The majority of roll-to-roll coating projects use “blanket” or uniform continuous high precision coatings. Products ranging from imaging films to battery membranes to optical display device components typically employ blanket coatings where exceptional thickness control is required and there are no intended patterns.

There are an increasing amount of applications that utilize patterning of coatings, including printed electronics components, displays, touchscreen input devices, photovoltaics, battery structures, RFIDs and sensors. Various patterning techniques exist to meet a wide range of project requirements on conventional roll-to-roll coating assets. Each method offers unique capabilities depending on the variables required for the final application. The list of patterning methods includes:

• Gravure, microgravure, flexo or variations involving very fine resolution structures for repeating patterns;
• Photolithography, in which a photoresist is applied and further processed with imaging, developing, and stripping to create a patterned mask. Etching is then often used for a subtractive process or coating for an additive process. Typically, a final stripping process is required to remove the mask. There are additive processes based on similar photoresist masks, and even a lift off scheme similar to integrated circuit fabrication;
• Coating on a patterned substrate to create specific topography of the final coating that conforms to the substrate;
• Stripe coating and patch coating such as that possible with high precision fluid delivery systems and slot die type coating;
• Continuous industrial resolution quality ink jet, which is extremely useful for non-repeating coatings and patterns that change frequently;
• Rotary screen printing;
• Laser ablation of continuous coating to form pattern.

The resolution capabilities of these techniques are quite different and dependent on various factors, including the material being patterned, the thickness, and a host of other variables like the skill and background knowledge of the coating entity.

In a recent contract-manufacturing project, Carestream partnered with a product company to do a stripe coating with different sizes on the top and bottom of the web. The application required very high-precision overlaps and a precise lamination step, followed by subsequent precision slitting and lamination. Carestream has also completed evaluations of adding all of the above processes into its various coating lines.

As such examples highlight, there is an increasing amount of applications that use patterned coatings, as well as a need for continuous layers in many applications that also require patterning. From planarization layers to dielectric layers to conductive layers, it is critical to understand the various patterning techniques that exist. Coating partners like Carestream deliver the unique experience to analyze the variables required for the final application to ensure that the proper patterning method is employed for success.