Abstract

Twisted nematic liquid crystal displays (TN-LCDs), doped with the nanoparticles of metal, such as Pd, Ag, or Ag-Pd, which are protected with ligand molecules, such as nematic liquid crystal, exhibit a frequency modulation (FM) electro-optical (EO) response with short response time of milliseconds (ms) or sub-ms order together with the ordinary rms voltage response. These devices are called FM/AM-TN-LCDs; they are distinct from the ordinary LCDs featured by the amplitude modulation (AM) response. The phenomena of the FM/AM LCDs may be attributed to the dielectric dispersion of a heterogeneous dielectric medium known as the Maxwell-Wagner effect. It is experimentally shown that the frequency range spreads from several tens hertz to several tens kilohertz and the spectrum is more or less centered about the dielectric relaxation frequency. We formulated a theory based on an equivalent circuit model to evaluate the dielectric relaxation frequency and the dielectric strengths; and we succeeded in explaining the dependence of the dielectric relaxation frequency on the concentration of nanoparticles and the their dielectric and electrical properties, whereas conventional theories based on electromagnetic theory are unable to explain this concentration dependence. This paper reports on the experimental results of the EO effects and the dielectric spectroscopy including the dielectric relaxation times and the dielectric strengths of nematic liquid crystal, 5CB (4-pentyl-4'-cyanobiphenyl), doped with the metal nanoparticles of Pd alone and Ag-Pd composite; and discusses how the observed dielectric relaxation frequency or dielectric relaxation time depend on the concentration of the doped nanoparticles and also their electrical and dielectric properties.

© 2006 IEEE

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  1. Y. Shiraishi, N. Toshima, K. Maeda, H. Yoshikawa, J. Xu, S. Kobayashi, "Frequency modulation response of a liquid-crystal electro-optic device doped with nanoparticles," Appl. Phys. Lett. 81, 2845-2847 (2002).
  2. H. Yoshikawa, K. Maeda, Y. Shiraishi, J. Xu, H. Shiraki, N. Toshima, S. Kobayashi, "Frequency modulation response of a tunable birefringent mode nematic liquid crystal electrooptic device fabricated by doping nanoparticles of Pd covered with liquid-crystal molecules," Jpn. Appl. Phys. 41, L1315-L1317 (2002).
  3. T. Miyama, J. Thisayukta, H. Shiraki, Y. Sakai, Y. Shiraishi, N. Toshima, S. Kobayashi, "Fast switching of frequency modulation twisted nematic liquid crystal display fabricated by doping nanoparticles and its mechanism," Jpn. J. Appl. Phys. 43, 2580-2584 (2004).
  4. J. Thisayukta, H. Shiraki, Y. Sakai, T. Masumi, S. Kundu, Y. Shiraishi, N. Toshima, S. Kobayashi, "Dielectric properties of frequency modulation twisted nematic LCD's doped with silver nanoparticles," Jpn. J. Appl. Phys. 43, 5430-5434 (2004).
  5. H. Shiraki, S. Kundu, Y. Sakai, T. Masumi, Y. Shiraishi, N. Toshima, S. Kobayashi, "Dielectric properties of frequency modulation twisted nematic LCD's doped with palladium (Pd) nanoparticles," Jpn. J. Appl. Phsy. 43, 5425-5429 (2004).
  6. J. C. Maxwell, Treatise on Electricity and Magnetism (Dover, 1945) pp. 451-461.
  7. K. W. Wagner, "Erklärung der dielektrischen Nachwirkun gs-vorgänge auf Grund Maxwellscher Vorstellungen," Erkl. Arch. Electrorech. 2, 371-387 (1914).
  8. J. C. Maxwell-Garnett, "Colors in metal glasses and in metal films," Phil. Trans. 203, 385-419 (1904).
  9. J. C. Maxwell-Garnett, "Colors in metal glasses, in metallic films, and in metallic solutions—II," Phil. Trans 205, 237-387 (1906).

Appl. Phys. Lett.

Y. Shiraishi, N. Toshima, K. Maeda, H. Yoshikawa, J. Xu, S. Kobayashi, "Frequency modulation response of a liquid-crystal electro-optic device doped with nanoparticles," Appl. Phys. Lett. 81, 2845-2847 (2002).

Erkl. Arch. Electrorech.

K. W. Wagner, "Erklärung der dielektrischen Nachwirkun gs-vorgänge auf Grund Maxwellscher Vorstellungen," Erkl. Arch. Electrorech. 2, 371-387 (1914).

Jpn. J. Appl. Phys.

T. Miyama, J. Thisayukta, H. Shiraki, Y. Sakai, Y. Shiraishi, N. Toshima, S. Kobayashi, "Fast switching of frequency modulation twisted nematic liquid crystal display fabricated by doping nanoparticles and its mechanism," Jpn. J. Appl. Phys. 43, 2580-2584 (2004).

Jpn. Appl. Phys.

H. Yoshikawa, K. Maeda, Y. Shiraishi, J. Xu, H. Shiraki, N. Toshima, S. Kobayashi, "Frequency modulation response of a tunable birefringent mode nematic liquid crystal electrooptic device fabricated by doping nanoparticles of Pd covered with liquid-crystal molecules," Jpn. Appl. Phys. 41, L1315-L1317 (2002).

Jpn. J. Appl. Phsy.

H. Shiraki, S. Kundu, Y. Sakai, T. Masumi, Y. Shiraishi, N. Toshima, S. Kobayashi, "Dielectric properties of frequency modulation twisted nematic LCD's doped with palladium (Pd) nanoparticles," Jpn. J. Appl. Phsy. 43, 5425-5429 (2004).

Jpn. J. Appl. Phys.

J. Thisayukta, H. Shiraki, Y. Sakai, T. Masumi, S. Kundu, Y. Shiraishi, N. Toshima, S. Kobayashi, "Dielectric properties of frequency modulation twisted nematic LCD's doped with silver nanoparticles," Jpn. J. Appl. Phys. 43, 5430-5434 (2004).

Phil. Trans

J. C. Maxwell-Garnett, "Colors in metal glasses, in metallic films, and in metallic solutions—II," Phil. Trans 205, 237-387 (1906).

Phil. Trans.

J. C. Maxwell-Garnett, "Colors in metal glasses and in metal films," Phil. Trans. 203, 385-419 (1904).

Other

J. C. Maxwell, Treatise on Electricity and Magnetism (Dover, 1945) pp. 451-461.

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