Array substrate, manufacturing method thereof, and display device

An array substrate, comprising a base substrate, and a first functional layer and a second functional layer laminated one on another on the base substrate, wherein

• the first functional layer forms a level-different region on the base substrate, and the second functional layer covers the level-different region;
• a portion of the first functional layer at the level-different region is provided with a target gradient angle, the target gradient angle is a maximum gradient angle when the second functional layer has a predetermined thickness, and the predetermined thickness is a thickness when a functional requirement of the second functional layer has been met and the second functional layer is not broken at the level-different region;
• and
• the target gradient angle of the first functional layer and the predetermined thickness of the second functional layer meet Tan(a)−1≤N(x−y)/y≤Tan(a)+1, where N=z×W×KIC, z is a constant, W is a predetermined value, KIC is a fracture toughness parameter of the second functional layer, x is the predetermined thickness of the second functional layer, y is a thickness of a portion of the first functional layer at the level-differential region, and a is the target gradient angle of the first functional layer,
• the first functional layer comprises a first functional pattern, and the first functional pattern forms a first level-different region on the base substrate;
• the second functional layer comprises a first functional film layer and a second functional film layer, the first functional film layer is arranged at a side of the first functional pattern away from the base substrate, the second functional film layer is arranged at a side of the first functional film layer away from the base substrate,
• the first functional film layer and the second functional film layer both cover the first level-different region, and the first functional film layer has a fracture toughness parameter approximately same as the second functional film layer;
• each of the first functional film layer and the second functional film layer has a uniform thickness;
• and
• a portion of the first functional pattern at the first level-different region is provided with a first target gradient angle, the first target gradient angle is a maximum gradient angle when each of the first functional film layer and the second functional film layer has a first predetermined thickness, and
• the first predetermined thickness is a sum of the thickness of the first functional film layer and the thickness of the second functional film layer when a functional requirement of each of the first functional film layer and the second functional film layer has been met and each of the first functional film layer and the second functional film layer is not broken at the first level-different region.