Backlight module

A backlight module, comprising:

• a light guide plate, having a bottom surface, a light emitting surface, a first light incident surface and a plurality of microstructures, wherein the bottom surface is opposite to the light emitting surface, the first light incident surface is connected to the bottom surface and the light emitting surface, each of the microstructures is recessed into or protrudes out of the bottom surface, and comprises at least two structural units, wherein a section line of each of the structural units on a first reference plane parallel to the first light incident surface is a curve, and the curve has a peak point, the peak point is a tangent point of the curve and a second reference plane parallel to the light emitting surface, and a distance between two peak points of two adjacent structural units of each microstructure along a first direction parallel to the first reference plane and the light emitting surface is greater than 0 and is smaller than a half of a total width of the two structural units along the first direction, and each of the microstructures has a symmetric plane perpendicular to the light emitting surface and perpendicular to the first light incident surface;
• at least one optical film, located on the light emitting surface;
• and
• a first light source, located beside the first light incident surface.