導入G7製程實現ISO 12647-2平版印刷標準規範之研究

Abstract

Print buyers prefer printers that are certified by the international color certification organization while placing order in the international market. Therefore, receiving ISO or other several of certifications are becoming the major goal for Taiwan's printing company while seeking for the international orders. However, the printing ink and the paper regulated in ISO 12647-2 Standard are not the common materials that used in Taiwan, and the differences in daily operating environments may also impact the outcomes. G7 process is a printing color control method that based on the ISO 12647-2 Standard. This process was original from North of America's General Requirements for Applications in Commercial Offset Lithography (GRACol). Instead of traditional densitometry, G7 utilizes colorimetry for process controls. The Neutral Print Density Curve (NPDC) is used to modify gray balance instead of TVI control. With this process the color reproduction can be achieved more precisely. With IDEAlliance's constant promotion, G7 process has been widely adopted by many printing companies all over the world. The purpose of this study is to clarify whether Taiwan printing companies can meet the ISO 12647-2 Standard by adopting G7 methods while using conventional materials. The experimental research method used in this study. The experimental printing conditions are: Kodak Magnus 800 Quantum computer-to-plate machine, Komori Lithrone S40 sheet-fed offset press, 150g/m2 gloss art paper manufactured by Yuen Foong Yu, and the ROSATHAL GS-Series process inks from Dah Bang. For the first test print, the printing plates were normally made using the company standard process. The test run was to adjust the press to meet the ISO 12647-2 specification use the traditional SID control method. Based on the first press run, the NPDC defined in G7 was used to adjust gray balance. Based on G7 the curves were applied on CTP for the second test run. The whole process was under a regular operating environment in the printing plant. The printing characteristics of these two processes were compared and analyzed with the ISO 12647-2 Standard. The results showed: Based on the SID process, the solid color tone: Cyan △E 3.82, Magenta △E 2.74, Yellow △E 4.26, Black △E1.83; overprint color: Red: △E 2.79, Green: △E 4.51, Blue: △E 1.70 were all within △E≦5 regulated in the ISO12647-2 Standard. And TVI value: Cyan 20%, Magenta 21%, Yellow 24%, Black 22% were within the tone 22% and tolerance value ±4% regulated in the ISO12647-2 Standard. Neutral gray HC △E 7.20, HR △E 8.38, and SC △E 8.56 exceeded the limit of △E≦5 in the ISO 12647-2. By adopting G7 process, the solid color tone: Cyan △E 2.88, Magenta △E 1.78, Yellow △E 3.81 and Black △E 1.60, overprint color: Red △E 2.79, Green △E 3.26, Blue △E 1.88; neutral gray HC △E 4.75, HR △E 4.23, SC △E 2.99 were all within △E≦5 regulated in the ISO12647-2 Standard. And TVI value: Cyan 15%, Magenta 15%, Yellow 10%, Black 21% were not within the 22% tone and ±4% tolerance value defined in ISO12647-2 Standard. However, the TVI values exceeded the limit of the ISO regulation. It was because the G7 process pursues a visual matching in neutral gray, and gives feedbacks to CMYK color tones. Therefore, this study indicates that the adopting of G7 process can help Taiwan printing companies to be integrated with ISO and other International organizations' color standard.