Plate and its printability test (2)

(Plates & Printability) 5. Change of Ink "Is the ink transfer and printing performance affected by its color, viscosity, and pH? Is there a difference between the inks produced by different manufacturers? The practical exploration found answers to these two ink-related questions. Three different colors of inks from three different manufacturers were used in the experiment, and each ink was for three different pH values ​​and three different types. The viscosity was tested.In this test, 3×3×3×3=81, that is to say there are altogether 81 parameters.In order to further reduce the workload, it was decided to test the ink of a single color, and GCM 139 took the test. The parameters were reduced to a range of 27 parameters that could be controlled.Ink of manufacturer #1 and manufacturer #3 was stored in 5 gallon drums, ink 1 had a pH of 9.0 and a viscosity of 23 seconds (measured using a #2 glass) ), Ink 3 had a pH of 9.1 and a viscosity of 30 seconds. Manufacturer #2 produced ink in a 1 gallon bottle with a pH of 8.6 and a viscosity of 46 seconds. During the test, we adjusted each The nine ink samples from each manufacturer were started and the parameters were set as follows: The PH value of the ink was set to 9.2, 8.8 and 8.4, correspondingly, the viscosities were 24 seconds, 21 seconds and 18 seconds respectively (#2 Zahn cup). Adjust the viscosity of the ink by adding it to each manufacturer pH stabilizers (amines) to increase the pH of each ink sample. If you want to reduce the pH of the ink, add a certain amount of water to the ink, or open the lid of the ink container to make the amine in the ink Volatilization reduces the pH of the ink, and the water's pH is 7.0, which is neutral, so water can reduce the ink's viscosity in addition to the ink's viscosity. The test was performed on the IGT F1 flexographic printability tester in conjunction with the previously used printing plates and substrates. The minimum pressure of the anilox roller was 30 N, and the minimum pressure of the embossing roller was 45 N. The printing speed of the anilox roller was maintained at At 3 m/s, the anilox roll used has an ink transfer rate of 9.0 BCM/inch 2. Then the 405 data points are used to plot the corresponding ink parameters (3 manufacturers × 9 adjustments × 5 color standard printing samples × Three times for each sample.) VI. REPORT RESULT The test results show that: when changing the inks from different manufacturers or when the viscosity and pH of the ink change, follow the yellow/green (a*) and red/blue (b* ) Hue deviation occurs in both axial directions. As predicted, brightness changes are greatest, but there is still a big difference between different manufacturers.When the ink has a pH of 9.2 and a viscosity of 24 seconds, only the ink of manufacturer #2 is closer to 1.5. ΔE error range The average color difference (ΔE) of the GCM1 39 MW standard is Ink #1 = 13.18, Ink #2 = 7.9, Ink #3 = 11.49, Seventh, the difference test of printing plates eventually includes 13 printing plates and involves The plates included in the post-processing of corrugated board.After the plate is shipped from the manufacturer, a random code is printed on the plate. After the plate is mounted on the tester, the hardness of the remaining chips is measured. Table 1 Plate hardness And Type Plate BCDEFGHIJKLM Hardness 23.53527.53029292930.529.5323324.5 Type Liquid Type Solid Type Liquid Type Liquid Type Solid Type Liquid Type Liquid Type Liquid Type Liquid Type Liquid Type  The inks of manufacturers #1 and #3 have extremely high performance Similar, so select manufacturer # 1 and manufacturer # 2 inks for testing. In addition, only three different pH/viscosity levels were tested: 1 pH 9.2, viscosity 24 seconds; 2 pH 8.8, viscosity 21 seconds; 3 pH 8.4, viscosity 18 seconds. For various ink parameter settings, various printing plates are measured by the contact angle method. Each printing plate is mounted on an IGT F1 flexographic printability tester, and the anilox roller used, printing pressure, The printing speed and substrate material are exactly the same as before. Three different viscosity and pH inks for manufacturer #1 and manufacturer #2 were tested on 13 plates, yielding a total of 390 printed samples. The color of each printed sample was measured, but due to the aperture size of the spectrophotometer used, the visually perceived difference was minimal. Therefore, it is necessary to measure the uniformity of the ink film layer. If the ink ink film is smooth and uniform, the ink-reducing coefficient is relatively low, and the coefficient is also affected by the smoothness of the substrate material. However, since the same batch of substrate material is used, the recorded value can be Reflect the performance of the printing plate. Nine, the performance of the printing plate Some printing plates have the same ink transfer performance, which means that inks with different properties are similar after printing. The printing plates A, C, D, G, H and M have the same ink transfer properties and are not affected by the ink condition. The printing plate G has the lowest ink density and the most consistent transfer performance. There is no relationship between the hardness of the plate and the transfer performance (ink-coefficient). For example, the plate G has a hardness of 29, this value is just right, and its printing characteristics are also the best. Our conclusion is that the hardness of the plate cannot be used as a good indicator of its printability! When the 390 sample data are further subdivided according to a certain relationship, the following aspects are studied: 1. If the transfer performance of the printing plate is poor, when using different manufacturer's ink or when the ink's parameter settings (PH value and viscosity ) Different print results will be different. 2. When only comparing the inks with different pH and viscosity of the two manufacturers, the printed matter printed with inks with a pH of 9.2 and a viscosity of 24 has the best consistency, except for the printing plate I. 3. As the PH value and viscosity of the ink drop, the predictability of the printed matter also decreases. 4, some plates are more affected by the ink condition. 5, the comparison between different ink manufacturers is very simple, the smaller the ink coefficient, the ink film is more smooth. 6, if you change the performance of the ink, the situation is more complicated. In the ideal case, the PH value and viscosity of the ink can be combined with each other to obtain a good printing effect. 7. The contact angles of the inks of manufacturer #1 and manufacturer #2 are measured on each plate. It seems that there is a relationship between the hardness of the plate and the contact angle, with the exception of plates C and M. X. Analysis of Substrate Materials Previously, five substrates were planned to be tested and later increased to 13 more. All printing presses, inks, and plate parameters were printed and tested at a printing pressure of 45 Newtons at a speed of 3 meters per second. Plates were selected for G, because the printing consistency of Plate G was highest in the previous tests. For each manufacturer's ink, the following settings were made: pH 8.8, viscosity 21 seconds. The number of samples obtained was 195 (13 substrate materials × 3 manufacturers × 5 printed patterns). Table 2 Substrates XIXIIXIIIXIVXVXVIXVII XVIIIXIXXXXXIXXIIXXIII White Cardboard Bleached Cardboard White Cardboard Cardboard Kraft Cardboard Kraft Cardboard White Cardboard Bleach Cardboard Kraft Cardboard White Cardboard Bleach Cardboard Kraft Cardboard Kraft Cardboard White Cardboard Cardboard Sheet Material Analysis Includes L *a*b*, ink smoothness and contact angle. Contact angles were measured with First Ten Angstroms (FTA) 125 in combination with 200 software. The FTA 125 is a dynamic video capture device that captures and prints images printed on substrate materials (every 0.5 seconds) at regular intervals. The thickness of the ink film is maintained at 1 to 2 microns. XI. Findings and Conclusions The comparison of the color difference ΔE can explain the vast majority of the differences in the materials of the substrates and the differences/differentiations of the inks. Each printed material is printed with the appropriate sample in the GCM1 sample booklet, such as the sample printed on Kraft board and the Kraft board sample in the atlas. The biggest difference has little to do with the substrate material, but it has a lot to do with ink. For example, when the ink produced by manufacturer #2 was used, there were 11 kinds of substrate materials among the 13 substrate materials with the smallest color difference (△E). With the printing material XX, the color difference value (ΔE) is minimized when the ink of manufacturer #1 is printed. On the substrate XIX, the difference between the inks of manufacturer #1 and manufacturer #2 is less than one color difference unit. On the substrate material XXI, the color difference (ΔE) of the ink of the manufacturer of #3 is the smallest, but it is worth noting that the color difference (ΔE) of the brown cardboard is greater than 15. When comparing the ink index and the ink contact angle on the substrate material, some interesting trends deserve our attention. When using the ink of manufacturer #1, 12 of the 13 substrate materials had the largest contact angles, but there were almost no significant differences in the first 6 substrates. Among the other substrate materials, the contact angle The range from high to medium and then low. When comparing the produced inks with the inks produced by manufacturers #2 and #3, it is interesting to see that the contact angles of the three materials on the sheet material XVIII are all as a result of printing with the substrate materials XVII, XVIII, and XIX. It is relatively small, but the contact angles on XVII and XIX are relatively large, but the situation of the ink-moisture coefficient is exactly the opposite. The coefficient of manufacturer #1 on substrate material XVIII is relatively small, and that of manufacturer #2 and manufacturer #3 is relatively small. It is comparatively large; while the coefficient of the manufacturer #1 on the substrate materials XVII and XIX is relatively large, the coefficient of the manufacturer #2 and the manufacturer #3 is relatively small. 12. Conclusions To accurately match the color of the print on the press, the actual ink must be pre-matched on the actual substrate material. Measuring the performance of the ink and keeping it as constant as possible is a critical and important point. It should be remembered that the industry guarantees that the color difference is controlled within 2 units, which emphasizes that the pH and viscosity of the ink should be continuously monitored and kept constant during the printing process. The setting and control of printing operations are also very important. If the pressure between the anilox roll and the printing plate or the pressure between the printing plate and the substrate material changes slightly, the color of the ink may change, resulting in a color difference of 1 unit. All kinds of plates can be printed, but not all plates can always maintain a good printing effect. When tested with a variety of performance inks, there are three types of printing plates with good printability: Plates A, G, and M, respectively. If the printer intends to use only one type of media, it is possible to select from among the above three media. On the other hand, the printer can also choose according to the specific circumstances of the graphic content of different printing jobs, and the range of selection may be greater. We now know that in the reproduction of a printing job, various variables (such as media, ink, paper, and printing pressure) should and can cooperate with each other. Therefore, testing in advance can avoid appearing in the printing process. Faults help us to recover losses. In most cases, these press failures are solved by a printer operator working one job. Prepress testing can avoid problems with press testing, saving material, reducing waste, and providing more control.