Back light module

A back light module, comprising:

• a light guide plate, comprising:
• a body, having at least one light incident surface, an upper surface, and at least one side surface, wherein the light incident surface is connected to the upper surface, and the side surface is connected to the light incident surface and the upper surface;
• a positioning structure, located at the side surface, wherein the upper surface has a first eliminating region adjacent to and surrounding the positioning structure;
• and
• a plurality of first micro-structures, extending along a first axial direction and arranged in parallel on the upper surface except the first eliminating region;
• a plurality of point light sources, arranged at one side of the light guide plate and facing the light incident surface, wherein the point light sources are adapted to emit light toward the light guide plate, and the light emitted by the point light sources enters the light guide plate from the light incident surface to be emitted from the upper surface;
• and
• a frame, wherein the light guide plate is arranged on the frame, the frame has a positioning component, and the light guide plate is positioned in the frame by matching the positioning structure with the positioning component.