Talk about newspaper printing ink

1 Newspaper Printing Ink and Environment Correspondence

In 1997, according to the review of the Ecolabelling Agency of the Japan Environment Association, the “Offset Printing Ink” was added as the eco-labeled product type No. 102. Since then, the ecology of newspaper ink has been greatly promoted. Five years later in 2002, the first time the standard was revised. Japan's Version 1.0 standard stipulates that chemical substances that are restricted in the NL Rules of the Printing Ink Industry Association should not be used, and the aromatic components in the solvents used must be less than 1%. That is, the solvents used are petroleum-based solvents that contain volatile aromatic components. Mainly. Version 2.0 is the same as Version 1.0 in that no chemicals subject to the NL rule are used, but the solvent used adds the following requirement: The aromatic component measured in accordance with JIS K2536 must not exceed 1% by volume; use vegetable oil Solvents; Petroleum solvent usage should be below 30%; VOC content should not exceed 3%, etc., intended to limit the use of petroleum-based solvents that are depleted resources, and to control the production of VOCs through high boiling point. However, the VOCs mentioned here are based on the definition of WHO.

After the above changes, it was already clear in 2005 that nearly 100% of newspaper inks in Japan were manufactured according to the Version 2.0 certification standards, and they have become eco-inks.

2 The rise of high-speed tower type multicolor rotary machines

With the formalization of additional pages and additional color pages in newspapers, a tower-type multicolor rubber machine that can print 8 pages of double-sided color newspapers was introduced at the newspaper's production technology exhibition held in 1991. It has been 14 years since. When fashion has problems such as overprinting due to fan-shaped expansion, it has now been resolved and can be proud of high register accuracy. During this period, the number of installations of tower multicolor machines has increased significantly in the wake of further colorization trends driven by social demand and so on, the decentralization of printing locations, space saving, and the upgrading of access equipment. In recent years, the increase in newspaper layout has not been significant. In general, ink shipments have increased year after year. It can be thought that this reflects the increase in color ink shipments. Tower cranes have surpassed 400 during the nine years since they were installed in 1991, especially in the last four years. According to a survey conducted by the Japan Newspaper Association in 2004, the total installed number of newspaper rubber gas turbines was approximately 2,750, which were installed at 178 printing sites; the number of tower-type multicolor rubber gas turbines was 849, accounting for approximately 30% of all newspaper rubber turbines. Up to 70% of the 124 printing locations.

The earliest ink supply devices developed were the ink pump method, the ink fountain method, and the no-key ink supply method. With the high quality of newspapers, the keyless method has been reduced. Now, digital ink pumps and ink fountains are the main methods.
On the other hand, the speed of printing has advanced to higher speeds, and ultra-high speed printing with normal speeds of 17 to 180,000 copies per hour has become possible.

The printing sequence of the high-speed tower rubber extruder is C, M, Y, Bk or Bk, C, M, Y. The following are the additional requirements for ink performance for high-speed tower multicolor rotary machines:

1) High-speed 1 on-machine stability enhancement - control of ink viscosity increases;
2 improve the ink performance - ink transfer performance, over-emulsification, ink reduction;
3-color turbidity prevention - correct wet overprinting;
4 The control of flying ink—adjustment of ink properties and discussion of resin structure.

2) High-quality 1 ink with high viscosity - improved image reproducibility;
2Durable control on the back side of double-sided printing - Maintains good ink performance in the case of ink film thinning.

3 Accelerating the Purchase of CTP and FM Screening

The CTP system for newspapers was introduced on Drupa 95. This system has been used in many areas in Europe, and the purchase in Japan has been delayed. In the following JANPS 03, CTP systems and plates that have made practical progress in several key aspects such as "speed", "print rate", and "cost" required for CTP in newspapers have been displayed in a concentrated manner. With the advantages of automation, labor saving, and high quality, we have accelerated the introduction of thermal imaging-based CTP.

The use of CTP purchases by newspapers has made it possible to use new technologies for newspaper printing. This is called FM screening. FM screening was first adopted by the Asahi Shimbun newspaper. On August 28th, 2004, the newspaper's affiliated morning newspaper adopted Creo's Staccato screening technology to formally print the "Japan's first FM FM color screen color advertisement" in its Tokyo-in-pipe factory and Kyoto factory, becoming the head of the newspaper at the time. A major topic of concern for the advertising industry. Asahi Shimbun and Oji Paper Co., Ltd. jointly developed high-white paper for FM screening, and used the same FM screening technology to produce commercial “FM Premium” and received high praise. On March 15, 2005, other newspapers also officially printed color page advertisements using AGFA's "Sublima" screening technology.

The advantages of the FM screening technology are improved image reproducibility (avoid moiré and rose spots, finer image, expanded color reproduction range), stable printing (reduced registration error), and reduced ink consumption ( The dot area decreases) and so on. The downside is that the midtone part will appear rough, and when using a rubber mill to print, it will cause problems with ink pile-up and bring about sensitive changes in ink density, etc., thus introducing a hybrid screen that combines both.

The difference between FM screening and AM screening is that FM expresses layers with the density of fine points, and the number of points on the same area rate increases. The dot expansion is proportional to the circumference of the dot, and the dot expansion of the FM screen is greatly changed. Therefore, the ink film becomes thin when using FM screen printing. In addition, since the dots are very small, the amount of ink transferred by the ink is reduced, and it is inevitably thinner. When designing an ink corresponding to an FM screen, it is of utmost importance to consider the influence of the ink film thickness on the ink.

The minimum dot diameter corresponding to the best quality that can be reproduced by newspaper printing using FM screening has not been found yet. However, compared with commercial printing, dot diameters that can be reproduced are still larger, so it can be considered that the ink film becomes thinner. The impact has diminished.

The following are ink design topics related to FM screening:

1 High Density of Ink Because the dots are small and the amount of ink transferred is reduced, it is important to ensure that the ink has a high density, but the color difference may occur.

2 Dot gain control By exploring the emulsifying properties of the ink, it controls the penetration of the ink to the non-image part dampening solution to improve the reproducibility of the small dots.

3 Improvement of emulsifying properties The thinning of the ink film due to the refinement of dot sites destroys the ink-moisture balance with the fountain solution and increases the possibility of over-emulsification. Over-emulsified inks have poor transfer properties and accumulate on the water rollers, ink rollers, and blankets, causing quality accidents.

(Translated by Yang Zhigang) Source: "Printing World"