Mask, flexible display panel and manufacturing method thereof

A method for manufacturing a flexible display panel, the flexible display panel comprising a display region and a flexible bendable region outside the display region, the method comprising:

• forming a buffer layer on a substrate;
• forming an insulating layer on a side of the buffer layer distal to the substrate;
• etching a portion of the insulating layer away in the flexible bendable region by using a first mask to form a first trench;
• etching a portion of the buffer layer away in the first trench by using a second mask to form a second trench;
• and
• forming a source-drain metal layer on a side of the insulating layer distal to the buffer layer, the source-drain metal layer covering the first trench and the second trench,
• wherein a size in a first direction of a surface of the first trench proximal to the second trench is larger than a size in the first direction of a surface of the second trench proximal to the first trench, a step is formed at a junction of the first trench and the second trench, and a slope angle of the step is smaller than 60°;
• wherein each of the first mask and the second mask is a mask configured to form a trench in the flexible bendable region of the flexible display panel, the mask comprising a first region, a second region, and a third region between the first region and the second region in the first direction, the third region having a same pattern as a pattern of a trench to be formed, wherein
• the first region and the second region are lightproof whereas the third region is light transmissive, or the first region and the second region are light transmissive whereas the third region is lightproof,
• an edge of at least one of the first region and the second region proximal to the third region has a plurality of protrusions, and each of the plurality of protrusions has a vertex angle that is at a side proximal to the third region and is not more than 90°, and
• a size of the third region of the first mask in the first direction is greater than a size of the third region of the second mask in the first direction.