Explore the application of offset printing ink in the printing process (1)

Offset ink is a sticky, thick paste-like body, which is physically called a plastic fluid. It does not deform or flow like an ideal fluid (water) with an external force. It must add a certain amount of external force before it begins to deform or flow.

Table 1 Comparison of ink particle area and dot area:

For another example, in the packaging and printing, often use the background color to highlight and highlight the subject, usually magenta, cyan, yellow and other colors, these need to be deployed, which requires the understanding of the color properties of the ink in order to be handy To obtain the desired color, the following points should be noted:

1. Ink color matching

The color matching of the ink is a subtractive effect, and the color of the mix is ​​getting darker and darker. Therefore, the color should be used as little as possible. Normally, the two colors are used to adjust the tone, and the third color is used as the micro ink. Adjust to achieve the desired color. (See Table 2 )

  Table 2 describes the color properties of three primary colors in Shanghai:

2. Dilution of ink

When the color is lighter, it is darker with the ink of the transparent ink, but it is not dark on the white paper, but it is brighter with the white ink, but with the pink color. It is required that the light color is not pink and bright, and some people often add a small amount of white ink when using a large amount of transparent diluting ink. Although the brighter requirements are achieved in the color tone, the white ink makes the ink with poor lightfastness more fading. The shortcomings must be noted. Therefore, it is best not to add white ink when paper with good whiteness is light, and paper with poor whiteness is another matter.

3. Tenderness

When adjusting the flesh color, some people often use gold and red ink to dilute the color, although the color is good, but the red and gold dilute easily fade, it is not appropriate. Pink ink is also easy to fade after dilute. With the dark red from 05 to 06 or dark red from 05 to 09 , the color is a little darker and the fade is much less. When the yellow tone is not enough, the orange ink is slightly added, and the ink is also lightfast and does not fade easily. Light yellow and lake blue should be diluted with sky blue ink, do not use medium blue or dark blue, because it is easy to fade. Green ink and Qinglian ink have two kinds of poor light resistance, and they should be light-fast when using light colors, otherwise they will easily fade. The yellow ink is now less lightfast than the sky blue and green ink. Therefore, when adjusting the color, consider that the yellow color will fade in the future, and the printed matter that needs to be laminated and displayed on the display window should be noticed. In recent years, people have added appropriate amounts of antioxidants to fugitive inks, and excessive amounts directly affect the drying of oxidized conjunctivae during printing.

4. The issue of transparency

When using aluminum foil, aluminum foil, or gold or silver cardboard, this is a key consideration when printing on the background or pattern. For example, the effects of opaque yellow ink and clear ink on the above materials are completely different. Many factories often print a layer of transparent yellow ink on them, and the metallic luster can be reflected through the yellow ink layer to become a golden color. This is usually achieved by adding an appropriate amount of bright paste to the ink. Note: 1 Insufficient transparency of the ink will be very bad; 2 varnish or thinner opaque opaque white, adjust the ink effect will be the same as above.

Therefore, the use of transparent high pink or magenta, sky blue, green ink background color, so that aluminum foil or gold, silver cardboard can show very beautiful and bright colors, sometimes with white ink base, it is completely covered with aluminum foil The metallic luster of paper or gold or silver paper is then printed as if printed on white paper.

5. Fineness control issues

The fineness of the offset ink is generally controlled below 15 microns, while the thickness of the PS plate is generally 7 microns to 10 microns. However, under the printing pressure and the substrate tension, the ink force of the ink is controlled at 0.05 . The ink film is about 7.5 microns. Fineness in Table 1, as listed in Table 1 in the line 1250 to a point 15 m area than the area of the ink feed particles 6 times, 4 to 23 times more points is large. What's more, most of the ink particles are much smaller than 15 micron, so the qualified factory ink will not affect the print quality due to fineness problems. On the other hand, when the ink is regulated, especially when additives are added, such as corn starch, the problems of printing quality are caused by the fact that the particles are dispersed due to the dispersion of the micelles.

However, except that the ink is thickened due to the accumulation of particles for a long time, or improper storage, the crust on the surface of the ink is mixed in. In addition, most of the paper is deinked and mixed into the ink to cause ink thickening.