ISO 12647-2標準印刷品上光後色彩差異 之研究-貼亮面聚丙烯膜為例

Abstract

在印後加工製程中，上光對於顏色會產生變化，本研究探討符合標準印刷品經過貼亮面聚丙烯膜後，以統計迴歸方式分析色彩差異情形。本文提出以ISO12647-2 標準印製之ECI2002印刷測試導具樣張，製作印刷機色彩描述檔，探討與分析印刷品上光前後明度L*值區間及△E的色差大小；再透過經色彩管理校正後之噴墨列印設備，使用數位方式模擬上光之ECI2002標準測試導具樣張，再量測及建立模擬上光前後之數位樣色彩模型，分析數位樣模擬上光色彩模型L*a*b*值及△E的差異。 統計結果經迴歸分析後，顯示印刷樣上光前後色彩L*a*b*的數據，△E色差值有顯著差異；數位樣上光前後色彩L*a*b*的數據，△E色差值無顯著差異；數位樣模擬上光前後色彩L*a*b*的數據，△E色差值無顯著差異;光澤度則與數位噴墨色階呈現一個趨近常數的關係。從實驗數據可知上光結果均被油墨及噴墨影響色彩呈現，對於上光製程中，操作者要參考不同ICC色彩描述檔的色彩管理方法，方能確保印刷上光色彩後的穩定。本研究透過上光後L*a*b*數據統計分析，藉此協助印刷上光色彩管理品質，減少人為因素產生影響，降低生產過程測試耗損，透過本研究能讓上光業者能得到參考之依據。

In post-press of printing, coating process might change the color of prints. The present study aims to investiage the color differences between uncoated and coated standard prints which use Polypropylene-film for lamination. ECI2002 test chart was printed based on ISO12647-2 standard to generate ICC profiles for a conventional offset printer. The relationship between lightness (L*) and color differences are estimated. A large format inkjet printer was used for color proofing. The inkjet printer simlulated the color of the coated prints using a color management system. The color variations made by the coating process can be predited using a linear regression. The experimental results show: 1. The color of coated print is significantly different from the uncoated print using offset printer. 2. The color differences between coated and uncoated color proofs are insignificant. 3. From the L*a*b* data of the color model simulation after the coating process in the color proof, the value of △E is not significantly changed. 4. Glossiness positively correlates to the number of ink layers and dot areas for uncoating prints. But after the coating process, the glossiness converges to a constant. From these data, we know that the result of coating is affected by printing ink and inkjet techniqe. Operators need to have different color profiles for both inkjet and offset printers in color management to make the color more stable during the coating process. Based on the regression model, we can predict the color after coating more accurately so as to reduce human errors and the cost of waste papers.