With the invention of conducting polymers, trend for flexible devices has extended into optoelectronics and; for example, involving the organic polymers for organic light-emitting diode (OLED) and flexible OLED (FOLED) applications, organic transistor for RFID (radio-frequency identification) applications, or even organic solar cell such as DSSC, which are still in the infancy stage. While these materials offer many attractive features, they also impose limitations and challenges such as high CTE, lower Tg, low processing temperatures, adhesive strength in multiple films stacking (with barrier, hard coat, or conductive transparent oxides), high O2 and water permeation, and device degradation.
A novel and transparent polyimide has been synthesized via a straightforward, high-yielding two-step thermal imidization method. In the thesis, the polyimide was prepared by using 4,4'-oxydiphthalic anhydride (ODPA) and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) in N,N-Dimethyl-acetamide. FTIR analysis showed that condensation reaction led to dehydrate and transform poly(amic-acid) into polyimide. The transparency of the BAPP-ODPA polyimide in the visible region was found to be 98 % when the thickness of polyimide was 80 μm because the ether linkage and bulky group destroyed benzene stacking to minimize or eliminate charge transfer and the light absorption by benzene rings.
Moreover, the BAPP-ODPA polyimide demonstrated superior thermal stability with Td at 495 ℃. The glass transition temperature of BAPP-ODPA was 230℃
primarily resulting from the flexible ether linkage and alky group in the backbone, which was a tradeoff between transmittance and mechanical rigidity. In summary, BPPA-ODPA with Tg about 230 ℃, high optical transparency, and excellent thermal stability is an excellent polymer substrate for flexible devices applications.
In the other hand, the adhesive strength between ITO and BAPP-ODPA polyimide had been investigated in order to improve the reliability of flexible devices. The surface of polyimide was modified by oxygen plasma in the different RF power and the changes of surface chemical states were characterized by XPS. The interfacial adhesive strength was determined by four-point bending system and the adhesive values shown for a large number of samples had prepared for plasma treatment in different RF power. The electric conductive of ITO and PI films measured by circuit tester were used to judge whether the crack interface occurred at the ITO/PI interface or not. According to the experimental results, the adhesion between ITO and BAPP-ODPA polyimide had improved from 3.01 to 8.7 J/m2 due to the component ratio of C-OH increased from 0 to 47.5%. The force of coordinate covalent bond was explained to help the improvement of adhesion. Because the oxygen element in C-OH bond provided a lone pair as donor to attract the metal elements in ITO structure, the interfacial adhesive strength between ITO and BAPP-ODPA polyimide had definitively improved.
In the thesis, we had successfully developed a high Tg and transparent of BAPP-ODPA polyimide. Furthermore, its adhesive strength with ITO had improved by oxygen plasma. The BAPP-ODPA polyimide had excellent thermal properties, high transparency and outstanding reliability; however, it could be applied in flexible devices such as solar cell, e-paper, display, and RFID, etc.
References
[1] C. J. Brabec, N. S. Sariciftci, and J. C. Hummelen, Adv. Funct. Mater. 11, 1 (2001).
[2] E. Abada, S. Zampolli, S. Marcoc, A. Scorzoni, B. Mazzolai, A. Juarros, D.
Gómeza, I. Elmi, G. C. Cardinali, J. M. Gómezc, F. Palacio, M. Cicioni, A.
Mondini, T. Becker, and I. Sayhan, Sensors and Actuators B. 127, 2 (2007).
[3] F. X. Qiu, Y. M. Zhou, and J. Z. Liu, Eur. Polym. J. 40, 713 (2004).
[4] P. C. Chiang and W. T. Whang, Polymer 44, 2249 (2003).
[5] I. K. Spiliopoulos and J. A. Mikroyannidis, Polymer 37, 3331 (1996).
[6] T. Yamamoto, T. Morikita, T. Maruyama, K. Kubota, and M. Katada, Macromolecules 30, 5390 (1997).
[7] T. Ade and H. Fukuro, J. Synth. Org. Chem. 49, 506 (1991).
[8] M. Asegawa, N. Nsui, Y. Hindo, and R. Okota, Photopolym. Sci. Technol. 9, 2 (1996).
[9] G. Lawton, Computer 39, 1 (2008).
[10] A. Sugimoto, H. Ochi, S. Fujimura, A. Yoshida, T. Miyadera, and M. Tsuchida, IEEE Journal of Selected Topics in Quantum Electronics 1, 10 (2004).
[11] C. C. Wu, S. D. Theiss, G. Gu, M. H. Lu, J. C. Sturm, S. Wagner, and S. R. Forrest, IEEE Electron Device Lett. 18, 12 (1997).
[12] S. E. Shaheen, C. J. Brabec, N. S. Sariciftci, Franz Padinger, T. Fromherz, and J. C.
Hummelen, Appl. Phys. Lett. 78, 6 (2001).
[13] K. Nomura, H. Hideo, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, NATURE 432, 25 (2004).
[14] Y. Li, L. W. Tan, X. T. Hao, K. S. Ong, and F. Zhu, Appl. Phys. Lett. 86, 153508 (2005).
[15] E. L. Bedia, S. Murakami, T. Kitade, and S. Kohjiya, Polymer 42, 7299 (2001).
[16] J. Si and T. Mitsuyu, Appl. Phys. Lett. 72, 762 (1998).
[17] A. Miyake, T. Yamada, H. Makino, N. Yamamoto, and T. Yamamoto, Thin Solid Films 517, 1037 (2008).
[18] H. Suzuki, T. Abe, K. Takaishi, M. Narita, and F. Hamada, J Polym Sci Part B:
Polym Phys. 38, 1 (2000).
[19] F. Wu, N. Deng, and H. Hua, Chemosphere 41, 1233 (2000).
[20] P. E. Burrows, G. L. Graff, M. E. Gross, P. M. Martin, M. K. Shi, M. Hall, E. Mast, C. Bonham, W. Bennett, and M. B. Sullivan, Display 22, 65 (2001).
[21] C. D. Sheraw, L. Zhou, J. R. Huang, D. J. Gundlach, T. N. Jackson, M. G. Kane, I.
G. Hill, M. S. Hammond, J. Campi, B. K. Greening, Appl. Phys. Lett. 80, 1088 (2002).
[22] C. J. Drury, C. M. J. Mutsaers, C. M. Hart, M. Matters, and D. M. de Leeuw, Appl.
Phys. Lett. 73, 108 (1998).
[23] G. Binnig, M. Despont, U. Drechsler, W. Häberle, M. Lutwyche, P. Vettiger, H. J.
Mamin, B. W. Chui and T. W. Kenny, Appl. Phys. Lett. 74, 1329 (1999).
[24] H. Ito, W. Oka, H. Goto, and H. Umeda, Jpn. J. Appl. Phys. 45, 4325 (2006).
[25] S. Elomari, M. D. Skibo, A. Sundarrajan, H. Richard, Compos. Sci. Technol. 58, 369 (1998).
[26] J. Xu, L. Yu, Y. Azuma, T. Fujimoto, H. Umehara, and I. Kojima, Appl. Phys. Lett.
81, 4139 (2002).
[27] G. Maier, Prog. Polym. Sci. 26, 3 (2001).
[28] R. A. Dine-Hart and W. W. Wright, Makromol. Chem. 143, 189 (1971).
[29] S. Ando, T. Matsuura, and S. Sasaki, Polym. J. 29, 69 (1997).
[30] M. Hasegawa and K. Horie, Prog. Polym. Sci. 26, 259 (2001).
[31] S. Ando, Y. Terui, Y. Aiki, and T. Ishizuka, J. Photopolym. Sci. Technol. 18, 233
(2005).
[32] W. Volksen, H. J. Cha, M. I. Sanchez, and D. Y. Yoon, React. Funct. Polym. 30, 61 (1996).
[33] T. Matsumoto and T. Kurosaki, Macromolecules, 30, 993 (1997).
[34] T. Matsumoto, Macromolecules, 32, 4933 (1999).
[35] H. Seino, A. Mochizuki, and M. Ueda, J. Polym. Sci. Part A: Polym. Chem. 37, 3584 (1999).
[36] J. Li, J. Kato, K. Kudo, and S. Shiraishi, Macromol. Chem. Phys. 201, 2289 (2000).
[37] M. Goyal, T. Inoue, M. A. Kakimoto, and Y. Imai, J. Polym. Sci. Part A: Polym.
Chem. 36, 39 (1998).
[38] H. Suzuki, T. Abe, K. Takaishi, M. Narita, and F. Hamada, J. Polym. Sci. Part A:
Polym. Chem. 38, 108 (2000).
[39] J. Yin, W. Zhang, H. J. Xu, J. H. Fang, Y. Sui, Z. Zhu, and Z. G. Wang, J. Polym.
Sci. Part A: Polym. Chem. 40, 524 (2002).
[40] C. P. Yang, S. H. Hsiao, and M. F. Hsu, J. Polym. Sci. Part A: Polym. Chem. 40, 524 (2002).
[41] D. Wolany, T. Fladung, L. Duda, J. W. Lee, T. Gantenfort, L. Wiedmann, and A.
Benninghoven, Surf. Interface Anal. 27, 609 (1999).
[42] P. N. Sanda, J. W. Bartha, J. G. Clabes, J. L. Jordan, C. Feger, B. D. Silverman, and P. S. Ho, J. Vac. Sci. Technol. A 4, 1035 (1985).
[43] R. Haight, R. C. White, B. D. Silverman, and P. S. Ho, J. Vac. Sci. Technol. A 6, 2188 (1988).
[44] Y. Nakamura, Y. Suzuki, and Y. Watanabe, Thin Solid Films 290, 367 (1996).
[45] Y. S. Lin, H. M. Liu, and H. T. Chen, J. Appl. Polym. Sci. 99, 744 (2006).
[46] K.L. Mittal, Adhesion Measurement of Films and Coatings. The Netherlands (1995).
[47] Y. S. Thio, A. S. Argon, and R. E. Cohen, Polymer, 45, 3139 (2004).
[48] I.B. Yoon, Jpn. J. Appl. Phys. 2, 849 (1974).
[49] X. Li, B. Bhushan, K. Takashima, C.W. Baek, and Y.K. Kim, Ultramicroscopy, 97, 481 (2003).
[50] A. A. Volinsky, N.R. Moody, and W. W. Gerberich, Acta Mater. 50, 441 (2002).
[51] X. Dai, Dissertation of The University of Texas at Austin, 1998.
[52] X. Li, T. Abe, and M. Esashi, Sensors and Actuators A, 87, 139 (2001) [53] F. Hasanaina and Z. Y. Wang, Polymer 49, 831 (2008)
[54] M. Lane, Ann. Rev. Mater. Res. 33, 27 (2003).
[55] G. Beamson and D. Briggs, Chichester 184 (1992).
[56] M. R. Elizalde, J. M. Sáncheza, J. M. Martínez-Esnaola, D. Pantuso, T. Scherban, B. Sun, and G. Xu, Acta Mater. 51, 4295 (2003).
[57] W. H. Lin, R. H. Vora, and T. S. Chung, J. Polym. Sci. Part B: Polym. Phys. 38, 2703 (2000).
[58] T. Arii, A. Kishi, and Y. Kobayashi, Thermochim. Acta 325, 151 (1999).
[59] H. Janseny, H. Gardeniers, M. de Boer, M. Elwenspoek, and J. Fluitman, J.
Micromech. Microeng. 6, 14 (1996).
[60] C. C. Chang, Surf. Sci. 25, 53 (1971).
[61] T. K. Lin, Dissertation of the University of Science and Technology Yunlin at Taiwan, 2003.
[62] R. W. M. Kwok, Ph. D. Dissertation: Fabrication of InP MISFET. Canada: Western University of Ontario, 1993.
[63] L. Wang, Y. Tian, H. Ding, and J. Li, Eur. Polym. J. 42, 2921 (2006).
[64] D. Wolany, T. Fladung, L. Duda, and J. W. Lee, Surf. Interface Anal. 27, 609 (1999).
[65] N. Yasui, H. Nomura, and A. Ide-Ektessabi, Thin Solid Films 447, 377 (2004).
[66] M. P. Hughey, D. J. Morris, R. F. Cook ,S. P. Bozeman , B. L. Kelly , S. L. N.
Chakravarty, D. P. Harkens , and L. C. Stearns, Eng. Fract. Mech. 71, 245 (2004).
[67] T. L. Cottrell, The Strengths of Chemical Bonds, 2nd ed. (Butterworths Scientific, London, 1958).
[68] S. Benson, J. Chem. Educ. 42, 502 (1965).