Inkjet is expected to be a promising manufacturing method for large size OLED displays. In this development, inkjet quality was focused and practical solutions were explored. The developed precise ink volume control method with improved inkjet print heads enabled uniform material deposition into pixels to the extent of 0.4% relative error in range. The achieved quality was confirmed using 3.1 inch test panel and complete uniformity of light emission was realized. The approach was applied to a large sized display to demonstrate that the improved inkjet method is scalable for fabricating large sized OLED displays in respects of both quality and productivity.