CN111716936B

CN111716936B - Optical anti-counterfeiting element and optical anti-counterfeiting product

Info

Publication number: CN111716936B
Application number: CN201910209112.0A
Authority: CN
Inventors: 张宝利; 胡春华; 王晓利; 朱军
Original assignee: China Banknote Printing and Minting Corp; Zhongchao Special Security Technology Co Ltd
Current assignee: Zhongchao Special Security Technology Co Ltd; China Banknote Printing and Minting Group Co Ltd
Priority date: 2019-03-19
Filing date: 2019-03-19
Publication date: 2021-08-06
Anticipated expiration: 2039-03-19
Also published as: WO2020187287A1; CN111716936A

Abstract

The embodiment of the invention provides an optical anti-counterfeiting element and an optical anti-counterfeiting product, and belongs to the field of optical anti-counterfeiting. The optical security element comprises: a base layer; a color functional layer on the base layer; a first micro-relief structure covering at least a part of a first area of the color functional layer, the first area being a partial area of the color functional layer; and a plating layer covering only the surface of the first micro-relief structure; the first micro-relief structure is defined such that when a light beam irradiates the first micro-relief structure at an incident angle, light of a wavelength or wavelength range in the light beam interferes constructively in a direction of reflected light, and the color functional layer and the first micro-relief structure are capable of providing optical features having different color characteristics. The method has the advantages of high reliability, easy identification and difficult counterfeiting.

Description

Optical anti-counterfeiting element and optical anti-counterfeiting product

Technical Field

The invention relates to the field of optical anti-counterfeiting, in particular to an optical anti-counterfeiting element and an optical anti-counterfeiting product.

Background

In order to prevent counterfeiting by means of scanning, copying and the like, diffraction light variable image (such as a hologram, a dynamic diffraction pattern and the like) anti-counterfeiting technology is widely adopted in various high-security or high-value-added printed matters such as bank notes, identification cards, product packages and the like, and a very good effect is achieved. For example, the large-denomination Euro paper money adopts diffraction light-variable image hot stamping marks, the small denomination Euro paper money adopts diffraction light-variable image hot stamping wide strips, and the Chinese 2005 edition RMB adopts diffraction light-variable image windowing safety lines except for the one denomination. The Visa, MasterCard and China Unionpay credit cards adopt diffraction light-variable image thermoprinting marks, and important certificates such as China identity cards, driving licenses, passports and the like also adopt diffraction light-variable image anti-counterfeiting technology. To date, most security cards such as bank notes, credit cards, passports and the like in the world adopt diffraction light variable image anti-counterfeiting technology.

The diffraction light variable image for anti-counterfeiting is a grating with a relief structure, when illumination light (such as natural light) is irradiated on the surface of the grating, diffraction effect is generated, and 1-order (or-1-order) diffraction light forms a reproduced image, so that the mass anti-counterfeiting characteristics such as striking dynamic effect, three-dimensional effect, color change and the like are realized.

With the increasing popularization of the diffraction light variable image technology, the technology is widely applied to common commodities and packages, such as packages of cigarettes, wine, medicines and the like, and even labels of textiles and toys. The anti-counterfeiting technology is easier to realize, so that the anti-counterfeiting performance of the technology is greatly reduced. Therefore, a new and more reliable anti-counterfeiting technology is needed.

Chinese patent application CN104249597A discloses an optical security element comprising microstructures defined such that when a light beam is irradiated at an incident angle, light of a wavelength or wavelength range in the light beam interferes constructively in the direction of transmitted light or reflected light. The optical anti-counterfeiting element is different from the diffraction light variable image, avoids the interference of diffraction light with rainbow characteristics of uncertain colors, and utilizes light with stable color which is formed by an interference mechanism and easy to describe, so that the area covered by the micro-relief structure in the optical anti-counterfeiting element has higher effect of easy identification and difficult counterfeiting when forming a specific pattern, but the optical anti-counterfeiting element is used as urgent demand for increasingly improving the high anti-counterfeiting technical level of products such as bank notes, identity documents and the like, and the optical anti-counterfeiting element needs to further improve uniqueness and the attribute of easy identification and difficult counterfeiting.

In order to prevent counterfeit of various high-security or high-value-added printed matters such as banknotes, certificates, product packages and the like, a multi-layer structure plating technology is widely adopted. The multilayer structure plating technology can present various color characteristics or different colors under different observation angles, and cannot be simulated or copied by electronic equipment such as a camera, a scanner, a printer and the like, so that the multilayer structure plating technology has high anti-counterfeiting capability. However, the requirement of the anti-counterfeiting field cannot be well met by adopting the multi-layer plating technology.

The combination of the multi-layer structure plating layer and the anti-counterfeiting element disclosed in the chinese patent application CN104249597A can bring rich and unique optical anti-counterfeiting features, however, since both of them selectively interfere constructively with the wavelength of incident light, the combination will produce contradiction, so that the color provided by the multi-layer structure plating layer or the color feature provided by the anti-counterfeiting element disclosed in the chinese patent application CN104249597A will be obviously weakened, which is not beneficial to the identification of the anti-counterfeiting features, and therefore, a new type of optical anti-counterfeiting element needs to be further developed.

Disclosure of Invention

The embodiment of the invention aims to provide an optical anti-counterfeiting element which is more reliable, easy to identify and difficult to forge and an optical anti-counterfeiting product.

In order to achieve the above object, the present invention provides an optical security element comprising: a base layer; a color functional layer on the base layer; a first micro-relief structure covering at least a part of a first area of the color functional layer, the first area being a partial area of the color functional layer; and a plating layer covering only the surface of the first micro-relief structure; the first micro-relief structure is defined such that when a light beam illuminates the first micro-relief structure at an angle of incidence, light of a wavelength or wavelength range in the light beam interferes constructively in the direction of reflected light.

Correspondingly, the invention also provides an optical anti-counterfeiting product comprising the optical anti-counterfeiting element.

Through the technical scheme, the optical anti-counterfeiting characteristic which is obviously different from a diffraction light variation image anti-counterfeiting technology and a single multilayer structure coating can be realized, the sample containing the characteristic provides different observation angles in the first micro-relief structure area to respectively present two color characteristics which are complementary colors, and the other areas provide the color characteristics of the color functional layer. The clear contrast and contrast can be realized by respectively defining the structural parameters of the first micro-relief structure and the color functional layer, and a unique optical anti-counterfeiting element with the characteristics of easy identification and difficult counterfeiting is formed.

Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:

fig. 1a to 1b show an optical security element according to an embodiment of the invention;

fig. 1c to 1d are schematic sectional shapes of relief units of a micro-relief structure;

fig. 2a to 2b show an optical security element according to an embodiment of the invention;

fig. 3a to 3c show an optical security element according to an embodiment of the invention;

fig. 4a to 4f are schematic diagrams illustrating a manufacturing process of an optical security element according to an embodiment of the present invention;

fig. 5a to 5c show schematic top views of an optical security element according to an embodiment of the invention;

fig. 6a to 6b show schematic top views of an optical security element according to an embodiment of the invention;

FIG. 7 shows a schematic cross-sectional view of an optical security element according to an embodiment of the invention; and fig. 8 shows a schematic cross-sectional view of a security element according to an embodiment of the invention.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.

The "characteristic dimension" referred to in the present invention means a dimension of a contour surrounding a convex or concave portion in any direction by dividing a surface of the micro-relief structure by an average of the lowest and highest surface heights thereof.

The "micro-relief structure" refers to an uneven microstructure formed on a two-dimensional surface as needed.

The 'relief unit' is the average value of the lowest and highest points of the surface height of the micro-relief structure, and is a single convex or concave part formed by dividing the surface, and the characteristic dimension of the relief unit is in the micrometer scale. The "depth d of the micro-relief structure" refers to the height difference between the highest and lowest surface heights in the micro-relief structure.

Fig. 1a shows an optical security element 1 according to an embodiment of the invention. Fig. 1a is a schematic cross-sectional view of a security element 1 according to an embodiment of the present invention, the optical security element 1 comprises a base layer 101, a color functional layer 103 on the base layer 101, a micro-embossed structure 102 on the color functional layer 103 and covering at least a part of an area B of the color functional layer 103, and a plating layer 104 only covering the micro-embossed structure 102. The region B is a partial region of the color functional layer 103, and the region of the color functional layer 103 other than the region B is referred to as a region a. The micro-relief structure 102 is defined such that when a light beam irradiates the micro-relief structure 102 at an incident angle, light of a wavelength or wavelength range in the light beam interferes constructively in the direction of reflected light, and the color functional layer 103 and the micro-relief structure 102 can provide optical features having different color features.

Preferably, the color functional layer 103 may be an interference type multilayer film structure, which forms a fabry-perot resonator having a selective function on incident white light, so that the emergent light only includes certain wave bands, thereby showing a specific color; when the incident angle changes, the relative optical path changes, the interference wave band also changes, and the color presented to the observer in the direction of the emergent angle also changes, thereby forming the light variable effect. The interference type multilayer film structure may include any one of the following structures: (1) composed of an absorption layer and a low-refractive-index mediumA plating layer formed by sequentially stacking a layer and a reflective layer, wherein the reflective layer is in contact with the surface of the base layer 101; (2) a coating formed by sequentially stacking a high-refractive-index dielectric layer, a low-refractive-index dielectric layer and a high-refractive-index dielectric layer; and (3) a coating layer formed by sequentially stacking an absorption layer, a high refractive index medium layer, and a reflection layer, wherein the reflection layer is in contact with the surface of the base layer 101. Preferably, the material of the reflective layer may be a material having high reflectivity, such as gold, silver, copper, aluminum, zinc, nickel, titanium, and the like, and alloys thereof; the material of the absorption layer is required to have a refractive index close to the absorption coefficient, and may be, for example, a semimetal material (e.g., silicon, germanium, etc.), or a metal material or an alloy thereof (e.g., chromium, copper, nickel, nichrome, etc.); the refractive index of the low-refractive-index dielectric layer is less than 1.7, and can be magnesium fluoride, silicon dioxide, cryolite and the like; the high refractive index dielectric layer has a refractive index of 1.7 or more, and may be ZnS, TiN, TiO₂、TiO、Ti₂O₃、Ti₃O₅、Ta₂O₅、Nb₂O₅、CeO₂、Bi₂O₃、Cr₂O₃、Fe₂O₃、HfO₂ZnO, etc. The interference type multilayer film structure can be obtained by physical or chemical vapor deposition methods such as thermal evaporation, electron beam evaporation, magnetron sputtering and the like.

Preferably, the color function layer 103 may be an absorption structure, wherein the absorption structure may be one or a combination of several of ink, pigment, and dye. It is further preferable to use, for example, OVI optically variable inks manufactured by Sicpa corporation.

Preferably, the color function layer 103 may also be a liquid crystal optically variable layer. Typically, the color functional layer 103 may be implemented, for example, using cholesteric liquid crystal materials, so that color characteristics such as green-to-blue, red-to-green, etc., which are generated as a function of the viewing angle, may be implemented. The liquid crystal optical variable layer can be produced in batch by coating, printing and the like.

Preferably, the color function layer 103 may also be a multi-layer co-extruded optically variable film. And a multilayer coextruded optically variable film may be directly used as the base layer 101.

For ease of describing micro-relief structure 102, an x-y-z spatial coordinate system is defined. As shown in fig. 1b, the micro-relief structures 102 may lie in the xoy plane (or a plane parallel to the xoy plane), and the feature size in the x-axis, y-axis direction may be, for example, 0.3 μm to 6 μm, preferably 0.6 μm to 3 μm, and the pattern of the micro-relief structures 102 (i.e., the relief elements of the micro-relief structures) may be randomly or pseudo-randomly distributed. The raised portions of the microrelief structure 102 can comprise 20% to 80%, preferably 35% to 65%, of the total area of the microrelief structure 102. As shown in fig. 1a, the cross-sectional shape of the relief units of the micro-relief structure 102 may be sinusoidal. As shown in fig. 1c, the cross-sectional shape of the relief unit of the micro-relief structure 102 may be a zigzag shape. As shown in fig. 1d, the cross-sectional shape of the relief unit of the micro-relief structure 102 may be rectangular. It will be appreciated by those skilled in the art that the cross-sectional shape of the relief cells of the micro-relief structure 102 may also be other shapes. The depth d of the micro-relief structure 102 may satisfy the condition that when natural light (white light) irradiates the micro-relief structure 102 at the incident angle α, light having a wavelength λ or a wavelength range interferes and grows in the reflected light direction after passing through the micro-relief structure 102, so that the optical security element 1 appears a first color when viewed in the reflected light direction and a second color when viewed in the scattered light direction (as shown in fig. 1 a) when the optical security element 1 is viewed.

The depth d of the microrelief structure 102 is typically between 100nm and 5 μm, preferably between 200nm and 3 μm. The depth d may be determined by the following method.

(ii) shows the complex-amplitude transmittance τ of the micro-relief structure 102_g，τ_gAs a function of depth d, design wavelength λ, the groove type of the micro-relief structure 102, the material refractive index profile n, and position (x, y); ② complex amplitude transmittance tau_gPerforming Fourier transform; finding out the maximum condition of the reflected light (namely zero-order diffraction light) with the wavelength of lambda; the depth d of the micro-relief structure 102 is calculated on the basis of the condition that the reflected light is maximum.

For example, when the design wavelength λ is 600nm, the refractive index n of the material of the micro-relief structure 102 is 1.5, the cross-sectional shape of the micro-relief structure 102 is sinusoidal, and the external medium is air, and d is 1528.8nm, the forgery prevention element 1 appears red in the reflected light direction and blue-green in the scattered light direction. If d is 2668.8nm, the light having a wavelength of 410.8nm also satisfies the condition of constructive interference of reflected light, and therefore the security element 1 appears magenta in the direction of reflected light and green in the direction of scattered light.

The micro relief structure can be made into a master plate by laser etching, electron beam etching, ion etching and the like, and then copied onto the base layer by processes of electroforming, mould pressing, UV copying and the like. A more common process is to coat an imaging layer on the surface of the substrate and replicate the micro-relief structure on the imaging layer in order to improve the replication quality and replication efficiency of the micro-relief structure.

The material constituting the micro-relief structure may be, for example, ZnS, ZnO, Ta₂O₅、SnO₂、Nb₂O₅、HfO₂、In₂O₃、CeO₂、Dy₂O₃、Bi₂O₃、MgF₂、Al₂O₃、AlF₃、CaF₂、SiO₂、SrF₂、YbF₃、NaF、Na₃AlF₆PET, PVC, PE, polyester glue, or polyurethane glue, and the like.

The base layer can be transparent material such as PET, PVC, PE and the like, and can also be a carrier such as paper, printed matter, package and the like. The substrate may also be a carrier during processing and be peeled off at a later application.

In this embodiment, the plating layer 104 may be, for example, a metal reflective layer. The material preferably constituting the metallic reflective layer may comprise, for example, gold, silver, copper, iron, tin, nickel, chromium, aluminum, zinc, titanium and alloys thereof, and may have a thickness of greater than 5nm, preferably greater than 10 nm. The coating 104 can be obtained by physical or chemical vapor deposition methods such as thermal evaporation, electron beam evaporation, magnetron sputtering, and the like. The plating layer 104 functions to provide a reflective function to the micro-relief structure 102, thereby enhancing the efficiency of reflecting light. When the plating layer 104 has a color characteristic, the effect is a superposition of the color characteristic and the color characteristic provided by the micro-relief structure 102.

The optical security feature of the optical security element 1 shown in fig. 1a to 1B in which the regions a and B are located is described below.

In general, the optical characteristics of the portion of the optical security element 1 in which the region a is located depend on the choice of the colour functional layer 103 in the above preferred embodiments, and there are two possibilities, one to provide a single, constant colour at each viewing angle and the other to provide a characteristic in which the colour changes with changing viewing angles. Regardless of the choice, it is assumed that the security features of the optical security element are provided only by the color functional layer 103, and the security effect is single and not prominent, while the security features provided by the portion of the region B complement this strongly: firstly, the part where the area B is located can provide color change and complementary color characteristics in the reflected light direction and the scattered light direction by itself, which are not possessed by the color function layer 103 of the part where the area a is located; secondly, the color characteristics of the part where the region B is located depend on the morphology of the micro-relief structure 102, the refractive index n, the parameter distribution of the micro-relief structure on the xoy plane and the structure depth d, so that the color or color change characteristics provided by the part where the region B is located and the part where the region A is located can be different through calculating and designing parameters, and even strong contrast and contrast are formed, so that the optical anti-counterfeiting element has stronger uniqueness, and the purposes of easier public identification and difficult counterfeiting by counterfeiters are achieved.

In practical applications, the following preferred schemes may be adopted to configure the portion of the area a and the portion of the area B:

(1) first configuration

Color functional layer: the color functional layer 103 is selected to be red nano ink.

Little relief structure: the refractive index n of the material of the micro-relief structure 102 is 1.50, the cross-sectional shape of the micro-relief structure 102 is sinusoidal, and the external medium is air, and d is 1528.8nm, so that the area of the micro-relief structure 102 in the security element 1 appears red in the direction of reflected light and blue-green in the direction of scattered light.

Optical anti-counterfeiting characteristics: when observed in the direction of reflected light, the part of the area A and the part of the area B both tend to be red; when viewed in the direction of scattered light, the region A was red, and the region B was blue-green.

(2) Second configuration

Color functional layer: the color functional layer 103 is selected to be a green metallic ink.

Little relief structure: the refractive index n of the material of the micro-relief structure 102 is 1.50, the cross-sectional shape of the micro-relief structure 102 is sinusoidal, and the external medium is air, and d is 2668.8nm, so that the region of the micro-relief structure 102 in the security element 1 appears magenta in the direction of reflected light and green in the direction of scattered light.

Optical anti-counterfeiting characteristics: when the light is observed in the direction of reflected light, the part of the area A is in the green color with metal texture, and the part of the area B is in the red color; when viewed in the direction of scattered light, the portion of the region a and the portion of the region B both turn green.

(3) Third configuration

Color functional layer: the color functional layer 103 was selected to be an OVI ink manufactured by Sicpa corporation that was green when viewed along the z-axis and blue when viewed at an angle of approximately 45 ° to the z-axis.

Little relief structure: the refractive index n of the material of the micro-relief structure 102 is 1.48, the cross-sectional shape of the micro-relief structure 102 is rectangular, and the d of the external medium is air, which is 600nm, so that the region of the anti-counterfeiting element 1 where the micro-relief structure 102 is located appears green in the direction of reflected light and magenta in the direction of scattered light.

Optical anti-counterfeiting characteristics: when the reflected light is observed, the part of the area A and the part of the area B both tend to be green; during oblique observation, the portion of the area a becomes green, and the portion of the area B becomes magenta.

(4) Fourth configuration

Color functional layer: the selective color functional layer 103 is an interference type multilayer film structure sequentially containing Al (thickness: 40nm)/SiO2 (thickness: 370nm)/Cr (thickness: 5nm), and the interference type multilayer film with the parameters has the characteristics of golden yellow in front view and green in oblique view.

Optical anti-counterfeiting characteristics: when the light is observed in the direction of reflected light, the part of the area A is golden yellow, and the part of the area B is green; during oblique observation, the portion of the area a becomes green, and the portion of the area B becomes magenta.

(5) Fifth configuration

Color functional layer: the selective color function layer 103 is a cholesteric liquid crystal light-variable film manufactured by Rolic corporation, switzerland, which adopts a red-green characteristic, i.e., a characteristic of being red as viewed from the front and green as viewed obliquely.

Little relief structure: the refractive index n of the material of the micro-relief structure 102 is 1.48, the cross-sectional shape of the micro-relief structure 102 is sinusoidal, and d is 500nm when the external medium is air, so that the area of the anti-counterfeiting element 1 where the micro-relief structure 102 is located appears yellow in the direction of reflected light and blue in the direction of scattered light.

Optical anti-counterfeiting characteristics: when the light is observed in the direction of reflected light, the part of the area A is red, and the part of the area B is yellow; in the oblique observation, the portion of the area a becomes green, and the portion of the area B becomes blue.

(6) Sixth configuration

Color functional layer: the color functional layer 103 is selected to be a multilayer co-extruded optically variable film produced by 3M company, which adopts the green-blue characteristic, i.e., the characteristic of being viewed as green on the front and blue on the oblique.

Optical anti-counterfeiting characteristics: the part where the observation area A is located appears green in the direction of reflected light, and the part where the observation area B is located appears yellow; during oblique observation, the portion of the area a and the portion of the area B both tend to be blue.

The above is an example in which the color functional layer 103 and the micro-relief structure are configured so that the portion where the area a is formed and the portion where the area B is formed have different colors or color change characteristics. It should be noted that, although there is a case where the color of the portion of the area a and the color of the portion of the area B converge at a specific viewing angle, there is still a difference between the absorption spectrum and the reflection spectrum of the two in practical terms, but this does not substantially affect the anti-counterfeiting performance and quality of the optical anti-counterfeiting element 1 of the present invention, and the difference can help attract and help users to identify the pattern of the portion of the area a or the portion of the area B.

Figures 2a and 2b show a reflective optical security element 2 according to an embodiment of the present invention. As shown in the figure, an optical security element 2 is provided, which comprises a base layer 201, a color functional layer 203 on the base layer 201, a micro-embossed structure 202 on the color functional layer 203 and covering at least a part of an area B of the color functional layer 203, and a plating layer 204 only covering the micro-embossed structure 202. The region B is a partial region of the color functional layer 203, and the region of the color functional layer 203 other than the region B is referred to as a region a. The micro-relief structure 202 is defined such that when a light beam irradiates the micro-relief structure 202 at an incident angle, light of a wavelength or wavelength range in the light beam interferes constructively in the direction of reflected light, and the color functional layer 203 and the micro-relief structure 202 can provide optical features having different color features.

For ease of description, an x-y-z spatial coordinate system is defined. As shown in fig. 2a, the micro-relief structures 202 may lie in the xoy plane (or a plane parallel to the xoy plane) and the characteristic dimension in the x-axis direction may be larger than 6 μm, preferably larger than 10 μm, whereby the micro-relief structures 202 have no diffractive effect in this direction, the characteristic dimension of the micro-relief structures 202 in the y-axis direction may be 0.3 μm to 6 μm, preferably 0.6 μm to 3 μm, and the pattern may be randomly or pseudo-randomly distributed. The raised portions of the microrelief structure 202 can comprise 20% to 80%, preferably 35% to 65%, of the total area of the microrelief structure 202. Fig. 2b is a schematic cross-sectional view of a security element according to one embodiment of the invention in the yoz plane (or a plane parallel to the yoz plane). As shown in fig. 2b, the cross-sectional shape of the relief units of the micro-relief structure 202 may be sinusoidal. It will be understood by those skilled in the art that the cross-sectional shape of the relief cells of the micro-relief structure 202 may be saw-tooth, rectangular, or other shapes. The depth d of the micro-relief structure 202 may satisfy the condition that when natural light (white light) irradiates the micro-relief structure 202 at the incident angle α, light having a wavelength λ or a wavelength range interferes and grows in the direction of reflected light after passing through the micro-relief structure 202, so that the optical security element 2 presents the first color in the direction of reflected light. Furthermore, if the light beam is in the yoz plane (or a plane parallel to the yoz plane), the optical security element 2 exhibits a second color in the direction of light scattered in the yoz plane (or a plane parallel to the yoz plane).

The depth d of the micro-relief structures 202 may be 100nm to 5 μm, preferably 200nm to 3 μm. The method for determining the depth d is the same as the above embodiment, and is not described herein again. In addition, other features and advantages of the optical security element 2 are the same as those of the optical security element 1, and are not described herein again.

Figures 3a-3c show a reflective optical security element 3 according to one embodiment of the present invention. As shown in the figure, an optical security element 3 is provided, comprising a base layer 301, a color functional layer 303 on the base layer 301, a micro-relief structure 302 on the color functional layer 303 and covering at least a part of a region B of the color functional layer 303, and a plating layer 304 only covering the microstructure. The region B is a partial region of the color functional layer 303, and the region of the color functional layer 303 other than the region B is referred to as a region a. The micro-relief structure 302 is defined such that when a light beam irradiates the micro-relief structure 302 at an incident angle, light of a wavelength or wavelength range in the light beam interferes constructively in the direction of reflected light, and the color functional layer 303 and the micro-relief structure 302 can provide optical features having different color features.

For ease of description, an x-y-z spatial coordinate system is defined. As shown in fig. 3a, the micro-relief structures 302 may lie in the xoy plane (or a plane parallel to the xoy plane), the feature size in the y-axis direction may be, for example, 0.3 μm to 6 μm, preferably 0.6 μm to 3 μm, the pattern may be randomly or pseudo-randomly distributed, the feature size in the x-axis direction may be, for example, 0.3 μm to 6 μm, preferably 0.6 μm to 3 μm, and the pattern may be, for example, a periodic structure. The raised portions of the micro-relief structure 302 may comprise 20% to 80%, preferably 35% to 65%, of the total area of the micro-relief structure 302. Fig. 3b is a schematic cross-sectional view of a security element 3 according to one embodiment of the invention in the yoz plane (or a plane parallel to the yoz plane), and fig. 3c is a schematic cross-sectional view of a security element 3 according to one embodiment of the invention in the xoz plane (or a plane parallel to the xoz plane). The cross-sectional shape of the relief elements of the micro-relief structure 302 may be sinusoidal, saw tooth, rectangular, or other shapes. The depth d of the micro-relief structure 302 may satisfy the condition that when natural light (white light) irradiates the micro-relief structure 302 at the incident angle α, light with a wavelength λ (or a wavelength range) interferes and grows in the direction of reflected light after passing through the micro-relief structure 302, so that the optical security element 3 observes the first color in the direction of reflected light. Furthermore, if the light beam is in the yoz plane (or a plane parallel to the yoz plane), the optical security element 3 exhibits a second color in the direction of light scattered in the yoz plane (or a plane parallel to the yoz plane); if the light beam is in the xoz plane (or a plane parallel to the xoz plane), the +1 or-1 order diffracted light color of the grating observed in the diffracted light direction of the optical security element 3 varies with the angle of observation.

The depth d of the microrelief structure 302 is typically between 100nm and 5 μm, preferably between 200nm and 3 μm. The method of determining the depth d is the same as in the first embodiment and will not be described here. In addition, other features and advantages of the optical security element 3 are the same as those of the optical security element 1, and are not described herein again.

The process flow of manufacturing the optical security element 1 in the embodiment of fig. 1 is illustrated by fig. 4 a-f.

The method comprises the following steps: as shown in fig. 4a, an optical original plate with a micro-relief structure 102 is manufactured by a laser etching process and electroformed into a metal plate roller, and the micro-relief structure on the metal plate roller is copied into a micro-relief structure 1021 on the lower surface of a base layer 1011 by a molding process, so that the refractive index of the material forming the micro-relief structure 1021 can be in the vicinity of 1.48.

Step two: as shown in fig. 4b, a coating layer 104 is deposited on the surface of the micro-relief structure 1021, and the coating layer may be a 40nm thick metallic aluminum thin film reflective layer.

Step three: as shown in fig. 4c, a protective layer 105 is coated on the surface of the plating layer 104 in the region B by printing, and the protective layer 105 may be made of acrylic material, and its refractive index may be about 1.48.

Step four: as shown in fig. 4d, the structure shown in fig. 4c is immersed in a solution capable of dissolving the plating layer 104 but not dissolving the protective layer 105, for example, a sodium hydroxide aqueous solution with a concentration of about 10% at 40 ℃, until the reflective layer (e.g., a metallic aluminum thin film reflective layer) in the area a not covered by the protective layer 105 is completely dissolved, so that the plating layer 104 forms a hollow pattern.

Step five: as shown in FIG. 4e, the color functional layer 103 is deposited on the upper surface of the base layer 101, and may be, for example, an interference type multilayer film, in which Al (thickness 40nm)/SiO are sequentially deposited₂(thickness of 370nm)/Cr (thickness of 5nm), wherein the aluminum layer is in contact with the base layer 101. The interference multilayer film of this parameter has a feature that it is golden yellow in front view and green in oblique view.

Step six: the structures shown in fig. 4d and 4e are bonded together as shown in fig. 4f by means of a compound glue with bonding properties, which has a refractive index of about 1.48, i.e. which corresponds to the optical properties of 1021 and 105, and thus the compound glue is shown in fig. 4f as 102 together with 1021 and 105.

The above is a preferred exemplary implementation method for producing the optical security element 1 illustrated in fig. 1. The production process of the optical security elements 2 and 3 is similar to that described above and will not be described in detail here.

The disadvantages of the optical security element 1 will be explained with reference to fig. 4a to 4f and 5a to 5c,

fig. 5a corresponds to a top view of the micro-relief structure 1021 with the plating 104 shown in fig. 4b in a plane parallel to or parallel to the xoy plane, wherein different areas C and D are filled with micro-relief structures of different parameters (e.g. parameters of the in-plane arrangement, structure depth, topography, etc. of the micro-relief structure). In practical application, the areas C and D may be further divided into macroscopic or microscopic sub-areas according to design requirements for filling the micro-relief structures with different parameters.

Fig. 5b corresponds to the micro-relief structure 1021 of fig. 4c to which the protective layer 105 is applied, and since the protective layer 105 and the micro-relief structure 1021 are processed separately in respective steps, the projections of the protective layer 105 and the micro-relief structure 1021 on the xoy plane are subject to unavoidable misalignment errors, which are usually more than 0.1 mm according to the existing processing level. When the area covered by the protective layer 105 is the area D covering the micro-relief structure 1021 without error as the initial design target, it actually covers the area B. This causes uncertainty in the remaining areas of the coating 104 and further in the position of the areas a and B in the optical security element 1. Such as the distortion and deformity of the image shown in fig. 5c, which inevitably occurs in practical applications.

Fig. 6a-b show an optimized embodiment for the image distortion and aliasing problems exposed in the embodiment of fig. 5 a-c. Fig. 6a shows a top view of a micro-relief structure 1021 with a coating 104 in a plane parallel to or in the xoy plane, wherein different areas C and D are filled with micro-relief structures of different parameters (e.g. arrangement of the micro-relief structures in plane, structure depth, topography, etc.).

Fig. 6b corresponds to the micro-relief structure 1021 shown in fig. 4c with the protective layer 105 applied. To avoid image distortion and debris, the protective layer 105 has a slightly larger footprint than the target footprint D, with an excess dimension of, for example, at least 0.1 mm, to ensure that the misalignment error is contained. Therefore, the target coverage area D can be completely contained in the actual coverage area B even if the misalignment error exists, thereby ensuring the integrity of the image. However, this optimized structure brings about another problem that the plating layer 104 protected by the protective layer 105 covers a region other than the design target region D, that is, a part of the region C, and image redundancy is caused while solving the image integrity. Also, the redundant plating layer 104 affects the area and integrity of the area a where the color functional layer 103 is located.

In addition, the optical security element 1 described in fig. 5 or 6 cannot realize a hollow pattern of the plating layer 104 with high fineness. This is limited by the printing process of the protective layer 105, and the line fineness in the existing printing process cannot break through the stroke width of 0.01 mm.

In order to solve the problems shown in fig. 5 and 6, the optical anti-counterfeiting element is ensured to have higher uniqueness and easily-identified difficult-to-forge property. The present invention further provides another optical security element, which is described below with reference to fig. 7.

Fig. 7 is a schematic cross-sectional view of a security element 7 according to an embodiment of the present invention, where the optical security element 7 includes a base layer 701, a color functional layer 703 on the base layer 701, a micro-embossed structure 702 on the color functional layer 703 and covering at least a part of a region B of the color functional layer 703, a micro-embossed structure 7022 covering a region a of the color functional layer 703, the region a and the region B not overlapping, and a plating layer 704 covering only the micro-embossed structure 702. Wherein the ratio of the surface area to the apparent area of the micro-relief structure layer 702 is less than the ratio of the surface area to the apparent area of the micro-relief structure 7022. I.e., the area covered by the plating layer 704, is determined by the difference in the ratio of the surface area to the apparent area of the

micro-relief structures

702 and 7022.

Specifically, the

micro relief structures

702 and 7022 are surface relief structures whose height varies with position distribution on the xoy plane, and the surface area per apparent area of the surface relief structures is larger than that of a flat surface, and the surface area is positively correlated with the degree of relief of the surface relief structures. In this context, the term "apparent area" refers to the area of an orthographic projection in a region in a plane parallel to the region, i.e. regardless of the area of the relief structure in the region; the term "surface area" refers to the actual area of the relief structure in said certain area. Obviously, the ratio of the surface area of the certain region to the apparent area thereof is a value not less than 1.

Preferably, the surface microstructure 7022 may be selected within the following ranges: one or more continuous curved structures, one or more rectangular structures, one or more sawtooth prisms, or a splice or combination thereof. Wherein, the continuous curved surface structure can be a spliced structure or a combined structure of one or more of a micro-lens structure, a sine structure, an ellipse structure, a hyperboloid structure, a paraboloid structure and the like. The microlens structure may be a refractive microlens, a diffractive microlens, or a combination or splice thereof, wherein the refractive microlens may include a spherical microlens, an ellipsoidal microlens, a cylindrical microlens, or other geometric optics-based microlens of any geometric shape, and the diffractive microlens includes a harmonic diffractive microlens, a planar diffractive microlens, a fresnel zone plate, and the like. In addition, the specific arrangement of the above structures may be periodic, locally periodic, aperiodic, random, or a combination thereof.

In the embodiment of fig. 7, the characteristic dimension of the micro-relief structure 702 in the x-axis and y-axis directions is 2.8 μm, the refractive index n of the material of the micro-relief structure 702 is 1.48, the cross-sectional shape of the micro-relief structure 702 is sinusoidal, the external medium is air, and d is 500 nm. The micro-relief structure 7022 is a sinusoidal grating with an arrangement period of 350nm and a depth of 300 nm. The optical security element 7 is processed as follows:

the method comprises the following steps: an optical original plate comprising a micro-relief structure 702 and a micro-relief structure 7022 is manufactured by a laser etching process, and is electroformed into a metal plate roller, the micro-relief structure on the metal plate roller is copied into the micro-relief structure 702 and the micro-relief structure 7022 on the lower surface of a base layer by a mould pressing process, and the refractive index of a material forming the micro-relief structure can be about 1.48.

Step two: a plating layer 704 is evaporated on the surface of the micro-relief structure 702, and the plating layer can be a metallic aluminum thin film reflecting layer with the thickness of 50 nm.

Step three: and (3) immersing the structure formed in the second step into a solution capable of dissolving the plating layer 704, for example, a sodium hydroxide aqueous solution with a concentration of about 5% at 40 ℃, until the reaction and dissolution of the plating layer (for example, a metal aluminum thin film reflective layer) on the surface of the micro-relief structure 7022 are completed, so that the plating layer 704 accurately covers the micro-relief structure 702, thereby forming a precise hollow pattern.

Step four: the color functional layer 703 is deposited on the upper surface of the other base layer 701, and may be, for example, an interference type multilayer film, that is, Al (thickness of 40nm)/SiO are sequentially deposited₂(thickness of 370nm)/Cr (thickness of 5nm), wherein the aluminum layer is in contact with the base layer 701.

Step five: and bonding the structures formed in the third step and the fourth step together by using a compound adhesive with bonding performance, wherein the refractive index of the compound adhesive is about 1.48 and is consistent with the optical performance of the

micro-relief structures

702 and 7022.

The steps for producing the optical security element 7 described in fig. 7 are described above. The optical anti-counterfeiting feature of the part of the area a is determined by the micro-embossed structure 7022 and the color functional layer 703, however, the refractive index of the compound glue used in the processing process is the same as that of the micro-embossed structure 7022, so that the micro-embossed structure 7022 does not contribute to the optical anti-counterfeiting feature of the area a, that is, the optical anti-counterfeiting feature of the part of the area a is determined by the color functional layer 703. Meanwhile, the optical anti-counterfeiting characteristic of the part where the area B is located is determined by the micro-relief structure 702 and the plating layer 704 on the surface of the micro-relief structure.

Taking the color function layer 703 as an interference type multilayer film and the plating layer 704 as a metal aluminum thin film reflective layer as an example, the portion of the area a in fig. 7 can provide the feature that the color of the interference type multilayer film changes from golden yellow to green, and the portion of the area B can provide the feature that the color of the area B appears yellow in the direction of reflected light and blue in the direction of scattered light. That is, when viewed in the direction of reflected light, the portion of area a and the portion of area B appear golden and yellow, respectively, while the two areas appear to change to green and blue, respectively, as the viewing angle continues to be tilted. The other features and advantages of the optical security element 7 are the same as those of the optical security element 1 described above and will not be described in detail here.

Fig. 8 is a schematic cross-sectional view of a security element 8 according to another embodiment of the present invention, the optical security element 8 comprising a base layer 801, a color functional layer 803 on the base layer 801, a micro-embossed structure 802 on the color functional layer 803 and covering at least a part of an area B of the color functional layer 803, a micro-embossed structure 8022 covering an area a of the color functional layer 803, the area a and the area B not overlapping, and a plating layer 804 only covering the micro-embossed structure 802. Wherein, the relief height of the micro-relief structure layer 802 is smaller than that of the micro-relief structure 8022. I.e., the area covered by the plating layer 804, is determined by the difference in the relief heights of the

micro-relief structures

802 and 8022.

Preferably, the surface microstructure 8022 can be selected within the following ranges: one or more continuous curved structures, one or more rectangular structures, one or more sawtooth prisms, or a splice or combination thereof. Wherein, the continuous curved surface structure can be a spliced structure or a combined structure of one or more of a micro-lens structure, a sine structure, an ellipse structure, a hyperboloid structure, a paraboloid structure and the like. The microlens structure may be a refractive microlens, a diffractive microlens, or a combination or splice thereof, wherein the refractive microlens may include a spherical microlens, an ellipsoidal microlens, a cylindrical microlens, or other geometric optics-based microlens of any geometric shape, and the diffractive microlens includes a harmonic diffractive microlens, a planar diffractive microlens, a fresnel zone plate, and the like. In addition, the specific arrangement of the above structures may be periodic, locally periodic, aperiodic, random, or a combination thereof.

In the embodiment of fig. 8, the characteristic dimension of the micro-relief structure 802 in the x-axis and y-axis directions is 4.0 μm, the refractive index n of the material of the micro-relief structure 802 is 1.48, the cross-sectional shape of the micro-relief structure 802 is rectangular, the external medium is air, and d is 600 nm. The micro relief structure 8022 is a one-dimensional array of cylindrical mirrors, the array period is 20 μm, the bottom interval of adjacent cylindrical mirrors is 1.5 μm, and the height of the cylindrical mirrors is 3.5 μm. The optical security element 8 is processed as follows:

the method comprises the following steps: an optical original plate containing the micro-relief structure 802 and the micro-relief structure 8022 is manufactured by a laser etching process, and is electroformed into a metal plate roller, the micro-relief structure on the metal plate roller is copied into the micro-relief structure 802 and the micro-relief structure 8022 on the lower surface of a base layer by a mould pressing process, and the refractive index of a material forming the micro-relief structure is about 1.48.

Step two: and (3) evaporating a coating 804 on the surface of the micro-relief structure 802, wherein the coating can be a metal aluminum thin film reflecting layer with the thickness of 50 nm.

Step three: a protective layer, preferably a polymer, especially a polymer containing cellulose, is applied to the surface of the plating layer 804. For example, the polymer forming the protective layer may comprise a mixture of nitrocellulose (preferably a nitroalcohol) with resins added to improve the resistance of the protective layer to subsequent treatments (such as gum arabic and rosin), and the like. In a preferred embodiment, the main resin is a resin material of polyester, which comprises the following components: (1) from about 20 wt% to about 30 wt% of a primary resin, said resin being a polyester having a hydroxyl number greater than 120, said polyester being a branched hydroxyl polyester having a viscosity of 25000 ± 5000 mpa.s; (2) from about 10 wt% to about 25 wt% of nitrocellulose, which is a low nitrogen nitrocellulose having a nitrogen content < 12.4%; (3) from about 5 wt% to about 25 wt% of a crosslinker, said crosslinker being an isocyanate oligomer; and (4) about 20 wt% to about 60 wt% of a solvent. The protective layer has a refractive index of about 1.48.

Step four: and (3) immersing the structure formed in the third step into a solution which can dissolve the plating layer 804 but can not dissolve the protective layer, wherein the solution can be a sodium hydroxide aqueous solution with the concentration of about 10% at 40 ℃, and the plating layer (for example, a metal aluminum thin film reflective layer) on the surface of the micro-relief structure 8022 is reacted and dissolved until the plating layer 804 accurately covers the micro-relief structure 802, so that a precise hollow pattern is formed. The specific reaction process is as follows: the protective layer does not completely cover the plating 804 on the micro-relief structure 8022, so that the environment reacts with the exposed plating 804 on the micro-relief structure 8022 to achieve hollowing of the area. Meanwhile, the next stage of the reaction process is that the environment permeates into the plating layer 804 covered by the protective layers on both sides with the plating layer 804 exposed in the micro relief structure 8022 as the center, so as to further react with the plating layer 804 covered by the protective layers on the micro relief structure 8022 to be semitransparent, and even to be completely transparent along with the continuous reaction process. The plating layer 804 on the micro-relief structure 802 is completely covered by the protective layer during the entire reaction process, and thus remains without participating in the reaction.

Step five: the color functional layer 803 is deposited on the upper surface of the base layer 801, and may be, for example, an interference multilayer film, in which Al (40 nm in thickness)/SiO are sequentially deposited₂(thickness 270nm)/Cr (thickness 5nm), wherein the aluminum layer is in contact with the base layer 801.

Step six: and (3) bonding the structures formed in the fourth step and the fifth step together by using composite glue with bonding performance, wherein the refractive index of the composite glue is about 1.48 and is consistent with the optical performance of the protective layer and the

micro-relief structures

802 and 8022.

The steps for producing the optical security element 8 described in fig. 8 are described above. The optical anti-counterfeiting feature of the area a is determined by the micro-embossed structure 8022 and the color functional layer 803, however, the refractive indexes of the composite glue, the protective layer and the micro-embossed structure 8022 used in the processing process are the same, so that the micro-embossed structure 8022 does not contribute to the optical anti-counterfeiting feature of the area a, that is, the optical anti-counterfeiting feature of the area a is determined by the color functional layer 803. Meanwhile, the optical anti-counterfeiting characteristic of the part where the area B is located is determined by the micro-relief structure 802 and the plating layer 804 on the surface of the micro-relief structure.

Taking the color function layer 803 as an interference type multilayer film and the plating layer 804 as a metal aluminum thin film reflective layer as an example, in fig. 8, the portion of the area a can provide the characteristic that the red color of the interference type multilayer film changes into green color, and the portion of the area B can provide the characteristic that the red color appears green in the direction of reflected light and magenta color appears in the direction of scattered light. That is, the portion where the area a is located and the portion where the area B is located respectively appear red and green when viewed in the direction of reflected light, and the two areas respectively appear to change to green and to magenta when the viewing angle is further tilted. The other features and advantages of the optical security element 8 are the same as those of the optical security element 1 described above and will not be described in detail here.

The security element of the present invention may incorporate a variety of other types of relief structures such as common diffractive optically variable images, blazed grating structures, and the like. Further in the area B in fig. 1a, for example, a rainbow or achromatic holographic image is added while the micro-relief structures 102 are present, which may take the form of sinusoidal, rectangular and/or sawtooth microstructures with diffractive or non-diffractive optical features, providing different color or image features than the micro-relief structures 102, which do not necessarily satisfy the interference constructive condition. The holographic image may be formed on the master simultaneously with the microrelief structures 102 to reduce process complexity, or may be generated in steps in subsequent processing, such as by two-pass stamping.

The anti-counterfeiting element can also be of a hot stamping type, namely, a stripping layer is coated on a base material, then the anti-counterfeiting element is manufactured on the stripping layer, and the base material is stripped off after the anti-counterfeiting element is transferred to a bearing object by a hot stamping process.

The anti-counterfeiting element further comprises other functional layers, such as a magnetic information layer, a fluorescent anti-counterfeiting characteristic layer, a printing pattern layer, an adhesive layer and the like.

The anti-counterfeiting element can be applied to transferring or sticking marks, hot stamping wide strips, sticking strips, safety lines and other forms to bearing objects. These carriers can be high-safety products such as bank notes, securities, credit cards, passports and the like, and can also be high-value-added commodities.

Correspondingly, the embodiment of the invention also provides an optical anti-counterfeiting product which comprises the optical anti-counterfeiting element.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and the simple modifications all belong to the protection scope of the embodiments of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention do not describe every possible combination.

In addition, any combination of various different implementation manners of the embodiments of the present invention is also possible, and the embodiments of the present invention should be considered as disclosed in the embodiments of the present invention as long as the combination does not depart from the spirit of the embodiments of the present invention.

Claims

1. An optical security element, comprising:

a base layer;

a color functional layer on the base layer;

a first micro-relief structure covering at least a part of a first area of the color functional layer, the first area being a partial area of the color functional layer; and

a plating layer covering only the surface of the first micro-relief structure;

the first micro-relief structure is defined such that when a light beam irradiates the first micro-relief structure at an incident angle, light of a wavelength or a wavelength range in the light beam interferes and grows in a reflected light direction so that an area where the first micro-relief structure is located presents different colors in the reflected light direction and a scattered light direction, wherein the color functional layer and the first micro-relief structure are capable of providing optical characteristics with different color characteristics, respectively.

2. The optical security element according to claim 1, wherein the optical security element further comprises:

and a second micro-relief structure covering a second region of the color functional layer other than the first region, wherein a ratio of a surface area to an apparent area of the first micro-relief structure is smaller than a ratio of a surface area to an apparent area of the second micro-relief structure.

3. The optical security element according to claim 1, wherein the optical security element further comprises:

and the second micro-relief structure covers a second area of the color functional layer except the first area, and the undulation height of the first micro-relief structure is smaller than that of the second micro-relief structure.

4. An optical security element according to any one of claims 1 to 3, wherein the depth of at least a portion of the first micro-relief structures satisfies the condition:

when the light beam irradiates at least one part of the first micro-embossed structure at an incident angle, after the light beam passes through at least one part of the micro-embossed structure, light with a wavelength or wavelength range in the light beam is interfered and lengthened in a reflection light direction, so that at least one part of the optical anti-counterfeiting element presents a first color in the reflection light direction.

5. The optical security element according to claim 4, wherein the pattern of at least a part of the first micro-relief structures is at least one or any combination of the following:

the relief units of the first micro-relief structure are distributed randomly or pseudo-randomly;

the relief units of the first micro-relief structure are randomly or pseudo-randomly distributed in one direction; and

the relief units of the first micro-relief structure are periodically distributed in a first direction and randomly or pseudo-randomly distributed in a second direction.

6. An optical security element according to claim 5, wherein, in the case that the pattern of the at least one portion of the first micro-relief structures is a random or pseudo-random distribution of relief units of the at least one portion of the first micro-relief structures, the feature size of the at least one portion of the first micro-relief structures is between 0.3 μm and 6 μm, the depth of the at least one portion of the micro-relief structures further satisfying the following condition:

when the light beam irradiates at least one part of the first micro-relief structure at an incident angle, at least one part of the optical anti-counterfeiting element presents a second color in a scattering light direction.

7. The optical security element according to claim 6, wherein at least a portion of the first micro-relief structures have a characteristic dimension of 0.6 μm to 3 μm.

8. An optical security element according to claim 5, wherein, in case the relief units of at least a part of the first micro-relief structures are patterned in a random or pseudo-random distribution in the second direction, the characteristic dimension of the at least a part of the first micro-relief structures in the second direction is 0.3 μm to 6 μm and the characteristic dimension in the first direction is greater than 6 μm, the depth of the at least a part of the first micro-relief structures further satisfying the following condition:

when the light beam irradiates at least one part of the first micro-relief structure at an incident angle, if the light beam is in a first plane which is perpendicular to the plane of the base layer and contains the second direction, at least one part of the optical anti-counterfeiting element presents a second color in the direction of light scattered in the first plane.

9. The optical security element according to claim 8, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the second direction of 0.6 μ ι η to 3 μ ι η.

10. An optical security element according to claim 8, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the first direction of greater than 10 μm.

11. An optical security element according to claim 5, wherein in the case that the relief units of at least one portion of the first micro-relief structures are patterned in such a way that they are periodically distributed in a first direction and randomly or pseudo-randomly distributed in a second direction, the characteristic dimension of at least one portion of the first micro-relief structures in the first direction is 0.3 μm to 6 μm and the characteristic dimension in the second direction is 0.3 μm to 6 μm, the depth of at least one portion of the micro-relief structures further satisfying the following condition:

when the light beam irradiates at least one part of the first micro-relief structure at an incident angle, if the light beam is in a first plane which is perpendicular to the plane of the base layer and contains the second direction, at least one part of the optical anti-counterfeiting element presents a second color in the direction of light scattered in the first plane; if the light beam is in a second plane which is perpendicular to the plane of the base layer and contains the first direction, at least one part of the optical anti-counterfeiting element presents the color of +1 order or-1 order diffraction light along the direction of diffraction light in the second plane, wherein the angle of the light beam changes along with the change of the angle.

12. An optical security element according to claim 11, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the first direction of from 0.6 μ ι η to 3 μ ι η.

13. An optical security element according to claim 11, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the second direction of from 0.6 μ ι η to 3 μ ι η.

14. The optical security element according to any one of claims 1 to 3, wherein the color functional layer is one or a combination of inks, pigments and dyes.

15. An optical security element according to any one of claims 1 to 3, wherein the colour functional layer is a liquid crystal optically variable layer.

16. An optical security element according to any one of claims 1 to 3, wherein the colour functional layer is a multilayer co-extruded optically variable film.

17. An optical security element according to any one of claims 1 to 3, wherein the colour functional layer is an interference multilayer film structure forming a Fabry-Perot resonant cavity.

18. The optical security element of claim 1 wherein the coating is a metallic reflective layer.

19. The optical security element according to claim 1, wherein the relief units of the first micro-relief structure have a cross-section of any one of: sinusoidal, saw tooth, or rectangular.

20. The optical security element according to claim 1, wherein the optical security element further comprises:

a holographic image overlaid on other portions of the first area except for the first micro-relief structure.

21. An optical security product comprising an optical security element according to any one of claims 1 to 20.