結論與未來展望 - 摻雜不同維度奈米碳材之液晶的低頻介電特性

本研究將量測重心放在低頻介電頻譜量測技術，因低頻的電極極化主要是來自材料內部離子電荷濃度造成，量測不同維度之奈米碳材於液晶中的極化機制，並利用理論公式擬合出離子濃度，比較碳奈材對液晶之可移動離子影響。所得到重要的結果如下：

1. 比較單一奈米添加物碳 60、奈米碳管及石墨烯，在最佳濃度摻雜下於液晶中之行為，經由量測及分析後發現在向列型液晶中有著最佳吸附可移動離子之能力，同時得知石墨烯有最佳吸附離子的效果，其降低離子濃度約 33.4 %。

2. 當二元奈米碳材摻雜於液晶，與單一奈米碳材之液晶混合物比較，二元液晶混合物有加強吸附離子的能力；其中奈米碳管與石墨烯形成之二元混合物有著最佳之離子吸附效果，使離子下降約 55.2 %。

3. 當將混合碳奈材形成三元奈米碳材液晶混合物後，實驗結果發現降低離子濃度約 58 %，與最佳二元奈米碳材液晶混合物相當，以上實驗結果可知混合液晶溶液中吸附離子的關鍵在於微量碳奈材的顆粒或形狀。

4. 考慮展透原理之情況下，將濃度減少後，比較三元奈米碳材液晶混合物，

發現亦未能有效降低可移動離子且吸附離子現象更差。因此吾人臆測，

由於液晶內部含多種成分之離子雜質，碳奈米粒子在進入液晶盒後各別

針對不同種類的離子具選擇性的吸附效果，因此在減少濃度後吸附離子效果變差。

本研究在探討摻雜不同維度奈米碳材之液晶混合物時，其向列型液晶 E7 之離子濃度在各節中有所差異，如單一濃度摻雜比較（圖 4.1.3與圖 4.1.6），

單一最佳摻雜、二元摻雜以及三元摻雜下（圖 4.1.9、圖 4.2.4 與圖 4.3.3），

以及考慮展透效應時之三元摻雜下（圖 4.3.6）。其原因為，實驗中所使用的液晶在第一次開瓶後，空氣中的塵埃或是水氣進入分裝瓶中，造成在實驗期間量測到不同的數據圖。

本論文結果顯示碳的奈米粒子在液晶中有吸附離子的效果，並且由實驗結果說明了吸附離子具有選擇性的吸附。在未來的研究當中，可以試著利用不同的液晶探討吸附離子之效果，或者在不同溫度起始條件，例如達到相轉變溫度後，探討奈米碳材對於離子之抑制能力。

參考文獻

[1] S. H. Perlmutter, D. Doroski, and G. Moddel, “Degradation of liquid crystal device performance due to selective adsorption of ions,” Applied

Physics Letters 69(9), 1182–1184 (1996).

[2] C. Colpaert, B. Maximus, and A. De Meyere, “Adequate measuring

techniques for ions in liquid crystal layers,” Liquid Crystals 21(1), 133–142 (1996).

[3] W. Lee, C.-Y. Wang, and Y.-C. Shih, “Effects of carbon nanosolids on the electro-optical properties of a twisted nematic liquid-crystal host,” Applied

Physics Letters 85(4), 513–515 (2004).

[4] H. Naito, K. Yoshida, M. Okuda, and A. Sugimura, “Transient current study of ultraviolet-light-soaked states in n-pentyl-p-n cyanobiphenyl,” Japanese

Journal of Applied Physics 33(10), 5890–5891 (1994).

[5] M. R. Costa, R. A. C. Altafim, and A. P. Mammana, “Ionic impurities in nematic liquid crystal displays,” Liquid Crystals 28(12), 1779–1783 (2001).

[6] H.-Y. Chen and W. Lee, “Electro-optical characteristics of a twisted nematic liquid-crystal cell doped with carbon nanotubes in DC electric field,” Optical Review 12(3), 223–225 (2005).

[7] W. Lee, J.-S. Gau, and H.-Y. Chen, “Electro-optical properties of planar nematic cells impregnated with carbon nanosolids,” Applied Physics B:

Laser and Optics 81(2-3), 171–175 (2005).

[8] H.-Y. Chen, and W. Lee, “Supression of field screening in nematic liquid crystals by carbon nanotubes,” Applied Physics Letters 88(22), 22105-1–3 (2006).

[9] T. Nakanishi, T. Takahashi, H. Mada, and S. Satio, “Transient behavior of voltage ratio in nematic liquid crystal cells,” Japanese Journal of Applied

Physics 41(6B), 3752–3757 (2002).

[10] N. Sasaki, “Simulation of the voltage holding ratio in liquid crystal displays with a constant charge model,” Japanese Journal of Applied Physics 37(11), 6065–6070 (1998).

[11] 趙孔雙，《介電譜方法及應用》，化學工業出版社，北京，2008。

[12] P. Debye, Polar Molecules (Chemical Catalog Company, New York, (1929).

[13] Y. Shiraishi, N. Toshima, K. Maeda, H. Yoshikawa, J. Xu, and S. Kobayashi,

“Frequency modulation response of a liquid-crystal electro-optic device doped with nanoparticles,” Applied Physics Letters 81(15), 2845–2847 (2002).

[14] S. Kobayashi, T. Miyama, N. Nishida, Y. Sakai, H. Shiraki, Y. Shiraishi, and N. Toshima, “Dielectric spectroscopy of metal nanoparticle doped liquid crystal displays exhibiting frequency modulation response,” Journal

of Display Technology 2(2), 121–129 (2006).

[15] W.-T. Chen, P.-S. Chen, and C.-Y. Chao, “Effect of doped insulating nanoparticles on the electro-optical characteristics of nematic liquid

crystals,” Japanese Journal of Applied Physics 48(1), 015006-1–5 (2009).

[16] T. Zhang, C. Zhong, and J. Xu, “CdS-nanoparticle-doped liquid crystal displays showing low threshold voltage,” Japanese Journal of Applied

Physics 48(5), 055002-1–6 (2009).

[17] R. Manohar, S. P. Yadav, A. K. Srivastata, A. K. Misra, K. K. pandey, P. K.

Sharma, and A. C. Pandey, “Zinc Oxide (1% Cu) nanoparticle in nematic liquid crystal: dielectric and electro-optical study,” Japanese Journal of

Applied Physics 48(10), 101501-1–6 (2009).

[18] Y. Reznikov, O. Buchnev, O. Tereshchenko, V. Reshetnyak, A.

Glushchenko, and J. West, “Ferroelectric nematic suspension,” Applied Physics Letters 82(12), 1917–1919 (2003).

[19] F. Li, O. Buchnev, C.I. Cheon, A. Glushchenko, V. Reshetnyak, Y. Reznikov, T. J. Sluckin, and J. L. West, “Orientational coupling amplification in

ferroelectric nematic colloids,” Physics Review Letters 97(21), 147801

[21] C.-W. Lee and W.-P. Shih, “Quantification of ion trapping effect of carbon nanomaterials in liquid crystals,” Materials Letters 64(3) 466–168 (2010).

[22] B.-R Jian, C.-Y. Tang, and W. Lee, “Temperature-dependent electrical properties of dilute suspensions of carbon nanotubes in nematic liquid crystals,” Carbon 49(3), 910–914 (2011).

[23] S.-J. Hwang, S.-C. Jeng, C.-Y. Yang, C.-W. Kuo, and C.-C. Liao,

“Characteristics of nanoparticle-doped homeotropic liquid crystal device,”

Journal of Applied Physics D: Applied Physics 42(2), 025102-1–6 (2009).

[24] S.-J Hwang, S.-C. Jeng, I.-M Hiseh, “Nanoparticle-doped polyimide for controllong the pretilt angle of liquid crystals device,” Optical Express 18(16), 16507–16512 (2010).

[25] B. Kinkead and T. Hegmann, “Effect of size, capping agent, and

concentration of CdSe and CdTe quantum dots into a nematic liquid crystal on the optical and electro-optical properties of the final colloidal liquid crystal mixture,” Journal of Materials Chemistry 20(3), 448–458 (2010).

[26] L. S. Hirst, J. Kirchhoff, R. Inman, and S. Ghosh, “Quantum dot self-assembly in liquid crystal media,” Proceeding of SPIE 7618, 76180F-1–7 (2010).

[27] C.-Y. Tang, S.-M. Huang and W. Lee, “Electrical properties of nematic liquid crystals doped with anatase TiO2 nanoparticles,” Journal of Physics

D: Applied Physics 44(35) 355102-1–5 (2011).

[28] 唐振育，《添加二氧化鈦奈米粒子液晶盒之光電與電學特性》，碩士論文，中原大學奈米科技碩士學程，民 100 年 1 月。

[29] H.-H. Liu and W. Lee, “Time-varying ionic properties of a liquid-crystal cell,” Applied Physics Letters 97(2), 023510-1–3 (2010).

[30] H.-H. Liu and W. Lee, “Ionic properties of liquid crystals dispersed with carbon nanotubes and montmorillonite nanoplatelets,” Applied Physics

Letters 97(17), 173501-1–3 (2010).

[31] 劉軒宏，《摻雜不同維度奈米粒子液晶之時變介電特性》，碩士論文，

中原大學物理學系，民 99 年 7 月。

[32] M. Rahman and W. Lee, “Scientific duo of carbon nanotubes and nematic liquid crystals,” Journal of Physics D: Applied Physics 42(6), 063001-1–12 (2009).

[33] 陳惠玉，《向列型液晶盒中離子傳輸之電動力學》，博士論文，中原大學應用物理所，民 96 年 6 月。

[34] G. Barbero and A. L. Alexe-Ionescu, “Role of the diffuse layer of the ionic charge on the impedance spectroscopy of a cell of liquid-crystal cell,”

Liquid Crystals, 32(7), 943–949 (2005).

圖 2.2.1 四大類介電極化機制。

圖 2.2.2 電子極化。（依

[31]

重新繪製）

圖 2.2.3 離子極化。（依

[31]

重新繪製）

圖 2.2.5 空間電荷極化。（依

[31]

重新繪製）

10

^-1

10

⁰

10

⁴

10

⁵

10

^-2

10

^-1

10

⁰

tan 

Frequency (Hz)

Pure E7 tan

圖 2.4.1 損耗正切與頻率的關係。

K15 C₅H₁₁ CN 51%

K21 C₇H₁₅ CN 25%

M24 C₈H₁₇O CN 16%

T15 C₅H₁₁ CN 8%

圖 3.1.1 向列型液晶 E7 的分子組成結構。（依

[31]

重新繪製）

圖 3.2.1 液晶盒規格。（美相公司提供）

圖 3.3.1 實驗裝置圖。

10

^-1

10

⁰

10

⁴

10

⁵

0.00 0.05 0.10

0.6

C₆₀ concentration (wt%)

圖 4.1.1 不同濃度之 C₆₀樣品之介電 (a) 實部與 (b) 虛部比較圖。

(a)

(b)

10

^-1

10

⁰

10

⁴

10

⁵

Ion concentration (1012 cm-3 )

Concentration of C₆₀ (wt%) 2.5 2.4

2.1 2.2

2.7

3.5

0.00

10

^-1

10

⁰

10

⁴

10

⁵

0.00 0.05 0.10

0.5 0.6 0.7 0.8

GNPs concentration (wt%)



圖 4.1.4 不同濃度之 GNP 樣品之介電 (a) 實部與 (b) 虛部比較圖。

(a)

(b)

10

^-1

10

⁰

10

⁴

10

⁵

Ion con c e nt rat ion (10

cm

-3

)

2.5 2.3 2.4

2.2 2.0

10

^-1

10

⁰

10

⁴

10

⁵

10

^-1

10

⁰

10

⁴

10

⁵

Ion con ce nt rat ion (10

cm

-3

)

13.5 12.7

10.6

8.99

C₆₀

0.03 ^CNT_0.05 _GNP

0.1 E7

10

^-1

10

⁰

10

⁴

10

⁵

10

^-1

10

⁰

10

⁴

10

⁵

Ion con c e nt rat ion (10

cm

-3

)

Materials

10

^-1

10

⁰

10

⁴

10

⁵

C₆₀/CNT/GNP CNT/GNP

10

^-1

10

⁰

10

⁴

10

⁵

10

^-1

10

⁰

10

⁴

10

⁵

ternary dopant 1 ternary dopant 2

10

^-1

10

⁰

10

⁴

10

⁵

ternary dopant 1 ternary dopant 2

圖 4.3.4 三元碳材之介電 (a) 實部與 (b) 虛部比較圖。

(b) (a)

10

^-1

10

⁰

10

⁴

10

⁵

ternary dopant 1 ternary dopant 2

圖 4.3.5 三元碳材導電度與頻率關係圖。

Ion con ce nt rat ion (10

cm

-3

)

pure E7 ternary

25 22.6

13.4

表 3.1 樣品摻雜濃度表

E7 doped with a monodopant

dopant C₆₀ CNT GNP

Concentration

(wt%) 0.010.1 0.05 0.010.1

E7 doped with a binary dopant

dopant C60/CNT C60/GNP CNT/GNP Concentration

(wt%) 0.03/0.05 0.03/0.1 0.05/0.1

E7 doped with a ternary dopant

dopant C60/CNT/GNP

Concentration (wt%)

0.03/0.05/0.1 (ternary dopant 1) 0.010/0.017/0.033 (ternary dopant 2)

附錄一液晶 E7 材料特性表

Property Notation Value Units

Cleaning point

T

c 59

C

Optical anisotropy

n

0.2255 (20 C, 589 nm)

n

e 1.7472

n

o 1.5217

Dielectric anisotropy

 

14.3 (20 C, 1 kHz)



 5.2



 19.2

Bulk Resistivity 1.0 × 10¹² Ωm (20 C)

Viscosity



39 mm²s^1

(20 C)

Elastic constant

K

11 11.01 × 10^12 N (20 C)

K

33 17.01 × 10^12 N

K

33/ K11 1.54 取自大立高分子公司

附錄二碳 60 特性

附錄三多壁奈米碳管之特性

Physical property Value Units All values are for single-wall carbon nanotubes unless otherwise stated.

Average diameter 1.2–1.4 nm

Lattice: bundles of ropes of nanotubes Triangular Lattice(2D) Lattice constant 17.00 Å

附錄四石墨烯之特性

Property Typical value - Typical value - Units parallel to surface perpendicular to surface

Density 2.2 2.2 grams/cc

Carbon content >99.5 >99.5 percent Thermal conductivity 3,000 6 watts/meter Thermal expansion (CTE) 4–6 × 10⁻⁶ 0.5–1 × 10⁻⁶ m/m/deg.-K Tensile modulus 1,000 na GPa

Tensile strength 5 na GPa

Electrical conductivity 10⁷ 10² siemens/meter 取自 XG Sciences

附錄五配向劑 SE-2170 相關參數

Material PI

Example of accrual use Auto equipment Characteristic Excellent printability Solid contents (%) 8  0.4

Viscosity (cp) 215  20

Standard curing schedule 80 C/15 min

Decomposition temperature (C) in air 460

Film hardness 3 H

Visible transmission (%) at 10



m film 91 Refractive index 1.64 Volume resistivity (10 Ω cm¹⁶  ³) 3 Dielectric constant at 1 KHz 3 Dielectric loss at 1 KHz 0.003 Pretilt angle (C) 2

取自 NISSAN CHEMICAL INDUSTERIES, lTD

在文檔中摻雜不同維度奈米碳材之液晶的低頻介電特性 (頁 40-69)