RECORDING MATERIAL FOR DYE SUBLIMATION PRINTING HAVING IMPROVED TRANSPORT PROPERTIES

Abstract

The invention relates to recording material for dye sublimation printing comprising base paper (1) having a front and a rear side, at least one synthetic resin layer (4) on at least the rear side of the base paper (1), a dye-receiving layer (2) which is arranged on the front side of the base paper (1), at least one plastic film (3) which is arranged between the base paper (1) and the dye-receiving layer (2) and optionally a barrier layer which is arranged between the plastic film (3) and the dye-receiving layer (2), wherein the synthetic resin layer (4) has an elastic modulus of at least 0.8 GPa.

Claims

1. A recording material for dye sublimation printing comprising a. a base paper (1) having a front and a rear side b. at least one synthetic resin layer (4) on at least the rear side of the base paper c. a dye-receiving layer (2) which is arranged on the front side of the base paper, d. at least one plastic film (3) which is arranged between the base paper and the dye-receiving layer and e. optionally a barrier layer which is arranged between the plastic film (3) and the dye-receiving layer (2), characterized in that the synthetic resin layer (4) has an elastic modulus of at least 0.8 GPa.

2. The recording material according to claim 1, characterized in that the synthetic resin layer (4) has an elastic modulus of at least 0.90 GPa, preferably at least 0.95 GPa.

3. The recording material according to any one of the preceding claims, characterized in that the synthetic resin layer (4) has a pigment content of at least 5 wt. %, preferably at least 10 wt. %, based on the dry weight of the synthetic resin layer.

4. The recording material according to claim 3, characterized in that the pigments are selected from calcium carbonate, aluminum oxides, aluminum silicates or mixtures thereof.

5. The recording material according to any one of the preceding claims, characterized in that the synthetic resin layer (4) comprises HD-PE, LD-PE, 4-methylpentene-1 homo- and copolymers (TPX), and mixtures thereof.

6. The recording material according to any one of the preceding claims, characterized in that the synthetic resin layer (4) contains a content of at least 5 wt. % of one of the polymers 4-methylpentene-1 homo- and copolymers (TPX).

7. The recording material according to any one of the preceding claims, characterized in that the plastic film (3) is a biaxially oriented plastic film, in particular a biaxially oriented polypropylene film.

8. The recording material according to any one of the preceding claims, characterized in that the plastic film (3) comprises a barrier layer (5).

9. The recording material according to claim 8, characterized in that a mixture of a water-dispersible polymeric binder and gelatin is used as the barrier layer (5).

10. The recording material according to claim 9, characterized in that the water-dispersible polymeric binder in the barrier layer (5) is a polyester-polyurethane copolymer.

11. The recording material according to any one of the preceding claims, characterized in that the dye-receiving layer (2) contains an optical brightener and a polar binder.

12. The recording material according to claim 11, characterized in that the polar binder in the dye-receiving layer (2) contains polyvinyl alcohol modified with carbonyl or carboxyl groups.

13. The recording material according to claim 12 or 13, characterized in that the polar binder constitutes a content of 5 to 20 wt. % of the dye-receiving layer (2).

14. The recording material according to one of the preceding claims, characterized in that an adhesive layer (6) which is arranged between the base paper (1) and the plastic film (3) is additionally applied to the front side of the base paper (1).

15. The recording material according to claim 14, characterized in that the adhesive layer (6) consists of LD-PE.

Description

[0067] The invention is described with examples in more detail below, with reference to exemplary embodiments.

[0068] FIG. 1 a schematic structure of an embodiment of a recording material according to the invention

[0069] FIG. 2 SEM image of the synthetic resin layer on the rear side of a recording material of the prior art with transport roller needle recesses, with offset

[0070] FIG. 3 SEM image of the synthetic resin layer on the rear side of a recording material according to the invention with transport roller needle recesses, without offset

[0071] FIG. 4 crosshairs for determining the offset

[0072] FIG. 1 shows a schematic structure of a preferred embodiment of a recording material according to the invention. According to this preferred embodiment, the recording material comprises a base paper 1, on the front side of which a dye-receiving layer 2 is arranged. A plastic film 3 is arranged between the base paper 1 and the dye-receiving layer 2. The recording material has a synthetic resin layer 4 on the rear side of the base paper 1. A barrier layer 5 is arranged on the front side of the base paper 1 between the plastic film 3 and the dye-receiving layer 2. Furthermore, an adhesive layer 6 is arranged on the front side of the base paper 1 between the plastic film 3 and the base paper 1.

[0073] FIG. 2 shows an SEM image of the surface of the synthetic resin layer on a rear side of a recording material of the prior art after successive printing processes. The rear side has recesses of the transport roller needles which show a offset. Due to friction between the recording material and the transport rollers, optimal positioning of the recording material relative to the print head was not ensured, with the result that in successive printing processes there is an offset between the print image already applied and the print image applied in the subsequent printing process, and thus impairment of the print image quality. This offset can be seen on the surface of the synthetic resin layer of the rear side of the recording material using the SEM image with reference to the offset transport needle recesses.

[0074] FIG. 3 shows an SEM image of the surface of the synthetic resin layer 4 on the rear side of a recording material according to the invention after successive printing processes. In contrast to the SEM image of a rear side of a recording material of the prior art after successive printing processes shown in FIG. 2, it can be seen from FIG. 3 that the surface of the synthetic resin layer 4 on the rear side of the recording material according to the invention has no offset of the recesses of the transport roller needles. The recording material according to the invention therefore ensures optimal positioning of the recording material relative to the print head during transport in the printer, allowing excellent print image quality to be achieved during successive printing processes.

[0075] FIG. 4 shows two print images of a crosshair for determining the offset. The offset is determined from the color shift of cyan, yellow, magenta (see right crosshair) in the crosshair using a microscope. The offset is given by the sum of all color shifts. The offset is a measure of transport properties in the printer. In this case, a small offset or no offset (left crosshair) is very desirable.

EXAMPLES

Production of a Base Paper

[0076] A base paper A was produced from eucalyptus pulp. For milling, the pulp was milled as an approximately 5% aqueous suspension (thick stock) to a freeness of 36 SR using a refiner. The concentration of pulp fibers in the thin stock was 1 wt. %, based on the mass of the pulp suspension. Additives were added to the thin stock, such as cationic starch in a quantity of 0.4 wt. %, as a neutral sizing agent alkyl ketene dimer (AKD) in a quantity of 0.48 wt. %, wet strength polyamine polyamide epichlorohydrin resin (Kymene) in a quantity of 0.36 wt. % and a natural CaCO.sub.3 in a quantity of 10 wt. %. The quantities given refer to the atro pulp mass. The thin stock, the pH value of which was adjusted to about 7.5, was transferred from the headbox to the screen of the paper machine, followed by sheet formation with dewatering of the web in the screen section of the paper machine. In the press section of the paper machine, further dewatering of the web was carried out to a water content of 60 wt. %, based on the web weight. Further drying was carried out in the drying section of the paper machine with heated drying cylinders. The result was a base paper with a weight per unit area of 132 g/m.sup.2 and a moisture content of about 7%.

Production of the Recording Materials According to the Invention and the Comparative Examples

[0077] The side (rear side) of the base paper opposite the side to be printed was coated in the extruder with a synthetic resin layer consisting of the polymer mixtures listed in Table 1. The cooling cylinder was selected such that the resulting surface of the rear side has a roughness of 0.9 m, measured as R.sub.z value according to DIN 4768.

[0078] The surface (front side) of the base paper intended for printing was laminated with a three-layer biaxially oriented polypropylene film (plastic film, HIPHANE BOPP, Hwaseung Industries Co. Ltd) in the extruder after irradiation with a corona discharge, and a film of low-density polyethylene (LD-PE) was extruded between the front side of the base paper and the biaxially oriented polypropylene film. The thickness of the adhesion-promoting polyethylene film (adhesive layer) was 20 m.

[0079] The carrier material obtained was then coated with a barrier layer on the side coated with the plastic film (25 wire doctor blade) and dried at 78 C. for three minutes. The composition of the respective barrier layer is given in Table 2. The application quantities of the barrier layer were selected such that a dry application of 1.6 g/m.sup.2 was obtained in each case.

[0080] In the next step, a dye-receiving layer was applied to the barrier layer (15 wire doctor blade) and dried (2 minutes, 78 C.). The application quantity of the coating compound for the dye-receiving layer was selected such that a dry application of 0.5 g/m.sup.2 was obtained. The composition of the coating compound for the dye-receiving layer is given in Table 3.

Production of the Coating Compound for the Dye-Receiving Layer

[0081] 31.70 g of a vinyl chloride/acrylate copolymer dispersion with a solids content of 56 wt. % (PrintRite DP 281.E, manufacturer Lubrizol) and 13.58 g of a vinyl chloride/vinyl acetate/vinylidene chloride dispersion with a solids content of 56 wt. % (Vycar 577 E, manufacturer Lubrizol) were mixed with 3.15 g of a 30% aqueous suspension of colloidal silica (Ludox AM X4931, manufacturer Grace), 0.95 g of polydimethylsiloxane (TegoGlide 482, manufacturer Evonik Industries), 0.25 g of a defoaming agent (Tego Foamex 825, manufacturer Evonik Industries), 0.08 g of a wetting agent (Capstone FS 30, 25%, manufacturer DuPont) and 50.29 g of water.

[0082] The structure of the recording materials obtained according to the examples and comparative examples can be found in Table 4. The offset in the printer was determined using the recording materials obtained in this way, and the dye migration and cloudiness (mottling) were evaluated by the methods described below.

[0083] As can be clearly seen from the results in Table 4, the quality of the synthetic resin layer on the rear side of the recording material plays a major role with regard to the offset that is critical in the printing process. Acceptable behavior in the multipass printing process, i.e., little or no offset, is only achieved with the recording materials according to the invention, the synthetic resin layer of which has an elastic modulus of at least 0.8 GPa.

Measurement Methods

Dye Migration Test

[0084] The samples are printed with the maximum color densities of yellow, cyan, magenta and black on the Mitsubishi CP-D70DW printer with a standard donor ribbon. The printing format is 1015 cm and the color areas are 11 cm. These samples are hung at 80 C. oven temperature for 5 days. After 5 days, an evaluation of the dye penetration on the rear side of the printed sample is carried out using grades.

[0085] The evaluation is made as follows: no color penetration on the rear side is evaluated as grade 1; heavy and large-area color penetration is evaluated as grade 5. For this purpose, the relative grading is from grade 1 to grade 5.

Mottle Evaluation (Cloudiness)

[0086] Samples and printer CP-D70DW from Mitsubishi are preconditioned for 12 h at 40 C. and 80% relative atmospheric humidity. A 1015 cm full-area black print is then performed in the existing climate. The mottle of the samples is evaluated in grades from 1 to 5. Grade 1 means no mottle (no cloudiness) and grade 5 means heavy mottle (heavy cloudiness). The grading between 1 and 5 is relative to the grades 1 and 5.

Elastic Modulus

[0087] The elastic modulus is determined according to the tensile strength test using the Lorentzen & Wettre tensile tester. For this purpose, samples of the synthetic resin layer are cut to 50 mm width and 120 mm length. The gauge length is set to 100 mm. The gauge speed is 100 mm/min. The thickness and weight per unit area of the samples are determined and entered into the Elastic modulus test program of the Lorentzen & Wettre tensile tester. The tensile strength test is then carried out on the samples. The elastic modulus is determined from the ratio between mechanical stress and strain in the linear region of the stress-strain diagram.

Method for Measuring Offset in the Print Image

[0088] The offset is determined using a crosshair. First, a print image is printed with different crosshairs. The printed crosshairs are then located on the print image. The offset is determined from the color shift of cyan, yellow, magenta (see FIG. 4, right crosshair) in the crosshair using a microscope. The offset is given by the sum of all color shifts. The offset is a measure of transport properties in the printer. In this case, a small offset or no offset (see FIG. 4, left cross hairs) is very desirable.

TABLE-US-00001 TABLE 1 Composition of the synthetic resin layer and the elastic modulus of the respective synthetic resin layer A B C D E F G H I HD-PE/wt. % 80 75 70 60 80 80 80 0 100 LD-PE/wt. % 20 20 20 20 15 10 0 100 0 TPX/wt. % 0 5 10 20 0 0 0 0 0 Calcium carbonate/wt. % 0 0 0 0 5 10 20 0 0 Thickness/m 20 20 20 20 20 20 20 20 20 Solids content/% 100 100 100 100 100 100 100 100 100 Elastic modulus/GPa 0.63 0.83 0.97 0.98 0.82 0.99 1.55 0.49 0.67

TABLE-US-00002 TABLE 2 Composition of the coating compound of the barrier layer in wt. % Commercial product and solids content, and pH value of the coating compound Coating Coating compound compound J K Desalinated water 79.16 79.00 Gelatin (Imagel AP 71979, 290 Bloom, 5.80 5.80 isoelectric. point = 8, Gelita AG) NH.sub.3 solution, 5% 1.20 1.20 TiO.sub.2 (Ti-Pure RPS Vantage 71% in water, 2.75 2.91 DuPont) Optical brightener (Leucohor UO, 25% 3.26 3.26 Archroma International) Polyester polyurethane copolymer (PU-Coat 5.00 5.00 DMP 105, 40% in water, Baumeister Chemicals & Consulting Gmbh & Co. KG) Wetting agent (Capstone FS 30, 25% in 0.07 0.07 water, DuPont) Polyaziridine (PZ-33, 50% in IPA, Flevo 2.76 2.76 Chemie B.V.) Solids content 10.04 12.31 pH value 8.5 8.5

TABLE-US-00003 TABLE 3 Composition of the coating compound for the dye-receptive layer in wt. % Commercial product as well as solids content and pH value of the coating compound for the dye-receiving layer Coating Coating Coating Coating compound compound compound compound L M N O Desalinated water 50.86 41.76 34.38 47.92 Defoaming agent 0.25 0.29 0.24 0.17 (TegoFoamex 825) Vinyl chloride/acrylate 31.37 37.18 48.28 40.08 copolymer dispersion (Printrite DP-281E) Vinyl chloride/vinyl 13.44 15.93 13.11 9.07 acetate/vinylidene chloride dispersion (Vycar 577 E) Colloidal silica 3.12 3.69 3.04 2.10 (Ludox AM X4931) Polydimethyl siloxane 0.89 1.06 0.87 0.60 (Tego Glide 482) Wetting agent 0.08 0.09 0.08 0.05 (Capstone FS 30) Solids content 27.00 32 36.4 29 pH 9 9 9 9

TABLE-US-00004 TABLE 4 Structure and properties of the comparative examples and of the recording material according to the invention Comparison Invention Invention Invention Invention Structure 1 1 2 3 4 Dye-receiving L L M M M layer Barrier layer J J J K K Plastic film HIPHANE HIPHANE HIPHANE HIPHANE HIPHANE BOPP BOPP BOPP BOPP BOPP Polymer H H H H H mixture of the adhesive layer Base paper Base Base Base Base Base paper paper paper paper paper Polymer A F G G D mixture of the synthetic resin layer Elastic 0.61 0.99 1.55 1.55 0.98 modulus of the synthetic resin layer/GPa Offset 6 mm 1 mm 0 mm 0 mm 0 mm Migration 1 1 1 1 1 (score) Mottle test 1 1 1 1 1 (score)