Light guide panel and back light module thereof

A back light module comprising a light source and an LGP, wherein the LGP comprising a light input surface, a bottom surface and a light output surface opposite to the bottom surface, the LGP is characterized in that the bottom surface and/or the light output surface is provided with a plurality of microstructures, which comprise a plurality of first microstructures and a plurality of second microstructures;

• the bottom surface and/or the light output surface is divided into the left side, the middle and the right side along the direction parallel to the light input surface, distribution rules for microstructures along the direction parallel to the light input surface are:
• the microstructures in the middle of the LGP are closely arranged, and the microstructures on the two sides are sparsely arranged, and each of the first microstructures is distributed on the left side and in the middle, each of the second microstructures is distributed in the middle and on the right side;
• the plurality of first microstructures are arranged in the mutually parallel manner, and the plurality of second microstructures are arranged in the mutually parallel manner.