Composite film, encapsulating structure of the same, and encapsulation method

A light-emitting diode (LED) backlight module, comprising:

• a light-emitting diode (LED) unit, having at least one surface;
• and
• a composite film, disposed on and encapsulating the at least one surface of the LED unit, wherein the LED unit comprises a substrate, and a plurality of LEDs disposed on the substrate;
• the composite film comprises:
• a first thermoplastic elastomer film layer, comprising a first styrenic block copolymer;
• and
• a second thermoplastic elastomer film layer, disposed on the first thermoplastic elastomer film layer, wherein the second thermoplastic elastomer film layer comprises a second styrenic block copolymer, a plurality of diffusion particles dispersed in the second thermoplastic elastomer film layer, wherein the diffusion particles comprise silicon dioxide, polymethyl methacrylate, polystyrene, titanium dioxide, or a combination thereof;
• a surface microstructure disposed on a surface of the second thermoplastic elastomer film layer opposite the first thermoplastic elastomer film layer, wherein the surface microstructure comprises pyramidal structure, sinusoidal wave structure or hemispherical structure, with an aspect ratio of 0.04 to 0.2;
• and
• wherein the first thermoplastic elastomer film layer is in direct contact with the substrate of the LED unit.