Backlight module having two optical sheets

A backlight module comprising:

• a case;
• a plurality of light sources located in the case;
• a plurality of needles mounted onto a bottom surface of the case;
• a plurality of supporting portions located on the plurality of needles;
• a first optical sheet held by tops of the plurality of needles;
• a second optical sheet located beneath the first optical sheet and held by the plurality of supporting portions, wherein the second optical sheet has a plurality of holes run through by the plurality of needles;
• and
• a plurality of first microstructures located on the first optical sheet or the second optical sheet to converge light, wherein each of the needles has a stem and a needle head, with the plurality of supporting portions being located on the stem, with the needle head being flexible, with the needle head having a bottom spaced from the supporting portion at a distance which is the same as the thickness of the second optical sheet, and when the needle head is not receiving an external force, outer diameter of the needle head being greater than an inner diameter of the plurality of holes of the second optical sheet.