Explore the quality control of newspaper printing II

2) Printability requirements for major raw materials

The main raw materials used in newspaper printing are newsprint and ink. With the increasing popularity of color newspapers, the quality requirements for newsprint and color inks are also increasing. The following is based on "Cold-ink offset printing for newsprint" (GB/T 17934.3-2003). The regulations stipulate its printability, and commercial and semi-commercial printing will not be introduced here.

1 Newsprint

Newsprint is the most important raw material in newspaper production. The color and glossiness of newsprint are stipulated in GB/T 17934.3-2003. For details, see the national standard. In addition, according to the provisions of GB 1910-89, the main technical requirements of newsprint are quantitative (gram weight), longitudinal slit length, transverse tear, smoothness, whiteness, opacity, and dustiness of the web. See the standard for details. .

2 ink

The ink used in newspaper printing should meet the requirements of rapid solidification, bright colors and other requirements. The quality requirements for the ink are mainly in the following areas: color, coloring strength, particle thickness, fluidity, transparency, viscosity, gloss, dryness (dryness) and fixing force. In the newly issued national standard GB/T 17934.3-2003, the color of the ink has been specially formulated, please refer to it.

3 Standardization, data, and standardized management

In the production and printing of newspapers, it is necessary to strengthen the control of quality and must implement standardization, data, and standardized management, and insist on achieving a total quality management system. Each newspaper printing factory shall, in accordance with the national standards, combine the actual conditions of the production equipment, technology, and technology of the factory to work out the quality standards and corresponding data for each process and test it. Management and operation should be standardized, work according to regulations, and operate in strict accordance with operating procedures. In addition, to enable all employees to consciously participate in quality management, the only way to ensure the printing quality of the newspaper.

2 Detection and Evaluation of Newspaper Printing Quality

Testing is a necessary means to evaluate the quality of printing, and it is also an important step to evaluate whether the quality of semi-finished products meets the standards in the production process. The following describes the testing methods, testing standards and instruments, as well as the evaluation of newspaper quality.

1) Testing standards, methods and evaluation of newspaper printing quality

In GB/T 1793.4-2003, an important content is the requirements for the quantitative inspection of newspaper printing quality.

In addition, the film density, number of screen lines, network line angle, and dot shape have been introduced. In addition, the color registration error is: the diagonal length error of a set of color separation films should be less than 0.02%; the sum of tone values ​​must not be the same More than 260%, when the total tone value reaches this limit, the black tone value should not exceed 85%.

Grey Balance International recommends a combination of the following tone values, expressed as a percentage of the dot area on the color separation sheet (see Table 1 on the next page).

With different paper, ink and printing conditions, the gray balance data will be different.

In the “Detailed Rules for the Inspection of Color and Black-and-white Newspaper Printing Quality” prepared by the evaluation team of the Newspaper Committee of the China Press Association, the following inspection rules were submitted in accordance with the provisions of the national standard:

1 appearance

The layout is clean and tidy, with no obvious signs of dirt or wrinkles; the ink is uniform, the text is clear, there is no ghosting, and there are no obvious lack of pens, cuts, pastes, or bad words.

2 pictures

The picture requirements are rich in layers, moderate colors, moderate contrasts, and there are no nets in the edges of the picture. The visual effects of the color pictures are bright, not boring and dark, basically in line with the natural tone, not color cast; overprinting is accurate, minimum The error is not more than 0.3mm.

3 inscription

Headings, headings above the number one and headings with nets, the density of the field is between 0.95 and 1.20.

4 Ink

A newspaper is divided into two sides. It requires uniform ink, and the text density is 0.18. Multi-format newspapers require that each version of the ink be basically the same.

After the above four parts are quantified, the rule will be checked and evaluated by the percentage system. 92 to 93 are qualified, 93 to 94 are excellent, 94 to 95 are excellent, and 95 or more are fine articles.

2) Newspaper inspection conditions and instrumentation tools

According to the provisions of GB/T 17934.3-2003, the inspection conditions shall be in accordance with: the operating environment is neutral gray, dust-proof, clean; the operating environment temperature is 23±5°C; the relative humidity is 60+15% or 60-10%; the color print The sample light source complies with CY/T3 regulations.

Inspection instruments and tools are as follows:

Meet the requirements and have passed the qualified densitometer, the densitometer aperture should be greater than or equal to 3.00mm; meet the requirements and have been qualified qualified colorimeter, the colorimeter aperture should be greater than or equal to 3.00mm. Another 50 to 100 times reading magnifier; 10 to 15 times the magnifying glass. And meet the requirements of the monitoring and control strips, the number of measurement line strips should be 34 to 48 lines / cm, circular outlets, edge width less than or equal to 4μm, the field density greater than or equal 4.0. There is also a need for a black undercoat that has no choice of a spectral, diffuse reflectance, and a reflectance of 1.50±0.20. (Author: Kecheng En)