Plastic intaglio printing is a common printing method. Due to good color reproducibility, realism, strong three-dimensional effect, easy to carry the finished product bag, aesthetic appearance, etc., it is widely used in various types of flexible packaging, such as food packaging, pharmaceutical packaging and other fields. In the printing process, no matter what kind of printing method is used, whether it is multi-color or monochrome printing, the most important problem encountered before printing is the preparation of ink color. No matter how bright the ink, if the operator does not understand some of the ink performance and color knowledge, the mixed ink can not achieve a satisfactory appearance and quality level. The deployment of ink colors is a crucial part. Some large-scale companies also have specialized dispensers. I have been engaged in the flexible packaging industry for many years, and now I will sort out the written opinions on the problem of the color grading process and hope to help my colleagues.
1 color matching principle
Any color is represented by the three characteristics of hue, lightness, and saturation. The above three characteristics must be considered in the color matching process. In the ink color matching process, the ink type should be selected according to the actual printing process, the ink layer thickness, and the printing substrate, and the ink itself should be considered for its luster, hue, coloring power, hiding power, and the like.
1 gloss. Luster can be measured either with the instrument or with the naked eye. It is usually observed with the naked eye during the color matching process. For special situations, it must be measured with instruments such as chromatographs. Luster is actually the size of the ability of ink printing to reflect light in the same direction after being irradiated with light. It directly affects the appearance of II printing, which is a very important indicator. At the same time, when selecting the ink, it is necessary to distinguish whether the ink itself is a bright, semi-glossy or matte type ink, and it should also be considered whether the same type of ink is used. If the printing ink is a RI (chlorinated polypropylene resin type) or surface printing (polyamide resin) ink, the same ink must be blended to avoid mixing errors and cause unnecessary losses.
2 hue. Is the basic characteristics of color, used for qualitative differences. When matching colors, the first thing to consider is whether or not the hue is the same. The detection method is usually to observe and compare by scraping.
The specific way to observe hue is:
1 On a flat glass color viewing platform, take the standard sample 1 to 2 cm away from the color pattern.
2 Take the scratch paper to flatten the glass stand, take the color ink, and use a glass crowbar to draw the sample and compare the results. (Figure 1) There are two important factors involved in the comparison of the color tone results:
1 Covering power. The degree to which the ink covers its background color, the better the hiding power, the worse the transparency. Transparency High and Low Shadow II The efficiency of ink color shifting, and the degree of influence by the printed substrate. General dark ink hiding power is lighter. Such as the blue light yellow is good, and the ink hiding power is good, but also has a close relationship with the ink itself factors, such as thickness factor, usually the white ink hiding power is related to the thickness of titanium dioxide particles, coarse particles, cover The force is not good, printing is easy to agglomerate; fine particles, good hiding power, uniform surface, smooth and delicate. The white ink generally requires a diameter of no more than 15 m, and other color inks cannot exceed 1 2 la m.
2 coloring power. A method of expressing ink density. The measurement is to take a certain amount of color ink, mixed with a certain amount of standard white ink, and then compared with the standard sample, the color strength reflects the ink mixed color level. The difference in gloss, hue, and hiding power between the ink sample and the standard sample can be compared by the color identification (scrape-stained-paper scraping test). The specific method is as follows: Put the standard ink in the upper left corner of the scratch paper and the color ink in the upper right corner. Make the scraper at a nearly perpendicular angle to the scraping paper, gently flatten the standard and color inks to be compared, and after the ink surface is dry, determine the difference in gloss between the two under a certain light source, and observe the appearance of the entire color ( figure 2). Black and color inks are generally white scraped paper, while white ink is black scraped paper. When observing the color sample, it is better to compare it with the indirect light source in the room during the daytime and it should not be exposed to direct sunlight. It is recommended to use at night observation: “Color price fluorescent tube and color temperature 5000~200.K. You can also use self-made hybrid light source: 2 blue fluorescent tubes, 3 6500K400W fluorescent tubes, 6 100W tungsten filament lamps, fixed in In a special hood, it is easy to observe color samples."
(to be continued)
