WO2015086766A1

WO2015086766A1 - Article comprising at least one surface having a security feature

Info

Publication number: WO2015086766A1
Application number: PCT/EP2014/077430
Authority: WO
Inventors: Oliver Weiss
Original assignee: Schreiner Group Gmbh & Co. Kg
Priority date: 2013-12-12
Filing date: 2014-12-11
Publication date: 2015-06-18
Also published as: DE102013113938A1

Abstract

Proposed is an article (10) comprising at least one surface (15) having a security feature (5), - wherein the surface (15) comprises a first surface region (11) and a second surface region (12), - wherein the first surface region (11) has a first colour (1) in the area surrounding the second surface region (12) and the second surface region (12) has a second colour (2), - wherein the first colour (1) and the second colour (2) are tailored to the colour sensitivity of the human eye in such a way that a colour difference can be seen between them when they are viewed by the human eye along the line of sight thereof, whereas no colour difference or only a lesser colour difference can be seen between the first colour (1) and the second colour (2) when they are viewed by the human eye outside of the line of sight thereof.

Description

description

The invention relates to an article having at least one surface having a security feature. The article may be any technical product or container that is provided with one or more security features. The surface provided with the security feature can be, for example, an outer surface of the marked object, for example a housing surface or housing wall or another accessible area on the object or container. The article may also be a label which serves to identify other objects, products, containers or devices and is attachable or otherwise attachable to them. The surface having the security feature preferably forms the inscribed or inscribable outside of a label or adhesive label. The article having the surface provided with the security feature may further be a document or other sheet of paper or paperboard, or a film, especially a plastic film. Such and other materials may also be associated with a tag provided with the security feature. The safety feature provided on the surface of the label, container, product or other article, as embodied according to the invention in a special way, can be used, for example, to prove the authenticity or actual origin of the article from the specified manufacturer or supplier and thus an original product of to differentiate between a forgery and a plagiarism.

The provided with the security feature surface is preferably colored, ie neither white nor completely black. The surface therefore leaves the viewer with a color impression, which manifests itself in the form of a perceived brightness, a perceived hue and in the form of a (more or less conscious) perceived color saturation. Often, the surface of the label or the other object at least partially monochrome designed, ie it appears (at least when viewed from a normal working distance and without magnifying glasses or other technical aids) for the user in a uniform base color. Nevertheless, parts of the surface of the label or of the other article may of course also be colored differently. rich, especially labels, which stand out clearly in color from the background or from their surrounding area, so that they are easy to read.

There are known security features that are such that they are not noticeable when viewing and therefore remain hidden without further knowledge. These include labeling of objects by fluorescent or phosphorescent materials, which are provided as lettering or other marking in or on parts of a surface and only light up by the action of UV radiation. Such security features appear in the same color as their background or surrounding area without UV radiation. The color resulting from local application or

Mixing a fluorescent or phosphorescent substance results, is thus mamer to the color of the remaining surface areas of the surface. Metamerism in this sense means that at least in normal light (in particular daylight) provided with the fluorescent or phosphorescent material surface area color lent not borrowed and thus leaves the same color impression as the surrounding areas of this security feature provided surface.

Such a security feature based on luminescence exploits the so-called illumination metamerism; Changing lighting makes it possible to visualize a safety feature which under normal circumstances, especially under normal lighting such as daylight or artificial light, is imperceptible. Although the detection of such a luminescence-based security feature is easily possible with the aid of special UV light sources, it requires that UV lamps be carried and used for this purpose. On the other hand, the normal consumer who normally does not carry such aids will not be able to identify such a security feature, even if he or she is aware of the nature of that security feature and its location on the item.

It is the object of the present invention to provide an article whose security feature is recognizable for anyone, in particular for a normal customer or consumer or an employee of customs, without the aid of specially designed detection devices. At least when the consumer is aware of the nature and nature of the security feature, he should immediately be able to to check the presence of the security feature. Such a review should also be quick and inconspicuous; in particular, in a manner that is not discernible to a bystander as a deliberate examination of the object.

This object is solved by the subject matter of independent claims 1, 4 and 8.

According to one embodiment, the object described here is provided with a security feature whose coloration is chosen in comparison to the surrounding area of the surface such that it depends on the viewing direction of the observer whether the security feature is perceptible to him or not. In this embodiment, it is utilized that the color perception of the retina of the human eye is different in the area corresponding to the viewing direction than in retinal areas at larger angles relative to the viewing direction. The color perception of the human eye in direct proximity to the viewing direction is determined by the nature of the retina in the area of the fovea or the yellow spot; this is the area of the retina upon which the axis of the line of sight (ie, the straight line along which the eye is looking straight and which crosses the pupil as a perpendicular bisector), when extended from the pupil back to the retina. Since the eye always follows along with the line of sight, the area behind the pupil along the line of sight (yellow spot) automatically moves with the line of sight. This retina region, which is arranged near the axis of the axis or approximately directly around the visual axis and which extends around the instantaneous line of sight or visual axis within small angles of up to ± 2 °, is the one of the greatest visual acuity, at least in the healthy eye. It lies in the region of the retina furthest from the pupil; the connecting line between the center of the pupil and the central, near-axis retinal area therefore traverses the center of the eyeball. The region of the retina which is close to the axis or arranged directly around the visual axis is occupied only by the cone-shaped visual cells responsible for color perception. Retinal areas located at larger angles to the viewing direction (ie further away from the axis of the viewing direction) also contain rod-shaped visual cells; where the ratio of the concentrations of the three types of cone-shaped cells is different than in the line of sight. In particular for the so-called 10 ° normal observer for whose visual impression the color perception of the human eye in the range of up to ± 10 ° relative to the viewing direction (in particular in the range of between ± 2 ° and ± 10 ° relative to the viewing direction) is established , colors appear slightly different than along the line of sight (ie within the angular range of ± 2 °). Although colors are not perceived completely differently along the viewing direction (or for the 2 ° normal observer) and outside the viewing direction (especially for the 10 ° normal observer), one and the same color (for example, that of a special dye mixture) can which is reflected from the surface of an object towards the eye, leaving a slightly different color impression in the outer visual field of the human eye (eg for the 10 ° normal observer) than in the viewing direction (ie for the 2 ° normal observer). This effect, in conjunction with the further circumstance that it is possible in principle to produce a certain color impression perceived by the human eye through different types of dyes and their mixing ratios, makes use of the first embodiment. For ease of explanation, reference will hereafter be made to color layers, ie dyes or pigments, which are arranged as opaque, opaque additives or colorant on or in the surface of an article and determine the color impression of the light reflected by the article. In the simplest case, the surface has a mixture or combination of two, three or more dyes or color pigments whose mixing ratio or their weighting of their surface portions (at a sufficiently large viewing distance to a point grid printing on the other side of the resolution of the human eye) gives the color impression, which arises on the respective part of the retina.

According to the first embodiment, the motif serving as a security feature is designed in a color which approximately matches the color of the surrounding surface of the object, but has such a color difference, in particular a color difference, to the color of the surrounding surface which is either only along the line of sight of the object Observer (within the angular range of ± 2 °) or only out of sight (for example, outside the angular range of ± 2 °, approximately in the angular range of 2 ° to 10 ° or outside the angular range of ± 10 °) is perceptible. This allows selective readability of the security feature (such as nes part of a longer alphanumeric lettering) only at that point of the surface of the object, which is currently fixed by the viewer (claim 1), or alternatively only at those points of the surface of the object, the parts of the retina outside or away from the viewing direction be (claim 4). This has the consequence that the viewer when looking at the object either unexpectedly encounters a lettering on the object when his gaze wanders this, or alternatively perceives a label away from his line of sight means, but disappears as soon as he looks at her. According to a second embodiment (claim 8) is exploited in the color of the security feature compared to its surrounding area, the fact that digital image sensor chips, as installed in commercially available cameras, cell phones, video cameras, smart phones and other entrained in everyday electronics, one relative to each other uniform, but different from the human eye color sensitivity course (over the spectrum of visible wavelengths between 380 and 780 nm) have. Although the cameras and mobile phones etc. are supposed to simulate the color perception of the eye, on closer inspection typical differences between the color sensitivity of the human eye and the course of the color sensitivity of a digital image sensor, ie the technically simulated color perception are detectable.

In the second embodiment, which takes advantage of this fact, the color of the color fields designed as security feature (lettering or other motif) and the color of the surrounding surface area of the object surface are selected such that the light beam reflected by the subject and the light beam reflected from the surrounding surface area, when measured in a digital image sensor of a digital camera (including devices such as a cell phone or smartphone, etc.), two light bundles of different colors (slightly different brightness, slightly different hues and / or slightly different color saturation) are detected. In particular, a digital image sensor detects the two light bundles as light bundles with a greater color difference ΔΕ from one another than would correspond to the direct observation with the human eye. While no difference in color between the subject and its surroundings is visible to the human eye (preferably neither in even while away from it), when photographing or filming with the aid of a digital camera, a picture appears on the display which shows the subject and its surroundings in different colors. As a result, by merely photographing slight differences in color between the subject and the surrounding area can be made visible, which are not visible to the naked eye.

These embodiments enable the viewer or user of an item to verify the presence of the security feature without the need for specialized tools. In particular, for the skilled observer who is aware of the presence of the security feature and its position on the surface of the article thus marked, a check for the presence of the security feature (optionally by targeted viewing or by photographing or filming) is easy and swiftly, and without a targeted verification of the authenticity of the object being

Some exemplary embodiments will be described below with reference to the figures. 1 to 3 show some schematically illustrated embodiments of an object provided with a security feature,

FIG. 4 shows an enlarged view of the security feature on the surface of the article of FIGS. 1 to 3,

FIG. 5 shows a schematic plan view of the surface of the object provided with the security feature,

Figure 6 shows the standardized color sensitivity curves of the human eye under

FIGS. 7A and 7B show a schematic representation of the visual visual impression produced by a security feature in the human eye, designed in two colors of observer geometry. FIG. FIG. 7C shows the reflection spectrum of two different dye mixtures as a function of the wavelength, FIGS. 8A and 8B show the reflection spectra of each of two exemplary dye mixtures which correspond to two colors of observer geometry, FIGS. 9A and 9B show the color difference between the respective two colors in FIGS

Examples of FIGS. 8A and 8B for the 2 ° observer and for the 10 ° observer, FIG. 10 a comparison of the spectral color sensitivity of digital image sensors on the one hand and the human eye on the other hand, FIGS. 11A and 11B are schematic representations of the respective image of the security feature FIGS. 12A and 12B show the reflection spectra of two exemplary dye mixtures tuned to the color sensitivity of digital sensor chips such that when picked up with a sensor chip as a result of the evaluation by the sensor chip two FIGS. 13A and 13B show the color difference between the two colors respectively obtained when recording with the digital camera and, if necessary, using a white light illumination source in the examples of FIGS. 12A and 12B,

FIG. 14 shows a typical emission spectrum of a white-light LED of a digital camera,

FIG. 15 is a cross-sectional view of a portion of the security feature surface of the article;

FIG. 16 shows an alternative embodiment to FIG. 15 and FIG Figure 17 is a schematic representation of the recording and playback of the surface of the article by means of a digital camera.

Figures 1 to 3 show some exemplary, schematic embodiments of the object provided with the security feature. The article 10 can, for example, as shown in Figure 1 in perspective view, be provided with a plurality of delimitable surfaces or outer surfaces object, such as a machine or other investment principle of any shape and size. The article 10 can also be a housing 70 or container 80 or at least have a housing. At least provided with the security feature 5 area of the surface 15 of the article 10 may for example consist of paper, cardboard, plastic, metal, ceramic or glass. These or other materials may be present on the outer surface, particularly on the security feature surface 15, as an outer coating or alternatively as a bulk material. On and / or in the respective material may be a color layer or lacquer layer, a color filter, a glaze or other coating that gives the object 10 on its outer surface or surface 15 its color.

The surface 15 of the article 10 (usually its outer surface, if necessary also also possible inner surfaces, insofar as these are accessible within the scope of conventional use of the article 15) comprises at least one Oberfiächenbereich which is at least partially provided with the security feature 5. The surface 15 may be formed, for example, as a rounded overall surface (for example, the outer surface of a cylinder, a pot or a bottle or other specially shaped body or housing) or, alternatively, a plurality of mutually delimitable partial surfaces (in particular multiple planes or curved partial surfaces of different orientation with identifiable edges be formed between them). At least one Oberfiächenbereich is at least partially provided with the security feature. Hereinafter, this surface area will be briefly referred to as surface 15; This can be flat or curved, for example.

The security feature described in this application is independent of the direction or orientation which the surface 15 or its surface normal in the area has the security feature 5 in relation to an observer or in relation to its viewing direction; The orientation of the security feature itself does not matter here. The security feature therefore differs from any security features in which minimal height variations of a print or otherwise ausgeflilte surface profiles are required to achieve such as by lateral rather than frontal view, a different visual impression. In particular, in the security feature 5 no differently colored, depending on the viewing angle more or less unearthed height structures (such as in the high pressure or gravure printing of a printing) is required. Rather, the security feature of the article 10 is based on its specific, purpose-matched color scheme.

The article 10 may be instead of compact and solid (Figure 1) also sheet-shaped; it may for example be a sticker or label 20, as shown in Figure 2. In particular, the label 20 is an adhesive label provided with an adhesive layer 19 on a side opposite the exposed outer surface 15. The sheet-like or flat article 10 may also be a bill 30, another sheet 50 or another film, in particular a plastic film 40 or a seal or packaging part of paper, cardboard and / or plastic. On at least one side, namely the surface 15, the security feature 5 is provided. It is preferably arranged on the outside of an underlying, layered or solid material, in particular printed thereon. However, the security feature 5 may also be incorporated in the layered or solid material of the surface 15. Furthermore, the security feature can also be arranged below the outer surface 15, for example below an outermost layer whose surface 15 is exposed. Thus, for example, in the case of a transparent, preferably colorless lacquer or plastic layer which forms the outer layer or coating of the article 10 in the area of the surface 15, the security feature 5 may also be arranged below this transparent layer but be visible from outside through it. The security feature 5 may, for example, be located between such an outer transparent layer and an underlying, layered or solid material, or may even be incorporated into or printed on the underlying layered or solid material itself. In the following, for the sake of brevity, no distinction is made between these possibilities. In all cases, the coloring of the security feature 5 described here on the surface 15 of the article 10 is selected so that it appears only under certain conditions. FIG. 4 shows a section of the surface 15 of the article 10 (for example that of FIGS. 1 to 3) in the region of the security feature 5. The security feature 5 consists, for example, of a motif 13 whose color is slightly offset from the color of the surrounding surface 14 under certain conditions ; In particular, the color of the motif 13 is optionally observer geometry metreter to the color of the surrounding area 14 or in another embodiment metamer to the color of the surrounding area 14 with respect to the evaluation of the colors by the human eye on the one hand and the evaluation of the colors when using a digital camera on the other hand. Depending on the viewing angle or when imaging with the aid of a digital camera, an increased color distance of the subject color to the color of the surrounding area 14 becomes clear, although the motif 13 is otherwise barely noticeable within the surrounding area 14. The security feature described here can only be achieved by the coordinated color scheme and does not require further security features, although it can be combined with other security features. Depending on the embodiment, a color difference from the surrounding area can only be detected as a function of the position of the intended surface area in comparison to the viewing direction of the observer or only with the aid of a digital camera.

In Figure 4, the surface 15 in a first surface area 11, which at the same time forms the surrounding area 14 of the security feature 5, is designed in a first color 1, e.g. in the first color 1 printed or painted.

The color of the surface 15 in the area of the surrounding area 14, ie the first surface area 11 (which usually extends laterally much further than the surface area shown in FIG. 4), can certainly vary over the surface 15, as is the case regularly with color gradients on surfaces , clearly legible labels or other designs is the case. But at least in the vicinity of the security feature 5 or motif 13, the color of the first surface area 11 is uniform. If the color scheme is composed of different printing dots of a print or of other sub-areas in different colors that are the reference color of the first Oberfiächenbereichs 11 or the Umgebungfiäche 14 merge, at least the mixing ratio or the relative proportion of the printing inks, dyes or color pigments used there is uniform - at least in the vicinity of the security feature 5. This also applies to the second area 12, ie for the color - surfaces 6, which form the motif 13; wherein the color applied there (possibly by optical fusion of the color dots applied there at sufficiently large viewing distance) give the second color 2 instead of the first color 1.

The security feature 5 is, as shown in FIG. 4, a surface area of the surface 15 in which the surrounding area 14 of the first color 1 (ie the first surface area 11) and the motif 13 (ie the second surface area 12 or its color fields 6) of the second color 2 lie next to each other or meet each other. Where both colors 1, 2 collide, color boundaries 7 lie between them. The color boundaries 7 form the contour of the motif 13, i. the outlines of the second surface area 12 and the color fields 6. The color boundaries 7 are, however, due to the metamerism of both colors 1, 2 normally not or barely perceptible; i.e. they become perceptible only in special circumstances. In the narrower sense, the security feature 5 consists of those surface areas or color fields 6, which occupies the motif 13 (such as a symbol, a pattern or alphanumeric or other characters) on the surface 15 or occupy its respective motif elements. These surface areas are summarized here as second surface area 12; they are designed in the second color 2. In the case of an alphanumeric lettering as in the example of FIG. 4, for example, each letter or number of the lettering forms its own color field 6, with the majority of the respective color patches or alphanumeric characters in this second color 2 together forming the security feature 5 in the narrower sense. Due to the small difference in color within and outside the color fields, which emerges only as a function of the position relative to the viewing direction of the observer or with the aid of a digital camera, the subject 13 stands out from its surrounding surface 14 only under special circumstances.

The color surfaces 6 of the motif 13 in the second color 2 are not or at least not immediately apparent to the viewer as different, different from the first color 1 colored surfaces recognizable. In particular, a color difference between the first 1 and the second color 2 only as a function of the angle between the connecting line from the eye of the viewer to the subject 13 and the viewing direction of the viewer or - in another embodiment - perceptible only with the aid of a digital camera. This manifests itself in this embodiment by only a small color difference between the first color 1 and the second color 2, which is below the detection limit of the human eye and, for example, has a value ΔΕ2000 less than 2.0.

FIG. 5 shows, by way of example, a larger section of the surface 15, which is shown in section in FIG. The detail shown in FIG. 5 can also represent the entire surface 15. The surface 15 according to FIG. 5 may be flat or curved and in particular an outer surface of an article 10, a housing 70 or a container 80 (FIG. 1) or the outside or viewing side of a label 20, banknote 30 or other sheet 50 or film piece, for example a plastic film 40 be. The surface 15 may, as in FIG. rectangular (with external dimensions AI and A2) be designed. The surface 15 may be a total area or partial area of a foil piece or sheet of paper, cardboard or foil bounded by edges, punching lines and / or creases, which may be used to form, e.g. Folding a three-dimensional packaging is intended. The surface 15 extends, for example, along a first x and a second

Direction y beyond the motif 13. In the example of FIG. 5, the motif 13 realized in the second color 2 is arranged near an edge of the surface 15, which is otherwise in the first color 1; at least in the immediate vicinity of the motif 13. Within the first surface area 11 (for example within a rectangle with dimensions AI and A2 along the directions x, y) additional graphical elements or even spatial structures may be present, but preferably only outside the immediate vicinity Thus, as shown in Figure 5, for example, a color clearly opposite the first color 1 prominent, visible marking 9 may be provided, which is designed in a contrasting color 8 or at least in a clearly different from the first color 1 third color and therefore directly is perceived. A conscious choice of the position of the clearly visible marking 9 is suitable for either directing the observer's eye to the security feature or for directing it away from it. For example, according to FIG. wisser positional offset p between the security feature 5 (ie, the color fields 6 in the first color 1 metameren second color 2) and the clearly visible marking 9 in the third color or contrast color 8 may be provided. In the example of FIG. 5, this positional offset p can be selected, for example, such that the viewer's gaze, after the initial form of the outer shape or boundary of the surface 15 has been detected in fractions of a second, is directed to the eye-catching marking 9 held in the contrasting color 8 and thus is deflected away from the security feature 5. If the color fields 6 are designed in a color that can only be distinguished from the first color 1 of the surrounding area 14 along the viewing direction or for the 2 ° normal observer, the motif 13 provided as a security feature 5 is virtually invisible to the viewer , Only when his eyes coincidentally on the surface area 12 of the otherwise monochrome acting surface 15 falls, in which the security feature 5 is arranged, it is suddenly perceptible, but only as long as the view of the viewer lingers there. Thus, the effect of observer geometry measurement can be exploited to hide a security feature from the eyes of casual observers, especially because the viewer's gaze involuntarily and unconsciously (within fractions of a second) attracted by the more striking visual stimuli, ie especially edges and contrasting colors on the subject becomes. Alternatively, the first color 1 and the second color 2 of the two surface areas 11, 12 may be selected so that the observer the color difference between the two colors only from the corner of the eye, or outside its closer viewing direction (for example, outside of 2 ° to the viewing direction or outside 10 ° to the viewing direction). The motif 13 is then dimly visible away from the immediate viewing direction, but apparently disappears as soon as the observer directs his gaze.

In both cases, at least for the unaware, uninitiated observer, the surprising effect of the only temporary visibility of the color fields 6 or of the motif 13 as a function of his viewing direction (first embodiment). The first and the second color 1, 2 and their color difference from each other can also be chosen so that only when photographing the surface 15 with a digital camera or the like, a color contrast between the two colors 1, 2 or at least between them during their playback the colors appearing on the camera become visible (second embodiment). FIG. 6 shows the standardized color sensitivity curves (for the relative wavelength-dependent sensitivity S) of the human eye, taking into account the angular dependence of the color perception on the angle relative to the viewing direction. The color sensitivity curves B, G, R of the respective suppositories on the retina of the human eye for the primary colors blue, green and red are shown in each case for the 2 ° observer (CIE 1931), the 10 ° observer (CIE 1964) and for the so-called standard deviate observer (CIE 1989) The color sensitivity curves for the 2 ° observer correspond to human color perception along its line of sight with a deviation of less than 2 ° relative sensitivity S of suppositories for blue (B2), green (G2) and red (R2) in the form of solid lines For the 10 ° observer as defined by CIE Standard 1964, Figure 6 shows slightly different color sensitivity characteristics as thin lines for blue (BIO), green (G10) and red (RIO) It can be seen from Figure 6 that for all three types of suppositories on the retina the ascending In the case of the 10 ° observer, the branch of the sensitivity curve is shifted in the direction of smaller wavelengths. Also the maximum value of the sensitivity for the colors blue and red is slightly larger for the 10 ° observer (BIO and RIO) compared to the sensitivity for green than for the 2 ° observer. Further deviations in a real subject can be explained by the sensitivity curves for the

Standard Deviate Observer (Bd, Gd and Rd, dashed lines) as defined by the CIE Standard 1989. The dependence of the spectral sensitivity curves on the angle deviation from the viewing angle is exploited in the first embodiment The angle deviation from the viewing angle is understood here to be the size of the angle which a straight line, which leads from the object point or the motif 13 through the pupil of the observer to the pixel on the retina, is relative The observer geometry metrology is exploited in conjunction with a specific choice of two conditionally equal or mutually metameric colors for the first and the second surface area. As far as in the present application of mutagen metameric colors is mentioned, this refers both to metameric colors in the strict sense, at least under a first condition (for example for the 2 ° observer, for the 10 ° observer or for the naked eye in general), but also on paramere colors, which even under such a condition are only perceived as approximately the same. In this respect, the term "metamer" should be understood in the sense of "paramer or metamer" or "paramer and / or metamer." This applies in principle to all embodiments of the present application The distinction of two distinguishable with the naked eye colors is depending on the experience of Viewers of different sizes, as a first approximation for the Distinctness or perceptibility limit, a color distance of about 2.0 to 3.0 are considered.

The first 1 and the second color 2 are chosen so that, for example, the color difference between them is only for the 2 ° observer, i. only perceptible along the line of sight (and in an angular range of up to ± 2 ° relative to it), but not in the more distant field of view of the human eye. According to a modification of this embodiment, this is just the opposite, i. a color difference is only noticeable above a certain deviation from the viewing direction, for example only perceptible to the 10 ° observer.

FIGS. 7A and 7B illustrate diagrammatically the visual impression which a security feature designed in color 2 leaves in the form of metameric (color fields 6 of the motif 13, in this case alphanumeric characters within the surrounding area 14 formed in the first color 1). FIG. 7A shows, in thin outlines, the contour of individual letters of the alphanumeric lettering, which are designed in a second color 2 metametric to the first color 1 and are therefore invisible to the eye or difficult to recognize, as long as the central 2 ° sight area is not around the viewing direction falls on the provided with this label surface area. As long as the view, for example, falls on a region of the surface 15 away from the motif 13 (for instance on the additional, strongly contrasting marking 9 in FIG. 5), the motif 13 is virtually invisible to the eye, since in this viewing direction no color difference between the light source 13 and the eye 13 is visible Color 2 of the motif 13 or the color fields 6 (second surface area 12) and the color 1 of the surrounding area 14 (first surface area 11) can be seen. However, the two colors 1, 2 are Selects that a color difference becomes recognizable as soon as the central 2 ° field of view of the human eye encounters the motif 13 or a part thereof. This effect is schematically illustrated in FIG. 7B, where at least a part of the motif 13, as soon as and as long as the eye's gaze falls on the motif or a part thereof, slightly stands out slightly from the surrounding color and thereby suddenly becomes perceptible to the eye, that is readable.

The caption is easy to read for the viewer initiated in this security feature. For the uninitiated observer, on the other hand, the sudden, possibly only occasional appearance of a caption is a surprising, at first inexplicable experience, insofar as he perceives the security feature at all. A similar surprising experience arises when the metamere (or paramere) colors are chosen so that a color difference only outside the 2 ° field of view or only for the 10 ° observer or at least only in a larger angular range (eg larger as 2 ° relative to the viewing direction) becomes observable.

Figure 7C shows schematically for two different dye mixtures (corresponding to the two surface regions 11, 12) the proportion of the intensity Ir of the light which is reflected by the dye mixtures. Furthermore, the approximate sensitivity curves B, G, R of the human eye are plotted for the primary colors blue, green and red. Although the sensitivity curves B, G, R are shown in FIG. 7C without taking into account the viewing-angle dependence of human color perception, this dependence is nevertheless utilized here (see FIG. FIG. 7C shows clearly different reflection spectra S 11, S 12 for the body colors 1, 2 reflected by two reflected mutagenic metameric dye mixtures; only at five points of intersection or wavelengths is the reflected proportion of the two dye mixtures approximately the same size and, on the other hand, significantly different at almost all other wavelengths. Taking into account the different sensitivity curves for the 10 ° observer compared to the 2 ° observer shown in FIG. 6, it is possible to determine two dye mixtures or color pigment mixtures which show a color difference on the retina either only in the 2 ° sight range or only outside it reveal. The concrete determination of suitable dyes and their mixing ratio can be determined by practical experiments with several different ones Determine samples and / or calculations, if necessary in conjunction with an iterative procedure.

Figures 8A and 8B each depict a pair of dye mixtures which give two colors which are metameric to one another, i. according to the observer geometry metamerism are metamer. In the example of FIG. 8A, which was developed for ink-jet printing, a mixture of 81% photocyan, 55% magenta and 13% yellow is used as the first color 1 for the first surface area 11 (reference color). For the second color 2, which is to be applied in the second surface area 12 or in the color fields 6 of the motif 13 (secondary color), a mixture of 51% cyan, 81% photomagenta and 15% red is used. These percentages refer to the density with which the surface area in the respective base color (eg cyan) is printed, or to the value of the color saturation or density of the respective base or base color, which is already set in advance in the respective graphics programs (for Illustrate, for example, 100% blue, 100% green and 100% red to produce black in three-color printing).

The reflectance spectra of both dye mixtures, ie the wavelength dependent respective courses of the reflected intensity Ir are shown in Figure 8A (and for another embodiment in Figure 8B). The reflection spectrum Si l corresponds to the first color 1 (as a reference color in the first surface area 11) and the reflection spectrum S12 of the second color 2 (as a second color or motif color in the second surface area 12). Compared to the reference color, the reflection spectrum S12 of the motif color contains an increased red content above 600 nm. Furthermore, in the shorter-wavelength region in the spectrum S12, the portion of stronger reflection is slightly shifted towards longer wavelengths, as can be seen between 400 nm and 525 nm. Furthermore, the second dye combination (with the spectrum S12) in the range between 530 and 595 nm reflects green light weaker than the first dye combination (with the spectrum Si l). On the basis of these reflection spectra S1, S12, the colors of both dye combinations are observer geometry metrics for the human eye, wherein a color difference between reference color and subject color is observable selectively in the range of ± 2 ° around the viewing direction, as illustrated by FIG. 9A. FIGS. 9A and 9B show, for the examples of FIGS. 8A and 8B, the respective color difference ΔΕ1976 (insofar as CIE standards from different years are mentioned in this application, the year of the respective CIE standard does not matter, but that in the relevant CIE standard The CIE standard, published as an example only, serves as an example and instead of the color difference, any other suitable quantity may be used for the quantitative and / or qualitative characterization of the difference between two colors). This color difference is applied in each case for the 2 ° observer (upper marking) and for the 10 ° observer (lower marking); in each case for the respective standard observers in indirect daylight with a color temperature of 6500 Kelvin (Case I), for a standard deviation observer or "Standard Deviate Observer" (ie one of the observers defined in the 1989 CIE standard, typically deviating from the norm, but still normal color perception) in indirect daylight (Case II) and for a standard observer in direct daylight at a color temperature of 5000 Kelvin (Case III) In Case I (left in Figure 9A) the color space is between the reference color 1 and the second color 2 the viewing direction, ie for the 2 °

Observers about 4.8 and for the 10 ° observer about 0.5. In case III (right in FIG. 9A), the color distance for the 2 ° observer is about 7.0 and for the 10 ° observer 2.7. In case II (middle in FIG. 9A), the color distance is 5.9 for the 2 ° observer and 1.6 for the 10 ° observer.

In all three cases, therefore, the color difference ΔΕ1976 between reference color and subject color for the 10 ° observer is significantly below that perceived by the 2 ° observer, and is also partly below the value range of about 2.0 to 3.0, which approximates can be considered as the limit of perceivability of different colors for an average, inexperienced observer. In the case I, the color difference ΔΕ1976 perceived by the 10 ° observer is also at the lower end of the value range of 0.5 to 1.0, below which even a trained observer can no longer recognize a color difference. The 10 ° observer therefore has the same reference color and subject color. For the 2 ° observer, on the other hand, a clear color difference between the reference color and the subject color of greater than 4.0 is recognizable; The motif used as a safety mark suddenly appears to the viewer in the direction of sight when and as long as his gaze falls on the motif. The basis of Figures 8A and 9A based dye or pigment mixtures for the reference and subject color are therefore capable, using the observer geometry metrics, of making visible a motif 13 serving as security feature 5 exclusively and selectively in the nearer area around the viewing direction (preferably in the range of ± 2 °), but otherwise conceal it.

Figures 8B and 9B show another example developed for flexographic printing. Reference dye 1 used a dye mixture of 56% orange, 6% warm red and 38% green. For the subject color or second color, a mixture of 62% o of the dye yellow, 12% of the dye green and 26% of the dye violet was used. The associated spectra Sl 1, S 12 of both dye mixtures, as shown in FIG. 8B for all wavelengths above 470 nm, are even more pronounced in this example. As a result, the color difference between both colors 1, 2 is larger in this example; it lies, as shown in Figure 9B (under the same measurement conditions for cases I to III as in Figure 9A), for the 2 ° observer in case I (standard observer, indirect daylight, 6500 Kelvin) at ΔΕ = 10.7 and otherwise even higher (13.3 in case II). However, this large color difference is only close to the line of sight, i. perceptible to the 2 ° observer. In the outer field of view, however, especially for the 10 ° observer, the perceived color difference is in each case only 0.5 (case I) or 2.3 (case II) or 4.0 (case III). Thus, away from the line of sight no larger, noticeable color difference between the subject and its surroundings can be seen. With the two dye mixtures for subject color and ambient color, which are based on FIGS. 8B and 9B, it is therefore possible to have a motif 13 serving as a security feature 5 selectively visible in the viewing direction; as well as with the two dye mixtures of Figures 8A and 9A. In the case of FIGS. 8B and 9B, the color distance, which can be perceived selectively depending on the viewing angle, is significantly greater in the viewing direction.

Alternatively, the previous embodiments - depending on the application - can also be modified such that the dye combinations are chosen so that a security feature is selectively perceived only outside the line of sight or only outside a certain minimum angle relative to the viewing direction. In all these variants, which can be summarized as a first embodiment, the angular dependence of the color sensation of the human eye is exploited. While only a 2 ° observer and a 10 ° observer are mentioned in this description for the sake of simplicity of illustration, the angle dependency utilized according to the invention is, of course, not limited to these definitions. Rather, any pair of two metameric dyes or dye mixtures can be used, which have a different, optionally smaller or larger color difference ΔΕ or produce perceptible color difference due to their reflection spectra in a first, smaller viewing angle around the viewing direction of the human eye than in a second , wider viewing angle around the viewing direction of the human eye. The second viewing angle range is, in particular, a viewing angle range that lies completely outside a minimum angle of, for example, 2 ° or another, larger minimum angle relative to the viewing direction.

As far as in this application from the point of view the angle is meant, from which the relevant surface area of the surface 15 is considered - relative to the direction of the surface normal of the surface itself - so not the angle between the point of view of the observer and the orientation of the Surface 15. Rather, the angle is meant, which is enclosed by the (each momentary) direction of view (perpendicular bisector through the pupil as an optical axis, which shows the direction in which the eye is looking) of the observer and through the straight line, that of the point of the surface 15 through the pupil leads to the image of this point on the retina of the observer. For a directly targeted point of the surface 15, this angle is 0 °, since the view is directed straight at him, regardless of the location of the viewer.

In the following variants, which can be summarized as a second embodiment, instead of the angle-dependent color perception of the human eye, the different color sensitivity of the eye on the one hand and digital image sensors on the other hand are exploited. FIG. 10 shows a comparison of the color sensitivity of a typical digital image sensor with that of the human eye-in each case as the course of the (relative) sensitivity S as a function of the wavelength. The sensitivity of each pin of the human eye is represented by the curves B, G and R for the colors blue, green and red. The lines Bc, Gc and Rc indicate the speaking sensitivity characteristic of typical digital image sensors, which are realized for example as a CMOS sensor or CCD sensor (with respective pixel-wise color filters in front of the individual sensor cells). A similar wavelength-dependent color sensitivity as shown in FIG. 10 is based on virtually all image sensors of commercially available digital cameras, video cameras, smartphones and camera phones. Although the color sensitivity curves differ slightly depending on the model, the similarities between them are so great that the curves Bc, Gc, and Rc shown in Figure 10, obtained by averaging over 25 cameras, are characteristic of a digital image sensor can be viewed. Even compared to the model-related deviations from the averaged sensitivity curves, the common differences compared to the color perception of the human eye are so clear that it is possible to speak of a typical, systematically detectable difference between the color sensitivity of a digital sensor chip and that of the human eye.

According to FIG. 10, the maximum of the color sensitivity curve is a digital one

Image sensor for the color green about the size of the human eye, however, the entire sensitivity curve Gc for green is shifted in the direction of smaller wavelengths compared to the sensitivity curve G of the eye. Additionally is at one

Image sensor, the sensitivity curve Bc for blue slightly shifted in the direction of larger wavelengths.

These differences are exploited in the second embodiment, in conjunction with a special observer metamerism (based on digital observer metamerism)

Image sensor chips compared to the human eye) to realize a security feature that is not or barely perceptible to the human eye, but at the latest on the display of a digital camera clearly visible. Thus, by photographing can be quickly determined whether and where the security feature in question or

Authenticity plate on the label or other item is present.

The effect achieved in this way is explained schematically with reference to FIGS. 1A and 1B, in which the surface 15 in the region of the security feature 5 is shown schematically, as it appears on the one hand to the unarmed eye and on the other hand in the display Digital camera (when photographing or filming) appears as a result of the different color sensitivity of the digital camera's digital sensor. The color fields 6 (second surface areas 12) of the motif 13 indicated in FIG. 1A by the thin contours are not or only schematically visible to the human eye, which only has a slight color difference between the color 1 of the first, surrounding surface area 11 and the Color 2 of the motif 13 perceives. The color difference ΔΕ is, for example, less than 2.0 for the naked eye (both for the 2 ° observer and for the 10 ° observer). However, due to the different color sensitivity of the image sensor compared to the eye, a digital image sensor detects a greater color difference between the colors 1 and 2 as soon as the motif 13 is captured by the digital image sensor during photography or filming, as indicated in FIG. 1B. This increased color distance is also reflected on the camera display or mobile phone display as soon as the image content is displayed. On the display, the surrounding area 14 of the motif 13 is then displayed in a third color and the motif 13 itself in a fourth color, the third and fourth colors having a visibly greater color difference from each other (FIG. 1B) than the first and second color from each other when looking directly at the object itself (Figure 11A). A look at the display is sufficient to recognize a security feature that is barely visible on the object itself. The color difference which is increased in FIG. 1 IB compared with FIG. 1A is indicated only schematically in FIG. 1B by the use of the black-and-white contrast is a color difference between a third color 3 or 3 'and a fourth color 4 or 4 '(see Figure 17), which usually do not correspond exactly to the original colors 1, 2, but emerge from those colors which the camera-internal sensor chip detected when he designed in the original colors 1, 2 surface 15 of the object 10 recorded. Insofar as the electronics of the camera convert the signals detected by the sensor chip into a third color 3 'and a fourth color 4' (see FIG. 17), the image colors of the first 1 and second color 2 detected by the sensor chip or digital sensor are shown on the display the camera are displayed or otherwise output, the third color 3 or 3 'and the fourth color 4 or 4' those colors to understand that indicates the digital camera as a representation of the first color 1 and the second color 2 on the display or otherwise. The image colors 3 ', 4' displayed on the display, in which the image of the original colors 1, 2 is displayed, can be viewed on the camera display viewed and distinguished from the eye. The original colors 1, 2 are matched in accordance with this embodiment to the color sensitivity of digital image sensors or sensor chips, that just such an increase of the color difference arises. The above remarks apply to all embodiments that provide for the use of a digital sensor chip or a digital camera, either with or without additional white light illumination source.

FIG. 12A is based on two dye mixtures for the first and the second color 1, 2, which are chosen so that their color distance to the human eye is below 2.5, but when photographing with a digital camera (already without using flash or a corresponding illumination) results in a significantly greater color difference ΔΕ above 4.0. Shown is the reflectance spectrum of both dye mixtures, i. the wavelength-dependent profile of the (reflected) intensity Ir of the light reflected by the respective dye mixture. For the first color 1, S l 1, a dye mixture of 37% photocyan, 66% magenta and 80% yellow was used. For the motif color or second color 2, S 12, a mixture of 11% of the dye cyan, 85% of the dye photomagenta and 71 of the dye red was used.

FIG. 12A shows the reflection spectra S 11, S 12 of two exemplary dye mixtures which are provided for realizing the first 1 and the second color 2 and which are tuned to the color sensitivity of digital sensor chips such that the evaluation of these spectra by the sensor chip has two colors with increased color difference from each other. The spectra S 1, S 12 are detected by a digital image sensor or by an electronic device equipped therewith when picking up the first and second surface regions 11, 12. On the display 180 of the digital camera (see FIG. 17), a third 3 'and a fourth color 4' are then reproduced as image colors of the first 1 and the second color 2. In this case, the (first) color 1 of the first surface area 11 (surrounding area 14 of the motif 13), ie the spectrum S1 of the first dye mixture, is detected and evaluated in that area area of the sensor chip area onto which the first surface area 11 is imaged. Analogously, the (second) color 2 of the second surface region 12 (motif 13), ie the spectrum S 12 of the second dye mixture, is evaluated in that area region of the sensor chip surface onto which the second surface region 12 is imaged. The two spectra S il and S 12 in Figure 12A intersect at about 550 nm, which corresponds approximately to the maximum of the sensitivity curve of the human eye for green. At wavelengths less than 550 nm, S il assumes lower values than S 12, but this is compensated for by the fact that S il assumes values greater than S 12 at wavelengths above 550 nm. For the human eye, therefore, both S il and S 12 give an equally great impression, for example, of the proportion of green. The sensitivity curve for green of an image sensor of a digital camera, on the other hand, is shifted towards smaller wavelengths (see FIG. 10 with the maximum at 530 nm instead of 550 nm). The color impression mediated by the spectrum S 12 therefore has a greater proportion of green when evaluated with a camera sensor than with the human eye, because the spectrum S 12 in the now-dominant sensitivity range around 530 nm assumes larger values than the spectrum S i , FIG. 13A shows the color difference ΔΕ between the two original colors observed with the eye as well as between the two image colors detected or determined by the image sensor. As in Figures 9A and 9B, the three illustrated cases I to III refer to a standard observer in indirect daylight of 6500 Kelvin (Case I), a standard deviation observer also in indirect daylight (Case II) and a standard observer in direct daylight of the color temperature of 5000 Kelvin. In the three cases, the color difference ΔΕ perceived by the naked eye is plotted for both the 2 ° observer and the 10 ° observer. The color difference ΔΕ10 of the 10 ° observer is somewhat greater than 2.0 in case I and even lower in the other cases. In addition, the color difference ΔΕ2 perceived by the 2 ° observer is always lower than that perceived by the 10 ° observer. By contrast, the color difference AEc resulting from the image data stored in the digital image sensor is significantly larger and is above a value of 5.0. The color difference provided by the sensor is thus sufficiently far above the perceptual limit of the human eye for distinguishing different colors. By looking at the display, which displays the colors measured by the image sensor, the operator of the camera immediately recognizes that two image areas of different color (with recognizable color separation AEc) are present, whereby the motif 13, which is not or hardly recognizable on the object, becomes recognizable and detectable , Also in case III the color difference measured by the digital sensor is sufficiently large to identify in the image displayed by the display the image of the security feature; the color difference value for this is 3.7 (not shown).

The effect of increasing the color difference between two metameric or parametric colors for the human eye, as explained with reference to FIGS. 10 to 12A and 13A with the aid of a device with a digital image sensor, can be increased still further by using a photograph or film White light LED is used as the illumination source. In today's photo and video cameras, a white light LED is available as a flash or as a continuous light for filming. The spectrum of a white light LED is not really evenly distributed over the visible wavelength range, but has, as shown in Figure 14, a first, narrow and very high intensity maximum at wavelengths around 450 nm and a less high, but over a larger wavelength range In between, there is an intensity minimum approximately in the range of 470 to 510 nm, in which the emitted light intensity is extremely low. In addition, the emitted spectrum of a white light LED in the blue and red spectral only asymmetrically lit a portion of the sensitivity curve of the camera, whereby the color difference or measured by the image sensor color distance compared to the color difference between the original colors 1, 2 is further increased.

With the aid of a white light LED as (at least additional) illumination source, the color difference detected during photographing or filming can thus be further increased. As in FIGS. 10 to 12A and 13A, this color difference is the one between the two colors detected by the image sensor, the image of the first color 1 giving a third color 3 or 3 'and the image of the second color 2 being a fourth color 4 or 4 'results; Their color difference from one another is greater than that between the two original colors 1 and 2. FIG. 12B shows the reflection spectra Si 1, S 12 of the image colors 3, 4 recorded by the image sensor during illumination with a white-light LED when imaging the two metameric color mixtures for the colors 1, 2. Furthermore, the sensitivity curves B, G, R of the eye for the three basic colors blue, green and red are shown. For the first color 1, Sl 1, a dye mixture of 30% cyan, 76% phot magenta and 72% red was used. For the motif color or second color 2, S12, a mixture of 80% of the photocyanide dye, 60% of the magenta dye and 86% of the yellow dye was used.

FIG. 12B shows the spectra S1, S12 of these two dye mixtures, which are provided for realizing the first color 1 (first area 11) and the second color 2 (second area 12) and which are coordinated with one another in such a way that the evaluation of these spectra by the sensor chip with the aid of a white light LED illumination source two colors with even greater color difference from each other results.

In FIG. 13B, for the explanation of which reference is first made to FIG. 13A, the in-camera evaluation of both colors results in an even greater color separation ΔEf = 9.2, which is significantly greater than the color differences perceived by the naked eye (both for the 2 ° observer) also for the 10 ° observer) and also above the color distance AEc measured according to FIG. 13A with the aid of the camera, but without white-light LED illumination. The motif serving as a security feature is therefore even more clearly visible on the camera's display than when photographing without the device's own white-light LED. In particular, the gap in the spectrum of the white-light LED leads to an even greater color difference between the camera-in each case rated colors 3 and 4.

FIG. 15 shows, in cross-section, a section of an object 10, on the surface 15 of which the motif 13 provided as a security feature is formed in a color 2 metamere to the color 1 of the surrounding area 14. The illustrated section is selected to be small and therefore exemplarily shows only a single color boundary 7 between the two colors 1 and 2. The article may be, for example, a label, a banknote, a document or other sheet or foil, a container, a packaging element or any other be another product. The article may in particular be one which is explained with reference to FIGS. 1 to 5, the remaining figures or the other exemplary embodiments of this application. The section shown in FIG. 15 may, for example, be a cross section through the layer thickness or the upper part of the layer thickness of a label, a banknote, a packaging, a sheet or a film. AI Alternatively, the section shown in FIG. 15 can be, for example, a partial area of a housing wall, a vessel or container or a partial area of a molded part of any other product. As shown in FIG. 15, the two surface regions 11, 12 may be formed, for example, as colorant surfaces of a respective dye or pigment layer, preferably as ink layers 21, 22 of a printing or an imprint according to any printing technique; alternatively also as lacquer layers 41, 42 of a lacquer or a lacquer coating. The color layers - especially if they are realized as imprints - need not be layered, coherent or compact in the strict sense, but may also (depending on the printing technique) be a varying pattern of individual, separable or overlapping dots or dye stains form, which are easy to make out, for example, only with a magnifying glass or other magnifying device and are therefore not shown individually in Figure 15 (this applies equally to both surface areas 11, 12, since they should be realized in the same printing technique).

FIG. 16 shows an alternative embodiment of an article 10-shown here as a still enlarged cross-sectional view of a subarea-in which the motif 13 provided as a security feature and the surrounding area 14 are not formed as printing or paint application but as holographic filters 31, 32, respectively. Thus, the article 10 has on its surface 15 in the first surface area (or in the first surface areas) 11 a first ho lographic filter 31 and in the second surface area (or in the second surface areas) 12 a second ho lographic filter 32 on. The reflection spectrum of the first holographic filter 31 in the first surface area 11 gives the first color 1 and the reflection spectrum of the second holographic filter 32 in the second surface area 12 gives the second color 2. This is especially true in daylight, artificial light or both.

The holographic filters 31, 32 may, for example, be notch filters having only a single, more or less narrow absorption band in the visible wavelength range, or they may be multi-band holographic filters arranged in at least two absorb wavelengths of visible light from each other. One of the two high-level filters may also be a notch filter and the other a multiband filter. The reflection spectra of the provided in the two surface regions 11, 12 ho lo graphic filters 31, 32 need only be sufficiently different from each other so that the two filters can produce two different reflection spectra, which correspond to the two metameric colors to be generated. For example, the refractive index n of the filter layer of one or both high-level filters 31, 32 can vary over the respective layer thickness s according to an overlay of at least two spatial frequency components, as indicated on the left in FIG. 16, so that the radiation incident from the outside is in two different Wavelength ranges or bands is absorbed. The respective holographic filter is then permeable to the remaining wavelength ranges; These radiation components are preferably reflected by a reflective layer or reflecting interface arranged on the underside of the respective filter and, after emerging from the surface 15, form the reflection spectrum of the respective holographic filter 31, 32 or surface region 11, 12. By suitable (different) Characteristics of the refractive index over the layer thickness s of both filters 31, 32 can be realized, in particular holographic filters on the surface 15, whose base spectra or reflection spectra are fundamentally arbitrarily narrow band designable.

The holographic filters 31, 32 may be constructed such that the course of the refractive index over the filter layer thickness has two or more periodic fluctuations over the layer thickness in the course of the refractive index; in contrast to filters arranged one behind the other, i. cascaded areas with only a single sinusoidal variation in the refractive index.

The embodiment according to FIG. 16 makes it possible to model the reflection spectra of both filters in such a way that two mutually (at least approximately) metameric reflection colors whose color difference ΔΕ2000 corresponds to the theoretical maximum value ΔΕ2000 = 44 for color differences of two observer geometry metramers of the 10 ° normal observer on the one hand and of the second Normal reflectors on the other hand, such as with reflection bands at 440 nm and 540 nm for the first color and at 480 nm, 500 nm and 630 nm for the second color. Regardless of whether the mutually metameric colors 1, 2 by printing inks or imprints 21, 22 (Figure 15), by lacquer layers 41, 42 (Figure 15) or by holo- graphical filters 31, 32 are realized (Figure 16) preferably on a carrier material 25; its outer surface then forms, for example, an interface 35, which, however, may coincide completely or at least partially with the surface 15, depending on the nature of the realization of the two colors or paint jobs. In the case of holographic filters, the interface 35 is preferably mirrored or reflective. Depending on the type of article 10, the carrier material 25 can be, for example, metal, plastic, paper, cardboard, ceramic, wood or glass. The carrier material 25 may itself be layered or solid, and the surface formed therefrom may instead also be curved.

FIG. 17 illustrates by way of example the recording and reproduction of the surface 15 of the article 10 for those embodiments of the application in which a digital camera 100 is used to recognize the security feature 5. Through the objective 140 of the camera 100 (photographic camera and / or video camera), the light which is reflected by the surface regions 11, 12 reaches the digital image sensor or sensor chip 150, which detects the light of the two original subject colors 1, 2. In the sensor chip 150 or at the latest in the evaluation electronics 160 connected downstream thereof, signals which actually reproduce the colors 1, 2 are recorded, but because of the color sensitivity characteristic of commercially available sensor chips 150 which are typically deviating from the human eye, record colors 3, 4 or save slightly different from the original subject colors 1, 2. The color 3 (or 4) is the color corresponding to the evaluation of the color 1 (or 2) by the digital sensor chip. This evaluation is carried out by the camera or its sensor chip (or possibly a downstream camera electronics) during or after the capture of the color 1 (or 2). Due to the special matching of the metameric colors 1, 2 to each other, colors 3, 4 are calculated inside the camera, which have a greater color difference from one another than the original colors 1, 2 of each other, if they are evaluated by the human eye. Even if further image colors 3 ', 4', which deviate once more from the colors 3, 4, should remain in the display 180 due to the camera-internal further processing and forwarding of the image data (for example via the lines 170) and / or by displaying the image data, the image remains by the sensor chip 150 caused enlargement of the color distance between the two colors concerned persist and is not or at least not significantly reduced by the subsequent further processing, forwarding and / or playback in the display, let alone reversed. Thus, two sufficiently different colors are shown to the observer - whether the colors 3, 4 actually stored in the sensor interior or the ultimately displayed colors 3 ', 4' in the display 180 of the camera 100. Their increased color difference or color difference from one another (in comparison to that between the original colors 1, 2 of the object) serves as a security feature 5 serving motif 13 now in the display 180, ie recognizable in the image of the surface 15 to the viewer. In this case, the color difference between the two observed colors can be further increased by the use of a camera-internal or other white-light illumination source 90. The color 3 'or 4' is that color which the camera or its display represents as representing the color 3 (or 4) obtained by the evaluation of the color 1 (or 2).

As far as in this application of a color is mentioned, so that the color of the associated spectrum, in particular the color of the reflection spectrum of the respective reflected light meant; this applies at least to the first color 1 and the second color 2. The practical production of suitable metameric or parametric color pairs for the embodiments mentioned in this application can be carried out in several steps; for example, by parallel and / or successive series of experiments on different color mixtures, by theoretical calculations and / or by iteratively limiting the optimum composition and the optimal color mixing ratio of the color mixture of both colors of the color pair. For example, in a first step for a set of printing inks (such as flexographic inks, inks for inkjet printers or toners for laser printers) or other dyes (such as for transparent filter layers) a plurality of color surfaces of slightly varying composition can be tentatively printed. For each of these mixture ratios and / or those of interpolated mixture combinations, the respective color distance can be calculated, for example that for the human eye and that for a digital camera (if necessary with white light illumination), or that for the human eye, taking into account two different viewing angles relative to line of sight. From this it is possible to select the combination of two dye mixtures for which the color difference is minimal under a first condition (for example for the 10 ° normal observer or for the human eye at all), but under a second condition (for the 2 ° normal observer, for example) or for the sensor chip of a digital camera) is maximum. The dye mixtures selected in this way can be reprinted - now preferably together with slightly different dye mixtures in which the respective mixing ratio is deliberately changed (for example by gradually increasing the proportion of one or some of the dyes contained in the dye mixture at the expense of the proportion of other dyes). Among the dyeing surfaces thus obtained, it is again possible to select that combination of two dye mixtures for which the color difference is lowest under the first condition but greatest under the second condition. Iterative iterations of these steps can be carried out again until two sufficiently metameric colors or dye mixtures are obtained. These two dye mixtures are then used to color the motif 13 and its surrounding area 14.

A conceivable procedure, for example, is that first a set of dye mixtures of somewhat similar color impressions is printed and measured with a reflection spectrometer. Alternatively, it is also possible to print measurements on color fields of the pure dyes and on color fields of the individual dyes or dye mixtures with transparent white (in, for example, two different-sized mixing ratios with transparent white) and reflect by reflection spectrometry. Theoretical calculations can supplement the further procedure. However, the particular procedure for obtaining a suitable pair of metameric colors is variable and ultimately results from the application of the experience and prior knowledge of the person skilled in the art. For the theoretical calculations, for example, the formula according to Kubelka / Munk can be used to determine the ratio of absorption to scattering. Where this is not possible with sufficient accuracy, comparable to the Neugebauer model, the reflection spectrum of mixtures of primary colors in arbitrary mixing ratios can be calculated from the interpolation between the reflection spectra of the pure primary colors or the combination of (undiluted and full-surface) Determine basic colors (Neugebauer primaries). Incidentally, the method of least squares is generally suitable for optimizing the color difference.

The present application is not limited to specific, concrete metameric colors or color combinations or color pairs. Furthermore, all conventional techniques for application of paint, in particular printing techniques or painting techniques can be used. Furthermore, with regard to the colorants for realizing the desired colors, use can be made of any conventional type of dye, pigment, colorant or filter material; in particular, to printing inks or pastes for any known printing techniques, such as inkjet or toner for laser printing, as well as conventional opaque or transparent lakes or conventional filter materials for making holographic filters.

LIST OF REFERENCE NUMBERS

1 first color

2 second color

3; 3 'third color

4; 4 'fourth color

5 security feature

6 color field

7 color border

8 contrasting color

9 visible marking

10 item

1 1 first surface area

12 second surface area

13 motif

14 surrounding area

15 surface

16 Viewing direction

17 2 ° - angle environment

18 eye

19 adhesive layer

20 label

21, 22 printing

25 carrier material

30 bill

31, 32 ho lo graphic filter

35 interface

40 plastic film

41, 42 lacquer layer

50 sheets

60 packing element

70 housing

75 Housing surface 80 containers

90 white light source

100 digital camera

140 lens

150 sensor chip

160 transmitter

170 lines

180 display

190 image

ABC exemplary label as a security feature

A 1, A2 outside dimensions

B, G, R Sensitivity of the three primary colors for the human

eye

B10, G10, R10 Sensitivity curve for the

10 ° standard observer

B2, G2, Pv2 sensitivity history for the

2 ° standard observer

Bc, Gc, Rc Sensitivity of a digital sensor

Bd, Gd, Rd Sensitivity curve for the

Standard deviation observers

ΔΕ color difference

AEc color separation when shooting with a

digital camera

ΔΕ ₂ color difference for the 2 ° standard observer

ΔΕ10 Color difference for the 10 ° normal observer

ΔΕ1976 color difference according to CIE 1976

ΔΕ2000 color difference according to CIE 2000

Ir reflected intensity

Ie emitted intensity

n refractive index

nm nanometer

p position offset

s layer thickness s

Sil, S12

Claims

claims

1. article (10) having at least one security feature (5) having surface (15),

wherein the surface (15) comprises a first surface area (11) and a second surface area (12),

- wherein the first Oberfiächenbereich (11) in the vicinity of the second Oberfiächenbe- rich (12) has a first color (1) and the second Oberfiächenbereich (12) has a second color (2),

wherein the first color (1) and the second color (2) are matched to the color sensitivity of the human eye so that a color difference can be seen between them when viewed with the human eye along its line of sight, whereas between the first ( 1) and the second color (2) no color difference or only a smaller color difference can be seen when they are perceived with the human eye out of sight.

2. An article according to claim 1,

characterized in that

the first color (1) and the second color (2) are chosen to be observer geometry metrics, the first and second colors appearing as different colors for the 2 ° normal observer and for the 10 ° normal observer as identical colors appear.

3. An article according to claim 1 or 2,

characterized in that

the first color (1) and the second color (2) are selected such that there is a color difference (ΔΕ2000) of 4.0 or greater, preferably 5.0 or greater, between them for the 2 ° normal observer, whereas between them for the 10 ° normal observer, there is a color difference (ΔΕ2000) of 2.0 or smaller, preferably 1.5 or smaller.

4. article (10) having at least one surface (15) having a security feature (5), - wherein the surface (15) has a first surface area (11) and a second surface area (12),

wherein the first surface area (11) has a first color (1) at least near the second surface area (12) and the second surface area (12) has a second color (2),

wherein the first color (1) and the second color (2) are matched to the color sensitivity of the human eye so that a color difference is recognizable between them when perceived with the human eye outside its line of sight, whereas between the first ( 1) and the second color (2) no color difference or only a minor color difference can be seen when viewed with the human eye along its line of sight.

5. An article according to claim 4,

characterized in that

the first color (1) and the second color (2) are selected to be observer geometry metrics, the first and second colors appearing as different colors for the 10 ° normal observer, and for the

2 ° -normal observers appear as identical colors.

6. An article according to claim 4 or 5,

characterized in that

the first color (1) and the second color (2) are selected so that between them for the 10 ° normal observer there is a color difference (ΔΕ2000) of 4.0 or greater, preferably 5.0 or greater, whereas between them for the 2 ° normal observer, a color difference (ΔΕ2000) of 2.0 or smaller, preferably 1.5 or smaller, exists.

7. An article according to any one of claims 1 to 6,

characterized in that

the first color (1) and the second color (2) are selected such that a color difference between the first color (1) and the second color (2) dependent on the position of the security feature (5) relative to the viewing direction of the human eye is included Daylight and / or artificial light is perceptible to the naked eye.

8. article (10) having at least one surface (15) having a security feature (5),

wherein the surface (15) has a first surface area (11) and a second surface area (12),

- Wherein the first color (1) and the second color (2) are tuned to the color sensitivity of the human eye and the color sensitivity of digital image sensors, that the first color (1) and the second color (2), if they digital

Image sensor are recorded simultaneously as two distinguishable colors are detected with increased color difference from each other, whereas between the first color (1) and the second color (2) when viewing with the naked eye, no difference in color or only a smaller color difference can be seen.

9. An article according to claim 8,

characterized in that

the first color (1) and the second color (2) are matched to the color sensitivity of digital image sensors such that when photographing or filming by means of a digital image sensor, the first color (1) as a third color (3; 3 ') and the second Color (2) is detected as a fourth color (4; 4 '), and when judged by the human eye, the color difference (ΔΕ2000) between the third color (3; 3') and the fourth color (4; 4 ') becomes larger is the color difference between the first color (1) and the second color (2).

10. An article according to claim 8 or 9,

characterized in that

the first color (1) and the second color (2) are matched to the color sensitivity of digital image sensors such that when photographing or filming by means of a digital image sensor, the first color (1) as a third color (3; 3 ') and the second Color (2) is detected as a fourth color (4; 4 '), and when judged by the human eye, the color difference (ΔΕ2000) between the third color (3; 3') and the fourth color (4; 4 ') 4 , 0 or greater, preferably 6.0 or greater.

11. An article according to any one of claims 8 to 10,

characterized in that

the first color (1) and the second color (2) are selected such that when viewed with the naked eye, they are perceived as colors of the same brightness, the same hue and the same color saturation, at least for the 2 ° normal viewer in daylight and / or artificial light.

12. An article according to any one of claims 8 to 1 1,

characterized in that

the first color (1) and the second color (2) are selected so that the color difference (ΔΕ2000) between them when viewed with the naked eye is 3.0 or less, preferably 2.0 or less.

13. An article according to any one of claims 8 to 12,

characterized in that

the first color (1) and the second color (2) are selected so that when recording using a digital camera, which is provided with a sensor with pixel-wise executed in the three basic additive colors blue, green and red color filters, from the first (1) and the second color (2), a third (3; 3 ') and a fourth color (4; 4') arise, the color difference (ΔΕ2000) between the third (3; 3 ') and the fourth color ( 4, 4 ') is at least 2.0 greater, preferably at least 4.0, larger than the color difference (ΔΕ2000) between the first color (1) and the second color (2).

14. An article according to any one of claims 8 to 13,

characterized in that

the first color (1) and the second color (2) are tuned to the emission spectrum of artificial white light sources such that when photographing or filming the article (10) using an artificial white light source as illumination, the first color (1) as a third color ( 3; 3 ') and the second color (2) is detected as a fourth color (4; 4'), wherein when evaluated with the human eye, the color difference (ΔΕ2000) between the third color (3; 3 ') and the fourth color Color (4; 4 ') is greater than the color difference between the first color (1) and the second color (2).

15. An article according to any one of claims 1 to 14,

characterized in that

the first color (1) and the second color (2) of the at least one surface (15) each in the form of a colored coating, a color layer, a varnish or a print or a mixture, a combination or an arrangement of a plurality of different dyes and / or color pigments is realized.

16. An article according to any one of claims 1 to 15,

characterized in that

the surface (15) of the article (10) in the first (11) and in the second surface region (12) each has a mixture, combination or arrangement of in each case two, three or more dyes or color pigments, the type and / or the mixing ratio of the respective dyes or color pigments in both surface regions (11, 12) differ from each other.

17. An article according to any one of claims 1 to 16,

characterized in that

the first color (1) and the second color (2) of the two surface regions (11, 12) of the article (10) as printing, in particular as by laser printing, inkjet printing, flexographic printing, screen printing, offset printing or by another digital or analog printing technology generated printing are realized.

18. An article according to any one of claims 1 to 17,

characterized in that

the first surface area (11) and the second surface area (12) are arranged side by side on the surface (15) and adjoin one another directly, wherein at the border between the two surface areas (11, 12) the first color (1) is in the second Color (2) passes.

19. An article according to any one of claims 1 to 14,

characterized in that

the surface (15) of the article (10) each having a ho lustrical filter (31, 32) in the first (11) and in the second surface region (12), wherein in daylight and / or artificial light, the reflection spectrum of the holographic filter (31) in the first surface region (11) generates the first color (1) and the reflection spectrum of the holographic filter (32) in the second surface region (12) the second color (2).

20. An article according to claim 19,

characterized in that

the holographic filters (31, 32) are notch filters or multi-band holographic filters which absorb visible light in at least two spaced-apart wavelength ranges.

21. An article according to any one of claims 1 to 20,

characterized in that

one of the surface regions (11; 12) comprises one or more contiguous or separate color fields, in particular graphic symbols, patterns and / or markings of alphanumeric characters or other motifs (13) and that the other of the two surface regions (12; 11) an environment surface (14) of the graphic symbols, patterns and / or labels from the alphanumeric characters or other motifs (13) forms.

22. An article according to claim 21,

characterized in that

the surrounding area (14) on all sides comes close to the graphic symbols, patterns and / or inscriptions from the alphanumeric characters or to the other motifs (13).

23. An article according to any one of claims 1 to 22,

characterized in that

both the first surface region (11) and the second surface region (12) is a non-fluorescent, fluorescence-free and phosphorescent-free surface region.

24. An article according to any one of claims 1 to 23,

characterized in that the article (10) a sheet-like article, in particular a label (20) or another sticker, a banknote (30), a plastic film (40) or other film or a sheet (50) or packaging element (60) formed from paper or cardboard. is.

25. An article according to any one of claims 1 to 23,

characterized in that

the article (10) has a housing (70) and that the surface (15) is a housing surface (75), in particular a painted or printed Gehäusoberfiäche (75).