Influence of Black Photo Spacer Material for TFT-LCD on Mark Reading in Exposure Process

For large size TFT-LCD displays, the black photo spacer (BPS) technology is adopted to replace the BM and PS (Photo Spacer) processes and shifted to the array substrate side in order to save the BM process and reduce panel costs. While the original BM process is the first production process, the new BPS process is located at the last process of the array. BPS exposure molding requires precise alignment using metal markers in the pre-array process to achieve fine patterns. Due to the low transmittance of BPS, it is very difficult to align the CCD by metal markers in the BPS pre-capture process. The principle of the exposure device to grasp the target is first analyzed, and then the BPS material with different transmittance is obtained by adjusting the composition of the BPS material. By exposure shaping of BPS materials with different transmittance, the minimum requirement of material transmittance during exposure alignment is studied to obtain the highest shading of BPS materials. The experimental results show that the wavelength of the NSK exposure machine alignment lamp source is located in the infrared region of 780 similar to 1 000 nm. When the transmittance of BPS material in this band is lower than 23%, the alignment fails. By using organic-inorganic mixed pigment components instead of organic black pigment components, nearly 90% transmittance can be obtained to meet the alignment requirements, and an optical density of 1.2/mu m can be obtained after curing and molding to meet the shading needs of BPS products. The optical index of BPS board produced by this method is up to standard.