Abstract: The difference in paper is one of the important factors that cause chromatic aberration. Under certain measurement conditions, the whiteness and printing color difference of different papers were measured. At the same time, the measurement data was analyzed, and the relationship between the paper color difference and the paper whiteness was studied, and the conclusion that there was no positive relationship between the paper color difference and the whiteness difference was obtained.
Keywords: paper; whiteness; color difference; printing quality
Chromatic aberration is one of the common problems in the quality of printed products. Whether it is within the same batch of products or between different batches of products, the appearance of color differences will greatly compromise the quality of the products. According to the survey, in packaging and printing companies, complaints about color aberrations account for a large proportion of customer complaints.
With the development of science and technology, people have higher and higher requirements for the quality of printed matter. In order to improve product quality, printing companies from the production equipment to the operating environment and other multi-pronged, in terms of solving color problems can be described as cost. As far as paper supply is concerned, the brands used are limited to those with excellent reputation on the market and the supply chain is very stable.
However, in the actual production process, many companies have certain problems in the use of paper. Specifically, when there is a lack of paper in the middle of printing, other brands of paper with the same grammage are often replaced by the machine. The selected paper is considered to be the closest to the original paper in terms of whiteness by visual inspection. The default premise is that the relationship between the paper color difference and the whiteness difference is a positive relationship. The author believes that this assumption premise is not only lack of theoretical basis, but no actual measurement data to testify, and the relationship between the two remains to be explored. Today's printing companies should get rid of the methods of relying on the eyes and experience in the evaluation of print quality. In order to obtain convincing results with the above problems, I spent a period of two months conducting a special survey and data collection work in a packaged EB/$1J company in Guangdong, and based on this, discussed different papers. The relationship between the color difference and the paper whiteness, and reached a conclusion.
1 Measurement method
Whiteness Tester: YQ-z-48B, D65 illuminator illumination, d/0 illumination observation geometry (ISO2469). Spectrophotometer: X-Rite 530, D65 illuminator, d/0 illumination observation geometry.
1) According to the brand name and grammage of the used paper on the work order on the machine E0$U, select 20 pieces of the same grammage of various brands of paper (including the same brand of paper printed on the machine). The whiteness value R457 of the paper was measured with a whiteness meter, taking into account the non-uniformity of the paper, a multi-point multiple measurement was used to obtain the average value.
2) The paper with good whiteness is marked as the paper to be tested, ready for printing on the machine.
3) The paper to be tested is printed together with the original printing paper without stopping the printing machine. The requirement to not stop is to eliminate the color difference caused by the print stop.
4) Take out the printed test product and place it until it is dry. Select the spot color screen block as the object to be measured, measure the Lab value of the brand block of the original brand paper with a spectrophotometer, and use this as the standard to measure the color difference of the color blocks of other brand papers. It is obtained by multiple measurements and then averaged.
5) Record the measurement results and organize the data.
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