Security paper and method for its production

Abstract

The application provides a kind of anti-fake paper and its preparation method;The preparation method comprises: papermaking raw paper, wherein the raw paper at least includes the surface layer, the surface lining layer, the core layer and the bottom layer which are sequentially stacked;The raw paper is dried for the first time;The surface of the raw paper after drying is sprayed with ink;The surface of the surface after spraying ink is sized;The paper product after sizing is dried for the second time.The preparation method of the anti-fake paper provided in the application accurately sprays the anti-fake ink on the paper before surface sizing during the online paper manufacturing process, forms graphics and texts, designs a suitable raw paper structure to allow the ink to penetrate, and further promotes the penetration of the ink into the deep layer of the paper by taking advantage of the favorable conditions of the sizing liquid migration to the deep layer of the paper during surface sizing, so that the anti-fake paper can be produced online on a high-speed paper machine, and has the characteristics of low cost and good anti-fake effect.

Description

Technical Field

[0001] This application relates to the technical field of anti-counterfeiting paper, specifically to an anti-counterfeiting paper and its preparation method. Background Technology

[0002] Anti-counterfeiting packaging paper substrate is the core carrier of anti-counterfeiting technology in packaging, and has important application value in fields such as pharmaceuticals, food, tobacco, cosmetics, and luxury goods. As counterfeiting technology continues to upgrade, anti-counterfeiting paper technology is also constantly evolving, from early physical anti-counterfeiting (such as watermarks) to today's multimodal composite anti-counterfeiting (such as the combination of optical, chemical, and digital anti-counterfeiting).

[0003] Anti-counterfeiting technologies can be broadly categorized into three types: physical anti-counterfeiting, chemical anti-counterfeiting, and digital anti-counterfeiting. Modern anti-counterfeiting paper typically combines multiple technologies to enhance security. Physical anti-counterfeiting relies on the microstructure or macroscopic characteristics of the paper. For example, watermarks create translucent, visible patterns through variations in paper thickness; security threads embed metal or polymer threads and incorporate microtext and dynamic optical effects; anti-counterfeiting fibers are randomly distributed colored or fluorescent fibers that enhance visual and ultraviolet light detection capabilities; microstructure anti-counterfeiting utilizes laser micro-perforation, embossing, and microlens arrays, requiring observation at specific angles or under specific lighting conditions. Chemical anti-counterfeiting achieves reversible or irreversible responses through specific chemical substances, such as thermochromic materials, photochromic materials, pH-sensitive dyes, and chemically encrypted inks. Digital anti-counterfeiting technologies combine information technology to improve the convenience and security of anti-counterfeiting verification, such as QR codes / RFID storing encrypted information, nanoprinting, and blockchain traceability.

[0004] Internal Printing Pattern Technology (IPM) is a rapidly developing anti-counterfeiting method in recent years. Its core lies in directly printing the anti-counterfeiting pattern onto the internal fiber layer of the paper, rather than through traditional surface printing. This technology effectively avoids the loss of anti-counterfeiting information due to surface wear or chemical corrosion, significantly increasing the difficulty of counterfeiting. Some existing technologies use highly permeable nano-inks, which are used to print the pattern between the fiber layers during the paper wet-pressing stage. After drying, the ink forms a chemical bond with the cellulose, permanently fixing the pattern inside the paper. The pattern remains intact even when the paper is torn, and the internal pattern remains visible after surface polishing. Some existing technologies construct a sandwich structure inside the paper: an upper layer of conventional fibers (including surface watermark); a middle layer of printed anti-counterfeiting pattern; and a lower layer of magnetic fibers. The patterns in each layer create a three-dimensional anti-counterfeiting effect when light is transmitted through them. As domestic paper mills continuously improve production efficiency and paper machine speeds, anti-counterfeiting technologies that involve printing patterns onto the wet paper sheets at the wet end of the paper machine and then laminating the various paper layers together are essentially impossible to implement on high-speed paper machines. This is because high-speed paper machines experience significant wet paper web vibration, and the wet end environment is characterized by high temperature and humidity, placing extremely high demands on the stability of the printing process and the temperature and humidity resistance of the equipment. Therefore, currently, there is no anti-counterfeiting technology for printing patterns onto the paper fiber layers on paper machines with speeds reaching 1000 m / min. Summary of the Invention

[0005] The first aspect of this application provides a method for preparing anti-counterfeiting paper, the method comprising: Papermaking base paper, wherein the base paper comprises at least a surface layer, a face liner layer, a core layer and a bottom layer stacked in sequence; The base paper is first dried; Ink is sprayed onto the surface of the dried base paper; Apply a surface adhesive to the surface layer after spraying ink; The sized paper products are then dried a second time.

[0006] In some optional embodiments, in the papermaking step, the pulp fiber ratio of the face layer and the face liner layer is 10-20% softwood chemical pulp and 80-90% hardwood chemical pulp.

[0007] In some optional embodiments, the softwood chemical pulp has a pulp freeness of 380±20ml and a pulp fiber length of 0.8-1.2mm, while the hardwood chemical pulp has a pulp freeness of 430±20ml and a pulp fiber length of 0.4-0.6mm.

[0008] In some optional embodiments, the amount of sizing agent used in the top layer and the top lining layer is zero.

[0009] In some optional embodiments, the base paper further includes a backing layer disposed between the core layer and the bottom layer, the total basis weight of the top layer and the top liner layer is 30-35 gsm, the basis weight of the core layer is 70-280 gsm, and the total basis weight of the bottom layer and the backing layer is 30-70 gsm.

[0010] In some optional embodiments, in the step of spraying ink onto the surface of the dried base paper, the ink is a water-based ink, and the ink contains 10-30% pigments, dyes or anti-counterfeiting materials, 20-40% water, 30-40% water-soluble resin, and 1-10% other additives.

[0011] In some optional embodiments, in the step of surface sizing after ink spraying, the surface sizing agent is a starch-based solution with a solid content of 13-16%, a viscosity of 40-60 cps, and a coating amount of 4-6 g / m². 2 .

[0012] In some optional embodiments, the preparation method further includes: coating the surface after surface sizing; wherein the coating includes pre-coating, intermediate coating and topcoat.

[0013] In some optional embodiments, the pre-coat, intermediate coat, and topcoat each comprise 70-80% GCC (55-98) by weight, 0-20% kaolin, 5-30% hiding agent, 10-12% adhesive, and a small amount of auxiliary additives.

[0014] Secondly, this application provides an anti-counterfeiting paper, which is prepared using the preparation method described in the above embodiments.

[0015] The method for preparing anti-counterfeiting paper provided in this application involves precisely inkjetizing anti-counterfeiting ink onto the paper before surface sizing during the online paper manufacturing process to form images and text. A suitable paper structure is designed to allow the ink to penetrate, and the favorable conditions of the sizing liquid migrating into the deeper layers of the paper during the surface sizing process are utilized to further promote the penetration of the ink into the deeper layers of the paper. This method enables the online production of anti-counterfeiting paper on a high-speed paper machine, and features low cost and good anti-counterfeiting effect. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic flowchart of an embodiment of the method for preparing anti-counterfeiting paper according to this application; Figure 2 This is a schematic diagram of the laminated structure of the base paper in one embodiment of this example; Figure 3 This is a schematic diagram of the laminated structure of another embodiment of the base paper in this embodiment; Figure 4 This is a schematic diagram of the ink coating on the surface of the base paper; Figure 5 This is a schematic diagram of the laminated structure after surface adhesive application; Figure 6 This is a schematic flowchart of another embodiment of the method for preparing anti-counterfeiting paper according to this application; Figure 7 This is a schematic diagram of the layered structure of another embodiment of the anti-counterfeiting paper of this application. Detailed Implementation

[0018] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0019] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] This application provides a method for preparing anti-counterfeiting paper. Please refer to [link / reference]. Figure 1 , Figure 1 This is a schematic flowchart of an embodiment of the method for preparing anti-counterfeiting paper according to this application. The preparation method includes, but is not limited to, the following steps.

[0022] Step S100: Making the original paper.

[0023] Please refer to the following: Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of the laminated structure of one embodiment of the base paper in this embodiment. Figure 3 This is a schematic diagram of the laminated structure of another embodiment of the base paper in this embodiment. Optionally, the base paper in this embodiment includes a 4-layer or 5-layer paper composite structure, wherein... Figure 2 The base paper 100 in this embodiment includes a top layer 110, a face liner layer 120, a core layer 130, and a bottom layer 150, which are stacked sequentially. Figure 3 The base paper 100 in the embodiment includes a surface layer 110, a face liner layer 120, a core layer 130, a bottom liner layer 140, and a bottom layer 150, which are stacked in sequence.

[0024] Optionally, in this embodiment, the pulp fiber ratio of the surface layer 110 and the liner layer 120 is 10-20% softwood chemical pulp and 80-90% hardwood chemical pulp, wherein the softwood chemical pulp has a pulp freeness of 380±20ml and a pulp fiber length of 0.8-1.2mm, and the hardwood chemical pulp has a pulp freeness of 430±20ml and a pulp fiber length of 0.4-0.6mm.

[0025] The amount of sizing agent used in the slurry for the surface layer 110 and the surface lining layer 120 is zero. The total basis weight of the surface layer 110 and the surface lining layer is 30-35 gsm, the basis weight of the core layer 130 is 70-280 gsm, and the total basis weight of the bottom layer 150 and the bottom lining layer 140 is 30-70 gsm.

[0026] The overall basis weight design of the surface layer 110 and the liner layer 120 is to allow the ink sprayed onto the paper surface to penetrate through the surface layer 110 and the liner layer 120 and permeate into the core layer 130. The selection of longer chemical pulp fibers facilitates the interweaving of the pulp itself, and the light beating of the pulp allows the interwoven pulp to have higher bulk and porosity, thus facilitating the penetration of the anti-counterfeiting pattern ink from the surface to the paper core layer. After the anti-counterfeiting ink reaches the paper surface through the inkjet device, it can penetrate through the paper surface layer or multiple layers of cardboard, including the surface layer, surface layer + liner layer, bottom layer, or bottom layer + liner layer, reaching the deep layers of the paper or the core layer of multiple cardboard layers, achieving a deep anti-counterfeiting effect.

[0027] Please continue reading. Figure 1 The preparation method in this embodiment also includes step S200, which involves drying the base paper for the first time.

[0028] This step can specifically be a pre-drying process, using a drying cylinder for drying.

[0029] Step S300: Spray ink onto the surface of the dried base paper.

[0030] Please see Figure 4 , Figure 4 This is a schematic diagram of ink coating on the surface of the base paper. In the diagram, 200 represents the ink layer, which may ultimately penetrate into the base paper.

[0031] In this embodiment, the ink is a water-based ink, comprising 10-30% pigments, dyes, or anti-counterfeiting materials, 20-40% water, 30-40% water-soluble resin, and 1-10% other additives. Based on preset patterns or text information, the corresponding ink ratio and spraying parameters are set in the control system. Then, paper is fed into the inkjet device for precise spraying of the anti-counterfeiting ink. Those skilled in the art can adjust the specific ink ratio according to their needs; no specific limitations are made here.

[0032] In this step, a high-precision inkjet printer is installed on the main section of the paper manufacturing line, after pre-drying and before surface sizing. This ensures a stable and reliable ink supply system, a precise and sensitive control system, and high precision and reliability of the inkjet heads. The selection and application of anti-counterfeiting ink: Inks with special anti-counterfeiting properties are selected, such as color-changing inks and fluorescent inks (specifically, water-based inks are chosen, with pigments, dyes, or anti-counterfeiting functional materials comprising 10-30%, solvents 20-40%, water-soluble resins 30-40%, and other additives 1-3%). Based on preset patterns or text information, the corresponding ink type, specific material ratios, and spraying parameters are set in the control system. Then, the paper is fed into the inkjet printer for precise inkjet application.

[0033] Please continue reading. Figure 1 The preparation method in this embodiment also includes step S400, which involves applying adhesive to the surface layer after ink spraying.

[0034] Please see Figure 5 , Figure 5 This is a schematic diagram of the laminated structure after surface sizing, where 300 marks the surface sizing layer. In this step, the surface sizing agent is a starch-based solution with a solid content of 13-16%, a viscosity of 40-60 cps, and a coating amount of 4-6 g / m². 2 The linear pressure of the application roller is 30-33 N*m. 2 .

[0035] Starch has a good affinity with paper cellulose. The lower the solid content of the sizing solution, the larger the sizing amount, and the more water is applied during sizing. Water easily migrates to the paper core layer. Combined with the pressure and temperature conditions of the sizing rod and the migration of the sizing solution, this promotes the penetration of ink into the deeper layers (core layer) of the paper. At the same time, the sizing solution, as a carrier, can guide the ink to penetrate deep into the paper fibers and firmly bond the ink to the fibers, forming a stable anti-counterfeiting structure.

[0036] Please continue reading. Figure 1 The preparation method in this embodiment also includes step S500, which involves drying the sized paper a second time.

[0037] The drying methods and processes are conventional and, as understood by those skilled in the art, can be drying or hot air drying, etc., which will not be elaborated here.

[0038] The method for preparing anti-counterfeiting paper provided in this application involves precisely inkjetizing anti-counterfeiting ink onto the paper before surface sizing during the online paper manufacturing process to form images and text. A suitable paper structure is designed to allow the ink to penetrate, and the favorable conditions of the sizing liquid migrating into the deeper layers of the paper during the surface sizing process are utilized to further promote the penetration of the ink into the deeper layers of the paper. This method enables the online production of anti-counterfeiting paper on a high-speed paper machine, and features low cost and good anti-counterfeiting effect.

[0039] Please see Figure 6 , Figure 6 This is a schematic flowchart of another embodiment of the method for preparing anti-counterfeiting paper according to this application. The preparation method includes, but is not limited to, the following steps.

[0040] Step S100: Making the original paper.

[0041] Please continue reading for more details. Figure 2 and Figure 3 In this embodiment, the base paper comprises a 4-layer or 5-layer paper composite structure, which can be... Figure 2The base paper 100 in this embodiment includes a top layer 110, a face liner layer 120, a core layer 130, and a bottom layer 150, which are stacked sequentially. Alternatively, it could be... Figure 3 The base paper 100 in the embodiment includes a surface layer 110, a face liner layer 120, a core layer 130, a bottom liner layer 140, and a bottom layer 150, which are stacked in sequence.

[0042] Optionally, in this embodiment, the pulp fiber ratio of the surface layer 110 and the liner layer 120 is 10-20% softwood chemical pulp and 80-90% hardwood chemical pulp, wherein the softwood chemical pulp has a pulp freeness of 380±20ml and a pulp fiber length of 0.8-1.2mm, and the hardwood chemical pulp has a pulp freeness of 430±20ml and a pulp fiber length of 0.4-0.6mm.

[0043] The amount of sizing agent used in the slurry for the surface layer 110 and the surface lining layer 120 is zero. The total basis weight of the surface layer 110 and the surface lining layer is 30-35 gsm, the basis weight of the core layer 130 is 70-280 gsm, and the total basis weight of the bottom layer 150 and the bottom lining layer 140 is 30-70 gsm.

[0044] The overall basis weight design of the surface layer 110 and the liner layer 120 is to allow the ink sprayed onto the paper surface to penetrate through the surface layer 110 and the liner layer 120 and permeate into the core layer 130. The selection of longer chemical pulp fibers facilitates the interweaving of the pulp itself, and the light beating of the pulp allows the interwoven pulp to have higher bulk and porosity, thus facilitating the penetration of the anti-counterfeiting pattern ink from the surface to the paper core layer. After the anti-counterfeiting ink reaches the paper surface through the inkjet device, it can penetrate through the paper surface layer or multiple layers of cardboard, including the surface layer, surface layer + liner layer, bottom layer, or bottom layer + liner layer, reaching the deep layers of the paper or the core layer of multiple cardboard layers, achieving a deep anti-counterfeiting effect.

[0045] Please continue reading. Figure 6 The preparation method in this embodiment also includes step S200, which involves drying the base paper for the first time.

[0046] This step can specifically be a pre-drying process, using a drying cylinder for drying.

[0047] Step S300: Spray ink onto the surface of the dried base paper.

[0048] Please continue reading. Figure 4The ink layer 200 can ultimately penetrate into the base paper. In this embodiment, the ink is a water-based ink, comprising 10-30% pigments, dyes, or anti-counterfeiting materials, 20-40% water, 30-40% water-soluble resin, and 1-10% other additives. Based on preset patterns or text information, the corresponding ink ratio and spraying parameters are set in the control system. Then, the paper is fed into the inkjet device for precise spraying of the anti-counterfeiting ink. Those skilled in the art can adjust the specific ink ratio according to their needs; no specific limitations are made here.

[0049] In this step, a high-precision inkjet printer is installed on the main section of the paper manufacturing line, after pre-drying and before surface sizing. This ensures a stable and reliable ink supply system, a precise and sensitive control system, and high precision and reliability of the inkjet heads. The selection and application of anti-counterfeiting ink: Inks with special anti-counterfeiting properties are selected, such as color-changing inks and fluorescent inks (specifically, water-based inks are chosen, with pigments, dyes, or anti-counterfeiting functional materials comprising 10-30%, solvents 20-40%, water-soluble resins 30-40%, and other additives 1-3%). Based on preset patterns or text information, the corresponding ink type, specific material ratios, and spraying parameters are set in the control system. Then, the paper is fed into the inkjet printer for precise inkjet application.

[0050] Please continue reading. Figure 6 The preparation method in this embodiment also includes step S400, which involves applying adhesive to the surface layer after ink spraying.

[0051] Please continue reading. Figure 5 , Figure 5 The 300 marked in the text refers to the surface sizing layer. In this step, the surface sizing agent is a starch-based solution with a solid content of 13-16%, a viscosity of 40-60 cps, and a coating amount of 4-6 g / m². 2 The linear pressure of the application roller is 30-33 N*m. 2 .

[0052] Starch has a good affinity with paper cellulose. The lower the solid content of the sizing solution, the larger the sizing amount, and the more water is applied during sizing. Water easily migrates to the paper core layer. Combined with the pressure and temperature conditions of the sizing rod and the migration of the sizing solution, this promotes the penetration of ink into the deeper layers (core layer) of the paper. At the same time, the sizing solution, as a carrier, can guide the ink to penetrate deep into the paper fibers and firmly bond the ink to the fibers, forming a stable anti-counterfeiting structure.

[0053] Please continue reading. Figure 6 The preparation method in this embodiment also includes step S500, which involves drying the sized paper a second time.

[0054] The drying methods and processes are conventional and, as understood by those skilled in the art, can be drying or hot air drying, etc., which will not be elaborated here.

[0055] Unlike the previous embodiments, the preparation method in this embodiment further includes step S600, which involves coating the surface after surface sizing.

[0056] The coating process includes pre-coating, intermediate coating, and topcoat. Please refer to [link / reference]. Figure 7 , Figure 7 This is a schematic diagram of the layered structure of another embodiment of the anti-counterfeiting paper of this application. In this embodiment, the coating layer 400 includes a pre-coating layer 410, a middle coating layer 420, and a top coating layer 430.

[0057] The pre-coat, intermediate coat, and topcoat all contain 70-80% GCC (55-98), 0-20% kaolin, 5-30% hiding agent, 10-12% adhesive, and a small amount of auxiliary additives by weight. See the table below for specific proportions.

[0058]

[0059] The anti-counterfeiting paper in this embodiment utilizes inkjet and coating technologies to adjust visual clarity, meeting various visual anti-counterfeiting needs, and features a watermark effect. Under strong light, the anti-counterfeiting pattern is clear and easily identifiable.

[0060] The anti-counterfeiting paper preparation method in this application involves inkjet printing followed by coating. A suitable coating formula can be selected according to customer needs for masking. Different coating properties result in varying degrees of clarity for the anti-counterfeiting pattern when viewed with the naked eye. When the pattern surface is coated, the anti-counterfeiting pattern is clearly visible under strong light. However, if the anti-counterfeiting pattern is not coated or is printed on the surface, although it is visible to the naked eye, the pattern is not clear under strong light.

[0061] This application primarily utilizes coating materials, microstructure, and optical properties to achieve precise control over light transmission and scattering. The refractive indices of the heavy calcium carbonate, kaolin, and adhesives used in the coating are generally between 1.4 and 1.6, while the refractive index of paper fibers is approximately 1.5. The refractive indices of both are essentially similar, and the surface gloss is controlled below 65, which reduces interfacial reflection and enhances transmission. The pigments used in the coating, such as heavy calcium carbonate and kaolin, have particle sizes of approximately 0.5-7 μm, effectively controlling scattering intensity. Simultaneously, the developed surface-masking pigment, with a particle size of 0.3-0.6 μm, partially fills the pigment pores, reducing light scattering paths and enhancing light transmission. These design features ensure that the anti-counterfeiting pattern is clearly visible under strong light.

[0062] Compared to existing inkjet anti-counterfeiting methods that rely on printing ink between paper sheets, the anti-counterfeiting paper in this embodiment is more suitable for high-speed paper machines upgraded through industrial automation, improving machine efficiency and reducing costs. The anti-counterfeiting pattern boasts higher precision and wider adaptability, offering varying levels of clarity to meet customer requirements. For example, with good coverage, a watermark-like effect is visible to the naked eye, while the pattern remains clearly identifiable under strong light, providing dual anti-counterfeiting verification. This effect cannot be achieved through simple surface printing, making it difficult to counterfeit. Even when illuminated with a mobile phone light, the internal pattern of the anti-counterfeiting paper remains visible, ensuring easy identification.

[0063] The method for preparing anti-counterfeiting paper provided in this application involves precisely inkjetizing anti-counterfeiting ink onto the paper before surface sizing during the online paper manufacturing process to form images and text. A suitable paper structure is designed to allow ink penetration, and the favorable conditions of the sizing liquid migrating deeper into the paper during surface sizing further promote ink penetration. The paper surface coating formula is designed to provide different levels of coverage for the anti-counterfeiting pattern, forming a stable and difficult-to-replicate anti-counterfeiting structure. This solves the practical problems of unstable inkjet printing and low precision caused by the high temperature and humidity and high speed of the paper machine during wet-end printing of special images and text information on the core layer to achieve anti-counterfeiting effects in paper machine wet-end printing. This invention avoids the influence of the wet-end environment by installing the anti-counterfeiting inkjet device after the pre-drying section and before surface sizing. This design not only facilitates process control but also offers high flexibility and printing precision. It allows for digital anti-counterfeiting traceability based on product requirements and enables online production of anti-counterfeiting paper on high-speed paper machines at low cost. This invention utilizes the light diffraction effect of the coating to make the pattern clearer under light, making it easier to identify with the naked eye.

[0064] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or directly or indirectly applied to other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A method for preparing anti-counterfeiting paper, characterized in that, The preparation method includes: Papermaking base paper, wherein the base paper comprises at least a surface layer, a face liner layer, a core layer and a bottom layer stacked in sequence; The base paper is first dried; Ink is sprayed onto the surface of the dried base paper; Apply a surface adhesive to the surface layer after spraying ink; The sized paper products are then dried a second time.

2. The preparation method according to claim 1, characterized in that, In the papermaking process, the pulp fiber ratio of the surface layer and the liner layer is 10-20% softwood chemical pulp and 80-90% hardwood chemical pulp.

3. The preparation method according to claim 2, characterized in that, The freeness of the softwood chemical pulp is 380±20ml, and the pulp fiber length is 0.8-1.2mm. The freeness of the hardwood chemical pulp is 430±20ml, and the pulp fiber length is 0.4-0.6mm.

4. The preparation method according to claim 3, characterized in that, The amount of sizing agent used in the surface layer and the lining layer is zero.

5. The preparation method according to claim 1, characterized in that, The base paper also includes a backing layer, which is disposed between the core layer and the bottom layer. The total basis weight of the top layer and the top liner is 30-35 gsm, the basis weight of the core layer is 70-280 gsm, and the total basis weight of the bottom layer and the backing layer is 30-70 gsm.

6. The preparation method according to claim 1, characterized in that, In the step of spraying ink onto the surface of the dried base paper, the ink is a water-based ink, and the ink contains 10-30% pigments, dyes or anti-counterfeiting materials, 20-40% water, 30-40% water-soluble resin, and 1-10% other additives.

7. The preparation method according to claim 1, characterized in that, In the step of surface sizing after ink spraying, the surface sizing agent is a starch-based solution with a solid content of 13-16%, a viscosity of 40-60 cps, and a coating amount of 4-6 g / m². 2 .

8. The preparation method according to claim 1, characterized in that, The preparation method further includes: coating the surface after surface sizing; wherein the coating includes pre-coating, intermediate coating and topcoat.

9. The preparation method according to claim 8, characterized in that, Pre-coat paint, intermediate coat paint and topcoat paint all contain 70-80% GCC (55-98) by weight, 0-20% kaolin, 5-30% hiding agent, 10-12% adhesive and a small amount of auxiliary additives.

10. A type of anti-counterfeiting paper, characterized in that, The anti-counterfeiting paper is prepared using the preparation method described in any one of claims 1-9.

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