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

Abstract

The invention relates to a method for generating a microoptical display arrangement which comprises a colored motif layer (26), arranged in a motif plane and having a plurality of different-colored micromotif elements (28-1, 28-2), and a focusing element grid (24) composed of a plurality of microfocusing elements for viewing the micromotif elements (28-1, 28-2), wherein, in the method for producing the colored motif layer (26), an at least regionally light-sensitive colored layer (200; 204; 212) is arranged in the motif plane, and the light-sensitive layer (200; 204; 212) is subjected to exposure radiation (B1; B2; B) through the focusing element grid (24) and is thereby modified in the exposed regions (202; 206; 218). Figure for the Abstract: Fig. 11(c)

Description

Method for producing a micro-optical display arrangement and micro-optical display arrangement The invention relates to a method for generating a microoptical display arrangement which comprises a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements. Data carriers, such as documents of value or identity documents, but also other articles of value, such as branded articles, are often provided, for safeguarding purposes, with security elements that make it possible to check the authenticity of the data carriers and at the same time serve as protection against unauthorized reproduction. The security elements may take the form, for example, of a security thread embedded into a banknote, a cover film for a banknote with aperture, an applied security strip, a self-supporting transfer element, or else a feature region which is applied directly to a document of value by printing. Security elements with a viewing angle-dependent or three-dimensional appearance play a particular role in safeguarding authenticity, since they are unable to be reproduced even with the most modern copying machines. The security elements are equipped with optically variable elements which convey a different perceived image to the viewer at different viewing angles and for example display a different perceived color or brightness, a different perspective view and / or a different graphic motif depending on the viewing angle. Microoptical systems, for example in the form of so-called moiré magnification arrangements, are among systems that have been used as security features for some time. In this context, moiré magnification refers to a phenomenon that occurs when a grid composed of identical image objects is viewed through a lens grid having approximately the same grid spacing. As with each pair of similar grids, a moiré pattern is obtained; in this case, each of the moiré strips appears in the form of an enlarged and rotated image of the repeated elements of the image grid (see "The moiré magnifier", M.C. Hutley, R. Hunt, R. F. Stevens and P. Savander, Pure Appl. Opt. 3 (1994), pp. 133-142). In addition to the moiré magnification, often also referred to as "synthetic magnification", moiré magnification arrangements generally have an optical variability, such as for instance movement or depth effects, which likewise results from the interaction of the lens grid with the motif grid. Typical security features equipped with microlenses comprisee, as lens grids, an arrangement of periodically arranged spherical or lenticular microlenses which for applications in security threads or LEAD (Longlasting Economical Anticopy Device) strips have dimensions of less than 25 µm in the lateral direction. This limitation results from the thickness restriction on the banknotes, which in turn have an effect on the specifications of the security features to be applied. Because of these small dimensions, the production of such security elements is very demanding, and for this reason the currently customary microlens security features usually offer only very limited possibilities from a designer standpoint. For example, in the case of film elements, such as embedded security threads, transferred film elements or applied film elements or patches, the microlenses frequently have a size of only about 25 µm or less. The small microlens size, the achievable focal size in the region of about 1 µm, and the line thickness of the microstructures that can be achieved with current methods, likewise in the region of about 1 µm, together lead to the fact that only very simple motifs can be presented to a viewer. In the field of banknotes, because of these difficulties, the known and frequently used film-based microoptical security features currently are generally only monochrome, which further greatly restricts the designer's freedom of design. The motifs are often difficult to recognize, and the monochrome surfaces look rather boring and fairly unattractive to the viewer. Although multicolored designs are visually more attractive, the existing multicolored microlens features have various disadvantages. If the different-colored microstructure elements are arranged, say, in vertically separated planes, a long-range phase relationship between the microstructure elements can be ensured only with difficulty or not at all from a production standpoint. Although other designs are in principle multicolored, the viewer always sees only a single color, which is independent of the viewing angle, at a defined point in the pattern. In contrast to the films used to safeguard documents, there are already postcards in which colorful image representations flip or show three-dimensional effects depending on the viewing angle. Since there are no comparably serious limitations with regard to product thickness with these products, as there are for the films used on banknotes, the rod lenses used are substantially larger (order of magnitude typically 150 µm or more) and the substrate used is very stable against distortions occurring during processing, so that the microstructures and the effects achievable therewith can be generated via printing methods. These methods cannot be readily transposed to the proportions customary in banknote technology, with substantially smaller microlens diameters. Proceeding from this, the invention is based on the object of avoiding the disadvantages of the prior art and, in particular, of specifying an advantageous method for producing multicolor microoptical display arrangements, and specifying advantageous microoptical display arrangements. This object is achieved by the features of the independent claims. Developments of the invention are the subject of the dependent claims. The invention includes a method for generating a microoptical display arrangement which comprises a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements. In this context, it is provided that in the method for producing the colored motif layer, _ an at least regionally light-sensitive colored layer is arranged in the motif plane, and the light-sensitive layer is subjected to exposure radiation through the focusing element grid and is thereby modified in the subjected regions. In the present description, the term "microoptical display arrangement" encompasses not only moiré magnification arrangements and so-called modulo magnification arrangements but also lens grid images without magnification effect. In the case of a moiré magnification arrangement, the micromotif elements of a unit cell are typically in each case reduced images of the target images to be displayed, which find space completely within a cell. In contrast, in the case of a modulo magnification arrangement, the micromotif elements of the cells of the motif image are in each case incomplete extracts of the target images to be displayed, said extracts being imaged by a modulo operation. While the micromotif elements in moiré magnification arrangements are generally of identical design, this is not the case in the micromotif elements of the modulo magnification arrangements, since there a plurality of micromotif elements interact in order to display a complete target image. The basic principle of these microoptical display arrangements is explained in the document WO 2009 / 000528 A1, the disclosure content of which to this extent is incorporated into the present description. In contrast to moiré and modulo magnification arrangements, lens grid images are geared to an unscaled display of target images, i.e., to a display which is neither enlarged nor reduced in size. Preferably, the solubility of the light-sensitive layer in a developing medium is altered by the exposure radiation and the light-sensitive layer after the exposure is developed in a developing step and thereby regionally removed. In a different, likewise advantageous variant of the invention, the exposure radiation, more particularly laser radiation, regionally removes the light-sensitive layer or alters its properties of color, reflection and / or transmission. Advantageously, the steps of arranging an at least regionally light-sensitive colored layer in the motif plane and of subjecting the light-sensitive layer to exposure radiation through the focusing element grid for modifying the light-sensitive layer are carried out two or more times with layers of different color and with subjection from different spatial directions. In a particularly advantageous configuration, it is provided here that a negative photoresist is applied as the at least regionally light-sensitive colored layer, the applied negative photoresist is subjected to exposure radiation through the focusing element grid and thereby made insoluble in the exposed regions, the negative photoresist is then developed in a development step and removed in the unexposed regions, 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. In another, likewise particularly advantageous configuration, it is provided that a positive photoresist is applied as the at least regionally light-sensitive colored layer, the applied positive photoresist is subjected to exposure radiation through the focusing element grid and thereby becomes soluble in the exposed regions, the positive photoresist is then developed in a development step and removed in the exposed regions, the recesses formed by the removal of the photoresist are filled with an ink and the positive photoresist is optionally finally removed without impairing the ink filling, said steps of application, exposure, development, ink filling and optionally stripping being carried out two or more times with different ink fillings and with exposure from different spatial directions. Preferably, for producing the colored motif layer, additionally _ in an embossing step, an embossment having a multiplicity of structural elements is introduced into an embossing varnish layer, _ wherein the structural elements are all generated with the same embossing tool in a single embossing step, such that the embossed structural elements are all in a defined phase relationship dictated by the embossing tool. A "defined phase relationship" of the structural elements means that the position of the structural elements, in particular also of the structural elements visible in different colors, relative to one another over the area of the display arrangement is dictated by the embossing tool and does not unintentionally vary. Only through a defined phase relationship extending over the entire area of the display arrangement can synchronous color and motif flips be produced, 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 correspondingly second color. The fixed phase relationship of these differently colored and interleaved microstructures to one another has the effect that a specific section of a display arrangement can be seen only in a single color at a specific viewing angle. This applies to all area sections of the overall display arrangement. If, moreover, particularly advantageously, a defined phase relationship to the arrangement of the focusing elements is also maintained, then the two differently colored displays can even be seen over the entire area of the display arrangement in a uniform color and without a jump in motif, with the different displays appearing at different spatial angles. After the embossing step, advantageously in a processing step _ a color layer in the form of a printing ink or of a colored positive or negative photoresist is applied to the embossing varnish layer, such that the color layer completely or partially fills those of the structural elements which are designed in the form of depressions, and / or _ a color layer in the form of a printing ink or of a colored positive or negative photoresist is applied over the full area to the embossing varnish layer, and / or the embossing varnish layer is provided with a metallization. In an advantageous development of one of the methods containing an embossing step, provision is made for _ the structural elements to be at least partially designed in the form of depressions in the embossing varnish layer, and _ in a processing step, __ in a first substep, a color layer in the form of a positive photoresist of a first color is applied to the embossing varnish layer, such that the color layer fills those of the structural elements which are designed in the form of depressions, such that the embossing varnish layer which is color-filled in subregions has the stated colored layer which is arranged in the motif plane and is at least regionally light-sensitive, __ in a second substep, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby rendered soluble in the exposed regions, and the exposed photoresist is developed, such that the photoresist remains in a first subregion of the depressions and is removed in a second subregion of the depressions, and in a third substep, a color layer of a second color is applied to the embossing varnish layer and fills the second subregion of the depressions, _ such that the first and second subregions of the depressions each form microstructure elements which are visible with a different color. Alternatively, in one of the methods containing an embossing step, provision is made for _ the structural elements to be at least partially designed in the form of depressions in the embossing varnish layer, and _ in a processing step, __ in a first substep, a color layer in the form of a negative photoresist of a first color is applied to the embossing varnish layer, such that the color layer fills those of the structural elements which are designed in the form of depressions, such that the embossing varnish layer which is color-filled in subregions forms the stated colored layer which is arranged in the motif plane and is at least regionally light-sensitive, __ in a second substep, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby rendered insoluble in the exposed regions, and the exposed photoresist is developed, such that the photoresist remains in a first subregion of the depressions and is removed in a second subregion of the depressions, and __ in a third substep, a color layer of a second color is applied to the embossing varnish layer and fills the second subregion of the depressions, such that the first and second subregions of the depressions each form microstructure elements which are visible with a different color. In an advantageous method variant, it is provided that _ in the embossing step, an embossment having a multiplicity of structural elements is introduced into the embossing varnish layer, said elements corresponding in each case to one of at least two different structure types having different physical properties, and _ in a processing step, the structural elements are selectively provided with at least one color-imparting material, utilizing the different physical properties of the respectively associated structure type, _ wherein at least one color-imparting material is light-sensitive and forms the stated, at least regionally light-sensitive, colored layer which is arranged in the motif plane and which is subjected to exposure radiation through the focusing element grid and is thereby modified in the exposed regions. In this context, thestructure types generated in the embossing step may _ comprise depressions with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer, which have different embossing depths, or _ comprise i) a depression with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer and ii) a subwavelength grating, or _ comprise i) a depression with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer and ii) a surface-enlarging relief structure, optionally recessed in a depression, or _ comprise linear gratings with parallel grating lines, which have different, in particular mutually perpendicular, orientations of the parallel grating lines. Alternatively, it may be provided that _ in the embossing step, a colored embossing varnish layer of a first color is embossed without residual varnish thickness, and _ the structure types generated in the embossing step represent embossing varnish islands with steep side walls and outer faces running substantially to the surface of the embossing varnish layer, which have different heights. The invention also includes a microoptical display arrangement obtainable by a method of the type described, comprising a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and _ a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements, wherein the microfocusing elements have a length and / or width below 30 μm, _ wherein the motif layer comprises an at least regionally light-sensitive colored layer, which is removed in subregions or has altered color, reflection and / or transmission properties in subregions. Advantageously, the motif layer here comprises an embossing varnish layer which is provided with an embossment having amultiplicity of structural elements, all of which are in a predetermined, defined phase relationship, and are provided with at least one color-imparting material. In this case, the embossing varnish layer which is color-filled in subregions preferably forms the stated at least regionally light- sensitive colored layer. Spherical microlenses, aspherical microlenses and lenticular lenses, in which the light-sensitive layer can be acted upon through the focusing element grid, are advantageous candidates as microfocusing elements. According to a further aspect of the invention, however, it is also possible to use more general micro-viewing elements for viewing the micromotif elements, which can also be used in order to regionally modify the light-sensitive layer. In this case, in addition to the already stated microlenses, microconcave mirrors, in particular, but also pinhole diaphragms, slit diaphragms, pinhole or slit diaphragms provided 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 else masking effect, are candidates as micro-viewing elements. This more general aspect of the invention includes a method for generating a microoptical display arrangement which comprises a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements. In this context, in the method for producing the colored motif layer, _ an at least regionally light-sensitive colored layer is arranged in the motif plane, and _ the light-sensitive layer is exposed to exposure radiation such that the micro- viewing elements generate, in a locationally modulated manner, 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. For example, when using microconcave mirrors, the light-sensitive layer can be exposed over the full area from the concave side of the microconcave mirrors. Although in this case the entire area of the light-sensitive layer is transmitted by the exposure radiation, high radiation intensities occur only where the reflected light impinges on the light-sensitive layer in a bundled manner due to the focusing effect of the microconcave mirrors. The light-sensitive layer is advantageously selected as a layer with a threshold effect, for example as a photoresist which becomes soluble (positive resist) or insoluble (negative resist) only on exposure to a certain threshold intensity. A modification of the light-sensitive layer by a change in the solubility therefore takes place only in regions subjected to higher radiation intensity, while the regions subjected to lower radiation intensity remain unmodified and do not alter their solubility. The detailed explanations made in the case of the more specific microfocusing elements apply correspondingly to advantageous configurations of the method. The more general aspect of the invention also includes a microoptical display arrangement obtainable by a method of the type just described, comprising a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and _ a viewing element grid composed of a plurality of micro-viewing elements for viewing the micromotif elements, wherein the micro-viewing elements have a length and / or width below 30 μm, _ wherein the motif layer comprises an at least regionally light-sensitive colored layer, which is removed in subregions or has altered color, reflection and / or transmission properties in subregions. Further working examples and advantages of the invention are elucidated hereinafter with reference to the figures, the representation of which dispenses with reproduction to scale and in proportion, in order to increase illustrativeness. In the figures, Fig. 1 schematically shows a banknote which is provided with two security elements produced according to the invention, Fig. 2 shows the construction and the basic functioning of moiré magnification arrangements produced according to the invention, Fig. 3-10 each illustrate, in a plurality of partial images, methods of a first method group, Fig. 11 illustrates, in a plurality of partial images, methods of a second method group, and Fig. 12 illustrates, in a plurality of partial images, an advantageous combination of methods of the first and second method groups. The invention is now be explained using the example of the production of microoptical security elements for a banknote. Fig. 1 in this regard shows a schematic representation of a banknote 10, which is provided with two security elements 12 and 16 produced according to the invention. The first security element represents a security thread 12, which protrudes on the surface of the banknote 10 at certain window regions 14, while it is embedded inside the banknote 10 in the regions located between said window regions. The second security element is formed by an adhesively bonded transfer element 16 of any shape. The security element 16 may also be designed in the form of a cover film that is arranged over a window region or a continuous opening of the banknote. 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 microoptical security feature. In the following, with reference to Fig. 2, the structure and the basic functioning of such moiré magnification arrangements are first briefly illustrated and a series of working examples for advantageous production methods according to the invention are then described in more detail. With reference to Fig. 2, a microoptical 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-shaped arrangement of microlenses 24 which form a grid of preselected symmetry on the surface of the carrier film. The usually spherical or aspherical microlenses 24 preferably have a diameter of 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 specific embodiments. On the lower side of the carrier film 22, a motif layer 26 is arranged which contains a grid-shaped arrangement of different-colored micromotif elements 28-1, 28-2 having a size of between 0.5 μm and 50 μm, in particular between 3 μm and 35 μm. The grid arrangements of the micromotif elements 28-1, 28-2 and of the microlenses 24 are matched to one another in a manner typical of moiré magnification arrangements, being more particularly slightly rotated with respect to one another or distorted with respect to one another, in order to achieve a moiré magnification and optically variable effects, for example running, pumping, morphing, flipping or stereo effects, through interaction of the micromotif elements and the microlenses. In different configurations, the micromotif elements and the microlenses can also be matched to one another in such a way that they form a modulo magnification arrangement or a non-magnifying lens grid image. The motif layer 26 can be part of the carrier film 22 or be applied to the carrier film 22, but it can also be present, for example, on a separate carrier film and be completed with an optical spacer layer with a microlens arrangement to form a moiré magnification arrangement. For a more detailed illustration of the functioning and for advantageous configuration of micromotif elements and microlenses, reference is made to the German patent application DE 10 2005 062 132 A1 and the international applications WO 2007 / 076952 A2 and WO 2009 / 000528 A1. The subject of the present invention is not the structure of moiré enlargement arrangements, which is known per se, but rather special production methods for the micromotif elements of the motif layer. These make it possible for the security elements produced according to the invention to have sections visible to the naked eye which change color when the viewing situation is changed, wherein the colored microstructures of the motif layer that generate the different colors are in a defined phase relationship with one another. It has been found that security elements with these characteristics combine good recognizability of the displayed motifs with high forgeproofing. The reliable production of a motif layer with a phase-accurate arrangement of multicolored micromotif elements represents a high technological obstacle, which can, however, be overcome with the methods described according to the invention. First, with reference to Figures 3 to 10, methods according to the invention of a first method group are described, which are essentially based on phase-accurate embossing of an embossing varnish layer with structural elements of various structure types. These methods are claimed in the present patent application only in combination with the methods of the second method group, described further on below, which are essentially based on a modification of the motif plane by irradiation from defined spatial angle ranges through the microlens array. Figure 3 illustrates a method according to a first example. Referring first to Fig. 3(a), for the production of the motif layer 26 of a moiré magnification arrangement, an embossing varnish layer 32, advantageously a UV embossing varnish layer, is applied to a carrier film 38. An embossment 30 is introduced into the embossing varnish layer 32 that comprises a multiplicity of structural elements 34, 36, which each correspond to one of two different structure types and which, after ink filling or other processing steps, in the finished security element form the micromotif elements 28-1, 28-2 with the different colors used for the motif to be displayed. In Fig. 3, as well as in the further figures, for illustration purposes only one unit cell 25 of the motif layer of the moiré magnification arrangement is shown in cross section in each case, but it is understood that the embossment 30 in the face of the motif layer 26 contains a multiplicity of structural elements 34, 36 which are arranged repeatedly in grid-like manner in order to generate the desired appearance of the finished moiré magnification arrangement in a manner known per se in interaction with the microlenses of the microlens grid. The entire embossment 30 is generated with an embossing tool which has a multiplicity of embossing elements corresponding to the structural elements 34, 36. In this case, all structural elements 34, 36 of the embossment 30 are produced by the same embossing tool in a single embossing step, with the result that the phase relationship between the embossing elements that is dictated by the embossing tool is converted over the entire area of the motif layer 26 into a corresponding phase relationship between the embossed structural elements 34, 36. In the example of Fig. 3, the two structure types of the structural elements 34, 36 are depressions with steep side walls (angle to the surface at least 75°, preferably even more than 85°) and with base faces running essentially parallel to the surface. The two structure types differ in the depth of the structures, that is to say in the distance from the base face to the surface of the embossing varnish layer 32, which has one of two predetermined values t1 and t2, respectively. The shallower structures 36 of the first structure type have a depth <semantics>t2<annotation encoding="application / x-tex">t_2< / annotation>< / semantics> of between 0.5 and 5 <semantics>μ<annotation encoding="application / x-tex">\mu< / annotation>< / semantics>m; the deeper structures 34 of the second structure type have a depth t1 of between 1 µm and 20 μm. Here, 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 <semantics>t2=2μm<annotation encoding="application / x-tex">t_2 = 2 \mu m< / annotation>< / semantics> and the deeper structures have a depth of <semantics>t1=6μm<annotation encoding="application / x-tex">t_1 = 6 \mu m< / annotation>< / semantics>, being thus 3 times as deep as the shallower structures. After the embossing step, in a first printing step, a first ink 40 is printed onto the film with the embossed embossing varnish layer 32, specifically in an amount which approximately fills all the depressions 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 method. As a special feature, the ink 40 used has a large solvent fraction, which is removed by drying by the doctor blade or wiping method and thus leads to contraction of the ink 40 in the depressions 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 contraction process than in the shallower structures 36, as shown in Fig. 3(c). For example, the shallower structures 36 after application and drying of the ink are 1.2 µm full and the deeper structures are 3.6 µm full (contraction in each case 40%) of ink 40 and a free space remains of 0.8 μm for the shallower structures 34 and of 2.4 μm for the deeper structures 36, respectively. Subsequently, in a second printing step, a second ink 42 is printed on which contains little or no additional solvent. The second ink 42 is also applied in an amount which fills the remaining depressions but does not leave large residual amounts on the surface of the film. After a subsequent doctor blade or wiping method, the second ink 42 covers the first ink 40 in the structural elements 34, 36, while outside the structural elements neither of the two inks is present, as shown in Fig. 3(d). After completion by a microlens arrangement 24, the structure elements 34, 36 filled with ink 40, 42 form the micromotif elements of the motif layer 26. In the finished security element, the microlens arrangement 24 can be arranged on each of the two sides of the varnish layer 32 of Fig. 3(c). If the microlens arrangement 24 is arranged on the upper side O of the varnish layer 32, the depths t1, t2 of the structural elements 34, 36 and the intensities of the two inks 40, 42, in particular the ink thickness and the pigmentation of the two inks 40, 42, are preferably chosen such that the first ink 40 in the shallower structures 36 still shows strongly through the second ink 42, while it is covered in the deeper structures 34 by the second ink 42 with so great a layer thickness that it is imperceptible or barely perceptible any longer there. As a result, the shallow structures 34 then appear in a mixed color of the first ink 40 and second ink 42, while the deeper structures 36 show substantially the second ink 42. For example, if the first ink 40 is a blue ink and the second ink 42 is a yellow ink, then when viewed from the upper side O, the shallow structures 34 appear with the mixed color green and the deeper structures 36 with the second color yellow. If, on the other hand, the microlens arrangement 24 is arranged on the lower side U of the varnish layer 30, the depths t1, t2 of the structural elements 34, 36 and the intensities of the two inks 40, 42, in particular the ink thickness and the pigmentation of the two inks 40, 42, are preferably chosen such that no light colored by the second ink 42 appears through the first ink 40 in the deeper structures 34, and so these structures can be seen in the first ink 40. In the shallower structures 36, the second ink 42 shows through the first ink 40, such that the viewer perceives the mixed color of the two inks. If, for example, the first ink 40 is again a blue ink and the second ink 42 is a yellow ink, then, when viewed from the lower side U, the shallow structures 34 appear with the mixed color green and the deeper structures 36 with the first color blue. In both variants, a motif layer 26 with two different-colored micromotif elements 34, 36 can be generated by the method described, these micromotif elements being in a fixed, predetermined phase relationship over the entire area of the motif layer, thus being arranged in phase-accurate fashion in the motif layer. In a modified, likewise advantageous procedure, the first ink 40 has a low opacity and a low solvent content. In this variant, ink transfer is set such that after the first printing step, only the shallower structures 36 are completely filled, as shown in Fig. 3(e), while filling volume is still available in the deeper structures 34. In the second printing step, a second ink 42 is then applied, which can only be absorbed by the deeper depressions and there covers the first ink 40 with the low opacity, as shown in Fig. 3(f). This modified procedure is advantageous in particular when viewing the microstructure arrangement from the lower side – only the first ink 40 is visible in the shallower structures 36, while in the deeper structures the second ink 42 shows through the first ink 40, such that the viewer perceives the mixed color of the two inks 40, 42. If, on the other hand, the microlens arrangement is arranged on the upper side O, then an ink with high opacity can also be selected for the first ink 40. In all variants, during the embossing step, embossing can take place into a still- liquid UV varnish as an embossing varnish layer on a carrier film before the UV curing takes place, typically while the film coated with UV varnish is wrapped around the embossing tool. On leaving the embossing tool, the structures are then already cured to such an extent that they retain their shape and no longer flow. Pre- curing of the UV varnish before reaching the embossing tool and / or post-curing after leaving the embossing tool may also be advantageous. As an alternative to UV embossing, embossing can take place into a thermoplastic embossing varnish as embossing varnish layer, which is so soft under the prevailing temperatures and the applied pressure between the embossing tool and the counter- pressure element that the structures are molded into the thermoplastic varnish with sufficiently good dimensional accuracy. Alternatively, it is also possible, although not explicitly preferred at present, to use a thermoplastically deformable film, so making the use of an additional thermoplastic embossing varnish unnecessary. The further examples of Figures 4 to 10 are also each substantially based on an embossing method in which, firstly, structural elements are introduced into the motif layer in a single embossing step by the same embossing tool, so that the phase relationship of the embossing elements that is dictated by the embossing tool is converted over the entire area of the motif layer into a corresponding phase relationship of the embossed structural elements. The embossed structural elements are then suitably further treated by ink filling, metallization and / or photoresist coating in order to form the desired different-colored microstructure elements of the motif layer. The differences between the further described methods and the method of figure 3 are predominantly highlighted below, while the basic observations made there also apply to the further examples. Figure 4 illustrates a second example, which uses a combination of ink filling of depressions and resonance effects in metallized subwavelength gratings for color generation. With reference to Fig. 4(a), in this example, an embossment 50 is introduced into an embossing varnish layer 32 in a single embossing step, said embossment having a multiplicity of structural elements 54, 56 which each correspond to one of two different structure types and which, in the finished security element, form the micromotif elements with the different colors used. In this case, the first structural elements 54 are formed substantially like the shallower structural elements 36 in Fig. 3 with steep side walls, a base face running approximately parallel to the surface, and a depth of 0.5 to 5 µm. The structural elements 56 are of a different structure type, which represents not a depression but rather a one-dimensional or two-dimensional subwavelength grating 58 with a period of between 100 and 400 nm and a depth of between 50 and 400 nm. After the embossing step, the embossed varnish layer 32 is provided in a metallization step with a metallization 52 over its full area, as shown in Fig. 4(b). For the metallization 52, it is possible in particular to use metals such as Al, Cr, Cu, Ti, Au, Fe, Ni and their alloys. The metallization advantageously represents a color- shifting multilayer system, consisting of a semitransparent metal, a dielectric such as SiO2 or ZnS, and a reflective metal layer. Alternatively, instead of the metallization 52, it is also possible to use layer systems which consist, for example, of a sequence of dielectric layers of low and high refractive index. In the regions provided with the subwavelength gratings, the metallization 52 produces color filters which spectrally absorb light of certain wavelengths on account of resonance phenomena such as plasmon excitations, whereas the light of other wavelengths is almost completely reflected. In this case, the grating parameters and the type of metal applied determine the observable color. If different grating structures are used, different color effects can also be achieved. In the next working step, as already described for Fig. 3, an ink 40 is printed onto the embossed and metallized varnish layer 32 and excess ink is removed by a doctor blade or wiping method, such that the ink remains substantially only in the depressions of the first structural elements 54, as shown in Fig. 4(c). In this case, care must be taken to ensure that the ink 40 is removed as completely as possible from the comparatively shallow and narrow subwavelength gratings 56, since otherwise a mixed color is produced in these sections, resulting from the absorption of the ink remaining there and the absorption effect of the subwavelength gratings. In order to minimize this effect, it is also possible here to use an ink 40 with an appropriate solvent fraction. When viewed from the upper side, the first recessed structural elements 54 then appear in the applied ink 40, while the structural elements 56 appear in the color defined by the grating parameters and the type of metallization of the subwavelength gratings. After completion by a microlens arrangement 24, the metallized or ink-filled structural elements 54, 56 form the micromotif elements of the motif layer. In one modification, antireflection structures, in particular so-called motheye structures, can also be used for the structural elements 56, instead of the subwavelength gratings. The area sections provided therewith have a dark to black effect for a viewer after the metallization 52, since the motheye structures absorb incident light in a broadband manner over the entire visible spectral range. By means of these methods, too, a motif layer 26 can thus be produced with two different-colored micromotif elements 54, 56, which are in a fixed, predetermined phase relationship over the area of the motif layer. In the example of Fig. 5, a combination of ink filling and regional coloring by full- area exposure is used to produce the micromotif elements. For a more detailed explanation, in this example, with reference to Fig. 5(a), an embossment 60 having a multiplicity of structural elements 54, 66 is introduced into an embossing varnish layer 32. In this case, the first structural elements 54 are designed as described in Fig. 3, while the second structural elements 66 are formed by surface-enlarging relief structures, which in the finished security element allow light to pass through more easily than the other regions. For this purpose, the structural elements 66 are designed preferably in the form of a relief structure with a large depth-to-width ratio. In particular, the relief structure can be designed periodically as a one-dimensional or two-dimensional grating, wherein the grating period advantageously varies between 300 nm and 20 µm and the depth lies between 0.5 times and 5 times the period. Alternatively, with the same structure sizes, the relief structure can also be aperiodic. In a subsequent metallization step, the embossing varnish layer is provided with a metallization 62 which is applied in all regions in a uniform amount and thus with a uniform nominal layer thickness. This nominal layer thickness refers to the layer thickness established during metallization on a flat surface region. Typical nominal layer thicknesses are in the range from 10 nm to 100 nm. Owing to the large depth- to-width ratio in the region of the second structural elements 66, these regions have an enlarged surface area, such that the actual layer thickness of the metallic coating resulting per unit surface area is smaller than in the shallow regions. This phenomenon is illustrated in the details 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. The type of metallization and the grating parameters can advantageously be selected such that light of certain wavelengths is transmitted particularly well in the second structural elements 66, while it is largely reflected, but not transmitted, by the metallization 62 in the remaining regions of the embossing varnish layer. In the next working step, as described in relation to Fig. 3, a first ink 40 is printed onto the embossed and metallized varnish layer 32 and excess ink is removed by a doctor blade or wiping method, such that the first ink 40 remains substantially only in the depressions in the first structural elements 54. Subsequently, over the full area, a negative photoresist 64 of a second color, i.e., a colored photosensitive varnish which becomes insoluble by exposure, is printed over the full area onto the metallized and partially filled varnish layer 32, as shown in Fig. 5(d). The structure coated with the photoresist 64 is then exposed (flood exposure B) over the full area from the lower side, i.e., through the metallized varnish layer 32, as shown in Fig. 5(e). The exposure radiation B is able to penetrate the metallization 62 only in the comparatively transparent regions of the second structural elements 66 and crosslink the photosensitive varnish 64 there to form crosslinked regions 68. In the other surface regions, the metallization 62 is substantially opaque for the exposure radiation B, on account of its greater layer thickness, and so the photoresist 64 behind it is not crosslinked there. In this case, care must be taken to ensure that the small amount of first ink 40 which may remain in the second structural elements 66 during the ink filling does not substantially attenuate the exposure radiation B. The photoresist 64 is then developed in a development step and is thereby removed wherever it has not been crosslinked, in other words everywhere except in the crosslinked regions 68 with the second structural elements 66. This results in a motif layer as illustrated in Fig. 5(f), in which the first structural elements 54 are filled with the first ink 40 and the second structural elements 66 are coated with the photosensitive varnish 64 of the second color. If necessary, the exposed regions of the metallization 62 can subsequently be removed by an etching step in order to create a largely transparent background. If this etching step is omitted, the background is perceived by the viewer as metallically reflecting. In both variants, the filled or coated structural elements 54, 66, after completion by a microlens arrangement 24, form the micromotif elements of the motif layer. In a particularly advantageous variant of the stated method, which is illustrated in Fig. 6, the second structural elements 76 of the embossment 70 are formed by depressions 72 of which the base faces are formed by surface-enlarging relief structures 74 of the type described in relation to Fig. 5. In this case, 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 µm, such that the surface- enlarging relief structures 74 are recessed completely in the depressions 72, as illustrated in Fig. 6(a). The varnish layer 32 embossed in this way is coated with a metallization 62 and then a negative photoresist 64 in the second color is applied to the metallization 62 in an ink filling process and excess ink is removed by a doctor blade or wiping method. The photoresist 64 then just fills the depressions 54, 72 in the first and second structural elements. The structure thus filled is then exposed (flood exposure B) over the full area from the lower side through the metallization, as shown in Fig. 6(b). The metallization 62 is transparent only in the region of the surface-enlarging relief structures 74 of the depressions 72, such that the photoresist 64 is crosslinked only there to form crosslinked regions 68. In the subsequent development step, the uncured photoresist 64 is removed from the depressions in the first relief structure 54, such that only the cured resist 64 remains in the depressions 72 of the second relief structure 76, as shown in Fig. 6(c). Subsequently, in a printing step, the first ink 40 is printed onto the varnish layer 32 thus obtained and the excess ink is removed by a doctor blade or wiping method, such that the first ink 40 remains substantially only in the depressions in the first structural elements 54, as shown in Fig. 6(d). After completion by a microlens arrangement, the structural elements 54, 76 filled with ink form the micromotif elements of the motif layer. 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 a subsequent flood exposure, but rather the enlarged surface ensures that the applied metallization 62 in these regions can be removed more easily by an interposed etching step than outside the structural elements 76 and can therefore be selectively etched. For a more detailed explanation, Fig. 7 in Fig. 7(a) firstly shows the embossed and metallized varnish layer 32 with the first structural elements 54, the second structural elements 76 with the surface-enlarging relief structures 74 recessed in a depression 72, and the metallization 62 already applied. In this example, too, the surface-enlarging relief structures 74 can be formed by relief structures having a large depth-to-width ratio and can have the same arrangements and dimensions as described for Figures 5 and 6. As explained above, the metallization 62 in the second structural elements 76 has a smaller layer thickness than outside the structural elements because of the locally enlarged surface area. In an etching step which takes place after the metallization, the etching can therefore be ended 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% strength sodium hydroxide solution. In order to influence the etching dynamics, the temperature of the alkali solution can be regulated, for example by means of a heating roll. The state after such a selective etching step with demetallized relief structures 74 is shown in Fig. <semantics>7(b)<annotation encoding="application / x-tex">7(b)< / annotation>< / semantics>. Now, as in the method of Fig. 6, a negative photoresist 64 of the second color is printed on in an ink filling method, the structure coated with photoresist is exposed over the full area from the lower side through the metallization 62, 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 depressions 72, such that after the development step only the depressions 72 of the second structural elements 76 are filled with cured varnish 64 of the second color, as shown in Fig. 7(c). Subsequently, in a printing step, the first ink 40 is printed onto the varnish layer 32 thus obtained and the excess ink is removed by a doctor blade or wiping method, such that the first ink 40 remains substantially only in the depressions of the first structural elements 54. The exposed regions of the metallization 62 can subsequently be removed by a further etching step in order to create a largely transparent background, as shown in Fig. 7(d). After completion by a microlens arrangement, the structural elements 54, 76 filled with ink form the micromotif elements of the motif layer. In an advantageous method variant, the two last-mentioned steps are changed in their order; that is to say, first the metallization 62 is removed and only then is the first ink 40 applied in a printing step. In this case, the motif layer no longer contains any metallization, as shown in Fig. 7(e), and can be combined for viewing with a microlens arrangement both on the upper side and on the lower side. In the method variants of Figures 5 to 7, instead of a negative photoresist which becomes insoluble by exposure, a positive photoresist can also be used, which in an already insoluble form becomes soluble again by exposure. When a positive photoresist is used, the first and second colors change places, as illustrated with reference to Fig. 8. Starting from the varnish layer of Fig. 7(b), which is demetallized in regions, a positive photoresist 78 of a second color is printed on in an ink filling method and the excess ink is removed by a doctor blade or wiping method, as shown in Fig. 8(a). The positive photoresist 78 is rendered soluble again only in the demetallized depressions 72 of the second structural elements 76 by full-area exposure from the lower side through the metallization 62 and is removed in the subsequent development step, while the photoresist 78 remains in the depressions of the first structural elements 54, as shown in Fig. 8(b). Subsequently, in a printing step, the first ink 40 is printed onto the varnish layer 32 thus obtained and the excess ink is removed by a doctor blade or wiping method, such that the first ink 40 remains substantially only in the depressions 72 of the second structural elements 76, as shown in Fig. 8(c). Here, too, the exposed regions of the metallization 62 can subsequently be removed by a further etching step in order to create a largely transparent background. In any case, the ink / color-filled structural elements 54, 76 form the micromotif elements of the motif layer after completion by a microlens arrangement 24. In the variant of the invention in Fig. 8, it may be advantageous to remove the metallization 62 of the background regions even during or after the selective etching, for example by peeling with a laminated film or kiss-printing of an etching solution. As a result, the end product becomes transparent, especially since any toning film of the photoresist present is likewise exposed during flood exposure and then removed completely during development. Figure 9 illustrates a further advantageous example, in which subregions appearing with different colors in the finished security element are defined by embossed, polarizing structures. These polarizing structures are defined by embossed structures, in particular by linear gratings with periods in the range from around 100 nm to 1 µm and a depth of 50 nm to 5 μm. The embossed gratings are subsequently provided with a metal layer and then act in transmission as polarizing filters, thus transmitting only light having the appropriate linear polarization direction, while they do not transmit light having the polarization direction perpendicular thereto. In the example, two polarizing structures with mutually perpendicular polarization directions are first established in the motif layer for the two colors to be generated. With two exposure steps with polarized light, in which the polarization direction corresponds in each case to that of one of the two embossed polarizers, the two colors can then be applied in a defined manner one after the other. For a more detailed explanation, Fig. 9(a) in cross section and Fig. 9(b) in plan view show a motif layer with an embossment 80 which is introduced into a varnish layer 32 and has first structural elements 84 in the form of first polarizing structures with parallel grating lines of a first orientation and has second structural elements 86 in the form of second polarizing structures with parallel grating lines of a second orientation perpendicular to the first orientation. In the example, the structural elements 84, 86 are formed by embossed linear gratings having a period of 200 nm and a depth of 0.3 µm. After the embossing step, the embossed varnish layer 32 was provided with a metal layer 82, it being advantageous for high transparency to demetallize the raised regions of the grating, for example by a metal transfer method, so that the wire grating polarizers shown in Figures 9(a) and (b) are produced. Depending on whether the background region is to be colored or not, the metal outside the structural elements 84, 86 can likewise be removed or it remains. In the next method step, the (partially) metallized structure is coated over the full area with a negative photoresist 90 of a first color and the coated structure is subjected from the lower side through the metallization 82 to linearly polarized exposure radiation B1, of which the polarization direction is matched to the polarization direction of the first structural elements 84. The polarized exposure radiation B1 is therefore transmitted by the metal layer 82 only in the region of the first structural elements 84, but otherwise blocked everywhere, such 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 illustrated in Fig. 9(d). Subsequently, a negative photoresist 92 of a second color is printed on over the full area and the coated structure is subjected from the lower side through the metallization 82 to linearly polarized exposure radiation B2 of which the polarization direction 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, such 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). Figure 9(g), analogously to figure 9(b), shows a plan view of a unit cell of the finished motif layer with the ink / color-coated structural elements 84, 86, which, after completion by a microlens arrangement 24, form the micromotif elements of the moiré magnification arrangement. Optionally, the metallic background can be subsequently removed, for example by etching. In modifications, instead of the negative photoresists 90, 92, positive photoresists can also be used; the use of a combination of positive and negative photoresists is also possible. A further advantageous method variant, in which a colored embossing varnish and a selective coloring method are used, is now described with reference to Fig. 10. In this method variant, an embossing varnish layer 102 colored with a first color is applied to a carrier film 38, as shown in Fig. 10(a). The colored embossing varnish layer 102 is then provided in an embossing step with an embossment 100 with structural elements 104, 106 which each correspond to one of two different structure types. In order to avoid background toning in the first color that is perceptible to the viewer, the embossing here takes place without residual varnish thickness, thus taking place such that the portions of the first embossing varnish 104, 106 that arise as a result of the embossing are not contiguous, but are separated via intermediate regions 108 that are free of a varnish layer. Such residual varnish thickness-free embossing can be achieved by good coordination of the surface energies of the substrate 38 and of the embossing tool with regard to the embossing varnish 102 used. A small residual amount of color 102 remaining in the intermediate regions 108 can be tolerated under certain circumstances if the contrast of the microstructures 106 is still sufficiently high in comparison with the background. In contrast to the method of Fig. 3, as structural elements, no depressions in the embossing varnish, but instead raised embossing varnish islands 104, 106, as shown in Fig. 10(b), are generated with this method. The embossing varnish islands 104, 106 have different heights above the surface of the carrier film 38, with the lower embossing varnish islands 106 have a height of between 0.5 and 5 μm, and the higher embossing varnish islands 104 have a height of between 0.75 μm and 20 μm. The higher islands are at least 1.5 times, preferably 2 to 4 times, as high as the lower islands. In a subsequent transfer step, a second ink 110 is then selectively transferred only to the higher embossing varnish islands 104, as shown in Fig. 10(c). Such selective ink transfer can be accomplished, for example, by the kiss-print method or with the aid of another color transfer method. This second ink 110 is advantageously chosen here such that, when viewed from above, the second color layer is opaque or at least largely opaque, irrespective of its thickness, such that the higher embossing varnish islands 104 as a result of the ink covering form structural elements which appear with the second color, while the lower embossing varnish islands 106 form structural elements which appear in the first color of the embossing varnish 102. In a modification, the second ink 110 can also be non-opaque, and the higher structure elements 104 then appear with the mixed color of the inks 102 and 110. If the first ink 102 is not opaque, but instead translucent, then it is also possible to view the motif layer from below. In both variants, such a method produces a motif layer 26 with two different- colored micromotif elements which have a fixed, dictated phase relationship over the area of the motif layer. In an alternative procedure, the structural elements can also be applied to the carrier film 38 via a micro-gravure printing process, as described, for example, in the document WO 2008 / 000350 A1. With reference to Fig. 11, methods of a second method group are now described, which are essentially based on a modification of the motif plane by irradiation from defined spatial angle ranges through the microlens array. In this case, laser light is preferably used, since it is particularly intensive and can be generated largely in parallel, such that very good control is possible over the spatial angle range from which the light strikes the sample. It is important that the exposure always takes place from the lens side and through the microlenses, so that the light-refractive effect of the lenses results in focusing of the radiation onto the motif plane. As a result, modifications which lead to the generation of the desired microstructure elements can be introduced into the motif plane in a well-defined manner with respect to the position of the microlenses. Because of the identical beam path, a viewer can later see the modified area region in the finished security element from the same spatial angle from which exposure was undertaken during production. This offers a considerable advantage even over the methods based on pure embossing, in which microstructure elements can be produced that are in a defined phase relationship relative to one another, but the positioning of the microstructure elements relative to the microlenses cannot easily be adjusted in a controlled manner. In addition, methods in which all microstructure elements are generated by exposure through the microlenses can also be used when the lenses are arranged not regularly but instead irregularly. By suitable fanning of the light incident on the microlens array, the exposed regions can be enlarged, since the lenses, which usually focus parallel light in the focal plane, in this case do not bring about complete focusing. A focal point or a focal line then turns into correspondingly expanded regions, such that the exposure step can be carried out more quickly, albeit generally at the expense of the spatial resolution. A similar effect can be achieved if the motif plane is deliberately established differently from the focal plane. Figure 11 illustrates schematically a method according to a first working example of the invention. The starting point is a carrier film 22 which is provided on its upper side O with an arrangement of microlenses 24. The lower side U of the carrier film defines a motif plane in which the microstructure elements are to be arranged and which lies in or close to the focal plane of the microlenses 24. With reference to Fig. 11(a), a first negative photoresist 200 of a first color is first applied over the full area to the lower side U of the carrier film 22. The arrangement is then subjected to exposure radiation B1 from the lens side from a defined first spatial angle range <semantics>R1<annotation encoding="application / x-tex">R_1< / annotation>< / semantics>. As a result of the focusing effect of the microlenses 24, the first surface portions 202 of the photoresist 200 situated in the focus are exposed under each lens, while the surrounding regions outside the first surface portions 202 receive no radiation intensity or hardly any 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 regions with the exception of the first surface portions 202, as shown in Fig. 11(b). Subsequently, a second negative photoresist 204 of a second color is applied over the full area to the lower side U of the carrier film 22. The arrangement is then subjected to exposure radiation B2 from the lens side from a defined second spatial angle range R2, as shown in Fig. 11(c). From this spatial angle range, different, second surface portions 206 lie in the focus below each lens, such that in this step only the different, second surface portions 206 are sufficiently exposed for crosslinking. In the subsequent development step, the second photoresist 204 is therefore removed in all regions with the exception of the second surface portions 206, as shown in Fig. 11(d). The first and second surface portions 202, 206 then form the different-colored micromotif elements of the motif layer, with the first surface portions 202 of the first color being visible from the first spatial angle range R1 and the second surface portions 206 of the second color from the second spatial angle range R2. In this case, the second spatial angle range lies at least partially outside and preferably predominantly or even completely outside the first spatial angle range. Instead of the stated negative photoresists 200, 204, positive photoresists can also be used, and a combined use of positive and negative photoresists is also possible. The cycle of resist application, exposure and development can also be carried out more than twice, in which case it is recommended to adapt the respective spatial angle ranges: the greater the number of exposures carried out, the smaller the associated spatial angle ranges should generally be in order to avoid disruptive overlap. When using positive photoresists, it is possible, for example, to proceed as follows: - applying a positive photoresist, - exposing from spatial angle 1, - developing, - ink filling with ink 1, - stripping (removing) the photoresist without impairing the ink filling, - again applying a positive photoresist, - exposing from spatial angle 2, - developing, - ink filling with ink 2, and - stripping (removing) the photoresist without impairing the ink filling. This variant consists of a combination of exposures and ink fillings. It is possible here always to use the same photoresist, since it does not remain on the film. The procedure can, of course, also be carried out more than twice. In a modification of the method described, exposure and development are replaced by laser ablation in each case. In this case, inks are used which are removed by the high achievable intensity of the laser radiation focused by the microlenses. Here, too, the cycle of coating and laser ablation can be performed more than twice. Furthermore, instead of a laser-induced ablation, it is also possible to use a method in which an applied ink is not removed but is instead modified in a targeted manner by the laser radiation. For example, it is possible to bleach or change the hue of specific inks by the high-intensity focused laser radiation. Instead of ink layers, it is also possible to apply one or more layers of a PCM (phase change material) material whose structure and thus interference color can be transformed by laser radiation. In the production of microoptical security elements, a combination of methods of the first and second method groups can also be used, i.e., both an embossing method and exposure through the microlenses can be used in order to produce the different-colored microstructure elements. In this case, in particular, microstructures can first be produced by embossing and ink filling and subsequently removed or changed again by an exposure step through the microlenses. In principle, all of the above-described process variants and partial process steps can be used, i.e. in particular the printing of an ink which, after a doctor blade or wiping step, fills only the depressions of an embossing, the application of a photosensitive filling ink (as a positive or negative photoresist) and an ablation or modification of a filling ink with the aid of laser radiation. This makes it possible to achieve, for example, a dynamic optically variable effect that changes its color or disappears in a specific viewing angle range. If microstructures are altered or removed by an exposure step by the microlenses, it may be sufficient to generate embossing elements of only a single structure type in the embossing step, since the color differentiation required for multicolor can be accomplished by the exposure step. Figure 12 illustrates a particularly preferred method variant in this respect. With reference to Fig. 12(a), a carrier film 22 is first provided, which is provided on its upper side O with an arrangement of microlenses 24. An embossing varnish layer 212 is applied on the lower side U of the carrier film defining the motif plane and is provided with an embossment 210 composed of a plurality of depressions 214. All depressions 214 are generated by the same embossing tool in a single embossing step and are therefore in a defined phase relationship to one another. With reference to Fig. 12(b), these structures established as depressions 214 are then filled with a positive photosensitive varnish 216 of a first color and excess ink is removed by a doctor blade or wiping method. The photoresist 216 is then exposed in a partial area region 218 by exposure B from a specific spatial angle range R. In a subsequent development step, the partial area region 218 captured 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 region of the depressions 214, as shown in Fig. 12(c). In the next step, ink filling is carried out with a filling ink 220 of a second, different color. After removal of excess ink by means of a doctor blade or wiping method, the design shown in Fig. 12(d) is obtained, with a motif layer 26 in which the surface portions 218 appear with the second color 220 and the remaining region of the depressions 214 appears with the first color of the photoresist 216. The result is a security feature with a dynamic effect which is the same over the entire viewing angle range. Viewing the feature from the spatial angle range R from which the exposure had taken place, the viewer recognizes the effect in the second color, while the first color is visible from all other perspectives. In general, combinations of the methods of the first and second method groups described here are likewise possible in the sense of serially successive production. By way of example, the methods of the first method group based on embossing structures can be combined with the exposure methods of the second group in the sense of steps carried out successively. The methods according to the invention have been explained illustratively on the basis of 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 for the production of the motif layer of a modulo magnification arrangement or of a lens grid image.

Claims

1. A method for generating a microoptical display arrangement which comprises a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements, wherein, in the method for producing the colored motif layer, an at least regionally light-sensitive colored layer is arranged in the motif plane, and the light-sensitive layer is subjected to exposure radiation through the focusing element grid and is thereby modified in the subjected regions.

2. The method as claimed in claim 1, characterized in that the solubility of the light-sensitive layer in a developing medium is altered by the exposure radiation and in that the light-sensitive layer after the exposure is developed in a developing step and thereby regionally removed.

3. The method as claimed in claim 1, characterized in that the exposure radiation, in particular laser radiation, regionally removes the light-sensitive layer or alters its properties of color, reflection and / or transmission.

4. The method as claimed in any of claims 1 to 3, characterized in that the steps of arranging an at least regionally light-sensitive colored layer in the motif plane and of subjecting the light-sensitive layer to exposure radiation through the focusing element grid for modifying the light-sensitive layer are carried out two or more times with layers of different color and with subjection from different spatial directions.

5. The method as claimed in claim 4, characterized in that a negative photoresist is applied as the at least regionally light-sensitive colored layer, the applied negative photoresist is subjected to exposure radiation through the focusing element grid and thereby made insoluble in the exposed regions, the negative photoresist is then developed in a development step and removed in the unexposed regions, 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 as claimed in claim 4, characterized in that a positive photoresist is applied as the at least regionally light-sensitive colored layer, the applied positive photoresist is subjected to exposure radiation through the focusing element grid and thereby becomes soluble in the exposed regions, the positive photoresist is then developed in a development step and removed in the exposed regions, the recesses formed by the removal of the photoresist are filled with an ink and the positive photoresist is optionally finally removed without impairing the ink filling, said steps of application, exposure, development, ink filling and optionally stripping being carried out two or more times with different ink fillings and with exposure from different spatial directions.

7. The method as claimed in any of claims 1 to 6, characterized in that, for producing the colored motif layer, additionally in an embossing step, an embossment having a multiplicity of structural elements is introduced into an embossing varnish layer, wherein the structural elements are all generated with the same embossing tool in a single embossing step, such that the embossed structural elements are all in a defined phase relationship dictated by the embossing tool.

8. The method as claimed in claim 7, characterized in that after the embossing step, in a processing step, a color layer in the form of a printing ink or of a colored positive or negative photoresist is applied to the embossing varnish layer, such that the color layer completely or partially fills those of the structural elements which are designed in the form of depressions, and / or a color layer in the form of a printing ink or of a colored positive or negative photoresist is applied over the full area to the embossing varnish layer, and / or the embossing varnish layer is provided with a metallization.

9. The method as claimed in claim 7 or 8, characterized in that the structural elements to be at least partially designed in the form of depressions in the embossing varnish layer, and in a processing step, in a first substep, a color layer in the form of a positive photoresist of a first color is applied to the embossing varnish layer, such that the color layer fills those of the structural elements which are designed in the form of depressions, such that the embossing varnish layer which is color-filled in subregions has the stated colored layer which is arranged in the motif plane and is at least regionally light-sensitive, in a second substep, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby rendered soluble in the exposed regions, and the exposed photoresist is developed, such that the photoresist remains in a first subregion of the depressions and is removed in a second subregion of the depressions, and in a third substep, a color layer of a second color is applied to the embossing varnish layer and fills the second subregion of the depressions, such that the first and second subregions of the depressions each form microstructure elements which are visible with a different color.

10. The method as claimed in claim 7 or 8, characterized in that the structural elements to be at least partially designed in the form of depressions in the embossing varnish layer, and in a processing step, in a first substep, a color layer in the form of a negative photoresist of a first color is applied to the embossing varnish layer, such that the color layer fills those of the structural elements which are designed in the form of depressions, such that the embossing varnish layer which is color-filled in subregions forms the stated colored layer which is arranged in the motif plane and is at least regionally light-sensitive, in a second substep, the light-sensitive layer is exposed to exposure radiation through the focusing element grid and the photoresist is thereby rendered insoluble in the exposed regions, and the exposed photoresist is developed, such that the photoresist remains in a first subregion of the depressions and is removed in a second subregion of the depressions, and in a third substep, a color layer of a second color is applied to the embossing varnish layer and fills the second subregion of the depressions, such that the first and second subregions of the depressions each form microstructure elements which are visible with a different color.

11. The method as claimed in claim 7 or 8, characterized in that in the embossing step, an embossment having a multiplicity of structural elements is introduced into the embossing varnish layer, said elements corresponding in each case to one of at least two different structure types having different physical properties, and in a processing step, the structural elements are selectively provided with at least one color-imparting material, utilizing the different physical properties of the respectively associated structure type, wherein at least one color-imparting material is light-sensitive and forms the stated, at least regionally light-sensitive, colored layer which is arranged in the motif plane and which is subjected to exposure radiation through the focusing element grid and is thereby modified in the exposed regions.

12. The method as claimed in claim 11, characterized in that thestructure types generated in the embossing step comprise depressions with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer, which have different embossing depths, or comprise i) a depression with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer and ii) a subwavelength grating, or comprise i) a depression with steep side walls and base faces running substantially parallel to the surface of the embossing varnish layer and ii) a surface-enlarging relief structure, optionally recessed 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. The method as claimed in claim 11, characterized in that in the embossing step, a colored embossing varnish layer of a first color is embossed without residual varnish thickness, and the structure types generated in the embossing step represent embossing varnish islands with steep side walls and outer faces running substantially to the surface of the embossing varnish layer, which have different heights.

14. A microoptical display arrangement obtainable by one of the methods of claims 1 to 13, comprising a colored motif layer, arranged in a motif plane and having a plurality of different-colored micromotif elements, and a focusing element grid composed of a plurality of microfocusing elements for viewing the micromotif elements, wherein the microfocusing elements have a length and / or width below 30 μm, wherein the motif layer comprises an at least regionally light-sensitive colored layer, which is removed in subregions or has altered color, reflection and / or transmission properties in subregions.

15. The display arrangement as claimed in claim 14, characterized in that the motif layer comprises anembossing varnish layer which is provided with an embossment having a multiplicity of structural elements, all of which have a predetermined, defined phase relationship, and are provided with at least one color-imparting material, wherein the embossing varnish layer which is color-filled in subregions preferably forms the stated at least regionally light- sensitive colored layer.