Metal mask and method to produce metal mask

A method to produce a metal mask, the method comprising:

• providing a metal panel, wherein the metal panel is provided with an evaporation surface and a back surface opposite to each other;
• forming a first patterned photoresist layer on the evaporation surface and forming a second patterned photoresist layer on the back surface, wherein the first patterned photoresist layer comprises a plurality of first photoresist openings, the second patterned photoresist layer comprises a plurality of second photoresist openings, the second photoresist openings correspond to the first photoresist openings in position, respectively, and the sizes of the second photoresist openings are smaller than those of the first photoresist openings, wherein each of the first photoresist openings comprises a primary photoresist opening part and a plurality of secondary photoresist opening parts, the primary photoresist opening part is provided with two long edges opposite to each other and two short edge opposite to each other, the two short edges are connected between the two long edges, and the secondary photoresist opening parts are connected to both ends of each of the two long edges;
• and
• etching the metal panel to form a plurality of through holes, wherein a size of each of the through holes decreases gradually from the evaporation surface towards the back surface, a first opening is formed by each of the through holes in the evaporation surface, the first opening comprises a primary opening part and a plurality of secondary opening parts, the primary opening part is provided with two long edges opposite to each other and two short edges opposite to each other, the two short edges are connected between the two long edges, and the secondary opening parts are connected at two ends of the long edges;
• each of the secondary opening parts has a length parallel to the long edges, and the length is greater than 15 μm but less than 45 μm, and each of the secondary opening parts has a width perpendicular to the length, and the width is greater than 0 μm but less than 10 μm.