Tacky microporous transfer material

Abstract

The invention relates to a transfer material for the dye sublimation transfer method (sublimation paper) for printing an inkjet print image, comprising a substrate and an ink receiving layer, which layer contains a pigment and a binding agent, on the front face of the transfer material, the ink receiving layer being porous and thermoplastic particles being arranged on the ink receiving layer. The porous ink receiving layer, together with the thermoplastic particles arranged thereon, have an air permeance according to Bendtsen of greater than 100 ml/min and the thermoplastic particles have a diameter of 0.3 m to 5 m and a melting point of 60 C. to 170 C.

Claims

1. A transfer material for the dye-sublimation transfer process of an inkjet print image (sublimation paper), wherein the transfer material comprises a support with a front face and a back face and an ink-receiving layer containing pigment and binder on the front face of the support, characterized in that the ink-receiving layer is porous and contains thermoplastic particles arranged thereon and not distributed within the ink-receiving layer, whereby the porous ink-receiving layer with the thermoplastic particles thereon has an air permeability from 200 ml/min to 500 ml/min according to the Bendtsen method, and whereby the thermoplastic particles have a diameter of 0.3 m to 5 m and a melting point of 60 C. to 170 C.

2. The transfer material according to claim 1, characterized in that the support is a paper support.

3. The transfer material according to claim 2, characterized in that the transfer material further includes a barrier layer either on the back face of the paper support or between the paper support and the porous ink-receiving layer.

4. The transfer material according to claim 3, characterized in that the barrier layer is arranged on the back face of the paper support that faces away from the ink-receiving layer.

5. The transfer material according to claim 3, characterized in that the air permeability of the barrier layer according to the Bendtsen method is less than 100 ml/min.

6. The transfer material according to claim 1, characterized in that a surface of the ink-receiving layer is negatively charged or neutral.

7. The transfer material according to claim 1, characterized in that the ink-receiving layer a surface of has pH value of at least 7.0.

8. The transfer material according to claim 1, characterized in that the ink-receiving layer contains a pigment selected from calcium carbonate, kaolin and silica.

9. The transfer material according to claim 3, characterized in that the barrier layer contains a water-soluble polymer.

10. The transfer material according to claim 3, characterized in that the barrier layer has a grammage of 2 g/m.sup.2 to 20 g/m.sup.2.

11. The transfer material according to claim 1, characterized in that the ink-receiving layer has a grammage of 3 g/m.sup.2 to 30 g/m.sup.2.

12. The transfer material according to claim 1, characterized in that the grammage of the thermoplastic particles on the ink-receiving layer is 0.3 g/m.sup.2 to 5 g/m.sup.2.

13. A method for transferring an image to a receiving material by means of sublimation, comprising printing an inkjet image onto a transfer material according to any one of claims 1 to 12; and transferring the inkjet image onto a surface of the receiving material by sublimation.

14. The method according to claim 13, characterized in that the surface of the receiving material is composed of polyester fabric, polyester fleece, a surface coated with a polyester layer or a polyester surface.

Description

(1) FIG. 1 shows a schematic representation of a cross-section of a microporous transfer paper according to the present invention. Herein 1 stands for a paper support. The porous or microporous ink-receiving layer 2 intended for inkjet printing contains a binder and an inorganic pigment. On top of the ink-receiving layer 2 a layer 3 with thermoplastic polymer particles is arranged.

(2) FIG. 2 shows another embodiment of the transfer paper of the invention in which a barrier layer 4 is positioned on the surface of the paper support facing away from the layer with the adhesive particles and the ink-receiving layer; in other words, the barrier layer is on the reverse of the paper support.

(3) FIG. 3 is a scanning electron microscope image and shows the cross-section of a transfer paper according to the invention that was obtained by cutting the paper with a razor blade. The transfer paper depicted here is identical to that described in FIG. 1. In the scanning electron microscope image (device: Hitachi SU 3500, magnification 1,500 times, 15.0 kV, BSE detector), the paper fibers and the adhesive polymer droplets are darker (gray) than the calcium carbonate pigment particles (lighter). FIG. 3 clearly shows that the adhesive polymer particles are distributed on the receiving layer and not within the receiving layer.

(4) The following examples and tests aim to provide a further explanation of the invention.

EXAMPLES

(5) 1. Manufacturing the Paper Support

(6) Eucalyptus pulp was used for manufacturing the base paper. As approximately 5% aqueous suspension (thick stock), the pulp was beaten with a refiner to 26 SR. The concentration of the pulp fibers in the thin stock was 1% by weight in relation to the total weight of the pulp suspension. Further additives were introduced to the thin stock, for instance a neutral sizing agent alkyl ketene dimer (AKD, 0.23% by weight), wet strength agent polyamine-polyamide-epichlorohydrin resin (Kymene, 0.60% by weight), starch (C*Bond HR 35845, 1.0% by weight) and natural ground CaCO.sub.3 (15% by weight). The amounts indicated are in relation to the mass of the pulp.

(7) The thin stock with a pH adjusted to about 7.5 was fed from the headbox to the wire of the paper machine. For sheet formation, the web was dewatered in the wire section of the paper machine. In the press section, the paper web was dewatered further to a water content of 60% by weight in relation to the web weight. Additional drying was carried out in the dryer section of the paper machine with the aid of heated cylinders. The final product was a base paper with a grammage of 90 g/m.sup.2, a filler content of 10% by weight and a moisture content of approximately 5.5%.

(8) In a size press, both sides of the base paper were surface sized with a starch solution containing 3% by weight C*Film 05731 starch manufactured by Cargill and water. The total weight of the starch applied on both sides is approximately 1.5 g/m.sup.2. The base paper is once again dried and smoothed following the application of the starch coating. The base paper thus obtained displays an air permeability of 700 ml/min determined according to the Bendtsen method as specified in DIN 53120-1.

(9) 2. Manufacturing a Coating Mass for the Ink-Receiving Layer

(10) 557 g of an aqueous 9.5%-by-weight solution of a partially saponified polyvinyl alcohol (Mowiol 18-88, Kuraray) is added to 441 g of a diluted dispersion of precipitated calcium carbonate (Precarb 800, Schaefer Kalk) with a solids content of 48% by weight and the mixture is stirred with a dissolver agitator. Subsequently, 0.5 g wetting agent Surfynol 440 marketed by Air Products is added to the mixture. The resulting coating material has a solids content of 26.6% by weight, a viscosity of 150 mPas, a pH value of 7.5 and a surface tension of 36 mN/m.

(11) 3. Manufacturing a Coating Compound with Thermoplastic Particles

(12) A dispersion of polyolefin particles (HYPOD 2000 manufactured by Dow Chemical Company) is diluted with water to a solids content of 48% by weight. The glass transition temperature of the polyolefin particles (adhesive polymer particles) in the dispersion is 26 C. The average particle diameter of the adhesive polymer particles is around 1 m. Furthermore, 4% by weight of Surfynol 440 marketed by Air Products is added to the dispersion. The resulting coating material has a viscosity of 50 mPas, a surface tension of 33 mN/m and a pH level of 9.9. Together with the ink-receiving layer, the coating compound with the thermoplastic particles is applied as an aqueous dispersion using the curtain coating process.

(13) 4. Manufacturing a Coating Compound for the Barrier Layer

(14) 4 g wetting agent Surfynol 440 from Air Products is added to 1000 g of a 10%-by-weight aqueous solution of saponified polyvinyl alcohol (Mowiol 28-99).

(15) 5. Reference Material V1

(16) A commercially available transfer material with a release and barrier layer (Transjet Sportsline 9310100 g/m.sup.2) serves as reference material V1. On the print side, this reference material possesses a non-porous coating that adheres to the fabric (industry benchmark for adhesion).

(17) 6. Reference Material V2

(18) A commercially available transfer material with a microporous ink-receiving layer (Transjet Boost 834085 g/m.sup.2) serves as reference material V2. Reference material V2 possesses a fast-drying, non-adhesive transfer layer (industry benchmark for drying).

(19) 7. Manufacturing Reference Material V3

(20) A laboratory product according to the coating formulation described in Example 1 in DE 10 2014 116550 A1, namely thermoplastic particles in a binder-rich layer, applied to the base paper described under item 1 serves as reference material V3. The dry coating of the ink-receiving layer weighs 8 g/m.sup.2.

(21) 8. Manufacturing a Transfer Paper with an Ink-Receiving Layer, Thermoplastic Particles and Base Paper (Invention E1)

(22) The coating compound for the ink-receiving layer (Example 2) and the coating compound for the thermoplastic particles (Example 3) are simultaneously applied to the base paper described under Example 1, whereby the thermoplastic particles are distributed on the top side (i.e. on the side facing away from the base paper). The dry coating of the ink-receiving layer from Example 2 weighs 12 g/m.sup.2 whereas that of the adhesive particles from Example 3 weighs 1 g/m.sup.2.

(23) 9. Manufacturing a Transfer Paper with an Ink-Receiving Layer, Thermoplastic Particles and a Barrier Layer on the Reverse of the Base Paper (Invention E2)

(24) In addition to the coatings for the transfer paper manufactured according to Invention 1, the coating described under Example 4 is also applied onto the transfer paper with the aid of a squeegee and allowed to dry. The dry coating weighs 5 g/m.sup.2 and the coating is applied on the side of the base paper opposing the ink-receiving layer and the layer with the thermoplastic particles.

(25) 10. Test Methods

(26) On the transfer materials obtained, a color image was printed with an EPSON WP-4015 inkjet printer and SubliJet IQ sublimation inks from Sawgrass.

(27) The quality of drying after obtaining the inkjet print was assessed using two test methods: a) Smearfastness test: After a specified time (fresh print, 30 seconds, 1 minute, 3 minutes, 5 minutes), the tester runs his/her finger over four full-color print fields in the colors cyan, magenta, yellow and black (CMYK) and assesses whether and to what extent the colors smear. b) Imprint test: Immediately after printing, the CMYK full-color areas are brought into direct contact with the reverse of a second sheet of the transfer material and pressed with a 5-kg cylinder (Cobb cylinder). The tester subsequently performs a visual check to assess how much ink has passed through to the rear side of the second sheet.

(28) Transfer of the printed image onto a fabric by sublimation:

(29) In a Rotex AutoSwing X heat transfer press from Sefa, the image side of the printed transfer material is brought into contact with a knitted polyester fabric (sports jersey 140 g/m.sup.2 from A. Berger, article no. 4245-3). A sheet of office copying paper with a grammage of 80 g/m.sup.2 is additionally placed on the reverse of the transfer material in order to assess the ink bleed-through. At a temperature of 200 C., a contact pressure at level 30 according to the indicator on the heat transfer press is applied. The fabric and the copying paper are subsequently separated from the transfer material.

(30) The print sharpness is assessed visually and with a microscope, both on the transfer material before the image transfer and on the fabric after the sublimation transfer.

(31) The color density for the CMYK full-color fields is measured with a SpectroEye spectrophotometer from X-rite.

(32) The ink bleed-through is visually assessed on the basis of the ink that is transferred onto the copying paper that was placed on the rear side during the sublimation transfer process.

(33) The level of adhesion of the printed sublimation paper on a fabric after transfer printing in the transfer press is determined by separating the fabric from the paper by hand at an angle of 90 to 120 after the transfer process. The following scores were awarded, in accordance with DE 10 2014 116550 A1: Grade 1: The pattern sticks strongly on the fabric. Grade 2: The pattern sticks lightly on the fabric. Grade 3: The pattern sticks very lightly on the fabric. Grade 4: The pattern does not stick on the fabric. Grade 5: The pattern can only be removed by damaging it. Grade 6: The pattern can only be removed by destroying it.

(34) 11. Test Results (Test Methods and Equipment) for V1, V2, V3, E1 and E2

(35) TABLE-US-00001 V1 V2 V3 E1 E2 Air permeability <25 ml/min <25 ml/min 120 ml/min 355 ml/min <25 ml/min (Bendtsen method, DIN 53120-1, issue 1998-06) Drying ++ +++ +++ (Average from smearfastness and imprint test) Print quality +/++ +/++ +/++ +++/+++ +++/+++ (line sharpness) Before and after sublimation transfer to fabric Transferred color ++ ++ ++ ++ +++ density Ink bleed- +++ ++ + +++ through to reverse Adhesion to fabric Grade 1 Grade 4 Grade 1 Grade 1 Grade 1 (The pattern (The pattern (The pattern (The pattern (The pattern sticks does not stick on sticks sticks strongly on sticks strongly on the fabric.) strongly on the fabric.) strongly on the fabric.) the fabric.) the fabric.)

(36) The test results in the table show that the transfer materials according to the present invention exhibit very good drying properties after inkjet printing; demonstrate excellent line sharpness, even in the image transferred to the fabric; transfer the sublimation ink to a large extent to the fabric during the sublimation transfer process and additionally exhibit excellent adhesion on the fabric (E1). In this regard, it needs to be emphasized that the drying characteristics of the ink of E1 are far superior to those of V3 and even surpass those of V2. Hence, the adhesion on the fabric of V1 is achieved with the drying process of V2, to date, this was not possible with the prior art methods. The application of an additional barrier layer (E2) creates a product that displays outstanding characteristics in terms of all the essential quality aspects expected from sublimation paper. The use of a barrier layer (E2) ensures that only a very small quantity of ink is released through the rear side. Moreover, the barrier layer can be applied either on the reverse or on the top side of the base paper. The application of the barrier layer on the reverse side enhances the drying characteristics by exploiting the water absorption capacity of the paper support.