Talking about offset printing quality and color sequence

Lithographic offset printing is the decomposition of a series of successively tuned originals into a half-tone monochromatic version, followed by halftone monochromatic printing to achieve color reproduction. Choosing the right color sequence under the guidance of the superimposed color rule can superimpose colorful and colorful prints to ensure the correct balance of printing gray. Due to the ink's transparency, hiding power, darkness and other properties, and its own defects, what color is printed before printing, what color after printing, will affect the color effect. Therefore, scientific and reasonable arrangement of the color sequence can only obtain a high-quality reproduction that is correct, soft, rich in levels and correct in color tone, and satisfies the needs of customers. Summary I have been engaged in more than ten years of professional printing teaching theory research and instructed students in printing training experience. Now I will talk about my own opinions on the relationship between lithographic offset quality and color sequence.

First, the arrangement of printing color sequence

In the multi-color printing, in the process of monochromatic printing as a unit, and sequentially overprinting and restoring originals in a certain order, the sequence of ink overprinting is called color sequential. In four-color printing, yellow, magenta, cyan, and black can be arranged in 24 different color orders.

Second, determine the principle of printing color sequence

Printing color sequence will directly affect the quality of printed products. In order to obtain a good copying effect, the following principles must be followed:

1. According to the brightness of three primary colors arranged color sequence: The brightness of the three primary colors of ink is reflected in the three primary colors of the ink on the spectrophotometric curve, the higher the reflectivity, the higher the brightness of the ink. Therefore, the brightness of the three primary inks is: yellow> cyan> magenta> black.

2. According to the transparency and hiding power of the three primary color inks, the color sequence is arranged: The transparency and hiding power of the ink depend on the difference between the refractive index of the pigment and the binder. The ink with high hiding power has a greater influence on the color after the color stacking. As the overprinting of the printing ink, the correct color cannot be displayed and the good color mixing effect cannot be achieved. Therefore, the ink with poor transparency is printed first, and the transparency is strong.

3. According to the size of the dot area arranged color sequence: In general, the small area of ​​the first printing area, a large area of ​​the post-printing.

4. According to the characteristics of the original arrangement color sequence: Each original has different characteristics, some warm, some cool. In the order of color arrangement, the predominantly warm tone is the first printing of black, and the later printing of red and yellow; the cold tone is the first printing of the red, and the latter is the printing of blue.

5. According to the different arrangement of the device color sequence: In general, the color sequence of a single-color or two-color machine is alternated between light and dark colors; the four-color printing machine generally prints dark colors first and then prints bright colors.

6. According to the nature of the paper arranged color sequence: paper smoothness, whiteness, tightness and surface strength vary, flat, tight paper first dark, bright after printing; thick, loose paper, printed bright yellow Ink, dark after printing, because the yellow ink can cover off paper and powder and other paper defects.

7. According to the drying performance of the ink arrangement color sequence: Practice has proved that the yellow ink is nearly twice as fast as the magenta ink, the magenta ink is twice as fast as the blue ink, and the black ink is the slowest. Slow drying inks should be printed first, and fast drying inks should be printed. The monochromator is glass-repellent, and it is generally printed with yellow to facilitate the rapid drying of the conjunctiva.

8. According to flat screen and field arrangement color sequence: When the replica has flat screen and field, in order to obtain good printing quality, make the plain clothes, bright and thick ink, generally flat printing network graphic, after printing the real structure.

9. According to the light and dark color array: To make the print with a certain degree of gloss and add light color, first print dark color, after printing light color.

10. The area of ​​the landscape version of the landscape product is much larger than that of the magenta version. According to the principle of the large-format color printing, the black, magenta, cyan, and yellow sequences should be adopted.

11. Text-based and black-field products generally use cyan, magenta, yellow, and black sequences, but they cannot print black text and patterns on yellow solids. Otherwise, due to the low viscosity of yellow ink and the large black viscosity, reverse printing occurs. Black or black prints are not true.

12. For a screen with a small four-color overprint area, the color registration sequence can generally use the principle of a large-format color printing after printing.

13. Gold and silver products. Since the adhesion of gold ink and silver ink is very small, the gold and silver inks should be placed on the last color as much as possible. Under normal circumstances, it is not appropriate to use three overlapping ink printings.

14. The color sequence of the printing should be consistent with the color sequence at the time of proofing, otherwise it will not be able to catch up with the effect of proofing.

The superiority of the yellow ink in the three-color printing

1. Since the yellow ink has good transparency, it is useful for the last color to inject enough white light into the upper and lower ink layers to obtain vivid and bright colors.

2. Yellow ink has a faster drying performance and has a larger printing area. The listing of yellow ink to the last color not only prevents the vitrification caused by the fast drying speed of yellow ink, but also makes use of its large printing area and the ability to quickly oxidize the conjunctiva, covering the surface of other ink layers, making Prints have a certain degree of gloss.

3. The yellow color is in the last color, which is convenient for controlling the amount of ink used in yellow, and can be adjusted at any time against the original.

4. The price of yellow ink is expensive. Arranging in the last color can save the amount of yellow ink and reduce costs.

In short, in the specific printing process, according to the quality requirements of the product, in accordance with the law of superposition color flexibility to choose the best printing color sequence, so that it prints the most ideal product.