CN111716937B

CN111716937B - Optical anti-counterfeiting element and optical anti-counterfeiting product

Info

Publication number: CN111716937B
Application number: CN201910209852.4A
Authority: CN
Inventors: 张宝利; 蹇钰; 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: 2021-10-26
Anticipated expiration: 2039-03-19
Also published as: CN111716937A; WO2020187286A1

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 surface of the base layer including a first region; a first micro-relief structure at least covering the first area and at least being translucent; a plating layer conformally covering at least a portion of the first micro-relief structure; and an at least partially cladding and at least translucent first coating; wherein the refractive index of the first micro-relief structure is different from the refractive index of the first coating, and the depth of at least one part of the first micro-relief structure satisfies the following condition: when a 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 first micro-embossed structure, light with a wavelength or wavelength range in the light beam is subjected to interference and constructive in a reflected light direction, so that at least one part of the optical anti-counterfeiting element presents a first color in the reflected light direction. 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.

Currently, anti-counterfeiting windows, which are a kind of hot-handable product form, appear in high-end anti-counterfeiting product platforms represented by banknotes internationally, for example, a new canadian series released since 2011, a new euro series released since 2013, a new zealand series released since 2015, and a new australian series released since 2016 all adopt anti-counterfeiting windows, which have profound influence and are widely accepted.

The anti-counterfeiting window is characterized in that two sides can be observed, but the inventor of the application finds that the current window product generally has the following two problems in the process of implementing the prior art:

(1) if a double-layer structure is adopted, for example, the anti-counterfeiting window of the new Euro series is formed by processing the images on the front side and the back side twice, under the condition, the position error is difficult to avoid between the images processed twice, namely, the correlation degree between the images on the front side and the back side is reduced, and meanwhile, the processing technology is too complex, the product batch production is difficult to realize, and the cost is higher;

(2) if a single-layer structure is adopted, for example, the anti-counterfeiting windows of the new edition addendum, the new Zealand element and the Australian element series are formed by processing the images of the front surface and the back surface at one time, in this case, the images of the front surface and the back surface are completely the same, have no uniqueness and have no outstanding anti-counterfeiting function.

Disclosure of Invention

The object of the present invention is to provide an optical security element and an optical security product, which are used to solve or at least partially solve the above technical problems.

In order to achieve the above object, the present invention provides an optical security element comprising: a base layer, a surface of the base layer comprising a first region; a first micro-relief structure at least covering the first area and at least being translucent; a plating layer conformally covering at least a portion of the first micro-relief structure; and an at least partially translucent first coating at least partially covering the plating; wherein a refractive index of the first micro-relief structure is different from a refractive index of the first coating layer, and a depth of at least a portion of the first micro-relief structure satisfies the following condition: when a 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 first micro-embossed structure, light with a wavelength or wavelength range in the light beam is subjected to interference and constructive in a reflected light direction, so that at least one part of the optical anti-counterfeiting element presents a first color in the reflected light direction.

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

The optical anti-counterfeiting element at least has the following advantages: (1) the images of the front surface and the back surface of the anti-counterfeiting element are formed in one step when the micro-relief structure is processed, so that the images of the front surface and the back surface are correlated with each other no matter the positions or the contents of the images are correlated, and the processing process flow is simplified; (2) the color characteristics of the front and back images are different, thereby ensuring the visual uniqueness of the anti-counterfeiting element.

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. 1e shows a schematic representation of the images provided on the front and back sides of the optical security element shown in FIG. 1 a;

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

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

fig. 4a to 4c show an optical security element according to a further embodiment of the invention;

FIG. 4d shows a schematic top view of the front and back sides of the optical security element shown in FIG. 4 c;

fig. 5 shows a cross-sectional view of an optical security element according to yet another embodiment of the present invention; and

fig. 6 shows a cross-sectional view of an optical security element according to a further 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.

The present invention provides an optical security element comprising: a base layer, a surface of the base layer comprising a first region; a first micro-relief structure at least covering the first area and at least being translucent; a plating layer conformally covering at least a portion of the first micro-relief structure; and an at least partially translucent first coating at least partially covering the plating; wherein a refractive index of the first micro-relief structure is different from a refractive index of the first coating layer, and a depth of at least a portion of the first micro-relief structure satisfies the following condition: when a 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 first micro-embossed structure, light with a wavelength or wavelength range in the light beam is subjected to interference and constructive in a reflected light direction, so that at least one part of the optical anti-counterfeiting element presents a first color in the reflected light direction.

The substrate surface may be an upper surface or a lower surface of a substrate, and the first region may be the entirety of the substrate surface or may be a partial region of the substrate surface. If the first area is a partial area of the surface of the base layer, other types of micro-relief structures may be covered on other areas of the surface of the base layer except the first area. The optical security element provided by the present invention will be described schematically with reference to fig. 1a to 6.

Fig. 1a to 1b show an optical security element 1 according to an embodiment of the invention, which is illustrated by way of example in which the first region of the substrate surface is the entire substrate surface. As shown in fig. 1, the optical security element 1 may include: a base layer 101; a micro-relief structure 102 located on the base layer 101 and at least partially covering the base layer, and a plating layer 104 at least partially covering the surface of the micro-relief structure 102; a coating 103 at least partially covering the plating 104, the plating 104 conformally covering the micro-relief structure 102, the micro-relief structure 102 being at least translucent to the coating 103, and the micro-relief structure 102 having a different refractive index than the coating 103. The depth of at least a portion of the micro-relief structure 102 satisfies the following condition: when a light beam irradiates at least a part of the micro-relief structure 102 at an incident angle, after the light beam passes through at least a part of the micro-relief structure 102, light of a wavelength or wavelength range in the light beam interferes and grows in the direction of reflected light, whereby at least a part of the optical security element 1 exhibits a first color in the direction of reflected light.

By the technical scheme, the anti-counterfeiting product which is obviously different from the diffraction light variation image can be realized. The sample containing the feature provides different color features determined by the micro-relief structures 102, the plating layer 104, and the coating layer 103 on the front side (positive z-axis coordinate) and the back side (negative z-axis coordinate), respectively, but with content correlated images, and the difference in color features between the front and back sides is determined by the difference in refractive index between the micro-relief structures 102 and the coating layer 103.

The base layer 101 may be a transparent material such as PET, PVC, and PE, or may be a carrier such as paper, printed matter, and packaging. The substrate 101 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 plating layer 104 may also be an interference type multilayer film structure. 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.

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 and y-axis directions 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 micro-relief structure 102, the material refractive index profile n of coatings 1031 and 1032 overlying the surface of plating layer 104, 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 micro-relief structure 102 is 1.5, the cross-sectional shape is sinusoidal, and the external medium is air, and d is 2668.8nm, the light with the wavelength of 410.8nm satisfies the condition of interference phase-lengthening of reflected light, so that the forgery-preventing element 1 appears magenta in the reflected light direction of the reverse side (negative z-axis direction), and appears green as the complement thereof in the scattered light direction, and the interference phase-lengthening element of the front side (positive z-axis direction) is shifted by the refractive index n of the coating layer 103 being 1.63, and appears green in the reflected light direction, and appears magenta as the complement thereof in the scattered light direction.

The difference in color characteristics of the front side (positive z-axis) and the back side (negative z-axis) of the optical security element 1 is determined by the difference in refractive index between the micro-relief structures 102 and the coating 103.

The micro-relief structure 102 may be mastered by laser etching, electron beam etching, ion etching, etc., and then replicated onto the substrate by electroforming, embossing, UV replication, etc. 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.

By the technical scheme, the anti-counterfeiting product which is obviously different from the diffraction light variation image can be realized. The sample containing the optical security element provides images with different color characteristics, determined by the micro-relief structures 102, the plating layer 104 and the coating layer 103, on the front side (positive z-axis coordinate) and the back side (negative z-axis coordinate), respectively, but with content correlated, and the difference in color characteristics between the front and back sides is determined by the difference in refractive index between the micro-relief structures 102 and the coating layer 103.

The advantages of the optical security element 1 according to the invention will be explained in more detail below:

the optical anti-counterfeiting element is not only easy to identify and difficult to forge, but also has feasibility of low-cost mass and industrial production. In the security element 1, since the micro-relief structure 102 is finished in one process, the image content provided by the front side and the back side is the same, as shown in fig. 1e, the image of the front side (front) of the optical security element is the same as the image of the back side (back). However, since the depth d of the front and back micro-relief structures 102 is the same and the refractive index of the micro-relief structures 102 is different from that of the coating layer 103, the interference phase condition of the reflected light is changed, and the complementary color of the scattered light as the reflected light is also changed accordingly. In summary, the front and back image contents are related, but the color characteristics are different.

For example, when d is 1528.8nm, the security element 1 appears red in the direction of reflected light and blue-green in the direction of scattered light. According to the method of 2013, a window in a new Euro series needs to process another image on the other side of the window to realize the difference of the anti-counterfeiting characteristics of the two sides, however, the manufacturing method increases the processing times and increases the cost on one hand, and on the other hand, due to the existence of alignment processing errors among different procedures, the anti-counterfeiting characteristics of the two sides cannot be satisfied to have enough relevance. The scheme of the micro-embossed structures 102 and the coating 103 with different refractive indexes adopted in the optical anti-counterfeiting element 1 effectively solves the problems, so that the front and back sides of the optical anti-counterfeiting element can present different color characteristics under the condition of the same depth d of the micro-embossed structures.

In industrial production, it is possible to obtain coatings with different refractive indexes, but the refractive index of a common polymer material coating is around 1.50, and the fluctuation range is ± 0.02, so that the modulation range generated for the depth d of the micro-relief structure 102 is 0.04 × d, and the modulation for the wavelength range in which the interference of reflected light is long is relatively limited, and it is difficult to satisfy the purpose of color feature contrast on both sides.

In order to realize that the front side and the back side of the optical anti-counterfeiting element 1 in the invention present obvious color contrast visible to human eyes, the invention further provides specific configurations of the micro-relief structure 102 and the coating 103 with refractive index difference:

preferably, the main resin of the micro-relief structure 102 and the coating layer 103 may be doped with silicon oxide, and adjusting the doping ratio of the silicon oxide can adjust the refractive index of the micro-relief structure 102 and the coating layer 103 to, for example, between 1.45 and 1.58;

preferably, the main resin of the micro-relief structure 102 and the coating layer 103 may be doped with physical holes, the physical holes are wrapped with air, and adjusting the doping ratio of the physical holes in the main resin can adjust the refractive index of the micro-relief structure 102 and the coating layer 103 to be, for example, 1.40 to 1.46;

preferably, the main resin of the micro-relief structure 102 and the coating layer 103 may be doped with fluoride having a low refractive index (e.g., less than 1.70), and adjusting the doping ratio of the fluoride in the main resin can adjust the refractive index of the micro-relief structure 102 and the coating layer 103 to, for example, 1.30 to 1.40;

preferably, the main resin of the micro-relief structure 102 and the coating layer 103 itself may have a high refractive index of, for example, 1.70, and then the refractive index of the micro-relief structure 102 and the coating layer 103 mixed with a curing agent or the like may be adjusted within a range of, for example, 1.50 to 1.60;

preferably, the main resin of the micro-relief structure 102 and the coating layer 103 may be doped with a high refractive index (e.g., higher than 1.70) oxide, such as zirconia, and the refractive index of the micro-relief structure 102 and the coating layer 103 can be adjusted to be 1.60 or more by adjusting the doping ratio.

The refractive indices of the micro-relief structure 102 and the coating layer 103 may be obtained by measurement with an abbe refractometer or an ellipsometer, and adjustment of the resin composition is performed according to the result.

The coating 103 may be applied to the plating layer 104 by printing. It should be understood that the thickness of the coating 103 only needs to be sufficient to fill the voids with depth d of the micro-embossed structures in the corresponding regions, and in addition, the excessive thickness of the coating will not affect the color characteristics provided by the front surface of the optical anti-counterfeiting element, so that the thickness of the coating 103 can be selected to be controlled precisely not to be larger than the depth d in the actual processing process to save the cost.

In order to obtain a large difference in color characteristics between the front and back surfaces of the optical security element, the difference in refractive index between the micro-embossed structures 102 and the coating 103 is preferably not less than 0.04, and more preferably not less than 0.1.

Fig. 2a and 2b show an optical security element 2 according to an embodiment of the invention, which is illustrated by way of example in which the first region of the substrate surface is the entire substrate surface. As shown, the optical security element 2 may comprise: a base layer 201; a plating layer 204 located on the base layer 201 and at least partially covering the base layer micro-relief structure 202 and at least partially covering the surface of the micro-relief structure 202; a coating 203 at least partially covering the plating 204, the plating 204 conformally covering the micro-relief structure 202, the micro-relief structure 202 being at least translucent and having a different refractive index than the coating 203. The depth of at least a portion of micro-relief structure 202 satisfies the following condition: when a light beam irradiates at least a part of the micro-relief structure 202 at an incident angle, after the light beam passes through at least a part of the micro-relief structure 202, light of a wavelength or wavelength range in the light beam interferes and grows in the direction of reflected light, whereby at least a part of the optical security element 2 exhibits a first color in the direction of reflected light.

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 may have a characteristic dimension in the x-axis direction of more than 6 μm, preferably more 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 randomOr pseudo-randomly distributed. The raised portions of the micro-relief structure 202 may comprise 20% to 80%, preferably 35% to 65%, of the total area of the micro-relief 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 with 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 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 2 observes a second color in the direction of light scattered in the yoz plane (or a plane parallel to the yoz plane). Due to the refractive index n of the micro-relief structure 202 and the coating 203₁And n₂Such that the optical path length of the front side (z-axis forward direction) is n₁X d, and the optical path of the back surface (negative z-axis) is n₂Xd, the interference contrast condition of the front and back surfaces is differentiated, and the reflected light color of either the front or back surface is shifted, i.e. the color characteristics of the front and back surface are contrasted.

The depth d of the microrelief structures 202 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 above embodiments and will not be described here. The other features and advantages of the optical security element 2 are the same as those of the optical security element 1 and will not be described in detail here.

Fig. 3a-3c show an optical security element 3 according to an embodiment of the invention, which is illustrated by way of example in which the first region of the substrate surface is the entire substrate surface. As shown, the optical security element 3 may comprise: a base layer 301; a micro-relief structure 302 on and at least partially covering the base layer 301; a plating layer 304 at least partially covering the surface of the micro-relief structure 302; a coating 303 at least partially covering the plating, the plating 304 conformally covering the micro-relief structure 302, the micro-relief structure 302 being at least translucent and having a different refractive index than the coating 303. The depth of at least a portion of the micro-relief structure 302 satisfies the following condition: when a light beam irradiates at least a part of the micro-relief structure 302 at an incident angle, after the light beam passes through at least a part of the micro-relief structure 302, light of a wavelength or wavelength range in the light beam interferes and grows in the direction of reflected light, whereby at least a part of the optical security element 3 exhibits a first color in the direction of reflected light.

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 observes a second color in the direction of light scattered in the yoz plane (or a plane parallel to the yoz plane); if the beam is in the xoz plane (or a plane parallel to the xoz plane), the optical security element 3 is in the direction of the diffracted lightThe +1 or-1 order diffracted light color of the grating is observed upward as a function of the angle of observation. Due to the refractive index n of the micro-relief structure 302 and the coating 303₁And n₂Such that the optical path length of the front side (z-axis forward direction) is n₁X d, and the optical path of the back surface (negative z-axis) is n₂Xd, so that the interference contrast conditions of the front and back surfaces are differentiated, corresponding to a shift in the color of either the reflected light or the reflected light of the front and back surfaces, i.e. contrast in the color characteristics of the front and back surfaces.

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 above embodiments and will not be described here. The other features and advantages of the optical security element 3 are the same as those of the optical security element 1 and will not be described in detail here.

In order to ensure that the optical anti-counterfeiting element has higher uniqueness and easily-identified property difficult to forge. The optical anti-counterfeiting element provided by the invention can be covered with other types of micro-embossed structures on the surface of the base layer, and the optical anti-counterfeiting element is described below with reference to fig. 4a to 6.

Fig. 4a to 4c show an optical security element 4 according to an embodiment of the invention. As shown in fig. 4a, the optical security element 4 may include a base layer 401, a micro-embossed structure 402 in an area a and a micro-embossed structure 4021 in an area B, which are located on the base layer 401 and at least partially cover the base layer 401; a plating layer 404 covering the surface of the micro-relief structure 402; a coating 403 at least partially covering the plating 404, the plating 404 conformally covering the micro-relief structure 402, the micro-relief structure 402 being at least translucent and having a different refractive index than the coating 403. The micro-relief structure 402 is defined such that when a light beam strikes the micro-relief structure 402 at an incident angle, light of a wavelength or range of wavelengths in the light beam interferes constructively in the direction of reflected light. The ratio of the surface area to the apparent area of the micro-relief structures 402 is less than the ratio of the surface area to the apparent area of the micro-relief structures 4021. I.e. the area covered by the plating 404, is determined by the difference in the ratio of the surface area to the apparent area of the

micro-relief structures

402 and 4021.

Specifically, the

micro relief structures

402 and 4021 are composed of 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 the present invention, the term "apparent area" refers to the area of an orthographic projection in a plane parallel to a certain region, i.e. the area of the relief structure in the region is disregarded; the term "surface area" refers to the actual area of the relief structure in a region that is considered. It is apparent that the ratio of the surface area of a certain region to its apparent area is a value not less than 1.

The selection range of the micro-relief structure 402 is the same as that of the micro-relief structure in the embodiment of fig. 1, and the details are not repeated here. Preferably, the micro-relief structures 4021 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. 4a, the characteristic dimension of the micro-relief structure 402 in the x-axis and y-axis directions is 2.8 μm, the refractive index n of the material of the micro-relief structure 402 is 1.48, the cross-sectional shape of the micro-relief structure 402 is sinusoidal, the external medium is air, and d is 500 nm. The micro relief structure 4021 is a sinusoidal grating, and has an arrangement period of 350nm and a depth of 300 nm. The optical security element 4 shown in fig. 4a is processed as follows:

the method comprises the following steps: an optical original plate containing the micro-relief structure 402 and the micro-relief structure 4021 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 402 and the micro-relief structure 4021 on the lower surface of the base layer by a die pressing process, and the refractive index of a material forming the micro-relief structure can be close to 1.48.

Step two: a plating layer 404, which may be, for example, a reflective layer of a 50nm thick metal aluminum thin film, is deposited on the surfaces of the

micro-relief structures

402 and 4021.

Step three: and (3) immersing the structure formed in the second step into a solution capable of dissolving the plating layer, wherein the solution can be, for example, a sodium hydroxide aqueous solution with the concentration of about 5% at 40 ℃, until the plating layer (for example, a metal aluminum thin film reflecting layer) on the surface of the micro-relief structure 4021 is completely dissolved by reaction, so that the plating layer 404 accurately covers the micro-relief structure 402, and a precise hollow pattern is formed.

Step four: the coating 403 with the refractive index of 1.61 is printed on the surface of the plating layer 404 in the area A.

The above steps are the implementation steps for producing the optical security element 4 shown in fig. 4 a. The coating 403 and the micro-relief structure 402 are respectively arranged on the upper surface and the lower surface of the plating layer 404, so that the front surface and the back surface of the area a are provided with different color characteristics and associated patterns due to the difference of the refractive indexes of the area a of the optical anti-counterfeiting element 4. The area B provides hollow features, and the hollow area is determined by the difference between the surface area ratio of the micro-relief structure 402 and the micro-relief structure 4021, so that the images provided by the hollow area B and the area a are aligned precisely without error.

Another configuration of the optical security element 4 is shown in fig. 4b, which may include: the coating comprises a base layer 401, a micro-relief structure 402 positioned in an area A and a micro-relief structure 4021 positioned in an area B, which are positioned on the base layer 401 and at least partially cover the base layer 401, and a plating layer 404 covered on the surface of the micro-relief structure 402; a coating 403 at least partially covering the plating 404, the plating 404 conformally covering the micro-relief structure 402, the micro-relief structure 402 being at least translucent and having a different refractive index than the coating 403. The micro-relief structure 402 is defined such that when a light beam strikes the micro-relief structure 402 at an incident angle, light of a wavelength or range of wavelengths in the light beam interferes constructively in the direction of reflected light. The relief height of the micro-relief structures 402 is less than the relief height of the micro-relief structures 4021. I.e. the area covered by the plating 404 is determined by the difference in the relief height of the

micro-relief structures

402 and 4021.

In the embodiment of fig. 4b, the characteristic dimension of the micro-relief structure 402 in the x-axis and y-axis directions is 4.0 μm, the refractive index n of the material of the micro-relief structure 402 is 1.48, the cross-sectional shape of the micro-relief structure 402 is rectangular, the external medium is air, and d is 600 nm. The micro relief structures 4021 are cylindrical mirrors arranged in one dimension, the arrangement period of the micro relief structures is 20 μm, the bottom interval between adjacent cylindrical mirrors is 1.5 μm, and the height of each cylindrical mirror is 3.5 μm. The optical security element 4 shown in fig. 4b is processed as follows:

the method comprises the following steps: an optical original plate containing the micro-relief structure 402 and the micro-relief structure 4021 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 402 and the micro-relief structure 4021 on the lower surface of the base layer by a die pressing process, and the refractive index of a material forming the micro-relief structure is near 1.48.

Step two: a plating layer 404 is evaporated on the surfaces of the

micro-relief structures

402 and 4021, and the plating layer may be a 50nm thick metallic aluminum thin film reflective layer.

Step three: the plating 404 is coated with a coating 403 in its entirety, the coating 403 completely covering the micro-relief structures 402, but not completely covering the raised portions of the micro-relief structures 4021. The coating 404 may have a refractive index of 1.62.

Step four: and immersing the structure formed in the third step into a solution which can dissolve the plating layer 404 but can not dissolve the coating 403, wherein the solution can be, for example, a sodium hydroxide aqueous solution with a concentration of about 10% at 40 ℃ until the plating layer (for example, a metal aluminum thin film reflecting layer) on the surface of the micro-relief structure 4021 is completely reacted and dissolved, so that the plating layer 404 accurately covers the micro-relief structure 402, and a precise hollow pattern is formed. The specific reaction process is as follows: the coating 403 does not completely mask the plating 404 on the microrelief structures 4021, thus allowing the environment to react with the exposed plating 404 on the microrelief structures 8022 to achieve hollowing of the area. Meanwhile, the next stage of the reaction process is that the environment permeates into the plating layer covered by the coating 403 on both sides with the plating layer 404 exposed in the micro relief structure 4021 as the center, so as to further react with the plating layer 804 covered by the coating 403 on the micro relief structure 4021 to be semitransparent, and even to be completely transparent as the reaction process continues. The plating 404 on the micro-relief structure 402 is completely covered by the coating 403 throughout the reaction process and thus remains unreacted.

The above is the implementation step for manufacturing the optical security element 4 shown in fig. 4 b. The optical anti-counterfeiting element area A is provided with a coating 403 and a micro-relief structure 402 on the upper surface and the lower surface of a plating layer 404, so that the front surface and the back surface of the area A are provided with different color characteristics and associated patterns due to the difference of the refractive indexes. The area B provides hollow-out features, and the hollow-out area is determined by the difference between the surface area ratio and the apparent area ratio of the

micro-embossed structures

402 and 4021, so that the hollow-out area B of the optical anti-counterfeiting element and the image provided by the area a are aligned precisely without error.

Fig. 4c shows an embodiment of the optical security element 4 formed by further adding a coating 4021 'to the surface of the optical security element 4 in fig. 4a or fig. 4B, where the coating 4021' has approximately the same refractive index as the

micro-relief structures

404 and 4021, so as to cover the micro-relief structures 4021 in the region B, so that the region B has at least translucent hollow-out features without the influence of the micro-relief structures. For example, the coating 4021' may have the same refractive index as the micro relief structures 4021, thereby further ensuring transparency of the covering micro relief structures 4021.

Fig. 4d shows top views of the front side (front: z-axis positive direction) and the back side (back: z-axis negative direction) of the optical security element shown in fig. 4c on the xoy plane, wherein the micro-relief structure 402 is associated with the front side and the back side formed by the coating 404 and the coating 403 covering the surface thereof and has a pattern with different color characteristics in an area a, and a hollow area, which is an area not covered by the coating 404, is in the area B. In general, since the processing of the plating layer 404, the formation of the hollow pattern, and the micro-relief structure 402 and the micro-relief structure 4021 are performed in different processes, a positional error therebetween inevitably occurs. The optical anti-counterfeiting element 4 solves the problem, so that the optical anti-counterfeiting element 4 is endowed with stronger uniqueness and stronger anti-counterfeiting capability by strictly controlling the area covered by the plating layer 404 to be only the area A where the micro-embossed structure 402 is located.

The other features and advantages of the optical security element 4 are the same as those of the optical security element 1 and will not be described in detail here.

Fig. 5 is an optical security element 5 according to another embodiment of the present invention, which includes a base layer 501, a micro-embossed structure 502 in an area a and a micro-embossed structure 5022 in an area B on the base layer 501 and at least partially covering the base layer 501, and a plating layer 504 covering the surfaces of the micro-embossed structure 502 and the micro-embossed structure 5022; the coating 503 at least partially covers the coating 504, the coating 504 covers the micro-relief structure 502 and the micro-relief structure 5022 in a conformal manner, the micro-relief structure 502, the micro-relief structure 5022 and the coating 503 are at least semi-transparent, the refractive indexes of the micro-relief structure 502 and the micro-relief structure 5022 are approximately the same, and the micro-relief structure 502 and the coating 503 have different refractive indexes.

The micro-relief structure 502 is defined such that when a light beam strikes the micro-relief structure 502 at an incident angle, light of a wavelength or range of wavelengths in the light beam interferes constructively in the direction of the reflected light. The micro-relief structure 5022 can be selected within the following range: 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.

The optical anti-counterfeiting element 5 has the structure that:

(1) the same plating 504 is used in both zone a and zone B,

(2) a coating 503 of the same refractive index is used in regions a and B,

(3) the refractive index of the micro-relief structure 502 in the region a and the micro-relief structure 5022 in the region B are the same,

the optical security element 5 exhibits the following security features: the images on the front and back sides of the area A are related but have different color characteristics, and the images on the front and back sides of the area B are related and have the same color characteristics. The reason for forming this feature is that the depth of the micro-embossed structure 5022 of the region B does not satisfy the condition that the interference of reflected light is long, so that the optical anti-counterfeiting feature thereof is not sensitive to the refractive index of the coating 503 or the micro-embossed structure 5022.

The selection range of the micro-relief structure 502 is the same as that of the micro-relief structure in the embodiment of fig. 1, and the details are not repeated here. The depth d of the microrelief structure 502 is typically between 100nm and 5 μm, preferably 200nm to 3 μm. The method of determining the depth d is the same as in the above embodiments and will not be described here. The other features and advantages of the optical security element 5 are the same as those of the optical security element 1 and will not be described in detail here.

Fig. 6 shows an optical security element 6 according to yet another embodiment of the present invention, the optical security element 6 includes a base layer 601, a micro-embossed structure 602 in an area a and a micro-embossed structure 6022 in an area B on the base layer 601 and at least partially covering the base layer 601, and a plating layer 604 covering the micro-embossed structures 602 and the micro-embossed structure 6022; a coating 603 at least partially covering the plating layer 604, the plating layer 604 conformally covering the micro-relief structures 602 and the micro-relief structures 6022, the micro-relief structures 602, the micro-relief structures 6022, and the coating 603 being at least translucent, and the micro-relief structures 602 and the micro-relief structures 6022 having substantially the same refractive index, the micro-relief structures 602 and the coating 603 having different refractive indices. The area C is a hollow area.

The area a and the area B in the optical anti-counterfeiting element 6 correspond to the area a and the area B of the optical anti-counterfeiting element 5 in the embodiment of fig. 5, and the structure, the features, and the implementation method thereof will not be described herein again. The optical security element 6 has an increased area C in relation to the optical security element 5, which is a hollow-out area that is not covered by the coating 604. Optionally, a coating 603 may be applied over the area C. Or alternatively, the structure, characteristics and implementation method of the region C may be the same as those of the region B of the optical anti-counterfeiting element 4 in the embodiment of fig. 4a-d, and are not described herein again. Further, although the region C shown in fig. 6 is disposed between the region a and the region B, it is understood that the region C may be disposed at any position.

The selection range of the micro-relief structure 602 is the same as that of the micro-relief structure in the embodiment of fig. 1, and the details are not repeated here. The depth d of the microrelief structure 602 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 above embodiments and will not be described here. The other features and advantages of the optical security element 6 are the same as those of the optical security element 1 and will not be described in detail here.

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 after the anti-counterfeiting element is transferred to a bearing object by a hot stamping process, the base material is stripped off.

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.

Correspondingly, the invention also provides an optical anti-counterfeiting product which comprises the optical anti-counterfeiting element. For example, the security element of the present application may be transferred or affixed to a carrier in a form that is applied to a logo, a stamped broadstrip, a sticker, a security thread, or the like. 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.

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 surface of the base layer comprising a first region;

a first micro-relief structure at least covering the first area and at least being translucent;

a plating layer conformally covering at least a portion of the first micro-relief structure; and

a first coating at least partially covering the plating and at least semi-transparent;

wherein the refractive index of the first micro-relief structure is different from the refractive index of the first coating layer so as to enable the front and back surfaces of the optical anti-counterfeiting element to have color characteristic difference, and the depth of at least one part of the first micro-relief structure meets the following conditions: when a light beam irradiates at least one part of the first micro-relief structure at an incident angle, after the light beam passes through at least one part of the first micro-relief 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,

wherein the optical anti-counterfeiting element is used for a window product.

2. The optical security element of claim 1, wherein the surface of the base layer further comprises a second region, the optical security element further comprising:

and the second micro-relief structure covers the second area and is at least semi-transparent, and the refractive index of the second micro-relief structure is the same as that of the first micro-relief structure.

3. The optical security element according to claim 2, wherein the second micro-relief structures are not covered by the plating.

4. The optical security element according to claim 3,

the ratio of the surface area to the apparent area of the first micro-relief structure is smaller than the ratio of the surface area to the apparent area of the second micro-relief structure; and/or

The undulation height of the first micro relief structure is smaller than the undulation height of the second micro relief structure.

5. The optical security element of claim 3, wherein the optical security element further comprises:

a second coating layer overlying the first coating layer and the second micro-relief structures, the second coating layer having a refractive index that is the same as the refractive index of the second micro-relief structures.

6. The optical security element according to claim 2, wherein the second micro-relief structures are covered with the plating and the first coating.

7. An optical security element according to claim 6, wherein the surface of the base layer further comprises a third region, the first coating overlying the third region.

8. The optical security element according to claim 2, wherein the second micro-relief structure is a continuous curved surface type structure, a rectangular structure, a sawtooth type prism structure and/or a splice or a combination thereof.

9. An optical security element according to any one of claims 1 to 8, wherein the pattern of at least a portion of the first micro-relief structures is at least one or any combination of:

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.

10. An optical security element according to claim 9, 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 characteristic dimension of the at least one portion of the first micro-relief structures is between 0.3 μ ι η and 6 μ ι η, the depth of the at least one portion 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, at least one part of the optical anti-counterfeiting element presents a second color in a scattering light direction.

11. The optical security element according to claim 10, wherein at least a portion of the first micro-relief structures have a characteristic dimension of 0.6 μ ι η to 3 μ ι η.

12. An optical security element according to claim 9, 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.

13. The optical security element according to claim 12, 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.

14. An optical security element according to claim 12, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the first direction of greater than 10 μm.

15. An optical security element according to claim 9, wherein in the case that the relief units of at least a part 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 a part 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 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; 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.

16. The optical security element according to claim 15, wherein at least a portion of the first micro-relief structures have a characteristic dimension in the first direction of 0.6 μ ι η to 3 μ ι η.

17. The optical security element according to claim 15, 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.

18. The optical security element according to any one of claims 1 to 8, wherein the coating is a metallic reflective layer or an interference multilayer film structure.

19. An optical security element according to any one of claims 1 to 8, wherein the difference between the refractive index of the first micro-relief structures and the refractive index of the coating is not less than 0.04.

20. The optical security element according to claim 19, wherein the difference between the refractive index of the first micro-relief structures and the refractive index of the coating is not less than 0.1.

21. An optical security element according to any one of claims 1 to 8, wherein the first micro-relief structures have a depth of from 100nm to 5 μm.

22. The optical security element according to claim 21, wherein the first micro-relief structures have a depth of 200nm to 3 μ ι η.

23. An optical security element according to any one of claims 1 to 8, wherein the relief elements of the first micro-relief structure have a cross-section of any one of: sinusoidal, saw tooth, or rectangular.

24. An optical security product comprising an optical security element according to any one of claims 1 to 23.