Optical security document and method for producing same

Abstract

This invention relates to the field of optical anti-counterfeiting technology, and discloses an optical anti-counterfeiting document and its preparation method. The optical anti-counterfeiting document includes: a substrate, an undulating structure layer, and a first ink layer, a reflective layer, and a second ink layer sequentially disposed in a first region. The undulating structure layer is disposed on one side surface of the substrate, including a first region having a first microstructure. The first ink layer and the second ink layer have different color characteristics. The first ink layer is disposed closer to the undulating structure layer than the reflective layer. The first ink layer, the reflective layer, and the second ink layer correspond to the projection of the first microstructure onto the surface of the undulating structure layer. The optical anti-counterfeiting document of this invention exhibits different high-chroma visual effects when viewed from both sides, without affecting identification, thus ensuring both anti-counterfeiting effectiveness and aesthetic appeal.

Description

Technical Field

[0001] This invention relates to the field of optical anti-counterfeiting technology, specifically to optical anti-counterfeiting documents and their preparation methods. Background Technology

[0002] To prevent counterfeiting through scanning and photocopying, optical anti-counterfeiting technologies are widely used in various high-security or high-value-added printed materials such as banknotes, credit cards, passports, securities, and product packaging. Among various optical anti-counterfeiting technologies, microstructures with diffraction and non-diffraction effects are widely used due to their high brightness and obvious dynamic effects. Currently, the most widely used optical anti-counterfeiting technology applied to optical thin films—holography—is an optical technology developed using the diffraction effects formed by microstructures.

[0003] One important method for implementing banknote security features is to apply a security stripe onto the banknote substrate using hot stamping, with the unprocessed side serving as the viewing side. The security stripe area is typically large. To achieve a good visual effect, a specific, error-free local removal of the reflective layer is generally performed. This ensures that the remaining reflective layer and the microstructure holographic image are perfectly aligned, creating a perforated feature and improving the quality of the holographic product. In recent years, optical security products with window structures, allowing observation from both sides and even through transmission, have been widely used. These products offer different visual effects on each side, significantly enhancing their anti-counterfeiting capabilities.

[0004] However, current optical anti-counterfeiting documents with dual-sided visual effects typically form anti-counterfeiting features on both sides of the substrate. This means different anti-counterfeiting microstructures are formed on the front and back of the document. For example, different microstructures can be formed, or different reflective coatings, such as aluminum, can be precisely aligned on the microstructures to enhance image brightness. However, preparing anti-counterfeiting microstructures on both sides carries the risk of mutual interference in the manufacturing process, which can negatively impact the accuracy of the anti-counterfeiting feature formation. Furthermore, the color effects of anti-counterfeiting features based on metal reflective layers and optical microstructures are relatively monotonous, limiting the overall appearance and anti-counterfeiting effectiveness of optical anti-counterfeiting documents. Summary of the Invention

[0005] In view of this, the present invention provides an optical anti-counterfeiting document and its preparation method to solve the problems that the accuracy of the anti-counterfeiting feature forming of existing optical anti-counterfeiting documents is difficult to guarantee, and the color effect of anti-counterfeiting features based on metal reflective layers and optical microstructures is relatively monotonous, resulting in limited appearance and anti-counterfeiting effect of optical anti-counterfeiting documents.

[0006] In a first aspect, the present invention provides an optical anti-counterfeiting document, comprising: a substrate, an undulating structure layer, and a first ink layer, a reflective layer, and a second ink layer sequentially disposed on a first region of the undulating structure layer. The undulating structure layer is disposed on one side surface of the substrate, and the undulating structure layer has a first region with a first microstructure. The first ink layer and the second ink layer have different color characteristics. The first ink layer is disposed closer to the undulating structure layer than the reflective layer. The projections of the first ink layer, the reflective layer, and the second ink layer onto the surface of the undulating structure layer correspond to the projections of the first microstructure onto the surface of the undulating structure layer.

[0007] Beneficial Effects: The optical anti-counterfeiting document of the present invention features a precisely aligned first ink layer, a reflective layer, and a second ink layer, formed on a first microstructure on the upper surface of the first region of the undulating structure layer. The lower surface of the optical anti-counterfeiting document does not have specific anti-counterfeiting features, facilitating strict alignment between the first and second ink layers and the first microstructure. That is, due to the strict alignment of the first and second ink layers and the isolation provided by the reflective layer, although the first and second ink layers are located on one side of the optical anti-counterfeiting document, they are independent of each other. The reflective layer enhances image brightness, so the high-chroma color features of the second ink layer are not visible from the substrate side, nor are the high-chroma color features of the first ink layer visible from the undulating structure layer side. Observers experience different high-chroma visual effects when viewing from either side, and identification remains unaffected, ensuring both anti-counterfeiting and aesthetic effects.

[0008] In one alternative embodiment, the first ink layer is conformally coated on the first microstructure.

[0009] Beneficial effects: The first ink layer and the first microstructure are basically the same shape, that is, the first ink layer and the first microstructure have the same shape. The first ink layer is uniformly covered along the upper surface of the first microstructure to ensure the clear presentation of the optical effect of the first microstructure when observed from the side of the substrate, thereby providing an optical effect of precise combination of the first ink layer and the first microstructure, and also providing a basis for the formation of the reflective layer and the second ink layer.

[0010] In one alternative embodiment, both the first ink layer and the second ink layer are semi-transparent layers.

[0011] Beneficial effect: Both the first ink layer and the second ink layer are semi-transparent layers, so that the high brightness of the reflective layer can be displayed on both sides of the optical anti-counterfeiting document through the first ink layer and the second ink layer.

[0012] In one optional embodiment, the first ink layer is an alkali-soluble or acid-soluble material, and the weight range of the first ink layer on the first microstructure is 0.1 g / m². 2 ~0.5g / m 2 .

[0013] Beneficial effects: The first ink layer is made of alkali-soluble or acid-soluble material so that excess first ink layer can be removed in subsequent cutout processes; the weight range of the first ink layer on the first microstructure is 0.1g / m2 to 0.5g / m2. Within this range, the first ink layer can ensure both conformal coverage with the first microstructure and sufficient high color saturation features.

[0014] In one optional embodiment, the second ink layer is an acid-resistant or alkali-resistant material, and the weight range of the second ink layer on the reflective layer is 0.2 g / m². 2 ~1g / m 2 .

[0015] Beneficial effects: The second ink layer should be an alkali or acid-resistant material, which not only provides high-saturation color but also protects the reflective layer on the first area during subsequent cutout processes, such as removing excess portions in the second area, to avoid damage to the reflective layer caused by localized removal processes. The weight range of the second ink layer on the reflective layer is 0.2 g / m². 2 ~1g / m 2 This ensures that the reflective layer in the first region is protected, but not that it provides protection for the excess reflective layer in the second region.

[0016] In one optional embodiment, the second ink layer includes a protective sublayer and a color sublayer. The protective sublayer is disposed on the side of the reflective layer relative to the color sublayer. The protective sublayer is made of an acid-resistant or alkali-resistant material, and the weight of the protective sublayer on the reflective layer ranges from 0.2 g / m². 2 ~1g / m 2 .

[0017] Beneficial effects: The second ink layer is designed as a dual-layer material, with a protective sublayer and a color sublayer respectively responsible for protection and color characteristics. The protective sublayer is made of alkali or acid-resistant material, possessing sufficient damage resistance. This dual-layer design simplifies the formulation of the second ink layer, eliminating the need to simultaneously consider both color characteristics and acid / alkali resistance.

[0018] In one optional embodiment, the undulating structure layer further includes a second region having a second microstructure; the specific volume of the first microstructure is smaller than the specific volume of the second microstructure; the specific volume of the first microstructure is in the range of 0 μm. 3 / μm 2 ~1μm 3 / μm 2 The specific volume range of the second microstructure is 0.4 μm. 3 / μm 2 ~2μm 3 / μm 2 .

[0019] Beneficial effects: Setting the specific volume of the first microstructure to be smaller than that of the second microstructure helps to remove the reflective layer and excess first and second ink layers in the second region in subsequent steps. Even if the first and second ink layers form excess portions on the second microstructure due to process errors, the minimum thickness of the second ink layer on the second microstructure in this excess coating area (generally located at the top of the second microstructure) will be smaller than the minimum thickness of the second ink layer on the first microstructure in the first region. It is easier to be penetrated and react with the reflective layer. Therefore, the protective effect of the reflective layer below the second ink layer that is mistakenly coated in the second region is poor, which helps to achieve accurate preservation of the reflective layer on the first microstructure.

[0020] In one alternative embodiment, the first microstructure includes a linear structure or a dot structure, wherein the width of the linear structure is less than 100 μm and the diameter of the dot structure is less than 100 μm.

[0021] Beneficial effects: The present invention sets the image line size of the first microstructure to be less than 100μm in each step of the molding process. That is, when the first microstructure is molded using a line structure, the width of the line structure is less than 100μm, and when a dot structure is used, the diameter of the dot structure is less than 100μm. This facilitates the subsequent combination with the reflective layer, the first ink layer and the second ink layer to form a high-precision and difficult-to-counterfeit anti-counterfeiting feature.

[0022] Secondly, the present invention also provides a method for preparing an optical anti-counterfeiting document, for preparing the above-mentioned optical anti-counterfeiting document, comprising:

[0023] An undulating structure layer is formed on one side surface of the substrate, the undulating structure layer having a first region, the first region having a first microstructure;

[0024] A first ink layer, a reflective layer, and a second ink layer are sequentially formed on a first region of the undulating structure layer. The first ink layer is positioned close to the undulating structure layer relative to the reflective layer. The first ink layer, the reflective layer, and the second ink layer correspond to the projection of the first microstructure onto the surface of the undulating structure layer.

[0025] Beneficial Effects: The method for preparing optical anti-counterfeiting documents of the present invention enables precise alignment of the first ink layer, the reflective layer, and the second ink layer. The first microstructure, formed on the upper surface of the first region of the undulating structure layer, is processed on the lower surface of the optical anti-counterfeiting document without specific anti-counterfeiting features, facilitating strict alignment of the first and second ink layers with the first microstructure. That is, due to the strict alignment of the first and second ink layers and the isolation of the reflective layer, although the first and second ink layers are located on one side of the optical anti-counterfeiting document, they are independent of each other. Furthermore, the reflective layer enhances image brightness, so the high-chroma color features of the second ink layer are not visible from the substrate side, nor are the high-chroma color features of the first ink layer visible from the undulating structure layer side. Observers experience different high-chroma visual effects when viewing from both sides, and identification remains unaffected, ensuring both anti-counterfeiting and aesthetic effects.

[0026] In one optional embodiment, the undulating structure layer further includes a second region having a second microstructure; a first ink layer, a reflective layer, and a second ink layer are sequentially formed on the first region of the undulating structure layer, including:

[0027] An initial first ink layer is formed on the undulating structure layer, and the initial first ink layer at least isomorphically covers the first microstructure;

[0028] An initial reflective layer is formed on the surface of the undulating structure layer facing away from the substrate, and the initial reflective layer covers the initial first ink layer;

[0029] An initial second ink layer is formed on the initial reflective layer, the initial second ink layer at least covers the first microstructure, and the minimum thickness of the initial second ink layer on the first microstructure is greater than the minimum thickness of the initial second ink layer on the second microstructure;

[0030] Remove the initial first ink layer, initial reflective layer and initial second ink layer on the second microstructure, and retain the first ink layer, initial reflective layer and second ink layer on the first microstructure to obtain the first ink layer, reflective layer and second ink layer located on the first microstructure.

[0031] Beneficial effects: By forming an initial first ink layer and an initial second ink layer in an area slightly larger than the first region, and forming an initial reflective layer across the entire surface, it is helpful to accurately remove excess initial first ink layer, initial reflective layer, and initial second ink layer in the atmosphere, thereby forming a first ink layer, a second ink layer, and a reflective layer precisely set on the first microstructure, achieving the presentation of different optical effects on both sides of the optical anti-counterfeiting document, thereby improving the optical anti-counterfeiting effect. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of the optical anti-counterfeiting document according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the optical anti-counterfeiting document on one side of the front according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the optical anti-counterfeiting document on one side of the back of an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of an optical anti-counterfeiting document with an auxiliary functional layer according to an embodiment of the present invention;

[0037] Figure 5 This is a flowchart of the method for preparing optical anti-counterfeiting documents according to an embodiment of the present invention;

[0038] Figure 6 This is a schematic diagram of the substrate and the undulating structure layer according to an embodiment of the present invention;

[0039] Figure 7 This is a flowchart illustrating the formation of the first ink layer, the reflective layer, and the second ink layer in the optical anti-counterfeiting document of this invention.

[0040] Figure 8 This is a schematic diagram of the structure after the initial first ink layer is set on the undulating structure layer according to an embodiment of the present invention;

[0041] Figure 9 This is a schematic diagram of the structure after the initial reflective layer is set on the undulating structure layer according to an embodiment of the present invention;

[0042] Figure 10 This is a schematic diagram of the structure after the initial second ink layer is set on the reflective layer according to an embodiment of the present invention.

[0043] Explanation of reference numerals in the attached figures:

[0044] a) First region; a1) First sub-region; a2) Second sub-region; b) Second region;

[0045] 1. Substrate;

[0046] 2. Undulating structural layer; 21. First microstructure; 22. Second microstructure;

[0047] 3. First ink layer; 30. Initial first ink layer;

[0048] 4. Reflective layer; 40. Initial reflective layer;

[0049] 5. Second ink layer; 50. Initial second ink layer;

[0050] 6. Auxiliary function layer. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the drawings, not all structures. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concept of the invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, and some details are enlarged for clarity, and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from actual practices due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if one layer / component is "above" another layer / component in one orientation, then when the orientation is reversed, that layer / component can be "below" that other layer / component.

[0052] In related technologies, optical anti-counterfeiting documents with dual-sided visual effects involve forming anti-counterfeiting structures on both sides of the substrate. This can be achieved by creating different microstructures or precisely aligning different reflective coatings on the microstructures, using metals such as aluminum as reflective layers to enhance image brightness. However, preparing anti-counterfeiting microstructures on both sides carries the risk of mutual interference in the manufacturing process, which can negatively impact the accuracy of anti-counterfeiting feature formation. Furthermore, the presentation of anti-counterfeiting features based on metal reflective layers and optical microstructures is relatively monotonous, limiting the appearance and anti-counterfeiting effectiveness of optical anti-counterfeiting products.

[0053] Based on this, the present invention provides an optical anti-counterfeiting document in which the metal reflective layer and the optical microstructure are precisely hollowed out without error. On both sides of the reflective layer set on one side of the optical anti-counterfeiting document, a specific high-chroma ink layer is superimposed to form an optical anti-counterfeiting feature in which the structural layer is set on one side but has different color visual effects when viewed from both sides, effectively improving the appearance and anti-counterfeiting effect of the anti-counterfeiting product.

[0054] like Figure 1 As shown, this embodiment provides an optical anti-counterfeiting document, including: a substrate 1, an undulating structure layer 2, and a first ink layer 3, a reflective layer 4, and a second ink layer 5 sequentially disposed on a first region a of the undulating structure layer 2. The undulating structure layer 2 is disposed on one side surface of the substrate 1, and the undulating structure layer 2 has a first region a, the first region a having a first microstructure 21; the first ink layer 3 and the second ink layer 5 have different color characteristics, the first ink layer 3 is disposed close to the undulating structure layer 2 relative to the reflective layer 4, and the projections of the first ink layer 3, the reflective layer 4, and the second ink layer 5 correspond to the projections of the first microstructure 21 on the surface of the undulating structure layer 2.

[0055] Specifically, the substrate 1 can be partially transparent, a colored dielectric layer, a transparent dielectric film with a functional coating on its surface, or a multilayer film formed by lamination. The substrate 1 is generally formed from a thin film material with good physicochemical resistance and high mechanical strength; in this embodiment, PET material is preferred. The undulating structure layer 2 forms a first microstructure 21 on a portion of its surface away from the substrate 1. The first microstructure 21 has a different specific volume than other areas of the surface of the undulating structure layer 2. Specifically, the specific volume refers to the ratio of the volume of liquid exactly filling the recessed area of ​​the undulating microstructure to its projected area when the optical anti-counterfeiting element is placed horizontally, expressed in μm. 3 / μm 2 For example, a structure with a completely flat and uniform surface has a specific volume of zero. A first ink layer 3, a reflective layer 4, and a second ink layer 5 are sequentially stacked on the surface of the first microstructure 21 in the first region a. The reflective layer 4 can be made of one or more of aluminum, silver, copper, tin, chromium, nickel, titanium, or their alloys, or a multilayer interference optical variable coating. Since aluminum is inexpensive and easily removed by chemical etching, it is preferred in this embodiment. The thickness of the aluminum reflective layer 4 is generally 20nm-50nm. When observed from the substrate 1 side, an observer can see the optical effect of the first microstructure 21, located precisely in the first region a, with the high-chroma color of the first ink layer 3, such as red. Figure 2 The recessed relief effect shown; when viewed from the side opposite to the substrate 1 (i.e., the side where the undulating structure layer 2 is located), the optical effect of the first microstructure 21 with the high-chroma second ink layer 5 color, strictly located in the first region a, can be seen, for example, yellow. Figure 3The raised relief effect shown (specific color features are not illustrated in the figure), that is, the optical effects of depression and convexity, are presented by the same microstructure, such as a Fresnel relief structure, only naturally different when viewed from both sides. Due to the presence of the high-brightness reflective layer 4, the relief of the letter "O" in the first area a has a strong metallic texture when viewed from both sides; in addition, when viewed through the light in the second area b, since the second area b does not have the reflective layer 4 and the ink layer, it has a hollowed-out feature.

[0056] In this embodiment of the optical anti-counterfeiting document, the first ink layer 3, the reflective layer 4, and the second ink layer 5 are precisely aligned and formed on the first microstructure 21 on the upper surface of the first region a of the undulating structure layer 2. The lower surface of the optical anti-counterfeiting document does not have specific anti-counterfeiting features, facilitating the strict alignment of the first ink layer 3 and the second ink layer 5 with the first microstructure 21. That is, due to the strict alignment of the first ink layer 3 and the second ink layer 5 and the isolation by the reflective layer 4, although the first ink layer 3 and the second ink layer 5 are located on one side of the optical anti-counterfeiting document, they are independent of each other. Furthermore, the reflective layer 4 enhances image brightness, so the high-chroma color features of the second ink layer 5 are not visible from the substrate 1 side, nor are the high-chroma color features of the first ink layer 3 visible from the undulating structure layer 2 side. Observers experience different high-chroma visual effects when viewing from both sides, and identification remains unaffected, ensuring both anti-counterfeiting and aesthetic effects.

[0057] In this embodiment, the region of the undulating structure layer 2 other than the first region a is referred to as the second region b. The second region b has a second microstructure 22, and the first microstructure 21 and the second microstructure 22 have different surface features.

[0058] In one embodiment, the optical features exhibited by the first microstructure 21 and the second microstructure 22 include rainbow holography, embossing, scaling, scrolling, etc. In practical applications, different surface features result in different applicable ranges. For example, interference is attenuated in parts with the first ink layer 3, making a full rainbow system unsuitable. The first microstructure 21 or the second microstructure 22, depending on the desired optical features, can be a periodic structure or an aperiodic structure, or a combination of periodic and aperiodic structures. Their cross-sectional structure along the extension direction can be a sinusoidal structure, a rectangular grating structure, a trapezoidal grating structure, a blazed grating structure, an arc grating structure, or a combination of at least two structures. Specifically, the first microstructure 21 can be selected from a flat structure, i.e., a structure with zero specific volume. The second microstructure 22, only required for hollowing out, can be set as a relatively simple structure, such as a one-dimensional sawtooth grating structure.

[0059] In one embodiment, the first ink layer 3 is conformally covered on the first microstructure 21. Specifically, the first ink layer 3 and the first microstructure 21 are substantially conformally covered, that is, the first ink layer 3 and the first microstructure 21 have the same shape. The first ink layer 3 is uniformly covered along the upper surface of the first microstructure 21 to ensure a clear presentation of the optical effect of the first microstructure 21 when observed from the side of the substrate 1, thereby providing an optical effect of precise bonding between the first ink layer 3 and the first microstructure 21, and also providing a basis for the formation of the reflective layer 4 and the second ink layer 5.

[0060] In one embodiment, both the first ink layer 3 and the second ink layer 5 are semi-transparent layers, so that the high-brightness properties of the reflective layer 4 can be observed on both sides of the optical anti-counterfeiting document when the first ink layer 3 and the second ink layer 5 are transmitted through them. In this embodiment, the transmittance of the first ink layer 3 and the second ink layer 5 to visible light is 20-40%.

[0061] Since the first ink layer 3 conformally covers the first microstructure 21, it is required that the first ink layer 3 be as thin as possible; the thinner the first ink layer 3, the better the conformal coverage. Simultaneously, to ensure high color saturation, the first ink layer 3 must also maintain a certain thickness. Therefore, in this embodiment, the first ink layer 3 is an alkali-soluble or acid-soluble material, so that excess first ink layer 3 can be removed in subsequent cutout processes, such as excess material coated on the second region b due to process precision requirements. In this embodiment, the binder of the first ink layer 3, excluding the solid ink component, is an alkali-soluble acrylic resin. The weight range of the first ink layer 3 on the first microstructure 21 is 0.1 g / m³. 2 ~0.5g / m 2 Within this range, the first ink layer 3 ensures both conformal coverage with the first microstructure 21 and sufficient high chroma characteristics. In this embodiment, the first ink layer 3 is generally formed by a wet coating process. That is, the first ink layer 3 is liquid before molding, and after being printed onto the undulating structure layer 2, it is dried. After the material of the first ink layer 3 loses its volatile components, the solid ink components will solidify and shape along the shape of the corresponding undulating structure layer 2, ultimately forming the first ink layer 3. The wet coating amount of the first ink layer 3 when it is coated and molded on the first microstructure 21 is 1g / m². 2 The dry weight, i.e., the weight mentioned above, is preferably 0.2 g / m³. 2 This further requires that the liquid ink solids content be very low before the first ink layer 3 is wet-coated, for example, less than 15%, or even less than 10%.

[0062] As an optional implementation, the second ink layer 5 is an acid-resistant or alkali-resistant material, and the weight range of the second ink layer 5 on the reflective layer 4 is 0.2 g / m². 2 ~1g / m 2 .

[0063] Specifically, the reflective layer 4 is made of aluminum or aluminum alloy, which is easy to manufacture industrially and has low cost. The process involves removing the reflective layer 4 located in the second region b while retaining the reflective layer 4 located in the first region a, and precisely forming the first ink layer 3, reflective layer 4, and second ink layer 5 in the first region a, which precisely correspond to the first microstructure 21. This cutout process can use common acids or alkalis. In this embodiment, the second ink layer 5 not only provides high-saturation color but also protects the reflective layer 4 in the first region a during subsequent cutout processes, such as removing excess portions in the second region b, to avoid damage to the reflective layer 4 from localized removal processes. Therefore, if the reflective layer 4 is made of aluminum or aluminum alloy, and the corrosive atmosphere used in the removal process is acid or alkali, the second ink layer 5 should be an alkali- or acid-resistant material. Furthermore, since the second ink layer 5 needs to serve as a protective layer for error-free, precise cutout, the amount applied should ensure sufficient protection for the reflective layer 4 in the first region a but not for the excess reflective layer 4 in the second region b. Generally, the weight range of the second ink layer 5 on the reflective layer 4 is 0.2 g / m². 2 ~1g / m 2 It should be noted that the reflective layer 4 removed here is initially formed on the entire upper surface of the undulating structure layer 2 before removal. Furthermore, since the second ink layer 5 needs to serve as a protective layer for precise, error-free cutouts, its application amount should ensure protection for the reflective layer 4 in the first region a but not for the reflective layer 4 in the second region b. That is, the minimum thickness of the second ink layer 5 on the reflective layer 4 in the first region a is significantly greater than the minimum thickness on the reflective layer 4 in the second region b. In this embodiment, the dry coating amount of the second ink layer 5 after forming is preferably 0.5 g / m². 2 The binder is a polyurethane resin with good acid and alkali resistance.

[0064] As another optional implementation, the second ink layer 5 includes a protective sublayer and a color sublayer. The protective sublayer is disposed on the side of the reflective layer 4 relative to the color sublayer. The protective sublayer is made of an acid-resistant or alkali-resistant material, and the weight of the protective sublayer on the reflective layer ranges from 0.2 g / m². 2 ~1g / m 2 .

[0065] That is, the second ink layer 5 can also be a dual-layer material, including a protective sublayer and a color sublayer, which respectively carry the protective function and the color feature. The protective sublayer is an alkali or acid-resistant material with sufficient damage resistance. This dual-layer design helps simplify the formulation of the second ink layer 5, eliminating the need to simultaneously consider color features and acid / alkali resistance. In this embodiment, the protective sublayer and color sublayer need to be limited so that the color sublayer is located on the outside. If the color sublayer is applied to the reflective layer 4 first, followed by the protective sublayer, the excess color sublayer applied to the second region b will further planarize the second microstructure 22, thereby strengthening the protection of the reflective layer 4 and the first ink layer 3 in that region, increasing the difficulty of precise cutout. Therefore, the protective sublayer should be applied to the reflective layer 4 first, followed by the color sublayer, i.e., the protective sublayer is located between the reflective layer 4 and the color sublayer. The amount of the protective sublayer applied is within the range of 0.2 g / m². 2 ~1g / m 2 Specifically, in this embodiment, the dry coating amount after the protective sublayer is formed is preferably 0.5 g / m². 2 The binder in the first ink layer 3, excluding the solid ink components, is a polyurethane resin with good acid and alkali resistance. Additionally, it should be noted that the color sublayer should not provide protection to the reflective layer 4 in alkaline or acidic corrosive atmospheres, but it also should not be dissolved. The color sublayer only provides color functionality; it only needs to meet the color requirements of the product, and its thickness is not overly restricted. Specifically, in this embodiment, the dry coating weight of the color sublayer after molding is 1 g / m². 2 The binder is a polyurethane resin with poor acid and alkali resistance; it should be noted that poor acid and alkali resistance here means that it cannot protect the reflective layer 4, not that it is dissolved by acid or alkali itself.

[0066] Based on the above scheme, the specific volume of the first microstructure 21 is smaller than that of the second microstructure 22; the specific volume range of the first microstructure 21 is 0 μm. 3 / μm 2 ~1μm 3 / μm 2 The specific volume range of the second microstructure 22 is 0.4 μm. 3 / μm 2 ~2μm 3 / μm 2 .

[0067] In this embodiment, the specific volume of the first microstructure 21 is set to be smaller than that of the second microstructure 22. This helps to remove the reflective layer 4 located in the second region b and the excess first ink layer 3 and second ink layer 5 in subsequent steps. Even if the first ink layer 3 and the second ink layer 5 form excess parts on the second microstructure layer due to process errors, the minimum thickness of the second ink layer 5 on the second microstructure 22 in this excess coating area (generally located at the top of the second microstructure 22) will be smaller than the minimum thickness of the second ink layer 5 on the first microstructure 21 in the first region a. It is easy to be penetrated and reflect the reflective layer 4. Therefore, the protective effect of the reflective layer 4 below the second ink layer 5 that is mistakenly coated in the second region b is poor, which helps to achieve the accurate preservation of the reflective layer 4 on the first microstructure 21.

[0068] The morphology and specific structural parameters of the first microstructure 21 and the second microstructure 22 are set according to the desired optical effect. For example, in this embodiment, the first microstructure 21 is an embossed optical microstructure with a Fresnel grating structure in cross-section, a width ranging from 5μm to 15μm, and a specific volume of approximately 0.5μm. 3 / μm 2 The second microstructure 22 is a hollow, transparent optical microstructure with a relatively simple design. For example, its cross-section can be a one-dimensional sinusoidal grating structure with a specific volume of approximately 1 μm. 3 / μm 2 .

[0069] In one embodiment, the first microstructure 21 includes a linear structure or a dot structure, wherein the width of the linear structure is less than 100 μm and the diameter of the dot structure is less than 100 μm.

[0070] In this embodiment, the image line size of the first microstructure 21 at each step of the forming process is less than 100μm. That is, when the first microstructure 21 is formed using a line structure, the width of the line structure is less than 100μm, and when it is formed using a dot structure, the diameter of the dot structure is less than 100μm. This is to facilitate the subsequent combination with the reflective layer 4, the first ink layer 3, and the second ink layer 5 to form a high-precision, difficult-to-counterfeit anti-counterfeiting feature.

[0071] In addition, such as Figure 4 As shown, in one embodiment, the optical anti-counterfeiting document further includes an auxiliary functional layer 6 and a release layer. The auxiliary functional layer 6 is formed on the side of the undulating structure layer 2 opposite to the substrate 1, and the auxiliary functional layer 6 covers the protective layer and the exposed second microstructure 22. The release layer is formed between the substrate 1 and the undulating structure layer 2.

[0072] The auxiliary functional layer 6 helps to realize other optical anti-counterfeiting functions or other auxiliary functions, such as forming an adhesive layer to achieve the adhesion and fixation of the optical anti-counterfeiting document to the terminal product; the peeling layer is used to achieve the separation of the substrate 1 and the undulating structure layer 2 when finally bonded to the terminal product. After the substrate 1 is separated, the other plating / coating structures of the optical anti-counterfeiting document bonded to the terminal product are very thin, making it difficult for counterfeiters to remove them from the terminal product for reuse, thus playing a role in preventing tampering.

[0073] In this embodiment, the substrate 1 can be understood as a carrier that carries optical anti-counterfeiting elements including the undulating structure layer 2, the first ink layer 3, the reflective layer 4, the second ink layer 5, and the auxiliary functional layer 6. Alternatively, the substrate 1 can be understood as the target object of the optical anti-counterfeiting elements, and the substrate 1 and the optical anti-counterfeiting elements ultimately constitute optical anti-counterfeiting documents such as banknotes and securities.

[0074] The optical anti-counterfeiting elements in this embodiment can be optical anti-counterfeiting products such as windowed security threads, labels, markings, wide stripes, transparent windows, and coatings. Optical anti-counterfeiting documents with windowed security threads or wide stripes can be used for anti-counterfeiting of various high-security products such as banknotes, passports, and securities.

[0075] refer to Figures 1 to 10 This embodiment also provides a method for preparing optical anti-counterfeiting documents, used to prepare the aforementioned optical anti-counterfeiting documents. Figure 5 The flowchart shows a method for preparing optical anti-counterfeiting documents. The method includes the following steps:

[0076] Step S501: An undulating structure layer 2 is formed on one side surface of the substrate 1. The undulating structure layer 2 has a first region a and the first region a has a first microstructure 21.

[0077] refer to Figure 6 For example, the substrate 1 can be partially transparent, a colored dielectric layer, a transparent dielectric film with a functional coating on its surface, or a multilayer film formed by lamination. The substrate 1 is generally formed of a film material with good physical and chemical resistance and high mechanical strength. For example, it can be formed of plastic films such as polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, or polypropylene (PP) film. In this embodiment, the substrate 1 is preferably formed of PET material.

[0078] The undulating structure layer 2 can be mass-produced through processing methods such as ultraviolet casting, molding, and nanoimprinting. For example, the undulating structure layer 2 is formed from thermoplastic resin using a molding process, where thermoplastic resin is pre-printed onto the substrate 1, and then softened and deformed by heat when passing through a high-temperature metal mold, thus forming a specific undulating structure. The undulating structure layer 2 is then cooled and solidified. Alternatively, the undulating structure layer 2 can be formed using a radiation-cured casting process, where radiation-cured resin is printed onto the substrate 1, and a template is pressed onto the radiation-cured resin while being irradiated with ultraviolet light or an electron beam to cure the resin material. Finally, the template is removed to form the undulating structure layer 2. The undulating structure layer 2 forms a first microstructure 21 and other types of microstructures in other regions on the surface away from the substrate 1. For example, in this embodiment, a second microstructure 22 is formed in a second region b outside the first region a, and the specific volume of the first microstructure 21 is set to be smaller than that of the second microstructure 22. In this way, after the second ink layer 5 is formed on the reflective layer 4 in the subsequent steps, the minimum thickness of the second ink layer 5 on the second microstructure 22 in the second region b (generally located at the top of the second microstructure 22) will be smaller than the minimum thickness of the second ink layer 5 on the first microstructure 21 in the first region a. Therefore, the second ink layer 5 that is misapplied in the second region b has a poorer protective effect on the reflective layer 4, which helps to achieve accurate retention of the reflective layer 4, the first ink layer 3 and the second ink layer 5 on the first microstructure 21.

[0079] In step S502, a first ink layer 3, a reflective layer 4, and a second ink layer 5 are sequentially formed on the first region a of the undulating structure layer 2. The first ink layer 3 is positioned close to the undulating structure layer 2 relative to the reflective layer 4. The first ink layer 3, the reflective layer 4, and the second ink layer 5 correspond to the projection of the first microstructure 21 on the surface of the undulating structure layer 2.

[0080] A first ink layer 3, a reflective layer 4, and a second ink layer 5 are sequentially stacked on the upper surface of the first microstructure 21 in the first region a. When viewed from the substrate 1 side, an observer can see the optical effect of the first microstructure 21, which is precisely located in the first region a and has a high-chroma first ink layer 3 color, such as red. Figure 2 The recessed relief effect shown; when viewed from the side opposite to the substrate 1 (i.e., the side where the undulating structure layer 2 is located), the optical effect of the first microstructure 21 with the high-chroma second ink layer 5 color, strictly located in the first region a, can be seen, for example, yellow. Figure 3The raised relief effect shown (specific color features are not illustrated in the figure), that is, the optical effects of depression and convexity, are presented by the same microstructure, such as a Fresnel relief structure, only naturally different when viewed from both sides. Due to the presence of the high-brightness reflective layer 4, the relief of the letter "O" in the first area a has a strong metallic texture when viewed from both sides; in addition, when viewed through the light in the second area b, since the second area b does not have the reflective layer 4 and the ink layer, it has a hollowed-out feature.

[0081] In the optical anti-counterfeiting document preparation method of this embodiment, the first ink layer 3, the reflective layer 4, and the second ink layer 5 can achieve precise alignment. The first microstructure 21 formed on the upper surface of the first region a of the undulating structure layer 2, without specific anti-counterfeiting features on the lower surface of the optical anti-counterfeiting document, facilitates the strict alignment of the first ink layer 3 and the second ink layer 5 with the first microstructure 21. That is, due to the strict alignment of the first ink layer 3 and the second ink layer 5 and the isolation of the reflective layer 4, although the first ink layer 3 and the second ink layer 5 are set on one side of the optical anti-counterfeiting document, they are independent of each other. The reflective layer 4 enhances the image brightness, and the high chroma color features of the second ink layer 5 are not visible from the substrate 1 side, nor are the high chroma color features of the first ink layer 3 visible from the undulating structure layer 2 side. When the observer observes from both sides, there are different high chroma visual effects, and the recognition is not affected, thus ensuring the anti-counterfeiting effect and the appearance effect.

[0082] In this embodiment, the undulating structure layer 2 further includes a second region b, which has a second microstructure 22. Figure 7 The flowchart for step S502 above is as follows: Step S502, which involves sequentially forming a first ink layer 3, a reflective layer 4, and a second ink layer 5 on the first region a of the undulating structure layer 2, includes:

[0083] Step S5021: An initial first ink layer 30 is formed on the undulating structure layer 2, the initial first ink layer 30 at least isomorphically covering the first microstructure 21.

[0084] refer to Figure 8 An initial first ink layer 30 is formed on the upper surface of the first microstructure 21 in the first region a. Due to process errors, the initial first ink layer 30 will partially cover the edge of the second region b, which is adjacent to the first region a. That is, the initial first ink layer 30 covers... Figure 8The first sub-region a1 is defined as follows. Exemplarily, the initial first ink layer 30 is generally formed using a wet coating process. In terms of the forming area, it can be formed over the entire area of ​​the first sub-region a1, i.e., using a coating process, or it can be formed over a partial area of ​​the first sub-region a1, i.e., using a printing process. In terms of specific implementation techniques, various methods can be used, such as spraying, roller coating, spin coating, flexographic printing, gravure printing, and screen printing. This embodiment uses a partial printing process, i.e., forming the initial first ink layer 30 material on the first sub-region a1, which is slightly larger than the first region a. Before forming, the initial first ink layer 30 material is liquid, with a solid content generally between 5% and 30%. After being coated or printed onto the undulating structure layer 2, it is dried to lose volatile components. The solid components of the initial first ink layer 30 material then solidify and shape along the corresponding position of the undulating structure layer 2, thus forming the initial first ink layer 30.

[0085] In step S5022, an initial reflective layer 40 is formed on the surface of the undulating structure layer 2 facing away from the substrate 1, and the initial reflective layer 40 covers the initial first ink layer 30.

[0086] refer to Figure 9 For example, the initial reflective layer 40 is generally formed by vapor deposition, whereby the liquid material of the initial reflective layer 40 is uniformly and conformally deposited onto the full-width surface, meaning the initial reflective layer 40 covers the initial first ink layer 30. The initial reflective layer 40 comprises a metallic material or an alloy of metallic materials, including one or more of aluminum, silver, copper, tin, chromium, nickel, and titanium, to exhibit a metallic luster. Specifically, in this embodiment, aluminum or an aluminum alloy is preferred, as it is less expensive and easier to remove through chemical etching. The thickness of the aluminum layer is generally set to 20 nm-50 nm.

[0087] In step S5023, an initial second ink layer 50 is formed on the initial reflective layer 40. The initial second ink layer 50 at least covers the first microstructure 21, and the minimum thickness of the initial second ink layer 50 on the first microstructure 21 is greater than the minimum thickness of the initial second ink layer 50 on the second microstructure 22.

[0088] refer to Figure 10Similarly, the initial second ink layer 50 is generally formed using a wet coating process. In terms of the formation area, it can be formed over the entire area of ​​the first region a, i.e., a coating process; or it can be formed over a partial area of ​​the first region a, i.e., a printing process. In terms of specific implementation techniques, various methods can be used, such as spraying, roller coating, spin coating, flexographic printing, gravure printing, and screen printing. This embodiment specifically uses a partial printing process, meaning that due to process errors or for ease of processing, the initial second ink layer 50 material is formed on a second sub-region a2 that is slightly larger than the first region a. Before molding, the initial second ink layer 50 material is liquid, with a solid content generally of 10-30%. After being coated or printed onto the undulating structure layer 2, it is dried to lose volatile components, and the solid portion of the initial second ink layer 50 material solidifies and sets, forming the initial second ink layer 50. In this embodiment, the raw material for the initial second ink layer 50 is a water-based ink with a solid content of 15%.

[0089] Step S5024: Remove the initial first ink layer 30, initial reflective layer 40 and initial second ink layer 50 on the second microstructure 22, and retain the first ink layer 3, initial reflective layer 40 and second ink layer 5 on the first microstructure 21 to obtain the first ink layer 3, reflective layer 4 and second ink layer 5 located on the first microstructure 21.

[0090] For example, the aforementioned semi-finished product is placed in an atmosphere capable of reacting with the initial first ink layer 30 and the initial reflective layer 40 until the initial reflective layer 40 and the initial first ink layer 30 on the second region b are removed, and the initial second ink layer 50 in this region is also peeled off. Specifically, the minimum thickness of the protective initial second ink layer 50 on the initial reflective layer 40 in the first region a is significantly greater than the minimum thickness on the initial reflective layer 40 in the second region b. Thus, in a corrosive atmosphere capable of reacting with the materials of the initial first ink layer 30 and the initial reflective layer 40, the corrosive atmosphere reaches the underlying initial first ink layer 30 and the initial reflective layer 40 through the weak points of the initial second ink layer 50 material in the hollowed-out region (i.e., corresponding to the top of the microstructure), and corrodes them. After the initial first ink layer 30 and the initial reflective layer 40 are corroded and dissolved, the initial second ink layer 50 on them is also floated off. Simultaneously, the initial second ink layer 50 located in the first region a can effectively protect the initial reflective layer 40 beneath it, thus obtaining the reflective layer 4, the first ink layer 3, and the second ink layer 5 precisely located in the first region a. (Refer to...) Figure 1 .

[0091] Furthermore, the initial first ink layer 30 and the initial second ink layer 50 described above can be formed on different local areas, on the same local area, or across the entire width. The advantage of full-width formation is that it eliminates the need for complex registration, facilitating production implementation, while local area formation helps reduce the impact on ink in additional areas.

[0092] In one embodiment, after step S5024 described above, an auxiliary functional layer 6 is formed on the side of the undulating structure layer 2 facing away from the substrate 1, the auxiliary functional layer 6 covering the second ink layer 5 and the exposed second microstructure 22.

[0093] like Figure 4 As shown, the auxiliary functional layer 6 can be an inorganic or organic plating or coating to achieve additional optical anti-counterfeiting functions or other auxiliary functions, such as forming an adhesive layer to achieve the adhesion and fixation of the optical anti-counterfeiting document to the terminal product.

[0094] Furthermore, before setting the undulating structure layer 2 on the substrate 1, a release layer is also set on the surface of the substrate 1 so that the substrate 1 can be separated from the final product when finally bonded to the end product. After the substrate 1 is separated, the other plating / coating structures of the optical anti-counterfeiting document bonded to the end product are very thin, making it difficult for counterfeiters to remove them from the end product for reuse, thus playing a role in preventing tampering.

[0095] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0096] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0097] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An optical anti-counterfeiting document, characterized in that, include: Substrate; An undulating structure layer is disposed on one side surface of the substrate, the undulating structure layer having a first region having a first microstructure; A first ink layer, a reflective layer, and a second ink layer are sequentially disposed on a first region of the undulating structure layer. The first ink layer and the second ink layer have different color characteristics. The first ink layer is disposed close to the undulating structure layer relative to the reflective layer. The first ink layer, the reflective layer, and the second ink layer correspond to the projection of the first microstructure on the surface of the undulating structure layer.

2. The optical anti-counterfeiting document according to claim 1, characterized in that, The first ink layer is shaped to cover the first microstructure.

3. The optical anti-counterfeiting document according to claim 2, characterized in that, Both the first ink layer and the second ink layer are semi-transparent layers.

4. The optical anti-counterfeiting document according to claim 3, characterized in that, The first ink layer is an alkali-soluble or acid-soluble material, and the weight range of the first ink layer on the first microstructure is 0.1 g / m². 2 ~0.5g / m 2 .

5. The optical anti-counterfeiting document according to claim 4, characterized in that, The second ink layer is an acid-resistant or alkali-resistant material, and the weight range of the second ink layer on the reflective layer is 0.2 g / m². 2 ~1g / m 2 .

6. The optical anti-counterfeiting document according to claim 4, characterized in that, The second ink layer includes a protective sub-layer and a color sub-layer. The protective sub-layer is disposed on the side of the reflective layer opposite to the color sub-layer. The protective sub-layer is made of an acid-resistant or alkali-resistant material, and the weight range of the protective sub-layer on the reflective layer is 0.2 g / m². 2 ~1g / m 2 .

7. The optical anti-counterfeiting document according to any one of claims 1-6, characterized in that, The undulating structure layer further includes a second region having a second microstructure; The specific volume of the first microstructure is smaller than that of the second microstructure, and the specific volume of the first microstructure is in the range of 0 μm. 3 / μm 2 ~1μm 3 / μm 2 The specific volume range of the second microstructure is 0.4 μm. 3 / μm 2 ~2μm 3 / μm 2 .

8. The optical anti-counterfeiting document according to claim 7, characterized in that, The first microstructure includes a linear structure or a dot structure, wherein the width of the linear structure is less than 100 μm and the diameter of the dot structure is less than 100 μm.

9. A method for preparing an optical anti-counterfeiting document, used to prepare the optical anti-counterfeiting document according to any one of claims 1-8, characterized in that, include: An undulating structure layer is formed on one side surface of a substrate, the undulating structure layer having a first region having a first microstructure; A first ink layer, a reflective layer, and a second ink layer are sequentially formed on a first region of the undulating structure layer. The first ink layer is disposed close to the undulating structure layer relative to the reflective layer. The first ink layer, the reflective layer, and the second ink layer correspond to the projection of the first microstructure on the surface of the undulating structure layer.

10. The method for preparing optical anti-counterfeiting documents according to claim 9, characterized in that, The undulating structure layer further includes a second region having a second microstructure; The formation of a first ink layer, a reflective layer, and a second ink layer sequentially on the first region of the undulating structure layer includes: An initial first ink layer is formed on the undulating structure layer, the initial first ink layer at least isomorphically covering the first microstructure; An initial reflective layer is formed on the surface of the undulating structure layer facing away from the substrate, and the initial reflective layer covers the initial first ink layer; An initial second ink layer is formed on the initial reflective layer, the initial second ink layer at least covering the first microstructure, and the minimum thickness of the initial second ink layer on the first microstructure is greater than the minimum thickness of the initial second ink layer on the second microstructure; Remove the initial first ink layer, initial reflective layer, and initial second ink layer on the second microstructure, and retain the first ink layer, initial reflective layer, and second ink layer on the first microstructure to obtain the first ink layer, reflective layer, and second ink layer located on the first microstructure.

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