[OPTICAL REVIEW Vol. 19, No. 6 (2012) 415-418]
© 2012 The Japan Society of Applied Physics

A Polarized Laser Backlight Using a Zero–Zero-Birefringence Polymer for Liquid Crystal Displays

Takahiro KURASHIMA1, Koichi SAKUMA1, Takayuki ARAI2, Akihiro TAGAYA1*, and Yasuhiro KOIKE1

1Keio Photonics Research Institute, Keio University, Kawasaki 212-0032, Japan
2Enplas Corporation, Kawaguchi, Saitama 332-0034, Japan

(Received May 26, 2012; Revised July 7, 2012; Accepted August 1, 2012)

We have demonstrated a polarized laser backlight for liquid crystal displays and have investigated its basic polarization properties. To maintain the state of polarization of light propagating through the light-guide plate (LGP) of the backlight, we fabricated the LGP by injection molding of a zero–zero-birefringence polymer, poly(methyl methacrylate-co-2,2,2-trifluoroethyl methacrylate-co-benzyl methacrylate) (52:42:6 by mass) that is free of both orientational and photoelastic birefringence. The degree of polarization of light from the resulting backlight (average: 92.4%) was much higher than that from a backlight with a polycarbonate LGP (average: 8.0%) in the defined effective range of the backlight. A laser speckle pattern was observed but the speckle contrast on the output surface of the backlight was reduced from 68 to 10% by vibrating a diffuser sheet situated in front of the output surface of the LGP. We also manufactured a white surface light source [chromaticity value: (x, y) = (0.310, 0.314)] by mixing the outputs from three primary-color-emitting lasers in the backlight.

Key words: liquid crystal display, backlight, polarized laser backlight, birefringence, zero–zero-birefringence polymer, speckle

*E-mail address: a-tagaya@kpri.keio.ac.jp