Micro structuring of large surfaces by means of step and repeat hot embossing

There exist an ever-increasing demand for complex, durable, energy efficient and low cost lighting solutions. Refractive gratings offer great opportunities for the design of optically functionalised surfaces. In order to manufacture the referring structures, grooves with a size in the range between 1 to 5 rnicron, having optical surface quality, need to be manufactured on large surfaces. Conventional ultra precision processes like flycutting are not suitable to machine these kind of structures. Therefore, by means of step and repeat hot embossing methods a suitable production process is developed. For the micro structuring by means of the step and repeat hot embossing method a tool is repeatedly positioned, heated, and pressed into a thermoplastic substrate. The heated thermoplastic material is deformed and even very precise geometrical structures are formed in the substrate surface. Limited deformation rates of the thermoplastic material result in a strong need for process optimisation and sophisticated mechanical solutions for the realisation of the stamping movement. Temperature, forces, and embossing speed need to be adapted to the tool geometry in order to achieve the highest degree of accuracies and manufacturing speed. The adaptive hot embossing process promises to be a powerful alternative process to existing ultra precision processes. The flexibility in terms of geometrical possibilities predestines this process for the production of diffractive gratings for light guiding systems on large surfaces. Combined with electroforming and injection moulding processes, the process is suitable to provide highly complex optical components for high volume production.