Method for producing a micro-optical display arrangement and micro-optical display arrangement

Abstract

The invention relates to a method for producing a micro-optical display arrangement, which has a coloured motif layer (26) arranged in a motif plane and has a plurality of multi-coloured micro-motif elements (28-1, 28-2) and a focusing element grid (24) made of a plurality of micro-focusing elements for viewing the micro-motif elements (28-1, 28-2), wherein in the method for producing the coloured motif layer (26) - a coloured layer (200; 204; 212) that is light-sensitive at least in some regions is arranged in the motif plane and is exposed to exposure radiation (B1; B2; B) through the focusing element grid (24) and is thereby modified in the exposed regions (202; 206; 218). The solubility of the light-sensitive layer (e.g. photoresist) can be changed and then removed in regions. The laser radiation can remove regions of the light-sensitive layer or change its colour, reflection and / or transmission properties. The motif layer can have recesses (34, 36) of different depths that can be filled with two different colours (40, 42).

Description

[0001] Method for producing a micro-optical display arrangement and micro-optical display arrangement

[0002] The invention relates to a method for producing a micro-optical display arrangement which has a coloured motif layer arranged in a motif plane with a plurality of differently coloured micro-motif elements and a focusing element grid comprising a plurality of micro-focusing elements for viewing the micro-motif elements.

[0003] Data storage devices, such as valuables or identification documents, as well as other valuable items such as branded goods, are often provided with security elements for security purposes. These elements allow verification of the authenticity of the data storage device and also serve as protection against unauthorized reproduction. These security elements can, for example, take the form of a security thread embedded in a banknote, a cover foil for a banknote with a hole, an applied security strip, a self-supporting transfer element, or even a feature area printed directly onto a valuable document.

[0004] Security elements with a viewing-angle-dependent or three-dimensional appearance play a special role in authenticity assurance, as these cannot be reproduced even with the most modern copying machines. For this purpose, the security elements are equipped with optically variable elements that convey a different image impression to the viewer at different viewing angles. For example, depending on the viewing angle, they display a different color or brightness impression, a different perspective view, and / or a different graphic motif.

[0005] For some time now, micro-optical systems, for example in the form of so-called moiré magnification arrays, have also been used as security features. In this context, moiré magnification refers to a phenomenon that occurs when a grid of identical image objects is viewed through a lenticular screen with approximately the same pitch. As with any pair of similar screens, this results in a moiré pattern, with each of the moiré fringes appearing as a magnified and rotated image of the repeated elements of the image screen (see "The moiré magnifier," MC Hutley, R. Hunt, RF Stevens, and P. Savander, Pure Appl. Opt. 3 (1994), pp. 133-142).

[0006] In addition to moiré magnification, often referred to as "synthetic magnification," moiré magnification arrangements typically exhibit optical variability, such as motion or depth effects, which also result from the interaction of the lens grid with the subject grid.

[0007] Typical security features equipped with microlenses have a lenticular array of periodically arranged spherical or lenticular microlenses, which, for applications in security threads or LEAD (Longlasting Economic Anticopy Device) strips, have lateral dimensions of less than 25 µm. This limitation results from the thickness restrictions of banknotes, which in turn affect the specifications of the security features to be applied.

[0008] Due to these small dimensions, the production of such security elements is very challenging, which is why the currently common microlens security features usually offer only very limited design options. For example, the microlenses in foil elements, such as embedded security threads, transferred foil elements, or applied foil elements or patches, often have a size of only about 25 μm or less. The small microlens size, the achievable focus size in the range of about 1 μm, and the line width of the microstructures achievable with current processes, also in the range of about 1 μm, combine to present only very simple motifs to the viewer.

[0009] Due to these difficulties, the well-known and frequently used foil-based micro-optical security features on banknotes are currently generally only available in one color, which further severely limits designers' design freedom. The motifs are often difficult to recognize, and the solid-colored areas appear rather dull and unattractive to the viewer.

[0010] While multicolored designs are visually more attractive, the multicolored microlens features known to date have several disadvantages. If the differently colored microstructure elements are arranged in vertically separated planes, for example, a long-range phase relationship between the microstructure elements is difficult or even impossible to ensure during manufacturing. Other designs are essentially multicolored, but the viewer always sees only a single color at a specific point in the pattern, regardless of the viewing angle.

[0011] In contrast to the films used to protect documents, there are already postcards in which colorful images flip or display three-dimensional effects depending on the viewing angle. Since these products do not have comparable, severe restrictions regarding the thickness of the product as with the films used on banknotes, the rod lenses used are considerably larger (typically on the order of 150 µm or more), and the substrate used is highly stable against distortions that occur during processing, so that the microstructures and the resulting effects can be created using printing processes. These processes cannot simply be transferred to the size ratios common in banknote technology, with significantly smaller microlens diameters.

[0012] Based on this, the invention is based on the object of avoiding the disadvantages of the prior art and in particular of providing an advantageous method for producing multi-coloured micro-optical display arrangements, as well as advantageous micro-optical display arrangements.

[0013] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims. The invention contains a method for producing a micro-optical display arrangement which has a colored motif layer arranged in a motif plane and comprising a plurality of differently colored micro-motif elements, and a focusing element grid comprising a plurality of micro-focusing elements for viewing the micro-motif elements. In this case, it is provided that in the method for producing the colored motif layer, a colored layer which is at least partially light-sensitive is arranged in the motif plane, and the light-sensitive layer is exposed to exposure radiation through the focusing element grid and is thereby modified in the exposed regions.

[0014] In this description, the term "micro-optical display arrangement" includes not only moiré magnification arrangements and so-called modulo magnification arrangements, but also lenticular images without a magnification effect. In a moiré magnification arrangement, the micromotif elements of a unit cell are typically reduced-size images of the target images to be displayed, which fit entirely within a cell. In a modulo magnification arrangement, however, the micromotif elements of the cells of the motif image are each imaged by a modulo operation as incomplete sections of the target images to be displayed. While the micromotif elements in moiré magnification arrangements are generally identical, this is not the case with the micromotif elements of modulo magnification arrangements, since several micromotif elements interact to display a complete target image.The basic principle of these micro-optical display arrangements is explained in WO 2009 / 000528 A1, the disclosure of which is incorporated into the present description in this respect. Unlike moiré and modulo magnification arrangements, lenticular images are oriented toward an unscaled display of target images, i.e., a display that is neither enlarged nor reduced in size. Preferably, the exposure radiation changes the solubility of the light-sensitive layer in a developing medium, and the light-sensitive layer is developed in a development step after exposure, thereby removing it in certain areas.

[0015] In another, equally advantageous variant of the invention, the light-sensitive layer is partially removed or its color, reflection and / or transmission properties are changed by the exposure radiation, in particular laser radiation.

[0016] Advantageously, the steps of arranging a colored layer which is at least partially light-sensitive in the motif plane and of exposing the light-sensitive layer through the focusing element grid to exposure radiation for modifying the light-sensitive layer are carried out two or more times with layers of different colors and with exposure from different spatial directions.

[0017] In a particularly advantageous embodiment, it is provided that a negative photoresist is applied as a colored layer that is at least partially light-sensitive, the applied negative photoresist is exposed to exposure radiation through the focusing element grid and is thereby made insoluble in the exposed areas, the negative photoresist is then developed in a development step and is removed in the non-exposed areas, wherein the above-mentioned steps of application, exposure and development are carried out two or more times with a photoresist of different color and with exposure from different spatial directions.

[0018] In another, likewise particularly advantageous embodiment, it is provided that a positive photoresist is applied as a colored layer that is at least partially light-sensitive, the applied positive photoresist is exposed to exposure radiation through the focusing element grid and thereby becomes soluble in the exposed areas, the positive photoresist is then developed in a development step and is removed in the exposed areas, the recesses formed by the removal of the photoresist are filled with a color and the positive photoresist is optionally finally removed without impairing the color filling, wherein the aforementioned steps of application, exposure, development, color filling and optionally stripping are carried out two or more times with different color fillings and with exposure from different spatial directions.

[0019] Preferably, in order to produce the colored motif layer, an embossing with a plurality of structural elements is additionally introduced into an embossing lacquer layer in an embossing step, wherein the structural elements are all produced with the same embossing tool in a single embossing step, so that the embossed structural elements are all in a defined phase relationship predetermined by the embossing tool.

[0020] A "defined phase relationship" of the structural elements means that the position of the structural elements, especially of the structural elements visible in different colors, relative to each other across the surface of the display arrangement is predetermined by the embossing tool and does not vary unintentionally.

[0021] Only by establishing a defined phase relationship extending across the entire surface of the display arrangement can synchronous color and motif flips be created, for example, in which the micromotif elements of one display are colored in a first color, while the micromotif elements of the other display appear in the corresponding second color. The fixed phase relationship between these differently colored and nested microstructures ensures that a specific section of a display arrangement can be seen in only a single color at a specific viewing angle. This applies to all surface sections of the entire display arrangement.If, in addition, a defined phase relationship to the arrangement of the focusing elements is also maintained, which is particularly advantageous, the two differently colored displays can be seen in a uniform color and without any motif jump over the entire surface of the display arrangement, whereby the different displays appear at different spatial angles.

[0022] After the embossing step, a color layer in the form of a printing ink or a colored positive or negative photoresist is advantageously applied to the embossing lacquer layer in a processing step, so that the color layer completely or partially fills those of the structural elements which are formed in the form of depressions, and / or a color layer in the form of a printing ink or a colored positive or negative photoresist is applied over the entire area of ​​the embossing lacquer layer, and / or the embossing lacquer layer is provided with a metallization.

[0023] In an advantageous development of one of the methods containing an embossing step, it is provided that the structural elements are at least partially formed in the form of depressions in the embossing lacquer layer, and in a processing step, in a first sub-step, a color layer in the form of a positive photoresist of a first color is applied to the embossing lacquer layer, so that the color layer fills those of the structural elements that are formed in the form of depressions, so that the embossing lacquer layer filled with color in partial areas forms the said colored layer arranged in the motif plane and at least partially light-sensitive, in a second sub-step, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby made soluble in the exposed areas, and the exposed photoresist is developed,so that the photoresist remains in a first partial area of ​​the depressions and is removed in a second partial area of ​​the depressions, and in a third partial step, a color layer of a second color is applied to the embossing resist layer and fills the second partial area of ​​the depressions, so that the first and second partial areas of the depressions each form microstructure elements that are visible with a different color.

[0024] Alternatively, in one of the methods containing an embossing step, it is provided that the structural elements are at least partially formed in the form of depressions in the embossing lacquer layer, and in a processing step, in a first sub-step, a color layer in the form of a negative photoresist of a first color is applied to the embossing lacquer layer, so that the color layer fills those of the structural elements that are formed in the form of depressions, so that the embossing lacquer layer, which is color-filled in partial areas, forms the said colored layer arranged in the motif plane and at least partially light-sensitive, in a second sub-step, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby made insoluble in the exposed areas, and the exposed photoresist is developed,so that the photoresist remains in a first partial area of ​​the depressions and is removed in a second partial area of ​​the depressions, and in a third partial step, a color layer of a second color is applied to the embossing resist layer and fills the second partial area of ​​the depressions, so that the first and second partial areas of the depressions each form microstructure elements that are visible in a different color. In an advantageous method variant, it is provided that in the embossing step, an embossing with a plurality of structural elements is introduced into the embossing resist layer, each corresponding to one of at least two different structural types with different physical properties, and in a processing step, the structural elements are selectively provided with at least one coloring material, utilizing the different physical properties of the respective associated structural type.wherein at least one coloring material is light-sensitive and forms the said colored layer arranged in the motif plane, which is at least partially light-sensitive, which is exposed to exposure radiation through the focusing element grid and is thereby modified in the exposed areas.

[0025] The structure types created in the embossing step can

[0026] comprise depressions with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer, which have different embossing depths, or i) comprise a depression with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer and ii) comprise a subwavelength grating, or i) comprise a depression with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer and ii) comprise a surface-enlarging relief structure, optionally sunk in a depression, or comprise linear gratings with parallel grating lines, which have different, in particular mutually perpendicular, orientations of the parallel grating lines.

[0027] Alternatively, it can be provided that in the embossing step a colored embossing lacquer layer of a first color is embossed without residual lacquer thickness, and the structure types produced in the embossing step represent embossing lacquer islands with steep sides and cover surfaces which essentially run to the surface of the embossing lacquer layer and which have different heights.

[0028] The invention also includes a micro-optical display arrangement, obtainable by a method of the type described, with a colored motif layer arranged in a motif plane with a plurality of differently colored micromotif elements and a focusing element grid consisting of a plurality of microfocusing elements for viewing the micromotif elements, wherein the microfocusing elements have a length and / or width of less than 30 µm, wherein the motif layer comprises a colored layer which is at least partially light-sensitive and which is removed in partial areas or has changed color, reflection and / or transmission properties in partial areas.

[0029] The motif layer advantageously comprises an embossed lacquer layer provided with an embossing comprising a plurality of structural elements, all of which are in a predetermined, defined phase relationship, and which are provided with at least one coloring material. The embossed lacquer layer, partially filled with color, preferably forms the aforementioned colored layer, which is at least partially light-sensitive.

[0030] Advantageously, spherical microlenses, aspherical microlenses, and lenticular lenses are considered as microfocusing elements, in which the light-sensitive layer can be exposed through the focusing element grid. According to a further aspect of the invention, however, it is also possible to use more general micro-viewing elements for viewing the micro-motif elements, which can also be used to modify the light-sensitive layer in specific areas. In addition to the microlenses already mentioned, micro-concave mirrors are particularly suitable as micro-viewing elements, but also pinhole diaphragms, slit diaphragms, pinhole or slit diaphragms equipped with mirrors, Fresnel lenses, GRIN lenses (Gradient Refraction Index lenses), zone plates, holographic lenses, Fresnel mirrors, zone mirrors, or other elements with a focusing or blocking effect.

[0031] This more general aspect of the invention includes a method for producing a micro-optical display arrangement comprising a colored motif layer arranged in a motif plane with a plurality of differently colored micro-motif elements and a viewing element grid composed of a plurality of micro-viewing elements for viewing the micro-motif elements. In the method for producing the colored motif layer, a colored layer that is at least partially light-sensitive is arranged in the motif plane, and the light-sensitive layer is exposed to exposure radiation in such a way that the micro-viewing elements spatially modulate regions of higher and lower radiation intensity in the light-sensitive layer, wherein the light-sensitive layer is modified only in the regions exposed to higher radiation intensity.

[0032] For example, when using concave micromirrors, the entire surface of the light-sensitive layer can be exposed from the concave side of the micromirror. Although the entire surface of the light-sensitive layer is transmitted by the exposure radiation, high radiation intensities only occur where the reflected light falls onto the light-sensitive layer in a bundled manner due to the focusing effect of the concave micromirror. The light-sensitive layer is advantageously chosen as a layer with a threshold effect, for example, as a photoresist, which only becomes soluble (positive resist) or insoluble (negative resist) upon exposure to a certain threshold intensity.A modification of the light-sensitive layer by a change in solubility therefore only takes place in areas exposed to higher radiation intensity, while the areas exposed to lower radiation intensity remain unmodified and do not change their solubility.

[0033] For advantageous embodiments of the method, the detailed explanations given for the more specific microfocusing elements apply accordingly. The more general aspect of the invention also includes a micro-optical display arrangement, obtainable by a method of the type just described, with a colored motif layer arranged in a motif plane, comprising a plurality of differently colored micromotif elements, and a viewing element grid comprising a plurality of microviewing elements for viewing the micromotif elements, wherein the microviewing elements have a length and / or width of less than 30 µm, wherein the motif layer comprises a colored layer that is at least partially light-sensitive, which is removed in partial areas or has modified color, reflection, and / or transmission properties in partial areas.

[0034] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0035] Shown are: Fig. 1 schematically a banknote provided with two security elements produced according to the invention,

[0036] Fig. 2 shows the structure and basic functioning of moiré magnification arrangements manufactured according to the invention,

[0037] Fig. 3-10 each illustrate in several partial images processes of a first process group,

[0038] Fig. 11 illustrates in several partial images processes of a second process group, and

[0039] Fig. 12 illustrates in several partial images an advantageous combination of methods of the first and second method group.

[0040] The invention will now be explained using the example of the production of micro-optical security elements for a banknote. Fig. 1 shows a schematic representation of a banknote 10 provided with two security elements 12 and 16 produced according to the invention. The first security element represents a security thread 12 that protrudes at certain window areas 14 on the surface of the banknote 10, while it is embedded in the intermediate areas inside the banknote 10. The second security element is formed by an adhesively bonded transfer element 16 of any desired shape. The security element 16 can also be in the form of a cover film arranged over a window area or a through opening in the banknote.

[0041] Both the security thread 12 and the transfer element 16 can contain, for example, a moiré magnification arrangement produced according to the invention as a micro-optical security feature. With reference to Fig. 2, the structure and basic functioning of such moiré magnification arrangements are briefly described below, followed by a series of exemplary embodiments for advantageous manufacturing methods according to the invention.

[0042] With reference to Fig. 2, a micro-optical security element 20 with a moiré magnification arrangement contains a transparent carrier film 22, for example in the form of a 20 μm thick PET film. The upper side of the carrier film 22 is provided with a grid-like arrangement of microlenses 24, which form a grid of preselected symmetry on the surface of the carrier film. The microlenses 24, which are usually spherical or aspherical, preferably have a diameter between 5 μm and 50 μm, in particular between 8 μm and 35 μm, and are therefore not visible to the naked eye. According to the invention, rod or lenticular lenses can also be used in special embodiments.

[0043] Arranged on the underside of the carrier film 22 is a motif layer 26 containing a grid-like arrangement of differently colored micromotif elements 28-1, 28-2 with a size between 0.5 pm and 50 pm, in particular between 3 pm and 35 pm. The grid arrangements of the micromotif elements 28-1, 28-2 and the microlenses 24 are coordinated with one another in a manner typical for moiré magnification arrangements, in particular slightly rotated or distorted relative to one another, in order to generate moiré magnification and optically variable effects, for example, running, pumping, morphing, flipping, or stereo effects, through the interaction of the micromotif elements and the microlenses. In other embodiments, the micromotif elements and the microlenses can also be coordinated with one another such that they form a modulo magnification arrangement or a non-magnifying lenticular image.

[0044] The motif layer 26 can be part of the carrier film 22 or applied to the carrier film 22. However, it can also be present on a separate carrier film, for example, and supplemented with an optical spacer layer containing a microlens array to form a moiré magnification array. For a more detailed description of the functionality and advantageous configurations of micromotif elements and microlenses, reference is made to German patent application DE 102005062132 A1 and international applications WO 2007 / 076952 A2 and WO 2009 / 000528 A1.

[0045] The subject of the present invention is not the known construction of moiré magnification arrangements, but rather special manufacturing processes for the micromotif elements of the motif layer. These enable the security elements produced according to the invention to have sections visible to the naked eye that change color when the viewing situation changes, with the colored microstructures of the motif layer that generate the different colors being in a defined phase relationship to one another. It has been found that security elements with these characteristics combine good recognizability of the displayed motifs with a high level of security against counterfeiting. The reliable production of a motif layer with a phase-true arrangement of multicolored micromotif elements represents a significant technological hurdle, which, however, can be overcome using the processes described according to the invention.

[0046] First, with reference to Figures 3 to 10, methods of a first group of methods are described, which essentially rely on phase-accurate embossing of an embossing lacquer layer with structural elements of various structural types. These methods are claimed in the present application only in combination with the methods of the second group of methods described below, which essentially rely on modifying the motif plane by irradiation from defined solid angle ranges through the microlens array.

[0047] Figure 3 illustrates a method according to a first example. Referring first to Fig. 3(a), to produce the motif layer 26 of a moiré magnification arrangement, an embossing lacquer layer 32, advantageously a UV embossing lacquer layer, is applied to a carrier foil 38. An embossing 30 is introduced into the embossing lacquer layer 32, which has a plurality of structural elements 34, 36, each corresponding to one of two different structural types and which, after a color filling or other processing steps in the finished security element, form the micromotif elements 28-1, 28-2 with the different

[0048] The colors used in the motif form the basis.

[0049] In Fig. 3, as well as in the other figures, only one unit cell 25 of the motif layer of the moiré magnification arrangement is shown in cross-section for illustration purposes, but it is understood that the embossing 30 in the surface of the motif layer 26 contains a plurality of structural elements 34, 36 arranged in a grid-like manner in order to produce the desired appearance of the finished moiré magnification arrangement in interaction with the microlenses of the microlens grid in a manner known per se.

[0050] The entire embossing 30 is created with an embossing tool that has a plurality of embossed elements corresponding to the structural elements 34, 36. All structural elements 34, 36 of the embossing 30 are created by the same embossing tool in a single embossing step, so that the phase relationship between the embossed elements specified by the embossing tool is converted into a corresponding phase relationship between the embossed structural elements 34, 36 over the entire surface of the motif layer 26.

[0051] In the example of Fig. 3, the two structural types of the structural elements 34, 36 are depressions with steep side walls (angle to the surface of at least 75°, preferably even more than 85°) and with base surfaces running essentially parallel to the surface. The two structural types differ in the depth of the structures, i.e., in the distance from the base surface to the surface of the embossing lacquer layer 32, which has one of two predetermined values ​​h or t2. The shallower structures 36 of the first structural type have a depth t2 of between 0.5 and 5 μm, while the deeper structures 34 of the second structural type have a depth h of between 1 μm and 20 μm. The deeper structures 34 are at least 1.5 times, preferably 2 to 4 times as deep as the shallower structures 36. For example, the shallower structures 36 have a depth of t2 = 2 pm and the deeper structures have a depth of ti = 6 pm, i.e. they are 3 times as deep as the shallower structures.After the embossing step, a first ink 40 is printed onto the film with the embossed embossing lacquer layer 32 in a first printing step, in an amount that approximately fills all recesses 34, 36, but preferably leaves only a small amount of ink on the film surface, as shown in Fig. 3(b). Excess ink residues can also be removed from the film surface by a doctor blade or wiping process.

[0052] A special feature of the ink 40 used is that it contains a large amount of solvent, which is removed by drying after the doctor blade or wiping process, thereby causing shrinkage of the ink 40 in the recesses of the structural elements 34, 36. Since more solvent escapes from the deeper structures 34 than from the shallower structures 36, more space remains in the deeper structures 34 after the shrinkage process than in the shallower structures 36, as shown in Fig. 3(c). For example, after the ink has been applied and dried, the shallower structures 36 are filled with ink 40 to a depth of 1.2 μm, and the deeper structures to a depth of 3.6 μm (40% shrinkage in each case), leaving a free space of 0.8 μm for the shallower structures 34 and 2.4 μm for the deeper structures 36.

[0053] Subsequently, a second color 42 is printed in a second layer, containing little or no additional solvent. The second color 42 is also applied in an amount that fills the remaining depressions but does not leave large residues on the surface of the film. After a subsequent doctor blade or wiping process, the second color 42 covers the first color 40 in the structural elements 34, 36, while neither color is present outside the structural elements, as shown in Fig. 3(d). The structural elements 34, 36 filled with color 40, 42 form the micromotif elements of the motif layer 26 after completion by a microlens array 24.

[0054] In the finished security element, the microlens array 24 can be arranged on either side of the resist layer 32 of Fig. 3(c). If the microlens array 24 is arranged on the top side O of the resist layer 32, the depths t1, t2 of the structural elements 34, 36 and the intensities of the two colors 40, 42, in particular the color thickness and the pigmentation of the two colors 40, 42, are preferably selected such that the first color 40 still shines strongly through the second color 42 in the shallower structures 36, while in the deeper structures 34 it is covered by the second color 42 with such a great layer thickness that it is not or hardly perceptible there. As a result, the shallow structures 34 then appear in a mixed color of the first color 40 and the second color 42, while the deeper structures 36 essentially display the second color 42.For example, if the first color 40 is a blue color and the second color 42 is a yellow color, when viewed from the top side O the shallow structures 34 appear with the mixed color green and the deeper structures 36 with the second color yellow.

[0055] If, on the other hand, the microlens arrangement 24 is arranged on the underside U of the resist layer 30, the depths ti, t2 of the structural elements 34, 36 and the intensities of the two colors 40, 42, in particular the color thickness and the pigmentation of the two colors 40, 42, are preferably selected such that in the deeper structures 34, no light colored by the second color 42 shines through the first color 40, so that these structures can be seen in the first color 40. In the shallower structures 36, the second color 42 shines through the first color 40, so that the viewer perceives the mixed color of the two colors. If, for example, the first color 40 is again blue and the second color 42 is yellow, when viewed from the underside U, the shallow structures 34 appear with the mixed color green and the deeper structures 36 with the first color blue.

[0056] In both variants, the described method can be used to produce a motif layer 26 with two differently colored micromotif elements 34, 36, which are in a fixed, predetermined phase relationship over the entire surface of the motif layer, i.e. are arranged in the motif layer in a phase-true manner.

[0057] In a modified, equally advantageous approach, the first

[0058] Ink 40 has a low opacity and a low solvent content. In this variant, the ink transfer is adjusted so that after the first printing step, only the shallower structures 36 are completely filled, as shown in Fig. 3(e), while there is still fill volume available in the deeper structures 34.

[0059] In the second print, a second color 42 is then applied, which can only be absorbed by the deeper depressions and covers the first color 40 with the low opacity, as shown in Fig. 3(f).

[0060] This modified procedure is particularly advantageous when viewing the microstructure arrangement from the underside—in the shallower structures 36, only the first color 40 is visible, while in the deeper structures, the second color 42 shines through the first color 40, so that the observer perceives the mixed color of the two colors 40, 42. However, if the microlens arrangement is arranged on the top side O, a color with high opacity can also be selected for the first color 40.

[0061] In all variants, the embossing step can involve embossing into a still-liquid UV varnish as an embossing varnish layer on a carrier film before UV curing takes place, typically while the film coated with UV varnish is still wrapping around the embossing tool. Upon leaving the embossing tool, the structures are already sufficiently cured to retain their shape and no longer flow. Pre-curing the UV varnish before reaching the embossing tool and / or post-curing after leaving the embossing tool can also be advantageous.

[0062] As an alternative to UV embossing, embossing can be carried out using a thermoplastic embossing lacquer layer. This layer is soft enough under the prevailing temperatures and the pressure applied between the embossing tool and the counter-pressure roller to allow the structures to be molded into the thermoplastic lacquer with sufficient dimensional accuracy. Alternatively, it is also possible, although not currently explicitly preferred, to use a thermoplastically deformable film, which eliminates the need for an additional thermoplastic embossing lacquer.

[0063] The other examples in Figures 4 to 10 are also each essentially based on an embossing process in which structural elements are first introduced into the motif layer in a single embossing step using the same embossing tool, so that the phase relationship of the embossed elements predetermined by the embossing tool is converted into a corresponding phase relationship of the embossed structural elements over the entire surface of the motif layer. The embossed structural elements are then suitably further treated by color filling, metallization, and / or a photoresist coating in order to form the desired, differently colored microstructure elements of the motif layer. The following primarily highlights the differences between the other described processes and the process in Figure 3, while the basic statements made there also apply to the other examples.

[0064] Figure 4 illustrates a second example that uses a combination of color filling of interlacings and resonance effects in metallized subwavelength gratings for color generation.

[0065] With reference to Fig. 4(a), in this example, an embossing 50 is introduced into an embossing lacquer layer 32 in a single embossing step, which embossing has a plurality of structural elements 54, 56, each corresponding to one of two different structural types and which, in the finished security element, form the micromotif elements with the different colors used.

[0066] The first structural elements 54 are essentially designed like the flatter structural elements 36 of Fig. 3, with steep sidewalls, a base area running approximately parallel to the surface, and a depth of 0.5 to 5 μm. The structural elements 56 are of a different structural type, which is not a depression, but rather a one-dimensional or two-dimensional subwavelength grating 58 with a period between 100 and 400 nm and a depth between 50 and 400 nm.

[0067] After the embossing step, the embossed lacquer layer 32 is provided with a metallization 52 over its entire surface in a metallization step, as shown in Fig. 4(b). Metals such as Al, Cr, Cu, Ti, Au, Fe, Ni, and their alloys can be used for the metallization 52. Advantageously, the metallization represents a color-shifting multilayer system consisting of a semitransparent metal, a dielectric such as SiCl or ZnS, and a reflective metal layer. Alternatively, layer systems consisting, for example, of a sequence of low- and high-refractive-index dielectric layers can be used instead of the metallization 52.

[0068] Metallization 52 creates color filters in the areas covered with subwavelength gratings. These filters spectrally absorb light of certain wavelengths due to resonance phenomena such as plasmon excitations, while almost completely reflecting light of other wavelengths. The grating parameters and the type of metal applied determine the observable color. Using different grating structures also allows for different color effects.

[0069] In the next step, as already described in Fig. 3, an ink 40 is printed onto the embossed and metallized lacquer layer 32, and excess ink is removed by a doctor blade or wiping process, so that the ink remains essentially only in the recesses of the first structural elements 54, as shown in Fig. 4(c). Care must be taken to ensure that the ink 40 is removed as completely as possible from the comparatively flat and narrow subwavelength gratings 56, since otherwise a mixed color would result in these sections due to the absorption of the ink remaining there and the absorption effect of the subwavelength gratings. To minimize this effect, an ink 40 with an appropriate solvent content can also be used here.When viewed from the top side, the first recessed structural elements 54 then appear in the applied color 40, while the structural elements 56 appear in the color defined by the grating parameters and the type of metallization of the subwavelength gratings. The metallized or color-filled structural elements 54, 56, after completion by a microlens array 24, form the micromotif elements of the motif layer.

[0070] In a modification, anti-reflective structures, in particular so-called moth-eye structures, can also be used for the structural elements 56 instead of the subwavelength gratings. The surface sections provided with these structures appear dark to black to an observer after the metallization 52, since the moth-eye structures absorb incident light across a broad band across the entire visible spectral range.

[0071] This method can also be used to produce a motif layer 26 with two differently colored micromotif elements 54, 56, which are in a fixed, predetermined phase relationship over the surface of the motif layer.

[0072] In the example of Fig. 5, a combination of color filling and area-specific coloring by full-surface exposure is used to produce the micromotif elements.

[0073] For further explanation, in this example with reference to Fig. 5(a), an embossing 60 with a plurality of structural elements 54, 66 is introduced into an embossing lacquer layer 32. The first structural elements 54 are formed as described in Fig. 3, while the second structural elements 66 are formed by surface-enlarging relief structures which allow light to pass through more easily than the remaining areas in the finished security element. For this purpose, the structural elements 66 are preferably formed as a relief structure with a large depth-to-width ratio. In particular, the relief structure can be formed periodically as a one-dimensional or two-dimensional grating, wherein the grating period advantageously varies between 300 nm and 20 µm and the depth is between 0.5 times and 5 times the period. Alternatively, the relief structure can also be formed aperiodically with the same structure sizes.

[0074] In a subsequent metallization step, the embossed lacquer layer is provided with a metallization 62, which is applied in all areas in a uniform amount and thus with a uniform nominal layer thickness. The nominal layer thickness is the layer thickness resulting from metallization on a flat surface area. Typical nominal layer thicknesses are in the range from 10 nm to 100 nm. Due to the large depth-to-width ratio in the area of ​​the second structural elements 66, these areas have an enlarged surface, so that the actual layer thickness of the metallic coating resulting per unit surface area is smaller than in the flat areas. This phenomenon is illustrated in the detailed sections 66-A and 66-B of Fig. 5(b) and is described and explained in more detail, for example, in the document EP 1 786 632 B1.

[0075] The type of metallization and the lattice parameters can advantageously be selected such that light of certain wavelengths is transmitted particularly well in the second structural elements 66, while in the remaining areas of the embossing lacquer layer it is largely reflected by the metallization 62 but not transmitted.

[0076] In the next step, as described in Fig. 3, a first color 40 is printed onto the embossed and metallized lacquer layer 32 and excess color is removed by a doctor blade or wiping process, so that the first color 40 remains essentially only in the recesses of the first structural elements 54.

[0077] Subsequently, a negative photoresist 64 of a second color, i.e., a colored photosensitive resist that becomes insoluble upon exposure, is printed over the entire surface of the metallized and partially filled resist layer 32, as shown in Fig. 5(d). The structure coated with the photoresist 64 is then exposed over its entire surface from the underside, i.e., through the metallized resist layer 32 (flood exposure B), as shown in Fig. 5(e). The exposure radiation B can penetrate the metallization 62 only in the comparatively transparent regions of the second structural elements 66 and crosslink the photosensitive resist 64 there to form crosslinked regions 68. In the other surface regions, the metallization 62 is essentially opaque to the exposure radiation B due to its greater layer thickness, so that the photoresist 64 behind it is not crosslinked there.Care must be taken to ensure that the small amount of first color 40, which may remain in the second structural elements 66 during color filling, does not significantly attenuate the exposure radiation B.

[0078] The photoresist 64 is then developed in a development step and thereby removed everywhere where it has not been crosslinked, i.e. everywhere except in the crosslinked areas 68 with the second structural elements 66. This results in a motif layer as shown in Fig. 5(f), in which the first structural elements 54 are filled with the first color 40 and the second structural elements 66 are coated with the photosensitive resist 64 of the second color.

[0079] If necessary, the exposed areas of the metallization 62 can subsequently be removed by an etching step to create a largely transparent background. If this etching step is omitted, the background is perceived by the observer as metallically reflective. In both variants, the filled or coated structural elements 54, 66, after completion by a microlens array 24, form the micromotif elements of the motif layer.

[0080] In a particularly advantageous variant of the above-mentioned method, which is illustrated in Fig. 6, the second structural elements 76 of the embossing 70 are formed by depressions 72, the bases of which are formed by surface-enlarging relief structures 74 of the type described in Fig. 5. The depth of the depressions 72 exceeds the maximum amplitude of the surface-enlarging relief structures 74, preferably by an amount of 0.5 to 5 pm, so that the surface-enlarging relief structures 74 are completely submerged in the depressions 72, as illustrated in Fig. 6(a).

[0081] The thus embossed resist layer 32 is coated with a metallization 62, and then, in a color-filling process, a negative photoresist 64 in the second color is applied to the metallization 62, and excess color is removed by a doctor blade or wiping process. The photoresist 64 then just fills the depressions 54, 72 of the first and second structural elements. The thus-filled structure is subsequently exposed over its entire surface from the underside through the metallization (flood exposure B), as shown in Fig. 6(b). The metallization 62 is transparent only in the area of ​​the surface-enlarging relief structures 74 of the depressions 72, so that the photoresist 64 is crosslinked to form crosslinked regions 68 only there.

[0082] In the subsequent development step, the uncured photoresist 64 is removed from the recesses of the first relief structure 54, so that only the cured resist 64 remains in the recesses 72 of the second relief structure 76, as shown in Fig. 6(c).

[0083] Subsequently, the first color 40 is printed onto the resulting lacquer layer 32, and the excess color is removed by a doctor blade or wiping process, so that the first color 40 remains essentially only in the recesses of the first structural elements 54, as shown in Fig. 6(d). The color-filled structural elements 54, 76, after completion by a microlens array, form the micromotif elements of the motif layer.

[0084] In an advantageous modification of the method of Figures 5 and 6, the surface-enlarging relief structures 74 of the second structural elements 76 are not used to create regions of increased transmission for subsequent flood exposure, but the enlarged surface ensures that the applied metallization 62 can be removed more easily in these regions by an intermediate etching step than outside the structural elements 76 and can therefore be selectively etched.

[0085] For further explanation, Fig. 7 in Fig. 7(a) first shows the embossed and metallized coating layer 32 with the first structural elements 54, the second structural elements 76 with the surface-enlarging relief structures 74 sunk into a recess 72 and the metallization 62 already applied. The surface-enlarging relief structures 74 can also be formed in this example by relief structures with a large depth-to-width ratio and have the same arrangements and dimensions as described in Figs. 5 and 6.

[0086] As explained above, the metallization 62 in the second structural elements 76 has a smaller layer thickness than outside the structural elements due to the locally enlarged surface. In an etching step following the metallization, the etching can therefore be terminated in a state in which the metal in the second structural elements 76 has already been largely removed, while it is still predominantly present outside the second structural elements 76. Specifically, for example, an Al metallization can be etched in a 10% sodium hydroxide solution. To influence the etching dynamics, the temperature of the eye can be controlled, for example by a heating roller. The state after such a selective etching step with demetallized relief structures 74 is shown in Fig. 7(b).

[0087] Now, as in the process of Fig. 6, a negative photoresist 64 of the second color is printed in a color-fill process. The photoresist-coated structure is exposed from the underside through the metallization 62 over its entire surface, and the photoresist 64 is thereby crosslinked only within the demetallized second structural elements 76. During development, the photoresist 64 is therefore removed everywhere outside the recesses 72, so that after the development step, only the recesses 72 of the second structural elements 76 are filled with hardened photoresist 64 of the second color, as shown in Fig. 7(c). - T7-

[0088] Then, in a print, the first color 40 is applied to the resulting

[0089] A resist layer 32 is printed, and the excess ink is removed by a doctor blade or wiping process, so that the first ink 40 remains essentially only in the recesses of the first structural elements 54. The exposed areas of the metallization 62 can then be removed by a further etching step to create a largely transparent background, as shown in Fig. 7(d). The ink-filled structural elements 54, 76, after completion by a microlens array, form the micromotif elements of the motif layer.

[0090] In an advantageous process variant, the order of the last two steps is reversed, i.e., the metallization 62 is removed first, and only then is the first color 40 applied in a printed layer. In this case, the motif layer no longer contains any metallization, as shown in Fig. 7(e), and can be combined with a microlens array for viewing on both the top and bottom sides.

[0091] In the process variants shown in Figures 5 to 7, instead of a negative photoresist, which becomes insoluble upon exposure, a positive photoresist can be used, which, in its already insoluble form, becomes soluble again upon exposure. When using a positive photoresist, the first and second colors swap places, as illustrated in Figure 8.

[0092] Starting from the partially demetallized resist layer of Fig. 7(b), a positive photoresist 78 of a second color is printed in a color filling process and the excess color is removed by a doctor blade or wiping process, as shown in Fig. 8(a).

[0093] By a full-surface exposure from the underside through the metallization 62, the positive photoresist 78 is made soluble again only in the demetallized recesses 72 of the second structural elements 76 and is removed in the subsequent development step, while the photoresist 78 remains in the recesses of the first structural elements 54, as shown in Fig. 8(b).

[0094] Subsequently, the first color 40 is printed onto the resulting coating layer 32, and the excess color is removed by a doctor blade or wiping process, so that the first color 40 remains essentially only in the recesses 72 of the second structural elements 76, as shown in Fig. 8(c). Here, too, the exposed areas of the metallization 62 can subsequently be removed by a further etching step to create a largely transparent background. In any case, the color-filled structural elements 54, 76, after completion by a microlens array 24, form the micromotif elements of the motif layer.

[0095] In the variant of the invention shown in Fig. 8, it may be advantageous to remove the metallization 62 of the background areas during or after selective etching, for example, by peeling it off with a laminated foil or a kiss print of an etching solution. This makes the final product transparent, especially since any toning film of the photoresist is also exposed during flood exposure and then completely removed during development.

[0096] Figure 9 illustrates a further advantageous example in which partial areas appearing with different colours in the finished security element are defined by embossed, polarising structures.

[0097] The polarizing structures are defined by embossed structures, in particular by linear gratings with periods in the range of approximately 100 nm to 1 pm and a depth of 50 nm to 5 pm. The embossed gratings are then coated with a metal layer and then act as polarizing filters in transmission, i.e. they only transmit light with the appropriate linear polarization direction, while not allowing light with a polarization direction perpendicular to it to pass through. In the example, two polarizing structures with mutually perpendicular polarization directions are first created in the motif layer for the two colors to be created. Using two exposure steps with polarized light, the polarization direction of which corresponds to one of the two embossed polarizers, the two colors can then be applied one after the other in a defined manner.

[0098] For further explanation, Fig. 9(a) in cross section and Fig. 9(b) in plan view show a motif layer with an embossing 80 introduced into a lacquer layer 32 with first structural elements 84 in the form of first polarizing structures with parallel grid lines of a first orientation and with second structural elements 86 in the form of second polarizing structures with parallel grid lines of a second orientation perpendicular to the first orientation.

[0099] In the example, the structural elements 84, 86 are formed by embossed linear gratings with a period of 200 nm and a depth of 0.3 pm. After the embossing step, the embossed lacquer layer 32 was provided with a metal layer 82. For high transparency, it is advantageous to demold the raised regions of the grating, for example, using a metal transfer process, to create the wire grid polarizers shown in Figures 9(a) and (b). Depending on whether the background region is to be colored or not, the metal outside the structural elements 84, 86 can also be removed or left in place.

[0100] In the next process step, the (partially) metallized structure is coated over its entire surface with a negative photoresist 90 of a first color, and the coated structure is exposed from the underside through the metallization 82 to linearly polarized exposure radiation Bi, the polarization direction of which is matched to the polarization direction of the first structural elements 84. The polarized exposure radiation Bi is therefore transmitted by the metal layer 82 only in the region of the first structural elements 84, but is otherwise blocked everywhere else, so that the photoresist 90 is crosslinked only in the region 94 of the first structural elements 84, as shown in Fig. 9(c). After development, the colored photoresist 90 therefore remains only in the region of the first structural elements 84, as shown in Fig. 9(d).

[0101] Subsequently, a negative photoresist 92 of a second color is printed over the entire surface, and the coated structure is exposed from the underside through the metallization 82 to linearly polarized exposure radiation B2, the polarization direction of which is matched to the polarization direction of the second structural elements 86. The polarized exposure radiation B2 is therefore transmitted by the metal layer 82 only in the region of the second structural elements 86, but otherwise blocked everywhere else, so that the photoresist 92 is crosslinked only in the region 96 of the second structural elements 86, as shown in Fig. 9(e). After development, the photoresist 92 therefore remains only in the region of the second structural elements 86, as shown in Fig. 9(f).

[0102] Figure 9(g) shows, analogously to Fig. 9(b), a plan view of a unit cell of the finished motif layer with the color-coated structural elements 84, 86, which, after completion by a microlens array 24, form the micromotif elements of the moiré magnification arrangement.

[0103] Optionally, the metallic background can then be removed, for example, by etching. In modifications, positive photoresists can be used instead of the negative photoresists 90 and 92; the use of a combination of positive and negative photoresists is also possible.

[0104] A further advantageous process variant, in which a colored embossing lacquer and a selective coloring process are used, is described with reference to Fig. 10.

[0105] In this process variant, an embossing lacquer layer 102 colored with a first color is applied to a carrier foil 38, as shown in Fig. 10(a). The colored embossing lacquer layer 102 is then provided in an embossing step with an embossing 100 with structural elements 104, 106, each corresponding to one of two different structural types. In order to avoid a background toning in the first color that is perceptible to the observer, the embossing is carried out without residual lacquer thickness, i.e., it is carried out in such a way that the sections of the first embossing lacquer 104, 106 created by the embossing are not continuous, but separated by intermediate regions 108 free of any lacquer layer. Such residual lacquer-thickness-free embossing can be achieved by a good coordination of the surface energies of the substrate 38 and the embossing tool with regard to the embossing lacquer 102 used.The retention of a small residual amount of color 102 in the intermediate regions 108 may be tolerated under certain circumstances if the contrast of the microstructures 106 is still sufficiently high compared to the background.

[0106] In contrast to the process of Fig. 3, this process does not produce depressions in the embossing lacquer, but rather raised embossing lacquer islands 104, 106, as shown in Fig. 10(b). The embossing lacquer islands 104, 106 have different heights above the surface of the carrier foil 38, with the lower embossing lacquer islands 106 having a height between 0.5 and 5 pm, and the higher embossing lacquer islands 104 having a height between 0.75 pm and 20 pm. The higher islands are at least 1.5 times, preferably 2 to 4 times, as high as the lower islands.

[0107] In a subsequent transfer step, a second color 110 is then selectively transferred only to the higher embossing lacquer islands 104, as shown in Fig. 10(c). Such selective color transfer can be achieved, for example, using the kiss-print process or with the aid of another color transfer process.

[0108] The second color 110 is advantageously selected such that, when viewed from above, the second color layer is opaque or at least largely opaque, regardless of its thickness, so that the higher embossing lacquer islands 104 form structural elements due to the color coverage that appear with the second color, while the lower embossing lacquer islands 106 form structural elements that appear in the first color of the embossing lacquer 102. In a modification, the second color 110 can also be non-opaque, the higher structural elements 104 then appear with the mixed color of the colors 102 and 110. If the first color 102 is not opaque but translucent, the motif layer can also be viewed from below.

[0109] In both variants, such a process produces a motif layer 26 with two differently colored micro-motif elements that are in a fixed, predetermined phase relationship over the surface of the motif layer.

[0110] In an alternative procedure, the structural elements can also be applied to the carrier film 38 using a microgravure printing process, as described, for example, in the document WO 2008 / 000350 A1.

[0111] With reference to Fig. 11, methods of a second group of methods are now described, which are essentially based on a modification of the motif plane by irradiation from defined solid angle ranges through the microlens array.

[0112] Laser light is preferred for this purpose because it is particularly intense and can be generated largely parallel, allowing very good control over the solid angle range from which the light falls onto the sample. It is important that the exposure always takes place from the lens side and through the microlenses, so that the refractive effect of the lenses focuses the radiation onto the image plane. This allows well-defined modifications to be introduced into the image plane with respect to the position of the microlenses, leading to the creation of the desired microstructure elements.

[0113] Because of the identical beam path, a viewer can later see the modified surface area of ​​the finished security element from the same solid angle from which it was exposed during production.

[0114] This offers a significant advantage even over processes based on pure embossing, since while these can create microstructure elements that have a defined phase relationship relative to one another, the positioning of the microstructure elements relative to the microlenses cannot be easily controlled. Furthermore, processes in which all microstructure elements are created by exposure to light through the microlenses can also be used when the lenses are arranged irregularly rather than regularly.

[0115] By appropriately spreading the light incident on the microlens array, the exposed areas can be enlarged, since the lenses, which typically focus parallel light at the focal plane, do not achieve complete focus in this case. A focal point or focal line is then correspondingly expanded, allowing the exposure step to be performed more quickly, although this usually results in a loss of spatial resolution. A similar effect can be achieved by deliberately positioning the subject plane at a different angle from the focal plane.

[0116] Figure 11 schematically illustrates a method according to an embodiment of the invention. The starting point is a carrier film 22 provided with an array of microlenses 24 on its upper side O. The underside U of the carrier film defines a motif plane in which the microstructure elements are to be arranged and which lies in or near the focal plane of the microlenses 24.

[0117] With reference to Fig. 11(a), a first negative photoresist 200 of a first color is first applied over the entire surface of the underside U of the carrier film 22. Then, the arrangement is exposed to exposure radiation Bi from the lens side from a defined first solid angle range Ri. Due to the focusing effect of the microlenses 24, the first surface sections 202 of the photoresist 200 located in focus under each lens are exposed, while the surrounding areas outside the first surface sections 202 receive little or no radiation intensity and are therefore not exposed or at least not sufficiently exposed for crosslinking. In the subsequent development step, the first photoresist 200 is therefore removed in all areas except the first surface sections 202, as shown in Fig. 11(b).

[0118] Subsequently, a second negative photoresist 204 of a second color is applied to the entire underside U of the carrier film 22. The arrangement is then exposed to exposure radiation B2 from the inset side within a defined second solid angle range R2, as shown in Fig. 11(c). From this solid angle range, other, second surface sections 206 are in focus below each inset, so that in this step, only the other, second surface sections 206 are sufficiently exposed for crosslinking.

[0119] In the subsequent development step, the second photoresist 204 is therefore removed in all areas except for the second surface sections 206, as shown in Fig. 11(d). The first and second surface sections 202, 206 then form the differently colored micromotif elements of the motif layer, with the first surface sections 202 of the first color being visible from the first solid angle range R1, and the second surface sections 206 of the second color being visible from the second solid angle range R2. The second solid angle range lies at least partially outside, and preferably predominantly or even completely outside, the first solid angle range.

[0120] Instead of the negative photoresists 200 and 204 mentioned above, positive photoresists can also be used; a combined application of positive and negative resists is also possible. The cycle of coating, exposure, and development can also be performed more than twice. In this case, an adjustment of the respective solid angle ranges is recommended: the more exposures are performed, the smaller the corresponding solid angle ranges should generally be to avoid disruptive overlap.

[0121] When using positive photoresists, for example, the following procedure can be used: - Applying a positive photoresist,

[0122] - Exposure from solid angle 1,

[0123] - Develop,

[0124] - Color fill with color 1,

[0125] - Stripping (removing) the photoresist without affecting the color filling,

[0126] - re-application of a positive photoresist,

[0127] - Exposure from solid angle 2,

[0128] - Develop,

[0129] - Color fill with color 2, and

[0130] - Stripping (removing) the photoresist without affecting the color fill.

[0131] This method consists of a combination of exposures and color fills. You can always use the same photoresist, as it doesn't remain on the film. The process can, of course, be repeated more than once.

[0132] In a variation of the described process, exposure and development are replaced by fiber ablation. This process uses inks that are removed by the high achievable intensity of the laser radiation focused by the microlenses. Here, too, the coating and laser ablation cycle can be performed more than twice.

[0133] Furthermore, instead of laser-induced ablation, a process can be used in which an applied color is not removed but specifically modified by the laser radiation. For example, it is possible to bleach specific colors or change their color tone using high-intensity, focused laser radiation. Instead of color layers, one or more layers of a PCM (phase change material) material can be applied, the structure and thus the interference color of which can be converted by laser radiation. When manufacturing micro-optical security elements, a combination of processes from the first and second process groups can also be used, i.e., both an embossing process and exposure through the microlenses can be used to create the differently colored microstructure elements.

[0134] In particular, microstructures can initially be created by embossing and ink filling, and then removed or modified again by an exposure step using microlenses. In principle, all of the process variants and sub-process steps described above can be used, including, in particular, printing an ink that, after a squeegee or wiping step, fills only the recesses of an embossed pattern, applying a photosensitive fill ink (as a positive or negative photoresist), and ablating or modifying a fill ink using laser radiation. In this way, for example, a dynamic optically variable effect can be achieved to disappear or change its color within a specific viewing angle range.If microstructures are modified or removed by the microlenses in an exposure step, it may be sufficient to create embossed elements of only a single structure type in the embossing step, since the color differentiation required for multicoloration can be achieved by the exposure step.

[0135] Figure 12 illustrates a particularly preferred method variant. Referring to Fig. 12(a), a carrier foil 22 is first provided, which is provided with an array of microlenses 24 on its upper side O. An embossing lacquer layer 212 is applied to the underside U of the carrier foil, which defines the motif plane, and is provided with an embossing 210 consisting of a plurality of depressions 214. All depressions 214 are created by the same embossing tool in a single embossing step and therefore have a defined phase relationship to one another.

[0136] Referring to Fig. 12(b), these structures, applied as interlacings 214, are then filled with a positive photosensitive resist 216 of a first color, and excess ink is removed by a doctor blade or wiping process. Then, by exposure B from a specific solid angle range R, the photoresist 216 is exposed in a partial area 218.

[0137] In a subsequent development step, the partial area 218 covered by the exposure radiation B is then removed again, since the positive resist has been made soluble there by the exposure, while the photoresist 216 remains in the remaining area of ​​the depressions 214, as shown in Fig. 12(c).

[0138] In the next step, a color fill is applied with a fill color 220 of a second, different color. After removing excess color by a doctor blade or wiping process, the design shown in Fig. 12(d) results, with a motif layer 26, in which the surface sections 218 appear with the second color 220 and the remaining area of ​​the depressions 214 with the first color of the photoresist 216.

[0139] The result is a security feature with a dynamic effect that is consistent across the entire viewing angle range. When viewed from the solid angle range R from which the exposure occurred, the viewer perceives the effect in the second color, while from all other perspectives the first color is visible.

[0140] In general, combinations of the processes described here in the first and second process groups are also possible in the sense of serial, consecutive production. For example, the processes based on embossed structures in the first process group can be combined with the exposure processes of the second group in the sense of sequentially executed steps.

[0141] The methods according to the invention have been explained by way of example with reference to the production of the motif layer of a moiré magnification arrangement, but it is understood that the methods can be used in the same way to produce the motif layer of a modulo magnification arrangement or a lenticular image.

Claims

Patent claims 1. A method for producing a micro-optical display arrangement which has a coloured motif layer arranged in a motif plane with a plurality of differently coloured micro-motif elements and a focusing element grid comprising a plurality of micro-focusing elements for viewing the micro-motif elements, wherein in the method for producing the coloured motif layer a coloured layer which is at least partially light-sensitive is arranged in the motif plane and the light-sensitive layer is exposed to exposure radiation through the focusing element grid and is thereby modified in the exposed regions.

2. A method according to claim 1, characterized in that the solubility of the light-sensitive layer in a development medium is changed by the exposure radiation and that the light-sensitive layer is developed in a development step after the exposure and is thereby removed in regions.

3. Method according to claim 1, characterized in that the exposure radiation, in particular laser radiation, removes the light-sensitive layer in regions or changes its color, reflection and / or transmission properties.

4. Method according to one of claims 1 to 3, characterized in that the steps of arranging an at least partially light-sensitive, colored layer in the motif plane and of exposing the light-sensitive layer through the focusing element grid with exposure radiation to modify the light-sensitive layer two or more times with layers different colors and with exposure from different spatial directions.

5. Method according to claim 4, characterized in that a negative photoresist is applied as at least partially light-sensitive, colored layer, the applied negative photoresist is exposed to exposure radiation through the focusing element grid and is thereby made insoluble in the exposed areas, the negative photoresist is then developed in a development step and is thereby removed in the non-exposed areas, the said steps of application, exposure and development being carried out two or more times with a photoresist of different color and with exposure from different spatial directions.

6. The method according to claim 4, characterized in that a positive photoresist is applied as a colored layer which is at least partially light-sensitive, the applied positive photoresist is exposed to exposure radiation through the focusing element grid and thereby becomes soluble in the exposed areas, the positive photoresist is then developed in a development step and is removed in the exposed areas, the recesses formed by the removal of the photoresist are filled with a color and the positive photoresist is optionally finally removed without impairing the color filling, the said steps of applying, exposing, developing, color filling and optionally stripping being carried out two or more times with different color fillings and with exposure from different spatial directions.

7. Method according to one of claims 1 to 6, characterized in that, in order to produce the colored motif layer, an embossing with a plurality of structural elements is additionally introduced into an embossing lacquer layer in an embossing step, wherein the structural elements are all produced with the same embossing tool in a single embossing step, so that the embossed Structural elements are all in a defined phase relationship specified by the embossing tool.

8. The method according to claim 7, characterized in that after the embossing step, in a processing step, a color layer in the form of a printing ink or a colored positive or negative photoresist is applied to the embossing lacquer layer, so that the color layer completely or partially fills those of the structural elements which are in the form of depressions, and / or a color layer in the form of a printing ink or a colored positive or negative photoresist is applied over the entire surface of the embossing lacquer layer, and / or the embossing lacquer layer is provided with a metallization.

9. Method according to claim 7 or 8, characterized in that the structural elements are at least partially formed in the form of depressions in the embossing lacquer layer, and in a processing step, in a first sub-step, a color layer in the form of a positive photoresist of a first color is applied to the embossing lacquer layer, so that the color layer fills those of the structural elements that are formed in the form of depressions, so that the embossing lacquer layer filled with color in partial areas forms the said colored layer arranged in the motif plane and at least partially light-sensitive, in a second sub-step, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby made soluble in the exposed areas, and the exposed photoresist is developed,so that the photoresist remains in a first partial area of the recesses and is removed in a second partial area of the recesses, and, in a third sub-step, a color layer of a second color is applied to the embossing lacquer layer and fills the second partial area of the depressions, so that the first and second partial areas of the depressions each form microstructure elements which are visible with a different color.

10. Method according to claim 7 or 8, characterized in that the structural elements are at least partially formed in the form of depressions in the embossing lacquer layer, and in a processing step, in a first sub-step, a color layer in the form of a negative photoresist of a first color is applied to the embossing lacquer layer, so that the color layer fills those of the structural elements that are formed in the form of depressions, so that the embossing lacquer layer filled with color in partial areas forms the said colored layer arranged in the motif plane and at least partially light-sensitive, in a second sub-step, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby made insoluble in the exposed areas, and the exposed photoresist is developed,so that the photoresist remains in a first partial area of the depressions and is removed in a second partial area of the depressions, and in a third partial step, a color layer of a second color is applied to the embossing lacquer layer and fills the second partial area of the depressions, so that the first and second partial areas of the depressions each form microstructure elements that are visible with a different color., 11. Method according to claim 7 or 8, characterized in that in the embossing step, an embossing with a plurality of structural elements is introduced into the embossing lacquer layer, each of which corresponds to one of at least two different structural types with different physical properties, and in a processing step, the structural elements are selectively provided with at least one coloring material by utilizing the different physical properties of the respectively associated structural type, wherein at least one coloring material is light-sensitive and forms the said colored layer arranged in the motif plane, which is at least partially light-sensitive, which is exposed to exposure radiation through the focusing element grid and is thereby modified in the exposed areas.

12. The method according to claim 11, characterized in that the structure types produced in the embossing step comprise depressions with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer, which have different embossing depths, or i) comprise a depression with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer and ii) comprise a subwavelength grating, or i) comprise a depression with steep side walls and base surfaces running essentially parallel to the surface of the embossing lacquer layer and ii) comprise a surface-enlarging relief structure, optionally sunk in a depression, or comprise linear gratings with parallel grating lines, which have different, in particular mutually perpendicular, orientations of the parallel grating lines.

13. Method according to claim 11, characterized in that in the embossing step, a colored embossing lacquer layer of a first color is embossed without any residual lacquer thickness, and the structure types produced in the embossing step represent embossing lacquer islands with steep sides and cover surfaces which essentially extend to the surface of the embossing lacquer layer and which have different heights.

14. A micro-optical display arrangement obtainable by one of the methods of claims 1 to 13, comprising a colored motif layer arranged in a motif plane with a plurality of differently colored micromotif elements and a focusing element grid comprising a plurality of microfocusing elements for viewing the micromotif elements, wherein the microfocusing elements have a length and / or width of less than 30 µm, wherein the motif layer comprises a colored layer which is at least partially light-sensitive and which is removed in partial areas or has changed color, reflection and / or transmission properties in partial areas.

15. Display arrangement according to claim 14, characterized in that the motif layer comprises an embossed lacquer layer which is provided with an embossing with a plurality of structural elements, all of which are in a predetermined, defined phase relationship, and are provided with at least one coloring material, wherein the embossed lacquer layer which is color-filled in partial areas preferably forms the said, at least partially light-sensitive, colored layer.

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