Dielectric metasurfaces, which consist of spatially distributed sub-wavelength structures that impart controlled local phase shifts to the exiting light, allow access to modifying the wavefront and achieve desired function of the output beam. By adjusting the sub-wavelength structures’ shape, size, and choice of material, one can locally control the effective refractive index that affects the output light’s phase, amplitude, and dispersion, allowing various degrees of freedom in design parameters. The first generation of metasurfaces consisted of individual lab prototypes that in crucial parts relied on electron beam lithography, which severely restricted scalability. Meanwhile, mask-based methods such as deep UV lithography have been successfully adopted. While such methods open the door to high-throughput fabrication of metasurfaces, they are still limited in their achievable sample dimensions due to size restrictions imposed by wafer-based methods. By using roll-to-roll (R2R) methods, we were able to make large area metasurfaces that could find their use in displays and AR/VR applications, for example. In addition, R2R creates a lower cost method of manufacture for large volumes. In order to utilize R2R methods, there are two important challenges to overcome. First, the pattern must be extended over the large area of a film surface. Second, standard metasurface designs need to be adapted to the material and process constraints of R2R manufacturing. The R2R fabrication route is an extension of large-scale industrial processes that can produce wide format rolls of film.
Laser Induced Thermal Imaging (LITI) allows for high-resolution patterning of a variety of materials that often cannot be patterned efficiently by other conventional techniques such as photolithography. Application of LITI towards patterning vacuum-coated OLED materials is particularly attractive because of high LITI patterning resolution and accuracy and good compatibility of vacuum-coated OLED materials. However, LITI may induce thermal transfer defects within OLED materials. We are developing methods to address these potential thermal defects while maintaining patterning quality, device operation efficiency, voltage, and lifetime. Recent results regarding optimization of LITI for patterning vacuum-coated OLEDs will be discussed.
Laser Induced Thermal Imaging (LITI) is a high resolution, digital patterning technique developed at 3M for use in a number of applications including the patterning of LCD color filters and OLED emitters. The LITI process is suited for the manufacture of flat panel displays, where both high resolution and absolute placement accuracy are required. In this paper, we present the capabilities of LITI, the basic design of a LITI laser imager, the construction of a LITI donor sheet, and the process by which OLED emitters may be patterned. An OLED device fabricated with the LITI process is described.