Several key technologies in silk screen printing decorative painting (on)

[Abstract] According to the groping and research in the screen printing practice, several important parameters such as the quality of originals, the number of dot lines, the number of screens, the screen color and the ink suitability in the decorative painting silk screen printing process are analyzed. And related key technologies were discussed. The conclusions have certain guiding significance for screen printing production and screen printing production.

Keywords: screen printing; decorative painting; screen printing; screen mesh number; dot number

Screen printing is widely used in decorating and decorating due to its thick ink layer, strong three-dimensional effect and simple operation, especially in the printing of decorative paintings such as oil paintings, prints, watercolors, fabric wall hangings, and thorn rust. The ability to realistically reproduce originals is unmatched by other printing methods. Therefore, screen printing has become an indispensable production technique for the arts and crafts industry. However, as an art worker, the use of screen printing methods to print decorative paintings tends to emphasize aesthetic requirements, and it is easy to ignore the requirements of screen printing technology, resulting in the design of a perfect decorative painting manuscript output after the film in the screen version The difficulty of copying the original was caused by the fact that the sun did not come out or the screen was not printed. Based on the author's experience in screen printing practice, this paper analyzes and summarizes some of the more important technical parameters and problems in the decorative painting silk screen for your reference.

1 Requirements of manuscripts for screen printing decoration

Compared with plain printing and gravure printing, silk screen printing has certain limitations on the reproducibility of the graphic and graphic art. It shows that the reproduced pictorial tone levels are not rich and delicate; the clearness and fineness are not typographical. It is high, which is determined by the performance of the screen plate. For example, plain printing can clearly reproduce 3% - 5% light colors, while silk screen printing can only reproduce more than 10% color tone. For dark areas, the relative contrast K value is also smaller than plain printing. According to this situation, not all decorative painting originals can be perfectly and accurately copied by the screen printing method, but are selective. There are several principles that should be taken into account when selecting and designing silkscreen manuscripts.

1) The bright spot of the original should not be too light. If the bright spot of the manuscript contains light colors below 10%, the dot area formed by color separation is less than 10%, which exceeds the reproducibility of the screen plate, and a large number of dots will be lost during screen printing or printing. The color of this area is not reproduced, resulting in a loss of light-tone areas, as shown in Figure 1.

Therefore, when selecting a manuscript for silk screen decoration, consider the reproduction range of the screen printing plate (10% - 100%). The light tone color should not be too light, and the level should not be too much.

2) The tone level of the screen color is less appropriate. Screen printing has no advantage in expressing color levels, and is far inferior to plain printing and gravure printing. It is suitable for the reproduction of those pictures whose colors are more jumpy and consist of block colors. For manuscripts that are more refined and rich in color gradation, many finer levels will be lost when copying with the silkscreen version, which will cause the copy to be far from the original.

3) Minimize the number of originals. In color screen printing, due to the role of dual moiré (produced by the cross between the four-color version of the screen hole and the four-color version of the color separation dots) and the limitation of overlay accuracy (especially in manual overprinting), and The thick ink layer reduces the effect of subtractive color mixing in color overprinting, resulting in the color of the overlapped color in the screen printing copying being more and the poorer the reproduction quality of the original, so that in order to obtain color, gradation, clarity, etc. For a copy that is closer to the original, the number of colors should be taken into account when determining the original. The smaller the number of colors of the original, the fewer the number of fits required for printing, and the better the effect of copying with a silk screen version.

2 The number of mesh screens used for decorative painting

It is very important to choose what kind of mesh screen when decorating the screen with silk screen printing. The number of meshes is too high. The ink is not printed when printing. This makes the printing artwork incomplete; the mesh number is too low, although it is easy to print. Ink leakage, but the screen hole poor bridge, the network is also easy to lose, and the picture is not clear enough.

The commonly used screen printing inks for printing decoration paintings are mainly two kinds of ordinary color screen printing inks and foam screen printing inks. The particle diameters are about 5 μm and 50 μm, respectively. According to the relationship between the screen size of the aperture M0 and the ink particle size d, M0 ≥3d[1], the screen aperture suitable for ordinary silk screen printing ink can be calculated as: M01 ≥ 15μm; the screen aperture suitable for foam screen printing ink is: M02 ≥ 150μm. And because the screen aperture M0 and mesh mesh number MC and wire diameter D have the following relationship [1]:

That is, for ordinary screen printing inks, if the screen area of ​​213 meshes/cm is used, the mesh area ratio is only 9.3%, and the ink permeability is poor. It is proved through experimental results that the value of the mesh area ratio during printing should be greater than 30. % to get good ink permeability. From this, it can be deduced that a screen size of 124 meshes/cm or less is best used for printing with ordinary screen printing inks to obtain better ink leakage.

(to be continued)

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