Plate and its printability test 2

Fifth, the ink changes "ink transfer and printing performance is subject to its color, viscosity and PH value of the impact?" Different manufacturers produce ink whether there is a difference? 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, there are a total of 81 parameters. In order to further reduce the workload, it was decided to test the inks of one color individually. The GCM 139 reduced the test parameters to a range of 27 parameters that could be controlled.

The inks of manufacturer #1 and manufacturer #3 were stored in 5 gallon drums. Ink 1 had a pH of 9.0 and a viscosity of 23 seconds (measured with a #2 glass). Ink 3 had a pH of 9.1 and a viscosity of 30. second. The ink produced by manufacturer #2 was held in a one-gallon bottle having a pH of 8.6 and a viscosity of 46 seconds.

During the test, we started by adjusting each of the nine ink samples from each manufacturer. The parameters were set as follows: The inks were set to pH 9.2, 8.8, and 8.4, respectively, corresponding to 24 seconds, 21 seconds, and 18 seconds ( #2 Zahn Cup). The viscosity of the ink is adjusted with water, and the pH of each ink sample is increased by adding a pH stabilizer (amine compound) produced by each manufacturer. If it is desired to lower the pH of the ink, a certain amount can be added to the ink. Water, or the lid of an open ink container, volatilizes the amine in the ink, thereby lowering the pH of the ink. In addition, the water has a pH of 7.0 and is neutral. Therefore, the water can reduce the pH of the ink in addition to the viscosity of the ink.

Next, tests were performed on the IGT F1 flexographic printability tester using these nine inks in combination with the previously used printing plates and substrates. The minimum pressure of the anilox roller is 30 Newton and the minimum pressure of the embossing roller is 45 Newton. The anilox printing speed was maintained at 3 m/s and the anilox roll used had an ink transfer rate of 9.0 BCM/inch2.

Then use the 405 data points to draw the corresponding ink parameters (3 manufacturers × 9 adjustments × 5 color standard printed samples × 3 measurements per sample).

VI. RESULT REPORT The test results show that when the inks of different manufacturers are changed or when the viscosity and pH of the ink are changed, hue occurs along both the yellow/green (a*) and red/blue (b*) axes. deviation.

As predicted, the brightness changes the most. However, there are still great differences between different vendors. When the pH of the ink was 9.2 and the viscosity was 24 seconds, only the ink of the manufacturer #2 was closer to the 1.5 ΔE error range.

The GCM1 39 MW standard average color difference (ΔE) is Ink #1 = 13.18, Ink #2 = 7.9, Ink #3 = 11.49.

Seventh, the difference test of the printing plate finally includes 13 kinds of printing plates and involve the plate that is included in the corrugated board post-processing. 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

Hardness 23.5 35 27.5 30 29 29 29 30.5 29.5 32 33 24.5
Type Liquid Type Solid Type Liquid Type Liquid Type Solid Type Liquid Type Liquid Type Liquid Type Liquid Type Liquid Type
Because the performance of the inks of manufacturer #1 and manufacturer #3 are very similar, the inks of manufacturer #1 and manufacturer #2 were selected 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 390 sample data were subdivided according to a certain relationship, the following aspects were studied:

1. If the transfer performance of the printing plate is poor, the printing results obtained when using different manufacturers' inks or when the ink's parameter settings (PH value and viscosity) are different 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 Substrate materials
White Cardboard Bleached Cardboard White Cardboard Kraft Cardboard Kraft Cardboard White Cardboard Bleach Cardboard Kraft Cardboard White Cardboard Bleach Cardboard Kraft Cardboard Kraft Cardboard White Cardboard

The analysis of the substrate material included 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 (â–³E).

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.

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