# Novel Yellow Aromatic Imine Derivative Incorporating Oxazolone Moiety for Color Resist Applications
## 3 Results and Discussion
This showed enhanced transmittance characteristics for PBMBO in comparison to the commercial yellow colorant Y138, which exhibited transmittance values of 0.71% at 435 nm and 95.1% at 530 nm [31]. In the case of image sensor applications of yellow colorants, they are added to green colorants to enhance the optical properties of green colorants. Especially when applied to small-sized image sensor pixel ranges, several important characteristics are required to minimize color interference between pixels and achieve high color purity of the pixels. Firstly, excellent transmittance characteristics are required at 435 nm and 530 nm, as mentioned earlier. Secondly, the slope of the transmittance spectrum between wavelengths corresponding to long wavelengths with near 0% transmittance in the blue region and wavelengths corresponding to short wavelengths with near 100% transmittance in the green region is important, and the steeper the slope, the better the performance [32]. Ex \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **MBIQO** & **PBMBO** \\ \hline Transmittance & 435 nm & 4.30 & 0.58 \\
[\%] & 530 nm & 99.80 & 95.90 \\ Molar extinction coefficient 1  & 1.23 \(\times\) 10\({}^{4}\) & 2.24 \(\times\) 10\({}^{4}\) \\ \multicolumn{4}{l}{[L/mol\(\cdot\)cm]} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Transmittance and molar extinction coefficient values of MBIQO and PBMBO in 1 \(\times\) 10\({}^{-4}\) M PGMEA solution. Figure 1: UV-Vis optical spectra: (**a**) absorbance spectra and (**b**) transmittance spectra of MBIQO and PBMBO in 1 \(\times\) 10\({}^{-4}\) M PGMEA solution. amining the results corresponding to the slope of the transmittance spectrum in Figure 1b, PBMBO exhibited a steeper slope in the 425 nm and 550 nm regions compared to MBIQO, confirming superior optical properties. The transmittance data of the synthesized materials in a film state are measured and presented in Figure 2 and Table 2. The film fabrication method of the yellow dye is described in the experimental section, and the transmittance values of MBIQO and PBMBO at 435 nm were 36.6% and 0.82%, respectively, while at 530 nm, they were 95.7% and 93.1%. At 435 nm, MBIQO did not meet the criterion of less than 5% transmittance, yielding unsatisfactory results; however, PBMBO exhibited excellent transmittance of less than 5%. At 530 nm, both materials exceeded the requirement of 90% transmittance. Additionally, the results regarding the slope between blue and green, as shown in Figure 2, indicated that PBMBO exhibited a very steep slope at 425 nm and 550 nm, demonstrating excellent performance. Therefore, PBMBO exhibited excellent optical properties suitable for commercialization in both solution and film states, and when applied as a yellow additive for image sensors, superior color purity can be expected. To be used as a color filter material for image sensors, the solubility of the colorant in PGMEA solvent, commonly used in the display and image sensor industries, is checked. MBIQO and PBMBO exhibited solubilities in PGMEA solvent, as summarized in Table 3, with 0.15 wt% and 0.32 wt%, respectively. The solubility of PBMBO was enhanced by 2.1 times compared to MBIQO. Compared to the reported solubility of 0.1 wt% for the commercial material yellow colorant Y138, PBMBO exhibited a 3.2-fold improvement, while MBIQO showed a similar value [31]. For MBIQO, its relatively low solubility is attributed to its planar molecular structure, which results in poor solubility due to intermolecular packing. The improved solubility of PBMBO compared to MBIQO is interpreted as resulting from the increased number of functional groups capable of effectively interacting with the solvent and the rotatable molecular structure of the (E)-4-(4-methoxybenzylidene)oxazol-5(4H)-one moiety within the molecule. It is anticipated that utilizing PBMBO with high solubility will enable the uniform preparation of solutions and the preparation of dense films during film fabrication.