Chapter 2:
History of Slot Die Coating

Origins and Early Development

Slot die coating technology traces its roots to the mid-20th century, primarily driven by the need for precise application in photographic film production.

 

The process was first patented by Eastman Kodak in 1951 for manufacturing photographic papers and films, revolutionizing the industry by enabling uniform multilayer coatings at high speeds. This innovation addressed limitations in earlier methods, such as uneven thickness in dip coating.

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Prior to slot die methods, coatings relied on less precise techniques like dip or roll coating, which often resulted in inconsistencies and higher waste.

 

The introduction of slot dies marked a shift toward pre-metered coating, where fluid flow is controlled upstream, ensuring exact deposition.

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Evolution Through the Decades

By the 1980s, advancements in materials science expanded slot die applications beyond photography. Companies began developing precision slot dies for packaging, electronics and battery manufacturing, incorporating better internal designs for handling diverse viscosities. The integration of computational tools in the 1990s allowed for virtual optimization of die geometries.

 

The late 20th century saw integration with semiconductor production, where thin-film uniformity became critical. Computational fluid dynamics (CFD) modeling emerged in the 1990s, allowing engineers to optimize die designs virtually, predicting flow behavior and reducing trial-and-error in setup.

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Modern Advancements and the Case for Updates

Today, slot die coating supports cutting-edge fields like solar cells and flexible electronics, with capabilities for sub-micron precision. However, many existing coating lines still use outdated dies from the 1980s or earlier, featuring inferior internal geometries that limit flow distribution and increase defects like non-uniformity.

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While these older systems may still function adequately for basic applications, modern dies incorporate advanced manifolds (e.g., coat-hanger designs) and materials resistant to corrosion, offering better uniformity, reduced shear, and compatibility with high-viscosity fluids.

 

Upgrading to contemporary technology can enhance efficiency by up to 30%, as noted in resources from the Association for Roll-to-Roll Converters. For example, newer designs handle particle-laden slurries better, reducing clogs and improving throughput.

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This historical context highlights why staying current with slot die innovations is crucial for competitive manufacturing, especially as demands for thinner, multi-functional coatings grow.