Abstract

The Taguchi method is applied to optimize the design of a micro-prism diffusion film in such a way as to maximize the luminance uniformity of a slim-type bottom-lit backlight unit illuminated by cold cathode fluorescent lamp (CCFL) light sources. The effects on the luminance uniformity of the filling density, apex angle and aspect ratio of the prism structures and the placement angle of the diffusion film are systematically examined using a three-level Taguchi L27(3<sup>13</sup>) orthogonal array. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) results show that the interaction between the filling density, apex angle and aspect ratio have a significant impact on the luminance uniformity. It is shown that the optimal design parameter settings are a filling density of 100%, an apex angle of 100°, an aspect ratio of 5:1 and a optical film placement angle of 20°. The optimized micro-prism optical film design not only results in a luminance uniformity of 97.8%, but also enables a significant reduction in the thickness of the bottom-lit backlight unit.

© 2011 IEEE

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2009

H. P. Kuo, M. Y. Chuang, C. C. Lin, "Design correlations for the optical performance of the particle-diffusing bottom diffusers in the LCD backlight unit," Powder Technol. 192, 116-121 (2009).

C. F. Lin, C. C. Wu, P. H. Yang, T. Y. Kuo, "Application of Taguchi method in light-emitting diode backlight design for wide color gamut displays," J. Display Technol. 5, 323-330 (2009).

2008

A. G. Olabi, "Using Taguchi method to optimize welding pool of dissimilar laser-welded components," Opt. Laser Tech. 40, 379-388 (2008).

R. Lu, S. Gauza, S. T. Wu, "LED-lit LCD TVs," Mol. Cryst. Liq. Cryst. 488, 246-259 (2008).

F. C. Lin, L. Y. Liao, C. Y. Liao, Y. P. Huang, H. P. D. Shieh, "Dynamic backlight gamma on high dynamic range LCD TVs," J. Disp. Tech. 4, 139-146 (2008).

Y. H. Ju, J. H. Park, J. H. Lee, J. Y. Lee, K. B. Nahm, J. H. Ko, J. H. Kim, "Study on the simulation model for the optimization of optical structures of edge-lit backlight for LCD applications," J. Opt. Soc. Kor. 12, 25-30 (2008).

2007

H. Oktem, T. Erzurumlu, I. Uzman, "Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part," Mater. Des. 28, 1271-1278 (2007).

J. Lee, S. C. Meissner, R. J. Sudol, "Optical film to enhance cosmetic appearance and brightness in liquid crystal displays," Opt. Express 15, 8609-8618 (2007).

K. Fujisawa, I. Onishi, Y. Fujiwara, "Edge-light backlight unit using optically patterned film," Jpn. J. Appl. Phy. 46, 149-199 (2007).

2006

S. I. Chang, J. B. Yoon, H. Kim, J. J. Kim, B. K. Lee, D. H. Shin, "Microlens array diffuser for a light-emitting diode backlight system," Opt. Lett. 31, 3016-3018 (2006).

W. G. Lee, J. H. Jeong, J. Y. Lee, K. B. Nahm, J. H. Ko, J. H. Kim, "Light output characteristics of rounded prism films in the backlight unit for liquid crystal display," J. Info. Disp. 7, 1-4 (2006).

M. Tjahjadi, G. Hay, D. J. Coyle, E. G. Olczak, "Advances in LCD backlight film and plate technology," Inf. Display 10, 22-27 (2006).

M. H. Lee, W. T. Moon, M. J. Kim, S. K. Lee, J. S. Yoon, Y. H. Jung, B. K. Jung, H. S. Soh, B. C. Ahn, "New light collimation film (LCF) for direct-lit BLU system," SID'06 Digest. 503-506 (2006).

2005

W. Y. Lee, T. K. Lim, Y. W. Lee, I. W. Lee, "Fast ray-tracing methods for LCD backlight simulation using the characteristics of the pattern," Opt. Eng. 44, 014004 (2005).

G. H. Kim, "A PMMA composite as an optical diffuser in a liquid crystal display backlighting unit (BLU)," Euro. Poly. J. 41, 1729-1737 (2005).

K. S. Kwon, R. M. Lin, "Robust finite element model updating using Taguchi method," J. Sound Vib. 280, 77-99 (2005).

2001

Appl. Opt.

Euro. Poly. J.

G. H. Kim, "A PMMA composite as an optical diffuser in a liquid crystal display backlighting unit (BLU)," Euro. Poly. J. 41, 1729-1737 (2005).

Inf. Display

M. Tjahjadi, G. Hay, D. J. Coyle, E. G. Olczak, "Advances in LCD backlight film and plate technology," Inf. Display 10, 22-27 (2006).

J. Disp. Tech.

F. C. Lin, L. Y. Liao, C. Y. Liao, Y. P. Huang, H. P. D. Shieh, "Dynamic backlight gamma on high dynamic range LCD TVs," J. Disp. Tech. 4, 139-146 (2008).

J. Display Technol.

J. Info. Disp.

W. G. Lee, J. H. Jeong, J. Y. Lee, K. B. Nahm, J. H. Ko, J. H. Kim, "Light output characteristics of rounded prism films in the backlight unit for liquid crystal display," J. Info. Disp. 7, 1-4 (2006).

J. Opt. Soc. Kor.

Y. H. Ju, J. H. Park, J. H. Lee, J. Y. Lee, K. B. Nahm, J. H. Ko, J. H. Kim, "Study on the simulation model for the optimization of optical structures of edge-lit backlight for LCD applications," J. Opt. Soc. Kor. 12, 25-30 (2008).

J. Sound Vib.

K. S. Kwon, R. M. Lin, "Robust finite element model updating using Taguchi method," J. Sound Vib. 280, 77-99 (2005).

Jpn. J. Appl. Phy.

K. Fujisawa, I. Onishi, Y. Fujiwara, "Edge-light backlight unit using optically patterned film," Jpn. J. Appl. Phy. 46, 149-199 (2007).

Mater. Des.

H. Oktem, T. Erzurumlu, I. Uzman, "Application of Taguchi optimization technique in determining plastic injection molding process parameters for a thin-shell part," Mater. Des. 28, 1271-1278 (2007).

Mol. Cryst. Liq. Cryst.

R. Lu, S. Gauza, S. T. Wu, "LED-lit LCD TVs," Mol. Cryst. Liq. Cryst. 488, 246-259 (2008).

Opt. Eng.

W. Y. Lee, T. K. Lim, Y. W. Lee, I. W. Lee, "Fast ray-tracing methods for LCD backlight simulation using the characteristics of the pattern," Opt. Eng. 44, 014004 (2005).

Opt. Express

Opt. Laser Tech.

A. G. Olabi, "Using Taguchi method to optimize welding pool of dissimilar laser-welded components," Opt. Laser Tech. 40, 379-388 (2008).

Opt. Lett.

Powder Technol.

H. P. Kuo, M. Y. Chuang, C. C. Lin, "Design correlations for the optical performance of the particle-diffusing bottom diffusers in the LCD backlight unit," Powder Technol. 192, 116-121 (2009).

SID'06 Digest.

M. H. Lee, W. T. Moon, M. J. Kim, S. K. Lee, J. S. Yoon, Y. H. Jung, B. K. Jung, H. S. Soh, B. C. Ahn, "New light collimation film (LCF) for direct-lit BLU system," SID'06 Digest. 503-506 (2006).

Other

J. Ha, J. Paek, T. Jang, J. Choi, "A new cost-effective optical plate for high performance LCD-TVs," SID'07 Dig. (2007) pp. 46-49.

C. H. Ahn, C. U. Moon, Light diffusing film U.S. Patent 7 218 450 (2007).

J. H. Lee, J. H. Jung, S. H. Yoon, J. D. Park, K. S. Kim, Optical member, method of fabricating the same and liquid crystal display apparatus having the same U.S. Patent 7 375 779 (2008).

J. F. Graf, E. G. Olczak, G. Hay, R. Hariharan, P. Schottland, Bulk diffuser for flat panel display U.S. Patent 6 908 202 (2005).

F. R. Tony, A. C. David, "Optimized selection of benchmark test parameters for image watermark algorithms based on Taguchi methods and corresponding influence on design decisions for real-world applications," Proc. SPIE (2003) pp. 215-228.

G. Taguchi, E. A. Elsayed, T. Hsaing, Quality Engineering in Production Systems (McGraw-Hill, 1989).

S. H. Park, Robust Design and Analysis for Quality Engineering (Chapman & Hall, 1996).

H. H. Lee, Taguchi Methods: Principles and Practices of Quality Design (Gau Lih, 2008).

C. C. Sun, I. Moreno, S. H. Chung, W. T. Chien, C. T. Hsieh, T. H. Yang, "Direct LED backlight for large area LCD TVs: Brightness analysis," Proc. SPIE 6669 (2007) pp. 666909.

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