Air Coupled Ultrasonic Guided Wave Measurement for Board Crease Integrity
Air-coupled ultrasonic guided waves quantify paperboard crease ply delamination and micro-cracking non-destructively, preventing box compression failure.
Snell Law
Optical Refraction
Physical law describes the relationship between the angles of incidence and refraction for a wave passing through the interface of two different media. The snell law explains how light bends when it enters a coating layer or a plastic film used in packaging. It states that the ratio of the sines of the angles is equal to the inverse ratio of the refractive indices.
This principle is fundamental for designing the gloss and opacity of printed surfaces.
Coating Performance
Pigments and binders in a paper coating have different refractive indices that scatter the incoming light. According to the snell law, the angle at which light enters a clay particle determines how much is reflected and how much is transmitted. A high refractive index difference between the air and the coating increases the brightness of the sheet.
Matte finishes are achieved by creating a rough surface that causes light to refract in many different directions. Diffuse scattering hides the underlying fibres and improves the print quality by providing a uniform background. The law also applies to the behavior of ink on the surface, where the penetration of the light into the ink layer affects the perceived color and saturation.
Engineers use these calculations to optimize the formulation of coatings for high speed inkjet or gravure printing.
Barrier Film
Laminates used in food packaging rely on specific optical properties to ensure that the product is visible while being protected from UV light. The snell law governs the path of light through the multiple layers of a polymer and aluminum foil structure. Mismatched refractive indices can lead to internal reflections.
This makes the packaging appear cloudy. Controlling the thickness and the material choice ensures that the final product meets the aesthetic requirements of the brand owner.