Optical film and display module having the same

A display module, comprising:

• a display panel having a display surface;
• and
• an optical film disposed on the display panel with a rough surface away from the display surface,
• wherein the rough surface defines a reference plane;
• in a given unit measuring area, the rough surface has a plurality of measuring points constituting a plurality of virtual measuring planes;
• a normal to each of the virtual measuring planes has an angle included with a normal to the reference plane;
• each of the measuring points has a height from the reference plane,
• wherein on the reference plane, a projection area of the virtual measuring planes having the angle larger than 20 degrees ranges from 31% to 60% of a projection area of the given unit measuring area, and a projection area of the virtual measuring planes having the angle larger than 50 degrees is less than 7% of the projection area of the given unit measuring area,
• wherein 25% of the measuring points has the height larger than a first height, 75% of the measuring points has the height larger than a second height, and the height difference between the first height and the second height is equal to or larger than 0.6 μm and smaller than or equal to 2.5 μm.