Preparation method of friction-induced self-repairing coating heat transfer film

Abstract

The invention discloses a preparation method of a friction-induced self-repairing coating heat transfer printing film, and relates to the technical field of heat transfer printing coating materials.The preparation method comprises the following steps that 1, a heat response topological template base film is prepared, specifically, a base material is pretreated to form a double-area microstructure array, and temperature-sensitive type release agents are coated in a partitioned mode; 2, preparing a two-factor response self-repairing coating precursor, wherein the coating precursor comprises a dynamic key matrix, a stress amplification microcapsule and a topology directing agent; according to the method, thermal transfer printing, namely performance programming, is realized through the thermal response topological template base membrane, the two-factor response coating precursor and multi-field coupling thermal transfer printing programming, so that thermal transfer printing is upgraded to a function customization platform; the method has the advantages that the space gradient of repairing performance is adjustable, the friction response direction is specific, self-repairing and wear resistance are synergistically enhanced, the membrane carrier can be reutilized and the like, the process is optimized, the cost is reduced, and the performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal transfer coating materials, and in particular to a method for preparing a friction-induced self-repairing coating thermal transfer film. Background Art

[0002] As an efficient and precise means of surface decoration and functionalization, thermal transfer technology has been widely used in consumer electronics, automotive interiors, packaging materials, and other fields. Its core principle is to transfer the pattern or functional layer from a film bearing a functional coating (thermal transfer film) to the target substrate surface through heat and pressure. This technology offers advantages such as a simple process flow, wide applicability to substrates (such as plastics, metals, and ceramics), and high production efficiency on a large scale. The structure of traditional thermal transfer films typically includes a base layer (such as PET film), a release layer, a decorative layer (or functional layer), and an adhesive layer. The performance of the functional layer directly determines the surface properties of the substrate after transfer (such as wear resistance, corrosion resistance, and aesthetics).

[0003] As end-products have increasingly demanded more surface performance, functional coatings that combine decorativeness and durability have become a research hotspot. Self-healing coatings, as intelligent materials that can autonomously repair surface scratches or damage, have been introduced into the field of thermal transfer films, forming a composite system of "self-healing coating thermal transfer films." The repair mechanisms of existing self-healing coatings primarily rely on external stimuli (such as heat, light, and pH) or mechanical force triggers (such as friction). Friction-induced self-healing is more valuable because it does not require additional energy and can respond to dynamic damage in actual use (such as daily scratches). Typical implementation paths include: activating the structural recovery of shape memory polymers through frictional heat generation, or triggering the rupture of microcapsules through frictional stress to release repair agents, thereby filling cracks or scratches.

[0004] However, existing technologies for combining friction-induced self-healing with thermal transfer films face a core contradiction: the core characteristics of the thermal transfer process (high temperature and pressure, the structural advantages of the film carrier, and precise roll-to-roll control) are completely disconnected from the performance control requirements of the friction-induced self-healing coating. This results in thermal transfer being used merely as a "transfer tool" for the coating, rather than a "functional customization tool." This core contradiction manifests itself in the following four interrelated technical limitations: 1. Decoupling of process and performance: In the preparation of existing thermal transfer films, the "high temperature (180-220°C) and high pressure (0.5-2MPa)" of thermal transfer only serve as physical conditions for transferring the coating from the base film to the substrate. Their core function is to achieve the peeling of the release layer and the curing of the adhesive layer, and they do not participate in the performance regulation of the self-healing coating. The repair activity of the self-healing coating (such as repair speed and strength) is completely predetermined by the coating formula (such as dynamic bond density and microcapsule content). It cannot be customized to meet the needs of different areas of the target substrate (such as higher repair activity in easily abraded edge areas and lower repair activity in the central decorative area to avoid appearance changes). This "one-size-fits-all" performance design results in insufficient adaptability of the coating in complex application scenarios. For example, the edges of mobile phone cases are frequently damaged due to insufficient repair activity, or the glossiness of the central pattern area changes due to excessive repair.

[0005] 2. The contradiction of spatial performance uniformity: Since the thermal transfer process does not participate in performance regulation, the existing friction-induced self-healing coatings show uniform repair performance after thermal transfer, while the surface damage risk of actual products has significant spatial differences. For example, the corners of a car's dashboard are prone to friction damage due to frequent contact, while the central display area has a low probability of damage but requires higher surface flatness; the opening and closing edges of high-end packaging boxes require high-frequency repair, while the main pattern area needs to maintain repair inertia to avoid blurred patterns. Existing technologies cannot achieve regional differentiation of self-healing performance through thermal transfer processes and can only compensate through subsequent local secondary processing (such as local coating of high-activity coatings), which increases the complexity and cost of the process.

[0006] 3. Limitations of the film carrier function: As a carrier for the coating, the core value of the thermal transfer film is limited to a "temporary support and transfer tool", and its advantage of achieving high-precision process control (such as zoned temperature control and gradient pressure) in roll-to-roll production has not been brought into play. The design of parameters such as the heat resistance of the base film and the peeling characteristics of the release layer are only designed around the optimization of "transfer efficiency" and are not associated with the performance control of the self-healing coating. For example, the thermal shrinkage rate of the base film does not match the activation temperature of the dynamic bonds in the coating, which may lead to the destruction of the coating structure due to shrinkage of the film material during the thermal transfer process; premature peeling of the release layer may interrupt the potential regulatory effect of high temperature and high pressure on the coating performance - these design flaws further aggravate the core contradiction of "the process cannot customize performance".

[0007] 4. Non-programmability of repair logic: The repair behavior of existing friction-induced self-healing coatings is a "passive response" - that is, after damage occurs, the coating repairs according to a fixed pattern. It is impossible to pre-set the repair logic (such as prioritizing repair in certain areas and delaying repair in other areas) through the thermal transfer process. This non-programmability is essentially an extension of the "decoupling of process and performance", which limits the application of coatings in multi-functional scenarios. For example, in the case of an electronic device with both fingerprint recognition and decorative functions, the fingerprint recognition area needs to suppress repair to maintain surface roughness, while the surrounding area needs to be efficiently repaired. Existing technologies cannot achieve this performance partitioning in one step through thermal transfer.

[0008] In summary, existing technologies haven't used thermal transfer processes to pre-program the performance of self-healing coatings. The high-temperature and high-pressure parameters of thermal transfer, the structural advantages of the membrane carrier, and the need to regulate the activity of the self-healing coating haven't been deeply coupled. This "process-performance" disconnect creates significant bottlenecks in the customization and adaptability of friction-induced self-healing thermal transfer films.

[0009] In view of this, a method for preparing a friction-induced self-repairing coating thermal transfer film is provided to overcome the above problems. Summary of the Invention

[0010] The object of the present invention is to provide a method for preparing a friction-induced self-repairing coating thermal transfer film to solve the problems raised in the above background technology.

[0011] In order to solve the above technical problems, the present invention provides a method for preparing a friction-induced self-repairing coating thermal transfer film, comprising the following steps: Step 1: preparing a thermally responsive topological template base film, including pre-treating the substrate to form a dual-region microstructure array and coating the substrate with a temperature-sensitive release agent in different regions; Step 2: preparing a dual-factor responsive self-healing coating precursor, which comprises a dynamic bond matrix, stress amplifying microcapsules and a topological directing agent; Step 3: Multi-field coupled thermal transfer programming, including magnetic response pre-aggregation and interface tension-assisted self-assembly in the coating precursor coating stage, coordinated regulation of temperature gradient, pressure gradient and alternating magnetic field in the partition parameter programming stage, and bidirectional replication of micro-nano textures and repair logic topology locking in the interface topology solidification stage.

[0012] Furthermore, in step 1, a PET film with a thickness of 25 μm is used for substrate pretreatment, and a dual-region microstructure array is formed by UV etching: In the high-repair-demand area, an inverted conical pit array with a diameter of 10 μm and a depth of 5 μm was etched. The inner wall of the pit was evaporated with a 5 nm thick nickel-chromium alloy, and the bottom was embedded with Fe3O4 magnetic nanoparticles with a diameter of 2 μm. A regular hexagonal bump array with a diameter of 5 μm and a depth of 1 μm is etched in the low repair demand area, and a 10 nm thick diamond-like carbon coating is coated on the surface of the bumps.

[0013] Furthermore, in step 1, the smart release layer coating is performed by micro-printing partitioning: The inverted cone-shaped pit area is coated with an organic silicone release agent containing azobisisobutyronitrile; The regular hexagonal convex area is coated with a fluorocarbon release agent containing hindered phenol.

[0014] Furthermore, the dual-factor response self-repairing coating precursor in step 2 includes, by mass: Dynamic bond matrix: polymerized from 30 parts of isophorone diisocyanate, 25 parts of polypropylene glycol, and 15 parts of N-isopropylacrylamide; Stress amplification microcapsules: A two-component repair agent containing 40 parts of epoxy resin and 10 parts of latent curing agent, with polydopamine as the wall material and surface modified with Fe3O4 nanosheets, with the addition amount being 8-12% of the dynamic bond matrix; Topological director: 5 parts of polysiloxane containing phenyl borate at the end group.

[0015] Furthermore, the magnetic response pre-aggregation during the coating precursor coating stage in step 3: The gradient magnetic field plate set under the basement membrane has a magnetic field strength that decreases linearly from the inverted cone pit area to the regular hexagonal convex area, so that the microcapsules in the high repair area form a single-layer close-packed structure, and the low repair area is in a dispersed suspension state.

[0016] Furthermore, the temperature gradient control in the partition parameter programming stage in step 3 adopts partition pulse heating: The high repair area adopts 160℃, 1 second low temperature pulse - 170℃, 4 seconds heat preservation mode; The low repair area adopts a high temperature instantaneous heating mode of 240℃ and 0.5 seconds and a rapid cooling mode of -200℃ and 1.5 seconds.

[0017] Furthermore, the pressure gradient in the partition parameter programming stage in step 3 is passively boosted by the basement membrane microstructure: The inverted cone-shaped pit area uses the wedge effect of the 45° inclined inner wall to amplify the local pressure to 0.8 MPa, forcing the microcapsules to form columnar channels; The regular hexagonal convex area disperses stress through 60° edges, reducing the local pressure to 0.5MPa and forming a honeycomb partition.

[0018] Furthermore, in step 3, the interface topology solidification stage uses room temperature plasma treatment to implement the repair logic lock: The high repair area was treated for 3 seconds, forming a covalent bond density of 3 per square micron; The low repair area treatment time is 1 second, forming a covalent bond density of 1 per square micron.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. A new mechanism for achieving "thermal transfer equals performance programming": The "temperature-pressure-time" parameters of the thermal transfer process are converted into "digitally encoded signals of self-healing performance." By designing a "decodable" coating precursor and a "programmable" membrane carrier, the thermal transfer process simultaneously completes "coating transfer" and "performance topology programming," allowing thermal transfer to evolve from a "transfer tool" to a "functional customization platform."

[0020] 2. "Spatial gradient programmable" repair performance: The repair efficiency (scratch repair rate) in high-repair areas is improved, while the repair efficiency in low-repair areas is reduced (avoiding appearance changes caused by over-repair), and the gradient change is continuously adjustable, solving the "one-size-fits-all" problem in traditional technologies.

[0021] 3. “Directional specificity” of friction response: The radial grooves in the high-repair zone make the friction repair speed along the groove direction faster than the vertical direction, which can adapt to the directionality of scratches in actual use (such as lateral friction on the edge of a mobile phone).

[0022] 4. Synergistic enhancement of "self-repairing and wear resistance": Directly arranged microcapsules form a "repairing agent delivery channel" in the direction of friction, which improves the wear resistance of the coating while maintaining the repair efficiency, breaking the traditional contradiction that "high repairability inevitably leads to low wear resistance."

[0023] 5. "Secondary utilization value" of the membrane carrier: After the base membrane is transferred, the magnetic particles and microstructures on its surface can be recovered by magnetic separation and reused after simple treatment (high utilization rate), reducing production costs.

[0024] 6. Breakthrough in base film function: The base film's microstructure is not only a physical template. Its thermal conductivity difference (nickel-chromium alloy vs. DLC) and magnetic particle distribution provide a material basis for the subsequent "temperature gradient focusing" and "microcapsule directional migration" of thermal transfer. The temperature response characteristics of the intelligent release agent enable the stripping process and performance regulation to be triggered simultaneously, breaking through the limitation of the traditional release layer that only serves as a separation function.

[0025] 7. Coating system: The nonlinear temperature response characteristics of the dynamic urea bond make the thermal transfer temperature a "digital signal" for regulating the bond density; the magnetic responsiveness of the microcapsules and the surface catechol groups enable them to be directed and aggregated under the magnetic guidance and pressure of the basement membrane, breaking through the limitations of the random distribution of traditional microcapsules.

[0026] 8. Process optimization: By utilizing the magnetic field gradient of an ordinary electromagnet, a "base" is laid for subsequent pressure regulation during the coating stage, avoiding the uneven distribution caused by "passive aggregation during transfer" in traditional processes. Ordinary factories only need to install a simple magnetic field plate under the coater to achieve this; pre-aggregation increases the final microcapsule concentration difference in the high repair area, and at the same time improves the consistency of particle orientation, laying a microscopic foundation for "direction-specific repair."

[0027] Combine the "interfacial tension regulation" of surfactants with magnetic guidance to form a "dual driving force".

[0028] By using pulse control of ordinary heating tubes to achieve "temperature and time-space dislocation", it not only avoids the use of high-end laser heating equipment, but also solves the traditional contradiction of "high temperature destroying the adhesion of the bottom layer"; the "high activity of the surface + high adhesion of the bottom layer" in the high repair area improves the peeling strength of the coating, while maintaining high repair efficiency; the "low activity of the surface + stable adhesion of the bottom layer" in the low repair area avoids the overall performance degradation caused by traditional high temperature.

[0029] There is no need for a complex partitioned hydraulic system, and pressure amplification and dispersion is achieved only through the geometric structure of the base film itself. The roll-to-roll equipment of ordinary factories only needs to adjust the hardness of the pressure roller to adapt, with almost no increase in cost; the "columnar channel" increases the release speed of the repair agent during friction, and the channel direction is consistent with the direction of daily friction (such as lateral friction on the edge of a mobile phone), realizing "release on demand".

[0030] An alternating magnetic field is generated using an ordinary industrial frequency power supply (50Hz), without the need for a high-frequency generator, and "resonance selective activation" is achieved through the pre-orientation of the microcapsules. Only the dynamic bonds in the high-repair area are preprocessed, solving the problem of "overall activation leading to performance loss". Resonance activation increases the friction response sensitivity of the high-repair area (minor scratches can trigger repair), while the low-repair area is unaffected, achieving "damage graded response".

[0031] By utilizing the deformation characteristics of ordinary elastic pressure rollers, accurate texture transfer can be achieved without the need for high-precision molds, solving the problem of "incomplete texture replication" of traditional rigid pressure rollers. Ordinary factories can achieve this by replacing the pressure roller material; the depth of the radial grooves on the coating surface is increased, the friction stress concentration coefficient is improved, and the repair trigger is more sensitive.

[0032] "Chemical locking" is achieved by using the time control of ordinary plasma equipment, without the need for complex surface modification processes, and the functional orientation of the texture is enhanced by the density difference of covalent bonds, making the repair logic stable in the long term. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the method for preparing the friction-induced self-repairing coating thermal transfer film of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] See also Figure 1 , the present invention provides a technical solution: See Figure 1 As shown, an embodiment of the method for preparing a friction-induced self-repairing coating thermal transfer film: The "temperature-pressure-time" parameters of the thermal transfer process are converted into "digital coding signals of self-healing performance". By designing a "decodable" coating precursor and a "programmable" membrane carrier, the thermal transfer process can simultaneously complete "coating transfer" and "performance topology writing", forming a new mechanism of "transfer and programming".

[0036] Step 1: Preparation of "thermal responsive topological template base film": Breaking through the single supporting function of traditional PET base film, a composite base film with "region-specific thermal-mechanical response" is constructed: ①. Substrate pretreatment: A 25μm thick PET film was selected and a "dual-region microstructure array" was etched on its surface by UV lithography: A: Areas requiring high repair (corresponding to the substrate edge): an inverted conical pit array with a diameter of 10 μm and a depth of 5 μm was etched. The inner walls of the pits were then vapor-deposited with a 5 nm thick nickel-chromium alloy (with a thermal conductivity three times that of PET). Fe3O4 magnetic nanoparticles with a diameter of 2 μm (saturation magnetization of 80 emu / g) were embedded in the bottom of the pits. B: Low repair demand area (corresponding to the center of the substrate): Etching a "regular hexagonal bump array" with a diameter of 5μm and a depth of 1μm. The bump surface is coated with a 10nm thick diamond-like carbon (DLC) coating (the thermal conductivity is reduced to 1 / 2 of PET); ② Intelligent release layer coating: Use micro-jet printing technology to apply "temperature-sensitive release agent" in different zones: A: Inverted cone pit area: Coated with a silicone release agent containing azobisisobutyronitrile (AIBN) (decomposes above 120°C to produce bubbles, reducing the peel force to 0.2N / 25mm); B: Hexagonal bump area: Coated with a fluorocarbon release agent containing hindered phenol (it starts to soften above 200°C and the peel force remains at 1.5N / 25mm).

[0037] The microstructure of the base film is not only a physical template. Its thermal conductivity difference (nickel-chromium alloy vs. DLC) and magnetic particle distribution provide a material basis for the subsequent "temperature gradient focusing" and "microcapsule directional migration" of thermal transfer. The temperature response characteristics of the intelligent release agent enable the peeling process and performance regulation to be triggered simultaneously, breaking through the limitation of the traditional release layer that only plays a separation role.

[0038] Step 2: Preparation of "dual-factor responsive self-healing coating precursor": Design a coating system that can be "decoded" by thermal transfer parameters. The formula (parts by weight) is as follows: ① Dynamic bond matrix: A "temperature-sensitive dynamic urea bond" replaces the traditional disulfide bond. It is composed of 30 parts of isophorone diisocyanate (IPDI), 25 parts of polypropylene glycol (PPG, Mn=1000), and 15 parts of N-isopropylacrylamide (NIPAM, lower critical solution temperature 32°C). The bond breaking activation energy decreases nonlinearly with increasing temperature. ② Stress amplification microcapsules: Polydopamine (containing catechol groups that can coordinate with metals) is used as the wall material, encapsulating a "two-component repair agent" (40 parts epoxy resin + 10 parts latent curing agent (amine-blocked isocyanate, deblocked at 120°C)). The microcapsules are surface-modified with Fe3O4 nanosheets (which generate magnetic attraction with magnetic particles in the basement membrane pits). The diameter of the microcapsules is 8-12μm, and the addition amount is 8-12% of the dynamic bond matrix. ③. Topological directing agent: Add 5 parts of polysiloxane containing phenyl borate at the end group (which can reversibly bind to the catechol group at pH = 6-8) to regulate the migration path of the microcapsules in the coating.

[0039] The nonlinear temperature response characteristics of the dynamic urea bond make the thermal transfer temperature a "digital signal" (rather than a simple physical condition) for regulating the bond density; the magnetic responsiveness of the microcapsules and the surface catechol groups enable them to be directed and aggregated under the magnetic guidance and pressure of the basement membrane, breaking through the limitations of the random distribution of traditional microcapsules.

[0040] Step 3: “Multi-field coupling” thermal transfer programming: Customized roll-to-roll thermal transfer equipment is used to achieve collaborative programming of the three parameters of "temperature, pressure, and magnetic field". The specific process is as follows: 1. Coating precursor coating stage: Asymmetric regulation of “magnetic response pre-aggregation”: 1. Microscopic distribution of magnetic gradient guidance: In traditional thermal transfer printing, the coating is evenly spread. However, in this step, during slit coating, a "gradient magnetic field plate" (a modified ordinary electromagnet with a linear decrease in magnetic field strength from the inverted cone pit area to the regular hexagonal convex area, 0.05-0.01T) is set under the base film to cause "asymmetric pre-aggregation" of microcapsules during the coating stage: 1.1. Inverted cone pit area (high repair demand): Due to the highest magnetic field intensity, the microcapsules spontaneously form a "single-layer close-packed structure" within 10 seconds after coating (the particle spacing can be observed by optical microscopy to be ≤1μm), and the Fe3O4 nanosheets in each microcapsule are oriented in the same direction as the magnetic field (forming a "magnetic dipole array"); 1.2. Regular hexagonal convex area (low repair requirements): The magnetic field intensity is low, the microcapsules are in a "dispersed suspension state" (spacing ≥ 5μm), and the nanosheets are arranged in an unoriented manner. To quantitatively demonstrate the regulatory effect of magnetic field gradient on microcapsule pre-aggregation, the following formula for microcapsule concentration distribution was established based on the magnetic dipole interaction and diffusion equilibrium theory, which can clarify the concentration difference mechanism between high and low remediation areas: formula: ; in: :Location Microcapsule concentration at (pieces / μm³); : initial concentration of microcapsules in the coating precursor (pieces / μm³); : Volume magnetic susceptibility of microcapsules (dimensionless, about 0.8 after Fe3O4 nanosheet modification); : Vacuum permeability ( ); :The saturation magnetization of Fe3O4 (80emu / g, converted to 6.37×10 4 A / m); :Location The magnetic field strength at ), high repair area , low repair area ; :Single microcapsule volume (μm³, diameter 10μm) ≈523.6μm³); : Boltzmann constant (1.38×10 -23 J / K); : absolute temperature (normal temperature 300K); :Microcapsule diffusion coefficient (μm² / s, about 10 -3 μm² / s); : Aggregation time (10s); :Microstructure feature size (high repair area =10μm, low repair area =5 μm); After substituting the parameters, the high repair area ( )of The calculated result is about the low repair area ( ), that is, the concentration difference of "microcapsules in high repair area are densely packed in a single layer (spacing ≤ 1 μm) and dispersed and suspended in low repair area (spacing ≥ 5 μm)" is consistent, proving that the magnetic field gradient can directionally regulate the aggregation of microcapsules.

[0041] By utilizing the magnetic field gradient of an ordinary electromagnet, a "base" is laid for subsequent pressure control during the coating stage, avoiding the uneven distribution caused by "passive aggregation during transfer" in the traditional process. Ordinary factories only need to install a simple magnetic field plate under the coating machine to achieve this.

[0042] Moreover: pre-aggregation increases the final microcapsule concentration difference in the high repair area, while improving the particle orientation consistency, laying a microscopic foundation for "direction-specific repair".

[0043] 2. Interfacial tension-assisted self-assembly mechanism: During coating, add 0.5 parts of "fluorocarbon surfactant" (common raw materials in ordinary factories) to the coating precursor, and take advantage of its "selective adsorption" characteristics on the surface of the base film microstructure: 2.1. Ni-Cr alloy surface with inverted conical pits (metallophilic): The hydrophilic ends of the surfactant molecules coordinate with the metal, while the hydrophobic ends face the coating, reducing the interfacial tension to 25 mN / m, making it easier for microcapsules to be adsorbed to the bottom of the pits; 2.2. DLC coating with regular hexagonal convex dots (hydrophobic): The hydrophobic end of the surfactant combines with the DLC, and the hydrophilic end faces the coating. The interfacial tension is maintained at 45mN / m, which inhibits the adsorption of microcapsules.

[0044] Combine the "interfacial tension regulation" of surfactants with magnetic guidance to form a "dual driving force".

[0045] 2. Partition parameter programming stage: Collaborative coupling of “temperature-pressure-magnetic field”: 1. “Time and space dislocation” regulation of temperature gradient: The traditional thermal transfer temperature is heated synchronously across the entire area, while this step uses "zone pulse heating" (modification of ordinary infrared heating tubes and installation of zone temperature controllers): 1.1. High-repair area (corresponding to inverted cone-shaped pits): Using the "low-temperature pulse (160°C, 1 second) followed by heat preservation (170°C, 4 seconds)" mode, the high thermal conductivity of nickel-chromium alloy (3 times faster than PET) is utilized to form a "temperature gradient field" inside the coating (160°C on the surface, 170°C on the bottom layer). The dynamic urea bonds in the surface layer retain 80% (high repair activity), while the bottom layer breaks 10% due to the slightly higher temperature (enhanced adhesion to the substrate); 1.2. Low repair area (corresponding to the regular hexagonal convex points): Using the "high temperature instantaneous heating (240℃, 0.5 seconds) - rapid cooling (200℃, 1.5 seconds)" mode, taking advantage of the low thermal conductivity of DLC (heat only stays on the surface of the coating), the dynamic urea bonds in the surface layer are broken by 50% (reducing the repair activity), and the bottom layer is only broken by 10% due to the rapid cooling (ensuring basic adhesion).

[0046] By using pulse control of ordinary heating tubes to achieve "temperature and time-space dislocation", it not only avoids the use of high-end laser heating equipment, but also solves the traditional contradiction of "high temperature destroying the adhesion of the bottom layer".

[0047] Moreover: the "high surface activity + high bottom layer adhesion" of the high repair area improves the coating peeling strength while maintaining high repair efficiency; the "low surface activity + stable bottom layer adhesion" of the low repair area avoids the overall performance degradation caused by traditional high temperature.

[0048] 2. Physical mechanism of “microstructure supercharging” of pressure gradient: The traditional thermal transfer pressure is a uniform pressure applied on the plane, while this step uses the microstructure of the base film itself to achieve "passive pressurization": 2.1. Inverted cone-shaped pit area: The "45° inclined inner wall" of the pit produces a "wedge effect" when under pressure, amplifying the local pressure and forcing the pre-aggregated microcapsules to align along the pit axis (perpendicular to the substrate surface), forming a "columnar channel" (with a diameter matching the microcapsule, about 10μm); 2.2. Regular hexagonal convex dot area: The "60° edges" of the convex dot generate "dispersed stress" when under pressure, reducing the local pressure from 0.8MPa to 0.5MPa. The microcapsules remain randomly distributed, and the convex dot extrusion coating forms a "honeycomb partition" (preventing the microcapsules from migrating to the high repair area).

[0049] There is no need for a complex zoned hydraulic system. Pressure amplification and dispersion is achieved only through the geometric structure of the base film itself. The roll-to-roll equipment of ordinary factories only needs to adjust the hardness of the pressure roller (Shore hardness 80A) to adapt, with almost no increase in cost.

[0050] Moreover, the "columnar channel" increases the release speed of the repair agent during friction, and the direction of the channel is consistent with the direction of daily friction (such as horizontal friction on the edge of a mobile phone), achieving "release on demand".

[0051] 3. "Low-frequency resonance" activation of alternating magnetic field: Traditional thermal transfer does not involve a magnetic field. The alternating magnetic field (50Hz, 0.1T) in this step is not simply applied, but resonates with the "magnetic dipole moment" of the microcapsules: High repair area: Due to pre-orientation, the Fe3O4 nanosheets in the microcapsule produce "synchronous swing" (the frequency is consistent with the magnetic field) in the alternating magnetic field, with the swing amplitude reaching 1 / 3 of its own diameter, causing "local shear stress" in the surrounding dynamic bond matrix, promoting bond activation; To quantify the swing characteristics of microcapsules under an alternating magnetic field, a formula was established to determine the relationship between the swing amplitude and magnetic field parameters based on the magnetic dipole resonance model. This demonstrates the mechanism by which the swing amplitude in the high-repair zone reaches 1 / 3 of the diameter: formula: ; in: : microcapsule swing amplitude (μm); :Magnetic moment of microcapsules (A・m², about 10 after Fe3O4 nanosheet modification -15 A·m²); : alternating magnetic field amplitude (T); : natural vibration frequency of the microcapsule (Hz, estimated to be approximately 50 Hz); : Alternating magnetic field frequency (Hz, i.e. resonance condition = ); : coating precursor viscosity (Pa・s, about 0.1Pa・s); : Microcapsule radius (μm, diameter 10μm =5 μm); when = (resonance), the formula simplifies to: ; Substitute the parameters and calculate ≈3.3μm, which is about 1 / 3 of the microcapsule diameter (10μm), that is: it proves that the alternating magnetic field can activate the swing of microcapsules in the high repair area through resonance and promote dynamic bond activation.

[0052] Low repair area: no magnetic field, no wiggling of microcapsules, dynamic bonds remain stable.

[0053] An alternating magnetic field is generated using ordinary industrial frequency power supply (50Hz), without the need for a high-frequency generator, and "resonance selective activation" is achieved through the pre-orientation of the microcapsules. Only the dynamic bonds in the high-repair area are pre-processed, solving the problem of "overall activation leading to performance out of control."

[0054] Furthermore: Resonance activation increases the friction response sensitivity of high-repair areas (a slight scratch can trigger repair), while low-repair areas are unaffected, achieving “graded damage response”.

[0055] 3. Interface topology solidification stage: “texture-performance” binding mechanism: 1. “Bidirectional replication” of micro-nano textures: The texture replication of traditional thermal transfer is a one-way transfer from "base film to coating". This step achieves two-way replication through the "elastic matching design" of "pressing roller-base film-coating-substrate": 1.1. Use a "polyurethane elastic pressure roller" (Shore hardness 60A). When applying pressure, the pressure in the inverted cone pit area is higher, and the surface of the pressure roller is reversely pressed out to form a "complementary convex texture" (depth 2μm), forming a triple match of "base film pits-coating grooves-pressure roller convex points"; 1.2. The pressure in the regular hexagonal convex area is low, and the pressure roller is only slightly deformed, ensuring that the convex texture on the coating surface is completely replicated (error ≤ 0.5μm).

[0056] By utilizing the deformation characteristics of ordinary elastic pressure rollers, accurate texture transfer can be achieved without the need for high-precision molds, solving the problem of "incomplete texture replication" of traditional rigid pressure rollers. Ordinary factories can achieve this by simply replacing the pressure roller material.

[0057] Moreover: the depth of the radial grooves on the coating surface increases, the friction stress concentration coefficient increases, and the repair trigger is more sensitive.

[0058] 2. The "topological locking" chemical mechanism of repair logic: After transfer, the coating is treated with room temperature plasma (using a standard air plasma device with a power of 500W) to form a reversible covalent bond between the phenylboronic acid ester groups (from the topological directing agent) on the coating surface and the hydroxyl groups on the substrate surface (such as the surface hydroxyl groups of PC / ABS substrates). 2.1. In the radial grooves of the high-repair area: the plasma treatment time is extended to 3 seconds to form a higher density of covalent bonds (3 per square micron), locking the "stress concentration" characteristics of the grooves; 2.2. Honeycomb bumps in low repair areas: The processing time is shortened to 1 second, the covalent bond density is low (1 per square micron), and the "stress dispersion" characteristics of the bumps are retained.

[0059] "Chemical locking" is achieved by using the time control of ordinary plasma equipment, without the need for complex surface modification processes, and the functional orientation of the texture is enhanced by the density difference of covalent bonds, making the repair logic stable in the long term.

[0060] Summarize: The "magnetic field parameters" are introduced into the thermal transfer process, and magnetically responsive microcapsules are used to achieve the directional distribution of the repair agent, breaking through the limitations of traditional formula control alone; "temperature-sensitive dynamic urea bonds" and "intelligent release agents" are designed to convert the thermal transfer temperature from a "transfer condition" to a "digital signal for bond density control"; the "inverted conical pits + magnetic particles" structure of the base film produces a "magnetic-pressure synergistic aggregation effect", realizing precise control of the regional concentration of microcapsules.

[0061] Programmable spatial gradient of repair performance: The repair efficiency (scratch repair rate) in high-repair areas is improved, while the repair efficiency in low-repair areas is reduced (avoiding appearance changes caused by over-repair). The gradient change is continuously adjustable, solving the traditional "one-size-fits-all" problem. Directional specificity of friction response: The radial grooves in the high-repair zone enable faster repair along the groove direction than in the perpendicular direction, adapting to the directionality of scratches in actual use (such as lateral friction on the edge of a mobile phone); Synergistic enhancement of self-repair and wear resistance: Directly arranged microcapsules form a "repair agent delivery channel" in the direction of friction, improving the coating's wear resistance (Taber abrasion test) while maintaining the same repair efficiency, breaking the traditional contradiction that "high repairability necessarily leads to low wear resistance"; The "secondary utilization value" of the membrane carrier: After the base membrane is transferred, the magnetic particles and microstructures on its surface can be recovered through magnetic separation and reused after simple treatment (high utilization rate), reducing production costs.

[0062] This invention combines a "thermally responsive topological template base film," a "dual-factor responsive coating precursor," and "multi-field coupled programming" to create a new technical approach: "thermal transfer equals performance programming." This technology transforms the physical parameters of the thermal transfer process into performance control signals that can be "decoded" by the coating, evolving thermal transfer from a "transfer tool" to a "functional customization platform." This technology enables effects such as directionally specific repair, gradient programmable performance, and synergistic enhancement of self-repair and wear resistance.

Claims

1. A method for preparing a friction-induced self-repairing coating thermal transfer film, characterized in that: The following steps are involved: Step 1: preparing a thermally responsive topological template base film, including pre-treating the substrate to form a dual-region microstructure array and coating the substrate with a temperature-sensitive release agent in different regions; Step 2: preparing a dual-factor responsive self-healing coating precursor, which comprises a dynamic bond matrix, stress amplifying microcapsules and a topological directing agent; Step 3: Multi-field coupled thermal transfer programming, including magnetic response pre-aggregation and interface tension-assisted self-assembly in the coating precursor coating stage, coordinated regulation of temperature gradient, pressure gradient and alternating magnetic field in the partition parameter programming stage, and bidirectional replication of micro-nano textures and repair logic topology locking in the interface topology solidification stage.

2. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: In step 1, a PET film with a thickness of 25 μm is used for substrate pretreatment, and a dual-region microstructure array is formed by UV etching: In the high-repair-demand area, an inverted conical pit array with a diameter of 10 μm and a depth of 5 μm was etched. The inner wall of the pit was evaporated with a 5 nm thick nickel-chromium alloy, and the bottom was embedded with Fe3O4 magnetic nanoparticles with a diameter of 2 μm. A regular hexagonal bump array with a diameter of 5 μm and a depth of 1 μm is etched in the low repair demand area, and a 10 nm thick diamond-like carbon coating is coated on the surface of the bumps.

3. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: In step 1, the intelligent release layer coating is divided into micro-printing zones: The inverted cone-shaped pit area is coated with an organic silicone release agent containing azobisisobutyronitrile; The regular hexagonal convex area is coated with a fluorocarbon release agent containing hindered phenol.

4. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: The dual-factor response self-repairing coating precursor in step 2 includes, by mass: Dynamic bond matrix: polymerized from 30 parts of isophorone diisocyanate, 25 parts of polypropylene glycol, and 15 parts of N-isopropylacrylamide; Stress amplification microcapsules: A two-component repair agent containing 40 parts of epoxy resin and 10 parts of latent curing agent, with polydopamine as the wall material and surface modified with Fe3O4 nanosheets, with the addition amount being 8-12% of the dynamic bond matrix; Topological director: 5 parts of polysiloxane containing phenyl borate at the end group.

5. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: Magnetic response pre-aggregation during the coating precursor application phase in step 3: The gradient magnetic field plate set under the basement membrane has a magnetic field strength that decreases linearly from the inverted cone pit area to the regular hexagonal convex area, so that the microcapsules in the high repair area form a single-layer close-packed structure, and the low repair area is in a dispersed suspension state.

6. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: The temperature gradient control in the partition parameter programming stage in step 3 adopts partition pulse heating: The high repair area adopts 160℃, 1 second low temperature pulse - 170℃, 4 seconds heat preservation mode; The low repair area adopts a high temperature instantaneous heating mode of 240℃ and 0.5 seconds and a rapid cooling mode of -200℃ and 1.5 seconds.

7. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: The pressure gradient in the partition parameter programming stage in step 3 is passively boosted by the basement membrane microstructure: The inverted cone-shaped pit area uses the wedge effect of the 45° inclined inner wall to amplify the local pressure to 0.8 MPa, forcing the microcapsules to form columnar channels; The regular hexagonal convex area disperses stress through 60° edges, reducing the local pressure to 0.5MPa and forming a honeycomb partition.

8. The method for preparing a friction-induced self-repairing coating thermal transfer film according to claim 1, wherein: In step 3, the interface topology solidification stage uses room temperature plasma treatment to implement the repair logic lock: The high repair area was treated for 3 seconds, forming a covalent bond density of 3 per square micron; The low repair area treatment time is 1 second, forming a covalent bond density of 1 per square micron.

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