A Novel Continuous Extrusion Process to Fabricate Wedge-Shaped Light Guide Plates

Backlight modules are key components in thin-film transistor liquid crystal displays (TFT-LCD). Among the components of a backlight module, the light guide plate (LGP) plays the most important role controlling the light projected to the eyes of users. A wedge-shaped LGP, with its asymmetrical structure, is usually fabricated by an injection proces, but the fabrication time of this process is long. This study proposes a continuous extrusion process to fabricate wedge-shaped LGPs. This continuous process has advantages for mass production. Besides a T-die and rollers, this system also has an in situ monitor of the melt-bank that forms during the extrusion process, helping control the plate thickness. Results show that the melt bank has a close relationship with the plate thickness. The temperature of the bottom heater and roller was adjusted to reduce the surface deformation of the wedge-shaped plate. This continuous extrusion system can successfully manufacture wedge-shaped LGPs for mass production. 1. Introduction All displays without self-luminance, such as liquid crystal displays (LCDs), use a backlight as a light source. Common backlight modules consist primarily of a light source, a reflector, a light guide plate (LGP), a diffusion film, a prism sheet, a cover sheet, a print circuit board, and a drive circuit. The LGP, also called the backlight plate, is the most important component of the backlight module because it integrates all other components to control the backlight source path. Poly(methylmethacrylate) (PMMA) material has excellent properties of optical transmittance, low weight, low cost, and easy processing. These features make PMMA useful in many applications, such as LCD backlight display panels, lens optics, optical fibers, and other photoelectric components, devices, and applications. Therefore, PMMA can replace traditional glass materials as the main material of LPGs. Kim [1] investigated a mechanism of warping behavior for PMMA diffusing plate. To avoid warpage of a diffuser plate, the various different composite glass fiber contents were adjusted. Results indicate that the warpage of the diffusing plate was reduced by using PMMA composites modified with glass fiber. Moreover, the thermal and optical properties such as thermophysical, diffusing characteristics, and uniformity were also improved. Tagaya et al. [2] demonstrated the advanced highly scattering optical transmission polymer backlight. Based on the reflection and refractive and light-scatting theory, the LGP with microprism structures was designed. This backlight exhibited