Method for producing pigment fragments with a predefined internal and/or external contour, and pigment fragments

Abstract

A method for producing pigments having a specified contour, comprises the steps of creating a pigment layer on a starting substrate; detaching from the starting substrate; and structuring the pigment layer into a plurality of the pigments; characterized by bringing into contact the pigment layer with an intermediate substrate, wherein the pigment layer adheres at least in sections to the intermediate substrate; and separating intermediate substrate and starting substrate.

Claims

1. A method for producing pigments having a specified contour, the method comprising the steps of: creating a pigment layer on a starting substrate; providing an intermediate substrate to the pigment layer, such that the pigment layer adheres at least in sections to the intermediate substrate; separating the intermediate substrate from the starting substrate; structuring the pigment layer into a plurality of the pigments; and detaching the plurality of pigments from at least one of the intermediate substrate and the starting substrate.

2. The method according to claim 1, wherein for the step of detaching and/or structuring the pigments are protected against breaking of the pigments by the contact with the intermediate substrate.

3. The method according to claim 1, wherein as the specified contour the pigments have a specified outer contour and/or a specified internal contour.

4. The method according to claim 1, wherein the pigment layer is structured into the plurality of the pigments by the step of separating the intermediate substrate and the starting substrate.

5. The method according to claim 1, wherein the pigments are detached by the step of separating the intermediate substrate from the starting substrate.

6. The method according to claim 1, wherein after separation of the intermediate substrate from the starting substrate the plurality of the pigments are present on the starting substrate and are subsequently detached from the starting substrate.

7. The method according to claim 1, wherein the pigment layer is structured prior to the step of separation.

8. The method according to claim 1, wherein in the starting substrate and/or the intermediate substrate a relief structure is created which specifies the specified contour of the pigments.

9. The method according to claim 8, wherein the relief structure is effected by embossing a curable, by means of UV light, embossing layer of the starting substrate and/or of the intermediate substrate.

10. The method according to claim 1, wherein an adhesion-determining structure is created on the pigment layer, the starting substrate and/or the intermediate substrate, which specifies the specified contour of the pigments.

11. The method according to claim 1, wherein the pigments contain contains a motif arranged in exact register to the specified contour of the pigments and/or has a contour which is independent of the specified contour.

12. The method according to claim 11, wherein in the step of creating the relief structure the motif is at least partially co-created, as an optically variable embossed structure; wherein in the starting substrate and/or the intermediate substrate a relief structure is created which specifies the specified contour of the pigments.

13. The method according to claim 12, wherein the relief structure is effected by embossing a curable, by means of UV light, embossing layer of the starting substrate and/or of the intermediate substrate.

14. The method according to claim 1, wherein the pigment layer comprises at least one continuous partial layer and an additional, non-continuous partial layer.

15. The method according to claim 1, wherein the pigment layer is created on a cured lacquer layer of the starting substrate, which is arranged on a foil layer of the starting substrate; and/or adheres to a lacquer 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, 1b two different pigments with specified contour in top view;

(4) FIG. 2a, b, c pigment layer, structured pigments and loose pigments each in top view;

(5) FIG. 3 a relief-structured starting substrate with pigment layer prior to being brought into contact with an intermediate carrier substrate;

(6) FIG. 4 the starting substrate and the intermediate carrier substrate of FIG. 3 after separation of the substrates;

(7) FIG. 5 an adhesion-structured starting substrate with pigment layer prior to being brought into contact with an intermediate carrier substrate;

(8) FIG. 6 the starting substrate and the intermediate carrier substrate of FIG. 5 after separation of the substrates;

(9) FIG. 7a, 7b a multilayer pigment of specified contour in top view and in cross-section; and

(10) FIG. 8 a production device for pigments.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

(11) The pigments 1 shown in FIGS. 1a and 1b have different outer contours 5. The Pigment 1 in FIG. 1b additionally comprises an internal contour 6 which limits an opening in pigment 1. The contour 5, 6 cannot be recognized by the viewer without aids due to the pigment size which is in the region from 100 nm to 100 μm. In this respect, the pigment can be used as a hidden security feature.

(12) Both pigments comprise an additional motif 8, which is arranged in exact register to a contour of the pigment. The contour of the additional motif 8 in FIG. 1a follows the outer contour 5 of the pigment at a specified distance. In FIG. 1b, the (here round) contour of the additional motif follows the (round) internal contour 6 of pigment 1. However, the additional motif may also have its own contour independent of the pigment contour.

(13) FIG. 2a shows a top view of a starting substrate with pigment layer 21. A continuous pigment layer 210 has been created on a pre-structured starting substrate. In accordance with the pre-structuring, the pigment layer 210 comprises a plurality of pigment sections 211 and the residual sections 212 located between the pigment sections.

(14) In the configuration shown in cross-section in FIG. 3, the starting substrate 20 is provided with a relief as a pre-structuring. The relief structure is formed by recessed sections 217. The starting substrate 20 comprises at least one starting substrate layer 215, in particular in the form of a PET foil, and an optional embossing lacquer layer 216. In a variant that is not represented but is preferred, the relief structure is executed only in the embossing lacquer layer 216. The pigment layer 210 created on the starting substrate is a continuous layer. In less advantageous configurations, the pigment layer is created to be already structured, for example by recessions that are accordingly wide and/or deep. Corresponding to the relief structure, pigment sections 211 and residual sections 212 of the pigment layer form. The pigment sections 211 lie on the raised sections of the relief structure and the residual sections 212 in the recesses 217. As can be recognized in FIG. 2a, the pigment sections 211 are already pre-structured according to the contour of the pigments 1. The residual sections 212 located between the pigment sections 211 have a contour inverse to the pigments.

(15) Also shown in FIG. 3 is an intermediate substrate 30 which comprises an intermediate substrate layer 315, for example a further PET foil, and an unstructured adhesive layer 316. As indicated by the arrow, the intermediate substrate layer 30 is brought into contact with the pigment layer 210. In this step, pressure can be exerted and the temperature can be increased. The pigment layer 210 adheres, due to the relief structure, with its pigment sections 211 to the adhesive layer 316 of the intermediate substrate. The residual sections 212 do not come into contact with the adhesive layer 316 at all or at least not sufficiently enough to adhere thereto.

(16) The starting substrate and the intermediate carrier substrate are again separated from each other, as indicated in FIG. 4, again by an arrow. FIG. 4 shows the starting substrate including residues of the pigment layer 23 and the intermediate substrate including pigment sections 33 already in the separated state.

(17) When the two substrates are separated, the pigment layer breaks. It is structured into the individual pigments, which are present as pigment sections 331. The pigment sections 331 adhere to the adhesive layer 316 of the intermediate substrate. Between the pigment sections 331, there are free intermediate substrate surfaces 338 on the intermediate substrate 33—as can be seen in FIG. 2b in top view. After separation, the residual sections 232 of the pigment layer are still present on the starting substrate 215, 216.

(18) As indicated in FIG. 2c, the pigment sections 331 are then detached from the intermediate substrate and are then present as a plurality of pigments 1. The pigments 1 are further processed into a printing ink.

(19) At the time of structuring the pigment layer into pigment sections—by breaking and detaching the pigment sections from the starting substrate—the pigment sections are protected against breakage by the intermediate substrate. The pigment sections are not exposed to any unnecessary force and can thus be designed substantially thinner or more filigree than conventional ones.

(20) FIG. 8 shows a device for producing pigments 1 starting out from a starting substrate having pigment layer.

(21) From a first starting substrate layer roll 88, the starting substrate having pigment layer 21 is unwound. From an intermediate substrate roll 87, an intermediate substrate 31 is unwound. The unwound intermediate substrate 31 is preferably provided with an adhesive layer, for example printed or sprayed. The substrates are brought into contact with each other, for example with the aid of a contact roller 82. The pigment layer of the starting substrate 22 adheres to the adhesive layer of the intermediate substrate 32. The substrates are separated at a separating roller 83, for example. The intermediate carrier web having pigment sections 33 is guided to a detachment unit 84. In the detachment unit 84, the pigments 1 are detached from the intermediate carrier web 315, for example by dissolving the adhesive layer 316 of the intermediate carrier web.

(22) The plurality of the pigments 1 can now be further processed into printing ink. The starting substrate having pigment layer residues 23 can be freed from the pigment layer residues in an optional further detachment unit 86 and rewound on a second starting substrate roll 89. The detachment unit 86 can dissolve the pigment layer residues 23 on the starting substrate (e.g. detach them by chemically decomposing and/or mechanically crushing). The starting substrate and/or the intermediate substrate can be reused for the production of further pigments.

(23) The device shown (with a separating roller) enables a continuous structuring, in particular a continuously effected breaking of the pigments out of the pigment layer. Other variants are conceivable, for example with a stamp, which execute the (contacting and) separating of the substrates one after the other for independent substrates—rather as shown in FIG. 3—or respectively for sections of a substrate web one after the other.

(24) The present method can be divided into several substeps.

(25) Step 1 (optional): Coating a starting substrate layer or a carrier material, e.g. a PET foil, with an embossing lacquer.

(26) The embossing lacquer layer is preferably a lacquer with low adhesion to the pigment layer. In particular, the embossing lacquer can be selected such that a (PVD) layer can be vapor-deposited thereon in a separable (or mechanically detachable) manner. The embossing lacquer can be a UV-curable lacquer or a thermoplastic embossing lacquer.

(27) Step 2: Pre-structuring the starting substrate layer, in particular with a relief structure.

(28) The relief structure is incorporated into the embossing lacquer by embossing (roll-to-roll) binary structures which correspond to the outline of the effect pigments. Depending on the embossing lacquer used, the embossing is effected under the influence of UV radiation or heat in order to generate and fix the structures in the lacquer. The depth of the embossed structure depends on the thickness of the effect pigments: for thin pigments (e.g. 300 nm) a depth of approx. 1 μm or more is sufficient. Thicker pigments require deeper embossed structures. The flanks of the binary embossed structure are sufficiently steep so that the pigment layers can be broken there later.

(29) If the pigments are to have not only their contour but also additional information later on, these can be embossed on the raised and/or recessed regions of the binary embossing as a surface modulation. This is preferably done during the same embossing step, i.e. the embossing tool contains the deep binary structure for defining the pigment outlines and at the same time the flatter surface structure for achieving additional, for example optical effects in the pigments. This procedure has the great advantage that the surface modulations effecting the optical effects are perfectly registered to the contour of the effect pigments. For example, in this way diffractive letterings can be placed exactly in the center of pigments.

(30) As an alternative to embossed lacquer, a release lacquer of suitable thickness which is applied in structured manner, for example printed, can also be used. A disadvantage of this variant, however, would be that with a printing method there can be achieved only lower resolutions than with an embossing method.

(31) Step 3 (optional): If no lacquer was used in step 1, on which the PVD layer deposited subsequently adheres only weakly anyway, as a third step there is required a measure which leads to the fact that no strong adhesion between the embossing lacquer and the coating deposited in the next step comes about. For example, an anti-adhesive layer can be applied.

(32) Step 4: Creating of the pigment layer on the embossed structure, including all partial layers of the pigment layer.

(33) The pigment layers are, in particular, vapor-deposited, e.g. by means of PVD coating of the embossed structure. In doing so, the previously described partial layers or sublayers of the partial layers are applied. It is important that the layers remain detachable from the embossed structure. Suitable methods are, for example, PVD methods, of which thermal vapour deposition is particularly preferred, as due to the directed particle flow it leads to a lower coating of the vertical walls between the raised and recessed regions of the binary embossing. This facilitates the separation of the coating later upon separating the substrates.

(34) Alternatively, a partial layer, in particular a metallic layer, could also be applied by gravure or flexographic printing method. Because of the necessary predetermined breaking point, solvents or water-based inks having metal flakes are preferably utilized, which preferably have a thickness of less than 200 nm, especially less than 150 nm.

(35) Step 5: Supplying a foil which is coated with tacky and possibly deformable lacquer as an intermediate substrate.

(36) Step 6: Bringing the pigment layer into contact with the intermediate substrate. The intermediate substrate is laminated with the embossed and coated first foil, the starting substrate, under the influence of pressure and, where applicable, at an increased temperature. The components of the coating which are located on the raised regions of the binary embossed structure, bond firmly with the tacky lacquer. A possibly present surface modulation, for example a holographic grating, will be embossed into the tacky lacquer. The pigment layer in the recesses of the embossed structure preferably does not touch the adhesive layer.

(37) Step 7: Upon separating or separatingly winding the two foils, the sections of the coating detachably connected to the raised regions of the binary embossing are transferred to the tacky lacquer of the second foil—the intermediate substrate. However, those sections of the coating which are located in the recesses of the binary embossing remain on the first foil—the starting substrate.

(38) Step 8: Finally, the pigments, which are well defined in their outline form, are detached from the respective carrier foil, for example by partially dissolving or dissolving the lacquer supporting them in a suitable solvent. The pigments being in detachment are subsequently further processed by suitable steps. Attention has to be paid that they do not clump together.

(39) Processed as pigments are the detached sections of the pigment layer transferred onto the intermediate substrate, the second foil.

(40) The starting substrate, the first foil, with the remaining pigment layer sections could be disposed of. As an alternative to disposal, also the coating components remaining on the first foil could be further processed into pigments (without specified contour or with negative contour). It is therefore also possible to process both the pigment layer sections on the first and the second foil into different pigments.

(41) However, the starting substrate can also be reused for the present method, optionally after the residual sections have been detached from the starting substrate. On the starting substrate having relief structure, the first foil, a pigment layer can be created (structured and . . . ) several times in a row. Thus, material costs and process steps can be saved, because the embossing lacquer and the embossing do not always have to be executed anew. A UV-curable material is preferably used as an embossing lacquer, into which the structures are permanently embossed. In particular, it can thus be achieved that the increased temperature in the laminating step does not affect the relief structure.

(42) In the configurations hitherto described, the starting substrate was provided with a relief structure in which the pigment sections with the specified contour form on the rises. Alternatively, the relief can also be designed inversely. It may comprise areal recessions having the specified contour for the pigment sections and rises for the residual sections. When separated the residual sections detach from the starting substrate and adhere to the intermediate substrate. The pigment sections (in the recesses) remain on the starting substrate and are detached from the starting substrate only after the separation of the substrates. Ultimately, in a less advantageous configuration it is even conceivable to provide the intermediate substrate layer with the relief structure, so that the (non-pre-structured) pigment layer remains adherent to the adhesive layer of the intermediate substrate in the region of the rises of the relief. The rises may here alternatively correspond either to the pigment sections having the specified contour or to the residual sections.

(43) The pigment sections 331 arranged on the intermediate substrate 33 in FIG. 4 (or alternatively the pigment sections arranged on rises of the intermediate substrate) may optionally be provided with a further partial layer. The further partial layer may be supplied all-over and advantageously applied only onto the pigment sections 331 by means of a contact printing method (kiss print). To the free sections 338 of the adhesive layer the partial layer is not transferred, since only the pigment sections 331 come into contact with the partial layer. The contact printing method here uses implicitly the existing differences in height of the pigment sections on the substrate as a printing master. The pigment sections including their further (backside) partial layer are detached from the intermediate substrate.

(44) Basically, also partial layers of the pigment layer could be created using a contact printing method. For example, a further pigment partial layer can be printed onto, for example vapor-deposited, existing pigment partial layers that are present on the starting substrate having a relief structure. The further partial layer (supplied over the full area) here is applied analogously only onto the raised sections of the pigment layer.

(45) In the configuration according to FIGS. 3 and 4, the pigment layer is pre-structured by a relief structure in order to specify the contour of the pigment. FIGS. 5 and 6 show alternative configurations in which an adhesion-determining layer is structured in order to define the contour.

(46) The starting substrate having pigment layer 21 in FIG. 5 comprises a substrate layer 516, 517, 518 and a pigment layer 510 which for its part contains two partial layers 513, 514. On the PET foil 515 a structured adhesion-determining layer is provided which can be configured as a continuous anti-adhesive layer 516 with adhesive layer sections 517 or as an adhesive layer 518 arranged on the substrate layer 515 (or the anti-adhesive layer 516). The pigment layer 510 comprises the continuous pigment partial layer 513 and a non-continuous (but already structured) pigment partial layer 514. Pigment sections 511 of the pigment layer and residual sections 512 are specified by the adhesion structure 517, 518.

(47) The starting substrate 21 is brought into contact with the adhesive layer 316 on the intermediate substrate, as symbolically shown by the arrow in FIG. 5. Here, the adhesive layer 316 can also come into contact with the residual sections 512, i.e. not only the pigment sections. The adhesive layer 316 and the adhesive structure 517, 518 are coordinated to each other such that the pigment layer adheres more strongly to the adhesive structure 517, 518. The pigment layer in turn is structured into the pigments (pigment sections) when the substrates are separated.

(48) FIG. 6 shows the starting substrate having pigment layer residues 23 and the intermediate substrate including pigment sections 33 after separating the substrates. Residual sections 532 of the pigment layer remain adhered to the adhesive structure 517, 518. The pigment sections 531 remain adherent to the intermediate substrate, i.e. upon separation they have detached from the starting substrate or its anti-adhesive layer 516. Free sections 338 of the bonding layer 316 remain between the pigment sections. The pigment sections 531 comprise the two partial layers 513, 514. The pigment sections 531 (after the separation) are detached from the intermediate substrate layer 315, 316 and further processed as pigments, in particular into a printing ink.

(49) If the solvent used for detaching the pigment sections (e.g. water) is compatible with the binder of the printing ink, the dispersion can also be added to a printing ink immediately. Where applicable, excess solvent can be drawn off by means of a vacuum mixer. In another variant, the pigments 1 are dried by means of a freeze dryer (solvent drawn off) and the dry pigments are mixed into a printing ink.

(50) In FIGS. 7a and 7b, a pigment 1 is shown in cross-section and in top view. The pigment comprises—like the pigment shown in FIGS. 5 and 6—two pigment partial layers 701 and 702. Both pigment partial layers can in turn be formed by sublayers, such as for example a three-layer construction with absorber, dielectric and absorber (or reflector). The second pigment layer 702 has a breaking edge 705, which corresponds to the outer contour of pigment 1. The first pigment partial layer 701 is provided as additional information 708 having a contour on pigment 1 that is independent of the outer contour. Only in FIG. 7b it is indicated that pigment 1 may also have—for example two—openings 706.

(51) In the following, variants of adhesion-determining pre-structurings are discussed that can be used analogously to the two variants represented in FIGS. 5 and 6. The structured adhesion-determining layer can be designed as an adhesive layer or as an anti-adhesive layer. It can be applied over the full area and removed in sections by means of laser irradiation, in particular either in accordance with the pigment sections or with the residual sections. Alternatively, the adhesion-determining layer is applied in sections by means of printing, i.e. only in the corresponding (pigment or residual) sections. The adhesion-determining layer may be formed by a lacquer which as an embossing lacquer preferably comprises an “optical” embossing which generates additional information in the pigment.

(52) In another optional variant, a structured print, respectively in pigment shape, i.e. in the later pigment sections, is applied onto an (untreated) layer 516 that does not adhere well. In a second process step, the substrate layer printed in a structured manner is pre-treated by means of a pretreatment plant (plasma, open-air plasma, flame pretreatment or corona pretreatment plant). The non-adhesive layer 516 is converted into an adhesive layer by the pretreatment. The previously printed sections in pigment shape here serve as a template for the pre-treatment. Accordingly, there arise adherent sections 517 on which the residual sections 512 of the pigment layer remain adhered upon separation, while the pigment sections 511 upon separation detach from the layer 516 which still does not adhere well.

(53) The adhesion-determining layer preferably has a thickness of at least 1 μm. Thus—analogous to the relief structure—predetermined breaking points are generated in the pigment layer created thereon, which for example has a thickness of 30 nm to 4 μm. It is also possible to apply an etching or washing ink by means of a printing method in order to structure the adhesion-determining layer. Rather only theoretically, it would be conceivable to structure the pigment layer directly by means of the washing or etching ink. However, the present method unfurls the most important advantages with still unstructured pigment layers.

(54) Another production method for pigments with narrow size distribution could be effected by means of crack template. 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. Ideally, the pigment layer is structured by the crack formation. The present, more relevant case is that the crack formation does not lead to a complete separation of the pigment layers.

(55) 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 it dissolves and releases the pigment—in the present case after the separation of the substrates.

(56) 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).

(57) 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).

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

(59) 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. 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. This crack template can be further 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. A counter laminating foil with glue detaches the pigments from the carrier foil, the glue being subsequently dissolved and thus releasing the pigments.

(60) 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. 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. 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. Hexagonal islands and thus pigments are also possible.

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

(62) Also pigment sections (or islands) created with the aid of a crack template can be detached from the starting substrate and preferably structured at the same time, according to the methods described in FIG. 3, 4, 5, 6 or 8.