Chapter 4 Result & Discussion
4.1.1 Contact angle of BM glass chemical surface treatment
Use chemical surface treatment to increase contact angle of color ink droplet. Fig. 4.3 shows the contact angle of red ink drop on blank BM and glass
(a) (b)
Fig. 4.3 Contact angle of red ink drop on blank BM and glass (a) blank BM (b)blank glass
Fig. 4.4 shows the contact angles of red ink drops on chemical treatment BM and glass. Contact angles increase after BM and glass chemical treatment as shown in Fig. 4.3 and Fig. 4.4. The contact angle increases obviously for red ink in chemical 1 treatment case.
In order to prevent overflowing, chemical 1 treatment for large contact angle increasing would better than chemical 2 treatment.
C/C/AA 1122oo C/C/AA 1177oo
Fig. 4.4 Contact angles of red ink drops on (a) chemical1 treated BM (b) chemical1 treated glass(c) chemical2 treated BM (d) chemical2 treated glass
The contact angles of red ink drops on chemical treated surface are increased. The effect of surface treatment to other inks will be discussed next. Fig. 4.5 shows the contact angle of green ink drop on blank BM and glass.
(a) (b)
Fig. 4.5 Contact angle of green ink drop on blank BM and glass (a) blank BM (b)blank glass
Fig. 4.6 shows the contact angles of green ink drops on chemical treatment BM and glass. Contact angles increase after BM and glass chemical treatment as shown in Fig. 4.5
C
C//AA 5522oo CC//AA 4411oo
C/A 30o C/C/AA 2244oo
(a) (b)
(c) (d)
CC//AA 1144oo CC//AA 1166oo
case. In order to prevent overflowing, chemical 1 treatment for large contact angle increasing would better than chemical 2 treatment.
Fig. 4.6 Contact angles of green ink drops on (a) chemical1 treated BM (b) chemical1 treated glass(c) chemical2 treated BM (d) chemical2 treated glass
The contact angles of red ink drops on chemical treated surface are increased. The effect of surface treatment to blue inks will be discussed next. Fig. 4.7 shows the contact angle of blue ink drop on blank BM and glass.
(a) (b)
Fig. 4.7 Contact angle of blue ink drop on blank BM and glass (a) blank BM (b)blank glass
Fig. 4.8 shows the contact angles of blue ink drops on chemical treatment BM and C
C//AA 5544oo
C
C//AA 3344oo
CC//AA 2288oo
C/C/AA 2299o o
(a) (b)
(c) (d)
CC//AA 77oo C/C/AA 1166oo
glass. Contact angles increase after BM and glass chemical treatment as shown in Fig. 4.7 and Fig. 4.8. The contact angle increases obviously for blue ink in chemical 1 treatment case. In order to prevent overflowing, chemical 1 treatment for large contact angle increasing would better than chemical 2 treatment.
Fig. 4.8 Contact angles of blue ink drops on (a) chemical1 treated BM (b) chemical1 treated glass(c) chemical2 treated BM (d) chemical2 treated glass
Contact angles increase after BM and glass chemical treatment. The contact angle increases obviously in chemical 1 treatment case for red, green, and blue ink. Chemical 1 treatment for large contact angle increasing would better than chemical 2 treatment. Contact angle increases both BM and glass side after chemical treatment. In ink-jet printing color filter application, increasing contact angle of ink on BM without on glass would be a best situation to prevent overflowing but not to influence color film uniformity and color properties.
C/A 39o
C/C/AA 4400oo
C/C/AA 3355oo
C/A 32o
(a) (b)
(c) (d)
Use CFx plasma surface treatment to increase contact angle of color ink droplet. The power of plasma is 400w, gas flowing rate is 300 sccm, and treatment time is 5 seconds. Fig.
4.9 shows the contact angles of red ink drops on plasma treatment BM and glass. For red ink, the contact angle of plasma treatment BM side increases as shown in Fig. 4.3 and Fig.
4.9. Plasma treatment is not so effective to glass side that contact angle of glass side is not increasing obviously.
(a) (b)
Fig. 4.9 Red ink drops on CFx plasma treatment (a) BM side (b) and glass side.
Fig. 4.10 shows the contact angles of green ink drops on plasma treatment BM and glass. For green ink, the contact angle of plasma treatment BM side increases as shown in Fig. 4.5 and Fig. 4.10. Plasma treatment is not so effective to glass side that contact angle of glass side is not increasing obviously.
(a) (b)
Fig. 4.10 Green ink drops on plasma treatment (a) BM side (b) and glass side.
Fig. 4.11 shows the contact angles of blue ink drops on plasma treatment BM and CC//AA 2277oo C/C/AA 1155oo
CC//AA 3300o o CC//AA 1155o o
glass. For blue ink, the contact angle of plasma treatment BM side increases as shown in Fig.
4.7 and Fig. 4.11. Plasma treatment is not so effective to glass side that contact angle of glass side is not increasing obviously.
(a) (b)
Fig. 4.11 Blue ink drops on plasma treatment (a) BM side (b) and glass side.
Table. 4.1 Contact angle of color inks on BM and glass without
treatment
Chemical I Chemical II CFx Plasma
BM (o)
Contact angles increase after plasma treatment for BM side. Contrast to chemical treatment, plasma treatment is not so effective for BM. Different treatment time will cause different hydrophobic effect.
C/C/AA 2255o o C/C/AA 1155oo
side effect of over etching was inevitable. To obtain an optimized condition, the plasma treatment was done experimentally between 10 to 50 seconds. Fig. 12 shows that the height of BM decreases with the treatment time increasing.
Fig. 4.12 Height of BM with the treatment time increasing from 0 to 50 seconds.
Height of BM decreases to 80% with treatment time increasing to 30 seconds. To prevent further damage on BM while keeping good hydrophobic condition, CF4 plasma treatment time should be limited within 30 seconds.
Fig. 4.13 shows the contact angles of red ink drops on plasma treatment BM and glass by different time. The contact angle increases with treatment time increasing. Plasma treatment is not so effective to glass side that contact angle of glass side is not increasing obviously even increasing treatment time.
Fig. 4.13 Contact angles of red ink drops on different time plasma treatment BM (a1) 10s (b1) 20s (c1) 30s and glass (a2) 10s (b2) 20s (c2) 30s.
4.1.3 Discussion of surface energy
The adhesion energy, Wa, is the energy dissociating from the original surface of two different kinds of material (for area 1cm2) and forming a new surface. Wc is the cohesion energy R.
Wa=γS+γL-γLS, Wc(L)=2γL
γS and γL are surface tensions of solid and liquid respectively. γLS is the interfacial tension between solid and liquid.
From Young’s equation:
γLcosθ=γS-γSL
where θ is contact angle. Rewrite Young’s equation and adhesion energy:
Wa=γL(1+cosθ)
As a result, the surface energy depends on the surface tension and contact angle. The contact angle was greatly increased after chemical or plasma treatment, therefore, the surface energy was greatly reduced.
4.2 Printed R G B single color film
Using Litrex ink-jet printing system print red, green, and blue single color films before printing three color films on same BM.
Use dip coating for BM glass as a chemical surface treatment. Fig. 4.14 shows the drop on dip coating surface treatment BM glass. The color ink is not wetting to form color film after dip coating chemical surface treatment. Chemical treatment by dip coating is not suitable in ink-jet printing color filter process. For this reason the printed BM is without any treatment in next sessions.
Fig. 4.14 Drops on chemical treated BM by dip coating
4.2.1 Printed Red single color film
Fig. 4.15 shows the printed red color film observed under POM (polarization optical microscope). There are 7 drops jetting into the bank. The profile of red color film is shown in Fig. 4.16. Thickness of color film is about 0.18 um
Fig. 4.15 The printed red color film observed under POM
0 100 200 300 400 500 600
Fig. 4.16 The profile of red color film and the thickness of color film are about 0.18 um measuring by α-step
Use spectrometer to observe the UV-visible spectrum of single color film. Fig. 4.17
300 350 400 450 500 550 600 650 700 750 75
80 85 90 95 100 105 110
Transmittance
wave length
Red
Fig. 4.17 UV-visible spectrum of single red color film for film thickness 0.18 um
In order to increase the thickness of color film, printing process is repeated for many times. Every time jetting 6 drops into the bank for 2 um thickness color film. Fig. 18 shows different printing times of color film thickness
(a) (b)
Fig. 18 Different printing times of color film thickness (a) film profile (b) OM picture
In Fig. 18, the color film is formed as a mountain shape not to be a flat film we want.
The drops are not wetting on the color film printed antecedently because the solvent on drops will be absorbed by antecedently printed color film. Drops would not flow and wetted on antecedently printed color film and a mountain-like color film is formed.
4.2.2 Printed Green single color film
Fig. 4.19 shows the printed green color film observed under POM (polarization optical microscope). There are 7 drops jetting into the bank. The profile of green color film is shown in Fig. 4.20. Thickness of color film is about 0.1 um
Fig. 4.19 The printed green color film observed under POM
0 100 200 300 400 500 600
Fig. 4.20 The profile of green color film and the thickness of color film are about 0.1 um measuring by α-step
Fig. 4.21 shows the UV-visible spectrum of single red color film.
300 350 400 450 500 550 600 650 700 750
75
Fig. 4.21 UV-visible spectrum of single green color film for film thickness 0.1 um
4.2.3 Printed Blue single color film
Fig. 4.22 shows the printed blue color film observed under POM (polarization optical microscope). There are 7 drops jetting into the bank. The profile of blue color film is shown in Fig. 4.23. Thickness of color film is about 0.2 um
Fig. 4.22 The printed blue color film observed under POM
1400 1500 1600 1700 1800 1900 2000 2100
-0.2
Fig. 4.23 The profile of blue color film and the thickness of color film are about 0.2 um measuring by α-step
300 350 400 450 500 550 600 650 700 750
Fig. 4.24 UV-visible spectrum of single blue color film for film thickness 0.2 um
4.3 Printed R G B color film
In session 4.2, red, green, and blue color films are printer on the BM. Printing process of RGB color film is printing red, green, and blue color film on the same BM step by step.
No color mixing in printing process. Fig. 4.25 shows the RGB color filter observed under POM. Different times of printing process repeat for red, green, and blue color film. Red, green, and blue color films are printed by repeating 1, 4, and 5 times of printing process and every printing process jets 6 droplets into the bank.
Fig. 4.25 RGB color filter observed under POM
Fig. 26 shows the profile of RGB color films. The thickness of red, green, and blue color films are 0.18, 0.76, and 1.0 (average) um. The color uniformity of blue is bad because of mountain-like shape of blue color film.
Fig. 4.26 The profile of RGB color films
4.4 Summery
Using Litrex 70L, we can print color films on BM accurately. Color films of red, green, and blue are single printed and printed together on BM. To prevent color ink overflowing, using surface treatment would be a method.
The contact angle is increased after chemical and CFx plasma treatment. Using chemical 1 surface treatment, the contact angles of color inks increase from about 15o to about 50o on BM side and from about 15o to 40o on glass side. Effect of chemical 2 surface
0 200 400 600 800 1000 1200 1400 1600
0.0
increase from about 15o to about 30o both on BM and glass side. The chemical treatment is efficiency to both BM side and glass side. Chemical treatment for ink-jet color filter applications could not use dip coating method. The color ink is not wetting to form color film after dip coating chemical surface treatment. Using plasma surface treatment, the contact angles of color inks increase from about 15o to about 30o on BM side but plasma surface treatment seems not so efficiency to glass side that contact angle do not increase.
Increasing the plasma treatment time would increase the contact angles of color inks but also destroy the BM. After plasma treatment for 30 seconds, the height of BM decreases to 80%.
Chapter 5
Conclusion & Future work
5.1 Conclusions
Generally speaking, there is an issue for color filter printing process that color ink overflows when printing. To solve this problem, many methods of preventing ink overflowing are published and used for ink-jet printing color filter process. Here, we use surface treatment as a method to block ink overflowing and the surface treatment uses only one step process.
Use chemical coating and plasma surface treating as two kinds of surface treatment for hydrophobic treatment. Color ink would not be wetting on hydrophobic treatment thus the color ink would be blocked in subpixels without overflowing when printing.
The contact angle is increased after chemical and CFx plasma treatment. Using chemical 1 surface treatment, the contact angles of color inks increase from about 15o to about 50o on BM side and from about 15o to 40o on glass side. Effect of chemical 2 surface treatment is lower than chemical 1 surface treatment that the contact angles of color inks increase from about 15o to about 30o both on BM and glass side. The chemical treatment is efficiency to both BM side and glass side. Using plasma surface treatment, the contact angles of color inks increase from about 15o to about 30o on BM side but plasma surface treatment seems not so efficiency to glass side that contact angle do not increase. Increasing the plasma treatment time would increase the contact angles of color inks but also destroy
5.2 Future work
The color films are not flat as shown in Fig. 4.26. The color ink drops are not wetting on the color film which has been previously printed in the bank. Adjust the ink formula to solve this problem would be the next step.
Fig. 5.1 shows the ink printing on the chemical coating BM. The drop is not wetting in the bank and the color film is not formed. Dip coating process for BM is not so suitable for ink-jet printing color filter process. Use ink-jet printing process to print the chemical solution only on the BM wall, and the color ink would be wetting in the bank and blocked in subpixel without overflowing.
Reference
[1] Horng-Show K., Po-Chuan P., and T. Kawai, Appl. Phys. Lett., 88, 111908 (2006)
[2] Jee-Hong Kim, Jan P. Allebach, IEEE Transactions on Consumer Electronics, 42, 4A (1996)
[3] Chi-Jung C., Feng-Mei W., Shinn-Jen C. and Mei-Wen H., Jpn. J. Appl. Phys., 43, 6280 (2004)
[4] Duncan J. A., Proc. SPIE, 4657, 46 (2002)
[5] Chi-Jung C., Shinn-Jen C., Kuo-Chen S., Fu-Lung P., Journal of Polymer Science: Part B:
Polymer Physics, 43, 3337 (2005)
[6] Po-Chuan P., Mi C., Horng-Show K., Feng-Mei W., and Shinn-Jen C., IEICE TRANS.
ELECTRON, E89–C, 1727,(2006)
[7] Gu X., Jonathan M., Curtis P., Lone R., and Gary B., Proc. SPIE, 4669, 377 (2002) [8] Chi-Jung C., Shinn-Jen C., Feng-Mei W., Mei-Wen H., Wanda W.W. CHIU2 and Kevin
C., Jpn. J. Appl. Phys., 43, 8227 (2004)
[9] Berend-Jan de G. and Ulrich S. S., Langmuir, 20, 7789 (2004)
[10] E. Bassous, H. H. Taub and L. Kuhn, Appl. Phys. Lett., 31, 135 (1977)
[11] Yuzo I., Shinji K., Yoshimitsu A. and Yashuhiro A., Jpn. J. Appl. Phys., 39, 1490 (2000)
[12] Masamichi M., Tomoyuki K., Hideyuki O. and Atsushi Takahara, Langmuir, 21, 911 (2005)
[13] W. C. Wang, Y. Zhang, E. T. Kang and K. G. Neoh, Plasma and Polymers, 7 , 207
[14] D. V. Nicolua, T. Taguchi, H. Taniguchi, S. Yoshikawa, Colloids and Surface A, 155, 51 (1999)
[15] N. Jnagaki, S. Tasaka, T. Umehara, J. Appl. Poly. Sci.,.71, 2191 (1999)
[16] Noda K., Miura M., Sugimitsu M., National Technical Report (Matsushita Electric Industry Company), 22, 543 (1976)
[17] Heinzl J., Hertz, C. H., Advances in Electronics and Electron Physics, 65, 91 (1985) [18] L. Dong Heon, Derby B., Journal of the European Ceramic Society, 24, 1069 (2004) [19] S. Xiao-Hong, Z. Tian-Wen, G. Mao-Zu, Wang. Ya-Dong, Journal of Harbin Institute
of Technology, 9, 270 (2002)
[20] P. Alfred I.-Tsung, Proc. SPIE, 3422, 38 (1998)
[21] Zhao X., Evans, J.R.G., Edirisinghe, M.J., Song J.H., Ceramics International, 29, 887 (2003)
[22] A. Heather, A. David M. Proc. SPIE, 4019, 446 (2000)
[23] Stephany, Timothy J., Journal of Microelectromechanical Systems, 16, 351 (2007) [24] S. Dae Ho, C. Min Hee, K. June Young, J. Jin, Kirchmeyer S., Appl. Phys. Lett., 90,
053504 (2007)
[25] L. Rastislav, S. Bogdan, P. Konstantinos N., Venetsanopoulos, Anastasios N., Proc.
SPIE, 5150 III, 1642 (2003)
[26] K. Takashi, S. Takahiro, Proc. SPIE, 5301, 334 (2004)
[27] Z. Baolong, K. Hoi-Sing, H. Ho-Chi, Journal of Applied Physics, 98, 123103 (2005) [28] S. Ram W., Displays, 20, 119 (1999)
[29] L. Baozhong, H. Tianbai, D. Mengxian, S. Xibin, H. Ximin, Thin Solid Films, 303, 213 (1997)
[30] Ishikawa T., Miyai H., Yamazaki T., Seid H., Kusunose H., Yoshimoto H., IDW/AD'05, 1 ,335 (2005)
[31] Huang H.C., Zhang B.L., Kwok H.S., Cheng P.W., Chen Y.C., Digest of Technical
Papers - SID International Symposium, 36, 880 (2005)
[32] Koo H.S., Liu Y.T., Cho L.P., Chang S.J., Wu F.M., Goang D.Y., IDMC'05, p 627-628 (2005)