Abstract

In this paper, we propose a self-assembled microlens on top of light-emitting diodes (LEDs) based on hydrophilic effect under ultraviolet (UV)/ozone treatment to improve extraction efficiency and to increase viewing angle. The LED chip was encapsulated by polydimethylsiloxane (PDMS) $(n=1.44)$ before the fabrication process of microlens. The microlens was made of transparent negative photoresist SU-8 $(n=1.63)$. The SU-8 photoresist became more hydrophilic after UV/ozone treatment. After hydrophilic zones were produced by using shadow masks and UV/ozone, the substrate with hydrophilic zones was dipped in and out of diluted SU-8 photoresist solution with slow and constant velocity. Meanwhile, a 200-$\mu{\hbox{m}}$ microlens was formed by self-surface tension and cohesion of diluted SU-8. Finally, microlens was hardened after UV curing. This approach is cost effective and low time-consuming. It did not require photo masks, heating, or etch-transfer processes. It's a new fabrication method that can be easily applied to opto-electronic devices. Integrated with LED, microlens can improve extraction efficiency 28% in total power and increase viewing angle 17 degree.

© 2012 IEEE

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  11. S.-M. Kuo, C.-H. Lin, "Fabrication of aspherical SU-8 microlens array utilizing novel stamping process and electro-static pulling method," Opt. Express 18, 19114-19119 (2010).
  12. C.-J. Chang, C.-S. Yang, L.-H. Lan, P.-C. Wang, F.-G. Tseng, "Fabrication of a SU-8-based polymer-enclosed channel with a penetrating UV/ozone-modified interior surface for electrokinetic separation of proteins," J. Micromechan. Microeng. 20, (2010) 115031.
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2011

W.-C. Chen, T.-T. Lai, M.-W. Wang, H.-W. Hung, "An optimization system for LED lens design," Expert Syst. With Appl. 38, 11976-11983 (2011).

K. Y. Chen, H. Y. Lin, M. K. Wei, J. H. Lee, Y. T. Hsiao, C. C. Lin, Y. H. Ho, J. H. Tsai, "Enhancement and saturation phenomena on luminous current and power efficiencies of organic light-emitting devices by attaching microlens array films," J. Display Technol. 7, 242-249 (2011).

2010

S. M. Kuo, C. H. Lin, "Fabrication of aspherical SU-8 microlens array utilizing novel stamping process and electro-static pulling method," Opt. Express 18, 19114-19119 (2010).

S.-M. Kuo, C.-H. Lin, "Fabrication of aspherical SU-8 microlens array utilizing novel stamping process and electro-static pulling method," Opt. Express 18, 19114-19119 (2010).

C.-J. Chang, C.-S. Yang, L.-H. Lan, P.-C. Wang, F.-G. Tseng, "Fabrication of a SU-8-based polymer-enclosed channel with a penetrating UV/ozone-modified interior surface for electrokinetic separation of proteins," J. Micromechan. Microeng. 20, (2010) 115031.

2009

2006

H. Ottevaere, R. Cox, H. P. Herzig, T. Miyashita, K. Naessens, M. Taghizadeh, R. Völkel, H. Woo, H. Thienpont, "Comparing glass and plastic refractive microlenses fabricated with different technologies," J.Opt. A: Pure Appl. Opt. 8, S407 (2006).

2005

A. Bateni, S. Laughton, H. Tavana, S. Susnar, A. Amirfazli, A. Neumann, "Effect of electric fields on contact angle and surface tension of drops," J. Colloid and Interface Sci. 283, 215-222 (2005).

2004

H. Hillborg, N. Tomczak, A. Olah, H. Schonherr, G. J. Vancso, "Nanoscale hydrophobic recovery: A chemical force microscopy study of UV/ozone-treated cross-linked poly (dimethylsiloxane)," Langmuir 20, 785-794 (2004).

2002

S. Moller, S. Forrest, "Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324 (2002).

2000

D. M. Hartmann, O. Kibar, S. G. Esener, "Characterization of a polymer microlens fabricated by use of the hydrophobic effect," Opt. Lett. 25, 975-977 (2000).

1994

H. A. Biebuyck, G. M. Whitesides, "Self-organization of organic liquids on patterned self-assembled monolayers of alkanethiolates on gold," Langmuir 10, 2790-2793 (1994).

Appl. Opt.

Expert Syst. With Appl.

W.-C. Chen, T.-T. Lai, M.-W. Wang, H.-W. Hung, "An optimization system for LED lens design," Expert Syst. With Appl. 38, 11976-11983 (2011).

J. Colloid and Interface Sci.

A. Bateni, S. Laughton, H. Tavana, S. Susnar, A. Amirfazli, A. Neumann, "Effect of electric fields on contact angle and surface tension of drops," J. Colloid and Interface Sci. 283, 215-222 (2005).

J. Micromechan. Microeng.

C.-J. Chang, C.-S. Yang, L.-H. Lan, P.-C. Wang, F.-G. Tseng, "Fabrication of a SU-8-based polymer-enclosed channel with a penetrating UV/ozone-modified interior surface for electrokinetic separation of proteins," J. Micromechan. Microeng. 20, (2010) 115031.

J. Appl. Phys.

S. Moller, S. Forrest, "Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays," J. Appl. Phys. 91, 3324 (2002).

J. Display Technol.

K. Y. Chen, H. Y. Lin, M. K. Wei, J. H. Lee, Y. T. Hsiao, C. C. Lin, Y. H. Ho, J. H. Tsai, "Enhancement and saturation phenomena on luminous current and power efficiencies of organic light-emitting devices by attaching microlens array films," J. Display Technol. 7, 242-249 (2011).

J.Opt. A: Pure Appl. Opt.

H. Ottevaere, R. Cox, H. P. Herzig, T. Miyashita, K. Naessens, M. Taghizadeh, R. Völkel, H. Woo, H. Thienpont, "Comparing glass and plastic refractive microlenses fabricated with different technologies," J.Opt. A: Pure Appl. Opt. 8, S407 (2006).

Langmuir

H. A. Biebuyck, G. M. Whitesides, "Self-organization of organic liquids on patterned self-assembled monolayers of alkanethiolates on gold," Langmuir 10, 2790-2793 (1994).

H. Hillborg, N. Tomczak, A. Olah, H. Schonherr, G. J. Vancso, "Nanoscale hydrophobic recovery: A chemical force microscopy study of UV/ozone-treated cross-linked poly (dimethylsiloxane)," Langmuir 20, 785-794 (2004).

Opt. Lett.

D. M. Hartmann, O. Kibar, S. G. Esener, "Characterization of a polymer microlens fabricated by use of the hydrophobic effect," Opt. Lett. 25, 975-977 (2000).

Opt. Express

Other

O. P. Parida, N. Bhat, "Characterization of optical properties of SU-8 and fabrication of optical components," Int. Conf. on Opt. and Photon. (CSIO) (2009).

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