Industry Insights
Precision Coating for Optical-Grade Applications January 4, 2017 | by Robert Wildman, Technical Account Manager and Brian Pahl, Business Development Manager

Carestream Contract Manufacturing engineers and material scientists deliver problem-solving expertise in roll-to-roll coating applications for optimal product design, technology integration and manufacturing support. As part of this commitment, we continuously work to improve our precision coating capabilities for growth into new applications and markets.

Optical films represent a major growth area where Carestream’s precision coating expertise is applied. Our multi-layer solution coating capabilities are well suited for many optical-grade applications including:

Since non-uniformity in coatings degrades optical properties, precision coating techniques and assets are required for optical-grade films. Carestream’s process knowledge, experience and quality-driven practices solve customers’ unique challenges to deliver a rapidly growing variety of optical film products. We can create structures of up to 20 precision-coated layers with options for two-sided coating, radiation cure, in-line inspection and lamination in the same pass to meet specific application needs.

Creating optical films involves complex variables and stringent quality guidelines, which require a holistic quality inspection approach. Our projects undergo a rigorous production release test, specialized to meet the unique requirements of optical applications. These exacting guidelines include 100% automated in-line optical inspection, extensive analytical testing and clean-room practices to meet stringent optical and cosmetic requirements.

100% In-line Optical Inspection

Carestream’s 100% in-line inspection features 30-micron resolution optimized to meet the needs of the most high-end optical films. Our sophisticated in-line process control and inspection techniques enable the coating process to run continuously while monitoring and controlling deviations that would negatively affect product performance. As a result, we can quickly identify and characterize quality issues to allow real-time process control and defect mapping for rapid root-cause analysis, process optimization and yield enhancement.

Our best-practice inspection techniques help to identify and characterize contaminants, minimize anomalies and defects, and ensure uniform thickness control for fast correction and the ability to tailor methodologies for each case. Coatings are applied to substrates to achieve optical properties or other attributes in finished products. These film coatings supply various engineered properties such as barrier qualities, selective permeability, reflectivity, conductivity or other attributes. Frequently, advanced coating materials can be applied in different layers, each meeting a unique purpose.

When implementing optical inspection methods, inspection can be reflective or transmissive with dark field and bright field results. Another consideration with optical inspection is the angle of incidence between light source and the inspected web material. Optimizing incidence angles and correlating multiple inspection methods enable anomalies to be spotted in the web.

In coating a clear product for example, a dark field inspection might be performed with the signal reflected because dark particles and clear gels will reflect light differently. By using multiple channel (bright field and dark field/transmissive and reflective) inspection methods, technicians can gain a good understanding of any defects and begin to characterize and correct them.

Analytical Laboratories

Our fully equipped, expertly staffed analytical laboratories, located in Carestream’s Oregon, Colorado and Minnesota facilities, provide the backbone for our complete diagnostic approach. Carestream’s laboratory scientists focus on three main areas to ensure impeccable quality of finished materials: raw materials’ incoming quality control (RM IQC), materials characterization and quality assurance. All three of these functions are interconnected and performed throughout the product development process.

Our analytical methods continually elevate standards for new products and processes, helping improve precision and accuracy. Carestream sometimes partners with vendors on process improvement and product performance. Customer issues are carefully deliberated and addressed to consistently meet or exceed expectations.

Carestream’s chemists design unique methods to enable analytical quantification of key quality requirements for a variety of custom optical products. Optical image analysis techniques are frequently adapted in our lab to analyze product images for particle size, number of particles, circularity and other values.

Additional quality testing metrics for optical film products include haze, transmission, film thickness, uniformity, optical clarity and density, color, index of refraction, reflectivity and opacity – to name just a few. Each factor plays a critical role in meeting specified characteristics and performance stipulations on a product-by-product basis.

Carestream’s comprehensive suite of testing equipment enables us to evaluate an immense range of material properties with precision. For example, we use interferometers, x-ray fluorescence (XRF), micrometers, gravimetric analysis and cross-sections to measure coating thickness. Optical properties are analyzed with HazeGard for haze, transmission and clarity. Additionally Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) are used for organic and elemental analysis. SEM can also be used for high-resolution imaging to assess film morphology and its impact on performance.

Clean-Room Commitment

To meet the stringent optical and cosmetic requirements of optical films, Carestream has significantly invested in upgrading clean-room operations. The company installed new air handling and filtration systems, as well as coater and web line enclosures that isolate clean-room operations from other facility traffic. The enclosures provide an environment in which the web lines are completely and exclusively bathed in clean-room air. Additionally new gowning and air shower procedures have been initiated to include full operator coverage, preventing the introduction of contaminants to clean-room air.

The clean-room area enhancements reduce airborne contamination down to levels approaching a Class 100 environment in the coating and slitting operations. These improvements also keep point defects, debris and imperfections to a minimum and result in higher yields for demanding products including optical-grade films and other advanced materials applications.

Carestream’s commitment to cleanliness extends beyond the clean room throughout the entire production facility, with staff solely dedicated to cleaning equipment and production spaces. This initiative allows equipment operators to focus on uninterrupted production, while ensuring optimal conditions for quality assurance.

The comprehensive, start-to-finish technical assessment approach described in this blog enables our ability to provide reliable, precision contract coating and development services that deliver high quality advanced material applications.

Tollcoating Newsletter Signup