Method for producing pigment fragments with a predefined internal and/or external contour using a crack-forming layer, and pigment fragments

Abstract

A method for producing pigments comprises the steps of creating a first layer on a substrate, structuring the first layer and detaching the pigments from the substrate. In the present case, the first layer is a crack-forming layer, so that the first layer is structured by the arising of cracks. Prior to detaching the pigments, a pigment layer is applied onto the first layer structured by the cracks.

Claims

1. A method for producing pigments, comprising the steps of: creating a first layer on a substrate; structuring the first layer; and detaching the pigments from the substrate; wherein the first layer is a crack-forming layer so that the first layer is structured by the arising of cracks; and prior to detaching the pigments, a pigment layer is applied onto the first layer structured by the cracks.

2. The method according to claim 1, wherein the pigments comprise: the pigment layer, or the pigment layer and the first layer.

3. The method according to claim 1, wherein the pigment layer is structured into a plurality of pigment sections by application to the structured first layer.

4. The method according to claim 1, wherein the applied pigment layer lies with pigment sections on pigment islands of the first layer and with pigment residues in the cracks on the substrate.

5. The method according to claim 1, wherein the first layer forms the cracks by itself, within the framework of a solidification of the first layer.

6. The method according to claim 1, wherein the first layer and/or a method parameter is adapted within the framework of the crack formation to generate pigments of specified size, with sizes within a target size distribution.

7. The method according to claim 1, wherein nucleus points for the crack formation are created in the form of partial recessions, in the substrate or the first layer, so that the shape of the pigments is determined by the nucleus points.

8. The method according to claim 1, wherein the first layer is applied in several stripes.

9. The method according to claim 1, wherein the pigment layer comprises several partial layers.

10. The method according to claim 1, wherein a soluble layer is dissolved in the step of detaching the pigments from the substrate.

11. The method according to claim 10, wherein the soluble layer is a partial layer of the substrate or the first layer.

12. The method according to claim 10, wherein the soluble layer is water-soluble.

13. The method according to claim 1, wherein the method comprises the further steps of: bringing into contact the pigment layer with an intermediate substrate, wherein the structured pigment layer adheres in sections to the intermediate substrate; and separating intermediate substrate and substrate, wherein the pigments are detached from the substrate by the step of separating.

14. The method according to claim 13, wherein at least the pigment layer adheres to a soluble layer of the intermediate substrate, which is arranged on a foil layer of the intermediate substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiment examples as well as advantages of the invention will be explained hereinafter with reference to the figures, in whose representation a rendition that is true to scale and to proportion has been dispensed with in order to increase the clearness.

(2) There are shown:

(3) FIG. 1a-d layer structure at different times in the production of pigments by means of a crack-forming layer;

(4) FIG. 2a, b two different examples of cracks in a crack-forming layer in a top view;

(5) FIG. 3 time course of crack formation in a configuration with several stripes of the crack-forming layer;

(6) FIGS. 4 and 5 detaching the pigments from the substrate with the aid of an intermediate substrate; and

(7) FIG. 6 use of nucleus points for the crack formation in the cross-section of the layer structure and for three different pigment shapes in a top view.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

(8) The production of pigments with narrow size distribution by means crack templates is hereinafter described using various examples.

(9) A crack template here means a layer on a carrier foil (e.g. PET) that has a network of continuous cracks so that the entire layer ultimately consists of individual islands. This crack template is metallized, at the island edges the metallization tearing off due to the height difference and the island size thus determining the pigment size. The pigment layer is structured by the crack formation.

(10) FIG. 1a shows a carrier foil 2 comprising a carrier layer 21 and an optional release layer 22. As shown in FIG. 1b, a continuous crack-forming layer 3 is applied to the carrier foil 2, in which cracks 32 form so that pigment islands 31 arise.

(11) As shown in FIG. 1c, a pigment layer 4 is applied onto the crack-forming layer 3. The pigment layer 4 comprises pigment sections 41 located on the pigment islands 31. In addition, the pigment layer comprises pigment residues 42, which are arranged in the cracks 32, which lie on the carrier foil or its release layer 22. The pigment layer 4 can be or comprise a metallization. The pigment layer may comprise several partial layers, in particular symmetrical multilayer constructions. For example, the pigment may comprise as partial layers: one or more reflector partial layers, one or more dielectric partial layers, and one or more absorber partial layers, for example in a construction with absorber-dielectric-reflector, dielectric-absorber-dielectric, dielectric-reflector-dielectric, or absorber-dielectric-absorber.

(12) In order to obtain the pigments, the crack template is either detachable from the foil (the crack template detaches from the foil but remains connected to the other pigment layers), or the crack template itself is water-soluble or soluble in another solvent so that, in the present case after the separation of the substrates, it dissolves and releases the pigment.

(13) Thus, two pigment types can be produced: pigments consisting of a first pigment partial layer, such as for example a vapor-deposited metallization, and of the crack-forming layer; or pigments that consist only of the pigment layer, such as a vapor-deposited metal layer (without a crack-forming layer).

(14) FIG. 1d shows a plurality of pigments 10, 11. The pigments 10 comprise only the pigment layer 4, i.e. where applicable, also the partial layers thereof. The pigments 11, on the other hand, comprise both the pigment layer 4 or the partial layers thereof and the crack-forming layer 3. The shape and size of the pigments 10, 11 correspond to the shape and size of the pigment islands 31 (or the pigment sections 41).

(15) The crack-forming layer may contribute to the stability of the pigments or the crack-forming material may possess functional properties (e.g. fluorescent dyes or magnetic particles).

(16) Different possibilities are known to produce the crack template.

(17) In a first implementation, a dispersion applied over the full area of a carrier foil forms at a sufficiently high minimum film formation temperature (MFT>50° C.) cracks during physical drying. The dispersion consists of particles dispersed in water and of organic-polymer nature (e.g. based on polyacrylates, polystyrenes, etc.) or inorganic nature (e.g. SiO2, TiO2, Al2O3, etc.) or mixtures thereof. To ensure solubility of the crack template in water, water-soluble compounds can be added (e.g. sugar molecules, starch or polyethylene glycols etc.).

(18) In another embodiment, a crack template is produced by means of the sol-gel technique. Here, alcoholates of metals and non-metals are employed, which under hydrolysis and condensation reactions form sol particles. Ultimately, they form a gel which in thin layers tends to crack formation during drying.

(19) In another embodiment, a brittle UV lacquer with high shrinkage is applied all-over onto a carrier foil. During radiation curing, cracks form throughout due to shrinkage.

(20) This crack template can, for example, be metallized to obtain the pigments. Ideally, the UV lacquer is designed such that it detaches by itself in water (water-soluble UV lacquers). For water-insoluble UV lacquers, a water-soluble intermediate layer is conceivable for detaching the pigments from the starting foil in water. On the carrier foil 2, then a corresponding release layer 22 is provided. The release layer 22 is soluble in a solvent, preferably in water as a solvent or alternatively in an organic solvent.

(21) Likewise, a counter laminating foil with glue can detach the pigments from the carrier foil, the glue being subsequently dissolved and thus releasing the pigments. This variant will be described below in more detail with reference to FIGS. 4 and 5.

(22) The control of crack formation is decisive for the size distribution and shape of the pigments and depends on the chosen production method of the crack template. In the case of physically drying dispersions, adjusting the island size (=pigment size) is effected via the known parameters such as minimum film formation temperature, layer thickness, particle size, additives or drying conditions.

(23) FIG. 2a shows an image of a crack template, where the cracks form islands of a size from a size region. The island size and thus the pigment size is <100 μm, in particular in the region of 10 to 30 μm (areas of 100 to 900 μm.sup.2).

(24) In addition, it is known that the first generation of cracks tears perpendicularly from the edge of the printed image inwards, whereupon the second generation of cracks now arises parallel to the edge of the printed image and thus between the first generation of cracks. The ladder-like crack template resulting therefrom leads to rectangular islands or pigments. FIG. 2b shows the image of a corresponding crack template having slightly larger islands. The pigment size here is also below 100 μm, but rather in the region of 20 to 60 μm (areas of 400 to 3600 μm.sup.2).

(25) However, this effect decreases with increasing distance from the edge of the printed image. If only rectangular islands are desired, the foil is printed in stripes.

(26) FIG. 3 shows three stripes of a crack-forming layer 3 on the carrier 2. For illustration purposes, in the figure the phases of drying and crack formation are represented from top to bottom. The time arrow t symbolizes that a temporal course from top to bottom is represented here. The wet crack-forming layer 3 is still free of cracks. Upon drying, first cracks 32a arise from the edge of the stripe inwards. The cracks 32b of the first generation then extend from edge to edge across the stripe. Cracks 32c then arise parallel to the edge. The dry crack-forming layer comprises the almost rectangular pigment islands 31 and the cracks 32 arranged therebetween.

(27) Hexagonal islands and thus pigments are also possible by other means.

(28) For crack templates based on UV lacquers, a predetermined breaking point can be introduced during radiation curing by means of suitable structures on an embossing tool. The embossing tool presses e.g. two notches into or through the UV lacquer (cf. nanoimprinting), whereby after radiation curing a crack is initiated at the shortest distance between the two notches due to the shrinkage. By a certain arrangement of the notches the cracks can now be controlled in targeted fashion in lines and gratings.

(29) FIG. 6 in the top row shows a notch 62 in the crack-forming layer which is arranged on carrier substrate 2. The notch 62 serves only as a nucleus point for the crack formation and can therefore be smaller, in particular narrower and shorter, than the later crack 32. Likewise, it is sufficient when the notch 62 only partially extends into the crack-forming layer 3. The pigment layer is applied onto the crack-forming layer so that the pigment sections 41 arise.

(30) Due to the variety of the arrangement of notches to each other and the type of the notches themselves, there is given a variety of shapes for the islands and therefore pigments.

(31) In the second row of FIG. 6, triangular edge notches 62a are used to generate linear cracks 32 so that rectangular pigments 10a arise. The third row shows that by means of a corresponding arrangement of star-shaped notches 62b there can be produced square pigments 10b.

(32) Of course, by this method there can also be produced hexagonal pigments 10c very easily by notches 62c generating cracks 32 at angles of 120° to each other, similar to a three-pointed star.

(33) The pigment layer or one or more of the partial layers are in particular vapor-deposited, e.g. by means of PVD coating. In doing so, the previously described partial layers or sublayers of the partial layers are applied. Alternatively, a partial layer, in particular a metallic layer, could also be applied by gravure or flexographic printing method.

(34) The substrate can also be reused for the present method, optionally after the residual sections have been detached from the substrate. On the substrate having relief structure, the first foil, crack-forming layer and pigment layer can be created several times in a row. Thus, material costs and process steps can be saved.