Flexible smart card substrate with self-healing protective layer

Abstract

This invention discloses a flexible smart card substrate with a self-healing protective layer, comprising a flexible substrate layer and a conductive circuit layer embedded within the substrate layer. The outer surface of the flexible substrate layer is covered with a self-healing protective layer, which, from the inside out, comprises: a microcapsule layer composed of urea-formaldehyde resin microcapsules with a particle size of 5-20 μm, wherein the microcapsules encapsulate repair monomers; a dynamic covalent bond layer composed of a reversible cross-linked polymer containing dynamic covalent bonds, wherein the dynamic covalent bonds are selected from disulfide bonds or acylhydrazone bonds; and a wear-resistant coating composed of a diamond-like carbon film with a thickness of 0.05-0.2 μm. The interface between the flexible substrate and the self-healing protective layer is plasma-treated to form a nanoscale anchoring structure. This invention, through a multi-layer composite structure design, achieves a synergistic enhancement of the self-healing properties, high wear resistance, and long-term stability of the flexible smart card substrate.

Description

Technical Field

[0001] This utility model relates to the field of smart card technology, specifically to a flexible smart card substrate with a self-healing protective layer. Background Technology

[0002] In the field of smart card technology, flexible smart cards are gradually gaining market favor due to their lightweight and bendable characteristics. However, traditional flexible smart card substrates often struggle to self-repair when faced with scratches, wear, or minor damage. This not only affects the smart card's appearance but may also further damage its internal circuitry, leading to functional failure. Furthermore, while existing protective layer technologies can improve the durability of smart cards to some extent, most require specific conditions (such as high temperatures) to achieve repair, and the repair effect is limited, failing to meet the need for rapid self-repair at room temperature.

[0003] Specifically, the main problems with traditional flexible smart card substrates include: Lack of self-healing capability: Traditional flexible smart card substrates usually require manual replacement or repair after being damaged, which not only increases the cost of use, but also affects the user experience.

[0004] Repair conditions are limited: Some existing self-healing technologies require specific conditions (such as high-temperature environments) to achieve repair, which limits the application scenarios of smart cards, especially in some temperature-sensitive or high-temperature environments. Summary of the Invention

[0005] To overcome the shortcomings of existing technical solutions, this utility model provides a flexible smart card substrate with a self-healing protective layer, which can effectively solve the problem of self-healing of room temperature card substrates mentioned in the background art.

[0006] The technical solution adopted by this utility model to solve its technical problem is: a flexible smart card substrate with a self-healing protective layer, comprising a flexible substrate layer and a conductive circuit layer embedded in the substrate layer, wherein the outer surface of the flexible substrate layer is covered with a self-healing protective layer, and the self-healing protective layer comprises, from the inside to the outside: Microcapsule layer: composed of urea-formaldehyde resin microcapsules with a particle size of 5-20μm, wherein the microcapsules are encapsulated with repair monomers; Dynamic covalent layer: composed of a reversible cross-linked polymer containing dynamic covalent bonds, wherein the dynamic covalent bonds are selected from disulfide bonds or acylhydrazone bonds; Wear-resistant coating: composed of a diamond-like carbon film with a thickness of 0.05-0.2μm; The interface between the flexible substrate layer and the self-healing protective layer is treated with plasma to form a nanoscale anchoring structure.

[0007] Furthermore, the microcapsule layer includes a first capsule layer and a second capsule layer, wherein the first capsule layer is disposed on the surface of the second capsule layer, the microcapsule density of the first capsule layer is 80-100 capsules / mm², and the microcapsule density of the second capsule layer is 20-40 capsules / mm².

[0008] Furthermore, the repair monomer is dicyclopentadiene, and the polymer matrix of the dynamic covalent layer contains a Grubbs catalyst, which is a phenylruthenium complex with a content of 0.3-0.8 wt%.

[0009] Furthermore, the thickness of the dynamic covalent bond layer is 20-30 μm, and it is composed of a polyurethane-disulfide copolymer with a disulfide bond content of 10-20 mol.

[0010] Furthermore, the flexible substrate layer is a polyimide film or a modified PET film with a thickness of 0.2-0.5 mm, and the conductive circuit layer is an etched copper or printed silver paste antenna with a linewidth ≤50 μm.

[0011] Furthermore, the urea-formaldehyde resin shell of the microcapsule layer has a wall thickness of 1-2 μm, and the encapsulation amount of the repair monomer is 70-85% of the microcapsule volume.

[0012] Furthermore, the wear-resistant coating has a friction coefficient ≤0.2, a hydrogen content <5%, and an sp³ bond ratio ≥40%.

[0013] Compared with the prior art, the beneficial effects of this utility model are: Microcapsule layer: Urea-formaldehyde resin microcapsules encapsulate repair monomers, precisely releasing monomers to the damaged area when the surface is damaged. Through rapid cross-linking reactions (such as olefin metathesis or free radical polymerization), the integrity of the coating is restored, effectively blocking water and oxygen erosion and avoiding short circuits in the internal circuitry.

[0014] Dynamic covalent bonds: Reversible cross-linked networks containing disulfide / hydrazone bonds trigger dynamic bond breakage and recombination under bending or thermal stimulation (such as free radical recombination after homolytic cracking of SS bonds), achieving self-healing of microcracks and significantly extending the fatigue life of the substrate.

[0015] Abrasion-resistant coating: Diamond-like carbon film (hardness > 20 GPa) combined with plasma interface anchoring structure, scratch width < 2μm, while maintaining substrate flexibility (bending radius ≤ 3mm).

[0016] Synergistic advantages: Plasma-treated nano-anchored interfaces enhance interlayer bonding (peel strength > 2.5 N / mm) and prevent delamination; microcapsule repair and dynamic bond recombination complement each other, covering the full-scale repair needs from macroscopic damage to microscopic cracks. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the smart card substrate structure of this utility model; Figure 2 This is a schematic diagram of the self-healing protective layer structure of this utility model; Figure 3 This is a schematic diagram of the microcapsule layer structure of this utility model; Figure 4 This is a schematic diagram of the microcapsule and repair monomer structure of this utility model.

[0018] Numbering on the map: 10-Flexible substrate layer, 20-Conductive circuit layer, 30-Self-healing protective layer, 31-Microcapsule layer, 32-Dynamic covalent bond layer, 33-Wear-resistant coating, 311-First capsule layer, 312-Second capsule layer, 313-Repair monomer. Detailed Implementation

[0019] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0020] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. Example

[0021] like Figure 1-4 As shown, this utility model provides a flexible smart card substrate with a self-healing protective layer 30, including a flexible substrate layer 10 and a conductive line layer 20 embedded in the substrate layer. The outer surface of the flexible substrate layer 10 is covered with a self-healing protective layer 30, which includes, from the inside to the outside: Microcapsule layer 31: Composed of urea-formaldehyde resin microcapsules with a particle size of 5-20 μm, the microcapsules encapsulate repair monomer 313; Dynamic covalent layer 32: composed of a reversible cross-linked polymer containing dynamic covalent bonds, wherein the dynamic covalent bonds are selected from disulfide bonds or acylhydrazone bonds; Wear-resistant coating 33: composed of a diamond-like carbon film with a thickness of 0.05-0.2 μm; The interface between the flexible substrate layer 10 and the self-healing protective layer 30 is subjected to plasma treatment to form a nanoscale anchoring structure.

[0022] The flexible substrate layer 10 serves as the support for the smart card, providing the necessary strength and flexibility, and also acts as the carrier for the conductive circuit layer 20. The conductive circuit layer 20 connects electronic components and serves to transmit signals and current. When the surface of the smart card is damaged, the microcapsule layer 31 ruptures and releases repair monomers 313. These repair monomers 313 can undergo a cross-linking reaction at the damaged site, restoring the physical shielding performance of the coating, thereby preventing external environment from corroding the internal circuitry of the smart card. The dynamic covalent layer 32 provides raw materials for the crosslinking reaction; The wear-resistant coating 33 provides extremely high hardness and wear resistance, protecting the smart card surface from physical damage such as scratches and abrasions.

[0023] Material selection for flexible substrate layer 10: Polyimide film: Excellent temperature resistance (-269℃~400℃), bending life >100,000 cycles; Modified PET film: Lower cost, improved bending resistance by adding nano silica (5wt%), bending radius up to 3mm.

[0024] The thickness of the flexible substrate layer 10 ranges from 0.2 to 0.5 mm, preferably 0.3 mm, balancing flexibility and rigidity.

[0025] Pre-treatment process of flexible substrate layer 10: The interface between the flexible substrate layer 10 and the self-healing protective layer 30 is treated with argon plasma cleaning to form a nanoscale anchoring structure. The plasma cleaning process parameters are 50W power and 5 minutes processing time to remove impurities and activate the surface.

[0026] Method for fabricating conductive circuit layer 20: Etched copper lines: Photolithography is used, with a line width of 50μm, a thickness of 18μm, and a resistance of <0.1Ω / sq; Printed silver paste antenna: screen-printed nano silver paste (particle size 50nm), sintering temperature 150℃, resistance <0.05Ω / sq.

[0027] Embedding method of conductive line layer 20: The circuit layer is embedded into the substrate layer by hot pressing. The hot pressing parameters are: temperature 180℃ (PI substrate) or 120℃ (PET substrate), hot pressing pressure 0.8MPa, and hot pressing time 30 seconds.

[0028] Microcapsule structure: The urea-formaldehyde resin shell has a microcapsule structure with a wall thickness of 1-2 μm, and the interior is encapsulated with dicyclopentadiene monomer (purity > 99%). The microcapsules have a particle size of 5-20 μm (preferably 10 μm) and are prepared by spray drying.

[0029] Microcapsule distribution design: Surface layer: Density > 80 particles / mm² (2 coats, solid content 40%) Base coat: density 30 particles / mm² (0.5 sprays) to avoid stress concentration.

[0030] Material formulation for dynamic covalent layer 32: Polyurethane-disulfide copolymer (PU-SS), disulfide bond content 15 mol% 0.5 wt% Grubbs catalyst (phenylruthenium complex) was added and dispersed in the polymer matrix.

[0031] Coating process of dynamic covalent layer 32: Spin coating (3000 rpm, 60 seconds), thickness 20-30 μm; Curing conditions: Bake at 80℃ for 30 minutes to form a cross-linked network.

[0032] The wear-resistant coating 33 is a diamond-like carbon (DLC) film. The deposition setup was achieved using magnetron sputtering, with a thickness of 0.1 μm (deviation ±0.02 μm); the hydrogen content was <5%, the sp³ bond ratio was >40%, and the friction coefficient was 0.15.

[0033] Scratch repair mechanism (microcapsule release) When the scratch depth on the card surface is greater than 5 μm, the surface microcapsules rupture and release dicyclopentadiene monomers. Under the action of Grubbs catalyst, DCPD undergoes ring-opening polymerization to generate polydicyclopentadiene (PDCPD). The microcapsules rupture and release DCPD monomers. DCPD contacts the Grubbs catalyst in the substrate and initiates ring-opening polymerization. The generated PDCPD fills the cracks and restores the structural integrity.

[0034] Its reaction time: cross-linking is completed within 30 minutes at room temperature, filling the cracks.

[0035] Dynamic bond recombination mechanism: When a material is subjected to bending stress, disulfide bonds (SS) break to generate sulfur free radicals (S·). After the stress is released, the free radicals recombine (S· + ·S → SS), restoring the cross-linked network.

[0036] See Figure 3The microcapsule layer 31 includes a first capsule layer 311 and a second capsule layer 312. The first capsule layer 311 is disposed on the surface of the second capsule layer 312. The microcapsule density of the first capsule layer 311 is 80-100 capsules / mm², and the microcapsule density of the second capsule layer 312 is 20-40 capsules / mm².

[0037] The first capsule layer 311 is disposed on the surface of the second capsule layer 312, and its microcapsule density is 80-100 capsules / mm². This high density distribution ensures that the coating can quickly and effectively trigger a self-healing mechanism when it is damaged by external forces or environmental damage. When microscopic damage occurs on the surface of the coating, the microcapsules of the first capsule layer 311 can quickly rupture, release repair agents or corrosion inhibitors, fill the cracks in the coating or form a protective film, thereby restoring the physical shielding performance and anti-corrosion performance of the coating.

[0038] The microcapsule density of the second capsule layer 312 is 20-40 capsules / mm², which is lower than that of the first capsule layer 311, but its presence provides the coating with additional self-healing capabilities. When the microcapsules of the first capsule layer 311 are exhausted or unable to completely repair the coating damage, the microcapsules of the second capsule layer 312 can continue to function.

[0039] The design of the second capsule layer 312 also takes into account the balance of the overall coating performance. By adjusting the density and distribution of the microcapsules, the self-healing ability can be guaranteed while avoiding an excessively thick coating or affecting other properties, such as mechanical properties and heat resistance.

[0040] Among them, the repair monomer 313 is dicyclopentadiene, and the polymer matrix of the dynamic covalent bond layer 32 contains a Grubbs catalyst, which is a phenylruthenium complex with a content of 0.3-0.8 wt%.

[0041] Dicyclopentadiene can rapidly polymerize after the microcapsules rupture, filling the coating cracks and restoring the coating's physical shielding properties. Under the action of Grubbs catalyst, dicyclopentadiene can undergo ring-opening metathesis polymerization (ROMP) to generate high molecular weight polydicyclopentadiene. This polymerization reaction is rapid and efficient, enabling the coating to complete its self-healing process in a short time.

[0042] Dicyclopentadiene exhibits good compatibility with other components in the coating and will not separate or deteriorate during storage and use. Furthermore, its stable chemical properties ensure the reliability of the coating during long-term use.

[0043] Grubbs catalyst is a highly efficient olefin metathesis catalyst with significant catalytic effects on the polymerization of dicyclopentadiene. Its high catalytic activity enables rapid initiation of the polymerization reaction at relatively low temperatures, improving the self-healing efficiency of the coating. Grubbs catalyst exhibits high selectivity for the polymerization of dicyclopentadiene, preventing unwanted side reactions. Furthermore, its strong stability allows it to maintain catalytic activity under various environmental conditions, ensuring that the self-healing performance of the coating remains unaffected.

[0044] The phenylruthenium complex content is 0.3-0.8 wt%. By adjusting the content of Grubbs catalyst, the polymerization rate of dicyclopentadiene can be precisely controlled, thereby optimizing the self-healing performance of the coating. A catalyst content of 0.3-0.8 wt% ensures that the polymerization reaction is both rapid and complete, achieving the best repair effect.

[0045] The dynamic covalent bond layer 32 has a thickness of 20-30 μm and is composed of polyurethane-disulfide copolymer. The disulfide bond content is 10-20 mol%, and the disulfide bond recovers the crosslinking network through sulfur free radical recombination after the bending stress is released, with a recombination efficiency of ≥80% (the change in free radical concentration is detected by ESR spectrum).

[0046] The 20-30μm thickness ensures that the dynamic covalent layer 32 has sufficient strength and toughness to withstand certain external forces without breaking. The structure of the polyurethane-disulfide copolymer gives the layer good elasticity and wear resistance, which can adapt to the bending and folding requirements of smart cards.

[0047] The 10-20 mol% disulfide bond content enables the dynamic covalent bond layer 32 to undergo reversible breakage and recombination when subjected to external forces, thereby achieving self-repair function. The introduction of disulfide bonds also improves the crosslinking density and stability of the coating, enhancing the physical barrier performance of the coating.

[0048] When the smart card is subjected to bending stress, the disulfide bonds in the dynamic covalent layer 32 break, forming sulfur free radicals. After the stress is released, these sulfur free radicals can restore the cross-linked network through a recombination reaction, thereby restoring the physical properties and self-healing ability of the coating. The recombination efficiency of the disulfide bonds can be assessed by detecting changes in free radical concentration using ESR spectroscopy. When the recombination efficiency is ≥80%, it indicates that the dynamic covalent layer 32 can rapidly restore its cross-linked network and physical properties after being subjected to external force, thus ensuring the stability and reliability of the smart card.

[0049] The flexible substrate layer 10 is a polyimide film or a modified PET film with a thickness of 0.2-0.5 mm, and the conductive circuit layer 20 is an etched copper or printed silver paste antenna with a line width ≤50 μm.

[0050] Polyimide film has extremely high electrical insulation properties, can withstand high voltage and high frequency, and is an ideal material in the electronics and electrical industries. It can maintain its performance stability at high temperatures and even extreme temperatures, making it suitable for applications in high-temperature environments. It also has good resistance to most chemical solvents and corrosive media, and is widely used in the chemical industry. In addition, it has high tensile strength and modulus, making it an excellent structural material.

[0051] Modified PET film has excellent physical properties, such as hardness, abrasion resistance and weather resistance. It is also easy to process, cut, bend and shape, and can be processed into various shapes and sizes. Compared with some high-performance materials, modified PET film has a lower cost, which helps to reduce the overall cost of electronic devices.

[0052] With a thickness of 0.2-0.5mm, it combines lightness and flexibility. The thinner thickness is conducive to heat dissipation and improves the heat dissipation performance of electronic devices.

[0053] Etched copper antennas: The etching process can produce high-precision antenna patterns to meet complex design requirements; copper has good conductivity, ensuring stable signal transmission; etched copper antennas have high strength and durability, and can adapt to harsh operating environments.

[0054] Printed silver paste antennas: The printing process is relatively simple, which can reduce production costs; suitable for small-batch production or the manufacture of antennas with special shapes; good conductivity: Although the conductivity is slightly inferior to that of copper foil, silver paste still has good conductivity and can meet the general signal transmission requirements.

[0055] Narrow line widths reduce signal loss and interference during transmission, improving signal transmission efficiency. Line widths ≤50μm facilitate high-density wiring, enhancing the integration and performance of electronic devices. Narrow line widths save space on circuit boards, making electronic devices more compact. High-density wiring helps reduce circuit board area and material usage, thereby lowering production costs.

[0056] The urea-formaldehyde resin shell of the microcapsule layer 31 has a wall thickness of 1-2 μm, and the encapsulation amount of the repair monomer 313 is 70-85% of the microcapsule volume.

[0057] An appropriate wall thickness provides sufficient mechanical strength to protect the internal repair monomer 313 from external environmental damage, such as physical impact and chemical corrosion. A wall thickness of 1-2 μm ensures strength while also facilitating the penetration and release of the repair monomer 313 when needed. An excessively thick wall may lead to release difficulties, while an excessively thin wall may not provide sufficient protection.

[0058] A 70-85% encapsulation content ensures the integrity of the microcapsule structure while allowing the repair monomer 313 to be released in a controlled manner when needed. Too much encapsulation may lead to release that is too rapid or uneven, while too little encapsulation may not meet the repair requirements. A 70-85% encapsulation content can balance the release rate and release amount to a certain extent, ensuring the stability and controllability of the repair process.

[0059] Among them, the friction coefficient of the wear-resistant coating is ≤0.2, the hydrogen content is <5%, and the proportion of sp³ bonds is ≥40%.

[0060] Setting the coefficient of friction to ≤0.2 can significantly improve the wear resistance of the coating and extend its service life.

[0061] Maintaining the hydrogen content within the range of <5% ensures coating stability and extends service life. Appropriate hydrogen content can positively impact certain coating properties, such as improving lubricity and reducing the coefficient of friction. However, excessive hydrogen content has negative effects. Therefore, controlling the hydrogen content within a reasonable range balances the various properties of the coating to meet practical application requirements.

[0062] sp³ bonds are among the hardest bond types in diamond-like carbon (DLC) coatings. Increasing the proportion of sp³ bonds can significantly enhance the coating's hardness, resulting in better scratch and wear resistance. Compared to sp² bonds, sp³ bonds exhibit higher energy stability and chemical inertness, leading to better wear and corrosion resistance in coatings with a high proportion of sp³ bonds. By adjusting the ratio of sp³ to sp² bonds, the overall properties of the coating, such as hardness, toughness, and coefficient of friction, can be optimized. Setting the sp³ bond proportion to ≥40% allows for consideration of other performance requirements while maintaining coating hardness.

[0063] In the description of this utility model, it should be understood that the terms "middle", "length", "upper", "lower", "front", "rear", "vertical", "horizontal", "inner", "outer", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0064] In this invention, unless otherwise expressly specified and limited, the first feature "on" the second feature may be in direct contact with the first feature, or indirect contact with the first feature through an intermediate medium. "A plurality of" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0065] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0066] The above description is merely illustrative of the embodiments of this utility model and is not intended to limit the scope of this utility model. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model without creative labor should be included within the protection scope of this utility model.

Claims

1. A flexible smart card substrate with a self-healing protective layer, comprising a flexible substrate layer and a conductive circuit layer embedded in the substrate layer, characterized in that: The outer surface of the flexible substrate is covered with a self-healing protective layer, which comprises, from the inside out: Microcapsule layer: composed of urea-formaldehyde resin microcapsules with a particle size of 5-20μm, wherein the microcapsules are encapsulated with repair monomers; Dynamic covalent layer: composed of a reversible cross-linked polymer containing dynamic covalent bonds, wherein the dynamic covalent bonds are selected from disulfide bonds or acylhydrazone bonds; Wear-resistant coating: composed of a diamond-like carbon film with a thickness of 0.05-0.2μm; The interface between the flexible substrate layer and the self-healing protective layer is treated with plasma to form a nanoscale anchoring structure.

2. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The microcapsule layer includes a first capsule layer and a second capsule layer. The first capsule is disposed on the surface of the second capsule layer. The microcapsule density of the first capsule layer is 80-100 capsules / mm², and the microcapsule density of the second capsule layer is 20-40 capsules / mm².

3. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The repair monomer is dicyclopentadiene, and the polymer matrix of the dynamic covalent layer contains a Grubbs catalyst, which is a phenylruthenium complex with a content of 0.3-0.8 wt%.

4. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The thickness of the dynamic covalent layer is 20-30 μm, and it is composed of polyurethane-disulfide copolymer with a disulfide bond content of 10-20 mol.

5. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The flexible substrate layer is a polyimide film or a modified PET film with a thickness of 0.2-0.5 mm, and the conductive circuit layer is an etched copper or printed silver paste antenna with a linewidth ≤50 μm.

6. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The urea-formaldehyde resin shell of the microcapsule has a wall thickness of 1-2 μm, and the amount of the repair monomer encapsulated is 70-85% of the microcapsule volume.

7. The flexible smart card substrate with a self-healing protective layer according to claim 1, characterized in that: The wear-resistant coating has a friction coefficient ≤0.2, a hydrogen content <5%, and an sp³ bond ratio ≥40%.

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