DE102011115589A1 - security element - Google Patents

Abstract

The invention relates to a security element for producing value documents, such as banknotes, checks or the like, comprising: a dielectric substrate (1), a first line grid structure (2) embedded in the substrate (1), of a plurality along a longitudinal direction and in one plane (L) arranged first lattice webs (3) made of metal or semiconductor and embedded in the substrate (1) second line grid structure (6) extending along the longitudinal direction of the second grid webs (7) made of metal or semiconductor, with respect to the plane (L ) is located above the first line grid structure (2), the first grid bars (3) each having a width (b) and juxtaposed at a distance (a) such that first grid gaps (4) extending between the first grid bars (3) along the longitudinal direction ) are formed with the distance (a) corresponding width, the second line grid structure (6) to the first line grid structure (2) inverted and gege is shifted over the first line grid structure (2) by half a period, so that in plan view of the plane, the second grid bars (7) over the first grid columns (4) and second grid column (8), which between the second grid bars (7) , over the first grid bars (3) and the width of the first grid bars (3) and the second grid slots (8), the width of the second grid bars (7) and the first grid column (4) and a thickness (t) of the first Grid webs (3) and the second grid webs (7) are each less than 300 nm.

Description

The invention relates to a security element for the production of value documents, such as banknotes, checks or the like, which has a line grid structure.

Security elements of value documents with periodic line grids are known, for example from the DE 10 2009 012 299 A1 . DE 10 2009 012 300 A1 or the DE 10 2009 056 933 A1 , You can have color filter properties in the subwavelength range if the grating profile is designed to produce resonance effects in the visible wavelength range. Such color filter properties are known for both reflective and transmissive subwavelength structures. These structures have a strong polarizing influence on the reflection or the transmission of an incident light beam. The color is relatively strongly dependent on the angle in reflection or transmission of such subwavelength gratings. However, the color saturation for these gratings weakens significantly when the incident light is unpolarized.

A line grating with subwavelength structures is known, which has angle-dependent, color-filtering properties. The line grid has a rectangular profile made of a dielectric material. The horizontal surfaces are covered with a high refractive dielectric. Above this structure is also a dielectric material, wherein preferably the refractive indices of the grating substrate and the cover material are identical. As a result, an optically active structure is formed, which consists of two gratings of the high refractive index material, which are spaced apart by the height of the original rectangular profile. The lattice webs forming the line grid are made of ZnS, for example. Although one can thus produce a color contrast in reflection, in transmission, a change in hue for different angles is barely perceptible. Therefore, this structure offers itself only as a security feature in reflection and has to be built on an absorbent surface.

Although the known two-dimensional periodic sub-wavelength gratings with non-contiguous surface show pronounced color filter properties. However, they are optimized for a large angular tolerance. Their color shade therefore hardly changes when tilted.

The invention is therefore based on the object to provide a security element that shows a good color also when viewed, which changes preferably when tilting.

This object is achieved by a security element for the production of documents of value, such as banknotes, checks or the like, comprising: a dielectric substrate, embedded in the substrate first line grid structure of a plurality of longitudinally extending and arranged in a plane first grid bars made of metal or A semiconductor and a second line grid structure embedded in the substrate of longitudinally extending second metal or semiconductor grid bars located above the first grid line structure with respect to the plane, wherein the first grid bars each have a width and are juxtaposed such that therebetween the first grid bars along the longitudinal direction extending first grid column are formed with the distance corresponding width, the second line grid structure is inverted to the first line grid structure, wherein in plan view of the plane, the second G Iterstege over the first grid columns and second grid column, which exist between the second grid bars over the first grid bars, and the width of the first grid bars and the second grid column and the width of the second grid bars and the first grid column is less than 300 nm. These grids are at a distance from each other, so that there is no closed half or half metal film. Optionally, the thickness of the grid webs may be below 300 nm.

In a periodic line grid structure, the phase shift corresponds to half a period.

According to the invention, a double-line grid is used which consists of two superposed complementary to each other, d. H. consists of mutually displaced line grid structures. Of course, the value of 90 ° is to be seen in the context of manufacturing accuracy. By manufacturing tolerances deviations may arise here, since usually a rectangular profile is not perfectly formed, but can be approximated only by a trapezoidal profile whose upper parallel edge is shorter than. The line grid structures are made of metal or semiconductor material. The layer thickness of the lattice webs is less than the modulation depth, that is, the spacing of the lattice planes of the line lattice structures.

It was found that a lattice constructed in this way surprisingly provides reproducible and readily perceptible color effects both in reflection and in transmission.

The security element according to the invention can be produced simply by a layer construction by first providing a base layer on which the first line grid structure is formed. Then you put on a dielectric intermediate layer, which is the first Line grid structure is covered and preferably thicker than the grid bars of the first line grid structure. The displaced second line grid structure can then be formed thereon, and a dielectric cover layer forms the termination of the substrate embedding the line grid structure. Alternatively, a sub-waveguide having a rectangular profile in cross-section can first be formed in the dielectric substrate as well. If this metallic is vaporized vertically, a metal layer is formed on the plateaus and in the trenches which form the first and second lattice webs. It thus has the desired non-contiguous metal film of the first and second grid bars in different planes when the layer thickness of the grid bars is less than the modulation depth of the rectangular profile of the previously structured dielectric substrate.

A particularly good color effect is obtained when the distance between the first and the second lattice webs, ie the modulation depth of the structure, is between 50 nm and 500 nm, preferably between 100 nm and 300 nm. The distance is to be dimensioned by respectively equivalent surfaces of the first and second line grid structure, d. H. for example, from the bottom of the first grid webs to the bottom of the second grid bars or from the top of the first grid bars to the top of the second grid bars. The distance is of course to measure perpendicular to the plane, so called the height difference between the rectified surfaces of the grid bars.

Suitable materials for the grid bars metals come into question, for example, aluminum, silver, copper, gold, chromium, platinum and alloys of these materials. The desired color effect is also evident when using semiconductors, such as silicon or germanium.

If one wishes to increase the chroma in reflection, the first lattice webs of the first line lattice structure and / or the second lattice webs of the second line lattice structure may be provided with a multilayer coating, e.g. B. as a trilayer of two superimposed metal or semiconductor coatings with an intervening dielectric layer can be constructed. The security element can be configured approximately color-neutral in the reflection even at approximately vertical angle of incidence. This has the advantage that the transmitted hue is not changed by the reflection. Preferred for the grid structures of the security element is a filling factor of 0.5, d. H. same width for the grid bars as for the grid column. Such a fill factor is not mandatory. With a deviation from this, one can make the hue of the reflection for reflection from the front different for a reflection hue, which occurs in the reflection at the back of the security element.

The security element with the double-line grid shows angle-dependent color filtering for reflection and transmission. This angle dependence is particularly striking when the grid lines are perpendicular to the light incidence plane. Color filtering can be used to make motifs multicolored so that they change color when tilted or twisted. It is therefore preferred that, in plan view of the plane, at least two regions are provided whose longitudinal directions of the line grid structures are oblique to one another, in particular at right angles. When viewed vertically, such a motif can be designed so that it has a uniform color in transmission and no other structure. If you rotate this motif around the vertical axis, the color of one area, for example of the background, changes differently than the color of the other area, for example a motif. Turning perpendicular to the viewing direction changes the colors of the subject and the background to a complete color change. Because the grid area, whose grid lines are parallel to the plane of incidence, hardly changes its color when tilted.

Of course, arrangements with several differently arranged areas are conceivable. This allows you to create motifs with multiple colors in transmission. Of course, the line grids in the individual areas may also have different geometry parameters in terms of width and spacing. In this case, however, the subject does not disappear when viewed vertically.

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. Show it:

1 a sectional view of a security element with a double-line grid,

2a -C the spectral dependence of the transmission, reflection and absorption of the security element of the 1 in a first embodiment,

3 Color values in the LCh color space for reflection and transmission for the security element of the 2 with variation of a modulation depth,

4 Color values in the LCh color space for reflection and transmission for the security element of the 2 with variation of a layer thickness,

5 Color values in the LCh color space for reflection and transmission for a security element of the 1 in a second embodiment with variation of a layer thickness,

6 a sectional view similar to the 1 for a double-line grid whose grid bars are provided with a trilayer coating,

7 Color values in the LCh color space for reflection and transmission for the security element of the 6 with variation of a layer thickness,

8a -B Two plan views of a subject using the security element 1 is formed,

9a -B Explanations of the change of the visual impression when considering the motive of the 8th .

10 Color values in the LCh color space for reflection and transmission for the security element of the 2 , where the polarization dependence is entered and the modulation depth is varied,

11 Color values in the LCh color space for reflection as well as transmission for the security element of the 2 , where the application of the 10 corresponds, but with variation of a layer thickness,

12 and 13 Representations similar to the 11 However, for different materials of the grid bars of the double-line grid, and

14 a representation similar to the 3 for a security element according to the prior art.

1 shows in section a security element 5 that one in a substrate 1 has embedded double-line grid. In the substrate 1 is a first line grid structure 2 incorporated, which is arranged in a plane L. The first line grid structure consists of first grid bars 9 with the width a, which extend along a longitudinal direction perpendicular to the plane of the drawing. Between the first grid bars 3 there are first grid column 4 that have a width b. The thickness of the first grid bars 3 (measured perpendicular to the plane L) is indicated by t. At a height h above the first grid bars 3 there is a second line grid structure 6 with second grid bars 7 , These have the width b. The second line grid structure 6 is so opposite the first line grid structure 2 out of phase, that the second grid bars 7 as exactly as possible (within the manufacturing accuracy) over the first grid gaps 4 to come to rest. At the same time there are second grid gaps 8th between the second grid bars 7 exist, over the first grid bars 3 ,

The thickness t is less than the height h, so no coherent film of the grid bars 3 and 7 is formed.

In the schematic sectional view of 1 is the width a of the first grid bars 3 equal to the width b of the second grid bars 7 , Based on a period d, the fill factor in each line grid structure is therefore 50%. However, this is not mandatory. According to the formula b + a = d, any variation can be made.

Also, in the schematic sectional view of 1 the thickness t of the first grid bars 2 equal to the thickness t of the second grid bars 7 , This is easier to manufacture but is not essential. However, it is essential that the modulation depth h, ie the height difference between the first line grid structure 2 and the second line grid structure 6 is greater than the sum of the thicknesses of the first grid bars 3 and the second grid bars 7 , otherwise there is no separation between the two line grid structures 2 and 6 would be given.

The security element S of 1 Reflects incident radiation E as reflected radiation R. Further, a radiation component is transmitted as transmitted radiation T. The reflection and transmission properties depend on the angle of incidence θ, as will be explained below.

The production of the security element S can be done, for example, that on a base layer 9 first the first line grid structure 2 and then an intermediate layer 5 is applied. In the case of the grid column shown up 4 can then the second line grid structure with the second grid bars 7 be introduced. A cover layer 10 covers the security element. The refractive indices of the layers 9 . 5 and 10 are substantially the same and may be, for example, about 1.5, especially 1.56.

The measures b, a and t are in the sub-wavelength range, i. H. less than 300 nm. The modulation depth is preferably between 50 nm and 500 nm.

But it is also a manufacturing method possible, in which first on an upper side of the substrate 1 a rectangular grid is made. The substrate 1 is thus structured so that trenches of width a are with webs of width b alternate. The patterned substrate is then vapor-deposited with the desired coating to form the first and second line grids and the first and second line grating structures. After vapor deposition, the structure is finally covered with a cover layer. This gives a layer structure in which the top and bottom sides have essentially the same refractive index.

The structured substrate can be obtained in various ways. One option is the reproduction with a master. The master form can z. B. now in UV varnish on foil, z. As PET film to be replicated. You then have the substrate 1 as a dielectric material having, for example, a refractive index of 1.56. Alternatively, hot stamping methods are also suitable.

The master, or even the substrate itself, can be fabricated using an e-beam, focused ion beam or interference lithography, writing the structure into a photoresist and then developing it.

The structure of a photolithographically produced master can be etched in a subsequent step into a quartz substrate in order to form as vertical as possible edges of the profile. The quartz wafer then serves as a preform and can, for. B. in Ormocer copied or duplicated by galvanic impression. Likewise, a direct impression of the photolithographically produced original in Ormocer or in nickel in a galvanic process is possible. Also, a motif with different lattice structures can be assembled in a nanoimprint process starting from a homogeneous lattice master.

Such manufacturing methods for sub-wavelength grating structures are known to the person skilled in the art.

The 2a to 2c show exemplarily the spectral properties of a security element S, whose double-line grating has the following profile parameters d = 360 nm, b = 180 nm, h = 200 nm, the material of the grid bars is aluminum, t = 30 nm, the dielectric has a refractive index of 1 , 56th 2a shows on the y-axis the transmission as a function of the wavelength plotted on the x-axis for different angles of incidence, namely 0 °, 15 °, 30 ° and 45 °. 2 B Analog shows the reflection and the 2c the absorption of the security element. The angle of incidence Θ is in 1 Are defined.

As you can see, a spectrally selective absorption occurs, so the security element develops a color property in transmission. A clear influence on the color properties in transmission, d. H. for the transmitted radiation T, is caused by the change in the direction of the peak at about 550 nm for the incidence angle 0 ° in a depression for non-perpendicular viewing angle (θ> 0 °). Reflection shows the reverse phenomenon.

This ultimately causes a color change in transmission from yellow to blue when tilting from vertical viewing at an angle of 30 °.

To illustrate the advantageous color effect of the security element S is to be compared to the 14 noted that for a known security element a representation similar to the 3 shows. The structure of the underlying security element essentially corresponds to that of 1 however, the first and second line lattice structures are not made of metal but of ZnS with a layer thickness of 70 nm. As can be seen, no spectrally selective absorptions occur. The color properties in transmission are significantly worse. The chroma is only about a quarter and the brightness is also modulated with respect to the angle of incidence. Therefore, the color contrast in transmission is drastically deteriorated with a variation of the incident angle. Such a grating can at best be used in reflective operation, ie on a black background layer.

The following 3 and 4 show how the modulation depth ( 3 ) or the layer thickness ( 4 ) on the color properties of the security element of 1 respectively. 2 impact. In each case in the left column of the figures, the reflection, in the right column, the transmission is shown. The representation takes place in the LCh color space. The top line shows the brightness L *, the middle line the chroma C *, and the bottom line the hue h °. The geometric parameters of the double line grid are d = 360 nm, b = 180 nm. The material for the line grid structure is aluminum, the substrate and the regions 4 and 5 from 1 have a refractive index of 1.56. This value corresponds approximately to the refractive index of PET films and UV varnishes.

It can be seen that the brightness and the chroma in transmission increase with increasing modulation depth h. A well-perceived color contrast is given in transmission when the transmitted brightness and chroma are higher than the reflected brightness and chroma. This is the case at modulation depths between 150 nm and 280 nm. It shows a much improved color property in transmission over the security element with ZnS grid bars. The brightness is also modulated with respect to the angle of incidence. Therefore, the color contrast in transmission is drastically increased with a variation of the incident angle. With a line grid structure with a modulation depth of h = 200 nm, tilting by 15 ° already causes a significant change in hue and brightness in transmission.

4 shows the influence of the layer thickness. The material is again aluminum, and the geometric parameters d, b, h correspond to those of 2 , It turns out that a layer thickness in the range of 20 nm and 30 nm produces favorable color properties in transmission. The brightness of the transmission is in the same order of magnitude of the brightness in reflection. The chroma in transmission, however, is significantly higher.

Similar color properties are evident for a lattice structure, which is that of the 4 corresponds, however, used as a material for the grid bars silicon. This grid has, like 5 shows a greater brightness in transmission than in reflection. With increasing layer thickness t, the chroma increases in transmission and for a viewing angle of 30 ° and a layer thickness greater than 70 nm, the transmission chroma is also greater than the chroma in reflection. A grating with a 100 nm thick silicon layer appears red in reflection, its chroma decreases with increasing angles of incidence. In transmission, on the other hand, the hue changes from a faint green to a rich yellow hue.

However, the angle-dependent color effect in transmission is not limited to only a line grid structure having a single metal layer or semiconductor layer in the grid bars. The effects described are also obtained for double-line gratings whose lattice webs consist of several layers. However, the total thickness of the layers is always smaller than the modulation depth h. At least one of the layers is made of a metal or a semiconductor. Trilayers are particularly preferred for the layer structure. A larger number of layers hardly improves the angle-dependent color effect, but increases the manufacturing cost.

6 shows an example of a security element, in which the first and second grid bars 3 and 7 each realized by a trilayer coating. They have a metallic layer 11 , a dielectric interlayer 12 and another metallic layer 13 on. Preferably, but not necessarily, the thickness of the two metal layers is identical.

7 shows the color values in the LCh color space for the security element S with the layer structure according to FIG 6 , wherein the metal layers 11 and 13 each 10 nm thick aluminum layers and the dielectric layer 12 is a silicon dioxide layer. 7 shows the color effect as a function of the thickness of the silicon dioxide layer. The other parameters are d = 360 nm, b = 180 nm and h = 200 nm. The substrate 1 and the areas 4 and 5 have, as in all other embodiments, a refractive index of 1.56.

The security element shows a slightly lower brightness in transmission, but a higher chroma than in reflection. Silicon dioxide layer thicknesses above 60 nm cause a strong hue in transmission when tilted. In reflection, the security element appears green. At 70 nm layer thickness of silicon dioxide, the security element is approximately neutral in reflection at approximately vertical angles of incidence. This has the advantage that the transmitted hue is not changed by the reflection.

The above statements always relate to grid profiles with a duty ratio b: a = 1: 1 (fill factor 0.5). This value is preferred, but not mandatory. Deviating from this value, it is possible to make the color tone of the reflection of the structure different for the front and the back.

The angle-dependent color filtering of the security elements described can now be used to make multi-colored motifs that change their color when tilted or twisted.

The simple embodiment of a multicolor motif with a double-line grid is an arrangement in which different areas are formed whose longitudinal direction of the line grid structures is rotated relative to one another, preferably by 90 °. For with a tilt of a grid, in which the grid lines are parallel to the plane of incidence, the spectral transmission or reflection characteristics hardly changes.

The 8a and 8b show a security element in which areas of a background 14 a motive 15 with vertical longitudinal direction and the motif 15 are formed with horizontally extending longitudinal direction. In the presentation of the 8b you can see these line directions indicated schematically. The motif 15 shows a butterfly as well as two numerical values. 8a shows the motif 15 schematic in white on a black background. The motif 15 like the background 14 are exemplary with the parameters of the embodiment according to 1 designed.

The 9a and 9b show different lighting conditions when the security element S the 8th in front of a backlight 16 is viewed in transmitted light. When viewed vertically (upper part of the figure 9a ), the security element appears uniform yellow in transmission. If the security element is now rotated around the vertical axis, the color of the background 14 from yellow to blue. If you tilt the horizontal axis instead, the subject will appear 15 blue (lower illustration of the 9a ). The situation for different azimuth angles shows the 9b , Here the colors of the motif change 15 and the background 14 to a complete inversion.

Of course, arrangements with gratings of different orientation in several motif areas are also conceivable, as already explained in the general part of the description.

The security element S also has polarizing properties in transmission. 10 shows the color behavior of a security element S with a line grid structure whose grid bars are made of aluminum, as a function of the modulation depth h in reflection (left column) and in transmission (right column) for TE and TM polarization at a normal angle of incidence. The application otherwise corresponds to that of 3 , The parameters of the security element are d = 360 nm, b = 180 nm, t = 30 nm. The refractive index of the substrate 1 is n = 1.56.

It turns out that the security element has a good brightness contrast for the two polarization directions in transmission at a modulation depth above 150 nm. Furthermore, the change in chroma is particularly large for modulation depths between 200 nm and 260 nm. The color change has a maximum at a modulation depth of 270 nm.

11 shows the influence of the layer thickness t for the grid of 10 at a modulation depth of 250 nm. The security element has good polarization properties in transmission at layer thicknesses above 20 nm. The chroma and the color contrast are particularly high at layer thicknesses between 20 nm and 30 nm. Here, a color change from blue to yellow is observed as the polarization of the illumination changes from TM polarization to TE polarization.

Safety elements whose line grid structures comprise silicon in the grid bars also have a polarization effect in transmission. 12 shows the LCh color values of a security element with the lattice parameters d = 360 nm, b = 180 nm and h = 300 nm, whose lattice webs were produced from an evaporation with amorphous silicon. So they are made of amorphous silicon. There are clear brightness differences in transmission for silicon layer thicknesses above 100 nm. For a silicon layer thickness of about 140 nm, the change in chroma is particularly large. The transmission appears orange for TM polarization, violet for TE polarization.

13 shows the color behavior when crystalline silicon is used instead of amorphous silicon. Otherwise the parameters correspond to those of the 12 , This security element shows clear brightness differences even for layer thicknesses above 40 nm. The layer thickness of 100 nm is particularly well suited as a polarizing filter. The orange / blue color contrast is strongest for a silicon layer thickness of 120 nm.

The polarization properties of the security element allow authenticity verification by considering the transmission in linearly polarized illumination. Such illumination is provided, for example, by LCD screens. Even the blue sky is partially linearly polarized (in contrast to the cloudy sky) and can be used as a beam source for the investigation of the security element.

The security element can serve in particular as a transparent window of banknotes or other documents. It may also be partially overprinted color or the grid areas may be partially demetallized or configured without line grid, so that such an area is completely metallized. Combinations with diffractive grating structures, such as holograms, are also conceivable.

The authenticity check of the security element can be made without any aids. A polarizer can provide additional authentication.

LIST OF REFERENCE NUMBERS

1

substratum

2

first line grid structure

3

first grid web

4

first grid gap

5

interlayer

6

second line grid structure

7

second grid bridge

8th

second grid gap

9

base layer

10

topcoat

11, 13

metal layer

12

dielectric interlayer

14

background

15

motive

16

Backlight

H

modulation depth

t, t1, t2

coating thickness

b

linewidth

a

column width

d

period

S

security element

L

level

e

incident radiation

R

reflected radiation

T

transmitted radiation

Θ

angle of incidence

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

• DE 102009012299 A1 [0002]
• DE 102009012300 A1 [0002]
• DE 102009056933 A1 [0002]

Claims (7)

Security element for producing value documents, such as banknotes, checks or the like, comprising: a dielectric substrate ( 1 ), - one in the substrate ( 1 ) embedded first line grid structure ( 2 ) of a plurality of first grid webs extending along a longitudinal direction and arranged in a plane (L) (US Pat. 3 ) of metal or semiconductor and one in the substrate ( 1 ) embedded second line grid structure ( 6 ) extending along the longitudinal direction of the second grid bars ( 7 ) made of metal or semiconductors, which with respect to the plane (L) over the first line grid structure ( 2 ), wherein - the first grid bars ( 3 ) each have a width (b) and are at a distance (a) next to each other, so that between the first grid bars ( 3 ) along the longitudinal direction extending first grid column ( 4 ) are formed with the spacing (a) of corresponding width, - the second line grid structure ( 6 ) to the first line grid structure ( 2 ) is inverted, wherein in plan view of the plane, the second grid webs ( 7 ) over the first grid columns ( 4 ) and second grid column ( 8th ) between the second grid bars ( 7 ), over the first grid bars ( 3 ), and - the width of the first grid bars ( 3 ) and the second grid column ( 8th ), the width of the second grid bars ( 7 ) and the first grid column ( 4 ) and a thickness (t) of the first grid webs ( 3 ) and the second grid bars ( 7 ) is each below 300 nm. A security element according to claim 1, wherein the dielectric substrate ( 1 ) a base layer ( 9 ) on which the first line grid structure ( 2 ) is formed, a dielectric interlayer applied thereto ( 5 ), which both the first grid bars ( 3 ) as well as the first grid column ( 4 ) and thicker than the first grid bars ( 3 ) and one above the second line grid structure ( 6 ) arranged dielectric cover layer ( 10 ), wherein preferably the intermediate layer ( 5 ), the top layer ( 10 ) and the substrate ( 9 ) have the same refractive index. A security element according to any one of the preceding claims, wherein between the first grid bars ( 3 ) and the second grid bars ( 7 ) measured perpendicular to the plane a distance (h), which is between 50 nm and 500 nm, preferably between 100 nm and 300 nm. Security element according to one of the above claims, wherein the first grid bars ( 3 ) and the second grid bars ( 7 ) has a coating of one or more of the following materials: Al, Ag, Cu, Au, Cr, Pt, Si, Ge, and alloys of these materials. Security element according to one of the above claims, wherein the first and / or the second grid webs ( 3 . 7 ) a trilayer coating of two superimposed metal or semiconductor coatings ( 11 . 13 ) with an intervening dielectric layer ( 12 ) exhibit. A security element according to any one of the preceding claims, wherein the width (b) is equal to the distance (a). Security element according to one of the preceding claims, which, in plan view of the plane (L), comprises at least two regions ( 14 . 15 ), whose longitudinal directions are at an angle to each other, in particular at right angles.

Images