Anti-delamination blue card composite paperboard and processing method

Abstract

The application relates to the technical field of paperboard, and discloses an anti-delamination blue card composite paperboard and a processing method, which comprise an ink printing layer and a paper base layer; the paper base layer is a multilayer composite blue core paper; a bidirectional stretching single-sided corona polypropylene layer is connected between the ink printing layer and the paper base layer; the bidirectional stretching single-sided corona polypropylene layer and the paper base layer are bonded through a chlorinated polyolefin adhesive layer; and the ink printing layer is bonded to the surface of the bidirectional stretching single-sided corona polypropylene layer. The bidirectional stretching single-sided corona polypropylene layer is used as an intermediate layer, a pattern is printed on one side of the corona layer, and chlorinated polyolefin is used as an adhesive layer, so that the waterproof effect of the bidirectional stretching single-sided corona polypropylene layer is improved, the use environment of the blue card is met, and it is difficult for counterfeiters to analyze and counterfeit. In the fields of card games and puzzles for the application of the blue card, anti-counterfeiting can more effectively reduce the economic losses of enterprises caused by counterfeiting.

Description

Technical Field

[0001] This invention relates to the field of cardboard technology, specifically to an anti-delamination blue cardboard composite paperboard and its processing method. Background Technology

[0002] The core material of blue core cardboard is high-density blue core paperboard, with a waterproof coating to ensure paper rigidity and enhance tear resistance through tight interlocking of fibers. Compared to traditional gray or white cardboard, blue cardboard has a higher fiber density and better light transmission resistance, preventing light penetration and visual impact on users when used in puzzles and cards. Since cards and puzzles often have collectible value, their market value can far exceed manufacturing costs. To ensure the lifespan of cards and puzzles, high-end products use blue core cardboard as the main base layer.

[0003] Blue core cardboard features a waterproof coating, but this coating is exposed on the surface and prone to damage from prolonged use and friction, leading to moisture absorption. BOPP film offers excellent waterproofing, and its integral structure results in a significantly higher tensile strength in the horizontal direction compared to the coating. Therefore, laminating blue core cardboard with BOPP film ensures both waterproofing and improved tensile strength. Furthermore, the BOPP film absorbs stress during cardboard bending, preventing core breakage due to excessive bending. Thus, the combination of BOPP film and blue core cardboard is more effective in various applications and addresses coating wear caused by frequent contact.

[0004] However, BOPP film has low surface energy, making it difficult to laminate BOPP film with paper. Therefore, the key to the combination of BOPP film and blue core cardboard is how to avoid interlayer separation.

[0005] Chinese patent (CN1559797A) discloses a packaging box made of color-printed biaxially oriented polypropylene film and paperboard composite and its manufacturing method. This patent adds inorganic fillers to the biaxially oriented polypropylene film, so that there are a large number of micropores on the surface of the film itself, and adds a corona treatment process to further increase the number of micropores on the surface of the film, thereby making the film performance reach 35N / m-50N / m.

[0006] Based on the aforementioned patent content, it is known that the comparative patent proposes adding silica to biaxially oriented polypropylene films, as detailed in existing literature: (“BOPP / SiO”). ２ @TiO ２ "Preparation of Nanocomposite Films and Study on Printing Performance of Water-based Inks", Liu Zhenzhong et al., Chemical New Materials, Vol. 53, No. 6, pp. 123-128, 2025. This article proposes that suitable SiO2 for BOPP films can be screened by adjusting the silicon-titanium molar ratio. ２ / TiO ２ Nano-coatings, compared with the appearance images of silicon-titanium mixed solutions with different silicon-titanium molar ratios, revealed that transparent SiO2 is formed after the hydrolysis reaction of pure silicon. ２ Sol, pure titanium hydrolyzes to form white TiO2 ２ Precipitation occurs when silicon-titanium mixed solutions with different silicon-titanium molar ratios hydrolyze to form pale yellow, uniform SiO₂. ２ / TiO ２ The transmittance of the sol-gel and multiple films was analyzed. The specific conclusions are as follows: Compared with BOPP films, the transmittance of BOPP corona-treated and polymer-grafted films, as well as BOPP / PAA-grafted films, showed almost no change, especially in the visible light region where the transmittance remained around 90%; while the transmittance of SiO2 films with different silicon-titanium molar ratios... ２ / TiO ２ After the nano-coating is applied, SiO ２ @TiO ２ The transmittance of nanocomposite films varies considerably, decreasing sharply with increasing titanium content. This indicates that using inorganic fillers in the coating reduces the film's transmittance. If BOPP is used as the intermediate layer, a six-layer composite process is formed: surface coating - coating layer - BOPP - coating layer - adhesive - core paper. The increased number of layers and total thickness makes interlayer separation more likely during bending.

[0007] Double-sided printing using transparent biaxially oriented polypropylene (BOPP) film requires double-sided corona treatment. However, BOPP film, due to double-sided corona treatment and the addition of filler micropores, has enhanced hydrophilicity. Single-sided corona treatment is more cost-effective than double-sided corona treatment. However, if single-sided corona treatment is used, the adhesion between the BOPP film and the paper is not strong. Since blue core cardboard is frequently in contact with the hands, it is easy to delaminate when the interlayer strength between the BOPP film and the paper is weak. This is not suitable for the application environment of blue core cardboard.

[0008] Furthermore, due to cost considerations, blue core cardstock is mainly used in high-end cards and puzzles, which have collectible value. Therefore, the increased resistance to delamination increases the difficulty of counterfeiting, thus achieving the purpose of anti-counterfeiting. Summary of the Invention

[0009] The purpose of this invention is to provide an anti-delamination blue cardboard composite paperboard, which uses biaxially stretched single-sided corona discharge combined with chlorinated polyolefin as the adhesive layer to achieve composite bonding, meeting the requirements of blue cardboard usage environments and increasing paper lifespan. Furthermore, because it exhibits tearing behavior during peeling, it makes it difficult for counterfeiters to disassemble and analyze forgery. This addresses the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: An anti-delamination blue cardboard composite paperboard includes an ink printing layer and a paper base layer. The paper base layer is a multi-layer composite blue core paper. A biaxially oriented single-sided corona-treated polypropylene layer is connected between the ink printing layer and the paper base layer. The biaxially oriented single-sided corona-treated polypropylene layer is bonded to the paper base layer by a chlorinated polyolefin adhesive layer. The ink printing layer is bonded to the surface of the biaxially oriented single-sided corona-treated polypropylene layer. The direction of the biaxially oriented single-sided corona-treated polypropylene layer with a larger stretch ratio is the same as the CD direction of the paper base layer.

[0011] As a further embodiment of the present invention: the ink printing layer is adhered to the corona surface of the biaxially oriented single-sided corona-electrode polypropylene layer, and the surface tension of the corona surface is 40-42 mN / m.

[0012] As a further embodiment of the present invention: the ink printing layer is adhered to the surface of the paper base layer, the chlorinated polyolefin adhesive layer is distributed between the biaxially oriented single-sided corona-electroplated polypropylene layer and the ink printing layer, and the corona layer of the biaxially oriented single-sided corona-electroplated polypropylene layer is exposed to the outside and the ink printing layer is printed again.

[0013] As a further embodiment of the present invention: the chlorinated polyolefin adhesive layer, in addition to the main adhesive chlorinated polyolefin, also includes resin, chlorinated paraffin, and mixed solvent.

[0014] As a further aspect of the present invention: the color of the chlorinated polyolefin adhesive layer is light yellow or transparent. When the color of the chlorinated polyolefin adhesive layer is light yellow, the ink printing layer covers the outer surface of the biaxially oriented single-sided corona-electroplated polypropylene layer to shield the color interference caused by the chlorinated polyolefin adhesive layer.

[0015] As a further aspect of the present invention, the processing method of the anti-delamination, high-toughness, and high-thickness blue cardboard composite paperboard includes the following steps: S1: After washing the BOPP film, it is extracted and impurities are removed in a mixture of acetone, ethyl acetate and alcohol. After extraction, it is dried. The dried BOPP film is fed into the corona treatment equipment at a uniform speed. The current intensity is adjusted to 8A. The surface tension of the polypropylene film after corona treatment is 40-42mN / m, and a biaxially oriented single-sided corona-treated polypropylene layer is obtained. S2: Chlorinated polyolefin is used as the main adhesive, 215 resin and natural resin are used as auxiliary adhesives, chlorinated paraffin is used as the additive, and the solvent is a mixed solvent of hydrocarbon solvent and ester solvent, wherein the mass ratio of hydrocarbon solvent to ester solvent is 8:2. All the above components except the additive are added to a stirring tank and dissolved at 50°C for 2 hours. Then the additive is added and mixed at 30°C for 1 hour to obtain the adhesive. S3: When the adhesive is transparent, follow these steps: Apply the adhesive to the corona layer of the biaxially oriented single-sided corona-electroplated polypropylene layer using a coating machine and dry it at 40°C. After drying, laminate it onto the paper base layer. A chlorinated polyolefin adhesive layer is formed between the biaxially oriented single-sided corona-electroplated polypropylene layer and the paper base layer, with the corona layer of the biaxially oriented single-sided corona-electroplated polypropylene layer located on the outside. The coating and lamination parameters are: adhesive dosage is 3g / m². 3 The equipment rollers are at 75°C, and the roller pressure is 2000 N / cm. 2 The compounding speed is 8 m / min; S4: Print a pattern onto the corona layer of a biaxially stretched single-sided corona-electrode polypropylene layer using printing equipment.

[0016] As a further embodiment of the present invention: In step S3: when the adhesive is light yellow, the following steps are performed: a deep pattern is printed on the surface of the paper base layer, the adhesive is coated onto the biaxially oriented single-sided corona-electroplated polypropylene layer by a coating machine and dried at a temperature of 40°C, and after drying, the biaxially oriented single-sided corona-electroplated polypropylene layer is laminated onto the deep pattern of the paper base layer.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This design employs a biaxially oriented single-sided corona-treated polypropylene layer as the intermediate layer, with patterns printed on one side of the corona layer. This reduces corona treatment costs and avoids the reduced corona effect caused by surface energy decay due to intervals in the bonding process. Simultaneously, chlorinated polyolefin is used as the adhesive layer to achieve composite bonding between the non-corona-treated side of the biaxially oriented single-sided corona-treated polypropylene layer and the deep pattern on the paper base surface. The addition of the biaxially oriented single-sided corona-treated polypropylene layer enhances the strength of the cardboard itself, preventing core breakage due to excessive bending, meeting the requirements of blue card usage environments. It also prevents delamination and peeling, and the combination of light and dark patterns and the color composite of the adhesive layer allows for richer and more diverse color variations as the paper's lifespan increases. Furthermore, because tearing occurs during peeling, it makes it difficult for counterfeiters to disassemble and analyze the forgery. For blue card applications in card games and puzzles, this anti-counterfeiting measure can more effectively reduce the economic losses caused by counterfeiting to businesses. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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.

[0019] Figure 1 This is a schematic diagram of the structure of an anti-delamination blue cardboard composite paperboard; In the diagram: 1. Ink printing layer; 2. Biaxially oriented single-sided corona-treated polypropylene layer; 3. Chlorinated polyolefin adhesive layer; 4. Paper base layer. Detailed Implementation

[0020] Please see Figure 1 Example 1: This embodiment aims to address the issue of BOPP film undergoing unidirectional corona treatment while maintaining its own strength to suit the application environment of Blue Card.

[0021] In this embodiment: Due to the characteristics of continuous industrial production, the fibers of the paper base layer 4 are oriented along the running direction during paper machine production, resulting in the tensile strength of industrial paper in the MD direction being greater than that in the CD direction. To compensate for the difference in tensile strength of the paper base layer 4, a biaxially oriented single-sided corona-treated polypropylene layer 2 is selected as the reinforcing layer.

[0022] The characteristic of the biaxially oriented single-sided corona-treated polypropylene layer 2 lies in its biaxial stretching. During the stretching process, the tensile strength increases significantly with the increase of the stretch ratio. Specifically, in biaxial stretching, the high stretch ratio direction of the biaxially oriented single-sided corona-treated polypropylene layer 2 is aligned with the CD direction, thereby reinforcing the CD direction of the industrial paper.

[0023] When the paper base layer 4 is a multi-layer composite with a certain thickness, it is necessary to increase the interlayer strength to avoid delamination and tearing. When the biaxially oriented single-sided corona-treated polypropylene layer 2 is not corona-treated, its surface structure is a non-polar polypropylene film with high chemical stability, resulting in poor adhesion between the biaxially oriented single-sided corona-treated polypropylene layer 2 and the paper and ink. If dye is added during the processing of the biaxially oriented single-sided corona-treated polypropylene layer 2, uneven color distribution may occur during stretching, affecting the appearance. Therefore, the addition of the biaxially oriented single-sided corona-treated polypropylene layer 2 significantly reduces the printability of the paper. To solve this problem, corona treatment is selected for the biaxially oriented single-sided corona-treated polypropylene layer 2.

[0024] The processing technology for biaxially oriented single-sided corona-treated polypropylene layer 2 is as follows: After washing, the BOPP film is extracted and impurities are removed in a mixture of acetone, ethyl acetate, and alcohol. After extraction, it is dried, preferably in a vacuum oven. The dried BOPP film is then fed into a corona treatment device at a uniform speed, with the current intensity adjusted to 8A. Under the influence of a high-voltage electric field, the electron flow impacts the film, roughening its surface and forming multiple tiny mechanical connection points, increasing the adhesion area of ​​the adhesive. Furthermore, the ozone plasma particles generated during the corona treatment react chemically with the plastic surface molecules and water in the air, introducing polar oxygen-containing groups such as CO=O and -OH, thus activating the polypropylene film surface. The relationship between corona treatment parameters and tension is shown in Table 1 below.

[0025] Table 1. Tension Changes under Corona Treatment

[0026] The critical surface tension of untreated BOPP film is only 30 mN / m. Solvent-based offset printing inks require a surface energy of approximately 40 mN / m for polypropylene film, while UV coating inks and emulsion inks require 42 mN / m. After corona treatment, the surface tension of the BOPP film increases significantly. The particle dynamic potential energy is positively correlated with the treatment power. This increase in dynamic potential energy positively impacts the opening of long-chain chemical bonds on the plastic surface, leading to a corresponding increase in surface activity. Therefore, the surface tension of the plastic increases with increasing current intensity, which aids in ink adhesion and bonding. When the corona treatment exceeds its limit, the air volume between the electrode and the corona roller remains relatively stable during the instantaneous corona treatment, resulting in a fixed oxygen molecule content. This prevents the activation of more oxygen molecules, causing more oxygen-containing functional groups to remain on the film surface. Furthermore, the surface structure is severely damaged due to excessive corona treatment, leading to a decrease in the plastic surface energy. Therefore, the surface energy exhibits a downward trend. From the above, it can be seen that after single-sided corona treatment, the surface of the BOPP film meets printing requirements.

[0027] After solving the adhesion problem between the BOPP film and the ink, it is necessary to solve the adhesion problem between the BOPP film and the paper substrate 4. To solve this problem, a chlorinated polyolefin adhesive layer 3 is set up.

[0028] The composition of chlorinated polyolefin adhesive layer 3 is as follows: Main adhesive: Chlorinated polyolefin with 25% chlorine content; Adhesive additives: 215 resin, natural resin; the purpose of adding resin is to increase adhesion, thereby ensuring bonding with paper.

[0029] Additives: Chlorinated paraffin; the additives enhance the slip properties and are suitable for coating processes.

[0030] Solvents: Hydrocarbon solvents and ester solvents. To dissolve the binder and adjust the viscosity, this technical solution uses a mixture of hydrocarbon and ester solvents at a mass ratio of 8:2 to form a mixed solvent for use.

[0031] Processing technology: Add all the above ingredients except the additives to a mixing tank and dissolve at a constant temperature of 50°C for 2 hours. Then add the additives and mix at 30°C for 1 hour to obtain the binder.

[0032] The adhesive was coated onto BOPP using a coating machine and dried at a temperature above 40°C. After drying, it was laminated onto the paper base layer 4 with the ink printing layer 1. The coating and lamination parameters were as follows: adhesive dosage was 3 g / m². 3The equipment rollers are at 75°C, and the roller pressure is 2000 N / cm. 2 The compounding speed is 8 m / min.

[0033] After lamination, the film underwent a 180° peel test. The adhesive layer showed no damage, while the biaxially oriented single-sided corona-treated polypropylene layer 2 or the paper base layer 4 exhibited cracking behavior. This effectively prevented delamination and cracking issues.

[0034] The advantages of this technical solution are as follows: Using a biaxially oriented single-sided corona-treated polypropylene layer 2 as the intermediate layer allows for adjustments to the appearance color and gloss using the ink printing layer 1. Simultaneously, the waterproof and breathable properties of the biaxially oriented single-sided corona-treated polypropylene layer 2 protect the paper base layer 4. The bonding mechanism of chlorinated polyolefins primarily utilizes the principle of "like dissolves like," employing an ethylene-propylene copolymer with polypropylene as the main component and introducing active groups into its molecular chain, increasing its affinity with polyolefins and other materials. Therefore, the BOPP film does not require corona treatment, and the non-corona-treated side of the biaxially oriented single-sided corona-treated polypropylene layer 2 can also firmly adhere to the printed paper base layer 4. Furthermore, the chlorinated polyolefin adhesive layer 3 significantly increases the interlayer strength between the biaxially oriented single-sided corona-treated polypropylene layer 2 and the paper base layer 4. The potential pale yellow tint of the chlorinated polyolefin adhesive layer 3 does not affect the overall color appearance, thus greatly improving the range of adjustments for the physical properties and appearance of the colored cardboard.

[0035] Example 2:

[0036] In Example 1, a chlorinated polyolefin adhesive layer 3 is used as the intermediate adhesive layer between the biaxially oriented single-sided corona-treated polypropylene layer 2 and the paper base layer 4 with printed patterns, achieving a peel-off and tear-off effect. Based on this, and considering the application environment of blue core cardboard, anti-counterfeiting measures and visual changes over its lifespan can be achieved. The specific implementation method is as follows. The difference between this technical solution and Example 1 is: The ink printing layer 1 is adhered to the surface of the paper base layer 4. The chlorinated polyolefin adhesive layer 3 is distributed between the biaxially oriented single-sided corona-electroplated polypropylene layer 2 and the ink printing layer 1. The corona layer of the biaxially oriented single-sided corona-electroplated polypropylene layer 2 is exposed to the outside and is reprinted to obtain the ink printing layer 1.

[0037] The ink-printed layer 1 on the surface of the paper base layer 4 serves as the deep pattern, while the ink-printed layer 1 on the corona-treated surface of the biaxially oriented single-sided corona-treated polypropylene layer 2 serves as the shallow pattern. The shallow pattern is fixed using the corona treatment, while the deep pattern is firmly adhered between the paper base layer 4 and the biaxially oriented single-sided corona-treated polypropylene layer 2 using a chlorinated polyolefin adhesive layer 3. Simultaneously, the pale yellow color of the chlorinated polyolefin adhesive layer 3 can cover the deep pattern on the surface of the paper base layer 4, giving the pattern a composite quality. During normal use, as the lifespan increases, the shallow pattern gradually peels off, revealing the deep pattern, thus enriching the color variations of the paper itself over its lifespan. Furthermore, because the peeling process involves tearing, it makes it difficult for counterfeiters to disassemble and analyze the forgery. For applications such as cards and puzzles using blue cards, this anti-counterfeiting measure can more effectively reduce the economic losses to businesses caused by counterfeiting.

[0038] This technical solution adopts a single corona-chlorinated polyolefin-paper base bonding method. Compared with the double corona paper base bonding method, single corona can reduce costs, and chlorinated polyolefin itself has a certain moisture barrier property, which enhances the barrier effect. In addition, chlorinated polyolefin, as a paper base-film base adhesive, exhibits peeling and cracking behavior during tearing, increasing the cost of counterfeiting. Furthermore, compared with double corona, single corona has less impact on light transmittance. With minimal impact on light transmittance, an anti-counterfeiting composite appearance can be formed, which is suitable for the application fields of blue core cardboard.

[0039] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A type of anti-delamination blue cardboard composite paperboard, comprising an ink printing layer (1) and a paper base layer (4), wherein the paper base layer (4) is a multi-layer composite blue core paper, characterized in that: A biaxially oriented single-sided corona-electroplated polypropylene layer (2) is connected between the ink printing layer (1) and the paper base layer (4). The biaxially oriented single-sided corona-electroplated polypropylene layer (2) and the paper base layer (4) are bonded together by a chlorinated polyolefin adhesive layer (3). The ink printing layer (1) is bonded to the surface of the biaxially oriented single-sided corona-electroplated polypropylene layer (2). The direction in which the biaxially oriented single-sided corona-electroplated polypropylene layer (2) has a larger stretch ratio is the same as the CD direction of the paper base layer (4).

2. The anti-delamination blue cardboard composite paperboard according to claim 1, characterized in that: The ink printing layer (1) is adhered to the corona surface of the biaxially oriented single-sided corona-electrode polypropylene layer (2), and the surface tension of the corona surface is 40-42 mN / m.

3. The anti-delamination blue cardboard composite paperboard according to claim 2, characterized in that: The ink printing layer (1) is adhered to the surface of the paper base layer (4), the chlorinated polyolefin adhesive layer (3) is distributed between the biaxially oriented single-sided corona-electroplated polypropylene layer (2) and the ink printing layer (1), and the corona layer of the biaxially oriented single-sided corona-electroplated polypropylene layer (2) is exposed to the outside and the ink printing layer (1) is printed again.

4. The anti-delamination blue cardboard composite paperboard according to claim 1, characterized in that: The chlorinated polyolefin adhesive layer (3) includes, in addition to the main adhesive chlorinated polyolefin, resin, chlorinated paraffin and mixed solvent. The resin is 215 resin and natural resin, and the mixed solvent is a mixture of hydrocarbon solvent and ester solvent.

5. The anti-delamination blue cardboard composite paperboard according to claim 4, characterized in that: The chlorinated polyolefin adhesive layer (3) is light yellow or transparent. When the chlorinated polyolefin adhesive layer (3) is light yellow, the ink printing layer (1) covers the outer surface of the biaxially oriented single-sided corona-electroplated polypropylene layer (2) to shield the color interference caused by the chlorinated polyolefin adhesive layer (3).

6. A processing method for an anti-delamination blue cardboard composite paperboard according to any one of claims 1-5, characterized in that: Includes the following steps: S1: After washing the BOPP film, it is extracted and impurities are removed in a mixture of acetone, ethyl acetate and alcohol. After extraction, it is dried. The dried BOPP film is fed into the corona treatment equipment at a uniform speed. The current intensity is adjusted to 8A. The surface tension of the corona-treated polypropylene film is 40-42mN / m. A biaxially oriented single-sided corona-treated polypropylene layer is obtained (2). S2: Chlorinated polyolefin is used as the main adhesive, 215 resin and natural resin are used as auxiliary adhesives, chlorinated paraffin is used as the additive, and the solvent is a mixed solvent of hydrocarbon solvent and ester solvent, wherein the mass ratio of hydrocarbon solvent to ester solvent is 8:

2. The main adhesive, auxiliary adhesive and solvent are added to a stirring tank and dissolved at 50°C for 2 hours. Then the additive is added and mixed at 30°C for 1 hour to obtain the adhesive. S3: When the adhesive is transparent, follow these steps: Apply the adhesive to the biaxially oriented single-sided corona-treated polypropylene layer (2) using a coating machine and dry it at 40°C. After drying, laminate it onto the paper base layer (4). A chlorinated polyolefin adhesive layer (3) is formed between the biaxially oriented single-sided corona-treated polypropylene layer (2) and the paper base layer (4), with the corona layer of the biaxially oriented single-sided corona-treated polypropylene layer (2) located on the outside. The coating and lamination parameters are: adhesive dosage is 3 g / m 3 The roller temperature is 75℃, and the roller pressure is 2000 N / cm. 2 The compounding speed is 8 m / min; S4: Print a pattern onto the corona layer of the biaxially stretched single-sided corona-electrode polypropylene layer (2) using a printing device.

7. The processing method of the anti-delamination blue cardboard composite paperboard according to claim 6, characterized in that: In step S3, when the adhesive is light yellow, the following steps are performed: a deep pattern is printed on the surface of the paper base (4), the adhesive is coated onto the biaxially oriented single-sided corona-electroplated polypropylene layer (2) by a coating machine and dried at 40°C, and after drying, the biaxially oriented single-sided corona-electroplated polypropylene layer (2) is laminated onto the deep pattern of the paper base (4).

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