Thomas R. Hoffend

Laser thermal patterning of OLED materials

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.

Laser induced thermal imaging of vacuum-coated OLED materials

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.

Efficient LED light distribution cavities using low loss, angle-selective interference transflectors

Recent advances in solid state light source efficiency and luminance present the technical challenge of distributing light from very small point sources to large areas, with area distribution ratios having orders of magnitude greater than previously addressed. Broad adoption of LEDs in lighting and liquid crystal displays is in part contingent on addressing this fundamental light distribution issue. Here we present new materials based on giant birefringent nanotechnology which address these deficiencies allowing us to guide light in air via a novel light distribution system. Resulting from controlled in-plane and out-of-plane x,y,z refractive indices of adjacent layers, these multilayer interference films possess both angle selective and polarization selective reflectance. The angle selectivity can be tuned in both azimuth and polar angle, relieving a key constraint of prior materials. Our work has been done on a physically large scale enabling demonstration of large light management systems of industrial and practical relevance.