Chapter 4 Result & Discussion
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.
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