Definition
A laboratory continuous coater is a precision device used to evenly and continuously coat liquid or slurry-like functional materials on the surface of flexible or rigid substrates in a laboratory environment. It provides controllable coating conditions for R&D and small-batch trial production by simulating the continuous coating process in industrial production, and is a key front-end process verification instrument in the fields of materials science, new energy, electronic films and functional coatings.
How it works:
The core working principle of a laboratory continuous coater is to transfer the coating solution to a uniformly moving substrate based on a predetermined coating method and to form a uniform coating through a subsequent drying or curing unit. The process typically consists of four basic units: feeding, coating, drying, and winding. The feeding system transports the slurry to the coating head; The coating head realizes the quantitative transfer and preliminary leveling of the slurry on the substrate through specific mechanical structures (such as scrapers, micro-gravures, slit extrusion, etc.). Subsequently, the wet coating enters the dry area with controllable temperature and airflow, and the solvent evaporates to form a dry film. Finally, the film-forming substrate is collected by the winding system to complete the continuous coating process.
Main measurement methods and parameters
The evaluation of coating quality relies on precise measurements of key parameters. Coating thickness is the most important parameter and is typically measured online or offline using a contact thickness gauge or a non-contact optical/β-ray thickness gauge. Wet film thicknessHwetand dry film thicknessHdryThe relationship can be approximated as: Hdry = Hwet × Csolid, among themCsolidIt is the solid content of the slurry. In addition, coating uniformity is quantified by measuring the standard deviation of the transverse versus longitudinal thickness of the layer. Other important measurement parameters include areal density, surface topography (observed by a microscope or profiler), and functional tests such as adhesion and conductivity depending on the application requirements.
Influencing factors
The coating quality is affected by the coupling of multiple factors. Slurry properties are fundamental, including viscosity, rheological properties, solids content, and solvent volatilization rate. The coating process parameters directly affect the film formation, such as coating speed, coating gap, feeding pressure, and the temperature distribution and wind field uniformity in the drying area. The properties of the substrate, such as surface energy, roughness and tension stability, can also affect the spread and adhesion of the coating solution. The accuracy of the equipment itself, such as transmission smoothness, processing accuracy of the coating head and temperature control accuracy, is the fundamental guarantee for obtaining repeatable results.
Applications:
Laboratory continuous coaters are used in a wide range of research and development areas that require the preparation of functional thin layers. In the field of new energy, it is used to prepare lithium-ion battery electrodes, fuel cell catalytic layers and photovoltaic films. In the field of electronics and display, it is used to coat conductive silver paste, optical glue, flexible circuit substrates, etc. In the field of advanced materials, it can be used to prepare special adhesive tapes, functional protective films, separation films, and various sensing coatings. Its value lies in providing an efficient experimental platform for formulation development, process window exploration and sample trial production of the above products.
Key points to consider in selection
The selection needs to be systematically matched based on the R&D goals. The type of coating process is the first to consider, such as whether high-precision coating with slit extrusion or universal coating with scraper is required. The range of core parameters should be clear, including the applicable substrate width, coating speed range, wet film thickness range, and drying temperature range. The key performance of the equipment should focus on the accuracy of coating thickness uniformity, the uniformity of temperature control in the drying area, and the stability of tension control. In addition, the scalability of the equipment, such as compatibility with multiple coating heads, online thickness measurement interface, and software control friendliness and data logging capabilities, are also considerations for long-term use. Safety designs, such as solvent discharge treatment, emergency braking, etc., should also not be ignored.