Abstract

We describe an advanced highly scattering optical transmission (HSOT) polymer backlight system that has shown twice the brightness of a conventional transparent system in spite of its having a thinner backlight. The HSOT polymer that contains optimized heterogeneous structures produced homogeneous scattered light with forward directivity and sufficient color uniformity. Although it was thought that polymers for light-guide plates (LGPs) must be transparent to minimize scattering, we have come to the conclusion that the HSOT polymer, which is not an absorping medium but a scattering medium, is a more suitable medium for LGPs.

© 2001 Optical Society of America

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References

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  1. A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).
  2. A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).
  3. A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
    [CrossRef]
  4. G. Mie, “Beiträge zur Optik truber Medien, speziell kolloidaler Metallösungen,” Ann. Phys. (Leipzig) 25, 377–445 (1908).
    [CrossRef]
  5. M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic, San Diego, Calif., 1969).
  6. I. Lux, L. Koblinger, Monte Carlo Particle Transport Methods: Neutron and Photon Calculations (CRC Press, Boca Raton, Fla., 1991).

1998

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

1995

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

1908

G. Mie, “Beiträge zur Optik truber Medien, speziell kolloidaler Metallösungen,” Ann. Phys. (Leipzig) 25, 377–445 (1908).
[CrossRef]

Baba, M.

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

Chichibu, S. F.

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

Chua, S. J.

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

Horibe, A.

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

Izuhara, M.

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

Kerker, M.

M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic, San Diego, Calif., 1969).

Koblinger, L.

I. Lux, L. Koblinger, Monte Carlo Particle Transport Methods: Neutron and Photon Calculations (CRC Press, Boca Raton, Fla., 1991).

Koike, Y.

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

Lux, I.

I. Lux, L. Koblinger, Monte Carlo Particle Transport Methods: Neutron and Photon Calculations (CRC Press, Boca Raton, Fla., 1991).

Mie, G.

G. Mie, “Beiträge zur Optik truber Medien, speziell kolloidaler Metallösungen,” Ann. Phys. (Leipzig) 25, 377–445 (1908).
[CrossRef]

Nihei, E.

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

Osinski, M.

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

Tagaya, A.

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

Ann. Phys. (Leipzig)

G. Mie, “Beiträge zur Optik truber Medien, speziell kolloidaler Metallösungen,” Ann. Phys. (Leipzig) 25, 377–445 (1908).
[CrossRef]

IEICE Trans. Electron.

A. Horibe, M. Baba, E. Nihei, Y. Koike, “High-efficiency and high-quality LCD backlight using highly scattering optical transmission polymer,” IEICE Trans. Electron. E81-C, 1697–1702 (1998).

SID J.

A. Horibe, M. Izuhara, E. Nihei, Y. Koike, “Brighter backlights using highly scattered optical transmission polymer,” SID J. 3, 169–171 (1995).

Other

A. Tagaya, Y. Koike, “Highly scattering optical transmission polymers for liquid crystal display,” in Design, Fabrication, and Characterization of Photonic Devices, M. Osinski, S. J. Chua, S. F. Chichibu, Proc. SPIE3896, 214–222 (1999).
[CrossRef]

M. Kerker, The Scattering of Light and Other Electromagnetic Radiation (Academic, San Diego, Calif., 1969).

I. Lux, L. Koblinger, Monte Carlo Particle Transport Methods: Neutron and Photon Calculations (CRC Press, Boca Raton, Fla., 1991).

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Figures (12)

Fig. 1
Fig. 1

Bulk HSOT polymer and conventional transparent bulk polymers. (a) Light injected into the HSOT bulk polymer is multiply scattered and homogenized because of the heterogeneous structures of the HSOT and then emerges as a directive illuminating light. (b) Injected light simply passes through conventional transparent bulk polymer.

Fig. 2
Fig. 2

Calculated single-scattering profiles based on Mie scattering theory. The vector from the origin of the coordinates to each curve is proportional to the logarithmic intensity scattered at the corresponding angle. Size parameters, α = 1.7, 11.5, 69.2; relative refractive index, m = 0.965.

Fig. 3
Fig. 3

Scattering efficiency curves of a single particle for 435-, 545-, and 615-nm wavelengths. Typical cold fluorescent lamps have spectral peaks near these wavelengths. Relative refractive index, m = 0.965. (A), (B) Particle diameters for heterogeneous structures (A) and (B), respectively.

Fig. 4
Fig. 4

Schematic diagrams of LCD backlighting systems. (a) Conventional transparent backlight system, in which the LGP is made from a transparent polymer. (b) Advanced HSOT polymer backlight system, in which the LGP is made from HSOT polymer.

Fig. 5
Fig. 5

Definition of angles α and β to describe the angular distribution of luminance. Vector A′, which is the projection of luminance vector A, lies in the yz plane at an angle α from the z axis.

Fig. 6
Fig. 6

Schematic diagram of the prism structures at the bottom of the LGP and definition of prism angle δ. Filled circles, points of reflection and refraction.

Fig. 7
Fig. 7

Simulated 3-D profiles of luminance from the HSOT LGP. Prism angles δ are indicated. Here, “photon” means an imaginary particle with which to analyze the multiple-scattering process. The photon number is proportional to the luminance; the various colors are related to the number of photons as shown in the scale at the right of each figure.

Fig. 8
Fig. 8

3-D luminance profile of the 10.4-in. HSOT LGP without a prism film.

Fig. 9
Fig. 9

Typical locus of a ray in the prism film optimized for the advanced HSOT LGP. The illuminating light is refracted and reflected and finally emerges in a direction vertical to the output surface through the prism.

Fig. 10
Fig. 10

3-D luminance profiles of (a) the advanced HSOT backlight with the prism film and (b) a transparent backlight with dot patterns under the same conditions. Lamp current, 3.0 mA; lamp voltage, 573 V rms.

Fig. 11
Fig. 11

Luminance profiles for the advanced HSOT LGP and the conventional transparent LGP with a diffuser film relative to angle α. Here β = 0.

Fig. 12
Fig. 12

Uniformity of color in the output surface of the advanced HSOT backlight. A backlight for a color LCD is a white-light source. A slight difference in color, for example, bluish white or yellowish white, for a white-light source is indicated by color temperature. Color temperature is almost constant in the output surface area.

Equations (10)

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I α ,   m ,   θ = λ 2 i 1 + i 2 / 8 π 2 ,
K α ,   m = λ 2 2 π 2 r 2 ν = 1 α 2 ν + 1 | a ν | 2 + | b ν | 2 ,
i 1 = ν = 1 2 ν + 1 ν ν + 1 a ν P ν 1 cos   θ sin   θ + b ν d P ν 1 cos   θ d θ 2 , i 2 = ν = 1 2 ν + 1 ν ν + 1 b ν P ν 1 cos   θ sin   θ + a ν d P ν 1 cos   θ d θ 2 ,
a ν = ψ ν m α ψ ν α - m ψ ν m α ψ ν α ψ ν m α ζ ν α - m ψ ν m α ζ ν α , b ν = m ψ ν m α ψ ν α - ψ ν m α ψ ν α m ψ ν m α ζ ν α - ψ ν m α ζ ν α ,
α = 2 π rn m / λ 0 ,
m = n s / n m ,
σ = π   0 0   r 2 n a r f λ K α ,   m d r d λ ,
L = - ln random 1 / σ ,
F θ = 0 θ   2 π I θ sin   θ d θ 0 π   2 π I θ sin   θ d θ ,
θ = F - 1 random 2 ,

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