A micro-concave coating secondary leveling device and secondary leveling method

Abstract

The application discloses a kind of micro concave coating secondary leveling device and micro concave coating secondary leveling method.To solve the problems of appearance defects such as stripe, uneven thickness, insufficient flow leveling of micro concave coating.The secondary leveling device includes: rack, micro concave coating roller, trough, doctor mechanism and guide roller group;The leveling roller is provided on the film outlet side of the micro concave coating roller, and the leveling roller is set at 300-800mm from the film outlet point of the micro concave coating roller;The leveling roller is driven by a servo motor, the rotation direction is opposite to the film running direction of the base film, and the rotation speed of the leveling roller is determined according to the preset ratio of the viscosity of the coating glue and the film running speed of the base film;The leveling roller and the coating surface of the base film are in contact and friction, to implement secondary leveling on the wet coating layer that has not dried after coating;The penetration amount between the leveling roller and the coating surface of the base film is adjustable, and the surface topography of the leveling roller is one of mirror surface, fine oblique lines or fine vertical lines.The application can significantly improve the appearance quality and production yield of coating layer.

Description

Technical Field

[0001] This invention relates to the field of thin film coating technology, and more specifically, to a micro-recessed coating secondary smoothing device and a micro-recessed coating secondary smoothing method. Background Technology

[0002] Microgravure coating is widely used in high-performance coating fields such as optical films, functional films, lithium battery electrodes, and adhesive products due to its precise coating amount and uniform coating. Conventional microgravure coating relies on a microgravure roller to coat the base film in reverse. Under high-speed, high-solids-content, and high-viscosity conditions, the slurry undergoes a complex fluid dynamic process of "transfer-separation-spreading" between the microgravure roller and the base film. After the slurry is transferred to the base film, it is often in a non-equilibrium spreading state, which easily leads to appearance defects such as longitudinal stripes, diagonal stripes, local thickness unevenness, insufficient leveling, and spot defects.

[0003] To address the aforementioned shortcomings, existing technologies primarily seek solutions from the following directions: Firstly, the flattening direction of the base film. For example, Chinese patent CN102921602B sets a first flattening roller and a second flattening roller on both sides of the micro-concave roller of the micro-concave coating head, and sets a vacuum flattening device in the baking and cooling chamber to eliminate wrinkles in the base film (diaphragm) itself through vacuum adsorption and thread flattening. This type of solution treats the base film itself, not the already coated wet coating, and cannot solve the problems of stripes and insufficient leveling in the coating itself.

[0004] Secondly, the scraping direction of the gravure roller. For example, Chinese patent CN103861769B adds secondary or even tertiary scraping devices to the material box, using multi-stage scrapers to remove defective paste from the surface of the gravure roller caused by scraper wear, preventing the defects from transferring to the substrate. This type of solution treats the paste layer on the surface of the gravure roller, belonging to the pre-control stage of the coating process, and does not involve the post-processing of the wet coating already transferred to the base film. It is powerless to address coating defects already formed after transfer.

[0005] Thirdly, the leveling effect of the coating itself. Currently, after microgravure coating, any defects in the coating appearance can only be compensated for by the leveling effect of the coating itself. However, for coatings with high solids content and high viscosity, the leveling properties are inherently poor, and the self-leveling compensation effect is very limited, resulting in a persistently high rate of appearance defects.

[0006] In summary, the existing technology lacks a device or method that can actively and controllably perform secondary processing on micro-recessed wet coatings after coating to eliminate various coating appearance defects without damaging the film surface and adapting to different types of adhesives.

[0007] Therefore, the present invention provides a micro-concave coating secondary smoothing device and smoothing method. Summary of the Invention

[0008] To address the technical challenges of existing microgravure coating processes under high-speed, high-solids-content, and high-viscosity conditions, where the leveling effect of the coating liquid itself is insufficient to eliminate appearance defects such as longitudinal streaks, diagonal streaks, localized thickness unevenness, insufficient leveling, and dot-like defects in wet coatings, this invention provides a microgravure coating secondary leveling device and a microgravure coating secondary leveling method. By setting a counter-rotating leveling roller on the film exit side of the coating roller, the device actively intervenes in the wet coating leveling process, effectively eliminating various streaks and thickness unevenness defects. The adjustable pressure of 0-1.0 mm ensures light-contact leveling without damaging the film surface. Three quick-change roller surface morphologies can be used to address different defect types without replacing the entire machine, significantly improving coating appearance quality and production yield.

[0009] In a first aspect, the present invention provides a micro-gravure coating secondary smoothing device, comprising a frame, a micro-gravure coating roller, a material trough, a scraper mechanism, and a guide roller assembly. A smoothing roller is provided on the film exit side of the micro-grooved coating roller, and the smoothing roller is located at a distance of 300mm to 800mm from the film exit point of the micro-grooved coating roller. The smoothing roller is driven by an active servo motor. The rotation direction of the smoothing roller is opposite to the film feeding direction of the base film. The rotation speed of the smoothing roller is determined according to a preset ratio of the viscosity of the coating adhesive to the film feeding speed of the base film. The smoothing roller contacts and rubs against the coating surface of the base film to perform a secondary smoothing of the wet coating that has not yet dried after coating. The frame is equipped with a smoothing roller support and pressure adjustment mechanism on both sides. The support and pressure adjustment mechanism includes a linear guide rail, a slider, and a servo electric cylinder. The bearing seats at both ends of the smoothing roller are mounted on the slider. The slider can slide along the linear guide rail. The servo electric cylinder is connected to the slider. The slider is driven to slide by the servo electric cylinder to adjust the pressure between the smoothing roller and the base film coating surface. The pressure is adjustable from 0 to 1.0 mm. The surface morphology of the smoothing roller is one of mirror finish, fine diagonal lines, or fine vertical lines.

[0010] Furthermore, the smoothing roller has a diameter of 20-40 mm and is made of one of the following materials: hard alloy, high carbon steel, stainless steel, or ceramic-coated metal.

[0011] Furthermore, the smoothing roller has a sleeve-type split structure, including a fixed roller core base and a replaceable roller surface sleeve; the fixed roller core base has conical surfaces machined at both ends, and the roller surface sleeve has inner cones at both ends that match the conical surfaces; the roller core and the roller surface sleeve are locked and positioned without gaps through the cooperation of the conical sleeve and the expansion sleeve; the end of the roller surface sleeve is provided with a quick chuck and a locking nut.

[0012] Furthermore, when the surface morphology of the smoothing roller is mirror-like, its surface finish Ra ≤ 0.02 μm, which is used to eliminate irregular uneven textures in the coating layer; when the surface morphology of the smoothing roller is fine diagonal grooves, its line count is 500-1000 lines / inch, which is used to eliminate regular diagonal textures in the coating layer; when the surface morphology of the smoothing roller is fine vertical grooves, its line count is 500-1000 lines / inch, which is used to eliminate regular transverse textures in the coating layer.

[0013] Furthermore, The servo electric cylinders are independently installed on both sides of the frame. The push rod of the servo electric cylinder is rigidly connected to the slider. The servo electric cylinder receives commands from the control system to realize fully automatic and precise adjustment of the pressing amount, with an adjustment accuracy of ±0.02mm. The parallelism error between the axis of the smoothing roller and the axis of the guide roller and the micro-coating roller is ≤0.03mm / m.

[0014] Furthermore, it also includes a combined cleaning and anti-sticking mechanism, which comprises: A carbide cleaning scraper, wherein the cutting edge of the cleaning scraper is obliquely attached to the surface of the smoothing roller, the gap between the cutting edge of the cleaning scraper and the surface of the smoothing roller is 0.02 to 0.05 mm, and an adhesive receiving groove is provided below the cleaning scraper; And a fluorinated anti-stick coating disposed on the surface of the smoothing roller, the fluorinated anti-stick coating being used to prevent the coating liquid from adhering to the surface of the smoothing roller, the fluorinated anti-stick coating being resistant to a temperature of 120 to 220°C.

[0015] Furthermore, The active servo motor driving the smoothing roller is directly connected to the smoothing roller via a synchronous belt or coupling; the speed of the smoothing roller is infinitely adjustable from 0 to 1000 r / min. The micro-concave coating secondary smoothing device also includes a speed closed-loop control system. The speed closed-loop control system includes a PLC host, a servo driver and a high-precision rotary encoder. The encoder is coaxially mounted on the output end of the servo motor and is used to collect speed signals in real time and feed them back to the servo driver. The steady-state speed control accuracy is ±1r / min. The PLC host collects the film feeding speed signal of the coating host in real time, and the rotation speed of the smoothing roller dynamically follows the speed change of the coating host according to a preset ratio to achieve synchronous speed increase and decrease. The micro-recessed coating secondary smoothing device also includes a safety interlock system. When the film feeding speed of the coating host is lower than the safety threshold, the safety interlock system controls the smoothing roller to automatically stop rotating and automatically lift to detach from the base film surface. When the coating host triggers an emergency stop signal, the safety interlock system controls the smoothing roller to immediately stop rotating and automatically lift.

[0016] Furthermore, the smoothing roller has a circulating channel inside its core, and the circulating channel is connected to a cooling medium for temperature control of the smoothing roller, with a temperature control accuracy of ±1℃.

[0017] Secondly, the present invention provides a method for secondary smoothing of micro-recessed coating, implemented using the micro-recessed coating secondary smoothing device described in any one of the first aspects, comprising the following steps: The surface morphology of the smoothing roller is selected according to the type of appearance defect of the coating: a mirror roller is selected for irregular uneven textures, a fine diagonal texture roller is selected for regular diagonal textures, and a fine vertical texture roller is selected for regular horizontal textures. The smoothing roller is positioned on the film exit side of the micro-concave coating roller, and the pressing amount between the smoothing roller and the base film coating surface is adjusted to within the range of 0 to 1.0 mm. The ratio of the linear speed of the smoothing roller (Vroller) to the linear speed of the base film (Vfilm) is determined based on the viscosity of the coating adhesive. When the adhesive viscosity is <300 cPs, the ratio is 0.8–1.2; when the adhesive viscosity is 300–600 cPs, the ratio is 1.2–1.5; and when the adhesive viscosity is >600 cPs, the ratio is 1.5–1.8. The smoothing roller is driven to rotate at the speed corresponding to the ratio, and the rotation direction is opposite to the film feeding direction of the base film.

[0018] Furthermore, the method also includes online detection and automatic closed-loop adjustment steps, including: Downstream of the smoothing roller, a machine vision system acquires images of the coating surface in real time, identifies the type and severity of defects, and automatically issues adjustment commands based on the defect type: adjusting the rotation speed of the smoothing roller for stripe defects, and adjusting the pressing amount on one side of the smoothing roller for local uneven thickness.

[0019] Beneficial effects

[0020] The micro-recessed coating secondary smoothing device and method provided by this invention have the following beneficial effects: First, by setting the smoothing roller on the film exit side of the micro-concave coating roller, the process window period before the coating dries is precisely grasped, and active intervention is carried out during the stage when the wet coating is still fluid, overcoming the fundamental defect of the traditional process that relies solely on the coating liquid itself for passive leveling and has limited effect.

[0021] Secondly, the smoothing roller adopts an active servo drive mode that is opposite to the direction of the base film. It uses relative motion to generate controllable shear force, which drives the slurry to migrate from the accumulation area to the depression area, eliminating longitudinal and diagonal stripes in a directional manner. At the same time, the adjustable pressure of 0 to 1.0 mm ensures that the smoothing roller only applies slight pressure to the coating. The shear force is concentrated within the coating thickness range and does not penetrate the base film. Under the premise of ensuring the smoothing effect, it completely eliminates the risk of secondary damage such as scratches and stretching deformation on the film surface.

[0022] Third, the device is equipped with three quick-change roller surface morphologies: mirror finish, fine diagonal groove, and fine vertical groove. This allows the device to select the appropriate roller for different defect types, such as irregular concave and convex patterns, regular diagonal patterns, and regular transverse patterns. Moreover, the quick-change structure eliminates the need to disassemble bearings and transmission components, greatly improving the equipment's versatility and production line changeover efficiency.

[0023] In summary, this invention systematically solves the problem of appearance defects in micro-recessed coatings, and significantly improves coating uniformity and product yield. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the overall structure of a micro-concave coating secondary smoothing device provided for an embodiment of the present invention; Figure 2 A schematic diagram of a smoothing roller support and pressing adjustment mechanism provided in an embodiment of the present invention; Figure 3 A schematic diagram of a quick-change structure for a smoothing roller provided in an embodiment of the present invention; Figure 4 A control system block diagram provided in an embodiment of the present invention; Figure 5 A schematic diagram of a micro-recessed coating secondary smoothing method provided in an embodiment of the present invention; Explanation of reference numerals: 1. Base film; 2. Micro-gravure coating roller; 3. Material trough; 4. Scraper mechanism; 5. Guide roller group; 6. Smoothing roller; 7. Frame; 8. Linear guide rail; 9. Slider; 10. Bearing housing; 11. Servo electric cylinder; 12. Roll core; 13. Expansion sleeve; 14. Conical sleeve; 15. Roll surface sleeve; 16. PLC host; 17. HMI touch screen; 18. Servo driver; 19. High-precision rotary encoder; 20. Active servo motor; 21. Coating host speed encoder. Detailed Implementation

[0026] 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 a part of the embodiments of the present invention, and not all of them. 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.

[0027] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0029] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0030] The purpose of this disclosure is to overcome the technical problem that existing microgravure coatings, under high-speed, high-solids-content, and high-viscosity conditions, cannot effectively eliminate appearance defects such as longitudinal streaks, diagonal streaks, local uneven thickness, insufficient leveling, and dot-like defects caused by wet coatings by relying solely on the leveling of the coating liquid itself. The disclosure provides a microgravure coating secondary leveling device and method that can actively and controllably perform secondary leveling treatment on the wet coating after coating.

[0031] To better understand the above technical solutions, the present disclosure will be further described below with reference to specific embodiments, but the scope of protection of the present disclosure is not limited thereto.

[0032] This invention provides a micro-gravure coating secondary smoothing device, including a frame, a micro-gravure coating roller, a material trough, a scraper mechanism, and a guide roller assembly. A smoothing roller is provided on the film exit side of the micro-grooved coating roller, and the smoothing roller is located at a distance of 300mm to 800mm from the film exit point of the micro-grooved coating roller. The smoothing roller is driven by an active servo motor. The rotation direction of the smoothing roller is opposite to the film feeding direction of the base film. The rotation speed of the smoothing roller is determined according to a preset ratio of the viscosity of the coating adhesive to the film feeding speed of the base film. The smoothing roller contacts and rubs against the coating surface of the base film to perform a secondary smoothing of the wet coating that has not yet dried after coating. The frame is equipped with a smoothing roller support and pressure adjustment mechanism on both sides. The support and pressure adjustment mechanism includes a linear guide rail, a slider, and a servo electric cylinder. The bearing seats at both ends of the smoothing roller are mounted on the slider. The slider can slide along the linear guide rail. The servo electric cylinder is connected to the slider. The slider is driven to slide by the servo electric cylinder to adjust the pressure between the smoothing roller and the base film coating surface. The pressure is adjustable from 0 to 1.0 mm. The surface morphology of the smoothing roller is one of mirror finish, fine diagonal lines, or fine vertical lines.

[0033] like Figure 1 As shown, Figure 1 This is a schematic diagram of the microgravure coating secondary smoothing device according to this embodiment, including a frame, a microgravure coating roller 2, a material tank 3, a scraper mechanism 4, and a guide roller group 5. The base film 1 runs under the guidance of the guide roller group 5. The microgravure coating roller 2 is partially immersed in the material tank 3. After the scraper mechanism 4 scrapes off the excess slurry on the surface of the microgravure coating roller 2, the slurry is transferred to the surface of the base film 1 to form a wet coating.

[0034] A smoothing roller 6 is provided on the film exit side of the gravure coating roller 2. The smoothing roller 6 is a cylindrical roller body, with its axis perpendicular to the film flow direction of the base film 1 and parallel to the axes of each guide roller in the guide roller group 5. The smoothing roller 6 is located at the station where the wet coating has not yet entered the oven for drying, that is, in the section between the gravure coating roller 2 and the oven inlet. Preferably, the smoothing roller 6 is installed about 500 mm from the film exit point of the gravure coating roller 2 (it can also be adjusted within the range of 300 mm to 800 mm according to the actual process conditions) to ensure that the smoothing operation is carried out during the window period when the wet coating still has good fluidity.

[0035] The smoothing roller 6 is driven by an active servo motor, and its rotation direction is opposite to the film feeding direction of the base film 1. The smoothing roller 6 maintains a light contact friction with the coating surface of the base film 1 to perform a secondary smoothing of the wet coating that has not yet dried after coating. The pressure between the smoothing roller 6 and the coating surface of the base film 1 can be adjusted within the range of 0 to 1.0 mm (preferably 0.3 to 0.5 mm) to ensure that the shearing force is concentrated within the coating thickness range and to avoid penetrating the coating and acting on the base film to cause film surface damage.

[0036] The diameter of the smoothing roller 6 is preferably 20-40 mm, and the specific value can be selected according to the coating width and process requirements. The material of the smoothing roller 6 can be selected from one of hard alloy, high carbon steel, stainless steel or ceramic-coated metal to ensure sufficient rigidity and wear resistance.

[0037] Smoothing roller support and pressing adjustment mechanism, such as Figure 2 As shown, the smoothing roller 6 is mounted on the frame 7 via a support and pressure adjustment mechanism. The support and pressure adjustment mechanism consists of linear guide rails 8 on both sides of the frame 7, sliders 9 slidably connected to the linear guide rails 8, and servo electric cylinders 11 rigidly connected to the sliders 9. The bearing seats at both ends of the smoothing roller are mounted on the sliders. The support and pressure adjustment mechanism is used to support the smoothing roller 6 and adjust the pressure between the smoothing roller 6 and the coating surface of the base film 1.

[0038] Specifically, the smoothing roller 6 is mounted on the bearing seat 10, and the bearing seat 10 is fixedly mounted on the slider 9. Linear guide rails 8 are installed on both sides of the frame 7, and the extension direction of the linear guide rails 8 is perpendicular to the film-running plane of the base film 1 (i.e., along the normal direction of the base film). The slider 9 can slide along the linear guide rails 8 in this direction, moving towards or away from the base film, to change the gap between the smoothing roller 6 and the base film 1, thereby adjusting the pressing amount. The bearing seat 10 adopts a dustproof and waterproof structure, and is filled with high-temperature resistant grease, allowing for long-term maintenance-free operation.

[0039] The two sets of vertical frames 7 on the left and right serve as the main load-bearing structures of the entire mechanism. They are fastened to the mounting base at the bottom with bolts, providing rigid support for the adjustment components and roller system components above. This ensures the coaxiality of the support structures on both sides and the deformation resistance of the overall structure, preventing structural displacement due to stress during the smoothing operation.

[0040] The linear guide rail 8 is rigidly locked to the frame 7, providing low-resistance and high-straightness guiding constraints for the overall forward and backward movement of the smoothing roller 6, ensuring that the smoothing roller 6 will not deviate laterally during the forward and backward sliding process, and guaranteeing the parallelism accuracy of the roller body throughout the entire process.

[0041] The sealed precision rolling bearings at both ends of the smoothing roller 6 are installed inside the bearing housing 10. The bearing housing 10 is rigidly fixed to the sliding components on both sides through the positioning structure, which not only provides rotational support for the smoothing roller 6, but also allows it to move synchronously in the front and back directions with the slider 9, ensuring the synchronicity of the movement at both ends of the roller. The slider 9 and the linear guide rail 8 form a high-precision sliding pair. At the same time, the slider 9 is rigidly connected to the end of the push rod of the servo electric cylinder 11. Under the drive of the electric cylinder, it can complete precise sliding in the front and back directions along the linear guide rail 8, and directly transmit the linear driving force of the electric cylinder to the support component of the smoothing roller, realizing zero-backlash transmission of motion.

[0042] Servo electric cylinders 11 are independently installed on both sides of the frame 7, and the push rods of the servo electric cylinders 11 are rigidly connected to the sliders 9. The servo electric cylinders 11 receive commands from the control system (PLC host 16) to drive the push rods to extend or retract, thereby moving the sliders 9 along the linear guide rails 8, thus achieving fully automatic and precise adjustment of the pressing amount, with an adjustment accuracy of ±0.02mm. The independent installation of servo electric cylinders 11 on both sides can, on the one hand, correct the parallelism of the axis of the smoothing roller 6 by independently adjusting the pressing amount on both sides after the equipment is installed or has been in operation for a long time; on the other hand, when uneven coating thickness is detected online, the thickness deviation can be compensated by adjusting the pressing amount on one side separately.

[0043] To ensure a uniform smoothing effect across the entire width of the smoothing roller 6, the parallelism error between the axis of the smoothing roller 6 and the axes of the guide rollers in the guide roller group 5 and the micro-concave coating roller 2 is controlled to ≤0.03mm / m. Specifically, the mounting reference surfaces on both sides of the frame 7 are integrally milled to ensure that the left and right mounting reference surfaces are at the same height and coplanar. After assembly, a dial indicator is used for coaxiality testing and adjustment. After long-term operation, the parallelism can be finely adjusted using independent servo electric cylinders 11 on both sides for secondary correction.

[0044] The surface morphology of the smoothing roller 6 is one of mirror finish, fine diagonal lines, or fine vertical lines, and can be selectively used according to the type of coating appearance defects.

[0045] Mirror-finish smoothing rollers have a surface finish Ra ≤ 0.02μm and are primarily used to eliminate irregular unevenness in coating layers. Their mechanism of action lies in the mirror surface providing a uniform, smooth, and rigid contact surface, which, through normal flattening, makes the coating surface tend to be flat. Fine-grained smoothing rollers have a fine, dense diagonal groove of 500–1000 lines / inch, primarily used to eliminate regular diagonal patterns in coating layers. Their mechanism of action lies in the matching of the groove direction of the diagonal stripes with the groove direction of the roller surface, guiding the slurry to flow and rearrange along the groove direction through the "comb effect" between the grooves, thus offsetting the flow traces of the original diagonal patterns. Fine-grained vertical smoothing rollers have a fine, dense vertical groove of 500–1000 lines / inch, primarily used to eliminate regular transverse patterns in coating layers. Their mechanism of action lies in the fact that the vertical grooves (along the film-flowing direction) create a micro-smoothing effect in the transverse direction, smoothing transverse patterns without creating new directional traces.

[0046] To enable rapid switching between different roller surface shapes, the smoothing roller 6 adopts a sleeve-type split structure. For example... Figure 3As shown, the smoothing roller 6 consists of a fixed roller core base 12 and a replaceable roller sleeve 15. The roller core 12 is permanently fixed to the bearing housing 10 and the transmission mechanism. Replacement only requires disassembling the outer roller sleeve 15, without disassembling the bearing housing 10, synchronous belt, servo motor, or other components. Tapered sleeves 14 are machined at both ends of the roller core 12, and inner cones matching the tapered sleeves 14 are provided at both ends of the roller sleeve 15. The roller core 12 and roller sleeve 15 are locked and positioned without clearance through the cooperation of the tapered sleeves 14 and the expansion sleeve 13. The end of the roller sleeve 15 is equipped with a quick-release chuck and a locking nut. During replacement, simply loosen the locking nuts at both ends of the chuck, pull out the old sleeve axially, select a mirror-finish / fine diagonal / fine vertical groove sleeve corresponding to the working condition, align the tapered surface, insert it into the roller core, and tighten the locking nuts at both ends in sequence to complete the replacement. The entire operation takes no more than 3 minutes.

[0047] The smoothing roller 6 is driven by a servo motor 20. The servo motor 20 driving the smoothing roller 6 is directly connected to the smoothing roller 6 via a synchronous belt or coupling. The servo motor 20 is equipped with a speed control unit, and the speed of the smoothing roller 6 can be steplessly adjusted within the range of 0 to 1000 r / min.

[0048] To achieve precise control of the smoothing roller's rotational speed, this device is also equipped with a closed-loop speed control system. For example... Figure 4 As shown, the speed closed-loop control system includes a PLC main unit 16, an industrial human-machine interface (HMI touch screen 17), a servo driver 18, and a high-precision rotary encoder 19. The encoder 19 is coaxially mounted at the output end of the active servo motor 20, used to acquire the actual speed signal of the smoothing roller 6 in real time and feed it back to the servo driver 18, forming a full closed-loop speed control with a steady-state speed control accuracy of ±1 r / min. The HMI touch screen 17 integrates functions such as parameter setting, running status display, fault alarm, and PID parameter adjustment. Operators can manually modify the proportional, integral, and derivative parameters on the HMI interface to adapt to different loads and different viscosity adhesives.

[0049] The PLC host 16 also collects the film feeding speed signal of the coating host in real time (via the coating host speed encoder 21). The rotation speed of the smoothing roller 6 dynamically follows the speed change of the coating host according to a preset ratio, achieving synchronous speed increase and decrease. The ratio is determined based on the adhesive viscosity: when the adhesive viscosity is <300 cPs, the ratio of the smoothing roller linear speed to the base film feeding linear speed is 0.8 to 1.2 (low speed for gentle smoothing, preventing coating liquid from splashing); when the adhesive viscosity is 300 to 600 cPs, the ratio is 1.2 to 1.5 (a common range); when the adhesive viscosity is >600 cPs, the ratio is 1.5 to 1.8 (enhancing the smoothing effect and improving the leveling properties of the coating liquid). The basis for this ratio rule is that: low-viscosity slurry has good fluidity, and excessive shear force will cause the coating liquid to splash or drip, so a low speed ratio is used for gentle smoothing; high-viscosity slurry has high internal friction, and a higher shear rate is needed to overcome viscous resistance for effective leveling, so a high speed ratio is used to enhance the smoothing effect.

[0050] To prevent the smoothing roller 6 from adhering to the surface of the wet coating after prolonged contact with the coating, thus affecting the smoothing effect and contaminating the coating, this device is also equipped with a combined cleaning and anti-sticking mechanism.

[0051] The cleaning and anti-sticking mechanism includes a carbide cleaning scraper and a fluorine-based anti-stick coating on the surface of the smoothing roller 6. The cutting edge of the cleaning scraper is angled against the surface of the smoothing roller 6, and the gap between the cutting edge of the cleaning scraper and the surface of the smoothing roller 6 is controlled at 0.02-0.05mm, which can continuously scrape off residual adhesive and adhesive droplets adhering to the roller surface. The angle of the cleaning scraper can be manually fine-tuned, and an adhesive collection groove is provided below the cleaning scraper for uniform collection of scraped waste adhesive.

[0052] The surface of the smoothing roller 6 is coated with a fluorinated anti-stick coating. This fluorinated anti-stick coating is formed on the surface of the smoothing roller 6 using a precision spraying process, and can withstand temperatures of 120–220°C, making it suitable for continuous operation of the coating machine under high-temperature conditions. The fluorinated anti-stick coating reduces the surface energy of the roller, making it difficult for adhesive to adhere firmly; even if a small amount adheres, it is easily removed by a cleaning scraper. For mirror-finish rollers, the anti-stick coating requires precision grinding and polishing after formation to ensure that the surface finish still meets the requirement of Ra≤0.02μm; for rollers with fine diagonal or vertical grooves, the coating thickness and curing process must be controlled to ensure that the number and depth of grooves meet design requirements. This anti-stick coating is resistant to various coating adhesives such as silicone resin, epoxy resin, polyurethane resin, and acrylic pressure-sensitive adhesive.

[0053] To ensure safe operation of the equipment, this device is also equipped with a safety interlock system.

[0054] When the film feeding speed of the coating machine falls below the safety threshold (preferably 5 m / min), the safety interlock system controls the smoothing roller 6 to automatically stop rotating and controls the servo electric cylinder 11 to automatically lift the smoothing roller 6 to detach it from the surface of the base film 1, preventing the smoothing roller 6 from contacting the base film 1 at low speeds and causing scratches or damage to the film surface. When the coating machine triggers an emergency stop signal, the safety interlock system controls the smoothing roller 6 to immediately stop rotating and automatically lift it. A transparent safety guard is provided on the outside of the smoothing roller 6, and the guard is equipped with a door control switch. When the guard is opened, the safety interlock system controls the equipment to automatically stop, preventing accidental contact by personnel. All of the above safety interlock actions are completed within milliseconds, ensuring maximum protection of the base film and coating in case of emergencies.

[0055] Preferably, the smoothing roller has a circulating channel inside its core, and the circulating channel is connected to a cooling medium for temperature control of the smoothing roller, with a temperature control accuracy of ±1℃.

[0056] For low-temperature curing, heat-sensitive, high-viscosity adhesives, mechanical smoothing alone may still cause viscosity changes due to temperature fluctuations, thus affecting the stability of the smoothing effect.

[0057] The smoothing roller 6 has an axially machined circulating channel inside its core 12. This circulating channel is a spiral or annular cavity structure arranged around the axis of the core 12 to ensure uniform flow of the cooling medium within the core 12, thus uniformly cooling the smoothing roller 6. The circulating channel has a medium inlet and a medium outlet at both ends, located at the same end or both ends of the core 12, and connected to an external cooling medium pipeline via a rotary joint. The rotary joint employs a mechanical seal structure to ensure no leakage of the cooling medium even when the smoothing roller 6 is rotating at high speed.

[0058] For low-temperature curing, heat-sensitive, high-viscosity adhesives, the roller body temperature is controlled at 20~25℃ to prevent the adhesive from deteriorating due to heat and adhering to the roller surface; the temperature control accuracy is ±1℃, and the temperature parameter can be freely set in the HMI interface.

[0059] It should be noted that the temperature control system is the preferred implementation. For conventional coating conditions (non-heat-sensitive adhesive, conventional base film), the smoothing roller 6 does not need to activate the temperature control function. The ideal smoothing effect can be achieved solely by relying on the mechanical smoothing and anti-stick cleaning mechanism.

[0060] This device also features fault interlock protection. When the servo motor is overloaded, the encoder signal is abnormal, or the vision system detects large-area film damage, the smoothing roller immediately stops and lifts, triggering an audible and visual alarm. It can also achieve machine emergency stop linkage. When the machine emergency stop button is pressed, all moving parts are instantly powered off, and the smoothing roller prioritizes lifting to protect the base film and coating.

[0061] The micro-gravure coating secondary smoothing device described in this invention, by placing the smoothing roller on the film exit side of the micro-gravure coating roller, precisely grasps the process window period before the coating dries. It actively intervenes while the wet coating still has fluidity, overcoming the fundamental defect of traditional processes that rely solely on the coating liquid's passive leveling, which has limited effectiveness. The smoothing roller employs an active servo drive method opposite to the film's flow direction, utilizing relative motion to generate controllable shear force, driving the slurry from the accumulation area to the recessed area, directionally eliminating longitudinal and diagonal streaks. Simultaneously, the adjustable pressure infeed of 0-1.0 mm ensures that the smoothing roller applies only slight pressure to the coating, concentrating the shear force within the coating thickness range without penetrating the base film. This eliminates the risk of secondary damage such as scratches and tensile deformation on the film surface while ensuring the smoothing effect. Equipped with three quickly interchangeable roller surface morphologies—mirror finish, fine diagonal stripe, and fine vertical stripe—this device can precisely select the appropriate roller for different defect types, such as irregular convex and concave patterns, regular diagonal patterns, and regular transverse patterns. The sleeve-type quick-change structure eliminates the need to disassemble bearings and transmission components, with a changeover time of no more than 3 minutes, significantly improving the equipment's versatility and production line changeover efficiency. Actual production verification shows that after adopting this device: the longitudinal stripes of the acrylic optical adhesive coating on PET base film improved from "dense line defects" to "basically no stripes, acceptable," and the coating thickness range decreased from ±1.0μm to ±0.5μm; the dot defects in the polyurethane functional coating of PET film decreased from 10 per square meter to 2 per square meter; and the transverse patterns of the copper foil thermal conductive paste coating were essentially eliminated, with the thickness range decreasing from ±1.5μm to ±0.5μm.

[0062] In summary, this embodiment systematically solves the problem of appearance defects in microgravure coating, significantly improves coating uniformity and product yield, and can be widely used in the field of microgravure coating such as optical films, functional films, lithium battery electrodes, and adhesive products.

[0063] This embodiment also provides a method for secondary smoothing of micro-recessed coating, implemented using the micro-recessed coating secondary smoothing device described in any of the above embodiments, such as... Figure 5 As shown, the method includes the following steps: Step S10: Select the surface morphology of the smoothing roller according to the type of appearance defect of the coating: select a mirror roller for irregular uneven texture, select a fine diagonal texture roller for regular diagonal texture, and select a fine vertical texture roller for regular horizontal texture. Step S20: Set the smoothing roller on the film exit side of the micro-grooved coating roller, and adjust the pressing amount between the smoothing roller and the base film coating surface to within the range of 0 to 1.0 mm; Step S30: Determine the ratio of the linear speed of the smoothing roller (Vroller) to the linear speed of the base film (Vfilm) based on the viscosity of the coating adhesive (Vroller / Vfilm). When the adhesive viscosity is <300 cPs, the ratio is 0.8 to 1.2; when the adhesive viscosity is 300 to 600 cPs, the ratio is 1.2 to 1.5; when the adhesive viscosity is >600 cPs, the ratio is 1.5 to 1.8. Step S40: Drive the smoothing roller to rotate at the speed corresponding to the ratio, and the rotation direction is opposite to the film feeding direction of the base film.

[0064] The secondary smoothing method of this embodiment specifically includes the following steps: Step S10: Select the surface morphology of the smoothing roller.

[0065] Select the surface morphology of smoothing roller 6 according to the type of appearance defects in the coating: For irregular, uneven textures, a mirror-finish smoothing roller is selected. The mirror-finish roller provides a uniform, smooth, and rigid contact surface, and through normal flattening action, it makes the coating surface tend to be flat, with a surface finish Ra≤0.02μm.

[0066] For regular diagonal patterns, a fine diagonal smoothing roller (500-1000 lines / inch) is selected. The pattern direction of the roller surface matches the direction of the diagonal stripes, and the "comb effect" between the patterns guides the slurry to flow and rearrange along the pattern direction, thus offsetting the flow traces of the original diagonal pattern.

[0067] For regular horizontal textures, use a fine vertical texture smoothing roller (500-1000 lines / inch). The vertical textures (along the film feeding direction) create a micro-smoothing effect in the horizontal direction, smoothing out the horizontal textures without creating new directional marks.

[0068] If the same production line needs to frequently switch between different products, the roller surface can be quickly changed using a sleeve-type quick-change structure while the equipment is stopped. The entire changeover process takes no more than 3 minutes.

[0069] Step S20: Set the position of the smoothing roller and adjust the pressing amount.

[0070] Position the smoothing roller 6 on the film exit side of the concave coating roller 2 (preferably about 500 mm from the film exit point) so that the smoothing roller 6 acts on the process window period before the wet coating enters the oven for drying. Adjust the pressing amount between the smoothing roller 6 and the coating surface of the base film 1 to the range of 0 to 1.0 mm (preferably 0.3 to 0.5 mm).

[0071] The pressure adjustment is automatically completed through the control system: the operator sets the target pressure value on the HMI touch screen 17, the PLC host 16 sends a command to the servo electric cylinder 11, the servo electric cylinder 11 drives the slider 9 to slide along the linear guide rail 8, driving the smoothing roller 6 forward or backward until the set pressure is reached. The two independent servo electric cylinders 11 can adjust the pressure at both ends of the smoothing roller 6 to ensure that the axis of the smoothing roller 6 is parallel to the axis of the guide roller 5 (parallelism error ≤0.03mm / m), or to compensate for uneven coating thickness by adjusting one side when it is detected.

[0072] The principle for selecting the pressing amount is: to use the smallest possible pressing amount while ensuring a smoothing effect, so as to avoid unnecessary pressure on the base film. For base films with good rigidity (such as PET and copper foil), the pressing amount can be appropriately increased; for soft or easily stretchable base films (such as polyolefin separators), a smaller pressing amount is preferable.

[0073] Step S30: Determine the speed ratio between the smoothing roller and the base film.

[0074] The ratio of the linear speed of the smoothing roller 6 (Vroller) to the linear speed of the base film 1 (Vfilm) is determined based on the viscosity of the coating adhesive. The specific rules are as follows: When the adhesive viscosity is <300 cPs (low viscosity adhesive, such as some acrylic optical adhesives and diluent coating liquids), the ratio should be 0.8 to 1.2. Low viscosity slurries have good fluidity, and excessive shear force can easily cause the coating liquid to splatter or drip. Therefore, a low speed ratio and gentle smoothing are sufficient.

[0075] When the adhesive viscosity is 300–600 cPs (medium viscosity adhesive, such as conventional polyurethane adhesive or pressure-sensitive adhesive), the ratio is 1.2–1.5. This range is a general range applicable to most microgravure coating processes.

[0076] When the adhesive viscosity is >600 cPs (high viscosity / high solids content adhesive, such as high solids content thermally conductive paste, lithium battery paste), the ratio is 1.5 to 1.8. High viscosity pastes have high internal friction, requiring a higher shear rate to effectively overcome viscous resistance and promote paste leveling. Therefore, a high-speed ratio is used to enhance the smoothing effect.

[0077] The above viscosity-speed ratio matching rule is based on the fact that most coating slurries are non-Newtonian fluids with shear-thinning properties—their viscosity decreases and their fluidity increases at high shear rates. High-viscosity slurries require higher shear rates to trigger a significant shear-thinning effect, allowing them to flow smoothly; while low-viscosity slurries already have sufficient fluidity, and excessive shear force may disrupt the surface tension balance of the coating.

[0078] In actual production, operators can first input the glue viscosity value on the HMI touch screen 17, and the system will automatically calculate and recommend the speed ratio and the corresponding smoothing roller speed. After the operator confirms, the operation will proceed. Alternatively, operators can manually input the speed value after accumulating experience.

[0079] Step S40: Drive the smoothing roller to rotate.

[0080] The smoothing roller 6 is driven to rotate at the speed corresponding to the speed ratio mentioned above (speed range 0 to 1000 r / min, steplessly adjustable), and the rotation direction of the smoothing roller 6 is opposite to the film-feeding direction of the base film 1. After the smoothing roller 6 rotates, relative sliding occurs between its surface and the coating surface of the base film 1, applying a controllable shear force to the wet coating, driving the slurry to migrate from the accumulation area to the depression area, thereby achieving secondary smoothing of the coating.

[0081] During continuous production, the PLC host 16 collects the film feeding speed signal of the coating host in real time, and the rotation speed of the smoothing roller 6 dynamically follows the speed change of the host according to the preset speed ratio. When the host speeds up, the speed of the smoothing roller increases synchronously, and the speed ratio remains constant; when the host decelerates, the speed of the smoothing roller decreases synchronously. When the host speed is lower than the safety threshold (e.g., 5m / min) or an emergency stop is triggered, the safety interlock system controls the smoothing roller 6 to automatically stop rotating and lift off the film surface to prevent damage to the film surface.

[0082] As a preferred embodiment of this method, a machine vision appearance inspection system (including a high-definition industrial camera and an image analysis module) is set downstream of the smoothing roller 6 to acquire images of the coating surface in real time and intelligently identify the type and severity of defects through the image analysis module.

[0083] The image analysis module communicates with the PLC host 16 and automatically issues adjustment commands based on the recognition results. When stripe-like defects (longitudinal stripes, diagonal stripes, or transverse stripes) are detected, the system determines that the smoothing shearing force is insufficient or excessive, and automatically fine-tunes the rotation speed of the smoothing roller 6 (e.g., increasing or decreasing by 50 to 100 r / min) to improve the smoothing effect by changing the shearing rate.

[0084] When uneven coating thickness is detected in some areas, the system determines that the pressing amount at both ends of the smoothing roller 6 is unbalanced or the lateral tension of the base film is uneven. It automatically fine-tunes the pressing amount of the servo electric cylinder 11 on the corresponding side (adjustment step 0.05~0.1mm) to compensate for the thickness deviation by changing the local smoothing pressure.

[0085] The aforementioned closed-loop process of "online detection - data analysis - automatic adjustment" runs continuously during the coating production process without manual intervention, ensuring that the smoothing parameters are always in the optimal state.

[0086] To more clearly illustrate the micro-recessed coating secondary smoothing method of the present invention, the present invention also provides the following specific embodiments.

[0087] Example 1: PET base film + acrylic optical adhesive (to eliminate longitudinal stripe defects)

[0088] Coating materials and process conditions: Base film: PET optical film, thickness 50μm; Coating solution: acrylic optical adhesive, solid content 18%, viscosity 530cPs; Coating speed 12m / min, dry adhesive thickness 10um; The main defect of the original process was dense longitudinal stripes.

[0089] Smoothing roller parameter selection: Select a mirror roller (surface roughness Ra=0.015μm), roller diameter 25mm; installation distance of smoothing roller from the exit point of micro-concave coating roller 500mm; pressing amount 0.3mm; smoothing roller speed 200r / min, roller body and base film rotate in opposite directions.

[0090] Operating steps: ① Before starting the machine, adjust the lifting mechanism, set the smoothing roller pressing amount to 0.3mm, and lock all adjustment mechanisms; ② Start the microgravure coating machine and wait for the film speed to stabilize at 12m / min; ③ The control system automatically starts the smoothing roller servo motor and matches the preset speed; ④ Observe the appearance of the coating and fine-tune the rotation speed to the optimal value of 200 r / min; ⑤ Run continuously for 30 minutes, and then sample and test various indicators of the coating.

[0091] The finished film, whether it has undergone secondary smoothing or not, is tested, including: Coating surface roughness: Ra and Rz values ​​were measured using a laser roughness meter. Samples were taken at multiple points at 100mm intervals along the film-moving direction, and the average value was taken.

[0092] Coating thickness uniformity: Using a film thickness tester, five test points were selected in the transverse direction of the coating to calculate the thickness range and standard deviation.

[0093] Appearance defect statistics: Select a 1㎡ effective coating area, and combine manual visual inspection and vision system to count the number of stripes and the density of point defects.

[0094] All tests were conducted in accordance with the general testing specifications for the thin film coating industry and the enterprise standards for appearance inspection of optical films and lithium battery electrodes. All data were measured under normal temperature and working conditions.

[0095] The results can be compared as shown in Table 1 below.

[0096] Table 1: Secondary smoothing effect of mirror roller

[0097] Example 2: PET film + polyurethane functional coating (eliminating unevenness defects)

[0098] Coating materials and process conditions: Base film: PET film, thickness 50μm; Coating liquid: polyurethane functional coating liquid, solid content 52%, viscosity 280cPs; Coating speed 20m / min, dry film thickness 15um; The main defect of the original process was regular diagonal stripes.

[0099] Smoothing roller parameter selection: Select a fine-twill smoothing roller (800 lines / inch), roller diameter 30mm; installation distance 500mm; pressing amount 0.1mm; smoothing roller speed 215r / min.

[0100] Operating steps: ①Stop the machine to replace the fine-patterned roller sleeve and check the parallelism of the roller body; ② Set the pressing amount to 0.1mm and lock the horizontal position; ③ After the main machine speed stabilizes at 20m / min, start the smoothing roller; ④ Fine-tune the rotation speed to 215 r / min, fix the parameters and enter continuous production.

[0101] Similarly, samples with and without secondary smoothing were tested, and the results are shown in Table 2 below.

[0102] Table 2: Secondary smoothing effect of the twill roller

[0103] Example 3: Copper foil + thermally conductive paste (to eliminate transverse texture defects)

[0104] Coating materials and process conditions: Base film: copper foil, thickness 12μm; Coating liquid: thermally conductive paste, solid content 36%, viscosity 350cPs; Coating speed 20m / min, dry film thickness 12um; The main defects of the original process were transverse lines and local uneven thickness.

[0105] Smoothing roller parameter selection: Select a fine vertical groove smoothing roller (700 lines / inch), roller diameter 30mm; installation distance 500mm; pressing amount 0.3mm; smoothing roller speed 280r / min.

[0106] The samples with and without secondary smoothing were tested, and the results are shown in Table 3 below.

[0107] Table 3: Secondary smoothing effect of fine vertical groove roller

[0108] It can be observed that after secondary smoothing with a fine vertical texture roller, the horizontal texture is basically eliminated; the coating thickness range is reduced from ±1.5μm to ±1.0μm, which meets the product requirements.

[0109] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

[0110] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, preferred embodiments are described in order to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art can make other changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of this invention.

[0111] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from the spirit and scope of this invention; if these modifications and variations of this invention fall within the scope of the claims of this invention and their equivalents, then this invention also intends to include these modifications and variations.

Claims

1. A microgravure coating secondary smoothing device, comprising a frame, a microgravure coating roller, a material trough, a scraper mechanism, and a guide roller assembly, characterized in that, A smoothing roller is provided on the film exit side of the micro-grooving coating roller, and the smoothing roller is located at a distance of 300mm to 800mm from the film exit point of the micro-grooving coating roller. The smoothing roller is driven by an active servo motor. The rotation direction of the smoothing roller is opposite to the film feeding direction of the base film. The rotation speed of the smoothing roller is determined according to a preset ratio of the viscosity of the coating adhesive to the film feeding speed of the base film. The smoothing roller contacts and rubs against the coating surface of the base film to perform a secondary smoothing of the wet coating that has not yet dried after coating. The frame is equipped with a smoothing roller support and pressure adjustment mechanism on both sides. The support and pressure adjustment mechanism includes a linear guide rail, a slider, and a servo electric cylinder. The bearing seats at both ends of the smoothing roller are mounted on the slider. The slider can slide along the linear guide rail. The servo electric cylinder is connected to the slider. The slider is driven to slide by the servo electric cylinder to adjust the pressure between the smoothing roller and the base film coating surface. The pressure is adjustable from 0 to 1.0 mm. The surface morphology of the smoothing roller is one of mirror finish, fine diagonal lines, or fine vertical lines.

2. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, The smoothing roller has a diameter of 20-40mm and is made of one of the following materials: hard alloy, high carbon steel, stainless steel, or ceramic-coated metal.

3. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, The smoothing roller has a sleeve-type split structure, including a fixed roller core base and a replaceable roller surface sleeve; the fixed roller core base has tapered surfaces machined at both ends, and the roller surface sleeve has inner cones at both ends that match the tapered surfaces. The roller core and the roller surface sleeve are locked and positioned without gaps through the cooperation of the tapered sleeve and the expansion sleeve. The end of the roller surface sleeve is provided with a quick chuck and a locking nut.

4. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, When the surface morphology of the smoothing roller is mirror-like, its surface finish Ra≤0.02μm, used to eliminate irregular uneven textures in the coating layer; when the surface morphology of the smoothing roller is fine diagonal grooves, its line count is 500~1000 lines / inch, used to eliminate regular diagonal textures in the coating layer; when the surface morphology of the smoothing roller is fine vertical grooves, its line count is 500~1000 lines / inch, used to eliminate regular transverse textures in the coating layer.

5. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, The servo electric cylinders are independently installed on both sides of the frame. The push rod of the servo electric cylinder is rigidly connected to the slider. The servo electric cylinder receives commands from the control system to realize fully automatic and precise adjustment of the pressing amount, with an adjustment accuracy of ±0.02mm. The parallelism error between the axis of the smoothing roller and the axis of the guide roller and the micro-coating roller is ≤0.03mm / m.

6. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, It also includes a combined cleaning and anti-sticking mechanism, which comprises: A carbide cleaning scraper, wherein the cutting edge of the cleaning scraper is obliquely attached to the surface of the smoothing roller, the gap between the cutting edge of the cleaning scraper and the surface of the smoothing roller is 0.02 to 0.05 mm, and an adhesive receiving groove is provided below the cleaning scraper; And a fluorinated anti-stick coating disposed on the surface of the smoothing roller, the fluorinated anti-stick coating being used to prevent the coating liquid from adhering to the surface of the smoothing roller, the fluorinated anti-stick coating being resistant to a temperature of 120 to 220°C.

7. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, The active servo motor driving the smoothing roller is directly connected to the smoothing roller via a synchronous belt or coupling; the speed of the smoothing roller is infinitely adjustable from 0 to 1000 r / min. The micro-concave coating secondary smoothing device also includes a speed closed-loop control system. The speed closed-loop control system includes a PLC host, a servo driver and a high-precision rotary encoder. The encoder is coaxially mounted on the output end of the servo motor and is used to collect speed signals in real time and feed them back to the servo driver. The steady-state speed control accuracy is ±1r / min. The PLC host collects the film feeding speed signal of the coating host in real time, and the rotation speed of the smoothing roller dynamically follows the speed change of the coating host according to a preset ratio to achieve synchronous speed increase and decrease. The micro-recessed coating secondary smoothing device also includes a safety interlock system. When the film feeding speed of the coating host is lower than the safety threshold, the safety interlock system controls the smoothing roller to automatically stop rotating and automatically lift to detach from the base film surface. When the coating host triggers an emergency stop signal, the safety interlock system controls the smoothing roller to immediately stop rotating and automatically lift.

8. The micro-recessed coating secondary smoothing device according to claim 1, characterized in that, The smoothing roller has a circulating channel inside its core, and a cooling medium is connected to the outside of the circulating channel to control the temperature of the smoothing roller. The temperature control accuracy is ±1℃.

9. A method for secondary smoothing of micro-recessed coating, characterized in that, The process, implemented using the micro-recessed coating secondary smoothing apparatus according to any one of claims 1 to 8, includes the following steps: The surface morphology of the smoothing roller is selected according to the type of appearance defect of the coating: a mirror roller is selected for irregular uneven textures, a fine diagonal texture roller is selected for regular diagonal textures, and a fine vertical texture roller is selected for regular horizontal textures. The smoothing roller is positioned on the film exit side of the micro-concave coating roller, and the pressing amount between the smoothing roller and the base film coating surface is adjusted to within the range of 0 to 1.0 mm. The ratio of the linear speed of the smoothing roller (Vroller) to the linear speed of the base film (Vfilm) is determined based on the viscosity of the coating adhesive. When the adhesive viscosity is <300 cPs, the ratio is 0.8–1.2; when the adhesive viscosity is 300–600 cPs, the ratio is 1.2–1.5; and when the adhesive viscosity is >600 cPs, the ratio is 1.5–1.

8. The smoothing roller is driven to rotate at the speed corresponding to the ratio, and the rotation direction is opposite to the film feeding direction of the base film.

10. The micro-recessed coating secondary smoothing method according to claim 9, characterized in that, The method further includes online detection and automatic closed-loop adjustment steps, including: Downstream of the smoothing roller, a machine vision system acquires images of the coating surface in real time, identifies the type and severity of defects, and automatically issues adjustment commands based on the defect type: adjusting the rotation speed of the smoothing roller for stripe defects, and adjusting the pressing amount on one side of the smoothing roller for local uneven thickness.

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