Process for printing on an eco-friendly material based on low temperature curing inks

Abstract

The application provides an environmentally-friendly material printing process based on low-temperature curing ink, and relates to the technical field of printing processes, and comprises the following steps: substrate pretreatment, microstructure imprinting, multi-layer inkjet printing, step-by-step low-temperature curing, online monitoring and post-treatment coating. The substrate pretreatment stabilizes the size and surface state of the substrate through a constant tension control system and a constant temperature and humidity channel. The microstructure imprinting forms a micro concave-convex structure on the surface of the substrate through a pressure roller, a back pressure roller and a high-frequency micro vibration system, so that mechanical anchoring of the ink is realized. The multi-layer inkjet printing realizes thickness and register accuracy control of the ink layer in combination with pressure embedding and a focusing air knife. The step-by-step low-temperature UV-LED curing and online near-infrared monitoring ensure sufficient crosslinking of the ink layer. The post-treatment includes plasma surface activation, protective layer coating and winding, and realizes high adhesion and good durability of the environmentally-friendly material printing product.

Description

Technical Field

[0001] This invention relates to the field of coal sampling and control technology, specifically to an environmentally friendly material printing process based on low-temperature curing ink. Background Technology

[0002] Traditional printing technologies, such as offset, gravure, and screen printing, face multiple technical challenges when applied to environmentally friendly, biodegradable roll materials. First, these environmentally friendly substrates generally have low surface energy, resulting in poor ink wetting and adhesion, easily leading to problems such as ink peeling, scratching, and damage after printing. Second, many environmentally friendly materials are heat-sensitive; traditional thermosetting inks or hot air drying methods may cause substrate deformation, shrinkage, or embrittlement, thus affecting the physical dimensions and structural stability of the printed product. Furthermore, in high-speed continuous roll-to-roll processes, even minute changes in substrate temperature and humidity can cause dimensional fluctuations, leading to registration accuracy issues during multi-layer printing, resulting in blurred or misaligned patterns, failing to meet the micron-level precision requirements of high-end manufacturing.

[0003] The aforementioned patent documents and prior art have the following technical problems when used:

[0004] Problem 1: Many environmentally friendly substrates, such as biodegradable plastic films, bio-based fiber films, and low surface energy polyolefin films, are prone to thermal shrinkage, warping, and mechanical property deterioration in traditional high-temperature thermosetting and solvent evaporation curing processes. This leads to a significant decrease in the dimensional stability and mechanical properties of the substrate after printing. At the same time, these substrates have high surface chemical inertness and low surface energy, making it difficult for ink to fully wet and penetrate them. After curing, they are still prone to delamination and peeling, which seriously affects the durability and reliability of printed products.

[0005] Question 2: Low-temperature curing inks used to avoid heat damage to the substrate generally exhibit rapid surface curing but insufficient internal cross-linking, resulting in a loose and fragile overall ink layer structure with poor adhesion. When subjected to mechanical stresses such as bending, impact, and friction, or environmental stresses such as temperature and humidity changes and ultraviolet light, they are prone to cracking and peeling, failing to meet the durability and reliability requirements of high-performance printed materials.

[0006] Problem 2: Traditional inkjet printing has low precision in position synchronization control during multiple overprints, which can easily cause layer misalignment. It also lacks the ability to finely control the ink layer thickness, which can easily lead to uneven thickness and stress concentration between printed layers. At the same time, the ink mostly relies on surface physical adhesion and fails to form an embedded mechanical interlocking structure with the substrate or the lower ink layer, resulting in insufficient overall interlayer bonding strength and poor durability of printed products. Summary of the Invention

[0007] Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides an environmentally friendly material printing process based on low-temperature curing inks, solving the following problems:

[0009] 1. Addressing the issues of poor heat resistance and low surface energy of environmentally friendly substrates, which lead to poor dimensional stability and insufficient adhesion after printing;

[0010] 2. To address the problem of uneven curing and poor adhesion of low-temperature curing inks, which leads to a fragile ink layer structure and easy failure under stress;

[0011] 3. To address the problems of low inkjet overprinting accuracy and lack of mechanical anchoring force, which lead to layer misalignment, uneven thickness, and insufficient interlayer bonding strength.

[0012] Technical solution

[0013] To achieve the above objectives, the present invention provides the following technical solution: an environmentally friendly material printing process based on low-temperature curing ink, characterized in that the process includes the following steps:

[0014] Sp1: Substrate pretreatment step: The roll of environmentally friendly substrate is conveyed through the pretreatment zone, which performs tension, temperature and humidity stabilization treatment on the substrate;

[0015] Sp2: Microstructure preforming step: A microstructure imprinting roller is used to imprint the surface of the substrate treated in the substrate pretreatment step to form a micro-unfold structure for mechanical anchoring in the subsequent printing area.

[0016] Sp3: Multi-layer inkjet printing step: The substrate processed by the microstructure pre-forming step is transported to the printing unit, and a piezoelectric printhead is used to perform thin-layer multiple overprinting according to the preset pattern.

[0017] Sp4: Pressure-assisted embedding step: After each thin layer is printed, pressure is immediately applied to the printing area using a pressure-assisted unit, so that the uncured ink droplets are compressed and filled into the micro-uneven structure, thereby achieving mechanical interlocking between the ink and the substrate.

[0018] Sp5: Step-by-step low-temperature curing process: Each layer of ink that is pressed in is cured in stages at low temperature, including surface pre-curing using a low-power light source and then deep curing using a higher-power light source to ensure that the ink layer is fully cross-linked from the inside out.

[0019] Sp6: Online monitoring and feedback adjustment steps: During the step-by-step low-temperature curing process, the curing status of the ink is monitored in real time by an online monitoring device, and the power of the curing light source or the irradiation time is adjusted according to the monitoring signal feedback.

[0020] SP7: Post-treatment and coating steps: After all ink layers have cured, the substrate is cooled and leveled, and a transparent protective layer is applied as needed to achieve final curing.

[0021] Preferably, the microstructure imprinting roller in the microstructure preforming step is a metal roller whose surface is prepared with a fixed micro-convex and concave pattern by one of three processes: etching, laser engraving, and electroforming; the typical depth of the micro-convex and concave structure is 0.5µm to 50µm, and the typical spacing is 1µm to 200µm.

[0022] Preferably, during the microstructure imprinting process in the microstructure preforming step, high-frequency micro-vibration is applied to the microstructure imprinting roller to assist in the plastic deformation of the substrate, thereby completing the microstructure forming under lower pressure and temperature; the frequency of the high-frequency micro-vibration is 20kHz to 100kHz.

[0023] Preferably, the pressure-assisted embedding unit in the pressure-assisted embedding step is a precision pressure roller and a focusing air knife module that are closely arranged following the printhead. The precision pressure roller has an elastic surface layer, and the contact pressure between it and the substrate is controlled and adjusted within the range of 0.05MPa to 2.0MPa. The focusing air knife module ejects a controlled high-pressure airflow to impact the printing area, thereby driving ink droplets to embed into the microstructure.

[0024] Preferably, in the multi-layer inkjet printing step, the ink thickness of each layer is controlled to not exceed 15µm to ensure that the curing energy can effectively penetrate and facilitate full embedding in the pressure-assisted embedding step.

[0025] Preferably, the online monitoring device in the online monitoring and feedback adjustment step is a near-infrared spectroscopy probe, which determines the curing degree of the ink by detecting changes in the absorption peaks of specific chemical bonds.

[0026] Preferably, a plasma surface activation process is set between the microstructure preforming step and the multilayer inkjet printing step to improve the chemical activity and wettability of the substrate surface, thereby enhancing the adhesion between the ink and the substrate.

[0027] Preferably, the transparent protective layer in the post-processing and coating steps is coated using a slot coating method, with the coating thickness controlled below 8µm, and cured using low-temperature ultraviolet light to improve the wear resistance and weather resistance of the product without damaging the substrate.

[0028] Preferably, the micro-uneven structure formed in the microstructure preforming step is characterized by including at least one of a barb shape, an undercut groove, and an inverted conical hole, which provides a locking space for the mechanical interlocking of the ink.

[0029] Beneficial effects

[0030] This invention provides an environmentally friendly printing process for materials based on low-temperature curing inks. It offers the following advantages:

[0031] 1. This process employs a substrate pretreatment zone comprised of a fully enclosed constant temperature and humidity channel and an active tension control system. This system precisely stabilizes the temperature, humidity, and tension of the substrate before printing. The constant temperature and humidity channel utilizes multi-zone closed-loop control through far-infrared heating, ultrasonic atomization humidification, and cooling coil dehumidification to thoroughly eliminate internal material stress and prevent dimensional expansion and contraction caused by environmental changes. The high-precision tension control system, through floating rollers, force-measuring rollers, and PLC PID closed-loop adjustment, maintains stable substrate transport under a preset tension, preventing deformation caused by tension fluctuations. Furthermore, a plasma surface activation unit is installed after pretreatment. Through atmospheric pressure dielectric barrier discharge, high-energy active groups are generated on the substrate surface, significantly increasing its surface energy and polarity, improving ink wetting and penetration, and providing chemical bonding support for the ink. This fundamentally solves the problems of poor substrate dimensional stability and insufficient adhesion.

[0032] 2. This process adopts an integrated solution of "pressure-assisted embedding + step-by-step low-temperature curing + online spectral monitoring". The pressure roller and focusing air knife unit, set after printing, embed ink droplets into the micro-uneven structure formed by the previous printing under PLC closed-loop control at an adjustable pressure of 0.05–2.0 MPa, constructing an embedded mechanical interlocking interface so that the ink no longer relies on simple surface adhesion to achieve deep anchoring. Subsequently, a two-stage UV-LED step-by-step low-temperature curing process is used. After each layer is printed, a near-field low-power UV-LED is used for surface pre-curing, rapidly gelling the surface layer to fix its shape and prevent interlayer flow. After all layers are completed, a high-power deep-curing UV-LED array is used to completely cross-link from the inside out. This avoids thermal damage to the substrate caused by high-temperature curing and solves the defect of rapid surface curing but insufficient internal cross-linking under low-temperature conditions. This results in a dense and tough ink layer with sufficient internal curing, significantly improving its resistance to bending, impact, damp heat, and UV radiation. Near-infrared spectral reflectance probes are installed at the end of the curing zone to monitor the conversion rate of carbon-carbon double bonds in the cured ink layer in real time. The output power of UV-LED or the speed of the production line is dynamically adjusted by the PID algorithm of PLC to achieve closed-loop control of curing quality. This ensures that the degree of crosslinking of each meter of product consistently reaches the set threshold, fundamentally improving the structural integrity and adhesion reliability of the ink layer.

[0033] 3. This process incorporates synergistic optimization in both structure and control systems. The printing unit employs a high-resolution rotary encoder with over 10,000 lines per second to provide the printhead with a unified micron-level time and position reference. Combined with an industrial-grade piezoelectric printhead and a RIP image processor, the target ink layer thickness is precisely decomposed into multiple 2-3 micron thin layers for sequential overprinting. The thickness control accuracy can reach ±1 micron, and the multi-layer registration accuracy is less than 0.1 mm, effectively avoiding stress concentration caused by layer misalignment and uneven thickness. Simultaneously, a pressure-assisted embedding module is installed adjacent to the printing area, pressing each ink droplet into the microstructure grooves on the substrate surface before it is fully cured, forming an embedded mechanical interlocking interface with the substrate. This achieves coordinated interlocking between layers and the substrate, significantly improving interlayer bonding strength and overall durability. Attached Figure Description

[0034] Figure 1 This is a flowchart of the printing process of the present invention;

[0035] Figure 2 This is a structural diagram of the printing process of the present invention;

[0036] Figure 3 This is a schematic diagram of the production line of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific Implementation Example 1:

[0039] like Figures 1 to 3 As shown, the printing process for environmentally friendly materials based on low-temperature curing inks includes the following steps:

[0040] Sp1: Substrate Pre-treatment Step: The pre-treatment zone ensures the substrate has highly stable physical dimensions and surface condition before entering the core forming and printing stations. This zone begins with an active servo motor-driven unwinding unit. This unit works in conjunction with the main drive system to maintain reference tension and is equipped with a pneumatic brake for emergency braking. After exiting the unwinding unit, the substrate enters a constant tension control system consisting of multiple precision guide rollers, a floating roller tension buffer mechanism, and a high-precision force measuring roller. The main drive roller on the production line is set as the speed spindle, and its high-resolution encoder generates pulse signals as a unified time base for the entire line, ensuring strict speed synchronization of all driven units. Tension control is independently performed by the servo motors of the take-up and unwinding units. These servo motors automatically adjust their speed and torque based on real-time tension data fed back from the force measuring roller, using a built-in tension control algorithm to precisely maintain the substrate's preset tension. The vertical displacement of the floating roller is monitored in real-time by a linear sensor, instantly absorbing and buffering instantaneous tension fluctuations caused by speed changes, while the force measuring roller provides precise tension values ​​to the central programmable logic controller (PLC). Based on this value, the PLC continuously adjusts the braking torque of the unwinding unit and the speed of the main drive motor in the later stage of the production line using an advanced PID algorithm to ensure that the tension of the substrate is strictly kept constant at the preset value throughout the pretreatment area. The PID algorithm adjusts the control quantity by calculating the error between the current measured value and the target setpoint, and combining the output of three components: Proportional: Adjusted in real time according to the current error magnitude. The larger the error, the greater the adjustment. Integral: Accumulates historical errors to eliminate steady-state errors and prevent long-term deviations. Derivative: Predicts the error change trend to reduce system oscillations and improve response speed. In tension control, the PLC calculates the adjustment amount through the PID algorithm and outputs it to the pneumatic brakes of the unwinding and rewinding units to continuously reduce tension errors and ultimately stabilize the tension at the target value. The pneumatic brake serves as a core safety redundancy, and its control logic is integrated with the main servo system in the PLC's safety program. During normal operation, the brake is in the released state. If the PLC detects a serious fault signal such as substrate breakage, loss of tension sensor signal, or operator pressing the emergency stop button, the system will immediately cut off the torque output of the main drive servo motor and simultaneously activate the pneumatic brake to achieve a safe shutdown as quickly as possible, maximizing the protection of equipment and materials. After troubleshooting, a manual reset via HMI is required for the system to resume operation according to the preset program. This process adds a high-speed timing synchronization control module based on FPGA to the central PLC. Using the pulses generated by the encoder as a unified reference, it achieves hardware-level synchronous control of inkjet triggering, pressure loading, air knife spraying, and UV-LED pre-curing lamp illumination, ensuring phase consistency and timing accuracy of each action during multi-layer printing and step-by-step curing. The PLC is responsible for macroscopic and logical control.It receives signals from all sensors, runs complex control algorithms such as PID control, and generates coarse, logical control commands based on the preset process formula. These commands include: production line speed, tension setpoint, total power of the curing lamp, and commands sent to the FPGA. The FPGA is responsible for microscopic, timing-based control. It is directly connected to the high-resolution encoder and inkjet printhead of the main drive roller. When the PLC issues a command, the FPGA receives the massive amount of high-frequency pulse signals generated by the encoder. Utilizing its hardware-level parallel processing capabilities, it calculates the precise position of the substrate in real time with nanosecond-level accuracy, and sends a trigger signal in milliseconds when the preset coordinate point is reached, driving the printhead to eject ink droplets.

[0041] After tension stabilization, the substrate enters a five-meter-long enclosed temperature and humidity control channel. This channel integrates multiple sets of far-infrared electric heating lamps, as well as a humidity control module containing an ultrasonic atomizing humidifier and a cooling coil dehumidifier. High-precision digital temperature and humidity sensors are evenly distributed at the channel's inlet, middle, and outlet, providing the PLC with multi-point real-time data. Based on this data, the PLC automatically adjusts the power of the heating and humidity modules using a multi-zone control strategy, stabilizing the substrate's temperature and relative humidity at specific levels. This completely eliminates potential internal stress, dimensional shrinkage, or expansion of the material caused by changes in ambient temperature and humidity, providing a perfectly prepared substrate for subsequent micron-level precision machining.

[0042] Sp2: Microstructure Pre-forming Step: This is the technical step to achieve a strong mechanical anchoring between the ink and the substrate. The key equipment is the microstructure impression roller. The roller core is precision-machined from alloy structural steel, and its working surface is prepared using different advanced processes depending on the complexity of the required microstructure and cost requirements. For relatively simple dot matrix or groove structures, chemical etching can be used. This involves forming an anti-etching mask on the roller surface using photolithography, followed by treatment with a chemical etching solution such as ferric chloride. For microstructures requiring complex three-dimensional morphologies with barbs or cones to enhance the locking effect, a high-precision femtosecond or picosecond laser is used to directly engrave on the metal roller surface through laser ablation. This method offers extremely high precision and eliminates the heat-affected zone. The geometric dimensions of the inverted hook structure are limited to a hook arm length of 0.5 to 20 micrometers and an opening angle of 30° to 75°. The geometric dimensions of the inverted cone structure are limited to a cone height of 0.5 to 15 micrometers and a apex angle of 40° to 80°. Furthermore, their lateral spacing is uniformly limited to 1 to 200 micrometers. Specific morphology and parameters can be optimized based on the hardness of the substrate and the rheological properties of the ink. To achieve the highest precision and aspect ratio, the electroforming LIGA process is used. First, a high-precision master mold is created on a substrate such as a silicon wafer, which is then used to create a polymer mold. Finally, a metal layer with microstructures is grown on the mold by electroplating a nickel-phosphorus alloy or other metal, and then firmly bonded to a steel roller core. The typical depth of these microstructures ranges from 0.5 to 50 micrometers, and the typical spacing ranges from 1 to 200 micrometers. Specific parameters need to be optimized based on the hardness of the substrate and the rheological properties of the ink used.

[0043] During the imprinting process, this microstructure imprinting roller and a back pressure roller coated with elastic materials such as polyurethane form a precision imprinting unit. The linear pressure between the two is precisely adjusted by either a cylinder or a servo motor to ensure the formation of a complete and consistent depth of microstructure on the substrate, while avoiding any macroscopic damage to the substrate. To further improve the imprinting effect and reduce the required pressure and temperature, the unit also integrates a high-frequency micro-vibration system. This system can be installed inside the imprinting roller or on its bearing housing as a high-power piezoelectric ceramic transducer array or magnetostrictive transducer, driven by an independent ultrasonic generator. Its operating frequency is adjustable from 20 kHz to 100 kHz, and the amplitude is controlled between 1 and 10 micrometers by adjusting the generator's output power. The PLC automatically selects the optimal frequency and amplitude parameters based on the characteristics of the substrate being produced, utilizing the acoustic softening effect to assist the plastic deformation of the substrate, thereby achieving low-energy consumption and high-fidelity microstructure forming.

[0044] Sp3: Multi-layer Inkjet Printing Steps: The substrate with completed microstructure shaping then enters the multi-layer inkjet printing unit. This unit uses industrial-grade on-demand piezoelectric printheads with a physical resolution of no less than 600 dpi and supports grayscale printing. It can precisely control the volume of ejected ink droplets, typically between 2 and 20 picoliters. The final thickness of the ink layer is precisely controlled by the raster image processor (RIP) software. To form a 10-micron-thick ink layer, the RIP software intelligently decomposes the image into five independent 2-micron-thick layers, driving the printing system to perform five precise reciprocating or sequential overprints, achieving a thickness control accuracy of ±1 micron. To achieve such high multi-layer registration accuracy, a high-resolution rotary encoder with over 10,000 lines is installed on the main drive roller of the printing platform. The pulse signals generated by the encoder serve as the time and position reference for the entire printing system, precisely triggering the printhead to eject ink droplets when the substrate moves to the micron-level target position, ensuring that the registration accuracy of multi-layer overprinting is less than 0.1 mm. The Raster Image Processor (RIP) software acts solely as a front-end data processing tool, responsible for parsing the input target image file into layered digital printing data and generating corresponding printing instruction files. These files contain information such as the resolution, grayscale level, droplet volume, and pixel coordinates of each layer. The print controller, as the core module directly controlling the actuators, receives and reads the printing instruction files output by the RIP software. Triggered by a high-precision position signal provided by a rotary encoder, it precisely drives the piezoelectric actuators of the inkjet printhead to complete droplet ejection. Therefore, the RIP software is limited to data preparation and image layering, not directly involved in the execution of the printing action. The print controller, on the other hand, is responsible for converting the data file into specific physical actions. This clear division of labor and collaborative work ensures the high precision and stability of the entire inkjet printing process.

[0045] Sp4: Pressure-Assisted Embedding Step: Immediately following each thin-layer print, the pressure-assisted embedding unit applies pressure to the just-printed area. This unit can be a precision pressure roller consisting of a metal core roller and an outer layer of EPDM rubber elastic with a thickness of 5 mm and a Shore A hardness between 40 and 70. This structure provides sufficient pressure while effectively accommodating minor unevenness on the substrate surface. Precision cylinders or servo motor-driven eccentric wheel mechanisms at both ends of the pressure roller, under closed-loop control of the PLC, precisely maintain the contact pressure within a set range of 0.05 MPa to 2.0 MPa based on real-time feedback from pressure sensors. A focusing air knife module is employed, whose Coanda effect nozzles generate a uniform, high-speed laminar flow air curtain. Controlled by a high-speed solenoid valve, this air curtain impacts ink droplets within an extremely short millisecond time synchronized with the printing area, powerfully driving and embedding them into the pre-formed micro-uneven structure, thus achieving a strong mechanical interlock between the ink and the substrate. The focusing air knife module is precisely installed upstream of the pressure roller, with its nozzle tilted at an acute angle of 45 to 60 degrees to the substrate surface. Its core function is not prolonged blowing, but rather, triggered by a micrometer-level position signal from an encoder, it performs nanosecond-level pulsed jetting via a high-speed solenoid valve. As the ink droplet lands on the substrate surface, this instantaneous high-speed laminar flow air curtain provides a precise vertical impact force, causing it to initially "settle" into the opening of the microstructure and breaking surface tension. This effectively prevents ink droplet tailing or extrusion that might occur when the pressure roller passes over it at high speed. Next, the substrate enters the pressure zone of the pressure roller, where a uniform and continuous mechanical pressure from an elastic rubber layer thoroughly and without air bubbles compacts and fills the bottom of the microstructure, forming a firm mechanical anchor.

[0046] S5. Step-by-Step Low-Temperature Curing: The entire step-by-step low-temperature curing process utilizes UV-LED cold light sources to completely avoid thermal damage to the environmentally friendly substrate. The first step is surface pre-curing. A row of low-power UV-LED lamps with a wavelength of approximately 1 to 4 watts per square centimeter (395 nm) is installed very close behind the printhead. Their function is to instantly gel the surface of the ink droplets after they are pressed into the microstructure, thereby fixing their shape and providing a stable, non-flowing surface for the next layer of printing. After all layers have been printed and pre-cured, the substrate enters the main curing zone. This zone is equipped with one or more arrays of high-power UV-LED lamps with a wavelength of approximately 16 to 25 watts per square centimeter (16 to 25 watts per square centimeter), using the more penetrating 365 nm or 385 nm wavelengths, with an irradiation distance of approximately 5 to 10 mm to ensure complete cross-linking and curing of the entire ink layer from the inside out. The PLC automatically calculates and adjusts the power of all UV-LED lamps according to the production line speed to ensure a constant energy density received by the printed material and guarantee the uniformity of the cured quality.

[0047] S6. Online Monitoring and Feedback Adjustment Steps: To achieve closed-loop quality control, a non-contact near-infrared spectral reflectance probe is installed after the deep curing unit, vertically illuminating the cured printed surface. This system continuously monitors the characteristic absorption peak region of the carbon-carbon double bonds in the acrylate monomers. The spectrometer analyzes the data in real time, quantifies the conversion rate of the curing reaction, and sends this data to the PLC. If the PLC detects that the real-time curing rate is lower than the preset threshold of 98.5%, it will automatically execute the PID algorithm, slightly increasing the UV-LED power of the deep curing unit. If the curing rate remains low, the system will issue an alarm and can be set to automatically reduce the linear speed to ensure that every meter of product leaving the factory meets the highest quality standards.

[0048] S7. Post-processing and Coating Steps: Between microstructure embossing and inkjet printing, a plasma surface activation process is added. This process uses an atmospheric pressure dielectric barrier discharge system. As the substrate passes between electrodes, a low-temperature plasma excited by high frequency and high voltage treats its surface, with the power density controlled at 5 to 15 watts per square centimeter and the treatment time a fraction of a second. This aims to improve the chemical activity and wettability of the substrate surface, enhance the chemical bonding between the ink and the substrate, and create a synergistic enhancement effect with mechanical anchoring. After all printing and curing steps are completed, the substrate enters the post-processing unit. First, it is cooled and leveled by cold air. Then, according to product requirements, a slot coater applies a transparent protective layer with a thickness of less than 8 micrometers. This coating device uses a high-precision gear pump and precision die head to precisely control the coating thickness based on linear velocity and flow rate. Finally, it is cured by a low-temperature UV-LED unit to improve the product's abrasion resistance and weather resistance.

[0049] The entire production line is laid out linearly according to the optimized process flow, consisting of an unwinding unit, a constant temperature and humidity pretreatment channel, a plasma activation unit, a microstructure imprinting unit, an integrated multi-layer inkjet printing and pressure embedding unit, UV-LED pre-curing and deep curing lamps, a near-infrared online monitoring probe, a cooling unit, a slot coating unit, a final curing unit, and a rewinding unit. Roll-to-roll transport between units is achieved through multiple sets of servo-motor driven precision guide rollers and main drive rollers, ensuring synchronized speed and stable tension throughout the process. At the heart of the production line is a high-performance central PLC or industrial computer. Operators input all process parameters and monitor the operating status through a human-machine interface (HMI). The central controller receives input signals from all sensors and, based on preset process formulas and complex closed-loop control algorithms, coordinates and controls the actions of all actuators, ultimately achieving a high degree of automation, synchronization, and intelligent production. The HMI serves as the window for operators to interact with the automated equipment; its software architecture and logic ensure intuitive operation and system reliability. HMI software typically employs a layered architecture. The data layer, located at the bottom, is responsible for exchanging data with hardware such as PLCs, servo drives, and sensors via communication protocols. It continuously reads status data from the devices and writes operator commands to them. The logic layer processes data and executes control logic. For example, it converts real-time temperature data from the PLC into a graphical display, or converts operator-set values ​​on the screen into control signals that the PLC can recognize. The user interface layer, located at the top, is the graphical interface directly seen by the operator. It intuitively presents system status and parameters in the form of charts, gauges, buttons, and text boxes. Operators send commands to the underlying devices by touching or clicking these controls, enabling monitoring and control of the production line. The software architecture of the human-machine interface ensures smooth data flow and reliable human-machine interaction. Specific Implementation Example 2:

[0051] like Figures 1 to 3 As shown, based on the content of the above-described specific embodiment one, the following content is further disclosed:

[0052] Based on the content of the above-described specific embodiment one, the following specific process flow is further disclosed:

[0053] System Initialization and Process Parameter Setting: Before production starts, the operator uses the HMI (Human-Machine Interface) to set and load the corresponding process formula according to the specific production task. This formula includes precise control parameters for all units of the entire production line, mainly including: Tension Control Parameters: Setting the baseline tension value; Environmental Pretreatment Parameters: Setting the target temperature of the constant temperature and humidity channel; Surface Activation Parameters: Setting the power density of plasma treatment; Microstructure Imprinting Parameters: Setting the imprinting line pressure, frequency and amplitude of the ultrasonic micro-vibration system; Inkjet Printing Parameters: Loading image files through raster image processor software, setting the target total ink layer thickness, single-layer thickness of layered printing, and grayscale mode; Pressure Embedding Parameters: Setting the contact pressure of the pressure roller and the trigger logic of the focusing air knife; Curing Process Parameters: Setting the base power of the pre-curing and deep curing UV-LED lamp groups, and setting a constant energy density target value; Quality Monitoring Parameters: Setting the conversion rate threshold for the online monitoring system to determine whether curing is qualified; Post-treatment Coating Parameters: Setting the target thickness of the protective layer coating; Production Line Speed: Setting the baseline operating speed of the entire production line. After the parameters are input and confirmed to be correct, the system enters standby mode, ready to start.

[0054] Substrate Pretreatment and State Standardization: After production starts, the unwinding unit driven by an active servo motor works in conjunction with the main drive system to begin conveying the substrate at a set reference tension. A high-precision force-measuring roller transmits real-time tension data to the central PLC. The PID algorithm running within the PLC compares this input value with the set value, calculates the deviation in real time, and continuously outputs control signals to fine-tune the braking torque of the unwinding unit and the speed of the subsequent main drive motor. Simultaneously, the linear sensor of the floating roller tension buffer mechanism monitors its vertical displacement. The PLC uses this information to determine and absorb instantaneous tension fluctuations caused by speed changes, ensuring that the tension is strictly kept constant at the preset value. If the tension exceeds the preset fluctuation range, the system automatically stops.

[0055] The substrate, after passing through the tension stabilization zone, enters a fully enclosed constant temperature and humidity channel. Digital temperature and humidity sensors evenly distributed within the channel transmit real-time data from multiple points to the PLC. The PLC employs a multi-zone control strategy, independently adjusting the power of the far-infrared heating lamps in each zone, as well as the operating status of the ultrasonic atomizing humidifier and cooling coil dehumidifier, based on the differences between the data at each point and the set values. This process aims to completely eliminate internal stress in the material, prevent dimensional expansion and contraction due to environmental changes, and provide a perfect initial condition for subsequent processing.

[0056] Surface activation and precision microstructure shaping: After leaving the pretreatment channel, the substrate first passes through an atmospheric pressure dielectric barrier discharge system. The PLC precisely controls the output of the high-frequency, high-voltage power supply based on the set power density and current linear velocity, exciting a low-temperature plasma to rapidly treat the substrate surface for a fraction of a second. This aims to improve the chemical activity and wettability of the substrate surface, providing chemical bonding force for subsequent ink adhesion and creating a synergistic enhancement effect with mechanical anchoring.

[0057] The activated substrate enters a precision imprinting unit consisting of a microstructured imprinting roller and an elastic back pressure roller. The PLC, based on the process formula, outputs commands to control a servo motor or precision cylinder to achieve the set imprinting line pressure. Simultaneously, the PLC activates an independent ultrasonic generator and selects the optimal frequency and amplitude parameters according to the substrate characteristics, driving a piezoelectric ceramic or magnetostrictive transducer to generate high-frequency micro-vibrations on the imprinting roller. This acoustic softening effect, without adding additional macroscopic heat, assists the substrate in achieving more efficient and faithful plastic deformation, accurately replicating the micron-level structure depth (0.5-50 μm) and spacing (1-200 μm) of the imprinting roller surface onto the substrate surface.

[0058] Multilayer inkjet printing and pressure-assisted embedding: The RIP software decomposes the target image into multiple thin layers. A high-resolution rotary encoder with over 10,000 lines per second, mounted on the main drive roller, begins operation, generating a massive amount of pulse signals that serve as the core timing base for the entire printing system. The PLC and printing controller use these pulse signals as a reference to precisely calculate the real-time displacement of the substrate. When the substrate moves to the predetermined coordinates, the system instantly triggers the industrial-grade on-demand inkjet piezoelectric printhead, causing it to eject ink droplets with a precise volume of 2-20 picoliters. This process is repeated or performed sequentially until all layers are overprinted. Precise encoder synchronization is crucial to ensuring multilayer registration accuracy of less than 0.1 mm.

[0059] Immediately following each single-layer inkjet print, the pressure-assisted embedding unit, consisting of a precision pressure roller and a focusing air knife, begins operation. A pressure sensor feeds back the real-time contact pressure with the substrate to the PLC, which, through closed-loop control, adjusts the servo eccentric wheel or precision cylinder to precisely maintain the pressure within a set range of 0.05 to 2.0 MPa. Simultaneously, based on the encoder's position signal, the PLC synchronously triggers a high-speed solenoid valve, causing the focusing air knife to eject a high-speed laminar flow air curtain. This air curtain impacts the newly landed ink droplets, powerfully driving them to fill the previously pre-formed micro-uneven structure, creating a robust mechanical interlock.

[0060] Step-by-step low-temperature curing and online closed-loop quality monitoring: A low-power (1-4W / cm²) UV-LED lamp with a wavelength of 395nm is installed very close to the back of the printhead. Each time a single layer of ink is pressed into the microstructure, it is immediately and briefly irradiated, causing the surface to gel rapidly. This fixes the shape of the ink droplets, providing a stable and non-flowing carrier surface for the next layer of printing.

[0061] After all layers are printed, the substrate enters the main curing zone. Here, a high-power (16-25W / cm²) UV-LED lamp array with stronger penetration at wavelengths of 365nm and 385nm is installed, the specific array depending on the photoinitiator formulation of the protective coating. The PLC automatically calculates and adjusts the output power of all UV-LED lamps in real time based on the current line speed, ensuring a constant cumulative energy density on the printed surface, thereby guaranteeing a high degree of consistency in curing quality at different production speeds.

[0062] Online Monitoring and Feedback Adjustment: After deep curing, a non-contact near-infrared spectral reflectance probe continuously irradiates the product surface, acquiring spectral data in real time. By analyzing the changes in the characteristic absorption peaks of carbon-carbon double bonds in acrylate monomers, the conversion rate of the curing reaction is quantified, and this percentage data is sent to the PLC. The PLC continuously compares the received real-time curing rate with a preset acceptable threshold in the HMI. If the real-time curing rate is greater than or equal to the threshold, the system determines that the quality is qualified, all parameters remain unchanged, and production proceeds normally. If the real-time curing rate is less than the threshold, the PLC will automatically execute a PID algorithm to smoothly increase the output power of the UV-LED lamp group of the deep curing unit in small steps, and continuously monitor whether the curing rate recovers to above the acceptable level. If the curing rate remains below the threshold after increasing the power, the system determines it to be abnormal. At this time, the PLC will trigger an audible and visual alarm, display a warning message on the HMI, and can automatically execute a speed reduction program according to preset logic to reduce the production line speed, thereby extending the curing time and ensuring that every part of the finished product meets the highest quality standards.

[0063] Post-processing, coating, and winding: The cured product is rapidly cooled by a cold air unit to eliminate residual heat and further stabilize its dimensions. Depending on product requirements, the substrate is coated using a slot coating device. The PLC precisely controls the speed of a high-precision gear pump based on the current line speed, thereby precisely controlling the flow rate to uniformly coat the product surface with a transparent protective layer less than 8 micrometers thick. The coated protective layer is then fully cured by a final low-temperature UV-LED irradiation unit. Finally, the finished product is wound up by a winding unit. The servo motor of the winding unit is also controlled by the central PLC, keeping synchronized with the overall line speed and maintaining stable winding tension to ensure the final product is neatly wound and of consistent quality. Specific Implementation Example 3:

[0065] like Figures 1 to 3 As shown, based on the content of the above specific embodiments, the following content is further disclosed:

[0066] Based on the content of the above-described Specific Embodiment 1 and Specific Embodiment 2, the following hardware components, installation locations, and models are further disclosed:

[0067] The substrate pretreatment and tension stabilization module is located at the beginning of the production line and is used for the precise delivery and standardization of the substrate's condition.

[0068] Unwinding Unit: Hardware Components: The active servo motor is a Siemens SINAMICSV90 series, equipped with a Heidenhain ECI4000 series unwinding shaft, a Warner Electric SF series pneumatic brake, an FMSPURE series tension sensor, and a roll support frame. The servo motor and pneumatic brake are directly mounted at both ends of the unwinding shaft and connected to it via couplings. The entire unit is fixed at the starting position of the production line base.

[0069] Constant Tension Control System: Hardware Components: Multiple precision guide rollers, typically made of lightweight aluminum alloy or carbon fiber with a hard anodized surface; a floating roller tension buffer mechanism with a linear sensor (using the SICKOD series displacement sensor); and a high-precision force-measuring roller (using the ReTension W200 / W300 series). The precision guide rollers are evenly arranged along the substrate transport path. The floating roller is located at the core of the tension control area, and its linear sensor is mounted on the roller's vertical guide rail. The force-measuring roller is installed at the end of the tension control area for directly measuring the substrate tension.

[0070] Constant Temperature and Humidity Chamber: Hardware Components: Enclosed chamber with inner walls lined with insulation material. Internally integrated are multiple HERAUS F-M series far-infrared electric heating lamps, Aobo-80 series ultrasonic atomizing humidifiers, and cooling coil dehumidifiers. Multiple SHT3x series high-precision digital temperature and humidity sensors are evenly installed at the inlet, middle, and outlet of the chamber. The entire chamber is installed after the tension control system and is airtightly connected to the front and rear substrate path interfaces.

[0071] The surface activation and microstructure forming module follows the pretreatment module and performs physical and chemical modifications on the substrate surface.

[0072] Plasma activation unit: Hardware components: Atmospheric pressure dielectric barrier discharge system, the core of which consists of two opposing electrodes encased in a ceramic or quartz glass dielectric layer. A high-frequency, high-voltage power supply from the PlasmaTreatOpenair series is connected to the electrodes to excite the cryogenic plasma. This unit is mounted above and below the substrate path to ensure uniform treatment of the substrate as it passes between the electrodes.

[0073] Microstructure Imprinting Unit: Hardware Components: A microstructure imprinting roller with an alloy steel core; the working surface is prepared using laser engraving or electroforming processes. A precision cylinder from the SMCCDQ series is used to apply line pressure. Two rollers form the imprinting unit on the production line frame, with the imprinting line located on the substrate transport path. A high-frequency micro-vibration system, consisting of a piezoelectric ceramic transducer array or magnetostrictive transducer and an independent ultrasonic generator, is directly mounted on the bearing housing of the microstructure imprinting roller.

[0074] Multilayer inkjet printing and pressure-assisted embedding modules are the core of the entire process, responsible for pattern formation and ink fixation.

[0075] High-speed multicolor inkjet printing unit: Hardware components: Industrial-grade on-demand inkjet piezoelectric printheads from the Fuji Dimatix StarFire series, with their nozzle array arranged along the width of the substrate. A high-resolution SMCCDQ series rotary encoder is mounted on the main drive roller of the printing platform as a timing reference. The inkjet heads are mounted above the main drive roller and can move laterally or be fixed. The main drive roller and encoder are located at the core of the printing platform, driving the substrate to pass precisely.

[0076] Pressure-Assisted Embedded Unit: Hardware Components: A precision pressure roller, with precision cylinders from the FestoVPPM series equipped with proportional valves at both ends. A SICKPBT series pressure sensor provides real-time pressure feedback. The focusing air knife module, using the EXAIR® series, consists of an air knife with a Coanda effect nozzle and a high-speed solenoid valve from the SMCVFS series. This unit is mounted immediately after the inkjet head. The precision pressure roller is positioned opposite the support roller on the back of the printing platform. The nozzle of the focusing air knife is arranged parallel to the substrate surface of the printing area.

[0077] The step-by-step low-temperature curing and online quality monitoring module is located after printing and is responsible for the complete curing and quality inspection of the ink.

[0078] UV-LED Curing System: Hardware Components: Surface pre-curing lamp assembly, low-power UV-LED lamps using Lumileds Luxeon UV series, wavelength 395nm. Deep curing lamp assembly, high-power UV-LED lamp array using Phoseon Technology LED series, wavelength 365nm or 385nm. All UV-LED lamps are connected to an adjustable power UV power supply. The surface pre-curing lamp assembly is installed 1-3mm behind each printhead. The deep curing lamp assembly is installed downstream of all printing units, approximately 5-10mm from the substrate surface.

[0079] Online quality monitoring system: Hardware components: A non-contact near-infrared spectral reflectance probe from the Avantes AvaSpec series and a spectrometer. The probe is vertically mounted downstream of the deep curing lamp assembly, facing the surface of the cured printed material.

[0080] The post-processing and winding module is located at the end of the production line and is used for product finishing and finished product winding.

[0081] Post-processing unit: Hardware components: Cooling and leveling unit, with upper and lower opposing cooling nozzles connected to the cooling fan and leveling roller assembly, driven by a servo motor. Slit coating device, consisting of a high-precision gear pump (Cole-Parmer series), liquid supply piping, and a precision die. The cooling and leveling unit is located after the NIR probe. The slit coating device is installed downstream of the cooling unit, with the precision die facing the substrate surface.

[0082] Rewinding unit: Hardware components include Mitsubishi or Siemens servo motors, encoders, tension controllers, and roll support frames. The entire unit is installed at the end of the production line. Specific Implementation Example 4:

[0084] like Figures 1 to 3 As shown, based on the content of the above specific embodiments, the following content is further disclosed:

[0085] To further verify the feasibility of this application in practical use, the method of this application is applied to a real-world case, demonstrating the feasibility and core technical effects of the environmentally friendly material printing process based on low-temperature curing ink in practical use. The following content is further disclosed:

[0086] Application Case 1: High-end product packaging printing for a consumer electronics company

[0087] Background: With increasing global focus on environmental protection, a well-known consumer electronics company decided to switch the packaging of its high-end products from plastic to biodegradable, environmentally friendly paper-based materials. However, traditional offset or gravure printing processes on paper-based materials suffer from problems such as poor ink adhesion, easy peeling, and significant influence of temperature and humidity on print quality, failing to meet the high quality requirements of its high-end brand.

[0088] To address this issue, the company introduced the roll-to-roll printing production line described in this technical solution. In the initial production stage, a constant temperature and humidity channel is used to precisely control the moisture content and temperature of the environmentally friendly paper base material within the target range, thereby eliminating internal stress in the substrate and ensuring that registration errors will not occur due to dimensional changes during subsequent precision printing. The plasma activation unit on the production line first treats the surface of the paper base material, significantly increasing its surface energy. Subsequently, a high-frequency micro-vibration system assists a microstructure impression roller to imprint micron-level inverted conical structures on the paper surface. These microstructures ensure the macroscopic integrity of the paper while providing strong physical anchoring points for the ink. Afterwards, the multi-color inkjet printing unit uses high-resolution piezoelectric printheads to print exquisite brand logos and patterns in layers. Simultaneously, a pressure-assisted embedding unit uses precision pressure rollers and a focusing air knife to forcefully press UV-curable ink into the microstructure of the paper, achieving a "physical welding" between the ink and paper fibers. An online near-infrared spectroscopy probe continuously monitors the curing process, ensuring that the ink curing rate of each roll reaches over 98.5%. If the curing rate fluctuates slightly, the PLC will automatically fine-tune the power of the UV-LED to ensure consistent curing quality.

[0089] Implementation Benefits: After implementing this solution, the company's product packaging ink adhesion improved by 300%. Even after repeated rubbing and folding, the ink layer showed no peeling or damage. The product defect rate decreased by 80%, production line speed increased by 15%, and production costs were significantly reduced. This case demonstrates that this process perfectly solves the core problem of low ink adhesion in the application of environmentally friendly materials while ensuring high-quality printing.

[0090] Application Case 2: High-precision functional thin film printing for automotive parts manufacturers

[0091] Background: An automotive parts manufacturer needs to print high-precision circuit patterns and transparent conductive inks on functional films for its cabin interior. Traditional screen printing is limited by precision and has uneven ink layer thickness, making it unable to meet its micron-level precision requirements for circuit patterns.

[0092] To address the problem, the company adopted this technical solution and customized it for its application. They collaborated with the technical team to customize the pattern on the microstructure imprint roller into a grooved structure that matched the circuit diagram. The depth and spacing of these grooves were precisely designed to ensure accurate ink filling, forming a conductive circuit with uniform thickness and stable resistance. On the production line, RIP software decomposed the complex circuit pattern into multiple layers based on the circuit design documents, which were then layered and printed by the inkjet unit. A high-resolution rotary encoder ensured that the registration accuracy of each ink layer was less than 0.1 mm, resulting in a final circuit pattern that perfectly matched the design. The pressure-assisted embedding unit played a crucial role in printing the conductive ink. It not only precisely pressed the conductive ink into the pre-formed grooves but also ensured that the particles within the ink layer were tightly packed, thereby improving the resistance uniformity of the printed circuit by 45%. Step-by-step low-temperature curing ensured that the thick conductive ink layer was completely cross-linked from the inside out, avoiding film deformation that could occur with traditional thermal curing. Online spectral monitoring ensured that the curing rate and conductivity of each batch of products met the preset standards.

[0093] Implementation Benefits: After introducing this process, the company successfully improved the precision of conductive circuit printing from the millimeter level of traditional screen printing to the sub-millimeter level, fully meeting the high-precision requirements of automotive electronics. Product yield increased from 70% to 95%, and production efficiency improved by 30%. This case demonstrates the enormous potential of this process in the field of functional thin film printing, especially in applications requiring micron-level precision and high reliability.

[0094] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a reference structure" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly printing process for materials based on low-temperature curing inks, characterized in that, The process includes the following steps: Sp1: Substrate pretreatment step: The roll of environmentally friendly substrate is conveyed through a pretreatment zone consisting of a fully enclosed constant temperature and humidity channel and an active tension control system. The pretreatment zone is used to stabilize the tension, temperature and humidity of the substrate. Sp2: Microstructure preforming step: A microstructure imprinting roller is used to imprint the surface of the substrate treated in the substrate pretreatment step to form a micro-unfold structure for mechanical anchoring in the subsequent printing area. Sp3: Multi-layer inkjet printing step: The substrate processed by the microstructure pre-forming step is transported to the printing unit, and a piezoelectric printhead is used to perform thin-layer multiple overprinting according to the preset pattern. Sp4: Pressure-assisted embedding step: After each thin layer is printed, pressure is immediately applied to the printing area using a pressure-assisted unit, so that the uncured ink droplets are compressed and filled into the micro-uneven structure, thereby achieving mechanical interlocking between the ink and the substrate. Sp5: Step-by-step low-temperature curing process: Each layer of ink that is pressed in is cured in stages at low temperature, including surface pre-curing using a low-power light source and then deep curing using a higher-power light source to ensure that the ink layer is fully cross-linked from the inside out. Sp6: Online monitoring and feedback adjustment steps: During the step-by-step low-temperature curing process, the curing status of the ink is monitored in real time by an online monitoring device, and the power of the curing light source or the irradiation time is adjusted according to the monitoring signal feedback. SP7: Post-treatment and coating steps: After all ink layers have cured, the substrate is cooled and leveled, and a transparent protective layer is applied as needed to achieve final curing.

2. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: The microstructure imprinting roller in the microstructure preforming step is a metal roller whose surface is prepared with a fixed micro-convex and concave pattern by one of three processes: etching, laser engraving, and electroforming. The typical depth of the micro-convex and concave structure is 0.5µm to 50µm, and the typical spacing is 1µm to 200µm.

3. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: During the microstructure imprinting process in the microstructure preforming step, high-frequency micro-vibration is applied to the microstructure imprinting roller to assist in the plastic deformation of the substrate, thereby completing the microstructure forming under lower pressure and temperature; the frequency of the high-frequency micro-vibration is 20kHz to 100kHz.

4. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: The pressure-assisted embedding unit in the pressure-assisted embedding step is a precision pressure roller and a focusing air knife module that are closely followed by the nozzle. The precision pressure roller has an elastic surface layer, and the contact pressure between it and the substrate is controlled and adjusted within the range of 0.05MPa to 2.0MPa. The focused air knife module ejects a controlled high-pressure airflow to impact the printing area, driving ink droplets to embed into the microstructure.

5. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: In the multilayer inkjet printing step, the ink thickness of each layer is controlled to not exceed 15µm to ensure that the curing energy can effectively penetrate and facilitate full embedding in the pressure-assisted embedding step.

6. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: The online monitoring device in the online monitoring and feedback adjustment step is a near-infrared spectral probe.

7. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: Between the microstructure preforming step and the multilayer inkjet printing step, a plasma surface activation process is set up to improve the chemical activity and wettability of the substrate surface, thereby enhancing the adhesion between the ink and the substrate.

8. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: The transparent protective layer in the post-processing and coating steps is applied using a slot coating method, with the coating thickness controlled below 8µm, and cured using low-temperature ultraviolet light to improve the product's wear resistance and weather resistance without damaging the substrate.

9. The environmentally friendly material printing process based on low-temperature curing ink according to claim 1, characterized in that: The microstructure formed in the microstructure preforming step is characterized by having at least one of the following: hook-shaped, groove-shaped, and inverted conical hole.

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