Perspective of Kodak Newspaper No-Flush Technology (Part 1)

At the IfraExpo exhibition in Amsterdam this year, the most important issue is expected to be the so-called "chemical-free" newspaper printing plates, or even "free-processing" newspaper printing plates. What meaning does this imply? CARYL HOLLAND visited the Kodak R & D Center in Windsor, Colorado, hoping to find out ...

Since the advent of computer-to-plate (CTP) technology, the development of no-process digital plates has become the general trend. This is not surprising. Who doesn't want to omit the printing process?

No-flush technology not only means less labor, and therefore lower labor costs, but also eliminates a large number of changes in the production process. In addition, there will be no more costs for processing consumables, and there is no need to clean and maintain the processor. If environmental factors are added, no-flush technology will undoubtedly have huge advantages.

To deeply understand the role of no-rinse printing plates, we need to talk about the basic principles. The occasion of the visit is undoubtedly the most suitable for the R & D center of the Kodak printing plate production plant in Windsor, Colorado, because Kodak is very unique in the newspaper platemaking field. Version and digital workflow, they also have thermal and violet laser technology. In addition, the core competence of Kodak's R & D center in Windsor is the so-called "no-flush" digital plate technology.

(Chris McCullough and scientist Jeffrey Collins discuss print quality)

(Jack Knadjian, Vice President of Newspapers of Kodak Graphic Group)

Chris McCullough, head of the R & D team at the Windsor factory, said that although offset printing is taken for granted by printers, technically, this is a remarkable achievement. For example, with an imaging area of ​​40 x 28 inches, the surface is covered by four micron-level ink layers, and these ink layers are not transferred once, but transferred twice-from the printing plate to the blanket, and then from Blanket to paper.

The emulsification level of the ink in the aqueous solution is a small number of molecules, and in the 40 x 28 inch image, the aqueous solution needs to carry 19,250,000 mesh tone dots, with an average size of 10 to 60 microns. In this 1,120 square inch image, the thickness of the final ink layer will reach 1 micron, its tolerance is +/- tenth of a micron, and the positioning accuracy must be within 40 microns. If this is not too harsh, then all these transfers must be completed in a quarter of a second, and some prints may have to be processed more than 1 million times.

As McCullough pointed out: "When you think of the processing between ink, fountain solution and printing plate, you will feel that offset printing is really a respectable technology."

Like offset printing technology, plate production is not simple. Not only is it extremely challenging to produce printing plates, McCullough believes it is more difficult to produce digital printing plates. Mike Rundle, Project Manager of Kodak Graphic Group explained: "In the simulated plate, energy is applied to the printing plate through continuous exposure equipment or a vacuum exposure machine. In fact, the energy is poured down. This will produce a great reaction. , Covering all coatings at once. "

"In the digital printing plate, whether it is a purple laser or a thermal printing plate, it seems to use an eye dropper to project a little energy onto the printing plate. Therefore, the reaction generated on the coating and the stability and reaction required by the reaction The analog printing plates are very different. "

The modern computer-to-plate (CTP) system has high automation capabilities, which also poses challenges for digital printing plate manufacturing. For example, if the printing plates cannot be cut into rectangles, the automatic direct plate-making machine will not be able to load these printing plates. In addition, if the printing plate is not inserted correctly, it cannot be removed correctly. McCullough also pointed out that there are countless challenges in coating: "The product of the printing plate is a lot of contradictory products. For example, a certain water / ink balance is required on the printing plate-the aluminum base needs to bring water to the printing machine, so Hydrophilic; and the coating needs to accept the ink on the printing press, so it needs ink affinity.

"However, the coating is an organic composition, not only requires an organic solvent, but also must be coated with a hydrophilic substrate. In addition, some ink-receptive resins need to be soluble in aqueous solutions, which requires hydrophilicity, while the remaining ink-receptive resins It must resist countless rolling of hydrophilic substrates in printing.

"It requires a lot of compromises. It's amazing that the printing plate can still work well in this situation, so that thousands of printers can use it.

"Of course, non-lithographic coatings, such as screen printing, have also been used, but they need to be cured immediately after use, such as after spraying a car. We must put down the coating under completely suitable conditions. When the reaction occurs, the customer also requires that the coating react as much as possible to allow faster imaging.

"However, the more the reaction, the lower the stability. Therefore, another compromise is that if the printing plate is to be imaged faster, then the printing plate must be preserved. All compromises must be balanced, which is exactly what the printing plate is produced. The challenge is. "

Nonetheless, since the launch of digital printing plates in the early 1990s, the development of digital printing plate technology has been rapid. Jack Knadjian, Vice President of Newspaper Marketing, Kodak Graphic Group explained that the technology was introduced: "Today, most newspapers in the world, whether they use thermal plates or purple laser plates, have at least two layers. Which plate manufacturer has the same basic technology, such as the composition and structure of the chemical agent. The main difference is the sensitive agent. "

"The printing plate is composed of a base (electrolytically polished anodized aluminum), an image photosensitive layer called a base layer (photosensitive resin compound and sensitizer), and a water-soluble polyvinyl alcohol (PVA) oxygen barrier top layer. In the middle, the grass-roots level is relatively soft, which allows the printing plate to respond more quickly to meet the requirements of the newspaper industry.

"In order to protect the soft substrate, the most important work of the top layer is to prevent oxygen from entering the substrate to prevent the reaction. If oxygen enters the substrate, the reaction must be prevented so that no image is formed on the printing plate, or only a weak image is formed."

Knadjian continued: "All printing plates, whether resin-thermosensitive or resin-sensitive, have to undergo multiple steps. First, exposure is required-the laser will excite the sensitizer and release 'free radicals', which will initiate the polymerization reaction. Let the monomer begin to crosslink. At this stage, a weak temporary latent image will be produced, but it cannot be printed on the printing press.
"In order to strengthen the image, the printing plate is placed in the preheating unit of the processor, which will increase the energy of the molecules and allow more cross-linking reactions of the monomers. The purpose is to create as many chains as possible, because The chain is an important factor for providing hardness to the coating, and will affect the life of the printing plate on the printing press.
"The next step is pre-cleaning, which will remove the top layer of water-soluble polyvinyl alcohol and expose the photosensitive resin imaging layer. The plate will then be placed in a dip tank to remove the unexposed layer, so the unexposed layer is a water-soluble coating. The developer in the tank is basically an alkaline solution at a pH of about 11, which will make the unexposed photosensitive resin layer soft and can be removed by the user using a brush.

"The particles of the photosensitive resin will remain in the developing solution, so they need to be replaced when they reach a certain concentration. This is called rehydration.

"After that, we clean the printing plate and remove all remaining developer. Next, we apply glue to form a protective layer. The protective layer needs to be dried. These are the six major steps required by a typical photosensitive resin processor, which is what we call Wet process. "

Knadjian then began to introduce the "chemical-free" purple laser technology, in which he believed it was necessary to elaborate on the combination of development and gluing processes.

"In the chemical-free violet laser plate, laser exposure is still required to create a latent image, and pre-heat treatment is still required to continue to produce cross-linking reactions and enhance the image. Pre-rinsing is omitted here, so the plate is sent directly to the dip tank And scrub with a brush.

"The immersion tank contains what I call a 'special condition' glue solution, because it contains more than just glue. The pH in the solution is lower than the pH of the developer in the wet process.

"This solution will remove the protective top layer of PVA, relax and remove the unexposed coating layer. According to the conventional treatment, a solid glue should be applied: but since the glue is already in the solution, the subsequent work of cleaning is also omitted. Finally drying Printing plate.

"Because both PVA and photosensitive resin particles remain in the glue solution, the solution needs to be changed from time to time. The immersion tank also needs to be cleaned like a wet process. In other words, in the violet laser 'chemical-free' process, it can be eliminated The process is only pre-rinsing and post-rinsing.

(Mike Rundle, Project Manager of Kodak Graphic Group, is checking the printed sheets)

Kodak Newspaper CTP Introduction:

Kodak Thermal CTP's true entry into the newspaper market started in 2000. At that time, the speed was very slow (40 pairs of openings / hour), and it was not very suitable for the newspaper's pursuit of effectiveness. Compared with the proposed newspaper CTP of 100 sheets per folio per hour, June 2008 launched the world's fastest CTP (140 folio per hour), a new generation of Kodak Newspaper, Kodak can provide A comprehensive product series that meets the needs of customers at any level, and in addition to the introduction of print quality into newspaper printing, the thermal newspaper CTP machine scalability and upgrade modules enable early (7, 8 years ago) investment customers to achieve on-site The speed, precision and format are fully upgraded to meet the current needs, and the compatibility of the plates is high. At present, the development of thermal CTP in the global newspaper industry is faster than that of thermal. The emerging markets of North and South America account for 53% of the market share, Asia-Pacific thermal is dominant, and Japanese thermal is 85% of the market share; I am gradually recognizing the incomparable advantages of light sensitivity that thermal sensitivity has. I believe it will have an impact on the development of the newspaper industry with increasingly fierce competition and decreasing cost pursuit.

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