WO2013177829A1

WO2013177829A1 - Optical anti-counterfeit element and preparation method thereof

Info

Publication number: WO2013177829A1
Application number: PCT/CN2012/076801
Authority: WO
Inventors: 张巍巍; 王晓利; 孙凯
Original assignee: 中钞特种防伪科技有限公司; 中国印钞造币总公司
Priority date: 2012-05-30
Filing date: 2012-06-12
Publication date: 2013-12-05
Also published as: CN103448411B; CN103448411A

Abstract

An optical anti-counterfeit element comprises a base material (3). The base material (3) comprises a first surface (31) and a second surface (32). A part of areas on the first surface (31) are of a sub-wavelength relief structure, and a part of the areas are of a flat surface structure. A first dielectric layer (101), a second dielectric layer (102), and a third dielectric layer (103) are successively stacked on the sub-wavelength relief structure and the flat surface structure. From a specific observing angle, the color of areas of the sub-wavelength relief structure is the same as that of areas of the flat surface structure, and from another observing angle, the color of the areas of the sub-wavelength relief structure is different from that of the areas of the flat surface structure. Also provided is a method for preparing an optical anti-counterfeit element. The optical anti-counterfeit element overcomes the defects that the process is complex and a coating thickness is difficult to be accurately controlled for two coating structures to implement color matching in the prior art.

Description

Optical security element and preparation method thereof

Technical field

The invention relates to the field of optical anti-counterfeiting, in particular to an optical anti-counterfeiting component and a preparation method thereof. Background technique

Because the optically altered coatings can be rendered in different colors at different viewing angles, are easy to describe, are easily identifiable to the public, and cannot be mimicked or reproduced using electronic devices such as cameras, scanners, printers, etc., the optically altered coatings have high anti-counterfeiting capabilities and It is widely used for public security of high security securities such as banknotes.

In order to improve the anti-counterfeiting ability of the optically-deformed layer, the prior art mostly combines two kinds of optically-deformed layers to realize two kinds of light-changing effects. For example, U.S. Patent No. 5,766,738, U.S. Patent No. 6,114, 018, issued to U.S. Pat. Specifically, the interference light-changing security element includes two light-varying regions, wherein one light-densing region includes a first light-varying structure, and the other light-variable region includes a second light-varying structure, and two regions at a certain viewing angle There are matching colors, and the two areas have different colors at other viewing angles.

In order to ensure a good color matching effect, it is necessary to precisely control the plating thickness of the two regions. However, in actual production, it is often difficult to accurately control the plating thickness of the above-mentioned interference light-changing security element to achieve the color matching requirement, thereby causing a significant difference in color at the matching angle of the design, which affects the anti-counterfeiting effect. In addition, the two coatings cannot be obtained in a single evaporation process, so that it is necessary to add precise processes such as printing protective glue, demetallization, and secondary vapor deposition, which increases process complexity and cost. SUMMARY OF THE INVENTION The present invention is directed to the above-described drawbacks existing in the prior art, and provides an optical security element capable of overcoming the above-mentioned drawbacks and a method of fabricating the same.

The present invention provides an optical security element comprising a substrate, the substrate comprising a first surface and a second surface, a partial region on the first surface being a sub-wavelength microrelief structure, and a partial region being flat a surface structure, the sub-wavelength microrelief structure and the flat surface structure are sequentially laminated with a first dielectric layer, a second dielectric layer and a third dielectric layer, and the sub-wavelength microrelief structure region is at a specific viewing angle The color of the flat surface structure region is the same, and the color of the sub-wavelength microrelief structure region and the flat surface structure region are different at other viewing angles.

The invention also provides a method of preparing an optical security element, the method comprising:

Providing a substrate, the substrate comprising a first surface and a second surface;

Forming a sub-wavelength microrelief structure on the first surface such that a portion of the first surface is a sub-wavelength microrelief structure and a portion of the region is a flat surface structure;

Forming a first dielectric layer simultaneously on the sub-wavelength microrelief structure region and the flat surface structure region;

Forming a second dielectric layer simultaneously on the first dielectric layer;

A third dielectric layer is simultaneously formed on the second dielectric layer.

Since a subwavelength microrelief structure and a flat surface structure are formed on a first surface of a substrate of the optical security element according to the present invention, and the first medium is sequentially laminated on the subwavelength microrelief structure and the flat surface structure The layer, the second dielectric layer and the third dielectric layer have a selective effect on the incident white light due to the plating structure composed of the three dielectric layers, so that when the incident angle changes, the corresponding optical path changes, and the interference band also A change occurs such that the color of the sub-wavelength microrelief structure region and the flat surface structure region changes as the viewing angle changes. When suitably designed by a first dielectric layer, a second dielectric layer, and a third dielectric layer, The subwavelength microrelief structure parameters can be achieved at a specific viewing angle, the subwavelength microrelief structure region and the flat surface structure region have the same color, and at other viewing angles, the subwavelength microrelief structure region and the flat surface structure There are significant differences in the colors of the areas. Here, "the same color" means that the perceived color of the human eye is the same or similar, and the reflection spectra of the two are not exactly the same.

The traditional process of achieving the same color in the two regions generally undergoes the process of "printing evaporation and demetallization evaporation", and in the above process, the precise positioning control of the printing and the precise control of the thickness of the coating in the two evaporation processes are large. Difficulty. The structure and preparation method of the optical security element according to the present invention can solve the above problems well. The subwavelength microrelief structure region and the flat surface structure region involved in the present invention can be obtained by laser direct etching or electron beam direct etching and other micromachining methods, and the laser direct etching or electron direct etching technology has extremely high precision. It is able to reach the nanometer level so that precise registration of these two regions can be achieved. After the parameters of the sub-wavelength microrelief structure are determined, the first dielectric layer, the second dielectric layer and the third dielectric layer are simultaneously vapor-deposited on the sub-wavelength microrelief structure region and the flat surface structure region, thereby realizing the two regions in a specific Observe the optical effects of the same color and different colors at other viewing angles. Therefore, it is possible to achieve a good anti-counterfeiting effect by designing an appropriate plating thickness without separately controlling the thickness of the plating in the two regions. In addition, since the three dielectric layers in the optical security element according to the present invention can be formed in one vapor deposition process, the process complexity is also simplified. DRAWINGS

1 is a cross-sectional view of an optical security element in accordance with an embodiment of the present invention;

Figure 2 is a diagram showing changes in color coordinates of different regions of the optical security element according to the present invention as a function of observation angle;

Figure 3 is another variation of the color coordinates of different regions of the optical security element according to the present invention as a function of viewing angle;

4 is a cross-sectional view of an optical security element having a hollow structure in accordance with an embodiment of the present invention. FIG. 5 is still another schematic diagram of an optical security element according to an embodiment of the present invention; FIG.

6 is a flow chart of preparing an optical security element in accordance with an embodiment of the present invention. detailed description

The optical security element according to the present invention and a method of manufacturing the same will be described in detail below with reference to the accompanying drawings. As shown in FIG. 1, an optical security element according to an embodiment of the present invention includes a substrate 3 including a first surface 31 and a second surface 32, and a partial region on the first surface 31 is a sub-region The wavelength microrelief structure and a partial region are flat surface structures. The first dielectric layer 101, the second dielectric layer 102, and the third dielectric layer 103 are sequentially laminated on the subwavelength microrelief structure and the flat surface structure region, thereby respectively forming the interference structure 10 located in the subwavelength microrelief structure region and An interference structure 20 located in a flat surface structure region. Here, the coordinate z in Fig. 1 indicates the vertical direction, and the coordinate X indicates the horizontal direction.

The three-layer dielectric layer structure composed of the first dielectric layer 101, the second dielectric layer 102 and the third dielectric layer 103 has a Fabry-Perot cavity structure, which has a selective effect on incident white light, and the emitted light only contains a certain The light of these bands forms a specific color; however, when the incident angle changes, the corresponding optical path changes, and the interference band changes, causing the color of the display to change accordingly, thereby exhibiting a light-changing effect.

When the three-layer dielectric layer optically variable structure according to the present invention is combined with the sub-wavelength microrelief structure, interference and diffraction work together to obtain other wavelength bands, which is related to the incident angle of the light, and also obtains a light-changing effect. . Thus, two kinds of light-changing effects are obtained by one vapor-deposited optically variable structure. When the characteristic period of the sub-wavelength microrelief structure and the dielectric layer parameters are properly selected, the same color asynchronous phenomenon can be realized, that is, the reflection/transmission spectrum of the sub-wavelength microrelief region and the planar region without the subwavelength microrelief are different under one observation angle. But the colors are the same or similar; when the observation angle changes, the two light-changing effects are different, and each undergoes different light-changing processes, resulting in a difference. This will be described in detail below in conjunction with specific parameters. The Maxwell equation can be used to calculate the intensity and phase changes of the electric and magnetic field vectors through the layers and interfaces, and the boundary conditions are used to obtain the phase difference and intensity variation parameters of the light in each dielectric layer and each interface. Parameter design of the three-layer dielectric layer plating structure in the optical security element of the invention. In the specific calculation, each interface of the dielectric layer can be considered as a virtual equivalent interface. By calculating the combined admittance and the characteristic matrix of the film layer, all the information of the light propagating in the coating layer is obtained, especially the relationship of the intensity with the wavelength, that is, the plating layer. The reflection spectrum. Finally, the color coordinates of the plating in the CIE color space are obtained by integrating the reflection spectrum with the tristimulus value function.

The sub-wavelength microrelief structure according to the present invention has a plurality of parameters, such as a period, a groove depth, a groove shape, etc., when combining a sub-wavelength microrelief structure with a three-layer dielectric layer structure, it is also necessary to consider three layers of dielectric layer plating. Parameters such as thickness of each layer and refractive index of the material. In the specific design, vector diffraction theory such as rigorous coupling wave method (RCW) and time domain finite difference method (FDTD) is used to solve Maxwell's equations in combination with boundary conditions. The theory of vector diffraction is discussed in detail in "Micro-Optics and Systems" edited by Yang Guoguang, published by Zhejiang University Press. When designing the structural parameters of the optical security element according to the present invention, it is possible to determine the design parameters of various aspects, such as the groove depth of the relief structure, based on the specific conditions of the problem and the optical feature design algorithm and programming calculation. The groove shape, the duty ratio, and the feature size in the X direction or/and the y direction, the number of layers of the plating layer according to the present invention, and the thickness of each layer, the metal material, the dielectric material, the substrate material, and the like. Then according to the optical vector theory, the program is programmed according to the boundary conditions of the sub-wavelength multi-layer structure plating structure: Calculate according to the initial structural parameters; optimize the structural parameters according to the calculation results; then calculate and optimize according to the optimized parameters until satisfactory results are achieved .

In a preferred embodiment according to the present invention, the first dielectric layer 101 and the third dielectric layer 103 have a refractive index greater than or equal to 1.7, and the material thereof is selected from, for example, ZnS, TiN, Ti0 ₂ , TiO, Ti ₂ 0 ₃ , Ti. Any material or combination of ₃ 0 ₅ , Ta ₂ 0 ₅ , Nb ₂ 0 ₅ , Ce0 ₂ , Bi ₂ 0 ₃ , Cr ₂ 0 ₃ , Fe ₂ 0 _{3 ,} etc., and further, the first dielectric layer 101 and the third medium The layer 103 may have a thickness of 10 nm to 300 nm, preferably 50 nm to 200 nm. The second dielectric layer 102 has a refractive index of less than 1.7, the material of which is selected from, for example, Any material or combination of Si0 ₂ , MgF ₂ , Na ₃ A10 ₆ , A1 ₂ 0 ₃ , and the second dielectric layer 102 may have a thickness of 50 nm to 100 nm, preferably 100 nm to 500 nm.

In a preferred embodiment according to the present invention, the sub-wavelength microrelief structure may be a one-dimensional grating and the direction is variable. Moreover, the period of the sub-wavelength microrelief structure is also variable, wherein the period of the sub-wavelength microrelief structure in the X direction and/or the y direction may be 50 nm to 500 nm, preferably 200 nm to 400 nm. Further, the groove depth of the sub-wavelength microrelief structure is also variable, wherein the groove depth is in the range of lOnm to 500 nm, preferably in the range of 50 nm to 200 nm. The groove shape of the sub-wavelength microrelief structure is also variable, for example, the groove shape may be at least one of a sinusoidal shape, a rectangular shape, and a zigzag shape.

Some specific structural parameters are given below to further describe the optical security element in accordance with the present invention.

For example, the sub-wavelength microrelief structure is a one-dimensional sinusoidal grating having a characteristic period of 340 nm and a trench depth of 180 nm _{; the} first dielectric layer 101 is TiN, the thickness is 50 nm, and the second dielectric layer 102 is A1 ₂ 0 ₃ , and the thickness is At 180 nm, the third dielectric layer 103 is Ti0 ₂ and has a thickness of 70 nm. Fig. 2 shows the variation of the color coordinate of the interference structure 10 and the interference structure 20 of the optical security element according to the present invention with the observation angle in this case. It can be seen that when the first viewing angle is 0 °, the color coordinate of the interference structure 10 is (-3.2, 67.8), which is yellow; the color coordinate of the interference structure 20 is (2.4, 78.1), which also appears yellow, both The color difference ΔΕ is 13.2, and the two colors are the same for human vision. When the second viewing angle is 40°, the color coordinate of the interference structure 10 is (1.9, -47.9), which is blue; the color coordinate of the interference structure 20 is (-24.4, 63.9), which is green, and the colors of the two are significant. The difference. It can be seen that when the first observation angle is 0°, that is, when the two regions of the sub-wavelength microrelief structure region and the flat surface structure are vertically observed, their colors are basically the same; as the observation angle increases, the color difference between the two regions becomes larger. , became significantly different in two shades. In this way, through the appropriate design on the plate making, the sub-wavelength micro-relief structure region and the flat surface region covered with the sub-wavelength grating can form characters and patterns of a specific meaning, and the characters and patterns are hidden in the background when the front view is observed, and the oblique observation is performed. Text, pattern appearing optics Anti-counterfeiting effect. The CIELAB chromaticity space is used when evaluating the color of the sub-wavelength microrelief structure region and the flat surface structure region. CIELAB (CIELab) Chromaticity space is the uniform color space recommended by the International Commission on Illumination in 1976. In 1987, GB792-87 released in China adopted LAB space as the national standard. In the current color design and reproduction industries, CIELAB space has been widely used in color correction, calculation and DTP systems. Where +a represents red, -a represents green, +b represents yellow, -b represents blue, and L represents brightness. Table 1 gives the L, a, b parameters of the interference structure 10 and the interference structure 20 in this example at 0 ° and 40 ° observation angles, respectively giving the difference ΔΕ between the two colors, where ΔΕ uses the following formula obtain:

AE=((LL ^, †+(aa ^, †+(bb ^, ) ² ) ^m Table 1 CIELab coordinates of the interference structure 10 and the interference structure 20 at different viewing angles

Preferably, different color matching conditions can be obtained by adjusting parameters such as the groove shape, the period, the groove depth and the like of the sub-wavelength microrelief structure and the materials, thicknesses and the like of the respective dielectric layers. For example, the sub-wavelength microrelief structure is a one-dimensional sinusoidal grating having a characteristic period of 280 nm and a groove depth of 150 nm; the first dielectric layer 101 is Ti0 ₂ , the thickness is 55 nm, and the second dielectric layer 102 is A1 ₂ 0 ₃ , thickness 270 nm, the third dielectric layer 103 is Ti0 ₂ and has a thickness of 85 nm. When the first viewing angle is 0°, both the interference structure 10 and the interference structure 20 are green; when the second viewing angle is 20°, the interference structure 10 Presenting purple, the interference structure 20 exhibits a cyan color, and the colors of the two have significant differences. Or the sub-wavelength microrelief structure is a one-dimensional sinusoidal grating having a characteristic period of 250 nm and a groove depth of 80 nm _{; the} first dielectric layer 101 is Ti0 ₂ , the thickness is 100 nm, the second dielectric layer 102 is A1 ₂ 0 ₃ , and the thickness is 210 nm, the third dielectric layer 103 is Ti0 ₂ , and the thickness is 100 nm, then the first observation angle When the degree is 0°, both the interference structure 10 and the interference structure 20 appear blue; when the second viewing angle is 20°, the interference structure 10 appears purple, and the interference structure 20 appears orange, and the colors of the two have significant differences.

3 shows the chromaticity coordinates of the interference structure 10 and the interference structure 20 of the optical security element according to the present invention as a function of the viewing angle, wherein the sub-wavelength microrelief structure is a one-dimensional sinusoidal grating with a characteristic period of 340 m. The trench depth is 130 nm; the first dielectric layer 101 is Ti0 ₂ , the thickness is 100 nm, the second dielectric layer 102 is Na ₃ AlF ₆ , the thickness is 250 nm, and the third dielectric layer 103 is ZnS and has a thickness of 40 nm. It can be seen that when the first viewing angle is 0°, the color coordinate of the interference structure 10 is (3.7, 46.0), which is yellow; the color coordinate of the interference structure 20 is (-44.2, -19.1), which is blue-green, two The color difference ΔΕ is 82.2, and the color has a significant difference. When the second viewing angle is 20°, the color coordinate of the interference structure 10 is (-32.3, -36.6), which is blue; the color coordinate of the interference structure 20 is (-9.2, -38.8), which also appears blue, two The color difference ΔΕ is 23.4, the colors are similar, and the human eye cannot distinguish the obvious difference. When the viewing angle continues to increase to 40°, the color difference ΔΕ increases to 110.2, and the color difference between the two becomes larger again. It can be seen that when the first observation angle is 0°, that is, when the two regions are observed vertically, the color difference between the two regions is large, which is two different color tones; as the observation angle increases, the colors of the two regions all change to blue. When it reaches 20°, both colors are blue, forming the same color; when the viewing angle continues to increase, the colors of the two changes again, and there is a significant difference. Table 2 gives the L, a, b parameters of the interference structure 10 and the interference structure 20 at different viewing angles in this case. Therefore, through proper design, the process of image and text from observation to hiding to visualization can be realized.

Table 2 Interference structure 10 and interference structure 20, a, b parameters under different viewing angles

Interference structure 10 interference structure 20

Observation angle ΔΕ

L a b L, a' b'

0. 69.6 3.7 46.0 54.8 -44.2 -19.1 82.2 20. 41.3 -32.3 -36.6 44.8 -9.2 -38.8 23.4

40. 20.2 44.4 -67.7 60.2 24.0 33.0 110.2 Of course, in order to constitute a pattern of characters, logos, etc., the optical security element according to an embodiment of the present invention may further have a hollow structure 5. As shown in FIG. 4, a first region 1 and a second region 2 are provided on the first surface 31 of the substrate 3 of the optical security element, wherein the first region 1 is a sub-wavelength microrelief structure covered with an interference structure 10; The second region 2 is a flat surface structure covered with the interference structure 20, wherein the interference structure 10 and the interference structure 20 can adopt various structures as described above. An absorbing layer 4 (for example, black ink or other color absorbing paint) is selectively applied or printed on the second surface 32 of the substrate 3, thereby forming a hollowed out region 5, wherein the hollowed out region 5 can be appropriately selected by Form words, logos, patterns. Thus, when viewed from the first surface 31, the interference structures 10 and 20 over the coated absorbing layer 4 have only a reflection spectrum, presenting a bright, easily recognizable color, and the interference structures 10 and 20 above the hollowed out region 5 are in a transparent state. In particular, when it is attached to a carrier such as paper, the color of the carrier such as paper is mainly exhibited. In particular, when the observation is made under the observation angle that the interference structure 10 and the interference structure 20 exhibit the same color, a graphic effect can be added through the hollowed out area 5, the visual capturing power of the security element is improved, and the anti-counterfeiting effect is enhanced. Thus, when the reflection observation mode is adopted, the absorption layer 4 absorbs the transmitted light, enhances the recognition of the reflected light by the human eye, and enhances the visual effect of the optical security element according to the present invention.

Figure 5 shows a further embodiment of an optical security element according to the invention. The first surface 31 of the substrate 3 is covered with at least two sub-wavelength gratings whose directions are perpendicular to each other, and the sub-wavelength grating is covered with the multi-layer dielectric layer plating structure as described above, thereby forming the interference structure 10 and interfering. The structure 20 and the interference structure 30, wherein the interference structure 10 and the interference structure 30 are respectively covered on two mutually perpendicular sub-wavelength gratings, and the interference structure 20 is located on a flat surface. By appropriately adjusting the parameters of the sub-wavelength grating and the parameters of the plating structure, the following effects can be obtained: In the vertical observation, the interference structure 10, the interference structure 20, and the interference structure 30 have the same color; when the angle is obliquely observed, the interference structure 10 is maintained in color. The color does not change, the color of the interference structure 20 and the interference structure 30 changes and the color obtained after the change is different; at this time, the optical security element is rotated by 90°, the interference structure 10 and the interference structure 30 undergo color exchange, and the color of the interference structure 20 remains. Keep the angle down There is no color. This feature can be used to realize the optical characteristics of the image when hidden, tilted and rotated during vertical observation. As an example, for example, the sub-wavelength microrelief structure is a one-dimensional sinusoidal grating having a characteristic period of 340 nm and a groove depth of 130 nm, and having two sub-wavelength grating regions perpendicular to each other on the first surface 31 of the substrate 3, thereby Forming an interference structure 10, an interference structure 20, and an interference structure 30, wherein the interference structure 10 and the interference structure 30 are respectively covered on two mutually perpendicular sub-wavelength gratings, the interference structure 20 is located on a flat surface, and the sub-wavelength grating is covered There is a multilayer dielectric layer plating structure as described above, wherein the first dielectric layer 101 is TiN, the thickness is 50 nm, the second dielectric layer 102 is A1 ₂ 0 ₃ , the thickness is 180 nm, and the third dielectric layer 103 is Ti0 ₂ , thickness It is 70 nm. Then, when the first viewing angle is 0°, the colors of the interference structure 10, the interference structure 20, and the interference structure 30 are both yellow; when the optical security element is tilted so that the second viewing angle is 40°, the color of the interference structure 10 becomes Blue, the interference structure 20 turns green, the color of the interference structure 30 remains yellow; when the optical security element is rotated 90° at the oblique angle, the color of the interference structure 20 is still green, and the color of the interference structure 10 turns blue The color of the interference structure 30 changes to yellow, and the color of the interference structure 10 and the interference structure 30 is interchanged.

It should be understood that FIG. 4 and FIG. 5 are only examples. In fact, according to actual needs, various parameters and arrangement manners of the sub-wavelength microrelief structure may be optimized, combined, and covered with corresponding dielectric layers. And combined with hollowing out to form a high security anti-counterfeiting component.

Preferably, the substrate 3 described above may be a transparent or non-transparent, colored or colorless film. For example, it may be polyethylene terephthalate, polyvinyl chloride, polyethylene, polycarbonate, polypropylene, metal, glass, paper, etc., and may have a thickness of 5 to 500 μm, preferably 10 to 100 μ. Micron.

In one embodiment according to the present invention, when the light-transmitting observation mode is employed, the substrate 3 may be subjected to no treatment or a transparent/translucent coating to transmit light.

In addition, it should be understood that color matching herein refers to a similarity in color to a certain degree, and does not mean that the colors must be identical.

Further, the optical security element according to the present invention can be manufactured in the form of a window security thread, a sticker, a label, and the like. One or both sides of the optical security element for ease of application on the product It is coated with an adhesive to adhere to the carrier by a process such as hot stamping or pasting. Moreover, the optical security element according to the present invention can be applied to high security or high value-added products such as banknotes, cards, and high-end goods.

As shown in FIG. 6, the present invention also provides a method of preparing an optical security element, the method comprising:

561. Providing a substrate, the substrate comprising a first surface and a second surface;

562. Form a sub-wavelength microrelief structure on the first surface, such that a partial region on the first surface is the sub-wavelength microrelief structure, and a partial region is a flat surface structure;

Wherein, the sub-wavelength microrelief structure can be formed by laser double beam interference exposure, laser direct exposure or electron beam direct engraving, or batch copying by ultraviolet casting, molding, nanoimprinting. For example, the sub-wavelength microrelief structure can be made into a master by a holographic interferometry, a laser direct lithography technique, an electron beam etching technique, etc., and can be made into a working plate by an electroforming process, and then transferred to a base by a molding process such as molding and UV replication. On the material.

563. Form a first dielectric layer simultaneously on the subwavelength microrelief structure region and the flat surface structure region;

564, simultaneously forming a second dielectric layer on the first dielectric layer;

565. Form a third dielectric layer on the second dielectric layer.

The first dielectric layer, the second dielectric layer and the third dielectric layer may be formed by physical vapor deposition or chemical vapor deposition such as thermal evaporation, electron beam evaporation, magnetron sputtering or the like.

In summary, the dielectric layer structure according to the present invention can be formed by a single evaporation process, and the micro-nano processing process such as laser direct etching or electron beam direct etching can control the position of the sub-wavelength microrelief structure on the micrometer or even nanometer level. And the feature size, therefore, the optical security element according to the present invention not only improves the anti-counterfeiting performance, but also reduces the process difficulty and saves cost.

It should be understood that the optical security element according to the present invention has been described above with reference to the preferred embodiments, but those skilled in the art will appreciate that various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention. modify.

Claims

Rights request

What is claimed is: 1. An optical security element comprising a substrate (3), the substrate (3) comprising a first surface (31) and a second surface (32), the first surface (31) The partial region is a sub-wavelength microrelief structure, and the partial region is a flat surface structure, and the first dielectric layer, the second dielectric layer and the third dielectric layer are sequentially laminated on the sub-wavelength microrelief structure and the flat surface structure. The color of the sub-wavelength microrelief structure region and the flat surface structure region are the same at a particular viewing angle, and the color of the sub-wavelength microrelief structure region and the flat surface structure region are different at other viewing angles.

2. The optical security element according to claim 1, wherein the specific viewing angle is 0 degrees or other values greater than 0 degrees.

The optical security element according to claim 1, wherein the first dielectric layer and the third dielectric layer have a refractive index greater than or equal to 1.7.

The optical security element according to claim 1, wherein the first dielectric layer and the third dielectric layer have a thickness of 10 nm to 300 nm.

The optical security element according to claim 1, wherein the first dielectric layer and the third dielectric layer have a thickness of 50 nm to 200 nm.

The optical security element according to any one of claims 3 to 5, wherein materials of the first dielectric layer and the third dielectric layer are selected from the group consisting of ZnS, TiN, Ti0 ₂ , TiO, Ti ₂ Any material of 0 ₃ , Ti ₃ 0 ₅ , Ta ₂ 0 ₅ , Nb ₂ 0 ₅ , Ce0 ₂ , Bi ₂ 0 ₃ , Cr ₂ 0 ₃ , Fe ₂ 0 ₃ or a combination thereof. The optical security element according to claim 1, wherein the second dielectric layer has a refractive index of less than 1.

7.

The optical security element according to claim 1, wherein the second dielectric layer has a thickness of 50 nm to 1000 nm.

The optical security element according to claim 1, wherein the second dielectric layer has a thickness of from 100 nm to 500 nm.

The optical security element according to any one of claims 7 to 9, wherein the material of the second dielectric layer is selected from any one of SiO ₂ , MgF ₂ , Na ₃ A10 ₆ , and A1 ₂ 0 ₃ Material or a combination thereof.

The optical security element according to claim 1, wherein the sub-wavelength microrelief structure is a one-dimensional grating and the direction is variable.

The optical security element according to claim 1, wherein at least one of a period, a groove depth, and a groove shape of the sub-wavelength microrelief structure is variable.

The optical security element according to claim 12, wherein the period of the sub-wavelength microrelief structure in the X direction and/or the y direction is 50 nm to 500 nm.

The optical security element according to claim 12, wherein the period of the sub-wavelength microrelief structure in the X direction and/or the y direction is 200 nm to 400 nm.

The optical security element according to claim 12, wherein the groove depth is at lOnm Up to 500nm

The optical security element according to claim 12, wherein the groove depth is in the range of 50 nm to 200 nm.

The optical security element according to claim 12, wherein the groove shape is at least one of a sinusoidal shape, a rectangular shape, and a zigzag shape.

The optical security element according to claim 1, wherein the substrate (3) is a transparent or non-transparent, colored or colorless film.

The optical security element according to claim 1, wherein the first surface (31) of the substrate (3) is covered with a transparent/translucent coating to transmit light.

The optical security element according to claim 1, wherein a part or all of the second surface (32) of the substrate (3) is covered with an absorbing layer.

21. A method of making an optical security element, the method comprising:

Providing a substrate (3) comprising a first surface (31) and a second surface (32); forming a sub-wavelength microrelief structure on the first surface (31) such that the a partial region on a surface (31) is the sub-wavelength microrelief structure, and a partial region is a flat surface structure; a first dielectric layer is simultaneously formed on the sub-wavelength microrelief structure region and the flat surface structure region;

Forming a second dielectric layer simultaneously on the first dielectric layer;

22. The method according to claim 21, wherein the sub-wavelength microrelief structure is formed by laser double beam interference exposure, laser direct exposure or electron beam direct etching, or by ultraviolet casting, molding, nanoimprinting The way to bulk copy.

23. The method according to claim 21, wherein the first dielectric layer, the second dielectric layer, and the third dielectric layer are formed by physical vapor deposition or chemical vapor deposition.