導入G7製程實現ISO 12647-2平版印刷標準規範之研究

Study of Introducing G7 Method to Comply ISO 12647-2 Offset Printing Standard

林威辰(Wei-Chen Lin) ； 馬立懿(Li-Yi Ma)

《中華印刷科技年報》 2012 (2012/06) Pp. 87-108

https://doi.org/10.30153/JCAGST.201206.0007

摘要

由於許多國外企業在選擇印刷廠時會優先考量具有國際色彩認證之印刷廠商，因此如ISO等商業印刷認證將是台灣印刷廠認證之趨勢。然而ISO 12647-2中所規範油墨與紙張並非台灣地區常規使用之本土或日本系統耗材，及日常操作環境條件等不同，是否會造成實現上困難。G7為架構於ISO 12647-2基礎下所創建之印刷色彩控制方式，此製程起源於美國之General Requirements for Applications in Commercial Offset Lithography（GRACol）。G7製程以除了以色度取代傳統之濃度控製外，使用Neutral Print Density Curve（NPDC）取代傳統之TVI來針對中性灰視覺匹配而對四色版階調進行調整，對印刷品之色彩品質做有效之控制。隨著IDEAlliance在全球不斷推廣G7製程，此製程已被全球印刷業廣泛應用。因此本研究目的在釐清台灣地區印刷廠，若以慣用耗材導入G7製程下是否能符合ISO 12647-2之規範。本研究採用實驗法，印刷條件為：Kodak Magnus 800 Quantum製版機、Komori Lithrone S40印刷機、永豐餘150 g/m2特級銅版紙、大鵬羅莎芙爾綠彩大豆油墨，過程中皆依照印刷廠平日操作環境下進行印製。以傳統應用滿版濃度（Solid Ink Density, SID）控墨製程，與再進行G7製程所定義NPDC及灰平衡色度值修正等兩種製程分別印製樣張。將此兩者製程之樣張與ISO 12647-2之規範進行比較分析。測試結果在以SID製程下所產出樣張與ISO 12647-2標準規範比較，滿版色度：青△E 3.82、洋紅△E 2.74、黃△E 4.26、黑△E1.83；疊印色：紅△E 2.79、綠△E 4.51、藍△E 1.70，符合ISO 12647-2 △E≦5標準規範；TVI值：青20%、洋紅21%、黃24%、黑22%，符合ISO 12647-2定義22%階調，寬容值±4%標準規範；中性灰的亮調反差△E 7.20、亮調範圍△E 8.38、暗調反差△E 8.56，皆超出ISO 12647-2△E≦5標準規範；導入G7製程控制下，滿版色度：青△E 2.88、洋紅△E 1.78、黃△E 3.81、黑△E 1.60；疊印色：紅△E 2.79、綠△E 3.26、藍△E 1.88；中性灰的亮調反差△E 4.75、亮調範圍△E 4.23、暗調反差△E 2.99皆符合ISO 12647-2△E≦5標準規範；TVI值：青15%、洋紅15%、黃10%、黑21%，未符合ISO 12647-2定義22%階調，寬容值±4%標準規範。然而TVI值因在G7製程中，追求中性灰視覺匹配，對四色版階調進行調整因而超出規範。本研究證實導入G7能幫助台灣地區印刷業與國際組織ISO色彩標準規範接軌。

關鍵字

G7 ； ISO 12647-2 ； 平版印刷 ； 印刷標準規範

並列摘要

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.

並列關鍵字

G7 ； ISO 12647-2 ； Offset Printing ； Printing Standard Regulation