Abstract

A novel polarized light-guide plate (LGP) for the illumination of liquid crystal display is proposed in this paper. For the substrate of the LGP, stress-induced birefringence is introduced to achieve the polarization state conversion. An aluminum sub-wavelength grating (SWG) is designed on the top surface as a polarizing beam-splitter (PBS). The structure of the novel LGP is optimized for three wavelengths of LEDs: 625nm, 533nm and 452nm, and high efficiencies of polarization conversion are obtained. The backlight system with the designed LGP does not require prism sheets and quarter wavelength plate. The backlight with the novel LGP achieved large gain in energy efficiency, and the peak luminous intensity is about 2 times higher than that of a conventional backlight.

© 2005 Optical Society of America

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References

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Appl. Opt.

Appl. Phys. Lett.

T. Okumura, A. Tagaya, Y. Koike, M. Horiguchi, and H. Suzuki, �??Highly-efficient backlight for liquid crystal display having no optical films,�?? Appl. Phys. Lett. 83, 2515 (2003).
[CrossRef]

IEICE Trans. Electron.

K. Käläntär, S. Matsumoto, and T. Onishi, �??Functional light-guide plate characterized by optical micro-deflector and micro-reflector for LCD backlight,�?? IEICE Trans. Electron. E84-C, 1637-1646 (2001).

J. Mod. Opt.

L. Li, �??A modal analysis of lamellar diffraction grating in conical mountings,�?? J. Mod. Opt. 40. 553-573 (1993).
[CrossRef]

J. Polym. Sci. B

G. D. Shyu, A.I. Isayev, and C.T. Li, �??Residual thermal birefringence in freely quenched plates of amorphous polymers: simulation and experiment,�?? J. Polym. Sci. B 41, 1850 (2003).
[CrossRef]

Opt. Express

Polym. Eng. Sci.

R. Winberger-Friedl, J.G. de Bruin, and H. F. M. Schoo, �??Residual birefringence in modified polycarbonates,�?? Polym. Eng. Sci. 43, 62 (2003).
[CrossRef]

SID 99 Technical DIGEST

Z. Pang and L. Li, �??Novel high-efficiency polarizing backlighting system with a polarizing beam splitter,�?? SID 99 Technical DIGEST (Society for Information Display, San Jose, Calif., 1999), 916 (1999).
[CrossRef]

H. J. B. Jagt, H. J. Cornelissen and D. J. Broer, �??Polarized light LCD backlight based on liquid crystalline polymer film: a new manufacturing process,�?? SID 99 Technical DIGEST (Society for Information Display, Boston, Mass., Calif., 1999), 1236, (2002).

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Figures (8)

Fig. 1.
Fig. 1.

Coordinate system of the LGP substrate with the applied stress

Fig. 2.
Fig. 2.

the objective function value with respect to the stress difference

Fig. 3.
Fig. 3.

the coordinate system and the structure of the SWG on the top surface of the LGP. Here, θ denotes the incident angle, φ denotes the azimuthal angle, and f denotes the grating duty cycle.

Fig. 4.
Fig. 4.

the calculated dependences of the transmission on the duty cycle for (a) p-polarized light and (b) s-polarized light of red, green and blue. Here, incident angle θ = 0.

Fig. 5.
Fig. 5.

the calculated dependences of the transmission on the grating depth for (a) p-polarized light and (b) s-polarized light of the red, green and blue light. Here, incident angle θ = 0.

Fig. 6.
Fig. 6.

Calculated results of the designed SWG with different wavelengths; (a) transmission of the p-polarized light, (b) transmission of s-polarized light and (c) extinction ratio as a function of the incident angle.

Fig. 7.
Fig. 7.

Ray tracing in the proposed LGP. The s light is converted into the p light by the stress-induced birefringence of the LGP substrate.

Fig. 8.
Fig. 8.

Polar luminous intensity plots of polarized light emitting form (a) the proposed BLS and (b) the conventional BLS. Here, φ denotes the azimuthal angle, and θ denotes inclination angle.

Equations (9)

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Δ n = n σ y n σ x = C Δ σ
δ = 2 π C Δ σ L λ ,
T = R ( β ) T δ R ( β ) = [ cos β sin β sin β cos β ] [ 1 0 0 e j δ ] [ cos β sin β sin β cos β ] .
E o = [ E ox E oy ] = T E i = A [ sin β cos β sin β cos β e j δ sin 2 β + cos 2 β e j δ ]
I ox = A 2 sin 2 2 β sin 2 ( δ 2 ) = A 2 sin 2 2 β sin 2 ( π C Δ σ L λ ) .
{ β = π 4 δ = 2 k π + π k = 0,1,2,3,4 , ,
y = min Δ σ { w R × abs [ mod ( δ R , 2 π ) π ] + w G × abs [ mod ( δ G , 2 π ) π ] +
w B × abs [ mod ( δ B , 2 π ) π ] } ,
{ δ R = 46 π + 0.97 π δ G = 54 π + 1.07 π δ B = 64 π + 0.94 π .

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