Determination of the quality space of inkjet printing paper
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The high-quality inkjet printing market is gradually expanding, and the amount of inkjet printers and inkjet papers is increasing. Therefore, it is important to analyze and continuously improve the quality of paper printing.
Quality factor
The quality factors associated with setting inkjet printing quality are mainly ink spots, sharpness, gray balance, gloss, density, and color gamut. Nine experimental inkjet printers were used to print on three desktop inkjet printers.
The above quality factors can be measured by the fact that the ink spots are measured on black and green patches in the field; the sharpness of the inkjet printed image can be obtained by measuring the black lines on the yellow background and the black lines on the non-image portions. .
Specific method: the above-mentioned printing area is measured twice, respectively, to obtain roughness and edge ambiguity. The sharpness can be reflected by monochrome roughness, monochrome edge blur, color roughness, and color edge blur. The gray balance can be defined by the chromaticity value of the 40% CMYK-gray print area. Solid black and green gloss values were determined at three different angles (20°, 60°, and 75°). Measure the CMYK four-color density value in the field. The color gamut is obtained by measuring the color scale, representing the color range of the paper surface, and calculating the excellent domain area.
Visual evaluation
Visual evaluation is to determine the overall visual quality through a specific group of observers. Each printer prints 3 different patterns, respectively, using pairwise comparison method (pairing comparison method is also called mutual comparison method, which is to evaluate all the evaluations. The patterns are listed together, and the pairwise comparisons are evaluated).
The surveyed papers all have high print quality, so the technical method measures lower interference factor values. The quality factors of monochrome roughness, color roughness, green ink spots and black ink spots are analyzed to determine the minimum value of the visual point. Print quality was evaluated using the ultimate method of Engeldrum (a tool for imaging system development), the absolute threshold (ie, the lowest stimulus energy that can be perceived).
The relationship between the different measured values is analyzed by the correlation coefficient (used to indicate the degree of relationship between the two sets of samples). The relationship between technical measurement and visual evaluation was analyzed by correlation coefficient, multiple regression and principal component analysis.
Important parameters
Among all the quality factors studied in this paper, the color gamut is the most important parameter. The printing effect of the color gamut is more correlated with the visual evaluation (0.67 is less than R less than 0.94). When the color gamut is combined by one or two quality factors, although the correlation between the printing effect and the visual evaluation is improved, other factors are equally important.
The correlation between monochrome roughness and color roughness and visual evaluation is good, and the monochrome roughness and color roughness value have a high correlation, so one of the factors can be used to evaluate the quality.
The correlation between color roughness and color gamut is higher. Since the main application of high-quality inkjet printing is image reproduction, measurement of bleeding phenomenon such as color roughness is more suitable as a quality factor.
Printing ink spots are common and difficult to resolve quality defects. Roughness and ink spots are not well correlated, so the ink spots are used as a third separate quality factor. It is rare to see black print spots on prints, and green print spots on most prints can be observed. Therefore, the effect of green ink spots on the quality of high quality inkjet prints is greater than that of black ink spots.
Experiment analysis
The experimental results are consistent with the results of McFadden and Donigian, and the print quality can be determined by the density of the print and the bleeding between the colors. In this paper, three important factors of color gamut and color roughness and green ink spots are determined. In summary, three quality factors (gamut, color roughness, and green ink spots) were used to determine the mass space of the inkjet paper (0.90 is less than R less than 0.97), and the resulting quality level is at least as close as the previous evaluation.