The best coating method for a given application depends on the end-product requirements, the conditions in which it will be manufactured, and the potential “robustness” of the method and coating solution – plus a view to the long-term economics. There is not a “best method” that fits all uses, but having both a palette of many methods and a good deal of experience helps greatly in choosing the right course for a project.
Hundreds of coating methods have been developed to meet distinct product specification needs, providing a wide range of process and performance characteristics. This breadth is useful in addressing new products as well as for improving and upgrading cost and quality of existing products. Many of the coating methods are from the past development of internally branded products by our predecessor companies 3M and Kodak, and they are characterized by exacting precision and cleanliness required by photographic and similar processes.
Carestream Contract Manufacturing helps customers identify strategy for the best possible coatings for their needs, providing a path based on experience to the right choice. We evaluate coating formulations to fit a range of requisite parameters when choosing a coating method, including:
- Coating thickness and weight targets before and after curing
- Substrate properties – dimensional stability, surface characterization, thickness and uniformity, and surface tension relative to the coating fluid
- Application speed and any tradeoff vs. thickness uniformity need
- Multiple layer need
- Recyclability and yield need, which may be different for fluid and substrate used
- Needed properties to be added during the coating or later (e.g., adhesion, security features, abrasion resistance, etc.)
- Filtering, mixing, or de-aeration challenges
- Need for proper drying temperature profile
- Conveyance issues
We typically begin with coating trials to determine the best coating method or to check assumptions on a specific coating strategy for a new application. This work includes up-front modeling, a powerful tool that identifies starting process variable ranges to make coating trials more efficient. Effective modeling reduces costs and development cycle time by quantifying process condition ranges that will produce initial coating quality. The models then provide direction for subsequent experiments to optimize the process. Customers benefit from many millions of dollars and many years of correlation in accessing these tools.
Despite their usefulness, models are only guides. Models typically assume idealized conditions that do not fully reflect actual process conditions and coating solutions’ physical properties. Experiments are run in combination with the models to verify predictions and refine future experiments.
Carestream uses pilot coating and Design of Experiment (DOE) exercises to perfect optimal coating methods in a particular application. In our pilot facilities, we can quickly adjust formulation and coating conditions for low-cost, small-run and experimental contract manufacturing projects before moving up to production volume. We perform rapid material and product screening, small product sample coating and efficient scale-up to pilot and production coating equipment in our Coating Assessment Lab (CAL) or full-scale pilot coaters. DOE and statistical analysis help us analyze testing results and their relative importance in meeting product needs. Our technicians, PhD chemists and coating experts, formulators, product and process engineers all use group experience to guide in selecting the best coating approaches.
Carestream Contract Manufacturing has experience with numerous specialized coatings, such as the following.
Hardcoated films improve performance and protect against abrasions, scratches and chemicals, either in finished products or during manufacturing processes. Carestream has devised a stringent hardness testing process for hardcoat films used in electronic, display, graphic and optical applications.
Membranes: Energy Recovery, Filtration, Electroactive Polymer, Battery Separator and Electronics
Carestream Contract Manufacturing’s experience with precision coating methods and high-speed, wide-web assets and technologies bring high yield and cost advantages to a variety of membrane applications. Carestream also works with companies developing new solvent cast polymers for membranes. The key quality properties needed for membranes and free-standing films often include:
- Tight thickness uniformity
- Absence of gels or pinholes
- High tensile strength
- Low retained solvents
- Desired release from casting liner
Carestream’s precision coating methods deliver +/-5% cross-web and down-web thickness consistency and sometimes better. Clean-room manufacturing practices and micron-level solution filtration help to avoid coating defects like dust, gels and pinholes. On-line laser and camera-based inspection systems provide secondary verification of the coating quality, and advanced analytical techniques stand ready to troubleshoot the cause of any defect.
Carestream’s multi-zone dryer temperature control enables gentle initial drying to avoid skinning and airflow-induced surface imperfections. Extensive dryer length gives the polymer time to coagulate or solidify gradually, optimizing internal structure for enhanced properties without sacrificing line speed, to keep costs down. This drying profile also minimizes retained solvent in the final membrane or coated film to avoid odor and health concerns.
Thin substrates and release liners can create unexpected manufacturing problems, such as tearing, wrinkling, creasing, stretching and more, which may ultimately reduce efficiency, yield and product quality. Carestream’s equipment investments, sophisticated process controls, engineering expertise and supplier relationships overcome these challenges for the highest-performance applications. We can also provide in-line lamination for those applications where a secondary substrate needs to be married with the coated or cast membrane.
Castings
There are a variety of optical, mechanical and electrical films, which Carestream Contract Manufacturing has worked with, including birefringence-free polymers for electronics applications, electroactive polymers and ceramic formable materials. The issues are very similar to the ones encountered and described above for membranes.
The ability to resist the penetration of moisture and gases is vital for many types of products, including pharmaceutical products (e.g., capsule blister-packs), food packaging, and electronics (such as OLED, quantum dots and photovoltaic applications). Moisture barrier materials are normally applied as coatings or membranes to help protect these and other products from being compromised.
These are just a few of the specialized coatings we develop for our customers. Sometimes new solutions are needed, and our expert chemists and engineers utilize Carestream’s state-of-the-art equipment and facilities to invent them.
Carestream uses typical coating methods including reverse roll, slot die, forward roll, gravure, and various other types of hopper and slide coating that are proprietary. There are two ways Carestream adds new methods to its capabilities portfolio: designing them from the ground up, and working side-by-side with customers developing new coating techniques for unique purposes.
Conclusion
Coatings and castings are developed to provide a range of properties for various products. The type of product, its base material, intended use and numerous other considerations will steer the coating method choice. Ideally, the coating method will be selected by a cast of experts with deep knowledge and expertise in providing this service. Carestream Contract Manufacturing brings tremendous history, facilities and experienced people to provide the best possible coating solution for each customer on a case-by-case basis. That is the advantage of working with a custom contract-coating partner for this type of specialized, technical service.