Jae-hyuk Chang

Overlay accuracy on a flexible web with a roll printing process based on a roll-to-roll system

For high-quality flexible devices from printing processes based on Roll-to-Roll (R2R) systems, overlay alignment during the patterning of each functional layer poses a major challenge. The reason is because flexible substrates have a relatively low stiffness compared with rigid substrates, and they are easily deformed during web handling in the R2R system. To achieve a high overlay accuracy for a flexible substrate, it is important not only to develop web handling modules (such as web guiding, tension control, winding, and unwinding) and a precise printing tool but also to control the synchronization of each unit in the total system. A R2R web handling system and reverse offset printing process were developed in this work, and an overlay between the 1st and 2nd layers of ±5μm on a 500 mm-wide film was achieved at a σ level of 2.4 and 2.8 (x and y directions, respectively) in a continuous R2R printing process. This paper presents the components and mechanisms used in reverse offset printing based on a R2R system and the printing results including positioning accuracy and overlay alignment accuracy.

P‐164: Single Cell Gap Transflective Mode for Vertically Aligned Negative Nematic Liquid Crystals

Single cell gap transflective liquid crystal display mode with vertically aligned negative liquid crystal was developed. Reflectance curve as a function of voltage matched exactly with transmittance curve. Threshold voltage in reflectance curve was around 2.0V, as in transmittance curve, and the voltage for maximum reflectance was around 4.5V∼5.0V, which gave also the maximum transmittance. Reflective region was divided into two parts. First reflective part was driven by the voltage supplied by switching transistor directly, while the second reflective part was driven by the voltage lower than that of first part using the voltage-dividing capacitor connected to switching transistor in series. Normal 8 mask-count process was applied to fabrication of real panels. No special optical film or extra driving circuit was required.

High performance microshutter device with space-division modulation

This paper presents a microshutter device with space-division modulation for high brightness and improved grayscale level. High brightness is achieved with a large aperture that originates from out-of-plane movement with a large deflection, and space-division modulation improves the grayscale level by overcoming the operating speed limitation of digital modulation. The proposed microshutter device has multiple microshutters consisting of a single pixel, and the grayscale level is modulated by the number of actuated microshutters. We adopted a novel electrostatic actuation method in which the number of actuated microshutters is proportional to the applied analog voltage level. The actuation method was verified theoretically by means of an equivalent electrical circuit model. Furthermore, to test the proposed actuation method, we fabricated quarter-circle curl-shaped microshutters and demonstrated the proposed microshutter device with a control signal of 20 V to 33 V. The switching time is 20 µs from the open state to the closed state, and the lifetime is estimated to be 500 billion cycles.

Fabrication of an all‐layer‐printed TFT‐LCD device via large‐area UV imprinting lithography

Abstract Nanoimprint lithography (NIL) using ultraviolet (UV) rays is a technique in which unconventional lithographic patterns are formed on a substrate by curing a suitable liquid resist in contact with a transparent patterned mold, then releasing the freshly patterned material. Here, various solutions are introduced to achieve sufficient overlay accuracy and to overcome the technical challenges in resist patterning via UV imprinting. Moreover, resist patterning of all the layers in TFT and of the BM layer in CF was carried out using UV imprinting lithography to come up with a 12.1‐inch TFT‐LCD panel with a resolution of 1280×800 lines (125 ppi).