A multi-prevention flexible label and a preparation method thereof

Abstract

The application discloses a preparation method of a multiple anti-fake flexible label, and comprises the following steps: mixing aromatic polyester polyol, aliphatic isocyanate, modified acrylic ester monomer and an additive to obtain an acrylic modified water-based polyurethane adhesive, and then mixing the adhesive with fluorescent powder to obtain a fluorescent adhesive; micro-concave coating the obtained fluorescent adhesive on Glaucin paper to form an adhesive layer after solidification, so as to obtain an initial base material; preparing a white solidification liquid and a black solidification liquid, coating the white solidification liquid on the initial base material for solidification, then coating the black solidification liquid, and obtaining a final base material after solidification; preparing a hidden mark forming liquid, solidifying the hidden mark forming liquid on the final base material, then coating a modified acrylic ester liquid, and obtaining a complete label after solidification. The adhesive layer is arranged, and fluorescent residues are left on commodities after the label is removed, so that the label can leave anti-fake marks after being removed.

Description

Technical Field

[0001] This invention relates to the field of label manufacturing, and in particular to a multi-layered anti-counterfeiting flexible label and its manufacturing method. Background Technology

[0002] With the development of technology and the intensification of market competition, the issue of product anti-counterfeiting has become increasingly important. Especially today, with the continuous strengthening of the crackdown on counterfeit products, anti-counterfeiting technology has become a research focus for all walks of life. Anti-counterfeiting labels, as a common anti-counterfeiting measure, are widely used in various consumer products, including food, cosmetics, pharmaceuticals, and electronic products. Currently, most anti-counterfeiting labels on the market rely on the material, printing process, and optical properties of the label itself to achieve anti-counterfeiting functions, such as QR codes, laser etching, microtext, holograms, and invisible ink.

[0003] Existing anti-counterfeiting labeling methods are relatively simple. Most anti-counterfeiting technologies rely solely on external features such as patterns and colors to identify the authenticity of goods. Furthermore, most current labels are attached to the surface of goods using adhesives or glues. These labels can be easily peeled off during use, and usually no anti-counterfeiting marks or traces are left on the goods after the labels are removed. Therefore, once the labels are removed, it is difficult to trace the authenticity of the goods.

[0004] Therefore, a multi-layered anti-counterfeiting flexible label and its preparation method are proposed to solve the problem that no anti-counterfeiting marks or traces are usually left on the product after the label is peeled off. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-layer anti-counterfeiting flexible label and its preparation method, which solves the problem that no anti-counterfeiting marks or traces are usually left on the product after the label is peeled off.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for preparing a multi-layered anti-counterfeiting flexible label includes the following steps:

[0008] S1. Mix aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer and additives to obtain acrylic modified waterborne polyurethane adhesive, and then add fluorescent powder to obtain fluorescent adhesive.

[0009] S2. After the obtained fluorescent adhesive is micro-coated onto glassine paper and cured to form an adhesive layer, the initial substrate is obtained.

[0010] S3. Prepare white curing liquid and black curing liquid. First, apply white curing liquid to the initial substrate and cure it. Then apply black curing liquid. After curing, the final substrate is obtained.

[0011] S4. Prepare the invisible label forming liquid. First, cure the invisible label forming liquid on the final substrate, then apply the modified acrylic ester liquid. After curing, a complete label is obtained.

[0012] The acrylic-modified waterborne polyurethane adhesive is obtained according to the following steps:

[0013] Step 1: Aromatic polyester polyol and aliphatic isocyanate are added to a reaction vessel and stirred for 2 hours at a stirring speed of 200 rpm and a stirring temperature of 80±5℃ to obtain a preliminary mixture. The –NCO groups in the preliminary mixture react fully to form a polyurethane prepolymer.

[0014] Step 2: Modified acrylate monomers are gradually added to the initial mixture, and then the mixture is stirred for 1 hour at a stirring speed of 300 rpm and a stirring temperature of 70±5℃. At this time, the acrylate monomers are grafted onto the polyurethane chain to form an acrylic modified polyurethane prepolymer.

[0015] Step 3: The chain extender is gradually added to the acrylic modified polyurethane prepolymer and stirred for 30 minutes at a speed of 300 rpm and a temperature of 50±5℃ to obtain a chain extender mixture. After no obvious gel or particle precipitation occurs in the chain extender mixture, deionized water is added and stirred for 30 minutes at a speed of 400 rpm and a temperature of 50±5℃. After the mixture of chain extender mixture and deionized water forms a milky white or semi-transparent homogeneous emulsion without obvious layering or large particles, a preliminary emulsion is obtained.

[0016] Step 4: After the preliminary emulsion cools to room temperature, add the additives and stir for 15 minutes at a speed of 300 rpm. After stirring, add triethylamine to adjust the pH of the mixture of preliminary emulsion and additives to 7-8 to obtain acrylic modified waterborne polyurethane adhesive.

[0017] The theoretical viscosity calculation formula for the acrylic-modified waterborne polyurethane adhesive is as follows:

[0018]

[0019] In the formula: The viscosity of the acrylic-modified waterborne polyurethane adhesive; These are empirical constants; The density of the acrylic-modified waterborne polyurethane adhesive; The glass transition temperature of the acrylic-modified waterborne polyurethane adhesive; For operating temperature; This represents the average molecular weight of the acrylic-modified waterborne polyurethane adhesive.

[0020] The fluorescent adhesive is obtained according to the following steps:

[0021] The fluorescent powder and acrylic-modified waterborne polyurethane adhesive were stirred and mixed for 15 minutes at a stirring speed of 400 rpm.

[0022] Obtain the actual viscosity of the acrylic-modified waterborne polyurethane adhesive. and compare and To determine whether the obtained acrylic-modified waterborne polyurethane adhesive needs to have its internal water content increased or decreased, if the actual viscosity of the obtained acrylic-modified waterborne polyurethane adhesive... Greater than the theoretical viscosity of acrylic-modified waterborne polyurethane adhesives Then add deionized water to dilute it and reduce the viscosity; conversely, if the actual viscosity of the obtained acrylic-modified waterborne polyurethane adhesive is high... The viscosity is less than the theoretical viscosity of acrylic-modified waterborne polyurethane adhesive. Continue stirring to reduce the water content and increase the viscosity.

[0023] The aromatic polyester polyol may be any one of polypropylene terephthalate, polyethylene phthalate, or polyethylene adipate-terephthalate.

[0024] The aliphatic isocyanate may be any one of isophorone diisocyanate, hexamethylene diisocyanate, or tetramethylene diisocyanate.

[0025] The modified acrylate monomer may be any one of hydroxyethyl acrylate, hydroxypropyl methacrylate, or butyl methacrylate;

[0026] The additives include stabilizers, thickeners, and antioxidants.

[0027] In the preparation of the modified acrylate monomer, the proportions of aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer, modified acrylate monomer, deionized water, chain extender and auxiliaries are 40%~50%, 20%~25%, 10%~15%, 15%~20%, 0.5%~1.5% and 5%~10%, respectively.

[0028] The additives include stabilizers, thickeners, and antioxidants;

[0029] The stabilizer accounts for 0.1% to 0.5%, the tackifier accounts for 1% to 5%, and the antioxidant accounts for 0.1% to 0.3%.

[0030] The fluorescent adhesive contains 8%~13% fluorescent powder and 87%~92% acrylic-modified waterborne polyurethane adhesive.

[0031] The initial substrate is obtained according to the following steps:

[0032] Step 1: Prepare a coating mold with a micro-concave structure, and apply a release layer coating to the coating mold so that the release layer coating covers the micro-concave structure. The coating mold has several equally spaced square grooves corresponding to its imprinting surface, and two adjacent square grooves enclose each other to form a micro-concave structure.

[0033] Step 2: Apply fluorescent adhesive to the coating mold and fill the micro-concave structure with fluorescent adhesive;

[0034] Step 3: The fluorescent adhesive is evenly printed onto the glassine paper using a coating mold. The release layer coating allows the fluorescent adhesive to be completely transferred from the micro-concave structure to the glassine paper. After coating, the glassine paper is subjected to six-stage heat curing. After the fluorescent adhesive forms an adhesive layer on the glassine paper, the initial substrate is finally obtained. The adhesive surface of the adhesive layer on the initial substrate has protrusions corresponding to the square grooves.

[0035] The depth of the micro-recessed structure on the coating mold is 20-30 μm, the width is 50-100 μm, and the groove spacing is 100-150 μm;

[0036] The coating thickness of the fluorescent adhesive is 25±5μm;

[0037] The six curing temperatures of the six-stage thermosetting process are 75±5℃, 85±5℃, 95±5℃, 115±5℃, 110±5℃, and 90±5℃, respectively; the six curing times of the six-stage thermosetting process are 5-10 minutes, 10-15 minutes, 10-20 minutes, 5-10 minutes, 5-10 minutes, and 10-15 minutes, respectively.

[0038] The final substrate is obtained according to the following steps:

[0039] Step 1: Apply a white curing liquid composed of modified acrylic ester liquid and white pigment to the adhesive layer on the initial substrate, and then heat-cure the white curing liquid. After curing, a white cured layer is formed on the adhesive layer.

[0040] Step 2: Apply a black curing liquid composed of modified acrylic ester liquid and black pigment onto the white curing layer, and then heat-cur the black curing liquid. After the black curing liquid cures to form a black curing layer, the final substrate is obtained.

[0041] The complete label is obtained according to the following steps:

[0042] Step 1: Apply the invisible label forming liquid, which is composed of modified acrylic ester liquid and fluorescent powder, onto the invisible label mold, and then transfer the invisible label forming liquid onto the surface of the final substrate through the invisible label mold. Then, heat curing is used to cure the invisible label forming liquid on the surface of the final substrate to form an invisible label layer.

[0043] Step 2: Apply the modified acrylic liquid onto the invisible label layer, and then cure it through heat curing. Once a transparent cured layer is formed on the invisible label layer, a complete label is obtained.

[0044] The invisible marker forming liquid is prepared by mixing modified acrylic ester liquid and fluorescent powder, with a mixing time of 10 to 20 minutes and a stirring speed of 200 to 600 rpm;

[0045] The modified acrylic ester solution and fluorescent powder in the invisible mark forming solution account for 92%–87% and 8%–13%, respectively.

[0046] A multi-layer anti-counterfeiting flexible label is made using the method described above. The multi-layer anti-counterfeiting flexible label includes glassine paper, an adhesive layer, a white curing layer, a black curing layer, an invisible identification layer, and a transparent curing layer, which are connected sequentially from bottom to top.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. The preparation method of this multi-layer anti-counterfeiting flexible label involves a layer of adhesive cured with fluorescent adhesive and placed on an initial substrate. This allows fluorescent adhesive residue to remain on the product after the label is peeled off. The residual fluorescent adhesive develops an image when exposed to ultraviolet light, thus achieving the anti-counterfeiting function. This solves the problem that no anti-counterfeiting mark is left on the product after the label is peeled off. Therefore, this invention can leave an anti-counterfeiting mark on the product after the label is peeled off.

[0049] 2. The preparation method of this multi-anti-counterfeiting flexible label, through the setting of invisible marks and the setting of adhesive layers, enables the label to achieve multiple anti-counterfeiting functions. With the invisible marks on the surface and the inner adhesive layer working together, the anti-counterfeiting effect of the label is effectively improved. Therefore, the present invention has multiple anti-counterfeiting functions.

[0050] 3. The preparation method of this multi-layer anti-counterfeiting flexible label uses an acrylic-modified waterborne polyurethane adhesive composed of aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer and additives. This effectively improves the adhesion of the fluorescent adhesive. With the help of a finely set micro-concave structure on the coating mold, the fluorescent adhesive can be coated onto glassine paper through micro-concave coating, forming bumps on the adhesive surface of the adhesive layer. These bumps allow more adhesive layer to remain on the label when it is peeled off from the product, improving the imaging effect under ultraviolet light. Therefore, this invention improves the imaging effect of fluorescent residue.

[0051] 4. The preparation method of this multi-layer anti-counterfeiting flexible label produces a fluorescent adhesive that not only allows the residual adhesive layer on the product to emit a clear fluorescent display effect after being irradiated with ultraviolet light, but also allows the adhesive area of ​​the label to show a fluorescent image after being irradiated with ultraviolet light after the residual adhesive layer on the product is cleaned. Therefore, the present invention further improves the anti-counterfeiting effect. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0054] Figure 1 This is a flowchart of the method steps of the present invention;

[0055] Figure 2 This is a flowchart of the preparation steps of the acrylic-modified waterborne polyurethane adhesive in this invention.

[0056] Figure 3 This is a flowchart of the preparation steps of the initial substrate in this invention;

[0057] Figure 4 This is a schematic diagram showing the disassembled structure of the coating mold and the adhesive layer in this invention;

[0058] Figure 5 This is a top view of the adhesive layer in this invention.

[0059] Figure 6 This is a flowchart illustrating the preparation steps of the final substrate in this invention;

[0060] Figure 7 This is a flowchart illustrating the complete label preparation steps in this invention.

[0061] Illustrations: 1. Coating mold; 11. Square groove; 12. Imprinting surface; 2. Adhesive layer; 21. Adhesive surface; 22. Protrusion. Detailed Implementation

[0062] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0063] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0064] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1:

[0066] Please see Figure 1 The preparation method of a multi-layer anti-counterfeiting flexible label in this embodiment includes the following steps: S1, mixing aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer and additives to obtain acrylic modified waterborne polyurethane adhesive, and then adding fluorescent powder to obtain fluorescent adhesive; S2, microgravure coating the obtained fluorescent adhesive onto glassine paper and curing it to form adhesive layer 2 to obtain the initial substrate; S3, preparing white curing liquid and black curing liquid, first coating the white curing liquid onto the initial substrate and curing it, then coating the black curing liquid, and obtaining the final substrate after curing;

[0067] S4. Prepare the invisible label forming liquid. First, cure the invisible label forming liquid on the final substrate, then apply the modified acrylic ester liquid. After curing, a complete label is obtained.

[0068] The label prepared by the above method, when affixed to the product, adheres firmly to the product under the action of adhesive layer 2. During the use of the label, the invisible mark formed by the invisible mark forming liquid enables the label to play an anti-counterfeiting role, giving the label an anti-counterfeiting function. After the label is peeled off from the product, adhesive layer 2 will remain on the product. When ultraviolet light shines on the remaining adhesive layer 2, the fluorescent powder in adhesive layer 2 will emit a fluorescent indication. Under the action of the remaining adhesive layer 2, an image can be seen on the product after the label has been peeled off, thus forming another anti-counterfeiting label. With the action of invisible mark and fluorescent residue, the label has multiple anti-counterfeiting functions, improving the anti-counterfeiting effect of the label. Even after the adhesive layer 2 remaining on the product is removed, there will still be fluorescent residue at the label adhesive area. When ultraviolet light shines on the label adhesive area, there will still be an imaging effect, further improving the anti-counterfeiting function of the label.

[0069] It should be noted that when using the label, after peeling the glassine paper off the label, the label can be adhered to the product through the adhesive layer 2; the label can be marked by laser etching and used as an identifier.

[0070] Example 2:

[0071] The basic content is from Example 1, the difference being:

[0072] Please see Figures 2-5The acrylic-modified waterborne polyurethane adhesive in this embodiment is obtained according to the following steps: Step 1: Aromatic polyester polyol and aliphatic isocyanate are added to a reaction vessel and stirred for 2 hours at a stirring speed of 200 rpm and a stirring temperature of 80±5℃ to obtain a preliminary mixture. The –NCO groups in the preliminary mixture react fully to form a polyurethane prepolymer. Step 2: Modified acrylate monomers are gradually added to the preliminary mixture, and then stirred for 1 hour at a stirring speed of 300 rpm and a stirring temperature of 70±5℃. At this time, the acrylate monomers are grafted onto the polyurethane chain, forming the acrylic-modified polyurethane prepolymer. Step 3: A chain extender is gradually added to the acrylic-modified polyurethane prepolymer, and stirring is continued. After stirring for 30 minutes at a speed of 300 rpm and a temperature of 50±5℃, a chain-extended mixture is obtained. Once no obvious gel or particle precipitation occurs in the chain-extended mixture, deionized water is added and stirred for another 30 minutes at a speed of 400 rpm and a temperature of 50±5℃. A preliminary emulsion is obtained when the mixture of the chain-extended mixture and deionized water forms a milky white or semi-transparent homogeneous emulsion without obvious layering or large particles. Fourth step: After the preliminary emulsion cools to room temperature, additives are added and stirred for 15 minutes at a speed of 300 rpm. After stirring, triethylamine is added to adjust the pH of the mixture of the preliminary emulsion and additives to 7-8, resulting in an acrylic-modified waterborne polyurethane adhesive.

[0073] The theoretical viscosity calculation formula for acrylic-modified waterborne polyurethane adhesives is as follows:

[0074]

[0075] In the formula: The viscosity of the acrylic-modified waterborne polyurethane adhesive; These are empirical constants; The density of the acrylic-modified waterborne polyurethane adhesive; The glass transition temperature of the acrylic-modified waterborne polyurethane adhesive; For operating temperature; The average molecular weight of the acrylic-modified waterborne polyurethane adhesive is given. The fluorescent adhesive is obtained by the following steps: the fluorescent powder and the acrylic-modified waterborne polyurethane adhesive are stirred and mixed for 15 minutes at a speed of 400 rpm.

[0076] Obtain the actual viscosity of acrylic-modified waterborne polyurethane adhesive and compare and To determine whether the obtained acrylic-modified waterborne polyurethane adhesive needs to have its internal water content increased or decreased, if the actual viscosity of the obtained acrylic-modified waterborne polyurethane adhesive... Greater than the theoretical viscosity of acrylic-modified waterborne polyurethane adhesives Then add deionized water to dilute it and reduce the viscosity; conversely, if the actual viscosity of the obtained acrylic-modified waterborne polyurethane adhesive is high... The viscosity is less than the theoretical viscosity of acrylic-modified waterborne polyurethane adhesive. Continue stirring to reduce water content and increase viscosity; the viscosity of the prepared acrylic-modified waterborne polyurethane adhesive is related to the polymer chain length, molecular weight, and water content.

[0077] The excessive viscosity of acrylic-modified waterborne polyurethane adhesives is caused by long polymer chains, high molecular weight, and low water content. Conversely, low viscosity is due to short polymer chains, weak intermolecular interactions, and higher water content. Controlling the polymer molecular weight directly affects both the theoretical and actual viscosity of the acrylic-modified waterborne polyurethane adhesive; a larger molecular weight generally results in higher viscosity, and vice versa. Furthermore, the water content significantly impacts the viscosity; increasing water content dilutes the polymer and reduces viscosity, while decreasing water content increases viscosity.

[0078] The acrylic-modified waterborne polyurethane adhesive prepared by the above method has the characteristics of high viscosity. The introduction of acrylate significantly improves the polarity and intermolecular forces of the acrylic-modified waterborne polyurethane adhesive, and increases the affinity of molecular chains. The high molecular weight polyurethane matrix further enhances the adhesion through chain segment flexibility regulation. At the same time, the high crosslinking density of the acrylic-modified polyurethane in the acrylic-modified waterborne polyurethane adhesive forms a network structure with high brittleness after curing, making the cured acrylic-modified waterborne polyurethane adhesive easy to break.

[0079] Specifically, in the above preparation process, the –NCO content in the initial mixture is monitored by titration to ensure complete reaction; infrared spectroscopy is used to confirm that the –OH groups are reduced and the acrylic acid grafting is completed, which ensures the formation of acrylic acid modified polyurethane prepolymer.

[0080] Aromatic polyester polyols can be any one of polypropylene terephthalate, polyethylene phthalate, or polyethylene adipate-terephthalate; aliphatic isocyanates can be any one of isophorone diisocyanate, hexamethylene diisocyanate, or tetramethylene diisocyanate; modified acrylate monomers can be any one of hydroxyethyl acrylate, hydroxypropyl methacrylate, or butyl methacrylate; additives include stabilizers, tackifiers, and antioxidants; the modified acrylate monomers are used in the preparation of aromatic polyesters. The proportions of polyol, aliphatic isocyanate, modified acrylate monomer, modified acrylate monomer, deionized water, chain extender and additives are 40%~50%, 20%~25%, 10%~15%, 15%~20%, 0.5%~1.5% and 5%~10%, respectively; among which, the additives include stabilizers, tackifiers and antioxidants; the proportion of stabilizers is 0.1%~0.5%, the proportion of tackifiers is 1%~5%, and the proportion of antioxidants is 0.1%~0.3%.

[0081] Preferably, the composition comprises 45% polyethylene phthalate, 22% isophorone diisocyanate, 12% hydroxyethyl acrylate, 16% deionized water, 1% chain extender, 3% tackifier, 0.3% stabilizer, and 0.2% antioxidant.

[0082] Furthermore, the proportions of fluorescent powder and acrylic-modified waterborne polyurethane adhesive in the fluorescent adhesive are 8%~13% and 87%~92%, respectively.

[0083] Preferably, the proportions of fluorescent powder and acrylic-modified waterborne polyurethane adhesive in the fluorescent adhesive are 10% and 90%, respectively; the fluorescent powder is zinc silicate-based fluorescent powder with a particle diameter of 1~2μm, specifically 1.5μm; the zinc silicate-based fluorescent powder has a high efficiency response to 365nm wavelength ultraviolet light, high luminous intensity, and strong weather resistance, and has a good imaging effect after being irradiated by ultraviolet light. At the same time, the 10% proportion of fluorescent powder can provide enough luminescent particles to ensure the imaging effect without affecting the flowability and adhesion performance of the fluorescent adhesive, and the medium particle diameter of the fluorescent powder particles can also balance fluorescence intensity and uniform distribution.

[0084] The initial substrate is obtained according to the following steps: Step 1: Prepare a coating mold 1 with a micro-recessed structure, and apply a release layer coating to the coating mold 1 to cover the micro-recessed structure. The coating mold 1 has several equally spaced square grooves 11 corresponding to its imprinting surface 12, and adjacent square grooves 11 enclose a micro-recessed structure. Step 2: Apply fluorescent adhesive to the coating mold 1, filling the micro-recessed structure. Step 3: Uniformly imprint the fluorescent adhesive onto glassine paper using the coating mold 1. The release layer coating allows the fluorescent adhesive to be completely transferred from the micro-recessed structure to the glassine paper. After coating, the glassine paper undergoes a six-stage heat curing process. After the fluorescent adhesive forms an adhesive layer 2 on the glassine paper, the initial substrate is finally obtained. (The text then repeats the steps.) Figures 6-7 As shown, a protrusion 22 is formed on the adhesive surface 21 of the adhesive layer 2 on the initial substrate, corresponding to the square groove 11.

[0085] By setting the depth, width, and spacing of the micro-concave structures on the coating mold 1, the cured adhesive layer 2 of the fluorescent adhesive can form a stronger adhesive effect on the surface of the product. When the label is peeled off the surface of the product, the amount of adhesive layer 2 remaining is significantly higher than that of ordinary labels. When the amount of adhesive layer 2 remaining on the product is increased, the fluorescence effect is more obvious when irradiated with ultraviolet light, thereby improving the anti-counterfeiting effect.

[0086] It should be noted that by performing micro-recessed coating, tiny bumps 22 can be formed on the adhesive surface of the adhesive layer 2. The tiny bumps 22 increase the contact area between the adhesive layer 2 and the product surface. When the label is peeled off from the product surface, the roughness and microstructure of the product surface will also interact with the bumps 22 on the adhesive layer 2. The rough surface of the product will generate stronger adhesion to the adhesive layer 2. Therefore, more adhesive layer 2 will be left on the product surface when peeling off.

[0087] Furthermore, the depth of the square groove 11 is 20-30 μm, the width is 50-100 μm, the distance between two adjacent square grooves 11 is 100-150 μm, and the coating thickness of the fluorescent adhesive is 25±5 μm.

[0088] Preferably, the square groove 11 has a depth of 25μm and a width of 80μm, and the distance between two adjacent square grooves 11 is 100μm; the coating thickness of the fluorescent adhesive is 25μm; after the fluorescent adhesive is coated and cured, bumps 22 imprinted by the square grooves 11 are formed on the adhesive layer 2; the bumps 22 contain 8000~9000 fluorescent powder particles, ensuring the imaging effect of the residual adhesive layer 2. At the same time, the square grooves 11 with a moderate depth can accommodate a sufficient amount of adhesive to ensure the imaging effect, the wider square grooves 11 increase the adhesive area and improve the residual amount, and the smaller spacing can cover a larger area and enhance the imaging effect.

[0089] Furthermore, the six curing temperatures of the six-stage thermosetting process are 75±5℃, 85±5℃, 95±5℃, 115±5℃, 110±5℃, and 90±5℃, respectively; the six curing times of the six-stage thermosetting process are 5~10 minutes, 10~15 minutes, 10~20 minutes, 5~10 minutes, 5~10 minutes, and 10~15 minutes, respectively.

[0090] Specifically, the first curing stage lasts 5-10 minutes. During this stage, a low temperature is maintained to prevent the fluorescent adhesive from cross-linking too quickly. The second curing stage lasts 10-15 minutes. This stage further enhances the curing reaction, gradually establishing a cross-linked structure. The cross-linking density begins to increase but remains moderate, ensuring a certain degree of micro-distribution unevenness within the adhesive layer 2. The third curing stage lasts 10-20 minutes. During this stage, the curing temperature approaches the optimal curing temperature of the fluorescent adhesive, further strengthening the cross-linking. The cross-linking density increases significantly during this stage, and excessively high cross-linking density is avoided by controlling the curing time. The fourth curing stage lasts 5-10 minutes. In this stage, the curing temperature reaches the highest curing temperature, and the fluorescent adhesive is fully cured, gradually... The process involves several stages: First, a second layer of adhesive is formed, introducing internal stress within it. The fourth stage of curing, achieved through high-temperature curing, causes microcracks or internal stress within the gradually forming adhesive layer 2 due to thermal expansion. These microcracks or internal stress reduce the overall toughness of the adhesive layer 2, making it more prone to breakage. The fifth stage of curing, lasting 5-10 minutes, slightly cools the formed adhesive layer 2 to slow down the cross-linking rate and stabilize the internal structure. Maintaining high temperature for a short period further improves curing and creates a certain thermal history effect. The sixth stage of curing, lasting 10-15 minutes, lowers the temperature of the formed adhesive layer 2, allowing it to cool slowly and preventing excessive internal stress concentration caused by rapid cooling. This process ultimately forms the second adhesive layer 2 with a moderate cross-linking density and some residual weak stress concentration points.

[0091] It should be noted that by using a higher cross-linking density to make the adhesive layer 2 harder and more brittle, and by gradually increasing the temperature and controlling the time of each stage, an uneven cross-linking network can be formed within the adhesive layer 2. This unevenness may make the adhesive layer 2 more prone to breakage under external force. At the same time, during the high-temperature curing in the fourth stage, the adhesive layer 2 will introduce certain residual stress due to thermal expansion. During the subsequent cooling processes in the fifth and sixth stages, the stress is not completely released, forming potential instability points inside the adhesive layer 2. These stress concentration points can reduce the overall strength of the adhesive layer 2, making it more prone to breakage. The stress remaining in the adhesive layer 2 and the higher cross-linking density make the label easier to break when it is peeled off the product, thereby increasing the amount of adhesive layer 2 remaining on the product.

[0092] Example 3:

[0093] The basic content is from Example 1, the difference being:

[0094] Please see Figures 6-7 In this embodiment, the final substrate is obtained according to the following steps: Step 1: A white curing liquid composed of modified acrylic ester liquid and white pigment is applied to the adhesive layer 2 on the initial substrate, and then the white curing liquid is heat-cured. After the white curing liquid cures, a white cured layer is formed on the adhesive layer 2. Step 2: A black curing liquid composed of modified acrylic ester liquid and black pigment is applied to the white cured layer, and then the black curing liquid is heat-cured. After the black curing liquid cures to form a black cured layer, the final substrate is obtained.

[0095] The complete label is obtained according to the following steps: Step 1: Apply an invisible label forming liquid composed of modified acrylic ester liquid and fluorescent powder to an invisible label mold, and transfer the invisible label forming liquid to the surface of the final substrate by the invisible label mold. Then, heat curing is used to cure the invisible label forming liquid on the surface of the final substrate to form an invisible label layer; Step 2: Apply the modified acrylic ester liquid to the invisible label layer, and then heat curing is used to cure it. When a transparent cured layer is formed on the invisible label layer, a complete label is obtained.

[0096] Specifically, the invisible label layer is set on the black curing layer and sealed by the transparent curing layer. The black curing layer allows the invisible label to have a better imaging effect when it is developed. The transparent curing layer can effectively protect the invisible label and the markings etched on the black curing layer. Its high transparency and gloss not only make the complete label brighter and clearer in visual effect, but also improve the visibility of the invisible label. In addition, it has good UV resistance and can effectively resist the ultraviolet radiation in the sunlight, preventing the complete label and the invisible label layer from fading, aging or being damaged when exposed to sunlight outdoors or for a long time.

[0097] Furthermore, the invisible marker forming liquid is prepared by mixing modified acrylate and fluorescent powder for 10 to 20 minutes and stirring at 200 to 600 rpm; the proportions of modified acrylate and fluorescent powder in the invisible marker forming liquid are 92% to 87% and 8% to 13%, respectively.

[0098] Example 4:

[0099] The basic content is from Example 1, the difference being:

[0100] The multi-layer anti-counterfeiting flexible label in this embodiment is prepared using the method of Example 1. The multi-layer anti-counterfeiting flexible label includes glassine paper, adhesive layer 2, white curing layer, black curing layer, invisible marking layer, and transparent curing layer connected sequentially from bottom to top.

[0101] In application, the glassine paper is peeled off, and the label is adhered to the product through the adhesive layer 2. The label, after being affixed, provides basic identification through laser-etched markings, while the hidden marking layer enables the label to have anti-counterfeiting functionality. After the label is removed from the product, the adhesive layer 2 remaining on the product will develop an image under ultraviolet light, performing secondary anti-counterfeiting work and improving the label's anti-counterfeiting effect. This solves the defect that the product loses its anti-counterfeiting function after the label is removed. Furthermore, after cleaning off the residual adhesive layer 2 on the product, the affixed area will also develop an image under ultraviolet light, further enhancing the label's anti-counterfeiting function.

[0102] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a multi-layered anti-counterfeiting flexible label, characterized in that, Includes the following steps: S1. Aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer and additives are mixed to obtain brittle acrylic modified waterborne polyurethane adhesive. Fluorescent powder is then added and mixed to obtain fluorescent adhesive. The fluorescent adhesive is developed after being irradiated with ultraviolet light. S2. After the obtained fluorescent adhesive is micro-coated onto glassine paper and cured to form an adhesive layer (2), the initial substrate is obtained. S3. Prepare white curing liquid and black curing liquid. First, apply white curing liquid to the initial substrate and cure it. Then apply black curing liquid. After curing, the final substrate is obtained. S4. Prepare the invisible label forming liquid. First, cure the invisible label forming liquid on the final substrate, then coat it with modified acrylic ester liquid. After curing, a complete label is obtained. The acrylic-modified waterborne polyurethane adhesive is obtained according to the following steps: Step 1: Aromatic polyester polyol and aliphatic isocyanate are added to a reaction vessel and stirred for 2 hours at a stirring speed of 200 rpm and a stirring temperature of 80±5℃ to obtain a preliminary mixture. The –NCO groups in the preliminary mixture react fully to form a polyurethane prepolymer. Step 2: Modified acrylate monomers are gradually added to the initial mixture, and then the mixture is stirred for 1 hour at a stirring speed of 300 rpm and a stirring temperature of 70±5℃. At this time, the acrylate monomers are grafted onto the polyurethane chain to form an acrylic modified polyurethane prepolymer. Step 3: The chain extender is gradually added to the acrylic modified polyurethane prepolymer and stirred for 30 minutes at a speed of 300 rpm and a temperature of 50±5℃ to obtain a chain extender mixture. After no obvious gel or particle precipitation occurs in the chain extender mixture, deionized water is added and stirred for 30 minutes at a speed of 400 rpm and a temperature of 50±5℃. After the mixture of chain extender mixture and deionized water forms a milky white or semi-transparent homogeneous emulsion without obvious layering or large particles, a preliminary emulsion is obtained. Step 4: After the preliminary emulsion cools to room temperature, add the additives and stir for 15 minutes at a speed of 300 rpm. After stirring, add triethylamine to adjust the pH of the mixture of preliminary emulsion and additives to 7-8 to obtain acrylic modified waterborne polyurethane adhesive. The acrylic modified polyurethane in the acrylic modified waterborne polyurethane adhesive has a high crosslinking density and forms a brittle network structure after curing. The fluorescent adhesive is obtained according to the following steps: The fluorescent powder and acrylic-modified waterborne polyurethane adhesive were stirred and mixed for 15 minutes at a stirring speed of 400 rpm. The aromatic polyester polyol may be any one of polypropylene terephthalate, polyethylene phthalate, or polyethylene adipate-terephthalate. The aliphatic isocyanate may be any one of isophorone diisocyanate, hexamethylene diisocyanate, or tetramethylene diisocyanate. The modified acrylate monomer may be any one of hydroxyethyl acrylate, hydroxypropyl methacrylate, or butyl methacrylate; The additives include stabilizers, thickeners, and antioxidants; In the preparation of the modified acrylate monomer, the proportions of aromatic polyester polyol, aliphatic isocyanate, modified acrylate monomer, modified acrylate monomer, deionized water, chain extender and auxiliaries are 40%~50%, 20%~25%, 10%~15%, 15%~20%, 0.5%~1.5% and 5%~10%, respectively. The additives include stabilizers, thickeners, and antioxidants; The stabilizer accounts for 0.1% to 0.5%, the tackifier accounts for 1% to 5%, and the antioxidant accounts for 0.1% to 0.3%. The fluorescent adhesive contains 8%~13% fluorescent powder and 87%~92% acrylic modified waterborne polyurethane adhesive, respectively. The fluorescent powder is zinc silicate-based fluorescent powder with a particle diameter of 1~2μm. The initial substrate is obtained according to the following steps: Step 1: Prepare a coating mold (1) with a micro-concave structure, and apply a release layer coating on the coating mold (1) to cover the micro-concave structure. The coating mold (1) has several equally spaced square grooves (11) on its imprinting surface (12), and two adjacent square grooves (11) enclose a micro-concave structure. Step 2: Apply fluorescent adhesive to the coating mold (1) and fill the micro-concave structure with fluorescent adhesive; Step 3: The fluorescent adhesive is uniformly printed onto the glassine paper using a coating mold (1). The release layer coating allows the fluorescent adhesive to be completely transferred from the micro-concave structure to the glassine paper. After coating, the glassine paper is subjected to six-stage heat curing. After the fluorescent adhesive forms an adhesive layer (2) on the glassine paper, the initial substrate is finally obtained. The adhesive surface (21) of the adhesive layer (2) on the initial substrate has a protrusion (22) corresponding to the square groove (11). The protrusion (22) is used to increase the contact area between the adhesive layer (2) and the product surface. The protrusion (22) contains 8000~9000 fluorescent powder particles. The depth of the square groove (11) is 20-30 μm, the width is 50-100 μm, and the distance between two adjacent square grooves (11) is 100-150 μm; The coating thickness of the fluorescent adhesive is 25±5μm; The six curing temperatures of the six-stage thermosetting process are 75±5℃, 85±5℃, 95±5℃, 115±5℃, 110±5℃, and 90±5℃ respectively; the six curing times of the six-stage thermosetting process are 5~10 minutes, 10~15 minutes, 10~20 minutes, 5~10 minutes, 5~10 minutes, and 10~15 minutes respectively. The six-stage thermosetting process forms instability points in the adhesive layer (2) that reduce the overall strength of the adhesive layer (2).

2. The method for preparing the multi-layer anti-counterfeiting flexible label according to claim 1, characterized in that, The final substrate is obtained according to the following steps: Step 1: Apply a white curing liquid composed of modified acrylic ester liquid and white pigment to the adhesive layer (2) on the initial substrate, and then heat cure the white curing liquid. After curing, a white curing layer is formed on the adhesive layer (2). Step 2: Apply a black curing liquid composed of modified acrylic ester liquid and black pigment onto the white curing layer, and then heat-cur the black curing liquid. After the black curing liquid cures to form a black curing layer, the final substrate is obtained.

3. The method for preparing the multi-layer anti-counterfeiting flexible label according to claim 1, characterized in that, The complete label is obtained according to the following steps: Step 1: Apply the invisible label forming liquid, which is composed of modified acrylic ester liquid and fluorescent powder, onto the invisible label mold, and then transfer the invisible label forming liquid onto the surface of the final substrate through the invisible label mold. Then, heat curing is used to cure the invisible label forming liquid on the surface of the final substrate to form an invisible label layer. Step 2: Apply the modified acrylic liquid onto the invisible label layer, and then cure it through heat curing. Once a transparent cured layer is formed on the invisible label layer, a complete label is obtained.

4. The method for preparing the multi-layer anti-counterfeiting flexible label according to claim 3, characterized in that, The invisible marker forming liquid is prepared by mixing modified acrylic ester liquid and fluorescent powder, with a mixing time of 10 to 20 minutes and a stirring speed of 200 to 600 rpm; The modified acrylic ester solution and fluorescent powder in the invisible mark forming solution account for 92%–87% and 8%–13%, respectively.

5. A multi-layered anti-counterfeiting flexible label, characterized in that, The multi-layer anti-counterfeiting flexible label is prepared by the method described in any one of claims 1 to 4, and includes glassine paper, adhesive layer (2), white curing layer, black curing layer, invisible marking layer and transparent curing layer connected in sequence from bottom to top.

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