Interpretation of printing standards (extract)

Printing standards (offset printing) are common national and international standards, as well as industry standards and corporate standards. In the implementation of the standardization process, it is mainly based on international standards and national standards, with reference to industry standards. The international standard code ISO12647-2:1996, the national standard code GB\T17934.2-1999.

A careful reading of these two standards will reveal that the national standards have been formulated on the basis of international standards and have basically retained the structure and content of international standards. They have only been edited to suit Chinese standards.

The main content of the printing standard is divided into five parts, namely the scope of application, citation standards, definitions, technical requirements, printing method for the adjustment of the upper order and the added value of the tone (extended value of outlets). In addition to the five parts of the international standard, In addition, printing conditions reports have also been added. The focus of the printing companies and operators on the standards is the technical requirements and the up-level adjustment of the printed matter.

Note: The order in the tone represents the level; the tone represents the tone. The tone represents the pattern of changes in shades of light and shade in the image. Divided into bright tone, midtone, dark tone, extremely high light. The tone value is expressed in terms of density.

Density is a characteristic measure of light absorbed by an object and is a parameter used to measure the amount of light absorbed by an object, that is, the ratio of the amount of incident light to the amount of reflected light or the amount of light transmitted, which can be divided into reflection density and transmission density. The unit of density is represented by the letter D. According to the definition of density, the object absorbs 90% of the incident light, the density is 1.0D, the absorption is 99%, the density is 2.0D, and so on. In the technical requirements, stricter standards are given for the processes and materials of color separation films and prints, respectively.

1) There are altogether seven aspects of the color separation film: quality, the number of screens, the angle of the screen, the relationship between the shape of the screen and the tone value, image size error, and gray balance.

1 Quality This section mainly describes the requirements for measuring a color separation film with a densitometer and gives numerical values. Such as: D through ≤ 0.15.

2 Number of network lines For four-color printing, the number of screen lines should be between 45L/cm and 80 lines/cm. Recommended standard network cable: Roll paper printing 45 lines / cm ~ 60 lines / cm Continuous form printing 52 lines / cm ~ 60 lines / cm Commercial \ special printing 60 lines / cm ~ 80 lines / cm International Standard in the line than the country The standard is higher. In the past, the commonly used unit was line/inch, and now it is unified as line/cm. The operator needs to convert, for example, 60 lines/cm=150 lines/inch 80 lines/cm=200 lines/inch.

3 Network Line Angle This section specifies two types of network line angles. One is the non-spindle network point, that is, the circle and square network points, and the other is the spindle network point, that is, the ellipse or diamond network, no spindle network, C, M, K The angle difference is 30°, the angle difference between Y and the other color plates should be 15°, and the main color version of the screen angle should be 45° (one direction of the dot arrangement and the reference direction form the smallest included angle). The CMK angle difference of the dots with a major axis is 60°. The angle difference between Y and other color plates should be 15°, and the main color version of the screen angle should be 45° or 135°. (The angle between the axis and the image base.)

4 dot shape and tone shape shape (slightly)

5 Image size error Under the condition of stable environment, the difference between the lengths of diagonal lines of a set of color separation films or printing plates shall not exceed 0.02%. Note: This error includes the repeatability of the imagesetters or plateetters and the errors caused by film stability.

The sum of the 6th-order adjustments and the sum of the sheet-fed print-level adjustments is less than or equal to 350%. The sum of the web-print printing tone values ​​is less than or equal to 300%. Note: In the case where the sum of the tone values ​​is high, phenomena such as overprinting and back stain may occur.

7 Gray balance Gray balance refers to the unequal mixing of yellow, magenta, and blue primary inks, and the formation of gray in prints. Monochrome gray and four-color gray are not the gray balance in printing.

2) There are seven contents of the printed matter in the print section, namely the color and gloss of the substrate, the ink, the range and value of the tone reproduction, and the error in the image position. There are mainly five types of paper substrates: glossy coated paper, matte coated paper, glossy coating web, and non-coated paper (yellow, white). There are seven types of inks: yellow, magenta, cyan, red, green, blue, and black.

1 Image Copy Range When the number of screen lines is between 40 lines/cm and 70 lines/cm, 3% to 97% of dots on the color separation sheet can be completely reproduced on the printed matter.

The second-order adjustment value increases the image position error (SIO) on the print. When printing on 65 g/m2 paper in a medium-format printer, the maximum position error between any two-color printed image centers must not exceed 0.08 mm. Under the maximum position error shall not exceed 0.12mm.

3 Measure method for upper level adjustment of printed materials The measurement and control strips should be printed along with the subject content. The number of screen lines should be within the range of 52 lines/cm to 70 lines/cm. The shape of dot lines should be circular.