## 3 Results and Discussion  
Figure 5 shows the printing patterns obtained at various off speeds for each resin. Referring to the process conditions when using glass- or Si-patterned cliches, the range of the normal printing speed to achieve fine patterns was set from 1 mm/s to 5 mm/s. At 1 mm/s, where the off-speed was slow, there was no significant change in the printing quality, irrespective of the resin used. However, as the off-speed increased to 10 mm/s and 20 mm/s, it was confirmed that a high printing quality could be obtained only when the resin with the highest surface energy was used as the cliche material. When the resin with a surface energy not significantly different from that of the blanket was used as the cliche material, the pattern off process was not effectively performed when the speed was increased. However, when PUA5 with a surface energy of 79.1 mN/m was used, which was considerably different from the surface energy of the blanket, the off process was effective at a high printing speed. Therefore, a high difference in the surface energies of the resin and blanket can enhance the printing speed. Figure 6 shows the results at a printing speed of 50 mm/s using the cliche with high surface energy. Although the speed is nearly 10 times faster than the conventional printing speed, the print quality does not show any sign of deterioration. The relationship between the maximum allowable printing speed and the surface energy difference is expressed by the graph shown in Figure 7. The larger the difference in the surface energy of the blanket and flexible cliche, the larger is the maximum allowable printing speed.  
Figure 5: Results for printed pattern with 2-μm line width in reverse offset printing: (**a**) 1 mm/s, (**b**) 10 mm/s, and (**c**) 20 mm/s printing speed using PUA1 (surface energy: 21.5 mN/m); (**d**) 1 mm/s, (**e**) 10 mm/s, and (**f**) 20 mm/s printing speed using PUA4 (surface energy: 30.5 mN/m); and (**g**) 1 mm/s, (**h**) 10 mm/s, and (**i**) 20 mm/s printing speed using PUA5 (surface energy: 79.1 mN/m).  
In addition, the printing quality varies depending on the angle between the movement direction of the roller and the pattern, which can also be explained by the relationship between the cohesion force and adhesion force of the ink and substrate. As shown in Figure 8a, if the direction of the roller is aligned with the direction of the pattern, the cliche detaches the ink easily because the amount of ink to be removed from the blanket at one time is relatively small. In addition, once separated ink has continuously encountered the pattern edge, detachment can occur easily, like crack propagation. However, if the direction of the roller is perpendicular to the direction of the pattern, it does not work well because a relatively large amount of ink should be detached from the blanket at one time. That is, in this case, the separation of the ink did not occur continuously, but the separation should be uniformly performed along a large width of the pattern edge. This angle dependency can be improved using a cliche having a high surface energy, as shown in Figure 8b. When a cliche with a surface energy of 79.1 mN/m was used, it was found that even if the direction of the pattern and the rolling were perpendicular to each other, the pattern detachment was efficiently performed and there was no significant difference in the direction of the roller.  
Figure 6: Results for the printed pattern with a 2-\(\upmu\)m line width in reverse offset printing using PUA5 resin as the cliché material with the highest surface energy (79.1 mN/m) at printing speeds ranging from 25 mm/s to 50 mm/s.  
Figure 7: Maximum allowable printing speed according to the surface energy difference between the blanket and the flexible cliché.  
no problem in printing. Therefore, it can be concluded that it is effective to use a cliche having a high surface energy to form various patterns, such as the gate line of a TFT.