An in situ sealing method for liquid-filled micro-cavities based on photoembossing

An in situ method for sealing an array of pre-filled micro-cavities, such as encountered in electrophoretic displays, is presented. The technique, which is based on photoembossing, forms a hermetic seal between the cover and the cavity walls. The seal locations are defined by ultraviolet exposure through a photolithographic mask, forming a latent image overlapping with the locations of the cavity walls. During a thermal development step, while the cover is mounted on top of the micro-cavities, the seal evolves and makes firm contact with the cavity walls. This technology is demonstrated to be insensitive to small deviations in cavity height, flatness of the cover and thin fluid films remaining between the cover and the top of the cavity walls. In the past, these aspects made it difficult to effectively seal large-area devices.