DE102014011692A1 - Security element with photochromic dye - Google Patents

Abstract

A security element (1) for a value document has a body (2) that is transparent in a window (6) for light. On a top side (6) a color layer (4) is printed with photochromic dye, which shows a photochromic effect when irradiated with light of a first color. On a lower side (8), a thin-film element (9) is mounted above the window (6), which transmits only a first color in the white light, and thus illuminates the photochromic dye with light of the first color in a transparent view (10). The thin-film element (9) shows in plan view (11) on the underside (8) a different color from the first color.

Description

The invention relates to a security element for a document of value, wherein the security element comprises: a body that is transparent or translucent at least in a region for light and has an upper side and a lower side in the region, a photochromic dye attached to the upper side when irradiated with light of a first color exhibits a photochromism effect, a filter element attached to the body, in particular on the underside, which filters light to the first color in transmission from a front side to a back side of the filter element, around the photochromic dye with light emerging from the rear side the first color to illuminate.

The invention further relates to a passport, a security or value document, in particular a banknote, with such a security element.

Finally, the invention also relates to a manufacturing method for a security element for a document of value, wherein a body is provided which is transparent or translucent at least in a region for light and in the region has an upper side and a lower side, on the upper side a photochromic dye attached, which exhibits a photochromic effect when irradiated with light of a first color, a filter element on the body, in particular at the bottom, is mounted, which filters in transmission from a front to a back of the filter element light to the first color to the photochromic dye with to illuminate light of the first color emanating from the back.

A security feature should also be able to be checked by laymen wherever possible, d. H. without requiring additional equipment. Common security features include holograms, luminescent displays, metallizations, and other features that are visually or machine-detectable, such as color-shifting features and micro-optic structures, such as moiré patterns.

Known are so-called photochromic security features, eg. B. from the EP 2484537 A2 , By photochromism is meant a reversible change of state of a substance caused by light, which changes its absorption spectrum. The perceived by a viewer color of a substance is conditioned by this absorption spectrum. In transmitted light, the complementary color of the absorbed light color is perceived. Starting product and end product of a photochromic state change have different absorption spectra. The back reaction (relaxation) can be spontaneous or stimulated, z. B. by light of different wavelength.

There are many known photochromic substances, both inorganic and organic. The reversible transformations between the states are triggered by light in different wavelength ranges. For example, the orange Triphenylfulgid colored bluish when exposed to short-wave light, and by irradiation with red light turns back to the orange color. Colorless spiropyranes change to a blue state on UV exposure, which reacts back to the colorless state upon irradiation with visible light. Photochromism also exists with acetanilides, stilbene, rhodamine and anthraquinone derivatives, with benzofuroxanes and other compounds. A natural photochromic system is that of the phytochrome. The reversibly interconvertible states have different lifetimes. Photochromic substances with rather short-lived states are suitable for producing visual features, while very long-lived states are required for data storage.

The named EP 2484537 A2 discloses a security feature with the protein bacteriorhodopsin (BR). BR in the so-called B-state has an absorption maximum at about 570 nm, so that a viewer perceives a violet color. The absorption of photons leads to chemical and structural changes, the corresponding states being distinguishable spectroscopically. By irradiation with light having a wavelength of 570 nm, it is switched to the so-called M state, which has a yellow-green color. The relaxation in the initial state (B state) occurs spontaneously and can be accelerated thermally or by irradiation with light having a wavelength of about 410 nm. Details about BR, also in connection with security elements, can be found in, among others WO 02/010207 A1 . WO 2010/124908 A1 and WO 2011/157838 A1 ,

The EP 2484537 A2 discloses combinations of photochromic inks with light-shielding materials, such as opaque imprints or metallizations. Upon irradiation with light of a suitable wavelength, color changes of the photochromic color occur only in the unshielded area, while the color in the shielded area remains unchanged. Furthermore, combinations with colored, possibly structured (pattern-shaped) colored films are proposed. It is exploited that certain thermally stable intermediate states of BR, for example, the M state, can be switched back to the initial state by irradiation with light of a suitable wavelength, for example 410 nm. A security element which has BR in B state and is covered on one side by a blue patterned film, changes its color from violet to yellowish green when irradiated from the non-blue-film side with light of about 570 nm wavelength , Upon irradiation from the opposite side, ie, through the blue patterned film, a color change back to violet occurs only in those areas where the irradiation light passed through blue film areas. The same applies to other photochromic dyes.

The EP 1404526 A1 discloses the use of BR for document security, where BR is embedded in the paper mass of the value documents. The WO 94/05008 proposes BR for storage media and also mentions sources of BR variants and suitable manufacturing processes. The EP 1 171 309 discloses photochromic BR compositions for use in the field of security technology, in particular printing inks with bacteriorhodopsin are disclosed.

The DE 10 2009 058 243 A1 describes a thin-layer element with a multilayer structure for security papers, documents of value and the like which appears gold-colored in plan view and which has at least two semitransparent mirror layers and at least one dielectric spacer layer arranged between the at least two mirror layers, so that when measuring the transmission of unpolarized light in the blue wavelength range of 420 nm to 490 nm shows a resonance with a half-width of 70 nm to 150 nm. Thin-film elements that show different colors in plan view and see-through are still missing DE 10 2009 00 88 543 A1 . DE 10 2009 041 583 A1 . DE 10 2012 018 434 A1 and DE 10 2014 001 842 A1 known. The EP 0735115 A1 . EP 2504400 A2 and WO 2011 / 064162A2 reveal printing inks with just such properties.

The invention has for its object to provide a security element based on a photochromic dye, which offers increased security against counterfeiting.

The object is achieved by a security element for a document of value, wherein the security element comprises: a body which is transparent or translucent at least in a region for light and has an upper side and a lower side in the region, a photochromic dye attached to the upper side when irradiated with light of a first color exhibits a photochromism effect, a filter element attached to the body, in particular on the underside, which filters light to the first color in transmission from a front side to a back side of the filter element, around the photochromic dye with light emerging from the rear side to illuminate the first color, wherein the filter element is formed as an interference element, which shows a different color of the first color in a plan view of a front side.

The object is further achieved by a value document with such a security element.

Finally, the object is also achieved by a production method for a security element for a document of value, wherein: a body is provided which is transparent or translucent at least in a region for light and has an upper side and a lower side in the region, a photochromic at the upper side A dye is applied, which exhibits a photochromic effect when irradiated with light of a first color, a filter element on the body, in particular at the bottom, is mounted, which filters in transmission from a front to a back of the filter element light to the first color to the photochromic dye to illuminate with light of the first color emanating from the back, wherein the filter element is formed as an interference element, which shows in a plan view of its front side a second color different from the first color.

The invention replaces the colored film, as is known from the EP 2484537 A2 for combination with a photochromic dye, by the inference element, which shows a second color different from the first color in plan view. Such interference elements are known per se, are now combined with the photochromic color so that there is a combination effect. In plan view of the interference element, you can see this in the known appearance. If the interference element lies above the region provided with the photochromic dye, one does not see the color appearance that would actually show the interference element from its back, but the photochromic effect of the photochromic dye, since it is arranged above the back of the interference element. At the same time the farbfilternde effect of the interference element in a plan view of the front is not visible.

The interference element may be attached to the body at the top above the underlying photochromic dye region. Alternatively, it is also possible to generate a self-certification by such as, for example, in 1c of the EP 2484537 A2 shown, the security element is folded so that the interference element comes to rest on the color layer. In such an embodiment, the interference element is located next to the photochromic dye on the top.

A further increased security against counterfeiting is obtained if the interference element is structured pattern-wise with respect to its filter effect and is thus supplemented with a second structure having the second color such that the pattern-like structuring of the interference element is not recognizable in plan view on its front side.

The interference system may preferably be formed as a thin-film structure, as is known from the aforementioned prior art. An ink which shows the first color in the transmitted light but makes a different second color recognizable in a plan view can also be used as the interference element.

In the following, the security feature will be explained with reference to bacteriorhodopsin (BR) as a photochromic dye. It is understood, however, that the description applies analogously to other photochromic dyes. The reference to BR is therefore only an example.

If the security element has layers, these layers are z. As transparent plastic films which are glued or laminated together, and may be the same or different. In one embodiment, the security element is protected on both sides from mechanical and chemical attack by this double-foil structure.

In one embodiment, the security element is arranged in a continuous opening of a value document. Then also security elements of a greater thickness can be accommodated well, without causing thickening points on the document of value. As a result, high application quantities of photochromic dye are possible, whereby very good contrast values can be achieved. Another particular advantage is that in combination with the transparency of the through opening particularly interesting effects can be achieved.

In further embodiments, a value document for copying or counterfeiting protection as well as for authentication is provided with the security element. Examples of value documents are banknotes, certificates, check forms, stocks, labels for product security and generally forgery-prone items of any kind, in particular banknotes. Wertdocumentsubstrate represent non-viable precursors in the production of the actual value documents, z. B. as a banknote paper. They can be present in particular in the form of sheets or endless belts and can be equipped with further security features, printing layers, film layers, etc. In other embodiments, value documents are, for example, polymer banknotes (banknotes made exclusively of plastic layers), hybrid banknotes (banknotes with a core layer of paper and two plastic cover layers which cover the core layer over the entire surface or two paper layers which cover the core layer of plastic), but also security elements such as badges , Labels, foil patches or security threads.

In other embodiments, the security element is designed as a transfer element. Characteristic of transfer elements is that the security elements are prepared on a carrier layer with a layer structure in reverse layer sequence, as it should be present later on the object to be protected. The carrier layer is either removed from the layer structure of the security element after the transfer or remains as a protective layer on the security element.

The security element has at least one photochromic dye. In principle, all photochromic dyes are suitable which have two sufficiently stable, reversibly interconvertible states, but preference is given to photochromic dyes from biomembranes of phototrophic organisms, in particular retinal-based (retinal as chromophore) pigments, such as rhodopsins. Particularly preferred are bacteriorhodopsin (BR), proteorhodopsin and xanthorhodopsin, with bacteriorhodopsin being most preferred.

The filter element is suitably designed with respect to the filter properties for the wavelength range (color) triggering the photochromic effect.

Suitable for the purposes of the invention are all photochromic dyes, for. B. BR variants, with at least two thermally stable states that a high number of switching operations, d. H. Transitions between the stable states allow, preferably several 10,000 switching operations, more preferably several 100,000 switching operations. Preference is given to photochromic dyes, for. B. the BR variants whose stable states are clearly distinguishable from each other in color; their conversion into one another can be brought about by means of a wavelength range within visible light, for example by means of normal flashlights or desk lamps, which have a high photosensitivity and which have a high temperature stability.

A condition is thermally stable if it is stable for so long that the color change can be visually or mechanically clearly perceived. This is the case for a duration of about one second.

In another embodiment, the security element has only one photochromic substance, for example only one BR variant. In other embodiments, several different BR variants, mixtures of BR and other photochromic substances or mixtures of BR with other, non-photochromic dyes are used. Similarly, BR compositions and compositions with other photochromic or non-photochromic substances may be applied side by side or on top of each other. Particularly preferred BR variants are wild-type BR (dehydrated), D96N, D36C and D85N and those BR variants which are in the M state under normal light conditions.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention.

The invention will be explained in more detail by way of example with reference to the accompanying drawings, which also disclose features essential to the invention. For better clarity, a scale and proportioned representation is omitted in the figures. In addition, only the features or layers essential for understanding the described effects are shown. It is understood that additional features or layers may be present. Like reference numerals designate like or corresponding elements throughout the figures. Show it:

1 a schematic sectional view through a security element with a photochromic dye,

2 and 3 further embodiments of the security element, wherein a layer with a photochromic dye and a thin-film element are arranged on the same side of the security element,

4 to 6 Further embodiments of the security element, based on a conventional banknote paper and

7 a plan view of a printing layer with a photochromic dye, which in modifications of the security elements of 1 to 6 can be used.

1 shows an embodiment of a security element 1 in which a photochromic dye, preferably BR, is used. The security element 1 has a body 2 on, on which a carrier foil 3 is attached, on which a color coat 4 printed, which the photochromic color, z. B. BR contains. The color layer is thus on an upper side 5 of the body over a window 6 , which is a transparent area of the body 2 forms. On the opposite side is also a slide 7 that is thus on the bottom 8th of the body 2 is appropriate. On the slide 7 is a thin film element 9 formed from the bottom 8th incident white light, such as incandescent light or daylight, so filters that the thin-film element 9 towards the color layer 4 and thus by the area 6 emits blue light, which is an appropriate wavelength for BR to trigger a photochromic effect in the color layer 4 is. Looking at the security element 1 from the top 5 in a transmitted light view 10 such that the bottom 8th and thus the thin-film element 9 backlit with white light, the viewer sees the photochromic effect. For example, in the case of BR, this can consist of a color layer which is yellow in and of itself by the irradiation with blue light, which is reflected light 10 due to the filter properties of the thin-film element is blue, to a purple color impression of the color layer 4 replaced. Without the backlighting through the color-filtering thin-film element BR appears yellow.

In a plan view 11 a viewer sees the thin-film element 9 from the bottom 8th not in the color that transmits the thin-film element, but in a different color, such as golden.

The security element 1 thus exploits that the thin-film element 9 transmitted only in the blue wave range, but in plan view, unlike a pure blue filter film, as it is known from the prior art, does not appear blue.

The adaptation of the thin-film element 9 can be done by choosing a suitable layer sequence. They come out DE 10 2009 00 88 543 A1 . DE 10 2009 041 583 A1 . DE 10 2012 018 434 A1 and DE 10 2014 001 842 A1 known thin-film structures or the color EP 0735115 A1 . EP 2504400 A2 and WO 2011 / 064162A2 in question.

In BR systems, which have a purple ground state under normal lighting conditions, the described effect can also be triggered with a green / yellow light (for example in the wavelength range of 570 nm). Therefore, in a modification of the embodiment of the 1 also an interference element conceivable that purple in plan view and appears in review green / yellow. Alternatively, it is also possible to use photochromic dyes which have an additional, further color change. This also color cycles are possible in embodiments, for example yellow-purple, purplish-yellow, blue-yellow, yellow-blue and various other color changes with a corresponding filtering interference element.

The embodiment of the 1 used as a transparent area between the thin-film element 9 and the color layer 4 a window with the photochromic dye 6 in a body 2 , It is of course equally possible to the body 2 as a transparent film, for example, PET or BOPP film form. Then the window 6 dispensable.

The 2 and 3 show such variants with transparent films 12 as a body, with additionally the thin-film element 9 and the color layer 4 on the same side, in this case the top 5 , are appropriate. Of course, a transparent film 12 also in the construction of the 1 be used.

In 2 lies the color layer 4 between thin-film element 9 and transparent foil 12 , With 10 designated sight of the 1 would be in 2 a reflection in transmitted light from the bottom 8th ago. With 11 designated sight of the 1 corresponds to 2 a consideration from the top 5 in the reflected light.

In the construction of the 3 is the order of color layer 4 and thin film element 9 swapped so that in total the 1 the intended viewing directions apply here again.

The use of the color layer 4 and the thin-film element 9 is also with a conventional paper, such as a banknote paper 13 possible. However, it is then necessary in the transmitted light view comparatively higher illumination intensity.

To the effect of this in 4 can improve the banknote paper 13 in the area 6 with perforations 14 be provided. Thus, on the one hand, the requirement for the illumination intensity in the transmitted light can be reduced; on the other hand, further information can be introduced, since the locally varying translucency of the banknote paper 13 passing through the perforations 14 also the photochromic effect in the color layer is generated 4 varies locally. This provides a further security against counterfeiting.

6 shows a modification in that the banknote paper 13 with an embossed structure 15 which is also the translucency of the banknote paper 13 varies locally. That in terms of perforations 14 to 5 The same applies equally to the embodiment according to 6 , Next, the transparency of the banknote paper 13 also be varied by a watermark, which also affects the photochromic effect. In the area of a watermark in which a banknote paper has a varying density, then the photochromic effect appears stronger where that of the thin-film element 9 filtered light hits the color layer in greater intensity according to the structure of the watermark.

The use of the thin-film element 9 can of course also be made to the effect that a self-authentication of the security element takes place as described in the EP 2484537 A2 or the EP 0930979 A1 is described.

The thin-film element 9 may of course contain other security elements, such as embossments, hologram grids, micromirrors, etc., as is known to those skilled in the art.

It is also possible the color layer 4 , which contains the photochromic dye, to structure. This structure can be combined in areas with other color imprints that have the same color impression as the color layer 4 without photochromic effect. Such an example is purely schematic in FIG 7 shown. The color layer 4 is there with a square recess 16 provided in which a color is imprinted, which gives the same color impression as the color layer without photochromic effect, ie without irradiation with light passing through the thin-film element 9 was filtered. In pure plan view is therefore the square recess 16 not recognizable. When viewed in transmitted light, however, the Photochromieeffekt in the color layer 4 but not in the square recess 16 which was printed with a color without photochromic dye (or with other photochromic dye). The square recess 16 This makes it visible in transmitted light.

In one embodiment, the thin-film element is applied to a window, for example on a data page of a security document, such as a passport, etc. On a subsequent data page the color layer becomes 4 applied so that the window and the color layer can be brought into coincidence. If you now bring the window with the thin-film element over the color layer, you can see the changed color impression of this color layer with the photochromic dye and thus receives a security check.

In the thin-film element 9 information may be present in a negative or positive form or in a combination thereof. A positive form is understood to mean that the information is darker / more opaque than the environment. Analog is a negative information one in which the information is more transparent / brighter / more translucent than the environment. This can be done by subsequently removing one or more layers of the thin-film element 9 can be achieved, as is known in the art. In particular, it is possible by means of laser individual information in the thin-film element 9 to write or to generate a grayscale image by screening.

This information is then found in the color layer 4 in accordance with transmitted light reflection again, since the photochromic effect is also structured accordingly by the structured thin-film element.

The thin-film element is designed to match the photochromic dye so that it precisely filters the color that has the photochromic effect.

The thin-film element 9 is in the described embodiments an example of an interference element that shows a different color impression in transmission than in plan view. The color impression in transmission is tuned so that it triggers the photochromic effect in the photochromic color.

Alternatively to a thin-film element 9 For example, it is also possible to use a corresponding printing ink which has the same properties in terms of transmission and top view.

LIST OF REFERENCE NUMBERS

1

security element

2

body

3

foil

4

coat of paint

5

top

6

window

7

foil

8th

bottom

9

thin-film element

10

inspection

11

Top view

12

PET film

13

Banknote paper

14

perforation

15

Embossed structure / watermark

16

square

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2484537 A2 [0005, 0007, 0008, 0015, 0016, 0047]
• WO 02/010207 A1 [0007]
• WO 2010/124908 A1 [0007]
• WO 2011/157838 A1 [0007]
• EP 1404526 A1 [0009]
• WO 94/05008 [0009]
• EP 1171309 [0009]
• DE 102009058243 A1 [0010]
• DE 1020090088543 A1 [0010, 0038]
• DE 102009041583 A1 [0010, 0038]
• DE 102012018434 A1 [0010, 0038]
• DE 102014001842 A1 [0010, 0038]
• EP 0735115 A1 [0010, 0038]
• EP 2504400 A2 [0010, 0038]
• WO 2011/064162 A2 [0010, 0038]
• EP 0930979 A1 [0047]

Claims (15)

Security element for a value document, the security element comprising: - a body ( 2 ), at least in one area ( 6 ) is transparent or translucent to light and in the area an upper side ( 5 ) and a bottom ( 8th ), - one at the top ( 5 ) attached photochromic dye ( 4 ), which shows a photochromic effect when irradiated with light of a first color, - one on the body ( 2 ), especially at the bottom ( 8th ) mounted filter element which filters in transmission from a front side to a rear side of the filter element light to the first color to the photochromic dye ( 4 ) to be illuminated with light of the first color emanating from the front, characterized in that - the filter element is designed as an interference element, which shows in plan view of its front side a different color from the first color. Security element according to claim 1, characterized in that the interference element ( 9 ) is structured pattern-like and is thus supplemented with a second structure, which has the second color, that the pattern-like structuring of the interference element in plan view is not recognizable. Security element according to claim 1 or 2, characterized in that the interference system as a thin film layer structure ( 9 ) is trained. A security element according to any one of the preceding claims, characterized in that the photochromic dye comprises a retinal-based dye, preferably a rhodopsin. A security element according to claim 4, characterized in that the photochromic dye comprises a bacteriorhodopsin or a proteorhodopsin. A security element according to claim 5, characterized in that the bacteriorhodopsin is selected from the group consisting of wild-type bacteriorhodopsin, D96N, D85N, D36C, and mixtures thereof. A security element according to any one of the preceding claims, characterized in that it is a combination element comprising at least a first region with the photochromic dye and at least one second region ( 10 ) without the photochromic dye, wherein the regions are arranged side by side and / or one above the other. ID card, security document or document of value ( 1 . 2 ), in particular banknote, characterized in that it comprises a security element according to one of claims 1 to 7 Manufacturing method for a security element for a value document, wherein: - a body ( 2 ), at least in one area ( 6 ) is transparent or translucent to light and in the area an upper side ( 5 ) and a bottom ( 8th ), - at the top ( 5 ) a photochromic dye ( 4 ) is applied, which shows a photochromic effect when irradiated with light of a first color, - a filter element on the body ( 2 ), especially at the bottom ( 8th ), which filters, in transmission from a front side to a back side of the filter element, light to the first color in order to obtain the photochromic dye ( 4 ) with light of the first color emanating from the rear, characterized in that - the filter element as an interference element ( 9 ) is formed, which shows a different from the first color second color in plan view on the front. Manufacturing method according to claim 9, characterized in that the interference element ( 9 ) is structured pattern-like and is thus supplemented with a second structure, which has the second color, that the pattern-like structuring of the interference element in plan view ( 11 ) is not recognizable. Manufacturing method according to claim 9 or 10, characterized in that the interference system as a thin film layer structure ( 9 ) is formed. Production method according to one of claims 9 to 11, characterized in that the photochromic dye comprises a retinal-based dye, preferably a rhodopsin. Production method according to claim 12, characterized in that the photochromic dye comprises a bacteriorhodopsin or a proteorhodopsin. The production method according to claim 13, characterized in that the bacteriorhodopsin is selected from the group consisting of wild-type bacteriorhodopsin, D96N, D85N, D36C, and mixtures thereof. Manufacturing method according to one of claims 9 to 14, characterized in that the security element is formed as a combination element, wherein at least a first region is provided with the photochromic dye and at least a second region ( 16 ) is formed without the photochromic dye, the regions be arranged side by side and / or one above the other.

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