Abstract
This study examined the uniformity of illuminance field distributions of light guide plates (LGPs). First, the authors designed microstructural patterns on the surface of an LGP. Then, a mold of the LGP with the optimal microstructural design was fabricated by a photolithography method. Micro-injection molding (μIM) was used to manufacture the molded LGPs. μIM technology can simultaneously manufacture large-sized wedge-shaped LGPs and micro-scale microstructures. Finally, illuminance values of the field distributions of the LGPs with various microstructures were obtained through optical field measurements. This study compared the illuminance field distributions of LGPs with various designs and structures, which included LGPs without and those with microstructure on the primary design and the optimal design. The average illuminance of the LGP with microstructures and the optimal design was roughly 196.1 cd/m2. Its average illuminance was 1.3 times that of the LGP without microstructures. This study also discusses illuminance field distributions of LGPs with microstructures that were influenced by various μIM process parameters. The mold temperature was found to be the most important processing parameter affecting the illuminance field distribution of molded LGPs fabricated by μIM. The molded LGP with microstructures and the optimal design had better uniformity than that with microstructures and the primary design and that without microstructures. The uniformity of the LGP with microstructures and the optimal design was roughly 86.4%. Its uniformity was nearly 1.65 times that of the LGP without microstructures. The optimized design and fabrication of LGPs with microstructure exhibited good uniformity of illuminance field distributions.
Highlights
The measurement method was based on the light emitted by a cold cathode fluorescent lamp (CCFL) through a self-designed fixture, and an added reflector to assemble a backlight module (BLM); we applied an illuminance measurement method to measure the influence of diffusion point designs of various microstructures on the uniformity of Light guide plates (LGPs), and employed the Taguchi method to find the optimal combination of the arrangement of the microstructure distribution, and design the microstructural form of the LGP according to the best uniformity
The optimal uniformity of illuminance field distributions of the LGP with microstructures was affected by various μIM process parameters
To maximize the optimal design for uniformity of the LGP with microstructures, the following equation was employed for the analysis to describe the bigger-the-better characteristics: 1 n 1
Summary
Light guide plates (LGPs) are a major component of liquid crystal displays (LCDs). An LGP uniformly transfers light from a cold cathode fluorescent lamp (CCFL) to the face of an LCD. The fidelity of the microstructures of the LGP and its optical properties are essential to ensure a good performance. Many methods of manufacturing LGPs have been developed, including an ultraviolet (UV)-based imprinting process on large and thin LGPs with a dot-size [1], replication of LGPs with microstructures by injection molding (IM) [2,3,4,5,6], and a hot-embossing method [7,8,9,10]. Nano-imprinting, UV-embossing, compression molding, and IM are low-cost mass-production methods suited to replicate LGP’s microstructures
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