Brightness Enhancement Film for LED Backlkight
BEF which is abbreviated for Brightness Enhancement Film and also is called Prism Sheet is the key components of backlight module and accounts for the highest proportion of the cost in the backlight module. It not only can concentrate the scattering light within 70 degree angle in the front, but also can make the light outside the view angle reuse by its precision micro-structure optical film. Typically, one BEF can increase 40-60% brightness, it will be much better if two BEF are placed in vertical.
The classification of Brightness Enhancement Film
It can be divided into Normal Prism Sheet, Multi-Functional Prism Sheet, Micro-Lens Film Prism Sheet and Reflective Polarizer Prism Sheet.
●Normal Prism Sheet
The main function of normal prism sheet is going to guide the light angle and increase the luminous efficiency. Currently, the famous normal prism sheet suppliers are 3M, Mitsubishi Rayon, LG Electronics, MNTech, Shinwha, DNP, LGS, Gamma ( Taiwan Cartwright ), E-fun ( Taiwan Ying-hui ), Suntech, SKC Haas, Samsung Cheil and so on.
●Multi-Functional Prism Sheet
It is a higher-level product which integrates with prism sheet and diffusion film. It has a better luminous efficiency than normal prism sheet. The major suppliers are 3M, Shinwha, MNTech, Samsung Cheil , E-fun and LG Electronics. It seems that South Korean panel manufacturers employ Multi-Functional Prism Sheet a lot faster than their competitors in Japan and Taiwan.
● Micro-Lens Film Prism Sheet
Micro-Lens Film Prism Sheet is made by several the same architecture prism sheets and diffusion films integrating. Many LCD panels are adopted the structure of two Micro-Lens Films instead of the structure of two Micro-Lens Films and the prim sheet in the middle. So far, it is applied in 32 “, 37″ and 40 “LCD TV panels. The main suppliers are the South Korean companies such as MNTech, SKC Hass, Shinwha, LG Chemical and LG Micron.
●Reflective Polarizer Prism Sheet
It is also called DBEF (Dual Brightness Enhancement Film) which is a unique patented product of 3M. It is the most important
Brightness Enhancement Film which is reflective polarizer. It reuses the light of the backlight unit by utilizing the recycling light mechanism which makes the light pass through more than 800 different refractive index optical material layers and fully reflect. It can easily enhance the brightness of the light 1.6 times. But now some South Korean and Japan companies have also launched some similar function products such as NPRF(MNTech), Shinwha (CLC and Woongjin) and Zeonor(Zeno).
The production process of Brightness Enhancement Film
Diffusion film achieves the diffuse light function by the micro particles (beads) which attach at the surface of the optical film material. Meanwhile, the brightness enhancement film (prism sheet) not only can redistribute the light and improved the light transmittance, but also can increase the brightness and viewing angle of the light by transparent optical micro stripes (raster) reflecting and refracting the light.
The production process of BEF (prism sheet) includes optical design, precision molding, chemical formulations and coating. The international advanced method is to realize the micro optical structure by the molding roller which is solidified by UV adhesive processing technology. The most critical technology of BEF is that carving the molding roller prism pattern.
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