. to Bendtsen* Coating formula [% oven-dry] [% oven-dry] Dextrin 10.9 7.32 Carboxymethylcellulose 33.74 22.66 (CMC) Sorbitol 55.36 37.17 Hypod 2000** 0 32.85 Water content 79% 73% (Total formula) Drying temperature [° C.] 105° C. Drying time [min]   3 min Notes: *For the values marked with an asterisk in Table I and in Tables II to IV below, methods for determination and/or evaluation are identified in more detail below. **Polyethylene-polypropylene copolymer, melting point 89° C., average particle size about 1 μm (manufacturer: Dow).

TABLE-US-00002 TABLE II (Measurement values for formulas in Table I) Comparative Inventive example 1 example 1 Air permeability acc. to 510 100 Bendtsen* [ml/min.] Cobb value top side [g/m.sup.2] 72.5 100.4 Cobb value reverse side [g/m.sup.2] 86 103.2 Wetting angle* top side [°] 38 100 J-Teck test ink Ink drying value as contrast 0.0 6.0 black field [%] Adhesion* [rating] >4 1 Mottling* [rating] 5 2 Optical density* measured on the textile black 1.18 1.36 blue 1.12 1.31 yellow 1.24 1.30 Sawgrass test ink Ink drying value* as contrast 0.0 2.7 black field [%] Adhesion* [rating] >4 1-2 Mottling* [rating] 6 2-3 Optical density* measured on the textile black 1.04 1.19 blue 1.04 1.25 yellow 1.21 1.26

TABLE-US-00003 TABLE III (Materials) Comp. Inv. Comp. Inv. Ex. 2 Ex. 2 Ex. 3 Ex. 3 Base paper Basis weight [g/m.sup.2] 94 94 Cobb value [g/m.sup.2] 137 137 Air permeability 407 407 [ml/min.] acc. to Bendtsen Coating formula [% oven- [% oven- [% oven- [% oven- dry] dry] dry] dry] Dextrin 10.9 7.32 10.9 7.32 Carboxymethylcellulose 33.74 22.66 33.74 22.66 (CMC) Sorbitol 55.36 37.17 55.36 37.17 Hypod 2000** 0 32.85 0 32.85 Water content 79% 73% 79% 73% (Total formula) Drying temperature 70° C. 105° C. [° C.] Drying time [min]   5 min   3 min Note: **Polyethylene-polypropylene copolymer, melting point 89° C., average particle size about 1 μm (manufacturer: Dow).

TABLE-US-00004 TABLE IV (Measurement values for Table III) Cooler Cham Comp. Inv. Comp. Inv. Concepts TRANSJET Coldenhove Ex. 2 Ex. 2 Ex. 3 Ex. 3 DIGITALL ™ S10 BOOST Xtreme Air permeability* acc. to 46 67 26 17 20 3.8 177 Bendtsen [ml/min.] Cobb value top side 83 88 93.2 92 Sticks/not 35 42 [g/m.sup.2] measurable Cobb value reverse side 99 104 97.6 108 123 22 24 [g/m.sup.2] Wetting angle* top side 24 80 30 110 44 <20 28 [°] J-Teck test ink Ink drying value* as 2.9 4.8 1.8 7.6 7.6 0.0 3.9 contrast black field [%] Adhesion* [rating] >4 1 >4 1 3 >4 >4 Mottling* [rating] 6 1-2 6 1-2 2 1 1 Optical density* measured on the textile black 1.32 1.36 1.30 1.36 1.26 1.36 1.33 blue 1.24 1.34 1.24 1.33 1.13 1.33 1.24 yellow 1.28 1.31 1.29 1.31 1.21 1.35 1.3 Sawgrass test ink Ink drying value* as 2.5 4.0 3.0 5.4 17.7 0.0 6.6 contrast black field [%] Adhesion* [rating] >4 1 >4 1 2 4 >4 Mottling* [rating] 6 2 6 2 1 1 1-2 Optical density* measured on the textile black 1.17 1.19 1.18 1.23 1.22 1.23 1.24 blue 1.20 1.24 1.22 1.28 1.25 1.25 1.27 yellow 1.21 1.27 1.23 1.27 1.19 1.22 1.21

[0043] Measurement and Evaluation Methods whose Results are Identified in Tables I to IV:

[0044] 1. The Cobb value is determined according to ISO-535, the Bendtsen air permeability (or porosity) according to ISO-5636-3, and the basis weight according to ISO-536.

[0045] 2. Ink Drying Value

[0046] The drying rate of the ink on the thermal sublimation paper is reported as a contrast value in percent in the black field. For this purpose, immediately after the end of printing, the printed thermal sublimation sheet was placed with the unprinted side downward onto a cardboard support; 15 s after the end of printing, a counter-strip (Phoenix Imperial II/II, APCO lightfast glossy white, wood-free 150 g/m.sup.2, from Scheufelen) was placed onto the printed area and was immediately rolled down using a metal roller weighing 2.3 kg, without pressure. The counter-strip was then removed and, on the side facing the original inkjet print, the contrast value was determined by measuring the reflection with a commercial measuring instrument (Elrepho SE 070 instrument from Lorentzen & Wettre) at a position (a) of the counter-strip, originally facing the black field, and also at a position (b) of the centre-strip facing an originally unprinted area, as follows:

[00001]$\mathrm{Contrast}.Math.\left[\%\right]=\frac{\left(R.Math..Math.2-R.Math..Math.1\right)*100}{R.Math..Math.2}$

[0047] (R2=reflection (Y 395 nm) of position b, R1=reflection of position a)

[0048] 3. Mottling

[0049] Determination of the mottling, as the degree of cloudiness of the transferred print on the textile, was accomplished visually and was evaluated according to the following scale of ratings: [0050] Rating 1: very good, print absolutely cloud-free [0051] Rating 2: good, print cloud-free [0052] Rating 3: satisfactory, print slightly unsettled [0053] Rating 4: adequate, print unsettled [0054] Rating 5: deficient, print cloudy [0055] Rating 6: inadequate, print very cloudy

[0056] 4. Wetting Angle

[0057] The wetting angle was determined using a commercial wetting angle measuring instrument from Lorentzen & Wettre. The droplet size (height and width) was measured 10 s after placement of the water droplet (demineralized water) with the syringe tip. In each case three measurements were carried out on a test strip 15 mm wide, and the average value without decimal places was reported.

[0058] 5. Adhesion

[0059] The adhesion of the thermal sublimation paper to the textile was determined as follows. After implementation of transfer printing in the transfer press, the adhesion of the thermal sublimation paper to the textile was characterized on manual separation of these layers, in ratings as characterized below, on a laboratory bench. Separation in this case was performed by parting one corner of the sheet-like textile from the paper layer and then peeling off the textile manually at an angle of 90° to 120° from the flat-lying paper. [0060] Rating 1: specimen sticks significantly to the textile [0061] Rating 2: specimen sticks slightly to the textile [0062] Rating 3: specimen sticks very slightly to the textile [0063] Rating 4: specimen does not stick to the textile [0064] Rating 5: detachment of the specimen from the textile is possible only with damage to the specimen [0065] Rating 6: detachment of the specimen from the textile is possible only with destruction of the specimen

[0066] 6. The Optical Density was Measured with a GretagMacbeth D19C in Automatic Colour Mode.