Abstract

This paper presents an optical film that enhances cosmetic appearance as well as brightness in a liquid crystal display (LCD) through microprisms that have a variable pitch. The optical film utilizes Fourier transformation to optimize the arrangement of microprisms for improving the cosmetic appearance in the display. The optical film has an improved light-collimating feature that redirects light more effectively, resulting in higher brightness. This paper shows details of the design procedure, but more importantly, presents optical measurement results of an actual optical film prototype to confirm the performance improvement.

© 2007 Optical Society of America

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References

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  1. Vikuiti Brightness Enhancement Film, http://solutions.3m.com/wps/portal/3M/en_US/VikuitiHome>.
  2. DIAART prism sheet for LCD backlights, http://www.mrc.co.jp/english/a>.
  3. T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
    [CrossRef]
  4. T. Idé, H. Mizuta, H. Numata, Y. Taira, M. Suzuki, M. Noguchi, and Y. Katsu, "Dot pattern generation technique using molecular dynamics," J. Opt. Soc. Am. A 20, 248-255 (2003).
    [CrossRef]
  5. K. Käläntär, "Functional light-guide plate for backlight unit," in Society for Information Display 1999 International Symposium, J. Morreale, ed., (San Jose, CA, 1999) 30, pp. 764-767.
  6. K. Käläntär, S. Matsumoto, T. Katoh, and T. Mizuno, "Double-side emissive backlight unit for transmissive LCD using a single functional light-guide plate," in The Tenth International Display Workshops, T. Uchida, ed., (Fukuoka, Japan, 2003), pp. 661-664.
  7. K. Käläntär, S. Matsumoto, T. Mizuno, and T. Katoh, "Backlight unit with double surface light emission using a single micro-structured light-guide plate," in Society for Information Display 2004 International Symposium, J. Morreale, ed., (San Jose, CA, 2004), pp. 1182-1185.
  8. K. Oki, "Novel backlight with high luminance and low power consumption by Prism-on-Light-Pipe Technology," in Society for Information Display 1998 International Symposium, J. Morreale, ed., (Anaheim, CA, 1998) 29, pp. 157-160.
  9. I. Amidror and R. D. Hersch, "Fourier-based analysis of phase shifts in the superposition of periodic layers and their moiré effects," J. Opt. Soc. Am. A 13, 974-987 (1996).
    [CrossRef]
  10. J. D. Gaskill, Linear Systems, Fourier Transforms, and Optics (John Wiley & Sons, New York, 1978).
  11. K. Creath and J. C. Wyant, "Moire and Fringe Projection Techniques," in Optical Shop Testing, D. Malacara, ed., (John Wiley & Sons, New York, 1992), pp. 653-655.
  12. J. E. Greivenkamp, Field Guide to Geometrical Optics (SPIE, Washington, 2004).
    [CrossRef]
  13. M. Madou, Fundamentals of Microfabrication (CRC Press, New York, 1997).

2003 (2)

T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
[CrossRef]

T. Idé, H. Mizuta, H. Numata, Y. Taira, M. Suzuki, M. Noguchi, and Y. Katsu, "Dot pattern generation technique using molecular dynamics," J. Opt. Soc. Am. A 20, 248-255 (2003).
[CrossRef]

1996 (1)

Amidror, I.

Hersch, R. D.

Idé, T.

Katsu, Y.

Koike, Y.

T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
[CrossRef]

Mizuta, H.

Noguchi, M.

Numata, H.

Okumura, T.

T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
[CrossRef]

Suzuki, M.

Tagaya, A.

T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
[CrossRef]

Taira, Y.

Appl. Phys. Lett. (1)

T. Okumura, A. Tagaya, and Y. Koike, "Highly-efficient backlight for liquid crystal display having no optical films," Appl. Phys. Lett. 83, 2515-2517 (2003).
[CrossRef]

J. Opt. Soc. Am. A (2)

Other (10)

J. D. Gaskill, Linear Systems, Fourier Transforms, and Optics (John Wiley & Sons, New York, 1978).

K. Creath and J. C. Wyant, "Moire and Fringe Projection Techniques," in Optical Shop Testing, D. Malacara, ed., (John Wiley & Sons, New York, 1992), pp. 653-655.

J. E. Greivenkamp, Field Guide to Geometrical Optics (SPIE, Washington, 2004).
[CrossRef]

M. Madou, Fundamentals of Microfabrication (CRC Press, New York, 1997).

K. Käläntär, "Functional light-guide plate for backlight unit," in Society for Information Display 1999 International Symposium, J. Morreale, ed., (San Jose, CA, 1999) 30, pp. 764-767.

K. Käläntär, S. Matsumoto, T. Katoh, and T. Mizuno, "Double-side emissive backlight unit for transmissive LCD using a single functional light-guide plate," in The Tenth International Display Workshops, T. Uchida, ed., (Fukuoka, Japan, 2003), pp. 661-664.

K. Käläntär, S. Matsumoto, T. Mizuno, and T. Katoh, "Backlight unit with double surface light emission using a single micro-structured light-guide plate," in Society for Information Display 2004 International Symposium, J. Morreale, ed., (San Jose, CA, 2004), pp. 1182-1185.

K. Oki, "Novel backlight with high luminance and low power consumption by Prism-on-Light-Pipe Technology," in Society for Information Display 1998 International Symposium, J. Morreale, ed., (Anaheim, CA, 1998) 29, pp. 157-160.

Vikuiti Brightness Enhancement Film, http://solutions.3m.com/wps/portal/3M/en_US/VikuitiHome>.

DIAART prism sheet for LCD backlights, http://www.mrc.co.jp/english/a>.

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Figures (10)

Fig. 1.
Fig. 1.

Schematics of conventional backlight unit used in LCD. Light emitted from CCFL, and guided by the wave-guiding plate, is redirected toward the viewing direction by a prism sheet.

Fig. 2.
Fig. 2.

3D rendering of the proposed microprism optical film. The figure shows the lateral waviness of the microprism array.

Fig. 3.
Fig. 3.

Conceptual illustration of creating varying pitch in a two-dimensional manner. The wiggly lines indicate apexes of microprisms while the triangles at the bottom of the figures illustrate a profile of the microprisms. The left figure shows the microprisms arranged to have a lateral waviness. The right figure shows random staggering in addition to the lateral waviness; as a result, the pitches in the right figure vary at any location.

Fig. 4.
Fig. 4.

Spatial frequency distribution of the example shown in Fig. 2. The solid line is a spatial frequency of one pattern with no lateral waviness and no random staggering, and the dotted line is a spatial frequency of one pattern that does have lateral waviness.

Fig. 5.
Fig. 5.

Ray-tracing in two microprisms (a) with a flat surface (b) with a curved surface.

Fig. 6.
Fig. 6.

Optical performance vs. various design parameters.

Fig. 7.
Fig. 7.

SEM figure of the proposed optical film sample. The figure shows the lateral waviness of the microstructure array.

Fig. 8.
Fig. 8.

Isoluminance measurement of optical films under EZContrast.

Fig. 9.
Fig. 9.

Brightness profile of two optical films. The solid line is a measurement result of the proposed optical film while the dotted line is the same data of the conventional optical film.

Fig. 10.
Fig. 10.

Moiré appearance when both optical films are superimposed with a grating.

Tables (1)

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Table 1. Best performers in design parameters.

Equations (11)

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F film ( ξ , η ) = FT [ f film ( x , y ) ] ,
F TFT LC ( ξ , η ) = FT [ f TFT LC ( x , y ) ] .
F s ( ξ , η ) = F TFT LC ( ξ , η ) * F film ( ξ , η )
F TFT LC ( ξ , η ) = n , m = a n , m δ ( ξ n P TFT LC ) δ ( η m Q TFT LC ) .
F film ( ξ , η ) = n , m = b n , m δ ( ξ n ´ P film ) δ ( η m Q film ) .
F s ( ξ , η ) = n , m = a n , m δ ( ξ n P TFT LC ) δ ( η m Q TFT LC ) +
n , m = b n , m δ ( ξ n P film ) δ ( η m Q film ) + ,
n , m = n , m = a n , m a n , m δ ( ξ n P TFT LC + n P film ) δ ( η m Q TFT LC + m Q film )
F Moire ( ξ , η ) = n , m = N , M N , M n , m = N , M N , M a n , m b n , m δ ( ξ n P TFT LC + n P film ) δ ( η m Q TFT LC + m Q film ) .
ξ = n P TFT LC n P film or η = m Q TFT LC m Q film .
Amplitude Moire = a n , m b n , m .

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