Micro-carving gold stamping printing method

Abstract

The invention is suitable for the technical field of printing, and provides a micro-carving gold stamping printing method which comprises the following steps: coating a gradient response release layer on the surface of a base material to be printed; preparing a light-induced lattice reconstruction metal foil; preparing an adhesive material, wherein the adhesive material comprises a dual-network polymer matrix and a surface modified two-dimensional nanosheet; coating one side, far away from the functional layer, of the transparent substrate of the metal foil with an adhesive material to form an adhesive layer, performing alignment compounding on the metal foil and the substrate coated with the release layer through the adhesive layer, performing pattern transfer by adopting a multi-frequency ultrasonic-assisted impressing device, and synchronously applying compound frequency vibration in the impressing process; the method has the beneficial effects that the pattern area / non-pattern area is accurately controlled through ultrasonic composite frequency auxiliary filling, high-precision microstructure transfer printing and laser activation; the adhesive force of the metal foil is improved, the glossiness of the metal foil is adjustable, and the multi-stage optical effect can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of printing, and particularly relates to a micro-engraving hot stamping printing method. Background Art

[0002] Hot stamping printing is to hot stamp hot stamping materials onto the surfaces of various substrates under certain temperature and pressure to form a special metallic effect. It can be applied to a variety of materials such as paper, leather, textiles, and plastics, and not only limited to gold color, but also various colors can be selected.

[0003] In the existing micro-engraving hot stamping printing methods, there may be quality problems such as incomplete transfer of micron-level patterns. The traditional mechanical embossing has insufficient microcavity filling rate and burrs are easily generated at the edges, affecting the pattern quality. Summary of the Invention

[0004] The present invention provides a micro-engraving hot stamping printing method, aiming to solve the above problems.

[0005] The present invention is implemented as follows. A micro-engraving hot stamping printing method includes the following steps: S100. Coating a gradient-responsive release layer on the surface of the substrate to be printed, and the release layer comprises a composite material of nano-silica aerogel and shape memory polyurethane; S200. Preparing a photoinduced lattice-reconstructed metal foil, and the photoinduced lattice-reconstructed metal foil includes a transparent substrate, a nanowire array functional layer, and a core-shell structured metal layer; S300. Preparing an adhesive material; S400. Coating the adhesive material on the side of the transparent substrate of the metal foil away from the functional layer to form an adhesive layer, and aligning and laminating the metal foil with the substrate coated with the release layer through the adhesive layer, and using a multi-frequency ultrasonic-assisted embossing device for pattern transfer, and synchronously applying a composite frequency vibration during the embossing process; S500. After embossing, crosslinking the adhesive material in the pattern area by thermal curing, and peeling off the untransferred metal foil to obtain a micron-level embossed hot stamping pattern.

[0006] Preferably, the mass ratio of nano-silica aerogel to shape memory polyurethane in the gradient-responsive release layer is 1:2 - 4, and the thickness is 8 - 10 μm.

[0007] Preferably, the surface of the nano-silica aerogel is grafted with azobenzene groups (immersing 40-nm silica aerogel in a 0.1 M ethanol solution of 3-aminopropyltriethoxysilane (APTES), reacting at 60-70 °C for 3-5 h to obtain an aminated aerogel, reacting the aminated aerogel with 4-nitrobenzoyl chloride in DMF, and performing an amidation reaction at 80-85 °C for 3-5 h to obtain an azobenzene-modified aerogel). The shape memory polyurethane contains a four-armed star-shaped polycaprolactone soft segment with a glass transition temperature of 85-105 °C.

[0008] Preferably, the specific method for coating a gradient-responsive release layer on the surface of the substrate to be printed is as follows: Add the nano-silica aerogel to 25-35 times its weight of tetrahydrofuran, and ultrasonically disperse (500-600 W, 30-50 min) until there is no agglomeration; Add the shape memory polyurethane and magnetically stir at 60-70 °C for 2-3 h to form a uniform slurry; Plasma clean the substrate (Ar / O2 = 3:1, 800-1000 W, 120-150 s); Use a gravure coater (anilox roll line count 200 LPI) to coat the slurry on the cleaned substrate at a speed of 2-3 m / min; After coating, dry with hot air at 60-70 °C for 5-10 min to form a release layer; According to the hot stamping pattern design file, laser activate the target area (pattern area) (1064-nm fiber laser, spot diameter 10 μm, power density 60 W / cm 2 ), the irradiation time is 80 ms / spot, triggering the glass transition of the shape memory polyurethane. The pores of the nano-silica aerogel in the target area (pattern area) collapse to form a dense structure, and the thermal conductivity increases. The non-pattern area is not activated and maintains a porous aerogel structure with low thermal conductivity to form a heat insulation barrier. During the hot curing process after embossing, the adhesive in the pattern area obtains sufficient curing energy and is completely cured. The non-pattern area is not cured, and the metal foil in the non-pattern area can be peeled off, thus solving the problems of metal residue in the non-pattern area caused by the unified release force in the whole area in the traditional process, the need for secondary cleaning, and the inability to selectively cure.

[0009] Preferably, the photoinduced lattice reconstruction metal foil includes a transparent polyimide substrate (thickness 12 μm), an europium-doped zinc oxide nanowire array functional layer (diameter 80 ± 5 nm, length 1.2-1.5 μm, aspect ratio ≥ 15:1), and a silver / titanium dioxide core-shell structure metal layer (silver core particle size 45-55 nm, TiO2 shell layer thickness 3-5 nm).

[0010] Preferably, the preparation method of the photoinduced lattice reconstruction metal foil is as follows: A. Pretreatment of the transparent polyimide substrate (1) Cleaning treatment: Immerse a 12-μm-thick transparent polyimide substrate into absolute ethanol, ultrasonically clean it for 15 - 25 min (power 300 - 500 W, frequency 40 - 50 kHz), rinse it 3 times with deionized water, and dry it with nitrogen gas. (2) Surface activation: Treat it with oxygen plasma (power 800 - 1000 W, O2 flow rate 50 - 60 sccm) for 5 - 10 min. After treatment, the surface contact angle decreases from 85° to 15°. B. Preparation of the europium-doped zinc oxide nanowire array functional layer (1) ZnO seed layer deposition: Use atomic layer deposition technology to obtain a ZnO seed layer with a thickness of about 50 nm. The precursors are diethylzinc and deionized water, the deposition temperature is 200 °C, and the number of cycles is 100 times. (2) Hydrothermal growth of Eu:ZnO nanowires: The reaction solution formula is 0.1 M zinc nitrate (Zn(NO3)2·6H2O), 0.02 M europium nitrate (Eu(NO3)3·6H2O), and 0.1 M hexamethylenetetramine. Vertically place the transparent polyimide substrate into the reaction kettle, with a reaction temperature of 93 - 97 °C and a reaction time of 3 - 5 h.

[0011] C. Preparation of the silver / titanium dioxide core-shell structure metal layer (1) Silver nanoparticle synthesis: Prepare a 0.01 M silver nitrate solution, add 0.1 M sodium citrate as a reducing agent, heat and stir it in a water bath at 80 - 90 °C for 30 - 40 min to obtain silver nanoparticles with a particle size of 45 - 55 nm. (2) TiO2 shell coating: Prepare an ethanol solution of tetrabutyl titanate (volume ratio 1:10), add 0.1 M nitric acid as a catalyst, disperse the silver nanoparticles in it, stir for 2 - 3 min and then centrifuge and wash, and anneal at 500 °C for 1 - 2 h to form an anatase-phase TiO2 shell. (3) Metal layer assembly: Use the Langmuir-Blodgett technique, with a surface pressure of 25 - 30 mN / m and a transfer speed of 2 - 3 mm / min, to obtain a single-layer dense Ag / TiO2 core-shell structure.

[0012] Preferably, the preparation method of the adhesive material is as follows: By weight, weigh 100 - 120 parts of epoxy resin, 4 - 6 parts of dicyandiamide, and 10 - 12 parts of silicon dioxide nanoparticles, and disperse them at a high speed (2000 rpm, 30 min) to obtain the adhesive material.

[0013] Preferably, the multi-frequency ultrasonic-assisted imprinting device includes the superimposed vibration of a 28-kHz main frequency (amplitude 10 - 15 μm) and a 132-kHz high frequency (amplitude 1 - 2 μm), and the vibration energy density is 15 - 25 J / cm 2, with a pressure of 1 - 7 MPa, a residence time of 50 - 150 ms, an ultrasonic head drives a nickel plate to press into the metal foil, a 28 kHz low-frequency vibration pushes the metal foil to fill the micropores of the nickel plate (such as a relief structure with a depth of 200 μm), and a 132 kHz high-frequency vibration reduces the friction between the metal foil and the nickel plate, prevents the microstructures from tearing, reduces the generation of burrs at the edges, and improves the printing quality.

[0014] Preferably, the cross-linking of the adhesive material by thermal curing after imprinting is specifically as follows: the substrate is preheated as a whole at 80 °C for 1 - 3 min by an infrared heater (the release layer in the pattern area rapidly absorbs heat, and the temperature in the non-pattern area lags behind), then the temperature is increased to 120 °C at a rate of 20 °C / min to activate the decomposition of dicyandiamide and initiate the ring-opening reaction of epoxy resin, and it is maintained at 120 °C for 1 - 3 min. The epoxy network in the pattern area is deeply cross-linked and cured, and the temperature in the non-pattern area is ≤ 80 °C and is hardly cured.

[0015] Preferably, after peeling off the untransferred metal foil in step S500, the local or whole metal foil on the substrate is irradiated with ultraviolet light, and the glossiness is adjusted by adjusting the ultraviolet light intensity or irradiation time to present a multi-level optical effect (such as achieving a matte background + high-brightness pattern on the same plate surface). The nanowires are periodically arranged to form a photonic crystal structure, enhancing the light localization in a specific wavelength band; Eu 3+ ions emit red light under ultraviolet excitation, which is coupled with the plasma resonance peak of silver to broaden the optical response range; surface plasmon resonance (SPR): 365 nm ultraviolet light excites the free electron oscillation of the Ag core, and the resonance peak position is regulated by the TiO2 dielectric environment; dynamic refractive index regulation: the TiO2 shell generates photo-generated electron-hole pairs under ultraviolet irradiation, the dielectric constant changes, resulting in a red shift of the SPR peak, and the macroscopic manifestation is a change in refractive index and dynamic regulation of glossiness.

[0016] Compared with the prior art, the embodiments of the present application mainly have the following beneficial effects: 1. High-precision microstructure transfer Ultrasonic-assisted filling, and the 28 kHz / 132 kHz composite vibration improves the filling rate of the microcavities; The laser-activated release force in the pattern area is low, enabling precise control of the pattern area / non-pattern area.

[0017] 2. Dynamic optical regulation ability The refractive index of the Ag / TiO2 core-shell layer increases under ultraviolet irradiation, and the glossiness is adjustable; after peeling off the waste foil, the finished product can be locally or wholly irradiated with ultraviolet light to present a multi-level optical effect. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of a micro-engraving hot stamping printing method provided by the present invention. Detailed Embodiments

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification and claims of this application or the above drawings are used to distinguish different objects and not to describe a specific order.

[0020] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0021] Embodiment 1 An embodiment of the present invention provides a micro-engraving hot stamping printing method, as Figure 1 shown, including the following steps: S100 Coat a gradient-responsive release layer on the surface of the substrate to be printed (such as polyimide, PET film, etc.), and the release layer contains a composite material of nano-silica aerogel and shape memory polyurethane; S200 Prepare a photoinduced lattice reconstruction metal foil, and the photoinduced lattice reconstruction metal foil includes a transparent substrate, a nanowire array functional layer, and a core-shell structure metal layer; S300 Prepare an adhesive material; S400 Coat the adhesive material on the side of the transparent substrate of the metal foil away from the functional layer to form an adhesive layer, and align and composite the metal foil with the substrate coated with the release layer through the adhesive layer, and use a multi-frequency ultrasonic-assisted embossing device to perform pattern transfer, and apply a composite frequency vibration synchronously during the embossing process; S500 After embossing, crosslink the adhesive material in the pattern area by thermal curing, peel off the untransferred metal foil, and obtain a micron-level relief hot stamping pattern.

[0022] In this embodiment, the mass ratio of nano-silica aerogel to shape memory polyurethane in the gradient-responsive release layer is 1:2, and the thickness is 8 μm.

[0023] Furthermore, azobenzene groups are grafted onto the surface of the nano-silica aerogel (immersing 40-nm silica aerogel into a 0.1 M ethanol solution of 3-aminopropyltriethoxysilane (APTES), reacting at 60 °C for 3 h to obtain an aminated aerogel, reacting the aminated aerogel with 4-nitrobenzoyl chloride in DMF, and performing amidation reaction at 80 °C for 3 h to obtain an azobenzene-modified aerogel). The shape memory polyurethane contains a four-arm star-shaped polycaprolactone soft segment, and the glass transition temperature is 85 - 105 °C.

[0024] Furthermore, the specific method for coating a gradient-responsive release layer on the surface of the substrate to be printed is as follows: Add the nano-silica aerogel to 25 times its weight of tetrahydrofuran, and ultrasonically disperse (500 W, 30 min) until there is no agglomeration; Add the shape memory polyurethane, and magnetically stir at 60 °C for 2 h to form a uniform slurry; Clean the substrate by plasma (Ar / O2 = 3:1, 800 W, 120 s); Use a gravure coater (anilox roll line count 200 LPI), and coat the slurry on the cleaned substrate at a speed of 2 m / min; After coating, dry with hot air at 60 °C for 5 min to form a release layer; According to the hot stamping pattern design file, laser activate the target area (pattern area) (1064-nm fiber laser, spot diameter 10 μm, power density 60 W / cm 2 ), the irradiation time is 80 ms / spot, triggering the glass transition of the shape memory polyurethane, the release force is reduced, the pores of the nano-silica aerogel in the target area (pattern area) collapse, forming a dense structure, the thermal conductivity is increased, while the non-pattern area is not activated, the release force is high, maintaining a porous aerogel structure with low thermal conductivity to form a heat insulation barrier. During the post-imprinting heat curing process, the adhesive material in the pattern area obtains sufficient curing energy and is completely cured, while the non-pattern area is not cured, enabling the peeling of the metal foil in the non-pattern area.

[0025] In this embodiment, the photoinduced lattice reconstruction metal foil includes a transparent polyimide substrate (thickness 12 μm), a europium-doped zinc oxide nanowire array functional layer (diameter 80 ± 5 nm, length 1.2 - 1.5 μm, aspect ratio ≥ 15:1), and a silver / titanium dioxide core-shell structure metal layer (silver core particle size 45 - 55 nm, TiO2 shell layer thickness 3 - 5 nm).

[0026] Preferably, the preparation method of the photoinduced lattice reconstruction metal foil is as follows: A. Pretreatment of the transparent polyimide substrate (1) Cleaning treatment: Immerse a 12-μm-thick transparent polyimide substrate in absolute ethanol, ultrasonically clean it for 15 min (power 300 W, frequency 40 kHz), rinse it 3 times with deionized water, and dry it with nitrogen gas. (2) Surface activation: Treat it with oxygen plasma (power 800 W, O2 flow rate 50 sccm) for 5 min. After treatment, the surface contact angle decreases from 85° to 15°. B. Preparation of Eu-doped ZnO nanowire array functional layer (1) Deposition of ZnO seed layer: Use atomic layer deposition technology to obtain a ZnO seed layer about 50 nm thick. The precursors are diethylzinc and deionized water, the deposition temperature is 200 °C, and the number of cycles is 100 times. (2) Hydrothermal growth of Eu:ZnO nanowires: The reaction solution formula is 0.1 M zinc nitrate (Zn(NO3)2·6H2O), 0.02 M europium nitrate (Eu(NO3)3·6H2O), and 0.1 M hexamethylenetetramine. Vertically place the transparent polyimide substrate into the reaction kettle, the reaction temperature is 93 °C, and the reaction time is 3 h.

[0027] C. Preparation of Ag / TiO2 core-shell structure metal layer (1) Synthesis of silver nanoparticles: Prepare a 0.01 M silver nitrate solution, add 0.1 M sodium citrate as a reducing agent, heat and stir it in a water bath at 80 °C for 30 min to obtain silver nanoparticles with a particle size of 45 - 55 nm. (2) Coating of TiO2 shell: Prepare an ethanol solution of tetrabutyl titanate (volume ratio 1:10), add 0.1 M nitric acid as a catalyst, disperse the silver nanoparticles in it, stir for 2 min and then centrifuge and wash, and anneal at 500 °C for 1 h to form an anatase-phase TiO2 shell. (3) Assembly of metal layer: Use the Langmuir-Blodgett technique, with a surface pressure of 25 mN / m and a transfer speed of 2 mm / min, to obtain a single-layer dense Ag / TiO2 core-shell structure.

[0028] In a specific implementation, the preparation method of the adhesive material is as follows: By weight, weigh 100 parts of epoxy resin, 4 parts of dicyandiamide, and 10 parts of silica nanoparticles, and disperse them at high speed (2000 rpm, 30 min) to obtain the adhesive material.

[0029] In this embodiment, the multi-frequency ultrasonic-assisted imprinting device includes the superimposed vibration of a 28-kHz main frequency (amplitude 10 μm) and a 132-kHz high frequency (amplitude 1 μm), and the vibration energy density is 15 J / cm 2, at a pressure of 1 MPa and a residence time of 50 ms, the ultrasonic head drives the nickel plate to press into the metal foil, and the 28 kHz low-frequency vibration pushes the metal foil to fill the micropores of the nickel plate (such as the relief structure with a depth of 200 μm), and the 132 kHz high-frequency vibration reduces the friction between the metal foil and the nickel plate to prevent the tearing of the microstructure.

[0030] In this embodiment, the cross-linking of the adhesive material by thermal curing after imprinting is specifically as follows: the substrate is preheated as a whole at 80 °C for 1 min by an infrared heater (the release layer in the pattern area rapidly absorbs heat, and the temperature in the non-pattern area lags behind), and then the temperature is raised to 120 °C at a rate of 20 °C / min to activate the decomposition of dicyandiamide and initiate the ring-opening reaction of epoxy resin. It is maintained at 120 °C for 1 min, and the epoxy network in the pattern area is deeply cross-linked and cured, while the temperature in the non-pattern area is ≤80 °C and hardly cured.

[0031] Preferably, after peeling the untransferred metal foil in step S500, the local or whole metal foil on the substrate is irradiated with ultraviolet light, and the gloss is adjusted by adjusting the ultraviolet light intensity or irradiation time. The nanowires are periodically arranged to form a photonic crystal structure, enhancing the light localization in a specific wavelength band; Eu 3+ ions emit red light under ultraviolet excitation, which is coupled with the plasma resonance peak of silver to broaden the optical response range; surface plasmon resonance (SPR): the free electrons of the Ag core are excited by 365 nm ultraviolet light to oscillate, and the resonance peak position is regulated by the TiO2 dielectric environment; dynamic refractive index regulation: the TiO2 shell generates photoinduced electron-hole pairs under ultraviolet irradiation, and the dielectric constant changes, resulting in a red shift of the SPR peak. Macroscopically, it is manifested as a change in refractive index and dynamic regulation of gloss.

[0032] Example 2 An embodiment of the present invention provides a micro-engraving hot stamping printing method, as Figure 1 shown, including the following steps: S100 Coating a gradient-responsive release layer on the surface of the substrate to be printed, and the release layer comprises a composite material of nano-silica aerogel and shape memory polyurethane; S200 Preparing a photo-induced lattice reconstruction metal foil, and the photo-induced lattice reconstruction metal foil includes a transparent substrate, a nanowire array functional layer and a core-shell structure metal layer; S300 Preparing an adhesive material; S400 Coating the adhesive material on the side of the transparent substrate of the metal foil away from the functional layer to form an adhesive layer, aligning and laminating the metal foil with the substrate coated with the release layer through the adhesive layer, and using a multi-frequency ultrasonic-assisted imprinting device for pattern transfer, and applying a composite frequency vibration synchronously during the imprinting process; S500 After imprinting, the adhesive material in the pattern area is cross-linked by thermal curing, and the untransferred metal foil is peeled off to obtain a micron-scale relief hot stamping pattern.

[0033] In this embodiment, the mass ratio of nano-silica aerogel to shape memory polyurethane in the gradient-responsive release layer is 1:3, and the thickness is 9 μm.

[0034] Furthermore, azobenzene groups are grafted onto the surface of the nano-silica aerogel (immersing 40-nm silica aerogel into 0.1 M ethanol solution of 3-aminopropyltriethoxysilane (APTES), reacting at 65 °C for 4 h to obtain aminated aerogel, reacting the aminated aerogel with 4-nitroazobenzoyl chloride in DMF, performing amidation reaction at 82 °C for 4 h to obtain azobenzene-modified aerogel), and the shape memory polyurethane contains a four-arm star-shaped polycaprolactone soft segment with a glass transition temperature of 85 - 105 °C.

[0035] Even further, the specific process of coating the gradient-responsive release layer on the surface of the substrate to be printed is as follows: Add nano-silica aerogel into 30 times its weight of tetrahydrofuran, and ultrasonically disperse (550 W, 40 min) until there is no agglomeration; Add shape memory polyurethane, and magnetically stir at 65 °C for 2.5 h to form a uniform slurry; Plasma clean the substrate (Ar / O2 = 3:1, 900 W, 135 s); Use a gravure coater (anilox roll line count 200 LPI) to coat the slurry on the cleaned substrate at a speed of 2.5 m / min; After coating, dry with hot air at 65 °C for 7.5 min to form a release layer; According to the hot stamping pattern design file, laser activate the target area (pattern area) (1064-nm fiber laser, spot diameter 10 μm, power density 60 W / cm 2 ), the irradiation time is 80 ms / spot, triggering the glass transition of the shape memory polyurethane, reducing the release force, the pores of the nano-silica aerogel in the target area (pattern area) collapse, forming a dense structure, improving the thermal conductivity, while the non-pattern area is not activated, with a high release force, maintaining a porous aerogel structure and a low thermal conductivity to form a thermal insulation barrier. During the post-imprinting heat curing process, the adhesive material in the pattern area obtains sufficient curing energy and is completely cured, while the non-pattern area is not cured, enabling the peeling of the metal foil in the non-pattern area.

[0036] In this embodiment, the photo-induced lattice reconstruction metal foil includes a transparent polyimide substrate (thickness 12 μm), an europium-doped zinc oxide nanowire array functional layer (diameter 80 ± 5 nm, length 1.2 - 1.5 μm, aspect ratio ≥ 15:1), and a silver / titanium dioxide core-shell structure metal layer (silver core particle size 45 - 55 nm, TiO2 shell layer thickness 3 - 5 nm).

[0037] Preferably, the preparation method of the photo-induced lattice reconstruction metal foil is as follows: A. Pretreatment of Transparent Polyimide Substrate (1) Cleaning treatment: Immerse a 12-μm-thick transparent polyimide substrate in absolute ethanol, ultrasonically clean it for 20 min (power 400 W, frequency 45 kHz), rinse it 3 times with deionized water, and dry it with nitrogen; (2) Surface activation: Treat it with oxygen plasma (power 900 W, O2 flow rate 55 sccm) for 7.5 min. After treatment, the surface contact angle decreases from 85° to 15°; B. Preparation of Europium-Doped Zinc Oxide Nanowire Array Functional Layer (1) Deposition of ZnO seed layer: Use atomic layer deposition technology to obtain a ZnO seed layer about 50 nm thick. The precursors are diethylzinc and deionized water, the deposition temperature is 200 °C, and the number of cycles is 100 times; (2) Hydrothermal growth of Eu:ZnO nanowires: The reaction solution formula is 0.1 M zinc nitrate (Zn(NO3)2·6H2O), 0.02 M europium nitrate (Eu(NO3)3·6H2O), and 0.1 M hexamethylenetetramine; Vertically place the transparent polyimide substrate into the reaction kettle, the reaction temperature is 95 °C, and the reaction time is 4 h.

[0038] C. Preparation of Silver / Titanium Dioxide Core-Shell Structure Metal Layer (1) Synthesis of silver nanoparticles: Prepare a 0.01 M silver nitrate solution, add 0.1 M sodium citrate as a reducing agent, heat and stir it in a water bath at 85 °C for 35 min to obtain silver nanoparticles with a particle size of 45-55 nm; (2) Coating of TiO2 shell layer: Prepare an ethanol solution of tetrabutyl titanate (volume ratio 1:10), add 0.1 M nitric acid as a catalyst, disperse the silver nanoparticles in it, stir for 2.5 min and then centrifuge and wash, and anneal at 500 °C for 1.5 h to form an anatase-phase TiO2 shell layer; (3) Assembly of metal layer: Use the Langmuir-Blodgett technique, with a surface pressure of 27 mN / m and a transfer speed of 2.5 mm / min, to obtain a single-layer dense Ag / TiO2 core-shell structure.

[0039] In a specific implementation, the preparation method of the adhesive material is as follows: By weight, weigh 110 parts of epoxy resin, 5 parts of dicyandiamide, and 11 parts of silicon dioxide nanoparticles, and disperse them at high speed (2000 rpm, 30 min) to obtain the adhesive material.

[0040] In this embodiment, the multi-frequency ultrasonic-assisted imprinting device includes the superimposed vibration of a 28-kHz main frequency (amplitude 12 μm) and a 132-kHz high frequency (amplitude 1 μm), and the vibration energy density is 20 / cm 2, at a pressure of 4 MPa and a residence time of 100 ms, the ultrasonic head drives the nickel plate to press into the metal foil, and the 28 kHz low-frequency vibration pushes the metal foil to fill the micropores of the nickel plate (such as a relief structure with a depth of 200 μm), and the 132 kHz high-frequency vibration reduces the friction between the metal foil and the nickel plate to prevent the microstructures from tearing.

[0041] In this embodiment, the crosslinking of the adhesive material by thermal curing after imprinting is specifically as follows: the substrate is preheated as a whole at 80 °C for 2 min by an infrared heater (the release layer in the pattern area rapidly absorbs heat, and the temperature in the non-pattern area lags behind), and then the temperature is raised to 120 °C at a rate of 20 °C / min to activate the decomposition of dicyandiamide and initiate the ring-opening reaction of epoxy resin. It is maintained at 120 °C for 2 min, and the epoxy network in the pattern area is deeply crosslinked and cured, while the temperature in the non-pattern area ≤ 80 °C is hardly cured.

[0042] Preferably, after peeling off the untransferred metal foil in step S500, the local or whole metal foil on the substrate is irradiated with ultraviolet light, and the glossiness is adjusted by adjusting the ultraviolet light intensity or irradiation time. The nanowires are periodically arranged to form a photonic crystal structure, enhancing the light localization in a specific wavelength band; Eu 3+ ions emit red light under ultraviolet excitation, which is coupled with the plasma resonance peak of silver to broaden the optical response range; surface plasmon resonance (SPR): the 365 nm ultraviolet light excites the free electron oscillation of the Ag core, and the resonance peak position is regulated by the TiO2 dielectric environment; dynamic refractive index regulation: the TiO2 shell generates photo-generated electron-hole pairs under ultraviolet irradiation, and the dielectric constant changes, resulting in a red shift of the SPR peak. Macroscopically, it is manifested as a change in refractive index and dynamic regulation of glossiness.

[0043] Example 3 An embodiment of the present invention provides a micro-engraving hot stamping printing method, as Figure 1 shown, including the following steps: S100 Coating a gradient-responsive release layer on the surface of the substrate to be printed, the release layer comprising a composite material of nano-silica aerogel and shape memory polyurethane; S200 Preparing a photo-induced lattice reconstruction metal foil, the photo-induced lattice reconstruction metal foil including a transparent substrate, a nanowire array functional layer and a core-shell structure metal layer; S300 Preparing an adhesive material; S400 Coating the adhesive material on the side of the transparent substrate of the metal foil away from the functional layer to form an adhesive layer, and aligning and laminating the metal foil with the substrate coated with the release layer through the adhesive layer, and using a multi-frequency ultrasonic-assisted imprinting device for pattern transfer, and synchronously applying a composite frequency vibration during the imprinting process; S500 After imprinting, crosslink the adhesive material in the pattern area by thermal curing, peel off the untransferred metal foil, and obtain a micro-scale relief hot stamping pattern.

[0044] In this embodiment, the mass ratio of nano-silica aerogel to shape memory polyurethane in the gradient-responsive release layer is 1:4, and the thickness is 10 μm.

[0045] Furthermore, azobenzene groups are grafted onto the surface of the nano-silica aerogel (immersing 40-nm silica aerogel into 0.1 M ethanol solution of 3-aminopropyltriethoxysilane (APTES), reacting at 70 °C for 5 h to obtain amino-functionalized aerogel, reacting the amino-functionalized aerogel with 4-nitroazobenzoyl chloride in DMF, and carrying out amidation reaction at 85 °C for 5 h to obtain azobenzene-modified aerogel). The shape memory polyurethane contains a four-armed star-shaped polycaprolactone soft segment, and the glass transition temperature is 85 - 105 °C.

[0046] Even further, the specific process of coating the gradient-responsive release layer on the surface of the substrate to be printed is as follows: Add nano-silica aerogel into 35 times its weight of tetrahydrofuran, and ultrasonically disperse (600 W, 50 min) until there is no agglomeration; Add shape memory polyurethane, and stir magnetically at 70 °C for 3 h to form a uniform slurry; Plasma clean the substrate (Ar / O2 = 3:1, 1000 W, 150 s); Use a gravure coater (the number of lines of the anilox roll is 200 LPI), and coat the slurry on the cleaned substrate at a speed of 3 m / min; After coating, dry with hot air at 70 °C for 10 min to form a release layer; According to the hot stamping pattern design file, laser activate the target area (pattern area) (1064-nm fiber laser, spot diameter 10 μm, power density 60 W / cm 2 ), the irradiation time is 80 ms / spot, triggering the glass transition of the shape memory polyurethane, reducing the release force, the pores of the nano-silica aerogel in the target area (pattern area) collapse, forming a dense structure, improving the thermal conductivity, while the non-pattern area is not activated, with a high release force, maintaining a porous aerogel structure and low thermal conductivity to form a heat insulation barrier. During the post-imprinting thermal curing process, the adhesive material in the pattern area obtains sufficient curing energy and is completely cured, while the non-pattern area is not cured, enabling the peeling of the metal foil in the non-pattern area.

[0047] In this embodiment, the photo-induced lattice reconstruction metal foil includes a transparent polyimide substrate (thickness 12 μm), an europium-doped zinc oxide nanowire array functional layer (diameter 80 ± 5 nm, length 1.2 - 1.5 μm, aspect ratio ≥ 15:1), and a silver / titanium dioxide core-shell structure metal layer (silver core particle size 45 - 55 nm, TiO2 shell layer thickness 3 - 5 nm).

[0048] Preferably, the preparation method of the photo-induced lattice reconstruction metal foil is as follows: A. Pretreatment of Transparent Polyimide Substrate (1) Cleaning treatment: Immerse a 12-μm-thick transparent polyimide substrate in absolute ethanol, ultrasonically clean it for 25 min (power 500 W, frequency 50 kHz), rinse it 3 times with deionized water, and dry it with nitrogen gas; (2) Surface activation: Treat it with oxygen plasma (power 1000 W, O2 flow rate 60 sccm) for 10 min. After treatment, the surface contact angle decreases from 85° to 15°; B. Preparation of Europium-Doped Zinc Oxide Nanowire Array Functional Layer (1) Deposition of ZnO seed layer: Use atomic layer deposition technology to obtain a ZnO seed layer about 50 nm thick. The precursors are diethylzinc and deionized water, the deposition temperature is 200 °C, and the number of cycles is 100 times; (2) Hydrothermal growth of Eu:ZnO nanowires: The reaction solution formula is 0.1 M zinc nitrate (Zn(NO3)2·6H2O), 0.02 M europium nitrate (Eu(NO3)3·6H2O), and 0.1 M hexamethylenetetramine; Vertically place the transparent polyimide substrate in the reaction kettle, the reaction temperature is 97 °C, and the reaction time is 5 h.

[0049] C. Preparation of Silver / Titanium Dioxide Core-Shell Structure Metal Layer (1) Synthesis of silver nanoparticles: Prepare a 0.01 M silver nitrate solution, add 0.1 M sodium citrate as a reducing agent, heat and stir it in a water bath at 90 °C for 40 min to obtain silver nanoparticles with a particle size of 55 nm; (2) Coating of TiO2 shell layer: Prepare an ethanol solution of tetrabutyl titanate (volume ratio 1:10), add 0.1 M nitric acid as a catalyst, disperse the silver nanoparticles in it, stir for 2 - 3 min and then centrifuge and wash, and anneal at 500 °C for 1 - 2 h to form an anatase-phase TiO2 shell layer; (3) Assembly of metal layer: Use the Langmuir-Blodgett technique, with a surface pressure of 30 mN / m and a transfer speed of 3 mm / min, to obtain a single-layer dense Ag / TiO2 core-shell structure.

[0050] In a specific implementation, the preparation method of the adhesive material is as follows: By weight, weigh 120 parts of epoxy resin, 6 parts of dicyandiamide, and 12 parts of silicon dioxide nanoparticles, and disperse them at high speed (2000 rpm, 30 min) to obtain the adhesive material.

[0051] In this embodiment, the multi-frequency ultrasonic-assisted imprinting device includes the superimposed vibration of a 28-kHz main frequency (amplitude 15 μm) and a 132-kHz high frequency (amplitude 2 μm), and the vibration energy density is 25 J / cm 2, at a pressure of 7 MPa and a dwell time of 150 ms, the ultrasonic head drives the nickel plate to press into the metal foil, and the 28 kHz low-frequency vibration pushes the metal foil to fill the micropores of the nickel plate (such as a relief structure with a depth of 200 μm), and the 132 kHz high-frequency vibration reduces the friction between the metal foil and the nickel plate to prevent the microstructures from tearing.

[0052] In this embodiment, the crosslinking of the adhesive material by heat curing after imprinting is specifically as follows: the substrate is preheated as a whole at 80 °C for 3 min by an infrared heater (the release layer in the pattern area absorbs heat rapidly, and the temperature in the non-pattern area lags behind), and then the temperature is raised to 120 °C at a rate of 20 °C / min to activate the decomposition of dicyandiamide and initiate the ring-opening reaction of epoxy resin. It is maintained at 120 °C for 3 min, and the epoxy network in the pattern area is deeply crosslinked and cured, while the temperature in the non-pattern area ≤ 80 °C is hardly cured.

[0053] Preferably, after peeling the untransferred metal foil in step S500, the local or whole metal foil on the substrate is irradiated with ultraviolet light, and the glossiness is adjusted by adjusting the ultraviolet light intensity or irradiation time. The nanowires are periodically arranged to form a photonic crystal structure to enhance the light localization in a specific wavelength band; Eu 3+ ions emit red light under ultraviolet excitation and are coupled with the plasma resonance peak of silver to broaden the optical response range; surface plasmon resonance (SPR): the 365 nm ultraviolet light excites the free electron oscillation of the Ag core, and the resonance peak position is regulated by the TiO2 dielectric environment; dynamic refractive index regulation: the TiO2 shell generates photo-generated electron-hole pairs under ultraviolet irradiation, and the dielectric constant changes, resulting in a red shift of the SPR peak, and the macroscopic manifestation is the change of refractive index and the dynamic regulation of glossiness.

[0054] Comparative Example 1: The difference from Example 2 is that a traditional release layer (uniform release wax) is used to verify the selective curing advantage of the gradient-responsive release layer.

[0055] Comparative Example 2: The difference from Example 2 is that the metal foil has no nanowire array functional layer (only the Ag / TiO2 layer) to verify the optical effect of the nanowire array.

[0056] Comparative Example 3: The difference from Example 2 is that single-frequency ultrasonic imprinting (only 28 kHz, without 132 kHz high frequency) is used to verify the influence of the composite frequency vibration on the integrity of the microstructures.

[0057] Performance Test 1 Metal residue rate: The content of metal elements (Ag, Ti) in the non-pattern area is analyzed by X-ray photoelectron spectroscopy (XPS); Adhesion: The bonding strength between the adhesive layer and the substrate is evaluated by the cross-cut method (ASTM D3359) (0-5B grade, 5B is the best).

[0058] Using the printing methods of Examples 1-3 and Comparative Example 1 to test the products, the results are shown in Table 1 below: Group Metal Residual Rate (%) Adhesion (5B Method) Example 1 0.37 5B Example 2 0.30 5B Example 3 0.34 5B Comparative Example 1 12.50 4B It can be seen from the above results that compared with Comparative Example 1, for the gradient release layer of the present application, through laser activation, the pattern area is densified. During thermal curing, the adhesive material in the pattern area is fully cross-linked and cured, while the non-pattern area is not cured due to the heat insulation effect. The residual rate after peeling is only 0.30%, which is significantly lower than 12.50% of Comparative Example 1. In Comparative Example 1 during the thermal curing stage (120 °C), the overall heat insulation of the release layer is too strong, resulting in the adhesive being unable to absorb sufficient heat, and the curing degree in both the pattern area and the non-pattern area is insufficient. The bonding force between the uncured adhesive layer and the substrate interface is weak, and it is easy to peel off from the substrate during the cross-cut test, so the adhesion is also less than that of the present application.

[0059] Performance Test Two Gloss regulation range: Measure the change in 60° gloss (GU) with a spectrophotometer (ultraviolet irradiation for 0 - 300 s).

[0060] Using the printing methods of Examples 1-3 and Comparative Example 2 to test the products, the results are shown in Table 3 below: Group Glossiness Change (ΔGU) after 300 s of UV Irradiation Example 1 122 Example 2 125 Example 3 124 Comparative Example 3 15 It can be seen from the above results that the metal foil of the present invention has a larger gloss regulation range compared with Comparative Document 2.

[0061] Performance Test Three Pattern resolution: Observe the edge clarity of the micro-relief by SEM (measurement at the μm level); Structural stability: Number of bending resistances. Using the printing methods of Examples 1-3 and Comparative Example 3 to test the products, the results are shown in Table 2 below: Group Minimum Line Width (μm) Number of Bending Resistances (times) Example 1 5.3±0.1 >5000 Example 2 5.2±0.3 >5000 Example 3 5.4±0.4 >5000 Comparative Example 3 7.8±0.9 3000 (Partial Peeling) It can be seen from the above results that through composite frequency-assisted imprinting, the present application improves the pattern quality and durability compared with Comparative Document 3.

[0062] It should be noted that for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps may be carried out in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0063] In the embodiments provided in the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the above division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection between devices or units can be in the form of telecommunications or other forms.

[0064] The units described above as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the protection scope of the invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still, without conflict, make combinations, additions, deletions or other adjustments to the features in the embodiments of the present invention according to the situation without creative efforts, so as to obtain different technical solutions that do not deviate from the concept of the present invention in essence. These technical solutions also belong to the scope of protection of the present invention.

Claims

1. A micro-engraving and hot stamping printing method, characterized in that, It includes the following steps: S100. Coating a gradient-responsive release layer on the surface of the substrate to be printed, where the release layer contains a composite material of nano-silica aerogel and shape memory polyurethane; S200. Preparing a photo-induced lattice reconstruction metal foil, where the metal foil includes a transparent substrate, a nano-wire array functional layer, and a core-shell structured metal layer; S300. Preparing an adhesive material, where the adhesive material includes a double-network polymer matrix and surface-modified two-dimensional nanosheets; S400. Coating the adhesive material on the side of the transparent substrate of the metal foil away from the functional layer to form an adhesive layer, aligning and laminating the metal foil with the substrate coated with the release layer through the adhesive layer, and using a multi-frequency ultrasonic-assisted imprinting device for pattern transfer, and synchronously applying a composite frequency vibration during the imprinting process; S500. After imprinting, cross-linking the adhesive material by thermal curing, peeling off the untransferred metal foil, and obtaining a micro-scale embossed gold stamping pattern.

2. The micro-engraving and gold stamping printing method according to claim 1, wherein, In the gradient-responsive release layer, the mass ratio of nano-silica aerogel to shape memory polyurethane is 1:2 - 4, and the thickness is 8 - 10 μm.

3. The micro-engraving bronzing printing method according to claim 2, characterized in that The nano-silica aerogel is grafted with azobenzene groups on its surface, and the shape memory polyurethane contains a four-armed star-shaped polycaprolactone soft segment, and the glass transition temperature is 85 - 105 °C.

4. The micro-engraving and gold stamping printing method according to claim 3, wherein The specific operation of coating the gradient-responsive release layer on the surface of the substrate to be printed is as follows: Adding nano-silica aerogel into 25 - 35 times the weight of tetrahydrofuran, and ultrasonic dispersing until there is no agglomeration; Adding shape memory polyurethane, and magnetically stirring at 60 - 70 °C for 2 - 3 h to form a uniform slurry; Plasma cleaning the substrate; Using a microgravure coater to coat the slurry on the cleaned substrate at a speed of 2 - 3 m / min; After coating, drying with hot air at 60 - 70 °C for 5 - 10 min to form a release layer; According to the gold stamping pattern design file, performing laser activation irradiation on the target area for 80 ms / point to trigger the glass transition of the shape memory polyurethane.

5. A micro-engraving hot stamping printing method according to claim 1, characterized in that, The photo-induced lattice reconstruction metal foil includes a transparent polyimide substrate, an europium-doped zinc oxide nano-wire array functional layer, and a silver / titanium dioxide core-shell structured metal layer.

6. The micro-engraving hot stamping printing method according to claim 5, characterized in that The preparation method of the photo-induced lattice reconstruction metal foil is as follows: A. Pretreatment of the transparent polyimide substrate (1) Cleaning treatment; (2) Surface activation; B. Preparation of the europium-doped zinc oxide nano-wire array functional layer (1) Depositing a ZnO seed layer; (2) Growing Eu:ZnO nano-wires by hydrothermal method; C. Preparation of the silver / titanium dioxide core-shell structured metal layer (1) Synthesizing silver nanoparticles; (2) Coating a TiO2 shell layer; (3) Assembling the metal layer.

7. The micro-carving bronzing printing method according to claim 6, wherein The preparation method of the adhesive material is as follows: By weight, weighing 100 - 120 parts of epoxy resin, 4 - 6 parts of dicyandiamide, and 10 - 12 parts of silicon dioxide nanoparticles, and dispersing at high speed to obtain the adhesive material.

8. The micro-engraving hot stamping printing method according to claim 1, wherein The multi-frequency ultrasonic-assisted imprinting device includes a superimposed vibration of a main frequency of 28 kHz and a high frequency of 132 kHz.

9. A micro-engraving hot stamping printing method according to claim 5, characterized in that The specific operation of cross-linking the adhesive material by thermal curing after imprinting is as follows: Preheating the substrate as a whole to 80 °C for 1 - 3 min through an infrared heater, and then heating to 120 °C at a rate of 20 °C / min, and maintaining at 120 °C for 1 - 3 min.

10. A micro-engraving and hot stamping printing method as described in claim 1, characterized in that, After stripping the untransferred metal foil in step S500, the local or overall metal foil on the substrate is irradiated with ultraviolet light, and the gloss is adjusted by adjusting the ultraviolet light intensity or irradiation time.

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