Definition
A roll-to-roll applicator is a continuous coating equipment that evenly coats an adhesive or other functional paste on the surface of a flexible substrate and undergoes a drying or curing process to form a specific coating. The equipment takes coil materials as the processing object to realize automatic continuous production from unwinding, coating, processing to winding, and is widely used in the composite and functional processing of various flexible materials.
How it works:
The equipment works together based on precision mechanical transmission and fluid control technology. After the unwinding mechanism unwinds the substrate roll, it is maintained by the tension control system to maintain stable transmission. The coating unit transfers the adhesive to the surface of the substrate at a predetermined thickness through devices such as metering rollers, scrapers or slit extrusion. The substrate then enters the drying area and cures the coating through hot air, infrared or ultraviolet light. Finally, the finished product is rewound by the winding mechanism to form a complete processing cycle. The entire process is coordinated by a programmable control system to ensure the uniformity of the coating and the stability of the process.
Measurement method
The coating quality evaluation is mainly based on relevant industry standards, using multi-parameter comprehensive measurement methods. Wet film thickness can be monitored in real time with an online thickness gauge, while dry film thickness can be measured after curing using a contact or non-contact thickness gauge. The uniformity of the coating is analyzed by the optical detection system, and the amount of coating per unit area is calculated by gravimetric method:
Wc= (Wt-Ws)/A
Among themWcrepresents the amount of coating per unit area,WtFor the quality of the specimen after coating,Wsfor the quality of the substrate,Ato measure the area. Adhesion testing can be determined by the scribing method or peeling method according to the characteristics of the substrate, and the degree of curing can be determined by infrared spectroscopy analysis of the characteristic absorption peak change.
Influencing factors
The coating quality is affected by the interaction of multiple parameters. The surface tension and roughness of the substrate determine the infiltration behavior of the glue, and the viscosity and rheological characteristics affect the coating form. The coating speed should match the drying capacity to avoid the buildup of uncured layers. The temperature gradient control affects the volatilization rate and internal stress distribution of solvents. Environmental cleanliness and humidity can cause surface defects. Tension fluctuations will cause coating thickness variations, and parallelism deviations between rolls will produce lateral unevenness. The ratio of solids content to volatile components of the glue needs to be precisely controlled according to the drying curve.
Applications:
It is used in the field of new energy for electrode slurry coating to achieve uniform loading of active substances. The electronics industry is used in the insulation coating of flexible circuit substrates and conductive adhesive printing. The packaging industry completes the functional coating processing of composite materials. In the textile field, polymer coating of waterproof and breathable membranes is realized. The optical industry is engaged in the precision coating of diffusion films and brightening films. Industrial tape production realizes the composite construction of adhesives and release layers through multi-layer coating. Each application scenario needs to adjust the process parameters according to the material properties.
Equipment selection
The selection should comprehensively consider technical parameters and production needs. The effective coating width is selected according to the width of the substrate, and the mechanical design speed is determined according to the production scale. The coating method needs to match the slurry characteristics: the scraper type is suitable for medium to high viscosity fluids, and slit extrusion is suitable for low viscosity precision coating. The drying system is configured with hot air circulation or radiation curing modules depending on the solvent type. The tension control accuracy affects the machining stability of thin substrates. Equipment scalability can be considered by considering multi-coating head configurations and in-line inspection interfaces. The energy consumption evaluation needs to comprehensively calculate the heat loss and transmission power consumption, and the maintenance convenience involves the design rationality of roller system disassembly and cavity cleaning.