Waterless printing technology

1. What is waterless printing technology?
Waterless printing is also a lithographic offset technology, except that it does not use the fountain solution necessary for conventional lithographic offset printing. It uses a special silicone rubber coated plate, special inks, and a strict temperature control system on the press.
In waterless printing, the printing process has changed from a chemical process using isopropyl alcohol or other fountain solution to a simple mechanical process. The print operator also does not have to adjust the ink-water balance. All waterless printing systems require a temperature range—the ink is transferred to the plate.
There are currently three manufacturers producing waterless printing plates. Toray Co., Ltd. of Japan produces two types of plates: one is a photosensitive and waterless version that requires film exposure and printing, and the other is a recently introduced computer-to-plate product.
The waterless version of PearlDry developed by the United States Presstek Corporation does not require exposure or printing.
PearDry waterless plate is mainly used in machine imaging plate making, used for DI printing presses, such as Heidelberger's QM-DI, Adast's Omni AdastDI and newly launched Karat 74DI. These printers occupy most of the color short live-demand printing market.
Kodak also recently introduced a waterless version that is in the testing phase.
The number of screens provided by these presses ranges from 150 lines/inch to 200 lines/inch.
Presstek's PearlDry waterless version is aluminum-based and is directly imaged on a direct platemaking machine. The maximum size of these plates is 102 cm, and the maximum number of screens is 240 lines/inch. The new product PearIDry Pus without watermark version can reach 300 lines/inch.
Waterless printing can quickly turn over the printing, reducing print preparation time and paper waste. It also eliminates the chemical contamination of fountain solution in traditional printing.
The waterless version can achieve a high number of screens and deliver more ink to the print. In color printing, a larger color range can be generated. The unwatermarked version is a flat intaglio with the graphic part below the surface of the printing plate. Since there is no wetted part, there is no emulsification problem with the ink. Therefore, you can print clear, bright images.
Second, the principle of waterless printing
1.Toray System
(1) Toray without watermark version
Troray waterless printing system is mainly composed of three parts: no watermark version, waterless ink and temperature control system on the machine.
Toray waterless version can be divided into three layers. At the bottom is an aluminum base, a photosensitive resin layer, and a two-micron thick silicone rubber coating. According to the type of Toray waterless version, the print volume varies from 150,000 to 600,000 prints. The amount of print also depends on the type of paper used. Like the traditional PS version, Toray has no watermarked version and is reborn. Toray waterless version can be used for sheetfed and web presses.
The Toray waterless version can be exposed using a conventional PS version of the printing device and light source. The exposure time is also not much different from the traditional PS version. At the time of exposure, the UV light, which is controlled by the film, penetrates the silicone rubber layer and reaches the photosensitive resin layer. The photosensitive resin in the graphic part absorbs UV light and reacts and falls off at the junction of the photosensitive resin and the silicone rubber layer. This kind of photoreaction is very fine, and the printing plate is also easy to get high resolution. When the number of screen lines is 175 lines/inch, it can reproduce 0.5% to 99.5% of the dots.
After the Toray waterless version is exposed, it needs to be processed. The processing equipment is unique to the system and uses special chemical and mechanical methods to process the plates.
The non-image area on the treated waterless plate is an ink-repellent silicone rubber layer; on the area of ​​the image, the silicone rubber layer is removed leaving the ink-receptive photosensitive resin layer. Also, the printing plate design can ensure that the printing plate does not use fountain solutions such as water and alcohol, and can selectively absorb ink or ink.
The non-watermark portion of the non-watermarked portion is sometimes easily scratched by the silicone rubber layer, exposing the photosensitive resin layer under which it absorbs ink. At this time it is necessary to use its special correction fluid (a kind of liquid silicone rubber) to repair the scratched part.
The biggest difference between waterless offset inks and traditional printing inks is the difference in the resin or binder used. Water-free ink binders should meet the rheological properties and have a higher viscosity than the binders in traditional printing inks.
The theoretical basis for waterless printing is that the surface energy of the non-graphical silicone rubber material on the printing plate is relatively low, and the viscosity of the waterless ink ensures that the affinity between the inks is greater than the affinity between the ink and the silicone rubber coating, so the silicone rubber The coating is ink-repellent.
(2) Temperature Control System
One factor that affects viscosity is temperature. Removing the dampening solution from the offset printing process will reduce the cooling effect on the surface of the printing plate. Due to friction, the temperature on the plate will increase. Because the viscosity of the waterless ink is large, the friction between the waterless ink and the ink roller will also increase the temperature.
Therefore, it is necessary to use a temperature control system on the printing press to precisely control the temperature. The most commonly used system is a cooling tandem roller, and the coolant circulates between the tandem rollers. This temperature control system has been used for many years on high speed web printing presses. Currently, this technology has been modified for use on sheetfed presses. Almost all sheet-fed press manufacturers use a hollow ink stringer to install this temperature control system.
The function of the temperature control system is to circulate enough coolant in the tandem roller to take away the heat generated by the mechanical action of the printing unit. It should be noted that this temperature control system is not designed to cool the ink roller. It only controls the temperature to a constant value during the printing process. With a constant temperature, the viscosity of the waterless ink will also remain.
Waterless proofing cannot be done using conventional proofers. Because the traditional proofer, outlets are larger than waterless printing. Many waterless printers use digital proofing systems.
2. Presstek System
Presstek PEARLdry waterless version of the system consists of two parts: a waterless version and waterless ink similar to Toray.
Presstek claims that the temperature control system on the press is an option. PEARL dry no watermark version with a maximum capacity of 50,000 impressions. If the print volume is less than 10,000 prints, there is no effect on the temperature on the press. Only the long-run version requires a temperature control system. PEARL dry is not watermarked, but it can also be recycled. The maximum size is four open.
The PEARL dry waterless version consists of four layers: an ink-repellent silicone rubber layer, a light-absorbing imaging layer, an ink-receiving layer, an aluminum base or a polyester base layer. PEARL dry without watermark imaging, no need for film, no exposure, no processing. Its imaging uses mainly an ablation technique. Use an infrared laser diode to ablate the silicone rubber coating on the plate to expose the underlying ink-receptive layer. During imaging, the laser rapidly heats the imaging layer to record images. The imaging layer is evaporated and the upper silicone rubber coating is stripped from the plate to form a graphic. After the plate is imaged, it must be cleaned and automatically mounted on the plate cylinder.
The system can be imaged in machine imaging (such as the octal QMDI) or using the Presstek direct platemaker. The platesetter has eight open or four open formats.
Due to the basic Postscipt system, proofing can also have a variety of digital proofing options: such as Iris's inkjet proofing and 3M's Rainbow proofing system.
Third, the main advantages of waterless printing:
· Protecting the environment: Without using fountain solution, it is very beneficial to environmental protection.
• Color consistency: Without a wetting system, the color change on the print is small during the printing process.
Color saturation: The four-color printing density is about 20% higher than the SWOP standard (web offset specification, commonly used ink set in the United States).
* Smaller dot gains: Good reproduction of details, small expansion of water-free printing dots, printable high-calorie lines, and good reproduction of details. Even with 175 lines/inch screens, waterless printing is quite good.
· Wide range of printing: waterless printing and printing on paper that cannot be used in traditional printing. Such as offset paper and so on. Without the wetting system, many paper problems disappeared in traditional printing.
• Short print preparation time: About 40% shorter than traditional print preparation time.
1. Waterless printing and environment
(1) Breakthrough in environmental protection. Fresh air, abundant water, dense forests, and safe working conditions are all environments that the countries of the world pursue. However, in some places, the printing industry has caused serious damage to the environment. Waterless printing will make a great contribution to environmental protection.
(2) No longer use volatile organics. Waterless printing eliminates the use of volatile organics in fountain solutions. Some volatile organic compounds can destroy Earth's helium-oxygen layers, creating a warm-temperate effect on Earth. Now, using water-based inks, bid farewell to volatile organics.
The revolution in ink technology has eliminated the need for organic solvents in cleaning blankets, greatly reducing the emission of volatile organic compounds. The car wash water is made up of 93% water and 7% harmless surfactants (such as soap, etc.) , is a water-based cleaning agent.
(3) Water resources protection. In 1995, 92% of the world's population had access to sufficient water. If water resources are consumed at current consumption rates, by 2050, only 58% of the world will have sufficient water resources. In the future, some countries even fight for water.
Waterless printing can protect water resources. For example, a Swiss printing company has introduced the world's first generation of waterless web presses, which saves 250,000 liters of water per year. Most of the water needs to come from a nearby lake. It is the source of drinking water for nearly 10,000 people.
(4) Protection of forest resources. The production of a ton of paper requires the use of 17 large trees, which can provide exactly 20 papers per day for reading.
Destroying forests, while providing raw materials for papermaking, has also destroyed the natural habitats of countless animals and plants and seriously damaged the ecological balance.
As the waterless printing process, the color can quickly come up, you can immediately register, and maintain the consistency of the color during the printing process, compared with the traditional printing, the book saves 30% to 40% of the paper. In addition to protecting forests, production costs are greatly reduced.
(5) cleaner environment, healthier humans. Because the printing workers breathe the gas containing toxic organics throughout the day, they greatly damage the health of the workers, greatly affecting the function of the kidneys, lungs, and dry skin. The county also causes dermatitis and damages to the nervous system.
When workers use highly volatile solvents to detect blankets, the damage is most serious.
Apparently, waterless printing does not use a dampening system, eliminating toxic substances in the solvent of washing blankets. It not only protects air, soil, and water, but also protects us ourselves—humans.
2. Comparison between waterless printing and traditional printing
(1) More vivid and bright colors. As shown in the figure, a waterless printing is compared with a traditional printed one.
Water-free printed products have a great contrast. That is, the darker parts are darker and the highlights are brighter. Can print printing quality that cannot reach traditional printing.
(2) Color reproduction is more summery. as the picture shows:
Waterless printing produces high ink density. Therefore, under the same number of screens, waterless printing products are richer and more real than traditional printing products.
(3) Better resolution. Now to compare, it is clear that waterless printing prints look sharper and more abundant. 300 lines/inch screen for waterless printing