Magnetic response optical anti-counterfeiting element and manufacturing method thereof

Abstract

The invention relates to a magnetic response optical anti-counterfeiting element and a manufacturing method thereof. The magnetic response optical anti-counterfeiting element comprises a base material layer and a microstructure forming layer on the base material layer, the microstructure forming layer comprises a microcavity, the microcavity contains a magnetic pigment sheet, and the magnetic pigment sheet can move in the microcavity and can be reversibly oriented through an external magnetic field. The magnetic pigment sheet is curved and / or a microcavity comprises a secondary microstructure, the magnetic response optical anti-counterfeiting element further comprises a sealing layer, and the sealing layer is used for sealing the magnetic pigment sheet in the microcavity. According to the invention, the magnetic pigment sheet is designed to be curved or / and the secondary microstructure is arranged in the micro-cavity, so that the magnetic pigment sheet is prevented from being in complete contact with the micro-cavity, the magnetic pigment sheet can better move and turn over under the action of a magnetic field, and the problem that the interaction effect is limited because the magnetic pigment sheet is easily and tightly attached to the inner wall of the micro-cavity is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical anti-counterfeiting, and in particular to a magnetic response optical anti-counterfeiting element and a manufacturing method thereof. Background Art

[0002] In order to prevent counterfeiting by means of scanning and copying, optical anti-counterfeiting technology is widely used in various high-security or high-value-added products such as banknotes and financial bills, and has achieved very good results. At present, the eye-catching technology is the combination of the microstructure determined by plate making and the optical variable layer, and the orientation angle of the optical variable layer is modulated by the pre-designed microstructure, so as to achieve the combination of the optical variable effect of color change and the dynamic effect of brightness change. In terms of optical anti-counterfeiting inks, the most important innovation is the optical gradient magnetic ink OVMI developed by Sicpa. For example, the magnetic interference pigment disclosed in the existing patent document CN104903009A is a 7-layer Fabry-Perot structure of absorption layer / isolation layer / reflection layer / magnetic layer / reflection layer / isolation layer / absorption layer, and the typical composition is Cr / MgF2 / Al / Ni / Al / MgF2 / Cr. The demolding layer is dissolved by an appropriate solvent, and the stacking layer is removed by peeling. The resulting fragments are further crushed and refined to obtain optically variable magnetic color sheets. During the printing process, the magnetic color sheets are arranged in a pre-designed magnetic field to obtain a concave or convex Fresnel-type reflective surface, and the color sheets are fixed in the designed position by UV curing to obtain the dynamic effect of brightness change required by the design. However, in the manufacturing implementation of the above-mentioned optical anti-counterfeiting elements, whether through microstructure or magnetic field orientation, the angle of the light-variable layer is pre-set and fixed after manufacturing. It is impossible to change the orientation angle of the light-variable layer again by applying external forces, such as magnetic field, electric field, pressure, temperature, humidity, atmosphere, etc. Therefore, the above anti-counterfeiting technology does not have an interactive anti-counterfeiting effect.

[0003] In this regard, the existing patent document CN103476596A further improves on the basis of Sicpa anti-counterfeiting ink, encapsulates optically variable pigments by means of microcapsules, and subsequently controls the rotation of pigments by means of magnetic fields to achieve control of optical effects. However, it does not provide a specific method for realizing hollow spherical microcapsules, and it is extremely difficult to obtain hollow spherical microcapsules without restricting the rotation of color sheets, and when using microcapsules, the walls of microcapsules are generally thicker, and there may also be a certain interval between capsules, reducing the proportion of effective interactive elements. At the same time, the present invention finds that there is a phenomenon of easy close fit between magnetic pigment sheets and microcapsules / microcavities, thereby affecting the movement of magnetic pigment sheets in the magnetic field and reducing the interactive effect. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the magnetic pigment flakes in the existing optical anti-counterfeiting elements are easy to fit tightly to the inner wall of the microcavity, resulting in limited interaction effect, thereby providing a magnetically responsive optical anti-counterfeiting element and a manufacturing method thereof to solve the above problem.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A magnetically responsive optical anti-counterfeiting element comprises a substrate layer and a microstructure forming layer on the substrate layer, wherein the microstructure forming layer comprises a microcavity, wherein the microcavity contains a magnetic pigment flake, wherein the magnetic pigment flake can move within the microcavity and can be reversibly oriented by an external magnetic field, wherein the magnetic pigment flake is curved and / or the microcavity comprises a secondary microstructure, and wherein the magnetically responsive optical anti-counterfeiting element further comprises a sealing layer, wherein the sealing layer is used to seal the magnetic pigment flake within the microcavity.

[0007] Preferably, the microcavity is filled with a dispersion medium;

[0008] And / or, the magnetic pigment flake is a magnetic optically variable pigment flake.

[0009] Preferably, the dispersion medium is gas, liquid and gel;

[0010] And / or, the dispersion medium is fully transparent or partially transparent;

[0011] And / or, the dispersion medium forms a solid by external stimulation.

[0012] Preferably, the dimensions of the microcavity in two directions in the horizontal plane are 10-500 μm;

[0013] and / or, the height of the microcavity is less than 100 μm;

[0014] And / or, the height of the secondary microstructure is smaller than the height of the microcavity.

[0015] Preferably, the microcavities are distributed in one dimension or / and two dimensions; that is, in the plane of the microstructure forming layer, the microcavities can be distributed in one dimension or in two dimensions. The so-called one-dimensional distribution means that in the plane of the microstructure forming layer, the partitions between the microcavities are continuous in one direction, or at least continuous on a macroscopic millimeter scale, and in the direction perpendicular to it, the partitions are repeated periodically or non-periodically, and these microcavities also extend in the direction in which the partitions extend and are discontinuous in the direction perpendicular to it. The so-called two-dimensional distribution means that the partitions appear at intervals in both directions in the plane, just like a chessboard that divides the plane into multiple microscopic sub-regions, and these sub-regions are microcavities. It should be noted that the "vertical" mentioned here is not vertical in the strict mathematical sense, and can be non-90°, and a crossed state can be considered vertical. For the convenience of design, the microcavities can be repeated periodically, and the position of each microcavity is periodic. However, this periodicity may bring about features such as diffraction, which sometimes interferes with observation, so it is also possible to form non-periodic positions in a random manner;

[0016] And / or, the secondary microstructure is one-dimensionally distributed or / and two-dimensionally distributed. That is, the concepts of one-dimensional and two-dimensional here are the same as described above. For example, when the secondary microstructure is two-dimensional, the specific shape can be a cone, facing upward, and the tip of the cone supports the pigment flakes.

[0017] Preferably, both sides of the magnetic pigment flakes have the same color;

[0018] And / or, the curved magnetic pigment flakes are obtained by attaching materials or material stacks with different stresses on both sides;

[0019] And / or, the curved magnetic pigment flakes are obtained by arranging different stress materials on both sides of the magnetic layer in the Fabry-Perot interference cavity structure.

[0020] Preferably, the magnetically responsive optical anti-counterfeiting element further includes a functional coating.

[0021] Preferably, the functional coating comprises a protective layer for providing protection for the anti-counterfeiting element, an adhesive layer for providing adhesion with the substrate layer, a hot stamping layer for hot stamping, and a peeling layer for transfer.

[0022] The present invention also provides a method for manufacturing the magnetic response optical anti-counterfeiting element, comprising: forming a microstructure forming layer having an open microcavity by molding on a substrate layer;

[0023] Filling the microcavity with magnetic pigment flakes;

[0024] The top of the microcavity is sealed with a sealing material to form a sealing layer;

[0025] The magnetic pigment flakes are curved and / or contain secondary microstructures in the microcavities.

[0026] Preferably, the molding is hot molding or / and UV molding; molding is an effective means of making open microcavities, and the molding methods include hot molding and UV molding. Preferably, UV molding is used to make the microcavities with openings described in the present invention. The equipment and process of UV molding have been disclosed in existing patent documents. Among them, the structure of the open microcavity manufactured by UV molding is determined by the plate making design, and the plate making design can realize open microcavities of any shape and size. As a mature production method, UV molding can efficiently, stably and mass-produce microcavities with openings;

[0027] And / or, the magnetically responsive optical anti-counterfeiting element is further provided with a composite functional coating.

[0028] In the present invention, the microstructure forming layer can be a UV curable material, which is initially in liquid form on the substrate. The master is pressed into the above UV curable material, and the UV curable material is cured and fixed by UV irradiation, and then the master is peeled from the above cured material, that is, the structure of the master is transferred and copied to the microstructure forming layer. Through the pre-designed master structure, a groove with a certain shape and a secondary microstructure, i.e., a "microcavity", can be obtained in the microstructure forming layer. The microstructure forming layer can be transparent or non-transparent, depending on the subsequent observation method. If it is necessary to observe through the substrate layer from the other side of the microstructure forming layer, the substrate layer and the microstructure forming layer need to have a certain degree of transparency, but when it is only necessary to observe from this side of the microstructure forming layer, the microstructure forming layer can be opaque. Within the scope of the present invention, a "transparent" material is understood as a material that can be substantially transparent to incident electromagnetic radiation (at least in the visible wavelength range of about 380nm to about 780nm). In the "transparent" material of the present invention, the transmittance should not be less than 75%.

[0029] In the present invention, a dispersion medium is filled in the microcavity, and the dispersion medium is a deformable material such as gas, liquid or gel, so that the magnetic pigment flakes can move and / or rotate therein. In order not to affect the expression of the properties of the magnetic pigment flakes themselves, the dispersion medium in the microcavity is transparent or at least partially transparent. At the same time, due to the presence of the secondary microstructure, it may have a certain impact on the optical effect of the magnetic pigment flakes. If the influence of the optical characteristics generated by the secondary microstructure itself is to be avoided, the refractive index of the dispersion medium in the microcavity should be close to the refractive index of the secondary microstructure. This is because when the refractive indexes of the two are similar, even if the material composition of the two is different or the solid and liquid states are different, the two can be considered to be the same or similar optically. Similar to spreading water on a frosted glass surface, although glass is solid and water is liquid, and the components of the two are different, because the refractive indexes of the two are similar, the two can be considered to be similar optically, and water and frosted glass are optically called a whole, and water fills the grooves on the surface of the glass, making the glass transparent. Therefore, if the influence of the optical characteristics generated by the secondary microstructure itself is to be avoided, the difference between the refractive index of the secondary microstructure and the refractive index of the dispersion medium is not greater than 0.2. On the contrary, if the secondary microstructure can bring a more special effect, without weakening the optical anti-counterfeiting characteristics of the magnetic pigment flakes, but enhancing their optical anti-counterfeiting characteristics, the type of dispersion medium can be selected so that the difference between the refractive index of the secondary microstructure and the refractive index of the dispersion medium is greater than 0.2. The optical effects brought by these secondary microstructures themselves can also be used as a supplementary effect in addition to the interactive characteristics. For example, using a holographic grating with a period of 1-5μm can bring a holographic effect, and using a wedge grating of 5-10μm can achieve a shining effect at a certain angle (the numbers are just for illustration and are not very strict). At this time, the secondary microstructure can not only separate the pigment flakes from the inner wall of the microcavity and play a supporting role for the pigment flakes, but also bring an optical effect that enhances the optical anti-counterfeiting characteristics, that is, one secondary microstructure realizes two characteristics.

[0030] In the present invention, when obtaining a magnetic pigment sheet with the same color and bending, one method is to use a film composed of different materials with different tensile stress or compressive stress to form a pull in different directions, and finally to form a deformation in one direction. Therefore, different materials or material stacks are attached to both sides of the magnetic pigment sheet. Another method is to select a Fabry-Perot interference cavity structure formed by different materials on both sides of the magnetic pigment sheet, and the middle of the Fabry-Perot interference cavity structure is a magnetic layer. Magnetic metals such as iron, cobalt, nickel, rolling, etc. or magnetic oxides such as iron oxide, chromium oxide, chromium iron oxide, etc., and the above-mentioned magnetic metals also include alloys with added rare earth elements. And the magnetic interference pigment sheet of the Fabry-Perot structure, such as the magnetic interference pigment sheet is a 7-layer Fabry-Perot structure of absorption layer / isolation layer / reflection layer / magnetic layer / reflection layer / isolation layer / absorption layer, the typical composition is Cr / MgF2 / Al / Ni / Al / MgF2 / Cr. In order to realize the bending property of the pigment sheet, the Fabry-Perot resonant cavity structure formed by different materials can be selected on both sides of the magnetic layer. For example, it can be Cr / MgF2 / Al / Ni / Al / SiO2 / Cr. Since SiO2 generally presents compressive stress and MgF2 generally presents tensile stress, the magnetic pigment flakes tend to bend toward the SiO2 side, so the magnetic pigment flakes are curved as a whole. At the same time, the thickness of the dielectric material can be appropriately adjusted according to the different refractive indices of the dielectric material to obtain the same or similar colors.

[0031] In the present invention, there are two paths for filling the magnetic pigment flakes inside the microcavity. One path is to fill the magnetic pigment flakes dispersed in the solution inside the microcavity, and then volatilize the solution by drying, so that after the microcavity is closed, the movement space of the magnetic pigment flakes in the microcavity is composed of air. Another path is to fill the magnetic pigment flakes dispersed in the solution inside the microcavity, and the solution is retained, so that after the microcavity is closed, the movement space of the magnetic pigment flakes in the microcavity is composed of liquid or part of liquid and part of air. According to the above two paths, those skilled in the art can obtain personalized equipment that meets the requirements of the above process paths. At the same time, the microcavity is closed by coating a sealing material with a density less than that of the filling liquid. The sealing material is selected from one or more of organic materials, inorganic materials, organic / inorganic hybrid materials, or mixed materials of organic and inorganic materials. Reactive materials are preferred, such as systems that can be cured by ultraviolet rays (UV), electron beams (EB), visible light, infrared rays, etc., as well as room temperature curing and heat curing systems. At the same time, a layer of sealing material can also be coated on the basis of the closed structure to obtain better sealing performance.

[0032] The technical solution of the present invention has the following advantages:

[0033] 1. A magnetically responsive optical anti-counterfeiting element, comprising a substrate layer and a microstructure forming layer on the substrate layer, wherein the microstructure forming layer comprises a microcavity, wherein the microcavity contains a magnetic pigment flake, wherein the magnetic pigment flake can move within the microcavity and can be reversibly oriented by an external magnetic field, wherein the magnetic pigment flake is curved and / or the microcavity comprises a secondary microstructure, and wherein the magnetically responsive optical anti-counterfeiting element further comprises a sealing layer, wherein the sealing layer is used to seal the magnetic pigment flake in the microcavity.

[0034] During ultraviolet replication, magnetic pigment flake filling or subsequent use, the substrate, dispersion medium, and magnetic pigment flake surface may all carry electric charges, and these materials may carry charges of different sexes, for example, the substrate is negatively charged, and the magnetic pigment flake is positively charged. In this way, due to the principle of mutual attraction between positive and negative charges, the magnetic pigment flake will be adsorbed at the bottom of the microcavity. Alternatively, the magnetic pigment flake may also settle to the bottom of the microcavity under its own gravity, and the existing magnetic pigment flakes are all symmetrical structures, and the materials are also symmetrical (that is, the magnetic pigment flakes are flat structures), and the microstructure is also required to be as smooth as possible to avoid affecting the optical effect. When the magnetic pigment flake and the microstructure are both flat structures, when the magnetic pigment flake contacts the microcavity, there is no gap between the two, which will cause excessive pressure, so that the magnetic pigment flake is firmly adsorbed at the bottom of the microcavity and is not easy to separate. Based on the above reasons, the existing magnetic response optical anti-counterfeiting element has the problem of being easy to fit closely to the inner wall of the microcavity, resulting in limited interactive effects. In this regard, the present invention provides two improved methods from the technical concept of making a certain space between the magnetic pigment flake and the inner wall of the microcavity to avoid the pigment flake from fitting completely with the microcavity. That is, on the one hand, a secondary microstructure can be added to the microcavity (especially the bottom of the microcavity), and the secondary microstructure forms a number of support points, which separate the magnetic pigment sheet from the microcavity and allow the dispersion medium to be filled therein. In this way, when the dispersion medium is spread around the magnetic pigment sheet, the pressure on the upper and lower parts of the magnetic pigment sheet is the same, which avoids the pressure pressing the magnetic pigment sheet firmly to the bottom. When a magnetic field is applied externally, even a smaller magnetic field strength can change the position and angle of the magnetic pigment sheet. On the other hand, the magnetic pigment sheet can also be made not flat, but curved. When the magnetic pigment sheet is curved, the magnetic pigment sheet cannot fit completely with the ground, and there is a gap to make the dispersion medium between the pigment sheet and the microcavity. The pressure on the upper and lower parts of the pigment sheet is the same, so that the pigment sheet can be better moved and flipped under the action of the magnetic field. Based on the above two improved methods, the above problems can be solved.

[0035] 2. In the magnetically responsive optical anti-counterfeiting element of the present invention, the dimensions of the microcavity in two directions in the horizontal plane are limited to the range of 10-500 μm. This is for the filling of magnetic pigment flakes. The opening size of the microcavity cannot be set too small, resulting in the magnetic pigment flakes not being able to be well filled into the microcavity. At the same time, when the microcavity is too large, the human eye will be able to observe the microcavity, affecting the observation effect, and the microcavity opening is large, and the magnetic pigment flakes are also more easily taken out of the microcavity again after filling, so the microcavity opening should not be too large.

[0036] 3. In the magnetically responsive optical anti-counterfeiting element of the present invention, the depth of the microcavity will also affect the effect of the interaction. Since the filling pigment flakes have a certain size, when the depth of the microcavity is small, the pigment flakes will no longer be able to rotate in the microcavity, limiting the interactive effect. When the depth of the microcavity is too deep, it means that the total thickness of the optical anti-counterfeiting element is large, which will also be limited in actual use. For example, when the above-mentioned optical anti-counterfeiting element is applied to paper in the form of a security line, the larger thickness will affect the production of the paper and its integration with the paper. The thickness of the optical anti-counterfeiting element position will be significantly greater than other positions. During batch production, the thickness difference at this position will be magnified, resulting in inability to produce continuously. And when the thickness is thicker, the paper will have obvious wrinkles, affecting the overall quality of the paper. Therefore, the height of the microcavity is less than 100μm.

[0037] 4. In the magnetically responsive optical anti-counterfeiting element of the present invention, since the magnetic pigment flakes are randomly oriented in the dispersion medium, the colors of both sides of the magnetic pigment flakes are required to be the same or similar, thereby ensuring that no matter whether the concave or convex surface of the pigment flake is seen by the observer, the same color is perceived, thereby ensuring color uniformity.

[0038] 5. In the magnetically responsive optical anti-counterfeiting element of the present invention, the preparation of traditional optically variable ink requires a set of special equipment, including integrated screen printing, UV pre-curing, UV curing and other units. The equipment structure is huge, involving ink, screen printing module, and magnetic positioning module. The equipment investment cost is large, the personnel operation is complicated, and it is not easy to quickly realize the development of multiple effects. The dispersion medium of the present invention can change through external stimulation to form a solid, and the pigment flakes therein will not be able to move. For example, the dispersion medium is a resin (UV glue) that can be cured by ultraviolet light. Customers do not need traditional complex systems such as silk screen printing and magnetic positioning. They only need to arrange the magnetically responsive optical anti-counterfeiting element of the above-mentioned curable dispersion medium in the required position, apply a magnetic field, and then position it. This greatly simplifies the equipment and operation complexity, while avoiding the waste of traditional magnetic optically variable pigments, improving production efficiency and reducing costs.

[0039] 6. In the magnetically responsive optical anti-counterfeiting element of the present invention, a functional coating is also processed to form a hot stamping transfer type wide strip, a security line or an anti-counterfeiting label product, thereby enabling the magnetically responsive optical range element to have a wider applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 is a schematic cross-sectional view of the magnetically responsive optical anti-counterfeiting element in Example 1 of the present invention;

[0042] Figure 2 is a schematic cross-sectional view of a magnetic pigment sheet in a magnetically responsive optical anti-counterfeiting element in Example 1 of the present invention;

[0043] Figure 3 is a top view of the secondary microstructure at the bottom of the microcavity in the magnetically responsive optical anti-counterfeiting element of Example 1 of the present invention;

[0044] Figure 4 is a cross-sectional schematic diagram of the image change produced by the magnetically responsive optical anti-counterfeiting element in Example 1 of the present invention in a magnetic field;

[0045] Figure 5 This is a diagram showing the state of the magnetically responsive optical anti-counterfeiting element in Example 1 of the present invention when it is on a carrier and there is no external magnetic field;

[0046] Figure 6 This is a diagram showing the state of the magnetically responsive optical anti-counterfeiting element in Example 1 of the present invention when it is on a carrier and there is an external magnetic field;

[0047] Figure 7 is a top view of the secondary microstructure at the bottom of the microcavity in the magnetically responsive optical anti-counterfeiting element of Example 2 of the present invention;

[0048] Figure 8 It is a schematic diagram of the process of magnetic directional solidification of the magnetically responsive optical anti-counterfeiting element in Example 5 of the present invention.

[0049] Explanation of the reference numerals: 1-optical anti-counterfeiting element, 2-substrate layer, 3-microstructure forming layer, 4-dispersion medium, 5-sealing layer, 6-bent magnetic optically variable pigment, 7-adhesive layer, 11-first microcavity, 12-second microcavity, 13-third microcavity, w11-microcavity width, h11-microcavity depth, w111-secondary microstructure width, h111-secondary microstructure depth, FP1-concave side "Fabry-Perot" structure of the bent magnetic pigment sheet, FP2-convex side "Fabry-Perot" structure of the bent magnetic pigment sheet Fabry-Perot" structure, 61-absorption layer in the "Fabry-Perot" structure on the concave side of the curved magnetic pigment sheet, 62-dielectric layer in the "Fabry-Perot" structure on the concave side of the curved magnetic pigment sheet, 63-reflection layer in the "Fabry-Perot" structure on the concave side of the curved magnetic pigment sheet, 64-magnetic layer, 65-reflection layer in the "Fabry-Perot" structure on the convex side of the curved magnetic pigment sheet, 66-dielectric layer in the "Fabry-Perot" structure on the convex side of the curved magnetic pigment sheet, 67-absorption layer in the "Fabry-Perot" structure on the convex side of the curved magnetic pigment sheet. DETAILED DESCRIPTION

[0050] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0051] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0052] Example 1

[0053] This embodiment provides a method for manufacturing a magnetically responsive optical anti-counterfeiting element, and the specific steps are as follows: first, a microstructure forming layer 3 with an open microcavity is formed on a substrate layer 2 by UV molding, and then a magnetic optically variable pigment sheet is filled inside the microcavity, and then a sealing material is used to seal the top of the microcavity to form a sealing layer 4. Among them, the material of the substrate layer 2 is polyethylene terephthalate (PET), and the material of the microstructure forming layer 3 is an ultraviolet curing material (UV glue). The sealing material used in this embodiment is specifically an ultraviolet curing material (1,6-hexanediol diacrylate). The cross-sectional view of the optical anti-counterfeiting element 1 obtained is as shown in FIG. Figure 1 As shown in Figure 2, it contains three typical areas. These three typical areas are as follows: Figure 1As shown, they are sub-region 11 (first microcavity), sub-region 12 (second microcavity) and sub-region 13 (third microcavity). In sub-region 11, the microstructure forming layer is recessed downward to form a microcavity, and the secondary microstructure at the bottom of the microcavity in sub-region 11 is a triangular cross-section in the x direction, and extends to the boundary of sub-region 11 in the y direction according to the triangular cross-section; in sub-region 12, the bottom is a flat structure; sub-region 13 is the same as the bottom secondary microstructure in sub-region 11. The z-direction depth h11 of the microcavity in sub-regions 11-13 is 12μm, and the x-direction width w11 is 100μm; the x-direction width w111 of the secondary microstructure at the bottom of the microcavity in sub-region 11 is 5μm, and the y-direction depth h111 is 2μm. Each sub-region in the microstructure forming layer 3 is filled with a dispersion medium 4. In the present embodiment, the dispersion medium is glycerol, and the refractive index of glycerol is about 1.47, while the microstructure forming layer 3 is UV glue, and its refractive index is 1.5. The refractive indices of the two are basically the same. Therefore, even if the secondary microstructure at the bottom of the sub-region 11 in the present embodiment is a triangle, when the dispersion medium glycerol exists in the microcavity, the bottom secondary microstructure is optically "fused" with the dispersion medium glycerol, and no other reflection, diffraction and other effects will be generated.

[0054] There are magnetic optically variable pigments in each of the above sub-regions. The size of the magnetic optically variable pigment flakes in each sub-region in the x-direction is 5-50 μm. Among them, the microcavity in sub-region 11 contains flat magnetic optically variable pigments, while the microcavities in sub-regions 12 and 13 contain curved magnetic optically variable pigments 6. The cross-section of the curved magnetic optically variable pigment is as follows: Figure 2 As shown. The structure and material of the flat magnetic optically variable pigment are symmetrical, namely "nickel / silicon dioxide / aluminum / iron / aluminum / silicon dioxide / nickel", where the thickness of nickel is 7nm, the thickness of silicon dioxide is 390nm, the thickness of aluminum is 40nm, and the thickness of iron is 40nm. The "nickel / silicon dioxide / aluminum" and "aluminum / silicon dioxide / nickel" symmetrically distributed on both sides form a "Fabry-Perot" structure, which appears golden when viewed from the side of the metal nickel. The iron in the middle is a magnetic layer that can deflect and move under the action of a magnetic field, and the nickel on both sides can also provide a certain degree of magnetism.

[0055] The structure of the curved magnetic optically variable pigment 6 is symmetrical, but the materials are different. The curved magnetic optically variable pigment 6 includes an absorption layer 61, the material is nickel, and the thickness is 7nm; a dielectric layer 62, the material is silicon dioxide, the thickness is 390nm; a reflective layer 63, the material is aluminum, and the thickness is 40nm; the absorption layer 61, the dielectric layer 62 and the reflective layer 63 constitute a "Fabry-Perot" structure FP1. In the middle is a magnetic layer 64, the material is iron, and the thickness is 40nm. Symmetrical to the "Fabry-Perot" structure FP1, on the other side of the magnetic layer there is a reflective layer 65, the material is aluminum, and the thickness is 40nm; a dielectric layer 66, the material is magnesium fluoride, and the thickness is 415nm; an absorption layer 67, the material is nickel, and the thickness is 7nm. That is, the curved magnetic optically variable pigment is "nickel / silicon dioxide / aluminum / iron / aluminum / magnesium fluoride / nickel", and the "nickel / silicon dioxide / aluminum" and "aluminum / magnesium fluoride / nickel" symmetrically distributed on both sides form a "Fabry-Perot" structure, which appears golden when viewed from the metal nickel side. The iron in the middle is a magnetic layer that can deflect and move under the action of a magnetic field, and the nickel on both sides can also provide a certain degree of magnetism.

[0056] Since the color of the optically variable pigment is mainly determined by the optical thickness of the dielectric material, and the two materials have different refractive indices, the physical thickness of the dielectric layer 62 and the dielectric layer 66 are different, but the same color can still be formed, which also ensures that the pigment can show the same color regardless of whether it is a "Fabry-Perot" structure FP1 or a "Fabry-Perot" structure FP2. However, since the silicon dioxide film and the magnesium fluoride film obtained by vacuum physical vapor deposition have different types of internal stress, the FP1 region presents tensile stress due to the effect of silicon dioxide, and presents a concave shape toward the side of the absorption layer 61; the FP2 region presents compressive stress due to the effect of magnesium fluoride, and presents a convex shape toward the side of the absorption layer 67. The combination of the two can superimpose the bending effect and form a curved magnetic optically variable pigment 6.

[0057] In this embodiment, the magnetic optically variable pigment flakes are not tightly fitted to the bottom of the microcavity. The secondary microstructure at the bottom of the microcavity microstructure formation layer in sub-region 11 is triangular, so a certain space is formed between the pigment and the secondary microstructure at the bottom. These spaces can be filled with the dispersion medium 4, so that the pressure on the upper and lower surfaces of the pigment is the same, which greatly increases the difficulty of the pigment flake deflection. This is because if the pigment flake is flat and the bottom of the microcavity is also flat, in some cases the pigment flake can be completely fitted with the bottom of the microcavity. At this time, the upper surface of the pigment in contact with the dispersion medium is at least subjected to an atmospheric pressure of about 1.01×10 5Pa, and the pressure in contact with the bottom is 0 because there is no dispersion medium, so it is subjected to a large pressure difference, which makes it difficult to rotate and move under the action of the external magnetic field. In this embodiment, different methods are used in sub-regions 11-13 to avoid this situation. Among them, the bottom secondary microstructure in the microcavity of sub-region 11 is continuous in one dimension in the xy plane and changes in another dimension. The top view of sub-region 11 is shown in FIG. Figure 3 As shown, the bottom secondary microstructure in the microcavity of sub-region 11 in the figure is represented by a gradient of black and white, where black represents a lower position and white represents a higher position.

[0058] like Figure 4 As shown, in this embodiment, the optical anti-counterfeiting element 1 generates a cross-sectional view of image changes in a magnetic field after a magnet is applied. When the magnet is arranged below the optical anti-counterfeiting element 1, the magnetic flux lines penetrate the optical anti-counterfeiting element 1 from bottom to top. Under the action of the magnetic flux lines, the magnetic optically variable pigment moves along the direction of the magnetic flux lines, and the left rear is basically parallel to the tangent direction of the magnetic flux lines at that location.

[0059] like Figure 5-Figure 6 As shown, when the optical anti-counterfeiting element 1 of this embodiment is on a carrier (paper), in the absence of an external magnetic field, the optical anti-counterfeiting element 1 presents a relatively uniform golden color and has a certain granular texture. When an external magnetic field is applied, such as placing a bar magnet near the optical anti-counterfeiting element 1, the original golden plane of the optical anti-counterfeiting element 1 will change. This change includes not only a change in color (golden when the pigment flakes are arranged in parallel, but green when the pigment flakes are tilted), but also a change in brightness, such as Figure 6 shown.

[0060] Example 2

[0061] The difference between this embodiment and embodiment 1 is that the secondary microstructure varies in two dimensions, such as Figure 7 As shown, the secondary microstructure at the bottom of the microcavity in sub-region 11 is two-dimensionally distributed, and other conditions are the same as those in Example 1. The technical effect brought by the magnetically responsive optical anti-counterfeiting element prepared in this example is the same as that in Example 1.

[0062] Example 3

[0063] The difference between this embodiment and embodiment 1 is that the dispersion medium is replaced by water, whose refractive index is 1.33, and the UV glue increases its refractive index to 1.7 by adding high refractive index material (titanium dioxide nanoparticles), and the difference between the two refractive indices is 0.36. At this time, the characteristic width w111 of the secondary microstructure at the bottom of the microcavity in sub-region 11 is 2 μm, and the secondary microstructure at the bottom of the microcavity in sub-region 11 and the dispersion medium water cannot be regarded as the same optically, so the whole can still present a relatively obvious holographic rainbow color, that is, the superposition effect of the holographic rainbow is presented on the basis of the color of the optically variable pigment.

[0064] Example 4

[0065] The difference between this embodiment and embodiment 1 is that the dispersion medium is replaced by nitrogen, whose refractive index is about 1, which is more different from the refractive index of the microstructure forming layer, and can better retain the optical characteristics of the secondary microstructure itself, that is, the superposition effect of the holographic rainbow on the basis of the color of the optically variable pigment is more prominent.

[0066] Example 5

[0067] The difference between this embodiment and embodiment 1 is that the magnetic optically variable pigment flakes in the microcavity are all flat pigment flakes, and the bottom of the microcavity is provided with a secondary microstructure (triangle). The dispersion medium glycerol is replaced with a UV-curable adhesive. When obtaining the optical anti-counterfeiting element, a bonding adhesive layer 7 is compounded at the bottom of the substrate layer, and then adhered to the carrier. A magnetic field is applied to make the magnetic optically variable pigment form a preset orientation. While maintaining the external magnetic field, ultraviolet light is applied to make the dispersion medium in the microcavity change from liquid to solid, so as to fix the orientation and position of the magnetic optically variable pigment. Finally, the external magnetic field and the ultraviolet light source are removed to obtain the final anti-counterfeiting element. The schematic diagram is shown in FIG. Figure 8 As shown. In the absence of external stimulation, the dispersion medium is in liquid form, and the magnetic optically variable pigment can rotate or move freely in the microcavity. When ultraviolet or electron beam irradiation is applied to solidify the dispersion medium while maintaining the magnetic field, the orientation and position of the magnetic optically variable pigment can be fixed. This method can more simply realize the control "programming" of the orientation and position of the magnetic optically variable pigment. Compared with the complex system that originally required special silk screen printing, pre-curing, and post-curing, now that the magnetic optically variable pigment is pre-dispersed in the microcavity, it is only necessary to transfer the required shape to the required carrier by hot stamping or film pasting, and then orient it through an independent magnetic orientation unit, and finally irradiate and cure it. However, with the original silk screen printing, pre-curing, and post-curing system, each unit must be connected and arranged, and delicate and continuous coordination is required. The residual ink of the printing unit needs to be processed later, and the preparation, operation, and subsequent cleaning are very complicated and cumbersome. With the optical anti-counterfeiting element in the present invention, since the magnetic optically variable pigment has been pre-sealed in the microcavity, it is very easy to handle, and each link is independent and does not need to be connected in series, which brings great convenience to preparation, operation, and cleaning.

[0068] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A magnetically responsive optical anti-counterfeiting element, characterized in that: The magnetically responsive optical anti-counterfeiting element includes a substrate layer and a microstructure forming layer on the substrate layer, the microstructure forming layer contains a microcavity, the microcavity contains magnetic pigment flakes, the magnetic pigment flakes can move in the microcavity and can be reversibly oriented by an external magnetic field, the magnetic pigment flakes are curved and / or the microcavity contains secondary microstructures, and the magnetically responsive optical anti-counterfeiting element also includes a sealing layer, which is used to enclose the magnetic pigment flakes in the microcavity.

2. The magnetically responsive optical anti-counterfeiting element according to claim 1, characterized in that: The microcavity is filled with a dispersion medium; And / or, the magnetic pigment flake is a magnetic optically variable pigment flake.

3. The magnetically responsive optical anti-counterfeiting element according to claim 2, characterized in that: The dispersion medium is gas, liquid and gel; And / or, the dispersion medium is fully transparent or partially transparent; And / or, the dispersion medium forms a solid by external stimulation.

4. The magnetically responsive optical anti-counterfeiting element according to any one of claims 1 to 3, characterized in that: The dimensions of the microcavity in two directions in the horizontal plane are 10-500 μm; and / or, the height of the microcavity is less than 100 μm; And / or, the height of the secondary microstructure is smaller than the height of the microcavity.

5. The magnetically responsive optical anti-counterfeiting element according to any one of claims 1 to 4, characterized in that: The microcavities are distributed in one dimension or / and two dimensions; And / or, the secondary microstructure is distributed in one dimension or / and two dimension.

6. The magnetically responsive optical anti-counterfeiting element according to any one of claims 1 to 5, characterized in that: The two sides of the magnetic pigment sheet have the same color; And / or, the curved magnetic pigment flakes are obtained by attaching materials or material stacks with different stresses on both sides; And / or, the curved magnetic pigment flakes are obtained by arranging different stress materials on both sides of the magnetic layer in the Fabry-Perot interference cavity structure.

7. The magnetically responsive optical anti-counterfeiting element according to any one of claims 1 to 6, characterized in that: The magnetically responsive optical anti-counterfeiting element further comprises a functional coating.

8. The magnetically responsive optical anti-counterfeiting element according to claim 7, characterized in that: The functional coating comprises a protective layer for providing protection for the anti-counterfeiting element, an adhesive layer for providing adhesion with the substrate layer, a hot stamping layer for hot stamping, and a peeling layer for transfer.

9. A method for manufacturing a magnetically responsive optical anti-counterfeiting element according to any one of claims 1 to 8, characterized in that: include: A microstructure forming layer having open microcavities is formed by molding on the substrate layer; Filling the microcavity with magnetic pigment flakes; The top of the microcavity is sealed with a sealing material to form a sealing layer; The magnetic pigment flakes are curved and / or contain secondary microstructures in the microcavities.

10. The method for manufacturing a magnetically responsive optical anti-counterfeiting element according to claim 9, characterized in that: The molding is heat molding and / or UV molding; And / or, the magnetically responsive optical anti-counterfeiting element is further provided with a composite functional coating.

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