5.2 Future work
5.3.1 Holding time enhancement
There are two paths for the leakage current. One is the TFT path. The dVhold at most is 17V as shown in table.5-1. The other various potential on the charged drain electrodes is acceptable for the LC holding at 60Hz. The second one is the LC path.
The VLC is almost zero as the resistance value of liquid crystal is about 10^9Ω-cm.
The low resistivity may causes by the purity of LC or the fabricated processes.
In order to enhance the lens holding state, the high resistivity value of liquid crystal is needed. The pollution such as moisture, dust particle causes the low LC resistivity value. Otherwise, the charging frequency should be increased and recharged again before the electric potential disappeared.
Table. 5- 1 TFT path various electric potential
10^-12 10^-11 10^-10 10^-09 10^-08
10pF
1.7E-03 1.7E-02 1.7E-01 1.7E+00 1.7E+01100pF
1.7E-04 1.7E-03 1.7E-02 1.7E-01 1.7E+001nF
1.7E-05 1.7E-04 1.7E-03 1.7E-02 1.7E-0110nF
1.7E-06 1.7E-05 1.7E-04 1.7E-03 1.7E-02100nF
1.7E-07 1.7E-06 1.7E-05 1.7E-04 1.7E-031uF
1.7E-08 1.7E-07 1.7E-06 1.7E-05 1.7E-0410uF
1.7E-09 1.7E-08 1.7E-07 1.7E-06 1.7E-05Cst Ioff
dVhold(V) <lleak*dthold/Chold dthold=16.67ms Chold=CLC+Cst CLC=εLCε0(A/d)= 3.98pF
57
Table. 5- 2 LC path various electric potential
5.3.2 Passive layer on a-IGZO film
For the chemical reaction may happen between a-IGZO film and liquid crystal.
The a-IGZO film has better protected by a passive layer to make sure the electrical properties won’t be affected by other materials. In addition, the air or the moisture will also affect the amorphous layer. Therefore, use the passive layer to protect amorphous layer can enhance its steadiness.
Fig. 5- 4 HR-TFT LC lens with passive layer on a-IGZO layer
5.3.3 Summary
As mentioned above, these two methods can improve the HR-TFT LC lens by increasing lens holding time and passive layer. Finally, we may realize these two methods to solve the issues of the HR-TFT lens. For the application on products, the
RLC (Ω—cm) 1.E+13 1E+12 1E+11 1.E+10 1.E+09 1.E+08
R
LC*C
LC(ms)
1.E+04 1.E+03 1.E+02 1.E+01 1.E+00 1.E-01V
LC(V)
5.E+00 5.E+00 4.E+00 1.E+00 8.E-07 3.E-68 CLC=12*8.85*10^-14 F/cm* 75*0.015/30 VLC(V)=V0*exp[-16.67/(RLC*CLC)]Passive layer SiO2(20nm)
58
electrode design is one of the methods to build storage capacitor into the cell.
Fig. 5- 5 HR-TFT LC lens electrode design
A’
B
B’
A
59
Reference
[1]J. Mansson, Stereovision: A model of human stereopsis, Lund Univ. Congnitive Science, Tech. Rep., 1998.
[2]E.A. Edirisinghe, J. Jiang, “Stereo image, an emerging technology”, Scuola Superiore G Reiss Romoli, L’Aquila, Italy, 2000.
[3]N. Holliman, “3D Display System,” Handbook of optoelectronics, Taylor & Francis, Oxford , 2005.
[4]L. Hill, A. Jacobs, “Invited paper: 3-D Liquid Crystal Displays and Their Applications,” Proceeding of the IEEE, Vol. 94, No. 3, pp.575-590, 2006.
[5]Joel S. Kollin, Stephen A Benton, and Mary Lou Jepsen, ‘‘Real-Time Display of 3-D Computed Holograms by Scanning the Image of an Acoustic-Optic Modulator,”
Proceeding SPIE, Vol. 1212, pp.174-178, 1990.
[6]R. V. Belfatto, W. J. Dahlke, F. Sanzone, P. Soltan, and J. A. Trias, “Laser Based 3D Volumetric Display System”, US Patent No. 5,854,613, 1998.
[7]K. Toyooka, T. Miyashita, and T. Uchida, “The 3D Display Using Field-Sequential LCD with Light Direction Controlling Back-light,” SID Symposium Digest, Vol.
32, pp.174-177, 2001.
[8]T. Sasagawa, A. Yuuki, S. Tahata, O. Murakami, and K. Oda, ‘‘Dual Directional Backlight for Stereoscopic LCD,” SID Symposium Digest, Vol. 34, pp.399-401, 2003.
[9]Y. M. Chu, K. W. Chien, H. P. D. Shieh, J.M. Chang, A. Hu, Y. C. Shiu, and V. Yang,
‘‘3-D mobile display based on dual-directional light guides with a fast-switching
60
liquid-crystal panel,” J. Soc. Inf. Display, Vol. 13, pp.875-879, 2005.
[10]K. W. Chien, H. P. D. Shieh, "Time-multiplexed three-dimensional displays based on directional backlights with fast-switching liquid-crystal displays," Appl. Opt., Vol. 45, pp.3106-3110, 2006.
[11]L. Lipton, M. Feldman, and S. Corporation, ‘‘New autostereoscopic display technology: the SynthaGram,” Proceeding SPIE, Vol. 4660, pp.229-235, 2002.
[12]G. J. Woodgate, J. Harrold, A. M. S. Jacobs, and D. Ezra, “Flat panel autostereoscopic displays-characterization and enhancement,” Proceeding SPIE, Vol. 3957, pp.153-164, 2000.
[13]D. Takemori, K. Kanatani, S. Kishimoto, S.Yoshii, and H. Kanayama,
‘‘3-D display with large double lenticular lens screens,” SID Symposium Digest, pp.55-58, 1995.
[14]H. Morishima, H. Nose, N. Taniguchi, K. Inogucchi, and S. Matsumura, “Rear cross lenticular 3D display without eyeglasses,” Proceeding SPIE, Vol. 3295, pp.193-202,1998.
[15]C. van Berkel, J. Clarke, “Characteisation and optimization of 3D-LCD module design,” Proceeding SPIE, Vol.3012, pp.179-187, 1997.
[16]J. Y. Son, B. Javidi, “Three-dimensional image methods based on multiview images,” IEEE/OSA Jol. of Display Technology, Vol.1, pp.125-140, 2005.
[17]H. Isono, Japanese Pat. Appln.JP03-119889, 1991.
[18]M. G. H. Hiddink, S. T. de Zwart, O. H. Willemsen, and T. Dekker, ““Locally Switchable 3D Displays,” SID Symposium Digest 37, pp.1142-1145, 2006.
[19]H. K. Hong, S. M. Jung, B. J. Lee, H. J. Im, and H. H. Shin, “Autostereoscopic
61
2D/3D switching display using electric-field-driven LC lens (ELC Lens),” SID Symposium Digest, Vol. 39, pp. 348-351, 2008.
[20]G. J. Woodgate, J. Harrold, “A new architecture for high resolution autostereoscopic 2D/3D displays using free-standing liquid crystal microlenses,”
SID Symposium Digest, Vol. 36, pp.378-381, 2005.
[21]G. J. Woodgate, J. Harrold, and O. Limited, “Key design issues for autostereoscopic 2D/3D displays,” Jol. of Display Technology, Vol. 14, pp.421-426, 2006.
[22]A. Takagi, T. Saishu, M. Kashiwagi, K. Taira, and Y. Hirayama, “Autostereoscopic Partial 2-D/3-D Switchable Display Using Liquid-Crystal Gradient Index Lens,”
SID Symposium Digest, Vol. 41, pp. 436-439, 2010.
[23]W. L. IJzerman, S. T. de Zwart, and T. Dekker, “Design of 2D/3D Switchable Displays,” SID Symposium Digest 36, pp.98-101, 2005.
[24]S. T. Kowel, D. S. Cleverly and P. G. Kornreich, “Focusing by electrical modulation of refraction in a liquid crystal cell,” Appl. Opt., Vol. 23, No. 2, pp.278-289, 1984.
[25]S. Sato, “Liquid-Crystal-Lens-Cell with Variable Focal Length,” Jpn. J. Appl.
Phys., Vol.18, pp.1679-1684, 1979.
[26]H. Ren, Y. H. Fan, S. Gauza, and S. T. Wu, “Tunable-Focus Cylindrical Liquid Crystal Lens,” Jpn. J. Appl. Phys., Vol.43, pp.652-653, 2004.
[27]E. Hecht, Optics , 4th edition, Wesley, New York, 2002.
[28]L. W. Liu, Y. C. Tsai, P. T. Liu, and H. P. D. Shieh, “Integration of surface state and geometry effects on high performance amorphous IGZO thin-film transistors,” SID Symposium Digest, Vol. 42, pp.1162-1165, 2011.
62
[29]L. Y. Liao, P. Y. Shieh, and Y. P. Huang, “Marginal Electrode with Over-drive Method for Fast Response Liquid Crystal Lens Applications,’’ SID Symposium Digest, Vol. 41, pp.1766-1769, 2009.
[30]Y. P. Huang, C. W. Chen, and T. C. Shen, “ High Resolution Autostereoscopic 3D Display with Scanning Multi-Electrode Driving Liquid Crystal Lens,” SID Symposium Digest 38, pp.336-339, 2009.
[31]L. Y. Liao, P. Y. Shieh, and Y. P. Huang, “Marginal electrodes with over-drive method for fast response liquid crystal lens applications,” SID Symposium Digest, Vol. 41, pp.1766-1769, 2010.
[32]P. C. Chen, C. W. Chen, Y. P. Huang, and J. J. Li, “Dual directional overdriving method for fast response LC-lenses on autostereoscopic 3D display,” SID Symposium Digest, Vol. 42, pp. 17-20, 2011.
[33]K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono,
“Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors,” Nature, Vol. 432, pp. 488-492, 2004.
[34]T. Kamiya, H. Hosono, “Material characteristics and applications of transparent amorphous oxide semiconductors,” NPG Asia Materials, Vol. 2, pp.15-22, 2010.
[35]N. Xu, S. Deng, J. Chen, J. She, H. P. D. Shieh, P. T. Liu, and Y. P.
Huang, “Electrical and Photosensitive Characteristics of a-IGZO TFTs Related to Oxygen Vacancy’’, IEEE Trans Electron Dev, Vol. 58, pp. 1121-1126, 2011.
[36]S. Y. Dai, Design and operation of TFT-LCD panels, 1st edition, Wunan, Taipei, 2008.