## 3 Results and Discussion  
Figure 1 shows the water droplet contact angle characteristics of the naturally-dried functional coating film, as well as the functional coating film annealed in H\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\), and vacuum ambient. The contact angle of the naturally-dried film was measured to be 26.1\({}^{\circ}\). The contact angles of the functional coating film annealed in Ar, N\({}_{2}\), and O\({}_{2}\) ambient ranged from 10.5\({}^{\circ}\) to 12.1\({}^{\circ}\). The contact angle of the film annealed in the H\({}_{2}\) ambient was 16.0\({}^{\circ}\). However, the contact angle of the film annealed in the vacuum ambient was 8.6\({}^{\circ}\), indicating the most excellent hydrophilic characteristics. Figure 2 shows the anti-pollution characteristics of the naturally-dried functional coating film according to the annealing gas, as well as the functional coating film, as well as the annealing gas, as shown in Figure 2. This result is in agreement with the result of contact angle, indicating that the annealing of the functional coating film in the vacuum ambient exhibits excellent anti-pollution characteristics by dropping water. Figure 3 shows AFM images of the functional coating film measured by AFM. The AFM image shows the roughness of naturally dried functional coating film as well as the functional coating film annealed in the H\({}_{2}\) and vacuum ambient. The roughness of the naturally dried functional coating film,  
Figure 1: Contact angle of the functional coating film according to the annealing gas; (**a**) is naturally dried, (**b–f**) are annealed with H\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\), and in a vacuum, respectively. Figure 2: Anti-pollution characteristics of the functional coating film according to the annealing gas, (**a**) is naturally dried, (**b–f**) are annealed with H\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\), and in a vacuum, respectively. coating film annealed in the H\({}_{2}\), and coating film annealed in the vacuum ambient were measured to be 6.53 nm, 3.50 nm, and 1.41 nm respectively. As the roughness decreased, the contact angle of the functional coating film decreased. This result shows that the surface roughness of the film has relations with the hydrophilicity. Figure 4 shows the average light transmittance measured in a wavelength of 400 to 800 nm of the naturally-dried functional coating film, as well as the functional coating film annealed in H\({}_{2}\), N\({}_{2}\), Ar, O\({}_{2}\), and vacuum ambient. The average light transmittance of the naturally dried functional coating film was measured to be 89%, however, it was increased with annealing treatment. The average light transmittance of the film annealed in the Ar, N\({}_{2}\), and O\({}_{2}\) ambient ranged from 98.5% to 98.7%, and the average light transmittance of the film annealed in the H\({}_{2}\) ambient was measured to be 96.1%. However, the average light transmittance of the film annealed in the vacuum ambient was 99.0%, indicating the most excellent average light transmittance characteristics. The optical properties were generally improved through the annealing process. Especially, it showed that the best optical characteristics were derived from the vacuum ambient. This means that annealing of the functional coating film mainly composed of nanosilica affects the increase of the average light transmittance by decreasing the bandgap of nanosilica energy and removing the impurities of the film. If the film is annealed while gas is being injected, the impurities to be removed by the annealing may be disturbed by the gas. Therefore, it means that the average light transmittance property improves when the film is annealed in a vacuum [19; 20]. Figure 4: Average light transmittance of the functional coating film according to the annealing method and ambient. Figure 3: AFM images of functional coating film according to the annealing condition, (**a**) is naturally dried, (**b**) is annealed with H\({}_{2}\), and (**c**) is annealed in a vacuum.