Release paper for sanitary napkins and printing method thereof

Abstract

The invention relates to the technical field of papermaking, and provides release paper for sanitary napkins and a printing method of the release paper. The release paper comprises: a base material; the printing layer is arranged on at least part of the surface of the base material, and the printing layer is formed by printing and curing body barrier type ink; the functional layer is arranged on at least part of the surface of the printing layer, and the functional layer comprises microcapsules encapsulated with active matters. The microcapsule is used for achieving the functions of resisting bacteria, removing odor and the like in the storage process of the sanitary napkin so as to maintain the cleanliness of the product; after the body barrier type ink is used for printing and is cured, the clearness and the wear resistance of images and texts are ensured, the barrier and interface matching effects between the microcapsule and a base material are achieved, and unexpected migration or failure of active matters in the printing, storage and transportation processes is avoided; therefore, while the printability and the appearance quality of the release paper are ensured, stable packaging of the active matter and function maintenance in the storage period are realized.

Description

Technical Field

[0001] This application relates to the field of papermaking technology, and in particular to a release paper for sanitary napkins and its printing method. Background Technology

[0002] With the continued growth of the personal care products market, disposable hygiene products such as sanitary napkins are facing increasingly higher demands for material functionality and user experience. Release paper, as a crucial interface between sanitary napkin production and final product performance, not only bears the visual function of printed patterns, product logos, and brand expression, but also needs to meet compatibility requirements with adhesives and surface treatment processes, as well as stable release properties. In recent years, to enhance the comfort and added value of sanitary napkins, manufacturers have increasingly introduced active components or encapsulants with antibacterial and deodorizing functions onto the surface of release paper to maintain product cleanliness. However, this places higher demands on the printing process, storage and transportation stability, and appearance quality of the release paper.

[0003] Existing technologies for integrating functional active ingredients into release paper often face the problem of unintended migration or loss of active ingredients during printing, curing, storage, and transportation. For example, shearing, thermal curing, or UV curing during the printing process can cause the encapsulation structure to break, resulting in the release of active ingredients or their penetration into the substrate and adhesive layer. Commonly used printing inks lack effective interfacial barriers between themselves and the functional layer, leading to interactions between active ingredients and ink components, resulting in smudging, reduced abrasion resistance of the graphics, or impaired release performance. Furthermore, conventional inks used to ensure pattern clarity and abrasion resistance often fail to prevent the migration of active ingredients, making it difficult to guarantee the functional performance and batch stability of the final product.

[0004] Therefore, there is an urgent need for a release paper for sanitary napkins and its printing method to solve the above-mentioned technical problems. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the prior art, the purpose of this application is to provide a release paper for sanitary napkins and a printing method thereof.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, embodiments of this application provide a release paper for sanitary napkins, the release paper comprising: a substrate; a printing layer disposed on at least a portion of the surface of the substrate, the printing layer comprising a bulk barrier ink formed by printing and curing; and a functional layer disposed on at least a portion of the surface of the printing layer, the functional layer comprising microcapsules encapsulating active ingredients.

[0007] In an optional embodiment, the release paper further includes an interface optimization layer disposed between the printing layer and the functional layer, the interface optimization layer comprising polyvinyl alcohol or modified polyester emulsion.

[0008] Secondly, embodiments of this application provide a printing method for release paper for sanitary napkins. The printing method is used to prepare release paper according to any of the above-mentioned methods. The printing method includes the following steps: S100, printing a bulk barrier ink on the surface of a substrate to form a printed wet film; S200, curing the printed wet film to form a printed layer; S300, coating at least a portion of the surface of the printed layer with a microcapsule suspension, and drying it to form a functional layer to obtain release paper; wherein, the microcapsule suspension includes microcapsules encapsulated with active ingredients through an in-situ polymerization process.

[0009] In an optional embodiment, prior to step S100, the method further includes: S001, performing a surface activation treatment on the substrate, wherein the surface activation treatment includes at least one of corona treatment and plasma treatment.

[0010] In an optional embodiment, in step S100, the substrate includes at least one of glassine base paper and polyethylene coated paper.

[0011] In an optional implementation, in step S200, the bulk barrier ink comprises a polyurethane-acrylic hybrid resin matrix, a crosslinking agent, and layered nanofillers; and / or in step S200, the dry film thickness of the printed layer is 1.0-3.0µm.

[0012] In an optional implementation, in step S200, curing includes a first stage and a second stage; the temperature of the first stage is 90-100°C; the temperature of the second stage is 110-120°C, and the time is 20-60 seconds.

[0013] In an optional implementation, between step S200 and step S300, the following step is further included: S210, applying a wetting primer with a solid content of 1-5 wt% onto the printed layer and drying it at 80-100°C to form an interface optimization layer.

[0014] In an optional implementation, in step S300, the microcapsules in the microcapsule suspension are prepared by the following steps: S311, emulsifying the oil phase formed by the active ingredient and the carrier oil to obtain an emulsion; S312, subjecting the emulsion to an in-situ polymerization reaction with the shell material monomer to form a coated shell to obtain microcapsules.

[0015] In an alternative embodiment, the microcapsules have a volume average particle size D50 of 3-15 µm.

[0016] The beneficial effects of this application include at least the following: (1) By separating the graphic carrier, barrier protection and active material encapsulation and controllable release through the printing layer and functional layer, the graphic carrier, barrier protection and active material encapsulation and controllable release are physically and technologically separated; the printing layer effectively blocks the unexpected migration and dissipation of active materials to the substrate and adhesive layer, while ensuring the high definition, wear resistance and release stability of the printed pattern, overcoming the problems of graphic smudging and active material failure caused by traditional mixing process. (2) The interface optimization layer serves as a buffer and bridge between the printed layer and the functional layer, improving the interlayer wettability and bonding force, effectively reducing the mechanical and thermal stresses during coating, curing and use that damage the microcapsule structure, thereby ensuring the uniformity and integrity of the functional layer and improving the batch consistency and long-term storage stability of the product. Detailed Implementation

[0017] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are only for explaining this application, but the implementation of this application is not limited thereto.

[0018] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this application pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; the amounts of experimental reagents used are, unless otherwise specified, the amounts used in conventional experimental operations; and the experimental methods used are, unless otherwise specified, conventional methods.

[0019] With the increasing demand for personal care products, the requirements for the functionality and printing quality of release paper for sanitary napkins are rising. When encapsulating and integrating active ingredients such as antibacterial, deodorizing, and moisturizing agents into release paper, migration, smudging, or damage to the encapsulation often occur during printing, curing, and storage, leading to instability in appearance and function. Therefore, there is an urgent need for a release paper for sanitary napkins and its printing method to solve the above-mentioned technical problems.

[0020] In a first aspect, embodiments of this application provide a release paper for sanitary napkins, the release paper comprising: Substrate; A printed layer is disposed on at least a portion of the surface of a substrate, the printed layer comprising a bulk barrier ink formed by printing and curing; A functional layer is disposed on at least a portion of the surface of the printed layer, and the functional layer includes microcapsules encapsulating active ingredients.

[0021] Preferably, the release paper for sanitary napkins provided in this application, through its layered structure of a bulk barrier printing layer and a microcapsule functional layer, effectively solves common problems such as migration, smudging, encapsulation damage, and functional failure when integrating active ingredients onto the release paper, while ensuring visual printing quality and mechanical release performance. Compared with traditional release papers that directly coat the functional layer onto the substrate or use only conventional printing inks, this application uses a cured bulk barrier ink as a functional barrier and graphic carrier, forming a continuous, dense printing layer compatible with the substrate and functional layer interface. Furthermore, the functional layer, which encapsulates the active ingredients into microcapsules and places them on the surface of the printing layer, separates the physical protection and controllable release function of the active ingredients from high-quality printing, significantly improving the stability of production, storage, and transportation processes, as well as the controllable release performance during final use. This layered design balances the adaptability to industrial printing with the reliability of release paper functionalization, facilitating integration with existing printing and coating equipment and promoting mass production.

[0022] Furthermore, the substrate, as the carrier of structure and release properties, is responsible for the overall strength, flexibility, and compatibility with the sanitary napkin adhesive system. The printed layer, through printing and curing, forms a continuous and dense organic polymer film, which not only presents the graphics and ensures wear-resistant and scratch-resistant appearance, but also acts as a barrier layer between the active ingredients and the substrate, blocking the diffusion channels of the active ingredients along the ink-substrate interface and reducing the probability of solvents or low-molecular-weight volatiles penetrating into the substrate. After heat or UV curing, a cross-linked structure is formed, improving the chemical resistance and weather resistance of the printed graphics, thereby preventing the graphics from being damaged by functional layer components or storage and transportation conditions. And by adjusting the film's flexibility and viscoelasticity through appropriate formulation, the damage caused by curing shrinkage or stress concentration to the covered microcapsules is reduced. The microcapsules of the functional layer physically encapsulate the active ingredient, protecting it during printing, curing, storage and transportation, preventing volatilization, degradation or interaction with ink components; they can also form a thin and uniform microcapsule dispersion layer through coating or printing, allowing the active ingredient to be released in a controlled manner during storage through mechanical, frictional or other triggering mechanisms; this changes the release kinetics from instantaneous dissipation to controlled release, thereby extending the duration of function and improving batch-to-batch consistency.

[0023] Furthermore, the release paper also includes an interface optimization layer, which is disposed between the printing layer and the functional layer. The interface optimization layer comprises polyvinyl alcohol or modified polyester emulsion, thereby significantly improving the overall structural reliability and the controllability of functional realization. The interface optimization layer reduces interfacial energy difference, improves wetting and adhesion between the printing layer and the functional layer, thereby reducing interlayer peeling and interfacial voids, ensuring the stability of the functional layer during subsequent use and peeling processes. After curing or drying, it can form a flexible film, acting as a buffer to disperse localized mechanical stress from printing curing shrinkage, printing roller shearing, or subsequent coating processes, reducing the microcapsule rupture rate. During heat and UV curing, the buffer layer can also reduce the transmission of thermal and optical stress to the functional layer, protecting the integrity of the microcapsule structure.

[0024] Secondly, embodiments of this application provide a printing method for release paper for sanitary napkins. The printing method is used to prepare the release paper according to any of the above-mentioned methods, and the printing method includes the following steps: S100: Print a bulk barrier ink onto the surface of a substrate to form a printed wet film; S200: Curing the printed wet film to form a printed layer; S300: A microcapsule suspension is coated on at least a portion of the surface of the printed layer, and after drying, a functional layer is formed to obtain release paper. Among them, microcapsule suspensions include microcapsules encapsulated with active ingredients through in-situ polymerization processes.

[0025] Preferably, the printing method of the present invention first prints and cures to form a dense bulk barrier printing layer, then coats a microcapsule suspension and dries to form a functional layer. This process strictly separates and coordinates the three functions of image carrying, barrier protection, and active release, thereby achieving compatibility of high-quality images, production stability, and controllable release during use. Compared with the traditional one-step method of directly mixing the active material with the printing or coating agent, this application establishes a physical and chemical barrier through the bulk barrier layer formed after curing, preventing the active material from migrating or interacting with ink components during printing and curing. The microcapsule functional layer is applied to the protected surface in a low-stress manner, thereby significantly reducing the microcapsule breakage rate, improving batch-to-batch consistency, and facilitating industrial production.

[0026] Furthermore, prior to step S100, the method includes: S001, performing a surface activation treatment on the substrate, which includes at least one of corona treatment and plasma treatment, to increase the surface energy of the substrate to approximately 42-48 mN / m. This significantly improves the wetting and spreading of the printed wet film on the substrate, reducing printing defects such as ink droplet recovery or ink breakage. Corona treatment and plasma treatment introduce polar groups on the substrate surface and remove organic contaminants, increasing the surface free energy and causing the bonding interface to change from hydrophobic to hydrophilic / polar. This allows the bulk barrier ink to form a continuous, pinhole-free wet film in stage S100, resulting in faster spreading and a more uniform dry film. The surface tension range of 42-48 mN / m provides a good wetting window for common water-based / weak solvent-based printing systems, reducing the risk of failures such as interlayer voids and wrinkling after curing.

[0027] Preferably, in step S100, the substrate includes at least one of glassine base paper and polyethylene coated paper. The substrate serves a triple function in the entire system: mechanical load-bearing, release properties, and compatibility with the sanitary napkin adhesive system. Glassine base paper exhibits good thermal stability and printability; polyethylene coated paper has low air permeability and excellent release oil isolation properties, which is beneficial for improving the preservation of active ingredients during storage. In step S100, a continuous wet film is formed on the substrate through a printing process, laying a uniform initial state for the subsequent curing to form a dense barrier layer. Appropriate wet film spreading and wettability ensure reduced pinholes and stress concentration during film formation, thereby achieving high density and good adhesion to the substrate after curing.

[0028] Preferably, in step S200, the bulk barrier ink comprises a polyurethane-acrylic hybrid resin matrix, a crosslinking agent, and layered nanofillers, and the dry film thickness is controlled to be 1.0-3.0 µm. The polyurethane-acrylic hybrid resin combines flexibility with post-crosslinking strength, ensuring that the printed graphics are abrasion-resistant and do not become brittle at the film thickness. The crosslinking agent forms a three-dimensional network during curing, improving chemical resistance and mechanical strength, thereby preventing the functional layer components from intruding during storage and transportation. The layered nanofillers, such as modified montmorillonite or layered disilicates, construct meandering diffusion channels in the film, improving the barrier coefficient for gas and low-molecular-weight migration. Curing includes a first stage and a second stage; the temperature of the first stage is 90-100°C; the temperature of the second stage is 110-120°C, and the time is 20-60 s. The first stage is used to remove solvent and water and complete the initial film formation, reducing the driving force of surface migration; the second stage activates the cross-linking reaction through temperature, densifies the film and fixes the dispersion state of the nanofiller; the synergistic effect of the two-stage curing not only avoids the formation of pores caused by excessively rapid desolvation, but also achieves stable cross-linking degree and barrier properties at industrial rates.

[0029] Furthermore, the preparation method of the bulk barrier ink includes: using polyurethane-acrylic hybrid resin as the matrix, adding a crosslinking agent and layered nanofillers, dispersing at high speed and degassing to obtain the bulk barrier ink.

[0030] Furthermore, if the surface tension measured after the printed layer has cured is less than 36 mN / m, it indicates that the surface of the printed layer is excessively hydrophobic or chemically inert, making it difficult to accept subsequent aqueous or hydrophilic microcapsule suspensions. This may result in droplet slippage, blemishes, pinholes, or uneven accumulation of functional layers. In this case, the process between steps S200 and S300 further includes: S210, applying a wetting primer with a solid content of 1-5 wt% onto the printed layer and drying it at 80-100°C to form an interface optimization layer. The wetting primer forms a very thin hydrophilic / neutral transition layer on the surface of the printed layer, significantly increasing the surface energy and reducing the contact angle, thereby improving the spread and distribution of the microcapsule suspension, enhancing interfacial adhesion, and reducing interlayer voids. In addition, the film, as a stress buffer layer, can absorb the local stress generated during the subsequent drying process, reducing the microcapsule rupture rate. Moreover, the solid content and dry film thickness are controlled and will not significantly affect the final release performance or graphic appearance.

[0031] Preferably, in step S300, a microcapsule suspension is coated onto the printing layer or interface optimization layer, and after drying, a functional layer is formed, resulting in release paper. The microcapsule layer provides a second layer of physical protection for the active ingredient and defines the release kinetics. The dense shell of the microcapsules allows the active ingredient to continuously release trace amounts of active ingredients through slow penetration or diffusion during storage, creating an antibacterial environment inside the sanitary napkin packaging. This protects the product during storage, maintains cleanliness, and helps extend shelf life. During use, the release paper is torn off, and the microcapsules on its surface may further exert their effects through subsequent friction and other mechanisms.

[0032] Further, in step S300, the microcapsules in the microcapsule suspension are prepared through the following steps: S311, emulsifying the oil phase formed by the active ingredient and the carrier oil to obtain an emulsion; S312, subjecting the emulsion to an in-situ polymerization reaction with the shell material monomer to form a coated shell, thereby obtaining microcapsules. The volume average particle size (D50) of the microcapsules is 3-15µm. Smaller particle sizes can easily cause increased viscosity of the coating emulsion, clogging during spraying and printing, and poor skin feel; excessively large particle sizes can lead to a rough coating surface, risk of cracking, and uneven release. The active ingredient is preferably a natural essential oil, whose volatile components can form a gas-phase antibacterial atmosphere in the sealed packaging space of the sanitary napkin, effectively inhibiting the growth of mold and bacteria. At the same time, the natural fragrance can neutralize any odors that may develop during storage. This is the most direct and effective choice for achieving antibacterial and deodorizing effects during storage. The carrier oil is selected from medium-chain triglycerides, because they can dissolve a variety of essential oils, have low volatility, are less irritating to the skin, and have good compatibility with the microcapsule shell material, thereby improving encapsulation efficiency and release stability.

[0033] This application has undergone multiple experiments, and some of the test results are presented here for reference to further describe the invention in detail. The following is a detailed description in conjunction with specific embodiments.

[0034] Example 1 This embodiment provides a release paper for sanitary napkins and a printing method thereof, including the following steps: S001, Select 80g / m 2 Using glassine base paper as the substrate, the substrate is corona treated to achieve a surface energy of 45 mN / m. S002. Using polyurethane-acrylic hybrid resin as the matrix, 3wt% of aziridine crosslinking agent and 5wt% of organic modified montmorillonite layered nanofiller are added, dispersed at high speed and degassed to obtain bulk barrier ink. S100: Using flexographic printing technology, body barrier ink is printed on the surface of the substrate to form a printed wet film; S200. The printed wet film is cured by first treating it at 95°C for 10 seconds and then drying it with hot air at 115°C for 40 seconds to form a printed layer with a dry film thickness of about 1.8µm. S300: A microcapsule suspension is coated on at least a portion of the surface of the printed layer, and after drying at 90°C, a functional layer is formed to obtain release paper. The methods for preparing microcapsules include: S311. Tea tree oil is dissolved in the oil phase of medium-chain triglycerides and emulsified to obtain an emulsion; S312. Gelatin and gum arabic are added to water as a composite wall material, and microcapsules are formed by in-situ polymerization with the emulsion. The volume average particle size D50 of the microcapsules is 8µm.

[0035] Example 2 This embodiment provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Embodiment 1, except that: between step S200 and step S300, the following is further included: S210. Prepare a 3wt% polyvinyl alcohol aqueous solution as a wetting primer. Use a microgravure coating method to uniformly coat the primer onto the surface of the printed layer. Dry at 90°C for 5 seconds to form an interface optimization layer.

[0036] Example 3 This embodiment provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Embodiment 1, except that: In step S001, polyethylene coated paper is selected as the substrate and subjected to plasma treatment. In step S200, the first stage is treated at 100°C for 8 seconds, and the second stage is hot air drying at 120°C for 20 seconds, with the dry film thickness controlled at 2.5µm. In step S311, tea tree oil is replaced with peppermint oil; In step S312, the volume average particle size D50 of the microcapsules is 5µm.

[0037] Example 4 This embodiment provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Embodiment 2, except that: In step S210, the wetting primer is a modified polyester emulsion with a solid content of 2 wt%. In step S312, the volume average particle size D50 of the microcapsules is 12µm.

[0038] Example 5 This embodiment provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Embodiment 1, except that: In step S311, lavender essential oil and medium-chain triglycerides are mixed at a ratio of 1:2 to form an oil phase, which is then emulsified at high speed in an aqueous phase containing an emulsifier to obtain a stable emulsion. In step S312, urea and formaldehyde are added to the above emulsion, and the temperature is slowly raised to 60°C under acidic conditions. The mixture is stirred and reacted for 3 hours to carry out in-situ polymerization and form microcapsules with a volume average particle size D50 of 10µm.

[0039] Example 6 This embodiment provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Embodiment 2, except that: In step S200, the first stage is treated at 90°C for 12s, and the second stage is hot air drying at 110°C for 60s, with the dry film thickness controlled at 1.0µm; In step S210, the wetting primer is a polyvinyl alcohol solution with a solid content of 1 wt%.

[0040] Interface optimization layer: Coated with a polyvinyl alcohol solution with a solid content of 1 wt%; In step S311, tea tree oil is replaced with a mixture of tea tree oil and peppermint oil; In step S312, the volume average particle size D50 of the microcapsules is 15µm.

[0041] Comparative Example 1 This comparative example provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Example 1, except that steps S200 and S300 are omitted. The microcapsule suspension prepared in Example 1 is mixed with ordinary acrylic printing ink and printed onto the substrate in one step, using the same curing conditions as in Example 1.

[0042] Comparative Example 2 This comparative example provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Example 1, except that step S200 is omitted, and a thin layer of varnish is coated on the surface of the activated substrate. The varnish is purchased externally.

[0043] Comparative Example 3 This comparative example provides a release paper for sanitary napkins and its printing method. The preparation method of the release paper is the same as that shown in Example 1, except that step S001 is omitted, i.e., no corona treatment is performed.

[0044] Test method: The release papers prepared in Examples 1-6 and Comparative Examples 1-3 were subjected to the following tests, and the test results are shown in Table 1: Printed graphic clarity and abrasion resistance: The integrity of the graphic and its abrasion resistance were assessed using visual inspection and a standard abrasion tester. Storage stability of active ingredients: After accelerated aging test, the residual rate of active ingredients in release paper was determined by high performance liquid chromatography. Interlayer adhesion: The adhesion strength between the printed layer and the substrate, and between the functional layer and the printed layer, is quantitatively measured according to the standard tape peel test or tensile test machine. Release force stability: Using a standard release force tester, measure and record the force value and batch stability when the release paper is peeled from the standard pressure-sensitive tape.

[0045] Table 1 As shown in Table 1, Examples 1-6 all exhibited excellent overall performance; the graphics were clear and wear-resistant, and the active ingredients had a high retention rate during storage and transportation; Examples 2, 4, and 6, with the addition of an interface optimization layer, showed better performance in interlayer adhesion; Comparative Example 1, with mixed printing, resulted in graphic smudging; Comparative Example 2, using a non-barrier varnish, had poor interlayer adhesion; Comparative Example 3, with an unactivated substrate, resulted in slightly poor adhesion of the printed layer, indirectly affecting overall stability.

[0046] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application, and should all be included within the protection scope of this application.

Claims

1. A release paper for sanitary napkins, characterized in that, The release paper includes: Substrate; A printed layer disposed on at least a portion of the surface of the substrate, the printed layer comprising a bulk barrier ink formed by printing and curing; A functional layer disposed on at least a portion of the surface of the printed layer, the functional layer comprising microcapsules encapsulating an active ingredient.

2. The release paper according to claim 1, characterized in that, The release paper also includes: An interface optimization layer is disposed between the printing layer and the functional layer, and the interface optimization layer comprises polyvinyl alcohol or modified polyester emulsion.

3. A printing method for release paper used in sanitary napkins, characterized in that, The printing method is used to prepare the release paper according to any one of claims 1 or 2, and the printing method includes the following steps: S100: Print a bulk barrier ink on the surface of the substrate to form a printed wet film; S200: The printed wet film is cured to form a printed layer; S300: A microcapsule suspension is coated on at least a portion of the surface of the printed layer, and after drying, a functional layer is formed to obtain the release paper; The microcapsule suspension comprises microcapsules encapsulated with active ingredients through an in-situ polymerization process.

4. The printing method according to claim 3, characterized in that, Before step S100, the method further includes: S001. The substrate is subjected to surface activation treatment, wherein the surface activation treatment includes at least one of corona treatment and plasma treatment.

5. The printing method according to claim 3, characterized in that, In step S100, the substrate includes at least one of glassine base paper and polyethylene coated paper.

6. The printing method according to claim 3, characterized in that, In step S200, The bulk barrier ink comprises a polyurethane-acrylic hybrid resin matrix, a crosslinking agent, and layered nanofillers; and / or In step S200, the dry film thickness of the printed layer is 1.0-3.0µm.

7. The printing method according to claim 3, characterized in that, In step S200, the curing includes a first stage and a second stage; The temperature in the first stage is 90-100℃; The temperature of the second stage is 110-120℃, and the time is 20-60s.

8. The printing method according to claim 3, characterized in that, The process between step S200 and step S300 also includes: S210. A wetting primer with a solid content of 1-5wt% is applied to the printed layer and dried at 80-100℃ to form an interface optimization layer.

9. The printing method according to claim 3, characterized in that, In step S300, the microcapsules in the microcapsule suspension are prepared through the following steps: S311. The active ingredient and the carrier oil are emulsified to obtain an emulsion; S312. The emulsion is subjected to an in-situ polymerization reaction with the shell material monomer to form a coated shell, thereby obtaining the microcapsule.

10. The printing method according to claim 9, characterized in that, The volume average particle size D50 of the microcapsules is 3-15µm.

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