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The hardness of the flexographic plate has an important influence on the dot gain during the printing process. In order to further study the relationship between the increase and the dot gain, we conducted related experiments to analyze the two sets of experimental proofs, which were obtained by printing with different Shore hardness. In addition, the printing pressure The number of screen lines is also used as a variable for the collection and analysis of experimental data.
(1) Experimental materials and experimental equipment
1. Beta
The experimental version of the test was made on the Apple Macintosh iMac using Freehand software and measures 400 mm x 480 mm. The following information is mainly included in the beta version.
(1) The left two columns are composed of five different screen images of different screen lines, which can reflect the gradation changes of the actual printed pattern. The first column on the left focuses on the changes in the mid-tone and shadow regions, and the pattern in the second column focuses on the change in the highlight region.
(2) The middle part is the module of 5%, 40%, 80% and 100% dot percentage when the number of screen lines is 48l/cm, because 48l/cm is the more commonly used screening value, and these four modules can be clearly It reflects the increase of the dot of the dot in the highlight area, the middle tone, the sub-dark area, and the dark adjustment area.
(3) The right side consists of five dot-screen lines with 36l/cm, 42l/cm, 48l/cm, 54l/cm, and 60l/cm. The percentage of dot points is from 1%, 3%, and 5%. ? It is composed of 18 grades of 98% and 100%. By observing these dot areas, we can easily detect the increase in dot size.
(4) The upper right part of the test version is a set of 8 sets of negative and negative lines of different widths of 0.01mm, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.10mm, 0.15mm and 0.25mm. According to the different thickness of the Yin and Yang lines, you can judge whether the exposure time is correct or not. In addition, you can check if the plate is deformed.
(5) There is also a part of the text area on the upper right side. The text area is composed of yin and yang characters. The characters are from 2pt to 3pt, 3pt, 4pt, 5pt, and 6pt. The change of the font from small to large can detect the influence of the flexographic version on the ability of text copying.
2. Plate making equipment
The manufacturing process of the flexographic plate is divided into the following steps: back exposure→front exposure→flush→dry→post-treatment (de-sticking)→post exposure. These tasks are all done on dedicated equipment. The related equipment is described as follows: 1NYLOFLEX? EXPOSUREFIV, its exposure unit consists of a set of PHILIPS140W UVA (365nm) lamps, which can provide high-quality UV light, exposure to the plate; 2HellF1200 laser engraving system; 3BASF washing system; 4BASF drying device, drying oven set to 60 °C, drying time is set to 2 hours; 5BASF post-processing unit, post-processing unit is to use short-wave radiation UVC light source (254nm) to irradiate the surface of the printing plate for a short time to remove the viscosity of the printing plate surface; 6BASF post-exposure unit.
3. Experimental plate
In this experiment, two types of digital flexographic versions of Flint Group were selected.
4. Selection of adhesive tape
During the experiment, the same type of tape was used for both plates, that is, Lohmann's standard foam tape with a hardness of 5.3 Shore hardness, which has good cushioning properties.
5. Ink
Magenta water-based ink with a viscosity of 2830s (4# Tu's cup).
6. Substrate
White coated paper having a basis weight of 70 g/m 2 and a surface roughness of 7.2 μm.
7. Anilox roller
The anilox roll cell volume and screen line number were 7.0 cm3/m2 and 320 l/cm, respectively.
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