Effect of Anisotropic Photo-crosslinking on Liquid Crystal Alignment with Duplicated Surface-relief-gratings†

doi:10.7503/cjcu20141141

Abstract

Abstract:

Surface-relief-gratings with further photo-crosslinkable property were prepared by softlithography using photo-sensitive polyimide containing cinnamate groups as “ink”. The effect of anisotropic photo-crosslinking on the thermos-stability of gratings and the alignment of liquid crystal(LC) on gratings was studied. The thermos-stability of the photo-cured gratings was significantly increased. No shape deformation was observed for the gratings after treated at a temperature 31 ℃ above the glass transition temperature of the un-cured polyimide. Both the un-exposed and exposed gratings induced uniform LC alignment on their surfaces. By irradiation with linear polarized UV light perpendicular to the gratings grooves, the LC alignment was enhanced. By changing the polarized direction of the UV light and controlling the depths of gratings, the LC alignment direction on the gratings was adjusted. This study result shows that the photo-crosslinkable gratings can achieve better thermo-stability, better LC alignment and adjustable aligned direction to achieve multi-domain alignment. The above research can lead to further understanding of the LC alignment mechanism.

Key words: Polyimide, Anisotropic photocrosslinkable, Liquid crystal alignment, Soft lithography, Surface-relief-grating

CLC Number:

TrendMD:

GUO Miaocai, HE Yaning, WANG Xiaogong. Effect of Anisotropic Photo-crosslinking on Liquid Crystal Alignment with Duplicated Surface-relief-gratings^†[J]. Chem. J. Chinese Universities, 2015, 36(4): 751.

Figures/Tables 7

Fig.1 Chemical structure of PI-C8O

Fig.2 Illustration of alignment layer fabrication through contact printing a. Irradiation with interfering laser beams; b. casting PDMS prepolymer against master; c. curing and peeling off PDMS stamp; d. “inked” with PI-C8O solution; e. contact printing on the ITO glass slide; f. peeling off the PDMS stamp and curing; g. UV light irradiation; h. fabricating anti-parallel assembled cell.

Fig.3 UV spectral change of the polyimide films during the course of irradiation with the UV light

Fig.4 Surface relief of the printed SRGs after various treatments ■ Without any treatment; □ 3 J/cm2 UV exposure; ▲ heat treatment; △ UV+heat treatment.

Fig.5 Optical micrographs of the LC films under POM At the dark state of region 1(A, B, C), at the bright state of region 1(A', B', C') and plots of transmitance as a function of rotating angle(A″, B″, C″). The alignment layers were without UV light exposure(A—A″) or irradiated with LPUVL with the polarization perpendicular(B—B″) parallel to the grating direction(C—C″).

Fig.6 Micrographs of the LC films under POM (A) The smooth film; (B) the gratings at dark state.The alignment layers were treated with LPUVL with its polarized direction 45° to the rolls of gratings.

Fig.7 Aligned direction of 5CB liquid crystal on gratings as a function of SRG depth

References 27

[1]	Shannon P. J., Gibbons W. M., Sun S. T., Nature,1994, 368, 532—533
[2]	Kim S. I., Ree M., Shin T. J., Jung J. C., J. Polym. Sci. Part A,1999, 37, 2909—2921
[3]	Hoogboom J., Rasing T., Rowan A. E., Nolte R. J. M., J. Mater. Chem., 2006, 16, 1305—1314
[4]	Yu H.F., Zhang M. X., Lian Y. Q., Wang X. G., Liu D. S.,Acta Polym. Sinica, 2004, (1), 22—26
	(于海峰, 张民锡, 连彦青, 王晓工, 刘德山. 高分子学报, 2004, (1), 22—26)
[5]	Guo M.C., Wang X. G.,Acta Polym. Sinica, 2008, (11), 1113—1117
	(郭妙才, 王晓工. 高分子学报, 2008,(11),1113—1117)
[6]	Wilson D., Stenzenberger H.D., Hergenrother P. M., Polyimide: Chemistry and Application, Blsckie and Sons Ltd., New York, 1990
[7]	He Y.N., Liu B., Ren H. F., Wang X. G.,Acta Polym. Sinica, 2006, (7), 908—911
	(和亚宁, 刘斌, 任鸿烽, 王晓工. 高分子学报, 2006, (7), 908—911
[8]	Kim M. H., Kim J. D., Liq. Cryst., 2000, 27, 1633—1640
[9]	Chung D. H., Fukuda T., Takanishi Y., Ishikawa K.,Matsuda H., Takezoe H., Osipov M. A., J. Appl. Phys., 2002, 92, 1841—1844
[10]	He Y.N., Ren H. F., Shi L., Wang X. G.,Acta Polym. Sinica, 2004, (4), 617—619
	(和亚宁, 任鸿烽, 石琳, 王晓工. 高分子学报, 2004, (4), 617—619
[11]	Guo M.C., He Y. N., Wang X. G.,Acta Polym. Sinica, 2013, (12), 1501—1507
	(郭妙才, 和亚宁, 王晓工. 高分子学报, 2013, (12), 1501—1507)
[12]	Schadt M., Schmitt K., Jpn. J. Appl.Phys., 1992, 31, 2155—2164
[13]	Hahm S. G., Lee T. J., Ree M., Adv. Func. Mater., 2007, 17, 1359—1370
[14]	Gu H. W., Xie P., Shen D. Y., Fu P. F., Zhang J. M., Shen Z. R., Tang Y. X., Cui L., Kong B., Wei X. F., Wu Q., Bai F. L., Zhang R. B., Adv. Mater., 2003, 15, 1355—1358
[15]	He Y.N., Liu B., Ren H. F., Wang X. G.,Acta Polym. Sinica, 2006, (7), 908—911
	(和亚宁, 刘斌, 任鸿烽, 王晓工. 高分子学报, 2006, (7), 908—911)
[16]	Kim Y. T., Hwang S., Hong J. H., Lee S. D., Appl. Phys. Lett., 2006, 89, 173506
[17]	Jager E. W. H., Smela E., Iganas O., Science,2000, 290, 1540—1545
[18]	Liu B., He Y. N., Wang X. G., Langmuir,2006, 22, 10233—10237
[19]	Xia Y. N., Whitesides G. M., Angew. Chem. Int. Ed., 1998, 37, 550—575
[20]	Huang C. Y., Hsieh C. T., Tina J. R., Optics Express,2006, 14, 9931—9938
[21]	Pan R. P., Chiu H. Y., Lin Y. F., Huang J. Y., Chinese J. Phys., 2003, 41, 177—184
[22]	Lin C. J., Hong G. T., Pan R. P., Mol. Cryst. Liq. Cryst., 2009, 512, 91—99
[23]	Lee C. R., Mo T. S., Cheng K. T., Fu T. L., Fuh A. Y. G., Appl. Phys. Lett., 2003, 83, 4285—4287
[24]	Chung D. H., Takanishi Y., Yu C. J., Lee S. D., Takezoe H., Jpn. J. Appl. Phys., 2003, 42, 1686—1689
[25]	Andrienko D., Kurioz Y., Nishikawa M., Reznikov Y., West J. L., Jpn. J. Appl. Phys., 2000, 39, 1217—1219
[26]	Jiao L., Song Y. Y., Li Y., Sun N. W., Chen C. H., Zhao X. G., Dang G. D., Chem. J. Chinese Universities,2014, 35(10), 2281—2284
	(矫龙, 宋永要, 李岩, 孙宁伟, 陈春海, 赵晓刚, 党国栋. 高等学校化学学报, 2014, 35(10), 2281—2284)
[27]	Fan H. B., Yang R. J., Chem. J. Chinese Universities,2014, 35(1), 180—185
	(范海波, 杨荣杰. 高等学校化学学报, 2014, 35(1), 180—185)