An attachment process for flexible substrates and a patterned sealant used therein are provided. The attachment process is mainly used to manufacture flexible liquid-crystal displays (LCDs). Firstly, a patterned sealant with an opening is applied to a first substrate, and then a liquid crystal material is filled in the patterned sealant. During a pressing process for combining the first substrate and a second substrate, bubbles can be automatically evacuated from the opening of the patterned sealant, and the patterned sealant will deform and expand to seal the opening after the pressing process. By applying the patterned sealant with an opening in the manufacturing process of flexible LCDs, bubbles are easily evacuated and the opening of the patterned sealant is directly and automatically sealed in the pressing process under the atmospheric pressure.