KR102511203B1 - Security element with subwavelength grating - Google Patents

Abstract

The present invention relates to a security element for generating important documents such as banknotes, checks, etc., which has a dielectric substrate (1), first lattice spacings (4) embedded in the substrate (1) and located therebetween. , a first periodic line lattice structure 2 made of a plurality of first lattice networks 3, extending in the longitudinal direction and disposed in a first plane L1, and embedded in the substrate 1 and between a second line lattice structure (6), made of second lattice nets (7) and extending in the longitudinal direction, having second lattice spacings (8) located at (6) is located above the first line grid structure 2 on a second plane L2 parallel to the first plane L1, and wherein the second line grid structure 6 is When viewed from above in the first plane L1 formed inversely to the line lattice structure 2, the second lattice networks 7 are located above the first lattice spacings 4 and the second lattice spacings s (8) are located above the first grid networks (3), the security element (S) creates a color effect in transmissive observation (T) and also the grid networks of the first line grid structure (2) (3) and the grating networks 7 of the second line grating structure 6 are formed from double layers, respectively, made of high refractive material layers 3a and 7a and metal material layers 3b and 7b.

Description

Security element with subwavelength grating

The present invention relates to a security element for generating important documents such as banknotes, checks, etc., the security element comprising a dielectric substrate, a plurality of first lattice networks having first lattice spacings embedded in the substrate and located therebetween. second longitudinally extending lattice networks having a first periodic line lattice structure made and extending in the longitudinal direction and disposed in a first plane, and second lattice spacings inherent in the substrate and located therebetween; A second line lattice structure of the same period made of, wherein the second line lattice structure is positioned over the first line lattice structure on a second plane, parallel to the first plane, and the second line lattice structure is formed inversely with respect to the first line lattice structure, such that when viewed from above in the first plane, the second lattice networks are located above the first lattice spacings and the second lattice spacings are located above the first lattice networks.

Security elements with periodic line grids are known, for example, from DE 102009012299 A1, DE 102009012300 A1 or DE 102009056933 A1. They may have color filter properties in the subwavelength range if the grating side is such that resonance effects occur in the visible range. These color filter properties are known as both reflective and transmissive subwavelength structures. These structures have a strong polarization effect on the reflection or transmission of an incident light beam. The color is relatively strongly angle dependent in the reflection or transmission of these subwavelength gratings. However, color saturation in these gratings is significantly reduced if the incident light is not polarized.

One-dimensional periodic gratings may have color filter properties in the subwavelength range if the grating side is such that resonance effects occur in the visible light wavelength range. These color filter characteristics depend on the angle of incident light.

n2

n3이다. 칼라 변경은 각도(

)의 변화에 따라 발생한다. 격자가 입사 평면에 대하여 수직으로 틸트되어 있다면(

>0°;

=90°), 칼라는 거의 일정하게 유지된다. 각도

는 방위각을 지시한다. 명칭 DID(Diffractive Identification Device)로 팔리는 보안 요소는 이러한 구조에 기초하고 반사에 있어서 칼라 필터 특성들을 이용한다. 칼라 효과를 인식하기 위해 광흡수 기판이 필요하다. DE 3248899 C2 describes a subwavelength structure with angle-dependent color-filtering properties. This grating has a visual cross-section and also has a high refractive index (HRI) layer deposited thereon, where the refractive indices are nHRI > n2, n1

n2

is n3. The color change angle (

) occurs according to the change of If the grating is tilted perpendicular to the plane of incidence (

>0°;

= 90°), the color remains almost constant. Angle

indicates the azimuth. A security element sold under the name Diffractive Identification Device (DID) is based on this structure and uses color filter properties for reflection. A light absorbing substrate is required to perceive the color effect.

WO 2012/019226 A1 describes embossed subwavelength gratings with similar square sides, printed on a horizontal plane, which are metal particles or metal nanoparticles. This grating exhibits color effects or polarization effects in transmission.

Also for example from DE 102011115589 A1 or Z.Ye et al. "Compact Color Filter and Polarizer of Double layer Metallic Nanowire Grating Based on Surface Plasmon Resonances", Plasmonics, 8, 555-5559 (2012), metal or semi-metallic double layer arrangement Subwavelength gratings as angle-dependent color filters are known, where the metallization is realized via vapor deposition and is embedded in the dielectric. The approach described in DE 102011115589 A1 discloses a security element having the properties mentioned above, which is based on the arrangement of two wire gratings with the same period, which are offset from each other by half a period. and consists of metallic or semi-metallic wires (eg ZnS with a thickness of 70 nm).

This known subwavelength structure with an approximately 70 nm thick ZnS coating is suitable as a color filter for reflection. Therefore, in order to achieve sufficient visible color contrast in reflection, this structure must additionally be applied on the light absorbing substrate. Subwavelength gratings with metallic coatings exhibit relatively high color saturation in transmission. Therefore, due to light absorption in metals, they appear relatively dark.

Sinusoidal gratings coated with a thin metal film can cause plasmon resonance effects. These resonances result in increased transmittance for TM polarization, as described in Y. Jourlin et al., “Spatially and polarization resolved plasmon mediated transmission through continuous metal films”; Opt. See Express 17, 12155-12166 (2009). This effect can be further optimized by an additional thin dielectric layer, as disclosed by T. Tenev et al., "High Plasmonic Resonant Reflection and Transmission at Continuous Metal Films on Undulated Photosensitve Polymer", Plasmonics (2013). The security element described in WO 2012/136777 A1 is based on this optical effect.

Similarly WO 2014/033324 A2 describes transmissive security elements based on subwavelength gratings and exhibits an angle dependent color. The optical properties of sinusoidal gratings coated in a highly refractive manner are described in more detail in this paper.

Known two-dimensional periodic subwavelength gratings with discontinuous surfaces exhibit color filter properties, but have a high angular error range. Therefore, its hue hardly changes upon tilting.

Therefore, the present invention is based on the object of detailing the visible security element when checking the good color effect that changes when tilting.

This object is achieved according to the present invention through a security element for generating important documents such as banknotes, checks, etc., said security element comprising:

- a dielectric substrate;

- a first periodic line lattice structure, made of a plurality of first lattice networks, extending longitudinally and disposed in a first plane, having first lattice spacings inherent in said substrate and located therebetween; and

- a second line lattice structure, extending in the longitudinal direction and made of second lattice networks, having second lattice spacings embedded in the substrate and located therebetween;

- wherein the second line lattice structure is located above the first line lattice structure on a second plane parallel to the first plane, and

- At this time, the second line lattice structure is formed in reverse with respect to the first line lattice structure so that when viewed from above the first plane, the second lattice networks are located above the first lattice spacings and the second lattice spacings are are located above the first grid networks,

- the security element creates a color effect in transparent observation and also

- The grating networks of the first line grating structure and the grating networks of the second line grating structure are each formed from a double layer made of a high refractive material layer and a metal material layer.

The high refractive material is preferably a dielectric or semiconductor, for example Si, Ge, C.

According to the present invention, a double line grating is used which consists of line grating structures in which two planes are located one above the other, in a complementary manner, ie offset with respect to each other. A phase shift of 90° is an ideal value, which of course must be considered in the context of manufacturing accuracy. Due to manufacturing tolerances, deviations from complementarity, ie a 90° phase shift, may occur here. In addition, square sides may not be perfectly formed, but may be approximated by trapezoidal sides where the upper parallel edge is shorter than the lower one. In the case of a line lattice structure having a rectangular cross section, the phase shift corresponds to a 1/2 period.

Line grating structures consist of a combination of a metal layer and a layer of a highly refractive, dielectric or semi-metallic material. The thickness of the grating networks is less than the modulation depth, ie the spacing of the planes of the grating structures, so that no closed film is created. For this reason, the spacing of the first and second planes is greater than the sum of (0.5 * first layer thickness) and (0.5 * second layer thickness).

Gratings of this structure are surprisingly known to provide reproducible and easily perceptible color effects upon tilting in transmissive observation.

The security element can be created simply as a layered structure by first providing a base layer on top of which the double layer of the first line lattice structure is formed. A dielectric intermediate layer covering the first line grating structure and thicker than the grating networks of the first line grating structure is applied thereon. There may then be an offset, second line grating structure thereon, and a dielectric cover layer completes the substrate in which the line grating structure is embedded. Alternatively, it is also possible that a subwavelength grating is first formed, eg embossed, on a dielectric substrate, wherein the subwavelength grating has a rectangular side surface in cross section. When vertically coated with a double layer of materials, for example by vapor deposition, the double layer is created on the horizontal surface and in the trenches, which form the first and second grating networks. As a result, the desired first and second grating networks are obtained in different planes.

A particularly good color effect is achieved if the vertical spacing between the first and second grating networks, ie the modulation depth of the structure, is between 100 nm and 500 nm. The measurement of the spacing is based on two planes that can be defined by the equally guided surfaces of the first and second line lattice structures, eg the lower face of the lattice nets or the upper face of the lattice nets. The vertical spacing must be measured here of course perpendicular to the plane. That is, it indicates the height difference between identically guided surfaces of the grids.

Suitable high refractive materials for the double layer of grating networks are all materials having a higher refractive index than the surrounding substrate, i.e. material, in particular by at least 0.3. The layer order of the double layers is irrelevant; Also, the first and second line lattice structures may be different.

The security element exhibits viewing angle dependent color filtering in transmission. This angular dependence is particularly pronounced if the grating lines are perpendicular to the plane of light incidence. Color filtering can be used to create motifs with multiple colors so that they change their color depending on the rotational position or different effects upon tilting the plane. it becomes visible Therefore, it is preferable that at least two regions are provided in a plan view of a plane, and the longitudinal directions of the line lattice structures are at a predetermined angle, particularly perpendicular to each other. When viewed vertically, the motif has a uniform color and also when viewed vertically, additional Structures can be created to have none. When this security element is tilted, the color of one area, eg the color of the background, changes in a different way from the color of another area, eg the color of the motif.

Embodiments with a plurality of differently arranged regions are of course also possible. For example, a security element is provided with a plurality of areas, wherein the areas differ from each other with respect to the lattice period of the line lattice structures and/or the orientation of the lattice lines. As a result, motifs having different color effects in transmission observation can be prepared.

The previously mentioned features and the features to be described may be used alone or in other combinations, without departing from the scope of the present invention, as well as in the combinations specified.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail below on the basis of the accompanying drawings, which disclose, for example, the essential features of the invention.
1 shows a cross-sectional view of a security element having double line gratings, each line grating having grating nets from a double layer.
2a to 2b show the spectral dependence of reflection and transmission of the security element in FIG. 1 upon changing the viewing angle;
3a to 3b show the spectral dependence of the reflection and transmission of the security element in FIG. 1 upon varying the modulation depth h.
4a to 4b show the spectral dependence of reflection and transmission of the security element in FIG. 1 at varying modulation depths h for different material combinations than in FIGS. 3a and 3b .
FIG. 5 shows color values in the LCh color space for reflection and transmission of the security element in FIG. 1 at different viewing angles and at varying layer thicknesses of the double layer.
6a-6b show CIE 1931 color diagrams for reflection and transmission of the security element in FIG. 1 with varying layer thicknesses.
7a-7b show CIE 1931 color diagrams for reflection and transmission of the security element in FIG. 1 at varying viewing angles and at different layer thicknesses than in FIGS. 6a and 6b.
8a-8b show CIE 1931 color diagrams of reflection and transmission of the security element in FIG. 1 at varying viewing angles and at different layer thicknesses than FIGS. 7a and 7b.
Figures 9a-9b show two top views of a security element constructed as a motif with the gratings of figure 1, but with different orientations of the gratings.
Figures 10a-10b show views similar to Figures 9a and 9b of another embodiment of a security element.

1 shows, in cross section, a security element S having a double line grating embedded in a substrate and consisting of two line grating structures 2 , 6 . The substrate comprises a dielectric carrier 1 , on which a first line grid structure 2 , arranged in plane L1 , is bonded with a dielectric layer, for example an embossed lacquer layer. The first line grid structure 2 is composed of first grid networks 3 having a width b, which extends in a longitudinal direction perpendicular to the drawing plane. Between the first grid networks 3 are located first grid spacings 4, having a width a.

Each grating network 3 is composed of a double layer of a high refractive index material 3a having a thickness t4 and a metallic material 3b having a thickness t2. The thickness of the first grid networks 3 (measured perpendicular to the plane L1) is thus (t2 +t4). In the plane L2, a second line grating structure 6 having second grating networks 7 is located at a height h above the first grating networks 3, similarly of a high refractive index material having a thickness t3. (7a) and a double layer of metal material (7b) having a thickness (t1). The second lattice networks 7 have a width a. The second line grating structure 6 is phase-shifted in the plane L2 with respect to the first line grating structure 2 so that the second grating networks 7 are as precisely as possible (in the context of manufacturing accuracy) the first grating spacings ( 4) is placed on top. At the same time, the second grid spacings 8 , which are located between the second grid networks 7 , are located above the first grid networks 3 . Meanwhile, the second line grating structure 6 is embedded in the substrate 1 with the same period d, and the period d is 200 to 700 nm.

The thickness (t2+t4) of the first grating nets 3 is less than the height h, so that adjacent films are not formed from the grating nets 3 and 7. The height h represents the modulation height of the grating structures.

In the schematic cross-sectional view of FIG. 1 , the width b of the first lattice networks 3 is equal to the width a of the second lattice networks 7 . As far as period d is concerned, the fill factor in each line grating structure is thus 50%. However, this is not essential. According to the formula b + a = d, the desired change can occur.

In addition, in the schematic cross-sectional view of Fig. 1, the thicknesses are t2 = t4 and t1 = t3 and (t2 + t4) = (t1 + t3). This is advantageous for simpler creation, but is not absolutely essential.

The modulation depth h, that is, the difference in height between the first line grating structure 2 and the second line grating structure 6 (corresponding to the spacing of the planes L1 and L2) is greater than the sum of the thicknesses of the meshes 3 and the second lattice meshes 7, so that a vertical spacing having dimension h-(t2 + t4) exists between the two line lattice structures 2 and 6 . A grating structure can be considered as an arrangement of two wire gratings having the same side, which are located at a distance of h - (t2 + t4) relative to each other.

The grating networks 3, 7 in all embodiments are formed from a dual layer of a high refractive index, dielectric or semi-metallic material 3a, 7a and a metallic material 3b, 7b. The high refractive material has a refractive index of nHRI and is surrounded by dielectrics, in particular dielectric intermediate layer 5 and dielectric cover layer 10 . In practice, the refractive indices of surrounding materials generally differ little and are approximately n1. The refractive index nHRI of the high refractive material is greater than the refractive index of the surrounding material, for example by at least 0.3 in absolute value.
And, the high refractive materials 3a and 7a are selected from Si, Ge, C, ZnS, ZnO, ZnSe, SiNx, SiOx, Cr2O3, Nb2O5, Ta2O5, TixOx and ZrO2, and the metal materials 3b and 7b are Al, Ag , Au, Cu, Cr and alloys thereof.

)에 종속되는데, 이것은 이하에서 설명될 것이다. The security element S of FIG. 1 reflects an incident light beam in the form of a reflected light beam R. Further, the ray component is transmitted in the form of a transmitted ray T. The reflection and transmission properties are determined at the angle of incidence (

), which will be explained below.

The security element S can be created, for example, by first applying a first line grid structure 2 to the carrier 1 and then applying an intermediate layer 5 thereon. A second line lattice structure with second lattice networks 7 can then be introduced at the lattice spacings 4 shown here upwards. A cover layer 10 covers the security element. The refractive indices of layers 5 and 10 and carrier 1 may in some embodiments be substantially equal, for example n1 = 1.5, in particular 1.56.

Dimensions b, a and t1 to t4 lie in the subwavelength range. That is, smaller than 300 nm. The modulation depth h is preferably between 100 nm and 500 nm.

First, a manufacturing method in which a square lattice is created on the upper side of the carrier 1 is also possible. In other words, the carrier 1 is structured such that networks having a width b alternate with trenches having a width a. The structured substrate is subsequently provided with a desired coating by vapor deposition to form first and second line grids and first and second line grid structures. After vapor deposition, the structure is finally covered with a cover layer. This results in a layered structure in which the upper and lower sides have substantially the same refractive index.

A structured substrate may be obtained in different ways. One option is reproduction using the master. The master mold can be replicated with UV lacquer onto a film, for example PET film. This makes the substrate 1 a dielectric material, which has a refractive index of eg 1.56. Alternatively, hot embossing methods may be used.

The master or substrate itself can be produced using e-beam setup, focused ion beam or interference lithography, and the structure is written in photoresist and subsequently printed.

The structure of the master, produced through photolithography, is then etched into the quartz substrate in a subsequent step to form as perpendicular lateral flanks as possible. The quartz wafer can then be used as a preform and copied to Ormocer, for example, or replicated via galvanic forming. Direct formation of photolithographically created originals on ohmic or nickel is similarly possible in electrical methods. It is also possible in the nanoimprint method to construct a motif in which different lattice structures start from a homogeneous lattice master.

Such manufacturing methods for subwavelength lattice structures and motifs composed of different subwavelength structures are known to the person skilled in the art, for example from DE 102011115589 A1, which is reflected here in its entirety in this aspect.

The optical properties of the security element will be described below for aluminum and high refractive materials such as zinc sulfide (ZnS) and titanium dioxide (TiO2) at visible wavelengths. The surrounding material is a polymer with a refractive index of n=1.52. Furthermore, the lateral geometries of the grids are assumed to be quadrangular. Minor deviations from the ideal square shape that actually occur, such as trapezoidal shape, do not greatly affect the optical phenomenon and give similar results to those of square gratings. Figures 2a and 2b show spectral reflectance (Figure 2a) and transmission ( Figure 2a) for a grating with parameters d = 360 nm, h = 220 nm, b = 180 nm, and coatings tAl = 30 nm and tZnS = 160 nm. 2b) is shown. The incident ray is unpolarized.

)은 도 1에 정의되어 있다. Figure 2a shows the y-axis reflection as a function of wavelength plotted on the x-axis for different angles of incidence, specifically 0°, 15° and 30°. Figure 2b similarly shows permeation. angle of incidence(

) is defined in Figure 1.

The spectral reflection, for normal incident light, has two significant dips at 404 nm and 672 nm, where the long-wavelength dip can be found as a peak in the transmission spectrum. For increasing angle of incidence, this peak shifts into the long-wavelength range, and additional peaks occur in the transmission spectrum with angle-dependent scattering.

) = 30°(도 3b)에 있어서 코팅들 tAl = 30 nm 및 tZnS = 140 nm를 가지는 격자에 있어서의 가시광선 범위에서의 파장의 함수로서 투과를 보여준다. 변조 깊이는 180 nm와 240 nm 사이에서 변한다. 수직 입사에 있어서, 3 개의 피크들을 볼 수 있는데, 이때 2 개의 단파 피크들은 변조 깊이의 변화에 의해 그들의 현저함의 측면에서 상당히 영향받는다. 청색 피크에 있어서의 세기는 강하게 증가되고 녹색으로 천이되는 한편, 파장 560 nm에서의 피크의 세기는 강하게 감소된다. 입사 각도

=30°에 있어서, 가시광선 범위의 피크들의 위치는 변조 깊이(h)가 변할 때 거의 변하지 않는다. 격자는 변수들 ㅇ = 360 nm, b = 180 nm, 및 코팅 tAl = 30 nm 및 tZnS = 140 nm를 가지고, n=1.52를 가지는 유전체에 내재되고 또한 변조 깊이들은 h = 180 nm - 240 nm이다. 3a and 3b relate the effect of modulation depth (h) on the transmission spectrum. The drawing shows a normal incident ray (Fig. 3a) and an incident angle (

) = 30° (Fig. 3b) shows the transmission as a function of wavelength in the visible range for a grating with coatings tAl = 30 nm and tZnS = 140 nm. The modulation depth varies between 180 nm and 240 nm. At normal incidence, three peaks can be seen, with the two shortwave peaks significantly affected in terms of their salience by the change in modulation depth. The intensity at the blue peak strongly increases and transitions to green, while the intensity of the peak at wavelength 560 nm strongly decreases. angle of incidence

= 30°, the position of the peaks in the visible range hardly changes when the modulation depth (h) changes. The grating is embedded in a dielectric with parameters o = 360 nm, b = 180 nm, and coating tAl = 30 nm and tZnS = 140 nm, n = 1.52 and modulation depths h = 180 nm - 240 nm.

= 30°에 대한 이 파장 범위에서의 공명은 더 많이 약하게 나타나는데, 이것은 더 낮은 광 흡수로 귀결된다. 4a and 4b relate the effect of a high refractive index material on the diffractive behavior of a grating. The figure shows the transmission spectrum of a grating with the parameters of FIG. 3 but with a coating of 140 nm thickness and with TiO ₂ instead of ZnS. The blue component in the spectrum is significantly larger here because TiO ₂ has a significantly lower absorption in the blue range. In addition to this, transmission in the red range is higher overall.

The resonance in this wavelength range for = 30° appears more weak, which results in lower light absorption.

To investigate the color properties of these security elements in the LCh color space, convolution of the sensitivity of the human eye and the transmission and reflection spectra with the emission curve of a D65 standard lamp was performed and the color coordinates X, Y, Z were calculated. . D65 illumination roughly corresponds to daylight. XYZ coordinates were subsequently converted to color values LCh. These values can be directly related to the human sense of color perception by an observer:

L*: luminance

C*: saturation (color density), and

h°: Hue.

= 0° 및 30°)에 있어서 ZnS 코팅(3a, 7a)의 두께 t3 = t4의 함수로서 변수들 d=360 nm, h=210nm, b=180nm을 가지는, 보안 요소의 LCh 칼라 다이어그램들(좌측에 반사 그리고 우측에 투과)을 보여준다.여기서 볼 수 있는 것은 대략 160 nm의 ZnS 층 두께가 틸팅시 투과에 있어서 채도에 있어서의 강한 변화, 즉 각도(

)에 있어서의 변화를 생성한다는 것이다. 한편, 색조에 있어서의 변화는 증가하는 두께들에 대하여 증가한다. 도 5의 값들은 x, y 칼라 좌표들로 변환되었고 CIE 1931 칼라 공간으로 도 6a, 도 6b에 도시되어 있다. 화이트 포인트는 "WP"로 지시되어 있다. 삼각형은 통상적으로 스크린들을 이용해 표현될 수 있는 칼라 영역을 정한다. 칼라 좌표들은 궤적들의 형태로 도면에 도시되어 있다. 두께 tZnS = 200 nm의 끝점은 점 형태의 기호로 지시된다. 반사에 있어서, 색조는 ZnS의 층 두께의 변화에 따라 변한다. 0°에서 30°까지 틸팅하는 동안, 칼라는 황색과 적색 사이에서 변한다. 투과에 있어서, 한편, 칼라 공간의 상대적으로 큰 영역이 ZnS 두께의 변화에 따라 덮이게 된다. 추가적인 ZnS 코팅 없이 DE 102011115589 A1에 따른 알루미늄 격자가 황색에서 진홍색(magenta)까지 칼라 천이 효과를 보일 때, 180 nm ZnS 코팅을 가지는 격자에 있어서 이러한 칼라들은 가상적으로 역순으로 나타난다. 5 shows angles of incidence (

LCh color diagrams of the security element (left It can be seen here that a ZnS layer thickness of approximately 160 nm has a strong change in chroma in transmission upon tilting, namely the angle (

) that produces a change in On the other hand, the change in color tone increases for increasing thicknesses. The values of FIG. 5 have been converted to x, y color coordinates and are shown in FIGS. 6A and 6B in the CIE 1931 color space. The white point is indicated by "WP". A triangle typically defines a color area that can be displayed using screens. Color coordinates are shown in the figure in the form of trajectories. The endpoint of the thickness tZnS = 200 nm is indicated by a dotted symbol. In reflection, the color tone changes with the change of the layer thickness of ZnS. While tilting from 0° to 30°, the color changes between yellow and red. In transmission, on the other hand, a relatively large area of the color space is covered with a change in ZnS thickness. While an aluminum grating according to DE 102011115589 A1 without an additional ZnS coating shows a color shift effect from yellow to magenta, for a grating with a 180 nm ZnS coating these colors appear virtually in reverse order.

Color characteristics of the reflection for the security element, with parameters d = 360 nm, h = 220 nm, b = 180 nm and layer thicknesses tAl = 30 nm and tZnS = 160 nm, excluded in the dielectric with n = 1.52 are shown in FIG. 7A and a color plot of transmission is shown in FIG. 7B. 7a and 7b show CIE 1931 color plots in reflection ( FIG. 7a ) and in transmission ( FIG. 7b ), where color coordinates are plotted as a function of angle of incidence from 0° to 30°. Here, the lighting of the security element having the layer order of FIG. 1 and the reverse lighting, the same as that of the reverse order of the layers, was investigated. The trajectory of the illumination of the front surface is indicated by "V", and the associated trajectory of illumination of the back surface is characterized by "R". It should be noted that the transmission in these two cases is the same due to the reciprocity of the light path. In transmission, a marked color transition effect from blue to green occurs. In reflection, the color change is significantly weaker. However, the reflected color on the front side is clearly distinguishable from the back side. This effect further increases anti-counterfeiting protection when using these lattice structures as security features.

= 0°-30°의 함수로서 반사 및 투과에 대하여 칼라 도면들로 도시되어 있다. 도 7a 및 도 7b와 대조적으로, 격자 주기는 여기서 d = 320 nm이다. b/d 비율은 유사하게 0.5이다. 층 두께들은 tAl = 30 nm 및 tZnS = 120 nm이다. 반사에 있어서, 녹색 색조는 틸팅시 거의 변하지 않는다. 이것은 주로 칼라 포화를 변경시킨다. 하지만, 투과에 있어서 색조는 높은 칼라 포화를 가지는 적색으로부터 청색까지 변한다. 도 7의 보안 요소와 반대로, 여기서 격자 변수들에 있어서의 변화로 인해, 특히 고굴절 층의 두께와 격자 주기, 투과에 있어서 틸트 칼라가 선택될 수 있다. Figures 8a and 8b show the x, y color coordinates of the security element similar to Figures 7a and 7b but with different grid parameters. The data are similarly

Color plots are shown for reflection and transmission as a function of = 0°-30°. In contrast to Figs. 7a and 7b, the grating period is here d = 320 nm. The b/d ratio is similarly 0.5. The layer thicknesses are tAl = 30 nm and tZnS = 120 nm. In reflection, the green tint hardly changes upon tilting. This mainly changes the color saturation. However, in transmission the hue changes from red to blue with high color saturation. Contrary to the security element of FIG. 7 , here a tilt collar can be selected due to variations in the grating parameters, in particular the thickness of the high refractive index layer and the grating period, transmission.

Due to the fact that no color change occurs upon tilting perpendicular to the angle of incidence, the security feature can be designed graphically so that the motif 15 is invisible under vertical viewing and appears only upon tilting. This can be done by arranging the two grating areas 14, 15 having the same grating side in such a way that they are rotated by 90° relative to each other. This arrangement is shown in Figures 9a and 9b.

The grid lines of region 14, forming the background, extend vertically, while the grid lines of region 15, forming the motif, extend horizontally. When the security element is tilted around a horizontal axis, the motif emerges. Additional orientations of the regions are also possible. Due to the finely incrementally oriented areas, it is also possible to create motion effects, for example in transmission. For this purpose, see, for example, DE 102011115589 A1. Furthermore, it is possible to form motifs using regions having different aspects, for example periods of a lattice structure.

Further, the metal layer or the high refractive index layer may be formed only in specific lattice regions, not over the entire region. 10A and 10B show the butterfly motif and the number "12", where the square area around the number "12" does not contain an additional high refractive index coating (region 16 in FIG. 10B). Under vertical viewing, the motifs butterfly and the number "25" cannot be seen, but regions 16 and 17 show different colors. Upon tilting, the motif appears additionally.

The security element can be used as a see-through to banknotes. It can also be partially overprinted in color. One or two materials of the double layer can also be partially removed by laser irradiation, for example using ultrashort pulses. Combinations with highly refractive transparent holograms are also possible. These holograms can also act as reflective properties. A part of the security element S can be located on the absorbing substrate, so that this part functions only as a reflective feature and forms a contrast with other parts of the security element S located in the area of the see-through window. do.

The security element may function as a see-through window, in particular to banknotes or other documents. It can also be partially overprinted in color or the grating areas can be partially demetallized or designed without line gratings, such that these areas are fully metallized. Combinations with diffraction grating structures, such as holograms, are also possible.

: 입사 각도1: carrier or substrate
2: first line lattice structure
3: first grid network
3a: high refractive material
3b: metal
4: first lattice spacing
5: middle layer
6: second line lattice structure
7: second grid network
7a: high refractive material
7b: metal
8: Second lattice spacing
10: cover layer
14:-17: Area
h: modulation depth or height
t1, t2, t3, t4: coating thickness
a, b: mesh and gap widths
d: period
S: secure element
L1, L2: flat
E: incident ray
R: reflected ray
T: transmitted light

: angle of incidence

Claims (9)

In the security element for generating important documents such as banknotes, checks, etc., the security element,
- a dielectric substrate (1);
- made of a plurality of first grid networks (3), with first grid spacings (4) embedded in said substrate (1) and located therebetween, extending longitudinally and in a first plane (L1); A first line lattice structure 2 periodically disposed, and
- made of second grid networks (7), which are inherent in the substrate (1) at the same period (d) and have second grid spacings (8) located therebetween, and extending in the longitudinal direction; It includes a two-line lattice structure (6),
- at this time, the second line grid structure 6 is located above the first line grid structure 2 on a second plane L2 parallel to the first plane L1, and
- At this time, the second line grid structure 6 is formed in reverse with respect to the first line grid structure 2, so that when viewed from the top of the first plane L1, the second grid networks 7 are 1 lattice spacings (4) are located above and the second lattice spacings (8) are located above the first lattice networks (3),
- the security element (S) creates a color effect in the transmissive observation (T) and also
- the grating nets 3 of the first line grating structure 2 and the grating nets 7 of the second line grating structure 6 are composed of high refractive material layers 3a, 7a and metal material layers 3b, A security element, each formed from a double layer, made of 7b). 2. Security element according to claim 1, wherein the layer of high refractive index material (3a, 7a) has a refractive index higher than that of the surrounding substrate (1) by at least 0.3. 3. Security element according to claim 1 or 2, wherein the period (d) is between 200 and 700 nm. The high refractive index material (3a, 7a) according to claim 1 or 2, is Si, Ge, C, ZnS, ZnO, ZnSe, SiN _x , SiO _x , Cr ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Ti _x O _x and ZrO ₂ , and the metal material (3b, 7b) is selected from Al, Ag, Au, Cu, Cr and alloys thereof. 3. Security element according to claim 1 or 2, wherein the distance (h) between the planes (L1, L2) is between 100 nm and 500 nm. 3. Security according to claim 1 or 2, wherein the security element (S), viewed from above in the plane (L1), has at least two regions (14, 15), the periods (d) of which differ. Element. 3. The method according to claim 1 or 2, wherein the security element, viewed from above in the plane (L1), has at least two areas (14, 15), the directions of the grids (3, 7) being mutually related. Another, secure factor by 90 degrees. 3. Security element according to claim 1 or 2, as a window element for important documents, in the form of a transparent element. An important document having a security element (S) according to claim 1 or 2, wherein the important document has a window or area for observation in transmission, and this window or area is attached to the security element (S). covered by, important documents.

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