Thermal transfer foil for producing a true color image, process for producing a true color image, and true color image

Patent metadata

Field	Value
Publication number	US-11090922-B2
Application number	US-201815977307-A
Country	US
Kind code	B2
Filing date	May 11, 2018
Priority date	May 12, 2017
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A thermal transfer foil and also a process for producing a true color image, and a true color image, wherein the thermal transfer foil includes at least one effect pigment layer and a carrier foil which has first effect pigments in one or more first regions.

First claim

The invention claimed is:

1. A process for producing a color image comprising:
providing one or more thermal foils having an effect pigment layer and a carrier foil, the effect pigment layer comprising effect pigments; and
applying subareas of the effect pigment layer of at least one of the one or more thermal transfer foils to a first surface of a substrate using one or more thermal transfer printheads, whereby effect pigments having different optical effects and/or orientations are transferred from the subareas to form two or more halftone dots on the substrate, said two or more halftone dots being formed in such a way that additive and/or subtractive color mixing of the two or more halftone dots form the color image,
wherein the color image consists of a multiplicity of color domains which, when illuminated and viewed in reflected light or in transmitted light show a color, and
wherein the at least two halftone dots are formed in at least 10% of the color domains.

2. The process according to claim 1 , wherein, in each of the color domains, two or more of the halftone dots are applied alongside one another and/or over one another and/or overlapping one another on the first surface of the substrate.

3. The process according to claim 1 , wherein the halftone dots have at least one lateral dimension in the range between 40 μm and 100 μm, wherein the lateral dimensions of the halftone dots amount to between two times and five times the lateral dimension of the effect pigments.

4. The process according to claim 1 , wherein the substrate is selected from or components of the substrate are selected from the following: PET, PP, PE, PA, PEN.

5. The process according to claim 1 , wherein the substrate is transparent, and the transparent substrate is applied, by a surface opposite to the first surface, to a colored background.

6. The process according to claim 1 , wherein a protective layer is applied to the first surface and/or to the surface of the substrate that is opposite to the first surface, said protective layer being selected from the following: transparent overprint, laminate, plastic sheet, glass sheet.

7. The process according to claim 1 , wherein the substrate is transparent, and the transparent substrate is applied, by the first surface, to a colored background.

8. The process according to claim 1 , wherein the substrate is opaque and/or is applied to a black or dark surface.

9. The process according to claim 1 , wherein the substrate has at least one colored varnish coat on a second surface that is opposite to the first surface.

10. The process according to claim 9 , wherein a colorimetric value of the visible intrinsic color of the colored varnish coat in a color space defined by coordinate axes a* and b* specifying the complementary colors and by coordinate axis L* specifying the luminance of the hue in a CIELAB color space, is provided in a range of L* of greater than or equal to 0 and less than or equal to 90.

11. The process according to claim 9 , wherein the colored varnish coat is provided with one or more dyes and/or one or more different-colored pigments.

12. The process according to claim 11 , wherein one or more of the pigments are selected from the following: optically variable pigments, pigments containing thin-film layers and/or liquid-crystal layers which generate a color shift effect dependent on viewing angle or illumination angle, organic pigments, inorganic pigments, luminescent additives, UV-fluorescent additives, UV-phosphorescent additives, IR-phosphorescent additives, IR upconverters, thermochromic additives.

13. The process according to claim 11 , wherein a pigmentation number of greater than or equal to 5 cm 3 /g and less than or equal to 120 cm 3 /g, is provided.

14. The process according to claim 1 , wherein a register tolerance in an advancement direction and/or perpendicular to the advancement direction between at least two regions, each of which is transferred or printed onto the substrate by different thermal transfer foils, to one another is greater than or equal to −0.15 mm and less than or equal to +0.15 mm.

15. The process according to claim 1 , wherein a first of the thermal transfer foils comprises a red effect pigment layer, and wherein a second of the thermal transfer foils comprises a green effect pigment layer, and wherein a third of the thermal transfer foils comprises a blue effect pigment layer.

16. The process according to claim 1 , wherein the thermal transfer foil has two or more regions in which the effect pigment layer comprises effect pigments which differ in respect of their color effect, and/or orientation.

17. The process according to claim 1 , wherein the process comprises the following further steps:
providing a multicolored motif;
determining two or more grayscale images assigned in each case to a color channel; converting a third grayscale image assigned to a blue color channel;
converting the respective grayscale images into a respective halftone image consisting of a multiplicity of halftone dots, based on frequency-modulated rastering and/or on periodic rastering; and
driving the thermal transfer printhead or of the thermal printheads in such a way that the subareas of the effect pigment layer or effect pigment layers, in halftone dot formation, are transferred to the first surface of the substrate in accordance with the size and disposition of the halftone dots of the halftone images.

18. The process according to claim 17 , wherein the periodic rastering is provided with two or more different halftone angles and/or two or more different halftone dot shapes.

19. The process according to claim 1 , wherein the halftone dot shapes are selected from the following: punctiform, rhomboidal, cruciform.

20. The process according to claim 17 , wherein the multicolored motif is selected from the following: photos, images, alphanumeric symbols, logos, microtexts, portraits, pictograms.

21. The process according to claim 1 , wherein the process comprises the following further steps:
applying further layers or layer sequences before and/or after the application of the true color image by means of a process selected from the following: thermal transfer printing, gravure printing, flexographic printing, screen printing, pad printing, inkjet printing, hot stamping, cold stamping.

22. The process according to claim 21 , wherein the layers or layer sequences are each or partially selected from the following: transparent, translucent and/or opaque color layer, transparent, translucent and/or opaque metallic layer, open or embedded replication layer comprising diffractive and/or refractive relief structures, transparent, translucent and/or opaque reflection layer, thin metal layer, HRI layer, LRI layer, volume hologram layer, transparent, translucent and/or opaque thin-film construction, Fabry-Perot layer with absorption layer, spacer layer and/or reflection layer.

23. A true color image produced according to claim 1 , wherein the true color image comprises a multiplicity of halftone dots applied to a first surface of a substrate, wherein the halftone dots are formed by subareas of an effect pigment layer of a thermal transfer foil or by subareas of effect pigment layers of two or more different thermal transfer foils.

24. The true color image according to claim 23 , wherein a halftone dot comprises 10 to 1000 effect pigments, which are disposed partly or completely above one another and/or along

Assignees

• Leonhard Kurz Stiftung & Co Kg

Inventors

• Unal Eser Alper
• Schulz Christian
• Huber Thimo
• Schmidt Norbert
• Klages Soren

Classifications

• B41M5/38228 Primary

  characterised by the use of two or more ink layers · CPC title

• B41M5/0253

  using a chemical colour-forming ink, e.g. chemical hectography (B41M5/035 takes precedence) · CPC title

• B41F16/0013 Primary

  combined with other printing presses · CPC title

• B41M5/38264

  Overprinting of thermal transfer images · CPC title

• B41M5/385 Primary

  characterised by the transferable dyes or pigments {(infrared absorbing dyes B41M5/465)} · CPC title